Some plants and fungi don’t really deserve their wicked-sounding names. The devil’s candle, for one, is simply a pretty purple flower with a knack for being shiny. Likewise, Dracula vampira won’t suck your blood, but it might stun you with its floral vampiric hood.
But then there’s the death cap mushroom, which truly lives up to its ominous moniker. The fungus is responsible for more than 90 percent of mushroom-related deaths worldwide with a fatality rate hovering between 25 and 50 percent in those who ingest the fungus. It also causes plenty of more non-lethal poisonings, which often follow large blooms of the mushroom, such as the 2016 superbloom in the San Francisco Bay Area.
The poisonous mushroom is also becoming an increasing concern as the fungus spreads more urban areas in places like British Columbia. Even though the invasive fungus has long since made its way from its native Europe to North America and around the globe, scientists are still struggling to understand the myriad molecular mechanisms that cause its lethal ends — much less able to develop a tried-and-tested antidote.
But that could all change with a new study published Tuesday in the journal Nature Communications. The research uses the emerging gene-editing technology, CRISPR, to identify an FDA-approved molecule that could potentially serve as an antidote to the mushroom’s most lethal toxin.
“Our groundbreaking research has tackled a crucial inquiry with remarkable results,” Qiaoping (Kevin) Wang tells Inverse. Wang is a co-author of the study and head of the Department of Pharmacology and Toxicology at Sun Yat-Sen University in China.
Why Is the Death Cap Mushroom Lethal?
The death cap mushroom (Amanita phalloides) is a fairly ordinary-looking mushroom with an olive or yellow-green covered cap, though mature mushrooms can have brown markings as well. But don’t be fooled — this unassuming appearance belies a highly toxic nature.
Several classes of toxins make up this poisonous mushroom, but there’s one in particular that makes the death cap lethal: α-amanitin. It’s also known as alpha-amanitin and falls into a broader class of poisons known as amatoxins.
A lethal dose of amatoxin is only 0.1 milligrams per one kilogram (2.2 pounds) of body weight. Therefore, consuming five to seven milligrams of the toxin — which a single death cap mushroom could easily contain — may very well kill you, but not right away.
You’ll often experience vomiting or nausea within eight to twelve hours of consuming the mushrooms, but those symptoms may fade afterward and you may feel perfectly normal. But this is actually when the most dangerous period of poisoning occurs. The toxin primarily acts on the liver, though other organs like the kidney could be affected. Liver and kidney damage will set in within three to six days after poisoning, leading to death if untreated. Victims of severe death cap mushroom poisoning who survive may require liver transplants.
We know that α-amanitin halts cellular production by targeting RNA, which is a molecule found in all cells that helps translate genetic information into essential proteins. But scientists haven’t been to identify the “key players” or all the molecular pathways that α-amanitin uses to trigger cellular death — until now.
How Scientists Found a Possible Antidote
Before scientists in the latest Nature study could find an antidote to the death cap mushroom, they needed to hone in on the pathways that α-amanitin takes to poison the body.
To figure this out, the researchers deployed a type of genetic technology known as CRISPR screens, which introduce “genetically encoded” disturbances into a group of cells according to a 2022 paper. These CRISPR screens are helpful tools for scientists to identify genes or molecular pathways involved in drug resistance, viral infections, and toxic poisoning.
Using this method on laboratory mice, scientists found a couple of different molecular pathways involved in α-amanitin poisoning, but one stood out: N-Glycan biosynthesis — a process that helps modify and maintain the function of different kinds of proteins in cells. And one particular enzyme — STT3B — was especially crucial for making N-Glycan biosynthesis happen. Problem solved, right? The scientists just needed to get a drug that could inhibit STT3B, and they could block α-amanitin from poisoning the body. Not so fast.
“So far, no FDA-approved molecule has been reported to specifically inhibit STT3B,” write the researchers.
But the scientists didn’t give up. After honing in on STT3B, the researchers did a virtual screening of existing FDA-approved molecules that could potentially block the toxin α-amanitin. After looking at 34 different compounds, they found one that worked especially well at increasing the survival of human and mouse cells exposed to the toxin.
“This molecule holds immense potential...”
The potential antidote: a type of fluorescent dye known as indocyanine green. Indocyanine green has been an FDA-approved compound since the 1950s and has been widely used as a diagnostic tool in liver function tests. According to their results, indocyanine green “significantly prevented” cell death due to α-amanitin poisoning and blocked the poison’s toxic effect on the liver.
“This molecule holds immense potential for treating cases of human mushroom poisoning and could mark the first-ever specific antidote with a targeted protein,” Wang says, adding that the molecule could “improve survival after amanitin poisoning.”
The scientists found few — if any — side effects of the drug at a low dose, though there was a caveat: indocyanine green was most effective when given four hours after poisoning occurred, and wasn’t very effective at all when administered eight or twelve hours after exposure to the toxin — perhaps because the toxin causes “irreversible damage” not long after poisoning. So if indocyanine green were given as an antidote, individuals would need to receive treatment quickly after poisoning. And, of course, there are inherent limitations in the study, because the antidote was tested on mice — not humans.
“While the results are promising, further clinical experiments are needed to determine whether [indocyanine green] has similar effects in humans,” Wang says.
Can We Use CRISPR to Find Other Antidotes?
But the implications of the study could extend far beyond just the death cap mushroom. Using the researchers’ novel approach of combining CRISPR screens with virtual review of FDA-approved molecules we could help find antidotes for any number of toxins.
In fact, the scientists behind the study told Inverse they were currently using their methods to research an antidote for another unnamed “common and important toxin.”
Ultimately, Wang believes this combination of CRISPR and virtual drug screens is a “very powerful strategy to find novel antidotes for other lethal toxins.”