2-amino-phenoxazine-3-one attenuates glucose-induced augmentation of embryonic form of myosin heavy chain, endothelin-1 and plasminogen activator inhibitor-1 in human umbilical vein endothelial cells

Prevention of carcinogenesis and development of gastric and colon cancers by 2-aminophenoxazine-3-one (Phx-3): direct and indirect anti-cancer activity of Phx-3

2-Aminophenoxazine-3-one (Phx-3), an oxidative phenoxazine, exerts strong anticancer effects on various cancer cell lines originating from different organs, in vitro. This article reviews new aspects for the prevention of carcinogenesis and development of gastric and colon cancers by Phx-3, based on the strong anticancer effects of Phx-3 on gastric and colon cancer cell lines (direct anticancer effects of Phx-3 for preventing development of cancer), the bacteriocidal effects of Phx-3 against Helicobacter pylori associated with carcinogenesis of gastric cancer (indirect anticancer effects for preventing carcinogenesis of gastric cancer), and the proapoptotic activity of Phx-3 against human neutrophils involved in the incidence of ulcerative colitis associated with a high colon cancer risk (indirect anticancer effects for preventing carcinogenesis of colon cancer).

2-Aminophenoxazine-3-one and 2-amino-4,4α-dihydro-4α,7-dimethyl-3H-phenoxazine-3-one cause cellular apoptosis by reducing higher intracellular pH in cancer cells

We examined intracellular pH (pHi) of ten cancer cell lines derived from different organs and two normal cell lines including human embryonic lung fibroblast cells (HEL) and human umbilical vein endothelial cells (HUVEC) in vitro, and found that pHi of most of these cancer cells was evidently higher (pH 7.5 to 7.7) than that of normal cells (7.32 and 7.44 for HEL and HUVEC, respectively) and that of primary leukemic cells and erythrocytes hitherto reported (≤7.2). Higher pHi in these cancer cells could be related to the Warburg effect in cancer cells with enhanced glycolytic metabolism. Since reversal of the Warburg effect may perturb intracellular homeostasis in cancer cells, we looked for compounds that cause extensive reduction of pHi, a major regulator of the glycolytic pathway and its associated metabolic pathway. We found that phenoxazine compounds, 2-aminophenoxazine-3-one (Phx-3) and 2-amino-4,4α-dihydro-4α,7-dimethyl-3H-phenoxazine-3-one (Phx-1) caused a rapid and drastic dose-dependent decrease of pHi in ten different cancer cells within 30 min, though the extent of the decrease of pHi was significantly larger for Phx-3 (ΔpHi = 0.6 pH units or more for 100 µM Phx-3) than for Phx-1 (ΔpHi = 0.1 pH units or more for 100 µM Phx-1). This rapid and drastic decrease of pHi in a variety of cancer cells caused by Phx-3 and Phx-1 possibly perturbed their intracellular homeostasis, and extensively affected the subsequent cell death, because these phenoxazines exerted dose-dependent proapoptotic and cytotoxic effects on these cells during 72 h incubation, confirming a causal relationship between ΔpHi and cytotoxic effects due to Phx-3 and Phx-1. Phx-3 and Phx-1 also reduced pHi of normal cells including HEL and HUVEC, although they exerted less proapoptotic and cytotoxic effects on these cells than on cancer cells. Drugs such as Phx-3 and Phx-1 that reduce pHi and thereby induce cellular apoptosis might serve as benevolent anticancer drugs.

Structure and antibacterial activity of the silver(I) complex of 2-aminophenoxazine-3-one

The crystal structure and antibacterial activity of the first metal complex of 2-aminophenoxazine-3-one is reported. We describe the silver(i) complex of this important biological molecule and show that the binding mode is through the phenoxazine ring nitrogen. A new synthetic route to 2-aminophenoxazine-3-one is also reported.

Inhibition of monocyte chemoattractant protein-1 by Krüppel-like factor 5 small interfering RNA in the tumor necrosis factor- alpha-activated human umbilical vein endothelial cells

Krüppel-like factor 5 (KLF5) is one of the pivotal transcriptional factors communicating with inflammatory cytokines. Regulation of monocyte chemoattractant protein-1 (MCP-1) is a target to prevent from inflammation and atherogenic changes in patient with diabetes mellitus. This study was made to determine whether KLF5 may associate with MCP-1 expression in human umbilical vein endothelial cells (HUVECs) induced by tumor necrosis factor-alpha (TNF-alpha), in terms of the initial events of damaged vascular cells in diabetes. MCP-1 expression was markedly augmented by the treatment of TNF-alpha to HUVECs, but this augmentation was inhibited by KLF5 small interfering RNA, which primarily suppressed the expression of KLF5 at mRNA levels in the cells. Though TNF-alpha augmented the levels of endothelin-1 (ET-1) and attenuated those of embryonic form of myosin heavy chain (SMemb) in HUVECs, the inhibition of KLF5 did not affect the levels of these cytokines in the cells. These results suggested that in HUVECs, KLF5 is playing a critical role in regulating the expression of MCP-1, which has been considered to be involved in the diabetic atherogenic events.

2-aminophenoxazine-3-one suppresses the growth of mouse malignant melanoma B16 cells transplanted into C57BL/6Cr Slc mice

Since phenoxazine is an essential structure of actinomycin D, which exerts a strong anticancer effect, we examined the anticancer effect of 2-aminophenoxazine-3-one (Phx-3) on mouse malignant melanoma B16 cells in vitro and in vivo. Phx-3 inhibited proliferation of the B16 cells in a dose-dependent manner in vitro. We furthermore studied the in vivo effects of Phx-3 on mouse malignant melanoma B16 cells transplanted in female C57BL/6Cr Slc mice. Treatment with Phx-3 (0.5 mg/kg) completely suppressed the growth of mouse malignant melanoma B16 cells transplanted in mice as compared with the control group. Phx-3 was found to exert few adverse effects, in terms of bodyweight loss, changes in serum levels of blood biochemical parameters such as aspartate transaminase (AST), alanine transaminase (ALT), blood urea nitrogen (BUN) and creatinine, dysfunction of the liver and the kidney examined by pathological methods, piloerection and wasting, when mice were treated with a dose of 0.5 mg/kg. These results suggest that Phx-3 may be used to treat patients affected by malignant melanoma in future.