Bryostatin-1 attenuates TNF-induced epithelial barrier dysfunction: role of novel PKC isozymes

• Published in: American journal of physiology: Gastrointestinal and liver physiology 2003-04, Vol.284 (4), p.G703-G712
• Main Authors: Yoo, James, Nichols, Anthony, Song, Jaekyung C, Mammen, Joshua, Calvo, Isabel, Worrell, Roger T, Cuppoletti, John, Matlin, Karl, Matthews, Jeffrey B
• Format: Article
• Language: English
• Subjects: Antigens, CD - metabolism; Antineoplastic Agents - pharmacology; Biological Transport - drug effects; Biological Transport - physiology; Bryostatins; Cells, Cultured; Dose-Response Relationship, Drug; Epithelial Cells - drug effects; Epithelial Cells - metabolism; Humans; Intestinal Mucosa - cytology; Intestinal Mucosa - metabolism; Iodine Radioisotopes; Lactones - pharmacology; Macrolides; Mannitol - pharmacokinetics; Protein Kinase C - metabolism; Protein Kinase C-delta; Protein Kinase C-epsilon; Receptors, Tumor Necrosis Factor - metabolism; Receptors, Tumor Necrosis Factor, Type I; Signal Transduction - drug effects; Signal Transduction - physiology; Tritium; Tumor Necrosis Factor-alpha - metabolism; Tumor Necrosis Factor-alpha - pharmacology
• ISSN: 0193-1857; 1522-1547
• DOI: 10.1152/ajpgi.00214.2002

Tumor necrosis factor (TNF) increases epithelial permeability in many model systems. Protein kinase C (PKC) isozymes regulate epithelial barrier function and alter ligand-receptor interactions. We sought to define the impact of PKC on TNF-induced barrier dysfunction in T84 intestinal epithelia. TNF induced a dose- and time-dependent fall in transepithelial electrical resistance (TER) and an increase in [(3)H]mannitol flux. The TNF-induced fall in TER was not PKC mediated but was prevented by pretreatment with bryostatin-1, a PKC agonist. As demonstrated by a pattern of sensitivity to pharmacological inhibitors of PKC, this epithelial barrier preservation was mediated by novel PKC isozymes. Bryostatin-1 reduced TNF receptor (TNF-R1) surface availability, as demonstrated by radiolabeled TNF binding and cell surface biotinylation assays, and increased TNF-R1 receptor shedding. The pattern of sensitivity to isozyme-selective PKC inhibitors suggested that these effects were mediated by activation of PKC-epsilon. In addition, after bryostatin-1 treatment, PKC-delta and TNF-R1 became associated, as determined by mutual coimmunoprecipitation assay, which has been shown to lead to receptor desensitization in neutrophils. TNF-induced barrier dysfunction occurs independently of PKC, but selective modulation of novel PKC isozymes may regulate TNF-R1 signaling.