Publications by authors named "Youenn Jouan"

Article Synopsis
  • Neutrophil subsets with regulatory properties are often seen as harmful to immune responses against tumors and infections, but new findings suggest otherwise in cases of severe viral respiratory infections (VRI).
  • A significant population of neutrophils expressing programmed death-ligand 1 (PD-L1) was identified in humans and mice with VRI, exhibiting strong regulatory functions but diminished antimicrobial capabilities.
  • Depleting these PD-L1 neutrophils or blocking their function during VRI led to worse outcomes, indicating that they play a crucial role in managing inflammation and could be potential targets for future treatments.
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Background: Activation of innate immunity is a first line of host defense during acute critical illness (ACI) that aims to contain injury and avoid tissue damages. Aberrant activation of innate immunity may also participate in the occurrence of organ failures during critical illness. This review aims to provide a narrative overview of recent advances in the field of innate immunity in critical illness, and to consider future potential therapeutic strategies.

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Like pneumonia, coronavirus disease 2019 (COVID-19) is characterized by a massive infiltration of innate immune cells (such as polymorphonuclear leukocytes) into the airways and alveolar spaces. These cells release proteases that may degrade therapeutic antibodies and thus limit their effectiveness. Here, we investigated the in vitro and ex vivo impact on anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) IgG1s and other IgG subclasses (IgG2 and IgG4) of the neutrophil elastase, proteinase 3 and cathepsin G (the three main neutrophil serine proteases) found in endotracheal aspirates from patients with severe COVID-19.

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Over the past 2 years, SARS-CoV-2 infection has resulted in numerous hospitalizations and deaths worldwide. As young intensivists, we have been at the forefront of the fight against the COVID-19 pandemic and it has been an intense learning experience affecting all aspects of our specialty. Critical care was put forward as a priority and managed to adapt to the influx of patients and the growing demand for beds, financial and material resources, thereby highlighting its flexibility and central role in the healthcare system.

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Article Synopsis
  • Post-intensive care syndrome (PICS) is a condition that causes lasting physical, cognitive, and mental impairments after leaving the ICU, significantly affecting patients' long-term health and quality of life.
  • The review discusses key issues related to PICS, including muscle weakness, cognitive deficits associated with delirium, and long-term effects on the immune system, kidneys, and lungs.
  • Understanding the biological processes underlying PICS can lead to improved patient care and new strategies for prevention and treatment.
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Article Synopsis
  • - Recent research links organ dysfunction in sepsis to disrupted metabolism and mitochondrial dysfunction, highlighting the importance of substrate utilization in understanding these conditions.
  • - Sepsis leads to significant metabolic changes, including altered oxygen consumption and impaired oxidation of glucose and lipids, which are associated with negative outcomes for both animals and humans.
  • - Advances in understanding metabolic dysfunctions may inform new diagnostic methods and treatment strategies for sepsis, enabling personalized approaches by identifying specific patient subgroups.
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Unlabelled: BACKGROUND AND PURPOSE 255: Pseudomonas aeruginosa is a main cause of ventilator-associated pneumonia (VAP) with drug-resistant bacteria. Bacteriophage therapy has experienced resurgence to compensate for the limited development of novel antibiotics. However, phage therapy is limited to a compassionate use so far, resulting from lack of adequate studies in relevant pharmacological models.

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Immune system dysfunction is paramount in coronavirus disease 2019 (COVID-19) severity and fatality rate. Mucosal-associated invariant T (MAIT) cells are innate-like T cells involved in mucosal immunity and protection against viral infections. Here, we studied the immune cell landscape, with emphasis on MAIT cells, in cohorts totaling 208 patients with various stages of disease.

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Article Synopsis
  • - CD1d-restricted invariant Natural Killer T (iNKT) cells are a special type of T cells that have important immune functions, but their development into specific subtypes is not fully understood.
  • - A study using single-cell transcriptomic analysis reveals a greater diversity in thymic iNKT cells, particularly in iNKT1 cells, and suggests iNKT2 cells play a key role in the development of iNKT1 and iNKT17 subsets.
  • - The research identifies FHL2 as a key regulator in the specification of iNKT1 cells, highlighting the complex changes in the transcriptional networks that influence iNKT cell functions.
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COVID-19 includes lung infection ranging from mild pneumonia to life-threatening acute respiratory distress syndrome (ARDS). Dysregulated host immune response in the lung is a key feature in ARDS pathophysiology. However, cellular actors involved in COVID-19-driven ARDS are poorly understood.

