Hypoxia-inducible factor (HIF1α) gene expression in human shock states

Stress hyperglycaemia following trauma - a survival benefit or an outcome detriment?

PURPOSE OF REVIEW

Stress hyperglycaemia occur often in critically injured patients. To gain new consideration about it, this review compile current as well as known immunological and biochemical findings about causes and emergence.

RECENT FINDINGS

Glucose is the preferred energy substrate for fending immune cells, reparative tissue and the cardiovascular system following trauma. To fulfil these energy needs, the liver is metabolically reprogrammed to rebuild glucose from lactate and glucogenic amino acids (hepatic insulin resistance) at the expenses of muscles mass and - to a less extent - fat tissue (proteolysis, lipolysis, peripheral insulin resistance). This inevitably leads to stress hyperglycaemia, which is evolutionary preserved and seems to be an essential and beneficial survival response. It is initiated by damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs), intensified by immune cells itself and mainly ruled by tumour necrosis factor (TNF)α and catecholamines with lactate and hypoxia inducible factor (HIF)-1α as intracellular signals and lactate as an energy shuttle. Important biochemical mechanisms involved in this response are the Warburg effect as an efficient metabolic shortcut and the extended Cori cycle.

SUMMARY

Stress hyperglycaemia is beneficial in an acute life-threatening situation, but further research is necessary, to prevent trauma patients from the detrimental effects of persisting hyperglycaemia.

Unraveling the role of HIF-1α in sepsis: from pathophysiology to potential therapeutics-a narrative review

Sepsis is characterized by organ dysfunction resulting from a dysregulated inflammatory response triggered by infection, involving multifactorial and intricate molecular mechanisms. Hypoxia-inducible factor-1α (HIF-1α), a notable transcription factor, assumes a pivotal role in the onset and progression of sepsis. This review aims to furnish a comprehensive overview of HIF-1α's mechanism of action in sepsis, scrutinizing its involvement in inflammatory regulation, hypoxia adaptation, immune response, and organ dysfunction. The review encompasses an analysis of the structural features, regulatory activation, and downstream signaling pathways of HIF-1α, alongside its mechanism of action in the pathophysiological processes of sepsis. Furthermore, it will delve into the roles of HIF-1α in modulating the inflammatory response, including its association with inflammatory mediators, immune cell activation, and vasodilation. Additionally, attention will be directed toward the regulatory function of HIF-1α in hypoxic environments and its linkage with intracellular signaling, oxidative stress, and mitochondrial damage. Finally, the potential therapeutic value of HIF-1α as a targeted therapy and its significance in the clinical management of sepsis will be discussed, aiming to serve as a significant reference for an in-depth understanding of sepsis pathogenesis and potential therapeutic targets, as well as to establish a theoretical foundation for clinical applications.

Comparative Molecular and Biological Characteristic of the Systemic Inflammatory Response in Adult and Old Male Wistar Rats with Different Resistance to Hypoxia

Morphological, molecular, and biological features of the systemic inflammatory response induced by LPS administration were assessed in adult and old male Wistar rats with high and low resistance to hypoxia. In 6 h after LPS administration, mRNA expression levels of Hif1a, Vegf, Nfkb, and level of IL-1β protein in old rats were higher than in adult rats regardless of hypoxia tolerance. The morphometric study showed that the number of neutrophils in the interalveolar septa of the lungs was significantly higher in low-resistant adult and old rats 6 h after LPS administration. Thus, in old male Wistar rats, systemic inflammatory response is more pronounced than in adult rats and depends on the initial tolerance to hypoxia, which should be considered when developing new approaches to the therapy of systemic inflammatory response in individuals of different ages.

Neuroinflammation and the immune system in hypoxic ischaemic brain injury pathophysiology after cardiac arrest

Hypoxic ischaemic brain injury after resuscitation from cardiac arrest is associated with dismal clinical outcomes. To date, most clinical interventions have been geared towards the restoration of cerebral oxygen delivery after resuscitation; however, outcomes in clinical trials are disappointing. Therefore, alternative disease mechanism(s) are likely to be at play, of which the response of the innate immune system to sterile injured tissue in vivo after reperfusion has garnered significant interest. The innate immune system is composed of three pillars: (i) cytokines and signalling molecules; (ii) leucocyte migration and activation; and (iii) the complement cascade. In animal models of hypoxic ischaemic brain injury, pro-inflammatory cytokines are central to propagation of the response of the innate immune system to cerebral ischaemia-reperfusion. In particular, interleukin-1 beta and downstream signalling can result in direct neural injury that culminates in cell death, termed pyroptosis. Leucocyte chemotaxis and activation are central to the in vivo response to cerebral ischaemia-reperfusion. Both parenchymal microglial activation and possible infiltration of peripherally circulating monocytes might account for exacerbation of an immunopathological response in humans. Finally, activation of the complement cascade intersects with multiple aspects of the innate immune response by facilitating leucocyte activation, further cytokine release and endothelial activation. To date, large studies of immunomodulatory therapies have not been conducted; however, lessons learned from historical studies using therapeutic hypothermia in humans suggest that quelling an immunopathological response might be efficacious. Future work should delineate the precise pathways involved in vivo in humans to target specific signalling molecules.

