The Macrophage Reprogramming Ability of Antifolates Reveals Soluble CD14 as a Potential Biomarker for Methotrexate Response in Rheumatoid Arthritis

Transcobalamin 2 orchestrates monocyte proliferation and TLR4-driven inflammation in systemic lupus erythematosus via folate one-carbon metabolism

Background

SLE is a complex autoimmune disease with deleterious effects on various organs. Accumulating evidence has shown abnormal vitamin B12 and one-carbon flux contribute to immune dysfunction. Transcobalamin II (TCN2) belongs to the vitamin B12-binding protein family responsible for the cellular uptake of vitamin B12. The role of TCN2 in SLE is still unclear.

Methods

We collected clinical information and blood from 51 patients with SLE and 28 healthy controls. RNA sequencing analysis, qPCR, and western blot confirmed the alteration of TCN2 in disease monocytes. The correlation between TCN2 expression and clinical features and serological abnormalities was analyzed. TCN2 heterozygous knockout THP1 cells were used to explore the effects of TCN2 dysfunction on monocytes. CCK-8 assay and EdU staining were used to detect cell proliferation. ELISA was conducted to assess vitamin B12, glutathione, and cytokines changes. UHPLC-MRM-MS/MS was used to detect changes in the intermediates of the one-carbon cycle. Flow cytometry is used to detect cell cycle, ROS, mitoROS, and CD14 changes.

Results

Elevated TCN2 in monocytes was correlated positively with disease progression and specific tissue injuries. Using CD14+ monocytes and TCN2 genetically modified THP1 cell lines, we found that the TCN2 was induced by LPS in serum from SLE patients. TCN2 heterozygous knockout inhibited cellular vitamin B12 uptake and one-carbon metabolism, leading to cell proliferation arrest and decreased Toll-like receptor 4 (TLR4)-mediated CCL2 release. Methionine cycle metabolites, s-adenosylmethionine and homocysteine, rescued these effects, whereas folate treatment proved to be ineffective. Folate deficiency also failed to replicate the impact of TCN2 downregulation on THP1 inflammatory response.

Conclusion

Our study elucidated the unique involvement of TCN2-driven one-carbon flux on SLE-associated monocyte behavior. Increased TCN2 may promote disease progression and tissue damage by enhancing one-carbon flux, fostering monocyte proliferation, and exacerbating TLR4 mediated inflammatory responses. The inhibition of TCN2 may be a promising therapeutic approach to ameliorate SLE.

Decreased serpin C1 in extracellular vesicles predicts response to methotrexate treatment in patients with pulmonary sarcoidosis

BACKGROUND

Sarcoidosis is a systemic granulomatous disease of unknown etiology primarily affecting the lungs. Treatment is needed when disease symptoms worsen and organ function deteriorates. In pulmonary sarcoidosis, prednisone and methotrexate (MTX) are the most common anti-inflammatory therapies. However, there is large inter-patient variability in response to treatment, and predictive response markers are currently lacking.

OBJECTIVE

In this study, we investigated the predictive potential of biomarkers in extracellular vesicles (EVs) isolated from biobanked serum of patients with pulmonary sarcoidosis stored prior to start of therapy.

METHODS

Protein concentrations of a four-protein test panel of inflammatory proteins were measured in a discovery (n = 16) and replication (n = 129) cohort of patients with sarcoidosis and 47 healthy controls. Response to therapy was defined as an improvement of the absolute score of > 5% forced vital capacity (FVC) and/or > 10% diffusion lung of carbon monoxide (DLCO) after 24 weeks compared to baseline (before treatment).

RESULTS

Serum protein levels differed between EV fractions and serum, and between sarcoidosis cases and controls. Serpin C1 concentrations in the low density lipid particle EV fraction were lower at baseline in the group of patients with a good response to MTX treatment in both the discovery cohort (p = 0.059) and in the replication cohort (p = 0.032). EV Serpin C1 showed to be a significant predictor for response to treatment with MTX (OR 0.4; p = 0.032).

CONCLUSION

This study shows that proteins isolated from EVs harbor a distinct signal and have potential as new predictive therapy response biomarkers in sarcoidosis.

