LPS and ATP-induced Death of PMA-differentiated THP-1 Macrophages and its Validation
May 3rd, 2024
This protocol is based on LPS and ATP-induced death of PMA-differentiated THP-1 macrophages. We use flow cytometry to analyze Annexin V and 7-AAD double staining to detect cell death, using the whole cell and employing scanning electron microscopy to observe the cell membrane morphology.
We are addressing LPS and ATP-introduced death of PMA-differentiated THP-1 macrophages. LPS and ATP-introduced deaths are not limited to pyroptosis, but apoptosis and necroptosis can also occur. This will add in your better understanding of cell death after LPS and ATP stimulation and choosing more suitable experimental methods.
Chrome technology mainly studies the outer structures in tissues, cells and microorganisms. Chrome provides neo-native structure data for diverse biomolecular complexes. For example, using Chrome techniques to perform 3D reconstruction can help us further understand the characteristic of pyroptotic and necroptotic parts.
Although pyroptosis is considered dominate in LPS and ATP-introduced cell death, one cannot determine the propagation of this death forms or whether they exist. Validating diverse cell death and measuring them will be our area of investigation in the future. To begin, obtain differentiated THP-1 cells and remove the spent medium from the wells of the culture plate.
After washing the cells with PBS, add a serum-free medium containing lipopolysaccharide or LPS to the cells and incubate the plate. Then, add the adenosine triphosphate or ATP stock solution to the model group and incubate the plate for 45 minutes at 37 degrees Celsius with 5%carbon dioxide. Next, aspirate all the supernatant from the wells of the culture plate.
After washing the cells two times with PBS, add 500 microliters of 0.05%trypsin without EDTA to each well and incubate for 30 seconds. To stop cell detachment, add one milliliter of RPMI 164O medium and transfer the cells into a five-milliliter tube. Centrifuge the tube at 300 G for three minutes at room temperature.
After resuspending the cells in one milliliter PBS, place the tube with cells in a water bath at 37 degrees Celsius for three minutes and centrifuge. To resuspend the cells, add 100 microliters of 1X binding buffer and transfer the cells into a new five-milliliter tube. Incubate the control and model tubes with appropriate reagents in the dark at room temperature.
To terminate the incubation, add 400 microliters of PBS to the tube and vortex it gently. Filter the cell suspension in a 35-micrometer nylon mesh, fixed to a five-milliliter polystyrene round bottom tube. Dip a clean cover glass in chromium alum solution for two hours and dry it in a 37 degrees Celsius oven.
Pellet the trypsinized cells as demonstrated earlier, and fix the cells with 500-microliters of electron microscope fixative for two hours at room temperature, followed by overnight incubation at four degrees Celsius. After collecting the cells from the fixed solution, pellet them at 300 G for three minutes at room temperature. Add 100 microliters of PBS and gently blow away the cells.
Drop the cell suspension onto a cover glass and let it stand for five minutes. Aspirate all the supernatant and wash the cells three times with PBS for five minutes each. Add 500 microliters of 1%osmic acid fixation solution.
After one hour, aspirate all the supernatant. After three PBS washes, dehydrate the samples in increasing concentrations of ethanol. Switch on the critical point dryer.
Open the carbon dioxide tank and cool the chamber to 10 degrees Celsius. Quickly wrap the sample with filter paper and put it into the chamber when the chamber pressure is zero pounds per square inch. Once the temperature stabilizes to 35 degrees Celsius and pressure reaches 1, 250 pounds per square inch, depressurize at 100 pounds per square inch per minute.
Take out the sample when the chamber pressure is zero. Finally, using conductive tape, mount the specimens on scanning electron microscope aluminum specimen holders. Employing a sputter coater, cover the samples with a two to five-nanometer layer of gold.
Flow cytometry analysis showed that after LPS/ATP stimulation, the cells in the QT region increased significantly, indicating cell death. Scanning electron micrographs of the plasma membrane surface showed characteristics of pyroptosis, including membrane blebbing and rupture in LPS/ATP stimulated cells, while the control cells looked normal. Additionally, LPS/ATP stimulation led to the appearance of apoptotic characteristics in the cells, such as membrane blebbing and cell shrinkage, and cells with necroptosis characteristics including cell swelling and ruptured membrane were observed.