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Importance: Coronavirus disease 2019 (COVID-19) is associated with severe lung damage. Corticosteroids are a possible therapeutic option.

Objective: To determine the effect of hydrocortisone on treatment failure on day 21 in critically ill patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and acute respiratory failure.

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Article Synopsis
  • ICU hospitalizations for elderly patients with acute respiratory infections (ARI) have risen, but the long-term impacts of these admissions are not well understood.
  • A study analyzed data on ICU survivors aged 80 and older, matching them with controls to assess differences in mortality, healthcare use, and frailty scores over two years post-discharge.
  • Findings revealed ICU survivors faced significantly higher mortality risk (10.1 times greater at 6 months and 3.6 times greater at 2 years), increased healthcare utilization, and a rise in frailty scores compared to controls, suggesting the need for improved post-ICU care strategies.
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Background: Obesity is associated with chronic low-grade inflammation, which has been linked to increased morbidity. However, inflammation variably and unpredictably improves after bariatric surgery. This study aimed at (1) evaluating the relationship between amplitude of weight loss and variation of inflammatory parameters after bariatric surgery, and (2) identifying, among clinical and biological baseline parameters, predictive factors of variation in inflammatory parameters.

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Article Synopsis
  • The study investigates how pre-existing health conditions (comorbidities) affect healthcare use after patients are discharged from the ICU, particularly focusing on those with post-intensive care syndrome (PICS).
  • Researchers analyzed data from over 800 adult patients in France who were admitted to the ICU for severe conditions (septic shock or ARDS) and found varying healthcare use patterns before and after their ICU stay.
  • Results indicated that most patients (83%) who had low or no pre-ICU healthcare usage experienced a significant increase in their healthcare needs after ICU discharge, suggesting that prior health status plays a crucial role in post-ICU healthcare trajectories.
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Article Synopsis
  • Interleukin-7 (IL-7) plays a crucial role in the development of B- and T-lymphocytes and has been identified as a key survival factor for certain innate T cells important in antibacterial immunity.
  • *Research shows that delivering IL-7 topically can enhance the number of RORγt IL-17A-producing innate T cells, leading to improved bacterial control during infections like those caused by Streptococcus pneumoniae.
  • *Combining IL-7 treatment with α-galactosylceramide can significantly increase survival rates during infections by boosting IL-17 production and neutrophil response, suggesting IL-7 could be a potential new treatment for bacterial infections.*
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Article Synopsis
  • * A post hoc analysis of the SEPSISPAM trial included 532 mechanically ventilated and sedated patients, assessing their levels of arousal using the Richmond Agitation and Sedation Scale (RASS).
  • * Results showed that patients in the high-target MAP group had significantly higher arousal levels at days 2, 4, and 5 compared to those in the low-target group, indicating potential benefits of higher MAP goals in improving patient responsiveness.
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Background: Iodinated contrast media may contribute to acute kidney injury. However, several recent works suggest that this toxicity is minimal in the clinical setting. Recently, urinary G1 cell-cycle arrest proteins tissue inhibitor of metalloproteinase 2 (TIMP-2) and insulin like growth factor binding protein 7 (IGFBP-7) were identified as highly sensitive and specific biomarkers for early detection of kidney aggression.

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Background: The consequences of the ageing population concerning ICU hospitalisation need to be adequately described. We believe that this discussion should be disease specific. A focus on respiratory infections is of particular interest, because it is strongly associated with old age.

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γδT cells comprise a unique T cell sublineage endowed with a wide functional repertoire, which allow them to play important-sometimes opposite-roles in many immune responses associated with infection, cancer, and inflammatory processes. This is largely dependent on the existence of pre-programmed discrete functional subsets that differentiate within the thymus at specific temporal windows of life. Since they represent a major early source of interleukin-17A in many models of immune responses, the γδT17 cell population has recently gained considerable interest.

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Article Synopsis
  • Sphingolipids (SLs) play a key role in various immune processes, with their acyl chain length influencing their function.
  • The study highlights that very-long acyl chain sphingolipids (VLC-SLs) are important for the maturation of invariant natural killer T (NKT) cells in the thymus and their maintenance in the liver.
  • Mice missing VLC-SLs were found to be more susceptible to a virus due to a decrease in NKT cells, indicating the essential role of VLC-SLs in NKT cell health.
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