Juan José Plaza

3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase and Isoprenylation Inhibitors Induce Apoptosis of Vascular Smooth Muscle Cells in Culture

Recent evidence suggests that apoptosis may be involved in the control of vascular smooth muscle cell (VSMC) number in atherosclerotic lesions. 3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors have been reported to induce apoptosis in a variety of tumor cell lines. To evaluate whether these agents also induce apoptosis of VSMCs, cultured rat VSMCs were treated with increasing doses of atorvastatin in the presence of FBS as a survival factor. The presence of apoptosis was evaluated by morphological criteria, annexin V binding, and DNA fragmentation and quantified as the proportion of hypodiploid cells by flow cytometry. Atorvastatin induced apoptosis in a dose-dependent manner, an effect also seen with simvastatin and lovastatin, but not with the hydrophilic drug pravastatin. The proapoptotic effect of statins was seen only when the inhibition of acetate incorporation into sterols was >95% and was fully reversed by mevalonate, farnesyl pyrophosphate, and geranylgeranyl pyrophosphate but not by isopentenyl adenosine, ubiquinone, or squalene, suggesting a role for prenylated proteins in the regulation of VSMC apoptosis. To further assess the role of protein prenylation, VSMCs were exposed to the prenyl transferase inhibitors perillic acid and manumycin A. Both agents induced VSMC apoptosis as evaluated by the above-mentioned criteria. Finally, VSMC treatment with lipophilic statins was associated with decreased prenylation of p21-Rho B, further supporting the role of protein prenylation inhibition in statin-induced VSMC apoptosis. The present data suggest that interference with protein prenylation by HMG-CoA reductase inhibitors or other agents may provide new strategies for the prevention of neointimal thickening.

3-Hydroxy-3-methyl-glutaryl coenzyme A reductase inhibitors, atorvastatin and simvastatin, induce apoptosis of vascular smooth muscle cells by downregulation of Bcl-2 expression and Rho A prenylation

The mechanism by which 3-hydroxy-3-methyl-glutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) induce apoptosis in vascular smooth muscle cells (VSMCs) is unknown. In this work, we demonstrate that treatment of VSMCs with simvastatin and atorvastatin inhibited Bcl-2 expression in a time and dose-dependent manner, while Bax expression was not modified. This effect was reversed by mevalonate (100 micromol/l), farnesylpyrophosphate (5 micromol/l) or geranylgeranylpyrophosphate (5 micromol/l), suggesting the involvement of protein prenylation. The treatment of VSMCs with lipophilic statins was associated with decreased prenylation of p-21 Rho A and mevalonate, farnesyl pyrophosphate (F-PP) and geranylgeranyl pyrophosphate (G-PP) reversed prenylation to basal levels. In addition, overexpression of constitutively active Q63L Rho A prevented, at least in part, apoptosis induced by statins and downregulation of Bcl-2. We also investigated the participation of caspases (proteases) in the apoptosis induced by statins. The treatment of VSMCs with lipophilic statins induced activation of the caspase 9, the first caspase of the mitochondrial pathway. Coincubation of VSMCs with the caspase inhibitor ZVAD-fmk (100 micromol/l) significantly inhibited lipophilic statin-induced apoptosis. These findings indicate that the downregulation of Bcl-2 by Rho GTPases mediates statin-induced apoptosis and suggest a new potential mechanism of action for these drugs on the regulation of cell number in the atherosclerotic lesions.

Effects and interactions of endothelin-1 and angiotensin II on matrix protein expression and synthesis and mesangial cell growth

