Salt-induced renal injury in spontaneously hypertensive rats: effects of nebivolol

Regulation of SARS CoV-2 host factors in the kidney and heart in rats with 5/6 nephrectomy-effects of salt, ARB, DPP4 inhibitor and SGLT2 blocker

Background

Host factors such as angiotensin-converting enzyme 2 (ACE2) and the transmembrane protease, serine-subtype-2 (TMPRSS2) are important factors for SARS-CoV-2 infection. Clinical and pre-clinical studies demonstrated that RAAS-blocking agents can be safely used during a SARS-CoV-2 infection but it is unknown if DPP-4 inhibitors or SGLT2-blockers may promote COVID-19 by increasing the host viral entry enzymes ACE2 and TMPRSS2.

Methods

We investigated telmisartan, linagliptin and empagliflozin induced effects on renal and cardiac expression of ACE2, TMPRSS2 and key enzymes involved in RAAS (REN, AGTR2, AGT) under high-salt conditions in a non-diabetic experimental 5/6 nephrectomy (5/6 Nx) model. In the present study, the gene expression of Ace2, Tmprss2, Ren, Agtr2 and Agt was assessed with qRT-PCR and the protein expression of ACE2 and TMPRSS2 with immunohistochemistry in the following experimental groups: Sham + normal diet (ND) + placebo (PBO); 5/6Nx + ND + PBO; 5/6Nx + high salt-diet (HSD) + PBO; 5/6Nx + HSD + telmisartan; 5/6Nx + HSD + linagliptin; 5/6Nx + HSD + empagliflozin.

Results

In the kidney, the expression of Ace2 was not altered on mRNA level under disease and treatment conditions. The renal TMPRSS2 levels (mRNA and protein) were not affected, whereas the cardiac level was significantly increased in 5/6Nx rats. Intriguingly, the elevated TMPRSS2 protein expression in the heart was significantly normalized after treatment with telmisartan, linagliptin and empagliflozin.

Conclusions

Our study indicated that there is no upregulation regarding host factors potentially promoting SARS-CoV-2 virus entry into host cells when the SGLT2-blocker empagliflozin, telmisartan and the DPP4-inhibitor blocker linagliptin are used. The results obtained in a preclinical, experimental non-diabetic kidney failure model need confirmation in ongoing interventional clinical trials.

Efficacy and safety of a low-sodium diet and spironolactone in patients with stage 1-3a chronic kidney disease: a pilot study

Background

Excessive salt intake is associated with the deterioration of chronic kidney disease (CKD). Aldosterone is also known as an independent risk factor for kidney injury. Dietary sodium intake acts as a main stimulator in aldosterone-mediated kidney injury. Hence, this study aimed to further investigate the renal protective effects and safety of a low-sodium diet in combination with spironolactone (SPL) in stage 1-3a CKD.

Methods

This single-center, SPL-blinded randomized controlled trial recruited patients with stage 1-3a CKD, randomized into three groups, low-sodium (3 g/d salt) + placebo, medium-sodium (5 g/d salt) + SPL, and low-sodium (3 g/d salt) + SPL. Patients received 12 weeks of intervention. The primary and secondary endpoints were 24-h urine protein and estimated glomerular filtration rate (eGFR) at the end of the intervention, respectively.

Results

A total of 74 patients were analyzed eventually. Significantly decreased 24-h urine protein was found in all three groups, from 0.37 to 0.23 g/d (P = 0.004) in the low-sodium+placebo group, from 0.44 to 0.29 g/d (P = 0.020) in the medium-sodium+SPL group, and from 0.35 to 0.31 g/d (P = 0.013) in the low-sodium +SPL group. There were no significant differences among the three groups in 24-h urine protein amount change after intervention from pre-treatment values (P = 0.760, ITT set). The results of the 24-h urine protein by using PP set analysis was similar to the ITT set. No significant differences in eGFR, nutritional, metabolic, inflammatory, and other biomarkers were observed across all three groups (P > 0.05). No safety signal was observed.

Conclusion

No additional benefit was observed when SPL was prescribed to patients already on a low-sodium diet (3.0 g/d). Still, small doses of SPL may benefit patients with poor sodium restriction. A combination of short-term low-dose SPL and ARB is safe for patients with stage 1-3a CKD, but blood potassium must be regularly monitored.

Trial registration

Name of the registry: Chinese clinical trial registry.

Trial registration number: ChiCTR1900026991.

Date of registration: Retrospectively registered 28 October 2019.

URL of trial registry record: http://www.chictr.org.cn/searchproj.aspx?title=&officialname=&subjectid=&secondaryid=&applier=&studyleader=ðicalcommitteesanction=&spo

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-022-02711-z.

