Homocysteine modulates the CD40/CD40L system.
OBJECTIVE
This study evaluated the impact of hyperhomocysteinemia (HHcy) on the CD40/CD40 ligand (CD40L) dyad in vivo and in vitro.


BACKGROUND
Hyperhomocysteinemia is associated with an increased incidence of atherothrombosis, although the molecular mechanisms of this association are incompletely defined. The CD40L pair triggers inflammatory signals in cells of the vascular wall, representing a major pathogenetic pathway of atherosclerosis.


METHODS
We used a commercially available enzyme-linked immunosorbent assay kit to evaluate circulating levels of soluble (s) CD40L in 24 patients with HHcy and 24 healthy subjects. We also used real-time polymerase chain reaction and flow cytometry to determine expression levels of CD40 and vascular cell adhesion molecule (VCAM)-1 in human umbilical vein endothelial cells (HUVECs) and of CD40L in human platelets.


RESULTS
The sCD40L levels were significantly increased in HHcy patients (median [interquartile range] 8.0 [0.7 to 10.5] ng/ml vs. 2.1 [1.9 to 2.3] ng/ml, p = 0.0001). Positive correlations were noted between log sCD40L and log homocysteine (Hcy) (R = 0.68, p < 0.0001) or log sVCAM-1 (R = 0.41, p < 0.005). Homocysteine significantly stimulated CD40 mRNA expression in HUVECs (p = 0.033). Consistently, 24-h exposure to Hcy increased the percentage of CD40-expressing cells (p = 0.00025). Homocysteine also significantly enhanced CD40L expression in platelets (p = 0.025) to a comparable extent as that of thrombin. Notably, Hcy increased VCAM-1 protein expression induced by CD40L in HUVECs (p = 0.0046).


CONCLUSIONS
The present results uncover a potential molecular target of Hcy, namely the CD40/CD40L dyad. Collectively, they indicate that upregulation of CD40/CD40L signaling may represent a link between HHcy and an increased risk of cardiovascular disease.
Prontera
Cesaria
C
Department of Medicine, Gabriele d'Annunzio University Foundation, Chieti-Pescara, Italy.
Martelli
Nicola
N
Evangelista
Virgilio
V
D'Urbano
Etrusca
E
Manarini
Stefano
S
Recchiuti
Antonio
A
Dragani
Alfredo
A
Passeri
Cecilia
C
Davì
Giovanni
G
Romano
Mario
M
D000328:Adult; D001792:Blood Platelets / Q000378:metabolism; D019013:CD40 Antigens / Q000097:blood* / Q000235:genetics / Q000502:physiology; D023201:CD40 Ligand / Q000097:blood* / Q000235:genetics / Q000502:physiology; D042783:Endothelial Cells / Q000378:metabolism; D005260:Female; D006710:Homocysteine / Q000097:blood / Q000235:genetics / Q000502:physiology*; D006801:Humans; D008297:Male; D042965:Methylenetetrahydrofolate Reductase (NADPH2) / Q000097:blood / Q000235:genetics; D008875:Middle Aged; D015398:Signal Transduction / Q000502:physiology; D015854:Up-Regulation / Q000502:physiology
D019013:CD40 Antigens; D006710:Homocysteine; D023201:CD40 Ligand; D042965:Methylenetetrahydrofolate Reductase (NADPH2)