The advent of a super-aged society poses urgent challenges in overcoming age-related neurological disorders and extending a healthy lifespan. Neurodegenerative diseases such as Alzheimer’s disease, dementia with Lewy bodies, and Parkinson’s disease are characterized by the accumulation of pathogenic proteins in the brain, leading to the formation of intracellular aggregates known as pathological hallmarks. In the early stages of protein accumulation, before the onset of clinical symptoms such as cognitive impairment or motor dysfunction, brain inflammation begins to occur. Subsequently, neuronal death progresses, and clinical symptoms manifest as dementia or Parkinson’s disease. Therefore, there is a need for early prediction of neurodegeneration and the development of disease-modifying drugs for pre-symptomatic prevention. To address this issue, we have focused on enhancing the degradation of amyloid-β protein by targeting Ca²⁺/calmodulin-dependent kinase II (CaMKII)/proteasome system and on suppressing the propagation and uptake mechanisms of α-synuclein by targeting fatty acid-binding proteins (FABPs) coupled with the long isoform of dopamine D2 (D_2L) receptor. Additionally, our analysis of FABP knockout mice has revealed an increased expression of FABPs in the neurodegenerative process, suggesting their involvement in mitochondrial dysfunction and neuronal death. Based on these findings, this article highlights the physiological significance of FABP family proteins in neurodegeneration and discusses the analysis of plasma biomarkers for predicting neurodegenerative disorders and the discriminatory methods for distinguishing between Alzheimer’s disease, dementia with Lewy bodies, and Parkinson’s disease. Furthermore, we explore the potential of ultra-early prediction of neurodegenerative disorders.

Parkinson’s disease (PD), which has characteristic motor symptoms such as tremor, muscle rigidity, and akinesia, and as the disease progresses, Lewy bodies spread throughout the brain, eventually causing Parkinson disease dementia (PDD). The clinical picture of PDD is similar to Dementia with Lewy bodies (DLB) and their pathological features are indistinguishable from each other. More than 80% of PD cases will eventually develop dementia and their prognosis are generally 3 to 4 years from the onset of dementia, regardless of disease duration or age of onset. We found that patients with severe olfactory impairment had lower cognitive function scores, more frequent onset of dementia, brain atrophy, and prominent cerebral metabolic abnormalities in a 3-year longitudinal study (Brain 135:161-169, 2012). This study demonstrated for the first time in the world that olfaction tests are useful in predicting dementia in PD, and similar results have been followed up worldwide. Based on these results, a randomized, double-blind, multicenter comparative study of donepezil in PD with severe olfactory dysfunction (DASH-PD study) was conducted and completed a 4-year follow-up period. The results were recently published showing the efficacy and safety of cholinesterase inhibitors for PD without dementia (eClinicalMedicine 51: 101571, 2022).

Biological phenomena are generated by the cooperative and hierarchical relationships between a variety of biomolecules, such as proteins, metabolites, signaling molecules, and ions. In many cases, however, these biomolecules do not have color, and it is difficult to observe them as they are. Therefore, it is necessary to “visualize” each molecule with color or fluorescence, and to analyze the functional relationships between them. The live cell imaging technology using single fluorescent protein (FP)-based indicators has contributed to the visualization of biomolecules. Single FP-based indicators, which change their fluorescence intensity upon binding to the target molecule, have been revolutionized into multicolor indicators by a series of innovative screening methods. On the other hand, we have established an original screening method using semi-rational molecular design and molecular evolution, and have developed many single FP-based indicators for various molecules such as cAMP and glucose. In this article, we focus on single FP-based indicators and introduce their development strategy and the history of screening method.

