Neuroprotective effects of pramipexole transdermal patch in the MPTP-induced mouse model of Parkinson's disease

Treating activated regulatory T cells with pramipexole protects human dopaminergic neurons from 6-OHDA-induced degeneration

BACKGROUND

Parkinson's disease (PD) is a chronic neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra, which promotes a sustained inflammatory environment in the central nervous system. Regulatory T cells (Tregs) play an important role in the control of inflammation and might play a neuroprotective role. Indeed, a decrease in Treg number and function has been reported in PD. In this context, pramipexole, a dopaminergic receptor agonist used to treat PD symptoms, has been shown to increase peripheral levels of Treg cells and improve their suppressive function. The aim of this work was to determine the effect of pramipexole on immunoregulatory Treg cells and its possible neuroprotective effect on human dopaminergic neurons differentiated from human embryonic stem cells.

METHODS

Treg cells were sorted from white blood cells of healthy human donors. Assays were performed with CD3/CD28-activated and non-activated Treg cells treated with pramipexole at concentrations of 2 or 200 ng/mL. These regulatory cells were co-cultured with in vitro-differentiated human dopaminergic neurons in a cytotoxicity assay with 6-hydroxydopamine (6-OHDA). The role of interleukin-10 (IL-10) was investigated by co-culturing activated IL-10-producing Treg cells with neurons. To further investigate the effect of treatment on Tregs, gene expression in pramipexole-treated, CD3/CD28-activated Treg cells was determined by Fluidigm analysis.

RESULTS

Pramipexole-treated CD3/CD28-activated Treg cells showed significant protective effects on dopaminergic neurons when challenged with 6-OHDA. Pramipexole-treated activated Treg cells showed neuroprotective capacity through mechanisms involving IL-10 release and the activation of genes associated with regulation and neuroprotection.

CONCLUSION

Anti-CD3/CD28-activated Treg cells protect dopaminergic neurons against 6-OHDA-induced damage. In addition, activated, IL-10-producing, pramipexole-treated Tregs also induced a neuroprotective effect, and the supernatants of these co-cultures promoted axonal growth. Pramipexole-treated, activated Tregs altered their gene expression in a concentration-dependent manner, and enhanced TGFβ-related dopamine receptor regulation and immune-related pathways. These findings open new perspectives for the development of immunomodulatory therapies for the treatment of PD.

Enhancing selegiline hydrochloride efficacy: Box Behnken-optimized liposomal delivery via intranasal route for Parkinson's disease intervention

The clinical use of selegiline hydrochloride in conventional dosage forms is to reduce the progression of Parkinson's disease (PD). However, its limited access to the brain, short half-life, and first-pass metabolism minimize brain uptake. Nano-based liposomes offer promising tools for brain-targeted delivery of therapeutics, especially intranasally administered cationic liposomes that target the brain region via the olfactory route and reduce biodistribution. In the present work, cationic liposomes encapsulated with selegiline hydrochloride were fabricated for intranasal administration against PD. The liposomes were initially optimized by Box Behnken design, and the selected run was coated with stearylamine to provide a cationic charge to the liposomes. The final coated liposomes, SH-LP3, demonstrated a minimum size of 173 ± 2.13 nm, an ideal zeta potential of +16 ± 1.98, and achieved a maximum entrapment efficiency of 40.14 ± 1.83%. Morphology analysis showed the spherical shape of liposomes in the size range of 100-200 nm. The in vitro cytotoxicity assay in SHSY5Y cell lines showed a significant decrease in toxicity, almost ten times less, compared to pure selegiline hydrochloride. Animal studies on rotenone-lesioned C57BL6 mice model for PD were performed to investigate the effect of intranasally administered liposomes. The SH-LP3 formulation exhibited remarkable effectiveness in relieving symptoms of PD. This extensive analysis emphasizes the possibility of intranasally administered SH-LP3 liposomes as a feasible treatment option for PD. The formulation not only delivers continuous drug release but also displays better safety and efficacy, providing a platform for additional studies and growth in the domain of PD treatment.

Pramipexole protects against diabetic neuropathy: Effect on oxidative stress, TLR4/IRAK-1/TRAF-6/NF-κB and downstream inflammatory mediators

BACKGROUND

Diabetic neuropathy (DN) is a serious microvascular complication and a major cause of morbidity and mortality in diabetes mellitus. It is characterized by neurodegeneration of terminal sensory nerve fibers with subsequent pain, loss of sensation, and paresthesia, thus compromising the quality of life of diabetic patients. It is considered the leading cause of non-traumatic amputations worldwide, reflecting the insufficiency of current therapies. Pramipexole (PPX) is a dopamine receptor agonist used for the treatment of Parkinson's disease. The current study aims to investigate the potential neuroprotective effect of PPX in an experimental model of DN.

METHODS

Sprague Dawley rats were randomly assigned into five groups: normal control, Normal + PPX (1 mg/kg) group, STZ control, STZ + PPX (0.25 and 1 mg/kg/day for eight weeks). The neuroprotective effect of PPX in rats was evaluated in terms of sciatic nerve histological alterations, oxidative stress, and protein expression of TLR4/MyD88/IRAK-1/TRAF-6/NF-κB axis and downstream inflammatory mediators.

RESULTS

PPX administration ameliorated histopathological signs of neuronal inflammation and apoptosis. Additionally, PPX attenuated STZ-induced sciatic nerve oxidative stress and downregulated neural tissue expression of TLR4, MyD88, IRAK-1, TRAF-6, NF-κB and downstream mediators (TNF-α, IL-1β and ICAM-1).

