Construction Strategies and Evaluation Indicators for Animal Models of Acute Lung Injury

Animal models of acute lung injury are used to simulate alveolar epithelial and pulmonary vascular endothelial injury, inflammatory cell infiltration, disruption of the alveolar-capillary barrier, pulmonary edema, and hypoxemic respiratory dysfunction. They are important experimental systems for studying the pathogenesis of ALI/ARDS, screening anti-inflammatory and barrier-protective agents, and evaluating the repair process after lung injury.

Keywords: acute lung injury; ALI animal model; ARDS model; LPS-induced lung injury; bleomycin; oleic acid-induced lung injury; pulmonary edema; bronchoalveolar lavage fluid

1 Experimental Positioning of Animal Models of Acute Lung Injury

1.1 Core Pathological Processes Simulated by the Models

(1) Alveolar-capillary barrier injury

The core pathological basis of ALI is injury to alveolar epithelial cells and pulmonary vascular endothelial cells. When barrier permeability increases, plasma proteins, inflammatory cells, and fluid enter the alveolar space or pulmonary interstitium, resulting in non-cardiogenic pulmonary edema. In animal models, the degree of barrier injury can be evaluated by lung wet/dry weight ratio, BALF protein content, Evans blue extravasation, lung tissue edema score, and oxygenation parameters.

(2) Inflammatory cell infiltration

Early acute lung injury is often accompanied by neutrophil recruitment, macrophage activation, and inflammatory cytokine release. LPS, acid aspiration, oleic acid, and ischemia-reperfusion models can all induce marked inflammatory responses, but the source of inflammation differs. Airway LPS primarily reflects local alveolar inflammation, intraperitoneal or intravenous LPS more closely reflects systemic inflammation followed by pulmonary endothelial injury, while the oleic acid model is characterized predominantly by vascular endothelial injury and pulmonary edema.

(3) Impaired gas exchange

Alveolar exudation, hyaline membrane-like changes, alveolar collapse, microthrombosis, and decreased lung compliance can reduce gas exchange efficiency and, in severe cases, develop into ARDS-like hypoxemic respiratory dysfunction. In animal experiments, comprehensive evaluation should combine blood gas analysis, oxygenation index, lung compliance, airway resistance, and lung histopathology, rather than relying solely on the result of a single inflammatory factor.

1.2 Basis for Model Selection

(1) Injury source

Direct lung injury models include intratracheal LPS instillation, acid aspiration, bleomycin exposure, and airway pathogen-associated stimulation, mainly simulating inflammatory injury of the alveolar epithelium, airway, and alveolar space. Indirect lung injury models include intraperitoneal or intravenous LPS administration, oleic acid administration, ischemia-reperfusion, and sepsis-associated models, which more strongly reflect systemic inflammation, vascular endothelial injury, and pulmonary microcirculatory dysfunction.

(2) Research objective

If the study focuses on inflammatory initiation, TLR4 signaling, and neutrophil infiltration, the LPS model is more commonly used. If the focus is repair after alveolar epithelial injury and the transition from acute inflammation to fibrosis, the bleomycin model is more suitable. If the study focuses on pulmonary vascular endothelial disruption, pulmonary edema, and ARDS-like barrier dysfunction, the oleic acid model is more representative. If ventilator-associated lung injury is being investigated, high tidal volume or mechanical ventilation-related models should be selected.

(3) Time window

ALI models have clear time-dependent characteristics. LPS models often show an inflammatory peak within several hours to 24 h. Bleomycin models initially present with acute inflammation and then progress into a fibrotic phase. Oleic acid models usually act rapidly and produce marked pulmonary edema and oxygenation impairment within a short period. Before formal experiments, sampling time points should be determined through time-course preliminary studies.

