Mitochondrial transcription factor A protects human retinal endothelial cell injury induced by hypoxia

Abstract

Purpose: To investigate the impact of mitochondrial transcription factor A (TFAM), as a modulator of NF-κB, on proliferation of hypoxia-induced human retinal endothelial cell (HREC), and the probable mechanism. Methods: After exposure to hypoxia (1 % O2) for 5 days, cell proliferation and cell cycle of HREC were measured by MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide) assay and flow cytometry. Cell signaling and mitochondrial DNA (mtDNA) copies were determined using real-time polymerase chain reaction and Western blot. NF-κB activity was evaluated by luciferase assay. Results: TFAM expression decreased to 40 % in HREC under hypoxic condition (p < 0.05). MTT results revealed that TFAM facilitated HREC proliferation under hypoxia (p < 0.05). Moreover, flow cytometry demonstrated that TFAM promoted HREC proliferation by accelerating cell cycle (p < 0.05). Western blot and luciferase assay exhibited NF-κB activation in HREC after TFAM overexpression (p < 0.05). Finally, real-time PCR results showed that mtDNA and targeted genes of NF-κB were upregulated 3-fold in HREC after TFAM transfection under hypoxia (p < 0.05). Conclusion: These results indicate that NF-κB activated by TFAM protects against hypoxia-induced HREC injury by accelerating cell cycle. The ability of TFAM to enhance NF-κB signaling may be part of the mechanism of hypoxia-induced cell injury. Thus, upregulation of TFAM may help to relieve diabetic retinopathy.

Kaempferia galanga L. extract and its main component, ethyl p-methoxycinnamate, inhibit the proliferation of Ehrlich ascites tumor cells by suppressing TFAM expression

“…TFAM regulates p21 expression, as TFAM depletion induces G1 cell cycle arrest via p21 upregulation in PC3 human prostate cancer cells [ 19 , 41 ]. Furthermore, TFAM is involved in the regulation of cyclin D1 expression as the knockdown of TFAM induces a decrease in cyclin D1, whereas the overexpression of TFAM shows the opposite effect [ 42 , 43 ]. In this study, EMC significantly decreased the expression level of TFAM.…”