Involvement of Kallikrein-Related Peptidases in Nervous System Disorders

Astrocytic PAR1 and mGluR2/3 control synaptic glutamate time course at hippocampal CA1 synapses

Astrocytes play an essential role in regulating synaptic transmission. This study describes a novel form of modulation of excitatory synaptic transmission in the mouse hippocampus by astrocytic G-protein-coupled receptors (GPCRs). We have previously described astrocytic glutamate release via protease-activated receptor-1 (PAR1) activation, although the regulatory mechanisms for this are complex. Through electrophysiological analysis and modeling, we discovered that PAR1 activation consistently increases the concentration and duration of glutamate in the synaptic cleft. This effect was not due to changes in the presynaptic glutamate release or alteration in glutamate transporter expression. However, blocking group II metabotropic glutamate receptors (mGluR2/3) abolished PAR1-mediated regulation of synaptic glutamate concentration, suggesting a role for this GPCR in mediating the effects of PAR1 activation on glutamate release. Furthermore, activation of mGluR2/3 causes glutamate release through the TREK-1 channel in hippocampal astrocytes. These data show that astrocytic GPCRs engage in a novel regulatory mechanism to shape the time course of synaptically-released glutamate in excitatory synapses of the hippocampus.

Inflammasome-Inhibiting Nanoligomers Are Neuroprotective against Space-Induced Pathology in Healthy and Diseased Three-Dimensional Human Motor and Prefrontal Cortex Brain Organoids

The microgravity and space environment has been linked to deficits in neuromuscular and cognitive capabilities, hypothesized to occur due to accelerated aging and neurodegeneration in space. While the specific mechanisms are still being investigated, spaceflight-associated neuropathology is an important health risk to astronauts and space tourists and is being actively investigated for the development of appropriate countermeasures. However, such space-induced neuropathology offers an opportunity for accelerated screening of therapeutic targets and lead molecules for treating neurodegenerative diseases. Here, we show a proof-of-concept high-throughput target screening (on Earth), target validation, and mitigation of microgravity-induced neuropathology using our Nanoligomer platform, onboard the 43-day SpaceX CRS-29 mission to the International Space Station. First, comparing 3D healthy and diseased prefrontal cortex (PFC, for cognition) and motor neuron (MN, for neuromuscular function) organoids, we assessed space-induced pathology using biomarkers relevant to Alzheimer's disease (AD), frontotemporal dementia (FTD), and amyotrophic lateral sclerosis (ALS). Both healthy and diseased PFC and MN organoids showed significantly enhanced neurodegeneration in space, as measured through relevant disease biomarkers, when compared to their respective Earth controls. Second, we tested the top two lead molecules, NI112 that targeted NF-κB and NI113 that targeted IL-6. We observed that these Nanoligomers significantly mitigate the AD, FTD, and ALS relevant biomarkers like amyloid beta-42 (Aβ42), phosphorylated tau (pTau), Kallikrein (KLK-6), Tar DNA-binding protein 43 (TDP-43), and others. Moreover, the 43-day Nanoligomer treatment of these brain organoids did not appear to cause any observable toxicity or safety issues in the target organoid tissue, suggesting good tolerability for these molecules in the brain at physiologically relevant doses. Together, these results show significant potential for both the development and translation of NI112 and NI113 molecules as potential neuroprotective countermeasures for safer space travel and demonstrate the usefulness of the space environment for rapid, high-throughput screening of targets and lead molecules for clinical translation. We assert that the use of microgravity in drug development and screening may ultimately benefit millions of patients suffering from debilitating neurodegenerative diseases on Earth.

Kallikrein-related peptidase's significance in Alzheimer's disease pathogenesis: A comprehensive survey

Alzheimer's disease (AD) and related dementias constitute an important global health challenge. Detailed understanding of the multiple molecular mechanisms underlying their pathogenesis constitutes a clue for the management of the disease. Kallikrein-related peptidases (KLKs), a lead family of serine proteases, have emerged as potential biomarkers and therapeutic targets in the context of AD and associated cognitive decline. Hence, KLKs were proposed to display multifaceted impacts influencing various aspects of neurodegeneration, including amyloid-beta aggregation, tau pathology, neuroinflammation, and synaptic dysfunction. We propose here a comprehensive survey to summarize recent findings, providing an overview of the main kallikreins implicated in AD pathophysiology namely KLK8, KLK6 and KLK7. We explore the interplay between KLKs and key AD molecular pathways, shedding light on their significance as potential biomarkers for early disease detection. We also discuss their pertinence as therapeutic targets for disease-modifying interventions to develop innovative therapeutic strategies aimed at halting or ameliorating the progression of AD and associated dementias.

Sex-Specific Differences in Serum Kallikrein-8 (KLK8): An Exploratory Study

Background

There are indications for sex-specific differences regarding the association between kallikrein-8 (KLK8) and cognitive impairment in early stages of Alzheimer's disease for which KLK8 may be an early blood-based biomarker. These may be due to different levels of sex hormones. To correctly interpret KLK8 blood concentrations, sex-specific analyses are needed.

