Phthalates have been used in a wide variety of consumer goods. Their versatility as plasticizers has translated into worldwide use in a vast array of consumer products. These compounds can leach into matrices, such as food and liquids that can be routed for human exposure. One of the most used phthalates is Diethylhexyl phthalate (DEHP). Diethylhexyl phthalate and its metabolite 2-ethyl-1-hexanol (2-EH) have demonstrated biological effects which merit further evaluation. In this work, we expand on our previous work with DEHP and screen the 2-EH metabolite for different cell death endpoints such as growth inhibition, apoptosis, autophagy, caspase activation, DNA fragmentation, and cell cycle arrest using fluorophores and the NC3000 instrument. Significant results (p < 0.05) revealed higher toxicity for the 2-EH metabolite when compared to DEHP. Also, 2-EH presented apoptosis induction with characteristic hallmarks, such as loss of mitochondrial membrane potential, caspase activation, DNA fragmentation and cell cycle arrest at the S phase. In addition, the presence of autophagosome was detected through L3CB protein staining. We conclude that 2-EH presents differences in cell death endpoints that interestingly differ from the DEHP parent compound. Further studies are needed to establish the molecular pathways responsible for the observed effects.

Human and ecological exposure to chemical contaminants continue to increase given anthropogenic activities and sources. Phthalates are among the most persistent toxic chemicals found in aquatic systems. Phthalates belong to a family of chemical compounds that are heavily used in global manufacturing, distinguished for being able to provide durability and elasticity to plastic products, with poor water solubility and low evaporation. In terms of health impact, these compounds have been shown to breach the placental barrier having effect on human development and neurodegeneration. The main purpose of our study has been to assess the neurotoxicity of phthalates implementing the zebrafish (Danio rerio) model to determine the cell death induction of DEHP on brain cells. For many years, the zebrafish embryonic model has been used to study vertebrate development. Our study, in contrast, used adult zebrafish to resemble mature species that can be continuously exposed to low concentrations of DEHP. To assess the neurotoxicity, brain tissue from zebrafish was extracted via dissection, and primary neural cells dissociated to obtain primary cell subcultures. The neural cells where subsequently exposed to DEHP (Di-ethylhexyl phthalate) at concentrations from 10µM to 100µM for 48 hours to observe cell growth inhibition (GI50). The results indicate neural cell death at a GI50 of 62.9 µM. Apoptosis induction, caspase activation, mitochondrial membrane damage as well as autophagy cell death were analyzed to identify DEHP cell death mechanism at the GI50 concentration. In conclusion, this study clearly demonstrated that DEHP can induce apoptosis cell death on zebrafish neural brain cells in culture through the activation of an intrinsic apoptotic pathways with caspases 3 and 7 activation as well as autophagic pathway and mitochondrial damage. The presence of phthalates as well as other chemical contaminants on aquatic environments needs to be earnestly controlled in order to reduce neurotoxicity to aquatic species as well as human.

The proposed project aims to test the applicability of a novel set of patented organic compounds as markers of hypoxic circulating tumor cells (H-CTC) with potential pre-clinical relevance. Circulating tumor cells (CTC) are individual cells or clusters that can move from tumors to circulation invading other tissues. Often cells in the tumor need to adapt to low oxygen levels, generating a population of cells known as hypoxic cells that can survive low oxygen levels. These hypoxic cells can produce more cell junction proteins, augmenting connections between cells causing them to break away in clusters rather than individually. Clustered CTCs are much more efficient at metastasis formation. Release of CTC can also be stimulated by cancer treatments such as radiation and chemotherapy. To date, our research has generated in-vitro studies with a set of 3-nitrobenzazolo[3,2- a]quinolinium chloride salts (NBQS) demonstrating its capacity as markers of hypoxic human cancer cells in vitro. Comparison with the control Pimonidazole demonstrated the advantages of novel NBQ-TOM compounds as hypoxic marker. We here, aim to test the applicability of NBQS to identify hypoxic cells among circulating tumor cells (H-CTC). To date limited commercially CTC detection methods are available. Our application can be described as pre-clinical detection technology of hypoxic cancer cells serving also in cancer management. To determine the capacity of novel compound, NBQ-345 TOM as hypoxic fluorescent marker, colon tumor cells (COLO 205) are culture under hypoxic and aerobic environment and treated with NBQ-345TOM (25uM) for 24 hours. After treatment fluorescence is measured with an OPTIMA BMG Fluorimeter. Fluorescence emission results demonstrated significant formation of the NBQ-234 TOM fluorescent metabolite on hypoxic tumor cells in contrast to cells treated under aerobic environment. Also, fluorescence microscopy analysis of colon cancer cells treated for 24 hours with NBQ-345 TOM at hypoxic and aerobic conditions confirmed the stronger fluorescence generation at hypoxic conditions in contrast to cells at aerobic conditions. Citation Format: Beatriz Zayas, Karoline Rios, Luis Ortiz, Osvaldo Cox. Markers of hypoxic cells: Testing a pre-clinical detection assay. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5602.

Objectives:The present study evaluates novel cationic quinoline derivatives known as benzimidazo[3,2-a]quinolinium salts (BQS) named NBQ-48 and ABQ-48 that have structural similarities to known anti-cancer substances such as ellipticine and berberine.Methods:Toledo human lymphoma (ATCC CRL2631) cells were treated for 24 to 48 hours. Apoptosis related endpoints such as cell cycle arrest, mitochondrial damage, RNS and ROS generation and the activity of several apoptosis related proteins such as caspases and apoptosis inducing factor (AIF) were studied using fluorescence staining and western blot respectively.Results:Results indicated a higher toxicity from the amino substituted ABQ-48 versus the NBQ-48 (GI50’s of 50uM versus 100uM respectively). Both compounds induced cell death through various apoptosis related endpoints including a decrease in mitochondrial membrane potential with an increase in ROS and activation of the effector caspase 3. Interestingly, AIF release was observed on cells treated with the amino substituted ABQ-48 but not on the nitro substituted NBQ-48 samples suggesting a caspase independent mechanism for ABQ-48.Conclusions:The results obtained presents the toxic effects of two novel benzimidazo[3,2-a]quinolinium salts in human lymphoma tumor cells. The identified mechanism of action includes multiple apoptosis related effects. Furthermore the data presents a clear variation in caspase dependent or independent mechanism for each compound.