ABSTRACT
OBJECTIVE ① To estimate the value of the subacute MPTP mouse model in aspects of behavioral performance, biochemical changes and pathological abnormalities. ② To find effective positive drugs. METHODS Male C57BL/6 mice were injected with MPTP (30 mg·kg- 1 ·d- 1, ip) for 5 consecutive days. Three days before MPTP injection, the mice were orally administered selegiline (3 mg·kg-1·d-1), pramipexole (3 mg·kg-1·d-1), or medopar (100 mg·kg-1·d-1) for 18 d. Behavioral perfor?mance was assessed in the open field test, pole test and rotarod test. Neurotransmitters in the striatum were detected using HPLC. Protein levels were measured by Western blot. Pathological characteristics were examined by immunohistochemistry. Ultrastructure changes were observed by electron microscopy. RESULTS The subacute MPTP treatment did not induce evident motor defects despite severe injuries in the dopaminergic system. Additionally, MPTP significantly increased the α-synuclein levels and the number of astrocytes in the striatum, and destroyed the blood-brain barrier (BBB) in the substantianigra pars compacta. Both selegiline and pramipexole were able to protect the mice against MPTP injuries. CONCLUSION The subacute MPTP mouse model does not show visible motor defects; it is not enough to evaluate the validity of a candidate just based on behavioral examination, much attention should also be paid to the alterations in neurotransmitters, astrocytes, α- synuclein and the BBB. In addition, selegiline or pramipexole is a better choice than medopar as an effective positive control for the subacute MPTP model.
ABSTRACT
OBJECTIVE To evaluate these activities of Rg1 in the 1-methyl-4-phenyl-1,2,3,6-tetrahy?dropyridine (MPTP)/probenecid (MPTP/p)-induced PD mouse model for the first time and to elucidate the underlying mechanisms. METHODS Male C57BL/6 mice were randomly assigned to six groups. One hour prior to MPTP/p injection, Group Ⅲ-Ⅵ mice received 10 mg·kg-1, 20 mg·kg-1, or 40 mg·kg-1 Rg1 or 3 mg·kg-1 selegiline, respectively, orally from D (-3) to D49. Group Ⅰ-Ⅱ mice received solvent water. Subsequently, GroupⅡ-Ⅵ mice received by injection MPTP-HCl (25 mg·kg- 1 bw dissolved in 0.9% saline, sc) on a 40-d schedule at intervals of 4 d between consecutive doses in combination with an adjuvant drug, probenecid (250 mg·kg- 1 bw in 0.03 mL of DMSO, ip); GroupⅠ mice were injected with saline and probenecid. Behavioral performance was assessed in the open field test, pole test and rotarod test. Neurotransmitters in the striatum were detected using HPLC. Protein levels were measured by Western blot. Pathological characteristics were examined by immunohistochemistry. Ultrastructure changes were observed by electron microscopy. RESULTS Oral treatment with Rg1 significantly attenuated the high MPTP-induced mortality, behavior defects, loss of dopamine neurons and abnormal ultrastructure changes in the SNpc. Other assays indicated that the protective effect of Rg1 may be mediated by its anti-neuroinflammatory properties. Rg1 regulated MPTP-induced reactive astrocytes and microglia and decreased the release of cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-1b (IL-1b) in the SNpc. Rg1 also alleviated the unusual MPTP induced increase in oligomeric, phosphorylated and disease-related a-synuclein in the SNpc. CONCLUSION Rg1 protects dopaminergic neurons, most likely by reducing aberrant a-synuclein-mediated neuroinflammation, and holds promise for Parkinson disease therapeutics.
ABSTRACT
20C, a bibenzyl compound isolated from Gastrodia elata, possesses antioxidative properties in PC12 cells, but its in-depth molecular mechanisms against rotenone-induced neurotoxicity remains unknown. Recent studies indicate that without intact DJ- 1, nuclear factor erythroid 2- related factor (Nrf2) protein becomes unstable, and the activity of Nrf2-mediated downstream antioxidant enzymes are thereby suppressed. Therefore, increasing the nuclear translocation of Nrf2 by DJ-1 may present a helpful means for the prevention and treatment of chronic diseases related to oxidative stress. Our results showed that 20C clearly protected PC12 and SH-SY5Y cells against rotenone-induced oxidative injury in a concentration-dependent manner. Furthermore, 20C markedly up-regulated the levels of DJ-1, which in turn activated phosphoinositide-3-kinase (PI3K)/Akt signaling and inhibited glycogen synthase kinase 3β (GSK3β) activation, eventually promoting Nrf2 nuclear translocation and inducing the expression of Nrf2-mediated downstream antioxidative enzymes such as HO-1. The antioxidative effects of 20C could be partially blocked by ShRNA-mediated knockdown of DJ-1 and inhibition of the PI3K/Akt pathways with Akt1/2 kinase inhibitor in PC12 and SH-SY5Y cells, respectively. Conclusively, our findings confirm that DJ- 1 is necessary for 20C- mediated protection against rotenone- induced oxidative damage, at least in part, by activating PI3K/Akt signaling, and subsequently enhancing the nuclear accumulation of Nrf2. The findings from our investigation suggest that 20C should be developed as a novel candidate for preventing or alleviating the consequences of PD in the future.