Amentoflavone inhibits the induction of nitric oxide synthase by inhibiting NF-κB activation in macrophages

Amentoflavone is a bi-flavonoid compound with anti-fungal and anti-inflammatory activities. We isolated amentoflavone from Selaginella tamariscina (Selaginellaceae) and studied its effects on nuclear factor-kappaB (NF-kappaB)-mediated inducible nitric oxide synthase (iNOS) gene expression in RAW 264.7 cells. Amentoflavone inhibited the production of nitric oxide in a concentration-dependent manner and also blocked the lipopolysaccharide (LPS)-induced expression of inducible nitric oxide synthase (iNOS). To clarify the mechanistic basis for its inhibition of iNOS induction, we examined the effect of amentoflavone on the transactivation of iNOS gene by luciferase reporter activity using -1.59 kb flanking region. Amentoflavone potently suppressed the reporter gene activity. The LPS-induced activation of NF-kappaB was also found to be significantly blocked by amentoflavone, but AP-1 activation was unaffected. Furthermore, the nuclear translocation of p65 by LPS was inhibited by amentoflavone. NF-kappaB activation is controlled by the phosphorylation and subsequent degradation of I-kappaBalpha, and the cytosolic degradation of I-kappaBalpha was found to be inhibited by amentoflavone. These findings suggest that the inhibition of LPS-induced NO formation by amentoflavone is due to its inhibition of NF-kappaB by blocking I-kappaBalpha degradation, which may be the mechanistic basis of the anti-inflammatory effects of amentoflavone.     

Sesamin exerts anti-tumor activity in esophageal squamous cell carcinoma via inhibition of TRIM44 and NF-κB signaling

Tripartite motif-containing 44 (TRIM44) is known to play an oncogenic role in multiple human cancers, including esophageal cancer. Sesamin possesses potent anti-inflammatory and anti-cancer properties for various cancers. This study is designed to unravel the biological functions of sesamin and TRIM44 in esophageal cancer. TRIM44 expression in esophageal squamous cell cancer (ESCC) cell lines and tissues was determined by RT-qPCR assay and Western blot. The effects of sesamin and TRIM44 on ESCC cell growth in vivo and in vitro were assessed by the mouse model and CCK-8 assay, respectively. We found that TRIM44 was significantly upregulated in ESCC cell lines and tissues when compared to their counterparts. Sesamin treatment or depletion of TRIM44 markedly reduced ESCC cell proliferation. The nuclear factor kappa B (NF-κB) and toll-like receptor 4 (TLR4) signaling pathway may be involved in sesamin-mediated TRIM44 suppression. Finally, we showed that oral administration of sesamin dramatically inhibited tumor growth or ESCC in nude mice. Our results suggest that sesamin exerts anti-tumor activity in ESCC via inhibition of NF-κB signaling pathway, demonstrating its potential for the treatment of esophageal cancer.     

Anti-inflammatory effect of leaves of Eriobotrya japonica correlating with attenuation of p38 MAPK, ERK, and NF-κB activation in mast cells

Mast cell-mediated allergic inflammation is involved in many diseases such as asthma and sinusitis. Mast cells induce synthesis and production of pro-inflammatory cytokines including tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-8 with immune regulatory properties. In the present study, we investigate the effect an unspecified aqueous extract from leaves of Eriobotrya japonica Lindl. (Rosaceae) (LEJL) on the expression of pro-inflammatory cytokines and its possible mechanisms of action in human mast cells (HMC-1). LEJL dose-dependently inhibited phorbol 12-myristate 13-acetate (PMA) and calcium ionophore A23187 (PMACI)-induced gene expression and secretion of TNF-α, IL-6, and IL-8. LEJL attenuated PMACI-induced activation of nuclear factor (NF)-κB, and specifically blocked activation of p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK) but not that of c-jun N-terminal kinase. The inhibitory effect of LEJL on the pro-inflammatory cytokines was likely NF-κB, p38 MAPK, and ERK dependent. Our in vitro studies provide evidence that LEJL might contribute to the treatment of mast cell-derived allergic inflammatory diseases.     

