Resistin as a new player in the regulation of porcine corpus luteum luteolysis: in vitro effect on proliferation/viability, apoptosis and autophagy.

The formation and luteolysis of the corpus luteum (CL) is strictly controlled by many factors. Imbalance between proliferation and apoptosis processes leads to deficiency of the luteal phase and infertility. Our previous study showed resistin expression in porcine luteal cells and an inhibitory effect on progesterone synthesis. Thus, the aim of the present study was to examine the in vitro effect of resistin on the proliferation/viability, apoptosis and autophagy of porcine luteal cells as well as the involvement of mitogen-activated kinase (MAP3/1), protein kinase B (AKT) and signal transducer and activator of transcription 3 (STAT3) in these processes. Porcine luteal cells were incubated with resistin (0.1-10 ng/mL) for 24-72 h and viability was assessed using the alamarBlue or 3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Then, the time-dependent effect of resistin on mRNA and protein expression of proliferating cell nuclear antigen (PCNA), caspase 3, BCL2-like protein 4 (BAX), B-cell lymphoma 2 (BCL2), beclin1, microtubule-associated protein 1A/1B-light chain 3 (LC3) and lysosomal-associated membrane protein 1 (LAMP1) was measured by real-time polymerase chain reaction (PCR) and immunoblotting, respectively. We found that resistin enhanced luteal cell viability with no effect on caspase 3 mRNA and protein, increased the BAX/BCL2 mRNA and protein ratio and significantly stimulated the initiation of autophagy, which promotes the maintenance of CL function rather than its regression. Additionally, using pharmacological inhibitors of MAP3/1 (PD98059), AKT (LY294002) and STAT3 (AG490), we observed that the effect of resistin was reversed to the control level in viability and, by influence, MAP3/1 and STAT3 in autophagy. Taken together, our results suggest that resistin, in addition to its well-known effect on granulosa cell function has direct influence on CL luteolysis and the formation and maintenance of luteal cell function.

New insights into cell apoptosis and proliferation: the potential role of vaspin.

Vaspin, also known as visceral adipose tissue-derived serine protease inhibitor; expression of this adipokine has been confirmed in many parts of the body like the hypothalamus, pancreas, thyroid gland, ovaries, placenta, and testes, where it may play a crucial role in osteogenesis, steroidogenesis, the formation of blood vessels, and food intake. In addition, there are many studies supporting an interaction between vaspin and cell proliferation and apoptosis, which are crucial processes for maintaining homeostasis of the body. Vaspin has an anti-apoptotic effect in ovarian cells, osteoblasts, macrophages, aortic endothelial cells, hepatocellular carcinoma cells, and cardiomyocytes. On the other hand, vaspin has no effect on apoptosis in aortic smooth muscle cells and cardiomyocytes. Interestingly, vaspin also promotes proliferation in normal and cancerous ovarian cells, pre-adipocytes, hepatocellular carcinoma cells, and bone mesenchymal stem cells, although other studies showed that this adipokine reduces the proliferation of aortic, and vascular smooth muscle cells. Furthermore, vaspin has no effect on the proliferation of chondrocytes, osteoblasts, macrophages, pre-adipocytes, umbilical vein endothelial cells, and coronary artery smooth muscle cells. Dysfunction and dysregulation in the apoptosis/proliferation ratio may lead to cancer development and progression as well as pathogenesis of many diseases. The molecular mechanism of vaspin action on cell apoptosis and proliferation is reviewed in this paper.

Effect of ghrelin on the apoptosis of various cells. A critical review.

Ghrelin is a protein hormone secreted from the gastric mucosa, but is also expressed in a variety of tissues. The biological function of ghrelin is widely known, including regulation of food intake, body weight, gastrointestinal, cardiovascular, reproductive, immune functions, cell proliferation and hormone secretion. The growth hormone secretagogue receptor (GHS-R) mediates the effect of ghrelin. Depending on cell type, ghrelin either induces apoptosis or has anti-apoptotic effect. Apoptosis is a physiological process that plays an important role in many biological actions such as proliferation, development or differentiation and regulation of physiological function in many cells. Dysfunction or dysregulation of apoptosis leads to pathology conditions. The action of ghrelin on cell apoptosis is reviewed in this paper.

Apelin decreased placental hormone secretion by human trophoblast BeWo cells via apelin receptor, protein kinase A and extracellular signal-regulated kinases 1/2 activation.

Apelin was thought to be an adipocyte-specific hormone, but recent studies have indicated a link between apelin and placenta function e.g. cell proliferation. The aim of the study was investigating dose- and time-dependent effect of apelin on hormone secretion including steroids: progesterone (P4) and estradiol (E2) and proteins: chorionic gonadotropin (hCG), human placental lactogen (hPL), placental growth factor (PLGF), as well as protein expression of steroid enzymes (3ßHSD, CYP19) and protein hormones (hCG, hPL and PLGF) in placental cells. Syncytiotrophoblast BeWo cells, as human trophoblast models, were treated for 24, 48, and 72 hours with the human recombinant apelin at doses 0.02, 0.2, 2.0, 20 and 200 ng/ml followed by culture medium. Concentrations of the above hormones were studied by ELISA kits. Furthermore, protein expression of steroid enzymes and protein hormones were measured using Western blot. Our results showed that apelin significantly decreased both steroid and protein hormones by inhibiting steroid enzymes or protein hormone expression. Moreover, we demonstrated that apelin at dose 2.0 ng/ml increased phosphorylation of protein kinase A (PKA) from 1 to 60 min of BeWo cell incubation. Inhibitory effect of apelin on P4, E2 and PLGF secretion were abolished when BeWo cells were cultured in the presence of ML221, an apelin receptor antagonist, PD98059, an extracellular signal-regulated kinases (ERK1/2) antagonist and KT5720, a PKA antagonist. In turn, secretion of hCG and hPL occurs only in the presence of ML221 and PD98059. In conclusion, our results indicate that apelin can be considered as a gestational hormone implied in the endocrine function of the human placenta, with an important role in controlling the production of steroid and protein hormones in placental BeWo cells.

Expression of peroxisome proliferator-activated receptors is regulated by gonadotropins and steroid hormones in in vitro porcine ovarian follicles.

The peroxisome proliferator-activated receptors (PPARs) are a family of transcription factors which are involved in the regulation of different processes such as lipid metabolism, inflammation, angiogenesis, tissue remodeling and steroidogenesis. Our previous data described the ovarian expression of PPAR isoforms (-α, -γ and -ß), and the increase of PPAR-α and PPAR-γ in porcine ovarian follicles during the estrous cycle. The current studies were undertaken to test the hypothesis that gonadotropin and steroid hormones can regulate the expression of PPAR isoforms in the ovary. Medium follicles (4 - 6 mm) at 10 - 12 days of the estrous cycle were obtained from mature crossbred gilts. Ovarian follicles were exposed to gonadotropins FSH and LH at 50, 100 and 150 ng/ml, and to steroid hormones such as progesterone (P4), testosterone (T) and estradiol (E2) at 10-8, 10-7, 10-6 M for 24 hours. Then mRNA and protein expression of PPAR-α/γ/ß via real time PCR and Western blot, respectively, were measured. We observed that FSH increased both mRNA and protein expression of all PPAR isoforms, while LH only increased PPAR-α/γ. We have also noted that P4 and E2 significantly increased expression of PPAR-α/γ without having an effect on ß isoform, while T had no effect on all PPARs expression. Our study clearly showed that local regulators of ovarian activity, both gonadotropin and steroid hormones are regulators of PPAR isoforms expression in porcine ovarian follicles.