Melatonin attenuates TNF-α and IL-1β expression in synovial fibroblasts and diminishes cartilage degradation: Implications for the treatment of rheumatoid arthritis

Detection of TNF-α using the established ab-MPs-CLIA

Tumor necrosis factor alpha (TNF-α) is a key cytokine in inflammation and immune responses, making its rapid and accurate detection essential for disease diagnosis and management. In this study, we developed a highly sensitive chemiluminescence immunoassay (CLIA) using antibody-coated magnetic particles (Ab-MPs-CLIA) for TNF-α detection. From nine candidate antibodies, we identified an optimal pair through epitope competition and affinity assessments, significantly improving assay performance. The Ab-MPs-CLIA achieved a detection limit of 0.25 pg/mL, 6.8 times more sensitive than Siemens commercial kits, with a broad linear range of 9.2-1077 pg/mL. The method demonstrated excellent stability, both under accelerated conditions at 37 °C for 7 days and long-term storage at 4 °C for 12 months. It showed no cross-reactivity with common interfering substances in human serum, ensuring high specificity. Notably, the entire process, from sample preparation to result, takes just 25 min, compared to 3-4 h for both ELISA and RIA, and CLIA typically offers 10-100 times higher sensitivity than these methods. These advantages make the Ab-MPs-CLIA an ideal option for clinical laboratories, providing superior sensitivity, specificity, broader dynamic range, and greater operational efficiency than existing TNF-α detection technologies.

Protective effects of Catalpol to attenuate TNF- α and collagen-induced inflammation in vitro HFLS-RA cells and in vivo mice models for the treatment of rheumatoid arthritis

BACKGROUND/RATIONALE

Rheumatoid Arthritis (RA) is a prolonged autoimmune condition marked by persistent inflammation, causing joint damage and bone erosion. Catalpol (CAT), an iridoid glycoside, offers anti-inflammatory benefits, warranting its study in RA models.

OBJECTIVE

To investigate the anti-inflammatory effects of CAT in RA by evaluating its impact on cellular and animal RA models.

METHODS

In vitro biological actions of CAT were investigated by the methods of cell viability, proliferation, migration, invasion, apoptosis, ROS generation, double luciferase reporter assay for NF-κB-p65 activity, Nitrite release detection, and RT-qPCR for gene expression in Tumor Necrosis Factor-alpha (TNF-α)-induced Human Fibroblast-Like Synoviocytes from RA patients (HFLS-RA) (cellular RA model). Arthritis severity, joint cellular structure, gene expression, inflammatory factors, and joint inflammation studies were investigated in mice with collagen-induced arthritis (CIA) (animal RA model).

KEY RESULTS

CAT treatment groups showed significant improvements (P < 0.001) in cell viability, migration, invasion, and apoptosis compared to the TNF-α-induced group. ROS generation and the activity of NF-κB-p65 were significantly reduced (P < 0.001). Nitrite release was decreased (P < 0.01, P < 0.001) in CAT-treatment groups. Pro-inflammatory and bone-metabolizing cytokine gene expression was markedly downregulated (P < 0.05, P < 0.001) in the cellular RA model. CIA mice treated with CAT exhibited significantly reduced arthritis severity, paw edema, and arthritis index (P < 0.05, P < 0.01). Joint pathology scores showed improvement (P < 0.001) in CAT-treatment groups. In the animal RA model, bone-metabolizing and inflammatory cytokine gene expression was significantly reduced in CAT-treatment groups (P < 0.01, P < 0.001).

CONCLUSION

CAT effectively reduces RA's inflammation and bone metabolism issues, suggesting its potential as a therapeutic agent for RA treatments. Key Points • Plant-derived Catalpol compound is an effective choice for rheumatoid arthritis treatment due to its anti-inflammatory potential. • CAT's effects were tested on TNF-α-induced HFLS-RA cells and in CIA mice, assessing cell viability, apoptosis, ROS generation, arthritis severity, inflammatory factors, and joint inflammation studies. • The administration of CAT could greatly enhance cell health and reduce inflammation markers and arthritis symptoms. • Observed significant reduction of RA inflammation and bone issues, confirming CAT as a therapeutic agent in RA treatment.

Analysis of how melatonin-upregulated clock genes PER2 and CRY2 alleviate rheumatoid arthritis-associated interstitial lung disease

Melatonin (Mel) serves as the central regulator for maintaining circadian rhythms and plays a crucial role not only in controlling the rhythmic clock, but also in several functional domains such as immunomodulation and anti-inflammation. In this study, we explored the clinical relevance of Mel and rheumatoid arthritis comorbid with interstitial lung disease (RA-ILD), and its potential therapeutic effects on arthropathy and pulmonary fibrosis (PF) in mice with collagen-induced arthritis (CIA). The results demonstrated that low serum levels of Mel were correlated with disease activity and severity of PF in RA-ILD patients. In addition, Mel was potentially efficacious in alleviating arthritis, bone destruction, and PF in a mouse model of CIA. Meanwhile, we observed that in lung tissues, the circadian-clock genes (CCGs) period circadian regulator 2 (PER2) and cryptochrome circadian regulator 2 (CRY2) were predominantly expressed in epithelial cells (ECs), and the regulation of their expression in ECs was closely correlated with Mel-mediated suppression of inflammatory responses and a significant reduction in macrophagic inflammatory activity. These results implied that Mel and its associated CCGs might play important regulatory roles in RA-ILD and its associated pathological processes.

Melatonin, an Antitumor Necrosis Factor Therapy

Tumor necrosis factor (TNF) is a biomarker of inflammation whose levels are elevated in patients with several diseases associated with dysregulation of the immune response. The main limitations of currently used anti-TNF therapies are the induction of immunodepression, which in many cases leads to serious adverse effects such as infection and cancer, and the inability to cross the blood-brain barrier in neuroinflammatory conditions. Melatonin, in addition to being a chronobiotic compound, is widely known for its antioxidant and immunomodulatory capacity to control inflammatory processes in different pathological contexts. The aim of the present review is to address human-based studies that describe the effect of melatonin on TNF production. The review includes all the articles published in PubMed databases until April 15, 2024. After depuration, 45 studies were finally included in the review, 23 related to the in vitro action of melatonin in human cells and 22 in vivo studies in humans. Most of the data reviewed support the idea that melatonin has an immunosuppressive effect on TNF levels, which, together with its low toxicity profile, low cost, and ability to cross the blood-brain barrier, points to melatonin as a potential anti-TNF therapy. Therefore, improving our knowledge of the action of melatonin in regulating TNF through appropriate clinical trials would reveal the true potential of this molecule as a possible anti-TNF therapy.

Melatonin mitigates intervertebral disc degeneration by suppressing NLRP3 inflammasome activation via the EGR1/DDX3X pathway

Intervertebral disc degeneration (IVDD), is one of the leading causes of low back pain. Inflammation is considered to be the main pathophysiological process of IVDD. The nucleotide-binding domain and leucine-rich pyrin domain containing 3 (NLRP3) inflammasome-mediated inflammatory responses are critically involved in the progression of IVDD. Melatonin is known for its anti-inflammatory and antioxidant effects. However, little is known about the potential effects of melatonin in the pathological process of IVDD. We found that the expression of EGR1, DDX3X, and NLRP3 inflammasome increased and extracellular matrix (ECM) degraded in IVDD. With the application of EGR1 siRNA, the expression of DDX3X and the activation of NLRP3 inflammasome were inhibited in stress-induced NP cells. DDX3X/NLRP3 was regulated on dependence of EGR1. Besides, the utility of melatonin mitigated the EGR1-induced overproduction of DDX3X and activation of NLRP3 inflammasome, thus protecting cells from pyroptosis and ECM degradation. In vivo, in a rat IVDD model, melatonin was found to be able to delay the development of IVDD by imageological and histological evaluation. In conclusion, our study demonstrated that melatonin prevented IVDD progression by regulating EGR1/DDX3X/NLRP3 axis. Our study provides insight into melatonin as a new target for therapeutic approaches for IVDD.

Albiflorin inhibits osteoclastogenesis and titanium particles-induced osteolysis via inhibition of ROS accumulation and the PI3K/AKT signaling pathway

Periprosthetic osteolysis (PPO), caused by wear particles, is a significant complication of total joint replacement, leading to prosthesis failure. Previous research has highlighted the crucial role of osteoclast-induced bone destruction in PPO progression. Albiflorin (AF), a monoterpene glycoside from Paeonia lactiflora, is a key active ingredient known for its antioxidant and anti-inflammatory properties. Although AF has shown promise in treating various conditions, its impact on osteoclasts and PPO remains unexplored. Our study revealed that AF could effectively inhibit osteoclast differentiation to reduce overactivated bone resorption and effectively inhibit the accumulation of reactive oxygen species (ROS) induced by wear particles. In vitro experiments also confirmed that AF could effectively inhibit the PI3K/AKT signaling pathway and inhibit inflammation to regulate osteoclast generation. Studies in animal models have also verified the antioxidant and anti-inflammatory properties of AF. In summary, the above studies indicate that AF inhibits osteoclastogenesis via inhibiting ROS accumulation and the PI3K/AKT signaling pathway, which may be a potential therapeutic method for PPO.

