Interaction of osteopontin with neutrophil alpha(4)beta(1) and alpha(9)beta(1) integrins in a rodent model of alcoholic liver disease.

Previous studies from our laboratory have reported that osteopontin (OPN) mediated higher hepatic neutrophil infiltration makes female rats more susceptible to alcoholic steatohepatitis (ASH) than their male counterparts. The objective of the current work was to investigate the patho-mechanism by which OPN attracts the hepatic neutrophils in ASH. We hypothesized that OPN-mediated hepatic neutrophil infiltration is a result of signaling by N-terminal integrin binding motif (SLAYGLR) of OPN through its receptor alpha(9)beta(1) (VLA9) and alpha(4)beta(1) (VLA4) integrins on neutrophils. Compared to the males, females in the ASH group exhibited higher expression of alpha(4)beta(1) and alpha(9)beta(1) protein and mRNA and a significant decrease in the expression of these integrins was observed in rats treated with neutralizing OPN antibody. Immunoprecipitation experiments suggested the binding of OPN to alpha(4)beta(1) and alpha(9)beta(1) integrins. OPN-mediated neutrophil infiltration was also confirmed using Boyden chamber assays, and antibodies directed against alpha(4) and beta(1) integrins was found to significantly inhibit neutrophilic migration in vitro. In conclusion, these data suggest that SLAYGLR-mediated alpha(4)beta(1) and alpha(9)beta(1) integrin signaling may be responsible for higher hepatic neutrophil infiltration and higher liver injury in the rat ASH model.