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AOP: 237

Title

A descriptive phrase which references both the Molecular Initiating Event and Adverse Outcome.It should take the form “MIE leading to AO”. For example, “Aromatase inhibition leading to reproductive dysfunction” where Aromatase inhibition is the MIE and reproductive dysfunction the AO. In cases where the MIE is unknown or undefined, the earliest known KE in the chain (i.e., furthest upstream) should be used in lieu of the MIE and it should be made clear that the stated event is a KE and not the MIE. More help

Substance interaction with lung resident cell membrane components leading to atherosclerosis

Short name

A name that succinctly summarises the information from the title. This name should not exceed 90 characters. More help

Interaction with lung cells leading to atherosclerosis

Graphical Representation

A graphical representation of the AOP.This graphic should list all KEs in sequence, including the MIE (if known) and AO, and the pair-wise relationships (links or KERs) between those KEs. More help

Click to download graphical representation template Explore AOP in a Third Party Tool

Authors

The names and affiliations of the individual(s)/organisation(s) that created/developed the AOP. More help

Claudia Torero Gutierrez¹, Sarah Søs Poulsen¹, Jorid Birkelund Sørli¹, Håkan Wallin², Sabina Halappanavar³, Carole L. Yauk⁴, Ulla Vogel^1,*

¹The National Research Centre for the Working Environment, Denmark

²Statens Arbeidsmiljøinstitutt, Norway

³Health Canada, Canada

⁴University of Ottawa, Canada

*Corresponding author: Ulla Vogel (ubv@nfa.dk)

Point of Contact

The user responsible for managing the AOP entry in the AOP-KB and controlling write access to the page by defining the contributors as described in the next section. More help

Ulla Vogel (email point of contact)

Contributors

Users with write access to the AOP page. Entries in this field are controlled by the Point of Contact. More help

Sarah Søs Poulsen
Ulla Vogel
Claudia Torero Gutierrez
Jorid Birkelund Sørli

Coaches

This field is used to identify coaches who supported the development of the AOP.Each coach selected must be a registered author. More help

Sabina Halappanavar

Status

Provides users with information concerning how actively the AOP page is being developed, what type of use or input the authors feel comfortable with given the current level of development, and whether it is part of the OECD AOP Development Workplan and has been reviewed and/or endorsed. OECD Status - Tracks the level of review/endorsement the AOP has been subjected to. OECD Project Number - Project number is designated and updated by the OECD. SAAOP Status - Status managed and updated by SAAOP curators. More help

Handbook Version	OECD status	OECD project
v2.5	Under Development	1.55

This AOP was last modified on November 23, 2023 10:17

Revision dates for related pages

Page	Revision Date/Time
Transcription of genes encoding acute phase proteins, Increased	November 23, 2023 10:17
Systemic acute phase response	October 13, 2023 07:58
Atherosclerosis	October 13, 2023 08:46
Substance interaction with the lung resident cell membrane components	May 17, 2023 15:10
Increased, secretion of proinflammatory mediators	May 17, 2023 15:18
Interaction with the lung cell membrane leads to Increased proinflammatory mediators	August 29, 2023 09:00
Interaction with the lung cell membrane leads to Increased transcription of genes encoding APP	October 19, 2023 04:38
Increased proinflammatory mediators leads to Increased transcription of genes encoding APP	October 18, 2023 09:15
Interaction with the lung cell membrane leads to Systemic APR	October 19, 2023 04:59
Increased proinflammatory mediators leads to Systemic APR	October 19, 2023 05:36
Increased transcription of genes encoding APP leads to Systemic APR	October 18, 2023 09:22
Interaction with the lung cell membrane leads to Atherosclerosis	November 01, 2023 12:09
Systemic APR leads to Atherosclerosis	October 18, 2023 09:34
Lipopolysaccharride	May 29, 2018 07:05
Graphene oxide nanoparticles	February 15, 2017 04:41
Carbon nanotubes	August 09, 2017 08:03
Insoluble nano-sized particles	May 29, 2018 07:09
Virus	May 29, 2018 07:10

Abstract

A concise and informative summation of the AOP under development that can stand-alone from the AOP page. The aim is to capture the highlights of the AOP and its potential scientific and regulatory relevance. More help

The present adverse outcome pathways (AOP) presents the link between the interaction of stressors of the pulmonary system and atherosclerosis. After interaction with the lung cell membrane, stressors can induce the release of pro-inflammatory factors, which in turn triggers the expression of acute phase proteins genes in the lungs and other tissues. Serum amyloid A (SAA) and C-reactive protein (CRP) are the major acute phase proteins in humans, and are considered risk factors for cardiovascular disease (Table 1 presents selected differences between acute phase response in humans and mice). In particular, serum amyloid A restricts the transport of cholesterol to the liver, allowing the accumulation of cholesterol in arteries and the formation of foam cells, an early marker of atherosclerosis.

Table 1. Selected differences in acute phase response between humans and mice.

