Mood Disorder in Systemic Lupus Erythematosus Induced by Antiribosomal P Protein Antibodies Associated with Decreased Serum and Brain Tryptophan

CD72 is an inhibitory pattern recognition receptor that recognizes ribosomes and suppresses production of anti-ribosome autoantibody

B cell responses to nucleic acid-containing self-antigens that involve intracellular nucleic acid sensors play a crucial role in autoantibody production in SLE. CD72 is an inhibitory B cell co-receptor that down-regulates BCR signaling, and prevents the development of SLE. We previously showed that CD72 recognizes the RNA-containing self-antigen Sm/RNP, a target of SLE-specific autoantibodies, and induces B cell tolerance to Sm/RNP by specifically inhibiting B cell response to this self-antigen. Here, we address whether CD72 inhibits B cell response to ribosomes because the ribosome is an RNA-containing self-antigen and is a target of SLE-specific autoantibodies as well as Sm/RNP. We demonstrate that CD72 recognizes ribosomes as a ligand, and specifically inhibits BCR signaling induced by ribosomes. Although conventional protein antigens by themselves do not induce proliferation of specific B cells, ribosomes induce proliferation of B cells reactive to ribosomes in a manner dependent on RNA. This proliferative response is down-regulated by CD72. These results suggest that ribosomes activate B cells by inducing dual signaling through BCR and intracellular RNA sensors and that CD72 inhibits B cell response to ribosomes. Moreover, CD72-/- but not CD72+/+ mice spontaneously produce anti-ribosome autoantibodies. Taken together, CD72 induces B cell self-tolerance to ribosomes by recognizing ribosomes and inhibiting RNA-dependent B cell response to this self-antigen. CD72 appears to prevent development of SLE by inhibiting autoimmune B cell responses to multiple RNA-containing self-antigens. Because these self-antigens but not protein self-antigens induce RNA-dependent B cell activation, self-tolerance to RNA-containing self-antigens may require a distinct tolerance mechanism mediated by CD72.

Pathogenetic associations of anti-ribosomal P protein antibody titres and their subclasses in patients with systemic lupus erythematosus

OBJECTIVES

We evaluated the association between anti-ribosomal P antibody (anti-RibP) titres and disease activity in Japanese SLE patients.

METHODS

Eighty patients admitted and treated in Niigata University Hospital for new-onset or flare-up of SLE were included in this retrospective cross-sectional study. Clinical data were obtained from medical records at admission. The anti-RibP index, and cytokine and tryptophan metabolite levels were determined by ELISA.

RESULTS

Of the 80 SLE patients, 30 had anti-RibP. Anti-RibP presence was associated with a greater prevalence of skin rash and more severe inflammatory responses, demonstrated by higher inflammatory cytokine levels, hypocomplementemia, and accelerated tryptophan metabolism, in younger patients. The serum anti-RibP index was correlated with age at diagnosis, clinical indicators, initial prednisolone dose, and cytokines and tryptophan metabolite levels in univariate analysis. Multivariate analysis showed that the anti-RibP index was independently associated with the initial prednisolone dose and the prevalence of skin rash. The anti-RibP IgGs were mainly the IgG2 and IgG3 subclasses, and anti-RibP IgG3 was associated with hypocomplementemia, higher DAS, accelerated kynurenine pathway activity, and higher proinflammatory cytokine production. The coexistence of anti-dsDNA IgG and anti-RibP IgG2 or IgG3 accompanied higher IL-10 and IFN-α2 levels; furthermore, anti-RibP IgG3 coexistence with anti-dsDNA antibody contributed to the requirement for higher initial prednisolone doses and accelerated kynurenine pathway activity.

CONCLUSION

Anti-RibP was associated with clinical manifestations and parameters in SLE, and its index might be a useful indicator of disease severity. Anti-RibP IgG3 was the IgG subclass most strongly associated with the pathogenesis of SLE.

Anti-ribosomal P protein antibodies and insomnia correlate with depression and anxiety in patients suffering from systemic lupus erythematosus

Objective

Anxiety and depression in patients with systemic lupus erythematosus (SLE) complicate clinical treatment and can seriously affect prognosis. The present study aims to investigate the effects of the anti-ribosomal P protein antibody (anti-RibP) in the peripheral blood and insomnia on the severity of anxiety and depression in case of SLE. The study compared both the results of the investigation on the objective perceptions of physicians concerning mood changes in patients with SLE and the results of self-rating scales that were completed by the enrolled patients. The conclusion of the comparation is used to determine the probability of the accurate detection of anxiety and depression by physicians. The study aims to assist in the early detection in clinical practice of abnormal emotions in patients with SLE and to summarize common clinical interventions for anxiety and depression.

Method

The relationship between anxiety and depression was evaluated by the Zung self-rating anxiety/depression scale (SAS/SDS). Basic information (e.g., blood type, smoking history, drinking history, educational background, duration of illness), the insomnia severity index (ISI) results, and anti-RibP in the peripheral blood, were investigated in 107 patients with SLE in northeastern China to further analyze the correlation between the severity of depression and anti-RibP, together with the consistency between results of the questionnaire for physicians and the self-rating scale for patients.

