Sympathetic Innervation Modulates Mucosal Immune Homeostasis and Epithelial Host Defense

Bidirectional regulation of the brain-gut-microbiota axis following traumatic brain injury

JOURNAL/nrgr/04.03/01300535-202508000-00002/figure1/v/2024-09-30T120553Z/r/image-tiff Traumatic brain injury is a prevalent disorder of the central nervous system. In addition to primary brain parenchymal damage, the enduring biological consequences of traumatic brain injury pose long-term risks for patients with traumatic brain injury; however, the underlying pathogenesis remains unclear, and effective intervention methods are lacking. Intestinal dysfunction is a significant consequence of traumatic brain injury. Being the most densely innervated peripheral tissue in the body, the gut possesses multiple pathways for the establishment of a bidirectional "brain-gut axis" with the central nervous system. The gut harbors a vast microbial community, and alterations of the gut niche contribute to the progression of traumatic brain injury and its unfavorable prognosis through neuronal, hormonal, and immune pathways. A comprehensive understanding of microbiota-mediated peripheral neuroimmunomodulation mechanisms is needed to enhance treatment strategies for traumatic brain injury and its associated complications. We comprehensively reviewed alterations in the gut microecological environment following traumatic brain injury, with a specific focus on the complex biological processes of peripheral nerves, immunity, and microbes triggered by traumatic brain injury, encompassing autonomic dysfunction, neuroendocrine disturbances, peripheral immunosuppression, increased intestinal barrier permeability, compromised responses of sensory nerves to microorganisms, and potential effector nuclei in the central nervous system influenced by gut microbiota. Additionally, we reviewed the mechanisms underlying secondary biological injury and the dynamic pathological responses that occur following injury to enhance our current understanding of how peripheral pathways impact the outcome of patients with traumatic brain injury. This review aimed to propose a conceptual model for future risk assessment of central nervous system-related diseases while elucidating novel insights into the bidirectional effects of the "brain-gut-microbiota axis."

Microbiota-neuroepithelial signalling across the gut-brain axis

Research over the past two decades has established a remarkable ability of the gut microbiota to modulate brain activity and behaviour. Conversely, signals from the brain can influence the composition and function of the gut microbiota. This bidirectional communication across the gut microbiota-brain axis, involving multiple biochemical and cellular mediators, is recognized as a major brain-body network that integrates cues from the environment and the body's internal state. Central to this network is the gut sensory system, formed by intimate connections between chemosensory epithelial cells and sensory nerve fibres, that conveys interoceptive signals to the central nervous system. In this Review, we provide a broad overview of the pathways that connect the gut and the brain, and explore the complex dialogue between microorganisms and neurons at this emerging intestinal neuroepithelial interface. We highlight relevant microbial factors, endocrine cells and neural mechanisms that govern gut microbiota-brain interactions and their implications for gastrointestinal and neuropsychiatric health.

Transcriptome profiling reveals the protective mechanism of sulfated Cyclocarya paliurus polysaccharides against oxidative damage of IEC-6 cell

Our previous studies have shown that sulfated Cyclocarya paliurus polysaccharides (SCP3) can alleviate intestinal oxidative stress (OS) damage by improving the antioxidant capacity of the intestine, but its mechanism still needs further exploration. This study aimed to reveal the possible underlying protective mechanism of SCP3 against OS damage of intestinal epithelial cells (IEC-6) based on transcriptome profiling. The results showed that SCP3 could increase the activity of superoxide dismutase and reduce the production of malondialdehyde and reactive oxygen species. In addition, the SCP3 could also alleviate the H2O2-induced high apoptosis rate and mitochondrial membrane potential decrease in IEC-6 cells. RNA-sequencing results showed that there were 2152 differentially expressed genes between the control group and the SCP3 group, and the mitogen-activated protein kinases (MAPK) and PI3K-Akt signaling pathways are the main signaling pathways that contributed to SCP3 protecting IEC-6 cells from OS damage. In summary, the SCP3 plays a role in improving intestinal cell damage by inhibiting OS, which may be closely related to the PI3K/Akt and MAPK signaling pathways. PRACTICAL APPLICATION: This study provides a theoretical basis for the practical application of Cyclocarya paliurus polysaccharides as an antioxidant ingredient in auxiliary medicines and functional foods.

Therapeutic approaches targeting the gut microbiota in ischemic stroke: current advances and future directions

Ischemic stroke (IS) is the predominant form of stroke pathology, and its clinical management remains constrained by therapeutic time frame. The gut microbiota (GM), comprising a multitude of bacterial and archaeal cells, surpasses the human cell count by approximately tenfold and significantly contributes to the human organism's growth, development, and overall well-being. The microbiota-gut-brain axis (MGBA) in recent years has established a strong association between gut microbes and the brain, demonstrating their intricate involvement in the progression of IS. The regulation of IS by the GM, encompassing changes in composition, abundance, and distribution, is multifaceted, involving neurological, endocrine, immunological, and metabolic mechanisms. This comprehensive understanding offers novel insights into the therapeutic approaches for IS. The objective of this paper is to examine the mechanisms of interaction between the GM and IS in recent years, assess the therapeutic effects of the GM on IS through various interventions, such as dietary modifications, probiotics, fecal microbiota transplantation, and antibiotics, and offer insights into the potential clinical application of the GM in stroke treatment.

