Dendritic Cells Waffled by Mercury

A few weeks ago we heard about new research out of UC Davis' MIND institute suggesting that thimerosal dysregulates Dendritic Cell (DC) signaling. Not really a surprise but let's look at how this may be relevant to autism, if at all. Again we'll need to look out for 'waffle words' where we would expect more specific terms. Words that hint at the direction of an effect in place of words like dysregulate and disrupt. Vague words can be misleading and may give the false impression that the immune dysregulation observed in the dendritic cells from these experiments is similar to patterns reported in autistic children.

I'll try to clarify the meanings of these waffle words as I read through the paper but first let's look at the press release.

A team of cell biologists, toxicologists and molecular bioscientists at UC Davis
has published a study connecting
thimerosal with disruptions in
antigen-presenting cells known as dendritic cells obtained from mice

.

Connecting thimerosal to effects on DC's in vitro isn't quite the same as a connecting it to autism. The only connection that I can see is the vaccine ingredient is suspected to play a role in the development of autism.

The study provides the first evidence that dendritic cells show unprecedented sensitivity to thimerosal, resulting in fundamental changes in the immune system's ability to respond to external
factors.

Right. So removing certain immune cells from C57BL/6J mice and incubating them with a mercury compound temporarily impairs their ability to function, but would thimerosal at vaccine concentrations cause immune or neurological dysfunction in living C57BL/6J mice? Apparently not: source

[...] Strains resistant to autoimmunity, C57BL/6J and BALB/cJ, were not susceptible.

Of course this comes from Mady Hornig and her NIH funding may be a conflict of interest by the logic of the mercury parents.
Moving on....

"This is the first time that thimerosal has been shown to selectively alter the normal functions of dendritic cells," said
Isaac Pessah, a toxicologist with the UC Davis School of Veterinary Medicine,
director of the Children's Center for Environmental Health and Disease
Prevention and senior author of the study. "Dendritic cells play pivotal roles in overcoming viral and
bacterial invaders by coordinating the immune system's overall combat response." One dendritic
cell can activate as many as 300 T-cells white blood cells that help find and
kill external agents that attack the immune system making them the most
effective immune system activators.

And

When thimerosal, at a concentration as low as 20 parts per billion, alters the fidelity of normal calcium signals,
dendritic cells show abnormal
secretion of IL-6 cytokine a potent chemical signal that initiates
inflammatory responses. Higher concentrations 200 parts per billion causes
programmed death of dendritic cells, preventing them from maturing and doing
their primary job of activating T-cells. Without proper feedback to guide its
response, a normal dendritic cell can quickly become "a rogue,
producing misinformation that could
activate aberrant and harmful immune responses,"
Pessah explained. "Even one rogue dendritic cell can activate many inappropriate immune responses."

Then we might expect the same sort of selective alterations in the dendritic cells of autistics? Are the immune systems of autistics less combat ready? Maybe, but there is more research to suggest the opposite. That some children with autism possess overactive immune systems, higher rates of allergy and autoimmune disorders. If this is true, inhibition of DC signaling would seem beneficial. Here's where words altered and dysregulated become confusing. The authors could say suppressed or inhibited, enhanced, stimulated, or activated, which still qualify as altered or dysregulated but are far less ambiguous. Precise language is important in scientific publications but the quotes were included in a press release possibly written by a non-scientist. Publicist are expected to dress up boring research to make it seem more exciting and significant. I'm sure the paper will help to clarify the specific effects thimerosal has on DC's in vitro. Let's check it out.

