Lovastatin-induced inhibition of renal epithelial tubular cell proliferation involves a p21ras activated, AP-1-dependent pathway

Signaling pathways of chronic kidney diseases, implications for therapeutics

Chronic kidney disease (CKD) is a chronic renal dysfunction syndrome that is characterized by nephron loss, inflammation, myofibroblasts activation, and extracellular matrix (ECM) deposition. Lipotoxicity and oxidative stress are the driving force for the loss of nephron including tubules, glomerulus, and endothelium. NLRP3 inflammasome signaling, MAPK signaling, PI3K/Akt signaling, and RAAS signaling involves in lipotoxicity. The upregulated Nox expression and the decreased Nrf2 expression result in oxidative stress directly. The injured renal resident cells release proinflammatory cytokines and chemokines to recruit immune cells such as macrophages from bone marrow. NF-κB signaling, NLRP3 inflammasome signaling, JAK-STAT signaling, Toll-like receptor signaling, and cGAS-STING signaling are major signaling pathways that mediate inflammation in inflammatory cells including immune cells and injured renal resident cells. The inflammatory cells produce and secret a great number of profibrotic cytokines such as TGF-β1, Wnt ligands, and angiotensin II. TGF-β signaling, Wnt signaling, RAAS signaling, and Notch signaling evoke the activation of myofibroblasts and promote the generation of ECM. The potential therapies targeted to these signaling pathways are also introduced here. In this review, we update the key signaling pathways of lipotoxicity, oxidative stress, inflammation, and myofibroblasts activation in kidneys with chronic injury, and the targeted drugs based on the latest studies. Unifying these pathways and the targeted therapies will be instrumental to advance further basic and clinical investigation in CKD.

Cholesterol, Cytokines and Diseases

A high level of cholesterol is associated with obesity, cardiovascular diseases and atherosclerosis. Immune response in atherosclerosis is mediated by chemokines which attract monocytes, leading to the innate immune response characterised by the production of cytokines. The immunoregulatory cytokines are an important bridge between innate and adductive immunity. TH1 cytokines are involved as effector T cells in inflammatory response, while TH2 cytokines can be anti-inflammatory such as IL-10 and IL-4. It is well known that statins enhance the production of TH2 cytokines whereas the secretion of TH1 cytokines is suppressed. For this purpose, we studied the significance of anti-inflammatory effect and suppression of inflammation by statins. In this paper we revisited the role of cholesterol and cytokines IL-18, IL-10, IL-12, TNF-α, interferon-γ, and chemokines in inflammatory diseases.

New pharmacological treatments for improving renal outcomes in diabetes

Diabetic nephropathy is the most common and most rapidly growing cause of end-stage renal failure in developed countries. Diabetic nephropathy results from complex interactions between genetic, metabolic and hemodynamic factors. Improvements in our understanding of the pathogenesis of fibrosis associated with diabetic kidney disease have led to the identification of several novel targets for the treatment of diabetic nephropathy. Albuminuria is a useful clinical marker of diabetic nephropathy, as it can be used to predict a decline in renal function. A reduction in albuminuria might not, however, be reflective of a protective effect of therapies focused on ameliorating renal fibrosis. Although new strategies for slowing down the progression of several types of renal disease have emerged, the challenge of arresting the relentless progression of diabetic nephropathy remains. In this Review, we discuss novel pharmacological approaches that aim to improve the renal outcomes of diabetic nephropathy, including the use of direct renin inhibitors and statins. We also discuss the promise of using antifibrotic agents to treat diabetic nephropathy. The need for novel biomarkers of diabetic nephropathy is also highlighted.

Human TMEM174 that is highly expressed in kidney tissue activates AP-1 and promotes cell proliferation

Mitogen-activated protein kinase (MAPK) cascades play an important role in regulation of AP-1 activity through the phosphorylation of distinct substrates. In the present study, we identified a novel protein, TMEM174, whose RNA transcripts are highly expressed in human kidney tissue. TMEM174 is comprised of 243 amino acids, and contains two predicted transmembrane helices which determine its subcellular localization in endoplasmic reticulum and influences its functions. Over-expression of TMME174 enhanced the transcriptional activity of AP-1 and promoted cell proliferation, whereas the truncated mutant TMEM174DeltaTM without the transmembrane regions did not retain these functions. The possible mechanism of activation of AP-1 by TMEM174 was further examined. Our results suggest the potential role of TMEM174 in renal development and physiological function.

Statins and congestive heart failure

Despite many post hoc analyses of cardiovascular databases in recent years suggesting a benefit of statins in the prevention and treatment of congestive heart failure (HF), a prospective study of statin therapy on two clinically relevant end points--HF morbidity and survival--had not been reported until 2007. However, a large-scale prospective trial, Controlled Rosuvastatin Multinational Trial in Heart Failure (CORONA), has just reported its primary results. These results somewhat surprisingly show no survival benefit in a group of patients with ischemic systolic HF given low-dose rosuvastatin. In addition to this uncertainty generated by the results of CORONA, there remains additional uncertainty in the existing, predominantly retrospective data on statins because of the potential bias in study designs, use of post hoc subgroup analyses, and lack of mechanistic data. This review critically evaluates the recent literature in this area.

Biphasic regulation of HMG-CoA reductase expression and activity during wound healing and its functional role in the control of keratinocyte angiogenic and proliferative responses

In this study, we determined the regulation and potential function of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (HMGR) during skin repair in mice. Upon skin injury, healthy mice exhibited a biphasic increase in HMGR expression and activity with elevated levels at days 3 and 13 post-wounding. In situ hybridization revealed wound margin keratinocytes as a cellular source of HMGR expression. In vitro experiments using cultured HaCaT keratinocytes uncovered epidermal growth factor (EGF), transforming growth factor (TGF)-alpha, and insulin as potent co-inducers of HMGR activity and vascular endothelial growth factor (VEGF) in the cells. Insulin-, but not EGF-mediated VEGF protein expression was functionally connected to co-induced HMGR activity, as simvastatin restrictively interfered only with insulin-induced translation of VEGF mRNA by inhibition of eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) phosphorylation. Functional ablation of insulin-induced sterol regulatory element-binding protein (SREBP)-2 by siRNA abolished HMGR expression and insulin-triggered VEGF protein release from keratinocytes. Simvastatin also blocked proliferation of cultured keratinocytes. The observed inhibitory effects of simvastatin on keratinocyte VEGF expression and proliferation could be reversed by mevalonate, the product of HMGR enzymatic activity. In accordance, simvastatin-mediated inhibition of HMGR activity in acutely regenerating tissue of wounded mice was paralleled by a marked loss of VEGF protein expression and disturbances of normal proliferation processes in wound margin keratinocytes during skin repair.

Multiorgan-protective actions of blockers of the renin-angiotensin system, statins and erythropoietin: common pleiotropic effects in reno-, cardio- and neuroprotection

Renal diseases induce nephroprotective measures that may affect the heart, brain and other organs. In addition, many cardiovascular and neurological diseases are accompanied by renal lesions. For these reasons, multiorgan-protective measures, including cardio-, reno- and neuro-protective measures, are necessary to treat these diseases. The drugs used in nephrology are often pleiotropic. Although they usually address a single organ or tissue, many of them have complex actions that may provide multiorgan-protection. The present paper aims to review 3 classes of drugs that are commonly prescribed in nephrological practice: statins, RAS blockers (such as ACEIs and ARBs) and erythropoietin (EPO). This paper highlights the renoprotective actions, as well as those that are protective of the heart, brain and other organs, of these drugs at the cellular and molecular level. Their protective actions are attributable to their main effects and pleiotropic effects. The protective pleiotropic actions of these drugs may be exerted on multiple organs, making them multiorgan-protective. Another objective is to analyse the shared multiorgan-protective pleiotropic effects of RAS blockers (ACEIs and ARBs), statins and erythropoietin. This will allow for the practical association of the main renoprotective drugs with multiorgan protection.