Adrenergic Blockade by Nebivolol to Suppress Oral Squamous Cell Carcinoma Growth via Endoplasmic Reticulum Stress and Mitochondria Dysfunction

Adrenergic nerve fibers in the tumor microenvironment promote tumor growth and represent a potential target for cancer therapy. However, the effectiveness of targeting adrenergic nerve fibers for oral squamous cell carcinoma (OSCC) therapy needs to be evaluated by preclinical data. Herein, the 4NQO-induced and orthotopic xenograft OSCC mice models were established. We demonstrated that using 6OHDA chemical denervation as well as using nebivolol adrenergic blockade could halt the oral mucosa carcinogenesis. Our preclinical studies suggested that nebivolol, which is widely used to treat cardiovascular diseases, can be repositioned as a potential candidate to treat OSCC. Remarkably, we revealed the precise effect and mechanism of nebivolol on OSCC cells proliferation, cell cycle, and cell death. Administration of nebivolol could activate the endoplasmic reticulum (ER) stress signaling pathway through increasing the expression of inducible nitric oxide synthase, which subsequently triggers the integrated stress response and cell growth arrest. Simultaneously, ER stress also induced mitochondrial dysfunction in OSCC cells. We found that the accumulation of dysfunctional mitochondria with the impaired electron transport chain caused increasing reactive oxygen species production, which ultimately resulted in OSCC cell death. Altogether, our finding suggested a novel therapeutic opportunity for OSCC by targeting adrenergic nerve fibers, and repurposing nebivolol to treat OSCC can be represented as an effective strategy.

Does nebivolol have renoprotective action in patients with chronic kidney disease conditions? An integrative review

Systemic arterial hypertension (SAH) is a chronic disease of multifactorial origin and one of the main risk factors for major adverse cardiovascular events (MACE), which are the leading causes of morbidity and mortality worldwide. The pharmacological treatment of SAH involves five main classes of drugs, and Nebivolol (NEB) is one of those drugs, belonging to the class of third generation β1-adrenoceptors selective blockers. NEB is composed of a racemic mixture of two enantiomers: d-nebivolol, which exerts antagonist effects on β₁-adrenoceptors, and l-nebivolol, a vascular β₃ receptor agonist. There are several studies that report different actions of NEB, not only for the treatment of SAH, but also as an antioxidant agent or even as a protector of renal damage. The aim of this systematic review was to investigate the available evidence regarding the effects of NEB on kidney diseases, evaluating its possible renoprotective action.

Perindopril Reduces Arterial Pressure and Does Not Inhibit Exercise-Induced Angiogenesis in Spontaneously Hypertensive Rats

ABSTRACT

Sympathetic activity, arteriolar structure, and angiogenesis are important mechanisms modulating hypertension and this study aimed to analyze the effects of perindopril treatment, associated or not with exercise training, on the mechanisms that control blood pressure (BP) in hypertensive rats. Spontaneously hypertensive rats (SHR) were allocated into 4 groups: 1/sedentary (S); 2/perindopril (P, 3.0 mg/kg/d); 3/trained (T); and 4/trained + perindopril (TP). Wistar rats were used as normotensive sedentary control group. SHR were assigned to undergo a treadmill training (T) or were kept sedentary. Heart rate, BP, sympathetic activity to the vessels (LF-SBP), and skeletal muscle and myocardial morphometric analyses were performed. BP was significantly lower after all 3 strategies, compared with S and was accompanied by lower LF-SBP (-76%, -53%, and -44%, for P, T, and TP, respectively). Arteriolar vessel wall cross-sectional area was lower after treatments (-56%, -52%, and -56%, for P, T, and TP, respectively), and only TP presented higher arteriolar lumen area. Capillary rarefaction was present in soleus muscle and myocardium in S group and both trained groups presented higher vessel density, although perindopril attenuated this increase in soleus muscle. Although myocyte diameter was not different between groups, myocardial collagen deposition area, higher in S group, was lower after 3 strategies. In conclusion, we may suggest that perindopril could be an option for the hypertensive people who practice exercise and need a specific pharmacological treatment to reach a better BP control, mainly because training-induced angiogenesis is an important response to facilitate blood flow perfusion and oxygen uptake and perindopril did not attenuate this response.

Identification of Aortic Proteins Involved in Arterial Stiffness in Spontaneously Hypertensive Rats Treated With Perindopril:A Proteomic Approach

Arterial stiffness, frequently associated with hypertension, is associated with disorganization of the vascular wall and has been recognized as an independent predictor of all-cause mortality. The identification of the molecular mechanisms involved in aortic stiffness would be an emerging target for hypertension therapeutic intervention. This study evaluated the effects of perindopril on pulse wave velocity (PWV) and on the differentially expressed proteins in aorta of spontaneously hypertensive rats (SHR), using a proteomic approach. SHR and Wistar rats were treated with perindopril (SHR_P) or water (SHRc and Wistar rats) for 8 weeks. At the end, SHR_C presented higher systolic blood pressure (SBP, +70%) and PWV (+31%) compared with Wistar rats. SHR_P had higher values of nitrite concentration and lower PWV compared with SHR_C. From 21 upregulated proteins in the aortic wall from SHR_C, most of them were involved with the actin cytoskeleton organization, like Tropomyosin and Cofilin-1. After perindopril treatment, there was an upregulation of the GDP dissociation inhibitors (GDIs), which normally inhibits the RhoA/Rho-kinase/cofilin-1 pathway and may contribute to decreased arterial stiffening. In conclusion, the results of the present study revealed that treatment with perindopril reduced SBP and PWV in SHR. In addition, the proteomic analysis in aorta suggested, for the first time, that the RhoA/Rho-kinase/Cofilin-1 pathway may be inhibited by perindopril-induced upregulation of GDIs or increases in NO bioavailability in SHR. Therefore, we may propose that activation of GDIs or inhibition of RhoA/Rho-kinase pathway could be a possible strategy to treat arterial stiffness.