CONCLUSION

Collectively, the current study sheds light on PPX as a potential protective medication to alleviate neuropathy progression in diabetic patients. PPX neuroprotective effect can be attributed to modulating TLR4/ MyD88/IRAK-1/TRAF-6/ NF-κB axis signaling in nerve tissues with subsequent attenuation of oxidative stress and inflammation.

Quantification of Non-Motor Symptoms in Parkinsonian Cynomolgus Monkeys

BACKGROUND

Parkinson's disease (PD) is a neurodegenerative disorder that features motor and non-motor deficits. The use of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopamine neuron degeneration has been widely practiced to produce reliable animal models of PD. However, most previous preclinical studies focused on motor dysfunction, and few non-motor symptoms were evaluated. Thus far, there is a lack of comprehensive investigations of the non-motor symptoms in animal models.

OBJECTIVES

In this study, we aim to use a battery of behavioral methods to evaluate non-motor symptoms in MPTP-induced non-human primate PD models.

METHODS

Cognitive function, sleep, and psychiatric behaviors were evaluated in MPTP-treated cynomolgus monkeys. The tests consisted of a delayed matching-to-sample (DMTS) task, the use of a physical activity monitor (PAM), an apathy feeding task (AFT), the human intruder test (HIT), novel fruit test (NFT), and predator confrontation test (PCT). In addition, we tested whether the dopamine receptor agonist pramipexole (PPX) can improve these non-motor symptoms.

RESULTS

The present results show that the MPTP-treated monkeys exhibited cognitive deficits, abnormal sleep, and anxiety-like behaviors when compared to the control monkeys. These symptoms were relieved partially by PPX.

CONCLUSIONS

These results suggest that MPTP-induced PD monkeys displayed non-motor symptoms that were similar to those found in PD patients. PPX treatment showed moderate therapeutic effects on these non-motor symptoms. This battery of behavioral tests may provide a valuable model for future preclinical research.

Role of dopamine agonists in Parkinson's disease therapy

Dopamine agonists are an important component of Parkinson's therapy. When weighing up the various therapy options, therapy with levodopa has recently been increasingly preferred due to its stronger efficacy and the ostensibly lower rate of side effects. The advantage of the lower incidence of motor complications during therapy with dopamine agonists was neglected. The occurrence of side effects can be explained by the different receptor affinity to the individual dopaminergic and non-dopaminergic receptors of the individual dopamine agonists. However, the different affinity to individual receptors also explains the different effect on individual Parkinson symptoms and can, therefore, contribute to a targeted use of the different dopamine agonists. Since comparative studies on the differential effect of dopamine agonists have only been conducted for individual substances, empirical knowledge of the differential effect is of great importance. Therefore, the guidelines for the treatment of Parkinson's disease do not consider the differential effect of the dopamine agonists. The historical consideration of dopamine agonists within Parkinson's therapy deserves special attention to be able to classify the current discussion about the significance of dopamine agonists.

Upregulation of APAF1 and CSF1R in Peripheral Blood Mononuclear Cells of Parkinson's Disease

Increased oxidative stress and neuroinflammation play a crucial role in the pathogenesis of Parkinson's disease (PD). In this study, the expression levels of 52 genes related to oxidative stress and inflammation were measured in peripheral blood mononuclear cells of the discovery cohort including 48 PD patients and 25 healthy controls. Four genes, including ALDH1A, APAF1, CR1, and CSF1R, were found to be upregulated in PD patients. The expression patterns of these genes were validated in a second cohort of 101 PD patients and 61 healthy controls. The results confirmed the upregulation of APAF1 (PD: 0.34 ± 0.18, control: 0.26 ± 0.11, p < 0.001) and CSF1R (PD: 0.38 ± 0.12, control: 0.33 ± 0.10, p = 0.005) in PD patients. The expression level of APAF1 was correlated with the scores of the Unified Parkinson's Disease Rating Scale (UPDRS, r = 0.235, p = 0.018) and 39-item PD questionnaire (PDQ-39, r = 0.250, p = 0.012). The expression level of CSF1R was negatively correlated with the scores of the mini-mental status examination (MMSE, r = -0.200, p = 0.047) and Montréal Cognitive Assessment (MoCA, r = -0.226, p = 0.023). These results highly suggest that oxidative stress biomarkers in peripheral blood may be useful in monitoring the progression of motor disabilities and cognitive decline in PD patients.

Cordycepin improved the cognitive function through regulating adenosine A2A receptors in MPTP induced Parkinson's disease mice model

BACKGROUND

Parkinson's disease (PD), the most common neurodegenerative disorder, primarily affects dopaminergic neurons in the substantia nigra (SN). In addition to severe motor dysfunction, PD patients appear apparent cognitive impairments in the late stage. Cognitive dysfunction is accompanied by synaptic transmission damage in the hippocampus. Cordycepin has been reported to alleviate cognitive impairments in neurodegenerative diseases.

PURPOSE

The study aimed to estimate the protection roles of cordycepin on cognitive dysfunction in PD model and explore the potential mechanisms.

METHODS

1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was used to establish the PD model in vivo and in vitro experiments. In the in vivo experiments, the C57BL / 6 mice were intraperitoneally injected with MPTP and intragastric administration with cordycepin. Open field test (OFT) was used to estimate the exercise ability. Spontaneous alternation behavioral (SAB) and morris water maze (MWM) tests were used to evaluate the learning and memory abilities. The hippocampal slices from C57BL / 6 and Kunming mice in the in vitro experiments were used to record field excitatory postsynaptic potential (fEPSP) by electrophysiological methods. Western blotting was used to examine the level of tyrosine hydroxylase (TH) in the in vivo experiments and the levels of adenosine A₁ and A_2A receptors (A₁R and A_2AR) in the in vitro experiments, respectively. The drugs of MPTP, cordycepin, DPCPX and SCH58261 were perfused through dissolving in artificial cerebrospinal fluid.

