Effects of acetyl L-carnitine on zebrafish embryos: Phenotypic and gene expression studies

Gene expression analyses reveal potential mechanism of inorganic arsenic-induced apoptosis in zebrafish

Our previous study showed that sodium arsenite (200 mg/L) affected the nervous system and induced motor neuron development via the Sonic hedgehog pathway in zebrafish larvae. To gain more insight into the effects of arsenite on other signaling pathways, including apoptosis, we have performed quantitative polymerase chain reaction array-based gene expression analyses. The 96-well array plates contained primers for 84 genes representing 10 signaling pathways that regulate several biological functions, including apoptosis. We exposed eggs at 5 h postfertilization until the 72 h postfertilization larval stage to 200 mg/L sodium arsenite. In the Janus kinase/signal transducers and activators of transcription, nuclear factor κ-light-chain-enhancer of activated B cells, and Wingless/Int-1 signaling pathways, the expression of only one gene in each pathway was significantly altered. The expression of multiple genes was altered in the p53 and oxidative stress pathways. Sodium arsenite induced excessive apoptosis in the larvae. This compelled us to analyze specific genes in the p53 pathway, including cdkn1a, gadd45aa, and gadd45ba. Our data suggest that the p53 pathway is likely responsible for sodium arsenite-induced apoptosis. In addition, sodium arsenite significantly reduced global DNA methylation in the zebrafish larvae, which may indicate that epigenetic factors could be dysregulated after arsenic exposure. Together, these data elucidate potential mechanisms of arsenic toxicity that could improve understanding of arsenic's effects on human health.

The mechanism and effects of remdesivir-induced developmental toxicity in zebrafish: Blood flow dysfunction and behavioral alterations

The antiviral drug remdesivir has been used to treat the growing number of coronavirus disease 2019 (COVID-19) patients. However, the drug is mainly excreted through urine and feces and introduced into the environment to affect non-target organisms, including fish, which has raised concerns about potential ecotoxicological effects on aquatic organisms. Moreover, studies on the ecological impacts of remdesivir on aquatic environments have not been reported. Here, we aimed to explore the toxicological impacts of microinjection of remdesivir on zebrafish early embryonic development and larvae and the associated mechanism. We found that 100 μM remdesivir delayed epiboly and impaired convergent movement of embryos during gastrulation, and dose-dependent increases in mortality and malformation were observed in remdesivir-treated embryos. Moreover, 10-100 μM remdesivir decreased blood flow and swimming velocity and altered the behavior of larvae. In terms of molecular mechanisms, eighty differentially expressed genes (DEGs) were identified by transcriptome analysis in the remdesivir-treated group. Some of these DEGs, such as manf, kif3a, hnf1ba, rgn, prkcz, egr1, fosab, nr4a1, and ptgs2b, were mainly involved in early embryonic development, neuronal developmental disorders, vascular disease and the blood flow pathway. These data reveal that remdesivir can impair early embryonic development, blood flow and behavior of zebrafish embryos/larvae, probably due to alterations at the transcriptome level. This study suggests that it is important to avoid the discharge of remdesivir to aquatic ecosystems and provides a theoretical foundation to hinder remdesivir-induced ecotoxicity to aquatic environments.

Acetyl l-carnitine protects adipose-derived stem cells against serum-starvation: regulation on the network composed of reactive oxygen species, autophagy, apoptosis and senescence

Adipose-derived stem cells (ADSCs) play an important role in cell therapy and regenerative medicine. However, local nutritional deficiency often limits therapeutical effect of the transplanted cells. Acetyl l-carnitine (ALC) is a common energy metabolism regulator and free radical scavenger. This study investigated the effect of ALC on ADSCs exposed to severe serum-deprivation and explored the relative machanisms. Treating with 1 mM ALC improved proliferation and alleviated senescence of starved cells, accompanied with reduced reactive oxygen species (ROS) and increased protein expression of SOD1 and catalase. In addition, ALC inhibited apoptosis but increased starvation-induced autophagy, which might be related to the regulation of phases of dissociation of Bcl-2-Beclin1 and Bcl-2-Bax complexes. Evidence obtained by replacing ALC with N-acetylcysteine (N-AC) suggested that ROS might be the central inducer of autophagy, apoptosis and senescence. There was a difference between ALC and N-AC in the protection mechanism, that was, compared with N-AC, ALC maintained autophagy well at the same time as anti-oxidation. Inhibition of autophagy by 3-methyladenine (3-MA) partially offset the protective effect of ALC. However, despite low-level ROS and enhanced autophagy, ALC with high concentration (10 mM) markedly aggravated cell apoptosis and senescence, thus losing cytoprotection and even causing damage.