The dynamics of nigrostriatal system damage and neurobehavioral changes in the rotenone rat model of Parkinson's disease

The Rotenone-Induced Sporadic Parkinsonism Model: Timeline of Motor and Non-Motor Features

The prevalence of Parkinson's disease (PD) requires better characterized animal models, in particular of the PD prodrome. Since pesticide are well-established triggers of Parkinsonism, we now undertook a detailed characterization of the time-dependent onset of behavioural and neurochemical alterations after the repeated daily intraperitoneal administration to adult male rats of a low dose of rotenone (2.75 mg/kg) during weekdays for 21 days. The onset of motor (bradykinesia in the open field test) and coordination deficits (balance in the rotarod and rearing in the open field) occurred after 14 days of exposure to rotenone, linked to a nigrostriatal dopaminergic degeneration and increased accumulation of α-synuclein, which are key features of PD. Moreover, we identified several modifications pre-dating the onset of PD-like motor symptoms, encompassing gastrointestinal alterations and a modified whole-body composition together with olfactory dysfunction and memory and emotional impairments, which were typified by: i) a delayed gastric emptying of liquids (13CO2 analysis), which was evident from the third day of rotenone administration and was aggravated over subsequent days; ii) a loss of total, visceral and subcutaneous body fat and dehydration (bioimpedance spectroscopy); iii) olfactory dysfunction (discrimination test and food buried test). The characterization of this prodrome period in this robust model of PD offers a new window of opportunity to investigate the pathophysiological mechanisms of PD onset and to devise and test novel neuroprotective strategies.

Treadmill intervention attenuates motor deficit with 6-OHDA-induced Parkinson's disease rat via changes in lipid profiles in brain and muscle

One of the key hallmarks of Parkinson's disease is the disruption of lipid homeostasis in the brain, which plays a critical role in neuronal membrane integrity and function. Understanding how treadmill training impacts lipid restructuring and its subsequent influence on motor function could provide a basis for developing targeted non-pharmacological interventions for individuals living with early stage of PD. This study aims to investigate the effects of a treadmill training intervention on motor deficits induced by 6-OHDA in rats model of PD. PD was induced by injecting 6-hydroxy dopamine (6-OHDA) into the medial forebrain bundle (MFB). For 10 weeks, rats underwent treadmill training on a four-lane motorized treadmill. Motor function deficits were evaluated through behavioral tests. Lipidomic analysis was performed through ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC MS/MS). Treadmill intervention significantly improved motor function and restored altered brain and muscle lipid profiles in PD rats. Among the lipid species identified in PD rats, brain abundance was highest for phosphatidylethanolamine (PE), correlating positively with the beam-walking scores; muscle abundance peaked with lysophosphatidylethanolamine (LysoPE), correlating positively with grip strength scores. In the brain, the levels of diacylglycerol (DG), triacylglycerol (TG), and lysophosphatidylcholine (PC) correlated positively with grip strength and rotarod scores, while only phosphatidylethanolamine (PE) linked to beam-walking scores. In the muscle, the levels of phosphatidylinositol (PI), lysophosphatidylethanolamine (PE), lysophosphatidic acid (PA), ceramide (Cer), and ganglioside were positively correlated with grip strength and rotarod scores. In conclusion, treadmill may protect the cortex, mitigating motor deficits via change lipid profiles in the brain and muscle.

Neuroprotective Effect of Maresin-1 in Rotenone-Induced Parkinson's Disease in Rats: The Putative Role of the JAK/STAT Pathway

