Expression Of Inflammatory Cytokines In Macrophages Research Articles

Low shear stress induces macrophage infiltration and aggravates aneurysm wall inflammation via CCL7/CCR1/TAK1/ NF-κB axis

BackgroundThis study aimed to elucidate the mechanism by which wall shear stress (WSS) influences vascular walls, accounting for the susceptibility of intracranial aneurysms (IAs) to rupture. MethodWe collected blood samples from the sacs of 24 ruptured and 28 unruptured IAs and analyzed the expression of chemokine CCL7 using enzyme-linked immunosorbent assay (ELISA). Univariate and multivariate logistic regression analyses were employed to assess clinical data, aneurysm morphology, and hemodynamics in both groups. Pearson correlation analysis investigated the relationship between CCL7 expression in aneurysm sac blood and WSS. Additionally, we established a bionic cell parallel plate co-culture shear stress model and a mouse low shear stress (LSS) model. The model was modulated using CCL7 recombinant protein, CCR1 inhibitor, and TAK1 inhibitor. We further evaluated CCL7 expression in endothelial cells and the levels of TAK1, NF-κB, IL-1β, and TNF-α in macrophages. Subsequently, the intergroup differences in expression were calculated. ResultsCCL7 expression was significantly higher in the ruptured group compared to the unruptured group. Hemodynamic analysis indicated that WSS was an independent predictor of the risk of aneurysm rupture. A negative linear correlation was observed between CCL7 expression and WSS. Upon addition of CCL7 recombinant protein, upregulation of CCR1 expression and increased levels of p-TAK1 and p-p65 were observed. Treatment with CCR1 and TAK1 inhibitors reduced inflammatory cytokine expression in macrophages under LSS conditions. Overexpression of TAK1 significantly alleviated the inhibitory effects of CCR1 inhibitors on p-p65 and inflammatory cytokines. ConclusionLSS prompts endothelial cells to secrete CCL7, which, upon binding to the macrophage surface receptor CCR1, stimulates the release of macrophage inflammatory factors via the TAK1/NF-κB signaling pathway. This process exacerbates aneurysm wall inflammation and increases the risk of aneurysm rupture.

Brd4 regulates metabolic reprogramming of macrophages upon H. pylori infection.

Abstract Metabolic reprogramming plays an important role in the regulation of several macrophage functions, including bacterial killing and cytokine production. Brd4 has emerged as a key innate immune response regulator by modulating the inflammatory cytokine expression in macrophages. However, the potential role of Brd4 in metabolic reprograming of macrophage activation remains unknown. Here, we showed that Brd4 facilitated a HIF-1α-dependent glycolytic shift for macrophage activation in response to H. pyloriinfection. H. pyloriinfection triggered Brd4-dependent polarization of macrophages to the M1 phenotype, which was associated with an increase in glycolysis and the upregulation of glycolytic genes, glucose transporter 1 (Glut1) and Hexokinase II (HK2). Mechanistically, Brd4 was recruited to the promoters of Glut1and Hk2by HIF-1α and regulated glycolysis by facilitating HIF-1α-dependent expression of Glut1and Hk2. Furthermore, we found that Brd4-mediated glycolysis was essential for M1 macrophage activation since the expression of iNOS, a marker of M1 polarization, was down-regulated in Brd4-deficient macrophages and could be rescued by the addition of pyruvate. Consistently, the iNOS-mediated killing of H. pyloriwas decreased in Brd4-deficient macrophages and also in mice with myeloid-specific deletion of Brd4. Our study identified a novel function of Brd4 in metabolic reprograming of macrophages through glycolysis and iNOS expression in response to bacterial infection. Supported by grant from NIH R03 AI163932

Cyclic stretch regulates immune responses via tank-binding kinase 1 expression in macrophages.

Macrophages distributed in tissues throughout the body contribute to homeostasis. In the inflammatory state, macrophages undergo mechanical stress that regulates the signal transduction of immune responses and various cellular functions. However, the effects of the inflammatory response on macrophages under physiological cyclic stretch are unclear. We found that physiological cyclic stretch suppresses inflammatory cytokine expression in macrophages by regulating NF-κB activity. NF-κB phosphorylation at Ser536 in macrophages was inhibited, suggesting that tank-binding kinase (TBK1) regulates NF-κB activity during physiological stress. Moreover, TBK1 expression was suppressed by physiological stretch, and TBK1 knockdown by siRNA induced the suppression of NF-κB phosphorylation at Ser536. In conclusion, physiological stretch triggers suppression of a TBK1-dependent excessive inflammatory response, which may be necessary to maintain tissue homeostasis.

