Neuropharmacology in traumatic brain injury: from preclinical to clinical neuroprotection?

Bradykinin 2 Receptors Mediate Long-Term Neurocognitive Deficits After Experimental Traumatic Brain Injury

The kallikrein-kinin system is one of the first inflammatory pathways to be activated following traumatic brain injury (TBI) and has been shown to exacerbate brain edema formation in the acute phase through activation of bradykinin 2 receptors (B2R). However, the influence of B2R on chronic post-traumatic damage and outcome is unclear. In the current study, we assessed long-term effects of B2R-knockout (KO) after experimental TBI. B2R KO mice (heterozygous, homozygous) and wild-type (WT) littermates (n = 10/group) were subjected to controlled cortical impact (CCI) TBI. Lesion size was evaluated by magnetic resonance imaging up to 90 days after CCI. Motor and memory function were regularly assessed by Neurological Severity Score, Beam Walk, and Barnes maze test. Ninety days after TBI, brains were harvested for immunohistochemical analysis. There was no difference in cortical lesion size between B2R-deficient and WT animals 3 months after injury; however, hippocampal damage was reduced in B2R KO mice (p = 0.03). Protection of hippocampal tissue was accompanied by a significant improvement of learning and memory function 3 months after TBI (p = 0.02 WT vs. KO), whereas motor function was not influenced. Scar formation and astrogliosis were unaffected, but B2R deficiency led to a gene-dose-dependent attenuation of microglial activation and a reduction of CD45+ cells 3 months after TBI in cortex (p = 0.0003) and hippocampus (p < 0.0001). These results suggest that chronic hippocampal neurodegeneration and subsequent cognitive impairment are mediated by prolonged neuroinflammation and B2R. Inhibition of B2R may therefore represent a novel strategy to reduce long-term neurocognitive deficits after TBI.

Preclinical Studies on Mechanisms Underlying the Protective Effects of Propranolol in Traumatic Brain Injury: A Systematic Review

Traumatic brain injury (TBI) is a leading cause of mortality and morbidity amongst trauma patients. Its treatment is focused on minimizing progression to secondary injury. Administration of propranolol for TBI maydecrease mortality and improve functional outcomes. However, it is our sense that its use has not been universally adopted due to low certainty evidence. The literature was reviewed to explore the mechanism of propranolol as a therapeutic intervention in TBI to guide future clinical investigations. Medline, Embase, and Scopus were searched for studies that investigated the effect of propranolol on TBI in animal models from inception until June 6, 2023. All routes of administration for propranolol were included and the following outcomes were evaluated: cognitive functions, physiological and immunological responses. Screening and data extraction were done independently and in duplicate. The risk of bias for each individual study was assessed using the SYCLE's risk of bias tool for animal studies. Three hundred twenty-three citations were identified and 14 studies met our eligibility criteria. The data suggests that propranolol may improve post-TBI cognitive and motor function by increasing cerebral perfusion, reducing neural injury, cell death, leukocyte mobilization and p-tau accumulation in animal models. Propranolol may also attenuate TBI-induced immunodeficiency and provide cardioprotective effects by mitigating damage to the myocardium caused by oxidative stress. This systematic review demonstrates that propranolol may be therapeutic in TBI by improving cognitive and motor function while regulating T lymphocyte response and levels of myocardial reactive oxygen species. Oral or intravenous injection of propranolol following TBI is associated with improved cerebral perfusion, reduced neuroinflammation, reduced immunodeficiency, and cardio-neuroprotection in preclinical studies.

