DataSheet_3_Effects of OxyR regulator on oxidative stress, Apx toxin secretion and virulence of Actinobacillus pleuropneumoniae.xlsx

IntroductionActinobacillus pleuropneumoniae, the causative agent of porcine pleuropneumonia, poses a significant threat to global swine populations due to its high prevalence, mortality rates, and substantial economic ramifications. Understanding the pathogen's defense mechanisms against host-produced reactive oxygen species is crucial for its survival, with OxyR, a conserved bacterial transcription factor, being pivotal in oxidative stress response.
MethodsThis study investigated the presence and role of OxyR in A. pleuropneumoniae serovar 1-12 reference strains. Transcriptomic analysis was conducted on an oxyR disruption mutant to delineate the biological activities influenced by OxyR. Additionally, specific assays were employed to assess urease activity, catalase expression, ApxI toxin secretion, as well as adhesion and invasion abilities of the oxyR disruption mutant on porcine 3D4/21 and PT cells. A mice challenge experiment was also conducted to evaluate the impact of oxyR inactivation on A. pleuropneumoniae virulence.
ResultsOxyR was identified as a conserved regulator present in A. pleuropneumoniae serovar 1-12 reference strains. Transcriptomic analysis revealed the involvement of OxyR in multiple biological activities. The oxyR disruption resulted in decreased urease activity, elevated catalase expression, enhanced ApxI toxin secretion—attributed to OxyR binding to the apxIBD promoter—and reduced adhesion and invasion abilities on porcine cells. Furthermore, inactivation of oxyR reduced the virulence of A. pleuropneumoniae in a mice challenge experiment.
DiscussionThe findings highlight the pivotal role of OxyR in influencing the virulence mechanisms of A. pleuropneumoniae. The observed effects on various biological activities underscore OxyR as an essential factor contributing to the pathogenicity of this bacterium.

引言
胸膜肺炎放线杆菌（Actinobacillus pleuropneumoniae）是猪胸膜肺炎的病原菌，因其高流行率、致死率及显著的经济影响，对全球猪群造成严重威胁。解析该病原菌抵御宿主产生的活性氧的防御机制对其存活至关重要，而OxyR作为一种保守的细菌转录因子，在氧化应激应答中发挥关键作用。
材料与方法
本研究针对血清型1至12的胸膜肺炎放线杆菌参考菌株，探究了OxyR的存在情况及其功能。通过构建oxyR缺失突变株并开展转录组分析，本研究明确了OxyR所调控的各类生物学活性。此外，本研究采用特异性实验手段，检测了oxyR缺失突变株在猪源3D4/21及PT细胞上的脲酶活性、过氧化氢酶表达水平、ApxI毒素分泌情况，以及黏附与侵袭能力。本研究还实施了小鼠攻毒试验，以评估oxyR失活对胸膜肺炎放线杆菌毒力的影响。
结果
本研究证实OxyR是一种保守调控因子，存在于血清型1至12的胸膜肺炎放线杆菌参考菌株中。转录组分析结果显示，OxyR参与调控多种生物学活性。oxyR缺失会导致脲酶活性降低、过氧化氢酶表达上调、ApxI毒素分泌增强——该现象归因于OxyR结合apxIBD启动子区域——同时会削弱菌株在猪源细胞上的黏附与侵袭能力。此外，小鼠攻毒试验结果表明，oxyR失活会降低胸膜肺炎放线杆菌的毒力。
讨论
本研究结果凸显了OxyR在调控胸膜肺炎放线杆菌毒力机制中的关键作用。针对各类生物学活性的上述调控效应进一步证实，OxyR是影响该病原菌致病性的核心因子。