Zoran Miloradovic

Effects of Rapamycin on Active Heymann Nephritis

Background/Aim: The effects of rapamycin (RAPA) were examined in active Heymann nephritis (HN), an experimental model of human membranous nephropathy (MN). Current opinion on the therapy of MN is controversial, and medications used for its treatment have not yielded the expected results. Methods: In a two-part study, we examined the effects of RAPA (1.5 mg/kg/day) during the induction phase of HN and on the evolving disease. In both parts, control groups of immunized rats not treated with RAPA and control groups of unimmunized rats were observed and sacrificed concurrently with the treated groups. Results: During the induction phase no significant changes in proteinuria were observed in the group treated with RAPA, in comparison to those in the untreated group (p < 0.001). During the evolving disease RAPA significantly lowered proteinuria (p < 0.001). The characteristic pathohistologic changes and IgG depositions along the glomerular basement membrane were considerably diminished, and infiltration of CD8+ cells completely prevented. Conclusion: RAPA demonstrated beneficial effects on disease progression, given either in the induction phase or during evolving HN. It would be desirable to investigate the effect of RAPA on patients with MN.

Reduced progression of adriamycin nephropathy in spontaneously hypertensive rats treated by losartan

BACKGROUND The aim of the study was to investigate the antihypertensive effects of angiotensin II type-1 receptor blocker, losartan, and its potential in slowing down renal disease progression in spontaneously hypertensive rats (SHR) with adriamycin (ADR) nephropathy. METHODS Six-month-old female SHR were randomly selected in six groups. Two control groups (SH(6), SH(12)) received vehicle. Groups ADR(6), ADR+LOS(6) and ADR(12), and ADR+LOS(12) received ADR (2 mg/kg/b.w. i.v.) twice in a 3-week interval. Group ADR+LOS(6) received losartan (10 mg/kg/b.w./day by gavages) for 6 weeks and group ADR+LOS(12) for 12 weeks after second injection of ADR. Animals were killed after 6 or 12 weeks, respectively. Haemodynamic measurements were performed on anaesthetized animals, blood and urine samples were taken for biochemical analysis and the left kidney was processed for morphological studies. RESULTS Short-term losartan treatment, besides antihypertensive effect, improved glomerular filtration rate and ameliorated glomerulosclerosis resulting in decreased proteinuria. Prolonged treatment with losartan showed further reduction of glomerulosclerosis associated with reduced progression of tubular atrophy and interstitial fibrosis, thus preventing heavy proteinuria and chronic renal failure. Losartan reduced uraemia and increased urea clearance in advanced ADR nephropathy in SHR. Histological examination showed that losartan could prevent tubular atrophy, interstitial infiltration and fibrosis in ADR nephropathy. CONCLUSION Losartan reduces the rate of progression of ADR-induced focal segmental glomerulosclerosis to end-stage renal disease in SHR.

Losartan improved antioxidant defense, renal function and structure of postischemic hypertensive kidney.

Ischemic acute renal failure (ARF) is a highly complex disorder involving renal vasoconstriction, filtration failure, tubular obstruction, tubular backleak and generation of reactive oxygen species. Due to this complexity, the aim of our study was to explore effects of Angiotensin II type 1 receptor (AT1R) blockade on kidney structure and function, as well as oxidative stress in spontaneously hypertensive rats (SHR) after renal ischemia reperfusion injury. Experiments were performed on anaesthetized adult male SHR in the model of ARF with 40 minutes clamping the left renal artery. The right kidney was removed and 40 minutes renal ischemia was performed. Experimental groups received AT1R antagonist (Losartan) or vehicle (saline) in the femoral vein 5 minutes before, during and 175 minutes after the period of ischemia. Biochemical parameters were measured and kidney specimens were collected 24h after reperfusion. ARF significantly decreased creatinine and urea clearance, increased LDL and lipid peroxidation in plasma. Treatment with losartan induced a significant increase of creatinine and urea clearance, as well as HDL. Lipid peroxidation in plasma was decreased and catalase enzyme activity in erythrocytes was increased after losartan treatment. Losartan reduced cortico-medullary necrosis and tubular dilatation in the kidney. High expression of pro-apoptotic Bax protein in the injured kidney was downregulated after losartan treatment. Our results reveal that angiotensin II (via AT1R) mediates the most postischemic injuries in hypertensive kidney through oxidative stress enhancement. Therefore, blockade of AT1R may have beneficial effects in hypertensive patients who have developed ARF.

