Effects of a Small-Molecule Perforin Inhibitor in a Mouse Model of CD8 T Cell-Mediated Neuroinflammation

Single-cell sequencing reveals intracranial microvasculature-derived CXCL12 promotes CD8+ T-cell infiltration and blood-brain barrier dysfunction after subarachnoid hemorrhage in mice

BACKGROUND

Processes related to how the intracranial microvasculature initiates brain‒peripheral crosstalk for subsequent blood‒brain barrier (BBB) dysfunction at an early stage after subarachnoid hemorrhage (SAH) ictus are still unknown. This study elucidated the effect and potential mechanism of intracranial microvasculature-mediated T-cell infiltration on BBB function after SAH.

METHODS

Publicly available single-cell RNA sequencing data related to SAH ( https://ngdc.cncb.ac.cn/omix ; Accession No. OMIX006611) were retrieved and analyzed. The dataset was derived from the white matter region of adult male C57BL/6J mice at 1 and 7 days after experimental SAH. The SAH model was induced by endovascular perforation, and experiments were subsequently conducted at 1, 3, 7, and 14 days after SAH to evaluate T-cell infiltration, BBB integrity, neuronal injury, and neurological function.

RESULTS

After SAH, CXCL12 expression was increased in endothelial cells and pericytes, promoting CD8+ T-cell infiltration via the CXCR4 pathway. This immune infiltration appeared to exacerbate BBB disruption and contribute to worsened neurological function. Blocking CXCL12-CXCR4 signaling with a CXCL12 neutralizing antibody or the CXCR4-specific inhibitor AMD3100 significantly reduced CD8+ T-cell infiltration, attenuated BBB damage and improved the neurobehavioral outcomes of SAH mice.

CONCLUSION

This study suggests that, following SAH, both pericytes and endothelial cells may contribute to immune regulation by producing CXCL12, which promotes CD8⁺ T-cell infiltration into the brain. This mechanism may play a role in BBB disruption and neurological dysfunction. Targeting the CXCL12-CXCR4 axis could offer a potential approach for mitigating immune-mediated injury after SAH.

The Multifaceted Role of L-Type Amino Acid Transporter 1 at the Blood-Brain Barrier: Structural Implications and Therapeutic Potential

L-type amino acid transporter 1 (LAT1) is integral to the transport of large neutral amino acids across the blood-brain barrier (BBB), playing a crucial role in brain homeostasis and the delivery of therapeutic agents. This review explores the multifaceted role of LAT1 in neurological disorders, including its structural and functional aspects at the BBB. Studies using advanced BBB models, such as induced pluripotent stem cell (iPSC)-derived systems and quantitative proteomic analyses, have demonstrated LAT1's significant impact on drug permeability and transport efficiency. In Alzheimer's disease, LAT1-mediated delivery of anti-inflammatory and neuroprotective agents shows promise in overcoming BBB limitations. In Parkinson's disease, LAT1's role in transporting L-DOPA and other therapeutic agents highlights its potential in enhancing treatment efficacy. In phenylketonuria, studies have revealed polymorphisms and genetic variations of LAT1, which could be correlated to disease severity. Prodrugs of valproic acid, pregabalin, and gabapentin help use LAT1-mediated transport to increase the therapeutic activity and bioavailability of the prodrug in the brain. LAT1 has also been studied in neurodevelopment disorders like autism spectrum disorders and Rett syndrome, along with neuropsychiatric implications in depression. Its implications in neuro-oncology, especially in transporting therapeutic agents into cancer cells, show immense future potential. Phenotypes of LAT1 have also shown variations in the general population affecting their ability to respond to painkillers and anti-inflammatory drugs. Furthermore, LAT1-targeted approaches, such as functionalized nanoparticles and prodrugs, show promise in overcoming chemoresistance and enhancing drug delivery to the brain. The ongoing exploration of LAT1's structural characteristics and therapeutic applications reiterates its critical role in advancing treatments for neurological disorders.

