THE RELATIONSHIP OF THE TOXIC EFFECTS OF MERCURY TO EXACERABATION OF
THE MEDICAL CONDITION CLASSIFIED AS ALZHEIMER'S DISEASE



By

Boyd E. Haley Ph.D.,
Professor and Chair,
Department of Chemistry,
University of Kentucky,
Lexington, KY 40506-0055
e-mail, behaley@...

Abstract: Mercury(II) or Hg2+, is neurotoxic and when exposed to
normal brain tissue homogenates, is capable of causing many of the
same biochemical aberrancies found in Alzheimer's diseased (AD)
brain. Also, rats exposed to mercury vapor show some of these same
aberrancies in their brain tissue. Specifically, the rapid
inactivation of the brain thiol-sensitive enzymes tubulin, creatine
kinase and glutamine synthetase occurs on the addition of low
micromolar levels of Hg2+ or exposure to mercury vapor, and these
same enzymes are significantly inhibited in AD brain. Further,
extended Hg2+ exposure to neurons in culture has been shown to
produce three of the widely accepted pathological diagnostic
hallmarks of AD. These are elevated amyloid protein, hyper-
phosphorylation of Tau, and formation of neurofibillary tangles. The
hypothesis is that mercury and other blood-brain permeable toxicants
that have enhanced specificity for thiol-sensitive enzymes are the
etiological source of AD. Included in this category are other heavy
metals such as lead and cadmium that act synergistically to enhance
to toxicity of mercury and organic-mercury compounds, like thimerosal
that is found in vaccines and other medicines. This hypothesis is
also able to explain the genetic susceptibility to AD that is
expressed through the APO-E gene family. Specifically, a reduction of
APO-E gene types carrying cysteines decreases the ability to remove
mercury and other thiol-reactive toxicants from the cerebrospinal
fluid. This increases brain exposure to thiol-reactive toxicants and
the risk of AD.

RATIONALE FOR THE HYPOTHESIS:

AD is a disease of unknown etiology. However, it is widely accepted
that most AD is not directly genetically inherited and that some
external vector, such as a toxicant exposure or an infection, must be
involved for the disease to progress into a clinically observable
condition. In the USA the rate of AD is very similar for rural versus
urban peoples and it does not vary appreciably from state to state.
Therefore, if a toxicant is involved then this toxicant must be of a
very personal nature, like what we eat or what is placed into our
bodies through other sources such as dental fillings, vaccines, etc.

The involvement of infectious agents such as bacteria, virus or
yeasts; while possible at this time, seems not to be directly
involved. This is based on the huge amount of National Institutes of
Health (USA) and other world-wide funds spent on AD to identify the
causal factors and they have not detected a consistent microbial
vector. If an infectious agent were involved (like in AIDS and polio)
it seems as if it would have been identified by now. However, focal
infections caused by microbes in the oral cavity must still be
considered as these microbes are known to produce toxicants such as
hydrogen sulfide, methyl-mercaptan, gliatoxin and other compounds
that inhibit thiol-sensitive enzymes.

For any toxicant, or class of toxicants, to be proposed as involved
in the etiology of AD they must be available equally to individuals
living in markedly different locations. The toxicant proposed must
explain the genetic susceptibility concept of AD. Further, under
experimental conditions the toxicants must be able to cause the
exacerbation of the many biochemical aberrancies found in AD brain.
Based on our research and a literature review, mercury and mercury
containing compounds from dental amalgams, vaccines, other medicinals
and preservatives used in paints, seed grains, etc. represent a class
of compounds that fill this requirement.

Mercury and organic mercurials are neurotoxicants. Further, the
enzyme inhibitory effects of mercury are synergistically enhanced by
exposures to other toxicants such as lead and cadmium (smokers). Even
the simultaneous presence of EDTA (ethylene-diamine-tetraacetic acid,
a common food additive) or metal binding antibiotics such as
tetracycline can enhance mercury toxicity. Therefore, any
determination of a safe level of mercury exposure using rats in a
cage being feed carefully monitored food and water is not reliable
for determination of a "safe level of exposure to mercury" for
humans. The fact is that science does not know what the combined
toxic effects of many toxicants or enhancers of toxicity would be if
present with mercury and therefore cannot identify a safe level of
exposure.

