Suppression of endotoxin-induced proinflammatory responses by citrus pectin through blocking LPS signaling pathways

Pectin is composed of complex polysaccharides rich in galactoside residues, and it is most abundant in citrus fruits. Pectin and modified pectin have been found to exhibit anti-mutagenic activity and inhibit cancer metastasis and proliferation, with no evidence of toxicity or other serious side effects. In this study, we investigated the inhibitory effect of pectin at different degrees of esterification (DEs) on the expressions of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in lipopolysaccharide (LPS)-activated macrophages. Western blot and RT-PCR analyses demonstrated that 30% esterified pectin (DE30), DE60 pectin, and DE90 pectin significantly inhibited the protein and mRNA expressions of iNOS and COX-2 in LPS-activated macrophages, and DE90 pectin was the most-potent inhibitor. To clarify the mechanisms involved, DE90 pectin was found to inhibit the phosphorylation of MAPKs and IKK kinase activity. In addition, DE90 pectin inhibited the activation of NF-kappaB and AP-1 by electrophoretic mobility shift assay and transient transfection experiments. Finally, we found that DE90 pectin could bind with LPS, and might result in decreased binding of LPS to its receptor. These results suggest that modulation of iNOS and COX-2 expressions by dietary pectin may be important in cancer chemoprevention and anti-inflammation.     

Prodelphinidin B-4 3'-O-gallate, a tea polyphenol, is involved in the inhibition of COX-2 and iNOS via the downregulation of TAK1-NF-kappaB pathway

Much is known about the bioactive properties of green tea flavan-3-ol. However, very little work has been done to determine the properties of proanthocyanidins, another kind of polyphenols in green tea. In this study, we have investigated the anti-inflammatory effect of tea prodelphinidin B-4 3'-O-gallate (PDG) by demonstrating the inhibitory effects on cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) in lipopolysaccharide (LPS)-activated murine macrophage RAW264 cells. PDG caused a dose-dependent inhibition of COX-2 and iNOS at both mRNA and protein levels with the attendant decrease of prostaglandin E2 (PGE2) and nitric oxide (NO) production. Molecular data revealed that PDG downregulated NF-kappaB signaling pathway. Electrophoretic mobility shift assay (EMSA) showed that PDG reduced the binding complex of NF-kappaB-DNA in the promoter of COX-2 and iNOS. Immunochemical analysis revealed that PDG suppressed LPS-induced phosphorylation and degradation of IkappaBalpha, and subsequent nuclear translocation of p65. Consequently, PDG suppressed phosphorylation of IkappaB kinase alpha/beta (IKKalpha/beta) and TGF-beta-activated kinase (TAK1). Taken together, our data indicated that PDG is involved in the inhibition of COX-2 and iNOS via the downregulation of TAK1-NF-kappaB pathway, revealing partial molecular basis for the anti-inflammatory properties of tea PDG.     

Inhibition of cyclooxygenase-2 and induction of apoptosis in estrogen-nonresponsive breast cancer cells by Antrodia camphorata.

The objective of this study was to investigate the fermented culture broth of Antrodia camphorata (A. camphorata) to induce apoptosis and inhibit cyclooxygenase-2 (COX-2) in estrogen-nonresponsive (MDA-MB-231) human breast cancer cells. Treatment of the highly invasive MDA-MB-231 cells with A. camphorata (40-240 microg/ml) resulted in dose and time-dependent sequences of events marked by apoptosis, as evidenced by loss of cell viability, chromatin condensation, and internucleosomal DNA fragmentation. Apoptosis in the MDA-MB-231 cells was accompanied by release of cytochrome c, activation of caspase-3, -8, and -9, and specific proteolytic cleavage of poly (ADP-ribose) polymerase (PARP). Although the A. camphorata-induced apoptosis was associated with a reduction in Bcl-2 protein levels, negligible Bax increase was observed. Furthermore, A. camphorata treatment inhibited COX-2 protein expression and prostaglandin E2 (PGE2) production in MDA-MB-231 cells. Analysis of the study data suggests that A. camphorata exerts growth inhibition on (highly invasive) estrogen-nonresponsive human breast cancer cells through apoptosis induction associated with COX-2 inhibition, and that it may possess anticancer properties potentially valuable for application in drug products.     

