Prevention of systemic and regional haemodynamic alterations, hypercreatininemia, hyperuremia and hyperphosphatemia by losartan in hypertension with acute renal failure

Patients with pre-existing hypertension are at a particular risk of fatal outcome due to acute renal failure (ARF). We investigate the effects of angiotensin II type-1 receptor blocker (ARB) losartan, on haemodynamics and biochemical parameters in adult male spontaneously hypertensive rats (SHR) with ischemia/reperfusion ARF. SHR were randomly selected in three experimental groups: sham-operated group (SHAM), ARF group, and ARF+LOS group (losartan, 10 mg/kg/b.w. given by infusion during the period of three hours after reperfusion). Beside the improvement of systemic haemodynamics 24 h after reperfusion, losartan significantly increased renal blood flow (RBF: 19.33±3.29 ml/min/kg vs. 8.03±1.04 ml/min/kg, p<0.05) and decreased renal vascular resistance (RVR) compared to ARF (8.85±1.21 mmHg × min × kg/ml vs. 19.90±2.35 mmHg × min × kg/ml, p<0.001). Plasma creatinine (Pcr), urea (Pu) and phosphates (Pphos) were significantly reduced in ARF+LOS group compared to ARF group (Pcr: 99.11±14.56 μmol/l vs. 242.71±20.25 μmol/l, p<0.001; Pu: 33.72±4.69 mmol/l vs. 61.90±3.93 mmol/l, p<0.001; 2.7±0.42 mmol/l vs. 5.57±0.61 mmol/l, p<0.01). Our results demonstrate that losartan improves systemic and regional haemodynamic and biochemical parameters in hypertension with ARF.     

Effects of angiotensin II type 1 receptor blockade on the oxidative stress in spontaneously hypertensive rat tissues

The aim of this work was to investigate the production of oxidative damage in homogenized kidney, liver and brain of spontaneously hypertensive rats (SHR), as well as the involvement of angiotensin (Ang) II in this process. Groups of 12-week-old SHR and Wistar Kyoto rats (WKY) were given 10 mg/kg/day losartan in the drinking water during 14 days. Other groups of WKY and SHR without treatment were used as controls. The production of thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH) and the activity of the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (Gpx) were determined. No significant difference in TBARS was observed between untreated SHR or WKY rats; GSH content was lower in the liver but higher in the brain of SHR compared to WKY rats. In tissues from the SHR group, SOD and Gpx activities were reduced, whereas CAT activity was slightly increased in kidney. TBARS levels did not change in WKY rats after losartan administration, but were reduced in SHR liver and brain. Losartan treatment decreased GSH content in WKY kidney, but increased GSH in SHR liver. The activity of the antioxidant enzymes was not modified by losartan in WKY rats; however, their activities increased in tissues from treated SHR. The lower activity of antioxidant enzymes in tissues from hypertensive rats compared to those detected in normotensive controls, indicates oxidative stress production. Ang II seems to play no role in this process in normotensive animals, although AT1 receptor blockade in SHR enhances the enzymatic activity indicating that Ang II is implicated in oxidative stress generation in the hypertensive animals.     

Changes in angiotensin receptors expression play a pivotal role in the renal damage observed in spontaneously hypertensive rats

The renal renin-angiotensin system plays a central role in the development of hypertension. The aim of this work was to verify the expression of angiotensin II receptors AT(1)R and AT(2)R in the microsomal fraction of renal cortex and correlate this with the development of hypertension and renal damage in spontaneously hypertensive rats (SHR) using Wistar-Kyoto rats (WKY) as controls. AT(1)R expression increased (126%) and AT(2)R expression decreased (66%) in 4-wk-old SHR; AT(2) expression decreased in 14-wk-old SHR (61%) compared with respective age-matched WKY. These modifications were correlated to the increase in protein kinase C activity and decrease in protein kinase A activity. Four-week-old SHR showed large accumulations of macrophages in kidney glomerulus and the tubulointerstitial area, dense cortical collagen deposition, and arterial proliferative changes in the walls of arterioles and medium-sized vessels. Similar modifications were also observed in 14-wk-old SHR. Four-week-old SHR treated with losartan (30 mg·kg(-1)·day(-1)) or hydralazine (15 and 30 mg·kg(-1)·day(-1)) by gavage for 10 wk did not develop hypertension. The decrease in AT(2)R expression and renal damage observed in SHR remained even after treatment with hydralazine. On the other hand, losartan treatment prevented the modifications observed in 14-wk-old SHR, indicating that renal injuries are caused specifically by AT(1) rather than an increase in blood pressure. Our results indicate that the imbalance in AT(1)R and AT(2)R expression is associated with an inflammatory process that contributes to renal injury in adult SHR and to the development of hypertension.     

