Pneumonia-induced sepsis in mice: temporal study of inflammatory and cardiovascular parameters

Lung-brain crosstalk: Behavioral disorders and neuroinflammation in septic survivor mice

Although studies have suggested an association between lung infections and increased risk of neuronal disorders (e.g., dementia, cognitive impairment, and depressive and anxious behaviors), its mechanisms remain unclear. Thus, an experimental mice model of pulmonary sepsis was developed to investigate the relationship between lung and brain inflammation. Male Swiss mice were randomly assigned to either pneumosepsis or control groups. Pneumosepsis was induced by intratracheal instillation of Klebsiella pneumoniae, while the control group received a buffer solution. The model's validation included assessing systemic markers, as well as tissue vascular permeability. Depression- and anxiety-like behaviors and cognitive function were assessed for 30 days in sepsis survivor mice, inflammatory profiles, including cytokine levels (lungs, hippocampus, and prefrontal cortex) and microglial activation (hippocampus), were examined. Pulmonary sepsis damaged distal organs, caused peripheral inflammation, and increased vascular permeability in the lung and brain, impairing the blood-brain barrier and resulting in bacterial dissemination. After sepsis induction, we observed an increase in myeloperoxidase activity in the lungs (up to seven days) and prefrontal cortex (up to 24 h), proinflammatory cytokines in the hippocampus and prefrontal cortex, and percentage of areas with cells positive for ionized calcium-binding adaptor molecule 1 (IBA-1) in the hippocampus. Also, depression- and anxiety-like behaviors and changes in short-term memory were observed even 30 days after sepsis induction, suggesting a crosstalk between inflammatory responses of lungs and brain.

Oxidative stress and the role of redox signalling in chronic kidney disease

Chronic kidney disease (CKD) is a major public health concern, underscoring a need to identify pathogenic mechanisms and potential therapeutic targets. Reactive oxygen species (ROS) are derivatives of oxygen molecules that are generated during aerobic metabolism and are involved in a variety of cellular functions that are governed by redox conditions. Low levels of ROS are required for diverse processes, including intracellular signal transduction, metabolism, immune and hypoxic responses, and transcriptional regulation. However, excess ROS can be pathological, and contribute to the development and progression of chronic diseases. Despite evidence linking elevated levels of ROS to CKD development and progression, the use of low-molecular-weight antioxidants to remove ROS has not been successful in preventing or slowing disease progression. More recent advances have enabled evaluation of the molecular interactions between specific ROS and their targets in redox signalling pathways. Such studies may pave the way for the development of sophisticated treatments that allow the selective control of specific ROS-mediated signalling pathways.

Cannabinoid CB2 receptor agonist reduces local and systemic inflammation associated with pneumonia-induced sepsis in mice

Sepsis is a severe condition secondary to dysregulated host response to infection leading to tissue damage and organ dysfunction. Cannabinoid CB2 receptor has modulatory effects on the immune response. Therefore, this study investigated the effects of a cannabinoid CB2 receptor agonist on the local and systemic inflammatory process associated with pneumonia-induced sepsis. Pneumonia-induced sepsis was induced in mice by intratracheal inoculation of Klebsiella pneumoniae. Tissue and bronchoalveolar lavage (BAL) were collected 6, 24, or 48 h after surgery. Mice were treated with CB2 agonist (AM1241, 0.3 and 3 mg/kg, i.p.) and several parameters of inflammation were evaluated 24 h after sepsis induction. Polymorphonuclear cell migration to the infectious focus peaked 24 h after pneumonia-induced sepsis induction in male and female animals. Septic male mice presented a significant reduction of cannabinoid CB2 receptor density in the lung tissue after 24 h, which was not observed in females. CB2 expression in BAL macrophages was also reduced in septic animals. Treatment of septic mice with AM1241 reduced cell migration, local infection, myeloperoxidase activity, protein extravasation, and NOS-2 expression in the lungs. In addition, the treatment reduced plasma IL-1β, increased IL-10 and reduced the severity and mortality of septic animals. These results suggest that AM1241 promotes an interesting balance in the inflammatory response, maintaining lung function and preventing organ injury. Therefore, cannabinoid CB2 receptors are potential targets to control the excessive inflammatory process that occurs in severe conditions, and agonists of these receptors can be considered promising adjuvants in pneumonia-induced sepsis treatment.

