Glucosamine promotes chondrocyte proliferation via the Wnt/β‑catenin signaling pathway

O-GlcNAcylation: roles and potential therapeutic target for bone pathophysiology

O-linked N-acetylglucosamine (O-GlcNAc) protein modification (O-GlcNAcylation) is a critical post-translational modification (PTM) of cytoplasmic and nuclear proteins. O-GlcNAcylation levels are regulated by the activity of two enzymes, O-GlcNAc transferase (OGT) and O‑GlcNAcase (OGA). While OGT attaches O-GlcNAc to proteins, OGA removes O-GlcNAc from proteins. Since its discovery, researchers have demonstrated O-GlcNAcylation on thousands of proteins implicated in numerous different biological processes. Moreover, dysregulation of O-GlcNAcylation has been associated with several pathologies, including cancers, ischemia-reperfusion injury, and neurodegenerative diseases. In this review, we focus on progress in our understanding of the role of O-GlcNAcylation in bone pathophysiology, and we discuss the potential molecular mechanisms of O-GlcNAcylation modulation of bone-related diseases. In addition, we explore significant advances in the identification of O-GlcNAcylation-related regulators as potential therapeutic targets, providing novel therapeutic strategies for the treatment of bone-related disorders.

Bauhinia championii alleviates extracellular matrix degradation in IL-1β induced chondrocytes via miRNA-145-5p/TLR4/NF-κB axis

Bauhinia championii is a herbal medicine used to treat osteoarthritis (OA) in Chinese traditional medicine. However, the molecular mechanisms underlying the therapeutic effects of this medicinal herb against OA have rarely been reported. Given that it has been established that extracellular matrix metabolism plays an important role in the pathogenesis of OA, the present study focused on the effects and mechanisms of Bauhinia championii in the regulation of extracellular matrix metabolism in chondrocytes induced by IL-1β. Rat chondrocytes were isolated, cultured and identified in vitro. The CCK-8 method was used to detect the cell viability of Bauhinia championii aqueous extract (BCAE)-treated chondrocytes. The chondrocyte inflammatory and degeneration models were induced by 10 ng/mL IL-1β, then chondrocytes were grouped into different groups to evaluate the effect of BCAE on extracellular matrix degradation and the regulation of TLR4/NF-κB signaling pathway. Furthermore, whether the regulatory effect of BCAE on TLR4/NF-κB signaling pathway is related to miRNA-145-5p was also investigated by cell transfection. We found that BCAE promoted chondrocyte viability in a dose- and time-dependent manner. BCAE delayed chondrocyte degeneration induced by IL-1β. BCAE could reduce the degradation of the cartilage extracellular matrix by inhibiting the TLR4/NF-κB signaling pathway. miRNA-145-5p negatively regulated the expression of TLR4 in chondrocytes, while BCAE could upregulate the expression of miRNA-145-5p in chondrocytes induced by IL-1β. These results suggest that BCAE upregulates the expression of miRNA-145-5p to inhibit the TLR4/NF-κB signaling pathway, thereby alleviating the metabolic imbalance of the extracellular matrix and protecting chondrocytes from degeneration.

Small-molecule amines: a big role in the regulation of bone homeostasis

Numerous small-molecule amines (SMAs) play critical roles in maintaining bone homeostasis and promoting bone regeneration regardless of whether they are applied as drugs or biomaterials. On the one hand, SMAs promote bone formation or inhibit bone resorption through the regulation of key molecular signaling pathways in osteoblasts/osteoclasts; on the other hand, owing to their alkaline properties as well as their antioxidant and anti-inflammatory features, most SMAs create a favorable microenvironment for bone homeostasis. However, due to a lack of information on their structure/bioactivity and underlying mechanisms of action, certain SMAs cannot be developed into drugs or biomaterials for bone disease treatment. In this review, we thoroughly summarize the current understanding of SMA effects on bone homeostasis, including descriptions of their classifications, biochemical features, recent research advances in bone biology and related regulatory mechanisms in bone regeneration. In addition, we discuss the challenges and prospects of SMA translational research.

