Desulfovibrio bacteria enhance alpha-synuclein aggregation in a Caenorhabditis elegans model of Parkinson's disease

Modulating the biosynthesis and TLR4-interaction of lipopolysaccharide as an approach to counter gut dysbiosis and Parkinson's disease: Role of phyto-compounds

The prevalence of the world's second leading neurodegenerative disorder Parkinson's disease (PD) is well known while its pathogenesis is still a topical issue to explore. Clinical and experimental reports suggest the prevalence of disturbed gut microflora in PD subjects, with an abundance of especially Gram-negative bacteria. The endotoxin lipopolysaccharide (LPS) released from the outer cell layer of these bacteria interacts with the toll-like receptor 4 (TLR4) present on the macrophages and it stimulates the downstream inflammatory cascade in both the gut and brain. Recent research also suggests a positive correlation between LPS, alpha-synuclein, and TLR4 levels, which indicates the contribution of a parallel LPS-alpha-synuclein-TLR4 axis in stimulating inflammation and neurodegeneration in the gut and brain, establishing a body-first type of PD. However, owing to the novelty of this paradigm, further investigation is mandatory. Modulating LPS biosynthesis and LPS-TLR4 interaction can ameliorate gut dysbiosis and PD. Several synthetic LpxC (UDP-3-O-(R-3-hydroxymyristoyl)-N-acetylglucosamine deacetylase; LPS-synthesizing enzyme) inhibitors and TLR4 antagonists are reported to show beneficial effects including neuroprotection in PD models, however, are not devoid of side effects. Plant-derived compounds have been long documented for their benefits as nutraceuticals and thus to search for effective, safer, and multitarget therapeutics, the present study focused on summarizing the evidence reporting the potential of phyto-compounds as LpxC inhibitors and TLR4 antagonists. Studies demonstrating the dual potential of phyto-compounds as the modulators of LpxC and TLR4 have not yet been reported. Also, very few preliminary studies have reported LpxC inhibition by phyto-compounds. Nevertheless, remarkable neuroprotection along with TLR4 antagonism has been shown by curcumin and juglanin in PD models. The present review thus provides a wide look at the research progressed to date in discovering phyto-compounds that can serve as LpxC inhibitors and TLR4 antagonists. The study further recommends the need for expanding the search for potential candidates that can render dual protection by inhibiting both the biosynthesis and TLR4 interaction of LPS. Such multitarget therapeutic intervention is believed to bring fruitful yields in countering gut dysbiosis, neuroinflammation, and dopaminergic neuron damage in PD patients through a single treatment paradigm.

Pesticides and the Gut Microbiota: Implications for Parkinson's Disease

Parkinson's disease (PD) affects more people worldwide than just aging alone can explain. This is likely due to environmental influences, genetic makeup, and changes in daily habits. The disease develops in a complex way, with movement problems caused by Lewy bodies and the loss of dopamine-producing neurons. Some research suggests Lewy bodies might start in the gut, hinting at a connection between these structures and gut health in PD patients. These patients often have different gut bacteria and metabolites. Pesticides are known to increase the risk of PD, with evidence showing they harm more than just dopamine neurons. Long-term exposure to pesticides in food might affect the gut barrier, gut bacteria, and the blood-brain barrier, but the exact link is still unknown. This review looks at how pesticides and gut bacteria separately influence PD development and progression, highlighting the harmful effects of pesticides and changes in gut bacteria. We have examined the interaction between pesticides and gut bacteria in PD patients, summarizing how pesticides cause imbalances in gut bacteria, the resulting changes, and their overall effects on the PD prognosis.

Unveiling the Journey from the Gut to the Brain: Decoding Neurodegeneration-Gut Connection in Parkinson's Disease

Parkinson's disease, a classical motor disorder affecting the dopaminergic system of the brain, has been as a disease of the brain, but this classical notion has now been viewed differently as the pathology begins in the gut and then gradually moves up to the brain regions. The microorganisms in the gut play a critical role in maintaining the physiology of the gut from maintaining barrier integrity to secretion of microbial products that maintain a healthy gut state. The pathology subsequently alters the normal composition of gut microbes and causes deleterious effects that ultimately trigger strong neuroinflammation and nonmotor symptoms along with characteristic synucleopathy, a pathological hallmark of the disease. Understanding the complex pathomechanisms in distinct and established preclinical models is the primary goal of researchers to decipher how exactly gut pathology has a central effect; the quest has led to many answered and some open-ended questions for researchers. We summarize the popular opinions and some contrasting views, concise footsteps in the treatment strategies targeting the gastrointestinal system.

