Hyperbaric Oxygen Reduces Oxidative Stress Impairment and DNA Damage and Simultaneously Increases HIF-1α in Ischemia-Reperfusion Acute Kidney Injury

The central exacerbating factor in the pathophysiology of ischemic-reperfusion acute kidney injury (AKI) is oxidative stress. Lipid peroxidation and DNA damage in ischemia are accompanied by the formation of 3-nitrotyrosine, a biomarker for oxidative damage. DNA double-strand breaks (DSBs) may also be a result of postischemic AKI. γH2AX(S139) histone has been identified as a potentially useful biomarker of DNA DSBs. On the other hand, hypoxia-inducible factor (HIF) is the "master switch" for hypoxic adaptation in cells and tissues. The aim of this research was to evaluate the influence of hyperbaric oxygen (HBO) preconditioning on antioxidant capacity estimated by FRAP (ferric reducing antioxidant power) and ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) assay, as well as on oxidative stress parameter 3-nitrotyrosine, and to assess its effects on γH2AX(S139), HIF-1α, and nuclear factor-κB (NF-κB) expression, in an experimental model of postischemic AKI induced in spontaneously hypertensive rats. The animals were divided randomly into three experimental groups: sham-operated rats (SHAM, n = 6), rats with induced postischemic AKI (AKI, n = 6), and group exposed to HBO preconditioning before AKI induction (AKI + HBO, n = 6). A significant improvement in the estimated glomerular filtration rate, eGFR, in AKI + HBO group (p < 0.05 vs. AKI group) was accompanied with a significant increase in plasma antioxidant capacity estimated by FRAP (p < 0.05 vs. SHAM group) and a reduced immunohistochemical expression of 3-nitrotyrosine and γH2AX(S139). Also, HBO pretreatment significantly increased HIF-1α expression (p < 0.001 vs. AKI group), estimated by Western blot and immunohistochemical analysis in kidney tissue, and decreased immunohistochemical NF-κB renal expression (p < 0.01). Taking all of these results together, we may conclude that HBO preconditioning has beneficial effects on acute kidney injury induced in spontaneously hypertensive rats.

Immunohistochemical Pattern of Histone H2A Variant Expression in an Experimental Model of Ischemia-Reperfusion-Induced Acute Kidney Injury

Ischemia-reperfusion injury (IRI) is a frequent cause of AKI, resulting in vasoconstriction, cellular dysfunction, inflammation and the induction of oxidative stress. DNA damage, including physical DNA strand breaks, is also a potential consequence of renal IRI. The histone H2A variants, primary H2AX and H2AZ participate in DNA damage response pathways to promote genome stability. The aim of this study was to evaluate the immunohistochemical pattern of histone H2A variants' (H2AX, γH2AX(S139), H2AXY142ph and H2AZ) expression in an experimental model of ischemia-reperfusion-induced acute kidney injury in spontaneously hypertensive rats. Comparing the immunohistochemical nuclear expression of γH2AX(S139) and H2AXY142ph in AKI, we observed that there is an inverse ratio of these two histone H2AX variants. If we follow different regions from the subcapsular structures to the medulla, there is an increasing extent gradient in the nuclear expression of H2AXY142ph, accompanied by a decreasing nuclear expression of γH2AX. In addition, we observed that different structures dominated when γH2AX and H2AXY142ph expression levels were compared. γH2AX was expressed only in the proximal tubule, with the exception of when they were dilated. In the medulla, H2AXY142ph is predominantly expressed in the loop of Henle and the collecting ducts. Our results show moderate sporadic nuclear H2AZ expression mainly in the cells of the distal tubules and the collecting ducts that were surrounded by dilated tubules with PAS (periodic acid-Schiff stain)-positive casts. These findings may indicate the degree of DNA damage, followed by postischemic AKI, with potential clinical and prognostic implications regarding this condition.

Optimization of the extraction of antioxidants from stinging nettle leaf using response surface methodology

The aim of this study was to optimize the parameters of the extraction of total flavonoids from stinging nettle leaf. Comparison of the effects of different solvents on total flavonoid content showed that, regardless of extraction time, aqueous-methanolic extracts had higher total flavonoid content than aqueous-ethanolic extracts. So, full factorial design and response surface methodology (RSM) were employed to estimate the effects of methanol content (50, 75, and 100 %) and extraction time (30, 60, and 90 minutes) on total flavonoid content and antioxidant capacities of the extracts. RSM analysis showed that methanol content in the solvent influenced significantly total flavonoid content and FRAP (Ferric Reducing Antioxidant Power Assay) antioxidant capacity, while extraction time had no significant effect on either of the responses. Extraction parameters for maximal total flavonoid content were estimated to be 69 % aqueous-methanol and 67 min, and 65 % aqueous-methanol and 83 min for maximal FRAP antioxidant capacity. DPPH (2,2-diphenyl-1-picrylhydrazyl) antioxidant capacity was not significantly affected by extraction time or methanol percentage in the solvent.

