Mitochondrial energy metabolism mediated via HIF-1 involves the proliferation and apoptosis of renal clear cell carcinoma cells regulated by propofol

Objective To investigate the role of mitochondrial energy metabolism mediated via hypoxia-inducible factor-1 (HIF-1) in the proliferation and apoptosis of renal clear cell carcinoma cells regulated by propofol. Methods We chose human renal clear cell carcinoma cell line RCC4 as the research object, which did not express VHL gene. The pcDNA3-VHL plasmid and the pcDNA3 empty plasmid were respectively transfected into RCC4 cells to obtain RCC4-VHL(+ ) cells stably expressing the exogenous VHL protein and RCC4-VHL(-) cells without expressing the VHL protein. These two kinds of cells were then exposed to propofol at dosage of 0, 25, 50 and 100 μmol/L. HIF-1 protein expression was detected by Western blotting in the two kinds of cells, cell proliferation activity and apoptosis rate were detected by flow cytometry, and mitochondrial energy metabolism was detected by energy metabolism analyzer. Results Compared with RCC4-VHL(-) cells, the relative expression of HIF-1α protein in RCC4-VHL(+ ) cells was significantly decreased (0.05±0.02 vs. 1.23±0.10, t=16.016, P<0.001). When propofol concentrations were 50 μmol/L and 100 μmol/L, the proliferation activity of RCC4-VHL(+ ) cells was significantly lower than that of RCC4-VHL(-) cells (50 μmol/L: 0.10±0.02 vs. 0.13±0.04, t=3.502, P=0.032; 100 μmol/L: 0.05±0.02 vs. 0.10±0.01, t=6.771, P=0.017), and the apoptotic rate was significantly higher than that of RCC4-VHL (-) cells [50 μmol/L: (35.50±1.84)% vs. (22.15±1.06)%, t=7.082, P=0.004; 100 μmol/L: (54.35±2.97)% vs. (35.10±3.25)%, t=10.241, P<0.001). Compared with 0 μmol/L propofol, 100 μmol/L propofol increased HIF-1α protein expression in RCC4-VHL (+ ) cells (0.93±0.05 vs. 0.04±0.02, t=18.500, P<0.001). Compared with RCC4-VHL(-) cells, the oxygen consumption rate (OCR) [(130.42±11.81) pmol/min vs. (48.27±7.66) pmol/min, t=11.672, P<0.001], basal aerobic respiration [(98.55±8.09) pmol/min vs. (41.63±6.21) pmol/min, t=11.162, P<0.001], aerobic maximum [(226.79±13.51) pmol/min vs. (70.18±6.82) pmol/min, t=20.697, P<0.001], non-mitochondrial respiration [(28.36±4.29) pmol/min vs. (8.92±1.70) pmol/min, t=8.426, P=0.001] and oxygen consumption rate of proton leak [(23.85±5.08) pmol/min vs. (7.80±1.24) pmol/min, t=6.139, P=0.006] were significantly increased in RCC4-VHL(+ ) cells, while the extracellular acidification rate (ECAR) was significantly decreased [(26.76±4.35) mpH/min vs. (39.48±5.17) mpH/min, t=3.765, P=0.010]. Compared with 0 μmol/L propofol added in RCC4-VHL(+ ) cells, 100 μmol/L propofol decreased OCR [(72.44±8.15) pmol/min vs. (131.56±9.04) pmol/min, t=9.751, P<0.001], basal aerobic respiration [(54.31±5.35) pmol/min vs. (96.49±6.86) pmol/min, t=9.697, P<0.001], aerobic maximum [(116.71±12.39) pmol/min vs. (219.53±11.80) pmol/min, t=12.019, P<0.001], non-mitochondrial respiration [(13.25±4.01) pmol/min vs. (29.04±5.11) pmol/min, t=4.862, P=0.002] and oxygen consumption rate of proton leak [(10.24±3.79) pmol/min vs. (22.92±4.12) pmol/min, t=4.530, P=0.003], and increased ECAR significantly [(37.69±3.75) mpH/min vs. (25.87±4.03) mpH/min, t=4.294, P=0.004]. Conclusion Loss of VHL up-regulates expression of HIF-1 protein, and mitochondrial energy metabolism mediated via HIF-1 involves the proliferation and apoptosis of RCC4 cells regulated by propofol. Key words: Hypoxia-inducible factor 1; Energy metabolism; Propofol; Cell proliferation; Renal clear cell carcinoma