Tnf modulates endothelial permeability and anticoagulant properties by activating phosphodiesterase and decreasing camp. Koga, S., S. Morris, Satoshi Ogawa, Hui Liao, J. P. Bilezikian, G. Chen, W. J. Thompson, T. Ashikaga, J. Brett, D. M. Stern, and D. J. Pinsky. Departments of Physiology and Medicine, Columbia University College of Physicians and Surgeons (New York, NY) and Department of Pharmacology, University of South Alabama College of Medicine (Mobile, AL)
APStracts 2:0004C, 1995.
Tumor necrosis factor-[alpha] (TNF), a monokine which contributes to vascular dysfunction accompanying the host response to gram negative sepsis, has been shown to increase vascular permeability in vivo and to diminish the barrier function of cultured endothelial cell (EC) monolayers. The studies reported here indicate that a mechanism through which TNF alters EC barrier function involves a reduction in intracellular cyclic AMP (cAMP) content, due in part to increased cyclic nucleotide phosphodiesterase (CN PDE) activities. TNF increased the diffusional transit of 3H-sorbitol, 3H-inulin, and 125I-albumin across confluent bovine aortic EC monolayers. This effect of TNF was both time- and dose-dependent, and occurred in parallel with a fall in EC cAMP. Cyclic AMP analogs, such as dibutyryl cAMP (db-cAMP), prevented TNF-induced perturbation of EC barrier function. TNF also mediated another important alteration in the EC phenotype, in that both mRNA and activity of the anticoagulant cofactor thrombomodulin was reduced following exposure of ECs to TNF and was normalized by the addition of db-cAMP. EC monolayers exposed to TNF[alpha] showed increased cAMP levels when exposed to isobutylmethylxanthine (IBMX), a non-specific CN PDE inhibitor. Ion exchange chromatography of cytosol derived from TNF-treated ECs consistently showed a near 245% increase in PDE IV (high affinity, cAMP specific PDE) activity as identified by rolipram inhibition. PDE II activity was increased by 150% following TNF[alpha] treatment of early passage ECs, identified by cGMP activated hydrolysis of cAMP. Western and Northern analyses, as well as activity studies, revealed that TNF treatment did not change the amount of PDE IV protein or mRNA, but rather increased the specific activity of the isozyme, suggesting a post -translational modification had occurred. These data indicate that activation of EC CN PDE activity and decreased intracellular cAMP may represent a mechanism by which TNF increases EC permeability and promotes a procoagulant EC phenotype. 

Received 1 October 1993; accepted in final form 1 November 1994
APS Manuscript Number C0485-3.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1994 The American Physiological Society.
Published in APStracts on 27 February 1995.