Exerkines and osteoarthritis.

Osteoarthritis (OA) is the most prevalent chronic joint disease, with physical exercise being a widely endorsed strategy in its management guidelines. Exerkines, defined as cytokines secreted in response to acute and chronic exercise, function through endocrine, paracrine, and/or autocrine pathways. Various tissue-specific exerkines, encompassing exercise-induced myokines (muscle), cardiokines (heart), and adipokines (adipose tissue), have been linked to exercise therapy in OA. Exerkines are derived from these kines, but unlike them, only kines regulated by exercise can be called exerkines. Some of these exerkines serve a therapeutic role in OA, such as irisin, metrnl, lactate, secreted frizzled-related protein (SFRP), neuregulin, and adiponectin. While others may exacerbate the condition, such as IL-6, IL-7, IL-15, IL-33, myostatin, fractalkine, follistatin-like 1 (FSTL1), visfatin, activin A, migration inhibitory factor (MIF), apelin and growth differentiation factor (GDF)-15. They exerts anti-/pro-apoptosis/pyroptosis/inflammation, chondrogenic differentiation and cell senescence effect in chondrocyte, synoviocyte and mesenchymal stem cell. The modulation of adipokine effects on diverse cell types within the intra-articular joint emerges as a promising avenue for future OA interventions. This paper reviews recent findings that underscore the significant role of tissue-specific exerkines in OA, delving into the underlying cellular and molecular mechanisms involved.

Mechanical stress protects against chondrocyte pyroptosis through TGF-ß1-mediated activation of Smad2/3 and inhibition of the NF-κB signaling pathway in an osteoarthritis model.

Osteoarthritis (OA) is a degenerative disease that is difficult to cure owing to its complicated pathogenesis. Exercise therapy has been endorsed as a primary treatment option. However, it remains controversial how exercise intensity regulates OA progression. Here, a declining propensity for TGF-ß1 was predicted via bioinformatics analysis of microarray GSE57218 and validated in cartilage samples obtained from arthroplasty. Based on this, cyclic tensile strain or TGF-ß1 intervention was performed on human OA chondrocytes, and we found that moderate-intensity mechanical loads protected chondrocytes against pyroptosis. During this process, the elevation of TGF-ß1 is mechanically stimuli-dependent and exerts an inhibitory effect on chondrocyte pyroptosis. Moreover, we elucidated that TGF-ß1 activated Smad2/3 and inhibited the NF-κB signaling pathway to suppress chondrocyte pyroptosis. Furthermore, we established a rat knee OA model by intra-articular injection of monosodium iodoacetate and performed treadmill exercises of different intensities. Similar to the in vitro results, we demonstrated that moderate-intensity treadmill exercise had an outstanding chondroprotective effect. An inappropriate intensity of mechanical stimulation may aggravate OA both in vivo and in vitro. Overall, our findings demonstrated that activation of the TGF-ß1/Smad2/Smad3 axis and inhibition of NF-κB coordinately inhibit chondrocyte pyroptosis under mechanical loads. This study sheds light on the future development of safe and effective exercise therapies for OA.

Exercise induced meteorin-like protects chondrocytes against inflammation and pyroptosis in osteoarthritis by inhibiting PI3K/Akt/NF-κB and NLRP3/caspase-1/GSDMD signaling.

The production of metrnl, a novel adipomyokine, is induced upon exercise in adipose tissue and skeletal muscle. In this study, we investigated the anti-inflammatory and antipyroptotic effects of exercise-induced metrnl producted in rats in vitro and in vivo. Forty Sprague-Dawley rats were divided randomly into five groups: control (CG), osteoarthritis (OA) with sedentary lifestyle (OAG), OA with low intensity exercise (OAL), OA with moderate intensity exercise (OAM), and OA with high intensity exercise (OAH). The correlation between the level of metrnl and OA degree was detected using ELISA, X-ray imaging, histology, and immunohistochemistry in vivo. Primary chondrocytes were preincubated with recombinant metrnl before interleukin-1ß administration to verify the anti-inflammatory and antipyroptotic effects of metrnl. Western blotting and quantitative reverse transcription (qRT)-PCR were used to evaluate the differences in protein and mRNA expression between groups, respectively. Reactive oxygen species (ROS) assay, immunofluorescence, transmission electron microscopy (TEM), and flow cytometry were used to evaluate morphological changes and pyroptosis in chondrocytes. In the moderate-intensity treadmill exercise group, the severity of OA showed maximum relief and the metrnl levels had the most significant increase. Metrnl exerted its anti-inflammatory effect through the suppression of the PI3K/Akt/NF-κB pathway in IL-1ß-induced OA chondrocytes, which was accompanied with the recovery of collagen II expression and the attenuation of MMP13 and ADAMTS5. Moreover, metrnl ameliorated chondrocyte pyroptosis by inhibiting the activation of the nod-like receptor protein-3/caspase-1/gasdermin D cascade. In conclusion, moderate-intensity exercise improves inflammation and pyroptosis by increasing metrnl release, which inhibits the PI3K/Akt/NF-κB and further NLRP3/caspase-1/GSDMD signaling pathways.

