Hemolytic iron regulation in traumatic brain injury and alcohol use.

Hemorrhage is a major component of traumatic brain injury (TBI). Red blood cells, accumulated at the hemorrhagic site, undergo hemolysis upon energy depletion and release free iron into the central nervous system. This iron must be managed to prevent iron neurotoxicity and ferroptosis. As prior alcohol consumption is often associated with TBI, we examined iron regulation in a rat model of chronic alcohol feeding subjected to fluid percussion-induced TBI. We found that alcohol consumption prior to TBI altered the expression profiles of the lipocalin 2/heme oxygenase 1/ferritin iron management system. Notably, unlike TBI alone, TBI following chronic alcohol consumption sustained the expression of all three regulatory proteins for 1, 3, and 7 days post-injury. In addition, alcohol significantly affected TBI-induced expression of ferritin light chain at 3 days post-injury. We also found that alcohol exacerbated TBI-induced activation of microglia at 7 days post-injury. Finally, we propose that microglia may also play a role in iron management through red blood cell clearance.

Synergistic effects of alcohol and HIV TAT protein on macrophage migration and neurotoxicity.

The trans-activator of transcription (TAT) is a human immunodeficiency virus (HIV-1) regulatory protein that is actively sloughed by infected cells. Once released, TAT can injure bystander cells and bring about their dysfunction. In the presence of ethanol, TAT-induced toxicity potentiates and, in so doing, exacerbates inflammation. One key aspect of neuroinflammation involves the infiltration of peripheral macrophage to the central nervous system. Here, we use an interactive neuroimmune cell coculture of brain endothelial, astrocyte, neuron, and macrophage cells to model the blood-brain barrier and evaluate macrophage migration upon challenge with ethanol and TAT concentrations. We have limited this study to examine TAT concentrations found in people living with HIV-1 with (5 ng/mL) or without (25 ng/mL) viral suppression and ethanol doses below the legal driving limit (10 mM). In so doing, we study the effects of casual drinking on people living with HIV-1 but experiencing the best possible clinical outcome. We found that TAT alone increases macrophage migration between 0.5 and 4 h. while ethanol alone increases migration in a delayed manner (occurring at 48 h.). Ethanol-induced NO production by endothelial cells and TAT's chemoattractant properties may explain this dichotomy in migration pattern. Combined low dose ethanol significantly increased migration under both 5 ng/mL and 25 ng/mL TAT injuries across all timepoints. Our findings suggest that co-presence of ethanol and TAT may be the combination of an initial TAT effect followed by subsequent ethanol treatment. We also examined the structural and behavioral changes of neurons treated with TAT and ethanol to understand their contribution to neurotoxicity. The lowest concentration of TAT still induced neurotoxicity while alcohol potentiated neuronal death, even at low doses.

Possible mechanisms of HIV neuro-infection in alcohol use: Interplay of oxidative stress, inflammation, and energy interruption.

Alcohol use and HIV-1 infection have a pervasive impact on brain function, which extends to the requirement, distribution, and utilization of energy within the central nervous system. This effect on neuroenergetics may explain, in part, the exacerbation of HIV-1 disease under the influence of alcohol, particularly the persistence of HIV-associated neurological complications. The objective of this review article is to highlight the possible mechanisms of HIV/AIDS progression in alcohol users from the perspective of oxidative stress, neuroinflammation, and interruption of energy metabolism. These include the hallmark of sustained immune cell activation and high metabolic energy demand by HIV-1-infected cells in the central nervous system, with at-risk alcohol use. Here, we discussed the point that the increase in energy supply requirement by HIV-1-infected neuroimmune cells as well as the deterrence of nutrient uptake across the blood-brain barrier significantly depletes the energy source and neuro-environment homeostasis in the CNS. We also described the mechanistic idea that comorbidity of HIV-1 infection and alcohol use can cause a metabolic shift and redistribution of energy usage toward HIV-1-infected neuroimmune cells, as shown in neuropathological evidence. Under such an imbalanced neuro-environment, meaningless energy waste is expected in infected cells, along with unnecessary malnutrition in non-infected neuronal cells, which is likely to accelerate HIV neuro-infection progression in alcohol use. Thus, it will be important to consider the factor of nutrients/energy imbalance in formulating treatment strategies to help impede the progression of HIV-1 disease and associated neurological disorders in alcohol use.

