Mercury, in both its elemental and bonded states, is noted for its negative effects on biological organisms. Recent anthropogenic and environmental disasters have spurred numerous comparative studies. These studies attempted to detail the biochemical implications of mercury ingestion, in low, persistent concentrations as well as elevated acute dosages. The studies propose models for mercuric action on healthy cells; which is centered on the element's disruption of key enzymatic processes at deposition sites. Mercury's high affinity for the sulfhydryl moieties of enzyme catalytic sites is a common motif for enzyme inactivation. These permanent covalent modifications inactivate the enzyme, thereby inducing devastating effects on an organism's metabolic functions. Mercury has been shown to be highly nonspecific in its binding to sulfhydryl moieties, and highly varied in terms of how it is encountered by living organisms. This review focuses on mercury's effects on a wide swath of enzymes, with emphasis on how these alterations deleteriously affect several metabolic pathways.

Background: Heavy metal contamination presents a constant threat to biological systems. Simultaneously, heavy metals have become one of the major contaminants in the aquatic ecosystems. In this regard, the investigation of heavy metal-tolerance genes in algae is relevant. Chlamydomonas reinhardtii is a unicellular green alga, and an excellent model organism used in heavy metal studies. In C. reinhardtii, a novel gene designated as Cia7, was hypothesized to play a role in heavy metal homeostasis due to CIA7’s conserved cysteine-residue motif. This study compared two strains of C. reinhardtii, cc4425, the wild-type with the functional CIA7 protein and cc5013, the mutant strain with the disrupted cia7- gene. The hypothesis was that the expression of Cia7 contributes to an increased cadmium (Cd)-tolerance in C. reinhardtii. The Cd-tolerance would be described by physiological markers of microalgae health, and by intracellular accumulation of the metal. Methods: The objectives of this study were (1) to compare chlorophyll fluorescence and cell size in cc4425 and cc5013 exposed to Cd2+, and (2) to compare Cd2+ bioaccumulation in cc4425 and cc5013 strains in different growth media. Flow cytometry, and inductively coupled plasma optical emission spectrometry (ICP-OES) analysis were performed. Results: There was no significant statistical difference in Cd2+ bioaccumulation between the two strains, cc4425 and cc5013, regardless of growth media. However, a statistically significant difference in Cd2+ bioaccumulation (p<0.0001) was determined between the media (with acetate and without acetate).  The cia7- mutant, cc5013 was found to be more susceptible to a Cd2+-induced decrease in chlorophyll fluorescence and had a reduced cell size compared to cc4425, the wild-type strain. Conclusions: These observed differences between the strains suggest that CIA7’s biological activity could play a direct or indirect role in increasing Cd tolerance in C. reinhardtii.

Pheochromocytomas and paragangliomas (PPGL) are rare catecholamine-secreting neuroendocrine tumors known for their genetic diversity. They can be categorized in discrete molecular subgroups, including tumors presenting with pseudohypoxia or kinase signaling activation. Metastatic and recurrent PPGLs have few therapeutic options, in part due to the lack of appropriate study models. Here, we report progress on the establishment of viable organoids from n=10 distinct sporadic or familial PPGLs spanning varios genotypes. We also perform detailed histological, molecular, biochemical, and functional characterization. The ten PPGLs were obtained from patients with distinct clinical history and diverse ethnic and genetic backgrounds. We show how we can generate PPGL organoids from fresh and frozen tissue in a format compatible with histologic characterization and high-throughput drug screening (mini-rings, Phan et al, 2019, Al Shihabi et al, 2022). Our mini ring approach uses fewer cells with no need for expansion in vitro, and is amenable to implement automation for facile high-throughput studies. We can quantify PPGL growth in culture using a machine learning-based pipeline (Al Shihabi et al, 2022). All PPGL organoids for which sufficient number of cells could be obtained grew, regardless of the genotype and molecular subtype. PPGL organoids could be cultured short term (6 days) as well as long term (4 weeks). We investigated cellular composition by staining for the neuroendocrine marker chromogranin A, the sustentacular cell marker S100, and the vascular marker CD34. We also analyzed the expression of catecholamines in the cell culture supernatant by LC/MS/MS. We confirmed that secreted catecholamines matched the primary tumor pattern. Lastly, we present the results of pilot drug screening on both short and long term cultures. Drug sensitivity profiles pinpoint tumor-specific responses. In conclusion, we can establish PPGL organoids that largely recapitulate features of the tumor of origin. These models will provide the ability to investigate tumor initiation and progression for various genetic backgrounds and may reveal novel patterns of drug sensitivity and resistance. Citation Format: Maite Calucho, ZiMing Cheng, Huyen Thi-Lam Nguyen, Ahmad Al Shihabi, Hector Gonzalez-Cantu, Qianjin Guo, Maneesha Thaker, Nicole Bechmann, Graeme Eisenhofer, Yanli Ding, Patricia Dahia, Alice Soragni. Establishment and validation of pheochromocytoma organoids for high-throughput drug screening [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 195.

Background: Heavy metal contamination presents a constant threat to biological systems. Simultaneously, heavy metals have become one of the major contaminants in the aquatic ecosystems. In this regard, the investigation of heavy metal-tolerance genes in algae is relevant. Chlamydomonas reinhardtii is a unicellular green alga, and an excellent model organism used in heavy metal studies. In C. reinhardtii, a novel gene designated as Cia7, was hypothesized to play a role in heavy metal homeostasis due to CIA7’s conserved cysteine-residue motif. This study compared two strains of C. reinhardtii, cc4425, the wild-type with the functional CIA7 protein and cc5013, the mutant strain with the disrupted cia7- gene. The hypothesis was that the expression of Cia7 contributes to an increased cadmium (Cd)-tolerance in C. reinhardtii. The Cd-tolerance would be described by physiological markers of microalgae health, and by intracellular accumulation of the metal. Methods: The objectives of this study were (1) to compare chlorophyll fluorescence and cell size in cc4425 and cc5013 exposed to Cd2+, and (2) to compare Cd2+ bioaccumulation in cc4425 and cc5013 strains in different growth media. Flow cytometry, and inductively coupled plasma optical emission spectrometry (ICP-OES) analysis were performed. Results: There was no significant statistical difference in Cd2+ bioaccumulation between the two strains, cc4425 and cc5013, regardless of growth media. However, a statistically significant difference in Cd2+ bioaccumulation (p<0.0001) was determined between the media (with acetate and without acetate).  The cia7- mutant, cc5013 was found to be more susceptible to a Cd2+-induced decrease in chlorophyll fluorescence and had a reduced cell size compared to cc4425, the wild-type strain. Conclusions: These observed differences between the strains suggest that CIA7’s biological activity could play a direct or indirect role in increasing Cd tolerance in C. reinhardtii.