Role of Dopamine in the Striatum, Renin-Angiotensin System and Renal Sympathetic Nerve on the Development of Two-Kidney, One-Clip Goldblatt Hypertension

The hydrogen sulfide donor 4-carboxyphenyl-isothiocyanate decreases blood pressure and promotes cardioprotective effect through reduction of oxidative stress and nuclear factor kappa B/matrix metalloproteinase (MMP)-2 axis in hypertension

AIMS

Our aim was to evaluate whether the hydrogen sulfide (H2S) donor, 4-carboxyphenyl-isothiocyanate (4-CPI), exerts cardioprotective effect in the two kidney- one clip (2K-1C) rats through oxidative stress and MMP-2 activity attenuation and compare it with the classical H2S donor, Sodium Hydrosulfide (NaHS).

MATERIALS AND METHODS

Renovascular hypertension (two kidneys-one clip; 2K-1C) was surgically induced in male Wistar rats. After two weeks, normotensive (2K) and hypertensive rats were intraperitoneally treated with vehicle (0.6 % dimethyl sulfoxide), NaHS (0.24 mg/Kg/day) or with 4-CPI (0.24 mg/Kg/day), for more 4 weeks. Systolic blood pressure (SBP) was evaluated weekly by tail-cuff plethysmography. Heart function was assessed by using the Millar catheter. Cardiac hypertrophy and fibrosis were evaluated by hematoxylin and eosin, and Picrosirius Red staining, respectively. The H2S was analyzed using WSP-1 fluorimetry and the cardiac oxidative stress was measured by lucigenin chemiluminescence and Amplex Red. MMP-2 activity was measured by in-gel gelatin or in situ zymography assays. Nox1, gp91phox, MMP-2 and the phospho-p65 subunit (Serine 279) nuclear factor kappa B (NF-κB) levels were evaluated by Western blotting.

KEY FINDINGS

4-CPI reduced blood pressure in hypertensive rats, decreased cardiac remodeling and promoted cardioprotection through the enhancement of cardiac H2S levels. An attenuation of oxidative stress, with inactivation of the p65-NF-κB/MMP-2 axis was similarly observed after NaHS or 4-CPI treatment in 2K-1C hypertension.

SIGNIFICANCE

H2S is a mediator that promotes cardioprotective effects and decreases blood pressure, and 4-CPI seems to be a good candidate to reverse the maladaptive remodeling and cardiac dysfunction in renovascular hypertension.

Acupuncture with twirling reinforcing and reducing manipulation shows a control of hypertension and regulation of blood pressure-related target brain regions in spontaneously hypertensive rat: a preliminary resting-state functional MRI study

Aim

To observe the effects of acupuncture manipulations on blood pressure and brain function in spontaneously hypertensive rats and elucidate the anti-hypertensive effect of the manipulations' central mechanism.

Methods

This study used acupuncture twirling reinforcing, acupuncture twirling reducing, and acupuncture twirling uniform reinforcing-reducing manipulations to act on the bilateral TaiChong point of rats. The depth of acupuncture was 1.5-2 mm, and twisting was performed at a frequency of 60 times/min within ±360° for 3 min, followed by the needle being retained for 17 min. Functional magnetic resonance imaging was performed at the end of the intervention. Regional homogeneity and amplitude of low-frequency fluctuations were used to assess the differences in brain regions in each group of rats, and the core brain region (left hypothalamus) among the differential brain regions was selected as the seed for functional connectivity analysis.

Results

(1) The anti-hypertensive effect was achieved by acupuncture manipulations, and the anti-hypertensive effect of twirling reducing manipulation on spontaneously hypertensive rats was better than that of twirling uniform reinforcing-reducing and twirling reinforcing manipulations. (2) After regional homogeneity and amplitude of low-frequency fluctuations analyses, the hypothalamus, the brain region related to blood pressure, was activated in the twirling uniform reinforcing-reducing manipulation group; the corpus callosum and cerebellum were activated in the twirling reinforcing manipulation group; and the hypothalamus, olfactory bulb, corpus callosum, brainstem, globus pallidum, and striatum were activated in the twirling reducing manipulation group. (3) According to the functional connectivity analysis, different acupuncture manipulations increased the functional connections between seed points and the brainstem, olfactory bulb, and cerebellum, etc.