Metabolic Glycoengineering: A Promising Strategy to Remodel Microenvironments for Regenerative Therapy

Cell-based regenerative therapy utilizes the differentiation potential of stem cells to rejuvenate tissues. But the dynamic fate of stem cells is calling for precise control to optimize their therapeutic efficiency. Stem cell fate is regulated by specific conditions called "microenvironments." Among the various factors in the microenvironment, the cell-surface glycan acts as a mediator of cell-matrix and cell-cell interactions and manipulates the behavior of cells. Herein, metabolic glycoengineering (MGE) is an easy but powerful technology for remodeling the structure of glycan. By presenting unnatural glycans on the surface, MGE provides us an opportunity to reshape the microenvironment and evoke desired cellular responses. In this review, we firstly focused on the determining role of glycans on cellular activity; then, we introduced how MGE influences glycosylation and subsequently affects cell fate; at last, we outlined the application of MGE in regenerative therapy, especially in the musculoskeletal system, and the future direction of MGE is discussed.

Unraveling the role of natural functional oils in modulating osteoarthritis related complications

Osteoarthritis (OA) is a common joint disease and has been studied extensively in recent years as no promising therapy available so far for its treatment and remains a great challenge for health care specialists. Although the identification of some major mechanisms that contribute to this disease suggests a plethora of bioactive agents in tackling the associated complications yet OA's pathophysiology is still poorly understood owing to complex mechanistic changes observed. Experimental research is now exploring a wide range of therapeutically effective agents in an effort to find a way to repair OA-related joint degeneration and halt it from getting worse. Data was acquired and reviewed from most relevant and recent studies. This review summarizes the studies that are currently available and focuses on how various unconventional functional oils affect osteoarthritis and the affected joint tissues. An analysis of the recent scientific literature allowed us to highlight the potential anti-arthritic properties of edible oils and their main constituents, which seems to suggest an interesting new potential therapeutic application. Due to eccentric nature of OA, it is necessary to concentrate initially on the management of symptoms. The evidence supporting functional oils chondroprotective potential is still accumulating, underpinning a global need for more sustainable natural sources of treatment. More clinical research that focuses on the consequences of long-term treatment, possible negative effects, and epigenetic implications is necessary to get optimistic results. However, different animal or clinical studies suggest that linolenic and linoleic fatty acids decreased chondrocyte oxidative stress, cartilage breakdown, and expression of inflammatory markers. Distinct fatty acids along with minor components of oils also reduced the generation of prostaglandins and decreased oxidative stress. Furthermore, the potential roles of the main components of edible oils and possible negative results (if any) are also reported. While no severe side effects have been reported for any edible oils. Overall, these studies identify and support the use of functional oils as an adjuvant therapy for the management of OA and as a means of symptomatic alleviation for OA patients. However, to prove the effectiveness or to draw precise conclusions, high-quality clinical trials are required.

Effects of Stress on Osteoblast Proliferation and Differentiation Based on Endoplasmic Reticulum Stress and Wntβ-Catenin Signaling Pathway

In order to investigate the effect of fluid shear stress on the proliferation of osteoblasts and the regulatory role of the Wnt/β-catenin signaling pathway in cell proliferation, a new method based on endoplasmic reticulum stress and Wnt/β-catenin signaling pathway stress-mediated was proposed. Taking MG63 osteoblasts as the research object, they were inoculated on glass slides (G group), polished titanium sheets (P group), and sandblasted acid-base treated pure titanium sheets (S group). In addition, FSS of 0 dunes/cm2 (static group) and 12 dunes/cm2 (stress group) were given, respectively. Then, quantitative reverse transcription-PCR (RT-qPCR) and western blot were used to detect the mRNA and protein expressions of low-density lipoprotein receptor-related protein 5 (LRP5) and β-catenin in MG63 cells. The results showed that the expression levels of β-catenin mRNA and protein in cells in the stress group were significantly increased (P < 0.05), and the protein expression level of LRP5 was significantly decreased (P < 0.05). The expression level of LRP5 in group S was greatly inhibited, while the expression level of β-catenin was significantly upregulated. Therefore, FSS can stimulate the expression of LRP5 and β-catenin in osteoblasts. Fluid shear stress can promote osteoblast proliferation in vitro; the Wnt/β-catenin signaling pathway is involved in regulating fluid shear stress to promote osteoblast proliferation.

