Phenoxazine derivatives 2-amino-4,4alpha-dihydro-4alpha-phenoxazine-3-one and 2-aminophenoxazine-3-one-induced apoptosis through a caspase-independent mechanism in human neuroblastoma cell line NB-1 cells

Targeting Lysosomes in Colorectal Cancer: Exploring the Anticancer Activity of a New Benzo[a]phenoxazine Derivative

Colorectal cancer (CRC) has been ranked as one of the cancer types with a higher incidence and one of the most mortal. There are limited therapies available for CRC, which urges the finding of intracellular targets and the discovery of new drugs for innovative therapeutic approaches. In addition to the limited number of effective anticancer agents approved for use in humans, CRC resistance and secondary effects stemming from classical chemotherapy remain a major clinical problem, reinforcing the need for the development of novel drugs. In the recent years, the phenoxazines derivatives, Nile Blue analogues, have been shown to possess anticancer activity, which has created interest in exploring the potential of these compounds as anticancer drugs. In this context, we have synthetized and evaluated the anticancer activity of different benzo[a]phenoxazine derivatives for CRC therapy. Our results revealed that one particular compound, BaP1, displayed promising anticancer activity against CRC cells. We found that BaP1 is selective for CRC cells and reduces cell proliferation, cell survival, and cell migration. We observed that the compound is associated with reactive oxygen species (ROS) generation, accumulates in the lysosomes, and leads to lysosomal membrane permeabilization, cytosolic acidification, and apoptotic cell death. In vivo results using a chicken embryo choriollantoic membrane (CAM) assay showed that BaP1 inhibits tumor growth, angiogenesis, and tumor proliferation. These observations highlight that BaP1 as a very interesting agent to disturb and counteract the important roles of lysosomes in cancer and suggests BaP1 as a promising candidate to be exploited as new anticancer lysosomal-targeted agent, which uses lysosome membrane permeabilization (LMP) as a therapeutic approach in CRC.

Novel Nile Blue Analogue Stains Yeast Vacuolar Membrane, Endoplasmic Reticulum, and Lipid Droplets, Inducing Cell Death through Vacuole Membrane Permeabilization

Phenoxazine derivatives such as Nile Blue analogues are assumed to be increasingly relevant in cell biology due to their fluorescence staining capabilities and antifungal and anticancer activities. However, the mechanisms underlying their effects remain poorly elucidated. Using S. cerevisiae as a eukaryotic model, we found that BaP1, a novel 5- and 9-N-substituted benzo[a]phenoxazine synthesized in our laboratory, when used in low concentrations, accumulates and stains the vacuolar membrane and the endoplasmic reticulum. In contrast, at higher concentrations, BaP1 stains lipid droplets and induces a regulated cell death process mediated by vacuolar membrane permeabilization. BaP1 also induced mitochondrial fragmentation and depolarization but did not lead to ROS accumulation, changes in intracellular Ca²⁺, or loss of plasma membrane integrity. Additionally, our results show that the cell death process is dependent on the vacuolar protease Pep4p and that the vacuole permeabilization results in its translocation from the vacuole to the cytosol. In addition, although nucleic acids are commonly described as targets of benzo[a]phenoxazines, we did not find any alterations at the DNA level. Our observations highlight BaP1 as a promising molecule for pharmacological application, using vacuole membrane permeabilization as a targeted approach.

Pharmacological Activities of Aminophenoxazinones

Aminophenoxazinones are degradation products resulting from the metabolism of different plant species, which comprise a family of natural products well known for their pharmacological activities. This review provides an overview of the pharmacological properties and applications proved by these compounds and their structural derivatives during 2000-2021. The bibliography was selected according to our purpose from the references obtained in a SciFinder database search for the Phx-3 structure (the base molecule of the aminophenoxazinones). Compounds Phx-1 and Phx-3 are among the most studied, especially as anticancer drugs for the treatment of gastric and colon cancer, glioblastoma and melanoma, among others types of relevant cancers. The main information available in the literature about their mechanisms is also described. Similarly, antibacterial, antifungal, antiviral and antiparasitic activities are presented, including species related directly or indirectly to significant diseases. Therefore, we present diverse compounds based on aminophenoxazinones with high potential as drugs, considering their levels of activity and few adverse effects.

The crystal structure of 10-(3,5-di(pyridin-4-yl)phenyl)-10H-phenoxazine dihydrate, C28H23N3O3

C28H23N3O3, orthorhombic, Pna21 (no. 33), a = 29.0466(11) Å, b = 5.2448(3) Å, c = 14.4825(7) Å, V = 2206.32(19) Å3, Z = 4, R gt (F) = 0.0511, wR ref (F 2) = 0.1341, T = 100.00(10) K.

