Chromogranin A-derived peptide CGA47-66 protects against septic brain injury by reducing blood-brain barrier damage through the PI3K/AKT pathway

Novel plasma protein biomarkers: A time-dependent predictive model for Alzheimer's disease

BACKGROUND

The accurate prediction of Alzheimer's disease (AD) is crucial for the efficient management of its progression. The objective of this research was to construct a new risk predictive model utilizing novel plasma protein biomarkers for predicting AD incidence in the future and analyze their potential biological correlation with AD incidence.

METHODS

A cohort of 440 participants aged 60 years and older from the Alzheimer's Disease Neuroimaging Initiative (ADNI) longitudinal cohort was utilized. The baseline plasma proteomics data was employed to conduct Cox regression, LASSO regression, and cross-validation to identify plasma protein signatures predictive of AD risk. Subsequently, a multivariable Cox proportional hazards model based on these signatures was constructed. The performance of the risk prediction model was evaluated using time-dependent receiver operating characteristic (t-ROC) curves and Kaplan-Meier curves. Additionally, we analyzed the correlations between protein signature expression in plasma and predicted AD risk, the time of AD onset, the expression of protein signatures in cerebrospinal fluid (CSF), the expression of CSF and plasma biomarkers, and APOE ε4 genotypes. Colocalization and Mendelian randomization analyses was conducted to investigate the association between protein features and AD risk. GEO database was utilized to analyze the differential expression of protein features in the blood and brain of AD patients.

RESULTS

We identified seven protein signatures (APOE, CGA, CRP, CCL26, CCL20, NRCAM, and PYY) that independently predicted AD incidence in the future. The risk prediction model demonstrated area under the ROC curve (AUC) values of 0.77, 0.76, and 0.77 for predicting AD incidence at 4, 6, and 8 years, respectively. Furthermore, the model remained stable in the range of the 3rd to the 12th year (ROC ≥ 0.74). The low-risk group, as defined by the model, exhibited a significantly later AD onset compared to the high-risk group (P < 0.0001). Moreover, all protein signatures exhibited significant correlations with AD risk (P < 0.001) and the time of AD onset (P < 0.01). There was no strong correlation between the protein expression levels in plasma and CSF, as well as AD CSF biomarkers. APOE, CGA, and CRP exhibited significantly lower expression levels in APOE ε4 positive individuals (P < 0.05). Additionally, colocalization analysis reveals a significant association between AD and SNP loci in APOE. Mendelian randomization analysis shows a negative correlation between NRCAM and AD risk. Transcriptomic analysis indicates a significant downregulation of NRCAM and PYY in the peripheral blood of AD patients (P < 0.01), while APOE, CGA, and NRCAM are significantly downregulated in the brains of AD patients (P < 0.0001).

CONCLUSION

Our research has successfully identified protein signatures in plasma as potential risk biomarkers that can independently predict AD onset in the future. Notably, this risk prediction model has demonstrated commendable predictive performance and stability over time. These findings underscore the promising utility of plasma protein signatures in dynamically predicting the risk of AD, thereby facilitating early screening and intervention strategies.

Deciphering Proteomic Expression in Inflammatory Disorders: A Mass Spectrometry Exploration Comparing Infectious, Noninfectious, and Traumatic Brain Injuries in Human Cerebrospinal Fluid

The central nervous system (CNS) evokes a complex inflammatory response to injury. Inflammatory cascades are present in traumatic, infectious, and noninfectious disorders affecting the brain. It contains a mixture of pro- and anti-inflammatory reactions involving well-known proteins, but also numerous proteins less explored in these processes. The aim of this study was to explore the distinct inflammatory response in traumatic brain injury (TBI) compared with other CNS injuries by utilization of mass-spectrometry. In total, 56 patients had their cerebrospinal fluid (CSF) analyzed with the use of mass-spectrometry. Among these, CSF was collected via an external ventricular drain (EVD) from n = 21 patients with acute TBI. The resulting protein findings were then compared with CSF obtained by lumbar puncture from n = 14 patients with noninfectious CNS disorders comprising relapsing-remitting multiple sclerosis, anti-N-methyl-d-aspartate-receptor encephalitis, acute disseminated encephalomyelitis, and n = 14 patients with progressive multifocal leukoencephalopathy, herpes simplex encephalitis, and other types of viral meningitis. We also utilized n = 7 healthy controls (HCs). In the comparison between TBI and noninfectious inflammatory CNS disorders, concentrations of 55 proteins significantly differed between the groups. Among them, 23 and 32 proteins were up- and downregulated, respectively, in the TBI group. No proteins were uniquely identified in either group. In the comparison of TBI and HC, 51 proteins were significantly different, with 24 and 27 proteins being up- and downregulated, respectively, in TBI. Two proteins (fibrinogen gamma chain and transketolase) were uniquely identified in all samples of the TBI group. Also in the last comparison, TBI versus infectious inflammatory CNS disorders, 51 proteins differed between the two groups, with 19 and 32 proteins being up- and downregulated, respectively, in TBI, and no unique proteins being identified. Due to large discrepancies between the groups compared, the following proteins were selected for further deeper analysis among those being differentially regulated: APOE, CFB, CHGA, CHI3L1, C3, FCGBP, FGA, GSN, IGFBP7, LRG1, SERPINA3, SOD3, and TTR. We found distinct proteomic profiles in the CSF of TBI patients compared with HC and different disease controls, indicating a specific interplay between inflammatory factors, metabolic response, and cell integrity. In relation to primarily infectious or inflammatory disorders, unique inflammatory pathways seem to be engaged, and could potentially serve as future treatment targets.

