The Biology of Pain: Through the Rheumatology Lens

Sinomenine ameliorates fibroblast-like synoviocytes dysfunction by promoting phosphorylation and nuclear translocation of CRMP2

ETHNOPHARMACOLOGICAL RELEVANCE

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by synovial inflammation and arthritic pain. Sinomenine (SIN), derived from the rhizome of Chinese medical herb Qing Teng (scientific name: Sinomenium acutum (Thunb.) Rehd. Et Wils), has a longstanding use in Chinese traditional medicine for treating rheumatoid arthritis. It has been shown to possess anti-inflammatory, analgesic, and immunosuppressive effects with minimal side-effects clinically. However, the mechanisms governing its effects in treatment of joint pathology, especially on fibroblast-like synoviocytes (FLSs) dysfunction, and arthritic pain remains unclear.

AIM

This study aimed to investigate the effect and underlying mechanism of SIN on arthritic joint inflammation and joint FLSs dysfunctions.

MATERIALS AND METHODS

Collagen-induced arthritis (CIA) was induced in rats and the therapeutic effects of SIN on joint pathology were evaluated histopathologically. Next, we conducted a series of experiments using LPS-induced FLSs, which were divided into five groups (Naïve, LPS, SIN 10, 20, 50 μg/ml). The expression of inflammatory factors was measured by qPCR and ELISA. The invasive ability of cells was detected by modified Transwell assay and qPCR. Transwell migration and cell scratch assays were used to assess the migration ability of cells. The distribution and content of relevant proteins were observed by immunofluorescence and laser confocal microscopy, as well as Western Blot and qPCR. FLSs were transfected with plasmids (CRMP2 T514A/D) to directly modulate the post-translational modification of CRMP2 protein and downstream effects on FLSs function was monitored.

RESULTS

SIN alleviated joint inflammation in rats with CIA, as evidenced by improvement of synovial hyperplasia, inflammatory cell infiltration and cartilage damage, as well as inhibition of pro-inflammatory cytokines release from FLSs induced by LPS. In vitro studies revealed a concentration-dependent suppression of SIN on the invasion and migration of FLSs induced by LPS. In addition, SIN downregulated the expression of cellular CRMP2 that was induced by LPS in FLSs, but increased its phosphorylation at residue T514. Moreover, regulation of pCRMP2 T514 by plasmids transfection (CRMP2 T514A/D) significantly influenced the migration and invasion of FLSs. Finally, SIN promoted nuclear translocation of pCRMP2 T514 in FLSs.

CONCLUSIONS

SIN may exert its anti-inflammatory and analgesic effects by modulating CRMP2 T514 phosphorylation and its nuclear translocation of FLSs, inhibiting pro-inflammatory cytokine release, and suppressing abnormal invasion and migration. Phosphorylation of CRMP2 at the T514 site in FLSs may present a new therapeutic target for treating inflammatory joint's destruction and arthritic pain in RA.

Satellite Glial Cells in Human Disease

Satellite glial cells (SGCs) are the main type of glial cells in sensory ganglia. Animal studies have shown that these cells play essential roles in both normal and disease states. In a large number of pain models, SGCs were activated and contributed to the pain behavior. Much less is known about SGCs in humans, but there is emerging recognition that SGCs in humans are altered in a variety of clinical states. The available data show that human SGCs share some essential features with SGCs in rodents, but many differences do exist. SGCs in DRG from patients suffering from common painful diseases, such as rheumatoid arthritis and fibromyalgia, may contribute to the pain phenotype. It was found that immunoglobulins G (IgG) from fibromyalgia patients can induce pain-like behavior in mice. Moreover, these IgGs bind preferentially to SGCs and activate them, which can sensitize the sensory neurons, causing nociception. In other human diseases, the evidence is not as direct as in fibromyalgia, but it has been found that an antibody from a patient with rheumatoid arthritis binds to mouse SGCs, which leads to the release of pronociceptive factors from them. Herpes zoster is another painful disease, and it appears that the zoster virus resides in SGCs, which acquire an abnormal morphology and may participate in the infection and pain generation. More work needs to be undertaken on SGCs in humans, and this review points to several promising avenues for better understanding disease mechanisms and developing effective pain therapies.

Pain sensitisation and joint inflammation in patients with active rheumatoid arthritis

INTRODUCTION

Despite better therapies and strategies, many people with rheumatoid arthritis (RA) have persistent pain, often from abnormal pain processing, now termed nociplastic pain. However, RA patients with fibromyalgia (FM), a central nociplastic pain syndrome, also have power doppler ultrasound (PDUS+) joint inflammation. To understand the complex causes of pain, we performed clinical examination and patient-reported outcome measures (PROMs) plus comprehensive PDUS evaluation not previously combined.

