In the development of pharmaceuticals and other chemical substances, it is important to evaluate their efficacy and safety. There is a growing trend toward reducing reliance on traditional in vivo testing using animals for safety assessments and utilizing new evaluation methods, such as in vitro and in silico testing, to refine human safety assessments. Furthermore, in medical and environmental fields, there is a growing demand for the utilization of vast amounts of information. This has led to the development of data-driven approaches that utilize large-scale medical information and artificial intelligence (AI). Machine learning enables computers to learn from known data, discover new patterns, and predict unknown data. This technology is also useful for in silico prediction of chemical toxicity and adverse reactions in humans. Recently, explainable AI, which presents the basis for forecasts obtained from machine learning models in a user-understandable manner, has attracted attention and is a useful technology for decision-making support. We have developed machine learning models focusing on a quantitative structure–activity relationship approach to predict toxicity and adverse reactions based on the structural information of chemical substances. Furthermore, we have begun to develop a model to predict package insert revisions based on post-marketing adverse reaction information. These efforts will contribute to solving regulatory science issues regarding the appropriate use of chemical substances such as pharmaceuticals.

Disruption of osteoblast differentiation can lead to severe bone diseases, such as osteoporosis and osteosclerosis. Our previous study showed that a reduced 4S/6S ratio promotes osteoblast differentiation, linking this specific chondroitin sulfate (CS) modification to bone pathology. This study investigated the effect of forced elevation of the 4S/6S ratio on differentiation. C4ST-1 was found to exhibit overexpression, increasing the 4S/6S ratio, significantly suppressing osteoblast differentiation, as evidenced by reduced Akp2 gene expression and ALP activity. This inhibition was far more potent than that caused by the enzymatic removal of CS. Notably, treating C4ST-1-overexpressing cells with chondroitinase reduced differentiation inhibition to a level similar to that in mock cells treated with chondroitinase. These results suggest that the strong inhibition was due to the excessive 4-sulfated CS produced by C4ST-1, implying a mechanism distinct from the inhibition caused by a lack of CS. To elucidate this mechanism, we investigated the potential feedback loop. The increase in 4-sulfated CS from C4ST-1 overexpression enhanced Wnt3a expression, which upregulated p53 expression. Pharmacological inhibition of β-catenin and p53 partially restored Akp2 expression, confirming their roles as key mediators. We propose that a high 4S/6S ratio activates a Wnt/β-catenin-p53 axis, where p53 acts as a brake on differentiation. Our findings highlight the critical role of CS sulfation patterns in fine-tuning the osteoblast fate.

Triple-negative breast cancer (TNBC) is characterized by the absence of hormone receptors and human epidermal growth factor receptor 2 (HER2) expression, rendering hormone therapy and HER2-targeted treatments ineffective. Consequently, conventional chemotherapy remains the primary therapeutic option, despite its severe side effects and poor prognosis. Hybrid liposomes (HL) composed of phospholipids and polyethylene glycol (PEG)-based surfactants have been reported to have therapeutic effects on various cancers without containing anticancer drugs. In this study, we investigated whether photodynamic therapy (PDT) with HL containing indocyanine green (HL/ICG) enhanced the therapeutic effect of HL alone in a mouse model of subcutaneous implantation of triple-negative breast cancer (TNBC) cells in vivo. HL/ICG selectively accumulated in tumors in mice implanted with 4T1-Luc cells, a TNBC cell line. Histological analysis of resected tumor tissues following HL/ICG-mediated PDT revealed a significant increase in cells positive for oxidative stress markers, indicating elevated intracellular oxidative damage. Additionally, a marked presence of apoptotic cells was observed, suggesting that PDT effectively induced programmed cell death in tumor tissues. These results indicate that PDT with HL/ICG induces oxidative stress-mediated apoptosis in tumors derived from 4T1-Luc cells and significantly enhances the therapeutic efficacy of HL alone in vivo, highlighting its potential as a promising strategy for the treatment of TNBC.

Recently, “readthrough compounds” have attracted attention as a promising approach to treat human hereditary diseases caused by nonsense mutations. These compounds enable ribosomes to bypass a premature termination codon (PTC) introduced into mRNA by a nonsense mutation, thereby restoring the expression of full-length functional proteins. We performed a structure–activity relationship study focusing on (+)-negamycin, a known readthrough compound, and identified potent derivatives, TCP-304 and TCP-306, featuring a cyclopropane moiety. In this study, we investigated how the nature of PTCs and their surrounding nucleotide sequences influence the readthrough activity of these negamycin derivatives, using nonsense mutation sequences derived from Duchenne muscular dystrophy and congenital muscular dystrophy genes. In cell-based reporter assay systems, TCP-306 exhibited potent readthrough efficiency against several nonsense mutation sequences containing the TGA-A. Moreover, its sequence preference differed from that of the aminoglycoside G418, a representative readthrough compound that preferentially induces readthrough at TGA-C sequences, suggesting that TCP-306 may serve as an alternative therapeutic option for muscular dystrophies associated with TGA-A nonsense mutations. Overall, this study provides valuable insights for the development of readthrough drugs for hereditary diseases such as muscular dystrophy caused by nonsense mutations.

Adjuvants are co-administered with antigens to enhance vaccine-induced protection. Saponins are plant-derived compounds with adjuvant properties, some of which are used in licensed vaccines. Macrophages and dendritic cells (DCs) exposed to saponin-based adjuvants have been reported to exhibit NLRP3-dependent interleukin-1 beta (IL-1β) release, and NLRP3 signaling has been shown to limit their adjuvant activity. Saponin-based adjuvants also induce plasma membrane rupture (PMR) and the release of high-molecular-weight intracellular molecules; however, the molecular mechanisms that mediate PMR and its impact on adjuvant-induced immune responses remain unclear. Here, we investigated the involvement of Ninjurin-1 (NINJ1), a key executor of PMR, in Quil-A-induced PMR and its immunological consequences. Upon stimulation with the saponin mixture Quil-A, peritoneal macrophages and bone marrow-derived dendritic cells (BMDCs) showed NLRP3-independent PMR but NLRP3-dependent IL-1β release. Quil-A-induced PMR was almost completely suppressed in Ninj1^−/− peritoneal macrophages and BMDCs compared with wild-type cells, whereas IL-1β release remained unaffected by NINJ1 deficiency. Immunization with Quil-A and ovalbumin (OVA) increased OVA-specific serum immunoglobulin G (IgG), IgG2b, and IgG2c levels in Ninj1^−/− mice compared with wild-type mice. Splenocytes from Ninj1^−/− mice produced higher levels of interferon-gamma upon stimulation with class I- and class II-restricted OVA peptides than those from wild-type mice. Ninj1^−/− mice also showed a higher frequency of OVA-bearing cells, particularly monocyte-derived DCs, in the draining lymph nodes. These results demonstrate that NINJ1 is critical for Quil-A-induced PMR and that NINJ1-mediated PMR negatively regulates Quil-A-induced humoral and cellular immune activation by restricting antigen delivery via antigen-presenting cells.