IDENTIFICATION AND CLINICAL VALIDATION OF HYPOXIA-INDUCIBLE FACTOR 1α PROTEIN AS THE POTENTIAL BIOMARKER IN PATIENTS WITH SEPSIS

ABSTRACT

Objective: Sepsis is a complex disease characterized by an inflammatory response and tissue hypoxia. Hypoxia-inducible factor 1α (HIF-1α) expression level is regulated by hypoxia and inflammation. This study aimed to explore the correlation between HIF-1α expression level and sepsis by bioinformatics analysis and clinical investigation. Methods: Bioinformatics tools were used to identify differentially expressed genes between sepsis and nonsepsis groups using the Gene Expression Omnibus data set. A clinical investigation was carried out to validate HIF-1α protein level in 54 nonseptic patients and 173 septic patients who were followed up for 28 days. Results: Bioinformatics analysis revealed that HIF-1α messenger RNA level was significantly different between septic and nonseptic patients ( P < 0.05). Consistent with the study hypothesis, higher HIF-1α levels in plasma were found in septic patients compared with those in nonseptic patients. The diagnostic accuracy for sepsis, as quantified by the area under the curve, was 0.926 (0.885-0.968) for HIF-1α expression level combined with oxygen saturation to fraction of inspired oxygen (SpO 2 /FiO 2 ), white blood cell, and blood urea nitrogen. The HIF-1α expression level was also significantly correlated with the severity of the disease. The results of the restricted cubic splines model indicated a U-shaped relationship between HIF-1α expression level and intensive care unit (ICU) mortality. Univariate and multivariate linear regression analyses indicated that septic patients with the elevated HIF-1α expression levels had shorter length of ICU stay versus those with the lower HIF-1α expression levels. Conclusion: Hypoxia-inducible factor 1α expression level can be used for diagnosing disease, assessing severity, and predicting length of ICU stay in septic patients.

Signals for Muscular Protein Turnover and Insulin Resistance in Critically Ill Patients: A Narrative Review

Sarcopenia in critically ill patients is a highly prevalent comorbidity. It is associated with a higher mortality rate, length of mechanical ventilation, and probability of being sent to a nursing home after the Intensive Care Unit (ICU). Despite the number of calories and proteins delivered, there is a complex network of signals of hormones and cytokines that affect muscle metabolism and its protein synthesis and breakdown in critically ill and chronic patients. To date, it is known that a higher number of proteins decreases mortality, but the exact amount needs to be clarified. This complex network of signals affects protein synthesis and breakdown. Some hormones regulate metabolism, such as insulin, insulin growth factor glucocorticoids, and growth hormone, whose secretion is affected by feeding states and inflammation. In addition, cytokines are involved, such as TNF-alpha and HIF-1. These hormones and cytokines have common pathways that activate muscle breakdown effectors, such as the ubiquitin-proteasome system, calpain, and caspase-3. These effectors are responsible for protein breakdown in muscles. Many trials have been conducted with hormones with different results but not with nutritional outcomes. This review examines the effect of hormones and cytokines on muscles. Knowing all the signals and pathways that affect protein synthesis and breakdown can be considered for future therapeutics.

Hypoxia Inducible Factors as Central Players in the Pathogenesis and Pathophysiology of Cardiovascular Diseases

Cardiovascular (CV) diseases are the major cause of death in industrialized countries. The main function of the CV system is to deliver nutrients and oxygen to all tissues. During most CV pathologies, oxygen and nutrient delivery is decreased or completely halted. Several mechanisms, including increased oxygen transport and delivery, as well as increased blood flow are triggered to compensate for the hypoxic state. If the compensatory mechanisms fail to sufficiently correct the hypoxia, irreversible damage can occur. Thus, hypoxia plays a central role in the pathogenesis and pathophysiology of CV diseases. Hypoxia inducible factors (HIFs) orchestrate the gene transcription for hundreds of proteins involved in erythropoiesis, glucose transport, angiogenesis, glycolytic metabolism, reactive oxygen species (ROS) handling, cell proliferation and survival, among others. The overall regulation of the expression of HIF-dependent genes depends on the severity, duration, and location of hypoxia. In the present review, common CV diseases were selected to illustrate that HIFs, and proteins derived directly or indirectly from their stabilization and activation, are related to the development and perpetuation of hypoxia in these pathologies. We further classify CV diseases into acute and chronic hypoxic states to better understand the temporal relevance of HIFs in the pathogenesis, disease progression and clinical outcomes of these diseases. We conclude that HIFs and their derived factors are fundamental in the genesis and progression of CV diseases. Understanding these mechanisms will lead to more effective treatment strategies leading to reduced morbidity and mortality.

Hemorrhage and saline resuscitation are associated with epigenetic and proteomic reprogramming in the rat lung

BACKGROUND

Epigenetic changes have been described in trauma patients in the form of histone acetylation events, but whether DNA-methylation occurs remains unknown. We hypothesized that the combination of hemorrhage and saline resuscitation would alter DNA-methylation and associated proteomic profiles in the rat lung.