DNA, protein and lipid oxidative damage in tissues of spontaneously hypertensive versus normotensive rats

Oxidative damage to protein and lipid macromolecules in target organs in hypertension has been recognized as a major factor contributing to cardiovascular, cerebrovascular, and renal diseases. Data on protein and lipid oxidative damage in spontaneously hypertensive rats are numerous, but there is no information on DNA damage in tissues measured by comet assay. The aim of this study was to determine the baseline damage to DNA, protein, and lipid macromolecules in different organs of spontaneously hypertensive rats. Markers of lipid peroxidation, protein oxidation, and DNA damage were measured in blood, heart, kidney, and liver of 24-week-old spontaneously hypertensive rats. Plasma prooxidant and antioxidant status were determined as well. Age-matched normotensive Wistar rats were used as control. A rise in markers of lipid peroxidation and protein oxidation, malondialdehyde, and advanced oxidation protein products, was detected in all tissues of spontaneously hypertensive rats, with particularly high values in the liver. DNA damage, measured by the comet assay, was significantly higher in all the studied tissues of spontaneously hypertensive rats compared to normotensive control, with more severe damage in the cardiac and renal cells. Significant depletion of the plasma antioxidant barrier in spontaneously hypertensive rats was also observed. This study showed increased damage to all macromolecules in all studied samples of spontaneously hypertensive rats in comparison with control Wistar rats.

Immunohistochemical Analysis of 4-HNE, NGAL, and HO-1 Tissue Expression after Apocynin Treatment and HBO Preconditioning in Postischemic Acute Kidney Injury Induced in Spontaneously Hypertensive Rats

Oxidative stress has been considered as a central aggravating factor in the development of postischemic acute kidney injury (AKI). The aim of this study was to perform the immunohistochemical analysis of 4-hydroxynonenal (4-HNE), neutrophil gelatinase-associated lipocalin (NGAL), and heme oxygenase-1 (HO-1) tissue expression after apocynin (APO) treatment and hyperbaric oxygenation (HBO) preconditioning, applied as single or combined protocol, in postischemic acute kidney injury induced in spontaneously hypertensive rats (SHR). Twenty-four hours before AKI induction, HBO preconditioning was carried out by exposing to pure oxygen (2.026 bar) twice a day, for 60 min in two consecutive days. Acute kidney injury was induced by removal of the right kidney while the left renal artery was occluded for 45 min by atraumatic clamp. Apocynin was applied in a dose of 40 mg/kg body weight, intravenously, 5 min before reperfusion. We showed increased 4-HNE renal expression in postischemic AKI compared to Sham-operated (SHAM) group. Apocynin treatment, with or without HBO preconditioning, improved creatinine and phosphate clearances, in postischemic AKI. This improvement in renal function was accompanied with decreased 4-HNE, while HO-1 kidney expression restored close to the control group level. NGAL renal expression was also decreased after apocynin treatment, and HBO preconditioning, with or without APO treatment. Considering our results, we can say that 4-HNE tissue expression can be used as a marker of oxidative stress in postischemic AKI. On the other hand, apocynin treatment and HBO preconditioning reduced oxidative damage, and this protective effect might be expected even in experimental hypertensive condition.

Olive leaf extract attenuates adriamycin-induced focal segmental glomerulosclerosis in spontaneously hypertensive rats via suppression of oxidative stress, hyperlipidemia, and fibrosis

Olive (Olea europaea L.) leaf extract (OLE) possesses powerful antioxidant, antihyperlipidemic, and anti-inflammatory properties. The aim was to investigated the effects of OLE on the hyperlipidemia, antioxidant defense, heme oxygenase/biliverdin reductase (HO/BVR) pathway, inflammation, and fibrosis in spontaneously hypertensive rats with focal segmental glomerulosclerosis (FSGS, a progressive form of chronic kidney disease) induced by adriamycin (2 mg/kg, i.v., twice in a 21-day period). Daily treatment of OLE (80 mg/kg, p.o.) for 6 weeks suppressed protein oxidation and lipid peroxidation (p < .01 and p < .001, respectively), significantly increased antioxidant enzymes activities and normalized antioxidant capacity, leading to the improvement of antioxidant defense independently of the HO/BVR pathway. Furthermore, the values of triglycerides (p < .01), total, and low-density lipoprotein cholesterol (p < .05, both) were improved by OLE. OLE strongly prevented glomerulosclerosis, interstitial inflammation, and fibrosis (renal injury score, FSGS: 8 ± 0.45 vs. FSGS+OLE: 4.20 ± 1.07; p < .01), as evidenced by normalized fibronectin content (p < .001), suppressed interstitial inflammatory cells infiltration and collagen deposition, without changing cytokines expressions. OLE decreased blood pressure with a tendency to reduce urine albumin loss. These data suggest that OLE may be effective in slowing down the progression of FSGS.

