Mithramycin A Alleviates Osteoarthritic Cartilage Destruction by Inhibiting HIF-2α Expression

miR-204 ameliorates osteoarthritis pain by inhibiting SP1-LRP1 signaling and blocking neuro-cartilage interaction

Osteoarthritis (OA) is a painful degenerative joint disease and is the leading cause of chronic disability among elderly individuals. To improve the quality of life for patients with OA, the primary goal for OA treatment is to relieve the pain. During OA progression, nerve ingrowth was observed in synovial tissue and articular cartilage. These abnormal neonatal nerves act as nociceptors to detect OA pain signals. The molecular mechanisms for transmitting OA pain in the joint tissues to the central nerve system (CNS) is currently unknown. MicroRNA miR-204 has been demonstrated to maintain the homeostasis of joint tissues and have chondro-protective effect on OA pathogenesis. However, the role of miR-204 in OA pain has not been determined. In this study, we investigated interactions between chondrocytes and neural cells and evaluated the effect and mechanism of miR-204 delivered by exosome in the treatment of OA pain in an experimental OA mouse model. Our findings demonstrated that miR-204 could protect OA pain by inhibition of SP1- LDL Receptor Related Protein 1 (LRP1) signaling and blocking neuro-cartilage interaction in the joint. Our studies defined novel molecular targets for the treatment of OA pain.

Mechanism of HIFs in osteoarthritis

Osteoarthritis (OA) is a common disabling disease which has a high incidence rate in the elderly. Studies have found that many factors are involved in the pathogenesis of OA. Hypoxia-inducible factors (HIFs) are core regulators that induce hypoxia genes, repair the cellular oxygen environment, and play an important role in the treatment of OA. For example, HIF-1α can maintain the stability of the articular cartilage matrix, HIF-2α is able to cause chondrocyte apoptosis and intensify in-flammatory response, and HIF-3α may be the target gene of HIF-1α and HIF-2α, thereby playing a negative regulatory role. This review examines the mechanism of HIFs in cartilage extracellular matrix degradation, apoptosis, inflammatory reaction, autophagy and then further expounds on the roles of HIFs in OA, consequently providing theoretical support for the pathogenesis of OA and a new target for OA treatment.

Hypoxia-Inducible Factors Signaling in Osteogenesis and Skeletal Repair

Sufficient oxygen is required to maintain normal cellular and physiological function, such as a creature’s development, breeding, and homeostasis. Lately, some researchers have reported that both pathological hypoxia and environmental hypoxia might affect bone health. Adaptation to hypoxia is a pivotal cellular event in normal cell development and differentiation and in pathological settings such as ischemia. As central mediators of homeostasis, hypoxia-inducible transcription factors (HIFs) can allow cells to survive in a low-oxygen environment and are essential for the regulation of osteogenesis and skeletal repair. From this perspective, we summarized the role of HIF-1 and HIF-2 in signaling pathways implicated in bone development and skeletal repair and outlined the molecular mechanism of regulation of downstream growth factors and protein molecules such as VEGF, EPO, and so on. All of these present an opportunity for developing therapies for bone regeneration.

Inflammatory-Dependent Bidirectional Effect of Bile Acids on NLRP3 Inflammasome and Its Role in Ameliorating CPT-11-Induced Colitis

