Post-traumatic arthritis (PTA) develops after an acute direct trauma to the joints. PTA causes about 12% of all osteoarthritis cases, and a history of physical trauma may also be found in patients with chronic inflammatory arthritis. Symptoms include swelling, synovial effusion, pain and sometimes intra-articular bleeding. Usually, PTA recoveries spontaneously, but the persistence of symptoms after 6 months may be considered pathological and so-called chronic PTA. A variety of molecular, mechanobiological and cellular events involved in the pathogenesis and the progression of PTA have been identified. The activation of inflammatory mechanisms during the PTA acute phase appears to play a critical role in the chronic disease onset. Human studies and experimental models have revealed that a series of inflammatory mediators are released in synovial fluid immediately after the joint trauma. These molecules have been proposed as markers of disease and as a potential target for the development of specific and preventative interventions. Currently, chronic PTA cannot be prevented, although a large number of agents have been tested in preclinical studies. Given the relevance of inflammatory reaction, anticytokines therapy, in particular the inhibition of interleukin 1 (IL-1), seems to be the most promising strategy. At the present time, intra-articular injection of IL-1 receptor antagonist is the only anticytokine approach that has been used in a human study of PTA. Despite the fact that knowledge in this area has increased in the past years, the identification of more specific disease markers and new therapeutic opportunities are needed.
Galectin-3 (gal-3) is a b-galactoside-binding lectin, which regulates cell-cell and extracellular interactions during self/ non-self-antigen recognition and cellular activation, proliferation, differentiation, migration and apoptosis. It plays a significant role in cellular and tissue pathophysiology by organizing niches that drive inflammation and immune responses. Gal-3 has some therapeutic potential in several diseases, including chronic inflammatory disorders, cancer and autoimmune diseases. Gal-3 exerts a broad spectrum of functions which differs according to its intra-or extracellular localization. Recombinant gal-3 strategy has been used to identify potential mode of action of gal-3; however, exogenous gal-3 may not reproduce the functions of the endogenous gal-3. Notably, gal-3 induces monocyte-macrophage differentiation, interferes with dendritic cell fate decision, regulates apoptosis on T lymphocytes and inhibits B-lymphocyte differentiation into immunoglobulin secreting plasma cells. Considering the influence of these cell populations in the pathogenesis of several autoimmune diseases, gal-3 seems to play a role in development of autoimmunity. Gal-3 has been suggested as a potential therapeutic agent in patients affected with some autoimmune disorders. However, the precise role of gal-3 in driving the inflammatory process in autoimmune or immune-mediated disorders remains elusive. Here, we reviewed the involvement of gal-3 in cellular and tissue events during autoimmune and immune-mediated inflammatory diseases.
Objectives To investigate the effects and mechanisms of action of high-density lipoproteins (HDL) in monosodium urate (MSU) crystal-induced inflammation -that is, gouty inflammation, in vivo. Methods Air pouches raised on the backs of mice were injected with MSU crystals or tumour necrosis factor (TNF) in the presence or absence of HDL and/or interleukin (IL)-1 receptor antagonist (IL-1Ra) for 3 h. Leucocyte count and neutrophil percentage in pouch fluids were measured using a haemocytometer and May-Grünwald-Giemsa staining. The cytokine production and expression in the pouch were measured by ELISA and quantitative RT-PCR. Results MSU crystals induced leucocyte infiltration, mostly neutrophils, and the release of IL-1β, IL-6, chemokine (C-X-C motif ) ligand 1 (CXCL1), chemokine (C-C motif ) ligand 2 (CCL2) and IL-1Ra in pouch fluids. TNF remained under the detection limit. MSU crystals triggered IL-1β, IL-6 and CXCL1 expression in both pouch exudates and membranes, whereas CCL2 and TNF mRNA were not modulated. The co-injection of MSU crystals and HDL inhibited leucocyte influx by 59% and neutrophil infiltration by 83% and, in turn, both protein and mRNA levels of all assessed proinflammatory cytokines were reduced, but not those of IL-1Ra. Similar results were obtained when mice were injected with MSU crystals pretreated with HDL or TNF instead of crystals. When HDL and IL-1Ra were added together they displayed additional inhibition, suggesting different mechanisms of action. Conclusions This study demonstrated that HDL may represent an important factor in the modulation of gouty inflammation by acting on both tissue and infiltrating cells -that is, synovial tissue and synovial fluid cells. HDL display anti-inflammatory activity, in part, by interacting with crystals but also by directly acting on cells.
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