NETosis: Molecular Mechanisms, Role in Physiology and Pathology

Tamm-Horsfall protein augments neutrophil NETosis during urinary tract infection

Urinary neutrophils are a hallmark of urinary tract infection (UTI), yet the mechanisms governing their activation, function, and efficacy in controlling infection remain incompletely understood. Tamm-Horsfall glycoprotein (THP), the most abundant protein in urine, uses terminal sialic acids to bind an inhibitory receptor and dampen neutrophil inflammatory responses. We hypothesized that neutrophil modulation is an integral part of THP-mediated host protection. In a UTI model, THP-deficient mice showed elevated urinary tract bacterial burdens, increased neutrophil recruitment, and more severe tissue histopathological changes compared with WT mice. Furthermore, THP-deficient mice displayed impaired urinary NETosis during UTI. To investigate the effect of THP on NETosis, we coupled in vitro fluorescence-based NET assays, proteomic analyses, and standard and imaging flow cytometry with peripheral human neutrophils. We found that THP increases proteins involved in respiratory chain, neutrophil granules, and chromatin remodeling pathways; enhances NETosis in an ROS-dependent manner; and drives NET-associated morphologic features including nuclear decondensation. These effects were observed only in the presence of a NETosis stimulus and could not be solely replicated with equivalent levels of sialic acid alone. We conclude that THP is a critical regulator of NETosis in the urinary tract, playing a key role in host defense against UTI.

Neutrophil extracellular traps promote the activation of the NLRP3 inflammasome and PBMCs pyroptosis via the ROS-dependent signaling pathway in Kawasaki disease

Kawasaki disease (KD) is an acute systemic vasculitis predominantly affecting infants and children under the age of 5. Recent studies have indicated that excessively released neutrophil extracellular traps (NETs) are involved in the progression of vasculitis. The purpose of this study was to investigate the role of NETs, especially their interaction with peripheral blood mononuclear cells (PBMCs), in the pathogenesis of KD. First, we demonstrated that the levels of NETs (cfDNA, MPO, and NE) in the serum of KD patients were significantly higher than those in healthy controls (HCs) and notably decreased after treatment. During the acute phase of KD, inflammatory markers (CRP and ESR) were positively correlated with NETs levels. Furthermore, we observed that neutrophils from KD patients in the acute phase produced elevated levels of NETs, and aspirin could effectively regulate the release of NETs. Additionally, NETs significantly increased the mRNA levels of NLRP3 and IL-1β in PBMCs, as well as the protein expression of NLRP3, caspase-1, ASC and gasdermin D, and the concentration of IL-1β in the cell supernatant. Moreover, NETs stimulated the production of reactive oxygen species (ROS) in PBMCs. N-acetylcysteine significantly reduced the expression of inflammatory factors and pyroptosis-related proteins in PBMCs. In conclusion, our findings suggest that NETs induce the generation of ROS, which in turn activates the NLRP3 inflammasome to mediate PBMCs pyroptosis and perpetuate inflammation in KD patients. This study reveals that targeting NETs or ROS could be a potential therapeutic approach for alleviating systemic inflammation, and that NETs may be a novel target for aspirin in the treatment of KD patients.

Ferroptosis: Latest evidence and perspectives on plant-derived natural active compounds mitigating doxorubicin-induced cardiotoxicity

Doxorubicin (DOX) is a chemotherapy drug widely used in clinical settings, acting as a first-line treatment for various malignant tumors. However, its use is greatly limited by the cardiotoxicity it induces, including doxorubicin-induced cardiomyopathy (DIC). The mechanisms behind DIC are not fully understood, but its potential biological mechanisms are thought to include oxidative stress, inflammation, energy metabolism disorders, mitochondrial damage, autophagy, apoptosis, and ferroptosis. Recent studies have shown that cardiac injury induced by DOX is closely related to ferroptosis. Due to their high efficacy, availability, and low side effects, natural medicine treatments hold strong clinical potential. Currently, natural medicines have been shown to mitigate DOX-induced ferroptosis and ease DIC through various functions such as antioxidation, iron ion homeostasis correction, lipid metabolism regulation, and mitochondrial function improvement. Therefore, this review summarizes the mechanisms of ferroptosis in DIC and the regulation by natural plant products, with the expectation of providing a reference for future research and development of inhibitors targeting ferroptosis in DIC. This review explores the mechanisms of ferroptosis in doxorubicin-induced cardiomyopathy (DIC) and summarizes how natural plant products can alleviate DIC by inhibiting ferroptosis through reducing oxidative stress, correcting iron ion homeostasis, regulating lipid metabolism, and improving mitochondrial function.

Endothelial CD38-induced endothelial-to-mesenchymal transition is a pivotal driver in pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a prevalent interstitial lung disease with high mortality. CD38 is a main enzyme for intracellular nicotinamide adenine dinucleotide (NAD+) degradation in mammals. It has been reported that CD38 participated in pulmonary fibrosis through promoting alveolar epithelial cells senescence. However, the roles of endothelial CD38 in pulmonary fibrosis remain unknown. In the present study, we observed that the elevated expression of CD38 was related to endothelial-to-mesenchymal transition (EndMT) of lung tissues in IPF patients and bleomycin (BLM)-induced pulmonary fibrosis mice and also in human umbilical vein endothelial cells (HUVECs) treated with BLM. Micro-computed tomography (MCT) and histopathological staining showed that endothelial cell-specific CD38 knockout (CD38EndKO) remarkably attenuated BLM-induced pulmonary fibrosis. In addition, CD38EndKO significantly inhibited TGFβ-Smad3 pathway-mediated excessive extracellular matrix (ECM), reduced Toll-like receptor4-Myeloid differentiation factor88-Mitogen-activated protein kinases (TLR4-MyD88-MAPK) pathway-mediated endothelial inflammation and suppressed nicotinamide adenine dinucleotide phosphate oxidases1 (NOX1)-mediated oxidative stress. Furthermore, we demonstrated that 3-TYP, a SIRT3-specific inhibitor, markedly reversed the protective effect of HUVECsCD38KD cells and 78 C, a CD38-specific inhibitor, on BLM-induced EndMT in HUVECs. Therefore, we concluded that CD38EndKO significantly ameliorated BLM-induced pulmonary fibrosis through inhibiting ECM, endothelial inflammation and oxidative stress, further alleviating EndMT in mice. Our findings suggest that endothelial CD38 may be a new therapeutic target for the prevention and treatment of pulmonary fibrosis clinically.

IDH1/MDH1 deacetylation promotes NETosis by regulating OPA1 and autophagy

BACKGROUND

As a heterogeneous and life-threatening disease, the pathogenesis of acute liver failure (ALF) is complex. Our previous study has shown that IDH1/MDH1 deacetylation promotes ALF by regulating NETosis (a novel mode of cell death). In this article, we explore the manners of IDH1/MDH1 deacetylation regulates NETosis.

METHODS

In vitro experiments, the formation of NETs was detected by immunofluorescence staining and Western blotting. LC3 fluorescence staining was used to detect autophagosome formation. To observe mitochondrial morphology, cells were stained by Mito-Tracker Red. Western blotting was used to detect the levels of autophagy protein and mitochondrial dynamin. In vivo experiments, the ALF model in mouse was established with LPS/D-gal, and the formation of NETs was detected by immunofluorescence staining and Western blotting. The autophagy levels were detected by Western blotting in liver samples.

RESULTS

In dHL-60 cells, Western blotting results showed that the expression of OPA1 was higher in the IDH1/MDH1 deacetylated group compared with the IDH1/MDH1 WT group. And histone deacetylase inhibitor 6 (HDAC6i, ACY1215) decreased the expression level of OPA1 in IDH1/MDH1 deacetylated group. IDH1/MDH1 deacetylation increased the expression levels of both LC3B-II and Beclin 1, while decreasing the expression level of P62. It was reversed by ACY1215. Combined with our previous experiments, IDH1/MDH1 deacetylation upregulated autophagy concomitant with the increased expression of the markers of NETs formation. In a mouse model of ALF, ACY1215 further decreased the expression levels of LC3B-II and Beclin 1, while increasing the expression level of P62 in IDH1/MDH1 deacetylated mice.

CONCLUSIONS

IDH1/MDH1 deacetylation promoted NETosis by regulating autophagy and OPA1 in vitro. The regulation of neutrophil autophagy on NETosis during IDH1/MDH1 deacetylation might be masked in mice. ACY1215 might attenuate NETosis by regulating neutrophil autophagy, which alleviated ALF aggravated by IDH1/MDH1 deacetylation.

