Tag Archive for: Devon Guerrelli

bisphenol A

Alternative synthetic compound might offer safer solution to children’s health

bisphenol A

Not only is bisphenol A (BPA) added to medical equipment used to treat patients, it can also be found in 60% of neonatal intensive care unit (NICU) supplies, such as bandages and items for feeding, suggesting that occupational and clinical environments have a higher exposure to this synthetic compound.

Researchers at Children’s National Hospital found that a commonly used plastic, known as bisphenol S (BPS), was the least disruptive to cardiac electrophysiology and may serve as a safer chemical alternative for plastic medical devices used to treat vulnerable populations compared to other compounds, according to a new preclinical study published in Toxicological Sciences.

For decades, the medical device industry has used bisphenol chemicals known to antagonize ion channels, impair electrical conduction and trigger arrhythmias that affect the overall cardiovascular health in children. Not only is bisphenol A (BPA) added to medical equipment used to treat patients, it can also be found in 60% of neonatal intensive care unit (NICU) supplies, such as bandages and items for feeding, suggesting that occupational and clinical environments have a higher exposure to this synthetic compound.

Yet, very little is known about the downstream impact of BPA, BPS or bisphenol F (BPF) exposure on cardiac physiology.

To shed light on the safety profile of BPA and its alternatives BPS and BPF in plastic medical devices, Children’s National researchers present the first study that compares the acute effects of these three chemicals on cardiac electrophysiology in a preclinical model.

According to the researchers, children should continue receiving medical care to treat their condition.

“It is important to investigate iatrogenic plastic chemical exposures in young patients, as biomonitoring studies have reported elevated chemical exposures in NICU and pediatric intensive care unit patients,” said Devon Guerrelli, M.S., a Ph.D. candidate at Children’s National. “Our lab is actively working with cardiac surgeons to investigate patient exposure to both BPA and phthalate plasticizer chemicals. Patients and their parents can rest assured that our team’s priority is safety and advancement of the field.”

Future studies are needed to fully understand the chemicals’ safety on cardiac electrical and mechanical function due to notable biological differences between humans and preclinical models. The researchers call for the scientific community to explore the impact of these compounds on other organ systems by comprehensively assessing intracellular targets, genomic and proteomic expression profiles.

While health concerns remain, there is no consensus among the scientific community on the potential use of safer compound alternatives in pediatric plastic medical devices.

“First, a variety of preclinical models have been used by the scientific community to assess BPA toxicity. But, there is considerable variability between these different models, including differences in ion channel expression, which may produce conflicting results and limit extrapolation of the data to humans,” said Nikki Posnack, Ph.D., principal investigator at Children’s National Sheikh Zayed Institute for Pediatric Surgical Innovation and senior author. “Accordingly, in the presented study, we tested the effects of bisphenol chemicals using three different preclinical models. Second, studies assessing the safety profile of new structural analogs to BPA are limited.”

The researchers compared the cardiac safety profile of BPA, BPS and BPF by using a whole-cell voltage clamping recording on cell lines to study voltage-gated channels Nav1.5, Cav 1.2 and hERG, allowing the measurements of the cell’s electrical properties and total current through all the channels on a membrane in non-human subjects and cardiomyocytes human cell lines. Results of the study found that BPA was the most potent inhibitor of sodium, calcium and potassium channel currents compared to the alternatives BPS and BPF. BPA and BPF exposure also slowed atrioventricular conduction and increased atrioventricular nodal refractoriness.

“Based on our findings, acute exposure to high concentrations of BPA could lead to changes in cardiac electrophysiology,” said Tomas Prudencio, M.S., a research technician at Children’s National and lead author. “This includes slowing of electrical conduction from the atria to the ventricles, which would present as a prolongation of the PR interval in an electrocardiogram.”

newborn baby

Study suggests chronic hypoxia delays cardiac maturation in CHD

newborn baby

Every year, nearly 40,000 babies are born with a congenital heart defect (CHD) — the leading cause of birth defect-associated infant illness and death.

Every year, nearly 40,000 babies are born with a congenital heart defect (CHD) — the leading cause of birth defect-associated infant illness and death. An event that may contribute to cyanotic CHD is the lack of oxygen, known as hypoxia, before and after birth, impacting gene expression and cardiac function that delay postnatal cardiac maturation, according to a new pre-clinical model led by researchers at Children’s National Hospital.

Single ventricle, transposition of the great arteries, truncus arteriosus and severe forms of tetralogy of Fallot, such cyanotic congenital heart diseases have lower circulating blood oxygen levels. The lack of oxygen in the blood begins prenatally and continues after birth until definitive repair, suggesting a delay on cardiac maturation.

There is little research on the underpinnings that explain the lack of oxygen’s effects on the developing heart, which could help inform adequate therapies in the pediatric population to promote cardiovascular health across the lifetime. The researchers developed the first pre-clinical model that explores the effects of chronic hypoxia in perinatal and postnatal stages on the developing heart under conditions seen in cyanotic CHD.

“To the best of our knowledge, ours is the first study to perform complete gene expression arrays on animals after perinatal hypoxia,” said Jennifer Romanowicz, senior noninvasive imaging fellow at Boston Children’s Hospital and lead author of the study. “Not only did these studies allow us to determine the effects of hypoxia on heart development, but the detailed results of our study will be available to other researchers to independently address other questions about perinatal hypoxia and heart development.”

The study published in the American Journal of Physiology: Heart and Circulatory Physiology suggests that chronic lack of oxygen alters the electrical properties of heart tissue, called the electrophysiological substrate, and the contractile apparatus, a muscle composed of proteins that control cardiac contraction. Multiple genes involved with the contractile apparatus were expressed differently in the non-human subjects.

“What was remarkable was that most abnormalities normalized after the animals recovered in normal oxygen levels,” said Romanowicz. “This is an optimistic sign that early repair of cyanotic congenital heart disease may allow the heart to finish development.”

The researchers placed pregnant non-human subjects in hypoxic chambers starting on embryonic day 16, mimicking the second trimester in humans. The same subjects gave birth in the hypoxic chambers, and the newborns were kept there until postnatal day eight when the heart muscle maturation is nearly complete. To understand how human infants recover with normalized oxygen levels after surgical repair of cyanotic CHD, the researchers moved hypoxic subjects to normal oxygen conditions for recovery and tested again at postnatal day 30.

“Next steps include using a pre-clinical model of cyanotic congenital heart disease that more accurately represents human neonatal physiology,” said Devon Guerrelli, Ph.D. candidate at Children’s National. We plan to work with the cardiac surgery team at Children’s National to investigate changes in the myocardium due to hypoxia in pediatric patients who are undergoing surgical repair.”

Nikki Posnack, Ph.D., principal investigator at Sheikh Zayed Institute for Pediatric Surgical Innovation and Nobuyuki Ishibashi, M.D., director of Cardiac Surgery Research Laboratory at Children’s National, led and guided the team of researchers involved in the study.