Sex differences in cardiovascular response to sepsis

Recently, there has been increased recognition of the importance of sex as a biological factor affecting disease and health. Many preclinical studies have suggested that males may experience a less favorable outcome in response to sepsis than females. The underlying mechanisms for these differences are still largely unknown but are thought to be related to the beneficial effects of estrogen. Furthermore, the immunosuppressive role of testosterone is also thought to contribute to the sex-dependent differences that are present in clinical sepsis. There are still significant knowledge gaps in this field. This mini-review will provide a brief overview of sex-dependent variables in relation to sepsis and the cardiovascular system. Preclinical animal models for sepsis research will also be discussed. The intent of this mini-review is to inspire interest for future considerations of sex-related variables in sepsis that should be addressed to increase our understanding of the underlying mechanisms in sepsis-induced cardiovascular dysfunction for the identification of therapeutic targets and improved sepsis management and treatment.

The role of nitric oxide in sepsis-associated kidney injury

Sepsis is one of the leading causes of acute kidney injury (AKI), and several mechanisms including microcirculatory alterations, oxidative stress, and endothelial cell dysfunction are involved. Nitric oxide (NO) is one of the common elements to all these mechanisms. Although all three nitric oxide synthase (NOS) isoforms are constitutively expressed within the kidneys, they contribute in different ways to nitrergic signaling. While the endothelial (eNOS) and neuronal (nNOS) isoforms are likely to be the main sources of NO under basal conditions and participate in the regulation of renal hemodynamics, the inducible isoform (iNOS) is dramatically increased in conditions such as sepsis. The overexpression of iNOS in the renal cortex causes a shunting of blood to this region, with consequent medullary ischemia in sepsis. Differences in the vascular reactivity among different vascular beds may also help to explain renal failure in this condition. While most of the vessels present vasoplegia and do not respond to vasoconstrictors, renal microcirculation behaves differently from nonrenal vascular beds, displaying similar constrictor responses in control and septic conditions. The selective inhibition of iNOS, without affecting other isoforms, has been described as the ideal scenario. However, iNOS is also constitutively expressed in the kidneys and the NO produced by this isoform is important for immune defense. In this sense, instead of a direct iNOS inhibition, targeting the NO effectors such as guanylate cyclase, potassium channels, peroxynitrite, and S-nitrosothiols, may be a more interesting approach in sepsis-AKI and further investigation is warranted.

Acute Pneumonia Caused by Clinically Isolated Legionella pneumophila Sg 1, ST 62: Host Responses and Pathologies in Mice

Legionnaires' disease is a severe form of lung infection caused by bacteria belonging to the genus Legionella. The disease severity depends on both host immunity and L. pneumophila virulence. The objective of this study was to describe the pathological spectrum of acute pneumonia caused by a virulent clinical isolate of L. pneumophila serogroup 1, sequence type 62. In A/JOlaHsd mice, we compared two infectious doses, namely, 104 and 106 CFU, and their impact on the mouse status, bacterial clearance, lung pathology, and blood count parameters was studied. Acute pneumonia resembling Legionnaires' disease has been described in detail.

ClpV1 in avian pathogenic Escherichia coli is a crucial virulence factor contributing to meningitis in a mouse model in vivo

Meningitis associated with avian pathogenic Escherichia coli (APEC) is an infectious disease of poultry that has gained significant attention because of its potential to infect humans. APEC can utilize two type Ⅵ secretion systems (T6SSs) to efficiently transport toxin effectors into hosts. ClpV1 is one of the core components of the T6SS1. To our knowledge, it has not been clarified how the clpV1 gene contributes to the pathogenicity of meningitis-associated APEC. To investigate the function of the clpV1 gene in the process of Escherichia coli meningitis, a mutant TW-XMΔclpV1 strain was constructed and characterized. In this study, the clpV1 deleted strain displayed a significant decrease in both motility and biofilm formation as well as a reduction in the expression of virulence genes fliC, luxS and ibeA. In vivo studies using mouse and duck models found that the clpV1 deleted groups showed decreased proliferation, fewer lesions and lower expression of inflammatory cytokines in the brain suggesting that clpV1 is involved in the pathogenicity of TWXM. Besides, the decreased quantity of Evans Blue (EB) and the down-regulation of tight junctions (TJs) proteins in the mouse clpV1 deleted group demonstrating a more intact blood-brain barrier (BBB). In conclusion, these results suggest that the clpV1 gene is associated with motility and biofilm formation of TWXM strain and contributes to meningitis by damaging the BBB and brain tissues.

