Exploratory Application of Neuropharmacometabolomics in Severe Childhood Traumatic Brain Injury

N-Acetylcysteine and Probenecid Adjuvant Therapy for Traumatic Brain Injury

N-Acetylcysteine (NAC) has shown promise as a putative neurotherapeutic for traumatic brain injury (TBI). Yet, many such promising compounds have limited ability to cross the blood-brain barrier (BBB), achieve therapeutic concentrations in brain, demonstrate target engagement, among other things, that have hampered successful translation. A pharmacologic strategy for overcoming poor BBB permeability and/or efflux out of the brain of organic acid-based, small molecule therapeutics such as NAC is co-administration with a targeted or nonselective membrane transporter inhibitor. Probenecid is a classic ATP-binding cassette and solute carrier inhibitor that blocks transport of organic acids, including NAC. Accordingly, combination therapy using probenecid as an adjuvant with NAC represents a logical neurotherapeutic strategy for treatment of TBI (and other CNS diseases). We have completed a proof-of-concept pilot study using this drug combination in children with severe TBI-the Pro-NAC Trial (ClinicalTrials.gov NCT01322009). In this review, we will discuss the background and rationale for combination therapy with probenecid and NAC in TBI, providing justification for further clinical investigation.

The association between N-acetylcysteine treatment and hepatic healing in patients with non-acetaminophen-induced liver injury in pediatric intensive care: A single-center retrospective study

OBJECTIVE

The aim of this study was to determine the association between the use of intravenous N-acetylcysteine (NAC) and hepatic healing in pediatric intensive care unit (PICU) patients with non-acetaminophen-induced hepatic injury, except for acute liver failure.

METHODS

The data of patients who received intravenous NAC as adjuvant therapy for transaminase levels more than sixfold normal values during their PICU stay between 2010 and 2014 were retrospectively collected from the medical records database. The patients who did not receive NAC with elevated transaminase levels during their PICU stay between 2014 and 2018 were also collected as the standard of care (SOC) cohort.

RESULTS

More than 50% of the liver injuries were secondary to acute hypoxia, hypotension, sepsis, and inflammation. The median number of elevated transaminase period (ETP) days of the NAC and SOC groups were 5 (IQR: 4) and 4 (IQR: 4), respectively (p = 0.17). There was no significant difference between the groups in terms of minimum and maximum laboratory values during ETP. There was no significant difference in terms of ETP and maximum ALT levels between the NAC and SOC groups in the hypoxia-hypotension subgroup.

CONCLUSION

This study did not show an association between indirect measures of hepatic healing and post-insult use of NAC in pediatric liver injury in the PICU setting.

Blood-Brain Barrier Dysfunction in CNS Disorders and Putative Therapeutic Targets: An Overview

The blood-brain barrier (BBB) is a fundamental component of the central nervous system (CNS). Its functional and structural integrity is vital to maintain the homeostasis of the brain microenvironment by controlling the passage of substances and regulating the trafficking of immune cells between the blood and the brain. The BBB is primarily composed of highly specialized microvascular endothelial cells. These cells’ special features and physiological properties are acquired and maintained through the concerted effort of hemodynamic and cellular cues from the surrounding environment. This complex multicellular system, comprising endothelial cells, astrocytes, pericytes, and neurons, is known as the neurovascular unit (NVU). The BBB strictly controls the transport of nutrients and metabolites into brain parenchyma through a tightly regulated transport system while limiting the access of potentially harmful substances via efflux transcytosis and metabolic mechanisms. Not surprisingly, a disruption of the BBB has been associated with the onset and/or progression of major neurological disorders. Although the association between disease and BBB disruption is clear, its nature is not always evident, specifically with regard to whether an impaired BBB function results from the pathological condition or whether the BBB damage is the primary pathogenic factor prodromal to the onset of the disease. In either case, repairing the barrier could be a viable option for treating and/or reducing the effects of CNS disorders. In this review, we describe the fundamental structure and function of the BBB in both healthy and altered/diseased conditions. Additionally, we provide an overview of the potential therapeutic targets that could be leveraged to restore the integrity of the BBB concomitant to the treatment of these brain disorders.

Mitochondria-Targeted Antioxidants: A Step towards Disease Treatment

Mitochondria are the main organelles that produce adenosine 5′-triphosphate (ATP) and reactive oxygen species (ROS) in eukaryotic cells and meanwhile susceptible to oxidative damage. The irreversible oxidative damage in mitochondria has been implicated in various human diseases. Increasing evidence indicates the therapeutic potential of mitochondria-targeted antioxidants (MTAs) for oxidative damage-associated diseases. In this article, we introduce the advantageous properties of MTAs compared with the conventional (nontargeted) ones, review different mitochondria-targeted delivery systems and antioxidants, and summarize their experimental results for various disease treatments in different animal models and clinical trials. The combined evidence demonstrates that mitochondrial redox homeostasis is a potential target for disease treatment. Meanwhile, the limitations and prospects for exploiting MTAs are discussed, which might pave ways for further trial design and drug development.

