New strategies for treatment of infectious sepsis

Streptococcus suis subtilisin-like serine proteases SspA-1 and SspA-2 interplay with complement C3a and C5a to facilitate bacterial immune evasion and infection

Streptococcus suis (S. suis), a significant zoonotic bacterial pathogen impacting swine and human, is associated with severe systemic diseases such as streptococcal toxic shock-like syndrome, meningitis, septicaemia, and abrupt fatality. The multifaceted roles of complement components C5a and C3a extend to orchestrating inflammatory cells recruitment, oxidative burst induction, and cytokines release. Despite the pivotal role of subtilisin-like serine proteases in S. suis pathogenicity, their involvement in immune evasion remains underexplored. In the present study, we identify two cell wall-anchored subtilisin-like serine proteases in S. suis, SspA-1 and SspA-2, as binding partners for C3a and C5a. Through Co-Immunoprecipitation, Enzyme-Linked Immunosorbent and Far-Western Blotting Assays, we validate their interactions with the aforementioned components. However, SspA-1 and SspA-2 have no cleavage activity against complement C3a and C5a performed by Cleavage assay. Chemotaxis assays reveal that recombinant SspA-1 and SspA-2 effectively attenuate monocyte chemotaxis towards C3a and C5a. Notably, the ΔsspA-1, ΔsspA-1, and ΔsspA-1/2 mutant strains exhibit compromised survival in blood, and resistance of opsonophagocytosis, alongside impaired survival in blood and in vivo colonization compared to the parental strain SC-19. Critical insights from the murine and Galleria mellonella larva infection models further underscore the significance of sspA-1 in altering mortality rates. Collectively, our findings indicate that SspA-1 and SspA-2 are novel binding proteins for C3a and C5a, thereby shedding light on their pivotal roles in S. suis immune evasion and the pathogenesis.

Cannabidiol Suppresses Cytokine Storm and Protects Against Cardiac and Renal Injury Associated with Sepsis

Background: Cytokine release syndrome, also termed "cytokine storm," is the leading cause of morbidity and mortality among patients with various conditions such as sepsis. While cytokine storm is associated with multiple organ damage, acute cardiac and renal injury represents a hallmark of cytokine storm. Since recent reports have suggested that cannabidiol (CBD) may assist in the treatment of inflammatory diseases, our objective was to examine the effect of CBD on cytokine storm-induced cardiac and renal injury using the lipopolysaccharide (LPS)-induced sepsis mouse model. Materials and Methods: At 8 weeks of age, mice were randomly assigned to receive CBD (15 mg/kg) or vehicle one hour before a single injection of either phosphate-buffered saline or LPS (10 mg/kg) for an additional 24 h. Results: Our results show that CBD improves cardiac function and reduces renal injury in a mouse model of cytokine storm. Moreover, our data indicate that CBD significantly reduces systemic and renal inflammation to contribute to the improvements observed in a cytokine storm-model of cardiac and renal injury. Conclusions: Overall, the findings of this study suggest that CBD could be repurposed to reduce morbidity in patients with cytokine storm particularly in severe infections such as sepsis.

PVB exerts anti-inflammatory effects by inhibiting the activation of MAPK and NF-κB signaling pathways and ROS generation in neutrophils

Pinaverium bromide (PVB) has been shown to protect mice against sepsis, which is predominantly attributed to PVB-mediated anti-inflammatory effects by inhibiting primed neutrophils to produce proinflammatory cytokines. However, the underlying mechanism(s) by which PVB affects neutrophils remains unknown. In this study, we report that treatment with PVB either before or after LPS stimulation attenuated IL-1β and TNF-α expression at both mRNA and protein levels in LPS-activated murine neutrophils. Further experiments revealed that PVB inhibited the phosphorylation of ERK, JNK, and IκBα in LPS-stimulated murine neutrophils. Moreover, PVB reduced reactive oxygen species (ROS) levels via regulating NADPH oxidase 2 (NOX2) activity, as represented by inhibiting p47phox translocation from the cytoplasm to the cellular membrane. Importantly, PVB significantly attenuated IL-1β, TNF-α, IL-6, CXCL1 production in both LPS-stimulated low density neutrophils (LDNs) and normal density neutrophils (NDNs) isolated from septic patients. Collectively, we demonstrated that PVB exerts anti-inflammatory effect by attenuating ROS generation and suppressing the activation of MAPK and NF-κB signaling pathways, suggesting that PVB may act as a potential therapeutic agent for sepsis by inhibiting neutrophil priming and activation.

p120-Catenin suppresses NLRP3 inflammasome activation in macrophages

Inflammasome activation is of central importance for the process of generation of overwhelming inflammatory response and the pathogenesis of sepsis. The intrinsic molecular mechanism for controlling inflammasome activation is still poorly understood. Here we investigated the role of p120-catenin expression in macrophages in regulating nucleotide-binding oligomerization domain (NOD) and leucine-rich repeat (LRR)- and pyrin domain-containing proteins 3 (NLRP3) inflammasome activation. Depletion of p120-catenin in murine bone marrow-derived macrophages enhanced caspase-1 activation and secretion of active interleukin (IL)-1β in response to ATP stimulation following LPS priming. Coimmunoprecipitation analysis showed that p120-catenin deletion promoted NLRP3 inflammasome activation by accelerating the assembly of the inflammasome complex comprised of NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and pro-caspase-1. Depletion of p120-catenin also increased the production of mitochondrial reactive oxygen species. Pharmacological inhibition of mitochondrial reactive oxygen species nearly completely abolished NLRP3 inflammasome activation, caspase-1 activation, and the production of IL-1β in p120-catenin-depleted macrophages. Furthermore, p120-catenin ablation significantly disrupted mitochondrial function, evidenced by decreased mitochondrial membrane potential and lower production of intracellular ATP. In alveolar macrophage-depleted mice challenged with cecal ligation and puncture, pulmonary transplantation of p120-catenin-deficient macrophages dramatically enhanced the accumulation of IL-1β and IL-18 in bronchoalveolar lavage fluid. These results demonstrate that p120-catenin prevents NLRP3 inflammasome activation in macrophages by maintaining mitochondrial homeostasis and reducing the production of mitochondrial reactive oxygen species in response to endotoxin insult. Thus, inhibition of NLRP3 inflammasome activation by stabilization of p120-catenin expression in macrophages may be a novel strategy to prevent an uncontrolled inflammatory response in sepsis.

Ginsenoside Rg1 protects cardiac mitochondrial function via targeting GSTP1 to block S-glutathionylation of optic atrophy 1

Mitochondrial dysfunction is a fundamental challenge in myocardial injury. Ginsenoside Rg1 (Rg1) is a bioactive compound with pharmacological potential for cardiac protection. Optic atrophy 1 (OPA1) acts as a mitochondrial inner membrane protein that contributes to the structural integrity and function of mitochondria. This study investigated the protective role of Rg1 in septic cardiac injury from the perspective of OPA1 stability. Rg1 protected cardiac contractive function against endotoxin injury in mice by maintaining mitochondrial cristae structure. In cardiomyocytes, lipopolysaccharide (LPS) evoked mitochondrial fragmentation and destruction of mitochondrial biogenesis, which were prevented by Rg1, possibly due to the preservation of the integrity of cristae structure. In support, the beneficial effects of Rg1 on cardioprotection and mitochondrial biogenesis were diminished by OPA1 deficiency subjected to the LPS challenge. Mechanistically, LPS stimulation triggered intracellular glutathione destabilization that promoted S-glutathionylation of OPA1 at Cys551, leading to the dissociation of OPA1-Mitofilin. Rg1 interacted with GSTP1 to inhibit its S-glutathionylation of OPA1, thereby promoting OPA1-Mitofilin interaction and protecting mitochondrial cristae structure. These findings suggest that GSTP1/OPA1 axis may be a beneficial strategy for the treatment of myocardial injury, and expand the clinical application of Rg1.