Exposure to rotenone results in similar pathophysiological features as Parkinson's disease. Inflammation and oxidative stress are essential to PD pathogenesis. Maresin-1 has potent anti-inflammatory properties and promotes the regression of inflammation function. The current study aimed to evaluate the protective effects of Maresin-1 (MaR1) in rotenone (ROT)-induced PD and whether this protective role is associated with the initiation of the Janus kinase (JAK)-signal transducers and activator of transcription (STAT) signaling pathway. Thirty male Wister rats were classified into control, ROT-treated, and ROT + MaR1-treated groups. Rats underwent rotarod, open field, grip strength, and stepping tests as part of their motor behavioral evaluation. Serum glial cell-derived neurotrophic factor (GDNF) and striatal dopamine, acetylcholine, malondialdehyde (MDA), reduced glutathione (GSH), TNF-α, IL-6, and IL-1β were evaluated. Expression of JAK1 and STAT3 genes was assessed in striatum. Then, the tissue was subjected to histological and immunohistochemical evaluation for caspase-3, GFAP, and NF-kB. The administrated group with rotenone showed significant motor behavioral impairment. This was accompanied by reduced levels of GDNF and dopamine and increased levels of acetylcholine, as well as augmented oxidative stress and inflammatory biomarkers and reduced antioxidant activity. Inflammatory pathways (JAK1/STAT3, caspase-3, and NF-kB) were upregulated. Histopathological changes and upregulation in GFAP immunopositive reaction were observed. Remarkably, MaR1 treatment effectively alleviated behavior, histopathological changes, and biochemical alterations induced by ROT. MaR1 exerts protective effects against ROT-induced PD by its anti-inflammatory, antiapoptotic, and antioxidant properties. MaR1 mechanisms of action may involve modulation of pathways such as JAK/STAT.

Safranal exerts a neuroprotective effect on Parkinson's disease with suppression of NLRP3 inflammation activation

BACKGROUND

Parkinson's disease (PD) is a common central nervous system neurodegenerative disease. Neuroinflammation is one of the significant neuropathological hallmarks. As a traditional Chinese medicine, Safranal exerts anti-inflammatory effects in various diseases, however, whether it plays a similar effect on PD is still unclear. The study was to investigate the effects and mechanism of Safranal on PD.

METHODS

The PD mouse model was established by 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine MPTP firstly. Next, the degree of muscle stiffness, neuromuscular function, motor retardation and motor coordination ability were examined by observing and testing mouse movement behavior. Immunofluorescence staining was used to observe the expression of tyrosine hydroxylase (TH). The dopamine (DA) content of the striatum was detected by High-performance liquid chromatography (HPLC). The expression of TH and NLRP3 inflammasome-related markers NLRP3, IL-1β, and Capase-1 were detected by Real-time Polymerase Chain Reaction (qRT-PCR) and western blotting (WB) respectively.

RESULTS

Through behavioral testing, Parkinson's mouse showed a higher muscle stiffness and neuromuscular tension, a more motor retardation and activity disorders, together with a worse motor coordination compared with sham group. Simultaneously, DA content and TH expression in the striatum were decreased. However, after using Safranal treatment, the above pathological symptoms of Parkinson's mouse all improved compared with Safranal untreated group, the DA content and TH expression were also increased to varying degrees. Surprisingly, it observed a suppression of NLRP3 inflammation in the striatum of Parkinson's mouse.

CONCLUSIONS

Safranal played a neuroprotective effect on the Parkinson's disease and its mechanism was related to the inhibition of NLRP3 inflammasome activation.

Ca2+ signalling: A common language for organelles crosstalk in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease caused by multifactorial pathogenic mechanisms. Familial PD is linked with genetic mutations in genes whose products are either associated with mitochondrial function or endo-lysosomal pathways. Of note, mitochondria are essential to sustain high energy demanding synaptic activity of neurons and alterations in mitochondrial Ca2+ signaling have been proposed as causal events for neurodegenerative process, although the mechanisms responsible for the selective loss of specific neuronal populations in the different neurodegenerative diseases is still not clear. Here, we specifically discuss the importance of a correct mitochondrial communication with the other organelles occurring at regions where their membranes become in close contact. We discuss the nature and the role of contact sites that mitochondria establish with ER, lysosomes, and peroxisomes, and how PD related proteins participate in the regulation/dysregulation of the tethering complexes. Unravelling molecular details of mitochondria tethering could contribute to identify specific therapeutic targets and develop new strategies to counteract the progression of the disease.

Neuroprotective Efficacy of a Nanomicellar Complex of Carnosine and Lipoic Acid in a Rat Model of Rotenone-Induced Parkinson's Disease

Oxidative stress, accompanied by mitochondrial dysfunction, is a key mechanism involved in the pathogenesis of Parkinson's disease (PD). Both carnosine and lipoic acid are potent antioxidants, the applicability of which in therapy is hindered by their limited bioavailability. This study aimed to evaluate the neuroprotective properties of a nanomicellar complex of carnosine and lipoic acid (CLA) in a rotenone-induced rat model of PD. Parkinsonism was induced via the administration of 2 mg/kg rotenone over the course of 18 days. Two doses of intraperitoneal CLA (25 mg/kg and 50 mg/kg) were administered alongside rotenone to assess its neuroprotective effect. At 25 mg/kg CLA decreased muscle rigidity and partially restored locomotor activity in animals that received rotenone. Furthermore, it caused an overall increase in brain tissue antioxidant activity, accompanied by a 19% increase in neuron density in the substantia nigra and increased dopamine levels in the striatum relative to animals that only received rotenone. Based on the acquired results, it may be concluded that CLA have neuroprotective properties and could potentially be beneficial in PD treatment when used in conjunction with the base therapy.

