Therapeutic effect of all-trans-retinoic acid (at-RA) on an autoimmune nephritis experimental model: role of the VLA-4 integrin.
BACKGROUND
Mercuric chloride (HgCl2) induces an autoimmune nephritis in the Brown Norway (BN) rats characterized by anti-glomerular basement membrane antibodies (anti-GBM Ab) deposition, proteinuria and a severe interstitial nephritis, all evident at day 13 of the disease. We assessed the effects of all-trans retinoic acid (at-RA) in this experimental model. At-RA is a vitamin A metabolite which has shown beneficial effects on several nephropathies, even though no clear targets for at-RA were provided.


METHODS
We separated animals in four different experimental groups (HgCl2, HgCl2+at-RA, at-RA and vehicle). From each animal we collected, at days 0 and 13, numerous biological samples: urine, to measure proteinuria by colorimetry; blood to determine VLA-4 expression by flow citometry; renal tissue to study the expression of VCAM-1 by Western blot, the presence of cellular infiltrates by immunohistochemistry, the IgG deposition by immunofluorescence, and the cytokines expression by RT-PCR. Additionally, adhesion assays to VCAM-1 were performed using K562 alpha4 transfectant cells. ANOVA tests were used for statistical significance estimation.


RESULTS
We found that at-RA significantly decreased the serum levels of anti-GBM and consequently its deposition along the glomerular membrane. At-RA markedly reduced proteinuria as well as the number of cellular infiltrates in the renal interstitium, the levels of TNF-alpha and IL-1beta cytokines and VCAM-1 expression in renal tissue. Moreover, we reported here for the first time in an in vivo model that at-RA reduced, to basal levels, the expression of VLA-4 (alpha4beta1) integrin induced by mercury on peripheral blood leukocytes (PBLs). In addition, using K562 alpha4 stable transfectant cells, we found that at-RA inhibited VLA-4 dependent cell adhesion to VCAM-1.


CONCLUSIONS
Here we demonstrate a therapeutic effect of at-RA on an autoimmune experimental nephritis model in rats. We report a significant reduction of the VLA-4 integrin expression on PBLs as well as the inhibition of the VLA4/VCAM1-dependent leukocyte adhesion by at-RA treatment. Thereby we point out the VLA-4 integrin as a target for at-RA in vivo.
Escribese
María M
MM
Department of Pathology, Hospital Ramón y Cajal, Universidad de Alcalá, Madrid, Spain. maria.escribese@mssm.edu
Conde
Elisa
E
Martín
Ana
A
Sáenz-Morales
David
D
Sancho
David
D
Pérez de Lema
Guillermo
G
Lucio-Cazaña
Javier
J
Sánchez-Madrid
Francisco
F
García-Bermejo
María L
ML
Mampaso
Francisco M
FM
D000818:Animals; D001327:Autoimmune Diseases / Q000188:drug therapy* / Q000276:immunology*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D007113:Immunity, Innate / Q000187:drug effects / Q000276:immunology; D007166:Immunosuppressive Agents / Q000008:administration & dosage; D039041:Integrin alpha4beta1 / Q000276:immunology*; D008297:Male; D008627:Mercuric Chloride; D009393:Nephritis / Q000188:drug therapy* / Q000276:immunology*; D051381:Rats; D016896:Treatment Outcome; D014212:Tretinoin / Q000008:administration & dosage*
D007166:Immunosuppressive Agents; D039041:Integrin alpha4beta1; D008627:Mercuric Chloride; D014212:Tretinoin