Allopurinol and Enalapril Failed to Conserve Urinary NOx and Sodium in Ischemic Acute Renal Failure in Spontaneously Hypertensive Rats

Background: Ischemia-reperfusion-induced acute renal failure (ARF) is associated with a high mortality in patients with hypertension and with an unfavorable outcome of kidney transplants from marginal donors. Aim: The influence of allopurinol and enalapril on urinary nitrate/nitrite (UNOx), glomerular filtration rate, plasma and urinary sodium, and hemodynamic parameters was examined in spontaneously hypertensive rats (SHR) with ARF. Methods: ARF was induced by right-kidney removal and clamping the left renal artery for 40 min in 50 male 26-week-old SHR weighing 300 ± 23 g. The rats were randomly allocated to five groups: (1) sham operated; (2) ARF; (3) ARF after pretreatment with 40 mg/kg allopurinol; (4) ARF after pretreatment with 40 mg/kg enalapril, and (5) ARF after pretreatment with 40 mg/kg allopurinol and 40 mg/kg enalapril. Creatinine clearance, UNOx (Griess reaction), cardiac output (dye dilution technique), mean arterial blood pressure, and renal blood flow were measured 24 h after reperfusion. Total vascular resistance and renal vascular resistance were calculated and compared between the groups. Results: A nonsignificant decrease was found in both daily UNOx excretion and creatinine clearance when pretreated ARF groups and the ARF group without pretreatment were compared (p > 0.05). Significantly lower plasma sodium values (139.5 ± 4.86 mmol/l) in the allopurinol-pretreated ARF group were found than in the ARF group without pretreatment, in the ARF group pretreated with enalapril, and in the sham SHR group (p = 0.029). The urinary sodium loss was greater in the enalapril-pretreated than in the allopurinol-pretreated ARF group (p = 0.047). Allopurinol and/or enalapril pretreatment decreased total vascular resistance (p = 0.003) in comparison with the sham SHR group. Conclusion: Neither allopurinol nor enalapril nor both were protective against ischemia-reperfusion injury in SHR, nor altered glomerular filtration rate and UNOx in a favorable direction.

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.

RESVERATROL REDUCES BLOOD PRESSURE, CHANGES OF ANTIOXIDANT ENZYME ACTIVITY AND HISTOLOGICAL PARAMETERS IN EXPERIMENTAL MODEL OF MALIGNANT HYPERTENSION: PP.29.171

Objective: Spontaneously hypertensive rats (SHR) treated with NO syntase inhibitor L-NAME, develop malignant hypertension. This study designed to examine the role of chronic administration of resveratrol on blood pressure, activity of antioxidant enzyme and histological parameters in model of malignant hypertension. Design and Methods: Experiments were performed in adult female SHR, weight 250 g. Two groups of 22 SHR each involved: L-NAME group treated with L-NAME (10 mg/kg per os) and COMB group treated with L-NAME (10 mg/kg per os) and resveratrol (10 mg/kg by gavage). Mean arterial pressure (MAP) and aortal blood flow (ABF) were measured at the end of the 4 weeks treatment period and aortal vascular resistance (AVR) was calculated. Activity of antioxidant enzyme, reduced glutathione (GR) and glutathione peroxidase (GSH-Px) were estimated in erythrocyte. The aorta was preceded for histopathological analysis. Results: The mean arterial pressure after treatment significantly dropped in COMB (157.10 ± 7.49 mmHg) compared L-NAME (182.79 ± 2.16 mmHg). Treatment reduced aortal blood flow that leads to significantly decrease of aortal vascular resistance in COMB (35.54 ± 3.31 mmHg min 100 g/ml) vs L-NAME (45.54 ± 3.06 mmHg min 100 g/ml). Resveratrol in COMB increased activity of GR (30951.23 ± 10253.54 μmol NADPH/min/g Hb) and GSH-Px (9.23 ± 2.10 μmol NADPH/min/g Hb) vs L-NAME (24034.13 ± 5743.76 μmol NADPH/min/g Hb; 3.88 ± 1.14 μmol NADPH/min/g Hb). In model of malignant hypertension histological structure of aorta showed disintegration of endothelial, marked atrophic in tunicae media and necrotic modification in smooth muscle cells. Treatment with resveratrol preserved endothelial and reduced morphological changes in tunica media and smooth muscle cells of aorta. Histopatological score of aorta was significantly reduced in the COMB group (2.50 ± 0.13) compared to L-NAME (3.31 ± 0.12). Conclusions: These results suggest that resveratrol reduced mean arterial pressure and aortal blood flow, probably by decreasing peripheral vascular resistance. Chronic treatment with resveratrol in model of malignant hypertension significantly increased activity of antioxidant enzymes, and reduced morphological changes of aorta. Thus, resveratrol possess antioxidative and antihypertensive effects.

Effects of long-term losartan and L-arginine treatment on haemodynamics, glomerular filtration, and SOD activity in spontaneously hypertensive rats.

