Evaluation of Pb-induced perturbations in the central and enteric nervous system

PROJECT SUMMARY Lead (Pb) is an everyday contaminant with low level exposure rates of one in every three children worldwide. A major source of exposure to this heavy metal is via drinking water delivered through Pb lines. Children are particularly vulnerable, with an exposure rate of up to 800 million globally, as they absorb Pb differently than adults. Even children exposed to very low levels of Pb often go on to experience intellectual deficits with associative macroscopic changes in the brain. While many of these poor neurological outcomes are ascribed to the ability of Pb to cross the blood brain barrier (BBB), how the affects of Pb on other compartments of the body contribute to an underdeveloped brain remains largely unknown. The gut brain-axis has recently been brought into clinical and preclinical spotlights as accumulating evidence confer bidirectional communication between the two organs. As a collective, the microorganisms/microbiota colonizing the vertebrate gut play a commensal role in training the immune system and promoting healthy brain development. This is particularly evident in cases of gut dysbiosis associated with an array of neurological diseases/disorders of developmental origins. Upon Pb contaminated water consumption, the gut microbiota is amongst the first exposed and are readily altered in species composition which has been reported in a limited number of preclinical animal studies. However, how Pb-induced gut dysbiosis impacts the enteric and central nervous system independent of Pb entry systemically remains elusive. Building on a novel germ-free piglet paradigm developed by our group, we will test the central hypothesis that low level Pb exposure impairs brain development by altering the gut microbiome which in turn negatively impacts distinct central and enteric nervous system cell types. We will employ a multipronged approach to test the following three independent yet complementary Aims. In Aim 1, we will determine the effects of a Pb-altered microbiome on key neurodevelopmental trajectories by recolonizing germ-free piglets with donor gut microbiota exposed to low doses of Pb orally. This will enable us to rule out any direct effects of Pb on the brain via entry through the blood brain barrier. In Aim 2, we will identify and characterize alterations that occur in the gut microbiome after Pb exposure. Using multiomics and several other in vivo and in vitro techniques, we will evaluate changes in microbial diversity, metabolites, and host physiology. Aim 3 will include assessments of both compartments to interrogate direct and indirect Pb-induced alterations in distinct central and enteric nervous system cell types. Completion of these studies will provide mechanistic insights on the cellular, microbial, and systems level and illuminate new aspects of Pb exposure that may lead to novel strategies for targeted therapeutic interventions to improve neurological outcomes in children exposed to Pb.