• Modeling Mechanism：

  Polyinosinic-polycytidylic acid (Poly (I:C)) combined with moderate tidal volume mechanical ventilation (MTV) induces ARDS through a "double-hit" mechanism: ① Initial hit (Poly (I:C)): activates the TLR3 signaling pathway in lung tissue, inducing mild lung injury and upregulating the expression of inflammatory factors; ② Second hit (MTV): increases intestinal permeability through the gut-lung axis, leading to the entry of endotoxin (LPS) into the bloodstream, activating non-classical inflammasomes (caspase-11) and classical inflammasomes (NLRP3/caspase-1), cleavage of Gasdermin D (GSDMD) and inducing pyroptosis of alveolar macrophages; ③ Ultimately, it leads to the rupture of the alveolar-capillary barrier and the massive release of inflammatory factors (IL-1β, IL-6, HMGB1), mimicking the core pathological process of clinical viral infection-induced mechanical ventilation-related ARDS.

• Related Products：

  Polyinosinic-polycytidylic acid (T23171)

• Modeling Method：

  Experimental Subject：

  Mice: C57 BL/6, male, 8–10 weeks old, body weight 20–25 g

  Dosage and Administration Route：

  ① Core modelling (two-hit protocol):
  - First challenge: Tracheal injection (i.t.), Poly (I:C), 3 mg/kg, Dissolved in sterile, endotoxin-free water, Volume 100 μL;
  - Second strike: 6 hours after first strike, connect to rodent ventilator; moderate tidal volume ventilation (MTV); tidal volume 10 mL/kg, respiratory rate 140 breaths/min, PEEP 0 cm H₂O, FiO₂ 0.21; maintain ventilation for 4 hours;
  ② Single-factor control modelling (optional):
  - Poly(I:C) alone group: intratracheal injection of 3 mg/kg Poly(I:C), spontaneous breathing for 10 hours;
  - MTV-only group: intratracheal injection of 100 μL endotoxin-free water, followed by 4 hours of ventilation after 6 hours;
  ③ Blank control: intratracheal injection of 100 μL endotoxin-free water, followed by 10 hours of spontaneous breathing;
  ④ Intervention validation group (optional):
  - Pyrostat inhibitors (e.g., MCC950) or GSDMD inhibitors: Administer intraperitoneally 1 hour prior to modelling at body weight-adjusted doses;
  - RAGE antagonist: administered concurrently with modelling to block gut-lung axis signalling;

  Dosing Frequency and Duration Model：

  First strike: single administration;
  Second challenge initiated 6 hours after first challenge, lasting 4 hours

• Validation：

  1. Pathological Indicators: - Lung Tissue Injury: HE staining showed alveolar edema, congestion, neutrophil infiltration, and alveolar hemorrhage, with a pathological score of ≥12 (control group <3, p<0.001); - Barrier Function: Evans blue albumin (EBA) permeability was significantly increased (more than 60% higher than the control group, p<0.01), and the total protein concentration in bronchoalveolar lavage fluid (BALF) reached ≥600 μg/mL (p<0.001); 2. Molecular Indicators: - Pyroptosis-related: Significantly upregulated expression of cleaved caspase-11, cleaved caspase-1, and cleaved GSDMD proteins in lung tissue/alveolar macrophages (Western blot detection); - Inflammatory Factors: IL-1β, IL-6, and HMGB1 levels in BALF reached 400 pg/mL, 800 pg/mL, and 150 pg/mL, respectively. The above results showed that: - Plasma IL-18 levels reached 200 pg/mL or higher (p<0.001); - Intestinal-lung axis: Serum FITC-glucan (4 kD) concentration reached 1000 μg/mL or higher (increased intestinal permeability), and serum and BALF endotoxin (LPS) levels increased more than 3-fold (p<0.01); 3. Cellular markers: - The total number of BALF cells increased significantly, with neutrophils accounting for 78% (p<0.001); - Pyroptosis rate of alveolar macrophages reached 15% or higher (double positive staining for caspase-1 and TUNEL, p<0.001).

*Precautions： The animal should be euthanized immediately after ventilation to avoid delays that could lead to the degradation of inflammatory factors.

*References：Jin S,et,al. Mechanical Ventilation Exacerbates Poly (I:C) Induced Acute Lung Injury: Central Role for Caspase-11 and Gut-Lung Axis. Front Immunol. 2021 Jul 19;12:693874.