Rapamycin for treatment of refractory dysthyroid compressive optic neuropathy

We report a patient with dysthyroid optic neuropathy refractory to steroids and orbital decompression treated with rapamycin, a fibroblast and T cell inhibitor. Symptoms, visual acuity, color plate testing, and visual fields improved. Aside from hypercholesterolemia, no complication related to this therapy was observed. By addressing the pathogenesis of thyroid eye disease, rapamycin may represent an alternative when standard treatments fail. Further investigation of rapamycin for treatment of dysthyroid orbitopathy is warranted.

Statins and clinical outcomes in heart failure

HMG-CoA (3-hydroxy-3-methylglutaryl-CoA) reductase inhibitors (statins) are well-established therapies in the prevention and treatment of cardiovascular disease, reducing all-cause mortality and cardiovascular events in many disease states. Studies have also suggested that statins given to patients after myocardial infarction improve event-free survival even in short time frames; however, evidence for the benefit of statins in established HF (heart failure) has not been demonstrated with the same rigour of a randomized clinical trial setting. In fact, clinical data examining the effect of statins in HF have been limited by the retrospective or observational nature of these analyses, examination of incompletely validated surrogate end points, small prospective studies in subgroups of HF subjects, and non-uniform doses and different statins being used. In this review, we examine the evidence for the effect of statins on mortality in HF, taking into account theoretical arguments, appropriateness of surrogate markers, animal data and analysis of the predominantly retrospective clinical data that is currently available.

HMG-CoA reductase inhibitors and the kidney

During the last two decades, numerous studies have demonstrated that 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) diminish the risk of cardiovascular morbidity and mortality. Although these studies have focused primarily on the ability of statins to lower circulating levels of low-density lipoprotein cholesterol, more recent research has shown that statins may protect the vasculature via pleiotropic effects not directly related to lipid lowering. These include adjustments in cell-signaling pathways that play a role in atherogenesis and that affect the expression of inflammatory elements, curtail oxidative stress, and enhance endothelial function. More recently, researchers have begun to explore whether these agents exert similar beneficial effects in renal parenchymal and renovascular disease. This review examines the available evidence that dyslipidemia may augment the inflammatory reaction of cytokines in patients with renal disease and that statins may improve renal dysfunction by altering the response of the kidney to dyslipidemia, even in persons with end-stage renal disease on dialysis or with renal transplantation. In this context, some data suggest that statin-mediated alterations in inflammatory responses and endothelial function may reduce proteinuria and the rate of progression of kidney disease.

Statins and renal diseases: from primary prevention to renal replacement therapy

In glomerular diseases with nephrotic syndrome or protracted severe proteinuria, alterations of the lipid metabolism occur and are characterized mainly by increase of LDL cholesterol and frequently also of triglycerides and by qualitative abnormalities of HDL cholesterol and LDL cholesterol. In all renal diseases, when renal insufficiency develops, hyperlipidemia also occurs, with a near-elective increase in VLDL and intermediate-density lipoprotein cholesterol and a decrease of mature HDL cholesterol. There is clear evidence that these abnormalities may induce cardiovascular complications and, probably, also an accelerated progression of the renal damage. The inhibitors of 3-hydroxy-3-methylglutaryl CoA reductase, the so-called statins, are effective in controlling hypercholesterolemia, even in the more advanced stages of renal failure and in patients who are on maintenance dialysis. This antilipidemic effect of statins combines with other effects--antioxidant, anti-inflammatory, immunomodulatory, and antithrombotic (called "pleiotropic" effects)--as a result of the inhibition of the mevalonate pathway induced by these agents. Also because of these non-lipid-dependent effects, statins could have an antiatherosclerotic and renoprotective effect, which has been demonstrated clearly in vivo on renal cells and in experimental models of nephropathy but is still less evident in human renal diseases. Ongoing large trials will establish more clearly whether such effects are present in renal patients.

Statins in nephrotic syndrome: a new weapon against tissue injury

The nephrotic syndrome is characterized by metabolic disorders leading to an increase in circulating lipoproteins levels. Hypertriglyceridemia and hypercholesterolemia in this case may depend on a reduction in triglyceride-rich lipoproteins catabolism and on an increase in hepatic synthesis of Apo B-containing lipoproteins. These alterations are the starting point of a self-maintaining mechanism, which can accelerate the progression of chronic renal failure. Indeed, hyperlipidemia can affect renal function, increase proteinuria and speed glomerulosclerosis, thus determining a higher risk of progression to dialysis. 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase is the rate-limiting enzyme in cholesterol synthesis from mevalonate and its inhibitors, or statins, can therefore interfere with the above-mentioned consequences of hyperlipidemia. Statins are already well known for their effectiveness on primary cardiovascular prevention, which cannot be explained only through their hypolipemic effect. As far as kidney diseases are concerned, statin therapy has been shown to prevent creatinine clearance decline and to slow renal function loss, particularly in case of proteinuria, and its favorable effect may depend only partially on the attenuation of hyperlipidemia. Statins may therefore confer tissue protection through lipid-independent mechanisms, which can be triggered by other mediators, such as angiotensin receptor blockers. Possible pathways for the protective action of statins, other than any hypocholesterolemic effect, are: cellular apoptosis/proliferation balance, inflammatory cytokines production, and signal transduction regulation. Statins also play a role in the regulation of the inflammatory and immune response, coagulation process, bone turnover, neovascularization, vascular tone, and arterial pressure. In this study, we would like to provide scientific evidences for the pleiotropic effects of statins, which could be the starting point for the development of new therapeutical strategies in different clinical areas.

Effect of pitavastatin on urinary liver-type fatty-acid-binding protein in patients with nondiabetic mild chronic kidney disease

BACKGROUND/AIM

Urinary liver-type fatty-acid-binding protein (L-FABP) is a useful clinical marker in the monitoring of chronic kidney disease (CKD) associated with tubulointerstitial damage. Statins have been shown to be effective in the treatment of renal disease. The aim of the present study was to determine whether pitavastatin, a newly developed statin, modulates the urinary L-FABP levels in normolipidemic patients with CKD.

METHODS

Thirty normolipidemic mild CKD patients (18 males and 12 females, mean age 40 years, mean serum creatinine level 1.0 mg/dl) were randomly assigned to two groups: (1) pitavastatin (1 mg/day, n = 15) and (2) placebo (n = 15). Urinary protein and urinary L-FABP levels were measured before the initiation of treatment and 3 and 6 months thereafter. Twenty age-matched healthy subjects were also studied as controls.

RESULTS

Before treatment, the urinary L-FABP levels in 30 CKD patients (84.0 +/- 68.5 microg/g creatinine) were significantly higher than those of healthy subjects (6.4 +/- 4.2 mug/g creatinine; p < 0.001). Pitavastatin slightly reduced serum total cholesterol and triglyceride levels, but this was not statistically significant. However, pitavastatin reduced the urinary protein excretion from 1.8 to 1.0 g/day (p < 0.01), while the urinary L-FABP levels fell from 88.5 +/- 70.5 to 28.0 +/- 16.5 mug/g creatinine (p < 0.01).

CONCLUSION

The present data suggest that pitavastatin ameliorates tubulointerstitial damage in CKD patients independent of the lipid-lowering effect.

Therapeutics in renal disease: the road ahead for antiproliferative targets

Discovery into the molecular basis of renal disease is occurring at an unprecedented rate. With the advent of the NIH Roadmap, there is a greater expectation of translating this knowledge into new treatments. Here, we review the therapeutic strategy to preserve renal function in proliferative renal diseases by directly inhibiting the mitogenic pathways within renal parenchymal cells that promote G0 to G1/S cell-cycle phase progression. Reductionist methodologies have identified several antiproliferative molecular targets, and promising preclinical testing of leading small-molecule drugs to modulate these targets has now led to landmark clinical trials. Yet, this advancement into targeted therapy highlights important differences between the therapeutic goals of molecular nephrology versus molecular oncology and, by extension, the poorly understood role of alternative target activity in drug efficacy. Systems research to clarify these issues should accelerate the development of this promising therapeutic strategy.