Structure-Based Function and Regulation of NCX Variants: Updates and Challenges

The plasma-membrane homeostasis Na⁺/Ca²⁺ exchangers (NCXs) mediate Ca²⁺ extrusion/entry to dynamically shape Ca²⁺ signaling/in biological systems ranging from bacteria to humans. The NCX gene orthologs, isoforms, and their splice variants are expressed in a tissue-specific manner and exhibit nearly 10⁴-fold differences in the transport rates and regulatory specificities to match the cell-specific requirements. Selective pharmacological targeting of NCX variants could benefit many clinical applications, although this intervention remains challenging, mainly because a full-size structure of eukaryotic NCX is unavailable. The crystal structure of the archaeal NCX_Mj, in conjunction with biophysical, computational, and functional analyses, provided a breakthrough in resolving the ion transport mechanisms. However, NCX_Mj (whose size is nearly three times smaller than that of mammalian NCXs) cannot serve as a structure-dynamic model for imitating high transport rates and regulatory modules possessed by eukaryotic NCXs. The crystal structures of isolated regulatory domains (obtained from eukaryotic NCXs) and their biophysical analyses by SAXS, NMR, FRET, and HDX-MS approaches revealed structure-based variances of regulatory modules. Despite these achievements, it remains unclear how multi-domain interactions can decode and integrate diverse allosteric signals, thereby yielding distinct regulatory outcomes in a given ortholog/isoform/splice variant. This article summarizes the relevant issues from the perspective of future developments.

Implication of Neutrophils Extracellular Traps in the Pathogenesis of SARS-CoV-2 pneumonia

Peripheral blood polymorphonuclear neutrophils (PMNs) forming extracellular traps (NETs), as well as endothelial- and platelet-derived parameters, have been analyzed in patients with SARS-CoV-2 pneumonia, and their prognostic role has been evaluated. Eighty-seven consecutive patients hospitalized with SARS-CoV-2 pneumonia were prospectively selected. A sample of 30 healthy individuals served as the control group. Clinical and oxygenation (oxygen saturation to fraction of inspired oxygen ratio—SpO²/FiO²) characteristics and PMNs forming NETs, serum levels of myeloperoxidase, E-selectin, vascular cell adhesion molecule 1—VCAM1—vascular endothelial growth factor, P-selectin, platelet factor 4 and plasma concentrations of D-dimer were evaluated at hospital admission, at discharge and 14 days after discharge. Intensive care unit admission or death was the primary composite endpoint. Patients showed a higher number of PMNs forming NETs than healthy controls. The absolute number of PMNs forming NETs was inversely correlated with oxygen status (SpO²/FiO²) and positively with inflammatory (C-reactive protein, ferritin) markers and VCAM1. A decrease in, but not a normalization of NETs and endothelial-derived parameters was observed in patients who survived. In conclusion, the formation of NETs runs parallel to that of other inflammatory and endothelial activation markers, and is inverse to the oxygenation parameters, supporting a pathogenic role for PMNs in this entity.

Protective Effect of Poria Cocos Polysaccharides on Fecal Peritonitis-Induced Sepsis in Mice Through Inhibition of Oxidative Stress, Inflammation, Apoptosis, and Reduction of Treg Cells

This study was conducted to investigate the potential pharmacological effects of Poria cocos polysaccharides (PCPs) on fecal-induced peritonitis (FIP) mice. Consequently, the fecal peritonitis (FP)-induced septic mice with the higher levels of tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), IL-1β, malondialdehyde (MDA), myeloperoxidase (MPO), histopathological lesion and bacterial burden, and lower levels of superoxide dismutase (SOD) and glutathione (GSH). Interestingly, PCP pre-treatment reduced inflammatory cytokines and oxidative stress in plasma and spleen and improved the resistance to FIP. Inflammatory infiltration and cell death in thymus or splenic tissue were alleviated with PCP pretreatment. Furthermore, Treg cells were moderated in the spleen with PCP pre-administration. In addition, PCP pretreatment downregulated Annexin-V in the thymus of FP-induced septic mice, and apoptosis of splenic cells was dose-dependent. In conclusion, PCPs have pharmacological and biological effects on FP-induced septic mice, and its molecular mechanism is related to antioxidative, anti-inflammation, anti-apoptosis, and the reduction of Treg activity in splenic cells.

Resolvin T-series reduce neutrophil extracellular traps

The newly identified 13-series (T-series) resolvins (RvTs) regulate phagocyte functions and accelerate resolution of infectious inflammation. Because severe acute respiratory syndrome coronavirus 2 elicits uncontrolled inflammation involving neutrophil extracellular traps (NETs), we tested whether stereochemically defined RvTs regulate NET formation. Using microfluidic devices capturing NETs in phorbol 12-myristate 13-acetate-stimulated human whole blood, the RvTs (RvT1-RvT4; 2.5 nM each) potently reduced NETs. With interleukin-1β-stimulated human neutrophils, each RvT dose and time dependently decreased NETosis, conveying ∼50% potencies at 10 nM, compared with a known NETosis inhibitor (10 μM). In a murine Staphylococcus aureus infection, RvTs (50 ng each) limited neutrophil infiltration, bacterial titers, and NETs. In addition, each RvT enhanced NET uptake by human macrophages; RvT2 was the most potent of the four RvTs, giving a >50% increase in NET-phagocytosis. As part of the intracellular signaling mechanism, RvT2 increased cyclic adenosine monophosphate and phospho-AMP-activated protein kinase (AMPK) within human macrophages, and RvT2-stimulated NET uptake was abolished by protein kinase A and AMPK inhibition. RvT2 also stimulated NET clearance by mouse macrophages in vivo. Together, these results provide evidence for novel pro-resolving functions of RvTs, namely reducing NETosis and enhancing macrophage NET clearance via a cyclic adenosine monophosphate-protein kinase A-AMPK axis. Thus, RvTs open opportunities for regulating NET-mediated collateral tissue damage during infection as well as monitoring NETs.

Citrullination in the pathology of inflammatory and autoimmune disorders: recent advances and future perspectives

Numerous post-translational modifications (PTMs) govern the collective metabolism of a cell through altering the structure and functions of proteins. The action of the most prevalent PTMs, encompassing phosphorylation, methylation, acylations, ubiquitination and glycosylation is well documented. A less explored protein PTM, conversion of peptidylarginine to citrulline, is the subject of this review. The process of citrullination is catalysed by peptidylarginine deiminases (PADs), a family of conserved enzymes expressed in a variety of human tissues. Accumulating evidence suggest that citrullination plays a significant role in regulating cellular metabolism and gene expression by affecting a multitude of pathways and modulating the chromatin status. Here, we will discuss the biochemical nature of arginine citrullination, the enzymatic machinery behind it and also provide information on the pathological consequences of citrullination in the development of inflammatory diseases (rheumatoid arthritis, multiple sclerosis, psoriasis, systemic lupus erythematosus, periodontitis and COVID-19), cancer and thromboembolism. Finally, developments on inhibitors against protein citrullination and recent clinical trials providing a promising therapeutic approach to inflammatory disease by targeting citrullination are discussed.

