Moderate intestinal immunopathology after acute oral infection with Toxoplasma gondii oocysts is associated with expressive levels of serotonin

The role of 5-hydroxytryptamine on expulsion of Trichinella spiralis during the intestinal stage

During the intestinal stage of Trichinella spiralis (T. spiralis) infection, it can stimulate host's intestinal peristalsis to expulse worms. 5-hydroxytryptamine (5-HT) is a neurotransmitter which can regulate the contraction of intestinal smooth muscle. IL-33 specifically binds to ST2 receptor to promote the secretion of 5-HT by intestinal enterochromaffin cells. However, it remains unclear whether the host is able to modulate the secretion of 5-HT to expulse worms through the IL-33-ST2 signaling pathway during the intestinal stage of T. spiralis infection. Therefore, ST2 inhibitor iST2 was used in a T. spiralis infected mouse model and MODE-K cells to analyze the role of IL-33-ST2 signaling pathway in the secretion of 5-HT during the intestinal phase of T. spiralis infection. The results indicated that the expression of ST2, IL-33, and TPH1(tryptophan hydroxylase 1, the rate-limiting enzyme in the biosynthesis of 5-HT) in the small intestine were increased during the intestinal phase of T. spiralis infection. Meanwhile the levels of secretory 5-HT and IL-33 in the small intestine were significantly increased. After iST2 treatment, the level of 5-HT was significantly decreased, resulting in diminished worms expulsion capability. The decrease of 5-HT was observed in MODE-K cells treated with excretory-secretory products of T. spiralis post iST2 treatment. The above results demonstrated that IL-33-ST2 signaling pathway might play a crucial role in promoting the secretion of 5-HT which enhancing the ability of the intestine to expulse worms during the intestinal stage of T. spiralis.

Mastocytosis and intraepithelial lymphocytosis in the ileum and colon characterize chronic Toxoplasma gondii infection in mice

Toxoplasma gondii is the causative agent of toxoplasmosis, a common zoonotic disease affecting vertebrates with high global incidence. For the parasite to disseminate throughout the body, it crosses the intestinal barrier, triggering inflammatory reactions. This study aimed to assess the tissue response in the ileum and colon of mice following chronic infection with T. gondii. Fourteen mice were divided into two groups: the infected group received 1000 T. gondii oocysts via gavage, and after 60 days, the mice were euthanized. The ileum and colon were collected and processed for histological analysis, inflammatory marker measurement and myenteric neuron analysis. Chronic infection resulted in a significant increase in intraepithelial lymphocytes and mast cells, as well as morphometric changes such as increased total intestinal wall thickness of the ileum, crypt depth, collagen fiber area, and a decrease in myeloperoxidase activity, without altering nitric oxide levels. While the number of myenteric neurons remained unchanged, there was an increase in vasoactive intestinal peptide expression. These results suggest persistence intestinal inflammatory stimuli in chronic T. gondii infection.

SARS-CoV-2 Spike protein triggers gut impairment since mucosal barrier to innermost layers: From basic science to clinical relevance

Studies have reported the occurrence of gastrointestinal (GI) symptoms, primarily diarrhea, in COVID-19. However, the pathobiology regarding COVID-19 in the GI tract remains limited. This work aimed to evaluate SARS-CoV-2 Spike protein interaction with gut lumen in different experimental approaches. Here, we present a novel experimental model with the inoculation of viral protein in the murine jejunal lumen, in vitro approach with human enterocytes, and molecular docking analysis. Spike protein led to increased intestinal fluid accompanied by Cl- secretion, followed by intestinal edema, leukocyte infiltration, reduced glutathione levels, and increased cytokine levels [interleukin (IL)-6, tumor necrosis factor-α, IL-1β, IL-10], indicating inflammation. Additionally, the viral epitope caused disruption in the mucosal histoarchitecture with impairment in Paneth and goblet cells, including decreased lysozyme and mucin, respectively. Upregulation of toll-like receptor 2 and toll-like receptor 4 gene expression suggested potential activation of local innate immunity. Moreover, this experimental model exhibited reduced contractile responses in jejunal smooth muscle. In barrier function, there was a decrease in transepithelial electrical resistance and alterations in the expression of tight junction proteins in the murine jejunal epithelium. Additionally, paracellular intestinal permeability increased in human enterocytes. Finally, in silico data revealed that the Spike protein interacts with cystic fibrosis transmembrane conductance regulator (CFTR) and calcium-activated chloride conductance (CaCC), inferring its role in the secretory effect. Taken together, all the events observed point to gut impairment, affecting the mucosal barrier to the innermost layers, establishing a successful experimental model for studying COVID-19 in the GI context.

Rosuvastatin enhances alterations caused by Toxoplasma gondii in the duodenum of mice

Infection by Toxoplasma gondii may compromise the intestinal histoarchitecture through the tissue reaction triggered by the parasite. Thus, this study evaluated whether treatment with rosuvastatin modifies duodenal changes caused by the chronic infection induced by cysts of T. gondii. For this, female Swiss mice were distributed into infected and treated group (ITG), infected group (IG), group treated with 40 mg/kg rosuvastatin (TG) and control group (CG). After 72 days of infection, the animals were euthanized, the duodenum was collected and processed for histopathological analysis. We observed an increase in immune cell infiltration in the IG, TG and ITG groups, with injury to the Brunner glands. The infection led to a reduction in collagen fibers and mast cells. Infected and treated animals showed an increase in collagen fibers, acidic mucin-producing goblet cells, intraepithelial lymphocytes and mast cells, in addition to the reduction of muscle, neutral mucin-producing and Paneth cells. While treatment with rosuvastatin alone led to increased muscle layer, proportion of neutral mucin-producing goblet cells, Paneth cells, and reduction of collagen fibers. These findings indicate that the infection and treatment caused changes in the homeostasis of the intestinal wall and treatment with rosuvastatin potentiated most parameters indicative of inflammation.