Paraventricular nucleus CRH neurons regulate acute lung injury via sympathetic nerve–neutrophil axis [neutrophil]

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are severe conditions with high morbidity and mortality, and effective treatments are limited. Neuroimmune interactions play a critical role in lung homeostasis, but it remains unclear if specific brain regions regulate lung inflammation. Here, we unveil the critical role of neuroimmune signaling in ALI, focusing on the regulatory function of corticotropin-releasing hormone (CRH) neurons in the paraventricular nucleus (PVN) of the hypothalamus. Using viral tracing, chemogenetic modulation, and pharmacological interventions in mouse models of ALI induced by intranasal lipopolysaccharide and cecal ligation and puncture (CLP), we found that lung injury activated CRHPVN neurons that projected to the lung. Activation of these neurons protected mice from ALI and death, reducing neutrophil infiltration and effector functions in the lung. In contrast, inhibiting CRHPVN neurons exacerbated ALI. Notably, the beneficial impact of CRHPVN neuron activation is compromised by the pulmonary chemical sympathectomy or inhibition of the β2-adrenergic receptor. These protective effects were dependent on sympathetic nerves, with norepinephrine released locally to modulate neutrophil functions via β2-AR–β-arrestin2 signaling, inhibiting the NF-κB pathway. Our findings reveal a brain-lung axis that regulates immune responses in ALI, suggesting novel therapeutic targets for ALI and ARDS. CRH-IRES-Cre mice were injected with AAV2/9-Ef1α-DIO-mCherry (control group) or AAV2/9-Ef1α-DIO-hM3Dq-mCherry (experimental group) into the paraventricular nucleus (PVN). After viral expression, CNO was intraperitoneally injected, and 1 hour later, LPS (20 mg/kg) was administered intranasally to induce acute lung injury (ALI). Neutrophils in the lung were isolated using magnetic beads after 24 h of modeling for neutrophil bulk RNA-seq.

急性肺损伤（Acute lung injury, ALI）与急性呼吸窘迫综合征（acute respiratory distress syndrome, ARDS）均为病情危重、发病率及病死率极高的疾病，目前有效治疗手段十分有限。神经免疫交互在肺稳态维持中发挥关键作用，但目前尚不清楚特定脑区是否可调控肺部炎症反应。本研究阐明了神经免疫信号通路在急性肺损伤中的核心作用，重点关注下丘脑室旁核（paraventricular nucleus, PVN）内促肾上腺皮质激素释放激素（corticotropin-releasing hormone, CRH）神经元的调控功能。本研究通过病毒示踪（viral tracing）、化学遗传学调控（chemogenetic modulation）及药理学干预手段，在鼻内脂多糖（lipopolysaccharide, LPS）诱导与盲肠结扎穿刺（cecal ligation and puncture, CLP）构建的急性肺损伤小鼠模型中开展实验，结果发现肺损伤可激活投射至肺部的PVN脑区CRH神经元。激活此类神经元可保护小鼠免受急性肺损伤侵袭并降低死亡率，同时减少肺部中性粒细胞（neutrophil）浸润与效应功能。反之，抑制PVN脑区CRH神经元则会加重急性肺损伤。值得注意的是，肺部化学交感神经切除术或β2肾上腺素能受体（β2-adrenergic receptor）阻断可削弱PVN脑区CRH神经元激活带来的有益效应。上述保护效应完全依赖交感神经：局部释放的去甲肾上腺素（norepinephrine）可通过β2-AR–β-arrestin2信号通路调控中性粒细胞功能，进而抑制核因子κB（NF-κB）通路。本研究结果揭示了一条调控急性肺损伤免疫应答的脑-肺轴，为急性肺损伤与急性呼吸窘迫综合征提供了全新的治疗靶点。本研究将腺相关病毒载体AAV2/9-Ef1α-DIO-mCherry（对照组）或AAV2/9-Ef1α-DIO-hM3Dq-mCherry（实验组）注射至CRH-IRES-Cre小鼠的下丘脑室旁核（PVN）中。待病毒表达完成后，向小鼠腹腔注射氯氮平-N-氧化物（Clozapine N-oxide, CNO），1小时后经鼻内给予脂多糖（LPS，20 mg/kg）以构建急性肺损伤模型。造模24小时后，通过磁珠分选法分离肺部中性粒细胞，用于中性粒细胞批量转录组测序（bulk RNA-seq）。