Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:1.6.3.1 (NADPH oxidase)
11,281 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Spermatozoa undergoing capacitation, a necessary prerequisite event to successful fertilization that can be induced in vitro by reactive oxygen species (ROS), generate superoxide anion (O2.-). Because, in neutrophils, the generation of O2.- is associated with tyrosine phosphorylation of several proteins, the aim of the present study was to investigate the association between protein-tyrosine phosphorylation and ROS-induced human sperm capacitation. Human spermatozoa express two major phosphotyrosine-containing proteins of 105 and 81 kDa, the phosphotyrosine content of which is increased when spermatozoa are incubated under capacitating conditions. Superoxide dismutase and catalase abolish both sperm capacitation and tyrosine phosphorylation of p105 and p81, suggesting the involvement of O2.- and hydrogen peroxide in these two processes. Inhibitors of NADPH oxidase, the enzyme responsible for the neutrophil's respiratory burst, decrease both p105 and p81 tyrosine phosphorylation and sperm capacitation while hydrogen peroxide stimulates these two processes. Tyrosine phosphorylation of p105 and p81 occurs through a herbimycin A-sensitive tyrosine kinase, and sperm incubation with phosphotyrosine-protein phosphatase inhibitors results in an increase in phosphotyrosine content of these two proteins. Indirect immunocytochemical studies reveal phosphotyrosine-containing proteins mostly in the principal piece of the flagellum, in agreement with the localization of p105 and p81 in the human sperm fibrous sheath. Although tyrosine phosphorylation of p105 and p81 and sperm capacitation are related in a time-dependent fashion, some discrepancies are observed in the regulation of these two processes according to the redox status of the spermatozoa.
...
PMID:Regulation of protein-tyrosine phosphorylation and human sperm capacitation by reactive oxygen derivatives. 901 27

The role of reactive oxygen species (ROS) in the pathophysiology of human sperm function has been emphasized in recent years. ROS production in semen has been associated with loss of sperm motility, decreased capacity for sperm-oocyte fusion and loss of fertility. There is a current presumption that the most prolific source of ROS in sperm suspensions is an NADPH oxidase located in leukocytes or in spermatozoa which produces superoxide which is further converted to peroxide by the action of superoxide dismutase. Hydrogen peroxide has been recognized as the most toxic oxidizing species for human spermatozoa, which are very sensitive to lipid peroxidation owing to the high content of polyunsaturated fatty acids in their plasma membrane, though this is not the sole mechanism by which sperm function might be impaired by ROS. Although the excessive production of ROS is detrimental to human spermatozoa, there is a growing body of evidence which suggests that ROS are also involved in the physiological control of some sperm functions. This review focuses on the nature and source of the ROS generated by human spermataozoa as well as their operational mechanisms and their effects, which may be detrimental or beneficial.
...
PMID:Reactive oxygen species and human spermatozoa: physiology and pathology. 929 15

Recent evidence indicated that human sperm capacitation is associated with an increased production of superoxide anion (O2.-). To further study the role and importance of O2.- in capacitation, we investigated whether the O2.- generation is a general feature of capacitating spermatozoa, irrespective of the inducer used, and is correlated with capacitation levels and increased tyrosine phosphorylation of two sperm proteins (p105/p81). We also studied the time courses of O2.- production and action. Percoll-washed human spermatozoa were incubated in Ham's F-10 medium, supplemented or not supplemented with various capacitation inducers and in the presence or absence of superoxide dismutase (SOD). Sperm capacitation was measured by induction of the acrosome reaction with lysophosphatidylcholine, O2.- production was measured by chemiluminescence, and tyrosine phosphorylation was measured by immunodetection after electrophoresis and western blotting of sperm proteins. Progesterone and ultrafiltrates of human fetal cord serum, follicular fluid, and seminal plasma individually promoted sperm generation of O2.-, tyrosine phosphorylation of p105/p81, and capacitation. Fetal cord serum ultrafiltrate triggered a fivefold higher O2.- production than the other inducers (1,700 +/- 300 and 300 to 400 mV/10s/8 x 10(6) cells, respectively), a phenomenon possibly associated with the higher potency of this fluid to promote sperm hyperactivation. The production of O2.- by spermatozoa was rapid and transient. SOD prevented sperm capacitation triggered by the inducers mentioned above, but only when SOD was added at the beginning of incubation, and not after 30 minutes, indicating that the O2.- initiates a chain of early events leading to sperm capacitation. NADH and NADPH (5 mM) triggered sperm capacitation and phosphorylation of p105/p81, but these processes were not prevented by SOD or catalase, nor were they associated with an increased O2.- production. Therefore, these cofactors appeared to act by mechanisms different from those used by the other inducers studied. The sperm enzyme responsible for the O2.- generation may be very different from the NADPH oxidase of neutrophils.
...
PMID:Human sperm capacitation induced by biological fluids and progesterone, but not by NADH or NADPH, is associated with the production of superoxide anion. 957 Jul 46