METHODS

In a cross-sectional study of sequential RA patients with at least moderate DAS28 erythrocyte sedimentation rate disease activity, we assessed 66/68 joints for swelling and tenderness, respectively, FM American College of Rheumatology 2010 diagnostic criteria, completed PROMs for function, quality of life and mood, alongside PDUS examination of 44 joints. Statistical analysis included logistic regression modelling and regularised (lasso) logistic regression methods.

RESULTS

From 158 patients, 72 (46%) patients met FM criteria, with significantly worse tender joint counts and PROMs, but no differences in PDUS compared with the non-FM group. Categorising patients by PDUS+ joint presence and/or FM criteria, we identified four distinct groups: 43 (27.2%) patients with -FM-PD, 43 (27.2%) with -FM+PD, 42 (26.6%) with +FM-PD and 30 (19%) with +FM+PD. Both FM+ groups had worse PROMs for fatigue, mood and pain, compared with the FM- groups. We were unable to develop algorithms to identify different groups.

CONCLUSION

The unexpected group -FM-PD group may have peripheral nociplastic pain, not commonly recognised in rheumatology. Only 46% of patients demonstrated PDUS+ inflammation. However clinical examination and PROMs did not reliably differentiate groups, emphasising PDUS remains an important tool.

Improving the nosology of Long COVID: it is not so simple

Long COVID is a diagnostic label currently given to those suffering from a poorly understood state of incomplete recovery or who have development of a myriad of medically unexplained symptoms occurring in the wake of infection with SARS CoV-2 that is both poorly understood and controversial. Many of the features of one of the most common clinical endotypes of Long COVID are shared by a condition well familiar to all rheumatologists and one with a large body of epidemiologic, clinical and basic research accrued over many decades namely the syndrome of fibromyalgia. Some have recently suggested that Long COVID may merely be a new name for fibromyalgia and that this diagnosis is indeed the condition that many or most may be suffering from as a post infectious sequela. In this Viewpoint we argue that while the parallels between the clinical syndrome experienced by many of those currently labeled as Long COVID and fibromyalgia are strong we should be not too quick to rename the disorder. We further argue that relabeling Long COVID as fibromyalgia is clinically reductionistic and any such relabeling may be attended by harm in both the design and execution of a future research agenda as well to patients who may be inadvertently and unfortunately pejoritised by such labeling. We further explore the parallels and differences between Long COVID and fibromyalgia and outline areas of needed future research and care.

Reprint of "Residual pain in rheumatoid arthritis: Is it a real problem?"

Pain is a significant issue in rheumatoid arthritis (RA) and can have a negative impact on patients' quality of life. Despite optimal control of inflammatory disease, residual chronic pain remains a major unmet medical need in RA. Pain in RA can be secondary to inflammation but can also generate neuroendocrine responses that initiate neurogenic inflammation and enhance cytokine release, leading to persistent hyperalgesia. In addition to well-known cytokines such as TNFα and IL-6, other cytokines and the JAK-STAT pathway play a role in pain modulation and inflammation. The development of chronic pain in RA involves processes beyond inflammation or structural damage. Residual pain is often observed in patients even after achieving remission or low disease activity, suggesting the involvement of non-inflammatory and central sensitization mechanisms. Moreover, fibromyalgia syndrome (FMS) is prevalent in RA patients and may contribute to persistent pain. Factors such as depression, sleep disturbance, and pro-inflammatory cytokines may contribute to the development of fibromyalgia in RA. It is essential to identify and diagnose concomitant FMS in RA patients to better manage their symptoms. Further research is needed to unravel the complexities of pain in RA. Finally, recent studies have shown that JAK inhibitors effectively reduce residual pain in RA patients, suggesting pain-reducing effects independent of their anti-inflammatory properties.

