Trophic modulation of gamma oscillations: The key role of processing protease for Neuregulin-1 and BDNF precursors

Major depressive disorder recognition by quantifying EEG signal complexity using proposed APLZC and AWPLZC

BACKGROUND

Seeking objective quantitative indicators is important for accurately recognizing major depressive disorder (MDD). Lempel-Ziv complexity (LZC), employed to characterize neurological disorders, faces limitations in tracking dynamic changes in EEG signals due to defects in the coarse-graining process, hindering its precision for MDD objective quantitative indicators.

METHODS

This work proposed Adaptive Permutation Lempel-Ziv Complexity (APLZC) and Adaptive Weighted Permutation Lempel-Ziv Complexity (AWPLZC) algorithms by refining the coarse-graining process and introducing weight factors to effectively improve the precision of LZC in characterizing EEGs and further distinguish MDD patients better. APLZC incorporated the ordinal pattern, while False Nearest Neighbor and Mutual Information algorithms were introduced to determine and adjust key parameters adaptively. Furthermore, we proposed AWPLZC by assigning different weights to each pattern based on APLZC. Thirty MDD patients and 30 healthy controls (HCs) were recruited and their 64-channel resting EEG signals were collected. The complexities of gamma oscillations were then separately computed using LZC, APLZC, and AWPLZC algorithms. Subsequently, a multi-channel adaptive K-nearest neighbor model was constructed for identifying MDD patients and HCs.

RESULTS

LZC, APLZC, and AWPLZC algorithms achieved accuracy rates of 78.29 %, 90.32 %, and 95.13 %, respectively. Sensitivities reached 67.96 %, 85.04 %, and 98.86 %, while specificities were 88.62 %, 95.35 %, and 89.92 %, respectively. Notably, AWPLZC achieved the best performance in accuracy and sensitivity, with a specificity limitation.

LIMITATION

The sample size is relatively small.

CONCLUSION

APLZC and AWPLZC algorithms, particularly AWPLZC, demonstrate superior effectiveness in differentiating MDD patients from HCs compared with LZC. These findings hold significant clinical implications for MDD diagnosis.

Correlation study of brain-derived neurotrophic factor, EEG γ activity and cognitive function in first-episode schizophrenia

BACKGROUND

Schizophrenia is characterised by neurotrophic, neuroelectrophysiological and cognitive dysfunction. However, there exists a paucity of research examining the association between serum brain-derived neurotrophic factor (BDNF) concentration, resting electroencephalogram (EEG) gamma activity, and cognitive impairment in individuals diagnosed with schizophrenia.

METHODS

In this study, 87 first-episode schizophrenia patients and 75 healthy controls were assessed. Measurements were conducted to determine the levels of BDNF, resting EEG γ-activity at left and right frontal pole EEG electrodes respectively (FP1/FP2) leads, and cognitive function as assessed by the Measurement and Treatment Research to Improve Cognition in Schizophrenia MATRICS Consensus Cognitive Battery (MCCB). Comparisons were made between the patient group and the control group, revealing lower BDNF levels, lower T-scores for 7 MCCB cognitive items, and higher EEG γ-activity among patients when compared to controls.

RESULTS

According to the correlation analysis, there were significant associations observed in the patient group. BDNF levels were found to be correlated with EEG γ activity as well as T-scores of speed of processing (SoP), verbal learning (VeL), and reasoning problem-solving (RPS). Moreover, EEG γ activity showed an association with both the total score of the Positive and Negative Syndrome Scale (PANSS) and T-score of SoP. These findings suggest a potential relationship between BDNF levels, EEG γ activity, cognitive domains, and clinical symptoms in individuals with first-episode schizophrenia.

CONCLUSIONS

In conclusion, our findings demonstrate the coexistence of neurobiochemical and electrophysiological abnormalities alongside cognitive dysfunction during the early stages of schizophrenia. These findings provide valuable insights into the mechanism of cognitive impairment in schizophrenia. By highlighting the simultaneous occurrence of these factors, our study contributes to a better understanding of the complex nature of schizophrenia and emphasizes the importance of studying its cognitive aspects.