Characteristic	Humans	Mice
Number of identified genes involved in acute phase reponse	62	62
Major acute phase proteins	CRP, SAA	Haptoglobin, SAA, serum amyloid P
Moderate and minor acute phase proteins	Haptoglobin, fibrinogen, α₁ acid glycoprotein	CRP, fibrinogen
SAA isoforms	Saa1, Saa2 and Saa4	Saa1, Saa2, Saa3 and Saa4

References: ^1-4.

This AOP mainly focus on particles or particulate matter as stressors, however other inflammatory conditions that induce acute phase response, can be consider stressors and lead to atherosclerosis. In addition, most of the evidence is based on animal studies (mice) as a model for the human system, however the adverse outcome of the present AOP, atherosclerosis, is only applicable for humans. The AOP can be used for regulatory purposes and to risk assess inhalable materials having acute phase response as the critical effect.

AOP Development Strategy

Context

Used to provide background information for AOP reviewers and users that is considered helpful in understanding the biology underlying the AOP and the motivation for its development.The background should NOT provide an overview of the AOP, its KEs or KERs, which are captured in more detail below. More help

Cardiovascular disease (CVD) is the leading cause of death worldwide, being responsible for 32% of all deaths in 2019 (WHO: http://www.who.int). The term CVD covers all diseases of the cardiovascular system, including atherosclerosis, which is manifested as increased plaque deposition or build-up in the arteries. Although, atherosclerosis is not a cause of death, it can lead to fatal conditions as stroke and myocardial infarction. Atherosclerosis is normally asymptotic disease and is initiated by a biological, chemical or physical insult to the artery walls. This leads to the expression of cell adhesion molecules (selectins, VCAM-1 and ICAM-1) on the endothelial lining of the arteries, which facilitates the activation, recruitment, and migration of monocytes through the endothelial monolayer ^5,6. Inside the intima layer, the monocytes differentiate into macrophages and internalize fatty deposits (mainly oxidized low-density lipoprotein). This results in them transforming into foam cells, which is a major component of the atherosclerotic fatty streaks. The fatty streaks reduce the elasticity of the artery walls and the foam cells promote a pro-inflammatory environment by secretion of cytokines and ROS. In addition, foam cells also induce the recruitment of smooth muscle cells to the intima. Added together, these changes lead to the formation of plaques on the artery walls. A fibrous cap of collagen and vascular smooth muscle cells protects the necrotic core and stabilizes the plaque ^7,8. However, blood clots can be formed if the plaque ruptures. These may travel with the bloodstream and obstruct the blood flow of smaller vessels, eg. the coronary arteries, which ultimately can lead to myocardial infarction.

Inhalation of particulate matter, chemicals and pathogens have been related to increased pulmonary inflammation. Whereas a normal immune reaction is crucial for effective elimination of threats to the body, chronic and unresolved inflammation has been linked to both adverse pulmonary and adverse systemic effects in humans. In concordance with this, various retrospective and prospective epidemiological studies have linked pulmonary exposure to respirable air particulates with increased the risk of developing CVD ^9-12. Inhalation of particles has been proposed to affect the cardiovascular system in several different ways, including through disruption of vasomotor function and through acceleration of plaque progression in atherosclerosis ^13,14.

The development of the present AOP was supported by the EU project NanoPASS (Grant number: 101092741) and the Focused Research Effort on Chemicals in the Working Environment (FFIKA) form the Danish Government.

Strategy

Provides a description of the approaches to the identification, screening and quality assessment of the data relevant to identification of the key events and key event relationships included in the AOP or AOP network.This information is important as a basis to support the objective/envisaged application of the AOP by the regulatory community and to facilitate the reuse of its components. Suggested content includes a rationale for and description of the scope and focus of the data search and identification strategy/ies including the nature of preliminary scoping and/or expert input, the overall literature screening strategy and more focused literature surveys to identify additional information (including e.g., key search terms, databases and time period searched, any tools used). More help

Summary of the AOP

This section is for information that describes the overall AOP.The information described in section 1 is entered on the upper portion of an AOP page within the AOP-Wiki. This is where some background information may be provided, the structure of the AOP is described, and the KEs and KERs are listed. More help

Events:

Molecular Initiating Events (MIE)

An MIE is a specialised KE that represents the beginning (point of interaction between a prototypical stressor and the biological system) of an AOP. More help

Key Events (KE)

A measurable event within a specific biological level of organisation. More help

Adverse Outcomes (AO)

An AO is a specialized KE that represents the end (an adverse outcome of regulatory significance) of an AOP. More help

Type	Event ID	Title	Short name

MIE

1495

Substance interaction with the lung resident cell membrane components

Interaction with the lung cell membrane

KE	1496	Increased, secretion of proinflammatory mediators	Increased proinflammatory mediators
KE	1438	Transcription of genes encoding acute phase proteins, Increased	Increased transcription of genes encoding APP
KE	1439	Systemic acute phase response	Systemic APR

1443

Atherosclerosis

Relationships Between Two Key Events (Including MIEs and AOs)

This table summarizes all of the KERs of the AOP and is populated in the AOP-Wiki as KERs are added to the AOP.Each table entry acts as a link to the individual KER description page. More help

