Dietary supplementation with geranylgeraniol suppresses lipopolysaccharide-induced inflammation via inhibition of nuclear factor-κB activation in rats

Purpose

The isoprenoid geranylgeraniol (GGOH) inhibits nuclear factor-kappa B (NF-κB) activation in the liver, yet the mechanism remains unclear. We investigated the modulation and inhibition of lipopolysaccharide (LPS)-induced NF-κB signaling in the liver of rats fed a GGOH-supplemented diet.

Methods

Rats were fed a diet supplemented with or without GGOH for 10 days. Rats were then intraperitoneally injected with 0.5 mg/kg LPS or vehicle (sterilized saline) and fasted for 18 h. Plasma levels of the inflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6, and the liver damage indicators alanine and aspartate aminotransferases (ALT and AST) were assessed. Liver mRNA and proteins were assayed for changes in NF-κB target genes and signal transduction genes.

Results

Rats fed a high-dose, GGOH-supplemented diet showed significantly lower levels of plasma inflammatory cytokines and ALT and AST activities. In the liver, GGOH significantly suppressed NF-κB activation and mRNA expression of its pro-inflammatory target genes. Furthermore, GGOH supplementation substantially suppressed mRNA expression of signal transducer genes upstream of the IκB kinase complex. Western blotting of liver extracts further demonstrated the substantial decrease in total IL-1 receptor-associated kinase 1 (IRAK1) and TNF receptor-associated factor 6 (TRAF6), leading to lower signal transduction and inhibition of NF-κB after LPS.

Conclusion

A 10-day, high-dose, GGOH-supplemented diet was sufficient to inhibit LPS-induced inflammation and activation of NF-κB in rat livers. GGOH significantly modulated NF-κB signaling molecules, inhibiting its signal transduction and activation in the liver, thus protecting against liver damage.     

High-fat diet blunts activation of the nuclear factor-κB signaling pathway in lipopolysaccharide-stimulated peritoneal macrophages of Wistar rats

ObjectiveThe present study was designed to investigate the effect of a high-fat diet (HFD) on the inflammatory response of peritoneal macrophages.MethodsMale Wistar rats were fed a control diet (n = 12) or an HFD (n = 12) for 12 wk. After euthanasia, peritoneal macrophages were collected and stimulated (or not) with lipopolysaccharide (LPS). Results from the assays using peritoneal macrophages were analyzed with one-way analysis of variance or an equivalent non-parametric test. The level of significance adopted was 0.05.ResultsConsumption of the HFD was associated with significant increases in weight gain and fat depots (P < 0.05). Despite having no influence in systemic markers of inflammation, such as interleukin (IL)-6, tumor necrosis factor-α, and plasminogen activator inhibitor-1, the HFD intake significantly decreased insulin sensitivity, as evaluated by the homeostasis model assessment index (P < 0.05). A decreased production of IL-1β, IL-6, IL-10, and nitric oxide in response to the LPS stimulation was observed in peritoneal macrophages from the HFD group (P < 0.05). Also, in HFD-fed animals, LPS incubation did not increase IL-1β and IL-6 mRNA expression (P < 0.05). These effects were associated with an attenuation of IκB inhibitor kinase-β phosphorylation and nuclear factor-κB activation in response to LPS and with a failure to decrease IκB inhibitor-α expression (P < 0.05).ConclusionChronic consumption of an HFD decreased the LPS-induced inflammatory response of peritoneal macrophages, which was associated with a downregulation of the nuclear factor-κB signaling pathway.     

Zinc-suppressed inflammatory cytokines by induction of A20-mediated inhibition of nuclear factor-κB

ObjectiveChronic generation of inflammatory cytokines and reactive oxygen species are implicated in atherosclerosis, aging, cancers, and other chronic diseases. We hypothesized that zinc induces A20 in premonocytic, endothelial, and cancer cells, and A20 binds to tumor necrosis factor (TNF)-receptor associated factor, and inhibits Iκ kinase-α (IKK-α)/nuclear factor-κB (NF-κB), resulting in downregulation of TNF-α and interleukin-1β (IL-1β).MethodsTo test this hypothesis, we used HL-60, human umbilical vein endothelial cells, and SW480 cell lines under zinc-deficient and zinc-sufficient conditions in this study. We measured oxidative stress markers, inflammatory cytokines, A20 protein and mRNA, A20–FRAF-1 complex, and IKK-α/NF-κB signaling in stimulated zinc-deficient and zinc sufficient cells. We also conducted antisense A20 and siRNA studies to investigate the regulatory role of zinc in TNF-α and IL-1β via A20.ResultsWe found that zinc increased A20 and A20–tumor necrosis factor-receptor associated factor-1 complex, decreased the IKK-α/NF-κB signaling pathway, oxidative stress markers, and inflammatory cytokines in these cells compared with zinc-deficient cells. We confirmed that zinc-induced A20 contributes to downregulation of TNF-α and IL-1β by antisense and short interfering RNA A20 studies.ConclusionOur studies suggest that zinc suppresses generation of NF-κB–regulated inflammatory cytokines by induction of A20.     