Dysregulated brain-gut axis in the setting of traumatic brain injury: review of mechanisms and anti-inflammatory pharmacotherapies

Traumatic brain injury (TBI) is a chronic and debilitating disease, associated with a high risk of psychiatric and neurodegenerative diseases. Despite significant advancements in improving outcomes, the lack of effective treatments underscore the urgent need for innovative therapeutic strategies. The brain-gut axis has emerged as a crucial bidirectional pathway connecting the brain and the gastrointestinal (GI) system through an intricate network of neuronal, hormonal, and immunological pathways. Four main pathways are primarily implicated in this crosstalk, including the systemic immune system, autonomic and enteric nervous systems, neuroendocrine system, and microbiome. TBI induces profound changes in the gut, initiating an unrestrained vicious cycle that exacerbates brain injury through the brain-gut axis. Alterations in the gut include mucosal damage associated with the malabsorption of nutrients/electrolytes, disintegration of the intestinal barrier, increased infiltration of systemic immune cells, dysmotility, dysbiosis, enteroendocrine cell (EEC) dysfunction and disruption in the enteric nervous system (ENS) and autonomic nervous system (ANS). Collectively, these changes further contribute to brain neuroinflammation and neurodegeneration via the gut-brain axis. In this review article, we elucidate the roles of various anti-inflammatory pharmacotherapies capable of attenuating the dysregulated inflammatory response along the brain-gut axis in TBI. These agents include hormones such as serotonin, ghrelin, and progesterone, ANS regulators such as beta-blockers, lipid-lowering drugs like statins, and intestinal flora modulators such as probiotics and antibiotics. They attenuate neuroinflammation by targeting distinct inflammatory pathways in both the brain and the gut post-TBI. These therapeutic agents exhibit promising potential in mitigating inflammation along the brain-gut axis and enhancing neurocognitive outcomes for TBI patients.

Mesenchymal stem cell-derived extracellular vesicles as a cell-free therapy for traumatic brain injury via neuroprotection and neurorestoration

Traumatic brain injury is a serious and complex neurological condition that affects millions of people worldwide. Despite significant advancements in the field of medicine, effective treatments for traumatic brain injury remain limited. Recently, extracellular vesicles released from mesenchymal stem/stromal cells have emerged as a promising novel therapy for traumatic brain injury. Extracellular vesicles are small membrane-bound vesicles that are naturally released by cells, including those in the brain, and can be engineered to contain therapeutic cargo, such as anti-inflammatory molecules, growth factors, and microRNAs. When administered intravenously, extracellular vesicles can cross the blood-brain barrier and deliver their cargos to the site of injury, where they can be taken up by recipient cells and modulate the inflammatory response, promote neuroregeneration, and improve functional outcomes. In preclinical studies, extracellular vesicle-based therapies have shown promising results in promoting recovery after traumatic brain injury, including reducing neuronal damage, improving cognitive function, and enhancing motor recovery. While further research is needed to establish the safety and efficacy of extracellular vesicle-based therapies in humans, extracellular vesicles represent a promising novel approach for the treatment of traumatic brain injury. In this review, we summarize mesenchymal stem/stromal cell-derived extracellular vesicles as a cell-free therapy for traumatic brain injury via neuroprotection and neurorestoration and brain-derived extracellular vesicles as potential biofluid biomarkers in small and large animal models of traumatic brain injury.

Interleukin-6 in Traumatic Brain Injury: A Janus-Faced Player in Damage and Repair

Traumatic brain injury (TBI) is a common and often devastating illness, with wide-ranging public health implications. In addition to the primary injury, victims of TBI are at risk for secondary neurological injury by numerous mechanisms. Current treatments are limited and do not target the profound immune response associated with injury. This immune response reflects a convergence of peripheral and central nervous system-resident immune cells whose interaction is mediated in part by a disruption in the blood-brain barrier (BBB). The diverse family of cytokines helps to govern this communication and among these, Interleukin (IL)-6 is a notable player in the immune response to acute neurological injury. It is also a well-established pharmacological target in a variety of other disease contexts. In TBI, elevated IL-6 levels are associated with worse outcomes, but the role of IL-6 in response to injury is double-edged. IL-6 promotes neurogenesis and wound healing in animal models of TBI, but it may also contribute to disruptions in the BBB and the progression of cerebral edema. Here, we review IL-6 biology in the context of TBI, with an eye to clarifying its controversial role and understanding its potential as a target for modulating the immune response in this disease.

