Curcumin Regulates Gut Microbiota and Exerts a Neuroprotective Effect in the MPTP Model of Parkinson's Disease

The Interaction Between Nutraceuticals and Gut Microbiota: a Novel Therapeutic Approach to Prevent and Treatment Parkinson's Disease

Parkinson's disease (PD) is a complex neurodegenerative disorder characterized by the progressive loss of dopaminergic neurons, leading to motor and non-motor symptoms. Emerging research has shed light on the role of gut microbiota in the pathogenesis and progression of PD. Nutraceuticals such as curcumin, berberine, phytoestrogens, polyphenols (e.g., resveratrol, EGCG, and fisetin), dietary fibers have been shown to influence gut microbiota composition and function, restoring microbial balance and enhancing the gut-brain axis. The mechanisms underlying these benefits involve microbial metabolite production, restoration of gut barrier integrity, and modulation of neuroinflammatory pathways. Additionally, probiotics and prebiotics have shown potential in promoting gut health, influencing the gut microbiome, and alleviating PD symptoms. They can enhance the gut's antioxidant capacity of the gut, reduce inflammation, and maintain immune homeostasis, contributing to a neuroprotective environment. This paper provides an overview of the current state of knowledge regarding the potential of nutraceuticals and gut microbiota modulation in the prevention and management of Parkinson's disease, emphasizing the need for further research and clinical trials to validate their effectiveness and safety. The findings suggest that a multifaceted approach involving nutraceuticals and gut microbiota may open new avenues for addressing the challenges of PD and improving the quality of life for affected individuals.

Gut microbiota dysbiosis contributes to α-synuclein-related pathology associated with C/EBPβ/AEP signaling activation in a mouse model of Parkinson's disease

JOURNAL/nrgr/04.03/01300535-202409000-00042/figure1/v/2024-01-16T170235Z/r/image-tiff Parkinson's disease is a neurodegenerative disease characterized by motor and gastrointestinal dysfunction. Gastrointestinal dysfunction can precede the onset of motor symptoms by several years. Gut microbiota dysbiosis is involved in the pathogenesis of Parkinson's disease, whether it plays a causal role in motor dysfunction, and the mechanism underlying this potential effect, remain unknown. CCAAT/enhancer binding protein β/asparagine endopeptidase (C/EBPβ/AEP) signaling, activated by bacterial endotoxin, can promote α-synuclein transcription, thereby contributing to Parkinson's disease pathology. In this study, we aimed to investigate the role of the gut microbiota in C/EBPβ/AEP signaling, α-synuclein-related pathology, and motor symptoms using a rotenone-induced mouse model of Parkinson's disease combined with antibiotic-induced microbiome depletion and fecal microbiota transplantation. We found that rotenone administration resulted in gut microbiota dysbiosis and perturbation of the intestinal barrier, as well as activation of the C/EBP/AEP pathway, α-synuclein aggregation, and tyrosine hydroxylase-positive neuron loss in the substantia nigra in mice with motor deficits. However, treatment with rotenone did not have any of these adverse effects in mice whose gut microbiota was depleted by pretreatment with antibiotics. Importantly, we found that transplanting gut microbiota derived from mice treated with rotenone induced motor deficits, intestinal inflammation, and endotoxemia. Transplantation of fecal microbiota from healthy control mice alleviated rotenone-induced motor deficits, intestinal inflammation, endotoxemia, and intestinal barrier impairment. These results highlight the vital role that gut microbiota dysbiosis plays in inducing motor deficits, C/EBPβ/AEP signaling activation, and α-synuclein-related pathology in a rotenone-induced mouse model of Parkinson's disease. Additionally, our findings suggest that supplementing with healthy microbiota may be a safe and effective treatment that could help ameliorate the progression of motor deficits in patients with Parkinson's disease.

