Cyclooxygenase and prostaglandin synthases in atherosclerosis: Recent insights and future perspectives

The landscape of drug discovery in atherosclerosis and dyslipidaemia revisited: an update of patenting activity

INTRODUCTION

This paper is an update of a previous paper I published in Expert Opinion of Therapeutic Patents in 2008. The paper was a survey of patenting activity in the fields of atherosclerosis and dyslipidaemia, which identified trends in patenting by reviewing two major mechanistic categories, metabolic/dyslipidaemia and vascular/inflammation, as well as examining the interest in certain specific targets over a period of 10 years.

METHODS

In this update, the same methodology was followed using the Espacenet of the European Patent Office (EPO) to identify patents claiming therapeutics for atherosclerosis or dyslipidaemia (excluding the wider metabolic syndrome).

EXPERT OPINION

A major change in the field over the past 5 years has been the departure of larger companies from the field. This is reflected in the patenting activity. Patenting has been at a stable rate over the recent years with few new targets being highlighted. It is suggested that, for this field to return to the higher rates of patenting seen over 10 years ago, breakthroughs in translational medicine and in the ability to conduct clinical trials, particularly in biomarkers and imaging, will need to take place.

Transactivation of EGFR/PI3K/Akt involved in ATP-induced inflammatory protein expression and cell motility

Phenotype transition of vascular smooth muscle cells (VSMCs) is important in vascular diseases, such as atherosclerosis and restenosis. Once released, ATP may promote activation of VSMCs by stimulating cyclooxygenase-2 (COX-2), cytosolic phospholipase A(2) (cPLA(2)) expression and prostaglandin (PG)E(2) synthesis via activation of MAPKs and NF-κB. However, whether alternative signaling pathways participated in regulating COX-2 and cPLA(2) expression associated with cell migration were investigated in rat VSMCs. Western blot analysis, RT-PCR, promoter assay and PGE(2) ELISA were used to determine expression of COX-2, cPLA(2) and PGE(2). Specific inhibitors and siRNAs against various protein kinases or transcription factors were used to investigate the related signaling components in inflammatory protein induction by ATPγS. We found that ATPγS-induced COX-2 and cPLA(2) expression and PGE(2) release was attenuated by the pharmacological inhibitors or transfection with siRNA against PKCδ, c-Src, EGFR, PI3-K, Akt, p44/p42 MAPK or Elk-1. Moreover, ATPγS-stimulated phosphorylation of PKCδ, c-Src, EGFR, Akt, p42/p44 MAPK and Elk-1, suggesting the participation of PKCδ/c-Src/EGFR/PI3-K/Akt/p42/p44 MAPK cascade in mediating Elk-1 activities in VSMCs. In addition, migration assay revealed that ATPγS promoted cell mobility through up-regulation of COX-2 and cPLA(2) expression and PGE(2) release, which was attenuated by pretreatment with PGE(2) receptor antagonists. Taken together, these data showed that ATPγS up-regulated the expression of COX-2 and cPLA(2) through transactivation of PKCδ/c-Src/EGFR/PI3K/Akt/Elk-1 pathway. Newly synthesized PGE(2) acted on its receptors to promote cell motility of ATPγS-stimulated VSMCs.

Diverse patterns of cyclooxygenase-independent metalloproteinase gene regulation in human monocytes

