The benefit of angiotensin AT1 receptor blockers for early treatment of hypertensive patients

Brain renin-angiotensin system in broiler chickens with cold-induced pulmonary hypertension

1. The relative expression of angiotensinogen (AGT), renin, angiotensin-converting enzyme (ACE) and angiotensin II type 1 receptor (AT₁R) was determined using quantitative real-time PCR on tissue from the brain (forebrain, midbrain and hindbrain) to investigate the effect of cold-induced pulmonary hypertension syndrome (PHS) in broilers aged 42 days. Brain angiotensin II (Ang II) and AT₁R levels were measured using enzyme immunoassay. 2. The right ventricle/total ventricles (RV/TV) ratio of the heart was increased in broilers exposed to cold stress (PHS group) at the end of the experiment. 3. ACE and renin transcripts in three parts of the brain were significantly increased in the PHS group at 42 d of age compared to controls while AGT transcript was significantly increased only in the hindbrain of PHS birds. The amount of AT1R transcript did not differ between control and PHS groups. 4. The amount of Ang II significantly decreased only in the midbrain of PHS birds compared with controls while the amounts of AT₁R were not different between treatments in the three segments of the brain. 5. It was concluded that brain gene expression of AGT (in the hindbrain), renin, and ACE was upregulated in broilers with PHS whereas Ang II and AT1R levels were not changed. These results provided evidence of diminished involvement of the renin-angiotensin system in the pathogenesis of chicken pulmonary hypertension.

Naringenin Ameliorates Renovascular Hypertensive Renal Damage by Normalizing the Balance of Renin-Angiotensin System Components in Rats

Background: Naringenin, a member of the dihydroflavone family, has been shown to have a protective function in multiple diseases. We previously demonstrated that naringenin played a protective role in hypertensive myocardial hypertrophy by decreasing angiotensin-converting enzyme (ACE) expression. The kidney is a primary target organ of hypertension. The present study tested the effect of naringenin on renovascular hypertensive kidney damage and explored the underlying mechanism. Methods and Results: An animal model of renovascular hypertension was established by performing 2-kidney, 1-clip (2K1C) surgery in Sprague Dawley rats. Naringenin (200 mg/kg/day) or vehicle was administered for 10 weeks. Blood pressure and urinary protein were continuously monitored. Plasma parameters, renal pathology and gene expression of nonclipped kidneys were evaluated by enzyme-linked immunosorbent assay, histology, immunohistochemistry, real-time polymerase chain reaction, and Western blot at the end of the study. Rats that underwent 2K1C surgery exhibited marked elevations of blood pressure and plasma Ang II levels and renal damage, including mesangial expansion, interstitial fibrosis, and arteriolar thickening in the nonclipped kidneys. Naringenin significantly ameliorated hypertensive nephropathy and retarded the rise of Ang II levels in peripheral blood but had no effect on blood pressure. 2K1C rats exhibited increases in the ACE/ACE2 protein ratio and AT1R/AT2R protein ratio in the nonclipped kidney compared with sham rats, and these increases were significantly suppressed by naringenin treatment. Conclusions: Naringenin attenuated renal damage in a rat model of renovascular hypertension by normalizing the imbalance of renin-angiotensin system activation. Our results suggest a potential treatment strategy for hypertensive nephropathy.

Angiotensin II enhances the acetylation and release of HMGB1 in RAW264.7 macrophage

The high-mobility group box-1 (HMGB1), as a highly conserved ubiquitous DNA-binding protein, has been widely studied in various diseases, including inflammation and tumor; however, fewer studies were focused on the mechanisms controlling HMGB1 release compared with the function of HMGB1. Previous studies have proven that ANG II can act as a pro-inflammatory cytokine, both of HMGB1 and ANG II were significantly upregulated in autoimmune diseases; however, the exact role of ANG II in regulating HMGB1 release have not been shown. The present study was to define the effects of ANG II on macrophages and the possible mechanisms in controlling HMGB1 release. Our results showed that ANG II can induce M1 macrophage polarization through upregulated the expression of HMGB1 and caused acetylation of HMGB1 and release via its dissociation from SIRT1, which in a positive feedback upregulates ANG II. Subsequently, HMGB1 inhibitors can reduce the ANG II-elicited polarize of macrophage. Meanwhile, we show that JAK/STAT pathways play an essential role in ANG II-induced HMGB1 nuclear translocation, JAK/STAT specific inhibitors can inhibit ANG II-induced HMGB1 expression. Taken together, our results provide a novel evidence that HMGB1 play a critical role in ANG II mediated macrophage polarization, and we suggest that ANG II mediated HMGB1 release via dissociation from SIRT1, induce hyperacetylation of HMGB1, thus for subsequent release, suggesting that the angiotensin II receptor antagonist is a potential drug target for inhibiting HMGB1 release in inflammation diseases.

Interplay between the renin-angiotensin system, the canonical WNT/β-catenin pathway and PPARγ in hypertension

PURPOSE OF REVIEW

Heterogeneous causes can determinate hypertension.

RECENT FINDINGS

The renin-angiotensin system (RAS) has a major role in the pathophysiology of blood pressure. Angiotensin II and aldosterone are overexpressed during hypertension and lead to hypertension development and its cardiovascular complications. In several tissues, the overactivation of the canonical WNT/β-catenin pathway leads to inactivation of peroxisome proliferator-activated receptor gamma (PPARγ), while PPARγ stimulation induces a decrease of the canonical WNT/β-catenin pathway. In hypertension, the WNT/β-catenin pathway is upregulated, whereas PPARγ is decreased. The WNT/β-catenin pathway and RAS regulate positively each other during hypertension, whereas PPARγ agonists can decrease the expression of both the WNT/β-catenin pathway and RAS. We focus this review on the hypothesis of an opposite interplay between PPARγ and both the canonical WNT/β-catenin pathway and RAS in regulating the molecular mechanism underlying hypertension. The interactions between PPARγ and the canonical WNT/β-catenin pathway through the regulation of the renin-angiotensin system in hypertension may be an interesting way to better understand the actions and the effects of PPARγ agonists as antihypertensive drugs.