Haem oxygenase protects against thrombocytopaenia and malaria-associated lung injury

Abstract

Background: Malaria-triggered lung injury can occur in both severe and non-severe cases. Platelets may interact with parasitized erythrocytes, leukocytes and endothelium. These interactions can lead to microvessel obstructions and induce release of inflammatory mediators. Induction of the haem oxygenase enzyme is important in the host's response to free haem and to several other molecules generated by infectious or non-infectious diseases. In addition, an important role for the haem oxygenase-1 isotype has been demonstrated in experimental cerebral malaria and in clinical cases. Therefore, the present work aims to determine the influence of haem oxygenase in thrombocytopaenia and acute pulmonary injury during infection with Plasmodium berghei strain NK65. Methods: C57BL/6 mice were infected with P. berghei and analysed 7-10 days post-infection. For each experiment, Cobalt Protoporphyrin IX/CoPPIX or saline were administered. Bronchoalveolar lavage fluid was used for total and differential leukocyte count and for protein measurement. Lungs were used for histological analyses or for analysis of cytokines and western blotting. The lung permeability was analysed by Evans blue dye concentration. Platelet-leukocyte aggregate formation was assayed using the flow cytometer. Results: Plasmodium berghei NK65 infection generated an intense lung injury, with increased levels of inflammatory mediators, oedema, and cell migration into the lung. Plasmodium berghei infection was also accompanied by marked thrombocytopaenia and formation of platelet-leukocyte aggregates in peripheral blood. Treatment with the HO-1 inducer cobalt protoporphyrin IX (CoPPIX) modified the inflammatory response but did not affect the evolution of parasitaemia. Animals treated with CoPPIX showed an improvement in lung injury, with decreased inflammatory infiltrate in the lung parenchyma, oedema and reduced thrombocytopaenia. Conclusion: Data here presented suggest that treatment with CoPPIX inducer leads to less severe pulmonary lung injury and thrombocytopaenia during malaria infection, thus increasing animal survival.

Experimental Models to Study the Pathogenesis of Malaria-Associated Acute Respiratory Distress Syndrome

“…In the last few decades, these cells were shown to play a dual role in the pathogenesis of Plasmodium infection, by preventing the exponential growth of parasitemia in the early stage, and promoting enhanced immune responses in the later stage ( Srivastava, 2014 ). Platelets were also associated with the pathogenesis and progression of MA-ARDS, because upon its activation, they release various inflammatory mediators (von Willebrand factor, PF4/CXCL4, RANTES/CCL5) that activate neutrophils, monocytes, macrophages, leukocytes, and endothelial cells, leading to pulmonary endothelial damage ( Vieira-de-Abreu et al., 2012 ; Srivastava, 2014 ; de Azevedo-Quintanilha et al., 2020 ).…”

“…Platelets are involved in thrombo-inflammation during malaria infection. Thrombocytopenia is a complication observed in infected patients (predominantly with vivax or falciparum infection) ( Lacerda et al., 2011 ; Bakhubaira, 2013 ) and mouse models ( de Azevedo-Quintanilha et al., 2020 ), and has been correlated with increase parasite density and disease severity ( Gerardin et al., 2002 ; Ladhani et al., 2002 ). The mechanism of platelet clearance observed during thrombocytopenia has been widely studied and is still being debated.…”

“…The mechanism of platelet clearance observed during thrombocytopenia has been widely studied and is still being debated. Some studies have suggested that it is associated with platelet activation ( Lacerda et al., 2011 ; Sharron et al., 2012 ), followed by platelet adhesion to the endothelium, resulting in endothelial cell activation causing the release of VWF, and hetero-aggregates of platelet and leukocytes ( de Azevedo-Quintanilha et al., 2020 ). When the endothelium is activated, coagulation related proteins are released, such as thrombomodulin and its ligand, thrombin, leading to platelet consumption ( Thachil, 2017 ).…”

“…demonstrated that thrombocytopenia could happen in the absence of platelet activation or disseminated intravascular coagulation ( de Mast et al., 2010 ). Treatment with heme oxyganese-1 inducer cobalt protoporphyrin IX (CoPPIX) reduced thrombocytopenia and decreased inflammatory infiltrate in the lung parenchyma in PbNK65-infected mice ( de Azevedo-Quintanilha et al., 2020 ). Although a few studies have been conducted to understand the role of platelets in the MA-ARDS pathogenesis, great caution must be taken in platelet-targeted therapeutic treatment.…”