Resveratrol inhibits nitric oxide and TNF-alpha production by lipopolysaccharide-activated microglia

Differential effects of ginsenosides on NO and TNF-alpha production by LPS-activated N9 microglia

Ginsenosides, the main active components of ginseng, have been reported to exert neuroprotective effects in the central nervous system. In this report, the effects of ginsenoside-Rd and -Rb2, two protopanaxadiols, and ginsenoside-Rg1 and -Re, two protopanaxatriols, on the production of nitric oxide (NO) and TNF-alpha (TNF-alpha) by lipopolysaccharide (LPS)-activated N9 microglial cells were studied. All ginsenosides studied potently suppressed TNF-alpha production in LPS-activated N9 cells. Ginsenoside-Rg1 and -Re, but not ginsenoside-Rb2 and -Rd, inhibited the production of NO in LPS-activated N9 cells. Ginsenosides inhibited the phosphorylation of c-Jun NH2-terminal kinase (JNK), c-Jun and extracellular signal-regulated kinase (ERK), The findings herein show that the inhibition of LPS-induced ERK1/2 and JNK activation may be a contributing factor to the main mechanisms by which ginsenosides inhibits RAW264.7. To clarify the mechanistic basis for its ability to inhibit TNF-alpha and NO induction, the effect of ginsenosides on transcription factor NF-kappaB protein level was also examined. These activities were associated with the down-regulation of inhibitor kappaB (IkappaB). These findings suggest that the inhibition of LPS-induced NO formation and TNF-alpha production in microglia by ginsenosides is due to its inhibition of NF-kappaB, which may be the mechanistic basis for the anti-inflammatory effects of ginsenosides. The significant suppressive effects of ginsenosides on proinflammatory responses of microglia implicate their therapeutic potential in neurodegenerative diseases accompanied by microglial activation.

Modulating TNF-alpha signaling with natural products

Natural products have been, and continue to be, a major source of pharmacologically active substances from which drugs can be developed. Currently, tumor necrosis factor-alpha (TNF-alpha) inhibitors from natural origins are being advanced for the treatment of inflammatory disorders. Elevated TNF-alpha synthesis has been associated with the development of diabetes, septic shock, tumorigenesis, rheumatoid arthritis, psoriatic arthritis and inflammatory bowel disease. Currently, only protein-based drugs are available for the clinical inhibition of TNF-alpha activity. Small-molecule drugs that can regulate TNF-alpha levels or activity might provide a cost-effective alternative to protein-based therapeutics. This review briefly highlights the physiological and pathological roles of TNF-alpha, and covers those natural compounds capable of interfering with TNF-alpha activity.

The dynamics of the LPS triggered inflammatory response of murine microglia under different culture and in vivo conditions

Overall, the inflammatory potential of lipopolysaccharide (LPS) in vitro and in vivo was investigated using different omics technologies. We investigated the hippocampal response to intracerebroventricular (i.c.v) LPS in vivo, at both the transcriptional and protein level. Here, a time course analysis of interleukin-6 (IL-6) and monocyte chemotactic protein-1 (MCP-1) showed a sharp peak at 4 h and a return to baseline at 16 h. The expression of inflammatory mediators was not temporally correlated with expression of the microglia marker F4/80, which did not peak until 2 days after LPS injection. Of 480 inflammation-related genes present on a microarray, 29 transcripts were robustly up-regulated and 90% of them were also detected in LPS stimulated primary microglia (PM) cultures. Further in vitro to in vivo comparison showed that the counter regulation response observed in vivo was less evident in vitro, as transcript levels in PM decreased relatively little over 16 h. This apparent deficiency of homeostatic control of the innate immune response in cultures may also explain why a group of genes comprising tnf receptor associated factor-1, endothelin-1 and schlafen-1 were regulated strongly in vitro, but not in vivo. When the overall LPS-induced transcriptional response of PM was examined on a large Affymetrix chip, chemokines and cytokines constituted the most strongly regulated and largest groups. Interesting new microglia markers included interferon-induced protein with tetratricopeptide repeat (ifit), immune responsive gene-1 (irg-1) and thymidylate kinase family LPS-inducible member (tyki). The regulation of the former two was confirmed on the protein level in a proteomics study. Furthermore, conspicuous regulation of several gene clusters was identified, for instance that of genes pertaining to the extra-cellular matrix and enzymatic regulation thereof. Although most inflammatory genes induced in vitro were transferable to our in vivo model, the observed discrepancy for some genes potentially represents regulatory factors present in the central nervous system (CNS) but not in vitro.

Potential pro-inflammatory action of resveratrol in vascular smooth muscle cells from normal and diabetic rats

BACKGROUND AND AIM

Based on the reported cardioprotective effects of resveratrol, a polyphenolic antioxidant abundant in grapes that binds to estrogen receptors, and the well-characterized anti-inflammatory properties of 17beta-estradiol, the effects of resveratrol on the functional expression of inflammatory enzymes were assessed in vascular smooth muscle cells (SMC) from normoglycaemic and streptozotocin-diabetic rats.

METHODS AND RESULTS

SMC were isolated from the aorta four weeks after treating rats with streptozotocin or its vehicle. In SMC exposed to a cytokine mixture for 24h, unexpectedly, treatment with resveratrol (0.1-100microM) as well as the structurally related isoflavone genistein (1nM-1microM) enhanced expression of inducible NO synthase (iNOS). Genistein failed to mimic the elevated iNOS activity induced by resveratrol. Inhibition of estrogen receptors by the pure antiestrogen ICI 182,780 reversed the action of resveratrol on iNOS. In addition, resveratrol failed to alter cyclooxygenase-2 protein levels but reduced the accumulation of prostaglandin E(2) in the culture medium of SMC from normoglycaemic, but not diabetic rats.