Abstract
Dendritic cells (DCs), a rare cell type widely
distributed in the soma, are potent antigen
presenting cells that initiate
primary immune responses. DCs rely on intracellular redox
state and calcium
(Ca2+) signals for proper development and function, but the relationship
between these two signaling systems
is unclear. Thimerosal (THI) is a mercurial used to
preserve
vaccines, consumer products, and experimentally to induce Ca2+ release from
microsomal stores. We tested ATP-mediated Ca2+ responses of DCs transiently
exposed
to nanomolar THI. Transcriptional and immunocytochemical analyses
show murine
myeloid immature and mature DC (IDCs, MDCs) express inositol 1,
4, 5-trisphosphate
and ryanodine receptor (IP3R, RyR) Ca2+ channels, known
targets of THI. IDCs express
the RyR1 isoform in a punctate distribution
that is densest near plasma membranes and
within dendritic processes whereas
IP3Rs are more generally distributed. RyR1 positively
and negatively
regulates purinergic signaling since ryanodine (Ry) blockade (1) recruited
80 percent more ATP responders, (2) shortened ATP-mediated Ca2+ transients
>2-fold,
(3) and produced a delayed and persistent rise (≥2-fold) in
baseline Ca2+. THI (100nM,
5min) recruited more ATP responders, shortened
the ATP-mediated Ca2+ transient (≥1.4-
fold) and produced a delayed rise
(≥3-fold) in the Ca2+ baseline, mimicking Ry. THI and
Ry, in combination,
produced additive effects leading to uncoupling of IP3R and RyR1
signals.
THI altered ATP-mediated IL-6
secretion, initially enhancing the
rate of but
suppressing overall
cytokine secretion in DCs. DCs are exquisitely
sensitive to THI, with
one
mechanism involving the uncoupling of positive and negative
regulation of Ca2+
signals contributed by RyR1.

The net effect seems to be a decrease in DC derived IL-6 secretion. If thimerosal exposure caused these types of alterations in living organisms then it stands to reason we would observe lower baseline IL-6 levels or a reduced capacity to secrete IL-6 in cells from children with autism, if the alterations are indeed a persistent effect of thimerosal exposure.

Maybe there are other studies to support this hypothesis. Since Judy Van De Water contributed to this study let's take a look at the IMFAR presentation from last year.

P1B.1.2 ALTERED CYTOKINE PROFILE IN
CHILDREN WITH
AUTISTIC SPECTRUM DISORDER
(ASD): EVIDENCE FOR IMMUNE DYSREGULATION.
P.
Ashwood, C. Kwong, J. Schauer, M. Cress and J.
Van De Water. Paul Ashwood.

[...]Following stimulation with PHA, patients with ASD had significantly
lower IL-2, IL-6, IL-10 and IL-12p40 (p<0.02)>

One vote for lower IL-6 secretion in response to stimulation. Without reading the full study it's difficult know if all of the 26 ASD subjects produced less IL-6 or if this is an average in response to the mitogen. Unfortunately the other cytokine levels weren't reported in the DC study for comparison. There's that word altered again.

Next up, Croonenberghs.

Biological Psychiatry. Main Editor: J. Mendlewicz (Brussels) / Original Paper
Activation of the Inflammatory Response System in Autism
Jan Croonenberghs, Eugene Bosmans, Dirk Deboutte, Gunter Kenis, Michael Maes

[...]There were no significant differences in the serum concentrations
of IL-6, IL-2R and IL-1RA between autistic and normal children.

One vote against.

Intestinal
cytokines in children with pervasive developmental disorders.

We have demonstrated no significant difference in production of IL-6, IL-8, and IL-1β between patients with pervasive developmental disorders and age-matched controls. In general, intestinal levels of IL-6 and IL-8 were lower in patients with pervasive developmental disorders than in age-matched controls

One maybe?

J Neuroimmunol. 2001 Nov 1;120(1-2):170-9.
Proinflammatory and regulatory cytokine production associated with
innate and adaptive immune responses in children with autism spectrum disorders and developmental regression.

[...] ASD patients produced >2
SD above the control mean (CM) values of TNF-alpha, IL-1beta, and/or IL-6 produced by control PBMCs.

Uh-oh, more Il-6 production here in response to stimulation but with a different stimulant and different types of cells. Jyonouchi's work in general indicates enhanced immune response toward dietary proteins such as gluten and casein antigens. Since dendritic cells are a type of antigen presenting cell (APC), increased sensitivity to food proteins suggests fully functional and even overactive APC function. In fact gluten sensitivity is completely dependent on DC stimulation of T-cells. Assuming that some autistic children are more sensitive to Gluten, attenuation of DC's would be therapeutic.

Hmmm, what about this one:

Neuroglial
Activation and Neuroinflammation in the Brain of Patients with Autism

[...] Interestingly, a larger spectrum of increased proinflammatory and
modulatory cytokines was seen in the ACG, where there was a significant increase in interleukin-6 (IL-6),

Plenty of IL-6 here but produced by different types of cells again.

J Neuroimmunol. 1996 May;66(1-2):143-5.
Plasma increase of interleukin-12 and interferon-gamma. Pathological
significance in autism.
Singh VK

[...] The levels of IL-12 and IFN-gamma were significantly (P
< or =""> 2005 Sep;33(3):195-201.

