Heat-shock protein-90 prolongs septic neutrophil survival by protecting c-Src kinase and caspase-8 from proteasomal degradation

MicroRNAs as regulators of cardiac dysfunction in sepsis: pathogenesis and diagnostic potential

Introduction

Sepsis, a life-threatening condition arising from an uncontrolled immune response to infection, can lead to organ dysfunction, with severe inflammation potentially causing multiple organ failures. Sepsis-induced cardiac dysfunction (SIMD) is a common and severe complication of sepsis, significantly increasing patient mortality. Understanding the pathogenesis of SIMD is crucial for improving treatment, and microRNAs (miRNAs) have emerged as important regulators in this process.

Methods

A comprehensive literature search was conducted in PubMed, Science Direct, and Embase databases up to September 2024. The search terms included ["miRNA" or "microRNA"] and ["Cardiac" or "Heart"] and ["Sepsis" or "Septic"], with the language limited to English. After initial filtering by the database search engine, Excel software was used to further screen references. Duplicate articles, those without abstracts or full texts, and review/meta-analyses or non-English articles were excluded. Finally, 106 relevant research articles were included for data extraction and analysis.

Results

The pathogenesis of SIMD is complex and involves mitochondrial dysfunction, oxidative stress, cardiomyocyte apoptosis and pyroptosis, dysregulation of myocardial calcium homeostasis, myocardial inhibitory factors, autonomic nervous regulation disorders, hemodynamic changes, and myocardial structural alterations. miRNAs play diverse roles in SIMD. They are involved in regulating the above-mentioned pathological processes.

Discussion

Although significant progress has been made in understanding the role of miRNAs in SIMD, there are still challenges. Some studies on the pathogenesis of SIMD have limitations such as small sample sizes and failure to account for confounding factors. Research on miRNAs also faces issues like inconsistent measurement techniques and unclear miRNA-target gene relationships. Moreover, the translation of miRNA-based research into clinical applications is hindered by problems related to miRNA stability, delivery mechanisms, off-target effects, and long-term safety. In conclusion, miRNAs play a significant role in the pathogenesis of SIMD and have potential as diagnostic biomarkers. Further research is needed to overcome existing challenges and fully exploit the potential of miRNAs in the diagnosis and treatment of SIMD.

Caspase-8: Arbitrating Life and Death in the Innate Immune System

The canonical function of caspase-8 is to control timely cellular apoptosis to maintain tissue homeostasis and clear dysfunctional cells; however, emerging findings reveal novel, non-canonical roles of caspase in addition to regulating cellular apoptosis, including inflammatory response regulation, immune function, and cell differentiation. Furthermore, the functional versatility of caspase-8 is reported to be contingent on the presence and dimerization of various isoforms, which are produced through alternative splicing, altering its function and protein-protein interactions. Equally important are post-translational modifications, including phosphorylation and ubiquitination, which can act as a nexus to control caspase-8 activity and cellular localization. Here, we review the alternative splicing and post-translational modifications made to caspase-8 and discuss their influence on its canonical and non-canonical roles.

Immunoadjuvant therapy in the regulation of cell death in sepsis: recent advances and future directions

Sepsis is characterized by a concomitant early pro-inflammatory response by immune cells to an infection, and an opposing anti-inflammatory response that results in protracted immunosuppression. The primary pathological event in sepsis is widespread programmed cell death, or cellular self-sacrifice, of innate and adaptive immune cells, leading to profound immunological suppression. This severe immune dysfunction hampers effective primary pathogen clearance, thereby increasing the risk of secondary opportunistic infections, latent viral reactivation, multiple organ dysfunction, and elevated mortality. The types of cell death include apoptosis (type I programmed cell death), autophagy (type II programmed cell death), NETosis (a program for formation of neutrophil extracellular traps (NETs)) and other programmed cell deaths like pyroptosis, ferroptosis, necroptosis, each contributing to immunosuppression in distinct ways during the later phases of sepsis. Extensive apoptosis of lymphocytes, such as CD4+, CD8+ T cells, and B cells, is strongly associated with immunosuppression. Apoptosis of dendritic cells further compromises T and B cell survival and can induce T cell anergy or promote regulatory Treg cell proliferation. Moreover, delayed apoptosis and impaired neutrophil function contribute to nosocomial infections and immune dysfunction in sepsis. Interestingly, aberrant NETosis and the subsequent depletion of mature neutrophils also trigger immunosuppression, and neutrophil pyroptosis can positively regulate NETosis. The interaction between programmed cell death 1 (PD-1) or programmed cell death 1 ligand (PD-L1) plays a key role in T cell modulation and neutrophil apoptosis in sepsis. The dendritic cell growth factor, Fms-like tyrosine kinase (FLTEL), increases DC numbers, enhances CD 28 expression, attenuates PD-L1, and improves survival in sepsis. Recently, immunoadjuvant therapies have attracted attention for their potential to restore host physiological immunity and homeostasis in patients with sepsis. This review focuses on several potential immunotherapeutic agents designed to bolster suppressed innate and adaptive immune responses in the management of sepsis.

