RIPK1 inhibitor ameliorates the MPP+/MPTP-induced Parkinson’s disease through the ASK1/JNK signalling pathway

Jing Liu , Huizheng Hu *, Binyan Wu
Department of Clinical Laboratory, No. 215 Hospital of Shaanxi Nuclear Industry, Xianyang 712000, Shaanxi, China


Receptor-interacting protein kinase 1 (RIPK1) is up-regulated in patients with neurodegenerative diseases. Our study aimed to explore the underlying mechanisms that involved in the neurotoXic function of RIPK1 in Par- kinson’s disease (PD). MPP+/MPTP-induced PD cellular and mice models were used in this study. The results showed that RIPK1 was high expressed and activated in MPP+-treated SH-SY5Y cells and MPTP-induced PD mice. Overexpression of RIPK1 facilitated cell apoptosis, necrosis, inflammation response, ROS production and mitochondrial dysfunction in MPP+- treated SH-SY5Y cells, while the RIPK1 inhibitor Nec-1s has an opposite effect. In addition, the Apoptosis-signaling kinase-1 (ASK1)/c-Jun N-terminal kinase (JNK) signalling pathway was activated during the overexpression of RIPK1, and inhibiting the ASK1/JNK signal by the ASK1 inhibitor partially reversed the decline of cell viability, the increase of cell apoptosis, necrosis and inflammation induced by RIPK1 overexpression in MPP+-treated SH-SY5Y cells. Further studies suggested that the inhibition of RIPK1 by Nec-1s largely alleviated the behavioural impairment in PD mice. Hence, our study indicated that the RIPK1 inhibitor Nec-1s has neuroprotective effects against PD through inactivating the ASK1/JNK signalling pathway.

1. Introduction

Parkinson’s disease (PD) is the second common neurodegenerative disease, with an incidence of approXimately 0.3% (Tysnes and Storstein, 2017). On pathology, PD is characterized by massive degeneration and the loss of dopaminergic neurons in the substantia nigra (Anglade et al., 1997). Although the pathogenesis of PD is not completely clear, aging, genetic susceptibility, oXidative stress and mitochondrial dysfunction are responsible for the occurrence of PD (Cacabelos, 2017). PD patients exhibited tremors, muscle rigidity, slow movements and postural instability (Sveinbjornsdottir, 2016). These symptoms seriously affected the quality of life of patients with PD. To date, dopamine replacement therapy is the most widely used treatment of PD; however, long-term treatment resulted in debilitating adverse effect.

Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) is a death-domain containing Ser/Thr kinase (Shutinoski et al., 2016). It transduces inflammatory and cell-death signals (programmed necrosis), the activation of pathogen recognition receptors (PRRs), and DNA damage (Berger et al., 2014). RIPK1 is overexpressed in the microglial cells of human Alzheimer’s disease brains, accelerating the inflamma- tion response and the accumulation of β-amyloid in Alzheimer’s disease (Ofengeim et al., 2017; Rubinsztein, 2017). Neuroinflammation and postoperative cognitive impairments were alleviated in RIPK1 knock- down D-galactose-induced aged mice (Duan et al., 2018). What is more, a recent report indicated that RIPK1 is upregulated in the substantia nigra of 1-methyl-4-phenyl-12,3,6-tetrahydropyridine (MPTP)-induced PD mice (Hu et al., 2019b). However, the underlying mechanisms responsible for the neuroprotective role of RIPK1 in PD are still unclear.

In the present study, 1-methyl-4-phenylpyridin’ium ion (MPP+) and MPTP were adopted to induce PD cellular and mouse models (Hu et al., 2019a; Liu et al., 2018). The overexpression vector and inhibitor of RIPK1 were adopted to test the effect of RIPK1 on cell viability, apoptosis, necrosis, inflammatory response, mitochondrial dysfunction, and ROS production in MPP+-treated SH-SY5Y cells. Our study indicates that RIPK1 may be a novel therapeutic target for the treatment of PD.