Melatonin enhances therapeutic outcomes of adipose tissue-derived mesenchymal stem cell therapy in rat osteoarthritis by reducing TNF-α and IL-1β-induced injuries

Although adipose tissue-derived mesenchymal stem cell (ADSC) transplantation has been effectively used to treat osteoarthritis (OA), the low cell survival rate induced by the inflammatory and oxidative stress, severely affects the therapeutic efficiency of ADSC transplantation in OA. This study was designed to evaluate whether melatonin pretreatment could improve ADSC survival and its therapeutic efficacy in OA. The papain-induced OA rats were pretreated with melatonin via intra-articular injection and then intra-articular injected with indocyanine green (ICG)-labeled ADSCs (3 × 106/rat). Afterward, ADSC retention was evaluated by NIR-II fluorescence imaging. The tibia and synovial fluid were collected for histopathological examination and ELISA assay, respectively. To confirm the anti-inflammatory effect of melatonin, a TNF-α and IL-1β-induced cell model was used to evaluate the protective effects of melatonin on ADSC viability, cell apoptosis, and migration. Our results showed that melatonin pretreatment enhanced ADSC survival and improved the therapeutic effects of ADSC transplantation on cartilage repair, and anti-inflammation by reducing TNF-α, IL-6, IL-1β, and IL-12 in vivo. In particular, we also found that melatonin promoted ADSC viability and migration, and reduced cell apoptosis in vitro. In conclusion, this study supports that melatonin pretreatment can effectively improve ADSC survival and therapeutic efficiency in OA by reducing inflammatory injuries, which provides a novel strategy for enhancing ADSC therapy.

Melatonin in animal husbandry: functions and applications

Melatonin (N-acetyl-5-methoxytryptamine) is an essential small molecule with diverse biological functions. It plays several key roles, including regulating the secretion of reproductive hormones and the reproductive cycle, enhancing the functionality of reproductive organs, improving the quality of sperm and eggs, and mitigating oxidative stress in the reproductive system. Melatonin effectively inhibits and scavenges excess free radicals while activating the antioxidant enzyme system and reduces the production of inflammatory factors and alleviates tissue damage caused by inflammation by regulating inflammatory pathways. Additionally, melatonin contributes to repairing the intestinal barrier and regulating the gut microbiota, thereby reducing bacterial and toxin permeation. The use of melatonin as an endogenous hormone in animal husbandry has garnered considerable attention because of its positive effects on animal production performance, reproductive outcomes, stress adaptation, disease treatment, and environmental sustainability. This review explores the characteristics and biological functions of melatonin, along with its current applications in animal production. Our findings may serve as a reference for the use of melatonin in animal farming and future developmental directions.

Melatonin Regulates Rheumatoid Synovial Fibroblasts-Related Inflammation: Implications for Pathological Skeletal Muscle Treatment

Melatonin has been reported to regulate circadian rhythms and have anti-inflammatory characteristics in various inflammatory autoimmune diseases, but its effects in diseases-associated muscle atrophy remain controversial. This study is aimed to determine the evidence of melatonin in rheumatoid arthritis (RA)-related pathological muscle atrophy. We used initially bioinformatics results to show that melatonin regulated significantly the correlation between pro-inflammation and myogenesis in RA synovial fibroblasts (RASF) and myoblasts. The conditioned medium (CM) from melatonin-treated RASF was incubated in myoblasts with growth medium and differentiated medium to investigate the markers of pro-inflammation, atrophy, and myogenesis. We found that melatonin regulated RASF CM-induced pathological muscle pro-inflammation and atrophy in myoblasts and differentiated myocytes through NF-κB signaling pathways. We also showed for the first time that miR-30c-1-3p is negatively regulated by three inflammatory cytokines in human RASF, which is associated with murine-differentiated myocytes. Importantly, oral administration with melatonin in a collagen-induced arthritis (CIA) mouse model also significantly improved arthritic swelling, hind limb grip strength as well as pathological muscle atrophy. In conclusion, our study is the first to demonstrate not only the underlying mechanism whereby melatonin decreases pro-inflammation in RA-induced pathological muscle atrophy but also increases myogenesis in myoblasts and differentiated myocytes.

Melatonin hyalurosomes in collagen thermosensitive gel as a potential repurposing approach for rheumatoid arthritis management via the intra-articular route

Despite the fact that several rheumatoid arthritis treatments have been utilized, none of them achieved complete joint healing and has been accompanied by several side effects that compromise patient compliance. This study aims to provide an effective safe RA treatment with minimum side effects through the encapsulation of melatonin (MEL) in hyalurosomes and loading these hyalurosomes in collagen thermos-sensitive poloxamer 407 (PCO) hydrogels, followed by their intra-articular administration in AIA model rats. In vitro characterization of MEL-hyalurosomes and PCO hydrogel along with in vivo evaluation of the selected formulation were conducted. Particle size, PDI and EE % of the selected formulation were 71.5 nm, 0.09 and 90 %. TEM micrographs demonstrated that the particles had spherical shape with no aggregation signs. Loading PCO hydrogels with MEL-hyalurosomes did not cause significant changes in pH although it increased its viscosity and injection time. FTIR analysis showed that no interactions were noted among the delivery system components. In vivo results revealed the superior effect of MEL-hyalurosomes PCO hydrogel over MEL-PCO hydrogel and blank PCO hydrogels in improving joint healing, cartilage repair, pannus formation and cell infiltrations. Also, MEL-hyalurosomes PCO hydrogel group showed comparable levels of TNF-α, IL1, MDA, NRF2 and HO-1 with the negative control group. These findings highlight the MEL encapsulation role in augmenting its pharmacological effects along with the synergistic effect of hyaluronic acid in hyalurosomes and collagen in PCO hydrogel in promoting joint healing.

Biological Clock Perspective in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by systemic polyarticular pain, and its main pathological features include inflammatory cell infiltration, synovial fibroblast proliferation, and cartilage erosion. Immune cells, synovial cells and neuroendocrine factors play pivotal roles in the pathophysiological mechanism underlying rheumatoid arthritis. Biological clock genes regulate immune cell functions, which is linked to rhythmic changes in arthritis pathology. Additionally, the interaction between biological clock genes and neuroendocrine factors is also involved in rhythmic changes in rheumatoid arthritis. This review provides an overview of the contributions of circadian rhythm genes to RA pathology, including their interaction with the immune system and their involvement in regulating the secretion and function of neuroendocrine factors. A molecular understanding of the role of the circadian rhythm in RA may offer insights for effective disease management.

Redefinition of Synovial Fibroblasts in Rheumatoid Arthritis

The breakdown of immune tolerance and the rise in autoimmunity contribute to the onset of rheumatoid arthritis (RA), driven by significant changes in immune components. Recent advances in single-cell and spatial transcriptome profiling have revealed shifts in cell distribution and composition, expanding our understanding beyond molecular-level changes in inflammatory cytokines, autoantibodies, and autoantigens in RA. Surprisingly, synovial fibroblasts (SFs) play an active immunopathogenic role rather than remaining passive bystanders in RA, with notable alterations in their subpopulation distribution and composition. This study examines these changes in SF heterogeneity, assesses their impact on RA progression, and elucidates the immune characteristics and functions of SF subsets in the RA autoimmunity, encompassing both intrinsic and adaptive immunity. Additionally, this review discusses therapeutic strategies targeting immune SF subsets, highlighting the potential of future interventions in SF phenotypic reprogramming. Overall, this review redefines the role of SFs in RA and suggests targeting SF phenotypic reprogramming and its upstream molecules as a promising therapeutic approach to restore immune balance and modulate immune tolerance in RA.

The Role and Therapeutic Potential of Melatonin in Degenerative Fundus Diseases: Diabetes Retinopathy and Age-Related Macular Degeneration

Degenerative fundus disease encompasses a spectrum of ocular diseases, including diabetic retinopathy (DR) and age-related macular degeneration (AMD), which are major contributors to visual impairment and blindness worldwide. The development and implementation of effective strategies for managing and preventing the onset and progression of these diseases are crucial for preserving patients' visual acuity. Melatonin, a neurohormone primarily produced by the pineal gland, exhibits properties such as circadian rhythm modulation, antioxidant activity, anti-inflammatory effects, and neuroprotection within the ocular environment. Furthermore, melatonin has been shown to suppress neovascularization and reduce vascular leakage, both of which are critical in the pathogenesis of degenerative fundus lesions. Consequently, melatonin emerges as a promising therapeutic candidate for degenerative ocular diseases. This review provides a comprehensive overview of melatonin synthesis, its localization within ocular tissues, and its mechanisms of action, particularly in regulating melatonin production, thereby underscoring its potential as a therapeutic agent for degenerative fundus diseases.

