Sophia Koutsogiannaki

Introduction/Background: CD11d (integrin αDβ2) is primarily expressed by myeloid cells, but its role in neutrophil signaling and maturation during sepsis remains poorly defined. Methods: We investigated the function of CD11d/Itgad using bulk RNA sequencing of blood and lung neutrophils from wild-type and CD11d-deficient mice at baseline and 12 h after cecal ligation and puncture (CLP), complemented by single-cell RNA-seq analyses of lung and bone marrow. Results: We found that CD11d deficiency had minimal effects on blood neutrophils but substantially altered the lung neutrophil transcriptome, particularly programs governing maturation. At baseline, CD11d KO lung neutrophils showed an alarmin-associated transcriptional signature ( S100a8, S100a9, Il1b ), reduced expression of genes encoding components of integrin outside-in signaling ( Syk, Ptk2b, Rac2 ), and an elevated immature neutrophil score relative to WT. Strikingly, this phenotype reversed after CLP: KO neutrophils acquired a more mature transcriptional state than WT, despite reduced expression of granulopoiesis regulators ( Cebpa, Cebpb, Csf3 ) and attenuated NF-κB-dependent inflammatory and acute-phase programs. Deconvolution of independent lung single-cell data corroborated this maturation shift. Comparison with CD11c-deficient neutrophils revealed divergent maturation phenotypes despite shared interferon and NF-κB pathway changes, with CD11d loss favoring a Cd101-high mature state versus CD11c loss favoring a Cebpb -high immature state. Single cell analyses localized Itgad expression to a small Mki67+Top2a+ pre-neutrophil population in the lung and to neutrophil precursors in bone marrow, with expression declining progressively across maturation stages. Discussion: Together, these findings associate CD11d deficiency with context-dependent changes in neutrophil maturation-associated transcriptional programs during sepsis, distinct from but partially overlapping with CD11c-dependent programs.

As survival rates following pediatric cardiac surgery have improved, neurodevelopmental impairment has emerged as a significant long‐term comorbidity. Neonates and infants are particularly vulnerable and are at the highest risk for neurodevelopmental impairment. Imaging study has identified new white matter injury in up to 20%–50% of this cohort postoperatively. Currently there is no clinical modality to accurately detect neurological events in real time during cardiac surgery. Brain imaging remains the gold standard for identifying cerebral injury, but it is only feasible postoperatively. In this study we intended to determine a plasma marker suitable to detect intraoperative brain injury by examining infant piglets undergoing cardiopulmonary bypass (CPB) and neonates/infants undergoing cardiac surgery on CPB. We compared two different CPB strategies; full‐flow bypass alone and bypass involving circulatory arrest (CA) in infant piglets where CA was associated with post CPB neurodevelopmental impairment in our previous study. We found that ubiquitin C‐terminal hydrolase L1 (UCHL1), a protein abundantly expressed in the neuronal body, was elevated in the blood after CA in infant piglets. CA group showed more proinflammatory profiles than full‐flow bypass group. Histological analysis of piglet brain demonstrated that neurons underwent more apoptosis after CA, along with lower UCHL1 expression. Plasma proteomics analysis in infant piglets suggested the disruption of blood brain barrier (BBB) after CA compared to full‐flow bypass. We hypothesized that UCHL1 could serve as a promising neurological injury marker in patients, too. We compared neonates and infants who underwent full‐flow bypass alone and bypass involving CA/regional perfusion (RP) groups. Neonates and infants subjected to CA/RP had higher odds of having neurodevelopmental impairment compared to full‐flow bypass group. CA/RP group showed more proinflammatory profiles than full‐flow bypass group. Plasma proteomics analysis in neonates and infants also demonstrated similar findings in CA/RP arm compared to full‐flow arm as we observed in piglets. UCHL1 level at the rewarming during CPB showed highest area under the curve (AUC) value of 0.7022 (95% CI 0.5692–0.8287). Overall, this study suggested UCHL1 to be a promising biomarker of brain injury associated with neurodevelopmental impairment following pediatric cardiac surgery involving CPB.

