Anthracyclines induce DNA damage response-mediated protection against severe sepsis

The interplay between probiotics and host autophagy: mechanisms of action and emerging insights

Autophagy, a lysosome-dependent protein degradation mechanism, is a highly conserved catabolic process seen in all eukaryotes. This cell protection system, which is present in all tissues and functions at a basic level, can be up- or downregulated in response to various stresses. A disruption in the natural route of the autophagy process is frequently followed by an interruption in the inherent operation of the body's cells and organs. Probiotics are live bacteria that protect the host through various mechanisms. One of the processes through which probiotics exert their beneficial effects on various cells and tissues is autophagy. Autophagy can assist in maintaining host homeostasis by stimulating the immune system and affecting numerous physiological and pathological responses. In this review, we particularly focus on autophagy impairments occurring in several human illnesses and investigate how probiotics affect the autophagy process under various circumstances.Abbreviation: AD: Alzheimer disease; AKT: AKT serine/threonine kinase; AMPK: 5'AMP-activated protein kinase; ATG: autophagy related; CCl4: carbon tetrachloride; CFS: cell-free supernatant; CMA: chaperone-mediated autophagy; CRC: colorectal cancer; EPS: L. plantarum H31 exopolysaccharide; HD: Huntington disease; HFD: high-fat diet; HPV: human papillomavirus; IFNG/IFN-γ: interferon gamma; IL6: interleukin 6; LGG: L. rhamnosus GG; LPS: lipopolysaccharide; MTOR: mechanistic target of rapamycin kinase; MTORC1: MTOR complex 1; NAFLD: non-alcoholic fatty liver disease; NASH: non-alcoholic steatohepatitis; PD: Parkinson disease; Pg3G: pelargonidin-3-O-glucoside; PI3K: phosphoinositide 3-kinase; PolyQ: polyglutamine; ROS: reactive oxygen species; SCFAs: short-chain fatty acids; SLAB51: a novel formulation of lactic acid bacteria and bifidobacteria; Slp: surface layer protein (of acidophilus NCFM); SNCA: synuclein alpha; ULK1: unc-51 like autophagy-activating kinase 1; YB: B. longum subsp. infantis YB0411; YFP: yeast fermentate prebiotic.

ATM in immunobiology: From lymphocyte development to cancer immunotherapy

Ataxia Telangiectasia Mutated (ATM) is a protein kinase traditionally known for its role in DNA damage response and cell cycle regulation. However, emerging research has revealed its multifaceted and crucial functions in the immune system. This comprehensive review explores the diverse roles of ATM in immune regulation, from lymphocyte development to its involvement in cancer immunotherapy. The review describes ATM's critical functions in V(D)J recombination and class switch recombination, highlighting its importance in adaptive immunity. It examines ATM's role in innate immunity, particularly in NF-κB signaling and cytokine production. Furthermore, the review analyzes the impact of ATM deficiency on oxidative stress and mitochondrial function in immune cells, providing insights into the immunological defects observed in Ataxia Telangiectasia (A-T). The article explores ATM's significance in maintaining hematopoietic stem cell function and its implications for bone marrow transplantation and gene therapy. Additionally, it addresses ATM's involvement in inflammation and immune senescence, linking DNA damage response to age-related immune decline. Finally, this review highlights the emerging role of ATM in cancer immunotherapy, where its inhibition shows promise in enhancing immune checkpoint blockade therapy. This review synthesizes current knowledge on ATM's functions in the immune system, offering insights into the pathophysiology of ATM-related disorders and potential therapeutic strategies for immune-related conditions and cancer immunotherapy.

Losmapimod ameliorates doxorubicin-induced cardiotoxicity through attenuating senescence and inflammatory pathways

Irreversible cardiotoxicity limits the clinical application of doxorubicin (DOX). DOX-induced cardiotoxicity has been associated with induction of senescence and activation of the p38 MAPK pathway. Losmapimod (LOSM), an orally active p38 MAPK inhibitor, is an anti-inflammatory agent with cardioprotective effects. Nevertheless, the effect of LOSM against DOX-induced cardiotoxicity has not been reported. In this study, we determined the effects of LOSM on DOX-induced chronic cardiotoxicity in C57BL/6 N mice. Five-week-old C57BL/6 N mice were fed diet containing LOSM (estimated daily intake 12 mg/kg/day) or a control diet for four days. Thereafter, mice were randomized to receive six weekly intraperitoneal injections of either DOX (4 mg/kg) or saline. Three days after the last injection, cardiac function was assessed by trans-thoracic echocardiography. Activation of p38, JNK, and ERK1/2 MAPKs were assessed by immunoblotting in the heart and liver. Gene expressions of senescence, inflammatory, oxidative stress, and mitochondrial function markers were quantified using real-time PCR and serum inflammatory markers were assessed by Luminex. Our results demonstrated that LOSM attenuated p38 MAPK activation, ameliorated DOX-induced cardiac dysfunction, and abrogated DOX-induced expression of the senescence marker p21Cip1. Additionally, LOSM demonstrated anti-inflammatory effects, with reduced cardiac Il-1α and Il-6 gene expression in DOX-treated mice. Systemic inflammation, assessed by serum cytokine levels, showed decreased IL-6 and CXCL1 in both DOX-treated mice and mice on LOSM diet. LOSM significantly increased mitofusin2 gene expression, which may enhance mitochondrial fusion. These findings underscore the potential therapeutic efficacy of p38 MAPK inhibition, exemplified by LOSM, in ameliorating DOX-induced cardiotoxicity, senescence, and inflammation.

The cytochrome P4501A1 (CYP1A1) inhibitor bergamottin enhances host tolerance to multidrug-resistant Vibrio vulnificus infection

PURPOSE

Vibrio vulnificus (V. Vulnificus) infection is characterized by rapid onset, aggressive progression, and challenging treatment. Bacterial resistance poses a significant challenge for clinical anti-infection treatment and is thus the subject of research. Enhancing host infection tolerance represents a novel infection prevention strategy to improve patient survival. Our team initially identified cytochrome P4501A1 (CYP1A1) as an important target owing to its negative modulation of the body's infection tolerance. This study explored the superior effects of the CYP1A1 inhibitor bergamottin compared to antibiotic combination therapy on the survival of mice infected with multidrug-resistant V. Vulnificus and the protection of their vital organs.

METHODS

An increasing concentration gradient method was used to induce multidrug-resistant V. Vulnificus development. We established a lethal infection model in C57BL/6J male mice and evaluated the effect of bergamottin on mouse survival. A mild infection model was established in C57BL/6J male mice, and the serum levels of creatinine, urea nitrogen, aspartate aminotransferase, and alanine aminotransferase were determined using enzyme-linked immunosorbent assay to evaluate the effect of bergamottin on liver and kidney function. The morphological changes induced in the presence of bergamottin in mouse organs were evaluated by hematoxylin and eosin staining of liver and kidney tissues. The bacterial growth curve and organ load determination were used to evaluate whether bergamottin has a direct antibacterial effect on multidrug-resistant V. Vulnificus. Quantification of inflammatory factors in serum by enzyme-linked immunosorbent assay and the expression levels of inflammatory factors in liver and kidney tissues by real-time quantitative polymerase chain reaction were performed to evaluate the effect of bergamottin on inflammatory factor levels. Western blot analysis of IκBα, phosphorylated IκBα, p65, and phosphorylated p65 protein expression in liver and kidney tissues and in human hepatocellular carcinomas-2 and human kidney-2 cell lines was used to evaluate the effect of bergamottin on the nuclear factor kappa-B signaling pathway. One-way ANOVA and Kaplan-Meier analysis were used for statistical analysis.

