Pentoxifylline Modulates Intestinal Tight Junction Signaling After Burn Injury: Effects on Myosin Light Chain Kinase

Abstract

Burn injury can result in loss of intestinal barrier function, leading to systemic inflammatory response syndrome and multiorgan failure. Myosin light chain kinase (MLCK), a tight junction protein involved in the regulation of barrier function, increases intestinal epithelial permeability when activated. Prior studies have shown that tumor necrosis factor (TNF)-alpha activates MLCK, in part through a nuclear factor (NF)-kappa B-dependent pathway. We have previously shown that pentoxifylline (PTX) decreases both TNF-alpha synthesis and NF-kappaB activation in models of shock. Therefore, we postulate that PTX will attenuate activation of the tight junction protein MLCK, which may decrease intestinal tight junction permeability after severe burn. Male balb/c mice undergoing a severe burn were randomized to resuscitation with normal saline (NS) or NS + PTX (12.5 mg/kg). Intestinal TNF-alpha levels were evaluated using enzyme linked immunosorbent assay. Gut extracts were obtained to assess MLCK, phosphorylated IKK, IkappaB-alpha, and NF-kappaB p65 levels by immunoblotting. Burn injury increased intestinal MLCK protein levels threefold in animals resuscitated with NS, whereas those receiving PTX had MLCK levels similar to control (p < 0.01). Treatment with PTX attenuated burn-induced intestinal permeability. PTX decreased cytoplasmic IKK, IkappaB-alpha phosphorylation, and nuclear NF-kappaB p65 translocation to sham levels (p < 0.05 vs. NS). Treatment with PTX attenuates activation of the tight junction protein MLCK, likely through its ability to decrease local TNF-alpha synthesis and NF-kappaB activation after burn. PTX may have therapeutic utility by decreasing intestinal barrier breakdown after burn.