Simvastatin prevents the inflammatory process and the dopaminergic degeneration induced by the intranigral injection of lipopolysaccharide

Statins as an adjuvant therapy for patients with schizophrenia: An up-to-date systematic review and meta-analysis

BACKGROUND

Evidence suggests that inflammatory processes play a role in the pathophysiology of schizophrenia. Statins exert anti-inflammatory and antioxidant effects and may be effective in improving the symptoms of schizophrenia. This study explored whether statins, as an adjunctive therapy, can alleviate the symptoms of schizophrenia.

METHODS

PubMed, EMBASE, and the Cochrane Library were searched for articles published up to March 2023. The risk-of-bias tool for randomized trials was used to assess study quality. Two researchers independently assessed the risks of bias and extracted data. Pooled data on Positive and Negative Syndrome Scale (PANSS) scores were analyzed. A random-effects model was employed to calculate pooled effect sizes. Statistical heterogeneity across studies was assessed using the I2 statistic. All analyses were performed using RevMan5 and Comprehensive Meta-Analysis software.

RESULTS

Nine trials enrolling 533 patients in total were included. Add-on statin therapy was found to be associated with a significantly better total PANSS score [standardized mean difference (SMD) = -0.42, 95% confidence interval (CI) -0.75 to -0.09, I2 = 72%; P = 0.01] and PANSS negative subscale score (SMD = -0.26, 95% CI -0.45 to -0.07, I2 = 0%; P = 0.009) in comparison with placebo. However, add-on statin therapy did not appear to improve scores for the PANSS positive and general subscales at the study-defined endpoint (6-24 weeks).

CONCLUSIONS

Our meta-analysis indicates that adjunctive statin therapy may confer benefits in ameliorating PANSS negative and total scores. It needs more solid data to confirm the results are related to clinical improvement and functioning.

Dissecting the Relationship Between Neuropsychiatric and Neurodegenerative Disorders

Neurodegenerative diseases (NDDs) and neuropsychiatric disorders (NPDs) are two common causes of death in elderly people, which includes progressive neuronal cell death and behavioral changes. NDDs include Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, multiple sclerosis, and motor neuron disease, characterized by cognitive defects and memory impairment, whereas NPDs include depression, seizures, migraine headaches, eating disorders, addictions, palsies, major depressive disorders, anxiety, and schizophrenia, characterized by behavioral changes. Mounting evidence demonstrated that NDDs and NPDs share an overlapping mechanism, which includes post-translational modifications, the microbiota-gut-brain axis, and signaling events. Mounting evidence demonstrated that various drug molecules, namely, natural compounds, repurposed drugs, multitarget directed ligands, and RNAs, have been potentially implemented as therapeutic agents against NDDs and NPDs. Herein, we highlighted the overlapping mechanism, the role of anxiety/stress-releasing factors, cytosol-to-nucleus signaling, and the microbiota-gut-brain axis in the pathophysiology of NDDs and NPDs. We summarize the therapeutic application of natural compounds, repurposed drugs, and multitarget-directed ligands as therapeutic agents. Lastly, we briefly described the application of RNA interferences as therapeutic agents in the pathogenesis of NDDs and NPDs. Neurodegenerative diseases and neuropsychiatric diseases both share a common signaling molecule and molecular phenomenon, namely, pro-inflammatory cytokines, γCaMKII and MAPK/ERK, chemokine receptors, BBB permeability, and the gut-microbiota-brain axis. Studies have demonstrated that any alterations in the signaling mentioned above molecules and molecular phenomena lead to the pathophysiology of neurodegenerative diseases, namely, Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis, and neuropsychiatric disorders, such as bipolar disorder, schizophrenia, depression, anxiety, autism spectrum disorder, and post-traumatic stress disorder.

Interplay between Systemic Glycemia and Neuroprotective Activity of Resveratrol in Modulating Astrocyte SIRT1 Response to Neuroinflammation

The flow of substances between the blood and the central nervous system is precisely regulated by the blood-brain barrier (BBB). Its disruption due to unbalanced blood glucose levels (hyper- and hypoglycemia) occurring in metabolic disorders, such as type 2 diabetes, can lead to neuroinflammation, and increase the risk of developing neurodegenerative diseases. One of the most studied natural anti-diabetic, anti-inflammatory, and neuroprotective compounds is resveratrol (RSV). It activates sirtuin 1 (SIRT1), a key metabolism regulator dependent on cell energy status. The aim of this study was to assess the astrocyte SIRT1 response to neuroinflammation and subsequent RSV treatment, depending on systemic glycemia. For this purpose, we used an optimized in vitro model of the BBB consisting of endothelial cells and astrocytes, representing microvascular and brain compartments (MC and BC), in different glycemic backgrounds. Astrocyte-secreted SIRT1 reached the highest concentration in hypo-, the lowest in normo-, and the lowest in hyperglycemic backgrounds. Lipopolysaccharide (LPS)-induced neuroinflammation caused a substantial decrease in SIRT1 in all glycemic backgrounds, as observed earliest in hyperglycemia. RSV partially counterbalanced the effect of LPS on SIRT1 secretion, most remarkably in normoglycemia. Our results suggest that abnormal glycemic states have a worse prognosis for RSV-therapy effectiveness compared to normoglycemia.

The Endotoxin Hypothesis of Parkinson's Disease

The endotoxin hypothesis of Parkinson's disease (PD) is the idea that lipopolysaccharide (LPS) endotoxins contribute to the pathogenesis of this disorder. LPS endotoxins are found in, and released from, the outer membrane of Gram-negative bacteria, for example in the gut. It is proposed that gut dysfunction in early PD leads to elevated LPS levels in the gut wall and blood, which promotes both α-synuclein aggregation in the enteric neurons and a peripheral inflammatory response. Communication to the brain via circulating LPS and cytokines in the blood and/or the gut-brain axis leads to neuroinflammation and spreading of α-synuclein pathology, exacerbating neurodegeneration in brainstem nuclei and loss of dopaminergic neurons in the substantia nigra, and manifesting in the clinical symptoms of PD. The evidence supporting this hypothesis includes: (1) gut dysfunction, permeability, and bacterial changes occur early in PD, (2) serum levels of LPS are increased in a proportion of PD patients, (3) LPS induces α-synuclein expression, aggregation, and neurotoxicity, (4) LPS causes activation of peripheral monocytes leading to inflammatory cytokine production, and (5) blood LPS causes brain inflammation and specific loss of midbrain dopaminergic neurons, mediated by microglia. If the hypothesis is correct, then treatment options might include: (1) changing the gut microbiome, (2) reducing gut permeability, (3) reducing circulating LPS levels, or (4) blocking the response of immune cells and microglia to LPS. However, the hypothesis has a number of limitations and requires further testing, in particular whether reducing LPS levels can reduce PD incidence, progression, or severity. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Repurposing Simvastatin in Parkinson's Disease Model: Protection Is throughout Modulation of the Neuro-Inflammatory Response in the Substantia nigra

Parkinson's disease is a neurodegenerative disorder characterized by oxidative stress and immune activation in the nigro-striatal pathway. Simvastatin regulates cholesterol metabolism and protects from atherosclerosis disease. Simvastatin-tween 80 was administered 7 days before sterotaxic intrastriatal administration of MPP⁺ (1-methyl-4-phenylpyridine) in rats. Fluorescent lipidic product formation, dopamine levels, and circling behavior were considered damage markers. Twenty-four hours and six days after, the animal group lesioned with MPP⁺ showed significant damage in relation to the control group. Animals pretreated with simvastatin significantly reduced the MPP⁺-induced damage compared to the MPP⁺ treated group. As apoptosis promotes neuroinflammation and neuronal degeneration in Parkinson's disease, and since there is not currently a proteomic map of the nigro-striatum of rats and assuming a high homology among the identified proteins in other rat tissues, we based the search for rat protein homologs related to the establishment of inflammation response. We demonstrate that most proteins related to inflammation decreased in the simvastatin-treated rats. Furthermore, differential expression of antioxidant enzymes in striated tissue of rat brains was found in response to simvastatin. These results suggest that simvastatin could prevent striatal MPP⁺-induced damage and, for the first time, suggest that the molecular mechanisms involved in this have a protective effect.