Pleiotropic effects of 3-hydroxy-3-methylglutaryl coenzyme a reductase inhibitors on renal function

Pleiotropic, or non-lipid-dependent, effects mediated by 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) have important clinical implications for the cardiovascular (CV) system. Atherosclerosis is an inflammatory process accompanied by increases in levels of plasma inflammatory markers and accumulation of immune cells within atherosclerotic plaques. Statins not only decrease serum lipid levels, but also inhibit signaling molecules at several points in inflammatory pathways. The anti-inflammatory effects and improved endothelial function associated with statin therapy are thought to be partly responsible for the reduction in CV morbidity and mortality. In analogy, patients with chronic kidney disease administered statins for CV risk reduction show evidence of improved renal function. However, whether statins confer similar protective benefits on the kidney has not been established. Several lines of evidence suggest that similar etiologic and pathological processes may be involved in CV and chronic kidney diseases. If inflammation and functional changes in the renovascular endothelium contribute to the progression of kidney disease, statins are likely to be effective in the treatment of renal disease. In this review, we critically consider emerging data indicating that statins may modulate renal function by altering the inflammatory response of the kidney and renal vasculature to dyslipidemia. Whether the amelioration of renal function by statins is separable from the lipid-lowering effects of these drugs still remains to be delineated. Other questions that remain to be addressed and issues that should be investigated also are presented.

HMG-CoA reductase inhibitors and the kidney

HMG-CoA (3-hydroxy-3-methylglutaryl-CoA) reductase inhibitors (statins) have been shown to reduce serum cholesterol and cardiovascular morbidity and mortality. The mechanisms of these beneficial effects are reviewed. Altered inflammatory responses and improved endothelial function mediated by statins are thought to be, in part, responsible for the reduction in cardiovascular events. It has not been well established whether statins confer similar benefits to the kidney. In this review, we critically consider the available data whereby dyslipidemia mediates renal dysfunction by modulating the inflammatory response to diverse cytokines. We also review the emerging database suggesting that statins may modulate renal dysfunction by altering the response of the kidney to dyslipidemia, particularly in patients with end-stage renal disease (ESRD) and post-kidney transplant.

Are 3-Hydroxy-3-Methylglutaryl-CoA Reductase Inhibitors Renoprotective?: Table 1

Statins reduce serum cholesterol and cardiovascular morbidity and mortality. The mechanisms for these beneficial effects are reviewed. Altered inflammatory responses and improved endothelial function mediated by statins are thought to be partly responsible for the reduction of morbidity and mortality as a result of cardiovascular events. In analogy, whether statins confer similar benefits on the kidney has not been established. This review critically considers the available data whereby dyslipidemia mediates renal dysfunction by modulating the inflammatory response to diverse cytokines. Also reviewed is the emerging database indicating that statins may modulate renal function by altering the response of the kidney to dyslipidemia.

The role of lipids in the development of diabetic microvascular complications: implications for therapy

Dyslipidemia is a major factor responsible for coronary heart disease and its reduction decreases coronary risk in patients with diabetes mellitus. However, the association of dyslipidemia with microvascular complications and the effect of intervention with lipid-lowering therapy in diabetes have been less investigated. We present the systematic review of association and intervention studies pertaining to dyslipidemia and microvascular disease in diabetes and also review possible mechanisms. Dyslipidemia may cause or exacerbate diabetic retinopathy and nephropathy by alterations in the coagulation-fibrinolytic system, changes in membrane permeability, damage to endothelial cells and increased atherosclerosis. Hyperlipidemia is associated with faster decline in glomerular filtration rate and progression of albuminuria and nephropathy. Recent evidence also suggests a role of lipoprotein(a) in progression of retinopathy and nephropathy in patients with diabetes mellitus. Lipid-lowering therapy, using single agents or a combination of drugs may significantly benefit diabetic retinopathy and diabetic nephropathy. In particular, hydroxymethyl glutaryl coenzyme A reductase inhibitors may be effective in preventing or retarding the progression of microvascular complications because of their powerful lipid-lowering effects and other additional mechanisms. However, most of the data are based on short-term studies, and need to be ascertained in long-term studies. Until more specific guidelines are available, aggressive management of diabetic dyslipidemia, according to currently accepted guidelines, should be continued for the prevention of macrovascular disease which would also benefit microvascular complications.

Studies of the isoprenoid-mediated inhibition of mevalonate synthesis applied to cancer chemotherapy and chemoprevention

Pools of farnesyl diphosphate and other phosphorylated products of the mevalonate pathway are essential to the post-translational processing and physiological function of small G proteins, nuclear lamins, and growth factor receptors. Inhibitors of enzyme activities providing those pools, namely, 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase and mevalonic acid-pyrophosphate decarboxylase, and of activities requiring substrates from the pools, the prenyl protein transferases, have potential for development as novel chemotherapeutic agents. Their potentials as suggested by the clinical responses recorded in Phase I and II investigations of inhibitors of HMG CoA reductase (the statins), of mevalonic acid-pyrophosphate decarboxylase (sodium phenylacetate and sodium phenylbutyrate), and of farnesyl protein transferase (R115777, SCH66336, BMS-214662, Tipifarnib, L-778,123, and, prematurely, perillyl alcohol) are dimmed by dose-limiting toxicities. These nondiscriminant growth-suppressive agents induce G1 arrest and initiate apoptosis and differentiation, effects attributed to modulation of cell signaling pathways either by modulating gene expression, suppressing the post-translational processing of signaling proteins and growth factor receptors, or altering diacylglycerol signaling. Diverse isoprenoids and the HMG CoA reductase inhibitor, lovastatin, modulate cell growth, induce cell cycle arrest, initiate apoptosis, and suppress cellular signaling activities. Perillyl alcohol, the isoprenoid of greatest clinical interest, initially was considered to inhibit farnesyl protein transferase; follow-up studies revealed that perillyl alcohol suppresses the synthesis of small G proteins and HMG CoA reductase. In sterologenic tissues, sterol feedback control, mediated by sterol regulatory element binding proteins (SREBPs) 1a and 2, exerts the primary regulation on HMG CoA reductase activity at the transcriptional level. Secondary regulation, a nonsterol isoprenoid-mediated fine-tuning of reductase activity, occurs at the levels of reductase translation and degradation. HMG CoA reductase activity in tumors is elevated and resistant to sterol feedback regulation, possibly as a consequence of aberrant SREBP activities. Nonetheless, tumor reductase remains sensitive to isoprenoid-mediated post-transcriptional downregulation. Farnesol, an acyclic sesquiterpene, and farnesyl homologs, gamma-tocotrienol and various farnesyl derivatives, inhibit reductase synthesis and accelerate reductase degradation. Cyclic monoterpenes, d-limonene, menthol and perillyl alcohol and beta-ionone, a carotenoid fragment, lower reductase mass; perillyl alcohol and d-limonene lower reductase mass by modulating translational efficiency. The elevated reductase expression and greater demand for nonsterol products to maintain growth amplify the susceptibility of tumor reductase to isoprenoids, therein rendering tumor cells more responsive than normal cells to isoprenoid-mediated growth suppression. Blends of lovastatin, a potent nondiscriminant inhibitor of HMG CoA reductase, and gamma-tocotrienol, a potent isoprenoid shown to post-transcription-ally attenuate reductase activity with specificity for tumors, synergistically affect the growth of human DU145 and LNCaP prostate carcinoma cells and pending extensive preclinical evaluation, potentially offer a novel chemotherapeutic strategy free of the dose-limiting toxicity associated with high-dose lovastatin and other nondiscriminant mevalonate pathway inhibitors.

