Protective Effects of Coenzyme Q10 Against Oxidative Stress Injury in Human Rpe Cells and Its Mechanisms

 Coenzyme Q10, also known as ubiquinone, is a fat-soluble molecule that is a potent antioxidant and a vitamin-like substance. Coenzyme Q10 is an important component of the mitochondrial respiratory chain, and it is a compound found in a wide range of cells in living organisms and plays a very important role in the body[1] . Studies[2-3] have shown that coenzyme Q10 has an antioxidant effect, can recycle vitamin E, scavenge free radicals in the body, enhance the body's humoral and cellular immunity, have a certain killing effect on tumor cells in the body, and can significantly relieve fatigue, improve motor function, and have preventive and therapeutic effects on cardiovascular and cerebrovascular diseases.

 

In recent years, studies[4-5] have also found that coenzyme Q10 is effective in the treatment of retinal diseases in the elderly. The occurrence of many ophthalmic diseases, such as glaucoma and age-related macular degeneration, is related to a variety of factors, including retinal aging, elevated intraocular pressure (IOP), nutrition, heredity, the environment, mechanical damage, oxidative damage, etc. Oxidative damage plays a very important role in the occurrence of ophthalmic diseases in the elderly, and is therefore attracting more and more attention. However, whether the effect of coenzyme Q10 on retinal epithelial cells is direct or not, and its possible mechanism of action have not been fully revealed, and in-depth study of these issues will hopefully provide ideas for the diagnosis and treatment of such diseases.

 

In this study, we used human retinal pigment epithelial cells (RPE) as the research object, and intervened with coenzyme Q10, used the drug gradient experiment to clarify whether Q10 had a protective effect on RPE, and used molecular immunology and other techniques to analyze the possible mechanism of coenzyme Q10 from the perspective of cellular oxidative stress, damage, apoptosis, etc., to provide a test basis for the prevention and treatment of ophthalmic diseases in the elderly. We also used molecular immunology and other techniques to analyze the possible mechanism of coenzyme Q10 from the perspective of oxidative stress damage and apoptosis, so as to provide experimental basis for the prevention and treatment of ophthalmic diseases in the elderly.

 

1 Materials and Methods

1. 1 Cell processing

The human retinal pigment epithelial cell line RPE-19 (purchased from Sun Yat-sen University Ophthalmic Center) was cultured in DMEM culture medium containing 10% calf serum at 37 ℃ (5% CO2). The experiments were divided into four groups: the oxidative stress model group, cells were cultured in 200 μmol/L H2 O2 solution for 2 h; the experimental group was divided into two groups, 10 μmol/L coenzyme Q10 group and 1 μmol/L coenzyme Q10 group, cells of the two groups were cultured in 10 μmol/L and 1 μmol/L coenzyme Q10 for 48 h, then cultured in 200 μmol/L H2 O2 solution for 2 h; and cells of the two groups were cultured in 10 μmol/L and 1 μmol/L coenzyme Q10 for 48 h, then cultured in 200 μmol/L H2 O2 solution for 2 h. The cells in the normal control group were not treated with coenzyme Q10 and H2 O2.

 

1.2 Cell Activity Assay

The cell activity was detected by CCK-8 method, 10% CCK-8 working solution was added into 4 groups of cells, and a control group was set up at the same time, then incubated in the incubator for 30 min, and the OD value of each well was measured by enzyme labeling at 450 nm, and 6 replicate wells were set up in each group, and the experiments were repeated for 3 times.

 

1.3 Intracellular reactive oxygen species detection

Intracellular reactive oxygen species (ROS) were detected by DCFH-DA fluorescent probe assay, and ROS expression was detected by DCFH-DA Reactive Oxygen Species Fluorescent Detection Kit (purchased from Suzhou Biyuntian Biotechnology Co., Ltd.) in the four groups of cells, and the experiments were repeated for three times.

 

1. 4 Detection of Caspase-3, Bcl-2, Bax, phosphorylated-Akt, Akt in Cells

The expression of Caspase-3, Bcl-2, Bax, phosphorylated-Akt and Akt in the cells was detected by Western blot, and the proteins of four groups of cells with different treatments were extracted, and the protein concentration was determined by BCA method. The protein concentration was determined by BCA method. The protein samples of each group were separated by electrophoresis, and the protein marker was added at the same time, the membrane was softened and sealed by skimmed milk powder, the primary antibody and secondary antibody were added sequentially, the exposure was performed, the film was scanned, and the bands were analyzed in grayscale by Image J software.

 

1.5 Statistical analysis

SPSS13.0 software was used to analyze the data, and the experiments were repeated three times, and the measurement data were expressed as (x- ± s), and different analysis methods were selected according to the characteristics of the data, and the data were inferred. The difference was considered statistically significant at P < 0.05.