Antimicrobial drugs for Parkinson's disease: Existing therapeutic strategies and novel drugs exploration

Parkinson's disease (PD), the second most common neurodegenerative disorder, is characterized by loss of dopaminergic neurons in the substantia nigra, as well as the abnormal accumulation of misfolded α-synuclein. Clinically, PD is featured by typical motor symptoms and some non-motor symptoms. Up to now, although considerable progress has been made in understanding the pathogenesis of PD, there is still no effective therapeutic treatment for the disease. Thus, exploring new therapeutic strategies has been a topic that needs to be addressed urgently. Noteworthy, with the proposal of the microbiota-gut-brain axis theory, antimicrobial drugs have received significant attention due to their effects on regulating the intestinal microbiota. Nowadays, there is growing evidence showing that some antimicrobial drugs may be promising drugs for the treatment of PD. Data from pre-clinical and clinical studies have shown that some antimicrobial drugs may play neuroprotective roles in PD by modulating multiple biochemical and molecular pathways, including reducing α-synuclein aggregation, inhibiting neuroinflammation, regulating mitochondrial structure and function, as well as suppressing oxidative stress. In this paper, we summarized the effects of some antimicrobial drugs on PD treatment from recent pre-clinical and clinical studies. Then, we further discussed the potential of a few antimicrobial drugs for treating PD based on molecular docking and molecular dynamics simulation. Importantly, we highlighted the potential of clorobiocin as the therapeutic strategy for PD owing to its ability to inhibit α-synuclein aggregation. These results will help us to better understand the potential of antimicrobial drugs in treating PD and how antimicrobial drugs may alleviate or reverse the pathological symptoms of PD.

Crosstalk between gut-brain axis: unveiling the mysteries of gut ROS in progression of Parkinson's disease

"Path to a good mood lies through the gut." This statement seems to imply that it has long been believed that the gut is connected with the brain. Research has shown that eating food activates the reward system and releases dopamine (DA), establishing a link between the peripheral and central nervous system. At the same time, researchers also trust that the gut is involved in the onset of many diseases, including Parkinson's disease (PD), in which gastrointestinal dysfunction is considered a prevalent symptom. Reports suggest that PD starts from the gut and reaches the brain via the vagus nerve. Recent studies have revealed an intriguing interaction between the gut and brain, which links gut dysbiosis to the etiology of PD. This review aims to explore the mechanistic pathway how reactive oxygen species (ROS) generation in the gut affects the makeup and operation of the dopamine circuitry in the brain. Our primary concern is ROS generation in the gut, which disrupts the gut microbiome (GM), causing α-synuclein accumulation and inflammation. This trio contributes to the loss of DA neurons in the brain, resulting in PD development. This review also compiles pre-clinical and clinical studies on antioxidants, demonstrating that antioxidants reduce ROS and increase DA levels. Collectively, the study highlights the necessity of comprehending the gut-brain axis for unraveling the riddles of PD pathogenesis and considering new therapeutic approaches.

Gardenin A treatment attenuates inflammatory markers, synuclein pathology and deficits in tyrosine hydroxylase expression and improves cognitive and motor function in A53T-α-syn mice

Oxidative stress and neuroinflammation are widespread in the Parkinson's disease (PD) brain and contribute to the synaptic degradation and dopaminergic cell loss that result in cognitive impairment and motor dysfunction. The polymethoxyflavone Gardenin A (GA) has been shown to activate the NRF2-regulated antioxidant pathway and inhibit the NFkB-dependent pro-inflammatory pathway in a Drosophila model of PD. Here, we evaluate the effects of GA on A53T alpha-synuclein overexpressing (A53TSyn) mice. A53TSyn mice were treated orally for 4 weeks with 0, 25, or 100 mg/kg GA. In the fourth week, mice underwent behavioral testing and tissue was harvested for immunohistochemical analysis of tyrosine hydroxylase (TH) and phosphorylated alpha synuclein (pSyn) expression, and quantification of synaptic, antioxidant and inflammatory gene expression. Results were compared to vehicle-treated C57BL6J mice. Treatment with 100 mg/kg GA improved associative memory and decreased abnormalities in mobility and gait in A53TSyn mice. GA treatment also reduced pSyn levels in both the cortex and hippocampus and attenuated the reduction in TH expression in the striatum seen in A53Tsyn mice. Additionally, GA increased cortical expression of NRF2-regulated antioxidant genes and decreased expression of NFkB-dependent pro-inflammatory genes. GA was readily detectable in the brains of treated mice and modulated the lipid profile in the deep gray brain tissue of those animals. While the beneficial effects of GA on cognitive deficits, motor dysfunction and PD pathology are promising, future studies are needed to further fully elucidate the mechanism of action of GA, optimizing dosing and confirm these effects in other PD models.