Early approaches of YKL-40 as a biomarker and therapeutic target for Parkinson's disease

Aim: To investigate whether the estimation of cerebrospinal fluid (CSF) and brain YKL-40 levels may be used as an efficient biomarker for Parkinson's disease (PD). Methods: Lipopolysaccharides (LPS) was injected into the right substantia nigra pars compacta (SNpc). Rats were divided into: control group, early LPS-induced PD group (14 days), and advanced LPS-induced PD group (28 days). YKL-40 and other related factors were detected in CSF and brain tissue. Results: Increased expression of YKL-40 was observed in brain tissue and CSF of PD-induced rats associated with triggered inflammatory cytokine release. Conclusion: The current study was limited to detecting YKL-40 and other inflammatory factors in brain and CSF. YKL-40 may be considered as an early biomarker and therapeutic target for PD.

Inflammatory Animal Models of Parkinson’s Disease

Accumulating evidence suggests that microglia and peripheral immune cells may play determinant roles in the pathogenesis of Parkinson’s disease (PD). Consequently, there is a need to take advantage of immune-related models of PD to study the potential contribution of microglia and peripheral immune cells to the degeneration of the nigrostriatal system and help develop potential therapies for PD. In this review, we have summarised the main PD immune models. From a historical perspective, we highlight first the main features of intranigral injections of different pro-inflammogens, including lipopolysaccharide (LPS), thrombin, neuromelanin, etc. The use of adenoviral vectors to promote microglia-specific overexpression of different molecules in the ventral mesencephalon, including α-synuclein, IL-1β, and TNF, are also presented and briefly discussed. Finally, we summarise different models associated with peripheral inflammation whose contribution to the pathogenesis of neurodegenerative diseases is now an outstanding question. Illustrative examples included systemic LPS administration and dextran sulfate sodium-induced colitis in rodents.

Implications of Gut Microbiota in Neurodegenerative Diseases

The morbidity associated with neurodegenerative diseases (NDs) is increasing, posing a threat to the mental and physical quality of life of humans. The crucial effect of microbiota on brain physiological processes is mediated through a bidirectional interaction, termed as the gut–brain axis (GBA), which is being investigated in studies. Many clinical and laboratory trials have indicated the importance of microbiota in the development of NDs via various microbial molecules that transmit from the gut to the brain across the GBA or nervous system. In this review, we summarize the implications of gut microbiota in ND, which will be beneficial for understanding the etiology and progression of NDs that may in turn help in developing ND interventions and clinical treatments for these diseases.

Atorvastatin prevents the development of diabetic neuropathic nociception by possible involvement of nitrergic system

AIMS

Diabetic neuropathy has been identified as a common complication caused by diabetes. However, its pathophysiological mechanisms are not fully understood yet. Statins, also known as HMG-CoA reductase inhibitors, alleviate the production of cholesterol. Despite this cholesterol-reducing effect of statins, several reports have demonstrated their beneficial properties in neuropathic pain. In this study, we used streptozotocin (STZ)-induced diabetic model to investigate the possible role of nitric oxide (NO) in the antineuropathic-like effect of atorvastatin.

METHODS

Diabetes was induced by a single injection of STZ. Male rats orally received different doses of atorvastatin for 21 days. To access the neuropathy process, the thermal threshold of rats was assessed using hot plate and tail-flick tests. Moreover, sciatic motor nerve conduction velocity (MNCV) studies were performed. To assess the role of nitric oxide, N(G)-nitro-L-arginine methyl ester (L-NAME), aminoguanidine (AG), and 7-nitroindazole (7NI) were intraperitoneally administered along with some specific doses of atorvastatin.

KEY FINDINGS

Atorvastatin significantly reduced the hyperalgesia in diabetic rats. L-NAME pretreatment with atorvastatin showed the antihyperalgesic effect, suggesting the possible involvement of the NO pathway in atorvastatin protective action. Furthermore, co-administration of atorvastatin with AG and 7NI resulted in a significant increase in pain threshold in diabetic rats.

SIGNIFICANCE

Our results reveal that the atorvastatin protective effect on diabetic neuropathy is mediated at least in a part via the nitric oxide system.

Statins in Parkinson's Disease: Influence on Motor Progression

BACKGROUND

It has been speculated that stains are neuroprotective and are associated with a reduced risk of Parkinson's disease (PD), but only a few studies have investigated the influence of statins on the progression of PD.

OBJECTIVE

To evaluate whether long-term statin use may affect motor progression in a large cohort of de novo patients with PD.

METHODS

We conducted a 4-year retrospective observational cohort study to assess patients with PD. The patients were consecutively recruited from a single tertiary center between January 2015 and January 2017. Information on motor function was obtained using the MDS-Unified Parkinson Disease Rating Scale (UPDRS)-III and all subjects were extensively characterized, including information about lifestyle habits, cardiovascular risk factors and cholesterol blood levels.

RESULTS

Of the 181 participants included in the study, 104 patients were evaluated for eligibility (42 patients were exposed to statin therapies and 62 were not treated with statins). They presented similar scores in UPDRS III at baseline but the statin users had a lower motor impairment at 4 years compared to non-user PD patients. Additionally, statin treatment resulted in slower progression of the rigidity score of UPDRS over 4 years. No other significant differences were observed between PD patients with and without statins.

CONCLUSION

Early PD patients with long-term statin usage showed lower motor deterioration after 4 years of disease duration compared with patients not taking statins at diagnosis, suggesting a possible influence of statins on disease progression in PD. Further investigation is warranted to understand the potential beneficial effects of statin treatment on clinical symptoms in PD.

Mechanistic insights into the protective effect of paracetamol against rotenone-induced Parkinson's disease in rats: Possible role of endocannabinoid system modulation

Parkinson's disease (PD) is a disabling progressive neurodegenerative disease. So far, PD's treatment remains symptomatic with no curative effects. Aside from its blatant analgesic and antipyretic efficacy, recent studies highlighted the endowed neuroprotective potentials of paracetamol (PCM). To this end: the present study investigated: (1) Possible protective role of PCM against rotenone-induced PD-like neurotoxicity in rats, and (2) the mechanisms underlying its neuroprotective actions including cannabinoid receptors' modulation. A dose-response study was conducted using three doses of PCM (25, 50, and 100 mg/kg/day, i.p.) and their effects on body weight changes, spontaneous locomotor activity, rotarod test, tyrosine hydroxylase (TH) and α-synuclein expression, and striatal dopamine (DA) content were evaluated. Results revealed that PCM (100 mg/kg/day, i.p.) halted PD motor impairment, prevented rotenone-induced weight loss, restored normal histological tissue structure, reversed rotenone-induced reduction in TH expression and striatal DA content, and markedly decreased midbrain and striatal α-synuclein expression in rotenone-treated rats. Accordingly, PCM (100 mg/kg/day, i.p.) was selected for further mechanistic investigations, where it ameliorated rotenone-induced oxidative stress, neuro-inflammation, apoptosis, and disturbed cannabinoid receptors' expression. In conclusion, our findings imply a multi-target neuroprotective effect of PCM in PD which could be attributed to its antioxidant, anti-inflammatory and anti-apoptotic activities, in addition to cannabinoid receptors' modulation.

