Low Doses of Glyphosate/Roundup Alter Blood-Testis Barrier Integrity in Juvenile Rats.

It has been postulated that glyphosate (G) or its commercial formulation Roundup (R) might lead to male fertility impairment. In this study, we investigated the possible effects of G or R treatment of juvenile male rats on blood-testis barrier function and on adult male sperm production. Pups were randomly assigned to the following groups: control group (C), receiving water; G2 and G50 groups, receiving 2 and 50 mg/kg/day G respectively; and R2 and R50 groups receiving 2 and 50 mg/kg/day R respectively. Treatments were performed orally from postnatal day (PND) 14 to 30, period of life that is essential to complete a functional blood-testis barrier. Evaluation was done on PND 31. No differences in body and testis weight were observed between groups. Testis histological analysis showed disorganized seminiferous epithelium, with apparent low cellular adhesion in treated animals. Blood-testis barrier permeability to a biotin tracer was examined. A significant increase in permeable tubules was observed in treated groups. To evaluate possible mechanisms that could explain the effects on blood-testis barrier permeability, intratesticular testosterone levels, androgen receptor expression, thiobarbituric acid reactive substances (TBARS) and the expression of intercellular junction proteins (claudin11, occludin, ZO-1, connexin43, 46, and 50 which are components of the blood-testis barrier) were examined. No modifications in the above-mentioned parameters were detected. To evaluate whether juvenile exposure to G and R could have consequences during adulthood, a set of animals of the R50 group was allowed to grow up until PND 90. Histological analysis showed that control and R50 groups had normal cellular associations and complete spermatogenesis. Also, blood-testis barrier function was recovered and testicular weight, daily sperm production, and epididymal sperm motility and morphology did not seem to be modified by juvenile treatment. In conclusion, the results presented herein show that continuous exposure to low doses of G or R alters blood-testis barrier permeability in juvenile rats. However, considering that adult animals treated during the juvenile stage showed no differences in daily sperm production compared with control animals, it is feasible to think that blood-testis barrier impairment is a reversible phenomenon. More studies are needed to determine possible damage in the reproductive function of human juvenile populations exposed to low doses of G or R.

Postnatal metformin treatment alters rat Sertoli cell proliferation and daily sperm production.

BACKGROUND: The direct correlation between Sertoli cell number and sperm production capacity highlights the importance of deciphering external factors that modify Sertoli cell proliferation. A growing body of evidence in vitro suggests that metformin, the main pharmacological agent for type 2 diabetes treatment in children, exerts anti-proliferative effects on Sertoli cells. OBJECTIVE: The aims of this study were to investigate the effect of metformin administration during postnatal period on Sertoli cell proliferation and on cell cycle regulators expression and to analyze the impact of this treatment on the sperm production capacity in adulthood. MATERIALS AND METHODS: Sprague Dawley rat pups were randomly divided into two groups: MET (receiving daily 200 mg/kg metformin, from Pnd3 to Pnd7 inclusive) and control (receiving vehicle). BrdU incorporation was measured to assess proliferation. Gene expression analyses were performed in Sertoli cells isolated from animals of both groups. Daily sperm production and sperm parameters were measured in adult male rats (Pnd90) that received neonatal treatment. RESULTS: MET group exhibited a significant decrease in BrdU incorporation in Sertoli cells. Concordantly, MET group showed a reduction in cyclin D1 and E2 expression and an increase in p21 expression in Sertoli cells. In addition, metformin-treated animals displayed lower values of daily sperm production on Pnd90. DISCUSSION AND CONCLUSION: These results suggest that metformin treatment may lead to a decrease in Sertoli cell proliferation, a concomitant altered expression of cell cycle regulators and ultimately, a reduction in daily sperm production in adult animals.

In vitro effects of glyphosate and Roundup on Sertoli cell physiology.

