Effect of Streptozotocin-Inducted Diabetes on the Pathophysiology of Enteric Neurons in the Small Intestine Based on the Porcine Diabetes Model

Glyphosate-induced changes in the expression of galanin and GALR1, GALR2 and GALR3 receptors in the porcine small intestine wall

Glyphosate is the active ingredient of glyphosate-based herbicides and the most commonly used pesticide in the world. The goal of the present study was to verify whether low doses of glyphosate (equivalent to the environmental exposure) evoke changes in galanin expression in intramural neurons in the small intestine in pigs and to quantitatively determine changes in the level of galanin receptor encoding mRNA (GALR1, GALR2, GALR3) in the small intestine wall. The experiment was conducted on 15 sexually immature gilts divided into three study groups: control (C)-animals receiving empty gelatin capsules; experimental 1 (G1)-animals receiving a low dose of glyphosate (0.05 mg/kg b.w./day); experimental 2 (G2)-animals receiving a higher dose of glyphosate (0.5 mg/kg b.w./day) orally in gelatine capsules for 28 days. Glyphosate ingestion led to an increase in the number of GAL-like immunoreactive intramural neurons in the porcine small intestine. The results of RT-PCR showed a significant increase in the expression of mRNA, which encodes the GAL-receptors in the ileum, a decreased expression in the duodenum and no significant changes in the jejunum. Additionally, intoxication with glyphosate increased the expression of SOD2-encoding mRNA in the duodenum and decreased it in the jejunum and ileum, but it did not affect SOD1 expression. The results suggest that it may be a consequence of the cytotoxic and/or neurotoxic properties of glyphosate and/or its ability to induce oxidative stress.

Pig Models in Retinal Research and Retinal Disease

The pig has been used as a large animal model in biomedical research for many years and its use continues to increase because induced mutations phenocopy several inherited human diseases. In addition, they are continuous breeders, can be propagated by artificial insemination, have large litter sizes (on the order of mice), and can be genetically manipulated using all of the techniques that are currently available in mice. The pioneering work of Petters and colleagues set the stage for the use of the pig as a model of inherited retinal disease. In the last 10 years, the pig has become a model of choice where specific disease-causing mutations that are not phenocopied in rodents need to be studied and therapeutic approaches explored. The pig is not only used for retinal eye disease but also for the study of the cornea and lens. This review attempts to show how broad the use of the pig has become and how it has contributed to the assessment of treatments for eye disease. In the last 10 years, there have been several reviews that included the use of the pig in biomedical research (see body of the review) that included information about retinal disease. None directly discuss the use of the pig as an animal model for retinal diseases, including inherited diseases, where a single genetic mutation has been identified or for multifactorial diseases such as glaucoma and diabetic retinopathy. Although the pig is used to explore diseases of the cornea and lens, this review focuses on how and why the pig, as a large animal model, is useful for research in neural retinal disease and its treatment.

Acetylsalicylic Acid Supplementation Affects the Neurochemical Phenotyping of Porcine Duodenal Neurons

Aspirin (ASA) is a popular nonsteroidal anti-inflammatory drug (NSAID), which exerts its therapeutic properties through the inhibition of cyclooxygenase (COX) isoform 2 (COX-2), while the inhibition of COX-1 by ASA results in the formation of gastrointestinal side effects. Due to the fact that the enteric nervous system (ENS) is involved in the regulation of digestive functions both in physiological and pathological states, the aim of this study was to determine the influence of ASA on the neurochemical profile of enteric neurons in the porcine duodenum. Our research, conducted using the double immunofluorescence technique, proved an increase in the expression of selected enteric neurotransmitters in the duodenum as a result of ASA treatment. The mechanisms of the visualized changes are not entirely clear but are probably related to the enteric adaptation to inflammatory conditions resulting from aspirin supplementation. A detailed understanding of the role of the ENS in the development of drug-induced inflammation will contribute to the establishment of new strategies for the treatment of NSAID-induced lesions.

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.

