The Role of Pericytes in Lipopolysaccharide-Induced Murine Acute Respiratory Distress Syndrome.

Acute respiratory distress syndrome (ARDS) is a heterogeneous clinical syndrome that is most commonly triggered by infection-related inflammation. Lung pericytes can respond to infection and act as immune and proangiogenic cells; moreover, these cells can differentiate into myofibroblasts in nonresolving ARDS and contribute to the development of pulmonary fibrosis. Here, we aimed to characterize the role of lung cells, which present characteristics of pericytes, such as peri-endothelial location and expression of a panel of specific markers. To study their role in ARDS, we used a murine model of lipopolysaccharide (LPS)-induced resolving ARDS. We confirmed the development of ARDS after LPS instillation, which was resolved 14 days after onset. Using immunofluorescence and flow cytometry, we observed early expansion of neural-glial antigen 2+ ß-type platelet-derived growth factor receptor+ pericytes in murine lungs with loss of CD31+ ß-type platelet-derived growth factor receptor+ endothelial cells. These changes were accompanied by specific changes in lung structure and loss of vascular integrity. On day 14 after ARDS onset, the composition of pericytes and endothelial cells returned to baseline values. LPS-induced ARDS activated NOTCH signaling in lung pericytes, the inhibition of which during LPS stimulation reduced the expression of its downstream target genes, pericyte markers, and angiogenic factors. Together, lung pericytes in response to inflammatory injury activate NOTCH signaling that supports their maintenance and in turn can contribute to recovery of the microvascular endothelium.

Renaissance of glucocorticoids in critical care in the era of COVID-19: ten urging questions.

The 40-year-old experience with glucocorticosteroids (GCs) in the context of severe infections is complex and troublesome. Recently, however, a clear indication for GCs in severe COVID-19 has been established. This may constitute a harbinger of a wider use of GCs in critical illnesses. A fundamental prerequisite of such an action is a better understanding of the heterogeneity of critical illness and GCs operationalization within the precision medicine approach. In this perspective, we formulate ten major questions regarding the use of GCs in critical illness. Answering them will likely facilitate a new era of effective and personalized GCs use in modern critical care.

Fas-positive lymphocytes are associated with systemic inflammation in obstructive sleep apnea syndrome.

PURPOSE: Obstructive sleep apnea syndrome (OSAS) is associated with alterations in immune system which may lead to serious complications. The aim of this study was to explore lymphocyte populations in OSAS with special attention to the Fas-positive cells. METHODS: Fifty-one patients with confirmed OSA and 20 healthy subjects were investigated. The OSA severity indices, data concerning comorbidities, and markers of inflammation and metabolic disorders were collected. Flow cytometry was used to analyze the lymphocyte profile and expression of Fas receptors (CD95). Concentration of adiponectin, IL-1ß, TNF-α, and sFas were measured. RESULTS: Proportions of Fas-positive cells in the pool of CD4+ and Fas-positive in the pool of CD8+ cells in the blood of patients were significantly increased when compared with healthy subjects (74.5% vs. 65.6% and 78.8% vs.70.9%, respectively, p < 0.05). No correlation with OSA severity was found. However, the proportion and number of Fas+ cells were elevated in obese patients, in non-smokers, and in patients suffering from COPD and hypertension. There were several significant relations of Fas+ cells with inflammatory markers of systemic inflammation. CONCLUSION: Lymphocytes with the expression of Fas receptor are associated with systemic inflammation in OSAS.

Monitoring of procalcitonin but not interleukin-6 is useful for the early prediction of anastomotic leakage after colorectal surgery.

