Homocysteine triggers mucosal microvascular activation in inflammatory bowel disease.
OBJECTIVE
Increased homocysteine contributes to the pathophysiology of several chronic inflammatory diseases. Whether homocysteine could participate in mucosal inflammation in inflammatory bowel disease (IBD) has not been explored yet. Our aims were to study the levels of plasma and mucosal homocysteine in IBD patients and to assess whether homocysteine can trigger an inflammatory reaction on human intestinal microvascular endothelial cells (HIMECs).


METHODS
Homocysteine was measured in the plasma, mucosal biopsy, and lamina propria mononuclear cell (LPMC) supernatants from normal and IBD subjects. HIMEC were cultured in presence of homocysteine, TNF-alpha, or folic acid, alone or in combination. Expression of vascular cell adhesion molecule 1 (VCAM-1) and intercellular cell adhesion molecule 1 was measured by flow cytometry and monocyte chemoattractant protein-1 (MCP-1) production by ELISA. Phosphorylation of p38 and p42/44 was assessed by immunoblot in HIMEC extracts. T-cell- and monocyte-HIMEC adhesion assays were used to evaluate the impact of homocysteine on leukocyte adhesion to intestinal endothelial cells.


RESULTS
Patients with IBD displayed significantly higher homocysteine plasma and mucosal levels than control subjects. IBD-derived LPMC released higher homocysteine than control-derived LPMC. Treatment of HIMEC with homocysteine, and synergistically with the combination of TNF-alpha and homocysteine, triggered HIMEC inflammation, resulting in VCAM-1 up-regulation, MCP-1 production, and p38 phosphorylation. These events lead to an increased capacity of HIMEC to adhere T- and monocyte cells and were blocked by folic acid treatment.


CONCLUSIONS
Homocysteine is increased in both the mucosa and plasma of patients with Crohn's disease and ulcerative colitis and contributes to the inflammatory state of the mucosal IBD endothelium. Therefore, homocysteine could play a proinflammatory role in IBD, which can be efficiently targeted by folic acid supplementation.
Danese
Silvio
S
Department of Internal Medicine, Institute of General Pathology, Catholic University, Rome, Italy. sdanese@hotmail.com
Sgambato
Alessandro
A
Papa
Alfredo
A
Scaldaferri
Franco
F
Pola
Roberto
R
Sans
Miquel
M
Lovecchio
Maria
M
Gasbarrini
Giovanni
G
Cittadini
Achille
A
Gasbarrini
Antonio
A
D000293:Adolescent; D000328:Adult; D000368:Aged; D018932:Chemokine CCL2 / Q000097:blood; D003093:Colitis, Ulcerative / Q000503:physiopathology*; D003424:Crohn Disease / Q000503:physiopathology*; D004730:Endothelium, Vascular / Q000503:physiopathology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D005492:Folic Acid / Q000097:blood; D006710:Homocysteine / Q000502:physiology*; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000097:blood; D007413:Intestinal Mucosa / Q000098:blood supply*; D007957:Leukocyte Adherence Inhibition Test; D008297:Male; D008833:Microcirculation / Q000503:physiopathology; D008875:Middle Aged; D012016:Reference Values; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D019010:Vascular Cell Adhesion Molecule-1 / Q000097:blood
D018932:Chemokine CCL2; D014409:Tumor Necrosis Factor-alpha; D019010:Vascular Cell Adhesion Molecule-1; D006710:Homocysteine; D018799:Intercellular Adhesion Molecule-1; D005492:Folic Acid