Altered expression profile of renal α(1D)-adrenergic receptor in diabetes and its modulation by PPAR agonists

Combined vaccines against angiotensin II receptor type 1 and alpha 1D-adrenergic receptor for hypertension

PURPOSE

Compared with monotherapy, combination therapy with multiple antihypertensive drugs has demonstrated superior efficacy in the management of hypertension. The aim of this study was to explore the efficacy of multitarget combined vaccines in achieving simultaneous antihypertensive and target organ protection effects.

METHODS

Our team has developed ATRQβ-001 and ADRQβ-004 vaccines targeting Ang II type 1 receptor (AT1R) and α1D-adrenergic receptor (α1D-AR), respectively. In NG-nitroarginine methyl ester ( l -NAME) + abilities spontaneously hypertensive rats (SHRs) model, SHRs were simultaneously inoculated with ATRQβ-001 and ADRQβ-004 vaccines. Histological and biochemical analyses were performed to evaluate the antihypertensive effects and target organ protection of the ATRQβ-001 and ADRQβ-004 combined vaccines in comparison with those of the single vaccine.

RESULTS

Both ATRQβ-001 and ADRQβ-004 vaccines induced robust antibody production, resulting in persistent high antibody titers in rats. Notably, the combined administration of both vaccines significantly decreased SBP in SHRs compared with treatment with a single vaccine, both before and after l -NAME administration. Furthermore, the combined vaccine regimen demonstrated superior efficacy in protecting against vascular remodeling, myocardial hypertrophy and fibrosis, and kidney injury in SHRs. Mechanistically, the combined vaccines exhibited significantly downregulated the expression of angiotensin II type 1 receptor (AT1R) and α1D-adrenergic receptor (α1D-AR). Importantly, no apparent immune-related adverse effects were observed in animals immunized with the combined vaccines.

CONCLUSION

Preliminary findings from this investigation suggest that co-administration of the novel ATRQβ-001 and ADRQβ-004 vaccines holds potential as a groundbreaking therapeutic strategy for managing hypertension.

QiShenYiQi ameliorates salt-induced hypertensive nephropathy by balancing ADRA1D and SIK1 expression in Dahl salt-sensitive rats

BACKGROUND

Hypertension is a leading risk factor for developing kidney disease. Current single-target antihypertensive drugs are not effective for hypertensive nephropathy, in part due to its less understood mechanism of pathogenesis. We recently showed that QiShenYiQi (QSYQ), a component-based cardiovascular Chinese medicine, is also effective for ischemic stroke. Given the important role of the brain-heart-kidney axis in blood pressure control, we hypothesized that QSYQ may contribute to blood pressure regulation and kidney protection in Dahl salt-sensitive hypertensive rats.

METHODS

The therapeutic effects of QSYQ on blood pressure and kidney injury in Dahl salt-sensitive rats fed with high salt for 9 weeks were evaluated by tail-cuff blood pressure monitoring, renal histopathological examination and biochemical indicators in urine and serum. RNA-seq was conducted to identify QSYQ regulated genes in hypertensive kidney, and RT-qPCR, immunohistochemistry, and Western blotting analysis were performed to verify the transcriptomics results and validate the purposed mechanisms.

RESULTS

QSYQ treatment significantly decreased blood pressure in Dahl salt-sensitive hypertensive rats, alleviated renal tissue damage, reduced renal interstitial fibrosis and collagen deposition, and improved renal physiological function. RNA-seq and subsequent bioinformatic analysis showed that the expression of ADRA1D and SIK1 genes were among the most prominently altered by QSYQ in salt-sensitive hypertensive rat kidney. RT-qPCR, immunohistochemistry and Western blotting results confirmed that the mRNA and protein expression levels of alpha-1D adrenergic receptor (ADRA1D) in the kidney tissue of the QSYQ-treated rats were markedly down-regulated, while the mRNA and protein levels of salt inducible kinase 1 (SIK1) were significantly increased.

CONCLUSION

QSYQ not only lowered blood pressure, but also alleviated renal damage via reducing the expression of ADRA1D and increasing the expression of SIK1 in the kidney of Dahl salt-sensitive hypertensive rats.

High-dose nitrate therapy recovers the expression of subtypes α1 and β-adrenoceptors and Ang II receptors of the renal cortex in rats with myocardial infarction-induced heart failures

BACKGROUND

Few studies examined the effect of long-acting nitrates on renal function in chronic heart failure (CHF). Thus, we aimed to investigate the effect of long-acting nitrate on the expression of adrenoceptors (AR) and angiotensin II receptor (ATR) subtypes of the renal cortex, in rats with myocardial infarction-induced CHF.