Small-molecule based activatable fluorescence probes for detecting specific enzyme activity with high sensitivity can visualize the expression site of marker genes and cancers where the enzyme is highly expressed. However, the enzyme-catalyzed fluorescent hydrolysis product easily leaks out and diffuses from the reaction site, making it difficult to perform long-term tracking and immunohistochemical analysis which needs washing/fixation procedure. Our group have focused on quinone methide chemistry and developed series of activatable fluorescence probes with excellent intracellular retention that are converted to quinone-methide or aza-quinone-methide intermediates upon reaction with enzymes, which are then react with intracellular nucleophiles such as proteins and glutathione to be retained in cells and to exhibit significant increase in fluorescence. Based on this molecular design, we have developed fluorescence probes targeting β-galactosidase and γ-glutamyltranspeptidase with different colors. We also developed photo-functional probes such as activatable photosensitizers and caged fluorophores. These probes can visualize or kill target enzyme-expressing cells with high selectivity by suppressing the leakage of hydrolysis products from target cells, and fluorescence imaging in combination with immunostaining was possible due to the high tolerance of the obtained fluorescence signal even after washing and fixation.

Fluorescent imaging sensors based on genetically-encoded and biocompatible proteins have become important tools in medical and biological research due to their high spatiotemporal resolution and ease of use. Protein engineering has led to the development of imaging sensors that visualize changes in the concentration of various target molecules/ions, such as calcium ions. In addition, the development of chemigenetic sensors based on complexes of proteins and synthetic molecules has been gaining momentum in recent years. In this article, the latest research trends in the development of these imaging sensors are introduced, with focus on the sensors developed by our group.

Basophils are the rarest granulocytes representing less than 1% of peripheral blood leukocytes. Even though basophils have been discovered more than 140 years ago, their roles in immune reactions had long been an enigma, partly because of their rarity and the similarity to tissue-resident mast cells. However, recent development of the analytical tools for basophil research, such as basophil-depletion antibody and basophil-related engineered mice, has uncovered the unique roles of basophils in various immune reactions. Basophils are now appreciated as a critical immune cell in various type 2-immune responses including the induction of chronic allergic inflammation and protective immunity against parasites. In this review, we summarize the recent understandings in the roles of basophils in allergic inflammation with especial focus on skin inflammation. We then focus on our recent findings in the differentiation and maturation pathways of basophils.

Adenosine-5'-triphosphate (ATP) is an important intracellular energy currency, but it is released extracellularly in response to various stimuli and acts as an intercellular signaling molecule by stimulating various P2 receptors. ATP and ADP are stored in synaptic vesicles and secretory granules, and are released extracellularly upon stimulation, playing important roles in neurotransmission and platelet aggregation. Furthermore, considerable amount of ATP is released by mechanical stimuli such as skin scraping or by cell damage, which in turn activates immune cells to promote inflammatory responses. Mast cells (MCs) are derived from hematopoietic stem cells and play a central role in type I allergic reactions. MCs are activated by IgE-mediated antigen recognition, leading to type I allergic reactions. MCs express P2X7 receptors that are activated by high concentrations of ATP (>0.5 ‍mM), and reported to aggravate inflammatory bowel disease and dermatitis. In contrast, role of MC P2 receptors that respond to lower concentrations of ATP remains to be investigated. We investigated in detail the effects of ATP in mouse bone marrow-derived MCs, and found that lower concentrations of ATP (<100 ‍μM) promotes IgE-dependent and GPCR-mediated degranulation via the ionotropic P2X4 receptor. In mouse allergic models, P2X4 receptor signal promote MC-mediated allergic responses through comprehensively increasing the sensitivity of MCs to different stimuli. Since ATP is known to be released from various cells upon mechanical stimuli such as cell damage or scratching, inhibition of P2X4 receptor signaling may represent a novel strategy to abrogate allergic reaction.

Mast cells and basophils share many characteristics, such as surface expression of the high affinity receptor of IgE, FcεRI, granule storage of histamine, which is released during their activation, and potentials to produce pro-/anti-inflammatory cytokines. These similar leukocytes, however, were found to have their own process of differentiation. Indeed, accumulating evidence suggests that these cells should play critical roles in type I allergy including anaphylaxis and in urticaria. Various inflammatory mediators derived from mast cells/basophils, such as histamine, platelet-activating factor, prostanoids, and leukotrienes, have been paid a particular attention to as the therapeutic targets for type I allergy and inflammatory diseases. Recent progress in the field of mast cell/basophil research has shed light on their physiological roles in bacterial infection, energy metabolism, and cutaneous/intestinal inflammation. This review makes a brief introduction of these recent studies, which are expected to provide novel therapeutic approaches for infectious and chronic inflammatory diseases.