2. Results
2.1. The expression of RIPK1 is increased in the MPP+-induced SH-SY5Y cells

SH-SY5Y cells were treated by different concentrations of MPP+ (0.1,0.25, 0.5, 1, and 2 mM) for 12, 24 and 48 h. As shown in Fig. 1A, MPP+ significantly decreased the cell survival rate at concentrations of 0.5, 1.0 and 2.0 mM after being treated for 12, 24 and 48 h. Next, the effect of MPP+ treatment on the expression levels of RIPK1 and ps166- RIPK1 (phospho-S166 RIPK1) was examined. SH-SY5Y cells were stimulated by 1 mM MPP+ for 0, 12, 24 and 48 h, the results suggested that the levels of RIPK1 mRNA and protein were increased by MPP+ in a time-dependent manner (Fig. 1B and C). Besides, the protein expression of ps166-RIPK1 was increased after treatment with MPP+ (Fig. 1D), also, the ratio of ps166-RIPK1/RIPK1 was increased after MPP+ treatment (Fig. 1E). What is more, the expression of RIPK1 and ps166-RIPK1 were increased in the hippocampal and substantia nigra pars compacta (SNpc) tissues of MPTP-induced PD mice, indicating that RIPK1 is activated in the PD model both in vivo and in vitro (Fig. 1E and F).

2.2. The effect of RIPK1 on cell viability and apoptosis in MPP+-treated SH-SY5Y cells

The overexpression vector of RIPK1 (ov-RIPK1) and inhibitor of RIPK1 (Nec-1s) were used to explore the role of RIPK1 in the MPP+-
induced PD cellular model. The results showed that ov-RIPK1 markedly increased the expression of the RIPK1 mRNA and protein in MPP+- treated SH-SY5Y cells (Fig. 2A and B). At the same time, the expression of RIPK1 mRNA and protein was significantly decreased by Nec-1s in both SH-SY5Y cells and MPP+-treated SH-SY5Y cells (Fig. 2C and D).

Furthermore, the overexpression of RIPK1 signally aggravated the decrease of cell viability, and the increase of cell apoptosis and necrosis induced by MPP+ treatment (Fig. 2E-G), while Nec-1s effectively inhibited cell apoptosis, necrosis, and the decline of cell viability in MPP+-treated SH-SY5Y cells (Fig. 2E-G).

2.3. The effect of RIPK1 on inflammatory response, oxidative stress and mitochondrial dysfunction in MPP+-induced SH-SY5Y cells

Next, the effect of RIPK1 on inflammatory response, ROS production and mitochondrial dysfunction in MPP+-induced SH-SY5Y cells was examined. As shown in Fig. 3A and B, the relative contents of TNFα and IL-1β were significantly increased in the culture medium of MPP+-
treated SH-SY5Y cells, which were further promoted by ov-RIPK1, while inhibited by RIPK1 inhibitor (Fig. 3A and B). The results of JC-1 kits showed that overexpression of RIPK1 facilitated the decline of Δψm that induced by MPP+, while Nec-1s prevented the decline of Δψm in SH- SY5Y cells induced by MPP treatment (Fig. 3C). Besides, the declined SOD activity and the increased ROS levels in MPP+-treated SH- SY5Y cells was promoted by RIPK1 overexpression and suppressed by RIPK1 inhibition(Fig. 3D and E).