Ursolic acid inhibits NF-κB signaling and attenuates MMP-9/TIMP-1 in progressive osteoarthritis: a network pharmacology-based analysis

Osteoarthritis (OA) is a degenerative joint disease, characterized by infiltration of monocytes into the synovial joint which promotes inflammation, stiffness, joint swelling, cartilage degradation and further bone destruction. The leaves of Ocimum forskolei have been used for inflammation-related disease management in traditional medicine. Additionally, the downregulation of NF-κB and the MMP/TIMP-1 ratio has been shown to protect against OA. The LC-HR-MS metabolic analysis of Ocimum yielded 19 putative compounds, among which ursolic acid (UA) was detected. Ursolic acid possesses significant anti-inflammatory effects and has been reported to downregulate oxidative stress and inflammatory biomarkers. It was tested on rats in a model of intra-articular carrageenan injection to investigate its efficacy on osteoarthritis progression. The UA emulgel exerted chondroprotective, analgesic and local anaesthetic efficacies confirmed via histopathological investigation and radiographical imaging. A network pharmacology followed by molecular docking highlighted TNF-α, TGF-β and NF-κB as the top filtered genes. Quantitative real-time PCR analysis showed that UA significantly attenuated serum levels of TNF-α, IL-1β, NF-κB, MMP-9/TIMP-1 and elevated levels of TGF-β. Taken together, these results suggest that UA could serve as a functional food-derived phytochemical with a multi-targeted efficacy on progression of OA, regulating the immune and inflammatory responses, particularly, attenuating chondrocytes degeneration via suppression of NF-κB and MMP-9/TIMP-1. Accordingly, UA might be a promising alternative to conventional therapy for safe, easily applicable and effective management of OA.

Mechanism investigation of Duhuo Jisheng pill against rheumatoid arthritis based on a strategy for the integration of network pharmacology, molecular docking and in vivo experimental verification

CONTEXT

Duhuo Jisheng pill (DHJS) is a classic traditional Chinese medicine (TCM) formula for rheumatoid arthritis (RA). The effective components and therapeutic mechanisms of DHJS for treating RA are still unclear.

OBJECTIVE

To explore the potential mechanism of DHJS against RA by means of network pharmacology and experimental verification.

MATERIALS AND METHODS

A network pharmacology and molecular docking analysis based on phytochemistry was used to elucidate the mechanism of DHJS against RA. The targets of DHJS anti-RA active ingredient were obtained by searching TCMSP, ETCM and TCMSID. The RA model induced by collagen was established in Wistar rats. The rats in the DHJS group were administered doses of 0.5, 1.0 and 2.0 g/kg for a period of 10 d. The expression of targets was measured with Western blot.

RESULTS

Network pharmacology analysis showed that the anti-RA effect of DHJS was mediated by targets involved in immunity, inflammation and apoptosis, as well as PI3K-Akt and NF-κB signalling pathways. Of 2.0 g/kg DHJS significantly alleviated the ankle inflammation (IL-6: 62.73 ± 8.39 pg/mL, IL-1β: 50.49 ± 11.47 pg/mL, TNF-α: 16.88 ± 3.05 pg/mL, IL-17A: 12.55 ± 1.87 pg/mL, IL-10: 16.24 ± 3.00 pg/mL), comparing with the model group (IL-6: 92.02 ± 13.25 pg/mL, IL-1β: 71.85 ± 4.12 pg/mL, TNF-α: 25.64 ± 3.69 pg/mL, IL-17A: 22.14 ± 4.56 pg/mL, IL-10: 9.51 ± 3.03 pg/mL) (p < 0.05). Moreover, the protein expression of p-PI3K, p-AKT and p-p65 significantly decreased after DHJS administration.

CONCLUSIONS

DHJS could alleviate the collagen-induced arthritis (CIA) by the PI3K/AKT/NF-κB signalling pathway.

Melatonin and bone-related diseases: an updated mechanistic overview of current evidence and future prospects

PURPOSE

Bone diseases account for an enormous cost burden on health systems. Bone disorders are considered as age-dependent diseases. The aging of world population has encouraged scientists to further explore the most effective preventive modalities and therapeutic strategies to overcome and reduce the high cost of bone disorders. Herein, we review the current evidence of melatonin's therapeutic effects on bone-related diseases.

METHODS

This review summarized evidences from in vitro, in vivo, and clinical studies regarding the effects of melatonin on bone-related diseases, with a focus on the molecular mechanisms. Electronically, Scopus and MEDLINE®/PubMed databases were searched for articles published on melatonin and bone-related diseases from inception to June 2023.

RESULTS

The findings demonstrated that melatonin has beneficial effect in bone- and cartilage-related disorders such as osteoporosis, bone fracture healing, osteoarthritis, and rheumatoid arthritis, in addition to the control of sleep and circadian rhythms.

CONCLUSION

A number of animal and clinical studies have indicated that various biological effects of melatonin may suggest this molecule as an effective therapeutic agent for controlling, diminishing, or suppressing bone-related disorders. Therefore, further clinical studies are required to clarify whether melatonin can be effective in patients with bone-related diseases.

Melatonin enhances the ability of M2 macrophages to secrete IL10 by inhibiting Erk5 signaling pathway

BACKGROUND

Melatonin plays a role in repairing damaged cartilage and regulating immune cells. The anti-inflammatory effect of Melatonin involves multiple pathways and molecular activation, which directly or indirectly inhibits inflammatory reaction. M2 macrophages have the ability to anti-inflammatory response and repair damaged tissues, secrete IL10 and IL-4, and participate in tissue repair and remodeling. Erk5 is a recently discovered member of the MAPK family and one of the least studied members. It plays an important role in cell differentiation, proliferation, secretion and other functions. This experiment aims to study how Melatonin affects M2 Macrophage polarization and secretion through ERK5 signaling pathway.

METHODS

The RAW 264.7 macrophages were used for cell culture. The cells were cultured according to the pre-experimental results. The effects of Melatonin on M2 macrophages were comprehensively evaluated by CCK8 activity detection, RT-PCR, ELISA, cellular immunofluorescence, and WB.SD mice were selected to evaluate the effect of Melatonin on cartilage damage in rats with knee Osteoarthritis through HE staining, immunohistochemistry and immunofluorescence.

RESULTS

Melatonin cultivates RAW 264.7 macrophages. Without affecting the polarization ratio of M2 Macrophage polarization, Melatonin may reduce Erk5 gene expression, reduce Erk5 and p-Erk5 protein synthesis, and cooperate with BIX 02189 to enhance the secretion function of existing M2 macrophages and increase the secretion of cytokines IL10. Immunohistochemistry of rat knee Osteoarthritis model confirmed that the expression of IL10 was up-regulated and the synthesis of type II collagen was enhanced, but immunofluorescence found that the polarization of M2 Macrophage polarization in subchondral bone was not obvious.

CONCLUSION

Melatonin enhances the ability of M2 macrophages to secrete IL10 by inhibiting Erk5 signaling pathway, but has no effect on M2 Macrophage polarization.

Injectable mesoporous bioactive glass/sodium alginate hydrogel loaded with melatonin for intervertebral disc regeneration

Intervertebral disc degeneration (IDD) is a major contributing factor to both lower back and neck pain. As IDD progresses, the intervertebral disc (IVD) loses its ability to maintain its disc height when subjected to axial loading. This failure in the weight-bearing capacity of the IVD is a characteristic feature of degeneration. Natural polymer-based hydrogel, derived from biological polymers, possesses biocompatibility and is able to mimic the structure of extracellular matrix, enabling them to support cellular behavior. However, their mechanical performance is relatively poor, thus limiting their application in IVD regeneration. In this study, we developed an injectable composite hydrogel, namely, Mel-MBG/SA, which is similar to natural weight-bearing IVD. Mesoporous bioactive glasses not only enhance hydrogels, but also act as carriers for melatonin (Mel) to suppress inflammation during IDD. The Mel-MBG/SA hydrogel further provides a mixed system with sustained Mel release to alleviate IL-1β-induced oxidative stress and relieve inflammation associated with IDD pathology. Furthermore, our study shows that this delivery system can effectively suppress inflammation in the rat tail model, which is expected to further promote IVD regeneration. This approach presents a novel strategy for promoting tissue regeneration by effectively modulating the inflammatory environment while harnessing the mechanical properties of the material.

Therapeutic potential of Coptis chinensis for arthritis with underlying mechanisms

Arthritis is a common degenerative disease of joints, which has become a public health problem affecting human health, but its pathogenesis is complex and cannot be eradicated. Coptis chinensis (CC) has a variety of active ingredients, is a natural antibacterial and anti-inflammatory drug. In which, berberine is its main effective ingredient, and has good therapeutic effects on rheumatoid arthritis (RA), osteoarthritis (OA), gouty arthritis (GA). RA, OA and GA are the three most common types of arthritis, but the relevant pathogenesis is not clear. Therefore, molecular mechanism and prevention and treatment of arthritis are the key issues to be paid attention to in clinical practice. In general, berberine, palmatine, coptisine, jatrorrhizine, magnoflorine and jatrorrhizine hydrochloride in CC play the role in treating arthritis by regulating Wnt1/β-catenin and PI3K/AKT/mTOR signaling pathways. In this review, active ingredients, targets and mechanism of CC in the treatment of arthritis were expounded, and we have further explained the potential role of AHR, CAV1, CRP, CXCL2, IRF1, SPP1, and IL-17 signaling pathway in the treatment of arthritis, and to provide a new idea for the clinical treatment of arthritis by CC.