BACKGROUND AND PURPOSE Matrix metalloproteinase (MMP) production from monocyte/macrophages is implicated in matrix remodelling and modulation of inflammation. However, knowledge of the patterns and mechanisms of gene regulation of MMPs and their endogenous tissue inhibitors (TIMPs) is fragmentary. MMP up-regulation may be a target for cyclooxygenase (COX) and prostaglandin (PG) receptor inhibition, but the extent and mechanisms of COX-independent MMP up-regulation are unclear. EXPERIMENTAL APPROACH We studied MMP mRNA expression and selected protein levels in human peripheral blood monocytes before and after adhesion, upon stimulation with bacterial lipopolysaccharide (LPS), PGE(2) or forskolin and after culturing with monocyte colony-stimulating factor on plastic or human fibronectin for up to 7 days. KEY RESULTS Monocyte adherence for 2 h transiently up-regulated COX-2, MMP-1, MMP-7 and MMP-10 mRNAs, and persistently up-regulated MMP-2, MMP-9, MMP-14 and MMP-19 mRNAs. LPS, PGE(2) or forskolin selectively increased MMP-1, MMP-9, MMP-10, MMP-12 and MMP-14 mRNAs. LPS increased PGE(2) production through COX but up-regulated MMP levels independently of COX. Differential dependence on inhibition of p42/44 and p38 mitogen-activated protein kinases, c-jun N-terminal kinase and inhibitor of κB kinase2 paralleled the diverse patterns of MMP stimulation by LPS. Differentiation on plastic increased mRNA levels of MMP-7, MMP-9, MMP-12 and MMP-14 and TIMP-2 and TIMP-3 independently of COX; fibronectin accelerated MMP but not TIMP up-regulation. CONCLUSIONS AND IMPLICATIONS Adhesion, LPS stimulation and maturation of human monocytes lead to selective, COX-independent MMP and TIMP gene regulation, which is a potential target for selective inhibition by signalling kinase inhibitors.

Inflammation-related gene expression by lipid oxidation-derived products in the progression of atherosclerosis

Vascular areas of atherosclerotic development persist in a state of inflammation, and any further inflammatory stimulus in the subintimal area elicits a proatherogenic response; this alters the behavior of the artery wall cells and recruits further inflammatory cells. In association with the inflammatory response, oxidative events are also involved in the development of atherosclerotic plaques. It is now unanimously recognized that lipid oxidation-derived products are key players in the initiation and progression of atherosclerotic lesions. Oxidized lipids, derived from oxidatively modified low-density lipoproteins (LDLs), which accumulate in the intima, strongly modulate inflammation-related gene expression, through involvement of various signaling pathways. In addition, considerable evidence supports a proatherogenic role of a large group of potent bioactive lipids called eicosanoids, which derive from oxidation of arachidonic acid, a component of membrane phospholipids. Of note, LDL lipid oxidation products might regulate eicosanoid production, modulating the enzymatic degradation of arachidonic acid by cyclooxygenases and lipoxygenases; these enzymes might also directly contribute to LDL oxidation. This review provides a comprehensive overview of current knowledge on signal transduction pathways and inflammatory gene expression, modulated by lipid oxidation-derived products, in the progression of atherosclerosis.

Sex differences in urinary biomarkers of vascular and endothelial function in HIV-infected persons receiving antiretroviral therapy

BACKGROUND

Cardiovascular disease (CVD) risk can be underestimated in HIV-infected patients receiving antiretroviral therapy (ART). Novel CVD risk markers in this population are needed. We hypothesized that eicosanoid metabolite production is increased with metabolic complications of ART. Our objective was to determine relationships between urine eicosanoids and traditional CVD risk factors in a cohort of HIV-infected persons receiving ART.

METHODS

Cross-sectional analysis of 107 individuals from a prospective cohort study with urine eicosanoids (isoprostane [15-F(2t)-IsoP], prostaglandin-E metabolite [PGE-M], thromboxane metabolite [11dTxB(2)], prostacyclin metabolite [PGI-M]) determined by gas or liquid chromatography-mass spectrometry.