Improving the Adjuvanticity of Small Molecule Immune Potentiators Using Covalently Linked NF-κB Modulators

Small molecule immune potentiators (SMIPs) such as imidazoquinolinone derivatives that activate Toll-like receptor (TLR) 7/8 have immense potential as vaccine adjuvants and as antitumor agents. However, these molecules have high bioavailability that results in unacceptable levels of systemic inflammation due to adjuvant toxicity, thereby greatly limiting their use. To address this challenge, here we report the design and synthesis of novel imidazoquinolinone-NF-κB immunomodulator dimers. Employing in vitro assays, we screened a select library of synthesized dimers and selected viable candidates for further in vivo experiments. With ovalbumin as a model antigen, we vaccinated mice and demonstrated that these dimers reduce the systemic toxicity associated with SMIPs to baseline levels while simultaneously maintaining the adjuvanticity in a vaccine formulation. Additionally, we showed that select dimers improved efficacy in a CT26 mouse colon carcinoma tumor model while eliciting minimal adjuvant toxicity.     

Staphylococcal Enterotoxin A Induces Intestinal Barrier Dysfunction and Activates NLRP3 Inflammasome via NF-κB/MAPK Signaling Pathways in Mice

Staphylococcal enterotoxin A (SEA), the toxin protein secreted by Staphylococcus aureus, can cause staphylococcal food poisoning outbreaks and seriously threaten global public health. However, little is known about the pathogenesis of SEA in staphylococcal foodborne diseases. In this study, the effect of SEA on intestinal barrier injury and NLRP3 inflammasome activation was investigated by exposing BALB/c mice to SEA with increasing doses and a potential toxic mechanism was elucidated. Our findings suggested that SEA exposure provoked villi injury and suppressed the expression of ZO-1 and occludin proteins, thereby inducing intestinal barrier dysfunction and small intestinal injury in mice. Concurrently, SEA significantly up-regulated the expression of NLRP3 inflammasome-associated proteins and triggered the mitogen-activated protein kinase (MAPK) and nuclear factor kappa-B (NF-κB) signaling pathways in jejunum tissues. Notably, selective inhibitors of MAPKs and NF-κB p65 ameliorated the activation of NLRP3 inflammasome stimulated by SEA, which further indicated that SEA could activate NLRP3 inflammasome through NF-κB/MAPK pathways. In summary, SEA was first confirmed to induce intestinal barrier dysfunction and activate NLRP3 inflammasome via NF-κB/MAPK signaling pathways. These findings will contribute to a more comprehensive understanding of the pathogenesis of SEA and related drug-screening for the treatment and prevention of bacteriotoxin-caused foodborne diseases via targeting specific pathways.     

Taurine prevents arsenic-induced cardiac oxidative stress and apoptotic damage: Role of NF-κB, p38 and JNK MAPK pathway

Cardiac dysfunction is a major cause of morbidity and mortality worldwide due to its complex pathogenesis. However, little is known about the mechanism of arsenic-induced cardiac abnormalities and the use of antioxidants as the possible protective agents in this pathophysiology. Conditionally essential amino acid, taurine, accounts for 25% to 50% of the amino acid pool in myocardium and possesses antioxidant properties. The present study has, therefore, been carried out to investigate the underlying mechanism of the beneficial role of taurine in arsenic-induced cardiac oxidative damage and cell death. Arsenic reduced cardiomyocyte viability, increased reactive oxygen species (ROS) production and intracellular calcium overload, and induced apoptotic cell death by mitochondrial dependent caspase-3 activation and poly-ADP ribose polymerase (PARP) cleavage. These changes due to arsenic exposure were found to be associated with increased IKK and NF-κB (p65) phosphorylation. Pre-exposure of myocytes to an IKK inhibitor (PS-1145) prevented As-induced caspase-3 and PARP cleavage. Arsenic also markedly increased the activity of p38 and JNK MAPKs, but not ERK to that extent. Pre-treatment with SP600125 (JNK inhibitor) and SB203580 (p38 MAPK inhibitor) attenuated NF-κB and IKK phosphorylation indicating that p38 and JNK MAPKs are mainly involved in arsenic-induced NF-κB activation. Taurine treatment suppressed these apoptotic actions, suggesting that its protective role in arsenic-induced cardiomyocyte apoptosis is mediated by attenuation of p38 and JNK MAPK signaling pathways. Similarly, arsenic intoxication altered a number of biomarkers related to cardiac oxidative stress and other apoptotic indices in vivo and taurine supplementation could reduce it. Results suggest that taurine prevented arsenic-induced myocardial pathophysiology, attenuated NF-κB activation via IKK, p38 and JNK MAPK signaling pathways and could possibly provide a protection against As-induced cardiovascular burden.     

