Matrix Metalloproteinase‐9 in Homocysteine‐Induced Intestinal Microvascular Endothelial Paracellular and Transcellular Permeability

Abstract

An elevated levels of homocysteine (Hcy), known as hyperhomocysteinemia (HHcy), is associated with inflammatory bowel disease, the mechanism of Hcy action is unclear. Therefore we hypothesize that HHcy activates matrix metalloproteinase‐9 (MMP‐9), which in turn enhances permeability of human intestinal microvascular endothelial cell (HIMEC) by decreasing expression of junction proteins and increasing caveolae. HIMECs were grown in Transwells and treated with Hcy in the presence or absence of MMP‐9 activity inhibitor. Hcy induced permeability was assessed by measuring fluorescence intensity of solutes in the Transwells’ lower chambers. The cell‐cell interaction and cell barrier function was estimated by measuring Trans‐ endothelial electrical impedance. Confocal microscopy and flow cytometry were used to study cell junction protein levels. Hcy‐induced changes in transcellular transport of HIMECs were estimated by observing formation caveolae and paracellular permeability was associated with degradation of vascular endothelial cadherin and zona occludin‐1. Elevation of Hcy content increases permeability of HIMEC layer affecting both paracellular and transcellular transport pathways, and this increased permeability was alleviated by inhibition of MMP‐9 activity. These findings contribute to clarification of mechanisms of inflammatory bowel disease development.