Dexamethasone enhances NT-3 expression in rat hippocampus after traumatic brain injury

A narrative review of the effects of dexamethasone on traumatic brain injury in clinical and animal studies: focusing on inflammation

Traumatic brain injury (TBI) is a type of brain injury resulting from a sudden physical force to the head. TBI can range from mild, such as a concussion, to severe, which might result in long-term complications or even death. The initial impact or primary injury to the brain is followed by neuroinflammation, excitotoxicity, and oxidative stress, which are the hallmarks of the secondary injury phase, that can further damage the brain tissue. Dexamethasone (DXM) has neuroprotective effects. It reduces neuroinflammation, a critical factor in secondary injury-associated neuronal damage. DXM can also suppress the microglia activation and infiltrated macrophages, which are responsible for producing pro-inflammatory cytokines that contribute to neuroinflammation. Considering the outcomes of this research, some of the effects of DXM on TBI include: (1) DXM-loaded hydrogels reduce apoptosis, neuroinflammation, and lesion volume and improves neuronal cell survival and motor performance, (2) DXM treatment elevates the levels of Ndufs2, Gria3, MAOB, and Ndufv2 in the hippocampus following TBI, (3) DXM decreases the quantity of circulating endothelial progenitor cells, (4) DXM reduces the expression of IL1, (5) DXM suppresses the infiltration of RhoA + cells into primary lesions of TBI and (6) DXM treatment led to an increase in fractional anisotropy values and a decrease in apparent diffusion coefficient values, indicating improved white matter integrity. According to the study, the findings show that DXM treatment has neuroprotective effects in TBI. This indicates that DXM is a promising therapeutic approach to treating TBI.

The Roles of Neurotrophins in Traumatic Brain Injury

Neurotrophins are a collection of structurally and functionally related proteins. They play important roles in many aspects of neural development, survival, and plasticity. Traumatic brain injury (TBI) leads to different levels of central nervous tissue destruction and cellular repair through various compensatory mechanisms promoted by the injured brain. Many studies have shown that neurotrophins are key modulators of neuroinflammation, apoptosis, blood–brain barrier permeability, memory capacity, and neurite regeneration. The expression of neurotrophins following TBI is affected by the severity of injury, genetic polymorphism, and different post-traumatic time points. Emerging research is focused on the potential therapeutic applications of neurotrophins in managing TBI. We conducted a comprehensive review by organizing the studies that demonstrate the role of neurotrophins in the management of TBI.

Intranasal delivery of exosomes from human adipose derived stem cells at forty-eight hours post injury reduces motor and cognitive impairments following traumatic brain injury

The neuroprotective role of human adipose-derived stems cells (hASCs) has raised great interest in regenerative medicine due to their ability to modulate their surrounding environment. Our group has demonstrated that exosomes derived from hASC (hASCexo) are a cell-free regenerative approach to long term recovery following traumatic brain injury (TBI). Previously, we demonstrated the efficacy of exosome treatment with intravenous delivery at 3 h post TBI in rats. Here, we show efficacy of exosomes through intranasal delivery at 48 h post TBI in mice lengthening the therapeutic window of treatment and therefore increasing possible translation to clinical studies. Our findings demonstrate significant recovery of motor impairment assessed by an elevated body swing test in mice treated with exosomes containing MALAT1 compared to both TBI mice without exosomes and exosomes depleted of MALAT1. Significant cognitive improvement was seen in the reversal trial of 8 arm radial arm water maze in mice treated with exosomes containing MALAT1. Furthermore, cortical damage was significantly reduced in mice treated with exosomes containing MALAT1 as well as decreased MHCII+ staining of microglial cells. Mice without exosomes or treated with exosomes depleted of MALAT1 did not show similar recovery. Results demonstrate both inflammation related genes and NRTK3 (TrkC) are target genes modulated by hASC exosomes and further that MALAT1 in hASC exosomes regulates expression of full length TrkC thereby activating the MAPK pathway and promoting recovery. Exosomes are a promising therapeutic approach following TBI with a therapeutic window of at least 48 h and contain long noncoding RNA's, specifically MALAT1 that play a vital role in the mechanism of action.

