Therapeutic strategies in pneumonia: going beyond antibiotics

SPAUTIN-1 alleviates LPS-induced acute lung injury by inhibiting NF-κB pathway in neutrophils

BACKGROUND

Acute lung injury (ALI) is an inflammatory condition characterized by acute damage to lung tissue. SPAUTIN-1, recognized as a small molecule drug targeting autophagy and USP10/13, has been reported for its potential to inhibit oxidative stress damage in various tissue injuries. However, the role and mechanism of SPAUTIN-1 in ALI remain unclear. This study aims to elucidate the protective effects of SPAUTIN-1 on ALI, with a particular focus on its role and mechanism in pulmonary inflammatory responses.

METHODS

Lipopolysaccharides (LPS) were employed to induce inflammation-mediated ALI. Bleomycin was used to induce non-inflammation-mediated ALI. The mechanism of SPAUTIN-1 action was identified through RNA-Sequencing and subsequently validated in mouse primary cells. Tert-butyl hydroperoxide (TBHP) was utilized to create an in vitro model of lung epithelial cell oxidative stress with MLE-12 cells.

RESULTS

SPAUTIN-1 significantly mitigated LPS-induced lung injury and inflammatory responses, attenuated necroptosis and apoptosis in lung epithelial cells, and inhibited autophagy in leukocytes and epithelial cells. However, SPAUTIN-1 exhibited no significant effect on bleomycin-induced lung injury. RNA-sequencing results demonstrated that SPAUTIN-1 significantly inhibited the NF-κB signaling pathway in leukocytes, a finding consistently confirmed by mouse primary cell assays. In vitro experiments further revealed that SPAUTIN-1 effectively mitigated oxidative stress injury in MLE-12 cells induced by TBHP.

CONCLUSION

SPAUTIN-1 alleviated LPS-induced inflammatory injury by inhibiting the NF-κB pathway in leukocytes and protected epithelial cells from oxidative damage, positioning it as a potential therapeutic candidate for ALI.

Immunomodulatory Effects of Fluoroquinolones in Community-Acquired Pneumonia-Associated Acute Respiratory Distress Syndrome

Community-acquired pneumonia is reported as one of the infectious diseases that leads to the development of acute respiratory distress syndrome. The innate immune system is the first line of defence against microbial invasion; however, its dysregulation during infection, resulting in an increased pathogen load, stimulates the over-secretion of chemokines and pro-inflammatory cytokines. This phenomenon causes damage to the epithelial-endothelial barrier of the pulmonary alveoli and the leakage of the intravascular protein into the alveolar lumen. Fluoroquinolones are synthetic antimicrobial agents with immunomodulatory properties that can inhibit bacterial proliferation as well as exhibit anti-inflammatory activities. It has been demonstrated that the structure of fluoroquinolones, particularly those with a cyclopropyl group, exerts immunomodulatory effects. Its capability to inhibit phosphodiesterase activity leads to the accumulation of intracellular cAMP, which subsequently enhances PKA activity, resulting in the inhibition of transcriptional factor NF-κB and the activation of CREB. Another mechanism reported is the inhibition of TLR and ERK signalling pathways. Although the sequence of events has not been completely understood, significant progress has been made in comprehending the specific mechanisms underlying the immunomodulatory effects of fluoroquinolones. Here, we review the indirect immunomodulatory effects of FQs as an alternative to empirical therapy in patients diagnosed with community-acquired pneumonia.

Pretreatment with 3-methyladenine ameliorated Pseudomonas aeruginosa-induced acute pneumonia by inhibiting cell death of neutrophils in a mouse infection model

Pseudomonas aeruginosa is one of the leading causes of nosocomial infections worldwide. Clinical isolates that are resistant to multiple antimicrobials make it intractable. The interactions between P. aeruginosa and host cell death have multiple effects on bacterial clearance and inflammation; however, the potential intervention effects remain to be defined. Herein, we demonstrated that intravenous administration of 3-methyladenine before, but not after, P. aeruginosa infection enhanced autophagy-independent survival, which was accompanied by a decrease in the bacterial load, alleviation of pathology and reduction in inflammatory cytokines, in an acute pneumonia mouse model. Interestingly, these beneficial effects were not dependent on neutrophil recruitment or phagocytosis, but on the enhanced killing capacity induced by inhibiting the cell death of 3-MA pretreated neutrophils. These findings demonstrate a novel protective role of 3-MA pretreatment in P. aeruginosa-induced acute pneumonia.

