Cyclosporine A induces apoptosis in murine tubular epithelial cells: role of caspases

Cyclosporine A inhibits MRTF-SRF signaling through Na+/K+ ATPase inhibition and actin remodeling

Calcineurin inhibitors (CNI) are the pillars of immunosuppression in transplantation. However, they display a potent nephrotoxicity whose mechanisms remained widely unsolved. We used an untargeted quantitative proteomic approach (iTRAQ technology) to highlight new targets of CNI in renal proximal tubular cells (RPTCs). CNI-treated RPTCs proteome displayed an over-representation of actin-binding proteins with a CNI-specific expression profile. Cyclosporine A (CsA) induced F-actin remodeling and depolymerization, decreased F-actin-stabilizing, polymerization-promoting cofilin (CFL) oligomers, and inhibited the G-actin-regulated serum response factor (SRF) pathway. Inhibition of CFL canonical phosphorylation pathway reproduced CsA effects; however, S3-R, an analogue of the phosphorylation site of CFL prevented the effects of CsA which suggests that CsA acted independently from the canonical CFL regulation. CFL is known to be regulated by the Na+/K+-ATPase. Molecular docking calculations identified two inhibiting sites of CsA on Na+/K+-ATPase and a 23% decrease in Na+/K+-ATPase activity of RPTCs was observed with CsA. Ouabain, a specific inhibitor of Na+/K+-ATPase also reproduced CsA effects on actin organization and SRF activity. Altogether, these results described a new original pathway explaining CsA nephrotoxicity.

Growth arrest and DNA damage 45γ is required for caspase-dependent renal tubular cell apoptosis

BACKGROUND

Growth Arrest and DNA Damage 45γ (GADD45γ) is a member of the DNA damage-inducible gene family which responds to environmental stresses. Apoptosis is a critical mode of renal tubular cell death in nephrotoxin-induced acute kidney injury. In this study, we investigated the role of GADD45γ in renal tubular cell apoptosis induced by nephrotoxic drugs.

METHODS

Primary human renal tubular epithelial (HRE) cells were used in this study. To derive stable cell lines in which GADD45γ expression was silenced, HRE cells were transduced with a plasmid encoding GADD45γ-specific shRNA. The recombinant adenovirus containing the GADD45γ gene was synthesized to overexpress GADD45γ protein. Cell death was induced by cisplatin and cyclosporine A (CsA). To prevent apoptotic cell death, pan-caspase inhibitor ZVAD-FMK was used. To prevent non-apoptotic cell death, necrostatin-1 and ferrostatin-1 were used. The degree of apoptosis and necrosis of cultured cells were evaluated by flow cytometry.

RESULTS

Expression of the GADD45γ gene was significantly upregulated in response to treatment with CsA and cisplatin. Apoptosis and necrosis induced by these drugs were significantly reduced by silencing of GADD45γ, and significantly augmented by the overexpression of GADD45γ. The activation of caspase-3 and caspase-7 as well as caspase-9 induced by cisplatin or CsA was reduced by silencing of GADD45γ, and was augmented by the overexpression of GADD45γ, indicating that caspase activation is dependent on the expression of GADD45γ. ZVAD-FMK significantly inhibited apoptosis induced by cisplatin or CsA, indicating a role of caspases in mediating apoptotic cell death. ZVAD-FMK was effective to prevent necrosis as well, indicating that the observed necrosis was a secondary event following apoptosis at least in part.

CONCLUSIONS

To our knowledge, this is the first study to show that GADD45γ is required for the caspase-dependent apoptosis of renal tubular cells induced by nephrotoxic drugs.

Deferasirox-induced iron depletion promotes BclxL downregulation and death of proximal tubular cells

Iron deficiency has been associated with kidney injury. Deferasirox is an oral iron chelator used to treat blood transfusion-related iron overload. Nephrotoxicity is the most serious and common adverse effect of deferasirox and may present as an acute or chronic kidney disease. However, scarce data are available on the molecular mechanisms of nephrotoxicity. We explored the therapeutic modulation of deferasirox-induced proximal tubular cell death in culture. Deferasirox induced dose-dependent tubular cell death and AnexxinV/7AAD staining showed features of apoptosis and necrosis. However, despite inhibiting caspase-3 activation, the pan-caspase inhibitor zVAD-fmk failed to prevent deferasirox-induced cell death. Moreover, zVAD increased deferasirox-induced cell death, a feature sometimes found in necroptosis. Electron microscopy identified mitochondrial injury and features of necrosis. However, neither necrostatin-1 nor RIP3 knockdown prevented deferasirox-induced cell death. Deferasirox caused BclxL depletion and BclxL overexpression was protective. Preventing iron depletion protected from BclxL downregulation and deferasirox cytotoxicity. In conclusion, deferasirox promoted iron depletion-dependent cell death characterized by BclxL downregulation. BclxL overexpression was protective, suggesting a role for BclxL downregulation in iron depletion-induced cell death. This information may be used to develop novel nephroprotective strategies. Furthermore, it supports the concept that monitoring kidney tissue iron depletion may decrease the risk of deferasirox nephrotoxicity.

TMBIM6 (transmembrane BAX inhibitor motif containing 6) enhances autophagy and reduces renal dysfunction in a cyclosporine A-induced nephrotoxicity model

Cyclosporine A (CsA) is widely used as an immunosuppressor in transplantation. Previous studies reported that CsA induces autophagy and that chronic treatment with CsA results in accumulation of autophagosomes and reduced autophagic clearance. Autophagy is a prosurvival process that promotes recovery from acute kidney injury by degrading misfolded proteins produced in the kidney. In the present study, we used TMBIM6-expressing HK-2, human kidney tubular cells (TMBIM6 cells) and Tmbim6 knockout (tmbim6(-/-)) mice. When exposed to CsA, the TMBIM6 cells maintained autophagy activity by preventing autophagosome accumulation. With regard to signaling, PRKKA/AMPK phosphorylation and mechanistic target of rapamycin (serine/threonine kinase) complex 1 (MTORC1) expression and its downstream target TFEB (transcription factor EB), a lysosome biogenesis factor, were regulated in the TMBIM6 cells. Lysosomal activity was highly increased or stably maintained in the presence of TMBIM6. In addition, treatment of tmbim6(-/-) mice with CsA resulted in increased autophagosome formation and decreased lysosome formation and activity. We also found that tmbim6(-/-) mice were susceptible to CsA-induced kidney injury. Taken together, these results indicate that TMBIM6 protects against CsA-induced nephrotoxicity both in vitro and in vivo by inducing autophagy and activating lysosomes.

Expression of erythropoietin and its receptor in kidneys from normal and cyclosporine-treated rats

Long-term treatment with cyclosporine A (CsA) is associated with various types of complications; however, CsA-induced anemia has not been reported. The present study examined the impact of CsA on hematopoietic parameters and intrarenal expression of erythropoietin (EPO) and the EPO receptor (EPOR) in a rat model of chronic CsA nephrotoxicity. Sprague-Dawley rats were fed a low-salt diet (0.05% sodium) and were treated daily for 4 weeks with vehicle (olive oil 1 mL/kg subcutaneously) or CsA (15 mg/kg subcutaneously). The expression of EPO and EPOR was evaluated by immunohistochemistry and immunoblotting, and hematopoietic parameters were assessed by measuring blood hemoglobin and hematocrit levels, and these variables were compared between treatment groups. Renal function, oxidative stress, histopathology (tubulointerstitial fibrosis), apoptotic cell death, and expression of transforming growth factor β-inducible gene-h3 (βig-h3) were also compared between treatment groups. In kidneys from vehicle-treated rats, endogenous EPO and EPOR protein were expressed constitutively in the outer stripe of the outer medulla and the cortex. EPO protein expression decreased significantly in kidneys from CsA-treated rats. By contrast, EPOR expression was higher in kidneys from CsA-treated rats than in vehicle-treated rats. These changes were accompanied by decreases in serum hemoglobin and hematocrit levels and correlated with the number of cells positive for terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (r = -0.769, P = .003) and βig-h3 protein expression (r = -0.910, P < .001). Long-term treatment with CsA suppresses renal endogenous EPO expression, resulting in anemia. Increases in apoptotic cell death and βig-h3 expression are closely associated with inhibition of EPO expression in chronic CsA nephrotoxicity.

Delayed treatment with oleanolic acid attenuates tubulointerstitial fibrosis in chronic cyclosporine nephropathy through Nrf2/HO-1 signaling

Background

Nuclear factor erythroid-2-related factor-2 (Nrf2) is known to protect against tissue injury by orchestrating antioxidant and detoxification responses to oxidative stress. This study investigated whether upregulation of Nrf2-dependent signaling by oleanolic acid (OA), which is known to activate Nrf2, could attenuate renal inflammation and fibrosis in cyclosporine (CsA)-induced kidney injury.

Methods

Male ICR mice were divided into four treatment groups: Vehicle (VH, n = 6), VH + OA (n = 6), CsA (n = 8), and CsA + OA (n = 8). For the OA-treated groups, OA (25 mg/kg/day) was administered by intraperitoneal injection for the final week of the 4-week experimental period. Renal function, morphologies and signaling were evaluated at the end of the study.

Results

Treatment with CsA resulted in decreased kidney function and urine osmolality and increased urine volume and urinary albumin levels. The CsA-induced changes were improved by OA treatment. Specifically, administration of OA decreased tubulointerstitial fibrosis and inflammation scores that were increased in CsA-treated mice. Furthermore, OA treatment decreased urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG) and 8-epi-prostaglandin F2α (8-iso-PGF2α) levels. The beneficial effects of OA were attributed to an increased ratio of nuclear/total Nrf2 and subsequently enhanced expression of heme oxygenase (HO)-1, as well as a stable level of Kelch-like ECH-associated protein 1 (Keap1) expression, indicating that OA enhanced nuclear translocation of Nrf2. Increased apoptotic cell death and a high ratio of B cell leukaemia/lymphoma 2 (Bcl-2)-associated X protein (Bax) to Bcl-2 in CsA-treated mice were also significantly ameliorated by OA treatment.

