Alcoholic liver disease (ALD) is a major public health problem in the United States and women are known to be more susceptible to ALD. However, the precise mechanism for increased susceptibility of females to ALD is not completely understood. The present study is based on the hypothesis that induction of
osteopontin (OPN), a matricellular
protein, is the likely contributing factor for higher neutrophil recruitment in females during
alcoholic steatohepatitis (ASH). ASH was induced in male and female Sprague-Dawley rats by feeding them a Lieber-DeCarli diet containing
ethanol (EtOH) for 6 weeks, followed by a single injection of
lipopolysaccharide (LPS, 10 mg/kg, ip). Liver injury, measured by plasma
transaminase elevations and confirmed by haematoxylin and
eosin-stained liver sections, revealed approximately 25-fold higher liver injury in the female ASH model compared with the males. Although steatosis,
necrosis, and neutrophil infiltration were evident in both male and female rats, hepatic neutrophilic necrotic foci were noted as early
as 2 h after LPS injection in the EtOH-treated female rats. Hepatic neutrophil infiltration correlated with higher expression of cleaved (cOPN) and uncleaved OPN in the EtOH + LPS-treated female rats compared with the males. OPN secretion was localized predominantly in the biliary epithelium and females had significantly higher OPN
mRNA than their male counterparts in the ASH model. The ability of OPN to attract neutrophils was further confirmed in vivo, in a
peritonitis rat model, and by neutralizing OPN (nOPN) antibody experiments. Hepatic neutrophil infiltration was largely inhibited ( approximately 50%) by nOPN antibody. Flow cytometry experiments revealed OPN-mediated up-regulation of the CD11b neutrophil adhesion molecule. In conclusion, these data suggest that higher hepatic expression of OPN is the likely reason for higher and early hepatic neutrophil infiltration making females more susceptible to ALD during ASH.