Effects of pravastatin on chronic rejection of rat cardiac allografts

Atorvastatin Inhibited ROS Generation and Increased IL-1β And IL-6 Release by Mononuclear Cells from Diabetic Patients

BACKGROUND

Atorvastatin (ATV) inhibits the conversion of 3-Hydroxy-3-Methylglutaryl Coenzyme A (HMG-CoA) to mevalonate formation and promotes lowering of the LDL cholesterol fraction. However, ATV exhibits pleiotropic metabolic actions beyond cholesterol-lowering properties.

OBJECTIVE

We aimed to evaluate the effect of ATV on oxidizing species generation and cytokine secretion in Peripheral Blood Mononuclear Cells (PBMNC) of Type 2 Diabetes Mellitus (T2DM) patients in comparison to healthy control.

METHODS

Both NADPH-oxidase-dependent and mitochondrial ROS generation were assessed by chemoluminescence luminol-dependent assay and fluorometric experiment, using Dichlorofluorescein Assay (DCFH-DA), respectively. IL-1β and IL-6 were quantified by classical ELISA.

RESULTS

ATV inhibited NADPH-oxidase dependent ROS generation, but showed no effect on mitochondrial ROS generation and activated IL-1β and IL-6 secretions in PBMNC from control and T2DM patients. ROS generation and cytokine secretion in the presence of an inhibitor of Protein Kinase Cβ (iPKCβ) and ATV led to similar results. The secretion of IL-1β, PDB-induced in the presence of iPKCβ, but not ATV, was increased. ATV and iPKCβ exacerbated PDB-induced IL-6 secretion. LPS activated the secretion of IL-1β and IL-6 which was potentiated by ATV.

CONCLUSION

ATV inhibited ROS generation and activated IL-1 β/IL-6 secretion in PBMNC of diabetes patients. Its effect was not affected by the hyperglycemia.

Neuroprotective Effect of Simvastatin via Inducing the Autophagy on Spinal Cord Injury in the Rat Model

Simvastatin, an inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, is invariably used to treat cardiovascular diseases. Simvastatin has been recently demonstrated to have a neuroprotective effect in nervous system diseases. The present study aimed to further verify the neuroprotection and molecular mechanism of simvastatin on rats after spinal cord injury (SCI). The expression of Beclin-1 and LC3-B was evidently enhanced at postoperation days 3 and 5, respectively. However, the reduction of the mTOR protein and ribosomal protein S6 kinase p70 subtype (p70S6K) phosphorylation level occurred at the same time after SCI. Simvastatin significantly increased the expression of brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF). Meanwhile, immunofluorescence results indicated that the expression of chondroitin sulfate proteoglycan (CSPG) and caspase-3 protein was obviously reduced by simvastatin. Furthermore, Nissl staining and Basso, Beattie, and Bresnahan (BBB) scores showed that the quantity and function of motor neurons were visibly preserved by simvastatin after SCI. The findings of this study showed that simvastatin induced autophagy by inhibiting the mTOR signaling pathway and contributed to neuroprotection after SCI.

Anti-inflammatory effect of simvastatin in an experimental model of spinal cord trauma: involvement of PPAR-α

BACKGROUND

Statins such as simvastatin are inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase used in the prevention of cardiovascular disease. In addition to their cholesterol-lowering activities, statins exert pleiotropic anti-inflammatory effects, which might contribute to their beneficial effects on lipid-unrelated inflammatory diseases. Recently it has been demonstrated that the peroxisome proliferator-activated receptor (PPAR)-α mediates anti-inflammatory effects of simvastatin in vivo models of acute inflammation. Moreover, previous results suggest that PPAR-α plays a role in control of secondary inflammatory process associated with spinal cord injury (SCI).

METHODS

With the aim to characterize the role of PPAR-α in simvastatin activity, we tested the efficacy of simvastatin (10 mg/kg dissolved in saline i.p. 1 h and 6 h after the trauma) in an experimental model of SCI induced in mice by extradural compression of the spinal cord (T6-T7 level) using an aneurysm clip with a closing force of 24 g via a four-level T5-T8 laminectomy, and comparing mice lacking PPAR-α (PPAR-α KO) with wild type (WT) mice. In order to elucidate whether the effects of simvastatin are due to activation of the PPAR-α, we also investigated the effect of a PPAR-α antagonist, GW6471 (1 mg/kg administered i.p. 30 min prior treatment with simvastatin) on the protective effects of on simvastatin.

RESULTS

Results indicate that simvastatin activity is weakened in PPAR-α KO mice, as compared to WT controls. In particular, simvastatin was less effective in PPAR-α KO, compared to WT mice, as evaluated by inhibition of the degree of spinal cord inflammation, neutrophil infiltration, nitrotyrosine formation, pro-inflammmatory cytokine expression, nuclear factor (NF)-κB activation, inducible nitric-oxide synthase (iNOS) expression, and apoptosis. In addition we demonstrated that GW6471 significantly antagonized the effect of the statin and thus abolished the protective effect.

CONCLUSIONS

This study indicates that PPAR-α can contribute to the anti-inflammatory activity of simvastatin in SCI.

Current therapeutic strategies to mitigate the eNOS dysfunction in ischaemic stroke

Impairment of endothelial nitric oxide synthase (eNOS) activity is implicated in the pathogenesis of endothelial dysfunction in many diseases including ischaemic stroke. The modulation of eNOS during and/or following ischaemic injury often represents a futile compensatory mechanism due to a significant decrease in nitric oxide (NO) bioavailability coupled with dramatic increases in the levels of reactive oxygen species that further neutralise NO. However, applications of a number of therapeutic agents alone or in combination have been shown to augment eNOS activity under a variety of pathological conditions by potentiating the expression and/or activity of Akt/eNOS/NO pathway components. The list of these therapeutic agents include NO donors, statins, angiotensin-converting enzyme inhibitors, calcium channel blockers, phosphodiesterase-3 inhibitors, aspirin, dipyridamole and ellagic acid. While most of these compounds exhibit anti-platelet properties and are able to up-regulate eNOS expression in endothelial cells and platelets, others suppress eNOS uncoupling and tetrahydrobiopterin (an eNOS stabiliser) oxidation. As the number of therapeutic molecules that modulate the expression and activity of eNOS increases, further detailed research is required to reveal their mode of action in preventing and/or reversing the endothelial dysfunction.

