Objective:To investigate the protective effects of p53/glucose transporter 4 (GLUT4) regulation on cardiomyocyte injury induced by high glucose combined with hypoxia/reoxygenation.Methods:Human myocardial AC16 cells were treated with 33 mmol/L glucose and a hypoxic chamber to establish an in vitro model of high glucose combined with hypoxia/reoxygenation. Based on the glucose concentration in the medium and hypoxia/reoxygenation conditions, AC16 cells were divided into control group, high glucose group, hypoxia/reoxygenation group and high glucose combined with hypoxia/reoxygenation group. On the basis of high glucose combined with hypoxia/reoxygenation group, cells were transfected with empty vector, p53 small interfering RNA (siRNA), and co-transfected with p53 and GLUT4 siRNA to establish negative control group, sip53 transfection group, and sip53+siGLUT4 transfection group, respectively. Western blotting was used to detect the levels of hypoxia-inducible factor-1α (HIF-1α), p53, GLUT4, dynamin-related protein 1 (Drp1), mitofusin 2 (Mfn2), B-cell lymphoma-2 (Bcl-2), Bcl-2 associated X protein (Bax) and cysteine aspartic acid specific protease-3 (Caspase-3). The levels of reactive oxygen species were detected using the 2′,7′-dichlorodihydrofluorescein diacetate fluorescent probe. Mitochondria were labeled with the Mito-Tracker Deep Red FM fluorescent probe to assess mitochondrial morphology and their related parameters. Mitochondrial membrance potential was meausred using the JC-1 detection kit. Adenosine triphosphate (ATP) content was determined using an ATP assay kit. Glucose uptake ability was evaluated by measuring the fluorescence intensity of 2-[ N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino]-2-deoxy- D-glucose (2-NBDG) using a multifunctional microplate reader. Apoptosis was assessed by TUNEL assay. Results:The relative expression of HIF-1α protein in the high glucose combined with hypoxia/reoxygenation group was 1.189±0.185, higher than that in the control group (0.086±0.071) ( P<0.05). The relative expression of p53 protein in the high glucose combined with hypoxia/reoxygenation group was 1.248±0.194, higher than those in the control group (0.730±0.184), high glucose group (0.932±0.161) and hypoxia/reoxygenation group (1.109±0.151) (all P<0.05). The relative expression of GLUT4 protein in the high glucose combined with hypoxia/reoxygenation group was 0.407±0.140, lower than those in the control group (1.061±0.060) and hypoxia/reoxygenation group (0.781±0.092) (both P<0.05). The fluorescence intensity of reactive oxygen species in the high glucose combined with hypoxia/reoxygenation group was 38.31±1.66, higher than that in the control group (11.59±1.02) ( P<0.05). The number of mitochondria in the high glucose combined with hypoxia/reoxygenation group was (62.00±15.26), lower than those in the control group (136.20±23.55) and high glucose group (96.55±13.72) (both P<0.05). The average mitochondrial area in the high glucose combined with hypoxia/reoxygenation group was (7.02±1.38) μm 2, lower than those in the control group [(13.74±0.67) μm 2], high glucose group [(9.27±1.99) μm 2] and hypoxia/reoxygenation group [(9.64±2.36) μm 2] (all P<0.05). The average perimeter of mitochondria in the high glucose combined with hypoxia/reoxygenation group was (9.10±1.14) μm, lower than those in the control group [(13.35±0.69) μm] and the hypoxia/reoxygenation group [(10.83±1.58) μm] (all P<0.05). The number of mitochondrial branches was 53.73±9.49, lower than those in the control group (147.10±25.99), high glucose group (97.08±13.65) and hypoxia/reoxygenation group (104.80±24.92) (all P<0.05). The average branch length of mitochondria in the high glucose combined with hypoxia/reoxygenation group was (1.45±0.26) μm, lower than that in the control group [(2.29±0.52) μm] ( P<0.05). The red-green fluorescence intensity ratio in the high glucose combined with hypoxia/reoxygenation group was 0.580±0.133, lower than those in the control group (2.379±0.242), high glucose group (1.200±0.112) and hypoxia/reoxygenation group (0.883±0.076) (all P<0.05). The ATP content of the high glucose combined with hypoxia/ reoxygenation group was (0.025±0.003) μmol/10 5 cells, lower than those of the control group [(0.137±0.012) μmol/10 5 cells], high glucose group [(0.078±0.003) μmol/10 5 cells] and hypoxia/reoxygenation group [(0.073±0.010) μmol/10 5 cells] (all P<0.05). The fluorescence intensity of 2-NBDG in the high glucose combined with hypoxia/reoxygenation group was 257 315±7 951, lower than those in the control group (339 597±10 165), high glucose group (317 293±8 