Signaling In RAW264 Research Articles

β-Sitosterol Contributes in the Resistance to Invasion and Survival of Brucella abortus 544 within RAW264.7 Cells, and Cytokine Production with Reduced Susceptibility to Infection in BALB/c Mice.

We previously identified β-sitosterol (BS) as one of the most abundant compounds found in Korean red ginseng oil. BS is a widely prevalent vegetable-derived phytosterol with many known health benefits. Here, we investigated the efficacy of BS against Brucella (B.) abortus infection. BS showed no effect on bacterial growth but attenuated internalization, intracellular survival and MAPKs-linked intracellular signaling in RAW264.7 cells. BS treatment in cells is also associated with increased nitrite concentration during infection at 24 h. Slightly enhanced resistance to B. abortus infection was observed in mice orally given BS, which could be mediated by induced production of proinflammatory cytokines. Taken together, our study demonstrates the contribution of BS treatment against B. abortus infection although further investigation is encouraged to maximize its beneficial effects against intracellular infection.

Wnt5A Signaling Mediated Cytoskeletal Actin Modulations Shape the Outcome of Host‐Bacteria Interactions

Many human diseases are caused by bacterial infections. Host factors play an important role in determining the persistence vs. eradication of the incumbent bacteria. Among the milieu of host factors involved in immune defense against infections, Wnt5A‐Frizzled5/ROR1 signaling has emerged as an important one based on its established role in bacterial phagocytosis and the maintenance of immune homeostasis. Accordingly, we have deciphered how this signaling pathway differentiates between pathogenic and non‐pathogenic bacteria. Wnt5A signaling results in both uptake and killing of pathogenic bacteria including Pseudomonas sp., Streptococcus sp. and E. coli sp. independent of species specificity through cytoskeletal modulations that involve Rac1/Dvl1 activation. However, some laboratory bacterial strains such as E.coli DH5α and E.coli K12MG1655, that lack pathogenicity islands get internalized but not killed by Wnt5A signaling (Figure 1). In comparison to the non‐pathogenic bacterial strains the pathogenic bacterial strains result in decrease of total cellular F‐actin in the host macrophage (Figure 2). Revamping of Wnt5A signaling not only aids in recovery of the host cytoskeletal actin but also helps in containment of the infection. As for the non‐pathogenic strains, Wnt5A signaling aided uptake and sustenance of the bacteria inside the host correlate with increased actin polymerization around bacteria containing phagosomes. Interestingly, disruption of Wnt5A dependent actin polymerization in macrophages by actin polymerization inhibitors leads to increased infection by the pathogenic bacteria but killing of the non‐pathogenic lab strains (Figure 2). Preliminary observations suggest that the relation of some host commensals with Wnt5A signaling is similar to that of the non‐pathogenic bacteria. Our experimental data suggest that the interplay between Wnt5A induced actin polymerization and the pathogenic potential of incumbent bacteria is a major factor determining the outcome of the host‐bacteria interactions and bacterial persistence vs. eradication.Support or Funding InformationThis work was supported by funding from DBT, Govt. of India (BT/PR7106/MED/29/639/2012, BT/PR27125/BRB/10/1635/2017) and Institutional funding. SJ and SS were supported by Research Scholar Fellowship from CSIR, Govt. of India.Wnt5A signaling regulates host response to pathogenic and non‐pathogenic bacterial strains.In line with our previous report of Wnt5A signaling mediated killing of Pseudomonas and Streptococcus (Jati et al. Frontiers in immunology, 2018) we observed Wnt5A mediated killing of pathogenic Escherichia coli K1 strain (MOI 10) in both RAW264.7 and peritoneal macrophages (PMϕ) (a,b). But Wnt5A signaling in RAW264.7 and peritoneal macrophages (PMϕ) resulted in enhanced survival of non‐pathogenic bacterial strain Escherichia coli K12MG1655 (MOI 10) (c,d). Data represented as mean ± SEM; *p ≤ 0.05, **p ≤ 0.005, ***p≤ 0.0005. PBS: vehicle control for Wnt5A, MOI: Multiplicity of Infection, CFU: Colony Forming UnitsFigure 1Alteration of cytoskeletal actin in relation to Wnt5A signaling modulates the outcome of host‐bacteria interaction.Infection with pathogenic Escherichia coli K1 strain results in decrease of total cellular F‐actin compared to the non‐pathogenic Escherichia coli K12MG1655 and Escherichia coli DH5α (a). After 3hrs post infection (T3) of pathogenic Escherichia coli K1 the cellular F‐actin level increased in the Wnt5A treated macrophage set (b) compared to vehicle control (PBS). But in case of non‐pathogenic Escherichia coli DH5α there was no such change (b). In presence of Wnt5A, Arp2 inhibitor CK‐666 (Arp2 inh.) induces clearance of non‐pathogenic Escherichia coli K12MG1655 and Escherichia coli DH5α at 3hrs post infection but inhibits the killing of pathogenic Escherichia coli K1 (c). Data represented as mean ± SEM; *p ≤ 0.05, **p≤ 0.005, ***p≤ 0.0005. MOI: Multiplicity of InfectionFigure 2