METHODS

Ten rats were subjected to a pressure-controlled hemorrhage and resuscitation model consisting of hemorrhage to a mean arterial pressure (MAP) of 35mmHg for 90 minutes, followed by saline resuscitation to a MAP >70mmHg for 90 minutes (n=5) or sham (only anesthesia and cannulation). Lungs were harvested and subjected to reduced genome wide DNA-methylation analysis through bisulphite sequencing as well as proteomics analysis. Data was analyzed for differentially methylated regions and associated alterations in proteomic networks through a weighted correlation network analysis (WCNA). Pathway analysis was used to establish biological relevance of findings.

RESULTS

Hemorrhage and saline resuscitation were associated with differential methylation of 353 sites across the genome compared to the sham group. Of these, 30 were localized to gene promoter regions, 31 to exon regions and 87 to intron regions. Network analysis identified an association between hemorrhage/resuscitation and DNA-methylation events located to genes involved in areas of endothelial and immune response signaling. The associated proteomic response was characterized by activations of mRNA processing as well as endothelial Nitric Oxide Synthase (eNOS) metabolism.

CONCLUSION

We demonstrated an association between DNA-methylation and hemorrhage/saline resuscitation. These results suggest a potential role of DNA-methylation in the host response to injury.

MAPK interacting serine/threonine kinase 1 (MKNK1), one target gene of miR-223-3p, correlates with neutrophils in sepsis based on bioinformatic analysis

Sepsis, resulting from a harmful or damaging response to infection, is a complex and severe disease that causes high mortality. Three independent expression profiles of miRNA – GSE94717, GSE149764, and GSE101639 – were collected and integrated to analyze miRNAs associated with sepsis. One miRNA, miR-223-3p, was detected significantly downregulated in patients with sepsis. The upregulated miR-223-3p target genes in patients with sepsis were enriched in central carbon metabolism associated with HIF-1 signaling and galactose metabolism. Specially, three HIF-1 signaling genes – hypoxia-inducible factor 1-alpha (HIF1A), hexokinase 2 (HK2), and MAP kinase-interacting serine/threonine-protein kinase 1 (MKNK1) – were found significantly upregulated in patients with sepsis. Additionally, MKNK1 expression was downregulated in septic responders to early therapeutic treatments. Neutrophils were significantly accumulated in patients with sepsis and decreased in responders after therapy; MKNK1 was significantly positively correlated with neutrophils. Our findings indicate MKNK1, one targets of miR-223-3p, might be involved in sepsis via regulating the neutrophils abundance by mediating the expression inflammation factors.

Suppression of Hypoxia-Inducible Factor 1α by Low-Molecular-Weight Heparin Mitigates Ventilation-Induced Diaphragm Dysfunction in a Murine Endotoxemia Model

Mechanical ventilation (MV) is required to maintain life for patients with sepsis-related acute lung injury but can cause diaphragmatic myotrauma with muscle damage and weakness, known as ventilator-induced diaphragm dysfunction (VIDD). Hypoxia-inducible factor 1α (HIF-1α) plays a crucial role in inducing inflammation and apoptosis. Low-molecular-weight heparin (LMWH) was proven to have anti-inflammatory properties. However, HIF-1α and LMWH affect sepsis-related diaphragm injury has not been investigated. We hypothesized that LMWH would reduce endotoxin-augmented VIDD through HIF-1α. C57BL/6 mice, either wild-type or HIF-1α–deficient, were exposed to MV with or without endotoxemia for 8 h. Enoxaparin (4 mg/kg) was administered subcutaneously 30 min before MV. MV with endotoxemia aggravated VIDD, as demonstrated by increased interleukin-6 and macrophage inflammatory protein-2 levels, oxidative loads, and the expression of HIF-1α, calpain, caspase-3, atrogin-1, muscle ring finger-1, and microtubule-associated protein light chain 3-II. Disorganized myofibrils, disrupted mitochondria, increased numbers of autophagic and apoptotic mediators, substantial apoptosis of diaphragm muscle fibers, and decreased diaphragm function were also observed (p < 0.05). Endotoxin-exacerbated VIDD and myonuclear apoptosis were attenuated by pharmacologic inhibition by LMWH and in HIF-1α–deficient mice (p < 0.05). Our data indicate that enoxaparin reduces endotoxin-augmented MV-induced diaphragmatic injury, partially through HIF-1α pathway inhibition.

Sepsis is associated with mitochondrial DNA damage and a reduced mitochondrial mass in the kidney of patients with sepsis-AKI

Background

Sepsis is a life-threatening condition accompanied by organ dysfunction subsequent to a dysregulated host response to infection. Up to 60% of patients with sepsis develop acute kidney injury (AKI), which is associated with a poor clinical outcome. The pathophysiology of sepsis-associated AKI (sepsis-AKI) remains incompletely understood, but mitochondria have emerged as key players in the pathogenesis. Therefore, our aim was to identify mitochondrial damage in patients with sepsis-AKI.