Minor polar compounds extra-virgin olive oil extract (MPC-OOE) inhibits NF-κB translocation in human monocyte/macrophages

Epidemiological studies demonstrate that the Mediterranean diet, in which olive oil is the major source of fat, reduces the risk of coronary heart disease and cancer. It has been proposed that the beneficial effects of olive oil not only depend on oleic acid, but are also associated with minor polar compounds (MPC). A positive correlation between inflammation and cardiovascular diseases has long been described, monocyte/macrophages and NF-kappaB playing a pivotal role. The aim of this work was to investigate the effects of an extra-virgin olive oil extract (MPC-OOE), particularly rich in MPC and prepared by some of us, on NF-kappaB translocation in monocytes and monocyte-derived macrophages (MDM) isolated from healthy volunteers. In a concentration-dependent manner, MPC-OOE inhibited p50 and p65 NF-kappaB translocation in both un-stimulated and phorbol-myristate acetate (PMA)-challenged cells, being particularly effective on the p50 subunit. Interestingly, this effect occurred at concentrations found in human plasma after nutritional ingestion of virgin olive oil and was quantitatively similar to the effect exerted by ciglitazone, a PPAR-gamma ligand. However, MPC-OOE did not affect PPAR-gamma expression in monocytes and MDM. These data provide further evidence of the beneficial effects of extra-virgin olive oil by indicating its ability to inhibit NF-kappaB activation in human monocyte/macrophages.     

Role of NF‐κB activation and Th1/Th2 imbalance in pulmonary toxicity induced by nano NiO

With the progress of nanotechnology, nano nickel oxide (NiO) has been extensively used as sensors, battery electrodes, catalysts, and cosmetics. Previous researches verified that nano NiO could exert pulmonary toxicity, but its mechanism was unclear. To shed light upon this, the role of nuclear factor‐κ B (NF‐κ B) activation and Th1/Th2 imbalance were to explore in pulmonary damage induced by nano NiO. Male Wistar rats were randomized into control group, nano NiO groups (0.015, 0.06, and 0.24 mg kg^?1) and micro NiO group (0.024 mg kg^?1) and treated by intratracheal instillation twice a week for 6 weeks. The results showed that the abnormal changes induced by nano NiO were found on indicators of nitrative stress (NO, TNOS, and iNOS), inflammatory cytokines (TNF‐α , IL‐2, and IL‐10) and cytokine‐induced neutrophil chemoattractants (CINC‐1, CINC‐2αβ , and CINC‐3) in lung tissue. In addition, nano NiO instillation induced the upregulated mRNA and protein expression of NF‐κ B, inhibitor of κB kinase‐α (IKK‐α ) and nuclear factor‐inducing kinase (NIK). The protein content of GATA‐3 increased as well as T‐bet decreased in nano NiO groups, and the ratio of T‐bet/GATA‐3, as a key evaluation indicator of Th1/Th2 balance, was lower than the control group. The findings indicated that nano NiO could enhance the nitrative stress and inflammatory response in lung tissue, and its mechanism was related to the NF‐κ B activation and Th1/Th2 imbalance. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1354–1362, 2017.     