Immunologic cell deaths: involvement in the pathogenesis and intervention therapy of periodontitis

Periodontitis is one of the most common diseases and primary causes of tooth loss. The main factor that causes periodontitis is an overactive host immunological response. An in-depth investigation into the molecular pathways that cause periodontitis can aid in creating novel therapeutic approaches for periodontitis and its related systemic disorders. Several immunologic cell death (ICD) pathways have been implicated in advancing periodontitis. Nevertheless, there is still a substantial lack of understanding surrounding the precise molecular mechanisms of ICD in periodontitis. Additionally, the beneficial feature of ICD in periodontitis, which involves its ability to eliminate pathogens, needs further confirmation. According to this, a comprehensive literature search utilizing the Web of Science™, PubMed®, and Scopus® databases was conducted. Only items published in the English language up until October 2024 were taken into account, and finally, 65 relevant papers were selected to be included in this review. In this article, we present a comprehensive analysis of the processes and outcomes of ICD activation in the progression of periodontitis. Lastly, the present difficulties linked to ICDs as a viable treatment option for periodontitis are emphasized.

Bile molecular landscape provides pathological insight and classifies signatures predictive of carcinoma of the gall bladder

Carcinoma of the gall bladder (CAGB) has a poor prognosis. Molecular analysis of bile could classify indicators of CAGB. Bile samples (n = 87; training cohort) were screened for proteomics and metabolomics signatures of cancer detection. In bile, CAGB showed distinct proteomic (217 upregulated, 258 downregulated) and metabolomic phenotypes (111 upregulated, 505 downregulated, p < 0.05, fold change > 1.5, false discovery rate <0.01) linked to significantly increased inflammation (coagulation, arachidonic acid, bile acid) and alternate energy pathways (pentose-phosphate pathway, amino acids, lipid metabolism); and decreased glycolysis, cholesterol metabolism, PPAR, RAS, and RAP1 signaling, oxidative phosphorylation, and others compared to gallstone or healthy controls (p < 0.05). Bile proteins/metabolites signatures showed significant correlation (r 2  > 0.5, p < 0.05) with clinical parameters. Metabolite/protein signature-based probability of detection for CAGB (cancer) was >90% (p < 0.05), with area under the receiver operating characteristic curve >0.94. Validation of the top four metabolites-toluene, 5,6-DHET, creatine, and phenylacetaldehyde-in separate cohorts (n = 80; bile [T1] and paired plasma [T2]) showed accuracy (99%) and sensitivity/specificity (>98%) for CAGB detection. Tissue validation showed bile 5,6-DHET positively correlated with tissue PCNA (proliferation), and caspase-3 linked to cancer development (r 2 >0.5, p < 0.05). In conclusion, the bile molecular landscape provides critical molecular understanding and outlines metabolomic indicator panels for early CAGB detection.

Trained innate immunity as a potential link between preeclampsia and future cardiovascular disease

Preeclampsia (PE) is a complex pregnancy syndrome characterized by hypertension with or without proteinuria, affecting 2-6% of pregnancies globally. PE is characterized by excessive release of damage-associated molecular patterns (DAMPs) into the maternal circulation. This DAMP-rich milieu acts on innate immune cells, inducing a proinflammatory state characterized by elevated cytokines such as IL-1β and IL-18. This proinflammatory state in the mother and placenta results in the endothelial dysfunction strongly associated with cardiovascular disorders. While the immediate maternal and fetal risks of PE are well-documented, accumulating evidence indicates that PE also confers long-term cardiovascular risks to the mother, including hypertension, coronary heart disease, stroke, and heart failure. The underlying mechanisms connecting PE to these chronic cardiovascular conditions remain unclear. This article explores the potential role of trained innate immunity (TRIM) as a mechanistic link between PE and increased long-term cardiovascular risk. We propose that the persistent exposure to DAMPs during PE may epigenetically reprogram maternal innate immune cells and their progenitors, leading to TRIM. This reprogramming enhances the inflammatory response to subsequent stimuli, potentially contributing to endothelial dysfunction and chronic inflammation that predispose women to cardiovascular diseases later in life. Understanding the role of TRIM in PE could provide novel insights into the pathophysiology of PE-related cardiovascular complications and identify potential targets for therapeutic intervention. Further research is warranted to investigate the epigenetic and metabolic alterations in innate immune cells induced by PE and to determine how these changes may influence long-term maternal cardiovascular health.

Neutrophils extracellular traps myeloperoxidase and elastase predict cerebral vasospasms after aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is a highly fatal and morbid disease. Despite successful coiling or clipping of a ruptured aneurysm, the patients suffer post-aSAH complications, including early brain injury, cerebral vasospasm (CVS), delayed cerebral ischemia (DCI), and systemic infections that mainly determine the clinical outcomes. Diagnostic biomarkers to predict accurately post-aSAH complications are needed. In this prospective exploratory study, we investigated the predictive value of neutrophil extracellular traps (NETs) components for CVS after aSAH. In the study, 62 patients with aSAH, 17 patients with unruptured cerebral aneurysms, and 12 healthy controls were included. The serum levels of myeloperoxidase (MPO), elastase (ELA), and citrullinated histone H3 (cH3) on day 1 and day 4 of hospital admission were measured with ELISA. Data were scaled using the Yeo-Johnson transformation. Values in two groups were compared using a t-test and in multiple groups using ANOVA. Logistic regression was used to model the outcome probability, including CVS, as the function of ELISA values. Among the patients with aneurysms, those who suffered aSAH had significantly higher levels of MPO (113.9 ± 294.4 vs. 422.3 ± 319.0 ng/ml, p < 0.05), ELA (84.8 ± 221.0 vs. 199.2 ± 218.9 ng/ml, p < 0.05), and cH3 (0.0 ± 0.0 vs. 2.8 ± 1.5, ng/ml, p < 0.05) on day one after aSAH, suggesting the involvement of NETs components in pathophysiology of aSAH and the events following aSAH. Individually, MPO and ELA levels taken on day 1 after SAH did not differ between patients with CVS and patients without CVS. However, when taken together into a logistic model, they allowed for predicting CVS with high sensitivity (91 %) and specificity (79 %). MPO and ELA, along with other clinical parameters, can be used as early predictors of CVS in aSAH patients and can serve as guidance during treatment decisions in the management of aSAH.

Enhanced apoptosis and inflammation allied with autophagic and apoptotic Leishmania amastigotes in the seemingly undamaged ear skin of clinically affected dogs with canine visceral Leishmaniasis

Programmed cell death plays a relevant role in the pathogenesis of visceral Leishmaniasis. Apoptosis selects suitable parasites, regulating parasite density, whereas autophagy eliminates pathogens. This study aimed to assess the inflammation and apoptosis in inflammatory cells and presents a unique description of the presence of autophagic and apoptotic Leishmania amastigotes in naturally Leishmania-infected dogs. Fragments from seemingly undamaged ear skin of sixteen Leishmania-infected dogs and seven uninfected dogs were evaluated through histomorphometry, ultrastructural, immunohistochemical and transmission electron microscopy (TEM) analyses. Leishmania amastigotes were present on seemingly undamaged ear skin only in clinically affected dogs. Parasite load, morphometrical parameters of inflammation and apoptotic index of inflammatory cells were higher in clinically affected animals and were related to clinical manifestations. Apoptotic index and morphometric parameters of the inflammatory infiltrate in undamaged ear skin were positively correlated with parasite load. Apoptotic and non-apoptotic Leishmania amastigotes were observed within neutrophils and macrophages. Leishmania amastigotes were positive for Bax, a marker for apoptosis, by immunohistochemistry. Morphological characteristics of apoptosis and autophagy in Leishmania amastigotes were observed only in phagocytes of clinically affected dogs. Positive correlations were found between histomorphometry and clinical manifestations. Our results showed that apoptosis and autophagy in Leishmania amastigotes may be related to both the increase in parasite load and apoptotic index in inflammatory cells, and with the intensity of the inflammatory response in clinically affected dogs. Thus, our study suggests that apoptotic and autophagy Leishmania within phagocytes may have facilitate the survival of the parasite and it appears to play an important role in the process of Leishmania infection.

