Azilsartan ameliorates ventricular hypertrophy in rats suffering from pressure overload-induced cardiac hypertrophy by activating the Keap1-Nrf2 signalling pathway.

OBJECTIVES: Investigate if azilsartan protects against myocardial hypertrophy by upregulating nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated pathways. METHODS: Abdominal aortic constriction (AAC)-induced cardiac hypertrophy in rats was applied. Azilsartan or vehicle was administered daily for 6 weeks in sham or AAC rats. Cardiac morphology and ventricular function were determined. Azilsartan effects upon neonatal rat cardiomyocyte (NRCM) hypertrophy and molecular mechanisms were studied in angiotensin (Ang) II-stimulated NRCMs in vitro. Nrf2-small interfering RNA (siRNA) was used to knockdown Nrf2 expression. Messenger RNA (mRNA)/protein expression of Kelch-like erythroid cell-derived protein (Keap)1 and Nrf2 and its downstream antioxidant enzymes was determined by real-time reverse transcription-quantitative polymerase chain reaction and western blotting, respectively. KEY FINDINGS: Azilsartan treatment ameliorated cardiac hypertrophy/fibrosis significantly in AAC rats. Azilsartan increased expression of Nrf2 protein but decreased expression of Keap1 protein. Upregulation of protein expression of Nrf2's downstream antioxidant enzymes by azilsartan treatment was observed. Azilsartan inhibited Ang II-induced NRCM hypertrophy significantly and similar effects on the Keap1-Nrf2 pathway were observed in vivo. Nrf2 knockdown markedly counteracted the beneficial effects of azilsartan on NRCM hypertrophy and the Keap1-Nrf2 pathway. CONCLUSIONS: Azilsartan restrained pressure overload-induced cardiac remodelling by activating the Keap1-Nrf2 pathway and increasing expression of downstream antioxidant enzymes to alleviate oxidative stress.

Puerarin ameliorated pressure overload-induced cardiac hypertrophy in ovariectomized rats through activation of the PPARα/PGC-1 pathway.

Estrogen deficiency induces cardiac dysfunction and increases the risk of cardiovascular disease in postmenopausal women and in those who underwent bilateral oophorectomy. Previous evidence suggests that puerarin, a phytoestrogen, exerts beneficial effects on cardiac function in patients with cardiac hypertrophy. In this study, we investigated whether puerarin could prevent cardiac hypertrophy and remodeling in ovariectomized, aortic-banded rats. Female SD rats subjected to bilateral ovariectomy (OVX) plus abdominal aortic constriction (AAC). The rats were treated with puerarin (50 mg·kg-1 ·d-1, ip) for 8 weeks. Then echocardiography was assessed, and the rats were sacrificed, their heart tissues were extracted and allocated for further experiments. We showed that puerarin administration significantly attenuated cardiac hypertrophy and remodeling in AAC-treated OVX rats, which could be attributed to activation of PPARα/PPARγ coactivator-1 (PGC-1) pathway. Puerarin administration significantly increased the expression of estrogen-related receptor α, nuclear respiratory factor 1, and mitochondrial transcription factor A in hearts. Moreover, puerarin administration regulated the expression of metabolic genes in AAC-treated OVX rats. Hypertrophic changes could be induced in neonatal rat cardiomyocytes (NRCM) in vitro by treatment with angiotensin II (Ang II, 1 µM), which was attenuated by co-treatemnt with puerarin (100 µM). We further showed that puerarin decreased Ang II-induced accumulation of non-esterified fatty acids (NEFAs) and deletion of ATP, attenuated the Ang II-induced dissipation of the mitochondrial membrane potential, and improved the mitochondrial dysfunction in NRCM. Furthermore, addition of PPARα antagonist GW6471 (10 µM) partially abolished the anti-hypertrophic effects and metabolic effects of puerarin in NRCM. In conclusion, puerarin prevents cardiac hypertrophy in AAC-treated OVX rats through activation of PPARα/PGC-1 pathway and regulation of energy metabolism remodeling. This may provide a new approach to prevent the development of heart failure in postmenopausal women.

Contributions of Nrf2 to Puerarin Prevention of Cardiac Hypertrophy and its Metabolic Enzymes Expression in Rats.

