The induction of hypoxia tolerance has emerged as a novel therapeutic strategy for the treatment of ischemic diseases. The disruption of hypoxic signaling by hyperglycemia has been shown to contribute to diabetic cardiomyopathy. In this study, we explored the potential molecular mechanisms by which high glucose (HG) impairs hypoxia-inducible factor-α (HIF-α) signaling in cardiomyocytes. The exposure of H9c2 cell lines to HG resulted in time- and concentration-dependent decreases in HIF-1α and HIF-2α expression together with an increase in prolyl hydroxylase-1,2 (PHD1 and PHD2) expression, the main regulators of HIF-α destabilization in the heart. The exposure of H9c2 cells to normal glucose (5.5 mM) and high glucose (15, 30, and 45 mM) led to dose-dependent increases in p53 and TIGAR and a decrease in SIRT3 expression. The pretreatment of H9c2 with p53 siRNA to knockdown p53 attenuated PHD1 and PHD2 expression, thus significantly enhancing HIF-1α and HIF-2α expression in H9c2 cells under HG conditions. Interestingly, pretreatment with p53 siRNA altered H9c2 cell metabolism by reducing oxygen consumption rate and increasing glycolysis. Similarly, pretreatment with TIGAR siRNA blunted HG-induced PHD1 and PHD2 expression. This was accompanied by an increase in HIF-1α and HIF-2α expression with a reduction in oxygen consumption rate in H9c2 cells. Furthermore, pretreatment with adenovirus-SIRT3 (Ad-SIRT3) significantly reduced the HG-induced expression of p53 and PHDs and increased HIF-1α levels in H9c2 cells. Ad-SIRT3 treatment also regulated PHDs-HIF-1α levels in the hearts of diabetic db/db mice. Our study revealed a novel role of the HG-induced disruption of PHDs-HIF-α signaling via upregulating p53 and TIGAR expression. Therefore, the p53/TIGAR signaling pathway may be a novel target for diabetic cardiomyopathy.

Hypertension is the key contributor to pathological cardiac hypertrophy. Growing evidence indicates that glucose metabolism plays an essential role in cardiac hypertrophy. TP53-induced glycolysis and apoptosis regulator (TIGAR) has been shown to regulate glucose metabolism in pressure overload-induced cardiac remodeling. In the present study, we investigated the role of TIGAR in cardiac remodeling during Angiotensin II (Ang-II)-induced hypertension. Wild-type (WT) and TIGAR knockout (KO) mice were infused with Angiotensin-II (Ang-II, 1 µg/kg/min) via mini-pump for four weeks. The blood pressure was similar between the WT and TIGAR KO mice. The Ang-II infusion resulted in a similar reduction of systolic function in both groups, as evidenced by the comparable decrease in LV ejection fraction and fractional shortening. The Ang-II infusion also increased the isovolumic relaxation time and myocardial performance index to the same extent in WT and TIGAR KO mice, suggesting the development of similar diastolic dysfunction. However, the knockout of TIGAR significantly attenuated hypertension-induced cardiac hypertrophy. This was associated with higher levels of fructose 2,6-bisphosphate, PFK-1, and Glut-4 in the TIGAR KO mice. Our present study suggests that TIGAR is involved in the control of glucose metabolism and glucose transporters by Ang-II and that knockout of TIGAR attenuates the development of maladaptive cardiac hypertrophy.