Neurotoxin-Induced Rodent Models of Parkinson's Disease: Benefits and Drawbacks

Parkinson's disease (PD), the second most common neurodegenerative disorder, is characterized by cardinal motor impairments, including akinesia and tremor, as well as by a host of non-motor symptoms, including both autonomic and cognitive dysfunction. PD is associated with a death of nigral dopaminergic neurons, as well as the pathological spread of Lewy bodies, consisting predominantly of the misfolded protein alpha-synuclein. To date, only symptomatic treatments, such as levodopa, are available, and trials aiming to cure the disease, or at least halt its progression, have not been successful. Wong et al. (2019) suggested that the lack of effective therapy against neurodegeneration in PD might be attributed to the fact that the molecular mechanisms standing behind the dopaminergic neuronal vulnerability are still a major scientific challenge. Understanding these molecular mechanisms is critical for developing effective therapy. Thirty-five years ago, Calne and William Langston (1983) raised the question of whether biological or environmental factors precipitate the development of PD. In spite of great advances in technology and medicine, this question still lacks a clear answer. Only 5-15% of PD cases are attributed to a genetic mutation, with the majority of cases classified as idiopathic, which could be linked to exposure to environmental contaminants. Rodent models play a crucial role in understanding the risk factors and pathogenesis of PD. Additionally, well-validated rodent models are critical for driving the preclinical development of clinically translatable treatment options. In this review, we discuss the mechanisms, similarities and differences, as well as advantages and limitations of different neurotoxin-induced rat models of PD. In the second part of this review, we will discuss the potential future of neurotoxin-induced models of PD. Finally, we will briefly demonstrate the crucial role of gene-environment interactions in PD and discuss fusion or dual PD models. We argue that these models have the potential to significantly further our understanding of PD.

Lipopolysaccharide animal models of Parkinson's disease: Recent progress and relevance to clinical disease

Parkinson's disease (PD) is one of the most common neurodegenerative movement disorders which is characterised neuropathologically by progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and the presence of Lewy bodies (made predominately of α-synuclein) in the surviving neurons. Animal models of PD have improved our understanding of the disease and have played a critical role in the development of neuroprotective agents. Neuroinflammation has been strongly implicated in the pathogenesis of PD, and recent studies have used lipopolysaccharide (LPS), a component of gram-negative bacteria and a potent activator of microglia cells, to mimic the inflammatory events in clinical PD. Modulating the inflammatory response could ameliorate PD associated complications and thus, it is essential to understand the extent to which LPS models reflect human PD. This review will outline the routes of administration of LPS such as stereotaxic, systemic and intranasal, their ability to recapitulate neuropathological markers of PD, and mechanisms of LPS induced toxicity. We will also discuss the ability of the models to replicate motor symptoms and non-motor symptoms of PD such as gastrointestinal dysfunction, olfactory dysfunction, anxiety, depression and cognitive dysfunction.

Nose-to-brain co-delivery of repurposed simvastatin and BDNF synergistically attenuates LPS-induced neuroinflammation

A therapeutic strategy that can combat the multifaceted nature of neuroinflammation pathology was investigated. Thus, we fabricated PEG-PdLLA polymersomes and evaluated the efficacy in co-delivery of simvastatin (Sim, as a repurposed anti-inflammatory agent) with brain derived neurotrophic factor (BDNF, as an exogeneous trophic factor supplementation). Using LPS model of neuroinflammation, intranasal administration of combination drug-loaded polymersomes (containing both Sim and BDNF; Sim-BDNF-Ps) markedly down-regulated brain levels of cytokines compared to free drug and single-drug-loaded polymersomes. Further, Sim-BDNF-Ps effectively replenished brain level of BDNF that was depleted following neuroinflammation, resulting in a 2-fold BDNF increase versus untreated LPS control group. We found out that the efficiency of the combination drug-loaded polymersomes to suppress microglia activation in brain regions followed the order: frontal cortex > striatum > hippocampus. Our findings indicated that Sim-BDNF-Ps could effectively inhibit microglial-mediated inflammation as well as potentially resolve the neurotoxic microenvironment that is often associated with neuroinflammation.

Effect of pioglitazone and simvastatin in lipopolysaccharide-induced amyloidogenesis and cognitive impairment in mice: possible role of glutamatergic pathway and oxidative stress

Neuroinflammation and β-amyloid (Aβ) deposition in the brain are well known characteristics of neurodegeneration. Diabetes and hypercholesterolemia are the main risk factors leading to memory loss and cognitive impairment. Recently, it was found that statins and thiazolidinediones have promising anti-inflammatory and neuroprotective effects that could delay neurodegeneration and neuronal loss in diabetic and hypercholesterolemic patients. The aim of the present study was to investigate the protective effect of simvastatin, pioglitazone, and their combination in lipopolysaccharide (LPS)-induced neuroinflammation and amyloidogenesis. Mice were divided into five groups: group 1 received 0.9% saline, group 2 received LPS (0.8 mg/kg in saline), group 3 received LPS (0.8 mgl kg)+simvastatin (5 mg/kg in saline), group 4 received LPS (0.8 mg/kg)+pioglitazone (20 mg/kg in saline), group 5 receiving LPS (0.8 mg/kg)+simvastatin (5 mg/kg)+pioglitazone (20 mg/kg). Y-maze and novel object recognition were used to assess the spatial and nonspatial behavioral changes. Nitric oxide levels and glutamate levels were measured to elucidate the anti-glutamatergic and anti-inflammatory effects of the tested drugs. Immunohistochemistry was performed to detect the presence of Aβ1-42 in the mice brain. LPS impaired memory, and increased Aβ deposition, nitric oxide, and glutamate brain levels. Both drugs produced a significant improvement in all parameters. We conclude that simvastatin and pioglitazone may have a protective effect against cognitive impairment induced by LPS, through targeting the glutamatergic and inflammatory pathways, especially in patients having hypercholesterolemia and diabetes.