MYOCD and SRF-mediated MLCK transcription prevents polymorphonuclear neutrophils from ferroptosis in sepsis-related acute lung injury

Persistent activation of polymorphonuclear neutrophils (PMNs) plays a crucial role in the development of sepsis-related acute lung injury (ALI). This study investigated key molecular mechanisms involved in the hyperactivation of PMNs during ALI. A mouse model of sepsis-related ALI was generated by lipopolysaccharide (LPS) injection. RNA sequencing identified myosin light chain kinase (MLCK) as the most significant differentially expressed gene (DEG) between PMNs isolated from model and control mice. Myocardin (MYOCD) and serum response factor (SRF) were two of the DEGs that could promote transcription of MLCK by binding to its promoter. Either knockdown of MLCK, MYOCD, or SRF ameliorated dysfunction and edema in the lungs of LPS-treated mice. Kyoto Encyclopedia of Genes and Genomes enrichment analysis suggested that the DEGs are enriched in a ferroptosis-related signaling pathway. The MLCK, MYOCD, or SRF knockdown increased contents of ROS, MDA, ferritin, and ferrous iron, and reduced levels of GSH and GPX4 in the PMNs. However, the MLCK overexpression restored ferroptosis resistance and activity of the PMNs, resulting in increased lung injury. Collectively, this study demonstrates that MYOCD and SRF-mediated MLCK upregulation is correlated with ferroptosis resistance and hyperactivation of PMNs in sepsis-related ALI.

Prediction of Prognosis in Patients with Sepsis Based on Platelet-Related Genes

The study aimed to develop a risk prognostic model using platelet-related genes (PRGs) to predict sepsis patient outcomes. Sepsis patient data from the Gene Expression Omnibus (GEO) database and PRGs from the Molecular Signatures Database (MSigDB) were analyzed. Differential analysis identified 1139 differentially expressed genes (DEGs) between sepsis and control groups. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed enrichment in functions related to immune cell regulation and pathways associated with immune response and infectious diseases. A risk prognostic model was established using LASSO and Cox regression analyses, incorporating 10 PRGs selected based on their association with sepsis prognosis. The model demonstrated good stratification and prognostic effects, confirmed by survival and receiver operating characteristic (ROC) curve analyses. It served as an independent prognostic factor in sepsis patients. Further analysis using the CIBERSORT algorithm showed higher infiltration of activated natural killer (NK) cells and lower infiltration of CD8 T cells and CD4 T cells naïve in the high-risk group compared to the low-risk group. Additionally, expression levels of human leukocyte antigen (HLA) genes were significantly lower in the high-risk group. In conclusion, the 10-gene risk model based on PRGs accurately predicted sepsis patient prognosis and immune infiltration levels. This study provides valuable insights into the role of platelets in sepsis prognosis and diagnosis, offering potential implications for personalized treatment strategies.

Caspase-8 in inflammatory diseases: a potential therapeutic target

Caspase-8, a renowned cysteine-aspartic protease within its enzyme family, initially garnered attention for its regulatory role in extrinsic apoptosis. With advancing research, a growing body of evidence has substantiated its involvement in other cell death processes, such as pyroptosis and necroptosis, as well as its modulatory effects on inflammasomes and proinflammatory cytokines. PANoptosis, an emerging concept of cell death, encompasses pyroptosis, apoptosis, and necroptosis, providing insight into the often overlapping cellular mortality observed during disease progression. The activation or deficiency of caspase-8 enzymatic activity is closely linked to PANoptosis, positioning caspase-8 as a key regulator of cell survival or death across various physiological and pathological processes. Aberrant expression of caspase-8 is closely associated with the development and progression of a range of inflammatory diseases, including immune system disorders, neurodegenerative diseases (NDDs), sepsis, and cancer. This paper delves into the regulatory role and impact of caspase-8 in these conditions, aiming to elucidate potential therapeutic strategies for the future intervention.

