Biomedical subjects

Hideo Fujita

Publications and source records attributed to Hideo Fujita.

6 recordsLinked to original sources

PubMed2026

Genome-Wide Association Study of Contrast Media Hypersensitivity in Japanese Patients.

Iodinated contrast media (ICM), commonly used in radiological tests such as coronary angiography, can cause hypersensitivity reactions (HSRs). The mechanism of ICM HSRs is thought to be complex; while IgE-mediated allergic reactions appear to be involved, the details remain unclear. This study aims to elucidate the pathogenesis of ICM HSRs through genetic analysis. To date, a few case-control studies have been conducted exclusively on East Asians, but the results have been inconclusive and have not been replicated.We conducted a multistage GWAS for ICM HSRs in Japanese individuals. The study population comprised 153 cases with ICM HSRs (ranging from mild to severe form), 632 controls with no history of ICM-induced allergies, and < 38,721 individuals from the general population. We identified genome-wide significant association signals in the HLA region and also found that these signals originated from the three HLA alleles-B*52:01, C*12:02, DRB1*15:02-previously reported in a Korean candidate gene study. Using instrumental variable analysis with a polygenic score for pediatric asthma (PGSasthma) as a proxy, we demonstrated that ICM HSRs are associated with the allergic predisposition thought to be shared by asthma and ICM HSRs. There was a significant difference in the distribution of PGSasthma between ICM HSR patients and non-disease controls (per-SD odds ratio: 1.26, P = 0.021).Our genome-wide approach shows that HLA alleles are among the genetic factors underlying ICM HSRs. Furthermore, it provides evidence for the potential usefulness of predicting the risk of developing ICM HSRs based on allergic predisposition.

Allergic predisposition↗

PubMed2006

Membrane potential of rat ventricular myocytes responds to axial stretch in phase, amplitude and speed-dependent manners.

OBJECTIVE: To elucidate the interdependence between the mechanical state of the myocardium and its electrical activity, previous studies have been performed at the cellular level. However, the information to date has been limited by the technical difficulties associated with stretching single myocytes. METHODS: We solved this problem by combining two techniques, namely a carbon fiber technique for stretching rat myocytes with wide ranges of amplitude and speed, and ratiometric measurement of a fluorescent indicator (di8-ANEPPS) for evaluating the membrane potential in the non-contact mode. RESULTS: During systole, stretching caused depolarization that prolonged the action potential duration without affecting the peak amplitude, but the effect was only significant in the late phase. Application of a stretch to quiescent myocytes depolarized the membrane potential in amplitude- and speed-dependent manners, but the response was suppressed by cytochalasin D treatment, suggesting participation of the cytoskeleton in the mechanotransduction mechanism. Finally, ion replacement experiments revealed that although Na+ was the dominant charge carrier for large amplitude stretches, Ca2+ permeation was involved in small amplitude stretches, suggesting amplitude-dependent ion selectivity. CONCLUSIONS: Application of axial stretching to rat ventricular myocytes changed the membrane potential in phase-, amplitude- and speed-dependent manners. Amplitude may also modulate the ion selectivity of stretch-activated channels.

Animals↗

PubMed2006

The forkhead transcription factors, Foxc1 and Foxc2, are required for arterial specification and lymphatic sprouting during vascular development.

Accumulating evidence suggests that in the vertebrate embryo, acquisition of arterial and venous identity is established early by genetic mechanisms, including those regulated by vascular endothelial growth factor (VEGF) and Notch signaling. However, although the COUP-TFII nuclear receptor has recently been shown to regulate vein identity, very little is known about the molecular mechanisms of transcriptional regulation in arterial specification. Here, we show that mouse embryos compound mutant for Foxc1 and Foxc2, two closely related Fox transcription factors, exhibit arteriovenous malformations and lack of induction of arterial markers whereas venous markers such as COUP-TFII are normally expressed, suggesting that mutant endothelial cells fail to acquire an arterial fate. Notably, consistent with this observation, overexpression of Foxc genes in vitro induces expression of arterial markers such as Notch1 and its ligand Delta-like 4 (Dll4), and Foxc1 and Foxc2 directly activate the Dll4 promoter via a Foxc-binding site. Moreover, compound Foxc mutants show a defect in sprouting of lymphatic endothelial cells from veins in early lymphatic development, due to reduced expression of VEGF-C. Taken together, our results demonstrate that Foxc transcription factors are novel regulators of arterial cell specification upstream of Notch signaling and lymphatic sprouting during embryonic development.