Therefore, thiol-reactive toxicants such as mercury, cadmium, lead
and certain organics are rational suggestions as being exacerbating
factors for AD, or possibly even causal. However, mercury is the one
toxicant that has been shown to reproduce many of the biochemical
aberrancies and diagnostic hallmarks of AD. Also, mercury exposure is
readily available to most humans. It is reasonable to propose that
exposure to mercury is one of the major toxic factors involved in
early onset AD. Further, that simultaneous exposures to other
toxicants or factors enhance the toxicity of mercury and hasten the
onset of AD, especially in those individuals who are genetically
susceptible.

RESEARCH REVIEW AND RESULTS:

Enzyme Inhibition and Protein Partitioning Results.

Research regarding Alzheimer's disease (AD) done in our laboratory in
the late 1980s was directed towards detecting aberrancies in the
nucleotide binding proteins of AD post-mortem brain tissue versus age-
matched, non-demented control brain samples. Basic to all of our
findings was the following observation. Two very important brain
nucleotide binding proteins, tubulin and creatine kinase (CK), showed
greatly diminished activity and nucleotide binding ability. Further,
they were abnormally partitioned into the particulate fraction versus
the soluble fraction of AD brain tissue by simple centrifugation
(1,2).

Both tubulin and CK are proteins that bind the nucleotides GTP
(guanosine-5'-triphosphate) and ATP (adenosine-5'-triphosphate),
respectively. We use a "photoaffinity labeling" technology to
determine the availability of these binding sites before and after
addition of mercury or other toxicants (21). This technology is
explained in detail at www.altcorp.com for those interested in the
detailed chemistry. Using this technology our laboratory has
demonstrated that both tubulin and CK had diminished biological
activity in AD brain compared to age-matched controls. Since AD is
not directly a genetically inherited disease we searched for possible
toxicants that might mimic the specific findings observed in AD brain.

Our first finding was simple and straight-forward. After testing
numerous heavy metals we observed that only Hg2+ could mimic the AD
effect in homogenates of normal brain at concentrations that might be
expected to be found in brain (3,4). The observation was that Hg2+ at
very low micromolar levels (@ 1 micromolar) could rapidly and
selectively abolish the GTP binding activity of tubulin (Mr = 55,000
daltons) without any noticeable effect on the other GTP binding
proteins protein(s) observed at an Mr of about 42,000 daltons, that
are present in both control and AD brain at approximately equal
levels. Therefore, concerning heavy metals the addition of only
mercury at low micromolar levels to control brain homogenates gave a
GTP binding profile that was identical to that observed in AD brain
and that chelation of Hg2+ by EDTA did not prevent but enhanced this
effect (4,5,6). Further, additional results have shown that the
addition of Hg2+ to control brain homogenates not only caused the
decrease in nucleotide interaction but could also support the
abnormal partitioning of tubulin into the particulate fraction as
observed in AD brain (7). This was especially effective in the
presence of other divalent metals, such as zinc, which is elevated in
AD brain. The recent video demonstrating Hg2+ specific stripping the
tubulin from the neurofibrils shows the tubulin abnormally
aggregating at the base of the neuron, supporting the partitioning we
observed in brain homogenates
(http://movies.commons.ucalgary.ca/mercury).

It is critical to understand that both tubulin and CK in normal brain
are found primarily in the soluble fraction of a homogenate. Yet,
both proteins appear of normal size and unmodified on reducing
polyacrylamide gel electrophoretic analysis (PAGE). This indicates
that both intact tubulin and CK have formed crosslinks with other
proteins that are insoluble under physiological conditions. Yet,
these crosslinks are readily disrupted by the common dithiolthreitol
(DTT) reduction procedure used before PAGE. What tubulin and CK have
in common is that both have a very reactive sulfhydryl in their
nucleotide binding sites that, if modified, inhibits their biological
activity (14, 15).

Mercury has a very high affinity for sulfhydryls and has been proven
to be a potent inhibitor of the biological activity of both of these
proteins. Also, mercury is divalent and can form crosslinks between
soluble proteins like tubulin and CK and is known to cause protein
aggregation. A generalized single step reaction would be as given in
reaction 1.

1: Protein-A-SH + Protein-B-SH + Hg2+ Þ Protein-A-S-Hg-S-Protein-B +
2 H+

This chemistry would allow the formation of aggregates that would
abnormally appear in the particulate fraction. Due to its dithiol
structure DTT is an excellent chelator of mercury. The massive
amounts of DTT used in reducing gels could chelate and remove mercury
from the proteins resulting in their becoming soluble again and
migrating as unmodified on gel electrophoresis as observed as shown
in reaction 2.