The anti-inflammatory effect of the gut lactic acid bacteria-generated metabolite 10-oxo-cis-6,trans-11-octadecadienoic acid on monocytes

We evaluated the effect of gut bacterial metabolites of polyunsaturated fatty acids on inflammation and found that 10-oxo-cis-6,trans-11-octadecadienoic acid (γKetoC) strikingly suppressed LPS-induced IL-6 release from bone marrow-derived macrophages (BMMs), which was accompanied by reduced mRNA expression of Il6, TNF, and Il1b. γKetoC decreased the cAMP concentration in BMMs, suggesting that γKetoC stimulated G protein-coupled receptors. A Gq agonist significantly suppressed LPS-induced IL-6 expression in BMMs, whereas a Gi inhibitor partially abrogated γKetoC-mediated IL-6 suppression. Cytosolic Ca2+ was markedly increased by γKetoC, which was partly but not fully abrogated by an ion channel inhibitor. Taken together, these data suggest that γKetoC suppresses inflammatory cytokine expression in macrophages primarily through Gq and partially through Gi. γKetoC suppressed osteoclast development and IL-6 expression in synovial fibroblasts from rheumatoid arthritis (RA) patients, suggesting the beneficial effect of γKetoC on the prevention or treatment of RA.

CXCR4 knockdown prevents inflammatory cytokine expression in macrophages by suppressing activation of MAPK and NF-\u03baB signaling pathways

BackgroundRecent evidence has shown that C-X-C chemokine receptor type 4 (CXCR4) plays a crucial role in acute lung injury (ALI). Macrophages are key factors in the pathogenesis of ALI. The aim of this study was to investigate the role of CXCR4 in macrophages after lipopolysaccharide (LPS) stimulation and confirm that CXCR4 knockdown can inhibit inflammatory cytokines by suppressing mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) signaling pathway activation.ResultsIn this study, we found that CXCR4 expression in lung tissue of ALI was significantly increased using immunofluorescence. We also found that the expression of CXCR4 in macrophages sorted from bronchoalveolar lavage fluid (BALF) of ALI was obviously upregulated through RT-qPCR. After CXCR4 knockdown using siRNA, we found that the expression of interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) was obviously down regulated in macrophages. Additionally, the phosphorylation of p38, Erk, and p65 was significantly decreased after CXCR4 knockdown through western blotting.ConclusionsTaken together, the present study suggests that CXCR4 knockdown may inhibit inflammatory cytokine expression in macrophages by suppressing MAPK and NF-κB signaling pathway activation. Therefore, CXCR4 knockdown may have potential clinical value in treating ALI.

Kinetics of cytokine mRNA and protein expression by plastic adherent cells in the thymus after split-dose irradiation

Whole body irradiation causes significant apoptosis in various tissues such as the thymus. If apoptotic cells outnumber the phagocytic capacity of macrophages, apoptosis becomes secondary necrosis, inducing inflammatory cytokine expression in macrophages. Radiation also induces thymic lymphomas in C57BL/6 mice after four consecutive irradiations with 1.6 Gy X-rays with nearly 100% incidence. Since cancer development is modulated by a microenvironment involving macrophages, we examined the kinetics of thymocyte number and plastic adherent cell number in the thymus as well as cytokine mRNA expression by plastic adherent cells in the thymus after split-dose irradiation. Upon split-dose irradiation, thymocyte number changed dramatically, whereas plastic adherent cell number did not. Among cytokine mRNAs tested, IL-1β, IL-11 and IL-12p40 mRNAs were up regulated 2 days after the 1st and 2nd, 3rd and 4th, and 2nd and 3rd irradiations, respectively. On the other hand, TNF-α mRNA was up regulated 2 days after the 3rd irradiation and 2 weeks after the 4th irradiation. The level of IL-11 protein was also increased 2 days after 3rd and 4th irradiations. These results suggest that, upon split-dose irradiation, macrophages in the thymus produce various cytokines in a time-dependent manner, thereby contributing to induction of thymic lymphomas.

3,5-Di-C-β-D-glucopyranosyl phloroacetophenone, a major component of Melicope ptelefolia, suppresses fibroblast activation and alleviates arthritis in a mouse model: Potential therapeutics for rheumatoid arthritis.