High-salt intake accelerates functional and histological renal damage associated with renal tissue overexpression of (pro)renin receptors and AT1 receptors in spontaneously hypertensive rats

OBJECTIVE

This study aimed to investigate the effect of combination of high-salt intake and hypertension on renal functional and histological damage, associated with renal (pro)renin receptor [(P)RR] and AT1 receptor in rats.

METHODS

Wistar Kyoto rats (WKYs) and spontaneously hypertensive rats (SHRs) received regular rat chow (normal-salt diet 0.9%) or high-salt rat chow (high-salt diet 8.9%) for 6 weeks from 6 to 12 weeks of age. Systolic blood pressure, serum creatinine and blood urea nitrogen (BUN) were measured. Histological analysis of the kidney was performed. Western blot analysis was performed on the expressions of (P)RR, angiotensinogen and AT1 receptor in the kidney.

RESULTS

High-salt intake significantly increased systolic blood pressure in WKYs and especially in SHRs. High-salt intake significantly increased serum creatinine and BUN, and accelerated renal tubulointerstitial fibrosis and glomerular sclerosis in SHRs. High-salt intake significantly enhanced the renal tissue expressions of (P)RR, angiotensinogen and AT1 receptor in SHRs.

CONCLUSION

High-salt intake accelerates functional and histological renal damage associated with renal tissue overexpression of (P)RR and AT1 receptors in SHRs.

Modulation of eNOS/iNOS by nebivolol protects against cyclosporine A-mediated nephrotoxicity through targeting inflammatory and apoptotic pathways

The aim of this study was to investigate effect of nitric oxide (NO) modulation on possible nephroprotective mechanisms of nebivolol (NEB) in cyclosporine A (CsA)-induced nephrotoxicity. Rats were treated with 20 mg/kg/day s.c. of CsA for 21 days, with NEB alone (10 mg/kg/day orally) or together with a NOS inhibitor, L-NAME (10 mg/kg/day i.p.). NEB conferred nephroprotection against CsA-induced toxicity, significantly decreasing serum kidney function tests and improving renal histopathology. NEB showed antioxidant effects, by significantly decreasing renal malondialdehyde levels, while increasing reduced glutathione levels and catalase activity. NEB showed anti-inflammatory and anti-apoptotic effects; reducing renal expression NF-κB and fas ligand. NEB also reversed CsA-induced effects on NO system; increasing renal NO level, with up-regulation of eNOS and down-regulation of iNOS expression. Administering L-NAME with NEB reversed all beneficial effects of NEB. Thus, NEB's modulation of NO system in CsA-induced nephrotoxicity might be the triggering mechanism controlling NEB's nephroprotective effect.

Inappropriate activity of local renin-angiotensin-aldosterone system during high salt intake: impact on the cardio-renal axis

Although there is a general agreement on the recommendation for reduced salt intake as a public health issue, the mechanism by which high salt intake triggers pathological effects on the cardio-renal axis is not completely understood. Emerging evidence indicates that the renin-angiotensin-aldosterone system (RAAS) is the main target of high Na⁺ intake. An inappropriate activation of tissue RAAS may lead to hypertension and organ damage. We reviewed the impact of high salt intake on the RAAS on the cardio-renal axis highlighting the molecular pathways that leads to injury effects. We also provide an assessment of recent observational studies related to the consequences of non-osmotically active Na⁺ accumulation, breaking the paradigm that high salt intake necessarily increases plasma Na⁺ concentration promoting water retention

Intrarenal Mas and AT1 receptors play a role in mediating the excretory actions of renal interstitial angiotensin-(1-7) infusion in anaesthetized rats

