The function of mitogen-activated protein kinase phosphatase-1 in peptidoglycan-stimulated macrophages.
Mitogen-activated protein (MAP) kinases play a pivotal role in the macrophages in the production of proinflammatory cytokines triggered by lipopolysaccharides. However, their function in the responses of macrophages to Gram-positive bacteria is poorly understood. Even less is known about the attenuation of MAP kinase signaling in macrophages exposed to Gram-positive bacteria. In the present study, we have investigated the regulation of MAP kinases and the role of MAP kinase phosphatase (MKP)-1 in the production of pro-inflammatory cytokines using murine RAW264.7 and primary peritoneal macrophages after peptidoglycan stimulation. Treatment of macrophages with peptidoglycan resulted in a transient activation of JNK, p38, and extracellular signal-regulated kinase. Most interestingly, MKP-1 expression was potently induced by peptidoglycan, and this induction was concurrent with MAP kinase dephosphorylation. Triptolide, a diterpenoid triepoxide, potently blocked the induction of MKP-1 by peptidoglycan and prolonged the activation of JNK and p38. Overexpression of MKP-1 substantially attenuated the production of tumor necrosis factor (TNF)-alpha induced by peptidoglycan, whereas knockdown of MKP-1 by small interfering RNA substantially increased the production of both TNF-alpha and interleukin-1 beta. Finally, we found that in primary murine peritoneal macrophages, MKP-1 induction following peptidoglycan stimulation also coincided with inactivation of JNK and p38. Blockade of MKP-1 induction resulted in a sustained activation of both JNK and p38 in primary macrophages. Our results reveal that MKP-1 critically regulates the expression of TNF-alpha and interleukin-1 beta in RAW264.7 cells and further suggest a central role for this phosphatase in controlling the inflammatory responses of primary macrophages to Gram-positive bacterial infection.
Center for Developmental Pharmacology and Toxicology, Children's Research Institute, Children's Hospital, the Department of Pediatrics, Ohio State University, Columbus, Ohio 43205, USA.
Edward G
EG
Shepherd
Qun
Q
Zhao
Stephen E
SE
Welty
Thomas N
TN
Hansen
Charles V
CV
Smith
Yusen
Y
Liu
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D004224:Diterpenes / Q000494:pharmacology; D054638:Dual Specificity Phosphatase 1; D004789:Enzyme Activation / Q000187:drug effects; D004852:Epoxy Compounds; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D017874:Immediate-Early Proteins / Q000235:genetics / Q000502:physiology*; D007249:Inflammation; D007375:Interleukin-1 / Q000096:biosynthesis; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D048670:MAP Kinase Kinase 4; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology*; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010457:Peptidoglycan / Q000494:pharmacology*; D010616:Phenanthrenes / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000502:physiology*; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
D000894:Anti-Inflammatory Agents, Non-Steroidal; D018797:Cell Cycle Proteins; D004224:Diterpenes; D004852:Epoxy Compounds; D017874:Immediate-Early Proteins; D007375:Interleukin-1; D010457:Peptidoglycan; D010616:Phenanthrenes; D014409:Tumor Necrosis Factor-alpha; C001899:triptolide; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054638:Dual Specificity Phosphatase 1; C517020:Dusp1 protein, mouse; D017027:Protein Tyrosine Phosphatases