Angiotensin II-dependent Hypertension Research Articles

Cardioprotective Effects of Sodium Glucose Cotransporter 2 Inhibition in Angiotensin II-Dependent Hypertension Are Mediated by the Local Reduction of Sympathetic Activity and Inflammation.

The cardioprotective effects of sodium glucose cotrasponter 2 (SGLT2) inhibitors seem to be independent from the effects on glycemic control, through little-known mechanisms. In this study, we investigate whether the cardioprotective effects of empagliflozin, a SGLT2 inhibitor, may be associated with myocardial sympathetic activity and inflammatory cell infiltration in an experimental model of angiotensin II-dependent hypertension. Angiotensin II (Ang II), Ang II plus Empagliflozin, physiological saline, or physiological saline plus empagliflozin were administered to Sprague Dawley rats for two weeks. Blood pressure was measured by plethysmographic method. Myocardial hypertrophy and fibrosis were analysed by histomorphometry, and inflammatory cell infiltration and tyrosine hydroxylase expression, implemented as a marker of sympathetic activity, were evaluated by immunohistochemistry. Ang II increased blood pressure, myocardial hypertrophy, fibrosis, inflammatory infiltrates and tyrosine hydroxylase expression, as compared to the control group. Empagliflozin administration prevented the development of myocardial hypertrophy, fibrosis, inflammatory infiltrates and tyrosine hydroxylase overexpression in Ang II-treated rats, without affecting blood glucose and the Ang II-dependent increase in blood pressure. These data demonstrate that the cardioprotective effects of SGLT2 inhibition in Ang II-dependent hypertension may result from the myocardial reduction of sympathetic activity and inflammation and are independent of the modulation of blood pressure and blood glucose levels.

Inappropriate activation of the renin-angiotensin system improves cardiac tolerance to ischemia/reperfusion injury in rats with late angiotensin II-dependent hypertension.

The aim of the study was to clarify the role of the interplay between hypertension and the renin-angiotensin system (RAS) in the pathophysiology of myocardial ischemia/reperfusion (I/R) injury. We hypothesized that in the late phase of hypertension with already developed signs of end-organ damage, inappropriate RAS activation could impair cardiac tolerance to I/R injury. Experiments were performed in male Cyp1a1-Ren-2 transgenic rats with inducible hypertension. The early phase of ANG II-dependent hypertension was induced by 5days and the late phase by the 13days dietary indole-3-carbinol (I3C) administration. Noninduced rats served as controls. Echocardiography and pressure-volume analysis were performed, angiotensins' levels were measured and cardiac tolerance to ischemia/reperfusion injury was studied. The infarct size was significantly reduced (by 50%) in 13days I3C-induced hypertensive rats with marked cardiac hypertrophy, this reduction was abolished by losartan treatment. In the late phase of hypertension there are indications of a failing heart, mainly in reduced preload recruitable stroke work (PRSW), but only nonsignificant trends in worsening of some other parameters, showing that the myocardium is in a compensated phase. The influence of the RAS depends on the balance between the vasoconstrictive and the opposed vasodilatory axis. In the initial stage of hypertension, the vasodilatory axis of the RAS prevails, and with the development of hypertension the vasoconstrictive axis of the RAS becomes stronger. We observed a clear effect of AT1 receptor blockade on maximum pressure in left ventricle, cardiac hypertrophy and ANG II levels. In conclusion, we confirmed improved cardiac tolerance to I/R injury in hypertensive hypertrophied rats and showed that, in the late phase of hypertension, the myocardium is in a compensated phase.

COMBINING RENIN-ANGIOTENSIN SYSTEM (RAS) BLOCKADE AND SODIUM-GLUCOSE COTRANSPORTER-2 (SGLT2) INHIBITION IN EXPERIMENTAL DIABETES RESULTS IN SYNERGISTIC BENEFICIAL EFFECTS