2. Protein-A-S-Hg-S-Protein-B + DTT Þ Protein-A-SH + Protein-B-SH +
DTT-Hg

The correct criticism of any homogenate test is that it may not occur
in a living animal. Therefore, experiments were done to determine if
mercury vapor, the primary form that escapes from dental amalgams,
could mimic the effect in rats exposed to such vapor for various
periods of time (5). Rats are different from humans in that they can
synthesize vitamin C whereas humans have to ingest vitamin C. Vitamin
C is thought to be somewhat protective against heavy metal toxicity
and other oxidative stresses. However, we observed that the tubulin
in the brains of rats exposed to mercury vapor lost between 41 and 75
percent of the nucleotide binding capability demonstrating a
similarity to the aberrancy observed in AD brain and confirming the
homogenate results (5).

There is also an "excito-toxic" amino acid hypothesis for the cause
of AD wherein excito-toxic amino acid glutmate builds up in brain
tissue causing neuronal death. This is a reasonable hypothesis and
could co-exist with the thiol-sensitive enzyme/mercury hypothesis.
The activity of Hg2+ sensitive glutamine synthetase (GS) was measured
in AD brain and the amount of GS in the cerebrospinal fluid of AD
versus control patients was determined. GS was found it to be
inhibited in AD brain and copies of GS were elevated in the
cerebrospinal fluid (12, 22). It has also been predicted by two
groups that the elevation of GS in the cerebrospinal fluid of AD
patients has potential as a diagnostic aid for AD (12,16). However,
it is reasonable to conclude that brain GS would be rapidly inhibited
by Hg2+ produced by oxidation of mercury vapor. This inhibition would
cause a rise in glutamate based excito-toxicity and could cause
neuron death. Further, glutamate is transported by molecular motors
down the microtubules that are destroyed by Hg2+. Therefore, both the
metabolism and transport of glutamate would be immediately affected
by exposure to mercury. The measurement of GS in cerebrospinal fluid
is most likely a measure of glial cell toxicity and death as would be
expected in several central nervous system diseases, including AD.

Illnesses that lower our metabolic energy levels also lower our
ability to synthesize the reducing equivalents that allow our body to
bind and dispose of excess mercury. Hg2+ is known to inhibit the
metabolic processes in mitochondria that produce ATP and NADH by
inhibiting the enzymes of the citric acid cycle and the electron
transport system. These nucleotides are absolutely required for both
the synthesis of reduced glutathione (GSH) and to reduce glutathione
after it is oxidized. GSH in the reduced state is the major
biomolecule involved in the natural removal of mercury from the body.
Therefore, as mercury slowly accumulates in the body it weakens the
body's natural defense against all forms of other heavy metal
toxicities and increases the overall oxidative stress expressed by
reactive oxygen species formation. It is well known that AD brain
tissue suffers from greater oxidative stress in all cellular
components versus similar tissues from control subjects. This would
be expected and it is well documented that mercury increases
oxidative stress in biological tissues. Further, Hg2+ is well known
to inhibit numerous other enzymes important to neurological function,
including the Na/K ATPase that is necessary for recovery from a nerve-
action potential. Therefore, the many numerous aberrancies observed
in AD brain would be expected within a hypothesis that proposes
exposure to Hg2+ is a major contributor to this disease.

Relevant Mercury Exposures and Measurments.

Mercury from Dental Amalgams;

The fact that mercury has inhibitory effects on tubulin, CK and GS
and that these proteins are proven to be aberrantly inhibited in AD
does not alone conclusively prove that mercury exposure causes AD.
However, it definitely proves that chronic, daily exposure to mercury
would at least exacerbate the clinical conditions of AD. Is such an
exposure to mercury likely? The answer is yes, and this makes mercury
involvement in AD plausible.

First, the question must be addressed if there is enough mercury in
an amalgam filling to continue a low chronic level exposure for
years? The answer is yes. For example, if a single large amalgam
filling contained 1 gram of mercury (1 million micrograms) and lost a
significantly toxic 10 micrograms per day there would be enough
mercury for 100,000 days or about 274 years of exposure. A small
tenth of a gram mercury filling would last 27 years. So enough
mercury is within amalgam fillings to provide a consistent chronic
toxic exposure for the life of most fillings.

