Neuroinflammation in early, late and recovery stages in a progressive parkinsonism model in rats

Preventive beneficial effects of cannabidiol in a reserpine-induced progressive model of parkinsonism

Introduction

Parkinson's disease (PD) is characterized by motor and non-motor symptoms such as tremors, difficulty in initiating movements, depression, and cognitive deficits. The pathophysiology of PD involves a gradual decrease in dopaminergic neurons in the substantia nigra, increased inflammatory parameters, and augmented oxidative stress in this region. Several new therapies aim to promote antioxidant and anti-inflammatory actions, including the use of cannabinoids, particularly cannabidiol (CBD). CBD is a non-psychotomimetic component of Cannabis sativa that acts broadly through several mechanisms.

Objective

The objective of this study was to investigate the potential protective effect of CBD in mice subjected to a low-dose (0.1 mg/kg) repeated reserpine protocol, which encompasses behavioral and neuronal alterations compatible with the progressiveness of PD alterations.

Materials and Methods

We used two approaches: (1) concurrent administration during the development of parkinsonism and (2) pre-administration to explore a possible preventive action. The effect of CBD (0.5 mg/kg) on reserpine-induced alterations was investigated on behavioral (catalepsy and vacuous chewing movements) and neuronal (immunolabeling for tyrosine hydroxylase - TH) parameters.

Results

Overall, groups that were treated with CBD and reserpine presented motor alterations later during the protocol compared to the groups that received only reserpine (except for vacuous chewing evaluation in the concomitant treatment). Additionally, CBD attenuated reserpine-induced catalepsy (preventive treatment) and prevented the decrease in TH labeling in the substantia nigra pars compacta in both concurrent and preventive protocols.

Conclusion

Based on these data, we observed a beneficial effect of CBD in motor and neuronal alterations reserpine-induced progressive parkinsonism, particularly after preventive treatment.

Sleep deprivation induces late deleterious effects in a pharmacological model of Parkinsonism

Parkinson's disease is a degenerative, chronic and progressive disease, characterized by motor dysfunctions. Patients also exhibit non-motor symptoms, such as affective and sleep disorders. Sleep disorders can potentiate clinical and neuropathological features and lead to worse prognosis. The goal of this study was to evaluate the effects of sleep deprivation (SD) in mice submitted to a progressive pharmacological model of Parkinsonism (chronic administration with a low dose of reserpine). Male Swiss mice received 20 injections of reserpine (0.1 mg/kg) or vehicle, on alternate days. SD was applied before or during reserpine treatment and was performed by gentle handling for 6 h per day for 10 consecutive days. Animals were submitted to motor and non-motor behavioral assessments and neurochemical evaluations. Locomotion was increased by SD and decreased by reserpine treatment. SD during treatment delayed the onset of catalepsy, but SD prior to treatment potentiated reserpine-induced catalepsy. Thus, although SD induced an apparent beneficial effect on motor parameters, a delayed deleterious effect on alterations induced by reserpine was found. In the object recognition test, both SD and reserpine treatment produced cognitive deficits. In addition, the association between SD and reserpine induced anhedonic-like behavior. Finally, an increase in oxidative stress was found in hippocampus of mice subjected to SD, and tyrosine hydroxylase immunoreactivity was reduced in substantia nigra of reserpine-treated animals. Results point to a possible late effect of SD, aggravating the deficits in mice submitted to the reserpine progressive model of PD.

Experimental Models to Study Immune Dysfunction in the Pathogenesis of Parkinson's Disease

Parkinson's disease (PD) is a chronic, age-related, progressive multisystem disease associated with neuroinflammation and immune dysfunction. This review discusses the methodological approaches used to study the changes in central and peripheral immunity in PD, the advantages and limitations of the techniques, and their applicability to humans. Although a single animal model cannot replicate all pathological features of the human disease, neuroinflammation is present in most animal models of PD and plays a critical role in understanding the involvement of the immune system (IS) in the pathogenesis of PD. The IS and its interactions with different cell types in the central nervous system (CNS) play an important role in the pathogenesis of PD. Even though culture models do not fully reflect the complexity of disease progression, they are limited in their ability to mimic long-term effects and need validation through in vivo studies. They are an indispensable tool for understanding the interplay between the IS and the pathogenesis of this disease. Understanding the immune-mediated mechanisms may lead to potential therapeutic targets for the treatment of PD. We believe that the development of methodological guidelines for experiments with animal models and PD patients is crucial to ensure the validity and consistency of the results.

