Antioxidant effects of JM-20 on rat brain mitochondria and synaptosomes: Mitoprotection against Ca2+-induced mitochondrial impairment

Abstract

Because mitochondrial oxidative stress and impairment are important mediators of neuronal damage in neurodegenerative diseases and in brain ischemia/reperfusion, in the present study, we evaluated the antioxidant and mitoprotective effect of a new promising neuroprotective molecule, JM-20, in mitochondria and synaptosomes isolated from rat brains. JM-20 inhibited succinate-mediated H₂O₂ generation in both mitochondria and synaptosomes incubated in depolarized (high K(+)) medium at extremely low micromolar concentration and with identical IC₅₀ values of 0.91 μM. JM-20 also repressed glucose-induced H₂O₂ generation stimulated by rotenone or by antimycin A in synaptosomes incubated in high sodium-polarized medium at extremely low IC₅₀ values of 0.395 μM and 2.452 μM, respectively. JM-20 was unable to react directly with H₂O₂ or with superoxide anion radicals but displayed a cathodic reduction peak at -0.71V, which is close to that of oxygen (-0.8V), indicating high electron affinity. JM-20 also inhibited uncoupled respiration in mitochondria or synaptosomes and was a more effective inhibitor in the presence of the respiratory substrates glutamate/malate than in the presence of succinate. JM-20 also prevented Ca(2+)-induced mitochondrial permeability transition pore opening, membrane potential dissipation and cytochrome c release, which are key pathogenic events during stroke. This molecule also prevented Ca(2+) influx into synaptosomes and mitochondria; the former effect was a consequence of the latter because JM-20 inhibition followed the patterns of carbonyl cyanide p-trifluoromethoxyphenyl hydrazone (FCCP), which is a classic mitochondrial uncoupler. Because the mitochondrion is considered an important source and target of neuronal cell death signaling after an ischemic insult, the antioxidant and protective effects of JM-20 against the deleterious effects of Ca(2+) observed at the mitochondrial level in this study may endow this molecule with the ability to succeed in mitochondrion-targeted strategies to combat ischemic brain damage.

Protective effects of leptin against cerebral ischemia/reperfusion injury (Review)

“…In mice, blocking PI3K with either LY294002 or wortmannin significantly attenuated the leptin-induced increase in renal sympathetic activity. Of note, leptin promotes the switch toward type 1 T-helper (Th1) cell immune responses by increasing interferon-γ secretion, facilitating Th17 responses (47), and stimulating the release of inflammatory cytokines, including interleukin (IL)-1beta, IL-6 and IL-8, and the chemokine monocyte chemotactic protein-1.…”

“…Mitochondrial biogenesis is promoted via the activation of JAK/STAT by leptin, via downstream proteins, such as proliferator-activated receptor γ a co-activator-1α and mitochondrial transcription factor A. Such activation has been indicated to be involved in neuronal cell protection via the enhancement of anti-oxidant enzyme activities (15,47). It has been demonstrated that leptin increases superoxide dismutase (SOD) levels, stabilizes the mitochondrial membrane and alleviates endoplasmic reticulum pressure (17); this in turn inhibits the production of free radicals and ischemic injury in mice by binding to OB-Rb in the cortex, hippocampus and striatum.…”

Procyanidin B2 attenuates neurological deficits and blood–brain barrier disruption in a rat model of cerebral ischemia

“…The mitochondria are the major sites for ROS generation in neurons . Mitochondrial dysfunction and oxidative stress were shown to be critical determinants of ischemic neuronal death and survival .…”

Multifunctional Molecule, JM-20, Reverses Aluminum Chloride-Induced Memory Impairment and Neuronal Damage in Rats

“…Mitochondrial swelling. Mitochondrial swelling induced by calcium (Ca 2+ ) plus inorganic phosphate (Pi) was estimated spectrophotometrically from the decrease in the absorbance at 540 nm measured using the spectrophotometer [12]. Brain mitochondria (0.5 mg/mL) were added to the standard incubation medium supplemented with Ca 2+ (50 µM) plus Pi (2 mM).…”