Cytokine-mediated mechanisms in rheumatoid arthritis: pathogenesis and emerging therapeutic target: Review article

the eyes, skin, lungs, heart, kidneys, and nervous system. Chronic systemic inflammation contributes to comorbidities such as cardiovascular disease, renal amyloidosis, interstitial Lung disease, and peripheral neuropathies, highlighting the complexity of disease management [Bilski et al., 2023] [8] . Although the precise etiology of rheumatoid arthritis (RA) remains unclear, the disease has attracted increasing research attention over the past few decades. Aberrant signaling pathways in RA have emerged as a central area of investigation, providing crucial insights into the underlying mechanisms and serving as a basis for the development of innovative therapeutic strategies. Further, it is widely accepted that disease development is driven by an interplay of genetic susceptibility, environmental triggers, and epigenetic modifications. Dysregulated immune responses lead to autoimmune-mediated joint attack, synovial inflammation, and cartilage and bone destruction. Laboratory assessments, imaging studies, and clinical evaluation facilitate accurate diagnosis and differentiation from related autoimmune disorders, such as systemic lupus erythematosus, psoriatic arthritis, and fibromyalgia [Magoni & Zinellu et al., 2024] [45] . RA imposes a substantial personal and socioeconomic burden, including reduced functional capacity, decreased quality of life, work productivity loss, and increased healthcare costs. Recent research has focused on the molecular mechanisms driving RA pathogenesis, particularly the roles of cytokines and intracellular signaling pathways. Advancements in understanding the interactions among genetic susceptibility, epigenetic modifications, and environmental factors have facilitated the development of targeted therapies aimed at modulating specific pathogenic pathways. This review provides an overview of the risk factors, signaling pathways, and molecular mechanisms involved in rheumatoid arthritis (RA). It also discusses existing treatment approaches, emerging preclinical and clinical therapeutic candidates, and innovative precision medicine strategies aimed at improving RA management.

Pathogenesis of rheumatoid arthritis

Rheumatoid arthritis (RA) begins as a state of persistent cellular activation that ultimately leads to autoimmunity in the joints and, in some cases, other organs. Clinically, disease manifestations typically follow synovial inflammation and joint injury, with fibroblast-like synoviocytes (FLS) playing a central role in disease progression. RA development is commonly described in three stages: an initial nonspecific inflammatory phase amplified by T-cell activation in the synovium, a chronic inflammatory phase, and a tissue-damage stage mediated by pro-inflammatory cytokines such as IL-1, IL-6, and TNF-α. The autoimmune response is characterized by the production of autoantibodies, which have been associated with more severe joint damage and increased mortality. Notably, autoantibodies against citrullinated proteins (ACPAs) form immune complexes with rheumatoid factors (RF), triggering complement activation and subsequent tissue injury. Detection of these autoimmune responses to citrullinated self-proteins represents a major advance in early RA diagnosis, as ACPAs can appear up to a decade before clinical disease onset. Importantly, ACPA-positive and ACPA-negative RA may represent genetically distinct subtypes, differing in HLA associations and non-HLA susceptibility genes. Environmental triggers can lead to citrullination of proteins via peptidylarginine deiminases (PADs), including PAD4, which is also recognized as a non-MHC genetic risk factor linked to bone damage in Asian RA populations.

