Ascl1-expressing cell differentiation in initially developed taste buds and taste organoids

Mammalian taste bud cells are composed of several distinct cell types and differentiated from surrounding tongue epithelial cells. However, the detailed mechanisms underlying their differentiation have yet to be elucidated. In the present study, we examined an Ascl1-expressing cell lineage using circumvallate papillae (CVP) of newborn mice and taste organoids (three-dimensional self-organized tissue cultures), which allow studying the differentiation of taste bud cells in fine detail ex vivo. Using lineage-tracing analysis, we observed that Ascl1 lineage cells expressed type II and III taste cell markers both CVP of newborn mice and taste organoids. However, the coexpression rate in type II cells was lower than that in type III cells. Furthermore, we found that the generation of the cells which express type II and III cell markers was suppressed in taste organoids lacking Ascl1-expressing cells. These findings suggest that Ascl1-expressing precursor cells can differentiate into both type III and a subset of type II taste cells.

Myogenic differentiation 1 and transcription factor 12 activate the gene expression of mouse taste receptor type 1 member 1

OBJECTIVES

Myogenic differentiation 1 (Myod1) is involved in the expression of taste receptor type 1 member 1 (Tas1r1) during myogenic differentiation. Further, the target genes of Myod1 participate in transcriptional control, muscle development, and synaptic function. We examined, for the first time, the function of Myod1 in the transcriptional regulation of Tas1r1.

METHODS

ENCODE chromatin immunoprecipitation and sequencing (ChIP-seq) data of myogenically differentiated C2C12 cells were analyzed to identify the Myod1 and transcription factor 12 (Tcf12) binding sites in the Tas1r1 promoter region. Luciferase reporter assays, DNA affinity precipitation assays, and co-immunoprecipitation assays were also performed to identify the functions of Myod1, Tcf12, and Krüppel-like factor 5 (Klf5).

RESULTS

Based on ENCODE ChIP-seq, Myod1 bound to the Tas1r1 promoter region containing E-boxes 1-3. Luciferase reporter assays revealed that site-directed E-box1 mutations significantly reduced promoter activation induced by Myod1 overexpression. According to the DNA affinity precipitation assay and co-immunoprecipitation assay, Myod1 formed a heterodimer with Tcf12 and bound to E-box1. Further, Klf5 bound to the GT box near E-box1, activating Tas1r1 expression.

CONCLUSIONS

During myogenic differentiation, the Myod1/Tcf12 heterodimer, in collaboration with Klf5, binds to E-box1 and activates Tas1r1 expression.

Time interval from left ventricular stimulation to QRS onset is a predictor of mortality in patients with cardiac resynchronization therapy

Introduction

In our previous report, the time interval from left ventricular (LV) pacing to the earliest onset of QRS (S-QRS interval) has been found to be an independent predictor of mechanical response to cardiac resynchronization therapy (CRT). The S-QRS interval may indicate the conduction disturbance relevant to the localized tissue property such as scar or fibrotic lesion. Therefore, S-QRS interval longer than 37ms was associated with poor response to CRT, and proposed as suboptimal LV lead position. Then, we hypothesized that the longer S-QRS interval at the LV pacing site could be related to long term mortality and heart failure events in patients with CRT.

Methods

This retrospective study included 82 consecutive heart failure patients with sinus rhythm, reduced LV ejection fraction (≤35%), and a wide QRS complex (≥120ms), who undergone CRT implantation between 2012 January and 2017 December. Patients were divided into Short S-QRS group (<37ms, SS-QRS) and Long S-QRS group (≥37ms, LS-QRS) according to the previously reported optimal cut off value. A responder was defined as one with ≥15% reduction in LV end-systolic volume assessed by echocardiography at 6 months after CRT. The primary endpoint was total mortality, which included LV assist device implantation or heart transplantation. The secondary endpoints included the composite endpoint of total mortality or heart failure hospitalization.

Results

The study patients were divided into SS-QRS (N=43, age 65.9±13.2 years, 77% male) and LS-QRS (N=39, age 63.0±13.4, 85% male). In the electrocardiographic measurements, there were no significant differences in baseline QRS duration (162.4±30.3ms in SS-QRS vs. 154.5±31.6ms in LS-QRS, P=0.19) and LV local activation time assessed as Q-LV interval (118.3±34.3ms in SS-QRS vs. 115.3±32.0ms in LS-QRS, P=0.71). S-QRS interval was 25.9±5.3ms in SS-QRS and 51.5±13.7ms in LS-QRS (P<0.01), and the responder rate was significantly higher in SS-QRS compared with LS-QRS (79% vs. 29%, P<0.01). During mean follow up of 47.7±22.4 months, 24 patients (29%) reached to the primary endpoint, while the secondary endpoints were observed in 47 patients (57%). LS-QRS patients had significantly worse event-free survival for both primary and secondary endpoints (Figure). After the multivariate Cox regression analysis, LS-QRS (≥37ms) was an independent predictor of total mortality (HR=2.6, 95% CI: 1.11 to 6.12, P=0.03) and the secondary composite events (HR=2.4, 95% CI: 1.31 to 4.33, P<0.01).

Conclusion

The S-QRS interval longer than 37ms, which may reflect the conduction disturbance relevant to the scar or fibrotic lesion at the LV pacing site, was a significant predictor of the total mortality and heart failure hospitalization. These findings have implications for the optimal LV lead placement in patients with CRT device.

