Restraint effects on stress-related hormones and blood natural killer cell cytotoxicity in pigs with a mutated ryanodine receptor

Pathogenesis of the crosstalk between reproductive function and stress in animals - part 2: Prolactin, thyroid, inflammation and oxidative stress

Stress has a significant impact on reproductive health and fertility in both humans as well as various animal species. In particular, chronic stress can disrupt the delicate balance of the hormonal system that regulates reproductive function, leading to a variety of reproductive disorders and fertility issues. Beside the action of the hypothalamic-pituitary-adrenal (HPA) system and the sympatho-adrenomedullary system (SAM), other subsequent mechanisms have been incriminated. Thus, stress has also been associated with increased prolactin level, resulting in an inhibition of the hypothalamo-pituitary-gonadal (HPG) system leading to several reproductive disorders. Thyroid function is inhibited during chronic stress, and therefore considered an important regulator of reproductive function. Thus, and in particular by interfering with the HPA system, stress-induced immune dysregulation can have adverse effects on reproduction. In addition, oxidative stress and inflammation have been proposed as potential mechanisms by which chronic stress affects reproductive function. This is caused by an increase in reactive oxygen species (ROS) production that has a harmful effect on cells. Furthermore, inflammation can lead to tissue damage and scarring, which can affect fertility. The present review completes the complex mechanism linking stress and reproduction through the current knowledge in various animal species in a comparative point of view.

Hypothalamic-Pituitary-Adrenal Hormones Impair Pig Fertilization and Preimplantation Embryo Development via Inducing Oviductal Epithelial Apoptosis: An In Vitro Study

Previous studies show that stressful events after ovulation in sows significantly impaired the embryo cleavage with a significant elevation of blood cortisol. However, the effects of corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH) and cortisol on fertilization and embryo development remain to be specified, and whether they damage pig embryos directly or indirectly is unclear. This study demonstrated that embryo development was unaffected when pig parthenotes were cultured with different concentrations of CRH/ACTH/cortisol. However, embryo development was significantly impaired when the embryos were cocultured with pig oviductal epithelial cells (OECs) in the presence of CRH/cortisol or cultured in medium that was conditioned with CRH/cortisol-pretreated OECs (CRH/cortisol-CM). Fertilization in CRH/cortisol-CM significantly increased the rates of polyspermy. CRH and cortisol induced apoptosis of OECs through FAS and TNFα signaling. The apoptotic OECs produced less growth factors but more FASL and TNFα, which induced apoptosis in embryos. Pig embryos were not sensitive to CRH because they expressed no CRH receptor but the CRH-binding protein, and they were tolerant to cortisol because they expressed more 11-beta hydroxysteroid dehydrogenase 2 (HSD11B2) than HSD11B1. When used at a stress-induced physiological concentration, while culture with either CRH or cortisol alone showed no effect, culture with both significantly increased apoptosis in OECs. In conclusion, CRH and cortisol impair pig fertilization and preimplantation embryo development indirectly by inducing OEC apoptosis via the activation of the FAS and TNFα systems. ACTH did not show any detrimental effect on pig embryos, nor OECs.

The effect of the ryanodine receptor gene on the reproductive traits of Welsh sows