RESULTS

In mice infected with multidrug-resistant V. Vulnificus, bergamottin prolonged survival (p = 0.014), reduced the serum creatinine (p = 0.002), urea nitrogen (p = 0.030), aspartate aminotransferase (p = 0.029), and alanine aminotransferase (p = 0.003) levels, and protected the cellular morphology of liver and kidney tissues. Bergamottin inhibited interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α expression in serum (IL-1β: p = 0.010, IL-6: p = 0.029, TNF-α: p = 0.025) and inhibited the protein expression of the inflammatory factors IL-1β, IL-6, TNF-α in liver (IL-1β: p = 0.010, IL-6: p = 0.011, TNF-α: p = 0.037) and kidney (IL-1β: p = 0.016, IL-6: p = 0.011, TNF-α: p = 0.008) tissues. Bergamottin did not affect the proliferation of multidrug-resistant V. Vulnificus or the bacterial load in the mouse peritoneal lavage fluid (p = 0.225), liver (p = 0.186), or kidney (p = 0.637).

CONCLUSION

Bergamottin enhances the tolerance of mice to multidrug-resistant V. Vulnificus infection. This study can serve as a reference and guide the development of novel clinical treatment strategies for V. Vulnificus.

Immunomodulatory Effects and Protection in Sepsis by the Antibiotic Moxifloxacin

Sepsis is a leading cause of death in Intensive Care Units. Despite its prevalence, sepsis remains insufficiently understood, with no substantial qualitative improvements in its treatment in the past decades. Immunomodulatory agents may hold promise, given the significance of TNF-α and IL-1β as sepsis mediators. This study examines the immunomodulatory effects of moxifloxacin, a fluoroquinolone utilized in clinical practice. THP1 cells were treated in vitro with either PBS or moxifloxacin and subsequently challenged with lipopolysaccharide (LPS) or E. coli. C57BL/6 mice received intraperitoneal injections of LPS or underwent cecal ligation and puncture (CLP), followed by treatment with PBS, moxifloxacin, meropenem or epirubicin. Atm-/- mice underwent CLP and were treated with either PBS or moxifloxacin. Cytokine and organ lesion markers were quantified via ELISA, colony-forming units were assessed from mouse blood samples, and DNA damage was evaluated using a comet assay. Moxifloxacin inhibits the secretion of TNF-α and IL-1β in THP1 cells stimulated with LPS or E. coli. Intraperitoneal administration of moxifloxacin significantly increased the survival rate of mice with severe sepsis by 80% (p < 0.001), significantly reducing the plasma levels of cytokines and organ lesion markers. Notably, moxifloxacin exhibited no DNA damage in the comet assay, and Atm-/- mice were similarly protected following CLP, boasting an overall survival rate of 60% compared to their PBS-treated counterparts (p = 0.003). Moxifloxacin is an immunomodulatory agent, reducing TNF-α and IL-1β levels in immune cells stimulated with LPS and E. coli. Furthermore, moxifloxacin is also protective in an animal model of sepsis, leading to a significant reduction in cytokines and organ lesion markers. These effects appear unrelated to its antimicrobial activity or induction of DNA damage.

Physiologic disruption and metabolic reprogramming in infection and sepsis

Effective responses against severe systemic infection require coordination between two complementary defense strategies that minimize the negative impact of infection on the host: resistance, aimed at pathogen elimination, and disease tolerance, which limits tissue damage and preserves organ function. Resistance and disease tolerance mostly rely on divergent metabolic programs that may not operate simultaneously in time and space. Due to evolutionary reasons, the host initially prioritizes the elimination of the pathogen, leading to dominant resistance mechanisms at the potential expense of disease tolerance, which can contribute to organ failure. Here, we summarize our current understanding of the role of physiological perturbations resulting from infection in immune response dynamics and the metabolic program requirements associated with resistance and disease tolerance mechanisms. We then discuss how insight into the interplay of these mechanisms could inform future research aimed at improving sepsis outcomes and the potential for therapeutic interventions.

S1PR3 agonism and S1P lyase inhibition rescue mice in the severe state of experimental sepsis

Sepsis is characterized as life-threatening organ dysfunction caused by a dysregulated host response to an infection. Despite numerous clinical trials that addressed this syndrome, there is still no causative treatment available to dampen its severity. Curtailing the infection at an early stage with anti-infectives is the only effective treatment regime besides intensive care. In search for additional treatment options, we recently discovered the inhibition of the sphingosine 1-phosphate (S1P) lyase and subsequent activation of the S1P receptor type 3 (S1PR3) in pre-conditioning experiments as promising targets for sepsis prevention. Here, we demonstrate that treatment of septic mice with the direct S1P lyase inhibitor C31 or the S1PR3 agonist CYM5541 in the advanced phase of sepsis resulted in a significantly increased survival rate. A single dose of each compound led to a rapid decline of sepsis severity in treated mice and coincided with decreased cytokine release and increased lung barrier function with unaltered bacterial load. The survival benefit of both compounds was completely lost in S1PR3 deficient mice. Treatment of the murine macrophage cell line J774.1 with either C31 or CYM5541 resulted in decreased protein kinase B (Akt) and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) phosphorylation without alteration of the mitogen-activated protein kinase (MAPK) p38 and p44/42 phosphorylation. Thus, activation of S1PR3 in the acute phase of sepsis by direct agonism or S1P lyase inhibition dampened Akt and JNK phosphorylation, resulting in decreased cytokine release, improved lung barrier stability, rapid decline of sepsis severity and better survival in mice.

Epirubicin for the Treatment of Sepsis and Septic Shock (EPOS-1): study protocol for a randomised, placebo-controlled phase IIa dose-escalation trial

INTRODUCTION

Sepsis remains the major cause of death among hospitalised patients in intensive care. While targeting sepsis-causing pathogens with source control or antimicrobials has had a dramatic impact on morbidity and mortality of sepsis patients, this strategy remains insufficient for about one-third of the affected individuals who succumb. Pharmacological targeting of mechanisms that reduce sepsis-defining organ dysfunction may be beneficial. When given at low doses, the anthracycline epirubicin promotes tissue damage control and lessens the severity of sepsis independently of the host-pathogen load by conferring disease tolerance to infection. Since epirubicin at higher doses can be myelotoxic, a first dose-response trial is necessary to assess the potential harm of this drug in this new indication.

METHODS AND ANALYSIS

Epirubicin for the Treatment of Sepsis and Septic Shock-1 is a randomised, double-blind, placebo-controlled phase 2 dose-escalation phase IIa clinical trial to assess the safety of epirubicin as an adjunctive in patients with sepsis. The primary endpoint is the 14-day myelotoxicity. Secondary and explorative outcomes include 30-day and 90-day mortality, organ dysfunction, pharmacokinetic/pharmacodynamic (PK/PD) and cytokine release. Patients will be randomised in three consecutive phases. For each study phase, patients are randomised to one of the two study arms (epirubicin or placebo) in a 4:1 ratio. Approximately 45 patients will be recruited. Patients in the epirubicin group will receive a single dose of epirubicin (3.75, 7.5 or 15 mg/m2 depending on the study phase. After each study phase, a data and safety monitoring board will recommend continuation or premature stopping of the trial. The primary analyses for each dose level will report the proportion of myelotoxicity together with a 95% CI. A potential dose-toxicity association will be analysed using a logistic regression model with dose as a covariate. All further analyses will be descriptive.

ETHICS AND DISSEMINATION

The protocol is approved by the German Federal Institute for Drugs and Medical Devices. The results will be submitted for publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT05033808.

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.

