Pravastatin and cyclosporine inhibit platelet-derived growth factor-stimulated vascular smooth muscle cell mitogenesis: an investigation of mechanisms

Pravastatin and Clopidogrel Combined Inhibit Intimal Hyperplasia in a Rat Carotid Endarterectomy Model

Intimal hyperplasia, resulting from a complex cascade of events involving platelets, leukocytes, and smooth muscle cells, may be inhibited by the HMG-CoA reductase inhibitor pravastatin, which demonstrates inhibition of platelet activity and leukocyte adhesion and may be associated with inhibition of vascular smooth muscle cell proliferation and migration. Clopidogrel, an adenosine diphosphate (ADP) receptor inhibitor, was shown to decrease platelet activity and aggregation but not intimal hyperplasia (IH). We postulated that the combination of both pravastatin and clopidogrel would significantly decrease IH in a rat carotid endarterectomy model. Male Sprague-Dawley rats (n = 18) divided by treatment regimen underwent treatment for 2 weeks both before and after an open carotid endarterectomy. Serum collected at the time of harvest was measured for C-reactive protein (CRP), platelet activity, and total serum cholesterol; carotid arteries were removed and processed for IH determination. Control rats (n = 7) received oral vehicle daily before and following endarterectomy. Pravastatin-alone rats (n = 6) received oral pravastatin (10 mg/kg/day) before and after endarterectomy. Pravastatin plus clopidogrel rats (n = 5) received oral pravastatin (10 mg/kg/day) plus a preendarterectomy bolus of oral clopidogrel (4.3 mg/kg) before endarterectomy and resumed pravastatin (10 mg/kg/day) plus oral clopidogrel (1 mg/kg/day) postendarterectomy. Pravastatin alone and pravastatin plus clopidogrel significantly decreased CRP compared to controls (120.2 ±11.2 and 134.1 ±9.9 vs 191.1 ±9.2 µg/mL, respectively p = 0.003 and p = 0.0024). CRP levels were not different between pravastatin alone and pravastatin plus clopidogrel (p = 0.35). Platelet activity was significantly decreased by pravastatin alone and pravastatin plus clopidogrel in comparison to controls (7.3 ±2.2 and 6.6 ±2.8 vs 19.2 ±6.1 platelet reactive units (PRU), respectively p = 0.048 and p = 0.045). No significant difference was noted in platelet activity between pravastatin alone and pravastatin plus clopidogrel (p = 0.89). Pravastatin plus clopidogrel significantly reduced serum cholesterol compared to control and pravastatin alone (84.0 ±6.6 vs 110.4 ±7.4 and 117.0 ±8.8 mg/dL, respectively p = 0.03 and p = 0.01). Pravastatin alone did not decrease serum cholesterol compared to controls (p = 0.54). IH was not reduced by pravastatin alone compared to controls (p = 0.61) but was significantly decreased by pravastatin plus clopidogrel in comparison to control and pravastatin alone (3.0 ±1.1 vs 46.3 ±13.7 and 37.4 ±14.6% luminal stenosis, respectively p = 0.01 and p = 0.05). Pravastatin plus clopidogrel significantly decreased CRP, platelet activity, total serum cholesterol, and IH while pravastatin alone decreased only CRP and platelet activity. Intimal hyperplasia reduction may therefore be dependent on other contributors, possibly growth factors, cytokines, and oxidative stress. The combination of pravastatin plus clopidogrel may have synergistic or even additional inhibitory effects on IH. Pravastatin plus clopidogrel was effective in decreasing IH in a rat carotid endarterectomy model and may prove a useful therapy for IH reduction in the clinical setting.

Survival, Graft Atherosclerosis, and Rejection Incidence in Heart Transplant Recipients Treated With Statins: 5-Year Follow-up

BACKGROUND

Few studies have examined the long-term benefits of statin treatment in heart transplant recipients.

METHODS

In this observational study, we retrospectively reviewed data pertaining to 5-year follow-up of patients who underwent heart transplantation between 1993 and 1996 and who survived the first 30 days after transplantation. Patients were assigned to groups according to whether or not they received pravastatin after transplantation, and then compared with regard to transplant rejection, transplant coronary artery disease, and survival.

RESULTS

Ninety-one patients received pravastatin after transplantation, whereas 37 did not receive any statins and served as controls. Pravastatin did not affect the overall incidence of rejections or number of rejection episodes. Hemodynamically significant rejection episodes occurred in 5 patients (5%) in the pravastatin group and 4 patients (11%) in the control group. Thus, pravastatin treatment apparently reduced the incidence of hemodynamically significant rejection episodes by 50% (p = 0.04). Transplant coronary artery disease (CAD) occurred in 10 patients (11%) in the pravastatin group and 9 patients (24%) in the control group. Treatment with pravastatin significantly reduced the incidence of transplant CAD (p = 0.05). Three- and 5-year survival rates in the pravastatin group were significantly better than in the control group (87% vs 68% and 82% vs 58%, respectively; p = 0.009).