P0557HYPERBARIC OXYGEN PRECONDITIONING INCREASES HEME OXYGENASE 1 EXPRESSION IN KIDNEY TISSUE AND IMPROVES KIDNEY FUNCTION IN SPONTANEOUSLY HYPERTENSIVE RATS WITH ISCHEMIC ACUTE KIDNEY INJURY

Background and Aims

Renal ischemia–reperfusion (RIR) injury is one of the factors in the development of acute kidney injury (AKI). AKI is multifactorially caused, but the mechanism of pathogenesis and development of this disease is still incompletely defined. AKI is characterized by the sudden appearance, rapid progression of disease and very uncertain and often fatal outcome. Heme oxygenase-1 (HO-1) is a cytoprotective enzyme that catalyzes the breakdown of heme to biliverdin, carbon monoxide, and iron. HO-1 is now recognized as a protection factor in acute kidney injury. The aim of this study was to determine the effect of preconditioning with hyperbaric oxygen (HBO) on HO-1 expression in kidney tissue and kidney function in spontaneously hypertensive rats (SHR) during kidney ischemia–reperfusion injury.

Method

An experiment was performed in anesthetized, adult six-month-old male SHR. The right kidney was removed and the renal ischemia was performed by clamping the left renal artery for 40 minutes. SHR were randomly selected in three experimental groups: sham operated group (SHAM; n=7); AKI control group (AKI; n=9); and AKI group with HBO (AKI+HBO; n=9). Treated group were placed into experimental HBO chambers and exposed to pure oxygen, twice a day (in a 12 hour period, 8AM and 8 PM) for two consecutive days in the following manner: 10 minutes slow compression, 2.026 bar for 60 minutes, 10 minutes slow decompression. Mean arterial pressure (MAP) and HO-1 expression in kidney tissue were measured 24h after reperfusion. Clearance of creatinine (CCr), urea (CUr) and phosphate (CPh) were calculated 24h after reperfusion.

Results

After AKI induction reduction of blood pressure was recorded in both groups with AKI. Preconditioning with HBO significantly improved kidney function in rats with AKI compared to control group. HO-1 expression in kidney tissue was significantly higher in the treated group (p&lt;0,01) compared to SHAM and AKI control group.

Conclusion

Our results suggest that HBO treatment improves kidney function in the AKI+HBO vs. AKI control group. This implies that increased level of HO-1 due to preconditioning with hyperbaric oxygen may have beneficial effects on kidney function, and potentially protective effect in an ischemic model of AKI with hypertension.

P0916OLIVE LEAF EXTRACT IMPROVES RENAL ANTIOXIDANT DEFENSE WITHOUT ALTERING THE HEME OXYGENASE-1/BILIVERDIN REDUCTASE PATHWAY IN HYPERTENSIVE RATS WITH FOCAL SEGMENTAL GLOMERULOSCLEROSIS

Background and Aims

Oxidative stress is implicated in the pathophysiology of chronic kidney disease. Previously, we showed that adriamycin (anticancer agent, enhances reactive oxygen species production) induced focal segmental glomerular sclerosis (FSGS) with massive proteinuria in spontaneously hypertensive rats (SHR). The heme oxygenase (HO) system plays an important role in regulating oxidative stress and is protective in chronic kidney disease. HO-1 is a cytoprotective enzyme that catalyzes the conversion of highly reactive free heme molecules into biliverdin, carbon monoxide, and iron. Biliverdin is subsequently converted to bilirubin by biliverdin reductase and has potent antioxidant effect. Olive leaf extract (OLE, Olea europaea L.) is rich in phenolic compounds that are known to possess powerful antioxidant properties. Here, we aimed to investigate the effects of OLE, focusing on its modulatory role on oxidative stress and HO-1/BVR pathway in the kidney of SHR with adriamycin-induced FSGS.

Method

Adult females SHR were divided into three groups. Control rats received vehicle. Two other groups, FSGS and FSGS+OLE, received adriamycin (2 mg/kg body weight i.v.) twice in 3-week-interval. After the second injection, FSGS+OLE group received OLE (80 mg/kg/day) by gavage for 6 weeks. Mean blood pressure (MAP), urine albumin-to-creatinine (Ualb/cr), renal HO-1 and biliverdin reductase protein expressions (Western Blot), protein carbonyl content (PCOs), and antioxidant capacity (ABTS) were analyzed.