Roundup (R), a formulation that contains glyphosate (G) as the active ingredient, is a commonly used nonselective herbicide that has been proposed to affect male fertility. It is well known that an adequate Sertoli cell function is essential to maintain germ cell development. The aim of the present study was to analyze whether G and R are able to affect Sertoli cell functions, such as energy metabolism and blood-testis barrier (BTB) integrity. Sertoli cell cultures from 20-day-old rats were exposed to 10 and 100 ppm of G or R, doses which do not decrease cell viability. Neither G nor R caused impairment in lactate production or fatty acid oxidation. G and R decreased Transepithelial Electrical Resistance, which indicates the establishment of a Sertoli cell junction barrier. However, neither G nor R modified the expression of claudin11, ZO1 and occludin, proteins that constitute the BTB. Analysis of cellular distribution of claudin11 by immunofluorescence showed that G and R induced a delocalization of the signal from membrane to the cytoplasm. The results suggest that G and R could alter an important function of Sertoli cell such as BTB integrity and thus they could compromise the normal development of spermatogenesis.

Apoptotic germ cells regulate Sertoli cell lipid storage and fatty acid oxidation.

The presence of lipid droplets (LD) and the utilization of fatty acids (FA) as a source of energy are Sertoli cell (SC) putative characteristics. It is well known that SCs can phagocyte and degrade apoptotic germ cells (AGC) resulting in increasing lipid content and ATP levels. A relationship between the regulation of lipid storage and of lipid oxidation in SC might be envisaged. The aim of this study was to analyze whether AGC and FA are able to simultaneously regulate molecular mechanisms involved in lipid storage and in FA oxidation in SC. The experimental model utilized in this study consisted in SC cultures obtained from 20-day-old rats that were co-cultured with AGC or treated with palmitic acid (PA, 500 µM) for 24 and 48 h. AGC and PA increase LD, triacylglycerol (TAG) content and mRNA levels of Plin1, Plin2, Plin3 (proteins involved in TAG storage). Simultaneously, AGC and PA rise the extent of FA oxidation and mRNA levels of Cpt1 and Lcad (proteins involved in FA degradation). Results also show that peroxisome proliferator-activated receptor (PPAR) transcriptional activity, transcription factor which participate in lipid metabolism regulation, increases by AGC and PA treatment in SC. Additionally, the presence of a PPARg antagonist decreases the upregulation of LD content and Plin1 expression. Similarly, the presence of a PPARb/d antagonist reduces the increase in FA oxidation and Cpt1 mRNA levels. Altogether these results suggest that AGC and FA, which probably generate PPAR ligands, regulate lipid storage and fatty acid utilization, contributing to the energy homeostasis in the seminiferous tubules.

HIF involvement in the regulation of rat Sertoli cell proliferation by FSH.

The final number of Sertoli cells reached during the proliferative periods determines sperm production capacity in adulthood. It is well known that FSH increases the rate of proliferation of Sertoli cells; however, little is known about the transcription factors that are activated by the hormone in order to regulate Sertoli cell proliferation. On the other hand, Hypoxia Inducible Factors (HIFs) are master regulators of cell growth. HIFs are dimers of HIF-ß and HIF-α subunits. Considering that HIF-ß is constitutively expressed, HIF transcriptional activity is regulated through the abundance of HIF-α subunits. To date, three HIF-α isoforms have been described. The association of the different HIF-α subunits with HIF-ß subunit constitutes three active transcription factors -HIF-1, HIF-2 and HIF-3- which interact with consensus hypoxia-response elements in the promoter region of target genes. Hypoxia has been classically considered the main stimulus that increases HIF transcriptional activity, however, regulation by hormones under normoxic conditions was also demonstrated. The aim of this work has been to investigate whether HIFs participate in the regulation of rat Sertoli cell proliferation by FSH. Sertoli cells obtained from 8-day old rats were cultured in the absence or presence of FSH. It has been observed that FSH increases HIF transcriptional activity and HIF-2α mRNA levels without modifying either HIF-1α or HIF-3α expression. Incubations with FSH have been also performed in the absence or presence of a pharmacological agent that promotes HIF-α subunit degradation, LW6. It has been observed that LW6 inhibits the FSH effect on proliferation, CCND1 expression and c-Myc transcriptional activity. Altogether, these results suggest that HIFs might be involved in the regulation of Sertoli cell proliferation by FSH.

Metformin counteracts the effects of FSH on rat Sertoli cell proliferation.