2-Butoxytetrahydrofuran, Isolated from Holothuria scabra, Attenuates Aggregative and Oxidative Properties of α-Synuclein and Alleviates Its Toxicity in a Transgenic Caenorhabditis elegans Model of Parkinson's Disease

Aggregative α-synuclein and incurring oxidative stress are pivotal cascading events, leading to dopaminergic (DAergic) neuronal loss and contributing to clinical manifestations of Parkinson's disease (PD). Our previous study demonstrated that 2-butoxytetrahydrofuran (2-BTHF), isolated from Holothuria scabra (H. scabra), could inhibit amyloid-β aggregation and its ensuing toxicity, which leads to Alzheimer's disease. In the present study, we found that 2-BTHF also attenuated the aggregative and oxidative activities of α-synuclein and lessened its toxicity in a transgenic Caenorhabditis elegans (C. elegans) PD model. Such worms treated with 100 μM of 2-BTHF showed substantial reductions in α-synuclein accumulation and DAergic neurodegeneration. Mechanistically, 2-BTHF, at this concentration, significantly decreased aggregation of monomeric α-synuclein and restored locomotion and dopamine-dependent behaviors. Molecular docking exhibited potential bindings of 2-BTHF to HSF-1 and DAF-16 transcription factors. Additionally, 2-BTHF significantly increased the mRNA transcripts of genes encoding proteins involved in proteostasis, including the molecular chaperones hsp-16.2 and hsp-16.49, the ubiquitination/SUMOylation-related ubc-9 gene, and the autophagy-related genes atg-7 and lgg-1. Transcriptomic profiling revealed an additional mechanism of 2-BTHF in α-synuclein-expressing worms, which showed upregulation of PPAR signaling cascades that mediated fatty acid metabolism. 2-BTHF significantly restored lipid deposition, upregulated the fat-7 gene, and enhanced gcs-1-mediated glutathione synthesis in the C. elegans PD model. Taken together, this study demonstrated that 2-BTHF could abrogate aggregative and oxidative properties of α-synuclein and attenuate its toxicity, thus providing a possible therapeutic application for the treatment of α-synuclein-induced PD.

In-vitro Approaches to Investigate the Detrimental Effect of Light on Dopaminergic Neurons

Our recent study revealed that fluorescent lamp light can penetrate deep into the brain of mice and rats leading to the development of typical histological characteristics associated with Parkinson's disease such as the loss of dopamine neurons in the substantia nigra. Monochromatic LED lights were thus used in this work to deepen our knowledge on the effects of the major wavelength peaks of fluorescent light on mouse and human dopaminergic cells. In particular, we exposed immortalized dopaminergic MN9D neuronal cells, primary cultures of mouse mesencephalic dopaminergic cells and human dopaminergic neurons differentiated from induced pluripotent stem cells (hiPSC) to different LED light wavelengths. We found that chronic exposure to LED light reduced overall undifferentiated MN9D cell number, with the most significant effects observed at wavelengths of 485 nm and 610 nm. Moreover, LED light especially at 610 nm was able to negatively impact on the survival of mouse mesencephalic dopaminergic cells and of human dopaminergic neurons derived from hiPSC. Notably, differentiated MN9D dopaminergic cells, which closely resemble mature dopamine neuronal phenotype, acutely exposed for 3 h at 610 nm, showed a clear increase in ROS production and cytotoxicity compared to controls undifferentiated MN9D cells. These increases were even more pronounced by the co-treatment with the oxidative agent H2O2. Collectively, these findings suggest that specific wavelengths, particularly those capable of penetrating deep into the brain, could potentially pose an environmental hazard in relation to Parkinson's disease.

Does gut brain axis has an impact on Parkinson's disease (PD)?

Parkinson's Disease (PD) is becoming a growing global concern by being the second most prevalent disease next to Alzheimer's Disease (AD). Henceforth new exploration is needed in search of new aspects towards the disease mechanism and origin. Evidence from recent studies has clearly stated the role of Gut Microbiota (GM) in the maintenance of the brain and as a root cause of various diseases and disorders including other neurological conditions. In the case of PD, with an unknown etiology, the GM is said to have a larger impact on the disease pathophysiology. Although GM and its metabolites are crucial for maintaining the normal physiology of the host, it is an undeniable fact that there is an influence of GM in the pathophysiology of PD. As such the Enteroendocrine Cells (EECs) in the epithelium of the intestine are one of the significant regulators of the gut-brain axis and act as a communication mediator between the gut and the brain. The communication is established via the molecules of neuroendocrine which are said to have a crucial part in neurological diseases such as AD, PD, and other psychiatry-related disorders. This review is focused on understanding the proper role of GM and EECs in PD. Here, we also focus on some of the metabolites and compounds that can interact with the PD genes causing various dysfunctions in the cell and facilitating the disease conditions using bioinformatical tools. Various mechanisms concerning EECs and PD, their identification, the latest studies, and available current therapies have also been discussed.

