Xingxiang Chen

Selenium-Enriched Probiotics Improve Antioxidant Status, Immune Function, and Selenoprotein Gene Expression of Piglets Raised under High Ambient Temperature

This research was conducted to evaluate the effects of selenium-enriched probiotics (SP) on growth performance, antioxidant status, immune function, and selenoprotein gene expression of piglets under natural high ambient temperature in summer. Forty-eight crossbred weanling piglets randomly allocated to four groups were fed for 42 days ad libitum a basal diet without (Con, 0.16 mg Se/kg) and with supplementation of probiotics (P, 0.16 mg Se/kg), sodium selenite (SS, 0.46 mg Se/kg), and SP (0.46 mg Se/kg). From each group, three piglets were randomly selected for blood collection on days 0, 14, 28, and 42 and tissue collection on day 42. The SP improved growth performance of piglets. Both SS and SP increased blood glutathione peroxidase activity and tissue thioredoxin reductase 1 mRNA expression, with SP being higher than SS. All P, SS, and SP supplementation increased the superoxide dismutase activity (40.1, 53.0, and 64.5%), glutathione content (84.6, 104, and 165%), TCR-induced T lymphocyte proliferation (20.8, 26.4, and 50.0%), and IL-2 concentration (24.9, 27.2, and 46.2%) and decreased malondialdehyde content (25.1, 26.3, and 49.3%), respectively. The greatest effects of SP supplementation suggest that SP may serve as a better feed additive than P or SS for piglets under high-temperature environments.

Reactive oxygen species regulate the replication of porcine circovirus type 2 via NF-κB pathway

Intracellular redox state has been suggested to have various effects on the replication of different viruses within host cells. The aim of the present study was to investigate the influence of reactive oxygen species (ROS) on replication of porcine circovirus type 2 (PCV2), in PK15 cells. Following PCV2 infection there was a time-dependent increase in ROS. Antioxidant N-acetyl-l-cysteine treatment of cells resulted in lower ROS levels and lower PCV2 replication. In contrast, treatment by buthionine sulfoximine (BSO), a GSH synthesis inhibitor, resulted in elevation of ROS levels and increased PCV2 replication. Furthermore, inhibiting the activity of NF-κB, a redox-responsive transcription factor, suppressed BSO-mediated increase of PCV2 replication, indicating that increased PCV2 replication likely occurs via ROS activation of NF-κB. Taken together, our results indicate that the generation of ROS during PCV2 infection is involved in its replication and this progression is associated with the alteration in NF-κB activity induced by ROS.

Effects of selenium-enriched probiotics on heat shock protein mRNA levels in piglet under heat stress conditions.

The effects of selenium-enriched probiotics (SP) on tissue selenium (Se) deposition, glutathione peroxidase-1 (GPx1) activity and mRNA level, and heat shock protein (Hsp) mRNA levels of piglets under heat stress conditions were investigated. A total of 48 crossbred ([Landrace × Yorkshire] × Duroc) piglets were randomly divided into 4 groups and fed a basal diet (Con, 0.16 mg Se/kg) or basal diets with added probiotics (P, 0.16 mg Se/kg), sodium selenite (SS, 0.46 mg Se/kg), or SP (0.46 mg Se/kg), respectively, for 42 days. Three piglets were randomly selected from each group for blood sample collection at days 0, 14, 28, and 42 and for liver, kidney, and spleen sample collection at day 42. The results showed that P, SS, and SP could significantly down-regulate the average mRNA levels of Hsp70 (17.3, 23.7, and 40.1%) and Hsp27 (22.4, 24.4, and 44.7%) of the tissues, respectively (P < 0.05), whereas SS and SP could significantly elevate Se concentration, GPx1 activity and mRNA level (P < 0.05). The maximal effects of these parameters were observed in SP. It was concluded that SP is a feasible dietary supplementation of piglets under heat stress conditions during the summer season.

Selenium Promotes T-Cell Response to TCR-Stimulation and ConA, but Not PHA in Primary Porcine Splenocytes

There is controversy in the literature over whether the selenium (Se) influences cellular immune responses, and the mechanisms possibly underlying these effects are unclear. In this study, the effects of Se on T-cell proliferation and IL-2 production were studied in primary porcine splenocytes. Splenocytes were treated with different mitogens in the presence of 0.5–4 µmol/L sodium selenite. Se significantly promoted T-cell receptor (TCR) or concanavalin A (ConA)-induced T-cell proliferation and IL-2 production but failed to regulate T-cell response to phytohemagglutinin (PHA). In addition, Se significantly increased the levels of cytosolic glutathione peroxidase (GPx1) and thioredoxin reductase 1 (TR1) mRNA, the activity of GPx1 and the concentration of reduced glutathione (GSH) in the unstimulated, or activated splenocytes. These results indicated that Se improved the redox status in all splenocytes, including unstimulated, TCR, ConA and PHA -stimulated, but only TCR and ConA-induced T-cell activation was affected by the redox status. N-acetylcysteine (NAC), a pharmacological antioxidant, increased T-cell proliferation and IL-2 production by TCR and ConA stimulated splenocytes but had no effect on the response to PHA in primary porcine splenocytes confirming that PHA-induced T-cell activation is insensitive to the redox status. We conclude that Se promotes GPx1 and TR1 expression and increases antioxidative capacity in porcine splenocytes, which enhances TCR or ConA -induced T-cell activation but not PHA-induced T-cell activation. The different susceptibilities to Se between the TCR, ConA and PHA -induced T-cell activation may help to explain the controversy in the literature over whether or not Se boosts immune responses.

