Putative functional variants of PI3K/AKT/mTOR pathway are associated with knee osteoarthritis susceptibility

Chrysin mitigated neuropathic pain and peripheral sensitization in knee osteoarthritis rats by repressing the RAGE/PI3K/AKT pathway regulated by HMGB1

BACKGROUND

Knee osteoarthritis (KOA) is a chronic progressive osteoarthropathy. Chrysin's anti-KOA action has been demonstrated, however more research is needed to understand how chrysin contributes to KOA.

METHODS

LPS/ATP-induced macrophages transfected with or without HMGB1 overexpression underwent 5 μg/mL chrysin. The cell viability and macrophage pyroptosis were examined by cell counting kit-8 and flow cytometer. In vivo experiments, rats were injected with 1 mg monosodium iodoacetate by the infrapatellar ligament of the bilateral knee joint to induce KOA. The histological damage was analyzed by Safranin O/Fast Green staining and hematoxylin and eosin staining. The PWT, PWL and inflammatory factors were analyzed via Von-Frey filaments, thermal radiometer and ELISA. Immunofluorescence assay examined the expressions of CGRP and iNOS. The levels of HMGB1/RAGE-, NLRP3-, PI3K/AKT- and neuronal ion channel-related markers were examined by qPCR and western blot.

RESULTS

Chrysin alleviated macrophage pyroptosis by inhibiting HMGB1 and the repression of chrysin on HMGB1/RAGE pathway and ion channel activation was reversed by overexpressed HMGB1. HMGB1 facilitated neuronal ion channel activation through the RAGE/PI3K/AKT pathway. Chrysin could improve the pathological injury of knee joints in KOA rats. Chrysin suppressed the HMGB1-regulated RAGE/PI3K/AKT pathway, hence reducing KOA damage and peripheral sensitization.

CONCLUSION

Chrysin mitigated neuropathic pain and peripheral sensitization in KOA rats by repressing the RAGE/PI3K/AKT pathway modulated by HMGB1.

Panax Notoginseng Saponins Regulate Angiogenic Cytokines Through the PI3K/AKT/mTOR Signaling Pathway to Promote Fracture Healing in Ovariectomized Rats

Osteoporotic fractures seriously affect the quality of life of the elderly. Panax notoginseng saponins (PNS) have the potential function of preventing osteoporosis. The Phosphatidylinositol 3-kinase (PI3K)/protein kinase (AKT)/mammalian target of rapamycin (mTOR) pathway is involved in the regulation of osteoporosis and has been proven to be related to VEGF secretion and angiogenesis. Therefore, this study aimed to explore the effects of PNS on ovariectomized rats with osteoporotic fracture through the PI3K/AKT/mTOR pathway and angiogenesis-related factors. Female Sprague-Dawley rats were randomly divided into normal control, fracture model, ovariectomized fracture model, low-dose PNS (100 mg/kg/d), and high-dose PNS (200 mg/kg/d). The ovariectomized rat fracture model was established. In low and high dose groups, PNS was administered intraperitoneally. The vascularization of fracture ends was detected in vitro by micro-CT on the 7th, 14th, and 21st day after modeling, and the area and number of blood vessels in the unit field of vision of the callus healing plane were seen by hematoxylin-eosin staining. The expression levels of PI3K, AKT1, mTOR, hypoxia inducible factor-1; VEGF: vascular endothelial growth factor (HIF-1), VEGF, Ang-1, VEGFR2, and angiopoietin like 2 Gene (ANGPTL2) were determined using Western blotting. In the PNS treatment group, the area of cortical bone increased, the area of callus decreased, and the number and area of blood vessels increased significantly when compared with the ovariectomized fracture model group. PNS regulates the PI3K/AKT/mTOR signaling pathway and promotes the expression of vascular-related cytokines (VEGF, Ang-1, VEGFR2, and ANGPTL2) in osteoporotic fractures. PNS may regulate the expression of vascular-related factors through the PI3K/AKT/mTOR pathway and promote the healing of osteoporotic fractures in ovariectomized rats.