IMMUNEPOTENT CRP induces cell cycle arrest and caspase-independent regulated cell death in HeLa cells through reactive oxygen species production

BACKGROUND

Regulated cell death (RCD) is a mechanism by which the cell activates its own machinery to self-destruct. RCD is important for the maintenance of tissue homeostasis and its deregulation is involved in diseases such as cervical cancer. IMMUNEPOTENT CRP (I-CRP) is a dialyzable bovine leukocyte extract that contains transfer factors and acts as an immunomodulator, and can be cytotoxic to cancer cell lines and reduce tumor burden in vivo. Although I-CRP has shown to improve or modulate immune response in inflammation, infectious diseases and cancer, its widespread use has been limited by the absence of conclusive data on the molecular mechanism of its action.

METHODS

In this study we analyzed the mechanism by which I-CRP induces cytotoxicity in HeLa cells. We assessed cell viability, cell death, cell cycle, nuclear morphology and DNA integrity, caspase dependence and activity, mitochondrial membrane potential, and reactive oxygen species production.

RESULTS

I-CRP diminishes cell viability in HeLa cells through a RCD pathway and induces cell cycle arrest in the G2/M phase. We show that the I-CRP induces caspase activation but cell death induction is independent of caspases, as observed by the use of a pan-caspase inhibitor, which blocked caspase activity but not cell death. Moreover, we show that I-CRP induces DNA alterations, loss of mitochondrial membrane potential, and production of reactive-oxygen species. Finally, pretreatment with N-acetyl-L-cysteine (NAC), a ROS scavenger, prevented both ROS generation and cell death induced by I-CRP.

CONCLUSIONS

Our data indicate that I-CRP treatment induced cell cycle arrest in G2/M phase, mitochondrial damage, and ROS-mediated caspase-independent cell death in HeLa cells. This work opens the way to the elucidation of a more detailed cell death pathway that could potentially work in conjunction with caspase-dependent cell death induced by classical chemotherapies.

Benzo[α]phenoxazines and benzo[α]phenothiazine from vitamin K3: synthesis, molecular structures, DFT studies and cytotoxic activity

Novel benzo[α]phenoxazines and benzo[α]phenothiazine from vitamin K3 are cytotoxic against HeLa, MCF-7 cell lines and potential topoisomerase II inhibitors.

Anticancer effects of phenoxazine derivatives revealed by inhibition of cell growth and viability, disregulation of cell cycle, and apoptosis induction in HTLV-1-positive leukemia cells

Adult T-cell leukemia (ATL) is a malignant tumor of human CD4(+) T cells infected with a human retrovirus, T lymphotropic virus type-1 (HTLV-1). The aim of the present study was to investigate the apoptotic effects of phenoxazines, 2-amino-4,4alpha-dihydro-4alpha,7-dimethyl-3H-phenoxazine-3-one (Phx-1), 3-amino-1,4alpha-dihydro-4alpha,8-dimethyl-2H-phenoxazine-2-one (Phx-2), and 2-aminophenoxazine-3-one (Phx-3) on a T cell leukemia cell line from ATL patients, MT-1 cells; HTLV-1 transformed T-cell lines, HUT-102 cells and MT-2 cells; and an HTLV-1-negative rat sarcoma cell line, XC cells. Among these phenoxazines, Phx-3 at concentrations of less than 10 microg/ml extensively inhibited growth and cell viability; arrested cell cycles at sub G(0)/G(1) phase; and augmented apoptosis of MT-1, HUT-102, and MT-2 cells. However, these phenoxazines did not affect the cell viability of an HTLV-1-negative rat sarcoma cell line, XC cells, and phytohemaggutinin-activated human peripheral blood mononuclear cells, although they markedly inhibited the growth of these cells. The transmission of HTLV-1 from HTLV-1-positive cells (MT-2 cells) to HTLV-1-negative cells (XC cells) was considered to be prevented by Phx-1, Phx-2, or Phx-3 because the syncytium formation between these cells was inhibited markedly in the presence of these phenoxazines. The present results suggest that Phx-1, Phx-2, and, in particular, Phx-3 may be useful as therapeutic agents against ATL, which is extremely refractory to current therapies.

Apoptosis induced by acrylamide is suppressed in a 21.5% fat diet through caspase-3-independent pathway in mice testis

This study investigates the simultaneous effect of acrylamide (ACR) and high-fat-intake on the apoptosis in testis cells, and also the expression and activity of caspase-3. Seventy-two male Kunming mice were divided into two blocks and fed with a high-fat diet (crude fat 21.5%) or basic diet (crude fat 4.4%), respectively; and animals in each diet block were exposed to ACR at the dose of 20 mg/kgbw x d or 40 mg/kgbw x d as ACR treated groups or the normal saline as control. Germ cells prepared from testis were stained with Hoechst dye 33258 and paraffin wax sections from testis were suffered to a TUNEL process. Expression of caspase-3 on protein level was investigated using an immunohistochemical analysis assay. The supernatant of unilateral testes were subjected to a Caspase-3 activity kit to determine the activity of Caspase-3 in testis. The concentration of ACR and glycidamide(GA), epoxide of ACR, in plasma and testis were detected by LC-ES/MS/MS analysis. Results based on the morphological changes, percentage of apoptotic cells, and integrated optical density (IOD) of positive amethyst staining which indicates the apoptotic DNA fragmentation, show that apoptosis was induced by acrylamide only; however, acrylamide-induced apoptosis was weakened by high-fat-intake. The protein expression and activity of Caspase-3 were not induced by ACR or high-fat-intake. Moreover, no significant differences of ACR and GA concentration were found between the high-fat and basic diet groups after exposure of ACR. Results indicate that high-fat-intake reverses the effects on apoptosis induced by ACR; and more possibly, apoptosis is induced by a caspase-3-independent mechanism.

