Synuclein and Amyloid Diseases

NSAIDs, such as ibuprofen and aspirin are possible treatments to inhibit the aggregation of proteins (synuclein, beta amyloid) on charged polymers in amyloid diseases, such as Parkinson’s disease, Alzheimer’s disease, etc. Contradictory studies show that intracellular aggregate formation may be protective, since dimers are more toxic than aggregates.

The list of amyloid diseases is long and there are few effective treatments. In each case a protein starts to accumulate in fibers that form amyloid plaques inside or outside the cells. The large aggregates outside are toxic. Inside it appears that the large aggregates are not as toxic as small clumps, oligomers, of the protein.

The amyloid proteins are stacked up in the fibers in a very organized way, so that the same portions of the protein are lined up on each side of the fibers. Outside the cell, the regions with basic amino acids interact with heparin, and in Alzheimer’s disease, for example, the beta amyloid plaque is half heparin. In test tube experiments, fiber formation from protein solutions is accelerated by adding heparin.

Amyloid fibers also form inside cells in the case of the tau fibers of Alzheimer’s disease or the synuclein aggregates in Parkinson’s disease. In theses cases, there should not be any intracellular heparin, and it is not known what polyanion (RNA?) serves to accelerate fiber formation in these cases.

Non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and aspirin, reduce the incidence of Parkinson’s and Alzheimer’s diseases. It has recently been shown that in test tube experiments, NSAIDs also decrease the formation of amyloid fibers from synuclein.

Amyloid fibers can be stained by Congo Red and thioflavin. Curcumin is the active component of tumeric and it has a structure related to Congo Red. Curcumin has been shown in recent studies to block synuclein amyloid formation.

In addition, the heparin in the fiber complexes can be stained with berberine. Berberine is a traditional herbal treatment for arthritis. It would not be surprising if it was also effective against Alzheimer’s amyloid plaque.

The large extracellular plaque aggregates appear to be toxic, but the small, oligomeric aggregate of protein appear to be the toxic form in cells. Recent experiments show that facilitating the formation of large intracellular aggregates minimizes the toxicity in animal models of Huntington’s and Parkinson’s diseases. It appears that the large visible aggregates are not the form that kills the cell.

For the time being, the only safe treatments that focus on amyloid fiber formation are the NSAIDs, curcumin and perhaps berberine.

references:
Hirohata M, Ono K, Morinaga A, Yamada M. 2008. Non-steroidal anti-inflammatory drugs have potent anti-fibrillogenic and fibril-destabilizing effects for alpha-synuclein fibrils in vitro. Neuropharmacology 54(3):620-7.

Pandey N, Strider J, Nolan WC, Yan SX, Galvin JE. 2008. Curcumin inhibits aggregation of alpha-synuclein. Acta Neuropathol. 115(4):479-89.

Bodner RA, Outeiro TF, Altmann S, Maxwell MM, Cho SH, Hyman BT, McLean PJ, Young AB, Housman DE, Kazantsev AG. 2006. Pharmacological promotion of inclusion formation: a therapeutic approach for Huntington's and Parkinson's diseases. Proc Natl Acad Sci U S A. 103(11):4246-51.

Outeiro TF, Kontopoulos E, Altmann SM, Kufareva I, Strathearn KE, Amore AM, Volk CB, Maxwell MM, Rochet JC, McLean PJ, Young AB, Abagyan R, Feany MB, Hyman BT, Kazantsev AG. 2007. Sirtuin 2 inhibitors rescue alpha-synuclein-mediated toxicity in models of Parkinson's disease. Science. 317(5837):516-9.

HIV TAT and Methamphetamine -- TNF

HIV infection and methamphetamine both cause inflammation of the brain and together they are paralyzing.

What’s worse than a TNF typhoon resulting from methamphetamine use? The answer is a TNF typhoon resulting in dementia from HIV infection of the brain.
Combine methamphetamine with HIV in the brain and the result is a Parkinson’s type of paralysis.

This sounds like very morbid subject matter to pursue out of curiosity, but if you put heparin into the equation, as I always do, it all becomes very interesting.

Here are pieces to the big picture:

HIV, the AIDS virus, infects cells of the immune system and causes chronic inflammation. The inflammation causes a disruption of heparin metabolism and since heparin is a major part of the matrix that holds together the endothelial cells that line the capillaries that feed the brain, the capillaries leak, i.e. there is a leak in the blood brain barrier. HIV-infected cells can pass out of the capillaries and into the brain. Here comes the insidious part, HIV produces a protein called TAT.