Bioactive components and potential mechanisms of Biqi Capsule in the treatment of osteoarthritis: based on chondroprotective and anti-inflammatory activity

Cartilage damage and synovial inflammation are vital pathological changes in osteoarthritis (OA). Biqi Capsule, a traditional Chinese medicine formula used for the clinical treatment of arthritis in China, yields advantages in attenuating OA progression. The drawback here is that the bioactive components and pharmacological mechanisms by which Biqi Capsule exerts its anti-inflammatory and chondroprotective effects have yet to be fully clarified. For in vivo studies, a papain-induced OA rat model was established to explore the pharmacological effects and potential mechanisms of Biqi Capsule against OA. Biqi Capsule alleviated articular cartilage degeneration and chondrocyte damage in OA rats and inhibited the phosphorylation of NF-κB and the expression of pro-inflammatory cytokines in synovial tissue. Network pharmacology analysis suggested that the primary biological processes regulated by Biqi Capsule are inflammation and oxidative stress, and the critical pathway regulated is the PI3K/AKT signaling pathway. The result of this analysis was later verified on SW1353 cells. The in vitro studies demonstrated that Glycyrrhizic Acid and Liquiritin in Biqi Capsule attenuated H2O2-stimulated SW1353 chondrocyte damage via activation of PI3K/AKT/mTOR pathway. Moreover, Biqi Capsule alleviated inflammatory responses in LPS-stimulated RAW264.7 macrophages via the NF-κB/IL-6 pathway. These observations were suggested to have been facilitated by Brucine, Liquiritin, Salvianolic Acid B, Glycyrrhizic Acid, Cryptotanshinone, and Tanshinone ⅡA. Put together, this study partially clarifies the pharmacological mechanisms and the bioactive components of Biqi capsules against OA and suggests that it is a promising therapeutic option for the treatment of OA. Chemical compounds studied in this article. Strychnine (Pubchem CID:441071); Brucine (Pubchem CID:442021); Liquiritin (Pubchem CID:503737); Salvianolic Acid B (Pubchem CID:6451084); Glycyrrhizic Acid (Pubchem CID:14982); Cryptotanshinone (Pubchem CID:160254); Tanshinone ⅡA (Pubchem CID:164676).

Genome-wide DNA methylation study identifies significant epigenomic changes associated with internalized stigma in adults with non-specific chronic low back pain

Non-specific chronic low back pain (cLBP) represents a common musculoskeletal condition with no identifiable cause. It cannot be diagnosed with conventional neuroimaging techniques such as computerized tomography (CT). The diagnostic uncertainty that characterizes non-specific cLBP can lead to stigmatizing responses from others that can become internalized Among individuals with non-specific cLBP, internalized stigma is associated with greater pain intensity and disability. Yet, no study has examined the biological mechanism linking high internalized stigma to worse outcomes in individuals with non-specific cLBP. We aimed to identify differentially methylated loci (DML), enrichment pathways, and associated network interactions among individuals with non-specific cLBP experiencing low vs. high internalized stigma. We examined DNA methylation in whole blood samples from 48 adults, ages 19-85, using reduced representation bisulfite sequencing (RRBS). After controlling for age, sex, race, and multiple testing, differentially methylated loci (DML) differed in adults with low vs. high internalized stigma by at least 10% and q < 0.01 in 3,665 CpG sites: 2,280 hypomethylated and 1,385 hypermethylated. Gene ontology (GO) analyses of the annotated genes from these sites revealed significant enrichment of 274 biological processes, 29 cellular components, and 24 molecular functions (adjusted p < 0.05). The top enriched molecular functions regulate protein binding and DNA binding of transcription factor activity. Pathway analyses indicated that many functional genomic pathways, including Hippo Signaling, Melanogenesis, and Pathways in Cancer, were enriched with differentially methylated genes. Also, there was a significant interaction between relevance pathways such as P53, mTOR, PI3K-Akt, and Wnt signaling pathways. These pathways have previously been associated with neuroinflammation, neurodegeneration, and stress-related conditions. Thus, findings point to possible stress-induced DNAm changes as the link between high levels of internalized stigma and worse outcomes in adults with non-specific cLBP.