Methods

We conducted a clinical laboratory study using “warm” postmortem biopsies from sepsis-associated AKI patients from a university teaching hospital. Biopsies were taken from adult patients (n = 14) who died of sepsis with AKI at the intensive care unit (ICU) and control patients (n = 12) undergoing tumor nephrectomy. To define the mechanisms of the mitochondrial contribution to the pathogenesis of sepsis-AKI, we explored mRNA and DNA expression of mitochondrial quality mechanism pathways, DNA oxidation and mitochondrial DNA (mtDNA) integrity in renal biopsies from sepsis-AKI patients and control subjects. Next, we induced human umbilical vein endothelial cells (HUVECs) with lipopolysaccharide (LPS) for 48 h to mimic sepsis and validate our results in vitro.

Results

Compared to control subjects, sepsis-AKI patients had upregulated mRNA expression of oxidative damage markers, excess mitochondrial DNA damage and lower mitochondrial mass. Sepsis-AKI patients had lower mRNA expression of mitochondrial quality markers TFAM, PINK1 and PARKIN, but not of MFN2 and DRP1. Oxidative DNA damage was present in the cytosol of tubular epithelial cells in the kidney of sepsis-AKI patients, whereas it was almost absent in biopsies from control subjects. Oxidative DNA damage co-localized with both the nuclei and mitochondria. Accordingly, HUVECs induced with LPS for 48 h showed an increased mnSOD expression, a decreased TFAM expression and higher mtDNA damage levels.

Conclusion

Sepsis-AKI induces mitochondrial DNA damage in the human kidney, without upregulation of mitochondrial quality control mechanisms, which likely resulted in a reduction in mitochondrial mass.

Coronavirus (Covid-19) sepsis: revisiting mitochondrial dysfunction in pathogenesis, aging, inflammation, and mortality

Background

Decline in mitochondrial function occurs with aging and may increase mortality. We discuss mitochondrial contribution to Covid-19 sepsis, specifically the complex interaction of innate immune function, viral replication, hyper-inflammatory state, and HIF-α/Sirtuin pathways.

Methods

Articles from PubMed/Medline searches were reviewed using the combination of terms “SARS-CoV-2, Covid-19, sepsis, mitochondria, aging, and immunometabolism”.

Results

Evidence indicates that mitochondria in senescent cells may be dysfunctional and unable to keep up with hypermetabolic demands associated with Covid-19 sepsis. Mitochondrial proteins may serve as damage-associated molecular pattern (DAMP) activating innate immunity. Disruption in normal oxidative phosphorylation pathways contributes to elevated ROS which activates sepsis cascade through HIF-α/Sirtuin pathway. Viral–mitochondrial interaction may be necessary for replication and increased viral load. Hypoxia and hyper-inflammatory state contribute to increased mortality associated with Covid-19 sepsis.

Conclusions

Aging is associated with worse outcomes in sepsis. Modulating Sirtuin activity is emerging as therapeutic agent in sepsis. HIF-α, levels of mitochondrial DNA, and other mitochondrial DAMP molecules may also serve as useful biomarker and need to be investigated. These mechanisms should be explored specifically for Covid-19-related sepsis. Understanding newly discovered regulatory mechanisms may lead to the development of novel diagnostic and therapeutic targets.

High mobilization of CD133+/CD34+ cells expressing HIF-1α and SDF-1α in septic abdominal surgical patients

Background

The control of endothelial progenitor cells (CD133+/CD34+ EPCs) migrating from bone marrow to peripheral blood is not completely understood. Emerging evidence suggests that stromal cell-derived factor-1α (SDF-1α) mediates egression of EPCs from bone marrow, while the hypoxia inducible factor (HIF) transcriptional system regulates SDF-1α expression. Our study aimed to investigate the time course of circulating CD133+/CD34+ EPCs and its correlation with the expression of HIF-1α protein and SDF-1α in postoperative laparoscopic abdominal septic patients.

Methods

Postoperative patients were divided in control (C group) and septic group (S group) operated immediately after the diagnosis of sepsis/septic shock. Blood samples were collected at baseline (0), 1, 3 and 7 postoperative days for CD133+/CD34+ EPCs count expressing or not the HIF-1α and SDF-1α analysis.

Results

Thirty-two patients in S group and 39 in C group were analyzed. In C group CD133+/CD34+ EPCs count remained stable throughout the study period, increasing on day 7 (173 [0–421] /μl vs baseline: P = 0.04; vs day 1: P = 0.002). In S group CD133+/CD34+ EPCs count levels were higher on day 3 (vs day 1: P = 0.006 and day 7: P = 0.026). HIF-1α expressing CD133+/CD34+ EPCs count decreased on day 1 as compared with the other days in C group (day 0 vs 1: P = 0.003, days 3 and 7 vs 1: P = 0.008), while it was 321 [0–1418] /μl on day 3 (vs day 1; P = 0.004), and 400 [0–587] /μl on day 7 in S group. SDF-1α levels were higher not only on baseline but also on postoperative day 1 in S vs C group (219 [124–337] pg/ml vs 35 [27–325] pg/ml, respectively; P = 0.01).

