FGF21 exerts comparable pharmacological efficacy with Adalimumab in ameliorating collagen-induced rheumatoid arthritis by regulating systematic inflammatory response

Fibroblast growth factor 21 alleviated atopic march by inhibiting the differentiation of type 2 helper T cells

BACKGROUND

The blood FGF21 expression has been previously suggested to increase in patients developing atopic dermatitis (AD) and asthma. However, its impact on atopic march is rarely analyzed. The present work focused on investigating the role of Fibroblast Growth Factor 21(FGF21) in atopic march mice and its underlying mechanisms.

METHODS

The models were induced with Diisononyl phthalate (DINP) and OVA in wild-type C57BL/6 and FGF21-/- mice. RAW264.7 cells were induced by LPS with/without FGF21 or KLB-SiRNA for in vitro analyses.

RESULTS

The data indicated that there were more severe allergic reactions including IgE levels and the proportion of mast cells in the blood of FGF21-/- mice in relative to WT model mice during the progression from AD to asthma. However, exogenous administration of FGF21 inhibited allergies. In this study, we reported that FGF21 mitigated AD-like lesions and Th1/2 or Th17/Treg cell imbalance in AD mice, and significantly decreased TSLP, IL-33, IL-4, IL-5, IL-13 and IL-17A expression on skin. During the asthma phase, FGF21 improved airway remodeling by downgrading inflammatory factors IL-4, IL-5, IL-13 and IL-17A; fibrotic markers α-SMA and Collagen I; and oxidative products MDA and ROS in wild-type model mice. Compared with WT model mice, the adverse consequences were aggravated in FGF21-/- asthmatic mice. From the mechanistic perspective, FGF21 suppressed NF-κB/NLRP3, TGF-β1/Smad3 and JNK signaling pathways and increased Nrf2 expression in vivo and in vitro. In addition, β-Klotho knockdown attenuated the ameliorative impact of FGF21 on cellular damage. Blocking AMPKα in the LPS-treated RAW264.7 cells inhibited the reduction of FGF21 and the phosphorylation of JNK.

CONCLUSIONS

To conclude, FGF21 alleviated atopic march by inhibiting Th2/17 immune response, and reduced airway remodeling by regulating NF-κB/NLRP3, TGF-β1/Smad3 and AMPKα/JNK pathways. Moreover, this study provides a rationale and novel ideas for applying FGF21 in treating AD and asthma.

Interorgan communication with the liver: novel mechanisms and therapeutic targets

The liver is a multifunctional organ that plays crucial roles in numerous physiological processes, such as production of bile and proteins for blood plasma, regulation of blood levels of amino acids, processing of hemoglobin, clearance of metabolic waste, maintenance of glucose, etc. Therefore, the liver is essential for the homeostasis of organisms. With the development of research on the liver, there is growing concern about its effect on immune cells of innate and adaptive immunity. For example, the liver regulates the proliferation, differentiation, and effector functions of immune cells through various secreted proteins (also known as "hepatokines"). As a result, the liver is identified as an important regulator of the immune system. Furthermore, many diseases resulting from immune disorders are thought to be related to the dysfunction of the liver, including systemic lupus erythematosus, multiple sclerosis, and heart failure. Thus, the liver plays a role in remote immune regulation and is intricately linked with systemic immunity. This review provides a comprehensive overview of the liver remote regulation of the body's innate and adaptive immunity regarding to main areas: immune-related molecules secreted by the liver and the liver-resident cells. Additionally, we assessed the influence of the liver on various facets of systemic immune-related diseases, offering insights into the clinical application of target therapies for liver immune regulation, as well as future developmental trends.

Fibroblast Growth Factor 21 Attenuates the Progression of Hyperuricemic Nephropathy through Inhibiting Inflammation, Fibrosis and Oxidative stress

Elevated levels of circulating fibroblast growth factor 21 (FGF21) have been reported in patients with hyperuricemia. However, the effect of FGF21 in hyperuricemic nephropathy (HN) remains unexplored. Here, we investigated the effect and mechanism of action of FGF21 on HN. HN model was induced with adenine and potassium oxysalt in wild-type C57BL/6 mice and FGF21^-/- mice. For in vitro studies, human renal tubular epithelial (HK-2) cells were exposed to uric acid with/without FGF21 or β-Klotho-siRNA. Here, we reported aggravated renal dysfunction and structural damage in the FGF21^-/- mice compared to the wild-type mice. These were evident in the upsurge of inflammatory factors IL-1β, TNF-α, IL-6 and IL-18, fibrotic markers Collagen I and α-SMA, and oxidation products ROS and MDA. However, exogenous administration of FGF21 to wild-type HN mice significantly reversed these negative effects. In terms of mechanism, FGF21 significantly inhibited NF-κB/NLRP3 and TGF-β1/Smad3 pathways and promoted nuclear translocation of Nrf2 both in vivo and in vitro. Furthermore, the silencing of β-Klotho was marked by the attenuation of the improved effect of FGF21 on cell damage. In conclusion, our studies revealed that exogenous FGF21 treatment significantly improved HN, which was achieved by the inhibition of inflammation, fibrosis and oxidative stress.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

