Biology subjects

White, A. C.

Publications and source records attributed to White, A. C..

7 recordsLinked to original sources

bioRxiv2025

The gut microbiome promotes detoxification responses to an environmental toxicant

At the host-environment interface, the indigenous microbiome is poised to facilitate interactions with exogenous components. Here, we show that the microbiome is necessary for metabolic and transcriptional detoxification responses to the neurotoxic pyrethroid insecticide, deltamethrin. While oral deltamethrin exposure shapes gut microbiome composition, it is not directly microbially metabolized. Instead, we observe microbiome-dependence on host hepatic and intestinal detoxification responses, with diminished activity in germ-free mice. Colonization with a complex microbiome in adulthood maintained limited hepatic responses, suggesting developmental contributions. However, mono-colonization with specific microbes increased colonic expression of a key detoxification enzyme, revealing a protective role for active microbial signaling in the colon. Overall, our data demonstrate that the microbiome is necessary to prime and activate a host response against a model environmental toxicant. Through both developmental and active signaling across organ compartments, these data support that the microbiome may contribute to risk and outcomes of toxicant-associated disease. HighlightsO_LIThe gut microbiome mediates the host response to environmental toxicants. C_LIO_LIKey xenobiotic metabolism genes are modulated by the microbiome C_LIO_LIEarly life signaling is necessary to promote hepatic responsiveness to toxicants in adulthood. C_LIO_LISpecific and active microbial signaling promotes colonic detoxification gene expression. C_LI

pharmacology and toxicology↗

bioRxiv2024

The pyrethroid insecticide deltamethrin disrupts neuropeptide and monoamine signaling pathways in the gastrointestinal tract

Enteroendocrine cells (EECs) are a rare cell type of the intestinal epithelium. Various subtypes of EECs produce distinct repertoires of monoamines and neuropeptides which modulate intestinal motility and other physiologies. EECs also possess neuron-like properties, suggesting a potential vulnerability to ingested environmental neurotoxicants. One such group of toxicants are pyrethroids, a class of prevalent insecticides used residentially and agriculturally. Pyrethroids agonize voltage-gated sodium channels (VGSCs), inducing neuronal excitotoxicity, and affect the function of monoamine-producing neurons. Given their anatomical location at the interface with the environment and their expression of VGSCs, EECs likely represent a vulnerable cell-type to oral pyrethroid exposure. In this study, we used the EEC cell line, STC-1 cells, to evaluate the effects of the common pyrethroid deltamethrin on the functional status of EECs. We find that deltamethrin impacts both expression of serotonergic pathways and inhibits the adrenergic-evoked release of an EEC hormone, GLP-1, in vitro. In a mouse model of oral exposure, we found that deltamethrin induced an acute, yet transient, loss of intestinal motility, in both fed and fasted conditions. This constipation phenotype was accompanied by a significant decrease in peripheral serotonin production and an inhibition of nutrient-evoked intestinal hormone release. Together, these data demonstrate that deltamethrin alters monoaminergic signaling pathways in EECs and regulates intestinal motility. This work demonstrates a mechanistic link between pyrethroid exposure and intestinal impacts relevant to pyrethroid-associated diseases, including inflammatory bowel disease, neurodegenerative disease, and metabolic disorders.

pharmacology and toxicology↗

bioRxiv2023

Molecular heterogeneity of quiescent melanocyte stem cells revealed by single-cell RNA-sequencing.

Melanocyte stem cells (McSCs) of the hair follicle are a rare cell population within the skin and are notably underrepresented in whole-skin, single-cell RNA sequencing (scRNA-seq) datasets. Using a cell enrichment strategy to isolate KIT+/CD45-cells from the telogen skin of adult female C57BL/6J mice, we evaluated the transcriptional landscape of quiescent McSCs (qMcSCs) at high resolution. Through this evaluation, we confirmed existing molecular signatures for qMcCS subpopulations (e.g., Kit+, Cd34+/-, Plp1+, Cd274+/-, Thy1+, Cdh3+/-) and identified novel qMcSC subpopulations, including two that differentially regulate their immune privilege status. Within qMcSC subpopulations, we also predicted melanocyte differentiation potential, neural crest potential, and quiescence depth. Taken together, the results demonstrate that the qMcSC population is heterogenous and future studies focused on investigating changes in qMcSCs should consider changes in subpopulation composition. SignificanceSingle cell transcriptomics has revolutionized our ability to interrogate the dynamic nature of tissues. Here we provide a high-resolution map of the melanocyte stem cell population during quiescence. This map provides one of few examples highlighting broad heterogeneity in stem cells during the quiescent cell state. The map also unifies previous observations using other cell, molecular and functional analyses to define the unique features of the quiescent melanocyte stem cell population. This data provides a valuable resource to individuals interested in further evaluating aspects of cellular quiescence in stem cells broadly or melanocyte stem cells specifically.

cell biology↗

bioRxiv2023

Sexual dimorphism in melanocyte stem cell behavior reveals combinational therapeutic strategies for cutaneous repigmentation

Vitiligo is an autoimmune skin disease caused by cutaneous melanocyte loss. Although phototherapy and T cell suppression therapy have been widely used to induce epidermal re-pigmentation, full pigmentation recovery is rarely achieved due to our poor understanding of the cellular and molecular mechanisms governing this process. Here, we identify unique melanocyte stem cell (McSC) epidermal migration rates between male and female mice, which is due to sexually dimorphic cutaneous inflammatory responses generated by ultra-violet B exposure. Using genetically engineered mouse models, and unbiased bulk and single-cell mRNA sequencing approaches, we determine that manipulating the inflammatory response through cyclooxygenase and its downstream prostaglandin product regulates McSC proliferation and epidermal migration in response to UVB exposure. Furthermore, we demonstrate that a combinational therapy that manipulates both macrophages and T cells (or innate and adaptive immunity) significantly promotes epidermal melanocyte re-population. With these findings, we propose a novel therapeutic strategy for repigmentation in patients with depigmentation conditions such as vitiligo.

