Immunotoxicological, histopathological, and ultrastructural effects of waterborne pyrogallol exposure on African catfish (Clariasgariepinus)

Reproductive and endocrine-disrupting toxicity of pyrogallol in catfish (Clariasgariepinus)

Endocrine disruptors are synthetic or natural chemicals that can agonize/antagonize hormone receptors or can interfere with the production and secretion of hormones, leading to altered tissue histology and physiology. Pyrogallol is a contaminant widely distributed in aquatic environments that presents health risks to both humans and animals. However, the potential for endocrine disruption by pyrogallol, particularly in fish, are lacking. The purpose of this study was to shed light on how pyrogallol may affect hormone signalling, histopathology, and reproductive outcomes in African catfish Clarias gariepinus. To investigate this, African catfish were exposed to one sublethal concentration of pyrogallol at either 0, 1, 5 or 10 mg/L for 15 days. We then assessed the effects of pyrogallol on the thyroid gland as well as the reproductive system by measuring sex hormone, seminal quality, gonadal histopathology, and histochemistry. Thyroid stimulating hormone and thyroxine showed notable decreases in catfish, and triiodothyronine was decreased with 10 mg/L pyrogallol. Unlike luteinizing hormone, follicle-stimulating hormone was significantly reduced in fish following exposure to pyrogallol relative to controls. Testosterone was also decreased in fish following pyrogallol exposure, whereas 17β-estradiol increased in catfish exposed to pyrogallol. Additionally, in response to pyrogallol toxicity, sperm quality indices, including count, spermatocrit, motility, and sperm viability were adversely affected in a concentration-dependent manner. Pyrogallol exposure also induced several changes in the gonad following exposure to 1, 5, or 10 mg/L. Deformed tubular structures, vacuolation, thickening of the basement membrane, hypertrophy of the seminiferous tubules, intense melanomacrophage localization, spermatozoa loss, and necrosis were all observed in the testes. In the ovary, atretic follicles, deteriorated mature oocytes, degenerated yolk globules, and an increase in perinucleolar oocytes were observed in catfish exposed to pyrogallol. These findings suggest that pyrogallol may act as endocrine disrupting substance in aquatic environments. Further research on the mechanisms by which pyrogallol impairs endocrine systems, particularly in fish, is recommended.

Neurotoxic and Cardiotoxic Effects of Pyrogallol on catfish (Clarias gariepinus)

Pyrogallol, a botanical hydrolysable tannin, has diverse medical and industrial applications. Its impact on aquatic ecosystems and fish health has been previously studied, revealing histopathological, immunological, biochemical, and haematological alterations in African catfish (Clarias gariepinus). In this study, the neurotoxic potential of pyrogallol was assessed through a 15-day exposure of catfish to concentrations of 1, 5, or 10mg/L. Enzyme activities such as acetylcholinesterase (AchE), monoamine oxidase (MAO), aldehyde oxidase (AO), and nitric oxide (NO) were measured in serum and brain, along with histopathological examinations in the brain and heart. Pyrogallol exposure led to decreased AchE activity in the brain and serum, increased serum MAO activity, elevated AO in both brain and serum, and suppressed NO levels. Morphological abnormalities and dose-dependent pathology were observed in the brain and heart, including neuropile deformities, shrunken Purkinje cells, cardiomyocyte degeneration, and increased collagen fibers. This suggests that pyrogallol induces adverse effects in fish.

Oxidative stress, antioxidant defense responses, and histopathology: Biomarkers for monitoring exposure to pyrogallol in Clarias gariepinus

Pyrogallol promotes free radicals leading to oxidative stress and toxicity. There are however a lack of studies on oxidative stress and the antioxidant system of fish following exposure to pyrogallol. This study measured oxidative stress markers, antioxidant responses, and histological changes in catfish exposed to pyrogallol. Fish were divided into one of four experimental groups: control only, or 1, 5 or 10 mg/L pyrogallol. After 15 days, glutathione-S-transferase in the serum was decreased in fish exposed to either 5 or 10 mg/L pyrogallol relative to controls while superoxide dismutase and total antioxidant capacity were decreased significantly in fish exposed to 1, 5, or 10 mg/L pyrogallol. Conversely, catalase was increased in serum of fish exposed to 1, 5, or 10 mg/L pyrogallol compared to controls. The liver of fish treated with 1, 5, or 10 mg/L pyrogallol had significantly higher levels of oxidative stress markers (malondialdehyde, lipid peroxidation, hydroperoxide content, oxidised protein content, and DNA fragmentation %) that varied with concentration. Catfish exposed to either 1, 5, or 10 mg/L pyrogallol presented with notable histological alterations in the intestine, kidney, and muscles with prominent fibrosis, as intense deposition of collagen fibre was observed by Masson's trichrome staining. Overall, endpoints related to oxidative stress and antioxidant defence enzymes in fish may be early biomarkers of pyrogallol exposure and contamination in aquatic ecosystems. Additional studies should characterize oxidative stress indicators for their utility as biomarkers of effect.