Kamebakaurin Suppresses Antigen-Induced Mast Cell Activation by Inhibition of FcεRI Signaling Pathway.

INTRODUCTION: Kamebakaurin is an active constituent of both Rabdosia japonica and Rabdosia excisa, which are utilized in Chinese traditional medicine for improving symptoms in patients with allergies. We investigated the molecular mechanisms of the anti-allergic effects of kamebakaurin using BMMCs. METHODS: The degranulation ratio, histamine release, and the interleukin (IL)-4, leukotriene B4 (LTB4), and cysteinyl leukotriene productions on antigen-triggered BMMC were investigated. Additionally, the effects of kamebakaurin on signal transduction proteins were examined by Western blot and binding to the Syk and Lyn kinase domain was calculated. The effects of kamebakaurin on antigen-induced hyperpermeability were investigated using mouse model. RESULTS: At 10 µm, kamebakaurin partially inhibited degranulation, histamine release, and IL-4 production. At 30 µm, kamebakaurin partially reduced LTB4 and cysteinyl leukotriene productions and suppressed degranulation, histamine release, and IL-4 production. Phosphorylation of both Syk Y519/520 and its downstream protein, Gab2, was reduced by kamebakaurin, and complete inhibition was observed with 30 µm kamebakaurin. In contrast, phosphorylation of Erk was only partially inhibited, even in the presence of 30 µm kamebakaurin. Syk Y519/520 is known to be auto-phosphorylated via intramolecular ATP present in its own ATP-binding site, and this auto-phosphorylation triggers degranulation, histamine release, and IL-4 production. Docking simulation study indicated kamebakaurin blocked ATP binding to the ATP-binding site in Syk. Therefore, inhibition of Syk auto-phosphorylation by kamebakaurin binding to the Syk ATP-binding site appeared to cause a reduction of histamine release and IL-4 production. Kamebakaurin inhibited antigen-induced vascular hyperpermeability in a dose-dependent fashion but did not reduce histamine-induced vascular hyperpermeability. CONCLUSION: Kamebakaurin ameliorates allergic symptoms via inhibition of Syk phosphorylation; thus, kamebakaurin could be a lead compound for the new anti-allergic drug.

A Rapid and Sensitive Determination of Histamine in Mast Cells Using a Didansyl Derivatization Method.

BACKGROUND: Mast cells play a central role in allergic responses such as food allergy, asthma, allergic rhinitis, and allergic conjunctivitis. Symptoms in the early phase of these allergic diseases are primarily caused by histamine. However, due to the high histidine content in the cytosol and low histamine content in secretory granules, separating and quantifying histamine from histidine is often difficult. OBJECTIVES: We studied a method for rapid and sensitive quantitation of mast cell-derived histamine and evaluated its application to allergic disease research. METHODS: Bone marrow-derived mouse mast cells (BMMCs) were employed in this study. IgE-sensitized BMMCs were activated by FcεRI cross-linking. After activation, both the histamine released to the supernatant and histamine remaining in BMMCs were didansylated and then analyzed by high-performance liquid chromatography with fluorescence detection (HPLC-FD). Didansyl histamine was synthesized as a standard material. RESULTS: Synthetic didansyl histamine was detected by HPLC-FD with a peak retention time of 18.5 min. Very high linearity of the standard curve was maintained at concentrations of 10 pg/µL or less when the didansyl histamine method was used. This method enables detection of histamine released from 1 × 105 BMMCs. In addition, the histamine concentration in the supernatant due to spontaneous release was also determined. Finally, the ratio of histamine release was highly correlated with the degranulation ratio. CONCLUSION: These results indicate that the proposed method using didansylated histamine to determine mast cell-derived histamine is highly useful for allergy research applications.

Potential Anti-allergic Effects of Bibenzyl Derivatives from Liverworts, Radula perrottetii.

The liverwort Radula perrottetii contains various bibenzyl derivatives which are known to possess various biological activities, such as anti-inflammatory effects. Mast cells (MC) play crucial roles in allergic and inflammatory diseases; thus, inhibition of MC activation is pivotal for the treatment of allergic and inflammatory disorders. We investigated the effects of perrottetin D (perD), isolated from Radula perrottetii, and perD diacetate (Ac-perD) on antigen-induced activation of MCs. Bone marrow-derived MCs (BMMCs) were generated from C57BL/6 mice. The degranulation ratio, histamine release, and the interleukin (IL)-4 and leukotriene B4 productions on antigen-triggered BMMC were investigated. Additionally, the effects of the bibenzyls on binding of IgE to FcεRI were observed by flow cytometry, and signal transduction proteins was examined by Western blot. Furthermore, binding of the bibenzyls to the Fyn kinase domain was calculated. At 10 µM, perD decreased the degranulation ratio (p < 0.01), whereas 10 µM Ac-perD down-regulated IL-4 production (p < 0.05) in addition to decreasing the degranulation ratio (p < 0.01). Both compounds tended to decrease histamine release at a concentration of 10 µM. Although 10 µM perD reduced only Syk phosphorylation, 10 µM Ac-perD diminished phosphorylation of Syk, Gab2, PLC-γ, and p38. PerD appeared to selectively bind Fyn, whereas Ac-perD appeared to act as a weak but broad-spectrum inhibitor of kinases, including Fyn. In conclusion, perD and Ac-perD suppressed the phosphorylation of signal transduction molecules downstream of the FcεRI and consequently inhibited degranulation, and/or IL-4 production. These may be beneficial potential lead compounds for the development of novel anti-allergic and anti-inflammatory drugs.