Clarithromycin for community-acquired pneumonia in adults: focus on anti-inflammatory properties

Aim. To evaluate clinical efficacy, anti-inflammatory and immunomodulatory activity of clarithromycin in adults with severe community-acquired pneumonia (sCAP). Materials and methods. A prospective observational study recruited adult hospitalized patients with verified sCAP. Clarithromycin was prescribed as a component of combination antibiotic therapy (ABT) with a -lactam antibiotic (AB). The choice of -lactam AB was carried out by the attending physician in accordance with national clinical guidelines and routine practice of the medical institution. Along with assessment clinical efficacy, the dynamics of inflammatory markers in blood serum was recorded: C-reactive protein, procalcitonin (PCT), tumor necrosis factor , interleukins 1-beta (IL-1) and interleukin 6 (IL-6). The total duration of ABT was 714 days. Results. Altogether 20 patients (13 males, 7 females) aged from 18 to 84 years old were enrolled. As a result of the use of combined ABT with -lactam AB and clarithromycin, a significant decrease in the level of C-reactive protein was noted by the 35th day of therapy (from 74.6 to 14.1 mg/l). An increase in serum PCT was observed in half of the patients; during treatment, the level of PCT significantly decreased. Similar dynamics was detected for IL-6 its content in the blood serum decreased by the time of the end of ABT by 6.8 times compared with the baseline. A decrease in the level of tumor necrosis factor to the reference value was observed in most patients already in the early stages by 35 days of ABT. The majority of patients showed positive dynamics of clinical signs and symptoms with resolution of respiratory failure and other complications of sCAP. In almost half of the patients, the criteria for clinical stability were achieved in the early stages, which made it possible to switch to oral ABT. Conclusion. The results of the study are consistent with literature data indicating a rapid decrease in inflammatory markers when clarithromycin is administered to patients with sCAP. Its results can be a starting point for comparative randomized trials assessing both clinical outcomes and immunological parameters when using different classes of antibiotics for the treatment of sCAP.

Adjunctive therapy with the Tie2 agonist Vasculotide reduces pulmonary permeability in Streptococcus pneumoniae infected and mechanically ventilated mice

Community acquired pneumonia, mainly caused by Streptococcus pneumoniae (S.pn.), is a common cause of death worldwide. Despite adequate antibiotic therapy, pneumococcal pneumonia can induce pulmonary endothelial hyperpermeability leading to acute lung injury, which often requires mechanical ventilation (MV) causing ventilator-induced lung injury (VILI). Endothelial stabilization is mediated by angiopoietin-1 induced Tie2 activation. PEGylated (polyethylene glycol) Tie2-agonist Vasculotide (VT) mimics Angiopietin-1 effects. Recently, VT has been shown to reduce pulmonary hyperpermeability in murine pneumococcal pneumonia. The aim of this study was to determine whether VT reduces lung damage in S.pn. infected and mechanically ventilated mice. Pulmonary hyperpermeability, immune response and bacterial load were quantified in S.pn. infected mice treated with Ampicillin + /−VT and undergoing six hours of MV 24 h post infection. Histopathological lung changes, Tie2-expression and -phosphorylation were evaluated. VT did not alter immune response or bacterial burden, but interestingly combination treatment with ampicillin significantly reduced pulmonary hyperpermeability, histological lung damage and edema formation. Tie2-mRNA expression was reduced by S.pn. infection and/or MV but not restored by VT. Moreover, Tie2 phosphorylation was not affected by VT. These findings indicate that VT may be a promising adjunctive treatment option for prevention of VILI in severe pneumococcal pneumonia.

Unmet needs in pneumonia research: a comprehensive approach by the CAPNETZ study group

Introduction

Despite improvements in medical science and public health, mortality of community-acquired pneumonia (CAP) has barely changed throughout the last 15 years. The current SARS-CoV-2 pandemic has once again highlighted the central importance of acute respiratory infections to human health. The “network of excellence on Community Acquired Pneumonia” (CAPNETZ) hosts the most comprehensive CAP database worldwide including more than 12,000 patients. CAPNETZ connects physicians, microbiologists, virologists, epidemiologists, and computer scientists throughout Europe. Our aim was to summarize the current situation in CAP research and identify the most pressing unmet needs in CAP research.

Methods

To identify areas of future CAP research, CAPNETZ followed a multiple-step procedure. First, research members of CAPNETZ were individually asked to identify unmet needs. Second, the top 100 experts in the field of CAP research were asked for their insights about the unmet needs in CAP (Delphi approach). Third, internal and external experts discussed unmet needs in CAP at a scientific retreat.