Conclusion

Our results indicate that sepsis in abdominal laparoscopic patients might constitute an additional trigger of the EPCs mobilization as compared with non-septic surgical patients. A larger mobilization of CD133+/CD34+ EPCs, preceded by enhanced plasmatic SDF-1α, occurs in septic surgical patients regardless of HIF-1α expression therein.

Trial registration

ClinicalTrials.gov no. NCT02589535. Registered 28 October 2015.

Low-Molecular-Weight Heparin Reduces Ventilation-Induced Lung Injury through Hypoxia Inducible Factor-1α in a Murine Endotoxemia Model

Patients with sepsis frequently require mechanical ventilation (MV) to survive. However, MV has been shown to induce the production of proinflammatory cytokines, causing ventilator-induced lung injury (VILI). It has been demonstrated that hypoxia-inducible factor (HIF)-1α plays a crucial role in inducing both apoptotic and inflammatory processes. Low-molecular-weight heparin (LMWH) has been shown to have anti-inflammatory activities. However, the effects of HIF-1α and LMWH on sepsis-related acute lung injury (ALI) have not been fully delineated. We hypothesized that LMWH would reduce lung injury, production of free radicals and epithelial apoptosis through the HIF-1α pathway. Male C57BL/6 mice were exposed to 6-mL/kg or 30-mL/kg MV for 5 h. Enoxaparin, 4 mg/kg, was administered subcutaneously 30 min before MV. We observed that MV with endotoxemia induced microvascular permeability; interleukin-6, tumor necrosis factor-α, macrophage inflammatory protein-2 and vascular endothelial growth factor protein production; neutrophil infiltration; oxidative loads; HIF-1α mRNA activation; HIF-1α expression; bronchial epithelial apoptosis; and decreased respiratory function in mice (p < 0.05). Endotoxin-induced augmentation of VILI and epithelial apoptosis were reduced in the HIF-1α-deficient mice and in the wild-type mice following enoxaparin administration (p < 0.05). Our data suggest that enoxaparin reduces endotoxin-augmented MV-induced ALI, partially by inhibiting the HIF-1α pathway.

Hypoxia-inducible factors in metabolic reprogramming during sepsis

Sepsis is a highly heterogeneous syndrome that is caused by an imbalanced host response to infection. Despite huge investments, sepsis remains a contemporary threat with significant burden on health systems. Vascular dysfunction and elevated oxygen consumption by highly metabolically active immune cells result in tissue hypoxia during inflammation. The transcription factor hypoxia-inducible factor-1a (HIF1α), and its family members, plays an important role in cellular metabolism and adaptation to cellular stress caused by hypoxia. In this review, we discuss the role of HIF in sepsis. We show possible mechanisms by which the inflammatory response activated during sepsis affects the HIF pathway. The activated HIF pathway in turn changes the metabolism of both innate and adaptive immune cells. As HIF expression in leukocytes of septic patients can be directly linked with mortality, we discuss multiple ways of interfering with the HIF signaling pathway.

Immunometabolism and Sepsis: A Role for HIF?

Metabolic reprogramming of innate immune cells occurs during both the hyperinflammatory and immunotolerant phases of sepsis. The hypoxia inducible factor (HIF) signaling pathway plays a vital role in regulating these metabolic changes. This review initially summarizes the HIF-driven changes in metabolic dynamics of innate immune cells in response to sepsis. The hyperinflammatory phase of sepsis is accompanied by a metabolic switch from oxidative phosphorylation to HIF-1α mediated glycolysis. Furthermore, HIF driven alterations in arginine metabolism also occur during this phase. This promotes sepsis pathophysiology and the development of clinical symptoms. These early metabolic changes are followed by a late immunotolerant phase, in which suppressed HIF signaling promotes a switch from aerobic glycolysis to fatty acid oxidation, with a subsequent anti-inflammatory response developing. Recently the molecular mechanisms controlling HIF activation during these early and late phases have begun to be elucidated. In the final part of this review the contribution of toll-like receptors, transcription factors, metabolic intermediates, kinases and reactive oxygen species, in governing the HIF-induced metabolic reprogramming of innate immune cells will be discussed. Importantly, understanding these regulatory mechanisms can lead to the development of novel diagnostic and therapeutic strategies targeting the HIF-dependent metabolic state of innate immune cells.

Induced Pluripotent Stem Cell-Derived Brain Endothelial Cells as a Cellular Model to Study Neisseria meningitidis Infection