Monoterpenoid Epoxidiol Ameliorates the Pathological Phenotypes of the Rotenone-Induced Parkinson’s Disease Model by Alleviating Mitochondrial Dysfunction

Parkinson’s disease is the second most common neurodegenerative disease. Unfortunately, there is still no definitive disease-modifying therapy. In our work, the antiparkinsonian potential of trans-epoxide (1S,2S,3R,4S,6R)-1-methyl-4-(prop-1-en-2-yl)-7-oxabicyclo [4.1.0]heptan-2,3-diol (E-diol) was analyzed in a rotenone-induced neurotoxicity model using in vitro, in vivo and ex vivo approaches. It was conducted as part of the study of the mitoprotective properties of the compound. E-diol has been shown to have cytoprotective properties in the SH-SY5Y cell line exposed to rotenone, which is associated with its ability to prevent the loss of mitochondrial membrane potential and restore the oxygen consumption rate after inhibition of the complex I function. Under the conditions of rotenone modeling of Parkinson’s disease in vivo, treatment with E-diol led to the leveling of both motor and non-motor disorders. The post-mortem analysis of brain samples from these animals demonstrated the ability of E-diol to prevent the loss of dopaminergic neurons. Moreover, that substance restored functioning of the mitochondrial respiratory chain complexes and significantly reduced the production of reactive oxygen species, preventing oxidative damage. Thus, E-diol can be considered as a new potential agent for the treatment of Parkinson’s disease.

Mitochondrial signaling on innate immunity activation in Parkinson disease

Parkinson's disease (PD) is a neurodegenerative disease characterized by the accumulation of alpha-synuclein (aSyn) in the nigrostriatal pathway that is followed by severe neuroinflammatory response. PD etiology is still puzzling; however, the mitocentric view might explain the vast majority of molecular findings not only in the brain, but also at systemic level. While neuronal degeneration is tightly associated with mitochondrial dysfunction, the causal role between aSyn accumulation and mitochondrial dysfunction still requires further investigation. Moreover, mitochondrial dysfunction can elicit an inflammatory response that may be transmitted locally but also in a long range through systemic circulation. Furthermore, mitochondrial-driven innate immune activation may involve the synthesis of antimicrobial peptides, of which aSyn poses as a good candidate. While there is still a need to clarify disease-elicited mechanisms and how aSyn has the ability to modulate mitochondrial and cellular dysfunction, recent studies provide insightful views on mitochondria-inflammation axis in PD etiology.

Long Non-coding RNA HOTAIR in Central Nervous System Disorders: New Insights in Pathogenesis, Diagnosis, and Therapeutic Potential

Central nervous system (CNS) disorders, such as ischemic stroke, neurodegenerative diseases, multiple sclerosis, traumatic brain injury, and corresponding neuropathological changes, often lead to death or long-term disability. Long non-coding RNA (lncRNA) is a class of non-coding RNA with a transcription length over 200 nt and transcriptional regulation. lncRNA is extensively involved in physiological and pathological processes through epigenetic, transcription, and post-transcriptional regulation. Further, dysregulated lncRNA is closely related to the occurrence and development of human diseases, including CNS disorders. HOX Transcript antisense RNA (HOTAIR) is the first discovered lncRNA with trans-transcriptional regulation. Recent studies have shown that HOTAIR may participate in the regulation of the occurrence and development of CNS disorders. In addition, HOTAIR has the potential to become a new biomarker for the diagnosis and prognosis assessment of CNS disorders and even provide a new therapeutic target for CNS disorders. Here, we reviewed the research results of HOTAIR in CNS disorders to provide new insights into the pathogenesis, diagnostic value, and therapeutic target potential of HOTAIR in human CNS disorders.