Other post-translational modification autoantibodies, such as anti-carbamylated protein (CarP) and acetylated protein antibodies, have been identified, indicating a broad spectrum of autoimmune responses in RA. Synovial inflammation underlies joint swelling in RA, characterized by infiltration of innate and adaptive immune cells. Innate immune cells-dendritic cells (DCs), monocytes, mast cells, and innate lymphoid cells-initiate inflammatory responses that activate T cells, which in turn stimulate B cells, macrophages, synoviocytes, chondrocytes, and osteoclasts. These cells secrete pro-inflammatory and bone-destructive mediators, including IL-1β, IL-6, TNF-α, and matrix metalloproteinases (MMPs). The interaction of innate and adaptive pathways within the synovium and adjacent bone marrow drives tissue injury and chronic inflammation, attracting circulating leukocytes to the inflamed joints and promoting angiogenesis to sustain the hypertrophic synovium. FLS undergo profound phenotypic changes in RA, transforming from normal mesenchymal cells into aggressive, tumor-like cells with reduced apoptosis sensitivity, overexpression of adhesion molecules, and abnormal cytokine, chemokine, and MMP production. These cells contribute significantly to synovial invasion and cartilage destruction. Cytokines and chemokines regulate the inflammatory environment by activating endothelial cells, attracting immune cells, and stimulating fibroblasts. Activated B cells, supported by antigen-presenting cells and T-helper cells, differentiate into plasma cells that produce pathogenic immunoglobulins. Meanwhile, T-helper cell subsets, including Th1, Th2, Th17, Treg, and follicular helper T (Tfh) cells, orchestrate immune responses within the synovium. In RA, Th1 and Th17 cells drive IL-17 production and inflammatory infiltration, while Tfh cells enhance germinal center activity, promoting high-affinity autoantibody production and disease perpetuation. Bone destruction in RA is mediated by osteoclast activation through RANK-RANKL interactions, facilitated by monocytes, macrophages, and fibroblasts. Erosions typically occur at the cartilage-bone interface, also known as the bare area. Cytokine signaling through their respective receptors triggers cascades of intracellular events that amplify inflammation, induce tissue remodeling, and perpetuate joint damage. Collectively, RA pathogenesis reflects a complex interplay between autoimmunity, innate and adaptive immune activation, stromal cell dysfunction, and dysregulated cytokine networks, establishing a selfsustaining inflammatory milieu that drives chronic joint and systemic damage (Fig. 34). Chemokines play a central role in orchestrating immune cell trafficking in rheumatoid arthritis, contributing to the chronic inflammation and joint destruction characteristic of the disease. By binding to their specific G protein-coupled receptors, chemokines create gradients that guide the migration of leukocytes, including T cells, B cells, macrophages, dendritic cells, and neutrophils, into inflamed synovial tissue. For instance, chemokines such as CCL2, CCL5, and CXCL10 promote the recruitment of monocytes and T cells, amplifying local inflammation and autoantibody production. Th17 cell migration, mediated by chemokine receptors like CCR4 and CCR6, is particularly important in sustaining synovial inflammation and cartilage damage. Additionally, chemokines like CXCL8 and CXCL5 attract neutrophils, which release proteolytic enzymes and reactive oxygen species, further aggravating tissue injury.

The dysregulated chemokine network not only drives immune cell infiltration but also facilitates the formation of ectopic lymphoid structures in the synovium, perpetuating autoimmunity and disease progression. Targeting these chemokine-mediated pathways has shown promise in preclinical models, highlighting their critical role in immune cell recruitment and the potential for therapeutic intervention in RA.

Role of cytokines in RA

Cytokines play a central and decisive role in the pathogenesis of rheumatoid arthritis (RA), acting as key mediators that regulate synovial inflammation, immune cell activation, cartilage degradation, and bone destruction. Current evidence indicates that RA is driven by a complex cytokine network rather than a single dominant mediator, with tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) serving as major proinflammatory cytokines that sustain chronic synovitis and systemic inflammation. TNF-α amplifies inflammatory cascades by activating NF-κB and MAPK signaling pathways, leading to increased production of additional cytokines and recruitment of immune cells into the synovial tissue (McInnes & Schett 2007) [10,19,32] IL-6 contributes to both local and systemic disease manifestations through activation of the JAK-STAT pathway, promoting B-cell differentiation, acute-phase protein synthesis, and autoantibody production, while IL-1β enhances cartilage breakdown and osteoclast-mediated bone resorption through Induction of matrix metalloproteinases (MMPs) (Smolen et al., 2018) [11,28] . In addition, IL-17 produced by Th17 cells and GM-CSF derived from T cells and synovial macrophages further intensify inflammatory responses by sustaining neutrophil recruitment and macrophage activation, respectively (Firestein, 2017) [12,24,27,31] . Recent studies also highlight upstream cytokines such as IL-23, IL-21, and BAFF, which regulate T follicular helper cell differentiation and autoantibody production, thereby linking innate and adaptive immune responses in RA pathogenesis (Weyand & Goronzy, 2021) [13,25,33] . Importantly, dysregulation of intracellular signaling pathways including NF-κB, MAPK, and JAK-STAT perpetuates cytokinedriven inflammation, while failure of regulatory cytokines such as IL-10 and TGF-β to suppress immune activation contributes to chronic disease persistence. The clinical importance of cytokine pathways is strongly validated by the success of targeted biologic therapies, including TNF inhibitors, IL-6 receptor blockers, and JAK inhibitors, which have significantly improved disease outcomes and represent current standard-of-care treatments (Brennan FM & McInnes IB) [14,19,32] . However, a subset of patients remains refractory to these agents, reflecting redundancy within cytokine networks and ongoing inflammation despite singlepathway inhibition. Recent advances therefore focus on broader cytokine modulation, biomarker-guided precision therapy, and novel strategies such as bispecific antibodies, CAR-T cell therapy, and immune reprogramming approaches aimed at achieving durable remission or functional cure (Mori et al., 2025; Fujimoto et al., 2025) [15,16, 18] . McInnes, Schett, Nat Rev Immunol, 2007 [10,19,32] IL-6 Acute phase response, B-cell activation, systemic inflammation FDA-approved IL-6 inhibitors Smolen et al. Nat Rev Dis Primers, 2018 [11,28] IL-1β Cartilage degradation, osteoclast activation Limited use; approved IL-1 blocker in select cases Firestein. Immunity, 2017 [12,24,31] IL-17 Th17-mediated inflammation, neutrophil recruitment Mixed efficacy; clinical trials ongoing Alunno et al. BMC Rheumatology, 2017 [26] GM [23,29]

