Progranulin Protects Hippocampal Neurogenesis via Suppression of Neuroinflammatory Responses Under Acute Immune Stress

Progranulin Protects against Aspergillus fumigatus Keratitis by Attenuating the Inflammatory Response through Enhancing Autophagy

Fungal keratitis (FK) is a severe corneal condition caused by pathogenic fungi and is associated with the virulence of fungi and an excessive tissue inflammatory response. Progranulin (PGRN), functioning as a multifunctional growth factor, exerts a pivotal influence on the regulation of inflammation and autophagy. The aim of our research was to analyze the role of PGRN in Aspergillus fumigatus (A. fumigatus) keratitis. We found that PGRN expression was increased in the mouse cornea with A. fumigatus keratitis. In our experiments, corneas of mice with FK were treated with 100 ng/mL of PGRN. In vitro, RAW 264.7 cells were treated with 10 ng/mL of PGRN before A. fumigatus stimulation. The findings suggested that PGRN effectively alleviated corneal edema and decreased the expression of pro-inflammatory cytokines in mice. In stimulated RAW 264.7 cells, PGRN treatment suppressed the expression of pro-inflammatory cytokines IL-6 and TNF-α but promoted the expression of the anti-inflammatory cytokines IL-10. PGRN treatment significantly upregulated the expression of autophagy-related proteins LC3, Beclin-1, and Atg-7. 3-Methyladenine (3-MA, autophagy inhibitor) reversed the regulation of inflammatory cytokines by PGRN. In addition, our study demonstrated that PGRN also enhanced phagocytosis in RAW 264.7 cells. In summary, PGRN attenuated the inflammatory response of A. fumigatus keratitis by increasing autophagy and enhanced the phagocytic activity of RAW 264.7 cells. This showed that PGRN had a protective effect on A. fumigatus keratitis.

Mapping knowledge of the stem cell in traumatic brain injury: a bibliometric and visualized analysis

Background

Traumatic brain injury (TBI) is a brain function injury caused by external mechanical injury. Primary and secondary injuries cause neurological deficits that mature brain tissue cannot repair itself. Stem cells can self-renewal and differentiate, the research of stem cells in the pathogenesis and treatment of TBI has made significant progress in recent years. However, numerous articles must be summarized to analyze hot spots and predict trends. This study aims to provide a panorama of knowledge and research hotspots through bibliometrics.

Method

We searched in the Web of Science Core Collection (WoSCC) database to identify articles pertaining to TBI and stem cells published between 2000 and 2022. Visualization knowledge maps, including co-authorship, co-citation, and co-occurrence analysis were generated by VOSviewer, CiteSpace, and the R package "bibliometrix."

Results

We retrieved a total of 459 articles from 45 countries. The United States and China contributed the majority of publications. The number of publications related to TBI and stem cells is increasing yearly. Tianjin Medical University was the most prolific institution, and Professor Charles S. Cox, Jr. from the University of Texas Health Science Center at Houston was the most influential author. The Journal of Neurotrauma has published the most research articles on TBI and stem cells. Based on the burst references, "immunomodulation," "TBI," and "cellular therapy" have been regarded as research hotspots in the field. The keywords co-occurrence analysis revealed that "exosomes," "neuroinflammation," and "microglia" were essential research directions in the future.

Conclusion

Research on TBI and stem cells has shown a rapid growth trend in recent years. Existing studies mainly focus on the activation mechanism of endogenous neural stem cells and how to make exogenous stem cell therapy more effective. The combination with bioengineering technology is the trend in this field. Topics related to exosomes and immune regulation may be the future focus of TBI and stem cell research.

Progranulin and GPNMB: interactions in endo-lysosome function and inflammation in neurodegenerative disease

BACKGROUND

Alterations in progranulin (PGRN) expression are associated with multiple neurodegenerative diseases (NDs), including frontotemporal dementia (FTD), Alzheimer's disease (AD), Parkinson's disease (PD), and lysosomal storage disorders (LSDs). Recently, the loss of PGRN was shown to result in endo-lysosomal system dysfunction and an age-dependent increase in the expression of another protein associated with NDs, glycoprotein non-metastatic B (GPNMB).

MAIN BODY

It is unclear what role GPNMB plays in the context of PGRN insufficiency and how they interact and contribute to the development or progression of NDs. This review focuses on the interplay between these two critical proteins within the context of endo-lysosomal health, immune function, and inflammation in their contribution to NDs.

SHORT CONCLUSION

PGRN and GPNMB are interrelated proteins that regulate disease-relevant processes and may have value as therapeutic targets to delay disease progression or extend therapeutic windows.

SorCS2 binds progranulin to regulate motor neuron development

Motor neuron (MN) development and nerve regeneration requires orchestrated action of a vast number of molecules. Here, we identify SorCS2 as a progranulin (PGRN) receptor that is required for MN diversification and axon outgrowth in zebrafish and mice. In zebrafish, SorCS2 knockdown also affects neuromuscular junction morphology and fish motility. In mice, SorCS2 and PGRN are co-expressed by newborn MNs from embryonic day 9.5 until adulthood. Using cell-fate tracing and nerve segmentation, we find that SorCS2 deficiency perturbs cell-fate decisions of brachial MNs accompanied by innervation deficits of posterior nerves. Additionally, adult SorCS2 knockout mice display slower motor nerve regeneration. Interestingly, primitive macrophages express high levels of PGRN, and their interaction with SorCS2-positive motor axon is required during axon pathfinding. We further show that SorCS2 binds PGRN to control its secretion, signaling, and conversion into granulins. We propose that PGRN-SorCS2 signaling controls MN development and regeneration in vertebrates.

