Electrophysiological characterization of a mitochondrial inner membrane chloride channel in rat brain

Abstract

Mitochondria are an essential component of cellular integrity and homeostasis, and their functions and pathological processes are highly dependent on mitochondrial ion channels. Anion channels of the inner mitochondrial membrane have been described by direct patch-clamp electrophysiological methods in mitoplasts prepared in cardiac, liver, and brown adipose tissue, but not in brain. Here, using acutely isolated rat brain mitoplasts, we describe the properties of a large conductance, voltage-gated, pH-sensitive, outwardly rectifying chloride channel with conductances of 98 pS and 129 pS at negative and positive membrane potentials, respectively. While the molecular identity of this chloride conductance is unknown, it is unlikely to be a CLIC channel due to differences in the observed electrophysiological properties.

Cannabidiol Impairs Brain Mitochondrial Metabolism and Neuronal Integrity

“…In patch-clamp recordings of mitoplasts prepared from acutely isolated brain mitochondria (from rats aged P35), we observed a chloride-selective conductance of ∼100 pS, as previously characterized. 27 Bath application of CBD resulted in a dose-dependent inhibition of chloride channel activity with an IC 50 of ∼2 μM ( Fig. 3A, B ).…”

“…In the present study, we demonstrate that low micromolar concentrations of CBD (≥1–3.75 μM) can impair brain mitochondrial function—possibly through its inhibitory effects on a recently described chloride conductance on the inner mitochondrial membrane in rodent brain (IC 50 1.9 μM). 27 Specifically, within and above this concentration range, CBD profoundly inhibits ATP production, reduces the threshold for Ca 2+ -induced mPT activation, and inhibits mitochondrial Ca 2+ uptake (IC 50 3.5 μM), effects that can collectively induce cellular injury and apoptotic neurodegeneration. Furthermore, we found that CBD can disrupt hippocampal LTP and the Morris water maze performance at low micromolar concentrations and at the high dose (300 mg/kg/day) used, respectively.…”

“…Patch-clamp recordings on mitoplasts prepared from acutely isolated Wistar rat brain and CB 1 KO mouse brain mitochondria were performed as previously described. 27 Currents are described using the standard convention, and voltages refer to the inside of the mitoplast (opposite of the command potential). Hippocampal long-term potentiation (LTP) studies were conducted on C3HeB/FeJ mice at P35–40.…”

NAD(H) Regulates the Permeability Transition Pore in Mitochondria through an External Site

“…The strongest evidence for the mPTP regulation through an external NAD(H)-binding site came from the data presented in Figures 3 and 4. It is well known that the IMM contains specialized transport systems for the uptake and extrusion of K + and Cl − ions, but not for sucrose and NAD(H) [47][48][49][50]. Therefore, with the opening of mPTP (non-selective channel) in KCl-BM and S-BM, both ions and sucrose enter into the matrix, causing the mitochondrial swelling.…”

Tracking intra‐ and inter‐organelle signaling of mitochondria

“…The Δψ m is not only essential for the generation of ATP , but also to regulate transfer of ions like K + , Na + , Cl − , and Ca 2+ across the mitochondrial membrane. Dysregulation of Ca 2+ homeostasis and mitochondrial Ca 2+ overload results in increased permeability of the IMM to protons, decreasing Δψ m as well as the mitochondrial pH gradient and initiating cell death .…”