ConcVAE: Conceptual Representation Learning.

Disentangled representation learning aims at obtaining an independent latent representation without supervisory signals. However, the independence of a representation does not guarantee interpretability to match human intuition in the unsupervised settings. In this article, we introduce conceptual representation learning, an unsupervised strategy to learn a representation and its concepts. An antonym pair forms a concept, which determines the semantically meaningful axes in the latent space. Since the connection between signifying words and signified notions is arbitrary in natural languages, the verbalization of data features makes the representation make sense to humans. We thus construct Conceptual VAE (ConcVAE), a variational autoencoder (VAE)-based generative model with an explicit process in which the semantic representation of data is generated via trainable concepts. In visual data, ConcVAE utilizes natural language arbitrariness as an inductive bias of unsupervised learning by using a vision-language pretraining, which can tell an unsupervised model what makes sense to humans. Qualitative and quantitative evaluations show that the conceptual inductive bias in ConcVAE effectively disentangles the latent representation in a sense-making manner without supervision. Code is available at https://github.com/ganmodokix/concvae.

Slow Dynamics in Microcolumnar Gap Junction Network of Developing Neocortical Pyramidal Neurons.

Gap junctions mediate electrical coupling between neurons and modulate their firing activity. In mouse neocortical layer 5, the major types of pyramidal neurons organize into cell type-specific microcolumns that exhibit modular neuronal activity. During cortical development, microcolumn neurons are electrically coupled in a cell type-specific manner at the stage of synaptogenesis, forming a dense network of gap junctions. However, modulation of neuronal activity by the gap junction network has not been examined. Here, we show that the electrical coupling induces amplification and slow synchronization of action potentials. This slow synchronization is mediated by electrical transmission that is an order of magnitude slower than that of gap junction-coupled neurons of other types. Theoretical and structural analyses suggested that apical dendrites are a major site of electrical coupling, providing slow electrical transmission. These results suggest that the gap junction network organizes neuronal activity of developing cortical circuit modules with unique slow dynamics.

[The Basic Modules of the Neocortex].

The mammalian neocortex contains diverse cell types but whether they organize into repeated modular circuits remains unknown. We discovered that major cell types in neocortical layer 5 form a lattice structure in many areas of the brain. Large-scale three-dimensional imaging revealed that distinct types of excitatory and inhibitory neurons form cell type-specific radial clusters termed microcolumns. Microcolumns form a hexagonal lattice tessellating a wide region of the neocortex. Neurons within individual microcolumns exhibit synchronized in vivo activity and visual responses with similar orientation preference and ocular dominance. During early postnatal development, microcolumns are coupled by cell type-specific gap junctions and later received convergent synaptic inputs. Thus, layer 5 neurons organize into a brain-wide modular system providing a template for cortical processing.

Lattice system of functionally distinct cell types in the neocortex.

The mammalian neocortex contains many cell types, but whether they organize into repeated structures has been unclear. We discovered that major cell types in neocortical layer 5 form a lattice structure in many brain areas. Large-scale three-dimensional imaging revealed that distinct types of excitatory and inhibitory neurons form cell type-specific radial clusters termed microcolumns. Thousands of microcolumns, in turn, are patterned into a hexagonal mosaic tessellating diverse regions of the neocortex. Microcolumn neurons demonstrate synchronized in vivo activity and visual responses with similar orientation preference and ocular dominance. In early postnatal development, microcolumns are coupled by cell type-specific gap junctions and later serve as hubs for convergent synaptic inputs. Thus, layer 5 neurons organize into a brainwide modular system, providing a template for cortical processing.

Identity of neocortical layer 4 neurons is specified through correct positioning into the cortex.

Many cell-intrinsic mechanisms have been shown to regulate neuronal subtype specification in the mammalian neocortex. However, how much cell environment is crucial for subtype determination still remained unclear. Here, we show that knockdown of Protocadherin20 (Pcdh20), which is expressed in post-migratory neurons of layer 4 (L4) lineage, caused the cells to localize in L2/3. The ectopically positioned "future L4 neurons" lost their L4 characteristics but acquired L2/3 characteristics. Knockdown of a cytoskeletal protein in the future L4 neurons, which caused random disruption of positioning, also showed that those accidentally located in L4 acquired the L4 characteristics. Moreover, restoration of positioning of the Pcdh20-knockdown neurons into L4 rescued the specification failure. We further suggest that the thalamocortical axons provide a positional cue to specify L4 identity. These results suggest that the L4 identity is not completely determined at the time of birth but ensured by the surrounding environment after appropriate positioning.

