AMPK Activation Inhibits Expression of Proinflammatory Mediators Through Downregulation of PI3K/p38 MAPK and NF-κB Signaling in Murine Macrophages
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Adenosine monophosphate (AMP)-activated protein kinase (AMPK) plays a central role in energy homeostasis and regulation of inflammatory responses. The present study is aimed to investigate the anti-inflammatory effects of ENERGI-F704, a nucleobase analogue isolated from bamboo leaves, on expression of proinflammatory mediators in murine macrophage RAW264.7 in response to lipopolysaccharide (LPS). ENERGI-F704 enhanced phosphorylation of AMPK(T172) but insignificantly affected the viability of RAW264.7 cells. Further investigation showed that ENERGI-F704 decreased mRNA expression of interleukin (IL)-6, IL-8, tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX2), and inducible nitric oxide synthase (iNOS) induced by LPS, as well as suppressed the production of prostaglandin E2 (PGE2) and nitric oxide (NO). Additionally, the inhibitory effects of ENERGI-F704 on the LPS-induced proinflammatory mediators were diminished by pretreatment of AMPK inhibitor Compound C. ENERGI-F704 also inhibited LPS-triggered activation of nuclear factor kappa B (NF-κB), phosphatidylinositol 3-kinase (PI3K), and p38 mitogen-activated protein kinase (p38), whereas extracellular signal-regulated kinase (Erk)1/2 and c-Jun N-terminal kinase (JNK) were insignificantly influenced. Our findings indicate that ENERGI-F704 may exert anti-inflammatory activity on RAW264.7 cells in response to LPS through the activation of AMPK and suppression of PI3K/P38/NF-κB signaling and the consequent decreased expression of proinflammatory mediators, suggesting that ENERGI-F704 is beneficial to the amelioration of inflammatory disorders.Keywords:
Proinflammatory cytokine
5'-Adenosine monophosphate-activated protein kinase (AMPK) is a potential therapeutic target for various medical conditions. We here identify a small-molecule compound (RX-375) that activates AMPK and inhibits fatty acid synthesis in cultured human hepatocytes. RX-375 does not bind to AMPK but interacts with prohibitins (PHB1 and PHB2), which were found to form a complex with AMPK. RX-375 induced dissociation of this complex, and PHBs knockdown resulted in AMPK activation, in the cultured cells. Administration of RX-375 to obese mice activated AMPK and ameliorated steatosis in the liver. High-throughput screening based on disruption of the AMPK-PHB interaction identified a second small-molecule compound that activates AMPK, confirming the importance of this interaction in the regulation of AMPK. Our results thus indicate that PHBs are previously unrecognized negative regulators of AMPK, and that compounds that prevent the AMPK-PHB interaction constitute a class of AMPK activator.
AMP-Activated Protein Kinase
Adenosine monophosphate
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2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a widespread environmental contaminant, exposure to it eliciting a broad spectrum of deleterious pathophysiological effects. Since mitogen-activated protein kinase (MAPK) pathways appear to play an important role in both cell survival and the apoptotic process, we assessed the effects of TCDD on the activation of extracellular signal-regulated kinase (ERK), Jun-N-terminal kinase (JNK), p38 MAPKs and caspase-3 in RAW 264.7 cells. TCDD treatment induced a transient upshift in ERK activity, followed by a decline, but a concomitant dramatic activation of p38. However, TCDD did not cause any apparent change in the activity of JNK, though it induced an up-regulation in caspase-3 activity. These results demonstrate that the equilibrium between the ERK and p38 pathways is critical to the fate of the cells, and that the activation of p38, upstream of caspase, plays an important role in the apoptotic process. The data obtained in this study also suggests that TCDD activates the MAPK pathway via an arylhydrocarbon receptor (AhR)-independent mechanism in RAW 264.7 murine macrophages.
