Inhibitory effect of fucoidan on nitric oxide production in lipopolysaccharide-activated primary microglia.

1. Microglial activation plays an important role in the pathogenesis of neurodegenerative diseases by producing various pro-inflammatory cytokines. Microglia-derived nitric oxide (NO) is critical for the lipopolysaccharide (LPS)-induced selective loss of dopaminergic neurons. 2. Fucoidan is a sulphated polysaccharide extracted from brown seaweeds. It has a variety of biological actions, including anticoagulant, antiviral and anti-inflammatory effects. The aim of the present study was to investigate the effects of fucoidan on LPS-induced cellular activation in microglia and to evaluate the inhibitory mechanisms involved. 3. To investigate the effects of fucoidan on LPS-induced cellular activation in microglia, primary microglial cells were preincubated with fucoidan (31.25, 62.5 and 125 microg/mL) for 10 min, followed by stimulation with LPS (0.01 microg/mL). Then, cell shape and NO production were determined 24 h after LPS stimulation, whereas inducible nitric oxide synthase (iNOS) mRNA and protein expression were determined at 6 and 18 h after LPS stimulation, respectively. To evaluate the inhibitory mechanisms involved, mitogen-activated protein kinase (MAPK) activation was also evaluated. 4. Lipopolysaccharide transformed cells into an amoeboid shape, whereas 62.5 microg/mL fucoidan inhibited this activation. Moreover, 125 microg/mL fucoidan significantly inhibited microglial NO production to 75% of that in LPS-treated group and also significantly diminished the expression of iNOS mRNA and protein by nearly 50%. Fucoidan (125 microg/mL) also suppressed phosphorylation of p38 and extracellular signal-regulated kinase (ERK) by approximately 50%, but not that of c-Jun N-terminal kinase. 5. The results provide the first evidence that fucoidan has a potent inhibitory effect against LPS-induced NO production by microglia. The results also suggest that this inhibitory action of fucoidan involves suppression of p38 and ERK phosphorylation.

(5R)-5-hydroxytriptolide inhibits the inflammatory cascade reaction in astrocytes.

Many studies have shown that (5R)-5-hydroxytriptolide is the optimal modified analogue of triptolide, possessing comparable immunosuppressive activity but much lower cytotoxicity than triptolide. Whether (5R)-5-hydroxytriptolide has preventive effects on neuroinflammation is unclear. This study was designed to pretreat primary astrocytes from the brains of neonatal Sprague-Dawley rats with 20, 100 and 500 nM (5R)-5-hydroxytriptolide for 1 hour before establishing an in vitro neuroinflammation model with 1.0 µg/mL lipopolysaccharide for 24 hours. The generation of nitric oxide was detected by Griess reagents. Astrocyte marker glial fibrillary acidic protein was measured by immunohistochemical staining. The levels of tumor necrosis factor-α and interleukin-1ß in the culture supernatant were assayed by enzyme linked immunosorbent assay. Nuclear factor-κB/p65 expression was examined by immunofluorescence staining. The phosphorylation of inhibitor of nuclear factor IκB-α and the location of nuclear factor-κB/P65 were determined using western blot assay. Our data revealed that (5R)-5-hydroxytriptolide inhibited the generation of nitric oxide, tumor necrosis factor-α and interleukin-1ß from primary astrocytes activated by lipopolysaccharide, decreased the positive reaction intensity of glial fibrillary acidic protein, reduced the expression of tumor necrosis factor alpha and interleukin-1ß in culture supernatant, inhibited the phosphorylation of IκB-α and the translocation of nuclear factor-κB/P65 to the nucleus. These results have confirmed that (5R)-5-hydroxytriptolide inhibits lipopolysaccharide-induced glial inflammatory response and provides cytological experimental data for (5R)-5-hydroxytriptolide in the treatment of neurodegenerative diseases.

[Fucoidan: advances in the study of its anti-inflammatory and anti-oxidative effects].

Fucoidan is a natural polysaccharide extracted from brown seaweeds, with a wide variety of biological features, especially the anti-inflammatory and anti-oxidative effects. Studies indicated that the anti-inflammatory effect of fucoidan related to its capacity to interact with the selectin or scavenger receptor on the cell membrane. Fucoidan can also inhibit the synthesis and release of reactive oxygen species (ROS), as well as promote its clearance, showing the anti-oxidative activity.

Triptolide Rescues Spatial Memory Deficits and Amyloid-ß Aggregation Accompanied by Inhibition of Inflammatory Responses and MAPKs Activity in APP/PS1 Transgenic Mice.

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease characterized by aggregation of amyloid-ß (Aß) peptide in the hippocampus and cortex of brain. Neuroinflammation is considered a driving force of the progression of cognitive decline in AD. During the neuroinflammatory process, activated astrocytes and microglia induced by Aß peptide produce pro-inflammatory factors and neurotoxins, which promote neurodegeneration in AD brain, eventually dementia. Thus, the suppression of glial over-activation in AD brain might result in therapeutic effect. Triptolide, a natural compound extracted from the Chinese medicinal herb Tripterygium wilfordii Hook F., has shown anti-inflammatory effects. Whether triptolide exhibits preventive effects on AD-like pathology via anti-inflammatory action is unclear. The present study showed that intraperitoneal injection of triptolide (20 µg/kg) for 15 weeks markedly alleviated deficits in learning and memory, and prevented Aß accumulation in the brain of AD transgenic mice (APP/PS1 mice). These results were accompanied by reduction in glial activation and contents of pro-inflammatory factors in the brain of APP/PS1 mice treated by triptolide compared to saline-treated APP/PS1 mice. In addition, we observed that the Mitogen-activated protein kinases (MAPKs, including p38, ERK and JNK) phosphorylation was also suppressed by treatment of triptolide in the brain of APP/PS1 mice. Taken together, our study suggests that molecular mechanisms underlying the therapeutic effects of triptolide on the AD model might involve inhibition of the neuroinflammation by suppressing MAPKs activity.

Fucoidan protects against lipopolysaccharide-induced rat neuronal damage and inhibits the production of proinflammatory mediators in primary microglia.

BACKGROUND: Fucoidan, a sulfated polysaccharide extracted from brown algae, possesses potent antiinflammatory effects. AIMS: To examine the effect of fucoidan treatment on inflammation-mediated dopaminergic neuronal damage and its potential mechanisms. METHODS: Microglial activation and injury of dopaminergic neurons were induced by intranigral injection of lipopolysaccharide (LPS), and the effects of fucoidan treatment on animal behavior, microglial activation and survival ratio of dopaminergic neurons were investigated. We further observed the efficacy of fucoidan on tumor necrosis factor-alpha (TNF-α) and the production of reactive oxygen species (ROS) in LPS-activated primary microglia. RESULTS: Fucoidan significantly improved the behavioral manifestation, prevented the loss of dopaminergic neurons and inhibited the deleterious activation of microglia in the substantia nigra pars compacta of LPS-treated rats. Further in vitro experiments indicated that the excessive production of TNF-α and ROS in LPS-induced primary microglia were significantly inhibited by fucoidan administration. CONCLUSION: This is the first study to demonstrate that fucoidan possesses neuroprotective effects on injured dopaminergic neurons in a LPS-induced animal model of Parkinson's disease. The mechanisms underlying these effects may include its potent down-regulation of intracellular ROS and subsequent proinflammatory cytokine release in LPS-activated microglia.