Central nervous system-associated macrophages modulate the immune response following stroke in aged mice.

Age is a major nonmodifiable risk factor for ischemic stroke. Central nervous system-associated macrophages (CAMs) are resident immune cells located along the brain vasculature at the interface between the blood circulation and the parenchyma. By using a clinically relevant thromboembolic stroke model in young and aged male mice and corresponding human tissue samples, we show that during aging, CAMs acquire a central role in orchestrating immune cell trafficking after stroke through the specific modulation of adhesion molecules by endothelial cells. The absence of CAMs provokes increased leukocyte infiltration (neutrophils and CD4+ and CD8+ T lymphocytes) and neurological dysfunction after stroke exclusively in aged mice. Major histocompatibility complex class II, overexpressed by CAMs during aging, plays a significant role in the modulation of immune responses to stroke. We demonstrate that during aging, CAMs become central coordinators of the neuroimmune response that ensure a long-term fine-tuning of the immune responses triggered by stroke.

The Potential Role of CA-125 as a Biomarker for Short-Term Mortality Risk in Patients with Acute Symptomatic Pulmonary Embolism.

Background: Antigen carbohydrate 125 (CA-125) is a complex glycoprotein extensively studied as a prognostic biomarker in heart failure, yet its potential role in the short-term prognosis of an acute pulmonary embolism (PE) remains unexplored. Methods: In this observational, prospective, single-center study, consecutive patients aged 18 and older with a confirmed acute symptomatic PE and no history of prior anticoagulant therapy were enrolled. Primary and secondary objectives aimed to assess the prognostic capacity of CA-125 at PE diagnosis for 30-day mortality and major bleeding, respectively. Results: A total of 164 patients were included (mean age 69.8 years, SD 17), with 56.1% being male. Within 30 days, 17 patients (10.4%) died and 9 patients (5.5%) suffered major bleeding. ROC curve analysis for 30-day mortality yielded an area under the curve of 0.69 (95% CI 0.53-0.85) with an optimal CA-125 cut-off point of 20 U/mL and a negative predictive value of 96%. Multivariate analysis revealed a significant association between CA-125 levels exceeding 20 U/mL and 30-day mortality (adjusted odds ratio 4.95; 95% CI 1.61-15.2) after adjusting for age, cancer, NT-proBNP > 600 ng/mL, and the simplified pulmonary embolism severity index score. Survival analysis for 30-day mortality exhibited a hazard ratio of 5.47 (95% CI 1.78-16.8). No association between CA-125 levels and 30-day major bleeding was found. Conclusions: CA-125 emerges as a promising surrogate biomarker for short-term mortality prediction in an acute symptomatic PE. Future investigations should explore the integration of CA-125 into PE mortality prediction scores to enhance the prognostic accuracy in this patient population.

MRI-based microthrombi detection in stroke with polydopamine iron oxide.

In acute ischemic stroke, even when successful recanalization is obtained, downstream microcirculation may still be obstructed by microvascular thrombosis, which is associated with compromised brain reperfusion and cognitive decline. Identifying these microthrombi through non-invasive methods remains challenging. We developed the PHySIOMIC (Polydopamine Hybridized Self-assembled Iron Oxide Mussel Inspired Clusters), a MRI-based contrast agent that unmasks these microthrombi. In a mouse model of thromboembolic ischemic stroke, our findings demonstrate that the PHySIOMIC generate a distinct hypointense signal on T2*-weighted MRI in the presence of microthrombi, that correlates with the lesion areas observed 24 hours post-stroke. Our microfluidic studies reveal the role of fibrinogen in the protein corona for the thrombosis targeting properties. Finally, we observe the biodegradation and biocompatibility of these particles. This work demonstrates that the PHySIOMIC particles offer an innovative and valuable tool for non-invasive in vivo diagnosis and monitoring of microthrombi, using MRI during ischemic stroke.

CNS-associated macrophages contribute to intracerebral aneurysm pathophysiology.

Intracerebral aneurysms (IAs) are pathological dilatations of cerebral arteries whose rupture leads to subarachnoid hemorrhage, a significant cause of disability and death. Inflammation is recognized as a critical contributor to the formation, growth, and rupture of IAs; however, its precise actors have not yet been fully elucidated. Here, we report CNS-associated macrophages (CAMs), also known as border-associated macrophages, as one of the key players in IA pathogenesis, acting as critical mediators of inflammatory processes related to IA ruptures. Using a new mouse model of middle cerebral artery (MCA) aneurysms we show that CAMs accumulate in the IA walls. This finding was confirmed in a human MCA aneurysm obtained after surgical clipping, together with other pathological characteristics found in the experimental model including morphological changes and inflammatory cell infiltration. In addition, in vivo longitudinal molecular MRI studies revealed vascular inflammation strongly associated with the aneurysm area, i.e., high expression of VCAM-1 and P-selectin adhesion molecules, which precedes and predicts the bleeding extent in the case of IA rupture. Specific CAM depletion by intracerebroventricular injection of clodronate liposomes prior to IA induction reduced IA formation and rupture rate. Moreover, the absence of CAMs ameliorated the outcome severity of IA ruptures resulting in smaller hemorrhages, accompanied by reduced neutrophil infiltration. Our data shed light on the unexplored role of CAMs as main actors orchestrating the progression of IAs towards a rupture-prone state.

