Perspectives on Primary Blast Injury of the Brain: Translational Insights Into Non-inertial Low-Intensity Blast Injury

Most traumatic brain injuries (TBIs) during military deployment or training are clinically “mild” and frequently caused by non-impact blast exposures. Experimental models were developed to reproduce the biological consequences of high-intensity blasts causing moderate to severe brain injuries. However, the pathophysiological mechanisms of low-intensity blast (LIB)-induced neurological deficits have been understudied. This review provides perspectives on primary blast-induced mild TBI models and discusses translational aspects of LIB exposures as defined by standardized physical parameters including overpressure, impulse, and shock wave velocity. Our mouse LIB-exposure model, which reproduces deployment-related scenarios of open-field blast (OFB), caused neurobehavioral changes, including reduced exploratory activities, elevated anxiety-like levels, impaired nesting behavior, and compromised spatial reference learning and memory. These functional impairments associate with subcellular and ultrastructural neuropathological changes, such as myelinated axonal damage, synaptic alterations, and mitochondrial abnormalities occurring in the absence of gross- or cellular damage. Biochemically, we observed dysfunctional mitochondrial pathways that led to elevated oxidative stress, impaired fission-fusion dynamics, diminished mitophagy, decreased oxidative phosphorylation, and compensated cell respiration-relevant enzyme activity. LIB also induced increased levels of total tau, phosphorylated tau, and amyloid β peptide, suggesting initiation of signaling cascades leading to neurodegeneration. We also compare translational aspects of OFB findings to alternative blast injury models. By scoping relevant recent research findings, we provide recommendations for future preclinical studies to better reflect military-operational and clinical realities. Overall, better alignment of preclinical models with clinical observations and experience related to military injuries will facilitate development of more precise diagnosis, clinical evaluation, treatment, and rehabilitation

Low-Intensity Blast Induces Acute Glutamatergic Hyperexcitability in Mouse Hippocampus Leading to Long-Term Learning Deficits and Altered Expression of Proteins Involved in Synaptic Plasticity and Serine Protease Inhibitors

Neurocognitive consequences of blast-induced traumatic brain injury (bTBI) pose significant concerns for military service members and veterans with the majority of invisible injury. However, the underlying mechanism of such mild bTBI by low-intensity blast (LIB) exposure for long-term cognitive and mental deficits remains elusive. Our previous studies have shown that mice exposed to LIB result in nanoscale ultrastructural abnormalities in the absence of gross or apparent cellular damage in the brain. Here we tested the hypothesis that glutamatergic hyperexcitability may contribute to long-term learning deficits. Using brain slice electrophysiological recordings, we found an increase in averaged frequencies with a burst pattern of miniature excitatory postsynaptic currents (mEPSCs) in hippocampal CA3 neurons in LIB-exposed mice at 1- and 7-days post injury, which was blocked by a specific NMDA receptor antagonist AP5. In addition, cognitive function assessed at 3-months post LIB exposure by automated home-cage monitoring showed deficits in dynamic patterns of discrimination learning and cognitive flexibility in LIB-exposed mice. Collected hippocampal tissue was further processed for quantitative global-proteomic analysis. Advanced data-independent acquisition for quantitative tandem mass spectrometry analysis identified altered expression of proteins involved in synaptic plasticity and serine protease inhibitors in LIB-exposed mice. Some were correlated with the ability of discrimination learning and cognitive flexibility. These findings show that acute glutamatergic hyperexcitability in the hippocampus induced by LIB may contribute to long-term cognitive dysfunction and protein alterations. Studies using this military-relevant mouse model of mild bTBI provide valuable insights into developing a potential therapeutic strategy to ameliorate hyperexcitability-modulated LIB injuries

Matrix metalloproteinase-9 : surrogate marker and therapeutic target against neurovascular impairment after cerebral ischemia

