Neurobiology of Disease最新文献

Addiction is a chronic and severe mental disorder with high gender- and sex-specificity. However, the pathogenesis of this disorder is not fully elucidated, and no targeted pharmacotherapy is available. A growing body of evidence points out the potential involvement of the ceramide system in the pathophysiology of addiction. A pathogenic pathway for several mental disorders based on the overexpression of an enzyme involved in ceramide formation, acid sphingomyelinase (ASM), was recently proposed. Here we show a crucial role of ASM specifically overexpressing in the forebrain for various types of addiction-related behaviours in a drug- and sex-specific way. In male mice, a forebrain ASM overexpression led to enhanced alcohol consumption in a free-choice paradigm. It also diminished the reinforcing properties of alcohol and cocaine, but not that of amphetamine, ketamine, or a natural reinforcer fat/carbohydrate-rich food in the conditioned place preference (CPP) test in males. In female mice, a forebrain ASM overexpression enhanced alcohol binge-like drinking, while moderate alcohol consumption was preserved. ASM overexpression in females contributed to CPP establishment for amphetamine, but not for other psychoactive substances. Altogether, this study shows a specific involvement of forebrain ASM in the development of conditioned reinforcing effects of different types of substances with addictive properties in a sex-specific way. Our data enlarge the current knowledge on the specific molecular mechanisms of dependence from various drugs of abuse and might serve as a basis for the development of drug- and sex-specific targeted therapy.

Chronic itch remains a clinically challenging condition with limited therapeutic efficacy, posing a significant burden on patients' quality of life. Despite its prevalence, the underlying neural mechanisms remain poorly understood. In this study, we explored the synaptic relationships between neuropeptide Y (NPY) neurons and gastrin-releasing peptide receptor (GRPR) neurons in the spinal cord. Our findings reveal a direct synaptic connection whereby Npy neurons provide inhibitory modulation to Grpr neurons. Notably, during chronic itch, the activity of Grpr neurons was significantly elevated, coinciding with a decrease in Y1 receptor expression and a reduction in both the frequency and amplitude of inhibitory postsynaptic currents (IPSCs). These results suggest a decline in NPY/Y1R system function during chronic itch, leading to a decreased inhibitory influence of Npy neurons on Grpr neurons and subsequent disinhibition and excitation of the latter. This disinhibitory mechanism may underlie the enhanced responsiveness to mechanical and chemical itch stimuli in chronic itch patients.

Abnormal tau phosphorylation is a key mechanism in neurodegenerative diseases. Evidence implicates infectious agents, such as Herpes Simplex Virus 1 (HSV-1), as co-factors in the onset or the progression of neurodegenerative diseases, including Alzheimer's disease. This has led to divergence in the field regarding the contribution of viruses in the etiology of neurodegenerative diseases. Research indicates that viruses may function as risk factors driving neurodegenerative disease rather than playing a causative role. Investigating HSV-1 in abnormal tau phosphorylation is important for understanding the role of infectious agents in neurodegeneration. We generated cellular models of HSV-1 acute, latent infection, and viral reactivation from latency in cortical brain organoids and investigated the interplay between tau phosphorylation and HSV-1 infection by employing human induced pluripotent stem cell (iPSC)-derived monolayer neuronal cultures and brain organoids. Acute infection with HSV-1 strains 17syn⁺ and KOS caused nuclear accumulation of phosphorylated tau (p-tau) in neurons and neural precursor cells. Antivirals prevented nuclear accumulation of p-tau. Viral reactivation was accompanied by the nuclear translocation of p-tau. Chromatin immunoprecipitation analysis indicated an interaction of p-tau with the viral chromatin. A reduction in abundance of component of nuclear speckles and their loss of organized morphology in low-denisty host chromatin regions was observed, with strain-specific differences. HSV-1 infection was followed by an increase in the abundance of BRSKs and TAOKs, kinases known to phosphorylate tau. These findings show interaction between p-tau and HSV-1 chromatin and demonstrate the ability of HSV-1 to activate mechanisms that are observed in Alzheimer's disease.

