Administration of secretoneurin is protective in hypoxic-ischemic neonatal brain injury predominantly in the hypoxic-only hemisphere

Intracerebroventricular infusion of secretoneurin inhibits neuronal NLRP3-Apoptosis pathway and preserves learning and memory after cerebral ischemia

Transient global cerebral ischemia (GCI) results in delayed neuronal death, primarily apoptosis, in the hippocampal CA1 subregion, which leads to severe cognitive deficits. While therapeutic hypothermia is an approved treatment for patients following cardiac arrest, it is associated with various adverse effects. Secretoneurin (SN) is an evolutionarily conserved neuropeptide generated in the brain, adrenal medulla and other endocrine tissues. In this study, SN was infused into the rat brain by intracerebroventricular injection 1 day after GCI, and we demonstrated that SN could significantly preserve spatial learning and memory in the Barnes maze tasks examined on days 14-17 after GCI. To further investigate underlying pathways involved, we demonstrated that, on day 5 after GCI, SN could significantly inhibit GCI-induced expression levels of Apoptosis Inducing Factor (AIF) and cleaved-PARP1, as well as neuronal apoptosis and synaptic loss in the hippocampal CA1 region. Additionally, SN could attenuate GCI-induced activation of both caspase-1 and caspase-3, and the levels of pro-inflammatory cytokines IL-1β and IL-18 in the CA1 region. Mechanically, we observed that treatment with SN effectively inhibited NLRP3 protein elevation and the bindings of NLRP3-ASC and ASC-caspase-1 in hippocampal neurons after GCI. In summary, our data indicate that SN could effectively attenuate NLRP3 inflammasome formation, as well as the activation of caspase-1 and -3, the production of pro-inflammatory cytokines, and ultimately the neuronal apoptotic loss induced by GCI. Potential neuronal pyroptosis, or caspase-1-dependent cell death, could also be involved in ischemic neuronal death, which needs further investigation.

Clinical Value of Serum Secretoneurin Levels in Prediction of Delayed Cerebral Ischemia and Prognostic Analysis of Aneurysmal Subarachnoid Hemorrhage: A Prospective Cohort Study

Background

Secretoneurin is a neuropeptide with several neuroprotective properties. Here, we discuss the importance of serum secretoneurin in assessing severity and predicting delayed cerebral ischemia (DCI) and functional outcomes following aneurysmal subarachnoid hemorrhage (aSAH).

Methods

A prospective cohort study of 167 patients with aSAH and 100 controls was performed to determine serum secretoneurin levels. Severity was reflected by the Hunt-Hess and modified Fisher scores. Prognostic parameters included DCI and poor 6-month prognosis (extended Glasgow outcome scale scores of 1-4). Univariate analysis followed by multivariate analysis was performed to determine the correlation between severity and prognosis.

Results

Compared to controls, patients exhibited a marked elevation in serum secretoneurin levels. Serum secretoneurin levels, which were independently correlated with Hunt-Hess scores and modified Fisher scores, independently predicted DCI and bad 6-month prognosis. Serum secretoneurin levels, which were linearly related to the risk of DCI and poor prognosis under a restricted cubic spline, effectively distinguished the risks under the receiver operating characteristic (ROC) curve. Subgroup analysis for prognosis or DCI prediction revealed no substantial interactions between serum secretoneurin levels and other variables, such as age, sex, hypertension, diabetes, alcohol consumption, and cigarette consumption. In addition, the prognosis model, in which serum secretoneurin, Hunt-Hess scale, and modified Fisher scale were merged, was graphically represented by a nomogram and performed well under the calibration, decision, and ROC curves.

Conclusion

Serum secretoneurin levels significantly increased after aSAH, which was intimately correlated with disease severity and independently associated with DCI and worse outcomes, indicating that serum secretoneurin may be a potential prognostic biomarker of aSAH.

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.

Evaluation of Serum Secretoneurin Levels in Patients With Ischemic Stroke Who Underwent Mechanical Thrombectomy

Background Ischemic stroke is a focal or global cerebral dysfunction of vascular origin; its treatment aims to provide reperfusion. Secretoneurin is a hypoxia-sensitive biomarker found in high concentrations in brain tissue. We aim to determine secretoneurin levels in patients with ischemic stroke, examine how secretoneurin levels change in the mechanical thrombectomy group, and evaluate the correlation with disease severity and prognosis. Methods Twenty-two patients diagnosed with ischemic stroke in the emergency department underwent mechanical thrombectomy, and twenty healthy volunteers were included in the study. Serum secretoneurin levels were measured by the enzyme-linked immunosorbent assay (ELISA) method. Secretoneurin levels were measured at the 0^th hour, 12^th hour, and 5^th day in patients who underwent mechanical thrombectomy. Results Serum secretoneurin levels were found to be statistically significantly higher in the patient group (7.43 ng/mL) compared to the control group (5.90 ng/mL) (p=0.023). The secretoneurin levels of the patients who underwent mechanical thrombectomy were 7.43 ng/mL, 7.04 ng/mL, and 8.65 ng/mL, measured at the 0^th hour, 12^th hour, and 5^th day, respectively, and no significant difference was detected in all three time periods (p=0.142). Conclusion Secretoneurin appears to be a useful biomarker in the diagnosis of stroke. However, it was found that there was no prognostic value in the mechanical thrombectomy group, and it was not correlated with the severity of the disease.

