Roadmap for Conducting Neuroscience Research in the COVID-19 Era and Beyond: Recommendations From the SNACC Research Committee.

The coronavirus disease 2019 (COVID-19) pandemic has impacted many aspects of neuroscience research. At the 2020 Society of Neuroscience in Anesthesiology and Critical Care (SNACC) Annual Meeting, the SNACC Research Committee met virtually to discuss research challenges encountered during the COVID-19 pandemic along with possible strategies for facilitating research activities. These challenges and recommendations are included in this Consensus Statement. The objectives are to: (1) provide an overview of the disruptions and challenges to neuroscience research caused by the COVID-19 pandemic, and; (2) put forth a set of consensus recommendations for strengthening research sustainability during and beyond the current pandemic. Specific recommendations are highlighted for adapting laboratory and human subject study activities to optimize safety. Complementary research activities are also outlined for both laboratory and clinical researchers if specific investigations are impossible because of regulatory or societal changes. The role of virtual platforms is discussed with respect to fostering new collaborations, scheduling research meetings, and holding conferences such that scientific collaboration and exchange of ideas can continue. Our hope is for these recommendations to serve as a valuable resource for investigators in the neurosciences and other research disciplines for current and future research disruptions.

Improving Understanding and Outcomes of Traumatic Brain Injury Using Bidirectional Translational Research.

Recent clinical trials in traumatic brain injury (TBI) have failed to demonstrate therapeutic effects even when there appears to be good evidence for efficacy in one or more appropriate pre-clinical models. While existing animal models mimic the injury, difficulties in translating promising therapeutics are exacerbated by the lack of alignment of discrete measures of the underlying injury pathology between the animal models and human subjects. To address this mismatch, we have incorporated reverse translation of bedside experience to inform pre-clinical studies in a large animal (pig) model of TBI that mirror practical clinical assessments. Cerebral autoregulation is impaired after TBI, contributing to poor outcome. Cerebral perfusion pressure (CPP) is often normalized by use of vasoactive agents to increase mean arterial pressure (MAP) and thereby limit impairment of cerebral autoregulation and neurological deficits. Vasoactive agents clinically used to elevate MAP to increase CPP after TBI, such as phenylephrine (Phe), dopamine (DA), norepinephrine (NE), and epinephrine (EPI), however, have not been compared sufficiently regarding effect on CPP, autoregulation, and survival after TBI, and clinically, current vasoactive agent use is variable. The cerebral effects of these clinically commonly used vasoactive agents are not known. This review will emphasize pediatric work and will describe bidirectional translational studies using a more human-like animal model of TBI to identify better therapeutic strategies to improve outcome post-injury. These studies in addition investigated the mechanism(s) involved in improvement of outcome in the setting of TBI.

Propranolol protects cerebral autoregulation and reduces hippocampal neuronal cell death through inhibition of interleukin-6 upregulation after traumatic brain injury in pigs.

BACKGROUND: Traumatic brain injury (TBI) is associated with reduced cerebral blood flow and impaired autoregulation after TBI, which may lead to poor outcome. Clinical evidence has implicated neurological injuries and associated neuroinflammation as causes of cardiac dysfunction. Studies on newborn pigs show an association of elevated catecholamines with a sex-dependent impairment of cerebral autoregulation after TBI. One strategy to decrease sympathetic hyperactivity is pharmacological intervention with beta blockade. We tested the hypothesis that propranolol would prevent the impairment of cerebral autoregulation and tissue changes after TBI via inhibition of interleukin-6 (IL-6) upregulation. METHODS: Using newborn pigs of both sexes equipped with a closed cranial window, TBI was induced via lateral fluid percussion injury. Propranolol was administered at 1 h post-TBI. Analyses included cerebral autoregulation (pial artery reactivity) before and 4 h post-TBI, CSF IL-6 analysed (enzyme-linked immunosorbent assay), and histopathology at 4 h post-TBI. RESULTS: Propranolol administration prevented impairment of hypotensive dilation in both male and female newborn pigs after fluid percussion injury, which was paralleled by reduced upregulation of IL-6 in the CSF. Moreover, propranolol prevented neuronal cell death in cornu amonis (CA)1 and CA3 hippocampus equivalently in male and female pigs after TBI. Papaverine-induced dilation was unchanged by TBI and propranolol. CONCLUSIONS: These data indicate that sympathetic hyperactivity noted after TBI can be limited by propranolol administration to result in improved brain outcome post-injury via block of IL-6 upregulation, and this effect is irrespective of sex.

