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Welcome to the deep dive
Today we're digging into something pretty fascinating a sort of survival strategy used by well arguably one of the tough a ells in your body
The pain neuron that's right what time i'm a excited toxicity
It sounds complicated
But it's this fundamenal uh paradox neurons need electrical exxicity work work
That's their job
But but much of it exactly too much excitement is massive over stimulation can actually kill them
It's the burandout of circuit
It we usually ally heabout this this excital toxity in the brain maybe be after stroker or something the lulutimate
You know the neurrotrxicity just goes haywire correct
That's the classic cns central nervous system context
Thanks
Stroke all hymers
Parkins and and glutimate toxicity is a big player
There
But today we're shifting focus to the prophery to the perural ervous system
Yeah Yeah
Specially ally primary censory neurons that well the you of of hurts thethe're called nnocous ceptors that well pain sensors and to understand how they handle this over datation risk
The research were looking at uses a really uh relatable trtrigger very relaable
If you like spicy food the the ily bepper right so capsazon that's asstuff ff that makes peppers bt
It directly targets a recept on these pain neurons
It's called trpv one and activating trpv one is in just a gentle signal
It basically throws the gate's wide open forcing this huge ge syrolled flood of calseum ions into the cell
Okay so massive cocium inflex that sounds bad
It is bit
It's the definition of toxico overload in this tetext
It les straight in a rocess esessentially cells as burst and depreprety dramatic
So the researchers use this
This frsesasand induced cell death as a model system
Exactly they use this painful process to conduct a well systematic deep analysis
And what they found was well frankly surprising
It's
Here's hihidresresiliprogragram builled into papaneurons and the key involves their mediconria
The powerhouses
The powerhouse is ah ah and using uuh the corery
The brilly counterintututive part
We need to to pack these payneuron seem to have figure out
That maybe operating ssort of alf powers actually better for long term survival than being able to run it full speed
How on that sounds completely backward
We always think you know more might a conondral power better cell health
Right that survival
You're saying these specialized urons deliberately throattle back
That's what the evidence points do
Think about what these cells do
They're on the front lines constantly dealing with heat
Toxon's information patagenence
It's a high risk job
Okay i see
So they need to be tough
Extremely tough
And this research starts to give us the blueprint for why they might be fundamentmore resilience especially compared to neuron stuck the away safely in the brain
And understanding this is huge for figuring out things like diabetic neuroopathy or that awful pain
They could linger after shingles stuff for a powerful nerves or damaged right looks get into the how
How did they discover this
You mentioned the systematic analysis
Yeah
They needed a way to look at everything at once basically
So they used a technique called a genome whde crisper interference screen
嗯的对
Chrp y cricrip p gene editing
But in interference means right so not quite editing like changing the dna sequence cricrisper uses a modifified crispp er system to just dial down or suppress the activity of specific genes tipuearly turned them off
Essentially like flicking demmer switches on thousands of genes one by one that's a great analogy
They did this in cells
They'd engineer to have that trpv one receptor
The capsusates and target so they hit these cells with capsates in the death signal and simultanously use crispry to turn down almost nineteen ty cices es individually wow okay
And the goal was to see which demmer switch when turned down protected the cell from dying precisely which silence gene acted like a shells against the capsusates and toxity
Ity they hit to map out the entire network of genes involved in surviving this kind of insult
They
They anyanything expected first like a sananity check they did
Yeah
The screen correctly flag genes known to be involved in getting that trpv one reception to the cell surface in the first place things related the protein trafficking like the emc complex and flutitelin one
So that told them
The screen was working
It was finding relevant stuff okay
Validation pass
But then came the big one
Then came the big one here's work is really interesting
The pathway that showed up most strongly the genes
Whose suppression offered the most protection belonged the the eletrtrtrananort ort in the etc
The the etc
The core machinery in ma contrary that makes atp p the energy currency that exact machinery
The system that uses oxygen to generate almost all the salelpower
But how if you suppress the etc
Shouldn't the cell just run out of energy and die faster
Especially
When it's already under attack from capsuittion