Objective

The aim of our exploratory study was to investigate sex-specific differences in blood-based KLK8 in participants of the population-based Heinz Nixdorf Recall study with different cognitive status and the association between KLK8 and sex hormones.

Methods

In 290 participants (45% women, 69.7±7.4 years (mean±SD)) we investigated sex-specific serum KLK8 differences between cognitively unimpaired (CU, 43%) and cognitively impaired (CI) participants and the association between KLK8 and dehydroepiandrosteronsulfate (DHEAS), estradiol and testosterone, using adjusted multiple linear regression.

Results

The mean±SD KLK8 was similar for CU men (808.1±729.6 pg/ml) and women (795.9±577.7 pg/ml); adjusted mean-difference [95%-CI]: -95.3 [-324.1;133.5] pg/ml. KLK8 was lower in CI women (783.5±498.7 pg/ml) than men (1048.4±829 pg/ml); -261 [-493.1; -29] pg/ml. In men but not women, there was a weak indication for a positive slope between estradiol (11.9 [-0.4;24.3] pg/ml) and DHEAS (1.4 [-0.5;3.3] pg/ml) with KLK8, while testosterone had no impact.

Conclusions

The results suggested a different role for KLK8 in the development of cognitive impairment in men and women, potentially influenced by sex hormones. To use blood KLK8 as an early biomarker, further research on hormonal regulation of KLK8 expression is needed as a part of the investigation of the KLK8 involvement in cognitive impairment and Alzheimer's disease pathology.

Perspective from single-cell sequencing: Is inflammation in acute ischemic stroke beneficial or detrimental?

BACKGROUND

Acute ischemic stroke (AIS) is a common cerebrovascular event associated with high incidence, disability, and poor prognosis. Studies have shown that various cell types, including microglia, astrocytes, oligodendrocytes, neurons, and neutrophils, play complex roles in the early stages of AIS and significantly affect its prognosis. Thus, a comprehensive understanding of the mechanisms of action of these cells will be beneficial for improving stroke prognosis. With the rapid development of single-cell sequencing technology, researchers have explored the pathophysiological mechanisms underlying AIS at the single-cell level.

METHOD

We systematically summarize the latest research on single-cell sequencing in AIS.

RESULT

In this review, we summarize the phenotypes and functions of microglia, astrocytes, oligodendrocytes, neurons, neutrophils, monocytes, and lymphocytes, as well as their respective subtypes, at different time points following AIS. In particular, we focused on the crosstalk between microglia and astrocytes, oligodendrocytes, and neurons. Our findings reveal diverse and sometimes opposing roles within the same cell type, with the possibility of interconversion between different subclusters.

CONCLUSION

This review offers a pioneering exploration of the functions of various glial cells and cell subclusters after AIS, shedding light on their regulatory mechanisms that facilitate the transformation of detrimental cell subclusters towards those that are beneficial for improving the prognosis of AIS. This approach has the potential to advance the discovery of new specific targets and the development of drugs, thus representing a significant breakthrough in addressing the challenges in AIS treatment.

Large-scale proximity extension assay reveals CSF midkine and DOPA decarboxylase as supportive diagnostic biomarkers for Parkinson's disease

BACKGROUND

There is a need for biomarkers to support an accurate diagnosis of Parkinson's disease (PD). Cerebrospinal fluid (CSF) has been a successful biofluid for finding neurodegenerative biomarkers, and modern highly sensitive multiplexing methods offer the possibility to perform discovery studies. Using a large-scale multiplex proximity extension assay (PEA) approach, we aimed to discover novel diagnostic protein biomarkers allowing accurate discrimination of PD from both controls and atypical Parkinsonian disorders (APD).

METHODS

CSF from patients with PD, corticobasal syndrome (CBS), progressive supranuclear palsy (PSP), multiple system atrophy and controls, were analysed with Olink PEA panels. Three cohorts were used in this study, comprising 192, 88 and 36 cases, respectively. All samples were run on the Cardiovascular II, Oncology II and Metabolism PEA panels.

RESULTS

Our analysis revealed that 26 and 39 proteins were differentially expressed in the CSF of test and validation PD cohorts, respectively, compared to controls. Among them, 6 proteins were changed in both cohorts. Midkine (MK) was increased in PD with the strongest effect size and results were validated with ELISA. Another most increased protein in PD, DOPA decarboxylase (DDC), which catalyses the decarboxylation of DOPA (L-3,4-dihydroxyphenylalanine) to dopamine, was strongly correlated with dopaminergic treatment. Moreover, Kallikrein 10 was specifically changed in APD compared with both PD and controls, but unchanged between PD and controls. Wnt inhibitory factor 1 was consistently downregulated in CBS and PSP patients in two independent cohorts.