In vitro evaluation of inhibitory effects of antidiabetic and antihyperlipidemic drugs on human carboxylesterase activities.

Human carboxylesterase (CES) 1A is responsible for the biotransformation of angiotensin-converting enzyme (ACE) inhibitors such as imidapril and temocapril. Because antidiabetic or antihyperlipidemic drugs are often coadministered with ACE inhibitors in clinical pharmacotherapy, the inhibitory effect of these drugs on CES1A1 enzyme activity was investigated. In addition, the inhibitory effect on CES2 enzyme activity was evaluated to compare it with that on CES1A1. The inhibitory effects were evaluated with 11 antidiabetic and 12 antihyperlipidemic drugs. The imidapril hydrolase activity by recombinant CES1A1 was substantially inhibited by lactone ring-containing statins such as simvastatin and lovastatin and thiazolidinediones such as troglitazone and rosiglitazone. The activity in human liver microsomes was also strongly inhibited by simvastatin and troglitazone (K(i) = 0.8 ± 0.1 and 5.6 ± 0.2 µM, respectively). However, statins containing no lactone ring such as pravastatin and fluvastatin did not show strong inhibition. 7-Ethyl-10-[4-(1-piperidono)-1-piperidono]carbonyloxycamptothecin hydrolase activity by recombinant human CES2 was substantially inhibited by fenofibrate (K(i) = 0.04 ± 0.01 µM) as well as by simvastatin (0.67 ± 0.09 µM). Other fibrates such as clinofibrate and bezafibrate did not show strong inhibition. Thus, the inhibitory effects of the thiazolidinediones and fenofibrate on CES1A1 and CES2 were different. Some statins such as simvastatin and lovastatin, thiazolidinediones, and fenofibrate might attenuate the drug efficacy of prodrugs biotransformed by CES1A and CES2.

Arylacetamide deacetylase is a determinant enzyme for the difference in hydrolase activities of phenacetin and acetaminophen.

Phenacetin was withdrawn from the market because it caused renal failure in some patients. Many reports indicated that the nephrotoxicity of phenacetin is associated with the hydrolyzed metabolite, p-phenetidine. Acetaminophen (APAP), the major metabolite of phenacetin, is also hydrolyzed to p-aminophenol, which is a nephrotoxicant. However, APAP is safely prescribed if used in normal therapeutic doses. This background prompted us to investigate the difference between phenacetin and APAP hydrolase activities in human liver. In this study, we found that phenacetin is efficiently hydrolyzed in human liver microsomes (HLM) [CL(int) 1.08 +/- 0.02 microl/(min . mg)], whereas APAP is hardly hydrolyzed [0.02 +/- 0.00 microl/(min . mg)]. To identify the esterase involved in their hydrolysis, the activities were measured using recombinant human carboxylesterase (CES) 1A1, CES2, and arylacetamide deacetylase (AADAC). Among these, AADAC showed a K(m) value (1.82 +/- 0.02 mM) similar to that of HLM (3.30 +/- 0.16 mM) and the highest activity [V(max) 6.03 +/- 0.14 nmol/(min . mg)]. In contrast, APAP was poorly hydrolyzed by the three esterases. The large contribution of AADAC to phenacetin hydrolysis was demonstrated by the prediction with a relative activity factor. In addition, the phenacetin hydrolase activity by AADAC was activated by flutamide (5-fold) as well as that in HLM (4-fold), and the activity in HLM was potently inhibited by eserine, a strong inhibitor of AADAC. In conclusion, we found that AADAC is the principal enzyme responsible for the phenacetin hydrolysis, and the difference of hydrolase activity between phenacetin and APAP is largely due to the substrate specificity of AADAC.

Effects of Japanese herbal medicine, Kampo, on human UGT1A1 activity.