Time Course of Neurobehavioral Disruptions and Regional Brain Metabolism Changes in the Rotenone Mice Model of Parkinson’s Disease

Parkinson’s disease (PD) is characterized by slow progression with a long prodromal stage and the gradual evolution of both neuropsychological symptoms and subtle motor changes, preceding motor dysfunction. Thus, in order for animal models of PD to be valid, they should reproduce these characteristics of the disease. One of such models, in which neuropathology is induced by chronic injections of low doses of mitochondrial toxin rotenone, is well established in rats. However, data on this model adapted to mice remain controversial. We have designed the study to describe the timecourse of motor and non-motor symptoms during chronic subcutaneous administration of rotenone (4 mg/kg daily for 35 days) in C57BL/6 mice. We characterize the underlying neuropathological processes (dopaminergic neuron degeneration, regional brain metabolism, monoamine neurotransmitter and lipid peroxidation changes) at different timepoints: 1 day, 2 weeks and 5 weeks of daily rotenone exposure. Based on the behavioral data, we can describe three stages of pathology: cognitive changes from week 2 of rotenone exposure, subtle motor changes in week 3–4 and motor dysfunction starting roughly from week 4. Neuropathological changes in this model include a general decrease in COX activity in different areas of the brain (acute effect of rotenone) and a more specific decrease in midbrain (chronic effect), followed by significant neurodegeneration in SNpc but not VTA by the 5th week of rotenone exposure. However, we were unable to find changes in the level of monoamine neurotransmitters neither in the striatum nor in the cortex, nor in the level of lipid peroxidation in the brainstem. Thus, the gradual progression of pathology in this model is linked with metabolic changes, rather than with oxidative stress or tonic neurotransmitter release levels. Overall, this study supports the idea that a low-dose rotenone mouse model can also reproduce different stages of PD as well as rats.

Environmental factors modulating protein conformations and their role in protein aggregation diseases

The adverse physiological conditions have been long known to impact protein synthesis, folding and functionality. Major physiological factors such as the effect of pH, temperature, salt and pressure are extensively studied for their impact on protein structure and homeostasis. However, in the current scenario, the environmental risk factors (pollutants) have gained impetus in research because of their increasing concentrations in the environment and strong epidemiologic link with protein aggregation disorders. Here, we review the physiological and environmental risk factors for their impact on protein conformational changes, misfolding, aggregation, and associated pathological conditions, especially environmental risk factors associated pathologies.

The potential neuroprotective effect of diosmin in rotenone-induced model of Parkinson's disease in rats

Most treatments for Parkinson's disease (PD) focus on improving the symptoms and the dopaminergic effects; nevertheless, they cannot delay the disease progression. Diosmin (DM), a naturally occurring flavone that is obtained from citrus fruits, has demonstrated anti-apoptotic, anti-inflammatory and antioxidative properties in many diseases. This study aimed to assess the neuroprotective effects of diosmin in rotenone-induced rat model of PD and investigate its potential underlying mechanisms. A preliminary dose-response study was conducted where rats were treated with DM (50,100 and 200 mg/kg, p.o.) concomitantly with rotenone (2 mg/kg, s.c.) for 4 weeks. Catalepsy, motor impairment, spontaneous locomotion, body weight, histological examination and tyrosine hydroxylase (TH) immunoreactivity were evaluated in both the midbrains and striata of rats. Treatment with DM (200 mg/kg) showed the most promising outcome therefore, it was selected for further evaluation of α-synuclein, Bax, Bcl2, nuclear factor kappa B (NF-кB), nuclear factor erythroid 2- related factor 2 (Nrf2), and heme oxygenase-1 (HO-1), in addition to biochemical analysis of tumor necrosis factor-α (TNF-α). Results showed that DM (200 mg/kg, p.o.) prevented rotenone-induced motor impairment, weight reduction and histological damage. Furthermore, it significantly inhibited rotenone-induced decrease in TH expression. These results were correlated with reduction in α-synuclein immunoreactivity, together with improvement of Bax/Bcl2 ratio compared to rotenone group. DM also attenuated rotenone-induced increase in NF-кB expression as well as TNF- α levels. Moreover, DM inhibited rotenone-induced upregulation of Nrf2/HO-1 pathway. Thus, the current study suggests that DM might be a promising candidate for managing the neuropathological course of PD.