The ability to distinguish between individuals is crucial for social species and supports behaviors such as reproduction, hierarchy formation, and cooperation. In rodents, social discrimination relies on memory and the recognition of individual-specific cues, known as "individual signatures". While olfactory signals are central, other sensory cues - such as auditory, visual, and tactile inputs - also play a role. However, little research has explored the fine discrimination of individuals with overlapping cues, such as siblings or cohabitating mice. This study investigates whether mice can discriminate between two closely related individuals: siblings from the same litter and cage. We tested the hypothesis that it would be more challenging for mice to distinguish between siblings than between unrelated mice due to shared cues. Moreover, social cognitive impairments are common in neurodegenerative diseases like Alzheimer's disease (AD), where difficulties in recognizing faces and voices progressively disrupt social interactions in patients. Using a mouse model of AD (Tg2576), known for the progressive onset of cognitive deficits, we assessed whether the ability to discriminate between siblings is preserved in "pre-symptomatic" animals. Thus, we first demonstrated that male and female C57BL6/J mice can discriminate siblings, regardless of sex. Next, we revealed that "pre-symptomatic" 3-month-old Tg2576 mice exhibit impairments in fine social memory, while their general social memory remains unaffected. Thus, we demonstrate that the inability to perform fine social discrimination is an early cognitive impairment that arises before other well-documented memory abnormalities in this AD mouse model.

Background: Investigating brain metabolic networks is crucial for understanding the pathogenesis and functional alterations in Creutzfeldt-Jakob disease (CJD). However, studies on presymptomatic individuals remain limited. This study aimed to examine metabolic network topology reconfiguration in asymptomatic carriers of the PRNP G114V mutation.

Methods: Seven asymptomatic PRNP G114V mutation carriers from a familial genetic CJD (gCJD) cohort, 43 CJD patients, and 35 healthy controls were included. All participants underwent neuropsychological assessments, genetic testing, and ¹⁸F-fluorodeoxyglucose positron emission tomography (18F-FDG PET)/MRI scans. Voxel-based gray matter volume and FDG PET standardized uptake value ratios (SUVRs) were analyzed between asymptomatic PRNP G114V mutation carriers and healthy controls and between CJD patients and controls. Graph theory and sparse inverse covariance estimation (SICE) were used to assess the whole-brain metabolic connectomes and topological properties. Spatial independent component analysis (ICA) was used to evaluate subnetworks, including the default mode network (DMN), salience network (SN), and central executive network (CEN).

Results: With respect to global properties, assortativity was significantly increased in asymptomatic carriers, which was consistent with the findings in CJD patients. We revealed lost hubs in the right anterior cingulate, left ventral prefrontal lobe, left parahippocampal gyrus, and left lingual gyrus and reconfigured hubs in prefrontal lobes, including right ventromedial prefrontal cortex, right anterior prefrontal cortex, and right middle frontal gyrus of the orbit in asymptomatic carriers compared with healthy controls, which overlapped with the comparisons between CJD patients and controls. Alterations in the local parameters and metabolic connectivity in the left parahippocampal gyrus were most pronounced. Among the subnetworks, asymptomatic carriers presented higher assortativity and lower hierarchy in the SN, whereas the global parameters of the DMN and CEN were not significantly altered. The DMN and SN showed partial hypoconnectivity and hyperconnectivity, whereas the CEN mainly showed significantly enhanced connectivity in asymptomatic PRNP carriers.

Conclusions: This study revealed altered brain metabolic topology and connectomics in asymptomatic PRNP G114V mutation carriers, which could be detected before gray matter or regional metabolic changes, suggesting that metabolism topology reconfiguration may serve as a sensitive imaging biomarker for investigating early CJD pathological changes.

Aggregation of alpha-synuclein (αsyn) plays an integral role in Parkinson's disease (PD) and Dementia with Lewy bodies (DLB). 14-3-3θ is a highly expressed brain protein with chaperone-like activity that regulates αsyn folding. 14-3-3θ overexpression reduces αsyn aggregation, transmission between cells, and neuronal loss, while 14-3-3 inhibition promotes αsyn pathology. We previously observed increased 14-3-3θ phosphorylation at serine 232 in human PD and DLB brains. Here we examine 14-3-3θ phosphorylation's effects on αsyn aggregation and toxicity. Using a paracrine αsyn model, we found that the non-phosphorylatable S232A 14-3-3θ protected while the phosphomimetic S232D 14-3-3θ failed to protect against αsyn paracrine toxicity. The S232A mutant reduced oligomerization of released αsyn while the S232D mutant did not. The S232D mutant showed significant reduction in αsyn binding compared to wildtype or S232A 14-3-3θ. Using knock-in mouse models expressing the S232A or S232D mutation in the cortex and hippocampus, we examined the impact of S232 phosphorylation on αsyn aggregation in the αsyn preformed fibril (PFF) model. Primary neurons from S232D mice showed increased αsyn inclusion formation compared to neurons from Cre control mice upon PFF treatment. In contrast, neurons from S232A mice showed reduced αsyn inclusions. αSyn PFF injection into the dorsolateral striatum induced higher αsyn inclusion numbers in the sensorimotor cortex of S232D mice compared to Cre control mice. In conclusion, 14-3-3θ phosphorylation at S232 interrupts the ability of 14-3-3θ to bind and regulate αsyn aggregation. Increased 14-3-3θ phosphorylation observed in human PD and DLB likely accelerates neurodegeneration in these disorders.