BACKGROUND: Early recognition of patients who have developed anastomotic leakage (AL) after colorectal surgery is crucial for the successful treatment of this complication. The aim of this study was to assess the usefulness of the assessment of procalcitonin (PCT) and interleukin-6 (IL-6) levels in the prognosis of AL. METHODS: This observational study included 157 patients who underwent major elective colorectal surgery. The most common indications for surgery were cancer and inflammatory bowel diseases. Serum samples were obtained directly before surgery (D0) and 1 day (D1) after surgery, and the relationships between the serum concentrations of PCT and IL-6 and development of AL were assessed. RESULTS: In total, 10.2% of patients developed post-surgical infections due to AL. PCT levels on D1 were significantly higher in patients who developed AL [2.73 (1.40-4.62)] than in those who recovered without complications [0.2 (0.09-0.44)]. The area under the ROC curve for PCT on D1 was 0.94, 95% CI (0.89-0.98). The sensitivity and specificity of the prediction of an infection were 87% and 87%, respectively, for PCT on D1, which was higher than 1.09 ng/mL. The increase in PCT concentration between D0 and D1 was significantly higher in patients with AL (p<0.001). Patients who developed AL had higher concentrations of IL-6 on D1, but the difference was not significant (p=0.28). CONCLUSIONS: This study confirms that surgical trauma increases serum PCT concentrations and that the concentration of PCT on D1 can predict AL after colorectal surgery. However, IL-6 is not a good early marker for developing AL.

Aspects of pericytes and their potential therapeutic use.

Pericytes, which are multi-potential stem cells, co-create the walls of the microvessels: capillaries, terminal arterioles and postcapillary venules. These cells are localized under the basement membrane, tightly encircling the endothelium. The most frequently mentioned molecular markers of pericytes include NG2 (neural-glial antigen 2), ß-type platelet-derived growth factor receptor (PDGFRß), smooth muscle α-actin (α-SMA), regulator of G protein signalling 5 (RGS5), the adhesion protein CD146 and nestin. Different functions in physiological processes are assigned to pericytes such as maintaining the integrity and senescence of endothelial cells, transregulation of vascular tone or the potential to differentiate into other cells. Probably they are also involved in pathological processes such as tissues fibrosis. In this review, we focus on the participation of pericytes in the process of blood vessel formation, the regeneration of skeletal muscle tissue and fibrosis. Strong evidence for pericytes' participation in endothelial homeostasis, as well as in pathological conditions such as fibrosis, reveals a broad potential for the therapeutic use of these cells. Targeted pharmacological modulation of pericytes, leading to blocking signalling pathways responsible for the differentiation of pericytes into myofibroblasts, seems to be a promising strategy for the treatment of fibrosis in the early stages.

The Early Expression of HLA-DR and CD64 Myeloid Markers Is Specifically Compartmentalized in the Blood and Lungs of Patients with Septic Shock.

Identification of reliable biomarkers is key to guide targeted therapies in septic patients. Expression monitoring of monocyte HLA-DR and neutrophil CD64 could fulfill the above need. However, it is unknown whether their expression on circulating cells reflects the status of tissue resident cells. We compared expressions of HLA-DR and CD64 markers in the circulation and airways of septic shock patients and evaluated their outcome prognostic value. The expression of CD64 on neutrophils and HLA-DR on monocytes was analyzed in the peripheral blood and mini-bronchoalveolar lavage fluid cells by flow cytometry. Twenty-seven patients with septic shock were enrolled into the study. The fluorescence intensity of HLA-DR on circulating monocytes was 3.5-fold lower than on the pulmonary monocytes (p = 0.01). The expression of CD64 on circulating and airway neutrophils was similar (p = 0.47). Only the expression of CD64 on circulating neutrophils was higher in nonsurvivors versus survivors (2.8-fold; p = 0.031). Pulmonary monocytes display a higher level of HLA-DR activation compared to peripheral blood monocytes but the expression of neutrophil CD64 is similar on lung and circulating cells. Death in septic patients was effectively predicted by neutrophil CD64 but not monocytic HLA-DR. Prognostic value of cellular activation markers in septic shock appears to strongly depend on their level of compartmentalization.

T, B, and NKT Cells in Systemic Inflammation in Obstructive Sleep Apnoea.

