Cerebrospinal fluid mitochondrial DNA in neuromyelitis optica spectrum disorder

4-Octyl itaconate inhibits inflammation via the NLRP3 pathway in neuromyelitis optica spectrum disorders

OBJECTIVE

Neuromyelitis optica spectrum disorders (NMOSD) are rare inflammatory astrocytic diseases of the central nervous system (CNS). The roles of immune response gene-1 (IRG1) and the IRG1-itaconic acid-NLRP3 inflammatory pathway in the pathogenesis of NMOSD and the effects of 4-octyl itaconate (4-OI) on the NLRP3 inflammatory pathway in NMOSD are unclear. This study aimed to determine the role of IRG1 and the activation status of the NLRP3 inflammatory pathway in acute-onset NMOSD and to investigate the inhibitory effects of 4-OI on NLRP3 inflammasome activation via the IRG1-itaconic acid-NLRP3 pathway in monocytes and macrophages by using in vitro models.

METHODS

Peripheral blood mononuclear cells (PBMCs) and serum were collected from patients with acute NMOSDs and healthy controls (HC), followed by monocyte typing and detection of the expression of NLRP3-related inflammatory factors. Subsequently, the effects of 4-OI on the IRG1-itaconic acid-NLRP3 pathway were investigated in peripheral monocytes from patients with NMOSD and in macrophages induced by human myeloid leukemia mononuclear cells (THP-1 cells) via in vitro experiments.

RESULTS

Patients with acute NMOSD exhibited upregulated IRG1 expression. In particular, the upregulation of the expression of the NLRP3 inflammasome and proinflammatory factors was notable in monocytes in acute NMOSD patients. 4-OI inhibited the activation of the IRG1-itaconic acid-NLRP3 inflammatory pathway in the PBMCs of patients with NMOSD.

INTERPRETATION

4-OI could effectively inhibit NLRP3 signaling, leading to the inhibition of proinflammatory cytokine production in patients with NMOSD-derived PBMCs and in a human macrophage model. Thus, 4-OI and itaconate could have important therapeutic value for the treatment of NMOSD in the future.

Case report: Use of granulocyte-colony stimulating factor as an immunomodulatory therapy in a patient with neuromyelitis optica spectrum disorder and comorbid immunodeficiency

Background

Autoimmune diseases can coexist with immunodeficiency. We describe a treatment approach in which granulocyte-colony stimulating factor (G-CSF) is used to restore immune competence without worsening autoimmunity. G-CSF is a polyfunctional cytokine that influences survival, proliferation, and differentiation of hematopoietic stem cells, and has immunomodulatory effects on the innate and adaptive immune systems.

Objective

To report a case of neuromyelitis optica spectrum disorder (NMOSD) with comorbid immunodeficiency and frequent infections.

Methods

Case report and review of literature.

Results

A 23 years-old man presented with a focal onset seizure with impaired awareness at age 12. At age 18, he developed headaches, recurrent multifocal seizures, and non-convulsive status epilepticus. Brain magnetic resonance imaging (MRI) showed extensive T2 hyperintense and gadolinium-enhancing periventricular and corpus callosum lesions. Serum aquaporin 4 antibody was positive 1:10,000 (normal value <1.5 titer), hence he was diagnosed with NMOSD. As a complication, patient developed mucormycotic pneumonia with cavitation, requiring thoracotomy precluding use of immunosuppressants. Gene testing demonstrated a mutation in MT-ND4 gene encoding for NADH dehydrogenase 4 in mitochondrial complex 1. Eventually, he began a treatment with filgrastim, a G-CSF analog, in addition to intravenous immunoglobulins and prednisone. Patient's NMOSD has been in remission without relapses, or coexistent infections ever since.

Conclusion

G-CSF is a polyfunctional cytokine with important immunomodulatory effects, which makes it an interesting therapeutic option when autoimmunity coexists with immunodeficiency and was used successfully in this case.

