Stroke victims may one day experience far less brain damage, but arachnophobes might not want to think too closely about their salvation. A molecule found in the venom of Australian funnel-web spiders has been shown to be highly effective at preventing stroke damage in rats, and human trials are next.
Strokes kill an estimated 6.4 million people a year. Far more are left with damage to parts of their brain that can range from mild to utterly debilitating, with treatment making up approximately 3 percent of global healthcare costs. At least 85 percent of these are ischemic strokes, where interruption to blood flow causes the loss of oxygen to part or all of the brain, inducing the death of brain cells.
The curious thing, Professor Glenn King of the University of Queensland told IFLScience, is that, damaging as oxygen deprivation can be, most of these deaths are unnecessary. They result from a process where the brain responds to oxygen loss by triggering cell death through the Acid-sensing ion channel (ASIC1a). Yet if ASIC1a serves any useful purpose, it is not clear what it is. When ASIC1a is turned off in rats they appear unharmed, and can survive ischemic strokes with far less damage than their unmodified counterparts.
We don't yet know the same is true in humans, but it appears likely, and naturally the race is on to find a drug that can block ASIC1a, and be administered quickly to stroke patients. Early this century it was discovered that the PcTx1 molecule in the venom of North American tarantulas has just such a blocking effect.
King was studying this molecule while one of his students, Sandy Pineda, was investigating the venom of Fraser Island funnel-web spiders. King told IFLScience that Pineda came to him one day saying: “You know that tarantula molecule you're working on, I've found one that looks just like it.” This was surprising, since funnel-webs and tarantulas are not closely related. King told Pineda to keep investigating, and she eventually found that the funnel-web molecule closely resembles two PcTx1 molecules with a small bridge between.
Fellow student Irene Chassagnon found the funnel-web molecule, dubbed Hi1a, is far more effective than PcTx1 at blocking ASIC1a, something King ascribed to small differences we don't as yet understand. The trio report in Proceedings of the National Academy of Sciences that when given to rats that had suffered ischemic strokes, Hi1a greatly reduced the damage hours after the stroke had occurred.
King explained to IFLScience, “We only have one current drug for strokes, and it only works if applied within a few hours. Less than 40 percent of people get surgical treatment.” Consequently, for many stroke victims it is a case of wait and hope. The situation is made worse by the fact that the existing drug for ischemic strokes dramatically worsens hemorrhagic strokes. Consequently, precious time is taken up establishing which sort of stroke has occurred.
Hi1a is yet to be tested for hemorrhagic strokes, but if it turns out to be even neutral, let alone beneficial, it could be applied to stroke patients on the way to hospital before the stroke type has been identified. Moreover, if the rodent findings translate to humans, Hi1a will save brain cells hours after existing treatments have ceased to provide any benefit.
There are obvious problems with getting informed consent from stroke victims or their families in the frantic first hours, but King hopes trials can be conducted soon, particularly in cases where alternatives are unsuitable. To arachnophobes' relief, King adds that while funnel-webs are “the easiest venomous animals to milk” there will be no need for a funnel-web farming industry, as Hi1a can already be produced by genetically modified bacteria, and yeast or chemical synthesis should provide cheaper options if mass production is required.
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