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  • [♪ INTRO]

  • Scientists have been turning to the animal world for inspiration for a long time.

  • Some of our first attempts at powered flight were

  • based on the flapping of birds' wings.

  • Velcro was invented after observing how burrs stick to fur.

  • And engineers are mimicking termite mounds when

  • designing ventilation systems for buildings.

  • But maybe the first thing we think of,

  • when it comes to deriving useful stuff from the natural world, is medicine.

  • And animals have clued us into all sorts of remedies over the years.

  • Take frogs, for instance.

  • They've been around for about 300 million years,

  • which has given them plenty of time to learn how to

  • defend themselves against disease-causing microbes.

  • That's only become more true as humans have reshaped their habitat,

  • so it's no surprise that these amphibians have developed a lot of defenses.

  • Scientists have identified more than 100 antibiotic substances

  • produced by frog species around the world, specifically, in their skin.

  • These substances are peptides,

  • which are short chains of organic compounds called amino acids.

  • Those are the same components that make up proteins,

  • a peptide is similar, but generally shorter and less complex.

  • Many organisms, including frogs and humans, make peptides that target microbes.

  • These play an important role in the body's innate immunity,

  • which is the part of your immune system that you're born with.

  • It's your first line of defense against pathogens.

  • Antimicrobial peptides work differently from traditional antibiotics.

  • Certain antibiotics kill bacterial cells by binding to

  • specific proteins on the cell membrane and weakening it until it bursts.

  • Antimicrobial peptides instead exploit the main component of cell membranes, phospholipids.

  • Those are molecules that form a double layer to enclose the cell.

  • And antimicrobial peptides disrupt those layers and punch the membrane open.

  • This makes it difficult for microbes to develop resistance to the peptides,

  • since they'd need to redesign their membrane to stop them.

  • Which is justsuper unlikely.

  • Scientists have known for a long time that frog skins contain peptides

  • capable of killing not just bacteria, but also viruses and fungi.

  • So it seems like they'd make a useful antibiotic.

  • Except, because these peptides are toxic to humans, our bodies destroy them.

  • Or at least they did... until one group of researchers found a way

  • to substitute some of the amino acids in the chain and

  • make the peptides less toxic and less easily destructible.

  • This opened up a world of antimicrobial peptides

  • for scientists to apply to various diseases.

  • One example is a peptide called Brevinin-1BYa,

  • found in the skin secretions of the foothill yellow-legged frog.

  • In a 2006 study, researchers found that a tweaked artificial version

  • of this peptide could inhibit the growth of

  • methicillin-resistant Staphylococcus aureus bacteria, better known as MRSA.

  • That's a superbug that causes outbreaks in hospitals, schools, and nursing homes.

  • The synthetic frog peptide still needs to be

  • studied further before it can be applied clinically.

  • But researchers have now identified more than 350 types of peptides

  • belonging to this Brevinin family, with applications ranging from

  • cancer treatment, to insulin production, to wound healing.

  • Another inspirational ancient animal with a robust immune system is the shark.

  • Sharks have existed for about 500 million years,

  • and have the oldest form of adaptive immunity we know of.

  • Unlike the innate immune system, the adaptive, or acquired, immune system

  • is one that you...

  • acquire.

  • When antigens like viruses or toxins enter the body,

  • it develops specialized proteins called antibodies to fight them off.

  • The antibodies recognize and bind to specific parts of the invader,

  • known as antigens.

  • In 1995, scientists discovered that sharks produce an antibody

  • that has some potential advantages compared to our human ones.

  • You could say when it comes to fighting pathogens,

  • this shark antibody has more teeth.

  • Researchers thought it could be really useful as a

  • diagnostic or treatment for a variety of diseases.

  • Sharks' secret weapon lies in the part of the antibody that binds to antigens.

  • It's called the variable domain, or VNAR.

  • Compared to your basic Y-shaped human antibody,

  • VNAR is smaller and has a different shape

  • that allows it to penetrate deeper into tissue.

  • That gives it better access to hidden or hard-to-reach binding points on antigens.

  • Scientists can also change how fast VNAR is broken down

  • or absorbed by your body.

  • On top of that, it's also more stable at high temperatures.

  • Armed with these advantages,

  • many research groups are developing VNAR as potential therapies

  • for conditions including malaria, multiple sclerosis, solid tumors, polyarthritis,

  • and even for treating viral diseases.

  • They're even creating a VNAR antibody library using nurse sharks.

  • Another animal-generated treatment comes from a more unlikely source: venom.

  • Venoms are some of the most complex chemical compounds on Earth.

  • They're produced by 15% of all animal species.

  • These toxins have incredible potency, stability, and speed.

  • But we know what you're thinking: How can something toxic be used in medicine?

  • First, not everything that's toxic to other animals is toxic to us.

  • Out of over 100,000 spider species, only a few are dangerous to humans.

  • Second, venoms can precisely target specific molecular components.

  • This amazing precision is what makes dangerous side effects very unlikely.

  • And it also makes venom a targeted tool for potential therapies.

  • Like frog skin, venom contains peptides.

  • But in this case, the peptides target ion channels.

  • The job of a cell membrane is to keep the stuff inside the cell on the inside,

  • and the stuff outside the cell on the outside.

  • But ion channels create a pathway

  • for electrically charged atoms or molecules, called ions, to pass through.

  • When this happens, the difference in charge on the outside

  • versus the inside changes.

