Pharmacologic inhibition of MEK1/2 reduces lung inflammation without impairing bacterial clearance in experimental Pseudomonas aeruginosa pneumonia

MEK1/2 inhibition decreases pro-inflammatory responses in macrophages from people with cystic fibrosis and mitigates severity of illness in experimental murine methicillin-resistant Staphylococcus aureus infection

Chronic pulmonary bacterial infections and associated inflammation remain a cause of morbidity and mortality in people with cystic fibrosis (PwCF) despite new modulator therapies. Therapies targeting host factors that dampen detrimental inflammation without suppressing immune responses critical for controlling infections remain limited, while the development of lung infections caused by antimicrobial resistant bacteria is an increasing global problem, and a significant challenge in CF. Pharmacological compounds targeting the mammalian MAPK proteins MEK1 and MEK2, referred to as MEK1/2 inhibitor compounds, have potential combined anti-microbial and anti-inflammatory effects. Here we examined the immunomodulatory properties of MEK1/2 inhibitor compounds PD0325901, trametinib, and CI-1040 on CF innate immune cells. Human CF macrophage and neutrophil phagocytic functions were assessed by quantifying phagocytosis of serum opsonized pHrodo red E. coli, Staphylococcus aureus, and zymosan bioparticles. MEK1/2 inhibitor compounds reduced CF macrophage pro-inflammatory cytokine production without impairing CF macrophage or neutrophil phagocytic abilities. Wild-type C57BL6/J and Cftr tm1kth (F508del homozygous) mice were used to evaluate the in vivo therapeutic potential of PD0325901 compared to vehicle treatment in an intranasal methicillin-resistant Staphylococcus aureus (MRSA) infection with the community-acquired MRSA strain USA300. In both wild-type and CF mice, PD0325901 reduced inflammation associated body mass loss. Wild-type mice treated with PD0325901 had significant reduction in neutrophil-mediated inflammation compared to vehicle treatment groups, with preserved clearance of bacteria in lung, liver, or spleen 1 day after infection in either wild-type or CF mouse models. In summary, this study provides the first data evaluating the therapeutic potential of MEK1/2 inhibitor to modulate CF immune cells and demonstrates that MEK1/2 inhibitors diminish pro-inflammatory responses without impairing host defense mechanisms required for acute pathogen clearance.

MEK1/2 inhibition decreases pro-inflammatory responses in macrophages from people with cystic fibrosis and mitigates severity of illness in experimental murine methicillin-resistant Staphylococcus aureus infection

Chronic pulmonary bacterial infections and associated inflammation remain a cause of morbidity and mortality in people with cystic fibrosis (PwCF) despite new modulator therapies. Therapies targeting host factors that dampen detrimental inflammation without suppressing immune responses critical for controlling infections remain limited, while the acquisition of antibiotic resistance bacterial infections is an increasing global problem, and a significant challenge in CF. Pharmacological compounds targeting the mammalian MAPK proteins MEK1 and MEK2, referred to as MEK1/2 inhibitor compounds, have potential combined anti-microbial and anti-inflammatory effects. Here we examined the immunomodulatory properties of MEK1/2 inhibitor compounds PD0325901, trametinib, and CI-1040 on CF innate immune cells. Human CF macrophage and neutrophil phagocytic functions were assessed by quantifying phagocytosis of serum opsonized pHrodo red E. coli , Staphylococcus aureus , and zymosan bioparticles. MEK1/2 inhibitor compounds reduced CF macrophage pro-inflammatory cytokine production without impairing CF macrophage or neutrophil phagocytic abilities. Wild-type C57BL6/J and Cftr tm1kth (F508del homozygous) mice were used to evaluate the in vivo therapeutic potential of PD0325901 compared to vehicle treatment in an intranasal methicillin-resistant Staphylococcus aureus (MRSA) infection with the community-acquired MRSA strain USA300. In both wild-type and CF mice, PD0325901 reduced infection related weight loss compared to vehicle treatment groups but did not impair clearance of bacteria in lung, liver, or spleen 1 day after infection. In summary, this study provides the first data evaluating the therapeutic potential of MEK1/2 inhibitor to modulate CF immune cells, and demonstrates that MEK1/2 inhibitors dampen pro-inflammatory responses without impairing host defense mechanisms mediating pathogen clearance.