Neuropathic Pain Causes a Decrease in the Dendritic Tree Complexity of Hippocampal CA3 Pyramidal Neurons

The International Pain Association defines neuropathic pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage.” Recent studies show that chronic neuropathic pain causes both morphological and functional changes within brain structures. Due to the impact of supraspinal centers on pain signal processing, patients with chronic pain often suffer from depression, anxiety, memory impairment, and learning disabilities. Changes in hippocampal neuronal and glial plasticity can play a substantial role in the development of these symptoms. Given the special role of the CA3 hippocampal area in chronic stress reactions, we suggested that this region may undergo significant morphological changes as a result of persistent pain. Since the CA3 area is involved in the implementation of hippocampus-dependent memory, changes in the neuronal morphology can cause cognitive impairment observed in chronic neuropathic pain. This study aimed to elucidate the structural and plastic changes within the hippocampus associated with dendritic tree atrophy of CA3 pyramidal neurons in mice with chronic sciatic nerve constriction. Behavioral testing revealed impaired working and long-term memory in mice with a chronic constriction injury. Using the Golgi-Cox method, we revealed a decrease in the number of branches and dendritic length of CA3 pyramidal neurons. The dendritic spine number was decreased, predominantly due to a reduction in mushroom spines. An ­immunohistochemical study showed changes in astro- and microglial activity, which could affect the morphology of neurons both directly and indirectly via the regulation of neurotrophic factor synthesis. Using ELISA, we found a decrease in brain-derived neurotrophic factor production and an increase in neurotrophin-3 production. Morphological and biochemical changes in the CA3 area are accompanied by impaired working and long-term memory of animals. Thus, we can conclude that morphological and biochemical changes within the CA3 hippocampal area may underlie the cognitive impairment in neuropathic pain.

Neurotrophin-3 provides neuroprotection via TrkC receptor dependent pErk5 activation in a rat surgical brain injury model

BACKGROUND

Surgical brain injury (SBI) which occurs due to the inadvertent injury inflicted to surrounding brain tissue during neurosurgical procedures can potentiate blood brain barrier (BBB) permeability, brain edema and neurological deficits. This study investigated the role of neurotrophin 3 (NT-3) and tropomyosin related kinase receptor C (TrkC) against brain edema and neurological deficits in a rat SBI model.

METHODS

SBI was induced in male Sprague Dawley rats by partial right frontal lobe resection. Temporal expression of endogenous NT-3 and TrkC was evaluated at 6, 12, 24 and 72 h after SBI. SBI rats received recombinant NT-3 which was directly applied to the brain surgical injury site using gelfoam. Brain edema and neurological function was evaluated at 24 and 72 h after SBI. Small interfering RNA (siRNA) for TrkC and Rap1 was administered via intracerebroventricular injection 24 h before SBI. BBB permeability assay and western blot was performed at 24 h after SBI.

RESULTS

Endogenous NT-3 was decreased and TrkC expression increased after SBI. Topical administration of recombinant NT-3 reduced brain edema, BBB permeability and improved neurological function after SBI. Recombinant NT-3 administration increased the expression of phosphorylated Rap1 and Erk5. The protective effect of NT-3 was reversed with TrkC siRNA but not Rap1 siRNA.

CONCLUSIONS

Topical application of NT-3 reduced brain edema, BBB permeability and improved neurological function after SBI. The protective effect of NT-3 was possibly mediated via TrkC dependent activation of Erk5.

Traumatic Brain Injury Disrupts Pain Signaling in the Brainstem and Spinal Cord

Chronic pain is a common consequence of traumatic brain injury (TBI) that can increase the suffering of a patient and pose a significant challenge to rehabilitative efforts. Unfortunately, the mechanisms linking TBI to pain are poorly understood, and specific treatments for TBI-related pain are still lacking. Our laboratory has shown that TBI causes pain sensitization in areas distant to the site of primary injury, and that changes in spinal gene expression may underlie this sensitization. The aim of this study was to examine the roles that pain modulatory pathways descending from the brainstem play in pain after TBI. Deficiencies in one type of descending inhibition, diffuse noxious inhibitory control (DNIC), have been suggested to be responsible for the development of chronic pain by allowing excess and uncontrolled afferent nociceptive inputs. Here we expand our knowledge of pain after TBI in two ways: (1) by outlining the neuropathology in pain-related centers of the brain and spinal cord involved in DNIC using the rat lateral fluid percussion (LFP) model of TBI, and (2) by evaluating the effects of a potent histone acetyl transferase inhibitor, anacardic acid (AA), on LFP-induced pain behaviors and neuropathology when administered for several days after TBI. The results revealed that TBI induces transient mechanical allodynia and a chronic persistent loss of DNIC. Further, while short-term AA treatment can block acute nociceptive sensitization and some early neuropathological changes, this treatment neither prevented the loss of DNIC nor did it alter long-term neuropathological changes in the brain or spinal cord.