RESULTS

Cordycepin could significantly reduce the impairments on motor, exploration, spatial learning and memory induce by MPTP. MPTP reduced the amplitude of LTP in hippocampal CA1 area but cordycepin could improve LTP amplitudes. Cordycepin at dosage of 20 mg/kg also increased the TH level in SN. In the in vitro experiments, MPTP inhibited synaptic transmission in hippocampal Schaffer-CA1 pathway with a dose-dependent relationship, while cordycepin could reverse the inhibition of synaptic transmission. Furthermore, the roles of cordycepin on synaptic transmission could been attenuated in the presence of the antagonists of A₁R and A_2AR, DPCPX and SCH58261, respectively. Interestingly, the level of A_2AR rather than A₁R in hippocampus was significantly decreased in the cordycepin group as compared to the control.

CONCLUSION

The present study has showed that cordycepin could improve cognitive function in the PD model induced by MPTP through regulating the adenosine A_2A receptors. These findings were helpful to provide a new strategy for the dementia caused by Parkinson's disease.

Pramipexole inhibits astrocytic NLRP3 inflammasome activation via Drd3-dependent autophagy in a mouse model of Parkinson's disease

Inflammation is one of the pathogenic processes in Parkinson's disease (PD). Dopamine receptor agonist pramipexole (PPX) is extensively used for PD treatment in clinics. A number of studies show that PPX exerts neuroprotection on dopaminergic (DA) neurons, but the molecular mechanisms underlying the protective effects of PPX on DA neurons are not fully elucidated. In the present study, we investigated whether PPX modulated PD-related neuroinflammation and underlying mechanisms. PD model was established in mice by bilateral striatum injection of lipopolyssaccharide (LPS). The mice were administered PPX (0.5 mg·kg^-1·d^-1, i.p.) 3 days before LPS injection, and for 3 or 21 days after surgery, respectively, for biochemical and histological analyses. We showed that PPX administration significantly alleviated the loss of DA neurons, and suppressed the astrocyte activation and levels of proinflammatory cytokine IL-1β in the substantia nigra of LPS-injected mice. Furthermore, PPX administration significantly decreased the expression of NLRP3 inflammasome-associated proteins, i.e., cleaved forms of caspase-1, IL-1β, and apoptosis-associated speck-like protein containing a caspase recruit domain (ASC) in the striatum. These results were validated in LPS+ATP-stimulated primary mouse astrocytes in vitro. Remarkably, we showed that PPX (100-400 μM) dose-dependently enhanced the autophagy activity in the astrocytes evidenced by the elevations in LC3-II and BECN1 protein expression, as well as the increase of GFP-LC3 puncta formation. The opposite effects of PPX on astrocytic NLRP3 inflammasome and autophagy were eliminated by Drd3 depletion. Moreover, we demonstrated that both pretreatment of astrocytes with autophagy inhibitor chloroquine (40 μM) in vitro and astrocyte-specific Atg5 knockdown in vivo blocked PPX-caused inhibition on NLRP3 inflammasome and protection against DA neuron damage. Altogether, this study demonstrates an anti-neuroinflammatory activity of PPX via a Drd3-dependent enhancement of autophagy activity in astrocytes, and reveals a new mechanism for the beneficial effect of PPX in PD therapy.

Advances in the Therapeutic Use of Non-Ergot Dopamine Agonists in the Treatment of Motor and Non-Motor Symptoms of Parkinson's Disease

Dopamine (DA) agonists, as an excellent dopamine replacement therapy for patients with early and advanced Parkinson's disease (PD), play a vital role in controlling motor and several nonmotor symptoms. Besides, the application of DA agonists may delay levodopa therapy and the associated risk of motor complications. Indeed, each DA agonist has unique pharmacokinetic and pharmacodynamic characteristics and therefore has different therapeutic efficacy and safety profile. The comorbidities, significant non-motor manifestations, concomitant medications, and clinical features of PD individuals should guide the selection of a specific DA agonist to provide a more patient-tailored treatment option. Thorough knowledge of DA agonists helps clinicians better balance clinical efficacy and side effects. Therefore, this review refers to recent English-written articles on DA agonist therapy for PD patients and summarizes the latest findings on non-ergot DA agonists as well as the advantages and disadvantages of each compound to help clinicians in the selection of a specific DA agonist. In addition, novel D1/D5 partial agonists and new formulations of DA agonists are also discussed.

Apolipoprotein A-I mimetic peptides (ApoAI MP) improve oxidative stress and inflammatory responses in Parkinson’s disease mice

Purpose: Parkinson’s disease (PD) is closely associated with oxidative stress and inflammatory situation. Apolipoprotein A-I mimetic peptides (ApoAI MP) have antioxidant and anti-inflammatory properties. We aimed to study the therapeutic effect of ApoAI MP on PD mice, and to explore the related mechanisms.

Methods: PD mice were induced by using 1-methyl-4-phenyl-1,2,3,6-tetrathydropyridine (MPTP). The model mice were treated with different concentrations of ApoAI MP. The open-field behavioral test assesses the total distance moved, the rest time, and the number of crossings and Rota-rod was used to evaluate motor coordination. Oxidative stress was identified by measuring the levels of superoxide dismutase (SOD), catalase (CAT), glutathionperoxidase (GSH-Px), malondialdehyde, ROS and H2O2. Inflammatory situation was analyzed by measuring the levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6). Meanwhile, the scavenging activities of ApoAI MP for ABTS, DPPH, hydroxyl radical and superoxide anion, and the effects of the peptide on neurotransmitters were evaluated.