Regulation of extracellular progranulin in medial prefrontal cortex

Progranulin is a secreted pro-protein that has anti-inflammatory and neurotrophic effects and is necessary for maintaining lysosomal function. Mutations in progranulin (GRN) are a major cause of frontotemporal dementia. Most pathogenic GRN mutations cause progranulin haploinsufficiency, so boosting progranulin levels is a promising therapeutic strategy. Progranulin is constitutively secreted, then taken up and trafficked to lysosomes. Before being taken up from the extracellular space, progranulin interacts with receptors that may mediate anti-inflammatory and growth factor-like effects. Modifying progranulin trafficking is a viable approach to boosting progranulin, but progranulin secretion and uptake by cells in the brain is poorly understood and may involve distinct mechanisms from other parts of the body. Understanding the cell types and processes that regulate extracellular progranulin in the brain could provide insight into progranulin's mechanism of action and inform design of progranulin-boosting therapies. To address this question we used microdialysis to measure progranulin in interstitial fluid (ISF) of mouse medial prefrontal cortex (mPFC). Grn+/- mice had approximately 50% lower ISF progranulin than wild-type mice, matching the reduction of progranulin in cortical tissue. Fluorescent in situ hybridization and immunofluorescence confirmed that microglia and neurons are the major progranulin-expressing cell types in the mPFC. Studies of conditional microglial (Mg-KO) and neuronal (N-KO) Grn knockout mice revealed that loss of progranulin from either cell type results in approximately 50% reduction in ISF progranulin. LPS injection (i.p.) produced an acute increase in ISF progranulin in mPFC. Depolarizing cells with KCl increased ISF progranulin, but this response was not altered in N-KO mice, indicating progranulin secretion by non-neuronal cells. Increasing neuronal activity with picrotoxin did not increase ISF progranulin. These data indicate that microglia and neurons are the source of most ISF progranulin in mPFC, with microglia likely secreting more progranulin per cell than neurons. The acute increase in ISF progranulin after LPS treatment is consistent with a role for extracellular progranulin in regulating inflammation, and may have been driven by microglia or peripheral immune cells. Finally, these data indicate that mPFC neurons engage in constitutive progranulin secretion that is not acutely changed by neuronal activity.

The Role of Progranulin (PGRN) in the Pathogenesis of Ischemic Stroke

Stroke is a life-threatening medical condition and is a leading cause of disability. Cerebral ischemia is characterized by a distinct inflammatory response starting with the production of various cytokines and other inflammation-related agents. Progranulin (PGRN), a multifunctional protein, is critical in diverse physiological reactions, such as cell proliferation, inflammation, wound healing, and nervous system development. A mature PGRN is anti-inflammatory, while granulin, its derivative, conversely induces pro-inflammatory cytokine expression. PGRN is significantly involved in the brain tissue and its damage, for example, improving mood and cognitive disorders caused by cerebral ischemia. It may also have protective effects against nerve and spinal cord injuries by inhibiting neuroinflammatory response and apoptosis or it may be related to the proliferation, accumulation, differentiation, and activation of microglia. PGRN is a neurotrophic factor in the central nervous system. It may increase post-stroke neurogenesis of the subventricular zone (SVZ), which is particularly important in improving long-term brain function following cerebral ischemia. The neurogenesis enhanced via PGRN in the ischemic brain SVZ may be attributed to the induction of PI3K/AKT and MAPK/ERK signaling routes. PGRN can also promote the proliferation of neural stem/progenitor cells through PI3K/AKT signaling pathway. PGRN increases hippocampal neurogenesis, reducing anxiety and impaired spatial learning post-cerebral ischemia. PGRN alleviates cerebral ischemia/reperfusion injury by reducing endoplasmic reticulum stress and suppressing the NF-κB signaling pathway. PGRN can be introduced as a potent neuroprotective agent capable of improving post-ischemia neuronal actions, mainly by reducing and elevating the inflammatory and anti-inflammatory cytokines. Expression, storage, cleavage, and function of progranulin (PGRN) in the pathogenesis of ischemic stroke.

Progranulin Protects against Hyperglycemia-Induced Neuronal Dysfunction through GSK3β Signaling

Type II diabetes affects over 530 million individuals worldwide and contributes to a host of neurological pathologies. Uncontrolled high blood glucose (hyperglycemia) is a major factor in diabetic pathology, and glucose regulation is a common goal for maintenance in patients. We have found that the neuronal growth factor progranulin protects against hyperglycemic stress in neurons, and although its mechanism of action is uncertain, our findings identified Glycogen Synthase Kinase 3β (GSK3β) as being potentially involved in its effects. In this study, we treated mouse primary cortical neurons exposed to high-glucose conditions with progranulin and a selective pharmacological inhibitor of GSK3β before assessing neuronal health and function. Whole-cell and mitochondrial viability were both improved by progranulin under high-glucose stress in a GSK3β-dependent manner. This extended to autophagy flux, indicated by the expressions of autophagosome marker Light Chain 3B (LC3B) and lysosome marker Lysosome-Associated Membrane Protein 2A (LAMP2A), which were affected by progranulin and showed heterogeneous changes from GSK3β inhibition. Lastly, GSK3β inhibition attenuated downstream calcium signaling and neuronal firing effects due to acute progranulin treatment. These data indicate that GSK3β plays an important role in progranulin's neuroprotective effects under hyperglycemic stress and serves as a jumping-off point to explore progranulin's protective capabilities in other neurodegenerative models.

The brain reacting to COVID-19: analysis of the cerebrospinal fluid proteome, RNA and inflammation

Patients with COVID-19 can have a variety of neurological symptoms, but the active involvement of central nervous system (CNS) in COVID-19 remains unclear. While routine cerebrospinal fluid (CSF) analyses in patients with neurological manifestations of COVID-19 generally show no or only mild inflammation, more detailed data on inflammatory mediators in the CSF of patients with COVID-19 are scarce. We studied the inflammatory response in paired CSF and serum samples of patients with COVID-19 (n = 38). Patients with herpes simplex virus encephalitis (HSVE, n = 10) and patients with non-inflammatory, non-neurodegenerative neurological diseases (n = 28) served as controls. We used proteomics, enzyme-linked immunoassays, and semiquantitative cytokine arrays to characterize inflammatory proteins. Autoantibody screening was performed with cell-based assays and native tissue staining. RNA sequencing of long-non-coding RNA and circular RNA was done to study the transcriptome. Proteomics on single protein level and subsequent pathway analysis showed similar yet strongly attenuated inflammatory changes in the CSF of COVID-19 patients compared to HSVE patients with, e.g., downregulation of the apolipoproteins and extracellular matrix proteins. Protein upregulation of the complement system, the serpin proteins pathways, and other proteins including glycoproteins alpha-2 and alpha-1 acid. Importantly, calculation of interleukin-6, interleukin-16, and CXCL10 CSF/serum indices suggest that these inflammatory mediators reach the CSF from the systemic circulation, rather than being produced within the CNS. Antibody screening revealed no pathological levels of known neuronal autoantibodies. When stratifying COVID-19 patients into those with and without bacterial superinfection as indicated by elevated procalcitonin levels, inflammatory markers were significantly (p < 0.01) higher in those with bacterial superinfection. RNA sequencing in the CSF revealed 101 linear RNAs comprising messenger RNAs, and two circRNAs being significantly differentially expressed in COVID-19 than in non-neuroinflammatory controls and neurodegenerative patients. Our findings may explain the absence of signs of intrathecal inflammation upon routine CSF testing despite the presence of SARS-CoV2 infection-associated neurological symptoms. The relevance of blood-derived mediators of inflammation in the CSF for neurological COVID-19 and post-COVID-19 symptoms deserves further investigation.

