Caffeine suppresses lipopolysaccharide-stimulated BV2 microglial cells by suppressing Akt-mediated NF-κB activation and ERK phosphorylation

Since the anti-inflammatory effect of caffeine is unclear in microglial cells, we performed whether caffeine attenuates the expression of pro-inflammatory mediators in lipopolysaccharide (LPS)-stimulated BV2 microglial cells. Caffeine substantially suppressed the LPS-induced pro-inflammatory mediators nitric oxide (NO), prostaglandin E₂ (PGE₂) and tumor necrosis factor-α (TNF-α) in BV2 microglial cells. These effects resulted from the inhibition of their regulatory genes inducible NO synthase (iNOS), cycloxygenase-2 (COX-2) and TNF-α. In addition, caffeine significantly decreased LPS-induced DNA-binding activity of nuclear factor-κB (NF-κB) by suppressing the nuclear translocation of p50 and p65 subunits. A specific NF-κB inhibitor, pyrrolidine dithiocarbamate (PDTC), attenuated the LPS-induced expression of iNOS, COX-2 and TNF-α genes. In addition, we elucidated that inhibition of Akt phosphorylation plays a crucial role in caffeine-mediated NF-κB regulation in LPS-stimulated BV2 microglial cells. Caffeine also attenuated the LPS-induced phosphorylation of extracellular signal-regulated kinase (ERK) and a specific inhibitor of ERK, PD98059, subsequently downregulated the expression of the pro-inflammatory genes iNOS, COX-2 and TNF-α. Taken together, our data indicate that caffeine suppresses the generation of pro-inflammatory mediators, such as NO, PGE₂ and TNF-α as well as their regulatory genes in LPS-stimulated BV2 microglial cells by inhibiting Akt-dependent NF-κB activation and the ERK signaling pathway.     

Hyperoside inhibits lipopolysaccharide-induced inflammatory responses in microglial cells via p38 and NFκB pathways

Hyperoside (quercetin-3-O-β-d-galactoside) is an active compound isolated from herbs. Neuroinflammation is a key mechanism involved in neurodegenerative disorders including Parkinson's disease. In this study, we aimed to investigate the potentiality of hyperoside in inhibiting microglia-mediated neuroinflammation. BV2 microglial cells were pretreated with hyperoside and stimulated with lipopolysaccharide (LPS). The results showed that hyperoside significantly inhibited LPS-induced production of nitric oxide and pro-inflammatory cytokines including IL-1β and TNF-α, as well as the expression of inducible nitric oxide synthase. Similar results were observed in primary microglial cells isolated from neonatal mice. Analyses in MAPK and NFκB signaling combined with specific inhibitors suggested that hyperoside attenuated the LPS-induced inflammatory responses via p38 and NFκB pathways. Furthermore, hyperoside suppressed reactive microglia-mediated neurotoxicity as evidenced by conditioned media culture, but had no direct impact on MPP⁺-induced toxicity in SH-SY5Y neuroblastoma cells. Collectively, our data suggest that hyperoside may serve as a protective agent by alleviating microglia activation in disorders such as Parkinson's disease.     

Vitisin A suppresses LPS-induced NO production by inhibiting ERK,p38, and NF-κB activation in RAW 264.7 cells

Vitisin A, a resveratrol tetramer isolated from Vitis vinifera roots, exhibits antioxidative, anticancer, antiapoptotic, and anti-inflammatory effects. It also inhibits nitric oxide (NO) production. Here, we examined the mechanism by which vitisin A inhibits NO production in lipopolysaccharide (LPS)-induced RAW 264.7 macrophage cells. Vitisin A dose dependently inhibited LPS-induced NO production and inducible NO synthase (iNOS) expression. In contrast, the production of proinflammatory cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) was not altered by vitisin A. To investigate the signaling pathway for NO inhibition by vitisin A, we examined nuclear factor-κB (NF-κB) activation in the mitogen-activated protein kinase (MAPK) pathway, an inflammation-induced signal pathway in RAW 264.7 cells. Vitisin A inhibited LPS-induced extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 phosphorylation and suppressed LPS-induced NF-κB activation in RAW 264.7 cells. This suggests that vitisin A decreased NO production via downregulation of ERK1/2 and p38 and the NF-κB signal pathway in RAW 264.7 cells.     

