Sympathetic Nerve Activity and Baroreflex are Strongly Altered in a Context of Severe Hypertension Using the Spontaneously Hypertensive Rat Model Associated with Chronic Reduction of Nitric Oxide

The aim of our study is to investigate the sympathetic output and baroreflex via renal sympathetic nerve activity (RSNA) recording in a model of severe hypertension which exhibits arterial, cardiac, and renal damages, the spontaneously hypertensive rat (SHR) under lowered NO bioavailability. SHR are treated from 18 to 20 weeks of age with a low dose of L-NAME, a NO synthase inhibitor, in drinking water (SHRLN) and compared to SHR and normotensive Wistar Kyoto (WKY) rats. After the two-week treatment, rats are anesthetized for RSNA, mean blood pressure (MBP), and heart rate (HR) recording. MBP is higher in SHR than in WKY and higher in SHRLN than in SHR. Compared to WKY, SHR displays an alteration in the baroreflex with a displacement of the sympathoinhibition curve to highest pressures; this displacement is greater in SHRLN rats. The bradycardic response is reduced in SHRLN compared to both SHR and WKY. In hypertensive rats, SHR and SHRLN, basal RSNA is modified, the maximal amplitude of burst is reduced, but minimal values are increased, indicating an increased basal RSNA with reduced bursting activity. The temporal correlation between RSNA and HR is preserved in SHR but altered in 10 SHRLN out of 10. The RSNA inhibition triggered by the Bezold–Jarisch reflex activation is not modified in hypertensive rats, SHR or SHRLN, in contrast to that triggered by the baroreflex. Histological analysis of the carotid bifurcation does not reveal any abnormality in SHRLN at the level of the carotid sinus. In conclusion, data indicate that the sympathetic outflow is altered in SHRLN with a strong reduction of the baroreflex sympathoinhibition and suggest that its central pathway is not involved. These additional results on SHRLN also confirm the usefulness of this model of severe hypertension with multiple target organ damages.

L-Theanine Protects Bladder Function by Suppressing Chronic Sympathetic Hyperactivity in Spontaneously Hypertensive Rat

Chronic sympathetic hyperactivity is known to affect metabolism and cause various organ damage including bladder dysfunction. In this study, we evaluated whether L-theanine, a major amino acid found in green tea, ameliorates bladder dysfunction induced by chronic sympathetic hyperactivity as a dietary component for daily consumption. Spontaneously hypertensive rats (SHRs), as an animal model of bladder dysfunction, were divided into SHR–water and SHR–theanine groups. After 6 weeks of oral administration, the sympathetic nervous system, bladder function, and oxidative stress of bladder tissue were evaluated. The mean blood pressure, serum noradrenaline level, and media-to-lumen ratio of small arteries in the suburothelium were significantly lower in the SHR–theanine than in the SHR–water group. Micturition interval was significantly longer, and bladder capacity was significantly higher in the SHR–theanine than in the SHR–water group. Bladder strip contractility was also higher in the SHR–theanine than in the SHR–water group. Western blotting of bladder showed that expression of malondialdehyde was significantly lower in the SHR–theanine than in the SHR–water group. These results suggested that orally administered L-theanine may contribute at least partly to the prevention of bladder dysfunctions by inhibiting chronic sympathetic hyperactivity and protecting bladder contractility.

NAP-22 and MARCKS mRNA expression levels in spontaneously hypertensive rat kidneys: the effect of drinking water with different calcium contents

Objective. The aim of study was to assess the effect of the level of calcium intake with drinking water on NAP-22 and MARCKS mRNA expression in cortical and medullar kidney layers of spontaneously hypertensive rats.Design and methods. The study involved 90-day-old SHR (n = 8) and WKY (n = 8) strain rats of both sexes. We assessed tissue samples from cortical and medullar kidney layers. NAP-22 and MARCKS mRNA expression levels were determined by RT-PCR.Results. Sufficient drinking water calcium intake was associated with similar the expression of NAP-22 and MARCKS mRNA in kidneys of spontaneously hypertensive and normotensive rats. Consumption of drinking water with insufficient calcium content it decreases in both rat strains, being more evident in spontaneously hypertensive rats, especially in the medullar layer.Conclusions. Our results show that genetically determined impairments of calcium metabolism in cells of spontaneously-hypertensive rats (SHR line) and their effect on intracellular signaling processes are more evident with the reduced intake of exogenous calcium.

NAP-22 and MARCKS mRNA expression levels in spontaneously hypertensive rat kidneys: the effect of drinking water with different calcium contents

Objective. The aim of study was to assess the effect of the level of calcium intake with drinking water on NAP-22 and MARCKS mRNA expression in cortical and medullar kidney layers of spontaneously hypertensive rats.Design and methods. The study involved 90-day-old SHR (n = 8) and WKY (n = 8) strain rats of both sexes. We assessed tissue samples from cortical and medullar kidney layers. NAP-22 and MARCKS mRNA expression levels were determined by RT-PCR.Results. Sufficient drinking water calcium intake was associated with similar the expression of NAP-22 and MARCKS mRNA in kidneys of spontaneously hypertensive and normotensive rats. Consumption of drinking water with insufficient calcium content it decreases in both rat strains, being more evident in spontaneously hypertensive rats, especially in the medullar layer.Conclusions. Our results show that genetically determined impairments of calcium metabolism in cells of spontaneously-hypertensive rats (SHR line) and their effect on intracellular signaling processes are more evident with the reduced intake of exogenous calcium.

Reno-protective Effect of Angiotensin Receptor Blocker in Spontaneously Hypertensive Rat Models: A Systematic Review

Background Chronic Kidney Disease (CKD) is highly prevalent among hypertensive population. Previous date from studies and experiments have confirmed the reno-protective effect and tolerability of angiotensin receptor blockers in diabetic nephropathy. However, clinical data are lacking in hypertensive population. Objectives This is the first meta-analysis to evaluate the surrogate outcomes of renal protection with ARBs in hypertensive rodents to serve as a baseline for further studies. Methods The systematic review was conducted following the PRISM checklist. Four different databases were searched including PubMed, EMBASE, ScienceDirect and SCOPUS. No restrictions were applied on dose, duration of follow up or ARBs used. Inclusion was restricted to experimental studies reporting means and SEM, published in English, addressing the PICO question and having a moderate to high quality. 37 total eligible articles were identified and Results: Of 25 reported primary outcomes in comparison to hypertensive untreated controls, 23 studies showed positive results supporting that ARBs induce reduction in proteinuria and/or albuminuria compared to hypertensive untreated controls. Similarly, in comparison to normotensive untreated controls, 9 of 12 studies showed positive results supporting that ARBs’ induced reduction in proteinuria and/or albuminuria can reach levels similar to normotensive controls. For the secondary outcomes, 12 of 18 reported outcomes showed significant improvement in CrCl or reduction in BUN compared to hypertensive untreated rats. Similarly, 10 of 17 outcomes reported showed that the improvement in secondary outcomes reached levels that are comparable to normotensive controls. Conclusion: Qualitative data from this systematic review support that ARBs have a Reno-protective effect in different hypertensive models and the effect is independent of BP lowering.

Study on the Mechanism of Hypertension Caused by Sorafenib in Liver Cancer-Bearing Rats Based on VEGF Signal Pathway

To explore the mechanism of hypertension caused by sorafenib in liver cancer-bearing rats based on Vascular Endothelial-Growth Factor (VEGF) signal pathway. After the three groups (blank, liver cancer and Spontaneously Hypertensive Rat (SHR) groups, n = 30) were administered orally with sorafenib (2 mg/kg), the non-invasive tail arterial pressure measurement was employed to determine the changes in blood pressure (BP). Enzyme-linked immunosorbent assay measured the changes of VEGF and Nitric Oxide (NO) in serum. The expressions of Kinase insert Domain Receptor tyrosine kinase (KDR-CD), endothelial Nitric Oxide Synthase (eNOS), Bax and Bcl-2 were detected by Western blot. TUNEL assay detected the Apoptosis Index (AI) of cardiomyocyte. CD31 immunohistochemical staining was observed the changes of Myocardial Capillary Density (MCD). The BP and VEGF levels of the blank and SHR groups were not significantly (P > 0.05) different from those in the before treatment cohort, while the BP of the liver cancer group was significantly (P < 0.05) higher. VEGF level was significantly (P < 0.05) lower than before. Compared with the blank group, the levels of NO, KDR-CD, eNOS, Bcl-2/Bax and MCD in the liver cancer group were significantly (P < 0.05) lower than those in the after administration, while the myocardial cell AI increased significantly (P < 0.05). After antagonist intervention, the BPs and myocardial AI of the liver cancer and SHR groups were significantly lower than before the intervention. Besides, levels of KDR-CD, eNOS, Bcl-2/Bax protein, MCD, serum VEGF and NO were significantly higher than before the intervention (P<0.05). Induction mechanism of hypertension induced by sorafenib may be owing to the inhibition of the VEGF signaling pathway, and reduction of endothelial cells proliferation leading to blockade of NO synthesis. This causes vasoconstriction, while promoting myocardial cell apoptosis and decreasing capillary density, thereby inducing the occurrence of hypertension.

