Central role of α7 nicotinic receptor in differentiation of the stratified squamous epithelium (original) (raw)
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Central role of alpha7 nicotinic receptor in differentiation of the stratified squamous epithelium
Journal of Cell Biology, 2002
S hand, inhibition of the ␣ 7 nAChR pathway favored cell cycle progression. In the epidermis of ␣ 7 Ϫ / Ϫ mice, the abnormalities in keratinocyte gene expression were associated with phenotypic changes characteristic of delayed epidermal turnover. The lack of ␣ 7 was associated with up-regulated expression of the ␣ 3 containing nAChR channels that lack ␣ 5 subunit, and both homomeric ␣ 9-and heteromeric ␣ 9 ␣ 10-made nAChRs. Thus, this study demonstrates that ACh signaling through ␣ 7 nAChR channels controls late stages of keratinocyte development in the epidermis by regulating expression of the cell cycle progression, apoptosis, and terminal differentiation genes and that these effects are mediated, at least in part, by alterations in transmembrane Ca 2 ϩ influx.
Functional role of alpha7 nicotinic receptor in physiological control of cutaneous homeostasis.
Non-neuronal nicotinic acetylcholine receptors (nAChRs) are abundantly expressed in skin and their function remains to be elucidated. Herein, we report that cutaneous alpha7 nAChR plays a role in the physiological control of cutaneous homeostasis. We studied in vitro effects of functional inactivation of alpha7 receptor on the expression of apoptosis regulators in keratinocytes (KC) lacking alpha7 nAChR, and extracellular matrix regulators in the skin of alpha7 knockout (KO) mice. Elimination of the alpha7 component of nicotinergic signaling in KC decreased relative amounts of the pro-apoptotic Bad and Bax at both the mRNA and the protein levels, suggesting that alpha7 nAChR is coupled to stimulation of keratinocyte apoptosis. The skin of alpha7 KO mice featured decreased amounts of the extracellular matrix proteins collagen 1alpha1 and elastin as well as the metalloproteinase-1. Taken together, these results suggest an important role for alpha7 nAChR in mediating plethoric effects of non-neuronal acetylcholine on cutaneous homeostasis.
Functional role of α7 nicotinic receptor in physiological control of cutaneous homeostasis
Life Sciences, 2003
Non-neuronal nicotinic acetylcholine receptors (nAChRs) are abundantly expressed in skin and their function remains to be elucidated. Herein, we report that cutaneous a7 nAChR plays a role in the physiological control of cutaneous homeostasis. We studied in vitro effects of functional inactivation of a7 receptor on the expression of apoptosis regulators in keratinocytes (KC) lacking a7 nAChR, and extracellular matrix regulators in the skin of a7 knockout (KO) mice. Elimination of the a7 component of nicotinergic signaling in KC decreased relative amounts of the pro-apoptotic Bad and Bax at both the mRNA and the protein levels, suggesting that a7 nAChR is coupled to stimulation of keratinocyte apoptosis. The skin of a7 KO mice featured decreased amounts of the extracellular matrix proteins collagen 1a1 and elastin as well as the metalloproteinase-1. Taken together, these results suggest an important role for a7 nAChR in mediating plethoric effects of non-neuronal acetylcholine on cutaneous homeostasis. D
Laboratory Investigation, 2003
Smoking is associated with aberrant cutaneous tissue remodeling, such as precocious skin aging and impaired wound healing. The mechanism is not fully understood. Dermal fibroblasts (DF) are the primary cellular component of the dermis and may provide a target for pathobiologic effects of tobacco products. The purpose of this study was to characterize a mechanism of nicotine (Nic) effects on the growth and tissue remodeling function of DF. We hypothesized that the effects of Nic on DF result from its binding to specific nicotinic acetylcholine receptors (nAChRs) expressed by these cells and that downstream signaling from the receptors alters normal cell functioning, leading to changes in skin homeostasis. Using RT-PCR and Western blotting, we found that a 24-hour exposure of human DF to 10 M Nic causes a 1.9-to 28-fold increase of the mRNA and protein levels of the cell cycle regulators p21, cyclin D1, Ki-67, and PCNA and a 1.7-to 