Patch clamp reveals powerful blockade of the mitochondrial permeability transition pore by the D2‐receptor agonist pramipexole

Abstract

The dopamine-D2-agonist pramipexole (PPX) was tested for blocking mitochondrial permeability transition (PT) in order to give a possible explanation for its neuroprotective effect seen in PPX-treated Parkinson's disease patients. Patch-clamp techniques for studying single-channel currents in the inner mitochondrial membrane and large-amplitude swelling of energized mitochondria were used to study PPX action on the permeability transition pore (PTP), a key player in the mitochondrial route of the apoptotic cascade. Identity of the PTP was proven by measuring the concentration-response relation for cyclosporin A-blockade (IC50=26 nM). PPX inhibits the PTP reversibly with an IC50 of 500 nM, which is close to the values determined earlier as plasma concentrations after PPX medication in patients. Interaction of PPX with the PTP is further supported by demonstrating that it abolished Ca2+-triggered swelling in functionally intact mitochondria. Blockade of the PTP by PPX was attenuated by increasing concentrations of inorganic phosphate and by acidification. We suggest that PPX could exert part of its neuroprotective effect by inhibition of the PTP and thus, probably, blocking of the mitochondrial pathway of the apoptosis cascade.

Dexpramipexole improves bioenergetics and outcome in experimental stroke

“…Interestingly, DEX has the unique ability to bind mitochondrial F1Fo-ATP synthase and improve mitochondrial efficiency by concomitant increase of ATP synthesis and reduction of O 2 consumption (Alavian et al, 2012;Alavian et al, 2015). Consistent with this, and with recent evidence that F1Fo-ATP synthase participates in the supramolecular complex organization of the mitochondrial transition pore complex (Bonora et al, 2015;Jonas et al, 2015), DEX inhibits depolarizing membrane currents in dysfunctional mitochondria and prevents organelle swelling in conditions predisposing to pore opening (Cassarino et al, 1998;Sayeed et al, 2006). Remarkably, DEX also detoxifies mitochondrial reactive oxygen species and reduces cell death in in vitro models of neurotoxicity (Cassarino et al, 1998;Danzeisen et al, 2006;Ferrari-Toninelli et al, 2010).…”

Inhibitory modulation of the mitochondrial permeability transition by minocycline

“…From mitoplasts single-channel currents were recorded by patch-clamp methods as explained in detail, previously [33]. Mitoplasts were obtained by hyposmotic shock: A c c e p t e d M a n u s c r i p t 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Test solutions were based on the HEPES-buffer and were applied through the glass capillaries of a peristaltic-pump driven flow system.…”

“…It must be noted, however, that a mitoplast constitutes an artificial system in that the outer membrane is missing and, secondly, the mitochondrial membrane potential is lost. Nevertheless, mitoplasts have been proved to be useful tools to study successfully biophysical questions and direct pharmacological interactions with the channel proteins in the inner membrane [33,34]. Additionally, it is remarkable that inhibition of the mPTP can be observed at relatively high Ca were reported before [33].…”

The Mitochondrial Complex V–Associated Large-Conductance Inner Membrane Current Is Regulated by Cyclosporine and Dexpramipexole

“…DEX is the nondopaminergic R(1) enantiomer of the high-affinity dopamine agonist and Parkinson's disease therapeutic pramipexole (Mirapex; Boehringer Ingelheim Pharmaceuticals, Inc., Ridgefield, CT) (Gribkoff and Bozik, 2008). Pramipexole is neuroprotective by a nondopaminergic mechanism (Gu et al, 2004), likely involving inhibition of mitochondrial permeability transition pore (mPTP) (Cassarino et al, 1998;Sayeed et al, 2006). Because DEX is not a high-affinity dopamine agonist, its use avoids the side effects of dopaminergic agonists, and it is tolerated at clinical doses that are neuroprotective (Bozik et al, 2011).…”