Cerebrospinal fluid and serum markers of inflammation in autism.Zimmerman
AW, Jyonouchi H, Comi AM, Connors SL, Milstien S, Varsou A, Heyes MP.

[...] Median interleukin-6 levels in Autism Group 3 sera (27;
5.4-629.1 pg/ml) did not differ from either Control Groups 3A (29.7; 10.8-181.6)
or 3B (24.3; 16.2-237.6) and was elevated in only 2 subjects with autism (100.6
and 629.1 pg/ml).

Oh well, enough of that. There doesn't seem to be any evidence of suppressed DC function, decreased IL-6, or reduced inflammatory immune response in children with autism. If anything the literature suggests an enhanced capacity to respond to immune stimulation.

At the Society of Toxicology meeting, Cure Autism Now (CAN) funded quiet a few mercury presentations including this one:

CHARACTERIZING HUMAN SUSCEPTIBILITY TO
MERCURY-INDUCED IMMUNOTOXICITY
E.
K. Silbergeld, R. M. Gardner and J. F. Nyland. Environmental Health Sciences,
Johns Hopkins University School of Public Health, Baltimore, MD.

[...]Our preliminary studies in human PBMCs demonstrate significant inhibition of LPS-stimulated production of interferon-γ and TNF-β at these subcytotoxic concentrations

.

PBMC from autistic children typically show normal or enhanced inflammatory cytokine production when stimulated with LPS in vitro, mercury would seem to inhibit this effect. Maybe that's the rationale behind the use of gold salts to treat autoimmune prone mercury sensitive SJL/J mice.

Clin Exp Rheumatol. 2002 Sep-Oct;20(5):683-8.

Gold sodium thiomalate
suppresses the differentiation and function of human dendritic cells from
peripheral blood monocytes.

Wang ZY, Morinobu A, Kawano S, Saegusa J,
Wang B, Kumagai S
Department of Clinical Pathology and Immunology, Kobe
University Graduate School of Medicine, Kobe, Hyogo, Japan.
OBJECTIVE: Gold
sodium thiomalate (GST) is a drug commonly used for the treatment of rheumatoid
arthritis (RA). To clarify the mechanism of therapeutic effects of GST on RA, we
investigated if GST affects the differentiation of dendritic cells (DC), which
are thought to play a pivotal role in RA pathogenesis. METHODS: We generated
immature DC (iDC) in vitro from PB monocytes during the 5 to 7-day culture in
the presence of IL-4 and GM-CSF. Mature DC (mDC) were induced by adding TNF
alpha on day 5 of the 7-day culture with GM-CSF and IL-4. DC capacity of
stimulating T cells was examined in allogenic MLR using generated DC as
stimulators. IL-12 production from DC was assayed with ELISA. RESULTS: We found
that: 1) mDC generated in the presence of GST showed lower expression of CD1a,
CD83, CD80, CD86, HLA-ABC and HLA-DR compared to control mDC on FACS analysis.
2) GST-treated mDC showed reduced capacity of stimulating allogenic T cells in
mixed leukocyte reaction. 3) IL-12p70 production after stimulation with SAC or
LPS plus IFN gamma was markedly reduced in GST-treated mDC. CONCLUSION: GST suppresses the differentiation and function of DC generated from
peripheral blood monocytes. This previously unknown action may explain
the in vivo effects of GST in the treatment of RA.

In Summary:

• Dendritic cells from one strain of mice are functionally suppressed after exposure to thimerosal in vitro but the actual mice are apparently unaffected.
• Immune cells from mice and humans produce less inflammatory cytokines in response to in vitro stimulation when exposed to mercury compounds.
• Immune cells from children with autism show a trend toward enhanced inflammatory cytokine production in vitro.
• The effects of thimerosal on immune cells is poorly defined at best and impossible to compare with the known immune parameters found in children with autism.
• Thimerosal alters DC function in ways more similar to anti-rheumatic drugs including gold salts that have been proposed as a treatment for mercury poisoned autoimmune prone SJL/J mice.
• This study tells us nothing about autism and very little about the immune effects of mercury in living organisms.

Or as Isaac Pessah says: "Our findings do not directly implicate thimerosal as a single causative agent for triggering neurodevelopmental disorders such as autism"

No Isaac. Not directly, not indirectly, not a single cause or cause at all, not a trigger, not for autism. Not Mercury