PMI-controlled mannose metabolism and glycosylation determines tissue tolerance and virus fitness

Host survival depends on the elimination of virus and mitigation of tissue damage. Herein, we report the modulation of D-mannose flux rewires the virus-triggered immunometabolic response cascade and reduces tissue damage. Safe and inexpensive D-mannose can compete with glucose for the same transporter and hexokinase. Such competitions suppress glycolysis, reduce mitochondrial reactive-oxygen-species and succinate-mediated hypoxia-inducible factor-1α, and thus reduce virus-induced proinflammatory cytokine production. The combinatorial treatment by D-mannose and antiviral monotherapy exhibits in vivo synergy despite delayed antiviral treatment in mouse model of virus infections. Phosphomannose isomerase (PMI) knockout cells are viable, whereas addition of D-mannose to the PMI knockout cells blocks cell proliferation, indicating that PMI activity determines the beneficial effect of D-mannose. PMI inhibition suppress a panel of virus replication via affecting host and viral surface protein glycosylation. However, D-mannose does not suppress PMI activity or virus fitness. Taken together, PMI-centered therapeutic strategy clears virus infection while D-mannose treatment reprograms glycolysis for control of collateral damage.

Prognostic stratification of sepsis through DNA damage response based RiskScore system: insights from single-cell RNA-sequencing and transcriptomic profiling

Background

A novel risk scoring system, predicated on DNA damage response (DDR), was developed to enhance prognostic predictions and potentially inform the creation of more effective therapeutic protocols for sepsis.

Methods

To thoroughly delineate the expression profiles of DDR markers within the context of sepsis, an analytical approach utilizing single-cell RNA-sequencing (scRNA-seq) was implemented. Our study utilized single-cell analysis techniques alongside weighted gene co-expression network analysis (WGCNA) to pinpoint the genes that exhibit the most substantial associations with DNA damage response (DDR). Through Cox proportional hazards LASSO regression, we distinguished DDR-associated genes and established a risk model, enabling the stratification of patients into high- and low-risk groups. Subsequently, we carried out an analysis to determine our model's predictive accuracy regarding patient survival. Moreover, we examined the distinct biological characteristics, various signal transduction routes, and immune system responses in sepsis patients, considering different risk categories and outcomes related to survival. Lastly, we conducted experimental validation of the identified genes through in vivo and in vitro assays, employing RT-PCR, ELISA, and flow cytometry.

Results

Both single-cell RNA sequencing (scRNA-seq) and bulk transcriptomic analyses have demonstrated a strong correlation between DNA damage response (DDR) levels and sepsis prognosis. Specific cell subtypes, including monocytes, megakaryocytes, CD4+ T cells, and neutrophils, have shown elevated DDR activity. Cells with increased DDR scores exhibited more robust and numerous interactions with other cell populations. The weighted gene co-expression network analysis (WGCNA) and single-cell analyses revealed 71 DDR-associated genes. We developed a four-gene risk scoring system using ARL4C, CD247, RPL7, and RPL31, identified through univariate COX, LASSO COX regression, and log-rank (Mantel-Cox) tests. Nomograms, calibration plots, and decision curve analyses (DCA) regarding these specific genes have provided significant clinical benefits for individuals diagnosed with sepsis. The study suggested that individuals categorized as lower-risk demonstrated enhanced infiltration of immune cells, upregulated expression of immune regulators, and a more prolific presence of immune-associated functionalities and pathways. RT-qPCR analyses on a sepsis rat model revealed differential gene expression predominantly in the four targeted genes. Furthermore, ARL4C knockdown in sepsis model in vivo and vitro caused increased inflammatory response and a worse prognosis.

Conclusion

The delineated DDR expression landscape offers insights into sepsis pathogenesis, whilst our riskScore model, based on a robust four-gene signature, could underpin personalized sepsis treatment strategies.

Targeting the host response in sepsis: current approaches and future evidence

Sepsis, a dysregulated host response to infection characterized by organ failure, is one of the leading causes of death worldwide. Disbalances of the immune response play an important role in its pathophysiology. Patients may develop simultaneously or concomitantly states of systemic or local hyperinflammation and immunosuppression. Although a variety of effective immunomodulatory treatments are generally available, attempts to inhibit or stimulate the immune system in sepsis have failed so far to improve patients' outcome. The underlying reason is likely multifaceted including failure to identify responders to a specific immune intervention and the complex pathophysiology of organ dysfunction that is not exclusively caused by immunopathology but also includes dysfunction of the coagulation system, parenchymal organs, and the endothelium. Increasing evidence suggests that stratification of the heterogeneous population of septic patients with consideration of their host response might led to treatments that are more effective. The purpose of this review is to provide an overview of current studies aimed at optimizing the many facets of host response and to discuss future perspectives for precision medicine approaches in sepsis.

Update on persistent acute kidney injury in critical illnesses

Acute kidney injury (AKI) affects about half of patients admitted to the intensive care unit (ICU), and worsens their short- and long-term outcomes. Apparently self-limiting AKI episodes initiate a progression toward chronic kidney disease (CKD) through cellular and molecular mechanisms that are yet to be explained. In particular, persistent AKI, defined in 2016 by the Acute Dialysis Quality Initiative as an AKI which lasts more than 48 h from its onset, has been correlated with higher morbidity and mortality, and with a higher progression to acute kidney disease (AKD) and CKD than transient AKI (i.e. AKI with a reversal within 48 h). This classification has been also used in the setting of solid organ transplantation, demonstrating similar outcomes. Due to its incidence and poor prognosis and because prompt interventions seem to change its course, persistent AKI should be recognized early and followed-up also after its recovery. However, while AKI and CKD are well-described syndromes, persistent AKI and AKD are relatively new entities. The purpose of this review is to highlight the key phases of persistent AKI in ICU patients in terms of both clinical and mechanistic features in order to offer to clinicians and researchers an updated basis from which to start improving patients' care and direct future research.

ATAXIA TELANGIECTASIA MUTATED PROTECTS AGAINST LIPOPOLYSACCARIDE-INDUCED BLOOD-BRAIN BARRIER DISRUPTION BY REGULATING ATK/DRP1-MEDIATED MITOCHONDRIAL HOMEOSTASIS

ABSTRACT

Background: Protein kinase ataxia telangiectasia mutated (ATM) regulates the function of endothelial cells and responds quickly to endotoxin. However, the function of ATM in lipopolysaccharide (LPS)-induced blood-brain barrier (BBB) disruption remains unknown. This study aimed to investigate the role and underlying mechanism of ATM in the regulation of the BBB function in sepsis. Methods: We used LPS to induce BBB disruption in vivo and to establish an in vitro model of cerebrovascular endothelial cells. Blood-brain barrier disruption was assessed by measuring Evans blue leakage and expression of vascular permeability regulators. To investigate the role of ATM, its inhibitor AZD1390 and clinically approved doxorubicin, an anthracycline that can activate ATM, were administered as scheduled. To explore the underlying mechanism, protein kinase B (AKT) inhibitor MK-2206 was administered to block the AKT/dynamin-related protein 1 (DRP1) pathway. Results: Lipopolysaccharide challenge induced significant BBB disruption, ATM activation, and mitochondrial translocation. Inhibiting ATM with AZD1390 aggravated BBB permeability as well as the following neuroinflammation and neuronal injury, while activation of ATM by doxorubicin abrogated these defects. Further results obtained in brain microvascular endothelial cells showed that ATM inhibition reduced the phosphorylation of DRP1 at serine (S) 637, promoted excessive mitochondrial fission, and resulted in mitochondrial malfunction. By activating ATM, doxorubicin increased the protein binding between ATM and AKT and promoted the phosphorylated activation of AKT at S473, which could directly phosphorylate DRP1 at S637 to repress excessive mitochondrial fission. Consistently, the protective role of ATM was abolished by the AKT inhibitor MK-2206. Conclusions: Ataxia telangiectasia mutated protects against LPS-induced BBB disruption by regulating mitochondrial homeostasis, at least in part, through the AKT/DRP1 pathway.

