Neuroprotective effects of silymarin in 3-nitropropionic acid-induced neurotoxicity in male mice: improving behavioral deficits by attenuating oxidative stress and neuroinflammation.

3-Nitropropionic acid (3-NP) is strongly believed to be an irreversible inhibitor of mitochondrial complex II, leading to neural damage. This study aimed to investigate the neuroprotective effects of silymarin against 3-NP-induced neurotoxicity in male mice. Six-week-old mice received subacute doses of 3-NP intraperitoneally for 17 days. Mice were given silymarin (70 mg/kg/day, P.O.) for 2 weeks before 3-NP administration or for 4 weeks after 3-NP administration. At the end of the treatment schedule, animals were evaluated for behavioral alterations. Subsequently, neuronal damage in the hippocampus region of the brain tissues, oxidative stress-related parameters (lipid peroxidation, nitric oxide, superoxide dismutase, glutathione, and total antioxidant capacity), and pro-inflammatory cytokine (TNF-α, IL-17, and IL-1ß) levels were evaluated. Our results indicated that 3-NP treatment significantly (p < 0.05) tended to reduce motor coordination, memory, and neuronal antioxidant status while increasing pro-inflammatory cytokine levels. However, silymarin in both treatment and pretreatment protocols markedly (p < 0.05) attenuated the behavioral deficits, oxidative stress status, and neuroinflammation. The results of the current study suggest that the neuroprotective effect of silymarin against 3-NP-induced neurotoxicity might be due to the mitigation of oxidative stress status and provide insight into the therapeutic potential of silymarin.

Silibinin chronic treatment in a rat model of Parkinson disease: A comprehensive in-vivo evaluation and in silico molecular modeling.

BACKGROUND: Apoptosis, oxidative stress, and neuroinflammation have been linked to the onset of Parkinson's disease (PD). Although the pre-treatment effects of Silibinin on a PD model have been evaluated, in the current study we investigated the chronic therapeutic effects of Silibinin microinjection on a rat model of established parkinsonism along with behavioral and laboratory markers assessments. METHOD: Parkinsonism was induced by 6-hydroxydopamine (6-OHDA, 8 µg/2µl/rat). 21 days after that, animals were treated with Silibinin (100, 200, and 300 mg/kg for 15 consecutive days). Every two days, the bar test was used to evaluate Silibinin's anti-cataleptic properties. At the end, myeloperoxidase (MPO) activity and toll-like receptor 4 (TLR4) expression in the substantia nigra pars compacta (SNc), along with cerebrospinal fluid (CSF) levels of tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1ß, IL-6, caspase-3, Bax and Bcl-2 levels were assessed. We used homology modeling to predict the 3D structure of TLR4. RESULT: Silibinin's Chronic treatment, dose-dependently decreased catalepsy. MPO activity and levels of TNF-α, IL-6, and IL-1ß were reduced in Silibinin-treated rats in all three doses. Silibinin decreased Bax/Bcl-2 ratio, caspase-3, and downregulated TLR4 expression. Molecular docking revealed that there were hydrophobic and hydrogen bond interactions between the studied ligand and TLR4. Silibinin formed a stable complex with both monomer and dimer forms of TLR4. CONCLUSION: In accordance with molecular modeling and alleviation of TLR4 activity with a consequent reduction in oxidative stress, restoration of CSF inflammatory cytokine, and minimization of SNc neuronal apoptosis, long-term therapy with Silibinin offers a potential opportunity for symptomatic PD treatment.

Post treatment with Gastrodin suppresses oxidative stress and attenuates motor disorders following 6-OHDA induced Parkinson disease.

