ACTH impairs the migratory and secretory profile of mononuclear cells during proestrus in cattle.

The aim was to evaluate the effect of ACTH on the mechanisms involved in peripheral blood mononuclear cells (PBMCs) infiltration into the ovary during dairy cattle proestrus. Regarding this, proper expression pattern of adhesion molecules must take place both in PBMCs and in endothelial cells. Argentinian Holstein cows (n = 12) were treated with 100 IU of ACTH every 12 h for 4 days before ovulation when ovariectomy was performed (day 18). Blood samples were taken on day 15 (0 h) and immediately before (72 h) and after (74 h) the last ACTH administration. In PBMCs, flow cytometry was performed to analyze CD44, CD11b and CD62-L expression along with gene expression of chemokines' receptors. Interleukin (IL)-4 and tumor necrosis factor-α (TNF-α) production was analyzed by flow cytometry after exposing PBMCs to autologous follicular fluid. In ovarian blood vessels, expression of the vascular endothelium cell adhesion-1 (VCAM-1) and the platelet endothelial cell adhesion molecule-1 was evaluated by immunohistochemistry. In T-lymphocytes, the expression of CD44 and CD11b was lower at 72 h in ACTH-treated cows (P < 0.05). In monocytes, the expression of CD11b and CD62-L was lower at 72 h in ACTH-treated cows (P < 0.05). Also, the percentage of IL-4+ cells was higher in ACTH-treated cows, meanwhile, the percentage TNF-α+ cells was lower in ACTH-treated cows (P < 0.05). Finally, in the vessels associated with the preovulatory follicle VCAM-1 immunoexpression was lower in ACTH-treated cows (P < 0.05). Here, we present novel insights into the effect of stress during the preovulatory period on the inflammatory pathway necessary for ovulation.

Association of glucocorticoid receptor expression with key members of the insulin signaling pathway and heat shock proteins in the bovine ovary.

Glucocorticoids (GCs) act through their receptor (GR) as regulators in different biological processes such as reproduction. In the absence of GCs, the GR remains inactive in the cytoplasm by associating with heat shock proteins (HSPs), which act as molecular chaperones, among which the most relevant are HSP90 and HSP70. Cytoplasmic GC-activated GR mediates non-genomic effects, interacting with members of signaling pathways such as PI3K/Akt, which participates in several metabolic processes, including the insulin signaling pathway. The aim of the present study was to evaluate possible associations between the cytoplasmic GR and the main intermediates of the insulin signaling pathway and HSP90 and HSP70 in ovaries of dairy cows. To this end, the protein expression of cytoplasmic GR, key members of the insulin signaling pathway, and HSPs was evaluated in ovarian preovulatory follicles of non-lactating Holstein cows in proestrus. Positive associations were observed between protein expression of GR and HSP90, IRS1, pIRS1, PI3K and pAkt (p < 0.05; ß > 0) in granulosa cells of dominant follicles of dairy cows. Instead, in theca cells, no associations were observed between protein expression of GR and members of the insulin signaling pathway or HSPs. These data provide evidence of the possible association between the non-genomic mechanisms of action of the GR and the insulin signaling pathway in the bovine ovary.

Exogenous ACTH stimulus during the preovulatory period alters patterns of leukocyte recruitment in the ovary of dairy cows.

Before ovulation, the ovary exhibits signs of local inflammation. However, the effects of adrenocorticotropin (ACTH) on the complexity of this inflammatory response are not yet well described. Thus, the aim of this study was to evaluate the effects of ACTH administered to dairy cows during the preovulatory period on the local distribution of different subsets of leukocytes infiltrated in the ovary, along with the gene expression of relevant chemokines (C-C motif chemokine ligand-2 (CCL2), C-X-C motif chemokine ligand-8 (CXCL8), CCL25 and CXCL1) involved in leukocyte chemotaxis and blood perfusion on the follicular wall of dominant follicles. Also, the direct effect of ACTH on chemokine gene expression was addressed in cultured antral follicular walls. For this purpose, both an in vivo and an in vitro experiment were performed. For the in vivo experiment, exogenous ACTH (100 IU) was administered intramuscularly to Holstein cows (n = 12) during proestrus every 12 h for four days before ovulation, when ovariectomy was performed (day 18). Daily ovarian Doppler ultrasonography was used to evaluate the percentage of irrigated area, the pulsatility index and the resistance index in the dominant follicles. The distribution of monocytes-macrophages (CD14), T- (CD2) and B-lymphocytes (CD79a) and granulocytes (CH138A) in the ovary was analyzed by immunohistochemistry. In follicular wall samples, gene expression of CCL2, CXCL8, CXCL1 and CCL25 was evaluated, whereas IL-17A expression was analyzed by Western blot. The total number of CD14, CD79a and CD2 infiltrated cells was lower in the ACTH-treated group than in the control group (p < 0.05). Chemokine gene expression showed lower mRNA of CCL2, CCL25 and CXCL1 (p < 0.05) in the ACTH-treated group. Meanwhile, IL-17A protein expression and hemodynamic parameters were similar between groups (p > 0.05). In the in vitro assay, antral follicular walls were stimulated with ACTH to corroborate the gene expression profile of chemokines. mRNA expression of CCL2 tended to be lower in the stimulated follicular walls (p = 0.092). Our results suggest that exogenous ACTH stimulus during the preovulatory period reduces the number of infiltrated leukocytes in the bovine ovary and this could be due to a lower chemotaxis capacity of the ovary.

