Polar phospholipids from bovine endogenously oxidized low density lipoprotein interfere with follicular thecal function

Abstract

The role of endogenously oxidized low density lipoprotein (oxLDL) in follicular steroidogenic regulation is unknown. Information may be important in order to elucidate ovulatory dysregulation in disordered lipid metabolism. To obtain specific data, we studied the effect of polar phospholipids (PL) isolated from oxLDL with different endogenous levels of lipohydroperoxides (LHP) on the thecal expression of mRNA encoding steroidogenic enzymes and cyclooxygenase 2 (COX-2), and on the thecal production of superoxide and progesterone. Large (preovulatory) bovine follicles were used and analyses of thecal fragments from single follicles were performed by radioimmunoassays, chemiluminescence assays and quantitative RT-PCR. Basal concentration of mRNA for several lipoprotein receptors exceeded by about 10-times the basal level of mRNA encoding steroidogenic enzymes, suggesting that preovulatory theca receptors may favour uptake of oxLDL. PL (5-11 pmol phosphorus/ml) decreased (up to 0·5-times the control) progesterone synthesis, production of superoxide and levels of P450 cholesterol side chain cleavage (P450 scc), 3 -hydroxysteroid dehydrogenase and COX-2 mRNA. Abundance of COX-2 transcripts in thecal tissue incubated with forskolin depended on the progesterone/17 -oestradiol ratio of the follicle fluid, i.e. the previous microenvironment in vivo. PL effects were mimicked by the platelet-activating factor (PAF). WEB 2086, a PAF receptor blocker, did not always abolish these responses, suggesting that the effects were not mediated solely by this receptor. PAF interfered dose-dependently with LH-induced responses, indicating interference with LH signalling. PL from mildly oxidized LDL (0·5 nmol/ml LHP) tended to exert greater effects than PL from oxLDL containing 1·5 nmol/ml LHP. In consideration of the known physiologic role of progesterone, COX-2 and possibly superoxide, these results provide evidence for a potential of PL from oxLDL to induce ovulatory dysregulation and suggest that the extent of the LDL oxidation seems to be important for interfering with thecal responses to the preovulatory LH surge.

Corpus luteum development and its morphology after aspiration of a preovulatory follicle is related to size and steroid content of the follicle in dairy cows

“…We showed in the current study for the first time that assessing the rate of CL development after the taking of follicle fluid samples from a pre-ovulatory follicle, allows discrimination between follicles with different qualities, which might be taken as the same group if they were judged commonly on the basis of oestradiol and progesterone concentrations (Lohrke et al 2005, Nishimoto et al 2009 or morphology (Acosta 2007). Both groups of pre-ovulatory follicles (with or without subsequent development of a corpus luteum) showed expected, or even higher, progesterone concentrations in their FF (Lohrke et al 2005;Nimz et al 2009). However, our results indicate that the oestradiol concentration is more important for predicting the further physiological development of a pre-ovulatory follicle into luteal tissue and this might fit with recent in vivo findings regarding plasma oestradiol and pregnancy rates (Jinks et al 2013).…”

Social Support Modulates Stress-Related Gene Expression in Various Brain Regions of Piglets

“…The mRNA expression of the NR3C1 gene encoding the GR, of the NR3C2 gene encoding the MR, of the HSD11B1 gene encoding the enzyme 11β-HSD1, of the HSD11B2 gene encoding the enzyme 11β-HSD2 and of the C-FOS gene was monitored using a reverse transcription (RT) with subsequent real-time polymerase chain reaction (PCR) as described previously (Löhrke et al, 2005; Kanitz et al, 2009, 2012). RT was carried out with 500 ng of total RNA using an iScript cDNA synthesis kit (BIO-RAD, München, Germany) following the guidelines of the manufacturer.…”

High and Low Protein∶ Carbohydrate Dietary Ratios during Gestation Alter Maternal-Fetal Cortisol Regulation in Pigs

“…The absolute quantification of mRNA using the real-time reverse transcriptase chain reaction (RT-PCR) was performed as previously described by Löhrke et al [30]. Fragments of mRNA encoding GR, MR, 11β-HSD1 and 11β-HSD2 were obtained from reverse transcription (RT) performed by an iScript cDNA synthesis kit (BIO-RAD, München, Germany) with 100 ng of total RNA following the guidelines of the manufacturer.…”