WalK, a histidine kinase, and WalR, a response regulator, make up a two-component signal transduction system that is indispensable for the cell-wall metabolism of low GC Gram-positive bacteria. WalK inhibitors are likely to show bactericidal effects against methicillin-resistant Staphylococcus aureus . We discovered a new WalK inhibitor, designated waldiomycin, by screening metabolites from actinomycetes. Waldiomycin belongs to the family of angucycline antibiotics and is structurally related to dioxamycin. Waldiomycin inhibits WalK from S. aureus and Bacillus subtilis at IC50s 8.8 and 10.2 μM, respectively, and shows antibacterial activity with MICs ranging from 4 to 8 μg ml(-1) against methicillin-resistant S. aureus and B. subtilis.

Abstract. The topoisomerase I inhibitor irinotecan is widely used in anticancer therapy, although the detailed mechanism is still unclear. We investigated the apoptotic mechanisms of irinotecan in human hepatocellular carcinoma (HCC) cell lines (Huh7). SN-38 caused a significant decrease in cell proliferation and induced apoptosis in Huh7 cells and HepG2 cells. SN-38 significantly increased the expression of p53 protein and its phosphorylation at Ser 15 in the nucleus and apoptosis-inducing proteins Bax, caspase-9, and caspase-3, while it significantly decreased the antiapoptosis protein Bcl-xL of Huh7 cells. SN-38-induced apoptosis was recovered after p53 antisense oligodeoxynucleotide (AS ODN) pretreatment, while Huh7 cells were precultured with p53 AS ODN, followed by the addition of SN-38 for 24 h. Furthermore, increases in p53 DNA-binding activity were observed in the nuclei of Huh7 cells after SN-38 treatment as shown by electrophoretic mobility shift analysis. SN-38 binding motifs were detected in the proximal promoter of p53 (bases −433 to −317 and −814 to −711). These results suggest that the p53-mediated apoptosis pathway is important in the anticancer effects of irinotecan in hepatocellular carcinoma.

Irinotecan, a DNA topoisomerase I inhibitor, is widely used in cancer chemotherapy. However, little is known of the mechanisms of its antitumor effects and the development of drug resistance in human hepatocellular carcinoma (HCC). In this study, we investigated the effects of short-term culture with SN-38, the active metabolite of irinotecan, on apoptosis in Huh7 cells. The cells were cultured with SN-38 for 24, 72, and 120 h, and apoptosis was determined using the terminal dUTP nick-end labeling (TUNEL) assay. The expressions of p53, apoptosis-related proteins, and P-glycoprotein (P-gp), a protein conferring the multidrug-resistant phenotype, were analyzed using Western blotting. Induced expression of P-gp was detected using fluorescence microscopy. SN-38 significantly induced apoptosis in Huh7 cells at 24 h. SN-38 also increased the expression of p53, Bax, and caspase-9 and decreased Bcl-xL expression in Huh7 cells. SN-38 decreased p53 expression and increased P-gp expression after 120 h, resulting in inhibition of apoptosis. This inhibition was reversed by the addition of verapamil to the culture medium during 120 h incubation. SN-38-induced P-gp expression was additionally enhanced by p53 decoy oligodeoxynucleotide. The changes in P-gp expression were directly moderated by p53 gene downregulation, suggesting that it plays a role in the mechanism of drug resistance. These results suggest that the accumulation of irinotecan in HCC leads to the development of drug resistance.

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Cytochrome P450 (CYP) 3A is the primary CYP isoenzyme subfamily responsible for phase I metabolism of Ͼ50% of drug doses administered to humans.1,2) CYP3A4 is the most prominent CYP in humans, comprising about 30% and 70% of total CYP in the liver and intestine, respectively. CYP3A has very broad substrate specificity, encompassing a wide variety of therapeutic agents.3) Many cancer chemotherapeutic agents such as vinca alkaloids, paclitaxel, irinotecan hydrochloride and other widely used drugs such as amiodarone, diltiazem, lovastatin, erythromycin, and midazolam are substrates for CYP3A. [4][5][6][7] Recently, individual variations in CYP3A activity in the human liver have been reported. 8)Because the pharmacokinetics of various drugs is influenced by individual variations in CYP3A activity, it is important to evaluate those variations in the clinical setting to achieve the optimum therapeutic outcomes. 9)Probe drugs including midazolam, erythromycin, nifedipine, lidocaine, and dextromethorphan and endogenous compounds such as cortisol and testosterone have been utilized to evaluate CYP3A activity.10,11) Watkins 12) proposed three specific CYP3A probes: erythromycin; midazolam; and cortisol. However, the probe drugs available for accurate, safe, and easy measurement of CYP3A activity remain limited.Lansoprazolebenzimidazole, is a proton-pump inhibitor (PPI) that suppresses gastric acid secretion by inhibiting (H ϩ /K ϩ )-ATPase and is prescribed commonly for the treatment of gastric ulcer, reflux esophagitis, etc., with few serious side effects reported. Following administration, lansoprazole is extensively metabolized to 5-hydroxylansoprazole and lansoprazole sulfone (LS) by CYP2C19 and CYP3A, respectively. 13) Masa et al. 14) reported that the metabolism to LS by CYP3A occurs independently of that to 5-hydroxylansoprazole by CYP2C19 in the human liver. Inhibition of one metabolic pathway caused by the genetic polymorphisms of CYPs leads to upregulation of another pathway in vivo. To use lansoprazole as probe drug, these problems should be elucidated in vitro or in vivo. The present study investigated the utility of lansoprazole in assessing CYP3A activity in comparison with previously reported in vitro methods. Miyamae-ku, Kawasaki, Kanagawa 216-8511, Japan: and b Research Laboratories, HAB Research Organization; 3rd Floor, Cornea Center Bldg., Ichikawa General Hospital, 5-11-13 Sugano, Ichikawa, Chiba 272-8523, Japan. Received April 13, 2009; accepted May 15, 2009; published online June 1, 2009 Cytochrome P450 (CYP) 3A enzymes are responsible for the metabolism of many drugs. It is useful to know CYP3A activity in individual patients undergoing drug therapy so as to predict the efficacies or adverse events. Lansoprazole is metabolized to Lansoprazole sulfone (LS) by CYP3A, while to 5-hydroxylansoprasole by CYP2C19. The aim of this study was to evaluate whether lansoprazole can be used to assess CYP 3A activity in human liver. Lansoprazole sulfoxidation activity in 14 human liver microsomes was det...

SARS-CoV-2 Omicron variants are highly resistant to vaccine-induced immunity and human monoclonal antibodies. Here, we demonstrate that a novel nanobody TP86 potently neutralized both BA.1 and BA.2 Omicron variants, and that the TP17 and TP86 nanobody cocktail broadly neutralized in vitro all VOCs as well as D614G. Furthermore, this cocktail showed therapeutic efficacy in vivo on VOCs using human ACE2 transgenic mice.