Rho-Proteins and Downstream Pathways as Potential Targets in Sepsis and Septic Shock: What Have We Learned from Basic Research

Sepsis and septic shock are associated with acute and sustained impairment in the function of the cardiovascular system, kidneys, lungs, liver, and brain, among others. Despite the significant advances in prevention and treatment, sepsis and septic shock sepsis remain global health problems with elevated mortality rates. Rho proteins can interact with a considerable number of targets, directly affecting cellular contractility, actin filament assembly and growing, cell motility and migration, cytoskeleton rearrangement, and actin polymerization, physiological functions that are intensively impaired during inflammatory conditions, such as the one that occurs in sepsis. In the last few decades, Rho proteins and their downstream pathways have been investigated in sepsis-associated experimental models. The most frequently used experimental design included the exposure to bacterial lipopolysaccharide (LPS), in both in vitro and in vivo approaches, but experiments using the cecal ligation and puncture (CLP) model of sepsis have also been performed. The findings described in this review indicate that Rho proteins, mainly RhoA and Rac1, are associated with the development of crucial sepsis-associated dysfunction in different systems and cells, including the endothelium, vessels, and heart. Notably, the data found in the literature suggest that either the inhibition or activation of Rho proteins and associated pathways might be desirable in sepsis and septic shock, accordingly with the cellular system evaluated. This review included the main findings, relevance, and limitations of the current knowledge connecting Rho proteins and sepsis-associated experimental models.

Environmental and clinical isolates of Herbaspirillum induce pulmonary infection in mice and its secretome is cytotoxic to human lung cells

Introduction. In recent years, the Herbaspirillum genus has emerged as a pathogen in healthcare-related infections and has became stablished as an opportunistic pathogen.Hypothesis/Gap Statement. Little is known about the pathogenesis induced by Herbaspirillum genus.Aim. To evaluate the cytotoxic effects of genus Herbaspirillum, its ability to adhere to lung human cells and the ability of environmental and clinical strains of Herbaspirillum to induce pneumonia in mice.Methodology. Environmental and clinical isolates of Herbaspirillum were examined for their cytotoxic effects on the Calu-3 cell lineage. Cytotoxic activity of secretome was tested using MTT/neutral red assays and cell morphology analysis. Herbaspirillum adhesion on Calu-3 cells was assessed using bright-field microscopy and cell-associated bacteria were counted. A mouse model of acute lung infection was done using a clinical and an environmental strain. Adult male mice were used, and the pneumonia was inducted by intra-tracheal inoculation of 10⁸ or 10⁹ bacteria. Mice weight variations were evaluated at the end of the experiment. Bronchoalveolar lavage was collected and evaluated for total and differential cytology. A histological examination of lungs was performed giving a histological score.Results. The secretomes of all the strains induced morphological alterations in cells, but only H. seropedicae SmR1 were cytotoxic in MTT and neutral red assays. Clinical strains of H. frisingense AU14459 and H. hutttiense subsp. huttiense AU11883 exhibited low adherence to lung cells, while SmR1 was non-adhesive. Following intratracheal inoculation, mice treated with 10⁹ c.f.u. of the SmR1 and AU11883 strains lost 18 and 6% of their weight over 7 days, respectively, and presented moderate clinical signs. Infected mice showed inflammatory cell infiltration in the perivascular and peribroncheal/peribronchiolar spaces. Bronchoalveolar fluid of mice inoculated with SmR1 10⁹ c.f.u. presented an increase in total leucocyte cells and in neutrophils population.Conclusion. These in vivo and in vitro results provide insights into how some Herbaspirillum strains cause infection in humans, providing a basis for the characterization of pathogenesis studies on this emerging infectious agent.

Angiotensin II receptor type 1 blockade improves hyporesponsiveness to vasopressors in septic shock

Sepsis activates the renin-angiotensin system and the production of angiotensin II, which has a key role in the regulation of blood pressure through AT1 receptors. However, excessive activation of AT1 receptor is associated with deleterious effects. We investigated the consequences of a differential blockade of AT1 receptor caused by two doses of losartan (0.25 mg/kg or 15 mg/kg, s.c), a selective AT1 receptor antagonist on sepsis outcome. These doses reduced the effect of angiotensin II in normal rats by 30% and >90% 8 h after administration, respectively, but only the higher dose maintained its inhibitory effect (~70%) 24 h after injection. Sepsis was induced by cecal ligation and puncture (CLP). Losartan was injected 2 h after CLP and parameters were evaluated 6 and 24 h after CLP. Septic rats developed hypotension and hyporesponsiveness to vasoconstrictors, an intense inflammatory process and increase in plasma markers of organ dysfunction. The lower dose of losartan improved the vasoconstrictive response to phenylephrine and angiotensin II, reduced lung myeloperoxidase and prevented leukopenia 24 h after CLP, but it did not reduce NOS-2 expression, plasma IL-6 levels or organ injury parameters of septic rats. On the other hand, the higher dose of losartan worsened the response to vasoconstrictors, potentiated the hypotension and increased further levels of creatine, urea and lactate in septic rats. Therefore, an early and partial blockade of AT1 receptor with a low dose of losartan may counteract sepsis-induced refractoriness to vasoconstrictors thus providing an opportunity to improve the outcome of this condition.