Objective: To study the combined effect of RAS blockade and SGLT2i in experimental diabetes. Design and method: TGR (mREN2)27 rats (a model of angiotensin II-dependent hypertension) were made diabetic with streptozotocin for 12 weeks and treated with either vehicle, the angiotensin receptor blocker valsartan (VAL: 4 mg/kg/day), the SGLT2 inhibitor empagliflozin (EMPA: 10 mg/kg/day) or their combination during the final 3 weeks. Mean arterial blood pressure (MAP) was measured by telemetry. Results: MAP before treatment was 120 ± 14 mm Hg. Diabetes resulted in albuminuria, accompanied by glomerulosclerosis, without a change in glomerular filtration rate (GFR). EMPA did not lower MAP, while VAL did (by 29 ± 7 mm Hg), and when combined the MAP drop was largest (44 ± 6 mm Hg). Only EMPA+VAL reduced the heart weight/tibia length ratio (P = 0.04 vs. vehicle). VAL, but not EMPA, increased plasma renin, and the largest renin rise was observed during EMPA+VAL (P < 0.0001 vs. vehicle) Although both VAL and EMPA alone tended to diminish albuminuria, the reduction was significant (P = 0.01 vs. vehicle) only when both drugs were combined (vehicle, VAL, EMPA and EMPA+VAL 108 ± 18, 89 ± 24, 55 ± 8 and 26 ± 6 ug/mL, respectively). This was accompanied by a reduction in glomerulosclerosis index and no change in GFR. EMPA either alone or in combination with VAL increased water intake and urine production and induced urinary glucose loss, and as a consequence reduced blood glucose and body weight. Renal expression of the fibrosis and inflammatory markers TIMP2, collagen 1alpha 1, fibronectin, Neph1, nephrin was lowest in the dual treatment group. Conclusions: RAS blockade and SGLT2i display synergistic beneficial effects on blood pressure, kidney jury and cardiac hypertrophy in a rat with hypertension and diabetes.

MYOCARDIAL REDUCTION OF SYMPATHETIC ACTIVITY IS INVOLVED IN THE ANTIFIBROTIC AND ANTIHYPERTROPHIC EFFECTS OF SGLT2 INHIBITION IN ANGIOTENSIN II-DEPENDENT HYPERTENSION

Objective: The beneficial myocardial effects of SGLT2 inhibitors, a new class of antidiabetic drugs, have been described not only in diabetic patients, but also in heart diseases not associated with diabetes. The positive effects of these drugs go beyond glycemic control and involve multiple mechanisms. In the present study we investigate whether the cardioprotective effects of empagliflozin, a SGLT2 inhibitor, may be dependent on myocardial sympathetic activity in experimental model of angiotensin II-dependent hypertension. Design and method: Experiments were performed in Sprague Dawley rats (n = 26) followed for 4 weeks and divided in the following groups: a) Angiotensin II-treated group (Ang II, 200 ng/kg/min, osmotic minipumps s.c, n = 7); b) Ang II +Empagliflozin-treated group (Empa, 10 mg/kg/day, per os, n = 6); c) control group (physiological saline s.c., n = 7); d) Control+Empagliflozin-treated group (n = 6). Systolic blood pressure was measured by tail cuff method. At the end of the experimental period myocardial interstitial fibrosis (Sirius Red staining) and myocardial hypertrophy were measured by histomorphometric analysis. Myocardial tyrosine hydroxylase expression, used as marker of sympathetic activity, was measured by immunohistochemistry. Results: Ang II caused a significant increase of blood pressure (p<0.0001), myocardial interstitial fibrosis (p<0.01), hypertrophy (p<0.01), and tyrosine hydroxylase expression (p<0.01) as compared to control groups. Empagliflozin treatment did not modify blood glucose in the different groups of rats. Empagliflozin administration did not modify the increase in blood pressure in Ang II treated rats, but prevented the development of myocardial fibrosis, hypertrophy, and tyrosine hydroxylase over-expression. Conclusions: These data demonstrate that in Ang II dependent hypertension Empagliflozin administration prevented the onset of myocardial fibrosis and hypertrophy through the reduction of local sympathetic activity. This effect is independent on the modulation of blood pressure and blood glucose levels.

611 - Angiotensin II type 1a receptors and Na+/H+ exchanger 3 in the proximal tubules play a key role in the development of angiotensin II-dependent hypertension in mice

611 - Angiotensin II type 1a receptors and Na+/H+ exchanger 3 in the proximal tubules play a key role in the development of angiotensin II-dependent hypertension in mice

PS-B12-2: ENDOTHELIN TYPE A RECEPTOR BLOCKADE ATTENUATES HEART FAILURE IN RATS WITH ANGIOTENSIN II-DEPENDENT HYPERTENSION.

