Redox-active endosomes mediate α5β1 integrin signaling and promote chondrocyte matrix metalloproteinase production in osteoarthritis

Novel insight into the role of Src family kinases in hepatocellular carcinoma and therapeutic potential

Hepatocellular carcinoma remains a highly aggressive malignancy, with the 5-year survival rate for advanced-stage patients persisting below 20 % despite progress in targeted therapies and immunotherapy. This clinical reality underscores the critical need for identifying novel therapeutic targets. Src family kinases (SFKs), critical regulators of cellular metabolism, coordinate regenerative repair through STAT3/ERK signaling in normal hepatic regeneration and preserve cellular polarity via FAK-mediated mechanisms following hepatic injury. Growing evidence suggests that dysregulation of SFKs expression and activity is closely associated with oxidative stress, inflammation-cancer transition, metabolic reprogramming disorders and microenvironmental remodeling in hepatocellular carcinoma. However, the underlying mechanisms remain inadequately understood. This review provides a comprehensive overview of the composition and structure of SFKs. We explored in depth the molecular and cellular mechanisms of SFKs in the pathological progression and risk factors of hepatocellular carcinoma, including viral hepatitis, metabolic dysfunction-associated steatohepatitis, and other established risk factors. Herein, we highlight the potential of SFKs as a pharmacological target against hepatocellular in the hope of inspiring translational research and innovative clinical approaches.

Endosomal H2O2 Molecules Act as Signaling Mediators in Akt/PKB Activation

Receptor-mediated endocytosis (RME) is a commonly recognized receptor internalization process of receptor degradation or recycling. However, recent studies have supported that RME is closely related to signal propagation and amplification from the plasma membrane to the cytosol. Few studies have elucidated the role of H2O2, a mild oxidant among reactive oxygen species (ROS) in RME and second messenger of signal propagation. In the present study, we investigated the regulatory function of H2O2 in early endosomes during signaling throughout receptor-mediated endocytosis. In mammalian cells with a physiological amount of H2O2 generated during epidermal growth factor (EGF) activation, fluorescence imaging showed that the levels of two activating phosphorylations on Ser473 and Thr308 of Akt were transiently increased in the plasma membrane, but the predominant p-Akt on Ser473 appeared in early endosomes. To examine the role of endosomal H2O2 molecules as signaling mediators of Akt activation in endosomes, we modulated endosomal H2O2 through the ectopic expression of an endosomal-targeting catalase (Cat-Endo). The forced removal of endosomal H2O2 inhibited the Akt phosphorylation on Ser473 but not on Thr308. The levels of mSIN and rictor, two components of mTORC2 that work as a kinase in Akt phosphorylation on Ser473, were also selectively diminished in the early endosomes of Cat-Endo-expressing cells. We also observed a decrease in the endosomal level of the adaptor protein containing the PH domain, the PTB domain, and the Leucine zipper motif 1 (APPL1) protein, which is an effector of Rab5 and key player in the assembly of signaling complexes regulating the Akt pathway in Cat-Endo-expressing cells compared with those in normal cells. Therefore, the H2O2-dependent recruitment of the APPL1 adaptor protein into endosomes was required for full Akt activation. We proposed that endosomal H2O2 is a promoter of Akt signaling.

Mitigating Oxidative Stress Enhances Cartilage Regeneration by Ameliorating Apoptosis of Cartilage Progenitor Cells in Adult Mice

Cartilage regeneration in juvenile mice was better than in adult mice. This study evaluated the roles of cytokines and reactive oxygen species (ROS) after cartilage injury in both juvenile and adult mice and attempted to correlate these with cartilage progenitor cells and age-related differences in cartilage regeneration. Full-thickness cartilage defects were created in the femoral trochlea of knee joints in both 4-week-old (juvenile) and 8-week-old (adult) mice. Adult mice showed higher ROS peaks than juveniles at day 7 post-injury. Protein expression levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) significantly decreased after surgery, while interleukin-1β (IL-1β) levels displayed no significant change. There were more cartilage progenitor cells together with more cell proliferation in juvenile versus adult mice, while there was much less apoptosis of cartilage progenitor cells in juvenile mice compared to adult mice. ROS inhibition enhanced cartilage regeneration in adult mice by promoting progenitor cell proliferation and reducing apoptosis, mimicking the regenerative pattern seen in juveniles. This study demonstrated that inhibiting ROS in adult mice promoted cartilage regeneration, possibly by enhancing proliferation and decreasing apoptosis of cartilage progenitor cells.