Title	Adjacency	Evidence	Quantitative Understanding

Interaction with the lung cell membrane leads to Increased proinflammatory mediators	adjacent	High	Low
Increased proinflammatory mediators leads to Increased transcription of genes encoding APP	adjacent	High	Moderate
Increased transcription of genes encoding APP leads to Systemic APR	adjacent	High	Moderate
Systemic APR leads to Atherosclerosis	adjacent	High	High

Interaction with the lung cell membrane leads to Increased transcription of genes encoding APP	non-adjacent	High	Moderate
Interaction with the lung cell membrane leads to Systemic APR	non-adjacent	High	Moderate
Increased proinflammatory mediators leads to Systemic APR	non-adjacent	High	Moderate
Interaction with the lung cell membrane leads to Atherosclerosis	non-adjacent	High	Moderate

Network View

This network graphic is automatically generated based on the information provided in the MIE(s), KEs, AO(s), KERs and Weight of Evidence (WoE) summary tables. The width of the edges representing the KERs is determined by its WoE confidence level, with thicker lines representing higher degrees of confidence. This network view also shows which KEs are shared with other AOPs. More help

Prototypical Stressors

A structured data field that can be used to identify one or more “prototypical” stressors that act through this AOP. Prototypical stressors are stressors for which responses at multiple key events have been well documented. More help

Name
Lipopolysaccharride
Graphene oxide nanoparticles
Carbon nanotubes
Insoluble nano-sized particles
Virus

Life Stage Applicability

The life stage for which the AOP is known to be applicable. More help

Life stage	Evidence
Adult	High

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) can be selected.In many cases, individual species identified in these structured fields will be those for which the strongest evidence used in constructing the AOP was available. More help

Term	Scientific Term	Evidence	Link
human	Homo sapiens	High	NCBI
mouse	Mus musculus	High	NCBI

Sex Applicability

The sex for which the AOP is known to be applicable. More help

Sex	Evidence
Male	High
Female	High

Overall Assessment of the AOP

Addressess the relevant biological domain of applicability (i.e., in terms of taxa, sex, life stage, etc.) and Weight of Evidence (WoE) for the overall AOP as a basis to consider appropriate regulatory application (e.g., priority setting, testing strategies or risk assessment). More help

Domain of Applicability

Addressess the relevant biological domain(s) of applicability in terms of sex, life-stage, taxa, and other aspects of biological context. More help

This AOP is applicable to adult humans of both sexes. Although atherosclerosis is a condition that begins during childhood and progresses through life, its clinical manifestation is mostly observed in older individuals ¹⁵.

The AOP is applicable to all stressors that can be inhaled and, therefore, interact with the pulmonary system, and induce pulmonary inflammation if the dose is high enough.

Essentiality of the Key Events

The essentiality of KEs can only be assessed relative to the impact of manipulation of a given KE (e.g., experimentally blocking or exacerbating the event) on the downstream sequence of KEs defined for the AOP. Consequently, evidence supporting essentiality is assembled on the AOP page, rather than on the independent KE pages that are meant to stand-alone as modular units without reference to other KEs in the sequence. The nature of experimental evidence that is relevant to assessing essentiality relates to the impact on downstream KEs and the AO if upstream KEs are prevented or modified. This includes: Direct evidence: directly measured experimental support that blocking or preventing a KE prevents or impacts downstream KEs in the pathway in the expected fashion. Indirect evidence: evidence that modulation or attenuation in the magnitude of impact on a specific KE (increased effect or decreased effect) is associated with corresponding changes (increases or decreases) in the magnitude or frequency of one or more downstream KEs. More help

Support for essentiality of KEs	Defining question	High	Moderate	Low
Support for essentiality of KEs	What is the impact on downstream KEs and/or the AO if an upstream KE is modified or prevented?	Direct evidence from specifically designed experimental studies illustrating prevention or impact on downstream KEs and/or the AO if upstream KEs are blocked or modified	Indirect evidence that modification of one or more upstream KEs is associated with a corresponding (increase or decrease) in the magnitude or frequency of downstream KEs	No or contradictory experimental evidence of the essentiality of any of the KEs.
MIE: Substance interaction with the lung resident cell membrane components	Moderate. It has been observed that there is a dose-response relationship between the dose of the stressor (i.e. substance interaction with lung cells), and acute phase response outcomes (KE2 and KE3). In addition, Danielsen et al. showed that Toll-like receptor 4 (Tlr4) knockout mice exposed to LPS, known to be a agonist for TLR4, did not induce an increase in cytokine/chemokines mRNA levels in lung and liver tissues (KE1) and did not produce a systemic acute phase response (KE3) ¹⁶. Toll-like receptor 2 (Tlr2) knockout mice exposed to multiwalled carbon nanotubes did not induce increased Saa1 mRNA levels in liver tissue (KE2) and did not induce increased SAA1 levels in plasma (KE3) ¹⁶.
KE1: Increased, secretion of proinflammatory mediators	Strong. Mice presenting IL-6 gene disruption (IL-6^-/-) shown a reduced response in liver mRNA levels (KE2) and serum levels (KE3) of the acute phase proteins haptoglobin, α1-acid glycoprotein and serum amyloid a, after challenged by turpentine, lipopolysaccharide and bacterial infection ¹⁷. In an in vitro study, blocking IL-6 receptors in hepatic cell lines resulted in a reduction of SAA1 mRNA (KE2), while blocking IL-1β and TNF-α receptors partially reduced the expression of SAA1 mRNA ¹⁸. In a clinical trial study, patients with a history of myocardial infarction where administered with a monoclonal antibody for IL-1β (canakinumab). The results showed that the treatment significantly reduced blood CPR levels in a dose-dependent manner (KE2 and KE3) after 48 months, and there was a decrease in incidence rate of recurrent cardiovascular events (AO) ¹⁹.
KE2: Acute phase proteins transcription, Increased	Strong. Gene transcription is necessary for the synthesis of proteins (KE3). Thompson et al. showed that suppression of SAA3 in SAA1/SAA2 double knockout mice produced a significant reduction of atherosclerotic plaque area (AO) ²⁰.
KE3: Systemic acute phase response	Strong. Studies using animal model of atherosclerosis have shown that elevated levels of SAA induces plaque progression (AO) ^20,21. In prospective epidemiological studies, CRP and SAA levels are predictive of risk of cardiovascular disease ^22,23.