Pharmacological modulators of epithelial immunity uncovered by synthetic genetic tracing of SARS-CoV-2 infection responses

Epithelial immune responses govern tissue homeostasis and offer drug targets against maladaptation. Here, we report a framework to generate drug discovery-ready reporters of cellular responses to viral infection. We reverse-engineered epithelial cell responses to SARS-CoV-2, the viral agent fueling the ongoing COVID-19 pandemic, and designed synthetic transcriptional reporters whose molecular logic comprises interferon-α/β/γ and NF-κB pathways. Such regulatory potential reflected single-cell data from experimental models to severe COVID-19 patient epithelial cells infected by SARS-CoV-2. SARS-CoV-2, type I interferons, and RIG-I drive reporter activation. Live-cell image-based phenotypic drug screens identified JAK inhibitors and DNA damage inducers as antagonistic modulators of epithelial cell response to interferons, RIG-I stimulation, and SARS-CoV-2. Synergistic or antagonistic modulation of the reporter by drugs underscored their mechanism of action and convergence on endogenous transcriptional programs. Our study describes a tool for dissecting antiviral responses to infection and sterile cues and rapidly discovering rational drug combinations for emerging viruses of concern.

Starvation Protects Hepatocytes from Inflammatory Damage through Paradoxical mTORC1 Signaling

Background and aims: Sepsis-related liver failure is associated with a particularly unfavorable clinical outcome. Calorie restriction is a well-established factor that can increase tissue resilience, protect against liver failure and improve outcome in preclinical models of bacterial sepsis. However, the underlying molecular basis is difficult to investigate in animal studies and remains largely unknown.

METHODS

We have used an immortalized hepatocyte line as a model of the liver parenchyma to uncover the role of caloric restriction in the resilience of hepatocytes to inflammatory cell damage. In addition, we applied genetic and pharmacological approaches to investigate the contribution of the three major intracellular nutrient/energy sensor systems, AMPK, mTORC1 and mTORC2, in this context.

RESULTS

We demonstrate that starvation reliably protects hepatocytes from cellular damage caused by pro-inflammatory cytokines. While the major nutrient- and energy-related signaling pathways AMPK, mTORC2/Akt and mTORC1 responded to caloric restriction as expected, mTORC1 was paradoxically activated by inflammatory stress in starved, energy-deprived hepatocytes. Pharmacological inhibition of mTORC1 or genetic silencing of the mTORC1 scaffold Raptor, but not its mTORC2 counterpart Rictor, abrogated the protective effect of starvation and exacerbated inflammation-induced cell death. Remarkably, mTORC1 activation in starved hepatocytes was uncoupled from the regulation of autophagy, but crucial for sustained protein synthesis in starved resistant cells.

CONCLUSIONS

AMPK engagement and paradoxical mTORC1 activation and signaling mediate protection against pro-inflammatory stress exerted by caloric restriction in hepatocytes.

PGLYRP1-mIgG2a-Fc inhibits macrophage activation via AKT/NF-κB signaling and protects against fatal lung injury during bacterial infection

Severe bacterial pneumonia leads to acute respiratory distress syndrome (ARDS), with a high incidence rate and mortality. It is well-known that continuous and dysregulated macrophage activation is vital for aggravating the progression of pneumonia. Here, we designed and produced an antibody-like molecule, peptidoglycan recognition protein 1-mIgG2a-Fc (PGLYRP1-Fc). PGLYRP1 was fused to the Fc region of mouse IgG2a with high binding to macrophages. We demonstrated that PGLYRP1-Fc ameliorated lung injury and inflammation in ARDS, without affecting bacterial clearance. Besides, PGLYRP1-Fc reduced AKT/nuclear factor kappa-B (NF-κB) activation via the Fc segment bound Fc gamma receptor (FcγR)-dependent mechanism, making macrophage unresponsive, and immediately suppressed proinflammatory response upon bacteria or lipopolysaccharide (LPS) stimulus in turn. These results confirm that PGLYRP1-Fc protects against ARDS by promoting host tolerance with reduced inflammatory response and tissue damage, irrespective of the host's pathogen burden, and provide a promising therapeutic strategy for bacterial infection.

Topoisomerases in Immune Cell Development and Function

DNA topoisomerases (TOPs) are complex enzymatic machines with extraordinary capacity to maintain DNA topology during torsion-intensive steps of replication and transcription. Recently, TOPs have gained significant attention for their tissue-specific function, and the vital role of TOPs in immune homeostasis and dysfunction is beginning to emerge. TOPs have been implicated in various immunological disorders such as autoimmunity, B cell immunodeficiencies, and sepsis, underscoring their importance in immune regulation. However, much remains unknown about immunological underpinnings of TOPs, and a deeper understanding of the role of TOPs in the immune system will be critical for yielding significant insights into the etiology of immunological disorders. In this review, we first discuss the recent literature highlighting the contribution of TOPs in the development of immune cells, and we further provide an overview of their importance in immune cell responses.

Research Progress on Autophagy Regulation by Active Ingredients of Traditional Chinese Medicine in the Treatment of Acute Lung Injury

Autophagy is a highly conserved process that maintains cell stability in eukaryotes, participates in the turnover of intracellular substances to maintain cell function, helps to resist pathogen invasion, and improves cell tolerance to environmental changes. Autophagy has been observed in many diseases, and the symptoms of these diseases are significantly improved by regulating autophagy. Autophagy is also involved in the development of lung diseases. Studies have shown that autophagy may play a beneficial or harmful role in acute lung injury (ALI), and ALI has been treated with traditional Chinese medicine designed to promote or inhibit autophagy. In this paper, the molecular mechanism and common pathways regulating autophagy and the relationship between autophagy and ALI are introduced, and the active ingredients of traditional Chinese medicine that improve ALI symptoms by regulating autophagy are summarized.

Disease tolerance: a protective mechanism of lung infections

Resistance and tolerance are two important strategies employed by the host immune response to defend against pathogens. Multidrug-resistant bacteria affect the resistance mechanisms involved in pathogen clearance. Disease tolerance, defined as the ability to reduce the negative impact of infection on the host, might be a new research direction for the treatment of infections. The lungs are highly susceptible to infections and thus are important for understanding host tolerance and its precise mechanisms. This review focuses on the factors that induce lung disease tolerance, cell and molecular mechanisms involved in tissue damage control, and the relationship between disease tolerance and sepsis immunoparalysis. Understanding the exact mechanism of lung disease tolerance could allow better assessment of the immune status of patients and provide new ideas for the treatment of infections.

Interactions of Autophagy and the Immune System in Health and Diseases

Autophagy is a highly conserved process that utilizes lysosomes to selectively degrade a variety of intracellular cargo, thus providing quality control over cellular components and maintaining cellular regulatory functions. Autophagy is triggered by multiple stimuli ranging from nutrient starvation to microbial infection. Autophagy extensively shapes and modulates the inflammatory response, the concerted action of immune cells, and secreted mediators aimed to eradicate a microbial infection or to heal sterile tissue damage. Here, we first review how autophagy affects innate immune signaling, cell-autonomous immune defense, and adaptive immunity. Then, we discuss the role of non-canonical autophagy in microbial infections and inflammation. Finally, we review how crosstalk between autophagy and inflammation influences infectious, metabolic, and autoimmune disorders.

Autophagy induced by taurolidine protects against polymicrobial sepsis by promoting both host resistance and disease tolerance

Disease resistance and tolerance are evolutionarily conserved yet distinct defense strategies that protect the host against microbial infection. Here, we report that taurolidine administered before the start of infection confers protection against polymicrobial sepsis by promoting resistance and tolerance. Notably, taurolidine given after the onset of infection also rescues mice from sepsis-associated lethality by enhancing disease tolerance to organ damage. This protection relies on an intact autophagy pathway, as taurolidine fails to protect autophagy-deficient mice against microbial sepsis. Specifically, taurolidine induces light chain 3-associated phagocytosis, but not xenophagy, in macrophages, resulting in an augmented bactericidal activity with enhanced cellular resistance to infection. These results highlight the importance of autophagy induction for taurolidine-augmented host resistance and disease tolerance and subsequent protection.

