Using Nicotine in a Silica-Exposed Mouse Model to Promote Lung Epithelial-Mesenchymal Transition
March 3rd, 2023
This study describes a mouse model to study the synergistic effect of nicotine on the progression of pulmonary fibrosis in experimental silicosis mice. The dual-exposure mouse model simulates the pathological progression in the lung after simultaneous exposure to nicotine and silica. The methods described are simple and highly reproducible.
The mouse model employed in this study effectively simulates the effect of chronic nicotine ingestion and repeated exposure to silica on lung fibroses through epithelial mesenchymal transition in human beings. The jury portion model was achieved by subcutaneous injection of nicotine and the nasal drip of silica in a simple and a reliable way. Suspend sterile crystalline silica in saline to prepare a 20 milligrams per liter suspension.
Oscillate it in an ultrasonic shaking water bath for 25 minutes. Place the silica suspension with a vortex oscillator for three minutes. Aspirate the suspension to mix it, and then use 50 microliters for the nasal drip.
To begin silica exposure, first, place the anesthetized mouse on the palm of one hand and expose the nasal cavity of the mouse. Inject 50 microliters of the silica suspension from one nostril within four to eight seconds. To allow for quick lung penetration of the suspension, gently press the mouse's chest with the index finger for three to five seconds, repeating the press three to five times each second to maintain its respiratory rate.
Once the mouse displays uniform respiration, place it under observation in a cage for three minutes. Prepare nicotine syringes by drawing air until the mark of 0.2 milliliter into a one milliliter syringe. Then, draw up 125 microliters of nicotine.
Tap the syringe to fill the needle and the front end with nicotine, and then place it in a tray protected from light. With the right hand, grasp the mouse's tail. When the mouse has relaxed, Use the left thumb and forefinger to apply moderate pressure on the skin from the tail to the edge of the ear.
Now, release the right hand and use the left, small, and ring fingers to pinch the tail and hind limbs to immobilize the mouse. Hold the injection syringe in the right hand and puncture the skin on the back of the neck in a head to tail direction. Inject the nicotine at a uniform rate.
Fix the anesthetized mouse on a foam test plate and spray the fur with 75%alcohol. Make an incision along the midline of the abdomen exposing the chest cavity. Make a small cut at the apex of the right side of the heart.
Inject 20 milliliters of pre-cooled PBS slowly and uniformly from the apex of the left heart, causing blood to flow out from the opening created at the apex of the right heart. Remove the entire lung lobe and refrigerate it at minus 80 degrees Celsius. Perfuse the remaining mice with 10 milliliters of 4%para-formaldehyde.
After the PBS perfusion, preserve the lungs in 30 milliliters of the para-formaldehyde solution. After 72 hours, immerse the lungs in the prepared fixative and place them in an ultrasonic water bath. Tempered at 40 degrees Celsius for 30 minutes.
Next, perform dehydration by placing the tissue in 75%ethanol, then in 95%ethanol, and then in anhydrous ethanol for 50 minutes each. Immerse the lung tissue in xylene for 50 minutes twice to wash the tissue. Place the tissue in melted paraffin wax for two to three hours at 55 to 60 degrees Celsius.
Once the wax has hardened, use a sectioning machine to obtain the lung slices of four to five micrometer thickness. Heat the sections at 45 degrees Celsius in ultrapure water. Place the lung sections onto an adherent microscope slide once the wax melts.
Hematoxylin and eosin staining studies showed that mice exposed to nicotine combined with silica had significantly more severe lung damage than those exposed to either nicotine or silica alone. Masson's staining revealed increased collagen fiber deposition in the lungs exposed to nicotine silica combination relative to the other groups. Alveolar structures were destroyed in the silica-exposed mice.
Immunohistochemical studies revealed increased CD two zero six positive macrophages and the pro-fibrotic factor, TGF beta one positive cells in the mice exposed to the combination of nicotine and silica. Vimentin expression was higher in mice subjected to the dual expression relative to the other groups. Immunohistochemical studies and protein quantification suggest severe epithelial mesenchymal transformation.
To ensure a successful nicotine injection, the operator has to become familiar with grasping the mice as grasping the skin at the back of the neck could be painful for them.
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Overview
This study describes a mouse model to investigate the synergistic effects of nicotine on pulmonary fibrosis progression in silicosis. The model effectively simulates lung pathology following simultaneous exposure to nicotine and silica.