Objective: Evaluation of the effects of endothelin type A (ETA) receptor blockade on the echocardiography, hemodynamic cardiac and renal parameters, and the course of high-output heart failure (HF) in rats with angiotensin II-dependent hypertension. Design and Methods: Eight-week-old male Ren-2 transgenic rats (TGR) were used as a model of angiotensin II-dependent hypertension. HF was induced by creating an aorto-caval fistula (ACF). Two weeks later, rats were divided into four groups: placebo (water) or three therapeutic groups (initial n minimum of 31 rats), and the treatment was initiated: in the first group, selective ETA receptor blockade was achieved by atrasentan, the second group received trandolapril, an angiotensin-converting enzyme inhibitor (ACEi), and the third was treated by combinational therapy (atrasentan + trandolapril), all in drinking water. The follow-up period was twenty weeks, then echocardiography, renal hemodynamics and albuminuria, invasive pressure-volume (P-V) analysis of left ventricle (LV), and organ weight measurement were done. Results: Eighteen days after creating ACF, untreated TGR began to die, and none was alive by day 79. Both atrasentan and trandolapril treatment improved the survival rate, ultimately to 56% (18 of 31 animals) and 69% (22 of 32 animals), respectively. Combined ACE and ETA receptor blockade improved the final survival rate to 52% (17 of 33 animals). The effects of the three treatment regimens on the survival rate did not significantly differ (Log-rank (Mantel-Cox) p = 0.345) (Figure 1, A). Untreated ACF TGR displayed marked renal dysfunction, cardiac hypertrophy, lung congestion, and impairment of LV contractility. None of the treatment regimens affected the progress of renal dysfunction, but they suppressed the albuminuria (Figure 1, B), development of cardiac hypertrophy and lung congestion and improved LV systolic function. Conclusion: The treatment with ETA receptor antagonist delays the onset of decompensation of volume-overload HF and improves the survival rate in hypertensive TGR similar to ACE inhibition.

AW-NI-3: EFFECTS OF RENAL DENERVATION ON LEFT AND RIGHT VENTRICULAR FUNCTION IN HYPERTENSIVE RATS WITH HEART FAILURE INDUCED BY VOLUME OVERLOAD

Objective: Clinical studies showed that renal denervation (RDN) is effective in blood pressure lowering in hypertension. Previously, we found that RDN prolongs survival in a hypertensive rodent model of heart failure due to volume overload from aorto-caval fistula (ACF). Whether it is due to afterload removal, or due to intrinsic effects of RDN on the right (RV) or left (LV) ventricular function, is currently unknown and was the focus of our investigation. Design and method: 8-week-old Ren-2 transgenic male rats (model of angiotensin II-dependent hypertension) underwent ACF surgery to induce volume overload. After one week, animals underwent bilateral RDN (mechanical and chemical by topical phenol application) from laparotomy. Two weeks after RDN, the functions of both ventricles were measured by simultaneous biventricular pressure-volume analysis, and the animals were examined using echocardiography each week. Results: RDN in ACF rats only slightly reduced maximum pressure in RV but did not affect maximum pressure in LV. Yet, RDN in ACF animals significantly reduced hypertrophy and dilatation of both ventricles and decreased lung and liver congestion. RDN in ACF rats improved load-independent measures of contractility of both ventricles (end-systolic elastance and preload recruitable stroke work). RDN in ACF rats reduced renal levels of norepinephrine (NE) but restored depleted NE both in RV and LV. At the gene expression level, RDN in ACF led to favorable remodeling which was reflected as increased transcription of beta-1 adrenergic receptors in LV and beta-2 adrenergic receptors in RV and LV, decreased transcription of natriuretic peptide A gene (NPPA), collagen 1, and monoaminoxidase A (MAOA). These changes were relatively more pronounced in RV than LV. Interestingly, RDN in ACF rats also significantly inhibited the activity of neprilysin in the kidney. Conclusions: Besides the effects on pressure, RDN favorably affected load-independent measures of chamber function, markers of myocardial remodeling, and restored myocardial norepinephrine levels. These data indicate that RDN effects extend beyond pressure lowering and could be a promising method in the treatment of both right and left ventricular heart failure.

Angiotensin II Modulates Calcium/Phosphate Excretion in Experimental Model of Hypertension: Focus on Bone.

A link between hypertension and long-term bone health has been suggested. The aim of this study was to investigate the effects of chronic angiotensin II administration on urinary calcium/phosphate excretion, bone mineral density, bone remodeling and osteoblast population in a well-established experimental model of hypertension, in the absence of possible confounding factors that could affect bone metabolism. Male Sprague-Dawley rats, divided in the following groups: (a) Angiotensin II (Ang II, 200 ng/kg/min, osmotic minipumps, sub cutis, n = 8); (b) Ang II+losartan (Los, 50 mg/kg/day, per os, n = 6); (c) control group (physiological saline, sub cutis, n = 9); and (d) control+losartan (n = 6) were treated for four weeks. During the experimental period, 24-hour diuresis, urinary calcium, phosphate and sodium excretion were measured prior to the treatment, at two weeks of treatment, and at the end of the treatment. Systolic blood pressure was measured by plethysmography technique (tail cuff method). At the end of the experimental protocol, the rats were euthanized and peripheral quantitative computed tomography at the proximal metaphysis and at the diaphysis of the tibiae and quantitative bone histomorphometry on distal femora were performed. Angiotensin II-dependent hypertension is associated with increased calcium and phosphate excretion. AT1 receptor blockade prevented the increase of blood pressure and phosphate excretion but did not affect the increase of calcium excretion. These changes took place without significantly affecting bone density, bone histology or osteoblast population. In conclusion, in our experimental conditions, angiotensin II-dependent hypertension gave rise to an increased urinary excretion of calcium and phosphate without affecting bone density.

