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  • {♫Intro♫}

  • When you get scared or stressed, your body sets off what's often called thefight

  • or flightresponse—a series of changes which includes an increased heart rate and

  • faster breathing.

  • And for years, we've thought this response was kicked off by hormones from your adrenal

  • glands.

  • But research published yesterday in the journal Cell Metabolism found that a hormone released

  • by your bones can trigger the response all on its own.

  • We've long known that the sympathetic nervous system, one of the automated branches of your

  • nervous system, prepares you to respond to danger.

  • And this is generally thought to be controlled by the release of stress hormones like adrenaline

  • and cortisol from your adrenal glands on top of your kidneys.

  • But that doesn't explain why people and animals that can't release these hormones

  • for whatever reason can still experience a heart-pounding, breath-quickening, acute stress

  • response.

  • In fact, you can completely remove the adrenal glands from mice and they still react to threats

  • with what looks like truefight or flight”.

  • That suggests there is another source of stress hormones in the body that can turn on the

  • sympathetic nervous system.

  • And for the past few years, one research group has suspected that source may be bones.

  • After all, the whole point of having a skeleton is to let us run away from predators and protect

  • our organs from harm.

  • And studies have found that a bone-derived hormone called osteocalcin improves muscle

  • function during exercise, so it seemed like a good place to start.

  • So, they took some mice, applied an electric shock to their feet to trigger a stress response,

  • and then looked at hormones in their blood.

  • Sure enough, osteocalcin levels surged to 150% in just fifteen minutes.

  • The researchers also exposed mice to a chemical found in fox urine.

  • And just like with the shocks, the mice's osteocalcin levels shot up.

  • They reached a peak just a few minutes after sniffing the scent, then stayed high for hours.

  • And human subjects also showed a similar elevation in osteocalcin when stressed out.

  • This time not smelling fox pee, but asked to do, like a public speaking task.

  • But the team still had to tie this bone hormone to how the brain processes stress.

  • They found that injecting osteocalcin was enough to trigger a mouse's stress response.

  • And injecting a neuron-quieting drug into the fear center of the mice's brains prevented

  • the surge of osteocalcin, while removing the mice's adrenal glands did not.

  • So the osteocalcin-induced response doesn't depend on adrenal stress hormonesit's

  • a complementary switch.

  • They also conducted experiments to figure out how the hormone turns on the fight or

  • flight response.

  • And it turns out it's more about what it turns off.

  • You see, the researchers found that when they injected osteocalcin into mice, the cells

  • within bones called osteoblasts took up more of the neurotransmitter glutamate.

  • Through a string of biological events, this dampens the activity of neurons in the parasympathetic

  • nervous system, a part of your nervous system that works against the sympathetic nervous

  • system a lot of the time, like by slowing down heart rate.

  • So basically, osteocalcin quiets one of your body's key regulating systems, allowing

  • your sympathetic nervous system do its thing unopposed.

  • This alternate stress response fills in some gaps in our understanding, but the researchers

  • say there's a lot more to learn about bone hormones and their effects on the body.

  • And more research is needed on how this alternate stress pathway interacts with adrenal responses

  • if we want to fully understand the relationship between brain and bone.

  • Speaking of needing more researchvaping

  • Ever since vaping became a thing, scientists have been trying to figure out how it compares

  • with smoking in terms of health effects.

  • Companies that make e-cigarettes like to claim that vaping is harmless, or at least way safer

  • that smoking...

  • but what we're finding is that it doesn't cause the same problems that smoking does,

  • it causes some problems of its own.

  • And a paper published recently in the Journal of Clinical Investigation adds to this idea.

  • They found that the presence of e-cigarette vapor altered lung immune cells in mice, making

  • them more prone to infection.

  • The researchers started by exposing the mice to traditional cigarette smoke, vapor from

  • e-cigarettes both with and without nicotine, and then just also regular old air.

  • The e-cigarette smoke didn't trigger the kind of inflammation and structural changes

  • to the lungs that can lead to conditions like emphysemastuff that is seen with traditional

  • cigarette smoke.

  • So, yay.

  • But, when they looked at the lung tissues under a microscope, they saw something strange

  • was happening.

  • Specifically, immune cells called macrophages were getting overly fatty.

  • These fats, called lipids, are important components of cells, and they play crucial roles in lung

  • function and immunity.

  • You see, your lungs are coated with a goo that helps trap foreign invaders while ensuring

  • enough oxygen can get through.

  • It works because it's composed of a special mix of lipids and proteins.

  • And macrophages are responsible for ensuring the goo has the right lipids in it.

  • If macrophages are accumulating lipids inside of them, that suggests there's something

  • going wrong with the goo.

  • And that could leave the lungs susceptible to infection.

  • So, the team ran another experiment.

  • This time, they exposed the mice to e-cig vapor with nicotine, e-cig vapor without nicotine,

  • or regular air for 3 months, and then gave them a lethal dose of flu virus.

  • And it didn't matter if the vapor had nicotine or notthe mice exposed to the vapors were

  • significantly more likely to die.

  • And when given sub-lethal doses, the mice exposed to e-cig vapors lost more weight,

  • which the researchers interpreted as a weaker immune response.

  • They also found increases of inflammatory markers in the lungs, so their conclusion

  • seemed clearexposure to vaping impairs the lung's immune system, even if it doesn't

  • contain nicotine.

  • In mice, anyway.

  • Though, if something similar happens in people, it could help explain the recent rush of pneumonia

  • cases in people who vape.

  • You see, tests have found macrophages similarly laden with fats in patient's lungs.

  • And that kind of connection between human cases and animal models is concerning.

  • But, it doesn't prove that vaping is directly responsible for people's lung infections.

  • Also, it's not yet clear what it is in the vapor causes these changes to lung immune

  • cells.

  • If we can pinpoint that, we might be able to make vaping products safer by switching

  • up the ingredients.

  • Still, studies seem to keep suggesting that vaping is harmful in its own unique waywhich

  • is why health regulatory agencies like the US FDA keep slamming companies for claiming

  • their products are safe.

  • And whether vaping is ultimately less risky than smoking unfortunately remains an open

  • question.

  • Thanks for watching this episode of SciShow News!

  • This episode was brought to you by today's President of Space, Matthew Brant.

  • Thank you, Matthew, for your presidential support!

  • If you want to join Matthew in supporting this channel, you can learn how over at Patreon.com/SciShow.

  • {♫Outro♫}

{♫Intro♫}

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更多的證據表明,吸菸可能是可怕的|科學秀新聞。 (Yet More Evidence That Vaping Is Probably Terrible | SciShow News)

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    林宜悉 發佈於 2021 年 01 月 14 日
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