Second, does mercury emit from amalgams at a rate that should cause
concern? The answer is yes. Dental amalgams, or "silver fillings" as
organized dentistry calls them, are approximately 50% mercury by
weight and it is quite easy to demonstrate that mercury vapors
readily emit from these fillings. The actual amount can only be
determined with the amalgam in a closed container and the amount of
mercury released being determined using solid, time proven chemical
techniques and instrumentation. The accurate level of mercury
released cannot be accomplished on amalgams in the mouth. In a
carefully designed study in a sealed container Chew et al. tested
the "long term dissolution of mercury from a non-mercury-releasing
amalgam (trade name Composil)" (9). Their results demonstrated "that
the overall mean release of mercury was 43.5 +/-3.2
micrograms/cm2/24hr, and the amount of mercury released remained
fairly constant during the duration of the experiment (2 years)".

In my opinion, this 43.5 micrograms/cm2/day is not an insignificant
amount of mercury exposure if one considers the number of years a 70
year old individual living today may have been exposed to chronic
mercury levels from his amalgams. Additionally, 43.5
micrograms/cm2/day is the level released without galvanism, excess
heat, or pressure from chewing, all factors that increase mercury
release from amalgams in the mouth (26).

Some may disagree with the figure presented above and indeed,
amalgams of different manufacture may release more or less. However,
the pro-amalgam supporters have not published any carefully
controlled study similar to the one above repudiating the finds of
this research group. They definitely have all of the scientific
laboratory expertise needed to do this. Instead, they
utilize "estimates" of release based on urine and blood levels that
are widely known to vary dramatically with time and not to be
reliable. In judging science one looks for what is not published that
obviously should have been.

Does the Presence of Amalgams Contribute Significantly to Mercury
Body Burden?

There have been numerous published reports of increased tissue
mercury levels in subjects and the relationship to increased number
of amalgams fillings (see 10, 11, 25 and references therein). Also,
the World Health Organization Scientific Panel found ranges of
mercury exposures from 3 to 70 micrograms/day with the bulk being
from amalgam fillings (31). Data relevant to this question was
addressed by a recent NIH study using 1,127 military personnel (20).
Soldiers in this study had an average of 20 amalgam surfaces with
ranges from 0 to 66 surfaces. Each 10 surfaces increased the urine
mercury level 1microgram/liter or an average of 4.5 micrograms/day.
This study indicated that individuals with an average number of
amalgam fillings had about 4.5 times the urine mercury levels as
controls without amalgams. Those soldiers with over 49 surfaces
averaged over 8 times the urine level observed in the non-amalgam
controls. Further, the blood and urine mercury levels corresponded
well with the number of amalgam fillings (20). The results above are
consistent with an earlier study where urinary mercury levels dropped
by a factor of 5 after the removal of several amalgam fillings. The
conclusion of the authors was that mercury from dental amalgams
exceeds that from all forms of food, air and fluids (23). All of the
data on urine or blood mercury levels must be considered with the
knowledge that approximately 80% of inhaled mercury vapor is retained
in the body. Mercury typifies a "retention" toxicity and much of the
mercury taken into the body is absorbed by the solid tissues. The
amount in urine represents mercury being excreted. However, the main
question is how much is being retained in the different body tissues.

In contrast to other reports there was published in the J. American
Dental Association research that measured mercury levels in brain and
other neurological tissues and concluded "Our results do not support
the hypothesis that dental amalgam is a major contributor to brain Hg
levels. They also do not support the hypothesis that Hg is a
pathogenetic factor in AD (25)." I can't explain how amalgams can
increase blood mercury levels and not increase brain mercury levels.
However, these researchers presented data showing no significant
increase in Hg level in several brain regions between control and AD
subjects. They surprisingly included data showing that the Hg levels
in control olfactory region was more than double that of the
corresponding AD olfactory tissue. This olfactory mercury increase in
control subjects could have several explanations.

One explanation could be they were not precise in estimating the
amount of mercury exposures of their subjects and the controls they
selected were much more exposed to mercury than the AD subjects
selected. The olfactory region is outside the blood-brain barrier and
should be a consistent internal standard for mercury exposure in the
air breathed in by the subjects.

Another explanation would be that the controls, even though exposed
to more than double the mercury levels of the AD subjects, as
evidenced by the olfactory region Hg levels, had a mechanism that
protected their brain tissues from also having double the mercury
levels. If this were true, then dividing the brain mercury levels by
the olfactory mercury levels would give results that clearly show a
significant ability of the controls to have a mechanism that protects
brain tissue from mercury that is lacking in the AD subjects. This
mechanism could be the presence of the protective APO-E protein
genotypes (see below) and other predisposition factors not yet known.

