Acute Ethanol Inhibition of Adult Hippocampal Neurogenesis Involves CB1 Cannabinoid Receptor Signaling.

BACKGROUND: Chronic ethanol (EtOH) exposure has been found to inhibit adult hippocampal neurogenesis in multiple models of alcohol addiction. However, acute EtOH inhibition of adult neurogenesis is not well studied. Although many abused drugs have been found to inhibit adult neurogenesis, few have studied cannabinoids or cannabinoids with EtOH, although human use of both together is becoming more common. We used an acute binge alcohol drinking model in combination with select cannabinoid receptor agonists and antagonists to investigate the actions of each alone and together on hippocampal neurogenesis. METHODS: Adult male Wistar rats were treated with an acute binge dose of EtOH (5 g/kg, i.g.), cannabinoid 1 receptor (CB1R) or cannabinoid 2 receptor (CB2R) agonists, as well as selective cannabinoid (CB) antagonists, alone or combined. Hippocampal doublecortin (DCX), Ki67, and activated cleaved caspase-3 (CC3) immunohistochemistry were used to assess neurogenesis, neuroprogenitor proliferation, and cell death, respectively. RESULTS: We found that treatment with EtOH or the CB1R agonist, arachidonoyl-2'-chloroethylamide (ACEA), and the combination significantly reduced DCX-positive neurons (DCX + IR) in dentate gyrus (DG) and increased CC3. Further, using an inhibitor of endocannabinoid metabolism, for example, JZL195, we also found reduced DCX + IR neurogenesis. Treatment with 2 different CB1R antagonists (AM251 or SR141716) reversed both CB1R agonist and EtOH inhibition of adult neurogenesis. CB2R agonist HU-308 treatment did not produce any significant change in DCX + IR. Interestingly, neither EtOH nor CB1R agonist produced any alteration in cell proliferation in DG as measured by Ki67 + cell population, but CC3-positive cell numbers increased following EtOH or ACEA treatment suggesting an increase in cell death. CONCLUSIONS: Together, these findings suggest that acute CB1R cannabinoid receptor activation and binge EtOH treatment reduce neurogenesis through mechanisms involving CB1R.

Expanded Glucose Import Capability Affords Staphylococcus aureus Optimized Glycolytic Flux during Infection.

UNLABELLED: Acquisition of numerous virulence determinants affords Staphylococcus aureus greater pathogenicity than other skin-colonizing staphylococci in humans. Additionally, the metabolic adaptation of S. aureus to nonrespiratory conditions encountered during infection (e.g., hypoxia, nitric oxide, iron chelation) has been implicated as contributing to S. aureus virulence. Specifically, S. aureus has been shown to ferment glycolytic substrates in nonrespiratory environments encountered within the host. Here, we show that S. aureus has acquired unique carbohydrate transporters that facilitate the maximal uptake of host sugars and serve to support nonrespiratory growth in inflamed tissue. The carbohydrate substrates of 11 S. aureus transporters were identified, and at least four of their genes encode S. aureus glucose transporters (glcA, glcB, glcC, and glcU). Moreover, two transporter genes (glcA and glcC) are unique to S. aureus and contribute disproportionately to the nonrespiratory growth of S. aureus on glucose. Targeted inactivation of sugar transporters reduced glucose uptake and attenuated S. aureus in a murine model of skin and soft tissue infections. These data expand the evidence for metabolic adaptation of S. aureus to invasive infection and demonstrate the specific requirement for the fermentation of glucose over all other available carbohydrates. Ultimately, acquisition of foreign genes allows S. aureus to adopt a metabolic strategy resembling that of infiltrating host immune cells: high glycolytic flux coupled to lactate excretion. IMPORTANCE: The bacterial pathogen Staphylococcus aureus causes a wide range of human infections that are costly and difficult to treat. S. aureus differs from closely related commensal staphylococci in its ability to flourish following the invasion of deeper tissue from the skin surface. There, S. aureus primarily uses glucose to grow under respiration-limiting conditions imposed by the immune system. It was previously unclear how S. aureus thrives in this environment when other Staphylococcus species cannot. Our results provide evidence that S. aureus has acquired an expanded repertoire of carbohydrate transporters. In particular, four glucose transporters contribute to efficient S. aureus growth during infection. Thus, S. aureus has evolved to maximize its glucose uptake abilities for enhanced glycolytic flux during tissue invasion. This dependence on glucose acquisition for S. aureus virulence may also explain links between serious infectious complications associated with diabetic patients exhibiting elevated blood glucose levels.

Identification of a lactate-quinone oxidoreductase in Staphylococcus aureus that is essential for virulence.

Staphylococcus aureus is an important human pathogen commonly infecting nearly every host tissue. The ability of S. aureus to resist innate immunity is critical to its success as a pathogen, including its propensity to grow in the presence of host nitric oxide (NO·). Upon exogenous NO· exposure, S. aureus immediately excretes copious amounts of L-lactate to maintain redox balance. However, after prolonged NO·-exposure, S. aureus reassimilates L-lactate specifically and in this work, we identify the enzyme responsible for this L-lactate-consumption as a L-lactate-quinone oxidoreductase (Lqo, SACOL2623). Originally annotated as Mqo2 and thought to oxidize malate, we show that this enzyme exhibits no affinity for malate but reacts specifically with L-lactate (K(M) = ∼330 µM). In addition to its requirement for reassimilation of L-lactate during NO·-stress, Lqo is also critical to respiratory growth on L-lactate as a sole carbon source. Moreover, Δlqo mutants exhibit attenuation in a murine model of sepsis, particularly in their ability to cause myocarditis. Interestingly, this cardiac-specific attenuation is completely abrogated in mice unable to synthesize inflammatory NO· (iNOS(-/-)). We demonstrate that S. aureus NO·-resistance is highly dependent on the availability of a glycolytic carbon sources. However, S. aureus can utilize the combination of peptides and L-lactate as carbon sources during NO·-stress in an Lqo-dependent fashion. Murine cardiac tissue has markedly high levels of L-lactate in comparison to renal or hepatic tissue consistent with the NO·-dependent requirement for Lqo in S. aureus myocarditis. Thus, Lqo provides S. aureus with yet another means of replicating in the presence of host NO·.