Nicotine acts as a potent modulator of normal cellular responses through the nicotinic acetylcholine receptor subtype alpha7. In a mouse genetic model of alpha7 receptor dysfunction, alpha7, 85 percent of 18 month-old mice exhibit an age-associated spontaneous loosening or complete loss of 3rd molars that was not present in the control mice. The adjacent soft tissues appeared largely unaffected.
View Article and Find Full Text PDFAm J Physiol Lung Cell Mol Physiol
October 2020
Nicotine of unprecedented concentrations and purity is being inhaled by those using commercially available electronic nicotine delivery systems (ENDS). The consequences of this route of self-administration on the immunological response to inhaled allergens are not known. In mice, sensitization and inhalation challenge with the common environmental house dust mite (HDM) allergen is an experimental model of this response.
View Article and Find Full Text PDFAm J Physiol Lung Cell Mol Physiol
October 2018
Eosinophilia (EOS) is an important component of airway inflammation and hyperresponsiveness in allergic reactions including those leading to asthma. Although cigarette smoking (CS) is a significant contributor to long-term adverse outcomes in these lung disorders, there are also the curious reports of its ability to produce acute suppression of inflammatory responses including EOS through poorly understood mechanisms. One possibility is that proinflammatory processes are suppressed by nicotine in CS acting through nicotinic receptor α7 (α7).
View Article and Find Full Text PDFCigarette smoking (CS) is a principal contributor to a spectrum of devastating lung diseases whose occurrence and severity may vary between individuals and not appear for decades after prolonged use. One explanation for the variability and delay in disease onset is that nicotine, the addictive component of CS, acts through the ionotropic nicotinic acetylcholine receptor (nAChR) alpha7 (α7) to modulate anti-inflammatory protection. In this study we measured the impact α7 signaling has on the mouse distal lung response to side-stream CS exposure for mice of the control genotype (α7G) and those in which the α7-receptor signaling mechanisms are restricted by point mutation (α7E260A:G).
View Article and Find Full Text PDFNicotine modulates multiple inflammatory responses in the lung through the nicotinic acetylcholine receptor subtype alpha7 (α7). Previously we reported that α7 modulates both the hematopoietic and epithelium responses in the lung to the bacterial inflammogen, lipopolysaccharide (LPS). Here we apply immunohistochemistry, flow cytometry and RNA-Seq analysis of isolated distal lung epithelium to further define α7-expression and function in this tissue.
View Article and Find Full Text PDFHigh affinity nicotine-binding sites in the mammalian brain are neuronal nicotinic acetylcholine receptors (nAChR) assembled from at least alpha4 and beta2 subunits into pentameric ion channels. When exposed to ligands such as nicotine, these receptors respond by undergoing upregulation, a correlate of nicotine addiction. Upregulation can be measured using HEK293 (293) cells that stably express alpha4 and beta2 subunits using quantification of [3H]epibatidine ([3H]Eb) binding to measure mature receptors.
View Article and Find Full Text PDFThe IfitmDel mouse lacks all five of the Ifitm genes via LoxP deletion. This animal breeds normally with no obvious defect in development. The IfitmDel animals exhibit a steady and significantly enhanced weight gain relative to wild-type controls beginning about three months of age and under normal feeding conditions.
View Article and Find Full Text PDFThe nicotinic acetylcholine receptor alpha7 (α7) is expressed by neuronal and non-neuronal cells throughout the body. We examined the mechanisms of the lung inflammatory response to intranasal (i.n.
View Article and Find Full Text PDFThe nicotinic acetylcholine receptor alpha 7 (α7) is a ligand-activated ion channel that contributes to a diversity of cellular processes involved in development, neurotransmission and inflammation. In this report the expression of α7 was examined in the mouse developing and adult adrenal gland that expresses a green fluorescent protein (GFP) reporter as a bi-cistronic extension of the endogenous α7 transcript (α7(G)). At embryonic day 12.
View Article and Find Full Text PDFHow inflammatory responses are mechanistically modulated by nicotinic acetylcholine receptors (nAChR), especially by receptors composed of alpha7 (α7) subunits, is poorly defined. This includes a precise definition of cells that express α7 and how these impact on innate inflammatory responses. To this aim we used mice generated through homologous recombination that express an Ires-Cre-recombinase bi-cistronic extension of the endogenous α7 gene that when crossed with a reporter mouse expressing Rosa26-LoxP (yellow fluorescent protein (YFP)) marks in the offspring those cells of the α7 cell lineage (α7(lin+)).