Low-dose-rate induces more severe cognitive impairment than high-dose-rate in rats exposed to chronic low-dose γ-radiation

Background

Owing to the long penetration depth of gamma (γ)-rays, individuals working in ionizing radiation environments are chronically exposed to low-dose γ-radiation, resulting in cognitive changes. Dose rate significantly affects radiation-induced biological effects; however, its role in chronic low-dose γ-irradiation-induced cognitive impairment remains unclear. We aimed to investigate whether chronic low-dose γ-irradiation at low-dose-rate (LDR) could induce cognitive impairment and to compare the cognitive alteration caused by chronic low-dose γ-irradiation at LDR and high-dose-rate (HDR).

Methods

The rats were exposed to γ-irradiation at a LDR of 6 mGy/h and a HDR of 20 mGy/h for 30 days (5 h/day). Functional imaging was performed to assess the brain inflammation and blood-brain barrier (BBB) destruction of rats. Histological and immunofluorescence analyses were used to reveal the neuron damage and the activation of microglia and astrocytes in the hippocampus. RNA sequencing was conducted to investigate changes in gene expression in hippocampus.

Results

The rats in the LDR group exhibited more persistent cognitive impairment than those in the HDR group. Furthermore, irradiated rats showed brain inflammation and a compromised BBB. Histologically, the number of hippocampal neurons were comparable in the LDR group but were markedly decreased in the HDR. Additionally, activated M1-like microglia and A1-like astrocytes were observed in the hippocampus of rats in the LDR group; however, only M1-like microglia were activated in the HDR group. Mechanistically, the PI3K-Akt signaling pathway contributed to the different cognitive function change between the LDR group and HDR group.

Conclusion

Compared with chronic low-dose γ-irradiation at HDR, LDR induced more severe cognitive impairment which might involve PI3K/Akt signaling pathway.

Interfering TRIB3 protects the blood brain barrier through PI3K/Akt pathway to alleviate cerebral ischemia-reperfusion injury in diabetes mellitus mice

This study aimed to treat diabetic cerebral ischemia-reperfusion injury (CI/RI) by affecting blood brain barrier (BBB) permeability and integrity. The CI/RI model in DM mice and a high glucose (HG) treated oxygen and glucose deprivation/reoxygenation (OGD/R) brain endothelial cell model were established for the study. Evans blue (EB) staining was used to evaluate the permeability of BBB in vivo. TTC staining was used to analyze cerebral infarction. The location and expression of tribbles homolog 3 (TRIB3) in endothelial cells were detected by immunofluorescence. Western blotting was used to detect the protein expressions of TRIB3, tight junction molecules, adhesion molecules, phosphorylated protein kinase B (p-AKT) and AKT. The levels of pro-inflammatory cytokines were detected by qRT-PCR. Trans-epithelial electrical resistance (TEER) and fluorescein isothiocyanate (FITC)-dextran were used to measure vascular permeability in vitro. TRIB3 ubiquitination and acetylation levels were detected. Acetyltransferase bound to TRIB3 were identified by immunoprecipitation. TRIB3 was localized in cerebral endothelial cells and was highly expressed in diabetic CI/R mice. The BBB permeability in diabetic CI/R mice and HG-treated OGD/R cells was increased, while the junction integrity was decreased. Interference with TRIB3 in vitro reduces BBB permeability and increases junction integrity. In vivo interfering with TRIB3 reduced cerebral infarction volume, BBB permeability and inflammation levels, and upregulated p-AKT levels. The phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin reversed the effects of TRIB3-interfering plasmid. In vitro HG treatment induced TRIB3 acetylation through acetyltransferase p300, which in turn reduced ubiquitination and stabilized TRIB3. Interfering TRIB3 protects BBB by activating PI3K/AKT pathway and alleviates brain injury, which provides a new target for diabetic CI/RI.