Clinical outcomes according to S-QRS

Funding Acknowledgement

Type of funding source: None

Msx1 Heterozygosity in Mice Enhances Susceptibility to Phenytoin-Induced Hypoxic Stress Causing Cleft Palate

OBJECTIVE

Cleft palate is among the most frequent congenital defects in humans. While gene-environment multifactorial threshold models have been proposed to explain this cleft palate formation, only a few experimental models have verified this theory. This study aimed to clarify whether gene-environment interaction can cause cleft palate through a combination of specific genetic and environmental factors.

METHODS

Msx1 heterozygosity in mice (Msx1^+/-) was selected as a genetic factor since human MSX1 gene mutations may cause nonsyndromic cleft palate. As an environmental factor, hypoxic stress was induced in pregnant mice by administration of the antiepileptic drug phenytoin, a known arrhythmia inducer, during palatal development from embryonic day (E) 11 to E14. Embryos were dissected at E13 for histological analysis or at E17 for recording of the palatal state.

RESULTS

Phenytoin administration downregulated cell proliferation in palatal processes in both wild-type and Msx1^+/- embryos. Bone morphogenetic protein 4 (Bmp4) expression was slightly downregulated in the anterior palatal process of Msx1^+/- embryos. Although Msx1^+/- embryos do not show cleft palate under normal conditions, phenytoin administration induced a significantly higher incidence of cleft palate in Msx1^+/- embryos compared to wild-type littermates.

CONCLUSION

Our data suggest that cleft palate may occur because of the additive effects of Bmp4 downregulation as a result of Msx1 heterozygosity and decreased cell proliferation upon hypoxic stress. Human carriers of MSX1 mutations may have to take more precautions during pregnancy to avoid exposure to environmental risks.

Mash1-expressing cells may be relevant to type III cells and a subset of PLCβ2-positive cell differentiation in adult mouse taste buds

Mammalian taste bud cells have a limited lifespan and differentiate into type I, II, and III cells from basal cells (type IV cells) (postmitotic precursor cells). However, little is known regarding the cell lineage within taste buds. In this study, we investigated the cell fate of Mash1-positive precursor cells utilizing the Cre-loxP system to explore the differentiation of taste bud cells. We found that Mash1-expressing cells in Ascl1^CreERT2::CAG-floxed tdTomato mice differentiated into taste bud cells that expressed aromatic _L-amino acid decarboxylase (AADC) and carbonic anhydrase IV (CA4) (type III cell markers), but did not differentiate into most of gustducin (type II cell marker)-positive cells. Additionally, we found that Mash1-expressing cells could differentiate into phospholipase C β2 (PLCβ2)-positive cells, which have a shorter lifespan compared with AADC- and CA4-positive cells. These results suggest that Mash1-positive precursor cells could differentiate into type III cells, but not into most of type II cells, in the taste buds.

P450The difference in the prognosis among three categories of the post-procedural left ventricular ejection fraction in patients undergoing atrial fibrillation ablation

Funding Acknowledgements

None

Background

Atrial fibrillation (AF) ablation has been known to contribute to a good prognosis in heart failure patients and improve their systolic function. However, the impact of the post-procedural systolic function on the prognosis in them remains unclear. 

Purpose

To investigate the impact of the left ventricular ejection fraction (LVEF) following AF ablation in patients with systolic dysfunction. 

Methods

Out of 1078 consecutive patients who underwent AF ablation including extensive pulmonary vein and superior vena cava isolation, 170 with an impaired pre-procedural LVEF (< 50%) were evaluated. They experienced at least one echocardiographic follow-up within one year after the index procedure. The primary outcome was the composite of all-cause death or heart failure hospitalisations (HFHs). In addition, we categorised the patients into three groups according to the post-procedural LVEF within one year to evaluate the outcome: reduced LVEF (rEF, LVEF < 40%), mid-range EF (mrEF, 40% ≤ LVEF < 50%) and preserved LVEF (pEF, LVEF > 50%). 

Results

After the index procedure, the patients’ LVEF improved with an average increase of 8%, and the post-procedural LVEF consisted of an rEF in 27 (16%), mrEF in 41 (24%), and pEF in 102 (60%) patients. During a median follow-up of 31 months, a total of 22 (13%) patients experienced the composite outcome, including 18 (11%) HFHs and 10 (6%) all-cause deaths (5 with cardiac issues, 2 any malignancies, and 3 other issues). In the Kaplan-Meier analysis using a Bonferroni correction, there was a significant difference in achieving the outcome between the rEF and mrEF, and rEF and pEF, but not between the mrEF and pEF groups (Figure). In a univariate analysis, the hazard ratio of the outcome was shown as follows: an age ≥ 65 years (hazard ratio, HR: 3.4 [95% confidence interval, CI: 1.4–8.5], p = 0.006), history of HFHs for AF (HR: 1.7 [95%CI: 0.7–4.0], p = 0.25), known underlying heart disease (HR: 1.9 [95%CI: 0.8–1.2], p = 0.13), pre-procedural LVEF < 40% (HR: 3.1 [95%CI: 1.3–7.5], p = 0.009), atrial tachyarrhythmia recurrence (HR: 3.0 [95%CI: 1.2–7.8], p = 0.01), and the post-procedural LVEF category (mrEF and rEF, compared with pEF) (HR: 2.0 [95%CI: 0.4–7.7], p = 0.34; and HR: 8.6 [95%CI: 2.7–37.5], p < 0.0001). Furthermore, in a multivariate analysis, patients with a rEF was the sole independent predictor of the composite outcome after adjusting for confounders including an age≥65 years and pre-procedural LVEF < 40% (HR: 12.0 [95%CI: 3.9–40.0], p < 0.0001), whereas those with a mrEF was not (HR: 1.8 [95%CI: 0.4–7.3], p = 0.42), as compared to those with a pEF. 