Greater mechanistic understanding of the cutaneous pathogenesis of Stevens-Johnson syndrome/toxic epidermal necrolysis can shed light on novel therapeutic strategies: a comprehensive review

PURPOSE OF REVIEW

Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) are severe cutaneous adverse drug reactions (SCARs) characterized by widespread epithelial detachment and blistering, which affects the skin and mucocutaneous membranes. To date, therapeutic interventions for SJS/TEN have focused on systematic suppression of the inflammatory response using high-dose corticosteroids or intravenous immunoglobulin G (IgG), for example. No targeted therapies for SJS/TEN currently exist.

RECENT FINDINGS

Though our understanding of the pathogenesis of SJS/TEN has advanced from both an immunological and dermatological perspective, this knowledge is yet to translate into the development of new targeted therapies.

SUMMARY

Greater mechanistic insight into SJS/TEN would potentially unlock new opportunities for identifying or repurposing targeted therapies to limit or even prevent epidermal injury and blistering.

Pharmacologic inhibition of dipeptidyl peptidase 1 (cathepsin C) does not block in vitro granzyme-mediated target cell killing by CD8 T or NK cells

Recently developed small-molecule inhibitors of the lysosomal protease dipeptidyl peptidase 1 (DPP1), also known as cathepsin C (CatC), can suppress suppurative inflammation in vivo by blocking the processing of zymogenic (pro-) forms of neutrophil serine proteases (NSPs), including neutrophil elastase, proteinase 3, and cathepsin G. DPP1 also plays an important role in activating granzyme serine proteases that are expressed by cytotoxic T lymphocytes (CTL) and natural killer (NK) cells. Therefore, it is critical to determine whether DPP1 inhibition can also cause off-target suppression of CTL/NK-cell-mediated killing of virus-infected or malignant cells. Herein, we demonstrate that the processing of human granzymes A and B, transitioning from zymogen to active proteases, is not solely dependent on DPP1. Thus, the killing of target cells by primary human CD8+ T cells, NK cells, and gene-engineered anti-CD19 CAR T cells was not blocked in vitro even after prior exposure to high concentrations of the reversible DPP1 inhibitor brensocatib. Consistent with this observation, the turnover of model granzyme A/B peptide substrates in the human CTL/NK cell lysates was not significantly reduced by brensocatib. In contrast, preincubation with brensocatib almost entirely abolished (>90%) both the cytotoxic activity of mouse CD8+ T cells and granzyme substrate turnover. Overall, our finding that the effects of DPP1 inhibition on human cytotoxic lymphocytes are attenuated in comparison to those of mice indicates that granzyme processing/activation pathways differ between mice and humans. Moreover, the in vitro data suggest that human subjects treated with reversible DPP1 inhibitors, such as brensocatib, are unlikely to experience any appreciable deficits in CTL/NK-cell-mediated immunities.

Vasari-Based Features Nomogram to Predict the Tumor-Infiltrating CD8+ T Cell Levels in Glioblastoma

RATIONALE AND OBJECTIVES

Tumor-infiltrating CD8 + T cells play a key role in glioblastoma (GB) development, malignant progression, and recurrence. The aim of the study was to establish nomograms based on the Visually AcceSAble Rembrandt Images (VASARI) features of multiparametric magnetic resonance imaging (MRI) to determine the expression levels of tumor-infiltrating CD8 + T cells in patients with GB.

MATERIALS AND METHODS

Pathological and imaging data of 140 patients with GB confirmed by surgery and pathology were retrospectively analyzed. The levels of tumor-infiltrating CD8 + T cells in tumor tissue samples obtained from patients were quantified using immunohistochemical staining. Patients were divided into high and low CD8 expression groups. The MRI images of patients with GB were analyzed by two radiologists using the VASARI scoring system.

RESULTS

A total of 25 MRI-based VASARI imaging features were evaluated by two neuroradiologists. The features with the greatest predictive power for CD8 expression levels were, cystic (OR, 3.063; 95% CI: 1.387, 6.766; P = 0.006), hemorrhage (OR, 2.980; 95% CI: 1.172, 7.575; P = 0.022), and ependymal extension (OR, 0.257; 95% CI: 0.114 0.581; P = 0.001). A logistic regression model based on these three features showed better sample predictive performance (AUC=0.745; 95% CI: 0.665, 0.825; Sensitivity=0.527; Specificity=0.857).

