Mild traumatic brain injury-induced persistent blood-brain barrier disruption is prevented by cyclosporine A treatment in hypertension

The blood-brain barrier as a treatment target for neurodegenerative disorders

INTRODUCTION

The blood-brain barrier (BBB) is a vascular endothelial membrane which restricts entry of toxins, cells, and microorganisms into the brain. At the same time, the BBB supplies the brain with nutrients, key substrates for DNA and RNA synthesis, and regulatory molecules, and removes metabolic waste products from brain to blood. BBB breakdown and/or dysfunction have been shown in neurogenerative disorders including Alzheimer's disease (AD). Current data suggests that these BBB changes may initiate and/or contribute to neuronal, synaptic, and cognitive dysfunction, and possibly other aspects of neurodegenerative processes.

AREAS COVERED

We first briefly review recent studies uncovering molecular composition of brain microvasculature and examine the BBB as a possible therapeutic target in neurodegenerative disorders with a focus on AD. Current strategies aimed at protecting and/or restoring altered BBB functions are considered. The relevance of BBB-directed approaches to improve neuronal and synaptic function, and to slow progression of neurodegenerative processes are also discussed. Lastly, we review recent advancements in drug delivery across the BBB.

EXPERT OPINION

BBB breakdown and/or dysfunction can significantly affect neuronal and synaptic function and neurodegenerative processes. More attention should focus on therapeutics to preserve or restore BBB functions when considering treatments of neurodegenerative diseases and AD.

Hybrid membrane-coated Cyclosporine A nanocrystals preventing secondary brain injury via alleviating neuroinflammatory and oxidative stress

Secondary brain injury (SBI), a prevalent complication following traumatic brain injury, remains a critical clinical challenge due to the lack of effective therapeutic interventions. Mitochondrial dysfunction in injured neurons and microglia has been identified as a pivotal driver of SBI pathogenesis. Cyclosporine A (CsA) exerts neuroprotective effects by inhibiting the over opening of the mitochondrial permeability transition pore, thereby preserving mitochondrial dysfunction in both neurons and microglia. These properties render CsA a promising candidate for SBI treatment. However, CsA shows systemic distribution and insufficient central nervous system penetration. In this study, a biomimetic SBI-targeted CsA nanocrystal system (CsA-NC@M-PB) was prepared by using hybrid membranes derived from platelets and microglia. A large amount of CsA-NC@M-PB actively accumulated in the damaged brain tissue in mild SBI mice. Mechanistically, CsA-NC@M-PB effectively attenuated mitochondrial dysfunction in both neuron and microglia, and promoted microglial polarization towards M2 phenotype by suppressing the overproduction of reactive oxygen species. Meanwhile, by suppressing neuroinflammation and enhancing the integrity of the BBB, CsA-NC@M-PB protected neuron from apoptosis and improved directional learning and memory abilities of mild SBI mice. These findings collectively demonstrated that CsA-NC@M-PB was a therapeutically viable strategy for SBI management.

Cyclosporine A Accelerates Neurorecovery Transcriptional Trajectory in a Swine Model of Diffuse Traumatic Brain Injury

Mild traumatic brain injury (mTBI) is a leading cause of morbidity in children with both short- and long-term neurological, cognitive, cerebrovascular, and emotional deficits. These deficits have been attributed to ongoing pathophysiological cascades that occur acutely and persist post-injury. Given our limited understanding of the transcriptional changes associated with these pathophysiological cascades, we studied formalin-fixed paraffin-embedded (FFPE) tissues from the frontal cortex (FC) and the hippocampus + amygdala (H&A) regions of swine (N = 40) after a sagittal rapid non-impact head rotation (RNR). We then sequenced RNA to define transcriptional changes at 1 day and 1 week after injury and investigated the protective influence of cyclosporine A (CsA) treatment. Differentially expressed genes (DEGs) were classified into five temporal patterns (Early, Transient, Persistent, Intensified, Delayed, or Late). DEGs were more abundant at 1 week than 1 day. Shared significant gene ontology annotations in both regions included terms associated with neuronal distress at 1 day and neurorecovery at 1 week. CsA (20 mg/kg/day) infused for 1 day (beginning at 6 h after injury) accelerated 466 DEGs in the FC and 2794 DEGs in the H&A, such that the CsA-treated transcriptional profile was associated with neurorecovery. Overall, our data reveal the effects of anatomic region and elapsed time on gene expression post-mTBI and motivate future studies of CsA treatment.

Ginsenoside Rb1 alleviates blood-brain barrier damage and demyelination in experimental autoimmune encephalomyelitis mice by regulating JNK/ ERK/NF-κB signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

The traditional Chinese herb Panax ginseng recorded in "Shennong Herbal Classic" is renowned for its purported vascular regulatory properties and immune-enhancing capabilities. Ginsenoside Rb1 (Rb1), a prominent bioactive compound in Panax, has demonstrated significant neuropharmacological activities. However, its impact on multiple sclerosis (MS) and blood-brain barrier (BBB) damage remains inadequately investigated.

