The complement component C5a induces the expression of plasminogen activator inhibitor-1 in human macrophages via NF-kappaB activation.
BACKGROUND
Atherosclerosis is considered to be a chronic inflammatory disorder. Activation of the complement cascade is a major aspect of chronic inflammatory diseases. Complement components were identified in atherosclerotic plaques, and a correlation between adverse events and C5a plasma levels was found. These findings support the notion that complement activation contributes to development and progression of atherosclerotic lesions.


OBJECTIVE
We investigated whether complement components C3a and C5a regulate plasminogen activator inhibitor (PAI-1) in human macrophages.


METHODS
Human monocyte-derived macrophages (MDM) and human plaque macrophages were cultured and incubated with the complement component C5a.


RESULTS
C5a increased PAI-1 up to 11-fold in human MDM and up to 2.7-fold in human plaque macrophages. These results were confirmed at the mRNA level using real time-polymerase chain reaction. Pertussis toxin or anti-C5aR/CD88 antibody completely abolished the effect of recombinant human C5a on PAI-1 production, suggesting a role of the C5a receptor. Experiments with antitumor necrosis factor (TNF)-alpha antibodies and tiron showed that the effect of C5a was not mediated by TNF-alpha or oxidative burst. Furthermore C5a induced NF-kappaB binding to the cis element in human macrophages and the C5a-induced increase in PAI-1 was completely abolished by an NF-kappaB inhibitor.


CONCLUSIONS
We conclude that C5a upregulates PAI-1 in macrophages via NF-kappaB activation. We hypothesize that - if operative in vivo- this effect could favor thrombus development and thrombus stabilization in the lesion area. On the other hand one could speculate that C5a-induced upregulation of PAI-1 in plaque macrophages could act as a defense mechanism against plaque destabilization and rupture.
Kastl
S P
SP
Department of Internal Medicine II, Medical University of Vienna, Vienna, Austria.
Speidl
W S
WS
Kaun
C
C
Rega
G
G
Assadian
A
A
Weiss
T W
TW
Valent
P
P
Hagmueller
G W
GW
Maurer
G
G
Huber
K
K
Wojta
J
J
D002478:Cells, Cultured; D015926:Complement C3a / Q000378:metabolism; D015936:Complement C5a / Q000378:metabolism / Q000502:physiology*; D004789:Enzyme Activation; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D008264:Macrophages / Q000201:enzymology* / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D009000:Monocytes / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D017395:Plasminogen Activator Inhibitor 1 / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000378:metabolism; D044087:Receptor, Anaphylatoxin C5a; D011951:Receptors, Complement / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry; D013997:Time Factors; D015854:Up-Regulation
C488033:C5AR1 protein, human; D008565:Membrane Proteins; D016328:NF-kappa B; D017395:Plasminogen Activator Inhibitor 1; D012333:RNA, Messenger; D044087:Receptor, Anaphylatoxin C5a; D011951:Receptors, Complement; D011994:Recombinant Proteins; D015926:Complement C3a; D015936:Complement C5a