Curcumin alleviates lung injury in diabetic rats by inhibiting nuclear factor‐κB pathway

Curcumin is a polyphenolic compound that is extracted from Curcuma longa. It has broad anti‐inflammation and anti‐tumor activities. Curcumin was previously reported to exert beneficial effects on diabetes. However, the effect of curcumin on diabetes‐induced lung injury is not yet clear. In this study, the effects of curcumin on lung injury induced by diabetes was explored using quantitative real time polymerase chain reaction (PCR), enzyme‐linked immunosorbent assay (ELISA), immunohistochemistry and electrophoretic mobility shift assay. The results of this study showed that curcumin reduced oxidative stress level, inhibited the synthesis of nitric oxide and prostaglandin E2, and reduced inflammatory responses in the lungs of diabetic rats, thereby alleviating diabetes‐induced lung injury. Further study of the mechanism revealed that curcumin inhibited the activation of nuclear factor (NF)‐κB which is a key player in inflammatory responses. In summary, our study demonstrated that curcumin inhibited the activation of NF‐κB in the lungs of diabetic rats, thus reducing pulmonary inflammatory responses and oxidative stress, and ultimately relieving diabetes‐induced lung injury. This study suggests that curcumin may be a promising agent to alleviate diabetic lung injury and also provides theoretical foundation for the development of diabetes therapy.     

A robust in vitro screening assay to identify NF-κB inhibitors for inflammatory muscle diseases

Specific therapies are not available for inflammatory muscle diseases. We and others have shown that the pro-inflammatory NF-κB pathway is highly activated in these conditions. Since NF-κB is an important therapeutic target, we decided to utilize an in vitro screening assay to identify potential inhibitors that block TNF-α induced NF-κB activation in a C2C12 muscle line stably expressing an NF-κB luciferase reporter gene. Upon evaluation of multiple anti-inflammatory agents in undifferentiated myoblasts as well as differentiated myotubes , we found different levels of inhibition depending on the state of differentiation. Interestingly, we found that some drugs that are known to inhibit NF-κB in immune cells were not effective in muscle cells. Drug toxicity was assessed for using an MTT cell viability assay, and the validity of the luciferase assay was verified by immunostaining for NF-κB nuclear translocation in myoblasts. In conclusion, we have determined the optimal assay conditions for detecting potentially valuable NF-κB inhibitors for the first time in a muscle cell line that may have significant therapeutic potential for inflammatory muscle diseases.     

Betulinic Acid Ameliorates the T-2 Toxin-Triggered Intestinal Impairment in Mice by Inhibiting Inflammation and Mucosal Barrier Dysfunction through the NF-κB Signaling Pathway

T-2 toxin, a trichothecene mycotoxin produced by Fusarium, is widely distributed in crops and animal feed and frequently induces intestinal damage. Betulinic acid (BA), a plant-derived pentacyclic lupane-type triterpene, possesses potential immunomodulatory, antioxidant and anti-inflammatory biological properties. The current study aimed to explore the protective effect and molecular mechanisms of BA on intestinal mucosal impairment provoked by acute exposure to T-2 toxin. Mice were intragastrically administered BA (0.25, 0.5, or 1 mg/kg) daily for 2 weeks and then injected intraperitoneally with T-2 toxin (4 mg/kg) once to induce an intestinal impairment. BA pretreatment inhibited the loss of antioxidant capacity in the intestine of T-2 toxin-treated mice by elevating the levels of CAT, GSH-PX and GSH and reducing the accumulation of MDA. In addition, BA pretreatment alleviated the T-2 toxin-triggered intestinal immune barrier dysregulation by increasing the SIgA level in the intestine at dosages of 0.5 and 1 mg/kg, increasing IgG and IgM levels in serum at dosages of 0.5 and 1 mg/kg and restoring the intestinal C3 and C4 levels at a dosage of 1 mg/kg. BA administration at a dosage of 1 mg/kg also improved the intestinal chemical barrier by decreasing the serum level of DAO. Moreover, BA pretreatment improved the intestinal physical barrier via boosting the expression of ZO-1 and Occludin mRNAs and restoring the morphology of intestinal villi that was altered by T-2 toxin. Furthermore, treatment with 1 mg/kg BA downregulated the expression of p-NF-κB and p-IκB-α proteins in the intestine, while all doses of BA suppressed the pro-inflammatory cytokines expression of IL-1β, IL-6 and TNF-α mRNAs and increased the anti-inflammatory cytokine expression of IL-10 mRNA in the intestine of T-2 toxin-exposed mice. BA was proposed to exert a protective effect on intestinal mucosal disruption in T-2 toxin-stimulated mice by enhancing the intestinal antioxidant capacity, inhibiting the secretion of inflammatory cytokines and repairing intestinal mucosal barrier functions, which may be associated with BA-mediated inhibition of the NF-κB signaling pathway activation.     

