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little boy using asthma inhaler

Searching for the molecular underpinnings of asthma exacerbations

little boy using asthma inhaler

It’s long been known that colds, flu and other respiratory illnesses are major triggers for asthma exacerbations, says asthma expert Stephen J. Teach, M.D., MPH. Consequently, a significant body of research has focused on trying to figure out what’s happening on the cellular or molecular level as these illnesses progress to exacerbations.

People with asthma can be indistinguishable from people who don’t have this chronic airway disease – until they have an asthma attack, also known as an exacerbation. During these events, their airways become inflamed and swollen and produce an abundance of mucus, causing dangerous narrowing of the bronchial tubes that leads to coughing, wheezing and trouble breathing. These events are a major cause of morbidity and mortality, leading to the deaths of 10 U.S. residents every day, according to the Centers for Disease Control and Prevention.

It’s long been known that colds, flu and other respiratory illnesses are major triggers for asthma exacerbations, says Children’s National in Washington, D.C., asthma expert Stephen J. Teach, M.D., MPH. Consequently, a significant body of research has focused on trying to figure out what’s happening on the cellular or molecular level as these illnesses progress to exacerbations. Targeted searches have identified several different molecular pathways that appear to be key players in this phenomenon. However, Dr. Teach says researchers have been missing a complete and unbiased snapshot of all the important pathways in illness-triggered exacerbations and how they interrelate.

To develop this big picture view, Dr. Teach and  Inner-City Asthma Consortium colleagues recruited 208 children ages 6-17 years old with severe asthma – marked by the need for daily doses of inhaled corticosteroids, two hospitalizations or systemic corticosteroid treatments over the past year, and a high concentration of asthma-associated immune cells – from nine pediatric medical centers across the country, including Children’s National. (Inhaled corticosteroids are a class of medicine that calms inflamed airways.) The researchers collected samples of nasal secretions and blood from these patients at baseline, when all of them were healthy.

Then, they waited for these children to show symptoms of respiratory illnesses. Within six days of cold symptoms, the researchers took two more samples of nasal secretions and blood. They also administered breathing tests to determine whether these respiratory illnesses led to asthma exacerbations and recorded whether these patients were treated with systemic corticosteroids to stem the associated respiratory inflammation.

The researchers examined nasal fluid samples for evidence of viral infection during illness and used analytical methods to identify the causative virus. They analyzed all the samples they collected for changes in concentrations of various immune cells. They also looked globally in these samples for changes in gene expression compared with baseline and between the two collection periods during respiratory illness.

Together, this information told the molecular story about what took place after these children got sick and after some of them developed exacerbations. Of the 208 patients recruited, 106 got respiratory illnesses during the six-month study period, leading to a total of 154 illness events. Of those, 47 caused exacerbations, and 107 didn’t.

About half the exacerbations appeared to have been triggered by a rhinovirus, a cause of common colds, the research team reports in a study published online April 8, 2019, in Nature Immunology. The other children’s cold-like symptoms could have been triggered by pollution, allergens or other irritants.

In most exacerbations, virally triggered or not, the researchers saw early activation of a network of genes that appeared to be associated with SMAD3, a signaling molecule already known to be involved in airway inflammation. At the same time, genes that control a set of immune cells known as lymphocytes were turned down. However, as the exacerbation progressed and worsened, the researchers saw gene networks turned on that related to airway narrowing, mucus hypersecretion and activation of other immune cells.

Exacerbations triggered by viruses were associated with multiple inflammatory pathways, in contrast to those in which viruses weren’t found, which were associated with molecular pathways that affected cells in the airway lining.

The researchers validated these findings in 19 patients who each got respiratory illnesses at least twice during the study period but only developed an exacerbation during one of these episodes, finding the same upregulated and downregulated molecular pathways in these patients as in the study population as a whole. They also identified a set of molecular risk factors in patients at baseline – signatures of gene activation that appeared to put patients at risk for exacerbations when they got sick. When patients were treated with systemic corticosteroids during exacerbations, these medicines appeared to restore only some of the affected molecular pathways to normal, healthy levels. Other molecular pathways remained markedly changed.

Each finding could represent a new target for drugs that could prevent or more effectively treat exacerbations, keeping more patients with asthma healthy and out of the hospital.

“Our consortium study found increased gene expression of enzymes that produce molecules that contribute to narrowed airways and dilated blood vessels,” Dr. Teach adds. “This is especially intriguing because drugs that target kallikreins or bradykinin may help treat asthma attacks that aren’t caused by viruses.”