Table 1 Key Points for Selecting Animal Models of Acute Lung Injury

Model Type	Representative Induction Method	Main Injury Mechanism	Typical Phenotype	Suitable Research Directions
Airway LPS administration model	Intratracheal instillation or aerosolized LPS	TLR4-mediated inflammation, neutrophil infiltration, alveolar epithelial injury	Increased BALF cell count, elevated inflammatory factors, alveolitis	Inflammatory initiation, anti-inflammatory agents, alveolar barrier studies
Systemic LPS administration model	Intraperitoneal or intravenous LPS	Systemic inflammatory response, pulmonary vascular endothelial injury	Increased serum inflammatory factors, pulmonary edema, endothelial injury	Sepsis-associated lung injury, endotoxin response
Bleomycin model	Intratracheal administration	DNA damage, oxidative stress, epithelial injury, and fibrotic progression	Early inflammation and late collagen deposition	Lung injury repair, inflammation-to-fibrosis transition
Oleic acid model	Intravenous oleic acid injection	Pulmonary capillary endothelial injury, pulmonary edema, microthrombosis	Acute pulmonary edema, hemorrhage, reduced oxygenation	ARDS-like pulmonary edema, endothelial protection studies
Acid aspiration model	Intratracheal instillation of acidic solution	Chemical injury mimicking gastric acid aspiration and epithelial disruption	Epithelial necrosis, alveolar exudation, inflammatory infiltration	Aspiration-induced lung injury, airway epithelial injury
Mechanical ventilation model	High tidal volume mechanical ventilation	Mechanical stretch, barrier disruption, inflammatory amplification	Decreased lung compliance, pulmonary edema, increased inflammatory factors	Ventilator-associated lung injury
Ischemia-reperfusion model	Reperfusion after pulmonary hilar occlusion	Ischemia/hypoxia, ROS burst, endothelial injury	Pulmonary edema, inflammatory response, oxidative injury	Transplantation, shock, and reperfusion injury studies

2 LPS-Induced Acute Lung Injury Model

2.1 Model Mechanism

(1) Direct lung injury induced by airway LPS

Airway administration of LPS directly activates alveolar macrophages, alveolar epithelial cells, and local airway immune cells. Through TLR4-related pathways, it induces the release of inflammatory mediators such as TNF-α, IL-1β, IL-6, CXCL1, and MCP-1, and promotes neutrophil migration into lung tissue and BALF. This model is suitable for studying early inflammatory initiation in ALI, alveolar barrier function, and the effects of local anti-inflammatory interventions.

(2) Indirect lung injury induced by systemic LPS

Intraperitoneal or intravenous LPS administration can induce systemic inflammatory responses. Inflammatory factors, complement activation, and endothelial injury further affect pulmonary microvessels. Compared with the airway LPS model, the systemic LPS model is more suitable for simulating sepsis-associated lung injury and systemic inflammation-mediated pulmonary vascular endothelial dysfunction, although the direct local injury to alveolar epithelium may be relatively weaker.

2.2 Modeling Design

(1) Administration route

Intratracheal instillation, intranasal administration, aerosol inhalation, intraperitoneal injection, and intravenous injection can all be used for LPS-induced lung injury. Intratracheal instillation allows controllable dosing and clear pulmonary exposure, but requires greater technical proficiency. Intranasal administration is relatively simple, but is affected by inhalation efficiency. Intraperitoneal or intravenous administration is more suitable for studies of systemic inflammation-associated lung injury.

(2) Sampling time

In the LPS model, inflammatory factors and neutrophil recruitment usually increase several hours after administration, while obvious lung tissue inflammatory infiltration and barrier injury can be observed at around 24 h. If early signaling pathways are being studied, earlier time points may be selected. If tissue injury, pulmonary edema, and pathological changes are being evaluated, the sampling window should be selected based on BALF results, lung wet/dry weight ratio, and HE staining.

2.3 Evaluation Indicators

(1) Inflammatory response

BALF total cell count, neutrophil proportion, lung tissue MPO activity, TNF-α, IL-6, IL-1β, and chemokines can be used to evaluate inflammatory intensity in the LPS model. Elevated inflammatory factors should be interpreted together with pathological changes and BALF cell infiltration, rather than directly equating a single cytokine change with successful model establishment.

(2) Barrier injury

Lung wet/dry weight ratio, BALF protein concentration, Evans blue extravasation, lung tissue edema score, and blood oxygen changes can reflect disruption of the alveolar-capillary barrier. If the study focuses on drug-mediated barrier protection, indicators related to pulmonary edema and permeability should be prioritized instead of measuring inflammatory factors alone.

Table 2 Key Parameters of LPS-Induced Acute Lung Injury Models

Design Element	Optional Strategy	Main Impact	Selection Recommendation
Administration route	Intratracheal instillation, intranasal administration, aerosolization, intraperitoneal injection, intravenous injection	Determines the characteristics of direct or indirect lung injury	Select according to whether local or systemic inflammation is being studied
Animal strain	C57BL/6, BALB/c, rats, etc.	Affects LPS sensitivity and inflammatory intensity	Use animals of the same strain and under the same conditions in one experiment
Sampling time	Early, intermediate, and recovery phases	Affects inflammatory factors, cellular infiltration, and pathological results	Determine the peak time by preliminary experiments
Evaluation indicators	BALF, pathology, pulmonary edema, blood oxygen	Determines the dimensions of model interpretation	Combine at least inflammatory and barrier indicators
Control settings	Saline, vehicle, positive drug	Affects reliability of efficacy evaluation	Set controls with the same route and volume

3 Bleomycin-Induced Lung Injury Model

3.1 Model Mechanism

(1) Acute inflammatory phase

Bleomycin (BLM) can induce DNA damage, reactive oxygen species generation, and alveolar epithelial cell death. Early pathological manifestations include alveolitis, neutrophil and lymphocyte infiltration, alveolar epithelial injury, and increased vascular permeability. This phase can be used to evaluate epithelial cell injury, inflammatory responses, and mechanisms of acute lung injury repair.