Conclusion

Our results suggest that OA activates Nrf2/HO-1 signaling in chronic CsA nephropathy, which may have beneficial effects on inflammation and oxidative stress.

Lovastatin attenuates effects of cyclosporine A on tight junctions and apoptosis in cultured cortical collecting duct principal cells

We used mouse cortical collecting duct principal cells (mpkCCDc14 cell line) as a model to determine whether statins reduce the harmful effects of cyclosporine A (CsA) on the distal nephron. The data showed that treatment of cells with CsA increased transepithelial resistance and that the effect of CsA was abolished by lovastatin. Scanning ion conductance microscopy showed that CsA significantly increased the height of cellular protrusions near tight junctions. In contrast, lovastatin eliminated the protrusions and even caused a modest depression between cells. Western blot analysis and confocal microscopy showed that lovastatin also abolished CsA-induced elevation of both zonula occludens-1 and cholesterol in tight junctions. In contrast, a high concentration of CsA induced apoptosis, which was also attenuated by lovastatin, elevated intracellular ROS via activation of NADPH oxidase, and increased the expression of p47phox. Sustained treatment of cells with lovastatin also induced significant apoptosis, which was attenuated by CsA, but did not elevate intracellular ROS. These results indicate that both CsA and lovastatin are harmful to principal cells of the distal tubule, but via ROS-dependent and ROS-independent apoptotic pathways, respectively, and that they counteract probably via mobilization of cellular cholesterol levels.

Sildenafil protects against nitric oxide deficiency-related nephrotoxicity in cyclosporine A treated rats

Cyclosporine A (CsA) is the most widely used immunosuppressant in organ transplant surgery and in treatment of autoimmune disease. Nevertheless, animal and clinical studies have demonstrated that nephrotoxicity is the major adverse effect limiting the prolonged CsA therapeutic use. The present study aimed to investigate possible protective effect of sildenafil, a phoshodiestrase-5 inhibitor, on CsA-induced nephrotoxicity and various mechanism(s) underlies this effect. Male Wistar rats were administered CsA (20 mg/kg/day, s.c.) for 21 days alone or in combination with sildenafil (5 mg/kg/day, p.o.). Sildenafil exhibited nephroprotective effects as evidenced by significant decrease in serum creatinine and urea levels, spot urine albumin-creatinine ratio, as well as renal level of malondialdehyde, with a concurrent increase in renal levels of reduced glutathione and nitric oxide along with catalase activity compared to CsA-treated rats. [corrected]. Additionally, immunohistochemical analysis demonstrated that sildenafil treatment markedly reduced inducible nitric oxide synthase, tumor necrosis factor-alpha, and caspase-3 expressions, while expression of endothelial nitric oxide synthase was prominently enhanced. The protective effects of sildenafil were confirmed by renal histopathological examination. Pretreatment with l-nitro-arginine methyl ester (10 mg/kg/day, i.p.), a non-selective nitric oxide synthase inhibitor, reversed the protection afforded by sildenafil. Taken together, the current study highlighted the renoprotective effects of sildenafil against CsA-induced nephrotoxicity in rats, which might be mediated, in part, through nitric oxide pathway as well as antioxidant, anti-inflammatory, and anti-apoptotic activities.

Renal fibrosis and proteomics: current knowledge and still key open questions for proteomic investigation

Renal tubulo-interstitial fibrosis is a non-specific process, representing the final common pathway for all kidney diseases, irrespective of their initial cause, histological injury, or etiology, leading to gradual expansion of the fibrotic mass which destroys the normal structure of the tissue and results in organ dysfunction and, ultimately, in end-stage organ failure. Proteomic studies of the fibrotic pathophysiological mechanisms have been performed in cell cultures, animal models and human tissues, addressing some of the key issues. This article will review proteomic contribution to the raising current knowledge on renal fibrosis biology and also mention seminal open questions to which proteomic techniques and proteomists could fruitfully contribute.

Mechanisms of renal cell apoptosis induced by cyclosporine A: a systematic review of in vitro studies

BACKGROUND

Chronic cyclosporine A (CsA) nephrotoxicity (CCN) is a major cause of chronic renal dysfunction and has no effective clinical interventions yet.

OBJECTIVE

To reveal the mechanisms of renal cell apoptosis in CCN, we analyzed all in vitro studies of such mechanisms.

METHODS

We collected all in vitro studies about the mechanisms of renal cell apoptosis induced by CsA in Medline (1966 to July 2010), Embase (1980 to July 2010) and ISI (1986 to July 2010), evaluated their quality according to in vitro standards and extracted data following the PICOS principles and synthesized the data.

RESULTS

First,CsA could upregulate Fas and Fas-L expression, increase FADD and apoptosis enzymes (caspase-2, -3, -4, -7, -8, -9 and -10) and downregulate the Bcl-2 and Bcl-xL. Second, CsA could induce oxidative stress and damage the antioxidant defense system. Third, CsA could increase the expression of HERP, GRP78 and CHOP. Fourth, CsA could induce renal cell apoptosis and increase their iNOS and p53 expression in cultured cells.

CONCLUSIONS

At least four pathways are involved in renal cell apoptosis induced by CsA in different cell species. Caspases might be their final common pathway in vitro. They might all provide potential points for interventions, but these need to be confirmed in vivo.

Melatonin suppresses cyclosporine A-induced autophagy in rat pituitary GH3 cells

Cyclosporine A (CsA) is a powerful immunosuppressive drug with side effects including the induction of chronic nephrotoxicity including endoplasmic reticulum (ER) stress in tubular cells. Recently, it was reported that autophagy is induced by ER stress and serves to alleviate the associated deleterious effects. In the current study, CsA treatment (0-100 microm) decreased cell survival of rat pituitary GH3 cells in a dose-dependent manner. At concentrations ranging from 1.0 to 10 microm, CsA induced a dose-dependent increase in the expression of microtubule-associated protein 1 light chain 3 (LC3)-I and LC3-II. Cells treated with 2.5 microm CsA exhibited cytoplasmic vacuolation, indicating that CsA induces autophagy in rat pituitary GH3 cells. In the presence of 1.0-10 microm CsA, the expression of catalase decreased while that of the ER stress markers, ER luminal binding protein (BiP) and inositol-requiring enzyme 1 alpha (IRE1alpha), increased as compared those levels in untreated cells. These results suggested that CsA-induced autophagy is dependent on ER stress. To determine whether melatonin would protect cells against CsA-induced autophagy, we treated rat pituitary GH3 cells with melatonin in the presence of CsA. Melatonin treatment (100 and 200 microm) suppressed autophagy induced by 2.5 and 5 microm CsA. Furthermore, co-treatment with 100 microm melatonin inhibited LC3-II expression, and increased catalase and phosphorylated p-ERK levels in the presence of 2.5 and 5 microm CsA. BiP and IRE1alpha expression in melatonin-co-treated cells was superior to that in cells treated with 2.5 and 5 microm CsA alone. Thus, melatonin suppresses CsA-mediated autophagy in rat pituitary GH3 cells.

Polymerized type I collagen reduces chronic cyclosporine nephrotoxicity

BACKGROUND

Polymerized type I collagen (P-collagen) has been successfully used to reduce human hypertrophic scars due to its anti-fibrotic and anti-inflammatory properties. We therefore carried out a study to determine if P-collagen reduces functional and structural injury in chronic cyclosporine [cyclosporine A (CsA)] nephropathy.

METHODS

Four groups of six male Wistar rats fed with a low sodium diet were treated with vehicle, P-collagen (0.8 mg/day, i.p.), CsA (15 mg/kg) or CsA + P-collagen for 15 days. Mean arterial pressure, renal blood flow and glomerular filtration rate were measured in all groups. Structural injury such as arteriolopathy, tubulo-interstitial fibrosis (TI-fibrosis) and positive apoptotic cells were quantified. The mRNA expression levels of transforming growth factor-beta (TGF-beta), kidney injury molecule (Kim-1), alpha-smooth muscle actin (alpha-SMA), glutathione peroxidase, catalase and Cu/Zn superoxide dismutase (SOD) as well as MnSOD were assessed. Antioxidant enzyme activity, renal lipoperoxidation and urinary excretion of oxygen peroxide (UH(2)O(2)V) were determined.

RESULTS

Cyclosporine produced renal dysfunction and induced the development of arteriolopathy, TI-fibrosis and tubular apoptosis. These alterations were associated with increases in TGF-beta, Kim-1 and alpha-SMA mRNA levels as well as with a significant increase of oxidative stress and a reduction of SOD activity. P-Collagen partially ameliorated CsA-induced renal dysfunction and structural injury and prevented both tubular apoptosis and increased oxidative stress. This renoprotective effect was found to be associated with a reduction of TGF-beta, Kim-1 and alpha-SMA mRNA levels.

CONCLUSIONS

This study has therefore demonstrated that P-collagen appears to have anti-fibrotic and anti-apoptotic properties and highlights the possibility that the compound might be useful in a strategy to reduce chronic CsA nephrotoxicity.