Pathogenesis of pneumonia and acute lung injury

Pneumonia and its sequelae, acute lung injury, present unique challenges for pulmonary and critical care healthcare professionals, and these challenges have recently garnered global attention due to the ongoing Sars-CoV-2 pandemic. One limitation to translational investigation of acute lung injury, including its most severe manifestation (acute respiratory distress syndrome, ARDS) has been heterogeneity resulting from the clinical and physiologic diagnosis that represents a wide variety of etiologies. Recent efforts have improved our understanding and approach to heterogeneity by defining sub-phenotypes of ARDS although significant gaps in knowledge remain. Improving our mechanistic understanding of acute lung injury and its most common cause, infectious pneumonia, can advance our approach to precision targeted clinical interventions. Here, we review the pathogenesis of pneumonia and acute lung injury, including how respiratory infections and lung injury disrupt lung homoeostasis, and provide an overview of respiratory microbial pathogenesis, the lung microbiome, and interventions that have been demonstrated to improve outcomes-or not-in human clinical trials.

MAP2K2 Delays Recovery in Murine Models of Acute Lung Injury and Associates with Acute Respiratory Distress Syndrome Outcome

Acute respiratory distress syndrome (ARDS) remains a significant problem in need of new pharmaceutical approaches to improve its resolution. Studies comparing gene expression signatures in rodents and humans with lung injury reveal conserved pathways, including MAPK (mitogen-activated protein kinase)/ERK (extracellular signal-related protein kinase) activation. In preclinical acute lung injury (ALI) models, inhibition of MAP2K1 (MAPK kinase 1)/MAP2K2 (MAPK kinase 2) improves measures of ALI. Myeloid cell deletion of MAP2K1 results in sustained MAP2K2 activation and nonresolving ALI, suggesting that MAP2K2 deactivation may be a key driver of ALI resolution. We used human genomic data from the iSPAAR (Identification of SNPs Predisposing to Altered Acute Lung Injury Risk) Consortium to assess genetic variants in MAP2K1 and MAP2K2 for association with mortality from ARDS. To determine the role of MAP2K2 in ALI recovery, we studied mice deficient in Map2k2 (Mek2-/-) and wild-type control mice in ALI models. We identified a MAP2K2 variant that was associated with death in ARDS and MAP2K2 expression. In Pseudomonas aeruginosa ALI, Mek2-/- mice had similar early alveolar neutrophilic recruitment but faster resolution of alveolar neutrophilia and vascular leak. Gene expression analysis revealed a role for MAP2K2 in promoting and sustaining select proinflammatory pathway activation in ALI. Bone marrow chimera studies indicate that leukocyte MAP2K2 is the key regulator of ALI duration. These studies implicate a role for MAP2K2 in ALI duration via transcriptional regulation of inflammatory programming with potential relevance to ARDS. Targeting leukocyte MAP2K2 may be an effective strategy to promote ALI resolution.

MEK1 regulates pulmonary macrophage inflammatory responses and resolution of acute lung injury

The MEK1/2-ERK1/2 pathway has been implicated in regulating the inflammatory response to lung injury and infection, and pharmacologic MEK1/2 inhibitor compounds are reported to reduce detrimental inflammation in multiple animal models of disease, in part through modulation of leukocyte responses. However, the specific contribution of myeloid MEK1 in regulating acute lung injury (ALI) and its resolution remain unknown. Here, the role of myeloid Mek1 was investigated in a murine model of LPS-induced ALI (LPS-ALI) by genetic deletion using the Cre-floxed system (LysMCre × Mekfl), and human alveolar macrophages from healthy volunteers and patients with acute respiratory distress syndrome (ARDS) were obtained to assess activation of the MEK1/2-ERK1/2 pathway. Myeloid Mek1 deletion results in a failure to resolve LPS-ALI, and alveolar macrophages lacking MEK1 had increased activation of MEK2 and the downstream target ERK1/2 on day 4 of LPS-ALI. The clinical significance of these findings is supported by increased activation of the MEK1/2-ERK1/2 pathway in alveolar macrophages from patients with ARDS compared with alveolar macrophages from healthy volunteers. This study reveals a critical role for myeloid MEK1 in promoting resolution of LPS-ALI and controlling the duration of macrophage proinflammatory responses.