BACKGROUND: Obstructive sleep apnoea syndrome (OSAS) brings risk of serious complications. The study objective was to assess elements of the cellular immune response in the course of OSAS. METHODS: Peripheral blood (PB) lymphocytes: T, B, NK, NKT-like, Th, Tc, and HLA DR+ T cells were evaluated by flow cytometry of 48 OSA patients; the concentration of adiponectin, interleukin 1ß, and TNFα was measured by ELISA method. The OSA complication score was developed and used for statistical analysis. RESULTS: The proportion of B cells and Th/Tc ratio were significantly lower in the BP of OSA patients when compared with control subjects (median 7.9 versus 10.9%, 0.9 versus 1.5, p < 0.05). The proportion of Tc, NK, NKT-like, and HLADR positive T cells were elevated in OSA patients when compared with healthy subjects (36.4 versus 26.8, 15.5 versus 8.5, 5.7 versus 3.0, and 8.4 versus 4.5%, p < 0.05, resp.) and were more pronounced in patients with metabolic syndrome. The grade of OSA complication score correlated with systemic inflammation markers and the proportion of B cells. The value of adiponectin/BMI ratio correlated significantly with SpO2 (r = 0.31, p < 0.05), CRP (r = -0.35, p < 0.05), TNFα concentration (r = -0.36, p < 0.05), and proportion of B cells (r = 0.32, p < 0.05). CONCLUSION: Lymphocytes B, Tc, NK, NKT-like, and adiponectin are involved in systemic immune response in OSA patients possibly predisposing them to cardiovascular and metabolic complications.

SARS-CoV-2 virus-like particle variants alpha and delta mimic the native viruses in their differential inflammasome activating potential.

The emerging SARS-CoV-2 variants are evolving to evade human immunity and differ in their pathogenicity. While evasion of the variants from adaptive immunity is widely investigated, there is a paucity of knowledge about their interactions with innate immunity. Inflammasome assembly is one of the most potent mechanisms of the early innate response to viruses, but when it is inappropriate, it can perpetuate tissue damage. In this study, we focused on the capacity of SARS-CoV-2 Alpha and Delta variants to activate the NLRP3 inflammasome. We compared the macrophage activation, particularly the inflammasome formation, using Alpha- and Delta-spike virus-like particles (VLPs). We found that VLPs of both variants activated the inflammasome even without a priming step. Delta-spike VLPs had a significantly stronger effect on triggering pyroptosis and inflammasome assembly in THP-1 macrophages than did Alfa-spike VLPs. Cells treated with Delta VLPs showed greater cleavage of caspase-1 and IL-1ß release. Furthermore, Delta VLPs induced stronger cytokine secretion from macrophages and caused essential impairment of mitochondrial respiration in comparison to Alpha VLPs. Additionally, infection of primary human monocyte-derived macrophages with the SARS-CoV-2 variants confirmed the observations in VLPs. Collectively, we revealed that SARS-CoV-2 Delta had a greater impact on the inflammasome activation, cell death and mitochondrial respiration in macrophages than did the Alpha variant. Importantly, the differential response to the SARS-CoV-2 variants can influence the efficacy of therapies targeting the host's innate immunity.

SARS-CoV-2 and its ORF3a, E and M viroporins activate inflammasome in human macrophages and induce of IL-1α in pulmonary epithelial and endothelial cells.

Inflammasome assembly is a potent mechanism responsible for the host protection against pathogens, including viruses. When compromised, it can allow viral replication, while when disrupted, it can perpetuate pathological responses by IL-1 signaling and pyroptotic cell death. SARS-CoV-2 infection was shown to activate inflammasome in the lungs of COVID-19 patients, however, potential mechanisms responsible for this response are not fully elucidated. In this study, we investigated the effects of ORF3a, E and M SARS-CoV-2 viroporins in the inflammasome activation in major populations of alveolar sentinel cells: macrophages, epithelial and endothelial cells. We demonstrated that each viroporin is capable of activation of the inflammasome in macrophages to trigger pyroptosis-like cell death and IL-1α release from epithelial and endothelial cells. Small molecule NLRP3 inflammasome inhibitors reduced IL-1 release but weakly affected the pyroptosis. Importantly, we discovered that while SARS-CoV-2 could not infect the pulmonary microvascular endothelial cells it induced IL-1α and IL-33 release. Together, these findings highlight the essential role of macrophages as the major inflammasome-activating cell population in the lungs and point to endothelial cell expressed IL-1α as a potential novel component driving the pulmonary immunothromobosis in COVID-19.

