A growth chamber for chronic exposure of mammalian cells to HS.

HS is a redox-active signaling molecule that exerts an array of cellular and physiological effects. While intracellular HS concentrations are estimated to be in the low nanomolar range, intestinal luminal concentrations can be significantly higher due to microbial metabolism. Studies assessing HS effects are typically conducted with a bolus treatment with sulfide salts or slow releasing sulfide donors, which are limited by the volatility of HS, and by potential off-target effects of the donor molecules. To address these limitations, we describe the design and performance of a mammalian cell culture incubator for sustained exposure to 20-500 ppm HS (corresponding to a dissolved sulfide concentrations of ∼4-120 μM in the cell culture medium). We report that colorectal adenocarcinoma HT29 cells tolerate prolonged exposure to HS with no effect on cell viability after 24 h although ≥50 ppm HS (∼10 μM) restricts cell proliferation. Even the lowest concentration of HS used in this study (i.e. ∼4 μM) significantly enhanced glucose consumption and lactate production, revealing a much lower threshold for impacting cellular energy metabolism and activating aerobic glycolysis than has been previously appreciated from studies with bolus HS treatment regimens.