Anti-inflammatory activity of the extracts from Rodgersia podophylla leaves through activation of Nrf2/HO-1 pathway, and inhibition of NF-κB and MAPKs pathway in mouse macrophage cells.

Recently, Rodgersia podophylla has been reported to exhibit anti-inflammatory activity. However, little is known about the potential mechanisms about its anti-inflammatory activity. We elucidated the anti-inflammatory mechanisms of leaves extracts from Rodgersia podophylla (RP-L) in RAW264.7 cells. LPS-induced NO was measured by Griess and mRNA of pro-inflammatory mediators was analyzed by RT-PCR. Cell viability was measured using MTT assay. The protein level was analyzed by Western blot. RP-L significantly inhibited the production of the pro-inflammatory mediators such as NO, iNOS, IL-1β and IL-6 in LPS-stimulated RAW264.7 cells. RP-L increased HO-1 expression in RAW264.7 cells, and the inhibition of HO-1 by ZnPP reduced the inhibitory effect of RP-L against LPS-induced NO production in RAW264.7 cells. Inhibition of p38, ROS and GSK3β attenuated RP-L-mediated HO-1 expression. Inhibition of ROS inhibited p38 phosphorylation and GSK3β expression induced by RP-L. In addition, inhibition of GSK3β blocked RP-L-mediated p38 phosphorylation. RP-L induced nuclear accumulation of Nrf2, and inhibition of p38, ROS and GSK3β abolished RP-L-mediated nuclear accumulation of Nrf2. Furthermore, RP-L blocked LPS-induced degradation of IκB-α and nuclear accumulation of p65. RP-L also attenuated LPS-induced phosphorylation of ERK1/2 and p38. In GC/MS analysis of RP-L, pyrogallol was detected as bioactive compound for anti-inflammatory activity of RP-L. Pyrogallol was observed to activate HO-1 expression through ROS/GSK3β/p38/Nrf2/HO-1 signaling. Our results suggest that RP-L exerts potential anti-inflammatory activity by activating ROS/GSK3β/p38/Nrf2/HO-1 signaling and inhibiting NF-κB and MAPK signaling in RAW264.7 cells. These findings suggest that RP-L may have great potential for the development of anti-inflammatory drug.

Interleukin-37 Ameliorates Influenza Pneumonia by Attenuating Macrophage Cytokine Production in a MAPK-Dependent Manner.

Viral pneumonitis caused by influenza A (H1N1) virus leads to high levels of morbidity and mortality. Given the limited treatment options for severe influenza pneumonia, it is necessary to explore effective amelioration approaches. Interleukin-37 (IL-37) has been reported to inhibit excessive immune responses and protect against a variety of inflammatory diseases. In this study, by using BALB/c mice intranasally infected with A/California/07/2009 (H1N1), we found that IL-37 treatment increases the survival rate and body weight, and reduces the pulmonary index, impaired the lung injury and decreased production of pro-inflammatory cytokines in the BALF and lung tissue. Moreover, IL-37 administration enhanced not only the percentage of macrophages, but also the percentage of IL-18Rα+ macrophages, suggesting that enhancing the macrophages function may improve outcomes in a murine model of H1N1 infection. Indeed, macrophages depletion reduced the protective effect of IL-37 during H1N1 infection. Furthermore, IL-37 administration inhibited MAPK signaling in RAW264.7 cells infected with H1N1. This study demonstrates that IL-37 treatment can ameliorate influenza pneumonia by attenuating cytokine production, especially by macrophages. Thus, IL-37 might serve as a promising new target for the treatment of influenza A-induced pneumonia.

