Functional linkage of cirrhosis-predictive single nucleotide polymorphisms of Toll-like receptor 4 to hepatic stellate cell responses.
In a recent study, a single nucleotide polymorphism (SNP) of the Toll-like receptor 4 (TLR4) gene (c.1196C>T [rs4986791, p.T399I]) emerged as conferring protection from fibrosis progression compared to a major, wild-type (WT) CC allele (p.T399). The present study examined the functional linkage of this SNP, along with another common, highly cosegregated TLR4 SNP (c.896A>G [rs4986790, p.D299G]), to hepatic stellate cell (HSC) responses. Both HSCs from TLR4(-/-) mice and a human HSC line (LX-2) reconstituted with either TLR4 D299G and/or T399I complementary DNAs were hyporesponsive to lipopolysaccharide (LPS) stimulation compared to those expressing WT TLR4, as assessed by the expression and secretion of LPS-induced inflammatory and chemotactic cytokines (i.e., monocyte chemoattractant protein-1, interleukin-6), down-regulation of bone morphogenic protein and the activin membrane-bound inhibitor expression (an inhibitory transforming growth factor beta pseudoreceptor), and activation of a nuclear factor kappaB (NF-kappaB)-responsive luciferase reporter. In addition, spontaneous apoptosis, as well as apoptosis induced by pathway inhibitors of NF-kappaB, extracellular signal-regulated kinase (ERK), and phosphatidylinositol 3-kinase were greatly increased in HSCs from either TLR4(-/-) or myeloid differentiation factor 88(-/-) (a TLR adaptor protein) mice, as well as in murine HSCs expressing D299G and/or T399I SNPs; increased apoptosis in these lines was accompanied by decreased phospho-ERK and Bcl-2.


CONCLUSIONS
TLR4 D299G and T399I SNPs that are associated with protection from hepatic fibrosis reduce TLR4-mediated inflammatory and fibrogenic signaling and lower the apoptotic threshold of activated HSCs. These findings provide a mechanistic link that explains how specific TLR4 SNPs may regulate the risk of fibrosis progression.
Guo
Jinsheng
J
Department of Internal Medicine, Division of Liver Diseases, Zhongshan Hospital, Shanghai Medical College, Fudan University, Shanghai, China.
Loke
Johnny
J
Zheng
Feng
F
Hong
Feng
F
Yea
Steven
S
Fukata
Masayuki
M
Tarocchi
Mirko
M
Abar
Olivia T
OT
Huang
Hongjin
H
Sninsky
John J
JJ
Friedman
Scott L
SL
D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000378:metabolism; D004195:Disease Models, Animal; D055166:Hepatic Stellate Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008103:Liver Cirrhosis / Q000235:genetics* / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D015398:Signal Transduction; D051197:Toll-Like Receptor 4 / Q000235:genetics*
C485671:BAMBI protein, human; C485672:Bambi protein, mouse; C111835:CCL2 protein, human; C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D015850:Interleukin-6; D008070:Lipopolysaccharides; C507779:MYD88 protein, human; D008565:Membrane Proteins; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; C495345:TLR4 protein, human; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4