Neurotrauma: The Crosstalk between Neurotrophins and Inflammation in the Acutely Injured Brain

Traumatic brain injury (TBI) is a major cause of morbidity and mortality among young individuals worldwide. Understanding the pathophysiology of neurotrauma is crucial for the development of more effective therapeutic strategies. After the trauma occurs, immediate neurologic damage is produced by the traumatic forces; this primary injury triggers a secondary wave of biochemical cascades together with metabolic and cellular changes, called secondary neural injury. In the scenario of the acutely injured brain, the ongoing secondary injury results in ischemia and edema culminating in an uncontrollable increase in intracranial pressure. These areas of secondary injury progression, or areas of “traumatic penumbra”, represent crucial targets for therapeutic interventions. Neurotrophins are a class of signaling molecules that promote survival and/or maintenance of neurons. They also stimulate axonal growth, synaptic plasticity, and neurotransmitter synthesis and release. Therefore, this review focuses on the role of neurotrophins in the acute post-injury response. Here, we discuss possible endogenous neuroprotective mechanisms of neurotrophins in the prevailing environment surrounding the injured areas, and highlight the crosstalk between neurotrophins and inflammation with focus on neurovascular unit cells, particularly pericytes. The perspective is that neurotrophins may represent promising targets for research on neuroprotective and neurorestorative processes in the short-term following TBI.

Dexamethasone reduces brain cell apoptosis and inhibits inflammatory response in rats with intracerebral hemorrhage

Spontaneous intracerebral hemorrhage (ICH) is associated with high rates of mortality and morbidity. Thus, the identification of novel therapeutic agents for preventing strokes and attenuating poststroke brain damage is crucial. Dexamethasone (DEX) is used clinically to reduce edema formation in patients with spinal cord injury and brain tumors. In this study, we sought to elucidate the effects of DEX treatment on apoptosis and inflammation following ICH in rats. A high dose of DEX (15 mg/kg) was administered immediately following ICH induction and again 3 days later. The inflammatory and apoptotic responses in the rat brains were evaluated by using hematoxylin-eosin, terminal deoxynucleotidyl transferase dUTP nick end labeling, Nissl, and neurofilament-H staining. Levels of phosphorylated neurofilaments and apoptosis-related proteins such as B-cell lymphoma 2 (Bcl-2), Bcl-2 associated X protein (Bax), caspase-3, and P53 were analyzed by Western blotting. This study shows that rats without ICH that received DEX treatment had a fourfold higher expression of Bcl-2 than sham-operated rats. ICH causes an increase in Bax, cleaved caspase-3, and P53 proteins from 4 hr to 7 days following ICH induction. In comparison with the ICH rats, the ICH/DEX rats showed significantly decreased apoptotic cell death and increased neuron survival and maintained neurofilament integrity in the perihematomal region. DEX increased the Bcl-2/Bax ratio and lowered the expression of cleaved caspase-3 at 12 hr and 5 days. The ICH rats were accompanied by activation of the inflammatory response, and DEX treatment modulated the expression of a variety of cell types and then decreased ICH-induced apoptosis.

Lettuce glycoside B ameliorates cerebral ischemia reperfusion injury by increasing nerve growth factor and neurotrophin-3 expression of cerebral cortex in rats

AIMS

The aim of the study was to investigate the effects of LGB on cerebral ischemia-reperfusion (I/R) injury in rats and the mechanisms of action of LGB.

MATERIALS AND METHODS

The study involved extracting LGB from P. laciniata, exploring affects of LGB on brain ischemia and action mechanism at the molecular level. The cerebral ischemia reperfusion injury of middle cerebral artery occlusion was established. We measured brain histopathology and brain infarct rate to evaluate the effects of LGB on brain ischemia injury. The expressions of nerve growth factor (NGF) and neurotrophin-3 (NT-3) were also measured to investigate the mechanisms of action by the real-time polymerase chain reaction and immunohistochemistry.