BACKGROUND & OBJECTIVE: Researchers are currently trying to find new therapies with better symptomatic activity and fewer side effects to manage Parkinson's disease (PD). Although the protective effect of pre-treatment by Gastrodin (Gst) on a PD model has been evaluated, in the current experimental study, we investigated the symptomatic therapeutic effects of Gst microinjection in the same PD model but in the post-parkinsonism induction condition. METHODS: Parkinsonism was induced by unilateral infusion of 6- hydroxydopamine (6-OHDA; 8 µg/ 2 µl/ rat) into the central region of the substantia nigra pars compacta (SNc). After the recovery period and confirmation of parkinsonism, daily Gst treatment in three doses (20, 40, 80 µg/ 2 µ/ rat, continued for ten days with motor monitoring by bar test and rotarod examinations. Moreover, lipid peroxidation and myeloperoxidase activity were evaluated. RESULTS: In this model of 6-OHDA-induced parkinsonism, Gst treatment in all three doses showed a dose dependent symptomatic improvement in motor imbalance (P < 0.001) catalepsy (P < 0.001), decreased lipid peroxidation (P < 0.001) and SNc myeloperoxidase activity (P < 0.001). CONCLUSIONS: 6-OHDA induced parkinsonism symptomatically improved behaviorally with Gst post-induction treatment along with decreased markers of oxidative stress and microglial activation. We suggest that this agent is a candidate for symptomatic treatment of human PD.

Silymarin and neurodegenerative diseases: Therapeutic potential and basic molecular mechanisms.

BACKGROUND: Neurodegenerative diseases (NDDs) are primarily characterized by selective neuronal loss in the brain. Alzheimer's disease as the most common NDDs and the most prevalent cause of dementia is characterized by Amyloid-beta deposition, which leads to cognitive and memory impairment. Parkinson's disease is a progressive neurodegenerative disease characterized by the dramatic death of dopaminergic neuronal cells, especially in the SNc and caused alpha-synuclein accumulation in the neurons. Silymarin, an extract from seeds of Silybum marianum, administered mostly for liver disorders and also had anti-oxidant and anti-carcinogenic activities. PURPOSE: The present comprehensive review summarizes the beneficial effects of Silymarin in-vivo and in-vitro and even in animal models for these NDDs. METHODS: A diagram model for systematic review is utilized for this search. The research is conducted in the following databases: PubMed, Web of Science, Scopus, and Science Direct. RESULTS: Based on the inclusion criteria, 83 studies were selected and discussed in this review. CONCLUSION: Lastly, we review the latest experimental evidences supporting the potential effects of Silymarin, as a neuroprotective agent in NDDs.

Neuronal degeneration and oxidative stress in the SNc of 6-OHDA intoxicated rats; improving role of silymarin long-term treatment.

Progressive loss in dopaminergic neurons (DA) of substantia nigra pars compacta (SNc) leads to Parkinson's disease with a hypothesis of oxidative stress generation. The present study was conducted to determine the long-term efficacy of silymarin (SM) post-treatment on 6-OHDA-induced oxidative stress in the SNc of male rats. Male Wistar rats were received 6-OHDA (8 µg/rat) into SNc. After 3 weeks, as recovery period, the animals were treated with i.p. injection of SM at different doses of 100, 200, or 300 mg/kg for 15 days. At the end of the treatment, motor function, neuronal cell count, antioxidant enzymes, and lipid peroxidation and tyrosine hydroxylase (TH) activities were evaluated in the ventral midbrain tissue. The 6-OHDA significantly decreased (p ≤ 0.05) motor function, antioxidant enzyme activity, GSH level, and GSH/GSSG ratio and caused an augmentation in GSSG and lipid peroxidation level. The 6-OHDA also reduced the population of neurons and TH expression. The SM repaired the 6-OHDA-induced motor impairment, antioxidant enzyme suppression, and TH down-regulation. All three doses of SM could restore the MDA level to the normal range in the 6-OHDA-lesioned rats and could reversed the effect of 6-OHDA on GSH, GSSG level, and GSH/GSSG ratio. The SM treatment significantly and dose-dependently increased (p ≤ 0.001) the total number of surviving neurons in the SNc. Silymarin chronic treatment restored the brain's antioxidant capacity and salvaged neurons from oxidative stress-induced neurodegeneration. The SM could also improve motor function in parkinsonian animals by increasing TH expression. These results recommend that application of SM over initial clinical stages may depict a hopeful approach versus PD. However, more research is needed to confirm this issue.