NF-κB

Master regulator of inflammatory genes Major therapeutic target (preclinical) Firestein. Immunity, 2017 [12,24,31] MAPK [13,25,33] Fibroblast-like synoviocytes (FLS) Synovial hyperplasia, cartilage invasion Emerging drug target Smolen et al. Nat Rev Dis Primers, 2018 [11,28] Th17 cells IL-17 production, inflammation amplification Targeted in immunotherapy trials Alunno et al. BMC Rheumatology, 2017 [26] B cells Autoantibody production (RF, ACPA) B-cell depletion therapy approved [11,28] Rheumatoid factor (RF)

Immune complex formation Clinical diagnostic marker Firestein. Immunity, 2017 [12,24,31] Bone Destruction Pathways

RANKL Osteoclast differentiation and bone erosion Denosumab approved

McInnes et al. Nat Rev Immunol, 2007 [10,19,32]

MMPs

Cartilage matrix degradation Experimental inhibitors Firestein. Immunity, 2017 [12,24,31] Angiogenesis & Chemotaxis

VEGF Synovial angiogenesis

Anti-angiogenic therapies under study Smolen et al. Nat Rev Dis Primers, 2018 [11,28] Chemokines (CCL2, CXCL8) Leukocyte recruitment Investigational targets Weyand et al. Nat Immunol, 2021 [13, 25, 33] Inflammasome Pathway NLRP3 Activates IL-1β and IL-18 Preclinical drug development Firestein. Immunity, 2017 [12,24,31] Emerging Targets

Emerging cytokines and mediators

Emerging cytokines and soluble mediators have gained increasing attention in the pathogenesis of rheumatoid arthritis (RA), expanding the traditional cytokine paradigm beyond TNF-α, IL-6, and IL-1β to include chemokines, adipokines, and organ-derived inflammatory mediators. Among chemokines, molecules such as CCL3 (MIP-1α), CCL2, CXCL8, and CXCL10 play a crucial role in directing leukocyte trafficking into the synovial microenvironment, thereby sustaining chronic synovial inflammation and pannus formation. Recent evidence highlights that chemokine networks not only regulate immune cell recruitment but also influence fibroblast-like synoviocyte activation and osteoclastogenesis, making them attractive therapeutic targets, although several chemokine receptor antagonists have shown limited success in clinical translation due to redundancy in signaling pathways and overlapping ligand-receptor interactions (Murayama et al., 2023) [4,17] . Concurrently, adipokines such as leptin, adiponectin, resistin, and visfatin have emerged as novel immunometabolic mediators linking metabolic dysfunction with inflammation in RA. These adipose-derived cytokines contribute to disease pathogenesis by promoting Th1/Th17 polarization, enhancing production of pro-inflammatory cytokines, and stimulating matrix metalloproteinases, thereby accelerating cartilage degradation and joint damage.