Z-ligustilide attenuates lipopolysaccharide-induced proinflammatory response via inhibiting NF-KB pathway in primary rat microglia

Aim:

To investigate the anti-inflammatory effect of Z-ligustilide (LIG) on lipopolysaccharide (LPS)-activated primary rat microglia.

Methods:

Microglia were pretreated with LIG 1 h prior to stimulation with LPS (1 μg/mL). After 24 h, cell viability was tested with MTT, nitric oxide (NO) production was assayed with Griess reagent, and the content of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and monocyte chemoattractant protein (MCP-1) was measured with ELISA. Protein expression of the nuclear factor-κB (NF-κB) p65 subunit, cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) was detected with immunocytochemistry 1 h or 24 h after LPS treatment.

Results:

LIG showed a concentration-dependent anti-inflammatory effect in LPS-activated microglia, without causing cytotoxicity. Pretreatment with LIG at 2.5, 5, 10, and 20 μmol/L decreased LPS-induced NO production to 75.9%, 54.4%, 43.1%, and 47.6% (P<0.05 or P< 0.01), TNF-α content to 86.2%, 68.3%, 40.1%, and 39.9% (P<0.01, with the exception of 86.2% for 2.5 μmol/L LIG), IL-1β content to 31.5%, 27.7%, 0.6%, and 0% (P<0.01), and MCP-1 content to 84.4%, 50.3%, 45.1%, and 42.2% (P<0.05 or P<0.01), respectively, compared with LPS treatment alone. LIG (10 μmol/L) significantly inhibited LPS-stimulated immunoreactivity of activated NF-κB, COX-2, and iNOS (P<0.01 vs LPS group).

Conclusion:

LIG exerted a potent anti-inflammatory effect on microglia through inhibition of NF-κB pathway. The data provide direct evidence of the neuroprotective effects of LIG and the potential application of LIG for the treatment of the neuroinflammatory diseases characterized by excessive microglial activation.     

Anti-inflammatory potential of Antrodia Camphorata through inhibition of iNOS, COX-2 and cytokines via the NF-kappaB pathway

Antrodia camphorata (A. camphorata), well known in Taiwan as a traditional Chinese medicine, has been shown to exhibit antioxidant and anticancer effects. In the present study, therefore, we have examined the effects of the fermented culture broth of A. camphorata (25-100 microg/ml) in terms of lipopolysaccharide (LPS)-induced nitric oxide (NO) and prostaglandin E2 (PGE2) production, and inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein expression in RAW 264.7 macrophages. Our results indicate concentration-dependent A. camphorata inhibition of LPS-induced NO and PGE2 production, without appreciable cytotoxicity on the RAW 264.7 cells. A. camphorata also attenuates the production of LPS-induced tumor necrosis factor (TNF-alpha) and interleukin (IL)-1beta. Furthermore, A. camphorata blocks the IkappaB-alpha degradation induced by LPS. These results indicate that A. camphorata inhibits LPS induction of cytokine, iNOS and COX-2 expression by blocking NF-kappaB activation. Therefore, we report the first confirmation of the anti-inflammatory potential of this traditionally employed herbal medicine in vitro.