Expression of proinflammatory cytokine mRNA in the lymphatic organs of adult and neonatal pigs

Age-associated differential production of IFN-γ, IL-10 and GM-CSF by porcine alveolar macrophages in response to lipopolysaccharide

The aim of the present study was to investigate the age-related production variation of T helper (Th)-type cytokines (IL-2, IL-4, IFN-γ and IL-10), granulocyte macrophage-colony stimulating factor (GM-CSF) and nitric oxide (NO) by lipopolysaccharide (LPS)-stimulated porcine alveolar macrophages (AMs) in a time-dependent manner. For this purpose, AMs were isolated from 5-days (newborn), 40-days (post-weaned) and 120-days (young) old pigs. Cells were incubated for 24h in the absence or presence of increasing concentrations of LPS (0.0, 0.01, 1.0, 5.0 and 10.0 μg/mL). IL-10, IFN-γ and GM-CSF mRNA expression was upregulated in a dose-dependent manner for all age groups (P<0.05). Age-related differences included a significantly increased IL-10 mRNA and protein production in newborn piglets compared to post-weaned and young pigs. IL-10 production pattern was similar with a higher peak between 12 and 36 h post-induction in all age groups. In contrast, IFN-γ mRNA and protein level was significantly elevated in young pigs 12h and 24h post-induction, respectively, while the time course production of IFN-γ was mostly consistent in newborn and post-weaned piglets. GM-CSF mRNA expression was significantly lower in newborn piglets than in post-weaned and young pigs. The kinetic of GM-CSF expression peaked at 12h in young and post-weaned pigs and at 24h in newborn piglets. IL-4 mRNA levels were very low and no apparent change of IL-2 expression was observed following LPS stimulation in all age groups. Only very low levels of NO were detected in the cell supernatants of young pigs. Collectively, these studies suggest age-related differences in time-dependent production of IL-10, IFN-γ and GM-CSF by porcine AMs with potential immunoregulatory consequences to be explored further.

Age-related changes in phagocytic activity and production of pro-inflammatory cytokines by lipopolysaccharide stimulated porcine alveolar macrophages

The aim of the present study was to determine the age-related changes of phagocytic capacity and the kinetic production of cytokines in lipopolysaccharide-stimulated porcine alveolar macrophages. For this purpose, AMs were isolated from 5 (newborn), 40 (post-weaned) and 120 (young) day old pigs. Results of phagocytosis assay showed that AMs from newborn piglets had less phagocytic capacity than those of young pigs (P<0.05). For the kinetics study, cells and supernatant were collected at 1, 6, 12, 24, 36 and 48 h after LPS stimulation for quantification of cytokine mRNA and protein by quantitative real-time PCR and ELISA, respectively. The kinetics results showed that AMs from newborn piglets were significantly less capable of producing IL1β, IL6, IL12β, TNFα and IL8 than post-weaned piglets or young pigs. IL18 mRNA did not show significant differences between ages. MIP2 and MCP1 mRNA was higher in young pigs. Hence, higher production of cytokines by AMs may be the surfactant factors in the pulmonary host defense system. These results indicate that AMs from newborn piglets might be functionally immature, which may lead to increased susceptibility to lung infections. Future studies of cytokine kinetics in more animals are clearly needed to confirm these results across a wider age range.

Expression of Toll-like receptors and downstream genes in lipopolysaccharide-induced porcine alveolar macrophages

The aim of the present study was to determine the age-related kinetic changes of Toll-like receptors (TLRs) and downstream genes expression, and secretion of cytokine in lipopolysaccharide (LPS) stimulated porcine alveolar macrophages (AM). For this purpose, AMs were isolated from 5-day-old newborn piglets and 120-day-old young pigs. mRNA expression and cytokine measurement was determined by quantitative real-time PCR and ELISA, respectively. First, AMs were incubated for 24 h in the absence or presence of increasing concentrations of LPS. Results showed the up-regulation of TLRs 2, 4, 5 and 9 mRNA from all concentrations of LPS used, as compared to non-stimulated cells, and TLR4 was the highest expression in both ages (P<0.05). Furthermore, quantitative analysis demonstrated increased expression of mRNAs encoding TLRs 2, 4, 5 and 9, LBP, CD14, MD2, MyD88, IRAK4 and TRAF6 in both ages in a time-dependant manner (P<0.05). Overall, LPS inducible mRNA for TLR4, LBP, CD14 and MyD88 had higher expression in newborn piglets compared with those of young pigs (P<0.05). The level of cytokine protein IL6 and TNFα in supernatant fluid significantly varied with time of incubation and age of animals. Their concentration increased immediately at 1 h after LPS stimulation and remained significantly higher up to 48 h in both ages. Production of pro-inflammatory cytokine protein IL6 and TNFα in supernatant was significantly higher in young pigs than those of piglets. This study suggests that differential age-related changes in the expression of TLRs and downstream genes, and pro-inflammatory cytokine could contribute to a different age-related innate immune response during pulmonary infection. Further investigation is warranted to determine the precise effects of LPS on porcine AMs by means of a functional study across a wider age range.