AIM OF THE STUDY

Inflammation and BBB disruption are pivotal to MS. Tightly packed brain capillary endothelial cells are fundamental to the structural and functional integrity of the BBB. Rb1 has been shown to alleviate BBB damage in stroke rats, but its effect on BBB damage in MS is not well understood. The objective of this study was to examine the role and mechanism of Rb1 on BBB injury in experimental autoimmune encephalomyelitis (EAE) mice.

MATERIALS AND METHODS

The BBB protection effect and mechanism of Rb1 were evaluated in LPS-treated bEnd.3 cells and EAE model mice. The mRNA expression levels of the inflammatory factor and the protein expressions of matrix metalloproteinases 9 (MMP9), zona occludens 1 (ZO-1), inhibitor of NF-κB (IκBα), occludin, Jun-amino-terminal kinase (JNK), and nuclear factor-κB (NF-κB) in bEnd.3 cells and mouse cerebral cortex were quantified. The permeability of bEnd.3 cells was examined by measuring trans-endothelial electrical resistance (TEER) and sodium fluorescein (NaF) leakage.

RESULTS

Rb1 administration in the early stages of EAE postponed the disease's onset and lessened its severity. Rb1 inhibited the destruction of the BBB in brain cortex of EAE mice. Rb1 reduced the lipopolysaccharide (LPS)-induced hyperpermeability of bEnd.3 cells and prevented the downregulation of TJ proteins. In addition, in LPS-induced bEnd.3 cells, Rb1 decreased the overproduction of reactive oxygen species. Moreover, Rb1 suppressed the phosphorylation of JNK, ERK, NF-κB, and IκB in vivo and in vitro. Furthermore, the JNK agonist anisomycin was observed to partially abolish the protective effect of Rb1 in bEnd.3 cells treated with LPS.

CONCLUSIONS

Taken together, we demonstrated that Rb1 improved demyelination and BBB damage in EAE mice by modulating JNK/ERK/NF-κB signaling pathway. This study can offer a theoretical foundation for the use of Rb1 in the treatment of MS/EAE by preventing BBB injury.

Resilience of Spontaneously Hypertensive Rats to Secondary Insults After Traumatic Brain Injury: Immediate Seizures, Survival, and Stress Response

Traumatic brain injury (TBI) is one of the primary causes of mortality and disability, with arterial blood pressure being an important factor in the clinical management of TBI. Spontaneously hypertensive rats (SHRs), widely used as a model of essential hypertension and vascular dementia, demonstrate dysfunction of the hypothalamic-pituitary-adrenal axis, which may contribute to glucocorticoid-mediated hippocampal damage. The aim of this study was to assess acute post-TBI seizures, delayed mortality, and hippocampal pathology in SHRs and normotensive Sprague Dawley rats (SDRs). Male adult SDRs and SHRs were subjected to lateral fluid-percussion injury. Immediate seizures were video recorded, corticosterone (CS) was measured in blood plasma throughout the study, and hippocampal morphology assessed 3 months post-TBI. Acute and remote survival rates were significantly higher in the SHRs compared to the SDRs (overall mortality 0% and 58%, respectively). Immediate seizure duration predicted acute but not remote mortality. TBI did not affect blood CS in the SHRs, while the CS level was transiently elevated in the SDRs, predicting remote mortality. Neuronal cell loss in the polymorph layer of ipsilateral dentate gyrus was found in both the SDRs and SHRs, while thinning of hippocampal pyramidal and granular cell layers were strain- and area-specific. No remote effects of TBI on the density of astrocytes or microglia were revealed. SHRs possess a unique resilience to TBI as compared with normotensive SDRs. SHRs show shorter immediate seizures and reduced CS response to the injury, suggesting the development of long-term adaptative mechanisms associated with chronic hypertension. Though remote post-traumatic hippocampal damage in ipsilateral dentate gyrus is obvious in both SHRs and SDRs, the data imply that physiological adaptations to high blood pressure in SHRs may be protective, preventing TBI-induced mortality but not hippocampal neurodegeneration. Understanding the mechanisms of resilience to TBI may also help improve clinical recommendations for patients with hypertension. Limitation: since more than a half of the SDRs with prolonged immediate seizures or elevated CS 3 days after TBI have died, survivorship bias might hamper correct interpretation of the data.