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Stroke ranks fourth among all causes of death, and acute ischemic stroke is the most common form. The neurovascular unit (NVU) describes a basic functional structure in the brain and is primarily composed of endothelial cells, pericytes, astrocytes, microglia and neurons. The dynamic structure of the NVU is highly regulated due to interactions between different cells and extracellular matrix (ECM) components. Proteolysis of the ECM by matrix metalloproteinases (MMPs), especially MMP-9, plays an important role in the pathophysiology of cerebral ischemia and administration of tissue plasminogen activator (tPA). The activation of gelatinases (MMP-2/9) is considered a key mechanism involved in the impairment of NVU. The overall goal of this research project is to examine the role of MMP-9 in the neurovascular impairment after ischemic stroke in mice. In this project, we implemented a new strategy using gelatinase-activatable cell-penetrating peptides (ACPPs) tagged with fluorescence and/or gadolinium-based contrast agents to investigate proteolysis of gelatinases as surrogate markers of neurovascular integrity. We presented evidence that the combination of a sensitive fluorescent chromatophore and MRI contrast enhancement agent can be used to monitor gelatinase activity and its distribution in cultured neurons as well as in mice after focal cerebral ischemia. Detection of the activity of gelatinases in vivo using ACPPs could provide insights into the underlying mechanism for gelatinase proteolysis that mediate ischemia-related neurovascular impairment. We also applied a two-dimensional (2D) gelatin zymography technique that combines isoelectric focusing (IEF) with zymographic electrophoresis. We demonstrated that the 2D zymography approach can improve separation of different isoforms of gelatinases in both in vitro and in vivo conditions. 2D zymography is an effective method to separate posttranslational modification isoforms of gelatinases and to identify modifications that regulate their enzymatic activity in acute brain injuries. In work that follows, we used a fibrin-rich blood clot to occlude the middle cerebral artery (MCA) in mice as a model to represent the critical thromboembolic features of ischemic stroke in humans. In this study, we evaluated effects of SB-3CT, a mechanism-based inhibitor selective for gelatinases. We demonstrated MMP-9 activation and neurovasculature impairment in this stroke model, and showed the ability of SB-3CT to inhibit MMP-9 activity in vivo, which in turn resulted in maintenance of laminin, antagonism of pericyte contraction and loss, preservation of laminin-positive pericytes and endothelial cells, and thus rescuing neurons from apoptosis and preventing intracerebral hemorrhage. We further demonstrated that SB-3CT/tPA combined treatment could attenuate MMP-9 -- mediated degradation of endothelial laminin, impairment of endothelial cells, and decrease of caveolae -- mediated transcytosis. Early inhibition of MMP-9 proteolysis by SB-3CT decreased brain damage, reduced BBB disruption, and prevented hemorrhagic transformation after delayed tPA treatment. Therefore usage of SB-3CT will be helpful in accessing combination therapy with tPA in ischemic stroke. Results from these studies indicate the important role of MMP-9 in cerebral ischemia and thus the need for further studies to explore the molecular mechanisms underlying its activation and regulation. Results further demonstrated that the combined use of MMP-9 inhibitor with tPA may extend tPA therapeutic window for mitigating stroke damage

Current and Future Potential Distribution of Wild Strawberry Species in the Biodiversity Hotspot of Yunnan Province, China

Based on 243 current valid distribution records for six wild strawberry species in China and data on 20 environmental variables, the geographical distributions of and potentially suitable areas for the wild strawberry species in Yunnan Province (China) under the current climate scenario were explored using the MaxEnt model and ArcGIS software, and major environmental variables affecting their geographical distributions were evaluated. In addition, the spatio-temporal dynamic patterns of the suitable areas for the six wild strawberry species in Yunnan Province in the 2050s and 2070s under the two climate models of RCP2.6 and RCP8.5 were predicted. Under the current climate scenario, the six wild strawberry species have suitable areas in Yunnan Province, which were mainly distributed in the high-altitude and low-temperature regions in the northwest and northeast, such as Diqing and Zhaotong. In addition, the average size of the highly suitable area for diploid wild strawberry species was greater than that for tetraploid species. Under the future climate scenarios, the average size of the highly suitable area for diploid species showed a tendency to expand, while that of tetraploid species showed a tendency to shrink. Altitude was a critical variable affecting the distribution of tetraploid species. Under the two future climate models of RCP2.6 and RCP8.5, the suitable areas for wild strawberry species shifted to the regions of high latitude, high altitude, and low temperature. In addition, the average distance in the shift of the suitable area for tetraploid strawberry species was greater than that for the suitable area for diploid strawberry species. The above results provide valuable information for the management and protection of the germplasm resources of Fragaria

Histological quantitation of brain injury using whole slide imaging: a pilot validation study in mice.

Quantitative assessment of serial brain sections provides an objective measure of neurological events at cellular and molecular levels but is difficult to implement in experimental neuroscience laboratories because of variation from person-to-person and the time required for analysis. Whole slide imaging (WSI) technology, recently introduced for pathological diagnoses, offers an electronic environment and a variety of computational tools for performing high-throughput histological analysis and managing the associated information. In our study, we applied various algorithms to quantify histologic changes associated with brain injury and compared the results to manual assessment. WSI showed a high degree of concordance with manual quantitation by Pearson correlation and strong agreement using Bland-Altman plots in: (i) cortical necrosis in cresyl-violet-stained brain sections of mice after focal cerebral ischemia; (ii) intracerebral hemorrhage in ischemic mouse brains for automated annotation of the small regions, rather than whole hemisphere of the tissue sections; (iii) Iba1-immunoreactive cell density in the adjacent and remote brain regions of mice subject to controlled cortical impact (CCI); and (iv) neuronal degeneration by silver staining after CCI. These results show that WSI, when appropriately applied and carefully validated, is a highly efficient and unbiased tool to locate and identify neuropathological features, delineate affected regions and histologically quantify these events

Two-dimensional zymography differentiates gelatinase isoforms in stimulated microglial cells and in brain tissues of acute brain injuries.

