Micheliolide suppresses LPS-induced neuroinflammatory responses

<div><p>Microglia-involved neuroinflammation is thought to promote brain damage in various neurodegenerative disorders. Thus, inhibition of microglial over-activation may have a therapeutic benefit for the treatment of neurodegenerative disorders. Micheliolide (MCL) is a sesquiterpene lactone which inhibits various inflammatory response. However, whether MCL can inhibit neuroinflammation caused by LPS-activated BV2 microglia has not yet been explored. In this study, we demonstrated that treatment of BV2 cells with MCL significantly repressed LPS-stimulated nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression, as well as tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and nitric oxide (NO) induction. MCL also attenuated mRNA levels of multiple pro-inflammatory cytokines and mediators such as iNOS, COX-2, TNF-α, IL-6 and IL-1β. Mechanistic studies revealed that MCL suppressed LPS-stimulated the activation of IκBα/NF-κB pathway and Akt pathway. Moreover, MCL inhibited LPS-induced the activition of c-Jun N-terminal kinase (JNK), p38 MAPK kinase, and extracellular signal-regulated kinases 1/2 (ERK1/2). Meanwhile, MCL markedly promoted antioxidant protein heme oxygenase-1 (HO-1) expression by enhancing NF-E2-related factor 2 (Nrf2) activity. Together, our results imply that MCL may serve as a neuroprotective agent in neuroinflammation-related neurodegenerative disorders.</p></div

DMAMCL alleviated LPS-induced IL-6 expression in the cortex and hippocampus in mice.

<p>Mice were administered with 100 mg/kg DMAMCL by gavage for five consecutive days. On the fifth day, mice were challenged with saline or 0.33 mg/kg LPS i.p for 3 h. Then, the cortex and hippocampus were collected and total RNAs were extracted. IL-6 (A) and TNF-α (B) mRNA levels were determined by RT-PCR. Data were presented as means ± SD (n = 6). *p < 0.05 vs. LPS alone.</p

MCL treatment did not affect BV2 cell viability.

<p>(A) BV2 cells were treated with the indicated doses of MCL for 24 h, then the cytotoxicity of MCL was measured by CCK-8 assay. The cell viability result was normalized to BV2 cells without MCL treatment for each other. Data were presented as means ± SD of three independent experiments. (B) BV2 cells were treated with indicated doses of MCL for 24 h. Then, the cells were stained with FITC-Phalloidin, green; and nuclei, Hoechst33258, blue; representative images by immunofluorescence were shown, scale bar = 50 μm.</p

MCL suppressed LPS-induced MAPKs and Akt activities.

<p>(A) and (B) BV2 cells were treated with MCL (10 μM) for 1 h then followed by LPS (1 μg/ml) addition for 30 min. Then, total cell lysates were subjected to Western blot analysis using antibodies against phospho- or total forms of JNK, p38, ERK, and Akt.</p