Plasma Levels, Temporal Trends and Clinical Associations between Biomarkers of Inflammation and Vascular Homeostasis after Pediatric Traumatic Brain Injury.

Expression of inflammatory (interleukin-6 [IL-6]) and vascular homeostatic (angiopoietin-2 [AP-2], endothelin-1 [ET-1], endocan-2 [EC-2]) biomarkers in pediatric traumatic brain injury (TBI) was examined in this prospective, observational cohort study of 28 children hospitalized with mild, moderate, and severe TBI by clinical measures (age, sex, Glasgow Coma Scale score [GCS], Injury Severity Score [ISS], and cerebral autoregulation status). Biomarker patterns suggest an inverse relationship between GCS and AP-2, GCS and IL-6, ISS and ET-1, but a direct relationship between GCS and ET-1 and ISS and AP-2. Biomarker patterns suggest an inverse relationship between AP-2 and ET-1, AP-2 and EC-2, but a direct relationship between AP-2 and IL-6, IL-6 and EC-2, and IL-6 and ET-1. Plasma concentrations of inflammatory and vascular homeostatic biomarkers suggest a role for inflammation and disruption of vascular homeostasis during the first 10 days across the severity spectrum of pediatric TBI. Although not statistically significant, without impact on cerebral autoregulation, biomarker patterns suggest a relationship between inflammation and alterations in vascular homeostasis. The large variation in biomarker levels within TBI severity and age groups, and by sex suggests other contributory factors to biomarker expression.

Cerebral Perfusion Pressure Directed-Therapy Modulates Cardiac Dysfunction After Traumatic Brain Injury to Influence Cerebral Autoregulation in Pigs.

BACKGROUND: Traumatic brain injury (TBI) is an important contributor to morbidity and mortality. Low cerebral perfusion pressure (CPP, mean arterial pressure [MAP] minus intracranial pressure) after TBI is associated with cerebral ischemia, impaired cerebral autoregulation, and poor outcomes. Normalization of CPP and limitation of cerebral autoregulation impairment is a key therapeutic goal. However, some vasoactive agents used to elevate MAP such as phenylephrine (Phe) improve outcome in females but not male piglets after TBI while dopamine (DA) does so in both sexes. Clinical evidence has implicated neurological injuries as a cause of cardiac dysfunction, and we recently described cardiac dysfunction after TBI. Cardiac dysfunction may, in turn, influence brain health. One mechanism of myocyte injury may involve catecholamine excess. We therefore tested the hypothesis that TBI caused cardiac dysfunction and catecholamine excess which may reciprocally be modulated by vasoactive agent choice to normalize CPP and prevent impairment of cerebral autoregulation after injury. METHODS: TBI was produced in anesthetized pigs equipped with a closed cranial window, and Phe or DA administered to normalize CPP. RESULTS: Plasma cardiac enzymes troponin and creatine kinase and catecholamines epinephrine and norepinephrine were elevated by TBI, such release potentiated by Phe in males but blocked in female piglets and blocked in both sexes after DA. Cerebral autoregulation was impaired after TBI, worsened by Phe in males but protected in females and males treated with DA. Papaverine-induced dilation was unchanged by fluid percussion brain injury, DA, and Phe. CONCLUSIONS: These data indicate that pressor choice in elevation of CPP is important in limiting cardiac dysfunction and suggest that DA protects cerebral autoregulation in both sexes via reduction of cardiac biomarkers of injury and catecholamines released after TBI.

Translational approach towards determining the role of cerebral autoregulation in outcome after traumatic brain injury.

