Regulation of Mcl-1 expression in rheumatoid arthritis synovial macrophages.
OBJECTIVE
Resistance to apoptosis may be an important mechanism contributing to the persistence of rheumatoid arthritis (RA). This study was undertaken to characterize the expression, regulation, and function of the antiapoptotic Bcl-2 family member Mcl-1 in macrophages isolated from the joints of patients with RA.


METHODS
Mononuclear cells were isolated from the synovial fluid (SF) of patients with RA. Mcl-1 expression was documented by intracellular staining of CD14+ cells using flow cytometry, and by real-time polymerase chain reaction or immunoblot analysis of isolated macrophages. The expression of Mcl-1 was suppressed with small interfering RNA (siRNA) or chemical inhibitors of the phosphatidylinositol 3-kinase (PI 3-kinase)/Akt-1 and signal transducer and activator of transcription 3 (STAT-3) pathways. Apoptosis was defined by the loss of mitochondrial transmembrane potential and by DNA fragmentation.


RESULTS
The expression of Mcl-1 was increased in CD14+ macrophages from the SF of patients with RA compared with normal in vitro-differentiated macrophages. Inhibition of the PI 3-kinase/Akt-1 or STAT-3 pathways significantly reduced the percentage of CD14+ cells within the SF and resulted in the reduction of Mcl-1 and the induction of apoptosis of synovial macrophages. Transfection of RA synovial macrophages with Mcl-1 siRNA resulted in apoptotic cell death.


CONCLUSIONS
Mcl-1 is critical for the survival of macrophages in the joints of patients with RA, and is therefore a potential therapeutic target in this disease.
Liu
Hongtao
H
Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA.
Huang
QiQuan
Q
Shi
Bo
B
Eksarko
Polikseni
P
Temkin
Vladislav
V
Pope
Richard M
RM
D017209:Apoptosis / Q000235:genetics; D001172:Arthritis, Rheumatoid / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D006801:Humans; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D008264:Macrophages / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D009000:Monocytes / Q000378:metabolism / Q000473:pathology; D009025:Morpholines / Q000494:pharmacology; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D012980:Sodium Salicylate / Q000494:pharmacology; D013583:Synovial Membrane / Q000378:metabolism* / Q000473:pathology; D014162:Transfection
D002867:Chromones; D004791:Enzyme Inhibitors; D018950:Lipopolysaccharide Receptors; D009025:Morpholines; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D050796:STAT3 Transcription Factor; D012980:Sodium Salicylate; C494086:STAT3 protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one