Exosomes Derived from M2 Macrophages Exert a Therapeutic Effect via Inhibition of the PI3K/AKT/mTOR Pathway in Rats with Knee Osteoarthritic

Macrophages are commonly classified as M1 macrophages or M2 macrophages. M2 macrophages are obtained by stimulation of IL-4 with anti-inflammatory and tissue repair effects. Exosomes are 30-150 nm lipid bilayer membrane vesicles derived from most living cells and have a variety of biological functions. Previous studies have shown that macrophage exosomes can influence the course of some autoimmune diseases, but their effect on knee osteoarthritis (KOA) has not been reported. Here, we analyze the roles of exosomes derived from M2 macrophage phenotypes in KOA rats. Exosomes were isolated from the supernatant of M2 macrophages and identified via transmission electron microscopy (TEM), Western blotting, and DLS. The results showed that M2 macrophage exosomes significantly attenuated the inflammatory response and pathological damage of articular cartilage in KOA rats. In addition, a key protein associated with KOA including Aggrecan, Col-10, SOX6, and Runx2 was significantly increased, while MMP-13 was significantly suppressed following treatment with M2 macrophage exosomes. The present study indicated that M2 macrophage exosomes exerted protective effects on KOA rats mainly mediated by the PI3K/AKT/mTOR signal pathway. These findings provide a novel approach for the treatment of KOA.

miR-7/EGFR/MEGF9 axis regulates cartilage degradation in osteoarthritis via PI3K/AKT/mTOR signaling pathway

Osteoarthritis (OA) is a common degenerative disease in middle-aged and elderly people. Our previous study has proved that microRNA-7 (miR-7) exacerbated the OA process. This study was aimed to explore the downstream genes and mechanism regulated by miR-7 to affect OA. Multiple EGF-like-domains 9 (MEGF9) was the predicted target of miR-7 by databases. Luciferase report experiment results confirmed that MEGF9 could bind to miR-7. Among the 10 collected pairs of OA and healthy samples, the expression levels of miR-7 and MEGF9 were both up-regulated when compared with healthy subjects by qRT-PCR and immunohistochemistry (IHC). The increased MEGF9 levels were due to the interaction with epidermal growth factor receptor (EGFR) by co-immunoprecipitation. Evaluations found that upregulation of miR-7 or MEGF9 can increase the expression of EGFR, matrix metalloproteinase-13 (MMP-13) and a disintegrin like and metallopeptidase with thrombospondin type 1 motif 5 (ADAMTS-5), so as to aggravate cartilage degradation. In addition, this effect induced by miR-7/EGFR/MEGF9 axis was by activation of PI3K/AKT signaling. The IHC and western blot assay results on OA model mice also demonstrated that miR-7/EGFR/MEGF9 axis regulated cartilage degradation in vivo. In summary, miR-7/EGFR/MEGF9 axis may perform a crucial function in the regulation of OA, providing potential for OA treatment.

Mechanism of Modified Danggui Sini Decoction for Knee Osteoarthritis Based on Network Pharmacology and Molecular Docking

Objective

This study aimed to explore the mechanism of Modified Danggui Sini Decoction in the treatment of knee osteoarthritis via a combination of network pharmacology and molecular docking.

Methods

The main chemical components and corresponding targets of Modified Danggui Sini Decoction were searched and screened in TCMSP database. The disease targets of knee osteoarthritis were summarized in GeneCards, OMIM, PharmGkb, TTD, and DrugBank databases. The visual interactive network of “drugs-active components-disease targets” was drawn by Cytoscape 3.8.1 software. The protein-protein interaction network was constructed by STRING database. Then, GO function and KEGG pathway enrichment were analyzed by Bioconductor/R, and the pathway of the highest degree of correlation with knee osteoarthritis was selected for specific analysis. Finally, molecular docking was used to screen and verify core genes by AutoDockTools software.

