Establishment of a Method for the Introduction of Poorly Water-Soluble Drugs in Cells and Evaluation of Intracellular Concentration Distribution Using Resonance Raman Imaging.

Label-free measurement is essential to understand the metabolism of drug molecules introduced into cells. Raman imaging is a powerful method to investigate intracellular drug molecules because it provides in situ label-free observation of introduced molecules. In this study, we propose that Raman imaging can be used not only to observe the intracellular distribution of drug molecules but also to quantitatively visualize the concentration distribution reflecting each organelle in a single living cell using the Raman band of extracellular water as an intensity standard. We dissolved poorly water-soluble all-trans-retinoic acid (ATRA) in water using a cytocompatible amphiphilic phospholipid polymer, poly[2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate] (PMB) as a solubilizing reagent, introduced it into cells, and obtained the intracellular concentration distribution of ATRA. ATRA was concentrated in the cells and mainly localized to mitochondria and lipid droplets, interacting strongly with mitochondria and weakly with lipid droplets. Poorly water-soluble ß-carotene was also introduced into cells using PMB but was not concentrated intracellularly, indicating that ß-carotene does not interact specifically with intracellular molecules. We established a protocol for the solubilization and intracellular uptake of poorly water-soluble molecules using PMB and obtaining their concentration distribution using Raman microscopy.

Supersulphides provide airway protection in viral and chronic lung diseases.

Supersulphides are inorganic and organic sulphides with sulphur catenation with diverse physiological functions. Their synthesis is mainly mediated by mitochondrial cysteinyl-tRNA synthetase (CARS2) that functions as a principal cysteine persulphide synthase (CPERS). Here, we identify protective functions of supersulphides in viral airway infections (influenza and COVID-19), in aged lungs and in chronic lung diseases, including chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF). We develop a method for breath supersulphur-omics and demonstrate that levels of exhaled supersulphides increase in people with COVID-19 infection and in a hamster model of SARS-CoV-2 infection. Lung damage and subsequent lethality that result from oxidative stress and inflammation in mouse models of COPD, IPF, and ageing were mitigated by endogenous supersulphides production by CARS2/CPERS or exogenous administration of the supersulphide donor glutathione trisulphide. We revealed a protective role of supersulphides in airways with various viral or chronic insults and demonstrated the potential of targeting supersulphides in lung disease.

Potential role of serotonin as a biological reductant associated with copper transportation.

Serotonin (5-HT) is a neurotransmitter that is derived from tryptophan. Owing to a hydroxyl group attached to the indole nucleus, 5-HT exhibits a considerably higher redox activity than tryptophan. To gain insight into the biological relevance of the redox activity of 5-HT, the effect of Cu(I)-binding ligands on the 5-HT-mediated copper reduction was investigated. The d-d transition band of Cu(II) complexed with glycine [Cu(II)-Gly2] was not affected by addition of 5-HT alone but was diminished when a thioether-containing compound coexists with 5-HT. Concomitant with disappearance of the d-d transition band of Cu(II)-Gly2, the π-π* transition band of 5-hydroxyindole of 5-HT exhibits a red-shift which is consistently explained by oxidation of 5-HT and subsequent formation of a dimeric species. The redox reactions between 5-HT and copper are also accelerated by a peptide composed of a methionine (Met)-rich region in the extracellular domain of an integral membrane protein, copper transporter 1 (Ctr1). Since Ctr1 transports copper across the plasma membrane with specificity for Cu(I), reduction of extracellular Cu(II) to Cu(I) is required for copper uptake by Ctr1. Metalloreductases that can donate Cu(I) for Ctr1 have been identified in yeast but not yet been found in mammals. The results of this study indicate that the Met-rich region in the N-terminal extracellular domain of Ctr1 promotes the 5-HT-mediated Cu(II) reduction in order to acquire Cu(I) via a non-enzymatic process.