MAPK and pro-inflammatory mediators in the walls of brain blood vessels following cerebral ischemia

INTRODUCTION Stroke is a serious neurological disease which may lead to death and severe disability [1, 2]. There are two major types of stroke: ischemic and hemorrhagic stroke. Both are associated with disruption of blood flow to a part of the brain with rapid depletion of cellular energy and oxygen, resulting in ionic disturbances and eventually neuronal cell death [3]. The pathologic process that develops after stroke is divided into acute (within hours), sub-acute (hours to days), and chronic (days to months) phases [4, 5]. Obviously, the most effective therapy requires the earliest possible intervention e.g. with removal of a thrombus. However, no specific treatment, apart from thrombolysis, that acts effectively to protect the neurons during the acute phase has yet been developed. Experimental and clinical data show an acute and prolonged inflammatory response in the brain after a stroke. Several investigators have reported that inflammation evolves within a few hours after stroke, and plays an important role in the development of the cerebral lesions [6]. This inflammatory reaction involves activation of resident cells (mainly microglia), infiltration and accumulation of various inflammatory cells (including neutrophils, leukocytes, monocytes, macrophages), and production of pro-inflammatory mediators in the injured brain areas [6, 7]. It has been established that the inflammatory reaction triggered by stroke affects not only the neuronal tissue itself but has impact also on the cerebral arteries [7]. Stroke is a vascular disease and despite extensive research in the area, the physiology and pathophysiology of the neurovascular unit, the complex network of endothelial cells, smooth muscle cells, inflammatory cells and mediators are not fully understood, which is necessary in order to develop effective therapies. The aim of the present thesis was to examine the role of pro-inflammatory mediators in cerebrovascular pathophysiology following stroke. The main focus was directed towards the expression and production of cytokines and inducible nitric oxide synthase (iNOS), the activation of matrix metalloproteinases (MMPs) and mitogen activated protein kinase (MAPK) pathway because microarray work [8] and published data [9] primarily pointed at these. These parameters and the relationships between them were studied in the cerebrovascular walls after ischemic and hemorrhagic strokes. This study lends further support to the view that inflammatory mediators are important contributing factors in brain injury after stroke. It provides evidence that blocking the intracellular signaling pathways involved in the transcription of these mediators may have therapeutic potential, as it may prevent or at least attenuate the inflammatory processes elicited by stroke. Ischemic stroke Ischemic stroke is the most common type of stroke (85% of cases). It is caused by a transient or permanent occlusion of a cerebral artery most often by a thrombus or an embolus [10, 11]. When an ischemic stroke occurs, blood flow to an area of the brain is reduced and the brain cells are starved of oxygen and nutrients, which quickly leads to neuronal cell death and the development of an infarct. The infarct region is divided into two parts: 1) A central part or an ischemic core, where the neurons die and have no chance to survive without rapid reperfusion. 2) A peripheral area or an ischemic penumbra, which surrounds the core [12]. Cells in the penumbra are impaired and cannot function due to compromised metabolism, but do not die immediately and have therefore become a prime target for neuroprotective treatments [13-15]. A number of neurochemical and pathophysiological events are triggered within the ischemic penumbra. As a result of energy depletion, there is disruption of ion homoeostasis, excessive release of excitatory neurotransmitters such as glutamate, calcium channel dysfunction, generation of oxidative stress and free radicals, activation of stress signaling, cell membrane disruption, inflammation, ultimately leading to necrotic and apoptotic cell death [1, 4, 15, 16]. The effect of ischemia on brain cells results not only in loss of structural integrity of brain tissue but affects also blood vessels, partly through the activation of inflammatory events and excess production of vasoconstrictor substances and increased receptor expression [17]. The early inflammatory response, which often is associated with the blood vessels, starts immediately or a few hours after the onset of the ischemia and contributes to the irreversible