One of defense mechanisms of the human immune system to counteract infection by the opportunistic fungal pathogen Candida albicans is the recruitment of neutrophils to the site of invasion, and the subsequent production of neutrophil extracellular traps (NETs) that efficiently capture and kill the invader cells. In the current study, we demonstrate that within these structures composed of chromatin and proteins, the latter play a pivotal role in the entrapment of the fungal pathogen. The proteinous components of NETs, such as the granular enzymes elastase, myeloperoxidase and lactotransferrin, as well as histones and cathelicidin-derived peptide LL-37, are involved in contact with the surface of C. albicans cells. The fungal partners in these interactions are a typical adhesin of the agglutinin-like sequence protein family Als3, and several atypical surface-exposed proteins of cytoplasmic origin, including enolase, triosephosphate isomerase and phosphoglycerate mutase. Importantly, the adhesion of both the elastase itself and the mixture of proteins originating from NETs on the C. albicans cell surface considerably increased the pathogen potency of human epithelial cell destruction compared with fungal cells without human proteins attached. Such an implementation of adsorbed NET-derived proteins by invading C. albicans cells might alter the effectiveness of the fungal pathogen entrapment and affect the further host colonization.

Neutrophils have been thought to play a major role in inflammation and diabetic complications especially in poor glycemic control patients as demonstrated by their aberrant inflammatory markers. The aim of the present study was to compare neutrophil proteome profiles between diabetic patients with good glycemic control and those with poor glycemic control to see whether there might be any differences that could be related to the cause of complications which are found more commonly in the latter. Using 2-dimensional gel electrophoresis (2-DE) followed by quadrupole time of flight mass spectrometry (Q-TOF MS) and/or tandem mass spectrometry (MS/MS), we identified 35 differentially expressed proteins, some of which were protein components of neutrophil extracellular traps (NETs), in the poor glycemic control group compared to the good glycemic control group. The observed alterations of protein components of NETs included downregulation of myeloperoxidase, azurocidin (CAP37), and S100A9; and upregulation of the glycolytic enzymes transketolase and alpha-enolase. Manganese superoxide dismutase (MnSOD), functioning in cellular response and defense, was also found downregulated in the poor control group. Most of the glycolysis-related proteins were downregulated in the good control group but upregulated in the poor control group, including phosphoglycerate kinase 1 (PGK1) and L-lactate dehydrogenase B chain (LDHB). The findings of this study demonstrate the dysregulation of protein components of NETs in neutrophils in patients with poorly controlled diabetes. More specifically, these findings suggest association between NETs and inflammation in diabetes and provide further insights into the role of neutrophils in the complications of poorly controlled diabetes.

Neutrophil extracellular traps (NET), extruded decondensated chromatin entangled with neutrophil proteases, have been first identified in neutrophils stimulated with bacteria or phorbol myristate acetate (PMA) via activation of NADPH oxidase and the generation of reactive oxygen species. Although the first findings demonstrated the beneficial role of NET formation by trapping the bacteria and limiting their dissemination, numerous studies in the recent decade revealed the multifunctional aspects of NET formation which manifests itself not only in the context of anti-microbial effect but also as a pathological trigger. Uncontrolled and exaggerated NET formation or inability to digest and remove NET have been reported in thrombosis, auto-immune diseases, cancer or even in infertility. Studies are ongoing to disclose the role of NET in different pathological situations and most importantly, NET regulation via compounds that either interfere with NET formation or target NET components such as DNA or neutrophil proteases. Although the final product of NET formation seems to be quite common i.e. DNA entangled with proteases, stimuli that induce NET have a wide range of varieties and the involved pathways are diverse too. Therefore, in every pathological condition, it is necessary to consider carefully the type of stimulus and the signaling pathways in order to target the disease more specifically. Here we briefly summarize some (out of many) NET triggers/pathways and discuss the potential interventions in the pathological situations.

