Of spice and dog breeds

Got some catching-up to do.  Since my last blog post about six months ago, I’ve retired from my professorial job at Rutgers, which means I’ve stopped seeing patients.  But I’ll still do clinical PSP trials as a volunteer, so I’ll still see that kind of patient.  Retiring from Rutgers also means that I retire from teaching.  But I’ll continue my work with PSP, so I’ll continue that kind of teaching.  Still working a little on my own research, which is mostly about that cluster of PSP in France.  Then there are all of my non-neurological retirement activities (see spouse for details).  I’ve been neglecting my PSP blog, but that has just changed.

Today a journal article caught my eye.  It found that a slight modification of a naturally-occurring component of turmeric may slow or halt the progression of the tau-based neurodegenerative disorders like PSP and Alzheimer’s disease. At least in cells growing in a dish.

First a little background: You probably know that the brain cells being damaged in PSP contain abnormal clumps of a normal protein called tau.   You also know that the clumps are called neurofibrillary tangles.  In the course of forming the tangles, tau molecules first form smaller accumulations called oligomers (Greek for “a few parts”).  The oligomers are toxic but they’re still soluble in water, like ordinary, monomeric tau (you got it: “one part”).  But the oligomers have an Achilles heel: They tend to form larger clumps, the neurofibrillary tangles, which are no longer soluble in the brain cells’ fluid.  The tangles’ inability to float around and interact with things renders them harmless and means that they serve the useful purpose of taking the toxic, soluble oligomers out of the brain cells’ internal soup.

More background: You’ve heard of turmeric, a popular spice related to ginger.  It’s a traditional remedy for what ails you and some responsible researchers feel that it may actually help certain inflammatory conditions and the metabolic syndrome (high blood pressure, diabetes, abnormal lipids and obesity).  But despite some success in animal models, it has never been proven by modern standards to help any medical condition in actual humans.  Furthermore, we don’t know which of the dozens of chemical components of turmeric explains its apparent benefits.  One minor component of turmeric is curcumin, which by itself is used as a coloring agent in food and cosmetics.  Its chemical structure renders it very difficult to absorb from the digestive tract into the blood or from the blood into the brain.  Here’s the good news: We’ve known for a few years that curcumin, when directly applied to brain cells in a dish, can actually can induce the water-soluble, toxic tau oligomers to form insoluble, harmless neurofibrillary tangles. 

The new journal paper is from neuroscientists at the University of Texas Medical Branch in Galveston and the University of Palermo, Italy.  The group’s leader is Rakez Kayed, PhD of UTMB, a respected and well-published researcher in tauopathies and other forms of neurodegeneration.  The first-named author is Filipa Lo Cascio, PhD, a young post-doctoral trainee in his lab.  They cultured two off-the-shelf types of neural cells and added abnormal tau extracted from autopsied brain tissue from people with PSP, Alzheimer’s disease and dementia with Lewy bodies.  Ordinarily, the abnormal tau would misfold, cause the normal host’s tau to misfold in the same disease-specific way, form oligomers, cause damage, spread to other cells and eventually be taken out of action by forming neurofibrillary tangles.  The curcumin caused the toxic oligomers to more rapidly form tangles, thereby reducing their cell-to-cell spread.  By making the tau less soluble, the curcumin also limited its ability to damage components of the cells with the result of improving the cells’ survival. 

The researchers didn’t actually use curcumin itself, as that compound has no future as a neurological treatment because, as mentioned, it can’t get into the brain. So they tweaked its structure by replacing some hydroxy (-OH) and methoxy (-O-CH3) groups (don’t worry about it) with fluorine atoms.  The resulting compound, which they dubbed CL3, had the same beneficial effect regardless of whether the abnormal tau introduced into the cells was from people with PSP, Alzheimer’s or dementia with Lewy bodies. 

The next step is for another lab to replicate the results using different methods.  At the same time, researchers could try the experiment in mice that have received an abnormal tau gene that forms aggregates and kills their brain cells.  That’s currently the best lab model for PSP and the other tauopathies.  But the multiple examples of drugs that prevented this sort of mouse tauopathy and then failed to prevent PSP in clinical trials show that the mouse models, albeit based on human tau, are inadequate as surrogates for people with real PSP or other tauopathies.

The experiments of Lo Cascio, Kayed and colleagues also confirmed that the aggregates forming from tau taken from people with different tau disorders differ from one another in some other important ways.  That’s the new, hot idea of tau strains – they’re like dog breeds.  They’re all tau, but they differ in some important details and when they reproduce (i.e., by templating their abnormal folding pattern onto normal copies of tau in a host cell), their specific variation continues in the next generation.  More about tau strains soon.

Now let’s see if I can keep this up.

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