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bacterial extracellular vesicle

Once overlooked cellular messengers could combat antibiotic resistance

bacterial extracellular vesicle

Children’s National Hospital researchers for the first time have isolated bacterial extracellular vesicles from the blood of healthy donors. The team theorizes that the solar eclipse lookalikes contain important signaling proteins and chromatin, DNA from the human host.

Children’s National Hospital researchers for the first time have isolated bacterial extracellular vesicles from the blood of healthy donors, a critical step to better understanding the way gut bacteria communicate with the rest of the body via the bloodstream.

For decades, researchers considered circulating bacterial extracellular vesicles as bothersome flotsam to be jettisoned as they sought to tease out how bacteria that reside in the gut whisper messages to the brain.

There is a growing appreciation that extracellular vesicles – particles that cells naturally release – actually facilitate intracellular communication.

“In the past, we thought they were garbage or noise,” says Robert J. Freishtat, M.D., MPH, associate director, Center for Genetic Medicine Research at Children’s National Research Institute. “It turns out what we throw away is not trash.”

Kylie Krohmaly, a graduate student in Dr. Freishtat’s laboratory, has isolated from blood, extracellular vesicles from Escherichia coli and Haemophilus influenzae, common bacteria that colonize the gut, and validated the results via electron microscopy.

“The images are interesting because they look like they have a bit of a halo around them or penumbra,” Krohmaly says.

The team theorizes that the solar eclipse lookalikes contain important signaling proteins and chromatin, DNA from the human host.

“It’s the first time anyone has pulled them out of blood. Detecting them is one thing. Pulling them out is a critical step to understanding the language the microbiome uses as it speaks with its human host,” Dr. Freishtat adds.

Krohmaly’s technique is so promising that the Children’s National team filed a provisional patent.

The Children’s research team has devised a way to gum up the cellular works so that bacteria no longer become antibiotic resistant. Targeted bacteria retain the ability to make antibiotic-resistance RNA, but like a relay runner dropping rather than passing a baton, the bacteria are thwarted from advancing beyond that step. And, because that gene is turned off, the bacteria are newly sensitive to antibiotics – instead of resistant bacteria multiplying like clockwork these bacteria get killed.

“Our plan is to hijack this process in order to turn off antibiotic-resistance genes in bacteria,” Dr. Freishtat says. “Ultimately, if a child who has an ear infection can no longer take amoxicillin, the antibiotic would be given in tandem with the bacteria-derived booster to turn off bacteria’s ability to become antibiotic resistant. This one-two punch could become a novel way of addressing the antibiotic resistance process.”

ISEV2020 Annual Meeting presentation
(Timing may be subject to change due to COVID-19 safety precautions)
Oral with poster session 3: Neurological & ID
Saturday May 23, 2020, 5 p.m. to 5:05 p.m. (ET)
“Detection of bacterial extracellular vesicles in blood from healthy volunteers”
Kylie Krohmaly, lead author; Claire Hoptay, co-author; Andrea Hahn, M.D., MS, infectious disease specialist and co-author; Robert J. Freishtat, M.D., MPH, associate director, Center for Genetic Medicine Research at Children’s National Research Institute and senior author.

preterm brain scans

Early lipids in micropreemies’ diets can boost brain growth

preterm brain scans

Segmentation of a preterm brain T2-weighted MRI image at 30 gestational weeks [green=cortical grey matter; blue=white matter; grey=deep grey matter; cyan=lateral ventricle; purple=cerebellum; orange=brainstem; red=hippocampus; yellow=cerebrospinal fluid].

Dietary lipids, already an important source of energy for tiny preemies, also provide a much-needed brain boost by significantly increasing global brain volume as well as increasing volume in regions involved in motor activities and memory, according to research presented during the Pediatric Academic Societies 2019 Annual Meeting.