Fig. 1. RIPK1 is increased in the MPP+-induced SH-SY5Y cells. A. The survival rate of SH-SY5Y cells was detected through CCK-8 assay after exposed to different concentrations of MPP+ for 12, 24 and 48 h. * P < 0.05, ** P < 0.01 compared with 0 mM MPP+ treatment group. B-D. The expression of RIPK1 mRNA, RIPK1 and ps166- RIPK1 protein was measured after treated by 1 mM MPP+ for different times. E. The ratio of ps166- RIPK1/RIPK1. * P < 0.05, ** P < 0.01 compared with 0 h treatment group. F-H. The expression of RIPK1 mRNA, RIPK1 and ps166- RIPK1 protein in hippocampus and SNpc tissues of control mice and MPTP-induced PD mice was analyzed. * P < 0.05, ** P < 0.01 compared with control group. Data are mean ±sD; n = 3 independent experiments. Statistical analysis was performed by one- way ANOVA followed by Bonferroni’s post hoc test (A-E) or Student’s t test (F and H). Fig. 2. The effect of RIPK1 on cell viability and apoptosis. A-D RIPK1 mRNA and protein were measured after transfection with overexpression vector of RIPK1 (ov- RIPK1) or stimulated by RIPK1 inhibitor (Nec-1s). E-G. Cell viability, cell apoptosis and necrosis were measured after overexpression or inhibition of RIPK1. * P < 0.05, ** P < 0.01 compared with the control group. # P < 0.05 compared with MPP+ treated group. Data are mean ± SD; n = 3 independent experiments. Statistical analysis was performed by one-way ANOVA followed by Bonferroni’s post hoc test. 2.4. Inhibition of the ASK1/JNK signalling pathway reversed the effect of ov-RIPK1 on MPP+-stimulated SH-SY5Y cells The activation of p38MAPK/JNK has been reported to be associated with PD (Jha et al., 2015), thus we explored the involvement of the p38MAPK/JNK signaling in the effect of ov-RIPK1 on MPP+-stimulated SH-SY5Y cells. The results showed that the ratios of P-ASK1/ASK1, P- p38/p38 and P-JNK/JNK were increased in MPP+-stimulated SH-SY5Y cells, and the overexpression of RIPK1 further promoted the MPP+- induced phosphorylation of ASK1 and JNK in SH-SY5Y cells (Fig. 4A and B). At the same time, the ratios of P-ASK1/ASK1 and P-JNK/JNK were remarkably lowered by Nec-1s in MPP+ stimulated SH-SY5Y cells (Fig. 4A and B). Nevertheless, there was no significant difference in the levels of P-p38 and p38 between the MPP+-treated group, the MPP+ ov-RIPK1-treated group and the MPP+ Nec-1s-treated group (Fig. 4A and B). What is more, the contributory effect of RIPK1 on the phos- phorylation of ASK1 and JNK in MPP+-treated SH-SY5Y cells was reversed by the ASK1 inhibitor (Fig. 4A and B). Next, to confirm the role of the ASK1/JNK signalling pathway in RIPK1-mediated cell viability, cell death and inflammation in MPP+-treated SH-SY5Y cells, inhibitors of ASK1 and JNK were adopted. As demonstrated in Fig. 4C-G, the declined cell viability, the increased cell apoptosis, cell necrosis and pro- inflammatory factors induced by RIPK1 were effectively inhibited by the ASK1 inhibitor and/or JNK inhibitor. Hence, it is suggested that RIPK1 promotes cell death and inflammation response partially by activating the ASK1/JNK signalling pathway. 2.5. The effect of RIPK1 inhibitor on the behaviour of MPTP-induced PD mice Further, the behaviour of MPTP-induced PD mice was assessed through the Rotarod test and the Open-field test. The results indicated that there is no significant difference between the Veh and Nec-1s treatment in the Rotarod test and the open-field test in the control group mice (Fig. 5A-E). A markedly decrease in the number of lines crossed, the time of rearing and grooming were found in MPTP Veh- treated PD mice, while the administration of Nec-1s effectively reversed this decline (Fig. 5A-D). In addition, the administration of Nec-1s significantly increased the latency time of fall off the rod in MPTP- induced PD mice, (Fig. 5E). Also, we found that the ratio of p-ASK1/ ASK1 was increased in the SNpc after MPTP treatment and decreased by Nec-1s (Fig. 5F). These results suggested that the RIPK1 inhibitor Nec-1s effectively relieved the behavioural impairment of PD mice. 3. Discussion In this study, RIPK1 mRNA was increased by 1.5 times in MPP+- treated SH-SY5Y cells, while the level of RIPK1 protein was increased by 3.4 times in SH-SY5Y cells after treated by MPP+. A