Biphasic Effects of Ethanol Exposure on Waste Metabolites Clearance in the CNS.

We have shown that the effects of low-dose ethanol promote the clearance of waste metabolites, such as amyloid-beta (Aß) proteins, from the brain through the perivascular space (PVS). We demonstrated that dilative reactivity of arterial smooth muscle and endothelial cells regulate this clearance. These findings indicate the importance of blood-brain barrier (BBB) transvascular clearance of large size metabolites from the central nervous system (CNS), where the lymphatic clearance system is absent. We next examined the contrasting effects of acute low-dose and chronic moderate ethanol exposure on BBB-associated perivascular clearance. We injected a high molecular weight fluorescent dye into the interstitial space or directly into the cerebrospinal fluid (CSF). Bio-distribution of this tracer was then examined in different brain regions by multiphoton imaging and whole brain tissue section scanning. Ethanol-induced molecular/cellular mechanisms that drive the increase or decrease in movement of the fluorescent tracer were correlated to BBB integrity and arterial vessel reactivity. We found that activation of endothelial nitric oxide synthase (eNOS) under low-dose ethanol conditions with a shift to activation of inducible NOS (iNOS) under chronic high ethanol exposure conditions, which appeared to regulate these contrasting effects. We validated these observations by qualitative and quantitative investigation of eNOS, iNOS, BBB integrity, and perivascular clearance of waste metabolites. We concluded that the effects of low-dose ethanol increased the diffusive movement of waste metabolites via eNOS-derived NO, which increased the arterial endothelial-smooth muscle cell dilative reactivity without affecting BBB integrity, whereas a prolonged induction of iNOS under chronic ethanol exposure conditions caused oxidative damage of the arterial endothelial-smooth muscle layers resulting in cerebral amyloid-like angiopathy. This led to dysfunction of the BBB, dilative reactivity, and impaired waste metabolites movement from the interstitial space or subarachnoid space (SAS) through perivascular clearance.

In vivo Neuroprotective Effect of a Self-assembled Peptide Hydrogel.

Traumatic brain injury (TBI) is associated with poor intrinsic healing responses and long-term cognitive decline. A major pathological outcome of TBI is acute glutamate-mediated excitotoxicity (GME) experienced by neurons. Short peptides based on the neuroprotective extracellular glycoprotein ependymin have shown the ability to slow down the effect of GME - however, such short peptides tend to diffuse away from target sites after in vivo delivery. We have designed a self-assembling peptide containing an ependymin mimic that can form nanofibrous matrices. The peptide was evaluated in situ to assess neuroprotective utility after an acute fluidpercussion injury. This biomimetic matrix can conform to the intracranial damaged site after delivery, due its shear-responsive rheological properties. We demonstrated the potential efficacy of the peptide for supporting neuronal survival in vitro and in vivo. Our study demonstrates the potential of these implantable acellular hydrogels for managing the acute (up to 7 days) pathophysiological sequelae after traumatic brain injury. Further work is needed to evaluate less invasive administrative routes and long-term functional and behavioral improvements after injury.

Alcohol induces programmed death receptor-1 and programmed death-ligand-1 differentially in neuroimmune cells.

Engagement of programmed death-1 (PD-1) receptor by its ligands (PD-L1/PD-L2) in activated immune cells is known to be involved in inflammatory neurological disease via a co-inhibitory signal pathway. Interaction of PD-1/PD-L1 is believed to occur only in activated neuroimmune cells because there are undetectable levels of PD-1/PD-L1 in normal physiological conditions. Here, we evaluated whether activation of neuroimmune cells such as human macrophage, brain endothelial cells (hBECs), astrocytes, microglia, and neurons by non-toxic concentrations of ethanol (EtOH) exposure can alter PD-1/PD-L1 expression. Thus, the present study is limited to the screening of PD-1/PD-L1 alterations in neuroimmune cells following ethanol exposure. We found that exposure of human macrophage or microglia to EtOH in primary culture immediately increased the levels of PD-L1 and gradually up-regulated PD-1 levels (beginning at 1-2 h). Similarly, ethanol exposure was able to induce PD-1/PD-L1 levels in hBECs and neuronal culture in a delayed process (occurring at 24 h). Astrocyte culture was the only cell type that showed endogenous levels of PD-1/PD-L1 that was decreased by EtOH exposure time-dependently. We concluded that ethanol (alcohol) mediated the induction of PD-1/PD-L1 differentially in neuroimmune cells. Taken together, our findings suggest that up-regulation of PD-1/PD-L1 by chronic alcohol use may dampen the innate immune response of neuroimmune cells, thereby contributing to neuroinflammation and neurodegeneration.

