Resolvin D1 controls inflammation initiated by glutathione-lipid conjugates formed during oxidative stress

Proresolution lipid mediators in multiple sclerosis - differential, disease severity-dependent synthesis - a clinical pilot trial

BACKGROUND

The severity and longevity of inflammation is controlled by endogenous counter-regulatory signals. Among them are long-chain polyunsaturated fatty acid (PUFA)-derived lipid mediators, which promote the resolution of inflammation, an active process for returning to tissue homeostasis.

OBJECTIVE

To determine whether endogenous production of lipid-derived resolution agonists is regulated differentially in patients with highly active and less active multiple sclerosis (MS).

DESIGN

Matched-pairs study in University hospital Neurology department.

PATIENTS

Based on clinical (relapse frequency) and paraclinical (MRI lesions, contrast enhancement) criteria, 10 pairs of age- and sex-matched patients with relapsing-remitting MS were assigned either to a group with highly active or less active MS. Lipid mediators were quantified in serum and cerebrospinal fluid using LC-MS/MS-based lipidomics.

RESULTS

Levels of the key arachidonic (ω-6) and docosahexaenoic acid (ω-6)-derived mediators prostaglandins (PG), leukotrienes, hydroxyeicosatetraenoic acids (HETE) and resolution agonists lipoxin A(4) (LXA(4)), resolvin D1 (RvD1) and neuroprotectin D1 (NPD1) were quantified. In the patient group with highly active MS, 15-HETE and PGE(2) were increased, which are products of the 15-lipoxygenase and cyclooxygenase pathways. The proresolution mediator RvD1 was significantly upregulated and NPD1 was detected in the highly active group only. LXA(4) levels were not increased in patients with highly active MS.

CONCLUSIONS

Lipid mediator pathways are regulated differentially in the cerebrospinal fluid of MS patients, depending on disease severity. Non-exhaustive or possibly 'delayed' resolution pathways may suggest a defective resolution program in patients with highly active MS. Longitudinal analyses are required to hetero-typify this differential resolution capacity, which may be associated with disease progression, longevity and eventual termination.

Pro-Resolving Lipid Mediators (SPMs) and Their Actions in Regulating miRNA in Novel Resolution Circuits in Inflammation

Unresolved inflammation is associated with several widely occurring diseases such as arthritis, periodontal diseases, cancer, and atherosclerosis. Endogenous mechanisms that curtail excessive inflammation and prompt its timely resolution are of considerable interest. In recent years, previously unrecognized chemical mediators derived from polyunsaturated fatty acids were identified that control the acute inflammatory response by activating local resolution programs. Among these are the so-called specialized pro-resolving lipid mediators (SPMs) that include lipoxins (LX), resolvins (Rv), protectins (PD), and maresins (MaR), because they are enzymatically biosynthesized during resolution of self-limited inflammation. They each possess distinct chemical structures and regulate cellular pathways by their ability to activate pro-resolving G-protein coupled receptors (GPCRs) in a stereospecific manner. For instance, RvD1 controls several miRNAs of interest in self-limited acute inflammation that counter-regulate the mediators and proteins that are involved in inflammation. Here, we overview some of the biosynthesis and mechanisms of SPM actions with focus on the recently reported miR involved in their pro-resolving responses that underscore their beneficial actions in the regulation of acute inflammation and its timely resolution. The elucidation of these mechanisms operating in vivo to keep acute inflammation within physiologic boundaries as well as stimulate resolution have opened resolution pharmacology and many new opportunities to target inflammation-related human pathologies via activating resolution mechanisms.

Resolvin D1 and its precursor docosahexaenoic acid promote resolution of adipose tissue inflammation by eliciting macrophage polarization toward an M2-like phenotype