Neuroprotective potential of Afzelin: A novel approach for alleviating catalepsy and modulating Bcl-2 expression in Parkinson's disease therapy

The lost dopaminergic neurons in the brain prevent mobility in Parkinson's disease (PD). It is impossible to stop the disease's progress by means of symptoms management. Research focuses on oxidative stress, mitochondrial dysfunction, and neuronal degeneration. Exploration of potential neuroprotective drugs against prosurvival B-cell lymphoma 2 (Bcl-2) protein is ongoing. An investigable cause behind PD, as well as preventive measures, could be discovered considering the association between such behavioural manifestations (cataleptic behaviours) and PD. The compound Afzelin, known to guard the nervous system, was chosen for this study. The study was done on rats divided into six different groups. First, there was a control group. The other group was treated with Reserpine (RES) (1 mg/kg). The third group received RES (1 mg/kg) and levodopa (30 mg/kg). The remaining three groups were given RES (1 mg/kg) in conjunction with Afzelin at the following doses: 5 mg/kg, 10 mg/kg, and 20 mg/kg. Cataleptic behavior and mobility in rats was assessed using the rotarod, open field, and modified forced-swim tests. thiobarbituric acid reactive substances (TBARS), nitric oxide (NO), biogenic amines, and Bcl-2 level in rat tissue homogenates were considered. According to the study's findings, the rats treated through co-administration of RES and Afzelin improved significantly in their cataleptic behaviours and locomotor activity. In addition, administering Afzelin itself caused Bcl-2 expression, which could have some neuroprotection properties. This study provides meaningful information on the effectiveness of Afzelin in handling catalepsy and other degenerative neurologic disorders. As a result, other studies need to be conducted to establish the reasons behind the reactions and determine the long-term effects of Afzelin on these conditions.

Transcranial photobiomodulation ameliorates midbrain and striatum neurochemical impairments and behavioral deficits in reserpine-induced parkinsonism in rats

Photobiomodulation (PBM) of deep brain structures through transcranial infrared irradiation might be an effective treatment for Parkinson's disease (PD). However, the mechanisms underlying this intervention should be elucidated to optimize the therapeutic outcome and maximize therapeutic efficacy. The present study aimed at investigating the oxidative stress-related parameters of malondialdehyde (MDA), nitric oxide (NO), and reduced glutathione (GSH) and the enzymatic activities of sodium-potassium-ATPase (Na+, K+-ATPase), Acetylcholinesterase (AChE), and monoamine oxidase (MAO) and monoamine levels (dopamine (DA), norepinephrine (NE) and serotonin (5-HT) in the midbrain and striatum of reserpine-induced PD in an animal model treated with PBM. Furthermore, the locomotor behavior of the animals has been determined by the open field test. Animals were divided into three groups; the control group, the PD-induced model group, and the PD-induced model treated with the PBM group. Non-invasive treatment of animals for 14 days with 100 mW, 830 nm laser has demonstrated successful attainment in the recovery of oxidative stress, and enzymatic activities impairments induced by reserpine (0.2 mg/kg) in both midbrain and striatum of adult male Wistar rats. PBM also improved the decrease in DA, NE, and 5-HT in the investigated brain regions. On a behavioral level, animals showed improvement in their locomotion activity. These findings have shed more light on some mechanisms underlying the treatment potential of PBM and displayed the safety, easiness, and efficacy of PBM treatment as an alternative to pharmacological treatment for PD.