Paths to Successful Translation of New Therapies for Severe Traumatic Brain Injury in the Golden Age of Traumatic Brain Injury Research: A Pittsburgh Vision

New neuroprotective therapies for severe traumatic brain injury (TBI) have not translated from pre-clinical to clinical success. Numerous explanations have been suggested in both the pre-clinical and clinical arenas. Coverage of TBI in the lay press has reinvigorated interest, creating a golden age of TBI research with innovative strategies to circumvent roadblocks. We discuss the need for more robust therapies. We present concepts for traditional and novel approaches to defining therapeutic targets. We review lessons learned from the ongoing work of the pre-clinical drug and biomarker screening consortium Operation Brain Trauma Therapy and suggest ways to further enhance pre-clinical consortia. Biomarkers have emerged that empower choice and assessment of target engagement by candidate therapies. Drug combinations may be needed, and it may require moving beyond conventional drug therapies. Precision medicine may also link the right therapy to the right patient, including new approaches to TBI classification beyond the Glasgow Coma Scale or anatomical phenotyping-incorporating new genetic and physiologic approaches. Therapeutic breakthroughs may also come from alternative approaches in clinical investigation (comparative effectiveness, adaptive trial design, use of the electronic medical record, and big data). The full continuum of care must also be represented in translational studies, given the important clinical role of pre-hospital events, extracerebral insults in the intensive care unit, and rehabilitation. TBI research from concussion to coma can cross-pollinate and further advancement of new therapies. Misconceptions can stifle/misdirect TBI research and deserve special attention. Finally, we synthesize an approach to deliver therapeutic breakthroughs in this golden age of TBI research.

Central nervous system diseases associated with blood brain barrier breakdown - A Comprehensive update of existing literatures

Blood vessels that supply and feed the central nervous system (CNS) possess unique and exclusive properties, named as blood–brain barrier (BBB). It is responsible for tight regulation of the movement of ions, molecules, and cells between the blood and the brain thereby maintaining controlled chemical composition of the neuronal milieu required for appropriate functioning. It also protects the neural tissue from toxic plasma components, blood cells and pathogens from entering the brain. In this review the importance of BBB and its disruption causing brain pathology and progression to different neurological diseases like Alzheimer’s disease (AD), Parkinson’s disease (PD), Amyotrophic lateral sclerosis (ALS), Huntington’s disease (HD) etc. will be discussed.

Oxidative Stress-Mediated Blood-Brain Barrier (BBB) Disruption in Neurological Diseases

The blood-brain barrier (BBB), as a crucial gate of brain-blood molecular exchange, is involved in the pathogenesis of multiple neurological diseases. Oxidative stress is caused by an imbalance between the production of reactive oxygen species (ROS) and the scavenger system. Since oxidative stress plays a significant role in the production and maintenance of the BBB, the cerebrovascular system is especially vulnerable to it. The pathways that initiate BBB dysfunction include, but are not limited to, mitochondrial dysfunction, excitotoxicity, iron metabolism, cytokines, pyroptosis, and necroptosis, all converging on the generation of ROS. Interestingly, ROS also provide common triggers that directly regulate BBB damage, parameters including tight junction (TJ) modifications, transporters, matrix metalloproteinase (MMP) activation, inflammatory responses, and autophagy. We will discuss the role of oxidative stress-mediated BBB disruption in neurological diseases, such as hemorrhagic stroke, ischemic stroke (IS), Alzheimer’s disease (AD), Parkinson’s disease (PD), traumatic brain injury (TBI), amyotrophic lateral sclerosis (ALS), and cerebral small vessel disease (CSVD). This review will also discuss the latest clinical evidence of potential biomarkers and antioxidant drugs towards oxidative stress in neurological diseases. A deeper understanding of how oxidative stress damages BBB may open up more therapeutic options for the treatment of neurological diseases.

Management of Traumatic Brain Injury: From Present to Future

TBI (traumatic brain injury) is a major cause of death among youth in industrialized societies. Brain damage following traumatic injury is a result of direct and indirect mechanisms; indirect or secondary injury involves the initiation of an acute inflammatory response, including the breakdown of the blood–brain barrier (BBB), brain edema, infiltration of peripheral blood cells, and activation of resident immunocompetent cells, as well as the release of numerous immune mediators such as interleukins and chemotactic factors. TBI can cause changes in molecular signaling and cellular functions and structures, in addition to tissue damage, such as hemorrhage, diffuse axonal damages, and contusions. TBI typically disturbs brain functions such as executive actions, cognitive grade, attention, memory data processing, and language abilities. Animal models have been developed to reproduce the different features of human TBI, better understand its pathophysiology, and discover potential new treatments. For many years, the first approach to manage TBI has been treatment of the injured tissue with interventions designed to reduce the complex secondary-injury cascade. Several studies in the literature have stressed the importance of more closely examining injuries, including endothelial, microglia, astroglia, oligodendroglia, and precursor cells. Significant effort has been invested in developing neuroprotective agents. The aim of this work is to review TBI pathophysiology and existing and potential new therapeutic strategies in the management of inflammatory events and behavioral deficits associated with TBI.