damage [18-21]. Currently, there are two major ways used for treating ischemic stroke: (i) Dissolution of the clot in the occluded artery by a thrombolytic drug, rt-PA (recombinant tissue-plasminogen activator) [22] and, (ii) administration of neuroprotective agents [23]. Treatment with rt-PA is limited by time and should be administered within 4.5 hours after the onset of stroke to reduce the risk of hemorrhagic transformation [24, 25]. Moreover, rt-PA is associated with the risk of disruption to the blood-brain barrier (BBB) which is due to activation of matrix metalloproteinases [26]. Despite intense research, the results obtained with neuroprotective drugs in clinical trials have not revealed positive results [27, 28]. Hemorrhagic stroke Hemorrhagic stroke (15% of all strokes) is often associated with hypertension, and is due to the rupture of an arterial aneurysm or a vascular malformation [1, 29]. Hemorrhagic stroke is divided into two categories: intracerebral and subarachnoid hemorrhage. Intracerebral hemorrhage (ICH) is due to the rupture of a small artery (arterioles) which bleeds within the brain tissue. It is often associated with chronic high blood pressure and the symptoms often begin with severe headache. Subarachnoid hemorrhage (SAH) occurs when an artery or an arterial aneurysm on the surface of the brain ruptures and bleeds into the space between the pia mater and the arachnoid (subarachnoid space) [1]. The most common cause of the SAH is the spontaneous rupture of an arterial aneurysm. This is associated with acute rise of the intracranial pressure (ICP), reduction of cerebral blood flow (CBF), rapid discharge of blood into the basal cisterns, and delayed cerebral ischemia (DCI), each of which may be fatal. The SAH is most common in women and younger people (below 55 years old). Around 50-70% of patients with SAH die or suffer severe disability, and is the cause of up to 10% of all strokes [30-33]. The disease is biphasic, with an early/short-lived phase that occurs immediately after SAH with a reduction in CBF, followed by a chronic or prolonged phase which is characterized by a varying degree of pathological contraction of cerebral arteries, known as vasospasm [34, 35]. The vasospasm (narrowing of arteries) typically occurs within 5-15 days after SAH and is present in approximately one-third of patients and is accompanied by DCI [36, 37]. It can occur not only at the site of the hemorrhage, but also in brain arteries at a distance from the bleeding. The narrowing of the cerebral vessel lumen leads to reduction in local blood flow and in cerebral metabolism, causing severe cerebral ischemia, with increase in mortality of 1.5-3 folds during the first two weeks after SAH [37-39]. Despite intense research, the pathogenesis of DCI after SAH is not well understood and no specific pharmacological treatment is available. Current treatment recommendations involve management in an intensive care unit. The blood pressure is maintained with consideration to the patient’s neurologic status. In addition, calcium channel blockers, endothelin-1 receptor antagonists, hemodynamic management and endovascular treatment are also used, but these treatments are expensive, time-consuming and only partly effective [40]. Many theories have been advanced to explain the mechanisms responsible for vasospasm and DCI that occur after SAH such as, endothelial damage [41-43], enhanced smooth muscle cell (SMC) contractility, morphologic changes in vessel walls [44], enhanced levels of free radicals [45-47], increased production and release of potent vasomotor substances such as endothelin-1 (ET-1) and angiotensin II (Ang II) [48, 49], local inflammation and immunological reactions in the vascular wall [50-52]. Yet, the exact mechanisms underlying the vasospasm and the DCI remain unknown [53]. There is evidence that the amount of blood in the subarachnoid space is related to development of vasospasm [54]. Oxyhemoglobin from extravasated blood may be an important trigger of vasospasm and DCI after SAH [55-57] by inducing inflammation [50, 58]. It may in addition correlate with structural damage to the vessel wall [59], release of spasmogenic substances, and inhibition of endothelium dependent relaxation [60, 61]. It is suggested that the extravasated blood could induce generation of free radicals that subsequently may exert a direct local toxic effect on the cerebral arteries [62, 63]. G-protein coupled receptors following stroke Recently, a novel aspect of the pathophysiology of stroke has been suggested, namely that the upregulation of vasoconstrictor receptors in the cerebral arteries after stroke may be an important