Profiling the dysregulated immune response in sepsis: overcoming challenges to achieve the goal of precision medicine.

Sepsis is characterised by a dysregulated host immune response to infection. Despite recognition of its significance, immune status monitoring is not implemented in clinical practice due in part to the current absence of direct therapeutic implications. Technological advances in immunological profiling could enhance our understanding of immune dysregulation and facilitate integration into clinical practice. In this Review, we provide an overview of the current state of immune profiling in sepsis, including its use, current challenges, and opportunities for progress. We highlight the important role of immunological biomarkers in facilitating predictive enrichment in current and future treatment scenarios. We propose that multiple immune and non-immune-related parameters, including clinical and microbiological data, be integrated into diagnostic and predictive combitypes, with the aid of machine learning and artificial intelligence techniques. These combitypes could form the basis of workable algorithms to guide clinical decisions that make precision medicine in sepsis a reality and improve patient outcomes.

A Bittersweet Kiss of Gram-Negative Bacteria: The Role of ADP-Heptose in the Pathogenesis of Infection.

Due to the global crisis caused by the dramatic rise of drug resistance among Gram-negative bacteria, there is an urgent need for a thorough understanding of the pathogenesis of infections of such an etiology. In light of the limited availability of new antibiotics, therapies aimed at host-pathogen interactions emerge as potential treatment modalities. Thus, understanding the mechanism of pathogen recognition by the host and immune evasion appear to be the key scientific issues. Until recently, lipopolysaccharide (LPS) was recognized as a major pathogen-associated molecular pattern (PAMP) of Gram-negative bacteria. However, recently, ADP-L-glycero-ß-D-manno-heptose (ADP-heptose), an intermediate carbohydrate metabolite of the LPS biosynthesis pathway, was discovered to activate the hosts' innate immunity. Therefore, ADP-heptose is regarded as a novel PAMP of Gram-negative bacteria that is recognized by the cytosolic alpha kinase-1 (ALPK1) protein. The conservative nature of this molecule makes it an intriguing player in host-pathogen interactions, especially in the context of changes in LPS structure or even in its loss by certain resistant pathogens. Here, we present the ADP-heptose metabolism, outline the mechanisms of its recognition and the activation of its immunity, and summarize the role of ADP-heptose in the pathogenesis of infection. Finally, we hypothesize about the routes of the entry of this sugar into cytosol and point to emerging questions that require further research.

1-Methylnicotinamide (1-MNA) inhibits the activation of the NLRP3 inflammasome in human macrophages.

The NLRP3 inflammasome is among the most potent intracellular sensors of danger and disturbances of cellular homeostasis that can lead to the release of IL-1ß and cell death, or pyroptosis. Despite its protective role, this mechanism is involved in the pathogenesis of numerous inflammatory diseases; therefore, it is seen as a potential therapeutic target. 1-methylnicotinamide (1-MNA) is a direct metabolite of nicotinamide and was previously shown to display several immunomodulatory properties, including a reduction in the reactive oxygen species (ROS). Here, we investigated whether 1-MNA could influence the activation of the NLRP3 inflammasome in human macrophages. In differentiated human macrophages we observed that 1-MNA specifically reduced the activation of the NLRP3 inflammasome. This effect was related to the scavenging of ROS, as exogenous H2O2 was able to restore NLRP3 activation. Additionally, 1-MNA increased the mitochondrial membrane potential, indicating that it did not inhibit oxidative phosphorylation. Moreover, at high but not low concentrations, 1-MNA decreased NF-κB activation and the level of pro-IL-1ß. Interestingly, 1-MNA did not reduce the secretion of IL-6 upon endotoxin stimulation, confirming that its primary immunomodulatory effect on human macrophages is dependent on the NLRP3 inflammasome. Taken together, we have shown for the first time that 1-MNA reduced the activation of the NLRP3 inflammasome in human macrophages via an ROS-dependent pathway. Our results indicate a novel potential use of 1-MNA in NLRP3-related disorders.