Cerebral Endothelial CXCR2 Promotes Neutrophil Transmigration into Central Nervous System in LPS-Induced Septic Encephalopathy

Septic encephalopathy (SE) represents a severe inflammatory syndrome linked to elevated septic mortality rates, lacking specific therapeutic interventions, and often resulting in enduring neurological sequelae. The present investigation endeavors to elucidate the involvement of C-X-C Motif Chemokine Receptor 2 (CXCR2) in the pathogenesis of SE and to explore the potential of CXCR2 modulation as a therapeutic avenue for SE. Employing a murine SE model induced by lipopolysaccharide (LPS) administration, CXCR2 knockout mice and the CXCR2 inhibitor SB225002 were utilized to assess neutrophil recruitment, endothelial integrity, and transendothelial migration. Our findings substantiate that either CXCR2 deficiency or its inhibition curtails neutrophil recruitment without impacting their adhesion to cerebral endothelial cells. This phenomenon is contingent upon endothelial CXCR2 expression rather than CXCR2's presence on neutrophils. Furthermore, the CXCR2 blockade preserves the integrity of tight junction protein ZO-1 and mitigates F-actin stress fiber formation in cerebral endothelial cells following septic challenge. Mechanistically, CXCL1-mediated CXCR2 activation triggers cerebral endothelial actin contraction via Rho signaling, thereby facilitating neutrophil transmigration in SE. These observations advocate for the potential therapeutic efficacy of CXCR2 inhibition in managing SE.

Reframing sepsis immunobiology for translation: towards informative subtyping and targeted immunomodulatory therapies

Sepsis is a common and deadly condition. Within the current model of sepsis immunobiology, the framing of dysregulated host immune responses into proinflammatory and immunosuppressive responses for the testing of novel treatments has not resulted in successful immunomodulatory therapies. Thus, the recent focus has been to parse observable heterogeneity into subtypes of sepsis to enable personalised immunomodulation. In this Personal View, we highlight that many fundamental immunological concepts such as resistance, disease tolerance, resilience, resolution, and repair are not incorporated into the current sepsis immunobiology model. The focus for addressing heterogeneity in sepsis should be broadened beyond subtyping to encompass the identification of deterministic molecular networks or dominant mechanisms. We explicitly reframe the dysregulated host immune responses in sepsis as altered homoeostasis with pathological disruption of immune-driven resistance, disease tolerance, resilience, and resolution mechanisms. Our proposal highlights opportunities to identify novel treatment targets and could enable successful immunomodulation in the future.

Preventing occludin tight-junction disruption via inhibition of microRNA-193b-5p attenuates viral load and influenza-induced lung injury

Virus-induced lung injury is associated with loss of pulmonary epithelial-endothelial tight junction integrity. While the alveolar-capillary membrane may be an indirect target of injury, viruses may interact directly and/or indirectly with miRs to augment their replication potential and evade the host antiviral defense system. Here, we expose how the influenza virus (H1N1) capitalizes on host-derived interferon-induced, microRNA (miR)-193b-5p to target occludin and compromise antiviral defenses. Lung biopsies from patients infected with H1N1 revealed increased miR-193b-5p levels, marked reduction in occludin protein, and disruption of the alveolar-capillary barrier. In C57BL/6 mice, the expression of miR-193b-5p increased, and occludin decreased, 5-6 days post-infection with influenza (PR8). Inhibition of miR-193b-5p in primary human bronchial, pulmonary microvascular, and nasal epithelial cells enhanced antiviral responses. miR-193b-deficient mice were resistant to PR8. Knockdown of occludin, both in vitro and in vivo, and overexpression of miR-193b-5p reconstituted susceptibility to viral infection. miR-193b-5p inhibitor mitigated loss of occludin, improved viral clearance, reduced lung edema, and augmented survival in infected mice. Our results elucidate how the innate immune system may be exploited by the influenza virus and how strategies that prevent loss of occludin and preserve tight junction function may limit susceptibility to virus-induced lung injury.