CONCLUSIONS

Using the large-scale PEA approach, we have identified potential novel PD diagnostic biomarkers, most notably MK and DDC, in the CSF of PD patients.

A novel approach to enhance the performance of kallikrein 6 enzyme using Pichia pastoris GS115 as a host

Background and purpose

Enzyme engineering is the process of raising enzyme efficiency and activity by altering amino acid sequences. Kallikrein 6 (KLK6) enzyme is a secreted serine protease involved in a variety of physiological and pathological activities. The increased expression of KLK6 plays a key role in various diseases. Instability and spontaneous activation and deactivation are major challenges in the study of this enzyme. This study aimed to create a stable pro-KLK6 enzyme by enzyme engineering, designing a specific cleavage site for enterokinase, and using Pichia pastoris GS115 as a host cell. Then, recombinant pro-KLK6 was used to introduce a novel inhibitor for it.

Experimental approach

An engineered pro-KLK6 gene was cloned into the pPICZα A expression vector. Then, it was expressed in P. pastoris GS115 and purified by Ni-NTA chromatography. An inactive engineered pro-KLK6 gene was cleaved by enterokinase and converted to an active KLK6. The KLK6 enzyme activity and its kinetic parameters were measured using N-benzoyl-L-arginine ethyl ester (BAEE) substrates.

Findings/Results

The secretory form of the pro-KLK6 was expressed at about 11 mg/L in P. pastoris (GS115). Before activation with enterokinase, pro-KLK6 was inactive and did not activate spontaneously. The kinetic parameters, including Km and Vmax, were estimated at 113.59 μM and 0.432 μM/s, respectively.

Conclusion and implications

A stable pro-KLK6 enzyme was produced using P. pastoris (GS115) as the host cell and a specific cleavage site for enterokinase. Additionally, this study assessed the kinetic parameters of the KLK6 enzyme using the BAEE substrate for the first time.

Minireview: functional roles of tissue kallikrein, kinins, and kallikrein-related peptidases in lung cancer

Despite campaigns and improvements in detection and treatment, lung cancer continues to increase worldwide and represents a major public health problem. One approach to treating patients suffering from lung cancer is to target surface receptors overexpressed on tumor cells, such as GPCR-family kinin receptors, and proteases that control tumor progression, such as kallikrein-related peptidases (KLKs). These proteases have been visualized in recent years due to their contribution to the progression of cancers, such as prostate and ovarian cancer, facilitating the invasive and metastatic capacity of tumor cells in these tissues. In fact, KLK3 is the specific prostate antigen, the only tissue-specific biomarker used to diagnose this malignancy. In lung cancer to date, evidence indicates that KLK5, KLK6, KLK8, KLK11, and KLK14 are the major peptidases regulated and involved in its progression. The expression levels of KLKs in this neoplasm are modulated by the secretome of the different cell types present in the tumor microenvironment, the cancer subtype and the tumor stage, among others. Considering the multiple functions of kinin receptors and KLKs, this review highlights their roles, even considering the SARS-CoV-2 effects. Since lung cancer is often diagnosed in advanced stages, our efforts should focus on early diagnosis, validating for example specific KLKs, especially in high-risk populations such as smokers and people exposed to carcinogenic fumes, oil fields, and contaminated workplaces, unexplored fields to investigate. Furthermore, their modulation could be considered as a promising approach in lung cancer therapeutics.

Chronic changes in oligodendrocyte sub-populations after middle cerebral artery occlusion in neonatal mice

Neonatal stroke is common and causes life-long motor and cognitive sequelae. Because neonates with stroke are not diagnosed until days-months after the injury, chronic targets for repair are needed. We evaluated oligodendrocyte maturity and myelination and assessed oligodendrocyte gene expression changes using single cell RNA sequencing (scRNA seq) at chronic timepoints in a mouse model of neonatal arterial ischemic stroke. Mice underwent 60 min of transient right middle cerebral artery occlusion (MCAO) on postnatal day 10 (p10) and received 5-ethynyl-2'-deoxyuridine (EdU) on post-MCAO days 3-7 to label dividing cells. Animals were sacrificed 14 and 28-30 days post-MCAO for immunohistochemistry and electron microscopy. Oligodendrocytes were isolated from striatum 14 days post-MCAO for scRNA seq and differential gene expression analysis. The density of Olig2+ EdU+ cells was significantly increased in ipsilateral striatum 14 days post-MCAO and the majority of oligodendrocytes were immature. Density of Olig2+ EdU+ cells declined significantly between 14 and 28 days post-MCAO without a concurrent increase in mature Olig2+ EdU+ cells. By 28 days post-MCAO there were significantly fewer myelinated axons in ipsilateral striatum. scRNA seq identified a cluster of "disease associated oligodendrocytes (DOLs)" specific to the ischemic striatum, with increased expression of MHC class I genes. Gene ontology analysis suggested decreased enrichment of pathways involved in myelin production in the reactive cluster. Oligodendrocytes proliferate 3-7 days post-MCAO and persist at 14 days, but fail to mature by 28 days. MCAO induces a subset of oligodendrocytes with reactive phenotype, which may be a therapeutic target to promote white matter repair.