A network pharmacology-based approach to explore the active ingredients and molecular mechanism of Lei-gong-gen formula granule on a spontaneously hypertensive rat model

Background Lei-gong-gen formula granule (LFG) is a folk prescription derived from Zhuang nationality, the largest ethnic minority among 56 nationalities in China. It consists of three herbs, namely Eclipta prostrata (L.) L., Smilax glabra Roxb, and Centella asiatica (L.) Urb. It has been widely used as health protection tea for hundreds of years to prevent hypertension in Guangxi Zhuang Autonomous Region. The purpose of this study is to validate the antihypertensive effect of LFG on the spontaneously hypertensive rat (SHR) model, and to further identify the effective components and anti-hypertension mechanism of LFG. Methods The effects of LFG on blood pressure, body weight, and heart rate were investigated in vivo using the SHR model. The levels of NO, ANG II, and ET-1 in the serum were measured, and pathological changes in the heart were examined by H&E staining. The main active components of LFG, their corresponding targets, and hypertension associated pathways were discerned through network pharmacology analysis based on the Traditional Chinese Medicine Systems Pharmacology (TCMSP), Traditional Chinese Medicine Integrated Database (TCMID), and the Bioinformatics Analysis Tool for Molecular Mechanism of Traditional Chinese Medicine (BATMAN-TCM). Then the predicted results were further verified by molecular biology experiments such as RT-qPCR and western blot. Additionally, the potential active compounds were predicted by molecular docking technology, and the chemical constituents of LFG were analyzed and identified by UPLC-QTOF/MS technology. Finally, an in vitro assay was performed to investigate the protective effects of potential active compounds against hydrogen peroxide (H2O2) induced oxidative damage in human umbilical vein endothelial cells (HUVEC). Results LFG could effectively reduce blood pressure and increase serum NO content in SHR model. Histological results showed that LFG could ameliorate pathological changes such as cardiac hypertrophy and interstitial inflammation. From network pharmacology analysis, 53 candidate active compounds of LFG were collected, which linked to 765 potential targets, and 828 hypertension associated targets were retrieved, from which 12 overlapped targets both related to candidate active compounds from LFG and hypertension were screened and used as the potential targets of LFG on antihypertensive effect. The molecular biology experiments of the 12 overlapped targets showed that LFG could upregulate the mRNA and protein expressions of NOS3 and proto-oncogene tyrosine-protein kinase SRC (SRC) in the thoracic aorta. Pathway enrichment analysis showed that the PI3K-AKT signaling pathway was closely related to the expression of NOS3 and SRC. Moreover, western blot results showed that LFG significantly increased the protein expression levels of PI3K and phosphorylated AKT in SHR model, suggesting that LFG may active the PI3K-AKT signaling pathway to decrease hypertension. Molecular docking study further supported that p-hydroxybenzoic acid, cedar acid, shikimic acid, salicylic acid, nicotinic acid, linalool, and histidine can be well binding with NOS3, SRC, PI3K, and AKT. UPLC-QTOF/MS analysis confirmed that p-hydroxybenzoic acid, shikimic acid, salicylic acid, and nicotinic acid existed in LFG. Pre-treatment of HUVEC with nicotinic acid could alleviate the effect on cell viability induced by H2O2 and increase the NO level in cell supernatants. Conclusions LFG can reduce the blood pressure in SHR model, which might be attributed to increasing the NO level in serum for promoting vasodilation via upregulating SRC expression level and activating the PI3K-AKT-NOS3 signaling pathway. Nicotinic acid might be the potential compound for LFG antihypertensive effect.