Recent studies further suggest that adipokines may serve as potential biomarkers of disease activity and therapeutic response, particularly in obese RA patients where metabolic inflammation exacerbates disease severity (Fujimoto et al., 2025) [16,18] . Current trends in RA research emphasize the concept of "immunometabolism," where adipokines and chemokines are integrated into broader cytokine networks that regulate both local joint inflammation and systemic disease manifestations (Smolen et al., 2018) [11,28] . However, despite strong preclinical evidence, translation into targeted therapies remains challenging, and ongoing research is focused on multi-target inhibition strategies, biomarker-guided patient stratification, and systems biology approaches to overcome redundancy in inflammatory signaling (McInnes & Schett, 2007) [10,19,32] . Collectively, emerging mediators such as chemokines and adipokines represent a rapidly evolving frontier in RA research, offering promising but still clinically underdeveloped avenues for next-generation therapeutic interventions.

Cytokine signaling pathways

Cytokine signaling pathways are central to the immunopathogenesis of rheumatoid arthritis (RA), functioning as key molecular networks that regulate inflammation, immune-cell activation, synovial proliferation, and joint destruction. Among these, the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway is one of the most extensively studied and clinically relevant signaling cascades. In RA, pro-inflammatory cytokines such as interleukin-6 (IL-6), interferons, interleukin-2, and granulocyte-macrophage colony-stimulating factor (GM-CSF) [27] bind to their respective cell-surface receptors and activate associated Janus kinases (JAK1, JAK2, JAK3, and TYK2). This leads to phosphorylation of STAT proteins, which dimerize and translocate to the nucleus, where they regulate transcription of genes involved in inflammation, cell survival, and immune activation (McInnes & Schett, 2007) [10,19,32] .

Recent evidence highlights that dysregulated JAK-STAT signaling not only sustains chronic synovial inflammation but also contributes to pain sensitization by enhancing neuroimmune interactions and increasing peripheral nociceptor responsiveness, linking cytokine signaling directly with RA-associated pain mechanisms (Simon et al., 2021) [21] . In addition, the JAK-STAT pathway does not function in isolation but interacts with other major inflammatory cascades such as NF-κB, MAPK, and PI3K-Akt signaling, forming an integrated and redundant signaling network that amplifies inflammatory responses within the synovial microenvironment. This crosstalk promotes fibroblast-like synoviocyte (FLS) activation, pannus formation, angiogenesis, and osteoclast differentiation, ultimately leading to cartilage degradation and bone erosion (Firestein, 2017) [12,24,31] . The clinical relevance of cytokine signaling pathways has been strongly validated by the successful development of targeted synthetic disease-modifying antirheumatic drugs (tsDMARDs), particularly JAK inhibitors such as tofacitinib, baricitinib, and upadacitinib. These agents block intracellular cytokine signaling and have demonstrated significant efficacy in reducing disease activity, improving physical function, and alleviating pain in patients with moderate to severe RA, including those who fail conventional biologic therapies (O'Shea et al., 2022) [23,29] . Recent clinical and translational studies further suggest that JAK inhibition may exert broader effects by modulating both peripheral inflammation and central pain processing, thereby improving patient-reported outcomes beyond traditional measures of inflammation (Smolen et al., 2018) [11] . However, despite these advances, therapeutic challenges remain due to pathway redundancy, incomplete response in a subset of patients, and potential safety concerns associated with long-term immunosuppression. Consequently, current research trends are focused on developing more selective JAK inhibitors, dual-pathway inhibitors, and combination therapeutic strategies aimed at achieving greater efficacy with improved safety profiles. Beyond JAK-STAT, emerging evidence also emphasizes the importance of multiple interconnected signaling pathways in RA pathogenesis. NF-κB signaling acts as a master regulator of inflammatory gene transcription, controlling the expression of TNF-α, IL-1β, and IL-6, while MAPK pathways regulate cellular proliferation and production of inflammatory mediators. PI3K-Akt signaling contributes to synoviocyte survival and resistance to apoptosis, thereby sustaining pannus formation. Recent systems biology approaches and transcriptomic studies published in high-impact journals such as Nature Reviews Rheumatology and Nature Immunology have highlighted that RA should be viewed as a network disease rather than a single-pathway disorder, where multiple signaling axes interact dynamically to maintain chronic inflammation (Fujimoto et al., 2025) [16,18] . This conceptual shift has important therapeutic implications, supporting the development of multi-target drugs, pathwayspecific inhibitors, and precision medicine approaches guided by molecular profiling. Overall, cytokine signaling pathways, particularly JAK-STAT and its associated networks, represent a central hub in RA pathogenesis. Their involvement in both inflammation and pain mechanisms, combined with successful clinical translation of pathway inhibitors, underscores their importance as both mechanistic drivers and therapeutic targets. Ongoing research continues to refine our understanding of signaling crosstalk, disease heterogeneity, and biomarker-guided therapy, aiming to improve long-term disease control and move toward personalized treatment strategies in rheumatoid arthritis.

