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Neutrophil membrane potential changes and homotypic aggregation kinetics are pH-dependent: studies of chronic
A Ahlin1, H Gyllenhammar, B Ringertz
1Department of Pediatrics, Karolinska Institute, Sachs Children's Hospital, Sweden.
Abstract:
Activated polymorphonuclear neutrophil granulocytes (PMN) from patients with chronic granulomatous disease (CGD) show reduced electron-proton shifts and an inability to acidify the cell. We studied whether this impaired pH-regulating capacity affected PMN membrane potential changes and the kinetics of homotypic aggregation by changing the extracellular pH over a wide range. At pH 7.4 normal PMN showed a rapid, transient membrane depolarization to leukotriene B4 (LTB4) and a slower response to N-formyl-methionyl-leucyl-phenylalanine. In contrast, PMN from 13 patients with CGD exhibited no or minute depolarization to these stimuli and 77% of tested patients with CGD displayed absence or marked reductions of the disaggregation to LTB4. On acidification of pH 5.0 to 6.4, PMN membrane depolarization appeared in six of nine tested patients. Likewise, disaggregation became evident in all of three patients. On alkalinization of normal PMN to pH 8.0 to 9.0, membrane depolarization and disaggregation to LTB4 disappeared, and cells reacted as CGD PMN. This change was not due to inefficient signal transduction, because normal PMN enhanced the superoxide ion production to N-formyl-methionyl-leucyl-phenylalanine on this alkalinization. Cytosolic pH changes in resting and LTB4-activated CGD cells at pH 6.0, 7.4, and 8.5 were similar those in control cells but for absence of an initial acidification. Thus neutrophil membrane potential changes and aggregation kinetics to LTB4 are abnormal in patients with CGD and return toward normal on extracellular acidification.
Insights
Patients with chronic granulomatous disease (CGD) have abnormal neutrophil function, including impaired membrane potential and aggregation. Acidifying the extracellular environment can restore these functions toward normal in CGD neutrophils.
Area of Science:
- Immunology
- Cell Biology
- Physiology
Background:
- Chronic granulomatous disease (CGD) is a primary immunodeficiency characterized by defective neutrophil function.
- Neutrophils play a crucial role in host defense, and their proper functioning relies on precise cellular processes like pH regulation.
- Impaired pH regulation in CGD neutrophils affects their ability to respond to stimuli and perform essential functions.
Purpose of the Study:
- To investigate the impact of extracellular pH on neutrophil membrane potential and aggregation in patients with CGD.
- To determine if modulating extracellular pH can restore normal neutrophil function in CGD.
Main Methods:
- Studied polymorphonuclear neutrophil granulocytes (PMN) from CGD patients and healthy controls.
- Manipulated extracellular pH over a wide range (pH 5.0-9.0).
- Assessed PMN membrane potential changes and homotypic aggregation kinetics in response to stimuli like leukotriene B4 (LTB4).
Main Results:
- CGD neutrophils exhibited impaired membrane depolarization and aggregation responses to LTB4 at physiological pH (7.4).
- Extracellular acidification (pH 5.0-6.4) partially restored membrane depolarization and aggregation in CGD neutrophils.
- Alkalinization (pH 8.0-9.0) of normal neutrophils mimicked CGD neutrophil dysfunction, indicating the critical role of extracellular pH.
Conclusions:
- Neutrophil membrane potential and aggregation kinetics are significantly altered in CGD patients.
- Extracellular acidification represents a potential therapeutic strategy to normalize neutrophil function in CGD.
- The findings highlight the critical role of pH homeostasis in neutrophil activation and function.