Sodium Fluoride Induces Splenocyte Autophagy via the Mammalian Targets of Rapamycin (mTOR) Signaling Pathway in Growing Mice

Aging (Albany NY). 2018 Jul 22;10(7):1649-1665. doi: 10.18632/aging.101499.

Abstract

Fluoride is known to impair organism's development and function via adverse effects, and autophagy plays a regulation role in human or animal health and disease. At present, there are no reports focused on fluoride-induced autophagy in the animal and human spleen. The objective of this study was to investigate sodium fluoride (NaF)-induced splenocyte autophagy and the potential mechanism via regulation of p-mTOR in growing mice by using the methods of transmission electron microscopy (TEM), immunohistochemistry (IHC), quantitative real-time polymerase chain reaction (qRT-PCR) and western blot. A total of 240 ICR mice were equally allocated into four groups with intragastric administration of distilled water in the control group and 12, 24, 48 mg/kg NaF solution in the experimental groups for 42 days. Results revealed that NaF increased autophagosomes or autolysosomes in spleen. Simultaneously, the autophagy marker LC3 brown punctate staining was increased with NaF dosage increase. On the other hand, NaF caused inhibition of mTOR activity, which was characterized by down-regulation of PI3K, Akt and mTOR mRNA and protein expression levels. And the suppression of mTOR activity in turn resulted in the significantly increased of ULK1 and Atg13 expression levels. Concurrently, NaF increased the levels of mRNA and protein expression of autophagy markers LC3, Beclin1, Atg16L1, Atg12, Atg5 and decreased the mRNA and protein expression levels of p62. The above-mentioned findings verify that NaF induces autophagy via mTOR signaling pathway. The inhibition of mTOR activity and alteration of autophagy-related genes and proteins are the potential molecular mechanism of NaF-induced splenocyte autophagy.

Keywords: autophagy; mTOR signaling pathway; mouse; sodium fluoride; spleen.

MeSH terms

  • Animals
  • Autophagy / drug effects*
  • Autophagy-Related Proteins / genetics
  • Autophagy-Related Proteins / metabolism
  • Beclin-1 / genetics
  • Beclin-1 / metabolism
  • Biomarkers
  • Gene Expression Regulation, Developmental / drug effects*
  • Mice
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism
  • Phosphorylation
  • RNA, Messenger
  • Signal Transduction
  • Sodium Fluoride / pharmacology*
  • Spleen / cytology*
  • Spleen / ultrastructure
  • mTOR Associated Protein, LST8 Homolog / genetics
  • mTOR Associated Protein, LST8 Homolog / metabolism*

Substances

  • Autophagy-Related Proteins
  • Beclin-1
  • Becn1 protein, mouse
  • Biomarkers
  • MAP1LC3 protein, mouse
  • Microtubule-Associated Proteins
  • RNA, Messenger
  • mTOR Associated Protein, LST8 Homolog
  • Sodium Fluoride