NEW FINDINGS

What is the central question of this study? Dietary sodium manipulation alters the magnitude of angiotensin-(1-7) [Ang-(1-7)]-induced natriuresis. The present study sought to determine whether this was related to relative changes in the activity of intrarenal Mas and/or AT₁ receptors. What is the main finding and its importance? Angiotensin-(1-7)-induced diuresis and natriuresis is mediated by intrarenal Mas receptors. However, intrarenal AT₁ receptor blockade also had an inhibitory effect on Ang-(1-7)-induced natriuresis and diuresis. Thus, Ang-(1-7)-induced increases in sodium and water excretion are dependent upon functional Mas and AT₁ receptors. We investigated whether angiotensin-(1-7) [Ang-(1-7)]-induced renal haemodynamic and excretory actions were solely dependent upon intrarenal Mas receptor activation or required functional angiotensin II type 1 (AT₁ ) receptors. The renin-angiotensin system was enhanced in anaesthetized rats by prior manipulation of dietary sodium intake. Angiotensin-(1-7) and AT₁ and Mas receptor antagonists were infused into the kidney at the corticomedullary border. Mas receptor expression was measured in the kidney. Mean arterial pressure, urine flow and fractional sodium excretion were 93 ± 4 mmHg, 46.1 ± 15.7 μl min^-1  kg^-1 and 1.4 ± 0.3%, respectively, in the normal-sodium group and 91 ± 2 mmHg, 19.1 ± 3.3 μl min^-1  kg^-1 and 0.7 ± 0.2%, respectively, in the low-sodium group. Angiotensin-(1-7) infusion had no effect on mean arterial pressure in rats receiving a normal-sodium diet but decreased it by 4 ± 5% in rats receiving a low-sodium diet (P < 0.05). Interstitial Ang-(1-7) infusion increased urine flow twofold and fractional sodium excretion threefold (P < 0.05) in rats receiving a normal-sodium diet and to a greater extent, approximately three- and fourfold, respectively, in rats receiving the low-sodium diet (both P < 0.05). Angiotensin-(1-7)-induced increases in urine flow and fractional sodium excretion were absent in both dietary groups during intrarenal AT₁ or Mas receptor inhibition after either losartan or A-779, respectively. Thus, AT₁ receptor activation, as well as Mas receptor activation, plays an essential role in mediating Ang-(1-7)-induced natriuresis and diuresis. Whether this is because Ang-(1-7) partly antagonizes AT₁ receptors or whether Ang-(1-7)-induced natriuresis is mediated through AT₁ -Mas receptor dimerization remains unclear.

Protective Effects of Vasodilatory Βeta-Blockers Carvedilol and Nebivolol against Glycerol Model of Rhabdomyolysis-Induced Acute Renal Failure in Rats

BACKGROUND

Rhabdomyolysis (RM)-induced acute renal failure (ARF) accounts for about 10-40% of all cases of ARF.

AIM

The present study investigated the possible protective effect of two nitric oxides (NO)-releasing third generation β-blockers, carvedilol (Carv) and nebivolol (Nebi), against RM-mimicking glycerol (Gly)-induced ARF in rats.

MATERIAL AND METHODS

After 24 h dehydration, rats received a single dose of 50% Gly (8 ml/kg, im). They were treated with vehicle, Carv (2.5 mg/kg/day, po) or Nebi (10 mg/kg, po) for 3 successive days starting from an hour prior to Gly injection. Evaluation of blood pressure and locomotor activity was performed during the experiment. 72 h following Gly administration, total protein in the urine, serum levels of creatinine, blood urea nitrogen, sodium and potassium as well as the renal contents of malondialdehyde, reduced glutathione and NO were assessed, together with a histopathological examination of renal tissues.

RESULTS

Carv and Nebi attenuated Gly-induced renal dysfunction and histopathological alterations. They decreased the Gly-induced oxidative stress and increased renal NO concentration. Restoration of normal blood pressure and improvement of locomotor activity were also observed.

CONCLUSION

The results clearly demonstrate protective effects of Carv and Nebi against renal damage involved in RM-induced ARF and suggest a role of their antioxidant and NO-releasing properties.

High salt intake as a multifaceted cardiovascular disease: new support from cellular and molecular evidence

Scientists worldwide have disseminated the idea that increased dietary salt increases blood pressure. Currently, salt intake in the general population is ten times higher than that consumed in the past and at least two times higher than the current recommendation. Indeed, a salt-rich diet increases cardiovascular morbidity and mortality. For a long time, however, the deleterious effects associated with high salt consumption were only related to the effect of salt on blood pressure. Currently, several other effects have been reported. In some cases, the deleterious effects of high salt consumption are independently associated with other common risk factors. In this article, we gather data on the effects of increased salt intake on the cardiovascular system, from infancy to adulthood, to describe the route by which increased salt intake leads to cardiovascular diseases. We have reviewed the cellular and molecular mechanisms through which a high intake of salt acts on the cardiovascular system to lead to the progressive failure of a healthy heart.

Recent advances in the treatment of renal diseases with nebivolol: A literature review

Reactive oxygen species play an important role in both acute and chronic kidney diseases. Chronic kidney disease is associated with various consequences to the cardiovascular system and metabolic profiles. Nebivolol, a highly cardioselective third-generation β-blocker, has nitric oxide (NO) induced vasodilation and antioxidant properties. Nebivolol affects the endothelial NO pathway in two complementary ways: it increases endothelial mediated NO expression and has antioxidant action, which leads to a decrease in degradation. Central blood pressure can be effectively lowered by nebivolol in the prehypertension phase. Clinically nebivolol's ability to modulate endothelial dysfunction may offer additional vascular protection in treating hypertension. As well, pre-treatment with 5mg nebivolol every 24 hours for 4 days is protective against nephrotoxic effects of contrast media. The aim of this study is to review the current literature on the efficacy and safety of nebivolol in the treatment of various states of renal diseases.

