Yasukatsu Yuda

Shikonin inhibits IgE-mediated histamine release by human basophils and Syk kinase activity

Abstract.Objective:Shikonin, a component of the herbal medicine “Shikon”, is known to suppress inflammatory reactions, but its molecular targets are not identified. This study examines the effect of shikonin on human basophil degranulation response and aims to identify its targets.Materials:Human basophils in isolated leukocytes from healthy volunteers’ peripheral blood; recombinant human Syk and Lyn tyrosine kinases. Methods:Histamine release from basophils stimulated with anti-IgE antibody was analyzed fluorimetrically. Syk and Lyn kinase activities were tested in Vitro with recombinant proteins and analyzed by off-chip mobility shift assay.Results:Shikonin dose-dependently inhibited the histamine release from basophils induced by anti-IgE antibody (IC50 = 2.6 ± 1.0 µM; mean ± SEM). A search for the target(s) of shikonin in the signal cascade of IgE-mediated activation showed that it strongly inhibits Syk (IC50 = 7.8 µM, in the recombinant kinase assay), which plays a pivotal role in the degranulation response. A less significant inhibition was found for Lyn, which phosphorylates FcεRI-βγ subunits and also Syk.Conclusions:These results indicate that the inhibition of Syk-dependent phosphorylation events might underlie the blocked histamine release from human basophils, thus contributing to the anti-inflammatory effects of shikonin.

Medicine reclassification processes and regulations for proper use of over-the-counter self-care medicines in Japan

Objectives Japan has actively reclassified substances ranging from prescription drugs to over-the-counter (OTC) drugs in recent years. The sale of most OTC drugs was deregulated several times and pharmacists’ supervision was deemed no longer mandatory. Japan established a new OTC evaluation system in 2015 to hear opinions from various stakeholders regarding medicine types to be reclassified. This study aimed to examine the new framework to identify candidate substances for reclassification. Moreover, we examined how to manage the safe, self-care use of OTC drugs in Japan. Methods The necessary regulatory information on OTC approvals as of January 2015 was collected using an Internet search and relevant databases. To highlight the characteristics of OTC drugs in Japan, the UK was selected as a comparison country because it too was actively promoting the reclassification of medicines from prescription to nonprescription status, and because of economic similarity. Results Japan and the UK have a risk-based classification for nonprescription medicines. Japan has made OTC drugs available with mandatory pharmacists’ supervision, face-to-face with pharmacists, or online instruction, which is similar to the “pharmacy medicine” practiced in the UK. Japan recently reformed the reclassification process to involve physicians and the public in the process; some interactions were back to “prescription-only medicine” in the UK. Conclusion It is expected that the opinion of marketers, medical professionals, and the public will improve the discussion that will greatly contribute to the safe use of drugs. Monitoring the new system will be noteworthy to ensure that OTC drug users are managing their self-care properly and visiting a doctor only when necessary. The supply methods are similar in Japan and the UK; however, the expected growth in the Japanese OTC market by the Cabinet and the industry is still uncertain.

Inhibition of neutrophil superoxide generation by shikonin is associated with suppression of cellular Ca2+ fluxes

Shikonin, an anti-inflammatory compound of “Shikon”, inhibits the neutrophil superoxide (O2•−) generation by NADPH oxidase 2 (Nox2); however, the mechanisms of how shikonin affects Nox2 activity remained unclear. We aimed to elucidate the relationship between the inhibition of Nox2 activity and influences on intracellular Ca2+ concentration ([Ca2+]i) by shikonin. For this purpose, we used a simultaneous monitoring system for detecting changes in [Ca2+]i (by fluorescence) and O2•− generation (by chemiluminescence) and evaluated the effects of shikonin on neutrophil-like HL-60 cells stimulated with N-formyl-l-methionyl-l-leucyl-l-phenylalanine (fMLP). Since fMLP activates Nox2 by elevation in [Ca2+]i via fluxes such as inositol 1,4,5-trisphosphate-induced Ca2+ release (IICR) and store-operated Ca2+ entry (SOCE), we also evaluated the effects of shikonin on IICR and SOCE. Shikonin dose-dependently inhibited the fMLP-induced elevation in [Ca2+]i and O2•− generation (IC50 values of 1.45 and 1.12 µM, respectively) in a synchronized manner. Analyses of specific Ca2+ fluxes showed that shikonin inhibits IICR and IICR-linked O2•− generation (IC50 values: 0.28 and 0.31 µM for [Ca2+]i and O2•−, respectively), as well as SOCE and SOCE-linked O2•− generation (IC50 values: 0.39 and 0.25 µM for [Ca2+]i and O2•−, respectively). These results suggested that shikonin inhibits the O2•− generation by Nox2 in fMLP-stimulated neutrophils by targeting Ca2+ fluxes such as IICR and SOCE.