Noncanonical functions of the autophagy machinery in pathways including LC3-associated phagocytosis and LC3-associated endocytosis have garnered increasing interest in both normal physiology and ...pathobiology. New discoveries over the past decade of noncanonical uses of the autophagy machinery in these distinct molecular mechanisms have led to robust investigation into the roles of single-membrane LC3 lipidation. Noncanonical autophagy pathways have now been implicated in the regulation of multiple processes ranging from debris clearance, cellular signaling, and immune regulation and inflammation. Accumulating evidence is demonstrating roles in a variety of disease states including host-pathogen responses, autoimmunity, cancer, and neurological and neurodegenerative pathologies. Here, we broadly summarize the differences in the mechanistic regulation between autophagy and LAP and LANDO and highlight some of the key roles of LAP and LANDO in innate immune function, inflammation, and disease pathology.
LAP and LANDO diverge from autophagy and regulate inflammation.
The aryl hydrocarbon receptor (AhR) is a ligand‐activated transcription factor, largely known for its role in xenobiotic metabolism and detoxification as well as its crucial role as a regulator of ...inflammation. Here, we have compared a cohort wild‐type and AhR‐null mice along aging to study the relationship between this receptor and age‐associated inflammation, termed as “inflammaging,” both at a systemic and the CNS level. Our results show that AhR deficiency is associated with a premature aged phenotype, characterized by early inflammaging, as shown by an increase in plasma cytokines levels. The absence of AhR also promotes the appearance of brain aging anatomic features, such as the loss of the white matter integrity. In addition, AhR–/– mice present an earlier spatial memory impairment and an enhanced astrogliosis in the hippocampus when compared with their age‐matched AhR+/+ controls. Importantly, we have found that AhR protein levels decrease with age in this brain structure, strongly suggesting a link between AhR and aging.—Bravo‐Ferrer, I., Cuartero, M. I., Medina, V., Ahedo‐Quero, D., Peña‐Martínez, C., Pérez‐Ruíz, A., Fernández‐Valle, M. E., Hernández‐Sánchez, C., Fernández‐Salguero, P. M., Lizasoain, I., Moro, M. A. Lack of the aryl hydrocarbon receptor accelerates aging in mice. FASEB J. 33, 12644–12654 (2019). www.fasebj.org
BACKGROUND AND PURPOSE—After stroke, the population of infiltrated neutrophils in the brain is heterogeneous, including a population of alternative neutrophils (N2) that express M2 phenotype markers. ...We explored the role of TLR4 (toll-like receptor 4) on neutrophil infiltration and polarization in this setting.
METHODS—Focal cerebral ischemia was induced by occlusion of the middle cerebral artery occlusion in TLR4-KO and WT (wild type) mice. Infarct size was measured by Nissl staining and magnetic resonance imaging. Leukocyte infiltration was quantified 48 hours after middle cerebral artery occlusion by immunofluorescence and flow cytometry. To elucidate mechanisms underlying TLR4-mediated N2 phenotype, a cDNA microarray analysis was performed in neutrophils isolated from blood 48 hours after stroke in WT and TLR4-KO mice.
RESULTS—As demonstrated previously, TLR4-deficient mice presented lesser infarct volumes than WT mice. TLR4-deficient mice showed higher density of infiltrated neutrophils 48 hours after stroke compared with WT mice, concomitantly to neuroprotection. Furthermore, cytometric and stereological analyses revealed an increased number of N2 neutrophils (YM1 cells) into the ischemic core in TLR4-deficient mice, suggesting a protective effect of this neutrophil subset that was corroborated by depleting peripheral neutrophils or using mice with TLR4 genetically ablated in the myeloid lineage. Finally, cDNA microarray analysis in neutrophils, confirmed by quantitative polymerase chain reaction, showed that TLR4 modulates several pathways associated with ischemia-induced inflammation, migration of neutrophils into the parenchyma, and their functional priming, which might explain the opposite effect on outcome of the different neutrophil subsets.
CONCLUSIONS—TLR4 deficiency increased the levels of alternative neutrophils (N2)—an effect associated with neuroprotection after stroke—supporting that modulation of neutrophil polarization is a major target of TLR4 and highlighting the crucial role of TLR4 at the peripheral level after stroke.