Conclusions

Patients with a mrEF had a comparable prognosis to those with a pEF in a relatively long follow-up, while those with a rEF had the poorest outcome of the three categories, regardless of the pre-procedural LVEF severity.

Abstract Figure. The difference in the rate of outcome

Hematogenous apoptotic mechanism in salivary glands in chronic periodontitis

OBJECTIVE

The aim of the study is to investigate the apoptotic mechanism in salivary glands in the rat experimental periodontitis model.

DESIGN

A rat periodontitis model was prepared by using a ligature around the second upper molar. In the salivary (parotid and submandibular) glands and blood samples, putative apoptotic factors and pathway molecules were investigated in vivo and in vitro.

RESULTS

Four weeks of ligation (chronic periodontitis) demonstrated significant apoptotic atrophy of the salivary gland, but one week of ligation (initial periodontitis) did not. In the blood plasma, tumor necrosis factor-α (TNF-α) was increased in the periodontitis model, but interleukin-1β and -6 were not. TNF-α receptor type 1, which has an intracellular apoptotic pathway, was expressed in the salivary glands of rats. Western blot analysis of cultured rat primary salivary gland cells demonstrated that TNF-α induced cleavage of poly (ADP-ribose) polymerase (PARP) and caspase-3 in a dose-dependent manner, indicating apoptosis induction. Additionally, we found increment of circulating lymphocytes in the model. Expression of mRNA and immunoreactive cells for the B lymphocyte marker CD19 were increased in the salivary gland in the model. Western blotting showed that coculture with extracted B cells from the periodontitis model increased cleaved PARP in salivary gland cells.

CONCLUSIONS

Chronic periodontitis status leads to an increase in circulating TNF-α and B lymphocyte infiltration, resulting in apoptotic atrophy of the salivary gland as a periodontitis-induced systemic response.

Evaluation of velopharyngeal function using high-speed cine-magnetic resonance imaging based on T2-weighted sequences: a preliminary study

The objective was to introduce a new technique for visualizing the three-dimensional (3D) movements of velopharyngeal-related muscles using high-speed cine-magnetic resonance imaging (MRI) based on T2-weighted sequences. The evaluation of phonation- and water swallowing-related events was performed in 11 healthy subjects. Specifically, whether cine-MRI could precisely visualize normal velopharyngeal function during these two events was examined. The 3D movements of the soft palate, superior pharyngeal constrictor muscles, and levator veli palatini muscles were visualized in all 11 subjects. A noteworthy finding was that the magnetic resonance signals of the superior constrictor pharyngeal muscles and the levator veli palatini muscles were significantly higher during phonation and during water swallowing than at rest. This initial study suggests that the 3D movements of velopharyngeal-related muscles can be successfully and precisely visualized without side effects. The magnetic resonance signal changes seen in the superior pharyngeal constrictor and levator veli palatini muscles using the technique described here should be useful to develop better methods of evaluation of velopharyngeal function.

Krüppel-like factor 5 (Klf5) regulates expression of mouse T1R1 amino acid receptor gene (Tas1r1) in C2C12 myoblast cells

T1R1 and T1R3 are receptors expressed in taste buds that detect L-amino acids. These receptors are also expressed throughout diverse organ systems, such as the digestive system and muscle tissue, and are thought to function as amino acid sensors. The mechanism of transcriptional regulation of the mouse T1R1 gene (Tas1r1) has not been determined; therefore, in this study, we examined the function of Tas1r1 promoter in the mouse myoblast cell line, C2C12. Luciferase reporter assays showed that a 148-bp region upstream of the ATG start codon of Tas1r1 had a promoter activity. The GT box in the Tas1r1 promoter was conserved in the dog, human, mouse, and pig. Site-directed mutagenesis of this GT box significantly reduced the promoter activation. The GT box in promoters is a recurring motif for Sp/KLF family members. RNAi-mediated depletion of Sp4 and Klf5 decreased Tas1r1 expression, while overexpression of Klf5, but not Sp4, significantly increased Tas1r1 expression. The ENCODE data of chromatin immunoprecipitation and sequencing (ChIP-seq) showed that Klf5 bound to the GT box during the myogenic differentiation. Furthermore, the Klf5 knockout cell lines led to a considerable decrease in the levels of Tas1r1 expression. Collectively, these results showed that Klf5 binds to the GT box in the Tas1r1 promoter and regulates Tas1r1 expression in C2C12 cells.