Pitavastatin, a Potent Hydroxymethylglutaryl Coenzyme a Reductase Inhibitor, Increases Cholesterol 7 .ALPHA.-Hydroxylase Gene Expression in HepG2 Cells

BACKGROUND

The effect of pitavastatin on the mRNA levels of apolipoprotein (apo) A-I, peroxisome proliferator-activated receptor alpha (PPARalpha), cholesterol 7alpha-hydroxylase (CYP7A1), and farnesoid X receptor (FXR) in HepG2 cells was examined to establish whether pitavastatin affects bile acid synthesis and if so, to determine a possible molecular mechanism.

METHODS AND RESULTS

HepG2 cells were cultured in serum-free Dulbecco's modified Eagle medium for 18 h before drug treatment. Total RNA was extracted at set times and mRNA levels were quantified by reverse transcription-real time polymerase chain reaction. Pitavastatin at 0.1, 1, 5, and 10 micromol/L increased the mRNA levels of apo A-I, PPARalpha, CYP7A1, and FXR in a dose-dependent manner. The mRNA levels of apo A-I, PPAR alpha, CYP7A1, and FXR similarly increased with increasing doses of pitavastatin. Coincubation of mevalonate (4 mmol/L) with pitavastatin (5 micromol/L) reversed the inductive effects of pitavastatin on the mRNA levels of these genes, indicating that the inductive effects of pitavastatin were related to its inhibition of HMG-CoA reductase.

CONCLUSIONS

Pitavastatin increased the mRNA levels of CYP7A1 in HepG2 cells, suggesting that increased conversion of cholesterol to bile acids may be the mechanism for its potent low-density lipoprotein cholesterol-lowering effects.

Association of dyslipidemia and effects of statins on nonmacrovascular diseases

BACKGROUND

Statins have mechanisms of action that expand their effects beyond cholesterol lowering and atherosclerotic medical conditions.

OBJECTIVE

This review summarizes clinical evidence for the association of dyslipidemia and the effects of statin use on aortic stenosis, Alzheimer's dementia (AD), osteoporosis, prevention of diabetes mellitus (DM), diabetic retinopathy, age-related macular degeneration, and diabetic/nondiabetic nephropathy.

METHODS

An English-language literature search was conducted using MEDLINE (1966-June 2003). Bibliographies of retrieved articles were reviewed. Search terms included statin, HMG-CoA reductase inhibitors, aortic stenosis, Alzheimer's dementia, osteoporosis, prevention of diabetis, diabetic retinopathy, age-related macular degeneration, diabetic nephropathy, and nondiabetic nephropathy.

RESULTS

Three retrospective cohort trials have shown an association between statin use and the progression of aortic stenosis; one of these trials observed a 45% decrease in aortic valve area in 1 year. In AD, one cross-sectional analysis found 60% to 73% lower AD rates in lovastatin or pravastatin recipients ( P<0.001 ). Of the multiple observational studies on the effect of statins on fracture risk, some have shown a decreased risk, with an odds ratio as low as 0.50 (95% CI, 0.33-0.76); others have demonstrated no association. A post hoc analysis of the West of Scotland Coronary Prevention Study found a 30% reduction in the development of DM ( P=0.042 ), but this was not duplicated in the Anglo-Scandinavian Cardiac Outcomes Trial-Lipid Lowering Arm. A small clinical trial of 6 patients (11 eyes) demonstrated improved retinal hard exudates with pravastatin treatment in patients with diabetic retinopathy. In a cross-sectional analysis, age-related macular degeneration was found to be less common among statin users than nonusers (4% [ 1/27 ] vs 22% [ 76/352 ]; P=0.02. Multiple small clinical trials of 19 to 56 patients with diabetic and nondiabetic nephropathy at various stages generated inconsistent results for an association between statin use and decreased albumin excretion rate and decreased rate of decline in glomerular filtration.

CONCLUSION

Data of variable quantity and quality support the use of statins as adjuncts in the treatment of nonmacrovascular diseases.

Drug Therapy in Transplant Recipients

Elderly patients with end-stage organ failure are now more frequently undergoing transplantation. Medication management in this population is challenging because of the combination of multiple comorbidities, polypharmacy, and immunological, pharmacokinetic and pharmacodynamic changes attributable to the aging process. Immunosuppressive medications can exacerbate pre-existing medical conditions and promote the development of disease processes. Cardiovascular disorders, such as hypertension, coronary artery disease, congestive heart failure and arrhythmias are common in elderly transplant recipients, and account for most of the deaths in this population. Blood pressure, blood glucose and cholesterol control is of particular concern because elderly transplant recipients frequently have or develop these complications. Elderly transplant recipients are commonly receiving anticoagulation therapy with warfarin and are at a higher risk of bleeding, especially if they have renal dysfunction. Infectious complications occur frequently in the transplanted population, with pneumonia being the most common infection seen in hospitalised patients. Attention to vaccination for the prevention of influenza and pneumococcal infections is important because of the increased risk of these diseases in this population. Depression itself has been associated with decreased survival in older individuals, and depression in elderly transplant recipients may be reversible with the administration of pharmacological agents. Effective long-term care of transplant recipients demands an understanding of how particular medications affect clinical evaluation and treatment. This article addresses some of the practical issues surrounding medication management and prevention of these particular problems in elderly transplant recipients.

Induction of connective tissue growth factor by angiotensin II: integration of signaling pathways

OBJECTIVE

Angiotensin II is recognized as one of the major mediators of cardiovascular pathology. Because connective tissue growth factor (CTGF) is involved in the pathophysiologic processes underlying fibrotic diseases, its regulation by angiotensin II was investigated.

METHODS AND RESULTS

In the 2-kidney, 1-clip model of renovascular hypertension, increased expression of CTGF was detectable in the hypertrophic left ventricle. By activation of angiotensin II type 1 receptors, angiotensin II caused rapid expression of CTGF mRNA and protein in a human fibroblast cell line. Activation of the p42/44 mitogen-activated protein (MAP) kinase signaling pathway proved to be essential for angiotensin II-stimulated CTGF expression. Inhibition of MAP kinase activation by forskolin prevented CTGF induction. Inhibition of the isoprenylation of small GTPases by simvastatin or pretreatment of the cells with toxin B reduced basal CTGF expression below detection limits and prevented induction by angiotensin II. Specific interference with RhoA signaling by Y27632 primarily reduced basal CTGF expression. There was no significant reduction of expression of angiotensin II type 1 receptors by simvastatin. These data indicate cooperation between the Rho signaling and the angiotensin II-activated MAP kinase pathways.

CONCLUSIONS

Direct induction of CTGF by angiotensin II is indicative of a role for CTGF in angiotensin II-mediated fibrosis and might be a target of antifibrotic interventions.

Simvastatin rescues rats from fatal pulmonary hypertension by inducing apoptosis of neointimal smooth muscle cells

BACKGROUND

Pulmonary vascular injury by toxins can induce neointimal formation, pulmonary arterial hypertension (PAH), right ventricular failure, and death. We showed previously that simvastatin attenuates smooth muscle neointimal proliferation and pulmonary hypertension in pneumonectomized rats injected with the alkaloid toxin monocrotaline. The present study was undertaken to investigate the efficacy of simvastatin and its mechanism of reversing established neointimal vascular occlusion and pulmonary hypertension.

METHODS AND RESULTS

Pneumonectomized rats injected with monocrotaline at 4 weeks demonstrated severe PAH at 11 weeks (mean pulmonary artery pressure [mPAP]=42 versus 17 mm Hg in normal rats) and death by 15 weeks. When rats with severe PAH received simvastatin (2 mg x kg(-1) x d(-1) by gavage) from week 11, there was 100% survival and reversal of PAH after 2 weeks (mPAP=36 mm Hg) and 6 weeks (mPAP=24 mm Hg) of therapy. Simvastatin treatment reduced right ventricular hypertrophy and reduced proliferation and increased apoptosis of pathological smooth muscle cells in the neointima and medial walls of pulmonary arteries. Longitudinal transcriptional profiling revealed that simvastatin downregulated the inflammatory genes fos, jun, and tumor necrosis factor-alpha and upregulated the cell cycle inhibitor p27Kip1, endothelial nitric oxide synthase, and bone morphogenetic protein receptor type 1a.

