A Brazilian pulp and paper mill effluent disrupts energy metabolism in immature rat testis and alters Sertoli cell secretion and mitochondrial activity

Mechanism of mitochondrial oxidative phosphorylation disorder in male infertility

ABSTRACT

Male infertility has become a global concern, accounting for 20-70% of infertility. Dysfunctional spermatogenesis is the most common cause of male infertility; thus, treating abnormal spermatogenesis may improve male infertility and has attracted the attention of the medical community. Mitochondria are essential organelles that maintain cell homeostasis and normal physiological functions in various ways, such as mitochondrial oxidative phosphorylation (OXPHOS). Mitochondrial OXPHOS transmits electrons through the respiratory chain, synthesizes adenosine triphosphate (ATP), and produces reactive oxygen species (ROS). These mechanisms are vital for spermatogenesis, especially to maintain the normal function of testicular Sertoli cells and germ cells. The disruption of mitochondrial OXPHOS caused by external factors can result in inadequate cellular energy supply, oxidative stress, apoptosis, or ferroptosis, all inhibiting spermatogenesis and damaging the male reproductive system, leading to male infertility. This article summarizes the latest pathological mechanism of mitochondrial OXPHOS disorder in testicular Sertoli cells and germ cells, which disrupts spermatogenesis and results in male infertility. In addition, we also briefly outline the current treatment of spermatogenic malfunction caused by mitochondrial OXPHOS disorders. However, relevant treatments have not been fully elucidated. Therefore, targeting mitochondrial OXPHOS disorders in Sertoli cells and germ cells is a research direction worthy of attention. We believe this review will provide new and more accurate ideas for treating male infertility.

Long-term effects of early postnatal stress on Sertoli cells

Sertoli cells are somatic cells in testis essential for spermatogenesis, that support the development, maturation, and differentiation of germ cells. Sertoli cells are metabolically highly active and physiologically regulated by external signals, particularly factors in the blood stream. In disease conditions, circulating pathological signals may affect Sertoli cells and consequentially, alter germ cells and fertility. While the effects of stress on reproductive cells have been well studied, how Sertoli cells respond to stress remains poorly characterized. We used a mouse model of early postnatal stress to assess the effects of stress on Sertoli cells. We developed an improved strategy based on intracellular stainings and obtained enriched preparations of Sertoli cells from exposed males. We show that adult Sertoli cells have impaired electron transport chain (ETC) pathways and that several components of ETC complexes particularly complex I, III, and IV are persistently affected. We identify serum as potential mediator of the effects of stress on Sertoli cells by showing that it can recapitulate ETC alterations in primary cells. These results highlight Sertoli cells as cellular targets of stress in early life that can keep a trace of exposure until adulthood.

Characteristics and treatment of Brazilian pulp and paper mill effluents: a review

Pulp and paper industries are very important for developing the Brazilian economy. During production processes, many effluents are generated with high polluting potential. The objective of this study is to conduct an extensive literature review on the characteristics of effluents and treatment forms adopted by Brazilian mills in this industrial sector. Most consulted studies address raw (without treatment) and secondary (after biological treatment) effluents, considering their main characteristics like pH, chemical and biochemical oxygen demands (COD and BOD, respectively), color, solids, organochlorines, toxicity, estrogenic activity, and phenols. Raw effluents differ considerably in composition, depending on the type of paper produced, the pulping process employed, and other steps, like pulp bleaching. Raw effluent characteristics indicate that this effluent cannot be directly disposed of into water bodies, because it does not comply with federal and state disposal standards. Secondary effluents normally comply with Brazilian legislations, although some studies have reported COD and total phenol concentrations higher than disposal standards, suggesting that additional treatments are necessary. Treated effluent reuse was verified in some Brazilian mills, while its disposal in eucalyptus plantations has been considered a promising alternative for irrigation purposes.

In vivo and in vitro short-term bisphenol A exposures disrupt testicular energy metabolism and negatively impact spermatogenesis in zebrafish

This study investigated the in vitro and short-term in vivo effects of Bisphenol A (BPA) on testicular energy metabolism and morphology in the zebrafish (Danio rerio). Testes were incubated in vitro for 1 h or fish were exposed in vivo to BPA in the tank water for 12 h. Testicular lactate, glycogen and cholesterol were measured and ¹⁴C-deoxy-d-glucose uptake and activity of lactate dehydrogenase (LDH), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were determined. In addition, testis samples from the in vivo exposures were subject to digital analysis of testicular cells using Ilastik software and the Pixel Classification module and estimation of apoptosis by Terminal deoxynucleotidyl transferase (TdT) dUTP Nick-End Labeling (TUNEL) immunohistochemical analysis. Our results from in vitro studies showed that BPA at 10 pM and 10 μM decreased testicular lactate content, glycogen content and LDH activity, but increased testicular AST activity. In addition, only BPA at 10 pM significantly decreased testicular ALT activity and cholesterol content. However, ¹⁴C-deoxy-d-glucose uptake was not changed. Furthermore, our results from in vivo studies showed that 10 pM BPA but not 10 μM BPA reduced testicular content of lactate and glycogen. In addition, both BPA concentrations decreased AST activity, whereas only BPA at 10 μM reduced ALT activity. However, LDH activity was not changed. Additionally, both concentrations of BPA induced spermatocyte apoptosis and a decrease in the proportion of the surface area of spermatids and spermatozoa. Collectively these data suggest that short-term BPA exposure affects energy metabolism and spermatogenesis in male zebrafish.

Triterpene betulin may be involved in the acute effects of pulp and paper mill effluent on testis physiology in zebrafish

Pulp and paper mill effluent can cause changes in the morphology and energy metabolism in the zebrafish (Danio rerio) testis. Betulin, a naturally occurring triterpene is commonly present in this type of effluent and is suspected of being involved in these effects. The aim of this study was to compare the effects pulp and paper mill effluent and betulin on various aspects of testicular physiology in the zebrafish. This included the in vitro effects of effluent and betulin on testicular lactate content and lactate dehydrogenase (LDH) activity. In addition, the effects of betulin on glucose uptake, glycogen, alanine aminotransferase (ALT), reactive oxygen and nitrogen species formation and oxidative damage in the testes were determined. Furthermore, we compared the effects and mechanism of action of betulin and effluent on calcium homeostasis in testes. In vitro exposure to both effluent and betulin decreased lactate and calcium influx, possibly due to the activation of the sodium‑calcium exchanger (NCX) pump. Additionally, betulin-treated testes had higher reactive oxygen species (ROS) and reduced glutathione (GSH) content, as well as increased glutathione transferase (GST) activity and a tendency towards decreased catalase (CAT) activity. Thus, this study shows that alterations in testis physiology caused by the pulp and paper mill effluent in the testis may be due in part to the actions of betulin.