Endothelin type A receptor blockade attenuates aorto-caval fistula-induced heart failure in rats with angiotensin II-dependent hypertension.

Evaluation of the effect of endothelin type A (ET A ) receptor blockade on the course of volume-overload heart failure in rats with angiotensin II-dependent hypertension. Ren-2 renin transgenic rats (TGR) were used as a model of hypertension. Heart failure was induced by creating an aorto-caval fistula (ACF). Selective ET A receptor blockade was achieved by atrasentan. For comparison, other rat groups received trandolapril, an angiotensin-converting enzyme inhibitor (ACEi). Animals first underwent ACF creation and 2 weeks later the treatment with atrasentan or trandolapril, alone or combined, was applied; the follow-up period was 20 weeks. Eighteen days after creating ACF, untreated TGR began to die, and none was alive by day 79. Both atrasentan and trandolapril treatment improved the survival rate, ultimately to 56% (18 of 31 animals) and 69% (22 of 32 animals), respectively. Combined ACEi and ET A receptor blockade improved the final survival rate to 52% (17 of 33 animals). The effects of the three treatment regimens on the survival rate did not significantly differ. All three treatment regimens suppressed the development of cardiac hypertrophy and lung congestion, decreased left ventricle (LV) end-diastolic volume and LV end-diastolic pressure, and improved LV systolic contractility in ACF TGR as compared with their untreated counterparts. The treatment with ET A receptor antagonist delays the onset of decompensation of volume-overload heart failure and improves the survival rate in hypertensive TGR with ACF-induced heart failure. However, the addition of ET A receptor blockade did not enhance the beneficial effects beyond those obtained with standard treatment with ACEi alone.

Blood pressure-independent renoprotective effects of small interference RNA targeting liver angiotensinogen in experimental diabetes.

Small interfering RNA (siRNA) targeting liver angiotensinogen lowers blood pressure, but its effects in hypertensive diabetes are unknown. To address this, TGR (mRen2)27 rats (angiotensin II-dependent hypertension model) were made diabetic with streptozotocin over 18 weeks and treated with either vehicle, angiotensinogen siRNA, the AT1 antagonist valsartan, the ACE inhibitor captopril, valsartan + siRNA or valsartan + captopril for the final 3weeks. Mean arterial pressure (MAP) was measured via radiotelemetry. MAP before treatment was 153 ± 2mmHg. Diabetes resulted in albuminuria, accompanied by glomerulosclerosis and podocyte effacement, without a change in glomerular filtration rate. All treatments lowered MAP and cardiac hypertrophy, and the largest drop in MAP was observed with siRNA + valsartan. Treatment with siRNA lowered circulating angiotensinogen by >99%, and the lowest circulating angiotensin II and aldosterone levels occurred in the dual treatment groups. Angiotensinogen siRNA did not affect renal angiotensinogen mRNA expression, confirming its liver-specificity. Furthermore, only siRNA with or without valsartan lowered renal angiotensin I. All treatments lowered renal angiotensin II and the reduction was largest (>95%) in the siRNA + valsartan group. All treatments identically lowered albuminuria, whereas only siRNA with or without valsartan restored podocyte foot processes and reduced glomerulosclerosis. Angiotensinogen siRNA exerts renoprotection in diabetic TGR (mRen2)27 rats and this relies, at least in part, on the suppression of renal angiotensin II formation from liver-derived angiotensinogen. Clinical trials should now address whether this is also beneficial in human diabetic kidney disease.

BLOOD PRESSURE-INDEPENDENT RENOPROTECTION IN DIABETIC RATS TREATED WITH SMALL INTERFERING RNA TARGETING LIVER ANGIOTENSINOGEN