The debate continues on whether or not human mercury exposures reach
levels in the brain and other tissues that could be considered toxic
or harmful (24,25). There are several reasons why the brain levels of
mercury would not directly correlate to the damage being done. The
level of selenium in the diet, which could bind with mercury
rendering it less toxic, is the most straight-forward example. Also,
the determination of the levels of mercury toxicity that could cause
neurological disease has been done using animals, such as rats and
monkeys, under tightly controlled laboratory conditions where the
diet is carefully monitored to exclude other toxicants. Further, any
test animal that becomes ill or infected by microbial sources is
removed from the study. However, humans do not live under such
restricted conditions. For example, we are exposed to numerous
infections and additional heavy metal imbalances in AD brains have
been reported numerous times. Cigarette smokers are exposed to excess
cadmium (Cd2+) and lead (Pb2+) toxicity is not that uncommon in the
inter-city environment or for those exposed to leaded gasoline fumes
for many years. This means that the synergistic toxicities of
combined heavy metals must be considered for humans.

It is also questionable whether or not brain mercury levels should be
expected to remain high in AD brain. A report by Hock et al. (27)
stated that in early onset AD the blood levels of mercury were almost
three fold higher than the control groups and that these increases
were unrelated to the patients' dental status. The concluded that the
explanation of increased mercury in AD would include yet unidentified
environmental sources or release from the brain tissue with the
advance in neuronal death. The AD brain loses 25% of its average
weight by time of death making the latter explanation reasonable. It
is a well-known biochemical event that cells or tissues rid
themselves of denatured, unusable protein.

The inhibition and break down of neuronal tissue may also explain
another observation related to AD. It is documented that AD patients
have elevated olfactory thresholds and impaired odor identification.
It is further suggested that in patients with mild cognitive
impairment, olfactory problems may have clinical value as an early
diagnostic predictor for diagnosis of AD(28, 29, 30). Mercury in the
oral cavity must interact with the olfactory bulb. Due to the
neurotoxicity of mercury, this could impair olfactory sensitivity.
Also, based on our hypothesis impaired olfactory response would
almost have to occur.

Our laboratory has shown that one can add various metals to human
brain homogenates to levels that alone do not affect nucleotide
binding to tubulin, yet the very presence of these metals
synergistically increases the toxicity of Hg2+. That is, the presence
of Pb2+, Zn2+ and Cd2+, at non-toxic levels, decrease the amount of
Hg2+ required for 50% inhibition of tubulin or creatine kinase
viability. It is important to remember the "Periodic Chart of the
Elements" which places Zn, Cd and Hg in the same IIB category and all
have high affinity for thiol groups. In other words, mercury is much
more toxic in the presence of other metals that compete with mercury
for the binding sites on protective biomolecules (e.g., APO-E2 & E3,
glutathione or GSH, metallo-thionine, etc.).

It is also important to note that the "test tube levels" of mercury
are not representative of what would happen in a dynamic system where
a constant level of mercury is being supplied by the amalgams. Since
mercury toxicity is a "retention toxicity" all mercury pulled from
the system, or retained by the tissue, is replaced by more mercury
being constantly released from the amalgams and the Hg2+ level and
toxicity in solution remains constant. In the test tube as the
mercury is pulled out of solution the free Hg2+ concentration in
solution drops making the soluble aspect less toxic with time.

Are Amalgams Capable of Producing Toxic Solutions?

To propose deleterious effects of amalgams while in the mouth the
amalgams must be able to produce toxic effects outside of the mouth.
Wataha et al. reported that extracts of the amalgam material (trade
name, Dispersalloy) "was severely cytotoxic when Zn release was
greatest, but less toxic between 48 and 72 hours as Zn release
decreased" (8). Zn is a trace material in dental amalgams and a
needed supplement for living neurons. Therefore, it did not seem
likely that the toxicity was due to Zn emitting from the amalgams.
When we compare the toxicity of Hg2+ in brain homogenates as
described above (refs. 3 & 4), the addition of 0, 10 and 20
micromolar Zn2+ increased the inhibition of GTP binding to tubulin
from 4% to 50% and 76%, respectively (7,13). This supports the
concept that the Zn correlation to increased toxicity was due to the
synergistically enhanced toxicity of the mercury released from the
amalgam. Further,other studies in our laboratory have shown that
soaking of amalgams in distilled water for less than one hour created
a solution that also caused rapid inhibition of brain tubulin and
creatine kinase similar to that observed on adding Hg2+ solutions.
Therefore, it appears that the toxicity of solutions in which
amalgams were soaked is not caused by direct Zn2+ toxic effects.
Rather, enhanced toxicity is due to the Zn2+ or other amalgam heavy
metals stimulating the toxicity of mercury by occupying biomolecule
chelation sites. This would result in a higher concentration of free
Hg2+ capable of inhibiting the activity of critical nucleotide
binding proteins such as tubulin and CK.

