Effects of interleukin-6 and IL-6/AMPK signaling pathway on mitochondrial biogenesis and astrocytes viability under experimental septic condition

Objective: Interleukin-6 (IL-6) Is a neuromodulation factor with extensive and complex biological activities. IL-6 has been reported to activate AMPK, while AMPK regulates mitochondrial biogenesis and autophagy. The aim of this study was to investigate the role of IL-6 in mitochondrial biogenesis using astrocytes under experimental septic condition and examined how IL-6/AMPK signaling pathway affected this process. Methods: The primary cultures of cerebral cortical astrocytes were randomly allocated into six groups: control group, LPS + IFN-gamma group, IL-6 group (LPS + IFN-gamma + IL-6), C group (LPS + IFN-gamma + IL-6 + Compound C), siRNA group (LPS + IFN-gamma + IL-6 + IL-6R siRNA) and siRNA +C group (LPS + IFN-gamma + IL-6 + IL-6R siRNA + Compound C). All groups were stimulated for 6 h. Cytokines and reactive oxygen species (ROS) analyses, detection of adenosine triphosphate (ATP), mtDNA content and cell viability, evaluation of the mitochondrial ultrastructure and volume density, western blots of proteins associated with mitochondrial biogenesis and phospho-adenosine monophosphate activated protein kinase (p-AMPK) were performed respectively. Results: Compared with LPS + IFN-gamma group, IL-6 group had milder ultrastructural damage of mitochondria, higher mtDNA content and mitochondrial volume density, higher expression of proteins associated with mitochondrial biogenesis (PGC-1 alpha, NRF-1 and TFAM) and p-AMPK, and thus higher cell viability, whereas blocking IL-6/AMPK signaling pathway, the protective effect of IL-6 has been diminished, compared with IL-6 group. Conclusion: IL-6 enhances mitochondrial biogenesis in astrocytes under experimental septic condition through IL-6/AMPK signaling pathway.