Renal mitochondrial dysfunction in spontaneously hypertensive rats is attenuated by losartan but not by amlodipine

Mitochondrial dysfunction is associated with cardiovascular damage; however, data on a possible association with kidney damage are scarce. Here, we aimed at investigating whether 1) kidney impairment is related to mitochondrial dysfunction; and 2) ANG II blockade, compared with Ca2+ channel blockade, can reverse potential mitochondrial changes in hypertension. Eight-week-old male spontaneously hypertensive rats (SHR) received water containing losartan (40 mg.kg-1.day-1, SHR+Los), amlodipine (3 mg.kg-1.day-1, SHR+Amlo), or no additions (SHR) for 6 mo. Wistar-Kyoto rats (WKY) were normotensive controls. Glomerular and tubulointerstitial damage, systolic blood pressure, and proteinuria were higher, and creatinine clearance was lower in SHR vs. SHR+Los and WKY. In SHR+Amlo, blood pressure was similar to WKY, kidney function was similar to SHR, and renal lesions were lower than in SHR, but higher than in SHR+Los. In kidney mitochondria from SHR and SHR+Amlo, membrane potential, nitric oxide synthase, manganese-superoxide dismutase and cytochrome oxidase activities, and uncoupling protein-2 content were lower than in SHR+Los and WKY. In SHR and SHR+Amlo, mitochondrial H2O2 production was higher than in SHR+Los and WKY. Renal glutathione content was lower in SHR+Amlo relative to SHR, SHR+Los, and WKY. In SHR and SHR+Amlo, glutathione was relatively more oxidized than in SHR+Los and WKY. Tubulointerstitial alpha-smooth muscle actin labeling was inversely related to manganese-superoxide dismutase activity and uncoupling protein-2 content. These findings suggest that oxidant stress is associated with renal mitochondrial dysfunction in SHR. The mitochondrial-antioxidant actions of losartan may be an additional or alternative way to explain some of the beneficial effects of AT1-receptor antagonists.     

Angiotensin receptors contribute to blood pressure homeostasis in salt-depleted SHR

This study evaluated the contribution of angiotensin peptides acting at various receptor subtypes to the arterial pressure and heart rate of adult 9-wk-old male conscious salt-depleted spontaneously hypertensive rats (SHR). Plasma ANG II and ANG I in salt-depleted SHR were elevated sevenfold compared with peptide levels measured in sodium-replete SHR, whereas plasma ANG-(1-7) was twofold greater in salt-depleted SHR compared with salt-replete SHR. Losartan (32.5 micromol/kg), PD-123319 (0.12 micromol. kg(-1). min(-1)), [d-Ala(7)]ANG-(1-7) (10 and 100 pmol/min), and a polyclonal ANG II antibody (0.08 mg/min) were infused intravenously alone or in combination. Combined blockade of AT(2) and AT((1-7)) receptors significantly increased the blood pressure of losartan-treated SHR (+15 +/- 1 mmHg; P < 0.01); this change did not differ from the blood pressure elevation produced by the sole blockade of AT((1-7)) receptors (15 +/- 4 mmHg). On the other hand, sole blockade of AT(2) receptors in losartan-treated SHR increased mean arterial pressure by 8 +/- 1 mmHg (P < 0.05 vs. 5% dextrose in water as vehicle), and this increase was less than the pressor response produced by blockade of AT((1-7)) receptors alone or combined blockade of AT((1-7)) and AT(2) receptors. The ANG II antibody increased blood pressure to the greatest extent in salt-depleted SHR pretreated with only losartan (+11 +/- 2 mmHg) and to the least extent in salt-depleted SHR previously treated with the combination of losartan, PD-123319, and [d-Ala(7)]ANG-(1-7) (+7 +/- 1 mmHg; P < 0.01). Losartan significantly increased heart rate, whereas other combinations of receptor antagonists or the ANG II antibody did not alter heart rate. Our results demonstrate that ANG II and ANG-(1-7) act through non-AT(1) receptors to oppose the vasoconstrictor actions of ANG II in salt-depleted SHR. Combined blockade of AT(2) and AT((1-7)) receptors and ANG II neutralization by the ANG II antibody reversed as much as 67% of the blood pressure-lowering effect of losartan.     