METHODS

Rats were randomly divided into the following groups: control, sham-operated, CHF, low- and high-dose nitrate, positive drug control (olmesartan), and high-dose of long-acting nitrate + olmesartan. Ultrasound echocardiography markers were compared, and the levels of AR subtypes, AT1R, and AT2R were measured using reverse transcription-polymerase chain reaction and western blot analysis. Histopathology of the kidney was determined on hematoxylin and eosin-stained sections.

RESULTS

CHF significantly increased plasma renin activity (PRA) and angiotensin II levels, upregulated AT1R expression and downregulated α1A-, β1-, β2-AR, and AT2R expression compared to the sham control. High-dose nitrate or olmesartan alone, and especially in combination, decreased the levels of PRA and angiotensin II and downregulated the CHF-induced expression of AT1R, α1A-, β1-, and β2-AR, and AT2R. CHF resulted in significant impairment of the renal tissue, including inflammatory cells infiltration to the tubular interstitium and surrounding the renal glomerulus, and tubular necrosis, which was alleviated in all treatment groups to different degrees.

CONCLUSIONS

Long-acting nitrates could reverse CHF-induced changes in AR and ATR subtypes in the kidney, and improve cardiac function to protect renal function. Compared with monotherapy, the combination of nitrates and olmesartan shows more significant benefits in regulating AR and ATR subtypes.

Vaccine Targeted Alpha 1D-Adrenergic Receptor for Hypertension

The α1-AR (α1 adrenergic receptor) blockers currently on the market cannot meet clinical needs because of low-selectivity for subtypes of α1-ARs, short half-life, and uncertain role in cardiovascular end point events. The study sought to find a vaccine specifically against α1D-AR (α1D-adrenergic receptor) for treating hypertension. A short peptide ADR-004 (cgiteeagy) belonging to α1D-AR was screened, and the ADRQβ-004 vaccine was produced and injected into spontaneously hypertensive rats model (including a short-term study, 10 weeks, and a long-term observation study, 39 weeks) and NG-nitro-l-arginine methyl ester + spontaneously hypertensive rats model (15 weeks). The antihypertensive effect and target organ protection of the ADRQβ-004 vaccine were carefully evaluated. The possible immune-mediated damage was detected in normal vaccinated Sprague Dawley rats. The ADR-004 peptide has perfect immunogenicity, and the ADRQβ-004 vaccine could induce strong antibody production. In the short-term study, the ADRQβ-004 vaccine averagely decreased the systolic blood pressure of spontaneously hypertensive rats up to 15 mm Hg and that of NG-nitro-l-arginine methyl ester+spontaneously hypertensive rats up to 29 mm Hg. In the long-term observation model, the antihypertensive effect of the ADRQβ-004 vaccine was quite stable, and the average decline of systolic blood pressure was 22 mm Hg. The ADRQβ-004 vaccine effectively prevented vascular structural remodeling, cardiac hypertrophy and fibrosis, and renal injury of hypertensive animals, superior to prazosin at renal level. Moreover, the ADRQβ-004 vaccine obviously downregulated the expression of α1D-AR, but not α1A-AR. Additionally, no significant immune-mediated damage was detected in immunized animals. The present results demonstrate that the ADRQβ-004 vaccine may provide a novel and promising method for the treatment of hypertension.

Sympathetic regulation of NCC in norepinephrine-evoked salt-sensitive hypertension in Sprague-Dawley rats

Salt sensitivity of blood pressure is characterized by inappropriate sympathoexcitation and renal Na⁺ reabsorption during high salt intake. In salt-resistant animal models, exogenous norepinephrine (NE) infusion promotes salt-sensitive hypertension and prevents dietary Na⁺-evoked suppression of the Na⁺-Cl^- cotransporter (NCC). Studies of the adrenergic signaling pathways that modulate NCC activity during NE infusion have yielded conflicting results implicating α₁- and/or β-adrenoceptors and a downstream kinase network that phosphorylates and activates NCC, including with no lysine kinases (WNKs), STE20/SPS1-related proline-alanine-rich kinase (SPAK), and oxidative stress response 1 (OxSR1). In the present study, we used selective adrenoceptor antagonism in NE-infused male Sprague-Dawley rats to investigate the differential roles of α₁- and β-adrenoceptors in sympathetically mediated NCC regulation. NE infusion evoked salt-sensitive hypertension and prevented dietary Na⁺-evoked suppression of NCC mRNA, protein expression, phosphorylation, and in vivo activity. Impaired NCC suppression during high salt intake in NE-infused rats was paralleled by impaired suppression of WNK1 and OxSR1 expression and SPAK/OxSR1 phosphorylation and a failure to increase WNK4 expression. Antagonism of α₁-adrenoceptors before high salt intake or after the establishment of salt-sensitive hypertension restored dietary Na⁺-evoked suppression of NCC, resulted in downregulation of WNK4, SPAK, and OxSR1, and abolished the salt-sensitive component of hypertension. In contrast, β-adrenoceptor antagonism attenuated NE-evoked hypertension independently of dietary Na⁺ intake and did not restore high salt-evoked suppression of NCC. These findings suggest that a selective, reversible, α₁-adenoceptor-gated WNK/SPAK/OxSR1 NE-activated signaling pathway prevents dietary Na⁺-evoked NCC suppression, promoting the development and maintenance of salt-sensitive hypertension.