Decipher the pharmacological mechanisms of raw and wine-processed Curculigo orchioides Gaertn. on bone destruction in rheumatoid arthritis rats using metabolomics

ETHNOPHARMACOLOGICAL RELEVANCE

Curculigo orchioides Gaertn. (CO), a traditional Chinese herb recorded in Chinese Pharmacopoeia, can nourish kidney yang, strengthen bones, and dispell cold-dampness. Raw CO (rCO) and wine-processed CO (pCO), the main processed products of CO for clinical application, show differences in nourishing kidney yang and ameliorate osteoporosis. However, the difference in efficacy and mechanism of rCO and pCO on bone destruction in rheumatoid arthritis (RA) remain unclear.

AIM OF THE STUDY

To compare the pharmacodynamics of rCO and pCO in the treatment of bone destruction in RA and to reveal the potential mechanism by which rCO and pCO exert effects by metabolomics approach.

MATERIALS AND METHODS

Ultra-high performance liquid chromatography Q exactive mass spectrometry (UHPLC-Q-Exactive-MS) combined with multivariate data analysis was applied to identify the differential chemical components in rCO and pCO. Collagen-induced arthritis (CIA) rats were orally administrated with different doses of rCO and pCO for 4 weeks. The body weight, paw swelling, arthritis scores, serum inflammatory cytokines concentration, knee tumor necrosis factor (TNF)-α, interleukin (IL)-6 protein levels, and inflammatory cell infiltration were determined to investigate the effects of rCO and pCO on arthritic symptoms and inflammatory responses in CIA rats. The effects of rCO and pCO on bone destruction were assessed using safranin O-fast green and tartrate-resistant acid phosphatase (TRAP) staining, immunohistochemical analysis of osteoprotegerin (OPG) and receptor activator of nuclear factor-κB ligand (RANKL) proteins, and micro-computed tomography (micro-CT) in rats. In addition, metabolomics was performed to explore the mechanism of rCO and pCO against bone destruction in RA.

RESULTS

A total of 41 chemical constituents were identified in both rCO and pCO, 9 of which were screened out as discriminatory compounds. According to the pharmacodynamic assays, pCO exhibited a stronger effect than rCO in attenuating the severity of arthritis, reducing inflammation, and inhibiting bone destruction. The metabolomics results showed that pentose phosphate pathway was the key metabolic pathways regulated by rCO, while pCO regulated multiple metabolic pathways including phenylalanine metabolism pathways, phenylalanine, tyrosine and tryptophan biosynthesis, taurine and hypotaurine metabolism, and glycerophospholipid metabolism pathways.

CONCLUSION

pCO displayed a better effect on alleviating bone destruction in RA was than rCO. This might be associated with that pCO can decrease inflammation in RA through regulating more metabolism pathways.

Characterization of aberrant glycosylation associated with osteoarthritis based on integrated glycomics methods

BACKGROUND

Osteoarthritis (OA) is the most common form of arthritis, affecting millions of aging people. Investigation of abnormal glycosylation is essential for the understanding of pathological mechanisms of OA.

METHODS

The total protein was isolated from OA (n = 13) and control (n = 11) cartilages. Subsequently, glycosylation alterations of glycoproteins in OA cartilage were investigated by lectin microarrays and intact glycopeptides analysis. Finally, the expression of glycosyltransferases involved in the synthesis of altered glycosylation was assessed by qPCR and GEO database.

RESULTS

Our findings revealed that several glycopatterns, such as α-1,3/6 fucosylation and high-mannose type of N-glycans were altered in OA cartilages. Notably, over 27% of identified glycopeptides (109 glycopeptides derived from 47 glycoproteins mainly located in the extracellular region) disappeared or decreased in OA cartilages, which is related to the cartilage matrix degradation. Interestingly, the microheterogeneity of N-glycans on fibronectin and aggrecan core protein was observed in OA cartilage. Our results combined with GEO data indicated that the pro-inflammatory cytokines altered the expression of glycosyltransferases (ALG3, ALG5, MGAT4C, and MGAT5) which may contribute to the alterations in glycosylation.

CONCLUSION

Our study revealed the abnormal glycopatterns and heterogeneities of site-specific glycosylation associated with OA. To our knowledge, it is the first time that the heterogeneity of site-specific N-glycans was reported in OA cartilage. The results of gene expression analysis suggested that the expression of glycosyltransferases was impacted by pro-inflammatory cytokines, which may facilitate the degradation of protein and accelerate the process of OA. Our findings provide valuable information for the understanding of molecular mechanisms in the pathogenesis of OA.

Research on the improvement effect of Saposhnikovia divaricata (Trucz.) Schischk on rheumatoid arthritis based on the "component-target-pathway" association

OBJECTIVE

To investigate the therapeutic effect and mechanism of the traditional Chinese medicine Saposhnikovia divaricata (Trucz.) Schischk in rats with complete Freund's adjuvant-induced rheumatoid arthritis (RA).

METHODS

The chemical targets and RA targets of Saposhnikovia divaricata (Trucz.) Schischk were acquired by the network pharmacological method. The complete Freund's adjuvant-induced rat RA model was used to further explore the mechanism of Saposhnikovia divaricata (Trucz.) Schischk in improving RA. Pathological changes in the volume of toes, body weight and synovial tissues of joints as well as serum inflammatory factor levels before and after the intervention of Saposhnikovia divaricata (Trucz.) Schischk were investigated. The key metabolic pathways were screened by correlations between metabolites and key targets. Finally, a quantitative analysis of key targets and metabolites was experimentally validated.

RESULTS

Saposhnikovia divaricata (Trucz.) Schischk administration increased body weight, mitigated foot swelling and downregulated inflammatory cytokine levels in model rats. The histopathology showed that treatment with Saposhnikovia divaricata (Trucz.) Schischk can induce inflammatory cell infiltration and synovial hyperplasia and obviously reduce cartilage injuries, thus improving arthritis symptoms in rats. According to the network pharmacology-metabonomics association analysis results, the purine metabolic signaling pathway might be the key pathway for RA intervention with Saposhnikovia divaricata (Trucz.) Schischk. Targeted metabonomics, Western blotting (WB) and reverse transcription-polymerase chain reaction (RT‒PCR) assays showed that the recombinant adenosine deaminase (ADA) mRNA expression level and metabolic level of inosine in Saposhnikovia divaricata (Trucz.) Schischk administration group were lower than those of the model group. This reflected that Saposhnikovia divaricata (Trucz.) Schischk could improve RA by downregulating ADA mRNA expression levels and the metabolic level of inosine in the purine signaling pathway.

CONCLUSION

Based on the "component-disease-target" association analysis, this study concludes that Saposhnikovia divaricata (Trucz.) Schischk improves complete Freund's adjuvant-induced RA symptoms in rats mainly by downregulating ADA mRNA expression levels in the purine metabolic signaling pathway, mitigating foot swelling, improving the levels of serum inflammatory factors (IL-1β, IL-6 and TNF-α), and decreasing the ADA protein expression level to intervene in purine metabolism.

Inhibition of Cdc37 Ameliorates Arthritis in Collagen-Induced Arthritis Rats by Inhibiting Synoviocyte Proliferation and Migration Through the ERK Pathway

Rheumatoid arthritis (RA) is a chronic autoimmune disease that can lead to synovial inflammation, pannus formation, cartilage damage, bone destruction, and ultimate disability. Fibroblast-like synoviocytes (FLS) are involved in the pathogenetic mechanism of RA. Cdc37 (cell division cycle protein 37) is regarded as a molecular chaperone involved in various physiological processes such as cell cycle progression, cell proliferation, cell signal transduction, tumorigenesis, and progression. However, the precise role of Cdc37 in the pathogenesis of rheumatoid arthritis (RA) remains uncertain. In our study, we found that Cdc37 expression was upregulated in human rheumatoid synovia in contrast with the normal group. Interestingly, Cdc37 activated the ERK pathway to promote RA-FLS proliferation and migration in vitro. Ultimately, in vivo experiments revealed that silencing of Cdc37 alleviated ankle swelling and cartilage destruction and validated the ERK signaling pathways in vitro findings. Collectively, we demonstrate that Cdc37 promotes the proliferation and migration of RA-FLS by activation of ERK signaling pathways and finally aggravates the progression of RA. These data indicated that Cdc37 may be a novel target for the treatment of RA.

