Lower expressions of the human bitter taste receptor TAS2R in smokers: reverse transcriptase-polymerase chain reaction analysis.

BACKGROUND: Despite the fact that smokers have deficit in detecting taste, particularly bitter taste, no study has investigated its biological correlate. METHODS: In this context, we compared the expression of the bitter taste receptor gene, taste 2 receptor (TAS2R) in the tongues of smokers and non-smokers. Tissue samples were collected from the lateral portion of the tongues of 22 smokers and 22 age- and gender-matched healthy volunteers (19 males and three females) with no history of smoking. Reverse transcriptase-polymerase chain reaction was used to examine the expression of TAS2R in the two groups, and the effect of aging on TAS2R expression was also assessed. RESULTS: TAS2R expression was significantly lower among smokers than non-smokers (t = 6.525, P < .0001, 11.36 ± 6.0 vs. 2.09 ± 2.8, mean ± SD, non-smokers vs. smokers). Further, a positive correlation between age and expression of TAS2R was observed in non-smokers (r = .642, P = .001), but not smokers (r = .124, P = .584). This correlation difference was significant (Z = 1.96, P = .0496). CONCLUSIONS: Smokers showed a significantly lower expression of the bitter taste receptor gene than non-smokers, which is potentially caused by their inability to acquire such receptors with age because of cigarette smoking, in contrast to non-smokers.

Expression and localization of taste receptor genes in the vallate papillae of rats: effect of zinc deficiency.

CONCLUSION: We found a difference in expression sites between TAS2Rs and ENaC (epithelial sodium channels). The number of TAS2R-positive cells and ENaC-positive cells were decreased in zinc-deficient diet rats. These findings suggest that decreased expression of taste receptor genes may play an important role in the onset of zinc deficiency-associated taste disorder. OBJECTIVE: The present study was aimed at histologically investigating the expression and localization of TAS2Rs and ENaC in the vallate taste buds of rats. Changes in expression of the taste receptor genes in zinc-deficient rats were also investigated. METHODS: The vallate papillae of five rats fed a normal diet and five rats fed a zinc-deficient diet were used. In situ hybridization was performed to investigate the expression and localization of TAS2Rs and ENaC. TAS2R-positive cells per taste bud were counted, and differences in number between the normal and zinc-deficient diet rats were investigated. RESULTS: In the normal rats, expression of TAS2Rs was observed specifically in the taste bud cells. In contrast, ENaC-positive cells were observed in a part of the taste bud cells and a large number of epithelial cells. Fewer cells were positive for TAS2Rs and ENaC in the zinc-deficient diet rats.

An epidermal growth factor motif from Del1 protein increases the efficiency of in vivo gene transfer with a non-viral vector.

Increasing the efficiency of gene transfer using non-viral vectors, which have the potential to be safe and economical, would improve upon available options for gene therapy. We previously reported that the third EGF motif of the extracellular matrix protein Del1 (E3) increases the transfection efficiency of non-viral vector methods. Here, we asked if E3 could increase the in vivo transfection efficiency of a polyplex-based approach. To test this, cDNA encoding a heat-stable alkaline phosphatase (AP) was first injected intravenously into mice along with recombinant E3. After 24 h, exogenous AP activity in serum was measured. We found that the introduction of E3 resulted in 50 % more AP activity as compared to the control. We next tested transfection into a tumour explant of SCCKN cells, an oral carcinoma-derived cell line. To do this, a cDNA encoding yellow fluorescent protein was locally injected into a tumour explant, followed by local injection of recombinant E3. Use of E3 increased the number of transfected cells to 2.5 times that of the control. Histochemical staining revealed that E3-induced apoptosis in a tumour explant. The data suggest that E3 might be a useful tool for cancer gene therapy using non-viral vectors.

Effects of zinc deficiency and supplementation on gene expression of bitter taste receptors (TAS2Rs) on the tongue in rats.

OBJECTIVES/HYPOTHESIS: We examined the effect of zinc deficiency and supplementation on the expression of bitter taste receptor (TAS2R) and epithelial sodium ion channel (ENaC) genes on the tongue in rats. STUDY DESIGN: Prospective animal study. METHODS: A total of 36 male Sprague-Dawley rats (3 weeks old) were used. Twelve rats were fed a normal diet for 28 (n = 6) or 56 (n = 6) days, another 12 were fed a zinc-deficient diet for the same periods, and still another 12 were fed a zinc-deficient diet for 28 days and then administered zinc for a further 28 days. The epithelium of the circumvallate papillae was collected, and expression of the TAS2R40, TAS2R105, TAS2R107, TAS2R118, TAS2R121, TAS2R136, TAS2R140, and ENaC genes was examined by reverse transcriptase-polymerase chain reaction. RESULTS: Gene expression frequency of TAS2R40 and TAS2R107 significantly decreased in rats fed a zinc-deficient diet, and frequency of TAS2R107 significantly increased following zinc administration. No changes were noted in expression of TAS2R105, TAS2R118, TAS2R121, or ENaC in zinc-deficient rats. CONCLUSIONS: Our findings suggest that zinc may affect gene expression for some TAS2Rs on the tongue in rats.

