CXCL6 regulates cell permeability, proliferation, and apoptosis after ischemia-reperfusion injury by modulating Sirt3 expression via AKT/FOXO3a activation.

Chemokine (C-X-C motif) ligand 6 (CXCL6), a member of the CXC chemokine family, reportedly mediates several processes such as inflammation, immunoreaction, cell growth, and metastasis through interaction with the chemokine receptors CXCR1 and CXCR2 in humans; further, CXCR1 and CXCR2 can promote repair and regeneration of organs or tissues after ischemia-reperfusion injury (IRI). In this study, we found that HIF-1α, CXCL6, and CXCR2 expression levels were elevated in human brain microvascular endothelial cells (HBMECs) after IRI, whereas silent information regulator of transcription (Sirt) 3 expression level had reduced. HIF-1α inhibition in an IRI model potently promoted HBMEC proliferation, accompanied by increased Sirt3 and decreased CXCL6/CXCR2 expression levels. CXCL6 knockdown in the IRI model significantly decreased HBMEC permeability and promoted HBMEC proliferation, concurrent with a decrease in apoptosis; it also increased Sirt3 expression levels and decreased CXCL6/CXCR2 protein and phosphorylated AKT (-AKT) and class O of forkhead box (FOXO) 3a (-FOXO3a) levels. In addition, CXCL6-induced HBMEC permeability and inhibition of HBMEC proliferation were counteracted by Sirt3 overexpression, and the AKT inhibitor LY294002 counteracted the effect of CXCL6 recombinant proteins on Sirt3, -AKT, and -FOXO3a expressions. These results suggest that CXCL6 and Sirt3 are downstream of HIF-1α and that CXCL6 regulatesHBMEC permeability, proliferation, and apoptosis after IRI by modulating Sirt3 expression via AKT/FOXO3a activation.