Growing evidence supports the suggestion that the peripheral immune system plays a role in different pathologies associated with cognitive impairment, such as vascular dementia (VD) or Alzheimer's ...disease (AD). The aim of this review is to summarize, within the peripheral immune system, the implications of different types of myeloid cells in AD and VD, with a special focus on post‐stroke cognitive impairment and dementia (PSCID). We will review the contributions of the myeloid lineage, from peripheral cells (neutrophils, platelets, monocytes and monocyte‐derived macrophages) to central nervous system (CNS)‐associated cells (perivascular macrophages and microglia). Finally, we will evaluate different potential strategies for pharmacological modulation of pathological processes mediated by myeloid cell subsets, with an emphasis on neutrophils, their interaction with platelets and the process of immunothrombosis that triggers neutrophil‐dependent capillary stall and hypoperfusion, as possible effector mechanisms that may pave the way to novel therapeutic avenues to stop dementia, the epidemic of our time.
LINKED ARTICLES
This article is part of a themed issue From Alzheimer's Disease to Vascular Dementia: Different Roads Leading to Cognitive Decline. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.6/issuetoc
Stroke is one of the most prevalent diseases worldwide caused primarily by a thrombotic vascular occlusion that leads to cell death. To date, t-PA (
) is the only thrombolytic therapy approved which ...targets fibrin as the main component of ischemic stroke thrombi. However, due to its highly restrictive criteria, t-PA is only administrated to less than 10% of all stroke patients. Furthermore, the research in neuroprotective agents has been extensive with no translational results from medical research to clinical practice up to now. Since we first described the key role of NETs (
) in platelet-rich thrombosis, we asked, first, whether NETs participate in fibrin-rich thrombosis and, second, if NETs modulation could prevent neurological damage after stroke. To this goal, we have used the thromboembolic
stroke model which produces fibrin-rich thrombotic occlusion, and the permanent occlusion of the middle cerebral artery by ligature. Our results demonstrate that NETs do not have a predominant role in fibrin-rich thrombosis and, therefore, DNase-I lacks lytic effects on fibrin-rich thrombosis. Importantly, we have also found that NETs exert a deleterious effect in the acute phase of stroke in a platelet-TLR4 dependent manner and, subsequently, that its pharmacological modulation has a neuroprotective effect. Therefore, our data strongly support that the pharmacological modulation of NETs in the acute phase of stroke, could be a promising strategy to repair the brain damage in ischemic disease, independently of the type of thrombosis involved.
The immune response subsequent to an ischemic stroke is a crucial factor in its physiopathology and outcome. It is known that TLR4 is implicated in brain damage and inflammation after stroke and that ...TLR4 absence induces neutrophil reprogramming toward a protective phenotype in brain ischemia, but the mechanisms remain unknown. We therefore asked how the lack of TLR4 modifies neutrophil function and their contribution to the inflammatory process.
In order to assess the role of the neutrophilic TLR4 after stroke, mice that do not express TLR4 in myeloid cells (TLR4
) and its respective controls (TLR4
) were used. Focal cerebral ischemia was induced by occlusion of the middle cerebral artery and infarct size was measured by MRI. A combination of flow cytometry and confocal microscopy was used to assess different neutrophil characteristics (circadian fluctuation, cell surface markers, cell complexity) and functions (apoptosis, microglia engulfment, phagocytosis, NETosis, oxidative burst) in both genotypes.
As previously demonstrated, mice with TLR4 lacking-neutrophils had smaller infarct volumes than control mice. Our results show that the absence of TLR4 keeps neutrophils in a steady youth status that is dysregulated, at least in part, after an ischemic insult, preventing neutrophils from their normal circadian fluctuation. TLR4-lacking neutrophils showed a higher phagocytic activity in the basal state, they were preferentially engulfed by the microglia after stroke, and they produced less radical oxygen species (ROS) in the first stage of the inflammatory process.
TLR4 is specifically involved in neutrophil dynamics under physiological conditions as well as in stroke-induced tissue damage. This research contributes to the idea that TLR4, especially when targeted in specific cell types, is a potential target for neuroprotective strategies.