Irinotecan (CPT-11) in combination with 5-fluorouracil and leucovorin is a first-line chemotherapy regimen for the treatment of colorectal cancer; however, its clinical application is limited by the dose-limiting gastrointestinal toxicity of colitis. In our previous studies, several bile acids (BAs) were found significantly elevated in the colon of the CPT-11-induced rat colitis model. On the other hand, NLRP3 inflammasome has been reported to play important roles in mediating colitis. Interestingly, BA was stated to activate the NLRP3 inflammasome in some studies, while in some other reports, it showed an inhibitory effect. We assumed that the inflammatory status in different circumstances might have contributed to the controversial findings. In this study, we first discovered, under non-inflammatory conditions, that supplementing BA could activate the NLRP3 inflammasome in THP-1-differentiated macrophages and promote inflammation. In lipopolysaccharide (LPS)-induced inflammatory macrophages, however, BA inhibited the NLRP3 inflammasome and reduced inflammation. Further experiments demonstrated that Takeda G protein-coupled receptor 5 (TGR5) is essential in mediating the inhibitory effect of BA, while phospho-SP1 (p-SP1) is key to the activation. Furthermore, we applied the above findings to ameliorate CPT-11-caused colitis in rats by inhibiting SP1 with mithramycin A (MitA) or activating TGR5 using oleanolic acid (OA). Our findings may shed light on the discovery of effective interventions for reducing dose-limiting chemotherapy-induced colitis.

Cordyceps militaris as a Bio Functional Food Source: Pharmacological Potential, Anti-Inflammatory Actions and Related Molecular Mechanisms

Cordyceps militaris (C. militaris) is a medicinal mushroom possessing a variety of biofunctionalities. It has several biologically important components such as polysaccharides and others. The diverse pharmacological potential of C. militaris has generated interest in reviewing the current scientific literature, with a particular focus on prevention and associated molecular mechanisms in inflammatory diseases. Due to rising global demand, research on C. militaris has continued to increase in recent years. C. militaris has shown the potential for inhibiting inflammation-related events, both in in vivo and in vitro experiments. Inflammation is a multifaceted biological process that contributes to the development and severity of diseases, including cancer, colitis, and allergies. These functions make C. militaris a suitable functional food for inhibiting inflammatory responses such as the regulation of proinflammatory cytokines. Therefore, on the basis of existing information, the current study provides insights towards the understanding of anti-inflammatory activity-related mechanisms. This article presents a foundation for clinical use, and analyzes the roadmap for future studies concerning the medical use of C. militaris and its constituents in the next generation of anti-inflammatory drugs.

Intra-Articular Administration of Cramp into Mouse Knee Joint Exacerbates Experimental Osteoarthritis Progression

Osteoarthritis (OA) is the most common type of arthritis and is associated with wear and tear, aging, and inflammation. Previous studies revealed that several antimicrobial peptides are up-regulated in the knee synovium of patients with OA or rheumatoid arthritis. Here, we investigated the functional effects of cathelicidin-related antimicrobial peptide (Cramp) on OA pathogenesis. We found that Cramp is highly induced by IL-1β via the NF-κB signaling pathway in mouse primary chondrocytes. Elevated Cramp was also detected in the cartilage and synovium of mice suffering from OA cartilage destruction. The treatment of chondrocytes with Cramp stimulated the expression of catabolic factors, and the knockdown of Cramp by small interfering RNA reduced chondrocyte catabolism mediated by IL-1β. Moreover, intra-articular injection of Cramp into mouse knee joints at a low dose accelerated traumatic OA progression. At high doses, Cramp affected meniscal ossification and tears, leading to cartilage degeneration. These findings demonstrate that Cramp is associated with OA pathophysiology.

Antiosteoarthritic Effect of Morroniside in Chondrocyte Inflammation and Destabilization of Medial Meniscus-Induced Mouse Model

Osteoarthritis (OA) is a common degenerative disease that results in joint inflammation as well as pain and stiffness. A previous study has reported that Cornus officinalis (CO) extract inhibits oxidant activities and oxidative stress in RAW 264.7 cells. In the present study, we isolated bioactive compound(s) by fractionating the CO extract to elucidate its antiosteoarthritic effects. A single bioactive component, morroniside, was identified as a potential candidate. The CO extract and morroniside exhibited antiosteoarthritic effects by downregulating factors associated with cartilage degradation, including cyclooxygenase-2 (Cox-2), matrix metalloproteinase 3 (Mmp-3), and matrix metalloproteinase 13 (Mmp-13), in interleukin-1 beta (IL-1β)-induced chondrocytes. Furthermore, morroniside prevented prostaglandin E2 (PGE2) and collagenase secretion in IL-1β-induced chondrocytes. In the destabilization of the medial meniscus (DMM)-induced mouse osteoarthritic model, morroniside administration attenuated cartilage destruction by decreasing expression of inflammatory mediators, such as Cox-2, Mmp3, and Mmp13, in the articular cartilage. Transverse microcomputed tomography analysis revealed that morroniside reduced DMM-induced sclerosis in the subchondral bone plate. These findings suggest that morroniside may be a potential protective bioactive compound against OA pathogenesis.