Expression of Vesicular Nucleotide Transporter in Rat Odontoblasts

Several theories have been proposed regarding pain transmission mechanisms in tooth. However, the exact signaling mechanism from odontoblasts to pulp nerves remains to be clarified. Recently, ATP-associated pain transmission has been reported, but it is unclear whether ATP is involved in tooth pain transmission. In the present study, we focused on the vesicular nucleotide transporter (VNUT), a transporter of ATP into vesicles, and examined whether VNUT was involved in ATP release from odontoblasts. We examined the expression of VNUT in rat pulp by RT-PCR and immunostaining. ATP release from cultured odontoblast-like cells with heat stimulation was evaluated using ATP luciferase methods. VNUT was expressed in pulp tissue, and the distribution of VNUT-immunopositive vesicles was confirmed in odontoblasts. In odontoblasts, some VNUT-immunopositive vesicles were colocalized with membrane fusion proteins. Additionally P2X3, an ATP receptor, immunopositive axons were distributed between odontoblasts. The ATP release by thermal stimulation from odontoblast-like cells was inhibited by the addition of siRNA for VNUT. These findings suggest that cytosolic ATP is transported by VNUT and that the ATP in the vesicles is then released from odontoblasts to ATP receptors on axons. ATP vesicle transport in odontoblasts seems to be a key mechanism for signal transduction from odontoblasts to axons in the pulp.

Expression of neuropeptide receptor mRNA during osteoblastic differentiation of mouse iPS cells

Various studies have shown a relationship between nerves and bones. Recent evidence suggests that both sensory and sympathetic nerves affect bone metabolism; however, little is known about how neuropeptides are involved in the differentiation of pluripotent stem cells into osteoblastic (OB) cells. To evaluate the putative effects of neuropeptides during the differentiation of mouse induced pluripotent stem (iPS) cells into calcified tissue-forming OB cells, we investigated the expression patterns of neuropeptide receptors at each differentiation stage. Mouse iPS cells were seeded onto feeder cells and then transferred to low-attachment culture dishes to form embryoid bodies (EBs). EBs were cultured for 4 weeks in osteoblastic differentiation medium. The expression of α1-adrenergic receptor (AR), α2-AR, β2-AR, neuropeptide Y1 receptor (NPY1-R), neuropeptide Y2 receptor (NPY2-R), calcitonin gene-related protein receptor (CGRP-R), and neurokinin 1-R (NK1-R) was assessed by reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR. Among these neuropeptide receptors, CGRP-R and β2-AR were expressed at all stages of cell differentiation, including the iPS cell stage, with peak expression occurring at the early osteoblastic differentiation stage. Another sensory nervous system receptor, NK1-R, was expressed mainly in the late osteoblastic differentiation stage. Furthermore, CGRP-R mRNA showed an additional small peak corresponding to EBs cultured for 3 days, suggesting that EBs may be affected by serum CGRP. These data suggest that the sensory nervous system receptor CGRP-R and the sympathetic nervous system receptor β2-AR may be involved in the differentiation of iPS cells into the osteoblastic lineage. It follows from these findings that CGRP and β2-AR may regulate cell differentiation in the iPS and EB stages, and that each neuropeptide has an optimal period of influence during the differentiation process.

Vaccination during the 2013-2014 influenza season in pregnant Japanese women

This questionnaire survey was conducted at 11 hospitals in Japan to determine vaccination coverage against seasonal influenza and the prevalence rate of influenza among pregnant Japanese women. Of 2,808 postpartum women who gave birth at the 11 hospitals during the study period from March 1, 2014, to July 31, 2014, 1,713 (61 %) participated in this study and 876 (51 %) reported having received vaccination against influenza in or after October 2013. Women aged <25 years had a significantly lower vaccination rate than those aged ≥25 years (31 % vs. 53 %, respectively; p = 0.0000). Eighty-seven (5.1 %) and 1,626 (94.9 %) women did and did not contract influenza, respectively. Although prior birth did not affect overall vaccination coverage (50 % for primiparous vs. 53 % for multiparous), multiparous women had a significantly higher rate of contracting influenza than primiparous women, irrespective of vaccination status (5.6 % vs. 2.2 % [p = 0.0216] and 9.7 % vs. 3.5 % [p = 0.0003] for women with and without vaccination, respectively). The 2013-2014 vaccination program significantly reduced the influenza infection rate by 35 % (3.9 % vs. 6.3 % for women with and without vaccination, respectively; p = 0.0272). Seventy-two (83 %) of the 87 women took antiviral agents for the treatment of influenza and two (2.3 %) required hospitalization. These results suggested that pregnant Japanese women had a high level of concern regarding seasonal influenza. However, campaigns targeting young pregnant Japanese women, as well as multiparous women, for vaccination are needed in order to further reduce the incidence of influenza among pregnant Japanese women.

Expression of GAD67 and Dlx5 in the taste buds of mice genetically lacking Mash1

It has been reported that a subset of type III taste cells express glutamate decarboxylase (GAD)67, which is a molecule that synthesizes gamma-aminobutyric acid (GABA), and that Mash1 could be a potential regulator of the development of GABAnergic neurons via Dlx transcription factors in the central nervous system. In this study, we investigated the expression of GAD67 and Dlx in the embryonic taste buds of the soft palate and circumvallate papilla using Mash1 knockout (KO)/GAD67-GFP knock-in mice. In the wild-type animal, a subset of type III taste cells contained GAD67 in the taste buds of the soft palate and the developing circumvallate papilla, whereas GAD67-expressing taste bud cells were missing from Mash1 KO mice. A subset of type III cells expressed mRNA for Dlx5 in the wild-type animals, whereas Dlx5-expressing cells were not evident in the apical part of the circumvallate papilla and taste buds in the soft palate of Mash1 KO mice. Our results suggest that Mash1 is required for the expression of GAD67 and Dlx5 in taste bud cells.