Flavonoids from Livistona chinensis fruit ameliorates LPS/D-GalN-induced acute liver injury by inhibiting oxidative stress and inflammation

Abstract Livistona chinensis fruit is a traditional Chinese medicine widely used for treating hepatitis, but its protective effect against hepatitis remains unknown. This study investigated the hepatoprotective effect and mechanism of flavonoids from Livistona chinensis fruit (FLCF). Mice received FLCF pre-treatment for 7 days and induced liver injury with LPS+D-GalN. RAW264.7 cells were triggered inflammation by LPS and received FLCF for 24 h. The result showed that FLCF ameliorated the liver pathology in mice, decreased the levels of AST, ALT, MDA, but increased SOD and GSH. Moreover, FLCF inhibited TLR4/NF-κB signaling, while activated Nrf2/HO-1 signaling in LPS+D-GalN mice. These effects were consistent with the in vitro data revealing that FLCF suppressed TLR4/NF-κB signaling, while promoting Nrf2/HO-1 signaling in RAW264.7 cell. The effects of FLCF were neutralized by Nrf2 siRNA. Taken together, these results demonstrated that FLCF has a protective role against acute liver injury and supports its use as a dietotherapy.

O-Methylbulbocapnine and Dicentrine Suppress LPS-Induced Inflammatory Response by Blocking NF-κB and AP-1 Activation through Inhibiting MAPKs and Akt Signaling in RAW264.7 Macrophages.

The natural aporphine alkaloids including crebanine (CN), O-methylbulbocapnine (OMP), and dicentrine (DC), and protoberberine alkaloids, tetrahydropalmatine (THP) and N-methyl tetrahydropalmatine (NTHP), have been found in Stephania venosa. Previous reports demonstrated CN and THP exhibited anti-inflammatory properties. In this study, we investigated anti-inflammatory effect of CN analogs including OMP, DC, THP, and NTHP in RAW264.7 macrophages. The pre-treatment of macrophages with CN, OMP and DC suppressed lipopolysaccharide (LPS)-induced pro-inflammatory cytokines and mediators including interleukin-6 (IL-6), tumor necrosis factor alpha, prostaglandin E2 and nitric oxide, in which the rank-order of inhibitory potency was DC>CN≥OMP. Whereas, high dose THP (30-40 µg/mL) reduced LPS-induced IL-6 production in RAW264.7 cells but NTHP did not effect. Moreover, CN, OMP and DC inhibited the LPS-induced expression of inducible nitric oxide synthase and cyclooxygenase-2. OMP and DC inhibited LPS-induced nuclear factor kappa B (NF-κB) activation by suppressing the phosphorylation of NF-κB at Ser536, but not the nucleus translocation and inhibitor of kappaB (IκB)-α degradation. In addition, OMP and DC also reduced the phosphorylation and nucleus translocation of activator protein-1 (AP-1). Furthermore, OMP and DC suppressed the LPS-activated myeloid differentiation factor 88 (MyD88), Akt and mitogen-activated protein kinases (MAPKs) signaling pathway, which were the upstream signaling regulators of AP-1 and NF-κB. Collectively, OMP and DC have an anti-inflammatory effect on RAW264.7 macrophages by the suppression of pro-inflammatory cytokines and mediators. The inhibitory property of OMP and DC is mediated by blockage the activation of MyD88, MAPKs, Akt, NF-κB and AP-1 signaling molecules.

Phloretin as a Potent Natural TLR2/1 Inhibitor Suppresses TLR2-Induced Inflammation.

Toll-like receptor 2 (TLR2) responses are involved in various inflammatory immune disorders. Phloretin is a naturally occurring dietary flavonoid that is abundant in fruit. Here, we investigated whether the anti-inflammatory activity of phloretin is mediated through TLR2 pathways, and whether phloretin acts as an inhibitor of TLR2/1 heterodimerization using the TLR2/1 agonist Pam3CSK4. We tested the effects of phloretin on tumor necrosis factor (TNF)-α production induced by various TLRs using known TLR-specific agonists. Phloretin significantly inhibited Pam3CSK4-induced TRL2/1 signaling in Raw264.7 cells compared to TLR signaling induced by the other agonists tested. Therefore, we further tested the effects of phloretin in human embryonic kidney (HEK) 293-hTLR2 cells induced by Pam3CSK4, and confirmed that phloretin has comparable inhibition of TLR2/1 heterodimerization to that induced by the known TLR2 inhibitor CU-CPT22. Moreover, phloretin reduced the secretion of the inflammatory cytokines TNF-α and interleukin (IL)-8 in Pam3CSK4-induced HEK293-hTLR2 cells, whereas it did not significantly reduce these cytokines under Pam2CSK4-induced activation. Western blot results showed that phloretin significantly suppressed Pam3CSK4-induced TLR2 and NF-κB p65 expression. The molecular interactions between phloretin and TLR2 were investigated using bio-layer interferometry and in silico docking. Phloretin bound to TLR2 with micromolar binding affinity, and we proposed a binding model of phloretin at the TLR2–TLR1 interface. Overall, we confirmed that phloretin inhibits the heterodimerization of TLR2/1, highlighting TLR2 signaling as a therapeutic target for treating TLR2-mediated inflammatory immune diseases.

