Brain ischemia is one of the major causes of chronic disability and death worldwide. It is related to insufficient blood supply to cerebral tissue, which induces irreversible or reversible intracellular effects depending on the time and intensity of the ischemic event. Indeed, neuronal function may be restored in some conditions, such as transient ischemic attack (TIA), which may be responsible for protecting against a subsequent lethal ischemic insult. It is well known that the brain requires high levels of oxygen and glucose to ensure cellular metabolism and energy production and that damage caused by oxygen impairment is tightly related to the brain’s low antioxidant capacity. Oxygen is a key player in mitochondrial oxidative phosphorylation (OXPHOS), during which reactive oxygen species (ROS) synthesis can occur as a physiological side-product of the process. Indeed, besides producing adenosine triphosphate (ATP) under normal physiological conditions, mitochondria are the primary source of ROS within the cell. This is because, in 0.2–2% of cases, the escape of electrons from complex I (NADPH-dehydrogenase) and III of the electron transport chain occurring in mitochondria during ATP synthesis leads to the production of the superoxide radical anion (O₂^•−), which exerts detrimental intracellular effects owing to its high molecular instability. Along with ROS, reactive nitrosative species (RNS) also contribute to the production of free radicals. When the accumulation of ROS and RNS occurs, it can cause membrane lipid peroxidation and DNA damage. Here, we describe the intracellular pathways activated in brain tissue after a lethal/sub lethal ischemic event like stroke or ischemic tolerance, respectively, highlighting the important role played by oxidative stress and mitochondrial dysfunction in the onset of the two different ischemic conditions.

Among the non-motor symptoms associated with Parkinson’s disease (PD), cognitive impairment is one of the most common and disabling. It can occur either early or late during the disease, and it is heterogeneous in terms of its clinical manifestations, such as Subjective Cognitive Dysfunction (SCD), Mild Cognitive Impairment (MCI), and Parkinson’s Disease Dementia (PDD). The aim of the present review is to delve deeper into the molecular mechanisms underlying cognitive decline in PD. This is extremely important to delineate the guidelines for the differential diagnosis and prognosis of the dysfunction, to identify the molecular and neuronal mechanisms involved, and to plan therapeutic strategies that can halt cognitive impairment progression. Specifically, the present review will discuss the pathogenetic mechanisms involved in the progression of cognitive impairment in PD, with attention to mitochondria and their contribution to synaptic dysfunction and neuronal deterioration in the brain regions responsible for non-motor manifestations of the disease.

Mitochondrial quality control is crucial for the homeostasis of the mitochondrial network. The balance between mitophagy and biogenesis is needed to reduce cerebral ischemia-induced cell death. Ischemic preconditioning (IPC) represents an adaptation mechanism of CNS that increases tolerance to lethal cerebral ischemia. It has been demonstrated that hypoxia-induced Seven in absentia Homolog 2 (Siah2) E3-ligase activation influences mitochondrial dynamics promoting the degradation of mitochondrial proteins. Therefore, in the present study, we investigated the role of Siah2 in the IPC-induced neuroprotection in in vitro and in vivo models of IPC. To this aim, cortical neurons were exposed to 30-min oxygen and glucose deprivation (OGD, sublethal insult) followed by 3 h OGD plus reoxygenation (lethal insult). Our results revealed that the mitochondrial depolarization induced by hypoxia activates Siah2 at the mitochondrial level and increases LC3-II protein expression, a marker of mitophagy, an effect counteracted by the reoxygenation phase. By contrast, hypoxia reduced the expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), a marker of mitochondrial biogenesis, whereas its expression was increased after reoxygenation thus improving mitochondrial membrane potential, mitochondrial calcium content, and mitochondrial morphology, hence leading to neuroprotection in IPC. Furthermore, Siah2 silencing confirmed these results. Collectively, these findings indicate that the balance between mitophagy and mitochondrial biogenesis, due to the activation of the Siah2-E3-ligase, might play a role in IPC-induced neuroprotection.

CircRNAs are covalently closed ncRNAs originating through back splicing; their expression is finely regulated, displaying specific patterns across different cell types, tissues, and developmental stages. While the molecular functions of circRNAs are not completely elucidated, their regulatory involvement in physiological processes is well established, alongside their dysregulation in several human disorders. These features, together with their higher stability compared to other ncRNAs, make this class of molecules promising theragnostic agents, particularly in biomarker discovery. Accordingly, it is crucial to develop and standardize experimental strategies that improve circRNA analysis, ensuring accurate and effective isolation of these molecules. In biomarker discovery, selecting the appropriate biological matrix is critical; whole blood is often preferred for its accessibility and minimally invasive collection. Because circRNAs are present in human peripheral blood and show promise as disease theragnostic biomarkers, we established a preliminary workflow tailored to isolate and analyze circRNAs from whole blood. The promising effectiveness and robustness of this workflow were demonstrated by qPCR analysis, suggesting highly reproducible detection and reliability in isolating and analyzing circRNAs. This, together with their stability and specific expression profiles, supports the utility of circRNAs in biomarker discovery and advanced circRNA research and contributes to accelerating their future integration into theragnostic applications in clinical settings.

The Na⁺ /Ca²⁺ exchanger plays a key role in the regulation of calcium homeostasis in most excitable cells. Three mammalian isoforms, NCX1, NCX2, and NCX3, are described, and with their splice variant, they are expressed in a tissue-specific manner and regulated by Ca²⁺ binding domains CBD1 and CBD2. Among the three isoforms, NCX3 is mainly expressed in the brain and skeletal muscle. The occurrence of [Na⁺]_i and [Ca²⁺]_i dyshomeostasis has been reported in several neurodegenerative diseases either at neuronal or glial levels. Although the role of each isoform is still under investigation, many lines of evidence point to a neuroprotective effect of NCX3 activation in several neurodegenerative diseases, including brain ischemia. On this light, we have designed, synthesized, and characterized novel 1,4-benzothiazepinonic derivatives structurally related to CGP37157, which is already described as a mitochondrial NCX (mNCX) blocker with a poor selectivity, where a cyclic amine has been linked in position 1 via an acetyl spacer. The newly synthesized compounds were screened for NCX3 activity by Fluo-4 single-cell microfluorimetry and patch-clamp electrophysiology in BHK cells singly expressing this isoform. Identification of the newly synthesized compounds modulating NCX3 activity was obtained by measuring Na⁺-free-dependent Ca²⁺ level changes above basal values and/or by electrophysiological detected NCX3 currents. Among the several newly synthesized pharmacological modulators of NCX3, compound 10 has shown the greatest capability of increasing the NCX3 activity in an in vivo model of focal brain ischemia.