Cyclic AMP has the ability to influence multiple events during B cell stimulation.
Negative regulators of cellular proliferation are important in maintaining a balanced growth control. In this study we have examined the effects of the diterpene forskolin on various parameters of B cell activation. Forskolin is known to elevate intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels and thereby to influence B cell stimulation. We found that forskolin exerted an inhibitory effect on early as well as late events during stimulation of resting normal human B cells. Cells were activated either by antibodies to surface immunoglobulins (anti-mu), by the monoclonal antibody 1F5 reactive with the CD20 antigen or by 12-O-tetradecanoylphorbol 13-acetate. While anti-mu stimulation induces increased phosphatidylinositol (PI) turnover and [Ca2+]i fluxes, the latter two reagents confer an activation of B cells independent of the PI/Ca2+ pathway. We found a clear inhibitory effect of forskolin on the anti-mu-induced PI turnover and [Ca2+]i fluxes as well as on later parameters of cell activation. There was also a clear inhibition of G1 entry and DNA synthesis when PI/Ca2+-independent activation was employed, indicating that cAMP interferes with B lymphocyte stimulation in several ways. Importantly, forskolin maintained its inhibitory effect when added late after anti-mu stimulation, implying an effect also at multiple stages of activation. When examining the inhibitory effect of forskolin on neoplastic B cells, we found essentially no differences from the responses in normal cells.
Holte
H
H
Department of Pathology, Institute for Cancer Research, Oslo, Norway.
Torjesen
P
P
Blomhoff
H K
HK
Ruud
E
E
Funderud
S
S
Smeland
E B
EB
D000911:Antibodies, Monoclonal / Q000276:immunology; D018951:Antigens, CD20; D000944:Antigens, Differentiation, B-Lymphocyte / Q000502:physiology; D001402:B-Lymphocytes / Q000502:physiology*; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D005576:Colforsin / Q000494:pharmacology*; D000242:Cyclic AMP / Q000502:physiology*; D004261:DNA Replication / Q000187:drug effects; D006801:Humans; D007148:Immunoglobulin mu-Chains / Q000276:immunology; D066298:In Vitro Techniques; D008213:Lymphocyte Activation / Q000187:drug effects*; D010716:Phosphatidylinositols / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D018951:Antigens, CD20; D000944:Antigens, Differentiation, B-Lymphocyte; D007148:Immunoglobulin mu-Chains; D010716:Phosphatidylinositols; D005576:Colforsin; D000242:Cyclic AMP; D013755:Tetradecanoylphorbol Acetate