Metformin (MET) is one of the most widely used anti-hyperglycemic agents for treating patients with type 2 diabetes and it has started to be used in pediatric population at ages when Sertoli cells are still proliferating. It is well known that follicle-stimulating hormone (FSH) is the major Sertoli cell mitogen. The aim of the study is to investigate a possible effect of MET, which has been shown to have anti-proliferative properties, on FSH regulation of postnatal Sertoli cell proliferation and on the molecular mechanisms involved in this regulation. The present study was performed in eight-day-old rat Sertoli cell cultures. The results obtained show that MET in the presence of FSH increases phosphorylated acetyl-CoA carboxylase and decreases phosphorylated p70S6K levels. Moreover, we show that MET decreases FSH-stimulated Sertoli cell proliferation, and this decrease is accompanied by a reduction in FSH-stimulated Ccnd1 and Ccnd2 expression and an increase in cell cycle inhibitor p21Cip expression. Altogether, these results suggest that MET can, at least in part, counteract the effect of FSH on postnatal Sertoli cell proliferation.

Germ cells regulate 3-hydroxybutyrate production in rat Sertoli cells.

Paracrine regulation of Sertoli cell function by germ cells is an outstanding characteristic of testicular physiology. It has been demonstrated that Sertoli cells produce ketone bodies and that germ cells may use them as energy source. The aim of the study was to analyze a possible regulation by germ cells of ketogenesis in Sertoli cells. Cultures of Sertoli cells (SC) obtained from 31-day-old rats were co-cultured with germ cells (GC). The results presented herein show that the presence of GC stimulated 3-hydroxybutyrate production and increased mRNA levels of two enzymes involved in ketogenesis-carnitine palmitoyltransferase 1a (CPT1a) and mitochondrial 3-hydroxy-3-methylglutaryl-CoA (mHMGCoA) synthase- in SC. Additionally, GC increased monocarboxylate transporter 4 (Mct4) expression in SC, a transporter involved in ketone bodies exit. To evaluate if the observed effects might be mediated by soluble factors, SC cultures were incubated with germinal cell-conditioned medium (GCCM) or with two growth factors, bFGF and IGF1, which are known to be secreted by GC. We observed that GCCM and bFGF stimulated ketone bodies production but that IGF1 did not modify it. Also, we observed that GCCM and bFGF increased Cpt1a and Mct4 mRNA levels. In summary, results presented herein demonstrate that Sertoli cells are able to produce ketone bodies and that its production is regulated in a paracrine way by germ cells. This study adds new information about communication between Sertoli cells and developing germ cells.

Participation of HIFs in the regulation of Sertoli cell lactate production.

Hypoxia Inducible Factors (HIFs) are master regulators of glycolytic metabolism. HIFs consist of a constitutive HIFbeta (HIFß) subunit and a HIFalpha (HIFα) subunit, whose half-life depends on prolyl-hydroxylases activity. Inhibition of prolyl-hydroxylases by hypoxia or transition metals, or augmentation of HIFα subunit levels by hormonal stimuli lead to a higher HIF transcriptional activity. On the other hand, it is well known that lactate produced by Sertoli cells is delivered to and used by germ cells as an energy substrate. The aim of this work was to investigate whether HIFs participate in the regulation of lactate production in rat Sertoli cells and whether they are involved in the FSH mechanism of action. In order to reach a higher HIF transcriptional activity, Sertoli cells were treated with CoCl2. We observed that a higher HIF transcriptional activity leads to an augmentation of: lactate production, glucose uptake and LDH activity. Besides, an increase in Glut1, Pkm2 and Ldha mRNA levels was observed. These findings suggested that HIFs may participate in the modulation of Sertoli cell nutritional function. As FSH regulates lactate production, we evaluated whether HIFs were involved in FSH action. Sertoli cells were stimulated with FSH in the absence or presence of LW6, a drug which promotes HIFα subunit degradation. On the one hand, we observed that FSH increases HIF1α protein, Hif1α and Hif2α mRNA levels and, on the other hand, that LW6 inhibits FSH-stimulated lactate production, glucose uptake, Glut1, Pkm2 and Ldha expression. It is proposed that HIFs are key components of the intricate pathways utilized by FSH to regulate the provision of lactate for germ cells. Considering that FSH is the master endocrine regulator of Sertoli cells, it is not surprising that this hormone may employ several regulatory mechanisms to fulfill the nourishing functions of this cell type.

FSH and bFGF regulate the expression of genes involved in Sertoli cell energetic metabolism.