Magnolol inhibits Streptococcus suis-induced inflammation and ROS formation via TLR2/MAPK/NF-κB signaling in RAW264.7 cells.

Our previous studies have shown that Magnolol (Mag) improves the symptoms and decreases the levels of cytokines during infection induced by Streptococcus suis (S. suis) in mice. Although some reports show that Mag inhibits lipopolysaccharide-induced inflammatory responses via downregulating mitogen-activated protein kinases (MAPK) and nuclear factor-κB (NF-κB) signaling pathways, the molecular mechanisms underlying Mag-mediated inhibition of S. suis-induced inflammatory responses are poorly understood. Here, RAW264.7 cells were stimulated with S. suis in the presence or absence of Mag. Cell viability and bactericidal effects were examined, and the concentrations of tumor necrosis factor-a (TNF-α), IL-1β (interleukin-1β), IL-6 (interleukin-6), and IL-8 (interleukin- 8) were determined by ELISA. The change in ROS (reactive oxygen species) was determined by fluorescence microscopy and ELISA. The levels of Toll-like receptor 2 (TLR2) and MAPK family proteins and NF-κB signaling were determined by Western blot analysis. S. suis induced massive RAW264.7 cell death, a decline in bactericidal activity, the release of inflammatory cytokines, increased oxidative stress, and activation of TLR2/MAPK/NF-κB signaling pathways. Mag treatment significantly suppressed macrophage cell death and caused a decline in bactericidal activity. Furthermore, Mag decreased inflammatory cytokines production and ROS generation. It also prevented p38, extracellular regulated protein kinases (ERK), c-Jun N-terminal kinase (JNK), inhibitor of NF-κB (IκB), and NF-κB phosphorylation induced by S. suis in a dose-dependent manner. Our results indicate that Mag exerts anti-inflammatory and cell-protective effects and mediates the activation of MAPK and NF-κB signaling by downregulating the expression of TLR2 upregulated by S. suis.

Cortisol modulates inflammatory responses in LPS-stimulated RAW264.7 cells via the NF-\u03baB and MAPK pathways

BackgroundThe uteruses of most dairy cattle are easily infected by bacteria, especially gram-negative bacteria, following parturition. Macrophages are important cells of the immune system and play a critical role in the inflammatory response. In addition, cortisol levels become significantly increased due to the stress of parturition in dairy cattle, and cortisol is among the most widely used and effective therapies for many inflammatory diseases. In this study, we assessed the anti-inflammatory effects and potential molecular mechanisms of cortisol using a Lipopolysaccharide (LPS)-induced RAW264.7 macrophage cell line.ResultsCortisol significantly suppressed the production of prostaglandin E2 (PGE2) and decreased the gene and protein expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) in a dose-dependent manner. Moreover, cortisol inhibited the mRNA expression of pro-inflammatory cytokines including tumor necrosis factor alpha (TNFα), interleukin-1β (IL-1β), and interleukin-6 (IL-6) and decreased IL-1β secretion in an LPS-treated RAW264.7 macrophage cell line. Moreover, we found that cortisol suppressed nuclear factor-kappa B (NF-κB) signaling in RAW264.7 macrophages stimulated with LPS. This suppression was mediated by the inhibition of IκBα degradation and NF-κB p65 phosphorylation. In addition, cortisol also suppressed the phosphorylation of mitogen-activated protein kinases (MAPK) such as extracellular signal-regulated kinase (ERK1/2), p38 MAPK, and c-Jun N-terminal kinase/stress-activated protein kinase (JNK).ConclusionsThese results suggest that high cortisol levels can attenuate LPS-induced inflammatory responses in the RAW264.7 macrophage cell line by regulating the NF-κB and MAPK signaling pathways.

