Danijela Karanovic

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.

Chronic changes of hematocrit value alter blood pressure and glomerular filtration in spontaneously hypertensive rats

Many studies in hypertensive humans and animals have shown that increased blood viscosity is in direct relation with essential hypertension. The aim of our studies was to investigate the effects of chronic hematocrit value changes on arterial blood pressure and kidney function in genetically induced hypertension. To this end, we studied the effects of several interventions, designed to increase/decrease hematocrit, on hemodynamic parameters, vascular reactivity, glomerular filtration and renal function curve in spontaneously hypertensive rats (SHR). Results of our study show that chronic hematocrit value elevation increases blood pressure and peripheral vascular resistance in SHR. On the other hand, chronic hematocrit lowering elucidates blood pressure and peripheral vascular resistance decrease followed by cardiac output rising. Both hematocrit value changes significantly reduce vasodilatory vascular response. Hematocrit lowering induces acute renal failure. Sodium excretion is shifted to higher blood pressure values in high hematocrit value animals and opposite - lower blood pressure values in low hematocrit value animals. Repeated transfusions develop salt sensitive malignant hypertension in SHR. Further studies are necessary to evaluate the degree of kidney damage after chronic hematocrit value changes in SHR.

Effects of Losartan, Tempol, and Their Combination On Renal Nitric Oxide Synthases in the Animal Model of Chronic Kidney Disease

Abstract Down-regulation of nitric oxide synthase (NOS) and NO deficiency in the kidneys have been implicated in the pathogenesis of chronic kidney disease (CKD). In this study we examined the effects of losartan, tempol, and combined treatment on three NOS isoforms expressions, kidney NO content and NOS correlation with renal function and structure in the early stage of adriamycin (ADR)-induced CKD in spontaneously hypertensive rats (SHR). Rats were divided into control group, and four other groups which were treated with ADR and received vehicle, losartan (L, angiotensin II type 1 receptor blocker), tempol (T, redox-cycling nitroxide) or T+L treatment (by gavage) in a six-week study. Reduction of all NOS isoforms expressions were significantly improved by losartan or tempol, and correlated with proteinuria amelioration. Combined treatment induced down-regulation of constitutive NOS isoforms, whilst inducible NOS was up-regulated and followed by increased nitrite content and a significant decline in the glomerular filtration rate. Losartan or tempol prevented ADR-induced neoexpression of vimentin in the glomeruli and tubulointerstital areas, whereas de novo vimentin expression was still observed in the atrophic tubules and in the interstitial fibroblasts and myofibroblasts in combined treatment. It can be concluded that single treatments, contrary to combined, were effective in improving NO bioavailability and slowing down the progression of CKD.

[PP.09.11] TEMPOL SUPPLEMENTATION DOES NOT OVERCOME BENEFICIAL EFFECT OF LOSARTAN IN HYPERTENSIVE RATS WITH EARLY COURSE OF FOCAL SEGMENTAL GLOMERULOSCLEROSIS