Chemically modified curcumin (CMC2.24) alleviates osteoarthritis progression by restoring cartilage homeostasis and inhibiting chondrocyte apoptosis via the NF-κB/HIF-2α axis

The disorders of cartilage homeostasis and chondrocyte apoptosis are major events in the pathogenesis of osteoarthritis (OA). Herein, we aim to assess the chondroprotective effect and underlying mechanisms of a novel chemically modified curcumin, CMC2.24, in modulating extracellular matrix (ECM) homeostasis and inhibiting chondrocyte apoptosis. Rats underwent the anterior cruciate ligament transection, and medial menisci resection was treated by intra-articular injection with CMC2.24. In an in vitro study, rat chondrocytes were pretreated with CMC2.24 before stimulation with sodium nitroprusside (SNP). Results from in vivo studies demonstrated that the intra-articular administration of CMC2.24 ameliorated osteoarthritic cartilage destruction by promoting collagen 2a1 production and inhibited cartilage degradation and apoptosis by suppressing hypoxia-inducible factor-2a (Hif-2α), matrix metalloproteinase-3, runt-related transcription factor 2, cleaved caspase-3, and vascular endothelial growth factor and the phosphorylation of IκBα and NF-κB p65. The in vitro results revealed that CMC2.24 exhibited a strong inhibitory effect on SNP-induced chondrocyte catabolism and apoptosis. The SNP-enhanced expression of Hif-2α, a catabolic and apoptotic factor, decreased in a dose-dependent manner after CMC2.24 treatment. CMC2.24 pretreatment effectively inhibited SNP-induced IκBα and NF-κB p65 phosphorylation in rat chondrocytes, whereas pretreatment with the NF-κB antagonist BMS-345541 significantly enhanced the effects of CMC2.24. Overall, these results demonstrated that CMC2.24 attenuates OA progression by modulating ECM homeostasis and chondrocyte apoptosis by suppressing the NF-κB/Hif-2α axis, thus providing a new perspective for therapeutic strategies in OA. KEY MESSAGES: • Intra-articular injection of CMC2.24 ameliorated osteoarthritic cartilage destruction. • CMC2.24 promoted cell viability and decreased SNP-induced apoptotic gene expression. • SNP-induced activation of Hif-2α is inhibited by CMC2.24. • CMC2.24 inhibits NF-κB/Hif-2α axis activation to modulate ECM homeostasis and inhibit chondrocyte apoptosis.

NF-κB Signaling Pathways in Osteoarthritic Cartilage Destruction

Osteoarthritis (OA) is a type of joint disease associated with wear and tear, inflammation, and aging. Mechanical stress along with synovial inflammation promotes the degradation of the extracellular matrix in the cartilage, leading to the breakdown of joint cartilage. The nuclear factor-kappaB (NF-κB) transcription factor has long been recognized as a disease-contributing factor and, thus, has become a therapeutic target for OA. Because NF-κB is a versatile and multi-functional transcription factor involved in various biological processes, a comprehensive understanding of the functions or regulation of NF-κB in the OA pathology will aid in the development of targeted therapeutic strategies to protect the cartilage from OA damage and reduce the risk of potential side-effects. In this review, we discuss the roles of NF-κB in OA chondrocytes and related signaling pathways, including recent findings, to better understand pathological cartilage remodeling and provide potential therapeutic targets that can interfere with NF-κB signaling for OA treatment.