The role and regulation of integrins in cell migration and invasion

Integrin receptors are the main molecular link between cells and the extracellular matrix (ECM) as well as mediating cell-cell interactions. Integrin-ECM binding triggers the formation of heterogeneous multi-protein assemblies termed integrin adhesion complexes (IACs) that enable integrins to transform extracellular cues into intracellular signals that affect many cellular processes, especially cell motility. Cell migration is essential for diverse physiological and pathological processes and is dysregulated in cancer to favour cell invasion and metastasis. Here, we discuss recent findings on the role of integrins in cell migration with a focus on cancer cell dissemination. We review how integrins regulate the spatial distribution and dynamics of different IACs, covering classical focal adhesions, emerging adhesion types and adhesion regulation. We discuss the diverse roles integrins have during cancer progression from cell migration across varied ECM landscapes to breaching barriers such as the basement membrane, and eventual colonization of distant organs.

Matrikine stimulation of equine synovial fibroblasts and chondrocytes results in an in vitro osteoarthritis phenotype

Osteoarthritis (OA) is a debilitating disease that impacts millions of individuals and has limited therapeutic options. A significant hindrance to therapeutic discovery is the lack of in vitro OA models that translate reliably to in vivo preclinical animal models. An alternative to traditional inflammatory cytokine models is the matrikine stimulation model, in which fragments of matrix proteins naturally found in OA tissues and synovial fluid, are used to stimulate cells of the joint. The objective of this study was to determine if matrikine stimulation of equine synovial fibroblasts and chondrocytes with fibronectin fragments (FN7-10) would result in an OA phenotype. We hypothesized that FN7-10 stimulation of equine articular cells would result in an OA phenotype with gene and protein expression changes similar to those previously described for human chondrocytes stimulated with FN7-10. Synovial fibroblasts and chondrocytes isolated from four horses were stimulated in monolayer culture for 6 or 18 h with 1 µM purified recombinant 42 kD FN7-10 in serum-free media. At the conclusion of stimulation, RNA was collected for targeted gene expression analysis and media for targeted protein production analysis. Consistent with our hypothesis, FN7-10 stimulation resulted in significant alterations to many important genes that are involved in OA pathogenesis including increased expression of IL-1β, IL-4, IL-6, CCL2/MCP-1, CCL5/RANTES, CXCL6/GCP-2, MMP-1, MMP-3, and MMP13. The results of this study suggest that the equine matrikine stimulation model of OA may prove useful for in vitro experiments leading up to preclinical trials.

Response eQTLs, chromatin accessibility, and 3D chromatin structure in chondrocytes provide mechanistic insight into osteoarthritis risk

Osteoarthritis (OA) poses a significant healthcare burden with limited treatment options. While genome-wide association studies (GWASs) have identified over 100 OA-associated loci, translating these findings into therapeutic targets remains challenging. To address this gap, we mapped gene expression, chromatin accessibility, and 3D chromatin structure in primary human articular chondrocytes in both resting and OA-mimicking conditions. We identified thousands of differentially expressed genes, including those associated with differences in sex and age. RNA sequencing in chondrocytes from 101 donors across two conditions uncovered 3,782 unique eGenes, including 420 that exhibited strong and significant condition-specific effects. Colocalization with OA GWAS signals revealed 13 putative OA risk genes, 6 of which have not been previously identified. Chromatin accessibility and 3D chromatin structure provided insights into the mechanisms and conditional specificity of these variants. Our findings shed light on OA pathogenesis and highlight potential targets for therapeutic development.

Osteoarthritis year in review 2024: Biology

Osteoarthritis (OA) research is a fast-growing and extremely wide field, in which a substantial increase in knowledge has been achieved over the last year. It covers many different topics, however, a PubMed search using the terms 'osteoarthritis' and 'biology' resulted in only a limited number of studies that were published between April 2023 and April 2024. In order to identify OA-relevant studies that focus on mechanistic studies of biological processes at the tissue, cellular, and molecular level, the following keywords were included as search terms: tissue interactions, single cell sequencing, transcriptomics, extracellular matrix, signaling, ion channels, and pain. The final selection of publications presented in this 'year in review' was influenced by the personal preferences of the authors, and eventually three larger key themes emerged: 1) Joint tissue interactions covering meniscus, subchondral bone, fat tissue, synovium, and synovial fluid. 2) Degeneration of the cartilage extracellular matrix and generation of bioactive fragments. 3) Receptors, ion channels, signaling pathways, and cellular metabolism. Many of the studies summarized here identified novel potential targets for OA treatment, and promising results were already obtained addressing these targets in different animal models. It will be exciting to see which findings can be translated into future clinical studies and eventually lead to novel treatment approaches for human OA.

