Orimetrically at 540 nm with a spectrophotometer (Tecan M200). The content of MDA in samples expressed as micromolar of MDA produced per gram of 
protein.CAL-120 site Protective Effect of ACS84 on 6-OHDA-induced Cell InjuryTo evaluate the protective effect of ACS84 against 6-OHDAinduced cell injury in SH-SY5Y cells, cells were pretreated with ACS84 at different concentrations for 1 h before the treatment of 6-OHDA (50 mM) for another 6 h or 12 h. As shown in Fig. 2A and 2B, ACS84 at 0.1 nM to 10 mM concentration-dependently increased cell viability (Fig. 2A) and decreased LDH release (Fig. 2B) in cells treated with 6-OHDA. As ACS84 is a compound constituted by L-Dopa and H2S-releasing moiety, we examined whether L-Dopa or H2S alone would be able to produce similar protective effect as ACS84 did. As shown in Fig. 2C and 2D, neither L-Dopa nor NaHS (an H2S donor) at the equal molar concentration (10 mM) was sufficient to exert the similar protective effects against 6-OHDA-induced cell injury as ACS84 did (Fig. 2C and 2D). This is consistent with our previous findings that NaHS produced significant protective effects only when its concentration is higher than 100 mM [22]. These data suggest that ACS84 may produce stronger protective effects than either L-Dopa or NaHS alone.Concentration Determination of Dopamine and its MetabolitesHigh-performance liquid chromatography (HPLC) was used to detect concentration of dopamine and its metabolites in the brain tissues. The method was described in the previous report [33]. The striatum was sonicated in 0.1 M perchloric acid. Homogenates were centrifuged at 14,000 g for 20min at 4251658240uC. The supernatants were collected and adjusted the pH value around 3. After that, the supernatants were subjected to HPLC (HTEC-500; Eicom, Kyoto, Japan) equipped with the column (EICOMPAK SC-3ODS; Eicom, Kyoto, Japan) and electrochemical detectorACS84 Reduced the Oxidative Stress Induced by 6-OHDAAs it was well-accepted that 6-OHDA selectively killed dopaminergic neuron via generating reactive oxygen species (ROS) and inducing oxidative stress in the cells, we proceeded to examine the effect of ACS84 on 6-OHDA-induced ROSProtective Effect of ACS84 a PD ModelFigure 6. Effect of ACS84 on 6-OHDA-induced TH+ neuronal degeneration. Immunofluorescence staining showed that ACS84 (10 mg kg21 day21, i.g) alleviated TH+ neuron loss in SN of 6-OHDA-lesioned PD rats. Photos were taken at x100 magnification, and the white bar indicated 0.1 mm. Samples were collected from two independent experiments. doi:10.1371/journal.pone.0060200.gformation in SH-SY5Y cells. As shown in Fig. 3A, ACS84 at 10 mM significantly reduced ROS production induced by 6OHDA (50 mM). Although NaHS also suppressed the 6-OHDAinduced ROS formation, this effect was much weaker when compared with that caused by ACS84 (Fig. 3B). Superoxide dismutases (SODs) are a family of enzymes which catalyze the dismutation of superoxide and play important roles in cell homeostasis. As shown in Figure 3C, ACS84, but not L-Dopa and NaHS, at 10 mM completely abolished the inhibitory effect of 6-OHDA on SOD activity.ACS84 Promoted Anti-oxidative Stress Associated Gene ExpressionCells express anti-oxidant enzymes to protect against oxidative stress and most of these enzyme-coding genes contain anti-oxidant reaction CAL 120 biological activity element (ARE). NF-E2-related factor 2 (Nrf-2) is an important transcription 23115181 factor which binds to ARE and initiates the expression of anti-oxidant enzymes, including glutamate.Orimetrically at 540 nm with a spectrophotometer (Tecan M200). The content of MDA in samples expressed as micromolar of MDA produced per gram of protein.Protective Effect of ACS84 on 6-OHDA-induced Cell InjuryTo evaluate the protective effect of ACS84 against 6-OHDAinduced cell injury in SH-SY5Y cells, cells were pretreated with ACS84 at different concentrations for 1 h before the treatment of 6-OHDA (50 mM) for another 6 h or 12 h. As shown in Fig. 2A and 2B, ACS84 at 0.1 nM to 10 mM concentration-dependently increased cell viability (Fig. 2A) and decreased LDH release (Fig. 2B) in cells treated with 6-OHDA. As ACS84 is a compound constituted by L-Dopa and H2S-releasing moiety, we examined whether L-Dopa or H2S alone would be able to produce similar protective effect as ACS84 did. As shown in Fig. 2C and 2D, neither L-Dopa nor NaHS (an H2S donor) at the equal molar concentration (10 mM) was sufficient to exert the similar protective effects against 6-OHDA-induced cell injury as ACS84 did (Fig. 2C and 2D). This is consistent with our previous findings that NaHS produced significant protective effects only when its concentration is higher than 100 mM [22]. These data suggest that ACS84 may produce stronger protective effects than either L-Dopa or NaHS alone.Concentration Determination of Dopamine and its MetabolitesHigh-performance liquid chromatography (HPLC) was used to detect concentration of dopamine and its metabolites in the brain tissues. The method was described in the previous report [33]. The striatum was sonicated in 0.1 M perchloric acid. Homogenates were centrifuged at 14,000 g for 20min at 
4251658240uC. The supernatants were collected and adjusted the pH value around 3. After that, the supernatants were subjected to HPLC (HTEC-500; Eicom, Kyoto, Japan) equipped with the column (EICOMPAK SC-3ODS; Eicom, Kyoto, Japan) and electrochemical detectorACS84 Reduced the Oxidative Stress Induced by 6-OHDAAs it was well-accepted that 6-OHDA selectively killed dopaminergic neuron via generating reactive oxygen species (ROS) and inducing oxidative stress in the cells, we proceeded to examine the effect of ACS84 on 6-OHDA-induced ROSProtective Effect of ACS84 a PD ModelFigure 6. Effect of ACS84 on 6-OHDA-induced TH+ neuronal degeneration. Immunofluorescence staining showed that ACS84 (10 mg kg21 day21, i.g) alleviated TH+ neuron loss in SN of 6-OHDA-lesioned PD rats. Photos were taken at x100 magnification, and the white bar indicated 0.1 mm. Samples were collected from two independent experiments. doi:10.1371/journal.pone.0060200.gformation in SH-SY5Y cells. As shown in Fig. 3A, ACS84 at 10 mM significantly reduced ROS production induced by 6OHDA (50 mM). Although NaHS also suppressed the 6-OHDAinduced ROS formation, this effect was much weaker when compared with that caused by ACS84 (Fig. 3B). Superoxide dismutases (SODs) are a family of enzymes which catalyze the dismutation of superoxide and play important roles in cell homeostasis. As shown in Figure 3C, ACS84, but not L-Dopa and NaHS, at 10 mM completely abolished the inhibitory effect of 6-OHDA on SOD activity.ACS84 Promoted Anti-oxidative Stress Associated Gene ExpressionCells express anti-oxidant enzymes to protect against oxidative stress and most of these enzyme-coding genes contain anti-oxidant reaction element (ARE). NF-E2-related factor 2 (Nrf-2) is an important transcription 23115181 factor which binds to ARE and initiates the expression of anti-oxidant enzymes, including glutamate.