The reaction of cerebral cortex to a nearby lesion: damage, survival, self-protection

Acute Response and Neuroprotective Role of Myo/Nog Cells Assessed in a Rat Model of Focal Brain Injury

Focal brain injury in the form of a needlestick (NS) results in cell death and induces a self-protective response flanking the lesion. Myo/Nog cells are identified by their expression of bone morphogenetic protein inhibitor Noggin, brain-specific angiogenesis inhibitor 1 (BAI1) and the skeletal muscle specific transcription factor MyoD. Myo/Nog cells limit cell death in two forms of retinopathy. In this study, we examined the acute response of Myo/Nog cells to a NS lesion that extended from the rat posterior parietal cortex to the hippocampus. Myo/Nog cells were identified with antibodies to Noggin and BAI1. These cells were the primary source of both molecules in the uninjured and injured brain. One day after the NS, the normally small population of Myo/Nog cells expanded approximately eightfold within a 1 mm area surrounding the lesion. Myo/Nog cells were reduced by approximately 50% along the lesion with an injection of the BAI1 monoclonal antibody and complement. The number of dying cells, identified by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL), was unchanged at this early time point in response to the decrease in Myo/Nog cells. However, increasing the number of Myo/Nog cells within the lesion by injecting BAI1-positive (+) cells isolated from the brains of other animals, significantly reduced cell death and increased the number of NeuN+ neurons compared to brains injected with phosphate buffered saline or exogenous BAI1-negative cells. These findings demonstrate that Myo/Nog cells rapidly react to injury within the brain and increasing their number within the lesion is neuroprotective.

Hydrogen and therapeutic gases for neonatal hypoxic-ischemic encephalopathy: potential neuroprotective adjuncts in translational research

Numerous studies have examined the potential use of therapeutic gases for the treatment of various neurological disorders. Hydrogen gas, a promising neuroprotective agent, has been a focus of study due to its potent antioxidative properties. In translational research into adult diseases, hydrogen has been shown to be neuroprotective in disorders such as cerebral ischemia and traumatic brain injury, and in neurodegenerative diseases such as Alzheimer's disease. Animal and human studies have verified the safety and feasibility of molecular hydrogen. However, despite extensive research on its efficacy in adults, only a few studies have investigated its application in pediatric and neonatal medicine. Neonatal hypoxic-ischemic encephalopathy (HIE) is characterized by damage to neurons and other cells of the nervous system. One of the major contributing factors is excessive exposure to oxidative stress. Current research interest in HIE is shifting toward new neuroprotective agents, as single agents or as adjuncts to therapeutic hypothermia. Here, we review therapeutic gases, particularly hydrogen, and their potentials and limitations in the treatment of HIE in newborns. IMPACT: Translational animal models of neonatal HIE are a current focus of research into the therapeutic usefulness of various gases. Hydrogen ventilation as a single agent or in combination with therapeutic hypothermia shows short- and long-term neuroprotection in neonatal translational HIE models. The optimal target severity for therapeutic interventions should be well established to improve outcomes.

Vi4-miR-185-5p-Igfbp3 Network Protects the Brain From Neonatal Hypoxic Ischemic Injury via Promoting Neuron Survival and Suppressing the Cell Apoptosis

Neonatal hypoxic ischemic encephalopathy (HIE) due to birth asphyxia is common and causes severe neurological deficits, without any effective therapies currently available. Neuronal death is an important driving factors of neurological disorders after HIE, but the regulatory mechanisms are still uncertain. Long non-coding RNA (lncRNA) or ceRNA network act as a significant regulator in neuroregeneration and neuronal apoptosis, thus owning a great potential as therapeutic targets in HIE. Here, we found a new lncRNA, is the most functional in targeting the Igfbp3 gene in HIE, which enriched in the cell growth and cell apoptosis processes. In addition, luciferase reporter assay showed competitive regulatory binding sites to the target gene Igfbp3 between TCONS00044054 (Vi4) and miR-185-5p. The change in blood miR-185-5p and Igfbp3 expression is further confirmed in patients with brain ischemia. Moreover, Vi4 overexpression and miR-185-5p knock-out promote the neuron survival and neurite growth, and suppress the cell apoptosis, then further improve the motor and cognitive deficits in rats with HIE, while Igfbp3 interfering got the opposite results. Together, Vi4-miR-185-5p-Igfbp3 regulatory network plays an important role in neuron survival and cell apoptosis and further promote the neuro-functional recovery from HIE, therefore is a likely a drug target for HIE therapy.