Sirolimus and cyclosporine A alter barrier function in renal proximal tubular cells through stimulation of ERK1/2 signaling and claudin-1 expression

Alteration of the tight junction complex in renal epithelial cells can affect renal barrier function and perturb normal kidney homeostasis. The immunosuppressant drugs cyclosporine A (CsA) and sirolimus (SRL) used in combination demonstrated beneficial effects in organ transplantation but this combination can also result in increased adverse effects. We previously showed that CsA treatment alone caused an alteration of the tight junction complex, resulting in changes in transepithelial permeability in Madin-Darby canine kidney distal tubular/collecting duct cells. The potential effect of SRL on transepithelial permeability in kidney cells is unknown. In this study, subcytotoxic doses of SRL or CsA were found to decrease the paracellular permeability of the porcine proximal tubular epithelial cells, LLC-PK1 cell monolayers, which was detected as an increase in transepithelial electrical resistance (TER). The cotreatment with SRL and CsA was found to increase TER in a synergistic manner. CsA treatment increased total cellular expression and membrane localization of the tight junction protein claudin-1 and this further increased with the combination of SRL/CsA. SRL and CsA treatment alone or in combination stimulated the phosphorylation of ERK1/2. The MEK-ERK1/2 pathway inhibitor, U0126, reduced the SRL, CsA, and CsA/SRL-induced increase in TER. U0126 also reduced the CsA and CsA/SRL-induced increase in the membrane localization of claudin-1. Alterations in claudin-2 and claudin-4 were also detected. However, the results suggest that the modulation in expression and localization of claudin-1 appears to be pivotal in the SRL- and CsA-induced modulation of the epithelial barrier function and that modulation is regulated by ERK1/2 signaling pathway.

A nanoconjugate Apaf-1 inhibitor protects mesothelial cells from cytokine-induced injury

Background

Inflammation may lead to tissue injury. We have studied the modulation of inflammatory milieu-induced tissue injury, as exemplified by the mesothelium. Peritoneal dialysis is complicated by peritonitis episodes that cause loss of mesothelium. Proinflammatory cytokines are increased in the peritoneal cavity during peritonitis episodes. However there is scarce information on the modulation of cell death by combinations of cytokines and on the therapeutic targets to prevent desmesothelization.

Methodology

Human mesothelial cells were cultured from effluents of stable peritoneal dialysis patients and from omentum of non-dialysis patients. Mesothelial cell death was studied in mice with S. aureus peritonitis and in mice injected with tumor necrosis factor alpha and interferon gamma.

Tumor necrosis factor alpha and interferon gamma alone do not induce apoptosis in cultured mesothelial cells. By contrast, the cytokine combination increased the rate of apoptosis 2 to 3-fold over control. Cell death was associated with the activation of caspases and a pancaspase inhibitor prevented apoptosis. Specific caspase-8 and caspase-3 inhibitors were similarly effective. Co-incubation with both cytokines also impaired mesothelial wound healing in an in vitro model. However, inhibition of caspases did not improve wound healing and even impaired the long-term recovery from injury. By contrast, a polymeric nanoconjugate Apaf-1 inhibitor protected from apoptosis and allowed wound healing and long-term recovery. The Apaf-1 inhibitor also protected mesothelial cells from inflammation-induced injury in vivo in mice.

Conclusion

Cooperation between tumor necrosis factor alpha and interferon gamma contributes to mesothelial injury and impairs the regenerative capacity of the monolayer. Caspase inhibition attenuates mesothelial cell apoptosis but does not facilitate regeneration. A drug targeting Apaf-1 allows protection from apoptosis as well as regeneration in the course of inflammation-induced tissue injury.

Established and newly proposed mechanisms of chronic cyclosporine nephropathy

Cyclosporine (CsA) has improved patient and graft survival rates following solid-organ transplantation and has shown significant clinical benefits in the management of autoimmune diseases. However, the clinical use of CsA is often limited by acute or chronic nephropathy, which remains a major problem. Acute nephropathy depends on the dosage of CsA and appears to be caused by a reduction in renal blood flow related to afferent arteriolar vasoconstriction. However, the mechanisms underlying chronic CsA nephropathy are not completely understood. Activation of the intrarenal renin-angiotensin system (RAS), increased release of endothelin-1, dysregulation of nitric oxide (NO) and NO synthase, up-regulation of transforming growth factor-beta1 (TGF-beta1), inappropriate apoptosis, stimulation of inflammatory mediators, enhanced innate immunity, endoplasmic reticulum stress, and autophagy have all been implicated in the pathogenesis of chronic CsA nephropathy. Reducing the CsA dosage or using other renoprotective drugs (angiotensin II receptor antagonist, mycophenolate mofetil, and statins, etc.) may ameliorate chronic CsA-induced renal injury. This review discusses old and new concepts in CsA nephropathy and preventive strategies for this clinical dilemma.

Differential proteomic analysis of cyclosporine A-induced toxicity in renal proximal tubule cells

BACKGROUND

The use of cyclosporine A (CsA) as a potent immunosuppressant has been limited by its severe nephrotoxic effects. The mechanisms involved are haemodynamic but also related to direct toxic effects of CsA on proximal tubule epithelial cells. We focused on defining a proteomic profile in CsA-treated proximal tubule cells to distinguish the direct impact of CsA on these cells from overlapping haemodynamically mediated phenomena that occur in an in vivo system.

METHODS

By means of high-throughput differential proteomic analyses and mass spectrometry techniques in CsA and vehicle-treated proximal tubule-derived cell lines of human and mouse origin, we determined proteins that change their expression in the presence of CsA.

RESULTS

CsA-induced toxicity analyses revealed that 10 mM CsA for 24 h was the threshold condition to induce significant changes in cell viability and proteomic profile. We identified 38 differentially expressed proteins on CsA-treated mouse PCT3 and human HK-2 cells, related to protein metabolism, response to damage, cell organization and cytoskeleton, energy metabolism, cell cycle and nucleobase/nucleoside/nucleotidic metabolism. 1D and 2D western blot assays in crude extracts from CsA-treated cells or kidneys with impaired function upon CsA treatment revealed a correlation with proteomic changes or differential isoform expression, in randomly selected proteins.

CONCLUSIONS

Proteins identified in this work might be useful markers to eventually distinguish CsA toxicity from chronic allograft nephropathy in protocol biopsies of transplanted patients, facilitating the adjustment of CsA doses to non-toxic ranges, as well as to study the impact of potential therapeutic interventions in an animal model.

The single insult of hypoxic preconditioning induces an antiapoptotic response in human proximal tubular cells, in vitro, across cold storage

OBJECTIVE

To examine whether hypoxia (one of the many components of ischaemic preconditioning) can induce a protective response in culture renal tubular cells, and thus determine if non-lethal periods of hypoxia could confer protection against apoptotic injury to human proximal tubular cells during cold storage and subsequent cytotoxic insult, and establish the cellular mechanisms by which this protection is induced.

MATERIALS AND METHODS

Human proximal tubular cells (HK-2) were pre-incubated for 24 h in normoxic or hypoxic conditions and then incubated at 4 degrees C for 6 h to mimic cold storage, before being returned to normal conditions and exposed to varying concentrations of cyclosporine A (CSA). Cell viability and apoptosis were measured using propidium iodide staining and flow cytometry. The expression of heat-shock protein (HSP)-70 was determined by Western blotting.

RESULTS

Hypoxia had no effect on cell viability or apoptosis. Pre-exposure of cells to hypoxia significantly protected against CSA-induced damage even after a period of cold storage. Western blotting analysis showed that hypoxia up-regulated the anti-apoptotic protein HSP-70. HK-2 cells over-expressing HSP-70 mimicked hypoxia preconditioning, in that they were protected during cold storage and CSA-induced apoptosis.

CONCLUSION

Exposure of renal tubular cells to a sequential model of cold storage, reperfusion and incubation with CSA resulted in apoptotic cell death. Preconditioning these cells with hypoxia induced a protective response and up-regulation of the anti-apoptotic protein HSP-70. There was a similar response in non-preconditioned cells over-expressing HSP-70. Further understanding of the cellular changes occurring during this period of preconditioning will allow the development of more targeted, clinically relevant methods of preconditioning in renal transplantation.

Renal cell apoptosis induced by nephrotoxic drugs: cellular and molecular mechanisms and potential approaches to modulation

Apoptosis plays a central role not only in the physiological processes of kidney growth and remodeling, but also in various human renal diseases and drug-induced nephrotoxicity. We present in a synthetic fashion the main molecular and cellular pathways leading to drug-induced apoptosis in kidney and the mechanisms regulating it. We illustrate them using three main nephrotoxic drugs (cisplatin, gentamicin, and cyclosporine A). We discuss the main regulators and effectors that have emerged as key targets for the design of therapeutic strategies. Novel approaches using gene therapy, antisense strategies, recombinant proteins, or compounds obtained from both classical organic and combinatorial chemistry are examined. Finally, key issues that need to be addressed for the success of apoptosis-based therapies are underlined.

Cytokine cooperation in renal tubular cell injury: the role of TWEAK

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK, TNFSF12) is a member of the TNF superfamily. TWEAK activates the Fn14 receptor, and may regulate apoptosis, proliferation, and inflammation, processes that play a significant role in pathological conditions. However, there is little information on the function and regulation of this system in the kidney. Therefore, TWEAK and Fn14 expression were studied in cultured murine tubular epithelial MCT cells and in mice in vivo. The effect of TWEAK on cell death was determined. We found that TWEAK and Fn14 expression was increased in experimental acute renal failure induced by folic acid. Cultured tubular cells express both TWEAK and the Fn14 receptor. TWEAK did not induce cell death in non-stimulated tubular cells. However, in cells costimulated with TNFalpha/interferon-gamma, TWEAK induced apoptosis through the activation of the Fn14 receptor. Apoptosis was associated with activation of caspase-8, caspase-9, and caspase-3, Bid cleavage, and evidence of mitochondrial injury. There was no evidence of endoplasmic reticulum stress. A pan-caspase inhibitor benzyloxycarbonyl-Val-Ala-DL-Asp prevented TWEAK-induced apoptosis, but it sensitized cells to necrosis via generation of reactive oxygen species. In conclusion, cooperation between inflammatory cytokines results in tubular cell death. TWEAK and Fn14 may play a role in renal tubular cell injury.