The purpose of this study was to investigate if FSH and bFGF regulate fatty acid (FA) metabolism and mitochondrial biogenesis in Sertoli cells (SC). SC cultures obtained from 20-day-old rats were incubated with 100ng/ml FSH or 30ng/ml bFGF for 6, 12, 24 and 48h. The expression of genes involved in transport and metabolism of FA such as: fatty acid transporter CD36 (FAT/CD36), carnitine-palmitoyltransferase 1 (CPT1), long- and medium-chain 3-hydroxyacyl-CoA dehydrogenases (LCAD, MCAD), and of genes involved in mitochondrial biogenesis such as: nuclear respiratory factors 1 and 2 (NRF1, NRF2) and transcription factor A (Tfam), was analyzed. FSH stimulated FAT/CD36, CPT1, MCAD, NRF1, NRF2 and Tfam mRNA levels while bFGF only stimulated CPT1 expression. A possible participation of PPARß/δ activation in the regulation of gene expression and lactate production was then evaluated. SC cultures were incubated with FSH or bFGF in the presence of the PPARß/δ antagonist GSK3787 (GSK; 20µM). bFGF stimulation of CPT1 expression and lactate production were inhibited by GSK. On the other hand, FSH effects were not inhibited by GSK indicating that FSH regulates the expression of genes involved in FA transport and metabolism and in mitochondrial biogenesis, independently of PPARß/δ activation. FA oxidation and mitochondrial biogenesis as well as lactate production are essential for the energetic metabolism of the seminiferous tubule. The fact that these processes are regulated by hormones in a different way reflects the multifarious regulation of molecular mechanisms involved in Sertoli cell function.

Novel molecular mechanisms involved in hormonal regulation of lactate production in Sertoli cells.

The aim of the study was to analyze molecular mechanisms involved in FSH and basic fibroblast growth factor (bFGF) regulation of lactate production in rat Sertoli cells. The regulation of the availability of pyruvate, which is converted to lactate, could be a mechanism utilized by hormones to ensure lactate supply to germ cells. On one hand, the regulation of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase (PFKFB) expression could result in increased glycolysis, while an increase in pyruvate availability may also result from a lower conversion to acetyl-CoA by negative regulation of pyruvate dehydrogenase complex (PDC) activity by phosphorylation. Sertoli cell cultures obtained from 20-day-old rats were used. Stimulation of the cultures with FSH or bFGF showed that FSH increases Pfkfb1 and Pfkfb3 expression while bFGF increases Pfkfb1 mRNA levels. Additionally, we observed that FSH-stimulated lactate production was inhibited in the presence of a PFKFB3 inhibitor, revealing the physiological relevance of this mechanism. As for the regulation of PDC, analysis of pyruvate dehydrogenase kinase (Pdk) expression showed that FSH increases Pdk3 and decreases Pdk4 mRNA levels while bFGF increases the expression of all Pdks. In addition, we showed that bFGF increases phosphorylated PDC levels and that bFGF-stimulated lactate production is partially inhibited in the presence of a PDK inhibitor. Altogether, these results add new information regarding novel molecular mechanisms involved in hormonal regulation of lactate production in Sertoli cells. Considering that lactate is essential for the production of energy in spermatocytes and spermatids, these mechanisms might be relevant in maintaining spermatogenesis and male fertility.

IL17A impairs blood-testis barrier integrity and induces testicular inflammation.

Experimental autoimmune orchitis is a useful model for studying testicular inflammation and germ/immune cell interactions. Th17 cells and their hallmark cytokine IL17A were reported to be involved in the development of autoimmune orchitis. The aim of the present work is to investigate the pathogenic role of IL17A in rat testis. In vitro experiments were performed in order to analyze effects of IL17A on Sertoli cell tight junctions. The addition of IL17A to normal rat Sertoli cell cultures induced a significant decline in transepithelial electrical resistance and a reduction of occludin expression and redistribution of occludin and claudin 11, altering the Sertoli cell tight junction barrier. Intratesticular injection of 1 µg of recombinant rat IL17A to Sprague-Dawley rats induced increased blood-testis barrier permeability, as shown by the presence of biotin tracer in the seminiferous tubule adluminal compartment, and delocalization of occludin and claudin 11. Results showed that IL17A induced focal inflammatory cell infiltration in the interstitium and germ cell sloughing in adjacent seminiferous tubules. Moreover, an increase in TUNEL+ apoptotic germ cells was also observed. Inflammatory ED1+ macrophages were the main population infiltrating the interstitium following IL17A injection. This correlated with an increase in mRNA expression of the monocyte chemoattractant protein Ccl2, its receptor Ccr2 and the vascular cell adhesion molecule Vcam1. Overall results suggest a relevant role of IL17A in the development of testicular inflammation, facilitating the recruitment of immune cells to the testicular interstitium and inducing impairment of blood-testis barrier function.

