Intracellular pathogens are responsible for much of the world-wide morbidity and mortality due to infectious diseases. To colonize their hosts successfully, pathogens must sense their environment and regulate virulence gene expression appropriately. Accordingly, on entry into mammalian cells, the facultative intracellular bacterial pathogen Listeria monocytogenes remodels its transcriptional program by activating the master virulence regulator PrfA. Here we show that bacterial and host-derived glutathione are required to activate PrfA. In this study a genetic selection led to the identification of a bacterial mutant in glutathione synthase that exhibited reduced virulence gene expression and was attenuated 150-fold in mice. Genome sequencing of suppressor mutants that arose spontaneously in vivo revealed a single nucleotide change in prfA that locks the protein in the active conformation (PrfA*) and completely bypassed the requirement for glutathione during infection. Biochemical and genetic studies support a model in which glutathione-dependent PrfA activation is mediated by allosteric binding of glutathione to PrfA. Whereas glutathione and other low-molecular-weight thiols have important roles in redox homeostasis in all forms of life, here we demonstrate that glutathione represents a critical signalling molecule that activates the virulence of an intracellular pathogen.

Tumour necrosis factor (TNF)-alpha inhibitors have emerged as a new treatment option for rheumatoid arthritis (RA). The scientific rationale for targeting TNF-alpha in RA derives from extensive work in the laboratory, showing the importance of this pro-inflammatory cytokine as a mediator of joint inflammation. Proof of principle has now been firmly established in clinical trials where TNF-alpha inhibitors have been shown to decrease the signs and symptoms of joint inflammation and slow radiological progression of joint damage. Presently, the two TNF-alpha inhibitors available for use in RA are etanercept and infliximab. Etanercept is a soluble TNF receptor: Fc fusion protein that competes with the endogenous TNF receptors for TNF-alpha binding. Infliximab is a chimeric anti-TNF-alpha monoclonal antibody, which also binds with high affinity to soluble TNF-alpha. Etanercept and infliximab will be rapidly incorporated into current treatment paradigms, which call for early and intensive treatment of RA using disease-modifying antirheumatic drugs (DMARDs), such as methotrexate, sulfasalazine and hydroxychloroquine. A major drawback to the widespread use of these biologics is their high costs. Some patients with limited financial means may be denied access to these effective anti-inflammatory agents. Moreover, long-term experience with TNF-alpha inhibitor therapy has been limited and concerns linger about the possibility that etanercept and infliximab may cause unforeseen side effects or increase the risk for opportunistic infection. Despite these caveats, TNF-alpha inhibitors represent a major advance for the treatment of RA and will likely spawn new indications for anti-TNF-alpha therapy and the development of novel therapeutic compounds with similar biological activity.

Hydrogen peroxide (H(2)O(2)) is a critically important signaling molecule. Endogenous H(2)O(2) mediates diverse physiological processes both intra- and intercellularly; and enzymatically generated H(2)O(2) is a widely used reporter molecule at biosensors that rely on enzymes to detect non-electroactive species. However, the development and application of electroanalytical methods for the direct detection of this molecule has been challenging because the electron transfer kinetics for the irreversible oxidation of H(2)O(2) are slow. We comparatively characterize the electrochemical oxidation of H(2)O(2) on bare and Nafion(®)-coated platinum and carbon-fiber microdisc electrodes using fast-scan cyclic voltammetry (FSCV). Using a waveform ranging from +0.2 to +1.3 V at 400 V s(-1), the electrocatalytic properties of the platinum surface were not readily apparent, and the carbon-fiber microelectrode demonstrated greater sensitivity and selectivity toward H(2)O(2). Nafion(®)-coating further enhanced detection on carbon electrodes. These results confirm that platinum electrodes, with or without Nafion(®), will not work acceptably with this approach, and confirm the value of carbon-fiber microelectrodes relative to more traditionally used platinum electrodes in the direct detection of rapid H(2)O(2) fluctuations using FSCV.