STATISTICAL ANALYSIS

All results were mentioned as mean ± standard deviation. One-way analysis of variance was used to determine statistically significant differences among the groups. Values of P < 0.05 were considered to be statistically significant.

RESULTS

Intraperitoneal injection of LGB at the dose of 12, 24, and 48 mg/kg after brain ischemia injury remarkably ameliorated the morphology of neurons and brain infarct rate (P < 0.05, P < 0.01). LGB significantly increased NGF and NT-3 mRNA (messenger RNA) and both protein expression in cerebral cortex at the 24 and 72 h after drug administration (P < 0.05, P < 0.01).

CONCLUSIONS

LGB has a neuroprotective effect in cerebral I/R injury and this effect might be attributed to its upregulation of NGF and NT-3 expression ability in the brain cortex during the latter phase of brain ischemia.

Polybutylcyanoacrylate nanoparticles for delivering hormone response element-conjugated neurotrophin-3 to the brain of intracerebral hemorrhagic rats

Hypertensive intracerebral hemorrhage (ICH) is a rapidly evolutional pathology, inducing necrotic cell death followed by apoptosis, and alters gene expression levels in surrounding tissue of an injured brain. For ICH therapy by controlled gene release, the development of intravenously administrable delivery vectors to promote the penetration across the blood-brain barrier (BBB) is a critical challenge. To enhance transfer efficiency of genetic materials under hypoxic conditions, polybutylcyanoacrylate (PBCA) nanoparticles (NPs) were used to mediate the intracellular transport of plasmid neurotrophin-3 (NT-3) containing hormone response element (HRE) with a cytomegalovirus (cmv) promoter and to differentiate induced pluripotent stem cells (iPSCs). The differentiation ability of iPSCs to neurons was justified by various immunological stains for protein fluorescence. The effect of PBCA NP/cmvNT-3-HRE complexes on treating ICH rats was studied by immunostaining, western blotting and Nissl staining. We found that the treatments with PBCA NP/cmvNT-3-HRE complexes increased the capability of differentiating iPSCs to express NT-3, TrkC and MAP-2. Moreover, PBCA NPs could protect cmvNT-3-HRE against degradation with EcoRI/PstI and DNase I in vitro and raise the delivery across the BBB in vivo. The administration of PBCA NP/cmvNT-3-HRE complexes increased the expression of NT-3, inhibited the expression of apoptosis-inducing factor, cleaved caspase-3 and DNA fragmentation, and reduced the cell death rate after ICH in vivo. PBCA NPs are demonstrated as an appropriate delivery system for carrying cmvNT-3-HRE to the brain for ICH therapy.

Polybutylcyanoacrylate nanoparticle-mediated neurotrophin-3 gene delivery for differentiating iPS cells into neurons

Guided neuronal differentiation of induced pluripotent stem cells (iPSCs) with genetic regulation is an important issue in biomedical research and in clinical practice for nervous regeneration and repair. To enhance the intracellular delivery of plasmid DNA (pDNA), polybutylcyanoacrylate (PBCA) nanoparticles (NPs) were employed to mediate the transport of neurotrophin-3 (NT-3) into iPSCs. The ability of iPSCs to differentiate into neuronal lineages was shown by immunofluorescent staining, western blotting, and flow cytometry. By transmission electron microscopy, we found that PBCA NPs could efficiently grasp pDNA, thereby increasing the particle size and conferring a negative surface charge. In addition, the treatments with PBCA NP/NT-3 complexes enhanced the expression of NT-3, TrkC, NH-H, NSE, and PSD95 by differentiating iPSCs. Neurons produced from iPSCs were incapable of returning to pluripotency, demonstrating with a series of differentiation scheme for adipogenesis and osteogenesis. The pretreatment with PBCA NP/NT-3 complexes can be one of critical biotechnologies and effective delivery systems in gene transfection to accelerate the differentiation of iPSCs into neurons.

