Mechanisms of Modulation of Gut Immunity by Ingested Uranium and Mixed Metal Exposures

BioProject- Gut (BP Gut) focuses on mechanisms of metal-induced immunotoxicity in the gastrointestinal tract
(GIT) of mice and humans in a series of studies using mouse and human cells and tissues. BP Gut is highly
integrated with all SRP METALS environmental and biologic projects, including BP Lung and BP Comm. BP
Gut relies on the work of the CEC and the DMAC. An overall theme of the studies is the understanding of how
metals present in or near mine sites in New Mexico might expose community members leading to
immunotoxicity. We focus on soluble and particulate forms uranium (U), and vanadium (V) given via oral routes
of exposure, because multiple exposures to these types of mixed metals has been observed in our community
partners. We have previously shown during Phase 1 that oral (45d) drinking water exposure of mice to U leads
to high exposures of GIT leading to significant changes in lymphoid and epithelial cells in the small and large
intestines. In SA1, mouse studies will explore in vivo, ex vivo, and in vitro studies following exposures to uranyl
acetate (UA, soluble) and uranium citrate (UCit, insoluble nanomaterial), sodium orthovanadate (Na3VO4,
soluble) and vanadium oxide (V2O4, insoluble). These metals will be explored alone and in combination with
other metals, including arsenic. Environmentally derived mine samples rich in carnotite will also be studied in
mice. We will screen for mRNA changes in small and large intestinal snips focusing on cytokines, oxidative
stress, and aromatic hydrocarbon receptor (AhR) pathways. An additional novel aspect of these studies is that
we will perform microbiome metagenomic analyses on the feces obtained from these mice, and we will screen
the feces using a large metabolomic panel to determine possible pathways responsible for immune
modulation. In SA2, we will examine the toxicity of these same metals and mixtures on human colonic
organoids obtained from normal human donors. We will assess metabolic changes in these tissues following in
vitro exposures and we will assess changes in epithelial barrier function using both organoids and human
colonic cell lines. Changes in transepithelial electrical resistances, mRNA and protein expression for
membrane tight junction molecules will be studied to understand mechanisms of barrier disruption. In SA3,
working with the CEC and BP Comm, we will examine stool samples from study participants in the community
for metal exposure, changes in inflammatory biomarkers, microbiome metagenomics, and metabolomic profiles
examined in SA1 and SA2. These studies will rely on statistical and mixed metal analyses developed by
DMAC. The ultimate goal of these studies is to address community concerns regarding exposure to mixed
metals from abandoned uranium mines and other hard metal mines leading to potential immunologic changes
and diseases. Data from these studies will inform communities through CEC on how to avoid exposures and
inform environmental projects (ESE PM, ESE Remed) on potential remediation of these sites.

Grant Number: 4P42ES025589-09
NIH Institute/Center: NIH
Principal Investigator: Eliseo Castillo