Caspase inhibition reduces tubular apoptosis and proliferation and slows disease progression in polycystic kidney disease.

We have previously demonstrated an increase in proapoptotic caspase-3 in the kidney of Han:SPRD rats with polycystic kidney disease (PKD). The aim of the present study was to determine the effect of caspase inhibition on tubular cell apoptosis and proliferation, cyst formation, and renal failure in the Han:SPRD rat model of PKD. Heterozygous (Cy/+) and littermate control (+/+) male rats were weaned at 3 weeks of age and then treated with the caspase inhibitor IDN-8050 (10 mg/kg per day) by means of an Alzet (Palo Alto, CA) minipump or vehicle [polyethylene glycol (PEG 300)] for 5 weeks. The two-kidney/total body weight ratio more than doubled in Cy/+ rats compared with +/+ rats. IDN-8050 significantly reduced the kidney enlargement by 44% and the cyst volume density by 29% in Cy/+ rats. Cy/+ rats with PKD have kidney failure as indicated by a significant increase in blood urea nitrogen. IDN-8050 significantly reduced the increase in blood urea nitrogen in the Cy/+ rats. The number of proliferating cell nuclear antigen-positive tubular cells and apoptotic tubular cells in non-cystic and cystic tubules was significantly reduced in IDN-8050-treated Cy/+ rats compared with vehicle-treated Cy/+ rats. On immunoblot, the active form of caspase-3 (20 kDa) was significantly decreased in IDN-8050-treated Cy/+ rats compared with vehicle-treated Cy/+ rats. In summary, in a rat model of PKD, caspase inhibition with IDN-8050 (i) decreases apoptosis and proliferation in cystic and noncystic tubules; (ii) inhibits renal enlargement and cystogenesis, and (iii) attenuates the loss of kidney function.

Endotoxemic acute renal failure is attenuated in caspase-1-deficient mice.

Caspase-1-deficient (-/-) mice are protected against sepsis-induced hypotension and mortality. We investigated the role of caspase-1 and its associated cytokines in a nonhypotensive model of endotoxemic acute renal failure (ARF). Mice were injected intraperitoneally with 2.5 mg of LPS that induces endotoxemic ARF. On immunoblot analysis of whole kidney, there was an increase in caspase-1 protein in LPS-treated mice compared with vehicle-treated controls. In LPS-treated mice, the glomerular filtration rate (GFR) was significantly higher in caspase-1 -/- vs. wild-type mice at 16 and 36 h after LPS. To determine the mechanism of this protection, the caspase-1-activated cytokines IL-1beta and IL-18 were investigated. IL-1beta and IL-18 protein were significantly increased in the kidneys of LPS- vs. vehicle-treated mice. To determine the role of these cytokines, mice were treated with recombinant IL-1 receptor antagonist (IL-1Ra) or IL-18-neutralizing antiserum. In LPS-treated mice, GFR was not different in IL-1Ra-treated or IL-18-neutralizing antiserum-treated or combination therapy (IL-1Ra plus IL-18-neutralizing antiserum-treated) compared with control mice. In addition, tubular cell apoptosis, neutrophil infiltration, myeloperoxidase activity, caspase-3 activity, and calpain activity were not different between wild-type and caspase-1 -/- mice with endotoxemic ARF. In LPS- vs. vehicle-treated wild-type mice, renal IL-1alpha was significantly increased. In both LPS- and vehicle-treated caspase-1 -/- mice, renal IL-1alpha was very low. In summary, caspase-1 -/- mice are functionally protected against endotoxemic ARF. Neutralization of IL-1beta and IL-18 is not functionally protective. The role of the intracellular proinflammatory cytokine IL-1alpha in endotoxemic ARF merits further study.

Interaction among nitric oxide, reactive oxygen species, and antioxidants during endotoxemia-related acute renal failure.

Acute renal failure (ARF) during sepsis is associated with increased nitric oxide (NO) and oxygen radicals, including superoxide (O(2)(-)). Because O(2)(-) reacts with NO in a rapid manner, it plays an important role in modulating NO levels. Therefore, scavenging of O(2)(-) by superoxide dismutase (SOD) may be critical for preserving NO bioavailability. In mice, substantial renal extracellular SOD (EC-SOD) expression implies its important role in scavenging O(2)(-) in the kidney. We hypothesized that during endotoxemic ARF, EC-SOD is decreased in the kidney, resulting in increased O(2)(-) and thus decreased vascular NO bioavailability with resultant renal vasoconstriction and ARF. In the present study, normotensive endotoxemic ARF was induced in mice using lipopolysaccharide (LPS; 5 mg/kg ip). Sixteen hours after LPS, glomerular filtration rate (GFR; 50 +/- 16 vs. 229 +/- 21 microl/min, n = 8, P < 0.01) and renal blood flow (RBF; 0.61 +/- 0.10 vs. 0.86 +/- 0.05 ml/min, n = 8, P < 0.05) were subsequently decreased. EC-SOD mRNA and protein expression in endotoxemic kidneys were decreased at 16 h compared with controls. A catalytic antioxidant, metalloporphyrin, reversed the deleterious effects of endotoxemia on renal function as GFR (182 +/- 40 vs. 50 +/- 16 microl/min, n = 6, P < 0.01) and RBF (1.08 +/- 0.10 vs. 0.61 +/- 0.10 ml/min, n = 6, P < 0.05) were preserved. Similar results were obtained with tempol, a chemically dissimilar antioxidant. Specific inhibition of inducible nitric oxide synthase (iNOS), l-N(6)-(1-iminoethyl)-lysine, reversed the renal protective effect on GFR and RBF observed with antioxidant treatment during endotoxemia. In summary, renal EC-SOD expression is decreased during endotoxemia. Antioxidant therapy preserved GFR and RBF during endotoxemia. The reversal of this protective effect by inhibition of iNOS suggests the importance of the bioavailability of NO for preservation of renal function during early endotoxemia.