similar result was reported that the increasing expression of RIPK1 protein may due to post-translational modifications in AD patients(Ofengeim et al., 2017). Also, we found that ps166-RIPK1, which is a marker of RIPK1 auto- phosphorylation and activation (Ofengeim et al., 2017), was activated in MPP+-treated SH-SY5Y cells and PD model. This is consistent with the previous findings that RIPK1 was activated in neurodegenerative diseases, such as Alzheimer’s disease, multiple sclerosis and amyotrophic lateral sclerosis (Ito et al., 2016; Ofengeim et al., 2017; Rubinsztein, 2017; Yuan et al., 2019). Fig. 3. The effect of RIPK1 on inflammatory response, mitochondrial dysfunction, and ROS production in MPP+- treated SH-SY5Y cells. A and B. Contents of TNF-α and IL-1β in culture medium of SH-SY5Y cells were detected by ELISA kits. B-E. The mitochondrial membrane potential alteration, SOD activity and ROS levels in MPP+-treated SH-SY5Y cells were examined after overexpression or inhibition of RIPK1. * P < 0.05, ** P < 0.01 compared with the control group. # P < 0.05 compared with MPP+ treated group. Data are mean ± SD; n = 3 independent experiments. Statistical analysis was performed by one-way ANOVA followed by Bonferroni’s post hoc test. RIPK1 is an important regulator of cell apoptosis, necroptosis and inflammation (Ito et al., 2016; Takahashi et al., 2014). In this study, we found RIPK1 inhibitor Nec-1s significantly suppressed the expression of RIPK1. It is consistent with a recent literature study that Nec-1s sup- pressed the mRNA and protein expression of RIPK1 in HaCaT cells, also suppressed RIPK1 expression in mice with IMQ-induced psoriasiform dermatitis (Duan et al., 2020). The inhibition of RIPK1 by Nec-1s markedly inhibited TNFα-induced systemic inflammation and neuro-degenerative diseases (Berger et al., 2014; Ito et al., 2016; Polykratis et al., 2014; Rubinsztein, 2017). It has been reported that the inhibition of RIPK1 suppressed the RIPK3/MLKL-dependent necroptosis, and in- flammatory response, increased the production of necroptotic DAMPs (damage associated molecular patterns),(Ito et al., 2016; On˜ate et al.,2020). RIP1/RIP3/MLKL-mediated necroptosis is involved in the path- ogenesis of MPTP-induced PD (Lin et al., 2020). Necroptosis has been found in several neurodegenerative disorders, and linked by strong neuroinflammatory features (Dionísio et al., 2019). In our study, we found that Nec-1s markedly suppressed cell apoptosis, necrosis and the secretion of pro-inflammatory factors in MPP+-treated SH-SY5Y cells, while the overexpression of RIPK1 in MPP+-treated SH-SY5Y cells has a contrasting effect. It is suggested that the inhibition of RIPK1 against MPP+-induced cytotoXicity in SH-SY5Y cells is via suppressing cell apoptosis, necroptosis and inflammation. In addition, oXidative stress induced mitochondrial dysfunction is linked to the neurodegeneration (Islam, 2017; Moon and Paek, 2015; Weng et al., 2018). High levels of ROS and the decreased expression of endogenous antioXidant systems such as SOD and GSH (glutathione) led to the loss of dopaminergic neurones in PD (Islam, 2017). SOD is an antioXidant enzyme, playing an important role in scavenging ROS (Kaur et al., 2011). In this study, we demonstrate that the inhibition of RIPK1 protects against MPP+-induced neuronal mitochondrial dysfunction by limiting the generation of ROS and promoting the activity of SOD. Further, our study indicated that RIPK1 inhibitor Nec-1s could effectively relieve the behavioural impairment of PD mice. A recently study indicated that nec-1s treatment suppressed forepaw akinesia and promoted motor performance of 6-OHDA-induced PD mice, neverthe- less, nec-1s treatment had no significant effect on the scheme of striatal region and striatal denervation, but suppressed the loss of axonal (On˜ate et al., 2020). Another study indicated that Nec-1s promoted the survival of neurons, and suppressed dopaminergic neuronal loss in MPTP-treated mice (Iannielli et al., 2018). Thus, Nec-1s may be an effective medicine for PD through relieving the behavioural impairment of PD patients. Apoptosis-signaling kinase-1 (ASK1) plays a crucial role in neuro- degenerative diseases, can be activated by