Involvement of N-type Ca²⁺channels in the fibrotic process of the kidney in rats

Abstract

type Ca 2ϩ channels are densely distributed in sympathetic nerves that innervate renal tubules. However, the role of N-type Ca 2ϩ channels in renal fibrosis remains unknown. To address this issue, we examined the difference between the effects of amlodipine (an L-type Ca 2ϩ channel blocker) and cilnidipine (a dual L/N-type Ca 2ϩ channel blocker) on fibrotic changes using a rat unilateral ureteral obstruction (UUO) model. The expression of both L-type and N-type Ca 2ϩ channels was significantly upregulated in UUO kidneys compared with that in contralateral kidneys. There were no significant differences in mean blood pressure among the rats tested. Both amlodipine and cilnidipine significantly attenuated fibrotic changes in UUO kidneys. The antifibrotic effect of cilnidipine was more potent than that of amlodipine. Amlodipine as well as cilnidipine reduced type III collagen deposition, ␣-smooth muscle actin (␣-SMA) expression, and interstitial cell proliferation. In addition, cilnidipine significantly reduced deposition of type I collagen and macrophage infiltration in UUO kidneys. With the use of in vivo bromodeoxyuridine labeling, label-retaining cells (LRCs) were identified as a population of tubular cells that participate in epithelial-mesenchymal transition after UUO. Some LRCs migrated into the interstitium, expressed ␣-SMA and vimentin, and produced several extracellular matrixes in UUO kidneys. The number of interstitial LRCs was significantly decreased by cilnidipine but not amlodipine. These data suggest that N-type Ca 2ϩ channels contribute to multiple steps of renal fibrosis, and its blockade may thus be a useful therapeutic approach for prevention of renal fibrosis.N-type calcium channel; renal fibrosis; unilateral ureteral obstruction; epithelial-mesenchymal transition THE RENAL SYMPATHETIC NERVES innervate the tubules, the vessels, and the juxtaglomerular granular cells of the kidney (5). Renal sympathetic nerve activation reduces urinary sodium and water excretion by increasing renal tubular water and sodium reabsorption throughout the nephron. It also decreases renal blood flow and glomerular filtration rate by constricting the renal vasculature and activates the renin-angiotensin system (RAS) by stimulating renin release from juxtaglomerular granular cells. Conversely, angiotensin II stimulates sympathetic nerve activity through central mechanisms and by facilitating adrenergic neurotransmission at the sympathetic nerve terminal, thus suggesting significant interactions between renal sympathetic nerves and the RAS in the control of renal function (4). N-type Ca 2ϩ channels are densely distributed in the sympathetic nervous system and play a predominant role in neurotransmitter release from the nerve endings of sympathetic neurons (8). In patients with chronic renal diseases, increased sympathetic nerve activity and plasma renin activity are observed (10), thus suggesting that sympathetic nerve activity via N-type Ca 2ϩ channels is involved in renal injury. Renal fibrosis is the common end point o...

Epigallocatechin‐3‐Gallate Attenuates Oxidative Stress and Inflammation in Obstructive Nephropathy via NF‐κB and Nrf2/HO‐1 Signalling Pathway Regulation

“…In addition, renal function was found impaired in UUO mice, which represented as increased levels of serum BUN and Cr and activities of GPT and LDH. For renal function of UUO models, different studies showed discrepant results and there is no reliable explanation for the discrepancy between these observations, and the clear reason still needs to be revealed. In our study, EGCG treatment prevented the tubular injury and restored the weight of obstructed kidney.…”

Follistatin, an Activin Antagonist, Ameliorates Renal Interstitial Fibrosis in a Rat Model of Unilateral Ureteral Obstruction

“…Sequences of primers used in this study were as follows: β A subunit (sense, 5′-GGACCTAACTCTCAGCCAGAGATG-3′; antisense, 5′-TCTCAAAATGCAGTGTCTTCCTGG-3′), activin receptor type I (sense, 5′-AGTCGTGGTTCAGGGAGACA-3′; antisense, 5′-GAGTGGTGAGCTGAAGGTAG-3′), activin receptor type II (sense, 5′-TGTGAAATGAGTAGGGTGCC-3′; antisense, 5′-CCTTCATATCCGTGTTGCAG-3′), follistatin (sense, 5′-AAAACCTACCGCAACGAATG-3′; antisense, 5′-AGGCATTATTGGTCTGATCC-3′), and GAPDH (sense, 5′-CTACCCACGGCAAGTTCAAT-3′; antisense, 5′-TACTCAGCACCAGCATCACC-3′). Quantitative real-time PCR was performed as described previously [14]. …”

“…Indirect immunofluorescence staining was performed as described previously [14]. Briefly, frozen sections were washed in PBS, pretreated with 3% BSA-PBS for 1 h, and covered with primary antibody at room temperature for 1 h. After washing in PBS, sections were covered with a mixture of a fluorescence-labeled secondary antibodies and 4′-diamidino-2-phenylindole (DAPI).…”

Mitochondrial dysfunction and endoplasmic reticulum stress in the promotion of fibrosis in obstructive nephropathy induced by unilateral ureteral obstruction

“…69 Furthermore, L-type and N-type Ca 2+ channels are also upregulated in proximal tubules in UUO-OKs and their inhibition reduces TGF-β-mediated damage. 70 In this way, the ectopic expression in Madin-Darby canine kidney (MDCK) cells of parvalbumin, a cytosolic Ca 2+ -binding protein that possibly acts as an intracellular Ca 2+ shuttle, decreases the levels of the cytochrome c oxidase subunit 1 (COX1) and reduces mitochondrial mass. 71 Taken together, these data suggest that with UUO, there is a dysregulation in cytosolic Ca 2+ levels related to mitochondrial alterations and FA accumulation that plays an important role in the processes that favor renal fibrosis development.…”