“Compared with macronutrients like carbohydrates and proteins, lipid intake during the first month of life is associated with increased overall and regional brain volume for micro-preemies,” says Catherine Limperopoulos, Ph.D., director of MRI Research of the Developing Brain at Children’s National and senior author. “Using non-invasive magnetic resonance imaging, we see increased volume in the cerebellum by 2 weeks of age. And at four weeks of life, lipids increase total brain volume and boost regional brain volume in the cerebellum, amygdala-hippocampus and brainstem.”

The cerebellum is involved in virtually all physical movement and enables coordination and balance. The amygdala processes and stores short-term memories. The hippocampus manages emotion and mood. And the brainstem acts like a router, passing messages from the brain to the rest of the body, as well as enabling essential functions like breathing, a steady heart rate and swallowing.

According to the Centers for Disease Control and Prevention, about 1 in 10 U.S. babies is born preterm, or before 37 weeks gestation. Regions of the brain that play vital roles in complex cognitive and motor activities experience exponential growth late in pregnancy, making the developing brains of preterm infants particularly vulnerable to injury and impaired growth.

Children’s research faculty examined the impact of lipid intake in the first month of life on brain volumes for very low birth weight infants, who weighed 1,500 grams or less at birth. These micro-preemies are especially vulnerable to growth failure and neurocognitive impairment after birth.

The team enrolled 68 micro-preemies who were 32 weeks gestational age and younger when they were admitted to Children’s neonatal intensive care unit during their first week of life. They measured cumulative macronutrients – carbohydrates, proteins, lipids and calories – consumed by these newborns at 2 and 4 weeks of life. Over years, Limperopoulos’ lab has amassed a large database of babies who were born full-term; this data provides unprecedented insights into normal brain development and will help to advance understanding of brain development in high-risk preterm infants.

“Even after controlling for average weight gain and other health conditions, lipid intake was positively associated with cerebellar and brainstem volumes in very low birthweight preterm infants,” adds Katherine M. Ottolini, the study’s lead author.

According to Limperopoulos, Children’s future research will examine the optimal timing and volume of lipids to boost neurodevelopment for micro-preemies.

Pediatric Academic Societies 2019 Annual Meeting presentation

  • “Early lipid intake improves brain growth in premature infants.”
    • Saturday, April 27, 2019, 1:15-2:30 p.m. (EST)

Katherine M. Ottolini, lead author; Nickie Andescavage, M.D., Attending, Neonatal-Perinatal Medicine and co-author; Kushal Kapse, research and development staff engineer and co-author; and Catherine Limperopoulos, Ph.D., director of MRI Research of the Developing Brain and senior author, all of Children’s National.

Zhe Han

$2M NIH grant for treating disease linked to APOL1

Zhe Han

Children’s researcher Zhe Han, Ph.D., has received a $2 million award from the National Institutes of Health (NIH) to study new approaches to treat kidney disease linked to inheriting Apolipoprotein L1 (APOL1) risk alleles. These risk alleles are particularly common among persons of recent African descent, and African Americans are disproportionately affected by the increased risk in kidney disease associated with these risk alleles.

Han, an associate professor in Children’s Center for Genetic Medicine Research, has established a leading research program that uses the fruit fly Drosophila as a model system to study how genetic mutations lead to disease.

Drosophila is a very basic model, but studies in the fly have led to major breakthroughs in understanding fundamental biological processes that underlie health and disease in humans,” Han says. “Since coming to Children’s National five years ago, I have focused a significant part of my research studying particular fly cells called nephrocytes that carry out many of the important roles of human kidney glomeruli, units within the kidney where blood is cleaned. Working together with clinician colleagues here, we have demonstrated that these Drosophila cells can be used to very efficiently study different types of renal disease caused by genetic mutations.”

The APOL1 risk alleles are genetic variants, termed G1 and G2, found almost exclusively in people of African ancestry and can lead to a four-fold higher risk of end-stage kidney disease, the last of five stages of chronic kidney disease. Exactly how inheriting these risk alleles increases the risk of kidney disease remains an unanswered question and the focus of considerable research activity. Han’s laboratory has developed a Drosophila model of APOL1-linked renal disease by producing the G1 and G2 forms of APOL1 specifically in nephrocytes. This led to defects in fly renal cells that strikingly overlap with disease-associated changes in experimental model and human kidney cells expressing APOL1 risk alleles.

