N-type calcium channel and renal injury

International Urology and Nephrology - Accumulating evidences indicated that voltage-gated calcium channels (VDCC), including L-, T-, N-, and P/Q-type, are present in kidney and contribute to renal...     

Endothelin-1 receptor blockade prevents renal injury in experimental hypercholesterolemia

BACKGROUND: The potent vasoconstrictor endothelin-1 is involved in regulation of renal function, and is up-regulated in hypercholesterolemia (HC), a risk factor for renal disease that increases oxidative stress and impairs renal hemodynamic responses. However, the involvement of endothelin (ET) in this disease process is yet unknown. METHODS: Regional renal hemodynamics and function in vivo were quantified in pigs at baseline and during infusion of acetylcholine using electron beam computed tomography after a 12-week normal diet (N = 6), HC diet (N = 6), and HC diet orally supplemented (4 mg/kg/day) with the selective ET receptor-A (ET-A) blocker ABT-627 (HC+ET-A, N = 6). Plasma levels of 8-epi-PGF2-alpha-isoprostanes, markers of oxidative stress, were measured using enzyme immunoassay, and renal tissue was studied ex vivo using Western blotting, electrophoretic mobility shift assay, and immunohistochemistry. RESULTS: Total and low-density lipoprotein (LDL) cholesterol were similarly increased, but isoprostanes were decreased in HC+ET-A compared to HC alone. Basal renal perfusion was similar among the groups, while glomerular filtration rate (GFR) increased in HC+ET-A compared to HC. Stimulated perfusion and GFR were blunted in HC, but normalized in HC+ET-A. Moreover, ET blockade increased expression of endothelial nitric oxide synthase, and decreased endothelial expression of the oxidized-LDL receptor LOX-1, as well as tubular immunoreactivity of inducible nitric oxide synthase, nitrotyrosine, nuclear factor-kappaB, transforming growth factor-beta, and tubulointerstitial and perivascular trichrome staining. CONCLUSION: ET-A blockade improves renal hemodynamic and function in HC, and decreases oxidative stress, and renal vascular and tubulointerstitial inflammation and fibrosis. These findings support a role for the endogenous ET system in renal injury in HC and atherosclerosis.     

T-type calcium channel blockade as a therapeutic strategy against renal injury in rats with subtotal nephrectomy

T-type calcium channel blockers have been previously shown to protect glomeruli from hypertension by regulating renal arteriolar tone. To examine whether blockade of these channels has a role in protection against tubulointerstitial damage, we used a stereo-selective T-type calcium channel blocker R(-)-efonidipine and studied its effect on the progression of this type of renal injury in spontaneously hypertensive rats that had undergone subtotal nephrectomy. Treatment with racemic efonidipine for 7 weeks significantly reduced systolic blood pressure and proteinuria. The R(-)-enantiomer, however, had no effect on blood pressure but significantly reduced proteinuria compared to vehicle-treated rats. Both agents blunted the increase in tubulointerstitial fibrosis, renal expression of alpha-smooth muscle actin and vimentin along with transforming growth factor-beta (TGF-beta)-induced renal Rho-kinase activity seen in the control group. Subtotal nephrectomy enhanced renal T-type calcium channel alpha1G subunit expression mimicked in angiotensin II-stimulated mesangial cells or TGF-beta-stimulated proximal tubular cells. Our study shows that T-type calcium channel blockade has renal protective actions that depend not only on hemodynamic effects but also pertain to Rho-kinase activity, tubulointerstitial fibrosis, and epithelial-mesenchymal transitions.     