Anti-inflammatory and antioxidant actions of extracts from Rheum rhaponticum and Rheum rhabarbarum in human blood plasma and cells in vitro.

Rheum rhaponticum L. (rhapontic rhubarb) and Rheum rhabarbarum L. (garden rhubarb) are edible and medicinal rhubarb species used for many centuries in traditional medicine. This work is focused on the biological activity of extracts from petioles and roots of R. rhaponticum and R. rhabarbarum as well as rhapontigenin and rhaponticin, typical stilbenes present in these rhubarbs, in a context of their effects on blood physiology and cardiovascular health. Anti-inflammatory properties of the examined substances were evaluated in human peripheral blood mononuclear cells (PBMCs) and THP1-ASC-GFP inflammasome reporter cells. Due to the coexistence of inflammation and oxidative stress in cardiovascular diseases, the study design included also antioxidant assays. This part of the work involved the assessment of the protective efficiency of the examined substances against the peroxynitrite-triggered damage to human blood plasma components, including fibrinogen, a protein of critical importance for blood clotting and maintaining the haemostatic balance. Pre-incubation of PBMCs with the examined substances (1-50 µg/mL) considerably decreased the synthesis of prostaglandin E2 as well as the release of pro-inflammatory cytokines (IL-2 and TNF-α) and metalloproteinase-9. A reduced level of secreted apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) specks in the THP-1-ASC-GFP cells was also observed. The examined substances significantly diminished the extent of ONOO‾induced oxidative modifications of blood plasma proteins and lipids and normalized, or even strengthened blood plasma antioxidant capacity. Furthermore, a reduction of oxidative damage to fibrinogen, including modifications of tyrosine and tryptophan residues along with the formation of protein aggregates was found.

THE EUROPEAN SHOCK SOCIETY MEETS THE IMMUNOSEP CONSORTIUM FOR PERSONALIZED SEPSIS TREATMENT.

ABSTRACT: The unacceptable high mortality of severe infections and sepsis led over the years to understand the need for adjunctive immunotherapy to modulate the dysregulated host response of the host. However, not all patients should receive the same type of treatment. The immune function may largely differ from one patient to the other. The principles of precision medicine require that some biomarker is used to capture the immune function of the host and guide the best candidate therapy. This is the approach of the ImmunoSep randomized clinical trial (NCT04990232) where patients are allocated to treatment with anakinra or recombinant interferon gamma tailored to immune signs of macrophage activation-like syndrome and immunoparalysis respectively. ImmunoSep is a first-in-class paradigm of precision medicine for sepsis. Other approaches need to consider classification by sepsis endotypes, targeting T cell and application of stem cells. Basic principle for any trial to be successful is the delivery of appropriate antimicrobial therapy as standard-of-care taking into consideration not just the likelihood for resistant pathogens but also the pharmacokinetic/pharmacodynamic mode of action of the administered antimicrobial.

Immune checkpoint inhibitors for the treatment of sepsis:insights from preclinical and clinical development.

INTRODUCTION: It is now well established that sepsis induces a state of acquired immunosuppression, with an increased risk of secondary infections that contributes to patients' worsening. Thus, tackling sepsis-induced immunosuppression represents a promising perspective. AREAS COVERED: Of mechanisms responsible for sepsis-induced immunosuppression, the increased expression of co-inhibitory receptors such as PD-1, CTLA4, TIM-3, LAG-3, or BTLA and their ligands recently received considerable interest since their inhibition, thanks to the so-called checkpoint inhibitors (CPI), provided astonishing results in cancer by rebooting immune functions. This review reports on the first landmarks of these molecules in sepsis. EXPERT OPINION: Preclinical results are positive and the first human early phase clinical trials showed a beneficial effect on immunological functions and/or markers and suggested that tolerance of CPIs side effects, mainly auto-immune disorders, is acceptable in sepsis. Elsewhere, in some specific severe ICU infections such as fungal infections, preliminary convincing case reports have been published. Overall, the first results regarding CPIs in sepsis appear encouraging. However, further efforts are warranted, especially in defining the right patients to be treated (i.e. in an individualized approach) and establishing the optimal time to start an immune restoration. Larger trials are now mandatory to confirm CPIs' potential in sepsis.