The effect of cyclosporin on cell division and apoptosis in human oral keratinocytes

BACKGROUND AND OBJECTIVE

Gingival overgrowth (GO) is a side-effect of cyclosporin A (CsA) therapy and is characterised by enlargement of the gingiva with epithelial thickening and overproduction of extracellular matrix components. The pathogenesis of the epithelial thickening in GO remains obscure. The objective of the present study was to investigate the effects of CsA on the growth of oral epithelial cells in vitro and to test the hypothesis that CsA influences apoptosis in these cells.

MATERIAL AND METHODS

Cyclosporin was cocultured with an immortalized normal human oral keratinocyte cell line (HOK-16B), an epitheloid cervical carcinoma cell line (HeLa) and primary oral keratinocytes. Cell division was quantified using a CyQUANT kit. Apoptosis was induced using tumour necrosis factor-alpha (TNF-alpha) and assayed by analysis of caspase-3 activity. Expression of the anti-apoptotic protein, Bcl-2, was measured by western blotting.

RESULTS

CsA exhibited a dose- and time-dependent inhibition of cell division in all three keratinocyte cell cultures. Significantly, HOK-16B cells treated with high doses of CsA (10 alphag/ml) did not recover their proliferative capacity 3 d after withdrawal of CsA, indicating that CsA-induced inhibition of growth is not temporary. Concentrations of CsA that inhibited cell division (1 microg/ml) did not have any effect on constitutive or TNF-alpha -induced apoptosis or Bcl-2 expression in HOK-16B cells.

CONCLUSION

CsA inhibits oral epithelial cell division and this effect is not associated with changes in apoptosis in these cells. The action of CsA on oral epithelial cells may be associated with a long-lasting stress signal, which might account for some of the pathological effects of this drug.

Renal and macrophage aminopeptidase activities in cyclosporin-treated mice

Cyclosporin, an immunosuppressive drug, is known to affect macrophage and to exert a nephrotoxic effect. Aminopeptidases play important roles for renal and macrophage functions. In this work, we attempt to test the hypothesis that the aminopeptidases participate within macrophage and renal effects induced by cyclosporin. Macrophage and renal aminopeptidase activities of cyclosporin-treated and control mice were evaluated, as well as renal caspase 3 activity, hematocrit, urinary protein and plasma osmolality, creatinine and uric acid concentrations. Cyclosporin treatment increased caspase 3 activity, hematocrit and osmolality, while urinary protein, creatinine and uric acid were unaltered. Soluble and particulate aminopeptidases in resident and elicited macrophages were unaffected by cyclosporin. The treatment with cyclosporin increased neutral, basic, cystyl, prolyl imino and pyroglutamyl soluble aminopeptidase activities in the renal cortex. Acid and basic soluble aminopeptidase activities increased in the renal medulla. Increased levels of particulate form in the cortex were detected for acid and pyroglutamyl aminopeptidase activities. Cyclosporin increased cortical soluble while decreased medullar particulate prolyl dipeptidyl aminopeptidase IV activity. With the exception of prolyl dipeptidyl aminopeptidase IV, particulate aminopeptidase activities returned to levels similar to controls after fifteen days of cyclosporin withdrawal, and soluble aminopeptidase activities did not regress. Our data indicate that the adopted regimen of cyclosporin treatment produced mild renal impairment with consistent changes on the levels of renal but not macrophage aminopeptidase activities. The obtained profiles of macrophage and renal aminopeptidase activities should be considered into the elaboration of new potential strategies for preventing nephrotoxicity during the treatment with cyclosporin.

IL-2-mediated apoptosis of kidney tubular epithelial cells is regulated by the caspase-8 inhibitor c-FLIP

BACKGROUND

Tubular epithelial cells (TECs) are essential in the maintenance of kidney function. Apoptosis of TECs occur during acute and chronic renal allograft rejection as well as other forms of renal injury, including autoimmune nephritis. The regulation of TEC apoptosis by proinflammatory cytokines associated with renal inflammation [e.g., interleukin (IL)-2 and interferon-gamma (IFN-gamma)] has not been extensively investigated.

METHODS

Apoptosis in murine TECs was determined by FACS with annexin-V or ligation-mediated-polymerase chain reaction (LM-PCR) and mRNA levels by reverse transcription (RT)-PCR or Northern blot. Protein expression was observed using Western blot.

RESULTS

IL-2R (CD25) was expressed by murine TECs and up-regulated by IL-2. Both IL-2 and IFN-gamma induced TEC apoptosis and activated caspase-8. Apoptosis with IL-2 was concentration-dependent and blocked by z-IETD-fmk, a specific caspase-8 inhibitor. Apoptosis with IFN-gamma was associated with increased surface expression of Fas, while IL-2 had no effect on Fas. IL-2 did not induce apoptosis in Fas-deficient TECs (M3.1-lpr) suggesting IL-2 regulation of caspase-8 activity requires Fas. Consistent with this, IL-2 but not IFN-gamma was found to decrease mRNA and protein expression of c-FLIP, an endogenous caspase-8 inhibitor in murine TECs. Overexpression of c-FLIP in TECs (CS3.7-FLIP) blocked apoptosis and caspase-8 activation with both IFN-gamma and IL-2. c-FLIP expression was found in kidney cortex, primary and cloned TECs, suggesting c-FLIP is likely a key regulator of caspase-8-mediated apoptosis in vivo.

CONCLUSION

This is the first report of c-FLIP regulation by IL-2 in renal TECs. Augmentation of c-FLIP in TECs may enhance an endogenous mechanism by which TECs normally resist injury to caspase-8-mediated apoptosis and thus may be a useful and novel strategy to prevent tubular injury in transplant rejection and autoimmune nephritis.

MEK inhibitor, U0126, attenuates cisplatin-induced renal injury by decreasing inflammation and apoptosis

BACKGROUND

Although inflammation and apoptosis are known to play important roles in cisplatin nephrotoxicity, the exact intracellular signaling mechanisms are not well understood. Recent reports that extracellular signal-regulated kinase (ERK1/2) pathway mediates cisplatin-induced caspase activation and apoptosis in cultured renal tubular cells led us to investigate the effect of MAPK/ERK kinase (MEK) inhibitor, an immediate upstream of ERK1/2 in cisplatin-induced acute renal failure (ARF) in mice.

METHODS

The effect of MEK/ERK1/2 inhibition on kidney tumor necrosis factor-alpha (TNF-alpha (gene expression, inflammation, the activation of tissue caspases, and apoptosis were examined in addition to its effects on renal function and histology in cisplatin-induced ARF in mice.

RESULTS

Pretreatment of MEK inhibitor, U0126, decreased ERK1/2 phosphorylation following cisplatin administration with significant functional and histologic protection. This beneficial effect was accompanied by decrease in TNF-alpha gene expression level and inflammation, as well as in caspase 3 activity and apoptosis.

CONCLUSION

These data provide evidence that ERK1/2 pathway functions as an upstream signal for TNF-alpha-mediated inflammation and caspase 3-mediated apoptosis in cisplatin-induced ARF in mice and suggest that ERK1/2 can be a novel therapeutic target in cisplatin nephrotoxicity.

Calcineurin Inhibitor–Induced Nephrotoxicity and Renal Expression of P-glycoprotein

STUDY OBJECTIVE

To evaluate immunohistochemistry staining patterns for P-glycoprotein (P-gp) and a marker of early apoptosis (active caspase-3) in renal biopsy specimens obtained from solid organ transplant recipients with nephrotoxicity and those from a control group.

DESIGN

Retrospective analysis of pathology specimens and medical records.

SETTING

Medical university.

SUBJECTS

Twenty-nine solid organ transplant recipients with nephrotoxicity and 32 control patients.

MEASUREMENTS AND MAIN RESULTS

Medical records were reviewed for patient demographics, clinical laboratory results, and prescribed drugs. Immunohistochemistry techniques using primary antibodies to P-gp and active caspase-3 were performed to evaluate staining patterns of these proteins in the kidney specimens. Differences in measures of interest between groups were compared with the Fisher exact test for categoric data and Wilcoxon rank sum test for continuous data. Logistic and linear modeling were used to evaluate difference in measures of P-gp and active caspase-3 between groups while controlling for confounders. Immunohistochemistry confirmed the presence of P-gp in the renal tubules (apical and basal membranes and cytoplasm). Intensity of P-gp staining (score range 0-4) was reduced in renal specimens of transplant recipients with nephrotoxicity compared with the control specimens (mean +/- SD intensity scores 3.2 +/- 0.7 vs 3.8 +/- 0.4, p=0.0002). Neither P-gp-inducing nor P-gp-inhibiting drugs predicted expression of P-gp in the renal specimens of either group. The extent of tubular staining (score range 1-4) for the apoptosis marker, active caspase-3, was less in the nephrotoxicity group than in the control group (mean +/- SD extent scores 1.7 +/- 0.6 vs 2.8 +/- 0.5, p=0.0003).

CONCLUSION

P-glycoprotein expression was less pronounced in renal biopsy specimens with calcineurin inhibitor-induced nephrotoxicity compared with the nonnephrotoxic control specimens. Reduced P-gp expression was evident even when the analysis controlled for factors such as renal function, age, sex, race, diabetes mellitus, level of proteinuria, or prescribed therapy with P-gp inducers or inhibitors. Interpretation of the results from active caspase-3 staining requires further study.

