LPS and ATP-induced Death of PMA-differentiated THP-1 Macrophages and its Validation

Summary

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.

Abstract

Cell death is a fundamental process in all living organisms. The protocol establishes a lipopolysaccharide (LPS) and adenosine triphosphate (ATP)-induced phorbol-12-myristate-13-acetate (PMA)-differentiated lipid deposition in human monocyte (THP-1) macrophage model to observe cell death. LPS combined with ATP is a classic inflammatory induction method, often used to study pyroptosis, but apoptosis and necroptosis also respond to stimulation by LPS/ATP. Under normal circumstances, phosphatidylserine is only localized in the inner leaflet of the plasma membrane. However, in the early stages of pyroptosis, apoptosis, and necroptosis, the cell membrane remains intact and exposed to phosphatidylserine, and in the later stages, the cell membrane loses its integrity. Here, flow cytometry was used to analyze Annexin V and 7-Aminoactinomycin D (AAD) double staining to detect the cell death from the whole cells. The results show that substantial cells died after stimulation with LPS/ATP. Using scanning electron microscopy, we observe the possible forms of cell death in individual cells. The results indicate that cells may undergo pyroptosis, apoptosis, or necroptosis after stimulation with LPS/ATP. This protocol focuses on observing the death of macrophages after stimulation with LPS/ATP. The results showed that cell death after LPS and ATP stimulation is not limited to pyroptosis and that apoptosis and necrotic apoptosis can also occur, helping researchers better understand cell death after LPS and ATP stimulation and choose a better experimental method.

Introduction

Cell death is a fundamental physiological process in all living organisms. In recent years, substantial studies have shown that cell death is involved in the immunity and balance within the organism. Studying cell death helps us better understand the onset and development of diseases. Several forms of programmed cell death have been described, and some key targets in these processes have been identified. Pyroptosis, apoptosis, and necroptosis are the three genetically defined programmed cell death pathways involved in internal balance and disease¹.

Pyroptosis is characterized by the formation of membrane pores and th....

Protocol

1. Cell line and cell culture

1. Grow the human monocytic cell line THP-1 in RPMI-1640 complete culture medium with 10% fetal bovine serum, 1% penicillin-streptomycin and 0.05 mM β-mercaptoethanol. Culture the cells at 37 °C in 5% CO₂ humidified air. Sub-culture cells every 2-3 days.
   NOTE: THP-1 is a suspension cell, select to change half of the medium for sub-culturing. When observing many cell fragments under the light microscope, centrifuge at 300 x g for 3 min at room temperature. Resuspend cells in the pre-warmed fresh complete cell culture medium.
2. Use cells (in passages 4-10) at the logarit....

Results

The cell samples were treated as described in the protocol and flow cytometry detection was done. Normal cells cannot be stained with Annexin V and 7-AAD (Annexin V-/7-AAD-). In the early stages of pyroptosis, apoptosis, and necroptosis, PS was exposed and bound to Annexin V, but the cell membrane was still intact and excluded 7-AAD from the extracellular space (Annexin V+/7-AAD-). In the later stages, the cell membrane loses its integrity, cells are simultaneously stained by Annexin V and 7-AAD, showing double positive .......

Discussion

In this manuscript, two methods were used to detect LPS and ATP-induced death of PMA-differentiated THP-1 macrophages. Annexin V/7-AAD double staining was used, and the results were analyzed by flow cytometry from overall staining. As with other flow cytometric analysis, a group of unstained cells and two groups of single-stained cells were set up to exclude false positive and false negative results. The results show that after LPS/ATP stimulation, several cells lost membrane integrity, indicating that cell death may hav.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
0.25% pancreatic enzyme solution (excluding EDTA)	BOSTER Biological Technology co.ltd	PYG0068
5 mL Polystyrene Round-Bottom Tube	CORNING	352235
5 mL centrifuge tube	Labgic Technology Co., Ltd.	BS-50-M
6-well plate	Sorfa Life Science Research Co.,Ltd	220100
Annexin V-PE/7-AAD apoptosis analysis kit	Absin (Shanghai) Biological Technology co.ltd	abs50007	Annexin V-PE, 7-AAD, 5×Binding buffer, Apoptosis Positive Control Solution
celculture CO2 incubator	Esco (Shanghai) Enterprise Development Co., Ltd.	N/A
cell culture dish, 100 mm	Sorfa Life Science Research Co.,Ltd	230301
Cellometer K2 Fluorescent Cell Counter	Nexcelom Bioscience LLC	Cellometer K2
Cellometer SD100 Counting Chambers	Nexcelom Bioscience LLC	CHT4-SD100-002
centrifuge machine	Hunan Xiangyi Laboratory Instrument Development Co., Ltd	L530
chromium alum	Guangdong Wengjiang Chemical Reagent Co., Ltd.	PA04354
cover glasses, 9 mm	Labgic Technology Co., Ltd.	BS-09-RC
critical point dryer	Quorum Technologies	K850
dimethyl sulfoxide	BOSTER Biological Technology co.ltd	PYG0040
electron microscope fixative	Servicebio Technology co.ltd	G1102	2.5% glutaric dialdehyde, 100 mM phosphorous salts
electronic balance	SHIMADZU	ATX124
ethanol absolute	Chengdu Kelong Chemical Co., Ltd	2021033102
flow cytometer	Becton,Dickinson and Company	FACSCanto
flow cytometry analysis software	Becton,Dickinson and Company	BD FACSDivaTM Software
gelatin	Guangdong Wengjiang Chemical Reagent Co., Ltd.	PA00256
High resolution cold field emission scanning electron microscope	TITACHI	Regulus 8100
human monocytic cell line THP-1	Procell Life Science&Technology Co.,Ltd.	CL0233
inverted microscope	Leica Microsystems Co., Ltd	DMi1
IR Vortex Mixer	VELP Scientifica Srl	ZX4
lipopolysaccharide	Beijing Solarbio Science & Technology Co.,Ltd.	L8880	LPS is derived from Escherichia coli 055:B5
Na2ATP	Beijing Solarbio Science & Technology Co.,Ltd.	A8270
phorbol-12-myristate-13-acetate	Beijing Solarbio Science & Technology Co.,Ltd.	P6741
phosphate-buffered saline	Servicebio Technology co.ltd	G4202
Pipette	Eppendorf AG	N/A
pipette tips, 10 μL	Servicebio Technology co.ltd	T-10PL
pipette tips, 1 mL	Servicebio Technology co.ltd	T-1250L
pipette tips, 200 μL	Servicebio Technology co.ltd	T-200L
RPMI-1640 complete culture media	Procell Life Science&Technology Co.,Ltd.	CM0233	RPMI-1640 + 10% FBS + 0.05mM β-mercaptoethanol + 1% P/S
RPMI-1640 culture media	Shanghai BasalMedia Technologies Co., LTD.	K211104
sheath fluid	BECKMAN COULTER	8546733
sputter coater	Cressington Scientific Instruments Ltd	108
thermostatic water bath	GUOHUA Electric Appliance CO.,Ltd	HH-1