Objective. Systemic sclerosis (SSc) is characterized by the fibrosis of various organs, vascular hyperreactivity, and immunologic dysregulation. Since Notch signaling is known to affect fibroblast homeostasis, angiogenesis, and lymphocyte development, we undertook this study to investigate the role of the Notch pathway in human and murine SSc.Methods. SSc was induced in BALB/c mice by subcutaneous injections of HOCl every day for 6 weeks. Notch activation was analyzed in tissues from mice with SSc and from patients with scleroderma. Mice with SSc were either treated or not treated with the ␥-secretase inhibitor DAPT, a specific inhibitor of the Notch pathway, and the severity of the disease was evaluated.Results. As previously described, mice exposed to HOCl developed a diffuse cutaneous SSc with pulmonary fibrosis and anti-DNA topoisomerase I antibodies. The Notch pathway was hyperactivated in the skin, lung, fibroblasts, and splenocytes of diseased mice and in skin biopsy samples from patients with scleroderma. ADAM-17, a proteinase involved in Notch activation, was overexpressed in the skin of mice and patients in response to the local production of reactive oxygen species. In HOCl-injected mice, DAPT significantly reduced the development of skin and lung fibrosis, decreased skin fibroblast proliferation and ex vivo serum-induced endothelial H 2 O 2 production, and abrogated the production of anti-DNA topoisomerase I antibodies.Conclusion. Our results show the pivotal role of the ADAM-17/Notch pathway in SSc following activation by reactive oxygen species. The inhibition of this pathway may represent a new treatment of this lifethreatening disease.

Immunotherapy is a promising antitumor strategy that can successfully be combined with current anticancer treatment. In this study, arsenic trioxide (As2O3) was shown to increase the antitumor immune response in CT26 colon tumor-bearing mice through the modulation of regulatory T cell (Treg) numbers. As2O3 induced Treg-selective depletion in vitro. In vivo, tumor-bearing mice injected with 1 mg/kg As2O3 showed a significant decrease in the Treg/CD4 cell ratio and in absolute Treg count versus controls. As2O3 exerted antitumor effects only in immunocompetent mice and enhanced adoptive immunotherapy effects. Inhibition of As2O3-induced Treg depletion by the NO synthase inhibitor NG-nitro-l-arginine methyl ester and the superoxide dismutase mimic manganese [III] tetrakis-(5, 10, 15, 20)-benzoic acid porphyrin suggested that it was mediated by oxidative and nitrosative stress. The differential effect of As2O3 on Treg versus other CD4 cells may be related to differences in the cells’ redox status, as indicated by significant differences in 2′7′dichlorodihydrofluorescein diacetate and 4,5-diaminofluorescein diacetate fluorescence levels. In conclusion, these results show for the first time, to our knowledge, that low doses As2O3 can delay solid tumor growth by depleting Tregs through oxidative and nitrosative bursts, and suggest that As2O3 could be used to enhance the antitumor activity of adoptive immunotherapy strategies in human cancer.

Despite the discovery of antibiotics, the battle against bacteria is so far in their favor, specifically because bugs are able to develop a superstructure named biofilm, to resist and to survive in the environment. Nosocomial infections, a major health problem, are due at 80% to biofilm-associated infection, and Staphylococcus aureus is the leading bacteria species in this domain. Moreover, the antimicrobial resistance of this bacterial community is accentuated when it is formed by superbugs such as methicillin-resistant S. aureus (MRSA). In this chapter, the mechanism and the physiology of S. aureus biofilm as well as their consequences in the clinical domains are described. To complete the vision on S. aureus biofilms, some "anti-biofilm" strategies will be highlighted.

The need for bone and joint prostheses is currently growing due to population aging, leading to an increase in prosthetic joint infection cases. Biofilms represent an adaptive and quite common bacterial response to several stress factors which confer an important protection to bacteria. Biofilm formation starts with bacterial adhesion on a surface, such as an orthopedic prosthesis, further reinforced by matrix synthesis. The biofilm formation and structure depend on the immediate environment of the bacteria. In the case of infection, the periprosthetic joint environment represents a particular interface between bacteria, host cells, and the implant, favoring biofilm initiation and maturation. Treating such an infection represents a huge challenge because of the biofilm-specific high tolerance to antibiotics and its ability to evade the immune system. It is crucial to understand these mechanisms in order to find new and adapted strategies to prevent and eradicate implant-associated infections. Therefore, adapted models mimicking the infectious site are of utmost importance to recreate a relevant environment in order to test potential antibiofilm molecules. In periprosthetic joint infections, Staphylococcus aureus is mainly involved because of its high adaptation to the human physiology. The current review deals with the mechanisms involved in the antibiotic resistance and tolerance of Staphylococcus aureus in the particular periprosthetic joint infection context, and exposes different strategies to manage these infections.