Nebivolol and valsartan as a fixed-dose combination for the treatment of hypertension

INTRODUCTION

The fixed-dose combination of nebivolol and valsartan drug has been clinically evaluated and demonstrated to represent a unique combination of nebivolol, a selective β1-adrenoceptor antagonist and a β3-adrenoceptor agonist; β3 receptor activation increases endothelial nitric oxide and produces vasodilation. Valsartan is highly selective angiotensin AT1 receptor blocker and exerts its major pharmacological effect by decreasing angiotensin II-induced vasoconstriction and production of aldosterone. The addition of nebivolol counteracts the effects of increased angiotensin II concentrations resulting from potent AT1 blockade. This review describes a recently completed trial establishing the efficacy of the nebivolol/valsartan combination.

AREAS COVERED

This review provides a literature search of pertinent pharmacological and clinical data that describes the mechanisms of both drugs individually and the results of a clinical trial comparing fixed-dose combinations of nebivolol with valsartan as compared with each drug as monotherapy.

EXPERT OPINION

Fixed-dose combination drugs are intended to improve patient compliance and reduce drug costs, as well as to reduce long-term cardiovascular event rates and block counter-regulatory effects due to monotherapy. The vast majority of hypertensive patients will require at least two medications. We believe that the clinical evidence suggests that the combination of nebivolol with valsartan offers a definite clinical benefit, combining β1-adrenoceptor and angiotensin AT1 receptor blockade with β3 receptor activation and resultant increase in nitric oxide and vasodilation.

High salt intake increases blood pressure in normal rats: putative role of 20-HETE and no evidence on changes in renal vascular reactivity

Background/Aims

High salt (HS) intake may elevate blood pressure (BP), also in animals without genetic salt sensitivity. The development of salt-dependent hypertension could be mediated by endogenous vasoactive agents; here we examined the role of vasodilator epoxyeicosatrienoic acids (EETs) and vasoconstrictor 20-hydroxyeicosatetraenoic acid (20-HETE).

Methods

In conscious Wistar rats on HS diet systolic BP (SBP) was examined after chronic elevation of EETs using 4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (c-AUCB), a blocker of soluble epoxide hydrolase, or after inhibition of 20-HETE with 1-aminobenzotriazole (ABT). Thereafter, in acute experiments the responses of renal artery blood flow (Transonic probe) and renal regional perfusion (laser-Doppler) to intrarenal acetylcholine (ACh) or norepinephrine were determined.

Results

HS diet increased urinary 20-HETE excretion. The SBP increase was not reduced by c-AUCB but prevented by ABT until day 5 of HS exposure. Renal vasomotor responses to ACh or norepinephrine were similar on standard and HS diet. ABT but not c-AUCB abolished the responses to ACh.

Conclusions

20-HETE seems to mediate the early-phase HS diet-induced BP increase while EETs are not engaged in the process. Since HS exposure did not alter renal vasodilator responses to Ach, endothelial dysfunction is not a critical factor in the mechanism of salt-induced blood pressure elevation.

Clinical utility of fixed-dose combinations in hypertension: evidence for the potential of nebivolol/valsartan

Despite significant advances in pharmacologic approaches to treat hypertension during the last decades, hypertension- and hypertension-related organ damage are still a high health and economic burden because a large proportion of patients with hypertension do not achieve optimal blood pressure control. There is now general agreement that combination therapy with two or more antihypertensive drugs is required for targeted blood pressure accomplishment and reduction of global cardiovascular risk. The goals of combination therapies are to reduce long-term cardiovascular events by targeting different mechanism underlying hypertension and target organ disease, to block the counterregulatory pathways activated by monotherapies, to improve tolerability and decrease the adverse effects of up-titrated single agents, and to increase persistence and adherence with antihypertensive therapy. Multiple clinical trials provide evidence that fixed-dose combinations in a single pill offer several advantages when compared with loose-dose combinations. This review discusses the advances in hypertension control and associated cardiovascular disease as they relate to the prospect of combination therapy targeting a third-generation beta (β) 1-adrenergic receptor (nebivolol) and an angiotensin II receptor blocker (valsartan) in fixed-dose single-pill formulations.

Female sex hormones protect against salt-sensitive hypertension but not essential hypertension

Initial studies found that female Dahl salt-sensitive (DS) rats exhibit greater blood pressure (BP) salt sensitivity than female spontaneously hypertensive rats (SHR). On the basis of the central role played by NO in sodium excretion and BP control, we further tested the hypothesis that blunted increases in BP in female SHR will be accompanied by greater increases in renal inner medullary nitric oxide synthase (NOS) activity and expression in response to a high-salt (HS) diet compared with DS rats. Gonad-intact and ovariectomized (OVX) female SHR and DS rats were placed on normal salt (NS; 0.4% salt) or HS (4% salt) diet for 2 wk. OVX did not alter BP in SHR, and HS diet produced a modest increase in BP. OVX significantly increased BP in DS rats on NS; HS further increased BP in all DS rats, although OVX had a greater increase in BP. Renal inner medullary NOS activity, total NOS3 protein, and NOS3 phosphorylated on serine residue 1177 were not altered by salt or OVX in either strain. NOS1 protein expression, however, significantly increased with HS only in SHR, and this corresponded to an increase in urinary nitrate/nitrite excretion. SHR also exhibit greater NOS1 and NOS3 protein expression than DS rats. These data indicate that female sex hormones offer protection against HS-mediated elevations in BP in DS rats but not SHR. We propose that the relative resistance to HS-mediated increases in BP in SHR is related to greater NOS expression and the ability to increase NOS1 protein expression compared with DS rats.