Decipher potential biomarkers of diagnosis and disease activity for NMOSD with AQP4 using LC-MS/MS and Simoa

BACKGROUND

Neuromyelitis optica spectrum disorders (NMOSD) is an autoimmune demyelinating disease, leading recurrently relapses and severe disability. There is a need for new biomarkers to meet clinical needs in diagnosis and monitoring.

METHODS

Through liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) analysis, brain lesions from NMO animal models were analyzed to identify potential biomarkers. Then, we assessed the levels of serum glial fibrillary acidic protein (sGFAP), neurofilament light chain (sNfL), Tau protein (sTau) and Ubiquitin C-terminal hydrolase L1 (sUCHL1) using an ultrasensitive single molecule array (Simoa) of AQP4-IgG + NMOSD patients, myelin oligodendrocyte glycoprotein antibody-associated disorder (MOGAD) patients, multiple sclerosis (MS) patients and healthy controls (HCs). Additionally, we further explored the early diagnosis value of these proteins.

RESULTS

There were 72 differentially expressed proteins between the NMO and control groups. NfL abundance was elevated when GFAP, UCHL1, and Tau abundance was decreased in the NMO group. Then, we observed that the sGFAP and sUCHL1 levels in patients with NMOSD in the early stage were significantly increased compared to those in control participants. Combined ROCs of the sGFAP, sNfL, and sUCHL1 levels to better predict NMOSD with relapse stages was optimal. Notably, univariate and multivariate analyses demonstrated that the sGFAP and sNfL levels were higher in patients with brain lesions, while the sUCHL1 levels were higher in those with spinal cord lesions during recent relapse.

CONCLUSIONS

These findings suggested that sGFAP, sNfL, and sUCHL1 displayed good diagnostic performance in AQP4-IgG + NMOSD and could be novel candidates for early discrimination.

Identification of double-stranded DNA in the cerebrospinal fluid of patients with acute neuromyelitis optica spectrum disorder

Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory disease of the central nervous system (CNS) characterized by severe myelitis and optic neuritis. Double-stranded DNA (dsDNA) is involved in the pathogenesis of various autoimmune diseases, such as systemic lupus erythematosus. However, its role in NMOSD remains unclear. In this study, the concentration of dsDNA in the cerebrospinal fluid (CSF) was quantified in 23 patients with NMOSD and 16 patients with other neurological diseases (ONDs). CSF dsDNA levels in patients with NMOSD (median: 0.03 ng/µL) were significantly higher than those in patients with ONDs (median: 0.01 ng/μl). CSF dsDNA levels showed no significant difference before and after treatment. Elevation of CSF dsDNA levels may suggest its essential role in the augmentation of CNS inflammation in patients with NMOSD.

Phosphorothioate-linked guanine/cytosine-based stem-loop oligonucleotides induce the extracellular release of mitochondrial DNA from peritoneal B1a cells

It has been previously demonstrated that phosphorothioate-linked GpC-based stem-loop oligonucleotides (GC-SL ODN) induce the release of mitochondrial DNA (mtDNA) from chronic lymphocytic leukemia (CLL) B cells. Although CLL B cells are believed to originate from CD5⁺ B cells because of their phenotypic similarities, it remains unclear whether GC-SL ODN can stimulate CD5⁺ B1 cells to secrete mtDNA. To explore this possibility, we compared the frequency of the mtDNA-producing population among peritoneal cells after GC-SL ODN treatment. We found that mtDNA-releasing cells are enriched for peritoneal CD19⁺ B cells upon GC-SL ODN challenge. Among peritoneal CD19⁺ B cells, the CD5⁺ B1a subpopulation was a primary cellular source of mtDNA secretion in GC-SL ODN-elicited immune responses. GC-SL ODN-stimulated mtDNA release by B1a cells was positively regulated by MyD88 and TRIF signaling pathways. In vivo GC-SL ODN treatment increased lipopolysaccharide-induced activation of innate immune cells such as NK cells, suggesting the immune-enhancing effects of mtDNA secretion. Furthermore, the loop size formed by GC-SL ODNs was a critical factor in inducing mtDNA release by B1a cells. Taken together, our results identified GC-SL ODN as promising biomaterials for enhancing immune responses.