The niche matters: origin, function and fate of CNS-associated macrophages during health and disease.

There are several cellular and acellular structural barriers associated with the brain interfaces, which include the dura, the leptomeninges, the perivascular space and the choroid plexus epithelium. Each structure is enriched by distinct myeloid populations, which mainly originate from erythromyeloid precursors (EMP) in the embryonic yolk sac and seed the CNS during embryogenesis. However, depending on the precise microanatomical environment, resident myeloid cells differ in their marker profile, turnover and the extent to which they can be replenished by blood-derived cells. While some EMP-derived cells seed the parenchyma to become microglia, others engraft the meninges and become CNS-associated macrophages (CAMs), also referred to as border-associated macrophages (BAMs), e.g., leptomeningeal macrophages (MnMΦ). Recent data revealed that MnMΦ migrate into perivascular spaces postnatally where they differentiate into perivascular macrophages (PvMΦ). Under homeostatic conditions in pathogen-free mice, there is virtually no contribution of bone marrow-derived cells to MnMΦ and PvMΦ, but rather to macrophages of the choroid plexus and dura. In neuropathological conditions in which the blood-brain barrier is compromised, however, an influx of bone marrow-derived cells into the CNS can occur, potentially contributing to the pool of CNS myeloid cells. Simultaneously, resident CAMs may also proliferate and undergo transcriptional and proteomic changes, thereby, contributing to the disease outcome. Thus, both resident and infiltrating myeloid cells together act within their microenvironmental niche, but both populations play crucial roles in the overall disease course. Here, we summarize the current understanding of the sources and fates of resident CAMs in health and disease, and the role of the microenvironment in influencing their maintenance and function.

Thrombolysis by PLAT/tPA increases serum free IGF1 leading to a decrease of deleterious autophagy following brain ischemia.

Cerebral ischemia is a pathology involving a cascade of cellular mechanisms, leading to the deregulation of proteostasis, including macroautophagy/autophagy, and finally to neuronal death. If it is now accepted that cerebral ischemia induces autophagy, the effect of thrombolysis/energy recovery on proteostasis remains unknown. Here, we investigated the effect of thrombolysis by PLAT/tPA (plasminogen activator, tissue) on autophagy and neuronal death. In two in vitro models of hypoxia reperfusion and an in vivo model of thromboembolic stroke with thrombolysis by PLAT/tPA, we found that ischemia enhances neuronal deleterious autophagy. Interestingly, PLAT/tPA decreases autophagy to mediate neuroprotection by modulating the PI3K-AKT-MTOR pathways both in vitro and in vivo. We identified IGF1R (insulin-like growth factor I receptor; a tyrosine kinase receptor) as the effective receptor and showed in vitro, in vivo and in human stroke patients and that PLAT/tPA is able to degrade IGFBP3 (insulin-like growth factor binding protein 3) to increase IGF1 (insulin-like growth factor 1) bioavailability and thus IGF1R activation.Abbreviations: AKT/protein kinase B: thymoma viral proto-oncogene 1; EGFR: epidermal growth factor receptor; Hx: hypoxia; IGF1: insulin-like growth factor 1; IGF1R: insulin-like growth factor I receptor; IGFBP3: insulin-like growth factor binding protein 3; Ka: Kainate; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MAPK/ERK: mitogen-activated protein kinase; MTOR: mechanistic target of rapamycin kinase; MTORC1: MTOR complex 1; OGD: oxygen and glucose deprivation; OGDreox: oxygen and glucose deprivation + reoxygentation; PepA: pepstatin A1; PI3K: phosphoinositide 3-kinase; PLAT/tPA: plasminogen activator, tissue; PPP: picropodophyllin; SCH77: SCH772984; ULK1: unc-51 like kinase 1; Wort: wortmannin.

[Isolated facial diplegia as an atypical variant of Guillain-Barre syndrome after suspected SARS-CoV-2 infection] / Diplejía facial aislada como variante atípica del síndrome de Guillain-Barré tras sospecha de infección por SARS-CoV-2.

