Deficient Mice as a Model for FMS
Investigator: Luc Jasmin, M.D., Ph.D.
University of California at San Francisco
Award: $56,925 - July 2001
Wouldn't it be great to have an
animal model for FMS in which therapies could be quickly and easily tested?
Then medications such as morphine, which ought to obliterate the pain of FMS
instead of just reducing it by 25-50%, could be tested to determine if the
addition of some other chemical that works on the pain system might boost
its action. These two goals are the primary aims of Jasmin's project.
With the aid of
an NIH grant received two years ago, Jasmin has already looked at the effects
of reduced levels of noradrenaline (NA) in rats. Not all the NA was depleted
from the rats and the process was only temporary. However, when the NA was
low, the rats were very pain sensitive and produced excessive amounts of substance
P, a situation that is analogous to that of people with FMS. When the NA levels
returned to normal (about two weeks later), the rats no longer showed any
signs of being in pain.
The results from
this ongoing study prompted Jasmin to take a genetic approach to modeling
FMS. For the AFSA-funded project, he will study the pain behavior of mice
that are missing the gene that codes for the enzyme that is needed for making
NA. Despite the lack of NA in their nervous system, these mice develop normally
... just like FMS patients who show no obvious signs of disease. Yet, these
mice show symptoms similar to FMS, such as increased pain responses to mild
pain stimuli (hyperalgesia), difficulty in concentration on tasks, tiredness,
and dysfunction of the autonomic nervous system (e.g., the "auto-pilot"
system that controls heart rate, breathing, responses to stress, digestion,
In the coming
year, Jasmin will be examining these mice to see if substance P is involved
in producing their hyperalgesia. Because nerve growth factor is also significantly
elevated in people with FMS, Jasmin will be looking at this substance as well.
Key to his studies in these mice is that NA can be restored, allowing him
to ensure that it is the absence of NA and not some unrecognized developmental
effect of the gene deletion that is responsible for his findings. It is hoped
that both the symptoms and the biochemical abnormalities (high levels of substance
P and nerve growth factor) will make this mouse a reliable model for further
evaluating new therapies for FMS as well as its underlying physiology.
Jasmin is taking
his project one step further. He will also be looking at a therapy that should
be highly effective for controlling FMS pain: morphine. Jasmin will
test the pain relieving effects of this opioid by itself and in conjunction
with adding NA . He hopes to determine if the low NA levels (which are known
to be present in FMS patients) could be the reason why opioids do not work
as optimally as they should in FMS. If so, then the addition of medications
that increase NA could also boost the pain relieving action of opioids in
people with FMS.
Mechanisms of Disordered Pain Perception
Principal Investigator: Thomas Fasy, M.D., Ph.D.
Mount Sinai School of Medicine,
- March 2001
It is now well
established that our bodies make natural anti-pain substances known as endorphins
or endogenous opioids. These endogenous opioids are peptides, (i.e., very
small proteins). From a chemical or structural point of view, they are quite
distinct from morphine or demeral. Yet, from a functional or pharmacological
point of view, they exert amazingly similar effects on the central nervous
system. These effects include a marked dampening of pain perception (i.e.,
reduction in pain), an enhanced sense of well-being or even euphoria, a suppression
of anxiety, and an improved ability to tolerate stress. Clearly, the endogenous
opioid peptides constitute a class of neurotransmitters that, if somehow disturbed,
could have important ramifications in producing the symptoms of FMS.
The first endogenous
opioids, the enkephalins, were discovered in 1975. Beta-endorphin is one of
the more commonly referred to enkephalins, but simply measuring beta-endorphin
alone to determine if the body's internal opioid system is working okay would
be a terrible oversight by today's standards. Currently more than 20 endogenous
opioid peptides have been identified. In fact, the endomorphins (which are
morphine-like substances) and nocistatin (another novel opioid peptide) were
discovered as recently as 1997 and 1998, respectively. Consequently, it is
possible that additional endogenous opioids produced by the human body still
remain undiscovered. Moreover, all of the mechanisms by which these recently
discovered endogenous opioids work have not yet been extensively studied and
their involvement in painful diseases such as FMS remains unclear.
