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

KAP degradation by calpain is associated with CK2 phosphorylation and provides a novel mechanism for cyclosporine A-induced proximal tubule injury

The use of cyclosporine A (CsA) is limited by its severe nephrotoxicity that includes reversible vasoconstrictor effects and proximal tubule cell injury, the latter associated whith chronic kidney disease progression. The mechanisms of CsA-induced tubular injury, mainly on the S3 segment, have not been completely elucidated. Kidney androgen-regulated protein (KAP) is exclusively expressed in kidney proximal tubule cells, interacts with the CsA-binding protein cyclophilin B and its expression diminishes in kidneys of CsA-treated mice. Since we reported that KAP protects against CsA toxicity in cultured proximal tubule cells, we hypothesized that low KAP levels found in kidneys of CsA-treated mice might correlate with proximal tubule cell injury. To test this hypothesis, we used KAP Tg mice developed in our laboratory and showed that these mice are more resistant to CsA-induced tubular injury than control littermates. Furthermore, we found that calpain, which was activated by CsA in cell cultures and kidney, is involved in KAP degradation and observed that phosphorylation of serine and threonine residues found in KAP PEST sequences by protein kinase CK2 enhances KAP degradation by calpain. Moreover, we also observed that CK2 inhibition protected against CsA-induced cytotoxicity. These findings point to a novel mechanism for CsA-induced kidney toxicity that might be useful in developing therapeutic strategies aimed at preventing tubular cell damage while maintaining the immunosuppressive effects of CsA.

Protective effect of docosahexaenoic acid against cyclosporine A-induced nephrotoxicity in rats: a possible mechanism of action

The aim of this experimental study was to investigate whether, and how then, docosahexaenoic acid (DHA) could alleviate the cyclosporine A (CsA)-induced nephrotoxicity. Three main groups of Sprague-Dawley rats were treated orally with CsA (25 mg/kg), DHA (100 mg/kg), and CsA along with DHA. A corresponding control group was also used. DHA administration significantly reduced CsA-induced nephrotoxicity and associated hyperlipidemia and proteinuria as assessed by estimating serum triacylglycerol, serum total cholesterol, serum total protein, serum urea, and creatinine clearance. Furthermore, urinary excretions of protein and N-acetyl-β-D-glucosaminidase were significantly inhibited following DHA administration. DHA supplementation slightly attenuated the oxidative damage in kidney tissues as evaluated by the levels of thiobarbituric acid-reacting substances and protein carbonyl content in the kidney homogenate, although there were no significant differences between CsA-intoxicated and DHA-treated animals. Moreover, DHA treatment significantly restored total nitric oxide (NO) levels in both renal tissues and urine. This study demonstrates the ability of DHA to ameliorate CsA-induced renal dysfunction, which might be beneficial to enhance the therapeutic index of CsA. The data suggest that the protective potential of DHA in the prevention of CsA nephrotoxicity in rats was mainly associated with the increase of total NO bioavailability in renal tissues. Nevertheless, the exact independent mechanism in which DHA exerts its beneficial effect is yet to be fully elucidated.

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.

Contrasting roles of neuronal Msk1 and Rsk2 in Bad phosphorylation and feedback regulation of Erk signalling

Activated extracellular-signal-regulated kinase (Erk) phosphorylates and activates downstream kinases including ribosomal S6 kinase 2 (Rsk2/RPS6KA3) and mitogen- and stress-activated kinase 1 (Msk1, RPS6KA5). Rsk2 plays an important role in neuronal plasticity, as patients with Coffin-Lowry syndrome, where Rsk2 is dysfunctional, have impaired cognitive function. However, the relative role of neuronal Rsk2 and Msk1 in activating proteins downstream of Erk is unclear. In PC12 cells and in cortical neurones, the calcium ionophore A23187-induced phosphorylation of Erk, Msk1, Rsk2 and also the Bcl-2-associated death protein (Bad), which protects against neurotoxicity. Specific knockdown of Msk1 with small interfering RNA reduced the ability of A23187 to induce Bad phosphorylation in both PC12 cells and cortical neurones. Conversely, specific knockdown of Rsk2 potentiated Bad phosphorylation following A23187 treatment, and also elevated Erk phosphorylation in both cell types. This indicates that Msk1 rather than Rsk2 mediates neuronal Bad phosphorylation following Ca(2+) influx and implicates Rsk2 in a negative-feedback regulation of Erk activity.

Effect of aristolochic acid on intracellular calcium concentration and its links with apoptosis in renal tubular cells

Aristolochic acid (AA) has been demonstrated to play a causal role in Chinese herbs nephropathy. However, the detailed mechanism for AA to induce apoptosis of renal tubular cells remains obscure. In this study, we show that AA evokes a rapid rise in the intracellular Ca(2+) concentration of renal tubular cells through release of intracellular endoplasmic reticulum Ca(2+) stores and influx of extracellular Ca(2+), which in turn causes endoplasmic reticulum stress and mitochondria stress, resulting in activation of caspases and finally apoptosis. Ca(2+) antagonists, including calbindin-D(28k) (an intracellular Ca(2+) buffering protein) and BAPTA-AM (a cell-permeable Ca(2+) chelator), are capable of ameliorating endoplasmic reticulum stress and mitochondria stress, and thereby enhance the resistance of the cells to AA. Moreover, we show that overexpression of the anti-apoptotic protein Bcl-2 in combination with BAPTA-AM treatment can provide renal tubular cells with almost full protection against AA-induced cytotoxicity. In conclusion, our results demonstrate an impact of AA to intracellular Ca(2+) concentration and its link with AA-induced cytotoxicity.