EXTRACELLULAR CIRP INHIBITS NEUTROPHIL APOPTOSIS TO PROMOTE ITS AGING BY UPREGULATING SERPINB2 IN SEPSIS

ABSTRACT

Background: Sepsis reduces neutrophil apoptosis. As the result, neutrophils may become aged, exacerbating inflammation and tissue injury. Extracellular cold-inducible RNA-binding protein (eCIRP) acts as a damage-associated molecular pattern to promote inflammation and tissue injury in sepsis. SerpinB2, a serine protease inhibitor, has been shown to inhibit apoptosis. We hypothesize that eCIRP upregulates SerpinB2 to promote aged neutrophil subset by inhibiting apoptosis in sepsis. Methods: We stimulated bone marrow-derived neutrophils (BMDNs) of wild-type (WT) mice with 1 μg/mL of recombinant mouse CIRP (i.e., eCIRP) and assessed cleaved caspase-3 and SerpinB2 by western blotting. Apoptotic neutrophils were assessed by Annexin V/PI. Bone marrow-derived neutrophils were stimulated with 1 μg/mL eCIRP and treated with or without PAC-1 (caspase-3 activator) and aged neutrophils (CXCR4 hi CD62L lo ) were assessed by flow cytometry. To induce sepsis, we performed cecal ligation and puncture in WT or CIRP -/- mice. We determined the percentage of aged neutrophils and SerpinB2 + neutrophils in blood and spleen by flow cytometry. Results: We found that cleaved caspase-3 levels were increased at 4 h of PBS treatment compared with 0 h but decreased by eCIRP treatment. Extracellular cold-inducible RNA-binding protein reduced apoptotic cells after 20 h of treatment. Extracellular cold-inducible RNA-binding protein also increased the frequencies of aged neutrophils compared with PBS after 20 h, while PAC-1 treatment reduced aging in eCIRP-treated BMDNs. Extracellular cold-inducible RNA-binding protein significantly increased the expression of SerpinB2 at protein levels in BMDNs at 20 h. In WT mice, the frequencies of aged and SerpinB2 + neutrophils in blood and spleen were increased after 20 h of cecal ligation and puncture, while in CIRP -/- mice, aged and SerpinB2 + neutrophils were significantly decreased compared with WT mice. We also found that aged neutrophils expressed significantly higher levels of SerpinB2 compared with non-aged neutrophils. Conclusions: eCIRP inhibits neutrophil apoptosis to increase aged phenotype by increasing SerpinB2 expression in sepsis. Thus, targeting eCIRP could be a new therapeutic strategy to ameliorate inflammation caused by neutrophil aging in sepsis.

Targeting Neutrophil β2-Integrins: A Review of Relevant Resources, Tools, and Methods

Neutrophils are important innate immune cells that respond during inflammation and infection. These migratory cells utilize β₂-integrin cell surface receptors to move out of the vasculature into inflamed tissues and to perform various anti-inflammatory responses. Although critical for fighting off infection, neutrophil responses can also become dysregulated and contribute to disease pathophysiology. In order to limit neutrophil-mediated damage, investigators have focused on β₂-integrins as potential therapeutic targets, but so far these strategies have failed in clinical trials. As the field continues to move forward, a better understanding of β₂-integrin function and signaling will aid the design of future therapeutics. Here, we provide a detailed review of resources, tools, experimental methods, and in vivo models that have been and will continue to be utilized to investigate the vitally important cell surface receptors, neutrophil β₂-integrins.

Ex Vivo Evaluation of Glutamine Treatment in Sepsis and Trauma in a Human Peripheral Blood Mononuclear Cells Model

We aimed to assess the lipopolysaccharide (LPS), or heat shock (HS) induction, and glutamine-modulating effects on heat shock protein-90α (HSP90α) and cytokines in an ex vivo model using peripheral blood mononuclear cells (PBMCs). The PBMCs of patients with septic shock, trauma-related systemic inflammatory response syndrome (SIRS), and healthy subjects were incubated with 1 μg/mL LPS at 43 °C (HS). Glutamine 10 mM was added 1 hour before or after induction or not at all. We measured mRNA HSP90α, monocyte (m) and lymphocyte (l) HSP90α proteins, interleukin (IL)-1b, -6, -8, -10, tumor necrosis factor-α (TNF-α), and monocyte chemoattractant protein-1 (MCP-1) supernatant levels. Heat shock increased the HSP90α mRNA and mHSP90α in all groups (10-fold in sepsis, p < 0.001 and p = 0.047, respectively). LPS induced the mHSP90α and lHSP90α in healthy (p < 0.001) and mHSP90α in SIRS (p = 0.004) but not in sepsis. LPS induced the cytokines at 24 and 48 h in all groups, especially in trauma (p < 0.001); HS only induced the IL-8 in healthy (p = 0.003) and septic subjects (p = 0.05). Glutamine at 10 mM before or after stimulation did not alter any induction effect of LPS or HS on HSP90α mRNA and mHSP90α protein in sepsis. In SIRS, glutamine before LPS decreased the mHSP90α but increased it when given after HS (p = 0.018). Before or after LPS (p = 0.049) and before HS (p = 0.018), glutamine decreased the lHSP90α expression in sepsis but increased it in SIRS when given after HS (p = 0.003). Regarding cytokines, glutamine enhanced the LPS-induced MCP-1 at 48 h in healthy (p = 0.011), SIRS (p < 0.001), and sepsis (p = 0.006). In conclusion, glutamine at 10 mM, before or after LPS and HS, modulates mHSP90α and lHSP90α in sepsis and SIRS differently and unpredictably. Although it does not alter the stimulation effect on interleukins, glutamine enhances the LPS induction effect on supernatant MCP-1 in all groups. Future research should seek to elucidate better the impact of glutamine and temperature modulation on HSP90α and MCP-1 pathways in sepsis and trauma.