Inflammasome-related Markers upon ICU Admission do not Correlate with Outcome in Critically Ill COVID-19 Patients.

PURPOSE: The development of targeted biological therapies for coronavirus disease 2019 (COVID-19) requires reliable biomarkers that could help indicate how patients are responding. The hyperactivation of inflammasomes by the SARS-CoV2 virus is hypothesized to contribute to a more severe course of the COVID-19 disease. Therefore, we aimed to evaluate the prognostic value of several inflammasome-related cytokines and proteins upon admission to the intensive care unit (ICU). PATIENTS AND METHODS: We performed a prospective cohort study. Plasma samples were obtained from 45 critically ill COVID-19 patients and 10 patients without any signs of infection (traumatic brain injury [TBI]) on admission to the ICU. Concentrations of IL-1a, IL-1ß, IL-18, IL-1RA, galectin-1, apoptosis-associated speck-like proteins, LDH, ferritin, and gasdermin D were analyzed. A cell-free caspase-1 plasma assay was done by inhibitor-based immunoprecipitation followed by a Western Blot. Demographic and clinical characteristics were recorded. RESULTS: Inhospital mortality in COVID-19 patients was 62%. Galectin-1 was 1.8-fold lower in COVID-19 than in TBI patients (17101.84 pg/mL vs. 30764.20 pg/mL, P = 0.007), but other inflammasome-related biomarkers had similar concentrations. Patients with a Sequential Organ Failure Assessment (SOFA) score of > 9 on admission who were at high risk of death had significantly higher galectin-1 but lower IL-1RA in comparison with low-risk patients (25551.3 pg/mL vs. 16302.7 pg/mL, P = 0.014; 14.5 pg/mL vs. 39.4pg/mL, P = 0.04, respectively). Statistically significant correlations were observed between: IL-1a and platelets (r = -0.37), IL-1 ß and platelets (r = -0.36), ferritin and INR (r = 0.39). Activated caspase-1 p35, whose presence was related to higher fibrinogen and lower D-dimers, was detected in 12 out of 22 COVID-19 patients and in none of the TBI patients. Moreover, densitometric analysis showed a significantly higher amount of p35 in patients with a SOFA score > 9. CONCLUSION: We found that the systemic markers of activation of inflammasomes in critically ill COVID-19 patients were not directly related to outcome. Therefore, potential interventions aimed at the inflammasome pathway in this group of patients may be of limited effectiveness and should be biomarker-guided.

Compartment-Specific Differences in the Activation of Monocyte Subpopulations Are Not Affected by Nitric Oxide and Glucocorticoid Treatment in a Model of Resuscitated Porcine Endotoxemic Shock.

Inhaled nitric oxide (iNO) remains one of the treatment modalities in shock, and in addition to its vasoactive properties, iNO exerts immunomodulatory effects. We used a porcine model of endotoxemia with shock resuscitation (control) and additional treatment with iNO and a steroid (treatment group). After 20 h, bone marrow (BM), peripheral blood (PB), and bronchoalveolar lavage fluid (BALF) were collected to analyze the immunophenotype and mitochondrial membrane potential (Δφ) in three subsets of monocytes. In both groups, SLA-DR expression decreased twofold on the circulating CD14+CD163+ and CD14−CD163+ monocytes, while it did not change on the CD14+CD163+. Δφ increased only in the CD14−CD163+ subpopulation (0.8 vs. 2.0, p < 0.001). The analysis of compartment-specific alterations showed that nearly 100% of BALF CD14+CD163+ and CD14−CD163+ monocytes expressed SLA-DR, and it was higher compared to PB (32% and 20%, p < 0.0001) and BM (93% and 67%, p < 0.001, respectively) counterparts. BALF CD14+CD163+ had a threefold higher Δφ than PB and BM monocytes, while the Δφ of the other subsets was highest in PB monocytes. We confirmed the compartmentalization of the monocyte response during endotoxemic shock, which highlights the importance of studying tissue-resident cells in addition to their circulating counterparts. The iNO/steroid treatment did not further impair monocyte fitness.

