Role of RIG-I, MDA-5, and PKR on the expression of inflammatory chemokines induced by synthetic dsRNA in airway epithelial cells.
BACKGROUND
We hypothesized that synthetic double-stranded (ds)RNA may mimic viral infection and reported that dsRNA stimulates expression of inflammatory chemokines through a receptor of dsRNA Toll-like receptor (TLR) 3 in airway epithelial cells. In this study, we focused our study on the role of other receptors for dsRNA, such as retinoic acid-inducible gene I (RIG-I), melanoma differentiation-associated gene 5 (MDA-5), and double-stranded RNA-dependent protein kinase (PKR).


METHODS
Airway epithelial cell BEAS-2B was cultured in vitro. Expression of target RNA and protein were analyzed by PCR and ELISA. To analyze the role of receptors for dsRNA, knockdown of theses genes was performed with short interfering RNA (siRNA).


RESULTS
We first investigated the effects of chloroquine, an inhibitor of lysosomal acidification, on the expression of chemokines. Preincubation with 100 microM chloroquine significantly inhibited the expression of mRNA for RANTES, IP-10, and IL-8, stimulated by poly I:C, indicating that poly I:C may react with a receptor expressed inside the cells. RIG-I, MDA-5, and PKR are supposed to be expressed inside the airway epithelial cells. However, the expression of chemokines stimulated with poly I:C was not significantly inhibited for these putative receptors in the cells which were transfected with siRNA.


CONCLUSIONS
Synthetic dsRNA poly I:C stimulates the expression of inflammatory chemokines in airway epithelial cells, but the putative receptors for dsRNA such as RIG-I, MDA-5, or PKR may not play pivotal roles in this process. TLR3 may play a major role as reported previously.
Matsukura
Satoshi
S
First Department of Internal Medicine, Showa University School of Medicine, Shinagawa, Tokyo, Japan. smatsuku@med.showa-u.ac.jp
Kokubu
Fumio
F
Kurokawa
Masatsugu
M
Kawaguchi
Mio
M
Ieki
Koushi
K
Kuga
Hideki
H
Odaka
Miho
M
Suzuki
Shintaro
S
Watanabe
Shin
S
Homma
Tetsuya
T
Takeuchi
Hiroko
H
Nohtomi
Kyoko
K
Adachi
Mitsuru
M
D001980:Bronchi / Q000166:cytology* / Q000378:metabolism; D002461:Cell Line, Transformed; D018946:Chemokine CCL5 / Q000096:biosynthesis* / Q000235:genetics; D054357:Chemokine CXCL10; D019743:Chemokines, CXC / Q000096:biosynthesis* / Q000235:genetics; D002738:Chloroquine / Q000494:pharmacology; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007249:Inflammation; D000072640:Interferon-Induced Helicase, IFIH1; D016209:Interleukin-8 / Q000096:biosynthesis* / Q000235:genetics; D011070:Poly I-C / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D034622:RNA Interference; D012330:RNA, Double-Stranded / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering / Q000494:pharmacology*; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000502:physiology*; D011971:Receptors, Immunologic; D051196:Toll-Like Receptor 3 / Q000187:drug effects / Q000502:physiology; D019892:eIF-2 Kinase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*
C114753:CXCL10 protein, human; D018946:Chemokine CCL5; D054357:Chemokine CXCL10; D019743:Chemokines, CXC; D016209:Interleukin-8; D012330:RNA, Double-Stranded; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; C495344:TLR3 protein, human; D051196:Toll-Like Receptor 3; C045250:poly I-C receptor; D002738:Chloroquine; D019892:eIF-2 Kinase; C452820:RIGI protein, human; C452815:IFIH1 protein, human; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases; D000072640:Interferon-Induced Helicase, IFIH1; D011070:Poly I-C