(2) Fibrotic progression phase

After acute inflammation, the BLM model can enter a stage characterized by fibroblast activation, extracellular matrix deposition, and pulmonary structural remodeling. If the research focuses on fibrotic progression after ALI, aberrant epithelial-mesenchymal repair, or antifibrotic drugs, this model is more suitable than a simple LPS model. If only short-term acute inflammation is being studied, early sampling points should be selected.

3.2 Modeling Design

(1) Administration route

BLM is commonly administered intratracheally to establish a lung injury model, although other airway exposure methods can also be used. Uniform administration is critical for model stability. Intratracheal administration should ensure that the solution enters the lungs rather than the esophagus, and operation-induced trauma that may cause additional lung injury should be avoided.

(2) Stage classification

The BLM model should be divided into inflammatory and fibrotic phases according to the research objective. Early sampling is suitable for observing BALF cell count, inflammatory factors, epithelial injury, and pulmonary edema. Later sampling is more suitable for detecting collagen deposition, Masson staining, hydroxyproline content, α-SMA, and fibrosis score.

3.3 Scope of Application

(1) Advantages

The BLM model has relatively clear pathological stages and can connect acute epithelial injury, inflammatory response, and subsequent fibrotic progression. It is suitable for studying failed repair after lung injury, persistent inflammatory activation, and fibrosis progression. Its operational cost is relatively manageable, and the model has a strong literature base, facilitating mechanistic research and pharmacodynamic evaluation.

(2) Limitations

The disease course induced by BLM in mice shows a certain degree of reversibility and does not fully reproduce chronic progressive pulmonary fibrosis in humans. If the article or experimental topic is limited to acute lung injury, an early sampling window should be clearly selected to avoid directly interpreting fibrotic-phase results as conclusions about early ALI inflammation.

Table 3 Stage-Specific Evaluation Indicators for the Bleomycin Model

Stage	Main Pathological Changes	Recommended Indicators	Suitable Research Questions
Early inflammatory phase	Epithelial injury, inflammatory infiltration, alveolar exudation	BALF cell count, TNF-α, IL-6, HE staining, lung wet/dry weight ratio	Acute lung injury, epithelial injury, and inflammatory response
Transitional phase	Persistent inflammation, abnormal repair, fibroblast activation	TGF-β, α-SMA, collagen-related genes, pathological score	Injury repair and initiation of fibrosis
Fibrotic phase	Collagen deposition, lung structural remodeling, decreased lung compliance	Masson staining, hydroxyproline, Ashcroft score, lung function	Pulmonary fibrosis and evaluation of antifibrotic efficacy

4 Oleic Acid-Induced Acute Lung Injury Model

4.1 Model Mechanism

(1) Vascular endothelial injury

Oleic acid (OA) can directly injure pulmonary capillary endothelial cells, leading to increased pulmonary vascular permeability, plasma component leakage, pulmonary interstitial and alveolar edema, and may be accompanied by microthrombosis, erythrocyte extravasation, and reduced oxygenation. This model more closely reflects the rapid disruption of the alveolar-capillary barrier and non-cardiogenic pulmonary edema that characterize ARDS.

(2) Inflammation and oxidative stress

Although OA models can show inflammatory cell infiltration and oxidative stress changes, the primary initiating factor is not typical pathogen-associated molecular recognition, but fatty acid-related endothelial injury and microcirculatory disturbance. Therefore, this model is suitable for studying endothelial protection, permeability regulation, and pulmonary edema clearance, but is not the preferred model for studying inflammatory initiation mechanisms.

4.2 Modeling Design

(1) Administration route

OA models are commonly established by intravenous administration. Administration speed, solution homogeneity, and the circulatory status of animals have obvious effects on injury severity. Excessively rapid administration or overly high doses may cause severe lung injury and increased mortality. Therefore, preliminary experiments should simultaneously monitor respiratory status, mortality, degree of pulmonary edema, and pathological changes.