Research progress on pleiotropic neuroprotective drugs for traumatic brain injury

Traumatic brain injury (TBI) has become one of the most important causes of death and disability worldwide. A series of neuroinflammatory responses induced after TBI are key factors for persistent neuronal damage, but at the same time, such inflammatory responses can also promote debris removal and tissue repair after TBI. The concept of pleiotropic neuroprotection delves beyond the single-target treatment approach, considering the multifaceted impacts following TBI. This notion embarks deeper into the research-oriented treatment paradigm, focusing on multi-target interventions that inhibit post-TBI neuroinflammation with enhanced therapeutic efficacy. With an enriched comprehension of TBI's physiological mechanisms, this review dissects the advancements in developing pleiotropic neuroprotective pharmaceuticals to mitigate TBI. The aim is to provide insights that may contribute to the early clinical management of the condition.

Roles of Astrocytic Endothelin ETB Receptor in Traumatic Brain Injury

Traumatic brain injury (TBI) is an intracranial injury caused by accidents, falls, or sports. The production of endothelins (ETs) is increased in the injured brain. ET receptors are classified into distinct types, including ET_A receptor (ET_A-R) and ET_B receptor (ET_B-R). ET_B-R is highly expressed in reactive astrocytes and upregulated by TBI. Activation of astrocytic ET_B-R promotes conversion to reactive astrocytes and the production of astrocyte-derived bioactive factors, including vascular permeability regulators and cytokines, which cause blood-brain barrier (BBB) disruption, brain edema, and neuroinflammation in the acute phase of TBI. ET_B-R antagonists alleviate BBB disruption and brain edema in animal models of TBI. The activation of astrocytic ET_B receptors also enhances the production of various neurotrophic factors. These astrocyte-derived neurotrophic factors promote the repair of the damaged nervous system in the recovery phase of patients with TBI. Thus, astrocytic ET_B-R is expected to be a promising drug target for TBI in both the acute and recovery phases. This article reviews recent observations on the role of astrocytic ET_B receptors in TBI.

P188 Therapy in In Vitro Models of Traumatic Brain Injury

Traumatic brain injury (TBI) is a significant cause of morbidity and mortality worldwide. Varied mechanisms of injury contribute to the heterogeneity of this patient population as demonstrated by the multiple published grading scales and diverse required criteria leading to diagnoses from mild to severe. TBI pathophysiology is classically separated into a primary injury that is characterized by local tissue destruction as a result of the initial blow, followed by a secondary phase of injury constituted by a score of incompletely understood cellular processes including reperfusion injury, disruption to the blood-brain barrier, excitotoxicity, and metabolic dysregulation. There are currently no effective pharmacological treatments in the wide-spread use for TBI, in large part due to challenges associated with the development of clinically representative in vitro and in vivo models. Poloxamer 188 (P188), a Food and Drug Administration-approved amphiphilic triblock copolymer embeds itself into the plasma membrane of damaged cells. P188 has been shown to have neuroprotective properties on various cell types. The objective of this review is to provide a summary of the current literature on in vitro models of TBI treated with P188.

Molecular and Computational Analysis Identify Statins as Selective Inhibitors of Human Butyrylcholinesterase

Cholinesterase enzyme family consists of acetylcholinesterase (AChE, 3.1.1.7), the major enzyme responsible for hydrolysis of acetylcholine at cholinergic synapses, and butyrylcholinesterase (BChE, 3.1.1.8) a detoxification enzyme of plasma. Statins are cholesterol-lowering medications utilized as protective medicaments in stroke and Alzheimer's disease, which cholinesterases are associated with. Thus, in this study, we characterized the inhibitory effects and mechanisms of common statins, rosuvastatin, atorvastatin, simvastatin and lovastatin, on human erythrocyte AChE and purified serum BChE using in vitro and in silico methods. Kinetic assays identified statins as selective non-competitive inhibitors of human serum BChE. The IC₅₀ and K_m values were found as 194.7 ± 55.2 µM and 1.03 ± 0.2 µM for rosuvastatin, 492.5 ± 55.1 µM and 7.2 ± 0.3 µM for atorvastatin, 14.2 ± 0.3 µM and 202.7 ± 23.2 µM for lovastatin, and 17.6 ± 0.1 µM and 207.2 ± 13.2 µM for simvastatin, respectively. The compounds did not display considerable inhibition against AChE. Molecular docking predicted good affinity and strong interactions with the BChE active site for atorvastatin and rosuvastatin. Current study identifies rosuvastatin as the most specific and selective inhibitor of human BChE among the tested statins. As selective inhibitors of BChE statins have the potential to be re-evaluated as medicaments due to their pleiotropic effects.