MC2R/MRAP2 activation could affect bovine ovarian steroidogenesis potential after ACTH treatment.

Stressors activate the hypothalamic-pituitary-adrenal (HPA) axis, reducing fertility by interfering with the mechanisms that regulate the timing of events within the follicular phase of the estrous cycle. In the HPA axis, melanocortin 2 receptor (MC2R) mediates responses to adrenocorticotropic hormone (ACTH) in concert with melanocortin receptor accessory protein 2 (MRAP2). The aims of the present study were: (1) to evaluate the effects of ACTH administered in cows in the preovulatory period on the expression of the MC2R/MRAP2 complex in the dominant follicle; and (2) to analyze the involvement of Extracellular signal Regulated Kinase 1 (ERK1) signaling in the activation of MC2R and the expression of key enzymes involved in the biosynthesis of glucocorticoids (GCs) in the dominant follicle. To this end, 100 IU ACTH was administered to Holstein cows from a local dairy farm during pro-estrus every 12 h for four days until ovariectomy, which was performed before ovulation. Protein immunostaining of MC2R was higher in the dominant follicles of ACTH-treated cows (p < 0.05). Also, Western blot analysis showed higher activation of the ERK1 signaling pathway in ACTH-treated cows (p < 0.05). Finally, immunohistochemistry performed in the dominant follicles of ACTH-treated cows detected higher expression of CYP17A1 and CYP21A2 (p < 0.05). These results suggest that the bovine ovary is able to respond locally to ACTH as a consequence of stress altering the expression of relevant steroidogenic enzymes. The results also confirm that the complete GC biosynthesis pathway is present in bovine dominant follicle and therefore GCs could be produced locally.

Effects of adrenocorticotrophic hormone on the expression of matrix metalloproteinases and their inhibitors in the bovine ovary.

Cattle undergo numerous environmental and management stressors that reduce fertility and affect ovulation. The extracellular matrix of the follicle wall can be altered by matrix metalloproteinases (MMPs), the activities of which are regulated by interleukins and tissue-specific inhibitors of metalloproteinases (TIMPs), especially during ovulation. The aims of the present study were to: (1) evaluate changes in the hormone milieu, the localisation and activity of MMP2 and MMP9 and the localisation of MMP14, TIMP1 and TIMP2 in response to adrenocorticotrophic hormone (ACTH) during the preovulatory period in cows; and (2) determine the direct effects of ACTH on the mRNA expression of MMP2 and MMP9 in the cultured follicle wall of bovine ovaries obtained from an abattoir. 100IU ACTH was administered during pro-oestrus every 12h until ovariectomy, which was performed before ovulation. Cortisol concentrations in the plasma and follicular fluid (FF) of preovulatory follicles were higher in ACTH-treated than control cows. Progesterone presented subluteal concentrations in plasma of ACTH-treated cows (P<0.05). MMP2 immunostaining and activity in ovaries were higher in ACTH-treated than control cows (P<0.05), whereas MMP9 immunostaining was similar between the two groups. However, unlike in control cows, MMP9 activity was absent in the FF of ACTH-treated cows. These results suggest that the administration of ACTH during the preovulatory period in cows could cause changes that culminate in modifications in the content and activation of MMPs and TIMPs in the ovary, which could interfere with the ovulation process.

Altered expression of IL-1ß, IL-1RI, IL-1RII, IL-1RA and IL-4 could contribute to anovulation and follicular persistence in cattle.