Isochlorogenic Acid C Restrains Erk/JNK/NF-κB Signaling to Alleviate Inflammatory Response and Promote Cell Apoptosis

Isochlorogenic acid C (ICAC) is found in a variety of natural foods and medicinal plant materials. This study aims to validate the biological activity of isochlorogenic acid C in limiting inflammation by the Erk/JNK/NF-κB pathway. In this study, TNF-α-induced human fibroblast-like synoviocytes and collagen-induced arthritis animal models were used to perceive the potential anti-inflammation mechanism of ICAC. The role of isochlorogenic acid C was evaluated by observing the migration, invasion ability, and apoptotic activity of TNF-α-induced fibroblast-like synoviocytes cells in humans and analysing foot swelling, joint index, and histopathological changes in a collagen-induced RA animal model. The results reveal that ICAC inhibited the proliferation of human fibroblast-like synoviocytes and promoted their apoptosis. ICAC also blocked the nuclear transfer of NF-κB, Erk, and JNK. It was observed that ICAC significantly inhibited the degree of posterior foot swelling in CIA, reducing arthritis scores, bone tissue injury, and articular synovitis. ICAC may promote cell apoptosis and inhibit the hyperactivation of inflammatory cells to alleviate inflammation-induced synovial proliferation through the Erk/JNK/NF-κB pathway.

Rat resistance to rheumatoid arthritis induction as a function of the early-phase adrenal-pineal crosstalk

Chronic inflammatory diseases are triggered by causal stimuli that might occur long before the appearance of the symptoms. Increasing evidence suggests that these stimuli are necessary but not always sufficient to induce the diseases. The murine model of type II collagen emulsified in Freund's incomplete adjuvant (collagen-induced arthritis) to induce rheumatoid arthritis (RA) follows this pattern as some animals do not develop the chronically inflamed phenotype. Considering that in the immune-pineal axis (IPA) theory adrenal-pineal cross-talk adjusts early phases of inflammatory processes, we investigated whether differences in IPA activation could explain why some animals are resistant (RES) while others develop RA. We observed a similar increase in 6-sulfatoxymelatonin (aMT6s) excretion from day 3 to 13 in both RES and RA animals, followed by a significant decrease in RA animals. This pattern of aMT6s excretion positively correlated with plasma corticosterone (CORT) in RES animals. Additionally, RA animals presented a lower aMT6s/CORT ratio than saline-injected or RES animals. Plasmatic levels of tumour necrosis factor were similar in both groups, but interleukin (IL)-1β and monocyte chemotactic protein 1 (MCP-1) levels were lower in RES compared to RA animals. IL-2 and IL-4 were decreased in RES animals compared to saline-injected animals. The aMT6s/CORT ratio inversely correlated with the paw thickness and the inflammatory score (levels of IL-1β, MCP-1, IL-2 and IL-4 combined). Thus, adrenocortical-pineal positive interaction is an early defence mechanism for avoiding inflammatory chronification. KEY POINTS: Immune-pineal axis imbalance is observed in early-phase rheumatoid arthritis development. Only resistant animals present a positive association between adrenal and pineal hormones. The 6-sulfatoxymelatonin/corticosterone ratio is decreased in animals that develop rheumatoid arthritis. The inflammatory score combining the levels of nocturnal interleukin (IL)-1β, monocyte chemotactic protein 1, IL-2 and IL-4 presents a very strong positive correlation with the size of inflammatory lesion. The 6-sulfatoxymelatonin/corticosterone ratio presents a strong negative correlation with the inflammatory score and paw oedema size.

Melatonin reduces IL-33 and TSLP expression in human nasal epithelial cells by scavenging ROS directly

BACKGROUND

Chronic rhinosinusitis (CRS) is a chronic mucosal inflammation of the nasal cavity and sinuses. It is classified into CRS without nasal polyps and CRS with nasal polyps (CRSwNP). CRSwNP has high recurrence, especially CRSwNP with massive eosinophil infiltration which is mediated by type 2 inflammatory response. Melatonin is a hormone secreted by the pineal gland, it has powerful antioxidant and anti-inflammatory effects in addition to regulating biological rhythms. There are no studies on melatonin for the treatment of CRS, so we aimed to explore whether melatonin could be used for the treatment of CRS.

MATERIALS AND METHODS

In this study, we used melatonin to treat a cell model of CRS. Subsequently, MTT assay was performed to examine the cell viability of human nasal epithelial cells (HNEpCs), a reactive oxygen species (ROS) kit to detect ROS production, a malondialdehyde (MDA) kit to detect the MDA content in the cell culture supernatant, and an apoptosis kit and Western blot analysis to detect apoptosis. The expressions of Nrf2, HO-1, IL-33, TSLP, and IL-25 were detected by Western blot analysis.

RESULTS

Melatonin improved the viability of HNEpCs, reduced lipopolysaccharide-induced ROS, reduced the MDA content, and inhibited their apoptosis. More importantly, melatonin reduced the expression of IL-33 and TSLP, an important phenomenon for the treatment of CRSwNP.

CONCLUSION

Melatonin protects HNEpCs from damage in inflammation and reduces IL-33 and TSLP expression of HNEpCs.

Exosomal long non-coding RNA TRAFD1-4:1 derived from fibroblast-like synoviocytes suppresses chondrocyte proliferation and migration by degrading cartilage extracellular matrix in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, autoimmune and systemic inflammatory disease affecting 1% of the population worldwide. Immune suppression of the activity and progress of RA is vital to reduce the disability and mortality rate as well as improve the quality of life of RA patients. However, the immune molecular mechanism of RA has not been clarified yet. Our results indicated that exosomes derived from TNFα-stimulated RA fibroblast-like synoviocytes (RA-FLSs) suppressed chondrocyte proliferation and migration through modulating cartilage extracellular matrix (CECM) determining by MTS assay, cell cycle analysis, Transwell assay and Western blot (WB). Besides, RNA sequencing and verification by qRT-PCR revealed that exosomal long non-coding RNA (lncRNA) tumor necrosis factor-associated factor 1 (TRAF1)-4:1 derived from RA-FLSs treated with TNFα was a candidate lncRNA, which also inhibited chondrocyte proliferation and migration through degrading CECM. Moreover, RNA sequencing and bioinformatics analysis identified that C-X-C motif chemokine ligand 1 (CXCL1) was a target mRNA of miR-27a-3p while miR-27a-3p was a target miRNA of lnc-TRAF1-4:1 in chondrocytes. Mechanistically, lnc-TRAF1-4:1 upregulated CXCL1 expression through sponging miR-27a-3p as a competing endogenous RNA (ceRNA) in chondrocytes identifying by Dual-luciferase reporter gene assay. Summarily, exosomal lncRNA TRAFD1-4:1 derived from RA-FLSs suppressed chondrocyte proliferation and migration through degrading CECM by upregulating CXCL1 as a sponge of miR-27a-3p. This study uncovered a novel RA-related lncRNA and investigated the roles of RA-FLS-derived exosomes and exosomal lnc-TRAF1-4:1 in articular cartilage impairment, which might provide novel therapeutic targets for RA.

Protocatechuic acid reduces H2O2-induced migration and oxidative stress of fibroblast-like synoviocytes in rheumatoid arthritis by activating Nrf2-Keap1 signaling pathway

Honeycomb (Nidus vespae) is traditional Chinese medicine and can treat rheumatoid arthritis (RA), and protocatechuic acid (PCA) is a bioactive component of honeycomb. This study aimed to investigate whether PCA could reduce the H₂O₂-induced migration and oxidative stress of RA fibroblast-like synoviocytes (RA-FLSs). H₂O₂-induced RA-FLSs were used to simulate the in vitro model of RA. The viability, apoptosis, migration, invasion, and oxidative stress of RA-FLSs were detected by Cell Counting Kit-8 (CCK-8), terminal deoxynucleotidyl transferase dUTP nick-end labeling assay, wound healing, transwell assays, DCFDA staining, and malonaldehyde and superoxide dismutase enzyme-linked immunosorbent assay kits. The expression of migration and invasion-related proteins and Nrf2/Keap1 signaling pathway-related proteins was analyzed by western blotting. As a result, PCA suppressed the viability, migration, invasion, and oxidative and promoted apoptosis of H₂O₂-induced RA-FLSs by activating the Nrf2/Keap1 signaling pathway. ML-385, an Nrf2 inhibitor, could enhance the viability, migration, invasion, and oxidative and inhibited apoptosis of H₂O₂-induced RA-FLSs. In conclusion, PCA reduced H₂O₂-induced migration and oxidative stress of RA-FLSs by activating the Nrf2-Keap1 signaling pathway.

Melatonin Maintains Homeostasis and Potentiates the Anti-inflammatory Response in Staphylococcus aureus-Induced Mastitis through microRNA-16b/YAP1

Staphylococcus aureus is a highly infectious pathogen and is a considerable threat to food hygiene and safety. Although melatonin is thought to exert an ameliorative effect on bovine mastitis, the regulatory mechanisms are unclear. In this study, we first verified the therapeutic effect of melatonin against S. aureus in vitro and in vivo, a screening of differentially expressed miRNAs and mRNAs among the blank, and S. aureus and melatonin + S. aureus groups by high-throughput sequencing identified miR-16b and YAP1, which exhibited 1.95-fold upregulated and 1.05-fold downregulated expression, respectively. Moreover, epigenetic studies showed that S. aureus inhibited miR-16b expression by methylation (increased DNMT1 expression). Additionally, the DNMT1 expression level was significantly decreased by melatonin treatment, which might indicate that the inhibition of DNMT1 by melatonin reduces the effect of S. aureus on miR-16b. The flow cytometry, scanning and transmission electron microscopy, EdU assay, and cell morphology results indicated that miR-16b in bovine mammary epithelial cells (in vitro) and in mice (in vivo) can modulate the maintenance of homeostasis and potentiate the anti-inflammatory response. In addition, YAP1 was demonstrated to be the target gene of miR-16b through quantitative real-time polymerase chain reaction, western blot, RNA immunoprecipitation, and functional assays. This study indicates that melatonin inhibits S. aureus-induced inflammation via microRNA-16b/YAP1-mediated regulation, and these findings might provide a new strategy for the prevention of bovine mastitis, facilitating further studies good of zoonotic diseases caused by S. aureus infection.