Introduction: Since the SARS-CoV-2 pandemics began, multiple cases of Guillain-Barre syndrome secondary to COVID-19 have been described. Its typical presentation consists of the triad of paresthesia, ascending muscle weakness and areflexia, although there are several regional variants such as facial diplegia. Case presentation: Two weeks after a contact with a confirmed case of COVID-19, a 35-year-old woman presents with viral myopericarditis. Laboratory studies for autoimmune diseases come back negative, as well as multiple viral serologies. She presents anti-SARS-CoV-2 IgG, with negative PCR. A week after discharge she presents with palsy of both facial nerves, without other neurological abnormalities. She undergoes examination with cranial CT without findings, and an EMG which shows bilateral alteration of facial nerves. She refuses the performance of a lumbar puncture. Discussion: Facial diplegia can occur because of several illnesses, such as meningeal or brainstem tumors, infectious agents, Guillain-Barre syndrome, autoimmune diseases, trauma, metabolic causes or congenital causes. In our patient, having discarded other etiologies with imaging and analytical studies, the most probable cause is the Guillain-Barre syndrome. It is possibly secondary to SARS-CoV-2 infection given the presence of anti-SARS-CoV-2 IgG antibodies after contact with a confirmed case. Conclusion: This case supports the hypothesis that COVID-19 may trigger the Guillain-Barre syndrome, specifically as facial diplegia, which is an atypical variant that should be known to be early diagnosed and treated as part of this syndrome.

Introducción: Desde que se inició la pandemia por el SARS-CoV-2, se han descrito numerosos casos de síndrome de Guillain-Barré secundario a la COVID-19. Su presentación típica es la triada de parestesias, debilidad muscular ascendente y arreflexia, aunque hay diversas variantes regionales como la diplejía facial. Presentación del caso: Mujer de 35 años que, dos semanas después de un contacto estrecho con un caso confirmado de COVID-19, ingresa por miopericarditis probablemente viral, con estudio de autoinmunidad negativo, múltiples serologías virales negativas y positividad para IgG anti-SARS-CoV-2 con PCR negativa. Una semana tras el alta presenta paresia de ambos nervios faciales sin otras alteraciones neurológicas. Se realiza TAC craneal sin hallazgos y EMG que evidencia afectación bilateral de los nervios faciales. La paciente rechaza realización de punción lumbar Discusión: La diplejía facial puede ocurrir en el contexto de diversas patologías, como tumores meníngeos o troncoencefálicos, agentes infecciosos, síndrome de Guillain-Barré, patologías autoinmunes, traumatismos, causas metabólicas o causas congénitas. En el caso descrito tras descartar mediante pruebas de imagen y analíticamente el resto de etiologías, y dada la presentación clínica, permanece como causa más probable el síndrome de Guillain-Barré, posiblemente secundario a infección por SARS-CoV-2 dada la positividad de IgG anti-SARS-CoV-2 tras un contacto con un caso confirmado. Conclusión: Este caso apoya la hipótesis de que la COVID-19 puede desencadenar el síndrome de Guillain-Barré, específicamente en forma de diplejía facial, una variante atípica que se debe conocer para su identificación y manejo precoz como parte de este síndrome.

Factor XII protects neurons from apoptosis by epidermal and hepatocyte growth factor receptor-dependent mechanisms.

BACKGROUND: Factor XII (FXII) is a serine protease that participates in the intrinsic coagulation pathway. Several studies have shown that plasma FXII exerts a deleterious role in cerebral ischemia and traumatic brain injury by promoting thrombo-inflammation. Nevertheless, the impact of FXII on neuronal cell fate remains unknown. OBJECTIVES: We investigated the role of FXII and FXIIa in neuronal injury and apoptotic cell death. METHODS: We tested the neuroprotective roles of FXII and FXIIa in an experimental model of neuronal injury induced by stereotaxic intracerebral injection of N-methyl-D-aspartic acid (NMDA) in vivo and in a model of apoptotic death of murine primary neuronal cultures through serum deprivation in vitro. RESULTS: Here, we found that exogenous FXII and FXIIa reduce brain lesions induced by NMDA injection in vivo. Furthermore, FXII protects cultured neurons from apoptosis through a growth factor--like effect. This mechanism was triggered by direct interaction with epidermal growth factor (EGF) receptor and subsequent activation of this receptor. Interestingly, the "proteolytically" active and two-chain form of FXII, FXIIa, exerts its protective effects by an alternative signaling pathway. FXIIa activates the pro-form of hepatocyte growth factor (HGF) into HGF, which in turn activated the HGF receptor (HGFR) pathway. CONCLUSION: This study describes two novel mechanisms of action of FXII and identifies neurons as target cells for the protective effects of single and two-chain forms of FXII. Therefore, inhibition of FXII in neurological disorders may have deleterious effects by preventing its beneficial effects on neuronal survival.

