Exercise training has a protective effect in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mice model with improved neural and intestinal pathology and modified intestinal flora

Parkinson's disease (PD) is a common neurodegenerative disease with the exact etiology still unclear, but gut microbial disorders are thought to be related to the initiation and progression of it. Exercise training has a significant effect on the intestinal flora, so to investigate the promotion effect of exercise training on Parkinson's disease, we performed a rotarod walking training (5 times a week at 25 rpm for 20 min for 8 weeks) on a chronic mouse model of Parkinson's disease induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and observed the locomotor function of mice, function of dopaminergic neurons, intestinal mucosal barrier condition, intestinal inflammation and the structure and composition of intestinal flora. The results showed in these PD mice, exercise training improved their motility, increased the dopamine (DA) content in the striatum, along with promoted the gene expression of tyrosine hydroxylase and brain-derived neurotrophic factor in the striatum, which suggests this exercise training might protect striatal dopaminergic neurons from MPTP damage; the results also showed exercise training promoted recovery from ileal pathology, reduced the gene expression of intestinal inflammatory factors, and significantly altered the composition and structure of the intestinal flora in these mice.

Investigating the importance of B cells and antibodies during Trichuris muris infection using the IgMi mouse

Abstract

The IgMi mouse has normal B cell development; its B cells express an IgM B cell receptor but cannot class switch or secrete antibody. Thus, the IgMi mouse offers a model system by which to dissect out antibody-dependent and antibody-independent B cell function. Here, we provide the first detailed characterisation of the IgMi mouse post-Trichuris muris (T. muris) infection, describing expulsion phenotype, cytokine production, gut pathology and changes in T regulatory cells, T follicular helper cells and germinal centre B cells, in addition to RNA sequencing (RNA seq) analyses of wild-type littermates (WT) and mutant B cells prior to and post infection. IgMi mice were susceptible to a high-dose infection, with reduced Th2 cytokines and elevated B cell-derived IL-10 in mesenteric lymph nodes (MLN) compared to controls. A low-dose infection regime revealed IgMi mice to have significantly more apoptotic cells in the gut compared to WT mice, but no change in intestinal inflammation. IL-10 levels were again elevated. Collectively, this study showcases the potential of the IgMi mouse as a tool for understanding B cell biology and suggests that the B cell plays both antibody-dependent and antibody-independent roles post high- and low-dose T. muris infection.

Key messages

During a high-dose T. muris infection, B cells are important in maintaining the Th1/Th2 balance in the MLN through an antibody-independent mechanism.

High levels of IL-10 in the MLN early post-infection, and the presence of IL-10-producing B cells, correlates with susceptibility to T. muris infection.

B cells maintain gut homeostasis during chronic T. muris infection via an antibody-dependent mechanism.

Electronic supplementary material

The online version of this article (10.1007/s00109-020-01954-3) contains supplementary material, which is available to authorized users.

Twice subacute MPTP administrations induced time-dependent dopaminergic neurodegeneration and inflammation in midbrain and ileum, as well as gut microbiota disorders in PD mice

Parkinson's disease (PD) is a common progressive neurodegenerative disease. PD produces a pathological state in the intestine and disordered gut microbiota (GM), which may be important for the pathogenesis and progression of PD, but it is not clear. To explore the conditions and characteristics of intestinal pathology and GM disorders when PD-related injuries occur, we used twice 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) subacute administration with an interval of 3 weeks (each was an intraperitoneal injection of 25 mg/kg MPTP for 5 consecutive days). We observed the changes in intestinal and brain immune status, intestinal barrier function and GM in different injury states one day, one week, and three weeks after the first stimulus and one day and one week after the second stimulus. Our study found that two subacute administrations of MPTP induced dopaminergic (DAergic) neuron injury and inflammation in the midbrain and ileum, impaired intestinal barrier function and GM disorders closely related to administration. These changes recovered after the first administration, but after repeated administration, some indicators showed more dramatic changes than during the first administration. Our results suggest that the intestinal tract is sensitive to PD-related injury, and the GM is susceptible to disturbances caused by intestinal function, which may be concerned in local immune disorders of the intestine.

Chronological analysis of the damages caused by the metacercariae of Centrocestus formosanus in the gills of Cyprinus carpio and lesions caused by the adult flukes in Ardeola ralloides: An experimental study

Centrocestus formosanus is a digenean that requires three host species to complete its life cycle. This study was conducted to observe the damage caused by two life stages of the C. formosanus on its host species. The snail Melanoides tuberculata was induced to shed cercariae by exposing to sunlight and specimens of koi carps were experimentally infected with cercariae. Gills of two infected fish were killed and fixed in Bouin's solution daily for 21 days. Infected fish were continuously fed to a pond heron (Ardeola ralloides) for three weeks and therafter the bird was killed. Small intestine was resected as duodenum, jejunum, and ileum and fixed in formol saline. Gills and small intestine were prepared to study the histopathological damages. Flared opercula with protruding gills and increased respiratory rate were identified as the primary clinical signs of the fish. Encysted metacercariae were observed in the basal, middle and in the apical portion of the gills' filaments and gradual distortions and extensive proliferation of the cartilage of the gills resulted in loss of the respiratory epithelium. A progression of fibroblast to chondroblast encapsulation of the parasite was observed in the gill of fish as a host response. The duodenum of the heron was severely infected with adult parasites than jejunum and ileum. Flukes were observed in the villi, mucosae, submucosae, and also in the tunica muscularis of the duodenum. In conclusion, this study revealed that the heavy infection of C. formosanus could cause severe pathological lesions in both koi carps and pond heron.