Epigallocatechin-3-Gallate and Genistein for Decreasing Gut Dysbiosis, Inhibiting Inflammasomes, and Aiding Autophagy in Alzheimer's Disease

There are approximately 24 million cases of Alzheimer's disease (AD) worldwide, and the number of cases is expected to increase four-fold by 2050. AD is a neurodegenerative disease that leads to severe dementia in most patients. There are several neuropathological signs of AD, such as deposition of amyloid beta (Aβ) plaques, formation of neurofibrillary tangles (NFTs), neuronal loss, activation of inflammasomes, and declining autophagy. Several of these hallmarks are linked to the gut microbiome. The gastrointestinal (GI) tract contains microbial diversity, which is important in regulating several functions in the brain via the gut-brain axis (GBA). The disruption of the balance in the gut microbiota is known as gut dysbiosis. Recent studies strongly support that targeting gut dysbiosis with selective bioflavonoids is a highly plausible solution to attenuate activation of inflammasomes (contributing to neuroinflammation) and resume autophagy (a cellular mechanism for lysosomal degradation of the damaged components and recycling of building blocks) to stop AD pathogenesis. This review is focused on two bioflavonoids, specifically epigallocatechin-3-gallate (EGCG) and genistein (GS), as a possible new paradigm of treatment for maintaining healthy gut microbiota in AD due to their implications in modulating crucial AD signaling pathways. The combination of EGCG and GS has a higher potential than either agent alone to attenuate the signaling pathways implicated in AD pathogenesis. The effects of EGCG and GS on altering gut microbiota and GBA were also explored, along with conclusions from various delivery methods to increase the bioavailability of these bioflavonoids in the body.

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.

Traumatic brain injury, abnormal growth hormone secretion, and gut dysbiosis

The gut microbiome has been implicated in a variety of neuropathologies with recent data suggesting direct effects of the microbiome on host metabolism, hormonal regulation, and pathophysiology. Studies have shown that gut bacteria impact host growth, partially mediated through the growth hormone (GH)/insulin-like growth factor 1 (IGF-1) axis. However, no study to date has examined the specific role of GH on the fecal microbiome (FMB) or the changes in this relationship following a traumatic brain injury (TBI). Current literature has demonstrated that TBI can lead to either temporary or sustained abnormal GH secretion (aGHS). More recent literature has suggested that gut dysbiosis may contribute to aGHS leading to long-term sequelae now known as brain injury associated fatigue and cognition (BIAFAC). The aGHS observed in some TBI patients presents with a symptom complex including profound fatigue and cognitive dysfunction that improves significantly with exogenous recombinant human GH treatment. Notably, GH treatment is not curative as fatigue and cognitive decline typically recur upon treatment cessation, indicating the need for additional studies to address the underlying mechanistic cause.

The link between the gut microbiome, inflammation, and Parkinson's disease

As our society ages, the growing number of people with Parkinson's disease (PD) puts tremendous pressure on our society. Currently, there is no effective treatment for PD, so there is an urgent need to find new treatment options. In recent years, increasing studies have shown a strong link between gut microbes and PD. In this review, recent advances in research on gut microbes in PD patients were summarized. Increased potential pro-inflammatory microbes and decreased potential anti-inflammatory microbes are prominent features of gut microbiota in PD patients. These changes may lead to an increase in pro-inflammatory substances (such as lipopolysaccharide and H2S) and a decrease in anti-inflammatory substances (such as short-chain fatty acids) to promote inflammation in the gut. This gut microbiota-mediated inflammation will lead to pathological α-synuclein accumulation in the gut, and the inflammation and α-synuclein can spread to the brain via the microbiota-gut-brain axis, thereby promoting neuroinflammation, apoptosis of dopaminergic neurons, and ultimately the development of PD. This review also showed that therapies based on gut microbiota may have a bright future for PD. However, more research and new approaches are still needed to clarify the causal relationship between gut microbes and PD and to determine whether therapies based on gut microbiota are effective in PD patients. KEY POINTS: • There is a strong association between gut microbes and PD. • Inflammation mediated by gut microbes may promote the development of PD. • Therapies based on the gut microbiome provide a promising strategy for PD prevention.

