Ex vivo immunomodulatory effect of all-trans-retinoic acid during Behcet's disease: a study in Algerian patients

Uveitis, recurrent oral and genital ulcerations associated with skin lesions are the major symptoms of a chronic multisystemic inflammatory disorder known as Behcet's disease (BD). High prevalence of this dreaded disease has been observed in the Mediterranean basin, including Algeria and along the Silk Road. Although the etiologic agent of this disease remains uncertain, many hypotheses have been advanced in its pathogenesis. Our team has previously reported high levels of nitric oxide (NO) in sera of BD patients, suggesting its deleterious effect during chronic inflammation. In our current study, the aim is to investigate the ex vivo immunomodulatory effect of all-trans-retinoic acid (ATRA) on NO pathway in Algerian BD patients. First, peripheral blood mononuclear cells isolated from active and inactive BD patients and healthy controls were cultured with different concentrations of ATRA. NO production was estimated with the Griess method. To elucidate the underlying mechanisms of ATRA effect on NO production, we analyze inducible nitric oxide synthase expression and nuclear factor-kappa B (NF-kappa B) activity by immunofluorescence test. Our results revealed a higher production of NO in active BD compared with the inactive stage and healthy controls. We observed that ATRA inhibits NO production in BD both in active and inactive stages and inhibits NF-kappa B translocation. In conclusion, we report a relationship between NO production and the disease activity. ATRA down-regulates NO production in BD patients. This immunomodulatory effect seems to be mediated through NF-kappa B pathway. All these findings suggest that ATRA could be considered as a promising therapy for BD.