Docosahexaenoic acid attenuates VCAM-1 expression and NF-κB activation in TNF-α-treated human aortic endothelial cells

This study was conducted to test the hypothesis that n-3 polyunsaturated fatty acids are able to down-regulate expression of adhesion molecules and nuclear factor-κB (NF-κB) activation in vascular endothelial cells, in addition to reducing atherosclerotic lesions in vivo. We report here that docosahexaenoic acid (DHA) reduces atherosclerotic lesions in the aortic arteries of apolipoprotein E knockout (apoE^-/-) mice. Consistent with the observation in animal study, DHA inhibited THP-1 cell adhesion to tumor necrosis factor α (TNF-α)-activated human aortic endothelial cells (HAECs). Expression of vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1) on the cell surface of HAECs was determined by cell-surface enzyme-linked immunosorbent assay. DHA and eicosapentaenoic acid decreased VCAM-1 expression in a dose-dependent manner in TNF-α treated HAECs, while cis-linoleic acid and arachidonic acid did not have any significant effect on either VCAM-1 or ICAM-1 expression. Moreover, DHA significantly reduced VCAM-1 protein expression in the cell lysates of TNF-α-treated HAECs, as determined by Western blot analysis. In line with NF-κB signaling pathway, DHA suppressed the TNF-α-activated IκBα phosphorylation and degradation as well as IκB kinase-β phosphorylation. Subsequently, translocation of the NF-κB (p50/p65) and AP-1 (c-Fos/c-Jun) subunits was down-regulated by DHA in the nucleus of HAECs. These results suggest that DHA negatively regulates TNF-α-induced VCAM-1 expression through attenuation of NF-κB signaling pathway and AP-1 activation. This study provides evidence that DHA may contribute to the prevention of atherosclerosis and inflammatory diseases in vivo.     

Omentin inhibits TNF-α-induced expression of adhesion molecules in endothelial cells via ERK/NF-κB pathway

In the present study, we investigated whether omentin affected the expression of intracellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in tumor necrosis factor-α (TNF-α) induced human umbilical vein endothelial cells (HUVECs). Our data showed that omentin decreased TNF-α-induced expression of ICAM-1 and VCAM-1 in HUVECs. In addition, omentin inhibited TNF-α-induced adhesion of THP-1 cells to HUVECs. Further, we found that omentin inhibited TNF-α-activated signal pathway of nuclear factor-κB (NF-κB) by preventing NF-κB inhibitory protein (IκBα) degradation and NF-κB/DNA binding activity. Omentin pretreatment significantly inhibited TNF-α-induced ERK activity and ERK phosphorylation in HUVECs. Pretreatment with PD98059 suppressed TNF-α-induced NF-κB activity. Omentin, NF-kB inhibitor (BAY11-7082) and ERK inhibitor (PD98059) reduced the up-regulation of ICAM-1 and VCAM-1 induced by TNF-α. These results suggest that omentin may inhibit TNF-α-induced expression of adhesion molecules in endothelial cells via blocking ERK/NF-κB pathway.     

The anti-atherosclerotic effect of tanshinone IIA is associated with the inhibition of TNF-α-induced VCAM-1, ICAM-1 and CX3CL1 expression

Tanshinone IIA is one of the major diterpenes in Salvia miltiorrhiza. The inhibitory effect of Tanshinone IIA on atherosclerosis has been reported, but the underlying mechanism is not fully understood. The present study aimed to study the anti-atherosclerosis effect of Tanshinone IIA on the adhesion of monocytes to vascular endothelial cells and related mechanism. Results showed that Tanshinone IIA, at the concentrations without cytotoxic effect, dose-dependently inhibited the adhesion of THP-1 monocytes to the TNF-α-stimulated human vascular endothelial cells. The expressions of cell adhesion molecules including VCAM-1, ICAM-1 and E-selectin were induced by TNF-α in HUVECs at both the mRNA and protein levels. The mRNA and protein expressions of VCAM-1 and ICAM-1, but not E-selectin, were both significantly suppressed by Tanshinone IIA in a dose dependent manner. In addition, the TNF-α-induced mRNA expression of fractalkine/CX3CL1 and the level of soluble fractalkine were both reduced by Tanshinone IIA. We also found that Tanshinone IIA significantly inhibited TNF-α-induced nuclear translocation of NF-κB which was resulted from the inhibitory effect of Tanshinone IIA on the TNF-α-activated phosphorylation of IKKα, IKKβ, IκB and NF-κB. As one of the major components of Salvia miltiorrhiza, Tanshinone IIA alone exerted more potent effect on inhibiting the adhesion of monocytes to vascular endothelial cells when compared with Salvia miltiorrhiza. All together, these results demonstrate a novel underlying mechanism for the anti-inflammatory effect of Tanshinone IIA by modulating TNF-α-induced expression of VCAM-1, ICAM-1 and fractalkine through inhibition of TNF-α-induced activation of IKK/NF-κB signaling pathway in human vascular endothelial cells.     