Our Hidden Enemy: Ultra-Processed Foods, Inflammation, and the Battle for Heart Health

Over the past few decades, we have witnessed unprecedented growth in new data that has fundamentally changed our traditional understanding of the progression of atherosclerotic plaques, as well as our strategies for preventing cardiovascular diseases, especially atherosclerosis. It was once believed that atherosclerosis was primarily caused by abnormal lipid buildup in the vessel intima, leading to plaque growth and luminal stenosis, with or without rupture. This perspective has now evolved to encompass more complex pathways, wherein the accumulation of abnormal products of oxidation and inflammation are the most likely factors mediating the growth of atherosclerotic plaques. The review aims to provide a comprehensive and detailed exploration of the relationship between ultra-processed foods, chronic inflammation, cardiovascular diseases, obesity, insulin resistance, and the role of the gut microbiota. It touches on several important aspects of modern diet and health.

In Vivo Functional Properties of Dairy Bacteria

This literature review aimed to collect investigations on the in vivo evidence for bacteria associated with fermented dairy foods to behave as probiotics with beneficial effects in the prevention and treatment of various diseases. All main bacterial groups commonly present in high numbers in fermented milks or cheeses were taken into account, namely starter lactic acid bacteria (SLAB) Lactobacillus delbrueckii subsp. bulgaricus and lactis, L. helveticus, Lactococcus lactis, Streptococcus thermophilus, non-starter LAB (NSLAB) Lacticaseibacillus spp., Lactiplantibacillus plantarum, dairy propionibacteria, and other less frequently encountered species. Only studies regarding strains of proven dairy origin were considered. Studies in animal models and clinical studies showed that dairy bacteria ameliorate symptoms of inflammatory bowel disease (IBD), mucositis, metabolic syndrome, aging and oxidative stress, cancer, bone diseases, atopic dermatitis, allergies, infections and damage caused by pollutants, mild stress, and depression. Immunomodulation and changes in the intestinal microbiota were the mechanisms most often involved in the observed effects. The results of the studies considered indicated that milk and dairy products are a rich source of beneficial bacteria that should be further exploited to the advantage of human and animal health.

Desulfovibrio in the Gut: The Enemy within?

Desulfovibrio (DSV) are sulfate-reducing bacteria (SRB) that are ubiquitously present in the environment and as resident commensal bacteria within the human gastrointestinal tract. Though they are minor residents of the healthy gut, DSV are opportunistic pathobionts that may overgrow in the setting of various intestinal and extra-intestinal diseases. An increasing number of studies have demonstrated a positive correlation between DSV overgrowth (bloom) and various human diseases. While the relationship between DSV bloom and disease pathology has not been clearly established, mounting evidence suggests a causal role for these bacteria in disease development. As DSV are the most predominant genera of SRB in the gut, this review summarizes current knowledge regarding the relationship between DSV and a variety of diseases. In this study, we also discuss the mechanisms by which these bacteria may contribute to disease pathology.

Aflatoxin B1 Increases Soluble Epoxide Hydrolase in the Brain and Induces Neuroinflammation and Dopaminergic Neurotoxicity

Parkinson's disease (PD) is an increasingly common neurodegenerative movement disorder with contributing factors that are still largely unexplored and currently no effective intervention strategy. Epidemiological and pre-clinical studies support the close association between environmental toxicant exposure and PD incidence. Aflatoxin B1 (AFB1), a hazardous mycotoxin commonly present in food and environment, is alarmingly high in many areas of the world. Previous evidence suggests that chronic exposure to AFB1 leads to neurological disorders as well as cancer. However, whether and how aflatoxin B1 contributes to the pathogenesis of PD is poorly understood. Here, oral exposure to AFB1 is shown to induce neuroinflammation, trigger the α-synuclein pathology, and cause dopaminergic neurotoxicity. This was accompanied by the increased expression and enzymatic activity of soluble epoxide hydrolase (sEH) in the mouse brain. Importantly, genetic deletion or pharmacological inhibition of sEH alleviated the AFB1-induced neuroinflammation by reducing microglia activation and suppressing pro-inflammatory factors in the brain. Furthermore, blocking the action of sEH attenuated dopaminergic neuron dysfunction caused by AFB1 in vivo and in vitro. Together, our findings suggest a contributing role of AFB1 to PD etiology and highlight sEH as a potential pharmacological target for alleviating PD-related neuronal disorders caused by AFB1 exposure.