Antioxidants Reduce Muscular Dystrophy in the dy2J/dy2J Mouse Model of Laminin α2 Chain-Deficient Muscular Dystrophy

Congenital muscular dystrophy with laminin α2 chain-deficiency (LAMA2-CMD) is a severe neuromuscular disorder without a cure. Using transcriptome and proteome profiling as well as functional assays, we previously demonstrated significant metabolic impairment in skeletal muscle from LAMA2-CMD patients and mouse models. Reactive oxygen species (ROS) increase when oxygen homeostasis is not maintained and, here, we investigate whether oxidative stress indeed is involved in the pathogenesis of LAMA2-CMD. We also analyze the effects of two antioxidant molecules, N-acetyl-L-cysteine (NAC) and vitamin E, on disease progression in the dy^2J/dy^2J mouse model of LAMA2-CMD. We demonstrate increased ROS levels in LAMA2-CMD mouse and patient skeletal muscle. Furthermore, NAC treatment (150 mg/kg IP for 6 days/week for 3 weeks) led to muscle force loss prevention, reduced central nucleation and decreased the occurrence of apoptosis, inflammation, fibrosis and oxidative stress in LAMA2-CMD muscle. In addition, vitamin E (40 mg/kg oral gavage for 6 days/week for 2 weeks) improved morphological features and reduced inflammation and ROS levels in dy^2J/dy^2J skeletal muscle. We suggest that NAC and to some extent vitamin E might be potential future supportive treatments for LAMA2-CMD as they improve numerous pathological hallmarks of LAMA2-CMD.

A prospective pilot study using metabolomics discloses specific fatty acid, catecholamine and tryptophan metabolic pathways as possible predictors for a negative outcome after severe trauma

Background

We wanted to define metabolomic patterns in plasma to predict a negative outcome in severe trauma patients.

Methods

A prospective pilot study was designed to evaluate plasma metabolomic patterns, established by liquid chromatography coupled to mass spectrometry, in patients allocated to an intensive care unit (in the University Hospital Arnau de Vilanova, Lleida, Spain) in the first hours after a severe trauma (n = 48). Univariate and multivariate statistics were employed to establish potential predictors of mortality.

Results

Plasma of patients non surviving to trauma (n = 5) exhibited a discriminating metabolomic pattern, involving basically metabolites belonging to fatty acid and catecholamine synthesis as well as tryptophan degradation pathways. Thus, concentration of several metabolites exhibited an area under the receiver operating curve (ROC) higher than 0.84, including 3-indolelactic acid, hydroxyisovaleric acid, phenylethanolamine, cortisol, epinephrine and myristic acid. Multivariate binary regression logistic revealed that patients with higher myristic acid concentrations had a non-survival odds ratio of 2.1 (CI 95% 1.1–3.9).

Conclusions

Specific fatty acids, catecholamine synthesis and tryptophan degradation pathways could be implicated in a negative outcome after trauma. The metabolomic study of severe trauma patients could be helpful for biomarker proposal.

Electronic supplementary material

The online version of this article (10.1186/s13049-019-0631-5) contains supplementary material, which is available to authorized users.

Membrane transporters in traumatic brain injury: Pathological, pharmacotherapeutic, and developmental implications

Membrane transporters regulate the trafficking of endogenous and exogenous molecules across biological barriers and within the neurovascular unit. In traumatic brain injury (TBI), they moderate the dynamic movement of therapeutic drugs and injury mediators among neurons, endothelial cells and glial cells, thereby becoming important determinants of pathogenesis and effective pharmacotherapy after TBI. There are three ways transporters may impact outcomes in TBI. First, transporters likely play a key role in the clearance of injury mediators. Second, genetic association studies suggest transporters may be important in the transition of TBI from acute brain injury to a chronic neurological disease. Third, transporters dynamically control the brain penetration and efflux of many drugs and their distribution within and elimination from the brain, contributing to pharmacoresistance and possibly in some cases pharmacosensitivity. Understanding the nature of drugs or candidate drugs in development with respect to whether they are a transporter substrate or inhibitor is relevant to understand whether they distribute to their target in sufficient concentrations. Emerging data provide evidence of altered expression and function of transporters in humans after TBI. Genetic variability in expression and/or function of key transporters adds an additional dynamic, as shown in recent clinical studies. In this review, evidence supporting the role of individual membrane transporters in TBI are discussed as well as novel strategies for their modulation as possible therapeutic targets. Since data specifically targeting pediatric TBI are sparse, this review relies mainly on experimental studies using adult animals and clinical studies in adult patients.