Complement component 5a receptor 1 and leukotriene B4 receptor 1 regulate neutrophil extracellular trap (NET) formation through Rap1a/B-Raf/ERK signaling pathway and their deficiency in term low birth weight newborns leads to deficient NETosis

BACKGROUND

Neutrophil extracellular traps (NETs) being one of the predominant activities of neutrophils has become its key defense mechanism owing to its extensive role in inflammation and infection. However, the mechanisms regulating NET formation or NETosis still remains to be better understood. Our earlier whole genome transcriptomic data revealed two G-protein couple receptors (GPCRs) - complement component 5a receptor 1 (C5aR1) and leukotriene B4 receptor 1 (LTB4R1) were downregulated in term low birth weight (tLBW) newborns with deficient NET formation abilities. Neutrophils employ C5aR1 and LTB4R1 for mediating their immune responses, inflammation and antimicrobial activity. Hence, this study was aimed to explore the role of two GPCRs, C5aR1 and LTB4R1 including their downstream signaling molecules in NETs induction and regulation.

METHODS

The validation of the transcriptomic data for C5aR1 and LTB4R1 was done using quantitative real time PCR. Pharmacological inhibition of C5aR1 and LTB4R1 using W-54011 and LY223982 on neutrophils of adults and newborns' was done to study their impact on NETosis. Extracellular DNA release, Reactive oxygen species (ROS) generation, expression of NET proteins, and signaling molecules downstream to C5aR1 and LTB4R1 were quantified using plate reader based assay, immunofluorescence, and western blotting. Myeloperoxidase (MPO)-DNA quantified by flow cytometry. Knockdown studies using siRNA against C5aR1 and LTB4R1 were done in HL-60 cells derived surrogate neutrophils and expression of downstream molecules of the two GPCRs, C5aR1 and LTB4R1 signaling axis along with NET proteins was quantified by western blotting.

RESULTS

The expression of C5aR1 and LTB4R1, extracellular DNA, ROS and NET associated proteins (NE, CitH3, PAD4 and MPO) was notably increased upon NET induction in healthy adults and normal birth weight (NBW) newborns' neutrophils. Pharmacological inhibition of these two GPCRs led to substantial reduction in NETosis, extracellular DNA, ROS generation, and expression of NET associated proteins like CitH3, NE, PAD4, MPO along with downstream signaling molecules Rap1a, B-Raf and pERK. Our observations suggest a precise role of C5aR1 and LTB4R1 on induction of NETs via Rap1a/B-Raf/ERK signaling axis.

CONCLUSION

The C5aR1 and LTB4R1 signaling via Rap1a/B-Raf/ERK axis acts as a signal-relay mechanism to regulate NET formation in neutrophils. Further, C5aR1 and LTB4R1 signaling cascade along with NET-associated proteins are remarkably downregulated in tLBW newborns' neutrophils leading to impaired NETosis in them. Therefore, C5aR1 and LTB4R1 and their signaling molecules could provide an effective therapeutic target for compromised NETosis like tLBW newborns.

Metabolism: a potential regulator of neutrophil fate

Neutrophils are essential components of the innate immune system that defend against the invading pathogens, such as bacteria, viruses, and fungi, as well as having regulatory roles in various conditions, including tissue repair, cancer immunity, and inflammation modulation. The function of neutrophils is strongly related to their mode of cell death, as different types of cell death involve various cellular and molecular alterations. Apoptosis, a non-inflammatory and programmed type of cell death, is the most common in neutrophils, while other modes of cell death, including NETOsis, necrosis, necroptosis, autophagy, pyroptosis, and ferroptosis, have specific roles in neutrophil function regulation. Immunometabolism refers to energy and substance metabolism in immune cells, and profoundly influences immune cell fate and immune system function. Intercellular and intracellular signal transduction modulate neutrophil metabolism, which can, in turn, alter their activities by influencing various cell signaling pathways. In this review, we compile an extensive body of evidence demonstrating the role of neutrophil metabolism in their various forms of cell death. The review highlights the intricate metabolic characteristics of neutrophils and their interplay with various types of cell death.

RNA-binding protein HuR inhibition induces multiple programmed cell death in breast and prostate cancer

The RNA-binding protein Hu antigen R (HuR) plays a pivotal role in cancer progression, and previous studies have demonstrated its involvement in suppressing cell death in cancer. However, the precise mechanisms underlying HuR inhibition-induced cell death remain elusive. Here, we investigated the impacts of HuR functional inhibition via the small molecule inhibitor KH-3 on cell proliferation, colony formation, and cell death across multiple cancer cell lines, with an emphasis on breast and prostate cancers. KH-3 treatment induced apoptotic cell death of various cancer cell lines, as well as autophagy-associated cell death and ferroptosis. Remarkably, KH-3-induced cell death was partially rescued by an autophagy inhibitor and a ferroptosis inhibitor. The anti-tumor effects of KH-3 were further validated in two mouse xenograft models of human prostate cancer. Mechanistically, KH-3 reduced the expression of HuR targets involved in apoptosis and ferroptosis suppression, including cFLIP and SLC7A11, respectively. Moreover, cFLIP silencing enhanced Caspase-8 activation as well as PARP cleavage in both breast cancer and prostate cancer cells. Both KH-3-induced pharmacological HuR inhibition and RNA interference-mediated HuR knockdown reduced the expression of SLC7A11. Additionally, KH-3 also reduced XIAP and Survivin, enhancing the activation of multiple caspases and leading to apoptosis. This study highlights the critical roles of HuR in programmed cell death regulation, advocating HuR inhibition as a promising anti-tumor strategy for cell-death-inducing cancer therapy.

Pro-inflammatory interactions of streptolysin O toxin with human neutrophils in vitro

The recent global resurgence of severe infections caused by the Group A streptococcus (GAS) pathogen, Streptococcus pyogenes, has focused attention on this microbial pathogen, which produces an array of virulence factors, such as the pore-forming toxin, streptolysin O (SOT). Importantly, the interactions of SOT with human neutrophils (PMN), are not well understood. The current study was designed to investigate the effects of pretreatment of isolated human PMN with purified SOT on several pro-inflammatory activities, including generation of reactive oxygen species (ROS), degranulation (elastase release), influx of extracellular calcium (Ca2+) and release of extracellular DNA (NETosis), using chemiluminescence, spectrophotometric and fluorimetric procedures, respectively. Exposure of PMN to SOT alone caused modest production of ROS and elastase release, while pretreatment with the toxin caused significant augmentation of chemoattractant (fMLP)-activated ROS generation and release of elastase by activated PMN. These effects of treatment of PMN with SOT were associated with both a marked and sustained elevation of cytosolic Ca2+concentrations and significant increases in the concentrations of extracellular DNA, indicative of NETosis. The current study has identified a potential role for SOT in augmenting the Ca2+-dependent pro-inflammatory interactions of PMN, which, if operative in a clinical setting, may contribute to hyper-activation of PMN and GAS-mediated tissue injury.

Lupus-prone NZM2328 mice exhibit enhanced UV-induced myeloid cell recruitment and activation in a type I interferon dependent manner

Though the exact causes of systemic lupus erythematosus (SLE) remain unknown, exposure to ultraviolet (UV) light is one of the few well-known triggers of cutaneous inflammation in SLE. However, the precise cell types which contribute to the early cutaneous inflammatory response in lupus, and the ways that UV dosing and interferons modulate these findings, have not been thoroughly dissected. Here, we explore these questions using the NZM2328 spontaneous murine model of lupus. In addition, we use iNZM mice, which share the NZM2328 background but harbor a whole-body knockout of the type I interferon (IFN) receptor, and wild-type BALB/c mice. 10-13-week-old female mice of each strain were treated with acute (300 mJ/cm2 x1), chronic (100 mJ/cm2 daily x5 days), or no UVB, and skin was harvested and processed for bulk RNA sequencing and flow cytometry. We identify that inflammatory pathways and gene signatures related to myeloid cells - namely neutrophils and monocyte-derived dendritic cells - are a shared feature of the acute and chronic UVB response in NZM skin greater than iNZM and wild-type skin. We also verify recruitment and activation of these cells by flow cytometry in both acutely and chronically irradiated NZM and WT mice and demonstrate that these processes are dependent on type I IFN signaling. Taken together, these data indicate a skewed IFN-driven inflammatory response to both acute and chronic UVB exposure in lupus-prone skin dominated by myeloid cells, suggesting both the importance of type I IFNs and myeloid cells as therapeutic targets for photosensitive patients and highlighting the risks of even moderate UV exposure in this patient population.