Results

Eleven topics for future CAP research were identified: detection of causative pathogens, next generation sequencing for antimicrobial treatment guidance, imaging diagnostics, biomarkers, risk stratification, antiviral and antibiotic treatment, adjunctive therapy, vaccines and prevention, systemic and local immune response, comorbidities, and long-term cardio-vascular complications.

Conclusion

Pneumonia is a complex disease where the interplay between pathogens, immune system and comorbidities not only impose an immediate risk of mortality but also affect the patients’ risk of developing comorbidities as well as mortality for up to a decade after pneumonia has resolved. Our review of unmet needs in CAP research has shown that there are still major shortcomings in our knowledge of CAP.

Title-Inflammatory Signaling Pathways in Allergic and Infection-Associated Lung Diseases

Lung inflammation can be caused by pathogen infection alone or by allergic disease, leading to pneumonitis. Most of the allergens (antigens) that cause allergic lung diseases, including asthma and hypersensitivity pneumonitis (HP), are derived from microorganisms, such as bacteria, viruses, and fungi, but some inorganic materials, such as mercury, can also cause pneumonitis. Certain allergens, including food and pollen, can also cause acute allergic reactions and lead to lung inflammation in individuals predisposed to such reactions. Pattern recognition-associated and damage-associated signaling by these allergens can be critical in determining the type of hypersensitization and allergic disease, as well as the potential for fibrosis and irreversible lung damage. This review discusses the signs, symptoms, and etiology of allergic asthma, and HP. Furthermore, we review the immune response and signaling pathways involved in pneumonitis due to both microbial infection and allergic processes. We also discuss current and potential therapeutic interventions for infection-associated and allergic lung inflammation.

Neutrophil-Derived Extracellular Vesicles Activate Platelets after Pneumolysin Exposure

Pneumolysin (PLY) is a pore-forming toxin of Streptococcus pneumoniae that contributes substantially to the inflammatory processes underlying pneumococcal pneumonia and lung injury. Host responses against S. pneumoniae are regulated in part by neutrophils and platelets, both individually and in cooperative interaction. Previous studies have shown that PLY can target both neutrophils and platelets, however, the mechanisms by which PLY directly affects these cells and alters their interactions are not completely understood. In this study, we characterize the effects of PLY on neutrophils and platelets and explore the mechanisms by which PLY may induce neutrophil–platelet interactions. In vitro studies demonstrated that PLY causes the formation of neutrophil extracellular traps (NETs) and the release of extracellular vesicles (EVs) from both human and murine neutrophils. In vivo, neutrophil EV (nEV) levels were increased in mice infected with S. pneumoniae. In platelets, treatment with PLY induced the cell surface expression of P-selectin (CD62P) and binding to annexin V and caused a significant release of platelet EVs (pl-EVs). Moreover, PLY-induced nEVs but not NETs promoted platelet activation. The pretreatment of nEVs with proteinase K inhibited platelet activation, indicating that the surface proteins of nEVs play a role in this process. Our findings demonstrate that PLY activates neutrophils and platelets to release EVs and support an important role for neutrophil EVs in modulating platelet functions in pneumococcal infections.

Age, Period and Cohort Analysis of Rates of Emergency Department Visits Due to Pneumonia in Taiwan, 1998-2012

Background

Emergency room (ER) physicians need to face clinically suspected pneumonia patients in the front line of medical care and must do to give major medical interventions if patients show severity in pneumonia.

Methods

The data of pneumonia-related ER visit rates were categorized based on the International Classification of Disease (ICD) Codes (480–486) between 1998 and 2012. We use an age-period-cohort (APC) model to separate the pneumonia-related ER visit rates to identify the effects of age, time period, and cohort for a total of 1,813,588 patients.

Results

The age effect showed high risk for pediatric and elder populations. There is a significant increasing period effect, which increased from 1998 to 2012. The cohort effect tended to show an oscillation from 1913 to 1988 and the reverse in a recent cohort. Furthermore, the visit rate of pneumonia showed an increase from 1998 to 2012 for both genders.

Conclusion

Age is a risk factor for pneumonia-related ER visits, especially for children and adolescents and older patients. Period and cohort effects were also found to increase the pneumonia visit rates. An APC model used to provide an advance clue for trend of pneumonia-related ER visit rates diversified.