Methoxyethyl-modified intercellular adhesion molecule-1 antisense phosphorothiateoligonucleotides inhibit allograft rejection, ischemic-reperfusion injury, and cyclosporine-induced nephrotoxicity

BACKGROUND

The addition of phosphorothioate (PS) groups to natural phosphodiester (PD) antisense oligodeoxynucleotides (oligo) prevents their in vivo hydrolysis by nucleases allowing an RNase-dependent elimination of targeted mRNA. To further improve oligo function 2'-methoxyethyl (ME) groups were attached to selected nucleotides at the 3'-end because ME groups block RNase activity.

METHODS/RESULTS

ME modification of PS- or PD/PS-oligo targeting human intracellular adhesion molecule (ICAM)-1 mRNA significantly increased the degree and duration of the in vitro inhibitory effects without compromising selectivity and specificity. A 7-day intravenous or oral therapy with rat ME/PS-modified ICAM-1 antisense oligo extended the survivals of kidney allografts. In addition, ME/PS-modified ICAM-1 antisense oligo reduced ischemic-reperfusion injury in kidneys, as measured by glomerular filtration rate, creatinine levels, and infiltration with leukocytes. Finally, a 14-day treatment with cyclosporine (CsA)-induced nephrotoxicity in syngeneic kidney transplants correlated with both increased ICAM-1 protein expression and infiltration with leukocytes. Graft perfusion and treatment of recipients with ICAM-1 antisense ME/PS-oligo alleviated the nephrotoxic effect and decreased ICAM-1 expression and leukocyte infiltration.

CONCLUSIONS

ME/PS-modified ICAM-1 antisense oligo is very effective in inhibiting the ICAM-1-dependent mechanism of graft infiltration and tissue damage involved in allograft rejection, ischemic-reperfusion injury, and CsA-induced nephrotoxicity.

Effect of Pirfenidone on Apoptosis-Regulatory Genes in Chronic Cyclosporine Nephrotoxicity

BACKGROUND

: Apoptosis was shown to play a role in the progression of fibrosis in a chronic cyclosporine A (CsA) nephrotoxicity animal model. In addition, the antifibrotic molecule pirfenidone (PFD) was shown to ameliorate fibrosis in this model. We evaluated the role of PFD on the expression of apoptosis-regulatory genes in the kidneys of CsA-treated rats.

METHODS

: Rats were administered CsA 7.5 mg/kg per day, CsA+PFD (250 mg/kg/day), vehicle (VH), or VH+PFD, and sacrificed at 28 days. Physiologic and histologic changes were studied, and apoptosis was detected by terminal deoxynucleotide transferase-mediated dUTP nick-end labeling stain. The mRNA expression of pro-apoptotic genes p53 and Fas-ligand was evaluated by quantitative polymerase chain reaction, and that of Bcl-xL, an anti-apoptotic gene, was evaluated by Northern blot analysis. In addition to mRNA expression, immunohistochemical studies of caspase 3 were performed.

RESULT

: PFD administration to CsA-treated rats significantly ameliorated nephrotoxicity. Apoptosis-positive cells were increased by CsA but significantly reduced by PFD treatment (68+/-19 vs. 3+/-1, P<0.01). In addition, PFD down-regulated the mRNA expression of CsA-induced p53 and Fas-ligand (P<0.01) and increased that of Bcl-xL, previously reduced by CsA (P<0.01). Finally, PFD significantly down-regulated caspase 3 expression, present mostly on renal tubular epithelial cells. None of these changes were observed in VH-treated rats.

CONCLUSION

: Whereas CsA favored the expression of pro-apoptotic genes, that effect was ameliorated by PFD. Because apoptosis can partly explain the loss of cells associated with fibrosis, the influence of PFD on apoptosis-regulatory genes in a manner that reduces apoptosis may explain some of its antifibrotic properties.

The effect of alpha-melanocyte-stimulating hormone on renal tubular cell apoptosis and tubulointerstitial fibrosis in cyclosporine A nephrotoxicity

BACKGROUND

The pathogenesis of cyclosporine A (CsA)-induced nephrotoxicity has been known to be secondary to hemodynamic changes, but increasing evidence indicates that CsA has a direct toxicity to renal tubular cells, leading to their apoptosis and tubulointerstitial fibrosis. This study evaluated the mechanism for CsA-induced tubular cell apoptosis, tubulointerstitial fibrosis and its associated proteins, and the therapeutic effects of alpha-melanocyte-stimulating hormone (MSH) on them.

METHODS

Male Sprague-Dawley rats fed with a low-sodium diet were divided into three treatment groups: group A (vehicle-injected group), group B (CsA 15 mg/kg-injected group), and group C(CsA+alpha-MSH-injected group). After 42 days, creatinine clearance; blood CsA level; apoptosis; inflammation and tubulointerstitial fibrosis in renal tissue; and the expression of Bax, Bcl2, Fas, FasL, and transforming growth factor (TGF)-beta protein were determined.

RESULTS

CsA-induced tubular cell apoptosis; cellular infiltration; and increase of Fas, Bax, TGF-beta protein expression with significant tubulointerstitial fibrosis, and reduced Bcl2 protein expression. alpha-MSH treatment prevented the Bax and TGF-beta protein increase and induced Bcl2 protein increase, together with reduction of apoptosis, inflammation, and tubulointerstitial fibrosis.

CONCLUSIONS

These findings suggest that chronic CsA nephrotoxicity is related to Bax and Bcl2-related apoptosis pathways, and that alpha-MSH can attenuate the CsA-induced tubulointerstitial fibrosis as well as tubular cell apoptosis.

Calcium ionophoretic and apoptotic effects of ferutinin in the human Jurkat T-cell line

We have investigated the ionophoretic and apoptotic properties of the daucane sesquiterpene ferutinin and three related compounds, ferutidin, 2-alpha-hydroxyferutidin and teferin, all isolated from various species of plants from the genus Ferula. Ferutinin induced a biphasic elevation of intracellular Ca2+ in the leukemia T-cell line, Jurkat. First, a rapid calcium peak was observed and inhibited by BAPTA-AM. This initial calcium mobilization was followed by a sustained elevation, mediated by the entry of extracellular calcium through L-type calcium channels and sensitive to inhibition by EGTA. Moreover, ferutinin-induced apoptosis in Jurkat cells, and this event was preceded, in a cyclosporine-A sensitive manner, by a loss of mitochondrial transmembrane potential (DeltaPsim) and by an increase in intracellular reactive oxygen species. Ferutinin-induced DNA fragmentation was mediated by a caspase-3-dependent pathway, and was initiated independently of any specific phase of the cell cycle. The evaluation of ferutinin analogs in calcium mobilization and apoptosis assays showed strict structure-activity relationships, with p-hydroxylation of the benzoyl moiety being requested for activity.

Effect of calbindin-D28K on cyclosporine toxicity in cultured renal proximal tubular cells

Cyclosporine A (CsA) is known to have direct toxicity to renal tubular cells. Its toxicity may be mediated by intracellular calcium because CsA increases intracellular calcium concentration and enhances the activities of calcium-dependent calpains and caspases. Calbindin-D28k, a cytosolic calcium binding protein, has been used as an intracellular Ca2+ buffer to reduce calcium-mediated cytotoxicity in non-renal cells such as neuronal cells. We investigated the effects of gene transfer of calbindin-D28k cDNA on CsA cytotoxicity and intracellular calcium concentration ([Ca2+]i) in cultured murine proximal tubular (MCT) cells. A plasmid containing calbindin-D28k cDNA under the control of CMV promoter was transfected to MCT cells with liposomes. Cytotoxicity was assessed by LDH release and cell viability assay, and [Ca2+]i was measured ratiometrically with fura-2. Compared with MCT cells, cells transfected with calbindin-D28k cDNA showed a reduction in LDH release by 27, 30, 32, 33, and 19% (all P < 0.05), respectively, after 24 h exposure to 1, 2.5, 5, 10, and 25 microM CsA. Cell viability after CsA treatment was also significantly higher in CB cells. A mock transfection using plasmid without calbindin-D28k cDNA insert did not affect the LDH release or cell viability after CsA treatment. CsA treatment did not affect the protein and mRNA abundance of transfected calbindin-D28k cDNA. The expression of calbindin-D28k did not affect the baseline [Ca2+]i, but significantly suppressed CsA-induced elevation in [Ca2+]i. The expression of calbindin-D28k in renal tubular cells provides cytoprotective effects against CsA toxicity, probably through its buffering effects on [Ca2+]i.

Persistent proteinuria up-regulates angiotensin II type 2 receptor and induces apoptosis in proximal tubular cells

Apoptosis is implicated in the progressive cell loss and fibrosis both at glomerular and tubulointerstitial level. In this study, we examined the potential mechanisms by which persistent proteinuria (protein-overload model) could induce apoptosis. After uninephrectomy (UNX), Wistar rats received daily injections of 0.5 g of bovine serum albumin (BSA)/100 g body weight or saline. Both at day 8 and day 28, rats receiving BSA had proteinuria and renal lesions characterized by tubular atrophy and/or dilation and mononuclear cell infiltration. In relation to control-UNX rats, renal cortex of nephritic rats showed an increment in AT2 mRNA (reverse transcriptase-polymerase chain reaction) and protein (Western blot) expression. In both groups, AT2 receptor immunostaining was mainly localized in proximal tubular cells. Rats with persistent proteinuria showed a significantly increased number of terminal dUTP nick-end labeling positive apoptotic cells compared with UNX-controls, both in glomeruli and tubulointerstitium. Double staining for apoptosis and AT2 receptor showed that most terminal dUTP nick-end labeling positive cells were found in tubules expressing AT2 receptor. Using an antibody that recognizes the active form caspase-3, we observed an increment in caspase-3 activation in rats receiving BSA with respect to those receiving saline. Rats with persistent proteinuria showed a diminution in the phosphorylation of Bcl-2 with respect to UNX-controls both at day 8 and day 28. By contrast, no changes were observed either in the Bax or in the Bcl-2 protein levels. The administration of BSA to UNX rats induced a diminution in the phosphorylation of ERK with respect to UNX-control at all times studied. The changes observed in ERK activities took place without alterations of ERK1/2 protein levels. In summary, our data suggest that persistent proteinuria causes apoptosis in tubular cells through the activation of AT2 receptor, which can, in turn, inhibit MAP kinase (ERK1/2) activation and Bcl-2 phosphorylation.

