Re: Fatigue and link between endotoxin and UC/PSC

[Guest guest]

Dear ;

Sorry, I don't know Jeff Bower at Purdue ... perhaps I should look him up?

I hope I am not going to bore everyone with more information on endotoxin

(lipopolysaccharide (LPS)) but I would like to make a few more observations

about this toxic product produced by certain gut bacteria, and try to link it

more to ulcerative colitis and PSC [i think I've exhausted the link with fatigue

already].

I've already mentioned that there are several lines of defense against endotoxin

in the body:

1. Secreted IgA in the gut can bind to endotoxin.

2. Intestinal alkaline phosphatase secreted by the gut detoxifies endotoxin by

removing a phosphate group from it.

3. Bacterial permeability-increasing protein (BPI) binds to endotoxin and

detoxifies it.

If the gut is leaky for some reason, and these defense mechanisms are

overwhelmed (e.g. inadequate secretion of IgA, antibodies against BPI, or by

deficiency of intestinal alkaline phosphatase), endotoxin can get across the

intestinal barrier, and be carried in the blood stream towards the liver, where

it can then cause inflammation.

The inflammation occurs when endotoxin binds to a protein called CD14; this

complex then activates a receptor called Toll-like receptor 4 (TLR4) which then

sets off an inflammatory cascade (production of lots of inflammatory cytokines).

Interestingly, if you look at some of the latest genetic studies on ulcerative

colitis, you'll see that the genes encoding 3 of the components that I've

mentioned above (BPI, CD14 and TLR4) are susceptibility genes for UC:

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Hum. Immunol. Mar 9 [Epub ahead of print] (2009)

Interactions among genes influencing bacterial recognition increase IBD risk in

a population-based New Zealand cohort.

mann I, Huebner C, Browning BL, Gearry RB, Barclay ML, Kennedy M,

R, Shelling AN, Philpott M, Han DY, Ferguson LR.

Discipline of Nutrition, The University of Auckland, New Zealand; Nutrigenomics

New Zealand.

Bacterial sensing is crucial for appropriate response by the innate and adaptive

immune system against invading microorganisms. Single nucleotide polymorphisms

(SNPs) in genes involved in bacterial recognition, CARD15 caspase-activated

recruitment domain (CARD15) (nucleotide-binding oligomerization domain protein 2

[NOD2]) and TLR9 Toll-like receptor 4 (TLR4), increased the risk of inflammatory

bowel disease (IBD) in a New Zealand Caucasian case-control cohort. We now

consider the effects of SNPs in CD14, TLR9, and

bactericidal/permeability-increasing protein (BPI), analyzed individually, in

association with one another, and with SNPs in CARD15 or TLR4 in this same

population group. SNPs in monocyte differentiation antigen CD14 (CD14) (c.-159

C>T), TLR9 (c.-1237T>C) and BPI (c.645A>G) showed no significant allele or

genotype frequency differences between IBD cases and controls.

Genotype-phenotype mapping reveals an association with BPI and ileocolonic

Crohn's disease (CD) as well as an association with CD14 and early-onset

ulcerative colitis (UC). Genotype interaction analyses using three different

statistical approaches provided significant evidence of interaction for the

following combinations: CARD15/TLR4 (CD and UC), CARD15/CD14 (CD and UC),

CD14/TLR4 (UC only), and CD14/BPI (UC only). A trend for an association between

BPI and TLR4 was observed in UC patients, but failed to reach statistical

significance. Our findings support the idea of gene-gene interactions for genes

involved in closely related pathways (i.e. bacterial detection). There is

evidence that carrying two SNPs in genes may lead to statistical significance

for genes and SNPs that do not otherwise confirm as risk alleles for disease

aetiology when analysed alone. PMID: 19275920.

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So this pathway would seem to be important in understanding the

gene-environment/gut bacterial interactions that may be going on in ulcerative

colitis.

There is limited evidence so far to indicate that these genes may be involved in

susceptibility to PSC, but I would like to note that the CD14 gene has been

associated with biliary atresia and infantile cholestasis:

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Pediatrics 116: 437-441 (2005)

Promoter polymorphism of the CD14 endotoxin receptor gene is associated with

biliary atresia and idiopathic neonatal cholestasis.

Shih HH, Lin TM, Chuang JH, Eng HL, Juo SH, Huang FC, Chen CL, Chen HL.

Department of Pediatrics, Chang-Gung Memorial Hospital at Chiayi, Pu-Tz City,

Chiayi Hsien, Taiwan.

