Microglia play a critical role in controlling the homeostasis of the brain, but over-activated microglia secrete pro-inflammatory mediators and cytokines, which induce neuronal cell death. Fucoxanthin (Fx), a marine carotenoid, has demonstrated a variety of beneficial health effects. Despite accumulating evidence supporting the immune-modulating effects of Fx in vitro, the underlying signaling pathways remain unknown. In the present study, Fx dose-dependently inhibited the secretion of lipopolysaccharide (LPS)-induced pro-inflammatory mediators including interleukin (IL)-6, tumor necrosis factor (TNF)-α, reactive oxygen species (ROS), prostaglandin (PG) E, and nitric oxide (NO) productions, and also suppressed the expression of inducible NO synthase (iNOS) and cyclooxygenase (COX)-2 enzymes. Further, the reverse transcription-polymerase chain reaction (RT-PCR) analysis indicated IL-6, TNF-α, iNOS, and COX-2 mRNA expression were suppressed by treatment with Fx in a dose-dependently manner. The mechanism studies indicated that Fx blocks protein kinase B (Akt)/nuclear factor-kappaB (NF-κB) and mitogen-activated protein kinase (MAPKs)/transcription factor (AP)-1 pathways. In addition, we demonstrated that Fx increases nuclear factor erythroid 2-related factor (Nrf)-2 activation and heme oxygenase (HO)-1 expression in LPS-activated BV-2 microglia. Subsequently, we found that Fx also mediates the reactive oxygen species (ROS) by activating protein kinase A (PKA)/cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) pathway, and promotes the production of brain-derived neurotrophic factor (BDNF). These results indicate that Fx may be more effective and potential than other candidates via either decreasing the pro-inflammatory factors production or increasing the neuroprotective molecules expression for therapy of neurodegenerative diseases.
Ginger, one of worldwide consumed dietary spice, is not only famous as food supplements, but also believed to exert a variety of remarkable pharmacological activity as herbal remedies. In this study, a ginger constituent, 12-dehydrogingerdione (DHGD) was proven that has comparable anti-inflammatory activity with positive control 6-shogaol in inhibiting LPS-induced interleukin (IL)-6, tumor necrosis factor (TNF)-α, prostaglandin (PG) E2, nitric oxide (NO), inducible NO synthase (iNOS) and cyclooxygenase (COX)-2, without interfering with COX-1 in cultured microglial cells. Subsequent mechanistic studies indicate that 12-DHGD may inhibit neuro-inflammation through suppressing the LPS-activated Akt/IKK/NF-κB pathway. Furthermore, 12-DHGD markedly promoted the activation of NF-E2-related factor (Nrf)-2 and heme oxygenase (HO)-1, and we demonstrated that the involvement of HO-1 on the production of pro-inflammatory mediators such as NO and TNF-α by using a HO-1 inhibitor, Zinc protoporphyrin (Znpp). These results indicate that 12-DHGD may protect against neuro-inflammation by inhibiting Akt/IKK/IκB/NF-κB pathway and promoting Nrf-2/HO-1 pathway.
These findings indicate that GUE and SB may function as PPARγ agonists, thereby inhibiting BACE1 expression and ultimately reducing the secretion of Aβ.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.