A Putative Role of Teneurin-2 and Its Related Proteins in Astrocytes

Teneurins are type II transmembrane proteins comprised of four phylogenetically conserved homologs (Ten-1-4) that are highly expressed during neurogenesis. An additional bioactive peptide named teneurin C-terminal-associated peptide (TCAP-1-4) is present at the carboxyl terminal of teneurins. The possible correlation between the Ten/TCAP system and brain injuries has not been explored yet. Thus, this study examined the expression of these proteins in the cerebral cortex after mechanical brain injury. Adult rats were subjected to cerebral cortex injury by needle-insertion lesion and sacrificed at various time points. This was followed by analysis of the lesion area by immunohistochemistry and conventional RT-PCR techniques. Control animals (no brain injury) showed only discrete Ten-2-like immunoreactive pyramidal neurons in the cerebral cortex. In contrast, Ten-2 immunoreactivity was significantly up-regulated in the reactive astrocytes in all brain-injured groups (p < 0.0001) when compared to the control group. Interestingly, reactive astrocytes also showed intense immunoreactivity to LPHN-1, an endogenous receptor for the Ten-2 splice variant named Lasso. Semi-quantitative analysis of Ten-2 and TCAP-2 expression revealed significant increases of both at 48 h, 3 days and 5 days (p < 0.0001) after brain injury compared to the remaining groups. Immortalized cerebellar astrocytes were also evaluated for Ten/TCAP expression and intracellular calcium signaling by fluorescence microscopy after TCAP-1 treatment. Immortalized astrocytes expressed additional Ten/TCAP homologs and exhibited significant increases in intracellular calcium concentrations after TCAP-1 treatment. This study is the first to demonstrate that Ten-2/TCAP-2 and LPHN-1 are upregulated in reactive astrocytes after a mechanical brain injury. Immortalized cerebellar astrocytes expressed Ten/TCAP homologs and TCAP-1 treatment stimulated intracellular calcium signaling. These findings disclose a new functional role of the Ten/TCAP system in astrocytes during tissue repair of the CNS.

Refinement of a chronic cranial window implant in the rat for longitudinal in vivo two-photon fluorescence microscopy of neurovascular function

Longitudinal studies using two–photon fluorescence microscopy (TPFM) are critical for facilitating cellular scale imaging of brain morphology and function. Studies have been conducted in the mouse due to their relatively higher transparency and long term patency of a chronic cranial window. Increasing availability of transgenic rat models, and the range of established behavioural paradigms, necessitates development of a chronic preparation for the rat. However, surgical craniotomies in the rat present challenges due to craniotomy closure by wound healing and diminished image quality due to inflammation, restricting most rat TPFM experiments to acute preparations. Long-term patency is enabled by employing sterile surgical technique, minimization of trauma with precise tissue handling during surgery, judicious selection of the size and placement of the craniotomy, diligent monitoring of animal physiology and support throughout the surgery, and modification of the home cage for long-term preservation of cranial implants. Immunohistochemical analysis employing the glial fibrillary acidic protein (GFAP) and ionized calcium-binding adaptor molecule-1 (Iba-1) showed activation and recruitment of astrocytes and microglia/macrophages directly inferior to the cranial window at one week after surgery, with more diffuse response in deeper cortical layers at two weeks, and amelioration around four weeks post craniotomy. TPFM was conducted up to 14 weeks post craniotomy, reaching cortical depths of 400 µm to 600 µm at most time-points. The rate of signal decay with increasing depth and maximum cortical depth attained had greater variation between individual rats at a single time-point than within a rat across time.

