Assessing calcium-stimulated mitochondrial bioenergetics using the seahorse XF96 analyzer.

The development of fluorescence-based oxygen sensors coupled with microplate-based assays for quantitative bioenergetics analyses enables screening multiple experimental conditions at once with small biological material and in a timely manner. In this chapter, we outline detailed protocols and practical tips to design and perform controlled measurements of (a) respiratory and glycolytic metabolism of intact cells, (b) substrate-dependent respiration in permeabilized cells and isolated mitochondria, and (c) calcium-dependent regulation of mitochondrial bioenergetics with Seahorse XF Flux Analyzers

Determining Macrophage Polarization upon Metabolic Perturbation.

Metabolic reprograming controlling macrophage activation and function is emerging as new regulatory circuit on shaping immune responses. Generally, lipopolysaccharides (LPS)-induced pro-inflammatory activated macrophages, known as M1 macrophages, display higher glycolysis. In contrast, interleukin-4 (IL-4)-skewed anti-inflammatory activated macrophages, known as M2 macrophages, mainly rely on oxidative phosphorylation for their bioenergetic demands. Emerging evidence reveals that these metabolic preferences further fine-tune macrophage polarization process, including signaling cascades and epigenetic reprogramming. Thus, specific nutrient microenvironments may affect inflammatory responses of macrophages by intervening these metabolic machineries. How to measure the metabolic switch of macrophages both in vitro and in vivo is an important issue for understanding immunometabolic regulations in macrophages. Here, we describe a basic protocol for examining how glutamine metabolism affects macrophage polarization by using the Extracellular Flux (XF <sup>(e)</sup> 96) Analyzer (Seahorse Bioscience), which takes real-time measurements of oxidative phosphorylation and glycolysis. We also present a detailed procedure for detecting the expression of inflammatory genes in polarized macrophages under glutamine-replete or -deprived conditions

Suppression of mitochondrial oxygen metabolism mediated by the transcription factor HIF-1 alleviates propofol-induced cell toxicity

A line of studies strongly suggest that the intravenous anesthetic, propofol, suppresses mitochondrial oxygen metabolism. It is also indicated that propofol induces the cell death in a reactive oxygen species (ROS)-dependent manner. Because hypoxia-inducible factor 1 (HIF-1) is a transcription factor which is involved in cellular metabolic reprogramming by modulating gene expressions of enzymes including glycolysis pathway and oxygen utilization of mitochondria, we examined the functional role of HIF-1 activity in propofol-induced cell death. The role of HIF-1 activity on oxygen and energy metabolisms and propofol-induced cell death and caspase activity was examined in renal cell-derived RCC4 cells: RCC4-EV cells which lack von Hippel-Lindau protein (VHL) protein expression and RCC4-VHL cells, which express exogenous VHL, and in neuronal SH-SY5Y cells. It was demonstrated that HIF-1 is involved in suppressing oxygen consumption and facilitating glycolysis in cells and that the resistance to propofol-induced cell death was established in a HIF-1 activation-dependent manner. It was also demonstrated that HIF-1 activation by treatment with HIFα-hydroxylase inhibitors such as n-propyl gallate and dimethyloxaloylglycine, alleviated the toxic effects of propofol. Thus, the resistance to propofol toxicity was conferred by HIF-1 activation by not only genetic deletion of VHL but also exposure to HIFα-hydroxylase inhibitors