Data_Sheet_3_Inflammasome Adaptor ASC Is Highly Elevated in Lung Over Plasma and Relates to Inflammation and Lung Diffusion in the Absence of Speck Formation.PDF

Rationale: Caspase-1 is a zymogen whose activation predominantly depends upon the assembly of ASC monomers into insoluble prion-like polymers (specks). ASC polymers support caspase-1 dimer formation inducing a proximity mediated auto-activation of caspase-1. Therefore, the amount and nature of ASC monomers and polymers in lung bronchoalveolar lavage fluid (BALF) might serve as a marker of lung inflammasome activity.
Objectives: To determine whether lung ASC concentrations or oligomerization status predicts lung function or activity of lung inflammation.
Methods: BALF ASC amount and oligomerization status was studied in three distinct cohorts: (1) young healthy non-smokers, vapers and smokers; (2) healthy HIV+ smokers who underwent detailed lung function studies; and (3) hospitalized patients with suspected pneumonia. We quantified cell free BALF ASC levels by ELISA and immunoblot. Oligomers (i.e., ASC specks) were identified by chemical crosslinking and ability to sediment with centrifugation.
Measurement and Main Results: ASC levels are significantly higher in lung lining fluid than in plasma as well as higher in smoker lungs compared to non-smoker lungs. In this context, ASC levels correlate with macrophage numbers, smoking intensity and loss of lung diffusion capacity in a well-characterized cohort of healthy HIV+ smokers. However, only monomeric ASC was found in our BALF samples from all subjects, including patients with lung infections.
Conclusions: Even though, most, if not all, extracellular ASC in BALF exists in the soluble, monomeric form, monomeric ASC concentrations still reflect the inflammatory status of the lung microenvironment and correlate with loss of lung function.

研究背景：半胱天冬酶-1（Caspase-1）是一种酶原，其激活主要依赖于凋亡相关斑点样蛋白（ASC）单体组装形成不溶性朊病毒样聚合物（斑点聚集体specks）。ASC聚合物可促进半胱天冬酶-1二聚体形成，通过邻近效应介导半胱天冬酶-1的自激活。因此，支气管肺泡灌洗液（BALF）中ASC单体与聚合物的含量及存在形式，或可作为肺部炎性小体活性的标志物。
研究目的：明确肺部ASC浓度及其寡聚化状态是否可预测肺功能或肺部炎症活动度。
研究方法：本研究针对3个独立队列开展BALF中ASC含量及寡聚化状态的分析：（1）年轻健康非吸烟者、电子烟使用者及吸烟者；（2）接受详细肺功能检测的HIV阳性吸烟健康人群；（3）疑似肺炎住院患者。我们通过酶联免疫吸附试验（ELISA）与免疫印迹（immunoblot）定量检测无细胞BALF中的ASC水平；通过化学交联法及离心沉降特性鉴定寡聚体（即ASC斑点聚集体specks）。
测量指标与主要结果：肺衬液中ASC水平显著高于血浆，且吸烟者肺组织中ASC水平高于非吸烟者。在队列特征明确的HIV阳性吸烟健康人群中，ASC水平与巨噬细胞数量、吸烟强度及肺弥散功能下降呈显著相关。但本研究所有受试者（包括肺部感染患者）的BALF样本中仅检测到单体形式的ASC。
研究结论：尽管BALF中绝大多数（若并非全部）细胞外ASC以可溶性单体形式存在，但单体ASC浓度仍可反映肺微环境的炎症状态，并与肺功能下降相关。