Phenoxazine derivatives inactivate human cytomegalovirus, herpes simplex virus-1, and herpes simplex virus-2 in vitro

We examined whether phenoxazine derivatives, 2-amino-4,4alpha-dihydro-4alpha-7-dimethyl-3H-phenoxazine-3-one (Phx-1), 3-amino-1,4alpha-dihydro-4alpha-8-dimethyl-2H-phenoxazine-2-one (Phx-2), and 2-amino-phenoxazine-3-one (Phx-3) may have antiviral activity against herpes family viruses: human cytomegalovirus (HCMV), herpes simplex virus type 1 (HSV-1), and herpes simplex virus type 2 (HSV-2). The antiviral activity was evaluated by the selectivity index (SI), which is the ratio of 50% cytotoxic concentration (CC(50)) and 50% antiviral concentration (IC(50)). Among these phenoxazines, Phx-2 exerted strong antiviral activity to HCMV with the SI of 200, while Phx-1 and Phx-3 exerted no marked anti-HCMV activity. Phx-2 also showed moderate inhibition of HSV-1 and HSV-2, with the SI of 6.7 and 17, respectively. In the time-of-addition experiments, inhibitory effect of Phx-2 against HCMV was active even when applied to cells at 100 h after HCMV infection, while ganciclovir (GCV) showed potent inhibition when applied to cells before 42-h post-infection, but its inhibitory effects disappeared thereafter. Attachment and penetration of HCMV was not affected by the presence of Phx-2. When HCMV was pretreated with Phx-2, concentration-dependent virucidal action was observed, suggesting that Phx-2 inactivates HCMV directly. From these data, it was found that Phx-2 might have a different anti-HCMV target from GCV.

Apoptosis induction preceded by mitochondrial depolarization in multiple myeloma cell line U266 by 2-aminophenoxazine-3-one

The aim of the present study was to investigate the mechanism of apoptosis in human multiple myeloma cell line, U266, caused by 2-aminophenoxazine-3-one (Phx-3). Flow-cytometrical and morphological analyses showed that Phx-3 increased the population of annexin V-positive cells including early stage apoptotic cells and late stage apoptotic cells and induced DNA fragmentation or apoptotic body formation in U266 cells, indicating that Phx-3 induced the apoptosis of U266 cells. Activity of caspase-3 was extensively increased in U266 cells treated with Phx-3 time-dependently within 24 h, but this Phx-3-stimulated activity of the enzyme in the cells was completely cancelled by the addition of N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (z-VAD-fmk), a pan-caspase inhibitor. The addition of z-VAD-fmk almost blocked the apoptotic effect of Phx-3 against U266 cells, indicating that Phx-3-induced apoptosis of U266 cells was dependent on a caspase signaling pathway. Moreover, the apoptosis of U266 cells occurred after the induction of cell cycle arrest of the cells in the S and G(2)/M phase, the loss of mitochondrial membrane potential, and activation of caspase-3 reached maximum, which were caused by Phx-3 within 24 h. These results support the views that the apoptosis of U266 cells caused by Phx-3 may be preceded by the cell cycle arrest, depolarization of mitochondria and activation of caspase-3. These results support the view that Phx-3 may be utilized in future as chemotherapeutic agent against multiple myeloma which is extremely refractory to chemotherapy.

Protonated nitro group as a gas-phase electrophile: experimental and theoretical study of the cyclization of o-nitrodiphenyl ethers, amines, and sulfides

A novel gas-phase electrophilic cyclization, initiated by the protonation of a nitro group, occurs for 2-nitrophenyl phenyl ether and for the analogous sulfide and amine, leading to heterocyclic intermediates in each case. Subsequently, the cyclic intermediates dissociate via two pathways: (1) unusual step-wise eliminations of two OH radicals to afford heterocyclic cations, [phenoxazine - H](+), [phenothiazine - H](+), and [phenazine + H](+), and (2) expulsion of H(2)O, to yield a heterocyclic ketone, followed by loss of CO. The proposed structures of the gas-phase product ions and reaction mechanisms are supported by chemical substitution, deuterium labeling, accurate mass measurements at high mass resolving power, product-ion mass spectra obtained by tandem mass spectrometry, mass spectra of reference compounds, and molecular orbital calculations. Using a mass spectrometer as a reaction vessel, we demonstrate that, upon protonation, a nitro group becomes an electrophile and participates in cyclization reactions in the gas phase.