Nordihydroguaiaretic acid microparticles are effective in the treatment of osteoarthritis

Several disease-modifying osteoarthritis (OA) drugs have emerged, but none have been approved for clinical use due to their systemic side effects, short half-life, and rapid clearance from the joints. Nordihydroguaiaretic acid (NDGA), a reactive oxygen species (ROS) scavenger and autophagy inducer, could be a potential treatment for OA. In this report, we show for the first time that sustained delivery of NDGA through polymeric microparticles maintains therapeutic concentrations of drug in the joint and ameliorates post-traumatic OA (PTOA) in a mouse model. In vitro treatment of oxidatively stressed primary chondrocytes from OA patients using NDGA-loaded poly(lactic-co-glycolic acid) (PLGA) microparticles (NDGA-MP) inhibited 15-lipoxygenase, induced autophagy, prevented chondrosenescence, and sustained matrix production. In vivo intra-articular delivery of NDGA-MP was non-toxic and had prolonged retention time (up to 35 days) in murine knee joints. Intra-articular therapy using NDGA-MP effectively reduced cartilage damage and reduced pain in the surgery-induced PTOA mouse model. Our studies open new avenues to modulate the immune environment and treat post-traumatic OA using ROS quenchers and autophagy inducers.

A novel small molecule screening assay using normal human chondrocytes toward osteoarthritis drug discovery

Osteoarthritis (OA) is the most common form of arthritis and a leading cause of pain and disability in adults. A central feature is progressive cartilage degradation and matrix fragment formation driven by the excessive production of matrix metalloproteinases (MMPs), such as MMP-13, by articular chondrocytes. Inflammatory factors, including interleukin 6 (IL-6), are secreted into the joint by synovial fibroblasts, and can contribute to pain and inflammation. No therapeutic exists that addresses the underlying loss of joint tissue in OA. To address this, we developed and utilized a cell-based high-throughput OA drug discovery platform using normal human chondrocytes treated with a recombinant fragment of the matrix protein fibronectin (FN-f) as a catabolic stimulus relevant to OA pathogenesis and a readout using a fluorescent MMP-13 responsive probe. The goal was to test this screening platform by identifying compounds that inhibited FN-f-induced MMP-13 production and determine if these compounds also inhibited catabolic signaling in OA chondrocytes and synovial fibroblasts. Two pilot screens of 1344 small molecules revealed five "hits" that strongly inhibited FN-f induced MMP-13 production with low cytotoxicity. These included RO-3306 (CDK1 inhibitor (i)), staurosporine (PKCi), trametinib (MEK1 and MEK2i), GSK-626616 (DYRK3i), and edicotinib (CSF-1Ri). Secondary testing using immunoblots and cells derived from OA joint tissues confirmed the ability of selected compounds to inhibit chondrocyte MMP-13 production and FN-f stimulated IL-6 production by synovial fibroblasts. These findings support the use of this high throughput screening assay for discovery of disease-modifying osteoarthritis drugs.

Response eQTLs, chromatin accessibility, and 3D chromatin structure in chondrocytes provide mechanistic insight into osteoarthritis risk

Osteoarthritis (OA) poses a significant healthcare burden with limited treatment options. While genome-wide association studies (GWAS) have identified over 100 OA-associated loci, translating these findings into therapeutic targets remains challenging. Integrating expression quantitative trait loci (eQTL), 3D chromatin structure, and other genomic approaches with OA GWAS data offers a promising approach to elucidate disease mechanisms; however, comprehensive eQTL maps in OA-relevant tissues and conditions remain scarce. We mapped gene expression, chromatin accessibility, and 3D chromatin structure in primary human articular chondrocytes in both resting and OA-mimicking conditions. We identified thousands of differentially expressed genes, including those associated with differences in sex and age. RNA-seq in chondrocytes from 101 donors across two conditions uncovered 3782 unique eGenes, including 420 that exhibited strong and significant condition-specific effects. Colocalization with OA GWAS signals revealed 13 putative OA risk genes, 10 of which have not been previously identified. Chromatin accessibility and 3D chromatin structure provided insights into the mechanisms and conditional specificity of these variants. Our findings shed light on OA pathogenesis and highlight potential targets for therapeutic development.

Integrin signalling in joint development, homeostasis and osteoarthritis

Integrins are key regulators of cell-matrix interactions during joint development and joint tissue homeostasis, as well as in the development of osteoarthritis (OA). The signalling cascades initiated by the interactions of integrins with a complex network of extracellular matrix (ECM) components and intracellular adaptor proteins orchestrate cellular responses necessary for maintaining joint tissue integrity. Dysregulated integrin signalling, triggered by matrix degradation products such as matrikines, disrupts this delicate balance, tipping the scales towards an environment conducive to OA pathogenesis. The interplay between integrin signalling and growth factor pathways further underscores the multifaceted nature of OA. Moreover, emerging insights into the role of endocytic trafficking in regulating integrin signalling add a new layer of complexity to the understanding of OA development. To harness the therapeutic potential of targeting integrins for mitigation of OA, comprehensive understanding of their molecular mechanisms across joint tissues is imperative. Ultimately, deciphering the complexities of integrin signalling will advance the ability to treat OA and alleviate its global burden.