AT(1) and AT(2) receptor expression and blockade after acute ischemia-reperfusion in isolated working rat hearts

We assessed ANG II type 1 (AT(1)) and type 2 (AT(2)) receptor (R) expression and functional recovery after ischemia-reperfusion with or without AT(1)R/AT(2)R blockade in isolated working rat hearts. Groups of six hearts were subjected to global ischemia (30 min) followed by reperfusion (30 min) and exposed to no drug and no ischemia-reperfusion (control), ischemia-reperfusion and no drug, and ischemia-reperfusion with losartan (an AT(1)R antagonist; 1 micromol/l), PD-123319 (an AT(2)R antagonist; 0.3 micromol/l), N(6)-cyclohexyladenosine (CHA, a cardioprotective adenosine A(1) receptor agonist; 0.5 micromol/l as positive control), enalaprilat (an ANG-converting enzyme inhibitor; 1 micromol/l), PD-123319 + losartan, ANG II (1 nmol/l), or ANG II + losartan. Compared with controls, ischemia-reperfusion decreased AT(2)R protein (Western immunoblots) and mRNA (Northern immunoblots, RT-PCR) and impaired functional recovery. PD-123319 increased AT(2)R protein and mRNA and improved functional recovery. Losartan increased AT(1)R mRNA (but not AT(1)R/AT(2)R protein) and impaired recovery. Other groups (except CHA) did not improve recovery. The results suggest that, in isolated working hearts, AT(2)R plays a significant role in ischemia-reperfusion and AT(2)R blockade induces increased AT(2)R protein and cardioprotection.     

Angiotensin AT(1) receptor inhibition-induced apoptosis by RhoA GTPase activation and pERK1/2 signaling pathways in neonatal obstructive nephropathy

Intrarenal renin-Angiotensin system (RAS) activity is increased during early development and is further enhanced by unilateral ureteral obstruction (UUO). We studied the involvement of mitogen-activated protein (MAP) kinase members and the RhoA GTPase signaling pathways on the regulation of renal cell response after AT1 Angiotensin II receptor inhibition in obstruction. Neonatal rats subjected to sham operation or complete UUO within the first 48 hours of life received saline vehicle, Losartan (AT1 inhibitor), or PD-123319 (AT2 inhibitor) during the first 14 days of life. Cortex tubular epithelial cell apoptotic response was shown by TUNEL and confirmed by electron microscopy associated with mitochondrial signaling pathway through the increased proapoptotic ratio Bax/BcL-2, and consequently increased caspase 3 expression and activity in obstructed kidney before and after Type 1 (AT1) receptor blockade. Non injury of contralateral kidney was shown. The convergence of two independent signal pathways, the RhoA GTPase and pERK and concurrent inhibition of JNK MAP kinase, were required for the apoptotic response in 14 day kidney obstructed tubular cells either with or without Losartan treatment. Absence of increased AT2 protein expression after AT1 receptor inhibition on day 14 of obstruction was shown. Selective AngiotensinAT2-receptor inhibition with PD-123319 had no protective effect on the renal response to complete 14 day UUO. We suggest a role of both RhoA GTPase activation and the opposing actions of the ERK and JNK-MAP kinase signaling pathways as events involved in tubular cell apoptosis regulation in neonatal UUO. The selective AT1-receptor inhibition had no effect on the renal cellular response in the kidney subjected to UUO for 14 days.     

Blocking P-selectin protects from ischemia/reperfusion-induced acute renal failure.

Acute renal failure (ARF) in response to ischemia-reperfusion is thought to be associated with neutrophil infiltration. Neutrophil recruitment depends on adhesion molecules, including P-selectin. Our study sought to characterize the role of P-selectin in ischemia-reperfusion (I/R) -induced acute renal failure (ARF). In wild-type (wt) and P-selectin-deficient (P-/-) mice (both C57BL/6), ARF was induced by 32 min bilateral renal ischemia, followed by reperfusion (I/R). Wt showed a 12- and 20-fold increase in creatinine at 24 and 48 h after I/R, respectively. Similar changes were seen in blood urea nitrogen (BUN). By contrast, in P-/- creatinine and BUN increased only moderately (fourfold over sham). In wt, renal myeloperoxidase activity, indicating neutrophil infiltration, peaked after 24 h (19-fold over sham). This was significantly attenuated in P-/- (fivefold over sham). Western blot analysis revealed maximum P-selectin expression 12 h after I/R in wt. Immunostaining detected P-selectin in glomerular endothelium and in platelets adherent in glomerular and peritubular vessels. Postischemic injection of P-selectin antibody at 10 min after reperfusion, but not isotype control antibody, protected wt from ARF similar to the protection seen in P-/-. We conclude that blocking P-selectin even after onset of reperfusion protects mice from I/R-induced ARF, suggesting potential therapeutic strategies aimed at blocking P-selectin.     