RESULTS

15-F(2t)-IsoP was higher (P=0.003), 11dTxB(2) tended to be higher (P=0.07) and PGE-M was lower (P=0.003) in females than in males. The overall median Framingham score was 4 (IQR 1-7). In multivariable analyses adjusting for age, CD4(+) T-cells, smoking status, non-steroidal anti-inflammatory drug use, aspirin use and body mass index (BMI), associations included: higher 15-F(2t)-IsoP with female sex (P=0.004) and current smoking (P=0.04), lower PGE-M with female sex (P=0.005) and higher BMI (P=0.03), higher 11dTxB(2) with increasing age (P=0.02) and current smoking (P=0.04), lower 11dTxB(2) with higher BMI (P=0.02), and higher PGI-M with current smoking (P=0.04).

CONCLUSIONS

In this pilot study of predominantly virologically suppressed HIV-infected individuals on ART, there were sex-specific differences in urinary eicosanoids, with females having more risk-associated parameters despite a low Framingham score. Eicosanoids might be useful CVD biomarkers in ART-treated, HIV-infected patients. Future studies should examine eicosanoids while assessing effects of specific ART regimens and targeted interventions on CVD outcomes.

The effect of renal administration of a selective cyclooxygenase-2 inhibitor or stable prostaglandin I2 analog on the progression of sclerotic glomerulonephritis in rats

BACKGROUND AND METHODS

There is increasing evidence that a change in glomerular hemodynamics may promote the development of glomerulosclerosis. In this study, we focused on the pharmacological effects of 2 contrasting agents, etodolac, a preferential cyclooxygenase-2 inhibitor, and beraprost sodium (BPS), a prostaglandin I(2) analog, delivered renally, on the disease course of progressive anti-Thy-1 (ATS) glomerulonephritis.

RESULTS

Intravital microscopic analysis showed that the diameters of glomerular capillaries and glomerular blood flow in unilaterally nephrectomized (Nx) rats treated locally with BPS were significantly increased, as compared to those of Nx rats treated locally with normal saline (NS) or etodolac. We then examined the effects of BPS and etodolac on the course of progressive glomerulosclerosis. Mesangial cell proliferation, adhesion of glomerular capillary tufts and crescent formation in the BPS-treated group appeared to be more severe compared to the ATS + NS and the ATS + etodolac groups. Scoring of mesangial proliferation and glomerulosclerosis revealed that local BPS treatment significantly worsened glomerular pathology. At day 28, there were significant differences in blood flow between the ATS + etodolac group and both the ATS + NS and ATS + BPS groups, indicating that local treatment with etodolac enhanced the recovery of glomerular circulation.

CONCLUSION

This study provides hemodynamic-based evidence showing that disturbance of intraglomerular microcirculation is a critical marker for progressive glomerulonephritis.

Triacylglycerol-rich lipoproteins derived from healthy donors fed different olive oils modulate cytokine secretion and cyclooxygenase-2 expression in macrophages: the potential role of oleanolic acid

PURPOSE

Current evidence suggests that consumption of virgin olive oil (VOO) helps to protect against the development of atherosclerosis and that minor components such as oleanolic acid contribute to this effect. In this study, the effects of triacylglycerol-rich lipoproteins (TRLs) derived from olive oil on inflammatory processes in macrophages and how they are modulated by oleanolic acid was investigated.

METHODS

TRLs isolated from healthy volunteers 2 and 4 h after a test meal containing VOO, pomace olive oil (POO) (the second pressing of olive oil, enriched in minor components) or POO enriched with oleanolic acid (OPOO) were incubated with macrophages derived from the human monocyte cell line, THP-1.

RESULTS

All types of TRLs caused a decrease of about 50% in the secretion of monocyte chemoattractant protein-1 (MCP-1) by the cells. Interleukin (IL)-6 secretion was also significantly decreased by 2 and 4 h VOO TRLs and by 4 h OPOO TRLs. In contrast, increased IL-1β secretion was observed with all 2 h TRL types, and increased tumour necrosis factor-α (TNF-α) production with 2 h VOO and POO, but not OPOO, TRLs. TRLs isolated after 4 h, however, had no significant effects on TNF-α secretion and increased IL-1β secretion only when they were derived from VOO. Cyclooxygenase-2 (COX-2) mRNA expression was strongly down-regulated by all types of TRLs, but protein expression was significantly depressed only by 4 h OPOO TRLs.