Lactate regulates rat male germ cell function through reactive oxygen species.

Besides giving structural support, Sertoli cells regulate the fate of germ cells by supplying a variety of factors. These factors include hormones, several pro- and anti-apoptotic agents and also energetic substrates. Lactate is one of the compounds produced by Sertoli cells, which is utilized as an energetic substrate by germ cells, particularly spermatocytes and spermatids. Beyond its function as an energy source, some studies have proposed a role of lactate in the regulation of gene expression not strictly related to the energetic state of the cells. The general hypothesis that motivated this investigation was that lactate affects male germ cell function, far beyond its well-known role as energetic substrate. To evaluate this hypothesis we investigated: 1) if lactate was able to regulate germ cell gene expression and if reactive oxygen species (ROS) participated in this regulation, 2) if different signal transduction pathways were modified by the production of ROS in response to lactate and 3) possible mechanisms that may be involved in lactate stimulation of ROS production. In order to achieve these goals, cultures of germ cells obtained from male 30-day old rats were exposed to 10 or 20 mM lactate. Increases in lactate dehydrogenase (LDH) C and monocarboxylate transporter (MCT)2 expression, in Akt and p38-MAPK phosphorylation levels and in ROS production were observed. These effects were impaired in the presence of a ROS scavenger. Lactate stimulated ROS production was also inhibited by a LDH inhibitor or a NAD(P)H oxidase (NOX) inhibitor. NOX4 expression was identified in male germ cells. The results obtained herein are consistent with a scenario where lactate, taken up by germ cells, becomes oxidized to pyruvate with the resultant increase in NADH, which is a substrate for NOX4. ROS, products of NOX4 activity, may act as second messengers regulating signal transduction pathways and gene expression.

Loss of occludin expression and impairment of blood-testis barrier permeability in rats with autoimmune orchitis: effect of interleukin 6 on Sertoli cell tight junctions.

Inflammation of the male reproductive tract is accepted as being an important etiological factor of infertility. Experimental autoimmune orchitis (EAO) is characterized by interstitial lymphomononuclear cell infiltration and severe damage of seminiferous tubules with germ cells that undergo apoptosis and sloughing. Because the blood-testis barrier (BTB) is relevant for the protection of haploid germ cells against immune attack, the aim of this study was to analyze BTB permeability and the expression of tight junction proteins (occludin, claudin 11, and tight junction protein 1 [TJP1]) in rats during development of autoimmune orchitis. The role of IL6 as modulator of tight junction dynamics was also evaluated because intratesticular content of this cytokine is increased in EAO rats. Orchitis was induced in Sprague-Dawley adult rats by active immunization with testicular homogenate and adjuvants. Control rats (C) were injected with saline solution and adjuvants. Untreated (N) rats were also studied. Concomitant with early signs of germ cell sloughing, a reduced expression of occludin and delocalization of claudin 11 and TJP1 were detected in the testes of rats with EAO compared to C and N groups. The use of tracers showed increased BTB permeability in EAO rats. Intratesticular injection of IL6 induced focal testicular inflammation, which is associated with damaged seminiferous tubules. Rat Sertoli cells cultured in the presence of IL6 exhibited a redistribution of tight junction proteins and reduced transepithelial electrical resistance. These data indicate the possibility that IL6 might be involved in the downregulation of occludin expression and in the modulation of BTB permeability that occur in rats undergoing autoimmune orchitis.

Exploring the cyclooxygenase 2 (COX2)/15d-Δ(12,14)PGJ(2) system in hamster Sertoli cells: regulation by FSH/testosterone and relevance to glucose uptake.