Glutathione peroxidase-1 deficiency augments proinflammatory cytokine-induced redox signaling and human endothelial cell activation

Glutathione peroxidase-1 (GPx-1) is a crucial antioxidant enzyme, the deficiency of which promotes atherogenesis. Accordingly, we examined the mechanisms by which GPx-1 deficiency enhances endothelial cell activation and inflammation. In human microvascular endothelial cells, we found that GPx-1 deficiency augments intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expression by redox-dependent mechanisms that involve NFκB. Suppression of GPx-1 enhanced TNF-α-induced ROS production and ICAM-1 expression, whereas overexpression of GPx-1 attenuated these TNF-α-mediated responses. GPx-1 deficiency prolonged TNF-α-induced IκBα degradation and activation of ERK1/2 and JNK. JNK or NFκB inhibition attenuated TNF-α induction of ICAM-1 and VCAM-1 expression in GPx-1-deficient and control cells, whereas ERK1/2 inhibition attenuated only VCAM-1 expression. To analyze further signaling pathways involved in GPx-1-mediated protection from TNF-α-induced ROS, we performed microarray analysis of human microvascular endothelial cells treated with TNF-α in the presence and absence of GPx-1. Among the genes whose expression changed significantly, dual specificity phosphatase 4 (DUSP4), encoding an antagonist of MAPK signaling, was down-regulated by GPx-1 suppression. Targeted DUSP4 knockdown enhanced TNF-α-mediated ERK1/2 pathway activation and resulted in increased adhesion molecule expression, indicating that GPx-1 deficiency may augment TNF-α-mediated events, in part, by regulating DUSP4.     

Flavonoids of <Emphasis Type="Italic">Rosa roxburghii</Emphasis> Tratt offers protection against radiation induced apoptosis and inflammation in mouse thymus

The present study evaluated the protective effect of the natural compound flavonoids of Rosa roxburghii Tratt (FRT) against γ-radiation-induced apoptosis and inflammation in mouse thymus cells in vivo and in vitro. Thymus cells and mice were exposed to ⁶⁰Co γ-ray at a dose of 6 Gy. The radiation treatment induced significant cell apoptosis and inflammation. Radiation increased the expressions of cleaved caspase 3/8–10, AIF, and PARP-1, and FRT could mitigate their activation and inhibit subsequent apoptosis in the thymus both in vitro or in vivo. Irradiation increased the mRNA expression of ICAM-1/VCAM-1, IL-1α/IL-6 and TNF-α/NF-κB. Our results also indicated that FRT alleviated gene expression of some inflammatory factors such as ICAM-1/VCAM-1, TNF-α/NF-κB, but not IL-1α/IL-6. Irradiation increased the protein expression levels of ICAM-1/VCAM-1, IL-1α/IL-6 and TNF-α/NF-Κb, and our results also indicated that FRT alleviated protein level expression of certain inflammatory factors such as ICAM-1, IL-1α/IL-6, TNF-α/NF-κB, but not VCAM-1. Our results suggested that FRT enhanced radioprotection at least partially by regulating caspase 3/8–10, AIF, and PARP-1 to reduce apoptosis and by regulating ICAM-1, IL-1α/IL-6, TNF-α/NF-κB to reduce inflammation.     