The reproductive performance of sows largely determines the efficiency of the entire pig farming industry. The purpose of our work is the evaluation of polymorphism of the ryanodine receptor gene and its impact on the reproductive traits of sows of the Welsh breed of pigs. For this study, 148 pigs of the Welsh breed were used. The reproductive traits of sows were evaluated in two adjacent generations. We conducted a comprehensive assessment of the reproductive ability of sows using the SIRQS (selection index of reproductive qualities of sows), determined phenotypic consolidation coefficients and assessed the genetic potential of the animals’ productivity. The polymorphism of the RYR1 gene was determined using polymerase chain reaction-restriction fragment length polymorphism analysis (PCR-RFLP). Data processing was performed using single-factor analysis of variance (ANOVA). Polymorphism of the ryanodine receptor gene in sows of the Welsh pig breed was evaluated. 8.0% of the animals were identified as carriers of the mutant allele of the RYR1 gene. However, no homozygous RYR1-nn animals were found. Pigs of the maternal generation carrying the homozygous NN genotype had better reproductive performance in all indicators. Sows that were carriers of the mutant allele were characterized by lower values of the genetic productivity potential compared with the entire estimated population for all productive traits. Sows which were free of the mutant allele of the RYR1 gene were characterized by large values of the SIRQS index. The values of the coefficients of phenotypic consolidation of the number of live born piglets in sows without the mutant allele were lower than in sows with the mutant allele n. Better performance of sows free of the mutant allele of the RYR1 gene was established over sows carrying it in all evaluated traits of reproductive capacity (for different traits P ranged from 0.021 to 1.0*10–4), except for number of piglets born alive per sow in the daughter generation. Sows with the NN genotype had better selection index values by 15.7% in the maternal generation and by 10.2% in the daughter generation. In order to increase the reproductive ability of sows in the studied population of Welsh pigs and achieve similar results in other herds of this breed, animals free from the mutant allele of the RYR1 gene should be selected for further reproduction in the process of breeding, while on the contrary, carriers of this gene should be gradually eliminated from the herd. To carry out breeding work, further research is needed on the entire population of Welsh pigs for the RYR1 gene.

Effects of CRH and ACTH exposure during in vitro maturation on competence of pig and mouse oocytes

Although it is known that stresses on females damage oocytes with increased production of stress hormones, whether corticotrophin-releasing hormone (CRH) or adrenocorticotropic hormone (ACTH) harm oocytes directly are largely unknown. We demonstrated that CRH exposure during in vitro maturation impaired competence of both pig and mouse cumulus-oocyte-complexes (COCs), and it impaired competence and induced apoptosis in pig cumulus-denuded oocytes (DOs) but not in mouse DOs. CRH receptor 1 was expressed in pig DOs and in cumulus cells (CCs) of both species but not in mouse DOs. In the presence of CRH, whereas mouse CCs underwent apoptosis, pig CCs did not. While pig CCs did, mouse CCs did not express CRH-binding protein. ACTH did not affect competence of either pig or mouse COCs or DOs although they all expressed ACTH receptor. Both pig and mouse CCs expressed steroidogenic acute regulatory protein (StAR), and ACTH enhanced their progesterone production while alleviating their apoptosis. Neither pig nor mouse DOs expressed StAR, but ACTH inhibited maturation-promoting factor and decelerated meiotic progression of DOs suggesting activation of protein kinase A (PKA). In conclusion, CRH impaired pig and mouse oocyte competence by interacting with CRH receptor and inducing CCs apoptosis, respectively. ACTH activated PKA in both DOs and CCs although it showed no effect on oocyte competence.

Glucocorticoids and Catecholamines Affect in Vitro Functionality of Porcine Blood Immune Cells

Simple Summary

In modern livestock husbandry, animals may face stressful events like weaning, regrouping, or transportation, all of which can impair animal welfare and health. Research in model organisms has revealed that stress hormones, such as glucocorticoids and catecholamines, strongly modulate the immune system and thus the animals’ ability to fight infections. In the pig, knowledge about this relationship is rare, and results from rodents cannot readily be transferred due to some physiological differences. Therefore, the effects of glucocorticoids and catecholamines on porcine immune cell proliferation and the production of the pro-inflammatory cytokine TNFα were investigated in an in vitro study. Blood was obtained from catheterized pigs to exclude pre-exposure to stress hormones. Glucocorticoids exerted inhibitory effects on both investigated immune functions. Catecholamines, on the other hand, showed diverse effects on lymphocyte proliferation and TNFα production of particular immune cell types. This suggests that studies from model species are not entirely transferrable to pigs. Future research should extend the preliminary findings on cytokine production and focus on the molecular mechanisms and health impacts of stress hormones in pigs.