We recently demonstrated that ω-3-polyunsaturated fatty acids ameliorate obesity-induced adipose tissue inflammation and insulin resistance. In this study, we report novel mechanisms underlying ω-3-polyunsaturated fatty acid actions on adipose tissue, adipocytes, and stromal vascular cells (SVC). Inflamed adipose tissue from high-fat diet-induced obese mice showed increased F4/80 and CD11b double-positive macrophage staining and elevated IL-6 and MCP-1 levels. Docosahexaenoic acid (DHA; 4 μg/g) did not change the total number of macrophages but significantly reduced the percentage of high CD11b/high F4/80-expressing cells in parallel with the emergence of low-expressing CD11b/F4/80 macrophages in the adipose tissue. This effect was associated with downregulation of proinflammatory adipokines in parallel with increased expression of IL-10, CD206, arginase 1, resistin-like molecule α, and chitinase-3 like protein, indicating a phenotypic switch in macrophage polarization toward an M2-like phenotype. This shift was confined to the SVC fraction, in which secretion of Th1 cytokines (IL-6, MCP-1, and TNF-α) was blocked by DHA. Notably, resolvin D1, an anti-inflammatory and proresolving mediator biosynthesized from DHA, markedly attenuated IFN-γ/LPS-induced Th1 cytokines while upregulating arginase 1 expression in a concentration-dependent manner. Resolvin D1 also stimulated nonphlogistic phagocytosis in adipose SVC macrophages by increasing both the number of macrophages containing ingested particles and the number of phagocytosed particles and by reducing macrophage reactive oxygen species production. No changes in adipocyte area and the phosphorylation of hormone-sensitive lipase, a rate-limiting enzyme regulating adipocyte lipolysis, were observed. These findings illustrate novel mechanisms through which resolvin D1 and its precursor DHA confer anti-inflammatory and proresolving actions in inflamed adipose tissue.

Emerging roles of resolvins in the resolution of inflammation and pain

Resolvins, including D and E series resolvins, are endogenous lipid mediators generated during the resolution phase of acute inflammation from the omega-3 polyunsaturated fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Resolvins have potent anti-inflammatory and pro-resolution actions in several animal models of inflammation. Recent findings also demonstrate that resolvin E1 and resolvin D1 can each potently dampen inflammatory and postoperative pain. This review focuses on the mechanisms by which resolvins act on their receptors in immune cells and neurons to normalize exaggerated pain via regulation of inflammatory mediators, transient receptor potential (TRP) ion channels, and spinal cord synaptic transmission. Resolvins may offer novel therapeutic approaches for preventing and treating pain conditions associated with inflammation.

The precursor of resolvin D series and aspirin-triggered resolvin D1 display anti-hyperalgesic properties in adjuvant-induced arthritis in rats

BACKGROUND AND PURPOSE

Resolution of inflammation is mediated by endogenous molecules with anti-inflammatory and pro-resolving activities and they have generated new possibilities for the treatment of inflammatory diseases. Here, we have investigated the possible anti-hyperalgesic effects of two lipids, aspirin-triggered resolvin D1 (AT-RvD1) and its precursor, 17(R)-hydroxy-4Z,7Z,10Z,13Z,15E,17R,19Z-docosahexaenoic acid (17(R)HDoHE).

EXPERIMENTAL APPROACH

The anti-hyperalgesic effects of both lipid mediators were evaluated, using mechanical and thermal stimuli, at different time-points in adjuvant-induced arthritis in rats. Cytokine levels were measured, and immunohistochemistry and real-time PCR for pro-inflammatory mediators were also performed.

KEY RESULTS

The precursor of resolvin D series, 17(R)HDoHE, given systemically, inhibited the development and the maintenance of mechanical hyperalgesia in acute inflammation. Such effects were likely to be associated with modulation of both NF-κB and COX-2 in dorsal root ganglia and spinal cord. 17(R)HDoHE was also effective against sub-chronic pain. Unexpectedly, repeated treatment with 17(R)HDoHE did not modify paw and joint oedema in the sub-chronic model, while joint stiffness was prevented. Notably, AT-RvD1 exhibited marked anti-hyperalgesic effects in acute inflammation when given systemically. The efficacy of long-term treatment with either 17(R)HDoHE or AT-RvD1 was partly related to decreased production of TNF-α and IL-1β in rat hind paw.

CONCLUSIONS AND IMPLICATIONS

Our findings provide fresh evidence for the anti-hyperalgesic properties of 17(R)HDoHE and its pro-resolution metabolite AT-RvD1. Such lipid mediators might be useful for treating pain associated with acute or chronic inflammation. LINKED ARTICLE This article is commented on by Xu and Ji, pp. 274-277 of this issue. To view this commentary visit http://dx.doi.org/10.1111/j.1476-5381.2011.01348.x.