Hemokinin-1 competitively inhibits substance P-induced stimulation of osteoclast formation and function

Hemokinin-1 (HK-1) is a novel member of the tachykinin family that is encoded by preprotachykinin 4 (TAC4) and shares the neurokinin-1 receptor (NK1-R) with substance P (SP). Although HK-1 is thought to be an endogenous peripheral SP-like endocrine or paracrine molecule in locations where SP is not expressed, neither the distribution of HK-1 in the maxillofacial area nor the role HK-1 in bone tissue have been examined. In this study, we investigated the distribution of HK-1 in trigeminal ganglion (TG) and maxillary bone, and assessed the expression of HK-1 during osteoclast differentiation. In vivo, rat molars were loaded for 5 days using the Waldo method. In vitro, rat osteoclast-like cells were induced from bone marrow cells. HK-1 distribution and expression were examined by immunofluorescence staining and reverse transcription polymerase chain reaction (RT-PCR). In vivo, HK-1 was localized in rat TG neurons; however, the number of HK-1-positive neurons was less than that of SP-positive neurons. In the maxillary bone, nerve fibers, blood vessels, and osteocytes were immunopositive for HK-1. Furthermore, HK-1-positive immunoreactivity was found in osteoclasts on the pressure side. In vitro, PCR showed that TAC4 and NK1-R mRNA was expressed in osteoclasts as well as in bone marrow cells. Although SP (10⁻⁷ M) treatment led to an increased number of osteoclasts, HK-1 (10⁻⁷ M) treatment did not. The numbers of biotin-labeled HK-1 peptides bound osteoclasts significantly decreased upon incubation with unlabeled SP and biotin-labeled HK-1 compared with biotin-labeled HK-1 alone. These results suggest that HK-1 may not stimulate the differentiation and function of osteoclasts. SP-stimulated osteoclast formation is competitively regulated by peripheral HK-1 through NK1-Rs.

Nerve Growth Factor Involves Mutual Interaction between Neurons and Satellite Glial Cells in the Rat Trigeminal Ganglion

Nerve growth factor (NGF) plays a critical role in the trigeminal ganglion (TG) following peripheral nerve damage in the oral region. Although neurons in the TG are surrounded by satellite glial cells (SGCs) that passively support neural function, little is known regarding NGF expression and its interactions with TG neurons and SGCs. This study was performed to examine the expression of NGF in TG neurons and SGCs with nerve damage by experimental tooth movement. An elastic band was inserted between the first and second upper molars of rats. The TG was removed at 0–7 days after tooth movement. Using in situ hybridization, NGF mRNA was expressed in both neurons and SGCs. Immunostaining for NGF demonstrated that during tooth movement the number of NGF-immunoreactive SGCs increased significantly as compared with baseline and reached maximum levels at day 3. Furthermore, the administration of the gap junction inhibitor carbenoxolone at the TG during tooth movement significantly decreased the number of NGF-immunoreactive SGCs. These results suggested that peripheral nerve damage may induce signal transduction from neurons to SGCs via gap junctions, inducing NGF expression in SGCs around neurons, and released NGF may be involved in the restoration of damaged neurons.

Apoptosis resistance in tumor cells

Various antitumor agents induce apoptotic cell death in tumor cells. Since the apoptosis program in tumor cells plays a critical role in the chemotherapy-induced tumor cell killing, it is suggested that the defect in the signaling pathway of apoptosis could cause a new form of multidrug resistance in tumor cells. This article describes the recent findings concerning the mechanisms of chemotherapy-induced apoptosis and discusses the implication of apoptosis resistance in cancer chemotherapy.

A2BR adenosine receptor modulates sweet taste in circumvallate taste buds

In response to taste stimulation, taste buds release ATP, which activates ionotropic ATP receptors (P2X2/P2X3) on taste nerves as well as metabotropic (P2Y) purinergic receptors on taste bud cells. The action of the extracellular ATP is terminated by ectonucleotidases, ultimately generating adenosine, which itself can activate one or more G-protein coupled adenosine receptors: A1, A2A, A2B, and A3. Here we investigated the expression of adenosine receptors in mouse taste buds at both the nucleotide and protein expression levels. Of the adenosine receptors, only A2B receptor (A2BR) is expressed specifically in taste epithelia. Further, A2BR is expressed abundantly only in a subset of taste bud cells of posterior (circumvallate, foliate), but not anterior (fungiform, palate) taste fields in mice. Analysis of double-labeled tissue indicates that A2BR occurs on Type II taste bud cells that also express Gα14, which is present only in sweet-sensitive taste cells of the foliate and circumvallate papillae. Glossopharyngeal nerve recordings from A2BR knockout mice show significantly reduced responses to both sucrose and synthetic sweeteners, but normal responses to tastants representing other qualities. Thus, our study identified a novel regulator of sweet taste, the A2BR, which functions to potentiate sweet responses in posterior lingual taste fields.