Intestinal Pathology and Gut Microbiota Alterations in a Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) Mouse Model of Parkinson's Disease

Patients with Parkinson's disease (PD) often have non-motor symptoms related to gastrointestinal (GI) dysfunction, such as constipation and delayed gastric emptying, which manifest prior to the motor symptoms of PD. Increasing evidence indicates that changes in the composition of the gut microbiota may be related to the pathogenesis of PD. However, it is unclear how GI dysfunction occurs and how gut microbial dysbiosis is caused. We investigated whether a neurotoxin model of PD induced by chronic low doses of MPTP is capable of reproducing the clinical intestinal pathology of PD, as well as whether gut microbial dysbiosis accompanies this pathology. C57BL/6 male mice were administered 18 mg/kg MPTP twice per week for 5 weeks via intraperitoneal injection. GI function was assessed by measuring the 1-h stool frequency and fecal water content; motor function was assessed by pole tests; and tyrosine hydroxylase and alpha-synuclein expression were analyzed. Furthermore, the inflammation, intestinal barrier and composition of the gut microbiota were measured. We found that MPTP caused GI dysfunction and intestinal pathology prior to motor dysfunction. The composition of the gut microbiota was changed; in particular, the change in the abundance of Lachnospiraceae, Erysipelotrichaceae, Prevotellaceae, Clostridiales, Erysipelotrichales and Proteobacteria was significant. These results indicate that a chronic low-dose MPTP model can be used to evaluate the progression of intestinal pathology and gut microbiota dysbiosis in the early stage of PD, which may provide new insights into the pathogenesis of PD.

Investigation of Host and Pathogen Contributions to Infectious Colitis Using the Citrobacter rodentium Mouse Model of Infection

Citrobacter rodentium is used as a model organism to study enteric bacterial infections in mice. Infection occurs via the oral-fecal route and results in the pathogen forming attaching and effacing lesions on infected epithelial cells. Moreover, infection leads to a subsequent host-mediated form of colitis. C. rodentium infection is thus an excellent model to study infectious colitis in vivo, while the ability to genetically manipulate C. rodentium virulence genes provides the opportunity to develop clear insights into the pathogenesis of this and related infectious microbes. This chapter outlines the basic techniques involved in setting up a C. rodentium infection in mice and several different methodologies to assess the severity of the infection.

Adrenomedullin regulates intestinal physiology and pathophysiology

Adrenomedullin (AM) and proadrenomedullin N-terminal 20 peptide (PAMP) are 2 biologically active peptides produced by the same gene, ADM, with ubiquitous distribution and many physiological functions. Adrenomedullin is composed of 52 amino acids, has an internal molecular ring composed by 6 amino acids and a disulfide bond, and shares structural similarities with calcitonin gene-related peptide, amylin, and intermedin. The AM receptor consists of a 7-transmembrane domain protein called calcitonin receptor-like receptor in combination with a single transmembrane domain protein known as receptor activity-modifying protein. Using morphologic techniques, it has been shown that AM and PAMP are expressed throughout the gastrointestinal tract, being specially abundant in the neuroendocrine cells of the gastrointestinal mucosa; in the enterochromaffin-like and chief cells of the gastric fundus; and in the submucosa of the duodenum, ileum, and colon. This wide distribution in the gastrointestinal tract suggests that AM and PAMP may act as gut hormones regulating many physiological and pathologic conditions. To date, it has been proven that AM and PAMP act as autocrine/paracrine growth factors in the gastrointestinal epithelium, play key roles in the protection of gastric mucosa from various kinds of injury, and accelerate healing in diseases such as gastric ulcer and inflammatory bowel diseases. In addition, both peptides are potent inhibitors of gastric acid secretion and gastric emptying; they regulate the active transport of sugars in the intestine, regulate water and ion transport in the colon, modulate colonic bowel movements and small-intestine motility, improve endothelial barrier function, and stabilize circulatory function during gastrointestinal inflammation. Furthermore, AM and PAMP are antimicrobial peptides, and they contribute to the mucosal host defense system by regulating gut microbiota. To get a formal demonstration of the effects that endogenous AM and PAMP may have in gut microbiota, we developed an inducible knockout of the ADM gene. Using this model, we have shown, for the first time, that lack of AM/PAMP leads to changes in gut microbiota composition in mice. Further studies are needed to investigate whether this lack of AM/PAMP may have an impact in the development and/or progression of intestinal diseases through their effect on microbiota composition.