Unique haplotype in exon 3 of cone opsin mRNA affects splicing of its precursor, leading to congenital color vision defect

Chemerin is a recently identified adipocytokine which plays a role on inflammation and adipocytes metabolism. However, its function in vasculature is largely unknown. We examined the effects of chemerin on vascular endothelial inflammatory states. Treatment of human umbilical vein endothelial cells with chemerin (300 ng/ml, 20 min) induced phosphorylation of Akt (Ser473) and endothelial nitric oxide (NO) synthase (eNOS) (Ser1177). Consistently, chemerin increased intracellular cyclic GMP content. Pretreatment with chemerin (1-300 ng/ml, 24 h) significantly inhibited phosphorylation of nuclear factor (NF)-κB p65 (Ser536) and p38 as well as vascular cell adhesion molecule (VCAM)-1 expression induced by tumor necrosis factor (TNF)-α (5 ng/ml, 20 min-6 h). Inhibitor of NF-κB or p38 significantly inhibited the TNF-α-induced VCAM-1 expression. Chemerin also inhibited TNF-α-induced VCAM-1 expression in rat isolated aorta. Moreover, chemerin significantly inhibited monocytes adhesion to TNF-α-stimulated endothelial cells. The inhibitory effect of chemerin on TNF-α-induced VCAM-1 was reversed by a NOS inhibitor. Conversely, an NO donor, sodium nitroprusside significantly inhibited TNF-α-induced VCAM-1. The present results for the first time demonstrate that chemerin plays anti-inflammatory roles by preventing TNF-α-induced VCAM-1 expression and monocytes adhesion in vascular endothelial cells. The effect is mediated via inhibiting activation of NF-κB and p38 through stimulation of Akt/eNOS signaling and NO production.     

Induction of vascular cell adhesion molecule-1 expression by IL-4 in human aortic smooth muscle cells is not associated with increased nuclear NF-κB levels

Vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) are upregulated in vascular endothelial and smooth muscle cells by cytokines produced at sites of inflammation. The cytokine profile for induction of VCAM-1, however, is different for the two cell types. Tumor necrosis factor-α (TNF-α) induced both VCAM-1 and ICAM-1 expression in human umbilical vein endothelial cells (HUVECs; ED₅₀ ∼ 300 and 30 U/ml, respectively). TNF-α and interleukin-1β (IL-1β) stimulated cell surface ICAM-1 expression, but not VCAM-1 expression, in human aortic smooth muscle cells (HASMCs). Conversely, IL-4 was a potent VCAM-1 inducer in HASMCs (ED₅₀ ∼ 100 pg/ml) but did not induce ICAM-1 expression. Nuclear extracts from IL-4-treated cells were compared with untreated cells for relative nuclear factor-kappa B (NF-κB) levels by using an electrophoretic mobility shift assay and surface plasmon resonance techniques. No significant increase in nuclear NF-κB DNA binding activity was detected in IL-4-treated HASMCs by either method of analysis. IL-1β and TNF-α stimulated nuclear NF-κB levels by about fourfold and fivefold, respectively, in HASMCs. The antioxidant pyrrolidine dithiocarbamate (PDTC) similarly inhibited VCAM-1 upregulation in HASMCs incubated with IL-4 and in HUVECs incubated with TNF-α (IC₅₀s of 25 and 40 μM, respectively). These data suggest that a significant increase in nuclear NF-κB levels is not necessary or sufficient for VCAM-1 upregulation in HASMCs and does not determine the relative sensitivity to inhibition of gene expression by PDTC. J. Cell. Physiol. 180:381–389, 1999. © 1999 Wiley-Liss, Inc.     

Cryptotanshinone inhibits oxidized LDL-induced adhesion molecule expression via ROS dependent NF-κB pathways

Adhesion molecules, such as intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin, play important roles in the initial stage of atherosclerosis. Cryptotanshinone (CPT), a natural compound isolated from Salvia miltiorrhiza Bunge, exhibits anti-atherosclerotic activity although the underlying mechanisms remain elusive. In this study, the protective effect of CPT against oxidized low-density lipoprotein (ox-LDL)-induced adhesion molecule expression was investigated in human umbilical vein endothelial cells. Ox-LDL significantly induced ICAM-1, VCAM-1, and E-selectin expression at the mRNA and protein levels but reduced eNOS phosphorylation and NO generation, which were reversed by CPT pretreatment. Sodium nitroprusside, a NO donor, N-acetyl-L-cysteine (NAC), a reactive oxygen species (ROS) scavenger, and BAY117082, a NF-κB inhibitor, inhibited ox-LDL-induced ICAM-1, VCAM-1, and E-selectin expression. Ox-LDL-induced ROS production was significantly inhibited by CPT and NAC. Furthermore, ox-LDL activated the NF-κB signaling pathway by inducing phosphorylation of IKKβ and IκBα, promoting the interaction of IKKβ and IκBα, and increasing p65 nuclear translocation, which were significantly inhibited by CPT. In addition, CPT, NAC, and BAY117082 inhibited ox-LDL-induced membrane expression of ICAM-1, VCAM-1, E-selectin, and endothelial–monocyte adhesion and restored eNOS phosphorylation and NO generation. Results suggested that CPT inhibited ox-LDL-induced adhesion molecule expression by decreasing ROS and inhibiting the NF-κB pathways, which provides new insight into the anti-atherosclerotic mechanism of CPT.     

