Modulation of tumor necrosis factor-induced increase in renal (LLC-PK1) transepithelial permeability

Abstract

Tumor necrosis factor-alpha (TNF) causes a spontaneously reversible increase in tight junction permeability. TNF was the only cytokine tested that produced this effect. The effect on transepithelial permeability proceeds in four distinct phases: 1) a 60- to 90-min delay from time of application of TNF, 2) a rapid decrease in transepithelial resistance, 3) a recovery of transepithelial resistance to control level within 1 h, and 4) a further increase of transepithelial resistance above control levels. The recovery of transepithelial resistance occurs with or without TNF in the culture medium. Different protein kinase inhibitors affected different phases of this overall process. The tyrosine kinase inhibitor genistein significantly blocked the TNF effect. Neither transcription nor protein synthesis was required for transepithelial permeability to increase, but were required for the recovery. After the tight junctions have opened at 2 h in response to TNF, a second application of TNF will not produce the effect again for at least 12 h. The tight junctions will, however, open in response to phorbol esters during this time frame. Electron microscopy studies using apically applied ruthenium red suggest that TNF action results in < 10% of the junctions having increased permeability at any given time during the resistance decrease. The role of epithelial barrier permeability changes in TNF action in vivo is discussed.

Alcohol, intestinal bacterial growth, intestinal permeability to endotoxin, and medical consequences: Summary of a symposium

“…Tumor necrosis factor-α (TNF-α) appears to play an important role in regulating intestinal epithelial barrier function since TNFα-neutralizing antibodies restored barrier function in Crohn's disease patients (Suenaert et al, 2002). Exposure of cultured epithelial monolayers to TNF-α in vitro caused epithelial barrier loss (Mullin et al, 1992;Marano et al, 1998). In another study, exposure of cultured epithelial monolayers to TNF-α increased MLC phosphorylation which was associated with impaired barrier function (Zolotarevsky et al, 2002).…”

Molecular Basis of Epithelial Barrier Regulation

“…50,51 There have been many hypotheses as to the mechanism of TNF-induced barrier dysfunction, including single cell epithelial apoptosis, 52 nonapoptotic mechanisms, 53 and reduced transcription of tight junction proteins. 54 Although a role for each of these processes cannot be excluded, a series of recent reports suggests that TNF regulates tight junction permeability via cytoskeletal contraction.…”

Decreased epithelial barrier function evoked by exposure to metabolic stress and nonpathogenicE. coliis enhanced by TNF-α

“…Since macrophages, even metabolically stressed macrophages (Table 1), release a variety of mediators following activation, we opted to focus subsequent studies on TNF-␣, a factor which has been implicated in IBD and has been shown to affect endothelial (11,12), gut (38), and kidney (25,26) epithelial permeability.…”

“…This loss of epithelial integrity was inhibited by neutralizing antibodies to TNF-␣. Although TNF-␣ can directly increase paracellular permeability across selected renal and enteric epithelial cell lines (25,38), by itself TNF-␣ has minimal direct effects on the barrier properties of T84 cell monolayers (4,23), indicating that TNF-␣ was either activating LPMC and/or working in concert with other mediators released from the LPMC to increase the permeability to T84 cell monolayers (50).…”