Overexpression of Delayed RectifierK+Channels PromotesIn situProliferation of Leukocytes in Rat Kidneys with Advanced Chronic Renal Failure

Abstract

Leukocytes, such as lymphocytes and macrophages, predominantly express delayed rectifier K+ channels (Kv1.3), and the channels play crucial roles in the activation and proliferation of the cells. Since lymphocytes are activated in patients with end-stage renal disease (ESRD), the channels expressed in those cells would contribute to the progression of renal fibrosis in advanced-stage chronic renal failure (CRF). In the present study, using a rat model with advanced CRF that underwent 5/6 nephrectomy followed by a 14-week recovery period, we examined the histopathological features of the kidneys and the leukocyte expression of Kv1.3-channels and cell cycle markers. Age-matched sham-operated rats were used as controls. In the cortical interstitium of advanced CRF rat kidneys, leukocytes proliferated in situ and overexpressed Kv1.3 channel protein in their cytoplasm. Treatment with margatoxin, a selective Kv1.3-channel inhibitor, significantly suppressed the number of leukocytes and the progression of renal fibrosis with a significant decrease in the cortical cell cycle marker expression. This study demonstrated for the first time that the number of leukocytes was dramatically increased in rat kidneys with advanced CRF. The overexpression of Kv1.3 channels in the leukocytes was thought to contribute to the progression of renal fibrosis by stimulating cell cycling and promoting cellular proliferation.

Benidipine Suppresses in situ Proliferation of Leukocytes and Slows the Progression of Renal Fibrosis in Rat Kidneys with Advanced Chronic Renal Failure

“…Rats with 5/6 nephrectomy with recovery periods as long as 14 weeks were used as the model of advanced CRF [8]. Briefly, subtotal nephrectomy was performed in male Sprague-Dawley rats weighing 150-180 g (Japan SLC Inc., Shizuoka, Japan), as described in our previous studies [8,14].…”

“…Briefly, subtotal nephrectomy was performed in male Sprague-Dawley rats weighing 150-180 g (Japan SLC Inc., Shizuoka, Japan), as described in our previous studies [8,14]. Then, the upper 1/3 and lower 1/3 of the right kidney was ligated to induce infarction.…”

“…In our previous study, the overexpression of Kv1.3 channels in those cells was strongly associated with their in situ proliferation in advanced CRF rat kidneys [8], and the channel inhibition actually decreased the number of infiltrating leukocytes and slowed the progression of renal fibrosis. In basic studies of renal fibrosis, unilateral ureteral obstruction is commonly used as a model of interstitial fibrosis, independently of glomerular injury [9].…”

“…On the other hand, 5/6 nephrectomy followed by a 4- to 8-week recovery period was originally developed as a model of CRF characterized by progressive glomerulosclerosis [2,10,11]. However, in our previous study, the kidneys from rats that underwent 5/6 nephrectomy were also characterized by diffuse renal fibrosis after as long as a 14-week recovery period [8], and the progression of fibrosis was deeply associated with the overexpression of Kv1.3-channels in leukocytes. Since the channels can be targeted pharmacologically, our rat model was thought to be useful to identify novel therapeutic approaches for renal fibrosis in advanced stage CRF.…”

“…Since these channels were overexpressed in leukocytes in advanced CRF rat kidneys [8], the pharmacological efficacy of benidipine was thought to be in slowing the progression of renal fibrosis. To clarify this, using a rat model with advanced CRF, we examined the therapeutic effects of benidipine on the histopathological features of the kidneys and the proliferation of leukocytes there.…”