Heme Oxygenase-1 Enhances Cell-Cell Contact By Upregulating Tight Junctions Proteins In Caco-2 Cells

Recent studies disclosed that the induction of heme oxygenase-1 (HO-1) expression plays a critical protective role in intestinal damage models. This indicates that activation of HO-1 may be involved in an endogenous defensive mechanism by reducing inflammation and tissue injury in the gastrointestinal tract. In this study, we investigated the role of HO-1 on cell-cell connections, cell motility, and the intracellular distribution of endogenous junctional proteins. We tested the alteration of Claudin-4, Occludin and ZO-1 expression in the hypoxia environment. We measured the gene expression after HO-1 overexpression in this condition. We also did the immunofluorescence experiment to see the expression of these proteins under microscope. After Caco-2 cells was cultured for 2 h, 4 h, 8 h in the hypoxia environment, Claudin-4 and HIF-1 alpha robustly increased in a time dependent manner, but Occludin and ZO-1 significantly decreased. With HO-1 overexpression by virus infection, the expression level of Occludin and ZO-1 were rescued in the hypoxia condition. The Caco-2 cells with control virus infection showed the similar expression panel with the control cells under hypoxia condition. In the immunofluorescence assay, under normal condition, the Occludin and ZO-1 proteins mostly distributed along the cell membrane and closely arranged as a linear with smooth edge. Hypoxia environment disrupted this structure, making these two proteins expressed in a non-close manner. HO-1 overexpression could rescue this type of derangement. Our study showed that HO-1 protein could upregulate the expression of Claudin-4 and ZO-1 proteins and enhance the cell-cell contact.