Menthol cigarette smoking and nicotine dependence

Since tobacco use is driven by dependence on nicotine, the primary addictive substance in tobacco, much research has focused on nicotine dependence. Less well understood, however, is the role that menthol plays in nicotine dependence. This review seeks to examine what role, if any, menthol plays in nicotine addiction in adults and youth. Based on research examining several indicators of heaviness of nicotine addiction, including time to first cigarette upon waking, night waking to smoke, as well as some other indications of dependence, it is suggested that menthol cigarette smokers are more heavily dependent on nicotine. Although other indicators of nicotine dependence, including number of cigarettes per day and the Fagerstrom Test of Nicotine Dependence, failed to consistently differentiate menthol and non-menthol smokers, these indicators are thought to be less robust than time to first cigarette. Therefore, though limited, the existing literature suggests that menthol smokers may be more dependence on nicotine

Lipocalin 2 is protective against E. coli pneumonia

<p>Abstract</p> <p>Background</p> <p>Lipocalin 2 is a bacteriostatic protein that binds the siderophore enterobactin, an iron-chelating molecule produced by <it>Escherichia coli </it>(<it>E. coli</it>) that is required for bacterial growth. Infection of the lungs by <it>E. coli </it>is rare despite a frequent exposure to this commensal bacterium. Lipocalin 2 is an effector molecule of the innate immune system and could therefore play a role in hindering growth of <it>E. coli </it>in the lungs.</p> <p>Methods</p> <p>Lipocalin 2 knock-out and wild type mice were infected with two strains of <it>E. coli</it>. The lungs were removed 48 hours post-infection and examined for lipocalin 2 and MMP9 (a myeloid marker protein) by immunohistochemical staining and western blotting. Bacterial numbers were assessed in the lungs of the mice at 2 and 5 days after infection and mortality of the mice was monitored over a five-day period. The effect of administering ferrichrome (an iron source that cannot be bound by lipocalin 2) along with E.coli was also examined.</p> <p>Results</p> <p>Intratracheal installation of <it>E. coli </it>in mice resulted in strong induction of lipocalin 2 expression in bronchial epithelium and alveolar type II pneumocytes. Migration of myeloid cells to the site of infection also contributed to an increased lipocalin 2 level in the lungs. Significant higher bacterial numbers were observed in the lungs of lipocalin 2 knock-out mice on days 2 and 5 after infection with <it>E. coli </it>(p < 0.05). In addition, a higher number of <it>E. coli </it>was found in the spleen of surviving lipocalin 2 knock-out mice on day 5 post-infection than in the corresponding wild-type mice (p < 0.05). The protective effect against <it>E. coli </it>infection in wild type mice could be counteracted by the siderophore ferrichrome, indicating that the protective effect of lipocalin 2 depends on its ability to sequester iron.</p> <p>Conclusions</p> <p>Lipocalin 2 is important for protection of airways against infection by <it>E. coli</it>.</p