876) and hypoxia/reoxygenation group (314 611±12 228) (all P<0.05). The relative expression of Drp1 protein in high glucose combined with hypoxia/reoxygenation group was 1.203±0.090, higher than those in the control group (0.705±0.170), high glucose group (0.910±0.106) and hypoxia/reoxygenation group (1.002±0.112) (all P<0.05). The relative expression of Mfn2 protein in the high glucose combined with hypoxia/reoxygenation group was 0.706±0.285, lower than those in the control group (1.988±0.139), high glucose group (1.305±0.076) and hypoxia/reoxygenation group (1.131±0.236) (all P<0.05). The relative expression levels of Bax/Bcl-2 and Caspase-3 proteins in the high glucose combined with hypoxia/reoxygenation group were 2.318±0.216 and 1.076±0.076, respectively, higher than those in the control group (0.281±0.046 and 0.442±0.084), high glucose group (0.673±0.043 and 0.662±0.159) and hypoxia/reoxygenation group (0.807±0.293 and 0.835±0.058), respectively (all P<0.05). The TUNEL fluorescence intensity of the high glucose combined with hypoxia/reoxygenation group was 70.55±7.22, higher than those of the control group (14.10±5.93), high glucose group (36.59±2.56) and hypoxia/reoxygenation group (39.04±6.016) (all P<0.05). The relative expression levels of p53 protein in the sip53 transfection group and sip53+siGLUT4 transfection group were 0.322±0.147 and 0.391±0.149, respectively, lower than that in the high glucose combined with negative control group (1.002±0.035) (both P<0.05). The relative expression of GLUT4 protein in the sip53 transfection group was 1.871±0.123, higher than that in the negative control group (1.281±0.232) ( P<0.05). The relative expression of GLUT4 protein in the sip53+siGLUT4 transfection group (0.951±0.193) was lower than that in the sip53 transfection group ( P<0.05). The fluorescence intensity of reactive oxygen species in the sip53 transfection group (27.73±0.74) was lower than that in the negative control group (38.83±0.83) ( P<0.05). The fluorescence intensity of reactive oxygen species in the sip53+siGLUT4 transfection group (43.12±5.08) was higher than that in the sip53 transfection group ( P<0.05). The number of mitochondria, the average area of mitochondria, the average perimeter of mitochondria, the number of mitochondrial branches and the average branch length of mitochondria in the sip53 transfection group were (92.27±10.10), (9.25±0.42) μm 2, (10.86±0.58) μm, (83.27±13.57), and (1.81±0.21) μm, respectively. They were higher than (52.36±16.87), (7.44±1.49) μm 2, (9.22±1.11) μm, (52.36±16.87), and (1.22±0.26) μm in the negative control group (all P<0.05). The number of mitochondria, the average area of mitochondria, the average perimeter of mitochondria, the number of mitochondrial branches and the average branch length of mitochondria in the sip53+siGLUT4 transfection group were (53.73±9.49), (6.89±0.61) μm 2, (8.88±0.47) μm, (53.73±9.49), and (1.22±0.17) μm, respectively, lower than those in the sip53 transfection group (all P<0.05). The red-green fluorescence intensity ratio, ATP content, 2-NBDG fluorescence intensity and relative expression of Mfn2 protein in the sip53 transfection group were 1.27±0.23, (0.048±0.021) μmol/10 5 cells, 275 923±10 447 and 2.608±0.581, respectively, higher than those in the negative control group [0.53±0.21, (0.020±0.007) μmol/10 5 cells, 254 875±8 078, and 0.687±0.146, respectively] (all P<0.05). The red-green fluorescence intensity ratio, ATP content, 2-NBDG fluorescence intensity and relative expression of Mfn2 protein in the sip53+siGLUT4 transfection group were 0.40±0.08, (0.011±0.012) μmol/10 5 cells, 199 511±6 855, and 0.649±0.070, respectively, lower than those in the sip53 transfection group (all P<0.05). The relative expression levels of Drp1, Bax/Bcl-2, Caspase-3 proteins and TUNEL fluorescence intensity in the sip53 transfection group were 0.759±0.063, 0.446±0.161, 1.048±0.300, and 48.93±1.48 respectively, lower than those (1.065±0.149, 1.197±0.133, 1.847±0.201, and 67.61±9.99) in the negative control group (all P<0.05). The relative expression levels of Drp1, Bax/Bcl-2, Caspase-3 proteins and TUNEL fluorescence intensity in the sip53+siGLUT4 transfection group were 0.958±0.166, 2.660±0.135, 1.587±0.220, and 63.39±12.84, respectively, higher than those in the sip53 transfection group (all P<0.05). Conclusions:Under the condition of high glucose combined with hypoxia/reoxygenation, p53 induces cardiomyocyte injury by down-regulating GLUT4. Inhibition of p53 can increase the expression of GLUT4, thereby reducing cardiomyocyte injury induced by high glucose combined with hypoxia/reoxygenation.