Mesangial cell growth and accumulation of extracellular matrix proteins constitute key features of progressive glomerular injury. Endothelin-1 (ET-1) and angiotensin II (Ang II), two potent vasoconstrictor agents, evoke a number of similar responses in mesangial cells. In rat mesangial cells, we compared ET-1 and Ang II effects on matrix protein production and cell proliferation as well as the potential interaction between the two hormones. When cells in 0.5% fetal calf serum were incubated for 24 hours with various concentrations of ET-1 or Ang II, both peptides stimulated, in a dose-dependent manner, fibronectin and type IV collagen mRNA expression, fibronectin synthesis, and mitogenesis. Incubation with specific receptor antagonists of both hormones demonstrated that endothelin subtype A (ETA) and angiotensin type 1 (AT1) receptors were involved. Preincubation of cells with two different protein kinase C inhibitors or with a neutralizing anti-transforming growth factor-beta antibody, but not an unrelated IgG, diminished the peptide-induced fibronectin synthesis. A dual interrelation seems to exist between ET-1 and Ang II. Thus, the AT1 receptor antagonist losartan and the angiotensin-converting enzyme inhibitors quinaprilat and captopril diminished the ET-1-mediated effects, whereas, the ETA receptor antagonist BQ-123 diminished the Ang II-induced fibronectin synthesis and mesangial cell proliferation. Our results suggest that ET-1 and Ang II stimulate matrix protein synthesis and mesangial cell mitogenesis through ETA and AT1 receptors, respectively, by complicated mechanisms, implicating protein kinase C activation, synthesis of transforming growth factor-beta, and release of one peptide by the other. These data could be important for a better understanding of the participation of vasoactive substances in the pathogenesis of glomerulosclerosis.

Endothelin-1, via ETA Receptor and Independently of Transforming Growth Factor-β, Increases the Connective Tissue Growth Factor in Vascular Smooth Muscle Cells

Endothelin (ET)-1 is a potent vasoconstrictor that participates in cardiovascular diseases. Connective tissue growth factor (CTGF) is a novel fibrotic mediator that is overexpressed in human atherosclerotic lesions, myocardial infarction, and experimental models of hypertension. In vascular smooth muscle cells (VSMCs), CTGF regulates cell proliferation/apoptosis, migration, and extracellular matrix (ECM) accumulation. Our aim was to investigate whether ET-1 could regulate CTGF and to investigate the potential role of ET-1 in vascular fibrosis. In growth-arrested rat VSMCs, ET-1 upregulated CTGF mRNA expression, promoter activity, and protein production. The blockade of CTGF by a CTGF antisense oligonucleotide decreased FN and type I collagen expression in ET-1–treated cells, showing that CTGF participates in ET-1–induced ECM accumulation. The ETA, but not ETB, antagonist diminished ET-1–induced CTGF expression gene and production. Several intracellular signals elicited by ET-1, via ETA receptors, are involved in CTGF synthesis, including activation of RhoA/Rho-kinase and mitogen-activated protein kinase and production of reactive oxygen species. CTGF is a mediator of TGF-&bgr;– and angiotensin (Ang) II–induced fibrosis. In VSMCs, ET-1 did not upregulate TGF-&bgr; gene or protein. The presence of neutralizing transforming growth factor (TGF)-&bgr; antibody did not modify ET-1–induced CTGF production, showing a TGF-&bgr;–independent regulation. We have also found an interrelationship between Ang II and ET-1 because the ETA antagonist diminished CTGF upregulation caused by Ang II. Collectively, our results show that, in cultured VSMCs, ET-1, independently of TGF-&bgr; and through the activation of several intracellular signals via ETA receptors, regulates CTGF. This novel finding suggests that CTGF could be a mediator of the profibrotic effects of ET-1 in vascular diseases.

Angiotensin-Converting Enzyme Is Upregulated in the Proximal Tubules of Rats With Intense Proteinuria

Persistent proteinuria is considered a deleterious prognostic factor in most progressive renal diseases. However, the mechanisms by which proteinuria induces renal damage remain undetermined. Since proximal tubular cells possess all the machinery to generate angiotensin II (Ang II), we approached the hypothesis that proteinuria could elicit the renal activation of the renin-angiotensin system in a model of intense proteinuria and interstitial nephritis induced by protein overload. After uninephrectomy (UNX), Wistar-Kyoto rats received daily injections of 1 g BSA or saline for 8 days. The mean peak of proteinuria was observed at the fourth day (538+/-89 versus 3+/-1 mg/24 h in UNX controls; n=12; P<0.05) and was increased during the whole study period (at the eighth day: 438+/-49 mg/24 h; n=12; P=NS). Morphological examination of the kidneys at the end of the study showed marked tubular lesions (atrophy, vacuolization, dilation, and casts), interstitial infiltration of mononuclear cells, and mesangial expansion. In relation to UNX control rats, renal cortex of BSA-overloaded rats showed an increment in the gene expression of angiotensinogen (2.4-fold) and angiotensin-converting enzyme (ACE) (2.1-fold), as well as a diminution in renin gene expression. No changes were observed in angiotensin type 1 (AT1) receptor mRNA expression in both groups of rats. By in situ reverse transcription-polymerase chain reaction and immunohistochemistry, ACE expression (gene and protein) was mainly localized in proximal and distal tubules and in the glomeruli. By immunohistochemistry, angiotensinogen was localized only in proximal tubules, and AT1 receptor was localized mainly in proximal and distal tubules. In the tubular brush border, an increase in ACE activity was also seen (5. 5+/-0.5 versus 3.1+/-0.7 U/mg protein x10(-4) in UNX control; n=7; P<0.05). Our results show that in the kidney of rats with intense proteinuria, ACE and angiotensinogen were upregulated, while gene expression of renin was inhibited and AT1 was unmodified. On the whole, these data suggest an increase in Ang II intrarenal generation. Since Ang II can elicit renal cell growth and matrix production through the activation of AT1 receptor, this peptide may be responsible for the tubulointerstitial lesions occurring in this model. These results suggest a novel mechanism by which proteinuria may participate in the progression of renal diseases.