Understanding the interplay between psoriatic arthritis and gout: "Psout"

The interplay between Psoriatic arthritis and Gout is a current diagnostic challenge faced by many physicians and researchers. We aimed at reviewing the coexistence of gout and its features such as hyperuricemia and deposition of monosodium urate crystals in patients with psoriatic arthritis (PsA). We also focused on a brief presentation of the pathophysiology underneath the interplay between PsA and gout, and ultimately on recommendation of approaches for the differential diagnosis. The literature search for this narrative review was conducted using PubMed and Medline and after retrieving and screening the references, articles were selected according to the inclusion and exclusion criteria. Part of the assessed studies reported the coexistence of PsA and gout (Psout) and its association with several clinical outcomes among affected patients. Other studies stressed incidences of misdiagnosis of gout with PsA and vice versa. Additionally, the presence of hyperuricemia in PsA patients could interfere with the patient's characteristics and outcomes of their treatment. Further research on the assessment and clinical course of Psout is required to develop an official protocol for its diagnosis and treatment.

Advances in Understanding of the Role of Immune Cell Phenotypes in Hypertension and Associated Vascular Disease

Many studies in the past 20 years have identified a contribution of inflammation and immune mechanisms to the pathophysiology of hypertension. Innate and adaptive immunity participate in this process. Among innate immune cells, macrophages and monocytes as well as dendritic cells, myeloid-derived suppressor cells, and neutrophils directly or via formation of neutrophil extracellular traps, play roles in the modulation of the inflammatory response in hypertension. Among adaptive immune cells, T and B cells have been implicated to varying degrees, particularly interleukin (IL)-17- and interferon γ-producing T lymphocytes, antagonized by T regulatory lymphocytes that are anti-inflammatory via production of IL-10. Among T cells that produce abundant IL-17, γδ T cells are unconventional T lymphocytes that are infrequent in the circulation in contrast to the much more abundant circulating αβ T lymphocytes, but are found mostly in tissues, and appear to play a role in triggering and sustaining inflammation in hypertension leading to vascular and renal injury. This review will provide an overview of these different immune cell phenotypes involved in the immune pathophysiology of hypertension and associated vascular disease.

5-oxoETE promote thrombosis in antiphospholipid syndrome by triggering NETs formation through PLC/PKC/ERK pathway

BACKGROUND

One mechanism by which antiphospholipid syndrome (APS) IgG contribute to thrombotic events in patients with APS is through the potentiation of neutrophil extracellular traps (NETs) release. However, the exact mechanism by which APS IgG induces NETs formation and thrombosis has not been fully elucidated.

METHODS

We conducted untargeted metabolomics on serum samples from thrombotic APS patients to identify metabolic changes. The effect of 5-oxoETE on NETs formation and oxidative stress was evaluated in vitro by treating neutrophils with various concentrations of 5-oxoETE. The involvement of the PLC/PKC/ERK signaling pathway in 5-oxoETE-induced NETs formation was examined using pharmacological inhibitors. In vivo, we assessed the effects of inhibiting 5-oxoETE synthesis or blocking its receptor (OXE-R) on NETs formation and thrombosis in APS mouse models.

RESULTS

Serum metabolomics revealed significantly elevated levels of 5-oxoETE in APS patients. In vitro experiments demonstrated that 5-oxoETE, via OXE-R activation of the PLC/PKC/ERK signaling pathway, increased NETs formation and oxidative stress in a dose-dependent manner. In vivo, inhibiting 5-oxoETE synthesis or OXE-R reduced NETs formation and attenuated venous thrombosis in APS mice models.

CONCLUSION

This study identifies 5-oxoETE as a critical mediator of NET formation and thrombosis in APS. Targeting 5-oxoETE or OXE-R may offer a promising therapeutic approach for thrombotic APS and other NET-associated autoimmune diseases.

CXCR2 mediated trafficking of neutrophils and neutrophil extracellular traps are required for myelin clearance after a peripheral nerve injury

Neutrophils are a vital part of the innate immune system. Many of their functions eliminate bacteria & viruses, like neutrophil extracellular traps (NETs), which trap bacteria, enhancing macrophage phagocytosis. It was surprising when it was demonstrated that neutrophils are a part of Wallerian degeneration, a process that is essential for nerve regeneration after a nerve injury. It is not known what signals attract neutrophils into the nerve and how they aid Wallerian degeneration. Neutrophils accumulate in the distal nerve within one day after an injury and are found in the nerve from one to three days. We demonstrate that CXCR2 mediates the trafficking of neutrophils into the distal nerve, and without CXCR2 Wallerian degeneration, as indicated by luxol fast blue staining, was reduced seven days after a sciatic nerve crush or transection injury. NETs were detected in the distal nerve after a sciatic nerve transection. NET formation has been shown to require protein arginine deiminase 4 (PAD4), which citrullinates histone 3. Inhibiting PAD4 reduced NET formation significantly in the distal nerve at two days and myelin clearance at seven days indicating that NETs aid myelin clearance. These results demonstrate another function for NETs other than clearing pathogens. Neutrophils have been detected after injuries to the central nervous system and diseases in humans and animal models. Our results demonstrate neutrophils aid myelin clearance, suggesting a role for their presence in central nervous system injuries and diseases.

Identification of Renal Ischemia-Reperfusion Injury Subtypes and Predictive Model for Graft Loss after Kidney Transplantation Based on Programmed Cell Death-Related Genes

Introduction

Ischemia-reperfusion injury (IRI) is detrimental to kidney transplants and may contribute to poor long-term outcomes of transplantation. Programmed cell death (PCD), a regulated cell death form triggered by IRI, is often indicative of an unfavorable prognosis following transplantation. However, given the intricate pathophysiology of IRI and the considerable variability in clinical conditions during kidney transplantation, the specific patterns of cell death within renal tissues remain ambiguous. Consequently, accurately predicting the outcomes for transplanted kidneys continues to be a formidable challenge.

Methods

Eight Gene Expression Omnibus datasets of biopsied transplanted kidney samples post-IRI and 1,548 PCD-related genes derived from 18 PCD patterns were collected in our study. Consensus clustering was performed to identify distinct IRI subtypes based on PCD features (IRI PCD subtypes). Differential enrichment analysis of cell death, metabolic signatures, and immune infiltration across these subtypes was evaluated. Three machine learning algorithms were used to identify PCD patterns related to prognosis. Genes associated with graft loss were screened for each PCD type. A predictive model for graft loss was constructed using 101 combinations of 10 machine learning algorithms.

Results

Four IRI subtypes were identified: PCD-A, PCD-B, PCD-C, and PCD-D. PCD-A, characterized by high enrichment of multiple cell death patterns, significant metabolic paralysis, and immune infiltration, showed the poorest prognosis among the four subtypes. While PCD-D involved the least kind of cell death patterns with the features of extensive activation of metabolic pathways and the lowest immune infiltration, correlating with the best prognosis in the four subtypes. Using various machine learning algorithms, 10 cell death patterns and 42 PCD-related genes were identified as positively correlated with graft loss. The predictive model demonstrated high sensitivity and specificity, with area under the curve values for 0.5-, 1-, 2-, 3-, and 4-year graft survival at 0.888, 0.91, 0.926, 0.923, and 0.923, respectively.

Conclusion

Our study explored the comprehensive features of PCD patterns in transplanted kidney samples post-IRI. The prediction model shows great promise in forecasting graft loss and could aid in risk stratification in patients following kidney transplantation.

Lenvatinib-activated NDUFA4L2/IL33/PADI4 pathway induces neutrophil extracellular traps that inhibit cuproptosis in hepatocellular carcinoma

BACKGROUND

Lenvatinib is a potent first-line therapy for patients with hepatocellular carcinoma (HCC), but it also increased the number of neutrophils in HCC tumor microenvironment.

METHODS

CitH3, MPO-DNA, elastase and MPO activity were measured for assessing neutrophil extracellular traps (NETs) in vivo and in vitro. Cell cuproptosis was assessed by measurement of copper content, FDX1, and pyruvate. The functions of lenvatinib, DNase I, interleukin 33 (IL33) neutralizing antibody and GPX4 in tumor growth were explored in mice.