The protective effect of simvastatin against low dose streptozotocin induced type 1 diabetes in mice is independent of inhibition of HMG-CoA reductase

Besides a cholesterol-lowering effect, simvastatin possesses anti-inflammatory properties attributed to inhibition of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and/or direct binding to, and inhibition of, the integrin lymphocyte function associated antigen-1 (LFA-1). We have shown that simvastatin protects against multiple low dose streptozotocin (MLDS) induced type 1 diabetes in mice. Presently, we examined if this effect could be abolished by co-administration of mevalonic acid, thus determining if the protective effect is dependent or independent of inhibition of HMG-CoA reductase. Mevalonic acid did not affect the protective effect of simvastatin against MLDS diabetes. Moreover, spleens from these mice did not show any signs of toxic side-effects, thus excluding the possibility that the protective effect is secondary to a general inflammatory response. We suggest that simvastatin's protective effect mainly is independent of HMG-CoA reductase inhibition. This implies that inhibition of LFA-1 activation is important for the protective effect exerted by simvastatin.

Action profiles of statins and calcineurin inhibitors during human mixed lymphocyte reaction

The cell-to-cell interaction through binding intercellular adhesion molecule (ICAM)-1 and CD40 on monocytes and their ligands such as lymphocyte function-associated antigen (LFA)-1 and CD40 ligand (CD40L) on T-cells plays roles in cytokine production and T-cell proliferation. Interleukin (IL)-18, which is elevated in the plasma during acute rejection after organ transplantation, induces the expression of ICAM-1 and CD40 on monocytes, the production of interferon (IFN)-gamma and IL-12 and the proliferation of T-cells during the human mixed lymphocyte reaction (MLR). In addition to the cholesterol lowering effect, statins improve patient survival and decrease rejection episodes in transplant recipients. In the present study, we investigated the difference of effect of statins and calcineurin inhibitors during MLR. 3-Hydroxy-3-methylglutaryl coenzyme-A (HMG-CoA) reductase inhibitors, fluvastatin and pravastatin and statin-derived LFA-1 inhibitors, LFA703 and LFA878, which did not inhibit HMG-CoA reductase, suppressed the production of IFN-gamma and IL-12 and the lymphocyte proliferation as well as the expression of ICAM-1 and CD40 on monocytes regardless of the presence of IL-18. However, the calcineurin inhibitors, tacrolimus and cyclosporine A (CsA), inhibited the IL-18-enhanced cytokine production and lymphocyte proliferation without any effect on the adhesion molecule expression. Thus, the action mechanism of stain is different from that of calcineurin inhibitors.

Inhibition of Chemokine Receptor CCR2 and CCR5 Expression Contributes to Simvastatin-induced Attenuation of Cardiac Allograft Vasculopathy

BACKGROUND

Accumulating evidence reveals that statins possess pleiotropic properties beyond cholesterol reduction, which may contribute to the attenuation of cardiac allograft vasculopathy (CAV). Recent in vitro data suggest that statins could down-regulate chemokine receptors. This study was designed to test the hypothesis that simvastatin ameliorates CAV development via the inhibition of chemokine receptor expression in an inbred rat model of cardiac transplantation.

METHODS

Animals were divided into four groups: isograft; control (cyclosporine [CsA] + vehicle); low-dose simvastatin (LSIM; CsA + 5 mg/kg simvastatin); and high-dose simvastatin (HSIM; CsA + 10 mg/kg simvastatin). Donor hearts from Fisher 344 rats were transplanted heterotopically into Lewis rat recipients. CsA was administered at 1.5 mg/kg/day for 2 weeks post-operatively. In addition, recipients were treated daily with simvastatin or vehicle for 8 weeks. Donor hearts were harvested for histopathologic and immunohistochemical examination. Intragraft concentration of chemokines and chemokine receptor expression were analyzed using enzyme-linked immunosorbent assay and quantitative real-time polymerase chain reaction, respectively.

RESULTS

Both low and high doses of simvastatin significantly decreased the CAV score; inhibited recruitment of T lymphocytes and macrophages; reduced levels of intragraft MCP-1 (monocyte chemoattractant protein-1), RANTES (regulated on activation, normal T-cell expressed and secreted) protein and IP-10 (interferon-inducible protein-10); and down-regulated expression of chemokine receptors CCR2 and CCR5. CXCR3 expression was not affected by simvastatin treatment.

CONCLUSIONS

Our results demonstrate that simvastatin may attenuate CAV development, possibly through retarding intragraft chemokine accumulation and chemokine receptor expression.

Pharmacotherapy of hyperlipidemia in pediatric heart transplant recipients: current practice and future directions

Lipoprotein abnormalities are fairly common after pediatric heart transplantation. Graft coronary artery disease (GCAD) limits long-term survival and has been linked to elevated serum triglyceride levels and decreased high-density lipoprotein levels. Histologically, GCAD represents intimal hyperplasia of the coronary vessel and is best imaged by intravascular ultrasound.A number of pharmacologic agents are available for the management of lipid disorders but experience with these drugs has mainly been in adults. HMG-CoA reductase inhibitors (statins) are currently used by many adult transplantation centers to alter lipid profiles in the hope of reducing GCAD. The use of statins among pediatric heart transplant centers is more limited. Although rhabdomyolysis is a concern with these agents, the incidence among individuals receiving immunosuppressant therapy is low. Aside from their lipid-lowering properties, statins may also protect against graft failure and rejection.

