title: Tissue-specific patterns of neurokinin-1 receptor (NK-1R) gene expression in mice exposed to sidestream cigarette smoke.
abstract: Neurokinin-1 receptor (NK-1R), a high-affinity plasma membrane-bound receptor for neurokinin substance P, plays important roles in the onset of the pathophysiological responses. To test whether the transcript levels of gene encoding NK-1R in organs are affected by sidestream cigarette smoke (SSCS) exposure, the C57BL/6 mice were randomly assigned to five groups (six/group) in a study of the dose-effect relationship. The mice were exposed to 0 (filtered room air), 2, 4, 8 and 16 mg total particulate matter (TPM) of SSCS/exposure/day, respectively, for seven days through a nose-only exposure chamber (IN-TOX, Albuquerque, NM, USA). The levels of NK-1R mRNA in the lung, heart, liver, kidney and spleen tissues were detected by reverse transcription-polymerase chain reaction (RT-PCR) techniques and normalized against GAPDH expression. NK-1R mRNA in heart tissue showed SSCS-induced dose-dependent downregulation, with minimum expression at a dose of 8.0 mg TPM. Whereas, the levels of NK-1R mRNA in the liver were upregulated to 2.86 and 5.13-fold after exposure to 2.0 and 4.0 mg TPM of SSCS respectively, then returned to 4.19 and 3.93-fold at the exposure doses of 8.0 and 16.0 mg TPM, respectively, when compared to that of the control. In the kidney, SSCS exposure at a dose of 2.0 TPM, but not higher than that level, induced significant elevation of NK-1R mRNA expression. These findings suggest that there are the paracrine and/or autocrine signalling mechanisms through receptor-ligand interactions. No alteration of NK-1R gene expression was observed in the lungs and spleen tissues in this study. The tissue-specific patterns by which SSCS affect NK-1R gene expression in these organs may partially explain dissimilarity of NK-1R activation and the associated toxicity caused by environmental tobacco smoke.
authors.affiliation: Department of Pediatrics, Southwest Environmental Health Sciences Center, University of Arizona, P.O. Box 245073, 1501 N. Campbell Avenue, Tucson, AZ 85724-5073, USA.
authors.forename: Simon S
authors.initials: SS
authors.lastname: Wong
authors.forename: Nina N
authors.initials: NN
authors.lastname: Sun
authors.forename: R Clark
authors.initials: RC
authors.lastname: Lantz
authors.forename: Mark L
authors.initials: ML
authors.lastname: Witten
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D020869:Gene Expression Profiling; D008024:Ligands; D008099:Liver / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010316:Particle Size; D011897:Random Allocation; D018040:Receptors, Neurokinin-1 / Q000096:biosynthesis* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014018:Tissue Distribution; D014028:Tobacco Smoke Pollution / Q000009:adverse effects*; D015854:Up-Regulation
chemical_list: D008024:Ligands; D018040:Receptors, Neurokinin-1; D014028:Tobacco Smoke Pollution