Hematopoiesis and innate immunity: an inseparable couple for good and bad times, bound together by an hormetic relationship

Hematopoietic and immune cells originate from a common hematopoietic/lymphopoietic stem cell what explains that these different cell types often share the same receptors and respond to similar factors. Moreover, the common goal of both lineages is to ensure tissue homeostasis under steady-state conditions, fight invading pathogens, and promote tissue repair. We will highlight accumulating evidence that innate and adaptive immunity modulate several aspects of hematopoiesis within the hormetic zone in which the biological response to low exposure to potential stressors generally is favorable and benefits hematopoietic stem/progenitor cells (HSPCs). Innate immunity impact on hematopoiesis is pleiotropic and involves both the cellular arm, comprised of innate immunity cells, and the soluble arm, whose major component is the complement cascade (ComC). In addition, several mediators released by innate immunity cells, including inflammatory cytokines and small antimicrobial cationic peptides, affect hematopoiesis. There are intriguing observations that HSPCs and immune cells share several cell-surface pattern-recognition receptors (PRRs), such as Toll-like receptors (TLRs) and cytosol-expressed NOD, NOD-like, and RIG-I-like receptors and thus can be considered "pathogen sensors". In addition, not only lymphocytes but also HSPCs express functional intracellular complement proteins, defined as complosome which poses challenging questions for further investigation of the intracellular ComC-mediated intracrine regulation of hematopoiesis.

Damage-Associated Molecular Patterns As Double-Edged Swords in Sepsis

Significance: Sepsis is defined as a life-threatening organ dysfunction caused by dysregulated host response to infection. This leads to an uncontrolled inflammatory response at the onset of infection, followed by immunosuppression. The development of a specific treatment modality for sepsis is still challenging, reflecting our inadequate understanding of its pathophysiology. Understanding the mechanism and transition of the early hyperinflammation to late stage of immunosuppression in sepsis is critical for developing sepsis therapeutics. Recent Advances: Damage-associated molecular patterns (DAMPs) are intracellular molecules and released upon tissue injury and cell death in sepsis. DAMPs are recognized by pattern recognition receptors to initiate inflammatory cascades. DAMPs not only elicit an inflammatory response but also they subsequently induce immunosuppression, both are equally important for exacerbating sepsis. Recent advances on a new DAMP, extracellular cold-inducible RNA-binding protein for fueling inflammation and immunosuppression in sepsis, have added a new avenue into the dual functions of DAMPs in sepsis. Critical Issues: The molecular modification of DAMPs and their binding to pattern recognition receptors transit dynamically by the cellular environment in pathophysiologic conditions. Correlation between the dynamic changes of the impacts of DAMPs and the clinical outcomes in sepsis still lacks adequate understanding. Here, we focus on the impacts of DAMPs that cause inflammation as well as induce immunosuppression in sepsis. We further discuss the therapeutic potential by targeting DAMPs to attenuate inflammation and immunosuppression for mitigating sepsis. Future Directions: Uncovering pathways of the transition from inflammation to immunosuppression of DAMPs is a potential therapeutic avenue for mitigating sepsis.

The pathophysiology of sepsis-2021 update: Part 1, immunology and coagulopathy leading to endothelial injury

Disclaimer

In an effort to expedite the publication of articles related to the COVID-19 pandemic, AJHP is posting these manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

Purpose

To provide an overview of current literature on the pathophysiology of sepsis, with a focus on mediators of endothelial injury and organ dysfunction.

Summary

Sepsis is a dysregulated response to infection that triggers cascades of interconnected systems. Sepsis has been a significant cause of mortality worldwide, and the recent viral pandemic that may produce severe sepsis and septic shock has been a major contributor to sepsis-related mortality. Understanding of the pathophysiology of sepsis has changed dramatically over the last several decades. Significant insight into the components of the inflammatory response that contribute to endothelial injury and trigger coagulation pathways has been achieved. Similarly, characterization of anti-inflammatory pathways that may lead to secondary infections and poor outcome has illustrated opportunities for improved therapies. Description of an increasing number of important mediators and pathways has occurred and may point the way to novel therapies to address immune dysregulation. Pharmacists will need a fundamental understanding of the overlapping pathways of the immune response to fully prepare for use of novel treatment options. While pharmacists typically understand coagulation cascade how to utilize anticoagulants, the issues in sepsis related coagulopathy and role of mediators such as cytokines and complement and role of activated platelets and neutrophils require a different perspective.

Conclusion

Pharmacists can benefit from understanding both the cellular and organ system issues in sepsis to facilitate assessment of potential therapies for risk and benefit.

Immunopathological Roles of Neutrophils in Virus Infection and COVID-19

ABSTRACT

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has been spread around the world and is currently affecting global public health. Clinical evidence indicates that the elevated number of peripheral neutrophils and higher ratio of neutrophils-to-lymphocytes are correlated with severe outcomes in COVID-19 patients, suggesting the possible immunopathological role of neutrophils during SARS-CoV-2 infection. As an abundant innate immune cell type, neutrophils are well known for their contributions to antimicrobial defense. However, their dysfunction is also associated with different inflammatory signatures during the pathogenesis of infection. Herein, in this mini-review, we summarize the recent progress on the potential role of neutrophils during COVID-19-associated inflammatory responses. In particular, we highlight the interactions between neutrophils and viruses as well as the relationship of neutrophils with cytokine storm and thrombosis in COVID-19 patients. Lastly, we discuss the importance of neutrophils as potential therapeutic targets for COVID-19.

Blood leukocyte transcriptomes in gram-positive and gram-negative community-acquired pneumonia

BACKGROUND

Gram-positive and Gram-negative bacteria are the most common causative pathogens in community-acquired pneumonia (CAP) on the intensive care unit (ICU). The aim of this study was to determine whether the host immune response differs between Gram-positive and Gram-negative CAP upon ICU admission.

METHODS

Sixteen host response biomarkers providing insight in pathophysiological mechanisms implicated in sepsis and blood leukocyte transcriptomes were analysed in patients with CAP upon ICU admission in two tertiary hospitals in the Netherlands.

RESULTS

309 patients with CAP with a definite or probable likelihood (determined by predefined criteria) were included. A causative pathogen was determined in 74.4% of admissions. Patients admitted with Gram-positive CAP (n=90) were not different from those admitted with Gram-negative CAP (n=75) regarding demographics, chronic comorbidities, severity of disease and mortality. Host response biomarkers reflective of systemic inflammation, coagulation activation and endothelial cell function, as well as blood leukocytes transcriptomes, were largely similar between Gram-positive and Gram-negative CAP. Blood leukocyte transcriptomes were also similar in Gram-positive and Gram-negative CAP in two independent validation cohorts. On a pathogen-specific level, Streptococcus pneumoniae and Escherichia coli induced the most distinct host immune response.

CONCLUSION

Outcome and host response are similar in critically ill patients with CAP due to Gram-positive bacteria compared to Gram-negative bacteria.

Circulating Complement C3-Alpha Chain Levels Predict Survival of Septic Shock Patients

BACKGROUND

Circulating complement C3 fragments released during septic shock might contribute to the development of complications such as profound hypotension and disseminated intravascular coagulation. The role of C3 in the course of septic shock varies in the literature, possibly because circulating C3 exists in different forms indistinguishable via traditional ELISA-based methods. We sought to test the relationship between C3 forms, measured by Western blotting with its associated protein size differentiation feature, and clinical outcomes.

