Trypanosoma brucei Lipophosphoglycan Induces the Formation of Neutrophil Extracellular Traps and Reactive Oxygen Species Burst via Toll-Like Receptor 2, Toll-Like Receptor 4, and c-Jun N-Terminal Kinase Activation

Toxoplasma gondii-induced neutrophil extracellular traps are relevant to glycolysis, TLR2, and TLR4 MAPK signaling pathway in goats

Toxoplasma gondii (T. gondii) exhibits a significantly high prevalence of infection in goats, leading to adverse consequences such as abortion and stillbirth in ewes, thereby posing a substantial challenge to the goat farming industry. Neutrophil extracellular traps (NETs) have been shown to capture T. gondii in goats; however, the precise mechanisms underlying NET release in goats remain poorly understood. Therefore, the aim of our research was to elucidate the involved mechanism. We assessed the cytotoxicity of T. gondii on neutrophils using CCK-8 assay, visualized the structure of T. gondii-induced goat NETs through immunofluorescence, quantified ROS release during T. gondii-induced NET formation using fluorescence microplate analysis, and employed inhibitors targeting TLR 2, TLR4, NADPH oxidase, ERK1/2, and P38 MAPK signaling pathways as well as glycolysis to dissect the mechanisms underlying T. gondii-induced NET release. Within 1 h, T. gondii did not exhibit significant cytotoxicity towards neutrophils in our findings. The formation of typical NET structures induced by T. gondii involved DNA, citrullinated histone 3 (citH3), and neutrophil elastase (NE). Additionally, T. gondii significantly stimulated the release of NETs in goats. The process was accompanied by the production of reactive oxygen species (ROS) mediated through NADPH oxidase, p38, and ERK1/2 signaling pathways. Inhibition of these pathways resulted in a decrease in NET release. Moreover, inhibition of TLR 2, TLR4, and glycolysis also led to a reduction in T. gondii-induced NET release. Overall, our study demonstrates that T. gondii can induce characteristic NET structures and elucidates the involvement of various mechanisms including TLR2/TLR4 signaling pathway activation, NADPH oxidase activity modulation via ROS production regulation through p38 MAPK and ERK1/2 signaling pathways, and glycolysis regulation during the innate immune response against T. gondii infection in goats.

Neutrophil metalloproteinase driven spleen damage hampers infection control of trypanosomiasis

Recent blood transcriptomic analysis of rhodesiense sleeping sickness patients has revealed that neutrophil signature genes and activation markers constitute the top indicators of trypanosomiasis-associated inflammation. Here, we show that Trypanosoma brucei infection results in expansion and differentiation of four splenic neutrophil subpopulations, including Mki67+Birc5+Gfi1+Cebpe+ proliferation-competent precursors, two intermediate immature subpopulations and Cebpb+Spi1+Irf7+Mcl1+Csf3r+ inflammation reprogrammed mature neutrophils. Transcriptomic scRNA-seq profiling identified the largest immature subpopulation by Mmp8/9 positive tertiary granule markers. We confirmed the presence of both metalloproteinases in extracellular spleen homogenates and plasma. During infection, these enzymes digest extracellular matrix components in the absence of sufficient TIMP inhibitory activity, driving remodeling of the spleen follicular architecture. Neutrophil depletion prevents the occurrence of organ damage, resulting in increased plasma cell numbers and prolonged host survival. We conclude that trypanosomiasis-associated neutrophil activation is a major contributor to the destruction of the secondary lymphoid architecture, required for maintaining an efficient adaptive immune response.

Novel neutrophil extracellular trap-related mechanisms in diabetic wounds inspire a promising treatment strategy with hypoxia-challenged small extracellular vesicles

Neutrophil extracellular traps (NETs) have been considered a significant unfavorable factor for wound healing in diabetes, but the mechanisms remain unclear. The therapeutic application of small extracellular vesicles (sEVs) derived from mesenchymal stem cells (MSCs) has received considerable attention for their properties. Hypoxic preconditioning is reported to enhance the therapeutic potential of MSC-derived sEVs in regenerative medicine. Therefore, the aim of this study is to illustrate the detailed mechanism of NETs in impairment of diabetic wound healing and develop a promising NET-targeting treatment based on hypoxic pretreated MSC-derived sEVs (Hypo-sEVs). Excessive NETs were found in diabetic wounds and in high glucose (HG)-induced neutrophils. Further research showed that high concentration of NETs impaired the function of fibroblasts through activating endoplasmic reticulum (ER) stress. Hypo-sEVs efficiently promoted diabetic wound healing and reduced the excessive NET formation by transferring miR-17-5p. Bioinformatic analysis and RNA interference experiment revealed that miR-17-5p in Hypo-sEVs obstructed the NET formation by targeting TLR4/ROS/MAPK pathway. Additionally, miR-17-5p overexpression decreased NET formation and overcame NET-induced impairment in fibroblasts, similar to the effects of Hypo-sEVs. Overall, we identify a previously unrecognized NET-related mechanism in diabetic wounds and provide a promising NET-targeting strategy for wound treatment.