mechanism in the development of the final damage [64]. Vasoconstrictor receptors such as those of angiotensin II receptor type 1 (AT1) and endothelin-1 receptor type B (ETB) belong to the seven transmembrane G-protein coupled receptor (GPCR) family [65-67]. They are upregulated in the SMCs of cerebral vessels within and associated with the ischemic region after focal ischemic stroke [68] and after SAH [69]. This results in enhanced contractility of the vessels, which further impairs local blood flow and aggravates tissue damage. Importantly, the receptor ligands (angiotensin II and endothelin-1) are formed in the cerebrovascular endothelium. In addition, contractile responses mediated by AT1 and ETB receptors were found to be increased in SMCs of human cerebral arteries after organ culture [70]. Experimental stroke induces upregulation of cerebrovascular contractile receptors in the SMCs which are caused by increased receptor gene transcription induced via activation of specific intracellular signaling pathways (such as MEK-ERK1/2 and PKC pathways) [64]. Importantly, inhibition of these signaling pathways prevents the receptor upregulation, reduces infarct volume after ischemic stroke and improves neurological score and CBF after SAH [71, 72]. This may indicate that the increased cerebrovascular contractility caused by the upregulated receptors contributes to worsening of the brain damage. Inflammation in general and following stroke Inflammation is the body's defense against injurious factors and foreign antigens, e.g., trauma, infection and toxins, and is considered to be both a beneficial and a detrimental element of a pathological process. It is a complicated and multifaceted response, characterized by acute and chronic phases [73, 74]. Among many mechanisms involved in the pathogenesis of stroke, inflammation is increasingly recognized as a key factor. However, all the mediators of the inflammatory response have not been clearly identified [6, 75-77]. There is evidence to suggest that inflammation and immune responses are involved in all three stages of the ischemic cascade, from the acute intravascular process triggered by the interruption of the blood supply to the parenchymal processes that lead to brain damage and subsequently to tissue repair. The early inflammatory response contributes to the ischemic injury, whereas late responses may represent endogenous mechanisms of recovery and repair [78] (Figure 1). When there is a switch from detrimental to beneficial effects might depend on the strength and the duration of the stroke and knowledge about the mechanisms involved is crucial for determining the time-window for effective pharmacotherapy [79]. As mentioned above, reduction in CBF after stroke can result in energy depletion and subsequent neuronal cell death. This triggers an immune response that results in activation of a variety of inflammatory cells and molecules [51, 80, 81]. In the acute phase (minutes to hours), extravasated blood following SAH (or following reperfusion after arterial occlusion in transient ischemia) induces generation of reactive oxygen species (ROS). They may stimulate ischemic cells to produce inflammatory molecules such as cytokines and chemokines which in turn may activate microglial cells and increase leukocyte infiltration. These produce more cytokines, causing an increase in adhesion molecules, which are normally required for the adherence and accumulation of leukocytes and neutrophils to vascular endothelial cells and infiltration of brain parenchyma. In the sub-acute phase (hours to days), increased activation of inflammatory cells results in further production of pro-inflammatory mediators including more cytokines, extracellular MMPs, as well as iNOS which generates nitric oxide (NO) and more ROS [79, 82]. The intravascular accumulation of leukocytes and of platelets results in occlusion of microvessels, leading to hypoxia and further increases in levels of ROS [83, 84]. Activation of mast cells and macrophages can in turn lead to release of histamine (a strong vasoactive substance) and production of more cytokines and proteases [85]. In addition, degradation of extracellular matrix components by MMPs (mostly MMP-9) leads to BBB disruption which contributes to secondary brain damage by releasing serum and blood elements into the brain tissue resulting in vasogenic brain edema and post-ischemic inflammation [83]. Disruption and permeability of the BBB can be either transient or permanent depending on severity of the insult. Permanent disruption is associated with endothelial swelling, astrocyte detachment and blood vessel rupture in the ischemic area, while