Differential expression of the glucose transporters in mouse gustatory papillae

Taste receptors and their downstream signaling molecules are activated by sugars and sweeteners in the gut and participate in the regulation of glucose transport into enterocytes. The glucose transporter families GLUT and SGLT are responsible for the absorption of glucose, GLUT4 and SGLT1 being expressed preferentially in T1R3-positive taste cells. However, the expression patterns of the other glucose transporters in mouse gustatory tissues have not yet been elucidated. Therefore, we have examined the expression patterns of the glucose transporters (GLUT1-4 and SGLT1-3) in mouse gustatory tissues. Reverse transcription/polymerase chain reaction assays have revealed that GLUT1, 3, and 4 and SGLT1 mRNAs are expressed in the circumvallate papillae. Immunohistochemical analysis has shown that SGLT1 is expressed in a subset of the epithelial cells: from the basal cell layer to the prickle cell layer and in intragemmal and extragemmal epithelium cells in the circumvallate, foliate, and fungiform papillae. GLUT1, GLUT3, and GLUT4 are expressed in the prickle cell layers and/or basal cell layers in these papillae. Moreover, GLUT1, but not GLUT3 or GLUT4, is expressed in a subset of intragemmal and extragemmal epithelium cells in these papillae. Double-labeling experiments have demonstrated that GLUT1-positive taste bud cells coexpress gustducin and inositol 1,4,5-triphosphate receptor type III. These results suggest that SGLT1 and GLUT1 play a role in glucose-sensing and/or transport in mouse taste buds.

Characterization of human-type monoclonal antibodies against reduced form of hemin binding protein 35 from Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

The gram-negative anaerobe Porphyromonas gingivalis has been implicated as an important pathogen in the development of adult periodontitis, and its colonization of subgingival sites is critical in the pathogenic process. We previously identified a 35 kDa surface protein (hemin binding protein 35; HBP35) from P. gingivalis that exhibited coaggregation activity, while additional analysis suggested that this protein possessed an ability to bind heme molecules. For development of passive immunotherapy for periodontal diseases, human-type monoclonal antibodies have been prepared using HBP35 as an antigen in TransChromo mice. In the present study, we focused on a single antibody, TCmAb-h13, which is known to inhibit heme binding to recombinant HBP35. The aim of our investigation was to clarify the redox-related function of HBP35 and consider the benefits of human-type monoclonal antibodies.

MATERIAL AND METHODS

To examine the antigen recognition capability of TCmAbs with immunoblotting and Biacore techniques, we used the native form as well as several Cys-to-Ser variants of recombinant HBP35.

RESULTS

We found that the redox state of recombinant HBP35 was dependent on two Cys residues, (48) C and (51) C, in the thioredoxin active center (WCGxCx). Furthermore, TCmAb-h13 recognized the reduced forms of recombinant HBP35, indicating its inhibitory effect on P. gingivalis growth.

CONCLUSION

Hemin binding protein 35 appears to be an important molecule involved in recognition of the redox state of environmental conditions. In addition, TCmAb-h13 had an inhibitory effect on heme binding to recombinant HBP35, thereby interfering with P. gingivalis growth.

Mash1 is required for the differentiation of AADC-positive type III cells in mouse taste buds

Mash1 is expressed in subsets of neuronal precursors in both the central nervous system and the peripheral nervous system. However, involvement of Mash1 in taste cell differentiation has not previously been demonstrated. In this study, we investigated the role of Mash1 in regulating taste bud differentiation using Mash1 KO mice to begin to understand the mechanisms that regulate taste bud cell differentiation. We found that aromatic L-amino acid decarboxylase (AADC) cells were not evident in either the circumvallate papilla epithelia or in taste buds in the soft palates of Mash1 KO mice. However gustducin was expressed in taste buds in the soft palates of Mash1 KO mice. These results suggest that Mash1 plays an important role in regulating the expression of AADC in type III cells in taste buds, which supports the hypothesis that different taste bud cell types have progenitor cells that are specific to each cell type.

Identification of the genes associated with a virulent strain of Porphyromonas gingivalis using the subtractive hybridization technique

BACKGROUND/AIMS

Porphyromonas gingivalis, a major etiological organism implicated in periodontal disease, can be classified into virulent and avirulent strains. Our aim was to identify a gene for the virulence of P. gingivalis.

METHODS

The subtractive hybridization technique was employed to identify the genes specific to P. gingivalis W83, a virulent strain. In this study, P. gingivalis W83 was used as the tester strain, and P. gingivalis ATCC 33277 was the driver strain. The prevalence of W83-specific genes was determined by Southern blot analysis of several P. gingivalis strains.

RESULTS

We obtained 575 colonies using the subtractive hybridization technique. From among these, 26 DNA fragments were subjected to a homology search using the BLAST program. Compared with strain ATCC 33277, strain W83 contained 12 unique clones. The specificities of the isolated DNA fragments were analyzed among four P. gingivalis strains by Southern blot analysis. Five genes showed specificity for strain W83 compared with strain ATCC 33277. All five genes were also identified in strain W50.

CONCLUSIONS

The subtractive hybridization technique was effective in screening the two strains for specific DNA sequences, some of which might be responsible for determining virulence. The results suggested that several genes specific to strain W83 were associated with its virulence. Further analysis of these DNA fragments will provide important information on the pathogenesis of virulent P. gingivalis strains.

