Colonic electrical stimulation improves colonic transit in rotenone-induced Parkinson's disease model through affecting enteric neurons

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.

Electroacupuncture improves gastrointestinal motility through a central-cholinergic pathway-mediated GDNF releasing from intestinal glial cells to protect intestinal neurons in Parkinson's disease rats

Constipation symptoms of Parkinson's disease (PD) seriously reduce the quality of life of patients and aggravate the development of the disease, but current treatment options still cannot alleviate the progress of constipation. Electroacupuncture (EA) is a new method for the treatment of constipation, which can effectively treat the symptoms of constipation in PD patients. However, the specific regulatory mechanisms of EA in the treatment of constipation symptoms in PD remain unclear. The aim of this study is to investigate the therapeutic effect of EA on PD constipation rats and its regulatory mechanism. A rotenone (ROT)-induced gastrointestinal motility disorder model was used to simulate the pathological process of constipation in PD. The results showed that EA could effectively promote gastrointestinal peristalsis, reduce α-synuclein accumulation in substantia nigra and colon and colonic injury in rats after ROT administration. Mechanistically, EA activation of the central-cholinergic pathway increases acetylcholine release in the colon. At the same time, EA up-regulated the co-expression of enteric glial cells (EGCs) and α7 nicotinic acetylcholine receptor (α7nAChR). EA increased the expression of choline acetyltransferase (ChAT), neuronal nitric oxide synthase (nNOS), and tyrosine hydroxylase (TH) in the colon of PD rats. Further mechanistic studies showed that EA increased the expression of glial cell-derived neurotrophic factor (GDNF), GFRa1 and p-AKT in colon tissues. The present study confirmed that EA upregulates α7nAChR through a central-cholinergic mechanism to promote GDNF release from EGCs, thereby protecting intestinal neurons and thereby improving gastrointestinal motility.

The role of stinging nettle (Urtica dioica L.) in the management of rotenone-induced Parkinson's disease in rats

Parkinson's disease (PD) is one of the most common neurodegenerative conditions. Alpha-synuclein deposition, Lewy bodies (LBs) formation, disruption of the autophagic machinery, apoptosis of substantia nigra dopaminergic neurons, oxidative stress, and neuroinflammation are all pathologic hallmarks of PD. The leaves of the stinging Nettle (Urtica dioica L.) have a long history as an herbal cure with antioxidant, anti-inflammatory, anti-cancer, immunomodulatory, and neuroprotective properties. The current study aims for the first time to investigate the role of Nettle supplementation on Rotenone-induced PD. Rats were divided into five groups; a Saline control, Nettle control (100 mg/kg/day), Rotenone control (2 mg/kg/day), Rotenone + Nettle (50 mg /kg/day), and Rotenone + Nettle (100 mg/kg). After four weeks, the rats were examined for behavioral tests. The midbrains were investigated for histopathological alteration and immunohistochemical reaction for Tyrosine hydroxylase in the dopaminergic neurons, α-synuclein for Lewy bodies, caspase 3 for apoptotic neurons, LC3 and P62 for autophagic activity. Midbrain homogenates were examined for oxidative stress markers. mRNA expression of TNFα and Il6; inflammatory markers, Bcl-2, BAX and Caspase 3; apoptosis markers, were detected in midbrains. The results showed that Nettle caused recovery of midbrain dopaminergic neurons, by inhibiting apoptosis, inflammation, and oxidative stress and by restoring the autophagic machinery with clearance of α-synuclein deposits. We can conclude that Nettle is a potentially effective adjuvant in the treatment of Parkinson's disease.

Colonic Electrical Stimulation for Chronic Constipation: A Perspective Review

Chronic constipation affects around 20% of the population and there is no efficient solution. This perspective review explores the potential of colonic electric stimulation (CES) using neural implants and methods of bioelectronic medicine as a therapeutic way to treat chronic constipation. The review covers the neurophysiology of colonic peristaltic function, the pathophysiology of chronic constipation, the technical aspects of CES, including stimulation parameters, electrode placement, and neuromodulation target selection, as well as a comprehensive analysis of various animal models highlighting their advantages and limitations in elucidating the mechanistic insights and translational relevance for CES. Finally, the main challenges and trends in CES are discussed.