Results

In FSGS group albuminuria was significantly increased in comparison to the level in control. Chronic consumption of OLE markedly, but not significantly decreased Ualb/cr compared to that in control. Analysis of renal PCOs revealed that significant enhancement of protein oxidation in the kidney of model group was reduced after OLE treatment to the level as in control. The ABTS level in kidney homogenates significantly decreased in FSGS group in comparison to the level in control. OLE significantly increased renal antioxidant capacity in FSGS+OLE group compared to that in model group. Western blot analysis of HO-1, and biliverdin reductase in the kidney revealed that protein expressions of both enzymes were significantly decreased in FSGS group compared to that in control. Following OLE treatment in FSGS+OLE group protein expressions of HO-1, and biliverdin reductase remained at similar level as in model group. No change in MAP values were observed between control and model groups. OLE significantly decreased MAP in FSGS+OLE group in comparison to the value of model group, and nearly significant reduction of MAP compared to the value of control.

Conclusion

Collectively, our results showed that OLE expressed its antioxidant property and improved oxidative status in the kidney of SHR with ADR-induced FSGS, independently of the HO-1/BVR pathway.

P0551THE EFFECTS OF HYPERBARIC OXYGEN PRECONDITIONING AND APOCYNIN TREATMENT IN POSTISCHEMIC ACUTE KIDNEY INJURY INDUCED IN SPONTANEOUSLY HYPERTENSIVE RATS

Background and Aims

Acute kidney injury (AKI) is associated with significant in-hospital morbidity and mortality, particularly in those admitted to the Intensive care units, where mortality rates may exceed 50%. Besides increased mortality rates, there are chronic consequences that carry high risk of developing or exacerbating chronic kidney disease and accelerated development of the end-stage renal disease. Renal ischemia/reperfusion injury is a common cause of AKI and hypertension might contribute to the increased incidence of AKI. The purpose of this study was to investigate the effects of combined hyperbaric oxygen (HBO) preconditioning and apocynin treatment on kidney hemodynamics, function and structure in spontaneously hypertensive rats (SHR) after renal ischemia reperfusion injury.

Method

Male SHR were randomly selected in three experimental groups: sham-operated group (SHAM, n=9), AKI control group (AKI, n=11) and AKI group with HBO preconditioning and apocynin treatment (AKI+APO+HBO, n=13). HBO preconditioning was performed by exposing to pure oxygen (2.026 bar) twice a day for two consecutive days for 60 minutes and day before AKI induction. All surgical procedures were performed in anaesthetized rats and AKI was induced by removal of the right kidney and atraumatic clamp occlusion of the left renal artery for 45 minutes. NADPH oxidase inhibitor, apocynin (40 mg/kg b.m., intravenously) was applied as a bolus injection 5 minutes before clamp removal. All hemodynamic parameters were measured 24 hours after reperfusion. After hemodynamic measurements, blood samples were collected and used for further analysis. Animals were sacrificed by pentobarbital overdose injection. Kidney tissue was removed and then prepared for histological examination.

Results

AKI significantly increased renal vascular resistance (RVR, p&lt;0.001) and reduced renal blood flow (RBF, p&lt;0.001), which were significantly improved in group with HBO preconditioning with apocynin treatment (RVR, p&lt;0.05; RBF, p&lt;0,01). AKI induction significantly increased plasma creatinine (p&lt;0.001), urea (p&lt;0.001), phosphate (p&lt;0.001) levels. Remarkable improvement, with decrease in creatinine (p&lt;0.001), urea (p&lt;0.01) and phosphate (p&lt;0.001) levels was observed in treated group. While AKI induction significantly increased plasma KIM – 1 levels (p&lt;0.001), HBO preconditioning with apocynin treatment decreased its levels (p&lt;0.05). Considering renal morphology, in SHAM operated rats, normal morphology of glomeruli, tubulointerstitium, and blood vessels were observed including rare kidney specimens with a few PAS positive casts in the lumen of the tubules. In animals with AKI significant morphological alterations were present: tubular cells necrosis, dilatation of certain segments of the proximal and distal tubules, mostly with loss of brush-border. The most notable changes were present in the cortico-medullary zone, where the broad areas of tubular necrosis and a large number of PAS positive casts in the collecting ducts were observed. In treated animals degrees of morphological changes were significantly lower compared to AKI control. There were reduced tubular dilatation, tubular necrosis in the cortico-medullary zone and PAS positive cast formation.

Conclusion

HBO preconditioning and apocynin treatment improve renal hemodynamics, function and in SHR which suffer AKI. These results suggest that it is reasonable to assume that HBO preconditioning and NADPH oxidase inhibition potentially may have beneficial effects, but further comprehensive experimental and clinical studies are needed to confirm these promising results.