 

2 Results

2.1 Effect of coenzyme Q10 on RPE-19 activity in human retinal pigment epithelial cells

The activity of the H2 O2-treated cells was significantly lower than that of the normal control group (P < 0.05). The cell activity of the coenzyme Q10 pretreated cells was significantly higher than that of the H2 O2-treated cells in the model group, and the differences between the 1 μmol/L coenzyme Q10 group and the 10 μmol/L coenzyme Q10 group and the oxidative stress model group were statistically significant (P < 0.05). The differences were statistically significant (P<0.05) when compared with the oxidative stress model group.

Table 1 Effects of coenzyme Q10 on RPE-19 activity in human retinal pigment epithelial cells.

Impact (x-  ± s)

 

groups	OD value
normal control group	0. 985 ± 0. 023
Oxidative stress model group (H O2 2  )	0. 356 ± 0. 012 ∗
1 μmol/L Coenzyme Q10 group	0. 496 ± 0. 022 ∗#
10 μmol/L Coenzyme Q10 group	0. 586 ± 0. 032 ∗#

∗P < 0. 05, compared with normal control group; #P < 0. 05, compared with oxidative stress model group.

2.2 Effect of coenzyme Q10 on RPE-19 reactive oxygen species in human retinal pigment epithelial cells

The levels of intracellular reactive oxygen species were significantly higher in the H2 O2-treated cells than in the normal control group (P < 0.05). The levels of intracellular reactive oxygen species in the cells pretreated with coenzyme Q10 were significantly lower than those in the model group treated with H2 O2 alone, and the differences between the 1 μmol/L coenzyme Q10 group and the 10 μmol/L coenzyme Q10 group and the oxidative stress model group were statistically significant (P ＜ 0.05). The differences were statistically significant (P < 0.05) when compared with the oxidative stress model group.

 

Table 2 Effect of coenzyme Q10 on RPE-19 reactive oxygen species in human retinal pigment epithelial cells

groups	ROS value
normal control group	556.36 ±66.78
Oxidative stress model group (H O2 2  )	879.12 ±75.45 ∗
1 μmol/L Coenzyme Q10 group	716.23 ±67.42 ∗#
10 μmol/L Coenzyme Q10 group	625.76 ±45.63 ∗#

∗P < 0. 05, compared with normal control group; #P < 0. 05, compared with oxidative stress model group.

2. 3 Effect of coenzyme Q10 on the expression of Caspase-3, Bcl-2, Bax, phosphorylated-Akt, and Akt in human retinal pigment epithelial cells

3. 

Coenzyme Q10 inhibited the expression of caspase-3 and Bax in human retinal pigment epithelial cells induced by H2 O2, and promoted the expression of Bcl-2, which can inhibit apoptosis. Compared with the oxidative stress model group, the expression of Caspase-3 and Bax was lower than that of the oxidative stress model group in the 1 μmol/L coenzyme Q10 group and the expression of Bcl-2 was higher than that of the oxidative stress model group in the 10 μmol/L coenzyme Q10 group.H2 O2 also induced the phosphorylation of Akt, and the phosphorylated-Akt was more than 1 μmol/L coenzyme Q10 group and the phosphorylated-Akt was more than 10 μmol/L coenzyme Q10 group in the 10 μmol/L coenzyme Q10 group. H2 O2 also induced the phosphorylation of Akt, and the expression of phosphorylated Akt in the 1 μmol/L coenzyme Q10 group and the 10 μmol/L coenzyme Q10 group was lower than that in the oxidative stress model. See Figure 1.

Fig. 1 Effect of coenzyme Q10 on the expression of Caspase-3, Bcl-2, Bax, phosphorylated-Akt, and Akt in human retinal pigment epithelial cells . *P < 0.05.

 

3 Discussion

Along with the aging of the society, the trend of age-related eye diseases is high. Age-related macular degeneration, glaucoma, cataract and other eye diseases cause serious visual impairment, and in severe cases, may lead to permanent blindness[6-8] . One of the most important factors causing these eye diseases is oxidative stress, and preventing and treating oxidative stress is of great significance in controlling the occurrence and treatment of these eye diseases.

 

Coenzyme Q10 is an antioxidant that is naturally present in the body and has been widely used in the prevention and treatment of many diseases[9 -11] . The content of coenzyme Q10 in various tissues and organs of the body decreases with age, and therefore its physiological capacity decreases accordingly, which is related to the occurrence of many chronic diseases. Exogenous supplementation of coenzyme Q10 can increase the level of coenzyme Q10 in the body, which can help it to play an antioxidant role in the body and prevent the occurrence of some chronic diseases[12 -13] .

