SkQ1 as a Tool for Controlling Accelerated Senescence Program: Experiments with OXYS Rats.

According to the concept suggested by V. P. Skulachev and co-authors, aging of living organisms can be considered as a special case of programmed death of an organism - phenoptosis, and mitochondrial antioxidant SkQ1 is capable of inhibiting both acute and chronic phenoptosis (aging). The authors of the concept associate effects of SkQ1 with suppression of the enhanced generation of ROS in mitochondria. Numerous studies have confirmed the ability of SkQ1 to inhibit manifestations of the "healthy", or physiological, aging. According to the results of our studies, SkQ1 is especially effective in suppressing the program of genetically determined accelerated senescence in OXYS rats, which appears as an early development of a complex of age-related diseases: cataracts, retinopathy (similar to the age-related macular degeneration in humans), osteoporosis, and signs of Alzheimer's disease. Accelerated senescence in OXYS rats is associated with mitochondrial dysfunction, but no direct associations with oxidative stress have been identified. Nevertheless, SkQ1 is able to prevent and/or suppress development of all manifestations of accelerated senescence in OXYS rats. Its effects are due to impact on the activity of many signaling pathways and processes, but first of all they are associated with restoration of the structural and functional parameters of mitochondria. It could be suggested that the use of SkQ1 could represent a promising strategy in prevention of accelerated phenoptosis - early development of a complex of age-related diseases (multimorbidity) in people predisposed to it.

A Simple Method of Synthesis of 3-Carboxy-2,2,5,5-Tetraethylpyrrolidine-1-oxyl and Preparation of Reduction-Resistant Spin Labels and Probes of Pyrrolidine Series.

Stable free radicals are widely used as molecular probes and labels in various biophysical and biomedical research applications of magnetic resonance spectroscopy and imaging. Among these radicals, sterically shielded nitroxides of pyrrolidine series demonstrate the highest stability in biological systems. Here, we suggest new convenient procedure for preparation of 3-carboxy-2,2,5,5-tetraethylpyrrolidine-1-oxyl, a reduction-resistant analog of widely used carboxy-Proxyl, from cheap commercially available reagents with the yield exceeding the most optimistic literature data. Several new spin labels and probes of 2,2,5,5-tetraethylpyrrolidine-1-oxyl series were prepared and reduction of these radicals in ascorbate solutions, mice blood and tissue homogenates was studied.

Disruptions of Autophagy in the Rat Retina with Age During the Development of Age-Related-Macular-Degeneration-like Retinopathy.

Age-related macular degeneration (AMD) is one of the main causes of vision impairment in the elderly. Autophagy is the process of delivery of cytoplasmic components into lysosomes for cleavage; its age-related malfunction may contribute to AMD. Here we showed that the development of AMD-like retinopathy in OXYS rats is accompanied by retinal transcriptome changes affecting genes involved in autophagy. These genes are associated with kinase activity, immune processes, and FoxO, mTOR, PI3K-AKT, MAPK, AMPK, and neurotrophin pathways at preclinical and manifestation stages, as well as vesicle transport and processes in lysosomes at the progression stage. We demonstrated a reduced response to autophagy modulation (inhibition or induction) in the OXYS retina at age 16 months: expression of genes Atg5, Atg7, Becn1, Nbr1, Map1lc3b, p62, and Gabarapl1 differed between OXYS and Wistar (control) rats. The impaired reactivity of autophagy was confirmed by a decreased number of autophagosomes under the conditions of blocked autophagosome-lysosomal fusion according to immunohistochemical analysis and transmission electron microscopy. Thus, the development of AMD signs occurs against the background of changes in the expression of autophagy-related genes and a decrease in autophagy reactivity: the ability to enhance autophagic flux in response to stress.

The Rat Prefrontal-Cortex Transcriptome: Effects of Aging and Sporadic Alzheimer's Disease-Like Pathology.