Hyperbaric oxygen preconditioning and the role of NADPH oxidase inhibition in postischemic acute kidney injury induced in spontaneously hypertensive rats

Renal ischemia/reperfusion injury is a common cause of acute kidney injury (AKI) and hypertension might contribute to the increased incidence of AKI. The purpose of this study was to investigate the effects of single and combined hyperbaric oxygen (HBO) preconditioning and NADPH oxidase inhibition on oxidative stress, kidney function and structure in spontaneously hypertensive rats (SHR) after renal ischemia reperfusion injury. HBO preconditioning was performed by exposing to pure oxygen (2.026 bar) twice a day for two consecutive days for 60 minutes, and 24h before AKI induction. For AKI induction, the right kidney was removed and ischemia was performed by clamping the left renal artery for 45 minutes. NADPH oxidase inhibition was induced by apocynin (40 mg/kg b.m., intravenously) 5 minutes before reperfusion. AKI significantly increased renal vascular resistance and reduced renal blood flow, which were significantly improved after apocynin treatment. Also, HBO preconditioning, with or without apocynin treatment showed improvement on renal hemodynamics. AKI significantly increased plasma creatinine, urea, phosphate levels and lipid peroxidation in plasma. Remarkable improvement, with decrease in creatinine, urea and phosphate levels was observed in all treated groups. HBO preconditioning, solitary or with apocynin treatment decreased lipid peroxidation in plasma caused by AKI induction. Also, combined with apocynin, it increased catalase activity and solitary, glutathione reductase enzyme activity in erythrocytes. While AKI induction significantly increased plasma KIM– 1 levels, HBO preconditioning, solitary or with apocynin decreased its levels. Considering renal morphology, significant morphological alterations present after AKI induction were significantly improved in all treated groups with reduced tubular dilatation, tubular necrosis in the cortico-medullary zone and PAS positive cast formation. Our results reveal that NADPH oxidase inhibition and hyperbaric oxygen preconditioning, with or without NADPH oxidase inhibition may have beneficial effects, but their protective role should be evaluated in further studies.

Hyperbaric oxygenation protects the kidney against ischemia-reperfusion injury

BACKGROUND

Acute kidney injury (AKI) as a consequence of ischemia is a common clinical event that can lead to unacceptably high morbidity and mortality. Hyperbaric oxygen (HBO2) preconditioning has been shown to prevent ischemia-reperfusion injury (IRI) in different tissues.

OBJECTIVES

The aim of our study was to compare the effects of HBO2 preconditioning on renal hemodynamics, kidney function and oxidative stress in normotensive and spontaneously hypertensive rats that suffered kidney IRI.

METHODS

An experiment was performed on Wistar (normotensive) and spontaneously hypertensive rats (SHR). The animals were divided into the following experimental groups: sham-operated rats and rats with or without HBO2 preconditioning 24 hours before post-ischemic AKI induction. Treated rats were placed into experimental HBO2 chambers and exposed to pure oxygen twice a day for two consecutive days (2.026 bar of oxygen) for 60 minutes. AKI was performed the next morning. The right kidney was removed and the renal ischemia was performed by clamping the left renal artery for 45 minutes.

RESULTS

In this study, HBO2 preconditioning significantly improved disturbed renal hemodynamics, major markers of kidney function in plasma (creatinine, urea and phosphate) as well as antioxidant enzymes (superoxide dismutase and catalase) activities in erythrocytes after AKI induction. Also, HBO2 preconditioning decreased lipid peroxidation in plasma after ischemic AKI. Positive effects were observed in both strains of rats.

CONCLUSIONS

Our results suggest that HBO2 treatment improves renal hemodynamic and kidney function and decreases oxidative stress of Wistar and SHR rats with an AKI episode. Furthermore, it also implies that pre-existing hypertension does not affect the beneficial effects of HBO2 preconditioning.

Urtica dioica L. leaf extract modulates blood pressure and oxidative stress in spontaneously hypertensive rats

BACKGROUND

Urtica dioica L. (Stinging nettle) has been used for centuries for the treatment of numerous health issues.

PURPOSE

This study investigates the antioxidant capacity and the most abundant phenolic compounds of Urtica dioica L. leaf extract (UE), and its antihypertensive and antioxidative effects in vivo.

STUDY DESIGN

Spontaneously hypertensive rats were supplemented with 10, 50, and 200 mg/kg/day of UE and 10 mg/kg/day of losartan during 4-week period.

METHODS

In this study, HPLC analysis of UE was performed, as well as the determination of antioxidant capacity, superoxide radical scavenging activity, and metal chelating ability. Hemodynamic parameters were measured directly in anesthetized rats. Also, antioxidant enzyme activity and concentration in erythrocytes were determined, as well as systemic oxidative stress and plasma antioxidant status.

RESULTS

UE showed higher ferric reducing antioxidant power and Trolox equivalent antioxidant capacity than BHT, but lower than vitamin C. Furthermore, UE showed good metal chelating ability, but weak superoxide radical scavenging activity. All three tested UE doses managed to reduce systolic and diastolic blood pressure, as well as cardiac index, and to improve the antioxidative defense by increasing the activity of superoxide dismutase and catalase, without changing the concentration of the enzymes. Moreover, UE supplementation increased plasma antioxidant capacity and reduced systemic oxidative stress.

CONCLUSION

Chronic UE dietary supplementation had beneficial effects in the experimental model of essential hypertension.