Usefulness and safety of percutaneous coronary interventions for cardiac transplant vasculopathy

Late morbidity and death as a result of progressive coronary vascular obliteration remains a major unsolved problem after orthotopic heart transplantation. Various percutaneous catheter intervention (PCI) methods have been used to treat transplant coronary artery disease (CAD), but few reports have assessed the longitudinal results of these procedures. Of 1,440 cardiac transplant patients at University of California, Los Angeles, Medical Center, treated between 1984 and 2004, 65 patients who had undergone orthotopic heart transplantation underwent PCI on a total of 156 coronary artery lesions because of transplant CAD between July 1993 and August 2004. The procedural success rate was 93%. Angiographic follow-up was available for 42 patients and 101 lesions 9.5 +/- 5.8 months after PCI. The global restenosis rate was 36%. Multivariate analysis was used to assess 49 clinical, angiographic, and immunologic variables per lesion. The use of a cutting balloon increased the risk of restenosis (odds ratio 11.5, p <0.01) and the use of stents decreased the risk of restenosis (odds ratio 0.34, p <0.05) compared with other PCI methods. The restenosis rate with drug-eluting stents was 19%, lower than that with bare metal stents (31%). Of the 65 patients, 20 (31%) died within 1.9 +/- 1.8 years after PCI. The actuarial survival rate was 56% at 5 years after the first PCI. In conclusion, although the restenosis rate after PCI was higher than that in nontransplant patients with CAD, the immediate and long-term results were acceptable in this high-risk population. Despite the intense inflammation associated with transplant CAD, drug-eluting stents appeared to reduce the occurrence of restenosis. Compared with historical controls, PCI may also improve the actuarial survival rate of patients undergoing orthotopic heart transplantation.

Immunosuppression for heart transplantation: where are we now?

The success of cardiac transplantation is largely attributable to the development of effective immunosuppressive regimens. The introduction of calcineurin inhibitors was pivotal in reducing the frequency of acute rejection and improving early survival. Newer agents, including mycophenolate mofetil (MMF) and proliferation-signal inhibitors, have shown promise in further reducing acute-rejection rates and, notably, reducing the frequency of cardiac allograft vasculopathy, which limits long-term graft survival. The introduction of first-year intravascular ultrasonography results as a surrogate marker for outcome after cardiac transplantation has helped assessment of the efficacy of immunosuppressive medications. Proliferation-signal inhibitors and MMF were shown by this imaging method to reduce cardiac allograft vasculopathy. The combination of these drugs, in tandem with the weaning of patients off calcineurin inhibitors, has been shown to reverse calcineurin-inhibitor-related nephrotoxic effects. A randomized trial that compared three of the more common immunosuppressive regimens suggested that tacrolimus and MMF are associated with a reduction in the frequency of rejection episodes that require treatment and have the fewest adverse effects. Finally, the use of statins has brought added benefit to immunosuppressive regimens by improving outcomes after cardiac transplantation, reportedly because of an immunomodulatory property. Promising newer immunosuppressive agents await clinical trials. This review presents an overview of the emerging data on immunosuppressive therapy for cardiac transplantation.

Changes of plasma inflammatory markers after withdrawal of statin therapy in patients with hyperlipidemia

BACKGROUND

Atherosclerosis has been considered to be an inflammatory process. In addition to its lipid-lowering properties, statin has been shown to decrease the concentrations of inflammatory markers resulting in reduction of cardiovascular events. Emerging data suggest that withdrawal of statin might be associated with increased cardiac events. The mechanism for this phenomenon, however, is still unclear. We investigated whether acute termination of statin treatment could result in rebound of inflammatory markers, such as C-reactive protein (CRP) and interleukin-6 (IL-6), in patients with hyperlipidemia.

METHODS

Seventeen patients (11 men and 6 women, mean age 51+/-7 years) with hyperlipidemia were given 40 mg/day of pravastatin for 6 weeks. The concentrations of plasma CRP and IL-6 were evaluated before receiving the statin therapy, immediately after 6 weeks of pravastatin therapy, and at days 1, 3 and 7 after withdrawal of pravastatin therapy. The lipid profile was also evaluated at baseline, 6 weeks of therapy, and at day 7 after terminating pravastatin.

RESULTS

Pravastatin therapy induced significant reductions in total cholesterol (TC, 6.88+/-0.36 vs. 5.27+/-0.23 mmol/l, p<0.01), low-density lipoprotein (LDL) cholesterol (4.28+/-0.25 vs. 3.06+/-0.14 mmol/l, p<0.01), CRP (0.28+/-0.16 vs. 0.20+/-0.08 mg/l, p<0.01), and IL-6 (8.4+/-0.6 vs. 6.7+/-0.4 pg/dl, p<0.01). Although the TC and LDL-cholesterol did not change during the 7-day period after withdrawal of pravastatin therapy, the concentrations of CRP and IL-6 increased at day 3 (CRP: 0.20+/-0.08 vs. 0.27+/-0.12 mg/l, and IL-6: 6.7+/-0.4 vs. 7.7+/-0.6 pg/dl, p<0.05 respectively) and at day 7 (CRP: 0.20+/-0.08 vs. 0.30+/-0.14 mg/l, and IL-6: 6.7+/-0.4 vs. 8.7+/-0.8 pg/dl, p<0.01 respectively) after withdrawal of pravastatin therapy. No correlation between increase of CRP as well as IL-6 and small changes of LDL-cholesterol concentrations was found after withdrawal of pravastatin therapy at day 7 (r=-0.021 and r=-0.044 respectively, p>0.05 respectively).

CONCLUSIONS

6 weeks after pravastatin therapy could significant modify the lipid profile and decrease the inflammatory markers including CRP and IL-6 in patients with hyperlididemia. Moreover, statin therapy discontinuation could induce a rebound phenomenon of inflammatory response representing an increase in some inflammatory markers, which is independent of changes of lipid parameters.

Rebound phenomenon of inflammatory response may be a major mechanism responsible for increased cardiovascular events after abrupt cessation of statin therapy

Inflammation has been recognized as having an important role in the development and progression of atherosclerosis. Statins reduce cardiovascular events mainly by cholesterol lowering. A large number of investigations have demonstrated that administration of statin could modify inflammatory response with a concurrent fall in cardiovascular events. Despite the known benefit of statin therapy, many cardiac patients abruptly discontinue therapy because of financial constraints, forgetfulness, or side effects. More recently, several studies have shown that abrupt cessation of statin therapy during treatment could increase the incidence of cardiac events in patients with atherosclerotic heart disease. However, the mechanisms of the increased incidence of cardiovascular events after abruptly stopping statin therapy are still unknown. A few data suggest that abrupt withdrawal of statin therapy deteriorates endothelial function, result in expression of pro-inflammatory gene involved in the development and progression of atherosclerosis. We hypothesis that rebound phenomenon of inflammatory response may be a major mechanism responsible for increased cardiovascular events after abrupt cessation of statin therapy. Our very recent data showed that abrupt termination of statin therapy resulted in a rapid increased C-reactive protein (CRP) and interleukin-6 (IL-6) levels in patients with hypercholesterolemia. This finding may be of important interest in the connection between inflammatory response and abrupt withdrawal of statin therapy in patients with coronary artery disease.

