Triclosan disrupts immune cell function by depressing Ca2+ influx following acidification of the cytoplasm

Triclosan (TCS) is an antimicrobial agent that was effectively banned by the FDA from hand soaps in 2016, hospital soaps in 2017, and hand sanitizers in 2019; however, TCS can still be found in a few products. At consumer-relevant, non-cytotoxic doses, TCS inhibits the functions of both mitochondria and mast cells, a ubiquitous cell type. Via the store-operated Ca2+ entry mechanism utilized by many immune cells, mast cells undergo antigen-stimulated Ca2+ influx into the cytosol, for proper function. Previous work showed that TCS inhibits Ca2+ dynamics in mast cells, and here we show that TCS also inhibits Ca2+ mobilization in human Jurkat T cells. However, the biochemical mechanism behind the Ca2+ dampening has yet to be elucidated. Three-dimensional super-resolution microscopy reveals that TCS induces mitochondrial swelling, in line with and extending the previous finding of TCS inhibition of mitochondrial membrane potential via its proton ionophoric activity. Inhibition of plasma membrane potential (PMP) by the canonical depolarizer gramicidin can inhibit mast cell function. However, use of the genetically encoded voltage indicators (GEVIs) ArcLight (pH-sensitive) and ASAP2 (pH-insensitive), indicates that TCS does not disrupt PMP. In conjunction with data from a plasma membrane-localized, pH-sensitive reporter, these results indicate that TCS, instead, induces cytosolic acidification in mast cells and T cells. Acidification of the cytosol likely inhibits Ca2+ influx by uncoupling the STIM1/ORAI1 interaction that is required for opening of plasma membrane Ca2+ channels. These results provide a mechanistic explanation of TCS disruption of Ca2+ influx and, thus, of immune cell function.

The effect of Na+-K+ ATPase inhibition by ouabain on histamine release from human cutaneous mast cells

BACKGROUND

There are controversial reports on the effect of sodium-potassium adenosine triphosphatase (Na+-K+ ATPase) inhibition on mast cell mediator release. Some of them have indicated that ouabain (strophanthin G), a specific Na+-K+ ATPase inhibitor, inhibited the release, whereas the others have shown that ouabain had no effect or even had a stimulatory effect on the mediator secretion. Most of these studies have utilized animal-derived mast cells. The aim of this study was to determine the effect of Na+-K+ ATPase inhibition on human skin mast cells.

METHODS

Unpurified and purified mast cells were obtained from newborn foreskins and stimulated by calcium ionophore A23187 (1 microM) for 30 min following a 1 hr incubation with various concentrations (10(-4) to 10(-8) M) of ouabain. Histamine release was assayed by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The results indicated that ouabain had no significant effect on the non-immunologic histamine release from human skin mast cells, in vitro.

CONCLUSIONS

Na+-K+ ATPase inhibition by ouabain had no significant effect on the non-immunologic histamine release from human cutaneous mast cells and suggested differences between human and animal mast cells.

A novel assay of cell rubidium uptake using graphite furnace atomic absorption: Application to rats on a magnesium-deficient diet

The [Na,K]ATPase or sodium pump (SP) is a ubiquitous membrane cation transport system. Because of its potential participation in the pathophysiology of essential hypertension and cataract formation, the SP is under active investigation to detail its function and control. In this paper, we describe a novel, nonradioactive method of measuring SP ion transport activity in intact red blood cells (RBCs) using graphite furnace atomic absorption measurement of rubidium ion (Rb) uptake. This method provided sensitivity comparable to radioactive techniques, as assessed by experiments with human red blood cells (RBC) and ouabain, a known SP inhibitor, but this analytical approach eliminates the use of radioisotopes common to other Rb uptake assay methods. As a demonstration of its broader utility, the assay was used to assess the effects of dietary magnesium intake on SP-mediated ion transport in the RBCs of diet-controlled rats. Rats on 7 weeks of a magnesium-deficient (MgD) diet showed significant reductions in serum magnesium concentration, although levels remained in the lower region of the reference interval for healthy, magnesium replete animals. Red cell Rb uptake was significantly reduced in cells from the magnesium-restricted animals, demonstrating the sensitivity of Rb uptake to reduced magnesium intake, despite serum levels that fell within the reported normal range, and the utility of this Rb uptake assay in measuring physiological changes in SP function.