 

There are few studies on the role of coenzyme Q10 in the occurrence and development of ocular diseases. In this study, we applied coenzyme Q10 to pre-treat human retinal pigment epithelial cells, and then induced oxidative damage with H2 O2, to investigate the protective effect of coenzyme Q10 against oxidative stress injury in human RPE cells and the mechanism of oxidative stress injury. The results showed that coenzyme Q10 was able to enhance the activity of H2 O2-treated retinal pigment epithelial cells and reduce the level of intracellular reactive oxygen species induced by H2 O2. A number of ophthalmic diseases are closely related to oxidative stress in retinal epithelial cells, such as senile cataract and diabetic retinopathy, etc. The anti-epithelial oxidative effect of coenzyme Q10 suggests that it has a potential value for clinical application.

 

 Meanwhile, the present study showed that coenzyme Q10 inhibited the expression of Caspase-3 and Bax and promoted the expression of Bcl-2 in human retinal pigment epithelial cells. Coenzyme Q10 inhibits apoptosis in human retinal pigment epithelial cells in vitro, which may be one of the mechanisms of its efficacy. Akt is an important signal that regulates apoptosis, and coenzyme Q10 significantly inhibited the phosphorylation of Akt in human retinal pigment epithelial cells, suggesting that the possible mechanism of coenzyme Q is to inhibit Akt signaling.

 

In conclusion, the present study demonstrated the protective mechanism of coenzyme Q10 against oxidative stress injury in human RPE cells by in vitro study. This may be due to oxidative damage, inhibition of apoptosis-related factors (e.g., caspase-3, Bax, etc.), promotion of apoptosis-suppressing factors (e.g., Bcl-2, etc.), and inhibition of Akt phosphorylation.

 

References:

[1] WANG Wenhui,WANG Lihao,GUO Yongxin,et al.  Research progress of coenzyme Q10 application[J] . Heilongjiang Agricultural Science ,2014 ,(3):147 - 149.

[2] WAN Yanjuan, WU Junlin, WU Qingping.  Progress of physiological function and application of coenzyme Q10 [J] . Food Industry Science and Technology ,2014 ,35(14):390 -395.

[3] Lohan SB ,Bauersachs S ,Ahlberg S ,et al. Ultra-small lipid nanop- articles promote the penetration of coenzyme Q10 in skin cells and counteract oxidative stress[J] . Eur J Pharm Biopharm ,2015 ,89 : 201 -207.

[4] Tawfik MK. Combination of coenzyme Q10 with methotrexate sup- presses Freund's complete adjuvant-induced synovial inflammation with reduced hepatotoxicity in rats : effect on oxidative stress and inflammation[J] . Int Immunopharmacol ,2015 ,24(1):80 -87.

[5] LI Manli, QI Hu, WU Yazhen.  Effects of hypoxia and oxidative stress on retinal pigment epithelial cell proliferation and glucose-regulated protein 78 expression[J] . New Progress in Ophthalmology , 2014 ,34(9):826 -829.

[6] WANG Hong, ZHOU Guoyi, LIN Zhouqiao.  Protective effects of coenzyme Q10 on retinal ganglion cells and oxidative stress injury in an animal model of high intraocular pressure[J] . Chinese Journal of Ophthalmology and Otolaryngology ,2014 ,14(3):165 - 170.

[7] Fatima S ,Al-Mohaimeed N ,Arjumand S ,et al. Effect of Pre- and Post-Combined Multidoses of EpigallocatechinGallate and Coen- zyme Q10 on Cisplatin- Induced Oxidative Stress in Rat Kidney [J] . J Biochem Mol Toxicol ,2015 ,29(2):91 -97.

[8] Soleimani M ,Jameie SB ,Barati M ,et al. Effects of coenzyme Q10 on the ratio of TH1/TH2 in experimental autoimmune encephalo- myelitis model of multiple sclerosis in C57BL/6[J] . Iran Biomed J ,2014 ,18(4):203 -211.

[9] Durán-Prado M ,Frontiñán J ,Santiago-Mora R ,et al. Coenzyme Q10 protects human endothelial cells from β-amyloid uptake and oxida- tive stress- induced injury[J] . PLoS One ,2014 ,9(10):e109223.

[10] LIU Kaixiang , ZHAN Zhipeng , XIE Xisheng .  Study on the role of mitochondrial autophagy in pulmonary fibrosis in a rat model of paraquat poisoning[J] . Journal of Sichuan North Medical College ,2017 ,32(3): 324 -328.

[11] Xuan Liao , Changjun Lan .  Thioltransferases and lens redox regulation[J] . Journal of Chuanbei Medical College ,2011 ,26(2):190 - 193.

[12] Cao Yanqun, Huang Kai, Luo Tejian.  Protective effects of ginsenoside Rg1 against retinal oxidative stress injury[J] . Journal of Neuroanatomy ,2015 ,31(4):515 -519.