CONCLUSION

These findings demonstrate that TRLs derived from olive oil influence inflammatory processes in macrophages and suggest that oleanolic acid may have beneficial effects.

Grape seed extract ameliorates tumor necrosis factor-α-induced inflammatory status of human umbilical vein endothelial cells

BACKGROUND

Inflammation has played a key role in the causation of atherosclerosis. However, the effects of grape seed extract (GSE) on the pro-inflammatory intracellular signaling, enzyme activity, and inflammatory mediators of endothelial cells have not been sufficiently studied, and less information exists on the comparison between GSE and vitamin C, a well-known antioxidant compound, on their anti-inflammatory properties.

PURPOSE

We investigated the effects of GSE and vitamin C on the cell viability, oxidative stress, monocyte adhesion, the expression of nuclear factor-κB inhibitor (IκB), intercellular adhesion molecule-1 (ICAM-1) and cyclooxygenase-2 (COX-2), and the production of prostaglandin E(2) (PG E(2)) in TNF-α-treated human umbilical vein endothelial cells (HUVECs).

METHODS

Cell viability was measured by MTT assay. The adhesion of THP-1 to HUVECs was evaluated by cell adhesion assay. The oxidized nucleoside 8-hydroxydeoxyguanosine (8-OHdG) (an indicator of oxidative damage to DNA), ICAM-1, and PG E(2) were measured by ELISA. IκB and COX-2 expression were evaluated by western blot analysis.

RESULTS

TNF-α (10, 20, and 50 ng/mL), GSE (50 and 200 μg/mL), or vitamin C (100 μM) did not affect cell viability. GSE (50-100 μg/mL) attenuated TNF-α (20 ng/mL)-induced 8-OHdG production, THP-1 adhesion, the expression of IκB degradation, ICAM-1 and COX-2, and the production of PGE(2) in a dose-dependent manner. Vitamin C (100 μM) also showed significant antioxidative and anti-inflammatory effects.

CONCLUSIONS

GSE effectively ameliorates TNF-α-induced inflammatory status of HUVECs. The findings of the present study suggest that consumption of GSE may be beneficial to inflammatory atherosclerosis.

The effect of the expression of angiotensin II on extracellular matrix metalloproteinase inducer (EMMPRIN) in macrophages is mediated via the AT1/COX-2/PGE2 pathway

AIM

To explore the expression of extracellular matrix metalloproteinase inducer (EMMPRIN) in THP-1 macrophages induced by angiotensin II (Ang II) and the mechanism of EMMPRIN expression.

METHODS

THP-1 cells were cultured and induced into macrophages, then stimulated with 10(-6) mol/L Ang II. Levels of EMMPRIN gene and its protein were measured by real-time polymerase chain reaction and western blotting. Prostaglandin E(2) (PGE(2)) expression was assayed by enzyme-linked immunosorbent assay. Antagonists of the angiotensin type-1 receptor (AT(1)R) and angiotensin type-2 receptor (AT(2)R) were used to inhibit the effect of Ang II, and PGE(2) added to detail the mechanism of Ang II-induced EMMPRIN expression.

RESULTS

Ang II clearly induced the expression of EMMPRIN mRNA and protein in macrophages; this expression peaked at 12 h and declined after 24 h. The tendency of enhancement of the levels of cyclooxygenase-2 (COX-2) and PGE(2) was coincident with EMMPRIN expression. AT(1)-receptor antagonists and COX-2 inhibitors inhibited the effect of Ang II, but AT(2)-receptor antagonists did not.

CONCLUSION

Ang II can up-regulate EMMPRIN expression in THP-1 macrophages via the AT(1)/COX-2/PGE(2) signal transduction pathway, and the effect can be inhibited by losartan and NS-398.