Cerebral autoregulation is impaired after traumatic brain injury (TBI), contributing to poor outcome. In the context of the neurovascular unit, cerebral autoregulation contributes to neuronal cell integrity and clinically Glasgow Coma Scale is correlated to intactness of autoregulation after TBI. Cerebral Perfusion Pressure (CPP) is often normalized by use of vasoactive agents to increase mean arterial pressure (MAP) and thereby limit impairment of cerebral autoregulation and neurological deficits. However, current vasoactive agent choice used to elevate MAP to increase CPP after TBI is variable. Vasoactive agents, such as phenylephrine, dopamine, norepinephrine, and epinephrine, clinically have not sufficiently been compared regarding effect on CPP, autoregulation, and survival after TBI. The cerebral effects of these clinically commonly used vasoactive agents are incompletely understood. This review will describe translational studies using a more human like animal model (the pig) of TBI to identify better therapeutic strategies to improve outcome post injury. These studies also investigated the role of age and sex in outcome and mechanism(s) involved in improvement of outcome in the setting of TBI. Additionally, this review considers use of inhaled nitric oxide as a novel neuroprotective strategy in treatment of TBI.

Inhaled nitric oxide protects cerebral autoregulation through prevention of impairment of ATP and calcium sensitive K channel mediated cerebrovasodilation after traumatic brain injury.

Hypotension and low cerebral perfusion pressure are associated with low cerebral blood flow, cerebral ischemia, and poor outcomes after traumatic brain injury (TBI). Cerebral autoregulation is impaired after TBI, contributing to poor outcome. In prior studies, ERK mitogen activated protein kinase (MAPK) and ET-1 had been observed to be upregulated and contribute to impairment of cerebral autoregulation and histopathology after fluid percussion brain injury (FPI). Activation of ATP and Calcium sensitive (Katp and Kca) channels produce cerebrovasodilation and contribute to autoregulation, both impaired after TBI. Upregulation of ERK MAPK and endothelin-1 (ET-1) produces K channel function impairment after CNS injury. Inhaled nitric oxide (iNO) has recently been observed to prevent impairment of cerebral autoregulation and hippocampal CA1 and CA3 neuronal cell necrosis after FPI via block of upregulation of ERK MAPK and ET-1. We presently investigated whether iNO prevented impairment of Katp and Kca-mediated cerebrovasodilation after FPI in pigs equipped with a closed cranial window. Results show that pial artery dilation in response to the Katp agonist cromakalim, the Kca agonist NS1619, PGE2 and the NO releaser sodium nitroprusside (SNP) were blocked by FPI, but such impairment was prevented by iNO administered at 2 h post injury. Protection lasted for at least 1 h after iNO administration was stopped. Using vasodilaton as an index of function, these data indicate that iNO prevents impairment of cerebral autoregulation and limits histopathology after TBI through protection of K channel function via blockade of ERK MAPK and ET-1.

Release of IL-6 After Stroke Contributes to Impaired Cerebral Autoregulation and Hippocampal Neuronal Necrosis Through NMDA Receptor Activation and Upregulation of ET-1 and JNK.

The sole FDA-approved drug treatment for ischemic stroke is tissue-type plasminogen activator (tPA). However, upregulation of JNK mitogen-activated protein kinase (MAPK) and endothelin 1 (ET-1) by tPA after stroke contributes to impaired cerebrovascular autoregulation. Wild-type (wt) tPA can bind to the lipoprotein-related receptor (LRP), which mediates vasodilation, or NMDA receptors (NMDA-Rs), exacerbating vasoconstriction. Elevations in IL-6, a marker of inflammation that accompanies stroke, are reported to be an adverse prognostic factor. We hypothesized that IL-6 released into CSF after stroke by wt-tPA through activation of NMDA-Rs and upregulation of ET-1 and JNK contribute to impairment of cerebrovascular autoregulation and increased histopathology. Results show that IL-6 was increased post stroke in pigs, which was increased further by wt-tPA. Co-administration of the IL-6 antagonist LMT-28 with wt-tPA prevented impairment of cerebrovascular autoregulation and necrosis of hippocampal cells. wt-tPA co-administered with the JNK inhibitor SP 600125 and the ET-1 antagonist BQ 123 blocked stroke-induced elevation of IL-6. Co-administration of LMT-28 with wt-tPA blocked the augmentation of JNK and ET-1 post stroke. In conclusion, IL-6 released after stroke, which is enhanced by wt-tPA through activation of NMDA-Rs and upregulation of ET-1 and JNK, impairs cerebrovascular autoregulation and increases histopathology. Strategies that promote fibrinolysis while limiting activation of NMDA-Rs and upregulation of IL-6 may improve the benefit/risk ratio compared to wt-tPA in treatment of stroke.