Upregulation of KLK8 contributes to CUMS-induced hippocampal neuronal apoptosis by cleaving NCAM1

Neuronal apoptosis has been well-recognized as a critical mediator in the pathogenesis of depressive disorders. Tissue kallikrein-related peptidase 8 (KLK8), a trypsin-like serine protease, has been implicated in the pathogenesis of several psychiatric disorders. The present study aimed to explore the potential function of KLK8 in hippocampal neuronal cell apoptosis associated with depressive disorders in rodent models of chronic unpredictable mild stress (CUMS)-induced depression. It was found that depression-like behavior in CUMS-induced mice was associated with hippocampal KLK8 upregulation. Transgenic overexpression of KLK8 exacerbated, whereas KLK8 deficiency attenuated CUMS-induced depression-like behaviors and hippocampal neuronal apoptosis. In HT22 murine hippocampal neuronal cells and primary hippocampal neurons, adenovirus-mediated overexpression of KLK8 (Ad-KLK8) was sufficient to induce neuron apoptosis. Mechanistically, it was identified that the neural cell adhesion molecule 1 (NCAM1) may associate with KLK8 in hippocampal neurons as KLK8 proteolytically cleaved the NCAM1 extracellular domain. Immunofluorescent staining exhibited decreased NCAM1 in hippocampal sections obtained from mice or rats exposed to CUMS. Transgenic overexpression of KLK8 exacerbated, whereas KLK8 deficiency largely prevented CUMS-induced loss of NCAM1 in the hippocampus. Both adenovirus-mediated overexpression of NCAM1 and NCAM1 mimetic peptide rescued KLK8-overexpressed neuron cells from apoptosis. Collectively, this study identified a new pro-apoptotic mechanism in the hippocampus during the pathogenesis of CUMS-induced depression via the upregulation of KLK8, and raised the possibility of KLK8 as a potential therapeutic target for depression.

Blood Kallikrein-8 and Non-Amnestic Mild Cognitive Impairment: An Exploratory Study

Background: Blood kallikrein-8 is supposed to be a biomarker for mild cognitive impairment (MCI) due to Alzheimer’s disease (AD), a precursor of AD dementia. Little is known about the association of kallikrein-8 and non-AD type dementias. Objective: To investigate whether blood kallikrein-8 is elevated in individuals with non-amnestic MCI (naMCI), which has a higher probability to progress to a non-AD type dementia, compared with cognitively unimpaired (CU) controls. Methods: We measured blood kallikrein-8 at ten-year follow-up (T2) in 75 cases and 75 controls matched for age and sex who were participants of the population-based Heinz Nixdorf Recall study (baseline: 2000–2003). Cognitive performance was assessed in a standardized manner at five (T1) and ten-year follow-up. Cases were CU or had subjective cognitive decline (SCD) at T1 and had naMCI at T2. Controls were CU at both follow-ups. The association between kallikrein-8 (per 500 pg/ml increase) and naMCI was estimated using conditional logistic regression: odds ratios (OR) and 95% confidence intervals (95% CI) were determined, adjusted for inter-assay variability and freezing duration. Results: Valid kallikrein-8 values were measured in 121 participants (45% cases, 54.5% women, 70.5±7.1 years). In cases, the mean kallikrein-8 was higher than in controls (922±797 pg/ml versus 884±782 pg/ml). Kallikrein-8 was not associated with having naMCI compared to being CU (adjusted; OR: 1.03 [95% CI: 0.80–1.32]). Conclusion: This is the first population-based study that shows that blood kallikrein-8 tends not to be elevated in individuals with naMCI compared with CU. This adds to the evidence of the possible AD specificity of kallikrein-8.

Alpha-1 antitrypsin expression is upregulated in multidrug-resistant cancer cells

Identification of the signature molecular profiles involved in therapy resistance is of vital importance in developing new strategies for treatments and disease monitoring. Protein alpha-1 antitrypsin (AAT, encoded by SERPINA1 gene) is an acute-phase protein, and its high expression has been linked with unfavorable clinical outcome in different types of cancer; however, data on its involvement in therapy resistance are still insufficient. We analyzed SERPINA1 mRNA expression in three different multidrug-resistant (MDR) cell lines-U87-TxR, NCI-H460/R, and DLD1-TxR-and in U87 cells grown in alginate microfibers as a 3D cellular model of glioblastoma. Expression of IL-6 as a major modulator of SERPINA1 was also analyzed. Additionally, AAT protein expression in MDR cells was analyzed by immunofluorescence. SERPINA1 gene expression and AAT protein expression were significantly upregulated in all the tested MDR cell lines compared with their sensitive counterparts. Moreover, SERPINA1 was significantly upregulated in 3D models of glioblastoma, previously found to have upregulated drug-resistance-related gene expression compared with 2D cells. With the exception of NCI-H460/R, in all cell lines as well as in a 3D model of U87 cells, increase in SERPINA1 expression correlated with the increase in IL-6 expression. Our results indicate that AAT could be utilized as a biomarker of therapy resistance in cancer; however, further studies are needed to elucidate the mechanisms driving AAT upregulation in therapy resistance and its biological significance in this process.

