title: PDE4 inhibition drives resolution of neutrophilic inflammation by inducing apoptosis in a PKA-PI3K/Akt-dependent and NF-kappaB-independent manner.
abstract: PDE4 inhibitors are effective anti-inflammatory drugs whose effects and putative mechanisms on resolution of inflammation and neutrophil apoptosis in vivo are still unclear. Here, we examined the effects of specific PDE4 inhibition on the resolution of neutrophilic inflammation in the pleural cavity of LPS-challenged mice. LPS induced neutrophil recruitment that was increased at 4 h, peaked at 8-24 h, and declined thereafter. Such an event in the pleural cavity was preceded by increased levels of KC and MIP-2 at 1 and 2 h. Treatment with the PDE4 inhibitor rolipram, at 4 h after LPS administration, decreased the number of neutrophils and increased the percentage of apoptotic cells in the pleural cavity in a PKA-dependent manner. Conversely, delayed treatment with a CXCR2 antagonist failed to prevent neutrophil recruitment. Forskolin and db-cAMP also decreased the number of neutrophils and increased apoptosis in the pleural cavity. The proapoptotic effect of rolipram was associated with decreased levels of the prosurvival protein Mcl-1 and increased caspase-3 cleavage. The pan-caspase inhibitor zVAD-fmk prevented rolipram-induced resolution of inflammation. LPS resulted in a time-dependent activation of Akt, which was blocked by treatment with rolipram or PI3K and Akt inhibitors, and PI3K and Akt inhibitors also enhanced apoptosis and promoted neutrophil clearance. Although LPS induced NF-kappaB activation, which was blocked by rolipram, NF-kappaB inhibitors did not promote resolution of neutrophil accumulation in this model. In conclusion, our data show that PDE4 inhibition resolves neutrophilic inflammation by promoting caspase-dependent apoptosis of inflammatory cells by targeting a PKA/PI3K/Akt-dependent survival pathway.
authors.affiliation: Setor de Patologia Clínica-Colégio Técnico, Imunofarmacologia-Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Lirlândia P
authors.initials: LP
authors.lastname: Sousa
authors.forename: Fernando
authors.initials: F
authors.lastname: Lopes
authors.forename: Douglas M
authors.initials: DM
authors.lastname: Silva
authors.forename: Luciana P
authors.initials: LP
authors.lastname: Tavares
authors.forename: Angélica T
authors.initials: AT
authors.lastname: Vieira
authors.forename: Bárbara M
authors.initials: BM
authors.lastname: Rezende
authors.forename: Aline F
authors.initials: AF
authors.lastname: Carmo
authors.forename: Remo C
authors.initials: RC
authors.lastname: Russo
authors.forename: Cristiana C
authors.initials: CC
authors.lastname: Garcia
authors.forename: Cláudio A
authors.initials: CA
authors.lastname: Bonjardim
authors.forename: Ana L
authors.initials: AL
authors.lastname: Alessandri
authors.forename: Adriano G
authors.initials: AG
authors.lastname: Rossi
authors.forename: Vanessa
authors.initials: V
authors.lastname: Pinho
authors.forename: Mauro M
authors.initials: MM
authors.lastname: Teixeira
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D015153:Blotting, Western; D002634:Chemotaxis, Leukocyte; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4 / Q000276:immunology / Q000378:metabolism*; D053938:DNA Fragmentation; D024202:Electrophoretic Mobility Shift Assay; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D007249:Inflammation / Q000139:chemically induced / Q000201:enzymology / Q000276:immunology*; D008070:Lipopolysaccharides / Q000276:immunology; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D009504:Neutrophils / Q000201:enzymology / Q000276:immunology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D035422:Pleural Cavity / Q000276:immunology / Q000473:pathology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology*
chemical_list: D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D017868:Cyclic AMP-Dependent Protein Kinases; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4