Cystic ovarian disease (COD) is an important cause of infertility in dairy cattle. The main signs of this infertility are ovulation failure and follicular persistence. The aim of this study was to examine the expression of the cytokines IL-1ß, IL-1RI, IL-1RII, IL-1RA and IL-4 in ovarian follicular structures at different times of persistence in a model of follicular persistence induced by prolonged administration of progesterone in dairy cows. Protein expression of IL-1ß, IL-1RI, IL-1RII, IL-1RA and IL-4 was evaluated by immunohistochemistry. Additionally, IL-1ß and IL-4 concentrations in follicular fluid and serum were determined by ELISA. In granulosa cells, IL1-RII and IL-4 expression was higher in follicles with different persistence times than in the control dominant follicles. IL-1RA expression was higher in persistent follicles of the P15 group (15 days of follicular persistence) than in those of the control group. In theca cells, IL-1RII expression was higher in persistent follicles of the P0 group (expected time of ovulation) than in dominant follicles from the control group (p < .05) and the other persistence groups, whereas IL-4 expression was higher in persistent follicles of groups P0 and P15 than in the dominant follicles of the control group (p < .05). Differences between serum and follicular fluid within each group were detected only in P0 for IL-1ß, and in the control, P10 and P15 groups for IL-4 (p < .05). These results complement previous results, evidencing that early development of COD in cows is concurrent with an altered expression of cytokines in different ovarian follicular structures and may contribute to the follicular persistence and ovulation failure found in cattle with follicular cysts.

Role of Components of the Insulin-like Growth Factor System in the Early Stages of Ovarian Follicular Persistence in Cattle.

Cystic ovarian disease (COD) is one of the main causes of infertility in dairy cattle. It has been postulated that the insulin-like growth factor (IGF) system may contribute to follicular persistence and development of COD. The initiation of the IGF response is a result of interactions between IGF-binding proteins (IGFBPs) and IGFBP proteases, mainly pregnancy-associated plasma protein A (PAPP-A). IGFBPs bind IGFs with high affinity and consequently regulate their access to IGF receptors (IGFRs). The aim of this research was to determine variations in components of the IGF system in the ovaries of cows with persistent follicles induced by long-term administration of progesterone. Proteins of the IGF system were evaluated at 0 (expected day of ovulation), 5, 10 and 15 days of follicular persistence to determine whether the changes occur early in the development of COD. The concentrations of IGF1 and IGFBP4 in follicular fluid were similar in all groups with follicular persistence and in control antral follicles. IGFR1 and IGFBP4 expression in situ were higher in granulose cells in persistent follicles than in control follicles. No differences were found in PAPP-A concentration within follicular fluid in persistent follicles relative to control antral follicles. These data support the hypothesis that the IGF system is altered in the initial stages of development of follicular persistence and has a determinant role in ovarian function in cattle.

Detection and activity of 11 beta hydroxylase (CYP11B1) in the bovine ovary.

Glucocorticoids (GCs) such as cortisol and corticosterone are important steroid hormones with different functions in intermediate metabolism, development, cell differentiation, immune response and reproduction. In response to physiological and immunological stress, adrenocorticotropic hormone (ACTH) acts on the adrenal gland by stimulating the synthesis and secretion of GCs. However, there is increasing evidence that GCs may also be synthesized by extra-adrenal tissues. Here, we examined the gene and protein expression of the enzyme 11ß-hydroxylase P450c11 (CYP11B1), involved in the conversion of 11-deoxycortisol to cortisol, in the different components of the bovine ovary and determined the functionality of CYP11B1 in vitro CYP11B1 mRNA was expressed in granulosa and theca cells in small, medium and large antral ovarian follicles, and CYP11B1 protein was expressed in medium and large antral follicles. After stimulation by ACTH, we observed an increased secretion of cortisol by the wall of large antral follicles. We also observed a concentration-dependent decrease in the concentration of cortisol in response to metyrapone, an inhibitor of CYP11B1. This decrease was significant at 10-5 µM metyrapone. In conclusion, this study demonstrated for the first time the presence of CYP11B1 in the bovine ovary. This confirms that there could be a local synthesis of GCs in the bovine ovary and therefore a potential endocrine responder to stress through these hormones.

Involvement of PAPP-A and IGFR1 in Cystic Ovarian Disease in Cattle.