In addition to Dr. Teach, study co-authors include Lead Author Matthew C. Altman, University of Washington; Michelle A. Gill, Baomei Shao and Rebecca S. Gruchalla, all of University of Texas Southwestern Medical Center; Elizabeth Whalen and Scott Presnell of Benaroya Research Institute; Denise C. Babineau and Brett Jepson of Rho, Inc.; Andrew H. Liu, Children’s Hospital Colorado; George T. O’Connor, Boston University School of Medicine; Jacqueline A. Pongracic, Ann Robert H. Lurie Children’s Hospital of Chicago; Carolyn M. Kercsmar and Gurjit K. Khurana Hershey, , Cincinnati Children’s Hospital; Edward M. Zoratti and Christine C. Johnson, Henry Ford Health System; Meyer Kattan, Columbia University College of Physicians and Surgeons; Leonard B. Bacharier and Avraham Beigelman, Washington University, St. Louis; Steve M. Sigelman, Peter J. Gergen, Lisa M. Wheatley and Alkis Togias, National Institute of Allergy and Infectious Diseases; and James E. Gern, William W. Busse and Senior author Daniel J. Jackson, University of Wisconsin School of Medicine and Public Health.

Funding for research described in this post was provided by the National Institute of Allergy and Infectious Diseases under award numbers 1UM1AI114271 and UM2AI117870; CTSA under award numbers UL1TR000150, UL1TR001422 and 5UL1TR001425; the National Institutes of Health under award number UL1TR000451;  CTSI under award number 1UL1TR001430; CCTSI under award numbers UL1TR001082 and 5UM1AI114271; and NCATS under award numbers UL1 TR001876 and UL1TR002345.

Cholesterol plaque in artery

Looking for atherosclerosis’ root cause

Cholesterol plaque in artery

A multi-institutional team led by research faculty at Children’s National in Washington, D.C., finds that extracellular vesicles derived from kids’ fat can play a pivotal role in ratcheting up risk for atherosclerotic cardiovascular disease well before any worrisome symptoms become visible.

According to the Centers for Disease Control and Prevention, about one in five U.S. kids aged 6 to 19 is obese, boosting their risk for a variety of other health problems now and later in life.

One of these is atherosclerosis, a term that translates literally as hardening of the arteries. Atherosclerosis causes blood vessels that carry oxygen-rich blood throughout the body to become inflamed. White blood cells called macrophages settle in the vessel wall, which becomes overloaded with cholesterol. A plaque forms that restricts blood flow. But it remains a mystery how fat cells residing in one place in the body can trigger mayhem in cells and tissues located far away.

Small, lipid-lined sacs called extracellular vesicles (EVs), released by cells into the bloodstream, are likely troublemakers since they enable intercellular communication. Now, a multi-institutional team led by research faculty at Children’s National in Washington, D.C., finds that EVs derived from kids’ fat can play a pivotal role in ratcheting up risk for atherosclerotic cardiovascular disease well before any worrisome symptoms become visible. What’s more, the team showed that EVs found in the body’s fat stores can disrupt disposal of cholesterol in a variety of kids, from lean to obese, the team reports online July 22, 2019, in the Journal of Translational Medicine.

“We found that seven specific small sequences of RNA (microRNA) carried within the extracellular vesicles from human fat tissue impaired the ability of white blood cells called macrophages to eliminate cholesterol,” says Robert J. Freishtat, M.D., MPH, senior scientist at the Center for Genetic Medicine Research at Children’s National and the study’s senior author. “Fat isn’t just tissue. It can be thought of as a metabolic organ capable of communicating with types of cells that predispose someone to develop atherosclerotic cardiovascular disease, the leading cause of death around the world.”

Research scientists and clinicians from Children’s National, the George Washington University, NYU Winthrop Hospital and the National Heart, Lung and Blood Institute collaborated to examine the relationship between the content of EVs and their effect on macrophage behavior. Their collaborative effort builds on previous research that found microRNA derived from fat cells becomes pathologically altered by obesity, a phenomenon reversed by weight-loss surgery.

Because heart disease can have its roots in adolescence, they enrolled 93 kids aged 12 to 19 with a range of body mass indices (BMIs), including the “lean” group, 15 youth whose BMI was lower than 22 and the “obese” group, 78 youths whose BMI was in the 99th percentile for their age. Their median age was 17. Seventy-one were young women. They collected visceral adipose tissue during abdominal surgeries and visited each other’s respective labs to perform the experiments.