Objective: Previously, we demonstrated that losartan had beneficial effect on renal function and structure in spontaneously hypertensive rats (SHR) with early course of adriamycin (ADR) nephropathy. Here, the aim was to investigate whether combination of losartan (L) with tempol (T), a membrane-permeable radical scavenger, could overcome this beneficial effects in the early course of ADR-induced focal segmental glomerulosclerosis (FSGS). Design and method: Females SHR (24-week-old) were divided in four groups. Control rats (SHC) received vehicle, while SHADR, SHADR+L, SHADR+L+T groups received ADR (2 mg/kg body weight i.v.) twice in 3-week-interval. After the second injection, SHADR+L received L (10 mg/kg/day), SHADR+L+T received L+T (10+100 mg/kg/day), while SHADR and SHC received tap water (by gavage) for 6 weeks. At the end of the experiment, albuminuria, kidney antioxidant enzymes activities (SOD-superoxide dismutase, catalase, and GPx-glutathione peroxidase) and histology were analyzed. Results: Albuminuria was significantly increased in SHADR group compared to control (p < 0.01). Losartan reduced albumin excretion to a value not significantly different from control. However, after combined L+T-treatment albuminuria remained significantly higher than in SHC (p < 0.05). SOD and GPx activities were diminished in ADR-treated SHR (p < 0.001). Losartan significantly improved these changes, and reverted SOD and GPx activities to the level as in control. Combined treatment failed to change SOD, while GPx activity became significantly decreased (p < 0.01) compared to both, SHADR+L and SHC groups. Adriamycin did not affect catalase activity, but chronic losartan or combined treatment significantly increased catalase activity compared to control. Glomerular sclerosis was significantly increased in SHR after ADR application (p < 0.001), and losartan alone, or in combination with tempol, did not alter it. ADR-induced tubular injury was significantly reduced after losartan treatment (p < 0.01) compared to SHADR. Conversely, in SHADR+L+T group tubular damage was similar to that of SHADR, and significantly elevated versus both, SHADR+L and SHC. Conclusions: Our results showed that combined treatment with tempol and losartan failed to improve kidney function, structure and antioxidant enzymes activities in experimental FSGS. Therefore, tempol supplementation does not overcome beneficial effect of losartan in hypertensive rats with early course of ADR-induced FSGS.

[PP.31.12] EFFECTS OF REGULAR CONSUMPTION OF RED WINE AND ALCOHOL-FREE RED WINE ON SYSTEMIC HAEMODYNAMICS, LIPID PROFILE AND OXIDATIVE STRESS IN SPONTANEOUSLY HYPERTENSIVE RATS

Objective: Numerous studies have shown that moderate wine consumption is associated with decreased incidence of cardiovascular disease, including hypertension. Other studies have observed that moderate alcohol consumption lowers the risk of cardiovascular events. The aim of the present study was to compare the effects of regular red wine (RW) and alcohol-free red wine (AFRW) consumption (1 ml/day) on systemic haemodynamics, lipid profile and oxidative stress in adult male spontaneously hypertensive rats (SHR). Design and method: Control SHRC group (n = 8), received tap water, SHR+RW (n = 8) received red wine (Prokupac wine, Cellar Braca Rajkovic, Serbia) and SHR+AFRW (n = 8) received alcohol-free red wine by gavage throughout the 4-week experimental period. Systolic (SBP), diastolic (DBP), mean blood pressure (MBP), heart rate (HR), cardiac index (CI) and total vascular resistance (TVR) were measured in anesthetized rats. Blood samples were collected for total cholesterol, triglycerides, high-density lipoproteins (HDL) cholesterol, low-density lipoproteins (LDL) cholesterol, bilirubin, uric acid and plasma TBARS (p-thiobarbituric acid reactive substances). Results: SBP was found to be lower in SHR+AFRW and SHR+RW groups compared to control. Chronic consumption of AFRW resulted in a significant decrease of DBP and MAP (p < 0.05), while chronic RW application significantly reduced only the DBP. None of the two types of wine had significant effect on HR, CI and TVR of SHRs. The lipid profile was significantly changed in SHR after RW but not after AFRW consumption. RW raise the level of total cholesterol (p < 0.05) relative to control, and the triglycerides were increased compared to the control as well as the AFRW group (p < 0.001). Although, HDL was slightly higher and LDL cholesterol was mildly to moderately lower in both wine groups compared to control. AFRW doubles the production of endogenous antioxidant bilirubin in the SHRs, while RW cause a significant increase of plasma uric acid (p < 0.05) compared to control. Both, RW and AFRW, significantly reduced p-TBARS. Conclusions: Chronic intake of AFRW has a better effect on blood pressure and lipid proifile of SHR than consumption of RW. Both, RW and AFRW, can increased antioxidant capacity and reduce susceptibility of SHR plasma to lipid peroxidation.