Angiogenic peptide hydrogels for treatment of traumatic brain injury.

Traumatic brain injury (TBI) impacts over 3.17 million Americans. Management of hemorrhage and coagulation caused by vascular disruption after TBI is critical for the recovery of patients. Cerebrovascular pathologies play an important role in the underlying mechanisms of TBI. The objective of this study is to evaluate a novel regenerative medicine for the injured tissue after brain injury. We utilized a recently described synthetic growth factor with angiogenic potential to facilitate vascular growth in situ at the injury site. Previous work has shown how this injectable self-assembling peptide-based hydrogel (SAPH) creates a regenerative microenvironment for neovascularization at the injury site. Supramolecular assembly allows for thixotropy; the injectable drug delivery system provides sustained in vivo efficacy. In this study, a moderate blunt injury model was used to cause physical vascular damage and hemorrhage. The angiogenic SAPH was then applied directly on the injured rat brain. At day 7 post-TBI, significantly more blood vessels were observed than the sham and injury control group, as well as activation of VEGF-receptor 2, demonstrating the robust angiogenic response elicited by the angiogenic SAPH. Vascular markers von-Willebrand factor (vWF) and α-smooth muscle actin (α-SMA) showed a concomitant increase with blood vessel density in response to the angiogenic SAPH. Moreover, blood brain barrier integrity and blood coagulation were also examined as the parameters to indicate wound recovery post TBI. Neuronal rescue examination by NeuN and myelin basic protein staining showed that the angiogenic SAPH may provide and neuroprotective benefit in the long-term recovery.

Hemorrhage Associated Mechanisms of Neuroinflammation in Experimental Traumatic Brain Injury.

Traumatic brain injury (TBI) is a major health problem for over 3.17 million people in the US, attracting increasing public attentions. Understanding the underlying mechanism of TBI is urgent for better diagnosis and treatment. Here, we examined the hypothesis that cerebral hemorrhagic coagulation and subsequent immune cells infiltration causes the progressive mechanisms of brain injury in moderate fluid percussion injury model. This represents a subdural hematoma and hemorrhagic head injury. We found increased hemorrhagic lesions and infarct volume in the injured brain with increment of pressure. The extent of hemorrhage was also validated by the bio-distribution of fluorescent tracer in cerebrospinal fluid (CSF) pathway after the injury. Bio-distribution of tracer was specifically diminished at the site of hemorrhage resulting from coagulation, which blocked the interstitial and CSF movement of the tracer. Increased expression of coagulation factor XII and necrotic cell death in and around the impact site confirmed the reason for this blockade. Different biomarkers, including immune cells accumulation and neuronal death showed that blood-brain barrier disruption played an important role for induction of neuroinflammation and neurodegeneration around the impact site. Our results suggest that instant hemorrhagic injury resulting from rupturing the brain blood vessels intertwined with coagulation causes onsite perivascular inflammation and neurodegeneration. Understanding of this sequential event should be valuable for development of therapeutic treatment in TBI. Graphical Abstract Underlying mechanisms in moderate/severe blunt TBI: hemorrhage following cerebrovascular disruption results in coagulation, thrombotic necrosis, and acute immune cell infiltration.

Antiretroviral drug-S for a possible HIV elimination.

