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In vitro Monitoring of Extracellular pH in Real-Time

Published: June 3rd, 2021



1Mucosal Inflammation Program, University of Colorado Anschutz Medical Campus, 2Department of Medicine, University of Colorado Anschutz Medical Campus, 3Rocky Mountain Regional Veterans Affairs Medical Center

This article represents a useful in vitro assay to measure changes in extracellular pH during neutrophil (PMN) transepithelial migration (TEM)

Early accumulation of neutrophils (PMN) is a hallmark of acute intestinal inflammation. This acute inflammation is either resolved or progresses to chronic inflammation. Without efficient PMN clearance at sites of infiltration, PMN can accumulate and contribute to chronic inflammatory conditions, including the intestinal diseases ulcerative colitis (UC) and Crohn's Disease (CD). The pH in the distal colon in individuals with active UC can range between a pH of 5 and 6, whereas healthy individuals maintain colonic pH in the range of 6.8-7.4. Extracellular pH has been shown to influence both intestinal epithelial cells and the infiltrating immune cells. More specifically, extracellular acidosis significantly impacts PMN. At pH below 6.5, there are increases in the production of H2O2, inhibition of apoptosis, and increases in the functional lifespan of PMN. Given the significant presence of PMN and extracellular acidification at sites of inflammation, we developed a novel model that allows for the monitoring of extracellular pH during PMN transepithelial migration in real time. Here, we describe this model and how it can be utilized to measure both the apical and basal pH during PMN trafficking. This model can be utilized to monitor extracellular pH under a wide range of conditions; including, hypoxia, PMN transepithelial migration, and for extended periods of time.

The extracellular microenvironment has been shown to play a significant role in modulating the inflammatory response. One aspect of the microenvironment which is often underappreciated is extracellular acidification. Extracellular acidification is often observed at sites of active inflammation, including mucosal disorders such as inflammatory bowel diseases. The luminal pH in the distal colon from patients with UC can range between a pH of 5 and 6, whereas healthy individuals have colonic pH's in the range of 6.8-7.41,2. This decrease in colonic pH is of particular interest because extracellular pH has been sh....

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1. Cell Preparation

Day 1

  1. Warm cell culture media (DMEM/F12 with 5% FBS, 2 mM L-alanyl-L-glutamine dipeptide, and Pen Strep) in a 37 °C water bath for 20 min.
  2. Prepare the tissue culture hood by spraying it with 70% ethanol and wiping down the surfaces with paper towels.
  3. Spray and wipe tissue culture flasks and media, PBS, and trypsin bottles with 70% ethanol and bring them into the tissue culture hood.
  4. Aspirate the media from the cell culture flas.......

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The results are usually via line graph to show change in pH over time (example shown in Figure 3A) or as a scatter plot showing extracellular pH at a single point in time (example shown in Figure 3B). Depending on experimental need, additional controls and treatments can be included. Additionally, this assay can be modified to monitor extracellular under a wide range of conditions. For example, the SDR reader can be placed in a hypoxic chamber and the extracellu.......

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In this protocol, there are several key steps. Monolayers should be confluent, but not overconfluent. For T84 IEC, they should be used 7-10 days after plating. Human and murine enteroids grow at different rates than T84 IEC and the researchers should determine how long it takes each line to reach confluency. It is important that the researchers need to use minimally buffered media to ensure shifts in extracellular pH are observed. HBSS+ contains glucose and is suitable for experiments shorter than 12 h. T84 IEC incubated.......

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Name Company Catalog Number Comments
10 mL serological pipettes Corning 4101
24-well plate Corning CLS3527-100EA
5 mm pore inserts Corning 3421
50 ml sterile conical tube Corning 0553855A
75 cm2 flask Corning 430641U
DMEM/F12 Gibco 10565-018
FBS Gibco 26140
GlutaMax ThermoFisher 35050061
HBSS- Sigma-Aldrich H4891-10X1L
HBSS+ Sigma-Aldrich H1387-10L
Histopaque T1077 Sigma-Aldrich 10771-6X100ML
Histopaque T1119 Sigma-Aldrich 11191-6X100ML
HydroDish HD24 PreSens NA
PBS Gibco 14190-144
Pen Strep Gibco 15140-122
RBC lysis buffer ThermoFisher 00-4333-57
SDR Reader PreSens NA
Trypsin Fisher Scientific 25200114

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