Chondroitin Sulfate Enhances Proliferation and Migration via Inducing β-Catenin and Intracellular ROS as Well as Suppressing Metalloproteinases through Akt/NF-κB Pathway Inhibition in Human Chondrocytes

BACKGROUND

Chondroitin sulfate (CS) is found in humans' cartilage, bone, cornea, skin, and arterial wall. It consists of the foundation substance in the extracellular matrix (ECM) of connective tissue. The oral supplement form of CS is clinically used in treating osteoarthritis (OA).

METHODS

Cell migration was observed by the transwell assay. The EMT, Akt/IKK/IκB pathways, TIMPs, collagen and MMPs in cell lysate were determined by Western blotting. The expression of MMP activity was determined by gelatin zymography. The production of reactive oxygen species (ROS) was determined by using a fluorescence spectrophotometer.

RESULTS

In the current report, we demonstrated that CS can increase the cell proliferation and migration of chon-001 chondrocytes. Treatment with CS induced the epithelial-mesenchymal transition and increased the expression of type II collagen and TIMP-1/TIMP2 and inhibited the expressions and activities of metalloproteinase-9 (MMP-9) and metalloproteinase-2 (MMP-2). The phosphorylation of Akt, IκB kinase (IKK), IκB and p65 was decreased by CS. CS treatment resulted in β-catenin production and XAV939, a β-catenin inhibitor, and inhibited the cell proliferation by CS treatment. In addition, also significantly induced intracellular ROS generation. Treatment with antioxidant propyl gallate blocked cell migration induced by CS.

CONCLUSION

We demonstrated that CS induced cell proliferation and migration of chondrocytes by inducing β-catenin and enhancing ROS production. Moreover, our studies demonstrated that CS can increase the activity of chondrocytes and help patients with osteoarthritis to restore cartilage function.

Regulatory effect between HMGA2 and the Wnt/β-catenin signaling pathway in the carcinogenesis of sporadic colorectal tubular adenoma

Due to the high incidence of colorectal cancer worldwide, the underlying molecular mechanisms have been extensively investigated. The Wnt/β-catenin signaling pathway plays a key role in the carcinogenesis of colorectal adenoma. In addition, the high mobility group AT-hook 2 (HMGA2) protein, which is involved in several biological processes, such as proliferation, differentiation, transformation and metastasis, is expressed at significantly high levels in colorectal cancer tissues compared with adjacent normal tissues. Currently, the role of HMGA2 in the carcinogenesis of sporadic colorectal tubular adenoma remains unclear. The downstream Wnt/β-catenin signaling molecule, T-cell factor/lymphoid enhancing factor (TCF/LEF), shares a similar domain with HMGA2, which enhances β-catenin transcriptional activity and TCF/LEF binding. Thus, the present study investigated the association between HMGA2 and the Wnt/β-catenin signaling pathway, and their role in the carcinogenesis of sporadic colorectal tubular adenoma via immunohistochemistry, siRNA, quantitative PCR and western blot analyses. The results demonstrated that the positive rate of HMGA2 expression gradually increased during tumor progression. Furthermore, HMGA2 expression was positively correlated with Wnt/β-catenin signaling protein expression [Wnt, β-catenin, cyclin-dependent kinase 4 (CDK4) and cyclin D1], suggesting its involvement in the carcinogenesis of sporadic colorectal tubular adenoma and its potential to synergistically interact with the Wnt/β-catenin signaling pathway. HMGA2 knockdown in the human colorectal cancer cell line, HCT 116 decreased β-catenin expression and its downstream targets, CDK4 and cyclin D1. Furthermore, silencing of Wnt or β-catenin decreased HMGA2 expression. Taken together, the results of the present study suggest the coordinated regulation of HMGA2 and the Wnt/β-catenin signaling pathway in the carcinogenesis of sporadic colorectal tubular adenoma.