Cordycepin blocks lung injury-associated inflammation and promotes BRCA1-deficient breast cancer cell killing by effectively inhibiting PARP

Cordycepin has been shown to interfere with a myriad of molecular processes from RNA elongation to kinase activity, and prevents numerous inflammatory processes in animal models. Here we show in a mouse model of LPS-induced acute lung injury that cordycepin prevents airway neutrophilia via a robust blockade of expression of several inflammatory genes, including the adhesion molecule ICAM-1 and VCAM-1, the cytokine/chemokine MCP-1, MIP-1α, MIP-2 and KC, and the chemokine receptor CXCR2. Such a blockade appears to be related to a severe reduction in TNF-α expression. Interestingly, in an in vitro system of A549 epithelial cell inflammation, cordycepin effectively blocked LPS-induced, but not TNF-α-induced, VCAM-1 expression. Such effects correlated with a marked reduction in p65-NF-κB activation as assessed by its phosphorylation at serine-536 but without an apparent effect on its nuclear translocation. The effects of cordycepin on the expression of VCAM-1 and ICAM-1, and of NF-κB activation and nuclear translocation upon TNF-α stimulation resembled the effects achieved upon poly(ADP-ribose) polymerase (PARP) inhibition, suggesting that cordycepin may function as a PARP inhibitor. Indeed, cordycepin blocked H(2)O(2)-induced PARP activation in A549 cells. In a cell-free system, cordycepin inhibited PARP-1 activity at nanomolar concentrations. Similar to PARP inhibitors, cordycepin significantly induced killing of breast cancer susceptibility gene (BRCA1)-deficient MCF-7 cells, supporting its therapeutic use for the treatment of BRCA-deficient breast cancers. With added antiinflammatory characteristics, therapies that include cordycepin may prevent potential inflammation triggered by traditional chemotherapeutic drugs. Cordycepin, to the best of our knowledge, represents the first natural product possessing PARP inhibitory traits.     

Nonsteroidal anti-inflammatory drug induces proinflammatory damage in gastric mucosa through NF-κB activation and neutrophil infiltration: Anti-inflammatory role of heme oxygenase-1 against nonsteroidal anti-inflammatory drug

Nonsteroidal anti-inflammatory drug (NSAID)-induced mitochondrial oxidative stress (MOS) is an important prostaglandin (PG)-independent pathway of the induction of gastric mucosal injury. However, the molecular mechanism behind MOS-mediated gastric pathology is still obscure. In various pathological conditions of tissue injury oxidative stress is often linked with inflammation. Here we report that MOS induced by indomethacin (an NSAID) induces gastric mucosal inflammation leading to proinflammatory damage. Indomethacin, time dependently stimulated the expression of proinflammatory molecules such as intercellular adhesion molecule 1(ICAM-1), vascular cell adhesion molecule 1(VCAM-1), interleukin1β (IL-1β), and monocyte chemotactic protein-1 (MCP-1) in gastric mucosa in parallel with the increase of neutrophil infiltration and injury of gastric mucosa in rat. Western immunoblotting and confocal microscopic studies revealed that indomethacin induced nuclear translocation of nuclear factor kappa-B (NF-κB) in gastric mucosal cells, which resulted in proinflammatory signaling. The prevention of MOS by antioxidant tryptamine-gallic acid hybrid (SEGA) inhibited indomethacin-induced expression of ICAM-1, VCAM-1, IL-1β, and MCP-1. SEGA also prevented indomethacin-induced NF-κB activation and neutrophil infiltration as documented by chromatin immunoprecipitation studies and neutrophil migration assay, respectively. Heme oxygenase-1 (HO-1), a cytoprotective enzyme associated with tissue repair mechanisms is stimulated in response to oxidative stress. We have investigated the role of HO-1 against MOS and MOS-mediated inflammation in recovering from gastropathy. Indomethacin stimulated the expression of HO-1 and indomethacin-stimulated HO-1 expression was reduced by SEGA, an antioxidant, which could prevent MOS. Thus, the data suggested that the induction of HO-1 was a protective response against MOS developed by indomethacin. Moreover, the induction of HO-1 by cobalt protoporphyrin inhibited inflammation and chemical silencing of HO-1 by zinc protoporphyrin aggravated the inflammation by indomethacin. Thus, NSAID by promoting MOS-induced proinflammatory response damaged gastric mucosa and HO-1 protected NSAID-induced gastric mucosal damage by preventing NF-κB activation and proinflammatory activity.     

