Gene expression of HUVECS treated with either siRNA to CTRL or PDHA1 and treated with TNF 16 hours
The endothelium is a major target of the proinflammatory cytokine, tumor necrosis factor alpha (TNFa). Exposure of endothelial cells (EC) to proinflammatory stimulileads to an increase in mitochondrial metabolism, however, the function and regulation of elevated mitochondrial metabolism in EC in response to pro-inflammatory cytokines remains unclear. Using high-resolution metabolomics and13C-glucose labeled flux techniques, we demonstrate thatpyruvate dehydrogenase activity (PDH) and tricarboxylic acid cycle flux is elevated in human umbilical vein ECs (HUVECs) in response to overnight (16 hrs) treatment withTNFa (10 ng/mL).Mechanistic studies indicate thatTNFa mediates these metabolic changes via mitochondrial specific protein degradation of pyruvate dehydrogenase kinase 4 (PDK4, inhibitor of PDH) by the Lon protease via an NF-?B dependent mechanism. Using RNA sequencing following siRNA mediated knockdown of thecatalytically active subunit of PDH, PDHE1a(PDHA1 gene), we show that PDH fluxcontrols the transcription of approximately one-third of the genes that are upregulated by TNFastimulation. Notably, TNFainduced PDHflux regulates a unique signature of proinflammatory mediators (cytokines and chemokines) but not inducible adhesion molecules.Using metabolomics and ChIP sequencing (H3AcK27), we demonstrate that TNFa induced PDH flux promotes histone acetylation of specific gene sets via citrate accumulation and ATP-citrate lyase activity.Together, these resultsindicate that targeting endothelial glucose oxidation and/or acetyl CoA generation may offer a novel therapeutic strategy in the treatment of vascular inflammation. Overall design: Comparative gene expression and acetylation of early passage HUVECs treated with either siRNA to CTRL or PDHA1 and treated with TNF 16 hours.