We have previously described a stimulatory effect of testosterone on cyclooxygenase 2 (COX2) expression and prostaglandin (PG) synthesis, and the involvement of PGs in the modulation of testosterone production in Leydig cells of the seasonal breeder Syrian hamster. In this study, we investigated the existence of a COX2/PGs system in hamster Sertoli cells, its regulation by testosterone and FSH, and its effect on glucose uptake. COX2 expression was observed in Sertoli cells of both reproductively active and inactive adult hamsters. Testosterone and the plasma membrane-impermeable testosterone-BSA significantly induced COX2 expression, mitogen activated protein kinases 1/2 (MAPK1/2) phosphorylation and 15d-Δ(12,14)PGJ(2) production in Sertoli cells purified from photoperiodically regressed hamsters. These actions were abolished by the antiandrogen bicalutamide and by the inhibitor of MAPK kinase (MEK1/2) U0126, suggesting that testosterone exerts its stimulatory effect on COX2/PGs through a non-classical mechanism that involves the presence of androgen receptors and MAPK1/2 activation. FSH also stimulated COX2/PGs via MAPK1/2 phosphorylation. FSH and testosterone stimulate, whereas 15d-Δ(12,14)PGJ(2) via PPARγ inhibits, [2,6-(3)H]-2-deoxy-d-glucose ([(3)H]-2-DOG) uptake. Meloxicam, a selective COX2 inhibitor, further increases [(3)H]-2-DOG uptake in the presence of FSH or testosterone. Thus, in addition to their positive effect, FSH and testosterone may also exert an indirect negative regulation on glucose uptake which involves the COX2/15d-Δ(12,14)PGJ(2)/PPARγ system. Overall, these results demonstrate the presence of a COX2/PG system in hamster Sertoli cells which might act as a local modulator of FSH and testosterone actions.

Regulation of expression of Sertoli cell glucose transporters 1 and 3 by FSH, IL1 beta, and bFGF at two different time-points in pubertal development.

Sertoli cells are necessary to provide adequate levels of lactate for germ cell development. Lactate production is hormonally regulated by follicle-stimulating hormone (FSH) and by a large set of intratesticular regulators such as interleukin-1 beta (IL1 beta) and basic fibroblast growth factor (bFGF). Little is known regarding the critical step in the production of this metabolite, viz., the entrance of glucose into the cell as mediated by GLUTs. The aim of the present study was to investigate the expression of the glucose transporters GLUT1 and GLUT3 and its possible regulation by FSH, IL1 beta, and bFGF in Sertoli cells at two different time-points in sexual development. Sertoli cells retaining the ability to undergo mitosis (obtained from 8-day-old rats) and in the process of terminal differentiation (obtained from 20-day-old rats) were examined. Testicular tissue sections and Sertoli cell monolayers obtained from 8- and 20-day-old rats showed positive immunostaining for GLUT1 and GLUT3 proteins. GLUT1 and GLUT3 mRNA levels were detected at the two ages analyzed. Treatment of Sertoli cells obtained from 8- and 20-day-old rats with FSH, IL1 beta, and bFGF for various periods of time (12, 24, and 48 h) increased GLUT1 without changing GLUT3 mRNA levels. Our results thus show that Sertoli cells express GLUT1 and GLUT3 throughout pubertal development, and that, in Sertoli cells, only GLUT1 is regulated by hormones during pubertal development. Hormonal regulation of GLUT1 expression and consequently glucose uptake and lactate production may be a key molecular event in the regulation of spermatogenesis by hormones.

Possible autocrine enkephalin regulation of catecholamine release in human pheochromocytoma cells.

AIMS: Pheochromocytomas are catecholamine-secreting tumors that also synthesize and secrete several neuropeptides, including opioids. A negative regulation of catecholamine secretion by opioids has been postulated in chromaffin cells. However, results obtained so far are contradictory when referred to human pheochromocytomas. The aim of this study was to define the role of locally produced enkephalins on catecholamine release in human pheochromocytoma cells. MAIN METHODS: Cells obtained from eleven human pheochromocytomas of different genetic origins were cultured for 5 days. Cultures were maintained under basal condition or under enkephalin, dexamethasone and naloxone alone or in combination with enkephalin or dexamethasone-stimulated conditions. Catecholamine and enkephalin levels in the culture medium were measured by HPLC-ED and RIA respectively. KEY FINDINGS: Enkephalin induced a decrease in norepinephrine levels in all tumor cultures. Dexamethasone treatment, which increased enkephalin levels, also decreased catecholamine levels. On the other hand, the addition of naloxone to the cultures reverted to normal the inhibitory action exerted by enkephalin and dexamethasone treatments. SIGNIFICANCE: These results suggest the existence of an autocrine negative regulatory loop exerted by enkephalin on norepinephrine release in human pheochromocytoma cells.