RESULTS

Lenvatinib induced NETs in the HCC tumor microenvironment via HCC cells, but not through the direct stimulation of neutrophils. In addition, NET clearance by DNase I improves the efficacy of lenvatinib therapy in HCC mouse models. Mechanistically, lenvatinib promoted the expression and secretion of IL33 by HCC cells that triggered NET formation. Moreover, IL33 knockdown in Hepa1-6 cells improved lenvatinib efficacy in Hepa1-6-bearing HCC model mice and reduced NET formation in the tumor microenvironment. Subsequently, lenvatinib increased IL33 production by increasing the NDUFA4L2 expression in HCC cells. Furthermore, we found that IL33 triggered NET formation in neutrophils by increasing the protein expression of PADI4 via the Akt/mTOR signaling pathway. Rapamycin inhibition of mTOR reduced PADI4 expression and NET formation. Consistently, PADI4 inhibition by the selective PAD4 inhibitor GSK484 hydrochloride (GSK484) improved lenvatinib response to HCC therapy. Importantly, NETs contribute to lenvatinib resistance by inhibiting cuproptosis, but not apoptosis, pyroptosis, or ferroptosis in HCC cells. Treatment with GSK484 reversed the inhibitory effects of NETs on cuproptosis and sensitized the HCC cells to lenvatinib.

CONCLUSIONS

Our study revealed that lenvatinib-induced NETs inhibited the cuproptosis of HCC cells, suggesting that targeting the IL33/PADI4/NET axis represents a promising therapeutic strategy for ameliorating lenvatinib resistance in HCC.

Insufficient FUNDC1-dependent mitophagy due to early environmental cadmium exposure triggers mitochondrial redox imbalance to aggravate diet-induced lipotoxicity

Cadmium (Cd) is a toxic contaminant widely spread in natural and industrial environments. Adolescent exposure to Cd increases risk for obesity-related morbidity in young adults including type 2 diabetes and metabolic dysfunction-associated steatotic liver disease (MASLD). Despite this recognition, the direct impact of adolescent Cd exposure on the progression of MASLD later in life, and the mechanisms underlying these effects, remain unclear. Here, adolescent rats received control diet or diets containing 2 mg Cd2+/kg feed for 4 weeks, and then HFD containing 15% lard or control diet in young adult rats was selected for 6 weeks to clarify this issue. Data firstly showed that HFD-fed rats in young adulthood due to adolescent Cd exposure exhibited more severe MASLD, evidenced by increased liver damage, disordered serum and hepatic lipid levels, and activated NLRP3 inflammasome. Hepatic transcriptome analysis revealed the potential effects of mitochondrial dysfunction in aggravated MASLD due to Cd exposure. Verification data further confirmed that mitochondrial structure and function were targeted and disrupted during this process, shown by broken mitochondrial ridges, decreased mitochondrial membrane potential, imbalanced mitochondrial dynamic, insufficient ATP concentration, and enhanced mitochondrial ROS generation. However, mitophagy is inactively involved in clearance of damaged mitochondria induced by early Cd in HFD condition due to inhibited mitophagy receptor FUNDC1. In contrast, FUNDC1-dependent mitophagy activation prevents lipotoxicity aggravated by early Cd via suppressing mitochondrial ROS generation. Collectively, our data show that insufficient FUNDC1-dependent mitophagy can drive the transition from HFD-induced MASLD to MASH, and accordingly, these findings will provide a better understanding of potential mechanism of diet-induced metabolic diseases in the context of early environmental Cd exposure.

Neutrophils enhance the clearance of systemic amyloid deposits in a murine amyloidoma model

Introduction

Amyloid-specific antibodies have been shown to opsonize and enhance amyloid clearance in systemic amyloidosis mouse models. However, the immunological mechanisms by which amyloid is removed have not been clearly defined. Previous reports from preclinical in vivo studies suggest polymorphonuclear cells (i.e., neutrophils) can affect amyloid removal. Therefore, we sought to analyze how neutrophils may contribute to the clearance of human AL amyloid extracts, using a murine amyloidoma model.

Methods

Immunocompromised nude mice injected subcutaneously with patient-derived AL amyloid extract (generating a localized "amyloidoma") were used to circumvent confounding factors contributed by the adaptive immune system and served as the model system. Two representative AL amyloid extracts were used, ALλ(CLA), which is refractory to clearance, and ALκ(TAL), which is readily cleared in mice. Neutrophil recruitment to the amyloid masses, cellular activation, and propensity to engulf amyloid were assessed.

Results

Immunophenotyping of amyloidomas from animals implanted with 2 mg of either ALλ or ALκ revealed that more neutrophils were recruited to ALκ amyloid masses as compared to the ALλ material, which was generally devoid of neutrophils. Ex vivo analyses indicated neutrophils do not efficiently phagocytose amyloid directly. However, histological evaluation of the ALκ amyloidoma revealed the abundant presence of neutrophil extracellular traps, which were absent in the ALλ amyloidomas. Using neutrophil depletion experiments in mice, we determined that mice devoid of neutrophils cleared the human amyloid lesions less efficiently. Moreover, mice devoid of neutrophils also had significantly reduced intra-amyloid expression of inflammatory cytokines.

Discussion

Neutrophils may not directly mediate amyloid clearance through phagocytosis; however, these cells can be stimulated by the amyloid and may function to facilitate phagocytosis and amyloid clearance by professional phagocytes (e.g., macrophages).

Environment-sensitive turn-on fluorescent probe enables live cell imaging of myeloperoxidase activity during NETosis

Myeloperoxidase (MPO) plays an important role in the immune response of human neutrophils and has been implicated in autoimmune conditions, cardiovascular disorders, and neurodegeneration. Current methods to detect MPO activity rely on the detection of HOCl using activatable probes or require challenging experimental procedures. Therefore, these tools provide limited information about the dynamics and localization of MPO in complex molecular processes such as NETosis in real time. In this study, we report a ''turn-on" activity-based probe that fluoresces exclusively upon binding to MPO, exhibits minimal background fluorescence in buffered aqueous media, and is blocked by MPO inhibitors. Our probe facilitates real-time imaging of direct MPO activity in human neutrophils and HL-60-derived granulocytes during NETosis under wash-free conditions. Furthermore, it allows for the discrimination between different triggers of NETosis in human neutrophils. These findings hold promise for advancing our understanding of the role of MPO in immune responses and inflammatory conditions.

Association of PADI4 Gene Polymorphisms With Susceptibility to Rheumatoid Arthritis: Evidence From 24 Case-Control Studies

This study aims to investigate the association of rs11203366, rs11203367, rs874881, rs2240340 and rs1748033 polymorphisms of protein-arginine deiminase type 4 (PADI4) gene with the risk of rheumatoid arthritis (RA) through a meta-analysis that was followed with a bioinformatics approach. The data were collected from reputable articles and underwent quantitative analysis, followed by in silico analysis using some bioinformatics tools. The results showed that rs874881 polymorphism in Latino (G vs. C: OR = 1.35, 95% CI = 1.11-1.65, p = 0.003; GG + CG vs. CC: OR = 2.02, 95% CI = 1.41-2.89, p = 0.0001; CG vs. CC + GG: OR = 1.38, 95% CI = 1.04-1.83, p = 0.027; GG vs. CC: OR = 2.09, 95% CI = 1.35-3.23, p = 0.001; CG vs. CC: OR = 1.98, 95% CI = 1.36-2.87, p = 0.00033) and rs1748033 in Caucasian population (T vs. C: OR = 1.25, 95% CI = 1.07-1.45, p = 0.005; TT vs. CT + CC: OR = 1.34, 95% CI = 1.09-1.64, p = 0.005, TT + CT vs. CC: OR = 1.26, 95% CI = 1.09-1.44, p = 0.001; TT vs. CC: OR = 1.59, 95% CI = 1.13-2.23, p = 0.007; CT vs. CC: OR = 1.20, 95% CI: 1.04-1.39, p = 0.015) are associated with increased risk of RA. Moreover, rs11203366 (G vs. A: OR = 1.46, 95% CI = 1.19-1.78, p = 0.0002, GG vs. AG + AA: OR = 1.42, 95% CI = 1.01-2.01, p = 0.043; GG + AG vs. AA: OR = 2.03, 95% CI = 1.45-2.86, p = 0.00004; GG vs. AA: OR = 2.29, 95% CI = 1.49-3.51, p = 0.0002; AG vs. AA: OR = 1.93, 95% CI = 1.35-2.76, p = 0.0003) and rs11203367 (T vs. C: OR = 1.50, 95% CI = 1.23-1.83, p = 0.00007; TT vs. CT + CC: OR = 1.56, 95% CI = 1.12-2.18, p = 0.009; TT + CT vs. CC: OR = 2.02, 95% CI = 1.43-2.84, p = 0.00007, TT vs. CC: OR = 2.43, 95% CI = 1.59-3.71, p = 0.0004; CT vs. CC: OR = 1.86, 95% CI = 1.30-2.68, p = 0.0007) had an impact in the Latino population. Bioinformatics tools showed the effect of these polymorphisms on gene function. These findings suggest that rs11203366, rs11203367, rs874881 and rs1748033 polymorphisms may be genetic risk factors for RA. Moreover, differences between populations suggest that ethnicity may play an important role in the effect of these polymorphisms on RA risk.