METHODS

Secondary analysis of two prospective cohorts of patients with septic shock: a discovery cohort of 24 patents and a validation cohort of 181 patients. C3 levels were measured by Western blotting in both cohorts using blood obtained at enrollment. Differences between survivors and non-survivors were compared, and the independent prognostic values of C3 forms were assessed.

RESULTS

In both cohorts there were significantly lower levels of the C3-alpha chain in non-survivors than in survivors, and persisted after controlling for sequential organ failure assessment score. Area under the receiver operating characteristics to predict survival was 0.65 (95% confidence interval: 0.56-0.75). At a best cutoff value (Youden) of 970.6 μg/mL, the test demonstrated a sensitivity of 68.5% and specificity of 61.5%. At this cutoff point, Kaplan-Meier survival analysis showed that patients with lower levels of C3-alpha chain had significantly lower survival than those with higher levels (P < 0.001).

CONCLUSION

Circulating C3-alpha chain levels is a significant independent predictor of survival in septic shock patients.

miR-484 targeting of Yap1-induced LPS-inhibited proliferation, and promoted apoptosis and inflammation in cardiomyocyte

Apoptosis and inflammation were the main hallmarks of sepsis-induced cardiomyopathy (SIC). Yes-associated protein isoform 1 (Yap1) and miR-484 were involved in mitochondrial fission and apoptosis, especially proapoptotic roles in SIC. Here, we investigated the role of Yap1 and miR-484 in lipopolysaccharide (LPS)-treated H9c2 cells. Yap1 was downregulated, while miR-484 was elevated by LPS treatment. Cell counting kit-8, flow cytometry, western blotting, and ELISA showed that miR-484 inhibitor significantly improved cell viability, decreased apoptosis, suppressed NLRP3 inflammasome formation, and reduced secretion of inflammatory cytokines TNF-α, IL-1β, and IL-6. Yap1, directly targeted by miR-484 shown in the luciferase assay, was more like a compensatory regulator of LPS stimulation. Knockdown of Yap1 inverted the effects of miR-484 inhibitor, including decreased cell viability, and promoted apoptosis and inflammation. These revealed miR-484 directly targeted mRNA of Yap1 to inhibit cell viability, and promote apoptosis and inflammation in LPS-treated H9c2 cells.

Refinement of an open-microcavity optical biosensor for bacterial endotoxin test

The Limulus Amebocyte Lysate (LAL) test is an in vitro assay widely used in the pharmaceutical and biotechnology industries to detect bacterial endotoxins. Endotoxin is a structural component of the cell wall of Gram-negative bacteria, which has serious pathogenic effects in the body and may cause dysfunction of multiple organ systems and increased risk of mortality. To address the growing need for LAL assays due to the increased demand from drug and vaccine manufacturers, we have developed a new LAL assay approach. Our detection mechanism is different and improved from those currently used in the industry, leading to increased test sensitivity and reduced assay time. Our study utilizes an open-microcavity photonic-crystal biosensor to quantify endotoxin concentrations. It has demonstrated an improved LAL assay sensitivity by 10 fold compared to the commercial standard methods and reduced the time needed for the assay by more than half. In addition, this approach requires as little as 5 μL of LAL reagent per test, thereby decreasing costs and conserving horseshoe crabs. The results reported in this paper indicate the possibility of using the photonic-crystal biosensor based approach for significant enhancements of endotoxin testing.

A focus on the roles of histones in health and diseases

Over time, the knowledge on the role of histones has significantly changed. Initially, histones were only known as DNA packaging proteins but later, it was discovered that they act extracellularly as powerful antimicrobial agents and also as potentially self-detrimental agents. Indeed, histones were found to be the most abundant proteins within neutrophil extracellular traps what ultimately highlighted their microbicidal function. In addition, extracellular histones proved to be involved in triggering exacerbated inflammatory and coagulation responses, depending on the cell type affected. Consequently, several investigations were conducted towards studying the potential of histones and their derivatives as either biomarkers or therapeutic target candidates in different diseases in which inflammation and thrombosis have a key pathophysiological role, such as sepsis, thrombosis and different types of cancer. The main objective of this review is to summarize and discuss the current state of the art with regard to both beneficial and harmful roles of histones and also their possible use as biomarkers and therapeutic targets.

The mitochondrial redistribution of eNOS is involved in lipopolysaccharide induced inflammasome activation during acute lung injury

Acute lung injury (ALI) is a devastating clinical syndrome with no effective therapies. Inflammasome activation has been reported to play a critical role in the initiation and progression of ALI. The molecular mechanisms involved in regulating the activation of inflammasome in ALI remains unresolved, although increases in mitochondrial derived reactive oxygen species (mito-ROS) are involved. Our previous work has shown that the mitochondrial redistribution of uncoupled eNOS impairs mitochondrial bioenergetics and increases mito-ROS generation. Thus, the focus of our study was to determine if lipopolysaccharide (LPS)-mediated inflammasome activation involves the mitochondrial redistribution of uncoupled eNOS. Our data show that the increase in mito-ROS involved in LPS-mediated inflammasome activation is associated with the disruption of mitochondrial bioenergetics in human lung microvascular endothelial cells (HLMVEC) and the mitochondrial redistribution of eNOS. These effects are dependent on RhoA-ROCK signaling and are mediated via increased phosphorylation of eNOS at Threonine (T)-495. A derivative of the mitochondrial targeted Szeto-Schiller peptide (SSP) attached to the antioxidant Tiron (T-SSP), significantly attenuated LPS-mediated mito-ROS generation and inflammasome activation in HLMVEC. Further, T-SSP attenuated mitochondrial superoxide production in a mouse model of sepsis induced ALI. This in turn significantly reduced the inflammatory response and attenuated lung injury. Thus, our findings show that the mitochondrial redistribution of uncoupled eNOS is intimately involved in the activation of the inflammatory response in ALI and implicate attenuating mito-ROS as a therapeutic strategy in humans.

Phenotypical Changes of Hematopoietic Stem and Progenitor Cells in Sepsis Patients: Correlation With Immune Status?

Background: Sepsis is life-threatening organ dysfunction associated with high risk of death. The immune response of sepsis is complex and varies over time. The immune cells are derived from hematopoietic stem and progenitor cells (HSPCs) which can respond to many infections. Our previous study found that sepsis causes HSPC dysregulation in mouse. But few studies have previously investigated the kinetics of HSPC and its contribution to immune system in sepsis patients.

Purpose: We aimed to identify the kinetics of HSPCs and their contribution to immune system in sepsis patients.

Methods: We enrolled eight sepsis patients and five healthy control subjects. Peripheral blood (PB) samples from each patient were collected three times: on the first, fourth, and seventh days, once from each healthy control subject. Peripheral blood mononuclear cells (PBMCs) were isolated by density centrifugation and stained with cocktails of antibodies. Populations of HSPCs and their subpopulation were analyzed by flow cytometry. Immune cells were characterized by flow cytometry and blood cell analysis. Correlations between HSPCs and immune cells were analyzed using the Pearson correlation test.

Results: We found that the frequency of HSPCs (CD34⁺ cells and CD34⁺CD38⁺ cells) in sepsis patients on day 4 was significantly higher than that in the healthy controls. The most pronounced change in subpopulation analysis is the frequency of common myeloid progenitors (CMPs; CD34⁺CD38⁺CD135⁺CD45RA⁻). But no difference in the immunophenotypically defined hematopoietic stem cells (HSCs; CD34⁺CD38⁻CD90⁺CD45RA⁻) in sepsis patients was observed due to rare HSC numbers in PB. The number of PBMCs and lymphocytes are decreased, whereas the white blood cell (WBC) and neutrophil counts were increased in sepsis patients. Importantly, we found a negative correlation between CD34⁺ on day 1 and WBC and lymphocytes on day 4 from correlation analysis in sepsis patients.

