Biochemistry

Mitochondrial dysfunction is a principal feature of acute pancreatitis (AP) although the underlying mechanisms are still unclear. AP precipitants induce Ca²⁺-dependent formation of the mitochondrial permeability transition pore (MPTP) in pancreatic acinar cells (PACs), leading to ATP depletion and necrosis. Evaluations of mitochondrial bioenergetics have mainly been performed in isolated PACs using confocal microscopy, with assessment of mitochondrial membrane potential, NADH/FAD⁺ and ATP levels, coupled with patch-clamp electrophysiology. These studies are technically demanding and time-consuming. Application of Seahorse flux analysis now allows detailed investigations of bioenergetics changes to be performed in cell populations using a multi-well plate-reader format; rates of oxygen consumption (OCR) and extracellular acidification (ECAR) provide important information about cellular respiration and glycolysis, respectively. Parameters such as maximal respiration, ATP-linked capacity and proton leak can be derived from application of a respiratory function “stress” test that involves pharmacological manipulation of the electron transport chain. The use of Seahorse Flux analysis therefore provides a quick, and convenient means to measure detailed cellular bioenergetics and allows results to be coupled with other plate-reader based assays, providing a fuller understanding of the pathophysiological consequences of mitochondrial bioenergetics alterations.

Mitochondria generate 90% of the energy required to sustain life. As a result, loss of mitochondrial function compromises almost every facet of human physiology. Accordingly, most mitochondrial diseases tend to present themselves as complex, multi-systemic disorders that can be difficult to diagnose. Depending on the severity of the mitochondrial dysfunction, the pathology can range from mild discomfort to severe epilepsy, blindness and paralysis. To develop therapies to these diseases, it will be important to optimize experimental techniques that can reliably quantify mitochondrial function, particularly in live cells or intact organisms. Here, we describe how a Seahorse XF24 Analyzer can be used to measure both basal and maximal respiration in the nematode Caenorhabditis elegans, and how this data can be interpreted to evaluate mitochondrial function.

Reactive oxygen species (ROS) are generated during normal metabolic processes under aerobic conditions. Since ROS production initiates harmful radical chain reactions on cellular macromolecules, including lipid peroxidation, DNA mutation, and protein denaturation, it has been implicated in a wide spectrum of diseases such as cancer, cardiovascular disease, ischemia-reperfusion and aging. Over the past several decades, antioxidants have received explosive attention regarding their protective potential against these deleterious reactions. Accordingly, many analytical methodologies have been developed for the evaluation of the antioxidant capacity of compounds or complex biological samples. Herein, we introduce a simple and convenient method to detect in vivo intracellular ROS levels photometrically in Caenorhabditis elegans using 2’,7’-dichlorofluorescein diacetate (H₂DCFDA), a cell permeant tracer.

Microbial biodegradation of rubber relies on extracellular rubber oxygenases that catalyze the oxidative cleavage of the double bond of the polyisoprene backbone into oligo-isoprenoids. This protocol describes the determination of rubber oxygenase activities by an online measurement of molecular oxygen consumption via a non-invasive fluorescence-based assay. The produced oligo-isoprenoid cleavage products with terminal keto- and aldehyde-groups are identified qualitatively and quantitatively by HPLC. Our method allows for the characterization of homologue rubber oxygenases, and can likely be adapted to assay other oxygenases consuming dioxygen. Here we describe the determination of rubber oxygenase activities at the examples of the so far two known types of rubber oxygenases, namely rubber oxygenase A (RoxA) and latex clearing protein (Lcp).

The rate of oxygen consumption is a vital marker indicating cellular function during lifetime under normal or metabolically challenged conditions. It is used broadly to study mitochondrial function (Artal-Sanz and Tavernarakis, 2009; Palikaras et al., 2015; Ryu et al., 2016) or investigate factors mediating the switch from oxidative phosphorylation to aerobic glycolysis (Chen et al., 2015; Vander Heiden et al., 2009). In this protocol, we describe a method for the determination of oxygen consumption rates in the nematode Caenorhabditis elegans.