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Updated: Dec 30, 2025
Author Spotlight: Advancing Male Infertility Research by Unraveling Sperm Metabolism and Mitochondrial Function
Published on: June 23, 2023
Melatonin Inhibits Formation of Mitochondrial Permeability Transition Pores and Improves Oxidative Phosphorylation of
Yi Fang1, Chengzhen Zhao1, Hai Xiang1
1Jilin Provincial Key Laboratory of Grassland Farming, Northeast Institute of Geography and Agoecology, Chinese Academy of Sciences, Changchun, China.
Abstract:
Structural and functional damages to mitochondria of frozen-thawed sperm are a typical cryoinjury, with mitochondrial permeability transition pore (MPTP) formation being the hallmark change. Mitochondria are both a primary synthesis site and principle target for melatonin; this compound can directly inhibit MPTP formation and therefore confer protection at a mitochondrial level. The objective was to determine effects of melatonin on MPTP opening, viability, motility, and oxidative phosphorylation (OXPHOS) of frozen-thawed ram sperm. Ram semen was diluted in glucose-egg yolk buffer with 0 or 10-7 M melatonin (frozen and frozen + melatonin groups, respectively) and slow frozen, with fresh semen as Control. In frozen-thawed sperm, melatonin inhibited MPTP opening and lactate concentrations and improved sperm viability, motility, acetyl-CoA concentration and adenosine triphosphate (ATP) production. With regard to the underlying physiological mechanism, melatonin suppressed movement of citrate synthase, isocitrate dehydrogenase, oxoglutarate dehydrogenase complex, and F0F1-ATP synthase permeability from mitochondrial to cytosolic fractions induced by MPTP opening; furthermore, it increased mRNA expressions of respiratory chain complex components and activities of complexes I, II, III, and IV and thereby improved oxygen consumption capacity in frozen-thawed sperm. In conclusion, melatonin improved OXPHOS of frozen-thawed ram sperm, attributed to inhibition of cryopreservation-induced MPTP opening.
Insights
Melatonin protects ram sperm from cryopreservation damage by inhibiting mitochondrial permeability transition pore (MPTP) opening. This improves sperm viability, motility, and oxidative phosphorylation (OXPHOS).
Area of Science:
- Reproductive Biology
- Mitochondrial Physiology
- Cryopreservation Science
Background:
- Cryopreservation of sperm causes mitochondrial damage, characterized by mitochondrial permeability transition pore (MPTP) formation.
- Melatonin is synthesized in and targets mitochondria, offering protection by inhibiting MPTP opening.
Purpose of the Study:
- To investigate the effects of melatonin on MPTP opening, viability, motility, and oxidative phosphorylation (OXPHOS) in frozen-thawed ram sperm.
- To elucidate the protective mechanisms of melatonin against cryoinjury in sperm mitochondria.
Main Methods:
- Ram semen was cryopreserved with or without melatonin (10⁻⁷ M).
- Sperm viability, motility, ATP production, and lactate concentration were assessed.
- Mitochondrial enzyme activity, mRNA expression of respiratory chain components, and MPTP opening were analyzed.
Main Results:
- Melatonin significantly inhibited MPTP opening and reduced lactate levels in frozen-thawed ram sperm.
- Sperm viability, motility, acetyl-CoA, and ATP production were improved by melatonin treatment.
- Melatonin enhanced the activity of respiratory chain complexes (I-IV) and oxygen consumption capacity.
Conclusions:
- Melatonin effectively protects ram sperm from cryopreservation-induced mitochondrial damage.
- The protective effects are attributed to the inhibition of MPTP opening and enhancement of mitochondrial oxidative phosphorylation (OXPHOS).
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