[13] Farhangi MA , Alipour B , Jafarvand E , et al. Oral coenzyme q10 supplementation in patients with nonalcoholic fatty liver disease : effects on serum vaspin , chemerin , pentraxin 3 , insulin resistance and oxidative stress[J] . Arch Med Res ,2014 ,45(7):589 -595.

 

Protective Effect of Water-Soluble Coenzyme Q10 Against Apoptosis of Pc12 Cells Caused by Rotenone and Its Mechanism

 Abstract : Objective To investigate the protective effect of water-soluble coenzyme Q10 (CoQ10) and its possible mechanism in the Rot-induced Parkinson's disease (PD) cell model, and to provide a theoretical basis for the use of CoQ10 in the treatment of PD. Methods PC12 cells in logarithmic growth phase were divided into control group, Rot group, CoQ10 group and CoQ10 treatment group; cell viability was detected by CCK8; intracellular reactive oxygen species (ROS) level was measured by fluorescence spectrophotometer using fluorescent probe 2 ′,7 ′-dihydrodichlorofluorescent yellow bis-acetate (DCFH-DA); and the effect of CoQ10 on the apoptosis signaling protein Bcl-2,3-dihydrodichlorofluorescent yellow bis-acetate (Bcl-2,4-dihydrodichlorofluorescent yellow bis-acetate) was detected by Western blot. The effects of CoQ10 on the expression of apoptosis signaling proteins Bcl-2, Bax, Cas pas e-9, active Cas pas e-3 and apoptosis-inducing factor (AIF) were detected by Western blot.

 

The survival rate of PC12 cells after 24 h of Rot treatment was significantly decreased (P＜0.01) and was negatively correlated with the dose, and the level of ROS was increased by Rot (P＜0.01). 01) and was negatively correlated with the dose, and Rot induced an increase in the ROS level (P＜0.01), CoQ10 improved the survival rate of PC12 cells induced by Rot treatment. 01), CoQ10 could improve the Rot treatment-induced decrease in PC12 cell survival (P＜0.01) and decrease ROS level (P＜0.01). CoQ10 improved the Rot treatment-induced decrease in PC12 cell viability (P<0.01) and ROS level (P<0.01); Western blotting improved PC12 cell viability (P<0.01) and ROS level (P<0.01). Western blot showed that CoQ10 reduced Rot-induced Cas pas e-9 (P<0.05), active Cas pas e-9 (P<0.05), and active Cas pas e-9 (P<0.05). Western blot showed that CoQ10 reduced Rot-induced Cas pas e-9 (P<0.05), active Cas pas e-3 (P<0.05) and Bax (P<0.05). (P<0.05), active Cas pas e-3 (P<0.05) and Bax (P<0.01). (P<0.05), active Cas pas e-3 (P<0.05), and Bax (P<0.01), and up-regulated Bcl-2 (P<0.01). (P<0.01); prevented AIF from translocating to the nucleus (P<0.05). (P < 0 .05) .

 

Conclusion: Water-soluble CoQ10 has a protective effect against apoptosis in Rot PC12 cells, which may be achieved by removing intracellular oxygen radicals to improve the cellular oxygenation stress state, blocking the translocation of AIF to the nucleus, up-regulating Bcl-2, down-regulating Bax, and decreasing the expression of active Cas pas e-3 and Cas pas e-9.

 

Parkinson's disease (PD), also known as paralysis agitans, is a neurodegenerative disease common in the elderly, clinically characterized by resting tremor, bradykinesia, myotonia and postural balance disorders. A combination of genetic and environmental factors plays an important role in the development of PD, and the main pathologic change is degeneration of nigrostriatal dopaminergic neurons. Although the exact pathogenesis of PD has not yet been clarified, a series of studies have shown that the pathogenesis of PD is mainly related to activation of the apoptotic pathway, oxidative stress and mitochondrial dysfunction[1-2] .

 

Coenzyme Q10 (CoQ10) acts as an uncoupling protein for mobile electron transport and cofactors in the mitochondrial respiratory chain, and is a powerful antioxidant in the human body, preventing oxidative damage by free radicals, including the oxidation of lipids in the mitochondrial membrane. It has been suggested that the occurrence of PD may be related to the reduction of CoQ10[3-4] . However, traditional CoQ10 is fat-soluble and has a low bioavailability, which is difficult to be absorbed and utilized by the human body. Recently developed water-soluble CoQ10 has a cellular uptake and mitochondrial uptake that are 60 and 20 times higher than that of traditional CoQ10, respectively[5] .

