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      Angiotensin Type 2 Receptor Pharmacological Agonist Relieves Neurocognitive Deficits via Reducing Neuroinflammation and Microglial Engulfment of Dendritic Spines

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          Abstract

          Mechanically ventilated patients suffering critical illness are at high risk of developing neurocognitive impairments. Angiotensin type 2 receptor (AGTR2) has been demonstrated to be anti-inflammatory and neuroprotective. The present study thus aimed to investigate whether AGTR2 can alleviate cerebral dysfunction in mice subjected to cochallenge with lipopolysaccharide (LPS) and mechanical ventilation (MV), and to reveal the underlying mechanism. We utilized a mice model that received a single injection of LPS (1 mg/kg, intraperitoneally) followed 2 h later by MV (10 ml/kg, lasting for 2 h). Pretreatment with the AGTR2 pharmacological agonist C21 (0.03, 0.3, and 3 mg/kg, intraperitoneally, once daily, lasting for 10 days). Locomotor activity and behavioral deficits were evaluated 24 h post-MV by open-field and fear-condition tests. Brain hippocampus and prefrontal cortex tissues were collected for immunofluorescence staining and western blotting to evaluate the resulting impacts on microglia, including morphological traits, functional markers, synaptic engulfment, superoxide production, and signaling molecules. Compared with vehicle-control, pre-administrated C21 reduced the branch endpoints and length of microglia processes in a dose-dependent manner in mice subjected to LPS/MV. The neuroprotective effect of AGTR2 was behaviorally confirmed by the improvement of memory decline in LPS/MV-treated mice following C21 pretreatment. In addition to morphological alterations, C21 reduced microglial functional markers and reduced microglial-dendrite contact and microglial engulfment of synaptic protein markers. In terms of the underlying molecular mechanism, AGTR2 stimulation by C21 leads to activation of protein phosphatase 2A, which subsequently mitigates microglial PKCδ and NF-κB activation, and inhibites NOX2-derived ROS production. The AGTR2 agonist C21 alleviates behavioral deficits in those mice subjected to LPS/MV, via mechanisms that involve reactive microglia and abnormal synaptic plasticity in NOX2-derived ROS and the PKCδ-NFκB pathway.

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          Supplementary Information

          The online version contains supplementary material available at 10.1007/s11481-022-10054-7.

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          Neurologic Features in Severe SARS-CoV-2 Infection

          Julie Helms, Stéphane Kremer, Hamid Merdji … (2020)
          To the Editor: We report the neurologic features in an observational series of 58 of 64 consecutive patients admitted to the hospital because of acute respiratory distress syndrome (ARDS) due to Covid-19. The patients received similar evaluations by intensivists in two intensive care units (ICUs) in Strasbourg, France, between March 3 and April 3, 2020. Six patients were excluded because of paralytic neuromuscular blockade when neurologic data were collected or because they had died without a neurologic examination having been performed. In all 58 patients, reverse-transcriptase–polymerase-chain-reaction (RT-PCR) assays of nasopharyngeal samples were positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The median age of the patients was 63 years, and the median Simplified Acute Physiology Score II at the time of neurologic examination was 52 (interquartile range, 37 to 65, on a scale ranging from 0 to 163, with higher scores indicating greater severity of illness). Seven patients had had previous neurologic disorders, including transient ischemic attack, partial epilepsy, and mild cognitive impairment. The neurologic findings were recorded in 8 of the 58 patients (14%) on admission to the ICU (before treatment) and in 39 patients (67%) when sedation and a neuromuscular blocker were withheld. Agitation was present in 40 patients (69%) when neuromuscular blockade was discontinued (Table 1). A total of 26 of 40 patients were noted to have confusion according to the Confusion Assessment Method for the ICU; those patients could be evaluated when they were responsive (i.e., they had a score of −1 to 1 on the Richmond Agitation and Sedation Scale, on a scale of −5 [unresponsive] to +4 [combative]). Diffuse corticospinal tract signs with enhanced tendon reflexes, ankle clonus, and bilateral extensor plantar reflexes were present in 39 patients (67%). Of the patients who had been discharged at the time of this writing, 15 of 45 (33%) had had a dysexecutive syndrome consisting of inattention, disorientation, or poorly organized movements in response to command. Magnetic resonance imaging (MRI) of the brain was performed in 13 patients (Figs. S1 through S3 in the Supplementary Appendix, available with the full text of this letter at NEJM.org). Although these patients did not have focal signs that suggested stroke, they underwent MRI because of unexplained encephalopathic features. Enhancement in leptomeningeal spaces was noted in 8 patients, and bilateral frontotemporal hypoperfusion was noted in all 11 patients who underwent perfusion imaging. Two asymptomatic patients each had a small acute ischemic stroke with focal hyperintensity on diffusion-weighted imaging and an overlapping decreased apparent diffusion coefficient, and 1 patient had a subacute ischemic stroke with superimposed increased diffusion-weighted imaging and apparent diffusion coefficient signals. In the 8 patients who underwent electroencephalography, only nonspecific changes were detected; 1 of the 8 patients had diffuse bifrontal slowing consistent with encephalopathy. Examination of cerebrospinal fluid (CSF) samples obtained from 7 patients showed no cells; in 2 patients, oligoclonal bands were present with an identical electrophoretic pattern in serum, and protein and IgG levels were elevated in 1 patient. RT-PCR assays of the CSF samples were negative for SARS-CoV-2 in all 7 patients. In this consecutive series of patients, ARDS due to SARS-CoV-2 infection was associated with encephalopathy, prominent agitation and confusion, and corticospinal tract signs. Two of 13 patients who underwent brain MRI had single acute ischemic strokes. Data are lacking to determine which of these features were due to critical illness–related encephalopathy, cytokines, or the effect or withdrawal of medication, and which features were specific to SARS-CoV-2 infection.
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            Long-term cognitive impairment after critical illness.