Although the combination of highly active antiretroviral therapy (cART) can remarkably control human immunodeficiency virus type-1 (HIV-1) replication, it fails to cure HIV/AIDS disease. It is attributed to the incapability of cART to eliminate persistent HIV-1 contained in latent reservoirs in the central nervous system (CNS) and other tissue organs. Thus, withdrawal of cART causes rebound viral replication and resurgent of HIV/AIDS. The lack of success on non-ART approaches for elimination of HIV-1 include the targeted molecules not reaching the CNS, not adjusting well with drug-resistant mutants, or unable to eliminate all components of viral life cycle. Here, we show that our newly discovered Drug-S can effectively inhibit HIV-1 infection and persistence at the low concentration without causing any toxicity to neuroimmune cells. Our results suggest that Drug-S may have a direct effect on viral structure, prevent rebounding of HIV-1 infection, and arrest progression into acquired immunodeficiency syndrome. We also observed that Drug-S is capable of crossing the blood-brain barrier, suggesting a potential antiretroviral drug for elimination of CNS viral reservoirs and self-renewal of residual HIV-1. These results outlined the possible mechanism(s) of action of Drug-S as a novel antiretroviral drug for elimination of HIV-1 replication by interfering the virion structure.

Alcohol promotes waste clearance in the CNS via brain vascular reactivity.

The efficient clearance of the interstitial waste metabolites is essential for the normal maintenance of brain homeostasis. The brain lacks the lymphatic clearance system. Thus, the drainage of waste metabolites in the brain is dependent on a slow flow of cerebrospinal fluid (CSF) system. Glymphatic system claims the direct bulk flow transport of small size water-soluble waste metabolites into to the perivenous space by aquaporin-4 water channels of the astrocyte end-feet, but it did not address the diffusive clearance of large size waste metabolites. Here, we addressed the clearance mechanisms of large size waste metabolites from interstitial fluid to perivascular space as well as from CSF subarachnoid into perivascular space via the paravascular drainage. A low dose ethanol acting as a potent vasodilator promotes the dynamic clearance of waste metabolites through this perivascular-perivenous drainage path. We observed that ethanol-induced increased in vascular endothelial and smooth muscle cell reactivity regulated the enhanced clearance of metabolites. Here, activation of endothelial specific nitric oxide synthase (eNOS) by ethanol and generation of vasodilator nitric oxide mediates the interactive reactivity of endothelial-smooth muscle cells and subsequent diffusion of the CNS waste metabolites towards perivascular space. Detection of tracer dye (waste metabolite) in the perivenous space and in the blood samples further confirmed the improved clearance of waste metabolites through this unraveled interstitial-perivascular-perivenous clearance path. Our results suggest that alcohol intake at low-dose levels may promote clearance of neurological disease associated entangled proteins.

Animal Models of Traumatic Brain Injury and Assessment of Injury Severity.

Traumatic brain injury (TBI) contributes a major cause of death, disability, and mental health disorders. Most TBI patients suffer long-term post-traumatic stress disorder, cognitive dysfunction, and disability. The underlying molecular and cellular mechanisms of such neuropathology progression in TBI remain elusive. In part, it is due to non-standardized classification of mild, moderate, and severe injury in various animal models of TBI. Thus, a better diagnosis and treatment requires a better understanding of the injury mechanisms in a well-defined severity of mild, moderate, and severe injury in different models that may potentially reflect the various types of human brain injuries. The purpose of this review article is to highlight the classification of mild, moderate, and severe injury in various animal models of TBI with special focus on mixed injury that represents a translational concussive head injury. We will classify animal models of TBI broadly into focal injury, diffuse injury, and mixed injury. Focal injury, a localized injury, is represented by animal models of controlled cortical impact, penetrating ballistic-like brain injury, and Feeney or Shohami weight drop injury. A global diffuse injury is best represented by shock tube model of primary blast injury, and Marmarou or Maryland weight drop model. A mixed injury consists of focal and diffuse injury which reproduces the concussive clinical syndrome, and it is best studied in animal model of lateral fluid percussion injury.

How does the brain remove its waste metabolites from within?