Meningococcal meningitis is a severe central nervous system infection that occurs when Neisseria meningitidis (Nm) penetrates brain endothelial cells (BECs) of the meningeal blood-cerebrospinal fluid barrier. As a human-specific pathogen, in vivo models are greatly limited and pose a significant challenge. In vitro cell models have been developed, however, most lack critical BEC phenotypes limiting their usefulness. Human BECs generated from induced pluripotent stem cells (iPSCs) retain BEC properties and offer the prospect of modeling the human-specific Nm interaction with BECs. Here, we exploit iPSC-BECs as a novel cellular model to study Nm host-pathogen interactions, and provide an overview of host responses to Nm infection. Using iPSC-BECs, we first confirmed that multiple Nm strains and mutants follow similar phenotypes to previously described models. The recruitment of the recently published pilus adhesin receptor CD147 underneath meningococcal microcolonies could be verified in iPSC-BECs. Nm was also observed to significantly increase the expression of pro-inflammatory and neutrophil-specific chemokines IL6, CXCL1, CXCL2, CXCL8, and CCL20, and the secretion of IFN-γ and RANTES. For the first time, we directly observe that Nm disrupts the three tight junction proteins ZO-1, Occludin, and Claudin-5, which become frayed and/or discontinuous in BECs upon Nm challenge. In accordance with tight junction loss, a sharp loss in trans-endothelial electrical resistance, and an increase in sodium fluorescein permeability and in bacterial transmigration, was observed. Finally, we established RNA-Seq of sorted, infected iPSC-BECs, providing expression data of Nm-responsive host genes. Altogether, this model provides novel insights into Nm pathogenesis, including an impact of Nm on barrier properties and tight junction complexes, and suggests that the paracellular route may contribute to Nm traversal of BECs.

Morphological Characteristics of the Thymus and Spleen and the Subpopulation Composition of Lymphocytes in Peripheral Blood during Systemic Inflammatory Response in Male Rats with Different Resistance to Hypoxia

On the model of the systemic inflammatory response (SIRS), induced by lipopolysaccharide (LPS), the morphological and functional changes in the thymus and spleen and the subpopulation composition of peripheral blood lymphocytes of rats differing in resistance to hypoxia were studied. It was demonstrated that the level of endotoxin in blood serum after 3 hours of LPS administration in susceptible-to-hypoxia rats was 64 times higher than in the control group, while in tolerant-to-hypoxia animals it was only 8 times higher in 6 hours. After 24 hours of LPS injection, only in susceptible-to-hypoxia rats did the level of C-reactive protein in blood serum increase. There is a difference in the dynamics of morphological changes of lymphoid organs after LPS injection in tolerant- and susceptible-to-hypoxia animals. After 3 hours of LPS administration, the tolerant-to-hypoxia rats showed no changes in the thymus, spleen, and subpopulation composition of lymphocytes in peripheral blood. After 6 hours there was only a decrease in B-lymphocytes and increase in cytotoxic T-lymphocytes and NK cells. After 1 day of LPS injection, the tolerant-to-hypoxia rats had devastation in PALS of the spleen. After 3 hours of LPS injection the susceptible-to-hypoxia animals had reactive changes in the lymphoid organs: decrease of the thymus cortex, narrowing of the marginal zones of spleen lymphoid follicles, widening of their germinal centers, and a decrease in the absolute number of cytotoxic T-lymphocytes, NK cells, and B-lymphocytes. After 24 hours of LPS injection the tolerant-to-hypoxia animals had a greater absolute number of T-lymphocytes and NK cells in comparison with the susceptible rats. Thus, in animals with different resistance to hypoxia the LPS-induced SIRS is characterized by different dynamics of morphological and functional changes of the thymus and spleen. The obtained data will serve as a basis for the development of new individual approaches to the prevention and treatment of infectious and inflammatory diseases.

Dependence of the severity of the systemic inflammatory response on resistance to hypoxia in male Wistar rats

Purpose

The aim of the study was to characterize the severity of the systemic inflammatory response induced by lipopolysaccharide (LPS) in animals with different resistance levels to hypoxia.

Materials and methods

Two to three months old male Wistar rats (220–240 g) were divided according to hypoxia tolerance in a hypobaric chamber. After a month, they were injected intraperitoneally with Escherichia coli LPS at a dose of 1.5 mg/kg. After 3, 6 and 24 hours of LPS injection, we studied the levels of IL-1β, C-reactive protein (CRP) and TGF-β in the serum, the expression of Hif-1α and Nf-kb in the liver, morphological disorders in the lung and ex vivo production of IL-10 by splenic cells activated by ConA.

Results

In the early periods after the injection of LPS, increase in Nf-kb expression in the liver was observed only in the rats susceptible to hypoxia. After 6 hours of LPS injection, the number of neutrophils in the interalveolar septa of the lungs of rats susceptible to hypoxia was higher than in tolerant rats. This points to the development of more pronounced LPS-induced inflammation in the rats susceptible to hypoxia and is accompanied by increased expression of Hif-1α in the liver after 6 hours of LPS administration, serum IL-1β level after 3 hours and CRP level after 24 hours. The production of the anti-inflammatory cytokine IL-10 by the spleen was significantly decreased after 6 hours of LPS injection only in the animals tolerant to hypoxia. After 24 hours of LPS injection, a significant decrease in serum TGF-β level occurred in the rats tolerant to hypoxia in comparison with the control group, which improved the survival rates of the animals.

Conclusion

We have demonstrated the differences in the severity of the LPS-induced inflammatory response in male Wistar rats with different resistance levels to hypoxia. Rats susceptible to hypoxia are characterized by a more pronounced inflammatory response induced by LPS.