MicroRNA-124 regulates the expression of p62/p38 and promotes autophagy in the inflammatory pathogenesis of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder characterized by motor and nonmotor symptoms due to the selective loss of midbrain dopaminergic neurons. The evidence for a chronic inflammatory reaction mediated by microglial cells in the brain is particularly strong in PD. In our previous study, we have shown that brain-specific microRNA-124 (miR-124) is significantly down-regulated in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model of PD and that it can also inhibit neuroinflammation during the development of PD. However, further investigation is required to understand whether the abnormal expression of miR-124 regulates microglial activation. In this study, we found that the expression of sequestosome 1 (p62) and phospho-p38 mitogen-activated protein kinases (p-p38) showed a significant increase in LPS-treated immortalized murine microglial cell line BV2 cells in an MPTP-induced mouse model of PD. Knockdown of p62 could suppress the secretion of proinflammatory cytokines and p-p38 of microglia. Besides, inhibition of p38 suppressed the secretion of proinflammatory cytokines and promoted autophagy in BV2 cells. Moreover, our study is the first to identify a unique role of miR-124 in mediating the microglial inflammatory response by targeting p62 and p38 in PD. In the microglial culture supernatant transfer model, the knockdown of p62 in BV2 cells prevented apoptosis and death of human neuroblastoma cell lines SH-SY5Y (SH-SY5Y) cells following microglia activation. In addition, the exogenous delivery of miR-124 could suppress p62 and p-p38 expression and could also attenuate the activation of microglia in the substantia nigra par compacta of MPTP-treated mice. Taken together, our data suggest that miR-124 could inhibit neuroinflammation during the development of PD by targeting p62, p38, and autophagy, indicating that miR-124 could be a potential therapeutic target for regulating the inflammatory response in PD.-Yao, L., Zhu, Z., Wu, J., Zhang, Y., Zhang, H., Sun, X., Qian, C., Wang, B., Xie, L., Zhang, S., Lu, G. MicroRNA-124 regulates the expression of p62/p38 and promotes autophagy in the inflammatory pathogenesis of Parkinson's disease.

Simvastatin as a Potential Disease-Modifying Therapy for Patients with Parkinson's Disease: Rationale for Clinical Trial, and Current Progress

Many now believe the holy grail for the next stage of therapeutic advance surrounds the development of disease-modifying approaches aimed at intercepting the year-on-year neurodegenerative decline experienced by most patients with Parkinson’s disease (PD). Based on recommendations of an international committee of experts who are currently bringing multiple, potentially disease-modifying, PD therapeutics into long-term neuroprotective PD trials, a clinical trial involving 198 patients is underway to determine whether Simvastatin provides protection against chronic neurodegeneration. Statins are widely used to reduce cardiovascular risk, and act as competitive inhibitors of HMG-CoA reductase. It is also known that statins serve as ligands for PPARα, a known arbiter for mitochondrial size and number. Statins possess multiple cholesterol-independent biochemical mechanisms of action, many of which offer neuroprotective potential (suppression of proinflammatory molecules & microglial activation, stimulation of endothelial nitric oxide synthase, inhibition of oxidative stress, attenuation of α-synuclein aggregation, modulation of adaptive immunity, and increased expression of neurotrophic factors). We describe the biochemical, physiological and pharmaceutical credentials that continue to underpin the rationale for taking Simvastatin into a disease-modifying trial in PD patients. While unrelated to the Simvastatin trial (because this conducted in patients who already have PD), we discuss conflicting epidemiological studies which variously suggest that statin use for cardiovascular prophylaxis may increase or decrease risk of developing PD. Finally, since so few disease-modifying PD trials have ever been launched (compared to those of symptomatic therapies), we discuss the rationale of the trial structure we have adopted, decisions made, and lessons learnt so far.

An adverse outcome pathway for parkinsonian motor deficits associated with mitochondrial complex I inhibition

Epidemiological studies have observed an association between pesticide exposure and the development of Parkinson's disease, but have not established causality. The concept of an adverse outcome pathway (AOP) has been developed as a framework for the organization of available information linking the modulation of a molecular target [molecular initiating event (MIE)], via a sequence of essential biological key events (KEs), with an adverse outcome (AO). Here, we present an AOP covering the toxicological pathways that link the binding of an inhibitor to mitochondrial complex I (i.e., the MIE) with the onset of parkinsonian motor deficits (i.e., the AO). This AOP was developed according to the Organisation for Economic Co-operation and Development guidelines and uploaded to the AOP database. The KEs linking complex I inhibition to parkinsonian motor deficits are mitochondrial dysfunction, impaired proteostasis, neuroinflammation, and the degeneration of dopaminergic neurons of the substantia nigra. These KEs, by convention, were linearly organized. However, there was also evidence of additional feed-forward connections and shortcuts between the KEs, possibly depending on the intensity of the insult and the model system applied. The present AOP demonstrates mechanistic plausibility for epidemiological observations on a relationship between pesticide exposure and an elevated risk for Parkinson's disease development.

Licochalcone A Prevents the Loss of Dopaminergic Neurons by Inhibiting Microglial Activation in Lipopolysaccharide (LPS)-Induced Parkinson's Disease Models

The neuroprotective effects of Licochalcone A (Lico.A), a flavonoid isolated from the herb licorice, in Parkinson's disease (PD) have not been elucidated. The prominent pathological feature of PD is the loss of dopaminergic neurons. The crucial role of neuroinflammation induced by activated microglia in dopaminergic neurodegeneration has been validated. In this study, we explore the therapeutic effects of Lico.A in lipopolysaccharide (LPS)-induced PD models in vivo and in vitro. We find that Lico.A significantly inhibits LPS-stimulated production of pro-inflammatory mediators and microglial activation by blocking the phosphorylation of extracellular signal-regulated kinase (ERK1/2) and nuclear factor κB (NF-κB) p65 in BV-2 cells. In addition, through cultured primary mesencephalic neuron-glia cell experiments, we illustrate that Lico.A attenuates the decrease in [³H] dopamine (DA) uptake and the loss of tyrosine hydroxylase-immunoreactive (TH-ir) neurons in LPS-induced PD models in vitro. Furthermore, LPS intoxication in rats results in microglial activation, dopaminergic neurodegeneration and significant behavioral deficits in vivo. Lico.A treatment prevents microglial activation and reduction of dopaminergic neuron and ameliorates PD-like behavioral impairments. Thus, these results demonstrate for the first time that the neuroprotective effects of Lico.A are associated with microglia and anti-inflammatory effects in PD models.

The beneficial effects of HMG-CoA reductase inhibitors in the processes of neurodegeneration

Statins, cholesterol lowering drugs, have been demonstrated to exert beneficial effects in other conditions such as primary and progressing neurodegenerative diseases beyond their original role. Observation that statins ameliorate the neurodegenerative diseases such as Parkinson's disease (PD), Alzheimer's disease (AD), multiple sclerosis (MS) and cerebral ischemic stroke, the neuroprotective effects of these drugs are thought to be linked to their anti-inflammatory, anti-oxidative, and anti-excitotoxic properties. Despite the voluminous literature on the clinical advantages of 3-hydroxy-3-methylglutaryl Co-enzyme A reductase (HMGCR) inhibitors (statins) in cardiovascular system, the neuroprotective effects and the underlying mechanisms are little understood. Hence, the present review tries to provide a critical overview on the statin-induced neuroprotection, which are presumed to be associated with the ability to reduce cholesterol, Amyloid-β and apolipoprotein E (ApoE) levels, decrease reactive oxygen and nitrogen species (ROS and RNS) formation, inhibit excitotoxicity, modulate matrix metalloproteinases (MMPs), stimulate endothelial nitric oxide synthase (eNOS), and increase cerebral blood perfusion. This review is also aimed to illustrate that statins protect neurons against the neuro-inflammatory processes through balancing pro-inflammatory/anti-inflammatory cytokines. Ultimately, the beneficial role of statins in ameliorating the development of PD, AD, MS and cerebral ischemic stroke has been separately reviewed.