(2) Sampling window

OA models act rapidly. Increased lung wet/dry weight ratio, reduced blood oxygen, increased BALF erythrocytes and protein, pulmonary hemorrhage, and edema can appear within a short period. If acute barrier disruption is being studied, early time points should be selected. If secondary inflammatory changes are being investigated, later time points can be combined to observe neutrophil infiltration and inflammatory factor changes.

4.3 Scope of Application

(1) Advantages

The OA model has a pronounced phenotype, rapid onset, and prominent pulmonary edema and endothelial injury features. It is suitable for evaluating intervention strategies that improve pulmonary microvascular permeability, reduce pulmonary edema, protect endothelial cells, and maintain oxygenation function.

(2) Limitations

The OA model can produce severe injury, with relatively high risks of mortality and operational variation. Etiologically, it does not fully represent infection-, sepsis-, or immune-mediated ALI. When used for pharmacodynamic evaluation, moderate injury intensity should first be established to avoid a model that is too severe to reveal drug-protective effects.

Table 4 Comparison of LPS, BLM, and OA Models

Model	Main Target	Typical Phenotype	Main Advantages	Main Limitations
LPS model	Alveolar macrophages, epithelial cells, endothelial cells	Elevated inflammatory factors, neutrophil infiltration, alveolitis	Simple operation; suitable for inflammatory mechanism studies	Does not fully simulate late-stage ARDS pathology
BLM model	Alveolar epithelium, DNA damage, and repair system	Early inflammation and late fibrosis	Can be used to study the transition from inflammation to fibrosis	The acute and fibrotic phases must be clearly distinguished
OA model	Pulmonary vascular endothelium and microcirculation	Acute pulmonary edema, hemorrhage, reduced oxygenation	Prominent ARDS-like barrier injury	Severe injury and relatively high mortality risk

5 Other Common Acute Lung Injury Models

5.1 Acid Aspiration Model

(1) Model mechanism

The acid aspiration model is used to simulate chemical lung injury caused by aspiration of gastric contents. Acidic stimulation directly damages the airway and alveolar epithelium, causing protein exudation, inflammatory cell infiltration, alveolar edema, and impaired gas exchange. This model is suitable for studying aspiration-induced lung injury, airway epithelial repair, and epithelial barrier protection.

(2) Evaluation focus

The acid aspiration model should focus on epithelial injury in lung tissue, BALF protein content, inflammatory cell infiltration, lung wet/dry weight ratio, and pathological scoring. If bacterial components or gastric contents are added to the model design, the combined effects of acidic chemical injury and infection/inflammatory components should be distinguished.

5.2 Mechanical Ventilation-Associated Lung Injury Model

(1) Model mechanism

High mechanical stretch can cause alveolar overdistension, disruption of epithelial and endothelial barriers, activation of mechanosensitive inflammatory pathways, and pulmonary edema formation. This is an important model for studying ventilator-associated lung injury. The model is more suitable for evaluating mechanical force, lung compliance, and barrier function changes than for studying the effects of simple inflammatory inducers.

(2) Evaluation focus

Mechanical ventilation models should focus on tidal volume, ventilation duration, PEEP setting, lung compliance, airway pressure, pulmonary edema, and histopathology. If combined with LPS or acid aspiration, the model can simulate a “two-hit” injury, but the contribution of each inducing factor to the results should be clearly defined.

5.3 Ischemia-Reperfusion Model

(1) Model mechanism

Pulmonary ischemia-reperfusion injury commonly occurs in lung transplantation, shock resuscitation, and pulmonary circulation occlusion-related scenarios. During ischemia, tissue hypoxia and metabolic disturbances occur; after reperfusion, ROS generation, endothelial injury, complement activation, and neutrophil infiltration jointly cause acute lung injury.

(2) Evaluation focus

This model is suitable for studying oxidative stress, endothelial injury, microcirculatory dysfunction, and transplantation-associated lung injury. Common indicators include lung wet/dry weight ratio, MDA, SOD, MPO, inflammatory factors, pathological score, and oxygenation function. Ischemia duration, reperfusion duration, and blood flow restoration conditions should be strictly controlled during the experiment.

