Ultrastructural changes during spermatogenesis, biochemical and hormonal evidences of testicular toxicity caused by TBT in freshwater prawn Macrobrachium rosenbergii (De Man, 1879)

Male Reproductive Toxicity of Antifouling Chemicals: Insights into Oxidative Stress-Induced Infertility and Molecular Mechanisms of Zinc Pyrithione (ZPT)

Zinc pyrithione (ZPT), a widely utilized industrial chemical, is recognized for its versatile properties, including antimicrobial, antibacterial, antifungal, and antifouling activities. Despite its widespread use, recent research has shed light on its toxicity, particularly towards the male reproductive system. While investigations into ZPT's impact on male reproduction have been conducted, most of the attention has been directed towards marine organisms. Notably, ZPT has been identified as a catalyst for oxidative stress, contributing to various indicators of male infertility, such as a reduced sperm count, impaired sperm motility, diminished testosterone levels, apoptosis, and degenerative changes in the testicular tissue. Furthermore, discussions surrounding ZPT's effects on DNA and cellular structures have emerged. Despite the abundance of information regarding reproductive toxicity, the molecular mechanisms underlying ZPT's detrimental effects on the male reproductive system remain poorly understood. This review focuses specifically on ZPT, delving into its reported toxicity on male reproduction, while also addressing the broader context by discussing other antifouling chemicals, and emphasizing the need for further exploration into its molecular mechanisms.

Combined effects of exposure to sub-lethal concentration of the insecticide chlorpyrifos and the herbicide glyphosate on the biochemical changes in the freshwater crayfish Pontastacus leptodactylus

Glyphosate is an herbicide that inhibits the growth of weed plants, while chlorpyrifos is an insecticide commonly applied to control the pests' population. This study aimed to investigate the combined effects of chlorpyrifos and glyphosate on biochemical, immunological parameters, and oxidative stress biomarkers in freshwater crayfish Pontastacus leptodactylus for 21 days. The experimental design of this study was factorial (3 × 3), including 0.0, 0.4, and 0.8 mg L-1 glyphosate and 0.0, 2.5, and 5 µg L-1 chlorpyrifos. The exposure to chlorpyrifos, glyphosate alone and a mixture of them significantly decreased acetylcholinesterase, alkaline phosphatase, phenoloxidase activities, and total protein levels. The lactate dehydrogenase, glutamic-pyruvic-transaminase, and catalase activities, the contents of glucose, and malondialdehyde levels were increased in the crayfish. No significant changes were detected in glutamic-oxaloacetic-transaminase (SGOT) activity, triglyceride, and total antioxidant (TAO) levels in the crayfish treated with 0.4 mg L-1 glyphosate and the control group. Co-exposure of crayfish to chlorpyrifos and glyphosate increased SGOT activity and TAO levels. Although chlorpyrifos combined with glyphosate decreased the γ-Glutamyltransferase (GGT) activity, the GGT activity was significantly increased in the P. leptodactylus exposed during 21 days to 5 µg L-1 chlorpyrifos alone and 0.8 mg L-1 glyphosate alone. In comparison with the reference group, no significant changes were evidenced in the cholesterol levels in the P. leptodactylus treated with 2.5 µg L-1 chlorpyrifos, but its levels were significantly increased in the other treatment groups. In conclusion, the mix of glyphosate and chlorpyrifos exhibited synergic effects on the different toxicological biomarkers in the narrow-clawed crayfish. Co-exposure to pesticides may result in disruption of homeostasis in the crayfish by altering the biochemical and immunological parameters.

Acute BPA exposure-induced oxidative stress, depressed immune genes expression and damage of hepatopancreas in red swamp crayfish Procambarus clarkii

Bisphenol A is a typical endocrine disrupting chemicals (EDCs) and produce various toxic effects on animals due to its potential endocrine disruption, oxidative damage effect, mutagenic effect and hypomethylation. To study its effect on the immune system of crustaceans, the Procambarus clarkii were utilized to detect the immune related indicators after 225 μg/L BPA exposure for 1 week. Hepatopancreatic histology and ultrastructure analysis showed that the brush border disappeared, the lumen increased, and the connection between the hepatic tubules fade away in BPA treated group. BPA could significantly increase the level of ROS, inhibit the activities of antioxidant-related enzymes (SOD, POD, and CAT), and thereby cause the oxidative stress. The enzyme activities of AKP, ACP and lysozyme in hepatopancreas after BPA exposure were also depressed even after Aeromonas hydrophila infections. The relative expression profiles of immune-related genes after BPA exposure and bacterial infection showed suppressed trends of most selected genes. Under A. hydrophila infections, the cumulative mortality of 225 μg/L BPA-treated crayfish was significantly higher than other groups. All these results indicated that BPA exposure had adverse effects on the immune ability of P. clarkii. The present study will provide an important foundation for further understanding the effects of EDCs on crustacean immune functions.