Progranulin from different gliocytes in the nucleus accumbens exerts distinct roles in FTD- and neuroinflammation-induced depression-like behaviors

BACKGROUND

Neuroinflammation in the nucleus accumbens (NAc) is well known to influence the progression of depression. However, the molecular mechanisms triggering NAc neuroinflammation in depression have not been fully elucidated. Progranulin (PGRN) is a multifunctional growth factor that is linked to the innate immune response and inflammation, and PGRN plays a key role in neurodegenerative diseases such as frontotemporal dementia (FTD). Here, the purpose of this study was to validate whether PGRN was involved in the NAc neuroinflammation-promoted depressive-like phenotype.

METHODS

A NAc neuroinflammation-relevant depression-like model was established using wild-type (WT) and PGRN-knockout (KO) mice after NAc injection with lipopolysaccharide (LPS), and various behavioral tests related to cognition, social recognition, depression and anxiety were performed with WT and PGRNKO mice with or without NAc immune challenge. RT‒PCR, ELISA, western blotting and immunofluorescence staining were used to determine the expression and function of PGRN in the neuroinflammatory reaction in the NAc after LPS challenge. The morphology of neurons in the NAc from WT and PGRNKO mice under conditions of NAc neuroinflammation was analyzed using Golgi-Cox staining, followed by Sholl analyses. The potential signaling pathways involved in NAc neuroinflammation in PGRNKO mice were investigated by western blotting.

RESULTS

Under normal conditions, PGRN deficiency induced FTD-like behaviors in mice and astrocyte activation in the NAc, promoted the release of the inflammatory cytokines interleukin (IL)-6 and IL-10 and increased dendritic complexity and synaptic protein BDNF levels in the NAc. However, NAc neuroinflammation enhanced PGRN expression, which was located in astrocytes and microglia within the NAc, and PGRN deficiency in mice alleviated NAc neuroinflammation-elicited depression-like behaviors, seemingly inhibiting astrocyte- and microglia-related inflammatory reactions and neuroplasticity complexity in the NAc via the p38 and nuclear factor of kappa (NF-κB) signaling pathways present in the NAc after neuroinflammation.

CONCLUSIONS

Our results suggest that PGRN exerts distinct function on different behaviors, showing protective roles in the FTD-like behavior and detrimental effects on the neuroinflammation-related depression-like behavior, resulting from mediating astrocyte and microglial functions from the NAc in different status.

Dexmedetomidine Attenuates LPS-Induced Acute Lung Injury in Rats by Activating the Nrf2/ARE Pathway

Background

To investigate the effect of dexmedetomidine (Dex) on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in rats and its mechanism.

Methods

Eighteen SD rats were randomly divided into 3 groups (6 rats in each group): control group (intratracheal instillation of saline), ALI group (intratracheal instillation of 5 mg/kg LPS), and ALI-Dex group (tail vein injection of 50 μg/kg/h Dex + intratracheal instillation of LPS). Subsequently, the water content of lung tissues was assessed using the wet-dry (W/D) ratio and the histopathological changes of lung tissues using H&E staining. Further activities of ROS, SOD, and GSH-Px in lung tissues of rats were measured by an automatic biochemistry analyzer. ELISA was performed to detect TNF-α, IL-1β, and IL-6 expression in alveolar lavage fluid (BALF) and Western blot to detect the expression of Nrf2/ARE pathway-related proteins.

Results

After Dex treatment, a reduction in water content in lung tissue and an improvement of lung injury were found in the ALI rats. Compared with the ALI group, rats in the ALI-Dex group had decreased ROS activity and increased activities of SOD and GSH-Px in lung tissues. Dex-treated rats were also associated with a decrease in TNF-α, IL-1β, and IL-6 expression in alveolar lavage fluid (BALF). Additionally, increased expression levels of HO-1 and NQO1 in lung tissues and elevated expression of Nrf2 in the nucleus were shown in the ALI-Dex group compared with the ALI group.

Conclusion

Dex alleviates LPS-induced ALI by activating the Nrf2/ARE signaling pathway.

Progranulin promotes hippocampal neurogenesis and alleviates anxiety-like behavior and cognitive impairment in adult mice subjected to cerebral ischemia

Aims

Cerebral ischemia can lead to anxiety and cognitive impairment due to the loss of hippocampal neurons. Facilitation of endogenous neurogenesis in the hippocampus is a potential therapeutic strategy for alleviating ischemia‐induced anxiety and cognitive impairment. Progranulin (PGRN), a secretory glycoprotein, has been reported to have a mitogentic effect on many cell types. However, it is not clear whether PGRN enhances hippocampal neurogenesis and promotes functional recovery.

Methods

Adult male C57BL/6 mice were subjected to permanent middle cerebral artery occlusion (pMCAO) and injected intracerebroventricularly with recombinant mouse PGRN 30 min after pMCAO. Anxiety‐like behavior was detected by the open field and the elevated plus maze tests, and spatial learning and memory abilities were evaluated by Morris water maze. Neurogenesis was examined by double labeling of BrdU and neural stem cells or neurons markers. For mechanism studies, the level of ERK1/2 and AKT phosphorylation were assessed by western blotting.

Results

Progranulin significantly alleviated anxiety‐like behavior and spatial learning and memory impairment induced by cerebral ischemia in mice. Consistent with the functional recovery, PGRN promoted neural stem cells (NSCs) proliferation and neuronal differentiation in the dentate gyrus (DG) after cerebral ischemia. PGRN upregulated the expression of phosphorylated ERK1/2 and Akt in the DG after cerebral ischemia.

Conclusions

Progranulin alleviates ischemia‐induced anxiety‐like behavior and spatial learning and memory impairment in mice, probably via stimulation of hippocampal neurogenesis mediated by activation of MAPK/ERK and PI3K/Akt pathways. PGRN might be a promising candidate for coping with ischemic stroke‐induced mood and cognitive impairment in clinic.