Abstract

Stress hormones exert important modulating influences on the functionality of immune cells. Despite its major role as a livestock animal and its increasing use as an animal model, knowledge about this relationship in the domestic pig is rare. This study therefore aimed to characterize the effect of glucocorticoids and catecholamines on the proliferation and cytokine production of porcine peripheral blood mononuclear cells (PBMC). Blood was obtained from donor pigs equipped with indwelling catheters to exclude stress hormone exposition before in vitro testing. PBMC were stimulated in the presence of cortisol, adrenaline or noradrenaline at concentrations resembling low to high stress conditions. Proliferation was determined via ³H-thymidine incorporation, and TNFα producers were quantified by intracellular cytokine staining. Cortisol led to a decrease in mitogen-induced lymphocyte proliferation and the number of TNFα producing cells. In contrast, catecholamines increased proliferation while exerting repressive or no effects on the number of cytokine producers. Remarkably, in concentrations presumably found in lymphatic tissue in stress situations, noradrenaline suppressed lymphocyte proliferation completely. The shown repressive effects might especially have implications on health and welfare in pigs. The obtained results provide a preliminary database for extended studies on the molecular mechanisms of glucocorticoid and catecholamine actions on porcine immune cells.

Semaphorin-3E Produced by Immature Dendritic Cells Regulates Activated Natural Killer Cells Migration

Natural killer (NK) cells and dendritic cells (DCs) are two innate immune cells that are critical in regulating innate and adaptive immunity. Cellular functions and migratory responses of NK or DC can be further regulated in NK-DC crosstalk that involves multiple cytokine signals and/or direct cell-cell contacts. Semaphorin-3E (Sema-3E) is a member of a large family of Semaphorin proteins that play diverse regulatory functions in different biological systems upon its binding to the cognate receptors. However, possible role(s) of Sema-3E on the regulation of NK-cell functions has not been elucidated. Here, we first demonstrated that DC and NK cells expressed Sema-3E and its receptors, respectively. To formally address the importance of DC-derived Sema-3E in regulating NK-cell migration, we compared in vitro migratory responses of activated NK cells (aNKs) toward different conditioned media of DCs (immature, lipopolysaccharide- or Poly I:C-stimulated) derived from Sema-3E^+/+ or Sema-3E^-/- mice. We observed that aNKs exhibited enhanced migrations toward the conditioned medium of the immature Sema-3E^-/- DC, when compared with that of the immature Sema-3E^+/+ DC. Addition of exogenous recombinant Sema-3E to the conditioned medium of the Sema-3E^-/- immature DC (iDC) abrogated such enhanced NK-cell migration. Our current work revealed a novel role of Sema-3E in limiting NK-cell migrations toward iDC in NK-DC crosstalk.

The effects of ryanodine receptor (RYR1) mutation on natural killer cell cytotoxicity, plasma cytokines and stress hormones during acute intermittent exercise in pigs

Stress susceptibility has been mapped to a single recessive gene, the ryanodine receptor 1 (RYR1) gene or halothane (Hal) gene. Homozygous (Hal(nn)), mutated pigs are sensitive to halothane and susceptible to Porcine Stress Syndrome (PSS). Previous studies have shown that stress-susceptible RYR1 gene mutated homozygotes in response to restraint stress showed an increase in natural killer cell cytotoxicity (NKCC) accompanied by more pronounced stress-related hormone and anti-inflammatory cytokine changes. In order to determine the relationship of a RYR1 gene mutation with NKCC, plasma cytokines and stress-related hormones following a different stress model - exercise - 36 male pigs (representing different genotypes according to RYR1 gene mutation: NN, homozygous dominant; Nn, heterozygous; nn, homozygous recessive) were submitted to an intermittent treadmill walking. During the entire experiment the greatest level of NKCC and the greatest concentrations of interleukin (IL-) 6, IL-10, IL-12, interferon (IFN-)γ and tumor necrosis factor-α and stress-related hormones (adrenaline, prolactin, beta-endorphin) were observed in nn pigs, and the greatest concentration of IL-1 and growth hormone in NN pigs. Immunostimulatory effects of intermittent exercise on NKCC in nn pigs were concomitant with increases in IL-2, IL-12 and IFN-γ, the potent NKCC activators. Our findings suggest that stress-susceptible pigs RYR1 gene mutated pigs develop a greater level of NKCC and cytokine production in response to exercise stress. These results suggest that the heterogeneity of immunological and neuroendocrine response to exercise stress in pigs could be influenced by RYR1 gene mutation.

