Toxicity of perfluorobutanesulfonate on gill functions of marine medaka (Oryzias melastigma): A time course and hypoxia co-exposure study

Perfluorooctanoic acid triggers premature ovarian insufficiency by impairing NAD+ synthesis and mitochondrial function in adult zebrafish

High-dose perfluorooctanoic acid (PFOA) impairs oocyte maturation and offspring quality. However, the physiological concentrations of PFOA in follicular fluids of patients with premature ovarian insufficiency (POI) were detected at lower levels, thus the relationship between physiological PFOA and reproductive disorders remains elusive. Here, we investigated whether physiological PFOA exposure affects gonad function in adult zebrafish. Physiological PFOA exposure resulted in POI-like phenotypes in adult females, which exhibited decreased spawning frequency, reduced number of ovulated eggs, abnormal gonadal index, and aberrant embryonic mortality. Meanwhile, oocytes from PFOA-exposed zebrafish showed mitochondrial disintegration and diminished mitochondrial membrane potential. Unlike the high-dose treated oocytes exhibiting high reactive oxygen species (ROS) levels and excessive apoptosis, physiological PFOA reduced the ROS levels and did not trigger apoptosis. Interestingly, physiological PFOA exposure would not affect testis function, indicating specific toxicity in females. Mechanistically, PFOA suppressed the NAD+ biosynthesis and impaired mitochondrial function in oocytes, thus disrupting oocyte maturation and ovarian fertility. Nicotinamide mononucleotide (NMN), a precursor for NAD+ biosynthesis, alleviated the PFOA-induced toxic effects in oocytes and improved the oocyte maturation and fertility upon PFOA exposure. Our findings discover new insights into PFOA-induced reproductive toxicity and provide NMN as a potential drug for POI therapy.

Protective effects of calcium against cadmium-induced toxicity in juvenile grass carp (Ctenopharyngodon idellus)

Cadmium (Cd) is one of the dominant metal pollutants present in the aquatic environment that affects ion homeostasis, oxidative stress (OS) and immune responses of aquatic organisms. Given the physicochemical similarities between Cd²⁺ and calcium (Ca²⁺) ions, their antagonism may facilitate the mitigation of Cd-induced toxicity. To better understand the role of Ca in protecting against Cd-induced toxicity in teleosts, juvenile grass carp were exposed to Cd (measured concentration 3 μg/L) and a gradient of Ca concentrations (measured concentration 1.5 mg/L, 2.5 mg/L, 3.0 mg/L, and 3.5 mg/L in the control (CTL) group, low calcium (LCA) group, medium calcium (MCA) group, and high calcium (HCA) group, respectively) for 30 days. Inductively coupled plasma mass spectrometry (ICP-MS) data analyses showed that simultaneous exposure to Ca impaired the accumulation of Cd in all tested tissues. Besides, Ca addition maintained the plasma ion (Na⁺, K⁺, Cl^-) homeostasis, alleviated Cd-induced oxidative stress (OS), and regulated the activities and transcriptional levels of ATPase. Furthermore, transcriptional heatmap analysis demonstrated that several indicator genes for OS and calcium signaling pathway were found to be significantly modulated by Ca addition. This work delineates a protective effect of Ca against Cd-induced toxicity in grass carp, providing new insight into the possible solutions to Cd pollution issues in aquaculture industry.