CONCLUSIONS

Pravastatin therapy offers long-term benefits to heart transplant recipients. It improves 5-year survival, lowers the risk of transplant CAD, and lowers the incidence of hemodynamically significant rejection episodes.

Simvastatin Therapy in Lymphocyte Cross-Match–Positive Kidney Transplantation Candidates

OBJECTIVES

Recent identification of several mechanisms by which statins decrease recruitment of monocytes and T cells into the arterial wall and inhibit both T-cell and B-cell activation and proliferation in vitro prompted us to study the immunomodulatory effects of statins. In this study, we examined the effect of simvastatin therapy on lymphocyte cross-match positivity in kidney transplantation candidates.

METHODS

Simvastatin therapy (20 mg/d) was administered to 25 patients (18 men, 7 women of mean age 34 +/- 11.7 years who displayed positive lymphocyte cross-matches between July 2002 and October 2004. The etiologies of end-stage renal disease were vesicoureteral reflux (n = 5), urinary stone disease (n = 4), glomerulonephritis (n = 6), amyloidosis secondary to familial Mediterranean fever (n = 1), and unknown (n = 9).

RESULTS

The lymphocyte cross-match became negative in 10 patients 4-9 months, and successful kidney transplantation was performed in 6 of them. The serum creatinine levels of these patients ranged between 0.8 and 1.4 mg/dL. Two patients required higher doses, but none suffered from adverse effects. The remaining 4 patients are still undergoing pretransplantation evaluation.

CONCLUSION

Simvastatin therapy seems to be a cost-effective and useful method for lymphocyte cross-match-positive kidney transplantation candidates compared with immunoadsorption or intravenous immunoglobulin use.

Effect of simvastatin in the treatment of highly sensitized dialysis patients: the pre and post-renal transplantation follow-up outcomes

The graft survival rates of sensitized kidney recipients have been shown to be lower than non-sensitized patients. Therefore, panel reactive antibody (PRA) and cross-match determination is accepted as mandatory screening for renal transplantation candidates. Our recent previous study has shown that simvastatin had a significant immunosuppressive effect in PRA-positive and/or crossmatch-positive patients. We present the pre and post-transplantation follow-up outcomes of simvastatin treatment in the highly sensitized dialysis patients. Thirty patients were followed for a mean period of 26 months. The PRA and flow cytometric measurements were performed at monthly intervals. Ten patients underwent successful kidney transplantation (eight living-related and two cadaveric). None of the patients developed hyperacute or acute rejection, and there was no graft loss during 19.8+/-6.2 months of post-transplantation follow-up. Of the 18 patients who stayed on dialysis throughout the study with PRA positivity, six were lost to follow-up and three spontaneously stopped taking the simvastatin. In the latter three cases, the PRA levels rose significantly after the drug was discontinued. Eight of the remaining nine PRA-positive patients showed significant drops in mean PRA level over the study period, and entered the range considered acceptable for transplantation. Only one patient showed persistently high PRA levels throughout the study. In one patient, the drug had to be discontinued due to acute toxic hepatitis. In conclusion, the results indicate that continuous simvastatin therapy effective in immunized and highly sensitized dialysis patients. Meanwhile, it has beneficial effect on 1-year graft survival in sensitized renal transplantation group.

Effect of HMG-CoA reductase inhibitors on chronic allograft rejection

BACKGROUND

Although chronic rejection is the most important cause of late allograft loss, none of the currently available immunosuppressive agents successfully target this problem. Clinical and laboratory studies suggest that 3-hydroxy-3-methyl-glutaryl co-enzyme A (HMG-CoA) reductase inhibitors (HRIs) may decrease the incidence of and pathophysiologic factors leading to chronic rejection.

METHODS

A number of clinical and laboratory investigations have been designed to evaluate the effect of HRIs on chronic rejection.

RESULTS

Clinical trials in heart transplant patients suggest that HRIs decrease the incidence of chronic rejection in a manner that may be independent of lipid lowering. Subsequent studies in animal transplant models confirm that HRIs reduce chronic rejection. In further studies to elucidate the possible mechanisms of this effect, it has been observed that HRIs have an inhibitory effect on an number of lymphoid cell lines and vascular smooth muscle cells. HRIs may also prevent chronic rejection by protecting the endothelium from injury and dysfunction, perhaps by up-regulating nitric oxide synthesis.

CONCLUSIONS

HRIs may be the first agents to be effective in preventing chronic rejection. Although the mechanism behind this protective effect is unclear, it seems likely that HRIs may affect multiple factors that could lead to chronic rejection.