transient BBB disruption is caused by endothelial hyperpermeability to macromolecules in the penumbra area. This follows a biphasic pattern with an initial opening 2-3 hours after the onset of the insult and a second opening 24-48 hours after reperfusion leading to edema and increased intracranial pressure. All these events involve pro-inflammatory cytokines, adhesion molecules and production of MMPs [86, 87]. Cerebral blood vessels are the first to be exposed to the ischemic insults and their reaction to injury sets the stage for the inflammatory response. Post-ischemic inflammation thus involves activation of microglial and endothelial cells accompanied by migration of peripheral circulating inflammatory cells into the brain such as leukocytes, neutrophils, platelet, mast cells and macrophages. These events amplify signaling along inflammatory cascades increasing the accumulation of toxic molecules that enhance the secondary damage leading to more cell stress, edema, hemorrhage and finally cell death (Figure 1) [76, 79, 84]. On the other hand, many pro-inflammatory mediators play a positive role in late stage of stroke. For example, MMPs have been reported to promote brain regeneration and neurovascular remodeling in the later repair phase [79, 88, 89]. Moreover, macrophages and microglial cells also contribute to tissue recovery by scavenging necrotic debris, by producing anti-inflammatory cytokines and by facilitating plasticity [90] (Figure 1). Yet, despite these beneficial effects there is evidence that administration of anti-inflammatory drugs may reduce infarct volume and improved outcomes in animal models of stroke [91]. On the other hand, to date, clinical trials with anti-inflammatory agents have not been able to demonstrate improved clinical outcome [92, 93]. With better knowledge about which cells and molecules that participate and which mechanisms regulate the inflammatory reactions triggered by cerebral ischemia, it may be possible to identify novel targets for suppression of inflammation following cerebral ischemia and thereby develop more effective stroke therapies. Figure 1. Main inflammatory pathways that respond to injury after a stroke. The generation of ROS and free radicals that occur after stroke triggers inflammatory responses. This involves activation of cytokines and chemokines which leads to activation of inflammatory cells such as microglia and leukocytes causing more production of inflammatory mediators (cytokines, iNOS, MMPs and more ROS) which then lead to brain edema, hemorrhage and cell death. Thus, these early inflammatory responses contribute to ischemic injury, whereas late responses may represent endogenous mechanisms of recovery and repair through activation of anti-inflammatory cytokines, scavenging necrotic debris by microglia and neurovascular remodeling by MMPs. Major inflammatory mediators in cerebral ischemia In this present thesis, I have studied the expression of some of the major cytokines (IL-1ß, IL-6, TNF-α, TNF-R1 and R2), of MMP-9 (BBB associated) and of iNOS (potential toxic molecule) in cerebral vessel walls. Increased levels and activation of these factors may lead to exacerbation of vasoconstriction, resulting in decreased CBF and enhanced neuronal damage following a stroke. Cytokines Cytokines are recognized as small proteins, generally associated with inflammation, immune activation, cell differentiation and hematopoiesis [94]. Most cytokines are pleiotropic and have multiple biologic activities that generally act over a short distance, during short periods of time and at low concentrations. They are produced and expressed by different cell types such as astrocytes, macrophages, monocytes, microglia, platelets, endothelial and smooth muscle cells, neurons, fibroblasts and neutrophils [52, 95, 96]. Normally, they have a beneficial role, but when their expression increases in an imbalanced fashion they become detrimental [97]. Evidence for the involvement of cytokines in the pathology following stroke comes from the detection of their high levels in CSF and plasma of patients [98, 99]. It is thought that increased production and activation of such cytokines in vessel walls after cerebral ischemia/reperfusion may facilitate and expand the ischemic core by inducing secondary brain damage (brain swelling, impaired microcirculation, hemorrhage and inflammation) that typically develops after a delay of hours or days after the original ischemia, trauma or SAH [100]. It is well known that cytokines are involved in the upregulation and activation of adhesion molecules, MMPs, leukocytes, microglial, increased leukocyte-endothelium interaction and increase