Previous evidence has suggested that puerarin may attenuate cardiac hypertrophy; however, the potential mechanisms have not been determined. Moreover, the use of puerarin is limited by severe adverse events, including intravascular hemolysis. This study used a rat model of abdominal aortic constriction (AAC)-induced cardiac hypertrophy to evaluate the potential mechanisms underlying the attenuating efficacy of puerarin on cardiac hypertrophy, as well as the metabolic mechanisms of puerarin involved. We confirmed that puerarin (50 mg/kg per day) significantly attenuated cardiac hypertrophy, upregulated Nrf2, and decreased Keap1 in the myocardium. Moreover, puerarin significantly promoted Nrf2 nuclear accumulation in parallel with the upregulated downstream proteins, including heme oxygenase 1, glutathione transferase P1, and NAD(P)H:quinone oxidoreductase 1. Similar results were obtained in neonatal rat cardiomyocytes (NRCMs) treated with angiotensin II (Ang II; 1 µM) and puerarin (100 µM), whereas the silencing of Nrf2 abolished the antihypertrophic effects of puerarin. The mRNA and protein levels of UGT1A1 and UGT1A9, enzymes for puerarin metabolism, were significantly increased in the liver and heart tissues of AAC rats and Ang II-treated NRCMs. Interestingly, the silencing of Nrf2 attenuated the puerarin-induced upregulation of UGT1A1 and UGT1A9. The results of chromatin immunoprecipitation-quantitative polymerase chain reaction indicated that the binding of Nrf2 to the promoter region of Ugt1a1 or Ugt1a9 was significantly enhanced in puerarin-treated cardiomyocytes. These results suggest that Nrf2 is the key regulator of antihypertrophic effects and upregulation of the metabolic enzymes UGT1A1 and UGT1A9 of puerarin. The autoregulatory circuits between puerarin and Nrf2-induced UGT1A1/1A9 are beneficial to attenuate adverse effects and maintain the pharmacologic effects of puerarin.

Nrf2 Is a Key Regulator on Puerarin Preventing Cardiac Fibrosis and Upregulating Metabolic Enzymes UGT1A1 in Rats.

Puerarin is an isoflavone isolated from Radix puerariae. Emerging evidence shown that puerarin possesses therapeutic benefits that aid in the prevention of cardiovascular diseases. In this study, we evaluated the effects of puerarin on oxidative stress and cardiac fibrosis induced by abdominal aortic banding (AB) and angiotensin II (AngII). We also investigated the mechanisms underlying this phenomenon. The results of histopathological analysis, as well as measurements of collagen expression and cardiac fibroblast proliferation indicated that puerarin administration significantly inhibited cardiac fibrosis induced by AB and AngII. These effects of puerarin may reflect activation of Nrf2/ROS pathway. This hypothesis is supported by observed decreases of reactive oxygen species (ROS), decreases Keap 1, increases Nrf2 expression and nuclear translocation, and decreases of collagen expressions in cardiac fibroblasts treated with a combination of puerarin and AngII. Inhibition of Nrf2 with specific Nrf2 siRNA or Nrf2 inhibitor brusatol attenuated anti-fibrotic and anti-oxidant effects of puerarin. The metabolic effects of puerarin were mediated by Nrf2 through upregulation of UDP-glucuronosyltransferase (UGT) 1A1. The Nrf2 agonist tBHQ upregulated protein expression of UGT1A1 over time in cardiac fibroblasts. Treatment with Nrf2 siRNA or brusatol dramatically decreased UGT1A1 expression in puerarin-treated fibroblasts. The results of chromatin immunoprecipitation-qPCR further confirmed that puerarin significantly increased binding of Nrf2 to the promoter region of Ugt1a1. Western blot analysis showed that puerarin significantly inhibited AngII-induced phosphorylation of p38-MAPK. A specific inhibitor of p38-MAPK, SB203580, decreased collagen expression, and ROS generation induced by AngII in cardiac fibroblast. Together, these results suggest that puerarin prevents cardiac fibrosis via activation of Nrf2 and inactivation of p38-MAPK. Nrf2 is the key regulator of anti-fibrotic effects and upregulates metabolic enzymes UGT1A1. Autoregulatory circuits between puerarin and Nrf2-regulated UGT1A1 attenuates side effects associated with treatment, but it does not weaken puerarin's pharmacological effects.