Uncertainties or Inconsistencies

Atherosclerosis is a disease influenced by multiple factors including high levels of lipoproteins in blood, elevated blood pressure, smoking, obesity, type 2 diabetes, diet, physical activity, among others ^15,24,25. As described by Libby, inflammation is also involved in atherosclerosis, providing mechanisms for the risk factors to induce atherosclerotic plaque formation and progression ^26,27. Therefore, although inflammation and acute phase response are not the only causes of atherosclerosis, the early key events (KE1, KE2 and KE3) can be used to evaluate the particle-induced risk to developing atherosclerosis.

CRP and SAA are risk factors for cardiovascular disease ²³. However, Mendelian randomization studies have shown that CRP genotypes are not associated with risk of coronary heart disease and that genetically elevated levels of CRP are not associated with coronary heart disease risk ^28,29. In humans, measuring gene expression of acute phase proteins is not very common, as a tissue sample is needed, while measuring acute phase protein in blood is more common.

In mice studies, it is possible to measure both SAA gene expression and protein levels, however the dynamic range for Saa gene expression is larger. Although it is suggested that acute phase proteins are mainly produced in the liver ², it has been shown that in mice the liver has little upregulation of Saa genes after exposure to ultrafine carbon particles or diesel exhaust particle. On the other hand, the lung shows a marked expression of Saa3 mRNA ^30,31.

There is an inconsistency with the results from human studies. It has been observed that in most controlled human studies, an increase in CRP and/or SAA was observed after exposure to particulate matter ^32-37. However, in other human studies the exposure did not induce acute phase response ^38,39, maybe due to low levels of exposure ⁴⁰ or limited statistical power.

In the case of nanomaterials, it has been shown that physicochemical characteristics as size, surface area, surface functionalization, shape, composition, among others, affect the magnitude and duration of acute phase response in mice ^41-43. In animal models, both inflammatory and acute phase response are predicted by the total surface area of the retained, insoluble particles ^42,44

Evidence Assessment

Addressess the biological plausibility, empirical support, and quantitative understanding from each KER in an AOP. More help

Biological plausibility of each KER

Support for Biological Plausibility of KERs	Defining question	High	Moderate	Low
	Is there a mechanistic (i.e., structural or functional) relationship between KEup and KEdown consistent with established biological knowledge?	Extensive understanding based on extensive previous documentation and broad acceptance -Established mechanistic basis	The KER is plausible based on analogy to accepted biological relationships but scientific understanding is not completely established.	There is empirical support for a statistical association between KEs (See 3.), but the structural or functional relationship between them is not understood.
MIE => KE1: Interaction with the lung cell membrane leads to Increased proinflammatory mediators	Biological Plausibility of the MIE => KE1 is High. Rationale: There is extensive evidence showing that interaction of stressors with the respiratory system induces the release of proinflammatory markers.
KE1 => KE2: Increased proinflammatory mediators leads to Increased transcription of acute phase proteins	Biological Plausibility of the KE1 => KE2 is High. Rationale: Acute phase proteins are induced by pro-inflammatory cytokines. These cytokines are produced at sites of inflammation mainly by monocytes and macrophages.
KE2 => KE3: Increased transcription of acute phase proteins leads to Systemic acute phase response	Biological Plausibility of the KE2 => KE3 is High. Rationale: After gene expression of acute phase proteins in tissues during inflammatory conditions, mRNA is translated and folded into proteins. These proteins are then release to the systemic circulation.
KE3 => AO: Systemic acute phase response leads to Atherosclerosis	Biological Plausibility of the KE3 => KE2 is High. Rationale: During acute phase response, serum amyloid A replaces apolipoprotein A-1 from high-density lipoprotein. This replacement obstructs the reverse transport of cholesterol to the liver, allowing the formation of foam cells, an early marker of atherosclerotic lesions.
Non-adjacent MIE => KE2: Interaction with the lung cell membrane leads to Increased transcription of acute phase proteins	Biological Plausibility of the MIE => KE2 is High. Rationale: Acute phase response occurs during inflammatory condition, including the interaction of stressor with the airways. There is extensive evidence that nanomaterials induce the expression of acute phase response genes in mice.
Non-adjacent MIE => KE3: Interaction with the lung cell membrane leads to Systemic acute phase response	Biological Plausibility of the MIE => KE3 is High. Rationale: There is plenty of evidence showing that inhalation or instillation of stressors induces systemic acute phase response in humans and mice.
Non-adjacent KE1 => KE3: Increased proinflammatory mediators leads to Systemic APR	Biological Plausibility of the KE1 => KE3 is High. Rationale: Pro-inflammatory cytokines induce the release of acute phase proteins. These proteins are releases from inflammatory sites to the systemic circulation.
Non-adjacent MIE => AO: Interaction with the lung cell membrane leads to Atherosclerosis	Biological Plausibility of the MIE => AO is Moderate. Rationale: There is evidence that the interaction of the lungs with stressor induces atherosclerotic plaque progression; however, the mechanistic relationship has not been clarified.

