The α7 nicotinic acetylcholine receptor (nAChR) was recently described as an anti-inflammatory target in both macrophages and T cells. Its expression by immune cells may explain the epidemiological data claiming a negative link between cigarette smoking and several inflammatory diseases. In this study, we determined the immunological effects of α7 nAChR activation by nicotine. Our results indicate that the α7 nAChR is expressed on the surface of CD4⁺ T cells and that this expression is up-regulated upon immune activation. Nicotine reduced T cell proliferation in response to an encephalitogenic Ag, as well as the production of Th1 (TNF-α and IFN-γ) and Th17 cytokines (IL-17, IL-17F, IL-21, and IL-22). IL-4 production was increased in the same setting. Attenuation of the Th1 and Th17 lineages was accompanied by reduced T-bet (50%) and increased GATA-3 (350%) expression. Overall, nicotine induced a shift to the Th2 lineage. However, α7^−/−-derived T cells were unaffected by nicotine. Furthermore, nicotine reduced NF-κB-mediated transcription as measured by IL-2 and IκB transcription. In vivo, administration of nicotine (2 mg/kg s.c.) suppressed the severity of CD4⁺ T cell-mediated disease experimental autoimmune encephalomyelitis. α7^−/− mice were refractory to nicotine treatment, although disease severity in those animals was reduced, due to impairment in Ag presentation. Accordingly, CD4⁺ and CD11b⁺ cells infiltration into the CNS, demyelination, and axonal loss were reduced. Our data implicate a role for the α7 nAChR in immune modulation and suggest that α7 nAChR agonists may be effective in the treatment of inflammatory disorders.

Exercise prevents cancer incidence and recurrence, yet the underlying mechanism behind this relationship remains mostly unknown. Here we report that exercise induces the metabolic reprogramming of internal organs that increases nutrient demand and protects against metastatic colonization by limiting nutrient availability to the tumor, generating an exercise-induced metabolic shield. Proteomic and ex vivo metabolic capacity analyses of murine internal organs revealed that exercise induces catabolic processes, glucose uptake, mitochondrial activity, and GLUT expression. Proteomic analysis of routinely active human subject plasma demonstrated increased carbohydrate utilization following exercise. Epidemiologic data from a 20-year prospective study of a large human cohort of initially cancer-free participants revealed that exercise prior to cancer initiation had a modest impact on cancer incidence in low metastatic stages but significantly reduced the likelihood of highly metastatic cancer. In three models of melanoma in mice, exercise prior to cancer injection significantly protected against metastases in distant organs. The protective effects of exercise were dependent on mTOR activity, and inhibition of the mTOR pathway with rapamycin treatment ex vivo reversed the exercise-induced metabolic shield. Under limited glucose conditions, active stroma consumed significantly more glucose at the expense of the tumor. Collectively, these data suggest a clash between the metabolic plasticity of cancer and exercise-induced metabolic reprogramming of the stroma, raising an opportunity to block metastasis by challenging the metabolic needs of the tumor. Significance: Exercise protects against cancer progression and metastasis by inducing a high nutrient demand in internal organs, indicating that reducing nutrient availability to tumor cells represents a potential strategy to prevent metastasis. See related commentary by Zerhouni and Piskounova, p. 4124