CT20126, a novel immunosuppressant, prevents collagen-induced arthritis through the down-regulation of inflammatory gene expression by inhibiting NF-kappaB activation

The colchicine-derived CT20126 compound has recently been shown to exert an immune regulatory effect and prolong the survival of allograft skins. In this study, we explored the anti-inflammatory and anti-arthritic effects of CT20126 in vivo and in vitro as well as investigated its underlying action mechanism. CT20126 suppressed the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2, tumor necrosis factor-alpha, and interleukin-1beta as well as the production of nitric oxide and prostaglandin E₂ in lipopolysaccharide (LPS)-treated macrophages as well as LPS-administered mice. This drug also inhibited the production of nitric oxide, prostaglandin E₂, and the chemokines, RANTES, GROα, and ENA-78, in cytokine-stimulated human synoviocytes. CT20126 suppressed NF-κB activation and iNOS promoter activity, which correlated with its inhibitory effect on phosphorylation-dependent IκB kinase activation, IκB phosphorylation and degradation, and NF-κB nuclear translocation, in LPS-stimulated macrophages. This compound also inhibited LPS-induced NF-κB-inducing kinase (NIK) and Akt phosphorylation, which are upstream of NF-κB activation. Furthermore, CT20126 significantly decreased the incidence and severity of arthritis as well as inhibited the expression of inflammatory cytokines, chemokines, iNOS, and cyclooxygenase-2 in the paws of collagen-induced arthritic mice. These findings indicate that CT20126 exerts an anti-inflammatory effect through NF-κB-responsive inflammatory gene expression by inhibiting the NIK- and Akt-dependent canonical NF-κB pathway and can be used as a therapeutic agent for rheumatoid arthritis related to chronic inflammation.     

The inhibition of inducible nitric oxide synthase and oxidative stress by agmatine attenuates vascular dysfunction in rat acute endotoxemic model

Vascular dysfunction leading to hypotension is a major complication in patients with septic shock. Inducible nitric oxide synthase (iNOS) together with oxidative stress play an important role in development of vascular dysfunction in sepsis. Searching for an endogenous, safe and yet effective remedy was the chief goal for this study. The current study investigated the effect of agmatine (AGM), an endogenous metabolite of l-arginine, on sepsis-induced vascular dysfunction induced by lipopolysaccharides (LPS) in rats. AGM pretreatment (10 mg/kg, i.v.) 1 h before LPS (5 mg/kg, i.v.) prevented the LPS-induced mortality and elevations in serum creatine kinase-MB isoenzyme (CK-MB) activity, lactate dehydrogenase (LDH) activity, C-reactive protein (CRP) level and total nitrite/nitrate (NOx) level after 24 h from LPS injection. The elevation in aortic lipid peroxidation illustrated by increased malondialdehyde (MDA) content and the decrease in aortic glutathione (GSH) and superoxide dismutase (SOD) were also ameliorated by AGM. Additionally, AGM prevented LPS-induced elevation in mRNA expression of iNOS, while endothelial NOS (eNOS) mRNA was not affected. Furthermore AGM prevented the impaired aortic contraction to KCl and phenylephrine (PE) and endothelium-dependent relaxation to acetylcholine (ACh) without affecting endothelium-independent relaxation to sodium nitroprusside (SNP). In conclusion: AGM may represent a potential endogenous therapeutic candidate for sepsis-induced vascular dysfunction through its inhibiting effect on iNOS expression and oxidative stress.     

Involvement of nitric oxide in the inhibition of angiogenesis by interleukin-2

Interleukin-2 (IL-2), an immunoregulatory cytokine possessing antitumour activity, is an inducer of nitric oxide (NO) synthesis in mice and man. In this study, the possibility that IL-2 possesses antiangiogenic properties that account for its antitumour effects in vivo was examined. IL-2 caused a dose-dependent inhibition of angiogenesis in the chick embryo chorioallantoic membrane (CAM). This inhibition was completely reversed by the NO synthase inhibitor N^G-nitro-L-arginine methylester (L-NAME). Furthermore, IL-2 was capable of stimulating NO synthase activity in the CAM in vitro and this effect was suppressed by L-NAME. Addition of IL-2 to human umbilical vein endothelial cells (HUVECs) in culture, had no effect on their growth characteristics. These results suggest that IL-2 may be an important antiangiogenic molecule causing its effect via nitric oxide synthesis. The antiangiogenic activity of IL-2 may be, at least in part, responsible for its antitumour properties.     

