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.

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) 1ß, IL-6, IL-10, IL-12 and tumor necrosis factor-α and plasma stress-related hormones including prolactin (PRL), growth hormone (GH), ß-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.

Month-of-birth effect on further body size in a pig model.

Previous studies unanimously confirmed the existence of a dependence of human body size on the month of birth. The cause of the phenomenon has not been identified yet, although some possible causes were proposed e.g. seasonal changes of climatic and nutritional conditions. This study explored the issue in an animal model of 20,513 pigs. We found that body weights of 6-month-old pigs were the highest for subjects born in February, but for 2-month-old pigs the peak fell in May. Any statistical correlation between the month of birth and later body weight may be induced by (1) a long-term effect of the month of birth on further growth potential (LTE), or by (2) a short-term effect of seasonal factors differentiating the growth rate (STE), so we developed a mathematical method to separate the effects. The analysis proved that (1) the observed correlations resulted only from the STE, with May-June being the months of the highest growth tempo, and that (2) there was no significant LTE. The short-term effect was responsible for differences between patterns of weight for 2- and 6-month-old animals by the month of birth: since a pig monthly gain of weight increases with age, it is favorable for it to be born in February to attain the greatest weight at the age of 6 months, whereas 2-month-old piglets are heaviest when born a month or two before the May/June optimum for growth. The lack of a long-term effect of the month of birth on pigs' weight supports the hypothesis of the cultural character of factor(s) responsible for the relationship between the month of birth and later body size in humans.

Stress-induced enhancement of activity of lymphocyte lysosomal enzymes in pigs of different stress-susceptibility.

To evaluate a possible mechanism of stress-induced lymphopenic effect we assessed the activity of lymphocyte lysosomal enzymes (LE) under immobilization. The effects of immobilization stress on LE (AP, acid phosphatase, cathepsin D and L, beta-N-acetyl-glucosamidase) activity in lymphocytes, number of lymphocytes and plasma cortisol (COR) level in the peripheral blood were examined in the cross-bred Pietrain pigs showing genotypic (presence or lack of RyR1 gene mutation) and phenotypic (reactivity to halothane) differences. It was found that immobilization stress evoked an increase in LE which was concomitant with lymphopenia and a rise of COR level. The most pronounced enhancement of LE, which may reflect a tendency to lymphocyte cytolysis, was found in the recessive homozygotes RyR1 (nn) phenotypically defined as stress/halothane susceptible as well as in the heterozygotes RyR1 (Nn) included in the group of stress/halothane resistant. Despite this individual variability the stress-induced increase in LE activity was present in all the animals. It seems that a possibility of destruction (lysis) of lymphocyte cells should not be excluded as one of the causes of stress lymphopenia.

Missense mutations in exon 4 of the porcine LEPR gene encoding extracellular domain and their association with fatness traits.

Three non-synonymous single nucleotide polymorphisms (T221C, T232A and C233T) were detected in exon 4 of the porcine leptin receptor (LEPR) gene. The T232A substitution could be identified as a (Tsp509I) restriction fragment length polymorphism. The frequency of genotype TT varied in six genetic groups from 0.62 (Duroc) to 0.99 (Polish Large White). Sequencing of exon 4, performed for 30 animals, revealed that only two intragenic haplotypes (TC and AT at nucleotide position 232-233) were present. The phenotypic effect of the Tsp509I polymorphism was tested for the Polish Landrace (n = 241) and a synthetic line 990 (n = 243). There was no statistical evidence for the direct effect of the LEPR polymorphisms on fatness traits. However, in Polish Landrace allele A at position 232 was associated with thicker backfat over shoulder.

The influence of immobilization stress on natural killer cytotoxic activity in halothane susceptible and resistant pigs.

In halothane-susceptible (Hal+) and halothane-resistant (Hal-) Belgian Landrace pigs, the influence of immobilization stress on cytotoxic activity of natural killer (NK) cells was evaluated. Four hour immobilization causes biphasic changes in cytotoxicity, i.e. an initial increase followed by a subsequent depression. In both groups of pigs stress-induced suppression of NK cell activity lasted for several days in the post stress period. Throughout the experiment, i.e. before, during and after stress, the level of cytotoxicity was higher in Hal+ than in Hal- pigs.