View Article and Find Full Text PDFNicotinic acetylcholine receptor alpha7 expression was examined in the developing and adult auditory system using mice that were modified through homologous recombination to coexpress either GFP (alpha7GFP) or Cre (alpha7Cre), respectively. The expression of alpha7GFP is first detected at embryonic (E) day E13.5 in cells of the spiral prominence.
View Article and Find Full Text PDFThe expression of nicotinic acetylcholine receptor (nAChR) subtype, alpha7, was investigated in the developing teeth of mice that were modified through homologous recombination to express a bi-cistronic IRES-driven tau-enhanced green fluorescent protein (GFP); alpha7GFP) or IRES-Cre (alpha7Cre). The expression of alpha7GFP was detected first in cells of the condensing mesenchyme at embryonic (E) day E13.5 where it intensifies through E14.
View Article and Find Full Text PDFLumbosacral spina bifida is a common debilitating birth defect whose multiple causes are poorly understood. Here, we provide the first genetic delineation of cholinergic nicotinic receptor alpha7 (Chrna7) expression and link the ablation of the Chrna7 cell lineage to this condition in the mouse. Using homologous recombination, an IRES-Cre bi-cistronic cassette was introduced into the 3' noncoding region of Chrna7 (Chrna7:Cre) for identifying cell lineages expressing this gene.
View Article and Find Full Text PDFBackground: A major site of initiation of inflammatory responses upon physical perturbation(s) and infection by invading organisms is the skin. Control of responses in this organ is, in part, modulated by the neuronal nicotinic acetylcholine receptor (nAChR) alpha7.
Methods: To further investigate the role of alpha7 in skin inflammatory responses, a local inflammatory response was induced by topical application of croton oil to the ear skin of wild-type (alpha7WT) and alpha7 knock-out (alpha7KO) mice.
In the mammalian brain high affinity nicotine-binding sites are composed of at least the alpha4 and beta2 subunits. Additional nicotinic acetylcholine receptor subunits that are often co-expressed with alpha4+beta2 include alpha5. The introduction of alpha5 into 293 cells expressing alpha4+beta2 strongly favors assembly of alpha4+alpha5+beta2 receptors, increases constitutive ligand binding density as measured using [(3)H]epibatidine, but reduces the magnitude of up-regulation in response to chronic nicotine.
View Article and Find Full Text PDFNeuronal nicotinic acetylcholine receptors (nAChR) composed of alpha4 + beta2 subunits, the high affinity nicotine-binding site in the mammalian brain, up-regulate in response to chronic nicotine exposure. The identities of endogenous mediators of this process are unknown. We find that choline also up-regulates alpha4 + beta2 nAChRs stably expressed by HEK293 cells as measured by increased [(3)H]epibatidine density.
View Article and Find Full Text PDFPeople who begin daily smoking at an early age are at greater risk of long-term nicotine addiction. We tested the hypothesis that associations between nicotinic acetylcholine receptor (nAChR) genetic variants and nicotine dependence assessed in adulthood will be stronger among smokers who began daily nicotine exposure during adolescence. We compared nicotine addiction-measured by the Fagerstrom Test of Nicotine Dependence-in three cohorts of long-term smokers recruited in Utah, Wisconsin, and by the NHLBI Lung Health Study, using a candidate-gene approach with the neuronal nAChR subunit genes.
View Article and Find Full Text PDFDifferences between isogenic mouse strains in cellular expression of the neuronal nicotinic acetylcholine (ACh) receptor subunit alpha 4 (nAChR alpha 4) by the dorsal hippocampus are well known. To investigate further the genetic basis of these variations, expression of the nAChR alpha 4 subunit was measured in congenic mouse lines derived from two strains exhibiting notable divergence in the expression of this subunit: C3H and C57BL/6. Congenic lines carrying reciprocally introgressed regions (quantitative trait loci; QTL) from chromosomes 4, 5, and 12 each retained the phenotype most closely associated with the parental strain.