Eupatilin inhibits H2O2-induced apoptotic cell death through inhibition of mitogen-activated protein kinases and nuclear factor-κB

Eupatilin (5,7-dihydroxy-3',4',6-trimethoxyflavone), an extract from Artemisia asiatica Nakai, is a flavonoid of pharmacologically active ingredients. Eupatilin is known to possess anti-cancer, anti-inflammatory, and anti-oxidative activity. Recently, eupatilin has been reported to be effective in producing gastric mucosal as an anti-gastritis agents. However, the mechanism of protective action is still unknown. We studied cytoprotective actions of eupatilin on H(2)O(2)-induced cell death and its possible mechanisms of action in human gastric (AGS) cells. Eupatilin dose-dependently inhibited H(2)O(2)-induced apoptosis as indicated by co-staining with Annexin V and propidium iodide. Hydrogen peroxide provoked phosphorylation of extracellular regulated kinase (ERK) and c-Jun NH(2)-terminal kinase (JNK), and activation of nuclear factor-kappaB (NF-kappaB). On the contrary, eupatilin decreased H(2)O(2)-induced activation of ERK, JNK and NF-kappaB. In addition, treatment of specific inhibitors for ERK, JNK, and NF-kappaB attenuated H(2)O(2)-induced apoptosis. Co-treatment of inhibitors and eupatilin was more effective in decreasing H(2)O(2)-induced apoptosis. Taken together, we suggest that eupatilin inhibits H(2)O(2)-induced apoptosis through the inhibition ERK, JNK, and NF-kappaB.     

Differential effects of selective and non-selective inhibition of nitric oxide synthase on the expression and activity of cyclooxygenase-2 during gastric ulcer healing

Nitric oxide synthases (NOS) and cyclooxygenase-2 (COX-2) are important enzymes involved in ulcer healing but interactions between them have not been clearly defined. The aim of this study was to investigate the effects of selective or non-selective inhibition of NOS on the expression and activity of COX-2 during healing of acetic acid-induced gastric ulcers in rats. N-[3-(aminomethyl)benzyl] acetamidine (1400 W), a potent selective inhibitor of inducible nitric oxide synthase (iNOS), at a dose of 0.1 mg/kg/day, was found to reduce the ulcer sizes at day 3 and 7 post-ulcer induction. On the other hand, 15 mg/kg/day of NG-nitro-L-arginine methyl ester (L-NAME), a non-selective NOS inhibitor that suppresses both iNOS and endothelial nitric oxide synthase (eNOS), enlarged the ulcer sizes over the same time periods. The expression of COX-2 and COX activity, together with NF-kappaB activation in the ulcer tissues were down-regulated by L-NAME but not 1400 W. It is concluded that iNOS may contribute to ulcer formation while COX-2 and eNOS promote ulcer healing. eNOS enhances COX-2 expression possibly through the activation of NF-kappaB.     

Therapeutic administration of 3,4,5-trimethoxy-4'-fluorochalcone,a selective inhibitor of iNOS expression,attenuates the development of adjuvant-induced arthritis in rats

We have previously investigated the effects of a series of dimethoxy- and trimethoxychalcone derivatives, with various patterns of fluorination, on nitric oxide production in LPS-stimulated murine RAW 264.7. The present study was designed to determine if 3,4,5-trimethoxy-4'-fluorochalcone (CH 17) could modulate the production of NO and/or prostaglandins in vivo. On the mouse macrophage cell line RAW 264.7 CH 17 inhibited dose-dependently NO production, with an IC₅₀ value in the nanomolar range, and reduced PGE₂ levels by a 58% at 10 M. This compound had no direct inhibitory effect on iNOS and COX-2 activities. NO reduction was the consequence of inhibition of the expression of iNOS. In vitro experiments indicated that CH 17 is an inhibitor of the nuclear factor-B (NF-B) pathway of cellular activation in macrophages. This compound exhibited in vivo an inhibitory behaviour correlated with its in vitro results on nitrite and PGE₂ accumulation. In the rat adjuvant-induced arthritis, oral administration of CH 17 (25 mg/kg) on days 17–24 after adjuvant injection, significantly inhibited paw oedema, protected from weight loss and reduced the levels of inflammatory mediators (nitrites and PGE₂) in paw homogenates, without affecting PGE₂ levels in stomach homogenates. The profile and potency of this compound, a selective inhibitor of iNOS expression that interferes with NF-B activation, may have relevance for the inhibition of the inflammatory response, representing a new approach to the modulation of different inflammatory pathologies.