Inducible nitric oxide synthase gene deletion exaggerates MAPK-mediated cyclooxygenase-2 induction by inflammatory stimuli

Cyclooxygenase (COX)-2 and inducible nitric oxide (NO) synthase (iNOS) are responsive to a wide array of inflammatory stimuli, have been localized to vascular smooth muscle cells (SMCs), and are intimately linked to the progression of vascular disease, including atherosclerotic lesion formation. We and others have shown that the production and subsequent impact of COX products appear to be correlative with the status of NO synthesis. This study examined the impact of inflammation-driven NO production on COX-2 expression in SMCs. Concurrent stimulation of quiescent rat aortic SMCs with lipopolysaccharide (LPS) and interferon (IFN)-gamma increased COX-2, iNOS, and nitrite production. Pharmacological inhibition of NO synthase (N(G)-monomethyl-l-arginine) concentration- and time-dependently magnified LPS + IFN-gamma-mediated COX-2 mRNA and protein induction in a cGMP-independent manner. COX-2 induction was associated with activation of the ERK, p38, and JNK mitogen-activated protein kinase (MAPK) pathways. Interestingly, NO synthase inhibition enhanced ERK, p38, and to a lesser extent JNK phosphorylation but suppressed MAPK phosphatase (MKP)-1 induction in response to LPS + IFN-gamma. Similarly, the exposure of SMCs from iNOS(-/-) mice to LPS + IFN-gamma produced an enhancement of COX-2 induction, p38, and JNK phosphorylation and an attenuated upregulation of MKP-1 versus their wild-type counterparts. Taken together, our data indicate that NO, in part derived from iNOS, negatively regulates the immediate early induction of COX-2 in response to inflammatory stimuli.

Biochemical, biological and histological evaluation of some culinary and medicinal herbs grown under greenhouse and field conditions

BACKGROUND

Increasing evidence supports the potential health benefits of herbal extracts displaying antioxidant, anti-inflammatory and antitumour activities. Environment can have a pronounced effect on phenolic content and antioxidant capacity. The objectives of this study were to evaluate the total phenolic contents and antioxidant capacities of five different herbs grown under greenhouse and field conditions and to assess their potential anti-inflammatory effects.

RESULTS

High total polyphenolic (TPP) content (measured by the Folin-Ciocalteu reagent method) and high Trolox equivalent antioxidant capacity (TEAC) were observed in all herbs evaluated. Leaves from thyme, sage, spearmint and peppermint grown in the greenhouse showed significantly higher TPP content and TEAC than those grown under field conditions, with a threefold difference being observed in peppermint. Rosemary, spearmint and peppermint extracts showed stronger inhibition of cyclooxygenase COX-2 than of COX-1.

CONCLUSION

The results show that producing herbs under greenhouse conditions can improve their biological activities by increasing TPP contents and antioxidant capacities. The selective inhibition of COX-2 activity by rosemary, spearmint and peppermint suggests that they may be useful as anti-inflammatory agents with fewer side effects than regular non-steroidal drugs.

mRNA levels of enzymes and receptors implicated in arachidonic acid metabolism in gliomas

BACKGROUND

Gliomas are tumors of the central nervous system derived from glial cells. They show cellular heterogeneity and lack specific diagnostic markers. Although a possible role for the eicosanoid cascade has been suggested in glioma tumorigenesis, the relationship between enzymes and receptors implicated in arachidonic acid metabolism, with histological tumor type has not yet been determined.

DESIGN AND METHODS

Quantitative real-time reverse transcription-polymerase chain reaction was performed to measure and compare transcript levels of enzymes and receptors implicated in both lipoxygenase and cyclooxygenase pathways between oligodendrogliomas, astrocytomas, glioblastomas and mixed oligoastrocytomas.