The role of gut-brain axis in a rotenone-induced rat model of Parkinson's disease

Parkinson's disease (PD) is a widespread neurodegenerative condition affecting millions globally. This investigation centered on the gut-brain axis in a rotenone-induced PD rat model. Researchers monitored behavioral shifts, histological modifications, neurodegeneration, and inflammation markers throughout the rats' bodies. Results revealed that rotenone-treated rats displayed reduced exploration (p = 0.004) and motor coordination (p < 0.001), accompanied by decreased Nissl staining and increased alpha-synuclein immunoreactivity in the striatum (p = 0.009). Additionally, these rats exhibited weight loss (T3, mean = 291.9 ± 23.67; T19, mean = 317.5 ± 17.53; p < 0.05) and substantial intestinal histological alterations, such as shortened villi, crypt architecture loss, and inflammation. In various regions, researchers noted elevated immunoreactivity to ionized binding adapter molecule (IBA)-1 (p < 0.05) and reduced immunoreactivity to glial fibrillary acidic protein (p < 0.05) and S100B (p < 0.001), indicating altered glial cell activity. Overall, these findings imply that PD is influenced by gut-brain axis changes and may originate in the intestine, impacting bidirectional gut-brain communication.

Identification of fatty acid-related subtypes, the establishment of a prognostic signature, and immune infiltration characteristics in lung adenocarcinoma

Abnormal fatty acid (FA) metabolism can change the inflammatory microenvironment and promote tumor progression and metastasis, however, the potential association between FA-related genes (FARGs) and lung adenocarcinoma (LUAD) is still unclear. In this study, we described the genetic and transcriptomic changes of FARGs in LUAD patients and identified two different FA subtypes, which were significantly correlated with overall survival and tumor microenvironment infiltrating cells in LUAD patients. In addition, the FA score was also constructed through the LASSO Cox to evaluate the FA dysfunction of each patient. Multivariate Cox analysis proved that the FA score was an independent predictor and created the FA score integrated nomogram, which offered a quantitative tool for clinical practice. The performance of the FA score has been substantiated in numerous datasets for its commendable accuracy in estimating overall survival in LUAD patients. The groups with high and low FA scores exhibited different mutation spectrums, copy number variations, enrichment pathways, and immune status. Noteworthy differences between the two groups in terms of immunophenoscore and Tumor Immune Dysfunction and Exclusion were observed, suggesting that the group with a low FA score was more responsive to immunotherapy, and similar results were also confirmed in the immunotherapy cohort. In addition, seven potential chemotherapeutic drugs related to FA score targeting were predicted. Ultimately, we ascertained that the attenuation of KRT6A expression impeded the proliferation, migration, and invasion of LUAD cell lines. In summary, this research offers novel biomarkers to facilitate prognostic forecasting and clinical supervision for individuals afflicted with LUAD.

The link between the gut microbiota and Parkinson's Disease: A systematic mechanism review with focus on α-synuclein transport

INTRODUCTION

Research has suggested a link between the gut microbiota and Parkinson's Disease (PD), and an early involvement of gastrointestinal dysfunction has been reported in patients. A mechanism review was performed to investigate whether the neurodegenerative cascade begins in the gut; mediated by gut dysbiosis and retrograde transport of α-synuclein. This review provides a summary of microbiome composition associated with PD, and evaluates pathophysiological mechanisms from animal and in vitro models of PD.

METHOD

A systematic literature search was performed in PubMed; 82 of 299 papers met the inclusion criteria.

RESULTS

All twenty-two human case-control studies demonstrated an altered gut microbiota in PD compared to healthy controls, with results suggesting a proinflammatory phenotype present in PD. A germ-free animal study has demonstrated that gut microbiota are required for microglia activation, α-synuclein pathology and motor deficits. Accumulation of phosphorylated α-synuclein has been observed in the enteric nervous system prior to the onset of motor symptoms in animal models of PD, and there is data to support retrograde transport of α-synuclein from the gut to the brain. Different animal models of PD have demonstrated neuroinflammation, microglial activation and loss of dopaminergic neurons in the brain.