Neurotrophin-3 mRNA a putative target of miR21 following status epilepticus

Status epilepticus induces a cascade of protein expression changes contributing to the subsequent development of epilepsy. By identifying the cascade of molecular changes that contribute to the development of epilepsy we hope to be able to design therapeutics for preventing epilepsy. MicroRNAs influence gene expression by altering mRNA stability and/or translation and have been implicated in the pathology of multiple diseases. MiR21 and its co-transcript miR21, microRNAs produced from either the 5' or 3' ends of the same precursor RNA strand, are increased in the hippocampus following status epilepticus. We have identified a miR21 binding site, in the 3' UTR of neurotrophin-3 that inhibits translation. Neurotrophin-3 mRNA levels decrease in the hippocampus following SE concurrent with the increase in miR21. MiR21 levels in cultured hippocampal neurons inversely correlate with neurotrophin-3 mRNA levels. Treatment of hippocampal neuronal cultures with excess K(+)Cl(-), a depolarizing agent mimicking the episode of status epilepticus, also results in an increase in miR21 and a decrease in neurotrophin-3 mRNA. MiR21 is a candidate for regulating neurotrophin-3 signaling in the hippocampus following status epilepticus.

Small molecule activators of the Trk receptors for neuroprotection

The neurotrophin signaling network is critical to the development and survival of many neuronal populations. Especially sensitive to imbalances in the neurotrophin system, cholinergic neurons in the basal forebrain are progressively lost in Alzheimer's disease. Therapeutic use of neurotrophins to prevent this loss is hampered, however, by a number of pharmacological challenges. These include a lack of transport across the blood-brain barrier, rapid degradation in the circulation, and difficulty in production. In this review we discuss the evidence supporting the neurotrophin system's role in preventing neurodegeneration and survey some of the pharmacological strategies being pursued to develop effective therapeutics targeting neurotrophin function.

Differential striatal levels of TNF-alpha, NFkappaB p65 subunit and dopamine with chronic typical and atypical neuroleptic treatment: role in orofacial dyskinesia

Long term use of typical neuroleptics such as haloperidol may be limited by unwanted motor side effects like tardive dyskinesia characterized by repetitive involuntary movements, involving the mouth, face and trunk. Atypical neuroleptics, such as clozapine and risperidone are devoid of these side effects. However the precise mechanisms of the neuronal toxicity induced by haloperidol are poorly understood. It is possible that typical and atypical antipsychotic differently affects neuronal survival and death and that these effects considerably contribute to the differences in the development of TD. The aim of the present study is to investigate the role of TNF-alpha and NFkappaB on the toxicity induced by chronic haloperidol administration in an animal model of tardive dyskinesia. Rats were treated for 21 days with: haloperidol (5 mg/kg), clozapine (5 and 10 mg/kg), risperidone (5 mg/kg) or saline. Orofacial dyskinetic movements and total locomotor activity was evaluated. Striatal levels of dopamine were measure by HPLC/ED whereas striatal levels of TNF-alpha and NFkappaB p65 subunit were measured by ELISA technique. Haloperidol increased orofacial dyskinetic movements and total locomotor activity (on day 22) (P<or=0.05). Clozapine and risperidone also increased the orofacial dyskinetic movements but that significantly less than haloperidol (P<or=0.05). Differential effect of haloperidol and atypical neuroleptics on striatal dopamine levels and striatal levels of TNF-alpha and NFkappaB p65 subunit was found out. Haloperidol significantly decreased the striatal dopamine levels whereas clozapine and risperidone did not. Haloperidol but not clozapine and risperidone significantly increased the levels of TNF-alpha and NFkappaB p65 subunit (P<or=0.05). The present study suggests the impossible involvement of striatal TNF-alpha and NFkappaB p65 subunit in haloperidol-induced orofacial dyskinesia in rats, an animal model for human tardive dyskinesia.

Dexamethasone suppresses infiltration of RhoA+ cells into early lesions of rat traumatic brain injury

Inflammatory cell infiltration is a major part of secondary tissue damage in traumatic brain injury (TBI). RhoA is an important member of Rho GTPases and is involved in leukocyte migration. Inhibition of RhoA and its downstream target, Rho-associated coiled kinase (ROCK), has been proven to promote axon regeneration and function recovery following injury in the central nervous system (CNS). Previously, we showed that dexamethasone, an immunosuppressive corticosteroid, attenuated early expression of three molecules associated with microglia/macrophages activation following TBI in rats. Here, the effects of dexamethasone on the early expression of RhoA have been investigated in brains of TBI rats by immunohistochemistry. In brains of rats treated with TBI alone, significant RhoA+ cell accumulation was observed at 18 h post-injury and continuously increased during our observed time period. The accumulated RhoA+ cells were distributed to the areas of pannecrosis and selective neuronal loss. Most accumulated RhoA+ cells were identified as active microglia/macrophages by double-labelling. Dexamethasone (1 mg/kg body weight) was intraperitoneally injected on day 0 and 2 immediately following brain injury. Numbers of RhoA+ cells were significantly reduced on day 1 and 2 following administration of dexamethasone but returned to vehicle control level on day 4. However, dexamethasone treatment did not change the proportion of RhoA+ cells. These observations suggest that dexamethasone has only a transient effect on early leukocyte recruitment.