Long non-coding RNA LINC01194 promotes the inflammatory response and apoptosis of LPS-treated MLE 12 cells through the miR-203a-3p /MIP-2 axis

Acute lung injury (ALI) induced by bacteria LPS is characterized by the upregulation of the apoptosis rate of tissue cells and aggravation of inflammatory response. Although many studies have focused on the pathogenesis of this disease, its mechanism remains unknown. This study examined the regulatory role of long non-coding RNA (lncRNA) LINC01194 in the progression of ALI through various bioinformatics analyses and experimental work, including ELISA assay, dual-luciferase reporter assay, biotinylated RNA pull-down assay, and western blot analysis. The result showed that the LINC01194 was overexpressed in the ALI-induced mice model. We observed a significant upregulation of LINC01194 in LPS-treated Mouse lung epithelial type II cells (MLE-12 cells) after 24 hrs of induction. Bioinformatics analysis, Elisa assay, qRT-PCR analysis, Biotinylated RNA pull-down assay, apoptosis test, and western blot analysis demonstrated that the LINC01194 could act as a miR-203a-3p sponge to activate the inflammatory response in LPS-induced ALI model through post-transcriptional upregulation of MIP-2. We showed that LINC01194 regulates the inflammatory response and apoptosis of LPS-induced mice and MLE-12 cells via the miR-203a-3p/MIP-2 axis. LINC01194 could be a potential biomarker for early diagnosis and the treatment of ALI.

Single intracerebroventricular progranulin injection adversely affects the blood-brain barrier in experimental traumatic brain injury

Progranulin (PGRN) is a neurotrophic and anti-inflammatory factor with protective effects in animal models of ischemic stroke, subarachnoid hemorrhage, and traumatic brain injury (TBI). Administration of recombinant (r) PGRN prevents exaggerated brain pathology after TBI in Grn-deficient mice, suggesting that local injection of recombinant progranulin (rPGRN) provides therapeutic benefit in the acute phase of TBI. To test this hypothesis, we subjected adult male C57Bl/6N mice to the controlled cortical impact model of TBI, administered a single dose of rPGRN intracerebroventricularly (ICV) shortly before the injury, and examined behavioral and biological effects up to 5 days post injury (dpi). The anti-inflammatory bioactivity of rPGRN was confirmed by its capability to inhibit the inflammation-induced hypertrophy of murine primary microglia and astrocytes in vitro. In C57Bl/6N mice, however, ICV administration of rPGRN failed to attenuate behavioral deficits over the 5-day observation period. (Immuno)histological gene and protein expression analyses at 5 dpi did not reveal a therapeutic benefit in terms of brain injury size, brain inflammation, glia activation, cell numbers in neurogenic niches, and neuronal damage. Instead, we observed a failure of TBI-induced mRNA upregulation of the tight junction protein occludin and increased extravasation of serum immunoglobulin G into the brain parenchyma at 5 dpi. In conclusion, single ICV administration of rPGRN had not the expected protective effects in the acute phase of murine TBI, but appeared to cause an aggravation of blood-brain barrier disruption. The data raise questions about putative PGRN-boosting approaches in other types of brain injuries and disease.

Progranulin promotes functional recovery and neurogenesis in the subventricular zone of adult mice after cerebral ischemia

Progranulin (PGRN), a secreted glycosylated protein, has been reported to attenuate ischemia-induced cerebral injury through anti-inflammation, attenuation of blood-brain barrier disruption and neuroprotection. However, the effect of PGRN on neurogenesis in the subventricular zone (SVZ) after cerebral ischemia remains unclear. In this study, adult C57BL/6 mice were subjected to permanent middle cerebral artery occlusion (pMCAO), and different doses of recombinant mouse PGRN (r-PGRN, 0.3 ng, 1 ng, 5 ng) were intracerebroventricularly administered 30 min after pMCAO. Results showed that 1 ng r-PGRN markedly reduced infarct volume and rescued functional deficits 24 h after pMCAO. Meanwhile, 1 ng r-PGRN increased SVZ cell proliferation, as shown by a high number of bromodeoxyuridine-positive (BrdU+) cells and Ki-67+ cells in the ischemic ipsilateral SVZ 7 d after pMCAO. Additionally, PGRN increased the percentage of BrdU+/Doublecortin (DCX)+ cells in the ipsilateral SVZ 14 d after pMCAO and increased the percentage of new neurons (BrdU+/NeuN+ cells) in the peri-infarct striatum 28 d after pMCAO, suggesting that PGRN promotes neuronal differentiation. PGRN also upregulated phosphorylation of ERK1/2 and Akt in the ipsilateral SVZ 3 d after pMCAO. Our data indicate that PGRN treatment promotes acute functional recovery; most importantly, it also stimulates neurogenesis in the SVZ, which could be beneficial for long-term recovery after cerebral ischemia. The increase in neurogenesis could be associated with activation of the MAPK/ERK and PI3K/Akt pathways. These results suggest a potential new strategy utilizing PGRN in ischemic stroke therapy.

Neuroinflammation modulates the association of PGRN with cerebral amyloid-β burden

Progranulin (PGRN) and neuroinflammatory markers increased over the course of Alzheimer's disease (AD). We aimed to determine whether neuroinflammation could modulate the association of PGRN with amyloid pathologies. Baseline cerebrospinal fluid (CSF) PGRN and AD pathologies were measured for 965 participants, among whom 228 had measurements of CSF neuroinflammatory markers. Causal mediation analyses with 10,000 bootstrapped iterations were conducted to explore the mediation effects within the framework of A/T/N biomarker profile. Increased levels of CSF PGRN and inflammatory markers (sTNFR1, sTNFR2, TGF-β1, ICAM1, and VCAM1) were associated with T- or N-positive (TN+) profile, irrespective of the amyloid pathology. In TN+ group, CSF PGRN was associated with increased levels of these inflammatory markers and CSF amyloid-β_1-42 (p < 0.01). The neuroinflammatory markers significantly modulated (proportion: 20%~60%) the relationship of amyloid burden with CSF PGRN, which could predict slower cognitive decline and lower AD risk in the TN+ group. The abovementioned associations became non-significant in the TN- group. These findings revealed a close relationship between neuroinflammation and CSF PGRN in contributing to AD pathogenesis, and also highlighted the specific roles of PGRN in neurodegenerative conditions. Future experiments are warranted to verify the causal relationship.