Mechanisms for anti-inflammatory effects of 1-[15(S)-hydroxyeicosapentaenoyl] lysophosphatidylcholine, administered intraperitoneally, in zymosan A-induced peritonitis

BACKGROUND AND PURPOSE

Lysophosphatidylcholines (lysoPCs) with polyunsaturated acyl chains are known to exert anti-inflammatory actions. 15-Lipoxygeanation is crucial for anti-inflammatory action of polyunsaturated acylated lysoPCs. Here, the anti-inflammatory actions of 1-(15-hydroxyeicosapentaenoyl)-lysoPC (15-HEPE-lysoPC) and its derivatives were examined in a mechanistic analysis.

EXPERIMENTAL APPROACH

Anti-inflammatory actions of 15-HEPE-lysoPC in zymosan A-induced peritonitis of mice were examined by measuring plasma leakage and leucocyte infiltration, and determining levels of lipid mediators or cytokines.

KEY RESULTS

When each lysoPC, administered i.v., was assessed for its ability to suppress zymosan A-induced plasma leakage, 15-HEPE-lysoPC was found to be more potent than 1-(15-hydroperoxyeicosapentaenoyl)-lysoPC or 1-eicosapentaenoyl-lysoPC. Separately, i.p. administration of 15-HEPE-lysoPC markedly inhibited plasma leakage, in contrast to 15-HEPE, which had only a small effect. 15-HEPE-lysoPC also decreased leucocyte infiltration. Moreover, it reduced the formation of LTC₄ and LTB₄, 5-lipoxygenation products, as well as the levels of pro-inflammatory cytokines. The time-course study indicated that 15-HEPE-lysoPC might participate in both the early inflammatory phase and resolution phase. Additionally, 15-HEPE-lysoPC administration caused a partial suppression of LTC₄-induced plasma leakage and LTB₄-induced leucocyte infiltration. In the metabolism study, peritoneal exudate was shown to contain lysoPC-hydrolysing activity, crucial for anti-inflammatory activity, and a system capable of generating lipoxin A from 15-hydroxy eicosanoid precursor.

CONCLUSIONS AND IMPLICATIONS

15-HEPE-lysoPC, a precursor for 15-HEPE in target cells, induced anti-inflammatory actions by inhibiting the formation of pro-inflammatory leukotrienes and cytokines, and by enhancing the formation of lipoxin A. 15-HEPE-lysoPC might be one of many potent anti-inflammatory lipids in vivo.

Mediterranean diet and cardioprotection: the role of nitrite, polyunsaturated fatty acids, and polyphenols

The continually increasing rate of myocardial infarction (MI) in the Western world at least partly can be explained by a poor diet lacking in green vegetables, fruits, and fish and enriched in food that contains saturated fat. In contrast, a number of epidemiologic studies provide strong evidence highlighting the cardioprotective benefits of the Mediterranean diet enriched in green vegetables, fruits, fish, and grape wine. Regular consumption of these products leads to an accumulation of nitrate/nitrite/NO, polyunsaturated fatty acids (PUFA), and polyphenolic compounds, such as resveratrol, in the human body. Studies have confirmed that these constituents are bioactive exogenous mediators, which induce strong protection against MI. The aim of this review is to provide a critical, in-depth analysis of the cardioprotective pathways mediated by nitrite/NO, PUFA, and phenolic compounds of grape wines discovered in the recent years, including cross-talk between different mechanisms and compounds. Overall, these findings may facilitate the design and synthesis of novel therapeutic tools for the treatment of MI.

Novel anti-inflammatory--pro-resolving mediators and their receptors

Resolution of inflammation, an actively coordinated program, is essential to maintain host health. It involves effective removal of inflammatory stimuli and the spatio-temporal control of leukocyte trafficking as well as chemical mediator generation. During the active resolution process, new classes of small, local acting endogenous autacoids, namely the lipoxins, D and E series resolvins, (neuro)protectins, and maresins have been identified. These specialized pro-resolving lipid mediators (SPM) prevent excessive inflammation and promote removal of microbes and apoptotic cells, thereby expediting resolution and return to tissue homeostasis. As part of their molecular mechanism, SPM exert their potent actions via activating specific pro-resolving G-protein coupled receptors. Together these SPM and their receptors provide new concepts and opportunities for therapeutics, namely promoting active resolution as opposed to the conventionally used enzyme inhibitors and receptor antagonists. This approach may offer new targets suitable for drug design for treating inflammation related diseases, for the new terrain of resolution pharmacology.

