Lactate Regulates Rat Male Germ Cell Function through Reactive Oxygen Species (original) (raw)

Lactate inhibits germ cell apoptosis in the human testis

Molecular Human Reproduction, 2002

Dysregulation of male germ cell apoptosis has been associated with the pathogenesis of male infertility. Therefore, factors involved in the regulation of germ cell death are being actively investigated. Here, we studied the effects of lactate on human male germ cell death, using as a model a testis tissue culture in which physiological contacts are maintained between the germ cells and the supportive somatic Sertoli cells. Apoptosis of spermatocytes, spermatids and a few spermatogonia was induced by culturing segments of seminiferous tubules under serum-free conditions. This germ cell death was inhibited effectively and dose-dependently by lactate, indicating that it plays a crucial role in controlling cell death cascades of male germ cells. Interestingly, the anti-apoptotic role of lactate was not associated with changes in testicular adenine nucleotide (ATP, ADP and AMP) levels. In the seminiferous tubules, the final site of the death-suppressing action of lactate appeared to be downstream along the cell death pathway activated by the Fas receptor of the germ cells. In conclusion, testicular cell death was effectively regulated by lactate, which may be regarded as a potential compound for optimizing in-vitro methods involving male germ cells for assisted reproduction.

FSH stimulation of the production of pyruvate and lactate by rat Sertoli cells may be involved in hormonal regulation of spermatogenesis

Reproduction, 1983

Sertoli cells were obtained from 3\p=n-\6-week-oldrats, which were sterile after prenatal irradiation. The production of lactate by these Sertoli cells, measured 24\p=n-\48h after isolation during incubation in the absence of hormones, increased with age of the rats from 3 to 6 weeks. At all ages investigated, the production of lactate was enhanced in the presence of FSH plus testosterone, but the stimulation was most pronounced at 4 weeks of age. Lactate production was increased by FSH alone but testosterone had no effect in the presence or absence of FSH. Sertoli cells from 4-week-old rats produced both pyruvate and lactate, which accumulated in the incubation medium in a ratio of 1:4. The stimulation of the production of pyruvate and lactate by FSH was dose\x=req-\ dependent (ED50 at~10 ng NIH-FSH-S13/ml). The production of pyruvate and lactate was stimulated 2-fold by insulin, 4-fold by FSH and > 6-fold by dibutyryl cyclic AMP (in the presence of 3-isobutyl-1-methylxanthine). The effects of FSH (0\m=.\5\ g=m\ g NIH-FSH-S13/ml) and insulin (5 \g=m\g/ml) were not additive. Leucine incorporation into isolated pachytene spermatocytes and round spermatids was stimulated by exogenous pyruvate and lactate in a dose-dependent way : maximal incorporation was obtained with 0\m=.\2 mM-pyruvate or 2 mM L-lactate. Spent medium from incubated Sertoli cells (from 4-week-old rats) stimulated the leucine incorporation into isolated pachytene spermatocytes and round spermatids 4\p=n-\8-fold.This effect could be explained by the amounts of pyruvate and lactate present in the spent medium. It is suggested that pyruvate and lactate are major products from Sertoli cells which can support synthetic activities in germ cells, and the present results indicate that pyruvate and lactate may play a role in the hormonal regulation of spermatogenesis.

Biochemical entities involved in reactive oxygen species generation by human spermatozoa

Protoplasma, 2003

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.

Metabolic regulation is important for spermatogenesis

Nature reviews. Urology, 2012

Male factor infertility is increasing in developed countries, and several factors linked to lifestyle have been shown to negatively affect spermatogenesis. Sertoli cells are pivotal to spermatogenesis, providing nutritional support to germ cells throughout their development. Sertoli cells display atypical features in their cellular metabolism; they can metabolize various substrates, preferentially glucose, the majority of which is converted to lactate and not oxidized via the tricarboxylic acid cycle. Why Sertoli cells preferentially export lactate for germ cells is not entirely understood. However, lactate is utilized as the main energy substrate by developing germ cells and has an antiapoptotic effect on these cells. Several biochemical mechanisms contribute to the modulation of lactate secretion by Sertoli cells. These include the transport of glucose through the plasma membrane, mediated by glucose transporters; the interconversion of pyruvate to lactate by lactate dehydrogenase...

NOX5 in Human Spermatozoa

Journal of Biological Chemistry, 2012

Background: The identity of the reactive oxygen species (ROS)-producing enzyme(s) in human spermatozoa remains uncertain. Results: NOX5 NADPH oxidase, but not NOX1/2/4, is expressed in human spermatozoa and produces superoxide. Inhibition of NOX5 activity reduces spermatozoa motility. Conclusion: NOX5 is the main source of superoxide and is implicated in human spermatozoa motility. Significance: NOX5 might control the numerous ROS-dependent (patho)physiological processes in human spermatozoa. Physiological and pathological processes in spermatozoa involve the production of reactive oxygen species (ROS), but the identity of the ROS-producing enzyme system(s) remains a matter of speculation. We provide the first evidence that NOX5 NADPH oxidase is expressed and functions in human spermatozoa. Immunofluorescence microscopy detected NOX5 protein in both the flagella/neck region and the acrosome. Functionally, spermatozoa exposed to calcium ionophore, phorbol ester, or H 2 O 2 exhibited superoxide anion production, which was blocked by addition of superoxide dismutase, a Ca 2؉ chelator, or inhibitors of either flavoprotein oxidases (diphenylene iododonium) or NOX enzymes (GKT136901). Consistent with our previous overexpression studies, we found that H 2 O 2induced superoxide production by primary sperm cells was mediated by the non-receptor tyrosine kinase c-Abl. Moreover, the H V 1 proton channel, which was recently implicated in spermatozoa motility, was required for optimal superoxide production by spermatozoa. Immunoprecipitation experiments suggested an interaction among NOX5, c-Abl, and H V 1. H 2 O 2 treatment increased the proportion of motile sperm in a NOX5-dependent manner. Statistical analyses showed a pH-dependent correlation between superoxide production and enhanced sperm motility. Collectively, our findings show that NOX5 is a major source of ROS in human spermatozoa and indicate a role for NOX5-dependent ROS generation in human spermatozoa motility.