AGGF1 is a novel anti-inflammatory factor associated with TNF-α-induced endothelial activation

Endothelial activation contributes to the development of vascular inflammation and subsequent vascular diseases, particularly atherosclerosis. AGGF1, a new member of angiogenic factors with a FHA and a G-patch domain, has been shown critical for the regulation of vascular differentiation and angiogenesis. In this study, we found that various inflammatory cytokines strongly induced the expression of AGGF1 in endothelial cells (ECs) and identified AGGF1 as a novel anti-inflammatory factor both in vivo and in vitro. Overexpression of AGGF1 significantly repressed the expression of pro-inflammatory molecules such as E-Selectin, ICAM-1, and IL-8 and the adhesion of monocytes onto ECs activated by TNF-α. Conversely, the knockdown of AGGF1 resulted in the increased expressions of these pro-inflammatory molecules and the enhanced monocyte-EC interaction. We further demonstrated that AGGF1 potently attenuated TNF-α triggered NF-κB pathway, as indicated by the decreased promoter activity, nuclear distribution and phosphorylation of NF-κB p65 subunit as well as the increased protein level of IκBα. This inhibitory effect of AGGF1 was further proved through blocking the phosphorylation of ERK induced by TNF-α. Finally, we showed that the FHA domain of AGGF1 was required for its anti-inflammatory effect. Thus, our findings for the first time demonstrate that AGGF1 suppresses endothelial activation responses to TNF-α by antagonizing the ERK/NF-κB pathway, which makes AGGF1 a promising therapeutic candidate for the prevention and treatment of inflammatory diseases.     

Aspirin prevents adhesion of T lymphoblasts to vascular smooth muscle cells

In the development of atherosclerosis, inflammatory cells adhere to and migrate into the vascular walls by interacting with vascular smooth muscle cells. To investigate the mechanism of aspirin’s anti-atherogenic activity, we examined whether aspirin inhibits the adhesion of lymphocytes to human aortic smooth muscle cells (AoSMC). Aspirin inhibited T-cell adhesion to AoSMC activated by interleukin 1β (IL-1β) in a dose-dependent manner. Antibodies to the adhesion molecules ICAM-1 or VCAM-1, but not to E-selectin, prevented T-cell adhesion. ICAM-1 and VCAM-1 expression stimulated by IL-1β was reduced by the treatment with aspirin, whereas the expression of E-selectin was unaffected. Nuclear factor κB (NF-κB) activity was enhanced by IL-1β and reduced by aspirin, indicating that decreased ICAM-1 and VCAM-1 expression was due to reduced NF-κB activity.Thus, aspirin inhibits the adhesion of Jurkat T cells to IL-1β-activated AoSMC by reducing NF-κB activity and decreasing expression of ICAM-1 and VCAM-1, and may prevent the development of atherosclerosis.     

Pharmacological targeting of HSP90 with 17-AAG induces apoptosis of myogenic cells through activation of the intrinsic pathway

Endothelial inflammation and monocyte plays an essential role in the initiation and progression of atherosclerosis. Ghrelin is beneficial for atherosclerosis progression. However, the detailed and precise molecular mechanisms of how ghrelin regulates endothelial inflammation are not clear. In this study, we investigated the regulation mechanism of ghrelin on TNF-α-activated endothelial inflammation and monocyte adhesion. It was found that TNF-α-induced monocyte adhesion on HUVEC was significantly attenuated by ghrelin. Furthermore, we found that ghrelin effectively suppressed TNF-α-induced inflammatory factors’ (including ICAM-1, VCAM-1, MCP-1, and IL-1β) expression through inhibiting AMPK phosphorylation and p65 expression both in HUVEC and THP-1. This phenomenon was further demonstrated by using AMPK agonist AICAR and inhibitor compound C, respectively. Our findings suggest that ghrelin may mediate TNF-α-induced endothelial inflammation and monocyte adhesion, in part via AMPK/NF-κB signaling pathway. These novel anti-inflammatory and immunoregulatory actions of ghrelin may play a certain role in understanding the formation and development of atherosclerosis.     

