cAMP protects neutrophils against TNF-alpha-induced apoptosis by activation of cAMP-dependent protein kinase, independently of exchange protein directly activated by cAMP (Epac).
It is unclear by which receptor cyclic adenosine monophosphate (cAMP) acts to promote neutrophil survival. We found that 8-(4-chlorophenylthio)-2'-O-methyl-cAMP, a specific activator of the recently discovered cAMP receptor, cAMP-regulated guanosine 5'-triphosphate exchange protein directly activated by cAMP, failed to protect human neutrophils from cell death. In contrast, specific activators of cAMP-dependent protein kinase type I (cA-PKI) could protect against death receptor [tumor necrosis factor receptor 1 (TNFR-1), Fas]-mediated apoptosis as well as cycloheximide-accelerated "spontaneous" apoptosis. A novel "caged" cA-PK-activating analog, 8-bromo (8-Br)-acetoxymethyl-cAMP, was more than 20-fold more potent than 8-Br-cAMP to protect neutrophils challenged with TNF-alpha against apoptosis. This analog acted more rapidly than forskolin (which increases the endogenous cAMP production) and allowed us to demonstrate that cA-PK must be activated during the first 10 min after TNF-alpha challenge to protect against apoptosis. The protective effect was mediated solely through cA-PK activation, as it was abolished by the cA-PKI-directed inhibitor Rp-8-Br-cAMPS and the general cA-PK inhibitor H-89. Neutrophils not stimulated by cAMP-elevating agents showed increased apoptosis when exposed to the cA-PK inhibitors Rp-8-Br-cAMPS and H-89, suggesting that even moderate activation of cA-PK is sufficient to enhance neutrophil longevity and thereby contribute to neutrophil accumulation in chronic inflammation.
Krakstad
Camilla
C
Cell Biology Research Group, Department of Biomedicine, Section of Anatomy and Cell Biology, Jonas Lies vei 91, N-5009 Bergen, Norway.
Christensen
Anne Elisabeth
AE
Døskeland
Stein Ove
SO
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D015703:Antigens, CD / Q000187:drug effects / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology*; D002470:Cell Survival / Q000187:drug effects / Q000276:immunology*; D002478:Cells, Cultured; D002634:Chemotaxis, Leukocyte / Q000187:drug effects / Q000276:immunology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020662:Guanine Nucleotide Exchange Factors / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007249:Inflammation / Q000201:enzymology / Q000276:immunology; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology; D018124:Receptors, Tumor Necrosis Factor / Q000187:drug effects / Q000378:metabolism; D047888:Receptors, Tumor Necrosis Factor, Type I; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology
D015703:Antigens, CD; D004791:Enzyme Inhibitors; D020662:Guanine Nucleotide Exchange Factors; C116122:RAPGEF3 protein, human; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D014409:Tumor Necrosis Factor-alpha; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases