TNF modulates endothelial properties by decreasing cAMP

Abstract

Tumor necrosis factor-alpha (TNF-alpha), a monokine that 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 adenosine 3',5'-cyclic monophosphate (cAMP) content, due in part to increased cyclic nucleotide phosphodiesterase (CNPDE) activities. TNF increased the diffusional transit of [3H]sorbitol, [3H]inulin, and 125I-labeled 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. cAMP analogues, such as dibutyryl cAMP (DBcAMP), 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 were reduced after exposure of EC to TNF and were normalized by the addition of DBcAMP. EC monolayers exposed to TNF-alpha showed increased cAMP levels when exposed to 3-isobutyl-1-methylxanthine, a nonspecific CNPDE inhibitor. Ion exchange chromatography of cytosol derived from TNF-treated EC consistently showed an approximately 245% increase in phosphodiesterase (PDE) IV (high-affinity, cAMP-specific PDE) activity as identified by rolipram inhibition. PDE II activity was increased by 150% after TNF-alpha treatment of early passage EC, which was 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 that a posttranslational modification had occurred. These data indicate that activation of EC CNPDE activity and decreased intracellular cAMP may represent a mechanism by which TNF increases EC permeability and promotes a procoagulant EC phenotype.

Knockdown of lung phosphodiesterase 2A attenuates alveolar inflammation and protein leak in a two-hit mouse model of acute lung injury

“…associated pneumonia (35) and gram-negative bacilli are also a common cause of ventilator-associated pneumonia in critically ill patients requiring mechanical ventilation (48). Moreover, TNF-␣, a proinflammatory cytokine generated by LPS stimulation, was shown to increase PDE2A expression in aortic (22) and human umbilical vein (41,44) endothelium. On the basis of these data, and our previous observation that HV T ventilation alone caused a PDE2A-mediated injury (39), we reasoned that the combination of LPS and HV T could represent a particularly potent stimulus of PDE2A expression in the lung.…”

“…PDE2A hydrolyzes both cGMP and cAMP but is stimulated by cGMP to preferentially hydrolyze cAMP when cGMP levels are high (8, 44). PDE2A expression was increased by TNF-␣ in cultured systemic endothelial cells (22,41,44) by a p38 MAPK-dependent mechanism (44). Under these conditions, the generation of cGMP by NO donors resulted in the loss of in vitro barrier function through hydrolysis of cAMP (41,44).…”

Adenoviral TNF-α gene therapy and radiation damage tumor vasculature in a human malignant glioma xenograft

“…[21][22][23][24] Apoptosis of endothelial cells can cause the loss of endothelial cell anticoagulant surface components and increased expression of phosphatidylserine leading to a procoagulant microenvironment. 25 In addition, TNF-␣ has been observed to promote a procoagulant state in vivo by directly inhibiting thrombomodulin production 26 and enhancing tissue factor synthesis. 27,28 Similarly, ionizing radiation has been associated with a procoagulant state 29,30 as well as endothelial apoptosis.…”

Acute bacterial pneumonia in rats increases alveolar epithelial fluid clearance by a tumor necrosis factor-alpha-dependent mechanism.

“…After binding to the receptor, TNF␣ may induce a variety of intracellular signals. Since TNF␣ is known to decrease cAMP (53,54), it is not likely that the enhanced sodium and fluid absorption in these studies is mediated by cAMP, a second messenger that is known to increase vectorial sodium transport in alveolar type II cells (35,40). However, interestingly, TNF␣ does regulate G proteins (55), and recently G proteins have been reported to regulate amiloride-sensitive sodium uptake in fetal alveolar type II epithelial cells (56).…”