RESULTS

Arachidonic acid metabolism-related enzymes and receptor transcripts (i) were underexpressed in classical oligodendrogliomas compared to astrocytomas and/or glioblastomas, (ii) differed between astrocytomas and glioblastomas and (iii) had an intermediate expression in mixed oligoastrocytomas.

CONCLUSIONS

mRNA levels of enzymes and receptors implicated both in lipoxygenase and cyclooxygenase pathways differed significantly in gliomas according to the histological type.

Thromboxane and the thromboxane receptor in cardiovascular disease

Thromboxane A(2) (TXA(2)), the primary product of COX-1-dependent metabolism of arachidonic acid, mediates its biological actions through the TXA(2) receptor, termed the TP. Irreversible inhibition of platelet COX-1-derived TXA(2) with low-dose aspirin affords protection against primary and secondary vascular thrombotic events, underscoring the central role of TXA(2) as a platelet agonist in cardiovascular disease. The limitations associated with aspirin use include significant gastrointestinal toxicity, bleeding complications, potential interindividual response variability and poor efficacy in some disease states. This, together with the broad role of TXA(2) in cardiovascular disease beyond the platelet, has refocused interest towards additional TXA(2)-associated drug targets, in particular TXA(2) synthase and the TP. The superiority of these agents over low-dose aspirin, in terms of clinical efficacy, tolerability and commercial viability, remain open questions that are the focus of ongoing research.

Absence of myeloid COX-2 attenuates acute inflammation but does not influence development of atherosclerosis in apolipoprotein E null mice

OBJECTIVE

The role of myeloid cell cyclooxygenase-2 (COX-2) in the progression of atherosclerosis has not been clearly defined.

METHODS AND RESULTS

We investigated the role of COX-2 expressed in the myeloid lineage in the development of atherosclerosis using a myeloid-specific COX-2(-/-) (COX-2(-M/-M)) mouse on a hyperlipidemic apolipoprotein (apo) E(-/-) background (COX-2(-M/-M)/apoE(-/-)). Myeloid COX-2 depletion resulted in significant attenuation of acute inflammation corresponding with decreased PGE(2) levels in an air pouch model. COX-2 depletion in myeloid cells did not influence development of atherosclerosis in COX-2(-M/-M)/apoE(-/-) when compared to apoE(-/-) littermates fed either chow or western diets. The unanticipated lack of contribution of myeloid COX-2 to the development atherosclerosis is not attributable to altered maintenance, differentiation, or mobilization of myeloid and lymphoid populations. Moreover, myeloid COX-2 depletion resulted in unaltered serum prostanoid levels and cellular composition of atherosclerotic lesions of COX-2(-M/-M)/apoE(-/-) mice.

CONCLUSIONS

Our results suggest that COX-2 expression in myeloid cells, including macrophages, does not influence the development of atherosclerosis in mice.

Activity of the cyclooxygenase 2-prostaglandin-E prostanoid receptor pathway in mice exposed to house dust mite aeroallergens, and impact of exogenous prostaglandin E2

Background

Prostaglandin E₂ (PGE₂), experimentally administered to asthma patients or assayed in murine models, improves allergen-driven airway inflammation. The mechanisms are unknown, but fluctuations of the endogenous cyclooxygenase (COX)-2/prostaglandin/E prostanoid (EP) receptor pathway activity likely contribute to the clinical outcome. We analyzed the activity of the pathway in mice sensitized to aeroallergens, and then studied its modulation under exogenous PGE₂.

Methods

Mice were exposed to house dust mite (HDM) aeroallergens, a model that enable us to mimic the development of allergic asthma in humans, and were then treated with either subcutaneous PGE₂ or the selective EP1/3 receptor agonist sulprostone. Simultaneously with airway responsiveness and inflammation, lung COX-2 and EP receptor mRNA expression were assessed. Levels of PGE₂, PGI₂, PGD₂ were also determined in bronchoalveolar lavage fluid.

