Sleep-related respiratory disruptions and laterodorsal tegmental nucleus in a mouse model of Parkinson's disease

Parkinson's disease (PD) is a chronic neurodegenerative disorder affecting the motor system, with non-classic symptoms such as sleep disturbances and respiratory dysfunctions. These issues reflect a complex pathophysiological interaction that severely impacts quality of life. Using a 6-hydroxydopamine (6-OHDA) mouse model of PD, we investigated these connections by analyzing sleep patterns and respiratory parameters during non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. Our findings revealed altered breathing, including reduced respiratory frequency and increased apneas during both NREM and REM. To address these abnormalities, we employed chemogenetic stimulation of cholinergic neurons in the laterodorsal tegmental nucleus (LDTg), a key region for sleep-wake regulation and respiratory modulation. This intervention normalized respiratory function. These results highlight the critical role of LDTg cholinergic neurons in the coordinating sleep and breathing, suggesting that targeting these neurons could offer a therapeutic strategy for managing PD-related respiratory complications.

Parkinson's disease models and death signaling: what do we know until now?

Parkinson's disease (PD) is the second neurodegenerative disorder most prevalent in the world, characterized by the loss of dopaminergic neurons in the Substantia Nigra (SN). It is well known for its motor and non-motor symptoms including bradykinesia, resting tremor, psychiatric, cardiorespiratory, and other dysfunctions. Pathological apoptosis contributes to a wide variety of diseases including PD. Various insults and/or cellular phenotypes have been shown to trigger distinct signaling events leading to cell death in neurons affected by PD. The intrinsic or mitochondrial pathway, inflammatory or oxidative stress-induced extrinsic pathways are the main events associated with apoptosis in PD-related neuronal loss. Although SN is the main brain area studied so far, other brain nuclei are also affected by the disease leading to non-classical motor symptoms as well as non-motor symptoms. Among these, the respiratory symptoms are often overlooked, yet they can cause discomfort and may contribute to patients shortened lifespan after disease diagnosis. While animal and in vitro models are frequently used to investigate the mechanisms involved in the pathogenesis of PD in both the SN and other brain regions, these models provide only a limited understanding of the disease's actual progression. This review offers a comprehensive overview of some of the most studied forms of cell death, including recent research on potential treatment targets for these pathways. It highlights key findings and milestones in the field, shedding light on the potential role of understanding cell death in the prevention and treatment of the PD. Therefore, unraveling the connection between these pathways and the notable pathological mechanisms observed during PD progression could enhance our comprehension of the disease's origin and provide valuable insights into potential molecular targets for the developing therapeutic interventions.

Nucleus of the solitary tract neuronal degeneration and impaired hypoxia response in a model of Parkinson's disease

Parkinson's disease (PD) involves the degeneration of dopaminergic neurons in the substantia nigra (SNpc) and manifests with both classic and non-classic motor symptoms, including respiratory failure. Our study aims to investigate the involvement of the commissural and intermediate nucleus of the solitary tract (cNTS and iNTS) in the attenuated respiratory response to hypoxia in PD. Using a PD rat model induced by bilateral injection of 6-hydroxydopamine (6-OHDA) into the striatum of male Wistar rats, we explored potential alterations in the population of Phox2b neurons or hypoxia-activated neurons in the NTS projecting to the retrotrapezoid nucleus (RTN). Additionally, we explored neuronal connectivity between SNpc and cNTS. Projections pathways were assessed using unilateral injection of the retrograde tracer Fluorogold (FG) in the cNTS and RTN. Neuronal activation was evaluated by analyzing fos expression in rats exposed to hypoxia. In the PD model, the ventilatory response, measured through whole-body plethysmography, was impaired at both baseline and in response to hypoxia. A reduction in Phox2b-expressing neurons or hypoxia-activated neurons projecting to the RTN was observed. Additionally, we identified an indirect pathway linking the SNpc and cNTS, which passes through the periaqueductal gray (PAG). In conclusion, our findings suggest impairment in the SNpc-PAG-cNTS pathway in the PD model, explaining the loss of Phox2b-expressing neurons or hypoxia-activated neurons in the cNTS and subsequent respiratory impairment during hypoxic stimulation. We propose that the reduced population of Phox2b-expressing neurons in the NTS may include the same neurons activated by hypoxia and projecting to the RTN.

Insulin-Like Growth Factor Binding Protein 2 Drives Neurodegeneration in Parkinson's Disease: Insights From In Vivo and In Vitro Studies

AIMS

Insulin-like growth factor binding protein 2 (IGFBP2) is implicated in various neurodegenerative diseases. However, its role in Parkinson's disease (PD) is unclear.

