Orexin A-mediated stimulation of 3β-HSD expression and testosterone production through MAPK signaling pathways in primary rat Leydig cells

BACKGROUND

Orexin A (ORA) regulates food intake, energy metabolism, gastrointestinal and reproductive functions.

AIM

The purpose of this study was to demonstrate whether the expression of 3β-hydroxysteroid dehydrogenase (3β-HSD) and testosterone was stimulated by ORA and mediated through mitogen-activated protein kinases (MAPK) in rat Leydig cells.

METHODS

Primary Leydig cells were isolated from male rat testes, cultured, and treated with ORA under various conditions.

RESULTS

Orexin receptor 1 (OX (1) R) mRNA, but not orexin receptor 2 mRNA, was detected in primary Leydig cells. ORA up-regulated the expression of OX( 1) R mRNA and protein in a dose-responsive manner and increased the phosphorylation of extracellular receptor kinase 1/2 (ERK1/2) and p38 MAPK levels, but did not affect the phosphorylation of the JNK MAPK. Phosphorylation of ERK1/2 and p38 MAPKs by ORA was blocked with U0126 and SB203580 inhibitors, respectively. An OX(1)R-specific inhibitor, SB334867, also blocked the phosphorylation of ERK1/2 and p38 by ORA. Inhibitor treatment also blocked 3β-HSD expression and testosterone production.

CONCLUSIONS

These results demonstrate that ORA activation of OX(1)R up-regulates 3β-HSD expression and testosterone production via the ERK1/2 and p38 MAPKs signaling pathways in primary rat Leydig cells.

Effects of orexin A on GLUT4 expression and lipid content via MAPK signaling in 3T3-L1 adipocytes

Orexin A regulates food intake, energy metabolism and gastrointestinal function; it also increases glucose uptake and inhibits lipolysis, suggesting a role for orexin A in glucose and lipid metabolism. In this study, the effects of orexin A on glucose transporter 4 (GLUT4) mRNA level and lipid content were explored in 3T3-L1 preadipocytes and adipocytes. Orexin receptor 1 (OX1R) protein expression was determined in the adipose tissue of normal and obese rats. In addition, 3T3-L1 preadipocytes and differentiated 3T3-L1 adipocytes were incubated with different concentrations of orexin A (10(-9) to 10(-7)M), without or with OX1R specific antagonist, then the peroxisome proliferator-activated receptor-γ2 (PPARγ2) mRNA expression was analyzed. Differentiated 3T3-L1 adipocytes were exposed to orexin A, without or with MAPK and OX1R antagonist, after which the GLUT4 and ERK1/2, JNK, and p38 MAPK activation, and triglyceride (TG) content were measured. We observed that OX1R protein expression was decreased in obese rats, and OX1R protein level was negatively correlated with body fat, Lee's index, TG, total cholesterol, and fasting insulin levels. Orexin A enhanced PPARγ2 mRNA expression in a dose-dependent manner in 3T3-L1 preadipocytes through OX1R. In differentiated 3T3-L1 adipocytes, orexin A significantly increased GLUT4 mRNA levels, which was blocked by the ERK1/2, JNK, and p38 MAPK inhibitors as well as OX1R antagonist. Furthermore, orexin A increased cellular TG content via ERK1/2, JNK, and p38 MAPK as well as OX1R. Thus, orexin A increases GLUT4 mRNA expression and lipid accumulation in differentiated 3T3-L1 adipocytes via ERK1/2, JNK, and p38 MAPK signaling. In addition, orexin A increases PPARγ2 mRNA expression in 3T3-L1 preadipocytes. Further studies are necessary to elucidate the impact of orexin A in metabolic disorders and adipocyte differentiation.

Orexin A Affects INS-1 Rat Insulinoma Cell Proliferation via Orexin Receptor 1 and the AKT Signaling Pathway

Our aim is to investigate the role of the AKT/PKB (protein kinase B) signaling pathway acting via orexin receptor 1 (OX1R) and the effects of orexin A (OXA) on cell proliferation in the insulin-secreting beta-cell line (INS-1 cells). Rat INS-1 cells were exposed to different concentrations of OXA in vitro and treated with OX1R antagonist (SB334867), PI3K antagonist (wortmannin), AKT antagonist (PF-04691502), or negative control. INS-1 amount of cell proliferation, viability and apoptosis, insulin secretion, OX1R protein expression, caspase-3 activity, and AKT protein levels were determined. We report that OXA (10(-10) to 10(-6) M) stimulates INS-1 cell proliferation and viability, reduces the proapoptotic activity of caspase-3 to protect against apoptotic cell death, and increases insulin secretion. Additionally, AKT phosphorylation was stimulated by OXA (10(-10) to 10(-6) M). However, the OX1R antagonist SB334867 (10(-6) M), the PI3K antagonist wortmannin (10(-8) M), the AKT antagonist PF-04691502 (10(-6) M), or the combination of both abolished the effects of OXA to a certain extent. These results suggest that the upregulation of OXA-OX1R mediated by AKT activation may inhibit cell apoptosis and promote cell proliferation in INS-1 cells. This finding provides functional evidence of the biological actions of OXA in rat insulinoma cells.