Effects of a novel microtubule-depolymerizer on pro-inflammatory signaling in RAW264.7 macrophages

The Nuclear Factor-kappa B (NF-κB) pathway is vital for immune system regulation and pro-inflammatory signaling. Many inflammatory disorders and diseases, including cancer, are linked to dysregulation of NF-κB signaling. When macrophages recognize the presence of a pathogen, the signaling pathway is activated, resulting in the nuclear translocation of the transcription factor, NF-κB, to turn on pro-inflammatory genes. Here, we demonstrate the effects of a novel microtubule depolymerizer, NT-07-16, a polysubstituted pyrrole compound, on this process. Treatment with NT-07-16 decreased the production of pro-inflammatory cytokines in RAW264.7 mouse macrophages. It appears that the reduction in pro-inflammatory mediators produced by the macrophages after exposure to NT-07-16 may be due to activities upstream of the translocation of NF-κB into the nucleus. NF-κB translocation occurs after its inhibitory protein, IκB-α is phosphorylated which signals for its degradation releasing NF-κB so it is free to move into the nucleus. Previous studies from other laboratories indicate that these processes are associated with the microtubule network. Our results show that exposure to the microtubule-depolymerizer, NT-07-16 reduces the phosphorylation of IκB-α and also decreases the association of NF-κB with tubulin which may affect the ability of NF-κB to translocate into the nucleus. Therefore, the anti-inflammatory activity of NT-07-16 may be explained, at least in part, by alterations in these steps in the NF-κB signaling pathway leading to less NF-κB entering the nucleus and reducing the production of pro-inflammatory mediators by the activated macrophages.

Extracts of Porphyra tenera (Nori Seaweed) Activate the Immune Response in Mouse RAW264.7 Macrophages via NF-κB Signaling.

Porphyra tenera, also known as nori, is a red algal species of seaweed. It is cultivated in Asia for culinary purposes. We report that P. tenera extract (PTE) enhances the immune response in mouse macrophages. We found that P. tenera extract regulates the NF-κB IκB kinase (IKK) signaling pathway, and we assessed the expression and translocation of p65, a subunit of NF-κB, in RAW264.7 mouse macrophage cells after treatment with PTE. We also investigated the effects of 10% ethanol PTE (PTE10) in RAW264.7 cells. The production of IL-10, IL-6, TNF-α, and IFN-γ was induced by PTE treatment of the macrophages, and PTE also enhanced p-IκB and p-AKT. PTE10 showed no cytotoxicity at 10-20 μg/mL in RAW264.7 cells. PTE10, in fact, increased cell viability at 24 h, stimulated macrophage cells, and induced the phosphorylation of Akt. Akt stimulates IKK activity through the phosphorylation of IKKα and enhances immune activity through the activation of NF-κB. In this study, NF-κB activation was induced by increasing p-NF-κB and p-IKK. A subunit of NF-κB, p65, was located in the nucleus and increased the expression of various cytokines. PTE thus enhanced the immune response through IκB-α immunostimulation signaling in RAW264.7 cells. PTE10 has potential therefore for development of future treatments requiring immune system stimulation.

Anti-inflammatory effect and mechanism of action of Lindera erythrocarpa essential oil in lipopolysaccharide-stimulated RAW264.7 cells.

The aim of this study was to investigate the chemical constituents of Lindera erythrocarpa essential oil (LEO) by gas chromatography-mass spectrometry and evaluate their inhibitory effect on the expression of pro-inflammatory mediators in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Fifteen compounds, accounting for 63.7 % of the composition of LEO, were identified. The main compounds were nerolidol (18.73 %), caryophyllene (14.41 %), α-humulene (7.73 %), germacrene-D (4.82 %), and α-pinene (4.47 %). LEO significantly inhibited the expression of inducible nitric oxide (NO) synthase and cyclooxygenase-2, and subsequent production of NO and prostaglandin E2. In addition, it reduced the release of pro-inflammatory cytokines in LPS-activated RAW264.7 cells. The molecular mechanism underlying the effect of LEO was associated with inhibition of the phosphorylation of mitogen-activated protein kinase (MAPK). Furthermore, LEO inhibited LPS-induced phosphorylation and degradation of inhibitor of kappa B-α, which is required for the activation of the p50 and p65 nuclear factor (NF)-κB subunits in RAW264.7 cells. Taken together, these data suggest that LEO exerted its anti-inflammatory effect by downregulating LPS-induced production of pro-inflammatory mediators through the inhibition of NF-κB and MAPK signaling in RAW264.7 cells.

