The immunosuppressant cyclosporin A antagonizes human formyl peptide receptor through inhibition of cognate ligand binding.
Cyclosporin A (CsA) is a fungus-derived cyclic undecapeptide with potent immunosuppressive activity. Its analog, cyclosporin H (CsH), lacks immunosuppressive function but can act as an antagonist for the human formyl peptide receptor (FPR). More recent studies have shown that CsA also inhibits fMLF-induced degranulation in differentiated HL-60 promyelocytic leukemia cells. However, it is unclear whether CsA interferes with ligand-receptor interaction, G protein activation, or other downstream signaling events. In this study we used human neutrophils, differentiated HL-60 cells, and rat basophilic leukemia (RBL)-2H3 cells expressing human FPR (RBL-FPR) to identify the action site of CsA. In functional assays, CsA inhibited fMLF-stimulated degranulation, chemotaxis, calcium mobilization, and phosphorylation of the MAPKs ERK 1/2 and the serine/threonine protein kinase Akt. CsA also blocked Trp-Lys-Tyr-Met-Val-D-Met (WKYMVm)-induced functions in RBL-FPR cells. Concentrations for half-maximal inhibition with CsA are generally 6- to 50-fold higher than that of CsH. CsA was compared with another immunosuppressant, ascomycin, relative to the inhibitory effects on FPR-mediated chemotaxis, calcium mobilization, and degranulation. In these experiments, ascomycin produced no inhibitory effects at low micromolar concentrations (1-4 microM), whereas the inhibitory effects of CsA were prominent at comparable concentrations. Finally, CsA dose-dependently inhibited the uptake of fNle-Leu-Phe-Nle-Tyr-Lys-fluoresceine and [3H]fMLF or [125I]WKYMVm binding to FPR. However, CsA and CsH did not show any obvious inhibitory effect on FPR-like 1-mediated cellular functions. These results demonstrate that CsA is a selective antagonist of FPR and that its inhibition of fMLF-stimulated leukocyte activation is at the level of cognate ligand binding.
Yan
Pangke
P
National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.
Nanamori
Masakatsu
M
Sun
Meiling
M
Zhou
Caihong
C
Cheng
Ni
N
Li
Na
N
Zheng
Wei
W
Xiao
Lihua
L
Xie
Xin
X
Ye
Richard D
RD
Wang
Ming-Wei
MW
D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects / Q000276:immunology; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism; D015550:Cell Degranulation / Q000187:drug effects / Q000276:immunology; D045744:Cell Line, Tumor; D002464:Cell Migration Inhibition; D002634:Chemotaxis, Leukocyte / Q000187:drug effects / Q000276:immunology; D016572:Cyclosporine / Q000494:pharmacology*; D018922:HL-60 Cells; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D008024:Ligands; D018375:Neutrophil Activation / Q000187:drug effects; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects / Q000276:immunology; D051381:Rats; D044042:Receptors, Formyl Peptide / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D016559:Tacrolimus / Q000031:analogs & derivatives / Q000494:pharmacology
D007166:Immunosuppressive Agents; D008024:Ligands; D044042:Receptors, Formyl Peptide; D016572:Cyclosporine; C058028:immunomycin; C050025:cyclosporin H; D002118:Calcium; D016559:Tacrolimus