Conclusion

These results suggest that acupuncture manipulations achieved the hypotensive effect and the twirling reducing manipulation had a better hypotensive effect on spontaneously hypertensive rats than twirling uniform reinforcing-reducing and twirling reinforcing manipulations; the central mechanism of the anti-hypertensive effect of twirling reinforcing and reducing manipulation may be related to the activation of brain regions associated with blood pressure regulation and the functional connections between them. Furthermore, brain regions involved in motor control, cognition, and hearing were also activated. We hypothesize that activation of these brain regions may help prevent or mitigate the onset and progression of hypertensive brain damage.

Clitoria ternatea (Linn.) flower extract attenuates vascular dysfunction and cardiac hypertrophy via modulation of Ang II/AT1 R/TGF-β1 cascade in hypertensive rats

BACKGROUND

Clitoria ternatea (CT) (the Fabaceae family) has been reported to elicit several biological responses, such as anti-inflammation and anti-depression effects. This study evaluated the effect of CT flower extract on blood pressure, vascular function, and left ventricular hypertrophy in a two-kidney, one-clip (2K-1C) rat model. Hypertensive rats were treated with CT extract at various doses (100, 300, or 500 mg kg^-1  day^-1 ) or losartan (10 mg kg^-1  day^-1 ) for 4 weeks (n = 8/group).

RESULTS

CT extract reduced blood pressure in a dose-dependent manner, and CT extract at a dose of 300 mg kg^-1 was an effective concentration (P < 0.05). Augmentation of contractile responses to electrical field stimulation and impairment of vascular responses to acetylcholine in mesenteric vascular beds and aortic rings of 2K-1C rats were suppressed by treatment with CT extract or losartan (P < 0.05). Serum angiotensin-converting enzyme activity and plasma angiotensin II concentration were high in 2K-1C rats but alleviated by CT extract or losartan treatment (P < 0.05). Increases in superoxide production and lipid peroxidation were attenuated in 2K-1C rats treated with CT extract or losartan compared with the untreated group (P < 0.05). Increased plasma concentration of nitric oxide metabolites was found in hypertensive rats that received CT extract or losartan. CT extract or losartan suppressed the overexpression of Ang II receptor subtype I (AT₁ -R) and transforming growth factor-β1 (TGF-β1) in 2K-1C rats.

CONCLUSION

CT extract had antihypertensive effects that were associated with improving vascular function and cardiac hypertrophy in 2K-1C rats. The mechanisms involved suppression of the renin-angiotensin system, of oxidative stress, and of the AT₁ R/TGF-β1 cascade. © 2021 Society of Chemical Industry.

C-type natriuretic peptide-induced relaxation through cGMP-dependent protein kinase and SERCA activation is impaired in two kidney-one clip rat aorta

AIMS

Hypertension underlies endothelial dysfunction, and activation of vasorelaxation signaling with low dependence on nitric oxide (NO) represents a good alternative for vascular modulation. C-type natriuretic peptide (CNP) causes relaxation by increasing cyclic guanosine 3',5'-monophosphate (cGMP) or Gi-protein activation through its natriuretic peptide receptor-B or -C, respectively. We have hypothesized that CNP could exerts its effects and could overcome endothelial dysfunction in two kidney-one clip (2K-1C) hypertensive rat aorta. Here, we investigate the intracellular signaling involved in CNP effects in hypertension.

MATERIALS AND METHODS

The 2K-1C hypertension was induced in male Wistar rats (200 g). CNP-induced vascular relaxation and cGMP production were investigated in rat thoracic aortas. The natriuretic peptide receptor-B and -C localization was evaluated by immunofluorescence. Calcium mobilization was assessed in endothelial cells from rat aortas.