CONCLUSION

Evidence from this review supports the hypothesis that pathology spreads from the gut to the brain. Future animal studies using oral LPS or microbiota transplants from human PD cases could provide further insight into the entire mechanism. Prospective longitudinal microbiome studies and novel modelling approaches could help to identify functional dysbiosis and early biomarkers for PD.

Electroacupuncture Alleviates Neuroinflammation and Motor Dysfunction by Regulating Intestinal Barrier Function in a Mouse Model of Parkinson Disease

Gastrointestinal dysfunction is the main nonmotor characteristic of Parkinson disease (PD), manipulation of gastrointestinal function by altering gut-brain axis is a potentially novel entry point for the treatment of PD. Acupuncture has been reported to confer beneficial effects in the gastrointestinal diseases. Therefore, this study aimed to explore the effects and mechanism of acupuncture on the pathophysiology and gastrointestinal function of PD. A PD mouse model was established by rotenone, and electroacupuncture was used to regulate the gastrointestinal function. Rotenone was found to induce the types of brain pathologies and gastrointestinal dysfunction that are similar to those observed with PD. Electroacupuncture significantly increased the spontaneous activity of mice with PD and increased the expression of tyrosine hydroxylase, while reducing the expression of Iba-1 in substantia nigra (SN), suggesting that motor dysfunction and neurological damage was alleviated. In addition, electroacupuncture significantly reduced the deposition of α-synuclein in both colon and SN, reduced intestinal inflammation, and exerted protective effects on enteric nervous system and intestinal barrier. In conclusion, electroacupuncture confers beneficial effects on the gastrointestinal system of mice with PD and can alleviate neuroinflammation and neuropathic injury by inhibiting intestinal inflammation, promoting intestinal barrier repair and reducing α-synuclein deposition in the colon.

The GABAA Receptor Influences Pressure Overload-Induced Heart Failure by Modulating Macrophages in Mice

Background

Myocardial macrophages have key roles in cardiac remodeling and dysfunction. The gamma-aminobutyric acid subtype A (GABAA) receptor was recently found to be distributed in macrophages, allowing regulation of inflammatory responses to various diseases. This study aimed to clarify the role of GABAA receptor-mediated macrophage responses in pressure overload-induced heart failure.

Methods and Results

C57BL/6J mice underwent transverse aortic constriction for pressure-overload hypertrophy (POH) and were intraperitoneally treated with a specific GABAA receptor agonist (topiramate) or antagonist (bicuculline). Echocardiography, histology, and flow cytometry were performed to evaluate the causes and effects of myocardial hypertrophy and fibrosis. Activation of the GABAA receptor by topiramate reduced ejection fraction and fractional shortening, enlarged the end-diastolic and end-systolic left ventricular internal diameter, aggravated myocardial hypertrophy and fibrosis, and accelerated heart failure in response to pressure overload. Mechanistically, topiramate increased the number of Ly6Clow macrophages in the heart during POH and circulating Ly6Chigh classic monocyte infiltration in late-phase POH. Further, topiramate drove Ly6Clow macrophages toward MHCIIhigh macrophage polarization. As a result, Ly6Clow macrophages activated the amphiregulin-induced AKT/mTOR signaling pathway, and Ly6ClowMHCIIhigh macrophage polarization increased expression levels of osteopontin and TGF-β, which led to myocardial hypertrophy and fibrosis. Conversely, GABAA receptor blockage with bicuculline reversed these effects.

Conclusions

Control of the GABAA receptor activity in monocytes/macrophages plays an important role in myocardial hypertrophy and fibrosis after POH. Blockade of the GABAA receptor has the potential to improve pressure overload-induced heart failure.