in vasoconstrictor substances like ET-1 following cerebral ischemia [52, 76, 101]. Tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1ß (IL-1ß) are the main cytokines which initiate inflammatory reactions and induce expression of other cytokines and inflammatory mediators after stroke. Ischemic brain has been shown to produce increased levels of TNF-α, IL-6 and IL-1ß, which are considered as a part of the damaging response [102]. Inhibiting the expression of these pro-inflammatory cytokines has been reported to reduce brain infarct size in animal models of stroke [103]. TNF-α TNF-α is a pleiotropic cytokine and exists as either a transmembrane or soluble protein. It is involved in the disruption of the BBB, as well as in inflammatory, thrombogenic and vascular changes associated with brain injury [104]. This cytokine promotes inflammation by stimulation of acute-phase protein secretion, enhances the permeability of endothelial cells to leukocytes, and the expression of adhesion molecules and other cytokines into the ischemic area [105, 106]. In addition, it has been suggested to stimulate angiogenesis after cerebral ischemia through induced expression of angiogenesis-related genes [107, 108]. It is known as a strong immunomediator, which is rapidly upregulated early in neuronal cells in and around the ischemic penumbra, and is associated with neuronal necrosis or apoptosis [105]. TNF-α effects are mediated via two receptors, TNF-R1 and TNF-R2, on the cell surface [109]. TNF-R1 is expressed on all cell types, can be activated by both membrane-bound and soluble forms of TNF-α and is a major signaling receptor for TNF-α. The TNF-R2 is expressed primarily on endothelial cells, responds to the membrane-bound form of TNF-α, and mediates limited biological responses [109]. There is evidence that TNF-α and its receptors may activate nuclear factor-κB (NF-κB), a transcription factor whose activation leads to expression of several genes involved in inflammation and cell proliferation [110-112]. In addition, NF-κB is involved in signaling cell death as well as cell survival, and the balance between these signals determines the toxic degree of TNF-α [112, 113]. TNF-α appears then to be not only neurotoxic but also neuroprotective. Increased TNF-α levels have been observed in brain tissue, plasma and CSF in several CNS diseases such as Alzheimer’s, multiple sclerosis and Parkinson’s [114-116]. Accordingly, a recent study demonstrated that blocking TNF-α significantly reduced infarct size after both permanent and transient MCAO, suggesting the involvement of TNF-α in neuronal cell damage [104]. In contrast, there is evidence to suggest that brain injury after ischemia becomes worse in mice lacking TNF-R1, suggesting that TNF-α mediates neuroprotection through this receptor [117]. The function of TNF-α appears to differ between brain regions. TNF-α released for instance in the striatum is considered as neurodegenerative, while release in the hippocampus has been suggested to promote neuroprotection [112]. Several investigators have suggested that the detrimental effects are activated in the early phase of the inflammatory

The role of microglia and Toll-like Receptor-4 in neuronal apoptosis in a subarachnoid hemorrhage model

BACKGROUND A subarachnoid hemorrhage (SAH) is a bleed into the subarachnoid space surrounding the brain. This disease affects roughly 30,000 Americans each year and approximately one in six affected individuals die at the time of the ictal event. Individuals that do survive suffer from many complications including delayed cerebral vasospasm (DCV), cerebral edema, fever, and increased intracranial pressure (ICP) amongst others. These patients often suffer from brain damage due to neuronal apoptosis as a consequence of excess neuroinflammation. Microglia, the resident macrophage of the central nervous system, and Toll-like Receptor-4 (TLR4), a pro-inflammatory transmembrane receptor, have both been shown to play a role in the neuroinflammation seen in SAH. RBC components have been shown to activate microglial TLR4, and this event is suggested to trigger downstream mechanisms leading to neuronal apoptosis. The presented research takes a closer look at the role of microglial TLR4 in early neuronal apoptosis seen in an SAH model. METHODS All mice used were 10- to 12-week-old males on a C57BL/6 background: TLR4−/−, MyD88−/−, TRIF−/− and wild type (WT). To induce an SAH, a total of 60 ul of arterial blood from a donor WT mouse was injected for over 30 seconds into another mouse. For in vitro experiments, either primary microglia (PMG) or murine microglial BV2 cells were used. Microglia were separated