            P.P. Pandharipande, T.D. Girard, J.C. Jackson … (2013)
            Survivors of critical illness often have a prolonged and disabling form of cognitive impairment that remains inadequately characterized. We enrolled adults with respiratory failure or shock in the medical or surgical intensive care unit (ICU), evaluated them for in-hospital delirium, and assessed global cognition and executive function 3 and 12 months after discharge with the use of the Repeatable Battery for the Assessment of Neuropsychological Status (population age-adjusted mean [±SD] score, 100±15, with lower values indicating worse global cognition) and the Trail Making Test, Part B (population age-, sex-, and education-adjusted mean score, 50±10, with lower scores indicating worse executive function). Associations of the duration of delirium and the use of sedative or analgesic agents with the outcomes were assessed with the use of linear regression, with adjustment for potential confounders. Of the 821 patients enrolled, 6% had cognitive impairment at baseline, and delirium developed in 74% during the hospital stay. At 3 months, 40% of the patients had global cognition scores that were 1.5 SD below the population means (similar to scores for patients with moderate traumatic brain injury), and 26% had scores 2 SD below the population means (similar to scores for patients with mild Alzheimer's disease). Deficits occurred in both older and younger patients and persisted, with 34% and 24% of all patients with assessments at 12 months that were similar to scores for patients with moderate traumatic brain injury and scores for patients with mild Alzheimer's disease, respectively. A longer duration of delirium was independently associated with worse global cognition at 3 and 12 months (P=0.001 and P=0.04, respectively) and worse executive function at 3 and 12 months (P=0.004 and P=0.007, respectively). Use of sedative or analgesic medications was not consistently associated with cognitive impairment at 3 and 12 months. Patients in medical and surgical ICUs are at high risk for long-term cognitive impairment. A longer duration of delirium in the hospital was associated with worse global cognition and executive function scores at 3 and 12 months. (Funded by the National Institutes of Health and others; BRAIN-ICU ClinicalTrials.gov number, NCT00392795.).
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              Is Open Access