GSDMD-mediated NETosis promotes the development of acute respiratory distress syndrome

Gasdermin D (GSDMD) is a classical molecule involved in pyroptosis. It has been reported to be cleaved into N-terminal fragments to form pores in the neutrophil membrane and promote the release of neutrophil extracellular traps (NETs). However, it remains unclear if GSDMD is involved in neutrophil regulation and NET release during ARDS. The role of neutrophil GSDMD in the development of ARDS was investigated in a murine model of ARDS induced by lipopolysaccharide (LPS) using the neutrophil specific GSDMD-deficient mice. The neutrophil GSDMD cleavage and its relationship with NETosis were also explored in ARDS patients. The cleavage of GSDMD in neutrophils from ARDS patients and mice was upregulated. Inhibition of GSDMD by genetic knockout or inhibitors resulted in reduced production of NET both in vivo and in vitro, and attenuation of LPS-induced lung injury. Moreover, in vitro experiments showed that the inhibition of GSDMD attenuated endothelial injury co-cultured with neutrophils from ARDS patients, while extrinsic NETs reversed the protective effect of GSDMD inhibition. Collectively, our data suggest that the neutrophil GSDMD cleavage is crucial in NET release during ARDS. The NET release maintained by cleaved GSDMD in neutrophils may be a key event in the development of ARDS.

DJ-1 binds to Rubicon to Impair LC-3 Associated Phagocytosis

The ability to effectively clear infection is fundamental to host survival. Sepsis, defined as dysregulated host response to infection, is a heterogenous clinical syndrome that does not uniformly clear intact bacterial or sterile infection (i.e., lipopolysaccharide). These findings were further associated with increased survival in DJ-1 deficient animals exposed to intact bacteria relative to DJ-1 deficient challenged with lipopolysaccharide. We analyzed bacterial and lipopolysaccharide clearance in bone marrow macrophages (BMM) cultured ex vivo from wild-type and DJ-1 deficient mice. Importantly, we demonstrated that DJ-1 deficiency in BMM promotes Rubicon-dependent increase in L3C-associated phagocytosis, non-canonical autophagy pathway used for xenophagy, during bacterial but not lipopolysaccharide infection. In contrast to DJ-1 deficient BMM challenged with lipopolysaccharide, DJ-1 deficient BMM exposed to intact bacteria showed enhanced Rubicon complexing with Beclin-1 and UVRAG and consistently facilitated the assembly of complete autophagolysosomes that were decorated with LC3 molecules. Our data shows DJ-1 impairs or/and delays bacterial clearance and late autophagolysosome formation by binding to Rubicon resulting in Rubicon degradation, decreased L3C-associated phagocytosis, and decreased bacterial clearance in vitro and in vivo - implicating Rubicon and DJ-1 as critical regulators of bacterial clearance in experimental sepsis.

Automated in vivo compound screening with zebrafish and the discovery and validation of PD 81,723 as a novel angiogenesis inhibitor

Angiogenesis is a critical process in tumor progression. Inhibition of angiogenesis by blocking VEGF signaling can impair existing tumor vessels and halt tumor progression. However, the benefits are transient, and most patients who initially respond to these therapies develop resistance. Accordingly, there is a need for new anti-angiogenesis therapeutics to delay the processes of resistance or eliminate the resistive effects entirely. This manuscript presents the results of a screen of the National Institutes of Health Clinical Collections Libraries I & II (NIHCCLI&II) for novel angiogenesis inhibitors. The 727 compounds of the NIHCCLI&II library were screened with a high-throughput drug discovery platform (HTP) developed previously with angiogenesis-specific protocols utilizing zebrafish. The screen resulted in 14 hit compounds that were subsequently narrowed down to one, with PD 81,723 chosen as the lead compound. PD 81,723 was validated as an inhibitor of angiogenesis in vivo in zebrafish and in vitro in human umbilical vein endothelial cells (HUVECs). Zebrafish exposed to PD 81,723 exhibited several signs of a diminished endothelial network due to the inhibition of angiogenesis. Immunochemical analysis did not reveal any significant apoptotic or mitotic activity in the zebrafish. Assays with cultured HUVECs elucidated the ability of PD 81,723 to inhibit capillary tube formation, migration, and proliferation of endothelial cells. In addition, PD 81,723 did not induce apoptosis while significantly down regulating p21, AKT, VEGFR-2, p-VEGFR-2, eNOS, and p-eNOS, with no notable change in endogenous VEGF-A in cultured HUVECs.

