Experimental Neurobiology最新文献

FAM19A5, a novel secretory protein highly expressed in the brain, is potentially associated with the progression of Alzheimer's disease (AD). However, its role in the AD pathogenesis remains unclear. Here, we investigated the potential function of FAM19A5 in the context of AD. We generated APP/PS1 mice with partial FAM19A5 deficiency, termed APP/PS1/FAM19A5^+/LacZ mice. Compared with control APP/PS1 mice, APP/PS1/FAM19A5^+/LacZ mice exhibited significantly lower Aβ plaque density and prolonged the lifespan of the APP/PS1 mice. To further explore the therapeutic potential of targeting FAM19A5, we developed a FAM19A5 antibody. Administration of this antibody to APP/PS1 mice significantly improved their performance in the Y-maze and passive avoidance tests, indicating enhanced cognitive function. This effect was replicated in 5XFAD mice, a model of early-onset AD characterized by rapid Aβ accumulation. Additionally, FAM19A5 antibody treatment in 5XFAD mice led to enhanced exploration of novel objects and increased spontaneous alternation behavior in the novel object recognition and Y-maze tests, respectively, indicating improved cognitive function. These findings suggest that FAM19A5 plays a significant role in AD pathology and that targeting with FAM19A5 antibodies may be a promising therapeutic strategy for AD.

The harmful effects of blue light on the retina and health issues attributed to flickering light have been researched extensively. However, reports on the effects of flickering blue light at a frequency in the visible range on the retina are limited. This study aimed to non-invasively investigate the structural and functional changes in mice retinas following exposure to flickering blue light. BALB/c mice were subjected to non-flickering and flickering blue light, and changes in the retinal function and structure were assessed using electroretinography (ERG) and spectral-domain optical coherence tomography (SD-OCT), respectively. Retinal damage progression was monitored on days 3, 7, 14, and 42 following light exposure. Significant reductions in scotopic and photopic ERG responses were observed on day 3 (p<0.05). On day 7, the non-flickering and flickering groups demonstrated different functional changes: the flickering group showed further ERG response reduction, while the non-flickering group showed no reduction or slight improvement that was statistically insignificant (p>0.05). A similar trend lasted by day 14. On day 42, however, the difference between the non-flickering and flickering groups was significant, which was corroborated by the normalized amplitudes at 0, 0.5, and 1 log cd s/m² (p<0.05). Quantitative and qualitative SD-OCT assays revealed more severe and progressive retinal damage in the flickering group throughout the study. Flickering blue light causes more persistent and severe retinal damage than non-flickering blue light and may be a risk factor for retinal degeneration even at frequencies as low as 20 Hz.

Obesity is a growing health concern, mainly caused by poor dietary habits. Yet, accurately tracking the diet and food intake of individuals with obesity is challenging. Although 3D motion capture technology is becoming increasingly important in healthcare, its potential for detecting early signs of obesity has not been fully explored. In this research, we used a deep LSTM network trained with individual identity (identity-trained deep LSTM network) to analyze 3D time-series skeleton data from mouse models with diet-induced obesity. First, we analyzed the data from two different viewpoints: allocentric and egocentric. Second, we trained various deep recurrent networks (e.g., RNN, GRU, LSTM) to predict the identity. Lastly, we tested whether these models effectively encode obese-like motion representations by training a support vector classifier with the latent features from the last layer. Our experimental results indicate that the optimal performance is achieved when utilizing an identity-trained deep LSTM network in conjunction with an egocentric viewpoint. This approach suggests a new way to use deep learning to spot health risks in mouse models of obesity and should be useful for detecting early signs of obesity in humans.