The role of reactive oxygen species in severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) infection-induced cell death

Coronavirus disease 2019 (COVID-19) represents the novel respiratory infectious disorder caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and is characterized by rapid spread throughout the world. Reactive oxygen species (ROS) account for cellular metabolic by-products, and excessive ROS accumulation can induce oxidative stress due to insufficient endogenous antioxidant ability. In the case of oxidative stress, ROS production exceeds the cellular antioxidant capacity, thus leading to cell death. SARS-CoV-2 can activate different cell death pathways in the context of infection in host cells, such as neutrophil extracellular trap (NET)osis, ferroptosis, apoptosis, pyroptosis, necroptosis and autophagy, which are closely related to ROS signalling and control. In this review, we comprehensively elucidated the relationship between ROS generation and the death of host cells after SARS-CoV-2 infection, which leads to the development of COVID-19, aiming to provide a reasonable basis for the existing interventions and further development of novel therapies against SARS-CoV-2.

Neutrophil extracellular traps in wound healing

Wound healing is a complex and orchestrated process that involves hemostasis, inflammation, proliferation, and tissue remodeling. Neutrophil extracellular traps (NETs) are intricate web-like structures released by neutrophils, comprising decondensed chromatin, myeloperoxidase (MPO), and neutrophil elastase (NE), which play vital roles in regulating neutrophil-mediated immune regulation. While NETs contribute to wound healing, excessive activation induced by dysregulated inflammation can hinder the healing process. Understanding the pivotal role of NETs in wound healing and tissue remodeling, as well as their intricate interactions within the wound microenvironment, presents opportunities for innovative wound healing strategies. In this review we discuss the process of NET formation, explore the interactions between NETs and skin cells, and examine therapeutic strategies targeting NETs and drug delivery platforms to accelerate wound healing. Additionally, we discuss current clinical investigations and research challenges towards advancing wound care practices.

Neutrophil-avid nanocarrier uptake by STAT3 dominant-negative hyper-IgE syndrome patient neutrophils

Recurrent infections are a hallmark of STAT3 dominant-negative hyper-IgE syndrome (STAT3 HIES), a rare immunodeficiency syndrome previously known as Jobs syndrome, along with elevated IgE levels and impaired neutrophil function. We have been developing nanoparticles with neutrophil trophism that home to the sites of infection via these first-responder leukocytes, named neutrophil-avid nanocarriers (NANs). Here, we demonstrate that human neutrophils can phagocytose nanogels (NGs), a type of NAN, with enhanced uptake after particle serum opsonization, comparing neutrophils from healthy individuals to those with STAT3 HIES, where both groups exhibit NG uptake; however, the patient group showed reduced phagocytosis efficiency with serum-opsonized NANs. Proteomic analysis of NG protein corona revealed complement components, particularly C3, as predominant in both groups. Difference between groups includes STAT3 HIES samples with higher neutrophil protein and lower acute-phase protein expression. The study suggests that despite neutrophil dysfunction in STAT3 HIES, NANs have potential for directed delivery of cargo therapeutics to improve neutrophil infection clearance.

Plasma levels of myeloperoxidase and resistin independently predict mortality in dialysis patients

BACKGROUND

In patients with kidney failure (KF) undergoing dialysis, neutrophils are dysfunctionally activated. Such chronic activation does not correspond to increased protection against infections and is thought to cause direct vascular damage accounting for the higher incidence of cardiovascular (CV) events. We hypothesized that circulating levels of neutrophil degranulation products (i.e. myeloperoxidase (MPO) and resistin) can predict overall and CV-specific mortality in dialysis patients.

METHODS

MPO and resistin levels were assessed in plasma samples from n = 1182 dialysis patients who were followed-up for median 2.9 years (IQR: 1.7-4.2).

RESULTS

Patients were 65 ± 14 (SD) years old and 36 % women. Median value of MPO and resistin were 78 ng/mL (IQR: 54 - 123) and 72 ng/mL (IQR: 46 - 110), respectively. MPO and resistin levels correlated with biomarkers of organ damage, nutritional status and inflammation. Both MPO and resistin levels predicted all-cause mortality even after adjustment for traditional risk factors and inflammation, nutritional and KF-related indexes (MPO, HRfor 1 ln unit increase: 1.26, 95 %CI 1.11 - 1.42, P < 0.001; Resistin, HRfor 1 ln unit increase: 1.25, 95 %CI 1.09 - 1.44, P = 0.001). Similarly, their predictive ability held true also for CV death (MPO, HRfor 1 ln unit increase: 1.19, 95 %CI 1.01 - 1.41, P = 0.04; Resistin, HRfor 1 ln unit increase: 1.29, 95 %CI 1.07 - 1.56, P = 0.007).

CONCLUSION

Plasma levels of MPO and resistin correlate with prospective overall and CV-specific mortality risk in KF patients undergoing dialysis and might be useful prognostic tools. Mediators of inflammation may be potential target to improve survival of those patients.

Dexamethasone and IFN-γ primed mesenchymal stem cells conditioned media immunomodulates aberrant NETosis in SLE via PGE2 and IDO

Background

Systemic Lupus Erythematosus (SLE) is characterized by dysregulated immune responses, with neutrophil extracellular traps (NETs) playing a significant role. NETs are recognized by autoantibodies in SLE patients, exacerbating pathology. Both excessive NET formation and impaired degradation contribute to SLE pathophysiology.

Objective

To investigate the immunomodulatory effects of Dexamethasone-primed Wharton's jelly (WJ) derived MSCs CM (DW) and IFN-γ-primed WJ-MSCs-CM (IW) on NETosis and associated protein markers in SLE patients' LPS or ribonucleoprotein immune complexes (RNP ICs) induced neutrophils and in pristane induced lupus (PIL) model. And to elucidate the mechanism involved therein.

Methods

We investigated the immunomodulatory effects of DW and IW on NETosis in SLE. Utilizing ex vivo and in vivo models, we assessed the impact of preconditioned media on NET formation and associated protein markers neutrophil elastase (NE), citrullinated histone (citH3), myeloperoxidase (MPO), cytoplasmic and mitochondrial ROS production. We also examined the involvement of key immunomodulatory factors present in DW and IW, including prostaglandin E2 (PGE2), indoleamine 2,3-dioxygenase (IDO), and transforming growth factor-beta (TGF-β).

Results

Preconditioned media effectively suppressed NETosis and reduced ROS generation in SLE neutrophils, indicating their immunomodulatory potential. Inhibition studies implicated IDO and PGE2 in mediating this effect. Combined treatment with DW or IW together with hydroxychloroquine (HCQ) demonstrated superior efficacy over HCQ alone, a standard SLE medication. In PIL mouse model, DW and IW treatments reduced NETosis, ROS generation, as evidenced by decreased NET-associated protein expression in vital organs.

Conclusion

Our study highlights the multifaceted impact of IW and DW on NETosis, ROS dynamics, and lupus severity in SLE. These findings underscore the potential of preconditioned media for the development of targeted, personalized approaches for SLE treatment.