The brain is the command center of the body that regulates the vital functions of circulation, respiration, motor function, metabolic activities, or autonomic nervous system outcomes. The brain coordinates these continuous activities at the expense of huge energy utilization. This energy demand is achieved by active transport of nutrients across the endothelial blood-brain barrier (BBB). This review discusses the barrier interfaces in the CNS that include the BBB, blood-spinal cord barrier, the epithelial choroid plexus, and the epithelial arachnoid. While transporting of nutrients across the BBB is a normal physiological function, the trafficking of xenobiotics and inflammatory cells/agents across these interfaces is harmful to brain cells. This leads to production of waste metabolites in the brain. Clearance of these waste metabolites maintains the normal brain homeostasis, while aggregation is detrimental to neurological complications. Since the CNS lacks lymphatic system, the CSF serves as the clearance path for water-soluble peptides/solutes, but not large size waste metabolites like Aß protein. In particular, this review will focus on the mechanisms of waste metabolites clearance paths in the CNS. This will include the recently discovered waste metabolites movement from interstitial space (IS) directly into perivascular clearance (PVC), or via IS-CSF-PVC, and its exchange from PVC to circulation. Concluding remarks will discuss the therapeutic approach to improve the clearance mechanisms for ameliorating neurological diseases.

Impairment of Thiamine Transport at the GUT-BBB-AXIS Contributes to Wernicke's Encephalopathy.

Wernicke's encephalopathy, a common neurological disease, is caused by thiamine (vitamin B1) deficiency. Neuropathy resulting from thiamine deficiency is a hallmark of Wernicke-Korsakoff syndrome in chronic alcohol users. The underlying mechanisms of this deficiency and progression of neuropathy remain to be understood. To uncover the unknown mechanisms of thiamine deficiency in alcohol abuse, we used chronic alcohol consumption or thiamine deficiency diet ingestion in animal models. Observations from animal models were validated in primary human neuronal culture for neurodegenerative process. We employed radio-labeled bio-distribution of thiamine, qualitative and quantitative analyses of the various biomarkers and neurodegenerative process. In the present studies, we established that disruption of thiamine transport across the intestinal gut blood-brain barrier axis as the cause of thiamine deficiency in the brain for neurodegeneration. We found that reduction in thiamine transport across these interfaces was the cause of reduction in the synthesis of thiamine pyrophosphate (TPP), an active cofactor for pyruvate dehydrogenase E1α (PDHE1α). Our findings revealed that decrease in the levels of PDHE1α cofactors switched on the activation of PD kinase (PDK) in the brain, thereby triggering the neuronal phosphorylation of PDHE1α (p-PDHE1α). Dysfunctional phosphorylated PDHE1α causes the reduction of mitochondrial aerobic respiration that led to neurodegeneration. We concluded that impairment of thiamine transport across the gut-BBB-axis that led to insufficient TPP synthesis was critical to Wernicke-neuropathy, which could be effectively prevented by stabilizing the thiamine transporters.

Activation of NLRP3 inflammasome by cholesterol crystals in alcohol consumption induces atherosclerotic lesions.

Epidemiological studies showed a strong association between alcoholism and incidence of stroke, for which the underlying causative mechanisms remain to be understood. Here we found that infiltration of immune cells and deposition of cholesterol at the site of brain artery/capillary injury induced atherosclerosis in chronic alcohol (ethanol) consumption in the presence or absence of high-fat diet. Conversion of cholesterol into sharp edges of cholesterol crystals (CCs) in alcohol intake was key to activation of NLRP3 inflammasome, induction of cerebral atherosclerosis, and development of neuropathy around the atherosclerotic lesions. The presence of alcohol was critical for the formation of CCs and development of the neuropathology. Thus, we observed that alcohol consumption elevated the level of plasma cholesterol, deposition and crystallization of cholesterol, as well as activation of NLRP3 inflammasome. This led to arteriole or capillary walls thickening and increase intracranial blood pressure. Distinct neuropathy around the atherosclerotic lesions indicated vascular inflammation as an initial cause of neuronal degeneration. We demonstrated the molecular mechanisms of NLRP3 activation and downstream signaling cascade event in primary culture of human brain arterial/capillary endothelial cells in the setting of dose-/time-dependent effects of alcohol/CCs using NLRP3 gene silencing technique. We also detected CCs in blood samples from alcohol users, which validated the clinical importance of the findings. Finally, combined therapy of acetyl-l-carnitine and Lipitor® prevented deposition of cholesterol, formation of CCs, activation of NLRP3, thickening of vessel walls, and elevation of intracranial blood pressure. We conclude that alcohol-induced accumulation and crystallization of cholesterol activates NLRP3/caspase-1 in the cerebral vessel that leads to early development of atherosclerosis.

