Journal of Neurochemistry最新文献

Chemotherapy-related cognitive impairment (CRCI) significantly impacts cancer survivors. Due to unclear mechanisms, effective treatments for cognitive deficits are lacking. Here, we examined if microglia-mediated deficits in synaptic plasticity drive CRCI. Adult male mice were treated with the chemotherapeutic drugs 5-fluorouracil and leucovorin (5-Fu/LV, intraperitoneal injection, I.P.) on Days 1, 8, and 15 at a dosage of 50 mg/kg for 5-Fu and 90 mg/kg for LV for 3 weeks. Cognitive function was assessed using a novel object recognition (NOR) test 4 weeks after completion of 5-Fu/LV treatment. Compared with vehicle treatment, 5-Fu/LV treatment reduced the preference for exploring novel objects in the NOR test. Treatment with 5-Fu/LV increased the numbers of Iba1-positive microglial and CD68-positive/Iba1-positive microglia with shortened process lengths and diminished endpoints but decreased the number of phagocytotic (≤ 1 FITC-labeled beads) Iba1-positive microglia. Furthermore, 5-Fu/LV treatment reduced the long-term potentiation (LTP) recorded in the hippocampal CA1 region in response to a theta burst stimulation of the CA3-CA1 pathway and decreased the evoked N-methyl-D-aspartic acid receptor (NMDAR)-excitatory postsynaptic currents (NMDAR-EPSCs) in CA1 neurons. Cotreatment with the microglial inhibitor minocycline (33 mg/kg, daily for 3 weeks) restored cognitive deficits and microglial ramification, decreased the number of CD68-positive microglia, and reversed the reductions in LTP and the amplitude of NMDAR-EPSCs in 5-Fu/LV-treated mice. Our data suggest that microglial dysfunction and related synaptic dysfunction contribute to 5-Fu/LV-induced cognitive impairment.

Fragile X mental retardation protein (FMRP) has been proposed to play a potential role in the pathogenesis of autonomy and nociceptive paresthesia. However, the involvement of spinal FMRP in neuropathic pain remains unexplored. Using a rat model of neuropathic pain induced by chronic constriction injury (CCI), our investigation demonstrated an upregulation of FMRP at 3, 7, and 14 days post-CCI operation in the spinal dorsal horn (SDH). Immunofluorescence staining revealed predominant FMRP expression in spinal neurons, which colocalized with Glutamate Ionotropic Receptor NMDA Type Subunit 2B (GluN2B). The Co-immunoprecipitation results suggested an interaction between spinal FMRP and GluN2B. Genetic knockout of the Fmr1 gene or transient interference with the FMRP protein alleviated CCI-induced pain hypersensitivity and suppressed the increase in spinal GluN2B expression. Conversely, intrathecal administration of the GluN2B-specific inhibitor Ifenprodil significantly suppressed the CCI-induced increase in spinal FMRP expression. In conclusion, our findings highlight the pivotal role of spinal FMRP in developing neuropathic pain and modulating GluN2B levels within the SDH. Furthermore, our results suggest a reciprocal regulatory relationship, indicating that GluN2B may also influence FMRP expression. This study provides insights into the molecular mechanisms underlying neuropathic pain, suggesting the potential for therapeutic intervention targeting the FMRP-GluN2B axis in pain management.

Cortical damage and dysfunction is a pathological hallmark of multiple sclerosis (MS) that correlates with the severity of physical and cognitive disability. Astrocytes participate in MS pathobiology through a variety of mechanisms, and abnormal astrocytic calcium signaling has been pointed as a pathogenic mechanism of cortical dysfunction in MS. However, in vivo evidence supporting deregulation of astrocyte calcium-dependent mechanisms in cortical MS is still limited. Here, we applied fiber photometry to the longitudinal analysis of spontaneous and sensory-evoked astrocyte network activity in the somatosensory cortex of mice in an experimental autoimmune encephalomyelitis (EAE). We found that freely moving EAE mice exhibit spontaneously occurring astrocyte calcium signals of increased duration and reduced amplitude. Concomitantly, cortical astrocytes in EAE mice responded to sensory stimulation with calcium events of decreased amplitude. The emergence of aberrant astrocyte calcium signals in the somatosensory cortex paralleled the onset of neurological symptomatology, and changes in the amplitude of both spontaneous and evoked responses were selectively correlated to the severity of neurological deficits. These results highlight the imbalance of astrocyte network activity in the brain cortex during autoimmune inflammation and further support the relevance of astrocyte-based pathobiology as an underlying mechanism of cortical dysfunction in MS.