Resolvin D1 attenuates activation of sensory transient receptor potential channels leading to multiple anti-nociception

BACKGROUND AND PURPOSE

Temperature-sensitive transient receptor potential ion channels (thermoTRPs) expressed in primary sensory neurons and skin keratinocytes play a crucial role as peripheral pain detectors. Many natural and synthetic ligands have been found to act on thermoTRPs, but little is known about endogenous compounds that inhibit these TRPs. Here, we asked whether resolvin D1 (RvD1), a naturally occurring anti-inflammatory and pro-resolving lipid molecule is able to affect the TRP channel activation.

EXPERIMENTAL APPROACH

We examined the effect of RvD1 on the six thermoTRPs using Ca(2+) imaging and whole cell electrophysiology experiments using the HEK cell heterologous expression system, cultured sensory neurons and HaCaT keratinocytes. We also checked changes in agonist-specific acute licking/flicking or flinching behaviours and TRP-related mechanical and thermal pain behaviours using Hargreaves, Randall-Selitto and von Frey assay systems with or without inflammation.

KEY RESULTS

RvD1 inhibited the activities of TRPA1, TRPV3 and TRPV4 at nanomolar and micromolar levels. Consistent attenuations in agonist-specific acute pain behaviours by immediate peripheral administration with RvD1 were also observed. Furthermore, local pretreatment with RvD1 significantly reversed mechanical and thermal hypersensitivity in inflamed tissues.

CONCLUSIONS AND IMPLICATIONS

RvD1 was a novel endogenous inhibitor for several sensory TRPs. The results of our behavioural studies suggest that RvD1 has an analgesic potential via these TRP-related mechanisms.

Novel lipid mediators promote resolution of acute inflammation: impact of aspirin and statins

The resolution of acute inflammation is a process that allows for inflamed tissues to return to homeostasis. Resolution was held to be a passive process, a concept now overturned with new evidence demonstrating that resolution is actively orchestrated by distinct cellular events and endogenous chemical mediators. Among these, lipid mediators, such as the lipoxins, resolvins, protectins, and newly identified maresins, have emerged as a novel genus of potent and stereoselective players that counter-regulate excessive acute inflammation and stimulate molecular and cellular events that define resolution. Given that uncontrolled, chronic inflammation is associated with many cardiovascular pathologies, an appreciation of the endogenous pathways and mediators that control timely resolution can open new terrain for therapeutic approaches targeted at stimulating resolution of local inflammation, as well as correcting the impact of chronic inflammation in cardiovascular disorders. Here, we overview and update the biosynthesis and actions of proresolving lipid mediators, highlighting their diverse protective roles relevant to vascular systems and their relation to aspirin and statin therapies.

Specialized pro-resolving lipid mediators in the inflammatory response: An update

A new genus of specialized pro-resolving mediators (SPM) which include several families of distinct local mediators (lipoxins, resolvins, protectins, and maresins) are actively involved in the clearance and regulation of inflammatory exudates to permit restoration of tissue homeostasis. Classic lipid mediators that are temporally regulated are formed from arachidonic acid, and novel local mediators were uncovered that are biosynthesized from ω-3 poly-unsaturated fatty acids, such as eicosapentaenoic acid, docosapentaenoic acid and docosahexaenoic acid. The biosynthetic pathways for resolvins are constituted by fatty acid lipoxygenases and cyclooxygenase-2 via transcellular interactions established by innate immune effector cells which migrate from the vasculature to inflamed tissue sites. SPM provide local control over the execution of an inflammatory response towards resolution, and include recently recognized actions of SPM such as tissue protection and host defense. The structural families of the SPM do not resemble classic eicosanoids (PG or LT) and are novel structures that function uniquely via pro-resolving cellular and molecular targets. The extravasation of inflammatory cells expressing SPM biosynthetic routes are matched by the temporal provision of essential fatty acids from circulation needed as substrate for the formation of SPM. The present review provides an update and overview of the biosynthetic pathways and actions of SPM, and examines resolution as an integrated component of the inflammatory response and its return to homeostasis via biochemically active resolution mechanisms.

