NLRX1 knockdown up-regulates expression level of mitochondrial fusion protein and attenuates hypoxia induced cardiomyocyte death

  AIM  To investigate the effects of pattern recognition receptor NLRX1 on cardiomyocytes upon hypoxia injury and the underlying molecular mechanisms.

  METHODS  Primary neonatal rat ventricular myocytes (NRVMs) of SD rats were isolated and cultured. NRVMs were transfected with NLRX1-siRNA for 48 hours and then subjected to hypoxia and glucose deprivation for different times to simulate myocardial ischemia. Cell viability was determined by CCK-8 kit and cell apoptosis was analyzed with flow cytometry. Protein expression levels of NLRX1 and mitochondrial fusion related proteins (Opa1, Mfn1, Mfn2) were determined by Western blot and mitochondrial morphology was analyzed with laser scanning confocal microscopy.

  RESULTS  NLRX1 was highly expressed in cardiomyocytes. Although total protein level of NLRX1 was not altered, cytoplasmic NLRX1 was up-regulated in NRVMs upon hypoxia and glucose deprivation (P<0.01). Compared with those in control group, NLRX1-siRNA up-regulated expression levels of mitochondrial fusion protein Mfn2 and Opa1, promoted mitochondrial fusion of hypoxic cardiomyocytes and reduced hypoxia induced cardiomyocyte death (P<0.05).

  CONCLUSION  NLRX1 modulates the expression of mitochondrial fusion proteins Mfn2 and Opa1, and the inhibition of NLRX1 up-regulates the protein levels of Mfn2 and Opa1, which contributes to reduced cardiomyocytes injury upon hypoxia.