Sepsis remains a leading cause of morbidity and mortality worldwide, with outcomes highly influenced by host immune responses. While environmental and pathogen‐related factors are well recognized, the contribution of host genomic variants to sepsis susceptibility and severity is increasingly appreciated. Because approximately 85% of known disease‐causing mutations reside in the exome, whole exome sequencing (WES) offers a powerful strategy to uncover pathogenic variants in critically ill patients and to identify potential inborn errors of immunity that may modulate disease course. In the present study, we performed WES on 31 sepsis patients across different age groups, stratified into pre‐school‐aged children, school‐aged children, and adults, and identified multiple genes harboring high‐ or medium‐impact variants. Of particular interest, a high‐impact TLR8 variant (rs3764880: A>G; p.Met1Val) was observed across all the age groups and predominantly in individuals with bacterial sepsis. Single‐cell RNA sequencing of peripheral blood mononuclear cells demonstrated that TLR8 was highly expressed in non‐classical monocytes, with transcription levels markedly elevated in carriers of the variant. Functional studies revealed that this TLR8 variant enhanced IFN‐β secretion upon ligand stimulation, suggesting that dysregulated TLR8 signaling might modulate host inflammatory responses during bacterial sepsis. Given the established role of IFN‐β in exacerbating sepsis severity, these findings support a model in which the TLR8 rs3764880 variant contributes to sepsis pathophysiology by amplifying IFN‐β‐mediated monocyte responses. This study underscores the importance of integrating genomic and functional immunologic analyses to identify host determinants of sepsis, highlights TLR8 as a potential biomarker and therapeutic target, and provides a framework for precision medicine approaches to predict and modulate outcomes in bacterial sepsis.

Sepsis is a life-threatening condition arising from a dysregulated host response to infection, characterized by a complex interplay between pro-inflammatory and anti-inflammatory immune mechanisms. B cells, that are key components of humoral immunity, are essential for antibody production, antigen presentation, and immune modulation. Sepsis is commonly associated with B cell lymphopenia, particularly in severe cases, as evidenced by a marked reduction in circulating B cells in both adult and pediatric patients. However, the mechanisms driving this depletion have not been completely understood, particularly in pediatric sepsis. In this study, we employed single-cell RNA sequencing (scRNA-seq) to profile peripheral blood leukocytes from pediatric patients with sepsis (three with mild and three with severe condition) alongside four healthy controls. Our analysis revealed a broad depletion of immune cells in sepsis, with B cells showing the most pronounced reduction and the strongest capacity to discriminate between mild and severe disease states. Subset-level analysis identified significant loss and transcriptional reprogramming of natural killer-like B cells (ΝΚΒ), MHC II ^high naïve, and MHC II ^low naïve B cells in severe sepsis, accompanied by signatures indicative of intrinsic and extrinsic apoptosis, disrupted differentiation, and enhanced migratory potential. Importantly, we identified and validated the population of NKB cells in both pediatric and adult cohorts, broadening the known landscape of B cell phenotypes in human sepsis. We also explored intercellular communications, focusing on B cell-neutrophil interactions, given the notable neutrophilia observed, revealing potential crosstalk that may contribute to the overall immune dysregulation in sepsis. Collectively, these findings offer new insights into the cellular and molecular drivers of immune dysfunction in pediatric sepsis, shedding light on B cell depletion as a central feature of disease severity. This work lays the foundation for future diagnostic and therapeutic strategies targeting B cell-mediated immunity in septic children. The study was registered on ClinicalTrials.gov (NCT04103268), with registration date on 2019-09-23, before the first patient was enrolled.

Adiponectin, a key adipokine primarily secreted by adipocytes, plays crucial roles in metabolic homeostasis and inflammation, exhibiting anti-diabetic, anti-atherogenic, and anti-inflammatory properties. Its various isoforms and signaling via receptors like AdipoR1, AdipoR2, and T-cadherin contribute to its diverse biological functions. Sepsis is a life-threatening syndrome triggered by a dysregulated host response to infection, leading to systemic inflammation, multi-organ failure, and high mortality, currently lacking specific treatments. Preclinical studies largely suggest a protective role for adiponectin, demonstrating that its deficiency exacerbates inflammation and endothelial dysfunction, while its administration or agonism improves outcomes in experimental sepsis models. Clinical findings, however, present a complex picture, with inconsistent correlations between adiponectin levels and sepsis outcomes reported, suggesting its potential as a dynamic biomarker influenced by disease stage, patient heterogeneity, and isoforms, rather than a simple prognostic factor. Notably, glucagon-like peptide-1 receptor agonists (GLP-1RAs), used in obesity and diabetes management, have been shown to increase adiponectin levels, linking metabolic therapies to potential sepsis immunomodulation. Consequently, targeting adiponectin signaling, either directly with adiponectin mimics like AdipoRon or indirectly via strategies like GLP-1RA administration, represents a promising therapeutic approach for sepsis. Harnessing the adiponectin axis holds potential for advancing precision medicine in critical care, necessitating further research into adiponectin-based interventions and synergistic metabolic therapies to improve sepsis outcomes. Graphical abstract