Results

Gender, smoking history, drinking history, educational background, and duration of illness were correlated with the SAS/SDS scores (P < 0.05). Family history had a significant effect on the SAS score (P = 0.031), while the SDS score was significantly correlated with blood type (P = 0.021). The ISI score was significantly and positively correlated with the SAS/SDS score (P < 0.001). The titer of anti-RibP showed a correlation with the SDS score (P < 0.05) but not with the SAS score (P = 0.198). The titer of anti-RibP was significantly higher in patients with major depression compared with those with no depression, patients with mild depression, and those with moderate depression (P < 0.001).

Conclusion

Anxiety and depression in patients with SLE were correlated with sleeping, educational background, blood type, smoking history, and alcohol consumption. Although anti-RibP was not significantly correlated with anxiety, it indicated a significant correlation with major depression. Clinicians were more accurate in assessing anxiety compared with depression.

Immunometabolomics provides a new perspective for studying systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic multi-organ autoimmune disease characterized by clinical heterogeneity, unpredictable progression, and flare ups. Due to the heterogeneous nature of lupus, it has been challenging to identify sensitive and specific biomarkers for its diagnosis and monitoring. Despite the fact that the mechanism of SLE remains unknown, impressive progress has been made over the last decade towards understanding how different immune cells contribute to its pathogenesis. Research suggests that cellular metabolic programs could affect the immune response by regulating the activation, proliferation, and differentiation of innate and adaptive immune cells. Many studies have shown that the dysregulation of the immune system is associated with changes to metabolite profiles. The study of metabolite profiling may provide a means for mechanism exploration and novel biomarker discovery for disease diagnostic, classification, and monitoring. Here we review the latest advancements in understanding the role of immunometabolism in SLE, as well as the systemic metabolite profiling of this disease along with possible clinical application.

Mendelian randomization study on the causal effects of systemic lupus erythematosus on major depressive disorder

The vast majority of epidemiological studies suggested a link between systemic lupus erythematosus (SLE) and major depressive disorder (MDD). However, the causality for SLE on the risk of MDD remained unknown due to confounding factors or reverse causality. Herein, we investigated the causality between SLE and MDD in those of European ancestry by a Mendelian randomization (MR) approach. Summary genetic data of cases with SLE/MDD were derived from independent largest public genome-wide association study. Forty-six single nucleotide polymorphisms associated with SLE were used as instrumental variables. The main causal inference was carried out using the MRE-IVW method. Additional, reverse-direction MR and multivariable MR analyses were further performed. Result indicated that SLE was causally associated with a lower risk of MDD (using the MRE-IVW method, odds ratio [OR] = 0.983, 95% confidence interval [CI] = 0.974-0.991, p = 1.18 × 10^-4). Complementary analysis found no heterogeneity or horizontal pleiotropy. Multivariate MR analysis yielded consistent results (OR =  0.981; 95% CI = 0.969-0.993; p = 2.75 × 10^-3). Reverse-direction MR analysis suggested non-causal relationship of MDD on the risk of SLE (using the IVW method, OR = 0.846, 95% CI = 0.345-2.072; p = 0.714). Thus, this is the first study providing evidence of potential causal links between SLE and MDD and further related research is needed.

Progress in the mechanism of neuronal surface P antigen modulating hippocampal function and implications for autoimmune brain disease

PURPOSE OF REVIEW

The aim of this study was to present a new regulation system in the hippocampus constituted by the neuronal surface P antigen (NSPA) and the tyrosine phosphatase PTPMEG/PTPN4, which provides mechanistic and therapeutic possibilities for cognitive dysfunction driven by antiribosomal P protein autoantibodies in patients with systemic lupus erythematosus (SLE).

RECENT FINDINGS

Mice models lacking the function of NSPA as an E3 ubiquitin ligase show impaired glutamatergic synaptic plasticity, decreased levels of NMDAR at the postsynaptic density in hippocampus and memory deficits. The levels of PTPMEG/PTPN4 are increased due to lower ubiquitination and proteasomal degradation, resulting in dephosphorylation of tyrosines that control endocytosis in GluN2 NMDAR subunits. Adult hippocampal neurogenesis (AHN) that normally contributes to memory processes is also defective in the absence of NSPA.

SUMMARY

NSPA function is crucial in memory processes controlling the stability of NMDAR at PSD through the ubiquitination of PTPMEG/PTPN4 and also through AHN. As anti-P autoantibodies reproduce the impairments of glutamatergic transmission, plasticity and memory performance seen in the absence of NSPA, it might be expected to perturb the NSPA/PTPMEG/PTPN4 pathway leading to hypofunction of NMDAR. This neuropathogenic mechanism contrasts with that of anti-NMDAR antibodies also involved in lupus cognitive dysfunction. Testing this hypothesis might open new therapeutic possibilities for cognitive dysfunction in SLE patients bearing anti-P autoantibodies.