Maternal separation diminishes α-adrenergic receptor density and function in renal vasculature from male Wistar-Kyoto rats

Adult rats exposed to maternal separation (MatSep) are normotensive but display lower glomerular filtration rate and increased renal neuroadrenergic drive. The aim of this study was to determine the renal α-adrenergic receptor density and the renal vascular responsiveness to adrenergic stimulation in male rats exposed to MatSep. In addition, baroreflex sensitivity was assessed to determine a component of neural control of the vasculature. Using tissue collected from 4-mo-old MatSep and control rats, α₁-adrenergic receptors (α₁-ARs) were measured in renal cortex and isolated renal vasculature using receptor binding assay, and the α-AR subtype gene expression was determined by RT-PCR. Renal cortical α₁-AR density was similar between MatSep and control tissues (B_max = 44 ± 1 vs. 42 ± 2 fmol/mg protein, respectively); however, MatSep reduced α₁-AR density in renal vasculature (B_max = 47 ± 4 vs. 62 ± 4 fmol/mg protein, P < 0.05, respectively). In a separate group of rats, the pressor, bradycardic, and renal vascular constrictor responses to acute norepinephrine injection (NE, 0.03-0.25 μg/μl) were determined under anesthesia. Attenuated NE-induced renal vasoconstriction was observed in rats exposed to MatSep compared with control (P < 0.05). A third group of rats was infused at steady state with the α₁ agonist phenylephrine (10 μg/min iv) and vasodilator sodium nitroprusside (5 μg/min iv). The difference between the change in heart rate/mean arterial pressure slopes was indicative of reduced baroreflex sensitivity in MatSep vs. control rats (-0.45 ± 0.04 vs. -0.95 ± 0.07 beats·min^-1·mmHg^-1, P < 0.05). These data support the notion that reduced α-adrenergic receptor expression and function in the renal vasculature could develop secondary to MatSep-induced overactivation of the renal neuroadrenergic tone.

ISN Forefronts Symposium 2015: Nuclear Receptors and Diabetic Nephropathy

Diabetic nephropathy (DN) is the major reason for end stage renal disease in the western world. Patients with DN developed more severe cardiovascular complications with worse prognosis. In spite of tight blood pressure and glucose control through applying angiotensin II receptor antagonism, angiotensin receptor inhibitors and even direct renin inhibitors, the progression and development of DN has continued to accelerate. Nuclear receptors are, with few exceptions, ligand-depended transcription factors some of which modulate genes involved in the transportation and metabolism of carbohydrate or lipid, and inflammation. Considering the diverse biological functions of nuclear receptors, efforts have been made to explore their contributions to the pathogenesis of DN and potential therapeutic strategies. This review is mainly focused on the association between various nuclear receptors and the pathogenesis of DN, the potential beneficial effects of targeting these receptors for preventing the progress of DN, and the important role that nuclear receptors may play in future therapeutic strategies for DN.

The potential signaling pathway between peroxisome proliferator-activated receptor gamma and retinoic acid receptor alpha in renal interstitial fibrosis disease

Peroxisome proliferator-activated receptorγ (PPARγ) can regulate the process of cell apoptosis and is related to the progression of renal disorders. Retinoic acid receptor alpha (RARα) is one of the nuclear receptors involved in a variety of kidney diseases. Renal interstitial fibrosis (RIF) is a common denominator of chronic kidney disease (CKD). This study investigated whether a potential signaling pathway existed between PPARγ and RARα in RIF rats with unilateral ureteral obstruction (UUO). The rats were randomly divided into four groups: a model group subjected to UUO (GU), and three other groups treated with rosiglitazone sodium (GRS), GW9662 and dimethyl sulfoxide (DMSO), n = 40, respectively. Renal tissues were collected two and four weeks after post-surgery. The relevant indicators were detected. In comparison with the GU group, the expressions of PPARγ and RARα (protein and mRNA) were increased in the GRS group, and decreased in the GW9662 group (all p < 0.01). The RIF index, mRNA and protein expression of transforming growth factor-β1 (TGF-β1), and the protein expressions of collagen-IV (Col-IV) and fibronectin (FN) in the GRS group were more markedly reduced than those in the GU group; their levels in the GW9662 group were elevated (all p < 0.01). PPARγ or RARα was negatively correlated to the RIF index, TGF-β1, Col-IV and FN. PPARγ was positively correlated with RARα (all p < 0.01). In conclusion, PPARγ agonist can elevate the expression of PPARγ or RARα in RIF rats. There might be a potential signaling pathway between PPARγ and RARα in RIF disease.