Fightaging’s post: A Review of Work on Targeting α-synuclein Aggregates

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Here I’ll point out a recent review of approaches to treat one of the more common synucleinopathies, conditions related to – and thought to be caused by – the abnormal accumulation of α-synuclein in tissues. The pathologies of numerous age-related diseases are linked to various different types of protein aggregate that are observed to build up with age: misfolded or simply overabundant proteins that precipitate to form solid clumps and fibrils. Amyloids are well known for their association with Alzheimer’s disease, but there are many types of amyloid and many corresponding amyloidosis conditions. Similarly tau aggregates are linked to the tauopathies. The list goes on, and of course includes α-synuclein.

Why do these various different aggregates appear in old individuals but not young ones? Most of the evidence to support various theories comes out of Alzheimer’s research, as that field has far more funding and far more scientists working on the problem. Amyloid levels in the brain are dynamic on a fairly short timescale, and the buildup of amyloid has the look of slowly failing clearance mechanisms. These might include general dysfunction in the choroid plexus filtration of cerebrospinal fluid, or in the drainage channels that carry away metabolic waste from the brain, or the mechanisms of the blood-brain barrier intended to shunt unwanted waste out of the brain and into the blood system. These and related forms of dysfunctions could plausibly arise from many of the forms of cell and tissue damage thought to cause aging, or from their consequences such as inflammation, loss of muscle strength, loss of tissue flexibility, and so forth.

The most promising near term approach to protein aggregates is to build treatments than can be periodically applied to clear out the buildup. Immunotherapies are so far the best of ongoing efforts, enlisting the immune system to attack and break down the aggregates, but there is still a way to go towards robust and reliably outcomes. Clinical trials have so far been disappointing, as is often the case in the first round of attempts in any area of medicine. Equally, other classes of rejuvenation therapy will be needed to repair the problems in clearance of aggregates that cause the buildup in the first place: just getting rid of the aggregrates themselves isn’t a full solution, just a much better class of sustaining treatment than is presently available.

Work on clearing α-synuclein runs in parallel to work on amyloid-β, and with the same general pattern of progress, in that immunotherapies look to be the best path forward for now, yet only incremental benefits have been shown to date via this appreach. This review is focused on Lewy body dementia, but the approaches to clearing α-synuclein might be applied to any of the other synucleinopathies, such as Parkinson’s disease.

Disease-modifying therapeutic directions for Lewy-Body dementias

2 thoughts on “Fightaging’s post: A Review of Work on Targeting α-synuclein Aggregates

  1. My reply:

    “Clinical trials have so far been disappointing, as is often the case in the first round of attempts in any area of medicine.”

    Any links to these disappointing trials?

    Also do any of the therapies currently in development deal with the intra-cellular α-synuclein?

    Could the SENSRF get a bit of seed funding from the Michael J Fox Foundation (MJFF) to researching build and deliver an enzyme to remove intra-cellular α-synuclein, similar to the enzyme they are creating to remove oxidized cholesterol from foam cells in artery walls?

  2. Michael Rae‘s reply to me:

    Hi Jim,

    On therapies currently in development targeting intracellular α-synuclein: there are a couple that do so specifically, such as this single-chain variable fragment α-synuclein-targeting antibody (“intrabody”), which would however have to be delivered as a gene rather than a protein (perhaps by plasmids, or once we’re confident of safety via integrating methods as a permanent, ongoing system of damage-repair).

    It’s also possible that some of the existing antibodies in development target intracellular AS, and not just the extracellular aggregate. There’s significant evidence that several of the immunotherapies targeting beta-amyloid do work in whole or in part by being endocytosed by neuronal cells and capturing intraneuronal beta-amyloid, which is then trafficked to the lysosome for destruction; the same may possibly be happening with AS, and I’m aware of little work to explore the question. The recent excitement over cell-to-cell transmission of AS (and of aberrant tau species) has made the capture of the extracellular soluble species an attractive target, and people may just not be bothering to look for intraneuronal effects as well.

    You asked, Could the SENSRF get a bit of seed funding from the Michael J Fox Foundation (MJFF) to researching build and deliver an enzyme to remove intra-cellular α-synuclein, similar to the enzyme they are creating to remove oxidized cholesterol from foam cells in artery walls?

    Amusingly, you’re now asking the reverse of Steve H’s question of the other day about applying GAIM to oxidized cholesterol products! These are quite different kinds of damage, and really need to be targeted differently. In particular, intraneuronal AS accumulates in the cytosol, not the lysosome, a lysoSENS-type approach wouldn’t help, unless you also use some mechanism (like, again, an antibody) to drag them into the lysosome first. Once there, it’s entirely possible that the existing complement of enzymes and low pH would be enough to tackle them; if not, you would have to then secondarily develop novel enzymes to take care of the damage you would cause by dragging a recalcitrant aggregate into the lysosome. I’m reluctant to start messing with that kind of elaborate multiplex therapy unless there’s a strong reason t think it’s necessary, and absent such evidence I doubt MJFF would fund it, either.

    As far as “disappointing trials:” I believe that Reason refers here to disappointing trials of antibodies targeting beta-amyloid, not AS. As I assume you know, the very first beta-amyloid-targeting vaccine was highly effective at clearing amyloid, but also caused a potent inflammatory reaction in the brain, which led to the emergence of meningoencephalitis in ~6% of patients and the termination of the trial. Several other vaccines have been shown to be safe or only have mild side-effects, but not to show robust clinical effects; this may have been real lack of efficacy, but it may also have been just because the trials were started in patients with existing mild-to-moderate Alzheimer’s disease, which may be too late in the disease process to be intervening. Please read up in detail on the new, better-designed trials of beta-amyloid vaccines that are now in the works. Finally, the first signs of new progress with beta-amyloid immunotherapies is emerging, even as several vaccines are entering (or re-entering) trials with more appropriate designs.

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