Early induction of secretoneurin expression following kainic acid administration at convulsant doses in the rat and gerbil hippocampus

Serum secretoneurin as a promising biomarker for predicting poor prognosis in intracerebral hemorrhage: A prospective cohort study

OBJECTIVE

Secretoneurin may play a brain-protective role. We aim to discover the relationship between serum secretoneurin levels and severity plus neurological outcome after intracerebral hemorrhage (ICH).

METHODS

In this prospective cohort study, serum secretoneurin levels were measured in 110 ICH patients and 110 healthy controls. Glasgow Coma Scale (GCS) and hematoma volume were used to assess stroke severity. Poor prognosis was defined as Glasgow Outcome Scale (GOS) scores of 1-3 at 90 days after ICH. A multivariate logistic regression model was constructed to determine independent correlation of serum secretoneurin levels with severity and poor prognosis. Under receiver operating characteristic (ROC) curve, prognostic ability of serum secretoneurin levels was assessed. Restricted cubic spline (RCS) model and subgroups analysis were used for discovering association of serum secretoneurin levels with risk of poor prognosis. Calibration curve and decision curve were evaluated to confirm performance of nomogram.

RESULTS

Serum secretoneurin levels of patients were significantly higher than those of healthy controls. Serum secretoneurin levels of patients were independently correlated with GCS scores and hematoma volume. There were 42 patients with poor prognosis at 90 days following ICH. Serum secretoneurin levels were significantly higher in patients with poor outcome than in those with good outcome. Under the ROC curve, serum secretoneurin levels significantly differentiated poor outcome. Serum secretoneurin levels ≥ 22.8 ng/mL distinguished patients at risk of poor prognosis at 90 days with a sensitivity of 66.2% and a specificity of 81.0%. Besides, serum secretoneurin levels independently predicted a 90-day poor prognosis. Subgroup analysis showed that serum secretoneurin levels had non-significant interactions with other variables. The nomogram, including independent prognostic predictors, showed reliable prognosis capability using calibration curve and decision curve. Area under the curve of the predictive model was significantly higher than those of GCS scores and hematoma volume.

CONCLUSION

Serum secretoneurin levels are strongly related to ICH severity and poor prognosis at 90 days after ICH. Thus, serum secretoneurin may be a promising prognostic biomarker in ICH.

Comparative analysis of hippocampal extracellular space uncovers widely altered peptidome upon epileptic seizure in urethane-anaesthetized rats

BACKGROUND

The brain extracellular fluid (ECF), composed of secreted neurotransmitters, metabolites, peptides, and proteins, may reflect brain processes. Analysis of brain ECF may provide new potential markers for synaptic activity or brain damage and reveal additional information on pathological alterations. Epileptic seizure induction is an acute and harsh intervention in brain functions, and it can activate extra- and intracellular proteases, which implies an altered brain secretome. Thus, we applied a 4-aminopyridine (4-AP) epilepsy model to study the hippocampal ECF peptidome alterations upon treatment in rats.

METHODS

We performed in vivo microdialysis in the hippocampus for 3-3 h of control and 4-AP treatment phase in parallel with electrophysiology measurement. Then, we analyzed the microdialysate peptidome of control and treated samples from the same subject by liquid chromatography-coupled tandem mass spectrometry. We analyzed electrophysiological and peptidomic alterations upon epileptic seizure induction by two-tailed, paired t-test.

RESULTS

We detected 2540 peptides in microdialysate samples by mass spectrometry analysis; and 866 peptides-derived from 229 proteins-were found in more than half of the samples. In addition, the abundance of 322 peptides significantly altered upon epileptic seizure induction. Several proteins of significantly altered peptides are neuropeptides (Chgb) or have synapse- or brain-related functions such as the regulation of synaptic vesicle cycle (Atp6v1a, Napa), astrocyte morphology (Vim), and glutamate homeostasis (Slc3a2).

CONCLUSIONS

We have detected several consequences of epileptic seizures at the peptidomic level, as altered peptide abundances of proteins that regulate epilepsy-related cellular processes. Thus, our results indicate that analyzing brain ECF by in vivo microdialysis and omics techniques is useful for monitoring brain processes, and it can be an alternative method in the discovery and analysis of CNS disease markers besides peripheral fluid analysis.

Serum levels of chromogranins and secretogranins correlate with the progress and severity of Parkinson's disease

Little is known about the relevance of chromogranins (Cgs) and secretogranins (Sgs) in Parkinson's disease (PD). In this study, we determined serum levels of CgA, CgB, and SgII in PD patients and assessed their association with disease severity. PD patients were recruited, identified, and classified as having early (n = 14), intermediate (n = 18), or late (n = 4) stage disease according to Hoehn-Yahr scores. The serum concentrations of CgA, CgB, and SgII in patients with well-defined PD (n = 36) and in healthy controls (n = 52) were measured by enzyme-linked immunosorbent assay. Compared with controls, serum CgA levels were significantly elevated and serum SgII levels were significantly reduced in PD patients (both P < 0.05). There was no difference in serum CgB levels between the two groups. Both serum CgA and SgII levels changed progressively over time from early to intermediate to late stage (P < 0.05). Spearman correlation analysis revealed that serum CgA and SgII levels correlated with Hoehn-Yahr and UPDRS scores (P < 0.001). These results indicate that changes in serum levels of CgA and SgII may be closely related to the severity of PD.