Reduction of asymmetric dimethylarginine involved in the cardioprotective effect of losartan in spontaneously hypertensive rats

Previous studies have indicated that nitric oxide synthase (NOS) inhibitors can induce an increase of blood pressure and exacerbate myocardial injury induced by ischemia and reperfusion, whereas angiotensin II receptor antagonists protect the myocardium against injury induced by ischemia and reperfusion. Isolated hearts from male spontaneously hypertensive rats (SHR) or male Wistar-Kyoto rats (WKY) were subjected to 20 min global ischemia and 30 min reperfusion. Heart rate, coronary flow, left ventricular pressure, and its first derivatives (+/-dP/dt(max)) were recorded, and serum concentrations of asymmetric dimethylarginine (ADMA) and NO and the release of creatine kinase in coronary effluent were measured. The level of ADMA was significantly increased and the concentration of NO was decreased in SHR. Ischemia and reperfusion significantly inhibited the recovery of cardiac function and increased the release of creatine kinase, and ischemia and reperfusion-induced myocardial injury in SHR was aggravated compared with WKY. Vasodilation responses to acetylcholine of aortic rings were decreased in SHR. Treatment with losartan (30 mg/kg) for 14 days significantly lowered blood pressure, elevated the plasma level of NO, and decreased the plasma concentration of ADMA in SHR. Treatment with losartan significantly improved endothelium-dependent relaxation and cardiac function during ischemia and reperfusion in SHR. Exogenous ADMA also aggravated myocardial injury induced by ischemia and reperfusion in isolated perfused heart of WKY, as shown by increasing creatine kinase release and decreasing cardiac function. The present results suggest that the protective effect of losartan on myocardial injury induced by ischemia and reperfusion is related to the reduction of ADMA levels.     

Protective role of cytosolic NADP(+)-dependent isocitrate dehydrogenase, IDH1, in ischemic pre-conditioned kidney in mice

Ischemic pre-conditioning protects the kidney against subsequent ischemia/reperfusion (I/R). This study investigated the role of cytosolic NADP(+)-dependent isocitrate dehydrogenase (IDH1), a producer of NADPH, in the ischemic pre-conditioning. Mice were pre-conditioned by 30 min of renal ischemia and 8 days of reperfusion. In non-pre-conditioned mice 30 min of ischemia had significantly increased the levels of plasma creatinine, BUN, lipid peroxidation and hydrogen peroxide in kidneys, whereas in pre-conditioned mice, the ischemia did not increase them. The reductions of reduced glutathione and NADPH after I/R were greater in non-pre-conditioned mice than in pre-conditioned mice. Ischemic pre-conditioning prevented the I/R-induced decreases in IDH1 activity and expression, but not in glucose-6-phosphate dehydrogenase activity. In conclusion, protection of the kidney afforded by ischemic pre-conditioning may be associated with increased activity of IDH1 which relates to increased levels of NADPH, increased ratios of GSH/total glutathione, less oxidative stress and less kidney injury induced by subsequent I/R insult.     

Improvement in Renal Hemodynamics following Combined Angiotensin II Infusion and AT1R Blockade in Aged Female Sheep following Fetal Unilateral Nephrectomy

