Cyclosporine stimulates the renal epithelial sodium channel by elevating cholesterol

Abstract

Cyclosporine A (CsA) is an efficient immunosuppressant used for reducing allograft rejection but with a severe side effect of causing hypertension. We hypothesize that the renal epithelial sodium channel (ENaC) may participate in CsA-induced hypertension. In the present study, we used the patch-clamp cell-attached configuration to examine whether and how CsA stimulates ENaC in A6 distal nephron cells. The data showed that CsA significantly increased ENaC open probability. Since CsA is an inhibitor of the ATP-binding cassette A1 (ABCA1) transporter, we employed 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), another ABCA1 inhibitor, and found that DIDS mimicked the effects of CsA on ENaC basal and cholesterol-induced activity but without any additive effect if combined with CsA. CsA and DIDS also had an identical effect on reduced ENaC activity caused by cholesterol extraction. ABCA1 protein was detected in A6 cells by Western blot analysis. Confocal microscopy data showed that both CsA and DIDS facilitated A6 cells to uptake cholesterol. Since enhanced ENaC activity is known to cause hypertension, these data together suggest that CsA may cause hypertension by stimulating ENaC through a pathway associated with inhibition of ABCA1 and consequent elevation of cholesterol in the cells.

Lovastatin-Induced Phosphatidylinositol-4-Phosphate 5-Kinase Diffusion from Microvilli Stimulates ROMK Channels

“…We have previously shown that CsA elevates intracellular cholesterol in distal nephron cells 12 and that lovastatin antagonizes CsA-induced damage of CCD cells. 17 Therefore, this study opens a new avenue for The whole blots are shown in Supplemental Figure 3.…”

“…Our recent studies suggest that CsA stimulates the epithelial sodium channel (ENaC) through elevation of intracellular cholesterol. 12 Interestingly, cholesterol inhibits Kir channels, 1 3 -1 5 including the Kir 1.1 (ROMK1) channel. 16 Therefore, CsA-induced elevation of cholesterol in CCD cells may account, at least in part, for CsA inhibition of ROMK channels.…”

Hydrogen Peroxide Stimulates the Epithelial Sodium Channel through a Phosphatidylinositide 3-Kinase-dependent Pathway

“…As described previously (24), prior to the experiments, A6 cells cultured on the polyester membrane of Snapwell inserts were thoroughly washed with NaCl solution containing 100 mM NaCl, 3.4 mM KCl, 1 mM CaCl 2 , 1 mM MgCl 2 , and 10 mM HEPES; pH was adjusted to 7.4 with NaOH. The glass micropipette was filled with NaCl solution (the pipette resistance is 7-10 megaohms).…”

Regulation of Renal Potassium Channels by Protein Kinases and Phosphatases

“…It has also been demonstrated that cyclosporin A (CyA), an inhibitor of Ca 2+ /calmodulindependent phosphatase, calcineurin (CaN) (Hemenway & Heitman, 1999), inhibited the activity of the K + channel in both proximal tubule (Ye et al, 2006, Kubokawa et al, 2009) and principal cells of CCD (Ling & Eaton, 1993). Cyclosporin A is a a well-known immunosuppressive agent (Morris, 1981;White & Calne, 1982;Cohen, 1984), and affects various functions of the kidney other than K + channels (Epting et al, 2006;Tumlin, 1993;Grinyó & Cruzado, 2004;J. Wang et al, 2009;Damiano et al, 2010).…”