from murine neuronal HT22 cells by 3um cell culture inserts or transwells, before being stimulated with lipopolysaccharide (LPS), red blood cells (RBCs), or RBC components including hemin (structurally similar to heme) and hemoglobin. In vivo samples were studied using either immunohistochemistry (IHC) or Fluorescence Activated Cell Sorting (FACS), and in vitro cells were studied using IHC and Light Microscopy. Neuronal cell death was measured using TUNEL and/or FloroJade C (FJC) assays. Cognitive function after SAH was measured using the Barnes Maze protocol. RESULTS In a 24-hour time course, more death occurred in the HT22 cells associated with BV2s treated with RBCs for 12-hour and 24-hour incubation time points as compared to 1-hour and 3-hour time points. Similar results were seen in the WT PMGs, as HT22 apoptosis increased in the RBC treated WT groups as the incubation time points increased. The WT PMG and MyD88−/− RBC treated PMGs showed significant death as compared to a WT untreated control (p<0.05) using a FJC assay, and both showed more death in a TUNEL assay as compared to an untreated control. WT mice treated with whole blood and hemoglobin had significantly more apoptosis as compared with a normal saline (NS)-treated control mouse (p<0.05). WT PMGs treated with whole blood and hemoglobin had more apoptosis as compared with an untreated control. MyD88-/- treated with RBC, hemoglobin, and hemin had more HT22 cell death compared with other genotypes treated with the same component. For the Barnes Maze, TLR4−/− mice performed significantly less total errors than WT mice on POD5 and 6 (p<0.01), and took significantly less time to reach the goal chamber on POD4, POD5 (p<0.05), and POD6 (p<0.01). CONCLUSION Our experimental results suggest that a microglial TLR4-dependent, MyD88-independent pathway is involved in neuronal apoptosis very early in an SAH model via RBC and hemoglobin activation, and that neuronal cell apoptosis due to TLR4 expression may be related to SAH-related cognitive and behavioral deficits. Our results suggest that TRIF may be the intracellular adaptor that is involved in this mechanism, but further experiments are needed to confirm this

Non-invasive Auricular Vagus nerve stimulation for Subarachnoid Hemorrhage (NAVSaH): Protocol for a prospective, triple-blinded, randomized controlled trial

BACKGROUND: Inflammation has been implicated in driving the morbidity associated with subarachnoid hemorrhage (SAH). Despite understanding the important role of inflammation in morbidity following SAH, there is no current effective way to modulate this deleterious response. There is a critical need for a novel approach to immunomodulation that can be safely, rapidly, and effectively deployed in SAH patients. Vagus nerve stimulation (VNS) provides a non-pharmacologic approach to immunomodulation, with prior studies demonstrating VNS can reduce systemic inflammatory markers, and VNS has had early success treating inflammatory conditions such as arthritis, sepsis, and inflammatory bowel diseases. The aim of the Non-invasive Auricular Vagus nerve stimulation for Subarachnoid Hemorrhage (NAVSaH) trial is to translate the use of non-invasive transcutaneous auricular VNS (taVNS) to spontaneous SAH, with our central hypothesis being that implementing taVNS in the acute period following spontaneous SAH attenuates the expected inflammatory response to hemorrhage and curtails morbidity associated with inflammatory-mediated clinical endpoints. MATERIALS AND METHODS: The overall objectives for the NAHSaH trial are to 1) Define the impact that taVNS has on SAH-induced inflammatory markers in the plasma and cerebrospinal fluid (CSF), 2) Determine whether taVNS following SAH reduces radiographic vasospasm, and 3) Determine whether taVNS following SAH reduces chronic hydrocephalus. Following presentation to a single enrollment site, enrolled SAH patients are randomly assigned twice daily treatment with either taVNS or sham stimulation for the duration of their intensive care unit stay. Blood and CSF are drawn before initiation of treatment sessions, and then every three days during a patient\u27s hospital stay. Primary endpoints include change in the inflammatory cytokine TNF-α in plasma and cerebrospinal fluid between day 1 and day 13, rate of radiographic vasospasm, and rate of requirement for long-term CSF diversion via a ventricular shunt. Secondary outcomes include exploratory analyses of a panel of additional cytokines, number and type of hospitalized acquired infections, duration of external ventricular drain in days, interventions required for vasospasm, continuous physiology data before, during, and