The role of macrophage-fibroblast interaction in lipopolysaccharide-induced pulmonary fibrosis: an acceleration in lung fibroblast aerobic glycolysis

This study demonstrates that lipopolysaccharide promotes activation of the JNK signaling pathway and endogenous TNF-alpha secretion in pulmonary macrophages, which facilitates lung fibroblast aerobic glycolysis and lactate production through PFKFB3 activation. These findings suggests that inflammation-metabolism interactions between lung macrophages and fibroblasts might play an essential role in lipopolysaccharide-induced pulmonary fibrosis. Recent evidence has shown that lipopolysaccharide (LPS)-induced aerobic glycolysis of lung fibroblasts is closely associated with the pathogenesis of septic pulmonary fibrosis. Nevertheless, the underlying mechanism remains poorly defined. In this study, we demonstrate that LPS promotes c-Jun N-terminal kinase (JNK) signaling pathway activation and endogenous tumor necrosis factor-alpha (TNF-alpha) secretion in pulmonary macrophages. This, in turn, could significantly promote aerobic glycolysis and increase lactate production in lung fibroblasts through 6-phosphofructo-2-kinase/fructose-2, 6-biphosphatase 3 (PFKFB3) activation. Culturing human lung fibroblast MRC-5 cell line with TNF-alpha or endogenous TNF-alpha (cell supernatants of macrophages after LPS stimulation) both enhanced the aerobic glycolysis and increased lactate production. These effects could be prevented by treating macrophages with JNK pathway inhibitor, by administering TNF-alpha receptor 1 (TNFR1) siRNA, PFKFB3 inhibitor, or by silencing PFKFB3 with fibroblasts-specific shRNA. In addition, the inhibition of TNF-alpha secretion and PFKFB3 expression prevented LPS-induced pulmonary fibrosis in vivo. In conclusion, this study revealed that LPS-induced macrophage secretion of TNF-alpha could initiate fibroblast aerobic glycolysis and lactate production, implying that inflammation-metabolism interactions between lung macrophages and fibroblasts might play an essential role in LPS-induced pulmonary fibrosis.

Automated summary

The study demonstrates that lipopolysaccharide induces activation of the JNK signaling pathway and TNF-alpha secretion in pulmonary macrophages, leading to interaction between inflammation and metabolism that promotes lung fibroblast glycolysis. This interaction plays a crucial role in lipopolysaccharide-induced pulmonary fibrosis.