Primary blast causes mild, moderate, severe and lethal TBI with increasing blast overpressures: Experimental rat injury model.

Injury severity in blast induced Traumatic Brain Injury (bTBI) increases with blast overpressure (BOP) and impulse in dose-dependent manner. Pure primary blast waves were simulated in compressed gas shock-tubes in discrete increments. Present work demonstrates 24 hour survival of rats in 0-450 kPa (0-800 Pa∙s impulse) range at 10 discrete levels (60, 100, 130, 160, 190, 230, 250, 290, 350 and 420 kPa) and determines the mortality rate as a non-linear function of BOP. Using logistic regression model, predicted mortality rate (PMR) function was calculated, and used to establish TBI severities. We determined a BOP of 145 kPa as upper mild TBI threshold (5% PMR). Also we determined 146-220 kPa and 221-290 kPa levels as moderate and severe TBI based on 35%, and 70% PMR, respectively, while BOP above 290 kPa is lethal. Since there are no standards for animal bTBI injury severity, these thresholds need further refinements using histopathology, immunohistochemistry and behavior. Further, we specifically investigated mild TBI range (0-145 kPa) using physiological (heart rate), pathological (lung injury), immuno-histochemical (oxidative/nitrosative and blood-brain barrier markers) as well as blood borne biomarkers. With these additional data, we conclude that mild bTBI occurs in rats when the BOP is in the range of 85-145 kPa.

Quantitative optical coherence elastography based on fiber-optic probe for in situ measurement of tissue mechanical properties.

We developed a miniature quantitative optical coherence elastography (qOCE) instrument with an integrated Fabry-Perot force sensor, for in situ elasticity measurement of biological tissue. The technique has great potential for biomechanics modeling and clinical diagnosis. We designed the fiber-optic qOCE probe that was used to exert a compressive force to deform tissue at the tip of the probe. Using the space-division multiplexed optical coherence tomography (OCT) signal detected by a spectral domain OCT engine, we were able to quantify the probe deformation that was proportional to the force applied, and to quantify the tissue deformation corresponding to the external stimulus. Simultaneous measurement of force and displacement allowed us to extract Young's modulus of biological tissue. We experimentally calibrated our qOCE instrument, and validated its effectiveness on tissue mimicking phantoms and biological tissues.

Role of Matrix Metalloproteinases in the Pathogenesis of Traumatic Brain Injury.

Traumatic brain injury (TBI) is a major cause of mortality and morbidity worldwide. Studies revealed that the pathogenesis of TBI involves upregulation of MMPs. MMPs form a large family of closely related zinc-dependent endopeptidases, which are primarily responsible for the dynamic remodulation of the extracellular matrix (ECM). Thus, they are involved in several normal physiological processes like growth, development, and wound healing. During pathophysiological conditions, MMPs proteolytically degrade various components of ECM and tight junction (TJ) proteins of BBB and cause BBB disruption. Impairment of BBB causes leakiness of the blood from circulation to brain parenchyma that leads to microhemorrhage and edema. Further, MMPs dysregulate various normal physiological processes like angiogenesis and neurogenesis, and also they participate in the inflammatory and apoptotic cascades by inducing or regulating the specific mediators and their receptors. In this review, we explore the roles of MMPs in various physiological/pathophysiological processes associated with neurological complications, with special emphasis on TBI.

Differential induction of PD-1/PD-L1 in Neuroimmune cells by drug of abuse.

Interaction of programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) plays a critical role in regulating the delicate balance between protective immunity and tolerance. Human neuroimmune cells express very low or undetectable levels of PD-1/PD-L1 in normal physiological condition.We seek to examine if exposure of these cells to drug of abuse such as methamphetamine (METH) alters the profile of PD-1/PD-L1 levels, thereby dampens the innate immune response of the host cells. Thus, we assessed the changes in the levels of PD-1/PD-L1 in primary human macrophages, brain endothelial cells (hBECs), astrocytes, microglia, and neurons after exposure to METH. We observed that stimulation of these neuroimmune cells by METH responded differentially to PD-1/PD-L1 expression. Stimulation of macrophage culture with 50 µM of METH exhibited immediate gradual upregulation of PD-L1, while increase in PD-1 took 2-4 hours later than PD-L1. The response of hBECs to PD-1/PD-L1 induction occurred at 24 hours, while increase of PD-1/PD-L1 levels in neurons and microglia was immediate following METH exposure. We found that astrocytes expressed moderate levels of endogenous PD-1/PD-L1, which was diminished by METH exposure. Our findings show a differential expression of PD-1/PD-L1 in neuroimmune cells in response to METH stimulation, suggesting that PD-1/PD-L1 interplay in these cell types could orchestrate the intercellular interactive communication for neuronal death or protection in the brain environment.

