The role of altered brain mitochondrial regulation in psychiatric pathologies, including Major Depressive Disorder (MDD), has attracted increasing attention. Aberrant mitochondrial functions were suggested to underlie distinct inter-individual vulnerability to stress-related MDD syndrome. In this context, insulin receptor sensitizers (IRSs) that regulate brain metabolism have become a focus of recent research, as their use in pre-clinical studies can help to elucidate the role of mitochondrial dynamics in this disorder and contribute to the development of new antidepressant treatment. Here, following 2-week chronic mild stress (CMS) using predation, social defeat, and restraint, MDD-related behaviour and brain molecular markers have been investigated along with the hippocampus-dependent performance and emotionality in mice that received the IRS dicholine succinate (DS). In a sucrose test, mice were studied for the key feature of MDD, a decreased sensitivity to reward, called anhedonia. Based on this test, animals were assigned to anhedonic and resilient-to-stress-induced-anhedonia groups, using a previously established criterion of a decrease in sucrose preference below 65%. Such assignment was based on the fact that none of control, non-stressed animals displayed sucrose preference that would be smaller than this value. DS-treated stressed mice displayed ameliorated behaviours in a battery of assays: sucrose preference, coat state, the Y-maze, the marble test, tail suspension, and nest building. CMS-vulnerable mice exhibited overexpression of the inflammatory markers Il-1β, tnf, and Cox-1, as well as 5-htt and 5-ht2a-R, in various brain regions. The alterations in hippocampal gene expression were the closest to clinical findings and were studied further. DS-treated, stressed mice showed normalised hippocampal expression of the plasticity markers Camk4, Camk2, Pka, Adcy1, Creb-ar, Nmda-2r-ar, and Nmda-2r-s. DS-treated and non-treated stressed mice who were resilient or vulnerable to anhedonia were compared for hippocampal mitochondrial pathway regulation using Illumina profiling. Resilient mice revealed overexpression of the mitochondrial complexes NADH dehydrogenase, succinate dehydrogenase, cytochrome bc1, cytochrome c oxidase, F-type and V-type ATPases, and inorganic pyrophosphatase, which were decreased in anhedonic mice. DS partially normalised the expression of both ATPases. We conclude that hippocampal reduction in ATP synthesis is associated with anhedonia and pro-inflammatory brain changes that are ameliorated by DS.

Fullerenes and fullerenols exhibit antioxidant and anti-inflammatory properties, making them promising candidates for Alzheimer’s disease (AD) therapy. Unlike conventional anti-inflammatory drugs, these compounds have multitargeted effects, including their ability to inhibit amyloid fibril formation. However, few studies have explored their efficacy in high-validity AD models. Female APPswe/PS1E9 (APP/PS1) mice and their wild-type (WT) littermates were orally administered with fullerene C₆₀ (0.1 mg/kg/day) or fullerenol C₆₀(OH)₂₄ (0.15 mg/kg/day) for 10 months starting at 2 months of age. Behavioral assessments were performed at 12 months of age. Amyloid plaque density and size were analyzed in the brain regions using Congo red staining. The expression of genes related to inflammation and plasticity was examined, and an in vitro assay was used to test the toxicity of fullerenol and its effect on amyloid β peptide 42 (Aβ42)-induced reactive oxygen species (ROS) production. Fullerenol reduced the maximum plaque size in the cortex and hippocampus, decreased the small plaque density in the hippocampus and thalamus, and prevented an increase in glial fibrillary acidic protein (GFAP) positive cell density in the mutants. Both treatments improved cognitive and emotional behaviors and reduced Il1β and increased Sirt1 expression. In vitro, fullerenol was non-toxic across a range of concentrations and reduced Aβ42-induced ROS production in brain endothelial cells and astrocytes. Long-term administration of fullerene or fullerenol improved behavioral and molecular markers of AD in APP/PS1 mice, with fullerenol showing additional benefits in reducing amyloid burden.

Neuroinflammation is a key feature of Alzheimer’s disease (AD), and stem cell therapies have emerged as promising candidates due to their immunomodulatory properties. Neuro-Cells (NC), a combination of unmodified mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs), have demonstrated therapeutic potential in models of central nervous system (CNS) injury and neurodegeneration. Here, we studied the effects of NC in APPswe/PS1dE9 mice, an AD mouse model. Twelve-month-old APPswe/PS1dE9 mice or their wild-type littermates were injected with NC or vehicle into the cisterna magna. Five to six weeks post-injection, cognitive, locomotor, and emotional behaviors were assessed. The brain was stained for amyloid plaque density using Congo red, and for astrogliosis using DAPI and GFAP staining. Gene expression of immune activation markers (Il-1β, Il-6, Cd45, Tnf) and plasticity markers (Tubβ3, Bace1, Trem2, Stat3) was examined in the prefrontal cortex. IL-6 secretion was measured in cultured human monocytes following endotoxin challenge and NC treatment. Untreated APPswe/PS1dE9 mice displayed impaired learning in the conditioned taste aversion test, reduced object exploration, and anxiety-like behavior, which were improved in the NC-treated mutants. NC treatment normalized the expression of several immune and plasticity markers and reduced the density of GFAP-positive cells in the hippocampus and thalamus. NC treatment decreased amyloid plaque density in the hippocampus and thalamus, targeting plaques of <100 μm². Additionally, NC treatment suppressed IL-6 secretion by human monocytes. Thus, NC treatment alleviated behavioral deficits and reduced amyloid plaque formation in APPswe/PS1dE9 mice, likely via anti-inflammatory mechanisms. The reduction in IL-6 production in human monocytes further supports the potential of NC therapy for the treatment of AD.