KLF4 downregulates FGF21 to activate inflammatory injury and oxidative stress of LPS‑induced ATDC5 cells via SIRT1/NF‑κB/p53 signaling

Ankylosing spondylitis (AS) is a chronic inflammatory disease. Transcriptional regulation of fibroblast growth factor 21 (FGF21) by the transcription factor Krüppel-like factor 4 (KLF4) serves an important role in chronic inflammatory disease. However, to the best of our knowledge, the role of both these factors in AS has not been previously reported. In the present study, ATDC5 cells were induced by lipopolysaccharide (LPS) to establish an AS inflammatory injury model. The expression levels of FGF21 and KLF4 were detected using reverse transcription-quantitative PCR and western blotting. Cell transfection was performed to alter the expression levels of KLF4 and FGF21. Subsequently, the regulatory effects and mechanisms underlying KLF4 and FGF21 on oxidative stress and inflammation in AS were investigated by performing Cell Counting Kit-8 assays, ELISAs, TUNEL staining and western blotting. Moreover, the expression levels of sirtuin 1 (SIRT1)/NF-κB/p53 pathway-related proteins were detected via western blotting. FGF21 overexpression promoted LPS-induced viability on ATDC5 cells, inhibited LPS-induced apoptosis, and decreased the LPS-induced inflammatory response and oxidative stress levels of ATDC5 cells. Overexpression of the transcription factor KLF4 reversed the protective effect of FGF21 overexpression on LPS-induced inflammatory injury in ATDC5 cells. The results suggested that this process may be achieved via regulating the SIRT1/NF-κB/p53 signaling pathway. Overall, the present study demonstrated that KLF4 downregulates FGF21 to activate inflammatory injury and oxidative stress of LPS-induced ATDC5 cells via SIRT1/NF-κB/p53 signaling.

Tumor necrosis factor‑α in systemic lupus erythematosus: Structure, function and therapeutic implications (Review)

Tumor necrosis factor‑α (TNF‑α) is a pleiotropic pro‑inflammatory cytokine that contributes to the pathophysiology of several autoimmune diseases, such as multiple sclerosis, inflammatory bowel disease, rheumatoid arthritis, psoriatic arthritis and systemic lupus erythematosus (SLE). The specific role of TNF‑α in autoimmunity is not yet fully understood however, partially, in a complex disease such as SLE. Through the engagement of the TNF receptor 1 (TNFR1) and TNF receptor 2 (TNFR2), both the two variants, soluble and transmembrane TNF‑α, can exert multiple biological effects according to different settings. They can either function as immune regulators, impacting B‑, T‑ and dendritic cell activity, modulating the autoimmune response, or as pro‑inflammatory mediators, regulating the induction and maintenance of inflammatory processes in SLE. The present study reviews the dual role of TNF‑α, focusing on the different effects that TNF‑α may have on the pathogenesis of SLE. In addition, the efficacy and safety of anti‑TNF‑α therapies in preclinical and clinical trials SLE are discussed.

Ultra-Low Dose Cytokines in Rheumatoid Arthritis, Three Birds with One Stone as the Rationale of the 2LARTH® Micro-Immunotherapy Treatment

Tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) are two cytokines involved in the perpetuation of the chronic inflammation state characterizing rheumatoid arthritis (RA). Significant advances in the treatment of this pathology have been made over the past ten years, partially through the development of anti-TNF and anti-IL-1 therapies. However, major side effects still persist and new alternative therapies should be considered. The formulation of the micro-immunotherapy medicine (MIM) 2LARTH^® uses ultra-low doses (ULD) of TNF-α, IL-1β, and IL-2, in association with other immune factors, to gently restore the body’s homeostasis. The first part of this review aims at delineating the pivotal roles played by IL-1β and TNF-α in RA physiopathology, leading to the development of anti-TNF and anti-IL-1 therapeutic agents. In a second part, an emphasis will be made on explaining the rationale of using multiple therapeutic targets, including both IL-1β and TNF-α in 2LARTH^® medicine. Particular attention will be paid to the ULD of those two main pro-inflammatory factors in order to counteract their overexpression through the lens of their molecular implication in RA pathogenesis.

