IL-17 and immunologically induced senescence regulate response to injury in osteoarthritis

[Interleukin-17A: Possible mediator and therapeutic target in hypertension]

Interleukin-17A (IL-17A) is a proinflammatory cytokine produced by cells of the immune system, predominantly Th17 lymphocytes and γδ lymphocytes. In this paper, we review the role of IL-17A in the pathogenesis of hypertension and target organ damage. Studies in mice have shown that IL-17A increases blood pressure, probably by acting on multiple levels. Furthermore, IL-17A plasma concentrations are already elevated in patients with mild or moderate hypertension. Preclinical studies on arterial hypertension have detected IL-17A-producing cells in target organs such as the heart, vessels and kidneys. Patients with hypertensive nephrosclerosis show kidney infiltration by Th17 lymphocytes and γδ lymphocytes that express IL-17A. In addition, in experimental models of hypertension, blocking IL-17A by genetic strategies, or using neutralising antibodies, lowers blood pressure by acting on the vascular wall and tubule sodium transport and reduces damage to target organs. As a whole, the data presented in this review suggest that IL-17A participates in the regulation of blood pressure and in the genesis and maintenance of arterial hypertension, and may constitute a therapeutic target in the future.

An Evidence-Based Systematic Review of Human Knee Post-Traumatic Osteoarthritis (PTOA): Timeline of Clinical Presentation and Disease Markers, Comparison of Knee Joint PTOA Models and Early Disease Implications

Understanding the causality of the post-traumatic osteoarthritis (PTOA) disease process of the knee joint is important for diagnosing early disease and developing new and effective preventions or treatments. The aim of this review was to provide detailed clinical data on inflammatory and other biomarkers obtained from patients after acute knee trauma in order to (i) present a timeline of events that occur in the acute, subacute, and chronic post-traumatic phases and in PTOA, and (ii) to identify key factors present in the synovial fluid, serum/plasma and urine, leading to PTOA of the knee in 23-50% of individuals who had acute knee trauma. In this context, we additionally discuss methods of simulating knee trauma and inflammation in in vivo, ex vivo articular cartilage explant and in vitro chondrocyte models, and answer whether these models are representative of the clinical inflammatory stages following knee trauma. Moreover, we compare the pro-inflammatory cytokine concentrations used in such models and demonstrate that, compared to concentrations in the synovial fluid after knee trauma, they are exceedingly high. We then used the Bradford Hill Framework to present evidence that TNF-α and IL-6 cytokines are causal factors, while IL-1β and IL-17 are credible factors in inducing knee PTOA disease progresssion. Lastly, we discuss beneficial infrastructure for future studies to dissect the role of local vs. systemic inflammation in PTOA progression with an emphasis on early disease.

Apremilast prevents IL‑17‑induced cellular senescence in ATDC5 chondrocytes mediated by SIRT1

Osteoarthritis is the most prevalent joint degenerative disease and has been considered a major cause of severe joint pain and physical disability in the elderly. The chondrocyte is the only cell type found in articular cartilage and chondrocyte senescence plays a pivotal role in the pathogenesis of osteoarthritis. Apremilast is an oral PDE4 inhibitor and has been used for the treatment of patients with active psoriatic arthritis. In the present study, the biological function of apremilast was examined in an interleukin (IL)-17-treated chondrocyte model. Expression levels of target genes and proteins were measured using reverse transcription-quantitative PCR, ELISA, and western blotting, respectively. ROS levels in chondrocytes were examined using the fluorescent dye DCFH-DA. Cellular senescence was determined using senescence-associated-β-galactosidase staining. The profile of cell cycle phases was analyzed via flow cytometry. It was revealed that treatment with apremilast reduced the expression of IL-1β, MCP-1, and the production of ROS. SA-β-gal staining results indicated that the presence of apremilast suppressed IL-17-induced cellular senescence. Furthermore, apremilast prevented IL-17-induced G0/G1 phase cell cycle arrest. In addition, it was demonstrated that apremilast suppressed IL-17-induced expression of p21 and PAI-1. Notably, the silencing of sirtuin 1 (SIRT1) abolished the protective effect of apremilast against IL-17-induced cellular senescence, suggesting that the action of apremilast in chondrocytes is dependent on SIRT1. In conclusion, the present results revealed that apremilast exerted a beneficial effect, thereby protecting chondrocytes from senescence induced by IL-17.