Mitochondrial delivery of bongkrekic acid using a MITO-Porter prevents the induction of apoptosis in human HeLa cells.

The fact that mitochondrial dysfunction has been implicated in a variety of human diseases suggests that they would be expected as a target organelle for these diseases. Bongkrekic acid (BKA) is a chemical that functions as a ligand of the adenine nucleotide translocator and is known to potently inhibit the mitochondrial permeability transition that is associated with apoptosis. Thus, delivering it to mitochondria would be an innovative therapy for the treatment of mitochondrial diseases that are largely associated with apoptosis. Here, we report on the use of a MITO-Porter, an innovative nanocarrier for mitochondrial delivery via mitochondrial membrane fusion, for delivering BKA to mitochondria. We first constructed a BKA-MITO-Porter, in which BKA is contained in lipid envelopes of a MITO-Porter. We then confirmed that the BKA-MITO-Porter was efficiently internalized into cells and is delivered to mitochondria, similar to a conventional MITO-Porter. Moreover, we evaluated the antiapoptosis effect of the BKA-MITO-Porter in HeLa cells by measuring caspase 3/7 activity. The findings confirmed that the BKA-MITO-Porter showed a strong antiapoptosis effect compared with naked BKA. The results reported here demonstrate its potential for the use in therapies aimed at mitochondrial diseases, as a mitochondrial medicine candidate.

Inhibition of mitochondrial membrane bound-glutathione transferase by mitochondrial permeability transition inhibitors including cyclosporin A.

AIMS: Effect of mitochondrial permeability transition (MPT) inhibitors on mitochondrial membrane-bound glutathione transferase (mtMGST1) activity in rat liver was investigated in vitro. MAIN METHODS: When mitochondria were incubated with MPT inhibitors, mtMGST1 activity was decreased dose dependently and their 50% inhibition concentration (IC(50)) were 1.2 microM (cyclosporin A; CsA), 31 microM (bongkrekic acid; BKA), 1.8 mM (ADP), and 3.2 mM (ATP). The decrease of mtMGST1 activity by the MPT inhibitors was not observed in the presence of detergent Triton X-100. On the contrary, mtMGST1 inhibition by GST inhibitors such as cibacron blue (IC(50), 4.2 microM) and S-hexylglutathione (IC(50), 480 microM) was not affected in the presence of detergent. Although mtMGST1 resides in both the inner (IMM) and outer mitochondrial membranes (OMM), only mtMGST1 in the IMM was inhibited by the MPT inhibitors in the absence of detergent. GST inhibitors decreased mtMGST1 activity both in the IMM and OMM regardless of the presence or absence of detergent. Cytosolic GSTs and microsomal MGST1 were not inhibited by the MPT inhibitors. KEY FINDINGS: These results indicate that mtMGST1 is inhibited by MPT inhibitors through membrane components, not directly by the inhibitors. SIGNIFICANCE: Since CsA binds to cyclophilin D (Cyp-D) in the mitochondrial matrix whereas BKA or ADP binds to adenine nucleotide translocator (ANT) in the IMM, it was suggested that mtMGST1 in the IMM interacts with Cyp-D/ANT and the binding of MPT inhibitors to Cyp-D or ANT causes their conformational change followed by an alteration of mtMGST1 conformation, resulting in decreasing mtMGST1 activity.

Bongkrekic acid ameliorates ischemic neuronal death in the cortex by preventing cytochrome c release and inhibiting astrocyte activation.

Mitochondrial release of cytochrome c (cyt-c) plays a critical role in initiating cell death after cerebral ischemia. The objective of this study was to determine whether bongkrekic acid (BKA) ameliorates ischemic neuronal damage by inhibiting the release of cyt-c. These results showed that a 10min period of global ischemia caused neuronal death, increased the release of cyt-c and activated astrocytes in the cortex and CA1. BKA treatment reduced ischemic-induced neuronal death, prevented cyt-c release and inhibited astrocyte activation in the cortex, but not in the CA1. These results suggest that the neuroprotective effect of BKA is associated with its ability to prevent cyt-c release and to inhibit astrocyte activation.