Oxidative stress is a main cause of piglet gut damage and diarrhea. Pyrroloquinoline quinone (PQQ), is a novel redox cofactor with antioxidant properties. However, the effect and mechanism that PQQ supplementation decreases oxidative injury in weaned pigs is not understood. Therefore, the aim of this study is to confirm the effect of PQQ on regulating redox status in weaned pigs and the mechanism for antioxidant function by porcine intestinal epithelial cell line (IPEC-J2) challenged with H2O2. Experiment 1, 144 Duroc × Landrace × Yorkshire pigs (weaned at 28 d) were allocated to four groups: received a basal diet (control) and diets supplemented with 0.15%, 0.30% and 0.45% PQQ, respectively. On d 28, growth performance, diarrhea incidence and redox factors were measured. Experiment 2, IPEC-J2 were treated with or without PQQ in the presence or absence of H2O2 for indicated time points. Experiment 3, IPEC-J2 were transfected with or without Nrf2 siRNA, then treated according to Experiment 2. The cell viability, redox factors, protein of tight junctions and Nrf2 pathway were determined. In vivo, PQQ supplementation demonstrated dose-related improvements in average daily gain, and gain to feed ratio (Linear P < 0.05). During d 0–28, compared to controls, 0.45% PQQ supplementation for pigs decreased diarrhea incidence and MDA content in liver and jejunum, and increased concentration of SOD in liver; 0.3% PQQ supplementation decreased ileal and liver MDA concentration; and 0.15% PQQ supplementation decreased ileal MDA concentration (P < 0.05). In vitro, compared to cells cultured with H2O2, pre-treatment with PQQ increased cell viability, tight junction proteins expression including ZO-1, ZO-2, Occludin and Claudin-1; and decreased ROS concentration and level of Caspase-3 (P < 0.05); as well as upregulated the ratio of Bcl-2 to Bax and protein expression of nuclear Nrf2, HO-1. Notably, Nrf2 knockdown by transfection with Nrf2 siRNA largely abrogated the positive effects of PQQ pretreatment on H2O2-induced intracellular changes. PQQ administration attenuated oxidative stress in weaned pigs which is associated with activation of Nrf2/HO-1 pathway.

中文翻译：

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吡咯并喹啉醌通过 Nrf2/HO-1 通路调节断奶仔猪体外和体内氧化还原状态

氧化应激是仔猪肠道损伤和腹泻的主要原因。吡咯并喹啉醌 (PQQ) 是一种具有抗氧化特性的新型氧化还原辅因子。然而，补充 PQQ 减少断奶猪氧化损伤的作用和机制尚不清楚。因此，本研究的目的是确认 PQQ 对断奶仔猪氧化还原状态的调节作用，以及用 H2O2 攻击的猪肠上皮细胞系 (IPEC-J2) 的抗氧化功能机制。实验 1，将 144 头杜洛克 × 长白 × 约克夏猪（28 天断奶）分为四组：分别接受基础日粮（对照）和添加 0.15%、0.30% 和 0.45% PQQ 的日粮。在第 28 天，测量生长性能、腹泻发生率和氧化还原因子。实验二，在指定的时间点，在 H2O2 存在或不存在的情况下，IPEC-J2 使用或不使用 PQQ 进行处理。实验3，IPEC-J2转染有无Nrf2 siRNA，然后按照实验2进行处理。测定细胞活力、氧化还原因子、紧密连接蛋白和Nrf2通路。在体内，PQQ 补充证明了平均日增重和增重与饲料比率的剂量相关改善（线性 P < 0.05）。在第 0-28 天，与对照组相比，添加 0.45% PQQ 的猪可降低腹泻发生率和肝脏和空肠 MDA 含量，增加肝脏 SOD 浓度；0.3% PQQ 补充降低回肠和肝脏 MDA 浓度；和 0.15% PQQ 补充降低回肠 MDA 浓度（P < 0.05）。在体外，与用 H2O2 培养的细胞相比，用 PQQ 预处理增加了细胞活力，紧密连接蛋白表达，包括 ZO-1、ZO-2、Occludin 和 Claudin-1；ROS 浓度和 Caspase-3 水平降低（P < 0.05）；以及上调 Bcl-2 与 Bax 的比率和核 Nrf2、HO-1 的蛋白质表达。值得注意的是，通过用 Nrf2 siRNA 转染 Nrf2 敲低在很大程度上消除了 PQQ 预处理对 H2O2 诱导的细胞内变化的积极影响。PQQ 给药减弱了断奶猪的氧化应激，这与 Nrf2/HO-1 通路的激活有关。通过用 Nrf2 siRNA 转染 Nrf2 敲低在很大程度上消除了 PQQ 预处理对 H2O2 诱导的细胞内变化的积极影响。PQQ 给药减弱了断奶猪的氧化应激，这与 Nrf2/HO-1 通路的激活有关。通过用 Nrf2 siRNA 转染 Nrf2 敲低在很大程度上消除了 PQQ 预处理对 H2O2 诱导的细胞内变化的积极影响。PQQ 给药减弱了断奶猪的氧化应激，这与 Nrf2/HO-1 通路的激活有关。