The Molecular Pathophysiology of Psoriatic Arthritis-The Complex Interplay Between Genetic Predisposition, Epigenetics Factors, and the Microbiome

Psoriasis is a symmetric autoimmune/inflammatory disease that primarily affects the skin. In a significant proportion of cases, it is accompanied by arthritis that can affect any joint, the spine, and/or include enthesitis. Psoriasis and psoriatic arthritis are multifactor disorders characterized by aberrant immune responses in genetically susceptible individuals in the presence of additional (environmental) factors, including changes in microbiota and/or epigenetic marks. Epigenetic changes can be heritable or acquired (e.g., through changes in diet/microbiota or as a response to therapeutics) and, together with genetic factors, contribute to disease expression. In psoriasis, epigenetic alterations are mainly related to cell proliferation, cytokine signaling and microbial tolerance. Understanding the complex interplay between heritable and acquired pathomechanistic factors contributing to the development and maintenance of psoriasis is crucial for the identification and validation of diagnostic and predictive biomarkers, and the introduction of individualized effective and tolerable new treatments. This review summarizes the current understanding of immune activation, genetic, and environmental factors that contribute to the pathogenesis of psoriatic arthritis. Particular focus is on the interactions between these factors to propose a multifactorial disease model.

Advances in Biological Functions and Clinical Studies of FGF21

Fibroblast growth factor 21 (FGF21) regulates many crucial biological processes in human and mammals, particularly metabolic modulation and protective effect after injury. Therefore, determining complex regulatory mechanisms and elucidating the signaling pathway may greatly promote the prevention, diagnosis, and treatment of related injury and metabolic diseases. This review focused on the metabolic modulation and protective effect of FGF21 and summarized the molecular mechanisms and clinical research developments.

An Overview of the NF-kB mechanism of pathophysiology in rheumatoid arthritis, investigation of the NF-kB ligand RANKL and related nutritional interventions

Nuclear Factor Kappa-Β (NF-kB) is recognized as one of the main inflammatory pathways in the Autoimmune Disease (AD) Rheumatoid Arthritis (RA), which exhibits high levels of inflammatory cytokines such as IL-1, TNFa and IL-6 linked to bone erosion and disease progression. NF-kB is also the most studied pathophysiological mechanism in RA, however, over the last few decades, a more recently discovered Receptor Activator of Nuclear Factor Kappa-Β Ligand (RANKL), also linked to NF-kB activation and bone erosion, has been the topic of interest for research in the area of AD management. As the non-discriminative long term suppression of the NF-kB pathway by pharmacological agents in the management of RA has been linked with a number of side effects and with the discovery of the RANKL mechanism, which may present a more targeted approach to the management of the AD, there has been renewed interest in research on the potential impact of nutritional interventions influencing the NF-kB pathway, RANKL as well as RA disease outcomes. Existing research highlights the potential utility of nutrients such as Omega 3 and Vitamin D, which may lower NF-kB activation in RA. There is, however, a gap in the knowledge of the effects of nutritional interventions on pathophysiological mechanisms contributing to RA and a more robust systematic analysis of whether nutrients or specific vitamins can have an effect on the NF-kB and RANKL main drivers of pathology in RA. Findings from this study suggest the potential of Vitamin D supplementation in lowering the levels of RANKL and related markers/cytokines such as Th17 cell levels, OPG/RANKL ratio and CXCL10 pathway, which may present as a viable nutrition intervention for the management of RA. The methodology of this review involved a Systematic Search of the Literature with a Critical Appraisal of papers. It incorporated three tranche searches of 1. review, 2. animal/in vitro and 3. intervention peer reviewed research published in the last 10 years, resulting in a total of 119 papers. Results provide an overview of the NF-kB pathway, a detailed mechanistic examination of the Receptor Activator of Nuclear Factor Kappa-Β Ligand (RANKL) which is linked to bone erosion, and finally a review of nutritional interventions relating to this mechanism of pathophysiology. The accepted papers were critically appraised using SIGN50 for human studies and the ARRIVE guidelines for animal studies; the narrative was and the extracted information coded into key themes.

Circulating Fibroblast Growth Factor-21 Levels in Rheumatoid Arthritis: Associations With Disease Characteristics, Body Composition, and Physical Functioning

OBJECTIVE

This study evaluated associations between fibroblast growth factor (FGF)-21, an adipokine associated with metabolic stress, and adverse longitudinal changes in body composition and physical functioning in patients with rheumatoid arthritis (RA).

METHODS

At baseline and follow-up, patients with RA aged 18-70 years completed whole-body dual-energy X-ray absorptiometry and peripheral quantitative computed tomography to quantify lean mass, fat mass, and muscle density. Dynamometry assessed muscle strength at the hand and knee, and physical functioning was measured with the Health Assessment Questionnaire (HAQ) and the Short Physical Performance Battery (SPPB). FGF-21 and inflammatory cytokines were measured at baseline. Linear and logistic regression analyses assessed associations between FGF-21 levels and both body composition and physical functioning over time.

