Toll-like receptor 2, 3, and 4 expression and function in human airway smooth muscle.
BACKGROUND
Host defense against microbial pathogens is elicited through the innate immune system by means of Toll-like receptors (TLRs). Airway smooth muscle cells (ASMCs) display proinflammatory and immunomodulatory functions. ASMCs might participate in airway inflammatory responses associated with innate immune activation.


OBJECTIVE
We determined the effects of cytokines, TLR ligands, and corticosteroids on TLR expression and function in human ASMCs.


METHODS
Real-time PCR and flow cytometry were used to assess TLR mRNA and protein expression, respectively. ASMCs were stimulated with TLR ligands, and chemokine release was measured by means of ELISA.


RESULTS
ASMCs expressed TLR1 to TLR10 mRNA, and TLR2 and TLR3 protein expression was demonstrated. TNF-alpha and double-stranded RNA (dsRNA; TLR3 ligand) were potent inducers of TLR2 and TLR3 mRNA expression, and both stimuli had additive or synergistic effects with IFN-gamma on TLR2 and TLR4, but not TLR3, mRNA expression. Peptidoglycan (TLR2 ligand) and LPS (TLR4 ligand) weakly enhanced TLR2 mRNA expression. Peptidoglycan, dsRNA, and LPS induced IL-8 and eotaxin release, with dsRNA being most potent. dsRNA also modulated cytokine-induced chemokine release in a differential manner. Dexamethasone inhibited cytokine- and ligand-induced TLR2, TLR3, and TLR4 expression and chemokine release. However, dexamethasone potentiated TLR2 expression induced by combined IFN-gamma and TNF-alpha stimulation.


CONCLUSIONS
Expression of TLR2, TLR3, and TLR4 is regulated by cytokines and TLR ligands, and their activation mediates chemokine release in ASMCs.


CONCLUSIONS
Proinflammatory responses mediated by activation of pathogen-recognition receptors in ASMCs might contribute to infectious exacerbations of airway inflammatory conditions, such as asthma and chronic obstructive pulmonary disease.
Sukkar
Maria B
MB
Experimental Studies Group, National Heart and Lung Institute, Imperial College, London, United Kingdom.
Xie
Shaoping
S
Khorasani
Nadia M
NM
Kon
Onn Min
OM
Stanbridge
Rex
R
Issa
Razao
R
Chung
Kian Fan
KF
D001980:Bronchi / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D002469:Cell Separation; D002478:Cells, Cultured; D018925:Chemokines / Q000378:metabolism; D006801:Humans; D008024:Ligands; D008168:Lung / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051195:Toll-Like Receptor 2 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D051196:Toll-Like Receptor 3 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D051197:Toll-Like Receptor 4 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D051193:Toll-Like Receptors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*
D018925:Chemokines; D008024:Ligands; D012333:RNA, Messenger; C495342:TLR2 protein, human; C495344:TLR3 protein, human; C495345:TLR4 protein, human; D051195:Toll-Like Receptor 2; D051196:Toll-Like Receptor 3; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors