The specific type IV phosphodiesterase inhibitor rolipram combined with adenosine reduces tumor necrosis factor-α-primed neutrophil oxidative activity

Abstract

Monocytes and macrophages produce tumor necrosis factor-α (TNFα) in response to microbial products including endotoxin. TNFα is a potent primer of neutrophil (PMN) oxidative activity. Certain xanthine phosphodiesterase (PDE) inhibitors such as pentoxifylline have been shown to inhibit stimulated oxidative activity in PMN. In the present study, the non-xanthine PDE type IV inhibitor rolipram (4-[3′-cyclopentyloxy-4′-methoxyphenyl]-2-pyrrolidone) alone and in combination with adenosine is examined as a potential modulator of TNFα-primed PMN oxidative activity. Attainable in vivo concentrations of rolipram and physiological concentrations of adenosine alone and together synergistically decreased rhTNFα-primed suspended PMN oxidative activity stimulated by the chemoattractant f-met-leu-phe. The rolipram effect was reversible by washing, and rolipram had a comparable effect if added before or after priming, indicating that its effect was on the primed response rather than on priming per se. In addition, rolipram especially when combined with adenosine, decreased rhTNFα-stimulated PMN adherence to a fibrinogen-coated surface, and the oxidative burst of rhTNFα-stimulated adherent PMN. The specific adenosine A 2a receptor agonists CGS 21680 and WRC-0474 had comparable activity to adenosine in these experiments. Adenosine (or CGS 21680) combined with rolipram synergistically increased f-met-leu-phe-stimulated PMN cAMP content. The effects of both adenosine and rolipram with adenosine could be only partly counteracted by treatment of the PMN with the protein kinase A inhibitor KT 5720, indicating that protein phosphorylation is only partially involved. Rolipram activity was about 1000x (by molar concentration) greater than pentoxifylline in comparable assays. Thus, rolipram, especially when combined with adenosine, has potent modulating effects on PMN activation and may be useful in decreasing inflammatory tissue damage in patients with sepsis.