Melicope ptelefolia has been traditionally used to treat rheumatism and fever. The present study aimed to investigate the therapeutic effect of 3,5-di-C-β-d-glucopyranosyl phloroacetophenone (βGP), a main component of M. ptelefolia, on rheumatoid arthritis (RA). A model of collagen-induced arthritis (CIA) was established in mice using the RAW 264.7 murine macrophage cell line and mouse embryonic fibroblasts (MEFs). The clinical scores of arthritis, swelling, histopathological findings, and micro-computed tomography in CIA mouse paws were assessed. The levels of anti-type II collagen antibody and cytokines were determined in the plasma and cell culture supernatant, respectively. Protein and gene expression levels were analyzed by western blot and reverse transcription-quantitative polymerase chain reaction analyses. βGP significantly decreased the gross arthritic scores of CIA mice and joint swelling, and decreased articular inflammation, cartilage degradation and bone erosion. However, βGP did not exert any effect on anti-type II collagen immunoglobulin G plasma levels or inflammatory cytokine expression in macrophages. βGP significantly suppressed the expression of interleukin-6 and leukemia inhibitory factor and decreased the phosphorylation of signal transducer and activator of transcription 3, and expression of receptor activator of nuclear factor-κB ligand in tumor necrosis factor-α-stimulated MEFs and in CIA mouse paws. Osteoclast-related gene expression was significantly reduced in CIA mouse paws. Taken together, βGP suppressed the development of RA by regulating the activation of synovial fibroblasts.

The membrane-type estrogen receptor G-protein-coupled estrogen receptor suppresses lipopolysaccharide-induced interleukin 6 via inhibition of nuclear factor-kappa B pathway in murine macrophage cells.

The female sex hormone estrogen exerts anti-inflammatory effects. The G-protein-coupled estrogen receptor (GPER) has been recently identified as a novel membrane-type estrogen receptor that can mediate non-genomic estrogenic effects on many cell types. We previously demonstrated that GPER inhibits tumor necrosis factor alpha-induced expression of interleukin 6 (IL-6) through repression of nuclear factor-kappa B (NF-κB) promoter activity using human breast cancer cells. Although several reports have indicated that GPER suppresses Toll-like receptor-induced inflammatory cytokine expression in macrophages, the molecular mechanisms of the inhibition of cytokine production via GPER remain poorly understood. In the present study, we examined GPER-mediated inhibition of IL-6 expression induced by lipopolysaccharide (LPS) stimulation in a mouse macrophage cell line. We found that the GPER agonist G-1 inhibited LPS-induced IL-6 expression in macrophage cells, and this inhibition was due to the repression of NF-κB promoter activity by GPER. G-1 treatment also decreased the phosphorylation of inhibitor of κB kinases. Among the mitogen-activated protein kinases, the phosphorylation of c-jun N-terminal kinase (JNK) was increased by G-1. These findings delineate the novel mechanism of the inhibition of LPS-induced IL-6 through GPER-activated JNK-mediated negative regulation of the NF-κB pathway in murine macrophage cells, which links anti-inflammatory effects to estrogen.

Eriodictyol, a Plant Flavonoid, Attenuates LPS-Induced Acute Lung Injury Through Its Antioxidative and Antiinflammatory Activity

Acute lung injury (ALI) is characterized by exces- sive inflammatory responses and oxidative injury in the lung tissue. It has been suggested that anti‑inflammatory or antioxidative agents could have therapeutic effects in ALI, and eriodictyol has been reported to exhibit antioxidative and anti‑inflammatory activit y in vitro. The aim of the present study was to investigate the effect of eriodictyol on lipopolysac- charide (LPS)-induced ALI in a mouse model. The mice were divided into four groups: Phosphate-buffered saline-treated healthy control, LPS-induced ALI, vehicle-treated ALI (LPS + vehicle) and eriodictyol-treated ALI (LPS + eriodic- tyol). Eriodictyol (30 mg/kg) was administered orally once, 2 days before the induction of ALI. The data showed that eriodictyol pretreatment attenuated LPS-induced ALI through its antioxidative and anti‑inflammatory activity. Furthermore, the eriodictyol pretreatment activated the nuclear factor erythroid-2-related factor 2 (Nrf2) pathway in the ALI mouse model, which attenuated the oxidative injury and inhibited the inflammatory cytokine expression in macrophages. In combination, the results of the present study demonstrated that eriodictyol could alleviate the LPS-induced lung injury in mice by regulating the Nrf2 pathway and inhibiting the expression of inflammatory cytokines in macrophages, suggesting that eriodictyol could be used as a potential drug for the treatment of LPS-induced lung injury.

