Developmental process in diffuse psychological/neuropsychiatric manifestations of neuropsychiatric systemic lupus erythematosus

Ectopic CD4+ T cells in choroid plexus mediate neuropsychiatric lupus symptoms in mice via interferon-γ induced microglia activation

Neuropsychiatric systemic lupus erythematosus (NPSLE) is a disabling and potentially life-threatening complication of SLE. This study aims to investigate whether ectopic CD4+ T cells in the choroid plexus mediate NPSLE in mice. Intracerebroventricular (ICV) injection of anti-CD4 antibody effectively depleted CP-resident CD4+ T cells and alleviated NPSLE-like symptoms in MRL/lpr mice. Following ICV injection, the majority of isolated lupus CD4+ T cells from donor MRL/lpr mice predominantly stayed in the CP for at least 28 days in recipient C57BL/6 mice, while nearly all isolated CD4+ T cells from MRL/MpJ mice disappeared within 7 days. ICV injection of lupus CD4+ T cells resulted in NPSLE-like symptoms, including impaired behavioral performances, increased microglial activation, and abnormal microstructure changes. Flow cytometry analysis revealed that the majority of isolated lupus CD4+ T cells were positive for IFN-γ. Neutralizing intracerebral IFN-γ alleviated NPSLE-like symptoms in MRL/lpr mice. Moreover, ICV injection of anti-IFN-γ antibody or microglial depletion by PLX3397 benefited most NPSLE-like symptoms in lupus CD4+ T-treated mice, while ICV injection of IFN-γ mimicked most NPSLE-like symptoms. In conclusion, CP-resident lupus CD4+ T cells contribute to NPSLE-like symptoms in mice via Interferon-γ induced microglia activation. Depleting CP-resident lupus CD4+ T cells, interferon-γ, or activated microglia may be potential therapeutic targets for NPSLE.

The pathogenic role of lupus-specific autoantibodies and Interleukin-6 on demyelination of the brainstem and spinal cord in systemic lupus erythematosus

OBJECTIVES

Demyelinating syndromes that result in brainstem and/or spinal cord lesions similar to those observed in neuromyelitis optica spectrum disorder (NMOSD) as neuropsychiatric syndromes in systemic lupus erythematosus (NPSLE) occasionally develop in patients with SLE. Cerebrospinal fluid (CSF) interleukin (IL)-6 is a known biomarker for NMOSD; however, its application in patients with SLE with brainstem and/or spinal cord lesions is unknown. Additionally, the breakdown of blood-brain barrier (BBB) integrity by autoantibodies is another mechanism of NMOSD; however, it is not elucidated in SLE. Therefore, this study was designed to clarify the use of CSF IL-6 and investigate whether autoantibodies contribute to BBB breaches and the development of brainstem and/or spinal cord lesions.

METHODS

Data from patients with NPSLE who had NMOSD-like demyelinating lesions in the central nervous system (CNS), including brainstem and/or spinal cord lesions, were retrospectively analyzed. We retrospectively investigated the interval changes in CSF IL-6 and clinical and serological factors related to BBB permeability using CSF/serum albumin ratio (QAlb).

RESULTS

Twelve patients with NPSLE who had demyelinating lesions in the brainstem and/or spinal cord were recruited. Before treatment, CSF IL-6 levels were 29.1 pg/mL and significantly decreased to 3.8 pg/mL by treatment (p = 0.008). Before treatment, CSF IL-6 was significantly correlated with the anti-dsDNA antibody titer (p = 0.027). Furthermore, before treatment, QAlb was significantly correlated with the serum anti-Smith antibody titer. In patients with atypical NMOSD who had specific lesions defined in the NMOSD diagnostic criteria but were negative for antiaquaporin four antibody, a significant correlation was observed between the serum anti-Smith antibody titer and CSF IL-6 (p = 0.025) and QAlb (p = 0.033) values before treatment.

CONCLUSION

CSF IL-6 could be a surrogating marker for disease activity, and serum anti-Smith antibody permeabilizes the BBB in patients with NPSLE, supporting the development of NMOSD-like CNS lesions.

Complement System and Alarmin HMGB1 Crosstalk: For Better or Worse

Our immune system responds to infectious (PAMPs) and tissue damage (DAMPs) signals. The complement system and alarmin High-Mobility Group Box 1 (HMGB1) are two powerful soluble actors of human host defense and immune surveillance. These systems involve molecular cascades and amplification loops for their signaling or activation. Initially activated as alarm raising systems, their function can be finally switched towards inflammation resolution, where they sustain immune maturation and orchestrate repair mechanisms, opening the way back to homeostasis. However, when getting out of control, these defense systems can become deleterious and trigger serious cellular and tissue damage. Therefore, they can be considered as double-edged swords. The close interaction between the complement and HMGB1 pathways is described here, as well as their traditional and non-canonical roles, their functioning at different locations and their independent and collective impact in different systems both in health and disease. Starting from these systems and interplay at the molecular level (when elucidated), we then provide disease examples to better illustrate the signs and consequences of their roles and interaction, highlighting their importance and possible vicious circles in alarm raising and inflammation, both individually or in combination. Although this integrated view may open new therapeutic strategies, future challenges have to be faced because of the remaining unknowns regarding the molecular mechanisms underlying the fragile molecular balance which can drift towards disease or return to homeostasis, as briefly discussed at the end.