Adiponectin induces pro-inflammatory cytokines in kupffer cells and tolerance to itself via the generation of IL-10

Exogenous adiponectin (Acrp) reduces the severity of CCl4-induced liver fibrosis and has been shown to abrogate LPS-induced cytokine release by Kupffer cells (KC). However, Acrp also directly stimulates pro-inflammatory and pro-fibrotic cytokine release by KCs. The mechanism for Acrp-induced pro-inflammatory responses in KCs has not been adequately defined. We sought to characterise the mechanisms which underlie the pro-inflammatory effects of Acrp. Methods Day 2 primary rat KCs were treated with 1 mg/ml full length Acrp (flAcrp) for 4 h. The induction of KC tolerance to adiponectin was examined by priming KCs with flAcrp for 18 h and subsequent re-treatment for 4 h. To test for the presence of an IL-10 autocrine loop, 5 mg/ml soluble anti-rat IL-10 antibody or 20 ng/ml recombinant rat IL-10 was applied in conjunction with flAcrp treatment for 4 h. We determined the relative expression of cytokines using real-time qPCR. To ascertain if any Acrp signal transduction pathways in KC were affected, we performed a time course study and examined for phospho-protein changes through Western Blot analysis. Results IL-10 mRNA was increased 68-fold following flAcrp treatment for 4 h. flAcrp induced TNFa mRNA 202-fold, TGFb mRNA 2-fold and IL-6 mRNA 20-fold, while PDGF mRNA remained unchanged when compared to control KCs. Priming KC for 18 h with flAcrp prior to treat- ment abrogated this up-regulation. TNFa mRNA decreased 2.5-fold (p < 0.05), TGFb mRNA deceased 5-fold (p < 0.005), PDGF mRNA decreased 4-fold (p < 0.005) and IL-6 mRNA decreased 5-fold (p < 0.005) compared to non-Acrp-primed KCs. Inflammatory cytokine up-regulation in 4 h Acrp treated KCs was overturned in KCs treated with flAcrp and exogenous IL-10 peptide. Conversely, IL-10 antibody prevented inflammatory cytokine down-regulation in Acrp-primed KCs. No change in Acrp signal transduction was recorded after Acrp-priming. We postulate that IL-10 synthesised during the priming period modulates the cytokine down-regulation in tolerized cells. Conclusions These observations suggest that Acrp mediates acute inflammatory responses in KCs that are down-regulated by IL-10. These pro-inflammatory effects may be important in mediating liver injury in conditions associated with rapid and massive weight loss.

Journal of Gastroenterology and Hepatology

Journal of Gastroenterology and Hepatology

24

1440-1746

N/A

Suppl. 2

1