Eosinophils are a prominent cell type in the host response to helminths, and some evidence suggests that neutrophils might also play a role. However, little is known about the activation status of these granulocytes during helminth infection.
We analyzed the expression of eosinophil and neutrophil activation markers in peripheral blood by flow cytometry and measured serum levels of eosinophil granule proteins in 300 subjects residing in an area endemic for soil-transmitted helminths (STH). The data generated are on samples before and after 1 year of 3-monthly albendazole treatment.
Anthelmintic treatment significantly reduced the prevalence of STH. While eosinophil numbers were significantly higher in STH-infected compared to uninfected subjects and significantly decreased following albendazole treatment, there was no effect exerted by the helminths on either eosinophil nor neutrophil activation. Although at baseline eosinophil granule protein levels were not different between STH-infected and uninfected subjects, treatment significantly reduced the levels of eosinophil-derived neurotoxin (EDN) in those infected at baseline.
These results show that besides decreasing eosinophil numbers, anthelmintic treatment does not significantly change the activation status of eosinophils, nor of neutrophils, and the only effect seen was a reduction in circulating levels of EDN.
http://www.isrctn.com/ISRCTN75636394.

Granulocytes are activated during Mycobacterium tuberculosis infection and act as immune effector cells, and granulocyte responses are implicated in tuberculosis (TB) pathogenesis. Plasma levels of neutrophil and eosinophil granular proteins provide an indirect measure of degranulation. In this study, we wanted to examine the levels of neutrophil and eosinophil granular proteins in individuals with pulmonary tuberculosis (PTB) and to compare them with the levels in individuals with latent TB (LTB). Hence, we measured the plasma levels of myeloperoxidase (MPO), neutrophil elastase, proteinase 3, major basic protein (MBP), eosinophil-derived neurotoxin (EDN), eosinophil cationic protein (ECP), and eosinophil peroxidase (EPX) in these individuals. Finally, we also measured the levels of all of these proteins in PTB individuals following antituberculosis treatment (ATT). Our data reveal that PTB individuals are characterized by significantly higher plasma levels of MPO, elastase, proteinase 3, as well as MBP and EDN in comparison to those in LTB individuals. Our data also reveal that ATT resulted in the reversal of all of these changes, indicating an association with TB disease. Finally, our data show that the systemic levels of MPO and proteinase 3 can significantly discriminate PTB from LTB individuals. Thus, our data suggest that neutrophil and eosinophil granular proteins could play a potential role in the innate immune response and, therefore, the pathogenesis of pulmonary TB.

Infection with the helminth parasite Strongyloides stercoralis (Ss) is commonly clinically asymptomatic that is often accompanied by peripheral eosinophilia. Granulocytes are activated during helminth infection and can act as immune effector cells. Plasma levels of eosinophil and neutrophil granular proteins convey an indirect measure of granulocyte degranulation and are prominently augmented in numerous helminth-infected patients. In this study, we sought to examine the levels of eosinophil, neutrophil, and mast cell activation-associated granule proteins in asymptomatic Ss infection and to understand their kinetics following anthelmintic therapy. To this end, we measured the plasma levels of eosinophil cationic protein, eosinophil-derived neurotoxin, eosinophil peroxidase, eosinophil major basic protein, neutrophil elastase, myeloperoxidase, neutrophil proteinase-3, mast cell tryptase, leukotriene C4, and mast cell carboxypeptidase-A3 in individuals with asymptomatic Ss infection or without Ss infection [uninfected (UN)]. We also estimated the levels of all of these analytes in infected individuals following definitive treatment of Ss infection. We demonstrated that those infected individuals have significantly enhanced plasma levels of eosinophil cationic protein, eosinophil-derived neurotoxin, eosinophil peroxidase, eosinophil major basic protein, elastase, myeloperoxidase, mast cell tryptase, leukotriene C4, and carboxypeptidase-A3 compared to UN individuals. Following the treatment of Ss infection, each of these granulocyte-associated proteins drops significantly. Our data suggest that eosinophil, neutrophil, and mast cell activation may play a role in the response to Ss infection.