What Is Our Understanding of the Influence of Gut Microbiota on the Pathophysiology of Parkinson’s Disease?

Microbiota have increasingly become implicated in predisposition to human diseases, including neurodegenerative disorders such as Parkinson’s disease (PD). Traditionally, a central nervous system (CNS)-centric approach to understanding PD has predominated; however, an association of the gut with PD has existed since Parkinson himself reported the disease. The gut–brain axis refers to the bidirectional communication between the gastrointestinal tract (GIT) and the brain. Gut microbiota dysbiosis, reported in PD patients, may extend this to a microbiota–gut–brain axis. To date, mainly the bacteriome has been investigated. The change in abundance of bacterial products which accompanies dysbiosis is hypothesised to influence PD pathophysiology via multiple mechanisms which broadly centre on inflammation, a cause of alpha-synuclein (a-syn) misfolding. Two main routes are hypothesised by which gut microbiota can influence PD pathophysiology, the neural and humoral routes. The neural route involves a-syn misfolding peripherally in the enteric nerves which can then be transported to the brain via the vagus nerve. The humoral route involves transportation of bacterial products and proinflammatory cytokines from the gut via the circulation which can cause central a-syn misfolding by inducing neuroinflammation. This article will assess whether the current literature supports gut bacteria influencing PD pathophysiology via both routes.

Neural Networks Recapitulation by Cancer Cells Promotes Disease Progression: A Novel Role of p73 Isoforms in Cancer-Neuronal Crosstalk

Mechanisms governing tumor progression differ from those of initiation. One enigmatic prometastatic process is the recapitulation of pathways of neural plasticity in aggressive stages. Cancer and neuronal cells develop reciprocal interactions via mutual production and secretion of neuronal growth factors, neurothrophins and/or axon guidance molecules in the tumor microenvironment. Understanding cancer types where this process is active, as well as the drivers, markers and underlying mechanisms, has great significance for blocking tumor progression and improving patient survival. By applying computational and systemic approaches, in combination with experimental validations, we provide compelling evidence that genes involved in neuronal development, differentiation and function are reactivated in tumors and predict poor patient outcomes across various cancers. Across cancers, they co-opt genes essential for the development of distinct anatomical parts of the nervous system, with a frequent preference for cerebral cortex and neural crest-derived enteric nerves. Additionally, we show that p73, a transcription factor with a dual role in neuronal development and cancer, simultaneously induces neurodifferentiation and stemness markers during melanoma progression. Our data yield the basis for elucidating driving forces of the nerve–tumor cell crosstalk and highlight p73 as a promising regulator of cancer neurobiology.

Development of Colonic Organoids Containing Enteric Nerves or Blood Vessels from Human Embryonic Stem Cells

The increased interest in organoid research in recent years has contributed to an improved understanding of diseases that are currently untreatable. Various organoids, including kidney, brain, retina, liver, and spinal cord, have been successfully developed and serve as potential sources for regenerative medicine studies. However, the application of organoids has been limited by their lack of tissue components such as nerve and blood vessels that are essential to organ physiology. In this study, we used three-dimensional co-culture methods to develop colonic organoids that contained enteric nerves and blood vessels. The development of enteric nerves and blood vessels was confirmed phenotypically and genetically by the use of immunofluorescent staining and Western blotting. Colonic organoids that contain essential tissue components could serve as a useful model for the study of colon diseases and help to overcome current bottlenecks in colon disease research.

Evolution of nitric oxide regulation of gut function

Although morphologies are diverse, the common pattern in bilaterians is for passage of food in the gut to be controlled by nerves and endodermally derived neuron-like cells. In vertebrates, nitric oxide (NO) derived from enteric nerves controls relaxation of the pyloric sphincter. Here, we show that in the larvae of sea urchins, there are endoderm-derived neuronal nitric oxide synthase (nNOS)-positive cells expressing pan-neural marker, Synaptotagmin-B (SynB), in sphincters and that NO regulates the relaxation of the pyloric sphincter. Our results indicate that NO-dependent pylorus regulation is a shared feature within the deuterostomes, and we speculate that it was a characteristic of stem deuterostomes.

Electrogastrography in Delayed Gastric Emptying

Disorders of gastric motility are generally manifested by an abnormal rate of gastric emptying. The emptying process of the stomach is very complex, and knowledge is limited to the observation that gastric emptying rate is a highly variable phenomenon, and that delayed gastric emptying is frequently the case. The advances in the knowledge of the physiology of gastric muscle and enteric nerves, and the recognition of the patterns of organization of smooth muscle contractions gave a new input to the study of gastric motility. The gastric emptying can be monitored in various ways, such as manometry, scintigraphy, or electrogastrography (EGG). Recently, EGG has received more attention. There is correlation between the EGG signal obtained from body surface electrodes and signals obtained directly from electrodes locates in the gastric muscle (serosal records). Some studies showed an association between EGG-findings and gastric motility disorders, and indicate that EGG is a reliable, non-invasive, useful method to detect gastric myoelectric activity.