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

Abstract

Background: 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)-α activates MLCK, in part through a nuclear factor (NF)-κ B-dependent pathway. We have previously shown that pentoxifylline (PTX) decreases both TNF-α synthesis and NF-κB 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. Methods: 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-α levels were evaluated using enzyme linked immunosorbent assay. Gut extracts were obtained to assess MLCK, phosphorylated IKK, IκB-α, and NF-κB p65 levels by immunoblotting. Results: 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, IκB-α phosphorylation, and nuclear NF-κB p65 translocation to sham levels (p < 0.05 vs. NS). Conclusion: Treatment with PTX attenuates activation of the tight junction protein MLCK, likely through its ability to decrease local TNF-α synthesis and NF-κB activation after burn. PTX may have therapeutic utility by decreasing intestinal barrier breakdown after burn.