A KLK6 Activity-Based Probe Reveals a Role for KLK6 Activity in Pancreatic Cancer Cell Invasion

Pancreatic cancer has the lowest survival rate of all common cancers due to late diagnosis and limited treatment options. Serine hydrolases are known to mediate cancer progression and metastasis through initiation of signaling cascades and cleavage of extracellular matrix proteins, and the kallikrein-related peptidase (KLK) family of secreted serine proteases have emerging roles in pancreatic ductal adenocarcinoma (PDAC). However, the lack of reliable activity-based probes (ABPs) to profile KLK activity has hindered progress in validation of these enzymes as potential targets or biomarkers. Here, we developed potent and selective ABPs for KLK6 by using a positional scanning combinatorial substrate library and characterized their binding mode and interactions by X-ray crystallography. The optimized KLK6 probe IMP-2352 (k_obs/I = 11,000 M^-1 s^-1) enabled selective detection of KLK6 activity in a variety of PDAC cell lines, and we observed that KLK6 inhibition reduced the invasiveness of PDAC cells that secrete active KLK6. KLK6 inhibitors were combined with N-terminomics to identify potential secreted protein substrates of KLK6 in PDAC cells, providing insights into KLK6-mediated invasion pathways. These novel KLK6 ABPs offer a toolset to validate KLK6 and associated signaling partners as targets or biomarkers across a range of diseases.

A transient inflammatory response contributes to oxaliplatin neurotoxicity in mice

OBJECTIVES

Peripheral neuropathy is a relevant dose-limiting adverse event that can affect up to 90% of oncologic patients with colorectal cancer receiving oxaliplatin treatment. The severity of neurotoxicity often leads to dose reduction or even premature cessation of chemotherapy. Unfortunately, the limited knowledge about the molecular mechanisms related to oxaliplatin neurotoxicity leads to a lack of effective treatments to prevent the development of this clinical condition. In this context, the present work aimed to determine the exact molecular mechanisms involved in the development of oxaliplatin neurotoxicity in a murine model to try to find new therapeutical targets.

METHODS

By single-cell RNA sequencing (scRNA-seq), we studied the transcriptomic profile of sensory neurons and satellite glial cells (SGC) of the Dorsal Root Ganglia (DRG) from a well-characterized mouse model of oxaliplatin neurotoxicity.

RESULTS

Analysis of scRNA-seq data pointed to modulation of inflammatory processes in response to oxaliplatin treatment. In this line, we observed increased levels of NF-kB p65 protein, pro-inflammatory cytokines, and immune cell infiltration in DRGs and peripheral nerves of oxaliplatin-treated mice, which was accompanied by mechanical allodynia and decrease in sensory nerve amplitudes.

INTERPRETATION

Our data show that, in addition to the well-described DNA damage, oxaliplatin neurotoxicity is related to an exacerbated pro-inflammatory response in DRG and peripheral nerves, and open new insights in the development of anti-inflammatory strategies as a treatment for preventing peripheral neuropathy induced by oxaliplatin.

KLK6 Functions as an Oncogene and Unfavorable Prognostic Factor in Bladder Urothelial Carcinoma

Background

Kallikrein-related peptidase 6 (KLK6) has been substantiated as a diagnostic, prognostic, and therapeutic molecular in several cancer types. In our study, we attempt to explore the biological functions of KLK6 in bladder urothelial carcinoma (BLCA).

Methods

KLK6 gene expression prognostic, gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), gene set enrichment analysis (GSEA), and immune infiltration were analyzed using The Cancer Genome Atlas (TCGA) database. In vitro and in vivo experimental measurements, including CCK8, transwell migration, TUNEL, and nude mouse transplanted tumor model, were used to evaluate the antineoplastic activities of KLK6 loss-of-function.

Results

The combination of bioinformatics analyses and experimental measurements demonstrate that KLK6 expression is aberrantly upregulated in human specimens and cell lines of BLCA. GO and GSEA enrichment analyses exhibited that KLK6 is implicated in the inflammatory response and immune infiltration, suggesting that upregulation of KLK6 may be associated with the progression of BLCA. Knockdown of KLK6 is able to inhibit the growth and migration and trigger apoptosis of RT4 and T24 cells. Moreover, the TCGA database indicates that KLK6 high expression in BLCA patients showed a poorer prognosis than those patients with KLK6 low expression. Univariate and multivariate regression analyses suggest KLK6 as an independent prognostic factor to predict unfavorable OS in patients with BLCA.