Dysregulation of neutrophil death in sepsis

Sepsis is a prevalent disease that has alarmingly high mortality rates and, for several survivors, long-term morbidity. The modern definition of sepsis is an aberrant host response to infection followed by a life-threatening organ dysfunction. Sepsis has a complicated pathophysiology and involves multiple immune and non-immune mediators. It is now believed that in the initial stages of sepsis, excessive immune system activation and cascading inflammation are usually accompanied by immunosuppression. During the pathophysiology of severe sepsis, neutrophils are crucial. Recent researches have demonstrated a clear link between the process of neutrophil cell death and the emergence of organ dysfunction in sepsis. During sepsis, spontaneous apoptosis of neutrophils is inhibited and neutrophils may undergo some other types of cell death. In this review, we describe various types of neutrophil cell death, including necrosis, apoptosis, necroptosis, pyroptosis, NETosis, and autophagy, to reveal their known effects in the development and progression of sepsis. However, the exact role and mechanisms of neutrophil cell death in sepsis have not been fully elucidated, and this remains a major challenge for future neutrophil research. We hope that this review will provide hints for researches regarding neutrophil cell death in sepsis and provide insights for clinical practitioners.

PD-L1 maintains neutrophil extracellular traps release by inhibiting neutrophil autophagy in endotoxin-induced lung injury

Programmed death ligand 1 (PD-L1) is not only an important molecule in mediating tumor immune escape, but also regulates inflammation development. Here we showed that PD-L1 was upregulated on neutrophils in lipopolysaccharide (LPS)-induced acute respiratory distress syndrome (ARDS). Neutrophil specific knockout of PD-L1 reduced lung injury in ARDS model induced by intratracheal LPS injection. The level of NET release was reduced and autophagy is elevated by PD-L1 knockout in ARDS neutrophils both in vivo and in vitro. Inhibition of autophagy could reverse the inhibitory effect of PD-L1 knockout on NET release. PD-L1 interacted with p85 subunit of PI3K at the endoplasmic reticulum (ER) in neutrophils from ARDS patients, activating the PI3K/Akt/mTOR pathway. An extrinsic neutralizing antibody against PD-L1 showed a protective effect against ARDS. Together, PD-L1 maintains the release of NETs by regulating autophagy through the PI3K/Akt/mTOR pathway in ARDS. Anti-PD-L1 therapy may be a promising measure in treating ARDS.

Salvianolic Acid A Protects against Lipopolysaccharide-Induced Acute Lung Injury by Inhibiting Neutrophil NETosis

Salvianolic acid A (SAA) is one of bioactive polyphenol extracted from a Salvia miltiorrhiza (Danshen), which was widely used to treat cardiovascular disease in traditional Chinese medicine. SAA has been reported to be protective in cardiovascular disease and ischemia injury, with anti-inflammatory and antioxidative effect, but its role in acute lung injury (ALI) is still unknown. In this study, we sought to investigate the therapeutic effects of SAA in a murine model of lipopolysaccharide- (LPS-) induced ALI. The optimal dose of SAA was determined by comparing the attenuation of lung injury score after administration of SAA at three different doses (low, 5 mg/kg; medium, 10 mg/kg; and, high 15 mg/kg). Dexamethasone (DEX) was used as a positive control for SAA. Here, we showed that the therapeutic effect of SAA (10 mg/kg) against LPS-induced pathologic injury in the lungs was comparable to DEX. SAA and DEX attenuated the increased W/D ratio and the protein level, counts of total cells and neutrophils, and cytokine levels in the BALF of ALI mice similarly. The oxidative stress was also relieved by SAA and DEX according to the superoxide dismutase and malondialdehyde. NET level in the lungs was elevated in the injured lung while SAA and DEX reduced it significantly. LPS induced phosphorylation of Src, Raf, MEK, and ERK in the lungs, which was inhibited by SAA and DEX. NET level and phosphorylation level of Src/Raf/MEK/ERK pathway in the neutrophils from acute respiratory distress syndrome (ARDS) patients were also inhibited by SAA and DEX in vitro, but the YEEI peptide reversed the protective effect of SAA completely. The inhibition of NET release by SAA was also reversed by YEEI peptide in LPS-challenged neutrophils from healthy volunteers. Our data demonstrated that SAA ameliorated ALI via attenuating inflammation, oxidative stress, and neutrophil NETosis. The mechanism of such protective effect might involve the inhibition of Src activation.