CONCLUSIONS

Simvastatin reverses pulmonary arterial neointimal formation and PAH after toxic injury.

Inhibition of pancreatic stellate cell activation by the hydroxymethylglutaryl coenzyme A reductase inhibitor lovastatin

Pancreatic stellate cells (PSCs) play a key role in pancreatic fibrosis, a constant feature of chronic pancreatitis. PSC activation occurs in response to profibrogenic mediators such as cytokines and involves proliferation, transition towards a myofibroblastic phenotype and enhanced production of extracellular matrix proteins. Previously, we have shown that PSC activation correlates with the activity of the Ras-Raf-ERK (extracellular signal-regulated kinase) signalling cascade [Gut 51 (2002) 579]. Using a rat culture model of PSCs, we have now evaluated the effects of lovastatin, a hydroxymethylglutaryl coenzyme A reductase inhibitor that interferes with protein isoprenylation, on PSC viability and activation as well as on signalling through Ras proteins. Apoptotic cells were detected applying the TUNEL assay. Proliferation of PSCs was quantitated using the bromodeoxyuridine DNA incorporation assay. Expression of alpha-smooth muscle actin (an indicator of the myofibroblastic phenotype), ERK activation and membrane translocation of the Ras superfamily member RhoA were analysed by immunoblotting. Lovastatin inhibited serum- and platelet-derived growth factor-stimulated PSC proliferation in a dose-dependent manner. At drug concentrations above the level required for growth inhibition, a strong increase of apoptotic cells was observed. Furthermore, lovastatin inhibited induction of alpha-smooth muscle actin expression in the course of primary culture. Immunoblot experiments indicated that lovastatin suppressed both Ras-mediated ERK 1/2 activation and platelet-derived growth factor-induced membrane translocation of RhoA. Together, our data suggest that lovastatin, through the interruption of Ras signalling, interferes with PSC activation. The antifibrotic efficiency of statins should be tested in animal models of chronic pancreatitis.

A controlled, prospective study of the effects of atorvastatin on proteinuria and progression of kidney disease

BACKGROUND

Chronic kidney diseases, particularly if presenting with significant proteinuria, are commonly associated with substantial alteration of serum lipid levels. Experimental evidence suggests that lipid abnormalities may contribute to the progression of kidney disease. However, studies in humans on the subject are scarce.

METHODS

In a prospective, controlled open-label study, the authors have evaluated the effects of one-year treatment with atorvastatin, a 3-hydroxy-3-methyglutaryl coenzyme A (HMG-CoA) reductase inhibitor, versus no treatment on proteinuria and progression of kidney disease in 56 patients with chronic kidney disease. Before randomization, all patients had already been treated for one year with angiotensin-converting enzyme (ACE) inhibitors or angiotensin AT1 receptor antagonists (ARBs) and other antihypertensive drugs.

RESULTS

By the end of one-year treatment, urine protein excretion decreased from 2.2 +/- 0.1 to 1.2 +/- 1.0 g every 24 hours (P < 0.01) in patients treated with atorvastatin in addition to ACE inhibitor and ARBs. By contrast, urinary protein excretion decreased only from 2.0 +/- 0.1 to 1.8 +/- 0.1 g every 24 hours (P value not significant) in patients who did not receive atorvastatin in addition to ACE inhibitor or ARBs. During this time, creatinine clearance decreased only slightly and not significantly (from 51 +/- 1.8 to 49.8 +/- 1.7) in patients treated with atorvastatin. By contrast, during the same period of observation, creatinine clearance decreased from 50 +/- 1.9 to 44.2 +/- 1.6 mL/min (P < 0.01) in patients who did not receive atorvastatin.

CONCLUSIONS

This study has shown that treatment with atorvastatin in addition to a regimen with ACE inhibitors or ARBs may reduce proteinuria and the rate of progression of kidney disease in patients with chronic kidney disease, proteinuria, and hypercholesterolemia. The benefits appear to occur in addition to those of treatment with ACE inhibitor and ARBs.

Anti-inflammatory and immunomodulatory effects of statins

Anti-inflammatory and immunomodulatory effects of statins. 3-Hydroxy-3-methyl-gutaryl coenzyme A (HMG-CoA) reductase inhibitors or statins constitute the most powerful class of lipid-lowering drugs. Clinical trials have demonstrated a marked reduction in cardiovascular mortality in patients treated with statins. However, the benefits observed with statin therapy appear to be related, at least in part, with their cholesterol-lowering independent effects. Extensive research carried out mainly in the last decade suggests that the clinical benefits of these drugs could be related to an improvement in endothelial dysfunction, a reduction in blood thrombogenicity, anti-inflammatory properties, and, recently, immunomodulatory actions. In this sense, statins decrease T cell activation, the recruitment of monocytes and T cells into the arterial wall, and enhance the stability of atherosclerotic lesions. Many of these effects are related with the inhibition of isoprenoid synthesis, which serve as a lipid attachment for a variety of proteins implicated in intracellular signaling. In fact, small G proteins, whose proper membrane localization and function are dependent on isoprenylation, may play an important role in the lipid-lowering independent effects of HMG-CoA reductase inhibitors. This article summarizes the anti-inflammatory and immunomodulatory effects of statins and their participation in the different steps of atherosclerotic lesion formation.

HMG-CoA reductase inhibitors regulate inflammatory transcription factors in human endothelial and vascular smooth muscle cells

OBJECTIVE

Pleiotropic atheroprotective effects of HMG-CoA reductase inhibitors may be mediated on the level of vascular gene transcription. The aim of this study was to characterize the effects of statins on the activation of transcription factors known to regulate inflammation and cell proliferation/differentiation.

METHODS AND RESULTS

Simvastatin, atorvastatin, and lovastatin (0.1 to 10 micro mol/L) inhibited the binding of nuclear proteins to both the nuclear factor-kappa B (NF-kappaB) and activator protein-1 (AP-1) DNA consensus oligonucleotides in human endothelial and vascular smooth muscle cells as assessed by electrophoretic mobility shift assay (EMSA). The inhibitory effects of statins on NF-kappaB or AP-1-dependent transcriptional activity were examined by transient transfection studies. HMG-CoA reductase inhibitors upregulated IkappaB-alpha protein levels in endothelial cells and decreased c-Jun mRNA expression in smooth muscle cells as analyzed by Western and Northern blotting, respectively. Furthermore, statins inhibited DNA binding of hypoxia-inducible factor-1alpha. Downstream effects of statins included inhibition of plasminogen activator inhibitor-1 and vascular endothelial growth factor-A mRNA levels in endothelial cells.

CONCLUSIONS

HMG-CoA reductase inhibitors downregulate the activation of transcription factors NF-kappaB, AP-1, and hypoxia-inducible factor-1alpha. These findings support the concept that statins have antiinflammatory and antiproliferative effects that are relevant in the treatment of atherosclerotic diseases.

Effect of combining ACE inhibitor and statin in severe experimental nephropathy

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitor therapy given soon after disease induction uniformly prevents proteinuria in virtually all models of disease progression. This does not necessarily apply to patients with proteinuric nephropathies, who might be referred late in the course of their disease. Here we used a severe rat model of passive Heymann nephritis (PHN), which may mimic advanced phases of human membranous nephropathy, to study the response to ACE inhibitor alone or in combination with a HMG CoA reductase inhibitor (statin) that independently of the cholesterol-lowering effect influences pathways involved in inflammatory and fibrogenic processes. Therapies started when animals had massive proteinuria and renal lesions.

