Targeting Neutrophils to Prevent Malaria-Associated Acute Lung Injury/Acute Respiratory Distress Syndrome in Mice

PLoS Pathog. 2016 Dec 7;12(12):e1006054. doi: 10.1371/journal.ppat.1006054. eCollection 2016 Dec.

Abstract

Malaria remains one of the greatest burdens to global health, causing nearly 500,000 deaths in 2014. When manifesting in the lungs, severe malaria causes acute lung injury/acute respiratory distress syndrome (ALI/ARDS). We have previously shown that a proportion of DBA/2 mice infected with Plasmodium berghei ANKA (PbA) develop ALI/ARDS and that these mice recapitulate various aspects of the human syndrome, such as pulmonary edema, hemorrhaging, pleural effusion and hypoxemia. Herein, we investigated the role of neutrophils in the pathogenesis of malaria-associated ALI/ARDS. Mice developing ALI/ARDS showed greater neutrophil accumulation in the lungs compared with mice that did not develop pulmonary complications. In addition, mice with ALI/ARDS produced more neutrophil-attracting chemokines, myeloperoxidase and reactive oxygen species. We also observed that the parasites Plasmodium falciparum and PbA induced the formation of neutrophil extracellular traps (NETs) ex vivo, which were associated with inflammation and tissue injury. The depletion of neutrophils, treatment with AMD3100 (a CXCR4 antagonist), Pulmozyme (human recombinant DNase) or Sivelestat (inhibitor of neutrophil elastase) decreased the development of malaria-associated ALI/ARDS and significantly increased mouse survival. This study implicates neutrophils and NETs in the genesis of experimentally induced malaria-associated ALI/ARDS and proposes a new therapeutic approach to improve the prognosis of severe malaria.

MeSH terms

  • Acute Lung Injury / immunology*
  • Acute Lung Injury / microbiology
  • Animals
  • Disease Models, Animal
  • Extracellular Traps / immunology
  • Fluorescent Antibody Technique
  • Malaria / complications
  • Malaria / immunology
  • Male
  • Mice
  • Mice, Inbred DBA
  • Neutrophils / immunology*
  • Polymerase Chain Reaction
  • Respiratory Distress Syndrome / immunology*
  • Respiratory Distress Syndrome / microbiology

Grants and funding

Financial support was provided by grants 2009/53256-7 (SE) and 2009/53889-0 (CRFM) from the São Paulo Research Foundation (FAPESP) and the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) 306668/2012-2 and 470590/2009-2 (SE). SP, MKS, LSO and EHA were supported by a FAPESP fellowship (2010/11925-7, 2010/19439-4, 2013/20718-3 and 2011/19525-0, respectively). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.