              Oxidative Stress, Synaptic Dysfunction, and Alzheimer’s Disease

              Eric Tönnies, Eugenia Trushina (2017)
              Alzheimer’s disease (AD) is a devastating neurodegenerative disorder without a cure. Most AD cases are sporadic where age represents the greatest risk factor. Lack of understanding of the disease mechanism hinders the development of efficacious therapeutic approaches. The loss of synapses in the affected brain regions correlates best with cognitive impairment in AD patients and has been considered as the early mechanism that precedes neuronal loss. Oxidative stress has been recognized as a contributing factor in aging and in the progression of multiple neurodegenerative diseases including AD. Increased production of reactive oxygen species (ROS) associated with age- and disease-dependent loss of mitochondrial function, altered metal homeostasis, and reduced antioxidant defense directly affect synaptic activity and neurotransmission in neurons leading to cognitive dysfunction. In addition, molecular targets affected by ROS include nuclear and mitochondrial DNA, lipids, proteins, calcium homeostasis, mitochondrial dynamics and function, cellular architecture, receptor trafficking and endocytosis, and energy homeostasis. Abnormal cellular metabolism in turn could affect the production and accumulation of amyloid-β (Aβ) and hyperphosphorylated Tau protein, which independently could exacerbate mitochondrial dysfunction and ROS production, thereby contributing to a vicious cycle. While mounting evidence implicates ROS in the AD etiology, clinical trials with antioxidant therapies have not produced consistent results. In this review, we will discuss the role of oxidative stress in synaptic dysfunction in AD, innovative therapeutic strategies evolved based on a better understanding of the complexity of molecular mechanisms of AD, and the dual role ROS play in health and disease.
              Article 0 comments Cited 440 times – based on 0 reviews     Review now
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                Author and article information

                Contributors
                Shan-shan Hu:
                ORCID: http://orcid.org/0000-0002-0058-4750
                shanshanhu@ahmu.edu.cn
                Journal
                Journal ID (nlm-ta): J Neuroimmune Pharmacol
                Journal ID (iso-abbrev): J Neuroimmune Pharmacol
                Title: Journal of Neuroimmune Pharmacology
                Publisher: Springer US (New York )
                ISSN (Print): 1557-1890
                ISSN (Electronic): 1557-1904
                Publication date (Electronic): 5 December 2022
                Pages: 1-17
                Affiliations
                [1 ]Anhui Provincial Hospita, Anhui Provincial Hospital Affiliated to Anhui Medical University, Anhui Medical University, Hefei, 230036 China
                [2 ]GRID grid.59053.3a, ISNI 0000000121679639, Department of Neurobiology, Division of Life Sciences and Medicine, , University of Science and Technology of China, ; Hefei, 230001 China
                [3 ]GRID grid.59053.3a, ISNI 0000000121679639, Department of Anesthesiology, First Affiliated Hospital of USTC (Anhui Provincial Hospita), , Division of Life Sciences and Medicine, University of Science and Technology of China (USTC), ; Hefei, 230001 China
                [4 ]GRID grid.59053.3a, ISNI 0000000121679639, Department of Clinical Laboratory, First Affiliated Hospital of USTC (Anhui Provincial Hospita), , Division of Life Sciences and Medicine, University of Science and Technology of China (USTC), ; Hefei, 230001 China
                Author information
                http://orcid.org/0000-0002-0058-4750
                Article
                Publisher ID: 10054
                DOI: 10.1007/s11481-022-10054-7
                PMC ID: 9734469
                PubMed ID: 36464726
                SO-VID: 0fa87efb-8647-4843-b8b8-7b000ac8abb6
                Copyright © © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2022, Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
                License:

                This article is made available via the PMC Open Access Subset for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemic.

                History
                Date received : 14 July 2022
                Date accepted : 8 November 2022
                Funding
                Funded by: FundRef http://dx.doi.org/10.13039/501100012165, Key Technologies Research and Development Program;
                Award ID: 2021ZD0203105
                Award Recipient :
                Funded by: FundRef http://dx.doi.org/10.13039/501100001809, National Natural Science Foundation of China;
                Award ID: 82171218
                Award ID: 81703524
                Award Recipient :
                Categories
                Subject: Original Article

                ScienceOpen disciplines: Pharmacology & Pharmaceutical medicine
                Keywords: neurocognitive disturbances,mechanical ventilation,systemic inflammation,microglia,synaptic engulfment,oxidative stress,agtr2
                Data availability:
                ScienceOpen disciplines: Pharmacology & Pharmaceutical medicine
                Keywords: neurocognitive disturbances, mechanical ventilation, systemic inflammation, microglia, synaptic engulfment, oxidative stress, agtr2

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