Role of Toll-Like Receptors in Neuroimmune Diseases: Therapeutic Targets and Problems

Toll-like receptors (TLRs) are a class of proteins playing a key role in innate and adaptive immune responses. TLRs are involved in the development and progression of neuroimmune diseases via initiating inflammatory responses. Thus, targeting TLRs signaling pathway may be considered as a potential therapy for neuroimmune diseases. However, the role of TLRs is elusive and complex in neuroimmune diseases. In addition to the inadequate immune response of TLRs inhibitors in the experiments, the recent studies also demonstrated that partial activation of TLRs is conducive to the production of anti-inflammatory factors and nervous system repair. Exploring the mechanism of TLRs in neuroimmune diseases and combining with developing the emerging drug may conquer neuroimmune diseases in the future. Herein, we provide an overview of the role of TLRs in several neuroimmune diseases, including multiple sclerosis, neuromyelitis optica spectrum disorder, Guillain-Barré syndrome and myasthenia gravis. Emerging difficulties and potential solutions in clinical application of TLRs inhibitors will also be discussed.

Anti-AQP4 autoantibodies promote ATP release from astrocytes and induce mechanical pain in rats

Background

Intractable neuropathic pain is a common symptom of neuromyelitis optica spectrum disorder (NMOSD). However, the underlying mechanism of NMOSD pain remains to be elucidated. In this study, we focused on ATP, which is one of the damage-associated molecular patterns, and also a well-recognized molecule involved in peripheral neuropathic pain.

Methods

We assessed the development of pain symptoms by injecting anti-AQP4 recombinant autoantibodies (rAQP4 IgG) into rat spinal cords. We incubated HEK293 cells expressing AQP4 (HEK-AQP4) and rat astrocytes with rAQP4 IgG and assessed the level of ATP in the supernatant. We performed transcriptome analysis of the spinal cords injected with rAQP4 IgG. Pharmacological inhibition was also applied to investigate the involvement of ATP in the development of neuropathic pain in our rat model. The ATP concentration within the cerebrospinal fluid was examined in patients with NMOSD and other neurological diseases.

Results

Development of mechanical allodynia was confirmed in rAQP4 IgG–treated rats. AQP4-Ab–mediated extracellular ATP release from astrocytes was observed in vitro, and pharmacological inhibition of ATP receptor reversed mechanical allodynia in the rAQP4 IgG–treated rats. Furthermore, transcriptome analysis revealed elevation of gene expressions related to several ATP receptors including P2rx4 and IL1B in the spinal cord of rAQP4 IgG–treated rats. In patients, CSF ATP concentration was significantly higher in the acute and remission phase of NMOSD than in multiple sclerosis or other neurological disorders.

Conclusion

Anti-AQP4 antibody was shown to induce the release of extracellular ATP from astrocytes. The ATP-mediated development of mechanical allodynia was also suggested in rats treated with anti-AQP4 antibody. Our study indicates the pivotal role of ATP in the pain mechanism of NMOSD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02232-w.

Mitochondria-A target for attenuation of astrocyte pathology

Astrocyte pathology is a feature of neuromyelitis optica spectrum disorder (NMOSD) pathology. Recently mitochondrial dysfunction and metabolic changes were suggested to play a role in NMOSD. To elucidate the role of mitochondrial dysfunction, astrocyte pathology was induced in C57BL/6 J female mice by intracerebral injection of aquaporin-4-immunoglobulin G from an NMOSD patient, together with complement. Etomoxir has been shown to cause mitochondrial dysfunction. Etomoxir was delivered to the central nervous system and resulted in decreased astrocyte pathology. The ameliorating effect was associated with increases in different acylcarnitines and amino acids. This suggests that mitochondria may be a therapeutic target in NMOSD.