The Potential of Hsp90 in Targeting Pathological Pathways in Cardiac Diseases

Heat shock protein 90 (Hsp90) is a molecular chaperone that interacts with up to 10% of the proteome. The extensive involvement in protein folding and regulation of protein stability within cells makes Hsp90 an attractive therapeutic target to correct multiple dysfunctions. Many of the clients of Hsp90 are found in pathways known to be pathogenic in the heart, ranging from transforming growth factor β (TGF-β) and mitogen activated kinase (MAPK) signaling to tumor necrosis factor α (TNFα), G_s and G_q g-protein coupled receptor (GPCR) and calcium (Ca²⁺) signaling. These pathways can therefore be targeted through modulation of Hsp90 activity. The activity of Hsp90 can be targeted through small-molecule inhibition. Small-molecule inhibitors of Hsp90 have been found to be cardiotoxic in some cases however. In this regard, specific targeting of Hsp90 by modulation of post-translational modifications (PTMs) emerges as an attractive strategy. In this review, we aim to address how Hsp90 functions, where Hsp90 interacts within pathological pathways, and current knowledge of small molecules and PTMs known to modulate Hsp90 activity and their potential as therapeutics in cardiac diseases.

Cytoprotective Mechanisms of DJ-1: Implications in Cardiac Pathophysiology

DJ-1 was originally identified as an oncogene product while mutations of the gene encoding DJ-1/PARK7 were later associated with a recessive form of Parkinson's disease. Its ubiquitous expression and diversity of function suggest that DJ-1 is also involved in mechanisms outside the central nervous system. In the last decade, the contribution of DJ-1 to the protection from ischemia-reperfusion injury has been recognized and its involvement in the pathophysiology of cardiovascular disease is attracting increasing attention. This review describes the current and gaps in our knowledge of DJ-1, focusing on its role in regulating cardiovascular function. In parallel, we present original data showing an association between increased DJ-1 expression and antiapoptotic and anti-inflammatory markers following cardiac and vascular surgical procedures. Future studies should address DJ-1's role as a plausible novel therapeutic target for cardiovascular disease.

Upregulated PD-L1 delays human neutrophil apoptosis and promotes lung injury in an experimental animal model of sepsis

PD-L1 is a ligand for PD-1 and its expression has been shown to be upregulated in neutrophils harvested from septic patients. However, the effect of PD-L1 on neutrophil survival and sepsis-induced lung injury remains largely unknown. Here we show PD-L1 expression negatively correlates with rates of apoptosis in human neutrophils harvested from patients with sepsis. Using co-immunoprecipitation assays on control neutrophils challenged with IFN-γ and LPS, we show PD-L1 complexes with the p85 subunit of PI3-K to activate AKT-dependent survival signaling. Conditional CRE/LoxP deletion of neutrophil PD-L1 in vivo further protected against lung injury and reduced neutrophil lung infiltration in a cecal ligation and puncture (CLP) experimental sepsis animal model. Compared to wild-type animals, PD-L1-deficient animals presented lower plasma levels of plasma TNF-α and IL-6 and higher IL-10 following CLP, and reduced seven-day mortality in CLP PD-L1 knockout animals. Taken together, our data suggest that increased PD-L1 expression on human neutrophils delays cellular apoptosis by triggering PI-3K-dependent AKT phosphorylation to drive lung injury and increase mortality during clinical and experimental sepsis.

HSP90 inhibitor NVP-BEP800 affects stability of SRC kinases and growth of T-cell and B-cell acute lymphoblastic leukemias

T-cell and B-cell acute lymphoblastic leukemias (T-ALL, B-ALL) are aggressive hematological malignancies characterized by an accumulation of immature T- or B-cells. Although patient outcomes have improved, novel targeted therapies are needed to reduce the intensity of chemotherapy and improve the prognosis of high-risk patients. Using cell lines, primary cells and patient-derived xenograft (PDX) models, we demonstrate that ALL cells viability is sensitive to NVP-BEP800, an ATP-competitive inhibitor of Heat shock protein 90 (HSP90). Furthermore, we reveal that lymphocyte-specific SRC family kinases (SFK) are important clients of the HSP90 chaperone in ALL. When PDX mice are treated with NVP-BEP800, we found that there is a decrease in ALL progression. Together, these results demonstrate that the chaperoning of SFK by HSP90 is involved in the growth of ALL. These novel findings provide an alternative approach to target SRC kinases and could be used for the development of new treatment strategies for ALL.