Immunity and Coagulation in COVID-19

Discovered in late 2019, the SARS-CoV-2 coronavirus has caused the largest pandemic of the 21st century, claiming more than seven million lives. In most cases, the COVID-19 disease caused by the SARS-CoV-2 virus is relatively mild and affects only the upper respiratory tract; it most often manifests itself with fever, chills, cough, and sore throat, but also has less-common mild symptoms. In most cases, patients do not require hospitalization, and fully recover. However, in some cases, infection with the SARS-CoV-2 virus leads to the development of a severe form of COVID-19, which is characterized by the development of life-threatening complications affecting not only the lungs, but also other organs and systems. In particular, various forms of thrombotic complications are common among patients with a severe form of COVID-19. The mechanisms for the development of thrombotic complications in COVID-19 remain unclear. Accumulated data indicate that the pathogenesis of severe COVID-19 is based on disruptions in the functioning of various innate immune systems. The key role in the primary response to a viral infection is assigned to two systems. These are the pattern recognition receptors, primarily members of the toll-like receptor (TLR) family, and the complement system. Both systems are the first to engage in the fight against the virus and launch a whole range of mechanisms aimed at its rapid elimination. Normally, their joint activity leads to the destruction of the pathogen and recovery. However, disruptions in the functioning of these innate immune systems in COVID-19 can cause the development of an excessive inflammatory response that is dangerous for the body. In turn, excessive inflammation entails activation of and damage to the vascular endothelium, as well as the development of the hypercoagulable state observed in patients seriously ill with COVID-19. Activation of the endothelium and hypercoagulation lead to the development of thrombosis and, as a result, damage to organs and tissues. Immune-mediated thrombotic complications are termed "immunothrombosis". In this review, we discuss in detail the features of immunothrombosis associated with SARS-CoV-2 infection and its potential underlying mechanisms.

Lipidome profiling of neutrophil-derived extracellular vesicles unveils their contribution to the ensemble of synovial fluid-derived extracellular vesicles during joint inflammation

The molecular signature of cell-derived extracellular vesicles (EVs) from synovial fluid (SF) offers insights into the cells and molecular processes associated with joint disorders and can be exploited to define biomarkers. The EV-signature is determined by cargo molecules and the lesser-studied lipid bilayer. We here investigated the lipidome of SF-EVs in inflamed joints derived from Rheumatoid Arthritis (RA) and Spondyloarthritis (SpA) patients, two autoimmune-driven joint diseases, and compared these signatures to the lipid profile of equine SF-EVs obtained during induced acute synovitis. Since neutrophils are primary SF-infiltrating cells during these inflammatory joint diseases, we also analyzed how inflammatory stimuli alter the lipidomic profile of human and equine neutrophil-derived EVs (nEVs) in vitro and how these signatures relate to the lipidome signatures of SF-EVs from inflamed joints. We identified neutrophil stimulation intensity-dependent changes in the lipidomic profile of nEVs with elevated presence of dihexosylceramide (lactosylceramide), phosphatidylserine, and phosphatidylethanolamine ether-linked lipid classes in human nEVs upon full neutrophil activation. In horses, levels of monohexosylceramide (glucosylceramide) increased instead of dihexosylceramide, indicating species-specific differences. The lipid profiles of RA and SpA SF-EVs were relatively similar and showed a relative resemblance with stimulated human nEVs. Similarly, the lipidome of equine synovitis-derived SF-EVs closer resembled the one of stimulated equine nEVs. Hence, lipidome profiling can provide insights into the contribution of nEVs to the heterogeneous pool of SF-EVs, deepening our understanding of inflammatory joint diseases and revealing molecular changes in joint homeostasis, which can lead to the development of more precise disease diagnosis and treatment strategies.

The Role of Myeloid Cells in Thromboinflammatory Disease

Inflammation contributes to the development of thrombosis, but the mechanistic basis for this association remains poorly understood. Innate immune responses and coagulation pathways are activated in parallel following infection or injury, and represent an important host defense mechanism to limit pathogen spread in the bloodstream. However, dysregulated proinflammatory activity is implicated in the progression of venous thromboembolism and arterial thrombosis. In this review, we focus on the role of myeloid cells in propagating thromboinflammation in acute inflammatory conditions, such as sepsis and coronavirus disease 2019 (COVID-19), and chronic inflammatory conditions, such as obesity, atherosclerosis, and inflammatory bowel disease. Myeloid cells are considered key drivers of thromboinflammation via upregulated tissue factor activity, formation of neutrophil extracellular traps (NETs), contact pathway activation, and aberrant coagulation factor-mediated protease-activated receptor (PAR) signaling. We discuss how strategies to target the intersection between myeloid cell-mediated inflammation and activation of blood coagulation represent an exciting new approach to combat immunothrombosis. Specifically, repurposed anti-inflammatory drugs, immunometabolic regulators, and NETosis inhibitors present opportunities that have the potential to dampen immunothrombotic activity without interfering with hemostasis. Such therapies could have far-reaching benefits for patient care across many thromboinflammatory conditions.

The multi-herbal decoction SH003 alleviates LPS-induced acute lung injury by targeting inflammasome and extracellular traps in neutrophils

BACKGROUND

Acute lung injury (ALI) is a devastating condition caused by sepsis, pneumonia, trauma, and more recently, COVID-19. SH003, an herbal formula consisted of Astragalus membranaceus, Angelica gigas and Trichosanthes kirilowii, is known for its effects on cancer and immunoregulation.

HYPOTHESIS/PURPOSE

Previous studies show SH003 exerts a promising anti-inflammatory effect. This study investigates the effect of modified SH003 on ALI using in silico, in vivo, and in vitro models.

STUDY DESIGN AND METHODS

We performed in silico-based analysis of SH003 on ALI-related pathways. C57BL/6 mice were intraperitoneally subjected to lipopolysaccharide (LPS) to induce septic ALI, followed by oral administration of SH003 for 2 weeks. Dexamethasone was used as the positive control. Human peripheral blood-derived polymorphonuclear neutrophils (PMN) were used to investigate the effect and mechanisms of SH003 on neutrophil extracellular trap (NET) formation.

RESULTS

Network pharmacology analysis suggested SH003 regulates lung inflammation by modulating NET formation. SH003 significantly reduced mortality in sepsis in vivo by inhibiting local and systemic inflammation, likely via nuclear factor kappa B and mitogen-activated protein kinase pathways-mediated inflammasome suppression. SH003 also decreased NET-related markers in lung tissues and inhibited LPS- and phorbol myristate acetate-induced NET formation in PMN. Cytometry time-of-flight analysis confirmed regulation of NETosis-related pathways by SH003.

CONCLUSION

SH003 effectively inhibits excessive immune responses in the lung by suppressing inflammasome activation and NET formation. These findings suggest SH003 as a potential therapeutic agent for septic ALI.

Neutrophil extracellular traps in homeostasis and disease

Neutrophil extracellular traps (NETs), crucial in immune defense mechanisms, are renowned for their propensity to expel decondensed chromatin embedded with inflammatory proteins. Our comprehension of NETs in pathogen clearance, immune regulation and disease pathogenesis, has grown significantly in recent years. NETs are not only pivotal in the context of infections but also exhibit significant involvement in sterile inflammation. Evidence suggests that excessive accumulation of NETs can result in vessel occlusion, tissue damage, and prolonged inflammatory responses, thereby contributing to the progression and exacerbation of various pathological states. Nevertheless, NETs exhibit dual functionalities in certain pathological contexts. While NETs may act as autoantigens, aggregated NET complexes can function as inflammatory mediators by degrading proinflammatory cytokines and chemokines. The delineation of molecules and signaling pathways governing NET formation aids in refining our appreciation of NETs' role in immune homeostasis, inflammation, autoimmune diseases, metabolic dysregulation, and cancer. In this comprehensive review, we delve into the multifaceted roles of NETs in both homeostasis and disease, whilst discussing their potential as therapeutic targets. Our aim is to enhance the understanding of the intricate functions of NETs across the spectrum from physiology to pathology.

How underappreciated autoinflammatory (innate immunity) mechanisms dominate disparate autoimmune disorders

Historically inflammation against self was considered autoimmune which stems back to the seminal observations by Ehrlich who described serum factors, now known to be autoantibodies produced by B lineage cells that mediate "horror autotoxicus". The 20th century elucidation of B- and T-cell adaptive immune responses cemented the understanding of the key role of adaptive immune responses in mediating pathology against self. However, Mechnikov shared the Nobel Prize for the discovery of phagocytosis, the most rudimentary aspect of innate immunity. Fast forward some 100 years and an immunogenetic understanding of innate immunity led to the categorising of innate immunopathology under the umbrella term 'auto inflammation' and terminology such as "horror autoinflammaticus" to highlight the schism from the classical adaptive immune understanding of autoimmunity. These concepts lead to calls for a two-tiered classification of inflammation against self, but just as innate and adaptive immunity are functionally integrated, so is immunopathology in many settings and the concept of an autoimmune to autoinflammation continuum emerged with overlaps between both. Herein we describe several historically designated disorders of adaptive immunity where innate immunity is key, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), systemic juvenile idiopathic arthritis (sJIA) and adult-onset Still's disease (AOSD) where the immunopathology phenotype is strongly linked to major histocompatibility complex (MHC) class II associations and responds to drugs that target T-cells. We also consider MHC-I-opathies including psoriasis and Behcet's disease(BD) that are increasingly viewed as archetype CD8 T-cell related disorders. We also briefly review the key role of barrier dysfunction in eczema and ulcerative colitis (UC) where innate tissue permeability barrier dysfunction and microbial dysbiosis contributes to prominent adaptive immune pathological mechanisms. We also highlight the emerging roles of intermediate populations of lymphocytes including gamma delta (γδ) and mucosal-associated invariant T (MAIT) cells that represent a blend of adaptive immune plasticity and innate immune rapid responders that may also determine site specific patterns of inflammation.