Melatonin Prevents Chondrocyte Matrix Degradation in Rats with Experimentally Induced Osteoarthritis by Inhibiting Nuclear Factor-κB via SIRT1

Osteoarthritis (OA) is a common degenerative joint disease characterized by an imbalance of cartilage extracellular matrix (ECM) breakdown and anabolism. Melatonin (MT) is one of the hormones secreted by the pineal gland of the brain and has anti-inflammatory, antioxidant, and anti-aging functions. To explore the role of MT in rats, we established an OA model in rats by anterior cruciate ligament transection (ACLT). Safranin O-fast green staining showed that intraperitoneal injection of MT (30 mg/kg) could alleviate the degeneration of articular cartilage in ACLT rats. Immunohistochemical (IHC) analysis found that MT could up-regulate the expression levels of collagen type II and Aggrecan and inhibit the expression levels of matrix metalloproteinase-3 (MMP-3), matrix metalloproteinase-13 (MMP-13), and ADAM metallopeptidase with thrombospondin type 1 motif 4 (ADAMTS-4) in ACLT rats. To elucidate the mechanism of MT in protecting the ECM in inflammatory factor-induced rat chondrocytes, we conducted in vitro experiments by co-culturing MT with a culture medium. Western blot (WB) showed that MT could promote the expression levels of transforming growth factor-beta 1 (TGF-β1)/SMAD family member 2 (Smad2) and sirtuin 2-related enzyme 1 (SIRT1) and inhibit the expression of levels of phosphorylated nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibi-tor (p-p65) and phosphorylated IκB kinase-α (p-IκBα). In addition, WB and real-time PCR (qRT-PCR) results showed that MT could inhibit the expression levels of MMP-3, MMP-13, ADAMTS-4, inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) in chondrocytes induced by interleukin-1β (IL-1β), and up-regulate the expression of chondroprotective protein type II collagen. We found that in vivo, MT treatment protected articular cartilage in the rat ACLT model. In IL-1β-induced rat chondrocytes, MT could reduce chondrocyte matrix degradation by up-regulating nuclear factor-kB (NF-κB) signaling pathway-dependent expression of SIRT1 and protecting chondrocyte by activating the TGF-β1/Smad2 pathway.

Recharge of chondrocyte mitochondria by sustained release of melatonin protects cartilage matrix homeostasis in osteoarthritis

Recent evidence indicates that the mitochondrial functions of chondrocytes are impaired in the pathogenesis of osteoarthritis (OA). Melatonin can attenuate cartilage degradation through its antioxidant functions. This study aims to investigate whether melatonin could rescue the impaired mitochondrial functions of OA chondrocytes and protect cartilage metabolism. OA chondrocytes showed a compromised matrix synthesis capacity associated with mitochondrial dysfunction and aberrant oxidative stress. In vitro treatments with melatonin promoted the expression of cartilage extracellular matrix (ECM) components, improved adenosine triphosphate production, and attenuated mitochondrial oxidative stress. Mechanistically, either silencing of SOD2 or inhibition of SIRT1 abolished the protective effects of melatonin on mitochondrial functions and ECM synthesis. To achieve a sustained release effect, a melatonin-laden drug delivery system (DDS) was developed and intra-articular injection with DDS successfully improved cartilage matrix degeneration in a posttraumatic rat OA model. These findings demonstrate that melatonin-mediated recharge of mitochondria to rescue the mitochondrial functions of chondrocytes represents a promising therapeutic strategy to protect cartilage from OA.

The role of melatonin in bone regeneration: A review of involved signaling pathways

Increasing bone resorption followed by decreasing bone mineralization are hallmarks of bone degeneration, which mostly occurs in the elderly population and post-menopausal women. The use of mesenchymal stem cells (MSCs) has raised many promises in the field of bone regeneration due to their high osteoblastic differentiation capacity and easy availability from abundant sources. A variety of compounds, including growth factors, cytokines, and other internal factors, have been combined with MSCs to increase their osteoblastic differentiation capacity. One of these factors is melatonin, whose possible regulatory role in bone metabolism and formation has recently been suggested by many studies. Melatonin also is a potential signaling molecule and can affect many of the signaling pathways involved in MSCs osteoblastic differentiation, such as activation of PI3K/AKT, BMP/Smad, MAPK, NFkB, Nrf2/HO-1, Wnt, SIRT/SOD, PERK/ATF4. Furthermore, melatonin in combination with other components such as strontium, vitamin D3, and vitamin K2 has a synergistic effect on bone microstructure and improves bone mineral density (BMD). In this review article, we aim to summarize the regulatory mechanisms of melatonin in osteoblastic differentiation of MSCs and underling involved signaling pathways as well as the clinical potential of using melatonin in bone degenerative disorders.

Cuproptosis and cuproptosis-related genes in rheumatoid arthritis: Implication, prospects, and perspectives

Rheumatoid arthritis (RA) is an autoimmune disease that severely affects patients' physical and mental health, leading to chronic synovitis and destruction of bone joints. Although various available clinical treatment options exist, patients respond with varying efficacies due to multiple factors, and there is an urgent need to discover new treatment options to improve clinical outcomes. Cuproptosis is a newly characterized form of cell death. Copper causes cuproptosis by binding to lipid-acylated components of the tricarboxylic acid cycle, leading to protein aggregation, loss of iron-sulfur cluster proteins, and eventually proteotoxic stress. Targeting copper cytotoxicity and cuproptosis are considered potential options for treating oncological diseases. The synovial hypoxic environment and the presence of excessive glycolysis in multiple cells appear to act as inhibitors of cuproptosis, which can lead to excessive survival and proliferation of multiple immune cells, such as fibroblast-like synoviocytes, effector T cells, and macrophages, further mediating inflammation and bone destruction in RA. Therefore, in this study, we attempted to elaborate and summarize the linkage of cuproptosis and key genes regulating cuproptosis to the pathological mechanisms of RA and their effects on a variety of immune cells. This study aimed to provide a theoretical basis and support for translating preclinical and experimental results of RA to clinical protocols.

Effects of Melatonin on Sleep Quality and Disease Activity in Patients With Rheumatoid Arthritis

Background and Objective In rheumatoid arthritis (RA) patients sleep disturbance is one of serious and prevalent problems. Considering the known effects of melatonin on sleep quality and inflammation, this study aimed to investigate melatonin supplementation effect on quality of sleep and disease activity in patients with RA.Methods In this randomized, placebo-controlled trial (double-blind), 64 RA patients were selected and divided into experimental and placebo groups randomly; experimental group received 3 mg/d of melatonin and another group consumed placebo for 60 days. Before and after the investigation, assessment of the quality of sleep determined using the Pittsburgh Sleep Quality Index (PSQI). Disease Activity Score-28 (DAS28) and the Visual Analogue Scale (VAS) questionnaires were used for evaluation of disease activity and pain intensity, respectively.Results Melatonin significantly reduced PSQI, DAS28 and VAS scores, when values compared with baseline. In contrast to placebo group, good sleep quality within the melatonin group increased significantly compared to baseline and this improvement in sleep quality was significant when compared between groups. The scores of DAS28 and pain VAS at the end of trial were significantly reduced compared to the baseline in both groups. However, reduction in the DAS28 and VAS scores of the melatonin group were stronger than reductions in the placebo receiving group.Conclusions This study results revealed that melatonin was safe and effective in improving sleep quality and reducing DAS28 and pain VAS scores in RA patients.

FABP4 secreted by M1-polarized macrophages promotes synovitis and angiogenesis to exacerbate rheumatoid arthritis

Increasing evidence shows that adipokines play a vital role in the development of rheumatoid arthritis (RA). Fatty acid-binding protein 4 (FABP4), a novel adipokine that regulates inflammation and angiogenesis, has been extensively studied in a variety of organs and diseases. However, the effect of FABP4 on RA remains unclear. Here, we found that FABP4 expression was upregulated in synovial M1-polarized macrophages in RA. The increase in FABP4 promoted synovitis, angiogenesis, and cartilage degradation to exacerbate RA progression in vivo and in vitro, whereas BMS309403 (a FABP4 inhibitor) and anagliptin (dipeptidyl peptidase 4 inhibitor) inhibited FABP4 expression in serum and synovial M1-polarized macrophages in mice to alleviate RA progression. Further studies showed that constitutive activation of mammalian target of rapamycin complex 1 (mTORC1) by TSC1 deletion specifically in the myeloid lineage regulated FABP4 expression in macrophages to exacerbate RA progression in mice. In contrast, inhibition of mTORC1 by ras homolog enriched in brain (Rheb1) disruption specifically in the myeloid lineage reduced FABP4 expression in macrophages to attenuate RA development in mice. Our findings established an essential role of FABP4 that is secreted by M1-polarized macrophages in synovitis, angiogenesis, and cartilage degradation in RA. BMS309403 and anagliptin inhibited FABP4 expression in synovial M1-polarized macrophages to alleviate RA development. Hence, FABP4 may represent a potential target for RA therapy.