Ten-Year Follow-Up of a Randomized Trial of Pravastatin in Heart Transplant Patients

BACKGROUND

Outcomes from this trial's first year data demonstrated significant benefit in heart transplant patients treated with pravastatin in cholesterol levels, survival, rejection with hemodynamic compromise, the development of cardiac allograft vasculopathy, and decreased natural killer cell cytotoxicity. Other heart transplant studies have shown similar benefit. We now report the 10-year follow-up of this study.

METHODS

Ninety-seven heart transplant recipients were randomized to pravastatin (n = 47) or no pravastatin (n = 50) within 2 weeks after surgery both in combination with cyclosporine and corticosteroids. Ten-year outcomes include survival, cholesterol levels, and development of cardiac allograft vasculopathy documented by coronary angiography.

RESULTS

Forty-two percent of the control patients crossed over to pravastatin treatment during the second year of the study, and 81% of the control patients were eventually placed on statin therapy by the 10-year follow-up. The control group had subsequent low and comparable cholesterol levels in Years 2 to 10 of the study compared with the patients originally randomized to pravastatin. Intent-to-treat analysis demonstrated that the pravastatin group compared with control had increased 10-year survival (68% vs 48%, p = 0.026). The 10-year freedom from angiographic cardiac allograft vasculopathy and/or death in the pravastatin group was significantly greater compared with the control group (43% vs 20%, p = 0.009).

CONCLUSION

The 10-year follow-up of this study suggests that the use of pravastatin in heart transplant patients maintains survival benefit and appears to reduce the development of cardiac allograft vasculopathy.

Right ventricular expression of extracellular matrix proteins, matrix-metalloproteinases, and their inhibitors over a period of 3 years after heart transplantation

Fibrillar collagens I and III, nonfibrillar collagen IV, and the glycoproteins fibronectin and laminin, are elements of the myocardial extracellular matrix (ECM). Alterations in the normal concentrations and ratios of these elements may reflect remodeling in response to physiologic stress. In the case of patients' post-heart transplantation (HTx), specific patterns of alteration may herald myocardial dysfunction. Right ventricular biopsies were taken from the same 28 HTx patients before implantation and 1 week, 2 weeks, and 1, 2, and 3 years after HTx. The above-noted five ECM proteins, six matrix metalloproteinases (MMPs) and two of their tissue inhibitors (TIMPs) were detected by immunohistochemistry and scored as cells per square millimeter or semiquantitatively. The total connective tissue fibers were detected by connective tissue stain and morphometry. Variations in these ECM components were followed in the same patient cohort over 3 years. In summary, during the first 2 weeks after HTx, a predominant increase in connective tissue occurred. Increases in MMP-8 and MMP-9 were found. By 3 years after transplantation, there was a decrease of connective tissue fibers and a significant reduction of all ECM components and an increase in MMPs and TIMPs. These findings may reflect a pattern of remodeling specific to the transplanted heart.

The effect of HMG-CoA reductase inhibitors on chronic allograft rejection

Hydroxy-methyl-glutaryl coenzyme A (HMG-CoA) reductase inhibitors have pleiotropic actions that affect many systems other than lowering blood cholesterol concentrations. Hypercholesterolaemia is an adverse effect of immunosuppressive drug therapy and hence it is a common finding after organ transplantation. HMG-CoA reductase inhibitors lower cholesterol concentrations in transplant recipients but they also offer additional benefits. Since they impair the production of mevalonate, they reduce the concentrations of downstream products including farnesyl and geranyl phosphate. These isoprenoid moieties are required for protein prenylation and HMG-CoA reductase inhibitors impair this function in some cells. This action affects the immune system, especially in patients taking cyclosporin, and has been proposed as the mechanism whereby these drugs increase the half-life of transplanted organs. Other mechanisms have also been proposed including an increase in the free fraction of cyclosporin and a reduction in the time that low density lipoprotein (LDL) spends in blood. The latter effect reduces the extent of oxidation of LDL and hence reduces the damage caused by oxidised LDL. Chronic rejection is poorly understood but appears to involve both immune and non-immune processes. HMG-CoA reductase inhibitors affect both processes. At present, the evidence of benefit from statin prescription is confined to heart and kidney transplant recipients but it is likely that recipients of other organ transplants would also benefit. Drug interactions between cyclosporin and HMG-CoA reductase inhibitors are a limiting factor to their use. Pravastatin appears to be the best HMG-CoA reductase inhibitor for organ transplant recipients because of its lesser potential to interact with cyclosporin and hence cause myositis, which may thus allow higher doses to be used. Other, non-immunosuppressive drugs (including diltiazem and ketoconazole) have been shown to reduce transplant organ damage by unknown mechanisms and are widely prescribed in some transplant centres. More specific inhibitors of protein prenylation may afford useful immunosuppression, thereby prolonging transplant organ half-lives and also reducing the risk of cancer.

Statin, like aspirin, should be given as early as possible in patients with acute coronary syndrome

It is estimated that about 1 million patients are hospitalized for acute coronary events each years in the United States. An acceptable theory is that the acute coronary syndrome is caused by rupture of the atherosclerotic plaque with superimposed thrombus, which is a complex process and involving a number of different stages. Previous studies indicated that inflammation is one of the most important features of vulnerable plaque, and occurs in most vulnerable plaque, comprised of monocytes, macrophages, and lymphocytes in both the cap and in the adventitia. This is supported by evidence that reduction in serum inflammatory marker levels, such as C-reactive protein, significantly decreased coronary events in patients with acute coronary syndrome. A large number of investigations have demonstrated that administration of statin could modify C-reactive protein concentrations with a concurrent fall in cardiovascular events. Our recent data indicated that reduction of inflammatory markers could be achieved within 24 h following a single dose of statin administration after admission in patients with coronary artery disease. Based on the available evidence and in light of the new understanding that statins have pleiotropic effects, especially as a potent anti-inflammatory agent, the statins, like aspirin, should be clinically given as early as possible in patients with acute coronary syndrome.

Chemopreventive effect of five drugs on renal interstitial fibrosis induced by an aristolochic acid-containing Chinese herb in rats

BACKGROUND/AIMS

This study focuses on the chemopreventive effect of five drugs on renal interstitial fibrosis induced by an aristolochic acid-containing Chinese herb Mu-Tong.