Sepsis, septic shock, and their sequelae are the leading causes of death in intensive care units, with limited therapeutic options. Disease resistance and tolerance are two evolutionarily conserved yet distinct defense strategies that protect the host against microbial infection. Here, we report that taurolidine administered at 6 h before septic challenge led to strong protection against polymicrobial sepsis by promoting both host resistance and disease tolerance characterized by accelerated bacterial clearance, ameliorated organ damage, and diminished vascular and gut permeability. Notably, taurolidine administered at 6 h after septic challenge also rescued mice from sepsis-associated lethality by enhancing disease tolerance to tissue and organ injury. Importantly, this in vivo protection afforded by taurolidine depends on an intact autophagy pathway, as taurolidine protected wild-type mice but was unable to rescue autophagy-deficient mice from microbial sepsis. In vitro, taurolidine induced light chain 3-associated phagocytosis in innate phagocytes and autophagy in vascular endothelium and gut epithelium, resulting in augmented bactericidal activity and enhanced cellular tolerance to endotoxin-induced damage in these cells. These results illustrate that taurolidine-induced autophagy augments both host resistance and disease tolerance to bacterial infection, thereby conferring protection against microbial sepsis.

Identification of Immune-Related Key Genes as Potential Diagnostic Biomarkers of Sepsis in Children

Objective

The pathogenesis of sepsis is still unclear due to its complexity, especially in children. This study aimed to analyse the immune microenvironment and regulatory networks related to sepsis in children at the molecular level and to identify key immune-related genes to provide a new basis for the early diagnosis of sepsis.

Methods

The GSE145227 and GSE26440 datasets were downloaded from the Gene Expression Omnibus. The analyses included differentially expressed genes (DEGs), functional enrichment, immune cell infiltration, the competing endogenous RNA (ceRNA) interaction network, weighted gene coexpression network analysis (WGCNA), protein–protein interaction (PPI) network, key gene screening, correlation of sepsis molecular subtypes/immune infiltration with key gene expression, the diagnostic capabilities of key genes, and networks describing the interaction of key genes with transcription factors and small-molecule compounds. Finally, real-time quantitative PCR (RT–qPCR) was performed to verify the expression of key genes.

Results

A total of 236 immune-related DEGs, most of which were enriched in immune-related biological functions, were found. Further analysis of immune cell infiltration showed that M0 macrophages and neutrophils infiltrated more in the sepsis group, while fewer activated memory CD4⁺ T cells, resting memory CD4⁺ T cells, and CD8⁺ T cells did. The interaction network of ceRNA was successfully constructed. Six key genes (FYN, FBL, ATM, WDR75, FOXO1 and ITK) were identified by WGCNA and PPI analysis. We found strong associations between key genes and constructed septic molecular subtypes or immune cell infiltration. Receiver operating characteristic analysis showed that the area under the curve values of the key genes for diagnosis were all greater than 0.84. Subsequently, we successfully constructed an interaction network of key genes and transcription factors/small-molecule compounds. Finally, the key genes in the samples were verified by RT–qPCR.

Conclusion

Our results offer new insights into the pathogenesis of sepsis in children and provide new potential diagnostic biomarkers for the disease.

Cancer-related accelerated ageing and biobehavioural modifiers: a framework for research and clinical care

A growing body of evidence indicates that patients with cancer who receive cytotoxic treatments (such as chemotherapy or radiotherapy) have an increased risk of accelerated physical and cognitive ageing. Furthermore, accelerated biological ageing is a suspected driving force behind many of these observed effects. In this Review, we describe the mechanisms of biological ageing and how they apply to patients with cancer. We highlight the important role of specific behavioural factors, namely stress, sleep and lifestyle-related factors such as physical activity, weight management, diet and substance use, in the accelerated ageing of patients with cancer and cancer survivors. We also present a framework of how modifiable behaviours could operate to either increase the risk of accelerated ageing, provide protection, or promote resilience at both the biological level and in terms of patient-reported outcomes.

DNA damage independent inhibition of NF-κB transcription by anthracyclines

Anthracyclines are among the most used and effective anticancer drugs. Their activity has been attributed to DNA double-strand breaks resulting from topoisomerase II poisoning and to eviction of histones from select sites in the genome. Here, we show that the extensively used anthracyclines Doxorubicin, Daunorubicin, and Epirubicin decrease the transcription of nuclear factor kappa B (NF-κB)-dependent gene targets, but not interferon-responsive genes in primary mouse (Mus musculus) macrophages. Using an NMR-based structural approach, we demonstrate that anthracyclines disturb the complexes formed between the NF-κB subunit RelA and its DNA-binding sites. The anthracycline variants Aclarubicin, Doxorubicinone, and the newly developed Dimethyl-doxorubicin, which share anticancer properties with the other anthracyclines but do not induce DNA damage, also suppressed inflammation, thus uncoupling DNA damage from the effects on inflammation. These findings have implications for anticancer therapy and for the development of novel anti-inflammatory drugs with limited side effects for life-threatening conditions such as sepsis.

Towards an ecological definition of sepsis: a viewpoint

In critically ill patients with sepsis, there is a grave lack of effective treatment options to address the illness-defining inappropriate host response. Currently, treatment is limited to source control and supportive care, albeit with imminent approval of immune modulating drugs for COVID-19-associated lung failure the potential of host-directed strategies appears on the horizon. We suggest expanding the concept of sepsis by incorporating infectious stress within the general stress response of the cell to define sepsis as an illness state characterized by allostatic overload and failing adaptive responses along with biotic (pathogen) and abiotic (e.g., malnutrition) environmental stress factors. This would allow conceptualizing the failing organismic responses to pathogens in sepsis with an ancient response pattern depending on the energy state of cells and organs towards other environmental stressors in general. Hence, the present review aims to decipher the heuristic value of a biological definition of sepsis as a failing stress response. These considerations may motivate a better understanding of the processes underlying "host defense failure" on the organismic, organ, cell and molecular levels.

Function and Molecular Mechanism of the DNA Damage Response in Immunity and Cancer Immunotherapy

The DNA damage response (DDR) is an organized network of multiple interwoven components evolved to repair damaged DNA and maintain genome fidelity. Conceptually the DDR includes damage sensors, transducer kinases, and effectors to maintain genomic stability and accurate transmission of genetic information. We have recently gained a substantially improved molecular and mechanistic understanding of how DDR components are interconnected to inflammatory and immune responses to stress. DDR shapes both innate and adaptive immune pathways: (i) in the context of innate immunity, DDR components mainly enhance cytosolic DNA sensing and its downstream STimulator of INterferon Genes (STING)-dependent signaling; (ii) in the context of adaptive immunity, the DDR is needed for the assembly and diversification of antigen receptor genes that is requisite for T and B lymphocyte development. Imbalances between DNA damage and repair impair tissue homeostasis and lead to replication and transcription stress, mutation accumulation, and even cell death. These impacts from DDR defects can then drive tumorigenesis, secretion of inflammatory cytokines, and aberrant immune responses. Yet, DDR deficiency or inhibition can also directly enhance innate immune responses. Furthermore, DDR defects plus the higher mutation load in tumor cells synergistically produce primarily tumor-specific neoantigens, which are powerfully targeted in cancer immunotherapy by employing immune checkpoint inhibitors to amplify immune responses. Thus, elucidating DDR-immune response interplay may provide critical connections for harnessing immunomodulatory effects plus targeted inhibition to improve efficacy of radiation and chemotherapies, of immune checkpoint blockade, and of combined therapeutic strategies.

miR-221-5p-Mediated Downregulation of JNK2 Aggravates Acute Lung Injury

Sepsis and acute lung injury (ALI) are linked to mitochondrial dysfunction; however, the underlying mechanism remains elusive. We previously reported that c-Jun N-terminal protein kinase 2 (JNK2) promotes stress-induced mitophagy by targeting small mitochondrial alternative reading frame (smARF) for ubiquitin-mediated proteasomal degradation, thereby preventing mitochondrial dysfunction and restraining inflammasome activation. Here we report that loss of JNK2 exacerbates lung inflammation and injury during sepsis and ALI in mice. JNK2 is downregulated in mice with endotoxic shock or ALI, concomitantly correlated inversely with disease severity. Small RNA sequencing revealed that miR-221-5p, which contains seed sequence matching to JNK2 mRNA 3’ untranslated region (3’UTR), is upregulated in response to lipopolysaccharide, with dynamically inverse correlation with JNK2 mRNA levels. miR-221-5p targets the 3’UTR of JNK2 mRNA leading to its downregulation. Accordingly, miR-221-5p exacerbates lung inflammation and injury during sepsis in mice by targeting JNK2. Importantly, in patients with pneumonia in medical intensive care unit, JNK2 mRNA levels in alveolar macrophages flow sorted from non-bronchoscopic broncholaveolar lavage (BAL) fluid were inversely correlated strongly and significantly with the percentage of neutrophils, neutrophil and white blood cell counts in BAL fluid. Our data suggest that miR-221-5p targets JNK2 and thereby aggravates lung inflammation and injury during sepsis.

