Spermidine attenuates copper overload-induced cuproptosis in porcine granulosa cells through the miR-194a-5p/DLAT axis

Abstract

Abstract Excess copper disrupts mitochondrial metabolism by triggering cuproptosis, a regulated cell-death program characterized by the aggregation of lipoylated tricarboxylic acid cycle proteins and the loss of Fe-S cluster proteins. This mitochondrial injury may be particularly consequential in atretic follicle granulosa cells (GCs), whose energy metabolism and biosynthetic activity sustain follicular growth. Spermidine supports mitochondrial and metabolic homeostasis, but whether it protects GCs from copper overload by restraining cuproptosis remains unclear. Here, we investigated whether spermidine limits copper-overload-induced follicular injury through the miR-194a-5p/dihydrolipoamide S-acetyltransferase (DLAT) axis. Porcine atretic follicles showed increased expression of the copper transporter solute carrier family 31 member 1 (SLC31A1) and elevated copper levels in GCs and follicular fluid. These changes were accompanied by reduced levels of FDX1, LIAS, DLAT, ACO2, and POLD1, diminished lipoate-associated signals, and increased DLAT oligomerization. In cultured GCs, CuSO₄ induced intracellular copper accumulation, mitochondrial dysfunction and cuproptosis-associated injury, which was preferentially attenuated by ammonium tetrathiomolybdate. Spermidine supplementation attenuated copper-overload-induced ovarian injury in mice and protected cultured GCs from mitochondrial dysfunction, whereas polyamine depletion aggravated the loss of Fe-S cluster proteins and lipoylated proteins. Mechanistically, spermidine reduced miR-194a-5p abundance, restored DLAT expression and preserved pyruvate dehydrogenase activity, ATP production, NDUFS1 concentration and ACO2 activity. Together, these findings support a spermidine/miR-194a-5p/DLAT axis that restrains copper-overload-induced cuproptosis-associated injury in GCs and may link copper stress to follicular atresia.