The AMP-activated protein kinase activator, 5-aminoimidazole-4-carboxamide-1-b-D-ribonucleoside, regulates lactate production in rat Sertoli cells.

The aim of the present study was to investigate whether the AMP-activated protein kinase (AMPK), a key regulator of cellular energy homeostasis, is present in Sertoli cells and whether its activation by 5-aminoimidazole-4-carboxamide-1-b-d-ribonucleoside (AICAR) results in the regulation of cell metabolism to ensure lactate supply for germ cell development. Sertoli cell cultures from 20-day-old rats were used. Western blot analysis for the alpha-subunit of AMPK showed that high levels of AMPK are present in Sertoli cells. Treatment of the cultures with AICAR resulted in a dose- and time-dependent increase of P-AMPK levels indicating activation of the enzyme. A possible effect of AICAR on Sertoli cell lactate production was then analyzed. A dose- and time-dependent increment in lactate secretion was observed. The participation of AMPK activation in different biochemical processes that may be implicated in the regulation of lactate production was also analyzed. AICAR stimulated glucose uptake in a dose- and time-dependent manner. Additionally, AICAR increased the glucose transporter 1 (GLUT1) and decreased the glucose transporter 3 (GLUT3) mRNA levels. As for the role of AMPK in the regulation of the monocarboxylate transporters 1 and 4 (MCT1 and MCT4), it has been observed that AICAR treatment decreased MCT1 and increased MCT4 mRNA levels. In summary, the results presented herein show that AMPK is present in Sertoli cells and that its activation by AICAR increases lactate production as a result, at least in part, of a) an increase in glucose uptake, b) an increase in GLUT1 expression, and c) a decrease in MCT1 and an increase in MCT4 levels. Altogether, these results suggest an important role of AMPK in modulating the nutritional function of Sertoli cells.

Participation of phosphatidyl inositol 3-kinase/protein kinase B and ERK1/2 pathways in interleukin-1beta stimulation of lactate production in Sertoli cells.

Interleukin-1beta (IL1beta ) belongs to a set of intratesticular regulators that provide the fine-tuning of cellular processes implicated in the maintenance of spermatogenesis. The aim of the present study was to analyze the signaling pathways that may participate in IL1beta regulation of Sertoli cell function. Sertoli cell cultures from 20-day-old rat were used. Stimulation of the cultures with IL1beta showed increments in phosphorylated protein kinase B (PKB), P70S6K, and ERK1/2 levels. A phosphatidyl inositol 3-kinase (PI3K) inhibitor (wortmannin (W)), a mammalian target of rapamycin inhibitor (rapamycin (R)), and a MEK inhibitor (PD98059 (PD)) were utilized to evaluate the participation of PI3K/PKB, P70S6K, and ERK1/2 pathways in the regulation of lactate production by IL1beta . PD and W, but not R, decreased IL1beta-stimulated lactate production. The participation of these pathways in the regulation of glucose uptake and lactate dehydrogenase (LDH) A mRNA levels by IL1beta was also analyzed. It was observed that W decreased IL1beta-stimulated glucose uptake, whereas PD and R did not modify it. On the other hand, PD decreased the stimulation of LDH A mRNA levels by IL1beta , whereas W and R did not modify it. In summary, results presented herein demonstrate that IL1beta stimulates PI3K/PKB-, P70S6K-, and ERK1/2-dependent pathways in rat Sertoli cells. Moreover, these results show that while IL1beta utilizes the PI3K/PKB pathway to regulate glucose transport, it utilizes the ERK1/2 pathway to regulate LDH A mRNA levels. This study reveals that IL1beta utilizes different signal transduction pathways to modify the biochemical steps that are important to regulate lactate production in rat Sertoli cells.