TNF-α induces CXCL1 chemokine expression and release in human vascular endothelial cells in vitro via two distinct signaling pathways

Aim: Chemokines usually direct the movement of circulating leukocytes to sites of inflammation or injury. CXCL1/GRO-α has been shown to be upregulated in atherosclerotic lesions and various cancers. The aim of this study was to investigate the mechanisms underlying the TNF-α-induced release of CXCL1 from human vascular endothelial cells in vitro.

Methods: Human umbilical vein endothelial cells (HUVECs) were treated with different proinflam-matory mediators and growth factors. CXCL1 expression and secretion were determined using RT-PCR and ELISA, respectively. TNF-α-induced cell signaling was assayed with Western blotting. Cell viability/growth was determined using MTT assay. Monocyte migration was measured with transwell migration assay.

Results: Among the 17 mediators and growth factors tested, TNF-α, LPS and Thrombin induced marked increase in CXCL1 release from HUVEC cells. TNF-α (2, 5 ng/mL) induced CXCL1 release and mRNA expression in the cells in concentration- and time-dependent manners. TNF-α (5 ng/mL) caused activation of JNK, p38 MAPK, PI3K and Akt, whereas pretreatment with JNK Inhibitor (SP600125), p38 MAPK Inhibitor (SB202190) or PI-3K inhibitor (LY294002) significantly suppressed TNF-α-induced CXCL1 release from the cells. But only SP600125 significantly reduced TNF-α-induced CXCL1 mRNA expression in the cells. Moreover, dexamethasone (up to 500 nmol/L) failed to affect TNF-α-induced CXCL1 release from the cells. In functional studies, recombinant CXCL1 enhanced HUVEC proliferation, and both recombinant CXCL1 and TNF-α-induced CXCL1 from HUVECs attracted human monocyte migration.

Conclusion: TNF-α stimulates CXCL1 release from human ECs through JNK-mediated CXCL1 mRNA expression and p38 MAPK- and PI-3K-mediated CXCL1 secretory processes.