Immune mechanisms of depression in rheumatoid arthritis

Depression is a common and disabling comorbidity in rheumatoid arthritis that not only decreases the likelihood of remission and treatment adherence but also increases the risk of disability and mortality in patients with rheumatoid arthritis. Compelling data that link immune mechanisms to major depressive disorder indicate possible common mechanisms that drive the pathology of the two conditions. Preclinical evidence suggests that pro-inflammatory cytokines, which are prevalent in rheumatoid arthritis, have various effects on monoaminergic neurotransmission, neurotrophic factors and measures of synaptic plasticity. Neuroimaging studies provide insight into the consequences of inflammation on the brain (for example, on neural connectivity), and clinical trial data highlight the beneficial effects of immune modulation on comorbid depression. Major depressive disorder occurs more frequently in patients with rheumatoid arthritis than in the general population, and major depressive disorder also increases the risk of a future diagnosis of rheumatoid arthritis, further highlighting the link between rheumatoid arthritis and major depressive disorder. This Review focuses on interactions between peripheral and central immunobiological mechanisms in the context of both rheumatoid arthritis and major depressive disorder. Understanding these mechanisms will provide a basis for future therapeutic development, not least in depression.

Residual pain in rheumatoid arthritis: Is it a real problem?

Pain is a significant issue in rheumatoid arthritis (RA) and can have a negative impact on patients' quality of life. Despite optimal control of inflammatory disease, residual chronic pain remains a major unmet medical need in RA. Pain in RA can be secondary to inflammation but can also generate neuroendocrine responses that initiate neurogenic inflammation and enhance cytokine release, leading to persistent hyperalgesia. In addition to well-known cytokines such as TNFα and IL-6, other cytokines and the JAK-STAT pathway play a role in pain modulation and inflammation. The development of chronic pain in RA involves processes beyond inflammation or structural damage. Residual pain is often observed in patients even after achieving remission or low disease activity, suggesting the involvement of non-inflammatory and central sensitization mechanisms. Moreover, fibromyalgia syndrome (FMS) is prevalent in RA patients and may contribute to persistent pain. Factors such as depression, sleep disturbance, and pro-inflammatory cytokines may contribute to the development of fibromyalgia in RA. It is essential to identify and diagnose concomitant FMS in RA patients to better manage their symptoms. Further research is needed to unravel the complexities of pain in RA. Finally, recent studies have shown that JAK inhibitors effectively reduce residual pain in RA patients, suggesting pain-reducing effects independent of their anti-inflammatory properties.

Upadacitinib effectiveness and factors associated with minimal disease activity achievement in patients with psoriatic arthritis: preliminary data of a real-life multicenter study

BACKGROUND

Upadacitinib (UPA) is a selective JAK inhibitor recently approved for the treatment of psoriatic arthritis (PsA). In this post-approval study, we aimed to evaluate the effectiveness and safety of UPA over 24 weeks and identify clinical predictors of response, in a multicentric cohort of patients affected by PsA.

METHODS

One hundred and twenty-six patients with PsA treated with UPA were enrolled in 10 Italian centres. UPA effectiveness outcomes, such as the proportion of patients with MDA status, DAPSA remission, and low disease activity, ASDAS-CRP inactive and low disease activity, and change from baseline in DAPSA and ASDAS-CRP scores, were evaluated every 12 weeks until week 24. The proportion of DAPSA minor, moderate, and major improvement, and ASDAS clinically important improvement (CII) and major improvement (MI) were considered as well. All treatment-related adverse events were collected during the observation period. Clinical predictors of MDA response at week 24 were evaluated through multivariate analysis.

RESULTS

At baseline, 124/126 (98%) and 54/126 (43%) patients showed peripheral and axial involvement, respectively; 110 (87%) patients were intolerant or resistant to biologic DMARDs.  At 24 weeks, MDA status, DAPSA remission, and ASDAS-CRP inactive disease were achieved in 47%, 23%, and 48% of patients, respectively. Minor, moderate, and major DAPSA improvement was observed in 67%, 39%, and 23%, respectively; while 65% and 35% achieved ASDAS-CRP CII and MI, respectively. The mean change from baseline was 15.9 ± 13.5 (p < 0.001) for DAPSA and 1.21 ± 0.97 (p < 0.001) for ASDAS-CRP. Thirteen patients (10%) discontinued UPA due to a lack of efficacy or non-serious adverse events. No serious adverse events were observed. Male gender (OR 2.54, 95% CI 1.03-6.25 p = 0.043), being naïve to biological DMARDs (OR 4.13, 95% CI 1.34-12.71, p = 0.013) and elevated baseline CRP (OR 2.49, 95% CI 1.02-6.12, p = 0.046) were associated with MDA response at week 24.

CONCLUSIONS

This is one of the first real-life studies supporting the effectiveness of UPA and its safety profile in PsA patients. Furthermore, the study identifies predictors of MDA response to UPA treatment at 6 months.