Neurotrophins modulate monocyte chemotaxis without affecting macrophage function

Neurotrophins nerve growth factor (NGF), brain-derived growth factor (BDNF), neurotrophin-3 (NT-3) and neurotrophin-4 (NT-4) and their high-affinity tyrosine protein kinase receptor (Trk) family, TrkA, TrkB, TrkC, and low-affinity p75(NTR) receptor, are key molecules implicated in the development of the central nervous system. Increasing evidence suggests that they also have physiological and pathological roles outside the nervous system. In this study we examined the expression of neurotrophins and their receptors in human activated macrophages and to what extent neurotrophins themselves modulate macrophage activation, in a model of primary adult monocyte-derived macrophage. Our data indicate that macrophages express neurotrophin and neurotrophin receptor genes differentially, and respond to cell stimulation by specific inductions. Neurotrophins did not modify the antigen-presenting capacities of macrophages or their production of proinflammatory cytokines, but somehow skewed their activation phenotype. In contrast, NGF clearly increased CXCR-4 expression in macrophage and their chemotactic response to low CXCL-12 concentration. The differential effect of specific macrophage stimuli on neurotrophin expression, in particular NGF and NT-3, and the specific enhancement of CXCR-4 expression suggest that neurotrophins might participate in tissue-healing mechanisms that should be investigated further in vivo.

The cell cycle hypothesis of Alzheimer's disease: Suggestions for drug development

The cell cycle of hypothesis of neural dysfunction in chronic neurodegenerative conditions such as Alzheimer's disease (AD) offers a unified approach to understanding both existing and novel strategies for drug development. At the present time, a ligand based approach is a pragmatic solution for identifying new chemical leads on which to base future discovery and optimisation. We have pursued a ligand based approach on the basis of public domain data to identify existing compounds capable of abrogating the cell cycle at the G0-G1 interface. Selected on this basis, irrespective of the tissue under study, we identified several classes of compounds as potential chemical leads. Of these compounds, at least ten have already been shown to be neuroprotective in animal models of acute neurodegeneration. Such compounds could form the basis of a screening exercise after development of suitable screening tools. Progressing of chemical leads through such an approach will be more efficient if future leads display relevant "drug-like" properties. Further, drug development in this arena should take account of the special concerns raised by targeting an elderly population. This will involve accounting for frequent polypharmacy in the aging population, and age-related alterations in physiology.

Role of nigral NFkappaB p50 and p65 subunit expression in haloperidol-induced neurotoxicity and stereotyped behavior in rats

Long-term use of typical neuroleptics such as haloperidol may be limited by unwanted motor side effects like tardive dyskinesia (TD) characterized by repetitive involuntary movements, involving the mouth, face and tongue. TD generally persists after haloperidol withdrawal indicating long lasting changes in brain function that are no longer related to the presence of the drug. The precise mechanisms of the neuronal toxicity induced by haloperidol are poorly understood. Haloperidol has been shown to induce the expression of the transcription factor nuclear factor-kappaB (NFkappaB). NFkappaB resembles a heterodimer protein composed of a 50 and a 65 kDa subunits and the role of the NFkappaB subunits on haloperidol-induced toxicity remains still unknown. The aim of the present study is to investigate the role of the p65 and p50 subunits of NFkappaB on the toxicity induced by chronic haloperidol administration in an experimental model of TD. Rats were treated for 21 days with: haloperidol (1mg/kg), clozapine (1mg/kg) or saline. Apomorphine-induced stereotyped behavior was evaluated. Striatal expression of the dopamine transporter (DAT) and the nigral expression of the NFkappaB p65 and p50 subunits were measured by Western Blot. Haloperidol, but not clozapine, increased stereotyped behavior associated to a decreased striatal DAT expression (p<0.01). Haloperidol did not modify the nigral expression of the p65 subunit whereas clozapine decreased it (p<0.01). Both drugs induced a significant decrease in the nigral expression of the NFkappaB p50 (p<0.05 and p<0.01, respectively). The decrease in nigral expression of the p50 subunit may increase the vulnerability of the dopaminergic neurons to a possible neurotoxic effect of p65 subunits in the haloperidol-treated rats.