Single base substitution signatures 17a, 17b, and 40 are induced by γ-ray irradiation in association with increased reactive oxidative species.

γ-Ray irradiation induces DNA double strand breaks (DSBs) and increases the risk of cancerization. Irradiated cells usually repair DSBs directly, but accumulate replication stress-associated DSBs, increasing the risk of structural variants (SVs). Although single nucleotide variants (SNVs) are also induced, it is still unclear which SNVs are induced by γ-ray irradiation. Here, we show that single base substitution (SBS) 17a, 17b, and 40 signatures were induced by γ-ray irradiation, which is mainly SNV induction in A-T bps. While SNVs induced by genomic instability were usually associated with SVs, SNVs induced by γ-ray irradiation and the associated signatures were not. As reactive oxygen species (ROS) are a possible cause of SBS17a and 17b, ROS were induced upon γ-ray irradiation (1-8 Gy), indicating the association of ROS for the SNV induction. Thus, our results reveal that ROS-associated SNVs are increased by irradiation, and that ROS-associated SNVs are induced independently of SVs.

Open-Circuit-Voltage Improvement Mechanism of Perovskite Solar Cells Revealed by Operando Spin Observation.

Organic-inorganic hybrid perovskite solar cells have attracted much attention as important next-generation solar cells. Their solar cell performance is known to change during operation, but the root cause of the instability remains unclear. This report describes an investigation using electron spin resonance (ESR) to evaluate an improvement mechanism for the open-circuit voltage, VOC, of inverted perovskite solar cells at the initial stage of device operation. The ESR study revealed electron transfer at the interface from the perovskite layer to the hole-transport layer not only under dark conditions but also under light irradiation, where electrons are subsequently trapped in the hole-transport layer. An electron barrier is enhanced at the perovskite/hole-transport-layer interface, improving field-effect passivation at the interface. Thereby, the interface recombination velocity is reduced, and thus the VOC improves. These findings are crucially important for elucidating the mechanisms of device performance changes under operation. They reveal a relation between charge transfer and performance improvement, which is valuable for the further development of efficient perovskite solar cells.

Genome destabilization-associated phenotypes arising as a consequence of therapeutic treatment are suppressed by Olaparib.

Malignancy is often associated with therapeutic resistance and metastasis, usually arising after therapeutic treatment. These include radio- and chemo-therapies, which cause cancer cell death by inducing DNA double strand breaks (DSBs). However, it is still unclear how resistance to these DSBs is induced and whether it can be suppressed. Here, we show that DSBs induced by camptothecin (CPT) and radiation jeopardize genome stability in surviving cancer cells, ultimately leading to the development of resistance. Further, we show that cytosolic DNA, accumulating as a consequence of genomic destabilization, leads to increased cGAS/STING-pathway activation and, ultimately, increased cell migration, a precursor of metastasis. Interestingly, these genomic destabilization-associated phenotypes were suppressed by the PARP inhibitor Olaparib. Recognition of DSBs by Rad51 and genomic destabilization were largely reduced by Olaparib, while the DNA damage response and cancer cell death were effectively increased. Thus, Olaparib decreases the risk of therapeutic resistance and cell migration of cells that survive radio- and CPT-treatments.

Echoed induction of nucleotide variants and chromosomal structural variants in cancer cells.

Generally, the number of single-nucleotide variants (SNVs) in somatic cells increases with age, which is expected for replication errors. The number of SNVs in cancer cells, however, is often much higher than that in somatic cells, raising the question of whether cancer cells possess SNV induction pathways. The present study shows that the number of SNVs in cancer cells correlates with the number of chromosomal structural variants (SVs). While Kataegis, localized hypermutations typically arising near SV sites, revealed multiple SNVs within 1 kb, SV-associated SNVs were generally observed within 0.1-1 Mb of SV sites, irrespective of Kataegis status. SNVs enriched within 1 Mb of SV regions were associated with deficiency of DNA damage repair, including HR deficiency-associated single base substitution 3 (SBS3) and exogenous damage-associated SBS7 and SBS36 signatures. We also observed a similar correlation between SVs and SNVs in cells that had undergone clonal evolution in association with genomic instability, implying an association between genomic instability and SV-associated induction of SNVs.