Therapeutic targeting of cytokines

Therapeutic targeting of cytokines represents the cornerstone of modern rheumatoid arthritis (RA) management, fundamentally transforming disease outcomes by directly interrupting key inflammatory signaling networks responsible for synovial inflammation, joint destruction, and systemic complications. Biologic diseasemodifying antirheumatic drugs (bDMARDs), particularly tumor necrosis factor-alpha (TNF-α) inhibitors such as adalimumab, infliximab, and etanercept, were the first major breakthrough in cytokine-targeted therapy and remain highly effective in reducing synovial inflammation, inhibiting osteoclast activation, and slowing radiographic progression of joint damage (Jain et al., 2025) [22,40,44] . Subsequently, interleukin-6 (IL-6) receptor blockers, including tocilizumab and sarilumab, have further expanded therapeutic options by suppressing JAK-STAT-mediated inflammatory signaling, thereby improving systemic manifestations such as fatigue, anemia, and elevated acutephase responses. Recent studies confirm that IL-6 inhibition is particularly beneficial in patients who are non-responsive to TNF inhibitors, highlighting the importance of cytokine heterogeneity in RA pathogenesis and treatment response (Avci et al., 2023). In parallel, targeted synthetic DMARDs (tsDMARDs), especially Janus kinase (JAK) inhibitors such as tofacitinib, baricitinib, and upadacitinib, have introduced an oral therapeutic strategy that blocks intracellular signaling pathways shared by multiple cytokines, thereby offering broader immunomodulation compared to singlecytokine blockade. These agents are increasingly recognized as effective options for moderate-to-severe RA and are particularly useful in patients with inadequate response to biologics (O'Shea et al., 2022) [23,29] . Current therapeutic trends are shifting beyond singlecytokine inhibition toward more integrated and precisionbased strategies. Emerging biologics targeting GM-CSF, [27] IL-17, and IL-23 pathways are being investigated in clinical trials, although their efficacy in RA remains variable due to redundancy in cytokine networks. Recent advances in molecular engineering have also introduced bispecific antibodies and next-generation JAK inhibitors with improved selectivity and safety profiles. Additionally, precision medicine approaches using cytokine profiling, genetic markers, and synovial tissue analysis are being explored to personalize treatment selection and improve therapeutic response rates. Contemporary reviews emphasize that RA is not driven by a single cytokine axis but rather by a complex, redundant inflammatory network involving TNF, IL-6, IL-1β, and downstream signaling pathways such as NF-κB and JAK-STAT, which explains both the success and limitations of current therapies (Smolen et al., 2018) [11,28] . Despite remarkable progress, a subset of patients remains refractory to existing treatments, driving ongoing research into combination biologic strategies, immune cell reprogramming, and novel cytokine network modulation. Overall, cytokine-targeted therapy continues to evolve rapidly, with current trends focusing on broader pathway inhibition, personalized medicine, and long-term immune modulation aimed at achieving sustained remission or potential disease modification in RA (Fujimoto et al., 2025) [16,18] .