钙拮抗剂对环孢素A所致药物性牙龈增生的协同作用

目的 探讨钙拮抗剂对环孢素A(CsA)所致药物性牙龈增生的协同作用.方法 130例服用CsA的肾移植受者,根据术后是否联合使用钙拮抗剂,分为钙拮抗剂组和未使用钙拮抗剂(对照组),记录和分析两组受者的年龄、性别、牙周指数、牙龈增生情况及严重程度、服用CsA的时间和剂量、血CsA浓度及血清肌酐等临床指标,并对牙龈增生者与牙龈未增生者进行进一步分析;分析使用不同钙拮抗剂者牙龈增生的发生率和严重程度.结果 钙拮抗剂组牙龈增生发生率为60%(44/73),显著高于对照组的39%(22/57,P＜0.05);钙拮抗剂组轻度牙龈增生受者的比例为37%,显著高于对照组的19%(P＜0.05);两组发生中、重度牙龈增生受者的比例差异无统计学意义(P＞0.05).两组受者中,牙龈增生者的牙龈菌斑指数和乳头出血指数均显著高于牙龈未增生者(P＜0.05),牙龈菌斑指数和乳头出血指数与牙龈增生严重程度呈正相关(P＜0.01).联合使用硝苯地平的受者,其牙龈增生发生率(77%)高于使用氨氯地平(57%)和非洛地平(50%)的受者.结论 联合使用钙拮抗剂对CsA所致药物性牙龈增生具有明显的协同作用;服用CsA的肾移植受者应避免使用硝苯地平以防止可能发生的牙龈增生.     

Hypertensive dysregulation and its modification by calcium channel blockade in nonoliguric renal failure

To investigate the pathogenetic constellation and its modification by calcium channel blockade in hypertension associated with chronic nonoliguric renal failure, blood pressure (BP), various pressor factors or correlates, cardiovascular responsiveness, and plasma atrial natriuretic peptide (ANP) were assessed in 15 hypertensive patients (serum creatinine 160-715 mumol/l) before and after 6 weeks of intervention with the agent nitrendipine. On placebo, these patients had a lower plasma angiotensin II (AngII) clearance and higher values of supine plasma AngII, aldosterone, norepinephrine (NE), and heart rate than healthy humans. Acute responses of BP to AngII and of heart rate to isoproterenol were blunted in the patients (p less than 0.05-0.001). Plasma ANP was elevated, correlated positively with systolic BP, and rose in response to NE pressor infusion (p less than 0.05-0.001). Exchangeable sodium and blood volume did not differ significantly from normal values. Nitrendipine reduced the cardiovascular responses to AngII, NE, and isoproterenol and lowered supine BP from 173/102 +/- 5/2 to 146/81 +/- 3/3 mm Hg and upright BP from 170/105 +/- 5/2 to 145/86 +/- 4/3 mm Hg (p less than 0.05-0.001); except for slightly increased plasma AngII, the levels of other endocrine variables, exchangeable sodium, blood volume, and creatinine clearance were not significantly modified. Conclusions: Hypertension accompanying chronic nonoliguric renal impairment seems to be strongly AngII and probably also NE dependent. Circulating ANP levels are high in this setting. Calcium channel blockade with nitrendipine effectively reduces cardiovascular AngII and NE dependence and BP.     

Protective effect of paricalcitol on cyclosporine-induced renal injury in rats

We evaluated the protective effect of paricalcitol on cyclosporine (CsA)-induced renal injury using an experimental model of chronic CsA nephropathy. Paricalcitol (50 and 200 ng/kg/d) was concomitantly administered with CsA (15 mg/kg/d) for 28 days in rats. We assessed the effects of paricalcitol by measuring degree of the tubulointerstitial fibrosis (TIF) and inflammation, a profibrotic cytokine (βig-h3), a proapoptotic gene (caspase-3), apoptotic cell death, and oxidative stress. The CsA-treated rats showed increased TIF and inflammatory cell infiltration, but paricalcitol treatment (200 ng/kg) significantly decreased those compared with the CsA-alone group. The expression of βig-h3, a biologic marker of transforming growth factor β1, which was increased in the CsA group, also decreased with paricalcitol treatment. The increased rates of excretion of urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG) and expression of tissue 8-OHdG produced by CsA treatment were significantly attenuated by paricalcitol treatment. The increased expression of caspase-3 and number of TUNEL-positive cells in the CsA group were decreased with concomitant paricalcitol treatment. The effect of paricalcitol was more evident high among the rather than low-dose cohort. In conclusion, paricalcitol showed antiinflammatory and antifibrotic effects. This finding may provide a rationale for use of paricalcitol in CsA-induced renal injury.     