KEY FINDINGS

CNP induced similar relaxation in normotensive and 2K-1C hypertensive rat aortas, which increased after endothelium removal. CNP-induced relaxation involved natriuretic peptide receptor-B and -C activation in 2K-1C rats. Nitric oxide synthase (NOS) and soluble guanylyl cyclase (sGC) counter-regulated CNP-particulate GC (pGC) activation in aortas. CNP reduced endothelial calcium and increased cGMP production, which was lower in 2K-1C. CNP-induced cGMP-dependent protein kinase (PKG) and sarcoplasmic/endoplasmic reticulum Ca²⁺-ATPase (SERCA) activation was impaired in 2K-1C rat aorta.

SIGNIFICANCE

Our results indicated CNP triggered relaxation through its natriuretic peptide receptor-B and -C in 2K-1C rat aortas, and that CNP-induced relaxation overcomes endothelial dysfunction in hypertension. In addition, NOS and sGC activities counter-regulate CNP-pGC activation to induce vascular relaxation.

The Role of the Renal Dopaminergic System and Oxidative Stress in the Pathogenesis of Hypertension

The kidney is critical in the long-term regulation of blood pressure. Oxidative stress is one of the many factors that is accountable for the development of hypertension. The five dopamine receptor subtypes (D₁R–D₅R) have important roles in the regulation of blood pressure through several mechanisms, such as inhibition of oxidative stress. Dopamine receptors, including those expressed in the kidney, reduce oxidative stress by inhibiting the expression or action of receptors that increase oxidative stress. In addition, dopamine receptors stimulate the expression or action of receptors that decrease oxidative stress. This article examines the importance and relationship between the renal dopaminergic system and oxidative stress in the regulation of renal sodium handling and blood pressure. It discusses the current information on renal dopamine receptor-mediated antioxidative network, which includes the production of reactive oxygen species and abnormalities of renal dopamine receptors. Recognizing the mechanisms by which renal dopamine receptors regulate oxidative stress and their degree of influence on the pathogenesis of hypertension would further advance the understanding of the pathophysiology of hypertension.

Hesperidin Suppresses Renin-Angiotensin System Mediated NOX2 Over-Expression and Sympathoexcitation in 2K-1C Hypertensive Rats

Hesperidin, a flavonoid derived from citrus fruits, possesses several beneficial effects including anti-oxidation and anti-inflammation. The aim of this study was to investigate the effects of hesperidin on the renin-angiotensin system (RAS) cascade that mediated oxidative stress and sympathoexcitation in two-kidney, one-clipped (2K-1C) hypertensive rats. 2K-1C hypertension was induced in male Sprague-Dawley rats. Hypertensive rats were treated with hesperidin at 20[Formula: see text]mg/kg or 40[Formula: see text]mg/kg or losartan at 10[Formula: see text]mg/kg beginning at three weeks after surgery and then continued for four weeks ([Formula: see text]/group). Hesperidin reduced blood pressure in a dose-dependent manner in hypertensive rats compared to untreated rats ([Formula: see text]). Increased plasma angiotensin converting enzyme (ACE) activity and angiotensin II levels, as well as, upregulated AT₁ receptor protein expression in aortic tissues were attenuated in hypertensive rats treated with hesperidin. Hesperidin suppressed oxidative stress markers and NADPH oxidase over-expression, and restored plasma nitric oxide metabolites in 2K-1C rats. This was associated with improvement of the vascular response to acetylcholine in isolated mesenteric vascular beds and aortic rings from 2K-1C rats treated with hesperidin ([Formula: see text]). Enhancement of nerve-mediated vasoconstriction related to high plasma noradrenaline in the 2K-1C group was alleviated by hesperidin treatment ([Formula: see text]). Furthermore, losartan exhibited antihypertensive effects by suppressing the RAS cascade and oxidative stress and improved vascular dysfunction observed in 2K-1C rats ([Formula: see text]). Based on these results, it can be presumed that hesperidin is an antihypertensive agent. Its antihypertensive action might be associated with reducing RAS cascade-induced NOX2 over-expression and sympathoexcitation in 2K-1C hypertensive rats.