Kampo is a traditional Japanese herbal medicine and widely used in clinical practice in Japan. Little is known about interactions between Kampo and other medicines. Kampo contains many aglycones, which can be conjugated by UDP-glucuronosyltransferase (UGT). Therefore, in the present study, the effects of Kampo on human UGT1A1 activity were investigated in vitro. Substrates of human UGT1A1, beta-estradiol or 7-ethyl-10-hydroxycamptothecin (SN-38), were incubated with human liver microsomes in the presence of 51 Kampos, 14 medicinal herbs and their components. Beta-estradiol 3-glucuronidation was strongly inhibited by some Kampos such as Bofu-tsusho-san, Mashinin-gan and Otsuji-to. Medicinal herbs such as Daio (Rhei Rhizoma), Kanzo (Glycyrrhizae Radix), Keihi (Cinnamomi Cortex) and Ogon (Scutellariae Radix) exhibited potent inhibition on that activity. On beta-estradiol 3-glucuronidation, the major component of Keihi (cinnamaldehyde) and Ogon (wogonin) exhibited mixed-type inhibition of K(i) with values of 0.7 microM and 2.8 microM, respectively. On SN-38 glucuronidation, the inhibitory potencies of Kampos, medicinal herbs and their components tended to be similar to those on beta-estradiol 3-glucuronidation. In the present study, Kampo was clarified to inhibit beta-estradiol and SN-38 glucuronidation mainly catalyzed by UGT1A1.

Metabolic activation of benzodiazepines by CYP3A4.

Cytochrome P450 3A4 is the predominant isoform in liver, and it metabolizes more than 50% of the clinical drugs commonly used. However, CYP3A4 is also responsible for metabolic activation of drugs, leading to liver injury. Benzodiazepines are widely used as hypnotics and sedatives for anxiety, but some of them induce liver injury in humans. To clarify whether benzodiazepines are metabolically activated, 14 benzodiazepines were investigated for their cytotoxic effects on HepG2 cells treated with recombinant CYP3A4. By exposure to 100 microM flunitrazepam, nimetazepam, or nitrazepam, the cell viability in the presence of CYP3A4 decreased more than 25% compared with that of the control. In contrast, in the case of other benzodiazepines, the changes in the cell viability between CYP3A4 and control Supersomes were less than 10%. These results suggested that nitrobenzodiazepines such as flunitrazepam, nimetazepam, and nitrazepam were metabolically activated by CYP3A4, which resulted in cytotoxicity. To identify the reactive metabolite, the glutathione adducts of flunitrazepam and nimetazepam were investigated by liquid chromatography-tandem mass spectrometry. The structural analysis for the glutathione adducts of flunitrazepam indicated that a nitrogen atom in the side chain of flunitrazepam was conjugated with the thiol of glutathione. Therefore, the presence of a nitro group in the side chain of benzodiazepines may play a crucial role in the metabolic activation by CYP3A4. The present study suggested that metabolic activation by CYP3A4 was one of the mechanisms of liver injury by nitrobenzodiazepines.

Inhibitory effects of Kampo medicine on human UGT2B7 activity.

Kampo medicine is traditional Japanese medicine modified from the Chinese original. Kampo medicine is a mixture of several medicinal herbs and includes many ingredients such as glycosides. Glycosides are hydrolyzed to aglycons by intestinal bacterial flora and absorbed into the body. Aglycons such as baicalein and glycyrrhetinic acid can be conjugated by UDP-glucuronosyltransferase (UGT) in human liver or small intestine. UGT2B7 is one of the major isoforms responsible for drug conjugation including morphine 3- and 3'- azido-3'-deoxythymidine (AZT) glucuronidation. The present study investigates the effects of 51 Kampo medicines, 14 medicinal herbs and 11 ingredients on UGT2B7 activity in human liver microsomes. Morphine 3-glucuronidation was inhibited by more than 50% by 9 of 51 Kampo medicines such as Ryo-kei-jutsu-kan-to. AZT glucuronidation was inhibited by more than 50% by 24 of 51 Kampo medicines such as Jumi-haidoku-to. Medicinal herbs such as Daio (Rhei Rhizoma), Kanzo (Glycyrrhizae Radix) and Keihi (Cinnamomi Cortex) exhibited more than 80% inhibition on both glucuronidations. The major ingredients of these medicinal herbs inhibited UGT2B7 activity with low K(i). Kampo medicines were found to inhibit the UGT2B7 activity and may cause drug interactions via the inhibition of UGT.