[PP.31.13] HAEMODYNAMIC DOSE-DEPENDENT RESPONSE TO OLIVE LEAF EXTRACTS IN SPONTANEOUSLY HYPERTENSIVE RATS

Objective: Numerous studies demonstrate that a Mediterranean diet leads to significant drops in elevated blood pressure. It is well known that different products of Olea europea L. are very important part of this diet. The aim of our study was to investigate the dose-dependent response of haemodynamic parameters to olive leaf extracts in SHR Design and method: Experiment was performed in anesthetized, six-month-old male spontaneously hypertensive rats (SHR). SHR were divided into 3 experimental groups: the group treated with 5 mg/kg of olive leaf extract (OE5; n = 8); the group treated with 25 mg/kg of olive leaf extract (OE25; n = 8); and the group treated with 50 mg/kg of olive leaf extract (OE50; n = 7). Different dosage of olive leaf extract was given by bolus, through the jugular vain. Mean arterial pressure (MAP), cardiac output (CO), heart rate (HR) were measured, and total peripheral vascular resistance (TPVR) was calculated before and after bolus. Results: Figure. No caption available. Conclusions: Our results suggest that dosages of 25 mg/kg and 50 mg/kg olive leaf extract lower blood pressure in SHR, but in two different ways. Lower dosage decreases MAP due to vascular response (decreases TPVR), and higher dosage decreases MAP because of cardiac response due to decrease of CO.

Combined Angiotensin II Type-1 Receptor Blockade and Superoxide Anion Scavenging Affect the Post-Ischemic Kidney in Hypertensive Rats

Abstract Ischemic acute kidney injury is characterized by renal vasoconstriction, filtration failure, tubular obstruction, tubular backleak and overproduction of angiotensin II and reactive oxygen species. Considering this complexity, the aim of our study was to investigate the effects of angiotensin II type-1 receptor blocker - Losartan and superoxide anion scavenger - Tempol, in a combined treatment on acute kidney injury in postischemic hypertensive rats. The experiment was performed in anesthetized, adult male spontaneously hypertensive rats. The right kidney was removed and the left renal artery was occluded for 40 minutes. Experimental groups received combined treatment (Losartan + Tempol) or saline in the femoral vein 5 minutes before, during and 175 minutes after clamp removal. Hemodynamics and biochemical parameters were measured and kidney specimens were collected 24h after reperfusion. Histological examination was performed by optical microscopy. Combined treatment improves renal haemodynamics parameters which were exacerbated due to acute kidney injury. Acute kidney injury significantly decreased creatinine and urea clearance and increased lipid peroxidation in the plasma. Treatment with Losartan and Tempol induced a significant increase of creatinine and urea clearance. Lipid peroxidation in the plasma decreased and glutathione peroxidase enzyme activity in the erythrocytes increased after Losartan + Tempol treatment. This combined treatment reduced cortico-medullary necrosis and tubular dilatation in the kidney. Our results indicate that synergism of Losartan and Tempol treatment could have beneficial effects on blood pressure and kidney function, during postischemic acute kidney injury development in experimental hypertension.

The effects of acute administration of losartan, angiotensin II type-1 receptor antagonist, on hemodynamics and oxidative stress parameters in malignant hypertensive rats

Malignant hypertension is a severe form of hypertension which pathogenesis is not fully elucidated. The aim of our study was to investigate the role of Angiotensin II on hemodynamic and oxidative stress parameters in model of malignant hypertension by using losartan. Adult males were divided into three groups: normotensive Wister rats, control SHR and losartan treated SHR. Control and SHR group received a single bolus dosage of saline, while the SHR + LOS group received a losartan. Blood pressure, cardiac output, both total peripheral and carotid vascular resistance and carotid blood flow were measured. CAT, SOD and TBARS were determined in the blood samples. The treatment significantly decreased the blood pressure. There was no significant change in cardiac output or carotid blood flow, but treatment resulted in diminishment of vascular resistances, both total peripheral and carotid. There was a tendency to restore the values of SOD activity towards those of the normotensive group, but there were no change in CAT and TBARS levels. Taken together, our results show that a single application of losartan has a strong hypotensive effect. Angiotensin II seems to have a significant role in the malignant hypertension syndrome and it partially affects oxidative stress parameters. [Projekat Ministarstva nauke Republike Srbije, br. OI 175096]