Assay for detecting changes in mitochondrial membrane permeability and method of using same
An assay for assessing the permeability of mitochondrial membranes is provided. The assay is based on enzymatic reactions that produce a detectable signal in the presence of intra-mitochondrial compounds. In some embodiments, the intra-mitochondrial compounds may be reduced and/or oxidized nicotinamide adenine dinucleotides (i.e., NADH and NAD + , respectively). The assay may optionally be provided in the form of a kit, and may further be useful in the discovery and interrogation of compounds that may serve to inhibit pathologic increase in mitochondrial membrane permeability, which is associated with numerous and varied mammalian disease.
1. A method of assessing the integrity of a mitochondrial membrane, comprising:
(a) contacting a sample comprising isolated mitochondria with a mixture of enzymes comprising alcohol dehydrogenase (ADH), NADH oxidase (Ox), and horseradish peroxidase (HRP), which mixture catalyzes at least two coupled, cyclic enzymatic reactions that utilize an intra-mitochondrial substance, if present in the sample, as a substrate in at least one of said coupled, cyclic enzymatic reactions and in which at least the other of said coupled, cyclic enzymatic reactions generates a detectable signal; and
(b) correlating said detectable signal, if generated, to the presence of said intra-mitochondrial substance, thereby implicating a breach in said mitochondrial membrane.
2. The method of claim 1 in which the intra-mitochondrial substance is a pyridine nucleotide.
3. The method of claim 2 in which the pyridine nucleotide is NAD + or NADH.
4. The method of claim 1 in which the isolated mitochondria are isolated from liver.
5. The method of claim 1 in which the detectable signal is a luminescent product, a fluorescent product, or a spectrophotometrically detectable product.
6. The method of claim 1 , wherein, prior to step (a), said sample is contacted with one or more test compounds; and then the detectable signal produced in the presence of the test compound is compared to the detectable signal produced in the absence of the test compound to determine the effect of the test compound on the integrity of the mitochondrial membrane.
7. The method of claim 6 , wherein the test agent is a mitochondrial membrane damaging agent.
8. The method of claim 7 , wherein said mitochondria damaging agent is cyclosporin A, calcium, or Bongkrekic acid.