Conclusion

KLK6 is an independent prognostic factor and an antitumor target of BLCA. KLK6 expression positively correlates with several immune cells infiltration, indicating that inhibition of KLK6 may contribute to immunotherapy of BLCA.

West Nile Virus Neuroinfection in Humans: Peripheral Biomarkers of Neuroinflammation and Neuronal Damage

Among emerging arthropod-borne viruses (arbovirus), West Nile virus (WNV) is a flavivirus that can be associated with severe neuroinvasive infections in humans. In 2018, the European WNV epidemic resulted in over 2000 cases, representing the most important arboviral epidemic in the European continent. Characterization of inflammation and neuronal biomarkers released during WNV infection, especially in the context of neuronal impairments, could provide insight into the development of predictive tools that could be beneficial for patient outcomes. We first analyzed the inflammatory signature in the serum of WNV-infected mice and found increased concentrations of several inflammatory cytokines. We next analyzed serum and cerebrospinal-fluid (CSF) samples from a cohort of patients infected by WNV between 2018 and 2019 in Hungary to quantify a large panel of inflammatory cytokines and neurological factors. We found higher levels of inflammatory cytokines (e.g., IL4, IL6, and IL10) and neuronal factors (e.g., BDNF, GFAP, MIF, TDP-43) in the sera of WNV-infected patients with neuroinvasive disease. Furthermore, the serum inflammatory profile of these patients persisted for several weeks after initial infection, potentially leading to long-term sequelae and having a deleterious effect on brain neurovasculature. This work suggests that early signs of increased serum concentrations of inflammatory cytokines and neuronal factors could be a signature underlying the development of severe neurological impairments. Biomarkers could play an important role in patient monitoring to improve care and prevent undesirable outcomes.

Comprehensive expression analysis with cell-type-specific transcriptome in ALS-linked mutant SOD1 mice: Revisiting the active role of glial cells in disease

Non-cell autonomous mechanisms are involved in the pathogenesis of amyotrophic lateral sclerosis (ALS), an adult neurodegenerative disease characterized by selective motor neuron loss. While the emerging role of glial cells in ALS has been noted, the detailed cell-type-specific role of glial cells has not been clarified. Here, we examined mRNA expression changes using microarrays of the spinal cords of three distinct lines of mutant superoxide dismutase (SOD) 1 transgenic mice, an established ALS model. Our analysis used a transcriptome database of component cell types in the central nervous system (CNS), as well as SOD1 ^G93A cell-type transcriptomes. More than half of the differentially expressed genes (DEGs) were highly expressed in microglia, and enrichment analysis of DEGs revealed that immunological reactions were profoundly involved and some transcription factors were upregulated. Our analysis focused on DEGs that are highly expressed in each cell type, as well as chemokines, caspases, and heat shock proteins. Disease-associated microglial genes were upregulated, while homeostatic microglial genes were not, and galectin-3 (Mac2), a known activated microglial marker, was predicted to be ectopically expressed in astrocytes in mutant SOD1 mice. In mutant SOD1 mice, we developed a prediction model for the pathophysiology of different cell types related to TREM2, apolipoprotein E, and lipoproteins. Our analysis offers a viable resource to understand not only the molecular pathologies of each CNS constituent cell type, but also the cellular crosstalk between different cell types under both physiological and pathological conditions in model mice for various neurodegenerative diseases.

Coexpression of Gene Transcripts with Monoamine Oxidase A Quantified by Human In Vivo Positron Emission Tomography

The monoamine oxidase A (MAO-A) is integral to monoamine metabolism and is thus relevant to the pathophysiology of various neuropsychiatric disorders; however, associated gene-enzyme relations are not well understood. This study aimed to unveil genes coexpressed with MAO-A. Therefore, 18 179 mRNA expression maps (based on the Allen Human Brain Atlas) were correlated with the cerebral distribution volume (VT) of MAO-A assessed in 36 healthy subjects (mean age ± standard deviation: 32.9 ± 8.8 years, 18 female) using [11C]harmine positron emission tomography scans. Coexpression analysis was based on Spearman's ρ, over-representation tests on Fisher's exact test with false discovery rate (FDR) correction. The analysis revealed 35 genes in cortex (including B-cell translocation gene family, member 3, implicated in neuroinflammation) and 247 genes in subcortex (including kallikrein-related peptidase 10, implicated in Alzheimer's disease). Significantly over-represented Gene Ontology terms included "neuron development", "neuron differentiation", and "cell-cell signaling" as well as "axon" and "neuron projection". In vivo MAO-A enzyme distribution and MAOA expression did not correlate in cortical areas (ρ = 0.08) while correlation was found in subcortical areas (ρ = 0.52), suggesting influences of region-specific post-transcriptional and -translational modifications. The herein reported information could contribute to guide future genetic studies, deepen the understanding of associated pathomechanisms and assist in the pursuit of novel therapeutic targets.

