Cyclosporine A decreases kallikrein and BK2 mRNA expression in the rat renal cortex

Cyclosporin A disrupts bradykinin signaling through superoxide

Cyclosporin A (CsA) is used to reduce transplant rejection rates. Chronic use, however, has a destructive toxic effect on the kidney, resulting in hypertension. In this study, we investigated the effects of CsA treatment on the bradykinin/soluble guanylate cyclase signaling cascade and the involvement of superoxide in LLC-PK1 porcine kidney proximal tubule cells. Treatment with 1 micromol/L CsA for 24 hours increased basal cGMP levels by 41%, whereas CsA inhibited bradykinin-stimulated cGMP production by 26%. Western blotting showed increased expression of eNOS, but no other protein in the bradykinin/soluble guanylate cyclase (sGC) pathway was affected. Using lucigenin-dependent chemiluminescence, we found that CsA treatment significantly increased superoxide production. Production of O2- was not significantly reduced by 10 micromol/L oxypurinol or 30 micromol/L ketoconazole. However, it was inhibited by the NADPH oxidase inhibitor diphenyleneiodonium chloride (10 micromol/L) as well as the O2- scavenger superoxide dismutase (SOD) (100 U). On treatment with 50 micromol/L quercetin, 10 mmol/L N-acetyl-cysteine, both antioxidants, as well as the O2- scavenger Tiron (10 mmol/L), concomitant with 1 micromol/L CsA for 24 hours the activation of cGMP production, was restored in combination with a reduction in O2-. Incubation with 100 micromol/L menadione, a reactive oxygen generator, and 10 nmol/L bradykinin showed similar effects on the level of cGMP as with CsA. CsA treatment was found to increase nitrotyrosine levels. These findings suggest that CsA activates a NADPH oxidase that releases O2- and disrupts the bradykinin/soluble guanylate cyclase pathway, probably by binding with NO to form peroxynitrite (ONOO-).

Culture of human renal tubular cells: positive selection of kallikrein-containing cells

Human renal tubular cells derived from nephrectomy specimens were maintained in culture and grown to confluence. Immunocytochemistry, using a panel of antibodies selected for their ability to bind to different cell types within the nephron, showed the cells to be predominantly of epithelial origin with no significant contamination by fibroblasts or cells of endothelial origin. Ten to thirty percent of the cells expressed the putative distal marker, epithelial membrane antigen (EMA), a finding confirmed by flow cytometry. Cells expressing EMA were positively selected from mixed cultures by magnetic activated cell sorting (MACS). Kallikrein activity, expressed as mU/10(6) cells, in the EMA +ve cells, was increased fourfold to sixfold when compared with that in the EMA -ve cells. Cultures of characterized human renal tubular cells and sub-populations enriched with distal cells should prove useful in studies of synthesis and release of parameters of the kallikrein kinin system (KKS) to physiological stimuli. Furthermore, a better understanding of the toxic effect on the KKS of clinically useful drugs, particularly those used for immunosuppression, may lead to therapeutic interventions to lessen unwanted effects.

Effect of cyclosporin A on the expression of tissue kallikrein, kininogen, and bradykinin receptor in rat

The tissue kallikrein-kinin system is involved in vasodilation and blood pressure regulation. In the present study, we investigated the effects of chronic cyclosporin A (CsA) administration on blood pressure and the expression of tissue kallikrein, kininogen, and bradykinin receptor in normotensive Wistar rats. Chronic administration of CsA significantly increased systolic blood pressure compared with control rats (n = 6, P < 0.01), although body weight was significantly lower than control rats (n = 6, P < 0.01). The development of hypertension was accompanied by the altered expression of kallikrein-kinin system components. Immunoreactive renal kallikrein and urinary excretion of tissue kallikrein levels were increased by chronic administration of CsA (n = 5 or 6, P < 0.05). Levels of N-tosyl-L-phenylalanine chloromethyl ketone-trypsin and kallikrein-releasable kininogens in sera increased in response to chronic CsA treatment (n = 5 or 6, P < 0.05). Chronic CsA treatment significantly increased renal kallikrein, bradykinin B2 receptor, and hepatic kininogen mRNA levels. The increased levels of tissue kallikrein-kinin system components were accompanied by significant increases in 24-h urine excretion and water intake after chronic CsA treatment (n = 5, P < 0.05). These results suggest that enhanced activity of the tissue kallikrein-kinin system may compensate for the CsA-induced vasoconstriction and hypertension.