Effects of Losartan on Blood Pressure, Oxidative Stress, and Nitrate/Nitrite Levels in the Nitric Oxide Deficient Hypertensive Rats

Large Cardamom Extract Enhances Ramipril's Vasoprotective Action in the Aorta by Modulating Endothelial Redox Biology. An Evaluation based on In-silico and In-vitro Research

BACKGROUND

The mechanisms that cause a patient's blood pressure to rise are diverse. Controlling blood pressure with monotherapy acting through a single pathway may be unachievable. Combining a clinically used medication with herbal medicine can result in an antihypertensive effect that is two to five times greater than monotherapy.

METHOD

This study examined the effects of aqueous extracts of large cardamom and ramipril on the redox biology of nitric oxide and vascular reactivity in the isolated aorta incubated with a nitro-L-arginine methyl ester. Molecular docking study was performed to predict the affinity of constituents of large cardamom extracts with the NOX 2 gene.

RESULTS

Nitric oxide (NO) levels, disordered antioxidant enzymes (glutathione and catalase), NADPH oxidase and lipid peroxidation were recovered when aqueous extract of large cardamom and ramipril were combined. A gradual increase in the percentage relaxation of acetylcholine in phenylephrine pre-contracted aorta indicates that the combination therapy prevents endothelial damage. The molecular docking study reveals the important phytoconstituents present in the large cardamom that can effectively bind with the NADPH oxidase for its antioxidant activity. Consculsion: According to our findings, it was evidenced that the large cardamom extract's vasoprotective action was mostly related to its ability to restore endothelial redox biology by suppressing NADPH oxidase activity. Our findings suggest that ramipril's direct impact on the eNOS/NO system, along with the antioxidant properties of AELC, could have a synergetic benefit in the treatment of hypertension, as well as lessen ramipril's existing side effects.

Nobiletin resolves left ventricular and renal changes in 2K-1C hypertensive rats

This study investigated the effects of nobiletin on cardiorenal changes and the underlying mechanisms involved in two-kidney, one-clip (2K-1C) hypertension. 2K-1C rats were treated with nobiletin (15 or 30 mg/kg/day) or losartan (10 mg/kg/day) for 4 weeks (n = 8/group). Nobiletin (30 mg/kg) reduced high levels of blood pressure and circulating angiotensin II and angiotensin-converting enzyme activity in 2K-1C rats. Left ventricular (LV) dysfunction and remodelling in 2K-1C rats were alleviated in the nobiletin-treated group (P < 0.05). Nobiletin reduced the upregulation of Ang II type I receptor (AT₁R)/JAK (Janus kinase)/STAT (signal transducer and activator of transcription) protein expression in cardiac tissue of 2K-1C rats (P < 0.05). The reduction in kidney function, and accumulation of renal fibrosis in 2K-1C rats were alleviated by nobiletin (P < 0.05). Overexpression of AT₁R and NADPH oxidase 4 (Nox4) protein in nonclipped kidney tissue was suppressed in the nobiletin-treated group (P < 0.05). The elevations in oxidative stress parameters and the reductions in antioxidant enzymes were attenuated in 2K-1C rats treated with nobiletin (P < 0.05). In summary, nobiletin had renin-angiotensin system inhibitory and antioxidant effects and attenuated LV dysfunction and remodelling via restoration of the AT₁R/JAK/STAT pathway. Nobiletin also resolved renal damage that was related to modulation of the AT₁R/Nox4 cascade in 2K-1C hypertension.

Cardioprotective Effects and In-Silico Antioxidant Mechanism of L-Ergothioneine In Experimental Type-2 Diabetic Rats

BACKGROUND

Diabetic cardiotoxicity is commonly associated with oxidative injury, inflammation, and endothelial dysfunction. L-ergothioneine (L-egt), a diet-derived amino acid, has been reported to decrease mortality and risk of cardiovascular injury, provides cytoprotection to tissues exposed to oxidative damage, and prevents diabetes-induced perturbation.

