Regulation of osteoarthritis-associated key mediators by TNFα and IL-10: effects of IL-10 overexpression in human synovial fibroblasts and a synovial cell line.

Synovial fibroblasts (SF) contribute to the pathogenesis of osteoarthritis (OA), but the effects of intra-articular cytokines on SF are not completely understood. The aim of this study was to characterize the interplay between tumor necrosis factor (TNF)α and the anti-inflammatory interleukin (IL)-10. Non-immortalized human SF and SF of the human cell line K4IM were stimulated with recombinant TNFα, IL-10, or TNFα + IL-10 (10 ng/ml each) for 24 h or transduced with an adenoviral vector overexpressing human IL-10 (hIL-10) and subsequently treated with 10 ng/ml TNFα for 24 h. Effects on the gene expression and protein synthesis of IL-6, IL-10, matrix metalloproteinases (MMP)-1, -3, type I collagen, ß1-integrin, and CD44 were investigated via real-time detection polymerase chain reaction, immunofluorescence labeling, flow cytometry, and Western blotting. IL-10 release by transduced SF was confirmed with enzyme-linked immunosorbent assay. Both cell populations were activated by TNFα and by TNFα + IL-10, increasing their gene expression and protein synthesis of IL-6, IL-10, MMP-1, and MMP-3 and altering the synthesis of type I collagen, ß1-integrin, and CD44. hIL-10 overexpression greatly elevated the gene expression and protein synthesis of IL-10. However, transduction did not significantly affect the gene expression of IL-6, MMP-1, and MMP-3 in SF. The increased expression of pro-inflammatory and catabolic mediators in TNFα-activated SF indicates their role in OA pathogenesis, suggesting they are a potential therapeutic target. Although the vigorousness of the responses of non-immortalized SF and K4IM clearly differ, the K4IM cell line seems to be a suitable model for non-immortalized human SF.

The role of pro-inflammatory and immunoregulatory cytokines in tendon healing and rupture: new insights.

Owing to limited self-healing capacity, tendon ruptures and healing remain major orthopedic challenges. Increasing evidence suggests that post-traumatic inflammatory responses, and hence, cytokines are involved in both cases, and also in tendon exercise and homeostasis. This review summarizes interrelations known between the cytokines interleukin (IL)-1ß, tumor necrosis factor (TNF)α, IL-6 and vascular endothelial growth factor (VEGF) in tendon to assess their role in tendon damage and healing. Exogenic cytokine sources are blood-derived leukocytes that immigrate in damaged tendon. Endogenous expression of IL-1ß, TNFα, IL-6, IL-10 and VEGF was demonstrated in tendon-derived cells. As tendon is a highly mechanosensitive tissue, cytokine homeostasis and cell survival underlie an intimate balance between adequate biomechanical stimuli and disturbance through load deprivation and overload. Multiple interrelations between cytokines and tendon extracellular matrix (ECM) synthesis, catabolic mediators e.g. matrix-degrading enzymes, inflammatory and angiogenic factors (COX-2, PGE2, VEGF, NO) and cytoskeleton assembly are evident. Pro-inflammatory cytokines affect ECM homeostasis, accelerate remodeling, amplify biomechanical adaptiveness and promote tenocyte apoptosis. This multifaceted interplay might both contribute to and interfere with healing. Much work must be undertaken to understand the particular interrelation of these inflammatory and regulatory mediators in ruptured tendon and healing, which has relevance for the development of novel immunoregulatory therapeutic strategies.

Burkholderia pseudomallei kills the nematode Caenorhabditis elegans using an endotoxin-mediated paralysis.

We investigated a non-mammalian host model system for fitness in genetic screening for virulence-attenuating mutations in the potential biowarfare agents Burkholderia pseudomallei and Burkholderia mallei. We determined that B. pseudomallei is able to cause 'disease-like' symptoms and kill the nematode Caenorhabditis elegans. Analysis of killing in the surrogate disease model with B. pseudomallei mutants indicated that killing did not require lipopolysaccharide (LPS) O-antigen, aminoglycoside/macrolide efflux pumping, type II pathway-secreted exoenzymes or motility. Burkholderia thailandensis and some strains of Burkholderia cepacia also killed nematodes. Manipulation of the nematode host genotype suggests that the neuromuscular intoxication caused by both B. pseudomallei and B. thailandensis acts in part through a disruption of normal Ca2+ signal transduction. Both species produce a UV-sensitive, gamma-irradiation-resistant, limited diffusion, paralytic agent as part of their nematode pathogenic mechanism. The results of this investigation suggest that killing by B. pseudomallei is an active process in C. elegans, and that the C. elegans model might be useful for the identification of vertebrate animal virulence factors in B. pseudomallei.