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Figure 1: Schematic representation of NAD(P)H oxidase activity. This enzymes transfers electrons from NAD(P)H to ground state oxygen to create the superoxide anion radical. The latter then dismutates to hydrogen peroxide under the influence of superoxide dismutase. The hydrogen peroxide is predominantly scavenged by glutathione peroxidase, since human spermatozoa possess little catalase activity. Once this peroxidase activity is overwhelmed, a state of oxidative stress may be induced that disrupts the fertilizing capacity of the spermatozoa and the integrity of their DNA.
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Figure 2: Schematic representation of the underlying chemistry of lucigenin chemiluminescence. Luc2+ = lucigenin; LH+• = a lucigenin radical created by the one electron reduction of Luc2+. The reaction of LH+• with oxygen generates O2-•. The latter then participates in an oxygenation reaction with LH+• generating a dioxetane that decomposes with the generation of chemiluminescence. Any entity that can bring about the one electron reduction of lucigenin can potentially create a redox cycle in the presence of oxygen that produces high levels of O2-• and chemiluminescence. It is impossible to distinguish the relative contribution of such probe-dependent and cell-dependent chemiluminescence. Hence data obtained with this probe should be interpreted with caution.
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Figure 3: Errors during spermiogenesis can lead to the retention of excess residual cytoplasm by human spermatozoa. A) arrows point to cells possessing an irregular cytoplasmic mass in the neck region of the spermatozoon; significantly, human spermatozoa have lost the ability, possessed by most other mammalian species, to create a cytoplasmic droplet which is later discharged from the cell B) The amount of cytoplasm retained by human spermatozoa is highly correlated with the ability of leukocyte-free sperm suspensions to generate a chemiluminescence response to 12-myristate, 13-acetate phorbol ester (PMA), using luminol-peroxidase as the detection system.
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