CONCLUSION

The VASARI feature-based nomogram model can show promise to predict the level of infiltrative CD8 expression in GB tumors non-invasively for earlier tissue diagnosis and more aggressive treatment.

The Interplay between Ferroptosis and Neuroinflammation in Central Neurological Disorders

Central neurological disorders are significant contributors to morbidity, mortality, and long-term disability globally in modern society. These encompass neurodegenerative diseases, ischemic brain diseases, traumatic brain injury, epilepsy, depression, and more. The involved pathogenesis is notably intricate and diverse. Ferroptosis and neuroinflammation play pivotal roles in elucidating the causes of cognitive impairment stemming from these diseases. Given the concurrent occurrence of ferroptosis and neuroinflammation due to metabolic shifts such as iron and ROS, as well as their critical roles in central nervous disorders, the investigation into the co-regulatory mechanism of ferroptosis and neuroinflammation has emerged as a prominent area of research. This paper delves into the mechanisms of ferroptosis and neuroinflammation in central nervous disorders, along with their interrelationship. It specifically emphasizes the core molecules within the shared pathways governing ferroptosis and neuroinflammation, including SIRT1, Nrf2, NF-κB, Cox-2, iNOS/NO·, and how different immune cells and structures contribute to cognitive dysfunction through these mechanisms. Researchers' findings suggest that ferroptosis and neuroinflammation mutually promote each other and may represent key factors in the progression of central neurological disorders. A deeper comprehension of the common pathway between cellular ferroptosis and neuroinflammation holds promise for improving symptoms and prognosis related to central neurological disorders.

Endothelial cells and macrophages as allies in the healthy and diseased brain

Diseases of the central nervous system (CNS) are often associated with vascular disturbances or inflammation and frequently both. Consequently, endothelial cells and macrophages are key cellular players that mediate pathology in many CNS diseases. Macrophages in the brain consist of the CNS-associated macrophages (CAMs) [also referred to as border-associated macrophages (BAMs)] and microglia, both of which are close neighbours or even form direct contacts with endothelial cells in microvessels. Recent progress has revealed that different macrophage populations in the CNS and a subset of brain endothelial cells are derived from the same erythromyeloid progenitor cells. Macrophages and endothelial cells share several common features in their life cycle-from invasion into the CNS early during embryonic development and proliferation in the CNS, to their demise. In adults, microglia and CAMs have been implicated in regulating the patency and diameter of vessels, blood flow, the tightness of the blood-brain barrier, the removal of vascular calcification, and the life-time of brain endothelial cells. Conversely, CNS endothelial cells may affect the polarization and activation state of myeloid populations. The molecular mechanisms governing the pas de deux of brain macrophages and endothelial cells are beginning to be deciphered and will be reviewed here.

Fragment-based and structure-guided discovery of perforin inhibitors

Perforin is a pore-forming protein whose normal function enables cytotoxic T and natural killer (NK) cells to kill virus-infected and transformed cells. Conversely, unwanted perforin activity can also result in auto-immune attack, graft rejection and aberrant responses to pathogens. Perforin is critical for the function of the granule exocytosis cell death pathway and is therefore a target for drug development. In this study, by screening a fragment library using NMR and surface plasmon resonance, we identified 4,4-diaminodiphenyl sulfone (dapsone) as a perforin ligand. We also found that dapsone has modest (mM) inhibitory activity of perforin lytic activity in a red blood cell lysis assay in vitro. Sequential modification of this lead fragment, guided by structural knowledge of the ligand binding site and binding pose, and supported by SPR and ligand-detected 19F NMR, enabled the design of nanomolar inhibitors of the cytolytic activity of intact NK cells against various tumour cell targets. Interestingly, the ligands we developed were largely inert with respect to direct perforin-mediated red blood cell lysis but were very potent in the context of perforin's action on delivering granzymes in the immune synapse, the context in which it functions physiologically. Our work indicates that a fragment-based, structure-guided drug discovery strategy can be used to identify novel ligands that bind perforin. Moreover, these molecules have superior physicochemical properties and solubility compared to previous generations of perforin ligands.