Interaction of osteopontin with neutrophil α4β1 and α9β1 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 α9β1 (VLA9) and α4β1 (VLA4) integrins on neutrophils. Compared to the males, females in the ASH group exhibited higher expression of α4β1 and α9β1 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 α4β1 and α9β1 integrins. OPN-mediated neutrophil infiltration was also confirmed using Boyden chamber assays, and antibodies directed against α4 and β1 integrins was found to significantly inhibit neutrophilic migration in vitro. In conclusion, these data suggest that SLAYGLR-mediated α4β1 and α9β1 integrin signaling may be responsible for higher hepatic neutrophil infiltration and higher liver injury in the rat ASH model.