Mitochondrial respiratory complexes are organized into supercomplexes (SC) to regulate electron flow and mitigate oxidative stress. Alterations in SC organization in the brain may affect energy expenditure, oxidative stress, and neuronal survival. In this report, we investigated the amount, activity and organization of mitochondrial complex I (CI) in the hippocampus of 12-month-old McGill-R-Thy1-APP transgenic (Tg) rats, an animal model of Alzheimer's-like cerebral amyloidosis. By means of BN-PAGE, we found that the organization of SC did not differ between genotypes, but a lower abundance of SC was detected in Tg compared to wild-type (WT) rats. Using a more sensitive technique (2-D electrophoresis followed by Western blot), higher levels of free CI and a decrease in the relative abundance of assembled CI in SC (I-III₂ and I-III₂-IV) were observed in Tg rats. In-gel activity assays showed that the total activity of CI (CI + SC-CI) is lower in Tg compared to WT, while Tg samples show a significant decrease in SC-CI-associated activity. This alteration in CI assembly was associated with nitro-oxidative stress and changes in mitochondrial fusion-fission parameters. To assess CI composition, we applied LC–MS/MS to the isolated CI from BN-PAGE and found that 11 of 45 subunits described in mammals were found to be less abundant in Tg. We examined the levels of the nuclear-derived NDUFA9 subunit, which is critical for CI assembly, and found higher levels in the cytoplasmic fraction and lower levels in the mitochondrial fraction in Tg, suggesting that brain amyloidosis affects the import of CI subunits from the cytosol to the mitochondria, destabilizing the SC. This is the first report to characterize the types, abundance and activity of SC in the hippocampus of an animal model of cerebral amyloidosis, providing additional experimental evidence for the molecular mechanisms underlying the brain bioenergetic deficit characteristic of Alzheimer's disease.

Inhibiting β-amyloid aggregation and enhancing its clearance are the key strategies in Alzheimer's disease (AD) treatment. Liver X receptors (LXRs) plays a crucial role in cholesterol homeostasis and inflammation, and their activation can clear Aβ aggregates in AD. Allopregnanolone, a neurosteroid, positively influences AD through LXR regulation, while ganaxolone, its synthetic analog, is known for its neuroprotective properties. This study explores the effect of ganaxolone on LXR activation and regulation of genes involved in mitigating Aβ toxicity and tauopathy in SH-SY5Y cells transfected with APP695 Swe/Ind plasmid and an Aβ1–42 induced AD mouse model. Molecular docking stimulations indicated ganaxolone's binding and interaction with LXRβ. Subsequently, transfected neuronal cells exhibited increased mRNA levels of APP, TNF-α and IL-1β, decreased cell viability, reduced MMP and altered protein expression of Aβ, LXR, BCL-2, APOE, ABCA1, along with increased levels of mROS, Bax, and caspase 3 activity. Ganaxolone treatment significantly abrogated Aβ-induced effect in transfected neuronal cells by enhancing LXRβ expression, inducing LXR:RXR colocalization, thereby increasing APOE and ABCA1 expression. It also decreased tau mRNA levels in transfected cells. Importantly, in AD mice, ganaxolone ameliorated cognitive impairment, reduced Aβ toxicity, tau levels, and neuroinflammatory markers, restored mitochondrial function, and decreased neuronal apoptosis. Taken together, these novel results highlight the central role of LXR in mediating Aβ-induced toxicity and provide preclinical evidence for ganaxolone as a potential agent to reduce toxicity in an LXR-dependent manner. This may serve as a promising treatment strategy to slow or prevent neurodegeneration in AD patients.