Results: PD model establishment increased oxidative stress and inflammatory status by increasing the concentrations of ROS and H2O2 production, and the levels of TNF-α, IL-1β and IL-6 (p &lt; 0.05). ApoAI MP intervention improved PD symptoms by reducing the total moved distance and the number of passes (p &lt; 0.01), and the falling times from Rota-rod, and increasing rest time (p &lt; 0.05). ApoAI MP increased antioxidant properties by increasing the activities of SOD, CAT and GSH-Px, and reducing MDA concentration (p &lt; 0.05). ApoAI MP addition reduced oxidative stress by scavenging ABTS, DPPH, hydroxyl radicals and superoxide anion and reducing the concentrations of ROS and H2O2 production (p &lt; 0.05). ApoAI MP treatment increased anti-inflammatory capacities by reducing the concentrations of TNF-α, IL-1β and IL-6 (p &lt; 0.05). HPLC analysis showed that the peptide treatment improved neurotransmitters.

Conclusion: ApoAI MP can improve the behavioral performance of PD mice by improving antioxidant and anti-inflammatory capacities.

Alhumaydhi F, Ashtekar H, D. S S, Adam Conte-Junior C. Development of Microneedle Patch Loaded with Bacopa monnieri Solid Lipid Nanoparticles for the Effective Management of Parkinson's Disease

The demand for drug delivery systems (DDS) to treat Parkinson's disease (PD) is still high, and microneedle (MN) assisted transdermal DDS offers enormous potential. Herbal products for PD have been shown to have antioxidant effects in reducing dopaminergic neurons from degeneration. Here, we attempted to incorporate solid lipid nanoparticles (SLNs) of Bacopa monnieri into dissolvable microneedle arrays and evaluate its neuroprotective activity. The bloodless and painless microneedle arrays through the transdermal route deliver the drug across the blood-brain barrier at the desired concentration. The quality by design (QbD) approach was employed for optimizing the SLNs formulations. The mechanical strength, in vitro release studies, ex-vivo permeation investigation, skin irritation test, histopathological studies, biochemical studies, and behavioural tests SLNs loaded microneedle arrays were performed. The microneedle patches obtained were shown to be mechanically robust and were also found to be nonirritant with a decreased degree of bradykinesia, high motor coordination, and balance ability. Compared to systemic delivery systems, such an MN method can achieve a considerably lower effective dose and allow long-term home-based treatment.

Reorienting of pramipexole as a promising therapy for acute pancreatitis in a rat model by suppressing TLR-4\NF-κB p65\NLRP3 inflammasome signaling

OBJECTIVE

Acute pancreatitis (AP), a disorder of global importance, has a growing incidence and prevalence, particularly in the western world. Its complications include pseudo-cysts and chronic pancreatitis. Pramipexole (PMX), a D2/3 receptor selecting agonist used in Parkinsonism, has reported anti-inflammatory effects lately.

PURPOSE

Exploring the potential curative role of PMX in an l-arginine-induced acute pancreatitis rat model besides a possible mechanistic pathway.

METHODS

Rats were divided randomly into three groups: control, l-arginine, and "l-arginine + PMX". 7 days after AP induction, rats decapitated and estimated for serum amylase, lipase, glucose, pancreatic inflammatory mediators "toll-like receptor-4, nuclear factor- kappa B p65 ,serum tumor necrosis factor-α, NLRP3 inflammasome, caspase-1, interleukin-1 beta, oxidative biomarkers "malondialdehyde, myeloperoxidase, nitrite/nitrate, reduced glutathione, and the apoptotic marker "caspase-3", with pancreatic histopathological changes.

RESULTS

L-arginine mediated AP proved by elevated serum lipase and amylase, pancreatic inflammatory, oxidative and apoptotic markers with infiltration of inflammatory cells using hematoxylin and eosin stain. PMX improved all these adverse signs of AP greatly.

CONCLUSION

PMX might be considered as an innovative therapy for AP due to its remarkable antioxidant, anti-apoptotic, and anti-inflammatory effects, which are attributed to the suppression of the NLRP3 inflammasome and its downstream inflammatory cytokines.

Pharmacological Modulation of Nrf2/HO-1 Signaling Pathway as a Therapeutic Target of Parkinson's Disease

Parkinson’s disease (PD) is a complex neurodegenerative disorder featuring both motor and nonmotor symptoms associated with a progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Oxidative stress (OS) has been implicated in the pathogenesis of PD. Genetic and environmental factors can produce OS, which has been implicated as a core contributor to the initiation and progression of PD through the degeneration of dopaminergic neurons. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) orchestrates activation of multiple protective genes, including heme oxygenase-1 (HO-1), which protects cells from OS. Nrf2 has also been shown to exert anti-inflammatory effects and modulate both mitochondrial function and biogenesis. Recently, a series of studies have reported that different bioactive compounds were shown to be able to activate Nrf2/antioxidant response element (ARE) and can ameliorate PD-associated neurotoxin, both in animal models and in tissue culture. In this review, we briefly overview the sources of OS and the association between OS and the pathogenesis of PD. Then, we provided a concise overview of Nrf2/ARE pathway and delineated the role played by activation of Nrf2/HO-1 in PD. At last, we expand our discussion to the neuroprotective effects of pharmacological modulation of Nrf2/HO-1 by bioactive compounds and the potential application of Nrf2 activators for the treatment of PD. This review suggests that pharmacological modulation of Nrf2/HO-1 signaling pathway by bioactive compounds is a therapeutic target of PD.