Berbamine, a novel nuclear factor κB inhibitor, inhibits growth and induces apoptosis in human myeloma cells

Aim:

We sought to investigate the effect of berbamine on the growth of human multiple myeloma cell line KM3 and elucidate the mechanism of its action.

Methods:

MTT assay was used to determine the inhibitory effect of berbamine alone or combined with chemotherapeutic drugs. Flow cytometry was performed to characterize cell cycle profile in response to berbamine treatment. Western blot was used to measure the protein levels of p65, IκB Kinase α (IKKα), TNFAIP3 (A20), IκBα, p-IκBα, cyclinD1, Bcl-2, BAX, Bcl-x_L, Bid, and survivin.

Results:

Berbamine inhibits the proliferation of KM3 cells in a dose- and time-dependent manner. Combination of berbamine with dexamethasone (Dex), doxorubicin (Dox) or arsenic trioxide (ATO) resulted in enhanced inhibition of cell growth. Flow cytometric analysis revealed that KM3 cells were arrested at G₁ phase and apoptotic cells increased from 0.54% to 51.83% for 36 h. Morphological changes of cells undergoing apoptosis were observed under light microscope. Berbamine treatment led to increased expression of A20, down-regulation of IKKα, p-IκBα, and followed by inhibition of p65 nuclear localization. As a result, NF-κB downstream targets such as cyclinD1, Bcl-x_L, Bid and survivin were down-regulated.

Conclusion:

Berbamine inhibits the growth of KM3 cells by inducing G₁ arrest as well as apoptosis. Berbamine blocks NF-κB signaling pathway through up-regulating A20, down-regulating IKKα, p-IκBα, and then inhibiting p65 nuclear translocation, and resulting in decreased expression of the downstream targets of NF-κB. Our results suggest that berbamine is a novel inhibitor of NF-κB activity with remarkable anti-myeloma efficacy.     

Tetrandrine suppresses amyloid-β-induced inflammatory cytokines by inhibiting NF-κB pathway in murine BV2 microglial cells

Microglial cells play an important role in mediating neuroinflammation in Alzheimer's disease (AD) by production of a series of proinflammatory mediators and clearance of Aβ peptides and senile plaques. Tetrandrine, a bisbenzylisoquinoline alkaloid isolated from the Chinese herb Radix Stephania tetrandra, has been demonstrated to decrease the expression of proinflammatory mediators by inhibition of NF-κB activation. Here we investigated whether tetrandrine may affect the phagocytosis of microglia and the expression of cytokines and NF-κB in murine BV2 microglial cells. We found that fibrillar Amyloid-β (fAβ) induced phagocytosis of microglia and dramatically increased the levels of interleukin 1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) as well as the expression of phospho NF-κB p65 in microglia cultures. The treatment with tetrandrine resulted in downregulation of phospho NF-κB p65 expression and strikingly reduced the production of IL-1β and TNF-α. However, tetrandrine did not affect fAβ induced phagocytosis of microglia. In conclusion, tetrandrine can decrease microglial detriment of neurotoxicity while maintaining microglial benefit of neuroprotection. Tetrandrine may be an efficacious and promising remedy in the treatment of AD.     

Downregulation of NO and PGE2 in LPS-stimulated BV2 microglial cells by trans-isoferulic acid via suppression of PI3K/Akt-dependent NF-κB and activation of Nrf2-mediated HO-1

