Regulation of IL-12 and IL-10 gene expression in SLE

Abstract

Introduction: It has been shown that abnormal cytokine profiles in SLE, especially over-production of IL-10 and IL-6, contribute to its pathogenesis. Recently we have demonstrated that IL-12 is under-produced in SLE and that IL-12 deficiency is closely correlated to other cytokine abnormalities and with disease activity. In this study we investigated regulation of IL-12 and IL-10 gene transcription in SLE. Materials and Methods: PBMCs from SLE patients and controls were cultured with or without 20ng/ml IL-12 and 10IU/ml IFN-r in the presence of 1:100000 SAC (w/v) for 4 hours, total cellular RNA was extracted and semi-quantitative RT-PCR was employed to measure IL-12, IL-10, IL-6, IFN-r mRNA levels. Results were expressed as mean relative units (RU)compared with β-actin. Results: IL-12p35 mRNA was constitutively expressed by control (37.32 RU) and SLE PBMC (20.21 RU). IFN-r increased SAC-stimulated IL-12p35 (2.68-fold) and IL-12p40 mRNA (1.71-fold) in SLE and normal PBMC (1.23-fold and 1.5-fold respectivly). IL-12 decreased IL-10 mRNA in both SLE (1.37-fold) and normal PBMC (1.99-fold) without affecting IL-6 mRNA levels. This inhibitory effect of IL-12 on IL-10 mRNA was enhanced by IFN-r (9.69-fold in SLE, 2.58-fold in controls) and was accompanied by increased IFN-r mRNA in SLE (3.46-fold) and normal PBMC (1.18-fold). Conclusion: IFN-r increased IL-12 mRNA and this effect was greater in SLE than in controls. IL-12 not only increased IFN-r but also decreased IL-10 mRNA. Stimulation of IL-12 in SLE may help to normalize IL-10 and reduce pathology.