That's the million dollar question
It's completely kind terintuitive
And they checked suppsuppss in the etc did harm the cells under normal conditions
It's so low conconwth mess with metabolim m so it asn't n't you free protection
There's a cost
Ok
It's not much good good suppsuppss the etc not generally
No
But specifically
When facing this massive calcium overload from complex shoit turning down components of the et c particularally and what called comcomplex a for complex third acted like a powerful break preventing cell death
So the low energy states
Somehow shieelded them from the toxic shock
They didn't just use the christp screreen dit right
They must have confirm this chemically
Absolutely
That's crucial they used well known drugs
The chriser inhibitors that specipletely blocked different parts of the etc like pierset in ck
Which it's complepleone and
And aa icica for compleplex three
And using low doses of of inhibitors
Mimics
The crucis
The results perfectly it protected the cells against capses and death
The conclusion became pretty clear in this specific exctetoxic scenarioh high etc activity isn't protective
It's actually of vulnerability
Wookay that really flips the script
Yes
The the next big question is why ledoes tlowing down the cells power plan protect the research pointed to two different mechanism
So working king in parall
That's right two distinct ways
The dampening the etc helps let's tackle the first one
Which is about managing the initial calcium hit pathway one the cells with the calcium overload itself exactly they found that
When they suppress the etc either using christperor or the chemical inhibitor
The cells actually took in less calcium
When challenge with capsaism
The initial flood wasn't in severe
Okay
So slowing the engine
Somehow partially close with the calcium flood gates
What's the link
The link appears to be metabolic specific actizen to the balance between two key molecules in ad plus and capsad h ah
Nad plus and mea dh
We hear a lot about those in metabolim m mindus of the connection to the etc
So the etc is main besides pumping protoons is to regenerate nad plus from nabh
It takes the electronds carried by nadh
When you slow down the etc regenerate less nad plus s it so the ratio of nad plus to nadh inside the et ac condrio drops you end up with relatively less nad plus in more sca dh okay
Lower nad plus na ggish
Because the etcs sluggisish
And that lower ratio to protective that seems to be the key for this first pathway
And the evidence they gathered was as really quite eleagain they the despecial tool
And
And i called mital lbnaox
Which basically acts like an nadh vacuum cleaner inside the meta grio so high
Ena ally raised the nad plus nadh ratio
And when they did that
When they forced that ratio higher
The cells became more sensitive glugism
They died more easily
The versely the lower ratio higher by etc supplusion was protective
So the nad plus seem to ean equal high risk in the scenario
So the cells essentially keeping its nad plus levels low as a defence mechanism
How did they can firm this link
Could beyond just you know observing the correlation
They uded another metaobattrick
They add piravate to the cells
Parivate is a fuel source
But critically its mettabolism health regenerate nad plus and a effect by ppassing the etc rule in nad plus regeneration for a moment uhh
So if the low nad plus is the reaseetc supplus reduces calcium influx and ding parovate should undo that bchannel in exactly
And that's processsing what happened
When they added piovate to the cells
Treated with etc inhibitors
It reversed the protective effect on calcium influx down tting flood
Flood went back up okay
That nails ls down down pthway one works because slowing the etc lowers the nad plus nadh ratix
And this somehow leads to less calcium getting x does it affect the trpv one channel
Itself the thinking is it might affect
How many trpv one channels ready to be present on the cell surface
Ready to be open talk perhaps
That lower nad plus ratio influence is protein trafficking maybe involving proteins like that fluutilin one they found in the screen
Which helps pull things off the membrane
So fewer gaves mean a smaller flood make sense turn down the power
Lower nad plus a pull some of the triggers off the surface okay solid mechanism
But even said two pathways what happens
If
If overririthe first first oright
And this work is even more interesting
They did overresrited and added both piiovate to restore the nad plus effect on calcium
So another molecule called eeurodine
Which helps bypmemetaolet blocks caused by etc and ambition restoring cell growth
So they basically cancelled out pathway one's benefits and patched up the general metabolet cost of slowing the etc pretty much
And even then even with normal calcium influcts restored and metabolism partially rescued suppressing the etc still provided significant protection the cells still survived much better which means
是的 对个
There has to be a second protective mechanism completely independent of that nad plus calcium regulation
