Cyclic ADP-ribose is a second messenger in the lipopolysaccharide-stimulated proliferation of human peripheral blood mononuclear cells.
Cyclic ADP-ribose (cADPR), a universal calcium mobilizer from intracellular stores, was recently demonstrated to stimulate proliferation of various cell types. The role of cADPR in a specific process of monocyte- and plasma-mediated activation of T-lymphocytes by lipopolysaccharide (LPS) was addressed using human mononuclear cells from peripheral blood (PBMCs). Incubation of PBMCs with 0.1 microg/ml of LPS for 24 h provided a doubling in the intracellular levels of cADPR as compared with unstimulated PBMCs. The cADPR increase was abolished either by prior removal of monocytes or by pre-incubating a whole PBMC population with a monoclonal antibody against the monocyte marker CD14. The increased concentrations of intracellular cADPR elicited by LPS stimulation were paralleled by significant increases in NAD+ levels and in the activities of ectocellular and membrane-bound fractions of ADP-ribosyl cyclase/cADPR hydrolase activities. A cytosolic ADP-ribosyl cyclase was also detectable in PBMCs and its activity was comparably enhanced by LPS stimulation. This soluble cyclase is distinguished from the membrane-bound cyclase by both substrate and inhibitor sensitivities. LPS-stimulated PBMCs showed 2-3-fold increases of intracellular calcium ([Ca2+]i), and these changes were prevented completely by the cADPR antagonist 8-Br-cADPR and by ryanodine. Both compounds, and the cyclase inhibitor nicotinamide, significantly inhibited the T-lymphocyte proliferation induced by LPS in PBMCs. These results demonstrate that cADPR plays a role of second messenger in the adaptive immune recognition process of LPS-stimulated proliferation of PBMCs.
Bruzzone
Santina
S
DI.ME.S. (Dipartimento di Medicina Sperimentale), Section of Biochemistry, University of Genova, Viale Benedetto XV/1, 16132 Genova, Italy.
De Flora
Antonio
A
Usai
Cesare
C
Graeff
Richard
R
Lee
Hon Cheung
HC
D036541:ADP-ribosyl Cyclase / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D036563:Cyclic ADP-Ribose / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018950:Lipopolysaccharide Receptors / Q000276:immunology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D009000:Monocytes / Q000502:physiology; D009699:N-Glycosyl Hydrolases / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D012433:Ryanodine / Q000494:pharmacology; D015290:Second Messenger Systems / Q000502:physiology*; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors
D000911:Antibodies, Monoclonal; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D009243:NAD; D036563:Cyclic ADP-Ribose; D012433:Ryanodine; D019284:Thapsigargin; C090939:GDP-ribosyl cyclase; D009699:N-Glycosyl Hydrolases; D036541:ADP-ribosyl Cyclase; D002118:Calcium