A single exposure to stress can induce functional changes in neurons, potentially leading to acute stress disorder or post-traumatic stress disorder. In this study, we used in vivo wide-field optical mapping to simultaneously measure neural calcium signals and hemodynamic responses over the whole cortical area. We found that cortical mapping to whisker stimuli was altered under acute stress conditions. In particular, callosal projections in the anterior cortex (primary/secondary motor, somatosensory forelimb cortex) relative to barrel field (S1BF) of somatosensory cortex were weakened. On the contrary, the projections in posterior cortex relative to S1BF were mostly unchanged or were only occasionally strengthened. In addition, changes in intra-cortical connection were opposite to those in inter-cortical connection. Thus, the S1BF connections to the anterior cortex were strengthened while those to the posterior cortex were weakened. This suggests that the well-known barrel cortex projection route was enhanced. In summary, our in vivo wide-field optical mapping study indicates that a single acute stress can impact whole-brain networks, affecting both neural and hemodynamic responses.

Cancer chemotherapy often triggers peripheral neuropathy in patients, leading to neuropathic pain in the extremities. While previous research has explored various nerve stimulation to alleviate chemotherapy-induced peripheral neuropathy (CIPN), evidence on the effectiveness of noninvasive auricular vagus nerve stimulation (aVNS) remains uncertain. This study aimed to investigate the efficacy of non-invasive aVNS in relieving CIPN pain. To induce CIPN in experimental animals, oxaliplatin was intraperitoneally administered to rats (6 mg/kg). Mechanical and cold allodynia, the representative symptoms of neuropathic pain, were evaluated using the von Frey test and acetone test, respectively. The CIPN animals were randomly assigned to groups and treated with aVNS (5 V, square wave) at different frequencies (2, 20, or 100 Hz) for 20 minutes. Results revealed that 20 Hz aVNS exhibited the most pronounced analgesic effect, while 2 or 100 Hz aVNS exhibited weak effects. Immunohistochemistry analysis demonstrated increased c-Fos expression in the locus coeruleus (LC) in the brain of CIPN rats treated with aVNS compared to sham treatment. To elucidate the analgesic mechanisms involving the adrenergic descending pathway, α₁-, α₂-, or β-adrenergic receptor antagonists were administered to the spinal cord before 20 Hz aVNS. Only the β-adrenergic receptor antagonist, propranolol, blocked the analgesic effect of aVNS. These findings suggest that 20 Hz aVNS may effectively alleviate CIPN pain through β-adrenergic receptor activation.

In the auditory system, the spontaneous activity of cochlear inner hair cells (IHCs) is initiated by the release of ATP from inner supporting cells (ISCs). This ATP release sets off a cascade, activating purinergic autoreceptors, opening of Ca²⁺-activated Cl^- channel TMEM16A, Cl^- efflux and osmotic cell shrinkage. Then, the shrunken ISCs efficiently regain their original volume, suggesting the existence of mechanisms for refilling Cland K⁺, priming them for subsequent activity. This study explores the potential involvement of NKCCs (Na⁺-K⁺-Cl^- cotransporters) and KCCs (K⁺-Cl^- cotransporters) in ISC spontaneous activity, considering their capability to transport both Cl^- and K⁺ ions across the cell membrane. Employing a combination of immunohistochemistry, pharmacological interventions, and shRNA experiment, we unveiled the pivotal role of NKCC1 in cochlear spontaneous activity. Immunohistochemistry revealed robust NKCC1 expression in ISCs, persisting until the 2nd postnatal week. Intriguingly, we observed a developmental shift in NKCC1 expression from ISCs to synaptophysin-positive efferent terminals at postnatal day 18, hinting at its potential involvement in modulating synaptic transmission during the post-hearing period. Experiments using bumetanide, a well-known NKCC inhibitor, supported the functional significance of NKCC1 in ISC spontaneous activity. Bumetanide significantly reduced the frequency of spontaneous extracellular potentials (sEP) and spontaneous optical changes (sOCs) in ISCs. NKCC1-shRNA experiments conducted in cultured cochlear tissues further supported these findings, demonstrating a substantial decrease in event frequency and area. Taken together, we revealed the role of NKCC1 in shaping the ISC spontaneous activity that govern auditory pathway development.