The Emerging Roles of Chromogranins and Derived Polypeptides in Atherosclerosis, Diabetes, and Coronary Heart Disease

Chromogranin A (CgA), B (CgB), and C (CgC), the family members of the granin glycoproteins, are associated with diabetes. These proteins are abundantly expressed in neurons, endocrine, and neuroendocrine cells. They are also present in other areas of the body. Patients with diabetic retinopathy have higher levels of CgA, CgB, and CgC in the vitreous humor. In addition, type 1 diabetic patients have high CgA and low CgB levels in the circulating blood. Plasma CgA levels are increased in patients with hypertension, coronary heart disease, and heart failure. CgA is the precursor to several functional peptides, including catestatin, vasostatin-1, vasostatin-2, pancreastatin, chromofungin, and many others. Catestatin, vasostain-1, and vasostatin-2 suppress the expression of vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 in human vascular endothelial cells. Catestatin and vasostatin-1 suppress oxidized low-density lipoprotein-induced foam cell formation in human macrophages. Catestatin and vasostatin-2, but not vasostatin-1, suppress the proliferation and these three peptides suppress the migration in human vascular smooth muscles. Chronic infusion of catestatin, vasostatin-1, or vasostatin-2 suppresses the development of atherosclerosis of the aorta in apolipoprotein E-deficient mice. Catestatin, vasostatin-1, vasostatin-2, and chromofungin protect ischemia/reperfusion-induced myocardial dysfunction in rats. Since pancreastatin inhibits insulin secretion from pancreatic β-cells, and regulates glucose metabolism in liver and adipose tissues, pancreastatin inhibitor peptide-8 (PSTi8) improves insulin resistance and glucose homeostasis. Catestatin stimulates therapeutic angiogenesis in the mouse hind limb ischemia model. Gene therapy with secretoneurin, a CgC-derived peptide, stimulates postischemic neovascularization in apolipoprotein E-deficient mice and streptozotocin-induced diabetic mice, and improves diabetic neuropathy in db/db mice. Therefore, CgA is a biomarker for atherosclerosis, diabetes, hypertension, and coronary heart disease. CgA- and CgC--derived polypeptides provide the therapeutic target for atherosclerosis and ischemia-induced tissue damages. PSTi8 is useful in the treatment of diabetes.

Excitotoxicity Alters Endogenous Secretoneurin Plasma Levels, but Supplementation with Secretoneurin Does Not Protect Against Excitotoxic Neonatal Brain Injury

Excitotoxicity plays an important role in the pathogenesis of developing brain injury. The neuropeptide secretoneurin (SN) has neuroprotective potential. The aim of this study was to investigate SN plasma concentrations following excitotoxicity and to evaluate the effect of SN as therapeutic strategy in excitotoxic newborn brain injury. Baseline SN plasma concentrations were established in healthy animals. To evaluate the effect of an excitotoxic insult on SN levels, mice pups were subjected to an intracranial injection of ibotenic acid and SN plasma concentrations were measured thereafter. To assess SN's neuroprotective potential, a subgroup of animals was randomly assigned to the following groups: i) "single treatment": vehicle 1× phosphate-buffered saline (PBS), SN 0.25 μg/g body weight (bw), SN 2.5 μg/g bw or SN 12.5 μg/g bw in a single dose 1 h after insult; ii) "acute repetitive treatment": vehicle 1× PBS or SN 0.25 μg/g bw every 24 h starting 1 h after insult; iii) "delayed repetitive treatment": vehicle 1× PBS or SN 0.25 μg/g bw every 24 h starting 60 h after insult. Animals subjected to excitotoxic injury showed significantly lower SN plasma concentrations 6 and 120 h after insult in comparison to healthy controls. Administration of SN did not positively affect lesion size, apoptotic cell death, microglial cell activation or cell proliferation. To conclude, endogenous SN plasma levels are lower in newborn mice subjected to an excitotoxic insult than in healthy controls. Supplementation with SN in various treatment regimens is not neuroprotective in the experimental animal model of excitotoxic newborn brain injury.