METHODS

PD rat model was established by 6-OHDA injection. After 3 weeks, mRNA-seq was conducted. Rats received rIGFBP2 via intra-MFB injection 6 h prior to 6-OHDA infusion, and the effect of IGFBP2 in PD rats was investigated by western blotting, IHC, specific kits, JC-1 staining, and TUNEL analysis. In vitro, PC12 cells were treated with 6-OHDA, and CCK-8, specific kits, Hoechst 33258 staining, Western blotting, and JC-1 staining were performed to assess the IGFBP2's role.

RESULTS

mRNA-seq revealed DEGs in PD, with attention to downregulated IGFBP2. rIGFBP2 treatment aggravated neurobehavioral deficits, decreased TH expression, Ψm, ATP level and SOD, GSH-Px activities but increased α-synuclein, ROS, MDA, mitochondrial cytochrome c contents, cell apoptosis in 6-OHDA-lesioned rats, which might be mediated through inactivating IGF-1R/AKT pathway. In 6-OHDA-treated PC12 cells, rIGFBP2 aggravated cell injury, demonstrated by decreased cell viability and increased apoptosis, oxidative stress, and mitochondrial dysfunction. Co-treatment with rIGFBP2 and rIGF-1 partially reversed the effect of rIGFBP2 on cell damage.

CONCLUSION

IGFBP2 exacerbates neurodegeneration in PD through increasing oxidative stress, mitochondrial dysfunction, and apoptosis via inhibiting IGF-1R/AKT pathway.

State-dependent alteration of respiration in a rat model of Parkinson's disease

Parkinson's disease (PD) is the second most frequent neurodegenerative disorder. Besides major deficits in motor coordination, patients may also display sensory and cognitive impairments, which are often overlooked despite being inherently part of the PD symptomatology. Amongst those symptoms, respiration, a key mechanism involved in the regulation of multiple physiological and neuronal processes, appears to be altered. Importantly, breathing patterns are highly correlated with the animal's behavioral states. This raises the question of the potential impact of behavioral state on respiration deficits in PD. To answer this question, we first characterized the respiratory parameters in a neurotoxin-induced rat model of PD (6-OHDA) across three different vigilance states: sleep, quiet waking and exploration. We noted a significantly higher respiratory frequency in 6-OHDA rats during quiet waking compared to Sham rats. A higher respiratory amplitude was also observed in 6-OHDA rats during both quiet waking and exploration. No effect of the treatment was noted during sleep. Given the relation between respiration and olfaction and the presence of olfactory deficits in PD patients, we then investigated the odor-evoked sniffing response in PD rats, using an odor habituation/cross-habituation paradigm. No substantial differences were observed in olfactory abilities between the two groups, as assessed through sniffing frequency. These results corroborate the hypothesis that respiratory impairments in 6-OHDA rats are vigilance-dependent. Our results also shed light on the importance of considering the behavioral state as an impacting factor when analyzing respiration.

Ursolic acid represses influenza A virus-triggered inflammation and oxidative stress in A549 cells by modulating the miR-34c-5p/TLR5 axis

BACKGROUND

Ursolic acid (UA) is a pentacyclic triterpenoid compound with a wide range of anti-tumor, anti-inflammatory, hypotensive and other pharmacological effects. Here, the biological roles and regulatory mechanisms of UA in influenza A virus (IAV)-treated A549 cells were investigated.

METHOD

The cytotoxic impacts of UA on A549 cells with or without IAV treatment were determined using MTT and LDH assays. The inflammatory responses and oxidative stress of IAV-treated A549 cells were measured by RT-qPCR, ELISA, DCFH-DA probe, and colorimetric assays. A dual luciferase assay was carried out to validate the molecular interaction between miR-34c-5p and TLR5. Promoter methylation was detected by MSP experiment. Methylation-related proteins were quantified by western blot. Virus replication was assessed by TCID50 and western blot assays.

RESULTS

UA significantly ameliorated IAV-triggered cell injury and inflammatory response, virus replication and oxidative stress by elevating cell viability, ROS level and the activities of SOD and GSH-Px but reducing the LDH, MDA, and TCID50 values and the expression of virus-related proteins (NP) and cytokines (TNF-α, IL-1β, IL-6, and IL-18). Moreover, UA promoted miR-34c-5p expression by repressing DNMTs-mediated methylation. TLR5 was verified to be a direct target of miR-34c-5p and could be downregulated by UA. Rescue experiments revealed that silencing miR-34c-5p diminished the regulatory roles of UA in IAV-treated A549 cells.