Despite all the
new advances in medical research, the underlying cause(s) of FMS remain a
mystery. Given the new insights that have developed in the area of endogenous
opioids, it begs the question of whether any of these molecules could be disrupted,
destroyed, or somehow inadequately produced in people with FMSand it
was Dr. Fasy who first came to AFSA with this question two years ago.
In Fasy's first
award from AFSA (June 1999), he looked for the presence of antibodies to more
than a dozen neuropeptide molecules. These antibodies could deplete or destroy
important pain relieving substances produced by the body and, if present,
Fasy postulated that they could be involved in generating the symptoms of
FMS. First he screened ten strains of mice that might be producing such antibodies.
Fasy found one particular strain that produced an abundance of antibodies
to a few important neuropeptides that could attack pain-relieving substances,
particularly the body's enkephalins and historphin. Historphin works not only
to reduce pain but also is reported in the medical literature to influence
various hormonal (endocrine) actions in the body, including bone mineralization.
So, a dysregulation of historphin by antibodies might plausibly contribute
to the hormonal abnormalities reported in FMS.
As it turns out,
this mouse strain displays many of the symptoms of FMS, but more testing on
pain sensitivity needs to be done. They are timid and lack aggression, suggesting
the possibility that this strain of mice are excessively fatigued. Fasy has
further analyzed how the antibodies produced in high quantity might be working
in the mice ... and potentially in human FMS patients as well. These data
were presented at the American College of Rheumatology (ACR) meeting last
November. Fasy was interviewed at that time and the answers to certain aspects
of his research are below.
of FMS suggest the possibility that these patients have a neuroendocrine imbalance
which might very well include either a suboptimal response to or a deficiency of endogenous opioids. Such a deficiency could result not only
from insufficient synthesis of one or more endogenous opioids, but also from
an acceleration of their breakdown or hastening of their removal from the
fluids which bathe the nervous system (these latter two modes could be due
to the production of autoantibodies).
award builds on the exciting findings of his first AFSA-funded study. He will
now test the hypothesis that, in many patients with FMS, the opioid peptide
signaling network is disrupted by autoantibodies which bind to enkephalins,
nocistatin, or historphin. This should prevent their normal functions and
create an autoantibody-induced depletion of these essential endogenous opioids
needed for relieving many FMS-like symptoms. A second goal of this project
is to develop mouse models which will make it possible to study the extent
to which enkephalin-, nocistain-, and historphin-binding autoantibodies perturb
normal mouse behavior, especially responses to mildly noxious stimuli.
First blood sera
from 30 patients with primary FMS (but no other disease), 30 healthy controls,
and 20 patients with secondary FMS (FMS plus another rheumatic disease such
as lupus or RA), will be screened. This amounts to a total of 80 samples from
project collaborator, I. Jon Russell, M.D., Ph.D., of UT at San Antonio.
Then the next step in the project will be to identify the most significant
autoantibody findings in the sera and analyze for these same autoantibodies
in the cerebral spinal fluid taken from the same subjects from which the sera
was drawn (naturally all sorts of symptom data have been recorded by Russell
for all study participants as well). The most remarkable and consistent findings
in FMS to date have been uncovered in the spinal fluid, such as several-fold
increases in substance P and nerve growth factor concentrations. Thus, this
latter phase of the project may be where the most "golden" findings
Based on just
preliminary findings from this study, Fasy was successful in getting three
scientific posters accepted for presentation at the September MYOPAIN 2001
meeting in Portland, OR. With a wealth of experience in molecular biology
and genetics, autoimmune diseases, and pathology, it is now hoped that these
two projects will launch Dr. Fasy into a career in FMS as well! What follows
are the answers to just three of many questions that you might have regarding
Fasy's exciting studies:
Q - When physicians order an autoantibody panel for
a patient, which would include the ANA test, the findings typically come back
negative. Does this mean that all autoimmune causes for their symptoms can
be ruled out?
A - No, this approach doesn't cover the whole waterfront
because the standard ANA test fails to detect some antinuclear antibodies.
The binding sites on certain nuclear antigens may be buried and not accessible,
so they just don't generate a colorful staining pattern that is needed for
identifying antibodies with the standard test kits that are commercially available
at laboratories. (In other words, Fasy's results can only be found in a
high-tech research setting at this point in time, but it is possible to develop
a standard test kit down the road, if warranted.)
Q - What about therapy options for patients who test
positive for antibodies that may be destroying their enkephalins?