Table 5 Applicable Scenarios of Other ALI Models

Model	Main Simulated Scenario	Key Evaluation Indicators	Suitable Directions
Acid aspiration model	Gastric acid aspiration and chemical epithelial injury	BALF protein, epithelial injury, pulmonary edema, HE staining	Aspiration-induced lung injury and epithelial protection
Mechanical ventilation model	Ventilator-associated lung injury	Lung compliance, airway pressure, pulmonary edema, inflammatory factors	Mechanisms of mechanical stretch and barrier disruption
Ischemia-reperfusion model	Lung transplantation, shock resuscitation, circulatory occlusion	MDA, SOD, MPO, pulmonary edema, oxygenation indicators	Reperfusion injury and endothelial protection
Combined-hit model	Infection + ventilation, acid aspiration + LPS, etc.	Inflammation, pulmonary edema, pathology, lung function	Simulation of clinically complex ALI/ARDS

6 Evaluation Indicators for Acute Lung Injury Models

6.1 Pulmonary Edema and Barrier Function

(1) Lung wet/dry weight ratio

The lung wet/dry weight ratio is one of the most commonly used indicators for evaluating pulmonary edema and reflects changes in tissue water content. During sampling, the lung lobe, weighing time, drying conditions, and calculation method should be standardized. When combined with BALF protein, Evans blue extravasation, and pathological edema scoring, it can more accurately evaluate barrier permeability.

(2) BALF protein and cell count

Increased total BALF protein indicates increased alveolar-capillary barrier permeability, while increased total BALF cell count and neutrophil proportion indicate inflammatory cell entry into the alveolar space. Lavage volume, recovery rate, and centrifugation conditions can affect the results and should be strictly standardized within the same experiment.

6.2 Inflammation and Oxidative Stress

(1) Inflammatory factors

TNF-α, IL-1β, IL-6, CXCL1, MCP-1, and related factors can be used to evaluate inflammatory pathway activation. Changes in inflammatory factors are most typical in LPS models. OA and acid aspiration models can also show secondary inflammatory responses, but inflammatory factors should not be used as the only primary endpoint for all models.

(2) Oxidative stress

MDA, SOD, GSH, CAT, MPO, and ROS can be used to evaluate oxidative stress, antioxidant capacity, and neutrophil-associated injury. Oxidative stress indicators can be included in BLM, OA, ischemia-reperfusion, and mechanical ventilation models, but the specific selection should correspond to the model mechanism.

6.3 Lung Histopathology and Functional Evaluation

(1) Histopathology

HE staining can reveal alveolar septal thickening, inflammatory infiltration, alveolar hemorrhage, pulmonary edema, hyaline membrane-like deposition, and tissue architecture disruption. If late-stage fibrosis after BLM is being studied, Masson staining, collagen deposition, and fibrosis scoring should be added. If cell death is being investigated, TUNEL or cleaved caspase-3 detection can be included.

(2) Lung function and blood gas analysis

Lung compliance, airway resistance, arterial oxygen partial pressure, and oxygenation index can reflect functional impairment in ALI. If ARDS-like hypoxemic respiratory dysfunction is the focus, functional indicators should be prioritized in the evaluation system. If only pathology and inflammatory factors are assessed, the degree of lung functional impairment cannot be fully explained.

Table 6 Common Evaluation Indicators for Acute Lung Injury Models

Indicator Category	Representative Indicators	Main Significance	Applicable Models
Pulmonary edema	Lung wet/dry weight ratio, BALF protein, Evans blue extravasation	Evaluation of vascular permeability and pulmonary edema	LPS, OA, acid aspiration, mechanical ventilation, ischemia-reperfusion
Inflammatory infiltration	BALF total cell count, neutrophil proportion, MPO	Evaluation of inflammatory cell recruitment	LPS, acid aspiration, BLM, ischemia-reperfusion
Inflammatory factors	TNF-α, IL-1β, IL-6, CXCL1, MCP-1	Evaluation of inflammatory pathway activation	LPS, DAMP-related models, mechanical ventilation models
Oxidative stress	MDA, SOD, GSH, ROS, CAT	Evaluation of oxidative injury and antioxidant defense	BLM, OA, ischemia-reperfusion, mechanical ventilation
Histopathology	HE staining, lung injury score, hyaline membrane, hemorrhage, edema	Evaluation of tissue structural injury	All ALI models
Fibrotic progression	Masson staining, hydroxyproline, α-SMA, collagen	Evaluation of post-injury fibrosis	BLM model
Lung function	Lung compliance, airway resistance, blood gas analysis	Evaluation of respiratory dysfunction	OA, mechanical ventilation, severe LPS, or combined models