oXidative stress, and ulti- mately leads to the activation of JNK (Guo et al., 2017). Actually, ASK1 is activated in the substantia nigra of MPTP stimulated mice (Lee et al., 2012). ASK1-deficient mice showed less dopaminergic neuronal loss and motor impairment when stimulated by MPTP, compared with the wild type mice (Lee et al., 2012). Hu et al indicated that ASK1 is also activated in the 6-hydroXydopamine-induced PD cellular model (Hu et al., 2011). Consistent with previous reports, our findings demonstrated that the ASK1/JNK pathway is activated in MPP+-stimulated SH-SY5Y cells. Previous studies reported that ASK1-deficient mice exhibited resistance to apoptosis induced by oXidative stress and JNK and p38 activation (Kadowaki et al., 2005). Various lines of evidence suggested that some compounds and genes exhibited neuroprotective effects by suppressing the activation of the ASK1/JNK pathway (Hu et al., 2011; Kim et al., 2012). Our findings demonstrated that RIPK1 inhibitor sup- pressed the activation of the ASK1/JNK pathway in MPP+-stimulated SH-SY5Y cells. Fig. 4. Inhibition of the ASK1/JNK signalling pathway reversed the effect of ov-RIPK1 on cell viability, apoptosis, and inflammation in MPP+-stimulated SH-SY5Y cells. A. The expression levels of ASK1, P-ASK1, P-p38, p38, P-JNK, JNK in SH-SY5Y cells were examined through Western blotting. B. Ratios of P-ASK1/ASK1, P-p38/ p38, P-JNK/JNK were analyzed. C-G. Cell viability, cell apoptosis, necrosis and the secretion of TNF-α and IL-1β in SH-SY5Y cells were tested. Transfected cells were pretreated with selonsertib (Sel; 1 µM) or SP600125 (20 µM) for 1 h, then incubated with MPP+ (1 μM) and cultured for 24 h. * P < 0.05, ** P < 0.01, compared with the control group. # P < 0.05 compared with MPP+ treated group. & P < 0.05 compared with MPP+ + ov-RIPK1 treated group. Data are mean ± SD; n = 3 in- dependent experiments. Statistical analysis was performed by one-way ANOVA followed by Bonferroni’s post hoc test. In summary, RIPK1 was increased and activated in MPP+-treated SH- SY5Y cells and MPTP-induced PD mice. The overexpression of RIPK1 exacerbated cell apoptosis, inflammatory response, mitochondrial dysfunction, and ROS production, while inhibiting RIPK1 by necrostatin-1 had the opposite effect. In addition, inactivation of the ASK1/JNK signalling pathway partially reversed the promoting effect of RIPK1 overexpression on MPP+-treated SH-SY5Y cells. What is more,targeting RIPK1 by necrostatin-1 improved the motor behaviour of MPTP-induced PD model mice. Our study indicated that the inhibition of RIPK1 may relieve PD through the ASK1/JNK signalling pathway. 4. Materials and methods 4.1. Cell lines SH-SY5Y neuroblastoma cells were purchased from the Stem Cell Bank (Chinese Academy of Sciences, Shanghai, China) and cultured in DMEM medium (Gibco, Rockville, MD, USA) containing 10% fetal bovine serum (Gibco). In this study, a PD cellular model was established by adding 1 μM MPP+ to the culture medium of SH-SY5Y cells and sustained for 24 h (Hu et al., 2019a; Song et al., 2018). Nec-1s treatment: 10 μM Nec-1s (R-7-ClO-necrostatin-1, RIPK1 kinase inhibitor) was added to the culture medium and incubated for 12 h (Yao-Qi et al., 2012). 4.2. Animal experiment SiX-month old male C57BL/6 mice were used in this study. PD model mice were induced through the intraperitoneal injection of MPTP (20 mg/kg/day, Sigma-Aldrich, USA) for 5 consecutive days (n 18) (Liu et al., 2018). The normal control group mice were intraperitoneally injected with equal volumes of saline as the MPTP-treated group for 5 days (n 6).The administration of Nec-1s was according to a previous report (Ofengeim et al., 2017). Nec-1s was dissolved in DMSO (dime- thylsulphoXide) 35% PEG (Polyethylene glycol) solution, and added to water containing 2% sucrose. Vehicle control and Nec-1s were supplied as drinking water ad libitum for one month. Each mouse drank about 5 to 10 mL/d of vehicle or Nec-1s containing water (0.5 mg/mL). All animal experiments were performed according to the protocols and guide lines of the National Institute of Health Guide for the Care and Use of Laboratory Animals, and approved by the Ethics Committee of NO.215 Hospital of Shaanxi Nuclear Industry.