Renin-angiotensin system (RAS) is a powerful modulator of renal hemodynamic and fluid homeostasis. Up-regulation in components of intra-renal RAS occurs with ageing. Recently we reported that 2 year old uninephrectomised (uni-x) female sheep have low renin hypertension and reduced renal function. By 5 years of age, these uni-x sheep had augmented decrease in renal blood flow (RBF) compared to sham. We hypothesised that this decrease in RBF in 5 year old uni-x sheep was due to an up-regulation in components of the intra-renal RAS. In this study, renal responses to angiotensin II (AngII) infusion and AngII type 1 receptor (AT1R) blockade were examined in the same 5 year old sheep. We also administered AngII in the presence of losartan to increase AngII bioavailability to the AT2R in order to understand AT2R contribution to renal function in this model. Uni-x animals had significantly lower renal cortical content of renin, AngII (∼40%) and Ang 1–7 (∼60%) and reduced cortical expression of AT1R gene than sham animals. In response to both AngII infusion and AT1R blockade via losartan, renal hemodynamic responses and tubular sodium excretion were significantly attenuated in uni-x animals compared to sham. However, AngII infusion in the presence of losartan caused ∼33% increase in RBF in uni-x sheep compared to ∼14% in sham (P<0.05). This was associated with a significant decrease in renal vascular resistance in the uni-x animals (22% vs 15%, P<0.05) without any changes in systemic blood pressure. The present study shows that majority of the intra-renal RAS components are suppressed in this model of low renin hypertension. However, increasing the availability of AngII to AT2R by AT1R blockade improved renal blood flow in uni-x sheep. This suggests that manipulation of the AT2R maybe a potential therapeutic target for treatment of renal dysfunction associated with a congenital nephron deficit.     

低氧诱导因子在肾炎大鼠肾小管间质中的表达及氯沙坦的保护作用研究

目的：观察低氧诱导因子在肾炎大鼠肾小管间质中表达的变化以及氯沙坦对肾炎的保护作用。方法：雄性Wistar 大鼠32只,随机分成假手术组、肾炎模型组、氯沙坦小剂量组、氯沙坦大剂量组各8 只,假手术组不做肾脏切除,其他组在右肾切除后尾静脉注射标记抗体。给药组则按量分别灌胃给药,8 周时处死。结果：大剂量给药组的血肌酐（Scr）、收缩压和24 h尿蛋白量较模型组显著降低,且小剂量给药组的血肌酐（Scr）和24h 尿蛋白量较模型组也显著降低。小剂量组和大剂量组大鼠的肾间质面积较肾炎模型组均显著降低。HIF-1αmRNA 大量表达于肾小管上皮细胞胞质和间质细胞胞质,且与模型组比较,小剂量给药组的HIF-1αmRNA显著降低;大剂量给药组较肾炎模型组HIF-1琢mRNA 的含量也显著降低。结论：氯沙坦可能可以通过影响低氧诱导因子（HIF-1α）的表达发挥对肾脏的保护作用。     

Sexual dimorphism in the renin-angiotensin system in aging spontaneously hypertensive rats

In young adult spontaneously hypertensive rats (SHR), mean arterial pressure (MAP) is higher in males than in females and inhibition of the renin-angiotensin system (RAS) eliminates this sex difference. After cessation of estrous cycling in female SHR, MAP is similar to that in male SHR. The purpose of this study was to determine the role of the RAS in maintenance of hypertension in aging male and female SHR. At 16 mo of age, MAP was similar in male and female SHR (183+/-5 vs. 193+/-8 mmHg), and chronic losartan (40 mg.kg-1.day-1 po for 3 wk) reduced MAP by 52% (to 90+/-8 mmHg, P<0.05 vs. control) in males and 37% (to 123+/-11 mmHg, P<0.05 vs. control) in females (P<0.05, females vs. males). The effect of losartan on angiotensin type 1 (AT1) receptor blockade was similar: MAP responses to acute doses of ANG II (62.5-250 ng/kg) were blocked to a similar extent in losartan-treated males and females. F2-isoprostane excretion was reduced with losartan more in males than in females. There were no sex differences in plasma renin activity, plasma angiotensinogen or ANG II, or renal expression of AT1 receptors, angiotensin-converting enzyme, or renin. However, renal angiotensinogen mRNA and protein expression was higher in old males than females, whereas renal ANG II was higher in old females than males. The data show that, in aging SHR, when blood pressures are similar, there remains a sexual dimorphism in the response to AT1 receptor antagonism, and the differences may involve sex differences in mechanisms responsible for oxidative stress with aging.     

