Research article

Therapeutic effect of all-trans-retinoic acid (at-RA) on an autoimmune nephritis experimental model: role of the VLA-4 integrin

María M Escribese^1,6 , Elisa Conde¹ , Ana Martín² , David Sáenz-Morales¹ , David Sancho³ , Guillermo Pérez de Lema⁴ , Javier Lucio-Cazaña⁵ , Francisco Sánchez-Madrid³ , María L García-Bermejo¹ and Francisco M Mampaso^{1^}

¹  Department of Pathology, Hospital Ramón y Cajal, Universidad de Alcalá, Madrid, Spain

²  Department of Biology, Universidad SEK, Segovia, Spain

³  Department of Immunology, Hospital de la Princesa, Universidad Autónoma de Madrid, Madrid, Spain

⁴  Medizinische Poliklinik der Ludwig Maximillians-Universität, Munich, Germany

⁵  Department of Physiology, Universidad de Alcalá, Madrid, Spain

⁶  Dpt. of Microbiology, Mount Sinai School of Medicine, New York (NY), USA

author email corresponding author email^Deceased

BMC Nephrology 2007, 8:3doi:10.1186/1471-2369-8-3

Published:	24 January 2007

Abstract

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 α4 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-α and IL-1β 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 (α4β1) integrin induced by mercury on peripheral blood leukocytes (PBLs). In addition, using K562 α4 stable transfectant cells, we found that at-RA inhibited VLA-4 dependent cell adhesion to VCAM-1.

Conclusion

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.