Background: Endothelial prolyl hydroxylase‐2 (PHD2) is essential for pulmonary remodeling and hypertension. In the present study, we investigated the role of endothelial PHD2 in angiotensin II–mediated arterial stiffness, pericyte recruitment, and cardiac fibrosis. Methods and Results: Chondroitin sulfate proteoglycan 4 tracing reporter chondroitin sulfate proteoglycan 4– red fluorescent protein (DsRed) transgenic mice were crossed with PHD2 ^flox/flox (PHD2 ^f/f ) mice and endothelial‐specific knockout of PHD2 (PHD2 ^EC KO) mice. Transgenic PHD2 ^f/f (TgPHD2 ^f/f ) mice and TgPHD2 ^EC KO mice were infused with angiotensin II for 4 weeks. Arterial thickness, stiffness, and histological and immunofluorescence of pericytes and fibrosis were measured. Infusion of TgPHD2 ^f/f mice with angiotensin II resulted in a time‐dependent increase in pulse‐wave velocity. Angiotensin II–induced pulse‐wave velocity was further elevated in the TgPHD2 ^EC KO mice. TgPHD2 ^EC KO also reduced coronary flow reserve compared with TgPHD2 ^f/f mice infused with angiotensin II. Mechanistically, knockout of endothelial PHD2 promoted aortic arginase activity and angiotensin II–induced aortic thickness together with increased transforming growth factor‐β1 and ICAM‐1/VCAM‐1 expression in coronary arteries. TgPHD2 ^f/f mice infused with angiotensin II for 4 weeks exhibited a significant increase in cardiac fibrosis and hypertrophy, which was further developed in the TgPHD2 ^EC KO mice. Chondroitin sulfate proteoglycan 4 pericyte was traced by DsRed ⁺ staining and angiotensin II infusion displayed a significant increase of DsRed ⁺ pericytes in the heart, as well as a deficiency of endothelial PHD2, which further promoted angiotensin II–induced pericyte increase. DsRed ⁺ pericytes were costained with fibroblast‐specific protein 1 and α‐smooth muscle actin for measuring pericyte–myofibroblast cell transition. The knockout of endothelial PHD2 increased the amount of DsRed ⁺ /fibroblast‐specific protein 1 ⁺ and DsRed ⁺ /α‐smooth muscle actin ⁺ cells induced by angiotensin II infusion. Conclusions: Knockout of endothelial PHD2 enhanced angiotensin II–induced cardiac fibrosis by mechanisms involving increasing arterial stiffness and pericyte–myofibroblast cell transitions.

Background: Hypertension is a major risk factor for heart failure. Acetylation of p53 is known to regulate its activities. We have previously identified that p53 acetylation is required for cardiac remodeling in a mouse model of pressure overload-induced heart failure. Acetylation mutant p53 (p53aceKO) mice have been shown to the ability to regulate SIRT3 KO-induced cardiac fibrosis. In the present study, we hypothesized that p53aceKO mice would exhibit cardiac protection and blunt cardiac fibrosis when subjected to Ang-II-induced hypertension. Methods: Control and p53aceKO mice received either a micro-osmotic pump implant administering Ang-II for 28 days or a sham procedure. Blood pressure was measured weekly, and echocardiography was performed every two weeks. Mice were euthanized and hearts were processed for histological analysis. Results: While both Control and p53aceKO mice receiving Ang-II exhibit increased systolic and diastolic blood pressures, Control mice also demonstrate increases in ejection fraction and fractional shortening compared to the sham, while p53aceKO mice do not. Furthermore, Control mice receiving Ang-II have decreased left ventricular diameter and volume at end-systole and end-diastole, as well as thickening of both the anterior and posterior walls, while p53aceKO mice exhibit no significant changes in any of these parameters. Additionally, p53aceKO mice do not exhibit the Ang-II infusion-induced cardiac fibrosis seen in Control mice treated with Ang-II. Conclusions: Mutation of p53 acetylation is protective against Ang-II infusion-induced cardiac fibrosis and dysfunction in mice. Acetylated p53 may therefore be a novel therapeutic target to address complications in the heart associated with hypertension.

Hypertension is a major risk factor for heart failure. Acetylation of p53 is known to regulate its activities. We have previously identified that p53 acetylation is required for cardiac remodeling in a mouse model of pressure overload-induced heart failure. Acetylation mutant p53 (p53aceKO) mice have been shown to have the ability to regulate SIRT3 KO-induced cardiac fibrosis. In the present study, we hypothesized that p53aceKO mice would exhibit cardiac protection and blunt cardiac fibrosis when subjected to Ang-II-induced hypertension. Control and p53aceKO mice received either a micro-osmotic pump implant administering Ang-II for 28 days or a sham procedure. Blood pressure was measured weekly, and echocardiography was performed every two weeks. Mice were euthanized and hearts were processed for histological analysis. While both control and p53aceKO mice receiving Ang-II exhibit increased systolic and diastolic blood pressures, control mice also demonstrate increases in ejection fraction and fractional shortening compared to the sham, while p53aceKO mice do not. Furthermore, control mice receiving Ang-II exhibit decreased left ventricular diameter and volume at end-systole and end-diastole, as well as thickening of both the anterior and posterior walls, while p53aceKO mice exhibit no significant changes in any of these parameters. Additionally, p53aceKO mice do not exhibit the Ang-II infusion-induced cardiac fibrosis seen in control mice treated with Ang-II. Mutation of p53 acetylation is protective against Ang-II infusion-induced cardiac fibrosis and dysfunction in mice. Acetylated p53 may, therefore, be a novel therapeutic target to address complications in the heart associated with hypertension.