Inactivation of a non-canonical gp130 signaling arm attenuates chronic systemic inflammation and multimorbidity induced by a high-fat diet

Interleukin-6 (IL-6) is a major pro-inflammatory cytokine for which the levels in plasma demonstrate a robust correlation with age and body mass index (BMI) as part of the senescence-associated secretory phenotype. IL-6 cytokines also play a crucial role in metabolic homeostasis and regenerative processes, primarily via the canonical STAT3 pathway. Thus, selective modulation of IL-6 signaling may offer a unique opportunity for therapeutic interventions. Recently, we discovered that a non-canonical signaling pathway downstream of tyrosine (Y) 814 within the intracellular domain of gp130, the IL-6 co-receptor, is responsible for the recruitment and activation of SRC family of kinases (SFK). Mice with constitutive genetic inactivation of gp130 Y814 (F814 mice) show accelerated resolution of inflammatory response and superior regenerative outcomes in skin wound healing and posttraumatic models of osteoarthritis. The current study was designed to explore if selective genetic or pharmacological inhibition of the non-canonical gp130-Y814/SFK signaling reduces systemic chronic inflammation and multimorbidity in a high-fat diet (HFD)-induced model of accelerated aging. F814 mice showed significantly reduced inflammatory response to HFD in adipose and liver tissue, with significantly reduced levels of systemic inflammation compared to wild type mice. F814 mice were also protected from HFD-induced bone loss and cartilage degeneration. Pharmacological inhibition of gp130-Y814/SFK in mice on HFD mirrored the effects observed in F814 mice on HFD; furthermore, this pharmacological treatment also demonstrated a marked increase in physical activity levels and protective effects against inflammation-associated suppression of neurogenesis in the brain tissue compared to the control group. These findings suggest that selective inhibition of SFK signaling downstream of gp130 receptor represents a promising strategy to alleviate systemic chronic inflammation. Increased degenerative changes and tissue senescence are inevitable in obese and aged organisms, but we demonstrated that the systemic response and inflammation-associated multi-morbidity can be therapeutically mitigated.

Songorine modulates macrophage polarization and metabolic reprogramming to alleviate inflammation in osteoarthritis

Introduction

Osteoarthritis (OA) is a prevalent joint disorder characterized by multifaceted pathogenesis, with macrophage dysregulation playing a critical role in perpetuating inflammation and joint degeneration.

Methods

This study focuses on Songorine, derived from Aconitum soongaricum Stapf, aiming to unravel its therapeutic mechanisms in OA. Comprehensive analyses, including PCR, Western blot, and immunofluorescence, were employed to evaluate Songorine's impact on the joint microenvironment and macrophage polarization. RNA-seq analysis was conducted to unravel its anti-inflammatory mechanisms in macrophages. Metabolic alterations were explored through extracellular acidification rate monitoring, molecular docking simulations, and PCR assays. Oxygen consumption rate measurements were used to assess mitochondrial oxidative phosphorylation, and Songorine's influence on macrophage oxidative stress was evaluated through gene expression and ROS assays.

Results

Songorine effectively shifted macrophage polarization from a pro-inflammatory M1 phenotype to an anti-inflammatory M2 phenotype. Notably, Songorine induced metabolic reprogramming, inhibiting glycolysis and promoting mitochondrial oxidative phosphorylation. This metabolic shift correlated with a reduction in macrophage oxidative stress, highlighting Songorine's potential as an oxidative stress inhibitor.

Discussion

In an in vivo rat model of OA, Songorine exhibited protective effects against cartilage damage and synovial inflammation, emphasizing its therapeutic potential. This comprehensive study elucidates Songorine's multifaceted impact on macrophage modulation, metabolic reprogramming, and the inflammatory microenvironment, providing a theoretical foundation for its therapeutic potential in OA.

Integrin-dependent recruitment of Src to ROS-producing endosomes in osteoarthritic cartilage

Fibronectin (FN) fragments stimulate catabolic signaling, and, by binding to integrins, they induce chondrocytes to increase the production of matrix metalloproteinases, including MMP-13. In this issue of Science Signaling, Miao et al. reveal that internalization of a FN fragment, but not intact FN, by α5β1 integrin results in the formation of ROS-producing endosomes (redoxosomes) through which chondrocytes detect and respond to damaged matrix by producing more MMP-13.