Chromofungin, a chromogranin A-derived peptide, protects against sepsis-induced acute lung injury by inhibiting LBP/TLR4-dependent inflammatory signaling

Chromofungin (CHR) is a biologically active peptide derived from chromogranin A that exhibits anti-inflammatory effects. However, it remains unclear whether and how CHR protects against sepsis-induced acute lung injury (ALI). A murine model of sepsis-induced ALI was established through cecal ligation and puncture, with intraperitoneal injection of CHR. Lung inflammation and macrophage polarization were examined by measuring the levels of cytokines and markers of M1 (CD86, inducible nitric oxide synthase [iNOS]) or M2 macrophages (arginase-1 [Arg1], resistin-like molecule α1 [Fizz1] and CD206). In vitro, mouse MH-S cells pretreated with CHR was employed to explore the interplay between the lipopolysaccharide-binding protein (LBP)/toll-like receptor 4 (TLR4) signaling pathway and M1/M2 polarity. The results revealed CHR's ability to enhance the 7-day survival rate and protect lung pathological injury in sepsis-induced ALI. CHR increased the expression of interleukin-4 and interleukin-10 but decreased the expression of tumour necrosis factor-α and interleukin-1β. In addition, CHR notably facilitated M2 macrophage polarization, while significantly suppressingM1 polarization of alveolar macrophages. Mechanistic investigations delineated CHR's role in macrophage polarization by downregulating nuclear factor-κB expression through modulation of the LBP/TLR4 signaling pathway. Therefore, CHR may represent a novel strategy for the prevention of sepsis-induced ALI.

Rett and Rett-related disorders: Common mechanisms for shared symptoms?

Rett syndrome is a neurodevelopmental disorder caused by loss-of-function mutations in the methyl-CpG binding protein-2 (MeCP2) gene that is characterized by epilepsy, intellectual disability, autistic features, speech deficits, and sleep and breathing abnormalities. Neurologically, patients with all three disorders display microcephaly, aberrant dendritic morphology, reduced spine density, and an imbalance of excitatory/inhibitory signaling. Loss-of-function mutations in the cyclin-dependent kinase-like 5 (CDKL5) and FOXG1 genes also cause similar behavioral and neurobiological defects and were referred to as congenital or variant Rett syndrome. The relatively recent realization that CDKL5 deficiency disorder (CDD), FOXG1 syndrome, and Rett syndrome are distinct neurodevelopmental disorders with some distinctive features have resulted in separate focus being placed on each disorder with the assumption that distinct molecular mechanisms underlie their pathogenesis. However, given that many of the core symptoms and neurological features are shared, it is likely that the disorders share some critical molecular underpinnings. This review discusses the possibility that deregulation of common molecules in neurons and astrocytes plays a central role in key behavioral and neurological abnormalities in all three disorders. These include KCC2, a chloride transporter, vGlut1, a vesicular glutamate transporter, GluD1, an orphan-glutamate receptor subunit, and PSD-95, a postsynaptic scaffolding protein. We propose that reduced expression or activity of KCC2, vGlut1, PSD-95, and AKT, along with increased expression of GluD1, is involved in the excitatory/inhibitory that represents a key aspect in all three disorders. In addition, astrocyte-derived brain-derived neurotrophic factor (BDNF), insulin-like growth factor 1 (IGF-1), and inflammatory cytokines likely affect the expression and functioning of these molecules resulting in disease-associated abnormalities.

Identification of biomarkers and therapeutic targets related to Sepsis-associated encephalopathy in rats by quantitative proteomics

BACKGROUND

Sepsis-associated encephalopathy (SAE) is a common and severe complication of sepsis. While several studies have reported the proteomic alteration in plasma, urine, heart, etc. of sepsis, few research focused on the brain tissue. This study aims at discovering the differentially abundant proteins in the brains of septic rats to identify biomarkers of SAE.

METHODS

The Prague-Dawley rats were randomly divided into sepsis (n = 6) or sham (n = 6) groups, and then the whole brain tissue was dissected at 24 h after surgery for further protein identification by Quantitative iTRAQ LC-MS/MS Proteomics. Ingenuity pathway analysis, Gene ontology knowledgebase, and STRING database are used to explore the biological significance of proteins with altered concentration.

RESULTS

Among the total of 3163 proteins identified in the brain tissue, 57 were increased while 38 were decreased in the sepsis group compared to the sham group. Bioinformatic analyses suggest that the differentially abundant proteins are highly related to cellular microtubule metabolism, energy production, nucleic acid metabolism, neurological disease, etc. Additionally, acute phase response signaling was possibly activated and PI3K/AKT signaling was suppressed during sepsis. An interaction network established by IPA revealed that Akt1, Gc-globulin, and ApoA1 were the core proteins. The increase of Gc-globulin and the decrease of Akt1 and ApoA1 were confirmed by Western blot.

CONCLUSION

Based on the multifunction of these proteins in several brain diseases, we first propose that Gc-globulin, ApoA1, PI3K/AKT pathway, and acute phase response proteins (hemopexin and cluster of alpha-2-macroglobulin) could be potential candidates for the diagnosis and treatment of SAE. These results may provide new insights into the pathologic mechanism of SAE, yet further research is required to explore the functional implications and clinical applications of the differentially abundant proteins in the brains of sepsis group.