C-reactive protein induces high-mobility group box-1 protein release through activation of p38MAPK in macrophage RAW264.7 cells.
BACKGROUND
C-reactive protein (CRP) is widely used as a sensitive biomarker for inflammation. Increasing evidence suggests that CRP plays a role in inflammation. High-mobility group box-1 (HMGB1), a primarily nuclear protein, is passively released into the extracellular milieu by necrotic or damaged cells and is actively secreted by monocytes/macrophages. Extracellular HMGB1 as a potent inflammatory mediator has stimulated immense curiosity in the field of inflammation research. However, the molecular dialogue implicated between CRP and HMGB1 in delayed inflammatory processes remains to be explored.


RESULTS
The levels of HMGB1 in culture supernatants were determined by Western blot analysis and enzyme-linked immunosorbent assay in macrophage RAW264.7 cells. Purified CRP induced the release of HMGB1 in a dose- and time-dependent fashion. Immunofluorescence analysis revealed nuclear translocation of HMGB1 in response to CRP. The binding of CRP to the Fc gamma receptor in RAW264.7 cells was confirmed by fluorescence-activated cell sorter analysis. Pretreatment of cells with IgG-Fc fragment, but not IgG-Fab fragment, efficiently blocked this binding. CRP triggered the activation of p38MAPK and ERK1/2, but not Jun N-terminal kinase. Moreover, both p38MAPK inhibitor SB203580 and small interfering RNA significantly suppressed the release of HMGB1, but not the MEK1/2 inhibitor U-0126.


CONCLUSIONS
We demonstrated for the first time that CRP, a prominent risk marker for inflammation including atherosclerosis, could induce the active release of HMGB1 by RAW264.7 cells through Fc gamma receptor/p38MAPK signaling pathways, thus implying that CRP plays a crucial role in the induction, amplification, and prolongation of inflammatory processes, including atherosclerotic lesions.
Kawahara
Ko-ichi
K
Department of Laboratory and Vascular Medicine Cardiovascular and Respiratory Disorders Advanced Therapeutics, Kagoshima University Graduate School of Medical and Dental Science, Kagoshima 890-8520, Japan.
Biswas
Kamal Krishna
KK
Unoshima
Masako
M
Ito
Takashi
T
Kikuchi
Kiyoshi
K
Morimoto
Yoko
Y
Iwata
Masahiro
M
Tancharoen
Salunya
S
Oyama
Yoko
Y
Takenouchi
Kazunori
K
Nawa
Yuko
Y
Arimura
Noboru
N
Jie
Meng Xiao
MX
Shrestha
Binita
B
Miura
Naoki
N
Shimizu
Toshiaki
T
Mera
Kentaro
K
Arimura
Shin-ichiro
S
Taniguchi
Noboru
N
Iwasaka
Hideo
H
Takao
Sonshin
S
Hashiguchi
Teruto
T
Maruyama
Ikuro
I
D000818:Animals; D015153:Blotting, Western; D002097:C-Reactive Protein / Q000378:metabolism*; D002460:Cell Line; D004789:Enzyme Activation / Q000502:physiology; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D024243:HMGB1 Protein / Q000378:metabolism*; D007249:Inflammation / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D021381:Protein Transport / Q000502:physiology; D034741:RNA, Small Interfering; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D024243:HMGB1 Protein; D034741:RNA, Small Interfering; D002097:C-Reactive Protein; D048051:p38 Mitogen-Activated Protein Kinases