METHODS

Renal interstitial fibrosis was induced in rats by administration of the Mu-Tong solution intragastrically for 6 weeks, and 36 rats were randomly divided into six groups: (1) Mu-Tong, (2) Mu-Tong + captopril, (3) Mu-Tong + losartan, (4) Mu-Tong + simvastatin, (5) Mu-Tong + spironolactone, and (6) Mu-Tong + diammonium glycyrrhizinate. Blood biochemistry and extracellular matrix were detected at weeks 0, 2, 4, and 6. At the end of week 6, kidney tissue of all groups was evaluated with special Masson staining for the degree of renal fibrosis as well as regular histopathology.

RESULTS

Mu-Tong caused progressive elevation of blood urea nitrogen, creatinine, hyaluronic acid, procollagen type III, and laminin. All five drugs suppressed elevation of blood biochemistry and extracellular matrix to some degree, but only the simvastatin group showed a significantly reduced percentage of positive Masson staining area in renal section compared to the Mu-Tong group (p < 0.05).

CONCLUSIONS

Our study indicates that Mu-Tong induces a similar kidney injury with general characteristics in patients with renal interstitial fibrosis. All five different drugs have suppressive effects on Mu-Tong-induced renal function damage, and in particular, simvastatin shows a protective effect on development of Mu-Tong-induced renal interstitial fibrosis to a certain degree.

AT-1 receptor blockade prevents proteinuria, renal failure, hyperlipidemia, and glomerulosclerosis in the Imai rat

BACKGROUND

The Imai rat is a model of spontaneous focal glomerulosclerosis which leads to nephrotic syndrome, hyperlipidemia, hypertension, and progressive renal failure. We evaluated the effects of angiotensin II receptor type 1 (AT-1)blockade, and compared the results with the effects of the administration of hypolipidemic treatment with a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor. All treatments were started at 10 weeks of age when the rats were already proteinuric and continued for 6 months when rats were sacrificed.

METHODS

The following groups (N= 6 each) were studied: (1) control Sprague-Dawley rats, 34 weeks old; (2) Imai group that received vehicle; (3) Imai + angiotensin II receptor blockade (ARB) group that received olmesartan (10 mg/kg/day by gastric gavage); (4) Imai + prava group, that received pravastatin (20 mg/kg/day by gastric gavage); and (5) Imai + ARB + prava group that received both ARB and pravastatin. Lipid profile, renal function, and structure were assessed at 6 months.

RESULTS

As expected, the untreated Imai rats exhibited heavy proteinuria, hypoalbuminemia, hypertension, renal insufficiency, marked glomerulosclerosis, tubulointerstitial inflammation, and profound hyperlipidemia. Pravastatin treatment alone led to a significant, but partial improvement of hyperlipidemia and renal disease. The ARB treatment alone or in combination with pravastatin resulted in normalization of the blood pressure, urinary protein excretion, plasma cholesterol, triglycerides, low-density lipoproteins (LDLs), very low-density lipoproteins (VLDLs), and albumin concentrations and renal function. Significant glomerulosclerosis was prevented and tubulointerstitial injury and immune cell infiltration were reduced by long-term AT-1 blockade.

CONCLUSION

The study revealed that long-term AT-1 blockade corrects proteinuria, hyperlipidemia, and nephropathy in this model of spontaneous glomerulosclerosis.

Palliation of allograft vasculopathy with transluminal angioplasty: a decade of experience

OBJECTIVES

The goal of this study was to examine the outcomes of percutaneous coronary interventions (PCI) and the predictors for restenosis after cardiac transplantation.

BACKGROUND

The role of PCI as definitive therapy for allograft coronary disease (ACD) remains contentious.

METHODS

Between January 1, 1990 and December 31, 2000, 62 patients (1.5 to 15.5 years after transplant) underwent 151 procedures resulting in PCIs of 219 lesions. Follow-up after PCI angiography was usually obtained at three and six months, then yearly. Repeat PCI was routinely done to lesions with >60% restenosis.

RESULTS

The primary procedural success was 97%. Repeat PCI occurred in 74 of 219 lesions (34%); PCI-related mortality was 2.6% (4 of 151). The freedom from re-PCI (of same vessel site) was 75% at six months, 65% at one year, and 57% at four years. The freedom from restenosis was 95% at one month, 81% at three months, and 57% at six months. Multivariate predictors of freedom from restenosis were the use of stents, higher anti-proliferative immunosuppressant dose, and an era effect. In the setting of one-vessel disease at first PCI, the two-year freedom for ACD death or graft loss was 74%, compared with 75% for two-vessel and 27% for three-vessel disease (p = 0.009).

CONCLUSIONS

Despite the increasing effectiveness of PCI for localized ACD, the survival after development of advanced ACD remains poor. Stents appear to increase effectiveness of PCI for ACD, but other factors in the current era contribute to improved outcomes.

Positive pleiotropic effects of HMG-CoA reductase inhibitor on vitiligo

Background

HMG-CoA reductase inhibitors (statins) are commonly used in medicine to control blood lipid disorder. Large clinical trials have demonstrated that statins greatly reduces cardiovascular-related morbidity and mortality in patients with and without coronary artery disease. Also, the use of HMG-CoA reductase inhibitors has been reported to have immunosuppressive effects.

Case presentation

We describe an unusual case of regression of vitiligo in a patient treated with high dose simvastatin. The relation between simvastatin and regression of vitiligo in this case report may be related to the autoimmune pathophysiology of the disease.

Conclusion

This unexpected beneficial impact provides another scientific credence to the hypothesis that immune mechanisms play a role in the development of vitiligo and that the use of statins as immuno-modulator could be of use not only for treatment relative to organ transplant but in other pathologies such as vitiligo.

HMG-CoA reductase inhibition aborts functional differentiation and triggers apoptosis in cultured primary human monocytes: a potential mechanism of statin-mediated vasculoprotection

BACKGROUND

Statins effectively lower blood cholesterol and the risk of cardiovascular death. Immunomodulatory actions, independent of their lipid-lowering effect, have also been ascribed to these compounds. Since macrophages participate in several vascular pathologies, we examined the effect of statin treatment on the survival and differentiation of primary human monocytes.