Conclusion: The present study demonstrated that the HSPC and its subpopulation in sepsis patients expanded. Importantly, the changes in HSPCs at early time points in sepsis patients have negative correlations with later immune cells. Our results may provide a novel diagnostic indicator and a new therapeutic approach.

Heparin Attenuates Histone-Mediated Cytotoxicity in Septic Acute Kidney Injury

Histones are considered potential risk factors that contribute to the development of septic acute kidney injury (SAKI) by inducing apoptosis and inflammation. This study aimed to explore the protective effects of heparin on septic acute kidney injury through the neutralization of extracellular histones (EH) and to uncover the underlying mechanism. C57BL mice (16 each) were randomly divided into the sham group, the sepsis group (established by cecal ligation and puncture operation, CLP), and the heparin intervention group. Mice in the heparin intervention group received a subcutaneous injection of unfractionated heparin (0.03 IU/g) 4 h after CLP. At 6 h after the operation, nine mice from each group were sacrificed by the removal of the eyeballs to harvest blood samples; the upper half of the right kidney was used as the study sample. Mice renal tubular epithelial cells cultivated in six-well plates were equally divided into five groups. We cultured cells treated with either histone (40 U), histone (40 U) + heparin (25 IU/ml), histone(40U) + lipopolysaccharides (LPS; 10 μg/ml), or histone (40 U) + LPS (10 μg/ml) + heparin (25 IU/ml) for 6 h. For the histone + heparin group and the histone + LPS + heparin group, histone (and LPS) were treated with heparin simultaneously. Mice in the heparin intervention group showed decreased levels of EH4, neutrophil gelatinase-associated lipocalin (NAGL), kidney injury molecule-1 (KIM-1), tumor necrosis factor-α (TNF-α), and interleukin (IL)-6 in the blood serum, longer average 72-h survival rate, significantly decreased kidney tissue edema, and a clearer glomerular structure coupled with decreased protein and mRNA expression levels of kidney apoptosis-related proteins (cleaved Caspase-3/Caspase-3 and Bax/Bcl-2) compared with those in the sepsis group at 6 h after CLP (P < 0.05). Meanwhile, cells in the heparin intervention group exhibited lower expression levels of serum EH4 and inflammatory cytokines, a lower apoptosis rate, and decreased expression of apoptosis-related proteins, both at protein and mRNA levels, than those in the histone-stimulated group at 6 h after stimulation (P < 0.05). Heparin may alleviate apoptosis and inflammation through the neutralization of histones, thus playing a protective role against septic acute kidney injury.

Neutrophil extracellular traps and thrombosis in COVID-19

Studies of patients with COVID-19 have demonstrated markedly dysregulated coagulation and a high risk of morbid arterial and venous thrombotic events. Elevated levels of blood neutrophils and neutrophil extracellular traps (NETs) have recently been described in patients with COVID-19. However, their potential role in COVID-19-associated thrombosis remains incompletely understood. In order to elucidate the potential role of hyperactive neutrophils and NET release in COVID-19-associated thrombosis, we conducted a case–control study of patients hospitalized with COVID-19 who developed thrombosis, as compared with gender- and age-matched COVID-19 patients without clinical thrombosis. We found that remnants of NETs (cell-free DNA, myeloperoxidase-DNA complexes, and citrullinated histone H3) and neutrophil-derived S100A8/A9 (calprotectin) in patient sera were associated with higher risk of morbid thrombotic events in spite of prophylactic anticoagulation. These observations underscore the need for urgent investigation into the potential relationship between NETs and unrelenting thrombosis in COVID-19, as well as novel approaches for thrombosis prevention.

Preliminary report of in vitro and in vivo effectiveness of dornase alfa on SARS-CoV-2 infection

Dornase alfa, the recombinant form of the human DNase I enzyme, breaks down neutrophil extracellular traps (NET) that include a vast amount of DNA fragments, histones, microbicidal proteins and oxidant enzymes released from necrotic neutrophils in the highly viscous mucus of cystic fibrosis patients. Dornase alfa has been used for decades in patients with cystic fibrosis to reduce the viscoelasticity of respiratory tract secretions, to decrease the severity of respiratory tract infections, and to improve lung function. Previous studies have linked abnormal NET formations to lung diseases, especially to acute respiratory distress syndrome (ARDS). It is well known that novel coronavirus disease 2019 (COVID-19) pneumonia progresses to ARDS and even multiple organ failure. High blood neutrophil levels are an early indicator of COVID-19 and predict severe respiratory diseases. Also it is reported that mucus structure in COVID-19 is very similar to that in cystic fibrosis due to the accumulation of excessive NET in the lungs. In this study, we showed the recovery of three individuals with COVID-19 after including dornase alfa in their treatment. We followed clinical improvement in the radiological analysis (two of three cases), oxygen saturation (Spo₂), respiratory rate, disappearance of dyspnoea, coughing and a decrease in NET formation and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral load after the treatment. Also here, we share our preliminary results suggesting that dornase alfa has an anti-viral effect against SARS-CoV-2 infection in a green monkey kidney cell line, Vero, and a bovine kidney cell line, MDBK, without determined cytotoxicity on healthy peripheral blood mononuclear cells.

Admission IL-32 concentration predicts severity and mortality of severe community-acquired pneumonia independently of etiology

BACKGROUND

Severe community-acquired pneumonia (SCAP) is a critical disorder with high morbidity and mortality, usually manifested as acute respiratory failure and septic shock generally caused by exaggerated systemic inflammation. Interleukin-32 (IL-32), a pro-inflammatory cytokine, has been reported involved in various infectious diseases. We investigated the efficacy of the plasma IL-32 as a biomarker for evaluating the severity and clinical outcomes in SCAP patients.

METHODS

A total of 124 adult immunocompetent SCAP patients and 87 healthy controls were enrolled in this observational, prospective cohort study.

RESULTS

We found that PBMCs IL-32 mRNA and plasma IL-32 concentrations on admission of SCAP patients were significantly higher than healthy controls. Plasma IL-32 concentrations closely correlated with increasing severity scores, the need for vasopressor support or invasive mechanical ventilation but not with the etiology. The area under the curve (AUC) for predicting 30-day mortality using IL-32 was 0.812, is superior to WBCs and CRP. Incorporation of IL-32 with the severity scores were shown to improve the prognostic accuracy considerably. Furthermore, the 30-day cumulative survival rate in high IL-32 concentration group was significantly lower than that in the low concentration group. In a multivariate Cox regression analysis, higher IL-32 concentration and higher PSI score were recognized as the independent risk factors for survival, and the relative risks were 2.568 and 3.362, respectively.

CONCLUSIONS

Admission IL-32 concentration closely related to the severity and mortality of SCAP, and it may be served as a potential biomarker to help clinical judgment and management.

Can the Cecal Ligation and Puncture Model Be Repurposed To Better Inform Therapy in Human Sepsis?