Inhaled Nitric Oxide Protects Cerebral Autoregulation and Reduces Hippocampal Necrosis After Traumatic Brain Injury Through Inhibition of ET-1, ERK MAPK and IL-6 Upregulation in Pigs.

OBJECTIVE: Traumatic brain injury (TBI) is an important contributor to morbidity and mortality. Cerebral autoregulation is impaired after TBI, contributing to poor outcome. Extracellular signal-related kinase (ERK) mitogen activated protein kinase (MAPK) and ET-1 are upregulated and contribute to impairment of cerebral autoregulation and histopathology after porcine fluid percussion brain injury (FPI). Recent studies show that inhaled nitric oxide (iNO) prevents impairment of cerebral autoregulation and histopathology after FPI in pigs. Unrelated studies indicated an association between ERK and increased IL-6 after FPI. However, the role of IL-6 in central nervous system (CNS) pathology is not well understood. We investigated whether iNO protects autoregulation and limits histopathology after FPI in pigs due to modulation of brain injury associated upregulation of ET-1, ERK MAPK, and IL-6. METHODS: Lateral FPI was produced in anesthetized pigs equipped with a closed cranial window and iNO administered at 30 min or 2 h post injury. RESULTS: CSF ET-1, ERK MAPK, and IL-6 were increased by FPI, but release was blocked by iNO administered at 30 min or 2 h after TBI. The IL-6 antagonist LMT-28 prevented impairment of cerebral autoregulation and hippocampal CA1 and CA3 neuronal necrosis after FPI. Papaverine induced dilation was unchanged by FPI and LMT-28. Protection lasted for at least 2 h after iNO administration was stopped. CONCLUSIONS: These data indicate that iNO protects cerebral autoregulation and reduces hippocampal necrosis after traumatic brain injury through inhibition of ET-1, ERK MAPK, and IL-6 upregulation in pigs.

Inhaled Nitric Oxide Protects Cerebral Autoregulation and Reduces Hippocampal Neuronal Cell Necrosis after Traumatic Brain Injury in Newborn and Juvenile Pigs.

Traumatic brain injury (TBI) contributes to morbidity in children, and boys are disproportionately represented. Cerebral blood flow (CBF) is reduced and autoregulation is impaired after TBI, contributing to poor outcome. Cerebral perfusion pressure (CPP) is often normalized by use of vasoactive agents to increase mean arterial pressure (MAP). In prior studies of male and female newborn and juvenile pigs, we observed that phenylephrine, norepinephrine, epinephrine, and dopamine demonstrated different sex- and age-dependent abilities to prevent impairment of cerebral autoregulation and limit histopathology after TBI, despite equivalent CPP values. This observation complicated treatment choice. Alternatively, administration of a cerebral vasodilator may improve cerebral hemodynamics after TBI by increasing CBF. In prior studies, intravenous sodium nitroprusside, a nitric oxide (NO) releaser, elevated CBF after TBI but failed to prevent impairment of cerebral autoregulation due to a confounding decrease in MAP, which lowered CPP. We presently test the hypothesis that inhaled NO (iNO) will protect cerebral autoregulation and prevent hippocampal histopathology after TBI. Results show that iNO administered at 30 min or 2 h after TBI protected cerebral autoregulation and prevented neuronal cell necrosis in CA1 and CA3 hippocampus equivalently in male and female newborn and juvenile pigs without change in MAP. Protection lasted for at least 2 h after iNO administration was stopped. Papaverine-induced dilation was unchanged by TBI and iNO. These data indicate that iNO offers the opportunity to have a single therapeutic that uniformly protects autoregulation and limits hippocampal neuronal cell necrosis across both ages and sexes.