I drew a graphic of TAT with the basic amino acids in blue. The sequence of this nasty little protein shows how it gets around. It is secreted from cells, attached to heparan sulfate proteoglycans. It sticks tightly to heparin (yellow and red stick figures, sticking to ribbon of TAT), because of the patches with three and four adjacent basic amino acids. Frequently, the TAT will just be secreted and then sweep over the surface of the infected cell and be brought back into the cell on the circulating HSPG.

DPVDPNIEPWNHPGSQPKTACN
RCHCKKCCYHCQVCFIKKGLGI
SYGRKKRRQRRRPSQGGQTHQ
DPIPKQPSSQPRGDPTGPKE

A protein with three adjacent basic amino acids will get swept into a cell. All allergens that I have examined have this internalization triplet of basic amino acids. TAT is so powerful, that if it is chemically linked to the larger fluorescent protein from jelly fish (left with green, fluorescent amino acid derivative down the center), the whole fluorescent protein is dragged into cells.

The TAT can move from the HSPGs of an HIV-infected cell to neighboring cells with HSPGs. The TAT then gets taken into the cytoplasm of the next cell. Four adjacent basic amino acids are the signal that transports a protein to the nucleus and into the nucleus. It is in the nucleus that TAT really causes trouble. The TAT can move from an infected immune cell in the brain to neurons. TAT can kill neurons and stimulate other cells to produce TNF.

Methamphetamine also causes a TNF storm in the brain. This is a quick way to start the wasting symptoms that TNF in known for -- it is also call cachexin, after the wasting process of cachexia. If methamphetamine is given to someone with neurological symptoms of HIV, then the neuropathology is further exaggerated into a Parkinson’s type of paralysis. The TNF production of both is additive.

TNF production by methamphetamine brings up the consequences of the very closely related compound amphetamine (Adderall, Dexedrine) used by children and young adults (college age) as a treatment for ADHD.

reference:
Theodore S, Cass WA, Nath A, Maragos WF. 2007. Progress in understanding basal ganglia dysfunction as a common target for methamphetamine abuse and HIV-1 neurodegeneration. Curr HIV Res. May;5(3):301-13.

Brain Arachidonic Acid: Alzheimer’s, Bipolar, Parkinson’s

A recent review article on brain lipid metabolism discussed the results obtained by looking at how the major omega-6 fatty acid, arachidonic acid is imported and used in brain tissue. Arachidonic acid conversion to inflammatory prostaglandins was monitored by extracting lipids from rat brains after a variety of treatments. Similarly, isotopes (13C) of fatty acids were imaged by PET scans in patients treated for Alzheimer’s, bipolar disorder and Parkinson’s disease.

The major findings on brain arachidonic acid (AA, omega-6) and docosahexaenoic acid (DHA, omega-3) are:

• Ca. 5% of daily dietary AA and DHA are converted to make prostaglandins in the brain. Converted AA and DHA are rapidly replaced by serum AA and DHA.
• Brain DHA and AA metabolisms are independent.
• AA and DHA are rapidly circulated into phospholipids (R2 on the diagram) on the endoplasmic reticulum, move to the cytoplasmic membrane (see diagram, gray and white strands) removed by phospholipase A2 in synapses, converted to prostaglandins, leukotrienes, etc., or recycled to phospholipids. Enzymes that catalyze these reactions are usually different for DHA and for AA.
• 
• Drugs used to treat bipolar disorder (lithium, carbamazepine, valproic acid, lamotrigine) lower AA conversion in rats, but do not affect DHA conversion.
• Experimentally induced brain inflammation or neurotoxicity increases AA conversion, but not DHA conversion to prostaglandins.
• An omega-3 fatty acid deficient diet also increases AA, but not DHA conversion.
• More AA is converted in Alzheimer’s patients. This is consistent with increased inflammation and neurotoxicity in postmortem examinations.
• Mice that have been genetically manipulated to eliminate alpha-synuclein, a protein implicated in Parkinson’s disease, also show an increase in AA conversion and a decrease in DHA conversion.

Interpretation: Inflammation in the brain is separate from the rest of the body, but is the foundation of many brain disorders, including Alzheimer’s disease, bipolar disorder and Parkinson’s disease. In these disorders, arachidonic acid is rapidly converted into inflammatory prostaglandins and leukotrienes. Drugs that reduce symptoms, reduce AA conversion.

A diet rich in omega-3 DHA and reduced omega-6 arachidonic acid reduces the symptoms of these diseases -- an anti-inflammatory diet and lifestyle should be the first line of defense against brain/mental disorders.

reference:
Rapoport SI. 2008. Brain arachidonic and docosahexaenoic acid cascades are selectively altered by drugs, diet and disease. Prostaglandins Leukot Essent Fatty Acids. Oct 28. [Epub ahead of print]