MAPK signaling pathways regulate IL-8 mRNA stability and IL-8 protein expression in cystic fibrosis lung epithelial cell lines.
Cystic fibrosis (CF) is characterized by a massive proinflammatory phenotype in the lung, caused by mutations in the CFTR gene. IL-8 and other proinflammatory mediators are elevated in the CF airway, and the immediate mechanism may depend on disease-specific stabilization of IL-8 mRNA in CF lung epithelial cells. MAPK signaling pathways impact directly on IL-8 protein expression in CF cells, and we have hypothesized that the mechanism may also involve stabilization of the IL-8 mRNA. To test this hypothesis, we have examined the effects of pharmacological and molecular inhibitors of p38, and downstream MK2, ERK1/2, and JNK, on stability of IL-8 mRNA in CF lung epithelial cells. We previously showed that tristetraprolin (TTP) was constitutively low in CF and that raising TTP destabilized the IL-8 mRNA. We therefore also tested these effects on CF lung epithelial cells stably expressing TTP. TTP binds to AU-rich elements in the 3'-UTR of the IL-8 mRNA. We find that inhibition of p38 and ERK1/2 reduces the stability of IL-8 mRNA in parental CF cells. However, neither intervention further lowers TTP-dependent destabilization of IL-8 mRNA. By contrast, inhibition of the JNK-2 pathway has no effect on IL-8 mRNA stability in parental CF cell, but rather increases the stability of the message in cells expressing high levels of TTP. However, we find that inhibition of ERK1/2 or p38 leads to suppression of the effect of JNK-2 inhibition on IL-8 mRNA stability. These data thus lend support to our hypothesis that constitutive MAPK signaling and proteasomal activity might also contribute, along with aberrantly lower TTP, to the proinflammatory phenotype in CF lung epithelial cells by increasing IL-8 mRNA stability and IL-8 protein expression.
Department of Health Systems, Risk, and Contingency Management, Center for Medical Genomics and Proteomics, Uniformed Services Univ. of the Health Sciences, Bethesda, MD 20814, USA.
Sharmistha
S
Bhattacharyya
Usha
U
Gutti
Jose
J
Mercado
Chad
C
Moore
Harvey B
HB
Pollard
Roopa
R
Biswas
D003550:Cystic Fibrosis / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology; D004791:Enzyme Inhibitors / Q000627:therapeutic use; D004847:Epithelial Cells / Q000502:physiology*; D005786:Gene Expression Regulation; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics*; D020935:MAP Kinase Signaling System / Q000235:genetics* / Q000502:physiology; D048056:Mitogen-Activated Protein Kinase 9 / Q000037:antagonists & inhibitors; D010641:Phenotype; D012333:RNA, Messenger / Q000235:genetics*; D051816:Tristetraprolin / Q000172:deficiency / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors
D004791:Enzyme Inhibitors; D016209:Interleukin-8; D012333:RNA, Messenger; D051816:Tristetraprolin; C497552:ZFP36 protein, human; D048056:Mitogen-Activated Protein Kinase 9; D048051:p38 Mitogen-Activated Protein Kinases