Beneficial effects of nebivolol and hydrochlorothiazide combination in spontaneously hypertensive rats

Objective

This study examined the combined effect of nebivolol (NEB) and hydrochlorothiazide (HCTZ) on cardiovascular function in spontaneously hypertensive rats (SHR).

Methods

SHR normotensive male rats were randomly assigned to five groups ( n = 8 per group): (i) SHR control group; (ii) NEB 2 mg/kg per day group; (iii) HCTZ 10 mg/kg per day group; (iv) NEB 2 mg/kg per day + HCTZ 10 mg/kg per day group; (v) Eight age-matched Wistar-Kyoto normotensive male rats served as the control group. All groups were treated orally for 8 weeks.

Results

The combination of NEB + HCTZ synergistically reduced systolic blood pressure and heart rate compared with either monotherapy. HCTZ increased water intake, which is a sign of diuresis. NEB reduced plasma angiotensin II concentration, which was increased in SHR and after HCTZ treatment. NEB + HCTZ increased plasma nitric oxide (NO) concentration and NO synthase activity, which were both reduced in SHR. NEB + HCTZ normalized femoral arterial vasorelaxation induced by acetylcholine, which was impaired in SHR.

Conclusions

The combination of NEB + HCTZ provided a number of beneficial and additive effects due to the synergistic characteristics of both drugs, in an experimental rat model of hypertension.

Predominance of AT(1) blockade over mas-mediated angiotensin-(1-7) mechanisms in the regulation of blood pressure and renin-angiotensin system in mRen2.Lewis rats

BACKGROUND

We investigated whether the antihypertensive actions of the angiotensin II (Ang II) receptor (AT(1)-R) blocker, olmesartan medoxomil, may in part be mediated by increased Ang-(1-7) in the absence of significant changes in plasma Ang II.

METHODS

mRen2.Lewis congenic hypertensive rats were administered either a vehicle (n = 14) or olmesartan (0.5 mg/kg/day; n = 14) by osmotic minipumps. Two weeks later, rats from both groups were further randomized to receive either the mas receptor antagonist A-779 (0.5 mg/kg/day; n = 7 per group) or its vehicle (n = 7 per group) for the next 4 weeks. Blood pressure was monitored by telemetry, and circulating and tissue components of the renin-angiotensin system (RAS) were measured at the completion of the experiments.

RESULTS

Antihypertensive effects of olmesartan were associated with an increase in plasma renin concentration, plasma Ang I, Ang II, and Ang-(1-7), whereas serum aldosterone levels and kidney Ang II content were reduced. Preserved Ang-(1-7) content in kidneys was associated with increases of ACE2 protein but not activity and no changes on serum and kidney ACE activity. There was no change in cardiac peptide levels after olmesartan treatment. The antihypertensive effects of olmesartan were not altered by concomitant administration of the Ang-(1-7) receptor antagonist except for a mild further increase in plasma renin concentration.

CONCLUSIONS

Our study highlights the independent regulation of RAS among plasma, heart, and kidney tissue in response to AT(1)-R blockade. Ang-(1-7) through the mas receptor does not mediate long-term effects of olmesartan besides counterbalancing renin release in response to AT(1)-R blockade.

A review on the role of quinones in renal disorders

Quinones are electron and proton carriers that play a primary role in the aerobic metabolism of virtually every cell in nature. Most physiological quinones are benzoquinones. They undergo highly regulated redox reactions in the mitochondria, Golgi apparatus, plasma membrane and endoplasmic reticulum. Important consequences of these electron transfer reactions are the production of and protection against reactive oxygen species (ROS). Quinones have been extensively studied for both their cytotoxic as well as cellular protective properties and they have been particularly useful in rational drug design. The role of quinones in medicine is explored in this literature review with a particular focus on renal diseases. Due to their high basal metabolism and detoxification role, the kidneys are particularly sensitive to oxidative stress. Regardless of the underlying etiology, ROS plays an important role in both acute kidney injury (AKI) and chronic kidney diseases (CKD). Depending on the oxidative state of the kidney, quinones can be nephrotoxoic or nephro-protective. Many factors play a role in the interaction between quinones and the kidney and the consequences of this are just beginning to be explored.

Mechanisms of cyclosporine-induced renal cell apoptosis: a systematic review

BACKGROUND/AIMS

Chronic cyclosporine A (CsA) nephrotoxicity (CCN) is an important cause of chronic renal dysfunction with no effective clinical intervention. To further elucidate the mechanisms of renal cell apoptosis in CCN, all relevant in vivo studies on this subject were analyzed.

METHODS

We searched for in vivo studies on the mechanisms of CsA-induced renal cell apoptosis in Medline (1966-July 2010), Embase (1980-July 2010) and ISI (1986-July 2010). The studies were evaluated for their quality according to a set of in vivo standards, data extracted according to PICOS, and then synthesized.

RESULTS

Renal cell apoptosis was an important feature of CCN and an important factor of renal dysfunction. First, CsA could upregulate Fas/Fas ligand, downregulate Bcl-2/Bcl-XL, and increase caspase-1 and caspase-3. Second, it could induce oxidative stress and damage the antioxidant defense system. Third, it could increase endoplasmic reticulum stress protein in a dose- and time-dependent manner. Fourth, CsA could impair the urine concentration and decrease the expression of hypertonicity-induced genes. Fifth, CsA-induced renal cell apoptosis was significantly decreased by blocking the angiotensin II type 1 receptor using losartan.

CONCLUSIONS

The in vivo mechanisms for CCN are more complex than those found in vitro. CsA can induce renal cell apoptosis using five pathways in vivo and activated caspases might be the ultimate intersection of these pathways and the common intracellular pathway mediating apoptosis. These data provide new potential points for intervention and need to be confirmed by further studies.

Nebivolol reduces cardiac angiotensin II, associated oxidative stress and fibrosis but not arterial pressure in salt-loaded spontaneously hypertensive rats

OBJECTIVES

Increased sympathetic outflow, renin-angiotensin system (RAS) activity, and oxidative stress are critical mechanisms underlying the adverse cardiovascular effects of dietary salt excess. Nebivolol is a third-generation, highly selective β1-receptor blocker with RAS-reducing effects and additional antioxidant properties. This study evaluated the hypothesis that nebivolol reduces salt-induced cardiac remodeling and dysfunction in spontaneous hypertensive rats (SHRs) by suppressing cardiac RAS and oxidative stress.

METHODS

Male SHRs (8 weeks of age) were given an 8% high salt diet (HSD; n = 22), whereas their age-matched controls (n = 10) received standard chow. In a subgroup of HSD rats (n = 11), nebivolol was given at a dose of 10 mg/kg per day by gastric gavage.

RESULTS

After 5 weeks, HSD exacerbated hypertension as well as increased left-ventricular weight and collagen deposition while impairing left-ventricular relaxation. Salt-induced cardiac remodeling and dysfunction were associated with increased plasma renin concentration (PRC), cardiac angiotensin II immunostaining, and angiotensin-converting enzyme (ACE)/ACE2 mRNA and activity ratio. HSD also increased cardiac 3-nitrotyrosine staining indicating enhanced oxidative stress. Nebivolol treatment did not alter the salt-induced increase in arterial pressure, left-ventricular weight, and cardiac dysfunction but reduced PRC, cardiac angiotensin II immunostaining, ACE/ACE2 ratio, oxidative stress, and fibrosis.

CONCLUSIONS

Our data suggest that nebivolol, in a blood pressure-independent manner, ameliorated cardiac oxidative stress and associated fibrosis in salt-loaded SHRs. The beneficial effects of nebivolol may be attributed, at least in part, to the decreased ACE/ACE2 ratio and consequent reduction of cardiac angiotensin II levels.

Renal-protective effect of nicousamide on hypertensive nephropathy in spontaneously hypertensive rats

Previous studies have demonstrated that a novel coumarin-aspirin derivative, nicousamide, has a significant renal-protective effect on diabetic nephropathy. The present study aimed to investigate the beneficial effect of nicousamide on hypertensive nephropathy, as well as the underlying mechanisms in spontaneously hypertensive rats (SHRs). SHRs were treated orally with saline, nicousamide at 15, 30 and 45 mg/kg, and losartan (10 mg/kg) daily for 17 weeks, during which blood pressure (BP) was measured every four weeks. At the end of the 17-week treatment, blood and urine samples were collected for biochemical analysis and kidney tissues were obtained for histopathological and reverse transcription-polymerase chain reaction (RT-PCR) analyses. The concentration of angiotensin (Ang) II in plasma was also examined. Results showed that nicousamide effectively attenuated the progression of hypertensive nephropathy by decreasing urinary albumin excretion (UAE) and blood urea nitrogen (BUN). This could significantly decrease BP (less effectively compared to losartan) and the incidence of glomerulosclerosis and glomerular arteriosclerosis, adequately alleviating tubular impairment. Nicousamide markedly reduced the plasma Ang II level in SHRs and reduced mRNA expression of angiotensin-converting enzyme (ACE) and chymase in the kidneys of SHRs. Thus, nicousamide may retard the progression of hypertensive nephropathy. Although the underlying mechanisms have yet to be fully elucidated, this may involve blocking of the renin-Ang system.

