Aryl hydrocarbon receptor antagonism mitigates cytokine-mediated inflammatory signalling in primary human fibroblast-like synoviocytes.
OBJECTIVE
Rheumatoid Arthritis (RA) is a chronic inflammatory disease of unclear aetiology, which is associated with inflamed human fibroblast-like synoviocytes (HFLS). Epidemiological studies have identified a positive correlation between tobacco smoking (a rich source of aryl hydrocarbon receptor (AHR) agonists) and aggressive RA phenotype. Thus, we hypothesise that antagonism of AHR activity by a potent AHR antagonist GNF351 can attenuate the inflammatory phenotype of HFLS-RA cells.


METHODS
Quantitative PCR was used to examine IL1B-induced mRNA expression in primary HFLS-RA cells. A structurally diverse AHR antagonist CH223191 and transient AHR repression using AHR small interfering RNA (siRNA) in primary HFLS-RA cells were used to demonstrate that effects observed by GNF351 are AHR-mediated. The levels of PTGS2 were determined by western blot and secretory cytokines such as IL1B and IL6 by ELISA. Chromatin-immunoprecipitation was used to assess occupancy of the AHR on the promoters of IL1B and IL6.


RESULTS
Many of the chemokine and cytokine genes induced by IL1B in HFLS-RA cells are repressed by co-treatment with GNF351 at both the mRNA and protein level. Pretreatment of HLFS-RA cells with CH223191 or transient gene ablation of AHR by siRNA confirmed that the effects of GNF351 are AHR-mediated. GNF351 inhibited the recruitment of AHR to the promoters of IL1B and IL6 confirming occupancy of AHR at these promoters is required for enhanced inflammatory signalling.


CONCLUSIONS
These data suggest that AHR antagonism may represent a viable adjuvant therapeutic strategy for the amelioration of inflammation associated with RA.
Department of Veterinary and Biomedical Sciences, Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, PA 16802, USA.
Tejas S
TS
Lahoti
Kaarthik
K
John
Jarod M
JM
Hughes
Ann
A
Kusnadi
Iain A
IA
Murray
Gowdahalli
G
Krishnegowda
Shantu
S
Amin
Gary H
GH
Perdew
D001172:Arthritis, Rheumatoid / Q000378:metabolism / Q000473:pathology*; D002478:Cells, Cultured; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D055786:Gene Knockout Techniques; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D007249:Inflammation / Q000378:metabolism / Q000473:pathology; D018836:Inflammation Mediators / Q000378:metabolism*; D053583:Interleukin-1beta / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology; D011687:Purines / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D018336:Receptors, Aryl Hydrocarbon / Q000037:antagonists & inhibitors* / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D013583:Synovial Membrane / Q000187:drug effects / Q000378:metabolism / Q000473:pathology
D007211:Indoles; D018836:Inflammation Mediators; D053583:Interleukin-1beta; D015850:Interleukin-6; C560625:N-(2-(3H-indol-3-yl)ethyl)-9-isopropyl-2-(5-methyl-3-pyridyl)purin-6-amine; D011687:Purines; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D018336:Receptors, Aryl Hydrocarbon
Arthritis; Chemokines; Cytokines; Fibroblasts; Inflammation