Senomorphic agent pterostilbene ameliorates osteoarthritis through the PI3K/AKT/NF-κB axis: an in vitro and in vivo study.

OBJECTIVES: Osteoarthritis (OA) is the most common joint disease in the world. Among the many risk factors for OA, aging is one of the most critical factors. The treatment with senop-associated secretory phenotype (SASP) is one of the important, promising anti-aging strategies at present. Pterostilbene (PTE) is a trans-stilbene compound with anti-tumor, anti-oxidation, anti-inflammatory, and anti-aging pharmacologic activities. The purpose of this study is to explore the therapeutic effects of PTE on articular chondrocyte senescence and OA and its related mechanisms. METHODS: Male Sprague-Dawley rats were operated on with transection of the anterior cruciate ligament (ACLT) and a destabilized medial meniscus (DMM) surgery to establish the OA model and then injected intraperitoneally with PTE (20 mg/kg) for 5 weeks. Finally, rats were sacrificed and knee joints were collected for histologic analysis. Rat chondrocytes were stimulated with interleukin-1ß (IL-1ß) with or without PTE treatment. The therapeutic effects of PTE and related mechanisms were investigated by examining and analyzing relative markers through senescence-associated ß-galactosidase (SA-ß-Gal) assay, cell cycle, qRT-PCR, western blot, bioinformatic analysis, immunofluorescence, and molecular modeling. RESULTS: With in vivo experiments, PTE can significantly reduce the Mankin scores and OARSI scores of the knee joint in ACLT+DMM OA model rats and reduce the interleukin-6 (IL-6) level in the knee lavage fluid. Immunohistochemical staining showed that compared to the OA group, the PTE treatment group had significantly increased expression of collagen type II in articular cartilage, and significantly decreased matrix metalloproteinase 13 (MMP-13) and IL-6, the main SASP proteins, and had expression of p16 and p21, markers of aging in chondrocytes. In vitro, PTE reduced the ratio of SA-ß-Gal positive chondrocytes and G0-G1 phase chondrocytes in IL-1ß-induced rat chondrocytes. PTE significantly inhibited the expression of MMP-13, IL-6, thrombospondin motif 5 (ADAMTS5), p16, and p21, and significantly increased the expression of collagen type II. Bioassay and subsequent western blot showed that PTE significantly inhibited the activation of PI3K/AKT and NF-κB signaling pathways. The results of molecular docking experiments showed that PTE could bind closely to the sites of PI3K protein, thereby inhibiting the phosphorylation of PI3K. CONCLUSIONS: The experimental results indicate that PTE plays an anti-chondrocyte senescence role in the treatment of OA by inhibiting the PI3K/AKT/NF-κB signaling pathway and reducing expression of SASP.

Mechanical stress protects against chondrocyte pyroptosis through lipoxin A4 via synovial macrophage M2 subtype polarization in an osteoarthritis model.

Our previous study found that lipoxin A4 (LXA4) exerts therapeutic effects on osteoarthritis (OA). In this study, we evaluated the effects of LXA4 via synovial macrophage M1/M2 subtype polarization on chondrocyte pyroptosis and corresponding mechanisms during mechanical stimulation. Synovial macrophages were subjected to various LXA4 concentrations and cyclic tensile strain (CTS) conditions to determine optimal co-culture conditions. The effects of LXA4 on chondrocyte pyroptosis, as represented by macrophage M1/M2 subtype polarization, were detected by western blot, immunofluorescence, and flow cytometry analyses. Forty male Sprague-Dawley rats were randomly divided into four groups (n = 10): control (CG), OA (OAG), OA with moderate-intensity treadmill exercise (OAE), and OAE + BOC-2 (an LXA4 antagonist). All rats were evaluated using histology, enzyme-linked immunosorbent assay, quantitative real-time polymerase chain reaction, and western blot analyses. We found that with increasing Kellgren-Lawrence grade, LXA4 expression was downregulated in articular fluid and that CD86 and Arg1 expression was upregulated in the synovium of patients. In vitro, CTS and LXA4 both promoted M2 subtype polarization of synovial macrophages, which inhibited the nuclear translocation of NF-κB p65 and formation of NLRP3 in chondrocytes. In vivo, the OAE treatment exerted protective effects on articular cartilage and facilitated M2 polarization of synovial macrophages. These effects were suppressed by BOC-2 treatment. We concluded that moderate CTS enhances therapeutic effects of LXA4 by inhibiting the nuclear translocation of NF-κB p65 and NLRP3. Furthermore, the therapeutic effects of LXA4 during treadmill exercise in monoiodoacetate-induced OA were driven by promotion of synovial macrophage M2 subtype polarization.

Mechanical Stimulation Protects Against Chondrocyte Pyroptosis Through Irisin-Induced Suppression of PI3K/Akt/NF-κB Signal Pathway in Osteoarthritis.

