ABSTRACT
Studies have provided evidences for the effects of nicotine on adipose tissues, as well as in inflammatory response. We hypothesized that nicotine affects adipokine gene expression in adipose tissues via specific neuronal nicotinic acetylcholine receptors (nAChRs). First, we described the expression of multiple nAChR subunit genes in mouse white and brown adipose tissues (WAT and BAT), and detected differential expression in WAT and BAT (α2>α5>ß2 and α2>ß2>ß4, respectively). Additionally, when nicotine was administered to wild-type mice, it significantly affected the expression of adipokine genes, such as Tnfα, AdipoQ, Haptoglobin and Mcp1 in WAT. Next, we demonstrated that in mice deficient for the ß2 nAChR subunit (ß2-/- mice), the expression levels of Cox2 and Ngfß genes in WAT, and Leptin, Cox2, AdipoQ and Haptoglobin in BAT, were significantly altered. Furthermore, interactions between mouse ß2 subunit and nicotine treatment affected the expression levels of the adipokine genes Tnfα, Cox2 and AdipoQ in WAT and of AdipoQ in BAT. Finally, analysis of a cellular model of cultured adipocytes demonstrated that application of nicotine after silencing of the ß2 nAChR subunit significantly elevated the expression level of Cox2 gene. Together, our data suggest a molecular link between the ß2 nACh receptor subunit and the expression levels of specific adipokines, which is also affected by nicotine.
Subject(s)
Adiponectin/genetics , Adipose Tissue, Brown/drug effects , Adipose Tissue, White/drug effects , Cyclooxygenase 2/genetics , Nicotine/pharmacology , Receptors, Nicotinic/metabolism , Tumor Necrosis Factor-alpha/genetics , Adipocytes/cytology , Adipocytes/drug effects , Adipocytes/metabolism , Adiponectin/metabolism , Adipose Tissue, Brown/metabolism , Adipose Tissue, White/metabolism , Animals , Cells, Cultured , Cyclooxygenase 2/metabolism , Gene Expression/drug effects , Gene Silencing , Male , Mice , Mice, Knockout , Organ Specificity , RNA, Small Interfering/genetics , Receptors, Nicotinic/genetics , Signal Transduction/drug effects , Tumor Necrosis Factor-alpha/metabolismABSTRACT
Diverse physiological and pathological effects of nicotine, including the alteration of body temperature, are presumably mediated by neuronal nicotinic acetylcholine receptors (nAChR). Previous studies have suggested the involvement of distinct nAChR subunits in nicotine-induced thermoregulation. We studied genetically manipulated knockout mice lacking the alpha7, alpha5 or beta4 subunit genes, in order to assess the effects of subunit deficiency on temperature regulation. Using a telemetry system, core body temperature was monitored continuously prior to and following nicotine administration in mutant mice and in wild-type littermates. Mice lacking in the beta4 nAChR subunit gene had significantly lower baseline core body temperature than all other mouse strains studied. beta4 null mice also demonstrated a reduced nicotine-induced hypothermic response and impaired desensitization following repeat nicotine exposure. These findings suggest the involvement of the beta4 nAChR subunit in both core body temperature homeostasis and nicotine-elicited thermo-alterations in mice.