The impact of postsynaptic density 95 blocking peptide (Tat-NR2B9c) and an iNOS inhibitor (1400W) on proteomic profile of the hippocampus in C57BL/6J mouse model of kainate-induced epileptogenesis

Antiepileptogenic agents that prevent the development of epilepsy following a brain insult remain the holy grail of epilepsy therapeutics. We have employed a label-free proteomic approach that allows quantification of large numbers of brain-expressed proteins in a single analysis in the mouse (male C57BL/6J) kainate (KA) model of epileptogenesis. In addition, we have incorporated two putative antiepileptogenic drugs, postsynaptic density protein-95 blocking peptide (PSD95BP or Tat-NR2B9c) and a highly selective inducible nitric oxide synthase inhibitor, 1400W, to give an insight into how such agents might ameliorate epileptogenesis. The test drugs were administered after the induction of status epilepticus (SE) and the animals were euthanized at 7 days, their hippocampi removed, and subjected to LC-MS/MS analysis. A total of 2,579 proteins were identified; their normalized abundance was compared between treatment groups using ANOVA, with correction for multiple testing by false discovery rate. Significantly altered proteins were subjected to gene ontology and KEGG pathway enrichment analyses. KA-induced SE was most robustly associated with an alteration in the abundance of proteins involved in neuroinflammation, including heat shock protein beta-1 (HSP27), glial fibrillary acidic protein, and CD44 antigen. Treatment with PSD95BP or 1400W moderated the abundance of several of these proteins plus that of secretogranin and Src substrate cortactin. Pathway analysis identified the glutamatergic synapse as a key target for both drugs. Our observations require validation in a larger-scale investigation, with candidate proteins explored in more detail. Nevertheless, this study has identified several mechanisms by which epilepsy might develop and several targets for novel drug development. OPEN PRACTICES: This article has been awarded Open Data. All materials and data are publicly accessible as supporting information. Learn more about the Open Practices badges from the Center for Open Science: https://osf.io/tvyxz/wiki.

Secretoneurin A Directly Regulates the Proteome of Goldfish Radial Glial Cells In Vitro

Radial glial cells (RGCs) are the main macroglia in the teleost brain and have established roles in neurogenesis and neurosteroidogenesis. They are the only brain cell type expressing aromatase B (cyp19a1b), the enzyme that synthesizes estrogens from androgen precursors. There are few studies on the regulation of RGC functions, but our previous investigations demonstrated that dopamine stimulates cyp19a1b expression in goldfish RGCs, while secretoneurin A (SNa) inhibits the expression of this enzyme. Here, we determine the range of proteins and cellular processes responsive to SNa treatments in these steroidogenic cells. The focus here is on SNa, because this peptide is derived from selective processing of secretogranin II in magnocellular cells embedded within the RGC-rich preoptic nucleus. Primary cultures of RGCs were treated (24 h) with 10, 100, or 1,000 nM SNa. By using isobaric tagging for relative and absolute quantitation and a Hybrid Quadrupole Obritrap Mass Spectrometry system, a total of 1,363 unique proteins were identified in RGCs, and 609 proteins were significantly regulated by SNa at one or more concentrations. Proteins that showed differential expression with all three concentrations of SNa included H1 histone, glutamyl-prolyl-tRNA synthetase, Rho GDP dissociation inhibitor γ, vimentin A2, and small nuclear ribonucleoprotein-associated protein. At 10, 100, and 1,000 nM SNa, there were 5, 195, and 489 proteins that were downregulated, respectively, whereas the number of upregulated proteins were 72, 44, and 51, respectively. Subnetwork enrichment analysis of differentially regulated proteins revealed that processes such as actin organization, cytoskeleton organization and biogenesis, apoptosis, mRNA processing, RNA splicing, translation, cell growth, and proliferation are regulated by SNa based on the proteomic response. Moreover, we observed that, at the low concentration of SNa, there was an increase in the abundance of proteins involved in cell growth, proliferation, and migration, whereas higher concentration of SNa appeared to downregulate proteins involved in these processes, indicating a dose-dependent proteome response. At the highest concentration of SNa, proteins linked to the etiology of diseases of the central nervous system (brain injuries, Alzheimer disease, Parkinson's disease, cerebral infraction, brain ischemia) were also differentially regulated. These data implicate SNa in the control of cell proliferation and neurogenesis.