Results

Seventy-one main components of Modified Danggui Sini Decoction and 116 potential therapeutic targets of knee osteoarthritis were selected. The KEGG pathway and the GO function enrichment analysis showed that the targets of Modified Danggui Sini Decoction in the treatment of knee osteoarthritis were mainly concentrated on PI3K-Akt signaling pathway, TNF signaling pathway, IL-17 signaling pathway, apoptosis signaling pathway, Toll-like receptor signaling pathway, Th17 cell differentiation signaling pathway, HIF-1 signaling pathway, and NF-κB signaling pathway. It mainly involved inflammatory reaction, regulation of apoptotic signaling pathway, cellular response to regulation of inflammatory response, cellular response to oxidative stress, and other biological processes. The molecular docking results showed that ESR1-wogonin, MAPK1-quercetin, RELA-wogonin, RELA-baicalein, TP53-baicalein, TP53-quercetin, and RELA-quercetin have strong docking activities.

Conclusion

Modified Danggui Sini Decoction has the hierarchical network characteristics of “multicomponent, multitarget, multifunction, and multipathway” in the treatment of knee osteoarthritis. It mainly regulates the proliferation and apoptosis of chondrocytes by regulating the PI3K-Akt signaling pathway and establishes cross-talk with many downstream inflammatory-related pathways to reduce the overall inflammatory response. Meanwhile, HIF-1 expression was used to ensure the normal function and metabolism of knee joint under hypoxia condition, and the above processes play a key role in the treatment of knee osteoarthritis.

Pathogenesis of Osteoarthritis: Risk Factors, Regulatory Pathways in Chondrocytes, and Experimental Models

As the most common chronic degenerative joint disease, osteoarthritis (OA) is the leading cause of pain and physical disability, affecting millions of people worldwide. Mainly characterized by articular cartilage degradation, osteophyte formation, subchondral bone remodeling, and synovial inflammation, OA is a heterogeneous disease that impacts all component tissues of the articular joint organ. Pathological changes, and thus symptoms, vary from person to person, underscoring the critical need of personalized therapies. However, there has only been limited progress towards the prevention and treatment of OA, and there are no approved effective disease-modifying osteoarthritis drugs (DMOADs). Conventional treatments, including non-steroidal anti-inflammatory drugs (NSAIDs) and physical therapy, are still the major remedies to manage the symptoms until the need for total joint replacement. In this review, we provide an update of the known OA risk factors and relevant mechanisms of action. In addition, given that the lack of biologically relevant models to recapitulate human OA pathogenesis represents one of the major roadblocks in developing DMOADs, we discuss current in vivo and in vitro experimental OA models, with special emphasis on recent development and application potential of human cell-derived microphysiological tissue chip platforms.

Putative functional variants of PI3K/AKT/mTOR pathway are associated with knee osteoarthritis susceptibility

BACKGROUND

Osteoarthritis (OA) is a degenerative musculoskeletal disease which causes joint deformity and pain and finally leads to limb dysfunction. Knee osteoarthritis (KOA) has the highest incidence among all kinds of OA. Strong evidence leads to the understanding that P13K/AKT/mTOR signaling is very important in cartilage degeneration.

METHODS

This research sought to understand the association between genetic variation of PI3K/AKT/mTOR genes and KOA susceptibility among Chinese population. All the genetic variants of PI3K/AKT/mTOR pathway were graded and selected using RegulomeDB database, and then, an association study including 278 osteoarthritis patients and 289 controls was conducted.

RESULTS

Finally, eight SNPs' genotypes' distributions and susceptibility to KOA were presented. AKT1 rs2498789 was associated with KOA susceptibility in dominate genetic model (AA + GA vs GG) after adjusted for BMI, age, and gender: OR = 1.46, 95% CI: 1.03-2.05, P = .03. PIK3CA rs7646409 was also associated with KOA susceptibility (TC vs TT) after adjusted for BMI, age, and gender: OR = 0.58, 95% CI: 0.36-0.93, P = .02. PIK3CA rs7646409 (TC vs TT) with KOA risk was more significant in age < 60 group (P for heterogeneity was .03). Risk score showed significant association with KOA susceptibility after cumulative analysis (OR = 2.45, 95% CI: 1.35-4.45, P = .003).

CONCLUSIONS

This study shows that genetic variation of PI3K/AKT/mTOR is associated with KOA susceptibility in Chinese Han population, indicating that PI3K/AKT/mTOR is very important in KOA pathogenesis.