The observed synergistic toxicity of other heavy metals with Hg2+ has
been supported in animal models. Combining an LD-1 solution of Pb2+
with an LD-1 solution of Hg2+ gave a solution with an LD of 100,
instead of an LD-2, when injected into rats (19). The bottom line is
that mercury toxicity is enhanced by the presence of other heavy
metals. Therefore, when one considers the toxicity of a certain body
level of mercury it is somewhat meaningless unless the body level of
other heavy metals is also considered.

With the complexity of our environment and the confounding factors
involving neurological diseases, and without major government
supported epidemiological studies proving safety, it is impossible to
state with assurance, as many amalgams supporters do, that this
exposure does not place the individuals at greater health risk.
The "lack of proof of damage" from mercury exposure seems unwarranted
to be used as "proving the safety of any material" that unnecessarily
exposes individuals daily to several micrograms of mercury.

Genetic Susceptibility Considerations.

Any hypothesis of the etiology of AD must consider information on
genetic susceptibility. The best known genetic risk factor for AD is
the correlation of APO-E genotypes to the age of onset of AD (24a,b).
Individuals can inherit any combination of the alleles APO-E2, E3 or
E4. Individuals inheriting APO-E2 or combinations of APO-E2 and E3
are much less likely to get early onset AD than are individuals who
have inherited APO-E4 genes. Also, APO-E2 appears to be more
protective than APO-E3 against early onset AD. Therefore, it is
necessary that the mechanism of mercury toxicity contain an
explainable relationship for the APO-E genetic susceptibility. This
is accomplished in a straight-forward manner by considering the basic
structural difference between these three alleles. Simply put, the
protective APO-E2 has two sulfhydryls (cysteines) that can bind
mercury or other heavy metals that APO-E4 lacks. For example, in APO-
E3, one of APO-E2 cysteines is replaced by an arginine and in APO-E4,
both of the APO-E2 cysteines are replaced by arginines (32).
Therefore, lack of protection against early onset AD was proposed to
follow the loss of mercury binding sulfhydryls from APO-E proteins
(6).

The protection provided by APO-E2 is reasonable when considering the
nature and biochemical assignment of APO-E proteins. APO-E proteins
are involved in cholesterol transport and all three alleles do this
reasonably well. However, APO-E is classified as a "housekeeping
protein". That is, in contrast to tubulin, GS and CK, which are meant
to stay inside of cells where they are synthesized, APO-E is meant to
leave the brain cells carrying damaged cholesterol through the
cerebrol spinal fluid (CSF), across the blood-brain barrier into the
blood where it is removed by the liver. It fits into the hypothesis
that while APO-E2 or E3 are leaving the brain cells and traversing
the CSF they likely bind and remove mercury, other heavy metals or
other sulfhydryl reactive toxins that may have made it into the
central nervous system thereby protecting the brain neurons (6). APO-
E4 cannot as effectively bind mercury and therefore does not provide
the protective parameters that APO-E2 and E3 have. It is interesting
to note that the second highest level of APO-E protein in the body is
in the CSF that bathes and protects the brain.

Oral Super-toxins Produced by Reaction With Dental Mercury.

Many recent literature and popular press reports state that the
presence of periodontal disease raises the risk factor or exacerbates
the condition of several other seemingly unrelated diseases such as
stroke, low birth weight babies, cardiovascular disease (See October
1996 issue of Periodontology). The anerobic bacteria of periodontal
disease produce hydrogen sulfide (H2S) and methyl thiol (CH3SH) from
cysteine and methionine, respectively. This accounts for the "bad
breath" many individuals have.

However, in a mouth that produces H2S, CH3SH (from periodontal
disease) and Hgo (from amalgam fillings) the very likely production
of their reaction products, HgS (mercury sulfide), CH3S-Hg-Cl (methyl-
thiol mercury chloride) and CH3S-Hg-S-CH3 (Dimethylthiol mercury) has
to occur. This is simple, straight-forward chemistry whose occurrence
is supported by easily observable "amalgam tattoos". These tattoos
are purple gum tissue surrounding certain teeth where the gum and
tooth meet and primarily caused by HgS as determined by elemental
analysis of such tissue.