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BACKGROUND: The effects of aging on the cardiovascular system contribute to substantial alterations in cellular morphology and function. The variables regulating these changes are unknown; however, one set of signaling molecules which may be of particular importance in mediating numerous cellular responses including control of cell growth, differentiation and adaptation are the proteins associated with the mitogen activated protein kinase (MAPK) signaling systems. Further MAPKs have emerged as critical components for regulating numerous mechanotrasductive cellular responses. Previous reports have suggested that agng impairs biaxial-loading induced MAPK phosphorylation. How agigng may affect uniaxial mechanotrasductive processes is not clear. PURPOSE: Here we investigate the ability of a uniaxial stretch activate MAPK pathways in adult (6 mo old), aged (30 mo old) and very aged (36 mo old) Fischer 344 x Brown Norway rats. METHODS: Aortea of adult (6 month), aged (30 month), and very aged (36 month) Fischer 344/NNiaHSD X Brown Norway / BiNia rats were subjected to acute bout of a 20% uniaxial stretch. MAPK protein expression, basal phosphorylation and the uniaxial stretch induced changes in phosphorylation were evaluated by immunoblotting. RESULTS: Western blotting of the MAPK family proteins extracellular signal-regulated kinase (ERK) 1/2, p38-, and c-Jun NH2-terminal kinase (JNK)-MAPKs showed differential expression and basal activation between these proteins with age, with notably higher phosphorylation in ERK1/2 and JNK compared to the 6 month aniumals. However, an acute bout of a 20% uniaxial stretch using an ex vivo aortic preparation demonstrated similar regulation of ERK 1/2 MAPK, p38-, and JNK MAPK. CONCLUSIONS: These observations confirm previous data demonstrating MAPK proteins are mechanically regulated, and in addition, suggest that MAPK signaling following uniaxial stretch is not altered with aging. Taken together, these data may help explain the age related changes in vascular morphology, function and response to injury. (Supported by funds from NSF Grant #0314742)
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AIM:To investigate the apoptotic effect of cepharanthine(CEP)on neonatal rat cardiomyocytes (NRCMs)and the underlying mechanisms.METHODS:MTT assay was used to detect the viability of the cells.CEP-induced apoptosis in NRCMs was evaluated by Hoechst 33342 staining and the expression of activated caspase-3.The phosphorylation levels of mitogen-activated protein kinases(MAPKs),such as extracellular signal-regulated kinase (ERK),c-jun N-terminal kinase(JNK)and p38 MAPK,were examined by Western blotting.The specific inhibitors of ERK and p38 MAPK were applied for identifying the roles of the corresponding signal pathways in CEP-induced apoptosis of cardiomyocytes.RESULTS:CEP inhibited the viability of NRCMs in a dose-and time-dependent manners.Positive nuclear fragmentation and activated caspase-3 were found in CEP-treated NRCMs.The phosphorylation levels of ERK and p38 MAPK were significantly elevated in CEP-treated NRCMs,but the change of JNK was not obvious.SB203580, an inhibitor of p38 MAPK,significantly alleviated the apoptotic effect induced by CEP.However,PD98059,an inhibitor of ERK1/2,did not significantly reduce the apoptotic effect.CONCLUSION:p38 MAPK is involved in CEP-induced apoptosis in NRCMs.
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Mangostenone F (MF) is a natural xanthone isolated from Garcinia mangostana. However, little is known about the biological activities of MF. This study was designed to investigate the anti-inflammatory effect and underlying molecular mechanisms of MF in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. MF dose-dependently inhibited the production of NO, iNOS, and pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β) in LPS-stimulated RAW264.7 macrophages. Moreover, MF decreased the NF-κB luciferase activity and NF-κB DNA binding capacity in LPS-stimulated RAW264.7 macrophages. Furthermore, MF suppressed the NF-κB activation by inhibiting the degradation of IκBα and nuclear translocation of p65 subunit of NF-κB. In addition, MF attenuated the AP-1 luciferase activity and phosphorylation of ERK, JNK, and p38 MAP kinases. Taken together, these results suggest that the anti-inflammatory effect of MF is associated with the suppression of NO production and iNOS expression through the down-regulation of NF-κB activation and MAPK signaling pathway in LPS-stimulated RAW264.7 macrophages.
