Gut region-specific TNFR expression: TNFR2 is more affected than TNFR1 in duodenal myenteric ganglia of diabetic rats

Resveratrol Mitigates Inflammation by Modulating Tumor Necrosis Factor-Alpha Receptors (TNFRs) in a 2,4,6-Trinitrobenzene Sulfonic Acid (TNBS)-Induced Rat Model of Colitis

Several substances with antioxidant and anti-inflammatory properties are currently being investigated as potential adjunctive or standalone treatments for inflammatory bowel disease (IBD). One such substance is resveratrol (RES), also known as 3,5,4'-trihydroxy-trans-stilbene, a natural dietary polyphenol with diverse health-promoting effects. In this study, male Wistar-Hannover rats received oral RES supplementation at doses of 5, 10, or 20 mg/kg/day for 28 days. On day 25 colitis was induced using intracolonic administration of 2,4,6-trinitrobenzene sulphonic acid (TNBS). Based on histological and planimetric analysis, the 10 mg/kg dose significantly reduced colonic ulceration and pro-inflammatory cytokine tumor necrosis factor-alpha (TNF-α) expression compared to the TNBS group. Immunohistochemistry also revealed that RES at this dose attenuated the intensity of TNF-α receptors, namely TNFR1 and TNFR2. Furthermore, the concentration of lipocalin-2 (Lcn-2) was significantly elevated in TNBS-induced colitis. In conclusion, our findings suggest that RES may exert its protective effects partly through the modulation of TNF receptor signaling in TNBS-induced colitis.

TNF-α antagonist alleviates muscular layer enlargement but does not prevent myenteric neuronal loss in the colon of streptozotocin-induced diabetic rats

BACKGROUND

this study aimed to examine the impact of a TNF-α antagonist on markers of neuronal death, the total number of myenteric neurons, and the volume of each colonic layer in diabetic rats.

METHODS

thirty male rats were divided into normal control (NC), diabetic control (DC), and diabetic etanercept (DE) groups. Diabetes was induced using streptozotocin and nicotinamide. The DE group received twice-weekly injections of etanercept. Immunohistochemistry staining and western blotting detected activated caspase-3, Gasdermin D, and phosphorylated-MLKL. Stereological methods were performed in colon sections stained with Toluidine-blue to estimate the total number of neurons in the colonic myenteric plexus and the colonic layer volume.

RESULTS

immunohistochemistry showed etanercept reduced expression of apoptosis and pyroptosis markers, but not necroptosis, in the myenteric plexus of the colon in diabetic rats. Diabetic rats exhibited a lower total number of neurons in the colonic myenteric ganglions, and etanercept did not prevent this neuronal loss. Furthermore, colonic layer enlargement was observed in diabetic rats, with only the muscular layer hypertrophy being prevented by etanercept administration.

CONCLUSIONS

the TNF-α antagonist did not prevent neuronal loss in the colonic myenteric plexus; it partially inhibited colonic muscular layer enlargement in diabetic rats.

Effect of Anti-TNF Monoclonal Antibody on Enteric Neurons and Enteric Glial Cells in Experimental Colitis

BACKGROUND

Inflammatory bowel diseases (IBD) affect both enteric neurons and enteric glia, with tumor necrosis factor-alpha (TNF-α) playing a role as an inflammatory mediator.

AIMS

Analyze the effects of the anti-TNF monoclonal antibody on the myenteric plexus in an experimental model of colitis.

METHODS

C57BL/6 mice received 3% dextran sodium sulfate (DSS) in drinking water for 7 days in both the DSS and DSS + ADA groups. The Sham group received water. The DSS + ADA group received ADA anti-TNF-α on day 2 of DSS intake. The ADA group was given water throughout the period and received an anti-TNF-α injection on day 2. The study evaluated the number of neurons per ganglion, and the area of the neuronal nitric oxide synthase (nNOS), choline acetyltransferase (ChAT), pan-neuronal marker (PGP9.5), and tumor necrosis factor receptor 2 (TNFR2) immunoreactive (-ir). Double labeling of PGP9.5 with an enteric glial marker (GFAP) was also performed.

RESULTS

DSS successfully induced experimental colitis (EC). TNFR2 was detected in the myenteric neurons in all groups. EC affected the enteric neurons, showing a decrease in the number of TNFR2-ir, ChAT-ir, nNOS-ir, and PGP9.5-ir neurons, whereas enteric glial cells increased in both the DSS and DSS + ADA groups. The DSS + ADA group showed number of nNOS-ir, ChAT-ir, and PGP9.5-ir neurons per ganglion similar to Sham group. EC also affected the neuronal profile, resulting in smaller areas in the DSS and DSS + ADA groups.

CONCLUSION

Myenteric neurons are immunoreactive to the TNFR2. DSS altered the myenteric plexus, and anti-TNF monoclonal antibody treatment proved effective against EC due to preventing the pathology from developing.