OBJECTIVE

This study investigated the cardioprotective effects of L-egt on diabetes-induced cardiovascular injuries and its probable mechanism of action.

METHODS

Twenty-four male Sprague-Dawley rats were divided into non-diabetic (n=6) and diabetic groups (n=18). Six weeks after the induction of diabetes, the diabetic rats were divided into three groups (n=6) and administered distilled water, L-egt (35mg/kg), and losartan (20mg/kg) by oral gavage for six weeks. Blood glucose and mean arterial pressure (MAP) were recorded pre-and post-treatment, while biochemical, ELISA, and Rt-PCR analyses were conducted to determine inflammatory, injury-related and antioxidant biomarkers in cardiac tissue after euthanasia. Also, an in-silico study, including docking and molecular dynamic simulations of L-egt toward the Keap1-Nrf2 protein complex, was done to provide a basis for the molecular antioxidant mechanism of L-egt.

RESULTS

Administration of L-egt to diabetic animals reduced serum triglyceride, water intake, MAP, biomarkers of cardiac injury (CK-MB, LDH), lipid peroxidation, and inflammation. Also, L-egt increased body weight, antioxidant enzymes, upregulated Nrf2, HO-1, NQO1 expression, and decreased Keap1 expression. The in-silico study showed that L-egt inhibits Keap1-Nrf2 complex by binding to the active site of Nrf2 protein, thereby preventing its degradation.

CONCLUSION

L-egt protects against diabetes-induced cardiovascular injury via the upregulation of Keap1-Nrf2 pathway and its downstream cytoprotective antioxidants.

Paeonol protects against hypertension in spontaneously hypertensive rats by restoring vascular endothelium

The present study focused on the effect of paeonol, one of the main components of Guizhi Fuling Pill, on blood pressure, cerebral blood flow, and vascular endothelium injury in spontaneously hypertensive rats to provide theoretical basis for the treatment of hypertension. After treatment with paeonol, the mean arterial pressure (MAP) of LSHRT and HSHRT rats decreased gradually with the prolongation of treatment time. The systolic blood flow velocity (Vs), diastolic blood flow velocity (Vd) and mean blood flow velocity (Vm) were significantly increased after paeonol treatment (p &lt; 0.05). Paeonol effectively improved the blood pressure and increased the cerebral blood flow velocity in spontaneously hypertensive rats. This may be related to the fact that paeonol reduced the blood viscosity and the oxidative stress and improved the antioxidant capacity. Moreover, paeonol protected vascular endothelial cells and reduced vascular endothelial injury in spontaneously hypertensive rats.

Enhanced dissolution/caco-2 permeability, pharmacokinetic and pharmacodynamic performance of re-dispersible eprosartan mesylate nanopowder

Eprosartan mesylate is an angiotensin receptor blocker which suffers from extremely poor bioavailability owing to its poor solubility and poor permeability. The rationale of the present work was to design the drug delivery system capable of overcoming these constraints. Nanoformulation of eprosartan mesylate was developed using ultrasonic wave-assisted liquid-antisolvent technique. Nanoformulation was further freeze dried with the addition of 1% of mannitol resulting in formation of re-dispersible EPM nanopowder. To prove our proof of principle, the re-dispersed nanopowder with z-average particle size 165.2 ± 1.8 nm was evaluated enormously for in-vitro dissolution behaviour and permeability assay through Caco-2 cell model. In-vitro dissolution study was performed at pH 1.2, pH 4.5 and pH 6.8. Result demonstrates enhanced dissolution from EPM nanopowder with negligible pH dependence. Transport studies accomplished using validated Caco-2 based cell model showed 11-fold enhanced apparent permeability of redispersed nanopowder when compared to pure EPM and corresponding physical mixture (p < 0.0001). In-vivo study reveals, exceptionally strong variations in plasma concentration of EPM through nanopowder (62 mg/kg) formulation when compared with physical mixture and pure EPM (62 mg/kg) group. Moreover, study manifests that 5-fold lower dose (12.4 mg/kg) of developed formulation yields higher exposure (4600 ± 36 ng·mL^-1·h) than pure EPM (2349 ± 34 ng·mL^-1·h) and corresponding physical mixture (2456 ± 49 ng·mL^-1·h) at therapeutic dose (62 mg/kg). Further, L-NAME induced hypertensive model was undertaken to investigate effect of reduced dose of EPM nanopowder on systolic blood pressure, biochemical analysis and histopathology of heart. Results revealed pronounced antihypertensive potential of re-dispersed EPM nanopowder at 5-fold lower dose (12.4 mg/kg). In conclusion, our study indicates that nanopowder delivery might be the promising approach for providing enhanced oral bioavailability at lower dose.