Highly potent antioxidant Olea europaea L. leaf extract affects carotid and renal haemodynamics in experimental hypertension: The role of oleuropein

Haemodynamic alterations in carotid and renal arteries are associated with the severity of target organ damage in patients with hypertension. Dietary habits, such as the Mediterranean diet, regulate blood pressure and oxidative stress, thus reduce the mortality rate due to cardiovascular diseases. In this study, our aim was to evaluate the reducing activity, antioxidant capacity and metal chelating ability of standardized Olea europaea L. leaf extract (OLE), and to test its (5, 25, 50 mg/kg) acute in vivo effects, as well as oleuropein's (OP, 10 mg/kg) on oxidative stress, carotid, renal and systemic haemodynamic parameters (blood pressure, heart rate, cardiac output, peripheral resistance) in spontaneously hypertensive rats (SHR). OLE has a higher antioxidative capacity than BHT, higher reducing ability than vitamin C, and 23 times lower capacity for metal ion chelation than EDTA. All three doses of OLE, and OP, improved oxidative stress in SHR. OLE5 improved carotid and renal haemodynamics, without significant effects on systemic haemodynamics. Two different mechanisms of antihypertensive responses to OLE were observed, OLE25 was most effective in reducing cardiovascular risks by improving systemic and regional (carotid and renal) haemodynamics, peripheral and regional vascular resistance. OLE50 causes the improvement of blood pressure and cardiac performances, but tends to retain elevated vascular resistance, therefore, reducing the inflow of blood into the brain and kidneys of the SHR. The OP did not alter systemic or regional haemodynamics, suggesting others constituents responsible for changes of cardiac function, as well as carotid and renal haemodynamics in response to OLE50.

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

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.

Effects of Single and Combined Losartan and Tempol Treatments on Oxidative Stress, Kidney Structure and Function in Spontaneously Hypertensive Rats with Early Course of Proteinuric Nephropathy

Oxidative stress has been widely implicated in both hypertension and chronic kidney disease (CKD). Hypertension is a major risk factor for CKD progression. In the present study we have investigated the effects of chronic single tempol (membrane-permeable radical scavenger) or losartan (angiotensin II type 1 receptor blocker) treatment, and their combination on systemic oxidative status (plasma thiobarbituric acid-reactive substances (pTBARS) production, plasma antioxidant capacity (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid, pABTS), erythrocyte antioxidant enzymes activities) and kidney oxidative stress (kTBARS, kABTS, kidney antioxidant enzymes activities), kidney function and structure in spontaneously hypertensive rats (SHR) with the early course of adriamycin-induced nephropathy. Adult SHR were divided into five groups. The control group received vehicle, while the other groups received adriamycin (2 mg/kg, i.v.) twice in a 21-day interval, followed by vehicle, losartan (L,10 mg/kg/day), tempol (T,100 mg/kg/day) or combined T+L treatment (by gavage) during a six-week period. Adriamycin significantly increased proteinuria, plasma lipid peroxidation, kidney protein oxidation, nitrite excretion, matrix metalloproteinase-1 (MMP-1) protein expression and nestin immunostaining in the kidney. Also, it decreased kidney antioxidant defense, kidney NADPH oxidase 4 (kNox4) protein expression and abolished anti-inflammatory response due to significant reduction of kidney NADPH oxidase 2 (kNox2) protein expression in SHR. All treatments reduced protein-to-creatinine ratio (marker of proteinuria), pTBARS production, kidney protein carbonylation, nitrite excretion, increased antioxidant capacity and restored kidney nestin expression similar to control. Both single treatments significantly improved systemic and kidney antioxidant defense, bioavailability of renal nitric oxide, reduced kMMP-1 protein expression and renal injury, thus retarded CKD progression. Losartan improved blood pressure, as well as tubular injury and restored anti-inflammatory defense by reverting kNox2 expression to the control level. Interestingly, tempol was more successful in reducing systemic oxidative stress, proteinuria, kMMP-1 and glomerulosclerosis. However, combined treatment failed to overcome the beneficial effects of single treatments in slowing down the progression of ADR-induced nephropathy in SHR.

Effect of carvedilol on pulse pressure and left ventricular hypertrophy in spontaneously hypertensive rats with adriamycin nephropathy