Interactions of oxidative stress and neurovascular inflammation in the pathogenesis of traumatic brain injury.

Traumatic brain injury (TBI) is a major cause of death in the young age group and leads to persisting neurological impairment in many of its victims. It may result in permanent functional deficits because of both primary and secondary damages. This review addresses the role of oxidative stress in TBI-mediated secondary damages by affecting the function of the vascular unit, changes in blood-brain barrier (BBB) permeability, posttraumatic edema formation, and modulation of various pathophysiological factors such as inflammatory factors and enzymes associated with trauma. Oxidative stress plays a major role in many pathophysiologic changes that occur after TBI. In fact, oxidative stress occurs when there is an impairment or inability to balance antioxidant production with reactive oxygen species (ROS) and reactive nitrogen species (RNS) levels. ROS directly downregulate proteins of tight junctions and indirectly activate matrix metalloproteinases (MMPs) that contribute to open the BBB. Loosening of the vasculature and perivascular unit by oxidative stress-induced activation of MMPs and fluid channel aquaporins promotes vascular or cellular fluid edema, enhances leakiness of the BBB, and leads to progression of neuroinflammation. Likewise, oxidative stress activates directly the inflammatory cytokines and growth factors such as IL-1ß, tumor necrosis factor-α (TNF-α), and transforming growth factor-beta (TGF-ß) or indirectly by activating MMPs. In another pathway, oxidative stress-induced degradation of endothelial vascular endothelial growth factor receptor-2 (VEGFR-2) by MMPs leads to a subsequent elevation of cellular/serum VEGF level. The decrease in VEGFR-2 with a subsequent increase in VEGF-A level leads to apoptosis and neuroinflammation via the activation of caspase-1/3 and IL-1ß release.

Reduction of brain mitochondrial ß-oxidation impairs complex I and V in chronic alcohol intake: the underlying mechanism for neurodegeneration.

Neuropathy and neurocognitive deficits are common among chronic alcohol users, which are believed to be associated with mitochondrial dysfunction in the brain. The specific type of brain mitochondrial respiratory chain complexes (mRCC) that are adversely affected by alcohol abuse has not been studied. Thus, we examined the alterations of mRCC in freshly isolated mitochondria from mice brain that were pair-fed the ethanol (4% v/v) and control liquid diets for 7-8 weeks. We observed that alcohol intake severely reduced the levels of complex I and V. A reduction in complex I was associated with a decrease in carnitine palmitoyltransferase 1 (cPT1) and cPT2 levels. The mitochondrial outer (cPT1) and inner (cPT2) membrane transporter enzymes are specialized in acylation of fatty acid from outer to inner membrane of mitochondria for ATP production. Thus, our results showed that alterations of cPT1 and cPT2 paralleled a decrease ß-oxidation of palmitate and ATP production, suggesting that impairment of substrate entry step (complex I function) can cause a negative impact on ATP production (complex V function). Disruption of cPT1/cPT2 was accompanied by an increase in cytochrome C leakage, while reduction of complex I and V paralleled a decrease in depolarization of mitochondrial membrane potential (ΔΨ, monitored by JC-1 fluorescence) and ATP production in alcohol intake. We noted that acetyl-L-carnitine (ALC, a cofactor of cPT1 and cPT2) prevented the adverse effects of alcohol while coenzyme Q10 (CoQ10) was not very effective against alcohol insults. These results suggest that understanding the molecular, biochemical, and signaling mechanisms of the CNS mitochondrial ß-oxidation such as ALC can mitigate alcohol related neurological disorders.