Abstract
Highlights
- Fluoride induces severe mitochondrial damage in Leydig cells, as well as in germ and Sertoli cells. Fluoride induces mitophagy in testicular tissues, especially in Leydig cells.
- Fluoride decreases the mitochondrial membrane potential and increases the number of lysosomes in Leydig cells.
- PINK1/Parkin pathway maybe plays an important role in fluoride-induced mitophagy in mice testes.
It is very important to explore the potential harm and underlying mechanism of fluoride due to the extensive distribution and the significant health risks of fluoride in environment. The objective of this study to investigate whether fluoride can induce mitochondrial impairment and mitophagy in testicular cells. For this, 40 male mice were randomly divided into four groups treated with 0, 0.6, 1.2, 2.4 mM NaF deionized water, respectively, for 90 days continuously. The results showed that mitophagy was triggered by F in testicular tissues, especially in the Leydig cells by transmission electron microscopy and mitophagy receptor PHB2 locations by immunofluorescence. Furthermore, TM3 Leydig cells line was employed and treated with 0, 0.125, 0.25, and 0.5 mM NaF for 24 h. The mitochondrial function indicators and mitophagy maker PHB2, COX IV and regulator PINK1 in transcript and protein levels in Leydig cells were examined by the methods of qRT-PCR, western blotting, and immunofluorescence co-localization. The results showed that fluoride decreased the mitochondrial membrane potential with a concomitant increase in the number of lysosomes. Meanwhile, fluoride exposure also increased the expressions of PINK1 and PHB2 in TM3 Leydig cells. These results revealed that fluoride could induce mitochondrial impairment and excessive PINK1/Parkin-mediated mitophagy in testicular cells, especially in Leydig cells, which could contribute to the elucidation of the mechanisms of F-induced male reproductive toxicity.
Graphical abstract
Mechanism of mitophagy formation in fluoride induced Leydig cells of testis. Mitochondrial depolarization, induced by F? attacking, causes the accumulation of PINK1 on the outer membrane, followed by subsequent ubiquitination and degradation of mitochondrial outer membrane proteins. The resulting rupture of the outer membrane allows the phagophore to bind the mitochondrial inner membrane protein PHB2, leading to mitophagy.