Recently, it has been reported that losartan, an angiotensin II receptor (ATR) antagonist, depresses the angiotensin II-induced production of superoxide radicals. Also, in spontaneously hypertensive rats (SHR) endothelial dysfunction is associated with decreased nitric oxide (NO) synthesis. In this study, we examined the effects of long-term ATR blockade and L-arginine supplementation on the haemodynamic parameters, glomerular filtration, and oxidative status in SHR. Adult male SHR were treated with losartan (10 mg/kg) and with the NO donor L-arginine (2 g/kg) for 4 weeks. The animals were divided into the following experimental groups: control (n = 7), L-arginine (n = 7), losartan (n = 7), and L-arginine + losartan (n = 7). Mean arterial pressure (MAP), regional blood flow, urea clearance, and activity of superoxide dismutase (SOD) were measured at the end of treatment. MAP was significantly reduced in the losartan group compared with the control group (133.3 +/- 7.3 vs. 161.5 +/- 14.5 mm Hg). Aortic blood flow was significantly higher and aortic vascular resistance was significantly lower in all treated groups than in the control. Urea clearance rose significantly in the L-arginine + losartan group compared with control (393.27 +/- 37.58 vs. 218.68 +/- 42.03 microL x min(-1) x 100 g(-1)) as did the activity of SOD (1668.97 +/- 244.57 vs. 1083.18 +/- 169.96 U/g Hb). Our results suggest that the antihypertensive effect of losartan and L-arginine in SHR is not primarily mediated by increased SOD activity. Also, combined treatment with ATR blockade and L-arginine supplementation has a beneficial effect on renal function that is, at least in part, mediated by increased SOD activity in SHR.

Nitric oxide supplementation in postischemic acute renal failure: normotension versus hypertension.

Nitric oxide (NO) has been suggested to play a pivotal role in ischemic acute renal failure (ARF) but there are controversies about its role in hypertensive and non hypertensive ischemic kidney. Multiple strategies including administration of exogenous NO donors have been shown to protect the kidney against toxic or ischemic injury, suggesting endothelial dysfunction as impaired NO generation due to ischemia. However, in postischemic kidney, NO derived from inducible nitric oxide synthase (iNOS) has been considered to enhance the tissue damage while iNOS inhibition decreased the tubular damage. It is well known decrease in basal production of NO in essential hypertension and that long lasting hypertension damages medium size and small-size blood vessels, therefore predisposes nephroangiosclerosis patients to ARF. Many studies have shown that long term stimulation of NO release in normotension improves renal haemodymnamics and kidney function in ischemic form of ARF. On the other hand, there are studies that have shown that NO synthesis stimulation has no effect or even worsens tubular damage in postischemic hypertensive kidney. Therefore, it seems likely that NO supplementation plays different role in postischemic renal damage development, beneficial in well preserved normotensive kidney and limited in postischemic hypertensive kidney due to disturbed tubuloglomerular response, vasoreactivity and kidney vascular structure.

Upregulation of Heme Oxygenase-1 in Response to Wild Thyme Treatment Protects against Hypertension and Oxidative Stress

High blood pressure is the most powerful contributor to the cardiovascular morbidity and mortality, and inverse correlation between consumption of polyphenol-rich foods or beverages and incidence of cardiovascular diseases gains more importance. Reactive oxygen species plays an important role in the development of hypertension. We found that wild thyme (a spice plant, rich in polyphenolic compounds) induced a significant decrease of blood pressure and vascular resistance in hypertensive rats. The inverse correlation between vascular resistance and plasma heme oxygenase-1 suggests that endogenous vasodilator carbon monoxide generated by heme oxidation could account for this normalization of blood pressure. Next product of heme oxidation, bilirubin (a chain-breaking antioxidant that acts as a lipid peroxyl radical scavenger), becomes significantly increased after wild thyme treatment and induces the reduction of plasma lipid peroxidation in hypertensive, but not in normotensive rats. The obtained results promote wild thyme as useful supplement for cardiovascular interventions.

Acute Superoxide Radical Scavenging Reduces Blood Pressure but Does Not Influence Kidney Function in Hypertensive Rats with Postischemic Kidney Injury

Acute kidney injury (AKI) is associated with significant morbidity and mortality in hypertensive surroundings. We investigated superoxide radical molecules influence on systemic haemodynamic and kidney function in spontaneously hypertensive rats (SHR) with induced postischemic AKI. Experiment was performed in anesthetized adult male SHR. The right kidney was removed, and left renal artery was subjected to ischemia by clamping for 40 minutes. The treated group received synthetic superoxide dismutase mimetic TEMPOL in the femoral vein 5 minutes before, during, and 175 minutes after the period of reperfusion, while the control AKI group received the vehicle via the same route. All parameters were measured 24 h after renal reperfusion. TEMPOL treatment significantly decreased mean arterial pressure and total peripheral resistance (P < 0.05) compared to AKI control. It also increased cardiac output and catalase activity (P < 0.05). Lipid peroxidation and renal vascular resistance were decreased in TEMPOL (P < 0.05). Plasma creatinine and kidney morphological parameters were unchanged among TEMPOL treated and control groups. Our study shows that superoxide radicals participate in haemodynamic control, but acute superoxide scavenging is ineffective in glomerular and tubular improvement, probably due to hypertension-induced strong endothelial dysfunction which neutralizes beneficial effects of O2 − scavenging.