Knowledge Palette, Inc. is a start-up company that aims to overcome incurable diseases by applying the world’s most accurate single-cell level and bulk level transcriptome technology to obtain large-scale data on the state of cells treated with various types of drugs and media, and using this information to highly control cells for improving human health. We are working on new phenotypic drug discovery and higher quality cells for regenerative medicine using big data. As one of its core technologies, the company is utilizing a single-cell-level whole gene expression analysis technology, Quartz-Seq2, which was originally developed in RIKEN. This technology received first place in accuracy of genes detection as well as marker identification, and was ranked No. 1 in overall score in the benchmarking in the international Human Cell Atlas project. By applying this technology to the bulk level analysis of ultra-multiple samples, it has enabled drug screening, analysis of human clinical specimens, and evaluation of numerous culture environments in a high-throughput way. This paper presents an omics-driven drug discovery and cell regulation approach that is combined with large-scale data and artificial intelligence technology.

Tezepelumab (TEZSPIRE^® Subcutaneous Injection 210 ‍mg), a biologic medicine with a novel mechanism, was approved in Japan in September 2022 for the treatment of bronchial asthma. Tezespire auto-injector was approved in Japan in August 2023 as an additional dosage. It is indicated for severe or refractory patients whose asthmatic symptoms cannot be controlled by currently available treatment. Tezepelumab binds to the epithelial cytokine thymic stromal lymphopoietin (TSLP) and disrupts TSLP signaling via the heterodimeric receptor. In the Phase 3 NAVIGATOR trial, the annual asthma exacerbation rate was significantly reduced by tezepelumab when administered subcutaneously every 4 weeks over a 52-week period to patients with uncontrolled, severe asthma who had received medium- or high-dose inhaled glucocorticoids. Its efficacy in reducing asthma exacerbations was observed regardless of blood eosinophil (bEOS) count, fractional exhaled nitric oxide (FeNO) levels, or serum total IgE at baseline. Significant improvements were noted in lung function, health-related quality of life, and change from baseline in asthma control. Reductions in the levels of inflammatory biomarkers (bEOS, FeNO, and IgE) was also noted. Clinical pharmacology trials demonstrated the efficacy of tezepelumab in improving airway hyperresponsiveness. In this article, we reviewed pharmacological characteristics, pharmacokinetics, clinical efficacy, and the safety profile of tezepelumab.

The prognosis of patients with B-cell non-Hodgkin lymphoma (B-NHL) has improved with the use of anti-CD20 based immunochemotherapy. However, management of relapsed or refractory disease remains a challenge, indicating a high unmet need for novel treatments. Epcoritamab (recombinant) is a humanized immunoglobulin G1 (IgG1) bispecific antibody that simultaneously binds to CD3 on T cells and CD20 on B cells or tumor cells inducing T-cell mediated cytotoxicity against CD20-positive B cells. It demonstrated consistent cytotoxic effects in B-cell lymphoma cell line-derived xenograft models, patient-derived xenograft models, and cynomolgus monkey studies. Pharmacological studies in cynomolgus monkeys showed peak plasma concentrations of cytokines were lower with subcutaneous versus intravenous administration. To reduce the risk of cytokine release syndrome (CRS) and improve convenience, Epcoritamab has been developed as a subcutaneous formulation.

To further reduce the risk of CRS, clinical trials utilized a priming dose and incremental dose increases. In Phase I/II overseas trials with relapsed, progressive, or refractory B-NHL patients, the recommended Phase II trial dose was determined based on safety, efficacy, and pharmacokinetic model simulation results. The Phase II dose-expansion part demonstrated the efficacy and high tolerability of epcoritamab monotherapy at the recommended dose. Similar efficacy and tolerability were observed in Japanese Phase I/II trials in relapsed or refractory B-NHL patients. Based on these results, epcoritamab received the approval in September 2023 for the treatment of “relapsed or refractory large B-cell lymphoma (DLBCL, HGBCL, PMBCL)” and “relapsed or refractory follicular lymphoma (Grade 3B)” in Japan.