High Frequency Electromagnetic Radiation Stimulates Neuronal Growth and Hippocampal Synaptic Transmission

Terahertz waves lie within the rotation and oscillation energy levels of biomolecules, and can directly couple with biomolecules to excite nonlinear resonance effects, thus causing conformational or configuration changes in biomolecules. Based on this mechanism, we investigated the effect pattern of 0.138 THz radiation on the dynamic growth of neurons and synaptic transmission efficiency, while explaining the phenomenon at a more microscopic level. We found that cumulative 0.138 THz radiation not only did not cause neuronal death, but that it promoted the dynamic growth of neuronal cytosol and protrusions. Additionally, there was a cumulative effect of terahertz radiation on the promotion of neuronal growth. Furthermore, in electrophysiological terms, 0.138 THz waves improved synaptic transmission efficiency in the hippocampal CA1 region, and this was a slow and continuous process. This is consistent with the morphological results. This phenomenon can continue for more than 10 min after terahertz radiation ends, and these phenomena were associated with an increase in dendritic spine density. In summary, our study shows that 0.138 THz waves can modulate dynamic neuronal growth and synaptic transmission. Therefore, 0.138 terahertz waves may become a novel neuromodulation technique for modulating neuron structure and function.

Reduced inhibitory and excitatory input onto parvalbumin interneurons mediated by perineuronal net might contribute to cognitive impairments in a mouse model of sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE) is commonly defined as diffuse brain dysfunction and can manifest as delirium to coma. Accumulating evidence has suggested that perineuronal net (PNN) plays an important role in the modulation of the synaptic plasticity of central nervous system. We here investigated the role of PNN in SAE induced by lipopolysaccharide (LPS) injection. Behavioral tests were performed by open field, Y-maze, and fear conditioning tests at the indicated time points. The densities of vesicular γ-aminobutyric acid transporter, vesicular glutamate transporter 1, PNN, and parvalbumin (PV) in the hippocampus were evaluated by immunofluorescence. Matrix metalloproteinases-9 (MMP-9) expression and its activity were detected by Western blot and gel zymography, respectively. Local field potential was recorded by in vivo electrophysiology. LPS-treated mice displayed significant cognitive impairments, coincided with activated MMP-9, decreased PNN and PV densities, reduced inhibitory and excitatory input onto PV interneurons enwrapped by PNN, and decreased gamma oscillations in hippocampal CA1. Notably, MMP-9 inhibitor SB-3CT treatment rescued most of these abnormalities. Taken together, our study demonstrates that active MMP-9 mediated PNN remodeling, leading to reduced inhibitory and excitatory input onto PV interneurons and abnormal gamma oscillations in hippocampal CA1, which consequently contributed to cognitive impairments after LPS injection.

Altered fronto-central theta-gamma coupling in major depressive disorder during auditory steady-state responses

OBJECTIVE

Neural oscillations during sensory and cognitive events interact at different frequencies. However, such evidence in major depressive disorder (MDD) remains scarce. We explored the possible abnormal neural oscillations in MDD by analyzing theta-phase/gamma-amplitude coupling (TGC).

METHODS

Resting-state and auditory steady-state response (ASSR) electroencephalography recordings were obtained from 35 first-episode MDD and 35 healthy controls (HCs). TGC during rest, ASSR stimulation, and ASSR baseline between and within groups were analyzed to evaluate MDD alterations. Receiver operating characteristic (ROC), TGC comparison between MDD severity subgroups (mild, moderate, major), and correlations were investigated to determine the potential use of altered TGC for identifying MDD.

RESULTS

In MDD, left fronto-central TGC decreased during stimulation, while right fronto-central TGC increased during baseline. The area under ROC curve for altered TGC was 0.863. Furthermore, during stimulation, moderate and major MDD groups exhibited significantly lower TGC than mild group, and fronto-central TGC was negatively correlated with depression scale scores.

CONCLUSIONS

Our results provided the first evidence for an abnormal TGC response of fronto-central regions in MDD during an ASSR task. Importantly, altered TGC may be promising biomarkers of MDD.

SIGNIFICANCE

Our findings enhance the understanding of physiological mechanisms underlying MDD and aid in its clinical diagnosis.