Vinpocetine restores cognitive and motor functions in Traumatic brain injury challenged rats

Traumatic brain damage is common worldwide and the treatments are not well-defined. Vinpocetine is a synthetic derivative of the vinca alkaloid vincamine and is clinically being used for various brain disorders. Here in the current study, we have investigated the neuroprotective potential of vinpocetine against traumatic brain injury. TBI was induced by the Marmarou weight drop method in rats. Brain damage was evaluated using cognitive and motor functions and the alterations in biomolecules. Injured rats were treated with different doses of vinpocetine (2.5, 5, and 10 mg/kg) for 4 weeks. Traumatic brain injury in rats produced significant deterioration of cognition and motor functions, which was accompanied by increased oxidative stress and significant alterations in brain monoamine levels as compared with the sham control group (p < 0.05). Vinpocetine alleviated TBI-induced oxidative burden, altered neurochemistry, and improved the cognitive and motor functions as compared with that of the TBI control group (p < 0.05). The observed neuroprotective potential of vinpocetine may be due to the observed antioxidant potential and its ability to restore the levels of brain neurochemicals under stressed conditions. The outcomes of the current study may help the repositioning of vinpocetine for preventing or treating traumatic brain injuries.

Mesenchymal stem cells protect against TBI-induced pyroptosis in vivo and in vitro through TSG-6

Background

Pyroptosis, especially microglial pyroptosis, may play an important role in central nervous system pathologies, including traumatic brain injury (TBI). Transplantation of mesenchymal stem cells (MSCs), such as human umbilical cord MSCs (hUMSCs), has been a focus of brain injury treatment. Recently, MSCs have been found to play a role in many diseases by regulating the pyroptosis pathway. However, the effect of MSC transplantation on pyroptosis following TBI remains unknown. Tumor necrosis factor α stimulated gene 6/protein (TSG-6), a potent anti-inflammatory factor expressed in many cell types including MSCs, plays an anti-inflammatory role in many diseases; however, the effect of TSG-6 secreted by MSCs on pyroptosis remains unclear.

Methods

Mice were subjected to controlled cortical impact injury in vivo. To assess the time course of pyroptosis after TBI, brains of TBI mice were collected at different time points. To study the effect of TSG-6 secreted by hUMSCs in regulating pyroptosis, normal hUMSCs, sh-TSG-6 hUMSCs, or different concentrations of rmTSG-6 were injected intracerebroventricularly into mice 4 h after TBI. Neurological deficits, double immunofluorescence staining, presence of inflammatory factors, cell apoptosis, and pyroptosis were assessed. In vitro, we investigated the anti-pyroptosis effects of hUMSCs and TSG-6 in a lipopolysaccharide/ATP-induced BV2 microglial pyroptosis model.

Results

In TBI mice, the co-localization of Iba-1 (marking microglia/macrophages) with NLRP3/Caspase-1 p20/GSDMD was distinctly observed at 48 h. In vivo, hUMSC transplantation or treatment with rmTSG-6 in TBI mice significantly improved neurological deficits, reduced inflammatory cytokine expression, and inhibited both NLRP3/Caspase-1 p20/GSDMD expression and microglial pyroptosis in the cerebral cortices of TBI mice. However, the therapeutic effect of hUMSCs on TBI mice was reduced by the inhibition of TSG-6 expression in hUMSCs. In vitro, lipopolysaccharide/ATP-induced BV2 microglial pyroptosis was inhibited by co-culture with hUMSCs or with rmTSG-6. However, the inhibitory effect of hUMSCs on BV2 microglial pyroptosis was significantly reduced by TSG-6-shRNA transfection.