Autophagy promotes T-cell survival through degradation of proteins of the cell death machinery

Autophagy is implicated in regulating cell death in activated T cells, but the underlying mechanism is unclear. Here, we show that inhibition of autophagy via Beclin 1 gene deletion in T cells leads to rampant apoptosis in these cells upon TCR stimulation. Beclin 1-deficient mice fail to mount autoreactive T-cell responses and are resistant to experimental autoimmune encephalomyelitis. Compared with Th17 cells, Th1 cells are much more susceptible to cell death upon Beclin 1 deletion. Cell death proteins are highly increased in Beclin 1-deficient T cells and inhibition of caspases and genetic deletion of Bim reverse apoptosis. In addition, p62/sequestosome 1 binds to caspase-8 but does not control levels of procaspase-8 or other cell death-related proteins. These results establish a direct role of autophagy in inhibiting the programmed cell death through degradation of apoptosis proteins in activated T cells.

Effects of cumulus cells on in vitro maturation of oocytes and development of cloned embryos in the pig

The purpose of this study was to investigate the role of porcine cumulus cells (CC) in oocyte maturation and somatic cell nuclear transfer (SCNT) embryo development in vitro. Denuded pig oocytes were co-cultured with CC or routinely cultured in maturation medium without a feeder layer. Porcine CC inactivated with mitomycin C or non-inactivated were used for the feeder layer in co-culture with porcine SCNT embryos to investigate comparatively the developmental competence of cloned embryos. The DNA damage aspects of apoptosis and expression pattern of genes implicated in apoptosis (Fas/FasL) as well as the mRNA expression of DNA methyltransferase (Dnmt1, Dnmt3a) of porcine SCNT embryos were also evaluated by comet assay or real-time RT-PCR, respectively. The results showed that co-culture with CC improved the extrusion rate of pbI (49.3% vs 31.5%, p<0.05) and survival rate (75.7% vs 53.3%, p<0.05) of denuded oocytes, but had no effects on blastocyst developmental rate or 2-cell-stage survival rate of in vitro fertilization embryos. Co-culture with CC inactivated by mitomycin C improved the blastocyst developmental rate (26.6% vs 13.0%, p<0.05) and decreased the apoptotic incidence (27.6% vs 46.2%, p<0.05) of porcine cloned embryos. Co-culture with inactivated CC reduced Fas and FasL mRNA expression of cloned embryos at the blastocyst stage compared with NT controls (p<0.05), but there were no differences in Dnmt1 and Dnmt3a mRNA expression among groups. Co-culture with inactivated cumulus cell monolayer significantly increased blastocyst formation and decreased the apoptotic incidence in porcine cloned embryos during in vitro development.

Identification of microRNA-target interaction in APRIL-knockdown colorectal cancer cells

MicroRNAs (miRNAs) regulate mammalian gene expression by targeting mRNAs and have key roles in several cellular processes, including differentiation, development, apoptosis and cancer pathomechanisms. Our previous studies have confirmed that a proliferation-inducing ligand (APRIL) gene is overexpressed in colorectal cancer (CRC) tumors and SW480 cells. To study the potential mechanisms of APRIL gene in the occurrence and development of the CRC, herein, we investigated whether APRIL-knockdown had the inhibitory effect on the growth of SW480 cells and had the simultaneous expression changes of miRNAs and mRNAs by microarrays. Our results suggest that siRNA-APRIL can effectively inhibit the growth of SW480 cells in vitro and in vivo and several miRNAs via specific pathways might be involved in regulating the phenotype of loss-of-function in APRIL-knockdown SW480 cells. Thus, our study highlights the possible mechanisms of miRNA-target regulating the function of APRIL gene in CRC cells, moreover, siRNA-APRIL holds great promise as a novel gene therapy approach for APRIL- positive CRC treatment.

Elaboration of an electroporation protocol for large plasmids and wild-type strains of Bacillus thuringiensis

AIMS

To elaborate an effective electroporation protocol for large plasmids and wild type strains of Bacillus thuringiensis.

METHODS AND RESULTS

The effect of DNA desalting, wall-weakening agency, cell growth conditions, electroporation solutions, and electric fields on electroporation efficiency was evaluated to optimize electroporation conditions for B. thuringiensis. By using this improved method, the greatest efficiency was reached 2 x 10(10 )CFU microg(-1) with pHT304, which is 10(4) times higher than previously reported. Four large plasmids (29.1, 44.9, 58 and 60 kb) were successfully transferred into the acrystalliferous B. thuringiensis strain BMB171; these results have not been achieved with previous protocols. Three wild type B. thuringiensis strains which could not be transformed previously were also transferred successfully.

CONCLUSIONS

This improved method is more efficient for small plasmids; it is also appropriate for large plasmids and wild type B. thuringiensis strains which were not transformed by previous procedures.

SIGNIFICANCE AND IMPACT OF THE STUDY

The present study established an effective electroporation protocol for large plasmids and wild type strains of B. thuringiensis. This method is well suited for the cloning and expression of huge DNA fragments such as gene clusters in B. thuringiensis. It also can be used as a reference method for other Bacillus strains that are refractory to electroporate.

[Noninvasive monitoring of the hepatocellular carcinoma growth by the method of 1H and 23Na nuclear magnetic resonance]

Using diffusion weighted 1H, single-quantum 23Na and triple-quantum-filtered 23Na magnetic resonance imaging water apparent diffusion coefficient (ADC), total tissue Na+ and intracellular Na+ were monitored in hepatocellular carcinoma (HCC) in rats and in the surrounding liver tissue. The tumor water ADC was approximately 50% higher compared to the nearby healthy liver tissue but did not increase during 28 days of tumor growth (double time 3.9 days). The HCC growth was associated with an increase in both total tissue and intracellular 23Na signal intensity especially after 21 days post-cell inoculation reflecting possible changes in extracellular space and in intracellular ionic metabolism.