Vps34 Knockdown Alleviated the Long-Term Effect of Nano-Alumina on Cognitive Impairment in Zebrafish When in Embryos.

Abstract

Nano-alumina (AlNPs) exposure induced learning and memory impairment, which was associated with over-activation of mitophagy. Our previous study found that reduction of Vacuolar Protein Sorting 34 (Vps34), a core initiating gene for autophagy, alleviated AlNPs-exposed neurodevelopmental toxicity, so we hypothesized that Vps34 knockdown may mitigate the damage to learning and memory induced by AlNPs. This study aimed to investigate the effects and mechanisms of Vps34 knockdown on the long-term cognitive impairment of AlNPs in the zebrafish brain. A 500 μL of morpholino oligonucleotide at 1 mmol/L was microinjected into embryos within 1 h postfertilization (hpf). These embryos and control embryos were randomly assigned to control, negative control, Vps34 knockdown, AlNPs exposure (100 mg/L), and AlNPs exposure with Vps34 knockdown up to 144 hpf. After zebrafish were given to brine shrimp and E3 medium up to 6 months, their locomotor activity and cognitive behavior were assessed. Meanwhile, we investigated brain structure, oxidative stress, mitochondria, and mitophagy. Our results indicated that AlNPs exposure with Vps34 knockdown significantly enhanced the average speed, moving distance, time spent in the outer zone, and cumulative time in the T-maze while decreasing latency in the T-maze compared with the AlNPs-exposed group. Moreover, AlNPs exposure with Vps34 knockdown increased the number of neurons while lowering the mitophagosome in the brain compared with exposure to AlNPs. Then, AlNPs exposure with Vps34 knockdown enhanced higher activities of superoxide dismutase (SOD), Na⁺-K⁺ATPase and Ca²⁺-Mg²⁺ATPase, and levels of mitochondrial membrane potential (MMP) and translocase of outer mitochondrial membrane 20 (TOMM20) protein, while decreasing activities of reactive oxygen species (ROS) and lactate dehydrogenase (LDH), and levels of microtubule-associated protein 1 light chain 3 (LC3II) and translation of the inner member (TIM23) protein compared with AlNPs exposure. At last, AlNPs exposure significantly increased the abundances of the Vps34 and PTEN-induced putative kinase 1 (PINK1) mRNA in the brain compared with the control and AlNPs exposure with Vps34 knockdown groups. Therefore, inhibiting Vps34 protected against the cognitive impairment caused by AlNPs exposure by reducing mitophagy and restoring mitochondrial structure and function.