Physiologic Concentrations of TNFα and IL-1β Released from Reperfused Human Intestine Upregulate E-Selectin and ICAM-1

Intestinal ischemia–reperfusion (I/R) causes local and distant tissue injury via neutrophil (PMN) activation and adhesion. Endothelial cell adhesion molecules (E-selectin, ICAM-1) mediate the adhesion and transmigration of PMN in the microcirculation. Expression of these receptors is influenced by cytokines. To determine the physiologic concentrations of two specific cytokines involved in I/R, tumor necrosis factor (TNF) and interleukin-1 (IL-1), human intestinal segments were exposed to 30 min of ischemia followed by reperfusion. Venous effluent samples were obtained; enzyme immunoassays measured maximum concentrations of TNF (30.5 ± 1.0 pg/ml) and IL-1 (59.0 ± 6.0 pg/ml). Cultured human endothelial cells were then exposed to physiologic concentrations of human recombinant TNF (10 pg/ml) and IL-1 (10 pg/ml), individually and in combination. Flow cytometric analysis of receptor expression demonstrated upregulation of E-selectin as early as 2 hr (P< 0.05) with maximum effects at 4 hr. At 4 hr, E-selectin expression (% shift from baseline) was greater with TNF and IL-1 combined (50.9 ± 2.9,P< 0.01) than with either cytokine alone (TNF 34.6 ± 4.0; IL-1 23.5 ± 4.0,P< 0.01). ICAM-1 receptor expression began at 4 hr with maximum effects at 24 hr. ICAM-1 expression after TNF and IL-1 exposure (15.4 ± 1.3,P< 0.001) was also greater than TNF (10.9 ± 0.3,P< 0.01) or IL-1 (3.1 ± 1.5) alone. TNF and IL-1 are present in venous effluent in concentrations capable of increasing PMN adhesion in the microcirculation. These findings support a role for these cytokines in local and distant organ injury from I/R. Since combined effects are greater than either cytokine alone, antagonism of both TNF and IL-1 may be required for a therapeutic benefit in clinical applications.