Excessive activation of gelatinases (MMP-2/-9) is a key cause of detrimental outcomes in neurodegenerative diseases. A single-dimension zymography has been widely used to determine gelatinase expression and activity, but this method is inadequate in resolving complex enzyme isoforms, because gelatinase expression and activity could be modified at transcriptional and posttranslational levels. In this study, we investigated gelatinase isoforms under in vitro and in vivo conditions using two-dimensional (2D) gelatin zymography electrophoresis, a protocol allowing separation of proteins based on isoelectric points (pI) and molecular weights. We observed organomercuric chemical 4-aminophenylmercuric acetate-induced activation of MMP-2 isoforms with variant pI values in the conditioned medium of human fibrosarcoma HT1080 cells. Studies with murine BV-2 microglial cells indicated a series of proform MMP-9 spots separated by variant pI values due to stimulation with lipopolysaccharide (LPS). The MMP-9 pI values were shifted after treatment with alkaline phosphatase, suggesting presence of phosphorylated isoforms due to the proinflammatory stimulation. Similar MMP-9 isoforms with variant pI values in the same molecular weight were also found in mouse brains after ischemic and traumatic brain injuries. In contrast, there was no detectable pI differentiation of MMP-9 in the brains of chronic Zucker obese rats. These results demonstrated effective use of 2D zymography to separate modified MMP isoforms with variant pI values and to detect posttranslational modifications under different pathological conditions

Low-Intensity Blast Induces Acute Glutamatergic Hyperexcitability in Mouse Hippocampus Leading to Long-Term Learning Deficits and Altered Expression of Proteins Involved in Synaptic Plasticity and Serine Protease Inhibitors

Neurocognitive consequences of blast-induced traumatic brain injury (bTBI) pose significant concerns for military service members and veterans with the majority of invisible injury. However, the underlying mechanism of such mild bTBI by low-intensity blast (LIB) exposure for long-term cognitive and mental deficits remains elusive. Our previous studies have shown that mice exposed to LIB result in nanoscale ultrastructural abnormalities in the absence of gross or apparent cellular damage in the brain. Here we tested the hypothesis that glutamatergic hyperexcitability may contribute to long-term learning deficits. Using brain slice electrophysiological recordings, we found an increase in averaged frequencies with a burst pattern of miniature excitatory postsynaptic currents (mEPSCs) in hippocampal CA3 neurons in LIB-exposed mice at 1- and 7-days post injury, which was blocked by a specific NMDA receptor antagonist AP5. In addition, cognitive function assessed at 3-months post LIB exposure by automated home-cage monitoring showed deficits in dynamic patterns of discrimination learning and cognitive flexibility in LIB-exposed mice. Collected hippocampal tissue was further processed for quantitative global-proteomic analysis. Advanced data-independent acquisition for quantitative tandem mass spectrometry analysis identified altered expression of proteins involved in synaptic plasticity and serine protease inhibitors in LIB-exposed mice. Some were correlated with the ability of discrimination learning and cognitive flexibility. These findings show that acute glutamatergic hyperexcitability in the hippocampus induced by LIB may contribute to long-term cognitive dysfunction and protein alterations. Studies using this military-relevant mouse model of mild bTBI provide valuable insights into developing a potential therapeutic strategy to ameliorate hyperexcitability-modulated LIB injuries

Integrated Transcriptome and Metabolome Analysis Reveals the Regulatory Mechanisms of <i>FASN</i> in <i>Geese</i> Granulosa Cells

FASN plays a critical role in lipid metabolism, which is involved in regulating ovarian follicular development. However, the molecular mechanisms of how FASN regulate the function of ovarian follicular cells still remain elusive. In this study, by overexpression or interference of FASN in pre-hierarchical follicle granulosa cells (phGCs) and hierarchical follicle granulosa cells (hGCs), we analyzed their effects on the granulosa cell transcriptome and metabolome profiles using RNA-Seq and LC-MS/MS, respectively. The results showed that overexpression of FASN promoted proinflammatory factors expression by activating TLR3/IRF7 and TLR3/NF-κB pathways in phGCs, but only by activating TLR3/IRF7 pathways in hGCs. Then, necroptosis and apoptosis were triggered through the JAK/STAT1 pathway (induced by inflammatory factors) and BAK/caspase-7 pathway, respectively. The combined analysis of the metabolome and transcriptome revealed that FASN affected the demand of GCs for 5-hydroxytryptamine (5-HT) by activating the neuroactive ligand-receptor interaction pathway in two categorized GCs and only altering the metabolic pathway of tryptophan in phGCs, and ultimately participated in regulating the physiological function of geese GCs. Taken together, this study showed that the mechanisms of FASN regulating the physiological function of geese phGCs and hGCs were similar, but they also had some different characteristics