 

Rotenone (Rot) is a common insecticide that acts in the same way as the pro-parkinsonian toxin 1-methyl-4-phenylpyridine (MPP+), specifically inhibiting NADH dehydrogenase (mitochondrial complex I) of the cellular respiratory chain[6] . The nature, enzymes and transmitters synthesized by rat pheochromo cytoma cell (PC12) are similar to those of midbrain dopamine neurons[7-8] . Therefore, the present group used PC12 cells as a model of dopaminergic neurons to study the inhibitory effect of water-soluble CoQ10 on apoptosis, and to provide a basis for clinical application. Therefore, our group used PC12 cells as a cell model of dopaminergic neurons to study the inhibitory effect of water-soluble CoQ10 on neuronal apoptosis and to provide experimental basis for clinical application.

 

1 Materials and Methods

1 . 1 Main reagents  

DMEM high sugar medium, fetal bovine serum (fe- tal bovine serum), PBS phosphate buffer were purchased from Hyclone; penicillin, streptomycin, trypsin were purchased from Solepol; Rot, high purity (>98%) CoQ10, polyoxyethanyl-α-tocopheryl sebacate (PTS) were purchased from Sigma; reactive oxygen species (ROS) detection kit was purchased from Nanjing Jianjian Institute of Biological Engineering; reactive oxygen species (ROS) detection kit was purchased from Nanjing Jianjian Institute of Biological Engineering; ROS detection kit was purchased from Nanjing Jianjian Institute of Biological Engineering; ROS detection kit was purchased from Nanjing Jianjian Institute of Biological Engineering. Rot, high purity (>98%) CoQ10, polyoxyethanyl-α-tocopheryl sebacate (PTS) were purchased from Sigma; reactive oxygen species (ROS) detection kit was purchased from Nanjing Jianjian Bioengineering Institute; anti-apoptosis-inducing factor antibody (anti-AIF antibody), anti-AIF antibody and anti-AIF antibody were purchased from Nanjing Jianjian Bioengineering Institute; and anti-AIF antibody and anti-AIF antibody were purchased from Nanjing Jianjian Bioengineering Institute. The anti-apoptosis-inducing factor antibody (anti-AIF antibody), anti-active Caspase3 antibody, anti-Caspase9 antibody, anti-beta actin antibody, Anti-Lamin B1 antibody, Goat Anti-Caspase3 antibody, and Anti-Lamin B1 antibody were purchased from Nanjing Jianjian Bioengineering Research Institute. Antibody and Goat Anti-rabbit antibody were purchased from Abcam, USA; plasma protein and nucleoprotein extraction kit was purchased from KGI Biotechnology Co.

 

1 . 2 Cell lines  

Rat adrenal pheochromocytoma PC12 cells (differentiated by nerve growth factor) were purchased from Shanghai Academy of Life Sciences.

 

1 . 3 Main instruments  

Carbon dioxide (CO2) incubator (For-ma Scientific, USA); common inverted microscope (Olympus CKX41, Japan); fluorescence microscope with camera (Nikon eclipse, Japan); fluorescence spectrophotometer (Olympus, Japan); flow cytometer (Olympus, Japan); multiwavelength enzyme assay (Thermo Fisher Scientific, USA). The results were summarized as follows: Fluorescence spectrophotometer (Olympus, Japan); Flow cytometer (Olympus, Japan); Multiwavelength enzyme assay (Thermo, USA).

 

1 . 4 Methodology

1 . 4 . 1 Reagent preparation   

Rot was dissolved in DMSO to make a storage solution and set aside; PTS was mixed with CoQ10 in a 2:1 molar ratio at 50 ℃ to make water-soluble CoQ10[9] .

 

1 . 4 . 2 Cell Culture    

PC12 cells were incubated in DMEM high glucose medium containing 100 mL/L fetal bovine serum, 1% streptomycin, 50 mL/L CO2, and 37 ℃ saturated humidity incubator for 24 h. When the cells were fused to about 80%, they were used for the following experiments.

 

1 . 4 . 3 Rot Modeling PD  

The logarithmic growth phase cells were inoculated into 96-well plates and incubated at 37 ℃ overnight in an incubator with different concentrations of Rot (0.25, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5). 25 、0 . 5 、1 . The cells were incubated at 37 ℃ overnight with different concentrations of Rot (0.25, 0.5, 1.0, 2.0). The logarithmic growth phase cells were inoculated into 96-well plates and incubated in a 37℃ incubator for 24 h. Different concentrations of Rot (0.25, 0.5, 1.0, 2.0 μmol/L) were used to act on the cells for 24 h. At the same time, a blank control group and a solvent control (vehicle) group (1 mL/L DMSO) were set up, and the cell viability was detected by using CCK8, and the morphology of the cells was observed under the inverted microscope.