Profiling in resolving inflammatory exudates identifies novel anti-inflammatory and pro-resolving mediators and signals for termination

A highly orchestrated inflammatory response and its completion, termed resolution, are essential for ongoing health. Thus, complete understanding of the cellular and molecular events that govern natural resolution is vital. Using an unbiased systems approach to profile self-limited inflammatory exudates, we identified a novel genus of specialized pro-resolving lipid mediators (SPMs) comprised of three new families coined the resolvins, protectins and most recently the maresins biosynthesized from omega-3 fatty acids. These join the lipoxin- and aspirin-triggered lipoxins as anti-inflammatory and pro-resolving lipid mediators formed from arachidonic acid with the genus. SPMs have proven stereoselective, and control both the duration and magnitude of inflammation. Mapping these endogenous resolution circuits provides new avenues to probe the molecular basis of many widely occurring diseases where uncontrolled inflammation is characteristic. The focus of this JIM review is to depict recent advances from studies by the authors and colleagues on the biosynthesis and actions of these novel anti-inflammatory, pro-resolving and protective lipid mediators. Together these findings indicate that defective mechanisms and pathways in resolution may underlie our current appreciation of the inflammatory phenotype(s) that characterize some prevalent human diseases.

Trans-4-hydroxy-2-hexenal, a product of n-3 fatty acid peroxidation: make some room HNE

Lipid peroxidation yields multiple aldehyde species. Of these, trans-4-hydroxy-2-nonenal (HNE), derived from n-6 poly-unsaturated fatty acids (PUFA) is one of the most studied products of lipid peroxidation. On the other hand, oxidative damage to n-3 PUFA, e.g. docosahexaenoic acid (DHA; 22:6, n-3) and eicosapentaenoic acid, is now recognized as an important effector of oxidative stress and is of particular interest in n-3 rich tissues such as brain and retina. Trans-4-hydroxy-2-hexenal (HHE) is a major alpha,beta-unsaturated aldehyde product of n-3 PUFA oxidation and, like HNE, is an active biochemical mediator resulting from lipid peroxidation. HHE adducts are elevated in disease states, in some cases, at higher levels than the corresponding HNE adduct. HHE has properties in common with HNE, but there are important differences particularly with respect to adduction targets and detoxification pathways. In this review, the biochemistry and cell biology of HHE will be discussed. From this review, it is clear that further study is needed to determine the biochemical and physiological roles of HHE and its related aldehyde, trans-4-oxo-2-hexenal.

Synthesis, quantification, characterization, and signaling properties of glutathionyl conjugates of enals

Oxidation of lipids generates large quantities of highly reactive alpha,beta-unsaturated aldehydes (enals). Enals and their protein adducts accumulate in the tissues of several pathologies. In vitro, low concentrations of enals such as HNE (4-hydroxy trans-2-nonenal) affect cell signaling whereas high concentrations of enals are cytotoxic. Direct conjugation of the C2-C3 double bond of enals with the sulfhydryl group of GSH is a major route for the metabolism and detoxification of enals. Recently, we found that glutathionyl conjugate of HNE (GS-HNE) enhances the peritoneal leukocyte infiltration and stimulates the formation of proinflammatory lipid mediators. Moreover, the reduced form of the glutathione conjugate of HNE (GS-DHN) elicits strong mitogenic signaling in smooth muscle cells. In this chapter we discuss the methods to study the metabolism of enals and the redox signaling properties of glutathionyl conjugates of HNE.

Lipid mediator interplay: resolvin D1 attenuates inflammation evoked by glutathione-conjugated lipid peroxidation products

Non-enzymatic oxidation of cellular lipids, one of the characteristic features of inflammation, leads to formation of highly reactive and toxic alpha,beta-unsaturated aldehydes, such as 4-hydroxy-trans-2-nonenal (HNE). Conjugation of HNE with reduced glutathione (GS-HNE) is widely believed to represent a form of detoxification. The study by Spite et al. in the current issue of the British Journal of Pharmacology shows that glutathiolation of HNE confers potent pro-inflammatory properties on this alpha,beta-unsaturated aldehyde. They find that GS-HNE directly activates human neutrophil granulocytes in vitro and evokes peritonitis in mice. Pre-treatment with resolvin D1, which is derived from omega-3 fatty acids, markedly attenuated the peritoneal leukocyte accumulation and production of prostaglandins and leukotrienes induced by GS-HNE. Their findings have profound implications for the analysis of inflammation in describing the generation of a novel class of pro-inflammatory mediators, through glutathione-dependent metabolism of lipid-peroxidation products, and emphasize the therapeutic potential of resolvin D1 in inflammatory diseases.