Current insights into pathogenesis of Parkinson's disease: Approach to mevalonate pathway and protective role of statins

Although Parkinson's disease (PD) is considered as the second most common life threatening age-related neurodegenerative disorder, but the underlying mechanisms for pathogenesis of PD are remained to be fully found. However, a complex relationship between genetic and environmental predisposing factors are involved in progression of PD. Dopaminergic neuronal cell death caused by mutations and accumulation of α-synuclein in Lewy bodies and neurites was suggested as the main strategy for PD, but current studies have paid attention to the role of mevalonate pathway in incidence of neurodegenerative diseases including PD. The discovery may change the therapeutic protocols from symptomatic treatment by dopamine precursors and agonists to neurodegenerative process halting drugs. Moreover, the downstream metabolites of mevalonate pathway may be used as diagnostic biomarkers for early diagnosis of PD. Statins, as cholesterol lowering drugs, may ameliorate the enzyme complex dysfunction, a key step in the progression of the neurodegenerative disorders, oxidative stress-induced damage and neuro-inflammation. Statins exert the neuroprotective effects on striatal dopaminergic neurons through blocking the mevalonate pathway. In the present review, we have focused on the new approaches to pathogenesis of PD regarding to mevalonate pathway, in addition to the previous understood mechanisms for the disease. It tries to elucidate the novel findings about PD for the development of future diagnostic and therapeutic strategies. Moreover, we explain the controversial role of statins in improvement or progression of PD and the position of these drugs in neuroprotection in PD patients.

Simvastatin adjunct therapy for negative symptoms of schizophrenia: a randomized double-blind placebo-controlled trial

We investigated the effects of simvastatin adjunctive therapy on the negative symptoms of schizophrenia. In this double-blind trial, inpatients with chronic schizophrenia were clinically stabilized on a constant dose of risperidone for at least 4 weeks before the study and were then randomized to receive risperidone (4-6 mg/day) plus either simvastatin (40 mg/day) (n=33) or placebo (n=33) for 8 weeks. The Positive and Negative Syndrome Scale was used to measure the negative, positive, and general symptoms of schizophrenia at baseline and every 2 weeks. The Hamilton Depression Rating Scale and the Extrapyramidal Symptom Rating Scale were used to measure depression and extrapyramidal symptoms at baseline and week 8. Difference in change in negative symptoms score from the baseline to week 8 was considered the single primary outcome. At baseline, negative symptoms scores were higher than positive symptoms scores in both simvastatin and placebo groups. There was no baseline difference between the two groups in terms of any of the measured variables. Compared with the placebo group, the simvastatin group showed a significantly higher reduction in negative symptoms scores from baseline to week 8 [mean difference: 95% confidence interval=-1.42 (-2.32 to -0.52), P=0.003]. Similar findings were observed for total scores [mean difference: 95% confidence interval=-1.85 (-2.87 to -0.83), P=0.001]. The results were not significant for positive symptoms or general psychopathology scores. We found a favorable effect of simvastatin on negative symptoms of patients with schizophrenia; however, future studies are warranted to confirm these results.

Sex Differences in Microglia Activity within the Periaqueductal Gray of the Rat: A Potential Mechanism Driving the Dimorphic Effects of Morphine

Although morphine remains the primary drug prescribed for alleviation of severe or persistent pain, both preclinical and clinical studies have shown that females require two to three times more morphine than males to produce comparable levels of analgesia. In addition to binding to the neuronal μ-opioid receptor, morphine binds to the innate immune receptor toll-like receptor 4 (TLR4) localized primarily on microglia. Morphine action at TLR4 initiates a neuroinflammatory response that directly opposes the analgesic effects of morphine. Here, we test the hypothesis that the attenuated response to morphine observed in females is the result of increased microglia activation in the periaqueductal gray (PAG), a central locus mediating the antinociceptive effects of morphine. We report that, whereas no overall sex differences in the density of microglia were noted within the PAG of male or female rats, microglia exhibited a more "activated" phenotype in females at baseline, with the degree of activation a significant predictor of morphine half-maximal antinociceptive dose (ED₅₀) values. Priming microglia with LPS induced greater microglia activation in the PAG of females compared with males and was accompanied by increased transcription levels of IL-1β and a significant rightward shift in the morphine dose-response curve. Blockade of morphine binding to PAG TLR4 with (+)-naloxone potentiated morphine antinociception significantly in females such that no sex differences in ED₅₀ were observed. These results demonstrate that PAG microglia are sexually dimorphic in both basal and LPS-induced activation and contribute to the sexually dimorphic effects of morphine in the rat.SIGNIFICANCE STATEMENT We demonstrate that periaqueductal gray (PAG) microglia contribute to the sexually dimorphic effects of morphine. Specifically, we report that increased activation of microglia in the PAG contributes to the attenuated response to morphine observed in females. Our data further implicate the innate immune receptor toll-like receptor 4 (TLR4) as an underlying mechanism mediating these effects and establish that TLR4 inhibition in the PAG of females reverses the sex differences in morphine responsiveness. These data suggest novel methods to improve current opioid-based pain management via inhibition of glial TLR4 and illustrate the necessity for sex-specific research and individualized treatment strategies for the management of pain in men and women.

Clk1 deficiency promotes neuroinflammation and subsequent dopaminergic cell death through regulation of microglial metabolic reprogramming

Clock (Clk)1/COQ7 is a mitochondrial hydroxylase that is necessary for the biosynthesis of ubiquinone (coenzyme Q or UQ). Here, we investigate the role of Clk1 in neuroinflammation and consequentially dopaminergic (DA) neuron survival. Reduced expression of Clk1 in microglia enhanced the LPS-induced proinflammatory response and promoted aerobic glycolysis. Inhibition of glycolysis abolished Clk1 deficiency-induced hypersensitivity to the inflammatory stimulation. Mechanistic studies demonstrated that mTOR/HIF-1α and ROS/HIF-1α signaling pathways were involved in Clk1 deficiency-induced aerobic glycolysis. The increase in neuronal cell death was observed following treatment with conditioned media from Clk1 deficient microglia. Increased DA neuron loss and microgliosis were observed in Clk1^+/- mice after treatment with MPTP, a rodent model of Parkinson's disease (PD). This increase in DA neuron loss was due to an exacerbated microglial inflammatory response, rather than direct susceptibility of Clk1^+/- DA cells to MPP⁺, the active species of MPTP. Exaggerated expressions of proinflammatory genes and loss of DA neurons were also observed in Clk1^+/- mice after stereotaxic injection of LPS. Our results suggest that Clk1 regulates microglial metabolic reprogramming that is, in turn, involved in the neuroinflammatory processes and PD.

Neuroimmune Interface in the Comorbidity between Alcohol Use Disorder and Major Depression

Bidirectional communication links operate between the brain and the body. Afferent immune-to-brain signals are capable of inducing changes in mood and behavior. Chronic heavy alcohol drinking, typical of alcohol use disorder (AUD), is one such factor that provokes an immune response in the periphery that, by means of circulatory cytokines and other neuroimmune mediators, ultimately causes alterations in the brain function. Alcohol can also directly impact the immune functions of microglia, the resident immune cells of the central nervous system (CNS). Several lines of research have established the contribution of specific inflammatory mediators in the development and progression of depressive illness. Much of the available evidence in this field stems from cross-sectional data on the immune interactions between isolated AUD and major depression (MD). Given their heterogeneity as disease entities with overlapping symptoms and shared neuroimmune correlates, it is no surprise that systemic and CNS inflammation could be a critical determinant of the frequent comorbidity between AUD and MD. This review presents a summary and analysis of the extant literature on neuroimmune interface in the AUD–MD comorbidity.