Antirheumatoid Arthritic Effects of Sabia parviflora Wall. Leaf Extracts via the NF-κB Pathway and Transient Receptor Potential Protein Family

As an important traditional medicine of Buyi and Miao ethnic groups in Guizhou, Sabia parviflora Wall. provides antiviral properties against hepatitis, eliminates wind and dampness, and exhibits anti-inflammatory and pain relief properties. It has also been shown to treat rheumatoid arthritis (RA) and other diseases. However, the pharmacodynamic mechanism of S. parviflora Wall. for RA has not been reported. In this study, we identified the effective compounds of S. parviflora Wall. leaves against RA and discussed the mechanism against complete Freund’s adjuvant-induced arthritis (AIA) based on inflammatory proteins and transient receptor potential (TRP) proteins. S. parviflora Wall. leaf extracts (0.64 g/kg, 0.32 g/kg, and 0.16 g/kg, once daily) were given orally for 21 days. On the 15th day of complete Freund’s adjuvant-induced RA, the effects of this medicine on RA rats were investigated. S. parviflora Wall. extracts increased body weight, decreased foot swelling, and reduced thymus and spleen indices in model rats. Most of pannus in the synovial tissue of RA rats disappeared upon treatment, and the local inflammatory cells were greatly reduced when given the fraction of n-butanol (0.64 g/kg/d, 0.32 g/kg/d, and 0.16 g/kg/d) of 70% alcohol-soluble fraction of S. parviflora Wall. leaves. In addition, the release of inflammatory factors such as tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-10 (IL-10), interleukin-15 (IL-15), and vascular endothelial growth factor (VEGF) in the RA rat serum was inhibited. The active compounds inhibited the expression of TNF-α, IL-1β, IL-6, IL-10, IL-15 and nuclear factor kappa-Bp65 (NF-κBp65) inflammatory protein and TRP protein transient receptor potential melastatin-5 (TRPM-5) and transient receptor potential channel-6 (TRPC-6), to reduce the expression of VEGF in synovial tissue of RA rats and relieve redness and edema. High-performance liquid chromatography identified six flavonoids and three triterpenoid saponins as active compounds. These findings suggest S. parviflora Wall. leaves may play a role in RA treatment by inhibiting the release of inflammatory factors as well as participating in the inflammatory protein expression in the NF-κB pathway and TRP protein family.

Pyroptosis and Its Role in Autoimmune Disease: A Potential Therapeutic Target

Autoimmune diseases are a group of heterogeneous diseases with diverse clinical manifestations that can be divided into systemic and organ-specific. The common etiology of autoimmune diseases is the destruction of immune tolerance and the production of autoantibodies, which attack specific tissues and/or organs in the body. The pathogenesis of autoimmune diseases is complicated, and genetic, environmental, infectious, and even psychological factors work together to cause aberrant innate and adaptive immune responses. Although the exact mechanisms are unclear, recently, excessive exacerbation of pyroptosis, as a bond between innate and adaptive immunity, has been proven to play a crucial role in the development of autoimmune disease. Pyroptosis is characterized by pore formation on cell membranes, as well as cell rupture and the excretion of intracellular contents and pro-inflammatory cytokines, such as IL-1β and IL-18. This overactive inflammatory programmed cell death disrupts immune system homeostasis and promotes autoimmunity. This review examines the molecular structure of classical inflammasomes, including NLRP3, AIM2, and P2X7-NLRP3, as the switches of pyroptosis, and their molecular regulation mechanisms. The sophisticated pyroptosis pathways, including the canonical caspase-1-mediated pathway, the noncanonical caspase-4/5/11-mediated pathway, the emerging caspase-3-mediated pathway, and the caspase-independent pathway, are also described. We highlight the recent advances in pyroptosis in autoimmune diseases, such as systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, Sjögren's syndrome and dermatomyositis, and attempt to identify its potential advantages as a therapeutic target or prognostic marker in these diseases.

Melatonin: A novel candidate for the treatment of osteoarthritis

Osteoarthritis (OA), characterized by cartilage erosion, synovium inflammation, and subchondral bone remodeling, is a common joint degenerative disease worldwide. OA pathogenesis is regulated by multiple predisposing factors, including imbalanced matrix metabolism, aberrant inflammatory response, and excessive oxidative stress. Moreover, melatonin has been implicated in development of several degenerative disorders owing to its potent biological functions. With regards to OA, melatonin reportedly promotes synthesis of cartilage matrix, inhibition of chondrocyte apoptosis, attenuation of inflammatory response, and suppression of matrix degradation by regulating the TGF-β, MAPK, or NF-κB signaling pathways. Notably, melatonin has been associated with amelioration of oxidative damage by restoring the OA-impaired intracellular antioxidant defense system in articular cartilage. Findings from preliminary application of melatonin or melatonin-loaded biomaterials in animal models have affirmed its potential anti-arthritic effects. Herein, we summarize the anti-arthritic effects of melatonin on OA cartilage and demonstrate that melatonin has potential therapeutic efficacy in treating OA.

Melatonin, an endogenous hormone, modulates Th17 cells via the reactive-oxygen species/TXNIP/HIF-1α axis to alleviate autoimmune uveitis

Background

Melatonin, an indoleamine produced by the pineal gland, plays a pivotal role in maintaining circadian rhythm homeostasis. Recently, the strong antioxidant and anti-inflammatory properties of melatonin have attracted attention of researchers. We evaluated the therapeutic efficacy of melatonin in experimental autoimmune uveitis (EAU), which is a representative animal model of human autoimmune uveitis.

Methods

EAU was induced in mice via immunization with the peptide interphotoreceptor retinoid binding protein 1–20 (IRBP_1–20). Melatonin was then administered via intraperitoneal injection to induce protection against EAU. With EAU induction for 14 days, clinical and histopathological scores were graded to evaluate the disease progression. T lymphocytes accumulation and the expression of inflammatory cytokines in the retinas were assessed via flow cytometry and RT-PCR, respectively. T helper 1 (Th1), T helper 17 (Th17), and regulatory T (Treg) cells were detected via flow cytometry for both in vivo and in vitro experiments. Reactive-oxygen species (ROS) from CD4 + T cells was tested via flow cytometry. The expression of thioredoxin-interacting protein (TXNIP) and hypoxia-inducible factor 1 alpha (HIF-1α) proteins were quantified via western blot.

Results

Melatonin treatment resulted in notable attenuation of ocular inflammation in EAU mice, evidenced by decreasing optic disc edema, few signs of retinal vasculitis, and minimal retinal and choroidal infiltrates. Mechanistic studies revealed that melatonin restricted the proliferation of peripheral Th1 and Th17 cells by suppressing their transcription factors and potentiated Treg cells. In vitro studies corroborated that melatonin restrained the polarization of retina-specific T cells towards Th17 and Th1 cells in addition to enhancing the proportion of Treg cells. Pretreatment of retina-specific T cells with melatonin failed to induce EAU in naïve recipients. Furthermore, the ROS/ TXNIP/ HIF-1α pathway was shown to mediate the therapeutic effect of melatonin in EAU.

Conclusions

Melatonin regulates autoimmune T cells by restraining effector T cells and facilitating Treg generation, indicating that melatonin could be a hopeful treatment alternative for autoimmune uveitis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02477-z.

Chemical constituents, biological activities and anti-rheumatoid arthritic properties of four citrus essential oils

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease with predominant synovitis that has no complete cure or preventive treatment. Citrus essential oils, used in natural fragrances, contain a variety of functional ingredients that are worthy of investigation for their potential as natural anti-inflammatory drug sources. In this study, essential oils were hydro distilled from the peels of four citrus species: Citrus sinensis (L.) Osbeck (CSEOs), Citrus paradisi Macfad. (CPEOs), Citrus limon (L.) Osbeck (CLEOs) and Citri Reticulatae Pericarpium (CREOs). Altogether, 81 compounds were identified using gas chromatography-mass spectrometry (GC-MS), of which d-limonene (17.96%-94.66%) was an abundant component of all four oils. The stable 1,1-diphenyl-2-pyrrole hydrazine (DPPH) free radical test showed that all four essential oils had excellent antioxidant properties (IC₅₀ , 0.76-13.86 μg/mL). Furthermore, the oils remarkably increased the first G1 phase of the cell cycle, which inhibited the pro-inflammatory factor expression. An immunohistochemical analysis indicated that the four essential oils inhibited the expression of tumor necrosis factor-α and cyclooxygenase-2 and they exhibited anti-inflammatory activity in a rat model that was similar to that of the common drug, Ibuprofen. These results show that the CSEOs, CPEOs, CLEOs, and CREOs have significant antirheumatic activities and thus have great potential in developing functional food or drugs for treating RA.

