Modulation of nuclear factor-kappaB activity can influence the susceptibility to systemic lupus erythematosus

Abstract

Autoimmune diseases, such as systemic lupus erythematosus (SLE), result from deficiencies in self-antigen tolerance processes, which require regulated dendritic cell (DC) function. In this study we evaluated the phenotype of DCs during the onset of SLE in a mouse model, in which deletion of the inhibitory receptor FcgammaRIIb leads to the production of anti-nuclear antibodies and glomerulonephritis. Splenic DCs from FcgammaRIIb-deficient mice suffering from SLE showed increased expression of co-stimulatory molecules. Furthermore, diseased mice showed an altered function of the nuclear factor-kappaB (NF-kappaB) transcription factor, which is involved in DC maturation. Compared with healthy animals, expression of the inhibitory molecule IkappaB-alpha was significantly decreased in mice suffering from SLE. Consistently, pharmacological inhibition of NF-kappaB activity in FcgammaRIIb-deficient mice led to reduced susceptibility to SLE and prevented symptoms, such as anti-nuclear antibodies and kidney damage. Our data suggest that the occurrence of SLE is significantly influenced by alterations of NF-kappaB function, which can be considered as a new therapeutic target for this disease.

Figure 1

Dendritic cells (DCs) obtained from spleens of FcγRIIb-deficient mice display a mature phenotype and show enhanced immunogenicity. (a) Splenic DCs (CD11c-positive cells) derived from FcγRIIb-deficient and wild-type mice were analyzed by fluorescence-activated cell sorter (FACS) for maturation markers CD40 and CD86. Representative FACS profiles from individual mice (filled histograms for wild-type mice and empty histograms for FcγRIIb-deficient mice) and graphs with mean fluorescence intensity (MFI) averages for each group are shown. (b) Interleukin (IL)-12 secretion, in response to lipopolysaccharide (LPS), by DCs obtained from spleens of FcγRIIb-deficient and wild-type mice. (c) Expression of CD69 (top panel, MFI averages), secretion of IL-2 (middle panel) and proliferation (bottom panel) by alloreactive T cells (BALB/c background) stimulated by DCs obtained from spleens of FcγRIIb-deficient or wild-type mice (C57BL/6 background). Phytohaemagglutinin (PHA) stimulation was included as a positive control. For CD69 up-regulation (top panel), representative fluorescence-activated cell sorter (FACS) profiles from individual mice are shown. Data on each panel are mean ± standard error of the mean (SEM) of at least three independent experiments [(a) *P< 0·05, Student’s t-test; (b and c) *P< 0·05, one-way analysis of variance (anova)]. WT, wild type.

Figure 2

IκB-α expression in FcγRIIb-deficient and wild-type mice. (a) IκB-α mRNA expression in total spleen. (b) IκB-α mRNA expression in dendritic cells (DCs) purified from spleens obtained from wild-type or FcγRIIb-deficient mice. Data are mean ± standard error of the mean (SEM) of at least three independent experiments (*P< 0·05, **P< 0·01, Student’s t-test). WT, wild type.

Figure 3

Nuclear factor-κB (NF-κB)inhibitors andrographolide (ANDRO) and rosiglitazone (RGZ) can reduce the severity of the symptoms of systemic lupus erythematosus (SLE) in FcγRIIb-deficient mice. Representative results of anti-nuclear antibodies (ANAs) (a), proteinuria (b), extractable nuclear antigens (ENAs) (c) and immunofluorescence detection of immune complex (IC) deposition in kidney sections (d), in treated and control FcγRIIb-deficient mice. Data are mean ± standard error of the mean (SEM) of at least three independent experiments [**P< 0·01, ***P< 0·001, one-way analysis of variance (anova)]. Abs, absorbance; PBS, phosphate-buffered saline; WT, wild type.

Figure 4

Maturation profile of dendritic cells (DCs) obtained from spleens of FcγRIIb-deficient mice treated with nuclear factor-κB (NF-κB) inhibitors. Relative expression of costimulatory molecules CD40 (a) and CD86 (b) in splenic CD11c-positive cells after treatment with phosphate-buffered saline (PBS) (white), andrographolide (light gray) and rosiglitazone (dark grey). Data are mean ± standard error of the mean (SEM) of at least two independent experiments.

Figure 5

IκB-α (a) and p65 (b) mRNA expression in total spleens from FcγRIIb-deficient mice after treatment with nuclear factor-κB (NF-κB) inhibitors. Graphs show real-time polymerase chain reaction (PCR) quantification of IκB-α (a) and p65 (b) in total mRNA from spleens of FcγRIIb-deficient mice treated with phosphate-buffered saline (PBS), andrographolide or rosiglitazone. Data are mean ± standard error of the mean (SEM) of three independent experiments [*P< 0·05, **P< 0·01, one-way analysis of variance (anova)].