Musca domestica pupae lectin improves the immunomodulatory activity of macrophages by activating nuclear factor-κB

In this study, Musca domestica pupae lectin (MPL) was screened for its immunomodulatory effect on macrophages. The phagocytosis of macrophages was improved significantly when they were treated with MPL: remarkable changes were observed in the morphology of the cells, the metabolic abilities of DNA and RNA were enhanced, and the production of hepatin was increased. Meanwhile, compared with the control group, not only the mRNA expressions of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interferon-γ (IFN-γ) in macrophages, but also the productions of proteins, were strongly induced by MPL; these effects were inhibited by pyrrolidine dithiocarbamate. Further study suggested that MPL could increase the nuclear factor-κB (NF-κB) p65 level in the nucleus. Overall, these results indicate that the improving immunomodulatory activity induced by MPL is mainly due to the increasing productions of TNF-α, IL-6, and IFN-γ and that the activation of macrophage by MPL is partly mediated via the NF-κB pathway.     

Modulation of the nuclear factor-kappa B (NF-κB) signalling pathway by glutamine in peritoneal macrophages of a murine model of protein malnutrition

Background and aims

Protein malnutrition affects resistance to infection by impairing the inflammatory response, modifying the function of effector cells, such as macrophages. Recent studies have revealed that glutamine—a non-essential amino acid, which could become conditionally essential in some situations like trauma, infection, post-surgery and sepsis—is able to modulate the synthesis of cytokines. The aim of this study was to evaluate the effect of glutamine on the expression of proteins involved in the nuclear factor-kappa B (NF-κB) signalling pathway of peritoneal macrophages from malnourished mice.

Methods

Two-month-old male Balb/c mice were submitted to protein-energy malnutrition (n = 10) with a low-protein diet containing 2 % protein, whereas control mice (n = 10) were fed a 12 % protein-containing diet. The haemogram and analysis of plasma glutamine and corticosterone were evaluated. Peritoneal macrophages were pre-treated in vitro with glutamine (0, 0.6, 2 and 10 mmol/L) for 24 h and then stimulated with 1.25 μg LPS for 30 min, and the synthesis of TNF-α and IL-1α and the expression of proteins related to the NF-κB pathway were evaluated.

Results

Malnourished animals had anaemia, leucopoenia, lower plasma glutamine and increased corticosterone levels. TNF-α production of macrophages stimulated with LPS was significantly lower in cells from malnourished animals when cultivated in supraphysiological (2 and 10 mmol/L) concentrations of glutamine. Further, glutamine has a dose-dependent effect on the activation of macrophages, in both groups, when stimulated with LPS, inducing a decrease in TNF-α and IL-1α production and negatively modulating the NF-κB signalling pathway.

Conclusions

These data lead us to infer that the protein malnutrition state interferes with the activation of macrophages and that higher glutamine concentrations, in vitro, have the capacity to act negatively in the NF-κB signalling pathway.     

Grape peel powder attenuates the inflammatory and oxidative response of experimental colitis in rats by modulating the NF-κB pathway and activity of antioxidant enzymes

Most phenolic compounds and dietary fiber reach intact to the colon. We hypothesized that grape peel powder (GPP), a rich source of these bioactive compounds, modulates inflammatory and oxidative pathways collaborating to attenuate colonic damage in experimental colitis. To determine which bioactive fraction would be responsible for this effect, the aim of this study was to evaluate the effect of dietary supplementation with whole GPP or the isolated bioactive-rich fractions from GPP (extractable polyphenols [EP], dietary fiber and fiber-bound polyphenols [NEP-F], and dietary fiber) in rats with experimental colitis. Colitis was induced by intrarectal injection of 2,4,6-trinitrobenzene sulfonic acid (TNBS) after 15 days of dietary supplementation. EP diet did not reverse the decrease in feed intake and indeed worsened colon shortening and increased spleen weight; however, these effects were not observed for the GPP group, which had polyphenols associated to the matrix besides the extractable ones. Colitis impaired the activity of colonic antioxidant enzymes and increased lipid peroxidation, protein oxidation, nitric oxide (NO) levels, and proinflammatory cytokines in serum and in the colon tissue. GPP restored the activity of antioxidant enzymes and decreased colon oxidation and NO levels. All grape peel fractions reduced the protein expression of the inhibitor of kappa kinase beta and NO levels in colon tissue, but only NEP-F reduced the expression of phosphorylated nuclear factor kappa B and myeloperoxidase activity. Results demonstrated that GPP attenuates inflammatory and oxidative response in TNBS–induced colitis by downregulating the nuclear factor kappa B pathway and upregulating antioxidant enzymes, with NEP-F being the fraction most likely associated to these protective effects.     