HgS is one of the most stable forms of mercury compounds and is the
mineral form found in ore, called cinnabar, from which mercury is
mined from the earth. All of these oral site produced compounds are
classified as extremely toxic and the latter compound, dimethylthiol-
mercury is very hydrophobic and its solubility would be similar to
dimethyl-mercury (CH3-Hg-CH3). Dimethyl-mercury was the compound that
was made famous in the press where only a small amount spilled on the
latex gloves of a Dartmouth University chemistry professor caused
severe neurological problems and finally death 10 months later. In my
opinion, the extreme lethality of CH3-Hg-CH3 compared to other forms
of mercury is due to its ability to collect in hydrophobic regions of
the body, like the central nervous system. CH3-Hg-CH3 is similar to
CH3-S-Hg-S-CH3 in its hydrophobic characteristics.

Logic implies that anyone with periodontal disease, anaerobic
bacterial infected teeth and mercury containing fillings would be
exposed daily to these very toxic compounds. In our laboratory we
synthesized the two methylthiol-mercury compounds and tested them.
They are extremely cytotoxic at 1 micromolar or less levels and are
potent, irreversible inhibitors of a number of important mammalian
enzymes, including tubulin and CK.

A recent report stated that the tissues of individuals who died of
Idiopathic Dilated Cardiomyopathy (IDCM) had mercury levels of
178,400 ng/g tissue or 22,000 times more than their controls who died
of other forms of heart disease. IDCM is a disease where young
athletes drop dead during strenuous exercise. It seems impossible for
a tissue to bind this much mercury on protein without early notice of
injury through pain and lack of bioenergy. However, if this mercury
were to combine with H2S produced by a local anerobic infection the
mercury could precipitate out in the tissue as HgS as it does
in "amalgam tattoos" causing a buildup without killing the tissue
immediately. However, one has to ask where does this excess mercury
come from. Many times this occurs to young intercity athletes who are
not on a high seafood diet. My opinion is that dental amalgam is the
source of this mercury. Also, if HgS is being made in the heart
tissue the very cytotoxic CH3-S-HgX and CH3-S-Hg-S-CH3 are also being
made.

To determine if toxic teeth could have an effect on the
enzymes/proteins of human brain we have done the following study.
Several very toxic teeth were incubated for 1 hour in distilled
water. Aliquots of these solutions were then added to control human
brain homogenates and the resulting samples tested for tubulin
viability and partitioning. The results showed that about 40%
inhibited the viability of tubulin and caused partitioning.
Therefore, depending on the type of anerobic microbial infection
existing in avital teeth it is possible to have a toxicant production
that would exacerbate the condition classified as AD. It is also
probable that many of these teeth were extracted from mouths
containing amalgam and the toxins in these teeth may also consist
partially of extremely organic-mercury compounds as described above.

Based on the potential clearance represented by elevated blood levels
of mercury in early onset AD patients, the synergistic effects of
other heavy metals, the fluctuating GSH levels during illness and
aging, and dietary factors (e.g. selenium levels) there is no reason
to believe that the adverse effects of mercury from amalgams would be
dose dependent in any straight-forward manner in post-mortem AD
brain. To expect this would fly in the face of published data and
scientific logic. Further, to eliminate mercury as a factor in AD
based on statistically insignificant increases above normal in post-
mortem brain samples is not warranted. Also, involvement of genetic
factors likely plays a key role.

Studies Involving Neuronal Cultures and Diagnostic Markers for AD.

A recent publication supports our contention that mercury from dental
amalgams poses a major threat to the exacerbation of AD. Olivieri et
al. demonstrated that exposure of neuroblastoma cells to sub-lethal
doses (36 X 10-9 molar) of Hg2+ caused a rapid drop in GSH, an
increased secretion of b–amyloid protein and an increased
phosphorylation of the microtubulin protein Tau (17). The latter two
of these biochemical changes are uniquely observed in AD brain
tissues and are widely considered to be diagnostic, pathological
markers of the disease. b-amyloid protein makes up the `amyloid
plaques' that was one of the first diagnostic markers reported for AD
brain pathology. A very strong component of AD researchers believe
that amyloid protein is the cause of AD. Therefore, mercury exposure
at nanomolar levels causes neuroblastoma cells to produce a protein
that is believed to be involved directly in AD. This lead the authors
of this paper to conclude that mercury would have to be consider as
causal for AD (17).