Alzheimer's disease (AD) is the most widespread late-life dementia and involves the prefrontal cortex, a vulnerable brain region implicated in memory, emotion, cognition, and decision-making behavior. To understand the molecular differences between the effects of aging and AD on the prefrontal cortex, this study characterized the age-dependent changes in gene expression in Wistar rats (control) and OXYS rats (rodents that simulate key characteristics of sporadic AD) using RNA sequencing. We found that major altered biological processes during aging in Wistar rats were associated with immune processes. Gene expression changes during development of AD-like pathology as well as at the preclinical stage were related to neuronal plasticity, catalytic activity, lipid and immune processes, and mitochondria. A comparison of genes between data sets "OXYS rats" and "human AD" revealed similarity in expression alterations of genes related primarily to mitochondrial function; immune, endocrine, and circulatory systems; signal transduction; neuronal and synaptic processes; hypoxia; and apoptosis. Expression changes in mitochondrial processes identified in OXYS rats by RNA sequencing were confirmed by ultrastructural neuronal organelle alterations and low activity of respiratory chain complexes I, IV, and V in cortical mitochondria, suggesting that mitochondrial dysfunction appears to mediate or possibly even initiate the development of AD.

Mitochondrial Dysfunction as a Predictor and Driver of Alzheimer's Disease-Like Pathology in OXYS Rats.

Growing evidence suggests that mitochondrial dysfunction is an early event in sporadic Alzheimer's disease (AD), but the impact of mitochondrial dysfunction on the transition from healthy aging to AD remains elusive. Here we estimated the influence of mitochondrial dysfunction on the initiation of AD signs in OXYS rats, which simulate key characteristics of sporadic AD. We assessed the mitochondrial ultrastructure of pyramidal neurons of the hippocampus at the age preceding the development (age 20 days), during manifestation (4-5 months), and at the well-pronounced stages (18-24 months) of the AD-like pathology in OXYS rats. Ultrastructural alterations were collated with the amounts of proteins mediating mitochondrial dynamics [mitofusins (MFN1 and MFN2) and dynamin-1-like protein (DRP1)]; with activity of respiratory chain complexes I, IV, and V in the hippocampal mitochondria; with reactive oxygen species (ROS) production; and with expression of uncoupling protein 2 (UCP2) regulating ROS production. Already at the preclinical stage, OXYS rats showed some characteristic changes in hippocampal mitochondria, which increased in size with the manifestation and progression of AD-like pathology, including decreased activity of respiratory complexes against the background of greater fusion and formation of larger mitochondria. Signs of AD developed simultaneously with increasing dysfunction of mitochondria, with a dramatic decrease in their number, and with increased fission but without upregulation of ROS production (observed only in 20-day-old OXYS rats). Summarizing the data from our present and previous studies, we conclude that mitochondrial dysfunction appears to mediate or possibly even initiate pathological molecular cascades of AD-like pathology in OXYS rats and can be considered a predictor of the early development of the late-onset form of AD in humans.

Antioxidant SkQ1 Alleviates Signs of Alzheimer's Disease-like Pathology in Old OXYS Rats by Reversing Mitochondrial Deterioration.

BACKGROUND: Mitochondrial dysfunction is called the missing link between brain aging and Alzheimer's disease (AD), the most common type of age-related dementia worldwide. Among the most advanced and promising of approaches to prevention or slowing of AD are therapeutic strategies targeting mitochondria. OBJECTIVE: Mitochondria-targeted antioxidant SkQ1 can suppress the development of AD signs, but its therapeutic potential in AD at clinical stages is currently unknown. METHOD: Using OXYS rats that simulate key characteristics of sporadic AD, we evaluated effects of SkQ1 treatment from the age of 19 to 24 months on the locomotor and exploratory activities, signs of neurodegeneration detectable by magnetic resonance imaging (MRI), amyloid-ß (Aß) protein levels in the hippocampus and serum, and structure of the mitochondrial apparatus in hippocampal neurons. RESULTS: Treatment with SkQ1 increased behavioral activity in OXYS and Wistar (control) rats. According to MRI, SkQ1 decreased the percentage of animals with demyelination only among Wistar rats. At the same time, the antioxidant reduced hippocampal Аß1-40 and Аß1-42 protein levels in both rat strains and did not affect serum Ðß levels. The number of mitochondria was significantly lower in OXYS rats; SkQ1 had no effect on this parameter but significantly reduced the destructive changes in mitochondria of both rat strains. As a result, in OXYS rats, the proportion of severely damaged mitochondria decreased, whereas in Wistar rats, the proportion of intact mitochondria increased. CONCLUSION: According to our past and present results, the repair of the mitochondrial apparatus by SkQ1 is a promising strategy against AD.