CONCLUSION

Our data elucidated that UA attenuated IAV-triggered inflammatory responses and oxidative stress in A549 cells by regulating the miR-34c-5p/TLR5 axis, suggesting that UA plays a protective role in IAV-induced pneumonia.

Respiratory deficits in a female rat model of Parkinson's Disease

NEW FINDINGS

What is the central question of this study? How does 6-OHDA-induced Parkinson's Disease model affect the respiratory response in female rats? What effect does ovariectomy have on that response? What is the main finding and its importance? Our results suggest a protective effect of ovarian hormones in maintaining normal neuroanatomical integrity of the medullary respiratory nucleus in females. It was observed that ovariectomy alone reduced NK1r density in preBotc and BotC, and there was an incremental effect of 6-OHDA and ovariectomy on RTN neurons.

ABSTRACT

Emerging evidence indicates that Parkinson's disease (PD) courses with autonomic and respiratory deficiencies in addition to the classical motor symptoms. The prevalence of PD is lower in women, and it has been hypothesized that neuroprotection by ovarian hormones can explain this difference. While male PD animal models present changes in the central respiratory control areas, as well as ventilatory parameters under normoxia and hypercapnia, little is known about sex differences regarding respiratory deficits in this disease background. This study aimed to explore the neuroanatomical and functional respiratory changes in intact and ovariectomized female rats subjected to chemically induced PD via a bilateral intrastriatal injection of 6-hydroxydopamine (6-OHDA). The respiratory parameters were evaluated by whole-body plethysmography, and the neuroanatomy was monitored using immunohistochemistry. It was found that dopaminergic neurons in the substantia nigra and neurokinin-1 receptor (NK1r) density in the rostral ventrolateral respiratory group, Botzinger and pre-Botzinger complex were reduced in the chemically induced PD animals. Additionally, reduced numbers of Phox2b neurons were only observed in the retrotrapezoid nucleus of PD-ovariectomized rats. Concerning respiratory parameters, in ovariectomized rats, the resting and hypercapnia-induced tidal volume (V_T ) is reduced, and ventilation (V_E ) changes independently of 6-OHDA administration. Notably, there is a reduction in the number of RTN phox2b neurons and hypercapnia-induced respiratory changes in PD-ovariectomized animals due to a 6-OHDA and OVX interaction. These results suggest a protective effect induced by ovarian hormones in neuroanatomical changes observed in a female experimental PD model. This article is protected by copyright. All rights reserved.

Ameliorative role of Syzygium aromaticum aqueous extract on synaptosomal tyrosine hydroxylase activity, oxidative stress parameters, and behavioral changes in lead-induced neurotoxicity in mice

This study reports the protective role of the aqueous extract of Syzygium aromaticum (ESA) against lead (Pb)-induced neurotoxicity in mice. Thirty male mice weighing between 18 g and 25 g were randomly divided into five groups. (1) Group 1 (control group), (2) group 2 (Pb-test group): was administered with a solution containing 0.1% (w/v) of lead acetate (PbAc), (3) group 3 (ESA + Pb100 group): was administered with 0.1% (w/v) of PbAc followed by 100 mg/kg of S. aromaticum extract by gavage, (4) group 4 (ESA + Pb200): was administered with 0.1% (w/v) of PbAc followed by 200 mg/kg of S. aromaticum extract, and (5) group 5 (ESA-group): was administered with 100 mg/kg of S. aromaticum. Level of lead was determined by atomic absorption spectroscopy. Cerebral cortex synaptosomes prepared from mice administered orally with lead-acetate shown a significantly increased (p < .05) in tyrosine hydroxylase and protein carbonyl level and significantly decreased (p < .05) superoxide dismutase, glutathione reductase, and glutathione transferase activities. Also, there was a significant increase in brain lead concentration level, however, it was observed that S. aromaticum significantly reduced (p < .05) the level of lead at all tested doses. S. aromaticum rescued cerebral cortex synaptosomes from lead-induced neurotoxicity by relieving oxidative stress and abating elevated tyrosine hydroxylase activity. Moreover, S. aromaticum at the different dose grade (100 mg and 200 mg) abrogated the loss of motor performance in mice groups induced with lead. Altogether, our findings showed that S. aromaticum possesses antioxidant and neuro-modulatory potential against lead-induced neuronal damage. PRACTICAL APPLICATIONS: Environmental pollution with heavy metals is a known public health concern and their incremental concentrations in soil and water have risen to an unprecedented degree. Lead is one of the top 10 contaminants on the WHO's list of substances of greatest public health concern that impact the brain. However, exogenous natural bioactive supplements molecules could be one of the remedies to reduce Pb-induced toxicity. Our findings indicate therefore that, S. aromaticum could be a good fit for lowering Pb neurotoxicity and could be suggested as a neuroprotective molecule against neurodegenerative diseases involving catecholaminergic dysfunction induced by metallic elements.