after treatment sessions, hospital length of stay, intensive care unit length of stay, and modified Rankin Scale score (mRS) at admission, discharge, and each at follow-up appointment for up to two years following SAH. DISCUSSION: Inflammation plays a central role in morbidity following SAH. This NAVSaH trial is innovative because it diverges from the pharmacologic status quo by harnessing a novel non-invasive neuromodulatory approach and its known anti-inflammatory effects to alter the pathophysiology of SAH. The investigation of a new, effective, and rapidly deployable intervention in SAH offers a new route to improve outcomes following SAH. TRIAL REGISTRATION: Clinical Trials Registered, NCT04557618. Registered on September 21, 2020, and the first patient was enrolled on January 4, 2021

Advances in the Treatment of Ischemic Stroke

In recent years research on ischemic stroke has developed powerful therapeutic tools. The novel frontiers of stem cells therapy and of hypothermia have been explored, and novel brain repair mechanisms have been discovered. Limits to intravenous thrombolysis have been advanced and powerful endovascular tools have been put at the clinicians' disposal. Surgical decompression in malignant stroke has significantly improved the prognosis of this often fatal condition. This book includes contributions from scientists active in this innovative research. Stroke physicians, students, nurses and technicians will hopefully use it as a tool of continuing medical education to update their knowledge in this rapidly changing field

Estudio del perfil inflamatorio y de la coagulopatía asociada a la hemorragia subaracnoidea aneurismática

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Medicina, Departamento de Medicina. Fecha de Lectura: 02-12-2021Introducción: La hemorragia subaracnoidea aneurismática (HSAa) representa una grave emergencia médica con elevada mortalidad y morbilidad en relación a las complicaciones asociadas a ella. Objetivo: Estudiar los perfiles de coagulopatía e inflamación y su relación con las complicaciones asociadas a la HSAa con el fin de identificar precozmente a los pacientes en riesgo mediante detección de marcadores inflamatorios, de coagulopatía o la combinación de ambas a través de escalas predictivas. Métodos: Estudio de cohortes prospectivo, observacional, descriptivo y unicéntrico en la Unidad de Cuidados Intensivos del Hospital Universitario La Paz. Se analizaron 15 pacientes, mayores de 18 años, ingresados con diagnóstico de HSAa. Se analizaron de manera seriada variables sociodemográficas, clínicas y analíticas (hematimetría, coagulación convencional, pruebas globales de la hemostasia como las pruebas viscoelásticas o el test de generación de trombina y parámetros inflamatorios específicos). Entre las variables de interés se recogió la incidencia de vasoespasmo, daño neurológico tardío, disfunción cardiopulmonar y pronóstico a los 6 meses entre otros. Resultados: El estudio de los parámetros de inflamación específica confirmó la participación de la vía del inflamosoma NLPR3 en la fisiopatología de la HSAa. La expresión de mRNA de biomarcadores de la segunda señal de dicha vía se muestran aumentados desde el primer día, lo cual se traduce en una mayor expresión proteica de dicha vía en el suero de los pacientes con HSAa con elevación de interleuquinas (IL) 1β, 18 y factor tisular (FT). Tanto la expresión de mRNA de NLPR3 como FT se asociaron de manera significativa al desarrollo de vasoespasmo y síndrome de Tako-Tsubo, con una capacidad predictiva del 100% usando la combinación de IL-1β y FT para el Tako-Tsubo. Por otro lado, la HSAa induce un estado de hipercoagulabilidad “precoz” evidenciado por la técnica de generación de trombina que se sigue de un estado de hipercoagulabilidad “tardío” detectado por pruebas viscoelásticas, no viéndose acelerados los procesos de fibrinólisis. Los pacientes que desarrollaron vasoespasmo mostraron un aumento significativo de los parámetros de hipercoagulabilidad por tromboelastometría rotacional. Conclusiones: La HSAa cursa con un estado proinflamatorio debido, al menos parcialmente, a la activación de la vía del inflamosoma NLPR3, cuya sobreexpresión se asoció al desarrollo de determinadas complicaciones (vasoespasmo y síndrome de Tako-Tsubo). Asimismo, y al menos parcialmente en relación a lo previo, la HSAa cursa con un estado de hipercoagulabilidad que no se evidencia en las pruebas de coagulación convencionales pero sí en las pruebas viscoelásticas y de generación de trombina, cuyo seguimiento rutinario podría ayudar a identificar pacientes en riesgo de desarrollar complicaciones asociadas a la HSA