Pemetrexed ameliorates Con A-induced hepatic injury by restricting M1 macrophage activation

Autoimmune hepatitis (AIH), characterized by immune-driven liver destruction and cytokine production, is a progressive inflammatory liver condition that may progress to hepatic cirrhosis or tumors. However, the underlying mechanism is not well understood, and the treatment options for this disease are limited. Pemetrexed (PEM), a clinically used anti-folate drug for treating various tumors, was found to inhibit the nuclear factor (NF)-κB signaling pathways that exert an important role in the development of AIH. Here, we investigated the impact of PEM on immune-mediated hepatic injuries using a murine model of Concanavalin A (Con A)-induced hepatitis, a well-established model for AIH. Mice received intraperitoneal PEM injections 3 times at 12-hour intervals, and two hours later, they were challenged with Con A. Liver samples and serum were collected after 10 h. The results indicate that PEM significantly improved mouse survival rates and lowered serum transaminase levels. Moreover, PEM effectively alleviated oxidative stress, reduced histopathological liver damage, and mitigated hepatocyte apoptosis. Notably, it reduced the activation of M1-type macrophages in the liver. The expression of proinflammatory cytokines and genes associated with M1 macrophages, such as tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, IL-12, IL-1β, and inducible nitric oxide synthase (iNOS), was also decreased. Finally, the results indicated that PEM regulates M1 macrophage activation by modulating the NF-κB signaling pathways. Overall, these results demonstrate that PEM effectively guards against immune-mediated hepatic injuries induced by Con A by inhibiting M1 macrophage activation through the NF-κB signaling pathways and indicate the potential of PEM as a practical treatment option for AIH in clinical settings.

Innate immune memory in inflammatory arthritis

The concept of immunological memory was demonstrated in antiquity when protection against re-exposure to pathogens was observed during the plague of Athens. Immunological memory has been linked with the adaptive features of T and B cells; however, in the past decade, evidence has demonstrated that innate immune cells can exhibit memory, a phenomenon called 'innate immune memory' or 'trained immunity'. Innate immune memory is currently being defined and is transforming our understanding of chronic inflammation and autoimmunity. In this Review, we provide an up-to-date overview of the memory-like features of innate immune cells in inflammatory arthritis and the crosstalk between chronic inflammatory milieu and cell reprogramming. Aberrant pro-inflammatory signalling, including cytokines, regulates the metabolic and epigenetic reprogramming of haematopoietic progenitors, leading to exacerbated inflammatory responses and osteoclast differentiation, in turn leading to bone destruction. Moreover, imprinted memory on mature cells including terminally differentiated osteoclasts alters responsiveness to therapies and modifies disease outcomes, commonly manifested by persistent inflammatory flares and relapse following medication withdrawal.

Impact of methotrexate treatment on vaccines immunogenicity in adult rheumatological patients - Lessons learned from the COVID-19 pandemic

Despite the development of new biological and synthetic targeted therapies, methotrexate remains one of the most commonly used immunomodulatory drugs in rheumatology. However, its effect on the immunogenicity of vaccines has been studied only to a limited extent until recently, resulting in the lack of clear guidelines on the use of methotrexate during vaccination. Significant progress was made during the COVID-19 pandemic due to the dynamic development of research on vaccines, including patients with autoimmune inflammatory rheumatic diseases. In the following literature review, we present a summary of what we know so far on the impact of methotrexate on post-vaccination response in adult rheumatology patients, taking into account the lessons learned from the COVID-19 pandemic. Studies on the effect of methotrexate on the immunogenicity of influenza, pneumococcal, herpes zoster, tetanus/diphtheria/pertussis, hepatitis A, yellow fever, and COVID-19 vaccines are described in detail, including the effect of methotrexate on the humoral and cellular response of individual vaccines. The available evidence for recommendations for withholding methotrexate in the post-vaccination period is presented. Lastly, an overview of potential immunological mechanisms through which MTX modulates the immunogenicity of vaccinations is also provided.

Role of CD14 in human disease

The cell surface antigen CD14 is primarily understood to act as a co-receptor for toll-like receptors (TLRs) to activate innate immunity responses to pathogens and tissue injury in macrophages and monocytes. However, roles for CD14 are increasingly being uncovered in disease responses in epithelial and endothelial cells. Consistent with these broader functions, CD14 expression is altered in a variety of non-immune cell types in response to a several of disease states. Moreover, soluble CD14 activated by factors from both pathogens and tissue damage may initiate signalling in a variety of non-immune cells. This review examined the current understanding CD14 in innate immunity as well as its potential functions in nonimmune cells and associated human diseases.

