Decrease of PECAM-1-gene-expression induced by proinflammatory cytokines IFN-γ and IFN-α is reversed by TGF-β in sinusoidal endothelial cells and hepatic mononuclear phagocytes

Abstract

Background and aim

The mechanisms of transmigration of inflammatory cells through the sinusoids are still poorly understood. This study aims to identify in vitro conditions (cytokine treatment) which may allow a better understanding of the changes in PECAM (platelet endothelial cell adhesion molecule)-1-gene-expression observed in vivo.

Methods and results

In this study we show by immunohistochemistry, that there is an accumulation of ICAM-1 (intercellular cell adhesion molecule-1) and ED1 positive cells in necrotic areas of livers of CCl ₄-treated rats, whereas there are few PECAM-1 positive cells observable. After the administration of CCl ₄, we could detect an early rise of levels of IFN-γ followed by an enhanced TGF-β protein level. As shown by Northern blot analysis and surface protein expression analysed by flow cytometry, IFN-γ-treatment decreased PECAM-1-gene-expression in isolated SECs (sinusoidal endothelial cells) and mononuclear phagocytes (MNPs) in parallel with an increase in ICAM-1-gene-expression in a dose and time dependent manner. In contrast, TGF-β-treatment increased PECAM-1-expression. Additional administration of IFN-γ to CCl ₄-treated rats and observations in IFN-γ ^-/- mice confirmed the effect of IFN-γ on PECAM-1 and ICAM-1-expression observed in vitro and increased the number of ED1-expressing cells 12 h after administration of the toxin.

Conclusion

The early decrease of PECAM-1-expression and the parallel increase of ICAM-1-expression following CCl ₄-treatment is induced by elevated levels of IFN-γ in livers and may facilitate adhesion and transmigration of inflammatory cells. The up-regulation of PECAM-1-expression in SECs and MNPs after TGF-β-treatment suggests the involvement of PECAM-1 during the recovery after liver damage.