METHODS

PHN was accelerated by uninephrectomy seven days after IV injection of rabbit anti-FX1A antibody. Four months later, when massive proteinuria and renal lesions were present, the rats were divided into five groups and daily given orally: vehicle; lisinopril 40 mg/L; lisinopril 400 mg/L; simvastatin 2 mg/kg b.i.d; or lisinopril 40 mg/L plus simvastatin. Six normal rats served as controls. Animals were sacrificed at 10 months.

RESULTS

By the end of the study three PHN rats died in the vehicle group, four in the group given lisinopril at 40 mg/L and two in the group at 400 mg/L, whereas all rats on simvastatin or combined therapy were alive. Blood pressure increased during time in PHN and was normalized by treatment with ACE inhibitor and combined therapy. Even at the high dose lisinopril failed to reduce proteinuria. Simvastatin only partially affected proteinuria. However, combining lisinopril with simvastatin had a remarkable antiproteinuric effect, such that at 10 months the urinary proteins were comparable to pre-treatment values and significantly lower than either the vehicle or lisinopril groups. Hypercholesterolemia of PHN rats was limited by combined therapy, and a positive correlation was found between serum cholesterol and proteinuria. Renal function was only partially ameliorated by simvastatin but significantly improved by combined therapy. Drug combination significantly limited glomerulosclerosis, tubular damage and interstitial inflammation, compared to vehicle or drugs alone. Up-regulation of monocyte chemoattractant protein-1 (MCP-1) mRNA in PHN kidneys was not affected by lisinopril, it was inhibited by 30% after simvastatin, and almost completely normalized by lisinopril plus simvastatin.

CONCLUSIONS

These data suggest that a combined ACE inhibitor and statin approach could represent a therapeutic option for patients with advanced renal disease in whom ACE inhibitors alone fail to lower proteinuria and injury to any substantial extent.

Statins and progressive renal disease

Thanks to the administration of hypocholesterolemic drugs, important advances have been made in the treatment of patients with progressive renal disease. In vitro and in vivo findings demonstrate that statins, the inhibitors of HMG-CoA reductase, can provide protection against kidney diseases characterized by inflammation and/or enhanced proliferation of epithelial cells occurring in rapidly progressive glomerulonephritis, or by increased proliferation of mesangial cells occurring in IgA nephropathy. Many of the beneficial effects obtained occur independent of reduced cholesterol levels because statins can directly inhibit the proliferation of different cell types (e.g., mesangial, renal tubular, and vascular smooth muscle cells), and can also modulate the inflammatory response, thus inhibiting macrophage recruitment and activation, as well as fibrosis. The mechanisms underlying the action of statins are not yet well understood, although recent data in the literature indicate that they can directly affect the proliferation/apoptosis balance, the down-regulation of inflammatory chemokines, and the cytogenic messages mediated by the GTPases Ras superfamily. Therefore, as well as reducing serum lipids, statins and other lipid-lowering agents may directly influence intracellular signaling pathways involved in the prenylation of low molecular weight proteins that play a crucial role in cell signal transduction and cell activation. Statins appear to have important potential in the treatment of progressive renal disease, although further studies are required to confirm this in humans.

Mechanical strains induced by tubular flow affect the phenotype of proximal tubular cells

The effects of flow-induced mechanical strains on the phenotype of proximal tubular cells were addressed in vivo and in vitro by subjecting LLC-PK(1) and mouse proximal tubular cells to different levels of flow. Laminar flow (1 ml/min) induced a reorganization of the actin cytoskeleton and significantly inhibited the expression of plasminogen activators [tissue-type (tPA) activity: 25% of control cells; tPA mRNA: 70% of control cells; urokinase (uPA) mRNA: 56% of control LLC-PK(1) cells]. In vivo, subtotal nephrectomy (Nx) decreased renal fibrinolytic activity and uPA mRNA content detectable in proximal tubules. Nx also induced a reinforcement of the apical domain of the actin cytoskeleton analyzed by immunofluorescence. These effects of flow on tPA and uPA mRNA were prevented in vitro when reorganization of the actin cytoskeleton was blocked by cytochalasin D and were associated, in vitro and in vivo, with an increase in shear stress-responsive element binding activity detected by an electrophoretic mobility shift assay in proximal cell nuclear extracts. These results demonstrate that tubular flow affects the phenotype of renal epithelial cells and suggest that flow-induced mechanical strains could be one determinant of tubulointerstitial lesions during the progression of renal diseases.

Rho-dependent inhibition of the induction of connective tissue growth factor (CTGF) by HMG CoA reductase inhibitors (statins)

It was supposed that inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG CoA) reductase (statins) might inhibit the expression of the fibrosis-related factor CTGF (connective tissue growth factor) by interfering with the isoprenylation of Rho proteins. The human renal fibroblast cell line TK173 was used as an in vitro model system to study the statin-mediated modulation of the structure of the actin cytoskeleton and of the expression of CTGF mRNA. Incubation of the cells with simvastatin or lovastatin time-dependently and reversibly changed cell morphology and the actin cytoskeleton with maximal effects observed after about 18 h. Within the same time period, statins reduced the basal expression of CTGF and interfered with CTGF induction by lysophosphatidic acid (LPA) or transforming growth factor beta. Simvastatin and lovastatin proved to be much more potent than pravastatin (IC(50) 1 - 3 microM compared to 500 microM). The inhibition of CTGF expression was prevented when the cells were incubated with mevalonate or geranylgeranylpyrophosphate (GGPP) but not by farnesylpyrophosphate (FPP). Specific inhibition of geranylgeranyltransferase-I by GTI-286 inhibited LPA-mediated CTGF expression whereas an inhibitor of farnesyltransferases FTI-276 was ineffective. Simvastatin reduced the binding of the small GTPase RhoA to cellular membranes. The effect was prevented by mevalonate and GGPP, but not FPP. These data are in agreement with the hypothesis that interference of statins with the expression of CTGF mRNA is primarily due to interference with the isoprenylation of RhoA, in line with previous studies, which have shown that RhoA is an essential mediator of CTGF induction. The direct interference of statins with the synthesis of CTGF, a protein functionally related to the development of fibrosis, may thus be a novel mechanism underlying the beneficial effects of statins observed in renal diseases.

Regulation of connective tissue growth factor (ccn2; ctgf) gene expression in human mesangial cells: modulation by HMG CoA reductase inhibitors (statins)

AIM

Connective tissue growth factor (ccn; ctgf) gene expression is upregulated in fibrotic renal glomeruli. Therefore, the regulation and pharmacological modulation of ccn2 (ctgf) mRNA expression was investigated in a human renal mesangial cell line.

METHODS

A human renal mesangial cell line was cultured in vitro under standard conditions. After stimulation, RNA was extracted and ccn2 (ctgf) mRNA expression assessed by northern blot analysis.

RESULTS

The expression of ccn2 (ctgf) mRNA was transiently upregulated by fetal calf serum. Very rapid onset but short lasting ccn2 (ctgf) mRNA expression was observed after stimulation with lysophosphatidic acid, a bioactive lipid, which activates G protein coupled receptors. Induction of ccn2 (ctgf) mRNA expression by transforming growth factor beta (TGF-beta) was more prolonged and lasted for more than one day. The small GTPases of the Rho family were essential for basal as well as induced ccn2 (ctgf) expression: preincubation of the cells with toxin B from Clostridium difficile abrogated ccn2 (ctgf) mRNA expression. HMG CoA reductase inhibitors, which are therapeutically used as lipid lowering drugs, interfere with the isoprenylation and thus activation of Rho proteins. Simvastatin, an HMG CoA reductase inhibitor, inhibited ccn2 (ctgf) mRNA expression in a concentration dependent manner (IC(50): 1-2 microM).