Organic solvent-induced proximal tubular cell apoptosis via caspase-9 activation

Long-term exposure to solvents is associated with apoptosis, which is implicated in the development and progression of tubulo-interstitial fibrosis and chronic renal failure. In our previous study, we demonstrated that toluene and p-xylene as the most commonly used organic solvents induced proximal tubular cells apoptosis. This study was conducted to assess the apoptotic pathway of toluene and p-xylene induced proximal tubular apoptosis. This was assessed by measuring the caspase-9 activity LLC-PK1 cells exposed to both compounds. A model of proximal tubular cell (LLC-PK1) cytotoxicity exposed to 1mM of either p-xylene or toluene was compared to untreated control for caspase-9 activity and Bax/Bcl-2 protein level. Furthermore, DNA fragmentation in the presence of caspase-9 inhibitor (Z-LEHD-FMK) in a dose-dependent manner was assessed. Both compounds induced caspase-9 activity, which was accompanied by up-regulation of Bax, whereas Bcl-2 level did not change. DNA fragmentation induced by both solvents was inhibited by caspase-9 inhibitor in dose-dependent manner. This data suggest that p-xylene or toluene induces nephrotoxicity via mitochondrial caspase-9 pathway. This mechanism involves up-regulation of the apoptotic protein, Bax.

Targeting apoptosis in acute tubular injury

Recent research has shown that apoptosis and its regulatory mechanisms contribute to cell number regulation in acute renal failure. Acute tubular necrosis is the most frequent form of parenchymal acute renal failure. The main causes are ischemia-reperfusion, sepsis and nephrotoxic drugs. Exogenous factors such as nephrotoxic drugs and bacterial products, and endogenous factors such as lethal cytokines promote tubular cell apoptosis. Such diverse stimuli engage intracellular death pathways that in some cases are stimulus-specific. We now review the role of apoptosis in acute renal failure, the potential molecular targets of therapeutic intervention, the therapeutic weapons to modulate the activity of these targets and the few examples of therapeutic intervention on apoptosis.

Role of Ca2+-activated Cl- channels in the mechanism of apoptosis induced by cyclosporin A in a human hepatoma cell line

The mechanism of apoptosis induced by cyclosporin A (CsA) in a human hepatoma cell line was investigated. CsA induced apoptosis in a dose- and time-dependent manner in HepG2 human hepatoma cells. CsA induced Cl- efflux, which was significantly blocked by niflumic acid (NA), a specific inhibitor, and flufenamic acid (FA), 5-nitro-2-(3-phenyl-propylamino)-benzoate (NPPB), and 4,4'-diisothiocyanoto-stibene-2,2'-disulfonic acid (DIDS), non-specific inhibitors of Ca2+-activated Cl- channels (CaCCs), not by calyculin A, an inhibitor of K+,Cl- -cotransport. In addition, CsA did not alter intracellular K+ concentration. Moreover, CsA increased intracellular Ca2+ concentration, and treatment with BAPTA/AM, an intracellular Ca2+ chelator, significantly inhibited the CsA-induced Cl- efflux, indicating that CsA induced Cl- efflux through the activation of CaCCs. Treatment with these CaCC inhibitors (NA, FA, NPPB, and DIDS) markedly prevented the CsA-induced apoptosis. Taken together, these results suggest that CaCCs may mediate apoptosis induced by CsA in HepG2 cells. Furthermore, these results provide a new insight into the novel function of CaCCs in the regulation of cancer cell apoptosis associated with perturbation of intracellular Ca2+ signal.

Evaluation of p53, bcl-2, and interleukin-15 levels in gingival crevicular fluid of cyclosporin A-treated patients

BACKGROUND

Apoptosis plays an important role in the maintenance of tissue homeostasis. Considering that apoptosis mediators may play a role in the pathogenesis of drug-induced gingival overgrowth, this study was conducted to evaluate p53, bcl-2, and interleukin-15 (IL-15) levels in gingival crevicular fluid (GCF) of cyclosporin A (CsA)-treated patients.

METHODS

Twenty renal transplant patients exhibiting CsA-induced gingival overgrowth and 15 systemically healthy gingivitis patients were included in the study; 15 systemically and periodontally healthy volunteer subjects served as the healthy control group. GCF samples were obtained from one interdental site with gingival overgrowth (GO+) and one site without (GO-) from each CsA-treated patient; hyperplasia index, probing depth, papilla bleeding index, and plaque presence were recorded. One site from each gingivitis patient and healthy control was selected, GCF samples were obtained, and the same clinical parameters were recorded. GCF p53, bcl-2, and IL-15 levels were analyzed by enzyme-linked immunosorbent assay. The results were tested statistically.

RESULTS

p53 and bcl-2 levels were below the minimum detectable level in all GCF samples analyzed. CsA GO+ and CsA GO- sites, as well as gingivitis sites, exhibited significantly higher GCF levels of IL-15 compared to healthy controls (P<0.05). The difference between CsA GO+ sites and gingivitis sites was not statistically significant, although the total amount of IL-15 in CsA GO+ sites was lower than gingivitis sites (P>0.05). The total amount of IL-15 in CsA GO- sites was significantly lower than gingivitis sites (P<0.05). No significant correlation was found between the clinical parameters and GCF IL-15 levels (P>0.05).

CONCLUSIONS

The pathogenesis of CsA-induced gingival overgrowth is multifactorial. The findings of the present study indicate that IL-15 may play a role in the pathogenesis of CsA-induced gingival overgrowth due to its interactions with CsA and its role in apoptosis and inflammation.

Therapeutic benefit of spironolactone in experimental chronic cyclosporine A nephrotoxicity

BACKGROUND

Cyclosporine A (CsA) is an immunosuppressive drug used to prevent tissue allograft rejection. However, its long-term utilization is limited due to chronic nephrotoxicity for which no prevention is available. This study evaluated the effect of spironolactone on renal functional and structural alterations induced by CsA, and assessed whether the protective effect was associated with a reduction of transforming growth factor-beta (TGF-beta) and the change of extracellular matrix protein mRNA level.

METHODS

Male Wistar rats fed with low sodium diet were divided in four treatment groups: vehicle, CsA (30 mg/kg), spironolactone (20 mg/kg), or CsA+spironolactone. After 21 days, creatinine clearance (CCr), blood CsA, arteriolopathy in renal tissue, and TGF-beta, collagen I, collagen IV, fibronectin, and epidermal growth factor (EGF) mRNA levels in renal cortex were determined.

RESULTS

CsA reduced the CCr and up-regulated TGF-beta, collagen I and fibronectin mRNA expression with a significant development of arteriolopathy, and reduced EGF mRNA levels. In contrast, spironolactone administration prevented the fall in renal function and TGF-beta, collagen I, and fibronectin up-regulation, together with a reduction of arteriolopathy and tubulointerstitial fibrosis.

CONCLUSION

Our data show that aldosterone plays an important role as a mediator of renal injury induced by CsA. Thus, mineralocorticoid receptor blockade may be a potential strategy to prevent CsA nephrotoxicity.

Colchicine decreases apoptotic cell death in chronic cyclosporine nephrotoxicity

Colchicine has been shown to prevent kidney injury in chronic cyclosporine nephrotoxicity; however, the mechanisms of its action are undetermined. The purpose of this study was to clarify whether colchicine prevents cyclosporine-induced kidney injury by decreasing kidney-cell apoptosis. We also sought to determine whether such an antiapoptotic effect was related to Bcl-2/Bax protein and caspase3 activity. Adult male Sprague-Dawley rats kept on a salt-depleted diet (0.05% sodium) were treated daily for 28 days with cyclosporine (15 mg/kg in 1 mL/kg olive-oil vehicle), colchicine (30 microg/kg in 100% ethanol, diluted with sterile saline solution to a final concentration of 30 microg/mL), or both cyclosporine and colchicine. Kidney function, histomorphologic findings, in situ terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate-biotin nick end-labeling assay, expressions of Bcl-2 and Bax proteins, and caspase-3 enzymatic activity were compared for the different treatment groups. Compared with the vehicle-treated rats, rats given cyclosporine showed a decline in creatinine clearance rate, an increase in serum creatinine concentration, tubulointerstitial fibrosis, and an increase in the number of apoptotic cells (all P <.01). Concomitant administration of colchicine significantly reversed all the above parameters (all P <.05). The decreased expression of Bcl-2 and the ratio of Bcl-2 to Bax protein seen in cyclosporine-treated rat kidneys were significantly increased after colchicine treatment, accompanying a suppression of caspase-3 activity (P <.05). Furthermore, the decreased apoptotic cell death was closely correlated with improved renal tubulointerstitial fibrosis (r = 0.583, P <.05). These findings strongly suggest that a renoprotective effect of colchicine on cyclosporine-induced nephrotoxicity is coassociated with a decrease in apoptotic cells.