Tributyltin impaired spermatogenesis and reproductive behavior in male zebrafish

Tributyltin (TBT) was reported to affect sexual behavior and gametogenesis in fish. However, the modes of action involved are largely unclear. In order to elucidate the toxicological mechanisms of TBT in reproduction, zebrafish (Danio rerio) males were exposed to TBT at concentrations of 100 and 500 ng/L for 28 days. After exposure, the sperm count of the treated fish was sharply decreased though the testis weight and gonadosomatic index remained unchanged. Moreover, reduced number of spermatogonia and spermatozoa and increased spermatocytes were observed in TBT-treated fish by histological observation and PCNA-immunostaining. Increased number of apoptotic-positive spermatocytes was also present in TBT-treated fish, indicating an enhanced apoptosis in these cells. Consistent to decreased number of spermatogonia, down-regulated expressions of genes responsible for germ cell proliferation (cyclind1 and pcna) were observed in TBT-treated fish. In contrast, TBT elevated the expressions of genes involved in meiotic entry and maintenance (aldhla2, sycp3 and dmc1) while suppressed the mRNA level of gene responsible for terminus of meiotic entry (cyp26a1), in agreement with arrested meiosis and reduced sperm count. Furthermore, TBT significantly elevated the ratios of bax/bcl-2 and tnfrsf1a/tnfrsf1b in testis, which are markers for intrinsic- and extrinsic-apoptotic pathways, consistent with the enhanced TUNEL positive signals in spermatocytes. Moreover, TBT also significantly affected the parameter of reproductive behaviors in treated fish (reflected by decreased frequency of meeting, visits and time spent in spawning area). Consistently, the expressions of genes responsible for the modulation of reproductive behaviors in brain (such as cyp19a1b, kiss2, gnrh3 and ompb) were significantly down-regulated in treated-fish. Interestingly, disrupted reproductive behaviors of untreated female fish were also observed in the present study. The present study indicated that TBT might affect the reproduction of zebrafish male by disrupting the spermatogenesis and reproductive behavior of the fish.

Effects of Organotins on Crustaceans: Update and Perspectives

Organotins (OTs) are considered some of the most toxic chemicals introduced into aquatic environments by anthropogenic activities. They are widely used for agricultural and industrial purposes and as antifouling additives on boat hull's paints. Even though the use of OTs was banned in 2008, elevated levels of OTs can still be detected in aquatic environments. OTs' deleterious effects upon wildlife and experimental animals are well documented and include endocrine disruption, immunotoxicity, neurotoxicity, genotoxicity, and metabolic dysfunction. Crustaceans are key members of zooplankton and benthic communities and have vital roles in food chains, so the endocrine-disrupting effects of tributyltin (TBT) on crustaceans can affect other organisms. TBT can disrupt carbohydrate and lipid homeostasis of crustaceans by interacting with retinoid X receptor (RXR) and crustacean hyperglycemic hormone (CHH) signaling. Moreover, it can also interact with other nuclear receptors, disrupting methyl farnesoate and ecdysteroid signaling, thereby altering growth and sexual maturity, respectively. This compound also interferes in cytochrome P450 system disrupting steroid synthesis and reproduction. Crustaceans are also important fisheries worldwide, and its consumption can pose risks to human health. However, some questions remain unanswered. This mini review aims to update information about the effects of OTs on the metabolism, growth, and reproduction of crustaceans; to compare with known effects in mammals; and to point aspects that still needs to be addressed in future studies. Since both macrocrustaceans and microcrustaceans are good models to study the effects of sublethal TBT contamination, novel studies should be developed using multibiomarkers and omics technology.

Influence of short term exposure of TBT on the male reproductive activity in freshwater prawn Macrobrachium rosenbergii (De Man)

In the present study, the effect of tributyltin (TBT) on the histopathological and hormonal changes during spermatogenesis in freshwater prawn Macrobrachium rosenbergii was documented. Three experimental concentrations such as 10, 100 and 1,000 ng/L were selected and exposed to prawns for 45 days. After TBT exposure, the reproductive activities like sperm count and sperm length were decreased when compared with control. Further, abnormal structure of the seminiferous tubule, decrease in spermatozoa concentration, diminution of the seminiferous tubule membrane and the abundance of spermatocytes in the testis were noticed in treated prawns. Interestingly, radioimmunoassay clearly revealed the reduction of testosterone level in TBT exposed groups. Thus, TBT has considerably reduced the level of testosterone and caused the impairment of spermatogenesis in the freshwater male prawn M. rosenbergii.

TBT effects on the development of intersex (ovotestis) in female fresh water prawn Macrobrachium rosenbergii

The impact of tributyltin (TBT) on the female gonad and the endocrine system in Macrobrachium rosenbergii was studied. Prawns were exposed to environmentally realistic concentrations of 10, 100, and 1000 ng/L of TBT for 6 months. Dose dependent effects were noticed in TBT exposed prawns. At 1000 ng/L TBT caused ovotestis formation (formation of male germ cells in ovary). Presence immature oocytes, fusion of developing oocytes, increase in interstitial connective tissues, and its modification into tubular like structure and abundance of spermatogonia in the ovary of TBT treated prawns. The control prawn ovary showed normal architecture of cellular organelles such as mature oocytes with type 2 yolk globules, lipid droplets, normal appearance of yolk envelop, and uniformly arranged microvilli. On the other hand, type 1 yolk globules, reduced size of microvilli, spermatogonial cells in ovary, spermatogonia with centrally located nucleus, and chromatin distribution throughout the nucleoplasm were present in the TBT treated group. Immunofluorescence staining indicated a reduction in vitellin content in ovary of TBT treated prawn. Moreover, TBT had inhibited the vitellogenesis by causing hormonal imbalance in M. rosenbergii. Thus, the present investigation demonstrates that TBT substantially affects sexual differentiation and gonadal development in M. rosenbergii.