[The complex effect of polyphenols on the gut microbiota and triggers of neurodegeneration in Parkinson's disease]

Intestinal dysfunction and microbiome changes are actively discussed in the modern literature as the most important link in the development of neurodegenerative changes in Parkinson's disease. The article discusses the pathogenetic chain «microbiome- intestine-brain», as well as factors that affect the development of intestinal dysbiosis. A promising direction for influencing microflora and inflammatory changes in the intestine is the use of polyphenols, primarily curcumin. The review of experimental, laboratory, clinical research proving the pleiotropic effect of curcumin, including its antioxidant, anti-inflammatory, neuroprotective effects, realized both through peripheral and central mechanisms is presented.

Gardenin A improves cognitive and motor function in A53T-α-syn mice

Oxidative stress and neuroinflammation are widespread in the Parkinson's disease (PD) brain and contribute to the synaptic degradation and dopaminergic cell loss that result in cognitive impairment and motor dysfunction. The polymethoxyflavone Gardenin A (GA) has been shown to activate the NRF2-regulated antioxidant pathway and inhibit the NFkB-dependent pro-inflammatory pathway in a Drosophila model of PD. Here, we evaluate the effects of GA on A53T alpha-synuclein overexpressing (A53TSyn) mice. A53TSyn mice were treated orally for 4 weeks with 0, 25, or 100 mg/kg GA. In the fourth week, mice underwent behavioral testing and tissue was harvested for immunohistochemical analysis of tyrosine hydroxylase (TH) and phosphorylated alpha synuclein (pSyn) expression, and quantification of synaptic, antioxidant and inflammatory gene expression. Results were compared to vehicle-treated C57BL6 mice. Treatment with 100 mg/kg GA improved associative memory and decreased abnormalities in mobility and gait in A53TSyn mice. GA treatment also reduced cortical and hippocampal levels of pSyn and attenuated the reduction in TH expression in the striatum. Additionally, GA increased cortical expression of NRF2-regulated antioxidant genes and decreased expression of NFkB-dependent pro-inflammatory genes. GA was readily detectable in the brains of treated mice and modulated the lipid profile in the deep gray brain tissue of those animals. While the beneficial effects of GA on cognitive deficits, motor dysfunction and PD pathology are promising, future studies are needed to further fully elucidate the mechanism of action of GA, optimizing dosing and confirm these effects in other PD models.

Significance Statement

The polymethoxyflavone Gardenin A can improve cognitive and motor function and attenuate both increases in phosphorylated alpha synuclein and reductions in tyrosine hydroxylase expression in A53T alpha synuclein overexpressing mice. These effects may be related to activation of the NRF2-regulated antioxidant response and downregulation of NFkB-dependent inflammatory response by Gardenin A in treated animals. The study also showed excellent brain bioavailability of Gardenin A and modifications of the lipid profile, possibly through interactions between Gardenin A with the lipid bilayer, following oral administration. The study confirms neuroprotective activity of Gardenin A previously reported in toxin induced Drosophila model of Parkinson's disease.

