Research in our lab focuses on the areas highlighted below.
The concept of a human exposome — which includes the totality of all chemical exposures from conception onward — has recently emerged as complement to the human genome for investigating risk factors associated with adverse health outcomes. To discover unidentified risk factor, our lab focuses on reactive electrophiles, which are a large and important class of chemicals arising from both xenobiotic insult (i.e., environmental toxicants) and endogenous production (i.e., oxidative stress). However, because electrophiles normally have very short life spans in vivo, they typically cannot be measured directly in blood samples. This challenge has motivated our group and others to focus on protein adducts (addition products) as biomarkers for estimating exposures to reactive electrophilic chemicals. In our lab we have helped to pioneer the emerging field of adductomics, which is an unbiased biomarker discovery approach for investigating environmental risk factors for adverse health outcomes. Current projects in our lab are focused on mapping the adductome from before birth throughout childhood development (1 R21 ES026776-01). In addition, we are currently collaborating with the University of Southern California to apply adductomics to investigate associations between early-life exposures to air pollution and children’s health as part of the LA DREAMERs Environmental Influences on Child Health Outcomes (ECHO) Pediatric Cohort Study (UG3/UH3 RFA-OD-16-003).
Dried Blood Spots (DBS)
The requirement of venipuncture for obtaining blood samples in epidemiological research is a major challenge, especially with perinatal and pediatric populations. To address this challenge, we utilize DBS sampling — drops of whole blood collected on filter paper following a simple heel or finger stick — as a minimally-invasive and cost effective alternative to venous blood draws. In addition, newborn DBS samples are routinely collected from virtually all newborns in the United States to screen for inherited metabolic errors and other disorders, and several state public health departments archive residual newborn DBS and make them available for research. Thus, state-archived residual newborn DBS represent a large and important resource for epidemiological research. A main focus of our lab is the development and validation of both untargeted (discovery) and targeted biomarker methods for estimating environmental risk factors associated with adverse health outcomes.
Targeted Adductomics in DBS
While unbiased approaches (i.e., omics strategies) are required to identify yet unknown biomarkers, high-throughput targeted methods are needed for quantifying candidate biomarkers in population-based epidemiological studies. The collection of plasma or serum via venipuncture is the current clinical standard, but logistical constraints associated with the collection of blood in non-clinical settings have been a significant impediment to including biomarkers in epidemiological research, especially in studies involving infants and children. DBS sampling provides a simple and minimally-invasive alternative to venipuncture that bridges this gap. In our lab we are currently developing and validating a highly sensitive multiple reaction monitoring (MRM) approach for quantifying panels of targeted adducts in DBS samples—which we refer to as the Multiple Adduct Panel (MAP) assay. Newborn DBS are especially well suited for adductomic experiments because adducts reflect an integration of exposures over weeks to months and therefore permit direct assessment of chemical exposures occurring during fetal development prior to birth that are otherwise go undetected. Current projects in our lab are focused on investigating associations between prenatal exposures and childhood asthma, obesity, and birth defects.
Heavy Metals and Cotinine in DBS
Toxic metals, including arsenic (As), lead (Pb), mercury (Hg), and cadmium (Cd), are ubiquitous environmental pollutants that are listed as the 1st, 2nd, 3rd, and 7th most important hazardous substances on the 2011 Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) priority list of 275 substances, respectively. Exposure to heavy metals can occur through a variety of exposure routes, including inhalation as dust and fumes, and ingestion from food and water, and can cause a wide spectrum of health problems including convulsions, coma, renal failure, injuries to the lungs and neurologic system, memory loss, delirium, diabetes, kidney damage, and a variety of cancers. Exposures are of particular concern with pediatric populations and younger children, for whom the developmental consequences of heavy metal exposure can be particularly severe. Toxic metals can be quantified in blood to estimate internal dose, which is essential for investigating links between environmental exposures and health outcomes. However, the requirement for venous blood, which is costly and invasive, is an obstacle for assessing heavy metal exposures. Over the past seven years our lab has pioneered the use of DBS sampling for estimating exposures to toxic metals using a new metals-free collection methodology (Pending US Patent Numbers 62/340261 & 61/803674). Using this new methodology we are currently working on two NIH funded studies to evaluate adverse health outcomes associated with heavy metal exposures (R01 HD075957-01A1, UG3/UH3 RFA-OD-16-003).
In addition, we recently developed a sensitive, high-throughput method for extracting and quantifying cotinine in DBS samples as a biomarker of tobacco smoke. Our sample preparation incorporates a pressure barocycler to extract up to 48 samples in parallel in less than 10 minutes, making it amenable for high throughput processing. We also use a state-of-the-art nanochip-LC interface and QQQ mass spectrometer for maximum sensitivity using a minimal sample volume, respectively. With this method, we can quantify cotinine levels using a single 3.2 mm DBS punch.