Autonomic Nervous System Dysfunction Is Related to Chronic Prostatitis/Chronic Pelvic Pain Syndrome

Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is a common and non-lethal urological condition with painful symptoms. The complexity of CP/CPPS's pathogenesis and lack of efficient etiological diagnosis results in incomplete treatment and recurrent episodes, causing long-term mental and psychological suffering in patients. Recent findings indicate that the autonomic nervous system involves in CP/CPPS, including sensory, sympathetic, parasympathetic, and central nervous systems. Neuro-inflammation and sensitization of sensory nerves lead to persistent inflammation and pain. Sympathetic and parasympathetic alterations affect the cardiovascular and reproductive systems and the development of prostatitis. Central sensitization lowers pain thresholds and increases pelvic pain perception in chronic prostatitis. Therefore, this review summarized the detailed processes and mechanisms of the critical role of the autonomic nervous system in developing CP/CPPS. Furthermore, it describes the neurologically relevant substances and channels or receptors involved in this process, which provides new perspectives for new therapeutic approaches to CP/CPPS.

Sympathetic activity regulates epithelial proliferation and wound healing via adrenergic receptor α2A

Innervation of the intestinal mucosa by the sympathetic nervous system is well described but the effects of adrenergic receptor stimulation on the intestinal epithelium remain equivocal. We therefore investigated the effect of sympathetic neuronal activation on intestinal cells in mouse models and organoid cultures, to identify the molecular routes involved. Using publicly available single-cell RNA sequencing datasets we show that the α2A isoform is the most abundant adrenergic receptor in small intestinal epithelial cells. Stimulation of this receptor with norepinephrine or a synthetic specific α2A receptor agonist promotes epithelial proliferation and stem cell function, while reducing differentiation in vivo and in intestinal organoids. In an anastomotic healing mouse model, adrenergic receptor α2A stimulation resulted in improved anastomotic healing, while surgical sympathectomy augmented anastomotic leak. Furthermore, stimulation of this receptor led to profound changes in the microbial composition, likely because of altered epithelial antimicrobial peptide secretion. Thus, we established that adrenergic receptor α2A is the molecular delegate of intestinal epithelial sympathetic activity controlling epithelial proliferation, differentiation, and host defense. Therefore, this receptor could serve as a newly identified molecular target to improve mucosal healing in intestinal inflammation and wounding.

Molecular Mechanisms of Chronic Intestinal Diseases in Response to Microbiota

Chronic disorders of the intestine, such as inflammatory bowel diseases (IBDs) and irritable bowel syndrome (IBS), involve complex interactions between host and microbiota [...].

Acute psychological stress increases paracellular permeability and modulates immune activity in rectal mucosa of healthy volunteers

BACKGROUND

Psychological stress and increased permeability are implicated as contributing factors in the initiation and worsening of gastrointestinal diseases. A link between stress and intestinal permeability has been shown in animal models as well as in human small intestine, but stress effects on the human colorectal mucosal barrier has not been reported.

OBJECTIVE

To investigate the potential effects of acute psychological stress on colorectal mucosal barrier function and to explore stress-induced molecular events in the rectal mucosa under healthy conditions.

METHODS

Endoscopic biopsies were taken from the rectosigmoid region of healthy volunteers, who had been subjected to dichotomous listening stress and after a control session, respectively. Paracellular and transcellular permeability were assessed in modified Ussing chambers. RNA expression (microarray technology confirmed by quantitative real-time polymerase chain reaction) and biological pathway analysis were used to investigate the local mucosal response to acute stress.

RESULTS

Dichotomous listening stress induced a subjective and objective stress response, and significantly increased paracellular but not transcellular permeability. We also identified a stress-induced reduction in RNA expression of genes related to immune cell activation and maturation (CR2, CD20, TCLA1, BANK1, CD22, FDCSP), signaling molecules of homing of immune cells to the gut (chemokines: CCL21, CXCL13, and CCL19, and receptors: CCR7, CXCR5), and innate immunity (DUOX2). Eight of the 10 top down-regulated genes are directly involved in B cell activation, signaling and migration. The systemic stress response correlated positively with paracellular permeability and negatively with DUOX2 expression.

CONCLUSION

Dichotomous listening stress increases paracellular permeability and modulates immune cell activity in the rectal mucosa. Further studies are warranted to identify the primary mechanisms of stress-mediated reduction of mucosal defensive activity and barrier dysfunction, and their potential implications for gastrointestinal disorders.

Crosstalk between the Gut and Brain in Ischemic Stroke: Mechanistic Insights and Therapeutic Options

There has been a significant amount of interest in the past two decades in the study of the evolution of the gut microbiota, its internal and external impacts on the gut, and risk factors for cerebrovascular disorders such as cerebral ischemic stroke. The network of bidirectional communication between gut microorganisms and their host is known as the microbiota-gut-brain axis (MGBA). There is mounting evidence that maintaining gut microbiota homeostasis can frequently enhance the effectiveness of ischemic stroke treatment by modulating immune, metabolic, and inflammatory responses through MGBA. To effectively monitor and cure ischemic stroke, restoring a healthy microbial ecology in the gut may be a critical therapeutic focus. This review highlights mechanistic insights on the MGBA in disease pathophysiology. This review summarizes the role of MGBA signaling in the development of stroke risk factors such as aging, hypertension, obesity, diabetes, and atherosclerosis, as well as changes in the microbiota in experimental or clinical populations. In addition, this review also examines dietary changes, the administration of probiotics and prebiotics, and fecal microbiota transplantation as treatment options for ischemic stroke as potential health benefits. It will become more apparent how the MGBA affects human health and disease with continuing advancements in this emerging field of biomedical sciences.