A recent report by the National Institutes of Health on sepsis research has implied there is a trend to move away from mouse models of sepsis. The most commonly used animal model to study the pathogenesis of human sepsis is cecal ligation and puncture (CLP) in mice. The model has been the mainstay of sepsis research for decades and continues to be considered the gold standard to inform novel pathways of sepsis physiology and its therapeutic direction. As there have been many criticisms of the model, particularly regarding its relevance to human disease, how this model might be repurposed to be more reflective of the human condition begs discussion. In this piece, we compare and contrast the mouse microbiome of the CLP model to the emerging science of the microbiome of human sepsis and discuss the relevance for mice to harbor the specific pathogens present in the human microbiome during sepsis, as well as an underlying disease process to mimic the characteristics of those patients with undesirable outcomes. How to repurpose this model to incorporate these "human factors" is discussed in detail and suggestions offered.

Deciphering SARS-CoV-2 Virologic and Immunologic Features

Severe acute respiratory syndrome coronavirus (SARS-CoV)-2 and its associated pathology, COVID-19, have been of particular concerns these last months due to the worldwide burden they represent. The number of cases requiring intensive care being the critical point in this epidemic, a better understanding of the pathophysiology leading to these severe cases is urgently needed. Tissue lesions can be caused by the pathogen or can be driven by an overwhelmed immune response. Focusing on SARS-CoV-2, we and others have observed that this virus can trigger indeed an immune response that can be dysregulated in severe patients and leading to further injury to multiple organs. The purpose of the review is to bring to light the current knowledge about SARS-CoV-2 virologic and immunologic features. Thus, we address virus biology, life cycle, tropism for many organs and how ultimately it will affect several host biological and physiological functions, notably the immune response. Given that therapeutic avenues are now highly warranted, we also discuss the immunotherapies available to manage the infection and the clinical outcomes.

Head, Neck, and Abdominopelvic Septic Thrombophlebitis: Current Evidence and Challenges in Diagnosis and Treatment

Septic thrombophlebitis (STP) is a complex, cross-disciplinary clinical condition that combines a localized infection with a neighboring venous thrombosis. STP can occur at several possible anatomic sites, such as dural sinuses, jugular vein (Lemierre syndrome), portal vein (pylephlebitis), and pelvic veins. Its high mortality in the preantibiotic era improved considerably with the introduction of modern antibiotics. However, little evidence exists to date to guide its clinical management. The incidence of STP or its risk factors may be increasing, and its mortality may still be considerable. These trends would have far-reaching implications, especially in the setting of increasing resistance to antimicrobial agents. No clinical assessment tools exist to support patient screening or guide treatment in STP. Few interventional studies exist on the efficacy and safety of anticoagulation. Recommendations on its indications, duration, and the agents of choice are mostly based on evidence derived from small observational studies. While all forms of STP pose similar challenges, future research may benefit from the distinction between bacteria-associated, virus-associated, and mycosis-associated thrombophlebitis. Addressing these gaps in evidence would enhance our ability to diagnose this condition and treat patients effectively.

Complement in sepsis-when science meets clinics

Sepsis as life-threatening organ dysfunction caused by microorganisms represents a dreadful challenge for the immune system. The role of the complement system as major column of innate immunity has been extensively studied in various sepsis models, but its translational value remains in the dark. Complement activation products, such as C3a and C5a, and their corresponding receptors provide useful diagnostic tools and promising targets to improve organ function and outcome. However, a monotherapeutic complement intervention irrespective of the current immune function seems insufficient to reverse the complex sepsis mechanisms. Indeed, sepsis-induced disturbances of cross talking complement, coagulation, and fibrinolytic cascades lead to systemic 'thromboinflammation', ultimately followed by multiple-organ failure. We propose to reliably monitor the complement function in the patient and to re-establish the immune balance by patient-tailored combined therapies, such as complement and Toll-like receptor inhibition. Our working hypothesis aims at blocking the 'explosive' innate immune recognition systems early on before downstream mediators are released and the inflammatory response becomes irreversible, a strategy that we name 'upstream approach'.

Thymopentin improves the survival of septic mice by promoting the production of 15-deoxy-prostaglandin J2 and activating the PPARγ signaling pathway

Sepsis, a systemic inflammatory response syndrome (SIRS) caused by infection, is a major public health concern with limited therapeutic options. Infection disturbs the homeostasis of host, resulting in excessive inflammation and immune suppression. This has prompted the clinical use of immunomodulators to balance host response as an alternative therapeutic strategy. Here, we report that Thymopentin (TP5), a synthetic immunomodulator pentapeptide (Arg-Lys-Asp-Val-Tyr) with an excellent safety profile in the clinic, protects mice against cecal ligation and puncture (CLP)-induced sepsis, as shown by improved survival rate, decreased level of pro-inflammatory cytokines and reduced ratios of macrophages and neutrophils in spleen and peritoneum. Regarding mechanism, TP5 changed the characteristics of LPS-stimulated macrophages by increasing the production of 15-deoxy-Δ^12,14 -prostaglandin J2 (15-d-PGJ2). In addition, the improved effect of TP5 on survival rates was abolished by the peroxisome proliferator-activated receptor γ (PPARγ) antagonist GW9662. Our results uncover the mechanism of the TP5 protective effects on CLP-induced sepsis and shed light on the development of TP5 as a therapeutic strategy for lethal systemic inflammatory disorders.

O Papel da Imunidade Inata na COVID-19

O sistema imune apresenta papel importante na pandemia da COVID-19, pois está envolvido na patogênese e agravamento da doença. O objetivo desta revisão é abordar os aspectos da imunidade inata na COVID-19, especialmente o papel dos neutrófilos. O sistema imune inato corresponde à primeira defesa do organismo, porém é necessário um equilíbrio para obter efetividade contra o invasor sem lesar excessivamente o hospedeiro. O desequilíbrio imune está relacionado com quadros mais graves e à ativação aberrante de neutrófilos, sendo a linfopenia e a neutrofilia preditores de pior prognóstico em pacientes com COVID-19.  Especula-se que a neutrofilia seja uma importante fonte para formação excessiva de NET (Neutrophil Extracellular Traps), levando ao aumento da resposta inflamatória e evolução desfavorável da doença. As NET também estão associadas à tempestade de citocinas, outro mecanismo relacionado a gravidade da COVID-19. Portanto, estratégias que envolvam a imunomodulação podem ter um papel importante no controle da doença.

Neutrophil extracellular traps in COVID-19

In severe cases of coronavirus disease 2019 (COVID-19), viral pneumonia progresses to respiratory failure. Neutrophil extracellular traps (NETs) are extracellular webs of chromatin, microbicidal proteins, and oxidant enzymes that are released by neutrophils to contain infections. However, when not properly regulated, NETs have the potential to propagate inflammation and microvascular thrombosis - including in the lungs of patients with acute respiratory distress syndrome. We now report that sera from patients with COVID-19 have elevated levels of cell-free DNA, myeloperoxidase-DNA (MPO-DNA), and citrullinated histone H3 (Cit-H3); the latter 2 are specific markers of NETs. Highlighting the potential clinical relevance of these findings, cell-free DNA strongly correlated with acute-phase reactants, including C-reactive protein, D-dimer, and lactate dehydrogenase, as well as absolute neutrophil count. MPO-DNA associated with both cell-free DNA and absolute neutrophil count, while Cit-H3 correlated with platelet levels. Importantly, both cell-free DNA and MPO-DNA were higher in hospitalized patients receiving mechanical ventilation as compared with hospitalized patients breathing room air. Finally, sera from individuals with COVID-19 triggered NET release from control neutrophils in vitro. Future studies should investigate the predictive power of circulating NETs in longitudinal cohorts and determine the extent to which NETs may be novel therapeutic targets in severe COVID-19.

