Klebsiella pneumoniae induces metabolic reprogramming in bronchial epithelial cells thereby promoting macrophage secretion of IL-1β and IL-18

Objective This study aims to investigate the mechanisms by which Klebsiella pneumoniae (Kp) infection induces metabolic reprogramming and extracellular ATP (eATP) secretion in bronchial epithelial cells, and to explore its role in promoting the maturation of IL-1β and IL-18 .Methods Normal bronchial epithelial cells (BEAS-2B) were cultured in vitro and infected with Kp at varying multiplicities of infection (MOI) for 24 hours. Gene expression differences before and after infection were analyzed using RNA-Seq. The mechanisms underlying Kp-induced metabolic reprogramming were examined using gene-deficient cells, metabolic assays, biochemical analyses, and quantitative real-time PCR. The mechanisms driving eATP secretion post-infection were assessed using luminescence assays in combination with inhibitor studies. Conditioned medium (CM) from Kp-infected BEAS-2B cells was co-cultured with macrophages to measure changes in IL-1β and IL-18 levels. Inhibitor studies were conducted to investigate how eATP, via purinergic receptors, promotes the secretion of IL-1β and IL-18 by macrophages .Results Following Kp infection of BEAS-2B cells, 1098 upregulated genes were identified, with enrichment in metabolic pathways, particularly glycolysis and gluconeogenesis. Kp infection reduced the oxygen consumption rate (OCR), while increasing the extracellular acidification rate (ECAR) and eATP secretion. Inhibition of glycolysis reduced eATP levels. In TLR2- and TLR4-deficient epithelial cells, OCR was further reduced, ECAR increased, and eATP secretion decreased compared to wild-type cells following Kp infection. However, intracellular re-expression of TLR2 or TLR4 restored and increased eATP secretion. Adding ATP-containing conditioned medium to Kp-macrophage co-cultures increased IL-1β and IL-18 secretion without significantly altering their mRNA transcription levels. Blocking the P2X7 receptor abolished the eATP-induced increase in IL-1β and IL-18 secretion .Conclusion Kp infection induces metabolic reprogramming in bronchial epithelial cells, leading to increased eATP secretion, which, via activation of the P2X7 receptor, promotes the maturation and secretion of IL-1β and IL-18 in macrophages.