Methotrexate Provokes Disparate Folate Metabolism Gene Expression and Alternative Splicing in Ex Vivo Monocytes and GM-CSF- and M-CSF-Polarized Macrophages

Macrophages constitute important immune cell targets of the antifolate methotrexate (MTX) in autoimmune diseases, including rheumatoid arthritis. Regulation of folate/MTX metabolism remains poorly understood upon pro-inflammatory (M1-type/GM-CSF-polarized) and anti-inflammatory (M2-type/M-CSF-polarized) macrophages. MTX activity strictly relies on the folylpolyglutamate synthetase (FPGS) dependent intracellular conversion and hence retention to MTX-polyglutamate (MTX-PG) forms. Here, we determined FPGS pre-mRNA splicing, FPGS enzyme activity and MTX-polyglutamylation in human monocyte-derived M1- and M2-macrophages exposed to 50 nmol/L MTX ex vivo. Moreover, RNA-sequencing analysis was used to investigate global splicing profiles and differential gene expression in monocytic and MTX-exposed macrophages. Monocytes displayed six-eight-fold higher ratios of alternatively-spliced/wild type FPGS transcripts than M1- and M2-macrophages. These ratios were inversely associated with a six-ten-fold increase in FPGS activity in M1- and M2-macrophages versus monocytes. Total MTX-PG accumulation was four-fold higher in M1- versus M2-macrophages. Differential splicing after MTX-exposure was particularly apparent in M2-macrophages for histone methylation/modification genes. MTX predominantly induced differential gene expression in M1-macrophages, involving folate metabolic pathway genes, signaling pathways, chemokines/cytokines and energy metabolism. Collectively, macrophage polarization-related differences in folate/MTX metabolism and downstream pathways at the level of pre-mRNA splicing and gene expression may account for variable accumulation of MTX-PGs, hence possibly impacting MTX treatment efficacy.

Predictors of improvement in disease activity in first hospitalized patients with systemic lupus erythematosus: a multicenter retrospective study of a Chinese cohort

Objectives

To analyze the relative factors of improvement in disease activity (IDA) after first hospitalized treatment based on the systemic lupus erythematosus disease activity index (SLEDAI).

Methods

A total of 1069 adult systemic lupus erythematosus (SLE) patients who were hospitalized for the first time in 26 hospitals in Jiangsu Province from 1999 to 2009 were retrospectively analyzed. SLEDAI decrease ≥ 4 during hospitalization was identified as IDA. Relative factors of IDA were assessed by univariate and multivariate logistic regression.

Results

A total of 783 (73.2%) adult SLE patients showed IDA after the first hospitalization, while the remaining patients (n = 286) were in the non-IDA group. The IDA group had higher SLEDAI at admission; fewer patients had SLICC/ACR damage index (SDI) ≥ 1, comorbidities at admission, especially Sjögren’s syndrome, abnormal serum creatinine, and glomerular filtration rate. More patients had mucocutaneous and musculoskeletal involvements, leukopenia, increased C-reactive protein, anti-dsDNA antibody positive, and hypocomplementemia at admission and were treated with methotrexate and leflunomide during hospitalization. After multivariate logistic regression analysis, SDI ≥ 1 (P = 0.005) and combined with Sjögren’s syndrome (P < 0.001) at admission had negative association with IDA. Musculoskeletal involvement (P < 0.001), anti-dsDNA antibody positive (P = 0.012), hypocomplementemia (P = 0.001), and use of leflunomide (P = 0.030) were significantly related with IDA.

Conclusion

Organ damage or comorbidities at admission were adverse to SLE improvement. Anti-dsDNA antibody positive, hypocomplementemia, musculoskeletal involvements, and leflunomide treatment had positive association with IDA of SLE.

Key Points • Organ damage or comorbidities at admission were negatively correlated with SLE improvement. • Anti-dsDNA antibody positivity, hypocomplementemia, musculoskeletal involvements, and leflunomide treatment were positively associated with SLE improvement.

Folate Receptor Beta for Macrophage Imaging in Rheumatoid Arthritis

Non-invasive imaging modalities constitute an increasingly important tool in diagnostic and therapy response monitoring of patients with autoimmune diseases, including rheumatoid arthritis (RA). In particular, macrophage imaging with positron emission tomography (PET) using novel radiotracers based on differential expression of plasma membrane proteins and functioning of cellular processes may be suited for this. Over the past decade, selective expression of folate receptor β (FRβ), a glycosylphosphatidylinositol-anchored plasma membrane protein, on myeloid cells has emerged as an attractive target for macrophage imaging by exploiting the high binding affinity of folate-based PET tracers. This work discusses molecular, biochemical and functional properties of FRβ, describes the preclinical development of a folate-PET tracer and the evaluation of this tracer in a translational model of arthritis for diagnostics and therapy-response monitoring, and finally the first clinical application of the folate-PET tracer in RA patients with active disease. Consequently, folate-based PET tracers hold great promise for macrophage imaging in a variety of (chronic) inflammatory (autoimmune) diseases beyond RA.