Important role of apoptosis signal-regulating kinase 1 in ischemic acute kidney injury

We investigated the role of apoptosis signal-regulating kinase 1 (ASK1) in ischemia/reperfusion (I/R)-induced acute kidney injury (AKI). Blood urea nitrogen (BUN) and serum creatinine were significantly higher in ASK1+/+ mice than in ASK1−/− mice after I/R injury. Renal histology of ASK1+/+ mice showed significantly greater tubular necrosis and degradation. In ASK1−/− mice, phosphorylation of ASK1, JNK, and p38K, and the number of TUNEL-positive cells and infiltrated leukocytes decreased after I/R injury. Apoptotic changes were significantly decreased in cultured renal tubular epithelial cells (TECs) from ASK1−/− mice under hypoxic condition. Transfection with dominant-active ASK1 induced apoptosis in TECs. Protein expression of monocyte chemoattractant protein-1 (MCP-1) was significantly weaker in ASK1−/− mice after I/R injury. Transfection with dominant negative-ASK1 significantly decreased MCP-1 production in TECs. These results demonstrated that ASK1 is activated in I/R-induced AKI, and blockage of ASK1 attenuates renal tubular apoptosis, MCP-1 expression, and renal function.     

Strain-Dependent Effects of Sub-chronically Infused Losartan Against Kainic Acid-Induced Seizures,Oxidative Stress,and Heat Shock Protein 72 Expression

We studied the involvement of angiotensin (Ang) II AT₁ receptors in the pathophysiology of kainate (KA)-induced neurotoxicity, focusing on the regulation of the oxidative stress state and expression of HSP 72 in the frontal cortex and hippocampus in two strains, spontaneously hypertensive rats (SHRs) and normotensive Wistar rats. The KA injection was executed after the rats were infused subcutaneously via osmotic mini-pumps with losartan (10 mg/kg day) for 14 days. Losartan delayed the onset of KA-induced seizures in SHRs but not in Wistar rats without affecting the seizure intensity score. This selective AT₁ receptor antagonist decreased the lipid peroxidation only in naive SHRs. However, it attenuated the KA-induced increase in lipid peroxidation in both SHRs and Wistar rats. The adaptive enhancement of cytosolic superoxide dismutase (SOD) activity in KA-treated SHRs was recovered to control level after sub-chronic losartan infusion while no change in mitochondrial SOD activity was detected in the two strains. Both losartan and KA produced a higher expression of HSP 72 in the hippocampus of the two strains compared to naive rats infused with vehicle. Taken together, our findings demonstrate that the efficacy of a sub-chronic systemic losartan infusion in preventing the KA-induced seizure activity and neurotoxicity is more pronounced in SHRs, considered as a model of essential hypertension, than in normotenisve Wistar rats. The results suggest that the blockade of AT1 receptors, commonly used as a strategy for prevention of high blood pressure, may be useful as an adjunctive treatment in status epilepticus to reduce oxidative stress and neurotoxicity.     

β-Arrestin-biased AT1R stimulation promotes cell survival during acute cardiac injury

Pharmacological blockade of the ANG II type 1 receptor (AT1R) is a common therapy for treatment of congestive heart failure and hypertension. Increasing evidence suggests that selective engagement of β-arrestin-mediated AT1R signaling, referred to as biased signaling, promotes cardioprotective signaling. Here, we tested the hypothesis that a β-arrestin-biased AT1R ligand TRV120023 would confer cardioprotection in response to acute cardiac injury compared with the traditional AT1R blocker (ARB), losartan. TRV120023 promotes cardiac contractility, assessed by pressure-volume loop analyses, while blocking the effects of endogenous ANG II. Compared with losartan, TRV120023 significantly activates MAPK and Akt signaling pathways. These hemodynamic and biochemical effects were lost in β-arrestin-2 knockout (KO) mice. In response to cardiac injury induced by ischemia reperfusion injury or mechanical stretch, pretreatment with TRV120023 significantly diminishes cell death compared with losartan, which did not appear to be cardioprotective. This cytoprotective effect was lost in β-arrestin-2 KO mice. The β-arrestin-biased AT1R ligand, TRV120023, has cardioprotective and functional properties in vivo, which are distinct from losartan. Our data suggest that this novel class of drugs may provide an advantage over conventional ARBs by supporting cardiac function and reducing cellular injury during acute cardiac injury.     