Astragalus polysaccharides inhibits PCV2 replication by inhibiting oxidative stress and blocking NF-κB pathway

Porcine circovirus type 2 (PCV2) is the primary causative agent of porcine circovirus-associated disease (PCVAD). Astragalus polysaccharide (APS), as one kind of biological macromolecule extracted from Astragalus, has antiviral activities. This study was undertaken to explore the effect of APS on PCV2 replication in vitro and the underlying mechanisms. Our results showed that adding APS before PCV2 infection decreased significantly PCV2 DNA copies, the number of infected cells, MDA level, ROS level and NF-κB activation in PK15 cells and increased significantly GSH contents and SOD activity compared to control without APS. Oxidative stress induced by BSO could eliminate the effect of PCV2 replication inhibition by APS. LPS, as a NF-κB activator, could attenuate the effect of PCV2 replication inhibition by APS. BAY 11-7082, as a NF-κB inhibitor, could increase the effect of PCV2 replication inhibition by APS. In conclusion, APS inhibits PCV2 replication by decreasing oxidative stress and the activation of NF-κB signaling pathway, which suggests that APS might be employed for the prevention of PCV2 infection.

Effects of dietary concentrations of methionine on growth performance and oxidative status of broiler chickens with different hatching weight

1. A study was conducted to evaluate the effects of two hatching weight (HW) levels and two dietary concentrations of methionine on the growth performance and oxidative status of broilers. Male Arbor Acres chickens were divided into two groups on their HW (low and high HW, H and L). Each HW group was then distributed into two subgroups, of similar HW, receiving either low or high dietary concentrations of methionine (4.9 g methionine/kg, LM; 5.9 g methionine/kg, HM). Thus, all day-old birds were distributed into 4 treatments (H-LM, H-HM, L-LM, L-HM) × 6 replicates × 10 birds for 21 d. 2. Broilers with high HW were heavier than those with low HW during the 21 d assay, which appeared to result from increased body weight gain rather than improved feed conversion efficiency. A higher dietary concentration of methionine (5.9 g/kg) improved growth performance of broilers with low HW in terms of body weight gain and feed conversion ratio. 3. Broilers with different HW had similar antioxidant status both in serum and liver. 4. Broilers given a diet containing 5.9 g/kg methionine had enhanced serum superoxide dismutase (SOD) activity and decreased hepatic malondialdehyde (MDA) content at day 7. 5. Broilers given a diet containing 5.9 g/kg methionine had a higher hepatic reduced glutathione (GSH):glutathione disulphide (GSSG) ratio than those given a diet containing 4.9 g/kg methionine at day 21. High dietary methionine concentration reduced hepatic GSH content and glutathione peroxidase (GPX) activity of broilers with high HW at day 7 and at day 21, respectively, but increased hepatic GSH content of broilers with low HW at day 7. 6. Although broilers with different HW had similar oxidative status as indicated by several parameters in blood and liver, HW can have positive effects on the subsequent growth performance of broilers, and a higher dietary methionine concentration (5.9 g/kg) can improve growth performance and antioxidant status in broilers exhibiting low HW.

Ochratoxin A promotes porcine circovirus type 2 replication in vitro and in vivo

Abstract Ochratoxin A (OTA), a worldwide mycotoxin found in food and feeds, is a potent nephrotoxin in animals and humans. Porcine circovirus-associated disease (PCVAD), including porcine dermatitis and nephropathy syndrome, is a worldwide swine disease. To date, little is known concerning the relationship between OTA and porcine circovirus type 2 (PCV2), the primary causative agent of PCVAD. The effects of OTA on PCV2 replication and their mechanisms were investigated in vitro and in vivo. The results in vitro showed that low doses of OTA significantly increased PCV2 DNA copies and the number of infected cells. Maximum effects were observed at 0.05μg/ml OTA. The results in vivo showed that PCV2 replication was significantly increased in serum and tissues of pigs fed 75μg/kg OTA compared with the control group and pigs fed 150μg/kg OTA. In addition, low doses of OTA significantly depleted reduced glutathione and mRNA expression of NF-E2-related factor 2 and γ-glutamylcysteine synthetase; increased reactive oxygen species, oxidants, and malondialdehyde; and induced p38 and ERK1/2 phosphorylation in PK15 cells. Adding N-acetyl-l-cysteine reversed the changes induced by OTA. Knockdown of p38 and ERK1/2 by their respective specific siRNAs or inhibition of p38 and ERK1/2 phosphorylation by their respective inhibitors (SB203580 and U0126) eliminated the increase in PCV2 replication induced by OTA. These data indicate that low doses of OTA promoted PCV2 replication in vitro and in vivo via the oxidative stress-mediated p38/ERK1/2 MAPK signaling pathway. This suggests that low doses of OTA are potentially harmful to animals, as they enhance virus replication, and partly explains why the morbidity and severity of PCVAD vary significantly in different pig farms.

