We hypothesized that inducible nitric oxide synthase (iNOS) upregulated in bone marrow stem cells (BMSCs) protect ischemic cardiomyocytes via hypoxia inducible factor-1α (HIF-1α) pathway.
Methods:
Isolated BMSCs were exposed to hypoxia for 24 hours. The level of HIF-1α protein and its activated form were measured by ELISA. The expression of iNOS and HIF-1α were analyzed by quantitative PCR and cellular localization was determined by immunohistochemistry. Cardiomyocytes in co-culture with BMSCs were subjected to hypoxia and H
2
O
2
(200 μmol). LDH release, DNA fragmentation and annexin-V positive cells were used as injury markers.
Results
: HIF-1α protein and its activated form were markedly increased (Fig. A, B
) and translocated to the nucleus or peri-nuclear area of BMSCs subjected to hypoxia, in parallel with increased expression of HIF-1α target gene iNOS, which was blocked by pretreating cells with neutralizing HIF-1α antibody (Fig. C
). Co-culture of cardiomyocytes with BMSCs not only prevented and reduced cardiomyocyte apoptosis induced by hypoxia and H
2
O
2
but also significantly reduced LDH release from cardiomyocytes (Fig. D–G
). The cardiac protection by BMSC was abolished by neutralizing HIF-1α antibodies, and by the selective iNOS inhibitor, 1400W (10 mg/L) as well as a potent competitive inhibitor of NOS, L-NAME (200 μmol/L). However, no effects of neutralizing HIF-1α antibody, L-NAME or 1400W on cardiomyocytes alone were seen. SNAP (300 μmol/L), a NO donor had no synergistic effect on the cardioprotective effect of BMSC.
Conclusion:
iNOS upregulated in bone marrow stem cells by hypoxia protects cardiomyocytes against ischemic injury via activating HIF-1α.
Effects of autologous SCF- and G-CSF-mobilized bone marrow stem cells on hypoxia-inducible factor-1 in rats with ischemia-reperfusion renal injury
