Klebsiella pneumoniae infection of murine neutrophils impairs their efferocytic clearance by modulating cell death machinery

Abstract

Neutrophils are the first infiltrating cell type essential for combating pneumoseptic infections by bacterial pathogens including Klebsiella pneumoniae (KPn). Following an infection or injury, removal of apoptotic infiltrates via a highly regulated process called efferocytosis is required for restoration of homeostasis, but little is known regarding the effect of bacterial infection on this process. Here we demonstrate that KPn infection impedes the efferocytic uptake of neutrophils in-vitro and in-vivo in lungs by macrophages. This impaired efferocytosis of infected neutrophils coincides with drastic reduction in the neutrophil surface exposure of apoptosis signature phospholipid phosphatidyserine (PS); and increased activity of phospholipid transporter flippases, which maintain PS in the inner leaflet of plasma membrane. Concomitantly, pharmacological inhibition of flippase activity enhanced PS externalization and restored the efferocytosis of KPn infected neutrophils. We further show that KPn infection interferes with apoptosis activation and instead activates non-apoptotic programmed cell death via activation of necroptosis machinery in neutrophils. Accordingly, pharmacological inhibition of necroptosis by RIPK1 and RIPK3 inhibitors restored the efferocytic uptake of KPn infected neutrophils in-vitro. Importantly, treatment of KPn infected mice with necroptosis inhibitor improved the disease outcome in-vivo in preclinical mouse model of KPn pneumonia. To our knowledge, this is the first report of neutrophil efferocytosis impairment by KPn via modulation of cell death pathway, which may provide novel targets for therapeutic intervention of this infection.

Competitive Cell Death Interactions in Pulmonary Infection: Host Modulation Versus Pathogen Manipulation

“…Particularly, Klebsiella was observed to inhibit the exposure of phosphatidylserine by agonizing flippases that invert phosphatidylserine from the outer to the inner leaflet of the plasma membrane. This inhibition of apoptosis in neutrophils was shown to drive neutrophils toward caspase-independent cell death via the necroptosis machinery (138). Preventing the containment of cytoplasmic contents in apoptotic bodies and inhibiting debris removal via efferocytic phagocytes are other means through which Klebsiella maintains a suitable intracellular niche during infection.…”

Epigenomics, genomics, resistome, mobilome, virulome and evolutionary phylogenomics of carbapenem-resistant Klebsiella pneumoniae clinical strains

“…In addition to K. pneumoniae, Pseudomonas aeruginosa , Acinetobacter baumannii and MRSA (methicillin-resistant Staphylococcus aureus ) are important hospital pathogens; K. pneumoniae accounts for 3–8 % of several reported infections [3, 4]. These infections are specifically a problem in the elderly, immunocompromised patients and neonates; less frequently, K.…”

Innate Immune Effectors Play Essential Roles in Acute Respiratory Infection Caused by Klebsiella pneumoniae

“…Therefore, alternative strategies for the prevention and treatment of K. pneumoniae infections are urgently needed and may indeed be useful. However, the development of these strategies should be based on a deeper understanding of the pathogenic mechanism of K. pneumoniae [ 10 ].…”