# Environmental Fluoride Compromises Male Fertility: Differentially Modulated miR-34a-5p Targets REST to Regulate Autophagy in Testicular Somatic Cells

## TL;DR

Fluoride exposure harms male fertility by disrupting autophagy in testicular cells through miR-34a-5p and REST regulation.

## Contribution

Identifies miR-34a-5p and REST as key regulators of fluoride-induced autophagy in Leydig and Sertoli cells.

## Key findings

- Fluoride reduces sperm quality and damages testicular somatic cells in mice.
- Fluoride differentially modulates miR-34a-5p and REST to alter autophagy in Leydig and Sertoli cells.
- REST activation in Leydig cells and suppression in Sertoli cells mediate fluoride-induced autophagic imbalance.

## Abstract

The worldwide decline in male fertility represents a growing public health challenge, with fluoride exposure recognized as a key environmental factor exacerbating this decline. Fluoride hurts male reproduction, yet the specific mechanism remains unclear. Here, we demonstrate that fluoride reduced mouse sperm quality, destroyed the structure of testicular tissue, and caused severe damage to testicular somatic cells (Leydig and Sertoli cells). Meanwhile, the number of autophagosomes increased in Leydig cells and decreased in Sertoli cells. Network toxicology and functional analysis identified miR-34a-5p as the pivotal miRNA orchestrating fluoride-induced autophagic imbalance in testicular somatic cells. REST was identified as a novel miR-34a-5p target gene exhibiting pro-autophagic activity. Fluoride down-regulates miR-34a-5p and up-regulates REST in Leydig cells, whereas it exerts the opposite effects in Sertoli cells. The rescue experiment elucidated specific mechanisms: Fluoride down-regulates miR-34a-5p in Leydig cells, thereby derepressing REST to activate autophagy. Conversely, in Sertoli cells, fluoride up-regulates miR-34a-5p to suppress REST expression and inhibit autophagy. Collectively, the present study reveals an important mechanism underlying fluoride-induced male reproductive toxicity and provides a potential therapeutic target.