Synergistic Antihypertensive Effect of Carthamus tinctorius L. Extract and Captopril in L-NAME-Induced Hypertensive Rats via Restoration of eNOS and AT₁R Expression

This study examined the effect of Carthamus tinctorius (CT) extract plus captopril treatment on blood pressure, vascular function, nitric oxide (NO) bioavailability, oxidative stress and renin-angiotensin system (RAS) in N^ω-Nitro-l-arginine methyl ester (l-NAME)-induced hypertension. Rats were treated with l-NAME (40 mg/kg/day) for five weeks and given CT extract (75 or 150 or 300 or 500 mg/kg/day): captopril (5 mg/kg/day) or CT extract (300 mg/kg/day) plus captopril (5 mg/kg/day) for two consecutive weeks. CT extract reduced blood pressure dose-dependently, and the most effective dose was 300 mg/kg/day. l-NAME-induced hypertensive rats showed abnormalities including high blood pressure, high vascular resistance, impairment of acetylcholine-induced vasorelaxation in isolated aortic rings and mesenteric vascular beds, increased vascular superoxide production and plasma malondialdehyde levels, downregulation of eNOS, low level of plasma nitric oxide metabolites, upregulation of angiotensin II type 1 receptor and increased plasma angiotensin II. These abnormalities were alleviated by treatment with either CT extract or captopril. Combination treatment of CT extract and captopril normalized all the abnormalities found in hypertensive rats except endothelial dysfunction. These data indicate that there are synergistic antihypertensive effects of CT extract and captopril. These effects are likely mediated by their anti-oxidative properties and their inhibition of RAS.

Role of Angiotensin II type 1 receptor on renal NAD(P)H oxidase, oxidative stress and inflammation in nitric oxide inhibition induced-hypertension

AIMS

Activation of the renin-angiotensin system (RAS), renal oxidative stress and inflammation are constantly present in experimental hypertension. Nitric oxide (NO) inhibition with N(w)-nitro-L-arginine methyl ester (L-NAME) has previously been reported to produce hypertension, increased expression of Angiotensin II (Ang II) and renal dysfunction. The use of Losartan, an Ang II type 1 receptor (AT1R) antagonist has proven to be effective reducing hypertension and renal damage; however, the mechanism by which AT1R blockade reduced kidney injury and normalizes blood pressure in this experimental model is still complete unknown. The current study was designed to test the hypothesis that AT1R activation promotes renal NAD(P)H oxidase up-regulation, oxidative stress and cytokine production during L-NAME induced-hypertension.

MAIN METHODS

Male Sprague-Dawley rats were distributed in three groups: L-NAME, receiving 70 mg/100ml of L-NAME, L-NAME+Los, receiving 70 mg/100ml of L-NAME and 40 mg/kg/day of Losartan; and Controls, receiving water instead of L-NAME or L-NAME and Losartan.

KEY FINDINGS

After two weeks, L-NAME induced high blood pressure, renal overexpression of AT1R, NAD(P)H oxidase sub-units gp91, p22 and p47, increased levels of oxidative stress, interleukin-6 (IL-6) and interleukin-17 (IL-17). Also, we found increased renal accumulation of lymphocytes and macrophages. Losartan treatment abolished the renal expression of gp91, p22, p47, oxidative stress and reduced NF-κB activation and IL-6 expression.