Pramipexole regulates depression-like behavior via dopamine D3 receptor in a mouse model of Parkinson's disease

Depression is one of the strongest predictors of quality of life in patients with Parkinson's disease (PD). Despite the high prevalence of depression, there is no clear guidance for its treatment in PD because the evidence for the efficacy of most antidepressants remains insufficient. Pramipexole, a dopamine agonist, is one of the few drugs that has proven to be clinically useful. However, the underlying mechanisms of antidepressive effects of pramipexole are still unknown. A 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model, dopamine D2 receptor (DRD2) and D3 receptor (DRD3) knockout mice were used in our study. Compared with other dopamine D2-like receptor agonists and madopar, pramipexole improved depression-like behavior and alleviate bradykinesia in an MPTP-induced mouse model of PD. Pramipexole significantly improved depression-like behavior in DRD2^-/- mice but not in DRD3^-/- mice. These results demonstrate that the antidepressive effect of pramipexole is mediated by DRD3 but not DRD2. Our findings highlight the need to develop novel dopamine agonists specifically targeting DRD3 for the treatment of depression in PD in the future.

Emerging Novel Approaches for the Enhanced Delivery of Natural Products for the Management of Neurodegenerative Diseases

Neurodegenerative diseases (NDs) such as Alzheimer's disease, Parkinson's disease, Huntington disease, amyotrophic lateral sclerosis, and prion disease affect any part of the brain. The complete mechanism of ND is unknown, but there are some molecular mechanism and chemical process. Natural compounds have better compatibility with the human body along with lesser side effects. Moreover, several studies showed that various natural compounds have significant neuroprotective, potent antioxidant, and anti-inflammatory properties, which are effective for treating the different type of ND. In ND, natural compounds act by various mechanisms such as preventing the generation of reactive oxygen species (ROS), eliminating destructed biomolecules before their accumulation affects cell metabolism, and improving the disease conditions. But due to the presence of the blood-brain barrier (BBB) layer and unfavorable pharmacokinetic properties of natural compounds, their delivery into the brain is limited. To minimize this problem and enhance drug delivery into the brain with an effective therapeutic dose, there is a need to develop a practical novel approach. The various studies showed that nanoformulations and microneedles (MN) containing natural compounds such as quercetin, curcumin, resveratrol, chrysin, piperine, ferulic acid, huperzine A, berberine, baicalein, hesperetin, and retinoic acid effectively improved many ND. In this review, the effect of such natural drug-loaded nanoformulation and MN patches on ND management is discussed, along with their merits and demerits. This review aims to introduce different novel approaches for enhancing natural drug delivery into the brain to manage various neurodegenerative diseases.

MPTP-induced mouse model of Parkinson's disease: A promising direction of therapeutic strategies

Among the popular animal models of Parkinson's disease (PD) commonly used in research are those that employ neurotoxins, especially 1-methyl- 4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP). This neurotoxin exerts it neurotoxicity by causing a barrage of insults, such as oxidative stress, mitochondrial apoptosis, inflammation, excitotoxicity, and formation of inclusion bodies acting singly and in concert, ultimately leading to dopaminergic neuronal damage in the substantia nigra pars compacta and striatum. The selective neurotoxicity induced by MPTP in the nigrostriatal dopaminergic neurons of the mouse brain has led to new perspectives on PD. For decades, the MPTP-induced mouse model of PD has been the gold standard in PD research even though it does not fully recapitulate PD symptomatology, but it does have the advantages of simplicity, practicability, affordability, and fewer ethical considerations and greater clinical correlation than those of other toxin models of PD. The model has rejuvenated PD research and opened new frontiers in the quest for more novel therapeutic and adjuvant agents for PD. Hence, this review summarizes the role of MPTP in producing Parkinson-like symptoms in mice and the experimental role of the MPTP-induced mouse model. We discussed recent developments of more promising PD therapeutics to enrich our existing knowledge about this neurotoxin using this model.

Contribution of Apaf-1 to the pathogenesis of cancer and neurodegenerative diseases

Deregulation of apoptosis is associated with various pathologies, such as neurodegenerative disorders at one end of the spectrum and cancer at the other end. Generally speaking, differentiated cells like cardiomyocytes, skeletal myocytes and neurons exhibit low levels of Apaf-1 (Apoptotic protease activating factor 1) protein suggesting that down-regulation of Apaf-1 is an important event contributing to the resistance of these cells to apoptosis. Nonetheless, upregulation of Apaf-1 has not emerged as a common phenomenon in pathologies associated with enhanced neuronal cell death, i.e., neurodegenerative diseases. In cancer, on the other hand, Apaf-1 downregulation is a common phenomenon, which occurs through various mechanisms including mRNA hyper-methylation, gene methylation, Apaf-1 localization in lipid rafts, inhibition by microRNAs, phosphorylation, and interaction with specific inhibitors. Due to the diversity of these mechanisms and involvement of other factors, defining the exact contribution of Apaf-1 to the development of cancer in general and neurodegenerative disorders, in particular, is complicated. The current review is an attempt to provide a comprehensive image of Apaf-1's contribution to the pathologies observed in cancer and neurodegenerative diseases with the emphasis on the therapeutic aspects of Apaf-1 as an important target in these pathologies.