As spermatozoa pass through the epididymis they complete a maturation process that enables these cells to participate in the process of fertilization. Epididymal maturation involves a complex cascade of changes involving the remodelling of the sperm surface, the induction of chromatin condensation, the acquisition of movement, and development of the potential for capacitation. In this review we shall consider how changes in the redox status of mammalian spermatozoa may contribute to the completion of these maturation events. Spermatozoa from all regions of the epididymis exhibit a spontaneous capacity for superoxide anion production which can be enhanced by exposure to NADPH, particularly in the caput region. It is hypothesized that this spontaneous free radical generating activity is mediated by a membrane-bound NADPH oxidase, the function of which is to generate the peroxides that are needed to serve as hydrogen acceptors for phospholipid hydroperoxide glutathione peroxidase in the induction of sperm chromatin condensation. As spermatozoa enter the cauda epididymidis they also express a capacity for hydrogen peroxide (H2O2) generation when released into simple, defined culture media. The onset of this activity is thought to be associated with the induction of sperm capacitation through stimulation of the tyrosine phosphorylation events involved in the attainment of a capacitated state. It is concluded that sperm maturation is a dynamic, redox regulated process, any imbalance in which could lead to the production of spermatozoa that are compromised in terms of their potential for fertilization and the integrity of their DNA.
...
PMID:Maturation of redox regulatory mechanisms in the epididymis. 1064 71

It has been suggested that human spermatozoa contain an NADPH oxidase that could generate reactive oxygen species involved in signalling pathways to promote fertility. The proposal depends on observations that the addition of NADPH to purified human spermatozoa stimulates chemiluminescence by the superoxide (O2-) probe, lucigenin. We confirmed these observations, but demonstrated that lucigenin increases NADPH consumption by spermatozoa and stimulates artefactual O2- production via a diphenyleneiodonium (DPI) sensitive flavoprotein. In the absence of cytochrome c, DPI-inhibitable NADPH oxidation by permeabilized spermatozoa was 8 times too small to account for the rate of NADPH-stimulated cytochrome c reduction. Thus NADPH can directly reduce cytochrome c by a flavoprotein dependent mechanism making this O2- assay also unreliable in sperm suspensions. We were unable to observe O2- production by 40 x 10(6) spermatozoa/ml using electron paramagnetic resonance spectroscopy but could identify O(2)(-) generation from 2000 4beta-phorbol-12-myristate-13-actetate (PMA)-stimulated leukocytes. Using spectrophotometry, we did not detect the reduced cytochrome b(558) component of the neutrophil NADPH oxidase in human spermatozoa. No hydrogen peroxide generation was observed using a sensitive Amplex Red assay. We conclude that human spermatozoa do not possess significant NADPH oxidase activity and that the mechanism by which NADPH promotes capacitation must be re-evaluated.
...
PMID:A critical investigation of NADPH oxidase activity in human spermatozoa. 1122 43

Superoxide and its derivatives are increasingly implicated in the regulation of physiological functions from oxygen sensing and blood pressure regulation to lymphocyte activation and sperm-oocyte fusion. Here we describe a novel superoxide-generating NADPH oxidase referred to as NADPH oxidase 5 (NOX5). NOX5 is distantly related to the gp91(phox) subunit of the phagocyte NADPH oxidase with conserved regions crucial for the electron transport (NADPH, FAD and heme binding sites). However, NOX5 has a unique N-terminal extension that contains three EF hand motifs. The mRNA of NOX5 is expressed in pachytene spermatocytes of testis and in B- and T-lymphocyte-rich areas of spleen and lymph nodes. When heterologously expressed, NOX5 was quiescent in unstimulated cells. However, in response to elevations of the cytosolic Ca(2+) concentration it generated large amounts of superoxide. Upon Ca(2+) activation, NOX5 also displayed a second function: it became a proton channel, presumably to compensate charge and pH alterations due to electron export. In summary, we have identified a novel NADPH oxidase that generates superoxide and functions as a H(+) channel in a Ca(2+)-dependent manner. NOX5 is likely to be involved in Ca(2+)-activated, redox-dependent processes of spermatozoa and lymphocytes such as sperm-oocyte fusion, cell proliferation, and cytokine secretion.
...
PMID:A Ca(2+)-activated NADPH oxidase in testis, spleen, and lymph nodes. 1148 96