Chrysophyllum albidum fruit peel attenuates nociceptive pain and inflammatory response in rodents by inhibition of pro-inflammatory cytokines and COX-2 expression through suppression of NF-κB activation

Chrysophyllum abidum fruit is a seasonal fruit commonly eaten as snacks with abundant health promoting phytochemicals in the fruit peels. The fruit peels have been reported to be rich in anti-inflammatory eleagnine, myricetin rhamnoside, quercetin, linoleic acid and oleic acid. We hypothesized that the anti-inflammatory effect of the peel extract involve suppression of pro-inflammatory cytokines, cyclooxygenase-2 and nuclear factor-kappa B (NF-κB). Hence, this study was designed to assess the anti-nociceptive and anti-inflammatory effects of fruit peel extract of Chrysophyllum albidum in animal models of nociception and inflammation. The anti-nociceptive activity of CAPEE (100 and 400 mg/kg) was evaluated in acetic acid-induced writhing and formalin-induced paw licking in mice. Formalin-induced paw edema and carrageenan-induced air pouch models of inflammation were used to evaluate the anti-inflammatory activity. CAPEE (100 and 400 mg/kg) significantly reduced abdominal writhing and paw licking in acetic acid and formalin tests in mice, respectively. CAPEE demonstrated significant inhibition of paw edema at 24 h (41.0% and 55.7%) and 72 h (52.3% and 86.6%) after formalin injection. CAPEE suppressed inflammatory responses in carrageenan-induced air pouch by reducing exudates, inflammatory cells infiltration, nitrites and myeloperoxidase activity. There was significant inhibition of tumor necrosis factor-alpha, interleukin-6 levels and reduced immunopositive expression of COX-2 and NF-κB. In conclusion, CAPEE has anti-nociceptive and anti-inflammatory potentials via mechanisms associated with inhibition of pro-inflammatory cytokines and cyclooxygenase-2 (COX-2) expression through suppression of nuclear factor kappa B (NF-κB) activation, and has potential as a functional food ingredient.     

Soy protein inhibits inflammation-induced VCAM-1 and inflammatory cytokine induction by inhibiting the NF-κB and AKT signaling pathway in apolipoprotein E–deficient mice

Purpose

Inflammation is a hallmark of many diseases, such as atherosclerosis, autoimmune diseases, obesity, and cancer. Isoflavone-free soy protein diet (SPI^?) has been shown to reduce atherosclerotic lesions in a hyperlipidemic mouse model compared to casein (CAS)-fed mice, despite unchanged serum lipid levels. However, possible mechanisms contributing to the athero-protective effect of soy protein remain unknown. Therefore, we investigated whether and how SPI^? diet inhibits inflammatory responses associated with atherosclerosis.

Methods

Apolipoprotein E knockout (apoE?/?) mice (5-week) were fed CAS or SPI^? diet for 1 or 5 week to determine LPS- and hyperlipidemia-induced acute and chronic inflammatory responses, respectively. Expression of NF-κB-dependent inflammation mediators such as VCAM-1, TNF-α, and MCP-1 were determined in aorta and liver. NF-κB, MAP kinase, and AKT activation was determined to address mechanisms contributing to the anti-inflammatory properties of soy protein/peptides.

Results

Isoflavone-free soy protein diet significantly reduced LPS-induced VCAM-1 mRNA and protein expression in aorta compared to CAS-fed mice. Reduced VCAM-1 expression in SPI^?-fed mice also paralleled attenuated monocyte adhesion to vascular endothelium, a critical and primary processes during inflammation. Notably, VCAM-1 mRNA and protein expression in lesion-prone aortic arch was significantly reduced in apoE?/? mice fed SPI^? for 5 weeks compared with CAS-fed mice. Moreover, dietary SPI^? potently inhibited LPS-induced NF-κB activation and the subsequent upregulation of pro-inflammatory cytokines, including TNF-α, IL-6, IL-1β, and MCP-1. Interestingly, SPI^? inhibited NF-κB-dependent inflammatory responses by targeting I-κB phosphorylation and AKT activation with no effect on MAP kinase pathway. Of the five putative soy peptides, four of the soy peptides inhibited LPS-induced VCAM-1, IL-6, IL-8, and MCP-1 protein expression in human vascular endothelial cells in vitro.

Conclusions

Collectively, our findings suggest that anti-inflammatory properties of component(s) of soy protein/peptides may be a possible mechanism for the prevention of chronic inflammatory diseases such as atherosclerosis.