Nebivolol does not protect against 5/6 ablation/infarction induced chronic kidney disease in rats - comparison with angiotensin II receptor blockade

AIMS

Nitric oxide (NO) deficiency contributes to chronic kidney disease progression. Nebivolol, a beta adrenergic receptor antagonist, may enhance endogenous NO. Here, we investigated whether Nebivolol attenuates hypertension and renal injury after 5/6 ablation/infarction (A/I). Efficacy was compared to the AT1 receptor antagonist Olmesartan.

MAIN METHODS

Kidney disease and hypertension were induced by right kidney ablation and ~2/3 infarction of the left kidney. Rats were treated orally with vehicle (placebo), Nebivolol (5mg/kg b.i.d.), or Olmesartan (2.5mg/kg/day) for 6 weeks after A/I.

KEY FINDINGS

With placebo, glomerular sclerosis and tubulointersititial fibrosis developed with increased blood pressure and proteinuria, and a fall in NO(x) excretion. Olmesartan prevented these changes, but Nebivolol had no effect on these measures but lowered heart rate. Neither treatment reduced systemic oxidative stress (urinary hydrogen peroxide and TBARS). Compared to controls, renal cortex abundance of nNOSα decreased and nNOSβ increased in rats after 5/6 A/I, with no changes in eNOS. Neither treatment restored nNOSα; however, both reduced nNOSβ. Activity of DDAH was decreased by 5/6 A/I but restored by both treatments despite no increase in DDAH protein abundance. Kidney cortex abundance of manganese SOD fell after 5/6 A/I and was restored by treatment with Olmesartan but not Nebivolol. Extracellular and copper/zinc SOD abundances were not changed.

SIGNIFICANCE

In conclusion, Nebivolol showed no benefit after 6 weeks in rapidly progressing, ANG II-dependent 5/6 A/I model of chronic kidney disease. This contrasts to the protection seen with 6 month treatment of Nebivolol in the slowly progressing 5/6 ablation model.

Nebivolol-induced vasodilation of renal afferent arterioles involves β3-adrenergic receptor and nitric oxide synthase activation

Nebivolol is a β(1)-adrenergic blocker that also elicits renal vasodilation and increases the glomerular filtration rate (GFR). However, its direct actions on the renal microvasculature and vasodilator mechanism have not been established. We used the in vitro blood-perfused juxtamedullary nephron technique to determine the vasodilator effects of nebivolol and to test the hypothesis that nebivolol induces vasodilation of renal afferent arterioles via an nitric oxide synthase (NOS)/nitric oxide (NO)/soluble guanylate cyclase (sGC)/cGMP pathway and the afferent arteriolar vasodilation effect may be mediated through the release of NO by activation of NOS via a β(3)-adrenoceptor-dependent mechanism. Juxtamedullary nephrons were superfused with nebivolol either alone or combined with the sGC inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) or the NOS inhibitor N(ω)-nitro-l-arginine (l-NNA) or the β-blockers metoprolol (β(1)), butoxamine (β(2)), and SR59230A (β(3)). Nebivolol (100 μmol/l) markedly increased afferent and efferent arteriolar diameters by 18.9 ± 3.0 and 15.8 ± 1.8%. Pretreatment with l-NNA (1,000 μmol/l) or ODQ (10 μmol/l) decreased afferent vasodilator diameters and prevented the vasodilator effects of nebivolol (2.0 ± 0.2 and 2.4 ± 0.6%). Metoprolol did not elicit significant changes in afferent vasodilator diameters and did not prevent the effects of nebivolol to vasodilate afferent arterioles. However, treatment with SR59230A, but not butoxamine, markedly attenuated the vasodilation responses to nebivolol. Using a monoclonal antibody to β(3)-receptors revealed predominant immunostaining on vascular and glomerular endothelial cells. These data indicate that nebivolol vasodilates both afferent and efferent arterioles and that the afferent vasodilator effect is via a mechanism that is independent of β(1)-receptors but is predominantly mediated via a NOS/NO/sGC/cGMP-dependent mechanisms initiated by activation of endothelial β(3)-receptors.

High-salt diet increases glomerular ACE/ACE2 ratio leading to oxidative stress and kidney damage

BACKGROUND

Angiotensin II (AngII) contributes to salt-driven kidney damage. In this study, we aimed at investigating whether and how the renal damage associated with a high-salt diet could result from changes in the ratio between angiotensin-converting enzyme (ACE) and angiotensin-converting enzyme 2 (ACE2).

METHODS

Forty-eight rats randomly allocated to three different dietary contents of salt were studied for 4 weeks after undergoing a left uninephrectomy. We focussed on kidney functional, structural and molecular changes. At the same time, we studied kidney molecular changes in 20 weeks old Ace2-knockout mice (Ace2KO), with and without ACE inhibition.

RESULTS

A high salt content diet significantly increased the glomerular ACE/ACE2 ratio. This was associated with increased oxidative stress. To assess whether these events were related, we measured renal oxidative stress in Ace2KO, and found that the absence of ACE2 promoted oxidative stress, which could be prevented by ACE inhibition.

CONCLUSION

One of the mechanisms by which a high-salt diet leads to renal damage seems to be the modulation of the ACE/ACE2 ratio which in turn is critical for the cause of oxidative stress, through AngII.