  • That triggers a physiological effect, like a muscle contraction.

  • So, by interacting with certain ion channels,

  • these peptides can alter certain bodily functions.

  • For example, Hi1a is a peptide found in the venom of

  • Australian funnel-web spiders, a group that includes a few dozen species.

  • This potentially deadly venom is a mixture of 3,000 molecules

  • and has been described asthe most complex chemical arsenal in the world.”

  • The Australian-based researchers responsible for that description were looking for

  • a way to reduce the amount of brain damage that occurs after a stroke.

  • And Hi1a proved to be exactly what they needed, because even though the

  • funnel-web spider can kill humans, this particular peptide is harmless to us.

  • And crucially, Hi1a has an interesting way of

  • interacting with a particular ion channel in the brain.

  • It's called acid-sensing ion channel 1a.

  • And it's responsible for the neuronal damage that results after a stroke,

  • due to a build-up of acid.

  • In experiments performed on rodents,

  • when this ion channel was inhibited through genetic manipulation or drugs

  • it decreased neuronal death.

  • The researchers found that Hi1a can also inhibit this ion channel.

  • A small dose given to rats within 4 hours of a stroke

  • reduced the brain damage that occurred by 90%.

  • And what's great about Hi1a is that it's reversible.

  • So it allows the ion channel to begin working again

  • after the dangers created by the stroke have passed.

  • In addition to Hi1a,

  • venoms provide many other useful peptides that are being investigated as

  • treatments for conditions including epilepsy, cancer,

  • autoimmune diseases, and chronic pain.

  • Another unlikely critter that's provided us with an arsenal of medicines

  • is the marine sponge.

  • They may seem simple and unassuming.

  • But in fact, they're something of a treasure trove.

  • Unlike most animals, sponges can't move and don't have physical defenses.

  • This makes them vulnerable to predators like fish and turtles.

  • But they do have a lot of defensive chemicals to deter these predators.

  • And many of these chemicals are useful to humans.

  • Each year, hundreds of new chemical compounds are discovered

  • from sponges that have interesting pharmacological possibilities.

  • Some have already made it into clinical trials as

  • treatments for cancer, microbial infections, inflammation, and more.

  • One of the earliest examples is a commonly used

  • chemotherapy drug called Cytarabine, also known as Ara-C.

  • It was developed from an extract of sponges that live on the Carribean Reef.

  • Specifically, it came from their nucleosides,

  • which are parts of nucleic acids like DNA and RNA.

  • It's currently used to treat lymphoma and leukemia, while a related medicine is

  • used to treat lung, pancreatic, breast, and bladder cancers.

  • Many forms of chemotherapy kill cancer cells by preventing them from dividing.

  • And Ara-C is in a specific class of chemotherapies called antimetabolites.

  • They prevent cell division by infiltrating the cells and gumming up the works.

  • Because Ara-C resembles a specific component of DNA,

  • cells can grab it by mistake when they're trying to copy their genomes and divide.

  • But because it's not quite right, it messes up DNA replication,

  • and therefore halts cell division.

  • And it's all thanks to the humble sponge,

  • which is one of several coral reef dwellers being looked at for potential treatments

  • for everything from viruses to Alzheimer's disease.

  • Finally, from coral reefs,

  • we go to a pretty unusual source of medical research subjects:

  • dead animals on the roadside.

  • Yes, we're talking about roadkill,

  • which has given us a new, hassle-free way to study the microbiome.

  • A microbiome is a community of microorganisms that live together.

  • All living things have them, including us.

  • But they're also found in soil, ocean water, and buildings.

  • In humans, they're an essential part of our development, nutrition, and immunity.

  • Studying them can help us learn more about infectious diseases

  • and chronic illnesses, and even discover new medicines.

  • And researchers at the University of Oklahoma came up with an

  • out-of-the-box idea for investigating microbiomes.

  • Rather than search for novel microbial samples in live critters in nature,

  • which presents a host of challenges, they find it more convenient to use roadkill.

  • They search for animals who haven't been dead too long,

  • so their microbiome closely resembles that of a live animal.

  • Then they swab them and bring the tubes back to the lab.

  • There, they isolate microbial samples and

  • identify potentially interesting compounds.

  • From bacteria found in the ear of an opossum,

  • they found molecules that can prevent a common fungal infection.

  • The molecules are called serrawettins.

  • And in the team's experiments,

  • they were able to prevent the growth of the yeast Candida albicans.

  • Candida naturally lives on and inside humans without causing any problems.

  • They even help with gut health, nutrient absorption, and digestion.

  • However, when this yeast overgrows, it causes

  • candidiasisthe most prevalent form of fungal infection in humans.

  • But because it's usually a harmless passenger,

  • instead of eliminating Candida completely,

  • it would be most beneficial to control its growth.

  • The team found that low concentrations of serrawettins could

  • moderate the growth of Candida, rather than wipe it out.

  • So it's possible that serrawettin-based therapies

  • could be on their way to a pharmacy near you.

  • And you can thank roadkill, researchers, and the field of

  • animal-inspired medicine for your cure.

  • But in the meantime, I'd like to thank our patrons for making this,

  • and every episode of SciShow possible.

  • We couldn't do it without you guys.

  • If you'd like to become a part of our amazing community,

  • you can check out patreon.com/scishow.

  • [♪ OUTRO]

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5 Times Animals Inspired Better Drugs

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    joey joey に公開 2021 年 07 月 15 日
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