Lysosomal Dysfunction and Other Pathomechanisms in FTLD: Evidence from Progranulin Genetics and Biology

It has been more than a decade since heterozygous loss-of-function mutations in the progranulin gene (GRN) were first identified as an important genetic cause of frontotemporal lobar degeneration (FTLD). Due to the highly diverse biological functions of the progranulin (PGRN) protein, encoded by GRN, multiple possible disease mechanisms have been proposed. Early work focused on the neurotrophic properties of PGRN and its role in the inflammatory response. However, since the discovery of homozygous GRN mutations in patients with a lysosomal storage disorder, investigation into the possible roles of PGRN and its proteolytic cleavage products granulins, in lysosomal function and dysfunction, has taken center stage. In this chapter, we summarize the GRN mutational spectrum and its associated phenotypes followed by an in-depth discussion on the possible disease mechanisms implicated in FTLD-GRN. We conclude with key outstanding questions which urgently require answers to ensure safe and successful therapy development for GRN mutation carriers.

Progranulin suppresses the age-dependent enhancement of neuronal activity in the hypothalamus

Our previous investigations revealed that progranulin (PGRN) is a lysosomal protein involved in hippocampal neurogenesis and neuroinflammation. However, the possible involvement of PGRN in regulating inflammatory response and mediating neuronal activity is still not well-defined. Here, we demonstrate that PGRN deficiency enhances the age-dependent increase of neuronal activity in the paraventricular nucleus (PVN) of the hypothalamus. Aging increased neuronal activity in the PVN of the hypothalamus, and PGRN deficiency enhanced the effects of age on hypothalamic neuronal activity. Aging increased the lysosomal biogenesis and inflammatory response in microglia, which was also aggravated in PGRN-knockout mice. Moreover, PGRN deficiency enhanced interleukin-1 beta and lysosomal genes levels. These results suggest that PGRN deficiency may enhance the age-dependent increase of neuronal activity possibly because PGRN facilitates immunological responses through regulating lysosomal function.

Recent advances in the study of progranulin and its role in sepsis

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. The mortality rate of in-hospital patients whose conditions are complicated by sepsis remains high in spite of intensive-care treatment, therefore placing a significant financial burden on the health care system. In recent years, progranulin (PGRN), a cysteine-rich secretory protein (CRISP), has been found to play a crucial role in sepsis. PGRN participates in the pathogenesis of sepsis via diverse pathways, including bacterial clearance, cell growth and survival, tissue repair, and the regulation of inflammation. PGRN knockout mice suffer from serious infectious processes, whereas therapeutic administration of recombinant PGRN to such mice enhances bacterial clearance and reduces organ injury and mortality rate. Even though PGRN plays an important role in regulating sepsis, its potential mechanisms have not been completely clarified. In this review, we summarize the most recent research advances in the study of PGRN and its role in sepsis.

Elevated progranulin as a novel biomarker to predict poor prognosis in community-acquired pneumonia

PURPOSE

Prognostic biomarkers help triage initial patients and inform targeted therapy selection. Here, we explored the role of progranulin (PGRN)-implicated in processes ranging from inflammation to neurodegeneration-in patients with community-acquired pneumonia (CAP).

METHODS

A prospective observational cohort study was conducted during 2017. Patients who required invasive mechanical ventilation and/or had septic shock and were discharged from the hospital were cohort II. Those who died at the hospital were cohort III. Remaining patients discharged from the hospital were cohort I. The primary endpoint was that patients progressed to served as cohort II; the secondary endpoint was that patients progressed to served as cohort III. Serum PGRN levels were detected by ELISA.

RESULTS

A total of 280 patients constituted the study cohort. 194 (69.3%) were categorized into cohort I, 61 (21.8%) were categorized into cohort II, and 25 (8.9%) were categorized into cohort III. Serum PGRN levels were increased in CAP patients, independently of etiology. Adjusting for clinical parameters, the odds ratios (95%CI) of cohort III and combined cohort II-III were 34.968 (3.743-326.692) and 3.741 (1.496-9.351), respectively, comparing lowest-to-highest quartile PGRN levels. PGRN exhibited high accuracy in predicting 30-day mortality, with AUC 0.862. PGRN combined with CURB-65 or PSI significantly improved prediction performance. Cox proportional regression analysis showed PGRN was an independent predictor for 30-day mortality risk. Cox survival curves confirmed PGRN ≥89.51 ng/mL had a significantly higher mortality rate than PGRN <89.51 ng/mL.

CONCLUSION

Higher PGRN levels at admission were associated with higher odds of poor prognosis. PGRN can improve the prognostic power of CURB-65 or PSI, so PGRN could be apparently a prognostic biomarker for assisting triage of CAP patients.

Complement activation sustains neuroinflammation and deteriorates adult neurogenesis and spatial memory impairment in rat hippocampus following sleep deprivation

BACKGROUND

An association between neuroinflammation, reduced adult neurogenesis, and cognitive impairment has been established in sleep deprivation (SD). Complement receptors are expressed on neuronal and glial cells, thus, regulate the neuroinflammation, neurogenesis and learning/memory. However, understanding of the effect of SD on the brain-immune system interaction associated with cognitive dysfunction and its mechanisms is obscure. We hypothesized that complement activation induced changes in inflammatory and neurogenesis related proteins might be involved in the cognitive impairment during SD.

METHODOLOGY

Adult male Sprague Dawley rats were used. Rats were sleep deprived for 48 h using a novel automated SD apparatus. Dosage of BrdU (50 mg/kg/day, i.p. in 0.07 N NaOH), complement C3a receptor antagonist (C3aRA; SB290157; 1 mg/kg/day, i.p.) in 1.16% v/v PBS and complement C5a receptor antagonist (C5aRA; W-54011; 1 mg/kg/day, i.p.) in normal saline were used. Rats were subjected to spatial memory evaluation following SD. Hippocampal tissue was collected for biochemical, molecular, and immunohistochemical studies. T-test and ANOVA were used for the statistical analysis.

