Additional effects of simultaneous treatment with C14-Cblin and celastrol on the clinorotation-induced rat L6 myotube atrophy.

Two novel reagents, N-myristoylated Cbl-b inhibitory peptide (C14-Cblin) and celastrol, a quinone methide triterpene, are reported to be effective in preventing myotube atrophy. The combined effects of C14-Cblin and celastrol on rat L6 myotubes atrophy induced by 3D-clinorotation, a simulated microgravity model, was investigated in the present study. We first examined their effects on expression in atrogenes. Increase in MAFbx1/atrogin-1 and MuRF-1 by 3D-clinorotation was significantly suppressed by treatment with C14-Cblin or celastrol, but there was no additive effect of simultaneous treatment. However, celastrol significantly suppressed the upregulation of Cbl-b and HSP70 by 3D-clinorotation. Whereas 3D-clinorotation decreased the protein level of IRS-1 in L6 myotubes, C14-Cblin and celastrol inhibited the degradation of IRS-1. C14-Cblin and celastrol promoted the phosphorylation of FOXO3a even in microgravity condition. Simultaneous administration of C14-Cblin and celastrol had shown little additive effect in reversing the impairment of IGF-1 signaling by 3D-clinorotation. While 3D-clinorotation-induced marked oxidative stress in L6 myotubes, celastrol suppressed 3D-clinorotation-induced ROS production. Finally, the C14-Cblin and celastrol-treated groups were inhibited decrease in L6 myotube diameter and increased the protein content of slow-twitch MyHC cultured under 3D-clinorotation. The simultaneous treatment of C14-Cblin and celastrol additively prevented 3D-clinorotation-induced myotube atrophy than single treatment. J. Med. Invest. 69 : 127-134, February, 2022.

Combinations of the Aromatic Rings in ß-1 Structure Formation of Lignin Based on Quantitative Analysis by Thioacidolysis.

The amount of ß-1 structures in lignin is small; however, they are assumed to significantly affect the reactivity of lignin because they form dienone structures. A method employing thioacidolysis and subsequent desulfurization yields products that can be analyzed via gas chromatography-mass spectrometry (GC-MS) to quantify these ß-1 structures. However, the retention times and response factors of the reaction products have not been accurately determined thus far. Here, 12 standard compounds combined with p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) units were synthesized, and their retention times and response factors were determined through GC-MS, using selective ions. Based on these data, we also investigated the ß-1 structures of lignocellulosic lignin samples. Our results clarified that the successful formation of the ß-1 structure was dependent on the type of aromatic rings present; there were very few ß-1 structures containing H units; and the amount of G-G type was higher and that of the heterotype, i.e., G-S type, was lower than the stochastic value.

Understanding Ligand-Exchange Reactions on Thiolate-Protected Gold Clusters by Probing Isomer Distributions Using Reversed-Phase High-Performance Liquid Chromatography.

Thiolate-protected gold clusters (Aun(SR)m) have attracted considerable attention as functional nanomaterials in a wide range of fields. A ligand-exchange reaction has long been used to functionalize these clusters. In this study, we separated products from a ligand-exchange reaction of phenylethanethiolate-protected Au24Pd clusters (Au24Pd(SC2H4Ph)18), in which Au25(SR)18 is doped with palladium, into each coordination isomer with high resolution by reversed-phase high-performance liquid chromatography. This success has enabled isomer distributions of the products to be quantitatively evaluated. We evaluated quantitatively the isomer distributions of products obtained by the reaction of Au24Pd(SC2H4Ph)18 with thiol, disulfide, or diselenide. The results revealed that the exchange reaction starts to occur preferentially at thiolates that are bound directly to the metal core (thiolates of a core site) in all reactions. Further study on the isomer-separated Au24Pd(SC2H4Ph)17(SC12H25) revealed that clusters vary the coordination isomer distribution in solution by the ligand-exchange reaction between clusters and that control of the coordination isomer distribution of the starting clusters enables control of the coordination isomer distribution of the products generated by ligand-exchange reactions between clusters. Au24Pd(SC2H4Ph)18 used in this study has a similar framework structure to Au25(SR)18, which is one of the most studied compounds in the Aun(SR)m clusters. Knowledge gained in this study is expected to enable further understanding of ligand-exchange reactions on Au25(SR)18 and other Aun(SR)m clusters.