The collagen-induced arthritis model in DA rats induced with homologous rat type II collagen was chosen to determine the therapeutic capacity and effects on autoimmunity by IL-10. Systemic IL-10 treatment (100 or 10 micrograms/day) with mini-osmotic pumps during the periods of arthritis onset (days 12-20 after immunization) decreased the frequency of arthritis and delayed the onset and reduced the severity of arthritis in the few rats that eventually developed arthritis. Concomitantly, levels of autoantibodies to CII were reduced. To test the activity on established arthritis, IL-10 was administered subcutaneously in the paws. This treatment reduced the swelling but did not block the arthritis process. The effective treatment required 100 micrograms of IL-10 every 12th hour while 50 micrograms of IL-10 had little effect, although a tendency of reduced paw swelling was observed. Surprisingly, therapeutic IL-10 treatment led to higher serum levels of autoantibodies to CII. The highest doses of IL-10 (100 micrograms) did not show any apparent toxic effects when given locally or systematically. Taken together, this study suggests that IL-10 is a candidate for treatment of rheumatoid arthritis.

The human skin exerts many functions in order to maintain its barrier integrity and protect the host from invading microorganisms. One such pathogen is Streptococcus pyogenes, which can cause a variety of superficial skin wounds that may eventually progress into invasive deep soft tissue infections. Here we show that keratinocytes recognize soluble M1 protein, a streptococcal virulence factor, as a pathogen-associated molecular pattern to release alarming inflammatory responses. We found that this interaction initiates an inflammatory intracellular signaling cascade involving the activation of the mitogen-activated protein kinases extracellular signal-regulated kinase (ERK), p38, and Jun N-terminal protein kinase and the subsequent induction and mobilization of the transcription factors NF-B and AP-1. We also determined the imprint of the inflammatory mediators released, such as interleukin-8 (IL-8), growth-related oncogene alpha, migration inhibitory factor, extracellular matrix metalloproteinase inducer, IL-1␣, IL-1 receptor a, and ST2, in response to streptococcal M1 protein. The expression of IL-8 is dependent on Toll-like receptor 2 activity and subsequent activation of the mitogen-activated protein kinases ERK and p38. Notably, this signaling seems to be distinct for IL-8 release, and it is not shared with the other inflammatory mediators. We conclude that keratinocytes participate in a proinflammatory manner in streptococcal pattern recognition and that expression of the chemoattractant IL-8 by keratinocytes constitutes an important protective mechanism against streptococcal M1 protein.

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Cold atmospheric plasma (CAP) has been demonstrated to be a successful antiseptic for chronic and infected wounds. Although experimental work has focused on elucidation of the curative power of CAP for wound healing, the molecular mechanisms behind this ability are less understood. To date, the direct effect of CAP on the activity of microbial virulence factors has not been investigated. In the present study, we therefore examined whether CAP can modulate the detrimental activity of M1 protein, one of the most studied Streptococcus pyogenes virulence determinant. Our results show that CAP abolishes the ability of M1 protein to trigger inflammatory host responses. Subsequent mass spectrometric analysis revealed that this effect was caused by oxidation of Met81 and Trp128 located at the sub-N-terminal region of M1 protein provoking a conformational change. Notably, our results also show that CAP has an insignificant effect on the host immune system, supporting the benefits of using CAP to combat infections. Considering the growing number of antibiotic-resistant bacteria, novel antimicrobial therapeutic approaches are urgently needed that do not bear the risk of inducing additional resistance. Our study therefore may open new research avenues for the development of novel approaches for the treatment of skin and wound infections caused by S. pyogenes.

Streptococcus pyogenes of the M1 serotype is commonly associated with invasive streptococcal infections and development of streptococcal toxic shock syndrome. The M1 protein is a powerful inducer of inflammatory responses for several human cell types, but the reason why M1 protein-related strains is over-represented in invasive streptococcal diseases is still not understood. This study was undertaken to investigate if soluble M1 protein can aggravate the severity of streptococcal skin infections in respect to inflammation, leucocyte recruitment, and tissue remodelling as seen in patients with cellulitis and necrotizing fasciitis. We found that HaCaT cells