Immunodetection of P2X2 Receptor in Enteric Nervous System Neurons of the Small Intestine of Pigs

Extracellular adenosine 5'-triphosphate (ATP) is one of the best-known and frequently studied neurotransmitters. Its broad spectrum of biological activity is conditioned by the activation of purinergic receptors, including the P2X2 receptor. The P2X2 receptor is present in the central and peripheral nervous system of many species, including laboratory animals, domestic animals, and primates. However, the distribution of the P2X2 receptor in the nervous system of the domestic pig, a species increasingly used as an experimental model, is as yet unknown. Therefore, this study aimed to determine the presence of the P2X2 receptor in the neurons of the enteric nervous system (ENS) of the pig small intestine (duodenum, jejunum, and ileum) by the immunofluorescence method. In addition, the chemical code of P2X2-immunoreactive (IR) ENS neurons of the porcine small intestine was analysed by determining the coexistence of selected neuropeptides, i.e., vasoactive intestinal polypeptide (VIP), substance P (sP), and galanin. P2X2-IR neurons were present in the myenteric plexus (MP), outer submucosal plexus (OSP), and inner submucosal plexus (ISP) of all sections of the small intestine (duodenum, jejunum, and ileum). From 44.78 ± 2.24% (duodenum) to 63.74 ± 2.67% (ileum) of MP neurons were P2X2-IR. The corresponding ranges in the OSP ranged from 44.84 ± 1.43% (in the duodenum) to 53.53 ± 1.21% (in the jejunum), and in the ISP, from 53.10 ± 0.97% (duodenum) to 60.57 ± 2.24% (ileum). Immunofluorescence staining revealed the presence of P2X2-IR/galanin-IR and P2X2-IR/VIP-IR neurons in the MP, OSP, and ISP of the sections of the small intestine. The presence of sP was not detected in the P2X2-IR neurons of any ganglia tested in the ENS. Our results indicate for the first time that the P2X2 receptor is present in the MP, ISP, and OSP neurons of all small intestinal segments in pigs, which may suggest that its activation influences the action of the small intestine. Moreover, there is a likely functional interaction between P2X2 receptors and galanin or VIP, but not sP, in the ENS of the porcine small intestine.

Markers of the sympathetic, parasympathetic and sensory nervous system are altered in the human diabetic choroid

BACKGROUND

We sought to evaluate alterations in markers of the autonomic nervous system in human diabetic choroid.

METHODS

Eighteen eyeballs from subjects with diabetes and 22 eyeballs from subjects without diabetes were evaluated in this study. Synaptophysin, tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DβH), neuronal nitric oxide synthase (nNOS), choline acetyltransferase (ChAT), vesicular monoamine transporter II (VMAT-2), vesicular acetylcholine transporter (VAChT), vasoactive intestinal peptide (VIP), neuropeptide Y (NPY), and calcitonin gene-related peptide (CGRP) levels were detected by western blot analysis and immunofluorescence was performed in some cases. Furthermore, differences in adrenergic (α1- and β2-subtypes) and cholinergic (M1 and M3) receptor levels between diabetic subjects and controls were noted.

RESULTS

Decreased synaptophysin levels were found in diabetic choroids by western blot analysis and a reduction of synaptophysin-immunoreactive nerves was also found by immunofluorescence. Furthermore, a decrease of the levels of the key enzyme (TH) and transporter (VMAT2) of norepinephrine was evident both by western blot analysis and immunofluorescence. Additionally, increased NPY, VAChT, nNOS, and CGRP levels were observed in diabetic choroids. The levels of adrenergic (β2 subtype) and acetylcholine (M1 subtype) receptors decreased in diabetic choroids, as shown by western blotting and although the differences in α1 and M3 were not significant, there was a downward trend.

CONCLUSIONS

In the diabetic choroid, the levels of neurotransmitters, enzymes, and receptors associated with choroidal blood flow regulation are altered. These changes may affect the regulation of choroidal blood flow and may be associated with impaired retinal function and retinal pathology.