Results

HDM-induced airway hyperreactivity and inflammation were accompanied by increased COX-2 mRNA production. In parallel, airway PGE₂ and PGI₂, but not PGD₂, were upregulated, and the EP2 receptor showed overexpression. Subcutaneous PGE₂ attenuated aeroallergen-driven airway eosinophilic inflammation and reduced endogenous PGE₂ and PGI₂ production. Sulprostone had neither an effect on airway responsiveness or inflammation nor diminished allergen-induced COX-2 and PGE₂ overexpression. Finally, lung EP2 receptor levels remained high in mice treated with PGE₂, but not in those treated with sulprostone.

Conclusion

The lung COX-2/PGE₂/EP2 receptor pathway is upregulated in HDM-exposed mice, possibly as an effort to attenuate allergen-induced airway inflammation. Exogenous PGE₂ downregulates its endogenous counterpart but maintains EP2 overexpression, a phenomenon that might be required for administered PGE₂ to exert its protective effect.

Laminar shear stress regulates endothelial kinin B1 receptor expression and function: potential implication in atherogenesis

OBJECTIVE

The proinflammatory phenotype induced by low laminar shear stress (LSS) is implicated in atherogenesis. The kinin B1 receptor (B1R), known to be induced by inflammatory stimuli, exerts many proinflammatory effects including vasodilatation and leukocyte recruitment. We investigated whether low LSS is a stimulus for endothelial B1R expression and function.

METHODS AND RESULTS

Human and mouse atherosclerotic plaques expressed high level of B1R mRNA and protein. In addition, B1R expression was upregulated in the aortic arch (low LSS region) of ApoE(-/-) mice fed a high-fat diet compared to vascular regions of high LSS and animals fed normal chow. Of interest, a greater expression of B1R was noticed in endothelial cells from regions of low LSS in aortic arch of ApoE(-/-) mice. B1R was also upregulated in human umbilical vein endothelial cells (HUVECs) exposed to low LSS (0 to 2 dyn/cm(2)) compared to physiological LSS (6 to 10 dyn/cm(2)): an effect similarly evident in murine vascular tissue perfused ex vivo. Functionally, B1R activation increased prostaglandin and CXCL5 expression in cells exposed to low, but not physiological, LSS. IL-1beta and ox-LDL induced B1R expression and function in HUVECs, a response substantially enhanced under low LSS conditions and inhibited by blockade of NFkappaB activation.

CONCLUSIONS

Herein, we show that LSS is a major determinant of functional B1R expression in endothelium. Furthermore, whereas physiological high LSS is a powerful repressor of this inflammatory receptor, low LSS occurring [corrected] at sites of atheroma is associated with substantial upregulation, identifying this receptor as a potential therapeutic target.

Atorvastatin Prevents Endothelial Dysfunction in Mesenteric Arteries From Spontaneously Hypertensive Rats