Objective: Small interfering RNA (siRNA) targeting liver angiotensinogen (AGT) exerts beneficial effects on blood pressure and kidney function, but its effects in diabetes are still unknown. Design and method: To address this, TGR(mREN2)27 rats (a model of angiotensin II-dependent hypertension) were made diabetic with streptozotocin for 18 weeks and treated with vehicle, AGT siRNA, the angiotensin receptor blocker valsartan, the ACE inhibitor captopril, valsartan + siRNA, or valsartan + captopril for the final 3 weeks. Arterial pressure was measured via radiotelemetry. Results: Baseline mean arterial pressure (MAP) was 164 ± 1 mm Hg. Diabetes resulted in albuminuria, accompanied by glomerulosclerosis and podocyte effacement, without a further rise in MAP or a change in glomerular filtration rate. All treatments lowered MAP (by ~50 mm Hg) and cardiac hypertrophy identically. Treatment with siRNA resulted in the largest reduction in AGT, while in combination with valsartan AGT virtually disappeared. Only the dual treatment groups and captopril lowered circulating angiotensin II and aldosterone. No treatment affected renal AGT mRNA expression, confirming the liver-specificity of the siRNA. Yet, siRNA with or without valsartan, and valsartan + captopril, but not valsartan alone, or captopril alone, reduced renal angiotensin I and II. All treatments lowered albuminuria and proteinuria, while only siRNA with or without valsartan improved glomerulosclerosis and podocyte dysfunction. Multiple linear regression confirmed both mean arterial pressure and renal angiotensin II as independent determinants of albuminuria. Conclusions: In conclusion, AGT siRNA exerts renoprotection in diabetic TGR(mREN2)27 rats, and this relies, at least in part, on the suppression of renal angiotensin II formation from liver-derived AGT. Consequently, AGT siRNA may prove beneficial in human diabetic kidney disease.

Abstract 9961: Combination Therapy with Selective Endothelin Type A Receptor Blockade and Angiotensin-converting Enzyme Blockade Improves Survival of Congestive Heart Failure Similarly to Both Monotherapies: Study in Ren-2 Transgenic Hypertensive Rats with Aorto-Caval Fistula

Introduction: New therapeutic strategies for congestive heart failure (CHF) are needed, and the current knowledge, including our previous studies, suggests that targeting the endothelin (ET) system could be a promising approach. Hypothesis: Chronic selective blockade of ET type A (ETA) receptors combined with angiotensin-converting enzyme inhibitor (ACEi) would attenuate the course of CHF induced by volume overload achieved by the creation of the aorto-caval fistula (ACF). Methods: ACF was created in Ren-2 transgenic rats (TGR), a model of angiotensin II-dependent hypertension, at the animal age of 8 weeks. Two weeks later the animals were randomly divided into four groups and the therapy began: chronic selective blockade of ETA receptors with atrasentan (ETA block.) (5 mg.kg-1.day-1 in drinking water, n = 31), angiotensin-converting enzyme inhibitor (ACEi) (trandolapril, 2 mg.L-1 in drinking water, n = 32), a combination of atrasentan plus trandolapril (ETA block. + ACEi) ( 5 mg.kg-1.day-1 + 2 mg.L-1 in drinking water, n = 31) or placebo (n = 30). Sham-operated TGR represented a control group (n = 8). The follow-up period was 20 weeks. GraphPad Prism 7 was used for statistical analysis with a log-rank (Mantel-Cox) test to analyze survival data. Results: All sham-operated rats survived till the end of the study. Contrary, all untreated CHF rats died by week 12. The treatment with the ETA block. or with ACEi similarly improved the survival rate, and the final rate was 45 % in ETA block. group (p < 0,01) and 62 % in ACEi group (p < 0,01), the combinational therapy (ETA block. + ACEi) improved survival rate over placebo (52 %, p < 0,01) but not compared with both monotherapies. Conclusions: Our present results suggest that in ACF TGR, the combination treatment with ETA block. and ACEi did not markedly attenuate CHF-dependent mortality over both monotherapies. Thus, more preclinical research needs to be done to deeper understand the endothelin system in CHF.

Potential therapeutic efficacy via avB3-integrin dependent interaction of developmental endothelial locus-1 (Del-1) after established angiotensin-II dependent hypertension