CONCLUSIONS

These results indicate that resveratrol, at concentrations approaching putative peak plasma levels in vivo, exhibited no anti-inflammatory properties in vascular SMC from normal and diabetic rats. By contrast, resveratrol displayed a potential pro-inflammatory activity in settings of vascular inflammation.

A nutritional supplement formula for influenza A (H5N1) infection in humans

By early February 2006, the World Health Organization had reported 165 human cases of H5N1 influenza since December 2003, with 88 fatalities. However, the avian H5N1 influenza virus apparently is not yet efficiently transmitted between humans. Though a near-term possibility of a global H5N1 influenza pandemic remains, currently there is no vaccine or anti-viral drug that is proven to be safe and effective in preventing or treating H5N1 influenza in humans. There is thus a compelling public interest in developing alternative prophylaxis and treatment strategies for H5N1 influenza, which would need to address the complex pathogenesis of H5N1 influenza that is responsible for its apparently unusually high virulence. The authors present here a significant body of medical and scientific evidence to support the prophylactic use of a carefully designed nutritional supplement formulation that may antagonize the major pathogenic processes of H5N1 influenza in humans. Through several independently-mediated mechanisms, the formulations may: (a) degrade H5N1 virulence by directly affecting the virus itself, (b) inhibit H5N1 viral replication by maintaining cellular redox equilibrium in host cells, (c) inhibit H5N1 replication by a blockade of the nuclear-cytoplasmic translocation of the viral ribonucleoproteins and reduced expression of late viral proteins related to the inhibition of protein kinase C activity and its dependent pathways, (d) down-regulate activation and proliferation of proinflammatory cytokines in respiratory epithelial cells and macrophages that are implicated in the pathogenesis of H5N1 influenza, and (e) protect the lungs and other vital organs from virus- and cytokine-induced oxidative stress by supplying and maintaining sufficient levels of exogenous and endogenous antioxidants. Key mediators in these processes include selenium, vitamin E, NAC/glutathione, resveratrol, and quercetin. Taken prophylactically, and throughout the duration and recovery of an H5N1 infection, the nutritional supplement formula may aid humans infected with H5N1 influenza to survive with a reduced likelihood of major complications, and may provide a relatively low-cost strategy for individuals as well as government, public-health, medical, health-insurance, and corporate organizations to prepare more prudently for an H5N1 pandemic. Some evidence also indicates that the supplement formulation may be effective as an adjunctive to H5N1 vaccine and anti-viral treatments, and should be tested as such.

Down-regulation of microglial activation may represent a practical strategy for combating neurodegenerative disorders

Chronic neurodegenerative disorders are characterized by activation of microglia in the affected neural pathways. Peroxynitrite, prostanoids, and cytokines generated by these microglia can potentiate the excitotoxicity that contributes to neuronal death and dysfunction in these disorders--both by direct effects on neurons, and by impairing the capacity of astrocytes to sequester and metabolize glutamate. This suggests a vicious cycle in which the death of neurons leads to microglial activation, which in turn potentiates neuronal damage. If this model is correct, measures which down-regulate microglial activation may have a favorable effect on the induction and progression of neurodegenerative disease, independent of the particular trigger or target involved in a given disorder. Consistent with this possibility, the antibiotic minocycline, which inhibits microglial activation, shows broad utility in rodent models of neurodegeneration. Other agents which may have potential in this regard include PPARgamma agonists, genistein, vitamin D, COX-2 inhibitors, statins (and possibly policosanol), caffeine, cannabinoids, and sesamin; some of these agents could also be expected to be directly protective to neurons threatened with excitotoxicity. To achieve optimal clinical outcomes, regimens which down-regulate microglial activation could be used in conjunction with complementary measures which address other aspects of excitotoxicity.

Roles of Ras and extracellular signal-regulated kinase-dependent IkappaBalpha degradation in oridonin-enhanced phagocytosis of apoptotic cells by human macrophage-like U937 cells

Rapid recognition and ingestion of apoptotic cells by phagocytes are important for the prevention of toxic intracellular contents release, thereby attenuate inflammation and autoimmune diseases such as systemic lupus erythematosus (SLE). We have reported that oridonin isolated from Rabdosia rubescens enhanced phagocytosis of apoptotic U937 cells by macrophage-like U937 cells through TNFalpha and IL-1beta release. In this study, the molecular mechanisms involved in this phagocytic process are investigated. Inhibitors of Ras and Raf1 kinase significantly reduced oridonin-induced phagocytic stimulation as well as extracellular signal-regulated kinase (ERK) phosphorylation. Simultaneously, oridonin-enhanced engulfment was partially blocked by a nuclear factor (NF)-kappaB inhibitor PDTC or proteasome inhibitor MG132. Further studies revealed that oridonin induced IkappaBalpha degradation, which was prevented by Ras inhibitor manumycin A, ERK inhibitor PD98059, but not prevented by c-Jun N-terminal kinase (JNK) MAPK inhibitor SP600125, and up-regulated expression of IL-1beta precursor. These results demonstrate that Ras/Raf1/ERK signaling pathway-dependent IkappaBalpha degradation, resulting in NF-kappaB activation, participates in regulation of oridonin-enhanced phagocytosis, and one of its effector functions is to induce synthesis of IL-1beta, which partially contribute to phagocytic activity of oridonin.