View Article and Find Full Text PDFMouse strains are well-characterized to exhibit differences in their physiological and behavioral responses to nicotine. This report examines the expression of the high-affinity nicotine binding receptor subunit, neuronal nicotinic receptor subunit alpha 4 (nAChR alpha 4), in the dorsal hippocampus of 27 inbred mouse strains. Multiple differences among mouse strains in the cellular expression of nAChR alpha 4 between subregions of the hippocampal field are evident.
View Article and Find Full Text PDFThe anti-inflammatory effects of the neuronal nicotinic receptor alpha7 (nAChRalpha7) are proposed to require acetylcholine release from vagal efferents. The necessity for vagal innervation in this anti-inflammatory pathway was tested in the skin, which lacks parasympathetic innervation, using ultraviolet radiation (UVB) to induce a local pro-inflammatory response. Cytokine responses to UV in mice administered chronic oral nicotine, a nAChR agonist, were reduced.
View Article and Find Full Text PDFA response by key neuronal nicotinic acetylcholine receptors (nAChRs) to sustained nicotine exposure is up-regulation. Although this unusual receptor characteristic contributes to processes ranging from aging to addiction, the normal physiologic reason for this response is unknown. We find that up-regulation of [(3)H]epibatidine binding and function in HEK293 cells stably expressing alpha4beta2-nAChR is significantly enhanced by co-application of the proinflammatory cytokine, tumor necrosis factor alpha.
View Article and Find Full Text PDFOf the thousands of proven carcinogens and toxic agents contained within a cigarette, nicotine, while being the addictive agent, is often viewed as the least harmful of these compounds. Nicotine is a lipophilic molecule whose effects on neuronal nicotinic acetylcholine receptors (nAChR) have been primarily focused on its physiologic impact within the confines of the brain and peripheral nervous system. However, recently, many studies have found neuronal nAChRs to be expressed on many different nonneuronal cell types throughout the body, where increasing evidence suggests they have important roles in determining the consequences of nicotine use on multiple organs systems and diseases as diverse as ulcerative colitis, chronic pulmonary obstructive disease, and diabetes, as well as the neurologic disorders of Parkinson's and Alzheimer's disease.
View Article and Find Full Text PDFWe have examined the impact of the inflammatory cytokines interleukin-1 beta (IL-1beta) and tumor necrosis factor alpha (TNFalpha) on assembly of nAChRs from subunit mixtures of nAChRalpha4, beta2 and beta4 transiently transfected into 293 cells. In control transfections approximately 55% of alpha4 associated preferentially with beta4, but less than 15% complexed with beta2 and the remainder was associated with both beta subunits. These relative ratios were modified by pro-inflammatory cytokines.
View Article and Find Full Text PDFThe onset and severity of age-related loss of neuronal nicotinic acetylcholine receptor (nAChR) expression in the mammalian hippocampus can vary considerably between individuals. We have examined the expression of four nAChR subunits (nAChR alpha4, nAChR alpha5, nAChR alpha7 and nAChR beta4) in the dorsal hippocampus of adult (12-14 months) and aged (24-28 month) animals from two-mouse strains (CBA/J and C57BL/6). The expression of nAChR alpha4 was selectively diminished with age in both strains, and there was a significant loss of nAChR alpha7 in CA1 of aged CBA/J, but not C57BL/6.
View Article and Find Full Text PDFAge-related changes in the mammalian dorsal hippocampus are associated with diminished expression of neuronal nicotinic acetylcholine receptors (nAChR), which is particularly severe in pathologies such as those associated with dementias, including Alzheimer's disease. Because the mouse is a useful model for age-related decline in nAChR expression in the basal forebrain and limbic system, we used immunohistochemistry to examine the influence of long-term (12-month) oral administration of nicotine and/or the cyclooxygenase-2 (COX-2) preferring non-steroidal anti-inflammatory drug (NSAID) NS398 on nAChR alpha4, alpha5, alpha7, and beta4 expression in the C57BL/6 mouse. Inhibitory neurons of the dorsal hippocampus that express nAChRs also constitutively express COX-2 and the peroxisome proliferator-antagonist receptor subtype gamma-2 (PPAR gamma2) which is also a target of NS398.
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