Cyclophilin D-Sensitive Mitochondrial Permeability Transition in Adult Human Brain and Liver Mitochondria

Abstract

The mitochondrial permeability transition (mPT) is considered to be a major cause of cell death under a variety of pathophysiological conditions of the central nervous system (CNS) and other organs. Pharmacological inhibition or genetic knockout of the matrix protein cyclophilin D (CypD) prevents mPT and cell degeneration in several models of brain injury. If these findings in animal models are translatable to human disease, pharmacological inhibition of mPT offers a promising therapeutic target. The objective of this study was to validate the presence of a CypD-sensitive mPT in adult human brain and liver mitochondria. In order to perform functional characterization of human mitochondria, fresh tissue samples were obtained during hemorrhage or tumor surgery and mitochondria were rapidly isolated. Mitochondrial calcium retention capacity, a quantitative assay for mPT, was significantly increased by the CypD inhibitor cyclosporin A in both human brain and liver mitochondria, whereas thiol-reactive compounds and oxidants sensitized mitochondria to calcium-induced mPT. Brain mitochondria underwent swelling upon calcium overload, which was reversible upon calcium removal. To further explore mPT of human mitochondria, liver mitochondria were demonstrated to exhibit several classical features of the mPT phenomenon, such as calcium-induced loss of membrane potential and respiratory coupling, as well as release of the pro-apoptotic protein cytochrome c. We concluded that adult viable human brain and liver mitochondria possess an active CypD-sensitive mPT. Our findings support the rationale of CypD and mPT inhibition as pharmacological targets in acute and chronic neurodegeneration.

Identification of ER-000444793, a Cyclophilin D-independent inhibitor of mitochondrial permeability transition, using a high-throughput screen in cryopreserved mitochondria

“…mPT has been demonstrated across many species, including mitochondria from human cells49, rodents21, fish50 and yeast51. To confirm the screening data and demonstrate consistent compound pharmacology in human samples, mitochondria were isolated from HeLa S3 cells and Ca 2+ retention capacity assessed.…”

“…To date, only CypD has been truly agreed by numerous independent laboratories as being a critical regulator of pore opening, with substantial genetic and pharmacological studies having identified the role of CypD in potentiating pore opening212549. Most mPTP inhibitors reported in the literature, such as NIM-811, CsA and SfA desensitize the pore to Ca 2+ -induced opening, through inhibition of CypD243052.…”

Adenosine receptors: regulatory players in the preservation of mitochondrial function induced by ischemic preconditioning of rat liver

“…In energized mitochondria, stabilization of the c conformation of the ANT (as it is by CAT) sensitizes the MPT to calcium. Also, oxidative stress activates the MPT by inhibiting ADP binding to the ANT and enhancing CypD-ANT interaction, decreasing the sensitivity of the calcium trigger [66]. Thus, inhibition of ATP/ADP translocation sensitizes mitochondria to MPT.…”

Spongionella Secondary Metabolites Regulate Store Operated Calcium Entry Modulating Mitochondrial Functioning in SH-SY5Y Neuroblastoma Cells

“…And mPTP deregulation is related with an increase of cell death. Due to this, the compounds that bind to Cyp D structure, could constitute an interesting tool for the treatment of many diseases where mitochondria are implicated, such as ischemic insults, muscular dystrophies, multiple sclerosis, amyotrophic lateral sclerosis and Alzheimer's disease (AD) while others [10].…”