Decrease of duodenal calcitonin gene-related peptide- and substance P-like immunoreactivity in rat duodenal ulcers

Influence of polyethylene terephthalate (PET) microplastic on selected active substances in the intramural neurons of the porcine duodenum

BACKGROUND

Currently, society and industry generate huge amounts of plastics worldwide. The ubiquity of microplastics is obvious, but its impact on the animal and human organism remains not fully understood. The digestive tract is one of the first barriers between pathogens and xenobiotics and a living organism. Its proper functioning is extremely important in order to maintain homeostasis. The aim of this study was to determine the effect of microplastic on enteric nervous system and histological structure of swine duodenum. The experiment was carried out on 15 sexually immature gilts, approximately 8 weeks old. The animals were randomly divided into 3 study groups (n = 5/group). The control group received empty gelatin capsules once a day for 28 days, the first research group received daily gelatin capsules with polyethylene terephthalate (PET) particles as a mixture of particles of various sizes (maximum particle size 300 µm) at a dose of 0.1 g/animal/day. The second study group received a dose ten times higher-1 g/animal/day.

RESULTS

A dose of 1 g/day/animal causes more changes in the enteric nervous system and in the histological structure of duodenum. Statistically significant differences in the expression of cocaine and amphetamine regulated transcript, galanin, neuronal nitric oxide synthase, substance P, vesicular acetylcholine transporter and vasoactive intestinal peptide between control and high dose group was noted. The histopathological changes were more frequently observed in the pigs receiving higher dose of PET.

CONCLUSION

Based on this study it may be assumed, that oral intake of microplastic might have potential negative influence on digestive tract, but it is dose-dependent.

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.

Effects of Substance P and Neurokinin A on the Contractile Activity of Inflamed Porcine Uterus

Disturbances in uterine contractile activity contribute to the development of inflammation, and recent evidence indicates that tachykinins, including substance P (SP) and neurokinin A (NKA), are involved in controlling uterine function. Here, we determined the effect of Escherichia coli (E. coli)-induced inflammation on expression of protein receptor subtypes for substance P (NK1R) and neurokinin A (NK2R) in the pig myometrium as well as their role in contractility of inflamed uterus. The severe acute endometritis developed in the E. coli group and the expression of NK1R and NK2R proteins increased in the myometrium. Compared to the pre-administration period, SP (10−6 M) reduced the amplitude and frequency in the myometrium of the E. coli group and the amplitude was higher and the frequency was lower versus other groups. NKA reduced the amplitude and increased the frequency in endometrium/myometrium of the E. coli group. In this group, the amplitude was lower and the frequency was higher than in the CON and SAL groups. Our research showed that NK2R (10−6 M) antagonist application abolished the NKA inhibitory effect on uterine amplitude. The application of the NK1R (10−5 M) antagonist together with SP revealed that the inhibitory effect of SP on uterine contractility is achieved independently of the NKR1. Additionally, taking into account the fact that NKA shows an inhibitory effect with the use of NK2R on uterine amplitude suggests the possibility of therapeutic use of the antagonist as a drug increasing uterine contractility in inflammation.

Long-term treatment with naproxen changes the chemical coding of the porcine intramural duodenum neurons

Due to numerous therapeutic applications and high availability, non-steroidal anti-inflammatory drugs (NSAIDs) are the most widely used drugs worldwide. However, long-term use of these drugs can lead to damage to the gastrointestinal mucosa. The enteric nervous system (ENS), which is part of the autonomic nervous system, controls most aspects of gastrointestinal activity. Enteric neurons are characterized by considerable chemical plasticity and the appearance of a pathological factor results in a change in the synthesis of neurotransmitters. The purpose of this study was to determine the effects of naproxen on expression of biologically active substances by intramural neurons supplying the porcine duodenum. The study was performed on eight immature pigs of the Pietrain x Duroc race (approximately 20kg of body weight). The animals were divided into two groups - a control (C group) and an experimental group (N group). Group C (n=4) consisted of animals which received empty gelatine capsules. Group N (n=4) was composed of pigs who received naproxen orally for 28 days, approximately one hour before feeding. After this time, animals from both groups were euthanized. Frozen sections (14μm thickness) were then prepared from the collected duodenum and subjected to double immunofluorescence staining. Antibodies against the neuronal marker PGP 9.5 and against vasoactive intestinal polypeptide (VIP), substance P (SP), neuronal nitric oxide synthase (nNOS), galanin (GAL), pituitary adenylate cyclase-activating polypeptide (PACAP) and cocaine- and amphetamine- regulated transcript peptide (CART) were used as primary antibodies. The polyclonal donkey anti-rabbit, anti-mouse and anti-guinea pig IgG antibodies - Alexa Fluor 488 and 546 - were also used for staining. Analysis of the results obtained with a fluorescence microscope showed a significant increase in the number of nNOS-, VIP-, GAL-, PACAP- and CART-immunoreactive ganglionated neurons and a decrease in the number of SP-positive neurons in the myenteric and submucosal plexuses of the porcine duodenum. The obtained results indicate the participation of enteric neurotransmitters in the neuronal duodenal response to naproxen-induced inflammation.

Cetraxate raises levels of calcitonin gene-related peptide and substance P in human plasma

Cetraxate hydrochloride (cetraxate), an anti-ulcer drug, produces a dose-related increase in mucosal blood flow. Recently, it was found that capsaicin-sensitive afferent nerves play an important role in gastric mucosal defence. Capsaicin stimulates afferent nerves and enhances the release of calcitonin gene-related peptide (CGRP) and substance P in the stomach. We studied the effect of cetraxate on human plasma CGRP and substance P in healthy subjects. Cetraxate (800 mg) or placebo were orally administered to five healthy males. Blood samples were taken before, and at 20, 40, 60, 90, 120, 180 and 240 min after administration, followed by the extracting procedure, and submitted to a highly sensitive enzyme immunoassay system for CGRP and substance P. Single administration of cetraxate caused significant increases in plasma CGRP concentration at 60-120 min compared with placebo. Cetraxate significantly increased plasma substance P levels at 40-90 min compared with placebo. In this study, we hypothesized that cetraxate might indirectly stimulate capsaicin-sensitive afferent nerves and increase mucosal blood flow, and that this may be a key mechanism underlying its gastroprotective action.