Endothelial ICAM-1 protein induction is regulated by cytosolic phospholipase A2α via both NF-κB and CREB transcription factors

The regulated expression of ICAM-1 plays an important role in inflammatory processes and immune responses. The present study aimed to determine the in vivo involvement of cytosolic phospholipase A(2)α (cPLA(2)α) in ICAM-1 overexpression during inflammation and to elucidate the cPLA(2)α-specific role in signal events leading to ICAM-1 upregulation in endothelial cells. cPLA(2)α and ICAM-1 upregulation were detected in inflamed paws of mice with collagen-induced arthritis and in periepididymal adipose tissue of mice fed a high-fat diet. Intravenous injection of 2 mg/kg oligonucleotide antisense against cPLA(2)α (AS) that reduced cPLA(2)α upregulation also decreased ICAM-1 overexpression, suggesting a key role of cPLA(2)α in ICAM-1 upregulation during inflammation. Preincubation of endothelial ECV-304 cells that express ICAM-1 and of HUVEC that express ICAM-1 and VCAM-1 with 1 μM AS prevented cPLA(2)α and the adhesion molecule upregulation induced by TNF-α and inhibited their adherence to phagocyte like-PLB cells. Whereas AS did not inhibit NADPH oxidase 4-NADPH oxidase activity, inhibition of oxidase activity attenuated cPLA(2)α activation, suggesting that NADPH oxidase acts upstream to cPLA(2)α. Attenuating cPLA(2)α activation by AS or diphenylene iodonium prevented the induction of cyclooxygenase-2 and the production of PGE(2) that were essential for ICAM-1 upregulation. Inhibition of cPLA(2)α activity by AS inhibited the phosphorylation of both p65 NF-κB on Ser(536) and protein kinase A-dependent CREB. To our knowledge, our results are the first to show that CREB activation is involved in ICAM-1 upregulation and suggest that cPLA(2)α activated by NADPH oxidase is required for sequential phosphorylation of NF-κB by an undefined kinase and CREB activation by PGE(2)-mediated protein kinase A.     

Docosahexaenoic acid inhibition of inflammation is partially via cross-talk between Nrf2/heme oxygenase 1 and IKK/NF-κB pathways

We examined the underlying mechanisms involved in n-3 docosahexaenoic acid (DHA) inhibition of inflammation in EA.hy926 cells. The present results demonstrated that pretreatment with DHA (50 and 100 μM) inhibited tumor necrosis factor-alpha (TNF-α)-induced intercellular adhesion molecule 1 (ICAM-1) protein, mRNA expression and promoter activity. In addition, TNF-α-stimulated inhibitory kappa B (IκB) kinase (IKK) phosphorylation, IκB phosphorylation and degradation, p65 nuclear translocation, and nuclear factor-κB (NF-κB) and DNA binding activity were attenuated by pretreatment with DHA. DHA triggered early-stage and transient reactive oxygen species (ROS) generation and significantly increased the protein expression of heme oxygenase 1 (HO-1), induced nuclear factor erythroid 2-related factor 2 (Nrf2) translocation to the nucleus and up-regulated antioxidant response element (ARE)-luciferase reporter activity. Moreover, DHA inhibited Nrf2 ubiquitination and proteasome activity. DHA activated Akt, p38 and ERK1/2 phosphorylation, and specific inhibitors of respective pathways attenuated DHA-induced Nrf2 nuclear translocation and HO-1 expression. Transfection with HO-1 siRNA knocked down HO-1 expression and partially reversed the DHA-mediated inhibition of TNF-α-induced p65 nuclear translocation and ICAM-1 expression. Importantly, we show for the first time that HO-1 plays a down-regulatory role in NF-κB nuclear translocation, and inhibition of Nrf2 ubiquitination and proteasome activity are involved in increased cellular Nrf2 level by DHA. In this study, we show that HO-1 plays a down-regulatory role in NF-κB nuclear translocation and that the protective effect of DHA against inflammation is partially via up-regulation of Nrf2-mediated HO-1 expression and inhibition of IKK/NF-κB signaling pathway.