Insights from Preclinical Models

Preclinical animal models have played a crucial role in advancing the understanding of rheumatoid arthritis (RA) pathogenesis and in the development of novel therapeutic strategies. Among these, the collagen-induced arthritis (CIA) model is the most widely used and well-characterized experimental system, as it closely mimics key pathological features of human RA, including synovial hyperplasia, immune cell infiltration, autoantibody production, and progressive cartilage and bone destruction. CIA is induced by immunization with type II collagen in genetically susceptible mouse strains and is particularly valuable for studying T-cell and B-cell mediated autoimmune mechanisms and cytokine-driven inflammation (Luan et al., 2021) [30,35] . In addition, collagen antibody-induced arthritis (CAIA) and K/BxN serum transfer models are frequently used to investigate effector phases of disease, especially neutrophil-driven inflammation and immune complexmediated joint damage. Recent literature highlights that these models consistently demonstrate the involvement of major inflammatory cytokines such as TNF-α, IL-6, and IL-1β, along with activation of downstream signaling pathways including NF-κB, MAPK, and JAK-STAT, thereby validating their translational relevance to human disease (Wei et al., 2025) [34] . Current trends in RA research emphasize that CIA and related models are not only used for mechanistic studies but also serve as essential platforms for preclinical drug evaluation, particularly for biologic DMARDs and targeted synthetic DMARDs such as JAK inhibitors (Chidomere et al., 2023) [36] . However, recent studies also reveal important limitations, including variability in disease severity, strain dependency, microbiome influence, and incomplete replication of chronic and systemic aspects of human RA, which can affect reproducibility and translational success. To address these gaps, emerging approaches are integrating humanized mouse models, multi-omics technologies, and systems biology analyses to better capture disease heterogeneity and improve predictive accuracy for therapeutic responses. Furthermore, contemporary research increasingly uses these models to explore extra-articular manifestations of RA, including cardiovascular and pulmonary comorbidities, reflecting a shift toward viewing RA as a systemic inflammatory disease rather than a joint-limited disorder (Marco-Bonilla et al., 2025) [37,39] (Krock et al., 2019) [38] . Overall, preclinical models remain indispensable in RA research, bridging the gap between molecular mechanisms and clinical therapy development while evolving toward more sophisticated and human-relevant experimental systems.

Luan et al., PMC, 2021 [30,35] Collagen Antibody-Induced Arthritis (CAIA)

Injection of anticollagen antibodies

Rapid joint inflammation, neutrophil-driven damage

Study of effector phase of RA Useful for studying innate immune mechanisms independent of adaptive immunity Luan et al., 2021 [30,35] K/BxN Serum Transfer Model

Transfer of arthritogenic serum

Severe acute arthritis, immune-complex mediated inflammation

Study of effector inflammatory pathways

Strong model for Fc receptor, complement, and neutrophil activation Firestein, Immunity, 2017 [12,24,31] Adjuvant-Induced Arthritis (AIA)

Injection of Freund's adjuvant

Systemic inflammation, polyarthritis

Drug screening and anti-inflammatory studies

Mimics chronic inflammation and cytokine storm Smolen et al., 2018 [11, 28] TNF-Transgenic Mouse Model

Genetic overexpression of TNF-α

Chronic progressive arthritis

Study of TNFdriven pathology

Highly relevant for testing TNF inhibitors

McInnes & Schett, 2007 [10,19,32] SKG Mouse Model Mutation in ZAP-70 gene

Spontaneous autoimmune arthritis

Study of T-cell mediated autoimmunity

Useful for studying Th17/IL-17 axis

Weyand & Goronzy, 2021 [13,25,33] Humanized Mouse Models

Engrafted human immune cells/tissues

Human-like immune response

Translational drug testing

Increasingly used for biologics and precision medicine studies Frontiers in Medicine, 2025 Glycoprotein-Induced Arthritis (GIA)

Immunization with cartilage glycoproteins

Joint inflammation & cartilage damage

Study of autoantigenspecific immunity

Models antigen-driven RA mechanisms

Luan et al., 2021 [30,35] Spontaneous Arthritis Models (e.g., SKG, IL-1RA knockout)

Genetic mutations Chronic autoimmune arthritis

Pathogenesis studies

Useful for studying genetic susceptibility factors Smolen et al., 2018 [11, 28]

Biomarkers and clinical implications

Biomarkers play a crucial role in improving the early diagnosis, disease monitoring, and risk stratification of rheumatoid arthritis (RA), particularly in identifying patients at higher risk of systemic complications such as cardiovascular disease. Among the most promising biomarker groups are circulating cell adhesion molecules (CAMs), including intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and selectins (E-, P-, and L-selectin), which reflect endothelial activation and vascular inflammation. A recent systematic review and meta-analysis by Mangoni and Zinellu demonstrated that RA patients exhibit significantly elevated circulating levels of ICAM-1, VCAM-1, E-selectin, and P-selectin compared with healthy controls, indicating persistent endothelial dysfunction and chronic systemic inflammation in RA patients (Mangoni & Zinellu, 2024) [9,45] . These findings are clinically important because endothelial activation is now recognized as a key link between RA and accelerated atherosclerosis, explaining the increased cardiovascular morbidity and mortality observed in these patients. Importantly, the study also highlighted that elevated adhesion molecules are present even in patients with short disease duration and low disease activity, suggesting that vascular inflammation begins early in RA and is not solely dependent on clinical disease severity.