SIGNIFICANCE

These findings indicate that NO induced-hypertension is associated with up-regulation of NADPH oxidase, oxidative stress production and overexpression of key inflammatory mediators. These events are associated with up-regulation of AT1R, as evidenced by their reversal with AT1R blocker treatment.

Angiotensin Type-1 Receptor Blockade May Not Protect Kidney against Cisplatin-Induced Nephrotoxicity in Rats

Background. Cisplatin (CDDP) is an anticancer drug, which is accompanied with major side effects including nephrotoxicity. We tested two doses of losartan (10 and 20 mg/kg/day) against nephrotoxicity in a rat model treated with daily administration of CDDP (2.5 mg/kg/day). Methods. Five groups of rats were examined. Groups 1 and 2 received losartan 10 and 20 mg/kg/day, i.p, for a period of 10 days. Group 3 received saline for 10 days, but from day 3 the animals received CDDP (2.5 mg/kg/day, i.p) for the next seven days. Groups 4 and 5 received treatment regimen the same as groups 1 and 2, but from day 3 they also received CDDP for the next seven days. At the end of the experiment, blood samples were obtained and the kidneys were removed to undergo pathological investigation and to obtain supernatant from homogenized tissue. Results. CDDP induced nephrotoxicity, but the serum levels of creatinine and blood urea nitrogen were not attenuated by losartan. The pathological findings confirmed that losartan did not have nephroprotective effect in this experimental model. Conclusion. According to the findings, losartan could not improve renal function impaired by toxicity induced by continuous doses of CDDP, and also it worsened the renal failure.

Cardiac autonomic function in acutely nitric oxide deficient hypertensive rats: role of the sympathetic nervous system and oxidative stress

We evaluated the role of the sympathetic nervous system and oxidative stress in hemodynamic and autonomic control after acute inhibition of the synthesis of nitric oxide, using intravenous (i.v.) injection of 30 mg·kg(-1) N(G)-nitro-l-arginine methyl ester (L-NAME) in adult Wistar rats. Baroreflex sensitivity (BRS) and heart rate variability (HRV) were measured as indices of cardiac autonomic control, before and after L-NAME treatment in rats with intact autonomic innervation, and in rats with chemical sympathectomy by 6-hydroxydopamine. Serum malondialdehyde (MDA) was measured as a marker of oxidative stress. In control rats, L-NAME treatment resulted in a significant rise in blood pressure, augmentation of BRS, and enhanced serum MDA. HRV showed an attenuation of total spectral power and high frequency spectral power, along with a rise of the low to high frequency ratio (LF:HF). Administration of L-NAME produced a pressor response even in sympathectomised rats, but augmented BRS was not observed, and the high frequency spectral power showed an increase, in addition to a significant decline of LF:HF and serum MDA. We therefore conclude that even though pressor response was unaffected, reversal of cardiac autonomic responses and decline in oxidative stress following sympathectomy in L-NAME-treated rats reflects a significant role for sympathetic innervation in acute L-NAME-induced hypertension.

Differential Effects of an Anti-Oxidant Intervention on Cardiomyocyte Expression of Adrenomedullin and Intermedin and their Receptor Components in Chronic Nitric Oxide Deficiency

BACKGROUND

Chronic inhibition of nitric oxide (NO) synthesis is associated with hypertension, myocardial oxidative stress and hypertrophic remodeling. Up-regulation of the cardiomyocyte adrenomedullin (AM) / intermedin (IMD) receptor signaling cascade is also apparent in NO-deficient cardiomyocytes: augmented expression of AM and receptor activity modifying proteins RAMP2 and RAMP3 is prevented by blood pressure normalization while that of RAMP1 and intermedin (IMD) is not, indicating that the latter is regulated by a pressure-independent mechanism.