Induction of apoptotic lesions in liver and lymphoid tissues and modulation of cytokine mRNA expression by acute exposure to deoxynivalenol in piglets

Six 1-month-old piglets were intravenously injected with deoxynivalenol (DON) at the concentration of 1 mg/kg body weight, with three pigs each necropsied at 6 and 24 h post-injection (PI) for investigation of hepatotoxicity and immunotoxicity with special attention to apoptotic changes and cytokine mRNA expression. Histopathological examination of the DON-injected pigs revealed systemic apoptosis of lymphocytes in lymphoid tissues and hepatocytes. Apoptosis of lymphocytes and hepatocytes was confirmed by the TdT-mediated dUTP-biotin nick end-labeling (TUNEL) method and immunohistochemical staining against single-stranded DNA and cleaved caspase-3. The number of TUNEL-positive cells in the thymus and Peyer's patches of the ileum was increased at 24 h PI compared to 6 h PI, but the peak was at 6 h PI in the liver. The mRNA expression of interleukin (IL)-1β, IL-6, IL-18, and tumor necrosis factor (TNF)-α in the spleen, thymus and mesenteric lymph nodes were determined by semi-quantitative RT-PCR, and elevated expression of IL-1β mRNA at 6 h PI and a decrease of IL-18 mRNA at 24 h PI were observed in the spleen. IL-1β and IL-6 mRNA expressions increased significantly at 6 h PI in the thymus, but TNF-α decreased at 6 h PI in the mesenteric lymph nodes. These results show the apoptosis of hepatocytes suggesting the hepatotoxic potential of DON, in addition to an immunotoxic effect on the modulation of proinflammatory cytokine genes in lymphoid organs with extensive apoptosis of lymphocytes induced by acute exposure to DON in pigs.

Age-dependent changes of proinflammatory cytokine production by porcine peripheral blood phagocytes

The aim of the present study was to determine postnatal ontogeny of proinflammatory cytokines IL-1beta, IL-8 and TNF-alpha production by in vitro stimulated porcine blood leukocytes. Four age categories of pigs were chosen. Cytokine production was determined using intracellular flow cytometry. It was found that IL-8 and TNF-alpha production by blood monocytes significantly increased during the postnatal period while production of IL-1beta remained unchanged. In blood neutrophils, the IL-8 production increased only during the postnatal period, while the levels of TNF-alpha and IL-1beta were undetectable during the whole postnatal period. Generally, the most intensive changes in cytokine production occurred before weaning. The production of low levels of cytokines by monocytes and neutrophils from young pigs was not caused by a delayed cytokine response because the cytokine production after 8-h stimulation was lower than that after 4-h stimulation in all age categories. The ontogenetical changes showed the same trends when two different stimulators (LPS, heat-inactivated E. coli) were used, suggesting that the ontogenetical changes are not caused by a simple defect in one signalling pathway, but it is probably a more complex process. No differences in cytokine production between the whole blood and the isolated cells supplemented with newborn or adult serum were found. Thus the ability of newborn monocytes and neutrophils to produce proinflammatory cytokines was not decreased due to the influence of composition of the microenvironment, where the cells were present. In conclusion, the ability of porcine blood leukocytes to produce cytokines develops during postnatal life.

Cellular localization of IL-18 and IL-18 receptor in pig anterior pituitary gland

Pro-inflammatory cytokine interleukin 18 (IL-18) has been proposed to have a role in modulating immuno-endocrine functions. Our previous study showed that IL-18 and IL-18 receptor (IL-18R) colocalized in somatotrophs of the bovine anterior pituitary gland, and the possibility that IL-18 acts on somatotrophs as an autocrine factor. In the present study, we investigated the localization of IL-18 and IL-18R in the pig anterior pituitary gland. RT-PCR analysis showed the expression of IL-18 and IL-18R mRNAin the pig anterior pituitary gland. Immunohistochemistry of IL-18 and specific hormones revealed the presence of IL-18 in somatotrophs, mammotrophs, thyrotrophs and gonadotrophs. IL-18R was localized in somatotrophs and thyrotrophs. Furthermore, the somatotrophs immunoreactive for IL-18 did not contain IL-18R. Thus, IL-18R and IL-18 were not colocalized in an identical somatotroph. These findings suggest that the localization of IL-18 in pig somatotrophs is different from that in bovine somatotrophs, although IL-18 closely associates with somatotrophs in the anterior pituitary glands in both species.

Immunohistochemical Detection of the Expression of Pro-inflammatory Cytokines by Ovine Pulmonary Macrophages

The aim of this study was to determine the expression of three proinflammatory cytokines by pulmonary macrophages of sheep in paraffin wax-embedded tissue. Samples of lung from seven healthy sheep were fixed by immersion in either 10% neutral buffered formalin, acetic formalin, paraformaldehyde-lysine-periodate or Bouin's solution and processed for structural and immunohistochemical studies. The expression of interleukin (IL)-1alpha, IL-6 and tumour necrosis factor (TNF)-alpha by pulmonary intravascular macrophages (PIMs) and alveolar macrophages (AMs) was detected by the avidin-biotin-peroxidase (ABC) technique. Bouin's solution proved to be the most suitable fixative and Tween 20 the most effective pretreatment for increasing permeability. Constitutive expression of IL-1alpha, IL-6 and TNF-alpha by both macrophage populations was detected. The number of PIMs expressing IL-1alpha (the predominant cytokine in ovine lung) was higher than that of AMs, while the expression of IL-6 was greater in AMs. No differences between PIMS and AMs were found in respect of TNF-alpha expression. The evaluation of cytokine expression represents a valuable tool for studying the pathogenesis of disease in the ovine lung.