Pentoxifylline modulates intestinal tight junction signaling after burn injury: effects on myosin light chain kinase.
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)-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.


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-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.


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, IkappaB-alpha phosphorylation, and nuclear NF-kappaB p65 translocation to sham levels (p < 0.05 vs. NS).


CONCLUSIONS
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.
Costantini
Todd W
TW
Department of Surgery, Division of Trauma, Surgical Critical Care, and Burns, University of California, San Diego School of Medicine, San Diego, California 92103-8896, USA.
Loomis
William H
WH
Putnam
James G
JG
Kroll
Lauren
L
Eliceiri
Brian P
BP
Baird
Andrew
A
Bansal
Vishal
V
Coimbra
Raul
R
D000704:Analysis of Variance; D000818:Animals; D002056:Burns / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D015151:Immunoblotting; D007413:Intestinal Mucosa / Q000378:metabolism*; D008297:Male; D051379:Mice; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism*; D010431:Pentoxifylline / Q000494:pharmacology*; D011897:Random Allocation; D015398:Signal Transduction / Q000187:drug effects*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D014409:Tumor Necrosis Factor-alpha; D009219:Myosin-Light-Chain Kinase; D010431:Pentoxifylline