Metabolic Reprogramming and Host Tolerance: A Novel Concept to Understand Sepsis-Associated AKI

Acute kidney injury (AKI) is a frequent complication of sepsis that increases mortality and the risk of progression to chronic kidney disease. However, the mechanisms leading to sepsis-associated AKI are still poorly understood. The recognition that sepsis induces organ dysfunction in the absence of overt necrosis or apoptosis has led to the consideration that tubular epithelial cells (TEC) may deploy defense mechanisms to survive the insult. This concept dovetails well with the notion that the defense against infection does not only depend on the capacity of the immune system to limit the microbial load (known as resistance), but also on the capacity of cells and tissues to limit tissue injury (known as tolerance). In this review, we discuss the importance of TEC metabolic reprogramming as a defense strategy during sepsis, and how this cellular response is likely to operate through a tolerance mechanism. We discuss the fundamental role of specific regulatory nodes and of mitochondria in orchestrating this response, and how this opens avenues for the exploration of targeted therapeutic strategies to prevent or treat sepsis-associated AKI.

Effective DNA damage response after acute but not chronic immune challenge: SARS-CoV-2 vaccine versus Systemic Lupus Erythematosus

Whether and how an acute immune challenge may affect DNA Damage Response (DDR) is unknown. By studying vaccinations against Influenza and SARS-CoV-2 (mRNA-based) we found acute increases of type-I interferon-inducible gene expression, oxidative stress and DNA damage accumulation in blood mononuclear cells of 9 healthy controls, coupled with effective anti-SARS-CoV-2 neutralizing antibody production in all. Increased DNA damage after SARS-CoV-2 vaccine, partly due to increased oxidative stress, was transient, whereas the inherent DNA repair capacity was found intact. In contrast, in 26 patients with Systemic Lupus Erythematosus, who served as controls in the context of chronic immune activation, we validated increased DNA damage accumulation, increased type-I interferon-inducible gene expression and induction of oxidative stress, however aberrant DDR was associated with deficiencies in nucleotide excision repair pathways. These results indicate that acute immune challenge can indeed activate DDR pathways, whereas, contrary to chronic immune challenge, successful repair of DNA lesions occurs.

Mechanisms of Ataxia Telangiectasia Mutated (ATM) Control in the DNA Damage Response to Oxidative Stress, Epigenetic Regulation, and Persistent Innate Immune Suppression Following Sepsis

Cells have evolved extensive signaling mechanisms to maintain redox homeostasis. While basal levels of oxidants are critical for normal signaling, a tipping point is reached when the level of oxidant species exceed cellular antioxidant capabilities. Myriad pathological conditions are characterized by elevated oxidative stress, which can cause alterations in cellular operations and damage to cellular components including nucleic acids. Maintenance of nuclear chromatin are critically important for host survival and eukaryotic organisms possess an elaborately orchestrated response to initiate repair of such DNA damage. Recent evidence indicates links between the cellular antioxidant response, the DNA damage response (DDR), and the epigenetic status of the cell under conditions of elevated oxidative stress. In this emerging model, the cellular response to excessive oxidants may include redox sensors that regulate both the DDR and an orchestrated change to the epigenome in a tightly controlled program that both protects and regulates the nuclear genome. Herein we use sepsis as a model of an inflammatory pathophysiological condition that results in elevated oxidative stress, upregulation of the DDR, and epigenetic reprogramming of hematopoietic stem cells (HSCs) to discuss new evidence for interplay between the antioxidant response, the DNA damage response, and epigenetic status.

Influence of the microenvironment on modulation of the host response by typhoid toxin

Bacterial genotoxins cause DNA damage in eukaryotic cells, resulting in activation of the DNA damage response (DDR) in vitro. These toxins are produced by Gram-negative bacteria, enriched in the microbiota of inflammatory bowel disease (IBD) and colorectal cancer (CRC) patients. However, their role in infection remains poorly characterized. We address the role of typhoid toxin in modulation of the host-microbial interaction in health and disease. Infection with a genotoxigenic Salmonella protects mice from intestinal inflammation. We show that the presence of an active genotoxin promotes DNA fragmentation and senescence in vivo, which is uncoupled from an inflammatory response and unexpectedly associated with induction of an anti-inflammatory environment. The anti-inflammatory response is lost when infection occurs in mice with acute colitis. These data highlight a complex context-dependent crosstalk between bacterial-genotoxin-induced DDR and the host immune response, underlining an unexpected role for bacterial genotoxins.

Adaptive Therapy for Metastatic Melanoma: Predictions from Patient Calibrated Mathematical Models

Adaptive therapy is an evolution-based treatment approach that aims to maintain tumor volume by employing minimum effective drug doses or timed drug holidays. For successful adaptive therapy outcomes, it is critical to find the optimal timing of treatment switch points in a patient-specific manner. Here we develop a combination of mathematical models that examine interactions between drug-sensitive and resistant cells to facilitate melanoma adaptive therapy dosing and switch time points. The first model assumes genetically fixed drug-sensitive and -resistant popul tions that compete for limited resources. The second model considers phenotypic switching between drug-sensitive and -resistant cells. We calibrated each model to fit melanoma patient biomarker changes over time and predicted patient-specific adaptive therapy schedules. Overall, the models predict that adaptive therapy would have delayed time to progression by 6-25 months compared to continuous therapy with dose rates of 6-74% relative to continuous therapy. We identified predictive factors driving the clinical time gained by adaptive therapy, such as the number of initial sensitive cells, competitive effect, switching rate from resistant to sensitive cells, and sensitive cell growth rate. This study highlights that there is a range of potential patient-specific benefits of adaptive therapy and identifies parameters that modulate this benefit.

Activation of the Cholinergic Anti-Inflammatory Pathway as a Novel Therapeutic Strategy for COVID-19

The outbreak of coronavirus disease 2019 (COVID-19) underlined the urgent need for alleviating cytokine storm. We propose here that activating the cholinergic anti-inflammatory pathway (CAP) is a potential therapeutic strategy. However, there is currently no approved drugs targeting the regulatory pathway. It is evident that nicotine, anisodamine and some herb medicine, activate the CAP and exert anti-inflammation action in vitro and in vivo. As the vagus nerve affects both inflammation and specific immune response, we propose that vagus nerve stimulation by invasive or non-invasive devices and acupuncture at ST36, PC6, or GV20, are also feasible approaches to activate the CAP and control COVID-19. It is worth to investigate the efficacy and safety of the strategy in patients with COVID-19.