RESULTS

An up-regulation in the levels of complement components (C3, C5, C3a, C5a) and receptors (C3aR and C5aR) in hippocampus, displayed the complement activation during SD. Selective antagonism of C3aR/C5aR improved the spatial memory performance of sleep-deprived rats. C3aR antagonist (C3aRA) or C5aR antagonist (C5aRA) treatment inhibited the gliosis, maintained inflammatory cytokines balance in hippocampus during SD. Complement C3aR/C5aR antagonism improved hippocampal adult neurogenesis via up-regulating the BDNF level following SD. Administration of C3aRA and C5aRA significantly maintained synaptic homeostasis in hippocampus after SD. Gene expression analysis showed down-regulation in the mRNA levels of signal transduction pathways (Notch and Wnt), differentiation and axogenous proteins, which were found to be improved after C3aRA/C5aRA treatment. These findings were validated at protein and cellular level. Changes in the corticosterone level and ATP-adenosine-NO pathway were established as the key mechanisms underlying complement activation mediated consequences of SD.

CONCLUSION

Our study suggests complement (C3a-C3aR and C5a-C5aR) activation as the novel mechanism underlying spatial memory impairment via promoting neuroinflammation and adult neurogenesis decline in hippocampus during SD, thereby, complement (C3aR/C5aR) antagonist may serve as the novel therapeutics to improve the SD mediated consequences.

Minocycline inhibits microglial activation and alleviates depressive-like behaviors in male adolescent mice subjected to maternal separation

Exposure to early adversity increases vulnerability to psychiatric disorders in later life. Microglia-mediated inflammation has been linked to psychopathology, so such inflammation may be a target for treating depression. Using a model of depression involving adolescent male C57BL/6J mice subjected to maternal separation, we explored whether using minocycline to mitigate inflammation can alleviate depression-like behaviors. Between postnatal days 1 and 14, male mice were separated from their mothers for 3 h per day. Minocycline (20 mg/kg) was administered intraperitoneally once daily for 2 weeks starting one week after weaning. Then the male mice were subjected to a second stress for 2 weeks. Results from the sucrose preference test, forced swimming test, and open field test showed that maternal separation did not obviously alter behavior of the male mice, but it did increase the risk of depression-like behaviors following a second stress. This increased risk disappeared if minocycline was given preemptively before the second stress. Maternal separation and second stress up-regulated pro-inflammatory markers and down-regulated anti-inflammatory markers in the hippocampus, and they activated microglia and promoted pro-inflammatory transitions in microglia. All these effects were reversed by minocycline. These changes in inflammatory processes correlated with changes in neurogenesis and BDNF expression in the hippocampus. Our results in this mouse model suggest the potential of minocycline for treating psychiatric disorders induced by early adversity.

Osthole alleviates inflammation by down-regulating NF-κB signaling pathway in traumatic brain injury

Traumatic brain injury (TBI) is a common neurotrosis disorder of the central nervous system (CNS), which has dramatic consequences on the integrity of damaged tissue. In this study, we investigated the neuroprotective effect and anti-inflammatory actions of osthole, a natural coumarin derivative, in both in vivo and in vitro TBI models. We first prepared a mouse model of cortical stab wound brain injury, investigated the capacity for osthole to prevent secondary brain injury and further examined the underlying mechanism. We revealed that osthole significantly improved the neurological function, increased the number of neurons beside injured site. Additionally, osthole treatment reduced the expression of microglia and glial scar, lowered the level of the proinflammatory cytokines interleukin (IL)-6, IL-1β, and tumor necrosis factor-α (TNF-α), and blocked the activation of nuclear factor kappa B (NF-κB). Furthermore, the protective effect of osthole was also examined in SH-SY5Y cells subjected to scratch injury. Treatment of osthole prominently suppressed cell apoptosis and inflammatory factors release by blocking injury-induced IκB-α phosphorylation and NF-κB translocation, and upregulated the IκB-α which functions in the NF-κB signaling pathway of SH-SY5Y cells. However, NF-κB signaling pathway was inhibited by pyrrolidine dithiocarbamate (PDTC), an NF-κB inhibitor, the anti-inflammatory effect of osthole was abolished. In conclusion, our findings demonstrated that osthole attenuated inflammatory response by inhibiting the NF-κB pathway in TBI.

Postnatal changes in constitutive cyclooxygenase‑2 expression in the mice hippocampus and its function in synaptic plasticity

Although the expression of cyclooxygenase-2 (COX-2) is closely associated with inflammation in the brain, it is constitutively expressed in the brain, and its expression is regulated by synaptic activity. The present study investigated postnatal expression of COX-2 in the hippocampus in C57BL/6 mice at postnatal days (P) 1, 7, 14, 28, and 56. In addition, the presented study examined the effects of COX-2 on synaptic plasticity through Arc, phosphorylated cAMP response element-binding protein (pCREB), N-methyl-d-aspartate receptor 1 (GluN1), and GluN2A/2B immunohistochemistry, which was performed on COX-2 knockout (KO) and wild-type (WT) mice. Extremely weak COX-2 immunoreactivity was detected in the hippocampal CA1-3 areas in addition to the dentate gyrus at P1. Conversely, COX-2 immunoreactivity was observed in the stratum pyramidale of the CA1-3 regions and in the outer granule cell layer of the dentate gyrus at P7. Additionally, although peak COX-2 immunoreactivity was observed in all hippocampal sub-regions, including the dentate gyrus at P14, it was significantly decreased at P14. Finally, COX-2 immunoreactivity and the distribution pattern seen at P56 in the hippocampal CA1-3 regions were similar to those observed at P28, whereas, they were identified in the inner half of the granule cell layer of the dentate gyrus. The western blot analysis revealed that the COX-2 protein levels peaked at P14 and were decreased at P28 and P56. Additionally, the number of Arc and pCREB immunoreactive cells as well as GluN1 and GluN2A/2B immunoreactivity of COX-2 KO mice were significantly decreased in the dentate gyrus when compared with that in WT mice. Taken together, the results of the present study suggest that COX-2 serves an important role in synaptic plasticity in the dentate gyrus and changes in the levels of its constitutive expression are associated with the hippocampal dentate gyrus postnatal development.

