Substance P-stimulated interleukin-8 expression in human colonic epithelial cells involves Rho family small GTPases.

Area of Science:

• Gastroenterology
• Cellular signaling
• Molecular biology

Background:

• Substance P (SP) and its neurokinin-1 receptor (NK-1R) are implicated in intestinal inflammation.
• SP activates p38 MAPK and NF-kappaB, leading to IL-6 and IL-8 production in astrocytoma cells.
• The precise signaling pathways for SP-induced NF-kappaB activation and IL-8 expression remain unclear.

Purpose of the Study:

• To elucidate the signaling mechanisms by which SP-NK-1R interaction induces NF-kappaB activation and IL-8 expression in human colonic epithelial cells.
• To investigate the role of Rho family proteins in SP-mediated IL-8 production.

Main Methods:

• Human colonic epithelial cells (NCM460) were transfected with NK-1R cDNA.
• SP stimulation was applied, and IL-8 secretion and promoter activity were measured.
• Dominant-negative mutants of RhoA, Rac1, and Cdc42 were used to inhibit Rho family proteins.
• NF-kappaB-dependent gene expression was assessed.

Main Results:

• SP stimulated IL-8 secretion and promoter activity in NK-1R-transfected NCM460 cells.
• Inhibition of RhoA, Rac1, and Cdc42 significantly reduced SP-induced IL-8 secretion and promoter activity.
• SP rapidly activated RhoA, Rac1, and Cdc42.
• Co-expression of dominant-negative Rho mutants inhibited SP-induced NF-kappaB-dependent gene expression.

Conclusions:

• Rho family small GTPases, specifically RhoA, Rac1, and Cdc42, are novel signal transducers for SP-stimulated IL-8 expression in colonic epithelial cells.
• These findings clarify the signaling pathway downstream of SP-NK-1R interaction in the context of intestinal inflammation.