The Effect of Curcumin on the Gut-Brain Axis: Therapeutic Implications

The gut-brain axis describes the bidirectional communication between the gut, the enteric nervous system, and the central nervous system. The gut-brain axis has attracted increasing attention owing to its regulatory effect on dysbiosis and a wide range of related diseases. Several types of nutrients, such as curcumin, have been proposed as regulators of the dysbiotic state, and preclinical experiments have suggested that curcumin is not only beneficial but also safe. This review focuses on the interplay between curcumin and the gut microbiota. Moreover, it provides a comprehensive review of the crosstalk between the gut-brain axis and disease, whilst also discussing curcumin-mediated gut-brain axis-dependent and -independent signaling about modulation of gut microbiota dysbiosis. This will help to define the utility of curcumin as a novel therapeutic agent to regulate intestinal microflora dysbiosis.

From-Toilet-to-Freezer: A Review on Requirements for an Automatic Protocol to Collect and Store Human Fecal Samples for Research Purposes

The composition, viability and metabolic functionality of intestinal microbiota play an important role in human health and disease. Studies on intestinal microbiota are often based on fecal samples, because these can be sampled in a non-invasive way, although procedures for sampling, processing and storage vary. This review presents factors to consider when developing an automated protocol for sampling, processing and storing fecal samples: donor inclusion criteria, urine-feces separation in smart toilets, homogenization, aliquoting, usage or type of buffer to dissolve and store fecal material, temperature and time for processing and storage and quality control. The lack of standardization and low-throughput of state-of-the-art fecal collection procedures promote a more automated protocol. Based on this review, an automated protocol is proposed. Fecal samples should be collected and immediately processed under anaerobic conditions at either room temperature (RT) for a maximum of 4 h or at 4 °C for no more than 24 h. Upon homogenization, preferably in the absence of added solvent to allow addition of a buffer of choice at a later stage, aliquots obtained should be stored at either -20 °C for up to a few months or -80 °C for a longer period-up to 2 years. Protocols for quality control should characterize microbial composition and viability as well as metabolic functionality.

Antiparkinsonian Effects of Polyphenols: A Narrative Review with a Focus on the Modulation of the Gut-brain Axis

Polyphenols, which are naturally occurring bioactive compounds in fruits and vegetables, are emerging as potential therapeutics for neurological disorders such as Parkinson's disease (PD). Polyphenols have diverse biological activities, such as anti-oxidative, anti-inflammatory, anti-apoptotic, and α-synuclein aggregation inhibitory effects, which could ameliorate PD pathogenesis. Studies have shown that polyphenols are capable of regulating the gut microbiota (GM) and its metabolites; in turn, polyphenols are extensively metabolized by the GM, resulting in the generation of bioactive secondary metabolites. These metabolites may regulate various physiological processes, including inflammatory responses, energy metabolism, intercellular communication, and host immunity. With increasing recognition of the importance of the microbiota-gut-brain axis (MGBA) in PD etiology, polyphenols have attracted growing attention as MGBA regulators. In order to address the potential therapeutic role of polyphenolic compounds in PD, we focused on MGBA. DATA AVAILABILITY: Data will be made available on request.

Phytochemicals as Immunomodulatory Agents in Melanoma

Cutaneous melanoma is an immunogenic highly heterogenic tumor characterized by poor outcomes when it is diagnosed late. Therefore, immunotherapy in combination with other anti-proliferative approaches is among the most effective weapons to control its growth and metastatic dissemination. Recently, a large amount of published reports indicate the interest of researchers and clinicians about plant secondary metabolites as potentially useful therapeutic tools due to their lower presence of side effects coupled with their high potency and efficacy. Published evidence was reported in most cases through in vitro studies but also, with a growing body of evidence, through in vivo investigations. Our aim was, therefore, to review the published studies focused on the most interesting phytochemicals whose immunomodulatory activities and/or mechanisms of actions were demonstrated and applied to melanoma models.