Dynamic Changes in Central and Peripheral Neuro-Injury vs. Neuroprotective Serum Markers in COVID-19 Are Modulated by Different Types of Anti-Viral Treatments but Do Not Affect the Incidence of Late and Early Strokes

The balance between neurodegeneration, neuroinflammation, neuroprotection, and COVID-19-directed therapy may underly the heterogeneity of SARS-CoV-2's neurological outcomes. A total of 105 patients hospitalized with a diagnosis of COVID-19 had serum collected over a 6 month period to assess neuroinflammatory (MIF, CCL23, MCP-1), neuro-injury (NFL, NCAM-1), neurodegenerative (KLK6, τ, phospho τ, amyloids, TDP43, YKL40), and neuroprotective (clusterin, fetuin, TREM-2) proteins. These were compared to markers of nonspecific inflammatory responses (IL-6, D-dimer, CRP) and of the overall viral burden (spike protein). Data regarding treatment (steroids, convalescent plasma, remdasavir), pre-existing conditions, and incidences of strokes were collected. Amyloid β42, TDP43, NF-L, and KLK6 serum levels declined 2-3 days post-admission, yet recovered to admission baseline levels by 7 days. YKL-40 and NCAM-1 levels remained elevated over time, with clusters of differential responses identified among TREM-2, TDP43, and YKL40. Fetuin was elevated after the onset of COVID-19 while TREM-2 initially declined before significantly increasing over time. MIF serum level was increased 3-7 days after admission. Ferritin correlated with TDP-43 and KLK6. No treatment with remdesivir coincided with elevations in Amyloid-β40. A lack of convalescent plasma resulted in increased NCAM-1 and total tau, and steroidal treatments did not significantly affect any markers. A total of 11 incidences of stroke were registered up to six months after initial admission for COVID-19. Elevated D-dimer, platelet counts, IL-6, and leukopenia were observed. Variable MIF serum levels differentiated patients with CVA from those who did not have a stroke during the acute phase of COVID-19. This study demonstrated concomitant and opposite changes in neurodegenerative and neuroprotective markers persisting well into recovery.

Ligand screening assay for the enzyme kallikrein immobilized on NHS-activated Sepharose

Human tissue kallikreins (KLKs) are serine proteases involved in various physiological and pathological conditions, including cancer and neurological disorders. These enzymes constitute attractive drug targets, which has stimulated the search for new KLK inhibitors. In this study, we have covalently immobilized porcine pancreas KLK on an NHS-activated Sepharose matrix, to obtain KLK-Sepharose-NHS. The immobilized enzyme showed high recovered activity and maintained the ability of free KLK to recognize the synthetic substrate Z-Phe-Arg-AMC (K_Mapp = 10.3 ± 0.9 μM). As proof of concept, we used leupeptin as a reference inhibitor to perform inhibition studies for KLK-Sepharose-NHS and to determine the half-maximal inhibitory concentration (IC₅₀ = 0.13 ± 0.01 μM), the inhibition constant (K_i = 0.06 μM), and the leupeptin inhibition mechanism. We evaluated several complex matrixes (plant crude extract) by the same bioassay, to demonstrate their applicability. The species Solanum lycocarpum, Stryphnodendron adstringens, and Psychotria carthagenensis gave the best results. KLK-Sepharose-NHS was fully active after six consecutive reaction cycles and retained about 60 % of its initial activity after being used for at least five months, so the bioassay developed herein is a promising strategy to screen and to identify KLK ligands.

A novel role of kallikrein-related peptidase 8 in the pathogenesis of diabetic cardiac fibrosis

Rationale: Among all the diabetic complications, diabetic cardiomyopathy, which is characterized by myocyte loss and myocardial fibrosis, is the leading cause of mortality and morbidity in diabetic patients. Tissue kallikrein-related peptidases (KLKs) are secreted serine proteases, that have distinct and overlapping roles in the pathogenesis of cardiovascular diseases. However, whether KLKs are involved in the development of diabetic cardiomyopathy remains unknown.The present study aimed to determine the role of a specific KLK in the initiation of endothelial-to-mesenchymal transition (EndMT) during the pathogenesis of diabetic cardiomyopathy.