Please also refer to AOP173: Substance interaction with the pulmonary resident cell membrane components leading to pulmonary fibrosis, which shares MIE and KE1 with the present AOP.

Empirical support for each KER

Empirical Support

Defining question

High

Moderate

Low

Does KEup occur at lower doses and earlier time points than KE down and at the same dose of prototypical stressor, is the incidence of KEup > than that for KEdown?

Are there inconsistencies in empirical support across taxa, species and prototypical stressor that don’t align with expected pattern for hypothesised AOP?

Multiple studies showing dependent change in both events following exposure to a wide range of specific prototypical stressors. (Extensive evidence for temporal, dose- response and incidence concordance) and no or few critical data gaps or conflicting data

Demonstrated dependent change in both events following exposure to a small number of specific prototypical stressors and some evidence inconsistent with expected pattern that can be explained by factors such as experimental design, technical considerations, differences among laboratories, etc.

Limited or no studies reporting dependent change in both events following exposure to a specific prototypical stressor (i.e., endpoints never measured in the same study or not at all); and/or significant inconsistencies in empirical support across taxa and species that don’t align with expected pattern for hypothesised AOP

MIE => KE1: Interaction with the lung cell membrane leads to Increased proinflammatory mediators

Empirical Support of the MIE => KE1 is Moderate.

Rationale: There are limited in vitro studies which show a temporal and dose-dependent relationship between these two events.

KE1 => KE2: Increased proinflammatory mediators leads to Increased transcription of acute phase proteins

Empirical Support of the KE1 => KE2 is High.

Rationale: There are is a large number of studies showing a dose concordance and temporal concordance.

KE2 => KE3: Increased transcription of acute phase proteins leads to Systemic acute phase response

Empirical Support of the KE2 => KE3 is High.

Rationale: There are is a large number of studies showing a dose concordance and temporal concordance. However, there are inconsistencies between gene expression and translation of acute phase proteins.

KE3 => AO: Systemic acute phase response leads to Atherosclerosis

Empirical Support of the KE3 => AO is Moderate.

Rationale: There is a limited number of animal studies showing the relationship between the key events, in addition of epidemiological studies showing association between the key events.

Non-adjacent

MIE => KE2:

Interaction with the lung cell membrane leads to Increased transcription of acute phase proteins

Empirical Support of the MIE => KE2 is Moderate.

Rationale: There are is a large number of studies showing a dose concordance and temporal concordance in animal studies. However, in the case of nanomaterials it has been shown that physicochemical characteristics affect the magnitude and duration of the expression of acute phase proteins in mice.

Non-adjacent

MIE => KE3:

Interaction with the lung cell membrane leads to Systemic acute phase response

Empirical Support of the MIE => KE3 is Moderate.

Rationale: There are plenty of studies showing a dose concordance and temporal concordance in animal and controlled human studies. It has been observed that systemic acute phase response is not always observed after exposure.

Non-adjacent KE1 => KE3: Increased proinflammatory mediators leads to Systemic APR

Empirical Support of the KE1 => KE3 is Moderate.

Rationale: There is plenty of studies showing a dose concordance and temporal concordance. However, there are inconsistencies between changes in blood levels of pro-inflammatory mediators and systemic APR.

Non-adjacent

MIE => AO:

Interaction with the lung cell membrane leads to Atherosclerosis

Empirical Support of the MIE => AO is Moderate.

Rationale: There is a number of studies showing the relationship between the key events.

Known Modulating Factors

Modulating factors (MFs) may alter the shape of the response-response function that describes the quantitative relationship between two KES, thus having an impact on the progression of the pathway or the severity of the AO.The evidence supporting the influence of various modulating factors is assembled within the individual KERs. More help

Modulating factor	Influence on outcome	KER involved
High body mass index	Increased risk of atherosclerosis.	KER4
Smoking	Increased risk of atherosclerosis.	KER4
Intake of non-steroidal anti-inflammatory drugs	Decreased risk of atherosclerosis.	KER4
Chronic inflammatory diseases	Increased risk of atherosclerosis.	KER4
Infectious diseases	Increased risk of atherosclerosis.	KER4

Quantitative Understanding

Optional field to provide quantitative weight of evidence descriptors. More help

The table below presents a characterization of every KER.