Little is known about whether trans-isoferulic acid (TIA) regulates the production of lipopolysaccharide (LPS)-induced proinflammatory mediators. Therefore, we examined the effect of TIA isolated from Clematis mandshurica on LPS-induced nitric oxide (NO) and prostaglandin E₂ (PGE₂) production in BV2 microglial cells. We found that TIA inhibited the production of LPS-induced NO and PGE₂ without accompanying cytotoxicity in BV2 microglial cells. TIA also downregulated the expression levels of specific regulatory genes such as inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) by suppressing LPS-induced NF-κB activity via dephosphorylation of PI3K/Akt. In addition, we demonstrated that a specific NF-κB inhibitor PDTC and a selective PI3K/Akt inhibitor, LY294002 effectively attenuated the expression of LPS-stimulated iNOS and COX-2 mRNA, while LY294002 suppressed LPS-induced NF-κB activity, suggesting that TIA attenuates the expression of these proinflammatory genes by suppressing PI3K/Akt-mediated NF-κB activity. Our results showed that TIA suppressed NO and PGE₂ production through the induction of nuclear factor erythroid 2-related factor 2 (Nrf2)-dependent heme oxygenase-1 (HO-1). Taken together, our data indicate that TIA suppresses the production of proinflammatory mediators such as NO and PGE₂, as well as their regulatory genes, in LPS-stimulated BV2 microglial cells, by inhibiting PI3K/Akt-dependent NF-κB activity and enhancing Nrf2-mediated HO-1 expression.     

Antrodia camphorata suppresses lipopolysaccharide-induced nuclear factor-κB activation in transgenic mice evaluated by bioluminescence imaging

In an earlier study, we found that Antrodia camphorata inhibited the production of lipopolysaccharide (LPS)-induced cytokines, inducible nitric oxide synthase, and cyclooxygenase-2 by blocking nuclear factor-κB (NF-κB) activation in cultured RAW 264.7 macrophages. This study was aimed at evaluating the inhibitory effects of the fermented culture broth of A. camphorata in terms of LPS-induced NF-κB activation in transgenic mice by using a non-invasive, real-time NF-κB bioluminescence imaging technique. Transgenic mice carrying the luciferase gene under the control of NF-κB were given A. camphorata (570 mg/kg, p.o.) for three consecutive days and then injected with LPS (4 mg/kg, i.p.). In vivo imaging showed that treatment with LPS increased the luminescent signal, whereas A. camphorata suppressed the LPS-induced inflammatory response significantly. Ex vivo imaging showed that A. camphorata suppressed LPS-induced NF-κB activity in the small intestine, mesenteric lymph nodes, liver, spleen, and kidney. Immunohistochemical staining revealed that A. camphorata suppressed production of the LPS-induced tumour necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and NF-κB p65 subunit in these organs. Furthermore, A. camphorata attenuated the productions of LPS-induced TNF-α and IL-1β in serum from transgenic mice. We report the first confirmation of the anti-inflammatory action in vivo of this potentially beneficial mushroom.     

Desoxyrhapontigenin,a potent anti-inflammatory phytochemical,inhibits LPS-induced inflammatory responses via suppressing NF-κB and MAPK pathways in RAW 264.7 cells

This study investigates the anti-inflammatory effects of a stilbene compound, desoxyrhapontigenin, which was isolated from Rheum undulatum. To determine the anti-inflammatory effects of this compound, lipopolysaccharide (LPS)-induced RAW 264.7 macrophages were treated with different concentrations of six stilbene derivatives. The results indicated that compared with other stilbene compounds, desoxyrhapontigenin (at 10, 30 and 50 μM concentrations) significantly inhibited nitric oxide (NO) production, nuclear factor kappa B (NF-κB) activation, the protein expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expression. Therefore, the anti-inflammatory mechanism of desoxyrhapontigenin was investigated in detail. The results of this investigation demonstrated that desoxyrhapontigenin suppressed not only LPS-stimulated pro-inflammatory cytokine secretions, including the secretions of tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6), but also PGE₂ release. As assayed by electrophoretic mobility shift assays (EMSAs), desoxyrhapontigenin also produced the dose-dependent inhibition of the LPS-induced activation of NF-κB and AP-1. Moreover, desoxyrhapontigenin inhibited the protein expression of myeloid differentiation primary response gene 88 (MyD88), IκB kinase (IKK) phosphorylation and the degradation of IκBα. Activations of p-JNK1 and p-Akt were also significantly inhibited, and phosphorylation of p38 and ERK was down-regulated. A further study revealed that desoxyrhapontigenin (5 and 25 mg/kg, i.p.) reduced paw swelling in carrageenan-induced acute inflammation model in vivo. On the whole, these results indicate that desoxyrhapontigenin showed anti-inflammatory properties by the inhibition of iNOS and COX-2 expression via the down-regulation of the MAPK signaling pathways and the inhibition of NF-κB and Akt activation.     

