Fluorescent Peptides Sequester Redox Copper to Mitigate Oxidative Stress, Amyloid Toxicity, and Neuroinflammation.

Alzheimer's disease is a progressive neurodegenerative disorder that significantly contributes to dementia. The lack of effective therapeutic interventions presents a significant challenge to global health. We have developed a set of short peptides (PNGln) conjugated with a dual-functional fluorophoric amino acid (NGln). The lead peptide, P2NGln, displays a high affinity for Cu2+, maintaining the metal ion in a redox-inactive state. This mitigates the cytotoxicity generated by reactive oxygen species (ROS), which are produced by Cu2+ under the reductive conditions of Asc and Aß16 or Aß42. Furthermore, P2NGln inhibits both Cu-dependent and -independent fibrillation of Aß42, along with the subsequent toxicity induced by Aß42. In addition, P2NGln exhibits inhibitory effects on the production of lipopolysaccharide (LPS)-induced ROS and reactive nitrogen species (RNS) in microglial cells. In vitro and cellular studies indicate that P2NGln could significantly reduce Aß-Cu2+-induced ROS production, amyloid toxicity, and neuroinflammation, offering an innovative strategy against Alzheimer's disease.

Synaptic mitochondria glycation contributes to mitochondrial stress and cognitive dysfunction.

Mitochondrial and synaptic dysfunction are pathological features of brain aging and cognitive decline. Synaptic mitochondria are vital for meeting the high energy demands of synaptic transmission. However, little is known about the link between age-related metabolic changes and the integrity of synaptic mitochondria. To this end, we investigate the mechanisms of advanced glycation endproducts (AGEs)-mediated mitochondrial and synaptic stress and evaluate the strategies to eliminate these toxic metabolites. Using aged brain and novel transgenic mice overexpressing neuronal glyoxalase 1 (GLO1), we comprehensively analyzed alterations in accumulation/buildup of AGEs and related metabolites in synaptic mitochondria and the association of AGE levels with mitochondrial function. We demonstrate for the first time that synaptic mitochondria are an early and major target of AGEs and the related toxic metabolite methylglyoxal (MG), a precursor of AGEs. MG/AGEs-insulted synaptic mitochondria exhibit deterioration of mitochondrial and synaptic function. Such accumulation of MG/AGEs positively correlated with mitochondrial perturbation and oxidative stress in aging brain. Importantly, clearance of AGEs-related metabolites by enhancing neuronal GLO1, a key enzyme for detoxification/of AGEs, reduces synaptic mitochondrial AGEs accumulation and improves mitochondrial and cognitive function in aging and AGE-challenged mice. Furthermore, we evaluated the direct effect of AGEs on synaptic function in hippocampal neurons in live brain slices as an ex-vivo model and in vitro cultured hippocampal neurons by recording long-term potentiation (LTP) and measuring spontaneously occurring miniature excitatory postsynaptic currents (mEPSCs). Neuronal GLO1 rescues deficits in AGEs-induced synaptic plasticity and transmission by fully recovery of decline in LTP or frequency of mEPSC. These studies explore crosstalk between synaptic mitochondrial dysfunction and age-related metabolic changes relevant to brain aging and cognitive decline. Synaptic mitochondria are particularly susceptible to AGEs-induced damage, highlighting the central importance of synaptic mitochondrial dysfunction in synaptic degeneration in age-related cognitive decline. Thus, augmenting GLO1 function to scavenge toxic metabolites represents a therapeutic approach to reduce age-related AGEs accumulation and to improve mitochondrial function and learning and memory.

New cyclophilin D inhibitor rescues mitochondrial and cognitive function in Alzheimer's disease.

Mitochondrial dysfunction is an early pathological feature of Alzheimer disease and plays a crucial role in the development and progression of Alzheimer's disease. Strategies to rescue mitochondrial function and cognition remain to be explored. Cyclophilin D (CypD), the peptidylprolyl isomerase F (PPIase), is a key component in opening the mitochondrial membrane permeability transition pore, leading to mitochondrial dysfunction and cell death. Blocking membrane permeability transition pore opening by inhibiting CypD activity is a promising therapeutic approach for Alzheimer's disease. However, there is currently no effective CypD inhibitor for Alzheimer's disease, with previous candidates demonstrating high toxicity, poor ability to cross the blood-brain barrier, compromised biocompatibility and low selectivity. Here, we report a new class of non-toxic and biocompatible CypD inhibitor, ebselen, using a conventional PPIase assay to screen a library of ∼2000 FDA-approved drugs with crystallographic analysis of the CypD-ebselen crystal structure (PDB code: 8EJX). More importantly, we assessed the effects of genetic and pharmacological blockade of CypD on Alzheimer's disease mitochondrial and glycolytic bioenergetics in Alzheimer's disease-derived mitochondrial cybrid cells, an ex vivo human sporadic Alzheimer's disease mitochondrial model, and on synaptic function, inflammatory response and learning and memory in Alzheimer's disease mouse models. Inhibition of CypD by ebselen protects against sporadic Alzheimer's disease- and amyloid-ß-induced mitochondrial and glycolytic perturbation, synaptic and cognitive dysfunction, together with suppressing neuroinflammation in the brain of Alzheimer's disease mouse models, which is linked to CypD-related membrane permeability transition pore formation. Thus, CypD inhibitors have the potential to slow the progression of neurodegenerative diseases, including Alzheimer's disease, by boosting mitochondrial bioenergetics and improving synaptic and cognitive function.