Impairment of TNF-alpha production and action by imidazo[1,2- alpha] quinoxalines, a derivative family which displays potential anti-inflammatory properties.
In a previous study, we analysed the synthesis and properties of a series of imidazo[1,2-alpha]quinoxalines designed in our laboratory as possible imiquimod analogues. We found that these imidazo[1,2-alpha]quinoxalines were in fact potent inhibitors of phosphodiesterase 4 enzymes (PDE4). PDE4 inhibition normally results in an increase in intracellular cAMP which, in PBMC, induces the suppression of TNF-alpha mRNA transcription and thus cytokine synthesis. Such an effect is antagonistic to that of imiquimod. Furthermore, some TNF-alpha-induced activity, such as cell apoptosis which is dependent on the intracellular cAMP levels might also be affected. Therefore, by counteracting the properties of TNF-alpha and/or its production, the imidazo[1,2-alpha]quinoxalines could be considered as potential anti-inflammatory drugs. The present study was performed to confirm or refute this hypothesis. For this, we characterized the effects of imidazo[1,2-alpha]quinoxalines both on TNF-alpha activity and synthesis in regard to their ability to act as inhibitors of PDE4 (IPDE4). We found that the imidazo[1,2-alpha]quinoxalines dose-dependently prevented the TNF-alpha-triggered death of L929 cells, with the 8-series (-NHCH3 in R4) being the most potent. Moreover, when the effect of the 8-series on TNF-alpha production was investigated using gamma9delta2 T cells, it was observed that these compounds impaired the TCR:CD3-triggered TNF-alpha production. Structure-activity analysis revealed that these properties of the drugs did not coincide with their IPDE4 properties. This prompted further exploration into other signalling mechanisms possibly involved in TNF-alpha action and production, notably the p38 MAPK and the PI3K pathway. We demonstrate here that the imidazo[1,2-alpha]quinoxalines targeted these pathways in a different way: they activated the p38 MAPK pathway whilst inhibiting the PI3K pathway. Such effects on cell signalling could account for the imidazo[1,2-alpha]quinoxalines effects on 1) action and 2) production of TNF-alpha, which define these drugs as potential anti-inflammatory agents.
Morjaria
S
S
INSERM U431, University of Montpellier, France.
Deleuze-Masquefa
C
C
Lafont
V
V
Gayraud
S
S
Bompart
J
J
Bonnet
P A
PA
Dornand
J
J
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors*; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D002460:Cell Line; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D004789:Enzyme Activation / Q000187:drug effects; D020935:MAP Kinase Signaling System / Q000187:drug effects; D051379:Mice; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011810:Quinoxalines / Q000494:pharmacology*; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000032:analysis; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis*; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology
D015105:3',5'-Cyclic-AMP Phosphodiesterases; D000893:Anti-Inflammatory Agents; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D019869:Phosphatidylinositol 3-Kinases; D010726:Phosphodiesterase Inhibitors; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011810:Quinoxalines; D016692:Receptors, Antigen, T-Cell, gamma-delta; D014409:Tumor Necrosis Factor-alpha; D048051:p38 Mitogen-Activated Protein Kinases