Mammalian spermatozoa must undergo a preparation period known as capacitation to become capable of fertilizing oocytes. Controlled amounts of reactive oxygen species (ROS), such as superoxide anion (O2.-) and hydrogen peroxide (H2O2) have been shown essential for capacitation and acrosome reaction. The presence of an oxidase in the sperm plasma membrane has been suggested. The objective of the present study was to provide evidence for the production of O2.- by capacitating cryopreserved bovine spermatozoa. Percentages of capacitation and acrosome reaction were determined by the chlortetracycline assay. The effect of several nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitors on capacitation was also studied. H2O2 production was determined by the fluorometric assay using the p-hydroxyphenylacetic acid-horseradish peroxidase system. Superoxide dismutase (SOD) activity was determined spectrophotometrically at 480 nm. Heparin-dependent capacitation was inhibited by all NADPH oxidase inhibitors tested (p < 0.05). Significant levels of H2O2 were produced during capacitation with heparin; such production was inhibited by diphenyleneiodonium, one of the NADPH oxidase inhibitors. The addition of catalase to the incubation medium failed to modify the capacitation rate; inhibition was only observed when SOD was present (p < 0.05). Endogenous SOD activity was diminished during heparin-dependent capacitation (p < 0.05). Similar levels of acrosome reaction induced by lysophosphatidylcholine were obtained in both heparin and O2.--dependent capacitation. Overall results suggest the participation of a sperm oxidase in bovine sperm capacitation. H2O2, generated by O2.- dismutation, failed to participate in capacitation, although this ROS may have been able to decrease endogenous SOD activity. Exogenous O2.- promotes physiological capacitation in cryopreserved bovine sperm, thus allowing the acquisition of fertilizing capacity.
...
PMID:Participation of superoxide anion in the capacitation of cryopreserved bovine sperm. 1264 29

Spermatozoa were the first cell type suggested to generate reactive oxygen species. However, a lack of standardization in sperm preparation techniques and the obfuscating impact of contaminating cell types in human ejaculates have made it difficult to confirm that mammalian germ cells do, in fact, make such reactive metabolites. By identifying, on a molecular level, those entities involved in reactive oxygen species generation and demonstrating their presence in spermatozoa, the role of redox chemistry in the control of sperm function can be elucidated. Two major proteins have apparently been identified in this context, namely, NOX5, a calcium-activated NADPH oxidase, and nitric oxide synthase. Understanding the involvement of these enzymes in sperm physiology is essential if we are to understand the causes of oxidative stress in the male germ line.
...
PMID:Biochemical entities involved in reactive oxygen species generation by human spermatozoa. 1276 52

Though the spermatozoa are known to produce superoxide anion radicals, the enzyme system(s) that produce superoxide in these cells are not yet identified. Using Western blot assays and confocal laser scan microscopy, we detected gp91(phox) and p67(phox) associated with spermatozoa from testis and epididymis. We could not detect p22(phox) in any of the sperm samples analyzed. While the expression of gp91(phox) p67(phox) appeared to be constitutive, p47(phox) was detectable only in spermatozoa from testis and vas deferens. Importantly, p40(phox) could be seen in very high quantities in testicular spermatozoa, which also showed the highest levels of NADPH-oxidase activity. Spermatozoa from cauda epididymidis and vas deferens also showed the presence of p40(phox), though the amount was low when compared with that of testicular spermatozoa. The absence of p22(phox) and the striking correlation between the presence of p40(phox) and the NADPH-oxidase activity suggest that the NADPH oxidase associated with spermatozoa is p22(phox)-independent and that its activity is positively modulated by p40(phox). Further, since the confocal imaging detected that the subunits of the NADPH oxidase are located significantly on the head domains, the spermatozoa appear to present a case with dominant non-mitochondrial superoxide anion producing capabilities.
...
PMID:Identification of non-mitochondrial NADPH oxidase and the spatio-temporal organization of its components in mouse spermatozoa. 1585 Jul 84

After capacitation, mammalian spermatozoa accomplish the acrosome reaction (AR), a well-controlled exocytosis process crucial to fertilize mature oocytes that involves several protein kinases such as protein kinase A (PKA), C (PKC), and tyrosine kinase (PTK). Reactive oxygen species (ROS) are involved in both bovine sperm capacitation and AR. Lactate dehydrogenase C4 (LDH-C4) was associated with bovine and mouse sperm capacitation. Our aims were to study the participation of LDH-C4 to contribute with the status redox required for AR and the role of ROS in the regulation of PKA, PKC, and PTK involved in the exocytotic event. Sodium oxamate, an inhibitor of LDH-C4, prevented the AR induced by lysophosphatidylcholine (LPC) or NADH. Hydrogen peroxide promoted and superoxide dismutase (scavenger of superoxide), catalase (scavenger of hydrogen peroxide), diphenyleneiodinum, diphenyliodonium, cibacron blue, and lapachol (inhibitors of NADPH oxidase) prevented the AR, suggesting that ROS and a sperm oxidase are involved in the AR induced by these compounds. Inhibitors of PKA, PKC, and PTK also prevented the AR induced by LPC or NADH, suggesting the involvement of these kinases in the process. These results suggest that LDH-C4 may participate in the regulation of the redox status required to achieve the AR in bovine spermatozoa and that ROS are key elements in the regulation of protein kinases associated with the AR process.
...
PMID:Acrosome reaction in bovine spermatozoa: role of reactive oxygen species and lactate dehydrogenase C4. 1611 12


1 2 3 Next >>

---