The new NIH award will fund large-scale screening and functional testing to identify new treatment targets and new drugs to treat kidney disease linked to APOL1. Using a genetic screening approach, Han’s lab will identify nephrocyte “modifier” genes that interact with APOL1 proteins and counter the toxic effects of risk-associated G1 and G2 variants.

The team also will identify nephrocyte genes that are turned on or off in the presence of APOL1 risk alleles, and confirm that such “downstream” APOL1-regulated genes are similarly affected in experimental model and human kidney cells. The potential of the newly identified “modifier” and “downstream” genes to serve as targets of novel therapeutic interventions will be experimentally tested in fly nephrocytes in vivo and in cultured mammalian kidney cells.

Finally, the Drosophila model will be used as a drug screening platform for in vivo evaluation of positive “hits” from a cell-based APOL1 drug screening study in order to identify compounds that are most effective with the fewest side effects.

“These types of studies can be most efficiently performed in Drosophila,” Han adds.  “They take advantage of the speed and low cost of the fly model system and the amazing array of well-established, sophisticated genetic tools available for the fly. Using this model to elucidate human disease mechanisms and to identify new effective therapies has truly become my research passion.”

Schistosoma haematobium egg

For hemorrhagic cystitis, harnessing the power of a parasite

Schistosoma haematobium egg

“Urogenital Schistosoma infestation, which is caused by S. haematobium, also causes hemorrhagic cystitis, likely by triggering inflammation when the parasite’s eggs are deposited in the bladder wall or as eggs pass from the bladder into the urinary stream. S. haematobium eggs secrete proteins, including IPSE, that ensure human hosts are not so sickened that they succumb to hemorrhagic cystitis,” says Michael H. Hsieh, M.D., Ph.D.

Every year, hundreds of thousands of U.S. patients – and even more throughout the world – are prescribed cyclophosphamide or ifosfamide. These two chemotherapy drugs can be life-saving for a wide range of pediatric cancers, including leukemias and cancers of the eyes and nerves. However, these therapies come with a serious side effect: Both cause hemorrhagic cystitis in up to 40 percent of patients. This debilitating condition is characterized by severe inflammation in the bladder that can cause tremendous pain, life-threatening bleeding, and frequent and urgent urination.

Infection with a parasitic worm called Schistosoma haematobium also causes hemorrhagic cystitis, but this organism has a fail-safe: To keep its host alive, the parasite secretes a protein that suppresses inflammation and the associated pain and bleeding.

In a new study, a Children’s-led research team harnessed this protein to serve as a new therapy for chemotherapy-induced hemorrhagic cystitis.

“Urogenital Schistosoma infestation, which is caused by S. haematobium, also causes hemorrhagic cystitis, likely by triggering inflammation when the parasite’s eggs are deposited in the bladder wall or as eggs pass from the bladder into the urinary stream. S. haematobium eggs secrete proteins, including IPSE, that ensure human hosts are not so sickened that they succumb to hemorrhagic cystitis,” says Michael H. Hsieh, M.D., Ph.D., senior author of the study published April 3, 2018, by The FASEB Journal. “This work in an experimental model is the first published report of exploiting an uropathogen-derived host modulatory molecule in a clinically relevant model of bladder disease, and it points to the potential utility of this as an alternate treatment approach.”

S. mansoni IPSE binds to Immunoglobulin E (IgE), an antibody produced by the immune system that is expressed on the surface of basophils, a type of immune cell; and mast cells, another immune cell that mediates inflammation; and sequesters chemokines, signaling proteins that alert white cells to infection sites. The team produced an ortholog of the uropathogen-derived protein. A single IV dose proved superior to multiple doses of 2-Mercaptoethane sulfonate sodium (MESNA), the current standard of care, in suppressing chemotherapy-induced bladder hemorrhaging in an experimental model. It was equally potent as MESNA in dampening chemotherapy-induced pain, the research team finds.