Glucocorticoid receptors modulate auditory sensitivity to acoustic trauma

Glucocorticoids are widely used to treat different hearing disorders yet the exact mechanisms of glucocorticoid action on the inner ear are not known. The inner ear of both humans and experimental animals demonstrate an abundance of glucocorticoid receptors (GRs) in both neuronal and non-neuronal tissues. In this review, we discuss how activation of the hypothalamic-pituitary-adrenal axis can directly modulate hearing sensitivity. Recent findings indicate that several factors define the responsiveness of the peripheral auditory system to glucocorticoids including the concentration of agonist, availability of the GR, and the activation of GR and NF-kappaB. These findings will further our understanding of individual glucocorticoid responsiveness to steroid treatment, and will help improve the development of pharmaceuticals to selectively target GR in the inner ear for individuals with increased sensitivity to acoustic trauma.

Potentiation of neurite outgrowth and reduction of apoptosis by immunosuppressive agents: implications for neuronal injury and transplantation

Object

Immunosuppressive agents are believed to play a role in recovery from spinal cord injury, but the underlying mechanisms by which neuronal function is improved by these agents are poorly understood. In this study, the authors evaluate the effect of immunosuppressive medications on neurite outgrowth and cell survival after a pharmacologically induced injury.

Methods

Differentiated human neuroblastoma SH-SY5Y cells were injured using the calcium agonist thapsigargin. After cellular injury, neurite outgrowth in the presence or absence of immunosuppressive agents was measured. Apoptosis was quantified with the aid of a terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick-end labeling assay.

Neurite outgrowth was severely restricted following thapsigargin injury. Outgrowth was potentiated, however, by the addition of concentrations of 1 and 10 μM cyclosporin A in a dose-dependent fashion. Similarly, addition of 10 nM FK506 increased the percentage of neurites in the 20- to 40-micron range. A low dose (1 μM) of dexamethasone did not have a significant effect on neurite outgrowth, but a higher dose (10 μM) increased the percentage of neurites in the 10- to 45-micron range. These agents also lessened the degree of thapsigargin-induced apoptosis.

Conclusions

Immunosuppressive agents such as cyclosporin A, FK506, and dexamethasone can potentiate neurite outgrowth and protect against apoptotic cell death in a human postmitotic neuronal cell line. Such effects may have implications for lessening neuronal injury after neurotrauma, stroke, or neurodegeneration.

Apoptosis-Related Gene Bcl-2 in Lung Tissue After Experimental Traumatic Brain Injury in Rats

BACKGROUND

We have recently shown that experimental traumatic brain injury resulted in ultra structural damage in lung tissue. The main objective of the current study was to investigate in a rat model of brain injury whether expression of Bcl-2 gene and lipid peroxidation levels in the lung tissue after traumatic brain injury were affected by methylprednisolone sodium succinate (MPSS) treatment.

METHODS

Fifty-six Wistar-Albino female rats weighing 180-220 g were used, which were allocated into seven groups. A weight-drop method was used to achieve head trauma. Real time quantitative PCR analyses for Bcl-2 gene expression and measurement of the levels of lipid peroxidation were carried out. All the data was analyzed by using SPSS 11.5 for Windows.

RESULTS

Mean Bcl-2 expression in the methylprednisolone group was considerably higher compared to that of all the other groups (p<.05). Mean lipid peroxidation levels were significantly higher in the trauma group and notably lower in the methylprednisolone group (p<.01).

CONCLUSIONS

The oxidative stress imposed on lung tissue, as seen by high levels of lipid peroxidation, after brain injury was significantly attenuated by MPSS treatment. MPSS treatment following brain injury also augmented putative anti-apoptotic Bcl-2 gene expression in lung tissue. Further studies are required to determine the full range and lower limits of effective MPSS dose. More importantly the optimal efficacy according to the timing of MPSS treatment after brain injury needs to be determined for impact on more diverse markers of cell inflammation, apoptosis and injury.