Aerobic exercise ameliorates survival, clinical score, lung inflammation, DNA and protein damage in septic mice

BACKGROUND AND OBJECTIVE

Sepsis is a potentially deadly organic dysfunction, and one of the main causes of mortality in intensive care units (ICU). Aerobic exercise (AE) is a preventive intervention in the establishment of inflammatory conditions, such as chronic lung diseases, but its effects on sepsis remain unclear. Therefore, this study aimed to evaluate the effects of AE on health condition, mortality, inflammation, and oxidative damage in an experimental model of pneumosepsis induced by Klebsiella pneumoniae (K.p).

METHODS

Animals were randomly allocated to Control; Exercise (EXE); Pneumosepsis (PS) or Exercise + Pneumosepsis (EPS) groups. Exercised animals were submitted to treadmill exercise for 2 weeks, 30 min/day, prior to pneumosepsis induced by K.p tracheal instillation.

RESULTS

PS produced a striking decrease in the health condition leading to massive death (85%). AE protected mice, as evidenced by better clinical scores and increased survival (70%). AE alleviated sickness behavior in EPS mice as evaluated in the open field test, and inflammation (nitrite + nitrate, TNF-α and IL-1β levels) in broncoalveolar fluid. Catalase activity, oxidative damage to proteins and DNA was increased by sepsis and prevented by exercise.

CONCLUSION

Overall, the beneficial effects of exercise in septic animals encompassed a markedly improved clinical score and decreased mortality, along with lower inflammation markers, less DNA and protein damage, as well as preserved antioxidant enzyme activity. Neural network risk analysis revealed exercise had a considerable effect on the overall health condition of septic mice.

Immunomodulatory Effects of Lactobacillus plantarum on Inflammatory Response Induced by Klebsiella pneumoniae

Some respiratory infections have been associated with dysbiosis of the intestinal microbiota. The underlying mechanism is incompletely understood, but cross talk between the intestinal microbiota and local immune cells could influence the immune response at distal mucosal sites. This has led to the concept of enhancing respiratory defenses by modulating the intestinal microbiota with exogenous supplementation of beneficial strains. In this study, we examined the effect of Lactobacillus plantarum CIRM653 on the inflammatory response induced by the pathogen Klebsiella pneumoniae Oral administration of L. plantarum CIRM653 to mice subsequently infected by K. pneumoniae via the nasal route (i) reduced the pulmonary inflammation response, with decreased numbers of lung innate immune cells (macrophages and neutrophils) and cytokines (mouse keratinocyte-derived chemokine [KC], interleukin-6 [IL-6], and tumor necrosis factor alpha [TNF-α]) in the bronchoalveolar fluid, and (ii) induced an immunosuppressive Treg response in lungs. In vitro coincubation of L. plantarum CIRM653 and K. pneumoniae with human dendritic cells and peripheral blood mononuclear cells resulted in decreased Th1 (IL-12p70 and interferon gamma [IFN-γ]) and Th17 (IL-23 and IL-17) and increased Treg (IL-10) cytokine levels compared to those observed for K. pneumoniae-infected cells. Neither K. pneumoniae nor L. plantarum CIRM653 had any effect on cytokine production by intestinal epithelial cells in vitro, but the induction of the NF-κB pathway and IL-8 and IL-6 production by K. pneumoniae in airway epithelial cells was significantly reduced when the pathogen was coincubated with L. plantarum CIRM653. The remote IL-10-mediated modulation of the K. pneumoniae inflammatory response by L. plantarum CIRM653 supports the concept of immunomodulation by beneficial bacteria through the gut-lung axis.

Treatment with andrographolide sulfonate provides additional benefits to imipenem in a mouse model of Klebsiella pneumoniae pneumonia

Klebsiella pneumoniae is a primary cause of community-acquired and nosocomial respiratory infections, and K. pneumoniae resistance to the current treatment approach with carbapenem is worsening. Andrographolide is a natural diterpenoid from Andrographis paniculata that was shown to exert anti-inflammatory activity. We herein show that pretreatment with a water-soluble andrographolide sulfonate significantly attenuate lung injury and infiltration of inflammatory cells. Interestingly, mice receiving combined treatment with andrographolide sulfonate displayed perfect survival rate than the mice treatment with imipenem alone, and monocyte chemotactic protein 5 (MCP-5) level was decreased further. These findings suggest that andrographolide sulfonate could as a potential synergist for antibiotic treatment of bacteria-induced inflammation.

