Organophosphorus poisoning is a public health issue, with 3,000,000 instances of poisoning and 220,000 deaths reported each year around the world, with the vast majority of cases occurring in developing countries (Craig 2019).
In the QP group, the antioxidant enzymes, CAT and GPx were shown to be decreased, which was linked to an elevation in MDA (biomarker for peroxidation) that's being used to evaluate oxidative stress indicators (OxS). This is in accordance with previous findings that also revealed that an increase in ROS formation causes OxS to be generated & it's attributed to a reduction in antioxidant defense system and an alteration in the cell's redox state. OxS is generated when the synthesis and scavenging of oxygen-free radicals are out of equilibrium (Moretti et al. 2018).
The antioxidant defense system involves enzymes like CAT and GPx. GPx is a lipid peroxidation detector as well as a free radical scavenger. The radical transformation of reactive oxygen is catalyzed by the catalytic enzyme CAT. As a consequence, any alteration in the antioxidant machinery's components will lead to the formation of ROS, leading to oxidative stress insult in cells (Singh et al. 2020). The cell's primary line of protection versus oxidation-induced tissue injury is the antioxidant enzymes. GPx and CAT activity have been lost in ileal tissues could be the mechanism whereby the QP enhances cellular disorders and oxidative stress, resulting in lipid peroxidation, degenerative alterations and the buildup ROS within the cell (Elwej et al. 2017).
OxS changes the structure and function of cellular macromolecules, as well as the cell membrane, as a result of difficulties produced by elevated levels of inflammatory biomarkers (Jakubczyk et al. 2020). When QP ileum was in comparison to ileum of the control group, IL-6 and TNF-α cytokines were observed to be elevated in the blood. According to the findings of our investigation, TNF-α and IL-6 may play a substantial role. The inflammatory process in the gut of patients with intestinal inflammation is characterized by elevated cytokine levels, resulting in mucosal damage (Joshi et al. 2015). TNF-α has previously been accustomed to enhance intestinal permeability in patients with inflammatory bowel disease by inducing the release of epithelial myosin light chain kinase (Gareb et al. 2020). IL-6 is a pro-inflammatory cytokine that offers a wide range of pro-inflammatory actions. It has been established that it has a significant impact on the intestinal epithelial barrier and that it modulates intestinal epithelial tight junctions via claudin-2 gene activation (Kuhn et al. 2018, Zhang et al. 2015).
The microscopic features of QP-induced cytotoxicity on the ileal mucosa were investigated in this study. The QP group's columnar cells had histopathological changes, according to LM analysis. The nuclei of the cryptal wall epithelial tissue were pale tained and had pale vacuolated cytoplasm. Flattened and vacuolated enterocytes were identified in prior studies of QP-induced mucositis. In the QP-treated group of our analysis, the proportion of goblet cells was diminished, and they seemed mucus-depleted. Cryptal goblet cells decreased significantly in the rat’s small intestine after QP injection (Gillois et al. 2018).
In the present research, secretory cells in the crypts continued to increase, also Paneth cell metaplasia and granule release into the crypt lumen were seen. These granules are easily identified in histological sections due to their intense eosin staining. Paneth cells produce such granules apically through the overlying crypt lumen after proper stimulation, where they help remove any pathogenic microbes (Clevers &Bevins 2013). The QP group's ileum was examined using TEM, which demonstrated significant ultrastructural alterations. The cell configuration of crypts was disrupted, with broadened intercellular spaces observed. Previously, similar findings in the small intestine were reported (Abe et al. 2015).
Columnar cells in the QP group showed areas of substantial loss of microvilli, cytoplasmic vacuolations, and ultrastructural degenerative changes incorporating cell organoids. Paneth cells exhibited degenerative alterations, cytoplasmic vacuolations, and autophagic vacuoles. Among the changes were patchy disruption and dissolution of the microvilli, enlarged mitochondria, some pyknotic nuclei, cytoplasmic vacuolations and endoplasmic reticulum dilatation. The accumulation of lipid peroxidation products caused by an increase in ROS level was essential for mitochondrial expansion and degradation; the same process could explain the mitochondrial damage seen in epithelial cells in our study (Chen et al. 2017).
Electron microscopy revealed cytoplasmic vacuolations in the ileal epithelial cells of the QP group, which might be caused by dilated organelles (rough endoplasmic reticulum and mitochondria), autophagic vacuoles, or hydropic degeneration. On a microscopic level, the injured cells have vacuoles in the cytoplasm with no apparent borders (Moriarty 1969).
Atypical Paneth cells with non-uniform granule diameters and electron-lucent halos at the granule periphery were identified in the QP-treated group. In the small intestine, Paneth cells are important for microbial growth regulation because they produce a variety of chemicals, such as the Wnt protein, that help to maintain the surrounding intestinal stem cell compartment, modulate stem cell proliferation, and build crypt architecture (Mei et al. 2020). Antimicrobial-containing granules discharged into the crypt lumen penetrate the mucus layer and extend outward towards the lumen, protecting the crypts from potentially hazardous microbes. Antimicrobials produced by Paneth cells have been shown to have a significant impact on the bacterial community in the small intestine, lowering total microbial numbers and altering bacterial composition (Wehkamp &Stange 2020, Yokoi et al. 2019).
The histological structure of the ileal mucosa was virtually entirely recovered in the QP and Vit C-treated group. The presence of intact microvilli with a consistent and well-defined brush border, as well as goblet cells packed with mucous granules, was confirmed by TEM analysis. The enzyme paraoxonase, which is concerned in the detoxification of organophosphorus insecticides, has been reported to enhance Vit C activity (Robea et al. 2020). Other minor antioxidant molecules, such as glutathione, urate, and beta-carotene, can be produced from their respective radical species (Medithi et al. 2021). Vit C is a water-soluble antioxidant that has been demonstrated to lower oxidative stress and neutralize ROSs by donating a hydrogen atom to make an ascorbyl-free radical that is adequately stable (Arruda et al. 2013).
In conclusion, this research's findings indicate that in QP-treated rats, Vit C co-administration protects against ileal dysfunction. Furthermore, Vit C mitigates the oxidative damage caused by QP. Vit C may play a role in ileal free radical generation by regulating it.