AIMS

to verify the ability of an anti-oxidant intervention to normalize cardiomyocyte oxidant status and to investigate the influence of such an intervention on expression of AM, IMD and their receptor components in NO-deficient cardiomyocytes.

METHODS

NO synthesis inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME, 35 mg/kg/day) was given to rats for 8 weeks, with/without con-current administration of antioxidants (Vitamin C (25mg/kg/day) and Tempol (25mg/kg/day)).

RESULTS

In left ventricular cardiomyocytes isolated from L-NAME treated rats, increased oxidative stress was indicated by augmented (3.6 fold) membrane protein oxidation, enhanced expression of catalytic and regulatory subunits of pro-oxidant NADPH oxidases (NOX1, NOX2) and compensatory increases in expression of anti-oxidant glutathione peroxidase and Cu/Zn superoxide dismutases (SOD1, SOD3). Vitamin C plus Tempol did not reduce systolic blood pressure but normalized augmented plasma levels of IMD, but not of AM, and in cardiomyocytes: (i) abolished increased membrane protein oxidation; (ii) normalized augmented expression of prepro-IMD and RAMP1, but not prepro-AM, RAMP2 and RAMP3; (iii) attenuated (by 42%) increased width and normalized expression of hypertrophic markers, skeletal-alpha-actin and prepro-endothelin-1 similarly to blood pressure normalization but in contrast to blood pressure normalization did not attenuate augmented brain natriuretic peptide (BNP) expression.

CONCLUSION

normalization specifically of augmented IMD/RAMP1 expression in NO-deficient cardiomyocytes by antioxidant intervention in the absence of blood pressure reduction indicates that these genes are likely to be induced directly by myocardial oxidative stress. Although oxidative stress contributed to cardiomyocyte hypertrophy, induction of IMD and RAMP1 is unlikely to be secondary to cardiomyocyte hypertrophy.

Role of superoxide and hydrogen peroxide in hypertension induced by an antagonist of adenosine receptors

Treatment of Wistar rats for 7 days with 1,3-dipropyl-8-sulfophenylxanthine (DPSPX), an antagonist of adenosine receptors, induces long-lasting hypertension associated with marked changes in vascular structure and reactivity and renin-angiotensin system activation. This study aimed at evaluating the role of oxidative stress in the development of DPSPX-induced hypertension and also at identifying the relative contribution of superoxide radical (O2.-) vs hydrogen peroxide (H2O2). Vascular and systemic prooxidant/antioxidant status was evaluated in sham (saline, i.p., 7 days) and DPSPX (90 microg/kg/h, i.p., 7 days)-treated rats. Systolic blood pressure was determined by invasive and non-invasive methods. The activity of vascular NADPH oxidase, superoxide dismutase (SOD), catalase and glutathione peroxidase was assayed by fluorometric/spectrophotometric methods. H2O2 levels were measured using an Amplex Red Hydrogen Peroxide kit. Plasma thiobarbituric acid reactive substances and plasma antioxidant capacity were also measured. In addition we tested the effects of antioxidants or inhibitors of reactive oxygen species generation on blood pressure, vascular hyperplasia and oxidative stress parameters. DPSPX-hypertensive rats showed increased activity of vascular NADPH oxidase, SOD, catalase and glutathione peroxidase, as well as increased H2O2 generation. DPSPX-hypertensive rats also had increased plasma lipid peroxidation and decreased plasma antioxidant capacity. Treatment with apocynin (1.5 mmol/l, per os, 14 days), or with polyethylene glycol (PEG)-catalase (10,000 U/kg/day, i.p., 8 days), prevented the DPSPX-induced effects on blood pressure, vascular structure and H2O2 levels. Tempol (3 mmol/l, per os, 14 days) failed to inhibit these changes, unless PEG-catalase was co-administered. It is concluded that O2.- generation with subsequent formation of H2O2 plays a major role in the development of DPSPX-induced hypertension.