Green lipped mussel oil complex suppresses lipopolysaccharide stimulated inflammation via regulating nuclear factor-κB and mitogen activated protein kinases signaling in RAW264.7 murine macrophages

Here we investigated the effect of green lipped mussel oil complex (GLMOC) on inflammation and underlying mechanism in lipopolysaccharide stimulated RAW264.7 murine macrophage cells. GLMOC containing green lipped mussel oil (GLMO), olive oil, and vitamin E (10:20:1) can induce significant suppression of iNOS, leading to reduced nitric oxide synthesis, and cyclooxygenase-2, leading to reduced prostaglandin E2 synthesis. In addition, it down-regulated the release of pro-inflammatory cytokines, including tumor necrosis factor-α, interleukin (IL)-6, and IL-1β. Similar to upstream signaling mediators, GLMCO inhibited the degradation of inhibitory κB, nuclear translocation of NF-κB, and phosphorylation of mitogen activated protein kinases (MAPKs) in a dose-dependent manner. Among the components of GLMOC, GLMO was responsible for anti-inflammatory efficacy. Taken together, GLMOC induces anti-inflammatory activity via regulating NF-κB and MAPK signaling in lipopolysaccharide-induced RAW264.7 cells, providing underlying mechanisms that elucidate the anti-inflammatory efficacy of GLMOC.

Manipulation of Curcumin Degradation to Enhance its Stability and Biological Activity

Curcumin, a dietary compound from turmeric, is one of the most promising dietary compounds for cancer prevention and inflammation. However, curcumin rapidly degrades at physiological pH with a half‐life of several minutes, making it difficult to discern whether the cancer preventing and inflammation reducing effects are due to curcumin itself or its degradation products. In order to determine which compounds were most responsible for the observed anti‐cancer and anti‐inflammatory effects, we compared the biological activities of curcumin with a mixture of its stable total degradation products (TDP) and the most abundant stable degradation product, bicyclopentadione (BCP). We compared the effects of these compounds on cell proliferation, cell cycle progression, and apoptosis in MC38 colon cancer cells and lipopolysaccharide (LPS)‐induced inflammatory responses and NF‐kB signaling in RAW 264.7 macrophages. Our results showed that compared with curcumin, both TDP and BCP have dramatically reduced effects on cell proliferation, cell cycle progression and apoptosis in MC38 cells, and reduced effects on inhibition of inflammatory responses and NF‐kB signaling in RAW264.7 cells. These results suggest that the observed effects of curcumin are mainly mediated by curcumin itself, rather than its degradation products. We further showed that co‐addition of redox active antioxidants, which stabilizes curcumin in aqueous buffer, significantly enhanced the biological effects of curcumin in MC38 cells. Together, these results suggest that manipulation of curcumin degradation is a promising strategy to enhance its anti‐cancer and anti‐inflammatory effects.Support or Funding InformationArmstrong Fund of Science Award from University of Massachusetts Amherst and USDA NIFA 2016‐67017‐24423

Stimulation of Alpha7 Nicotinic Acetylcholine Receptor Attenuates Nicotine-Induced Upregulation of MMP, MCP-1, and RANTES through Modulating ERK1/2/AP-1 Signaling Pathway in RAW264.7 and MOVAS Cells.

Vagus nerve stimulation through alpha7 nicotine acetylcholine receptors (α7-nAChR) signaling had been demonstrated attenuation of inflammation. This study aimed to determine whether PNU-282987, a selective α7-nAChR agonist, affected activities of matrix metalloproteinase (MMP) and inflammatory cytokines in nicotine-treatment RAW264.7 and MOVAS cells and to assess the underlying molecular mechanisms. RAW264.7 and MOVAS cells were treated with nicotine at different concentrations (0, 1, 10, and 100 ng/ml) for 0–120 min. Nicotine markedly stimulated the phosphorylation of extracellular signal-regulated kinase1/2 (ERK1/2) and c-Jun in RAW264.7 cells. Pretreatment with U0126 significantly suppressed phosphorylation of ERK1/2 and further attenuated nicotine-induced activation of c-Jun and upregulation of MMP-2, MMP-9, monocyte chemotactic protein- (MCP-) 1, and regulated upon activation normal T cell expressed and secreted (RANTES). Similarly, nicotine treatment also increased phosphorylation of c-Jun and expressions of MMP-2, MMP-9, MCP-1, and RANTES in MOVAS cells. When cells were pretreated with PNU-282987, nicotine-induced activations of ERK1/2 and c-Jun in RAW264.7 cells and c-Jun in MOVAS cells were effectively inhibited. Furthermore, nicotine-induced secretions of MMP-2, MMP-9, MCP-1, and RANTES were remarkably downregulated. Treatment with α7-nAChR agonist inhibits nicotine-induced upregulation of MMP and inflammatory cytokines through modulating ERK1/2/AP-1 signaling in RAW264.7 cells and AP-1 in MOVAS cells, providing a new therapeutic for abdominal aortic aneurysm.