Involvement of PI3K/Akt/GSK-3β and mTOR in the antidepressant-like effect of atorvastatin in mice

Atorvastatin is a cholesterol-lowering statin that has been shown to exert several pleiotropic effects in the nervous system as a neuroprotective and antidepressant-like agent. Antidepressant-like effect of atorvastatin in mice is mediated by glutamatergic and serotoninergic receptors, although the precise intracellular signaling pathways involved are unknown. PI3K/Akt/GSK-3β/mTOR signaling pathway has been associated to neurobiology of depression and seems to be modulated by some pharmacological antidepressant strategies. The present study investigated the participation of the PI3K/Akt/GSK-3β/mTOR signaling pathway in the antidepressant-like effect of an acute atorvastatin treatment in mice. Atorvastatin sub-effective (0.01 mg/kg) or effective (0.1 mg/kg) doses in the tail suspension test (TST) was administered orally alone or in combination with PI3K, GSK-3β or mTOR inhibitors. The administration of PI3K inhibitor, LY294002 (10 nmol/site, i.c.v) completely prevented the antidepressant-like effect of atorvastatin (0.1 mg/kg, p.o.). The participation of GSK-3β in the antidepressant-like effect of atorvastatin was demonstrated by co-administration of a sub-effective dose of atorvastatin (0.01 mg/kg, p.o.) with AR-A014418 (0.01 μg/site, i.c.v., a selective GSK-3β inhibitor) or with lithium chloride (10 mg/kg, p.o., a non-selective GSK-3β inhibitor). The mTOR inhibitor, rapamycin (0.2 nmol/site, i.c.v.) was also able to prevent atorvastatin (0.1 mg/kg, p.o.) antidepressant-like effect. These behavioral findings were supported by neurochemical observations, as atorvastatin treatment increased the immunocontent of the phosphorylated isoforms of Akt, GSK-3β and mTOR in the hippocampus of mice. Taken together, our results suggest an involvement of the PI3K/Akt/GSK-3β/mTOR signaling pathway in the antidepressant-like effect of atorvastatin in mice.

In vitro 6-hydroxydopamine-induced toxicity in striatal, cerebrocortical and hippocampal slices is attenuated by atorvastatin and MK-801

Parkinson's disease (PD) involves the loss of striatal dopaminergic neurons, although other neurotransmitters and brain areas are also involved in its pathophysiology. In rodent models to PD it has been shown statins improve cognitive and motor deficits and attenuate inflammatory responses evoked by PD-related toxins. Statins are the drugs most prescribed to hypercholesterolemia, but neuroprotective effects have also been attributed to statins treatment in humans and in animal models. This study aimed to establish an in vitro model of 6-hydroxydopamine (6-OHDA)-induced toxicity, used as an initial screening test to identify effective drugs against neural degeneration related to PD. The putative neuroprotective effect of atorvastatin against 6-OHDA-induced toxicity in rat striatal, cerebrocortical and hippocampal slices was also evaluated. 6-OHDA (100μM) decreased cellular viability in slices obtained from rat cerebral cortex, hippocampus and striatum. 6-OHDA also induced an increased reactive oxygen species (ROS) production and mitochondrial dysfunction. Co-incubation of 6-OHDA with atorvastatin (10μM) or MK-801 (50μM) an N-methyl-d-aspartate (NMDA) receptor antagonist, partially attenuated the cellular damage evoked by 6-OHDA in the three brain areas. Atorvastatin partially reduced ROS production in the hippocampus and striatum and disturbances of mitochondria membrane potential in cortex and striatum. 6-OHDA-induced toxicity in vitro displays differences among the brain structures, but it is also observed in cerebrocortical and hippocampal slices, besides striatum.

Simvastatin inhibits the expression of inflammatory cytokines and cell adhesion molecules induced by LPS in human dental pulp cells

AIM

To investigate the effect of simvastatin on lipopolysaccharide (LPS)-stimulated inflammatory cytokines, cell adhesion molecules and nuclear factor-κB (NF-κB) transcription factors in human dental pulp cells (HDPCs).

METHODOLOGY

The effect of LPS and simvastatin on human dental pulp cell (HDPCs) viability was measured using a 3-[4, 5-dimethylthiazol-2-yl]-2, 5 diphenyltetrazolium bromide (MTT) assay. The expression of inflammatory cytokines and cell adhesion molecules was evaluated by reverse-transcription polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA) and Western blot analysis. NF-κB transcription factors were evaluated by Western blot analysis. Statistical analysis was performed with analysis of variance (anova).

RESULTS

The viability of cells exposed to different concentrations of E. coli LPS, P. gingivalis LPS and simvastatin was not significantly different compared with that of control cells (P > 0.05). LPS significantly increased interleukin (IL)-1β (P < 0.05) and IL-6 mRNA expression (P < 0.05) and vascular cell adhesion molecule-1 (VCAM-1) (P < 0.05) and intercellular adhesion molecule-1 (ICAM-1) protein expression (P < 0.05) in HDPCs. Treatment with simvastatin significantly attenuated LPS-stimulated production of IL-1β, IL-6, VCAM-1 and ICAM-1 (P < 0.05). Treatment with simvastatin decreased LPS-induced expression of p65 and phosphorylation of IκB and also significantly decreased the phosphorylation of p65 and IκB in the cytoplasm and the level of p65 in the nucleus (P < 0.05).

CONCLUSIONS

Simvastatin has a suppressing effect on LPS-induced inflammatory cytokine, cell adhesion molecules and NF-κB transcription factors in HDPCs. Therefore, simvastatin might be a useful candidate as a pulp-capping agent in vital pulp therapy.

Antioxidant effect of simvastatin throught oxidative imbalance caused by lisdexamfetamine dimesylate

The present study aims to directly investigate the behavioral and antioxidant effects of simvastatin in a model of bipolar mania induced by lisdexamfetamine dimesylate. Wistar rats were treated for 30 days with simvastatin. On the 24th day after the start of treatment, each rat was administered lisdexamfetamine dimesylate for 7 days. The results suggest that simvastatin combined with lisdexamfetamine dimesylate induced a significant increased locomotion and lisdexamfetamine dimesylate administration causes an oxidative imbalance determined by an increment in lipid peroxidation, protein oxidation and alterations in the activities of antioxidant enzymes in brain areas; moreover, in the presence of simvastatin, most of these effects were prevented. These findings contribute to a better understanding of the critical roles of lisdexamfetamine dimesylate in the treatment of neuropsychiatric disorders, associated with increased oxidative stress and changes in antioxidant enzymatic defense. In view of the central role played by lisdexamfetamine dimesylate, the established antioxidant effect of simvastatin therapy is of major interest.

Glucocorticoid receptor is involved in the neuroprotective effect of ginsenoside Rg1 against inflammation-induced dopaminergic neuronal degeneration in substantia nigra

Accumulating clinical and experimental evidence suggests that chronic neuroinflammation is associated with dopaminergic neuronal death in Parkinson's disease (PD). Ginsenoside Rg1, the most active components of ginseng, possesses a variety of biological effects on the central nervous system, cardiovascular system and immune system. The present study aimed to evaluate the protective effects of ginsenoside Rg1 on lipopolysaccharide (LPS)-induced microglia activation and dopaminergic neuronal degeneration in rat substantia nigra (SN) and its potential mechanisms. Treatment with Rg1 could ameliorate the apomorphine-induced rotational behavior in LPS-lesioned rats. GR antagonist RU486 partly abolished the protective effect of Rg1. Rg1 treatment significantly attenuated LPS-induced loss of tyrosin hydroxlase (TH) positive neurons in substantial nigra par compacta (SNpc) and decreased content of dopamine (DA) and its metabolites in striatum of the lesioned side. Meanwhile, Rg1 significantly inhibited LPS-induced microglial activation and production of tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β) and nitric oxide (NO). These effects were abolished by co-treatment with RU486. In addition, Rg1 treatment significantly inhibited the LPS-induced phosphorylation of IκB, extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal protein kinase (JNK) and p38 mitogen-activated protein kinase (p38 MAPK) in the lesioned side of substantial nigra. These effect could be also partly blocked by RU486. Taken together, these data indicate that Rg1 has protective effects on mesencephalic dopaminergic neurons from LPS-induced microglia inflammation. GR signaling pathway might be involved in the anti-inflammatory effect of Rg1.