Expression of apoptosis-related genes in chronic cyclosporine nephrotoxicity in mice

To define the mechanism of cyclosporine (CsA)-induced apoptosis, we investigated the expression of apoptosis-related genes in experimental chronic CsA nephrotoxicity. Mice on a low-salt (0.01%) diet were given vehicle (VH, olive oil, 1 mg/kg/day), or CsA (30 mg/kg/day), and sacrificed at 1 and 4 weeks. Apoptosis was detected with deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) stain, and the expressions of apoptosis-related genes were evaluated by reverse transcription-polymerase chain reaction, immunoblot or immunohistochemistry. The activity of caspase 1 and 3 was also evaluated. The CsA group showed increases in apoptotic cells compared with the VH group (54 +/- 41 vs. 3 +/- 3, p < 0.05), and the number of apoptotic cells correlated well with interstitial fibrosis scores (r = 0.83, p < 0.01). The CsA group showed a significant increase in Fas-ligand mRNA (0.20 vs. 0.02 amol/microgram total RNA, p < 0.05) and Fas protein expression (146% vs. 95%, p < 0.05), compared with the VH group. The CsA group showed significant increases in ICE mRNA (0.21 vs. 0.03 amol/microgram total RNA at 4 weeks, p < 0.05) and CPP32 mRNA (0.18 vs. 0.03 amol/microgram total RNA at 4 weeks, p < 0.05), compared with the VH group. The enzymatic activity of ICE (16.6 vs. 7.9 rho mol/microgram/h, p < 0.05) and CPP32 protease (15.6 vs. 2.7 rho mol/microgram/h, p < 0.05) proteases were increased in the CsA group, compared with the VH group. The ratio between bax and bcl-2 protein increased significantly in the CsA group (5.3-fold), compared with the VH group. Levels of p53 protein also increased in the CsA group. Immunohistochemical detection of Fas, Fas-ligand, ICE and CPP32 revealed strong immunoreactivity in renal tubular cells in areas of structural injury. These findings suggest that local activation of the apoptosis-related genes is associated with CsA-induced apoptotic cell death.

Effect of calcium channel antagonist diltiazem and calcium ionophore A23187 on cyclosporine A-induced apoptosis of renal tubular cells

Calcium channel antagonists have been reported to have a favorable impact on cyclosporin A (CsA)-treated kidney transplant recipients. However, it is not clear whether this is because of their direct effect on antagonizing the toxicity of CsA to renal tubular cells. In this study, we have used Madin-Darby canine kidney tubular cells as a model to examine the effect of diltiazem, a calcium channel antagonist, on CsA-induced apoptosis. Moreover, to investigate the possible regulation of CsA cytotoxicity by intracellular calcium level, the effect of the calcium ionophore A23187 on CsA-induced apoptosis was also examined. We found that treatment of CsA (20 microM) alone caused 20-30% cell death, which was apparently (30-40%) enhanced by diltiazem at 100 microg/ml, accompanied by more severe DNA fragmentation, activation of caspases, and a decreased level of Bcl-2. The caspase inhibitor ZVAD-fmk or Bcl-2 overexpression was capable of suppressing apoptosis induced by the synergistic effect of diltiazem and CsA. Moreover, the survival rate of cells treated with CsA (30 microM) alone remained only 30%, however, it was markedly (approximately 40%) elevated by co-treatment with A23187 (75 ng/ml). The rescue of cells from CsA-induced apoptosis by A23187 was correlated with AKT activation, BAD phosphorylation, and caspase-3 inactivation. Taken together, our results suggest that the reported favorable impact of diltiazem on kidney grafts is likely not because of its direct protection on renal tubular cells. Instead, it enhances the toxicity of CsA to renal tubular cells. In addition, our findings raise a possibility that the intracellular calcium level and the AKT pathway may participate in the regulation of CsA cytotoxicity.

Endoplasmic reticulum membrane-sorting protein of lymphocytes (BAP31) is highly expressed in neurons and discrete endocrine cells

BAP31 is a transmembrane protein that associates with nascent membrane proteins in transit between endoplasmic reticulum (ER) and cis-Golgi. Its C-terminal dilysine (KKEE) motif, mediating return to the ER, is consistent with a role in early sorting of membrane proteins. An initiator caspase-binding site in the C-terminal domain of BAP31 is implicated in cytoplasmic membrane fragmentation events of apoptosis. Although BAP31 RNA is ubiquitous, the protein's anatomic localization has not been determined. To gain further insight into its possible functions, we localized BAP31 in primate tissues using monoclonal antibodies. Immunoreactivity was prominent in T- and B-lymphocytes in blood and in thymus, in cerebellar Purkinje neuron bodies and dendrites, in gonadotrophs of the anterior pituitary, ovarian thecal and follicular cells, active but not quiescent thyroid epithelium, adrenal cortex more than medulla, and proximal more than distal renal tubules. Blood vessels and skeletal muscle were nonreactive. The anatomic distribution of BAP31 and the nature of proteins identified thus far as its cargo exiting the ER, suggest an interaction with proteins assembling in macromolecular complexes en route to selected sites of exocytotic and signaling activities. Apoptotic associations in mature tissues could be physiological (lymphocytes, endocrine cells) or pathological (Purkinje neurons, renal tubules).

Renal cell apoptosis in chronic obstructive uropathy: the roles of caspases

BACKGROUND

Apoptosis of tubular and interstitial cells is well documented in kidneys with chronic obstructive uropathy (COU) and probably plays an important role in the pathogenesis of this condition. The molecular control of apoptosis in COU remains poorly understood. Apoptosis in general is known to proceed initially along distinct pathways, which later converge into a common arm characterized by orderly activation of caspases. Caspases are cytosolic enzymes that belong to a 12-member family and serve as effector molecules for apoptosis. The role of individual caspases in mediating renal cell apoptosis in kidneys with COU is studied.

METHODS

Kidneys were harvested from sham-operated mice and mice with COU created by left ureter ligation at days 4, 7, 15, 20, and 30. The following studies were performed: (1) determination of dried kidney weight; (2) in situ end labeling of fragmented DNA to detect apoptotic tubular and interstitial cells; (3) ribonuclease protection assay with specific anti-sense RNA probes for caspases 1, 2, 3, 6, 7, 8, 9, 11, and 12 to detect the expression of individual caspases; (4) immunostaining for caspases; and (5) assay for caspase 3. To assess the role of caspases in COU-associated renal cell apoptosis, the frequencies of apoptotic tubular and interstitial cells were separately quantitated for each experimental time point, and their patterns of variation were correlated with those of individual caspases.

RESULTS

The obstructed kidneys showed progressive tissue loss (60% of control at day 15). Apoptosis of both tubular and interstitial cells was seen in obstructed kidneys. Tubular cell apoptosis peaked at four days after ureter ligation (13-fold of control), remained high between days 4 to 15, and thereafter decreased rapidly. Apoptotic interstitial cells were scanty initially, but gradually increased throughout the entire experiment. Apoptosis was minimal throughout the experiment in control and contralateral kidneys. In control and contralateral kidneys, caspases 2, 3, 6, 7, 8, and 9 mRNAs were expressed at low levels, whereas those for caspases 1, 11, and 12 were not detected. The obstructed kidneys displayed increased expression of all tested caspases. Caspases 1, 11, and 12 mRNAs were detected in obstructed kidneys in a common pattern characterized by a sharp increase at day 4, followed by a decrease until day 20, and a subsequent sharp increase until the end of the study at day 30. A similar pattern was noted for other caspases (2, 3, 6, 7, 8, and 9), which maximally reached twofold to fourfold that of controls. Immunostaining for caspases 1, 2, 3, 6, 7, 8, and 9 showed the same pattern characterized by focal and weak expression in proximal tubules of control or contralateral kidney, contrasting with increased staining in atrophic or dilated tubules of obstructed kidneys. Interstitial cells also displayed staining for several caspases, which paralleled the increasing density of interstitial cells toward the end of the experiment. Caspase-3 assay showed a marked increased activity in obstructed kidneys that reached fourfold and sevenfold of control at days 4 and 30, respectively. The rise and fall of caspase mRNAs between days 4 and 30 paralleled a similar fluctuation in tubular cell apoptosis. The subsequent increase of mRNAs was correlated with a continuous rise of interstitial cell apoptosis.

CONCLUSIONS

Urinary obstruction in mice induces apoptosis of both tubular and interstitial cells in the affected kidney in a distinctive pattern that parallels an increased expression of caspases. This correlation suggests that these caspases mediate COU-associated renal cell apoptosis. Among the evaluated caspases, increased renal caspase 3 activity implies its central role in renal cell apoptosis associated with urinary obstruction.

Cyclosporine reduces left ventricular mass with chronic aortic banding in mice, which could be due to apoptosis and fibrosis

A tacit assumption in studies of left ventricular (LV) hypertrophy is that left ventricular/body weight (LV/BW) reflects the extent of myocyte hypertrophy. The goal of the current investigation was to determine if there was another explanation for the reduced LV/BW observed after inhibiting calcineurin with cyclosporine during the development of pressure overload LV hypertrophy as compared with animals that did not receive cyclosporine. Accordingly, we examined the prevalence of fibrosis and apoptosis and measured cell size in the hearts from mice at 1 and 3 weeks after transverse aortic banding with and without chronic cyclosporine. Although LV/BW, compared to aortic banded vehicle treated mice, was reduced by 30% in aortic banded cyclosporine treated mice, myocyte cross sectional area was similar in both banded groups (346+/-9 microm2 v 336+/-13 microm2). The volume percent interstitial fibrosis was greater in aortic banded cyclosporine treated animals (1.4+/-0.2%) compared with aortic banded vehicle treated animals (0.9+/-0.2%, P<0.05) or in sham animals (0.6+/-0.1%). Surprisingly, lesions including myocytes containing iron were observed and were most prominent in aortic banded cyclosporine treated animals. Apoptosis, quantitated with TUNEL staining as percent of myocytes, was increased in aortic banded cyclosporine treated animals at 7 days (1.6+/-0.4%) compared with aortic banded vehicle treated animals (0.4+/-0.1%, P<0.01) and was still increased at 21 days. Immunoblotting demonstrated a decrease in the phosphorylation of Akt and Bad, and also Bcl-2 levels were reduced in aortic banded cyclosporine treated animals at 7 days compared with aortic banded vehicle treated animals. These proteins protect against apoptosis, and support the concept that cyclosporine inhibited the calcineurin pathway, resulting in enhanced apoptosis. Thus, the decrease in LV/BW in the aortic banded cyclosporine treated animals actually may be due, at least in part, to cell loss and death, as reflected by the enhanced fibrosis and apoptosis and the focal iron deposits in myocytes.