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A random mutagenesis technique was used to predict the evolutionary potential of ␤-lactamase CTX-M-9 toward the acquisition of improved catalytic activity against ceftazidime. Thirty CTX-M mutants were obtained during three rounds of mutagenesis. These mutants conferred 1-to 128-fold-higher MICs of ceftazidime than the parental enzyme CTX-M-9. The CTX-M mutants contained one to six amino acid substitutions. Mutants harbored the substitutions Asp240Gly and Pro167Ser, which were previously observed in clinical CTX-M enzymes. Additional substitutions, notably Arg164His, Asp179Gly, and Arg276Ser, were observed near the active site. The kinetic constants of the three most active mutants revealed two distinct ways of improving catalytic efficiency against ceftazidime. One enzyme had a 17-fold-higher k cat value than CTX-M-9 against ceftazidime. The other two had 75-to 300-fold-lower K m values than CTX-M-9 against ceftazidime. The current emergence of CTX-M ␤-lactamases with improved activity against ceftazidime may therefore be the beginning of an evolutionary process which might subsequently generate a great diversity of CTX-M-type ceftazidimases.The most prevalent mechanism of resistance against ␤-lactams in gram-negative bacilli is the production of ␤-lactamases belonging to structural class A (1). Class A ␤-lactamases are active-site serine enzymes which cleave the amide bond in the ␤-lactam ring via an acyl-enzyme intermediate.Oxyimino cephalosporins, such as ceftazidime or cefotaxime, are highly resistant to this hydrolysis by class A penicillinases such as TEM-1, TEM-2, and SHV-1. However, the extensive use of these ␤-lactams has resulted in the emergence of extended-spectrum ␤-lactamases (ESBLs). The first ESBLs were derived from the TEM-1/2 and SHV-1 ␤-lactamases by critical amino acid substitutions which confer hydrolytic activity against oxyimino cephalosporins. The major substitutions are located in two elements of the binding site: the ␤3 strand at position 238 and the omega loop at positions 164 and 179 (27).Non-TEM, non-SHV ESBLs designated CTX-M enzymes were identified in the early 1990s (2, 36). The frequency of CTX-M enzymes has increased sharply worldwide since 1995, and they now form a growing family that comprises more than 40 enzymes (3). Most CTX-M enzymes exhibit a much greater hydrolytic efficiency against cefotaxime than against ceftazidime, unlike TEM-and SHV-type ESBLs. However, seven CTX-M mutants harboring point mutations which improve enzymatic efficiency against ceftazidime have been reported recently, suggesting that CTX-Ms are altering their substrate specificity in response to continued antibiotic selective pressure. Five mutants harbor substitution Asp240Gly (4,5,16,29,31), and two mutants harbor substitutions Pro167Ser/Thr (33, 38). These substitutions have not been previously observed in natural TEM or SHV ESBLs, suggesting that CTX-M enzymes have a singular evolutionary potential. In this work, a random mutagenesis technique was applied to the CTX-M-9-encoding gene to predict wh...

Prosthesis and joint infections are an important threat in public health, especially due to the development of bacterial biofilms and their high resistance to antimicrobials. Biofilm-associated infections increase mortality and morbidity rates as well as hospitalization costs. Prevention is the best strategy for this serious issue, so there is an urgent need to understand the signals that could induce irreversible bacterial adhesion on a prosthesis. In this context, we investigated the influence of the bone environment on surface adhesion by a methicillin-susceptible Staphylococcus aureus strain. Using static and dynamic biofilm models, we tested various bone environment factors and showed that the presence of Mg2+, lack of oxygen, and starvation each increased bacterial adhesion. It was observed that human osteoblast-like cell culture supernatants, which contain secreted components that would be found in the bone environment, increased bacterial adhesion capacity by 2-fold (p = 0.015) compared to the medium control. Moreover, supernatants from osteoblast-like cells stimulated with TNF-α to mimic inflammatory conditions increased bacterial adhesion by almost 5-fold (p = 0.003) without impacting on the overall biomass. Interestingly, the effect of osteoblast-like cell supernatants on bacterial adhesion could be counteracted by the activity of synthetic antibiofilm peptides. Overall, the results of this study demonstrate that factors within the bone environment and products of osteoblast-like cells directly influence S. aureus adhesion and could contribute to biofilm initiation on bone and/or prosthetics implants.

Oxidative stress plays a role in the regulation of cancer cell metastasis which involves cell invasion and adhesion that could be supported by ADAM proteins through the activities of their metalloprotease and disintegrin domains. We hypothesized that oxidative stress could act through the induction of ADAM9 protein in some cancer cells. Indeed, Western blot analysis for ADAM9 performed on A549 cells exposed to H 2 O 2 reveals a dose-dependent induction of two proteins (80 and 68 kDa) correlated with a sharp increase of the ADAM protease activity measured in supernatant while the activity measured on the cell layer was slightly affected. The 80kDa protein corresponds to the mature form of ADAM9. Immunoprecipitation analysis performed on concentrated supernatants revealed that the 68 kDa protein is a secreted form of ADAM9. When exposed to H 2 O 2 , A549 cells cocultured with confluent endothelial vascular cells resulted in a 5.5 fold (p < 0.001) increase in the number of adherent cells. Similarly, matrigel assay revealed a 3.25 fold (p < 0.01) increase in the number of invasive cells. The suppression of ADAM9 expression by specific small interfering RNA reduced oxidative stress-induced invasiveness and adhesiveness. These functions could be mediated by an interaction between ADAM9 and b1 integrin because each of them were inhibited when the experiment is performed in presence of mAbs targeting ADAM9 ectodomain or b1-integrin. These results emphasize the importance of oxidative stress in the regulation of cancer cell metastasis and suggest that ADAM9 and its secreted isoform can be important determinants in the ability of cancer cells to disseminate.