Irisin, a myokine secreted by muscle during physical exercise, is known to have biological activities in different cell types. Chondrocyte inflammation and pyroptosis have been shown to play important roles in osteoarthritis (OA). In this study, we investigated the effects of exercise-induced irisin during different intensities of treadmill exercise in a rat OA model and the anti-inflammatory and antipyroptosis mechanism of irisin in OA chondrocytes. Forty-eight SD rats (n = 8) were randomly assigned to control (CG), OA (OAG), OA groups under different intensities of treadmill exercise (OAL, OAM, and OAH), OAM + irisin neutralizing antibodies group (OAM + irisin (NA)). The levels of irisin and the severity of OA between groups were detected using ELISA, histology, immunohistochemistry, X-ray and computed tomography and magnetic resonance imaging. The anti-inflammatory and antipyroptosis mechanisms of irisin were investigated in vitro in OA chondrocytes preincubated with recombinant irisin (0, 5, or 10 ng/ml) for 1 h before treatment with interleukin-1ß (IL-1ß) for 24 h mRNA and protein expression levels were determined using quantitative reverse transcription polymerase chain reaction, and western blot analyses. Morphological changes and cell death associated with pyroptosis were examined using transmission electron microscopy, flow cytometry and immunofluorescence. Moderate-intensity treadmill exercise increased the levels of irisin, exhibiting the best therapeutic effects on OA which could be suppressed by irisin neutralizing antibodies. Irisin not only recovered the expression of collagen II and attenuated that of MMP-13 and ADAMTS-5 in IL-1ß-induced OA chondrocytes by inhibiting the PI3K/Akt/NF-κB signaling pathway, but also inhibited the activity of nod-like receptor protein-3 (NLRP3)/caspase-1, thus ameliorating pyroptosis in chondrocytes. In conclusion, moderate mechanical stimulation protects against chondrocyte pyroptosis through irisin-induced suppression of PI3K/Akt/NF-κB signal pathway in osteoarthritis.

16S rDNA Full-Length Assembly Sequencing Technology Analysis of Intestinal Microbiome in Polycystic Ovary Syndrome.

Objective: To study the characteristics and relationship of the gut microbiota in patients with polycystic ovary syndrome (PCOS). Method: We recruited 45 patients with PCOS and 37 healthy women from the Reproductive Department of Shengjing Hospital. We recorded their clinical indexes, and sequenced their fecal samples by 16S rDNA full-length assembly sequencing technology (16S-FAST). Result: We found decreased α diversity and different abundances of a series of microbial species in patients with PCOS compared to healthy controls. We found LH and AMH were significantly increased in PCOS with Prevotella enterotype when compared to control women with Prevotella enterotype, while glucose and lipid metabolism level remained no significant difference, and situations were opposite in PCOS and control women with Bacteroides enterotype. Ruminococcus gnavus, Prevotella stercorea, Dialister succinatiphilus and Bacteroides fragilis were more abundant while Christensenellaceae spp. were less abundant in the PCOS group. P. stercorea was significantly more prevalent in PCOS-not insulin resistance (NIR) compared to control-NIR and PCOS-not overweight (NOW) patient groups compared to control-NOW groups. Kyoto Encyclopedia Genes and Genomes reflecting pathways related to lipopolysaccharide biosynthesis were more abundant in the PCOS group. Conclusion: Our study found gut microbiota that had different abundance in patients with PCOS compared to healthy controls. An intimate relationship was shown between the gut microbiota and pathological changes in PCOS. We suggest the gut microbiota should be taken into consideration in the treatment of symptoms of PCOS via drugs and diet.

The anti-inflammatory effects of 15-HETE on osteoarthritis during treadmill exercise.

AIMS: Investigate the involvement of 15-hydroxyeicosatetraenoic acid (15-HETE), an anti-inflammatory molecule, on the beneficial effects of exercise therapy for osteoarthritis (OA). MAIN METHODS: 15-HETE (10 µM, twice a week) and monosodium iodoacetate (MIA) (1 mg) were injected into rat knee joints. Treadmill exercise was applied on OA rat. Primary rat chondrocytes were treated with 15-HETE, LY294002 and interleukin (IL)-1ß. Rats undergo a 1 hour single session treadmill exercise once. 15-HETE levels in the knee joint were evaluated using ELISA after a single session of treadmill exercise on healthy and OA rats. Matrix metalloproteinase (MMP)3, MMP-13, a disintegrin and metalloproteinase with thrombospondin motif (ADAMTS)-5, p-Akt, Akt, and collagen type 2 (COL2) expression were evaluated using RT-PCR and western blotting. OA degree was evaluated using X-ray, scored by Osteoarthritis Research Society International (OARSI) and Mankin scores. COL2 and MMP-13 expression in articular was evaluated using immunohistochemistry. KEY FINDINGS: Medium intensity exercise alleviated OA. 15-HETE levels after exercise was increased. 15-HETE inhibited IL-1ß-induced inflammation in primary chondrocytes and increased p-Akt levels. LY294002 blocked the effect of 15-HETE in vitro. Finally, 15-HETE alleviated cartilage damage, inhibited MMP-13 expression, and increased COL2 expression in joint cartilage tissue. SIGNIFICANCE: Treadmill exercise alleviates OA and increases 15-HETE levels in the knee joint, which suppresses inflammation in chondrocytes via PI3k-Akt signalling in vitro and in vivo.