HMG-CoA reductase inhibitors reduce vascular monocyte chemotactic protein-1 expression in early lesions from hypercholesterolemic swine independently of their effect on plasma cholesterol levels.

Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase are widely used in the treatment of dyslipemias and have shown beneficial effects in primary and secondary prevention of cardiovascular diseases. There is new information that seems to suggest that the beneficial effects observed may not be solely attributable to plasma cholesterol reduction. Our objective has been to evaluate the effect of two statins at similar dose, although unequivalent plasma lipid lowering potential, on vessel wall expression of two proteins involved in atherosclerotic lesion progression. We have studied the effects of treatment on vessel wall expression of monocyte chemotactic protein-1 (MCP-1) and the inducible form of nitric oxide synthase (NOS II). Atherosclerosis was induced in pigs by feeding a high cholesterol and saturated fatty acid diet for 50 days. Mild atherosclerotic lesions were found at this early stage of induction. Animals were simultaneously treated with atorvastatin (3 mg/kg/day), pravastatin (3 mg/kg/day) or placebo. Non-HDL-cholesterol levels induced by diet were reduced in the atorvastatin-treated group (63+/-8%, P=0.03) and not as much in the pravastatin treated group (44+/-3, P=0.08). The average MCP-1 expression in carotid, femoral and thoracic aorta was significantly reduced with both statins by 37% (P<0.05), while NOS II expression was unaffected. Therefore, vascular MCP-1 expression was downregulated by statins regardless of their lipid lowering potential and lipo/hydrophilic characteristics. Early downregulation of MCP-1 could attenuate the inflammation within the vascular wall and prevent the development of atherosclerotic lesions.

Effect of gemfibrozil on peripheral atherosclerosis and platelet activation in a pig model of hyperlipidemia.

BACKGROUND: Gemfibrozil has been shown to have beneficial effects in the primary and secondary prevention of atherosclerosis. However, a platelet pro-activating effect induced by the drug has been reported. MATERIAL AND METHODS: We analysed the effect of hyperlipidemia and its treatment with gemfibrozil on platelet-fibrinogen binding and the development of early fibrinogen-rich vascular lesions in a porcine model of atherosclerosis. Polyclonal antibodies were raised against purified pig fibrinogen and intact platelets. Two groups of animals were fed a cholesterol/saturated fat-enriched diet for 50 days; one group was treated with gemfibrozil and the other with placebo. RESULTS: The hyperlipidemic diet induced a significant increase in total cholesterol; this was prevented by gemfibrozil (P<0.05). The increase in platelet-fibrinogen binding induced by hypercholesterolemia was mildly reduced in the gemfibrozil treated animals. Histological analysis of aortic vascular wall (abdominal aorta at the iliac bifurcation) from hyperlipidemic animals showed early lesions with fibrinogen infiltration; the lesions were reduced in the fibrate-treated animals. CONCLUSIONS: Gemfibrozil delayed the development of peripheral atherosclerotic plaque, normalised the impaired lipid profile induced by the hyperlipidemic diet and did not show a functionally detectable platelet pro-activating effect able to increase platelet-fibrinogen binding.

Nitric oxide synthase II (NOS II) gene expression correlates with atherosclerotic intimal thickening. Preventive effects of HMG-CoA reductase inhibitors.

HMG-CoA reductase inhibitors have been shown to be effective in primary and secondary prevention of coronary heart disease. Their mechanism of action is attributed to their cholesterol lowering activity but recent results seem to indicate additional effects related to the modulation of other processes that regulate the presentation of vascular diseases. Our objective has been to study the effects of atorvastatin and simvastatin, two HMG-CoA reductase inhibitors, on lesion composition and expression of genes involved in lesion development in a diet-induced atherosclerotic rabbit model. Both HMG-CoA reductase inhibitors were administered at identical doses of 2.5 mg/kg per day with the hyperlipemic diet for 10 weeks. Both statins significantly prevented the diet-induced increase in cholesterol levels. Relative lesion composition in fibrinogen, macrophages and smooth muscle cells was unaltered by the treatment although lesion size was reduced; therefore, both HMG-CoA reductase inhibitors reduced total amounts of fibrinogen, macrophages and smooth muscle cells (simvastatin, P < 0.05). NOS II gene expression was positively and significantly correlated with lesion size and inversely correlated with HDL plasma levels. NOS II expression was markedly downregulated in simvastatin treated animals while MCP-1 was unaltered. Therefore, HMG-CoA reductase inhibition seems to interfere with atherosclerotic lesion development by reducing intimal thickening development and the expression of the cytotoxic NOS II.

Platelet deposition on eroded vessel walls at a stenotic shear rate is inhibited by lipid-lowering treatment with atorvastatin.

Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase are widely used in the treatment of dyslipemias and have shown beneficial effects in the primary and secondary prevention of cardiovascular diseases. However, regression studies with lipid-lowering drugs have not shown significant lesion reduction associated with the improvement in clinical events. Therefore, our objective has been to study whether treatment with a lipid-lowering drug of this family, atorvastatin, could reduce platelet deposition on the damaged vessel wall at different shear stress conditions, simultaneously with retardation of the development of atherosclerotic lesions. Using cholesterol-fed swine as the model, we found that atorvastatin significantly diminished platelet deposition on the mildly damaged vessel wall at high shear rates (50%, P<0.01), but it did not have any effect in preventing platelet deposition triggered by a severely injured vessel wall. Development of coronary lesions was also reduced by treatment. These findings suggest that atorvastatin may prevent platelet attachment to eroded vessels and hence, contribute to reducing the thrombotic risk associated with the erosions of the luminal surface and the platelet-dependent progression of atherosclerotic plaques.

Effects of statins in thrombosis and aortic lesion development in a dyslipemic rabbit model.

HMG-CoA reductase inhibitors (statins) are effective in primary and secondary prevention of coronary heart disease. The mechanism of action is mainly attributed to their plasma cholesterol lowering activity, although additional effects have been suggested. Our objective was to study whether atorvastatin and simvastatin exhibited an inhibitory effect on platelet deposition onto a triggering damaged vessel wall in addition to an antiatherosclerotic effect in the dyslipemic rabbit model. Statins were administered at identical doses of 2.5 mg/kg/day with a hyperlipidemic diet during 10 weeks. Both drugs similarly lowered total cholesterol and, moderately, triglycerides. Mural platelet deposition on damaged vessel wall placed in an ex-vivo flow perfusion system was reduced in atorvastatin treated animals (39.7+/-6.2 X 10(6) PLT/cm2) vs. controls (94.8+/-15.9 x 10(6) PLT/cm2, p <0.02). Simvastatin reduced aortic fatty streak surface coverage (31,7+/-5.3%) vs. controls (47.9+/-4.1%, p <0.005) and intimal thickening in thoracic aorta (0.15+/-0.05 intima to total area ratio in simvastatin treated animals vs. 0.36+/-0.03 in control animals, p <0.05). Atherosclerotic fatty streak coverage correlated positively with total cholesterol, tryglicerides and LDL-cholesterol levels in all groups. HMG-CoA reductase inhibitors similarly lowered plasma lipids but exhibited significantly different effects in the modulation of atherosclerotic development and platelet response at the tested dose. Therefore, the effect of statins on the progression and manifestation of cardiovascular disease might be also mediated by regulating platelet response to vessel injury.

Effects of reducing LDL and increasing HDL with gemfibrozil in experimental coronary lesion development and thrombotic risk.

The use of lipid-lowering drugs has been shown to have beneficial effects in primary and secondary prevention of cardiovascular disease. Gemfibrozil has shown beneficial effects as a lipid lowering agent; however, some proactivating effects on platelet function in vitro have been described. We have studied in a porcine model of atherosclerosis if gemfibrozil could prevent the early vascular effects of a cholesterol-rich diet without inducing platelet activation and, hence, mural thrombosis. Pigs were fed for 50 days with a diet rich in saturated fat and cholesterol (cho). The longitudinal follow-up study showed that in control animals LDL-cho increased significantly up to 181.9 +/- 34.2 mg/dl or 79% of total-cho, while HDL-cho was reduced to 19% of total-cho. Gemfibrozil, at average therapeutic plasma levels (peak levels of 28 micrograms/ml) [corrected], induced a significant reduction in the relative amount of LDL (P < 0.05) and increased HDL (P < 0.05). The increase in fibrinogen plasma levels observed in the control group due to the dietary intervention (+25%) was prevented in the treated animals (-5%). In treated animals, vascular lesions were significantly less severe, platelet deposition upon exposure of damaged vessel wall was unchanged and the fibrin layer deposited on the damaged vessel wall was significantly reduced over control animal values. This short term pharmacologic lipid lowering intervention has been able to slow down lesion development and to reduce fibrin formation onto lesioned disrupted vascular substrates without increasing platelet mural thrombosis.

Cell biology of restenosis post-angioplasty.

PTCA is a well established intervention to reduce the severity of atherosclerotic coronary stenosis. In spite of a primary success rate of 90 - 95%, late restenosis occurs in 30 - 50% of patients within 3/6 months of the procedure. Angioplasty in swine induces similar events to those found in humans, thus providing a model for studying strategies for intervention. Blood interaction to the damaged vessel wall occurs with reperfusion after the intervention. Therefore, the in vivo characterization of the interaction of cellular elements (platelets and white cells) and blood proteins with the exposed vascular cells in the vessel wall post-angioplasty may be necessary to identify early triggers of restenosis. Angioplasty was performed simultaneously in the coronary and carotid arteries of swine by fluoroscopy assisted standard techniques. Angiography was performed acutely post-dilatation and residual lumen diameter evaluated. Dilated vessels from 30 min to 6 h postintervention were processed to prepare RNA and preserved to perform immunohistochemistry. Dilatation injury induces maximal expression of c-fos 30 min and c-myc from 2 to 4 h postdilatation. Platelet deposition is initiated immediately post-dilatation as well as infiltration of fluid phase proteins on the damaged areas.