High glutamate levels after head trauma or cerebral ischemia have neurotoxic effects. The objective of the present study was to evaluate the efficacy of hemodialysis to remove glutamate from the ...blood and to assess the behavior of this small molecule. Ten patients with end‐renal disease on hemodialysis were included in the study. Glutamate clearance was evaluated within the first hour of hemodialysis on a midweek dialysis day on five patients who underwent low flux hemodialysis, whereas the other five patients underwent highly efficient hemodialysis (high flux hemodialysis on one day and online hemodiafiltration on another day). Glutamate clearance with hemodialysis was very effective and did not show any differences between the techniques (low flux: 214 55, high flux: 204 37, online hemodiafiltration: 202 16, median (interquartile range), P = .7). Glutamate clearance was almost equivalent to vascular access plasma flow and it was not affected by dialyzer permeability or ultrafiltration rate. After a hemodialysis session, a significant decrease in glutamate blood level was observed (prehemodialysis: 59.7 36.1, posthemodialysis 37.0 49.2, P = .005). Dialysis performed under fasting condition showed higher glutamate reduction rate (60%) than that under feeding condition (20%). Hemodialysis may be an effective method to reduce glutamate blood levels, and the molecule clearance does not differ between the different techniques used. Considering previous results in experimental models, hemodialysis without hemodynamic stress, could be considered for reducing glutamate neurotoxic effects in acute ischemic strokes of patients in chronic hemodialysis programs.
High glutamate levels after head trauma or cerebral ischemia have neurotoxic effects. Glutamate clearance with hemodialysis is very effective .After a hemodialysis session, a significant decrease in glutamate blood level is observed. Dialysis performed under fasting condition shows higher glutamate reduction rate than that under feeding condition.
Stroke is a cerebrovascular pathology for which the only approved treatment is fibrinolysis. Several studies have focused on the development of new drugs but none has led to effective therapies to ...date, due, among others, to the difficulty to evaluate clinical deficits in experimental animal models. The present study aims to explore the applicability of known behavioral tests not commonly used in ischemia for the neurological assessment of mice after experimental stroke in different brain areas. A total of 225 CD1 male mice were randomly assigned to permanent middle cerebral artery occlusion by ligature (pMCAO) or permanent anterior cerebral artery occlusion by photothrombosis (pACAO) models. Modified neuroseverity score, footprint test, forced swim test and elevated plus maze were performed. Under these experimental conditions, modified neuroseverity score showed neurological impairment early after experimental stroke in both models. By contrast, the footprint test and the elevated plus maze detected short-term neurological deterioration in the pMCAO model but not in the pACAO model. Furthermore, the forced swim test identified depression-like behavior in mice after ischemia only when the left hemisphere was affected. In conclusion, we propose the repositioning of known neurobehavioral tests, but not commonly used in the stroke field, for the fast detection of neurological impairments early after ischemia, and even specific to discriminate the territory affected by arterial occlusion as well as the hemisphere where brain damage occurs. All these findings may prove useful to improve the experimental design of neuroprotective drugs in order to bridge the gap between experimental studies and clinical trials.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
BACKGROUND AND PURPOSE—Recanalization of the occluded artery is a primary goal in stroke treatment. Unfortunately, endovascular treatment is not always available, and tPA (tissue-type plasminogen ...activator) therapy is limited by its narrow therapeutic window; importantly, the rate of early arterial recanalization after tPA administration is low, especially for platelet-rich thrombi. The mechanisms for this tPA resistance are not well known. Since neutrophil extracellular traps (NETs) have been implicated in this setting, our aim was to study whether NET pharmacological modulation can reverse tPA resistance and the role of TLR4 (Toll-like receptor 4), previously related to NET formation, in thrombosis.
METHODS—To this goal, we have used a mouse photothrombotic stroke model, which produces a fibrin-free thrombus composed primarily of aggregated platelets and thrombi obtained from human stroke patients.
RESULTS—Our results demonstrate that (1) administration of DNase-I, which promotes NETs lysis, but not of tPA, recanalizes the occluded vessel improving photothrombotic stroke outcome; (2) a preventive treatment with Cl-amidine, impeding NET formation, completely precludes thrombotic occlusion; (3) platelet TLR4 mediates NET formation after photothrombotic stroke; and (4) ex vivo fresh platelet-rich thrombi from ischemic stroke patients are effectively lysed by DNase-I.
CONCLUSIONS—Hence, our data open new avenues for recanalization of platelet-rich thrombi after stroke, especially to overcome tPA resistance.
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