Objective:To explore the alteration of brain‐derived neurotrophic factor (BDNF) signaling and the influ‐ence of irbesartan on it in hippocampus of angiotensin‐converting enzyme 2 (ACE2) knock‐out (KO) mice . Meth‐ods:The 10~11‐week ACE2 KO (Ace2/y ) mice received daily treatment with angiotensin II (Ang II) type 1 (AT1) receptor blocker irbesartan (50 mg/kg) or placebo for two weeks. The wild‐type mice (WT ,Ace2+ /y ) were regarded as normal control. Western blotting method was used to measure levels of BDNF and extracellular signal regulated kinase 1/2 (ERK1/2) in the mice hippocampus. Radioimmunoassay was used to measure plasma Ang level in mice . Results :Compared with normal WT control mice ,there were significant down‐regulations of BDNF protein expres‐sion [ (1 ± 0.16) vs .(0.54 ± 0.16)] in hippocampus and plasma Ang‐ (1‐7) level [ (55.6 ± 7.5) pg/ml vs .(42.8 ± 5.8) pg/ml] ,and significant rise in ERK1/2 phosphorylation [ (1 ± 0.28) vs .(1.79 ± 0.29)] in ACE2 KO mice (P<0.01 all). After irbesartan treatment ,there were significant rise in BDNF protein expression (0.88 ± 0.13) in hippocampus and plasma Ang‐ (1‐7) level [(59.4 ± 8.4) pg/ml] ,and significant reduction in ERK1/2 phosphoryla‐tion level (1.33 ± 0.19) in ACE2 KO mice (P<0.05 or <0.01) .Conclusion:There are BDNF protein expression down‐regulation and enhanced ERK1/2 phosphorylation in hippocampus of ACE2 KO mice. AT1 receptor blockade irbesartan can improve Ang‐ (1‐7 ) level and hippocampus BDNF expression , while reducing hippocampus ERK phosphorylation signal in ACE2 KO mice ,suggesting that AT1 receptor blockade possesses certain brain protective effect.

AIM:To investigate regulatory roles of Apelin in adventitial remodeling and fibrosis in rats with transverse aortic constriction ( TAC) .METHODS:The male Sprague-Dawley rats with TAC were randomized to daily deliver either pyroglutamyl Apelin-13 ( 50μg/kg) or saline for 4 weeks.RESULTS:Histomorphometric analysis by HE and Masson Trichrome staining revealed increased medi -al and adventitial thicknesses , especially in the adventitia , in ascending aortas in rats with TAC when compared with the sham-operated rats.Downregulation of APJ receptor and elevations in phosphorylated mTOR and ERK 1/2 levels were observed in rats with TAC . There are marked increases in heart weight ( HW) , HW/body weight ratio , and aortic fibrosis in rats with TAC .The pressure over-load-mediated pathological adventitial remodeling was strikingly rescued by Apelin-13, associated with attenuation of aortic fibrosis and reduced mRNA expression of TGF-β1, fibronectin and collagen I .CONCLUSION:Our results demonstrate the importance of Apelin-13 in amelioration of aortic adventitial remodeling and fibrosis in rats with TAC via modulation of the mTOR /ERK signaling , thus indi-cating potential therapeutic strategies by enhancing Apelin /APJ action for preventing pressure overload-and fibrosis-associated cardio-vascular disorders .