Background: The relationship between sepsis outcomes and obesity has attracted significant interest in the medical community. However, this association has not been tested under Phoenix criteria, which represent the new pediatric sepsis definition, defining sepsis as life-threatening organ dysfunction in the setting of infection. Methods: A single-center, observational, retrospective study of pediatric sepsis patients from January 2014 to December 2019. The PICU was located within a tertiary pediatric center in the United States. Children more than one month old, but less than 18 years old, with a diagnosis of sepsis were included. Results: Six hundred and twenty-seven patients with a diagnosis of sepsis based on the Sepsis-2 definition were identified. Within the cohort, 554 patients met the definition of sepsis under the Phoenix criteria. Patients were classified based on the body habitus as underweight, normal, overweight, and obese. Obese patients had significantly higher mortality compared to the normal weight group (p = 0.033). More renal dysfunction was also seen in the obesity group (p = 0.0007). No difference in the frequency of identified Gram-positive, Gram-negative bacterial, viral, or fungal sepsis was observed between normal-weight and obese patients. Conclusions: In our cohort of pediatric sepsis, obesity was significantly associated with a higher degree of organ dysfunction and mortality. However, no difference in the incidence of identified bacterial, fungal, or viral sepsis was observed.

Objectives: The relationship between sepsis outcome and obesity has attracted a significant interest in medical community. However, this association has not been tested under a new pediatric sepsis definition- Phoenix criteria. DESIGN: A single-center, observational, retrospective study of pediatric sepsis patients from January 2014 to December 2019 SETTING: The PICU located within a tertiary pediatric center in the United States. PATIENTS: Children less than 18 years old with the diagnosis of sepsis. INTERVENTIONS: Not applicable. MEASUREMENT AND MAIN RESULTS: 640 patients with the diagnosis of sepsis based on the sepsis-2 definition were identified. Within the cohort, 631 patients met the definition of sepsis under Phoenix criteria. Patients were classified based on the body habitus as underweight, normal, overweight, and obese. Obese patients had significantly higher mortality compared to normal weight group (p=0.029). More respiratory and renal dysfunction was also seen in obesity group (p=0.008, and p= 0.0008, respectively). No difference in the frequency of identified gram positive, gram negative bacterial, viral, or fungal sepsis was observed based on the body habitus. CONLUSIONS: In our cohort of pediatric sepsis, obesity was significantly associated with higher degree of organ dysfunction and mortality. However, no difference in the incidence of identified bacteria, fungal, or viral sepsis was observed.

Sedatives/anesthetics are important medical tools to facilitate medical care and increase patients' comfort. Increasingly, there is recognition that sedatives/anesthetics can modulate immune functions. Toll‐like receptors (TLRs) are major pattern recognition receptors involved in the recognition of microbial components. TLR7 recognizes single‐strand RNA virus such as influenza and SARS‐CoV2 viruses and initiates interferon (IFN) responses. IFN production triggered by TLR7 stimulation is a critical anti‐viral response. For example, patients with TLR7 variants including loss‐of‐ function variants were associated with severe COVID‐19. Taken together, it is important to determine if sedatives/anesthetics mitigate TLR7 function. We have previously showed that TLR7‐mediated activation was not affected by volatile anesthetics. However, we found that propofol attenuated TLR7 activation among intravenous sedatives in the reporter assay. TLR7 agonist R837 stimulation increased TNF‐α, IL‐1β, IL‐6, IL‐10, and IFN‐β mRNA levels in bone marrow‐derived dendritic cells, while these levels were attenuated by propofol. Our murine lung slice experiments showed that propofol attenuated IFN production. R837 increased IFN‐β expression in the lungs, and propofol attenuated IFN‐β expression in an in vivo model of R837 intranasal instillation. We also found that propofol directly bound to and hindered its association of TLR7 with MyD88. Our analysis using fropofol, propofol derivative showed that the hydroxyl group in propofol was important for propofol–TLR7 interaction.

Mechanical ventilation is an important part of medical care in intensive care units and operating rooms to support respiration. While it is a critical component of medical care, it is well known that mechanical ventilation itself can be injurious to the lungs. Despite a large number of clinical and preclinical studies that have been done so far, there still exists a gap of knowledge regarding how to ventilate patients mechanically without increasing lung injury. Here, we will review what we have learned so far from preclinical and clinical studies and consider how to use preclinical models of ventilation-induced lung injury that better recapitulate the clinical scenarios.