 

1 . 4 . 4 Effect of water-soluble CoQ10 on the survival of normal cells and PD-model cells    

Logarithmic growth phase cells were inoculated into 96-well plates, incubated at 37 ℃ for overnight, pre-treated with different concentrations of water-soluble CoQ10 (25, 50, 100 μmol/L) for 3 h, and then treated with ichthyospermone for 24 h. The survival rate of the cells was examined by CCK8, and the cell morphology was observed in an inverted microscope.

 

1. 4. 5 Experimental groups   

The cells were divided into vehicle group (1 mL/L DMSO), Rot group (1 μmol/L Rot), CoQ10 group (50 μmol/L CoQ10), and CoQ10 treatment group (1 μmol/L Rot + 50 μmol/L CoQ10).

 

1 . 4 . 6 Intracellular ROS Detection    

ROS was detected by using the Nanjing Built ROS Assay Kit. 1 × 106 cells were collected from vehicle group, Rot group, CoQ10 group, CoQ10 treatment group and positive control group (Ros up, 50 mg/L, provided in the kit), and resuspended in PBS containing 10 μmol/L 2′,7′-dihydrodichlorofluorescent yellow bis-acetic acid sodium salt (DCFH-DA), incubated for 30 min in CO2 incubator, washed three times in PBS, and the cell density was adjusted with PBS to make the concentration of cells in each group consistent. Incubate in CO2 incubator for 30 min, wash with PBS for 3 times, resuspend the cells with PBS, and adjust the cell density so that the concentration of cells in each group is the same. The positive control group was incubated with Rosup at a final mass concentration of 50 mg/L for 30 min according to the requirements of the kit, and the fluorescence intensity was detected by a fluorescence spectrophotometer, with an excitation wavelength of 488 nm and an emission wavelength of 525 nm. The ratio of each treatment group/control group was used as the value of ROS.

 

1 . 4 . 7 Effect of CoQ10 on the expression of apoptotic signaling proteins AIF, Bcl-2, Bax, Caspas e-9, and active Caspas e-3 by Western blotting    

The processed cells were collected, and plasma proteins and nuclear proteins were extracted according to the requirements of the kit (KGI Nuclear Protein Plasma Protein Extraction Kit), and the protein content was determined by Bradford's method, and the protein content was separated and mirrored by SDS-PAGE (Nikon eclipse, Nikon, Japan), fluorescence spectrophotometer (Olympus, Japan), flow cytometer (Olympus, Japan), and multiwavelength enzyme assay (Thermo, USA). The results were analyzed by a flow cytometer (Olympus, Japan) and a multiwavelength enzyme assay (Thermo Fisher Scientific, U.S.A.).

1.5 Statistical Processing All data were analyzed using Excel as the database and GraphPad Prism 5.0 as the statistical software.

Measurements were expressed as ± s. One-way ANOVA (Newman-Keul s) was used to analyze the two-way comparisons between groups and between groups, and differences were considered statistically significant at P<0.05.

 

2 Results

2.1 Effect of different concentrations of Rot on the survival rate of PC12 cells In this experiment, cells were treated with gradient concentration of Rot for 24 h. The cell survival rate was shown in Fig. 1. One-way ANOVA showed that there was a statistically significant difference in the cell survival rate between different concentrations of Rot (P＜0.01), and the cell survival rate was negatively correlated with the concentration of Rot, and the higher the concentration of Rot, the lower the cell survival rate was. Under the inverted microscope, the morphology of the cells was observed. In the normal control group and the solvent control group, the cell protrusions were obvious and pike-shaped, but after treatment with different concentrations of Rot, most of the cell bodies were wrinkled, the protrusions were shortened or even disappeared, and the cells were similar to a round shape, and the number of cells was reduced. At a concentration of 1 μmol/L Rot, the cell survival rate was about 50%, and 1 μmol/L Rot will be used to establish the cell model in the subsequent experiments. there was no statistical significance in the difference between the control group and the vehicle group (P＞0.05), and the effect of DMSO on the cells could be ignored.

 

Fig. 1 Effect of different concentrations of Rot on the viability of PC12 cells.

Fig. 1 Effects of Rot of different concentration on survival rate of PC12 cells

Compared with the Vehicle group,∗ P < 0. 05,∗ ∗ P < 0. 01.

 

2.2 Effect of water-soluble CoQ10 on the morphology and survival of Rot PC12 cells  

PC12 cells in the model group were treated with 25, 50 and 100 μmol/L CoQ10, and the results showed that 50 and 100 μmol/L CoQ10 increased the cell survival rate of the Rot group compared with that of the Rot group (P＜0.05), but there was no significant difference between 50 μmol/L and 100 μmol/L CoQ10 on the survival rate of PC12 cells (Figure 2). However, there was no significant difference between 50 μmol/L and 100 μmol/L CoQ10 on PC12 cell viability (Figure 2). Therefore, 50 μmol/L CoQ10 was chosen as the therapeutic concentration in the subsequent experiments.