Prevalence, Evolution, and Extent of Impaired Cerebral Autoregulation in Children Hospitalized With Complex Mild Traumatic Brain Injury.

OBJECTIVES: To examine cerebral autoregulation in children with complex mild traumatic brain injury. DESIGN: Prospective observational convenience sample. SETTING: PICU at a level I trauma center. PATIENTS: Children with complex mild traumatic brain injury (trauma, admission Glasgow Coma Scale score 13-15 with either abnormal head CT, or history of loss of consciousness). INTERVENTIONS: Cerebral autoregulation was tested using transcranial Doppler ultrasound between admission day 1 and 8. MEASUREMENTS AND MAIN RESULTS: The primary outcome was prevalence of impaired cerebral autoregulation (autoregulation index < 0.4),determined using transcranial Doppler ultrasonography and tilt testing. Secondary outcomes examined factors associated with and evolution and extent of impairment. Cerebral autoregulation testing occurred in 31 children 10 years (SD, 5.2 yr), mostly male (59%) with isolated traumatic brain injury (91%), median admission Glasgow Coma Scale 15, Injury Severity Scores 14.2 (SD, 7.7), traumatic brain injury due to fall (50%), preadmission loss of consciousness (48%), and abnormal head CT scan (97%). Thirty-one children underwent 56 autoregulation tests. Impaired cerebral autoregulation occurred in 15 children (48.4%) who underwent 19 tests; 68% and 32% of tests demonstrated unilateral and bilateral impairment, respectively. Compared with children on median day 6 of admission after traumatic brain injury, impaired autoregulation was most common in the first 5 days after traumatic brain injury (day 1: relative risk, 3.7; 95% CI, 1.9-7.3 vs day 2: relative risk, 2.7; 95% CI, 1.1-6.5 vs day 5: relative risk, 1.33; 95% CI, 0.7-2.3). Children with impaired autoregulation were older (12.3 yr [SD, 1.3 yr] vs 8.7 yr [SD, 1.1 yr]; p = 0.04) and tended to have subdural hematoma (64% vs 44%), epidural hematoma (29% vs 17%), and subarachnoid hemorrhage (36% vs 28%). Eight children (53%) were discharged home with ongoing impaired cerebral autoregulation. CONCLUSIONS: Impaired cerebral autoregulation is common in children with complex mild traumatic brain injury, despite reassuring admission Glasgow Coma Scale 13-15. Children with complex mild traumatic brain injury have abnormal cerebrovascular hemodynamics, mostly during the first 5 days. Impairment commonly extends to the contralateral hemisphere and discharge of children with ongoing impaired cerebral autoregulation is common.

Red blood cell-hitchhiking boosts delivery of nanocarriers to chosen organs by orders of magnitude.

Drug delivery by nanocarriers (NCs) has long been stymied by dominant liver uptake and limited target organ deposition, even when NCs are targeted using affinity moieties. Here we report a universal solution: red blood cell (RBC)-hitchhiking (RH), in which NCs adsorbed onto the RBCs transfer from RBCs to the first organ downstream of the intravascular injection. RH improves delivery for a wide range of NCs and even viral vectors. For example, RH injected intravenously increases liposome uptake in the first downstream organ, lungs, by ~40-fold compared with free NCs. Intra-carotid artery injection of RH NCs delivers >10% of the injected NC dose to the brain, ~10× higher than that achieved with affinity moieties. Further, RH works in mice, pigs, and ex vivo human lungs without causing RBC or end-organ toxicities. Thus, RH is a clinically translatable platform technology poised to augment drug delivery in acute lung disease, stroke, and several other diseases.

Pre-Clinical Testing of Therapies for Traumatic Brain Injury.