Hearing Loss as the Main Clinical Presentation in NLRP3-Associated Autoinflammatory Disease.

The NLRP3 gene mutations are the cause of autosomal dominant autoinflammatory disorders (NLRP3-AID). Recently, hearing loss (HL) has been found to be the sole or major manifestation of NLRP3-AID. Here, we tested 110 autosomal dominant HL families with a custom panel of 237 HL genes and found one family carrying the NLRP3 c.1872C>G, p.Ser624Arg mutation. Functional studies revealed that this novel variant is a gain of function mutation, leading to increased activity of caspase-1 and subsequent oversecretion of proinflammatory interleukin-1ß. Clinical reanalysis of the affected individuals, together with serological evidence of inflammation and pathological cochlear enhancement on FLAIR-MRI images, guided our diagnosis to atypical NLRP3-AID. The study highlights the role of genetic analysis in patients with progressive postlingual HL. This can help to identify individuals with hereditary HL as a consequence of NLRP3-AID and allow timely and effective treatment with interleukin-1-receptor antagonist.

An Early Myelosuppression in the Acute Mouse Sepsis Is Partly Outcome-Dependent.

Adult hematopoietic stem and progenitor cells (HSPCs) respond to bacterial infections by expansion to myeloid cells. Sepsis impairs this process by suppressing differentiation of stem cells subsequently contributing to an ineffective immune response. Whether the magnitude of HSPCs impairment in sepsis is severity-dependent remains unknown. This study investigated dynamics of the HSPC immune-inflammatory response in the bone marrow, splenic, and blood compartments in moribund and surviving septic mice. The 12-week-old outbred CD-1 female mice (n=65) were subjected to a cecal ligation and puncture (CLP) sepsis, treated with antibiotics and fluid resuscitation, and stratified into predicted-to-die (P-DIE) and predicted-to-survive (P-SUR) cohorts for analysis. CLP strongly reduced the common myeloid and multipotent progenitors, short- and long-term hematopoietic stem cell (HSC) counts in the bone marrow; lineage-ckit+Sca-1+ and short-term HSC suppression was greater in P-DIE versus P-SUR mice. A profound depletion of the common myeloid progenitors occurred in the blood (by 75%) and spleen (by 77%) of P-DIE. In P-SUR, most common circulating HSPCs subpopulations recovered to baseline by 72 h post-CLP. Analysis of activated caspase-1/-3/-7 revealed an increased apoptotic (by 30%) but not pyroptotic signaling in the bone marrow HSCs of P-DIE mice. The bone marrow from P-DIE mice revealed spikes of IL-6 (by 5-fold), CXCL1/KC (15-fold), CCL3/MIP-1α (1.7-fold), and CCL2/MCP-1 (2.8-fold) versus P-SUR and control (TNF, IFN-γ, IL-1ß, -5, -10 remained unaltered). Summarizing, our findings demonstrate that an early sepsis-induced impairment of myelopoiesis is strongly outcome-dependent but varies among compartments. It is suggestive that the HSCPC loss is at least partly due to an increased apoptosis but not pyroptosis.

Bridging animal and clinical research during SARS-CoV-2 pandemic: A new-old challenge.

Many milestones in medical history rest on animal modeling of human diseases. The SARS-CoV-2 pandemic has evoked a tremendous investigative effort primarily centered on clinical studies. However, several animal SARS-CoV-2/COVID-19 models have been developed and pre-clinical findings aimed at supporting clinical evidence rapidly emerge. In this review, we characterize the existing animal models exposing their relevance and limitations as well as outline their utility in COVID-19 drug and vaccine development. Concurrently, we summarize the status of clinical trial research and discuss the novel tactics utilized in the largest multi-center trials aiming to accelerate generation of reliable results that may subsequently shape COVID-19 clinical treatment practices. We also highlight areas of improvement for animal studies in order to elevate their translational utility. In pandemics, to optimize the use of strained resources in a short time-frame, optimizing and strengthening the synergy between the preclinical and clinical domains is pivotal.