Neuroprotective Effects of Resveratrol in In vivo and In vitro Experimental Models of Parkinson's Disease: a Systematic Review

Parkinson's disease (PD) is currently the second most common neurodegenerative disease, being characterized by motor and non-motor symptoms. The therapeutic options available for its treatment are limited, do not slow the progression of the disease, and have serious side effects. For this reason, many studies have sought to find compounds with neuroprotective properties that bring additional benefits to current therapy. In this context, resveratrol is a phenolic compound, found in many plant species, capable of crossing the blood-brain barrier and having multiple biological properties. Experimental studies in vitro and in vivo have shown that it can prevent or slow the progression of a variety of diseases, including PD. In this systematic review, we summarize the effects of resveratrol in experimental in vivo and in vitro models of PD and discuss the molecular mechanisms involved in its action. The bibliographic search was performed in the databases of PubMed, Web of Science, SciELO, and Google Scholar, and based on the inclusion criteria, 41 articles were selected and discussed. Most of the included studies have demonstrated neuroprotective effects of resveratrol. In general, resveratrol prevented behavioral and/or neurological disorders, improved antioxidant defenses, reduced neuroinflammatory processes, and inhibited apoptosis. In summary, this systematic review offers important scientific evidence of neuroprotective effects of resveratrol in PD and also provide valuable information about its mechanism of action that can support future clinical studies.

Respiratory disorders of Parkinson's disease

Parkinson's disease (PD) is characterized by the progressive loss of dopaminergic neurons in the substantia nigra, mainly affecting people over 60 yr of age. Patients develop both classic symptoms (tremors, muscle rigidity, bradykinesia, and postural instability) and nonclassical symptoms (orthostatic hypotension, neuropsychiatric deficiency, sleep disturbances, and respiratory disorders). Thus, patients with PD can have a significantly impaired quality of life, especially when they do not have multimodality therapeutic follow-up. The respiratory alterations associated with this syndrome are the main cause of mortality in PD. They can be classified as peripheral when caused by disorders of the upper airways or muscles involved in breathing and as central when triggered by functional deficits of important neurons located in the brainstem involved in respiratory control. Currently, there is little research describing these disorders, and therefore, there is no well-established knowledge about the subject, making the treatment of patients with respiratory symptoms difficult. In this review, the history of the pathology and data about the respiratory changes in PD obtained thus far will be addressed.

Neuropeptide-S prevents 6-OHDA-induced gastric dysmotility in rats

This study aims to explore the effect of chronic central neuropeptide-S (NPS) treatment on gastrointestinal dysmotility and the changes of cholinergic neurons in the dorsal motor nucleus of the vagus (DMV) of a Parkinson's disease (PD) rat model. The PD model was induced through a unilateral medial forebrain bundle (MFB) administration of the 6-hydroxydopamine (6-OHDA). Locomotor activity (LMA), solid gastric emptying (GE), and gastrointestinal transit (GIT) were measured 7 days after the surgery. NPS was daily administered (1 nmol, icv, 7 days). In substantia nigra (SN), dorsal motor nucleus of the vagus (DMV), and gastric whole-mount samples, changes in tyrosine hydroxylase (TH), choline acetyltransferase (ChAT), neuronal nitric oxide synthase (nNOS), glial fibrillary acidic protein (GFAP), NPS receptor (NPSR), and alpha-synuclein (Ser129) were examined by immunohistochemistry. Cuprolinic blue staining was used to evaluate the number of neuronal cells in myenteric ganglia. The GIT rate, the total number of myenteric neurons, and the expressions of ChAT, nNOS, TH, and GFAP in the myenteric plexus were not changed in rats that received the 6-OHDA. Chronic NPS treatment reversed 6-OHDA-induced impairment of the motor performance, and GE, while preventing the loss of dopaminergic and cholinergic neurons in SN and DMV, respectively. NPS attenuated 6-OHDA-induced α-syn (Ser129) pathology both in SN and DMV. Additionally, expression of NPSR protein was detected in gastro-projecting cells in DMV. Taken together, centrally applied NPS seems to prevent 6-OHDA-induced gastric dysmotility through a neuroprotective action on central vagal circuitry.