Okazaki Institute for Integrative Bioscience

The aim of this study was to examine the relationship between ghrelin levels and the subjective effects of alcohol in heavy drinkers, and to compare them to healthy controls. Ghrelin levels were collected as part of two laboratory studies. Both groups received either IV infusion of saline or high dose of alcohol (100 mg%). In the study of heavy drinkers, ghrelin was gathered on all subjects, but data was analyzed only for participants who received placebo (N=12). Healthy controls (N=20) came from another study that collected data on family history. Ghrelin levels and measures of alcohol effects (BAES, VAS, NDS, YCS [see manuscript for details]) were collected at 4 timepoints: baseline, before infusion, during infusion and after infusion. IV alcohol significantly reduced ghrelin levels and higher fasting ghrelin levels were associated with more intense subjective alcohol effects. There were no differences in fasting ghrelin levels or subjective effects between heavy drinkers and controls. However, while both groups showed similar decline in ghrelin levels following alcohol infusion, on the placebo day, ghrelin levels in the healthy subjects increased significantly and exponentially over time while for the heavy drinkers ghrelin levels remained flat. Our findings support the role of ghrelin in reward mechanisms for alcohol. Contrary to others, we found no differences in fasting ghrelin levels or subjective experiences of alcohol between heavy drinkers and healthy controls. However, the group differences on the IV placebo day may be a possible indication of ghrelin abnormalities in heavy drinkers.

The regulation of leaf size has been studied for decades. Enhancement of post-mitotic cell expansion triggered by impaired cell proliferation in Arabidopsis is an important process for leaf size regulation, and is known as compensation. This suggests a key interaction between cell proliferation and cell expansion during leaf development. Several studies have highlighted the impact of this integration mechanism on leaf size determination; however, the molecular basis of compensation remains largely unknown. Previously, we identified extra-small sisters (xs) mutants which can suppress compensated cell enlargement (CCE) via a specific defect in cell expansion within the compensation-exhibiting mutant, angustifolia3 (an3). Here we revealed that one of the xs mutants, namely xs2, can suppress CCE not only in an3 but also in other compensation-exhibiting mutants erecta (er) and fugu2. Molecular cloning of XS2 identified a deleterious mutation in CATION CALCIUM EXCHANGER 4 (CCX4). Phytohormone measurement and expression analysis revealed that xs2 shows hyper activation of the salicylic acid (SA) response pathway, where activation of SA response can suppress CCE in compensation mutants. All together, these results highlight the regulatory connection which coordinates compensation and SA response.

Taste buds are comprised of taste cells, which are classified into types I to IV. Transient receptor potential (TRP) channels play a significant role in taste perception. TRP vanilloid 4 (TRPV4) is a non-selective cation channel that responds to mechanical, thermal, and chemical stimuli. The present study aimed to define the function and expression of TRPV4 in taste buds using Trpv4-deficient mice. In circumvallate papillae, TRPV4 colocalized with a type IV cell and epithelial cell marker but not type I, II, or III markers. Behavioural studies showed that Trpv4 deficiency reduced sensitivity to sourness but not to sweet, umami, salty, and bitter tastes. Trpv4 deficiency significantly reduced the expression of type III cells compared with that in wild type (WT) mice in vivo and in taste bud organoid experiments. Trpv4 deficiency also significantly reduced Ki67-positive cells and β-catenin expression compared with those in WT circumvallate papillae. Together, the present results suggest that TRPV4 contributes to sour taste sensing by regulating type III taste cell differentiation in mice.

The article Hypotonicity-induced cell swelling activates TRPA1, written by Fumitaka Fujita, Kunitoshi Uchida, Yasunori Takayama, Yoshiro Suzuki, Masayuki Takaishi and Makoto Tominaga, was originally published electronically on the publisher’s internet portal (currently SpringerLink) on 16 June 2017 without open access.

Although DNA can form triplex and quadruplex structures through hydrogen bonds, design and preparation of structures with more than five strands is difficult even when artificial nucleic acids are used. Herein we report a hexaplex formed by oligomers of artificial nucleic acids bearing bifacial molecules on d-threoninol. Aminopyrimidine and cyanuric acid derivatives were selected as bases because they have complementary hydrogen bonding patterns. The complex formed by aminopyrimidine and cyanuric acid decamers melted with large hysteresis. Hexaplex formation was indicated by gel electrophoresis, size exclusion chromatography and atomic force microscopy imaging, and proven directly through native mass spectrometry. CD measurements and molecular dynamics simulations indicated that the hexaplex adopts a helical structure. The hexaplex formation was highly dependent on pH and the presence of divalent cations. The hexaplex was stable in aqueous solution, and its unique structure and properties may lead to novel nanostructures, molecular assemblies, metal sensors, and ion channels.