Exactly pathway one reduces the initial trigger the calcium flood
But pathway two seems to deal of what happens
Next it stops the actual executioner
Okay letalk k pathway too
What is the executioner
If it's not just the calcium
Itself react the oxygen species ros those damaging free raticals
Yes
The usual suspects
So the etc is a known source of ros isn't it like a bioproduct of its normal function
If the main source in the celya especially superoxide onions and hyrogen prooxde normally the cell managers them
But understress so things get a hand
So the capcapsasand induce calciine flood triggers
Ros production massively they measured it directly using fllusand censors as soon is that councium rush in from the cacapsazine activation
There was this immediate steady and really dramatic surge in ros inside the metaicticgy
Inside the metaicgy is specifically
But pacritically
If they did the experiment with out calcium in the surrounding medium
So no calcium influx occurred despite trpv one activation
Then this ros burst didn't happen
It absolutely requires the calcium overload entering the mydocondva the cocium overload triggers mitoconconrial ros
And that what kills the cell
That appears to be the lethal blow
And here's the punchline for paath way too the cossing the et c prevents this legal ros burst
Even when calcium influx is normal like in that parvvitorddian experiment exactly
Even when they restored normal calcium influx using pirivate the e tc inhabitors like peercin a or anta isand a still significantly damping that calcium triggered ros production and rescue the cells from death so slowing down the etc engine makes it less likely to sort of explode with ros one flooded with cosc that's the idea and the even pinpoint of the likely source of this lethal ros
Using some very specificc invoitors
They narrowit down to a particular spot on complex three of the etc notice the coo site complex there again
So it seems the complex there is a real weak point
Here it generates the deadly ros
When calcium levels get too high
It appears to be the critical site
You can think of it is a lekey velve in the engine that bursts under the pressure of the calcium m flood right spewing out toxic ros slowing down the whole engine etc supppoo reduces the pressure at that vulf
That's a really specific find
Okay Okay
If ros from complex
There is the direct killer
Then theoretically you could just neutralize the ros directly with anti oxydence right
And that should also save the cells even without touching the etc
And that's the crucial confirmasite
They did exactly that they added compounds
That mimic the cells own anti oxian enzes and without proxite didimutes tes sod things called m for o zero
Foro three and medo tempo
And it work
It worked beautifully adding these the compleicence rescue the cells from the pxzand induced death
Without affecting the initial calcium inflects at all
It directly intercept the executionoah that that des it all together
Nicels let's recap the whole mechanism suppression the electron transport chain protects these cells in two parallels right
Pathway one it loers the medicontural nad plus nadh ratio
This somehow likely a trafficc reduces the amounts councium that initially flims into the cell through the rpv one
And the pathway is sensitive to piravy
Okay
Then pathway two
Pathway two it directly reduces the amount of lethal reactive oxygen species generated by complex third
This response to whatever cocium does get it in this pathway is sensitive
Tive pirave
But stops the ultimate death signal
It's like having two layers of defence
First try to reduce the incoming attack
And second disabled the main weapon
The attacker uses once inside the very good way to put
It's a robust two prongs strategy and the elegance
Here is how widespspread seems to be you mentioned earlier wasn't just about ultilie peppers
This etc suppression strategy worked against other threats too yes
Remarkably
So they tested other things
That caused similar cocium overload problems
It worked against another trpv one activator a toxson from spider vemum
Okay Stop
Trpv one
What else it also protected cells engineered with a gainof function mutation in a different calcium channel
Trpv for this specific mutation is linked to a human eopathy sharkommary tooth disease type to sea so different channel same protection
That's significant it suggest the defence is against the calcium overload
Itself not just trpv one
Exactly
And maybe even more broadly
It also protected against st poor forming toxson called alphaim moleicine
Which is secreted by the bacterium stafle of caucus ororious staff infections
Wow
That toxon just punches holes in the summ brand
Right it causing caucium flux
Right it creates non specific poors leading to calcium overload
And again dalling down the etc helthe celell viviright
It seems to be a general defence against death
Triggered just excessive sustained calcium entry
Which brings us right back to the beginning
Why not accepters