Parkinson's Disease (PD) is a multisystem disorder in which dysregulated neuroimmune crosstalk and inflammatory relay via the gut-blood-brain axis have been implicated in PD pathogenesis. Although alterations in circulating inflammatory cytokines and reactive oxygen species (ROS) have been associated with PD, no biomarkers have been identified that predict clinical progression or disease outcome. Gastrointestinal (GI) dysfunction, which involves perturbation of the underlying immune system, is an early and often-overlooked symptom that affects up to 80 % of individuals living with PD. Interestingly, 50-70 % of individuals with inflammatory bowel disease (IBD), a GI condition that has been epidemiologically linked to PD, display chronic illness-induced anemia - which drives toxic accumulation of iron in the gut. Ferroptotic (or iron loaded) cells have small and dysmorphic mitochondria-suggesting that mitochondrial dysfunction is a consequence of iron accumulation. In pro-inflammatory environments, iron accumulates in immune cells, suggesting a possible connection and/or synergy between iron dysregulation and immune cell dysfunction. Peripheral blood mononuclear cells (PBMCs) recapitulate certain PD-associated neuropathological and inflammatory signatures and can act as communicating messengers in the gut-brain axis. Additionally, this communication can be modulated by several environmental factors; specifically, our data further support existing literature demonstrating a role for non-steroidal anti-inflammatory drugs (NSAIDs) in modulating immune transcriptional states in inflamed individuals. A mechanism linking chronic gut inflammation to iron dysregulation and mitochondrial function within peripheral immune cells has yet to be identified in conferring risk for PD. To that end, we isolated PBMCs and simultaneously evaluated their directed transcriptome and bioenergetic status, to investigate if iron dysregulation and mitochondrial sensitization are linked in individuals living with PD or IBD because of chronic underlying remittent immune activation. We have identified shared features of peripheral inflammation and immunometabolism in individuals living with IBD or PD that may contribute to the epidemiological association reported between IBD and risk for PD.

The underlying cause of neuronal loss in Parkinson's disease (PD) remains unknown, but evidence implicates neuroinflammation in PD pathobiology. The pro-inflammatory cytokine soluble tumor necrosis factor (TNF) seems to play an important role and thus has been proposed as a therapeutic target for modulation of the neuroinflammatory processes in PD. In this regard, dominant-negative TNF (DN-TNF) agents are promising antagonists that selectively inhibit soluble TNF signaling, while preserving the beneficial effects of transmembrane TNF. Previous studies have tested the protective potential of DN-TNF-based therapy in toxin-based PD models. Here we test for the first time the protective potential of a DN-TNF therapeutic against α-synuclein-driven neurodegeneration in the viral vector-based PD female rat model. To do so, we administered the DN-TNF agent XPro1595 subcutaneously for a period of 12 weeks. In contrast to previous studies using different PD models, neuroprotection was not achieved by systemic XPro1595 treatment. α-Synuclein-induced loss of nigrostriatal neurons, accumulation of pathological inclusions and microgliosis was detected in both XPro1595- and saline-treated animals. XPro1595 treatment increased the percentage of the hypertrophic/ameboid Iba1+ cells in SN and reduced the striatal MHCII+ expression in the α-synuclein-overexpressing animals. However, the treatment did not prevent the MHCII upregulation seen in the SN of the model, nor the increase of CD68+ phagocytic cells. Therefore, despite an apparently immunomodulatory effect, this did not suffice to protect against viral vector-derived α-synuclein-induced neurotoxicity. Further studies are warranted to better elucidate the therapeutic potential of soluble TNF inhibitors in PD.

Bank voles are susceptible to prion strains from many different species, yet the molecular mechanisms underlying the ability of bank vole prion protein (BVPrP) to function as a universal prion acceptor remain unclear. Potential differences in molecular environments and protein interaction networks on the cell surface of brain cells may contribute to BVPrP's unusual behavior. To test this hypothesis, we generated knock-in mice that express physiological levels of BVPrP (M109 isoform) and employed mass spectrometry to compare the interactomes of mouse (Mo) PrP and BVPrP following mild in vivo crosslinking of brain tissue. Substantial overlap was observed between the top interactors for BVPrP and MoPrP, with established PrP-interactors such as neural cell adhesion molecules, subunits of Na⁺/K⁺-ATPases, and contactin-1 being equally present in the two interactomes. We conclude that the molecular environments of BVPrP and MoPrP in the brains of mice are very similar. This suggests that the unorthodox properties of BVPrP are unlikely to be mediated by differential interactions with other proteins.