Torsion-Induced Traumatic Optic Neuropathy (TITON): A Physiologically Relevant Animal Model of Traumatic Optic Neuropathy

Traumatic optic neuropathy (TON) is a common cause of irreversible blindness following head injury. TON is characterized by axon damage in the optic nerve followed by retinal ganglion cell death in the days and weeks following injury. At present, no therapeutic or surgical approach has been found to offer any benefit beyond observation alone. This is due in part to the lack of translational animal models suitable for understanding mechanisms and evaluating candidate treatments. In this study, we developed a rat model of TON in which the eye is rapidly rotated, inflicting mechanical stress on the optic nerve and leading to significant visual deficits. These functional deficits were thoroughly characterized up to one week after injury using electrophysiology and immunohistochemistry. The photopic negative response (PhNR) of the light adapted full field electroretinogram (LA ffERG) was significantly altered following injury. This correlated with increased biomarkers of retinal stress, axon disruption, and cell death. Together, this evidence suggests the utility of our model for mimicking clinically relevant TON and that the PhNR may be an early diagnostic for TON. Future studies will utilize this animal model for evaluation of candidate treatments.

Metabolic disorders after traumatic brain injury: a narrative review of systemic consequences

Traumatic brain injury (TBI) is characterized as a heterogeneous and pathological remodeling of brain physiology because of various external mechanisms, including blows, falls, and rapid acceleration and deceleration of the skull. Its pathophysiology consists of two distinct moments, beginning with a primary lesion resulting from the impact that evolves into a secondary lesion as biochemical and molecular mechanisms are activated. The severity and prognosis after TBI vary widely, depending on factors such as the site of the injury, the patient's premorbid history, and the severity of the injury, and can result in long-term sequelae impacting multiple organs and systems, with a reduction in the life expectancy of these individuals. A relevant point to be investigated is the correlation between metabolic syndrome (MS), defined as the combination of glucose intolerance, dyslipidemia, systemic arterial hypertension (SAH), and acute or chronic coronary heart disease, and the prognosis of these individuals after a TBI. Therefore, this review seeks to verify the correlation between the occurrence of MS in patients who have suffered TBI as a pre-existing comorbidity and whether it develops later, looking for evidence in studies based on animal models and cohort follow-ups of individuals who have suffered TBI in the short and long term to assess the prognosis presented.

SCG2 mediates blood-brain barrier dysfunction and schizophrenia-like behaviors after traumatic brain injury

Traumatic brain injury (TBI), which is characterized by acute neurological dysfunction, is also one of the most widely recognized environmental risk factors for various neurological and psychiatric disorders. However, the role of TBI in neurological perturbation and the mechanisms underlying these disorders remain unknown. We evaluated transcriptional changes in cells of the frontal cortex after TBI by exploiting single-cell RNA sequencing (scRNA-Seq). We adopted the gene expression omnibus and scRNA-Seq to identify the mediation by secretogranin II (SCG2) of TBI-induced schizophrenia. Astrocytes are a principal source of SCG2 in the frontal cortex after TBI. Our analysis indicated that SCG2-triggered disruption of the blood-brain barrier (BBB) via the CypA-MMP-9 signaling pathway. Furthermore, astrocytic SCG2 knockout in the frontal cortex reduced BBB damage, mitigated inflammation, and inhibited schizophrenia after TBI. In conclusion, we identified the SCG2-CypA-MMP-9 signaling pathway in reactive astrocytes as a key switch in the protection of the BBB and provided a novel therapeutic avenue for treating psychiatric disorders after TBI.

Influence of Blood Components on Neuroinflammation, Blood-Brain Barrier Breakdown, and Functional Damage After Acute Subdural Hematoma in Rats

A central component of injury development after acute subdural hematoma (ASDH) is the increased intracranial pressure and consecutive mechanical reduction of cerebral blood flow (CBF). However, the role of different blood constituents in ASDH as additional lesioning factors remains unclear. This study examines the influence of blood components on neuroinflammation, blood-brain barrier (BBB) breakdown, and functional deficits in a rat model of ASDH. We infused corpuscular (whole blood, whole blood lysate, and red cell blood) and plasmatic (blood plasma, anticoagulated blood plasma, and aqueous isotonic solution) blood components into the subdural space while CBF was monitored. Rats then underwent behavioral testing. Lesion analysis and immunohistochemistry were performed 2 days after ASDH. Inflammatory reaction was assessed using staining for ionized calcium-binding adaptor molecule 1 and glial fibrillary acidic protein, interleukin-1ß, tumor necrosis factor-alpha, and membrane attack complex. Integrity of the BBB was evaluated with albumin and matrix metalloproteinase 9 (MMP9) staining. We observed a significant drop in CBF in the corpuscular group (75% ± 7.5% of baseline) with distinct post-operative deficits and larger lesion volume compared to the plasmatic group (13.6 ± 5.4 vs. 1.3 ± 0.4 mm3). Further, inflammation was significantly increased in the corpuscular group with stronger immunoreaction. After whole blood infusion, albumin and MMP9 immunoreaction were significantly increased, pointing toward a disrupted BBB. The interaction between corpuscular and plasmatic blood components seems to be a key factor in the detrimental impact of ASDH. This interaction results in neuroinflammation and BBB leakage. These findings underscore the importance of performing surgery as early as possible and also provide indications for potential pharmacological targets.