Animal models for the study of primary and secondary hypertension in humans

Hypertension is a significant cause of morbidity and mortality worldwide. It is defined as systolic and diastolic blood pressures (SBP/DBP) >140 and 90 mmHg, respectively. Individuals with an SBP between 120 and 139, or DBP between 80 and 89 mmHg, are said to exhibit pre-hypertension. Hypertension can have primary or secondary causes. Primary or essential hypertension is a multifactorial disease caused by interacting environmental and polygenic factors. Secondary causes are renovascular hypertension, renal disease, endocrine disorders and other medical conditions. The aim of the present review article was to examine the different animal models that have been generated for studying the molecular and physiological mechanisms underlying hypertension. Their advantages, disadvantages and limitations will be discussed.

Animal Models in Cardiovascular Research: Hypertension and Atherosclerosis

Hypertension and atherosclerosis are among the most common causes of mortality in both developed and developing countries. Experimental animal models of hypertension and atherosclerosis have become a valuable tool for providing information on etiology, pathophysiology, and complications of the disease and on the efficacy and mechanism of action of various drugs and compounds used in treatment. An animal model has been developed to study hypertension and atherosclerosis for several reasons. Compared to human models, an animal model is easily manageable, as compounding effects of dietary and environmental factors can be controlled. Blood vessels and cardiac tissue samples can be taken for detailed experimental and biomolecular examination. Choice of animal model is often determined by the research aim, as well as financial and technical factors. A thorough understanding of the animal models used and complete analysis must be validated so that the data can be extrapolated to humans. In conclusion, animal models for hypertension and atherosclerosis are invaluable in improving our understanding of cardiovascular disease and developing new pharmacological therapies.

Renin, endothelial NO synthase and endothelin gene expression in the 2kidney-1clip Goldblatt model of long-term renovascular hypertension

Objective

Numerous reports have shown the influence of renin, nitric oxide (NO) and the endothelin (ET) systems for regulation of blood pressure and renal function. Furthermore, interactions between these peptides have been reported. Aim of our study was to investigate the relative contribution of these compounds in long-term renovascular hypertension/renal ischemia.

Methods

Hypertension/left-sided renal ischemia was induced using the 2K1C-Goldblatt rat model. Renal renin, ET-1, ET-3 and endothelial NO synthase (eNOS) gene expression was measured by means of RNAse protection assay at different timepoints up to 10 weeks after induction of renal artery stenosis.

Results

Plasma renin activity and renal renin gene expression in the left kidney were increased in the clipped animals while eNOS expression was unchanged. Furthermore, an increase in ET-1 expression and a decrease of ET-3 expression was detected in early stenosis.

Conclusions

While renin is obviously involved in regulation of blood pressure and renal function in unilateral renal artery stenosis, ET-1, ET-3 and endothelium derived NO do not appear to play an important role in renal adaptation processes in long-term renal artery stenosis, although ET-1 and ET-3 might be involved in short-term adaptation processes.

Dopamine and renal function and blood pressure regulation

Dopamine is an important regulator of systemic blood pressure via multiple mechanisms. It affects fluid and electrolyte balance by its actions on renal hemodynamics and epithelial ion and water transport and by regulation of hormones and humoral agents. The kidney synthesizes dopamine from circulating or filtered L-DOPA independently from innervation. The major determinants of the renal tubular synthesis/release of dopamine are probably sodium intake and intracellular sodium. Dopamine exerts its actions via two families of cell surface receptors, D1-like receptors comprising D1R and D5R, and D2-like receptors comprising D2R, D3R, and D4R, and by interactions with other G protein-coupled receptors. D1-like receptors are linked to vasodilation, while the effect of D2-like receptors on the vasculature is variable and probably dependent upon the state of nerve activity. Dopamine secreted into the tubular lumen acts mainly via D1-like receptors in an autocrine/paracrine manner to regulate ion transport in the proximal and distal nephron. These effects are mediated mainly by tubular mechanisms and augmented by hemodynamic mechanisms. The natriuretic effect of D1-like receptors is caused by inhibition of ion transport in the apical and basolateral membranes. D2-like receptors participate in the inhibition of ion transport during conditions of euvolemia and moderate volume expansion. Dopamine also controls ion transport and blood pressure by regulating the production of reactive oxygen species and the inflammatory response. Essential hypertension is associated with abnormalities in dopamine production, receptor number, and/or posttranslational modification.