Protein Tyrosine Phosphatase N2 Is a Positive Regulator of Lipopolysaccharide Signaling in Raw264.7 Cell through Derepression of Src Tyrosine Kinase

T cell protein tyrosine phosphatase N2 (PTPN2) is a phosphotyrosine-specific nonreceptor phosphatase and is ubiquitously expressed in tissues. Although PTPN2 functions as an important regulator in different signaling pathways, it is still unclear what is specific target protein of PTPN2 and how is regulated in lipopolysaccharide (LPS)-induced inflammatory signaling pathway. Here, we found that PTPN2 deficiency downregulated the expression of LPS-mediated pro-inflammtory cytokine genes. Conversely, overexpression of PTPN2 in Raw264.7 cells enhanced the expression and secretion of those cytokines. The activation of MAPK and NF-κB signaling pathways by LPS was reduced in PTPN2-knockdowned cells and ectopic expression of PTPN2 reversed these effects. Furthermore, we found that PTNP2 directly interacted with Src and removed the inhibitory Tyr527 phosphorylation of Src to enhance the activatory phosphorylation of Tyr416 residue. These results suggested that PTPN2 is a positive regulator of LPS-induced inflammatory response by enhancing the activity of Src through targeting the inhibitory phosphor-tyrosine527 of Src.

Mer receptor tyrosine kinase negatively regulates lipoteichoic acid-induced inflammatory response via PI3K/Akt and SOCS3.

Activation of toll-like receptor (TLR) signaling that initiates an innate immune response to pathogens must be strictly regulated to prevent excessive inflammatory damage in the host. Here, we demonstrate that Mer receptor tyrosine kinase (MerTK) is a negative regulatory molecule in the lipoteichoic acid (LTA)-induced inflammatory response. LTA that activated TLR2 signaling concomitantly induced activation of MerTK signaling in RAW264.7 macrophages, including phosphoinositide 3-kinase (PI3K)/Akt and suppressor of cytokine signaling 3 (SOCS3). Moreover, LTA induced MerTK activation in a time-dependent manner, and LTA-induced MerTK activation was dependent on the ligand Gas6. Additionally, pretreatment with a specific Mer-blocking antibody significantly inhibited LTA-induced phosphorylation of MerTK, while further enhancing LTA-induced phosphorylation of IκB-α and NF-κBp65 as well as production of TNF-α and IL-6. Meanwhile, the antibody blockade of MerTK markedly prevented LTA-induced Akt phosphorylation and SOCS3 expression, both of which were crucial for the inhibition of TLR2-mediated immune response. Collectively, these results suggest, for the first time, that MerTK is an intracellular negative feedback regulator that inhibits the inflammatory response of LTA-stimulated macrophages through the PI3K/Akt pathway and SOCS3 protein.

A pterostilbene derivative suppresses osteoclastogenesis by regulating RANKL-mediated NFκB and MAPK signaling in RAW264.7 cells.

