Negative feedback regulation of IL-32 production by iNOS activation in response to dsRNA or influenza virus infection.
iNOS plays an important role in mediating inflammation. In this study, we found that iNOS-derived NO was increased 2.4-fold in the serum samples of 101 patients infected with influenza A virus in comparison with samples of 105 healthy individuals. In A549 human lung epithelial cells, infection with influenza A virus or stimulation with poly(I:C)+IFN-gamma resulted in increased mRNA and protein levels of both IL-32 and iNOS, with subsequent release of NO. Over-expression of IL-32 resulted in upregulated iNOS expression with subsequent NO production. Knock down of IL-32 by IL-32-specific siRNA resulted in the inhibition of dsRNA-induced expression of iNOS and NO release, indicating that IL-32 is an upstream regulatory factor of dsRNA-triggered iNOS production. Surprisingly, over-expression of iNOS resulted in the reduction of IL-32 expression, and suppression of iNOS by the selective iNOS inhibitor S-methylisothiourea sulfate stimulated IL-32 expression, indicating that a negative feedback mechanism operates between the iNOS/NO and IL-32 systems. These findings suggest that influenza A virus infection activates IL-32 and iNOS expression by a heretofore unrecognized complex mechanism, in which the two pro-inflammatory factors regulate each other, involving positive and negative feedback regulatory loops.
Li
Wei
W
The State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, PR China.
Yang
Fang
F
Liu
Yan
Y
Gong
Rui
R
Liu
Li
L
Feng
Yong
Y
Hu
Pan
P
Sun
Wei
W
Hao
Qian
Q
Kang
Lei
L
Wu
Jianguo
J
Zhu
Ying
Y
D000328:Adult; D002460:Cell Line; D045744:Cell Line, Tumor; D004789:Enzyme Activation; D025461:Feedback, Physiological; D005260:Female; D055785:Gene Knockdown Techniques; D006801:Humans; D009980:Influenza A virus / Q000276:immunology*; D007251:Influenza, Human / Q000201:enzymology / Q000276:immunology*; D007371:Interferon-gamma / Q000494:pharmacology; D007378:Interleukins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000097:blood*; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011070:Poly I-C / Q000276:immunology; D012330:RNA, Double-Stranded / Q000276:immunology / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics
C496971:IL32 protein, human; D007378:Interleukins; D012330:RNA, Double-Stranded; D034741:RNA, Small Interfering; D009569:Nitric Oxide; D007371:Interferon-gamma; C496319:NOS2 protein, human; D052247:Nitric Oxide Synthase Type II; D011070:Poly I-C