T cells and their immunometabolism: A novel way to understanding sepsis immunopathogenesis and future therapeutics

Sepsis has always been considered as a big challenge for pharmaceutical companies in terms of discovering and designing new therapeutics. The pathogenesis of sepsis involves aberrant activation of innate immune cells (i.e. macrophages, neutrophils etc.) at early stages. However, a stage of immunosuppression is also observed during sepsis even in the patients who have recovered from it. This stage of immunosuppression is observed due to the loss of conventional (i.e. CD4⁺, CD8⁺) T cells, Th17 cells and an upregulation of regulatory T cells (Tregs). This process also impacts metabolic processes controlling immune cell metabolism called immunometabolism. The present review is focused on the T cell-mediated immune response, their immunometabolism and targeting T cell immunometabolism during sepsis as future therapeutic approach. The first part of the manuscripts describes an impact of sepsis on conventional T cells, Th17 cells and Tregs along with their impact on sepsis. The subsequent section further describes the immunometabolism of these cells (CD4⁺, CD8⁺, Th17, and Tregs) under normal conditions and during sepsis-induced immunosuppression. The article ends with the therapeutic targeting of T cell immunometabolism (both conventional T cells and Tregs) during sepsis as a future immunomodulatory approach for its management.

Increased Levels of VEGF-A and HIF-1α in Turkish Children with Crimean-Congo Hemorrhagic Fever

BACKGROUND

Crimean-Congo Hemorrhagic Fever (CCHF) is a disease characterized by serious course, including acute viral fever, ecchymosis, thrombocytopenia, liver dysfunction and high rate of mortality. Hypoxia Inducible Factor-1α (HIF-1α) and Vascular Endothelial Growth Factor-A (VEGF-A) play an important role both in the inflammatory process and plasma leakage. The aim of this study was to define HIF-1α and VEGF-A serum levels obtained from CCHF patients and control group and to investigate whether these factors were correlated with the pathogenesis of this disease.

METHODS

Thirty cases younger than 17yr confirmed by RT-PCR and/or ELISA for CCHF were included in this study. Thirty age and sex matched healthy peoples were enrolled as controls. Blood samples collected from the patient and control groups. Serum levels of HIF-1α and VEGF-A were measured with ELISA.

RESULTS

Levels of HIF-1α and VEGF-A were statistically significantly increased in CCHF patients compared to the control group (P< 0.05). A significant positive correlation was found between the levels of HIF-1α and VEGF-A in the patient group (P< 0.01). The levels of ALT, AST, CK, aPTT, WBC and Thrombocyte count were significantly higher in the patients than in the control group (P< 0.001). A positive correlation was found among the levels of AST and CK from biochemical parameters and VEGF and HIF-1α in the patient group (P< 0.05).

CONCLUSION

HIF-1α and VEGF-A might play an important role in CCHF pathogenesis.

Hypoxia and HIF-1 activation in bacterial infections

For most of the living beings, oxygen is one of the essential elements required to sustain life. Deprivation of oxygen causes tissue hypoxia and this severely affects host cell and organ functions. Tissue hypoxia is a prominent microenvironmental condition occurring in infections and there is a body of evidence that hypoxia and inflammation are interconnected with each other. The primary key factor mediating the mammalian hypoxic response is hypoxia inducible factor (HIF)-1, which regulates oxygen homeostasis on cellular, tissue and organism level. Recent studies show that HIF-1 plays a central role in angiogenesis, cancer and cardiovascular disease but also in bacterial infections. Activation of HIF-1 depends on the nature of the pathogen and the characteristics of infections in certain hosts. Up to date, it is not completely clear whether the phenomenon of HIF-1 activation in infections has a protective or detrimental effect on the host. In this review, we give an overview of whether and how hypoxia and HIF-1 affect the course of infections.

Involvement of hypoxia-inducible factors in the dysregulation of oxygen homeostasis in sepsis

Sepsis is a state of infection with serious systemic manifestations, and if severe enough, can be associated with multiple organ dysfunction and systemic hypotension, which can cause tissues to be hypoxic. Inflammation, as part of the multifaceted biological response to injurious stimuli, such as pathogens or damaged tissues and cells, underlies these biological processes. Prolonged and persistent inflammation, also known as chronic inflammation, results in progressive alteration in the various types of cells at the site of inflammation and is characterized by the simultaneous destruction and healing of tissue during the process. Tissue hypoxia during inflammation is not just a simple bystander process, but can considerably affect the development or attenuation of inflammation by causing the regulation of hypoxia-dependent gene expression. Indeed, the study of transcriptionally regulated tissue adaptation to hypoxia requires intense investigation to help control hypoxia-induced inflammation and organ failure. In this review, I have described the pathophysiology of sepsis with respect to oxygen metabolism and expression of hypoxia-inducible factor 1.

Atelectasis causes alveolar hypoxia-induced inflammation during uneven mechanical ventilation in rats

BACKGROUND

Patients with acute respiratory distress syndrome receiving mechanical ventilation show inhomogeneous lung aeration. Atelectasis during uneven mechanical ventilation leads to alveolar hypoxia and could therefore result in lung inflammation and injury. We aimed to elucidate whether and how atelectasis causes alveolar hypoxia-induced inflammation during uneven mechanical ventilation in an open-chest differential-ventilation rat model.