The candidate sour taste receptor, PKD2L1, is expressed by type III taste cells in the mouse

The transient receptor potential channel, PKD2L1, is reported to be a candidate receptor for sour taste based on molecular biological and functional studies. Here, we investigated the expression pattern of PKD2L1-immunoreactivity (IR) in taste buds of the mouse. PKD2L1-IR is present in a few elongate cells in each taste bud as reported previously. The PKD2L1-expressing cells are different from those expressing PLCbeta2, a marker of Type II cells. Likewise PKD2L1-immunoreactive taste cells do not express ecto-ATPase which marks Type I cells. The PKD2L1-positive cells are immunoreactive for neural cell adhesion molecule, serotonin, PGP-9.5 (ubiquitin carboxy-terminal transferase), and chromogranin A, all of which are present in Type III taste cells. At the ultrastructural level, PKD2L1-immunoreactive cells form synapses onto afferent nerve fibers, another feature of Type III taste cells. These results are consistent with the idea that different taste cells in each taste bud perform distinct functions. We suggest that Type III cells are necessary for transduction and/or transmission of information about "sour", but have little or no role in transmission of taste information of other taste qualities.

Effects of KP-496, a novel dual antagonist at the cysteinyl leukotriene receptor 1 and the thromboxane A(2) receptor, on airway obstruction in guinea pigs

BACKGROUND AND PURPOSE

KP-496 is a novel dual antagonist for cysteinyl leukotriene receptor 1 (CysLT(1)) and thromboxane A(2) (TXA(2)) receptor (TP). The aim of this study was to evaluate the pharmacological profile of inhaled KP-496 and its effects on airway obstruction.

EXPERIMENTAL APPROACH

Antagonist activities of inhaled KP-496 were investigated using bronchoconstriction induced in guinea pigs by LTD(4) or U46619, a stable TXA(2) mimetic. Guinea pigs sensitized with injections of ovalbumin were used to assess the effects of inhaled KP-496 on bronchoconstriction induced by antigen (i.v.). Another set of guinea pigs were sensitized and challenged with ovalbumin by inhalation and the effects of inhaled KP-496 on immediate and late airway responses and airway hyperresponsiveness were investigated.

KEY RESULTS

KP-496 significantly inhibited LTD(4)- and U46619-induced bronchoconstriction in a dose-dependent manner. The inhibitory effects of KP-496 (1%) were comparable to those of montelukast (a CysLT(1) antagonist, p.o., 0.3 mg kg(-1)) or seratrodast (a TP antagonist, p.o., 3 mg kg(-1)). KP-496 (1%) and oral co-administration of montelukast (10 mg kg(-1)) and seratrodast (20 mg kg(-1)) significantly inhibited antigen-induced bronchoconstriction, whereas administration of montelukast or seratrodast separately did not inhibit antigen-induced bronchoconstriction. KP-496 exhibited dose-dependent and significant inhibitory effects on the immediate and late airway responses and airway hyperresponsiveness following antigen challenge.

CONCLUSIONS AND IMPLICATIONS

KP-496 exerts effects in guinea pigs which could be beneficial in asthma. These effects of KP-496 were greater than those of a CysLT(1) antagonist or a TP antagonist, in preventing antigen-induced airway obstruction.

Endosialin/TEM1: Cellular localization and prevalence in soft-tissue tumors and carcinomas

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Background: Tumors grow more slowly in endosialin/TEM1 KO mice compared to WT, suggesting that host endosialin/TEM1-positive stroma promotes malignancy (Nanda, PNAS, 2006). Methods: We surveyed 92 human clinical samples by IHC (52 epithelial tumors, 40 sarcomas) to measure the extent of endosialin/TEM1 expression and assess cellular localization. Expression was also studied in primary cell cultures and 49 cancer lines. Results: 46/52 adenocarcinomas and carcinomas (88.5%) expressed endosialin/TEM1 mainly in pericytes (7/7 bladder, 7/11 breast, 5/5 colon, 7/8 ovarian, 7/7 renal, 2/2 liver, 4/5 lung, and 7/7 gastric). In some tumors, endosialin/TEM1 was present in pericytes and in fibroblasts (2/7 bladder, 4/11 breast, 5/5 colon, 5/8 ovarian, 2/7 renal, 2/2 liver, 1/5 lung and 7/7 gastric cancers). 32/40 sarcomas (80%) expressed endosialin/TEM1 mainly in pericytes (10/11 synovial sarcomas, 9/10 malignant fibrous histiocytomas, 3/5 Ewing's sarcomas, 3/5 angiosarcomas, 3/4 rhabdomyosarcomas, 2/2 pleiomorphic sarcomas, 1/1 Kaposi's sarcoma, 0/1 leiomyosarcoma and 1/1 liposarcoma). Synovial sarcomas displayed intense fibroblast staining. Endosialin/TEM1 was expressed by sarcoma cells in a few samples. In culture, we previously showed expression in human fibroblasts, endothelial precursor cells, pericytes and mesenchymal stem cells (MSC). We now report that endosialin/TEM1 mRNA is present in MSC during osteogenic and adipogenic differentiation. In 49 human tumor lines, expression was restricted to sarcoma cells (7/15 sarcoma, 0/5 melanoma, 0/2 neuroblastoma, 0/4 breast, 0/1 ovarian, 0/3 prostate, 0/1 renal, 0/1 liver, 0/3 pancreatic, 0/6 colorectal and 0/8 hematopoietic cancer lines). Conclusions: Endosialin/TEM1 is frequently expressed in clinical cancer (85% of 92 samples), both in epithelial and mesenchymal tumors. Cellular expression is mesenchymal in clinical samples and in culture. In tissues, endosialin/TEM1 is present in pericytes and fibroblasts, with some expression in sarcoma cells. The importance of endosialin/TEM1-positive stroma in experimental animals and prevalence in patient samples warrant further investigation. Endosialin/TEM1 may be a useful therapeutic target.