Recent meta-regression analyses further indicate that inflammatory markers such as erythrocyte sedimentation rate (ESR) correlate with VCAM-1 levels, reinforcing the close interaction between systemic inflammation and endothelial dysfunction. Moreover, differential effects of treatments, particularly glucocorticoids, appear to modulate ICAM-1 expression, suggesting that commonly used antiinflammatory therapies may partially influence biomarker levels. From a clinical perspective, these adhesion molecules are emerging as potential tools for cardiovascular risk stratification, allowing earlier identification of RA patients who may benefit from aggressive anti-inflammatory and cardioprotective strategies. Current trends in RA research are increasingly focused on integrating such biomarkers into precision medicine frameworks, combining inflammatory profiling, genetic susceptibility markers, and imaging techniques to improve individualized disease management. However, despite strong evidence supporting their association with disease pathology, routine clinical use of adhesion molecules remains limited due to assay variability, lack of standardized thresholds, and incomplete validation in prospective studies. Therefore, ongoing research is directed toward validating these biomarkers in large longitudinal cohorts and integrating them into multibiomarker panels for improved diagnostic and prognostic accuracy in RA.

Challenges and limitations

Despite remarkable advances in the management of rheumatoid arthritis (RA) through biologic and targeted synthetic disease-modifying antirheumatic drugs (DMARDs), several important challenges and limitations continue to hinder optimal disease control. One of the major issues is the variable treatment response among patients, as RA is a highly heterogeneous disease influenced by genetic, immunological, environmental, and microbiome-related factors. Recent studies emphasize that nearly 30-40% of patients show inadequate or partial response to first-line biologics or JAK inhibitors, leading to persistent disease activity and the need for multiple therapeutic switches, reflecting the complexity of cytokine redundancy and overlapping inflammatory pathways in RA pathogenesis (Jain et al., 2025) [22,40,44] . Another significant limitation is long-term safety concerns, particularly with prolonged use of biologics and JAK inhibitors, which have been associated with increased risks of infections, malignancy, cardiovascular events, and thromboembolic complications. Although newer selective agents aim to improve safety profiles, real-world evidence continues to highlight the need for long-term pharmacovigilance and risk stratification in vulnerable populations (Tanaka et al., 2025) [43] . A further major barrier is the high cost of biologic therapies, which limits accessibility in low-and middle-income countries and contributes to treatment inequity globally. Even with the introduction of biosimilars, cost remains a significant healthcare burden, especially for lifelong therapy required in chronic RA management (Yiu et al., 2025) [41] . In addition, a critical unresolved challenge is the incomplete understanding of disease heterogeneity, where RA is now recognized as a spectrum of molecularly distinct subtypes rather than a single uniform disease. This heterogeneity contributes to unpredictable treatment responses and underscores the need for biomarker-driven precision medicine approaches. Current research trends are increasingly focused on overcoming these limitations through precision medicine, multi-omics profiling, artificial intelligence-based prediction models, and synovial tissue stratification, which aim to identify patient-specific inflammatory signatures and optimize therapeutic selection. Emerging strategies such as combination biologic therapy, novel cytokine network modulation, and immune cell reprogramming are also being explored to address refractory disease and reduce treatment failure rates. Moreover, realworld data registries and machine learning approaches are being integrated to better predict treatment response and long-term outcomes, marking a shift toward individualized and adaptive RA management strategies (Skydel & Hsiao, 2026) [42] . Overall, while current therapies have transformed RA prognosis, addressing variability in response, safety concerns, cost barriers, and disease heterogeneity remains essential for achieving sustained remission and true precision medicine in RA care.

