Responses of Human Intestinal Microvascular Endothelial Cells to Shiga Toxins 1 and 2 and Pathogenesis of Hemorrhagic Colitis

Abstract

Endothelial damage is characteristic of infection with Shiga toxin (Stx)-producing Escherichia coli (STEC). Because Stx-mediated endothelial cell damage at the site of infection may lead to the characteristic hemorrhagic colitis of STEC infection, we compared the effects of Stx1 and Stx2 on primary and transformed human intestinal microvascular endothelial cells (HIMEC) to those on macrovascular endothelial cells from human saphenous vein (HSVEC). Adhesion molecule, interleukin-8 (IL-8), and Stx receptor expression, the effects of cytokine activation and Stx toxins on these responses, and Stx1 and Stx2 binding kinetics and bioactivity were measured. Adhesion molecule and IL-8 expression increased in activated HIMEC, but these responses were blunted in the presence of toxin, especially in the presence of Stx1. In contrast to HSVEC, unstimulated HIMEC constitutively expressed Stx receptor at high levels, bound large amounts of toxin, were highly sensitive to toxin, and were not further sensitized by cytokines. Although the binding capacities of HIMEC for Stx1 and Stx2 were comparable, the binding affinity of Stx1 to HIMEC was 50-fold greater than that of Stx2. Nonetheless, Stx2 was more toxic to HIMEC than an equivalent amount of Stx1. The decreased binding affinity and increased toxicity for HIMEC of Stx2 compared to those of Stx1 may be relevant to the preponderance of Stx2-producing STEC involved in the pathogenesis of hemorrhagic colitis and its systemic complications. The differences between primary and transformed HIMEC in these responses were negligible. We conclude that transformed HIMEC lines could represent a simple physiologically relevant model to study the role of Stx in the pathogenesis of hemorrhagic colitis.

Pectins and pectic-oligosaccharides inhibit Escherichia coli O157:H7 Shiga toxin as directed towards the human colonic cell line HT29

“…These di¡erences in toxicity have also been found in mice, where Stx2 had an LD 50 that was 400 times lower than that of Stx1 [20]. Similar results have been reported in endothelial cell studies [21].…”

Escherichia coli, cattle and the propagation of disease

“…The amount of the Gb 3 receptor that is present on human renal microvascular endothelial cells is about 50 times larger than the amount found in larger blood vessels (Obrig et al 1993;Amaral et al 2013). A key mechanism of action of Stx1 and Stx2 involves their ability to inhibit the synthesis of proteins, but they have additional effects, such as the activation of cellular stress signaling pathways (Jacewicz et al 1999;Lee et al 2016). These molecular effects were linked to necrosis and apoptosis in the cells of the microvascular endothelium (Pruimboom-Brees et al 2000).…”

Virulence factors of Escherichia coli O157 and other Shiga toxin-producing E. coli

“…The association of Stx2-producing E. coli with the development of HUS may re£ect a preferential ability of Stx2 to damage renal glomerular vasculature. Using transformed human intestinal microvascular endothelial cells Jacewicz et al (1999) showed that Stx2 was more toxic than Stx1 for these cells.The authors concluded that the increased toxicity of Stx2 to endothelial cells may be relevant to the preponderance of Stx2 producers in the pathogenesis of HC.…”