Involvement of the Spinal Cord in Primary Mitochondrial Disorders: A Neuroimaging Mimicker of Inflammation and Ischemia in Children

BACKGROUND AND PURPOSE

Little is known about imaging features of spinal cord lesions in mitochondrial disorders. The aim of this research was to assess the frequency, imaging features, and pathogenic variants causing primary mitochondrial disease in children with spinal cord lesions.

MATERIALS AND METHODS

This retrospective analysis included patients seen at Children's Hospital of Philadelphia between 2000 and 2019 who had a confirmed diagnosis of a primary (genetic-based) mitochondrial disease and available MR imaging of the spine. The MR imaging included at least both sagittal and axial fast spin-echo T2-weighted images. Spine images were independently reviewed by 2 neuroradiologists. Location and imaging features of spinal cord lesions were correlated and tested using the Fisher exact test.

RESULTS

Of 119 children with primary mitochondrial disease in whom MR imaging was available, only 33 of 119 (28%) had available spine imaging for reanalysis. Nineteen of these 33 individuals (58%) had evidence of spinal cord lesions. Two main patterns of spinal cord lesions were identified: group A (12/19; 63%) had white ± gray matter involvement, and group B (7/19; 37%) had isolated gray matter involvement. Group A spinal cord lesions were similar to those seen in patients with neuromyelitis optica spectrum disorder, multiple sclerosis, anti-myelin oligodendrocyte glycoprotein-IgG antibody disease, and leukoencephalopathy with brain stem and spinal cord involvement and lactate elevation. Group B patients had spinal cord findings similar to those that occur with ischemia and viral infections. Significant associations were seen between the pattern of lesions (group A versus group B) and the location of lesions in cervical versus thoracolumbar segments, respectively (P < .01).

CONCLUSIONS

Spinal cord lesions are frequently observed in children with primary mitochondrial disease and may mimic more common causes such as demyelination and ischemia.

Autophagy alleviates mitochondrial DAMP-induced acute lung injury by inhibiting NLRP3 inflammasome

AIM

Acute lung injury (ALI) is characterized by alveolar macrophage overactivation and uncontrolled pulmonary inflammation. Mitochondrial damage-associated molecular patterns (MTDs), one type of damage-associated molecular patterns (DAMPs) released from ruptured mitochondrial, can induce inflammation which participates in the pathogenesis of ALI. Despite the critical role of autophagy in inflammatory response, little is known about its function in MTDs-induced ALI. Herein we have studied how autophagy attenuates MTDs-induced ALI in vitro and in vivo.

MAIN METHODS

Exogenous MTDs were injected into mice through tail vein injection or directly treated with cultured alveolar macrophage cell lines to construct MTDs-induced ALI models. Rapamycin and 3-MA were used to regulate autophagy in vivo and in vitro. The expressions of Caspase-1, IL-1β, and their precursor were measured. Inhibition the activation of NLRP3 inflammasome to discover the candidate targets and potential molecular pathways involved in autophagy mitigating the MTDs-induced ALI.

KEY FINDINGS

After treatment with MTDs the expression levels of inflammatory cytokines and NLRP3 inflammasome-associated proteins were gradually increased in vitro and in vivo. Most importantly, with autophagy enhanced by rapamycin, all the secretion of inflammation cytokine, the level of lung injury, and the expression level of NLRP3 inflammasome-associated proteins were greatly decreased in MTDs-induced mouse model. MTDs-induced inflammation and lung injury were alleviated by autophagy enhancement. Autophagy can function as an effective way to alleviate inflammation in MTDs-induced ALI by inhibiting NLRP3 inflammasome and may represent a therapeutic target in modulating MTDs-induced inflammatory response.