OBJECTIVE: To investigate whether single-nucleotide polymorphisms in the

promoter regions of endotoxin-responsive genes CD14 and tumor necrosis

factor-alpha (TNF-alpha) are associated with biliary atresia (BA) and idiopathic

neonatal cholestasis (INC). METHODS: We obtained genomic DNA from 90 patients

with established diagnosis of BA and 28 patients with INC. Forty-two adult

patients with hepatitis B-related cirrhosis and 143 healthy children served as

control populations. The genotypes of CD14/C(-159)T and TNF-alpha/G(-308)A (G

allele, TNF*1; A allele, TNF*2) were determined by using a restriction

enzyme-based assay. Plasma soluble CD14 levels were determined in different

disease stages and genotypes of BA. RESULTS: The frequencies of T allele and T/T

homozygosity of the CD14/-159 promoter polymorphism were significantly higher in

patients with BA (T allele: 61.7%; T/T genotype: 42.2%) and in patients with INC

(T allele: 67.9%; T/T genotype: 53.6%) but not in control populations. Decrease

of plasma soluble CD14 from the early stage of BA when the patients received a

Kasai operation to the late stage of liver cirrhosis was observed in carriers of

the T/T and T/C genotypes but not in carriers of the C/C genotype. The

TNF-alpha/-308 promoter polymorphisms (TNF*1 and TNF*2) were not associated with

BA. CONCLUSION: These findings show that the single-nucleotide polymorphism at

CD14/-159 is associated with the development of BA and INC. Endotoxin

susceptibility may play a role in the pathogenesis of infantile cholestasis.

PMID: 16061600.

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I'd also like to note that something unusual might be going on with TLR4

expression in the biliary epithelial cells of PSC patients. Antibodies produced

in biliary epithelial cells of PSCers seem to make them much more sensitive to

stimulation by lipopolysaccharide (endotoxin).

_______________________

Gastroenterology 132: 1504-1514 (2007)

Biliary epithelial cell antibodies link adaptive and innate immune responses in

primary sclerosing cholangitis.

Karrar A, Broomé U, Södergren T, Jaksch M, Bergquist A, Björnstedt M,

Sumitran-Holgersson S.

Division of Transplantation Surgery, Division of Clinical Immunology, Karolinska

University Hospital-Huddinge, Stockholm, Sweden.

BACKGROUND & AIMS: Primary sclerosing cholangitis (PSC) is an autoimmune liver

disease with destruction of hepatic bile ducts. A high frequency of biliary

epithelial cell antibodies (BEC-Ab) is present in PSC. Here, we studied the

mechanisms and signaling pathways used by these Ab in causing BEC dysfunction.

METHODS: Immunoassays were performed using freshly isolated BECs to study the

signaling capacity of purified immunoglobulin (Ig) G and F(ab)'(2) fractions

from 33 patients with PSC with anti-BEC-Ab. RESULTS: We provide evidence that

stimulation of BECs with PSC IgG, but not control IgG, induced expression of

Toll-like receptor (TLR) 4 and TLR9 and specific phosphorylation of

extracellular signal-regulated kinase (ERK) 1/2 as well as the transcription

factors ELK-1 and nuclear factor kappaB. A specific inhibitor of ERK1/2

abrogated phosphorylation of ELK-1 and protein expression of TLR4 but not TLR9

on BECs. TLR-expressing BECs, when further stimulated with lipopolysaccharide

and CpG DNA, produced high levels of interleukin-1beta, interleukin-8,

interferon gamma, tumor necrosis factor alpha, granulocyte-macrophage

colony-stimulating factor, and transforming growth factor beta. Bile ducts

stained positively for TLR4 and TLR9 in 58% of liver specimens taken from

patients with PSC with BEC-Ab, as compared with 14% in those without BEC-Ab and

also less frequently in diseased control livers. CONCLUSIONS: Our data show that

binding of PSC BEC-Ab initiates ERK1/2 signaling and up-regulation of TLR, which

upon ligation induces BECs to produce cytokines/chemokines, leading to the

possible recruitment of inflammatory cells. Thus, in PSC, BECs are not only

targets of the immune attack but may also be active participants and mediators

of their own destruction. BEC-Ab may be critical regulators of cholangitis in

PSC. PMID: 17408653.

_____________________

So these various pieces of the puzzle (plus some others that I've mentioned in

the last couple of days; e.g. endotoxin is found at high levels in livers of PSC

patients; intestinal alkaline phosphatase deficiency can cause colitis in an

animal model; intestinal alkaline phosphatase is a promising new treatment for

ulcerative colitis; BPI-antibodies are found in IBD and PSC patients; IgA

deficiency is associated with PSC) begin to fit together a bit more clearly, and

point to endotoxin as a major culprit.

Intestinal alkaline phosphatase would be a good candidate gene to look at for

ulcerative colitis susceptibility. Interestingly, if you look up the intestinal

alkaline phosphatase gene in the human genome, it is very close to a Crohn's

disease susceptibility gene called ATG16L1.

Best regards,

Dave

(father of (23); PSC 07/03; UC 08/03)

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> Thanks , your emails and answers are truly amazing. Do you know Jeff

Brower (a philosophy professor at Purdue)?  We know Jeff and his wife from our

common residence in Iowa City, IA. 

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