 

2.3 Detection of intracellular ROS level As shown in Figure 3, the fluorescence intensity of Rot-treated cells in the model group increased significantly after 24 h, suggesting that the intracellular ROS level was elevated; the fluorescence intensity of the treatment group weakened after 3 h of CoQ10 pretreatment, suggesting that the intracellular ROS level was reduced (P＜0.01), and the fluorescence intensity of the CoQ10 group was slightly reduced compared with that of the vehicle group, but the difference was not statistically significant (P＞0.05). The fluorescence intensity of the CoQ10 group was slightly lower than that of the vehicle group, but the difference was not statistically significant (P＞0.05).

 

2.4 Effects of water-soluble CoQ10 on the expression of apoptosis-inducing protein AIF and apoptosis signaling proteins Bcl-2, Bax, Caspase-9 and active-Caspase-3 The expression of apoptosis signaling proteins was also significantly altered, mainly showing a decrease in Bcl-2 expression (P < 0.01), an increase in Bax and Caspas e-9 expression (P < 0.01), and a significant increase in active-Caspas e-3 expression (P < 0.05). Water-soluble CoQ10 reversed the expression of the above apoptotic signaling proteins (Figure 4).

 

3 Discussion

The pathogenesis of PD is still controversial, and mitochondrial dysfunction, oxygenation stress, and cellular apoptosis are important causes of PD [10-11]. Mitochondria are important organelles for intracellular energy production and play a key role in the regulation of energy metabolism and apoptosis. Their energy production relies on the transfer of electrons through the mitochondrial respiratory chain, which consists of five enzyme complexes (Complexes Ⅰ to Ⅴ). Not only does the mitochondrial respiratory chain produce energy, but it is also the main site of free radical production in the body, and damage to any of its parts will result in an increase in the production of free radicals. Complex I (NADH-CoQ reductase) is the largest and the most vulnerable one.

 

CoQ10 is an important component of complex I, an electron acceptor for I/II, and an important natural antioxidant that scavenges free radicals and promotes ATP production in mitochondria. Rot, a common pesticide, is a selective repressor of mitochondrial complex I and inhibits ATP production by the mitochondrial respiratory chain, which leads to oxidative stress. Oxidative stress is an important factor in the selective damage of nigrostriatal dopaminergic neurons, which can initiate PD induced by environmental factors, and can be continuously enhanced by other cellular factors. In the present study, it was observed that the intracellular ROS content of PC12 cells increased significantly after 24 h of Rot treatment, and the intracellular ROS level decreased after the administration of CoQ10, suggesting that CoQ10 can reduce the Rot-induced increase in ROS level, and that CoQ10 can play a neuroprotective role by scavenging the excessive oxygen radicals in the cytoplasm.

 

In the present study, we found that Rot has obvious cytotoxicity to PC12 cells, with the increase of Rot concentration, the cell damage becomes more obvious, the synapses are shortened or even disappeared, and the cell survival rate is reduced, and CoQ10 can improve the damage and apoptosis of PC12 cells caused by Rot. PD is a series of pathological processes caused by pathological apoptosis, which can be induced by both endogenous and exogenous pathways. At least three pathways have been identified to be involved in cell death, namely, the mitochondrial pathway, the death receptor pathway, and the endoplasmic reticulum pathway, of which the mitochondrial pathway is the most classical[12-13] . The Bcl-2 protein family located in the mitochondrial membrane plays a crucial role in the regulation of cellular apoptosis. The Bcl-2 protein family is divided into anti-apoptotic proteins and pro-apoptotic proteins, with the former including Bcl-2, Bcl-xl, etc., and the latter including Bax, Bad, etc. The mitochondrial pathway is the most classic one [12-13].

 

It has been shown that Bcl-2 can prevent neuronal apoptosis by resisting the toxicity of intracellular ROS[14] . Elevated Bcl-2/Bax expression ratio can protect cells from apoptosis.Caspas e-3 is the execution protein of apoptosis, including the inactive precursor procaspas e-3 and the activated active Caspas e-3, which is found in very low levels in normal cells. Under physiological conditions, AIF exists between the inner and outer mitochondrial membranes and is a mitochondrial oxygen reductase. When stimulated by apoptosis, it will be transferred to the nucleus through the nuclear localization sequence, causing chromosome condensation and DNA damage, and initiating apoptosis that does not depend on caspases[15-16] . In this experiment, we found that the expression ratio of Bcl-2/Bax in PC12 cells after Rot treatment was down-regulated, and active caspase-3, which was originally low, was also expressed in large quantities.CoQ10 could increase the expression ratio of Bcl-2/Bax, i.e., it could up-regulate Bcl-2 and down-regulate Bax, and at the same time, it could reduce the expression of active caspase-3.

