Changes caused by low doses of glyphosate in the population of substance P - like immunoreactive enteric neurons in the small intestine in pigs

Abstract

Food safety has become a priority for highly developed societies. Glyphosate is an active ingredient of the most widely used herbicide formulations in protecting agricultural and horticultural crops. The aim of the current study was to determine how administration of glyphosate affects the quantitative population of substance P (SP)- synthesizing neurons in the porcine small intestine.Fifteen sexually immature gilts divided into 3 groups were used: control (C) - animals receiving empty gelatin capsules; E1 - animals receiving a low dose of glyphosate - corresponding to the theoretical maximum daily intake (TMDI) - 0.05 mg/kg of b.w./day; E2 - animals receiving a higher dose of glyphosate - corresponding to the acceptable daily intake (ADI) - 0.5 mg/kg of b.w./day) in gelatin capsules with morning feeding. After 4 weeks period of glyphosate supplementation, all pigs were euthanized and small intestine samples were collected for further examination. 12 μm-thick frozen intestinal sections were then double-stained by incubating with primary (HuC/D- used as a pan neuronal marker and SP) as well as secondary (Alexa Fluor 488 and 546) antisera.Glyphosate supplementation increased the number of intramural neurons showing immunoreactivity to SP. In the duodenum, both doses of glyphosate evoked marked changes in population of SP-like immunoreactive (LI) neurons in the outer submucous plexus (OSP) (from 22.36±1.12% to 26.65±0.96% in the E2 group and to 38.53±1.44% in the E2 group) as well as in the inner submucous plexus (ISP) (from 12.30±0.89% to 20.21±2.34% and 35.71±1.90%). In the myenteric plexus (MP) administration of higher dose of glyphosate led to an increase in the number of SP-LI neurons (from 1.22±0.15% to 6.75±0.84%). In the jejunum, an increased number of SP-positive neurons was noted in all type of enteric plexuses and both experimental groups (in the MP: from 1.25±0.20% in the C group to 3.27±0.30% in the E1 group and to 5.41±0.26% in the E2 group; in the OSP: from 23.03±1.43% to 31.25±1.34% and 42.26±1.04%; in the ISP: from 12.35±0.70% to 16.36±0.68% and 43.06±1.21%). In the ileum, the greatest increase was recorded in the ISP (from 20.22±0.96% to 31.16±1.84% in the E1 group and to 43.11±1.34% in the E2 group) and in the OSP (from 15.63±0.79% to 22.10±1.52% and 35.93±2.27%). Whereas in the MP only in the E2 group an increase was observed (from 1.01±0.19% to 6.11±0.53%).Neurons in the ENS underwent adaptive changes in response to the glyphosate intoxication, which manifested themselves as increased population of cells displaying SP- immunoreactivity. SP engaged in defensive reactions of neurons and conduction of sensory stimuli may play an important role in protecting the ENS neurons against the harmful effect of glyphosate. the National Science Centre in Poland [grant no. 2020/04/X/NZ7/00338] This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.