METHODS

We first investigated inflammatory and histological changes in the bilateral lungs of unilaterally ventilated rats, in which the right lung was atelectatic and the left lung was ventilated with high tidal volume (HTV). In the next series, we investigated the effects of normal tidal volume (NTV) ventilation of the right lungs with 60 % O2 or 100 % N2 during HTV ventilation of the left lungs. Then, proinflammatory cytokine secretions were quantified from murine lung epithelial (MLE15) and murine alveolar macrophage (MH-S) cells cultured under a hypoxic condition (5 % O2) mimicking atelectasis. Further, activities of nuclear factor (NF)-κB and hypoxia-inducible factor (HIF)-1 were assessed in the nonventilated atelectatic lung and MLE15 cells cultured under the hypoxic condition. Finally, effects of NF-κB inhibition and HIF-1α knockdown on the cytokine secretions from MLE15 cells cultured under the hypoxic condition were assessed.

RESULTS

The nonventilated atelectatic lungs showed inflammatory responses and minimal histological changes comparable to those of the HTV-ventilated lungs. NTV ventilation with 60 % O2 attenuated the increase in chemokine (C-X-C motif) ligand (CXCL)-1 secretion and neutrophil accumulation observed in the atelectatic lungs, but that with 100 % N2 did not. MLE15 cells cultured with tumor necrosis factor (TNF)-α under the hypoxic condition showed increased CXCL-1 secretion. NF-κB and HIF-1α were activated in the nonventilated atelectatic lungs and MLE15 cells cultured under the hypoxic condition. NF-κB inhibition abolished the hypoxia-induced increase in CXCL-1 secretion from MLE15 cells, while HIF-1α knockdown augmented it.

CONCLUSIONS

Atelectasis causes alveolar hypoxia-induced inflammatory responses including NF-κB-dependent CXCL-1 secretion from lung epithelial cells. HIF-1 activation in lung epithelial cells is an anti-inflammatory response to alveolar hypoxia in atelectatic lungs.

Sepsis-associated hyperlactatemia

There is overwhelming evidence that sepsis and septic shock are associated with hyperlactatemia (sepsis-associated hyperlactatemia (SAHL)). SAHL is a strong independent predictor of mortality and its presence and progression are widely appreciated by clinicians to define a very high-risk population. Until recently, the dominant paradigm has been that SAHL is a marker of tissue hypoxia. Accordingly, SAHL has been interpreted to indicate the presence of an ‘oxygen debt’ or ‘hypoperfusion’, which leads to increased lactate generation via anaerobic glycolysis. In light of such interpretation of the meaning of SAHL, maneuvers to increase oxygen delivery have been proposed as its treatment. Moreover, lactate levels have been proposed as a method to evaluate the adequacy of resuscitation and the nature of the response to the initial treatment for sepsis. However, a large body of evidence has accumulated that strongly challenges such notions. Much evidence now supports the view that SAHL is not due only to tissue hypoxia or anaerobic glycolysis. Experimental and human studies all consistently support the view that SAHL is more logically explained by increased aerobic glycolysis secondary to activation of the stress response (adrenergic stimulation). More importantly, new evidence suggests that SAHL may actually serve to facilitate bioenergetic efficiency through an increase in lactate oxidation. In this sense, the characteristics of lactate production best fit the notion of an adaptive survival response that grows in intensity as disease severity increases. Clinicians need to be aware of these developments in our understanding of SAHL in order to approach patient management according to biological principles and to interpret lactate concentrations during sepsis resuscitation according to current best knowledge.

Pulsed high oxygen induces a hypoxic-like response in human umbilical endothelial cells and in humans

It has been proposed that relative changes of oxygen availability, rather than steady-state hypoxic or hyperoxic conditions, play an important role in hypoxia-inducible factor (HIF) transcriptional effects. According to this hypothesis describing the "normobaric oxygen paradox", normoxia following a hyperoxic event is sensed by tissues as an oxygen shortage, upregulating HIF-1 activity. With the aim of confirming, at cellular and at functional level, that normoxia following a hyperoxic event is "interpreted" as a hypoxic event, we report a combination of experiments addressing the effects of an intermittent increase of oxygen concentration on HIF-1 levels and the activity level of specific oxygen-modulated proteins in cultured human umbilical vein endothelial cells and the effects of hemoglobin levels after intermittent breathing of normobaric high (100%) and low (15%) oxygen in vivo in humans. Our experiments confirm that, during recovery after hyperoxia, an increase of HIF expression occurs in human umbilical vein endothelial cells, associated with an increase of matrix metalloproteinases activity. These data suggest that endothelial cells "interpret" the return to normoxia after hyperoxia as a hypoxic stimulus. At functional level, our data show that breathing both 15 and 100% oxygen 30 min every other day for a period of 10 days induces an increase of hemoglobin levels in humans. This effect was enhanced after the cessation of the oxygen breathing. These results indicate that a sudden decrease in tissue oxygen tension after hyperoxia may act as a trigger for erythropoietin synthesis, thus corroborating the hypothesis that "relative" hypoxia is a potent stimulator of HIF-mediated gene expressions.