Recent studies indicated pulse pressure as a risk factor for left ventricular hypertrophy, myocardial infarction, congestive heart failure and stroke as well as chronic renal failure progression. The present study examined the effects of carvedilol and its combination with captopril on blood pressure, left ventricular hypertrophy, kidney vascular changes and kidney function in spontaneously hypertensive rats with adriamycin nephropathy. Four groups of 20 SHR each were involved: (1) control group: SHR; (2) ADR group: SHR treated with ADR (2mg/kg i.v. twice in 20 days); (3) ADR-C group: SHR treated with ADR and carvedilol (30 mg/kg/day) and (4) ADR-CC group: SHR treated with ADR and carvedilol (30 mg/kg/day) and captopril (60 mg/kg/day). Systolic-, diastolic- and mean-pressures and pulse pressure were determined at weeks 6 and 12 after the second ADR injection; and body weight, creatinine clearance and proteinuria at weeks -3, 6 and 12. The rats were sacrificed at week 6 or 12, the weights of the left and right ventricles and kidneys measured and the kidney vascular index was calculated as described by Bader and Mayer. Both carvedilol alone and combined with captopril significantly reduced systemic blood pressure but the effect of the latter was more pronounced and registered from week 4 till the end of the study. Carvedilol and its combination with captopril significantly decreased SBP, DBP and MAP. They also decreased PP, prevented the development of LVH, and renal vascular changes and slowed the progression of chronic renal failure and these effects were stronger in the ADR-CC group than in the ADR-C group. The antihypertensive drugs failed to prevent proteinuria in ADR SHR. Significant positive correlations were found between PP (but not SBP, DBP and MAP) and both proteinuria and Ccr in all groups of rats. In conclusion, carvedilol alone, but more strongly in combination with captopril, significantly reduced blood pressure, PP, LVH, renal blood vessel changes and chronic renal failure progression.

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.

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.

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.

Influence of carvedilol on chronic renal failure progression in spontaneously hypertensive rats with adriamycin nephropathy

BACKGROUND

In this study, the effects of carvedilol, antihypertensive (alpha-beta blocker) agent with antiproliferative and antioxidative properties, on slowing down of chronic renal failure (CRF) progression in spontaneously hypertensive rats (SHR) with adriamycin (ADR) nephropathy were examined.

METHODS

Eighty adult (24 weeks) SHR were divided into four groups:

CONTROL GROUP

20 SHR; ADR group: 20 SHR treated with ADR (2 mg/kg i.v. twice in 20 days); ADR-C group: 20 SHR treated with ADR and with carvedilol (30 mg/kg/day); ADR-CC group: 20 SHR treated with carvedilol and captopril (60 mg/kg/day). Systolic blood pressure was measured every two weeks, renal blood flow (RBF), mean arterial pressure (MAP) and renal vascular resistance (RVR) were determined at Weeks 6 and 12, creatinine clearance and proteinuria at Weeks -3 (see measurements), 6 and 12. The rats were sacrificed at Weeks 6 and 12 after the second ADR injection. Glomerular sclerosis, tubulointerstitial and blood vessel changes were determined by semiquantitative scoring.

RESULTS

Carvedilol decreased systolic blood pressure. It decreased RVR and MAP, and increased RBF significantly. Carvedilol also significantly decreased interstitial infiltration in the early phase of the study, slowed down the development of interstitial fibrosis and tubular atrophy and decreased blood vessel changes. The hemodynamic and morphological effects of carvedilol were associated with slowing down the CRF progression as well as a mild decrease in proteinuria. Captopril addition to carvedilol improved its effects especially on prevention of tubulointerstitial changes.

CONCLUSIONS

Results of this experimental study showed beneficial effect of carvedilol and its combination with captopril on CRF progression, indicating that clinical studies are warranted.

Regional hemodynamics after chronic nitric oxide inhibition in spontaneously hypertensive rats

BACKGROUND

Inhibition of nitric oxide (NO) synthase by L-arginine analogs is associated with elevation of blood pressure in rats. Because endothelium-dependent vasomotion in different vascular beds is not homogenous, the aim of this study was to characterize and compare regional hemodynamic responses in carotid, femoral, and renal vascular beds after chronic NO inhibition in spontaneously hypertensive rats. The possible role of circulating endothelin and renin angiotensin systems in mediating the effects of chronic NO inhibition was also studied.

METHODS

Systemic and regional hemodynamics, left ventricular mass, plasma renin activity, and plasma endothelin-1 were determined in control and Nomega-nitro-Larginine methyl ester (L-NAME)-treated (10 mg/kg/day, 4 weeks) spontaneously hypertensive rats.

RESULTS

L-NAME treatment increased arterial pressure and total peripheral and regional vascular resistance and decreased cardiac output, stroke volume, and regional blood flow. An increase in blood flow ratio and a decrease in vascular resistance ratio between carotid and renal as well as femoral and renal vascular beds in rats treated with L-NAME was found. Blood flow and vascular resistance ratios between femoral and carotid vascular beds remained unchanged. L-NAME increased plasma renin activity and left ventricular weight/body weight ratio, whereas plasma endothelin-1 was not modified.

CONCLUSIONS

The results of this study showed that the renal circulation seemed to be more sensitive to the effects of chronic NO inhibition than carotid and femoral vascular beds. Simultaneous activation of the renin angiotensin system may further potentiate cardiovascular effects of chronic NO inhibition. No evidence that circulating endothelin-1 plays a role in this model of hypertension was found.

