Expression of NLRC4 in children with septicaemia and mechanisms of NLRC4 in invitro cytokine secretion.

Abstract

Septicaemia, a systemic bacterial infection, frequently leads to morbidity and mortality in children. The NOD-like receptor (NLR) family, CARD domain containing4 (NLRC4) is involved in the control of infections. The aim of the present study was to detect the expression of NLRC4 in the blood samples of children with septicaemia, in addition to investigating the importance of NLRC4 in cytokine production, and the signaling pathways that regulate NLRC4 expression in lipopolysaccharide (LPS)-stimulated macrophages. It was determined that when compared with the control, the mRNA and protein expression levels of NLRC4 were significantly increased in the blood samples of children with septicaemia, as demonstrated by the reverse transcription‑quantitative polymerase chain reaction and western blot analysis. The results from the western blotting indicated that treatment with LPS induced NLRC4 expression in a time‑ and dose‑dependent manner in RAW264.7 cells. A knockdown of NLRC4 by siRNA transfection enhanced the effect of LPS on interleukin (IL)‑1β and IL‑18 production, as determined by enzyme‑linked immunosorbent assay. Inhibitors of extracellular regulated protein kinases, c‑Jun N‑terminal kinases and p38 were used in the present study to block the mitogen‑activated protein kinase (MAPK) signaling pathway, and it was determined that LPS‑induced NLRC4 expression was reversed by the suppression of the MAPK signaling pathway. To the best of our knowledge, this is the first report regarding the expression of NLRC4 in children with septicaemia. Furthermore, a novel molecular mechanism for NLRC4 regulation in LPS‑induced RAW264.7 macrophage cells has been elucidated. The data in the present study supports the hypothesis that LPS activates the MAPK pathway in macrophages, thus resulting in the upregulation of NLRC4; however, NLRC4 inhibits IL‑1β and IL‑18 production, contributing to the anti-inflammatory response.