Granulocyte-targeted therapies for airway diseases

The average respiration rate for an adult is 12-20 breaths per minute, which constantly exposes the lungs to allergens and harmful particles. As a result, respiratory diseases, which includes asthma, chronic obstructive pulmonary disease (COPD) and acute lower respiratory tract infections (LTRI), are a major cause of death worldwide. Although asthma, COPD and LTRI are distinctly different diseases with separate mechanisms of disease progression, they do share a common feature - airway inflammation with intense recruitment and activation of granulocytes and mast cells. Neutrophils, eosinophils, basophils, and mast cells are crucial players in host defense against pathogens and maintenance of lung homeostasis. Upon contact with harmful particles, part of the pulmonary defense mechanism is to recruit these cells into the airways. Despite their protective nature, overactivation or accumulation of granulocytes and mast cells in the lungs results in unwanted chronic airway inflammation and damage. As such, understanding the bright and the dark side of these leukocytes in lung physiology paves the way for the development of therapies targeting this important mechanism of disease. Here we discuss the role of granulocytes in respiratory diseases and summarize therapeutic strategies focused on granulocyte recruitment and activation in the lungs.

Pretreatment of nafithromycin attenuates inflammatory response in murine lipopolysaccharide induced acute lung injury

Acute respiratory distress syndrome following an acute lung injury (ALI) is a life threatening inflammatory condition predominantly characterized by vascular protein leakage, neutrophil recruitment and overexpression of proinflammatory cytokines. Pulmonary and systemic bacterial infections are the major cause of ALI wherein the bacterial cell components play a crucial role. Macrolide/ketolide antibiotics are reported to possess immunomodulatory activity; as a result improved survival has been noted in pneumonia patients. Hence immunomodulatory activity of nafithromycin, a novel lactone ketolide antibacterial agent was assessed in the murine LPS induced ALI model. Vehicle, nafithromycin (100 mg/kg), azithromycin (600 mg/kg) and dexamethasone (20 mg/kg) were administered orally, 1 h prior to LPS challenge and bronchoalveolar lavage (BAL) fluid was collected thereafter at 18, 24 and 48 h to determine the total cell count, total protein, myeloperoxidase (MPO), tumor necrosis factor (TNF)-α and interleukin (IL)-6. Results from the current study showed that pretreatment with nafithromycin significantly reduced the total cell count, total protein, MPO, TNF-α and IL-6 levels in BAL fluid compared to LPS control group. Histopathological evaluations also suggest significant reduction in neutrophil infiltration by nafithromycin. Dexamethasone, a positive reference standard as expected exhibited potent anti-inflammatory activity. The immunomodulatory effect of nafithromycin at dose of 100 mg/kg was comparable to azithromycin dosed at 600 mg/kg. As a result of immunomodulatory activity, nafithromycin is expected to provide additional clinical benefits by resolving the secondary complications associated with severe pneumonia and thereby improving survival in such patients.

Btk inhibitor ibrutinib reduces inflammatory myeloid cell responses in the lung during murine pneumococcal pneumonia

Background

Streptococcus pneumoniae is a major causative agent in community-acquired pneumonia and sepsis. Overwhelming lung inflammation during pneumococcal pneumonia may hamper lung function. Ibrutinib is an irreversible inhibitor of Bruton’s tyrosine kinase (Btk), a key signaling protein controlling the activation of various immune cells, including macrophages and neutrophils. The aim of this study was to determine whether ibrutinib treatment ameliorates acute lung inflammation during pneumococcal pneumonia.

Methods

Mice were treated orally with ibrutinib and the effect on acute pulmonary inflammation elicited by the gram-positive bacterial cell wall component lipoteichoic acid (LTA) and during ceftriaxone-treated pneumococcal pneumonia was assessed.

Results

Treatment with ibrutinib prior to and after intranasal LTA instillation reduced alveolar macrophage activation, neutrophil influx, cytokine release and plasma leakage into the lung. Postponed treatment with ibrutinib supplementing antibiotic therapy during ongoing pneumococcal pneumonia did not impair bacterial killing in lung, blood and spleen. In this setting, ibrutinib reduced alveolar macrophage and systemic neutrophil activation and substantially diminished further monocyte and neutrophil influx in the lung. In vitro, ibrutinib inhibited macrophage TNF secretion and neutrophil activation upon LTA and pneumococcal stimulation.

Conclusions

Taken together, these data indicate that the Btk inhibitor ibrutinib reduces inflammatory myeloid cell responses during acute pulmonary inflammation evoked by LTA and antibiotic-treated pneumococcal pneumonia and suggest that ibrutinib has the potential to inhibit ongoing lung inflammation in an acute infectious setting.

Electronic supplementary material

The online version of this article (10.1186/s10020-018-0069-7) contains supplementary material, which is available to authorized users.