Pulmonary and muscle profile in pneumosepsis: A temporal analysis of inflammatory markers

In sepsis, greater understanding of the inflammatory mechanism involved would provide insights into the condition and into its extension to the muscular apparatus in critically ill patients. Therefore, this study evaluates the inflammatory profile of pneumosepsis induced by Klebsiella pneumoniae (K.p.) in lungs and skeletal muscles during the first 72 h. Male BALB/c mice were divided into 4 groups, submitted to intratracheal inoculation of K.p. at a concentration of 2 × 10⁸ (PS) or PBS, and assessed after 24 (PS24), 48 (PS48) and 72 (PS72) hours. The Maximum Physical Capacity Test (MPCT) was performed before and after induction. Pulmonary inflammation was assessed by total cell number, nitric oxide levels (NOx), IL-1β and TNF-α levels in bronchoalveolar lavage fluid (BALF); inflammation and muscle trophism were evaluated by the levels of TNF-α, IL-6, TGF-β and BDNF by ELISA and NF-κB by western blotting in muscle tissue. Cells and colony forming units (CFU) were also analyzed in blood samples. The PS groups showed an increase in total cells in the BALF (p < 0.05), as well in the number of granulocytes in the blood (p < 0.05) and a decrease in performance in the MPCT (p < 0.05). NOx levels showed significant increase in PS72, when compared to Control group (p = 0.03). The PS24 showed a significant increase lung in TNF-α levels (p < 0.001) and in CFU (p = 0.013). We observed an increase in muscular IL-6 and nuclear NF-κB levels in PS24 group, when compared to PS48 and Control groups (p < 0.05). Nevertheless, mild signs of injury in the skeletal muscle tissue does not support the idea of an early muscular injury in this experimental model, suggesting that the low performance of the animals during the MPCT may be related to lung inflammation.

Experimental Sepsis Severity Score Associated to Mortality and Bacterial Spreading is Related to Bacterial Load and Inflammatory Profile of Different Tissues

Pneumonia-induced sepsis is responsible for about 50% of cases in the world. Patients who develop severe sepsis and septic shock present organ dysfunction and elevated plasma cytokine levels, which may lead to death. Clinical scores are important to evaluate the framework of septic patients and are used to predict the syndrome progress, prognostics, and mortality. The objective of the present study was to verify the applicability of a murine clinical score system to experimental sepsis (pneumonia-induced sepsis in male mice) and to correlate it with mortality and bacterial dissemination in different organs. Results demonstrated that animals which present higher clinical scores (>3) are more likely to die. Animals presenting high clinical scores exhibited transient bacteremia and displayed bacterial spreading to different organs such as heart, kidney, liver, and brain. There is a correlation between clinical score and bacterial dissemination and consequently greater risk of death. In addition, animals which showed bacterial dissemination in more than three organs and high clinical scores presented high levels of cytokines (TNF-α, MCP-1, IL-6, and IL-10) in plasma, lung, heart, liver, kidney, and brain. Therefore, our study suggests that (1) severity scores have predictive power in experimental models of sepsis and (2) high concentrations of tissue cytokines may contribute to localized inflammation and be one of the factors responsible for the systemic inflammatory syndrome of sepsis.

Treatment with Atorvastatin Provides Additional Benefits to Imipenem in a Model of Gram-Negative Pneumonia Induced by Klebsiella pneumoniae in Mice

The clinical pathogen Klebsiella pneumoniae is a relevant cause of nosocomial infections, and resistance to current treatment with carbapenem antibiotics is becoming a significant problem. Statins are inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) used for controlling plasma cholesterol levels. There is clinical evidence showing other effects of statins, including decrease of lung inflammation. In the current study, we show that pretreatment with atorvastatin markedly attenuated lung injury, which was correlated with a reduction in the cellular influx into the alveolar space and lungs and downmodulation of the production of proinflammatory mediators in the initial phase of infection in C57BL/6 mice with K. pneumoniae However, atorvastatin did not alter the number of bacteria in the lungs and blood of infected mice, despite decreasing local inflammatory response. Interestingly, mice that received combined treatment with atorvastatin and imipenem displayed better survival than mice treated with vehicle, atorvastatin, or imipenem alone. These findings suggest that atorvastatin could be an adjuvant in host-directed therapies for multidrug-resistant K. pneumoniae, based on its powerful pleiotropic immunomodulatory effects. Together with antimicrobial approaches, combination therapy with anti-inflammatory compounds could improve the efficiency of therapy during acute lung infections.