NOX5 in Human Spermatozoa EXPRESSION, FUNCTION, AND REGULATION

2012

Alteration of lactate production and transport in the adult rat testis exposed in utero to flutamide

Molecular and Cellular Endocrinology, 2003

Although it is established that in utero exposure to the antiandrogen flutamide induces alteration of spermatogenesis in the adult rat testis offspring, the cellular and molecular mechanisms involved in such an effect remain to be investigated. In the present paper, by using as model adult rats exposed in utero to flutamide (0, 2, 10 mg/kg per day), we have investigated the hypothesis that germ cell alterations could be related to defects of energy metabolism and particularly to defects of the production and transport of lactate. Lactate is a preferential energy substrate produced by Sertoli cells and transported to germ cells by monocarboxylate transporters (MCT). A significant decrease (60%, P B/0.001) in lactate production was observed in cultured Sertoli cells from rat testes exposed in utero to flutamide from the dose of 2 mg/kg per day. Such a decrease is concurrent to a decrease in lactate dehydrogenase A (LDHA) mRNA levels (evaluated through semiquantitative RT-PCR) and LDHA4 activity. The decrease in LDHA mRNA levels (to 649/9% of the control, P B/0.05) was observed with the lowest dose (2 mg/kg per day) of flutamide tested. The decrease in LDHA mRNA levels was observed in both the whole testis and in isolated Sertoli cells, suggesting that such a decrease in LDHA expression occurred also in the (Sertoli) cells producing lactate. Lactate is transported from Sertoli cells to germ cells via MCT1 and MCT2. We immunolocalized MCT1 to all the different germ cell types and MCT2 exclusively to elongated spermatids. In the adult testis exposed in utero to flutamide, MCT1 (539/8%, P B/0.02) and MCT2 (529/9%, P B/0.02) mRNA levels were significantly reduced indicating that lactate transport to germ cells could be also altered. Together, these data support (i) the existence of a relationship between the antiandrogen activity and the energy metabolism in the testis and (ii) the concept of an androgen-dependent programming, occurring early in the fetal life in relation to the expression of some of the key genes involved in the production and transport of lactate in the seminiferous tubules. #

Analysis of Reactive Oxygen Species Generating Systems in Rat Epididymal Spermatozoa

Biology of Reproduction, 2001

Epididymal sperm maturation culminates in the acquisition of functional competence by testicular spermatozoa. The expression of this functional state is dependent upon a redox-regulated, cAMP-mediated signal transduction cascade that controls the tyrosine phosphorylation status of the spermatozoa during capacitation. Analysis of superoxide anion (O 2 Ϫ· ) generation by rat epididymal spermatozoa has revealed a two-component process involving electron leakage from the sperm mitochondria at complexes I and II and a plasma membrane NAD(P)H oxidoreductase. Following incubation in a glucose-, lactate-, and pyruvate-free medium (ϪGLP), O 2 Ϫ· generation was suppressed by 86% and 96% in caput and cauda spermatozoa, respectively. The addition of lactate, malate, or succinate to spermatozoa incubated in medium ϪGLP stimulated O 2 Ϫ· gen-

Role of Reactive Oxygen Species in Male Reproduction

Novel Prospects in Oxidative and Nitrosative Stress

The production of reactive oxygen species (ROS) is a normal physiological event in the male germ line. ROS are a double-edged sword, despite its role as key signaling molecules in physiological processes such as capacitation and hyperactivation, its overproduction which overwhelms the body's antioxidant defenses is thought to affect male fertility and normal embryonic development. The excess generation of ROS in semen by exogenous and endogenous factors has been recognized as detrimental etiologies for male infertilities. Spermatozoa are vulnerable to ROS attack because they are rich in mitochondria, have abundance of substrates for free radical attack and their capacity to protect themselves from oxidative stress is limited. The cytotoxic aldehydes generated as a result of lipid peroxidation are known to form adduct with the mitochondrial protein involved in electron transport chain and stimulate generation of ROS in mitochondria. ROS and their metabolites can lead to oxidative DNA damage in mitochondria and nucleus that eventually culminates in DNA fragmentation. The presence for large amount of damaged DNA is a major characteristic of defective human spermatozoa, which affect the fertility and pregnancy outcome. Thus, as a comprehensive approach, treatment of oxidative stress should involve strategies to reduce stress-provoking conditions to help reverse sperm dysfunction.

Regulation of survival of rat pachytene spermatocytes by lactate supply from Sertoli cells

Journal of reproduction and fertility, 1982

During incubation of fragments of seminiferous tubules in the absence of glucose, pachytene spermatocytes and round spermatids died within 24 h, while Sertoli cells were still viable. The germ cells survived for at least 72 h in seminiferous tubule fragments which were incubated in the presence of glucose. Lactate rather than glucose is essential for [3H]uridine incorporation and survival of isolated pachytene spermatocytes. However, if the spermatocytes were incubated in the presence of Sertoli cells, glucose maintained the incorporation of [3H]uridine into the germ cells. Sertoli cells secreted lactate in the presence of glucose and the lactate secretion was stimulated 2--4-fold by FSH. It is concluded that the activity and survival of pachytene spermatocytes in vitro can be regulated by the supply of lactate from Sertoli cells.

Lactate Regulates Rat Male Germ Cell Function through Reactive Oxygen Species (original) (raw)

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