RESULTS

There were 113 patients with RA enrolled, and 84 (74%) returned for follow-up at a median of 2.68 years. At baseline, FGF-21 was associated with age, smoking, methotrexate use, adiposity, and inflammatory cytokines: tumor necrosis factor receptor type I, YKL-40, vascular endothelial growth factor (VEGF), and resistin. The highest FGF-21 quartile was associated with worse SPPB and HAQ. Higher baseline FGF-21 levels (per 1 SD) were associated with worsening in muscle density and area Z-scores (β -0.06, 95% CI -0.12 to 0.008, P = 0.08; and β -0.05, 95% CI -0.10 to 0.006, P = 0.08, respectively) and a greater probability of a clinically meaningful worsening of HAQ (OR 2.37, 95% CI 1.21-4.64, P = 0.01). The fourth FGF-21 quartile was associated with worsening of SPPB (β -0.57, 95% CI -1.04 to -0.09, P = 0.02).

CONCLUSION

FGF-21 levels are associated with obesity and inflammatory cytokines, and with worsening in physical functioning in RA. These data support the hypothesis that FGF-21 can identify patients at risk of functional decline.

The Adipokine Network in Rheumatic Joint Diseases

Rheumatic diseases encompass a diverse group of chronic disorders that commonly affect musculoskeletal structures. Osteoarthritis (OA) and rheumatoid arthritis (RA) are the two most common, leading to considerable functional limitations and irreversible disability when patients are unsuccessfully treated. Although the specific causes of many rheumatic conditions remain unknown, it is generally accepted that immune mechanisms and/or uncontrolled inflammatory responses are involved in their etiology and symptomatology. In this regard, the bidirectional communication between neuroendocrine and immune system has been demonstrated to provide a homeostatic network that is involved in several pathological conditions. Adipokines represent a wide variety of bioactive, immune and inflammatory mediators mainly released by adipocytes that act as signal molecules in the neuroendocrine-immune interactions. Adipokines can also be synthesized by synoviocytes, osteoclasts, osteoblasts, chondrocytes and inflammatory cells in the joint microenvironment, showing potent modulatory properties on different effector cells in OA and RA pathogenesis. Effects of adiponectin, leptin, resistin and visfatin on local and systemic inflammation are broadly described. However, more recently, other adipokines, such as progranulin, chemerin, lipocalin-2, vaspin, omentin-1 and nesfatin, have been recognized to display immunomodulatory actions in rheumatic diseases. This review highlights the latest relevant findings on the role of the adipokine network in the pathophysiology of OA and RA.

Mechanism and Prevention of Titanium Particle-Induced Inflammation and Osteolysis

The worldwide number of dental implants and orthopedic prostheses is steadily increasing. Orthopedic implant loosening, in the absence of infection, is mostly attributable to the generation of wear debris. Dental peri-implantitis is characterized by a multifactorial etiology and is the main cause of implant failure. It consists of a peri-implant inflammatory lesion that often results in loss of supporting bone. Disease management includes cleaning the surrounding flora by hand instruments, ultrasonic tips, lasers, or chemical agents. We recently published a paper indicating that US scaling of titanium (Ti) implants releases particles that provoke an inflammatory response and osteolysis. Here we show that a strong inflammatory response occurs; however, very few of the titanium particles are phagocytosed by the macrophages. We then measured a dramatic Ti particle-induced stimulation of IL1β, IL6, and TNFα secretion by these macrophages using multiplex immunoassay. The particle-induced expression profile, examined by FACS, also indicated an M1 macrophage polarization. To assess how the secreted cytokines contributed to the paracrine exacerbation of the inflammatory response and to osteoclastogenesis, we treated macrophage/preosteoclast cultures with neutralizing antibodies against IL1β, IL6, or TNFα. We found that anti-TNFα antibodies attenuated the overall expression of both the inflammatory cytokines and osteoclastogenesis. On the other hand, anti-IL1β antibodies affected osteoclastogenesis but not the paracrine expression of inflammatory cytokines, whereas anti-IL6 antibodies did the opposite. We then tested these neutralizing antibodies in vivo using our mouse calvarial model of Ti particle-induced osteolysis and microCT analysis. Here, all neutralizing antibodies, administered by intraperitoneal injection, completely abrogated the particle-induced osteolysis. This suggests that blockage of paracrine inflammatory stimulation and osteoclastogenesis are similarly effective in preventing bone resorption induced by Ti particles. Blocking both the inflammation and osteoclastogenesis by anti-TNFα antibodies, incorporated locally into a slow-release membrane, also significantly prevented osteolysis. The osteolytic inflammatory response, fueled by ultrasonic scaling of Ti implants, results from an inflammatory positive feedback loop and osteoclastogenic stimulation. Our findings suggest that blocking IL1β, IL6, and/or TNFα systemically or locally around titanium implants is a promising therapeutic approach for the clinical management of peri-implant bone loss.