Curcumin, a diferuloylmethane, attenuates cyclosporine-induced renal dysfunction and oxidative stress in rat kidneys

Background

In India, Curcumin (CMN) is popularly known as "Haldi", and has been well studied due to its economic importance. Traditional Indian medicine claims the use of its powder against biliary disorders, anorexia, coryza, cough, diabetic wounds, hepatic disorder, rheumatism and sinusitis. This study was designed to examine the possible beneficial effect of CMN in preventing the acute renal failure and related oxidative stress caused by chronic administration of cyclosporine (CsA) in rats. CMN was administered concurrently with CsA (20 mg/kg/day s.c) for 21 days. Oxidative stress in kidney tissue homogenates was estimated using thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH) content, superoxide dismutase (SOD), and Catalase (CAT). Nitrite levels were estimated in serum and tissue homogenates.

Results

CsA administration for 21 days produced elevated levels of TBARS and marked depletion of renal endogenous antioxidant enzymes and deteriorated the renal function as assessed by increased serum creatinine, Blood Urea Nitrogen (BUN) and decreased creatinine and urea clearance as compared to vehicle treated rats. CMN markedly reduced elevated levels of TBARS, significantly attenuated renal dysfunction increased the levels of antioxidant enzymes in CsA treated rats and normalized the altered renal morphology.

Conclusion

In conclusion our study showed that CMN through its antioxidant activity effectively salvaged CsA nephrotoxicity.

Differential Effect of the Focal Adhesion Kinase Y397F Mutant on v-Src-Stimulated Cell Invasion and Tumor Growth

Upon cell adhesion to extracellular matrix proteins, focal adhesion kinase (FAK) rapidly undergoes autophosphorylation on its Tyr-397 which consequently serves as a binding site for the Src homology 2 domains of the Src family protein kinases and several other intracellular signaling molecules. In this study, we have attempted to examine the effect of the FAK Y397F mutant on v-Src-stimulated cell transformation by establishing an inducible expression of the Y397F mutant in v-Src-transformed FAK-null (FAK(-/-)) mouse embryo fibroblasts. We found that the FAK Y397F mutant had both positive and negative effects on v-Src-stimulated cell transformation; it promoted v-Src-stimulated invasion, but on the other hand it inhibited the v-Src-stimulated anchorage-independent cell growth in vitro and tumor formation in vivo . The positive effect of the Y397F mutant on v-Src-stimulated invasion was correlated with an increased expression of matrix metalloproteinase-2, both of which were inhibited by the specific phosphatidylinositol 3-kinase inhibitor wortmannin or a dominant negative mutant of AKT, suggesting a critical role for the phosphatidylinositol 3-kinase/AKT pathway in both events. However, the expression of the Y397F mutant rendered v-Src-transformed FAK(-/-) cells susceptible to anoikis, correlated with suppression on v-Src-stimulated activation of ERK and AKT. In addition, under anoikis stress, the induction of the Y397F mutant in v-Src-transformed FAK(-/-) cells selectively led to a decrease in the level of p130(Cas), but not other focal adhesion proteins such as talin, vinculin, and paxillin. These results suggest that FAK may increase the susceptibility of v-Src-transformed cells to anoikis by modulating the level of p130(Cas).

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.

Cyclosporine A and FK506 induce osteoclast apoptosis in mouse bone marrow cell cultures

Studies were carried out to characterize the effects of cyclosporines and FK506 on the formation and survival of osteoclasts deriving from mouse bone marrow cultures. Cyclosporin A (CsA), cyclosporin B (CsB), cyclosporin H (CsH), and FK506 all inhibited receptor activator of NFkappaB ligand (RANKL)-stimulated tartrate-resistant acid phosphatase (TRAP) activity and generation of TRAP+ multinucleated cells in the cultures. CsA and CsG were approximately equipotent, CsH was approximately one order of magnitude less potent than the other cyclosporines, and FK506 was approximately two orders of magnitude more potent than CsA and CsG. All of the inhibitors demonstrated greater potency and efficacy on decreasing the number of TRAP+ multinucleated cells than on decreasing total TRAP activity. Further evidence that late stages were more sensitive to inhibition was obtained in experiments in which CsA was present for different segments of the RANKL-stimulated culture period. CsA was as efficacious when added for the final 2 days of a 4-day culture as when added for the entire culture period, whereas it was less effective if added for only the first 2 days of the culture. When CsA or FK506 were added for 1 day to cultures in which osteoclasts had already formed, the numbers of TRAP+ osteoclasts decreased. Treatment with CsA or FK506 produced nuclear fragmentation and disruption of the multinucleated osteoclasts and an increase in caspase-3 activity. The apoptosis inhibitor z-VAD partially prevented the inhibitory effects of CsA and FK506 on the survival of TRAP+ multinucleated cells in the cultures and also preserved the normal osteoclast morphology. The data indicate that an important component of the inhibitory effects of CsA and FK506 on marrow-derived osteoclasts is the induction of apoptosis.

Blockade of v-Src-stimulated tumor formation by the Src homology 3 domain of Crk-associated substrate (Cas)

Crk-associated substrate (Cas) is highly phosphorylated by v-Src and plays a critical role in v-Src-induced cell transformation. In this study, we found that the Src homology (SH) 3 domain of Cas blocked v-Src-stimulated anchorage-independent cell growth, Matrigel invasion, and tumor growth in nude mice. Biochemical analysis revealed that the Cas SH3 domain selectively inhibited v-Src-stimulated activations of AKT and JNK, but not ERK and STAT3. Attenuation of the AKT pathway by the Cas SH3 domain rendered v-Src-transformed cells susceptible to apoptosis. Inhibition of the JNK pathway by the Cas SH3 domain led to suppression of v-Src-stimulated invasion. Taken together, our results indicate that the Cas SH3 domain has an anti-tumor function, which severely impairs the transforming potential of v-Src.