2-fold increase of the apoptosis regulators Bcl-2 and caspase 3. Nic exposure also up-regulated expression of the dermal matrix proteins collagen type I␣1 and elastin as well as matrix metalloproteinase-1. Mecamylamine (Mec), the specific antagonist of nAChRs, abolished Nic-induced alterations, indicating that they resulted from a pharmacologic stimulation of nAChRs expressed by DF. To establish the relevance of these findings to a specific nicotinergic pathway, we studied human DF transfected with anti-␣3 antisense oligonucleotides and murine DF from ␣3 nAChR knockout mice. In both cases, lack of ␣3 was associated with alterations in fibroblast growth and function that were opposite to those observed in DF treated with Nic, suggesting that the nicotinic effects on DF were mostly mediated by ␣3 nAChR. In addition to ␣3, the nAChR subunits detected in human DF were ␣5, ␣7, 2, and 4. The exposure of DF to Nic altered the relative amounts of each of these subunits, leading to reciprocal changes in [ 3 H]epibatidine-binding kinetics. Thus, some of the pathobiologic effects of tobacco products on extracellular matrix turnover in the skin may stem from Nic-induced alterations in the physiologic control of the unfolding of the genetically determined program of growth and the tissue remodeling function of DF as well as alterations in the structure and function of fibroblast nAChRs. (Lab Invest 2003, 83:207-225).
Life Sciences, 2012
Aim-To characterize how nicotinic acetylcholine receptors (nAChRs) influence epidermal barrier function and recovery following prolonged stress or direct nAChR activation or antagonism. Main Methods-Mice were subjected to psychological stress or treated topically with nAChR agonist or antagonist for 3 days. We assessed barrier permeability and recovery by measuring transepidermal water loss (TEWL) before and after barrier disruption. In parallel, we analyzed the production and localization of several epidermal cornified envelope proteins in mouse skin and in human EpiDerm ™ organotypic constructs stimulated with a nAChR agonist (nicotine) and/or a nAChR selective antagonist (α-bungarotoxin). Key Findings-We determined that psychological stress in mice impairs barrier permeability function and recovery, an effect that is reversed by application of the α7 selective nAChR antagonist, α-bungarotoxin (Bung). In the absence of stress, both topical nicotine or Bung treatment alone impaired barrier permeability. We further observed that stress, topical nicotine, or topical Bung treatment in mice influenced the abundance and/or localization of filaggrin, loricrin, and involucrin. Similar alterations in these three major cornified envelope proteins were observed in human EpiDerm ™ cultures. Significance-Perceived psychological stress and nicotine usage can both initiate or exacerbate several dermatoses by altering the cutaneous permeability barrier. Modulation of nAChRs by topical agonists or antagonists may be used to improve epidermal barrier function in skin diseases associated with defects in epidermal barrier permeability.
A Receptor-Mediated Mechanism of Nicotine Toxicity in Oral Keratinocytes
Laboratory Investigation, 2001
Smoking and smokeless tobacco cause morbidity that originates from the epithelium lining of the skin and upper digestive tract. Oral keratinocytes (OKC) express nicotinic acetylcholine receptors (nAChRs) that bind nicotine (Nic). We studied the mechanism of the receptor-mediated toxicity of tobacco products on OKC. Preincubation of normal human OKC with Nic altered the ligand-binding kinetics of their nAChRs, suggesting that
The FASEB Journal, 2007
Tobacco products and nicotine alter the cell cycle and lead to squamatization of oral keratinocytes (KCs) and squamous cell carcinoma. Activation of nicotinic acetylcholine receptors (nAChRs) elicits Ca 2؉ influx that varies in magnitude between different nAChR subtypes. Normal differentiation of KCs is associated with sequential expression of the nAChR subtypes with increasing Ca 2؉ permeability, such as ␣5-containing ␣3 nAChR and ␣7 nAChR. Exposure to environmental tobacco smoke (ETS) or an equivalent concentration of nicotine accelerated by severalfold the ␣5 and ␣7 expression in KCs, which could be abolished by mecamylamine and ␣-bungarotoxin with different