Inhibition of the Epigenetic Regulator REST Ameliorates Ischemic Brain Injury

Cerebral ischemia is known to activate the repressor element-1 (RE1)-silencing transcription factor (REST) which silences neural genes via epigenetic remodeling and promotes neurodegeneration. We presently determined if REST inhibition derepresses target genes involved in synaptic plasticity and promotes functional outcome after experimental stroke. Following transient focal ischemia induced by middle cerebral artery occlusion (MCAO) in adult rats, REST expression was upregulated significantly from 12 h to 1 day of reperfusion compared to sham control. At 1 day of reperfusion, REST protein levels were increased and observed in the nuclei of neurons in the peri-infarct cortex. REST knockdown by intracerebral REST siRNA injection significantly reduced the post-ischemic expression of REST and increased the expression of several REST target genes, compared to control siRNA group. REST inhibition also decreased post-ischemic markers of apoptosis, reduced cortical infarct volume, and improved post-ischemic functional recovery on days 5 and 7 of reperfusion compared to the control siRNA group. REST knockdown resulted in a global increase in synaptic plasticity gene expression at 1 day of reperfusion compared to the control siRNA group and significantly increased several synaptic plasticity genes containing RE-1 sequences in their regulatory regions. These results demonstrate that direct inhibition of the epigenetic remodeler REST prevents secondary brain damage in the cortex and improves functional outcome potentially via de-repression of plasticity-related genes after stroke.

Short-, Mid-, and Long-Term Effect of Granulocyte Colony-Stimulating Factor/Stem Cell Factor and Fms-Related Tyrosine Kinase 3 Ligand Evaluated in an In Vivo Model of Hypoxic-Hyperoxic Ischemic Neonatal Brain Injury

Hematopoietic growth factors are considered to bear neuroprotective potential. We have previously shown that delayed treatment with granulocyte colony-stimulating factor (G-CSF)/stem cell factor (SCF) and Fms-related tyrosine kinase 3 ligand (FL) ameliorates excitotoxic neonatal brain injury. The effect of these substances in combined-stressor neonatal brain injury models more closely mimicking clinical conditions has not been investigated. The aim of this study was to assess the short-, mid-, and long-term neuroprotective potential of G-CSF/SCF and FL in a neonatal model of hypoxic-hyperoxic ischemic brain injury. Five-day-old (P5) CD-1 mice were subjected to unilateral common carotid artery ligation and subsequent alternating periods of hypoxia and hyperoxia for 65 minutes. Sixty hours after injury, pups were randomly assigned to intraperitoneal treatment with (i) G-CSF (200 μg/kg)/SCF (50 μg/kg), (ii) FL (100 μg/kg), or (iii) vehicle every 24 hours for three or five consecutive days. Histopathological and functional outcomes were evaluated on P10, P18, and P90. Baseline outcome parameters were established in sham-treated and healthy control animals. Gross brain injury did not significantly differ between treatment groups at any time point. On P10, caspase-3 activation and caspase-independent apoptosis were similar between treatment groups; cell proliferation and the number of BrdU-positive vessels did not differ on P18 or P90. Neurobehavioral assessment did not reveal significant differences between treatment groups in accelerod performance, open field behavior, or novel object recognition capacity on P90. Turning behavior was more frequently observed in G-CSF/SCF- and FL-treated animals. No sex-specific differences were detected in any outcome parameter evaluated. In hypoxic-hyperoxic ischemic neonatal brain injury, G-CSF/SCF and FL treatment does not convey neuroprotection. Prior to potential clinical use, meticulous assessment of these hematopoietic growth factors is mandated.

Gene therapy with the angiogenic neuropeptide secretoneurin ameliorates experimental diabetic neuropathy

The pathogenesis of diabetic neuropathy remains enigmatic. Damage to the vasa nervorum may be responsible for this disorder. Recently, we showed that secretoneurin (SN) induces angiogenesis in hindlimb and myocardial ischemia. Moreover, beneficial effects were observed in wound healing. We therefore hypothesized that SN therapy may ameliorate diabetic neuropathy. We used db/db mice as animal model for neuropathy. Gene therapy was accomplished by intramuscular injection of SN plasmid along the sciatic nerve. Sciatic nerve motor and sensory conduction velocities were then measured for 9 wk. Nerve conduction velocities showed normal values in heterozygous mice for the observational period, but were severely reduced in homozygous mice in which velocities were significantly improved by SN, but not by control plasmid gene therapy. The reaction time in the tail-flick test improved significantly in SN-treated animals. The induction of growth of vasa nervorum seems to be part of the underlying mechanism. In addition, SN positively affected Schwann cell function in vitro and induced activation of important signaling pathways. Our observations suggest that SN exerts beneficial effects on nerve function in vivo and on Schwann cells in vitro. It therefore may be a promising treatment option for diabetic neuropathy.-Theurl, M., Lener, D., Albrecht-Schgoer, K., Beer, A., Schgoer, W., Liu, Y., Stanzl, U., Fischer-Colbrie, R., Kirchmair, R. Gene therapy with the angiogenic neuropeptide secretoneurin ameliorates experimental diabetic neuropathy.