A dysfunctional osteoclast activity is often the cause of bone destructive diseases, such as osteoporosis, periodontitis, erosive arthritis, and cancer. The NFκB ligand (RANKL) has been identified as a major mediator of bone resorption. Agents that suppress RANKL signaling have the potential to inhibit bone resorption or osteoclastogenesis. The present study aimed to determine the effect of a pterostilbene derivative (PTERC-T) for suppressing RANKL or tumor cells-induced osteoclastogenesis in RAW264.7 murine macrophages. Cytotoxicity was measured by MTT assay and inhibitory effect on osteoclastogenesis was analyzed by counting the number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells and measuring the expression levels of the osteoclast-specific genes. The reactive oxygen species (ROS) generation was detected by FACS. Further, signaling pathways were analyzed by immunofluorescence and immunoblot analyses. PTERC-T suppressed the differentiation of monocytes to osteoclasts in a dose and time-dependent manner. The expression of osteoclast marker genes like TRAP, cathepsin K (CTSK), matrix metalloproteinase 9 (MMP9) and transcription factors c-Fos, and nuclear factor of activated T cells cytoplasmic 1 (NFATc1) were also diminished by PTERC-T. PTERC-T scavenged intracellular ROS generation within osteoclast precursors during RANKL-stimulated osteoclastogenesis. Mechanistically, PTERC-T abrogated the phosphorylation of MAPKs (ERK and JNK) and inhibited RANKL-induced activation of NFκB by suppressing IκBα phosphorylation and preventing NFκB/p65 nuclear translocation. This study thus identifies PTERC-T as an inhibitor of osteoclast formation and provides evidence for its role in preventing osteoporosis and other bone related disorders. However, further studies are needed to establish its efficacy in vivo.

Anti-inflammatory effects of Perilla frutescens leaf extract on lipopolysaccharide-stimulated RAW264.7 cells.

Perilla leaves are widely used in Chinese herbal medicine and in Japanese herbal agents used to treat respiratory diseases. This study aimed to investigate the anti‑inflammatory effects and the underlying mechanisms of Perilla frutescens leaf extract (PLE). Murine macrophage RAW264.7 cells were used as a model. Cell viability and morphological changes were studied by the MTT assay and microscopy. mRNA expression of pro‑inflammatory mediators was assessed by both semi‑quantitative reverse transcription‑polymerase chain reaction(RT‑PCR) and quantitative (q) RT‑PCR. Nitric oxide(NO) and prostaglandinE2 (PGE2) production were analyzed by the Griess test and sandwich enzyme‑linked immunosorbent assay (ELISA), respectively. The activation of kinase cascades was studied by immunoblotting. Our findings showed that PLE slightly affects cell viability, but alleviates LPS‑induced activation of RAW264.7 cells. Furthermore, PLE significantly reduced the LPS‑induced mRNA expression of the interleukin (IL)‑6, IL‑8, tumor necrosis factor‑α(TNF‑α), cyclooxygenase‑2(COX‑2) and inducible nitric oxide synthase(iNOS), genes in a dose‑dependent manner. In addition, PLE reduced NO production and PGE2 secretion induced by LPS. PLE also inhibited activation of mitogen‑activated protein kinases(MAPKs), increased the cytosolic IκBα level, and reduced the level of nuclear factor (NF)‑κB. Taken together, these findings indicate that PLE significantly decreases the mRNA expression and protein production of pro‑inflammatory mediators, via the inhibition of extracellular‑signal‑regulated kinase (ERK)1/2, c‑Jun N‑terminal kinase (JNK), p38, as well as NF‑κB signaling in RAW264.7 cells stimulated with LPS.

Prostate cancer-derived CCN3 induces M2 macrophage infiltration and contributes to angiogenesis in prostate cancer microenvironment.

Tumor-associated macrophages (TAMs) are M2-polarized macrophages that infiltrate the tumor microenvironment and promote tumorigenesis. However, the mechanisms by which TAMs modulate prostate cancer (PCa) growth are poorly understood. Here, we found that expression of Nephroblastoma Overexpressed (NOV/CCN3) is upregulated in PCa cells and correlated with M2 macrophage infiltration. RAW264.7 macrophage migration was induced by conditioned media (CM) from various PCa cells in proportion to the cellular level of CCN3 expression and was inhibited by an anti-CCN3 neutralizing antibody. CCN3 and PCaCM treatment skewed RAW264.7 cell differentiation from an M1 phenotype to an M2 phenotype. PCa-derived CCN3 induced focal adhesion kinase (FAK)/Akt/NF-κB signaling in RAW264.7 cells, which resulted in VEGF expression and subsequently increased tube formation in endothelial progenitor cells. Finally, PCa-secreted CCN3 stimulated RAW264.7 cells and promoted angiogenesis in the chick chorioallantoic membrane assay (CAM), and increased tumor growth and tumor-associated angiogenesis in a PCa xenograft mouse model. Our results indicate that PCa-secreted CCN3 can recruit macrophages and skew their differentiation to an M2 phenotype. In turn, CCN3-stimulated macrophages contribute to VEGF-dependent angiogenesis. This study reveals a novel mechanism by which TAMs enhance PCa angiogenesis and identifies a potential therapeutic target for PCa.