Modified Signaling of Membrane Formyl Peptide Receptors in NADPH-Oxidase Regulation in Obesity-Resistant Mice

The signaling of membrane receptors is modified in obesity characterized by low-grade inflammation. The obesity-resistant state of organisms is poorly understood. We analyzed the generation of reactive oxygen species (ROS) initiated though membrane formyl peptide receptors (Fpr1, Fpr2) in bone-marrow granulocytes of obesity-resistant mice (ORM). A chemiluminescence assay was used to assess NADPH-oxidase-related intensity of ROS generation. ORM were chosen from animals that received high-fat diets and had metric body parameters as controls (standard diet). High spontaneous ROS production was observed in ORM cells. The EC50 for responses to bacterial or mitochondrial peptide N-formyl-MLF was higher in ORM with and without inflammation vs. the same control groups, indicating an insignificant role of high-affinity Fpr1. Increased responses to synthetic peptide WKYMVM (Fpr2 agonist) were observed in controls with acute inflammation, but they were similar in other groups. Fpr2 was possibly partially inactivated in ORM owing to the inflammatory state. Weakened Fpr1 and Fpr2 signaling via MAPKs was revealed in ORM using specific inhibitors for p38, ERK1/2, and JNK. P38 signaling via Fpr2 was lower in ORM with inflammation. Thus, a high-fat diet modified FPRs' role and suppressed MAPK signaling in NADPH-oxidase regulation in ORM. This result can be useful to understand the immunological features of obesity resistance.

The Pathogenesis of African Trypanosomiasis

African trypanosomes are bloodstream protozoan parasites that infect mammals including humans, where they cause sleeping sickness. Long-lasting infection is required to favor parasite transmission between hosts. Therefore, trypanosomes have developed strategies to continuously escape innate and adaptive responses of the immune system, while also preventing premature death of the host. The pathology linked to infection mainly results from inflammation and includes anemia and brain dysfunction in addition to loss of specificity and memory of the antibody response. The serum of humans contains an efficient trypanolytic factor, the membrane pore-forming protein apolipoprotein L1 (APOL1). In the two human-infective trypanosomes, specific parasite resistance factors inhibit APOL1 activity. In turn, many African individuals express APOL1 variants that counteract these resistance factors, enabling them to avoid sleeping sickness. However, these variants are associated with chronic kidney disease, particularly in the context of virus-induced inflammation such as coronavirus disease 2019. Vaccination perspectives are discussed.

Trypanosoma brucei brucei Induced Hypoglycaemia Depletes Hepatic Glycogen and Altered Hepatic Hexokinase and Glucokinase Activities in Infected Mice

PURPOSE

Little progress has been made in understanding the effect of Trypanosoma brucei brucei infection that was allowed to run its course without treatment on human and animal carbohydrate metabolism even though most of the symptoms associated with the disease can be clearly linked with interference with host energy generation. The present study therefore assessed the course of untreated Trypanosoma brucei brucei infection on hepatic glycogen, hepatic hexokinase and glucokinase activities.

METHODS

Mice were grouped into two: control and infected group. Trypanosomiasis was induced by intraperitoneal inoculation of 1 × 10⁴ parasites/mice in 0.3 ml of phosphate saline glucose. The infection was allowed to run its course until the first mortality was recorded with all the mice showing chronic symptoms of the second stage of the disease before the research was terminated. Blood and liver samples were collected from the mice in each group for the assessment of hepatic glycogen and total protein, hepatic hexokinase and glucokinase activities, liver biomarkers, blood glucose and protein with packed cell volume.

RESULTS

The infection resulted in decrease in blood glucose, hepatic glycogen, liver protein, PCV, hepatic hexokinase and glucokinase activities, but increase in serum total protein and liver biomarkers.

CONCLUSION

Trypanosomiasis negatively affects hepatic integrity, resulting in the depletion of hepatic glycogen content and suppression of both hepatic hexokinase and glucokinase activities. The suppression of hepatic hexokinase and glucokinase activities suggested that trypanosomiasis affected the oxidation of glucose and host energy generation via glycolysis. This probably denied the host of the needed energy which is likely the reason for early death in untreated African trypanosomiasis.

Hookworm infections: Reappraising the evidence for a role of Neutrophils in light of NETosis

In Hookworm infection, neutrophils have long had the image of the villain, being recruited to the site of larval migration because of damage but participating themselves in tissue injury. With recent developments in neutrophil biology, there is an increasing body of evidence for the role of neutrophils as effector cells in hookworm immunity. In particular, their ability to release extracellular traps, or neutrophil extracellular traps (NETs), confer neutrophils a larvicidal activity. Here, we review recent evidence in this nascent field and discuss the avenue for future research on NETs/hookworm interactions.