Mitochondrial Metabolism in the Intestinal Stem Cell Niche-Sensing and Signaling in Health and Disease

Mitochondrial metabolism, dynamics, and stress responses in the intestinal stem cell niche play a pivotal role in regulating intestinal epithelial cell homeostasis, including self-renewal and differentiation. In addition, mitochondria are increasingly recognized for their involvement in sensing the metabolic environment and their capability of integrating host and microbial-derived signals. Gastrointestinal diseases such as inflammatory bowel diseases and colorectal cancer are characterized by alterations of intestinal stemness, the microbial milieu, and mitochondrial metabolism. Thus, mitochondrial function emerges at the interface of determining health and disease, and failure to adapt mitochondrial function to environmental cues potentially results in aberrant tissue responses. A mechanistic understanding of the underlying role of mitochondrial fitness in intestinal pathologies is still in its infancy, and therapies targeting mitochondrial (dys)function are currently lacking. This review discusses mitochondrial signaling and metabolism in intestinal stem cells and Paneth cells as critical junction translating host- and microbe-derived signals into epithelial responses. Consequently, we propose mitochondrial fitness as a hallmark for intestinal epithelial cell plasticity, determining the regenerative capacity of the epithelium.

Role of the inflammatory response in community-acquired pneumonia: clinical implications

INTRODUCTION

Despite adequate antibiotic coverage, community-acquired pneumonia (CAP) remains a leading cause of hospitalization and mortality worldwide. It induces both a local pulmonary and a systemic inflammatory response, particularly significant in severe cases. The intensity of the dysregulated host response varies from patient to patient and has a negative impact on survival and other outcomes.

AREAS COVERED

This comprehensive review summarizes the pathophysiological aspects of the inflammatory response in CAP, briefly discusses the usefulness of biomarkers, and assesses the clinical evidence for modulating the inflammatory pathways. We searched PubMed for the most relevant studies, reviews, and meta-analysis until August 2020.

EXPERT OPINION

Notable efforts have been made to identify biomarkers that can accurately differentiate between viral and bacterial etiology, and indeed, to enhance risk stratification in CAP. However, none has proven ideal and no recommended biomarker-guided algorithms exist. Biomarker signatures from proteomic and metabolomic studies could be more useful for such assessments. To date, most studies have produced contradictory results concerning the role of immunomodulatory agents (e.g. corticosteroids, macrolides, and statins) in CAP. Adequately identifying the population who may benefit most from effective modulation of the inflammatory response remains a challenge.

The leukocyte non-coding RNA landscape in critically ill patients with sepsis

The extent of non-coding RNA alterations in patients with sepsis and their relationship to clinical characteristics, soluble mediators of the host response to infection, as well as an advocated in vivo model of acute systemic inflammation is unknown. Here we obtained whole blood from 156 patients with sepsis and 82 healthy subjects among whom eight were challenged with lipopolysaccharide in a clinically controlled setting (human endotoxemia). Via next-generation microarray analysis of leukocyte RNA we found that long non-coding RNA and, to a lesser extent, small non-coding RNA were significantly altered in sepsis relative to health. Long non-coding RNA expression, but not small non-coding RNA, was largely recapitulated in human endotoxemia. Integrating RNA profiles and plasma protein levels revealed known as well as previously unobserved pathways, including non-sensory olfactory receptor activity. We provide a benchmark dissection of the blood leukocyte ‘regulome’ that can facilitate prioritization of future functional studies.

Sphingosine 1-phosphate in sepsis and beyond: Its role in disease tolerance and host defense and the impact of carrier molecules

Sphingosine 1-phosphate (S1P) is an important immune modulator responsible for physiological cellular responses like lymphocyte development and function, positioning and emigration of T and B cells and cytokine secretion. Recent reports indicate that S1P does not only regulate immunity, but can also protect the function of organs by inducing disease tolerance. S1P also influences the replication of certain pathogens, and sphingolipids are also involved in pathogen recognition and killing. Certain carrier molecules for S1P like serum albumin and high density lipoproteins contribute to the regulation of S1P effects. They are able to associate with S1P and modulate its signaling properties. Similar to S1P, both carrier molecules are also decreased in sepsis patients and likely contribute to sepsis pathology and severity. In this review, we will introduce the concept of disease tolerance and the involvement of S1P. We will also discuss the contribution of S1P and its precursor sphingosine to host defense mechanisms against pathogens. Finally, we will summarize current data demonstrating the influence of carrier molecules for differential S1P signaling. The presented data may lead to new strategies for the prevention and containment of sepsis.

Tetracycline Antibiotics Induce Host-Dependent Disease Tolerance to Infection

Several classes of antibiotics have long been known to have beneficial effects that cannot be explained strictly on the basis of their capacity to control the infectious agent. Here, we report that tetracycline antibiotics, which target the mitoribosome, protected against sepsis without affecting the pathogen load. Mechanistically, we found that mitochondrial inhibition of protein synthesis perturbed the electron transport chain (ETC) decreasing tissue damage in the lung and increasing fatty acid oxidation and glucocorticoid sensitivity in the liver. Using a liver-specific partial and acute deletion of Crif1, a critical mitoribosomal component for protein synthesis, we found that mice were protected against sepsis, an observation that was phenocopied by the transient inhibition of complex I of the ETC by phenformin. Together, we demonstrate that mitoribosome-targeting antibiotics are beneficial beyond their antibacterial activity and that mitochondrial protein synthesis inhibition leading to ETC perturbation is a mechanism for the induction of disease tolerance.

•

Doxycycline protects from sepsis beyond its direct antibacterial activity

•

Doxycycline protection from infection is microbiome-independent

•

Inhibition of mitochondrial protein synthesis induces disease tolerance

•

Mild and transient perturbations of the mitochondrial ETC induce disease tolerance

Pathogenic Germline Mutations in DNA Repair Genes in Combination With Cancer Treatment Exposures and Risk of Subsequent Neoplasms Among Long-Term Survivors of Childhood Cancer

PURPOSE

To investigate cancer treatment plus pathogenic germline mutations (PGMs) in DNA repair genes (DRGs) for identification of childhood cancer survivors at increased risk of subsequent neoplasms (SNs).

METHODS

Whole-genome sequencing was performed on blood-derived DNA from survivors in the St Jude Lifetime Cohort. PGMs were evaluated in 127 genes from 6 major DNA repair pathways. Cumulative doses of chemotherapy and body region-specific radiotherapy (RT) were abstracted from medical records. Relative rates (RRs) and 95% CIs of SNs by mutation status were estimated using multivariable piecewise exponential models.

RESULTS

Of 4,402 survivors, 495 (11.2%) developed 1,269 SNs. We identified 538 PGMs in 98 DRGs (POLG, MUTYH, ERCC2, and BRCA2, among others) in 508 (11.5%) survivors. Mutations in homologous recombination (HR) genes were significantly associated with an increased rate of subsequent female breast cancer (RR, 3.7; 95% CI, 1.8 to 7.7), especially among survivors with chest RT ≥ 20 Gy (RR, 4.4; 95% CI, 1.6 to 12.4), or with a cumulative dose of anthracyclines in the second or third tertile (RR, 4.4; 95% CI, 1.7 to 11.4). Mutations in HR genes were also associated with an increased rate of subsequent sarcoma among those who received alkylating agent doses in the third tertile (RR, 14.9; 95% CI, 4.0 to 38.0). Mutations in nucleotide excision repair genes were associated with subsequent thyroid cancer for those treated with neck RT ≥ 30 Gy (RR, 12.9; 95% CI, 1.6 to 46.6) with marginal statistical significance.

CONCLUSION

Our study provides novel insights regarding the contribution of genetics, in combination with known treatment-related risks, for the development of SNs. These findings have the potential to facilitate identification of high-risk survivors who may benefit from genetic counseling and/or testing of DRGs, which may further inform personalized cancer surveillance and prevention strategies.

S1P lyase inhibition protects against sepsis by promoting disease tolerance via the S1P/S1PR3 axis

Background

One-third of all deaths in hospitals are caused by sepsis. Despite its demonstrated prevalence and high case fatality rate, antibiotics remain the only target-oriented treatment option currently available. Starting from results showing that low-dose anthracyclines protect against sepsis in mice, we sought to find new causative treatment options to improve sepsis outcomes.

