Scientists Build Ferroptosis Inhibitors to Curb Cell Death Process Linked to Alzheimer’s Disease and Cancer
Mouse intestinal cells without radiation exposure (image 1) show intact actin layers, in green. Cells exposed to radiation (image 2) show ferroptosis-driven actin damage. Treatment with FerroLOXIN-1 (image 3) and FerroLOXIN-2 (image 4) reduced ferroptosis-driven cellular damage caused by radiation exposure. (University of Pittsburgh)
November 20, 2023
Scientists have struggled to tame ferroptosis, a cell death process linked to brain trauma, acute radiation syndrome, Alzheimer’s disease and cancer. Unlike apoptosis, ferroptosis is not a routine part of a cell’s life cycle. Using a creative trick to block a first step in the process, a team involving NCATS translational scientists created a new class of targeted treatments to stop ferroptosis.
Researchers at the University of Pittsburgh, the University of Toruń in Poland, NCATS and other institutions worked together to design, build and test two new ferroptosis inhibitors. Their work appears in the Proceedings of the National Academy of Sciences.
Ferroptosis kills cells that have too much and too little of three things: too much iron, too many destructive oxidized versions of fatty molecules called lipids, and too few thiol compounds to turn oxidized lipids into less harmful alcohols. Existing drugs that target iron or oxidized lipids could stop ferroptosis. However, targeting iron and oxidized lipids also can interfere with healthy cell processes, leading to unwanted side effects.
The researchers began building their ferroptosis inhibitors using molecules that block the enzyme 15LOX-2. 15LOX-2 uses oxygen to break down lipids as part of healthy cell functioning, so simply shutting it down to stop ferroptosis could damage healthy cells. Instead, the researchers targeted 15LOX-2 at the start of ferroptosis, when it combines with a structural protein, PEBP1.
“In ferroptosis, this normal 15LOX-2 enzyme becomes a zombie when it combines with PEBP1 and starts metabolizing the cell membrane,” explained Ganesha Rai, Ph.D., a study coauthor and NCATS chemistry technology scientist. The 15LOX-2/PEBP1 combination oxidizes lipids in the cell’s membrane, igniting a cascade that kills the cell.
The scientists focused on an empty “pocket” in the structure of 15LOX-2. 15LOX-2 uses the pocket to hold a key piece of the lipids before breaking them down by adding oxygen. That pocket gets bigger when 15LOX-2 combines with PEBP1. The researchers attached pieces to their inhibitor molecules that would find and partially fill only the bigger pocket of 15LOX-2/PEBP1, not the smaller pocket of 15LOX-2.
Like a pants pocket that’s too full to fit a wallet, a 15LOX-2/PEBP1 pocket with an inhibitor in it has no room to correctly hold oxygen and a lipid. This means 15LOX‑2/PEBP1 can’t oxidize lipids and trigger ferroptosis.
New Inhibitors Show Focus, Effectiveness
The team tested two pocket-filling ferroptosis inhibitors: FerroLOXIN-1 and FerroLOXIN-2. Both prevented formation of 15LOX-2/PEBP1’s telltale oxidized lipid in human lung cells, yet neither blocked apoptosis nor other non-ferroptosis cell death processes. Both inhibitors ignored 15LOX-2 enzymes without PEBP1 and protected bronchial epithelial cells from human lungs against ferroptosis triggered by a compound known to start ferroptosis.
The scientists also tested their new inhibitors in mice with acute radiation syndrome, a condition in which ferroptosis plays a fundamental role. Without FerroLOXIN-1 or FerroLOXIN-2, irradiation was 100% fatal in mice after 19 days. In mice treated with FerroLOXIN-1 or FerroLOXIN-2, 75% and 80%, respectively, were alive after 19 days.
The results suggest the inhibitors may have many uses. “This opens up the field for researchers to test these molecules in many diseases and conditions in which ferroptosis may play a role,” said Anton Simeonov, Ph.D., a study coauthor and NCATS scientific director.
Additional funding was provided by the National Cancer Institute; the National Heart, Lung, and Blood Institute; the National Institute of Allergy and Infectious Diseases; the National Institute of Diabetes and Digestive and Kidney Diseases; the National Institute of General Medical Sciences; and the National Institute of Neurological Disorders and Stroke.