Filling the gaps on stroke research: Focus on inflammation and immunity.

For the last two decades, researchers have placed hopes in a new era in which a combination of reperfusion and neuroprotection would revolutionize the treatment of stroke. Nevertheless, despite the thousands of papers available in the literature showing positive results in preclinical stroke models, randomized clinical trials have failed to show efficacy. It seems clear now that the existing data obtained in preclinical research have depicted an incomplete picture of stroke pathophysiology. In order to ameliorate bench-to-bed translation, in this review we first describe the main actors on stroke inflammatory and immune responses based on the available preclinical data, highlighting the fact that the link between leukocyte infiltration, lesion volume and neurological outcome remains unclear. We then describe what is known on neuroinflammation and immune responses in stroke patients, and summarize the results of the clinical trials on immunomodulatory drugs. In order to understand the gap between clinical trials and preclinical results on stroke, we discuss in detail the experimental results that served as the basis for the summarized clinical trials on immunomodulatory drugs, focusing on (i) experimental stroke models, (ii) the timing and selection of outcome measuring, (iii) alternative entry routes for leukocytes into the ischemic region, and (iv) factors affecting stroke outcome such as gender differences, ageing, comorbidities like hypertension and diabetes, obesity, tobacco, alcohol consumption and previous infections like Covid-19. We can do better for stroke treatment, especially when targeting inflammation following stroke. We need to re-think the design of stroke experimental setups, notably by (i) using clinically relevant models of stroke, (ii) including both radiological and neurological outcomes, (iii) performing long-term follow-up studies, (iv) conducting large-scale preclinical stroke trials, and (v) including stroke comorbidities in preclinical research.

Alcohol exposure-induced neurovascular inflammatory priming impacts ischemic stroke and is linked with brain perivascular macrophages.

Alcohol abuse is a major public health problem worldwide, causing a wide range of preventable morbidity and mortality. In this translational study, we show that heavy drinking (HD) (≥6 standard drinks/day) is independently associated with a worse outcome for ischemic stroke patients. To study the underlying mechanisms of this deleterious effect of HD, we performed an extensive analysis of the brain inflammatory responses of mice chronically exposed or not to 10% alcohol before and after ischemic stroke. Inflammatory responses were analyzed at the parenchymal, perivascular, and vascular levels by using transcriptomic, immunohistochemical, in vivo 2-photon microscopy and molecular MRI analyses. Alcohol-exposed mice show, in the absence of any other insult, a neurovascular inflammatory priming (i.e., an abnormal inflammatory status including an increase in brain perivascular macrophages [PVM]) associated with exacerbated inflammatory responses after a secondary insult (ischemic stroke or LPS challenge). Similar to our clinical data, alcohol-exposed mice showed larger ischemic lesions. We show here that PVM are key players on this aggravating effect of alcohol, since their specific depletion blocks the alcohol-induced aggravation of ischemic lesions. This study opens potentially new therapeutic avenues aiming at blocking alcohol-induced exacerbation of the neurovascular inflammatory responses triggered after ischemic stroke.

Chronic treatment with CP 55,940 during the peri-adolescent period differentially affects the behavioural responses of male and female rats in adulthood.

RATIONALE: Despite the increasing use of cannabis among adolescents, there is scarce information about the long-term effects of cannabinoid receptor agonists in appropriate animal models. OBJECTIVES: We aimed to investigate the behavioural features of adult male and female Wistar rats that had been exposed to a chronic treatment with the cannabinoid receptor agonist CP 55,940 (CP) during the juvenile period. METHODS: CP (0.4 mg/kg i.p.) or its corresponding vehicle was administered once daily, from day 35 to day 45. In adulthood, the animals were tested in the holeboard, the open field and the elevated plus-maze, under different stress (illumination) conditions. After a resting period, the serum corticosterone levels (radioimmunoassay) of the animals were measured. The effects of CP on food intake and somatic growth were monitored throughout the experimental period. RESULTS: The CP treatment induced significant sex-dependent effects on holeboard activity, as well as a decrease in the level of emotionality/anxiety in the open field and in the plus-maze. The animals receiving CP also showed diminished food intake and body weights during the treatment period, but both parameters recovered normal values during the period after treatment. No significant effect of the CP treatment on corticosterone levels was found. CONCLUSIONS: The results demonstrate that chronic administration of CP during the peri-adolescent period resulted in marked behavioural effects in adulthood. The nature of these effects depended on the sex of the animals and on the specific behavioural test. The possible neurobiological substrates underlying the effects of CP are discussed.