Secretoneurin A regulates neurogenic and inflammatory transcriptional networks in goldfish (Carassius auratus) radial glia

Radial glial cells (RGCs) are the most abundant macroglia in the teleost brain and have established roles in neurogenesis and neurosteroidogenesis; however, their transcriptome remains uncharacterized, which limits functional understanding of this important cell type. Using cultured goldfish RGCs, RNA sequencing and de novo transcriptome assembly were performed, generating the first reference transcriptome for fish RGCs with 17,620 unique genes identified. These data revealed that RGCs express a diverse repertoire of receptors and signaling molecules, suggesting that RGCs may respond to and synthesize an array of hormones, peptides, cytokines, and growth factors. Building upon neuroanatomical data and studies investigating direct neuronal regulation of RGC physiology, differential gene expression analysis was conducted to identify transcriptional networks that are responsive to the conserved secretogranin II-derived neuropeptide secretoneurin A (SNa). Pathway analysis of the transcriptome indicated that cellular processes related to the central nervous system (e.g., neurogenesis, synaptic plasticity, glial cell development) and immune functions (e.g., immune system activation, leukocyte function, macrophage response) were preferentially modulated by SNa. These data reveal an array of new functions that are proposed to be critical to neuronal-glial interactions through the mediator SNa.

Acute responses of DNA repair proteins and StarD6 in rat hippocampus after domoic acid-induced excitotoxicity

StarD6, which might be considered to be neuroprotective, and DNA repair proteins can play a role against oxidative damages by excitotoxin in the nervous system. In order to investigate the relationship between StarD6 and DNA repair proteins, excitotoxicity was induced by domoic acid in male Sprague-Dawley rats. Western blot analysis revealed transitorily elevated levels in StarD6, apurinic/apyrimidinic endonuclease (APE) and 8-oxoguanine DNA-glycosylase (Ogg1) in accord with the DNA damage marker phosphorylated H2AX. Immunohistochemistry revealed that increased intensity was transiently seen not only in the Stratum (Str.) radiatum and Str. lacunosum-moleculare with StarD6 and APE, but also in the Str. pyramidale with Ogg1. Intensities decreased 24h after domoic acid injection in CA3 with APE and Ogg1 as well as in the Str. radiatum and Str. lacunosum-moleculare with StarD6 and APE. These results suggested that StarD6 may not be closely related with DNA repair proteins in the hippocampus after domoic acid-induced excitotoxicity, although the activities of these proteins might be positively affected by excitotoxic stimuli.

Species-difference of cyclooxygenase-2 in the hippocampus of rodents

Cyclooxygenase (COX) generates free radicals and it is important in inflammatory response. In this study, we observed the immunoreactivity in mice (ICR and C57BL/6 strain), rats and gerbils. In these animals, COX-2 immunoreactivity was mainly detected in pyramidal cells of the hippocampal CA2/3 region and in granule cells of the dentate gyrus. COX-2 immunoreactivity in the CA2/3 region was the highest in ICR mice, while in gerbils COX-2 immunoreactivity was the lowest; COX-2 immunoreactivity in the dentate gyrus was the highest in rats and the lowest in gerbils. The protein levels of COX-2 were similar to the immunohistochemical data. COX-2 mRNA transcript was the highest in the gerbil and the lowest in the rat. In brief, COX-2 protein, not mRNA, in the hippocampus is generally higher in mice (ICR and C57BL/6 strain) than rats and gerbils.

Secretoneurin promotes neuroprotection and neuronal plasticity via the Jak2/Stat3 pathway in murine models of stroke

Secretoneurin (SN), a neuropeptide derived from secretogranin II, promotes neurite outgrowth of immature cerebellar granule cells. SN also aids in the growth and repair of neuronal tissue, although the precise mechanisms underlying the promotion of brain tissue neuroprotection and plasticity by SN are not understood. Here, in a rat model of stroke and in ischemic human brain tissue, SN was markedly upregulated in both neurons and endothelial cells. SN-mediated neuroprotection rescued primary cortical cell cultures from oxygen/glucose deprivation. SN also induced expression of the antiapoptotic proteins Bcl-2 and Bcl-xL through the Jak2/Stat3 pathway and inhibited apoptosis by blocking caspase-3 activation. In addition, rats with occluded right middle cerebral arteries showed less cerebral infarction, improved motor performance, and increased brain metabolic activity following i.v. administration of SN. Furthermore, SN injection enhanced stem cell targeting to the injured brain in mice and promoted the formation of new blood vessels to increase local cortical blood flow in the ischemic hemisphere. Both in vitro and in vivo, SN not only promoted neuroprotection, but also enhanced neurogenesis and angiogenesis. Our results demonstrate that SN acts directly on neurons after hypoxia and ischemic insult to further their survival by activating the Jak2/Stat3 pathway.