Oxidative stress (OS) and disrupted antioxidant defense mechanisms play a pivotal role in the etiology of male infertility. The alterations in reactive oxygen species (ROS) production and calcium (Ca2+) homeostasis are the main activators for the mitochondrial permeability transition pore (mPTP) opening. The mPTP opening is one of the main mechanisms involved in mitochondrial dysfunction in spermatozoa. This alteration in mitochondrial function adversely affects energy supply, sperm motility, and fertilizing capacity and contributes to the development of male infertility. In human spermatozoa, the mPTP opening has been associated with ionomycin-induced endogenous oxidative stress and peroxynitrite-induced nitrosative stress; however, the effect of exogenous oxidative stress on mPTP opening in sperm has not been evaluated. The aim of this study was to determine the effect of exogenous oxidative stress induced by hydrogen peroxide (H2O2) on mPTP opening, mitochondrial function, motility, and cell death markers in human spermatozoa. Human spermatozoa were incubated with 3 mmol/L of H2O2 for 60 min, and intracellular Ca2+ concentration, mPTP opening, mitochondrial membrane potential (ΔΨm), ATP levels, mitochondrial reactive oxygen species (mROS) production, phosphatidylserine (PS) externalization, DNA fragmentation, viability, and sperm motility were evaluated. H2O2-induced exogenous oxidative stress caused increased intracellular Ca2+, leading to subsequent mPTP opening and alteration of mitochondrial function, characterized by ΔΨm dissipation, decreased ATP levels, increased mROS production, and the subsequent alteration of sperm motility. Furthermore, H2O2-induced opening of mPTP was associated with the expression of apoptotic cell death markers including PS externalization and DNA fragmentation. These results highlight the role of exogenous oxidative stress in causing mitochondrial dysfunction, deterioration of sperm motility, and an increase in apoptotic cell death markers, including PS externalization and DNA fragmentation, through the mPTP opening. This study yielded new knowledge regarding the effects of this type of stress on mitochondrial function and specifically on mPTP opening, factors that can contribute to the development of male infertility, considering that the role of mPTP in mitochondrial dysfunction in human sperm is not completely elucidated. Therefore, these findings are relevant to understanding male infertility and may provide an in vitro model for further research aimed at improving human sperm quality.

Apoptosis is the most thoroughly studied type of regulated cell death. Certain events, such as externalization of phosphatidylserine (PS) into the outer leaflet of plasma membrane, mitochondrial outer membrane permeabilization, caspase cascade activation, DNA fragmentation and blebbing, are widely considered to be hallmarks of apoptosis as well as being traditionally viewed as irreversible. This review shows that under particular circumstances these events can also participate in physiological processes not associated with initiation of apoptosis, such as cell differentiation, division, and motility, as well as non-apoptotic types of cell death. Moreover, these events may often be reversible. This review focuses on three processes: phosphatidylserine externalization, blebbing, and activation of apoptotic caspases. Mitochondrial outer membrane permeabilization and DNA fragmentation are not discussed.

Chronic hyperglycemia is one of the characteristic conditions associated with Diabetes Mellitus (DM), which often exerts deleterious effects on erythrocyte morphology and hemodynamic properties leading to anemia and diabetes-associated vascular complications. High glucose-induced over production of reactive oxygen species (ROS) can alter the blood cell metabolism and biochemical functions subsequently causing eryptosis (red blood cell death), yet another complication of concern in DM. Therefore, blocking high glucose-induced oxidative damage and subsequent eryptosis is of high importance in the better management of DM and associated vascular complications. In this study, we synthesized an oxolane derivative 1-(2,2-dimethyltetrahydrofuro[2,3][1,3]dioxol-5-yl)ethane-1,2-diol (DMTD), and demonstrated its efficacy to mitigate hyperglycemia-induced ROS generation and subsequent eryptosis. We showed that DMTD effectively inhibits high glucose-induced ROS generation, intracellular calcium levels, phosphaditylserine (PS) scrambling, calpain and band 3 activation, LDH leakage, protein glycation and lipid peroxidation, meanwhile enhances the antioxidant indices, osmotic fragility and Na+/K+-ATPase activity in erythrocytes. DMTD dose dependently decreased the glycated hemoglobin level and enhances the glucose utilization by erythrocytes in vitro. Further, DMTD alleviated the increase in ROS production, intracellular Ca2+ level and PS externalization in the erythrocytes of human diabetic subjects and enhanced the Na+/K+-ATPase activity. Taken together, the synthesized oxolane derivative DMTD could be a novel synthetic inhibitor of high glucose-induced oxidative stress and eryptosis. Considering the present results DMTD could be a potential therapeutic to treat DM and associated complications and open new avenues in developing synthetic therapeutic targeting of DM-associated complications.