Abstract: 【Objective】 This experiment was to investigate the effect of cold stimulation on lung injury of piglets induced by Actinobacillus pleuropneumoniae (APP) infection and the role of silent information regulator 1 (SIRT1) in this process.【Method】 12 healthy 4-week-old male weaned Landrace piglets with similar body weight (8.0 kg±0.5 kg) were randomly divided into 4 groups:Control group (Control),cold stimulation group (Cold),APP infection group (APP) and cold stimulation with APP infection group (Cold＋APP),with 3 piglets in each group.After 1 week of pre-feeding,piglets in Control group were fed at room temperature.Piglets in Cold group were subjected to continuous cold stimulation at (4±1) ℃ for 6 h.Piglets in APP group were infected with APP by nasal drip (2×10⁹ CFU/mL),and 1.5 mL was injected into each of the left and right nostrils.Piglets in Cold＋APP group were first infected according to the APP group method,and then exposed at (4±1) ℃ for 6 h.After the experiment,the piglets were slaughtered and lung tissue samples were collected.The pathological changes of lung tissue were observed by hematoxylin-eosin (HE) staining and the fibrosis of lung tissue was observed by Masson staining.The contents of malondialdehyde (MDA) and glutathione (GSH) in lung tissues were determined by ELISA.The mRNA expression level of the inflammatory factors interleukin-6 (IL-6),IL-1β,and tumor necrosis factor-α (TNF-α) genes in lung was detected by Real-time quantitative PCR.Western blotting was used to detect the expression levels of nuclear factor E2-related factor 2 (Nrf2),Kelch-like ECH-associated protein 1 (Keap1),heme oxygenase-1 (HO-1),SIRT1,and acetylated nuclear factor κB subunit p65 (Ace-NF-κB p65) proteins. 【Result】 HE staining results showed that compared with APP group,there was a large number of inflammatory cell infiltration in lung tissues,capillary dilation and congestion in piglets in Cold＋APP group.Masson staining showed that,compared with APP group,a large number of diffuse collagen fiber deposition appeared in the lung tissues of piglets in Cold＋APP group.ELISA results showed that compared with APP group,MDA content in lung tissues of piglets in Cold＋APP group was significantly increased (P＜0.05),and GSH content was significantly decreased (P＜0.05).The results of Real-time quantitative PCR showed that compared with APP group,the mRNA relative expression levels of IL-6,IL-1β and TNF-α genes in lung tissues of piglets in Cold＋APP group were significantly increased (P＜0.05).Western blotting test results showed that compared with APP group,the relative expressions of Nrf2,HO-1 and SIRT1 proteins in lung tissues of piglets in Cold＋APP group were significantly decreased (P＜0.05)，the relative expression levels of Keap1 and Ace-NF-κB p65 proteins were significantly increased (P＜0.05).【Conclusion】 Cold stimulation could enhance the oxidative stress and inflammatory response of piglet lung tissues induced by APP infection.SIRT1 could aggravate the lung injury of piglets after APP infection under cold stimulation by regulating the acetylation of NF-κB p65.

Key words: cold stimulation; Actinobacillus pleuropneumoniae(APP); silent information regulator 1 (SIRT1); lung injury