It is important to clarify that when assessing stressors in mice studies, it is possible to measure the gene expression of acute phase proteins (KE2) in different tissues, however in humans this is not likely as a tissue sample would be required. On the other hand, in humans it is much more common and easier to measure systemic acute phase response (KE3) through a blood sample. In mice, it has been shown that Saa3 mRNA in lung tissue and blood levels of SAA3 are correlated ⁴². In addition, SAA levels in mice and humans seem to be in level in magnitude after exposure to zinc oxide nanoparticles ⁴². This suggest, that systemic acute phase response in humans can be estimated from mice studies.

In the case of nanomaterials and mice studies, Saa3 mRNA in lung tissue is also correlated to pulmonary inflammation measured as neutrophil numbers, and both of these endpoints can be estimated by calculating the dosed surface area (specific surface area multiplied by dose level) ⁴².

Finally, the relative risk of people developing a cardiovascular disease can be calculated from blood level of acute phase proteins in epidemiological studies.

KER

Quantitative understanding

MIE => KE1: Interaction with the lung cell membrane leads to Increased proinflammatory mediators

The quantitative understanding of MIE => KE1 is Low.

Rationale: The quantitative prediction of the release of proinflammatory factors can be made from the interaction of the stressors with the pulmonary system.

In the case of some stressors (nanomaterials) it is possible to make a prediction using the dosed surface area of the materials and neutrophil numbers as an indirect marker of the release of pro-inflammatory factors.

KE1 => KE2: Increased proinflammatory mediators leads to Increased transcription of acute phase proteins

The quantitative understanding is of KE1 => KE2 is Moderate.

Rationale: In mice, the gene expression of the acute phase protein SAA after exposure to metal oxide nanomaterials can be estimated using an indirect marker of the release of pro-inflammatory factors (neutrophil numbers).

KE2 => KE3: Increased transcription of acute phase proteins leads to Systemic acute phase response

The quantitative understanding of KE2 => KE3 is Moderate.

Rationale: In mice, the systemic levels of the acute phase protein SAA after exposure to metal oxide nanomaterials can be estimated from the gene expression in lung tissue.

KE3 => AO: Systemic acute phase response leads to Atherosclerosis

The quantitative understanding is of KE3 => AO is High.

Rationale: The risk of developing a cardiovascular disease at population level can be calculated from blood levels of acute phase proteins.

Non-adjacent

MIE => KE2:

Interaction with the lung cell membrane leads to Increased transcription of acute phase proteins

The quantitative understanding of MIE => KE2 is Moderate.

Rationale: In mice, the gene expression of the acute phase protein SAA after exposure to metal oxide nanomaterials can be estimated from the dosed surface area.

Non-adjacent

MIE => KE3:

Interaction with the lung cell membrane leads to Systemic acute phase response

The quantitative understanding of MIE => KE3 is Moderate.

Rationale: In mice, the blood levels of the acute phase protein SAA after exposure to metal oxide nanomaterials can be estimated from the dosed surface area.

Non-adjacent KE1 => KE3: Increased proinflammatory mediators leads to Systemic APR

The quantitative understanding of KE1 => KE3 is Moderate.

Rationale: In mice, the blood levels of the acute phase protein SAA after exposure to metal oxide nanomaterials and multiwalled carbon nanotubes can be estimated from neutrophil numbers in broncheoalveolar lavage fluid.

Non-adjacent

MIE => AO:

Interaction with the lung cell membrane leads to Atherosclerosis

The quantitative understanding of MIE => AO is Moderate.

Rationale: Epidemiological studies have shown the risk ratios of having a cardiovascular event per increase or decrease of exposure to particulate matter.

Considerations for Potential Applications of the AOP (optional)

Addressess potential applications of an AOP to support regulatory decision-making.This may include, for example, possible utility for test guideline development or refinement, development of integrated testing and assessment approaches, development of (Q)SARs / or chemical profilers to facilitate the grouping of chemicals for subsequent read-across, screening level hazard assessments or even risk assessment. More help

Particle-induced acute phase response can be regarded as a critical effect linking particle-exposure to cardiovascular disease. Dose-response relationships can be used to establish no-observed-adverse-effect levels (NOAEL) for regulatory purposes and occupational exposure limits for inhalable materials can be determined through health-based risk assessments. This approach was taken by the Danish National Research Centre for the Working Environment at request of the Danish Working Environment Authority and an occupational exposure limit for zinc oxide was proposed based on the induction of acute phase response as the critical effect (the report can be found in: Dokumentation for helbredsbaserede grænseværdier for kemiske stoffer i arbejdsmiljøet (nfa.dk)).