METHODS

Peripheral blood mononuclear cells (PBMCs) from healthy individuals were cultured in the presence or absence of mevastatin. Apoptosis was monitored by annexin V / PI staining and flow cytometry. In parallel experiments, cultures were stimulated with LPS in the presence or absence of mevastatin and the release of IL-1beta and IL-1Ra was measured by ELISA.

RESULTS

Among PBMCs, mevastatin-treated monocytes were particularly susceptible to apoptosis, which occurred at doses >1 microM and was already maximal at 5 microM. However, even at the highest mevastatin dose used (10 microM), apoptosis occurred only after 24 h of culture, possibly reflecting a requirement for cell commitment to differentiation. After 72 h of treatment the vast majority (>50%) of monocytes were undergoing apoptosis. Stimulation with LPS revealed that mevastatin-treated monocytes retained the high IL-1beta output characteristic of undifferentiated cells; conversely, IL-1Ra release was inhibited. Concurrent treatment with mevalonolactone prevented the induction of apoptosis and suppressed both IL-1beta and IL-1Ra release in response to LPS, suggesting a rate-limiting role for HMG-CoA reductase in monocyte differentiation.

CONCLUSIONS

Our findings indicate that statins arrest the functional differentiation of monocytes into macrophages and steer these cells into apoptosis, suggesting a novel mechanism for the vasculoprotective properties of HMG-CoA reductase inhibitors.

Statins as anti-inflammatory agents

The beneficial effects of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) in cardiovascular disease have generally been attributed to their cholesterol-lowering property. However, an increasing number of in vitro and in vivo studies indicate that statins have direct anti-inflammatory effects that are not mediated by their hypocholesterolemic activity. In this article, the HMG-CoA-reductase-dependent and -independent mechanisms by which statins might affect leukocyte adhesion and migration to sites of inflammation are reviewed and the implications for the design of new statin-derived drugs are discussed.

Prevention of chronic rejection by pravastatin in a rat kidney transplant model

BACKGROUND

Pravastatin when administered with cyclosporine (CsA) has been shown to ameliorate transplant vasculopathy in the clinical setting. Previously we showed that pravastatin prevents chronic rejection in rat cardiac and liver transplant models. Here we determine whether pravastatin prevents chronic rejection in a rat renal allograft model.

METHODS

Orthotopic renal transplantations were performed using Fisher 344 rats as donors and Lewis rats as recipients. Recipients were treated with low-dose CsA for 10 days to prevent acute rejection. Recipients were divided into three groups: CsA, CsA + pravastatin, and syngeneic. Renal function was assessed by serum creatinine level at day 130. Allografts were evaluated by histology and immunohistochemistry. Serum levels of alloantibodies were measured by flow cytometry. Intragraft cytokine mRNA expression was determined by semiquantitative reverse transcriptase-polymerase chain reaction. Intragraft levels of the antiapoptotic Bag-1 gene were measured by Western blot.

RESULTS

Unlike allografts from the pravastatin group, control allografts demonstrated glomerulosclerosis, vascular obliteration, tubular atrophy, and interstitial fibrosis. Serum creatinine levels and graft infiltration of T cells and macrophages in the pravastatin-treated animals were significantly lower. Intragraft cytokines showed a T helper 2 polarization and decreased transforming growth factor-beta in the pravastatin group. Intragraft expression of Bag-1 was increased in the pravastatin group.

CONCLUSION

This study demonstrates the ability of pravastatin to inhibit chronic rejection in rat renal allografts. Pravastatin's pleiotropic effects of reducing intragraft inflammatory cytokines, inhibiting immune cell infiltration, and causing up-regulation of the antiapoptotic gene Bag-1 suggest that its ability to prevent transplant chronic rejection may be multifactorial.

Distribution of cyclosporin in organ transplant recipients

Cyclosporin is an immunosuppressive agent with a narrow therapeutic index. The total concentration of cyclosporin in blood is usually monitored to guide dosage adjustment and to compensate for substantial interindividual and intraindividual variability in cyclosporin pharmacokinetics. Cyclosporin is a highly lipophilic molecule and widely distributes into blood, plasma and tissue components. It mainly accumulates in fat-rich organs, including adipose tissue and liver. In blood, it binds to erythrocytes in a saturable fashion that is dependent on haematocrit, temperature and the concentration of plasma proteins. In plasma, it binds primarily to lipoproteins, including high-density, low-density and very-low-density lipoprotein, and, to a lesser extent, albumin. The unbound fraction of cyclosporin in plasma (CsA(fu)) expressed as a percentage is approximately 2%. It has been shown that both the pharmacokinetic and pharmacodynamic properties of cyclosporin are related to its binding characteristics in plasma. Furthermore, there is some evidence to indicate that the unbound concentration of cyclosporin (CsA(U)) has a closer association with both kidney and heart allograft rejection than the total (bound + unbound) concentration. However, the measurement of CsA(fu) is inherently complex and cannot easily be performed in a clinical setting. Mathematical models that calculate CsA(fu), and hence CsA(U), from the concentration of plasma lipoproteins may be a more practical option, and should provide a more accurate correlate of effectiveness and toxicity of this drug in transplant recipients than do conventional monitoring procedures. In conclusion, the distribution characteristics of cyclosporin in blood, plasma and various tissues are clinically important. Further investigations are needed to verify whether determination of CsA(U) improves the clinical management of transplant recipients.

Reversal of diabetes-induced rat graft transplant coronary artery disease by metformin

BACKGROUND

Induction of diabetes in rat heterotopic heart transplantation models leads to an accelerated form of severe transplant coronary artery disease (TxCAD). We undertook this study to determine whether treatment of diabetes with metformin would favorably affect TxCAD.

METHODS

Heterotopic abdominal heart transplantation was performed in rat isograft and allograft models. After transplantation, diabetes was induced with streptozotocin. Fifty percent of the animals received metformin at 500 mg/kg twice daily. We quantitatively assessed TxCAD using histologic sections of harvested hearts at 30 and 60 days with computer-assisted morphometry. We compared vessels in the first tertile of the area distribution with vessels in the last tertile.

RESULTS

Fasting glucose levels in metformin-treated animals were 161 +/- 45 mg/dl compared with 400 +/- 120 mg/dl (p < 0.05) in untreated rats. Treatment with metformin led to decreased diabetes-induced TxCAD in the larger vessels. This effect was sustained during the study course in the isografts but not in the allografts. Treatment with metformin did not prevent progression of TxCAD in the smaller vessels at 60 days.