Dual Role For A MEK Inhibitor As A Modulator Of Inflammation And Host Defense Mechanisms With Potential Therapeutic Application In COPD

Background

Unlike p38 mitogen-activated protein Kinases (MAPK) that has been extensively studied in the context of lung-associated pathologies in COPD, the role of the dual-specificity mitogen-activated protein kinase kinase (MEK1/2) or its downstream signaling molecule extracellular signal-regulated kinases 1/2 (ERK1/2) in COPD is poorly understood.

Objectives

The aim of this study was to address whether MEK1/2 pathway activation is linked to COPD and that targeting this pathway can improve lung inflammation through decreased immune-mediated inflammatory responses without compromising bacterial clearance.

Methods

Association of MEK1/2 pathway activation to COPD was investigated by immunohistochemistry using lung tissue biopsies from COPD and healthy individuals and through analysis of sputum gene expression data from COPD patients. The anti-inflammatory effect of MEK1/2 inhibition was assessed on cytokine release from lipopolysaccharide-stimulated alveolar macrophages. The effect of MEK1/2 inhibition on bacterial clearance was assessed using Staphylococcus aureus killing assays with RAW 264.7 macrophage cell line and human neutrophils.

Results

We report here MEK1/2 pathway activation demonstrated by increased pERK1/2 staining in bronchial epithelium and by the presence of MEK gene activation signature in sputum samples from COPD patients. Inhibition of MEK1/2 resulted in a superior anti-inflammatory effect in human alveolar macrophages in comparison to a p38 inhibitor. Furthermore, MEK1/2 inhibition led to an increase in bacterial killing in human neutrophils and RAW 264.7 cells that was not observed with the p38 inhibitor.

Conclusion

Our data demonstrate the activation of MEK1/2 pathway in COPD and highlight a dual function of MEK1/2 inhibition in improving host defense responses whilst also controlling inflammation.

Matrix metalloproteinase 28 is regulated by TRIF- and type I IFN-dependent signaling in macrophages

Matrix metalloproteinases (MMPs) are transcriptionally regulated proteases that have multiple roles in modifying the extracellular matrix (ECM) and inflammatory response. Our previous work identified Mmp28 as a key regulator of inflammation and macrophage polarization during experimental models of pulmonary infection, fibrosis, and chronic smoke exposure. However, the signaling pathways responsible for regulation of macrophage Mmp28 expression remain undefined. This study utilized murine macrophages obtained from wild type, Tlr2^-/-, Tlr4^-/-, MyD88^-/-, Ticam1 ^Lps2 ( Trif_mutant), and Ifnar1^-/- mice to test the hypothesis that macrophage Mmp28 expression was dependent on TRIF and type I IFN. Our results support the hypothesis, demonstrating that increased macrophage Mmp28 expression was dependent on type I IFN after LPS and poly(I:C) stimulation. To gain further insight into the function of MMP28, we explored the inflammatory response of macrophages derived from wild type or Mmp28^-/- mice to stimulation with poly(I:C). Our data support a role for MMP28 in regulating the macrophage inflammatory response to poly(I:C) because expression of Ccl2, Ccl4, Cxcl10, and Il6 were increased in Mmp28^-/- macrophages. Together, these data support a model in which macrophages integrate TRIF- and type I IFN-dependent signaling to coordinate regulation of proteins with the capacity to modify the ECM.