Neutrophil extracellular traps and thrombosis in COVID-19

BACKGROUND

Early studies of patients with COVID-19 have demonstrated markedly dysregulated coagulation and a high risk of morbid arterial and venous thrombotic events. While elevated levels of blood neutrophils and neutrophil extracellular traps (NETs) have been described in patients with COVID-19, their potential role in COVID-19-associated thrombosis remains unknown.

OBJECTIVES

To elucidate the potential role of hyperactive neutrophils and NET release in COVID-19-associated thrombosis.

PATIENTS/METHODS

This is a retrospective, case-control study of patients hospitalized with COVID-19 who developed thrombosis (n=11), as compared with gender- and age-matched COVID-19 patients without clinical thrombosis (n=33). In addition to capturing clinical data, we measured remnants of NETs (cell-free DNA, myeloperoxidase-DNA complexes, and citrullinated histone H3) and neutrophil-derived S100A8/A9 (calprotectin) in patient sera.

RESULTS

The majority of patients (9/11) were receiving at least prophylactic doses of heparinoids at the time thrombosis was diagnosed. As compared with controls, patients with COVID-19-associated thrombosis had significantly higher blood levels of markers of NETs (cell-free DNA, myeloperoxidase-DNA complexes, citrullinated histone H3) and neutrophil activation (calprotectin). The thrombosis group also had higher levels of D-dimer, CRP, ferritin, and platelets, but not troponin or neutrophils. Finally, there were strong associations between markers of hyperactive neutrophils (calprotectin and cell-free DNA) and D-dimer.

CONCLUSION

Elevated levels of neutrophil activation and NET formation in patients hospitalized with COVID-19 are associated with higher risk of morbid thrombotic complications. These observations underscore the need for urgent investigation into the potential relationship between NETs and unrelenting thrombosis in COVID-19.

Neutrophil extracellular traps (NETs) as markers of disease severity in COVID-19

In severe cases of coronavirus disease 2019 (COVID-19), viral pneumonia progresses to respiratory failure. Neutrophil extracellular traps (NETs) are extracellular webs of chromatin, microbicidal proteins, and oxidant enzymes that are released by neutrophils to contain infections. However, when not properly regulated, NETs have potential to propagate inflammation and microvascular thrombosis, including in the lungs of patients with acute respiratory distress syndrome. While elevated levels of blood neutrophils predict worse outcomes in COVID-19, the role of NETs has not been investigated. We now report that sera from patients with COVID-19 (n=50 patients, n=84 samples) have elevated levels of cell-free DNA, myeloperoxidase(MPO)-DNA, and citrullinated histone H3 (Cit-H3); the latter two are highly specific markers of NETs. Highlighting the potential clinical relevance of these findings, cell-free DNA strongly correlated with acute phase reactants including C-reactive protein, D-dimer, and lactate dehydrogenase, as well as absolute neutrophil count. MPO-DNA associated with both cell-free DNA and absolute neutrophil count, while Cit-H3 correlated with platelet levels. Importantly, both cell-free DNA and MPO-DNA were higher in hospitalized patients receiving mechanical ventilation as compared with hospitalized patients breathing room air. Finally, sera from individuals with COVID-19 triggered NET release from control neutrophils in vitro. In summary, these data reveal high levels of NETs in many patients with COVID-19, where they may contribute to cytokine release and respiratory failure. Future studies should investigate the predictive power of circulating NETs in longitudinal cohorts, and determine the extent to which NETs may be novel therapeutic targets in severe COVID-19.

Complement as a Major Inducer of Harmful Events in Infectious Sepsis

There is abundant evidence that infectious sepsis both in humans and mice with polymicrobial sepsis results in robust activation of complement. Major complement activation products involved in sepsis include C5a anaphylatoxin and its receptors (C5aR1 and C5aR2) and, perhaps, the terminal complement activation product, C5b-9. These products (and others) also cause dysfunction of the innate immune system, with exaggerated early proinflammatory responses, followed by decline of the innate immune system, leading to immunosuppression and multiorgan dysfunction. Generation of C5a during sepsis also leads to activation of neutrophils and macrophages and ultimate appearance of extracellular histones, which have powerful proinflammatory and prothrombotic activities. The distal complement activation product, C5b-9, triggers intracellular Ca fluxes in epithelial and endothelial cells. Histones activate the NLRP3 inflammasome, products of which can damage cells. C5a also activates MAPKs and Akt signaling pathways in cardiomyocytes, causing buildup of [Ca]i, defective action potentials and substantial cell dysfunction, resulting in cardiac and other organ dysfunction. Cardiac dysfunction can be quantitated by ECHO-Doppler parameters. In vivo interventions that block these complement-dependent products responsible for organ dysfunction in sepsis reduce the intensity of sepsis. The obvious targets in sepsis are C5a and its receptors, histones, and perhaps the MAPK pathways. Blockade of C5 has been considered in sepsis, but the FDA-approved antibody (eculizumab) is known to compromise defenses against neisseria and pneumonococcal bacteria, and requires immunization before the mAb to C5 can be used clinically. Small molecular blocking agents for C5aRs are currently in development and may be therapeutically effective for treatment of sepsis.

Current Status of Septic Cardiomyopathy: Basic Science and Clinical Progress

Septic cardiomyopathy (SCM) is a complication that is sepsis-associated cardiovascular failure. In the last few decades, there is progress in diagnosis and treatment despite the lack of consistent diagnostic criteria. According to current studies, several hypotheses about pathogenic mechanisms have been revealed to elucidate the pathophysiological characteristics of SCM. The objective of this manuscript is to review literature from the past 5 years to provide an overview of current knowledge on pathogenesis, diagnosis and treatment in SCM.

Immunotherapy in sepsis - brake or accelerate?

Sepsis, a life threating syndrome characterized by organ failure after infection, is the most common cause of death in hospitalized patients. The treatment of sepsis is generally supportive in nature, involving the administration of intravenous fluids, vasoactive substances and oxygen plus antibiotics to eliminate the pathogen. No drugs have been approved specifically for the treatment of sepsis, and clinical trials of potential therapies have failed to reduce mortality - suggesting that new approaches are needed. Abnormalities in the immune response elicited by the pathogen, ranging from excessive inflammation to immunosuppression, contribute to disease pathogenesis. Although hundreds of immunomodulatory agents are potentially available, it remains unclear which patient benefits from which immune therapy at a given time point. Results indicate the importance of personalized therapy, specifically the need to identify the type of intervention required by each individual patient at a given point in the disease process. To address this issue will require using biomarkers to stratify patients based on their individual immune status. This article reviews recent and ongoing clinical investigations using immunostimulatory or immunosuppressive therapies against sepsis including non-pharmacological and novel preclinical approaches.

Vitamin lipid nanoparticles enable adoptive macrophage transfer for the treatment of multidrug-resistant bacterial sepsis

Sepsis, a condition caused by severe infections, affects more than 30 million people worldwide every year and remains the leading cause of death in hospitals^1,2. Moreover, antimicrobial resistance has become an additional challenge in the treatment of sepsis³, and thus, alternative therapeutic approaches are urgently needed^2,3. Here, we show that adoptive transfer of macrophages containing antimicrobial peptides linked to cathepsin B in the lysosomes (MACs) can be applied for the treatment of multidrug-resistant bacteria-induced sepsis in mice with immunosuppression. The MACs are constructed by transfection of vitamin C lipid nanoparticles that deliver antimicrobial peptide and cathepsin B (AMP-CatB) mRNA. The vitamin C lipid nanoparticles allow the specific accumulation of AMP-CatB in macrophage lysosomes, which is the key location for bactericidal activities. Our results demonstrate that adoptive MAC transfer leads to the elimination of multidrug-resistant bacteria, including Staphylococcus aureus and Escherichia coli, leading to the complete recovery of immunocompromised septic mice. Our work provides an alternative strategy for overcoming multidrug-resistant bacteria-induced sepsis and opens up possibilities for the development of nanoparticle-enabled cell therapy for infectious diseases.