Conclusion

In TBI mice, microglial pyroptosis was observed. Both in vivo and in vitro, hUMSCs inhibited pyroptosis, particularly microglial pyroptosis, by regulating the NLRP3/Caspase-1/GSDMD signaling pathway via TSG-6.

Electroacupuncture improves TBI dysfunction by targeting HDAC overexpression and BDNF-associated Akt/GSK-3β signaling

Background

Acupuncture or electroacupuncture (EA) appears to be a potential treatment in acute clinical traumatic brain injury (TBI); however, it remains uncertain whether acupuncture affects post-TBI histone deacetylase (HDAC) expression or impacts other biochemical/neurobiological events.

Materials and methods

We used behavioral testing, Western blot, and immunohistochemistry analysis to evaluate the cellular and molecular effects of EA at LI4 and LI11 in both weight drop-impact acceleration (WD)- and controlled cortical impact (CCI)-induced TBI models.

Results

Both WD- and CCI-induced TBI caused behavioral dysfunction, increased cortical levels of HDAC1 and HDAC3 isoforms, activated microglia and astrocytes, and decreased cortical levels of BDNF as well as its downstream mediators phosphorylated-Akt and phosphorylated-GSK-3β. Application of EA reversed motor, sensorimotor, and learning/memory deficits. EA also restored overexpression of HDAC1 and HDAC3, and recovered downregulation of BDNF-associated signaling in the cortex of TBI mice.

Conclusion

The results strongly suggest that acupuncture has multiple benefits against TBI-associated adverse behavioral and biochemical effects and that the underlying mechanisms are likely mediated by targeting HDAC overexpression and aberrant BDNF-associated Akt/GSK-3 signaling.

Current and Potential Pharmacologic Therapies for Traumatic Brain Injury

The present article reviewed the pharmacologic therapies of traumatic brain injury (TBI), including current and potential treatments. Pharmacologic therapies are an essential part of TBI care, and several agents have well-established effects in TBI care. In the acute phase, tranexamic acid, antiepileptics, hyperosmolar agents, and anesthetics are the mainstay of pharmacotherapy, which have proven efficacies. In the post-acute phase, SSRIs, SNRIs, antipsychotics, zolpidem and amantadine, as well as other drugs, have been used to manage neuropsychological problems, while muscle relaxants and botulinum toxin have been used to manage spasticity. In addition, increasing numbers of pre-clinical and clinical studies of pharmaceutical agents, including potential neuroprotective nutrients and natural therapies, are being carried out. In the present article, we classify the treatments into established and potential agents based on the level of clinical evidence and standard of practice. It is expected that many of the potential medicines under investigation will eventually be accepted as standard practice in the care of TBI patients.

The methods of vibrational microspectroscopy reveals long-term biochemical anomalies within the region of mechanical injury within the rat brain

Traumatic brain injury (TBI), meaning functional or structural brain damage which appear as a result of the application of the external physical force, constitutes the main cause of death and disability of individuals and a great socioeconomic problem. To search for the new therapeutic strategies for TBI, better knowledge about posttraumatic pathological changes occurring in the brain is necessary. Therefore in the present paper the Fourier transform infrared microspectroscopy and Raman microscopy were used to examine local and remote biochemical changes occurring in the rat brain as a result of focal cortex injury. The site of the injury and the dorsal part of the hippocampal formation together with the above situated cortex and white matter were the subject of the study. The topographic and quantitative biochemical analysis followed with the statistical study using principal component analysis showed significant biomolecular anomalies within the lesion site but not in the area of the dorsal hippocampal formation and in the above situated white matter and cortex. The observed intralesional anomalies included significantly decreased accumulation of lipids and their structural changes within the place of injury. Also the levels of compounds containing phosphate and carbonyl groups were lower within the lesion site comparing to the surrounding cortex. The opposite relation was, in turn, found for the bands characteristic to proteins and cholesterol/cholesterol esters.