Comparison of pramipexole and levodopa/benserazide combination therapy versus levodopa/benserazide monotherapy in the treatment of Parkinson's disease: a systematic review and meta-analysis

The purpose of this research was to evaluate the clinical efficacy and safety of pramipexole plus levodopa/benserazide (P+LB) combination therapy in the treatment of Parkinson's disease (PD) compared to that of LB monotherapy, in order to confer a reference for clinical practice. Randomized controlled trials (RCTs) of P+LB for PD published up to April 2020 were retrieved. Heterogeneity and sensitivity analysis were executed. Twenty-nine RCTs with 3017 participants were included. Clinical efficacy of P+LB combination therapy was significantly better than LB monotherapy (RR 1.27, 95% CI 1.22 to 1.32, P<0.00001). Compared with LB monotherapy, the pooled effects of P+LB combination therapy on UPDRS score were (SMD -1.41, 95% CI -1.71 to -1.11, P<0.00001) for motor UPDRS score, (SMD -1.65, 95% CI -2.25 to -1.04, P<0.00001) for activities of daily living UPDRS score, (SMD -2.20, 95% CI -3.32 to -1.09, P=0.0001) for mental UPDRS score, and (SMD -1.60, 95% CI -2.06 to -1.15, P<0.00001) for complication UPDRS score. The HAMD score showed significant decrease in the P+LB combination therapy compared to LB monotherapy (SMD -1.32, 95% CI -1.80 to -0.84, P<0.00001). In contrast to LB monotherapy, P+LB combination therapy decreased the number of any adverse events obviously in PD patients (RR 0.53, 95% CI 0.45 to 0.63, P<0.00001). In conclusion, P+LB combination therapy is superior to LB monotherapy for improvement of clinical symptoms in PD patients. Moreover, the safety profile of P+LB combination therapy is better than that of LB monotherapy. Further well-designed, multi-center RCTs needed to identify these findings.

Pramipexole attenuates 6-OHDA-induced Parkinson's disease by mediating the Nurr1/NF-κB pathway

Neuroinflammation is the key factor associated with the progression of Parkinson's disease (PD). Pramipexole (PPX) has anti-inflammatory and antioxidant properties. This study explored the effects of PPX on PD and its related mechanisms. A PD rat model was established using 6-hydroxydopamine (6-OHDA). Thirty rats were divided into the following three groups: control, PD, and PD + PPX. The rats in the PD and PD + PPX groups were first administered 6-OHDA and then respectively treated with saline and PPX. Afterward, rotational behavior tests were performed to evaluate the efficiency of PPX. The level of tyrosine hydroxylase (TH) was measured using immunohistochemical staining. Subsequently, real-time quantitative PCR (RT-qPCR) and western blot were used to determine the expression of α-synuclein (α-syn), nuclear receptor subfamily 4 group A member 2 (Nurr1), and nuclear factor kappa B (NF-κB). PPX improved the motor behavior of PD rats caused by 6-OHDA. The number of TH-positive neurons in the PD group was significantly lower than that in the control group (P < 0.05), while PPX could rescue 6-OHDA-induced TH loss. RT-qPCR and western blot showed that Nurr1 expression was significantly downregulated in the PD group compared to that of the control group (P < 0.05), while after PPX treatment, its expression was significantly upregulated (P < 0.05). For α-syn and NF-κB, 6-OHDA significantly upregulated their expressions (P < 0.05), whereas PPX reversed them. PPX improved the motor behavior of PD through mediating the inflammatory response and regulating the Nurr1/NF-κB signaling pathway.

Pramipexole attenuates neuronal injury in Parkinson's disease by targeting miR-96 to activate BNIP3-mediated mitophagy

BACKGROUND

Parkinson's disease is a common neurodegenerative problem. Pramipexole (PPX) plays protective role in Parkinson's disease. Nevertheless, the mechanism of PPX in Parkinson's disease-like neuronal injury is largely uncertain.

METHODS

1-methyl-4-phenylpyridinium (MPP⁺)-stimulated neuronal cells and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mice were used as the model of Parkinson's disease. MPP⁺-induced neuronal injury was assessed via cell viability, lactic dehydrogenase (LDH) release and apoptosis. microRNA-96 (miR-96) and BCL2/adenovirus E1B 19 kDa interacting protein 3 (BNIP3) abundances were examined by quantitative reverse transcription polymerase chain reaction (qRT-PCR) or Western blotting. Mitophagy was tested by Western blotting and immunofluorescence staining. MPTP-induced neuronal injury in mice was investigated via behavioral tests and TUNEL.

RESULTS

PPX alleviated MPP⁺-induced neuronal injury via increasing cell viability and decreasing LDH release and apoptosis. PPX reversed MPP⁺-induced miR-96 expression and inhibition of mitophagy. miR-96 overexpression or BNIP3 interference weakened the suppressive role of PPX in MPP⁺-induced neuronal injury. miR-96 targeted BNIP3 to inhibit PTEN-induced putative kinase 1 (PINK1)/Parkin signals-mediated mitophagy. miR-96 overexpression promoted MPP⁺-induced neuronal injury via decreasing BNIP3. PPX weakened MPTP-induced neuronal injury in mice via regulating miR-96/BNIP3-mediated mitophagy.

CONCLUSION

PPX mitigated neuronal injury in MPP⁺-induced cells and MPTP-induced mice by activating BNIP3-mediated mitophagy via directly decreasing miR-96.

Oxidative Stress in Parkinson's Disease: Potential Benefits of Antioxidant Supplementation

Parkinson's disease (PD) occurs in approximately 1% of the population over 65 years of age and has become increasingly more common with advances in age. The number of individuals older than 60 years has been increasing in modern societies, as well as life expectancy in developing countries; therefore, PD may pose an impact on the economic, social, and health structures of these countries. Oxidative stress is highlighted as an important factor in the genesis of PD, involving several enzymes and signaling molecules in the underlying mechanisms of the disease. This review presents updated data on the involvement of oxidative stress in the disease, as well as the use of antioxidant supplements in its therapy.