Why would these painon the specifically have evolved develops such a strong reliance on this
This low power high resilience strategy
Well think about their job aga there are primary interface with potentially harmful things in the environment heat chemical irritants
Toxes from microbes
Which flamatory signals
Many these directly activate channels like trpv one
Or even the damage leading to calcium influx
They live in a state of constant potential thread
So they need to be inherently tough
Or the researchers compare them directly to other neuron types
They did
Did they islated ted types es of censorory sigurons from mice the trpv one positive noseseptors painting sensors and compare them to other types
Like mechanical receptors that sense touch and meporeceptors that involved in body positions
And where the nsseseceptors tougher significantly yes
They found that the trpv one plus nsseseptors were inherently more resence ence when exposed to general triggers of excited toxicity
Like using a drug called ionomizen
Which flood cells with councitions
They did didict meyeconroal oxy sentions from stress
Using something called meddoparaaqute
They just vivived than than the censory neuron types
So the resresiliit isn't just something they can turn it
It's part of their baseline state
It seems to be built right into their fundamental biology
And they looked for the reason
Why they get yes
It has to do with their baseline etc levels let it get sing techniques and rna tequencing and protein analysis
They found that trpv one plus nasis eceptors atatally ally a normal conceptions maintain lower bassal expression levels
So many etc components compared to other sensory neurons
Like those high frequency firing mecano acceptors
So they'just built with a smaller engine from the start essentially yes
Yeah
They expressed less of the machinery needed for high capacity and robot receptors
They also found lower levels of factors that promote the building of new metaicconria
So like they've deliberately chose en a lower metoblic ceiling that's fascinating
So the cell body of a pain neuron is prometiably tununto this lower wer eertic tunt this mettolic sweet spots as they apers right
It might mean
They can't support the same kind of sustained high frequency firing that may be a mechanarious after needs for transpitting rapid touch information less atp output overall perhaps
But the trade offis huge the trade office survival by maintaining this lower etc activity intrinsically they gain this building in prooned protection against the sudden potentially lethal councium floods triggered by the very stimulate their design to detect resresence ence prioritize over peak power
It's a really elegant bioological solution for cells living in a dangerous world
A brilliant strategy really for a cell type that needs it the lomemeconal ning signals and survive constant challenges this lower metrocontriary activity is like a preset safety configuration ation
So we started this journey with a jilly paper thinking about pain
And we've ended up
Uncovering what looks like a potentially universal principle of neuroprotection tuning down the meddoconrorial etc
Nasseceptors seem to leverage this inherently
Exactly the achieve resence ence by operating at a lower metaobal capacity
Which simultaneously helps limit the initial councium influx and prevents that lethal ros explosion from complex free
When councium does get too high and understanding this
I mean it a real implicous for doesn't especially for conditions
Where metabooism is already stressed like diabetes
Where we see painful neuropothies
Maybe part of the problem is that the disease disrupts this protective low etc state that's a critical question
This research completely refraged how we might think about about selular health and vulnerility
We often push for maximum efficficereny y maximum advantage
But here evolution seems to have selected maxxmum tic capacity is maxvimual advantage
But this complec ewest st tet it really does flip the script which leaves us with a big thought
Right if this lower etc level l is proprotect tive swedespot for healthy pain neurons what happens when systemic metablic problems hit this like aging severe diabetes chchonic advformation 对不对
Do these conditions push the neurons mettabolism out of that sweet spot
Does that disruption make them paradoxically more vulnerable perhaps contributing to the switch from detecting a cute pain to a generating chronic pathological pain or even nerve degeneration
It's really important avenue for future research
It makes you wonder
If other long lived cells
Ls elells face conconstant strels might use similar metabolic tradeffs
What really stands out to you listening to this
This idea of balancing power versuresresence ence
How could we maybe even use this knowledge
There repeutically for neuropathies lots to think about there
It shows there's still so much
To learn about how sells adapt and survives even down to the level of their power plants
It's absolutely will leave you with those questions to ponder
Thanks for joining us for this deep dive
