Increased secretion of cellular proteins via classical and nonclassical pathways in alcohol-exposed human HepG2 hepatoma cells and rats

Tuesday, October 25, 2011 — Poster Session II
Noon – 2:00 p.m.	Natcher Conference Center	NIAAA	OXIDSTRESS-5

Authors

• BJ Kim
• KH Moon
• MA Abdelmegeed
• BJ Song

Abstract

In this study, we investigated whether secretion of cellular proteins could be increased by oxidative stress in E47 HepG2 hepatoma cells with transduced human CYP2E1 exposed to ethanol or hydrogen peroxide for a short period of time to have minimal levels of cell damage. The presence of thioredoxin (Trx), peroxiredoxin (Prx), and CYP2E1 in the culture media were confirmed by mass-spectral analysis. Immunoblot analyses with specific antibodies confirmed increased secretion of Trx, Prx, and CYP2E1 in the culture supernatant in ethanol-exposed E47 HepG2 cells. Increased levels of Trx, Prx, and CYP2E1 were significantly reduced by pretreatment with antioxidants trolox and vitamin C or CYP2E1 inhibitors diallylsulfide and chlormethiazole. Treatment with brefeldin-A did not significantly change the ethanol- and H2O2-mediated secretion of these proteins while it significantly decreased the secretion of α-fetoprotein through the classical endoplasmic reticulum-Golgi pathway. These data suggest that some of these proteins are likely secreted through a nonclassical pathway. Furthermore, increased levels of CYP2E1, Trx and Prx were also observed in the sera from alcohol-exposed rats compared to those in pair-fed control rats. Taken together, these results indicate that oxidative stress is responsible for increased secretion of these cellular proteins, possibly through inactivation of cellular chaperone proteins.

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