UC Irvine-led study is first to find brain hemorrhage cause other than injured blood vessels
Discovery deepens understanding of cerebral microbleeds, may offer new therapeutic targets
November 22, 2023
Orange, Calif. — A first-of-its-kind study led by the University of California, Irvine has revealed a new culprit in the formation of brain hemorrhages that does not involve injury to the blood vessels, as previously believed. Researchers discovered that interactions between aged red blood cells and brain capillaries can lead to cerebral microbleeds, offering deeper insights into how they occur and identifying potential new therapeutic targets for treatment and prevention.
The findings, published online recently in the Journal of Neuroinflammation, describe how the team was able to watch the process by which red blood cells stall in the brain capillaries and then observe how the hemorrhage happens. Cerebral microbleeds are associated with a variety of conditions that occur at higher rates in older adults, including hypertension, Alzheimer’s disease and ischemic stroke.
“We have previously explored this issue in cell culture systems, but our current study is significant in expanding our understanding of the mechanism by which cerebral microbleeds develop,” said co-corresponding author Dr. Mark Fisher, professor of neurology in the UCI School of Medicine. “Our findings may have profound clinical implications, as we identified a link between red blood cell damage and cerebral hemorrhages that occurs at the capillary level.”
The team exposed red blood cells to a chemical called tert-butyl hydroperoxide that caused oxidative stress; the cells were then marked with a fluorescent label and injected into mice. Using two different methods, the researchers observed the red blood cells getting stuck in the brain capillaries and then being cleared out in a process called endothelial erythrophagocytosis. As they moved out of the capillaries, microglia inflammatory cells engulfed the red blood cells, which led to the formation of a brain hemorrhage.
“It has always been assumed that in order for cerebral hemorrhage to occur, blood vessels need to be injured or disrupted. We found that increased red blood cell interactions with the brain capillaries represent an alternative source of development,” said co-corresponding author Xiangmin Xu, UCI professor of anatomy & neurobiology and director of the campus’s Center for Neural Circuit Mapping. “We need to examine in detail the regulation of brain capillary clearance and also analyze how that process may be related to insufficient blood supply and ischemic stroke, which is the most common form of stroke, to help advance the development of targeted treatments.”
Leveraging the broad, collaborative infrastructure and robust resources of the Center for Neural Circuit Mapping, other team members were Rachita Sumbria, co-first author/co-corresponding author and associate professor in the Chapman University School of Pharmacy; Hai Zhang, co-first author and postdoctoral researcher in the UCI Department of Anatomy & Neurobiology; Rudy Chang, co-first author and Chapman University School of Pharmacy graduate student; Jiahong Sun, postdoctoral researcher at Chapman University; David Cribbs, professor-in-residence at the UCI Institute for Memory Impairments and Neurological Disorders; and Todd Holmes, UCI professor of physiology & biophysics.
This work was supported by the National Institute on Aging under award numbers R01AG062840, R01AG072896, R35127102, RF1 AG065675 and R01NS121246 and by National Institute of Neurological Disorders and Stroke grant R01NS20989.
Related stories
About UCI Health
UCI Health is the clinical enterprise of the University of California, Irvine, and the only academic health system in Orange County. Patients can access UCI Health at primary and specialty care offices across Orange County and at its main campus, UCI Medical Center in Orange, Calif. The 459-bed, acute care hospital, listed among America’s Best Hospitals by U.S. News & World Report for 23 consecutive years, provides tertiary and quaternary care, ambulatory and specialty medical clinics, behavioral health and rehabilitation services. UCI Medical Center is home to Orange County’s only National Cancer Institute-designated comprehensive cancer center, high-risk perinatal/neonatal program and American College of Surgeons-verified Level I adult and Level II pediatric trauma center and regional burn center. UCI Health serves a region of nearly 4 million people in Orange County, western Riverside County and southeast Los Angeles County. Follow us on Facebook, Instagram, LinkedIn and Twitter.
About UCI School of Medicine
Each year, the UCI School of Medicine educates more than 400 medical students and nearly 150 PhD and MS students. More than 700 residents and fellows are trained at the UCI Medical Center and affiliated institutions. Multiple MD, PhD and MS degrees are offered. Students are encouraged to pursue an expansive range of interests and options. For medical students, there are numerous concurrent dual degree programs, including an MD/MBA, MD/MPH, or an MD/MS degree through one of three mission-based programs: the Health Education to Advance Leaders in Integrative Medicine (HEAL-IM), the Program in Medical Education for Leadership Education to Advance Diversity-African, Black and Caribbean (PRIME LEAD-ABC), and the Program in Medical Education for the Latino Community (PRIME-LC). The UCI School of Medicine is accredited by the Liaison Committee on Medical Accreditation and ranks among the top 50 nationwide for research. For more information, visit medschool.uci.edu.
About the UCI Brilliant Future campaign
The Brilliant Future campaign, publicly launched on Oct. 4, 2019, aims to raise awareness and support for UCI. By engaging 75,000 alumni and garnering $2 billion in philanthropic investment, UCI seeks to reach new heights of excellence in student success, health and wellness, research and more. The School of Medicine plays a vital role in the success of the campaign. Learn more by visiting https://brilliantfuture.uci.edu/uci-school-of-medicine.
About the University of California, Irvine
Founded in 1965, UCI is a member of the prestigious Association of American Universities and is ranked among the nation’s top 10 public universities by U.S. News & World Report. The campus has produced five Nobel laureates and is known for its academic achievement, premier research, innovation and anteater mascot. Led by Chancellor Howard Gillman, UCI has more than 36,000 students and offers 224 degree programs. It’s located in one of the world’s safest and most economically vibrant communities and is Orange County’s second-largest employer, contributing $7 billion annually to the local economy and $8 billion statewide. For more on UCI, visit www.uci.edu.