Abstract Introduction Cardiovascular diseases (CVDs) contribute to about 31% of global death. Hypertension is a major risk factor and also increases the risk of CVDs. An important regulator of systemic blood pressure in the body, the Renin Angiotensin Aldosterone system becomes overactivated during hypertension releasing a critical product, angiotensin-II (ANG-II), a known vasoconstrictor, activating the immune system leading to inflammation and as such mediating the effects of hypertension and subsequent end-organ damage due to the critical role of the innate and adaptive cells in producing pro-inflammatory cytokines such interleukin-17. Del-1, an extracellular matrix protein expressed mostly by endothelial cells is a known potent inhibitor of leukocyte recruitment. Aim We tested the hypothesis that, Del-1 via αvβ3-integrin dependent interaction protects against ANG-II induced cardiovascular remodeling after established hypertension. Methods Wild type (WT) mice were infused with 2 mg/kg/day of ANG-II for 14 days. Soluble Del-1 (Del-1-Fc) and a point mutant unable to bind to αvβ3-integrin (Del-1-RGE-Fc) was injected (50 μg/per injection) daily after 6 days of ANG-II infusion. SBP was measured using tail-cuff. Endothelial function was assessed using Mulvany myograph and quantification of inflammatory cells and IL-17 by flow cytometry. Histological staining for fibrosis, myocardial/medial hypertrophy and elastin degradation was used to evaluate both aortic and cardiac remodeling. Results After 6 days, mice infused with ANG-II showed significantly higher SBP of 140 mmHg as compared to control mice (110 mmHg). However, further progression of SBP after 6 days was blunted in infused mice treated with soluble Del-1 (ANGII+Del-1-Fc) as compared to similar increase in SBP in both infused mice treated with the point mutant (ANGII+Del-1-RGE-Fc) and non-treated infused mice (ANGII+Fc) leading to a difference of ∼20 mmHg. This effect was due to, the well protected endothelium dependent relaxation and reduced wall tension of the aorta in ANGII+Del-1-Fc mice. Further infiltration of CD45+ leukocytes, CD45+/IL-17A+ and TCRβ+T cells was significantly reduced in the aorta and heart of ANGII+Del-1-Fc mice as compared to both ANGII+Del-1-RGE-Fc and ANGII+Fc mice. However, the aorta and heart of ANGII+Del-1-Fc mice showed increased levels of anti-inflammatory regulatory T-cells (CD25+FOXP3+Treg). Also, aortic medial thickness, adventitial collagen and elastin degradation was decreased significantly in ANGII+Del-1-Fc mice. Additionally, in comparison to both ANGII+Del-1-RGE-Fc and ANGII+Fc mice, the hearts of ANGII+Del-1-Fc mice had significantly less interstitial and pericoronary collagen, smaller cardiomyocyte area and subsequently higher lumen-to-wall ratio. Conclusion Our study reveals the cardiovascular protective effects of Del-1 mediated via its association with αvβ3-integrin after established hypertension which could serve as potential therapeutic target. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): German Research Foundation (DFG)National Institutes of Health (NIH)

The promoting role of Cx43 on the proliferation and migration of arterial smooth muscle cells for angiotensin II-dependent hypertension

BackgroundRecent studies have shown that endothelin-1 and angiotensin II (AngII) can increase gap junctional intercellular communication (GJIC) by activating Mitogen-activated protein kinases (MAPKs) pathway. However, not only the precise interaction of AngII with Connexin43(Cx43) and the associated functions remain unclear, but also the regulatory role of Cx43 on the AngII-mediated promotion proliferation and migration of VSMCs is poorly understood. Material and methodsOur research applicated pressure myography measurements, immunofluorescence and Western blot analyses to investigate the changes in physiological indicators in spontaneously hypertensive rats (SHRs) and AngII-stimulated proliferation and migration of A7r5 SMCs(Rat vascular smooth muscle cells). The aim was to elucidate the role of CX43 in hypertension induced by AngII. ResultsChronic ramipril (angiotensin converting enzyme inhibitor) management for SHRs significantly attenuated blood pressure and blood vessel wall thickness, also reduced contraction rate in the cerebral artery. The cerebral artery contraction rates, mRNA and protein expression of Cx43, osteopontin (OPN) and proliferating cell nuclear antigen (PCNA) protein expression in the SHR + ramipril and SHR + ramipril + carbenoxolone (CBX, Cx43 specific blocker) groups were significantly lower than those in the SHR group. Cx43 protein expression and Ser368 phosphorylated Cx43 protein levels increased significantly in AngII-stimulated A7r5 cells. However, the levels of phosphorylated Cx43 decreased after pre-treatment with candesartan (AT1 receptor blocker), GF109203X (protein kinase C (PKC) blocker) and U0126 (mitogen-activated protein kinases/extracellular signal-regulated kinase1/2(MEK/ERK1/2)-specific blocker) in AngII-stimulated A7r5 cells. Cx43 was widely distributed in the cell membrane, nucleus, and cytoplasm of the SMCs. Furthermore, pre-treatment of the AngII- stimulated A7r5 cells with Gap26 (Cx43 blocker) significantly inhibited cell migration and decreased the expression levels of MEK1/2, ERK1/2, P-MEK1/2, and P-ERK1/2. ConclusionOur research confirms that Cx43 plays an important role in the regulation of proliferation and migration of VSMCs via MEK/ERK and PKC signal pathway in AngII-dependent hypertension.

Effects of Epoxyeicosatrienoic Acid-Enhancing Therapy on the Course of Congestive Heart Failure in Angiotensin II-Dependent Rat Hypertension: From mRNA Analysis towards Functional In Vivo Evaluation.

