USU’s Dr. Regina Day Secures $340K NIH Grant to Stop 'Brittle Blood' and Toxic Iron Following Radiation Exposure

Backed by a newly awarded NIH/NIEHS R21 grant, the Uniformed Services University's Dr. Regina Day explores the molecular mechanics of red blood cell lysis to prevent iron-associated systemic organ failure following radiation exposure.

March 10, 2026 by Hadiyah Brendel

When ionizing radiation strikes the body-whether from a misplaced industrial, medical, or military source-the immediate damage to internal organs is invisible. Yet, a deadly, secondary threat quietly unfolds in the bloodstream as red blood cells begin to shatter.

To combat this, Dr. Regina Day, a professor and vice chair of the Department of Pharmacology and Molecular Therapeutics at the Uniformed Services University's (USU) School of Medicine, has been awarded a $340,000 National Institutes of Health (NIH)/NIEHS R21 grant. Day will spearhead a two-year study titled "Mechanisms of Radiation-Induced Hemolysis" to find out why these cells break apart and how to stop them.

While current U.S. Food and Drug Administration (FDA) radiation countermeasures focus on prompting the bone marrow to produce new blood cells, Day's research takes a different approach. She is investigating how to protect the cells already circulating in the body. This award builds on more than five years of her research into why a healthy cell suddenly begins spilling toxic debris after radiation exposure.

The Threat of "Brittle" Blood

Day's research investigates radiation-induced hemolysis, a process in which red blood cells (RBCs) physically break apart. While scientists have documented this reaction since the 1950s, the molecular "why" has remained a mystery.

Her team discovered that ionizing radiation acts as a potent stressor, oxidizing at least two critical proteins inside the RBCs: hemoglobin and carbonic anhydrase II.

"RBCs have some proteins in high concentration," Day explains. "If these proteins change in shape or rigidity, then that can cause the cell to be less flexible and more susceptible to fracturing."

This stiffness creates a lethal defect when the cells reach the spleen, the body's internal quality-control filter. To pass through the spleen's incredibly tiny blood vessels, healthy RBCs must effortlessly fold and flex.

Day's research shows that oxidized RBCs are simply too brittle to bend. Instead, they deform. The spleen's specialized cells recognize this damage and attempt to remove them, but the sheer volume of damaged cells overwhelms the system.

"Following total body irradiation, when there is a large population of defective RBCs, the spleen has difficulty performing the normal uptake and removal process," Day says. "Instead, the radiation-damaged RBCs break open, releasing their contents, including iron, into the blood."

The Iron "Second Wave"

The danger extends far beyond the loss of the blood cells themselves. When RBCs rupture, they release their internal contents directly into the bloodstream. This sudden flood of free iron acts as a secondary poison, shutting down the liver, bone marrow, and other vital tissues.

Worse, this iron toxicity suppresses the body's already-weakened ability to regenerate new, life-saving blood cells.

"A number of recent studies show that iron chelators-specialized drugs that act like 'chemical claws' to bind to iron and safely remove it from the body-increase survival from total body irradiation and decrease tissue damage when used alone as radiation countermeasures," Day notes. "These findings suggest that iron itself is a secondary toxicity following ionizing radiation."

A Two-Pronged Defense

Collaborating with Dr. Yuichiro Suzuki at Georgetown University and Dr. Nicholas Chartrain at USU's 4D Bio³, Day is developing a "shield and clean-up" strategy to stabilize the blood before it releases its toxic contents:

• Antioxidant Shields: The team is testing agents like Vitamin E and N-acetylcysteine to reverse the radiation-induced protein oxidation before the cells break open. The goal is to keep the cells flexible enough to survive the spleen's microvascular squeeze test.
• Iron Chelators as Chemical Claws: If cells do shatter, iron chelators circulating in the blood can grab the free iron. This allows the body to safely flush the poison out before it damages surrounding organs.

Readiness for the Battlefield and Beyond

For military service members and first responders operating in radiation-contaminated environments, this research could offer a critical golden window for medical intervention.

"If you know that a radiation exposure has occurred, then you know that red blood cells are going to be damaged," says Day. "Then you could be prepared to treat it during the early period … well before too many red blood cells lyse, and well before iron reaches a toxic level."

Beyond the battlefield, Day's findings could help cancer patients better tolerate radiation therapy or even address the root cause of "space anemia" in astronauts. By identifying these molecular shields, USU is paving the way for novel methods to protect the body's ultimate lifeline.