Cystic ovarian disease (COD) is one of the main causes of infertility in dairy cattle. It has been shown that intra-ovarian factors, such as members of the insulin-like growth factor (IGF) system, may contribute to follicular persistence. The bioavailability of IGF to initiate its response by binding to specific receptors (IGFRs) depends on interactions with related compounds, such as pregnancy-associated plasma protein A (PAPP-A). The aim of this study was to determine IGFR1 and PAPP-A expression both in follicles at different stages of development and in cysts, to evaluate the roles in the etiopathogenesis of COD in cattle. The mRNA expression of PAPP-A was higher in granulosa cells of large tertiary follicles than in cysts, whereas the protein PAPP-A present in the follicular fluid from these follicles showed no differences. Although no PAPP-A mRNA expression was detected in smaller tertiary follicles, in their follicular fluid, this protease was detected in lesser concentration than in cysts. The mRNA expression of IGFR1 was lower in granulosa cells from cystic follicles than in those from tertiary ones. However, the protein expression of this receptor presented the highest levels in cystic structures, probably to increase the possibility of IGF response. The data obtained would indicate that animals with COD have an altered regulation of the IGF system in the ovary, which could be involved in the pathogenesis of this disease in cattle.

Ovarian localization of 11ß-hydroxysteroid dehydrogenase (11ßHSD): effects of ACTH stimulation and its relationship with bovine cystic ovarian disease.

Cystic ovarian disease (COD) is an important cause of infertility in cattle, and ACTH has been involved in regulatory mechanisms related to ovarian function associated with ovulation, steroidogenesis, and luteal function. Here, we examined the localization of 11ß-hydroxysteroid dehydrogenase type 1 (11ßHSD1) and 11ßHSD2 proteins in the ovary of healthy cows and animals with spontaneous and ACTH-induced COD and the in vitro response of the follicular wall exposed to ACTH. After stimulation by ACTH, we documented changes in 11ßHSD expression and cortisol secretion by the follicular wall of large antral and follicular cysts. Follicular cysts showed a higher constitutive expression of both enzymes, whereas ACTH induced an increase in 11ßHSD1 in tertiary follicles and follicular cysts and a decrease in 11ßHSD2 in follicular cysts. Moderate expression of 11ßHSD1 was observed by immunohistochemistry in granulosa of control animals, with an increase (P < 0.05) from primary to secondary, tertiary, and atretic follicles. The level of immunostaining in theca interna was lower than that in granulosa. The expression of 11ßHSD2 was lower in the granulosa of primary follicles than in that of secondary, tertiary, and atretic follicles and was lower in the theca interna than in the granulosa. In ACTH-induced and spontaneously occurring follicular cysts, differences from controls were observed only in the expression of 11ßHSD1 in the granulosa, being higher (P < 0.05) than in tertiary follicles. These findings indicate that follicular cysts may be exposed to high local concentrations of active glucocorticoids and indicate a local role for cortisol in COD pathogenesis and in regulatory mechanisms of ovarian function.

Expression of melanocortin receptors mRNA, and direct effects of ACTH on steroid secretion in the bovine ovary.

Melanocortin receptors (MCRs) are involved in physiological responses to ACTH, as well as to α-, ß- and γ-melanocyte-stimulating hormone (α-, ß- and γ-MSH). Their expression has previously been analyzed in various bovine tissues; however, there are apparently no reports regarding their localization in the ovaries. In the present study, the expression of MCR mRNA in various bovine ovarian structures was characterized with reverse transcription polymerase chain reaction (RT-PCR). Furthermore, whether ACTH affected follicular components by affecting steroid secretion in fragments of ovarian follicular wall of medium and large antral follicles cultured in serum free medium with 1, 10, and 100 nM ACTH, was also determined. Melanocortin receptors mRNA was localized in the theca cells of various follicular stages, whereas only MC3R mRNA was weakly evident in granulosa cells. Melanocortin receptors 1, 2, and 3 mRNA were present in the CL, whereas in stroma, only MC2R mRNA was expressed. There were significant increases in estradiol and cortisol concentrations in response to ACTH in medium follicles, as well as increased concentrations of testosterone and cortisol in large follicles. These results confirmed earlier reports in other species, and demonstrated that MCRs were present in bovine ovaries. Since ACTH induced steroid secretion from the ovary in vitro, we inferred that melanocortin peptides could be involved in regulatory mechanisms related to ovarian functions, e.g. ovulation, steroidogenesis, and luteal function.