A cell-based assay for detection of anti-fibrillarin autoantibodies with performance equivalent to immunoprecipitation

FBL Promotes LPS-Induced Neuroinflammation by Activating the NF-κB Signaling Pathway

Purpose

Neuroinflammation occurs in response to central nervous system (CNS) injury, infection, stimulation by toxins, or autoimmunity. We previously analyzed the downstream molecular changes in HT22 cells (mouse hippocampal neurons) upon lipopolysaccharide (LPS) stimulation. We detected elevated expression of Fibrillarin (FBL), a nucleolar methyltransferase, but the associated proinflammatory mechanism was not systematically elucidated. The aim of this study was to investigate the underlying mechanisms by which FBL affects neuroinflammation.

Methods

RT-real-time PCR, Western blotting and immunofluorescence were used to assess the mRNA and protein expression of FBL in HT22 cells stimulated with LPS, as well as the cellular localization and fluorescence intensity of FBL. BAY-293 (a son of sevenless homolog 1 (SOS1) inhibitor), SR11302 (an activator protein-1 (AP-1) inhibitor) and KRA-533 (a KRAS agonist) were used to determine the molecular mechanisms underlying the effect of FBL. AP-1 was predicted to be the target protein of FBL by molecular docking analysis, and validation was performed with T-5224 (an AP-1 inhibitor). In addition, the downstream signaling pathways of FBL were identified by transcriptome sequencing and verified by RT-real-time PCR.

Results

LPS induced FBL mRNA and protein expression in HT22 cells. In-depth mechanistic studies revealed that when we inhibited c-Fos, AP-1, and SOS1, FBL expression decreased, whereas FBL expression increased when KRAS agonists were used. In addition, the transcript levels of inflammatory genes in the NF-kB signaling pathway (including CD14, MYD88, TNF, TRADD, and NFKB1) were elevated after the overexpression of FBL.

Conclusion

LPS induced the expression of FBL in HT22 cells through the RAS/MAPK signaling pathway, and FBL further activated the NF-kB signaling pathway, which promoted the expression of relevant inflammatory genes and the release of cytokines. The present study reveals the mechanism by which FBL promotes neuroinflammation and offers a potential target for the treatment of neuroinflammation.

A Case of Dermatomyositis with Coexistence of Positive Anti-MDA5 Antibodies and Anti-SSA/RO52 Antibodies, Combined with Necrotic Skin Ulcers

Background

Dermatomyositis (DM) is an idiopathic inflammatory myopathy that is clinically challenging to diagnose and has a poor prognosis. It is characterized by symmetric proximal muscle weakness, muscle tenderness, dysphagia, characteristic skin rash (heliotrope rash, Gottron's sign), elevated muscle enzyme levels, abnormal electromyography, and muscle biopsy findings. DM with positive anti-MDA5 antibodies is mainly characterized by Gottron's sign, skin ulcers, facial erythema, mechanic's hands, and V-sign. In this case, the patient presented with the rare manifestation of severe necrotic skin ulcers in association with Gottron's sign, prompting us to report this case.

Case Presentation

A 45-year-old female was admitted to the hospital with systemic joint pain, fatigue, multiple ulcers, and purulent discharge on both hands. Her myositis-specific antibody profile revealed positive anti-MDA5 and anti-SSA/RO52 antibodies. Treatment included a combination of glucocorticoids, immunosuppressants, gastric and liver protection, infection control, and wound care. After two weeks of treatment, the patient showed improvement in symptoms. However, on the 24th day of hospitalization, the wound at the right elbow joint ruptured and became infected, requiring debridement and skin grafting in the appropriate department.

Conclusion

There has been limited research and reported cases of dermatomyositis with coexistence of positive anti-MDA5 and anti-SSA/RO52 antibodies combined with severe skin ulcers. Therefore, we present this rare case and emphasize the need for close follow-up on pulmonary involvement and skin ulcer progression, as well as timely implementation of new treatment strategies to actively improve the prognosis.

Serum markers in systemic sclerosis with cardiac involvement

Cardiac involvement in systemic sclerosis is a common clinical entity that may range from subclinical to life-threatening complications. The classification of cardiac involvement may be expressed as either primary or secondary involvement. Primary systemic sclerosis heart involvement (SSc-pHI) refers to cardiac pathologies primarily ascribed to systemic sclerosis rather than concomitant conditions like ischemic heart disease and pulmonary hypertension. The timely recognition of cardiac involvement holds significant clinical relevance. Therefore, numerous screening or diagnostic tools have been evaluated to forecast the likelihood of cardiac involvement, particularly in the absence of clinically evident cardiac symptoms. Of these modalities, serum biomarkers are often preferred due to their expeditiousness and non-invasive nature. Hence, the crucial goal of this narrative review is to review serum biomarkers that can be a valuable or promising tool in diagnosing cardiac involvement, especially SSc-pHI, in the early stages or predicting disease prognosis.

Effect on cell survival and cytoophidium assembly of the adRP-10-related IMPDH1 missense mutation Asp226Asn

Introduction: Inosine monophosphate dehydrogenase 1 (IMPDH1) is a critical enzyme in the retina, essential for the correct functioning of photoreceptor cells. Mutations in IMPDH1 have been linked to autosomal dominant retinitis pigmentosa subtype 10 (adRP-10), a genetic eye disorder. Some of these mutations such as the Asp226Asn (D226N) lead to the assembly of large filamentous structures termed cytoophidia. D226N also gives IMPDH1 resistance to feedback inhibition by GDP/GTP. This study aims to emulate the adRP-10 condition with a long-term expression of IMPDH1-D226N in vitro and explore cytoophidium assembly and cell survival. We also assessed whether the introduction of an additional mutation (Y12C) to disrupt the cytoophidium has an attenuating effect on the toxicity caused by the D226N mutation. Results: Expression of IMPDH1-D226N in HEp-2 cells resulted in cytoophidium assembly in ∼70% of the cells, but the presence of the Y12C mutation disrupted the filaments. Long-term cell survival was significantly affected by the presence of the D226N mutation, with a decrease of ∼40% in the cells expressing IMPDH1-D226N when compared to IMPDH1-WT; however, survival was significantly recovered in IMPDH1-Y12C/D226N, with only a ∼10% decrease when compared to IMPDH1-WT. On the other hand, the IMPDH1 expression level in the D226N-positive cells was <30% of that of the IMPDH1-WT-positive cells and only slightly higher in the Y12C/D226N, suggesting that although cell survival in Y12C/D226N was recovered, higher expression levels of the mutated IMPDH1 were not tolerated by the cells in the long term. Conclusion: The IMPDH1-D226N effect on photoreceptor cell survival may be the result of a sum of problems: nucleotide unbalance plus a toxic long-life cytoophidium, supported by the observation that by introducing Y12C in IMPDH1 the cytoophidium was disrupted and cell survival significantly recovered, but not the sensibility to GDP/GTP regulation since higher expression levels of IMPDH1-D226N were not tolerated.