Acquired Resilience: An Evolved System of Tissue Protection in Mammals

This review brings together observations on the stress-induced regulation of resilience mechanisms in body tissues. It is argued that the stresses that induce tissue resilience in mammals arise from everyday sources: sunlight, food, lack of food, hypoxia and physical stresses. At low levels, these stresses induce an organised protective response in probably all tissues; and, at some higher level, cause tissue destruction. This pattern of response to stress is well known to toxicologists, who have termed it hormesis. The phenotypes of resilience are diverse and reports of stress-induced resilience are to be found in journals of neuroscience, sports medicine, cancer, healthy ageing, dementia, parkinsonism, ophthalmology and more. This diversity makes the proposing of a general concept of induced resilience a significant task, which this review attempts. We suggest that a system of stress-induced tissue resilience has evolved to enhance the survival of animals. By analogy with acquired immunity, we term this system 'acquired resilience'. Evidence is reviewed that acquired resilience, like acquired immunity, fades with age. This fading is, we suggest, a major component of ageing. Understanding of acquired resilience may, we argue, open pathways for the maintenance of good health in the later decades of human life.

Protection by Neuroglobin Expression in Brain Pathologies

Astrocytes play an important role in physiological, metabolic, and structural functions, and when impaired, they can be involved in various pathologies including Alzheimer, focal ischemic stroke, and traumatic brain injury. These disorders involve an imbalance in the blood flow and nutrients such as glucose and lactate, leading to biochemical and molecular changes that cause neuronal damage, which is followed by loss of cognitive and motor functions. Previous studies have shown that astrocytes are more resilient than neurons during brain insults as a consequence of their more effective antioxidant systems, transporters, and enzymes, which made them less susceptible to excitotoxicity. In addition, astrocytes synthesize and release different protective molecules for neurons, including neuroglobin, a member of the globin family of proteins. After brain injury, neuroglobin expression is induced in astrocytes. Since neuroglobin promotes neuronal survival, its increased expression in astrocytes after brain injury may represent an endogenous neuroprotective mechanism. Here, we review the role of neuroglobin in the central nervous system, its relationship with different pathologies, and the role of different factors that regulate its expression in astrocytes.

Thyroid hormone modulates neuroglobin and cytoglobin in rat brain

Thyroid hormones (THs) are essential and crucial for brain development, playing a role in growth and differentiation. Two globins named neuroglobin (Ngb) and cytoglobin (Cygb) are located in the brain, and each one has different distribution and function: They seem to have similar action by providing O(2) for respiratory chain, and detoxification of reactive oxygen species (ROS) and nitric oxide (NO) protecting tissues against irreversible lesions. We aimed to investigate the influence of thyroid state in Ngb and Cygb metabolism in different brain regions and evaluate their responses in cerebellum, hippocampus and cerebral cortex (hereafter called as cortex) after supraphysiological doses at different time points of TH administration. Experiments were carried out in rats, divided in eight experimental groups Control (C), thyroidectomy (Tx), and thyroidectomy treated with jugular intravenous injection (i.v). T3 (100 μl/100 g) injection and sacrificed after 30, 60, 120 min and 6, 12 and 24 h. In cortex, we found increase in Ngb gene and protein expression in different time points compared to C group, however Cygb gene and protein expression were decreased. In hippocampus, Ngb and Cygb protein expression increased 24 h after i.v. T3 injection in comparison to Tx. In cerebellum, we found increased Ngb gene expression after 120 min, 6, 12 and 24 h after T3 administration compared to Tx, and in contrast, protein expression was found to be significantly increased only 12 and 24 h compared to Tx. Ngb and Cygb expression in brain is influenced by thyroid hormone state both by its lack or excess.