Methods and Results-By screening gene expression profiles of KLKs, it was found that KLK8 was highly induced in the myocardium of mice with streptozotocin-induced diabetes. KLK8 deficiency attenuated diabetic cardiac fibrosis, and rescued the impaired cardiac function in diabetic mice. Small interfering RNA (siRNA)-mediated KLK8 knockdown significantly attenuated high glucose-induced endothelial damage and EndMT in human coronary artery endothelial cells (HCAECs). Diabetes-induced endothelial injury and cardiac EndMT were significantly alleviated in KLK8-deficient mice. In addition, transgenic overexpression of KLK8 led to interstitial and perivascular cardiac fibrosis, endothelial injury and EndMT in the heart. Adenovirus-mediated overexpression of KLK8 (Ad-KLK8) resulted in increases in endothelial cell damage, permeability and transforming growth factor (TGF)-β1 release in HCAECs. KLK8 overexpression also induced EndMT in HCAECs, which was alleviated by a TGF-β1-neutralizing antibody. A specificity protein-1 (Sp-1) consensus site was identified in the human KLK8 promoter and was found to mediate the high glucose-induced KLK8 expression. Mechanistically, it was identified that the vascular endothelial (VE)-cadherin/plakoglobin complex may associate with KLK8 in HCAECs. KLK8 cleaved the VE-cadherin extracellular domain, thus promoting plakoglobin nuclear translocation. Plakoglobin was required for KLK8-induced EndMT by cooperating with p53. KLK8 overexpression led to plakoglobin-dependent association of p53 with hypoxia inducible factor (HIF)-1α, which further enhanced the transactivation effect of HIF-1α on the TGF-β1 promoter. KLK8 also induced the binding of p53 with Smad3, subsequently promoting pro-EndMT reprogramming via the TGF-β1/Smad signaling pathway in HCAECs. The in vitro and in vivo findings further demonstrated that high glucose may promote plakoglobin-dependent cooperation of p53 with HIF-1α and Smad3, subsequently increasing the expression of TGF-β1 and the pro-EndMT target genes of the TGF-β1/Smad signaling pathway in a KLK8-dependent manner.

Conclusions: The present findings uncovered a novel pro-EndMT mechanism during the pathogenesis of diabetic cardiac fibrosis via the upregulation of KLK8, and may contribute to the development of future KLK8-based therapeutic strategies for diabetic cardiomyopathy.

Characterization and Biomarker Analyses of Post-COVID-19 Complications and Neurological Manifestations

As the SARS-CoV-2 pandemic continues, reports have demonstrated neurologic sequelae following COVID-19 recovery. Mechanisms to explain long-term neurological sequelae are unknown and need to be identified. Plasma from 24 individuals recovering from COVID-19 at 1 to 3 months after initial infection were collected for cytokine and antibody levels and neuronal-enriched extracellular vesicle (nEV) protein cargo analyses. Plasma cytokine IL-4 was increased in all COVID-19 participants. Volunteers with self-reported neurological problems (nCoV, n = 8) had a positive correlation of IL6 with age or severity of the sequalae, at least one co-morbidity and increased SARS-CoV-2 antibody compared to those COVID-19 individuals without neurological issues (CoV, n = 16). Protein markers of neuronal dysfunction including amyloid beta, neurofilament light, neurogranin, total tau, and p-T181-tau were all significantly increased in the nEVs of all participants recovering from COVID-19 compared to historic controls. This study suggests ongoing peripheral and neuroinflammation after COVID-19 infection that may influence neurological sequelae by altering nEV proteins. Individuals recovering from COVID-19 may have occult neural damage while those with demonstrative neurological symptoms additionally had more severe infection. Longitudinal studies to monitor plasma biomarkers and nEV cargo are warranted to assess persistent neurodegeneration and systemic effects.

Neuroprotective Effect of Cudrania tricuspidata Fruit Extracts on Scopolamine-Induced Learning and Memory Impairment

Cudrania tricuspidata has diverse biological activities, such as antioxidant, anti-inflammatory, anticancer, and neuroprotective effects. This study investigated the protective effects of C. tricuspidata fruit extracts (CTFE) against scopolamine (SCO)-induced neuron impairment. The neuroprotective effects of CTFE on SCO-induced memory dysfunction were confirmed in mice using the Barnes maze test. The results showed that co-treatment of SCO and CTFE increased the stay time in the target zone compared with SCO treatment alone. Similarly, the results obtained by the fear conditioning test revealed that SCO-CTFE co-treatment induced the freezing action time under both the contextual fear condition and the cued fear condition compared with SCO treatment alone. Moreover, we showed that CTFE reduced the SCO-induced acetylcholinesterase (AChE) activity, thereby increasing the acetylcholine concentration in mice hippocampal tissues. Consistent with the improvement of memory and recognition function in vivo, our in vitro results showed that CTFE induced cAMP response element binding protein (CREB) and extracellular regulated kinase 1/2 (ERK1/2) activity in PC12 cells and reduced SCO-induced AChE activity. In addition, the microarray results of the hippocampal tissue support our data showing that CTFE affects gene expressions associated with neurogenesis and neuronal cell differentiation markers such as spp1 and klk6. Overall, CTFE exerts a neuroprotective effect via regulation of the CREB and ERK1/2 signaling pathways and could be a therapeutic candidate for neurodegenerative diseases.