Fig. 5. Behavioural assessment of MPTP-induced PD mice. A-D. The results of the open-field test, number of lines crossed, the time of rearing, grooming and immobility were recorded and analyzed. E. The results of rotarod test for motor coordination ability of mice. The latency time to fall off the rod was recorded and analyzed. F. EXpression of ASK1, P-ASK1 in SNpc was measured through Western blotting. * P < 0.05, ** P < 0.01, compared with the Veh-administration control group. # P < 0.05 compared with Veh-administration PD mice group. Veh: Vehicle, DMSO + 35% PEG solution. Data are mean ± SD; n = 6 independent experiments. Statistical analysis was performed by Student’s t test. 4.3. Behavioural assessment The accelerated rotarod test was conducted in a rotarod apparatus and performed as previously reported (Castelhano-Carlos et al., 2010). Before treatment with MPTP, all mice were trained in 4 trials per day with a 20-minute interval, which lasted for 3 days on a rotating rod. After receiving MPTP injections for 5 days, the accelerated rotarod test was performed on the siXth day. Mice were placed on the rotarod apparatus that rotated with a constant accelerating rate. The latency time for mice to fall off the rod was automatically recorded. Each mouse was tested twice with a 20-minute interval, and the mean was calculated. The open field test was performed to evaluate the locomotive ac- tivity, exploration and anxiety-like behaviour of rodents (Hirata et al., 2016; Kraeuter et al., 2019). An open-field chamber with an inner diameter of 50 cm and height of 40 cm was used in this study. The mice were individually placed in the centre of the chamber and allowed free and uninterrupted movement for 5 min. The behaviour of mice was recorded by video, and the number of lines crossed, as well as rearing, grooming and immobility times were analyzed. Each animal was tested three times. 4.4. RNA extraction and realtime quantitative PCR Total RNA was extracted using the RNA extraction kit (Promega, Madison, WI, USA) according to the manufacturer’s instructions. cDNA reverse transcription kit (Takara, Japan) was used to synthesize the cDNA. A specific primer of RIPK1 was designed and purchased by Biotech Engineering Company (Shanghai, China). Real-time qPCR was performed according to a previous report (Li et al., 2018). 4.5. Construction and transduction of RIPK1 overexpression plasmid Overexpression plasmids of RIPK1 were constructed and purchased from Sino Biological Inc. (Beijing, China). Lipofectamine 3000 was adopted for the transfection of RIPK1 plasmid into SH-SY5Y cells (Invitrogen, Carlsbad, CA, USA). 4.6. Cell viability test SH-SY5Y cells (0.5 105 cells/well) were planted into 96 microwell plate and cultured for 12 h. Then, different concentrations of MPP+ (0, 0.1, 0.25, 0.5, 1.0, and 2.0 mM) were added to fresh culture medium and incubated for 12, 24 and 48 h. Cell viability was detected by the Cell Counting Kit-8 (CCK-8, Dojindo Molecular Technologies, Kumamoto, Japan) following the manufacturer’s instructions. 4.7. Apoptosis and necrosis quantification Cell apoptosis and necrosis were detected through an Apoptosis and Necrosis Assay Kit according to the manufacturer’s recommendations (Beyotime Institute of Biotechnology, China). 4.8. The enzyme-linked immunosorbent assay (ELISA) The content of TNFα and IL-1β in culture medium was detected using ELISA kits following the manufacturer’s instructions (Thermo Fisher, USA). 4.9. Mitochondrial dysfunction detection Mitochondrial dysfunction was evaluated by detecting the mito- chondrial membrane potential (ΔΨm) using a mitochondrial membrane potential assay kit with JC-1 (Beyotime) and following the manufac- turer’s instructions. 4.10. Reactive oxygen species (ROS) levels and Superoxide dismutase (SOD) activity detection ROS levels in SH-SY5Y cells were examined by the Cellular ROS/ SuperoXide detection assay kit (Abcam, UK) following the manufac- turer’s protocol. SOD activity was detected through a SOD Colorimetric Activity Kit (Thermo Fisher, USA). 4.11. Western blotting Cells were lysed and centrifuged to obtain protein samples. Protein quantification was performed using the BCA Protein Assay Reagent (Beyotime). Then, protein samples were separated by SDS-PAGE, and transferred to nitrocellulose blotting membranes. Membranes were blocked with 5% non-fat dried milk and then probed with primary an- tibodies (overnight, 4 ◦C) and horseradish peroXidase (HRP)-conjugated secondary antibodies (2 h, room temperature). Protein blots were visualised using the ECL kit. Actin was used as the internal control. 4.12. Data analysis Data were analysed through the GraphPad Prism 7.0 software and expressed as the means ±sD. In vitro experiments were repeated at least three times. Student’s t test was used for comparison between two groups. One-way ANOVA followed by Bonferroni’s post hoc test was applied to analyse more than two groups. P < 0.05 was considered to indicate statistical significance. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements Not applicable. Funding None. Availability of data and materials The data in the present study are available from the corresponding author on reasonable request. Author contributions Jing Liu: Conceptualization, Investigation, Writing - original draft. Binyan Wu: Methodology. Huizheng Hu: Conceptualization, Writing - review & editing. Ethics approval and consent to participate The present study was approved by the Ethics Committee of NO.215 Hospital of Shaanxi Nuclear Industry. 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