As mentioned previously, not all KE can easily be measured in humans, therefore animal studies can be used to measure early KE and perform a risk assessment of different stressors. Additionally, physicochemical properties, such as specific surface area and dissolution, are important predictors of particle-induced acute phase response that can be used for hazard assessment ⁴²

References

List of the literature that was cited for this AOP. More help

1 Cray, C. Acute phase proteins in animals. Prog Mol Biol Transl Sci 105, 113-150, doi:10.1016/B978-0-12-394596-9.00005-6 (2012).

2 Gabay, C. & Kushner, I. Acute-phase proteins and other systemic responses to inflammation. N Engl J Med 340, 448-454, doi:10.1056/NEJM199902113400607 (1999).

3 Medicine, N. L. o. Acute phase response related genes.

4 Tannock, L. R. et al. Serum amyloid A3 is a high density lipoprotein-associated acute-phase protein. J Lipid Res 59, 339-347, doi:10.1194/jlr.M080887 (2018).

5 Cybulsky, M. I. et al. A major role for VCAM-1, but not ICAM-1, in early atherosclerosis. J Clin Invest 107, 1255-1262, doi:10.1172/JCI11871 (2001).

6 Hansson, G. K. & Libby, P. The immune response in atherosclerosis: a double-edged sword. Nat Rev Immunol 6, 508-519, doi:10.1038/nri1882 (2006).

7 Libby, P. Inflammation in atherosclerosis. Arterioscler Thromb Vasc Biol 32, 2045-2051, doi:10.1161/ATVBAHA.108.179705 (2012).

8 Virmani, R. et al. Atherosclerotic plaque progression and vulnerability to rupture: angiogenesis as a source of intraplaque hemorrhage. Arterioscler Thromb Vasc Biol 25, 2054-2061, doi:10.1161/01.ATV.0000178991.71605.18 (2005).

9 Clancy, L., Goodman, P., Sinclair, H. & Dockery, D. W. Effect of air-pollution control on death rates in Dublin, Ireland: an intervention study. Lancet 360, 1210-1214, doi:10.1016/S0140-6736(02)11281-5 (2002).

10 Dockery, D. W. et al. An association between air pollution and mortality in six U.S. cities. N Engl J Med 329, 1753-1759, doi:10.1056/NEJM199312093292401 (1993).

11 Pope, C. A., 3rd et al. Cardiovascular mortality and long-term exposure to particulate air pollution: epidemiological evidence of general pathophysiological pathways of disease. Circulation 109, 71-77, doi:10.1161/01.CIR.0000108927.80044.7F (2004).

12 Pope, C. A., 3rd et al. Particulate air pollution as a predictor of mortality in a prospective study of U.S. adults. Am J Respir Crit Care Med 151, 669-674, doi:10.1164/ajrccm/151.3_Pt_1.669 (1995).

13 Cao, Y. et al. Vascular effects of multiwalled carbon nanotubes in dyslipidemic ApoE-/- mice and cultured endothelial cells. Toxicol Sci 138, 104-116, doi:10.1093/toxsci/kft328 (2014).

14 Moller, P. et al. Atherosclerosis and vasomotor dysfunction in arteries of animals after exposure to combustion-derived particulate matter or nanomaterials. Crit Rev Toxicol 46, 437-476, doi:10.3109/10408444.2016.1149451 (2016).

15 Raitakari, O., Pahkala, K. & Magnussen, C. G. Prevention of atherosclerosis from childhood. Nat Rev Cardiol 19, 543-554, doi:10.1038/s41569-021-00647-9 (2022).

16 Danielsen, P. H. et al. Nanomaterial- and shape-dependency of TLR2 and TLR4 mediated signaling following pulmonary exposure to carbonaceous nanomaterials in mice. Part Fibre Toxicol 18, 40, doi:10.1186/s12989-021-00432-z (2021).

17 Kopf, M. et al. Impaired immune and acute-phase responses in interleukin-6-deficient mice. Nature 368, 339-342, doi:10.1038/368339a0 (1994).

18 Hagihara, K. et al. IL-6 plays a critical role in the synergistic induction of human serum amyloid A (SAA) gene when stimulated with proinflammatory cytokines as analyzed with an SAA isoform real-time quantitative RT-PCR assay system. Biochem Biophys Res Commun 314, 363-369, doi:10.1016/j.bbrc.2003.12.096 (2004).

19 Ridker, P. M. et al. Antiinflammatory Therapy with Canakinumab for Atherosclerotic Disease. N Engl J Med 377, 1119-1131, doi:10.1056/NEJMoa1707914 (2017).

20 Thompson, J. C. et al. Serum amyloid A3 is pro-atherogenic. Atherosclerosis 268, 32-35, doi:10.1016/j.atherosclerosis.2017.11.011 (2018).

21 Christophersen, D. V. et al. Accelerated atherosclerosis caused by serum amyloid A response in lungs of ApoE(-/-) mice. FASEB J 35, e21307, doi:10.1096/fj.202002017R (2021).

22 Pai, J. K. et al. Inflammatory markers and the risk of coronary heart disease in men and women. N Engl J Med 351, 2599-2610, doi:10.1056/NEJMoa040967 (2004).

23 Ridker, P. M., Hennekens, C. H., Buring, J. E. & Rifai, N. C-reactive protein and other markers of inflammation in the prediction of cardiovascular disease in women. N Engl J Med 342, 836-843, doi:10.1056/NEJM200003233421202 (2000).