Biochanin A protects dopaminergic neurons against lipopolysaccharide-induced damage and oxidative stress in a rat model of Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease, which is characterized by loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). Accumulated evidences have suggested that oxidative stress is closely associated with the dopaminergic neurodegeneration of PD that can be protected by antioxidants. Biochanin A that is an O-methylated isoflavone in chickpea is investigated to explore its protective mechanism on dopaminergic neurons of the unilateral lipopolysaccharide (LPS)-injected rat. The results showed that biochanin A significantly improved the animal model's behavioral symptoms, prevented the loss of dopaminergic neurons and inhibited the deleterious microglia activation in the LPS-induced rats. Moreover, biochanin A inhibited nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase) activation and malondialdehyde (MDA) production, increased superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in the rat brain. These results suggested that biochanin A might be a natural candidate with protective properties on dopaminergic neurons against the PD.

Relevance of chronic stress and the two faces of microglia in Parkinson's disease

This review is aimed to highlight the importance of stress and glucocorticoids (GCs) in modulating the inflammatory response of brain microglia and hence its potential involvement in Parkinson’s disease (PD). The role of inflammation in PD has been reviewed extensively in the literature and it is supposed to play a key role in the course of the disease. Historically, GCs have been strongly associated as anti-inflammatory hormones. However, accumulating evidence from the peripheral and central nervous system have clearly revealed that, under specific conditions, GCs may promote brain inflammation including pro-inflammatory activation of microglia. We have summarized relevant data linking PD, neuroinflamamation and chronic stress. The timing and duration of stress response may be critical for delineating an immune response in the brain thus probably explain the dual role of GCs and/or chronic stress in different animal models of PD.

Apocyanin, a Microglial NADPH Oxidase Inhibitor Prevents Dopaminergic Neuronal Degeneration in Lipopolysaccharide-Induced Parkinson's Disease Model

Microglia-associated inflammatory processes have been strongly implicated in the development and progression of Parkinson's disease (PD). Specifically, microglia are activated in response to lipopolysaccharide (LPS) and become chronic source of cytokines and reactive oxygen species (ROS) production. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex is responsible for extracellular as well as intracellular production of ROS by microglia and its expression is upregulated in PD. Therefore, targeting NADPH oxidase complex activation using an NADPH oxidase inhibitor, i.e., apocyanin seems to be an effective approach. The aim of present study was to investigate the neuroprotective effects of apocyanin in a LPS-induced PD model. LPS (5 μg) was injected intranigral and apocyanin was administered daily at a dose of 10 mg/kg b.wt (i.p.) during the experiment. LPS when injected into the substantia nigra (SN) reproduced the characteristic hallmark features of PD in rats. It elicited an inflammatory response characterized by glial cell activation (Iba-1, GFAP). Furthermore, LPS upregulated the gene expression of nuclear factor-κB (NFκB), iNOS, and gp91PHOX and resulted in an elevated total ROS production as well as NADPH oxidase activity. Subsequently, this resulted in dopaminergic loss as depicted by decreased tyrosine hydroxylase (TH) expression with substantial loss in neurotransmitter dopamine and its metabolites, whereas treatment with apocyanin significantly reduced the number of glial fibrillary acidic protein (GFAP) and Iba-1-positive cells in LPS-treated animals. It also mitigated microglial activation-induced inflammatory response and elevation in NADPH oxidase activity, thus reducing the extracellular as well as intracellular ROS production. The present study indicated that targeting NADPH oxidase can inhibit microglial activation and reduce a broad spectrum of toxic factors generation (i.e., cytokines, ROS, and reactive nitrogen species [RNS]), thus offering a hope in halting the progression of PD.

Effects of simvastatin on the expression of inducible nitric oxide synthase and brain-derived neurotrophic factor in a lipopolysaccharide-induced rat model of Parkinson disease

OBJECTIVE

To investigate the effects of simvastatin on the expression of inducible nitric oxide synthase (iNOS) and brain-derived neurotrophic factor (BDNF) in the substantia nigra in a lipopolysaccharide (LPS)-induced rat model of Parkinson disease (PD), and to study the mechanisms underlying the neuroprotective effects of simvastatin in PD.

METHODS

The LPS-PD model was established by injection of LPS (5 mg/mL, 2.0 μL) into the right substantia nigra compacta (SNC). Rats in the sham-operated group received saline. The simvastatin treatment group was intraperitoneally administered simvastatin (5 mg/kg, 2.0 μL) at 1 h before, and daily for 14 days after surgery, while the sham-operated and LPS-model groups received saline. Iba-1-positive cells and tyrosine hydroxylase (TH), as well as iNOS and BDNF in the SNC were detected by immunohistochemistry and Western blotting, respectively. The effect of simvastatin in the PD model was also examined in behavioral tests.

RESULTS

The LPS-model group exhibited typical animal PD behaviors. Compared with the control group, the LPS-model group exhibited a decreased number of DA neurons (p < 0.01) in the SNC, as well as increases in the Iba-1-positive cell number and iNOS expression (p < 0.05), while BDNF expression was downregulated (p < 0.01). These effects were inhibited by simvastatin treatment (p < 0.05).

CONCLUSION

Simvastatin mediates a protective effect on dopaminergic neurons in the SNC in the LPS-PD model, possibly by promoting neuronal repair and regeneration, and by inhibiting oxidative stress, thus improving substantia nigra function.

Parkinson's disease and enhanced inflammatory response

Parkinson's disease (PD) is the first and second most prevalent motor and neurodegenerative disease, respectively. The clinical symptoms of PD result from a loss of midbrain dopaminergic (DA) neurons. However, the molecular cause of DA neuron loss remains elusive. Mounting evidence implicates enhanced inflammatory response in the development and progression of PD pathology. This review examines current research connecting PD and inflammatory response.

Anti-inflammatory effects of BHBA in both in vivo and in vitro Parkinson's disease models are mediated by GPR109A-dependent mechanisms

BACKGROUND

Accumulating evidence suggests that neuroinflammation plays an important role in the progression of Parkinson's disease (PD). Excessively activated microglia produce several pro-inflammatory enzymes and pro-inflammatory cytokines, leading to damage to surrounding neurons and eventually inducing neurodegeneration. Therefore, the inhibition of microglial overactivation may be a potential therapeutic strategy to prevent the further progression of PD. β-Hydroxybutyric acid (BHBA) has been shown to suppress lipopolysaccharide (LPS)-induced inflammation in BV-2 cells and to protect dopaminergic neurons in previous studies, but the underlying mechanisms remain unclear. Thus, in this study, we further investigated this mechanism in LPS-induced in vivo and in vitro PD models.

