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Osteoarthritis (OA) is a common chronic degenerative disease characterized by degeneration in the joints and subsequent destruction of cartilage and bone, yet much remains to be elucidated regarding its molecular mechanism. Ghrelin is a recently discovered neuropeptide with anti-inflammatory actions, but it is unknown whether ghrelin is involved in OA. Human primary chondrocyte and cartilage samples were collected from patients with OA, and the expression pattern of ghrelin was assessed. Human chondrocyte and cartilage samples were stimulated with IL-1β and TNF-α, and exogenous ghrelin-alleviated disorganization of catabolism and anabolism were mediated by IL-1β and TNF-α. Destabilization of the medial meniscus and anterior cruciate ligament transection models were established in wild-type mice that were administered ghrelin or PBS. Severity of inflammation and degeneration in the joints were determined by measuring the levels of various inflammatory cytokines and degeneration-associated molecules. Ghrelin down-regulated the production of various inflammatory cytokines, inhibited apoptosis of chondrocytes, decreased the levels of metalloproteinases (including matrix metalloproteinase-13 and a disintegrin and metalloproteinase with thrombospondin motif-5), and maintained the expression of critical matrix components, such as aggrecan and collagen 2. Moreover, suppression of the Akt signaling pathway and activation of NF-κB signaling in chondrocytes during OA development was antagonized by ghrelin administration. This supports the assessment of ghrelin as a potential therapeutic approach to treat degenerative cartilage diseases, including OA.-Qu, R., Chen, X., Wang, W., Qiu, C., Ban, M., Guo, L., Vasilev, K., Chen, J., Li, W., Zhao, Y. Ghrelin protects against osteoarthritis through interplay with Akt and NF-κB signaling pathways.

Background Osteoarthritis (OA) is a common degenerative disease, and tumor necrosis factor (TNF-α) is known to play a critical role in OA. Cortistatin (CST) is a neuropeptide discovered over 20  years ago, which plays a vital role in inflammatory reactions. However, it is unknown whether CST is involved in cartilage degeneration and OA development. Methods The interaction between CST and TNF-α receptors was investigated through Coimmunoprecipitation and Biotin-based solid-phase binding assay. Western blot, Real-time PCR, ELISA, immunofluorescence staining, nitrite production assay and DMMB assay of GAG were performed for the primary chondrocyte experiments. Surgically induced and spontaneous OA models were established and western blot, flow cytometry, Real-time PCR, ELISA, immunohistochemistry and fluorescence in vivo imaging were performed for in vivo experiments. Findings CST competitively bound to TNFR1 as well as TNFR2. CST suppressed proinflammatory function of TNF-α. Both spontaneous and surgically induced OA models indicated that deficiency of CST led to an accelerated OA-like phenotype, while exogenous CST attenuated OA development in vivo. Additionally, TNFR1- and TNFR2-knockout mice were used for analysis and indicated that TNFRs might be involved in the protective role of CST in OA. CST inhibited activation of the NF-κB signaling pathway in OA. Interpretation This study provides new insight into the pathogenesis and therapeutic strategy of cartilage degenerative diseases, including OA. Fund The , the , .

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Contact dermatitis and psoriasis are skin disorders caused by immune dysregulation, yet much remains unknown about their underlying mechanisms. Ghrelin, a recently discovered novel peptide and potential endogenous anti-inflammatory factor expressed in the epidermis, is involved in skin repair and disease. In this study, we investigated the expression pattern and therapeutic effect of ghrelin in both contact dermatitis and psoriasis mouse models induced by oxazolone (OXA) and imiquimod (IMQ), respectively, and in TNF-α-stimulated RAW264.7 macrophages, NHEKs and skin fibroblasts. Ghrelin expression was reduced in both the OXA-induced contact dermatitis and IMQ-induced psoriasis mouse models. Furthermore, treatment with ghrelin attenuated skin inflammation in both the contact dermatitis and psoriasis mouse models. Mice administered PBS after OXA- or IMQ-induced model generation exhibited typical skin inflammation, whereas ghrelin treatment in these mouse models substantially decreased the dermatitis phenotype. In addition, exogenous ghrelin attenuated the inflammatory reaction induced by TNF-α in RAW264.7 cells. Moreover, ghrelin administration limited activation of NF-κB signaling. In summary, ghrelin may represent a potential molecular target for the prevention and treatment of inflammatory skin diseases, including contact dermatitis and psoriasis.

The objective of the present study was to examine the potential role of ghrelin in degeneration of nucleus pulposus (NP). Lower expression levels of ghrelin were found in human NP cells stimulated with interleukin-1β (IL-1β). Moreover, exogenous ghrelin suppressed IL-1β induced degeneration and inflammation associated biomarkers in human NP cells, including matrix metalloproteinase-13, a disintegrin and metalloproteinase with thrombospondin motifs-5, tumor necrosis factor-α and iNOS, which was possibly mediated by antagonization of NF-κB signaling. Moreover, ghrelin enhanced production of critical extracellular matrix of NP cells, including collagen 2, aggrecan, and Sox-9 in NP cells. Ghrelin also promoted NP tissue regeneration in a rabbit IVD degeneration model, which seems to be associated with growth hormone secretagogue receptor. Additionally, the protective role of ghrelin in anabolism potentially relies on activation of Akt signaling pathway. Taken together, ghrelin may represent a molecular target for prevention and treatment of intervertebral disc degeneration.

Growth differentiation factor 11 (GDF11), a key member of the TGF‐β superfamily, plays critical roles in various medical conditions. Recently, GDF11 was found to suppress the nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NF‐κB) signaling pathway and protect against inflammation. This study aimed to investigate the role of GDF11 in the development of rheumatoid arthritis (RA). We demonstrated that GDF11 treatment antagonized TNF‐α‐induced inflammation in macrophages. Moreover, GDF11 inhibited the development of arthritis in the collagen‐induced arthritis and collagen antibody‐induced arthritis models. Local gene transfer of GDF11 via adeno‐associated virus exerted therapeutic effects, while local knockdown of GDF11 exaggerated inflammation in our collagen‐induced arthritis model, as detected by expression levels of inflammatory biomarkers and the destruction of joint structures. Additionally, the results from both in vitro experiments and luciferase reporter gene mouse experiments implied that the NF‐κB pathway might play a critical role in the therapeutic effect of GDF11 in RA. This study presents GDF11 as a potential target for the treatment of inflammatory arthritis, including RA.—Li, W., Wang, W., Liu, L., Qu, R., Chen, X., Qiu, C., Li, J., Hayball, J., Liu, L., Chen, J., Wang, X., Pan, X., Zhao, Y. GDF11 antagonizes TNF‐α‐induced inflammation and protects against the development of inflammatory arthritis in mice. FASEB J. 33, 3317–3329 (2019). http://www.fasebj.org

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