Memory dysfunction in primary Sjögren's syndrome is associated with anti-NR2 antibodies.

OBJECTIVE: Our understanding of the etiology and pathogenesis of neuropsychiatric involvement in primary Sjögren's syndrome (SS) is incomplete. In systemic lupus erythematosus, it has been reported that antibodies directed against N-methyl-D-aspartate receptor subtype NR2 (anti-NR2) interfere with memory and learning function, as well as mood. This has not been investigated in primary SS; however, the present study was undertaken to advance our understanding of neuropsychiatric involvement in this disease. METHODS: Sixty-six patients with primary SS and 66 age- and sex-matched healthy control subjects underwent clinical examination and neuropsychological evaluation. Anti-NR2 antibodies were measured in serum and cerebrospinal fluid. Hippocampus volume was estimated using software extensions to SPM5. RESULTS: Patients with primary SS had smaller hippocampi than healthy subjects (mean ± SD 8.15 ± 0.98 cm(3) versus 8.49 ± 0.88 cm(3); P = 0.01). In patients with primary SS, anti-NR2 antibodies in cerebrospinal fluid were associated with a worse performance in 8 of 10 memory and learning tests, and anti-NR2 antibodies in serum were associated with a worse performance in 6 of those same tests. In addition, a higher proportion of patients with depression than patients without depression had serum anti-NR2 antibody levels above the cutoff value. CONCLUSION: Results of this study indicate that anti-NR2 antibodies may represent one of the pathogenetic mechanisms for cognitive disturbances and mood disorders in patients with primary SS.

Neurofilament light in plasma is a potential biomarker of central nervous system involvement in systemic lupus erythematosus.

BACKGROUND: Neuropsychiatric manifestations (NP) are common in systemic lupus erythematosus (SLE). However, the pathophysiological mechanisms are not completely understood. Neurofilament light protein (NfL) is part of the neuronal cytoskeleton. Increased NfL concentrations, reflecting neurodegeneration, is observed in cerebrospinal fluid (CSF) in several neurodegenerative and neuroinflammatory conditions. We aimed to explore if plasma NfL could serve as a biomarker for central nervous system (CNS) involvement in SLE. METHODS: Sixty-seven patients with SLE underwent neurological examination; 52 underwent lumbar puncture, while 62 underwent cerebral magnetic resonance imaging (MRI). We measured selected auto-antibodies and other laboratory variables postulated to have roles in NP pathophysiology in the blood and/or CSF. We used SPM12 software for MRI voxel-based morphometry. RESULTS: Age-adjusted linear regression analyses revealed increased plasma NfL concentrations with increasing creatinine (ß = 0.01, p < 0.001) and Q-albumin (ß = 0.07, p = 0.008). We observed higher plasma NfL concentrations in patients with a history of seizures (ß = 0.57, p = 0.014), impaired motor function (ß = 0.36, p = 0.008), increasing disease activity (ß = 0.04, p = 0.008), and organ damage (ß = 0.10, p = 0.002). Voxel-based morphometry suggested an association between increasing plasma NfL concentrations and the loss of cerebral white matter in the corpus callosum and hippocampal gray matter. CONCLUSION: Increased plasma NfL concentrations were associated with some abnormal neurological, cognitive, and neuroimaging findings. However, plasma NfL was also influenced by other factors, such as damage accrual, creatinine, and Q-albumin, thereby obscuring the interpretation of how plasma NfL reflects CNS involvement. Taken together, NfL in CSF seems a better marker of neuronal injury than plasma NfL in patients with SLE.

Neurofilament light is a biomarker of brain involvement in lupus and primary Sjögren's syndrome.

BACKGROUND: To test the hypothesis that neurofilament light (NfL) in CSF is a biomarker of CNS involvement in patients with systemic lupus erythematosus (SLE) and primary Sjögren's syndrome (pSS), we measured NfL in CSF from 52 patients with lupus and 54 with pSS and explored associations with clinical, structural, immunological and biochemical abnormalities. METHODS: In CSF, we measured NfL, anti-P antibodies, protein S100B and TWEAK by ELISA and anti-NR2 antibodies by electrochemiluminescence. Anti-phospholipid antibodies and routine immunological tests were performed in blood. IgG and albumin were measured in CSF and serum for assessment of the blood-brain barrier function (Q-albumin) and intrathecal IgG production (IgG index). Cerebral MRI and neuropsychological testing were performed. RESULTS: A multivariable regression model showed that increasing CSF anti-NR2 antibody levels were associated with increasing NfL levels in patients with SLE (B 1.27, 95% CI 0.88-1.65, p < 0.001). Age contributed significantly in the model (B 0.04, 95% CI 0.03-0.05, p < 0.001). Similar findings were observed in the pSS group. Adjusted for age and sex, no associations were found between NfL levels and any MRI data. In SLE patients, higher NfL concentrations were associated with impairments in psychomotor speed and motor function, and in pSS with motor dysfunction. These associations remained in multivariable regression models. CONCLUSIONS: Increased concentration of NfL in CSF is a marker of cerebral involvement in patients with SLE and pSS, is strongly associated with the presence of anti-NR2 antibodies, and correlates with cognitive impairment in several domains.