7 Selection of Related Reagents and Materials

Table 7 Products Related to Acute Lung Injury Model Establishment

Cat. No.	Product Name	Grade & Purity	Model/Application Category	Application Positioning
L1508370	Lipopolysaccharide (LPS) Solution (500X)	sterile-filtered,BioReagent,500X (1mg/mL)	LPS-induced ALI model	Used for LPS airway administration, intraperitoneal or intravenous stimulation-related acute lung injury models, and in vitro inflammatory stimulation validation
L384562	Lipopolysaccharides from Escherichia coli O111:B4	purified by phenol extraction	LPS-induced ALI model	Used for studies of endotoxin-induced pulmonary inflammation, neutrophil infiltration, and TLR4-related mechanisms
L386714	Lipopolysaccharide(LPS)	Derived from Escherichia coli 055:B5, purified by trichloroacetic acid extraction	LPS-induced ALI model	Used for LPS-related inflammatory lung injury and endotoxin response studies
L755723	Lipopolysaccharides from Escherichia coli O127:B8	γ-irradiated, BioReagent, for cell culture	LPS in vitro inflammatory stimulation	Suitable for in vitro validation in alveolar macrophages, lung epithelial cells, or inflammatory pathways
L755735	Lipopolysaccharides from Escherichia coli O26:B6	γ-irradiated, BioReagent, for cell culture	LPS in vitro inflammatory stimulation	Used for endotoxin stimulation and anti-inflammatory efficacy validation in cell culture systems
L1435638	Lipopolysaccharides, from E. coli O111:B4		LPS-induced ALI model	Can be used for LPS-induced inflammatory responses and optimization of acute lung injury modeling conditions
L1435394	Lipopolysaccharides, from E. coli O127:B8		LPS-induced ALI model	Can be used to compare the effects of LPS from different sources on pulmonary inflammatory responses
L1435329	Lipopolysaccharides, from E. coli O26:B6		LPS-induced ALI model	Can be used for LPS-related pulmonary inflammation and endotoxin stimulation experiments
B107423	Bleomycin Sulfate(mixture)	1.5-2.0 units/mg	Bleomycin lung injury/pulmonary fibrosis model	Used for BLM-induced early pulmonary inflammatory injury, epithelial injury, and late fibrotic progression studies
B408760	Bleomycin (NSC125066) sulfate	10mM in DMSO	In vitro pulmonary epithelial injury validation	Suitable for cell-level bleomycin injury, epithelial cell death, or supplementary fibrosis mechanism experiments
O1520032	Oleic acid	Injection grade,≥98%	Oleic acid-induced ALI/ARDS-like model	Used for oleic acid-induced pulmonary vascular endothelial injury, pulmonary edema, and ARDS-like permeability elevation models
O431503	Oleic acid	Moligand™, BioReagent, for cell culture	In vitro fatty acid injury/mechanistic validation	Used in cell culture systems for oleic acid-related lipid stress or endothelial/epithelial injury mechanisms
O108485	Oleic acid	Moligand™, ≥99%(HPLC)	Oleic acid model/method validation	Suitable for optimization of oleic acid-induced modeling conditions and high-purity oleic acid-related experiments
O108486	Oleic acid	Moligand™, analytical standard, ≥99%(GC)	Oleic acid standard	Suitable for oleic acid-related method validation or quantitative analysis
O1456059	Oleic acid	USP, ≥98%	Oleic acid model/experimental preparation	Can be used in oleic acid-induced lung injury-related experimental systems

Table 8 Products for Evaluating Inflammation and Endotoxin Responses in Acute Lung Injury