The development of the olfactory system is influenced by sensory inputs, and it maintains neuronal generation and plasticity throughout the lifespan. The olfactory bulb contains a higher proportion of interneurons than other brain regions, particularly during the early postnatal period of neurogenesis. Although the relationship between sensory stimulation and olfactory bulb development during the postnatal period has been well studied, the molecular mechanisms have yet to be identified. In this study, we used western blotting and immunohistochemistry to analyze the expression of the transcription factor Npas4, a neuron-specific immediate-early gene that acts as a developmental regulator in many brain regions. We found that Npas4 is highly expressed in olfactory bulb interneurons during the early postnatal stages and gradually decreases toward the late postnatal stages. Npas4 expression was observed in all olfactory bulb layers, including the rostral migratory stream, where newborn neurons are generated and migrate to the olfactory bulb. Under sensory deprivation, the olfactory bulb size and the number of olfactory bulb interneurons were reduced. Furthermore, Npas4 expression and the expression of putative Npas4 downstream molecules were decreased. Collectively, these findings indicate that Npas4 expression induced by sensory input plays a role in the formation of neural circuits with excitatory mitral/tufted cells by regulating the survival of olfactory bulb interneurons during the early stages of postnatal development.

Anosmia, characterized by the loss of smell, is associated not only with dysfunction in the peripheral olfactory system but also with changes in several brain regions involved in olfactory processing. Specifically, the orbitofrontal cortex is recognized for its pivotal role in integrating olfactory information, engaging in bidirectional communication with the primary olfactory regions, including the olfactory cortex, amygdala, and entorhinal cortex. However, little is known about alterations in structural connections among these brain regions in patients with anosmia. In this study, high-resolution T1-weighted images were obtained from participants. Utilizing the volumes of key brain regions implicated in olfactory function, we employed a structural covariance approach to investigate brain reorganization patterns in patients with anosmia (n=22) compared to healthy individuals (n=30). Our structural covariance analysis demonstrated diminished connectivity between the amygdala and entorhinal cortex, components of the primary olfactory network, in patients with anosmia compared to healthy individuals (z=-2.22, FDR-corrected p=0.039). Conversely, connectivity between the orbitofrontal cortex-a major region in the extended olfactory network-and amygdala was found to be enhanced in the anosmia group compared to healthy individuals (z=2.32, FDR-corrected p=0.039). However, the structural connections between the orbitofrontal cortex and entorhinal cortex did not differ significantly between the groups (z=0.04, FDR-corrected p=0.968). These findings suggest a potential structural reorganization, particularly of higher-order cortical regions, possibly as a compensatory effort to interpret the limited olfactory information available in individuals with olfactory loss.

Multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) are two of the most devastating immune-mediated central demyelinating disorders. NMOSD was once considered as a variant of MS until the discovery of an antibody specific to the condition. Despite both MS and NMOSD being considered central demyelinating disorders, their pathogenesis and clinical manifestations are distinct, however the exact mechanisms associated with each disease remain unclear. Extracellular vesicles (EVs) are nano-sized vesicles originating in various cells which serve as intercellular communicators. There is a large body of evidence to show the possible roles of EVs in the pathogenesis of several diseases, including the immune-mediated central demyelinating disorders. Various types of EVs are found across disease stages and could potentially be used as a surrogate marker, as well as acting by carrying a cargo of biochemical molecules. The possibility for EVs to be used as a next-generation targeted treatment for the immune-mediated central demyelinating disorders has been investigated. The aim of this review was to comprehensively identify, compile and discuss key findings from in vitro, in vivo and clinical studies. A summary of all findings shows that: 1) the EV profiles of MS and NMOSD differ from those of healthy individuals, 2) the use of EV markers as liquid biopsy diagnostic tools appears to be promising biomarkers for both MS and NMOSD, and 3) EVs are being studied as a potential targeted therapy for MS and NMOSD. Any controversial findings are also discussed in this review.