Ganoderma lucidum extract protects dopaminergic neurons through inhibiting the production of inflammatory mediators by activated microglia

Abundant evidence has suggested that neuroinflammation participates in the pathogenesis of Parkinson's disease (PD). The emerging evidence has supported that microglia may play key roles in the progressive neurodegeneration in PD and might be a promising therapeutic target. Ganoderma lucidum (GL), a traditional Chinese medicinal herb, has been shown potential neuroprotective effect in our clinical trials that lead us to speculate that it might possess potent anti-inflammatory and immunomodulating properties. To test this hypothesis, the present study investigated the potential neuroprotective effect of GL and underlying mechanism through inhibiting microglial activation using co-cultures of dopaminergic neurons and microglia. The cultures of microglia or MES23.5 cells alone or together were treated for 24 h with lipopolysaccharide (LPS, 0.25 μg/mL) as a positive control, GL extracts (50-400 μg/mL) or MES23.5 cell membrane fragments (150 μg/mL) were used in treatment groups. Microglia activation, microglia-derived harmful factors and (3)H]dopamine ((3)H]DA) uptake of MES23.5 cells were analyzed. The results showed that microglia were activated by LPS and MPP(+)-treated MES23.5 cell membrane fragments, respectively. Meanwhile, GL extracts significantly prevented the production of microglia-derived proinflammatory and cytotoxic factors, including nitric oxide, tumor necrosis factor-α (TNF-α) and interleukin 1β (IL-1β), in a dose-dependent manner and down-regulated the TNF-α and IL-1β expressions on mRNA level. In addition, GL extracts antagonized the reduction of (3)H]DA uptake induced by MPP(+) and microglial activation. In conclusion, these results suggest that GL may be a promising agent for the treatment of PD through anti-inflammation.