This study evaluates the effects of chronic treatment with EET-A, an orally active epoxyeicosatrienoic acid (EETs) analog, on the course of aorto-caval fistula (ACF)-induced heart failure (HF) in Ren-2 transgenic rats (TGR), a model characterized by hypertension and augmented activity of the renin-angiotensin system (RAS). The results were compared with standard pharmacological blockade of the RAS using angiotensin-converting enzyme inhibitor (ACEi). The rationale for employing EET-A as a new treatment approach is based on our findings that apart from increased RAS activity, untreated ACF TGR also shows kidney and left ventricle (LV) tissue deficiency of EETs. Untreated ACF TGR began to die 17 days after creating ACF and were all dead by day 84. The treatment with EET-A alone or ACEi alone improved the survival rate: in 156 days after ACF creation, it was 45.5% and 59.4%, respectively. The combined treatment with EET-A and ACEi appeared to improve the final survival to 71%; however, the difference from either single treatment regimen did not reach significance. Nevertheless, our findings support the notion that targeting the cytochrome P-450-dependent epoxygenase pathway of arachidonic acid metabolism should be considered for the treatment of HF.

Increased Endogenous Activity of the Renin-Angiotensin System Reduces Infarct Size in the Rats with Early Angiotensin II-dependent Hypertension which Survive the Acute Ischemia/Reperfusion Injury.

We investigated the role of the interaction between hypertension and the renin-angiotensin system in the pathophysiology of myocardial ischemia/reperfusion injury. We hypothesized that in the early phase of angiotensin II (ANG II)-dependent hypertension with developed left ventricular hypertrophy, cardioprotective mechanism(s) are fully activated. The experiments were performed in transgenic rats with inducible hypertension, noninduced rats served as controls. The early phase of ANG II-dependent hypertension was induced by five-days (5 days) dietary indole-3-carbinol administration. Cardiac hypertrophy, ANG II and ANG 1–7 levels, protein expression of their receptors and enzymes were determined. Separate groups were subjected to acute myocardial ischemia/reperfusion injury, and infarct size and ventricular arrhythmias were assessed. Induced rats developed marked cardiac hypertrophy accompanied by elevated ANG levels. Ischemia/reperfusion mortality was significantly higher in induced than noninduced rats (52.1 and 25%, respectively). The blockade of AT1 receptors with losartan significantly increased survival rate in both groups. Myocardial infarct size was significantly reduced after 5 days induction (by 11%), without changes after losartan treatment. In conclusion, we confirmed improved cardiac tolerance to ischemia/reperfusion injury in hypertensive cardiohypertrophied rats and found that activation of AT1 receptors by locally produced ANG II in the heart was not the mechanism underlying infarct size reduction.

MiR-124-3p reduces angiotensin II-dependent hypertension by down-regulating EGR1.

Through previous literature studies, we found that miR-124-3p may be associated with hypertension. Therefore, we investigated the relationship between miR-124-3p and hypertension in Human Umbilical Vein Endothelial Cells (HUVECs) induced by angiotensin II (AngII). AngII-induced HUVECs model was constructed and the expression of miR-124-3p was detected by qRT-PCR. After transfected cells, apoptosis and ROS production were detected by flow cytometry, caspase-3 kit, and DCFH-DA staining. The target genes of miR-124-3p were predicted and verified by TargrtScan, Luciferase assay, qRT-PCR, and western blot. After silencing Early growth response factor 1 (siEGR1), its effects on apoptosis and ROS production were explored. Finally, the rescue experiments were conducted to explore the mechanism of miR-124-3p to reduce hypertension. MiR-124-3p was underexpressed in the cell model. In Ang II-induced HUVECs, the number of apoptosis increased, the content of caspase-3 was higher, and ROS production increased. However, these effects could be partially inhibited by miR-124-3p mimic. EGR1 was down-regulated by miR-124-3p, and siEGR1 was able to inhibit apoptosis and ROS production of cell model. In the final rescue experiments, miR-124-3p partially reversed the effect of Ang-II on the viability, migration, invasion and apoptosis and ROS production in HUVECs by down-regulating EGR1. MiR-124-3p inhibits Ang II-induced apoptosis and ROS production in HUVECs by down-regulating EGR1.

Angiotensin-neprilysin inhibition confers renoprotection in rats with diabetes and hypertension by limiting podocyte injury.