cell biology↗

bioRxiv2022

RNA-based therapy for Cryptosporidium parvum infection: proof-of-concept studies

Cryptosporidium is a leading cause of moderate-to-severe diarrhea in children. Nitazoxanide, the only FDA-approved treatment for cryptosporidiosis, has limited efficacy in those at highest risk for sequelae. RNA-argonaute (Ago) complexes to Cryptosporidium nucleoside diphosphate kinase (cpNDK) decreased the Cryptosporidium parvum mRNA by 95% in infected cells in vitro. Treatment of mice by oral gavage with ssRNA/Ago complexes encapsulated in lipid nanoparticles led to delivery of the complexes into intestinal epithelial cells. Treatment of C. parvum infected mice with ssRNA/Ago complexes targeting cpNDK led to the resolution of oocyst shedding in 4/5 SCID/beige mice. These results confirm the potential use of antisense therapy as an alternative approach to cryptosporidiosis treatment.

microbiology↗

bioRxiv2020

PLEKHA4 Promotes Wnt/β-catenin Signaling-Mediated G1/S Transition and Proliferation in Melanoma

Melanoma patients incur substantial mortality, despite promising recent advances in targeted therapies and immunotherapies. In particular, inhibitors targeting BRAF-mutant melanoma can lead to resistance, and no targeted therapies exist for NRAS-mutant melanoma, motivating the search for additional therapeutic targets and vulnerable pathways. Here, we identify a regulator of Wnt/{beta}-catenin signaling, PLEKHA4, as a factor required for melanoma proliferation and survival. PLEKHA4 knockdown in vitro leads to lower Dishevelled levels, attenuated Wnt/{beta}-catenin signaling, and a block of progression through the G1/S cell cycle transition. In mouse xenograft models, inducible PLEKHA4 knockdown attenuated tumor growth in BRAF- and NRAS-mutant melanomas and synergized with the clinically used inhibitor encorafenib in a BRAF-mutant model. As an E3 ubiquitin ligase regulator with both lipid and protein binding partners, PLEKHA4 presents several opportunities for targeting with small molecules. Our work identifies PLEKHA4 as a promising drug target for melanoma and clarifies a controversial role for Wnt/{beta}-catenin signaling in the control of melanoma proliferation.

cancer biology↗

bioRxiv2019

Gene silencing in Cryptosporidium: A rapid approach to identify novel targets for drugdevelopment

BackgroundCryptosporidiosis is a major cause of diarrheal disease. However, the only drug approved for cryptosporidiosis does not work well in high risk populations. Therefore, novel drugs are urgently needed. Then, the identification of novel is necessary to develop new therapies against this parasite. Recently, we have developed a rapid method to block gene expression in Cryptosporidium by using pre-assembled complexes of Cryptosporidium antisense RNA and human protein with slicer activity (Argonaute 2). We hypothesized that structural proteins, proteases, enzymes nucleotide synthesis and transcription factors are essential for parasite development, thus in this work we knock down expression of 4 selected genes: Actin, Apicomplexan DNA-binding protein (AP2), Rhomboid protein 1 (Rom 1) and nucleoside diphosphate kinase (NDK) and elucidated its role during invasion, proliferation and egress of Cryptosporidium.\n\nMethodsWe used protein transfection reagents (PTR) to introduce pre-assembled complexes of antisense RNA and human Argonaute 2 into Cryptosporidium parvum oocysts, the complexes blocked expression of Actin (Act), Transcription factor AP2 (AP2), nucleoside diphosphate kinase (DKN), and rhomboid protein 1 (Rom1). After gene silencing, we evaluated parasite reduction using In vitro models of excystation, invasion, proliferation and egress. We evaluated the potency of ellagic acid, a nucleoside diphosphate kinase inhibitor for anti-cryptosporidial activity using a model of in vitro infection with human HCT-8 cells.\n\nResultsSilencing of Act, AP2, NDK and Rom1 reduce significantly invasion, proliferation and egress of Cryptosporidium. We showed that silencing of NDK markedly inhibited Cryptosporidium proliferation. This was confirmed by demonstration that ellagic acid reduced the number of parasites at micro molar concentrations (EC 50 =15-30 {micro}M) without showing any toxic effect on human cells.\n\nConclusionsOverall the results confirmed the usefulness RNA silencing can be used to identify novel targets for drug development against Cryptosporidium. We identified ellagic acid (EA), a nucleoside diphosphate kinase inhibitor also blocks Cryptosporidium proliferation. Since EA is a dietary supplement approved for human use, then this compound should be studied as a potential treatment for cryptosporidiosis.\n\nAuthor summaryThe World Health Organization reports diarrhea kills around 760,000 children under five every year. Cryptosporidium infection is a leading cause of diarrhea morbidity and mortality. Current therapies to treat this infection are suboptimal, therefore novel treatments are urgently needed. We used genetic tools to identify novel targets for drug development, thus in this work we evaluated the role of 4 genes during Cryptosporidium infection. We demonstrated that silencing of nucleoside-diphosphate kinase (NDK) drastically reduced invasion, proliferation and egress of this parasite. To validate these finding we used the Ellagic acid (EA) an inhibitor of NDK to treat infected intestinal cells. Our results confirmed that the EA blocks parasite proliferation on infected cells. Interestingly we observed that the ellagic acid also has anti cryptosporidial activity by inducing apoptosis. Since EA is a dietary supplement already approved for human use, then this compound has potential to be used as a rapid alternative to treat Cryptosporidiosis.

microbiology↗