Acting downstream of many growth factors, extracellular signal-regulated kinase (ERK) plays a pivotal role in regulating cell proliferation and tumorigenesis, where its spatiotemporal dynamics, as well as its strength, determine cellular responses. Here, we uncover the ERK activity dynamics in intestinal epithelial cells (IECs) and their association with tumour characteristics. Intravital imaging identifies two distinct modes of ERK activity, sustained and pulse-like activity, in IECs. The sustained and pulse-like activities depend on ErbB2 and EGFR, respectively. Notably, activation of Wnt signalling, the earliest event in intestinal tumorigenesis, augments EGFR signalling and increases the frequency of ERK activity pulses through controlling the expression of EGFR and its regulators, rendering IECs sensitive to EGFR inhibition. Furthermore, the increased pulse frequency is correlated with increased cell proliferation. Thus, ERK activity dynamics are defined by composite inputs from EGFR and ErbB2 signalling in IECs and their alterations might underlie tumour-specific sensitivity to pharmacological EGFR inhibition.

Background: Arterial remodeling and endothelial dysfuntions are defining features of age-dependent hypertension and the molecular key determinant of this phenomenon involves oxidative stress induced-dysregulation of protective signaling pathways. Purinergic receptors (P2YRs), activated by adenine, uridine nucleotides and nucleotide sugars, play pivotal roles in cardiovascular homeostasis. P2Y6R, an inflammation inducible G protein-coupled receptor is ubiquitously expressed in cardiovascular system and was shown to play significant role in vascular tone regulation. Study in mice shows that P2Y6R-G12/13 signaling activation triggers pressure overload-induced cardiac fibrosis, an event speculated to be the upstream mediator of Ang II Type 1 receptor (AT1R) signaling. Here, we inverstigate the role of P2Y6R in Ang II-induced pathophysiology during aging in mice model.

Background & Aim: Transient receptor potential vanilloid 4 (TRPV4) is a non-selective cation channel and responds to physical stimuli and various endogenous ligands such as arachidonic acid metabolites. Inflammatory bowel diseases are known as one of risk factors for colon cancer. We recently reported that the alteration of TRPV4 in vascular endothelia contributes to progression of colonic inflammation via increased vascular permeability. The present study attempts to clarify the involvement of TRPV4 in colitis-associated cancer in mice.

T-type Ca2+ channels and TRPA1 are expressed in sensory neurons and both are associated with pain transmission, but their functional interaction is unclear. Here we demonstrate that pharmacological evidence of the functional relation between T-type Ca2+ channels and TRPA1 in mouse sensory neurons. Low concentration of KCl at 15 mM (15K) evoked increases of intracellular Ca2+ concentration ([Ca2+ ]i ), which were suppressed by selective T-type Ca2+ channel blockers. RT-PCR showed that mouse sensory neurons expressed all subtypes of T-type Ca2+ channel. The magnitude of 15K-induced [Ca2+ ]i increase was significantly larger in neurons sensitive to allylisothiocyanate (AITC, a TRPA1 agonist) than in those insensitive to it, and in TRPA1-/- mouse sensory neurons. TRPA1 blockers diminished the [Ca2+ ]i responses to 15K in neurons sensitive to AITC, but failed to inhibit 40 mM KCl-induced [Ca2+ ]i increases even in AITC-sensitive neurons. TRPV1 blockers did not inhibit the 15K-induced [Ca2+ ]i increase regardless of the sensitivity to capsaicin. [Ca2+ ]i responses to TRPA1 agonist were enhanced by co-application with 15K. These pharmacological data suggest the possibility of functional interaction between T-type Ca2+ channels and TRPA1 in sensory neurons. Since TRPA1 channel is activated by intracellular Ca2+ , we hypothesize that Ca2+ entered via T-type Ca2+ channel activation may further stimulate TRPA1, resulting in an enhancement of nociceptive signaling. Thus, T-type Ca2+ channel may be a potential target for TRPA1-related pain.