Protective effects of melatonin in cisplatin-induced cardiac toxicity: possible role of BDNF-TNF-α signaling pathway

Purpose:

The present study explored the role of melatonin in cisplatin-induced cardiac injury along with the possible role of brain-derived neurotrophic factor (BDNF) in melatonin-mediated effects.

Methods:

Wistar rats were administered cisplatin (10 mg/kg), and cardiac injury was assessed by measuring the levels of cardiac troponin (cTnT) and lactate dehydrogenase (LDH-1).The extent of apoptosis was measured by measuring caspase-3 (pro-apoptotic) and Bcl-2 (anti-apoptotic) in hearts. The levels of BDNF, tumour necrosis factor α (TNF-α) and reduced glutathione were measured in heart. Melatonin (5 and 10 mg/kg) was administered for 15 days, and the role of BDNF was identified by co-administering BDNF inhibitor, ANA-12 (0.25 and 0.5 mg/kg).

Results:

Melatonin attenuated cTnT and LDH-1 levels along with reduction in caspase-3 and increase in Bcl-2. It also increased cisplatin-induced decrease in BDNF, increase in TNF-α and decrease in reduced glutathione levels. Moreover, ANA-12 abolished the cardioprotective effects, anti-inflammatory and antioxidant effects of melatonin suggesting the role of BDNF in melatonin-mediated effects in cisplatin-induced cardiac injury.

Conclusions:

Melatonin is useful in cisplatin-induced cardiac injury, which may be due to an increase in BDNF, decrease in inflammation and increase in antioxidant activities.

Melatonin Prevents Cartilage Degradation in Early-Stage Osteoarthritis Through Activation of miR-146a/NRF2/HO-1 Axis

Reactive oxygen species (ROS) are implicated in induction of inflammatory response and cartilage degradation in osteoarthritis (OA). Melatonin has been shown to improve the chondrogenic differentiation and promote cartilage matrix synthesis in mesenchymal stem cells. However, the underlying mechanisms of melatonin-regulated antioxidant activity in OA cartilage are not known. The aim of this study was to explore the effect of melatonin on nuclear factor-erythroid 2-related factor 2 (NRF2), a key antioxidant transcription factor, and its target antioxidant genes in early-stage OA cartilage. Primary chondrocytes were isolated from rats with surgically induced OA. In vitro treatment of melatonin significantly increased cartilage matrix synthesis and upregulated antioxidant enzymes, mainly heme oxygenase 1 (HO-1), while decreasing matrix degradation enzymes and intracellular ROS. In vivo intraarticular injection of melatonin effectively ameliorated cartilage degeneration in an experimental rat OA model. Inhibition of melatonin membrane receptors by Luzindole or 4-P-PDOT reversed the beneficial effects of melatonin on cartilage matrix synthesis, implying that melatonin receptor-mediated pathway is involved in its anti-arthritic effects. Interestingly, melatonin showed no significant effect on the mRNA level of Nrf2 but significantly increased its protein level. Silencing of Nrf2 or HO-1 expression abolished the protective effects of melatonin, as shown by increased ROS levels and matrix degradation enzyme expression. Microarray assays revealed that miR-146a, a predicted target for Nrf2, was significantly upregulated in OA chondrocytes but was markedly reduced by melatonin treatment. Overexpression of miR-146a diminished the protective effects of melatonin by inhibiting NRF2 expression and aggravating OA-induced cartilage degradation. These findings demonstrate that melatonin supports the anabolic metabolism of cartilage matrix in OA chondrocytes by enhancing the protein levels of NRF2 via suppressing miR-146a. Melatonin-mediated activation of the NRF2/HO-1 axis prevents cartilage degeneration and represents a promising therapeutic target for treatment of early-stage OA. © 2022 American Society for Bone and Mineral Research (ASBMR).

High dose melatonin as an adjuvant therapy in intubated patients with COVID-19: A randomized clinical trial

Objective

In the COVID-19 pandemic, the SARS-CoV-2 virus has infected millions of people worldwide. Mortality primarily results from the inflammation state and its complications. High-dose melatonin has been established as an anti-inflammatory agent. This study evaluated high-dose melatonin as an adjuvant therapy in critically ill patients with SARS-CoV-2 infection.

Methods

We conducted a double-blinded, randomized clinical trial of 21 mg of melatonin per day compared with a placebo in 67 patients with COVID-19. We enrolled patients older than 18 years of age with documented SARS-CoV-2 infection, who were admitted to the intensive care unit and underwent invasive mechanical ventilation. Administration of melatonin and placebo through a nasogastric tube continued for 5 days. The main outcomes were mortality rate, duration of mechanical ventilation, changes in oxygenation indices, and C-reactive protein (CRP) levels.

Results

No significant differences were observed in mortality and duration of mechanical ventilation between the control and intervention groups. After 5 days of the intervention, the mean (±standard deviation) CRP and platelet count were 47.28 (±38.86) mg/L and 195.73 (±87.13) × 1000/μL, respectively, in the intervention group and 75.52 (±48.02) mg/L and 149.62 (±68.03) × 1000/μL, respectively, in the control group (P < 0.05).

Conclusion

High-dose melatonin in intubated patients with COVID-19 was associated with a decrease in CRP levels. However, this treatment did not apparently affect patient outcomes.

Identification of key candidate genes and biological pathways in the synovial tissue of patients with rheumatoid arthritis

The aim of the present study was to identify potential key candidate genes and mechanisms associated with rheumatoid arthritis (RA). Gene expression data from GSE55235, GSE55457 and GSE1919 datasets were downloaded from the Gene Expression Omnibus database. These datasets comprised 78 tissue samples collectively, including 25 healthy synovial membrane samples and 28 RA synovial membrane samples, whilst the 25 osteoarthritis (OA) samples were not included in the analysis. The differentially expressed genes (DEGs) between the two types of samples were identified with the Linear Models for Microarray Analysis package in R. Gene Ontology (GO) functional term and Kyoto Encyclopedia of Genes and Genomes (KEGG) signaling pathway enrichment analyses were also performed. In addition, Protein-Protein Interaction (PPI) network and module analyses were visualized using Cytoscape, and subsequent hub gene identification as well as GO and KEGG enrichment analyses of the modules was performed. Finally, reverse transcription-quantitative PCR (RT-qPCR) was used to validate the expression of the DEGs identified by GO and KEGG analysis in vitro. The analysis identified 491 DEGs, including 289 upregulated and 202 downregulated genes, which were mainly enriched in the following pathways: ‘Cytokine-cytokine receptor interaction’, ‘Rheumatoid arthritis’, ‘Chemokine signaling pathway’, ‘Intestinal immune network for IgA production’ and ‘Primary immunodeficiency’. The top 10 hub genes identified from the PPI network were IL-6, protein tyrosine phosphatase receptor type C, VEGFA, CD86, EGFR, C-X-C chemokine receptor type 4, matrix metalloproteinase 9, CC-chemokine receptor type (CCR)7, CCR5 and selectin L. KEGG signaling pathway enrichment analysis of the top two modules identified from the PPI network revealed that the genes in Module 1 were mainly enriched in the ‘Cytokine-cytokine receptor interaction’ and ‘Chemokine signaling pathway’, whereas analysis of Module 2 revealed that the genes were mainly enriched in ‘Primary immunodeficiency’ and ‘Cytokine-cytokine receptor interaction’. Finally, the results of the RT-qPCR and western blot analysis demonstrated that the expression levels of inflammation and NF-κB signaling pathway-related mRNAs were significantly upregulated following lipopolysaccharide stimulation. In conclusion, the findings of the present study identified key genes and signaling pathways associated with RA, which may improve the current understanding of the molecular mechanisms underlying its development and progression. The identified hub genes may also be used as potential targets for RA diagnosis and treatment.

Melatonin abolished proinflammatory factor expression and antagonized osteoarthritis progression in vivo

Progressive structural changes in osteoarthritis (OA) involve synovial inflammation and angiogenesis, as well as activation of the proinflammatory cytokines tumor necrosis factor alpha (TNF-α) and interleukin (IL)-8, and the angiogenic factor vascular endothelial growth factor (VEGF). The endogenous hormone melatonin (N-acetyl-5-methoxytryptamine) is involved in antioxidative and anti-inflammatory activities, but how it antagonizes OA progression via its specific receptors is unclear. Here, we demonstrate that the MT₁ melatonin receptor, but not the MT₂ receptor, is highly expressed in normal tissue and only minimally in OA tissue. By targeting the MT₁ receptor, melatonin reversed OA-induced pathology and effectively reduced levels of TNF-α, IL-8, and VEGF expression in OA synovial fibroblasts and synovium from rats with severe OA. Interestingly, we found that the anabolic activities of melatonin involved the MT₁ receptor, which upregulated microRNA-185a through the PI3K/Akt and ERK signaling pathways in OA synovial fibroblasts. Our investigation confirms the role of the MT₁ receptor in melatonin-induced anti-catabolic effects in OA disease.