Garcinia Mangostana
IκBα
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Abeliophyllum distichum is a medicinal plant used in regional traditional medicine to relieve pain in inflammatory processes. In this study, anti-inflammatory effects of Abeliophyllum distichum flower (ADF) extract were examined. Furthermore, possible molecular mechanisms of the anti-inflammatory effects were dissected. The anti-inflammatory activity was investigated by inhibition of lipopolysaccharide (LPS) induced pro-inflammatory cytokine production in murine macrophage-like cell line Raw264.7 cells. The measurement of the induced pro-inflammatory cytokine levels were carried out by ELISA. The phosphorylation of ERK1/2, JNK, and MAPK, and the nuclear expression of nuclear factor NF-κ B p65 were investigated by Western blot analysis. The extract of ADF significantly decreased the production of pro-inflammatory cytokines. In addition, the extract suppressed the phosphorylation of ERK1/2, JNK, and p38 MAPK, and the nuclear translocation of NF-κB p65 in activated cells. Our findings provide evidence for the popular use of Abeliophylli distichum in inflammation around Goesan region and also suggest that the flower extract has potential therapeutic benefits against various inflammatory diseases.
Proinflammatory cytokine
THP1 cell line
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Monocyte
IκBα
THP1 cell line
Blocking (statistics)
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Neurotropin (NTP) is a widely used drug in China and Japan mainly for the treatment of chronic pain and peripheral inflammation. Nevertheless, the effects of NTP on neuroinflammation have not been explored. In this study, we investigated the anti-inflammatory effects of NTP in lipopolysaccharide (LPS)-stimulated BV-2 microglial cells and its underlying mechanisms. BV-2 cells were pretreated with NTP for 12 h before exposure to LPS. The expression of pro-inflammatory cytokines (TNF-α and IL-6) were detected by RT-PCR and EILSA at mRNA and protein levels, respectively. Western blotting was conducted to measure the protein levels of major genes in MAPKs and NF-κB signaling pathways. Results demonstrated that NTP could attenuate the production of pro-inflammatory cytokines. Furthermore, NTP inhibited the activation of NF-κB signaling by decreasing the translocation of NF-κB p65 to the nucleus and suppressed the MAPKs signaling pathway via inhibition of the phosphorylation of p38, ERK and JNK. Taken together, these findings suggest that neurotropin exerts anti-inflammatory effects by suppressing the production of pro-inflammatory mediators via inhibition of NF-κB and MAPKs signaling pathways in LPS-stimulated BV-2 cells.
Proinflammatory cytokine
IκBα
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Calorie Restriction
Senescence
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Aromadendrin, a flavonol, has been reported to possess a variety of pharmacological activities such as anti-inflammatory, antioxidant, and anti-diabetic properties. However, the underlying mechanism by which aromadendrin exerts its biological activity has not been extensively demonstrated. The objective of this study is to elucidate the anti-inflammatory mechanism of aromadedrin in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells. Aromadendrin significantly suppressed LPS-induced excessive production of pro-inflammatory mediators such as nitric oxide (NO) and $PGE_2$ . In accordance, aromadendrin attenuated LPS-induced overexpression iNOS and COX-2. In addition, aromadendrin significantly suppressed LPS-induced degradation of $I{\kappa}B$ , which sequesters NF-${\kappa}B$ in cytoplasm, consequently inhibiting the nuclear translocation of pro-inflammatory transcription factor NF-${\kappa}B$ . To elucidate the underlying signaling mechanism of anti-inflammatory activity of aromadendrin, MAPK signaling pathway was examined. Aromadendrin significantly attenuated LPS-induced activation of JNK, but not ERK and p38, in a concentration-dependent manner. Taken together, the present study clearly demonstrates that aromadendrin exhibits anti-inflammatory activity through the suppression of nuclear translocation of NF-${\kappa}B$ and phosphorylation of JNK in LPS-stimulated RAW 264.7 macrophage cells.
IκBα
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