Innate Anti-microbial and Anti-chemotaxis Properties of Progranulin in an Acute Otitis Media Mouse Model

Acute otitis media (AOM) is one of the most common infectious diseases primarily caused by Streptococcus pneumoniae (S.pn) among children. Progranulin (PGRN) is a multifunctional growth factor widely expressed in various tissues and cells. Studies have confirmed that PGRN is involved in the development of a variety of inflammatory diseases. We found that the expression of PGRN increased significantly in the middle ear of wild mice with AOM. However, its physiological functions in AOM still remain unknown. To examine the role of PGRN during AOM, we established an acute otitis media model in both C57BL/6 wild mice and PGRN-deficient (PGRN^−/−) mice via transbullar injection with S.pn clinical strain serotype 19F. Interestingly, we observed dual results: on one hand, macrophage recruitment notably increased in PGRN^−/− mice compared with WT mice; on the other hand, the overall bacterial clearance was surprisingly dampened in PGRN^−/− mice. The enhanced recruitment of macrophages was associated with increased production of chemokine (C-C motif) ligand 2 (CCL2), while the decreased bacterial clearance was associated with impaired endocytosis capacity of macrophages. The scavenging ability of bacteria in PGRN^−/− mice was recovered with administration of recombinant PGRN. These results suggested a novel dual role of PGRN in affecting the activities of macrophages.

miR-34b-5p inhibition attenuates lung inflammation and apoptosis in an LPS-induced acute lung injury mouse model by targeting progranulin

Inflammation and apoptosis play important roles in the initiation and progression of acute lung injury (ALI). Our previous study has shown that progranulin (PGRN) exerts lung protective effects during LPS-induced ALI. Here, we have investigated the potential roles of PGRN-targeting microRNAs (miRNAs) in regulating inflammation and apoptosis in ALI and have highlighted the important role of PGRN. LPS-induced lung injury and the protective roles of PGRN in ALI were first confirmed. The function of miR-34b-5p in ALI was determined by transfection of a miR-34b-5p mimic or inhibitor in intro and in vivo. The PGRN level gradually increased and subsequently significantly decreased, reaching its lowest value by 24 hr; PGRN was still elevated compared to the control. The change was accompanied by a release of inflammatory mediators and accumulation of inflammatory cells in the lungs. Using bioinformatics analysis and RT-PCR, we demonstrated that, among 12 putative miRNAs, the kinetics of the miR-34b-5p levels were closely associated with PGRN expression in the lung homogenates. The gain- and loss-of-function analysis, dual-luciferase reporter assays, and rescue experiments confirmed that PGRN was the functional target of miR-34b-5p. Intravenous injection of miR-34b-5p antagomir in vivo significantly inhibited miR-34b-5p up-regulation, reduced inflammatory cytokine release, decreased alveolar epithelial cell apoptosis, attenuated lung inflammation, and improved survival by targeting PGRN during ALI. miR-34b-5p knockdown attenuates lung inflammation and apoptosis in an LPS-induced ALI mouse model by targeting PGRN. This study shows that miR-34b-5p and PGRN may be potential targets for ALI treatments.

Omega-3 polyunsaturated fatty acid attenuates the inflammatory response by modulating microglia polarization through SIRT1-mediated deacetylation of the HMGB1/NF-κB pathway following experimental traumatic brain injury

Background

Microglial polarization and the subsequent neuroinflammatory response are contributing factors for traumatic brain injury (TBI)-induced secondary injury. High mobile group box 1 (HMGB1) mediates the activation of the NF-κB pathway, and it is considered to be pivotal in the late neuroinflammatory response. Activation of the HMGB1/NF-κB pathway is closely related to HMGB1 acetylation, which is regulated by the sirtuin (SIRT) family of proteins. Omega-3 polyunsaturated fatty acids (ω-3 PUFA) are known to have antioxidative and anti-inflammatory effects. We previously demonstrated that ω-3 PUFA inhibited TBI-induced microglial activation and the subsequent neuroinflammatory response by regulating the HMGB1/NF-κB signaling pathway. However, no studies have elucidated if ω-3 PUFA affects the HMGB1/NF-κB pathway in a HMGB1 deacetylation of dependent SIRT1 manner, thus regulating microglial polarization and the subsequent neuroinflammatory response.

Methods

The Feeney DM TBI model was adopted to induce brain injury in rats. Modified neurological severity scores, rotarod test, brain water content, and Nissl staining were employed to determine the neuroprotective effects of ω-3 PUFA supplementation. Assessment of microglia polarization and pro-inflammatory markers, such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and HMGB1, were used to evaluate the neuroinflammatory responses and the anti-inflammatory effects of ω-3 PUFA supplementation. Immunofluorescent staining and western blot analysis were used to detect HMGB1 nuclear translocation, secretion, and HMGB1/NF-κB signaling pathway activation to evaluate the effects of ω-3 PUFA supplementation. The impact of SIRT1 deacetylase activity on HMGB1 acetylation and the interaction between HMGB1 and SIRT1 were assessed to evaluate anti-inflammation effects of ω-3 PUFAs, and also, whether these effects were dependent on a SIRT1-HMGB1/NF-κB axis to gain further insight into the mechanisms underlying the development of the neuroinflammatory response after TBI.

Results

The results of our study showed that ω-3 PUFA supplementation promoted a shift from the M1 microglial phenotype to the M2 microglial phenotype and inhibited microglial activation, thus reducing TBI-induced inflammatory factors. In addition, ω-3 PUFA-mediated downregulation of HMGB1 acetylation and its extracellular secretion was found to be likely due to increased SIRT1 activity. We also found that treatment with ω-3 PUFA inhibited HMGB1 acetylation and induced direct interactions between SIRT1 and HMGB1 by elevating SIRT1 activity following TBI. These events lead to inhibition of HMGB1 nucleocytoplasmic translocation/extracellular secretion and alleviated HMGB1-mediated activation of the NF-κB pathway following TBI-induced microglial activation, thus inhibiting the subsequent inflammatory response.

Conclusions

The results of this study suggest that ω-3 PUFA supplementation attenuates the inflammatory response by modulating microglial polarization through SIRT1-mediated deacetylation of the HMGB1/NF-κB pathway, leading to neuroprotective effects following experimental traumatic brain injury.

Hypothyroidism increases cyclooxygenase-2 levels and pro-inflammatory response and decreases cell proliferation and neuroblast differentiation in the hippocampus

The present study investigated the effects of hypothyroidism on cyclooxygenase-2 (COX-2) and pro‑inflammatory cytokines in the dentate gyrus to elucidate the roles of COX‑2 in the hypothyroid hippocampus. Hypothyroidism was induced in rats by treating with 0.03% 2‑mercapto‑1‑methyl‑imidazole dissolved in drinking water for 5 weeks. The animals were sacrificed at 12 weeks of age. Hypothyroidism rats exhibited decreased triiodothyronine and thyroxine levels in the serum, while the levels of thyroid‑stimulating hormone and the weight of thyroid glands were significantly higher in the hypothyroid rats compared with those in the vehicle‑treated group. COX‑2 immunoreactivity was significantly increased in the hippocampal CA2/3 region and the dentate gyrus compared with the vehicle‑treated group. Levels of pro‑inflammatory cytokines including interleukin (IL)‑1β, IL‑6 and tumor necrosis factor‑α were significantly higher in the hippocampal homogenates of hypothyroid rats. Cell proliferation and neuroblast differentiation based on Ki67 and doublecortin immunohistochemistry were decreased in the dentate gyrus of hypothyroid rats compared with those in the vehicle‑treated group. These results suggested that hypothyroidism‑mediated COX‑2 expression affected hippocampal plasticity by upregulating the levels of pro‑inflammatory cytokines in the hippocampus. Therefore, COX‑2 may be suggested as a candidate molecule for preventing hypothyroidism‑induced neurological side effects.