The effect of immunosuppression by total-body irradiation on the pharmacodynamics of centrally active drugs in rats.

The aim of this investigation was to assess whether immunosuppression induced by total-body irradiation (TBI) affects the pharmacodynamics of centrally acting drugs. Female Sabra rats were exposed to a single dose of gamma irradiation (5.3 Gy). Four days later, when both the cellular and the humoral immune responses were impaired, they received an i.v. infusion of either phenobarbital (0.8 mg/min), ethanol (16.3 mg/min), pentylenetetrazol (PTZ; 0.618 mg/min), or theophylline (as aminophylline; 2 mg/min). The infusion was stopped at the onset of the pharmacologic end point--loss of righting reflex for the depressant agents or maximal seizures for the stimulant drugs--and the concentrations of the neuroactive drugs at that point were determined. In the ethanol experiment, blood samples were also taken upon awakening. The radiation-induced immunosuppression significantly decreased the CNS sensitivity to the depressant action of both phenobarbital and ethanol as indicated by the higher CSF phenobarbital concentrations required to induce sleep in the irradiated rats versus controls (156 +/- 4 vs 133 +/- 5 mg/L, respectively; P < 0.05), and the higher serum ethanol concentrations at the onset and offset of sleep in the immunosuppressed group versus control values (4.6 +/- 0.2 and 1.68 +/- 0.01 vs 3.79 +/- 0.17 and 1.32 +/- 0.9 mg/mL, respectively; P < 0.04). Exposure to TBI did not alter the pharmacodynamics of the two convulsant drugs (theophylline and PTZ).

Pharmacodynamics of phenobarbital anesthesia and pentylenetetrazol-induced maximal seizures in a rat model of neoplastic spinal cord compression.

The purpose of this investigation was to determine whether paraplegia induced by neoplastic cord compression affects the pharmacodynamics of phenobarbital general anesthesia or of pentylenetetrazol (PTZ)-induced convulsions. Paraplegic rats harboring a thoracolumbar epidural tumor, or an identical hindlimb tumor mass, received an i.v. infusion of phenobarbital until the onset of anesthesia. At that point, the phenobarbital concentrations in the CSF and serum were measured. Similarly, PTZ was infused until the onset of maximal seizures. It was found that changes related to systemic tumor growth and newly developed paraplegia due to neoplastic spinal cord compression did not attenuate the pharmacodynamics of phenobarbital. However, sustained paraplegia of 4 days' duration reduced CNS sensitivity to the hypnotic action of the barbiturate as evidenced by the higher cerebrospinal fluid phenobarbital concentration required to induce anesthesia (170 +/- 31 vs 125 +/- 20 mg/L; P < 0.05). On the other hand, sustained paraplegia did not affect brain threshold concentration for PTZ-induced seizures.

High-dose methotrexate does not affect the pharmacodynamics of phenobarbital hypnotic action but decreases the central nervous system (CNS) sensitivity to pentylenetetrazol-induced maximal seizures in rats.

Chemotherapy with high-dose methotrexate (HD-MTX) is often associated with acute neurotoxicity. We determined whether the altered neuronal function after HD-MTX [such as the reduced regional cerebral metabolic glucose rate (rCMRGlc) and slow electroencephalographic pattern] affects the sensitivity of the CNS to centrally acting drugs: the depressant phenobarbital, which reduces rCMRGlc, and the analeptic agent pentylenetetrazol (PTZ), which elevates rCMRGlc. Adult male Sabra rats received an i.v. infusion of MTX, 0.51 mg/min, to induce neurotoxicity or saline solution for 24 hr. Subsequently, MTX-treated and control groups were infused in one experiment with phenobarbital until loss of the righting reflex and in the second experiment with PTZ until the onset of maximal seizures. HD-MTX did not affect the infused hypnotic dose or serum, brain, and cerebrospinal fluid concentrations of phenobarbital at the onset of anesthesia. The convulsive dose and PTZ concentrations in the serum and brain at the onset of maximal seizures were significantly higher in the HD-MTX-treated animals. These outcomes indicate that HD-MTX and the reduced rCMRGlc that follows this treatment do not contribute to the hypnotic action of phenobarbital. On the other hand, treatment with HD-MTX exhibited anticonvulsant properties as evidenced by the reduced CNS sensitivity to PTZ-induced seizures.