DAMPs and NETs in Sepsis

Sepsis is a deadly inflammatory syndrome caused by an exaggerated immune response to infection. Much has been focused on host response to pathogens mediated through the interaction of pathogen-associated molecular patterns (PAMPs) and pattern recognition receptors (PRRs). PRRs are also activated by host nuclear, mitochondrial, and cytosolic proteins, known as damage-associated molecular patterns (DAMPs) that are released from cells during sepsis. Some well described members of the DAMP family are extracellular cold-inducible RNA-binding protein (eCIRP), high mobility group box 1 (HMGB1), histones, and adenosine triphosphate (ATP). DAMPs are released from the cell through inflammasome activation or passively following cell death. Similarly, neutrophil extracellular traps (NETs) are released from neutrophils during inflammation. NETs are webs of extracellular DNA decorated with histones, myeloperoxidase, and elastase. Although NETs contribute to pathogen clearance, excessive NET formation promotes inflammation and tissue damage in sepsis. Here, we review DAMPs and NETs and their crosstalk in sepsis with respect to their sources, activation, release, and function. A clear grasp of DAMPs, NETs and their interaction is crucial for the understanding of the pathophysiology of sepsis and for the development of novel sepsis therapeutics.

Association of CFH polymorphism with susceptibility to sepsis caused by Pseudomonas aeruginosa in Chinese Han populations: A multi-center study

Complement factor H (CFH) serves as a major down-regulator in the complement system, often utilized by bacterial pathogens to evade complement attack. Yet, little is currently known about the genetic correlation of CFH polymorphisms with sepsis due to various microbial infections. A case-control method (488 septic patients and 527 healthy individuals) was carried out in this study to investigate the genetic relationship between CFH polymorphisms (rs3753394 C/T, rs1065489 G/T and rs1061170 C/T) and susceptibility to sepsis caused by bacterial infections in Chinese Han populations. Our findings indicated that the frequency of rs3753394 CT/TT genotype in the septic patients with P. aeruginosa was significantly higher than that in the control individuals (P = 0.033, OR = 2.668, 95%CI = 1.072-6.334). The rs3753394 T allele frequency in the P. aeruginosa-infected patients was significantly increased, compared to that in the healthy controls (P = 0.014, OR = 1.68, 95%CI = 1.118-2.538). Moreover, these significant differences of rs3753394 genotype and allele frequencies remained after multiple testing corrections [P (corr.) = 0.033 for genotype; P (corr.) = 0.033 for allele]. The current study highlighted the significance of CFH polymorphism rs3753394 as a potential biomarker for targeting P. aeruginosa infection in critically ill patients.

Penehyclidine Hydrochloride Alleviates Lipopolysaccharide-Induced Acute Lung Injury by Ameliorating Apoptosis and Endoplasmic Reticulum Stress

BACKGROUND

Penehyclidine hydrochloride (PHC), a novel anticholinergic reagent, has been shown to exert anti-endoplasmic reticulum stress (ERS), antioxidant, and antiinflammation functions in various rat models. However, the definite pathogenesis of lung defensive roles of PHC remains unclear. This study measured the functions of PHC on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in rats.

METHODS

In this research, the LPS-induced ALI model was assessed through the branchial injection of LPS for 24 h. Male Sprague-Dawley rats were randomly allocated into 5 groups: sham, LPS, LPS + PHC (0.5 mg/kg), LPS + PHC (1 mg/kg), and LPS + PHC (2.5 mg/kg). The concentrations of superoxide dismutase, malondialdehyde, myeloperoxidase, and glutathione peroxidase were measured by enzyme-linked immunosorbent assay and immunohistochemistry analysis. Western blotting, real-time PCR, and immunofluorescence analysis were used to determine the ERS-associated protein levels and mRNA expression. The protein levels of Bax, Bcl-2, caspase-3, and caspase-9 were used to measure lung tissue apoptosis.

RESULTS

The results revealed that PHC administration inhibited LPS-induced ALI as indicated by the loss in the ratio of injury production evaluated through hematoxylin-eosin staining, in particular the lung sample sections, compared with the LPS group. PHC administration inhibited LPS-induced lung myeloperoxidase and serum concentrations of malondialdehyde, superoxide dismutase, and glutathione peroxidase in rats. PHC administration repressed the LPS-activated ERS-correlated pathway and apoptosis-associated protein levels in rats.

CONCLUSIONS

In summary, our findings indicated that PHC has a defensive effect on LPS-induced ALI by inhibiting oxidative stress, attenuating PERK and ATF6 signals, and suppressing ERS-mediated apoptosis.

H2 Protects Against Lipopolysaccharide-Induced Cardiac Dysfunction via Blocking TLR4-Mediated Cytokines Expression

Background and Purpose: Septic cardiomyopathy, which is one of the features of multi-organ dysfunction in sepsis, is characterized by ventricular dilatation, reduced ventricular contractility, and reduction in ejection fraction and, if severe, can lead to death. To date, there is no specific therapy that exists, and its treatment represents a large unmet clinical need. Herein, we investigated the effects and underlying anti-inflammatory mechanisms of hydrogen gas in the setting of lipopolysaccharide (LPS)-induced cardiomyocytes injury.

Experimental Approach: Hydrogen gas was intraperitoneally injected to mice in LPS plus hydrogen group and hydrogen group for 4 days. On fourth, LPS was given by intraperitoneal injection to mice in LPS group and to mice in LPS plus hydrogen group. In addition, H9c2 cardiomyocytes were treated with hydrogen-rich medium for 30 min before LPS. The transthoracic echocardiography was performed at 6 h post‐LPS to assess left ventricular end-systolic diameter (LVESD), left ventricular end-diastolic diameter (LVEDD), left ventricular ejection fraction (EF%), fractional shortening (FS%), left ventricular mass average weight (LV mass AW), and LV mass AW (Corrected). The histological and morphological analyses of left ventricular were performed by hematoxylin and eosin (H&E) staining and Masson’s trichrome staining. The mRNA levels of ANP and BNP were examined by PCR in vitro. The expression of cytokines were assayed by Enzyme Linked Immunosorbent Assay (ELISA) and PCR. Moreover, Western blotting was performed to examine the expression of TLR4, the activation of ERK1/2, p38, JNK, and the expression of NF-κB in nucleus after 6 h of LPS challenge in vivo and in vitro.

Key Results: LPS induced cardiac dysfunction; hydrogen therapy improved cardiac function after LPS challenge. Furthermore, pretreatment with hydrogen resulted in cardioprotection during septic cardiomyopathy via inhibiting the expression of pro-inflammatory cytokines TNFα, IL-1β, and IL-18; suppressing the phosphorylation of ERK1/2, p38, and JNK; and reducing the nuclear translocation of NF-κB and the expression of TLR4 by LPS.

Conclusion and Implications: Hydrogen therapy prevents LPS-induced cardiac dysfunction in part via downregulation of TLR4-mediated pro-inflammatory cytokines expression.