Polystyrene Nanoplastics in Aquatic Microenvironments Affect Sperm Metabolism and Fertilization of Mytilus galloprovincialis (Lamark, 1819).

The continuous and unregulated discharge of wastes and pollutants into the aquatic environment has required constant monitoring of the risks incurred by aquatic ecosystems. Alarmism arises from plastic pollution as larger artifacts release nanoscale fragments that can contact free-living stages such as gametes, embryos, and larvae. Specifically, the interaction between spermatozoa, released in water in externally fertilizing species, and the surrounding microenvironment is essential for successful fertilization. Activation and kinematics of movement, proper maintenance of ionic balance, and chemotactism are processes highly sensitive to even minimal perturbations caused by pollutants such as polystyrene nanoplastics. Spermatozoa of Mytilus galloprovincialis (M. galloprovincialis), an excellent ecotoxicological model, undergo structural (plasma membrane ruptures, DNA damage) and metabolic (reduced motility, fertilizing capacity) damage upon exposure to 50 nm amino-modified polystyrene nanoplastics (nPS-NH2). Nanoplastics of larger diameter (100 nm) did not affect sperm parameters. The findings highlighted the negative impact that plastic pollution, related to nanoparticle diameter and concentration, could have on sperm quality and reproductive potential of organisms, altering the equilibrium of aquatic ecosystems.

Sublethal Effects of Polystyrene Nanoplastics on the Embryonic Development of Artemia salina (Linnaeus, 1758).

Currents, wave motion, solar radiation, and abrasion are mechanisms responsible for the degradation of large plastic artifacts and contribute to the dispersion of micro and nanoplastics into aquatic ecosystems, which are, currently, the most dangerous threats due to their invisibility and persistence. The present work evaluated the possible lethal and sublethal effects of amino-modified polystyrene nanoplastics (nPS-NH2) with diameters of 50 nm and 100 nm on Artemia salina (A. salina), an organism at the base of the trophic chain of the aquatic system, using a widely used model for the analysis of embryotoxicity from environmental pollutants. For this purpose, after evaluating the biodistribution of nanoplastics in the body of the tested animals, several endpoints such as anomalies, apoptosis, and ROS production were assessed. In addition, particular attention was dedicated to evaluating the correlation between toxicity and the particle size tested. The results reported that, despite the absence of a lethal impact, several sublethal effects involving gut and body size malformations, as well as the enhancement of apoptosis and oxidative stress in relation to an increase in tested concentration and a decrease in nanoparticle size.

In Vitro Nano-Polystyrene Toxicity: Metabolic Dysfunctions and Cytoprotective Responses of Human Spermatozoa.

The ubiquitous spread of Polystyrene nanoplastics (PS-NPs) has rendered chronic human exposure an unavoidable phenomenon. The biodistribution of such particles leads to bioaccumulation in target organs including the testis, the site of sperm maturation. The purpose of this research has been to estimate the impact of PS-NPs (50 and 100 nm) on the metabolism of mature spermatozoa. The analysis of the semen parameters has revealed a higher toxicity of the smaller sized PS-NPs, which have negatively affected major organelles, leading to increased acrosomal damage, oxidative stress with the production of ROS, DNA fragmentation, and decreased mitochondrial activity. PS-NPs of 100 nm, on the other hand, have mainly affected the acrosome and induced a general state of stress. An attempt has also been made to highlight possible protective mechanisms such as the expression of HSP70s and their correlation among various parameters. The results have evinced a marked production of HSP70s in the samples exposed to the smaller PS-NPs, negatively correlated with the worsening in oxidative stress, DNA fragmentation, and mitochondrial anomalies. In conclusion, our results have confirmed the toxicity of PS-NPs on human spermatozoa but have also demonstrated the presence of mechanisms capable of counteracting at least in part these injuries.

Toxicity of Titanium Dioxide-Cerium Oxide Nanocomposites to Zebrafish Embryos: A Preliminary Evaluation.

The widespread use of metal nanoparticles in different fields has raised many doubts regarding their possible toxicity to living organisms and the accumulation and discharge of metals in fish species. Among these nanoparticles, titanium dioxide (TiO2) and cerium oxide (CeO2) nanoparticles have mainly been employed in photocatalysis and water depuration. The aim of this research was to evaluate the potential toxic effects, after a co-exposure of TiO2-3%CeO2 nanoparticles, on zebrafish development, using an acute toxicity test. Increasing concentrations of TiO2-3%CeO2 nanoparticles were used (0.1-1-10-20 mg/L). The heartbeat rate was assessed using DanioscopeTM software (version 1.2) (Noldus, Leesburg, VA, USA), and the responses to two biomarkers of exposure (Heat shock proteins-70 and Metallothioneins) were evaluated through immunofluorescence. Our results showed that the co-exposure to TiO2-3%CeO2 nanoparticles did not affect the embryos' development compared to the control group; a significant difference (p < 0.05) at 48 hpf heartbeat for the 1, 10, and 20 mg/L groups was found compared to the unexposed group. A statistically significant response (p < 0.05) to Heat shock proteins-70 (Hsp70) was shown for the 0.1 and 1 mg/L groups, while no positivity was observed in all the exposed groups for Metallothioneins (MTs). These results suggest that TiO2-3%CeO2 nanocomposites do not induce developmental toxicity; instead, when considered separately, TiO2 and CeO2 NPs are harmful to zebrafish embryos, as previously shown.

HIPK2 deficiency causes chromosomal instability by cytokinesis failure and increases tumorigenicity.

HIPK2, a cell fate decision kinase inactivated in several human cancers, is thought to exert its oncosuppressing activity through its p53-dependent and -independent apoptotic function. However, a HIPK2 role in cell proliferation has also been described. In particular, HIPK2 is required to complete cytokinesis and impaired HIPK2 expression results in cytokinesis failure and tetraploidization. Since tetraploidy may yield to aneuploidy and chromosomal instability (CIN), we asked whether unscheduled tetraploidy caused by loss of HIPK2 might contribute to tumorigenicity. Here, we show that, compared to Hipk2+/+ mouse embryo fibroblasts (MEFs), hipk2-null MEFs accumulate subtetraploid karyotypes and develop CIN. Accumulation of these defects inhibits proliferation and spontaneous immortalization of primary MEFs whereas increases tumorigenicity when MEFs are transformed by E1A and Harvey-Ras oncogenes. Upon mouse injection, E1A/Ras-transformed hipk2-null MEFs generate tumors with genetic alterations resembling those of human cancers derived by initial tetraploidization events, such as pancreatic adenocarcinoma. Thus, we evaluated HIPK2 expression in different stages of pancreatic transformation. Importantly, we found a significant correlation among reduced HIPK2 expression, high grade of malignancy, and high nuclear size, a marker of increased ploidy. Overall, these results indicate that HIPK2 acts as a caretaker gene, whose inactivation increases tumorigenicity and causes CIN by cytokinesis failure.