Further, the recent report of the response of neurons in culture
rapidly forming neurofibillary tangles on exposure to extremely low
levels of mercury, by a process involving loss of microtublin
structure, completes the picture that mercury is capable of causing
the formation of three widely accepted major pathological diagnostic
hallmarks of AD in neuronal cultures (18). An impressive video
accompanying this publication and available at
http://movies.commons.ucalgary.ca/mercury shows the addition of 2
microliters of 10-7M mercury to a 2 milliliter solution bathing
neurons caused a rapid stripping of the tubulin from the neurofibrils
leaving them bare. This would be predictable from our earlier data
showing mercury interfering with normal tubulin-GTP interactions and
the abnormal partitioning of tubulin into the particulate fraction of
brain tissue(3,4,6). The bare neurofibrils then aggregate forming
neurofibrillary tangles (NFTs) similar to those observed in AD brain.
The final mercury concentration of 10-10M in these experiments is
roughly 100 to 1000 times lower than the 10-7M levels normally found
in human brain of individuals with amalgam fillings. The majority of
the mercury in brain is likely bound by protective compounds like GSH
or selenium and not free to cause neuronal damage. However, it is not
unreasonable to consider that some of this mercury is present as free
Hg2+ some fraction of the time, especially when illness or other
toxicities lower the GSH levels.

However, these two recent publications supports the initial
contention that mercury first rapidly inhibits thiol-sensitive
enzymes like tubulin, creatine kinase and glutamine synthetase and
dramatically affects metabolism and membrane structure. The stripping
of tubulin leads to the formation of NFTs and the exposing Tau for
hyper-phosphorylation. This is followed by elevated production of b –
amyloid protein that can aggregate into senile plaques. all
diagnostic markers for AD. It is consistent with the mercury toxicity
hypothesis for AD that neurofibillary tangles, hyper-phosphorylated
Tau, amyloid plaques and increased oxidative stress observations are
the result of neuronal toxicity and death in AD, they are not the
cause. The cause is exposure to environmental toxicants like mercury
that attack enzymes with the most reactive thiol groups.

CONCLUSION:

The data on the effects of mercury on the nucleotide binding
properties and the abnormal partitioning of two very important brain
nucleotide binding proteins proven to be aberrant in AD brain first
suggested that mercury must be considered as an exacerbating factor
to the condition classified as AD. This has been strongly supported
by the recent finds that nanomolar levels of mercury causes
neuroblastoma cells to secrete b-amyloid protein and increase
phosphorylation of the microtubulin associated protein Tau, both
major biochemical observations related to AD. Also, neurons in
culture exposed to Hg2+ at the 10-7 to 10-10 M levels have
conclusively been visually shown to rapidly produce abnormal tubulin
aggregation, resulting in particulate partitioning as observed in AD
brain. Also, this stripping of tubulin from the neurofibrils results
in the formation of NFTs that are indistinguishable from those
observed in AD brain. and used as a diagnostic marker of the disease
(18). These facts alone warrant serious consideration of mercury as a
certain exacerbating factor for AD, if not causal.

Consideration of mercury as a causal or exacerbating factor for AD is
especially relevant when mercury is present in combination with other
heavy metals such as zinc (Zn) cadmium (Cd) and lead (Pb).
Synergistic toxicity is not an exception but is observed as a general
rule (19). This obviates the argument that mercury must be
significantly elevated in AD brains to be considered causal or
contributing to the disease state. Further, the reaction of oral
mercury from amalgams with toxic thiols produced by periodontal
disease bacteria very likely enhances the toxicity of the mercury
being released. Humans are likely the only mammals with amalgam
fillings and periodontal disease. Bluntly, the determination of safe
body levels of mercury by using animal data where the animals have
not been exposed to other heavy metals is not scientifically
justifiable. Mercury is much more toxic to individuals with other
heavy metal exposures. It is my opinion that one of the major
unanswered questions concerning the toxic effects of mercury is "does
the combination of mercury with different heavy metals lead to
different clinical observations of toxicity?"

Finally, mercury biochemically mimics numerous observations seen in
AD brain tissues including inducing the formation of widely accepted
diagnostic hallmarks of the disease. Further, the synergistically
toxicity of mercury with other heavy metals, microbial produced oral
toxins and certain metal chelators is obvious. It is also a
scientific fact that amalgams contribute greatly to overall mercury
body burden and are capable of producing cytotoxic solutions with
properties like mercury solutions. Therefore, it seems very
reasonable to consider a hypothesis that mercury would be the major
contributor to early onset AD.

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