Autophagy is a cell biological pathway affecting immune responses. In vitro, autophagy acts as a cell-autonomous defense against Mycobacterium tuberculosis, but its role in vivo is unknown. Here we show that autophagy plays a dual role against tuberculosis: antibacterial and anti-inflammatory. M. tuberculosis infection of Atg5 fl/fl LysM-Cre + mice relative to autophagy-proficient littermates resulted in increased bacillary burden and excessive pulmonary inflammation characterized by neutrophil infiltration and IL-17 response with increased IL-1α levels. Macrophages from uninfected Atg5 fl/fl LysM-Cre + mice displayed a cell-autonomous IL-1α hypersecretion phenotype, whereas T cells showed propensity toward IL-17 polarization during nonspecific activation or upon restimulation with mycobacterial antigens. Thus, autophagy acts in vivo by suppressing both M. tuberculosis growth and damaging inflammation.utophagy is a fundamental cell biological process (1) with impact on aging, development, cancer, neurodegeneration, myodegeneration, metabolic disorders (2), idiopathic inflammatory diseases, and infection and immunity (3). Much of the physiological effects of autophagy are the result of degradative activities of autophagy (1), although biogenesis and secretory roles (4-6) of autophagy are beginning to be recognized (7). The execution of autophagy depends on factors collectively termed "Atg proteins," such as Atg5 (1) and Beclin 1 (Atg6) (8), whereas regulation of autophagy responds to various inputs via mammalian target of rapamycin (mTOR), including the presence of microbes (9), the TAB2/3-TAK1-IKK signaling axis (10), and processes downstream of pattern-recognition receptors and immune cytokine activation (3,(11)(12)(13).In the context of its immunological functions, autophagy acts in four principal ways (14). (i) Autophagy cooperates with conventional pattern-recognition receptors (PRRs), such as Toll-like receptors, RIG-I-like receptors (RLRs), and NOD-like receptors, and acts as both a regulator (11,12,15,16) and an effector of PRR signaling (17-19). (ii) Autophagy affects the presentation of cytosolic antigens in the context of MHC II molecules (20) in T-cell development, differentiation, polarization, and homeostasis (21,22). (iii) Most recently, autophagy has been shown to contribute to both the negative (6,7,(23)(24)(25) and positive (6, 7) regulation of unconventional secretion of the leaderless cytosolic proteins known as "alarmins," such as IL-1β and HMGB1. (iv) Autophagy can capture and eliminate intracellular microbes, including Mycobacterium tuberculosis (17, 26-29), which was one of the first two bacterial species (26, 30) to be recognized as targets for autophagic removal. This activity recently has been shown to depend on the recognition and capture of microbes by adaptors that represent a specialized subset of PRRs termed "sequestosome-like receptors" (SLRs) (31).M. tuberculosis is one of the first microbes recognized as being subject to elimination by immunological autophagy by murine and human...

Mycobacterium tuberculosis (Mtb) parasitizes host macrophages and subverts host innate and adaptive immunity. Several cytokines elicited by Mtb are mediators of mycobacterial clearance or are involved in tuberculosis pathology. Surprisingly, interleukin-1beta (IL-1beta), a major proinflammatory cytokine, has not been implicated in host-Mtb interactions. IL-1beta is activated by processing upon assembly of the inflammasome, a specialized inflammatory caspase-activating protein complex. Here, we show that Mtb prevents inflammasome activation and IL-1beta processing. An Mtb gene, zmp1, which encodes a putative Zn(2+) metalloprotease, is required for this process. Infection of macrophages with zmp1-deleted Mtb triggered activation of the inflammasome, resulting in increased IL-1beta secretion, enhanced maturation of Mtb containing phagosomes, improved mycobacterial clearance by macrophages, and lower bacterial burden in the lungs of aerosol-infected mice. Thus, we uncovered a previously masked role for IL-1beta in the control of Mtb and a mycobacterial system that prevents inflammasome and, therefore, IL-1beta activation.

SummaryFor decades after its introduction, the mechanisms of action of the front-line antituberculosis therapeutic agent isoniazid (INH) remained unclear. Recent developments have shown that peroxidative activation of isoniazid by the mycobacterial enzyme KatG generates reactive species that form adducts with NAD + and NADP+ that are potent inhibitors of lipid and nucleic acid biosynthetic enzymes. A direct role for some isoniazid-derived reactive species, such as nitric oxide, in inhibiting mycobacterial metabolic enzymes has also been shown. The concerted effects of these activities -inhibition of cell wall lipid synthesis, depletion of nucleic acid pools and metabolic depression -drive the exquisite potency and selectivity of this agent. To understand INH action and resistance fully, a synthesis of knowledge is required from multiple separate lines of research -including molecular genetic approaches, in vitro biochemical studies and free radical chemistry -which is the intent of this review.

It is postulated that, in addition to cell density, other factors, such as the dimensions and diffusional characteristics of the environment, could influence quorum sensing (QS) and induction of genetic reprogramming. Modeling studies predict that QS may operate at the level of a single cell, but, due to experimental challenges, the potential benefits of QS by individual cells remain virtually unexplored. Here we report a physical system that mimics isolation of a bacterium, such as within an endosome or phagosome during infection, and maintains cell viability under conditions of complete chemical and physical isolation. For Staphylococcus aureus, we show quorum sensing and genetic re-programming to occur in a single isolated organism. Quorum sensing allows S. aureus to sense confinement and to activate virulence and metabolic pathways needed for survival. To demonstrate the benefit of confinement-induced quorum sensing to individuals, we showed quorum sensing bacteria to have significantly greater viability over non-QS bacteria.

Summary:Stroke causes heterogeneous changes in tissue oxygenation, with a region of decreased blood flow, the penumbra, surrounding a severely damaged ischemic core. Treatment of acute ischemic stroke aims to save this penumbra before its irreversible damage by continued ischemia. However, effective treatment remains elusive due to incomplete understanding of processes leading to penumbral death. While oxygenation is central in ischemic neuronal death, it is unclear exactly what actual changes occur in interstitial oxygen tension (pO 2 ) in ischemic regions during stroke, particularly the penumbra. Using the unique capability of in vivo electron paramagnetic resonance (EPR) oximetry to measure localized interstitial pO 2 , we measured both absolute values, and temporal changes of pO 2 in ischemic penumbra and core during ischemia and reperfusion in a rat model. Ischemia rapidly decreased interstitial pO 2 to 32% ± 7.6% and 4% ± 0.6% of pre-ischemic values in penumbra and core, respectively 1 hour after ischemia. Importantly, whilst reperfusion restored core pO 2 close to its pre-ischemic value, penumbral pO 2 only partially recovered. Hyperoxic treatment significantly increased penumbral pO 2 during ischemia, but not in the core, and also increased penumbral pO 2 during reperfusion. These divergent, important changes in pO 2 in penumbra and core were explained by combined differences in cellular oxygen consumption rates and microcirculation conditions. We therefore demonstrate that interstitial pO 2 in penumbra and core is differentially affected during ischemia and reperfusion, providing new insights to the pathophysiology of stroke. The results support normobaric hyperoxia as a potential early intervention to save penumbral tissue in acute ischemic stroke.