A - There are numerous potentially useful drugs that
have been developed in the test tube that are awaiting clinical trials. So
pharmacological interventions may be possible.
Q - The enkephalins mostly act on the delta opioid
receptor, yet it is the mu receptor that morphine and other available opioids
work on. What do you think about the work presented by AFSA-funded researcher Haiko Sprott, M.D., who found an 81-fold increase in the mRNA for the
delta opioid receptor in the skin of FMS patients?
A - I think that disturbances of delta opioid receptors,
which might also be called "enkephalin-receptors," may play a very
important role in FMS. Maybe a small or large fraction of FMS patients have
some difficulty in producing the enkephalin molecule that binds to delta opioid
receptors to activate them. Perhaps there are autoantibodies or other processes
accelerating the removal of enkephalins needed for turning on the delta receptor
that delivers pain relief in the tissues.
out that promising delta opioid agonist drugswhich activate the delta
opioid receptorhave already been developed by Astra Zenera, Smith-Kline-Beecham
and other major pharmaceutical companies, but are still in the testing phase.)
Receptors in the Skin and Muscle Tissue of FMS Patients - Part 2
Principal Investigator: Haiko Sprott, M.D.
- April 2001
The purpose of
Part 1 of Dr. Sprott's study was to look at the expression of opioid receptors
on the cell surfaces of both skin and muscle tissue, with a focus on patients
with FMS. There are three major types of opioid receptors: mu, kappa, and
delta. Sprott measured the distribution of these various receptors in the
skin and muscle tissue, and compared it to the normal brain tissue of one
deceased age-matched woman. At the October 2000 American College of Rheumatology
(ACR) meeting, he provided data that showed for the first time that a high
population of opioid receptors, particularly kappa and delta, reside outside
the central nervous system (i.e., the brain tissue). On the other hand, the
mu receptor was not found in the skin and muscle tissues of healthy controlsonly
in the brain tissue.
opioids work on the mu receptor, meaning that they must act within the central
nervous system (CNS) and this can usually lead to unwanted side effects at
doses needed to effectively alleviate the pain. Now that Sprott has established
that the peripheral tissues are densely populated with delta and kappa opioid
receptors (in particular the skin of FMS patients), this opens up other opportunities
to treat pain without having to deal with the CNS side effects.
comparing the expression of delta and kappa opioid receptors in the skin and
muscle tissue of FMS patients to that of healthy age-matched controls was
also presented by Sprott and his colleague Souzan Salemi, Ph.D., at
the ACR meeting. Based on half of the people to be tested, an 81-fold increase
in delta and a 14-fold increase in kappa opioid receptors were found in the
skin of FMS patients. Ironically, no differences could be found for these
same receptors in the muscle tissues.
The findings in
the muscle tissues may seem odd at first, because most patients will say that
their muscles hurt. Sprott explained that FMS patients may not be able to
distinguish between pain arising from the skin and pain arising from the muscle
tissues beneath the skin. Also, the vast majority of findings on FMS point
to a dysfunctional pain regulating system that thrives off of noxious inputs
to the CNS from the peripheral tissues. The abnormalities in the skin of FMS
patients could function as the "food" that keeps this pain state
All of the above
findings, funded in part by AFSA, are so amazing that Dr. Sprott has been
awarded additional funding to continue his investigations in this area (Part
2). Not only are Sprott's initial findings novel, but the potential for treatments
is high given that delta opioid agonists have only recently been developed.
Sprott is performing
a number of tests to better understand why the opioid receptors in the tissues
are present in abnormally high concentrations in FMS. At the September 2001
MYOPAIN meeting in Portland, OR, Sprott will be presenting both a lecture
and a poster abstract to explain the findings just described. Then at the
November 2001 ACR meeting in San Francisco, CA, he will present the results
of two new findings that were funded in part by AFSA.
As Sprott continues
with his investigations in this area, he is keeping an open mind as to the
cause of his findings on delta opioid receptors in the skin of FMS patients.
It is possible that the receptors may be damaged or flawed, so that the body's
endogenous opioids don't work on them properly. Sprott will need a delta agonist
to test this hypothesis, but they are not available yet. If the delta opioid
receptors are abnormal, Sprott says the next step will be to create a delta-like
drug that would fit these receptors to treat FMS patients. This would require
more funding, but it can be done!