Animals↗

PubMed2006

Foxc2 is a common mediator of insulin and transforming growth factor beta signaling to regulate plasminogen activator inhibitor type I gene expression.

Elevated plasma levels of plasminogen activator inhibitor type I (PAI-1), a significant risk factor of ischemic heart disease, are associated with insulin resistance in which insulin and transforming growth factor (TGF)-beta play a pivotal role in regulating PAI-1 production. Forkhead transcription factor FOXC2 is an important regulator of insulin resistance. However, the underlying molecular mechanisms to link FOXC2 to PAI-1 levels in insulin resistance remain to be elucidated. Here, we demonstrate that Foxc2 is a common transcriptional activator of insulin and TGF-beta signaling to directly regulate PAI-1 expression via 2 distinct target sites, an insulin response element (IRE) and a novel forkhead-binding element (FBE), adjacent to a Smad-binding site. We found that in adipocytes and endothelial cells Foxc2 mediates insulin action competing with another Forkhead protein, FOXO1, via the insulin response element, and simultaneously cooperate with the TGF-beta/Smad pathway to transactivate PAI-1. Importantly, Foxc2 haploinsufficiency in mice significantly attenuates TGF-beta1-induced PAI-1 expression in the cardiovascular system and adipose tissue. Taken together, we propose that Foxc2 is a key molecule to regulate PAI-1 gene expression.

Animals↗

PubMed2004

Development of a pioneering clinical support system utilizing information technology.

Nowadays, evidence-based medicine has entered the mainstream of clinical judgement and the human genome has been completely decoded. Even the concept of individually designed medicine, that is, tailor-made medicine, is now being discussed. Due to their complexity, however, management methods for clinical information have yet to be established. We have conducted a study on a universal technique which enables one to select or produce by employing information processing technology clinical findings from various clinical information generated in vast quantity in day-to-day clinical practice, and to share such information and/or the results of analysis between two or more institutions. In this study, clinically useful findings have been successfully obtained by systematizing actual clinical information and genomic information obtained by an appropriate collecting and management method of information with due consideration to ethical issues. We report here these medical achievements as well as technological ones which will play a role in propagating such medical achievements.

Artificial Intelligence↗

PubMed2003

Myosin light chain isoforms modify force-generating ability of cardiac myosin by changing the kinetics of actin-myosin interaction.

OBJECTIVE: To investigate the functional role of myosin light chain (MLC) isoforms in cardiac muscles, we examined the motor function of two different myosins the structure of which differed only in the MLC. METHODS: We purified myosin from atria (A-myosin) and ventricles (V-myosin) of young rats, which contained atrial-type and ventricular-type MLCs, respectively, but having identical alpha-heavy chain isoform. Actin filament velocity (Vel) was determined in the in vitro motility assay. Average force of myosin molecules (F) was estimated and single events of actin-myosin interaction were recorded with the laser trap technique. RESULTS: Vel was slightly higher in A-myosin than in V-myosin, while actin-activated ATPase activity was not different. F, determined from force versus actin filament length relation, was approximately 60% higher in V-myosin (3.3 vs. 2.1 pN/microm). The mean duration of isometric force events was longer in V-myosin than in A-myosin (323+/-13 vs. 294+/-30 ms, p<0.05), while the amplitudes of unitary displacement and force of a single myosin molecule did not differ between them. CONCLUSION: The MLC isoform can be a determinant of force-generating ability of cardiac myosin by modulating crossbridge kinetics without affecting the catalytic activity.

Actin Cytoskeleton↗