Mitochondrial permeability transition pore (MPTP) desensitization increases sea urchin spermatozoa fertilization rate

Abstract

Mitochondrial permeability transition pore (MPTP) is a protein complex whose opening promotes an abrupt increase in mitochondrial inner membrane permeability. Calcium signaling pathways are described in gametes and are involved in the fertilization process. Although mitochondria may act as Ca(2+) store and have a fast calcium-releasing mechanism through MPTP, its contribution to fertilization remains unclear. The work aimed to investigate the MPTP phenomenon in sea urchin spermatozoa and its role on the fertilization. Several pharmacological tools were used to evaluate the MPTP's physiology. Our results demonstrated that MPTP occurs in male gametes in a Ca(2+) - and voltage-dependent manner and it is sensitive to cyclosporine A. Additionally, our data show that MPTP opening does not alter ROS generation in sperm cells. Inhibition of MPTP in spermatozoa strongly improved the fertilization rate, which may involve mechanisms that increase the spermatozoa lifespan. The present work is the first report of the presence of a voltage- and Ca(2+) -dependent MPTP in gametes of invertebrates and indicates MPTP opening as another evolutionary feature shared by sea urchins and mammals. Studies about MPTP in sea urchin male gametes may contribute to the elucidation of several mechanisms involved in sperm infertility.

Melatonin Inhibits Formation of Mitochondrial Permeability Transition Pores and Improves Oxidative Phosphorylation of Frozen-Thawed Ram Sperm

“…In this study, based on increasing viability and motility of sperm, we inferred that melatonin inhibited apoptosis and improved quality of frozen-thawed sperm. Inhibition of the opening of MPTP during cryopreservation significantly reduced apoptotic markers (e.g., caspase activity) and mitochondrial membrane permeability in equine sperm (33); furthermore, it also increased m and improved fertilization in frozen-thawed sea urchin sperm (34). Therefore, results of the current study confirmed that melatonin effectively prevented cryopreservation-induced MPTP opening in ram sperm.…”

The effects of oxidative stress and intracellular calcium on mitochondrial permeability transition pore formation in equine spermatozoa

“…31 Close associations between MMP loss and mPTP formation have been reported in neurons, 32 and previous studies have equated a loss of MMP with mPTP formation in several cell types, 33 including spermatozoa. 17,23 In the present study, we set out to establish whether such a close association between mPTP formation and MMP depolarization existed in stallion spermatozoa, by simultaneously examining mitochondrial membrane status using JC-1, and mPTP formation using a loss of C-AM-V fluorescence. Our results demonstrate that in this cell type, a loss of MMP does not necessarily coincide with mPTP formation (Figure 1); indeed, one of the gating controls for the JC-1/C-AM-V assay used in the present study is CCCP, which collapsed MMP without any loss of C-AM-V fluorescence (and therefore no mPTP formation; Figure 1C), demonstrating that a loss of MMP may be due to reasons other than mPTP formation.…”

“…Nonetheless, several studies have recently emerged in which mPTP formation has been confirmed in the spermatozoa of several species, including the horse. 17 , 19 , 20 , 21 , 22 , 23 A limitation of many of these studies has been the use of downstream markers of mPTP formation, such as caspase activation, oxidative stress, loss of viability and/or motility, and mitochondrial membrane depolarisation, to quantify mPTP formation following various treatments. However, these events may be initiated by any number of insults and cannot definitively be attributed to mPTP formation in the absence of a C‐AM assay.…”

Melatonin improves cryopreservation of ram sperm by inhibiting mitochondrial permeability transition pore opening

“…Using a specific inhibitor of the mPTP opening during cryopreservation significantly reduced the presence of apoptotic markers (e.g. caspase activity) and increased mitochondrial membrane permeability in equine sperm (Ferrusola et al, 2010), and it increased ΔΨm and improved fertilization in sea urchin sperm after thawing (Torrezan-Nitao, Boni, & Marques-Santos, 2016). In this study, based on increasing sperm plasmatic membrane integrity, ΔΨm, mitochondrial Cyt c concentration and fertilization whether in vitro or in vivo, we inferred that melatonin inhibited apoptosis and improved quality of frozen-thawed sperm.…”