Intestinal Region-Dependent Impact of NFκB-Nrf Crosstalk in Myenteric Neurons and Adjacent Muscle Cells in Type 1 Diabetic Rats

BACKGROUND/OBJECTIVES

Type 1 diabetes affects cytokines as potential inducers of NFκB signalling involved in inflammation and neuronal survival. Our goal was to assess the expression of NFκB p65 and its negative regulator, Nrf2, in myenteric neurons and adjacent smooth muscle of different gut segments after chronic hyperglycaemia and immediate insulin treatment.

METHODS

After ten weeks of hyperglycaemia, intestinal samples of control, streptozotocin-induced diabetic and insulin-treated diabetic rats were prepared for fluorescent immunohistochemistry, immunogold electron microscopy, ELISA and qPCR.

RESULTS

In the diabetic rats, the proportion of NFκB p65-immunoreactive myenteric neurons decreased significantly in the duodenum and increased in the ileum. The density of NFκB p65-labelling gold particles increased in the ileal but remained unchanged in the duodenal ganglia. Meanwhile, both total and nuclear Nrf2 density increased in the myenteric neurons of the diabetic duodenum. In smooth muscle, NFκB p65 and Nrf2 density increased in the small intestine of diabetic rats. While on the mRNA level, NFκB p65 and Nrf2 were induced, on the protein level, NFκB p65 increased and Nrf2 decreased in muscle/myenteric plexus homogenates. Insulin treatment had protective effects.

CONCLUSIONS

Our findings reveal a segment-specific NFκB and Nrf expression in myenteric neurons and ganglionic muscular environments, which may contribute to regional neuronal survival and motility disturbances in diabetes.

Untargeted metabolomics analysis reveals spatial metabolic heterogeneity in different intestinal segments of type 1 diabetic mice

Type 1 diabetes (T1D) has been reported to cause systematic metabolic disorders, but metabolic changes in different intestinal segments of T1D remain unclear. In this study, we analyzed metabolic profiles in the jejunum, ileum, cecum and colon of streptozocin-induced T1D and age-matched control (CON) mice by an LC-MS-based metabolomics method. The results show that segment-specific metabolic disorders occurred in the gut of T1D mice. In the jejunum, we found that T1D mainly led to disordered amino acid metabolism and most amino acids were significantly lower relative to CON mice. Moreover, fatty acid metabolism was disrupted mainly in the ileum, cecum and colon of T1D mice, such as arachidonic acid, alpha-linolenic acid and linoleic acid metabolism. Thus, our study reveals spatial metabolic heterogeneity in the gut of T1D mice and provides a metabolic view on diabetes-associated intestinal diseases.

The role of gut microbiota in diabetic peripheral neuropathy rats with cognitive dysfunction

Introduction

Owing to advancements in non-invasive magnetic resonance imaging, many studies have repeatedly showed that diabetes affects the central nervous system in the presence of peripheral neuropathy, suggesting a common or interacting pathological mechanism for both complications.

Methods

We aimed to investigate the role of abnormal gut microbiota in rats with diabetic peripheral neuropathy (DPN) combined with cognitive dysfunction. Glucose-compliant rats with nerve conduction deficits were screened as a successful group of DPN rats. The DPN group was then divided into rats with combined cognitive impairment (CD) and rats with normal cognitive function (NCD) based on the results of the Novel object recognition test. Rat feces were then collected for 16S rRNA gene sequencing of the intestinal flora.

Results and Discussion

The results revealed that abnormalities in Firmicutes, Ruminococcaceae, Bacteroidia, and Actinobacteria-like microorganisms may induce DPN complicated by cognitive dysfunction.

Gut Region-Specific Interleukin 1β Induction in Different Myenteric Neuronal Subpopulations of Type 1 Diabetic Rats

Interleukin 1β (IL1β) is a pro-inflammatory cytokine that may play a crucial role in enteric neuroinflammation in type 1 diabetes. Therefore, our goal is to evaluate the effects of chronic hyperglycemia and insulin treatment on IL1β immunoreactivity in myenteric neurons and their different subpopulations along the duodenum-ileum-colon axis. Fluorescent immunohistochemistry was used to count IL1β expressing neurons as well as the neuronal nitric oxide synthase (nNOS)- and calcitonin gene-related peptide (CGRP)-immunoreactive myenteric neurons within this group. Tissue IL1β level was measured by ELISA in muscle/myenteric plexus-containing homogenates. IL1β mRNA was detected by RNAscope in different intestinal layers. The proportion of IL1β-immunoreactive myenteric neurons was significantly higher in the colon than in the small intestine of controls. In diabetics, this proportion significantly increased in all gut segments, which was prevented by insulin treatment. The proportion of IL1β-nNOS-immunoreactive neurons only increased in the diabetic colon, while the proportion of IL1β-CGRP-immunoreactive neurons only increased in the diabetic ileum. Elevated IL1β levels were also confirmed in tissue homogenates. IL1β mRNA induction was detected in the myenteric ganglia, smooth muscle and intestinal mucosa of diabetics. These findings support that diabetes-related IL1β induction is specific for the different myenteric neuronal subpopulations, which may contribute to diabetic motility disturbances.