CONCLUSIONS

Metformin reduced luminal occlusion and severe TxCAD in the larger vessels but did not alter the course of TxCAD in the smaller vessels. These results may have therapeutic implications for patients.

Prevention of primary nonfunction of canine islet autografts by treatment with pravastatin

BACKGROUND

Nonspecific inflammation is the primary cause of early islet graft loss. We have shown in mice that pravastatin, a 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor, prevents primary nonfunction of islet isografts by reducing inflammatory reactions at the graft site. This study was designed to test the effectiveness of this agent in a large animal model, dogs, by transplanting autologous islets.

METHODS

After total pancreatectomy, islets were isolated by using a two-step digestion method, followed by discontinuous gradient centrifugation on EuroFicoll. A known number of freshly isolated islets were immediately transplanted back into the same dog via the portal vein.

RESULTS

First, we determined the minimal islet number required to reverse diabetes by transplanting 3,000-10,000 IEQ/kg with no additional treatment. The number was found to be 4,000 IEQ/kg, and islets less than 4,000 IEQ/kg consistently failed. To test the effect of pravastatin, 3,000 IEQ/kg were transplanted into dogs that either received no further treatment or were treated daily with 20 mg/kg of pravastatin from days -2 to 14. Without pravastatin, this number of islets lowered blood glucose only transiently, and all four of these dogs became hyperglycemic within 1 week. In contrast, four of the five dogs treated with pravastatin became normoglycemic (<150 mg/dL) and maintained this level during the observation period of 12 weeks (P<0.05). Postprandial plasma glucose and insulin levels returned to normal, and K values of intravenous glucose tolerance tests were significantly higher in pravastatin-treated dogs than in controls (P<0.04 at week 2 and P<0.01 at week 4).

CONCLUSION

Peritransplant pravastatin treatment reduced the number of autologous islets required to reverse diabetes in totally pancreatectomized dogs. These results suggest that pravastatin may also facilitate better islet graft survival and function in clinical transplantation.

Effect of fluvastatin on acute renal allograft rejection: a randomized multicenter trial

BACKGROUND

Statin therapy has been reported to reduce the acute rejection rate following renal transplantation in a pilot study. The present study is the first randomized, double-blind and adequately powered study to examine the effect of statins on acute rejection of renal allografts.

METHODS

A total of 364 patients were randomly assigned to receive either fluvastatin 40 mg or placebo in combination with conventional cyclosporine-based immunosuppressive therapy. The primary end point was treated first acute rejection. Secondary end points included biopsy-proven rejection, histological severity of rejection, occurrence of steroid-resistant rejection, and serum creatinine at three months following transplantation.

RESULTS

Fluvastatin was well tolerated; no patients developed myositis or rhabdomyolysis. There was no difference in the acute rejection rate [86 (47.3%) fluvastatin vs. 87 (47.8%) placebo] and no significant difference in the severity of rejection, steroid resistant rejection or mean serum creatinine at three months (160 micromol/L vs. 160 micromol/L). Total cholesterol, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol and triglyceride levels increased following renal transplantation. With the exception of the increase in HDL-C, which was augmented, the increases in lipid parameters were significantly reduced by fluvastatin (total cholesterol +17.5% vs. 35.7%; LDL-C +6.3% vs. 46.7%; HDL-C +43.3% vs. 38.1%; triglyceride +52.2% vs 77.6%).

CONCLUSIONS

Contrary to the reported effects of statins, fluvastatin had no effect on the incidence or severity of acute rejection following renal transplantation. There were no increases in adverse events. A significant and potentially beneficial alteration in the lipid profile was observed in the early post transplant period. We conclude that fluvastatin may be used safely to correct dyslipidemia in patients with end-stage renal failure through the peri-transplant period.

Fluvastatin in combination with rad significantly reduces graft vascular disease in rat cardiac allografts

BACKGROUND

RAD is a potent immunosuppressive agent that has been shown to be effective in preventing acute and chronic allograft rejection in animal models. The HMGCoA reductase inhibitors have been found to reduce the incidence of graft vascular disease (GVD) in heart transplant patients and in animal models. This study was designed to investigate the effects of fluvastatin or pravastatin in a rodent model of GVD produced using low doses of RAD to prevent acute rejection.

METHODS

Hearts from Fisher 344 rats were heterotopically transplanted to Lewis rat recipients. RAD was administered orally at 0.5 mg/kg per day for days 0 to 14 and then 0.25 mg/kg per day for an additional 85 days to prevent acute rejection but allow for the development of GVD. Pravastatin (20 mg/kg per day) or fluvastatin (2 or 6 mg/kg per day) was added to the RAD treatment. At the end of a 100-day treatment period, the hearts were harvested for morphometric and histopathologic examinations.

RESULTS

Rats treated with fluvastatin, at either dose, had a significant (P< or =0.0239) decrease in coronary arterial intimal thickening (GVD) of approximately 43%. Rats treated with pravastatin had a 22% reduction in GVD that did not reach statistical significance. Treatment with fluvastatin, but not pravastatin, decreased the degree of endomyocardial mononuclear cell infiltration seen with RAD administered alone.

CONCLUSIONS

Fluvastatin significantly decreased GVD in a rat model produced using low-dose RAD immunosuppression. To a lesser extent, pravastatin also decreased GVD in this model. These data lend further support for the study of fluvastatin, pravastatin, and other HMG-CoA reductase inhibitors for the prevention of GVD in cardiac transplant patients.

Statins as immunosuppressive agents

BACKGROUND

Coronary artery disease in the transplanted heart, also known as cardiac allograft vasculopathy, is one of the major causes of mortality late after heart transplantation. This accelerated form of atherosclerosis also affects the donor organs of other transplant recipients including that of liver, kidney and lung. There are multiple immune and non-immune risk factors associated with this disease process, one of which is hyperlipidemia. Use of lipid lowering agents, specifically HMG-CoA reductase inhibitors (statins) was initially reported to have outcomes benefit and possibly immunosuppressive effects in a single center study of heart transplant recipients. Other subsequent studies have supported this beneficial effect.