Angiotensin II Increases Connective Tissue Growth Factor in the Kidney

Connective tissue growth factor (CTGF) has been described as a novel fibrotic mediator. CTGF is overexpressed in several kidney diseases and is induced by different factors involved in renal injury. Angiotensin II (AngII) participates in the pathogenesis of kidney damage, contributing to fibrosis; however, whether AngII regulates CTGF in the kidney has not been explored. Systemic infusion of AngII into normal rats for 3 days increased renal CTGF mRNA and protein levels. At day 7, AngII-infused rats presented overexpression of CTGF in glomeruli, tubuli, and renal arteries, as well as tubular injury and elevated fibronectin deposition. Only treatment with an AT(1) receptor antagonist, but not an AT(2), diminished CTGF and fibronectin overexpression and ameliorated tubular damage. In rats with immune complex nephritis, renal overexpression of CTGF was diminished by the ACE inhibitor quinapril, correlated with a diminution in fibrosis. In cultured renal cells (mesangial and tubular epithelial cells) AngII, via AT(1), increased CTGF mRNA and protein production, and a CTGF antisense oligonucleotide decreased AngII-induced fibronectin synthesis. Our data show that AngII regulates CTGF in the kidney and cultured in mesangial and tubular cells. This novel finding suggests that CTGF could be a mediator of the profibrogenic effects of AngII in the kidney.

HMG-CoA Reductase Inhibitors Decrease Angiotensin II–Induced Vascular Fibrosis: Role of RhoA/ROCK and MAPK Pathways

3-hydroxy-3-methylglutaryl (HMG)-coenzyme A (CoA) reductase inhibitors (statins) present beneficial effects in cardiovascular diseases. Angiotensin II (Ang II) contributes to cardiovascular damage through the production of profibrotic factors, such as connective tissue growth factor (CTGF). Our aim was to investigate whether HMG-CoA reductase inhibitors could modulate Ang II responses, evaluating CTGF expression and the mechanisms underlying this process. In cultured vascular smooth muscle cells (VSMCs) atorvastatin and simvastatin inhibited Ang II–induced CTGF production. The inhibitory effect of statins on CTGF upregulation was reversed by mevalonate and geranylgeranylpyrophosphate, suggesting that RhoA inhibition could be involved in this process. In VSMCs, statins inhibited Ang II–induced Rho membrane localization and activation. In these cells Ang II regulated CTGF via RhoA/Rho kinase activation, as shown by inhibition of Rho with C3 exoenzyme, RhoA dominant-negative overexpression, and Rho kinase inhibition. Furthermore, activation of p38MAPK and JNK, and redox process were also involved in Ang II–mediated CTGF upregulation, and were downregulated by statins. In rats infused with Ang II (100 ng/kg per minute) for 2 weeks, treatment with atorvastatin (5 mg/kg per day) diminished aortic CTGF and Rho activation without blood pressure modification. Rho kinase inhibition decreased CTGF upregulation in rat aorta, mimicking statin effect. CTGF is a vascular fibrosis mediator. Statins diminished extracellular matrix (ECM) overexpression caused by Ang II in vivo and in vitro. In summary, HMG-CoA reductase inhibitors inhibit several intracellular signaling systems activated by Ang II (RhoA/Rho kinase and MAPK pathways and redox process) involved in the regulation of CTGF. Our results may explain, at least in part, some beneficial effects of statins in cardiovascular diseases.

