Ethanol effects on pulmonary innate immunity in a murine model of aging

项目总结

Project Summary An increasingly common behavior in the elderly ( ≥ 65 years old) is alcohol consumption, with 40% consuming an average of 1-2 drinks/day 3 days a week, considered “moderate” intake. Even though the elderly typically drink less than younger adults do, the negative health effects of alcohol may be more potent in older drinkers due to slower metabolism and medication use. Alcohol consumption correlates with heightened systemic inflammation and reduced cell-mediated immunity, similar to the effects of “inflamm-aging,” the elevated basal inflammatory state which is present even in healthy elderly individuals. Further, alcohol use and advanced age are associated with increased incidence and severity of infection with otherwise innocuous pathogens such as Streptococcus pneumoniae; however, the effects of alcohol on immunity in the elderly have yet to be investigated. Alveolar macrophages (AMs), the resident innate immune cells in the lung, regulate homeostasis and become critical effector cells to initiate inflammation in response to pulmonary pathogens. Macrophage stimulation by pathogens results in intracellular activation of the mitogen-activated protein kinase (MAPK) and NF-κB pathways, and the production of chemoattractants to recruit and activate additional immune cells at the site of infection. Previous studies from our laboratory have shown that advanced age and acute in vivo ethanol exposure independently contribute to decreased production of pro-inflammatory cytokines by macrophages stimulated with Toll-like receptor (TLR) agonists ex vivo, which paralleled suppression of p38 MAPK activation. In addition, preliminary in vivo data show that moderate, multi-day ethanol exposure leads to decreased Interleukin- (Il-) 6, Tumor necrosis factor- (Tnf-) α, and monocyte chemoattractant C-C motif chemokine ligand 2 (Ccl2) gene expression in lung homogenates of aged mice, compared to aged mice given vehicle, and young mice regardless of ethanol exposure. Given these findings, we hypothesize that advanced age and ethanol exposure act synergistically to suppress p38 MAPK activation in murine AMs, leading to decreased production of pro-inflammatory mediators, impaired phagocytosis, and/or dysregulated immune cell recruitment following infection. To test this, in Aim 1, we will examine the impact of ethanol and advanced age on MAPK activation and macrophage function. Following multi-day vehicle or ethanol treatment, we will modulate p38 MAPK expression in alveolar macrophages ex vivo and measure phagocytosis and production of pro-inflammatory cytokines and chemokines. In Aim 2, we will assess the role of CCL2 in pulmonary immune cell recruitment after treatment with CCL2 recombinant protein and in vivo S. pneumoniae infection. During the course of infection, we will measure respiratory function by plethysmography and quantify lung bacterial burden by quantitative PCR. Collectively, these studies will expand our knowledge of the immunological consequences of alcohol consumption in the elderly, and potentially identify therapeutic targets to improve infection-related health outcomes in older adults who consume alcohol.