We investigated the effect of atorvastatin on cyclooxygenase (COX) contribution to endothelial dysfunction in spontaneously hypertensive rat (SHR) mesenteric resistance arteries. Atorvastatin (10 mg/kg per day, oral gavage) or its vehicle was administered for 2 weeks to male SHR or Wistar-Kyoto rats. Endothelial function of mesenteric arteries was assessed by pressurized myograph. In Wistar-Kyoto rats, relaxation to acetylcholine was inhibited by N G -nitro- l -arginine methyl ester and unaffected by SC-560 (COX-1 inhibitor), DuP-697 (COX-2 inhibitor), or ascorbic acid. In SHRs, the response to acetylcholine was attenuated, less sensitive to N G -nitro- l -arginine methyl ester, unaffected by SC-560, and enhanced by DuP-697 or SQ-29548 (thromboxane-prostanoid receptor antagonist) to a similar extent. Endothelium-dependent relaxation was normalized by ascorbic acid or apocynin (NADPH oxidase inhibitor), which also restored the inhibition by N G -nitro- l -arginine methyl ester. In atorvastatin-treated SHRs, relaxation to acetylcholine was normalized, fully sensitive to N G -nitro- l -arginine methyl ester, and not affected by SC-560, DuP-697, SQ 29548, or antioxidants. Dihydroethidium assay showed an increased intravascular superoxide generation in SHRs, which was abrogated by atorvastatin. RT-PCR revealed a COX-2 induction in SHR arteries, which was downregulated by atorvastatin. The release of prostacyclin and 8-isoprostane was higher from SHR than Wistar-Kyoto mesenteric vessels. COX-2 inhibition and apocynin decreased 8-isoprostane without affecting prostacyclin levels. Atorvastatin increased phosphorylated extracellular signal-regulated kinase 1/2, pAkt, peNOS 1177 , and inducible NO synthase levels in SHR mesenteric vessels and decreased 8-isoprostane release. In conclusion, COX-2-derived 8-isoprostane contributes to endothelial dysfunction in SHR mesenteric arteries. Atorvastatin restores NO availability by increasing phosphorylated extracellular signal-regulated kinase 1/2, pAkt, peNOS 1177 , and inducible NO synthase levels and by abrogating vascular NADPH oxidase-driven superoxide production, which also results in a downregulation of COX-2-dependent 8-isoprostane generation.

Translational mini-review series on immunology of vascular disease: inflammation, infections and Toll-like receptors in cardiovascular disease

Cardiovascular disease, in which atherosclerosis is the major underlying cause, is currently the largest cause of death in the world. Atherosclerosis is an inflammatory disease characterized by the formation of arterial lesions over a period of several decades at sites of endothelial cell dysfunction. These lesions are composed of endothelial cells, vascular smooth muscle cells, monocytes/macrophages and T lymphocytes (CD4(+)). As the lesions progress some can become unstable and prone to disruption, resulting in thrombus formation and possibly a myocardial infarction or stroke depending upon the location. Although the exact triggers for plaque disruption remain unknown, much recent evidence has shown a link between the incidence of myocardial infarction and stroke and a recent respiratory tract infection. Interestingly, many reports have also shown a link between a family of pattern recognition receptors, the Toll-like receptors, and the progression of atherosclerosis, suggesting that infections may play a role in both the progression of atherosclerosis and in inducing the more severe complications associated with the disease.

The monocyte/macrophage as a therapeutic target in atherosclerosis

It is now clear that the monocyte/macrophage has a crucial role in the development of atherosclerosis. This cell appears to be involved in all stages of atherosclerotic plaque development and is increasingly seen as a candidate for therapeutic intervention and as a potential biomarker of disease progression and response to therapy. The main mechanisms related to the activity of the monocyte/macrophage that have been targeted for therapy are those that facilitate recruitment, cholesterol metabolism, inflammatory activity and oxidative stress. There is also increasing evidence that there is heterogeneity within the monocyte/macrophage population, which may have important implications for plaque development and regression. A better insight into how specific phenotypes may influence plaque progression should facilitate the development of novel methods of imaging and more refined treatments.

Monoacylglycerol lipase regulates 2-arachidonoylglycerol action and arachidonic acid levels

The structure-activity relationships of organophosphorus (OP) and organosulfur compounds were examined in vitro and in vivo as inhibitors of mouse brain monoacylglycerol lipase (MAGL) hydrolysis of 2-arachidonoylglycerol (2-AG) and agonist binding at the CB1 receptor. Several compounds showed exceptional potency toward MAGL activity with IC(50) values of 0.1-10 nM in vitro and high inhibition at 10mg/kg intraperitoneally in mice. We find for the first time that MAGL activity is a major in vivo determinant of 2-AG and arachidonic acid levels not only in brain but also in spleen, lung, and liver. Apparent direct OP inhibition of CB1 agonist binding may be due instead to metabolic stabilization of 2-AG in brain membranes as the actual inhibitor.