Expression of leucocyte chemoattractants by interstitial renal fibroblasts: up-regulation by drugs associated with interstitial fibrosis.

Interstitial inflammation is a strong predictor of long‐term renal damage. The potential role of renal interstitial fibroblasts in recruitment of inflammatory leucocytes into the interstitium is unclear. We have thus studied the mRNA expression of several leucocyte chemotactic factors by rat renal interstitial fibroblasts and its modulation by cytokines. In addition, the effects of two unrelated drugs associated with the development of interstitial fibrosis, namely puromycin aminonucleoside (PAN) and cyclosporin A (CsA), were also studied. Rat renal interstitial fibroblasts showed constitutive mRNA expression for the chemokines monocyte chemoattractant protein 1 (MCP‐1) and interferon‐inducible protein 10 (IP‐10). In addition, these cells also exhibited constitutive mRNA expression for cyclophilin B, an immunophilin recently found to have leucocyte chemoattractant properties. The inflammatory cytokine tumour necrosis factor‐alpha up‐regulated IP‐10 and MCP‐1 mRNA expression (10‐ and four‐fold, respectively), but had no effect on cyclophilin B mRNA levels. IP‐10 and MCP‐1 produced about a four‐fold increase in MCP‐1 and cyclophilin B mRNA expression, but did not affect IP‐10 mRNA. PAN caused an augmentation in IP‐10, MCP‐1 and cyclophilin B mRNA levels (12‐, 9.5, and two‐fold, respectively), while CsA increased only cyclophilin B mRNA in a dose‐dependent manner. In conclusion, rat renal interstitial fibroblasts express mRNA for chemotactic factors and this expression is up‐regulated by inflammatory cytokines, PAN and CsA. The present findings suggest that renal interstitial fibroblasts may play an active role in the recruitment of inflammatory leucocytes into the interstitium.

Severe everolimus-associated pneumonitis in a renal transplant recipient

Inhibitors of mTOR (mammalian target of rapamycin) are immunosuppressants with less nephrotoxic potential than calcineurin inhibitors and antiproliferative effects, which are advantageous in the case of malignancy. However, a series of adverse events has been reported with the first-generation mTOR inhibitor sirolimus that includes hypersensitivity-like interstitial pneumonitis. To our knowledge, only one case of a pneumonitis associated with everolimus in a heart transplant patient has been reported, and it was related to elevated trough blood levels. We report herein the first case of a kidney graft recipient who developed everolimus-associated pneumonitis with normal trough blood levels that was completely reversed after drug withdrawal.

Long-term graft function changes in kidney transplant recipients

Background. Monitoring changes in glomerular filtration rate (GFR) is the recommended method for assessing the progression of kidney disease. The aim of this study was to assess the decline of graft function defined by the annualized change in GFR and the factors which affect it. Methods. Four thousand four hundred and eighty-eight patients, transplanted during the years 1990, 1994, 1998 and 2002 in 34 centres in Spain with allograft survival of at least 1 year, were included in the study. GFR was estimated using the four-variable equation of the Modification of Diet in Renal Diseases (MDRD) study. Linear mixed effects model was applied to determine the relation between the covariates and the annualized change in GFR after transplantation. Results. The average GFR at 12 months was 51.4 ± 18.9 mL/min/1.73 m2; most patients were in stage 3 of chronic kidney disease classification. The average patient slope, calculated in a linear model with varying-intercept and varying-slope without covariates, was −1.12 ± 0.05 mL/min/year (slope ± standard error). Some variables were related to both the 12-month GFR (intercept) and the slope: recipient gender, hepatitis C virus (HCV) status, estimated GFR (eGFR) at 3 months and proteinuria at 12 months. Some variables were only related to the slope of eGFR: time on dialysis, primary renal disease and immunosuppression. Others affected only the 12-month GFR: donor age, delayed graft function, acute rejection and systolic blood pressure at 12 months. Higher graft function at 3 months had a negative impact on the GFR slope. Cyclosporine-based immunosuppression had a less favourable effect on the rates of change in allograft function. Conclusions. There was a slow decline in GFR. Poor graft function was not associated with an increased rate of decline of allograft function. Immunosuppression with cyclosporine displayed the worst declining GFR rate.