Key Study Components
Area of Science
- Neuroscience
- Pulmonary Biology
- Toxicology
Background
- Chronic nicotine ingestion and silica exposure contribute to lung diseases.
- Understanding the interaction between these factors is crucial for developing therapeutic strategies.
- The study utilizes a dual-exposure mouse model for better simulation of human conditions.
- Previous research has highlighted the role of epithelial mesenchymal transition in lung fibrosis.
Purpose of Study
- To create a reliable mouse model for studying the effects of nicotine and silica on lung fibrosis.
- To elucidate the mechanisms involved in the progression of pulmonary fibrosis.
- To provide a framework for future research on therapeutic interventions.
Methods Used
- Subcutaneous injection of nicotine.
- Nasal drip of silica prepared in saline.
- Preparation of silica suspension using ultrasonic shaking and vortex mixing.
- Administration of 50 microliters of silica suspension for nasal exposure.
Main Results
- The model successfully simulates the pathological effects of dual exposure.
- Chronic exposure leads to significant lung fibrosis as observed in the study.
- Findings support the hypothesis of nicotine exacerbating silica-induced lung damage.
- The methods used are simple and reproducible for further research.
Conclusions
- The dual-exposure mouse model is effective for studying lung fibrosis.
- Results indicate a synergistic effect of nicotine on silica-induced lung pathology.
- This model can aid in understanding the mechanisms of pulmonary diseases.
Frequently Asked Questions
Executive Industry Relevance
Modeling the combined effects of nicotine and silica exposure addresses a critical gap in understanding occupational lung disease mechanisms relevant to biopharma R&D. This dual-exposure mouse model enables precise interrogation of epithelial-mesenchymal transition (EMT) as a driver of pulmonary fibrosis, supporting predictive confidence in target validation and mechanistic de-risking for antifibrotic drug discovery. The approach offers translational continuity for evaluating interventions in disease-relevant systems reflective of real-world exposures.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables mechanistic interrogation of EMT pathways implicated in lung fibrosis progression.
- Supports functional target validation by isolating nicotine's role in silica-induced pathology.
- Facilitates biological de-risking by modeling multifactorial disease triggers in vivo.
- Improves predictive confidence for prioritizing antifibrotic targets in occupational lung disease.
Screening & Assay Development
- Provides a validated in vivo system for quantitative assessment of fibrosis biomarkers.
- Enables reproducible measurement of histological and immunohistochemical endpoints.
- Supports assay standardization for evaluating candidate therapeutics targeting EMT or fibrosis.
- Prepares a platform for scalable compound screening in a disease-relevant context.
Translational & Preclinical Research
- Aligns preclinical models with human exposure scenarios for translational biomarker development.
- Ensures continuity from discovery through preclinical validation in occupational lung fibrosis.
- Enables risk-adjusted advancement decisions based on quantitative fibrosis and EMT readouts.
- Provides mechanistic de-risking for pipeline assets targeting fibrotic lung disease.
Pipeline & Workflow Integration
This dual-exposure model integrates into the discovery-to-preclinical continuum for antifibrotic drug development, supporting hypothesis testing, target validation, and translational research.
- Discovery Biology: Facilitates hypothesis-driven testing of EMT and fibrosis mechanisms under combined exposures.
- Screening: Delivers reproducible, quantitative histological and biomarker outputs for compound evaluation.
- Analytics: Enables statistical comparison of fibrosis severity and EMT marker expression across experimental groups.
- Translational Research: Bridges occupational exposure models to human disease-relevant endpoints for biomarker alignment.
- Enterprise Reuse: Establishes a reusable in vivo platform for multifactorial lung disease research and therapeutic screening.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence and reduces mechanistic ambiguity in lung fibrosis research.
- Operational Value: Standardizes in vivo modeling and quantitative analysis for reproducibility and scalability.
- Strategic Value: Informs go/no-go decisions and capital allocation by clarifying target-pathway relationships.
- Portfolio Impact: Supports risk-adjusted prioritization of antifibrotic assets and translational biomarker strategies.
Implementation Considerations
- Requires expertise in animal handling, subcutaneous injection, and inhalation exposure techniques.
- Demands access to histology, immunohistochemistry, and quantitative image analysis infrastructure.
- Necessitates cross-team standardization of exposure protocols and endpoint measurements.
- Adaptation may be needed for other species or exposure regimens to match specific translational goals.
- Operator proficiency is critical to minimize animal stress and ensure reproducible dosing.