Arctigenin suppresses receptor activator of nuclear factor κB ligand (RANKL)-mediated osteoclast differentiation in bone marrow-derived macrophages

Osteoclasts, multinucleated bone-resorbing cells, are closely associated with bone diseases such as rheumatoid arthritis and osteoporosis. Osteoclasts are derived from hematopoietic precursor cells, and their differentiation is mediated by two cytokines, including macrophage colony stimulating factor and receptor activator of nuclear factor κB ligand (RANKL). Previous studies have shown that arctigenin exhibits an anti-inflammatory effect. However, the effect of arctigenin on osteoclast differentiation is yet to be elucidated. In this study, we found that arctigenin inhibited RANKL-mediated osteoclast differentiation in bone marrow macrophages in a dose-dependent manner and suppressed RANKL-mediated bone resorption. Additionally, the expression of typical marker proteins, such as NFATc1, c-Fos, TRAF6, c-Src, and cathepsin K, were significantly inhibited. Arctigenin inhibited the phosphorylation of Erk1/2, but not p38 and JNK, in a dose-dependent manner. Arctigenin also dramatically suppressed immunoreceptor tyrosine-based activation motif-mediated costimulatory signaling molecules, including Syk and PLCγ2, and Gab2. Notably, arctigenin inhibited the activation of Syk through RANKL stimulation. Furthermore, arctigenin prevented osteoclast differentiation in the calvarial bone of mice following stimulation with lipopolysaccharide. Our results show that arctigenin inhibits osteoclast differentiation in vitro and in vivo. Therefore, arctigenin may be useful for treating rheumatoid arthritis and osteoporosis.     

Saucerneol G, a new lignan, from Saururus chinensis inhibits matrix metalloproteinase-9 induction via a nuclear factor κB and mitogen activated protein kinases in lipopolysaccharide-stimulated RAW264.7 cells

This study was conducted to demonstrate the inhibitory effect of saucerneol G (SG), a new lignan, isolated from the aerial part of Saururus chinensis (Saururaceae) on lipopolysaccharide (LPS)-stimulated matrix metalloproteinase-9 (MMP)-9 inductions in RAW 264.7 cells. Aimed at evaluating the mechanism of action by which SG inhibits the LPS-mediated induction of MMP-9, the effects of SG on nuclear factor-κB (NF-κB) DNA binding activity, NF-κB-dependent reporter gene activity, inhibitory factor-κB (IκB) phosphorylation, degradation and p65 nuclear translocation were assessed. SG profoundly suppressed the DNA binding activity and the reporter gene activity as well as translocation of NF-κB p65 subunit. Furthermore, SG also dose dependently inhibited LPS-stimulated activation of mitogen-activated protein kinases (MAPKs). These findings suggest that SG may inhibit LPS-stimulated MMP-9 induction by blocking NF-κB and MAPKs activation.     

Effects of oxaprozin and of other 2-arylpropionic acid derivatives on nuclear factor κB(NF-κB) activation

The translocation to the nucleus and the binding of NF-B to DNA is thought to play a fundamental role in the activation of immune and inflammatory cells in order to activate the genes that in turn produce cytokines. We evaluated the ability of some 2-arylpropionic acid derivatives (fenoprofen, flurbiprofen, ketoprofen, S- and R-isomers of ibuprofen, ibuprofen, naproxen, and oxaprozin) to affect NF-B binding to DNA in human peripheral mononuclear cells. We observed NF-B inhibition by oxaprozin (IC₅₀ = 50 M), ibuprofen (185 M) and S-ibuprofen (51 M). Since oxaprozin reaches higher concentrations in synovial tissues and fluid (4—5 times higher than in plasma, i.e. around 100 M) its inhibitory activity is clinically relevant. The inhibitory activity observed with all other tested drugs was outside their clinically relevant concentrations. At the concentrations observed to affect the NF-B binding, oxaprozin and ibuprofen also inhibited the release of TNF- and interleukin 1 in cells stimulated by Escherichia coli lipolysaccharide. By administering oxaprozin or ibuprofen at high dosage it should be possible to inhibit NF-B DNA binding in humans in vivo.