Eriodictyol, a plant flavonoid, attenuates LPS-induced acute lung injury through its antioxidative and anti-inflammatory activity.

Acute lung injury (ALI) is characterized by excessive inflammatory responses and oxidative injury in the lung tissue. It has been suggested that anti-inflammatory or antioxidative agents could have therapeutic effects in ALI, and eriodictyol has been reported to exhibit antioxidative and anti-inflammatory activity in vitro. The aim of the present study was to investigate the effect of eriodictyol on lipopolysaccharide (LPS)-induced ALI in a mouse model. The mice were divided into four groups: Phosphate-buffered saline-treated healthy control, LPS-induced ALI, vehicle-treated ALI (LPS + vehicle) and eriodictyol-treated ALI (LPS + eriodictyol). Eriodictyol (30 mg/kg) was administered orally once, 2 days before the induction of ALI. The data showed that eriodictyol pretreatment attenuated LPS-induced ALI through its antioxidative and anti-inflammatory activity. Furthermore, the eriodictyol pretreatment activated the nuclear factor erythroid-2-related factor 2 (Nrf2) pathway in the ALI mouse model, which attenuated the oxidative injury and inhibited the inflammatory cytokine expression in macrophages. In combination, the results of the present study demonstrated that eriodictyol could alleviate the LPS-induced lung injury in mice by regulating the Nrf2 pathway and inhibiting the expression of inflammatory cytokines in macrophages, suggesting that eriodictyol could be used as a potential drug for the treatment of LPS-induced lung injury.

High Glucose Increases the Expression of Inflammatory Cytokine Genes in Macrophages Through H3K9 Methyltransferase Mechanism.

Recent studies suggest that histone modification is one of the mechanisms regulating inflammatory cytokine gene expression in hyperglycemic conditions. However, it remains unknown how histone methylation is initiated and involved in changes of inflammatory cytokine gene expression under high glucose (HG) conditions. Our aim was to investigate whether H3K9 methylation was involved in HG-induced expression of inflammatory cytokines in macrophages. Expression profile of cytokine genes under hyperglycemia in THP-1-derived macrophages was determined by human cytokine antibody array. Based on the results from the human cytokine antibody array analyses, the H3K9me3 levels of 4 inflammatory cytokine genes, including interleukin-6 (IL-6), IL-12p40, macrophage inflammatory protein-1α (MIP-1α), and MIP-1β under HG were determined by ChIP assays. Furthermore, the expression of these 4 inflammatory cytokine genes under either HG or chaetocin (an inhibitor of SUV39H1 methyltransferase) exposure or overexpression of SUV39H1 (a H3K9me3-specific methyltransferase) was analyzed by quantitative polymerase chain reaction. Macrophages cultured in HG conditions showed increased gene expression and decreased H3K9me3 levels of inflammatory cytokine genes compared with macrophages incubated in normal glucose (NG) culture. Inhibition of SUV39H1 with chaetocin in NG-treated macrophages also increased the expression of IL-6, IL-12p40, MIP-1α, and MIP-1β. Furthermore, inhibition of SUV39H1 with chaetocin in HG-treated macrophages further increased the expression of these inflammatory cytokines. Contrarily, NG-treated macrophages transfected with SUV39H1 plasmids show decreased expression of inflammatory cytokines. Furthermore, overexpression of SUV39H1 in HG-treated macrophages alleviated the expression of inflammatory cytokines under HG conditions. Finally, HG also increases the expression of inflammation cytokines in mouse bone marrow-derived macrophages. Our data demonstrated that HG increases the expression of inflammatory cytokines in macrophages through decreased H3K9me3 levels, which was partly mediated by SUV39H1. Dysregulation of epigenetic histone modification may be one of the underlying mechanisms for HG-induced inflammatory cytokine expression in macrophages.