Nrf2/HO-1 mediates the neuroprotective effects of pramipexole by attenuating oxidative damage and mitochondrial perturbation after traumatic brain injury in rats

Pramipexole (PPX), a D2-like receptor agonist, is generally used in the treatment of Parkinson's disease and restless leg syndrome. Its neuroprotective effects have been shown against various neurological disorders. Recent research work has demonstrated that PPX exerts neuroprotection through mitochondria. However, the neuromodulator-related effects of PPX against traumatic brain injury (TBI) remain unexplored. The present study, therefore, investigated the mechanism of neuroprotection by PPX against oxidative stress, mitochondrial dysfunction and neuronal damage following TBI in rats. We hypothesized that the neuroprotection by PPX in TBI-subjected rats might involve activation of the Nrf2/HO-1 (also known as Nfe2l2/Hmox1) signaling pathway. PPX was injected intraperitoneally (0.25 mg/kg body weight and 1.0 mg/kg body weight) at different time intervals post-TBI. Several neurobehavioral parameters were assessed at 48 h post-TBI, and the brain was isolated for molecular and biochemical analysis. The results demonstrated that PPX treatment significantly improved the behavioral deficits, decreased the lipid peroxidation rate, increased glutathione levels and decreased 4-hydroxynonenal levels in TBI-subjected rats. PPX also increased the activities of glutathione peroxidase and superoxide dismutase enzymes. In addition, PPX treatment inhibited mitochondrial reactive oxygen species production, restored mitochondrial membrane potential and increased ATP levels after a TBI. Further, PPX treatment reduced the Bax/Bcl2 ratio and translocation of Bax to mitochondria and cytochrome-c to the cytosol. Finally, PPX treatment greatly accelerated the translocation of Nrf2 to the nucleus and upregulated HO-1 protein expression. We conclude that the neuroprotective effects of PPX are mediated by activation of the Nrf2/HO-1 signaling pathway following TBI.This article has an associated First Person interview with the first author of the paper.

An update on the use of non-ergot dopamine agonists for the treatment of Parkinson's disease

INTRODUCTION

Long-term treatment of Parkinson's disease (PD) with levodopa is hampered by motor complications related to the inability of residual nigrostriatal neurons to convert levodopa to dopamine (DA) and use it appropriately. This generated a tendency to postpone levodopa, favoring the initial use of DA agonists, which directly stimulate striatal dopaminergic receptors. Use of DA agonists, however, is associated with multiple side effects and their efficacy is limited by suboptimal bioavailability.

AREAS COVERED

This paper reviewed the latest preclinical and clinical findings on the efficacy and adverse effects of non-ergot DA agonists, discussing the present and future of this class of compounds in PD therapy.

EXPERT OPINION

The latest findings confirm the effectiveness of DA agonists as initial treatment or adjunctive therapy to levodopa in advanced PD, but a more conservative approach to their use is emerging, due to the complexity and repercussions of their side effects. As various factors may increase the individual risk to side effects, assessing such risk and calibrating the use of DA agonists accordingly may become extremely important in the clinical management of PD, as well as the availability of new DA agonists with better profiles of safety and efficacy.

Pramipexole Reduces zif-268 mRNA Expression in Brain Structures involved in the Generation of Harmaline-Induced Tremor

Essential tremor is one of the most common neurological disorders, however, it is not sufficiently controlled with currently available pharmacotherapy. Our recent study has shown that pramipexole, a drug efficient in inhibiting parkinsonian tremor, reduced the harmaline-induced tremor in rats, generally accepted to be a model of essential tremor. The aim of the present study was to investigate brain targets for the tremorolytic effect of pramipexole by determination of the early activity-dependent gene zif-268 mRNA expression. Tremor in rats was induced by harmaline administered at a dose of 15 mg/kg ip. Pramipexole was administered at a low dose of 0.1 mg/kg sc. Tremor was measured by Force Plate Actimeters where four force transducers located below the corners of the plate tracked the animal's position on a Cartesian plane. The zif-268 mRNA expression was analyzed by in situ hybridization in brain slices. Harmaline induced tremor and increased zif-268 mRNA levels in the inferior olive, cerebellar cortex, ventroanterior/ventrolateral thalamic nuclei and motor cortex. Pramipexole reversed both the harmaline-induced tremor and the increase in zif-268 mRNA expression in the inferior olive, cerebellar cortex and motor cortex. Moreover, the tremor intensity correlated positively with zif-268 mRNA expression in the above structures. The present results seem to suggest that the tremorolytic effect of pramipexole is related to the modulation of the harmaline-increased neuronal activity in the tremor network which includes the inferior olive, cerebellar cortex and motor cortex. Potential mechanisms underlying the above pramipexole action are discussed.

