Causal associations between prodromal infection and neuromyelitis optica spectrum disorder: A Mendelian randomization study

Sex hormones and neuromyelitis optica spectrum disorder: a bidirectional Mendelian randomization study

BACKGROUND

Females are considered to have an increased susceptibility to neuromyelitis optica spectrum disorder (NMOSD) than males, especially aquaporin-4 (AQP4) antibody positive NMOSD, indicating that sex hormones may be involved in the NMOSD pathogenesis. However, the causality between sex hormones and NMOSD still remains unclear.

METHODS

Based on the genome-wide association study (GWAS) data of three sex hormones (estradiol (E2), progesterone (PROG) and bioavailable testosterone (BAT)), sex hormone-binding globulin (SHBG), age of menarche, age of menopause, and NMOSD (total, AQP4 + and AQP4 -), we performed a two-sample bidirectional Mendelian randomization (MR) study. Sex-stratified GWAS data of E2, PROG, BAT, and SHBG was obtained for gender-specific MR analysis. Causal inferences were based on the inverse variance weighted method, MR-Egger regression, and weighted median method. The reverse MR analysis was also performed to assess the impact of NMOSD on hormone levels.

RESULTS

PROG in females had aggravative effects on NMOSD (P < 0.001), especially AQP4 - NMOSD (P < 0.001). In the reverse MR analysis, total NMOSD was found to decrease the level of BAT (P < 0.001) and increase the level of SHBG (P = 0.001) in females.

CONCLUSION

Findings of this MR analysis revealed mutual causal associations between sex hormones and NMOSD, which provided novel perspectives about the gender-related pathogenesis of NMOSD.

The levels of circulating cytokines and risk of neuromyelitis optica spectrum disorder: a Mendelian randomization study

Background

Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory autoimmune disease affecting the central nervous system (CNS). NMOSD pathogenesis involves systemic inflammation. However, a causal relationship between circulating cytokine levels and NMOSD remains unclear.

Methods

Mendelian randomization (MR) approaches were used to investigate the potential association between genetically determined circulating 19 inflammatory cytokines and 12 chemokines levels and the risk of developing NMOSD.

Results

After Bonferroni correction, the risk of aquaporin 4-antibody (AQP4-ab)-positive NMOSD was suggested to be causally associated with the circulating levels of three cytokines, including interleukin (IL)-4 [odds ratio (OR): 11.01, 95% confidence interval (CI): 1.16-104.56, P = 0.037], IL-24 (OR: 161.37; 95% CI: 2.46-10569.21, P = 0.017), and C-C motif chemokine 19 (CCL19) (OR: 6.87, 95% CI: 1.78-26.93, P = 0.006).

Conclusion

These findings suggest that a genetic predisposition to higher levels of IL-4, IL-24, and CCL19 may exert a causal effect on the risk of AQP4-ab-positive NMOSD. Further studies are warranted to clarify how these cytokines affect the development of AQP4-ab-positive NMOSD.

Relapses and Serious Infections in Patients with Neuromyelitis Optica Spectrum Disorder Treated with Rituximab: A Swedish Single-Center Study

Neuromyelitis optica spectrum disorder (NMOSD) is a rare immune-mediated relapsing-remitting disease of the central nervous system. The usage of rituximab, as relapse-preventive therapy, in NMOSD is common. We performed a single-center retrospective cohort study to assess the risk of relapses and severe infectious events (SIEs) in rituximab-treated NMOSD patients. This study included 24 aquaporin-4 IgG+ (AQP4+), 8 myelin-oligodendrocyte-protein IgG+ (MOG+), and 10 double-seronegative NMOSD patients. Relapses were observed in 50% of all patients during a mean treatment time of 4.0 (range: 0.5-8.25) years. The incidence risk ratio (IRR) of relapse was three times higher in MOG+ compared to AQP4+ patients (IRR: 3.0, 95% confidence interval (CI); 1.2-7.7). SIEs occurred in 40% of all patients during follow-up. AQP4+ patients conferred an increased risk of SIEs compared to MOG+ patients (IRR; 5.3, 95% CI; 1.2-24.3). Incomplete CD19+ B-lymphocyte suppression was not correlated with relapse risk (hazard ratio; 1.9, 95% CI; 0.7-5.2), and there was no correlation between IgG-levels and SIE risk (odds ratio; 2.0, 95% CI; 0.8-4.8). In conclusion, considerable risks of both relapses and SIEs were observed in NMOSD patients exposed to rituximab, which underlines the need for close clinical vigilance of disease activity and infections during treatment.