Down‐regulation of miR‐301a suppresses pro‐inflammatory cytokines inToll‐like receptor‐triggered macrophages

In many types of tumours, especially pancreatic adenocarcinoma, miR-301a is over-expressed. This over-expression results in negative regulation of the target gene of miR-301a, the nuclear factor-κB (NF-κB) repressing factor (NKRF), increasing the activation of NF-κB and production of NF-κB-responsive pro-inflammatory cytokines such as interleukin-8, interferon-β, nitric oxide synthase 2A and cytochrome oxidase subunit 2 (COX-2). However, in immune cells, mechanisms that regulate miR-301a have not been reported. Similar to tumour cells, Toll-like receptor (TLR) -activated macrophages produce NF-κB-responsive pro-inflammatory cytokines. Therefore, it is of considerable interest to determine whether miR-301a regulates the secretion of cytokines by immune cells. In the present study, we demonstrate that the expression of miR-301a was decreased in TLR-triggered macrophages. Through targeting NKRF, miR-301a affected the activity of NF-κB and the expression of pro-inflammatory genes downstream of NF-κB such as COX-2, prostaglandin E2 and interleukin-6. In addition, when lipopolysaccharide-treated macrophages were simultaneously stimulated with trichostatin A, an inhibitor of histone deacetylases, the expression of miR-301a increased, whereas NKRF and pro-inflammatory cytokine expression decreased. However, further investigation revealed that there was no correlation between the induction of miR-301a and the inhibitory effect of trichostatin A on lipopolysaccharide-induced gene expression in macrophages. In summary, our study indicates a new mechanism by which miR-301a regulates inflammatory cytokine expression in macrophages, which may clarify the regulatory role of microRNAs in immune-mediated inflammatory responses.

Fenretinide Corrects the Imbalance between Omega-6 to Omega-3 Polyunsaturated Fatty Acids and Inhibits Macrophage Inflammatory Mediators via the ERK Pathway

We previously identified Fragile X-related protein 1 (FXR1) as an RNA-binding protein involved in the post-transcriptional control of TNF and other cytokines in macrophages. Macrophages derived from FXR1-KO mice overexpress several inflammatory cytokines including TNF. Recently, we showed that fenretinide (4HPR) is able to inhibit several inflammatory cytokines in the lungs of cystic fibrosis mice, which also have abnormal immune responses. Therefore, we hypothesized that 4HPR might also be able to downregulate excessive inflammation even in macrophages with ablated FXR1. Indeed, our results demonstrate that 4HPR inhibited the excessive production of inflammatory mediators, including TNF, IL-6, CCL2 and CCL-5 in LPS-stimulated FXR1-KO macrophages, by selectively inhibiting phosphorylation of ERK1/2, which is naturally more phosphorylated in FXR1-KO cells. We also found that LPS stimulation of FXR1-KO macrophages led to significantly higher ratio of arachidonic acid/docosahexaenoic acid than observed in FXR1-WT macrophages. Interestingly, treatment with 4HPR was associated with the normalization of arachidonic acid/docosahexaenoic acid ratio in macrophages, which we found to impact phosphorylation of ERK1/2. Overall, this study shows for the first time that 4HPR modulates inflammatory cytokine expression in macrophages by correcting a phospholipid-bound fatty acid imbalance that impacts the phosphorylation of ERK1/2.

6,6′-Bieckol, isolated from marine alga Ecklonia cava, suppressed LPS-induced nitric oxide and PGE2 production and inflammatory cytokine expression in macrophages: The inhibition of NFκB

Ecklonia cava is an edible brown alga that contains high levels of phlorotannins, which are unique marine polyphenolic compounds. In the present study, we investigated the anti-inflammatory effects and the underlying molecular mechanism of phlorotannin 6,6′-bieckol, which is an active component isolated from E. cava, on lipopolysaccharide (LPS)-stimulated primary macrophages and RAW 264.7 macrophage cells. 6,6′-Bieckol was found to inhibit nitric oxide (NO) and prostaglandin E2 (PGE2) production and to suppress the LPS-induced expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) at the mRNA and protein levels. In addition, 6,6′-bieckol downregulated the production and mRNA expression of the inflammatory cytokines TNF-α and IL-6. Moreover, pretreatment with 6,6′-bieckol decreased LPS-induced transactivation of nuclear factor-kappa B (NFκB) and nuclear translocation of p50 and p65 subunits of NFκB. Furthermore, chromatin immunoprecipitation assay revealed that 6,6′-bieckol inhibited LPS-induced NFκB binding to the TNF-α and IL-6 promoters. Taken together, these data suggest that the anti-inflammatory properties of 6,6′-bieckol are related to the down-regulation of iNOS, COX-2, and pro-inflammatory cytokines through the negative regulation of the NFκB pathway in LPS-stimulated macrophages.