Cat. No.	Product Name	Grade & Purity	Indicator Category	Application Positioning
M1515794	Myeloperoxidase (MPO) Activity Assay Kit (o-Dianisidine, Micro Method)	BioReagent	Neutrophil infiltration/MPO activity	Used for detecting MPO activity in lung tissue; suitable for evaluating neutrophil recruitment and inflammatory injury in ALI models
EJ1513379	Mouse Myeloperoxidase (MPO) ELISA Kit	BioReagent	Mouse MPO	Used for detecting MPO levels in mouse LPS, BLM, OA, and other lung injury models
EJ1512429	Rat Myeloperoxidase (MPO) ELISA Kit	BioReagent	Rat MPO	Used for evaluating neutrophil infiltration in rat acute lung injury models
EJ1511731	Mouse Interleukin 1 Beta (IL-1β) ELISA Kit	BioReagent	Mouse IL-1β	Used for detecting inflammasome-related factors and acute inflammatory responses in mouse ALI models
EJ1512912	Mouse Interleukin 1 Beta (IL-1β) ELISA Kit	BioReagent	Mouse IL-1β	Used for IL-1β detection related to acute pulmonary inflammation and alveolar injury in mice
EJ1512147	Rat Interleukin 1 Beta (IL-1β) ELISA Kit	BioReagent	Rat IL-1β	Used for evaluating IL-1β inflammatory responses in rat ALI models
EJ1511733	Mouse Interleukin 6 (IL-6) ELISA Kit	BioReagent	Mouse IL-6	Used for IL-6 detection in mouse LPS or other ALI models
EJ1512935	Mouse Interleukin 6 (IL-6) ELISA Kit	BioReagent	Mouse IL-6	Used for evaluating IL-6 levels in mouse lung tissue, serum, or BALF
EJ1512162	Rat Interleukin 6 (IL-6) ELISA Kit	BioReagent	Rat IL-6	Used for detecting inflammatory factors in rat ALI models
EJ1511734	Mouse Tumor Necrosis Factor Alpha (TNF-α) ELISA Kit	BioReagent	Mouse TNF-α	Used for detecting early pro-inflammatory factors in mouse ALI models
EJ1513094	Mouse Tumor Necrosis Factor Alpha (TNF-α) ELISA Kit	BioReagent	Mouse TNF-α	Used for inflammatory evaluation in mouse LPS, acid aspiration, or BLM models
EJ1512250	Rat Tumor Necrosis Factor Alpha (TNF-α) ELISA Kit	BioReagent	Rat TNF-α	Used for detecting TNF-α-related inflammatory responses in rat ALI models
EJ1515540	Mouse Lipopolysaccharides(LPS) ELISA Kit	BioReagent	Mouse LPS	Used for evaluating endotoxin exposure, LPS-induced ALI, or gut-derived endotoxin responses in mice
EJ1515430	Rat Lipopolysaccharide (LPS) ELISA Kit	BioReagent	Rat LPS	Used for LPS-related lung injury or endotoxin level detection in rats
EJ1513133	Mouse Lipopolysaccharide Binding Protein (LBP) ELISA Kit	BioReagent	Mouse LBP	Used for evaluating endotoxin responses, gut-lung axis-related inflammation, and LPS exposure in mice
EJ1512280	Rat Lipopolysaccharide Binding Protein (LBP) ELISA Kit	BioReagent	Rat LBP	Used for mechanistic studies of endotoxin responses, pulmonary inflammation, and barrier injury in rats

Table 9 Products for Evaluating Oxidative Stress and Cellular Injury in Acute Lung Injury

Cat. No.	Product Name	Grade & Purity	Indicator Category	Application Positioning
M1508248	Malondialdehyde (MDA) Content Assay Kit (TBA, Colorimetric Method)	BioReagent	Lipid peroxidation/MDA	Used for evaluating lipid peroxidation in lung tissue from BLM, OA, ischemia-reperfusion, or mechanical ventilation-related models
M1508267	Malondialdehyde (MDA) Content Assay Kit (TBA, Fluorometric Method)	BioReagent	Lipid peroxidation/MDA	Used for low-content samples or high-sensitivity MDA detection
L486287	Lipid Peroxidation (MDA) Assay Kit	sufficient for 100colorimetricorfluorometrictests	Lipid oxidation/MDA	Used for evaluating lipid oxidation and oxidative stress injury in lung tissue
T1521744	Total Glutathione (T-GSH) Content Assay Kit (DTNB, Micro Method)	BioReagent	Glutathione system	Used for detecting total glutathione in lung tissue; suitable for evaluating oxidative stress and antioxidant capacity
T1521745	Total Glutathione (T-GSH) Content Assay Kit (DTNB, Colorimetric Method)	BioReagent	Glutathione system	Used for colorimetric detection of total glutathione
R1492762	Reduced Glutathione (GSH) Content Assay Kit (DTNB, Micro Method)	BioReagent	GSH content	Used for evaluating GSH depletion and antioxidant defense in lung tissue
R1505409	Reduced Glutathione (GSH) Content Assay Kit (DTNB, Colorimetric Method)	BioReagent	GSH content	Used for colorimetric detection of GSH content
G1505763	Glutathione Peroxidase (GSH-Px) Activity Assay Kit (DTNB, Micro Method)	BioReagent	GSH-Px activity	Used for evaluating antioxidant enzyme activity and oxidative stress injury in lung tissue
G1505754	Glutathione Peroxidase (GSH-Px) Activity Assay Kit (DTNB, Colorimetric Method)	BioReagent	GSH-Px activity	Used for colorimetric detection of GSH-Px activity
T1373303	Total Superoxide Dismutase (SOD) Assay Kit (NBT Riboflavin Microplate Method)	BioReagent	SOD activity	Used for microplate-based evaluation of total SOD levels in lung tissue
T1373360	Total Superoxide Dismutase (SOD) Assay Kit (NBT Riboflavin Colorimetric Method)	BioReagent	SOD activity	Used for colorimetric total SOD detection
T1505644	Total Superoxide Dismutase (T-SOD) Activity Assay Kit (WST-8, Micro Method)	BioReagent	SOD activity	Used for detecting SOD activity in lung tissue using the WST-8 system
T1521754	Total Superoxide Dismutase (SOD) Activity Assay Kit (Pyrogallol, UV Colorimetric Method)	BioReagent	SOD activity	Used for SOD activity detection by UV colorimetry
L1501786	Lactate Dehydrogenase (LDH) Cytotoxicity Assay Kit (DNPH, Micro Method)	BioReagent	Cell injury/LDH release	Used for detecting LDH release and cell membrane integrity damage
L1521750	Lactate Dehydrogenase (LDH) Cytotoxicity Assay Kit (DNPH, Colorimetric Method)	BioReagent	Cytotoxicity	Used for colorimetric detection of lung-related cell injury or cytotoxicity after drug intervention
L1510342	Lactate Dehydrogenase (LDH) Activity Assay Kit (LD-L, Colorimetric Method)	BioReagent	LDH activity	Used for LDH activity detection in tissue, BALF, or cell samples
L1521751	Lactate Dehydrogenase (LDH) Activity Assay Kit (LD-P, UV Colorimetric Method)	BioReagent	LDH activity	Used for LDH activity detection in UV colorimetric systems