Shared cerebral metabolic pathology in non-transgenic animal models of Alzheimer's and Parkinson's disease

Parkinson's disease (PD) and Alzheimer's disease (AD) are the most common chronic neurodegenerative disorders, characterized by motoric dysfunction or cognitive decline in the early stage, respectively, but often by both symptoms in the advanced stage. Among underlying molecular pathologies that PD and AD patients have in common, more attention is recently paid to the central metabolic dysfunction presented as insulin resistant brain state (IRBS) and altered cerebral glucose metabolism, both also explored in animal models of these diseases. This review aims to compare IRBS and alterations in cerebral glucose metabolism in representative non-transgenic animal PD and AD models. The comparison is based on the selectivity of the neurotoxins which cause experimental PD and AD, towards the cellular membrane and intracellular molecular targets as well as towards the selective neurons/non-neuronal cells, and the particular brain regions. Mitochondrial damage and co-expression of insulin receptors, glucose transporter-2 and dopamine transporter on the membrane of particular neurons as well as astrocytes seem to be the key points which are further discussed in a context of alterations in insulin signalling in the brain and its interaction with dopaminergic transmission, particularly regarding the time frame of the experimental AD/PD pathology appearance and the correlation with cognitive and motor symptoms. Such a perspective provides evidence on IRBS being a common underlying metabolic pathology and a contributor to neurodegenerative processes in representative non-transgenic animal PD and AD models, instead of being a direct cause of a particular neurodegenerative disorder.

Pharmacological Enhancement of Regeneration-Dependent Regulatory T Cell Recruitment in Zebrafish

Regenerative capacity varies greatly between species. Mammals are limited in their ability to regenerate damaged cells, tissues and organs compared to organisms with robust regenerative responses, such as zebrafish. The regeneration of zebrafish tissues including the heart, spinal cord and retina requires foxp3a+ zebrafish regulatory T cells (zTregs). However, it remains unclear whether the muted regenerative responses in mammals are due to impaired recruitment and/or function of homologous mammalian regulatory T cell (Treg) populations. Here, we explore the possibility of enhancing zTreg recruitment with pharmacological interventions using the well-characterized zebrafish tail amputation model to establish a high-throughput screening platform. Injury-infiltrating zTregs were transgenically labelled to enable rapid quantification in live animals. We screened the NIH Clinical Collection (727 small molecules) for modulators of zTreg recruitment to the regenerating tissue at three days post-injury. We discovered that the dopamine agonist pramipexole, a drug currently approved for treating Parkinson’s Disease, specifically enhanced zTreg recruitment after injury. The dopamine antagonist SCH-23390 blocked pramipexole activity, suggesting that peripheral dopaminergic signaling may regulate zTreg recruitment. Similar pharmacological approaches for enhancing mammalian Treg recruitment may be an important step in developing novel strategies for tissue regeneration in humans.

Pramipexole prevents ischemic cell death via mitochondrial pathways in ischemic stroke

A dopamine D2 receptor agonist, pramipexole, has been found to elicit neuroprotection in patients with Parkinson's disease and restless leg syndrome. Recent evidence has shown that pramipexole mediates its neuroprotection through mitochondria. Considering this, we examined the possible mitochondrial role of pramipexole in promoting neuroprotection following an ischemic stroke of rat. Male Wistar rats underwent transient middle cerebral artery occlusion (tMCAO) and then received pramipexole (0.25 mg and 1 mg/kg body weight) at 1, 6, 12 and 18 h post-occlusion. A panel of neurological tests and 2,3,5-triphenyl tetrazolium chloride (TTC) staining were performed at 24 h after the surgery. Flow cytometry was used to detect the mitochondrial membrane potential, and mitochondrial levels of reactive oxygen species (ROS) and Ca²⁺, respectively. Mitochondrial oxidative phosphorylation was analyzed by oxygraph (oxygen electrode). Western blotting was used to analyze the expression of various proteins such as Bax, Bcl-2 and cytochrome c Pramipexole promoted the neurological recovery as shown by the panel of neurobehavioral tests and TTC staining. Post-stroke treatment with pramipexole reduced levels of mitochondrial ROS and Ca²⁺ after ischemia. Pramipexole elevated the mitochondrial membrane potential and mitochondrial oxidative phosphorylation. Western blotting showed that pramipexole inhibited the transfer of cytochrome c from mitochondria to cytosol, and hence inhibited the mitochondrial permeability transition pore. Thus, our results have demonstrated that post-stroke administration of pramipexole induces the neurological recovery through mitochondrial pathways in ischemia/reperfusion injury.

Efficacy of low-dose D2/D3 partial agonist pramipexole on neuroleptic-induced extrapyramidal symptoms and symptoms of schizophrenia: a stage-1 open-label pilot study

OBJECTIVE

Some lines of evidence show that D₂/D₃ receptor partial agonist pramipexole may be effective in the treatment of extrapyramidal symptoms (EPS) and psychiatric symptoms of schizophrenia. Therefore, we analyzed whether a low dose of pramipexole (0.375-0.75 mg/day) has efficacy on EPS and symptoms of schizophrenia while maintaining tolerability.

METHODS

Ten subjects with EPS [including drug-induced parkinsonism (DIP) and akathisia] were recruited in a stage-1, open-label pilot study. All the subjects were treated with a low dose of pramipexole. The evaluations were performed at baseline, day 3, week 1, week 2, week 4, week 6, and week 8. The ratings of SAS, BARS, PANSS, CDSS, and CGI-S and adverse effects (AE) were recorded in every visit.

RESULTS

SAS total scores decreased significantly during the study in patients with DIP (P<0.001), and mild AEs were detected. Treatments with pramipexole did not show an anti-akathisia effect during the study, while 2 subjects experienced deterioration of akathisia and mood symptoms. The psychiatric symptoms of schizophrenia showed a trend of improvement during the study, but there was no improvement in depressive mood.

CONCLUSION

A low dose of pramipexole can significantly relieve antipsychotic-induced parkinsonism, but not akathisia. Improvements in psychiatric symptoms of schizophrenia were found, but the results of this study need to be validated in a larger sample. No improvement of mood disorder was detected.