[Ca²⁺]_i and pH_in Homeostasis in Kaposi Sarcoma Cells

Abstract

Changes in intracellular pH (pH_in) and intracellular calcium concentration [Ca²⁺]_i play a major role in signal transduction leading to cell growth, differentiation and transformation. In some tumor cell lines, vacuolar (V-type) H⁺-adenosine triphosphatases (ATPases) are important in pH_in regulation. To clarify the neoplastic nature and endothelial origin of Kaposi sarcoma (KS), pH_in and [Ca²⁺]_i and the functional expression of V-type H⁺-ATPases were evaluated in cultured endothelial marker-positive KS cells derived from AIDS-KS skin lesions as compared to human umbilical vein endothelial cells (HUVEC). Human skin fibroblasts (HSF) were also examined. Cells were examined using fluorescence spectroscopy with the pH_in indicator SNARF-1 and the [Ca²⁺]i indicator Fura-2. We found that whereas pH_in recovery from acid loading occurred in the absence of Na⁺ and HCO^–₃ in HUVEC and HSF, KS cells did not recover. Moreover, removal of extracellular Na⁺ had no effect on [Ca²⁺]_i in HUVEC, but transiently increased [Ca²⁺]_i in KS cells and HSF. This [Ca²⁺]_i spike was unaffected by Ca²⁺-free medium, suggesting that it is not due to Na⁺/Ca²⁺ exchange. In addition, use of K⁺-containing and K⁺-free medium to mimic depolarization or hyperpolarization, which may occur during Na⁺ removal, did not cause [Ca²⁺]_i changes. The [Ca²⁺]_i levels were also not sensitive to intracellular acidification but were specifically sensitive to [Na⁺]. Thus, KS cells differ from normal endothelial cells in the kinetics of pH_in recovery to acid loads, and in the presence of a specific [Na⁺]-sensitive intracellular Ca²⁺ pool. These differences in ion homeostasis indicate that these cell types are not developmentally related or that alterations in ion transport are a part of the etiology of the KS lesion.

Retracted: A Naphthalenediimide‐Based Fluorescent Sensor for Detecting the pH within the Rough Endoplasmic Reticulum of Living Cells

“…Fluorescent chemosensor probes are applied intensively in cell biology to monitor pH, which plays an essential and sophisticated role in many cellular events 1. Small changes in intracellular pH are involved in various biological processes such as apoptosis,2 cell proliferation,3 cell growth,4 calcium regulation,5 endocytosis,6 chemotaxis,7 and other cellular functions. Thus, the detection and monitoring of pH changes in living cells is one of the most important targets for precise understanding of the relationship between changes in pH and cellular processes.…”

Ratiometric Fluorescence Nanoprobes for Subcellular pH Imaging with a Single-Wavelength Excitation in Living Cells

“…Intracellular pH balance plays many vital roles in various biological processes, including cell proliferation, apoptosis, − multidrug resistance, phagocytosis, and endocytosis. , Anomalous pH values in cells and tissues are associated with the cellular dysfunctions, which are correlated with many severe diseases such as cancer − and Alzheimer’s disease . Moreover, intracellular pH distribution is heterogeneous in different subcellular compartments, and the unique functions of organelles determine the pH values of each separate compartment.…”

A water-soluble pH fluorescence probe based on quaternary ammonium salt for bioanalytical applications

“…On the one hand, intracellular H + plays a pivotal role in many cellular events, including cell growth [1], apoptosis, endocytosis [2,3], homeostasis, ion transport [4], cell adhesion [5], and other cellular processes [6][7][8][9], on the other hand, the disorder of the H + within different organelles may lead to the dysfunction of the organization and even to a diseased state [10][11][12][13][14][15][16], which have made the detection of intracellular pH be particularly important. In the past decades, quite a few fluorescence probes have been developed for various bio-related targets based on target-triggered fluorescence intensity changes [17][18][19][20][21][22][23][24][25] due to their high sensitivity, fast analysis with spatial resolution for providing in situ and real-time information and nondestructive sample preparation.…”