24 Herrington, W., Lacey, B., Sherliker, P., Armitage, J. & Lewington, S. Epidemiology of Atherosclerosis and the Potential to Reduce the Global Burden of Atherothrombotic Disease. Circ Res 118, 535-546, doi:10.1161/CIRCRESAHA.115.307611 (2016).

25 Libby, P. et al. Atherosclerosis. Nat Rev Dis Primers 5, 56, doi:10.1038/s41572-019-0106-z (2019).

26 Libby, P. The changing landscape of atherosclerosis. Nature 592, 524-533, doi:10.1038/s41586-021-03392-8 (2021).

27 Libby, P. Inflammation during the life cycle of the atherosclerotic plaque. Cardiovasc Res 117, 2525-2536, doi:10.1093/cvr/cvab303 (2021).

28 Collaboration, C. R. P. C. H. D. G. et al. Association between C reactive protein and coronary heart disease: mendelian randomisation analysis based on individual participant data. BMJ 342, d548, doi:10.1136/bmj.d548 (2011).

29 Elliott, P. et al. Genetic Loci associated with C-reactive protein levels and risk of coronary heart disease. JAMA 302, 37-48, doi:10.1001/jama.2009.954 (2009).

30 Saber, A. T. et al. Lack of acute phase response in the livers of mice exposed to diesel exhaust particles or carbon black by inhalation. Part Fibre Toxicol 6, 12, doi:10.1186/1743-8977-6-12 (2009).

31 Saber, A. T. et al. Particle-induced pulmonary acute phase response correlates with neutrophil influx linking inhaled particles and cardiovascular risk. PLoS One 8, e69020, doi:10.1371/journal.pone.0069020 (2013).

32 Monse, C. et al. Concentration-dependent systemic response after inhalation of nano-sized zinc oxide particles in human volunteers. Part Fibre Toxicol 15, 8, doi:10.1186/s12989-018-0246-4 (2018).

33 Monse, C. et al. Health effects after inhalation of micro- and nano-sized zinc oxide particles in human volunteers. Arch Toxicol 95, 53-65, doi:10.1007/s00204-020-02923-y (2021).

34 Walker, E. S. et al. Acute differences in blood lipids and inflammatory biomarkers following controlled exposures to cookstove air pollution in the STOVES study. Int J Environ Health Res 32, 565-578, doi:10.1080/09603123.2020.1785402 (2022).

35 Wyatt, L. H., Devlin, R. B., Rappold, A. G., Case, M. W. & Diaz-Sanchez, D. Low levels of fine particulate matter increase vascular damage and reduce pulmonary function in young healthy adults. Part Fibre Toxicol 17, 58, doi:10.1186/s12989-020-00389-5 (2020).

36 Baumann, R. et al. Systemic serum amyloid A as a biomarker for exposure to zinc and/or copper-containing metal fumes. J Expo Sci Environ Epidemiol 28, 84-91, doi:10.1038/jes.2016.86 (2018).

37 Haase, L. M. et al. Cross-sectional Study of Workers Employed at a Copper Smelter-Effects of Long-term Exposures to Copper on Lung Function and Chronic Inflammation. J Occup Environ Med 64, e550-e558, doi:10.1097/JOM.0000000000002610 (2022).

38 Andersen, M. H. G. et al. Association between polycyclic aromatic hydrocarbon exposure and peripheral blood mononuclear cell DNA damage in human volunteers during fire extinction exercises. Mutagenesis 33, 105-115, doi:10.1093/mutage/gex021 (2018).

39 Andersen, M. H. G. et al. Assessment of polycyclic aromatic hydrocarbon exposure, lung function, systemic inflammation, and genotoxicity in peripheral blood mononuclear cells from firefighters before and after a work shift. Environ Mol Mutagen 59, 539-548, doi:10.1002/em.22193 (2018).

40 Andersen, M. H. G. et al. Health effects of exposure to diesel exhaust in diesel-powered trains. Part Fibre Toxicol 16, 21, doi:10.1186/s12989-019-0306-4 (2019).

41 Poulsen, S. S. et al. Multi-walled carbon nanotube-physicochemical properties predict the systemic acute phase response following pulmonary exposure in mice. PLoS One 12, e0174167, doi:10.1371/journal.pone.0174167 (2017).

42 Gutierrez, C. T. et al. Acute phase response following pulmonary exposure to soluble and insoluble metal oxide nanomaterials in mice. Part Fibre Toxicol 20, 4, doi:10.1186/s12989-023-00514-0 (2023).

43 Bengtson, S. et al. Differences in inflammation and acute phase response but similar genotoxicity in mice following pulmonary exposure to graphene oxide and reduced graphene oxide. PLoS One 12, e0178355, doi:10.1371/journal.pone.0178355 (2017).

44 Cosnier, F. et al. Retained particle surface area dose drives inflammation in rat lungs following acute, subacute, and subchronic inhalation of nanomaterials. Part Fibre Toxicol 18, 29, doi:10.1186/s12989-021-00419-w (2021).