CONCLUSION

Statins were identified as potent inhibitors of ccn2 (ctgf) mRNA expression in mesangial cells, and therefore might be of potential use to modulate the excessive ccn2 (ctgf) expression in mesangial cells related to glomerular fibrosis.

Lovastatin induces apoptosis of spontaneously immortalized rat brain neuroblasts: involvement of nonsterol isoprenoid biosynthesis inhibition

We have examined the effects of lovastatin and pravastatin (competitive HMG-CoA reductase inhibitors) on the growth and survival of rat brain neuroblasts. Lovastatin, but not pravastatin, suppressed cell growth by inducing apoptosis of neuroblasts in a dose- and time-dependent manner. Apoptosis was accompanied by a decrease in both Bcl-2 and Bcl-xL protein levels, suggesting that changes in the expression of these genes may contribute to apoptosis following lovastatin treatment. Lovastatin treatment was also associated with decreased prenylation of both Ras and Rho A proteins whereas Rac 1 geranylgeranylation was not affected. Lovastatin effects were fully prevented by mevalonate. The present data suggest that lovastatin induces apoptosis of rat brain neuroblasts by its capacity to decrease the prenylation of specific proteins involved in signal transduction pathways that control growth and survival of neuronal cells.

Dopamine induces ERK activation in renal epithelial cells through H2O2 produced by monoamine oxidase

BACKGROUND

The rat renal proximal tubule cells contain a large amount of monoamine oxidase, which catalyzes the oxidative deamination of catecholamines such as dopamine (DA). The aim of this study is to investigate the potential role of hydrogen peroxide (H2O2) produced by monoamine oxidase (MAO) isoform on regulation of cell signaling and function.

METHODS

Primary rat proximal tubular cells, which contain almost exclusively MAO-A, and human embryonic kidney 293 (HEK 293) cells stably transfected with human MAO-B cDNA were treated with DA or tyramine in the presence or the absence of some inhibitors. Then, Shc protein tyrosine phosphorylation and extracellular-regulated kinase (ERK) activation were evaluated by immunoprecipitation/immunoblot analysis and cell proliferation by [3H]thymidine incorporation or cell counting.

RESULTS

In rat proximal tubule cells, DA induced tyrosine phosphorylation of Shc, ERK activation, and a significant increase in DNA synthesis. The involvement of MAO-dependent H2O2 generation induced by DA (5 micromol/L) was supported by the demonstration that the DA effects were (1) fully prevented by cell pretreatment with the MAO inhibitor pargyline, the antioxydant N-acetylcysteine (NAC), and the DA uptake inhibitor GBR 12909; (2) not abrogated by the D1 and D2 receptor antagonists; (3) observed in HEK 293 MAO-B cells but not in HEK 293 wild-type cells, which do not express MAO; and (4) similar to those induced by another MAO substrate, tyramine.

CONCLUSIONS

Taken together, these results show that in addition to the effects related to receptor stimulation, DA, and probably the other catecholamines, may induce some of its effects through the MAO-dependent H2O2 production.

Evidence for Rho protein regulation of renal tubular epithelial cell function

BACKGROUND

Rho proteins are small guanine 5'-triphosphate (GTP)-binding proteins felt to be important regulators of several aspects of cell function, including the organization of the actin cytoskeleton. The effects of Rho proteins on the regulation of renal tubular epithelial cell function are not known.

METHODS

Selected bacterial toxins that inhibit Rho protein function were used to examine the effect of Rho in cultured renal tubular epithelial cells.

RESULTS

Clostridium difficile toxin A significantly and dose dependently inhibited LLC-PK(1) cell (3)H-thymidine uptake and healing of small wounds made in confluent monolayers, and it induced apoptosis. A second Clostridium difficile toxin (toxin B) that acted via a different receptor also impaired LLC-PK(1) thymidine uptake and wound healing, and it induced apoptosis. A third bacterial toxin, C3 toxin from Clostridium botulinum, also impaired LLC-PK(1) thymidine uptake and stimulated apoptosis in LLC-PK(1) cells. Since Rho inhibition disrupted organization of the actin cytoskeleton, we examined the effects of another agent that disrupted the actin cytoskeleton (cytochalasin D) and found significant dose-dependent effects that impaired LLC-PK1 thymidine uptake and wound healing and that induced apoptosis. The effects of toxin A and cytochalasin D to induce apoptosis were not associated with significant changes in expression of Bcl-2, BAD, or BAK proteins and were significantly attenuated by a pancaspase inhibitor.

CONCLUSIONS

Our results suggest that Rho proteins are important endogenous regulators of several aspects of renal tubular epithelial cell function, including proliferation, migration, and apoptosis. Further studies are needed to clarify the cellular mechanisms of Rho regulation of renal epithelial cell function.

Involvement of Rho GTPases in the transcriptional inhibition of preproendothelin-1 gene expression by simvastatin in vascular endothelial cells

Endothelial dysfunction is characterized by an impaired vasodilatory response to endothelial agonists as well as by alterations in adhesion and coagulation processes. 3-Hydroxy-3-methylglutaryl-CoA reductase inhibitors (statins) have been shown to be useful in the reversal of endothelial dysfunction, an effect that may be independent of the reduction in cholesterol levels. Both the L-arginine-nitric oxide-cGMP and endothelin pathways are involved in the regulation of vascular tone. Here, we show that the basal transcription rate of the preproendothelin-1 gene was decreased by simvastatin (10 micromol/L) in bovine aortic endothelial cells. Transfection studies with the preproendothelin-1 gene promoter showed that mevalonate (100 micromol/L) was able to prevent the inhibitory effect mediated by simvastatin. Protein geranylgeranylation, but not farnesylation, proved to be crucial for a correct expression of the preproendothelin-1 gene. The C3 exotoxin from Clostridium botulinum that selectively inactivates Rho GTPases, the processing of which involves geranylgeranylation, reproduced the inhibitory effect of simvastatin on the expression of preproendothelin-1. Overexpression of dominant-negative mutants of RhoA and RhoB led to a significant reduction in the preproendothelin-1 promoter activity, whereas the expression of wild-type and constitutively active forms of these proteins resulted in an increase, in support that Rho proteins are required for the basal expression of the preproendothelin-1 gene. Finally, we show that the Rho-dependent activation of the preproendothelin-1 gene transcription was inhibited by simvastatin. Thus, the control of vascular tone and proliferative response mediated by endothelin-1 is regulated at multiple levels, among which the Rho proteins play an essential role.

Do pleiotropic effects of statins beyond lipid alterations exist in vivo? What are they and how do they differ between statins?

The inhibition of cellular proliferation, the restoration of endothelial activity, the inhibition of platelet reactivity, and an antioxidant potential are only a few examples of pleiotropic effects of statins. This review analyzes the current knowledge on the pleiotropic properties of this class of drugs and examines the relevant data that support the presence of these effects in vivo. The favorable outcome of major trials of statins has indicated that pleiotropic factors indeed play a role in cardiovascular protection. In addition, recent data indicate that many pleiotropic effects influence mechanisms that belong to the extravascular compartment, as well. Perhaps, some of these properties may eventually justify additional indications for statins and improve the treatment of other diseases, including inflammation and cancer.

Cyclosporine A-induced cell cycle arrest and cell death in renal epithelial cells

We studied the effects of cyclosporine A (CsA) on the proliferation of LLC-PK1 proximal tubule epithelial cells. DNA damage was found to be an early event in CsA nephrotoxicity and could be a sensitive indicator of CsA injury in renal epithelial cells. Cell cycle arrest induced by CsA was coincident with elevated p53 levels. It is possible that trans-activating p21 may mediate the halting of the cell cycle through the CsA-induced accumulation of p53.