Sea buckthorn (Hippophae rhamnoides L.) oil protects against chronic stress-induced inhibitory function of natural killer cells in rats

Chronic stress can suppress natural killer (NK) cell activity; this may also be related to the effect of stress on the neuroendocrine-immune network. Sea buckthorn (SBT) (Hippophae rhamnoides L.) is a thorny nitrogen fixing deciduous shrub, native to both Europe and Asia. It has been used as a medicinal plant in Tibetan and Mongolian traditional medicines. SBT has multifarious medical properties, including anti-fatigue as well as immunoregulatory effects. This study reports the effects of SBT oil with regard to the cytotoxicity and quantity of NK cells in the blood of a chronic-stress rat model, in addition to its mechanisms on the neuroendocrine-immune network. These results show that SBT oil, given by gavage to rats with chronic stress, could increase the following: body weight, NK cell quantities, and cytotoxicity, as well as the expression of perforin and granzyme B. The results also show that SBT oil in rats with chronic stress could suppress cortisol, ACTH, IL-1β and TNF-α levels, in addition to increasing 5-HT and IFN-γ serum levels. This leads to suggest that SBT oil, in rats with chronic stress, can increase NK cell cytotoxicity by upregulating the expression of perforin and granzyme B, thus causing associated effects of SBT oil on the neuroendocrine-immune network.

The effects of ryanodine receptor 1 (RYR1) mutation on plasma cytokines and catecholamines during prolonged restraint in pigs

In the current study, plasma cytokines, including interleukin (IL) 1, IL-2, IL-6, IL-10, IL-12, interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) and catecholamines (adrenaline and noradrenaline) were evaluated during 4h restraint and recovery phase in 60 male pigs. Blood samples were collected from three groups of pigs representing different RYR1 genotypes, namely NN homozygotes (wild-type), Nn heterozygous and nn homozygous (mutant). The 4h restraint evoked an increase in plasma cytokine concentrations in each of the RYR1 genotype groups. During the restraint, the greatest concentrations of plasma IL-6, IL-10, IL-12 and TNF-α in nn homozygous pigs and IFN-γ in NN homozygous were observed. Interleukin 1, IL-2, IL-10, and TNF-α measures were positively intercorrelated in each of the three RYR1 genotype group. A positive correlation was seen between all measured cytokines (with the exception of IL-6) and plasma catecholamine concentrations in Nn heterozygous and nn homozygous pigs. The results suggest that of the cytokine parameters evaluated, IL-6, IL-10, IL-12 and TNF-α of the nn homozygous group seem to show a stronger stress-related response as compared with those of the other two (NN and Nn) groups.

Natural killer cell cytotoxicity, cytokine and neuroendocrine responses to opioid receptor blockade during prolonged restraint in pigs

This study evaluated porcine natural killer cell cytotoxicity (NKCC), plasma cytokines including interleukin (IL) 1β, IL-6, IL-10, IL-12 and tumor necrosis factor-α and plasma stress-related hormones including prolactin (PRL), growth hormone (GH), β-endorphin (BEND), ACTH and cortisol (COR) during a 4h restraint and recovery phase after saline or naloxone (1mg/kg BW) administration. The restraint preceded with saline altered NKCC and IL-12 concentration (an early from 15 to 60 min increase followed by a decrease) and increased other measured cytokines and hormones concentrations. Naloxone pretreatment blocked the suppressive effects of the restraint on NKCC and IL-12 and altered IL-10, IL-6, TNF-α, PRL and ACTH concentrations. Furthermore, in naloxone-injected pigs, a positive correlation was found between NKCC and all measured cytokines (with the exception of IL-6) and BEND, ACTH and COR. Results suggest that naloxone-sensitive opioid pathways could influence the mechanisms underlying the immune system (including NKCC) response during stress.