Ischemic postconditioning prevents ischemic acute renal failure

INTRODUCTION: Delayed graft function (DGF), a frequent complication after kidney transplantation, decreases graft survival. Ischemia/reperfusion (I/R) injuries play a major role in DGF pathophysiology. Because ischemic postconditioning (IP) is efficient to prevent myocardial I/R injuries and reduce infarct size, we sought to describe renal effects of IP. MATERIALS AND METHODS: Swiss mice were divided into three groups after left nephrectomy. Thirty minutes of right kidney ischemia followed by three cycles of 30 seconds of ischemia and reperfusion (IP group: n = 12) versus immediate reperfusion (n = 7). Left nephrectomized and right kidney sham operated mice were used as control groups (n = 6). Mice were followed for an 8-day survival analysis. Serum levels of creatinine and protein as well as weights were determined 2 days before and at days 2 and 8 after surgery. RESULTS: IP improved kidney function on day 2; the mean serum creatinine level was 1.25 +/- 0.71 versus 2.9 +/- 1.3 mg/dL in the immediate reperfusion group (P < .02). We also observed a trend toward increased animal survival (25% vs. 0% in the immediate reperfusion group; P = .10). Despite a significant increase in proteinuria among all groups, there was no significant difference. CONCLUSION: In a mouse model, IP seems to prevent postischemic acute renal failure after 30 minutes of kidney ischemia.     

Improved liver preservation for transplantation due to calcium channel blockade.

Intracellular calcium is an important determinant for cell death in organ hypothermic preservation for transplantation. In this study, we show that prevention of calcium entry improves the result of liver cold storage in UW solution. The isolated perfused rabbit liver was used. After 48 hr of cold storage in UW solution, bile production was reduced by 70% (P less than 0.005). However, by adding the calcium channel blockers verapamil or nifedipine (40 microM) to the UW solution, this reduction was abolished, and the livers produced the same amount of bile as unpreserved livers. Furthermore, addition of the calcium channel activator, BAY K8644 (40 microM), to the UW solution, reduced bile production by 50% (P less than 0.01) already after preservation for 24 hr. We conclude that calcium entry is of importance for liver function after preservation and cold storage, and that including a calcium channel blocker to the preservation solution makes long-term liver preservation safer.     

The ATP-sensitive potassium channel blocker glibenclamide prevents renal ischemia/reperfusion injury in rats

BACKGROUND: Renal ischemia/reperfusion (I/R) is a complex neutrophil-mediated syndrome. Adenosine-triphosphate (ATP)-sensitive potassium (K(ATP)) channels are involved in neutrophil migration in vivo. In the present study, we have investigated the effects of glibenclamide, a K(ATP) channel blocker, in renal I/R injury in rats. METHODS: The left kidney of the rats was excised through a flank incision and ischemia was performed in the contralateral kidney by total interruption of renal artery flow for 45 minutes. Renal perfusion was reestablished, and the kidney and lungs were removed for analysis of vascular permeability, neutrophil accumulation, and content of cytokines [tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, and IL-10] 4 and 24 hours later. Renal function was assessed by measuring creatinine, Na(+), and K(+) levels in the plasma and by determination of creatinine clearance. Drugs were administered subcutaneously after the onset of ischemia. RESULTS: Reperfusion of the ischemic kidney induced local (kidney) and remote (lung) inflammatory injury and marked renal dysfunction. Glibenclamide (20 mg/kg) significantly inhibited the reperfusion-associated increase in vascular permeability, neutrophil accumulation, increase in TNF-alpha levels and nuclear factor-kappaB (NF-kappaB) translocation. These inhibitory effects were noticed in the kidney and lungs. Moreover, glibenclamide markedly ameliorated the renal dysfunction at 4 and 24 hours. CONCLUSION: Treatment with glibenclamide is associated with inhibition of neutrophil recruitment and amelioration of renal dysfunction following renal I/R. Glibenclamide may have a therapeutic role in the treatment of renal I/R injury, such as after renal transplantation.     

Hemodynamic effect of calcium channel blockade during anesthesia for coronary artery surgery.

