Impaired V-ATPase leads to increased lysosomal pH, results in disrupted lysosomal degradation and autophagic flux blockage, contributes to fluoride-induced developmental neurotoxicity

Abstract

Fluoride is capable of inducing developmental neurotoxicity, yet its mechanisms remain elusive. We aimed to explore the possible role and mechanism of autophagic flux blockage caused by abnormal lysosomal pH in fluoride-induced developmental neurotoxicity, focusing on the role of V-ATPase in regulating the neuronal lysosomal pH. Using Sprague-Dawley rats exposed to sodium fluoride (NaF) from gestation through delivery until the neonatal offspring reached six months of age as an in vivo model. The results showed that NaF impaired the cognitive abilities of the offspring rats. In addition, NaF reduced V-ATPase expression, diminished lysosomal degradation capacity and blocked autophagic flux, and increased apoptosis in the hippocampus of offspring. Consistently, these results were validated in SH-SY5Y cells incubated with NaF. Moreover, NaF increased the SH-SY5Y lysosomal pH. Mechanistically, V-ATPase B2 overexpression and ATP effectively restored V-ATPase expression, reducing NaF-induced lysosomal alkalinization while increasing lysosomal degradation capacity. Notably, those above pharmacological and molecular interventions diminished NaF-induced apoptosis by restoring autophagic flux. Collectively, the present findings suggested that NaF impairs the lysosomal pH raised by V-ATPase. This leads to reduced lysosomal degradation capacity and triggers autophagic flux blockage and apoptosis, thus contributing to neuronal death. Therefore, V-ATPase might be a promising indicator of developmental fluoride neurotoxicity.

Keywords: Developmental neurotoxicity; Fluoride; Lysosomal degradation capacity; Lysosomal pH; V-ATPase.