Cardiac hyporesponsiveness in severe sepsis is associated with nitric oxide-dependent activation of G protein receptor kinase

G protein-coupled receptor kinase isoform 2 (GRK2) has a critical role in physiological and pharmacological responses to endogenous and exogenous substances. Sepsis causes an important cardiovascular dysfunction in which nitric oxide (NO) has a relevant role. The present study aimed to assess the putative effect of inducible NO synthase (NOS2)-derived NO on the activity of GRK2 in the context of septic cardiac dysfunction. C57BL/6 mice were submitted to severe septic injury by cecal ligation and puncture (CLP). Heart function was assessed by isolated and perfused heart, echocardiography, and β-adrenergic receptor binding. GRK2 was determined by immunofluorescence and Western blot analysis in the heart and isolated cardiac myocytes. Sepsis increased NOS2 expression in the heart, increased plasma nitrite + nitrate levels, and reduced isoproterenol-induced isolated ventricle contraction, whole heart tension development, and β-adrenergic receptor density. Treatment with 1400W or with GRK2 inhibitor prevented CLP-induced cardiac hyporesponsiveness 12 and 24 h after CLP. Increased labeling of total and phosphorylated GRK2 was detected in hearts after CLP. With treatment of 1400W or in hearts taken from septic NOS2 knockout mice, the activation of GRK2 was reduced. 1400W or GRK2 inhibitor reduced mortality, improved echocardiographic cardiac parameters, and prevented organ damage. Therefore, during sepsis, NOS2-derived NO increases GRK2, which leads to a reduction in β-adrenergic receptor density, contributing to the heart dysfunction. Isolated cardiac myocyte data indicate that NO acts through the soluble guanylyl cyclase/cGMP/PKG pathway. GRK2 inhibition may be a potential therapeutic target in sepsis-induced cardiac dysfunction.

NEW & NOTEWORTHY The main novelty presented here is to show that septic shock induces cardiac hyporesponsiveness to isoproterenol by a mechanism dependent on nitric oxide and mediated by G protein-coupled receptor kinase isoform 2. Therefore, G protein-coupled receptor kinase isoform 2 inhibition may be a potential therapeutic target in sepsis-induced cardiac dysfunction.

Artesunate Protects Against the Organ Injury and Dysfunction Induced by Severe Hemorrhage and Resuscitation

OBJECTIVE

To evaluate the effects of artesunate on organ injury and dysfunction associated with hemorrhagic shock (HS) in the rat.

BACKGROUND

HS is still a common cause of death in severely injured patients and is characterized by impairment of organ perfusion, systemic inflammatory response, and multiple organ failure. There is no specific therapy that reduces organ injury/dysfunction. Artesunate exhibits pharmacological actions beyond its antimalarial activity, such as anticancer, antiviral, and anti-inflammatory effects.

METHODS

Rats were submitted to HS. Mean arterial pressure was reduced to 30 mm Hg for 90 minutes, followed by resuscitation. Rats were randomly treated with artesunate (2.4 or 4.8 mg/kg i.v.) or vehicle upon resuscitation. Four hours later, parameters of organ injury and dysfunction were assessed.

RESULTS

Artesunate attenuated the multiple organ injury and dysfunction caused by HS. Pathway analysis of RNA sequencing provided good evidence to support an effect of artesunate on the Akt-survival pathway, leading to downregulation of interleukin-1 receptor-associated kinase 1. Using Western blot analysis, we confirmed that treatment of HS rats with artesunate enhanced the phosphorylation (activation) of Protein kinase B (Akt) and endothelial nitric oxide synthase and the phosphorylation (inhibition) of glycogen synthase kinase-3β (GSK-3β). Moreover, artesunate attenuated the HS-induced activation of nuclear factor kappa B and reduced the expression of proinflammatory proteins (inducible nitric oxide synthase, tumor necrosis factor-α, and interleukin 6).

CONCLUSIONS

Artesunate attenuated the organ injury/dysfunction associated with HS by a mechanism that involves the activation of the Akt-endothelial nitric oxide synthase survival pathway, and the inhibition of glycogen synthase kinase-3β and nuclear factor kappa B. A phase II clinical trial evaluating the effects of good manufacturing practice-artesunate in patients with trauma and severe hemorrhage is planned.

Inflammatory Responses Regulating Alveolar Ion Transport during Pulmonary Infections

The respiratory epithelium is lined by a tightly balanced fluid layer that allows normal O₂ and CO₂ exchange and maintains surface tension and host defense. To maintain alveolar fluid homeostasis, both the integrity of the alveolar–capillary barrier and the expression of epithelial ion channels and pumps are necessary to establish a vectorial ion gradient. However, during pulmonary infection, auto- and/or paracrine-acting mediators induce pathophysiological changes of the alveolar–capillary barrier, altered expression of epithelial Na,K-ATPase and of epithelial ion channels including epithelial sodium channel and cystic fibrosis membrane conductance regulator, leading to the accumulation of edema and impaired alveolar fluid clearance. These mediators include classical pro-inflammatory cytokines such as TGF-β, TNF-α, interferons, or IL-1β that are released upon bacterial challenge with Streptococcus pneumoniae, Klebsiella pneumoniae, or Mycoplasma pneumoniae as well as in viral infection with influenza A virus, pathogenic coronaviruses, or respiratory syncytial virus. Moreover, the pro-apoptotic mediator TNF-related apoptosis-inducing ligand, extracellular nucleotides, or reactive oxygen species impair epithelial ion channel expression and function. Interestingly, during bacterial infection, alterations of ion transport function may serve as an additional feedback loop on the respiratory inflammatory profile, further aggravating disease progression. These changes lead to edema formation and impair edema clearance which results in suboptimal gas exchange causing hypoxemia and hypercapnia. Recent preclinical studies suggest that modulation of the alveolar–capillary fluid homeostasis could represent novel therapeutic approaches to improve outcomes in infection-induced lung injury.