 

In summary, the protective effect of soluble CoQ10 on Rot-PC12 cell apoptosis may be achieved by scavenging intracellular oxygen radicals to improve the oxidative stress status, up-regulating Bcl-2 and down-regulating Bax, and decreasing the expression of active Caspas e-3 and Caspas e-9.

 

References .

[1] SUBEDI L, KWON OW, PAK C, et al . N,N-disubstituted az - ines attenuate LPS-mediated neuroinflammation in micro glia and neuronal apoptosis via inhibiting MAPK signaling pathways [J] . . BMC Neurosci, 2017 , 18(1) :82 .

[2] ARAWAKA S, FUKUSHIMA S, SATO H, et al .  Zonisamide attenuates α-synuclein neurotoxicity by an aggregation-inde - pendent mechanism in a rat model of familial Parkinson's dis - ease[J] . PLoS One, 2014, 9(2) :e89076 .

[3] BERGAMINI C, MORUZZI N, SBLENDIDO A, et al . A wa - ter soluble CoQ10 formulation improves intracellular distribu - tion and promotes mitochondrial respiration in cultured cells [J] . PLoS One, 2012;7(3) :e33712 .

[4] STORCH A, JOST WH , VIEREGGE P , et al .  Randomized, double-blind, placebo-controlled trial on symptomatic effects of coenzyme Q(10) in Parkinson disease[J] . Arch Neurol, 2007 , 64(7) :938-944 .

[5] MA D, STOKES K, MAHNGAR K, et al . Inhibition of stress induced premature senescence in presenilin-1 mutated cells with water soluble Coenzyme Q10[J] .  Mitochondrion , 2014 , 17 : 106-115 .

[6] sanders lh, greenamyre jt . Oxidative damage to macro - molecules in human Parkinson disease and the rotenone model[J] .  Free Radic Biol Med, 2013 , 9(62) :111 -120 .

[7] VOSHAVAR C, SHAH M , XU L , et al . Assessment of pro - tective role of multifunctional dopamine a gonist D-512 against oxidative stress produced by depletion of glutathione in PC12 cells . Implication in neuro protective therapy for Parkinson 's disease[J] . Neurotox Res, 2015 , 8(4) :302-318 .

[ 8] ZHAO XE, ZHU S, YANG H, et al . Simultaneous determina - tion of amino acid and monoamine neurotransmitters in PC12 cells and rats models of Parkinson's disease using a sensitizing derivatization reagent by UHPLC-MS/MS[J] . J Chromato gr B Analyt Technol Biomed Life Sci, 2015 , 995(996) :15-23 .

[9] SIKORSKA M, BOROWY-BOROWSKI H, ZURAKOWSKI B, et al . Derivatized alpha-tocopherol as a CoQ10 carrier in a novel wa- ter-soluble formulation[J] . Biofactors, 2003 , 18(1 -4) :173-83 .

[ 10] BUCHMAN AS, WILSON RS, SHULMAN JM, et, al . Parkin - sonism in older adults and its association with adverse health outcomes and neuro pathology[J] .  J Gerontol A Biol Sci Med Sci, 2016 , 71(4) :549-556 .

[11] verma ak , raj j , sharma v , et , al .  Plasma prolidase activity and oxidative stress in patients with Parkinson's disease [J] . Parkinsons Dis, 2015 ,(2015) :598028 .

[12] shi wy, cao c , liu l .  Interferon α induces the apoptosis of cervical cancer HeLa cells by activating both the intrinsic mitochondrial pathway and endoplasmic reticulum stress-in - duced pathway[J] . Int J Mol Sci, 2016 , 17(11) :e1832 .

[13] kim sm, park yj, shin ms, et al . Acacetin inhibits neuro - nal cell death induced by 6-hydroxydopamine in cellular Parkin - son's disease model[J] . Bioorg Med Chem Lett, 2017 , 27(23) : 5207-5212 .

[14] mei jm, niu cs .  Effects of CDNF on 6-OHDA-induced ap - optosis in PC12 cells via modulation of Bcl-2/Bax and Cas pase-3 activation[J] . Neurol Sci, 2014, 35(8) :1275-1280 .

[15] YANG R, CUI HJ, WANG H, et al .  N-stearoyltyrosine pro - tects against glutamate-induced oxidative toxicity by an a popto - sis-inducing factor ( AIF)-mediated Cas pase-independent cell death pathway[J] . J Pharmacol Sci, 2014, 124(2) :169-179 .

[16] LI H , CHEN G , MA W , et al .  Water-soluble coenzyme q10 inhibits nuclear translocation of apoptosis inducing factor and cell death caused by mitochondrial complex I inhibition[J ] . Int J Mol Sci, 2014, 15(8) :13388-13400 .