Because the choice of anesthetic technique does not influence the incidence of perioperative myocardial ischemia, reduction of ischemic risk may require specific antianginal therapy. Calcium entry blockers are effective drugs in antianginal therapy. Diltiazem reduces myocardial oxygen demand through decreases in heart rate, inotropy, and systolic function, while increasing myocardial oxygen delivery through coronary vasodilation. These potentially beneficial effects of diltiazem were evaluated in 15 of 29 patients (diltiazem v placebo, double-blind study) scheduled for coronary artery bypass graft surgery. Continuous infusion of diltiazem (0.15 mg/kg bolus followed by 2 micrograms/kg/min), during anesthesia and surgery before cardiopulmonary bypass, significantly reduced the major MVO2 determinants during anesthesia with moderate doses of fentanyl and a benzodiazepine (midazolam in 8 of 14 control patients and 9 of 15 treated patients, or flunitrazepam in the others). Heart rate, mean arterial pressure, and inotropy were decreased during the most stressful events of surgery when plasma diltiazem concentrations were in the therapeutic range (greater than 96 ng/mL). The number of patients with perioperative ischemia was 2 of 15 in the treated group and 4 of 14 in the control group. Provided that diltiazem plasma concentrations are sufficient, it can contribute to lowering the ischemic burden during anesthesia for coronary artery surgery.     

Effects of calcium channel blockade on histamine induced bronchoconstriction in mild asthma.

Inhalation histamine dose-response curves were constructed 15 minutes after inhalation of saline placebo or verapamil (4 mg) for eight patients with mild atopic asthma in a double blind, random manner. No significant change in baseline specific airways conductance occurred after inhalation of verapamil, though there was a significant decrease in sensitivity to histamine (increase in threshold of response) (p less than 0.01). There was, however, an associated significant increase (p less than 0.01) in the slopes of the subsequent histamine dose-response curves.     

Alterations of gluconeogenesis by ischemic renal injury in rats.

This study was designed to determine changes in one metabolic function, gluconeogenesis (GLG), after ischemic renal injury. Tubule suspensions were prepared by collagenase treatment of SD rat kidneys on 1, 3, and 7 days after left renal artery and vein occlusion for 0-90 min and incubated in Krebs-Henseleit buffer with or without 2 mM pyruvate or malate aerobically. Glucose contents were assayed photometrically. On days 1 and 3 after ischemia for longer than 60 min, serum creatinine levels rose significantly. The tendency of increase of GLG was observed on days 1 and 3 after 10-60 min of ischemia. GLG increased significantly on day 1 after 30-min ischemia. On the other hand, GLG decreased significantly on day 1 after 90-min treatment. Morphologic damage was limited to the corticomedullary region on days 1 and 3 after ischemic times of 30 and 60 min. These results suggest that renal GLG is stimulated to supply energy for ATP decrease by ischemia and for further regeneration in extraproximal segments along the nephron.     

Variable results of calcium blockade in post-ischaemic renal failure

The effects of three chemically dissimilar calcium-blocking drugs were studied in experimental post-ischaemic renal failure, in the rat. After 45 min unilateral clamping and contralateral nephrectomy, post-ischaemic verapamil administration protected renal function (p less than 0.025), but flunarizine, either before or after ischaemia, was not beneficial. Following 60 min bilateral renal pedicle clamping, nifedipine administration was not beneficial. Verapamil was the only calcium-blocking drug which attenuated the post-ischaemic renal dysfunction. Calcium blockers which differ in their modes of action, differ in their ability to protect the kidney from ischaemia.     

Thromboxane receptor blockade reduces renal injury in murine lupus nephritis.