METHODS

For the in vitro experiments, primary mesencephalic neuron-glia cultures were pretreated with BHBA and stimulated with LPS. [(3)H]dopamine (DA) uptake, tyrosine hydroxylase-immunoreactive (TH-ir) neurons and morphological analysis were evaluated and analyzed in primary mesencephalic neuron-glia cultures. In vivo, microglial activation and the injury of dopaminergic neurons were induced by LPS intranigral injection, and the effects of BHBA treatment on microglial activation and the survival ratio and function of dopaminergic neurons were investigated. Four our in vitro mechanistic experiment, primary microglial cells were pretreated with BHBA and stimulated with LPS; the cells were then assessed for the responses of pro-inflammatory enzymes and pro-inflammatory cytokines, and the NF-κB signaling pathway was evaluated and analyzed.

RESULTS

We found that BHBA concentration-dependently attenuated the LPS-induced decrease in [(3)H]DA uptake and loss of TH-ir neurons in the primary mesencephalic neuron/glia mixed culture. BHBA treatment significantly improved the motor dysfunction of the PD model rats induced by intranigral injection of LPS, and this beneficial effect of BHBA was attributed to the inhibition of microglial overactivation and the protection of dopaminergic neurons in the substantia nigra (SN). Our in vitro mechanistic study revealed that the inhibitory effect of BHBA on microglia was mediated by G-protein-coupled receptor 109A (GPR109A) and involved the NF-κB signaling pathway, causing the inhibition of pro-inflammatory enzyme (iNOS and COX-2) and pro-inflammatory cytokine (TNF-α, IL-1β, and IL-6) production.

CONCLUSIONS

In conclusion, the present study supports the effectiveness of BHBA in protecting dopaminergic neurons against inflammatory challenge.

Neuroinflammation in Parkinson's disease animal models: a cell stress response or a step in neurodegeneration?

The motor symptoms of Parkinson's disease are due to the progressive degeneration of dopaminergic neurons in the substantia nigra. Multiple neuroinflammatory processes are exacerbated in Parkinson's disease, including glial-mediated reactions, increased expression of proinflammatory substances, and lymphocytic infiltration, particularly in the substantia nigra. Neuroinflammation is also implicated in the neurodegeneration and consequent behavioral symptoms of many Parkinson's disease animal models, although it is not clear whether these features emulate pathogenic steps in the genuine disorder or if some inflammatory features provide protective stress responses. Here, we compare and summarize findings on neuroinflammatory responses and effects on behavior in a wide range of toxin-based, inflammatory and genetic Parkinson's disease animal models.

The ongoing pursuit of neuroprotective therapies in Parkinson disease

Many agents developed for neuroprotective treatment of Parkinson disease (PD) have shown great promise in the laboratory, but none have translated to positive results in patients with PD. Potential neuroprotective drugs, such as ubiquinone, creatine and PYM50028, have failed to show any clinical benefits in recent high-profile clinical trials. This 'failure to translate' is likely to be related primarily to our incomplete understanding of the pathogenic mechanisms underlying PD, and excessive reliance on data from toxin-based animal models to judge which agents should be selected for clinical trials. Restricted resources inevitably mean that difficult compromises must be made in terms of trial design, and reliable estimation of efficacy is further hampered by the absence of validated biomarkers of disease progression. Drug development in PD dementia has been mostly unsuccessful; however, emerging biochemical, genetic and pathological evidence suggests a link between tau and amyloid-β deposition and cognitive decline in PD, potentially opening up new possibilities for therapeutic intervention. This Review discusses the most important 'druggable' disease mechanisms in PD, as well as the most-promising drugs that are being evaluated for their potential efficiency in treatment of motor and cognitive impairments in PD.

Lovastatin for the adjunctive treatment of schizophrenia: a preliminary randomized double-blind placebo-controlled trial

While statins target many of the pathways to neuroprogression in schizophrenia, the safety and efficacy of statins for treating schizophrenia has never been examined. This is an 8-week randomized double blind controlled clinical trial examining the efficacy and safety of adjunctive lovastatin (20 mg/day) treatment or placebo for people with schizophrenia. The baseline characteristics of the two groups were not different. Endpoint changes in Positive and Negative Syndrome Scale (PANSS) total and subscale scores did not differ between the two groups. However there was a significant difference between the doses of risperidone used in the two groups. The mean dose in the lovastatin and placebo groups were 4.8(1.8) and 3.4(1.4) mg/day, respectively (P<.03). No serious adverse events were reported. Slowness of movements, muscle rigidity, increased appetite, and decreased energy were the most common adverse effects, and these rates did not differ between the two groups. This study failed to demonstrate a benefit of lovastatin on symptoms of schizophrenia. This combination was well tolerated. However, a higher dosage of risperidone was used for treating the disorder in those taking concomitant lovastatin compared to placebo.

Augmentation of fluoxetine with lovastatin for treating major depressive disorder, a randomized double-blind placebo controlled-clinical trial

BACKGROUNDS

There are contradictory evidence about the effect of statins on depression. This 6-week-randomized placebo-controlled clinical trial assessed the efficacy and safety of lovastatin as an adjuvant agent for treating major depressive disorder (MDD).

METHODS

The participants were 68 patients with MDD according to DSM-IV diagnostic criteria. The sample was randomly allocated into fluoxetine (up to 40 mg/day) plus lovastatin (30 mg/day) group or fluoxetine plus placebo group. Hamilton Depression Rating scale was used to measure depression score at baseline, week 2, and week 6.

RESULTS

Both groups showed a significant decrease of depression score on the Hamilton Depression scale. However, the treatment group decreased depression score more than placebo group [12.8(6.3) vs. 8.2(4.0), t = 3.4, df = 60, P < .001]. Any serious adverse effect was not found.

DISCUSSION

These results suggest that lovastatin as an adjuvant treatment may be effective for treating patients with MDD.

Blockade of Toll-like receptor 4 attenuates morphine tolerance and facilitates the pain relieving properties of morphine

The ventrolateral periaqueductal gray (vlPAG) is an integral locus for morphine action. Although it is clear that glia contribute to the development of morphine tolerance, to date, the investigation of their role has been limited to spinal and medullary loci. Opioids induce a neuroinflammatory response that opposes acute and long-term analgesia, thereby limiting their efficacy as therapeutic agents. Recent data suggest that the innate immune receptor Toll-like receptor 4 (TLR4), along with its coreceptor myeloid differentiation factor-2 (MD-2), mediates these effects. To date, the brain loci through which TLR4 modulates morphine tolerance have not been identified. We have previously demonstrated that chronic subcutaneous morphine results in tolerance that is accompanied by increases in vlPAG glial cell activity. Using in vivo pharmacological manipulations of vlPAG glia and TLR4 in the adult male rat, we show that intra-vlPAG administration of the general glial cell metabolic inhibitor propentofylline or the astrocyte activity inhibitor fluorocitrate attenuate tolerance to morphine. Characterization of MD-2 expression within the PAG revealed dense MD-2 expression throughout the vlPAG. Further, antagonizing vlPAG TLR4 dose dependently prevented the development of morphine tolerance, and vlPAG microinjections of TLR4 agonists dose dependently produced a "naive" tolerance to subsequent challenge doses of morphine. Finally, using a model of persistent inflammatory pain and pharmacological manipulation of TLR4 we demonstrate that systemic antagonism of TLR4 potentiated acute morphine antihyperalgesia. These results, together, indicate that vlPAG glia regulate morphine tolerance development via TLR4 signaling, and implicate TLR4 as a potential therapeutic target for the treatment of pain.