Nicotinic acid and DP1 blockade: studies in mouse models of atherosclerosis.

The use of nicotinic acid to treat dyslipidemia is limited by induction of a "flushing" response, mediated in part by the interaction of prostaglandin D(2) (PGD(2)) with its G-protein coupled receptor, DP1 (Ptgdr). The impact of DP1 blockade (genetic or pharmacologic) was assessed in experimental murine models of atherosclerosis. In Ptgdr(-/-)ApoE(-/-) mice versus ApoE(-/-) mice, both fed a high-fat diet, aortic cholesterol content was modestly higher (1.3- to 1.5-fold, P < 0.05) in Ptgdr(-/-)ApoE(-/-) mice at 16 and 24 weeks of age, but not at 32 weeks. In multiple ApoE(-/-) mouse studies, a DP1-specific antagonist, L-655, generally had a neutral to beneficial effect on aortic lipids in the presence or absence of nicotinic acid treatment. In a separate study, a modest increase in some atherosclerotic measures was observed with L-655 treatment in Ldlr(-/-) mice fed a high-fat diet for 8 weeks; however, this effect was not sustained for 16 or 24 weeks. In the same study, treatment with nicotinic acid alone generally decreased plasma and/or aortic lipids, and addition of L-655 did not negate those beneficial effects. These studies demonstrate that inhibition of DP1, with or without nicotinic acid treatment, does not lead to consistent or sustained effects on plaque burden in mouse atherosclerotic models.

11ß-HSD1 inhibition reduces atherosclerosis in mice by altering proinflammatory gene expression in the vasculature.

11ß-Hydroxysteroid dehydrogenase type 1 (11ß-HSD1) is implicated in the etiology of metabolic syndrome. We previously showed that pharmacological inhibition of 11ß-HSD1 ameliorated multiple facets of metabolic syndrome and attenuated atherosclerosis in ApoE-/- mice. However, the molecular mechanism underlying the atheroprotective effect was not clear. In this study, we tested whether and how 11ß-HSD1 inhibition affects vascular inflammation, a major culprit for atherosclerosis and its associated complications. ApoE-/- mice were treated with an 11ß-HSD1 inhibitor for various periods of time. Plasma lipids and aortic cholesterol accumulation were quantified. Several microarray studies were carried out to examine the effect of 11ß-HSD1 inhibition on gene expression in atherosclerotic tissues. Our data suggest 11ß-HSD1 inhibition can directly modulate atherosclerotic plaques and attenuate atherosclerosis independently of lipid lowering effects. We identified immune response genes as the category of mRNA most significantly suppressed by 11ß-HSD1 inhibition. This anti-inflammatory effect was further confirmed in plaque macrophages and smooth muscle cells procured by laser capture microdissection. These findings in the vascular wall were corroborated by reduction in circulating MCP1 levels after 11ß-HSD1 inhibition. Taken together, our data suggest 11ß-HSD1 inhibition regulates proinflammatory gene expression in atherosclerotic tissues of ApoE-/- mice, and this effect may contribute to the attenuation of atherosclerosis in these animals.

Cholesterol in human atherosclerotic plaque is a marker for underlying disease state and plaque vulnerability.

BACKGROUND: Cholesterol deposition in arterial wall drives atherosclerosis. The key goal of this study was to examine the relationship between plaque cholesterol content and patient characteristics that typically associate with disease state and lesion vulnerability. Quantitative assays for free cholesterol, cholesteryl ester, triglyceride, and protein markers in atherosclerotic plaque were established and applied to plaque samples from multiple patients and arterial beds (Carotid and peripheral arteries; 98 lesions in total). RESULTS: We observed a lower cholesterol level in restenotic than primary peripheral plaque. We observed a trend toward a higher level in symptomatic than asymptomatic carotid plaque. Peripheral plaque from a group of well-managed diabetic patients displayed a weak trend of more free cholesterol deposition than plaque from non-diabetic patients. Plaque triglyceride content exhibited less difference in the same comparisons. We also measured cholesterol in multiple segments within one carotid plaque sample, and found that cholesterol content positively correlated with markers of plaque vulnerability, and negatively correlated with stability markers. CONCLUSIONS: Our results offer important biological validation of cholesterol as a key lipid marker for plaque severity. Results also suggest cholesterol is a more sensitive plaque marker than routine histological staining for neutral lipids.