Notch1 Deficiency Results in Decreased Inflammation during Wound Healing and Regulates Vascular Endothelial Growth Factor Receptor-1 and Inflammatory Cytokine Expression in Macrophages

We investigated whether Notch signaling plays a role in regulating macrophage responses to inflammation. In a wound healing assay, macrophage recruitment was decreased in Notch1(+/-) mice, and the wounds were characterized by decreased TNF-α expression. As wound healing progressed, Notch1(+/-) wounds had increased vascularization and collagen deposition compared with wild-type wounds. In mice with myeloid-specific Notch1 deletion, wounds had decreased macrophage recruitment as well as decreased TNF-α expression, indicating the specific role of Notch1 in the inflammatory response in these cells. In vitro, we found that vascular endothelial growth factor receptor-1 (VEGFR-1) was upregulated in macrophages in response to LPS/IFN-γ and that this upregulation depended on Notch signaling. Furthermore, macrophages from Notch1(+/-) mice had decreased expression of VEGFR-1 compared with macrophages from wild-type mice, whereas VEGFR-1 expression in Notch4(-/-) macrophages was normal. Inhibition of Notch signaling decreased induction of the inflammatory cytokines IL-6, IL-12, CXCL10, MCP-1, monokine induced by IFN-γ, and TNF-α in macrophages in response to LPS/IFN-γ. Additionally, macrophages from Notch1(+/-) mice demonstrated decreased induction of IL-6, IL-12, and TNF-α in response to stimulation compared with wild-type mice. Thus, both pharmacological inhibition of Notch and genetic analysis demonstrate that Notch1 regulates VEGFR-1 and cytokine expression in macrophages. We have also established that Notch1 is important for the inflammatory response during wound healing in mice.

MiR-147, a microRNA that is induced upon Toll-like receptor stimulation, regulates murine macrophage inflammatory responses

Toll-like receptors (TLRs) are major receptors that enable inflammatory cells to recognize invading microbial pathogens. MicroRNAs are small non-coding RNAs that play important regulatory roles in a variety of biological processes. In this study, we found that a microRNA, miR-147, was induced upon stimulation of multiple TLRs and functioned as a negative regulator of TLR-associated signaling events in murine macrophages. We first demonstrated that the NMES1 transcript was a functional primary miR-147. miR-147 was induced in LPS-stimulated mouse macrophages and under in vivo conditions in the lungs of LPS-treated mice. Expression of miR-147 was greater after cellular activation by TLR4 than after engagement of either TLR2 or TLR3, suggesting that maximal induction of miR-147 required activation of both NF-kappaB and IRF3. TLR4-induced miR-147 expression was both MyD88- and TRIF-dependent. The miR-147 promoter was responsive to TLR4 stimulation and both NF-kappaB and STAT1alpha bound to the miR-147 promoter. miR-147 mimics or induced expression of miR-147 decreased, whereas miR-147 knockdown increased inflammatory cytokine expression in macrophages stimulated with ligands to TLR2, TLR3, and TLR4. These data demonstrate a negative-feedback loop in which TLR stimulation induces miR-147 to prevent excessive inflammatory responses.

Dehydrodiisoeugenol, an isoeugenol dimer, inhibits lipopolysaccharide-stimulated nuclear factor kappa B activation and cyclooxygenase-2 expression in macrophages

o-Methoxyphenols such as eugenol and isoeugenol exhibit anti-oxidant and anti-inflammatory activities, but at higher concentrations act as oxidants and potent allergens. We recently demonstrated the eugenol dimer bis-eugenol to be an efficient inhibitor of lipopolysaccharide (LPS)-induced inflammatory cytokine expression in macrophages without cytotoxicity. This result suggested that dimer compound of o-methoxyphenols may possess anti-inflammatory activity. Thus, we further synthesized dehydrodiisoeugenol and α-diisoeugenol from isoeugenols, and investigated whether these dimers could inhibit LPS-stimulated nuclear factor kappa B (NF-κB) activation and cyclooxygenase (COX)-2 gene expression, both of which are closely involved in inflammation and mutagenesis. The expression of the COX-2 gene was strongly inhibited by dehydrodiisoeugenol in RAW264.7 murine macrophages stimulated with LPS. In contrast, isoeugenol and α-diisoeugenol did not inhibit it. Dehydrodiisoeugenol also significantly inhibited LPS-stimulated phosphorylation-dependent proteolysis of inhibitor κB-α and transcriptional activity of NF-κB in the cells. These findings suggest that dehydrodiisoeugenol acts as a potent anti-inflammatory agent.