Fetal Kidney Cells Can Ameliorate Ischemic Acute Renal Failure in Rats through Their Anti-Inflammatory,Anti-Apoptotic and Anti-Oxidative Effects

Fetal kidney cells may contain multiple populations of kidney stem cells and thus appear to be a suitable cellular therapy for the treatment of acute renal failure (ARF) but their biological characteristics and therapeutic potential have not been adequately explored. We have culture expanded fetal kidney cells derived from rat fetal kidneys, characterized them and evaluated their therapeutic effect in an ischemia reperfusion (IR) induced rat model of ARF. The fetal kidney cells grew in culture as adherent spindle shaped/polygonal cells and expressed CD29, CD44, CD73, CD90, CD105, CD24 and CD133 markers. Administration of PKH26 labeled fetal kidney cells in ARF rats resulted in a significant decrease in the levels of blood urea nitrogen, creatinine, and neutrophil gelatinase-associated lipocalin and decreased tubular necrosis in the kidney tissues (p<0.05 for all). The injected fetal kidney cells were observed to engraft around injured tubular cells, and there was increased proliferation and decreased apoptosis of tubular cells in the kidneys (p<0.05 for both). In addition, the kidney tissues of ARF rats treated with fetal kidney cells had a higher gene expression of renotropic growth factors (VEGF-A, IGF-1, BMP-7 and bFGF) and anti-inflammatory cytokine (IL10); up regulation of anti-oxidative markers (HO-1 and NQO-1); and a lower Bax/Bcl2 ratio as compared to saline treated rats (p<0.05 for all). Our data shows that culture expanded fetal kidney cells express mesenchymal and renal progenitor markers, and ameliorate ischemic ARF predominantly by their anti-apoptotic, anti-inflammatory and anti-oxidative effects.     

Negative Regulation of TGFβ Signaling by Stem Cell Antigen-1 Protects against Ischemic Acute Kidney Injury

Acute kidney injury, often caused by an ischemic insult, is associated with significant short-term morbidity and mortality, and increased risk of chronic kidney disease. The factors affecting the renal response to injury following ischemia and reperfusion remain to be clarified. We found that the Stem cell antigen-1 (Sca-1), commonly used as a stem cell marker, is heavily expressed in renal tubules of the adult mouse kidney. We evaluated its potential role in the kidney using Sca-1 knockout mice submitted to acute ischemia reperfusion injury (IRI), as well as cultured renal proximal tubular cells in which Sca-1 was stably silenced with shRNA. IRI induced more severe injury in Sca-1 null kidneys, as assessed by increased expression of Kim-1 and Ngal, rise in serum creatinine, abnormal pathology, and increased apoptosis of tubular epithelium, and persistent significant renal injury at day 7 post IRI, when recovery of renal function in control animals was nearly complete. Serum creatinine, Kim-1 and Ngal were slightly but significantly elevated even in uninjured Sca-1-/- kidneys. Sca-1 constitutively bound both TGFβ receptors I and II in cultured normal proximal tubular epithelial cells. Its genetic loss or silencing lead to constitutive TGFβ receptor—mediated activation of canonical Smad signaling even in the absence of ligand and to KIM-1 expression in the silenced cells. These studies demonstrate that by normally repressing TGFβ-mediated canonical Smad signaling, Sca-1 plays an important in renal epithelial cell homeostasis and in recovery of renal function following ischemic acute kidney injury.     

Differential effect of losartan in female and male spontaneously hypertensive rats

We demonstrated that the decreased response to acetylcholine observed in aorta of male and female spontaneously hypertensive rats is corrected after sustained (15 days) reduction of blood pressure levels by losartan. In order to verify if the same occurs in resistance vessels, vascular diameter changes induced by topical application of acetylcholine and bradykinin (endothelium-dependent vasodilators) and sodium nitroprusside (endothelium-independent vasodilator) to mesenteric arterioles studied in vivo, in situ were determined in rats treated with losartan for 24 h (acute) or 15 days (chronic). Rats that presented similar reduction (in %) of the blood pressure levels after losartan treatment were chosen. Sodium nitroprusside induced similar responses in losartan-treated and untreated male or female SHR. Whereas in female SHR, losartan corrected the diminished arteriolar response to endothelium-dependent vasodilators after acute and chronic treatment, in male SHR this correction only occurred after chronic treatment. Thus, losartan corrected the endothelial dysfunction more easily in female than in male SHR and independently of the normalization or the magnitude of the reduction of the blood pressure levels. In an attempt to explain the difference, we evaluated the losartan effect on nitric-oxide synthase (NOS) activity and angiotensin II AT1 and AT2 receptor gene expression in these animals. In male and female SHR, NOS activity and AT1 receptor expression were not altered by acute or chronic treatment. On the other hand, AT2 receptor expression was augmented only in female SHR by these treatments. Therefore, augmented AT2 receptor expression, but not alteration of NOS activity or AT1 receptor expression, might explain the difference observed.