Maternal immune activation-induced proBDNF-mediated neural information processing dysfunction at hippocampal CA3-CA1 synapses associated with memory deficits in offspring

Prenatal exposure to maternal infection increases the risk of offspring developing schizophrenia in adulthood. Current theories suggest that the consequences of MIA on mBDNF secretion may underlie the increased risk of cognitive disorder. There is little evidence for whether the expression of its precursor, proBDNF, is changed and how proBDNF-mediated signaling may involve in learning and memory. In this study, proBDNF levels were detected in the hippocampal CA1 and CA3 regions of male adult rats following MIA by prenatal polyI:C exposure. Behaviorally, learning and memory were assessed in contextual fear conditioning tasks. Local field potentials were recorded in the hippocampal CA3-CA1 pathway. The General Partial Directed Coherence approach was utilized to identify the directional alternation of neural information flow between CA3 and CA1 regions. EPSCs were recorded in CA1 pyramidal neurons to explore a possible mechanism involving the proBDNF-p75NTR signaling pathway. Results showed that the expression of proBDNF in the polyI:C-treated offspring was abnormally enhanced in both CA3 and CA1 regions. Meanwhile, the mBDNF expression was reduced in both hippocampal regions. Intra-hippocampal CA1 but not CA3 injection with anti-proBDNF antibody and p75NTR inhibitor TAT-Pep5 effectively mitigated the contextual memory deficits. Meanwhile, reductions in the phase synchronization between CA3 and CA1 and the coupling directional indexes from CA3 to CA1 were enhanced by the intra-CA1 infusions. Moreover, blocking proBDNF/p75NTR signaling could reverse the declined amplitude of EPSCs in CA1 pyramidal neurons, indicating the changes in postsynaptic information processing in the polyI:C-treated offspring. Therefore, the changes in hippocampal proBDNF activity in prenatal polyI:C exposure represent a potential mechanism involved in NIF disruption leading to contextual memory impairments.

Kallikrein 8: A key sheddase to strengthen and stabilize neural plasticity

Neural networks are modified and reorganized throughout life, even in the matured brain. Synapses in the networks form, change, or disappear dynamically in the plasticity state. The pre- and postsynaptic signaling, transmission, and structural dynamics have been studied considerably well. However, not many studies have shed light on the events in the synaptic cleft and intercellular space. Neural activity-dependent protein shedding is a phenomenon in which (1) presynaptic excitation evokes secretion or activation of sheddases, (2) sheddases are involved not only in cleavage of membrane- or matrix-bound proteins but also in mechanical modulation of cell-to-cell connectivity, and (3) freed activity domains of protein factors play a role in receptor-mediated or non-mediated biological actions. Kallikrein 8/neuropsin (KLK8) is a kallikrein family serine protease rich in the mammalian limbic brain. Accumulated evidence has suggested that KLK8 is an important modulator of neural plasticity and consequently, cognition. Insufficiency, as well as excess of KLK8 may have detrimental effects on limbic functions.

Modulating Gamma Oscillations Promotes Brain Connectivity to Improve Cognitive Impairment

Dementia causes a substantial global economic burden, but effective treatment is lacking. Recently, studies have revealed that gamma-band waves of electrical brain activity, particularly 40 Hz oscillations, are closely associated with high-order cognitive functions and can activate microglia to clear amyloid-β deposition. Here, we found that compared with sham stimulation, applying 40-Hz high-frequency repetitive transcranial magnetic stimulation (rTMS) over the bilateral angular gyrus in patients with probable Alzheimer's disease (AD; n = 37) resulted in up to 8 weeks of significantly improved cognitive function. Power spectral density analysis of the resting-state electroencephalography (EEG) demonstrated that 40-Hz rTMS modulated gamma-band oscillations in the left posterior temporoparietal region. Further testing with magnetic resonance imaging and TMS-EEG revealed the following: 40-Hz rTMS 1) prevented gray matter volume loss, 2) enhanced local functional integration within bilateral angular gyrus, as well as global functional integration in bilateral angular gyrus and the left middle frontal gyrus, 3) strengthened information flow from the left posterior temporoparietal region to the frontal areas and strengthened the dynamic connectivity between anterior and posterior brain regions. These findings demonstrate that modulating gamma-band oscillations effectively improves cognitive function in patients with probable AD by promoting local, long-range, and dynamic connectivity within the brain.

DNA methylation of the KLK8 gene in depression symptomatology

Background

Depression is a common, complex, and debilitating mental disorder estimated to be under-diagnosed and insufficiently treated in society. Liability to depression is influenced by both genetic and environmental risk factors, which are both capable of impacting DNA methylation (DNAm). Accordingly, numerous studies have researched for DNAm signatures of this disorder. Recently, an epigenome-wide association study of monozygotic twins identified an association between DNAm status in the KLK8 (neuropsin) promoter region and severity of depression symptomatology.