Overview
This study investigates the mechanisms of cell death in PMA-differentiated THP-1 macrophages induced by lipopolysaccharide (LPS) and adenosine triphosphate (ATP). Key techniques include flow cytometry and scanning electron microscopy, revealing characteristics of pyroptosis, apoptosis, and necroptosis.
Key Study Components
Research Area
- Cell death mechanisms
- Macrophage biology
- Inflammation responses
Background
- LPS and ATP can induce different cell death pathways
- PMA-differentiated THP-1 cells serve as a model system
- Understanding these pathways can inform experimental designs
Methods Used
- Flow cytometry for cell death analysis
- PMA-differentiated THP-1 macrophages
- Scanning electron microscopy for membrane morphology
Main Results
- Flow cytometry indicated increased cell death post LPS/ATP stimulation
- Scanning electron microscopy showed pyroptotic characteristics such as membrane blebbing
- Additional signs of apoptosis and necroptosis were observed
Conclusions
- This study elucidates the complexities of cell death mechanisms under inflammatory conditions
- Findings have implications for understanding immune responses and related diseases
Frequently Asked Questions
Executive Industry Relevance
Discriminating between pyroptosis, apoptosis, and necroptosis in PMA-differentiated THP-1 macrophages following LPS and ATP stimulation is critical for target validation and mechanistic de-risking in inflammation research. Quantitative flow cytometry and ultrastructural analysis enable predictive confidence in cell death pathway assignment, supporting robust early discovery decisions. This workflow informs portfolio triage by clarifying the biological consequences of inflammatory triggers in human macrophage models.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables precise interrogation of cell death pathways in response to inflammatory stimuli.
- Supports functional target validation by distinguishing pyroptosis, apoptosis, and necroptosis.
- Improves predictive confidence for pathway-specific drug discovery programs.
- Facilitates mechanistic de-risking in macrophage-driven disease models.
Screening & Assay Development
- Establishes validated flow cytometry and electron microscopy readouts for cell death quantification.
- Standardizes detection of phosphatidylserine exposure and membrane integrity loss.
- Enables reproducible assessment of compound effects on distinct cell death modalities.
- Prepares robust biological systems for downstream screening workflows.
Translational & Preclinical Research
- Aligns in vitro macrophage death phenotypes with disease-relevant inflammatory mechanisms.
- Supports translational biomarker development for cell death pathway activation.
- Provides continuity from discovery-stage validation to preclinical model selection.
- De-risks advancement by clarifying the spectrum of cell death responses to inflammatory triggers.
Pipeline & Workflow Integration
This method integrates into the discovery-to-preclinical continuum by enabling hypothesis-driven testing of inflammatory cell death mechanisms in human macrophage models.
- Discovery Biology: Supports null hypothesis testing for pathway-specific cell death induction.
- Screening: Delivers quantitative, reproducible readouts for cell death phenotyping.
- Analytics: Provides flow cytometry and electron microscopy outputs for comparative analysis.
- Translational Research: Bridges in vitro findings to disease-relevant inflammatory responses.
- Enterprise Reuse: Offers a standardized platform for repeated evaluation of cell death modulators.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence in cell death pathway assignment and target validation.
- Operational Value: Enhances reproducibility and standardization of cell death assays.
- Strategic Value: Informs go/no-go decisions by clarifying mechanistic ambiguity in inflammatory models.
- Portfolio Impact: Enables risk-adjusted prioritization of inflammation-targeted assets.
Implementation Considerations
- Requires expertise in flow cytometry and electron microscopy for accurate cell death phenotyping.
- Demands access to analytical infrastructure for quantitative and ultrastructural analysis.
- Necessitates cross-team standardization of staining and imaging protocols.
- May require adaptation for other cell types or inflammatory triggers.
- Interpretation is limited to cell death modalities observable by Annexin V/7-AAD and ultrastructural features.