Effects of captopril on morphologic changes in kidney of spontaneously hypertensive rats with adriamycin nephropathy

Antihypertensive therapy has been shown to slow down the progression of chronic renal failure. Angiotensin converting enzyme inhibitors and calcium antagonists have been emphasized as the agents with the most protective effect. Our previous study showed that captopril slowed down renal function deterioration in the early course of adriamycin (ADR) nephropathy in spontaneously hypertensive rats (SHR). The present study was undertaken with the aim to examine morphologic changes associated with that slower renal function deterioration. Adult (24 weeks) female SHR were randomly divided into the following groups: the control group (n = 12) was given tap water to drink; the adriamycin (ADR) group (n = 25) was treated with ADR; the ADR-captopril (ADR-C) group (n = 27) was treated with ADR and thereafter with captopril (60 mg/kg/day). Rats were sacrificed at weeks 6, 12 and 18 and histologic analysis was semiquantitatively performed. In the control group the glomeruli exhibited only minor changes at the end of the study. In the ADR group slight glomerular mesangial hypercellularity appeared in the sixth week and progressed in focal and segmental sclerosis. Some glomeruli showed segmental proliferation and increased fibrular matrix of a tuft adherent to a fibrocellular crescents. In the ADR-C group, glomeruli with a slight increase of mesangial matrix were seen at the end of the sixth week, mesangial hypercellularity developed until the end of the sixth week, mesangial hypercellularity developed until the end of the 12th week and segmental glomerulosclerosis until the end of the study. Semiquantitative analysis revealed that the mean semiquantitative scores for mesangial expansion and glomerular sclerosis were significantly lower in ADR-C group than in ADR group throughout the study. We concluded that captopril slowed down mesangial expansion and reduced the development of glomerular sclerosis.

Antihypertensive action of heparin: role of the renin-angiotensin aldosterone system and prostaglandins

Chronic subcutaneous administration of heparin consistently lowers blood pressure in hypertensive rats. This antihypertensive effect is related at least in part to a concomitant decrease in hematocrit. Groups of spontaneously hypertensive (SHR) and normotensive Wistar (NWR) rats were treated with subcutaneous heparin (700 U/d) for 6 weeks. Weekly determinations of systolic blood pressure (tail-cuff) and hematocrit were done. Peripheral plasma renin activity, plasma aldosterone, plasma prostaglandins (PGs) (PGF2 alpha, PGI2), thromboxane A2, and urinary kallikrein were measured. Blood pressure responses of acute and chronic heparin treatment to vasoconstrictor substances, including angiotensin I, angiotensin II, and norepinephrine, were determined. As before, heparin produced a significant (P < .01) decrease in hematocrit in both SHRs and NWRs, but a parallel decrease in blood pressure was noted only in SHRs. A significant (P < .001) increase in plasma renin activity was found in heparin-treated SHRs and NWRs; however, a corresponding elevation of plasma aldosterone level was noted only in heparin-treated NWR. Plasma aldosterone level significantly (P < .01) decreased in heparin-treated SHRs. Plasma PGs and urinary kallikrein levels were not different among the groups. The blood pressure responses to vasoconstrictor substances were essentially similar among the heparin-treated and control groups. These findings suggest that PGs or kallikrein have a slight or no role in determining the antihypertensive effect of heparin. Conversely, the results suggest that a reduced aldosterone level contributes to the antihypertensive mechanism of heparin.

The effect of acute and chronic hematocrit changes on cardiovascular hemodynamics in spontaneously hypertensive rats

Heparin given over a long term by a subcutaneous route consistently lowers blood pressure in the hypertensive rat models. The decrease in blood pressure is accompanied by a parallel decrease in hematocrit suggesting a causal relationship between hematocrit and blood pressure. The aim of this study was to define the relationships between acute and chronic hematocrit changes and blood pressure in the normotensive and hypertensive states. Normotensive Wistar (NWR) and spontaneously hypertensive (SHR) rats were used. Hematocrit was decreased acutely by blood-letting, and chronically by treatment with either heparin (H) or phenylhydrazine (P) for 4 weeks. Acute and chronic hematocrit increase was accomplished by packed cells transfusion. Systolic blood pressure was measured weekly; and at the end of the experimental period, plasma volume, cardiac output, and mean arterial pressure were obtained. Acute hematocrit decrease or increase (hematocrit ranging from 25 to 65%) did not affect blood pressure in either strain of rats; whereas chronic hematocrit changes (hematocrit ranging from 35 to 61%) significantly affected blood pressure only in SHR. Thus, chronic hematocrit decrease induced by H or P resulted in a significant fall in blood pressure compared to control (201 +/- 3 v 175 +/- 4, 167 +/- 4 mm Hg, respectively; P < .05). Conversely, a chronic hematocrit increase resulted in a significant rise in blood pressure (201 +/- 3 v 219 +/- 4 mm Hg; P < .05). Similar hematocrit changes produced in NWR, as in SHR, did not affect blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)