Future perspectives

Future perspectives in rheumatoid arthritis (RA) research are increasingly focused on transforming disease management from a standardized treatment approach to a highly individualized and mechanism-based strategy. One of the most promising directions is personalized medicine, which aims to tailor therapy based on genetic, molecular, and immunological profiling of patients. Recent advances in multi-omics technologies, including genomics, transcriptomics, proteomics, and synovial tissue analysis, are enabling researchers to identify distinct RA endotypes associated with differential cytokine signatures and treatment responses, thereby improving prediction of therapeutic outcomes and minimizing trial-and-error prescribing strategies. A growing body of literature highlights that integrating clinical data with molecular biomarkers and machine learning approaches can significantly enhance early diagnosis and optimize drug selection, particularly for biologics and JAK inhibitors, supporting a shift toward precision rheumatology models (Jain et al., 2025) [22,40,44] . Another major emerging trend is multi-cytokine targeting strategies, which address the limitation of single-cytokine inhibition by simultaneously modulating multiple inflammatory pathways such as TNF-α, IL-6, IL-17, GM-CSF, [27] and JAK-STAT signaling. Recent studies emphasize that RA pathogenesis is driven by highly redundant and interconnected cytokine networks, which often compensate when a single pathway is inhibited, leading to incomplete therapeutic responses or drug resistance. Consequently, next-generation biologics, including bispecific antibodies and combination biologic approaches, are being developed to achieve broader and more sustained suppression of inflammation, especially in refractory RA cases (Smolen et al., 2018; Weyand CM & Goronzy, 2021) [11,13,25,28,33] . A third important advancement is the integration of clinical and preclinical data, which is reshaping drug discovery and translational research. Preclinical models such as collageninduced arthritis are now being combined with patientderived datasets, real-world evidence, and systems biology approaches to better simulate human disease heterogeneity and improve predictive accuracy of therapeutic responses. This integrated framework is further supported by artificial intelligence and computational modeling, which help identify optimal drug combinations and predict disease progression patterns. Recent reviews suggest that such integrative strategies bridge the gap between bench and bedside, accelerating the development of more effective and safer RA therapies while improving translational success rates in clinical trials (Firestein, 2017; Mangoni AA & Zinellu, 2024) [9,12,24,31,45] . Overall, the future of RA management is moving toward a precision-driven, multi-target, and data-integrated therapeutic paradigm, aiming not only to control inflammation but also to achieve sustained remission and potentially prevent disease onset in high-risk individuals.

Conclusion

Rheumatoid arthritis (RA) is now widely recognized as a network-driven cytokine disease, where complex and interconnected signaling systems rather than single mediators govern disease initiation, persistence, and progression. The concept of network-based cytokine mechanisms has reshaped traditional views of RA pathogenesis by highlighting how pro-inflammatory cytokines such as TNF-α, IL-6, IL-1β, IL-17, and GM-CSF operate within tightly linked signaling circuits involving JAK-STAT, [27] NF-κB, and MAPK pathways. These interconnected networks amplify synovial inflammation, promote immune cell activation, and drive irreversible structural damage to cartilage and bone, while also contributing to systemic manifestations. Importantly, recent advances in molecular immunology and systems biology demonstrate that cytokine interactions are highly redundant and dynamic, which explains both disease heterogeneity and variable therapeutic responses observed in clinical practice. From a therapeutic perspective, the success of biologic DMARDs and targeted synthetic DMARDs has validated cytokines as central drug targets and significantly improved clinical outcomes in RA patients. However, limitations such as incomplete response rates, long-term safety concerns, and treatment resistance underscore the need for more comprehensive approaches that move beyond singlecytokine inhibition. In this context, precision therapy guided by cytokine network profiling, multi-omics integration, and artificial intelligence-based prediction models represents a major advancement toward individualized treatment strategies. Emerging approaches, including multi-cytokine blockade, bispecific antibodies, and immune network modulation, further reflect a shift toward targeting the broader inflammatory network rather than isolated pathways. Overall, understanding RA through the lens of networkbased cytokine mechanisms bridges molecular immunopathology with clinical therapeutics and provides a strong foundation for next-generation precision medicine. Continued research integrating mechanistic biology, clinical data, and computational modeling will be essential to refine therapeutic strategies, overcome disease heterogeneity, and ultimately achieve sustained remission or functional cure in rheumatoid arthritis.

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