Astrocytes in the Traumatic Brain Injury: the Good and the Bad

Astrocytes control many processes of the nervous system in health and disease, and respond to injury quickly. Astrocytes produce neuroprotective factors in the injured brain to clear cellular debris and to orchestrate neurorestorative processes that are beneficial for neurological recovery after traumatic brain injury (TBI). However, astrocytes also become dysregulated and produce cytotoxic mediators that hinder CNS repair by induction of neuronal dysfunction and cell death. Hence, we discuss the potential role of astrocytes in neuropathological processes such as neuroinflammation, neurogenesis, synaptogenesis and blood-brain barrier repair after TBI. Thus, an improved understanding of the dual role of astrocytes may advance our knowledge of post-brain injury recovery, and provide opportunities for the development of novel therapeutic strategies for TBI.

Traumatic Brain Injury: An Age-Dependent View of Post-Traumatic Neuroinflammation and Its Treatment

Traumatic brain injury (TBI) is a leading cause of death and disability all over the world. TBI leads to (1) an inflammatory response, (2) white matter injuries and (3) neurodegenerative pathologies in the long term. In humans, TBI occurs most often in children and adolescents or in the elderly, and it is well known that immune responses and the neuroregenerative capacities of the brain, among other factors, vary over a lifetime. Thus, age-at-injury can influence the consequences of TBI. Furthermore, age-at-injury also influences the pharmacological effects of drugs. However, the post-TBI inflammatory, neuronal and functional consequences have been mostly studied in experimental young adult animal models. The specificity and the mechanisms underlying the consequences of TBI and pharmacological responses are poorly understood in extreme ages. In this review, we detail the variations of these age-dependent inflammatory responses and consequences after TBI, from an experimental point of view. We investigate the evolution of microglial, astrocyte and other immune cells responses, and the consequences in terms of neuronal death and functional deficits in neonates, juvenile, adolescent and aged male animals, following a single TBI. We also describe the pharmacological responses to anti-inflammatory or neuroprotective agents, highlighting the need for an age-specific approach to the development of therapies of TBI.

Pathophysiological Responses and Roles of Astrocytes in Traumatic Brain Injury

Traumatic brain injury (TBI) is immediate damage caused by a blow to the head resulting from traffic accidents, falls, and sporting activity, which causes death or serious disabilities in survivors. TBI induces multiple secondary injuries, including neuroinflammation, disruption of the blood–brain barrier (BBB), and brain edema. Despite these emergent conditions, current therapies for TBI are limited or insufficient in some cases. Although several candidate drugs exerted beneficial effects in TBI animal models, most of them failed to show significant effects in clinical trials. Multiple studies have suggested that astrocytes play a key role in the pathogenesis of TBI. Increased reactive astrocytes and astrocyte-derived factors are commonly observed in both TBI patients and experimental animal models. Astrocytes have beneficial and detrimental effects on TBI, including promotion and restriction of neurogenesis and synaptogenesis, acceleration and suppression of neuroinflammation, and disruption and repair of the BBB via multiple bioactive factors. Additionally, astrocytic aquaporin-4 is involved in the formation of cytotoxic edema. Thus, astrocytes are attractive targets for novel therapeutic drugs for TBI, although astrocyte-targeting drugs have not yet been developed. This article reviews recent observations of the roles of astrocytes and expected astrocyte-targeting drugs in TBI.

Role of Citicoline in the Management of Traumatic Brain Injury

Head injury is among the most devastating types of injury, specifically called Traumatic Brain Injury (TBI). There is a need to diminish the morbidity related with TBI and to improve the outcome of patients suffering TBI. Among the improvements in the treatment of TBI, neuroprotection is one of the upcoming improvements. Citicoline has been used in the management of brain ischemia related disorders, such as TBI. Citicoline has biochemical, pharmacological, and pharmacokinetic characteristics that make it a potentially useful neuroprotective drug for the management of TBI. A short review of these characteristics is included in this paper. Moreover, a narrative review of almost all the published or communicated studies performed with this drug in the management of patients with head injury is included. Based on the results obtained in these clinical studies, it is possible to conclude that citicoline is able to accelerate the recovery of consciousness and to improve the outcome of this kind of patient, with an excellent safety profile. Thus, citicoline could have a potential role in the management of TBI.