To investigate the role of thromboxane A2 (TxA2) in murine lupus, we assessed the effects of the specific thromboxane receptor antagonist GR32191 on immune complex glomerulonephritis in MRL-lpr/lpr mice. Forty mg/kg/day GR32191 was given by twice daily subcutaneous injection for eight weeks beginning at 12 weeks of age. This dose completely blocked the renal vasoconstriction produced by the thromboxane agonist U46619. After eight weeks of treatment, both glomerular filtration rate (GFR) (8.9 +/- 0.6 vs. 6.8 +/- 1.1 ml/min/kg; P less than 0.05) and PAH clearance (CPAH) (37.4 +/- 2.5 vs. 29.9 +/- 3.3 ml/min/kg; P less than 0.05) were significantly higher in mice given GR32191 compared to vehicle treated animals. Administration of GR32191 also reduced proteinuria from 18.1 +/- 11.6 to 3.7 +/- 1.3 mg/24 hours (P less than 0.05). In GR32191 treated MRL-lpr/lpr mice, renal hemodynamic function and proteinuria were not significantly different from congenic MRL-+/+ controls. Thromboxane receptor blockade had striking affects on renal histomorphology reducing both hyaline thrombi in glomeruli (P = 0.022) and interstitial inflammation (P = 0.006). Glomerular crescents and severity of vasculitis also tended to be reduced in mice receiving the thromboxane receptor antagonist. The overall histopathologic score in mice given GR32191 was significantly lower than vehicle treated animals (4.7 +/- 0.5 vs. 8.4 +/- 1.5; P = 0.016). These effects of GR32191 were associated with decreased excretion of thromboxane B2 (TxB2) in urine (292 +/- 37 vs. 747 +/- 155 pg/24 hr; P less than 0.005) as well as a modest reduction in glomerular deposits of IgG (semiquantitative score 2.6 +/- 0.2 vs. 3.5 +/- 0.2; P less than 0.02). Thus, chronic thromboxane receptor blockade markedly altered the course of renal disease in MRL-lpr/lpr mice, suggesting that TxA2 is an important mediator of renal dysfunction and injury in this murine model of lupus nephritis.     

Cyclosporine and experimental renal ischemic injury

To investigate the interaction of cyclosporine nephrotoxicity and renal ischemia, an animal model in rats with bilateral renal artery clamping was used. Rats given cyclosporine had a lower rate of recovery from ischemia. However, the percentages of reduction in glomerular filtration rate in vehicle and cyclosporine groups were the same in sham-operated or ischemically treated group. This suggests a superimposition of cyclosporine nephrotoxicity on the recovering kidneys rather than synergistic potentiation between ischemia and cyclosporine nephrotoxicity.     

缺血再灌注对肾细胞内钙水平和细胞凋亡的影响

目的　观察缺血再灌注损伤对肾细胞游离钙 ([Ca2 ]i)水平和细胞凋亡的影响。　方法　 30只Wistar大鼠 ,分组建立急性缺血再灌注肾损伤模型 ,应用Fura 2 /AM荧光指示剂测定缺血再灌注大鼠肾细胞 [Ca2 ]i水平 ,流式细胞术检测肾细胞凋亡率。　结果　缺血再灌注 1、2、2 4h肾细胞Ca2 超载水平分别为 15 6 .2、181.6和 2 6 0 .6nmol/L ,与对照组 (10 9.7nmol/L)相比差异有统计学意义(P <0 .0 1) ;1、2、2 4h肾细胞凋亡率分别为 9.5 8%、9.79%和 11.2 3% ,与对照组 (1.5 1% )相比差异有统计学意义 (P <0 .0 5 )。缺血再灌注细胞Ca2 超载与肾细胞凋亡率有正相关趋势 (r =0 .83,P >0 .0 5 )。　结论　缺血再灌注肾细胞呈现Ca2 超载 ,与肾细胞凋亡率呈正相关趋势 ,提示肾细胞钙超载可能是再灌注损伤肾功能障碍的重要原因。     

线粒体Ca2+超载与缺血性脑损伤

人们致力于脑缺血的研究已有数十年,然而其予后仍然较差。溶栓治疗仅对部分病人有效,但2/3以上的病人即使在中风发病3 h内开始溶栓治疗其治疗效果仍不理想[1]。缺血和再灌注时间是决定脑损伤程度的重要因素。缺血后神经细胞的死亡常延迟到缺血后数小时直到数日,临床实验表明,缺     

Renal preservation following severe ischemia and prophylactic calcium channel blockade

The ability of the calcium channel blocker verapamil to prevent renal ischemic damage was assessed in a randomized double blind study of 41 rats. Study animals received either intravenous verapamil or placebo prior to renal pedicle occlusion and contralateral nephrectomy. Rats receiving verapamil pretreatment demonstrated significantly greater functional preservation 48 hours after ischemia (p less than 0.005) and exhibited better overall survival rates. In this study verapamil provided protection against renal damage following ischemia.