Effects of angiotensin receptor blockade on haemodynamics and gene expression after myocardial infarction.

INTRODUCTION: Despite the fact that congestive heart failure (CHF) remains the most common disease in the developed world and has been extensively studied, there is little known about the molecular and cellular mechanisms of cardiac dysfunction. Angiotensin has been implicated as a mediator of cardiac injury; however, the mechanisms of its action have not been delineated. The objective of this study was to examine the relationship between the haemodynamic and molecular events during cardiac dysfunction and the role of the angiotensin system. STUDY DESIGN: We examined the effects of the angiotensin receptor blocker, valsartan, on changes in the haemodynamic and gene expression patterns in a postmyocardial infarction model in the rat. METHODS: Myocardial infarction (MI) was induced in rats by coronary artery ligation. Cardiac haemodynamics were monitored using echocardiography. Gene expression profiles after myocardial infarction were identified using Affymetrix Genechip oligonucleotide arrays. RESULTS: Myocardial contractility, as assessed by cardiac output and left ventricle (LV) fraction of shortening, was reduced in untreated animals by week 3 after MI (p < 0.05 versus baseline), and preserved with valsartan treatment as observed by the nonsignificant changes versus baseline. LV dilatation, as demonstrated by increases in LV systolic and diastolic diameters, developed by week 3 in untreated animals (p < 0.05 versus baseline) while valsartan-treated animals were protected and showed no significant increases in diameter size compared with baseline. LV hypertrophy, as shown by LV posterior wall thickness, was more profound in untreated animals (p < 0.05 versus baseline) than in those treated with valsartan at weeks 3 and 4. Changes in gene expression at 4 weeks after MI included those encoding muscle-specific genes, fibrous tissue proliferation, immune response and various others. Treatment with valsartan reversed these changes in 67% of overexpressed genes and 83% of underexpressed genes. CONCLUSION: Angiotensin receptor blockade with valsartan was found to protect cardiac function, and this beneficial effect was accompanied by a reversal of changes in gene expression induced by MI.

Protective effect of renal denervation on normotensive endotoxemia-induced acute renal failure in mice.

Acute renal failure (ARF) contributes substantially to the high morbidity and mortality observed during endotoxemia. We hypothesized that selective blockade of the renal nerves would be protective against ARF during the early (16 h) stage of endotoxemia [5 mg lipopolysaccharide (LPS)/kg ip in mice]. At 16 h after LPS, there was no change in mean arterial pressure, but plasma epinephrine (4,604 +/- 719 vs. 490 +/- 152 pg/ml, P < 0.001), norepinephrine (2,176 +/- 306 vs. 1,224 +/- 218 pg/ml, P < 0.05), and plasma renin activity (40 +/- 5 vs. 27 +/- 2 ng x ml(-1) x h(-1), P < 0.05) were higher in the LPS-treated vs. control mice. The high plasma renin activity level decreased to the control level with renal denervation in endotoxemic mice. After intravenous injection of phentolamine (200 microg/kg), the decrement in mean arterial pressure was significantly greater in LPS-treated vs. control mice (19.4 +/- 3.5 vs. 8.1 +/- 1.5 mmHg, P < 0.01). Sixteen hours after LPS administration, there were significant decreases in glomerular filtration rate (52 +/- 18 vs. 212 +/- 23 microl/min, P < 0.01) and renal blood flow (0.58 +/- 0.08 vs. 0.85 +/- 0.06 ml/min, P < 0.01) in sham-operated mice. The decrement in glomerular filtration rate during endotoxemia was significantly attenuated in mice with denervated kidneys (32 vs. 79%). Moreover, there was no change in renal blood flow during endotoxemia in mice with renal denervation. The present results therefore demonstrate a protective role of renal denervation during normotensive endotoxemia-related ARF in mice, an effect that may be, at least in part, due to a diminished activation of the renin-angiotensin system.