Quercetin has multiple potential to control various cell function keeping our body condition healthy. In this review article, we describe the molecular mechanism on how quercetin exerts its action on blood pressure, neurite elongation and epithelial ion transport based from a viewpoint of cytosolic Cl- environments, which is recently recognized as an important signaling factor in various types of cells. Recent studies show various roles of cytosolic Cl- in regulation of blood pressure and neurite elongation, and prevention from bacterial and viral infection. We have found the stimulatory action of quercetin on Cl- transporter, Na+-K+-2Cl- cotransporter 1 (NKCC1; an isoform of NKCC), which has been recognized as one of the most interesting, fundamental actions of quercetin. In this review article, based on this stimulatory action of quercetin on NKCC1, we introduce the molecular mechanism of quercetin on: 1) blood pressure, 2) neurite elongation, and 3) epithelial Cl- secretion including tight junction forming in epithelial tissues. 1) Quercetin induces elevation of the cytosolic Cl- concentration via activation of NKCC1, leading to anti-hypertensive action by diminishing expression of epithelial Na+ channel (ENaC), a key ion channel involved in renal Na+ reabsorption, while quercetin has no effects on the blood pressure with normal salt intake. 2) Quercetin also has stimulatory effects on neurite elongation by elevating the cytosolic Cl- concentration via activation of NKCC1 due to tubulin polymerization facilitated through Cl--induced inhibition of GTPase. 3) Further, in lung airway epithelia quercetin stimulates Cl- secretion by increasing the driving force for Cl- secretion via elevation of the cytosolic Cl- concentration: this leads to water secretion, participating in prevention of our body from bacterial and viral infection. In addition to transcellular ion transport, quercetin regulates tight junction function via enhancement of tight junction integrity by modulating expression and assembling tight junction-forming proteins. Based on these observations, it is concluded that quercetin is a useful medicinal compound keeping our body to be in healthy condition.

Nucleic acid medicines have been developed as new therapeutic agents against various diseases; however, targeted delivery of these reagents into cancer cells, particularly hematologic cancer cells, via systemic administration is limited by the lack of efficient and cell-specific delivery systems. We previously demonstrated that monoclonal antibody (mAb)-oligonucleotide complexes targeting exosomal microRNAs with linear oligo-D-arginine (Arg) linkers were transferred into solid cancer cells and inhibited exosomal miRNA functions. In this study, we developed exosome-capturing anti-CD63 mAb-conjugated small interfering RNAs (siRNAs) with branched Arg linkers and investigated their effects on multiple myeloma (MM) cells. Anti-CD63 mAb-conjugated siRNAs were successfully incorporated into MM cells. The incorporation of exosomes was inhibited by endocytosis inhibitors. We also conducted a functional analysis of anti-CD63 mAb-conjugated siRNAs. Ab-conjugated luciferase+ (luc+) siRNAs significantly decreased the luminescence intensity in OPM-2-luc+ cells. Moreover, treatment with anti-CD63 mAb-conjugated with MYC and CTNNB1 siRNAs decreased the mRNA transcript levels of MYC and CTNNB1 to 52.5% and 55.3%, respectively, in OPM-2 cells. In conclusion, exosome-capturing Ab-conjugated siRNAs with branched Arg linkers can be effectively delivered into MM cells via uptake of exosomes by parental cells. This technology has the potential to lead to a breakthrough in drug delivery systems for hematologic cancers.

The Wnt/β-catenin pathway is an attractive target for the treatment of acute myelogenous leukemia (AML), since aberrant activation of the Wnt/β-catenin pathway contributes to carcinogenesis in various types of cancers including AML. Screening of an in-house compound library, constructed at Kyoto Pharmaceutical University, identified a novel compound designated "31" that was found to be an inhibitor of the Wnt/β-catenin pathway. The compound inhibited T-cell factor (TCF) activity in a TCF firefly luciferase-reporter assay and suppressed the proliferation of several human AML cell lines in a dose-dependent manner. Compound 31 arrested the cell cycle of AML cells at the G1 stage and induced apoptosis. Decrease in protein and mRNA expression level of Wnt pathway-related molecules was confirmed by the analyses of western blotting and quantitative reverse transcription-polymerase chain reaction. In addition, compound 31 combined with idarubicin synergistically inhibited the proliferation of AML cells. In conclusion, these results strongly suggest that compound 31 has potential as a novel anti-AML agent targeting the Wnt/β-catenin signaling pathway.

Ambroxol (ABX), a frequently prescribed secretolytic agent which enhances the ciliary beat frequency (CBF) and ciliary bend angle (CBA, an index of amplitude) by 30%, activates a voltage-dependent Ca²⁺ channel (Ca_V1.2) and a small transient Ca²⁺ release in the ciliated lung airway epithelial cells (c-LAECs) of mice. The activation of Ca_V1.2 alone enhanced the CBF and CBA by 20%, mediated by a pH_i increase_i and a [Cl⁻]_i decrease in the c-LAECs. The increase in pH_i, which was induced by the activation of the Na⁺-HCO₃⁻ cotransporter (NBC), enhanced the CBF (by 30%) and CBA (by 15–20%), and a decrease in [Cl⁻]_i, which was induced by the Cl⁻ release via anoctamine 1 (ANO1), enhanced the CBA (by 10–15%). While a Ca²⁺-free solution or nifedipine (an inhibitor of Ca_V1.2) inhibited 70% of the CBF and CBA enhancement using ABX, Ca_V1.2 enhanced most of the CBF and CBA increases using ABX. The activation of the Ca_V1.2 existing in the cilia stimulates the NBC to increase pH_i and ANO1 to decrease the [Cl⁻]_i in the c-LAECs. In conclusion, the pH_i increase and the [Cl⁻]_i decrease enhanced the CBF and CBA in the ABX-stimulated c-LAECs.