Methods

Sepsis was induced in mice, and different treatment options were evaluated regarding cytokine and biomarker expression, lung epithelial cell permeability, autophagy induction, and survival benefit. Results were validated in cell culture experiments and correlated with patient samples.

Findings

Effective low-dose epirubicin treatment resulted in substantial downregulation of the sphingosine 1-phosphate (S1P) degrading enzyme S1P lyase (SPL). Consequent accumulation and secretion of S1P in lung parenchyma cells stimulated the S1P-receptor type 3 (S1PR3) and mitogen-activated protein kinases p38 and ERK, reducing tissue damage via increased disease tolerance. The protective effects of SPL inhibition were absent in S1PR3 deficient mice. Sepsis patients showed increased expression of SPL, stable expression of S1PR3, and increased levels of mucin-1 and surfactant protein D as indicators of lung damage.

Interpretation

Our work highlights a tissue-protective effect of SPL inhibition in sepsis due to activation of the S1P/S1PR3 axis and implies that SPL inhibitors and S1PR3 agonists might be potential therapeutics to protect against sepsis by increasing disease tolerance against infections.

Funding

This study was supported by the Center for Sepsis Control and Care (CSCC), the German Research Foundation (DFG), RTG 1715 (to M. H. G. and I. R.) and the National Institutes of Health, Grant R01GM043880 (to S. S.).

Taking the STING Out of Sepsis?

In this issue of Cell Host & Microbe, Zhang et al. use a sepsis mouse model to show that macrophage-specific release of coagulation factor F3 depends on pathogen detection and responses mediated by TMEM173/STING. The therapeutic power of targeting TMEM173/STING-F3 is evident in mice, but will it penetrate the sepsis bedside?

Replication Stress, DNA Damage, Inflammatory Cytokines and Innate Immune Response

Complete and accurate DNA replication is essential to genome stability maintenance during cellular division. However, cells are routinely challenged by endogenous as well as exogenous agents that threaten DNA stability. DNA breaks and the activation of the DNA damage response (DDR) arising from endogenous replication stress have been observed at pre- or early stages of oncogenesis and senescence. Proper detection and signalling of DNA damage are essential for the autonomous cellular response in which the DDR regulates cell cycle progression and controls the repair machinery. In addition to this autonomous cellular response, replicative stress changes the cellular microenvironment, activating the innate immune response that enables the organism to protect itself against the proliferation of damaged cells. Thereby, the recent descriptions of the mechanisms of the pro-inflammatory response activation after replication stress, DNA damage and DDR defects constitute important conceptual novelties. Here, we review the links of replication, DNA damage and DDR defects to innate immunity activation by pro-inflammatory paracrine effects, highlighting the implications for human syndromes and immunotherapies.

The cellular basis of organ failure in sepsis-signaling during damage and repair processes

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. This definition, updated in 2016, shifted the conceptual focus from exclusive attention to the systemic inflammatory response toward the multifactorial tissue damage that occurs during the progression of infection to sepsis and shock. Whereas targeting the inflammatory host response to infection did not translate into improved clinical management of sepsis, recent findings might shed new light on the maladaptive host–pathogen interaction in sepsis and pave the way for “theranostic” interventions. In addition to the well-known resistance responses of the immune system that result in pathogen clearance, “disease tolerance” has recently been acknowledged as a coping mechanism of presumably equal importance. We propose that both defense mechanisms, “resistance” and “disease tolerance”, can get out of control in sepsis. Whereas excessive activation of resistance pathways propagates tissue damage via immunopathology, an inappropriate “tolerance” might entail immunoparalysis accompanied by fulminant, recurrent or persisting infection. The review introduces key signaling processes involved in infection-induced “resistance” and “tolerance”. We propose that elaboration of these signaling pathways allows novel insights into sepsis-associated tissue damage and repair processes. Moreover theranostic opportunities for the specific treatment of sepsis-related hyperinflammation or immunoparalysis will be introduced. Agents specifically affecting either hyperinflammation or immunoparalysis in the course of sepsis might add to the therapeutic toolbox of personalized care in the field of organ dysfunction caused by infection. (This article is freely available.)

Reprogramming of macrophages employing gene regulatory and metabolic network models

Upon exposure to different stimuli, resting macrophages undergo classical or alternative polarization into distinct phenotypes that can cause fatal dysfunction in a large range of diseases, such as systemic infection leading to sepsis or the generation of an immunosuppressive tumor microenvironment. Investigating gene regulatory and metabolic networks, we observed two metabolic switches during polarization. Most prominently, anaerobic glycolysis was utilized by M1-polarized macrophages, while the biosynthesis of inosine monophosphate was upregulated in M2-polarized macrophages. Moreover, we observed a switch in the urea cycle. Gene regulatory network models revealed E2F1, MYC, PPARγ and STAT6 to be the major players in the distinct signatures of these polarization events. Employing functional assays targeting these regulators, we observed the repolarization of M2-like cells into M1-like cells, as evidenced by their specific gene expression signatures and cytokine secretion profiles. The predicted regulators are essential to maintaining the M2-like phenotype and function and thus represent potential targets for the therapeutic reprogramming of immunosuppressive M2-like macrophages.

Bacterial Genotoxin-Induced DNA Damage and Modulation of the Host Immune Microenvironment

: Bacterial genotoxins (BTGX) induce DNA damage, which results in senescence or apoptosis of the target cells if not properly repaired. Three BTGXs have been identified: the cytolethal distending toxin (CDT) family produced by several Gram-negative bacteria, the typhoid toxin produced by several Salmonella enterica serovars, and colibactin, a peptide-polyketide, produced mainly by the phylogenetic group B2 Escherichia coli. The cellular responses induced by BTGXs resemble those of well-characterized carcinogenic agents, and several lines of evidence indicate that bacteria carrying genotoxin genes can contribute to tumor development under specific circumstances. Given their unusual mode of action, it is still enigmatic why these effectors have been acquired by microbes and what is their role in the context of the biology of the producing bacterium, since it is unlikely that their primary purpose is to induce/promote cancer in the mammalian host. In this review, we will discuss the possibility that the DNA damage induced by BTGX modulates the host immune response, acting as immunomodulator, leading to the establishment of a suitable niche for the producing bacterium. We will further highlight open questions that remain to be solved regarding the biology of this unusual family of bacterial toxins.

Transcriptional Suppression of the NLRP3 Inflammasome and Cytokine Release in Primary Macrophages by Low-Dose Anthracyclines

Tissue-resident macrophages play critical roles in controlling homeostasis, tissue repair, and immunity. Inflammatory macrophages can sustain tissue damage and promote the development of fibrosis during infections and sterile tissue injury. The NLRP3 inflammasome and its effector cytokine IL-1β have been identified as important mediators of fibrosis. Epirubicin, an anthracycline topoisomerase II inhibitor, has been reported to inhibit myeloid inflammatory cytokine production and to promote tissue tolerance following bacterial infection. We investigated the anti-inflammatory properties of epirubicin on the NLRP3 inflammasome and TLR4-mediated inflammation in PMA-primed THP-1 and in primary human peritoneal macrophages (PM). Low-dose epirubicin at non-cytotoxic doses downregulated NLRP3 inflammasome components and reduced the release of cleaved caspase-1, bioactive IL-1β, and TNF-α following NLRP3 activation in a dose-dependent fashion. In addition, epirubicin attenuated inflammatory macrophage responses after TLR4 and TLR2 ligation. These anti-inflammatory effects were not mediated by the induction of autophagy or altered MAPK signaling, but as the result of a global transcriptional suppression of LPS-dependent genes. Epirubicin-treated macrophages displayed reduced acetylation of histone 3 lysine 9 (H3K9ac), suggesting anti-inflammatory epigenetic imprinting as one underlying mechanism.