Microglia at center stage: a comprehensive review about the versatile and unique residential macrophages of the central nervous system

Microglia cells are the unique residential macrophages of the central nervous system (CNS). They have a special origin, as they derive from the embryonic yolk sac and enter the developing CNS at a very early stage. They play an important role during CNS development and adult homeostasis. They have a major contribution to adult neurogenesis and neuroinflammation. Thus, they participate in the pathogenesis of neurodegenerative diseases and contribute to aging. They play an important role in sustaining and breaking the blood-brain barrier. As innate immune cells, they contribute substantially to the immune response against infectious agents affecting the CNS. They play also a major role in the growth of tumours of the CNS. Microglia are consequently the key cell population linking the nervous and the immune system. This review covers all different aspects of microglia biology and pathology in a comprehensive way.

Inhibiting the microglia activation improves the spatial memory and adult neurogenesis in rat hippocampus during 48 h of sleep deprivation

BACKGROUND

Sleep deprivation (SD) leads to cognitive impairment. Neuroinflammation could be a significant contributing factor in the same. An increase in regional brain pro-inflammatory cytokines induces cognitive deficits, however, the magnitude of the effect under SD is not apparent. It is plausible that microglia activation could be involved in the SD-induced cognitive impairment by modulation of neuronal cell proliferation, differentiation, and brain-derived neuronal factor (BDNF) level. The present study aimed to evaluate the possible beneficial effect of minocycline in amelioration of spatial memory decline during SD by its anti-inflammatory and neuroprotective actions. We scrutinized the effect of minocycline on the inflammatory cytokine levels associated with glial cells (microglia and astrocytes) activity and neurogenesis markers crucial for behavioral functions during SD.

METHODS

Male Sprague-Dawley rats weighing 230-250 g were sleep deprived for 48 h using automated cage shaking apparatus. The spatial memory was tested using MWM apparatus immediately after completion of SD with and without minocycline. The animals were euthanized, blood was collected, and brain was extracted for neuroinflammation and neurogenesis studies. The set of experiments were also conducted with use of temozolomide, a neurogenesis blocker.

RESULTS

Minocycline treatment increased the body weight, food intake, and spatial memory performance which declined during SD. It reduced the pro-inflammatory and increased the anti-inflammatory cytokine levels in hippocampus and plasma and inhibited the reactive gliosis in the hippocampus evidenced by improved cell count, morphology, and immunoreactivity. Additionally, minocycline administration promoted neurogenesis at different stages: proliferation (BrdU, Ki-67), differentiation (DCX) cells and growth factor (BDNF). However, no significant change was observed in maturation (NeuN) during SD. In addition, molecules related to behavior, inflammation, and neurogenesis were shown to be more affected after temozolomide administration during SD, and changes were restored with minocycline treatment. We observed a significant correlation of neurogenesis with microglial activation, cytokine levels, and spatial memory during SD.

CONCLUSION

The present study demonstrated that the SD-induced decline in spatial memory, neuronal cells proliferation, differentiation, and BDNF level could be attributed to upregulation of neuroinflammatory molecules, and minocycline may be an effective intervention to counteract these changes. Microglial activation is involved in SD-induced changes in inflammatory molecules, neurogenesis, and spatial memory.

Progranulin and Its Related MicroRNAs after Status Epilepticus: Possible Mechanisms of Neuroprotection

The current knowledge about neuroprotective mechanisms in humans after status epilepticus is scarce. One reason is the difficulty to measure possible mediators of these neuroprotective mechanisms. The dawn of microRNA detection in the cerebrospinal fluid (CSF) and the recent advancements in measuring proteins in the CSF such as progranulin, which is, e.g., responsible for neurite outgrowth and limiting exceeding neuroinflammatory responses, have given us new insights into putative neuroprotective mechanisms following status epilepticus. This should complement the animal data. In this review, we cover what is known about the role of progranulin as well as the links between microRNA changes and the progranulin pathway following status epilepticus in humans and animals hypothesizing neuroprotective and neurorehabilitative effects. Progranulin has also been found to feature prominently in the neuroprotective processes under hypoxic conditions and initiating neurorehabilitative processes. These properties may be used therapeutically, e.g., through drugs that raise the progranulin levels and therefore the cerebral progranulin levels as well with the goal of improving the outcome after status epilepticus.

Degradomics in Neurotrauma: Profiling Traumatic Brain Injury

Degradomics has recently emerged as a subdiscipline in the omics era with a focus on characterizing signature breakdown products implicated in various disease processes. Driven by promising experimental findings in cancer, neuroscience, and metabolomic disorders, degradomics has significantly promoted the notion of disease-specific "degradome." A degradome arises from the activation of several proteases that target specific substrates and generate signature protein fragments. Several proteases such as calpains, caspases, cathepsins, and matrix metalloproteinases (MMPs) are involved in the pathogenesis of numerous diseases that disturb the physiologic balance between protein synthesis and protein degradation. While regulated proteolytic activities are needed for development, growth, and regeneration, uncontrolled proteolysis initiated under pathological conditions ultimately culminates into apoptotic and necrotic processes. In this chapter, we aim to review the protease-substrate repertoires in neural injury concentrating on traumatic brain injury. A striking diversity of protease substrates, essential for neuronal and brain structural and functional integrity, namely, encryptic biomarker neoproteins, have been characterized in brain injury. These include cytoskeletal proteins, transcription factors, cell cycle regulatory proteins, synaptic proteins, and cell junction proteins. As these substrates are subject to proteolytic fragmentation, they are ceaselessly exposed to activated proteases. Characterization of these molecules allows for a surge of "possible" therapeutic approaches of intervention at various levels of the proteolytic cascade.