Poison isn't always bad for you. The venom of some creatures may actually have medical applications.
The practice of turning venoms from animals into cures for people dates back to at least ancient Rome, according to a 2015 paper in the World Journal of Biological Chemistry. The Romans looked to animal venoms for ways to treat conditions including smallpox and leprosy.
Today's researchers still look to the animal kingdom's many venoms in their search for treatments. Live Science has rounded up some of the early research on seven creatures whose poisons may one day be made into drugs. These could treat diseases ranging from type 2 diabetes to breast cancer.
1. Platypus' spurs
During mating season, the male platypus (Ornithorhynchus anatinus) has an unusual trick up its sleeve: venom-filled spurs. The spurs [pictured above] are located on the animal's hind leg and are active only in spring. Scientists speculate the spurs are used in competition, to disable other males during fights. But the venom may also help treat type 2 diabetes: A 2016 study published in the journal Nature described how a hormone called glucagon-like peptide 1 (GLP-1), which is produced in the gut of the platypus and helps regulate the animal's blood-glucose levels, is also found in the platypus's venom.
When injected into a victim, the hormone may rapidly lower blood glucose levels to the point of debilitation, the researchers said. But a compound that quickly lowers blood sugar levels could be a handy treatment for people with diabetes, the scientists added.
Much more research is needed to determine whether this compound can be made into a safe drug for people, the investigators said. But the researchers also found that this hormone breaks down at a much slower rate than the same hormone in humans, which suggests that it could be used to help maintain a proper blood sugar balance in people's bodies.
2. Spiders' fangs
Credit: The Lancet
Spiders have evolved a wide variety of venoms to subdue their prey, making these creatures a rich avenue for drug discovery, said a 2010 review of spider venom research published in the journal Toxins. For example, a protein called M-TRTX-Gr1a that is found in the venom of the Chilean rose tarantula [pictured above] could help treat muscular dystrophy by preventing or slowing down the deterioration of muscles, the researchers wrote.
In addition, researchers said they hope that further study of spider venoms may lead to treatments for cardiac arrhythmias, spinal cord damage and other conditions. [Spider-Man: 5 Weird Effects of Real Spider Bites]
Spider venom could also one day treat erectile dysfunction, the researchers said. In their review, they noted that people in South America who are bitten by a spider called the "armed spider" can experience priapism, or a long-lasting erection. The researchers also cited a 2008 study published in the journal BJU International that showed that rats injected with one toxin from the Brazilian spider Phoneutria nigriventer developed an erection, with no side effects.
3. Sea anemones' tentacles
The sea anemone Heteractis magnifica [pictured above] uses its venom as both a defense against predators and as a way to capture prey. The venom includes a mix of poisons, such as neurotoxins, and is found in cells within the creature's tentacles. Recently, researchers discovered that this venom can also destroy human lung and breast cancer cells, according to findings published in 2016 in the book "The Cnidaria, Past, Present and Future" (Springer International Publishing, 2016).
In experiments conducted in lab dishes, researchers found that this anemone's venom kills human lung and breast cancer cells by inducing the cells to undergo apoptosis, or programmed cell death. Furthermore, the sea anemone's venom also helped control cell cycle progression in these cancer cells, limiting the uncontrollable growth that is characteristic of cancer cells. More research is needed to determine how exactly the venom exerts these effects, and whether a drug based on this venom would work the same in people, the researchers said.
4. Scorpions' stingers
The scorpion's tail ends in a telson, or stinger, which the scorpion uses to inject its prey with a venom that can paralyze or kill. But in a 2013 review in the journal Molecular Aspects of Inflammation, researchers suggested that a drug based on the venom could one day also be used to treat people with autoimmune diseases.
Many autoimmune conditions develop when the body loses the ability to regulate certain controls of the immune system, which then attacks the body's own tissues. Scorpion venom contains compounds that could stop this response by inhibiting certain potassium channels in cells, preventing inflammation. Working via a similar method, the venom could also have applications in preventing the rejection of donated organs, the study noted. [9 Most Interesting Organ Transplants]
5. Cone snails' barbs
Cone snails are sea snails that, depending on their size, prey on small fish or marine worms. The snails use a needle-like barbed "tooth" that contains venom, and shoots out and paralyzes their prey. But their venom actually has therapeutic properties as well: Researchers have developed a painkiller called Prialt, which is 1,000 times more powerful than morphine, from cone snail venom.
The drug is a synthetic form of a peptide found in the venom and was approved by the FDA in 2004. However, it has to be directly injected into the spinal column, because it cannot cross the blood-brain barrier, meaning that if the drug is taken orally or even injected into the bloodstream, it cannot enter the brain.
However, a 2015 study in the journal Nature showed how certain carrier molecules could help Prialt cross the blood-brain barrier. This might mean that, eventually, Prialt will become easier to administer, perhaps even being produced in pill form.
6. Centipedes' fangs
Credit: Siriwut, W. et al. ZooKeys 2016
Large centipedes, such as those in the order Scolopendromorpha and the family Scolopendridae, have venomous fangs located on their first pair of legs. They use these fangs to defend themselves against predators and capture prey that can include rats, amphibians and even some reptiles. But this venom may have a number of medical uses as well, a 2015 review in the journal Toxins showed. So far, about 50 compounds in centipede venom have been found to have pharmacological properties, the researchers wrote.
For example, a drug based on centipede venom could be used as a local anesthetic to dull pain, as an anticonvulsant to treat epilepsy or as a potential antibiotic. However, these possibilities, which are based on discoveries such as inhibitors or microbial properties in the venom, require further research before the venom could be used clinically, researchers said. [No Creepy Crawlies Here: Gallery of the Cutest Bugs]
7. Leeches' teeth
The leech Hirudo medicinalis [pictured above] has about 100 tiny, sharp teeth that it uses to dig into a host, before it injects compounds that reduce pain and prevent blood from coagulating. The leech's venom, called hirudin, is produced in the animal's salivary glands.
In a 2016 study published in the journal Molecular Genetics and Genomics, researchers dove into the many genes of the leech that encode compounds within hirudin, and showed that leeches can actually express numerous types of the venom. A drug based on the compounds in hirudin could have therapeutic use, for example, in treating varicose veins or increasing circulation, the study authors said.
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