Methods

In this study, we aimed to investigate: (i) if blood DNAm levels, quantified by pyrosequencing, at two CpG sites in the KLK8 promoter are associated with depression symptomatology and depression diagnosis in an independent clinical cohort and (ii) if KLK8 DNAm levels are associated with depression, postpartum depression, and depression symptomatology in four independent methylomic cohorts, with blood and brain DNAm quantified by either MBD-seq or 450 k methylation array.

Results

DNAm levels in KLK8 were not significantly different between depression cases and controls, and were not significantly associated with any of the depression symptomatology scores after correction for multiple testing (minimum p value for KLK8 CpG1 = 0.12 for ‘Depressed mood,’ and for CpG2 = 0.03 for ‘Loss of self-confidence with other people’). However, investigation of the link between KLK8 promoter DNAm levels and depression-related phenotypes collected from four methylomic cohorts identified significant association (p value < 0.05) between severity of depression symptomatology and blood DNAm levels at seven CpG sites.

Conclusions

Our findings suggest that variance in blood DNAm levels in KLK8 promoter region is associated with severity of depression symptoms, but not depression diagnosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-021-01184-5.

M1 muscarinic receptor is a key target of neuroprotection, neuroregeneration and memory recovery by i-Extract from Withania somnifera

Memory loss is one of the most tragic symptoms of Alzheimer's disease. Our laboratory has recently demonstrated that 'i-Extract' of Ashwagandha (Withania somnifera) restores memory loss in scopolamine (SC)-induced mice. The prime target of i-Extract is obscure. We hypothesize that i-Extract may primarily target muscarinic subtype acetylcholine receptors that regulate memory processes. The present study elucidates key target(s) of i-Extract via cellular, biochemical, and molecular techniques in a relevant amnesia mouse model and primary hippocampal neuronal cultures. Wild type Swiss albino mice were fed i-Extract, and hippocampal cells from naïve mice were treated with i-Extract, followed by muscarinic antagonist (dicyclomine) and agonist (pilocarpine) treatments. We measured dendritic formation and growth by immunocytochemistry, kallikrein 8 (KLK8) mRNA by reverse transcription polymerase chain reaction (RT-PCR), and levels of KLK8 and microtubule-associated protein 2, c isoform (MAP2c) proteins by western blotting. We performed muscarinic receptor radioligand binding. i-Extract stimulated an increase in dendrite growth markers, KLK8 and MAP2. Scopolamine-mediated reduction was significantly reversed by i-Extract in mouse cerebral cortex and hippocampus. Our study identified muscarinic receptor as a key target of i-Extract, providing mechanistic evidence for its clinical application in neurodegenerative cognitive disorders.

BDNF Val66Met Polymorphism and Gamma Band Disruption in Resting State Brain Functional Connectivity: A Magnetoencephalography Study in Cognitively Intact Older Females

The pathophysiological processes undermining brain functioning decades before the onset of the clinical symptoms associated with dementia are still not well understood. Several heritability studies have reported that the Brain Derived Neurotrophic Factor (BDNF) Val66Met genetic polymorphism could contribute to the acceleration of cognitive decline in aging. This mutation may affect brain functional connectivity (FC), especially in those who are carriers of the BDNF Met allele. The aim of this work was to explore the influence of the BDNF Val66Met polymorphism in whole brain eyes-closed, resting-state magnetoencephalography (MEG) FC in a sample of 36 cognitively intact (CI) older females. All of them were ε3ε3 homozygotes for the apolipoprotein E (APOE) gene and were divided into two subgroups according to the presence of the Met allele: Val/Met group (n = 16) and Val/Val group (n = 20). They did not differ in age, years of education, Mini-Mental State Examination scores, or normalized hippocampal volumes. Our results showed reduced antero-posterior gamma band FC within the Val/Met genetic risk group, which may be caused by a GABAergic network impairment. Despite the lack of cognitive decline, these results might suggest a selective brain network vulnerability due to the carriage of the BDNF Met allele, which is linked to a potential progression to dementia. This neurophysiological signature, as tracked with MEG FC, indicates that age-related brain functioning changes could be mediated by the influence of particular genetic risk factors.