Evaluation of Ventilation-Induced Lung Inflammation Through Multi-Scale Simulations

Ventilation-induced lung injury is a common problem faced by patients with respiratory problems who require mechanical ventilation (MV). This injury may lead to a greater chance of developing or exacerbating the acute respiratory distress syndrome which further complicates the therapeutic use of MV. The chain of events begins with the MV initiating an immune response that leads to inflammation induced tissue material alteration (stiffening) and eventually the loss of lung resistance. It is clear from this sequence of events that the phenomenon of ventilation induced injury is multi-scale by nature and, hence, requires holistic analysis involving simulations and informatics. An effective approach to this problem is to break it down into several major physical models. Each physical model is developed separately and can be seen as a component in a larger system that comprises the scale of the problem being investigated. In this paper, a multi-scale system consisting of breathing mechanics, tissue deformation, and cellular mechanics models is developed to assess the immune response. To demonstrate the potential of the model, a fluid–solid model is employed for breathing mechanics, a plane-strain elasticity model is applied to assess tissue deformation, and a cellular automata (CA) model is developed to account for immune response. A case study of three lower airways is presented. The CA model shows that this increased the immune response by five times, which correlates with alteration in the tissue microstructure. This alteration in turn is reflected in the material constant value obtained in the tissue mechanics model. However, the changes in strain rates in the airways after inflammation (and hence, lung compliance) were not as significant as the rates of change in immune response. Finally, results from the fluid–solid model demonstrate its potential for airflow characterization caused by tissue deformation that could lead to disease identification.

An update on the pharmacotherapeutic management of lower respiratory tract infections

INTRODUCTION

Our knowledge about lower respiratory tract infections (LRTIs) has improved substantially in the last years, but the management of respiratory infections is still a challenge and we are still far from using precision medicine in their treatment. Areas covered: The approaches developed in recent years to improve the pharmacotherapeutic management of LRTIs, such as novel diagnostic assays to facilitate medical decision-making, attempts for selecting an optimal empiric antibiotic regimen, and the role of new and possibly unproven adjunctive therapies, are described. Expert opinion: Early and appropriate antibiotics remain the cornerstone in the treatment of LRTIs. The updated trend is to apply antimicrobial stewardship principles and initiatives to optimize both the management and the outcomes of LTRIs. Biomarkers, mainly C-reactive protein (CRP) and procalcitonin (PCT), can improve the diagnostic and prognostic assessment of LRTIs and aid to guide antibiotic therapy. The widespread use of antimicrobial agents has greatly contributed to faster development of antibiotic resistance and the emergence of opportunistic pathogens, which substitute the indigenous microbiota. However, very few new antibiotics in development to overcome existing resistance and ensure continued success in the treatment of LRTIs have been approved, likely because antibiotic stewardship programs discourage the use of new agents.

Simulation of Healing Threshold in Strain-Induced Inflammation Through a Discrete Informatics Model

Respiratory diseases such as asthma and acute respiratory distress syndrome as well as acute lung injury involve inflammation at the cellular level. The inflammation process is very complex and is characterized by the emergence of cytokines along with other changes in cellular processes. Due to the complexity of the various constituents that makes up the inflammation dynamics, it is necessary to develop models that can complement experiments to fully understand inflammatory diseases. In this study, we developed a discrete informatics model based on cellular automata (CA) approach to investigate the influence of elastic field (stretch/strain) on the dynamics of inflammation and account for probabilistic adaptation based on statistical interpretation of existing experimental data. Our simulation model investigated the effects of low, medium, and high strain conditions on inflammation dynamics. Results suggest that the model is able to indicate the threshold of innate healing of tissue as a response to strain experienced by the tissue. When strain is under the threshold, the tissue is still capable of adapting its structure to heal the damaged part. However, there exists a strain threshold where healing capability breaks down. The results obtained demonstrate that the developed discrete informatics based CA model is capable of modeling and giving insights into inflammation dynamics parameters under various mechanical strain/stretch environments.

Current therapeutics and prophylactic approaches to treat pneumonia

Bacterial pneumonia caused by Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, Mycoplasma pneumoniae, and Klebsiella pneumoniae represents a frequent cause of mortality worldwide. The increased incidence of pneumococcal diseases in both developed and developing countries is alarmingly high, affecting infants and aged adult populations. The growing rate of antibiotic resistance and biofilm formation on medical device surfaces poses a greater challenge for treating respiratory infections. Over recent years, a better understanding of bacterial growth, metabolism, and virulence has offered several potential targets for developing therapeutics against bacterial pneumonia. This chapter will discuss the current and developing trends in treating bacterial pneumonia.