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Nicotinic acid receptor abnormalities in human skin cancer: implications for a role in epidermal differentiation.

Bermudez Y, Benavente CA, Meyer RG, Coyle WR, Jacobson MK, Jacobson EL - PLoS ONE (2011)

Bottom Line: Receptor transcripts are greatly over-expressed in squamous cell cancers.In normal human primary and immortalized keratinocytes, nicotinic acid receptors show plasma membrane localization and functional G(i)-mediated signaling.The results of these studies justify future genetic and pharmacological intervention studies to define possible specific role(s) of nicotinic acid receptors in human skin homeostasis.

View Article: PubMed Central - PubMed

Affiliation: Arizona Cancer Center and Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona, United States of America.

ABSTRACT

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.

Results: Nicotinic acid increases epidermal differentiation in photodamaged human skin as judged by the terminal differentiation markers caspase 14 and filaggrin. Both GPR109A and GPR109B genes are transcribed in human skin and in epidermal keratinocytes, but expression in dermal fibroblasts is below limits of detection. Receptor transcripts are greatly over-expressed in squamous cell cancers. Receptor protein in normal skin is prominent from the basal through granular layers of the epidermis, with cellular localization more dispersive in the basal layer but predominantly localized at the plasma membrane in more differentiated epidermal layers. In normal human primary and immortalized keratinocytes, nicotinic acid receptors show plasma membrane localization and functional G(i)-mediated signaling. In contrast, in a squamous cell carcinoma derived cell line, receptor protein shows a more diffuse cellular localization and the receptors are nearly non-functional.

Conclusions: The results of these studies justify future genetic and pharmacological intervention studies to define possible specific role(s) of nicotinic acid receptors in human skin homeostasis.

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Related in: MedlinePlus

GPR109A/B couple through Gi in normal keratinocytes while SCC-25 cells are insensitive to pertussis toxin and nicotinic acid.NHEK (open columns) and SCC-25 (grey columns) cells were pretreated with or without 100 ng/mL pertussis toxin overnight and stimulated with 10 µM forskolin in the presence or absence of 100 µM nicotinic acid and intracellular cAMP levels were measured. Data represent the mean ± SEM from three independent experiments calculated as forskolin-induced cAMP relative to cellular protein. Students t-test was used to compare to cAMP produced without nicotinic acid to that produced with nicotinic acid, * p≤0.05.
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pone-0020487-g007: GPR109A/B couple through Gi in normal keratinocytes while SCC-25 cells are insensitive to pertussis toxin and nicotinic acid.NHEK (open columns) and SCC-25 (grey columns) cells were pretreated with or without 100 ng/mL pertussis toxin overnight and stimulated with 10 µM forskolin in the presence or absence of 100 µM nicotinic acid and intracellular cAMP levels were measured. Data represent the mean ± SEM from three independent experiments calculated as forskolin-induced cAMP relative to cellular protein. Students t-test was used to compare to cAMP produced without nicotinic acid to that produced with nicotinic acid, * p≤0.05.

Mentions: To determine whether the response to nicotinic acid is signaling through the inhibitory Gα subunit and to further examine receptor functionality in SCC-25 cells, cAMP production in NHEK and SCC-25 was examined in the presence of pertussis toxin, a known inhibitor of the heterotrimeric Gi protein subunit (Fig. 7). Pertussis toxin completely abolished nicotinic acid-mediated inhibition of forskolin-stimulated cAMP formation in NHEK cells. In contrast, the response to nicotinic acid is very small in SCC-25 cells in the absence or presence of pertussis toxin. These data indicate that the nicotinic acid receptor(s) are signaling via Gi and further demonstrate that the receptor has greatly reduced functionality in SCC-25 cells.


Nicotinic acid receptor abnormalities in human skin cancer: implications for a role in epidermal differentiation.

Bermudez Y, Benavente CA, Meyer RG, Coyle WR, Jacobson MK, Jacobson EL - PLoS ONE (2011)

GPR109A/B couple through Gi in normal keratinocytes while SCC-25 cells are insensitive to pertussis toxin and nicotinic acid.NHEK (open columns) and SCC-25 (grey columns) cells were pretreated with or without 100 ng/mL pertussis toxin overnight and stimulated with 10 µM forskolin in the presence or absence of 100 µM nicotinic acid and intracellular cAMP levels were measured. Data represent the mean ± SEM from three independent experiments calculated as forskolin-induced cAMP relative to cellular protein. Students t-test was used to compare to cAMP produced without nicotinic acid to that produced with nicotinic acid, * p≤0.05.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3105069&req=5

pone-0020487-g007: GPR109A/B couple through Gi in normal keratinocytes while SCC-25 cells are insensitive to pertussis toxin and nicotinic acid.NHEK (open columns) and SCC-25 (grey columns) cells were pretreated with or without 100 ng/mL pertussis toxin overnight and stimulated with 10 µM forskolin in the presence or absence of 100 µM nicotinic acid and intracellular cAMP levels were measured. Data represent the mean ± SEM from three independent experiments calculated as forskolin-induced cAMP relative to cellular protein. Students t-test was used to compare to cAMP produced without nicotinic acid to that produced with nicotinic acid, * p≤0.05.
Mentions: To determine whether the response to nicotinic acid is signaling through the inhibitory Gα subunit and to further examine receptor functionality in SCC-25 cells, cAMP production in NHEK and SCC-25 was examined in the presence of pertussis toxin, a known inhibitor of the heterotrimeric Gi protein subunit (Fig. 7). Pertussis toxin completely abolished nicotinic acid-mediated inhibition of forskolin-stimulated cAMP formation in NHEK cells. In contrast, the response to nicotinic acid is very small in SCC-25 cells in the absence or presence of pertussis toxin. These data indicate that the nicotinic acid receptor(s) are signaling via Gi and further demonstrate that the receptor has greatly reduced functionality in SCC-25 cells.

Bottom Line: Receptor transcripts are greatly over-expressed in squamous cell cancers.In normal human primary and immortalized keratinocytes, nicotinic acid receptors show plasma membrane localization and functional G(i)-mediated signaling.The results of these studies justify future genetic and pharmacological intervention studies to define possible specific role(s) of nicotinic acid receptors in human skin homeostasis.

View Article: PubMed Central - PubMed

Affiliation: Arizona Cancer Center and Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona, United States of America.

ABSTRACT

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.

Results: Nicotinic acid increases epidermal differentiation in photodamaged human skin as judged by the terminal differentiation markers caspase 14 and filaggrin. Both GPR109A and GPR109B genes are transcribed in human skin and in epidermal keratinocytes, but expression in dermal fibroblasts is below limits of detection. Receptor transcripts are greatly over-expressed in squamous cell cancers. Receptor protein in normal skin is prominent from the basal through granular layers of the epidermis, with cellular localization more dispersive in the basal layer but predominantly localized at the plasma membrane in more differentiated epidermal layers. In normal human primary and immortalized keratinocytes, nicotinic acid receptors show plasma membrane localization and functional G(i)-mediated signaling. In contrast, in a squamous cell carcinoma derived cell line, receptor protein shows a more diffuse cellular localization and the receptors are nearly non-functional.

Conclusions: The results of these studies justify future genetic and pharmacological intervention studies to define possible specific role(s) of nicotinic acid receptors in human skin homeostasis.

Show MeSH
Related in: MedlinePlus