NLRP3 level in cerebrospinal fluid of patients with neuromyelitis optica spectrum disorders: Increased levels and association with disease severity

BACKGROUND

Neuromyelitis optica spectrum disorder (NMOSD) and MS are the most common autoimmune inflammatory demyelinating diseases of the CNS. However, the mechanisms of pathogenesis are still unclear. nucleotide-binding leucine-rich repeat (NLR) family pyrin domain containing 3 (NLRP3), an important protein of the innate immune system that is activated by mitochondrial DNA (mtDNA), has been reported to be associated with various autoimmune disorders.

OBJECTIVE

To assess the levels of cerebrospinal fluid (CSF) NLRP3, mtDNA and inflammation-associated cytokines (IL-1β, IL-6 and IL-17) in patients with NMOSD and MS, and to examine the correlations between these factors.

METHODS

28 NMOSD patients, 15 MS patients, and 16 controls with non-inflammatory neurological diseases were recruited. NLRP3 inflammasome, IL-1β, IL-6 and IL-17 were measured by ELISA. CSF extracellular mtDNA was measured by qPCR. The severity of clinical presentation was evaluated by EDSS score.

RESULTS

CSF levels of NLRP3, mtDNA, IL-1β, IL-6 and IL-17 were higher in NMOSD patients than in controls. Elevated CSF NLRP3, mtDNA and IL-6 were found in MS patients compared with controls. CSF NLRP3 and IL-6 levels were significantly higher in NMOSD patients than in MS patients. The EDSS scores of NMOSD patients during relapse were positively correlated with CSF NLRP3 and mtDNA.

CONCLUSION

Our findings suggest that CSF levels of the NLRP3 inflammasome may serve as a diagnostic biomarker for distinguishing NMOSD and MS. Pyroptosis mediated by the NLRP3 inflammasome following mitochondrial damage may play an important role in the pathogenesis of these neuroinflammatory disorders, especially NMOSD.

IRAK1 polymorphisms are associated with susceptibility to neuromyelitis optica spectrum disorder

BACKGROUND

X chromosome-linked interleukin-1 receptor-associated kinase (IRAK1) polymorphisms have been demonstrated to be associated with the risks of several autoimmune diseases, such as systemic lupus erythematosus, systemic sclerosis, rheumatoid arthritis, and autoimmune thyroid diseases. However, no studies have investigated the association of IRAK1 polymorphisms with neuromyelitis optica spectrum disorder (NMOSD). This case-control study was performed to determine the correlation between IRAK1 polymorphisms and the risk of NMOSD.

METHODS

Two single nucleotide polymorphisms (SNPs) rs1059703G>A and rs3027898C>A of IRAK1 were selected and genotyped using SNPscan in a Chinese cohort, including 332 patients with NMOSD and 520 healthy controls. Chi-square tests and logistic regression analyses were used to determine the associations between IRAK1 polymorphisms and the risk of NMOSD.

RESULTS

Patients with NMOSD showed a lower frequency of the minor allele A of rs1059703 than did controls (Odds ratio [OR] = 0.68; 95% confidence intervals [CI], 0.52-0.88; P^corr = 0.007). Compared with wild genotype GG of rs1059703, homozygous mutation AA and heterozygous mutation GA were significantly associated with the decreased risk of NMOSD after adjusting for sex and age (adjusted OR = 0.64; 95%CI, 0.49-0.84; P^corr = 0.002). Similar associations were also observed for IRAK1 rs3027898C>A. Stratification analysis according to sex revealed that the significantly different allele distributions of the two SNPs were mainly found in females. However, IRAK1 polymorphisms were not correlated with aquaporin-4-IgG, onset symptoms, or age at onset.

CONCLUSIONS

This study is first to demonstrate that X-chromosome-linked IRAK1 polymorphisms are associated with the risk of NMOSD and provide novel insights into the underlying mechanisms of this disease. Further studies are needed to elucidate the function of IRAK1 variants in the pathogenesis of NMOSD and the underlying molecular mechanisms.