Stem cell therapies, including mesenchymal (MSCs) and haematopoietic stem cells (HSCs), have shown promise in neurodegenerative diseases. Here, we investigated the therapeutic effects of a defined combination of unmanipulated MSCs and CD34⁺ HSCs, termed Neuro-Cells (NC), in a murine model of Alzheimer’s disease (AD), the APPswe/PS1dE9 mouse. At 12 months of age, mice received intracisternal injections of NC (1.39 × 10⁶ MSCs + 5 × 10⁵ HSCs) or vehicle. After 45 days, behavioural testing, immunohistochemical analyses of amyloid plaque density (APD), and cortical gene expression profiling were conducted. NC-treated APP/PS1 mice exhibited preserved object recognition memory and reduced anxiety-like behaviours, contrasting with deficits observed in untreated transgenic controls. Histologically, NC treatment significantly reduced the density of small amyloid plaques (<50 μm²) in the hippocampus and thalamus, and total plaque burden in the thalamus. Gene expression analysis revealed that NC treatment normalised or reversed disease-associated changes in insulin receptor (IR) signalling and neurotrophic pathways. Specifically, NC increased expression of Bdnf, Irs2, and Pgc-1α, while attenuating aberrant upregulation of Insr, Igf1r, and markers of ageing and AD-related pathology (Sirt1, Gdf15, Arc, Egr1, Cldn5). These findings indicate that NC therapy mitigates behavioural and molecular hallmarks of AD, potentially via restoration of BDNF and insulin receptor-mediated signalling.

Background: The inheritance of the short SLC6A4 allele, encoding the serotonin transporter (SERT) in humans, increases susceptibility to neuropsychiatric and metabolic disorders, with aging and female sex further exacerbating these conditions. Both central and peripheral mechanisms of the compromised serotonin (5-HT) system play crucial roles in this context. Previous studies on SERT-deficient (Sert-/-) mice, which model human SERT deficiency, have demonstrated emotional and metabolic disturbances, exacerbated by exposure to a high-fat Western diet (WD). Growing evidence suggests the significance of hepatic regulatory mechanisms in the neurobiology of central nervous system disorders, supporting the ‘liver-brain’ concept. However, the relationship between aberrant behavior and hepatic alterations under conditions of SERT deficiency remains poorly investigated. Methods: One-year-old female Sert-/- mice and their wild-type (WT) littermates were subjected to a control diet (CD) or the WD for a duration of three weeks. The WD had a higher caloric content and was characterized by an elevated saturated fat content (21%) compared to the CD (4.5%) and contained 0.2% cholesterol. Mice were evaluated for anxiety-like behavior, exploration and locomotor activity in the open field test, as well as glucose tolerance and histological indicators of hepatic steatosis. Hepatic pro-inflammatory and metabolism-related gene expression and markers of nitrosative stress, were analyzed utilizing real-time polymerase chain reaction (RT-PCR) and correlated with behavioral and histological outcomes. Results: In comparison to unchallenged mice, Sert-/-/WD mutants, but not the WT/WD group, had increased locomotion and anxiety-like behavior, increased hepatic steatosis, and elevated expression of insulin receptor B and pro-inflammatory cytokines interleukin-1β (Il-1β) and Tnf, as well as decreased expression of leptin receptor B. The two genotypes displayed distinct gene expression patterns of nitric oxide (NO)-related molecules inducible NO synthase (iNos) and arginase (Arg2), insulin receptor-related signaling factors: cluster of differentiation 36 (Cd36), ecto-nucleotide pyrophosphatase/phosphodiesterase (Enpp), protein tyrosine phosphatase N1 (Ptpn1), cytochrome P450 omega-hydroxylase 4A14 (Cyp4a14), acyl-CoA synthetase 1 (Acsl1) and phosphatase and tensin homolog (Pten). Furthermore, there were profound differences in correlations between molecular, histological, and behavioral measurements across the two genotypes. Conclusions: Our findings suggest that the genetic deficiency of SERT results in abnormal hepatic pro-inflammatory and metabolic adaptations in response to WD. The significant correlations observed between behavioral measures and pro-inflammatory and metabolic alterations in WD-fed mice suggest the importance of liver-brain interactions and their role in the aberrant behaviors exhibited by Sert-/- mutants. This study presents the first evidence that altered liver functions are associated with pathological behaviors arising from genetic SERT deficiency.