ABSTRACT
Nitric oxide (NO) is an important signaling molecule in both the central nervous system and the periphery, where it is involved in neurotransmission, vascular and bronchial tone, inflammation, and cutaneous immune function. More recently, NO has been implicated in intracellular signaling and may have a role in cellular differentiation, cytokine expression, and apoptosis. The experiments described herein examined the effect of calcitonin gene-related protein (CGRP), a cutaneous nerve neuropeptide, on NO production in human keratinocytes in vitro. CGRP stimulated two distinct increases in NO production: one within 30 minutes and a second at 24 hours. CGRP stimulated a modest increase in inducible nitric oxide synthase (iNOS) at 3-6 hours. Experimental evidence suggested that CGRP stimulated both constitutive NOS activity and generation of NO via nitrosothiol degradation within the first hour. Production of NO was paralleled by a decrease in nitrosothiol levels for 2 hour, suggesting that immediate NO release may originate from pre-existing stores. Nitrosothiols are ubiquitous molecules that comprise an important NO pool and have intracellular regulatory roles, particularly linked to oxidative stress. The present data indicate that, in addition to its known cAMP signaling pathway, CGRP may act to regulate keratinocyte biology through intracellular NO by modulation of S-nitrosothiol stores and stimulation of NOS activity.
Subject(s)
Calcitonin Gene-Related Peptide/metabolism , Keratinocytes/metabolism , Nitric Oxide/metabolism , Signal Transduction/physiology , Calcitonin Gene-Related Peptide/pharmacology , Cell Line , Enzyme Activation/drug effects , Enzyme Activation/physiology , Enzyme Inhibitors/pharmacology , Epidermal Cells , Humans , In Vitro Techniques , Keratinocytes/cytology , Nitric Oxide Synthase Type II/antagonists & inhibitors , Nitric Oxide Synthase Type II/metabolism , Oxidative Stress/physiology , S-Nitrosothiols/metabolism , Signal Transduction/drug effectsABSTRACT
Our purpose was to evaluate the efficacy and safety of a combination of benzoyl peroxide 6% cleanser and tretinoin 0.1% microsphere gel versus monotherapy with tretinoin 0.1% microsphere gel. Eighty-seven healthy males and nonpregnant nonlactating females between the ages of 12 and 30 years with moderate inflammatory acne vulgaris were enrolled in this randomized controlled, investigator-blind, parallel group clinical trial. Subjects were evaluated over 12 weeks for a total of 4 visits. The investigators and subjects completed questionnaires about the test medications. Data from the 56 subjects completing the protocol were considered in the analyses of efficacy and tolerability. The reduction in inflammatory lesions from baseline was significant for both treatment groups at the end of the study. However, there was a significantly greater reduction in the group receiving the combination regimen. Both treatment groups had significant reductions from baseline in noninflammatory lesions at week 12, but no differences were observed between treatment groups. With the exception of skin tightness, which was significantly greater at week 12 in the subjects who received the monotherapy, there were no significant differences between the 2 treatment groups with respect to localized irritation. Adverse events were rare in all subjects. Not only did the combination regimen result in a greater reduction of inflammatory acne lesions than use of the monotherapy but also it did not result in an increase in local irritation.