Lipid oxidation and peroxidation in CNS health and disease: from molecular mechanisms to therapeutic opportunities

Reactive oxygen species (ROS) are produced at low levels in mammalian cells by various metabolic processes, such as oxidative phosphorylation by the mitochondrial respiratory chain, NAD(P)H oxidases, and arachidonic acid oxidative metabolism. To maintain physiological redox balance, cells have endogenous antioxidant defenses regulated at the transcriptional level by Nrf2/ARE. Oxidative stress results when ROS production exceeds the cell's ability to detoxify ROS. Overproduction of ROS damages cellular components, including lipids, leading to decline in physiological function and cell death. Reaction of ROS with lipids produces oxidized phospholipids, which give rise to 4-hydroxynonenal, 4-oxo-2-nonenal, and acrolein. The brain is susceptible to oxidative damage due to its high lipid content and oxygen consumption. Neurodegenerative diseases (AD, ALS, bipolar disorder, epilepsy, Friedreich's ataxia, HD, MS, NBIA, NPC, PD, peroxisomal disorders, schizophrenia, Wallerian degeneration, Zellweger syndrome) and CNS traumas (stroke, TBI, SCI) are problems of vast clinical importance. Free iron can react with H(2)O(2) via the Fenton reaction, a primary cause of lipid peroxidation, and may be of particular importance for these CNS injuries and disorders. Cholesterol is an important regulator of lipid organization and the precursor for neurosteroid biosynthesis. Atherosclerosis, the major risk factor for ischemic stroke, involves accumulation of oxidized LDL in the arteries, leading to foam cell formation and plaque development. This review will discuss the role of lipid oxidation/peroxidation in various CNS injuries/disorders.

The vicious circle between oxidative stress and inflammation in atherosclerosis

The initial event in atherogenesis is the increased transcytosis of low density lipoprotein, and its subsequent deposition, retention and modification in the subendothelium. It is followed by the infiltration of activated inflammatory cells from the coronary circulation into the arterial wall. There they secrete reactive oxygen species (ROS) and produce oxidized lipoproteins capable of inducing endothelial cell apoptosis, and thereby plaque erosion. Activated T lymphocytes, macrophages and mast cells, accumulate in the eroded plaque where they secrete a variety of proteases capable of inducing degradation of extracellular proteins, thereby rendering the plaques more prone to rupture. This review summarizes the recent advancements in the understanding of the roles of ROS and oxidized lipoproteins in the activation of inflammatory cells and inducing signalling pathways related to cell death and apoptosis. In addition, it presents evidence that this vicious circle between oxidative stress and inflammation does not only occur in the diseased arterial wall, but also in adipose tissues. There, oxidative stress and inflammation impair adipocyte maturation resulting in defective insulin action and adipocytokine signalling. The latter is associated with increased infiltration of inflammatory cells, loss of anti-oxidant protection and cell death in the arterial wall.

The vicious circle between oxidative stress and inflammation in atherosclerosis

The initial event in atherogenesis is the increased transcytosis of low density lipoprotein, and its subsequent deposition, retention and modification in the subendothelium. It is followed by the infiltration of activated inflammatory cells from the coronary circulation into the arterial wall. There they secrete reactive oxygen species (ROS) and produce oxidized lipoproteins capable of inducing endothelial cell apoptosis, and thereby plaque erosion. Activated T lymphocytes, macrophages and mast cells, accumulate in the eroded plaque where they secrete a variety of proteases capable of inducing degradation of extracellular proteins, thereby rendering the plaques more prone to rupture. This review summarizes the recent advancements in the understanding of the roles of ROS and oxidized lipoproteins in the activation of inflammatory cells and inducing signalling pathways related to cell death and apoptosis. In addition, it presents evidence that this vicious circle between oxidative stress and inflammation does not only occur in the diseased arterial wall, but also in adipose tissues. There, oxidative stress and inflammation impair adipocyte maturation resulting in defective insulin action and adipocytokine signalling. The latter is associated with increased infiltration of inflammatory cells, loss of anti-oxidant protection and cell death in the arterial wall.