efficacies, suggesting the following sequence of autoregulation of the expression of nAChR subtypes: ␣3(2/4) > ␣3(2/4)␣5 > ␣7 > ␣7. This conjecture was corroborated by results of quantitative assays of subunit mRNA and protein levels, using nAChRspecific pharmacologic antagonists and small interfering RNAs. The genomic effects of ETS and nicotine involved the transcription factor GATA-2 that showed a multifold increase in quantity and activity in exposed KCs. Using protein kinase inhibitors and dominant negative and constitutively active constructs, we characterized the principal signaling cascades mediating a switch in the nAChR subtype. Cumulative results indicated that the ␣3(2/4) to ␣3(2/4)␣5 nAChR transition predominantly involved protein kinase C, ␣3(2/ 4)␣5 to ␣7 nAChR transition-Ca 2؉ /calmodulindependent protein kinase II and p38 MAPK, and ␣7 self-up-regulation-the p38 MAPK/Akt pathway, and JAK-2. These results provide a mechanistic insight into the genomic effects of ETS and nicotine on KCs and characterize signaling pathways mediating autoregulation of stepwise overexpression of nAChR subtypes with increasing Ca 2؉ permeability in exposed cells. These observations have salient clinical implications, because a switch in the nAChR subunit composition can bring about a corresponding switch in receptor function, leading to profound pathobiologic effects observed in KCs exposed to tobacco products. Arre
PLoS ONE, 2011
Background: Chronic UV skin exposure leads to epidermal differentiation defects in humans that can be largely restored by pharmacological doses of nicotinic acid. Nicotinic acid has been identified as a ligand for the human G-protein-coupled receptors GPR109A and GPR109B that signal through G i -mediated inhibition of adenylyl cyclase. We have examined the expression, cellular distribution, and functionality of GPR109A/B in human skin and skin derived epidermal cells.
Faseb Journal, 2007
Tobacco products and nicotine alter the cell cycle and lead to squamatization of oral keratinocytes (KCs) and squamous cell carcinoma. Activation of nicotinic acetylcholine receptors (nAChRs) elicits Ca 2؉ influx that varies in magnitude between different nAChR subtypes. Normal differentiation of KCs is associated with sequential expression of the nAChR subtypes with increasing Ca 2؉ permeability, such as ␣5-containing ␣3 nAChR and ␣7 nAChR. Exposure to environmental tobacco smoke (ETS) or an equivalent concentration of nicotine accelerated by severalfold the ␣5 and ␣7 expression in KCs, which could be abolished by mecamylamine and ␣-bungarotoxin with different efficacies, suggesting the following sequence of autoregulation of the expression of nAChR subtypes: ␣3(2/4) > ␣3(2/4)␣5 > ␣7 > ␣7. This conjecture was corroborated by results of quantitative assays of subunit mRNA and protein levels, using nAChRspecific pharmacologic antagonists and small interfering RNAs. The genomic effects of ETS and nicotine involved the transcription factor GATA-2 that showed a multifold increase in quantity and activity in exposed KCs. Using protein kinase inhibitors and dominant negative and constitutively active constructs, we characterized the principal signaling cascades mediating a switch in the nAChR subtype. Cumulative results indicated that the ␣3(2/4) to ␣3(2/4)␣5 nAChR transition predominantly involved protein kinase C, ␣3(2/ 4)␣5 to ␣7 nAChR transition-Ca 2؉ /calmodulindependent protein kinase II and p38 MAPK, and ␣7 self-up-regulation-the p38 MAPK/Akt pathway, and JAK-2. These results provide a mechanistic insight into the genomic effects of ETS and nicotine on KCs and characterize signaling pathways mediating autoregulation of stepwise overexpression of nAChR subtypes with increasing Ca 2؉ permeability in exposed cells. These observations have salient clinical implications, because a switch in the nAChR subunit composition can bring about a corresponding switch in receptor function, leading to profound pathobiologic effects observed in KCs exposed to tobacco products. Arre-dondo, J., Chernyavsky, A. I., Jolkovsky, D. L., Pinkerton, K. E., Grando, S. A. Receptor-mediated tobacco toxicity: acceleration of sequential expression of ␣5 and ␣7 nicotinic receptor subunits in oral keratinocytes exposed to cigarette smoke. FASEB J. 22, 1356 -1368 (2008)