Pneumolysin Induces 12-Lipoxygenase–Dependent Neutrophil Migration during Streptococcus pneumoniae Infection

Abstract

Streptococcus pneumoniae is a major cause of pneumonia, wherein infection of respiratory mucosa drives a robust influx of neutrophils. We have previously shown that S. pneumoniae infection of the respiratory epithelium induces the production of the 12-lipoxygenase (12-LOX)-dependent lipid inflammatory mediator hepoxilin A3, which promotes recruitment of neutrophils into the airways, tissue damage, and lethal septicemia. Pneumolysin (PLY), a member of the cholesterol-dependent cytolysin (CDC) family, is a major S. pneumoniae virulence factor that generates ∼25-nm diameter pores in eukaryotic membranes and promotes acute inflammation, tissue damage, and bacteremia. We show that a PLY-deficient S. pneumoniae mutant was impaired in triggering human neutrophil transepithelial migration in vitro. Ectopic production of PLY endowed the nonpathogenic Bacillus subtilis with the ability to trigger neutrophil recruitment across human-cultured monolayers. Purified PLY, several other CDC family members, and the a-toxin of Clostridium septicum, which generates pores with cross-sectional areas nearly 300 times smaller than CDCs, reproduced this robust neutrophil transmigration. PLY non-pore-forming point mutants that are trapped at various stages of pore assembly did not recruit neutrophils. PLY triggered neutrophil recruitment in a 12-LOX-dependent manner in vitro. Instillation of wild-type PLY but not inactive derivatives into the lungs of mice induced robust 12-LOXdependent neutrophil migration into the airways, although residual inflammation induced by PLY in 12-LOX-deficient mice indicates that 12-LOX-independent pathways also contribute to PLY-triggered pulmonary inflammation. These data indicate that PLY is an important factor in promoting hepoxilin A3-dependent neutrophil recruitment across pulmonary epithelium in a pore-dependent fashion.

Neutrophils require SKAP2 for reactive oxygen species production following C-type lectin and Candida stimulation

“…Human neutrophils from peripheral whole blood were obtained by the Leong lab at Tufts University ( Adams et al., 2020 ). All human cell work were handled in accordance with protocols approved by the Institutional Review Board (IRB) of Tufts Medical Center and Tufts University under protocol #10489, and informed consent was obtained from subjects.…”

ACE2 in the Gut: The Center of the 2019-nCoV Infected Pathology

“…Additionally, the alterations in the number of lymphocytes within one organ may affect that in plasma, which could possibly cause physiological changes in others, as both 2019-nCoV and IBD patients show immune dysregulation characterized by elevated levels of neutrophils and inflammation markers (Boros et al, 2020;Mehta et al, 2020). Similar changes have been observed in other organ diseases, such as Streptococcus pneumoniae infection and tubular injury (Adams et al, 2020). Given the ACE2 regulation of the immune system, more detailed research studies with careful variant control are required, especially those performed on typical diseases and cell lines.…”

Impact of Bacterial Toxins in the Lungs

“…In addition, the pore-forming toxin can increase PAF and thromboxane A2 synthesis by these cells [336]. Apart from promoting IL-8 generation, PLY also fosters a hepoxilin A3-dependent neutrophil recruitment across the pulmonary epithelium in a pore-dependent fashion [337]. Together these actions will impair immune defense against S. pneumoniae.…”