Patients with phantogeusia show increased expression of T2R taste receptor genes in their tongues.

OBJECTIVES: The taste receptor gene family T2R has been implicated in the sensation of bitter taste. Phantogeusia is a spontaneous abnormal taste with no external stimulus. We analyzed the expression of T2R taste receptor genes in the tongues of patients with phantogeusia to assess their role in the pathogenesis of phantogeusia. METHODS: We obtained specimens from 43 patients with phantogeusia and 24 normal volunteers by scraping the foliate papillae and examined these specimens for the expression of 10 T2R taste receptor genes using reverse transcription-polymerase chain reaction and electrophoresis. RESULTS: The expression rate (subjects with detectable expression) of the 10 taste receptor genes in the healthy subjects ranged from 16.7% to 100%; 3 receptor genes were found in 50% or fewer of these subjects. In the patients with phantogeusia, the expression rate was increased significantly compared to that in the healthy control subjects for 3 of the 10 receptor genes examined. CONCLUSIONS: Our results show that the expression rate of some of the T2R taste receptor genes was increased significantly in patients with phantogeusia. These results suggest that increased expression of taste receptor genes is involved in the pathogenesis of phantogeusia; this finding may contribute to elucidation of the mechanism of this disorder.

Patients with hypogeusia show changes in expression of T2R taste receptor genes in their tongues.

OBJECTIVES/HYPOTHESIS: Taste receptor genes associated with bitterness belong to the T2R gene family. In this study, we compared the expression of genes of the T2R family in the tongues of patients with hypogeusia to those in healthy subjects and examined the possibility that T2R genes are involved in the pathogenesis of hypogeusia. STUDY DESIGN: Prospective clinical and basic study. METHODS: The control group consisted of 24 healthy people. The patient group consisted of 40 subjects with hypogeusia who were confirmed to have abnormally elevated taste thresholds including that of bitter taste. A tissue sample was collected from each individual by scraping the mucosa on the foliate papillae of the tongue. Total RNA was extracted from each sample and reverse transcribed. The expression of 10 T2R genes (TAS2R40, -R42, -R43, and -R48, and T2R3, -R8, -R9, -R10, -R13, and -R16) was evaluated by reverse transcriptase-polymerase chain reaction. RESULTS: Comparison of the frequency of gene expression between the control group and patients with hypogeusia showed that the frequency of expression of six receptor genes were significantly reduced in the hypogeusia patients. In particular, TAS2R40 showed a significant and marked decrease in the frequency of expression regardless of the cause or severity of hypogeusia. CONCLUSIONS: Our results suggest that decreased expression of taste-associated genes may be involved in hypogeusia in humans. In addition, the evaluation of taste receptor gene expression may be useful clinically for an objective diagnosis of hypogeusia or to evaluate the severity of the disorder.

Stimulation of increases in intracellular calcium and prostaglandin E2 generation in Chinese hamster ovary cells expressing receptor-Galpha16 fusion proteins.

We examined whether fusion proteins of G protein-coupled receptors with the alpha subunit of G(16) (Galpha(16)) could activate downstream signals. We expressed fusion proteins of G(i)-coupled receptors, i.e. CX(3)C chemokine receptor 1 (CX(3)CR1) and M(2) receptor, in Chinese hamster ovary cells. An agonist for CX(3)CR1 induced greater increases in intracellular Ca(2+) and prostaglandin E(2) generation in cells expressing CX(3)CR1-Galpha(16) fusion protein than in cells expressing CX(3)CR1 alone or both CX(3)CR1 and Galpha(16) separately. Similarly, agonist-induced prostaglandin E(2) generation was greater in cells expressing M(2)-Galpha(16) fusion protein than ones expressing M(2) alone or both M(2) and Galpha(16) separately. In cells expressing fusion proteins with Galpha(16) of G(q)-coupled receptors, i.e. urotensin II receptor and M(1) receptor, the relevant agonists induced similar increases in intracellular Ca(2+) and prostaglandin E(2) generation as in ones expressing the receptor alone. In cells expressing urotensin II receptor-Galpha(16) fusion protein, prostaglandin E(2) generation exhibited a lower EC(50) value than the intracellular Ca(2+) increase. These results indicate that agonist-stimulated receptor-Galpha(16) fusion proteins are coupled to downstream signaling pathways, and suggest that receptor-Galpha(16) fusion proteins may be useful for screening for ligands of orphan G protein-coupled receptors and G(i)-coupled receptors.