The association of enteric neuropathy with gut phenotypes in acute and progressive models of Parkinson's disease

Parkinson's disease (PD) is associated with neuronal damage in the brain and gut. This work compares changes in the enteric nervous system (ENS) of commonly used mouse models of PD that exhibit central neuropathy and a gut phenotype. Enteric neuropathy was assessed in five mouse models: peripheral injection of MPTP; intracerebral injection of 6-OHDA; oral rotenone; and mice transgenic for A53T variant human α-synuclein with and without rotenone. Changes in the ENS of the colon were quantified using pan-neuronal marker, Hu, and neuronal nitric oxide synthase (nNOS) and were correlated with GI function. MPTP had no effect on the number of Hu+ neurons but was associated with an increase in Hu+ nuclear translocation (P < 0.04). 6-OHDA lesioned mice had significantly fewer Hu+ neurons/ganglion (P < 0.02) and a reduced proportion of nNOS+ neurons in colon (P < 0.001). A53T mice had significantly fewer Hu+ neurons/area (P < 0.001) and exhibited larger soma size (P < 0.03). Treatment with rotenone reduced the number of Hu+ cells/mm2 in WT mice (P < 0.006) and increased the proportion of Hu+ translocated cells in both WT (P < 0.02) and A53T mice (P < 0.04). All PD models exhibited a degree of enteric neuropathy, the extent and type of damage to the ENS, however, was dependent on the model.

Enlightening the frontiers of neurogastroenterology through optogenetics

Neurogastroenterology refers to the study of the extrinsic and intrinsic nervous system circuits controlling the gastrointestinal (GI) tract. Over the past 5-10 yr there has been an explosion in novel methodologies, technologies and approaches that offer great promise to advance our understanding of the basic mechanisms underlying GI function in health and disease. This review focuses on the use of optogenetics combined with electrophysiology in the field of neurogastroenterology. We discuss how these technologies and tools are currently being used to explore the brain-gut axis and debate the future research potential and limitations of these techniques. Taken together, we consider that the use of these technologies will enable researchers to answer important questions in neurogastroenterology through fundamental research. The answers to those questions will shorten the path from basic discovery to new treatments for patient populations with disorders of the brain-gut axis affecting the GI tract such as irritable bowel syndrome (IBS), functional dyspepsia, achalasia, and delayed gastric emptying.

The protective effect of inosine against rotenone-induced Parkinson's disease in mice; role of oxido-nitrosative stress, ERK phosphorylation, and A2AR expression

Parkinson's disease (PD) is a severe disabling syndrome in which neuroinflammation and various signaling pathways are believed to mediate dopaminergic neurodegeneration. Here, the possible disease-modifying effects of the purine nucleoside inosine were examined against rotenone-induced PD. Mice were allocated into six groups, namely, a normal control group receiving dimethylsulfoxide, a PD control group receiving rotenone, a standard treatment group receiving L-dopa/carbidopa together with rotenone, and three treatment groups receiving inosine in low, medium, and high doses together with rotenone. At the end of the experimental protocol, three behavioral tests were performed to assess PD motor manifestations, namely, wire-hanging test, wood-walking test, and stair test. After performing the behavioral study, mice striata were isolated for the colorimetric assay of hypoxanthine, the enzyme-linked immunosorbent assay of dopamine, tumor necrosis factor-α, interleukin-6 and nitrite, the Western blot estimation of total and phosphorylated extracellular signal-regulated kinase (tERK and pERK), the polymerase chain reaction estimation of adenosine A_2A receptor (A2AR) expression, as well as the histopathological examination of substantia nigra and striatal tissue. Inosine protected against PD progression in a dose-dependent manner, with the effect comparable to the standard treatment L-dopa/carbidopa, evidenced by behavioral, biochemical, and histologic findings. The beneficial antiparkinsonian effect of inosine could be attributed to the ability of the drug to ameliorate neuroinflammation and oxido-nitrosative stress, together with suppression of ERK phosphorylation and down-regulation of A2AR expression. Inosine could therefore be considered as a disease-modifying agent against PD, but further studies are claimed to confirm such effects clinically.