“We were surprised to find that EVs could hobble the macrophage cholesterol outflow system in adolescents of any weight,” says Matthew D. Barberio, Ph.D., the study’s lead author, a former Children’s National scientist who now is an assistant professor at the George Washington University’s Milken Institute School of Public Health. “It’s still an open question whether young people who are healthy can tolerate obesity—or whether there are specific differences in fat tissue composition that up kids’ risk for heart disease.”

The team plans to build on the current findings to safeguard kids and adults against future cardiovascular risk.

“This study was a huge multi-disciplinary undertaking,” adds Allison B. Reiss, M.D., of NYU Winthrop Hospital and the study’s corresponding author. “Ultimately, we hope to learn which properties belonging to adipose tissue EVs make them friendly or unfriendly to the heart, and we hope that gaining that knowledge will help us decrease morbidity and mortality from heart disease across the lifespan.”

In addition to Dr. Freishtat, additional study co-authors include Samuel B. Epstein, Madeleine Goldberg, Sarah C. Ferrante, and Evan P. Nadler, M.D., director of the Bariatric Surgery Program, all of Children’s National’s Center for Genetic Medicine Research; Lead Author, Matthew D. Barberio, of Millken Institute School of Public Health at the George Washington University; Lora J. Kasselman, Heather A. Renna, Joshua DeLeon, Iryna Voloshyna, Ashley Barlev, Michael Salama and Allison B. Reiss, all of NYU Winthrop Hospital; and Martin P. Playford and Nehal Mehta, of the National Heart, Lung and Blood Institute.

Financial support for research described in this post was provided by the National Institutes of Health National Center for Advancing Translational Sciences under award number UL1TR000075, the National Heart, Lung and Blood Institute under award number Z1AHL-06193-4, the American Heart Association under award number 17POST33670787, the Clark Charitable Foundation, the Elizabeth Daniel Research Fund, and Robert Buescher.

Sadiqa Kendi

Sadiqa Kendi, M.D., FAAP, CPST, is 2019 Bloomberg Fellow

Sadiqa Kendi

Sadiqa Kendi, M.D., FAAP, CPST, a pediatric emergency physician at Children’s National and medical director of Safe Kids DC, is among the 2019 cohort of Bloomberg Fellows, an initiative that provides world-class training to public health professionals tackling some of the most intractable challenges facing the U.S.

The Bloomberg American Health Initiative at the Johns Hopkins Bloomberg School of Public Health on June 6, 2019, announced fellows who will receive full scholarships to earn an MPH or DrPH as they tackle five U.S. health challenges: addiction and overdose, environmental challenges, obesity and the food system, risks to adolescent health and violence. Now in its third year, the largest group of fellows to date includes representatives from organizations headquartered in 24 states and the District of Columbia.

As part of her environmental challenges fellowship, Dr. Kendi will attempt to lessen the significant morbidity and mortality suffered by children, especially children of color, due to unintentional injuries. Children’s emergency department handles more than 100,000 pediatric visits per year, 1,200 of which result in hospital admission.

“The numbers are staggering: 25% of emergency department visits by kids and more than $28 billion in health care spending are associated with injuries. These preventable injuries claim the highest number of pediatric lives, and children of color and lower income families often disproportionately bear this burden,” Dr. Kendi says.

Bloomberg Fellows Graphic

“Regrettably, I have seen the personal toll close up, and it has been sobering to hug a sobbing parent whose child clings to life after being struck by a car; to clasp the hand of a frightened child who has fallen from playground equipment and suffered a severe fracture; to see the angst written on a caregiver’s face as I lead our team in trying to save a life that easily could have been safeguarded by installing a window guard,” she adds.

Under the auspices of Safe Kids District of Columbia, Dr. Kendi is developing a one-stop Safety Center at Children’s National to provide injury prevention equipment and education to families in five focus areas: child passenger safety, home, pedestrian, sleep and sports.

Safe Kids Worldwide, the umbrella non-profit organization for Safe Kids DC, started at Children’s National and has grown to more than 400 coalitions around the world. Safe Kids DC is the local coalition that is working to address the burden of injury in local District of Columbia communities.

“I’m grateful to be named a Bloomberg Fellow because this opportunity will enable me to better understand the theories, methods of evaluation and tools for addressing the burden of injury in the District of Columbia, including how to assess and address the built environment. This training will help me to better lead my Safe Kids DC team in developing projects, outreach programs and legislative advocacy that have the potential to directly impact the communities we serve,” she adds.