Despite the large number of promising neuroprotective agents identified in experimental traumatic brain injury (TBI) studies, none has yet shown meaningful improvements in long-term outcome in clinical trials. To develop recommendations and guidelines for pre-clinical testing of pharmacological or biological therapies for TBI, the Moody Project for Translational Traumatic Brain Injury Research hosted a symposium attended by investigators with extensive experience in pre-clinical TBI testing. The symposium participants discussed issues related to pre-clinical TBI testing including experimental models, therapy and outcome selection, study design, data analysis, and dissemination. Consensus recommendations included the creation of a manual of standard operating procedures with sufficiently detailed descriptions of modeling and outcome measurement procedures to permit replication. The importance of the selection of clinically relevant outcome variables, especially related to behavior testing, was noted. Considering the heterogeneous nature of human TBI, evidence of therapeutic efficacy in multiple, diverse (e.g., diffuse vs. focused) rodent models and a species with a gyrencephalic brain prior to clinical testing was encouraged. Basing drug doses, times, and routes of administration on pharmacokinetic and pharmacodynamic data in the test species was recommended. Symposium participants agreed that the publication of negative results would reduce costly and unnecessary duplication of unsuccessful experiments. Although some of the recommendations are more relevant to multi-center, multi-investigator collaborations, most are applicable to pre-clinical therapy testing in general. The goal of these consensus guidelines is to increase the likelihood that therapies that improve outcomes in pre-clinical studies will also improve outcomes in TBI patients.

Early changes in cerebral autoregulation among youth hospitalized after sports-related traumatic brain injury.

OBJECTIVE: To examine early cerebral haemodynamic changes among youth hospitalized with sports-related traumatic brain injury (TBI). STUDY DESIGN: Youth 0-18 years admitted to a level one trauma centre with sports-related TBI were enrolled. Daily measures included clinical symptoms and Glasgow Coma Scale (GCS) score. Using Transcranial Doppler (TCD) ultrasonography and tilt testing, we measured middle cerebral artery flow velocity (Vmca) and cerebral autoregulation index (ARI). RESULTS: Six previously healthy males age 14 (IQR 12-16) years with headache and abnormal head CT were admitted with median admission GCS 15. Six patients underwent 12 TCD examinations between hospital days 0-9. Low Vmca occurred in 3/6 patients and on the side of TBI, whereas high Vmca occurred in 2/6 patients. Five patients had at least one measurement of impaired and five patients had absent cerebral autoregulation of at least one hemisphere; all these five patients had GCS 15 and headache during TCD examinations. Three patients were discharged with absent cerebral autoregulation. Five (83%) patients were discharged to home and one patient was discharged to a rehabilitation facility. CONCLUSION: Headache, abnormal Vmca and impaired cerebral autoregulation occur after sports-related TBI, despite normal GCS. Headache may signal underlying neurovascular abnormality in sports-related TBI.

tPA variant tPA-A296-299 Prevents impairment of cerebral autoregulation and necrosis of hippocampal neurons after stroke by inhibiting upregulation of ET-1.

Tissue-type plasminogen activator (tPA) is neurotoxic and exacerbates uncoupling of cerebral blood flow (CBF) and metabolism after stroke, yet it remains the sole FDA-approved drug for treatment of ischemic stroke. Upregulation of c-Jun-terminal kinase (JNK) after stroke contributes to tPA-mediated impairment of autoregulation, but the role of endothelin-1 (ET-1) is unknown. Based on the Glasgow Coma Scale, impaired autoregulation is linked to adverse outcomes after TBI, but correlation with hippocampal histopathology after stroke has not been established. We propose that given after stroke, tPA activates N-Methyl-D-Aspartate receptors (NMDA-Rs) and upregulates ET-1 in a JNK dependent manner, imparing autoregulation and leading to histopathology. After stroke, CBF was reduced in the hippocampus and reduced further during hypotension, which did not occur in hypotensive sham pigs, indicating impairment of autoregulation. Autoregulation and necrosis of hippocampal CA1 and CA3 neurons were further impaired by tPA, but were preserved by the ET-1 antagonist BQ 123 and tPA-A,296-299 a variant that is fibrinolytic but does not bind to NMDA-Rs. Expression of ET-1 was increased by stroke and potentiated by tPA but returned to sham levels by tPA-A296-299 and the JNK antagonist SP600125. Results show that JNK releases ET-1 after stroke. Tissue-type plasminogen activator -A296-299 prevents impairment of cerebral autoregulation and histopathology after stroke by inhibiting upregulation of ET-1.