“The current array of medicines we use to treat hemorrhagic cystitis all have shortcomings, so there is a definite need for novel therapeutic options,” says Dr. Hsieh, a Children’s National Health System urologist. “And other ongoing research projects have the potential to further expand patients’ treatment options by leveraging other urogenital parasite-derived, immune-modulating molecules to treat inflammatory bowel diseases and autoimmune disorders.”

Future research will aim to describe the precise molecular mechanisms of action, as well as to generate other orthologs that boost efficacy while reducing side effects.

In addition to Dr. Hsieh, Children’s study co-authors include Lead Author, Evaristus C. Mbanefo; Loc Le and Luke F. Pennington; Justin I. Odegaard and Theodore S. Jardetzky, Stanford University; Abdulaziz Alouffi, King Abdulaziz City for Science and Technology; and Franco H. Falcone, University of Nottingham.

Financial support for this research was provided by National Institutes of Health under award number RO1-DK113504.

Preemie Baby

Brain food for preemies

Preemie Baby

Babies born prematurely – before 37 weeks of pregnancy – often have a lot of catching up to do. Not just in size. Preterm infants typically lag behind their term peers in a variety of areas as they grow up, including motor development, behavior and school performance.

New research suggests one way to combat this problem. The study, led by Children’s researchers and presented during the Pediatric Academic Societies 2018 annual meeting, suggests that the volume of carbohydrates, proteins, lipids and calories consumed by very vulnerable premature infants significantly contributes to increased brain volume and white matter development, even though additional research is needed to determine specific nutritional approaches that best support these infants’ developing brains.

During the final weeks of pregnancy, the fetal brain undergoes an unprecedented growth spurt, dramatically increasing in volume as well as structural complexity as the fetus approaches full term.

One in 10 infants born in the U.S. in 2016 was born before 37 weeks of gestation, according to the Centers for Disease Control and Prevention. Within this group, very low birthweight preemies are at significant risk for growth failure and neurocognitive impairment. Nutritional support in the neonatal intensive care unit (NICU) helps to encourage optimal brain development among preterm infants. However, their brain growth rates still lag behind those seen in full-term newborns.

“Few studies have investigated the impact of early macronutrient and caloric intake on microstructural brain development in vulnerable preterm infants,” says Katherine Ottolini, lead author of the Children’s-led study. “Advanced quantitative magnetic resonance imaging (MRI) techniques may help to fill that data gap in order to better direct targeted interventions to newborns who are most in need.”

The research team at Children’s National Health System enrolled 69 infants who were born younger than 32 gestational weeks and weighed less than 1,500 grams. The infants’ mean birth weight was 970 grams and their mean gestational age at birth was 27.6 weeks.

The newborns underwent MRI at their term-equivalent age, 40 weeks gestation. Parametric maps were generated for fractional anisotropy in regions of the cerebrum and cerebellum for diffusion tensor imaging analyses, which measures brain connectivity and white matter tract integrity. The research team also tracked nutritional data: Grams per kilogram of carbohydrates, proteins, lipids and overall caloric intake.

“We found a significantly negative association between fractional anisotropy and cumulative macronutrient/caloric intake,” says Catherine Limperopoulos, Ph.D., director of Children’s Developing Brain Research Laboratory and senior author of the research. “Curiously, we also find significantly negative association between macronutrient/caloric intake and regional brain volume in the cortical and deep gray matter, cerebellum and brainstem.”

Because the nutritional support does contribute to cerebral volumes and white matter microstructural development in very vulnerable newborns, Limperopoulos says the significant negative associations seen in this study may reflect the longer period of time these infants relied on nutritional support in the NICU.

In addition to Ottolini and Limperopoulos, study co-authors include Nickie Andescavage, M.D., Attending, Children’s Neonatal-Perinatal Medicine; and Kushal Kapse.