Combined angiotensin receptor--neprilysin inhibition (ARNI) reduces glomerulosclerosis better than single angiotensin receptor blockade (ARB) in diabetic, hypertensive rats. The renoprotective mechanism remains unknown, but may depend on superior blood pressure control, improved renal hemodynamics, suppressed renal inflammation or prevention of podocyte loss. To address this, TGR(mREN2)27 rats (a model of angiotensin II-dependent hypertension) were made diabetic for 12 weeks and treated with vehicle (n = 10), valsartan (ARB; n = 7) or sacubitril/valsartan (ARNI; n = 8) for the final 3 weeks. Arterial pressure was measured via radiotelemetry. Sacubitril/valsartan lowered mean arterial pressure by -50 ± 4 mmHg and valsartan by -43 ± 4 mmHg (P = 0.3). Both treatments lowered albuminuria, but only sacubitril/valsartan maintained high urinary atrial natriuretic peptide, improved glycemic control and protected podocyte integrity, reflected by increased nephrin expression and suppression of transient receptor potential canonical 6 and regulator of calcineurin 1. This resulted in markedly reduced glomerulosclerosis (P < 0.05 vs. control and valsartan). Despite higher effective renal plasma flow and glomerular filtration rates, sacubitril/valsartan did neither improve filtration fraction nor renal immune cell infiltration. Sacubitril/valsartan offers drug-class-specific renoprotection in a preclinical model of diabetes and hypertension. Renoprotection is unrelated to antihypertensive efficacy, renal hemodynamics or inflammation, but may be related to protective effects of natriuretic peptides on podocyte integrity.

α2A-Adrenoceptors Modulate Renal Sympathetic Neurotransmission and Protect against Hypertensive Kidney Disease.

Increased nerve activity causes hypertension and kidney disease. Recent studies suggest that renal denervation reduces BP in patients with hypertension. Renal NE release is regulated by prejunctional α2A-adrenoceptors on sympathetic nerves, and α2A-adrenoceptors act as autoreceptors by binding endogenous NE to inhibit its own release. However, the role of α2A-adrenoceptors in the pathogenesis of hypertensive kidney disease is unknown. We investigated effects of α2A-adrenoceptor-regulated renal NE release on the development of angiotensin II-dependent hypertension and kidney disease. In uninephrectomized wild-type and α2A-adrenoceptor-knockout mice, we induced hypertensive kidney disease by infusing AngII for 28 days. Urinary NE excretion and BP did not differ between normotensive α2A-adrenoceptor-knockout mice and wild-type mice at baseline. However, NE excretion increased during AngII treatment, with the knockout mice displaying NE levels that were significantly higher than those of wild-type mice. Accordingly, the α2A-adrenoceptor-knockout mice exhibited a systolic BP increase, which was about 40 mm Hg higher than that found in wild-type mice, and more extensive kidney damage. In isolated kidneys, AngII-enhanced renal nerve stimulation induced NE release and pressor responses to a greater extent in kidneys from α2A-adrenoceptor-knockout mice. Activation of specific sodium transporters accompanied the exaggerated hypertensive BP response in α2A-adrenoceptor-deficient kidneys. These effects depend on renal nerves, as demonstrated by reduced severity of AngII-mediated hypertension and improved kidney function observed in α2A-adrenoceptor-knockout mice after renal denervation. Our findings reveal a protective role of prejunctional inhibitory α2A-adrenoceptors in pathophysiologic conditions with an activated renin-angiotensin system, such as hypertensive kidney disease, and support the concept of sympatholytic therapy as a treatment.

G Protein-Coupled Estrogen Receptor Protects From Angiotensin II-Induced Increases in Pulse Pressure and Oxidative Stress.

Our previous work showed that the G protein-coupled estrogen receptor (GPER) is protective in the vasculature and kidneys during angiotensin (Ang) II-dependent hypertension by inhibiting oxidative stress. The goal of the current study was to assess the impact of GPER deletion on sex differences in Ang II-induced hypertension and oxidative stress. Male and female wildtype and GPER knockout mice were implanted with radiotelemetry probes for measurement of baseline blood pressure before infusion of Ang II (700 ng/kg/min) for 2 weeks. Mean arterial pressure was increased to the same extent in all groups, but female wildtype mice were protected from Ang II-induced increases in pulse pressure, aortic wall thickness, and Nox4 mRNA. In vitro studies using vascular smooth muscle cells found that pre-treatment with the GPER agonist G-1 inhibited Ang II-induced ROS and NADP/NADPH. Ang II increased while G-1 decreased Nox4 mRNA and protein. The effects of Ang II were blocked by losartan and Nox4 siRNA, while the effects of G-1 were inhibited by adenylyl cyclase inhibition and mimicked by phosphodiesterase inhibition. We conclude that during conditions of elevated Ang II, GPER via the cAMP pathway suppresses Nox4 transcription to limit ROS production and prevent arterial stiffening. Taken together with our previous work, this study provides insight into how acute estrogen signaling via GPER provides cardiovascular protection during Ang II hypertension and potentially other diseases characterized by increased oxidative stress.