Tanshinone I selectively suppresses pro-inflammatory genes expression in activated microglia and prevents nigrostriatal dopaminergic neurodegeneration in a mouse model of Parkinson's disease

Ethnopharmacological relevance: Radix Salviae Miltiorrhizae, known as Danshen, is a well-known traditional Chinese herb which has been used extensively for the treatment of various diseases, including cardiovascular and cerebrovascular disease and neurodegenerative diseases for thousands of years. Tanshinone I is one of major bioactive flavonoids of Radix Salviae Miltiorrhizae. Modulation of microglial over-reaction may represent a therapeutic target to alleviate the progression of neurodegenerative diseases. Here, we tested the effect of Tanshinone I on neuro-inflammation and whether it can provide neuroprotection through inhibition of neuro-inflammation. Materials and methods: The effects of Tanshinone I on the production and/or mRNA expression of proinflammatory and anti-inflammatory factors in lipopolysaccharide(LPS)-induced BV-2 microglia cells were tested by Griess reaction, enzyme-linked immunosorbent assay (Elisa) or real time polymerase chain reaction. Activation of nuclear factor kappa B (NF-kappa B) was measured by the nuclear translocation p65 and DNA binding activity. A model of Parkinson's disease was established by treatment of 1-methyl-4-phenyl-1,2,3, 6-tetrahydropyridine (MPTP) in C57BL/6 mice. The effect of Tanshinone I on the behavioral changes, dopamine and its metabolites levels, expression of tyrosine hydroxylase (TH) and IBA-1, production of cytokines in the midbrain were investigated by the rotarod test, high-performance liquid chromatography (HPLC)-ECD, immunohistochemistry and Elisa. 1-methyl-4-phenylpyridinium (MPP+) concentration was tested by HPLC. Liver toxicity was determined by biochemical assay and histochemistty. Results: We found that the productions and/or expressions of several pro-inflammatory M1 factors such as nitric oxide (NO), tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta) and IL-6 were highly suppressed by Tanshinone I in LPS-induced microglia. Interestingly, it did not affect the enhancement of expression of some anti-inflammatory M2 microglia markers, including IL-10, IL-1 receptor antagonist (IL-1Ra) and Cox-2. But it could significantly inhibit LPS-induced granulocyte colony-stimulating factor (G-CSF) expression. Tanshinone I could also inhibit LPS-induced NF-kappa B activation in microglia. Furthermore, it improved motor functions, normalized striatal neurotransmitters, and provided dopaminergic neuronal protection in MPTP-intoxicated mice. In vivo results also indicated that Tanshinone I could modulate MPTP-induced microglial activation, attenuated the increase of TNF-alpha, reserved the increase of IL-10 concentrain of MPTP-intoxicated mice. Tanshinone I does not alter MPIP toxic metabolite (MPP+) concentration. Oral administration of Tanshinone I at 10 mg/kg daily for 2 weeks did not show liver toxicity. Conclusions: Tanshinone I selectively suppressed pro-inflammatory M1 genes expression in activated microglia, interestingly, partially reserved anti-inflammatory M2 genes expression. It also could provide neuroprotection in a mouse model of Parkinson's disease. These data indicated that Tanshinone I could make the most of the beneficial side and minimize the detrimental side of activated microglia simultaneously, and provide neuroprotection by modulating the immune response of microglia. (C) 2015 Elsevier Ireland Ltd. All rights reserved.