Aims: We have recently reported that tumour necrosis factor-alpha (TNF-alpha) increases oxidative stress and apoptosis in cardiomyocytes by upregulating p38 mitogen-activated protein (MAP) kinase (MAPK) phosphorylation. Interleukin-10 (IL-10) blocked these effects of TNF-alpha by upregulating extracellular signal-regulated kinase 1/2 (ERK 1/2) MAPK phosphorylation. However, the precise site of this IL-10 action is still unknown, and this is investigated in the present study.
Methods and results: Cardiomyocytes isolated from adult Sprague-Dawley rats were exposed to TNF-alpha (10 ng/mL), IL-10 (10 ng/mL), and IL-10+TNF-alpha (ratio 1) for 4 h. Hydrogen peroxide and antioxidant trolox were used as positive controls. Exposure to TNF-alpha resulted in an increase in the production of reactive oxygen species, the number of apoptotic cells, caspase-3 activation, and poly-ADP ribose polymerase (PARP) cleavage. Increased oxidative stress by using hydrogen peroxide also caused apoptosis. The changes due to TNF-alpha were associated with an increase in the inhibitor of kappaB kinase (IKK) and nuclear factor kappa-B (NF kappaB) phosphorylation. IL-10 by itself had no effect, but it prevented the above mentioned TNF-alpha-induced changes. Trolox also mitigated TNF-alpha induced changes. Pre-exposure of cells to an IKK inhibitor (PS-1145) prevented TNF-alpha-induced caspase-3 and PARP cleavage. Inhibition of ERK 1/2 MAPK with PD98059 attenuated the protective role of IL-10 against TNF-alpha-induced activation of IKK and NF kappaB as well as cardiomyocyte apoptosis.
Conclusion: The present study shows that TNF-alpha-induced activation of the NF kappaB pathway plays a critical role in cardiomyocyte apoptosis. IL-10 prevents TNF-alpha-induced NF kappaB activation and pro-apoptotic changes in cardiomyocytes by inhibiting IKK phosphorylation through the activation of ERK 1/2 MAPK.