Suppression/stimulation of chemiluminescence by human seminal plasma

Update on the protective molecular pathways improving pancreatic beta-cell dysfunction

The primary function of pancreatic beta-cells is to produce and release insulin in response to increment in extracellular glucose concentrations, thus maintaining glucose homeostasis. Deficient beta-cell function can have profound metabolic consequences, leading to the development of hyperglycemia and, ultimately, diabetes mellitus. Therefore, strategies targeting the maintenance of the normal function and protecting pancreatic beta-cells from injury or death might be crucial in the treatment of diabetes. This narrative review will update evidence from the recently identified molecular regulators preserving beta-cell mass and function recovery in order to suggest potential therapeutic targets against diabetes. This review will also highlight the relevance for novel molecular pathways potentially improving beta-cell dysfunction.

Lucigenin chemiluminescence in human seminal plasma

Seminal plasma protects spermatozoa from the detrimental effects of reactive oxygen species such as hydrogen peroxide. We investigated the lucigenin-dependent chemiluminescence in cell-free seminal plasma from andrological patients. The seminal plasma was separated from cells by centrifugation. In all seminal plasmas studied lucigenin-dependent chemiluminescence (LCL) was detected. The LCL showed a strong pH-dependence. The signal was stable if samples were stored at +4 degrees C for up to 4 days or up to 8 days at -80 degrees C. Filtration of the samples (0.45 and 0.22 microm pore size) did not lower their luminescence. The addition of superoxide dismutase (SOD) and ascorbic acid oxidase (AAO) lowered LCL nearly to baseline values while trolox and desferal showed moderate effect, whereas allopurinol had no effect. Electron paramagnetic resonance spectroscopy demonstrated ascorbyl radicals in seminal plasma. Physiological concentrations of ascorbic acid yielded SOD-inhibitable lucigenin-chemiluminescence. The nitroblue-tetrazolium assay showed that ascorbic acid in buffer solution produced formazan. Superoxide-anion radicals were not detected in seminal plasma by the spin-trap DEPMPO due to their low steady state concentration. It is concluded that in seminal plasma ascorbate reacts with molecular oxygen yielding ascorbyl radicals and superoxide anion. If lucigenin is added to seminal plasma, reducing substances present, such as ascorbate, reduce lucigenin to the corresponding radical; this radical reacts with molecular oxygen and also forms O2-. So LCL in human seminal plasma results from the autoxidation of ascorbate and the oxidation of the reduced lucigenin. While the physiological relevance of the former mechanism is unknown, the latter is an artifact.

Immunosuppression by human seminal plasma fractionated by DEAE Sephadex A-50 ion exchange chromatography

We fractionated the whole human seminal plasma on DEAE Sephadex A-50 ion exchange columns. Complete separation was achieved in seven peaks using different salt concentrations in phosphate buffer pH 6. The seminal plasma proteins were separated by sodium dodecyl-sulphate polyacrylamide gel electrophoresis. Human seminal plasma (SP) and its fractions were used in mixed lymphocyte reaction in vitro. Fractions 3, 4, and 7 were found to suppress the proliferation of human peripheral blood mononuclear cells to phytohemagglutinin and pokweed mitogen at a concentration of 10 micrograms ml-1 while stimulatory effect was observed at lower concentrations (1 microgram and 2.5 micrograms ml-1). Whole human SP and other fractions failed to suppress the proliferation of lymphocytes in vitro. Furthermore, the effect of human SP and its fractions was also investigated on phagocytic function of polymorphonuclear leukocytes (PMNs) using luminol dependent chemiluminescence assay stimulated with phorbol myristate acetate and opsonized yeast. Fractionated SP was found to have a suppressive effect on the luminol-dependent chemiluminescence of PMNs in the whole blood.