Reactive oxygen species (ROS) are known to play an important role in the regulation of human sperm function. In this study, we demonstrate for the first time that human spermatozoa possess interleukin-induced gene 1 (IL4I1), an l-amino acid oxidase (LAAO) which is capable of generating ROS on exposure to aromatic amino acids in the presence of oxygen. The preferred substrates were found to be phenylalanine and tryptophan while the enzyme was located in the acrosomal region and midpiece of these cells. In contrast to equine and bovine spermatozoa, enzyme activity was lost as soon as the spermatozoa became non-viable. On a cell-to-cell basis human spermatozoa were also shown to generate lower levels of hydrogen peroxide than their equine counterparts on exposure to phenylalanine. Stimulation of LAAO activity resulted in the induction of several hallmarks of capacitation including tyrosine phosphorylation of the sperm flagellum and concomitant activation of phospho-SRC expression. In addition, stimulation of LAAO resulted in an increase in the levels of acrosomal exocytosis in both the presence and absence of progesterone stimulation, via mechanisms that could be significantly reversed by the presence of catalase. As is often the case with free radical-mediated phenomena, prolonged exposure of human spermatozoa to phenylalanine resulted in the stimulation of apoptosis as indicated by significant increases in mitochondrial superoxide generation and the activation of intracellular caspases. These results confirm the existence of an LAAO in human spermatozoa with a potential role in driving the redox regulation of sperm capacitation and acrosomal exocytosis.
You are looking at 1 - 3 of 3 items for
- Author: B J Houston x
- Refine by Access: All content x
B Houston, B Curry, and R J Aitken
B J Houston, B Nixon, B V King, G N De Iuliis, and R J Aitken
Mobile phone usage has become an integral part of our lives. However, the effects of the radiofrequency electromagnetic radiation (RF-EMR) emitted by these devices on biological systems and specifically the reproductive systems are currently under active debate. A fundamental hindrance to the current debate is that there is no clear mechanism of how such non-ionising radiation influences biological systems. Therefore, we explored the documented impacts of RF-EMR on the male reproductive system and considered any common observations that could provide insights on a potential mechanism. Among a total of 27 studies investigating the effects of RF-EMR on the male reproductive system, negative consequences of exposure were reported in 21. Within these 21 studies, 11 of the 15 that investigated sperm motility reported significant declines, 7 of 7 that measured the production of reactive oxygen species (ROS) documented elevated levels and 4 of 5 studies that probed for DNA damage highlighted increased damage due to RF-EMR exposure. Associated with this, RF-EMR treatment reduced the antioxidant levels in 6 of 6 studies that discussed this phenomenon, whereas consequences of RF-EMR were successfully ameliorated with the supplementation of antioxidants in all 3 studies that carried out these experiments. In light of this, we envisage a two-step mechanism whereby RF-EMR is able to induce mitochondrial dysfunction leading to elevated ROS production. A continued focus on research, which aims to shed light on the biological effects of RF-EMR will allow us to test and assess this proposed mechanism in a variety of cell types.
C. S. Asa, E. W. Houston, M. T. Fischer, J. E. Bauman, K. L. Bauman, P. K. Hagberg, and B. W. Read
Changes in serum oestradiol and progesterone were measured to study their dynamics during ovulatory cycles in six female addax, an endangered antelope. Blood was collected three times per week, during chute restraint, for 3 months (November to February) before introduction of a male, and continued until pregnancy was diagnosed with ultrasound. Serum was analysed by enzymeimmunoassay. Mean luteal phase, interluteal phase, and cycle durations were 22.7 ± 2.0, 8.78 ± 0.5 and 32.3 ± 1.7 days, respectively. Ultrasonography revealed coiled uterine horns and maximum follicle and corpus luteum diameters of 15 and 27 mm, respectively. Each female experienced an anovulatory period, during which oestradiol continued to fluctuate, but progesterone remained below 2 ng ml−1. These periods ranged from 39 to 131 days and were not synchronous; ovulatory cycles resumed spontaneously in all females. All four females placed with a male conceived. Because addax give birth all year round, they are not considered seasonal breeders. The sporadic periods of anovulation that occurred during the winter months of this study suggest a possible seasonal effect. However, systematic sampling has not been conducted during summer and early autumn and will be necessary to address this question.