Apoptosis contributes to amphotericin B-induced nephrotoxicity

The aim of this study was to investigate whether apoptosis contributes to nephrotoxicity caused by amphotericin B (AmB). By detecting apoptosis-specific DNA fragmentation, it is demonstrated that proximal tubular cells (LLC-PK(1)) and medullary interstitial cells (RMIC) respond with programmed cell death when treated with therapeutic doses of AmB. Concomitant application of AmB and recombinant human insulin-like growth factor-1 (rhIGF-1), a known antiapoptotic agent, abrogated apoptosis in vitro. To validate that the observed apoptotic effects on renal tissue culture cells are applicable to an in vivo setting, an animal model was used for verification. Therefore, Sprague-Dawley rats were treated with AmB. The drug caused hypokalemia, decreased weight gain, loss of renal concentrating ability, and dehydration in a dose-dependent fashion. Microscopic examination of renal tissue sections revealed apoptotic alterations predominantly in proximal and distal tubular epithelial cells. To verify that the observed clinical side effects were linked to apoptosis, rhIGF-1 was applied concomitantly with AmB. In all animals, rhIGF-1 prevented the above-mentioned clinical side effects. Moreover, significantly reduced apoptosis was observed in renal tissue sections of these animals, indicating the relevance of apoptosis in nephrotoxicity. This is the first report to demonstrate that AmB induces apoptosis in the rat kidney in a dose-dependent fashion. The incidence of apoptosis correlates with renal toxicity and can be abrogated by concomitant treatment with rhIGF-1.

Hepatocyte growth factor, but not insulin-like growth factor I, protects podocytes against cyclosporin A-induced apoptosis

Cyclosporin A (CsA) nephropathy is associated with altered expression of apoptosis regulatory genes such as Fas-ligand and Bcl-2 family members in the glomerular, tubulointerstitial, and vascular compartments. Both hepatocyte growth factor (HGF) and insulin-like growth factor (IGF-I) protect against apoptosis, and HGF specifically up-regulates Bcl-xL, a protein that regulates apoptosis. We investigated whether Bcl-xL and Fas/Fas-ligand were regulated by CsA in cultured podocytes and whether CsA-induced apoptosis was prevented by HGF or IGF-I. A murine podocyte cell line was treated with CsA in the presence or absence of HGF or IGF-I. Apoptosis was quantitated by ELISA and by flow cytometry; Bcl-xL, Fas, and Fas-ligand were measured by Western blotting. Inhibitors of MAP kinase/ERK kinase (MEK)-1 and of phosphatidylinositol 3'-kinase (PI3'-K) were used to determine the signaling pathways involved in Bcl-xL regulation. Apoptosis was induced by CsA in a dose- and time-dependent fashion. CsA also decreased Bcl-xL levels. HGF, but not IGF-I, prevented apoptosis and restored Bcl-xL levels. The regulation of Bcl-xL by HGF was mediated by the PI3'-K but not by the MEK-1 pathway. In summary, we showed that CsA induces apoptosis in podocytes. Apoptosis was prevented by pretreatment with HGF but not IGF-I. Decreased apoptosis appeared to be mediated by regulation of Bcl-xL via the PI3'-K pathway. Our data suggest that the effect of CsA on podocytes may contribute to the glomerular damage and that HGF could provide protection.

Proapoptotic Fas ligand is expressed by normal kidney tubular epithelium and injured glomeruli

Fas ligand (FasL) is a cell membrane cytokine that can promote apoptosis through activation of Fas receptors. Fas receptor activation induces glomerular cell apoptosis in vivo and participates in tubular cell death during acute renal failure. However, there is little information on the expression of FasL in the kidney. This study reports that FasL mRNA and protein are present in normal mouse and rat kidney. In situ hybridization and immunohistochemistry showed that proximal tubular epithelium is the main site of FasL expression in the normal kidney. In addition, increased total kidney FasL mRNA and de novo FasL protein expression by glomerular cells were observed in two different models of glomerular injury : rat immune-complex proliferative glumerulonephritis and murine lupus nephritis. Both full-length and soluble FasL were increased in the kidneys of the mice with nephritis. Cultured murine proximal tubular epithelial MCT cells and primary cultures of murine tubular epithelial cells expressed FasL mRNA and protein. Tubular epithelium-derived FasL induced apoptosis in Fassensitive lymphoid cell lines but not in Fas-resistant lymphoid cell lines. By contrast, MCT cells grown in the presence of the survival factors of serum were resistant to FasL, and only became partially sensitive to apoptosis induced by high concentrations (100 ng/ml) of FasL upon serum deprivation. However, MCT cells stimulated with inflammatory mediators (tumor necrosis factor-alpha, interferon-gamma, and lipopolysaccharide) increased cell surface Fas expression and were sensitized to apoptosis induced by FasL (FasL 55 +/- 5% versus control 8.3 +/- 4.1% apoptotic cells at 24 h, P < 0.05). Cytokine-primed primary cultures of tubular epithelial cells also acquired sensitivity to FasL-induced apoptosis. These results suggest that FasL expression by intrinsic renal cells may play a role in cell homeostasis in the normal kidney and during renal injury.

Cyclosporine induces different responses in human epithelial, endothelial and fibroblast cell cultures

BACKGROUND

Nephrotoxicity, accelerated atherosclerosis, and graft vascular disease are common complications of cyclosporine long-term treatment characterized by a wide disruption of organ architecture with increased interstitial areas and accumulation of extracellular matrix (ECM). How cyclosporine induces these changes is not clear, but it is conceivable that they are the sum of changes induced at the cell level.

METHODS

We studied the effects of cyclosporine on human endothelial (HEC), epithelial (HK-2), and fibroblast (MRC5) cells. Cell proliferation was evaluated by cell counting, apoptosis and collagen production by enzyme-linked immunosorbent assay, and nitric oxide by measuring the concentration of nitrite/nitrate in the cell supernatant. (alpha1)I and (alpha2)IV collagen, matrix metalloprotease-9 (MMP9), and tissue inhibitors of metalloprotease-1 (TIMP-1) mRNA levels were measured by reverse transcription-polymerase chain reaction. Proteolytic activity was evaluated by zymography.

RESULTS

Cyclosporine showed a marked antiproliferative and proapoptotic effect on endothelial and epithelial cells. Fibroblast growth was not affected by cyclosporine. Nitric oxide was up-regulated by cyclosporine in epithelial cells and fibroblasts but not in endothelial cells. (alpha1)I and (alpha2)IV collagen synthesis was increased in cyclosporine-treated endothelial and epithelial cells, respectively. Proteolytic activity was increased in endothelial and epithelial cells. TIMP-1 mRNA was up-regulated by cyclosporine in fibroblasts.

CONCLUSIONS

Our results demonstrate that cyclosporine exhibits an antiproliferative effect on endothelial and epithelial cells. This effect is associated with induction of apoptosis probably via nitric oxide up-regulation in epithelial cell cultures. Cyclosporine treatment induces ECM accumulation by increasing collagen synthesis in endothelial and epithelial cells and reducing its degradation by up-regulating TIMP-1 expression in fibroblasts. We conclude that cyclosporine affects cell types differently and that the disruption of organ architecture is the result of multiple effects at the cell level.

Cocaine induces apoptosis in human coronary artery endothelial cells

This study was designed to determine the direct cytotoxic effect of cocaine on human coronary artery endothelial cells (HCAECs). Cocaine treatment of cultured HCAECs induced a time- and dose-dependent increase in apoptotic cell death in HCAECs. Cocaine-induced surface exposure of phosphatidylserine in HCAECs was seen as early as at 6 h. With prolonged treatment < or =72 h, cocaine (10-500 microM) produced a dose-dependent increase in apoptosis in the cells. Corresponding DNA fragmentation induced by cocaine was demonstrated in situ by terminal deoxynucleotidyl transferase (Tdt) UTP nick end-labeling TUNEL assay and by electrophoresis of labeled DNA fragments, showing the characteristic apoptotic ladders. Both caspase-9 (Z-LEHD-FMK) and caspase-3 (Ac-DEVD-CHO) inhibitors blocked cocaine-induced apoptosis. In addition, cyclosporin A inhibited cocaine-induced apoptosis in a concentration-dependent manner with a median inhibitory concentration (IC50) of 0.3 microM. The maximum of 62% inhibition was obtained with 3 microM cyclosporin A. Cocaine-induced apoptosis also was blocked by naloxone and nifedipine in a dose-dependent manner. These findings suggest that cocaine induces apoptosis in cultured HCAECs, which may be mediated by opioid receptors. The release of cytochrome c from the mitochondria and its subsequent activation of caspase-9 and caspase-3 may play a key role in cocaine-induced apoptosis.