A Combination of Celecoxib and Glucosamine Sulfate Has Anti-Inflammatory and Chondroprotective Effects: Results from an In Vitro Study on Human Osteoarthritic Chondrocytes

This study investigated the possible anti-inflammatory and chondroprotective effects of a combination of celecoxib and prescription-grade glucosamine sulfate (GS) in human osteoarthritic (OA) chondrocytes and their possible mechanism of action. Chondrocytes were treated with celecoxib (1.85 µM) and GS (9 µM), alone or in combination with IL-1β (10 ng/mL) and a specific nuclear factor (NF)-κB inhibitor (BAY-11-7082, 1 µM). Gene expression and release of some pro-inflammatory mediators, metalloproteinases (MMPs), and type II collagen (Col2a1) were evaluated by qRT-PCR and ELISA; apoptosis and mitochondrial superoxide anion production were assessed by cytometry; B-cell lymphoma (BCL)2, antioxidant enzymes, and p50 and p65 NF-κB subunits were analyzed by qRT-PCR. Celecoxib and GS alone or co-incubated with IL-1β significantly reduced expression and release of cyclooxygenase (COX)-2, prostaglandin (PG)E2, IL-1β, IL-6, tumor necrosis factor (TNF)-α, and MMPs, while it increased Col2a1, compared to baseline or IL-1β. Both drugs reduced apoptosis and superoxide production; reduced the expression of superoxide dismutase, catalase, and nuclear factor erythroid; increased BCL2; and limited p50 and p65. Celecoxib and GS combination demonstrated an increased inhibitory effect on IL-1β than that observed by each single treatment. Drugs effects were potentiated by pre-incubation with BAY-11-7082. Our results demonstrated the synergistic effect of celecoxib and GS on OA chondrocyte metabolism, apoptosis, and oxidative stress through the modulation of the NF-κB pathway, supporting their combined use for the treatment of OA.

The Hexosamine Biosynthetic Pathway as a Therapeutic Target after Cartilage Trauma: Modification of Chondrocyte Survival and Metabolism by Glucosamine Derivatives and PUGNAc in an Ex Vivo Model

The hexosamine biosynthetic pathway (HBP) is essential for the production of uridine diphosphate N-acetylglucosamine (UDP-GlcNAc), the building block of glycosaminoglycans, thus playing a crucial role in cartilage anabolism. Although O-GlcNAcylation represents a protective regulatory mechanism in cellular processes, it has been associated with degenerative diseases, including osteoarthritis (OA). The present study focuses on HBP-related processes as potential therapeutic targets after cartilage trauma. Human cartilage explants were traumatized and treated with GlcNAc or glucosamine sulfate (GS); PUGNAc, an inhibitor of O-GlcNAcase; or azaserine (AZA), an inhibitor of GFAT-1. After 7 days, cell viability and gene expression analysis of anabolic and catabolic markers, as well as HBP-related enzymes, were performed. Moreover, expression of catabolic enzymes and type II collagen (COL2) biosynthesis were determined. Proteoglycan content was assessed after 14 days. Cartilage trauma led to a dysbalanced expression of different HBP-related enzymes, comparable to the situation in highly degenerated tissue. While GlcNAc and PUGNAc resulted in significant cell protection after trauma, only PUGNAc increased COL2 biosynthesis. Moreover, PUGNAc and both glucosamine derivatives had anti-catabolic effects. In contrast, AZA increased catabolic processes. Overall, “fueling” the HBP by means of glucosamine derivatives or inhibition of deglycosylation turned out as cells and chondroprotectives after cartilage trauma.

Role of Physical Exercise and Nutraceuticals in Modulating Molecular Pathways of Osteoarthritis

Osteoarthritis (OA) is a painful and disabling disease that affects millions of patients. Its etiology is largely unknown, but it is most likely multifactorial. OA pathogenesis involves the catabolism of the cartilage extracellular matrix and is supported by inflammatory and oxidative signaling pathways and marked epigenetic changes. To delay OA progression, a wide range of exercise programs and naturally derived compounds have been suggested. This literature review aims to analyze the main signaling pathways and the evidence about the synergistic effects of these two interventions to counter OA. The converging nutrigenomic and physiogenomic intervention could slow down and reduce the complex pathological features of OA. This review provides a comprehensive picture of a possible signaling approach for targeting OA molecular pathways, initiation, and progression.