8 Frequently Asked Questions

8.1 Should LPS or oleic acid be prioritized for acute lung injury modeling?

If the research focus is inflammatory initiation, neutrophil infiltration, and anti-inflammatory drug evaluation, the LPS model is more suitable. If the focus is pulmonary vascular endothelial injury, pulmonary edema, and ARDS-like permeability changes, the oleic acid model is more appropriate. Both models can cause lung injury, but their initiating mechanisms and main pathological phenotypes differ.

8.2 Is the bleomycin model an acute lung injury model or a pulmonary fibrosis model?

The bleomycin model is stage-dependent. In the early phase, it can present as acute inflammation and epithelial injury, while in the later phase, it can progress to fibrosis. If used for acute lung injury research, an early sampling time should be clearly selected. If used for pulmonary fibrosis research, collagen deposition, Masson staining, and fibrosis scoring should be included.

8.3 What is the significance of BALF detection in ALI models?

BALF reflects inflammatory cells, protein exudation, and local cytokine levels within the alveolar space. BALF total cell count, neutrophil proportion, protein concentration, TNF-α, IL-6, and related indicators help determine changes in alveolar inflammation and barrier permeability, making BALF an important sample type for ALI model evaluation.

8.4 Does an increased lung wet/dry weight ratio prove successful ALI model establishment?

An increased lung wet/dry weight ratio indicates pulmonary edema, but it does not independently prove a complete ALI phenotype. Successful modeling should be judged by combining BALF inflammation, histopathology, barrier permeability, and necessary lung function indicators. In drug intervention studies, conclusions should not be based solely on pulmonary edema results.

8.5 Why do results vary greatly among laboratories using the same LPS model?

LPS source, batch, serotype, administration route, animal strain, anesthesia method, airway administration success rate, and sampling time can all affect results. Before establishing the model, the LPS source and experimental conditions should be fixed, and preliminary experiments should be performed to determine the appropriate injury intensity for the specific laboratory.

8.6 Why is mortality relatively high in the oleic acid model?

Oleic acid can rapidly injure the pulmonary vascular endothelium and induce marked pulmonary edema and oxygenation impairment. Excessively high doses or overly rapid intravenous administration can cause severe respiratory failure or death. Before formal use, dose and administration speed should be optimized to select conditions that produce stable injury while preserving an observation window.

Animal models of acute lung injury should be selected according to the research mechanism and evaluation endpoints. The LPS model is suitable for studying inflammatory initiation and anti-inflammatory drugs; the bleomycin model is suitable for studying epithelial injury, repair, and fibrotic progression; the oleic acid model is suitable for studying ARDS-like endothelial injury and pulmonary edema; and acid aspiration, mechanical ventilation, and ischemia-reperfusion models are more suitable for simulating specific clinical scenarios.

For more related articles, please see below:

[1] The Technology Driving Biomedical Revolution — Animal Modeling

[2] Animal Modeling—Tumor Disease Models

[3] A Detailed Guide to the Construction of Animal Models for Metabolic Diseases

[4] Methods for Establishing Animal Models of Cardiovascular Diseases

[5] Methods for Establishing Models of Nervous System Diseases

[6] Construction of a subcutaneous hormonal tumor model of melanoma