CCR5 blockade modulates inflammation and alloimmunity in primates.

Pharmacologic antagonism of CCR5, a chemokine receptor expressed on macrophages and activated T cells, is an effective antiviral therapy in patients with macrophage-tropic HIV infection, but its efficacy in modulating inflammation and immunity is only just beginning to be investigated. In this regard, the recruitment of CCR5-bearing cells into clinical allografts is a hallmark of acute rejection and may anticipate chronic rejection, whereas conventionally immunosuppressed renal transplant patients homozygous for a nonfunctional Delta32 CCR5 receptor rarely exhibit late graft loss. Therefore, we explored the effects of a potent, highly selective CCR5 antagonist, Merck's compound 167 (CMPD 167), in an established cynomolgus monkey cardiac allograft model. Although perioperative stress responses (fever, diminished activity) and the recruitment of CCR5-bearing leukocytes into the graft were markedly attenuated, anti-CCR5 monotherapy only marginally prolonged allograft survival. In contrast, relative to cyclosporine A monotherapy, CMPD 167 with cyclosporine A delayed alloantibody production, suppressed cardiac allograft vasculopathy, and tended to further prolong graft survival. CCR5 therefore represents an attractive therapeutic target for attenuating postsurgical stress responses and favorably modulating pathogenic alloimmunity in primates, including man.

Double-label expression studies of prostacyclin synthase, thromboxane synthase and COX isoforms in normal aortic endothelium.

We have performed double-label immunofluorescence microscopy studies to evaluate the extent of co-localization of prostacyclin synthase (PGIS) and thromboxane synthase (TXS) with cyclooxygenase (COX)-1 and COX-2 in normal aortic endothelium. In dogs, COX-2 expression was found to be restricted to small foci of endothelial cells while COX-1, PGIS and TXS were widely distributed throughout the endothelium. Quantification of the total cross-sectioned aortic endothelium revealed a 6- to 7-fold greater expression of COX-1 relative to COX-2 (55 vs. 8%) and greater co-distribution of PGIS with COX-1 compared to COX-2 (19 vs. 3%). These results are in contrast to the extensive co-localization of PGIS and COX-2 in bronchiolar epithelium. In rat and human aortas, immunofluorescence studies also showed significant COX-1 and PGIS co-localization in the endothelium. Only minor focal COX-2 expression was detected in rat endothelium, similar to the dog, while COX-2 was not detected in human specimens. Inhibition studies in rats showed that selective COX-1 inhibition caused a marked reduction of 6-keto-PGF(1alpha) and TXB(2) aortic tissue levels, while COX-2 inhibition had no significant effect, providing further evidence for a functionally larger contribution of COX-1 to the synthesis of prostacyclin and thromboxane in aortic tissue. The data suggest a major role for COX-1 in the production of both prostacyclin and thromboxane in normal aortic tissue. The extensive co-localization of PGIS and COX-2 in the lung also indicates significant tissue differences in the co-expression patterns of these two enzymes.

A small molecule very late antigen-4 antagonist can inhibit ovalbumin-induced lung inflammation.

A nonpeptidyl small molecule antagonist, compound A, to nonactivated very late antigen-4 (VLA4) was examined in lung inflammation induced by a single dose of ovalbumin challenge. Compound A presented a good pharmacokinetic property, when given intratracheally, and the blood cells from such pharmacokinetic study showed good receptor occupancy of the compound for approximately 8 hours. Compound A was then tested in an ovalbumin-induced airway inflammation model by intranasal or intravenous route of administration. There was a dose-dependent inhibition of eosinophilia in the bronchiolar lavage fluid, when compound A was given intranasally but not when it was given intravenously. For comparison, antibody to VLA4 and another compound, BIO1211, which reacts only with activated VLA4, were examined in this system. Immunohistochemical analyses of the lung tissue substantiated the findings in the bronchiolar lavage fluid. Specific staining of the major basic protein of eosinophils showed peribronchiolar infiltration of eosinophils. Some of these eosinophils were also positive for nitrotyrosine, suggesting activation of eosinophils in the lung interstitium. There was deposition of major basic protein and nitrotyrosine at the base of the perivascular endothelium, indicative of degranulation of eosinophils in the area. After intranasal treatment with compound A, eosinophils in the lungs and their activation products were substantially decreased, documenting its effectiveness in inhibiting lung inflammation.