Silymarin prevents apoptosis through inhibiting the Bax/caspase-3 expression and suppresses toll like receptor-4 pathway in the SNc of 6-OHDA intoxicated rats.

BACKGROUND AND PURPOSE: Several lines of evidence show that apoptosis, oxidative stress and neuroinflammation are associated with the development of Parkinson's disease (PD). In the present study, we investigated the effect of pre-treatment with silymarin (SM) on oxidative stress, apoptosis and toll-like receptor 4 (TLR4) expression in substantia nigra pars copmacta (SNc) of 6-hydroxydopamine (6-OHDA)-lesioned rats. METHODS: Animals were pretreated with 100, 200 or 300 mg/kg of SM daily for 5 days and at 6th day 6-OHDA (8 µg/2 µl) was infused unilaterally into the central region of the SNc. RESULTS: 6-OHDA decreased the total glutathione and antioxidant enzymes activity in the SNc. Interestingly, we found that 6-OHDA caused to TLR4 up regulation. The SNc levels of glutathione, superoxide dismutase, glutathione peroxidase, glutathione reductase and catalase were significantly higher in the SM pretreated rats. SM strongly decreased 6-OHDA-induced elevation of SNc apoptosis, caspase-3 and Bax/Bcl-2 ratio. Furthermore, SM markedly (p < 0.001) prevented from SNc over expression of TLR4 caused by 6-OHDA. A significantly high positive correlation was seen between TLR4 activity with caspase-3 protein levels (r = 0.896, P < 0.01), Bax protein levels (r = 0.96, P < 0.01). CONCLUSION: Pre-treatment of 6-OHDA-lesioned rats with SM reduces SNc neuronal apoptosis possibly through inhibition of TLR4 over expression. Further clinical study should be carried out to prove potential application of SM for protection against PD in susceptible individuals.

Short-Term Treatment with Silymarin Improved 6-OHDA-Induced Catalepsy and Motor Imbalance in Hemi-Parkisonian Rats.

PURPOSE: Parkinson's disease (PD) is a common neurodegenerative disorder characterized by disabling motor abnormalities, which include tremor, muscle stiffness, paucity of voluntary movements, and postural instability. Silymarin (SM) or milk thistle extract, is known to own antioxidative, anti-apoptotic, anti-inflammatory and neuroprotective effects. In the present study, we investigated the effect of intraperitoneal (i.p) administration of SM, on 6-OHDA-induced motor-impairments (catalepsy and imbalance) in the rats. METHODS: Experimental model of PD was induced by unilateral infusion of 6-hydroxydopamine (6-OHDA; 8 µg/2 µl/rat) into the central region of the substantia nigra pars compacta (SNc). Catalepsy and motor coordination were assessed by using of bar test and rotarod respectively. RESULTS: The results showed a significant (p<0.001) increase in catalepsy of 6-OHDA-lesioned rats whereas; in SM (100, 200 and 300 mg/kg, i.p for 5 days) treated hemi-parkinsonian rats catalepsy was decreased markedly (p<0.001). Furthermore, there was a significant (p<0.001) increase in motor-imbalance of 6-OHDA-lesioned rats. SM improved motor coordination significantly (p<0.001) in a dose dependent manner and increased motor balance. CONCLUSION: In conclusion, we found that short-term treatment with SM could improve 6-OHDA-induced catalepsy and motor imbalance in rats. We suggest that SM can be used as adjunctive therapy along with commonly used anti-parkinsonian drugs. However, further clinical trial studies should be carried out to prove this hypothesis.