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Expression of ATP-gated P2X3 receptors in rat gustatory papillae and taste buds

It has recently become evident that ATP and other extracellular nucleotides could play an important role in signal transductions. ATP mediates excitatory signaling by means of P2X receptors. P2X3, one of its subtypes, a membrane ligand-gated ion channel, is strongly expressed in peripheral sensory neurons. The aim of the present study was to examine the distribution of nerve fibers expressing P2X3 receptors in taste buds in the gustatory papillae and soft palate of rats by immunohistochemistry. We found that the fluorescence ATP marker quinacrine stained subsets of taste bud cells. Numerous nerve fibers innervating taste buds were intensely immunostained with the P2X3 receptor antibody. These nerve fibers ascended among intragemmal cells and terminated just below the taste pores. In order to examine whether P2X3 receptors are involved in signal modulation within taste buds, we used fluorescent double stainings to analyze the distribution of P2X3 receptors and their relationship to alpha-gustducin immunopositive taste receptor cells. Many varicose nerve fibers expressing P2X3 receptor-immunoreactivities were entangled with alpha-gustducin-immunopositive taste receptor cells and ended closely below the taste pores. In fungiform papillae, nerve fibers expressing both P2X3 receptors and PGP 9.5 were observed. In contrast, only PGP 9.5 immunoreactive nerve fibers were recognized in filiform papillae. These results suggest that P2X3 receptors might be involved in taste transmission pathways within taste buds. ATP may act as a neurotransmitter, co-transmitter, or neuromodulator at P2X3 receptors to generate activating gustatory nerve fibers.

Changes in electrical resistance of sound fissure enamel in first molars for 66 months from eruption

The purposes of this study were to investigate the enamel maturation process in the occlusal pit of sound first molars by measuring electrical resistance. Ninety-nine sound first molars in 34 children (mean age of 6.47 +/- 0.51 years) were measured electrically once every 6 months and were monitored for a maximum of 66 months. Electrical resistance increased during the posteruptive period. However, the results suggest that posteruptive enamel maturation in the occlusal pits may not be completed even 66 months after tooth eruption.

Expression of group II metabotropic glutamate receptors in rat gustatory papillae

Glutamate is one candidate for the neurotransmitters and/or neuromodulators involved in taste signaling in taste buds. Group II metabotropic glutamate receptors (mGluRs: mGluR2 and mGluR3) are known to function as presynaptic receptors that regulate the release of glutamate and/or other neurotransmitters in the central nervous system. Group II mGluRs are negatively linked to adenylyl cyclase through Galphai subunits and thereby reduce the turnover of cAMP. In rat taste tissues, a subset of adenylyl-cyclase-8-expressing taste cells coexpress the Galphai subunits gustducin and Galphai2. However, the expression patterns of group II mGluRs in rat taste tissues have not yet been elucidated. We have therefore examined the expression patterns of mGluR2, mGluR3, and gustducin in rat gustatory tissues. Reverse transcription/polymerase chain reaction assays have revealed that mGluR2 and mGluR3 mRNAs are expressed in the circumvallate papillae. In situ hybridization analyses have detected positive signals for mGluR2 and mGluR3 mRNAs only in the circumvallate taste buds. Among the fungiform, foliate, and circumvallate papillae, an antibody against mGluR2/3 labels a subset of taste bud cells and nerve fibers immediately beneath the taste lingual epithelium. Double-labeling experiments have demonstrated that mGluR2/3-positive cells coexpress gustducin. These results indicate that mGluR2 and mGluR3 are coupled to Galphai subunits and play roles in glutamate-mediated signaling in taste transductions.

Immunohistochemical localization of aromatic l-amino acid decarboxylase in mouse taste buds and developing taste papillae

Aromatic L-amino acid decarboxylase (AADC) catalyses the decarboxylation of all aromatic L-amino acids. In mammals, AADC is expressed in many tissues besides the nervous system, and is associated with additional regulatory roles of dopamine and serotonin in a wide range of tissues. We examined the expression of AADC by using reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. RT-PCR analysis showed that mRNA of AADC was detected in the taste bud-containing epithelium of the circumvallate papilla of mice. By immunohistochemical analyses, AADC was detected in a subset of taste bud cells of fungiform, foliate, and circumvallate papillae. Double-label studies showed that AADC colocalized with serotonin, NCAM, PLCbeta2, and PGP9.5. On the other hand, AADC never colocalized with alpha-gustducin. Our results of double staining with AADC and taste cell markers indicate that only the type III cells could convert 5-hydroxytryptophan (5-HTP) to serotonin within taste buds. Taken together with previous studies, the properties of the type III cell of taste buds exactly fit into the APUD (amine and amine precursor uptake and decarboxylation) cell scheme. Furthermore, in the developing circumvallate papilla, AADC are first detected in a small number of papillary epithelial cells at E14.5. By E18.5, AADC-positive epithelial cells also express PGP9.5, which is one of marker of taste cells, and these cells have been contacted by developing nerve fibers. These results suggest that AADC expression begins at early stages of taste bud cell differentiation, and biogenic amines may act on taste bud differentiation of tongue epithelial cells, and further may regulate innervation of taste bud progenitor cells.