Neurotoxic lupus autoantibodies alter brain function through two distinct mechanisms

Differences in regional brain activation patterns assessed by functional magnetic resonance imaging in patients with systemic lupus erythematosus stratified by disease duration

The mediators of tissue damage in systemic lupus erythematosus (SLE) such as antibodies, cytokines and activated immune cells have direct access to most organs in the body but must penetrate the blood-brain barrier (BBB) to gain access to brain tissue. We hypothesized that compromise of the BBB occurs episodically such that the brain will acquire tissue damage slowly and not at the same rate as other organs. On the basis of these assumptions, we wished to determine if duration of disease correlated with brain injury, as measured with functional magnetic resonance imaging (fMRI), and if this was independent of degree of tissue damage in other organs. We investigated differences in brain activation patterns using fMRI in 13 SLE patients stratified by disease duration of ≤2 years (short-term [ST]) or ≥10 years (long-term [LT]). Two fMRI paradigms were selected to measure working memory and emotional response (fearful faces task). Performance in the working memory task was significantly better in the ST group for one and two shape recall; however, both groups did poorly with three shape recall. Imaging studies demonstrated significantly increased cortical activation in the ST group in regions associated with cognition during the two shape retention phase of the working memory task (P < 0.001) and increased amygdala (P < 0.05) and superior parietal (P < 0.01) activation in response to the fearful faces paradigm. In conclusion, analysis of activation patterns stratified by performance accuracy, differences in co-morbid disease, corticosteroid doses or disease activity suggests that these observed differences are attributable to SLE effects on the central nervous system exclusive of vascular disease or other confounding influences. Our hypothesis is further supported by the lack of correlation between regional brain abnormalities on fMRI and the Systemic Lupus International Collaborating Clinics (SLICC) damage index.

Generation of a unique small molecule peptidomimetic that neutralizes lupus autoantibody activity

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the presence of pathogenic autoantibodies, many of which are directed against nuclear antigens, in particular double-stranded (ds) DNA. Both clinical studies and animal models have shown that anti-dsDNA antibodies contribute to kidney disease, which is present in 50% of lupus patients and is a major cause of mortality. We previously demonstrated that a subset of nephrotoxic anti-dsDNA antibodies also recognizes the pentapeptide consensus sequence D/E W D/E Y S/G (DWEYS) present in the NR2A and NR2B subunits of the N-methyl-d-aspartate receptor (NMDAR). Autoantibodies with this specificity are present in ≈40% of lupus patient sera and are both nephrotoxic and neurotoxic. Elevated titers are present in cerebrospinal fluid of patients with central nervous system manifestations of SLE. Administration of the nonnaturally occurring D form of the DWEYS pentapeptide prevents these antibodies from depositing in glomeruli and from mediating neuronal excitotoxicity. To craft a more useful therapeutic, we used the structural features of the DWEYS peptide to design a unique, selective, and potent small molecule peptidomimetic, FISLE-412, which neutralizes anti-dsDNA/NMDAR lupus autoantibodies and prevents their pathogenic interaction with tissue antigens. This compound, or others derived from it, may provide a unique strategy for the development of lupus therapeutics.

Memantine in systemic lupus erythematosus: a randomized, double-blind placebo-controlled trial

OBJECTIVES

Cognitive impairment affects up to 80% of systemic lupus erythematosus (SLE) patients within 10 years of diagnosis. Memantine, a seronergic receptor and nicotine acetylcholine receptor antagonist, acts on the glutamatergic system through the NMDA receptor and is used to treat dementia. We investigated whether it had benefit for SLE cognitive impairment.

METHODS

A randomized double-blind, placebo-controlled single-center 12-week trial of memantine titrated to 20 mg/d was performed, using a 2:1 randomization ratio, in 51 SLE patients. The primary outcome measures were change in the Automated Neuropsychological Assessment Metrics throughput scores at 12 weeks.

RESULTS

There were no statistically significant differences between treatment groups or change from baseline in any of the Automated Neuropsychological Assessment Metrics throughput scores at 6 or 12 weeks. For the American College of Rheumatology cognitive battery, the only statistically significant findings were for the Controlled Oral Word Association Test-S words at 6 and 12 weeks. At 12 weeks, the memantine group exhibited greater improvement compared with the placebo group (3.6 ± 1.8 vs 0.5 ± 3.8 words, P = 0.03). In a subset analysis limited to patients that scored ≥1 standard deviation below normal controls at baseline, no significant differences between treatment groups were found.

CONCLUSIONS

In this first clinical trial of memantine in SLE, patients treated with memantine did not exhibit significant improvement in cognitive performance compared with the placebo group, regardless of the degree of impairment at baseline, with the exception of controlled oral word association.

Lessons from an anti-DNA autoantibody

R4A is an anti-DNA antibody derived by hybridoma technology from a BALB/c mouse. The study of its properties has helped to elucidate aspects of the physiopathology of Systemic Lupus Erythematosus (SLE). It has been useful to decipher the mechanisms implicated in breaks in B cell self tolerance by B cell extrinsic or B cell intrinsic factors. Furthermore, it illustrates the importance of molecular mimicry in understanding the cellular and molecular effects relevant to some manifestations of neuropsychiatric lupus, as it cross-reacts with the D/E W D/E YS/G peptide sequence present in subunits of the N-methyl d-aspartate receptor (NMDAR).

Moving towards a cure: blocking pathogenic antibodies in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is characterized by the presence of autoantibodies that can mediate tissue damage in multiple organs. The underlying aetiology of SLE autoantibodies remains unknown, and treatments aimed at eliminating B cells, or limiting their function, have demonstrated limited therapeutic benefit. Thus, the current therapies for SLE are based on the concept of nonspecific immunosuppression and consist of nonsteroidal anti-inflammatory drugs (NSAIDS), corticosteroids, anti-malarials and cytotoxic drugs, all of which have serious adverse side effects including organ damage. The major auto-specificity in SLE is double-stranded (ds) DNA. Many anti-dsDNA antibodies cross-react with non-DNA antigens that may be the direct targets for their pathogenic activity. Studying anti-dsDNA antibodies present in SLE patients and in animal models of lupus, we have identified a subset of anti-dsDNA antibodies which is pathogenic in the brain as well as in the kidney. We have recently demonstrated that specific peptides, or small molecules, can protect target organs from antibody-mediated damage. Thus, it might be possible to treat the aspects of autoimmune disease without inducing major immunosuppression and ensuing infectious complications.