Cyclosporin-A Induced Toxicity in Rat Renal Collecting Duct Cells: Interference with Enhanced Hypertonicity Induced Apoptosis

Abstract

Background/ Aims: Rat renal inner medullary collecting duct (IMCD) cells are physiologically exposed to a wide range of ambient tonicity. To maintain their function upon changes in osmolality, IMCD cells induce expression of osmoprotective and antiapoptotic genes, mainly mediated by the transcription factor Tonicity Enhancer Binding Protein (TonEBP). Some drugs like Cyclosporin-A (CsA) are discussed to interfere with the activity of TonEBP and thereby mediate their nephrotoxic effects. The aim of our study was to further understand CsA toxicity during elevation of ambient osmolality. Methods: First we examined cytotoxicity of CsA in IMCD exposed to elevated tonicity. Employing microarray analysis of gene expression, real-time PCR and immunoassays, we scrutinized pathways contributing to this effect. Results: We show that in IMCD cells CsA but not FK506 increases apoptosis upon an increase in tonicity. This effect is independent of cellular TonEBP localization or activity and reactive oxygen species. Microarray studies revealed marked quantitative differences in gene expression. Functional analysis showed overrepresentation of genes associated with cell death in presence of CsA. This correlated with increased mRNA expression of genes associated with the death receptor pathway and detection of TNFΑ in culture medium of cells treated with CsA. Conclusion: Our results show that CsA cytotoxicity is induced under elevated ambient osmolality and that death receptor signaling probably contributes to CsA cytotoxicity.

Different effects of CsA and FK506 on aquaporin-2 abundance in rat primary cultured collecting duct cells

“…Here, we did not see any difference in TonEBP localization as well as TonEBP mediated transcription [40].…”

“…However, there are conflicting results concerning the effect of CsA on TonEBP activity and localization [40,41]. Very similar to these previous studies, we analyzed expression of characteristic target genes and the subcellular distribution of TonEBP to estimate its activation status by different osmolality compositions of the culture media (6 days cultivation, 300 and 600 mOsm/ kg, medium differing in supplemental urea and NaCl).…”

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

“…It has long been known that CsA induces apoptosis of proximal tubule cells (9,33). A recent study (40) has shown that CsA also induces apoptosis of inner medullary collecting duct cells by elevating osmolality. However, it remains unclear whether CsA can induce apoptosis of cortical collecting duct (CCD) cells.…”

Mitochondrial-Based Therapeutics for the Treatment of Spinal Cord Injury: Mitochondrial Biogenesis as a Potential Pharmacological Target

“…Differences in the efficacy of CsA between TBI and SCI may be attributed to fundamental differences in spinal cord and cortical mitochondria (Sullivan et al, 2004a). Regardless of any positive results, however, CsA is highly toxic, making it less than ideal as a therapeutic (Caramelo et al, 2004;Schenk et al, 2010;Rabchevsky et al, 2011;Szalowska et al, 2015). NIM811 (N-methyl-4-isoleucine cyclosporin) is an analog of CsA that also inhibits the mPTP, is much less toxic, and lacks immunosuppressive properties (Waldmeier et al, 2002).…”