State-of-the-Art lecture. Statins and blockers of the renin-angiotensin system: vascular protection beyond their primary mode of action

In addition to their primary mode of action, statins and blockers of the renin-angiotensin system possess common additional properties that are under active investigation. The inhibition of cellular proliferation, the restoration of endothelial activity, the inhibition of platelet reactivity, and an antioxidant potential are only a few examples of shared effects that target the arterial wall. These and other properties may eventually become exploited for the improved treatment of cardiovascular diseases and of other diseases apparently unrelated to the cardiovascular field, including inflammation and cancer. This review analyzes the current knowledge on the pleiotropic properties of these classes of drugs. Direct comparison indicates that study of the associations among these drugs may eventually disclose additive or synergistic effects that, perhaps even at lower dosages, may provide improved vascular protection and a strong alliance against several atherogenic mechanisms.

Recent advances in statins and the kidney

BACKGROUND

Experimental and clinical studies have suggested a correlation between the progression of renal disease and dyslipidemia. Indeed, apolipoprotein B-containing lipoproteins have been demonstrated to be an independent risk factor for the progression of renal disease in humans. Interventional strategies in experimental models of renal disease have clearly demonstrated a beneficial effect on renal structure and function in a variety of models of renal disease. Investigations into the mechanisms whereby reduction of lipids by lipid-lowering agents benefits renal disease have suggested that the 3-hydroxy-3-methylglutaryl coenzyme reductase inhibitors, the so-called statin class of lipid-lowering agents, may have additional effects on the biology of inflammation that are germane to the progression of renal disease.

METHODS

Both in vivo and in vitro studies that investigated secondary mechanisms of statin effects are reviewed. In addition, new studies that investigated the effects on novel cellular mechanisms are presented.

RESULTS

Lipid-lowering agents appear to have biologically important effects in modulating a variety of intracellular signaling systems involved in cell proliferation, inflammatory responses that involve macrophage adhesion, recruitment, and maturation. In addition, the effects on fibrogenesis have been recently defined. These latter effects may influence not only the development of glomerulosclerosis, but also interstitial fibrosis. These potentially major effects of lipid-lowering agents appear to be related to the effects on intracellular synthesis of nonsterol isoprenoids, which are involved in prenylation of critical small molecular weight proteins involved in cell signal transduction.

CONCLUSIONS

In addition to the beneficial effects of the reduction in serum lipids, statins and other lipid-lowering agents may influence important intracellular pathways that are involved in the inflammatory and fibrogenic responses, which are common components of many forms of progressive renal injury.

Effect of lipid-lowering strategies on tubular cell biology

BACKGROUND

Interstitial fibrosis and the development of renal cysts are crucial phenomena in renal disease progression. While 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors has been shown to reduce the progression of several experimental nephropathies, the mechanism of their potential protective effect remaines unclear.

METHODS

The antiproliferative, apoptotic, and fibrinolytic effects of HMG-CoA reductase inhibitors were assessed in primary cultured rat (rPTCs) and mouse proximal tubule cells (mPTCs), in isolated rat proximal tubules, and in vivo in 5/6 nephrectomized rats (Nx).

RESULTS

In vitro, lovastatin inhibited rPTC proliferation in a manner selectively prevented by mevalonate, farnesyl-, or geranylgeranyl-pyrophosphate (FPP or GGPP). Lovastatin reduced membrane-bound p21ras and fetal calf serum-induced c-fos and c-jun protein expression. Gel shift assay showed that lovastatin reduced activated protein-1 (AP-1) binding activity. In vivo, lovastatin inhibited tubular cell proliferation after Nx, as measured by proliferative cell nuclear antigen staining. Lovastatin-treated mPTCs displayed nucleus cleavage and DNA ladder formation, which were prevented by GGPP. Like C3 exoenzyme, lovastatin induced actin filament disruption, which preceded evidence of apoptosis. Lovastatin increased tissue-type plasminogen activator (PA) and decreased PA inhibitor activities and antigens; these effects were prevented by mevalonate and GGPP but not FPP, and were reproduced by C3 exoenzyme in a manner insensitive to GGPP.

CONCLUSIONS

HMG-CoA reductase inhibitors decreased proliferation, increased apoptosis, and enhanced fibrinolytic activity of renal tubular cells via modulation of different isoprenylated proteins. These effects could participate to reduce the progression of renal diseases.

In vitro effects of simvastatin on tubulointerstitial cells in a human model of cyclosporin nephrotoxicity

To investigate the possibility that 3-hydroxy-3-methylglutaryl CoA (HMGCoA) reductase inhibitors ameliorate renal disease via direct effects on the tubulointerstitium, primary cultures of human proximal tubule cells (PTC) and renal cortical fibroblasts (CF) were exposed for 24 h to simvastatin (0.1-10 micromol/l) under basal conditions and in the presence of 1,000 ng/ml of cyclosporin (CsA), which we have previously shown to promote in vitro interstitial matrix accumulation at least partially via activation of local cytokine networks. Simvastatin, in micromolar concentrations, engendered cholesterol-independent inhibition of CF and PTC thymidine incorporation and cholesterol-dependent suppression of PTC apical Na+/H+ exchange (NHE) (ethylisopropylamiloride-sensitive apical 22Na+ uptake). Similarly, CF secretion of insulin-like growth factor-I (IGF-I) and IGF binding protein-3 were depressed, whereas CF collagen synthesis ([3H]proline incorporation) and PTC secretion of the fibrogenic cytokines, transforming growth factor-beta1, and platelet-derived growth factor were unaffected. A lower concentration (0.1 micromol/l) of simvastatin did not affect any of the above parameters under basal conditions but completely prevented CsA-stimulated CF collagen synthesis (control, 6.6 +/- 0.6; CsA, 8.3 +/- 0.6; CsA+simvastatin, 6.2 +/- 0.5%; P < 0.05) and IGF-I secretion (89.5 +/- 16.6, 204.7 +/- 57.0, and 94.6 +/- 22.3 ng. mg protein-1. day-1, respectively; P < 0.05). The results suggest that simvastatin exerts direct cholesterol-dependent and -independent effects on the human kidney tubulointerstitium. HMGCoA reductase inhibitors may ameliorate interstitial fibrosis complicating CsA therapy via direct actions on human renal cortical fibroblasts.

In situ non-radioactive detection of nuclear factors in paraffin sections by Southwestern histochemistry

BACKGROUND

Transcriptional activities of genes require intermediary regulators (nuclear factors) that bind to specific segments of nuclear DNA. A method to localize in situ the distribution of these factors using nonradioactive oligonucleotides in paraffin wax-embedded tissues is described. The distribution of two nuclear factors, activated protein-1 (AP-1) and nuclear factor-kappaB (NF-kappaB), was studied in two experimental models of immune complex glomerulonephritis in rats and atherosclerosis in rabbits.

METHODS

Sections were fixed with 0.2% paraformaldehyde and were digested with pepsin A. Oligonucleotides containing the consensus sequence of NF-kappaB and AP-1 were 3'-labeled with digoxigenin. The preparations were incubated with the labeled probes (4 degreesC, overnight). After washing, the sections were incubated with an antidigoxigenin antibody conjugated with alkaline phosphatase, and the color reaction was developed. In addition, this method was combined with standard immunohistochemistry to identify the cell-type-specific localization of these DNA-binding factors.

RESULTS

Kidney sections from rats with immune complex nephritis showed positive nuclear staining for AP-1 in the nuclei of several glomerular and tubulointerstitial cells. Arteries from rabbits with focal atherosclerosis presented nuclear staining for NF-kappaB in the neointima and media. The nuclear staining was highly specific, as assessed by several negative controls. In addition, Southwestern histochemistry in rabbits, followed by immunohistochemistry, demonstrated that the NF-kappaB activity was present in the area occupied by macrophages and smooth muscle cells.

CONCLUSION

These results show a novel method of in situ transcription factors detection using nonradioactive probes in paraffin wax-embedded tissues, which allows a simultaneous visualization of the cell-type-specific localization of these nuclear factors.