Characterization of the interactome of c-Src within the mitochondrial matrix by proximity-dependent biotin identification

C-Src kinase is localized in several subcellular compartments, including mitochondria where it is involved in the regulation of organelle functions and overall metabolism. Surprisingly, the characterization of the intramitochondrial Src interactome has never been fully determined. Using in vitro proximity-dependent biotin identification (BioID) coupled to mass spectrometry, we identified 51 candidate proteins that may interact directly or indirectly with c-Src within the mitochondrial matrix. Pathway analysis suggests that these proteins are involved in a large array of mitochondrial functions such as protein folding and import, mitochondrial organization and transport, oxidative phosphorylation, tricarboxylic acid cycle and metabolism of amino and fatty acids. Among these proteins, we identified 24 tyrosine phosphorylation sites in 17 mitochondrial proteins (AKAP1, VDAC1, VDAC2, VDAC3, LonP1, Hsp90, SLP2, PHB2, MIC60, UBA1, EF-Tu, LRPPRC, ACO2, OAT, ACAT1, ETFβ and ATP5β) as potential substrates for intramitochondrial Src using in silico prediction of tyrosine phospho-sites. Interaction of c-Src with SLP2 and ATP5β was confirmed using coimmunoprecipitation. This study suggests that the intramitochondrial Src could target several proteins and regulate different mitochondrial functions.

Toll-Like Receptors, Associated Biochemical Signaling Networks, and S100 Ligands

ABSTRACT

Host cells recognize molecules that signal danger using pattern recognition receptors (PRRs). Toll-like receptors (TLRs) are the most studied class of PRRs and detect pathogen-associated molecular patterns and danger-associated molecular patterns. Cellular TLR activation and signal transduction can therefore contain, combat, and clear danger by enabling appropriate gene transcription. Here, we review the expression, regulation, and function of different TLRs, with an emphasis on TLR-4, and how TLR adaptor protein binding directs intracellular signaling resulting in activation or termination of an innate immune response. Finally, we highlight the recent progress of research on the involvement of S100 proteins as ligands for TLR-4 in inflammatory disease.

Circulating Ligands of the Receptor for Advanced Glycation End Products and the Soluble Form of the Receptor Modulate Cardiovascular Cell Apoptosis in Diabetes

We determined whether plasma concentrations of the receptor for advanced glycation end products (RAGE) and the soluble (s) form of RAGE (sRAGE) in healthy individuals and patients with type 2 diabetes (T2D) modulate vascular remodeling. Healthy individuals and patients with T2D were divided into two age groups: young = <35 years old or middle-aged (36-64 years old) and stratified based on normal glucose tolerance (NGT), impaired (IGT), and T2D. Plasma titers of sRAGE, the RAGE ligands, AGEs, S100B, S100A1, S100A6, and the apoptotic marker Fas ligand Fas(L) were measured by enzyme-linked immunosorbent assay (ELISA). The apoptotic potential of the above RAGE ligands and sRAGE were assessed in cultured adult rat aortic smooth muscle cells (ASMC). In NGT individuals, aging increased the circulating levels of AGEs and S100B and decreased sRAGE, S100A1 and S100A6. Middle-aged patients with T2D presented higher levels of circulating S100B, AGEs and FasL, but lower levels of sRAGE, S100A1 and S100A6 than individuals with NGT or IGT. Treatment of ASMC with either AGEs or S100B at concentrations detected in T2D patients increased markers of inflammation and apoptosis. Responses attenuated by concomitant administration of sRAGE. In middle-aged patients with T2D, lower circulating plasma levels of sRAGE may limit decoy and exogenous trapping of deleterious pro-apoptotic/pro-inflammatory RAGE ligands AGEs and S100B, increasing the risk for diabetic complications.

Exosomes in Sepsis

Sepsis is a severe state of infection with high mortality. Pathogen-associated molecular patterns and damage-associated molecular patterns (DAMPs) initiate dysregulated systemic inflammation upon binding to pattern recognition receptors. Exosomes are endosome-derived vesicles, which carry proteins, lipids and nucleic acids, and facilitate intercellular communications. Studies have shown altered contents and function of exosomes during sepsis. In sepsis, exosomes carry increased levels of cytokines and DAMPs to induce inflammation. Exosomal DAMPs include, but are not limited to, high mobility group box 1, heat shock proteins, histones, adenosine triphosphate, and extracellular RNA. Exosomes released during sepsis have impact on multiple organs, including the lungs, kidneys, liver, cardiovascular system, and central nervous system. Here, we review the mechanisms of inflammation caused by exosomes, and their contribution to multiple organ dysfunction in sepsis.