Macrophage Galactose-Type Lectin-1 Deficiency Is Associated with Increased Neutrophilia and Hyperinflammation in Gram-Negative Pneumonia

C-type lectin receptors (CLRs), the carbohydrate-recognizing molecules, orchestrate host immune response in homeostasis and in inflammation. In the present study we examined the function of macrophage galactose-type lectin-1 (MGL1), a mammalian CLR, in pneumonic sepsis, a deadly immune disorder frequently associated with a nonresolving hyperinflammation. In a murine model of pneumonic sepsis using pulmonary infection with Klebsiella pneumoniae, the expression of MGL1 was upregulated in the lungs of K. pneumoniae-infected mice, and the deficiency of this CLR in MGL1(-/-) mice resulted in significantly increased mortality to infection than in the MGL1-sufficient wild-type mice, despite a similar bacterial burden. The phagocytic cells from MGL1(-/-) mice did not exhibit any defects in bacterial uptake and intracellular killing and were fully competent in neutrophil extracellular trap formation, a recently identified extracellular killing modality of neutrophils. Instead, the increased susceptibility of MGL1(-/-) mice seemed to correlate with severe lung pathology, indicating that MGL1 is required for resolution of pulmonary inflammation. Indeed, the MGL1(-/-) mice exhibited a hyperinflammatory response, massive pulmonary neutrophilia, and an increase in neutrophil-associated immune mediators. Concomitantly, MGL1-deficient neutrophils exhibited an increased influx in pneumonic lungs of K. pneumoniae-infected mice. Taken together, these results show a previously undetermined role of MGL1 in controlling neutrophilia during pneumonic infection, thus playing an important role in resolution of inflammation. To our knowledge, this is the first study depicting a protective function of MGL1 in an acute pneumonic bacterial infection.

Inhibition of IκB Kinase Attenuates the Organ Injury and Dysfunction Associated with Hemorrhagic Shock

Nuclear factor-kappa B (NF-κB) activation is widely implicated in multiple organ failure (MOF); however, a direct inhibitor of IκB kinase (IKK), which plays a pivotal role in the activation of NF-κB, has not been investigated in shock. Thus, the aim of the present work was to investigate the effects of an IKK inhibitor on the MOF associated with hemorrhagic shock (HS). Therefore, rats were subjected to HS and were resuscitated with the shed blood. Rats were treated with the inhibitor of IKK or vehicle at resuscitation. Four hours later, blood and organs were assessed for organ injury and signaling events involved in the activation of NF-κB. Additionally, survival following serum deprivation was assessed in HK-2 cells treated with the inhibitor of IKK. HS resulted in renal dysfunction, lung, liver and muscular injury, and increases in serum inflammatory cytokines. Kidney and liver tissue from HS rats revealed increases in phosphorylation of IKKαβ and IκBα, nuclear translocation of NF-κB and expression of inducible isoform of nitric oxide synthase (iNOS). IKK16 treatment upon resuscitation attenuated NF-κB activation and activated the Akt survival pathway, leading to a significant attenuation of all of the above parameters. Furthermore, IKK16 exhibited cytoprotective effects in human kidney cells. In conclusion, the inhibitor of IKK complex attenuated the MOF associated with HS. This effect may be due to the inhibition of the NF-κB pathway and activation of the survival kinase Akt. Thus, the inhibition of the IKK complex might be an effective strategy for the prevention of MOF associated with HS.

FPR2/ALX activation reverses LPS-induced vascular hyporeactivity in aorta and increases survival in a pneumosepsis model

The formylpeptide receptor 2 (FPR2/ALX) is a very promiscuous receptor, utilized by lipid and protein ligands that trigger pro- or anti-inflammatory responses. FPR2/ALX expression is increased in lung tissues of septic animals and its activation has a beneficial therapeutic effect by controlling exacerbated inflammation. Although FPR2/ALX expression was observed in vascular smooth muscle cells, its role in vascular reactivity in inflammatory conditions has not been studied. In this study, we report that LPS increases FPR2/ALX expression in vascular smooth muscle cells (A7r5 cells) and aorta tissue, and that the selective agonist WKYMVm reverses LPS-induced vascular hyporeactivity in mouse aorta rings. Mice bearing pneumosepsis by Klebsiella pneumoniae and treated with WKYMVm recovered the reactivity to vasoconstrictors and the survival improved by 40%. As for the mechanisms involved, FPR2/ALX activation decreases NO production in LPS-stimulated cells and aorta, but it does not seem involve the regulation of NOS-2 expression. The molecular mechanism by which the peptide inhibits NO production still needs to be elucidated, but our data suggests an important role for NO in the WKYMVm beneficial effect observed in LPS injury and sepsis. In conclusion, our data suggest, for the first time, that a receptor, primarily described as a mediator of immune responses, may have an important role in the vascular dysfunctions observed in sepsis and may be a possible target for new therapeutic interventions.