Oxalate-degrading capacities of lactic acid bacteria in canine feces.

In this study, lactic acid bacteria in canine feces were isolated and identified, and their oxalate-degrading capacities were evaluated. The oxalate-degrading capacities were determined for 24 of 47 (51.06%) lactic acid bacteria isolates. Of these, 8 isolates [Leuconostoc mesenteroides (RL75), Lactococcus garvieae (CD2), Lactococcus subsp. lactis (CS21), Enterococcus faecium (CL71 and CL72), and Enterococcus faecalis (CD14, CS62, and CD12)] degraded more than 5% of the oxalate present, while the others degraded less than 5% of the oxalate in vitro. Isolates that degraded more than 5% of the oxalate present were selected for further examination. The oxalate-degrading capacities of individual isolates, a mixture of Enterococcus, a mixture of Lactococcus, and a mixture of the eight isolates were evaluated in media containing different concentrations of glucose (sufficient, insufficient, or no glucose). In comparison with the control medium, all of the individual isolates and mixtures of isolates could degrade oxalate in all three groups (P<0.05). In most cases, the isolates growing in medium with 20 g/L of glucose had higher oxalate-degrading capacities than those growing in medium with 2.5 g/L of glucose or no glucose. The mixture of all isolates showed higher oxalate-degrading capacity than the individual isolates and other mixtures. The oxalate-degrading capacities of the isolates were isolate dependent.

Methionine improves breast muscle growth and alters myogenic gene expression in broilers

To investigate the mechanism underlying the regulatory effect of Met on broiler growth, the growth performance, organ development, serum profile, myogenic gene expression, and methylation of myostatin gene exon 1 region in response to dietary Met status were evaluated. A total of 192 one-day-old Arbor Acres broiler chicks were housed in 3-layer cages in a temperature-controlled room with continuous lighting. The temperature of the room was maintained at 32 to 34°C for the first 3 d and then reduced by 2 to 3°C per week to a final temperature of 20°C. Cages were randomly allocated to 2 dietary treatments with 6 replicate cages (8 males and 8 females/cage) per treatment. Control starter and finisher diets contained 0.50 and 0.43% Met, respectively. Corresponding values for a +Met treatment were 0.60 and 0.53% Met, respectively. The birds receiving the +Met diets had a greater (P < 0.05) G:F throughout the experiment. The +Met diets increased (P < 0.05) the relative weight of breast muscle and the concentrations of uric acid and triglyceride in serum at 42 d of age, whereas other serum measurements were not affected by treatments. Increased myogenic factor 5 (Myf5) and myocyte enhancer factor 2B (MEF2B) and decreased myostatin mRNA expression were observed in broilers fed the +Met diets (P < 0.05). However, methylation of myostatin gene exon 1 region was not different between groups. In conclusion, broilers fed the +Met diets increased breast muscle growth that was reflected in the expected expression of myostatin, Myf5, and MEF2B genes.

Interaction of porcine circovirus type 2 replication with intracellular redox status in vitro

Abstract Objectives Redox status influences replication of some viruses but its effect on porcine circovirus type 2 (PCV2), the primary causative agent of the emerging swine disease post-weaning multisystemic wasting syndrome is not known. The interaction of PCV2 replication with intracellular redox status in PK15 cells was examined in this study. Methods Intracellular glutathione (GSH) was measured spectrophotometrically by reaction with 5, 5′-dithiobis (2-nitrobenzoic acid). Total superoxide dismutase activity (SOD) was assayed by inhibition of oxyamine oxidation by the xanthine oxidase system. Malondialdehyde (MDA) was assayed spectrophotometrically using the thiobarbituric acid reaction. Both quantification of PCV2 DNA by real-time polymerase chain reaction and indirect immunofluorescence of PCV2-infected cells were used to evaluate the replication of PCV2. Results Both GSH and SOD decreased significantly at 48 hours after PCV2 infection, whereas MDA concentration increased significantly after 48 hour post-infection. Furthermore, PCV2 replication in PK15 cells was significantly impaired after the elevation of intracellular GSH through treatment with the antioxidant N-acetyl-l-cysteine (NAC), a precursor in GSH synthesis. In contrast, PCV2 replication in PK15 cells was enhanced after reduction of GSH levels through H2O2-mediated oxidation. In addition, NAC treatment blocked the increase of virus replication induced by H2O2. Conclusions This study suggests that PCV2 infection induces oxidative stress and that intracellular redox status influences PCV2 replication in PK15 cells.