METHOD AND RESULTS

In a recent paper by Kwak and colleagues, the specific mechanism for this immunosuppressive effect has been elucidated through the use of experiments monitoring cell surface expression assayed by fluorescence-activated cell sorting and by immunofluorescence as well as mRNA levels of major histocompatibility complex class II (MHC-II). They report that statins repress induction of MHC-II by interferon-gamma and that this in turn represses activation of T-lymphocytes and other cell types including primary human smooth muscle cells and fibroblasts, as well as in established cell lines such as ThP1, melanomas, and HeLa cells.

CONCLUSION

In addition to previous clinical and laboratory publications this work by Kwak and colleagues has provided a firm scientific rationale to support the use of statins as adjunct immunosuppressive agents in organ transplantation.

Safety and efficacy of pravastatin therapy for the prevention of hyperlipidemia in pediatric and adolescent cardiac transplant recipients

BACKGROUND

Hyperlipidemia is common after cardiac transplantation and it is a risk factor for post-transplantation coronary artery disease. Immunosuppression with corticosteroids and cyclosporine has been associated with hyperlipidemia. Pravastatin, a HMG-CoA reductase inhibitor, has been shown to be effective and safe for cholesterol reduction in adult heart transplant recipients. To our knowledge the safety and efficacy of pravastatin therapy in pediatric and adolescent heart transplant populations have not been previously analyzed. Therefore, we evaluated lipid profiles, liver transaminases, rejection data, and possible side effects in pediatric and adolescent cardiac transplant recipients treated with pravastatin.

METHODS

The study group consisted of 40 cardiac transplant recipients 10 to 21 years old (mean age 16.9 years). Twenty-two patients received pravastatin in addition to an immunosuppressive regimen of either cyclosporine or tacrolimus, azathioprine or mycophenolate mofetil, and prednisone. Serial determinations of total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein, and triglycerides were available for all pravastatin-treated patients. Pre-treatment lipid values and hepatic transaminases were compared with those measured after therapy with pravastatin. Comparison of pravastatin-induced lipid reduction between groups treated with cyclosporine vs tacrolimus was also made.

RESULTS

Patients receiving pravastatin experienced a mean 32 mg/dl decrease in TC (p < 0.005) and a mean 31 mg/dl decrease in LDL (p < 0.005), regardless of their immunosuppressive regimen. No statistical differences occurred in the magnitude of mean lipid reduction induced by pravastatin between the groups treated with cyclosporine vs tacrolimus. No significant changes in hepatic transaminase levels were noted, and no clinical evidence of pravastatin-induced myositis occurred in any subjects.

CONCLUSION

Pravastatin therapy is effective and safe when used in pediatric and adolescent cardiac transplant recipients. Although the pravastatin-induced reduction in TC and LDL was more pronounced in patients receiving cyclosporine, the reduction was not statistically different from that in the tacrolimus group. No evidence of hepatic dysfunction or rhabdomyolysis in patients treated with pravastatin was noted. Long-term studies are required to evaluate the effect of pravastatin therapy on the incidence of accelerated coronary atherosclerosis in this population.

Morphology and immunohistochemistry of rat aortic grafts

Allotransplantation (TPL) of the abdominal aortic segments of BN donors was performed in 32 Lewis recipients with or without cyclosporin A (CyA) immunosuppression, and the vascular changes were compared to those of 10 syngeneic grafts (Lewis-->Lewis) and to the autologous rat aortae. The vessels were examined 2, 3, 4 and 5 months post TPL by light microscopy, the thickness of intima and media was measured morphometrically and the cell infiltration of adventitia and intima was assessed semiquantitatively. Thirty-six aortae were examined by three-step enzyme immunohistochemistry (proof of selected differentiation, proliferation, cytoskeletal and connective tissue matrix antigens). The adventitia displayed an intense focal and scattered mononuclear cell infiltration; it was more discrete and focal in the intima. This cellularity persisted in the allografts but disappeared from the intima and was reduced in the adventitia of the isografts after four and five months. Disseminated ED1+ activated macrophages were the most prominent population of infiltrates whereas modest numbers of adventitial ED2+ tissue macrophages remained constant throughout the intervals examined. CD4+ cells (focal and scattered) outnumbered (roughly twice) the scattered CD8+ lymphocytes; both these types were rare in the intima. Leukocyte invasion of the media was lacking (except for scarce isolated CD8+ cells in some allografts). In syngeneic grafts the smooth muscle cells (SMC) of media remained intact and the intimal thickening was slight to absent (about 5 microns) four and five months post TPL. On the other hand, the allograft media underwent severe destructive changes (karyolysis, depletion of alpha-SMC actin, focal calcification and general thinning without rupture or aneurysm). The prominent allograft intimal thickening (70-80 microns) was due to the proliferation of longitudinally oriented myointimal cells (alpha-SMC actin, FD2, PCNA and Ki67+) and an increase in matrix substance (strong metachromasia and positivity of chondroitin-sulfate proteoglycan). The deposition of lipids remained discrete, without atheromatous plaques and mural thrombosis. All changes were comparable in CyA-treated and untreated animals. Thus the main lesions of the allografts were (i) persistent mononuclear infiltration chiefly in adventitia, (ii) destruction of medial SMC, and (iii) intimal thickening by proliferation of myointimal cells. At the postTPL intervals examined the proliferation and intimal migration of medial SMC were not apparent and a morphological correlate of significant anti-medial-SMC cytotoxic attack was lacking.

What is the optimal prophylaxis for treatment of cardiac allograft vasculopathy?

Coronary artery disease in the transplanted heart, also known as cardiac allograft vasculopathy (CAV), is one of the major causes of mortality late after transplantation. It affects up to 50% of all heart transplant recipients within 5 years of surgery. The mechanisms of CAV are multifactorial and include both immune and nonimmune factors. Ischemia of the graft at the time of transplantation is one of the more important nonimmune factors, because this leads to endothelial cell injury. Immune factors involving cellular and humoral rejection can further insult the vascular endothelial cell, leading to a cascade of immunologic responses. The optimal treatment prophylaxis for CAV has not been established. The treatment approach to this major post-transplant complication includes modification of risk factors through medical therapies and strategies. The early use of diltiazem and/or pravastatin or simvastatin has been demonstrated to be effective in reducing the development of CAV, but does not completely prevent it. There are many ongoing studies involving newer immunosuppressive agents that may hold promise for the future.

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.