The role of leptin in the development of pulmonary neutrophilia in infection and acute lung injury

OBJECTIVES

One of the hallmarks of severe pneumonia and associated acute lung injury is neutrophil recruitment to the lung. Leptin is thought to be up-regulated in the lung following injury and to exert diverse effects on leukocytes, influencing both chemotaxis and survival. We hypothesized that pulmonary leptin contributes directly to the development of pulmonary neutrophilia during pneumonia and acute lung injury.

DESIGN

Controlled human and murine in vivo and ex vivo experimental studies.

SETTING

Research laboratory of a university hospital.

SUBJECTS

Healthy human volunteers and subjects hospitalized with bacterial and H1N1 pneumonia. C57Bl/6 and db/db mice were also used.

INTERVENTIONS

Lung samples from patients and mice with either bacterial or H1N1 pneumonia and associated acute lung injury were immunostained for leptin. Human bronchoalveolar lavage samples obtained after lipopolysaccharide-induced lung injury were assayed for leptin. C57Bl/6 mice were examined after oropharyngeal aspiration of recombinant leptin alone or in combination with Escherichia coli- or Klebsiella pneumoniae-induced pneumonia. Leptin-resistant (db/db) mice were also examined using the E. coli model. Bronchoalveolar lavage neutrophilia and cytokine levels were measured. Leptin-induced chemotaxis was examined in human blood- and murine marrow-derived neutrophils in vitro.

MEASUREMENTS AND MAIN RESULTS

Injured human and murine lung tissue showed leptin induction compared to normal lung, as did human bronchoalveolar lavage following lipopolysaccharide instillation. Bronchoalveolar lavage neutrophilia in uninjured and infected mice was increased and lung bacterial load decreased by airway leptin administration, whereas bronchoalveolar lavage neutrophilia in infected leptin-resistant mice was decreased. In sterile lung injury by lipopolysaccharide, leptin also appeared to decrease airspace neutrophil apoptosis. Both human and murine neutrophils migrated toward leptin in vitro, and this required intact signaling through the Janus Kinase 2/phosphatidylinositol-4,5-bisphosphate 3-kinase pathway.

CONCLUSIONS

We demonstrate that pulmonary leptin is induced in injured human and murine lungs and that this cytokine is effective in driving alveolar airspace neutrophilia. This action appears to be caused by direct effects of leptin on neutrophils.

Dual role of lipoxin A4 in pneumosepsis pathogenesis

Lipoxin A4 (LXA4) is an endogenous lipid mediator with potent anti-inflammatory actions but its role in infectious processes is not well understood. We investigated the involvement of LXA4 and its receptor FPR2/ALX in the septic inflammatory dysregulation. Pneumosepsis was induced in mice by inoculation of Klebsiella pneumoniae. LXA4 levels and FPR2/ALX expression in the infectious focus as well as the effects of treatment with receptor agonists (LXA4 and BML-111) and antagonists (BOC-2 and WRW(4)) in early (1h) and late (24h) sepsis were studied. Sepsis induced an early increase in LXA4, FPR2/ALX lung expression, local and systemic infection and inflammation, and mortality. Treatment with BOC-2 in early sepsis increased leukocyte migration to the focus, and reduced bacterial load and dissemination. Inhibition of 5- and 15-lipoxygenase in early sepsis also increased leukocyte migration. Early treatment with WRW(4) and BOC-2 improved survival. Treatment with authentic LXA4 or BML-111 in early sepsis decreased cell migration and worsened the infection. In late sepsis, treatment with BOC-2 had no effect, but LXA4 improved the survival rate by reducing the excessive inflammatory response, this effect being abolished by pretreatment with BOC-2. Thus, the anti-inflammatory and pro-resolution mediator LXA4 and its receptor FPR2/ALX levels were increased in the early phase of sepsis, contributing to the septic inflammatory dysregulation. In addition, LXA4 has a dual role in sepsis and that its beneficial or harmful effects are critically dependent on the time. Therefore, a proper interference with LXA4 system may be a new therapeutic avenue to treat sepsis.