Abstract
In an attempt to elaborate in vitro on a therapeutic strategy that counteracts an inflammatory signal, we previously reported a novel immunopharmacological potential of glutathione, an antioxidant thiol, in regulating inflammatory cytokines. In the present study, we investigated the hypothesis that selective regulation of phosphodiesterases (PDEs), a family of enzymes that controls intracellular cAMP/cGMP degradation, differentially regulates proinflammatory cytokines. Selective PDE1 inhibition (8-methoxymethyl-3-isobutyl-1-methylxanthine) blockaded lipopolysaccharide-endotoxin (LPS)-mediated biosynthesis of interleukin (IL)-6, but this pathway had no inhibitory effect on tumor necrosis factor-α (TNF-α). Furthermore, inhibition of PDE3 (amrinone) abolished the effect of LPS on IL-6, but attenuated TNF-α production. Reversible competitive inhibition of PDE4 (rolipram) exhibited a potent inhibitory effect on IL-6 and a dual, biphasic (excitatory/inhibitory) effect on TNF-α secretion. Blockading PDE5 (4-{[3′,4′-(methylenedioxy)benzyl] amino}-6-methoxyquinazoline) showed a high potency in reducing IL-6 production, but in a manner similar to the inhibition of PDE4, exhibited a biphasic effect on TNF-α biosynthesis. Simultaneous inhibition of PDE5, 6, and 9 (zaprinast), purported to specifically elevate intracellular cGMP, reduced, in a dose-independent manner, IL-6 and TNF-α biosynthesis. Finally, nonselective inhibition of PDE by pentoxifylline suppressed LPS-mediated secretion of IL-6 and TNF-α. The involvement of specific PDE isoenzymes in differentially regulating LPS-mediated inflammatory cytokine biosynthesis indicates a novel approach to unravel the potential therapeutic targets that these isozymes constitute during the progression of inflammation within the respiratory epithelium.
Footnotes
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This study was supported by grants from the Medical Research Council, Anonymous Trust, and Tenovus-Scotland (to S.C.L.), and R.L. allocated grants for supporting this research. J.J.H. holds the Georges John Livanos prize (London). Parts of this work were presented at Experimental Biology meeting; 2001 March 31–April 4; Orlando, FL.
- Abbreviations:
- LPS
- lipopolysaccharide-endotoxin
- PDE
- phosphodiesterase
- DMEM
- Dulbecco's modified Eagle's medium
- FCS
- fetal calf serum
- ELISA
- enzyme-linked immunosorbent assay
- IL
- interleukin
- TNF-α
- tumor necrosis factor-α
- PDEI
- phosphodiesterase inhibitor
- 8-methoxymethyl-IBMX
- 8-methoxymethyl-3-isobutyl-1-methylxanthine
- MBMQ
- 4-{[3′,4′-(methylenedioxy)benzyl]amino}-6-methoxyquinazoline
- RNS
- reactive nitrogen species
- ROS
- reactive oxygen species. SB-207499,c-4-cyano-4-(3-cyclopentyloxy-4-methoxyphenyl-r-l-cyclohexane carboxylic acid
- RPR-73401
- 3-cyclopentyloxy-N-(3,5-dichloro-4-pyridyl)-4-methoxybenzamide
- Received July 27, 2001.
- Accepted November 2, 2001.
- The American Society for Pharmacology and Experimental Therapeutics
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