Cyclic stretch enhances neutrophil extracellular trap formation

BACKGROUND

Neutrophils, the most abundant leukocytes circulating in blood, contribute to host defense and play a significant role in chronic inflammatory disorders. They can release their DNA in the form of extracellular traps (NETs), which serve as scaffolds for capturing bacteria and various blood cells. However, uncontrolled formation of NETs (NETosis) can lead to excessive activation of coagulation pathways and thrombosis. Once neutrophils are migrated to infected or injured tissues, they become exposed to mechanical forces from their surrounding environment. However, the impact of transient changes in tissue mechanics due to the natural process of aging, infection, tissue injury, and cancer on neutrophils remains unknown. To address this gap, we explored the interactive effects of changes in substrate stiffness and cyclic stretch on NETosis. Primary neutrophils were cultured on a silicon-based substrate with stiffness levels of 30 and 300 kPa for at least 3 h under static conditions or cyclic stretch levels of 5% and 10%, mirroring the biomechanics of aged and young arteries.

RESULTS

Using this approach, we found that neutrophils are sensitive to cyclic stretch and that increases in stretch intensity and substrate stiffness enhance nuclei decondensation and histone H3 citrullination (CitH3). In addition, stretch intensity and substrate stiffness promote the response of neutrophils to the NET-inducing agents phorbol 12-myristate 13-acetate (PMA), adenosine triphosphate (ATP), and lipopolysaccharides (LPS). Stretch-induced activation of neutrophils was dependent on calpain activity, the phosphatidylinositol 3-kinase (PI3K)/focal adhesion kinase (FAK) signalling and actin polymerization.

CONCLUSIONS

In summary, these results demonstrate that the mechanical forces originating from the surrounding tissue influence NETosis, an important neutrophil function, and thus identify a potential novel therapeutic target.

Clinical complications in envenoming by Apis honeybee stings: insights into mechanisms, diagnosis, and pharmacological interventions

Envenoming resulting from Apis honeybee stings pose a neglected public health concern, with clinical complications ranging from mild local reactions to severe systemic manifestations. This review explores the mechanisms underlying envenoming by honeybee sting, discusses diagnostic approaches, and reviews current pharmacological interventions. This section explores the diverse clinical presentations of honeybee envenoming, including allergic and non-allergic reactions, emphasizing the need for accurate diagnosis to guide appropriate medical management. Mechanistic insights into the honeybee venom's impact on physiological systems, including the immune and cardiovascular systems, are provided to enhance understanding of the complexities of honeybee sting envenoming. Additionally, the article evaluates emerging diagnostic technologies and therapeutic strategies, providing a critical analysis of their potential contributions to improved patient outcomes. This article aims to provide current knowledge for healthcare professionals to effectively manage honeybee sting envenoming, thereby improving patient care and treatment outcomes.

Construction of a NETosis-related gene signature for predicting the prognostic status of sepsis patients

Background

Sepsis is a common traumatic complication of response disorder of the body to infection. Some studies have found that NETosis may be associated with the progression of sepsis.

Methods

Data of the sepsis samples were acquired from Gene Expression Omnibus (GEO) database. Gene set enrichment score was calculated using single-sample gene set enrichment analysis (ssGSEA). Weighted gene co-expression network analysis (WGCNA), protein-protein interaction (PPI) networks analysis, and stepwise multivariable regression analysis were performed to identify NETosis-associated genes for sepsis prognosis. To assess the infiltration of immune cells, the ESTIMATE and CIBERPSORT algorithms were used. Functional enrichment analysis was conducted in the clusterProfiler package.

Results

Different programmed death pathways were abnormally activated in sepsis patients as compared to normal samples. We screened five important NETosis associated genes, namely, CEACAM8, PGLYRP1, MAPK14, S100A12, and LCN2. These genes were significantly positively correlated with entotic cell death and ferroptosis and negatively correlated with autophagy. A clinical prognostic model based on riskscore was established using the five genes. The ROC curves of the model at 7 days, 14 days and 21 days all had high AUC values, indicating a strong stability of the model. Patients with high riskscore had lower survival rate than those with low riskscore. After the development of a nomogram, calibration curve and decision curve evaluation also showed a strong prediction performance and reliability of the model. As for clinicopathological features, older patients and female patients had a relatively high riskscore. The riskscore was significantly positively correlated with cell cycle-related pathways and significantly negatively correlated with inflammatory pathways.

Conclusion

We screened five NETosis-associated genes that affected sepsis prognosis, and then established a riskscore model that can accurately evaluate the prognosis and survival for sepsis patients. Our research may be helpful for the diagnosis and clinical treatment of sepsis.

The Potential of Molecular Remission: Tissue Neutrophil Elastase Is Better Than Histological Activity for Predicting Long-Term Relapse in Patients With Ulcerative Colitis in Endoscopic Remission

BACKGROUND

Growing interest exists in deep remission, beyond clinical and endoscopic remission, to enhance long-term prognosis in patients with ulcerative colitis (UC). Our study aimed to evaluate the risk of relapse according to tissue expression levels of calprotectin and neutrophil elastase (NE) in patients with quiescent UC.

METHODS

Rectal biopsies were performed on 218 patients with UC in clinical and endoscopic remission. Histological activity was prospectively scored using the Robarts Histological Index. Tissue calprotectin and NE levels were evaluated using immunohistochemistry. Optimal tissue calprotectin and NE cutoffs for relapse were determined using log-rank analysis. Cox proportional hazard analyses evaluated relapse risk factors.

RESULTS

Tissue calprotectin and NE levels were significantly higher in patients with histological activity than in those in histological remission (P < .001). The optimal cutoffs of tissue calprotectin and NE for relapse were 10.61 and 22.08 per mm2, respectively. The 3-year clinical relapse risk was significantly lower in the low-tissue NE group than in the high-tissue NE group (P = .009); however, it did not differ between the low- and high-tissue calprotectin group (P = .094). In multivariate analyses, a low level of tissue NE expression was independently associated with a lower risk of 3-year clinical relapse (adjusted hazard ratio = 0.453, 95% confidence interval = 0.225-0.911, P = .026), unlike histological index and tissue calprotectin.

CONCLUSIONS

In patients with UC who have achieved clinical and endoscopic remission, tissue expression of NE is a better predictor of long-term relapse than histological activity.

Tumor microenvironment induced switch to mitochondrial metabolism promotes suppressive functions in immune cells

Understanding the intricacies of the metabolic phenotype in immune cells and its plasticity within the tumor microenvironment is pivotal in understanding the pathology and prognosis of cancer. Unfavorable conditions and cellular stress in the tumor microenvironment (TME) exert a profound impact on cellular functions in immune cells, thereby influencing both tumor progression and immune responses. Elevated AMP:ATP ratio, a consequence of limited glucose levels, activate AMP-activated protein kinase (AMPK) while concurrently repressing the activity of mechanistic target of rapamycin (mTOR) and hypoxia-inducible factor 1-alpha (HIF-1α). The intricate balance between AMPK, mTOR, and HIF-1α activities defines the metabolic phenotype of immune cells in the TME. These Changes in metabolic phenotype are strongly associated with immune cell functions and play a crucial role in creating a milieu conducive to tumor progression. Insufficiency of nutrient and oxygen supply leads to a metabolic shift in immune cells characterized by a decrease in glycolysis and an increase in oxidative phosphorylation (OXPHOS) and fatty acid oxidation (FAO) rates. In most cases, this shift in metabolism is accompanied by a compromise in the effector functions of these immune cells. This metabolic adaptation prompts immune cells to turn down their effector functions, entering a quiescent or immunosuppressive state that may support tumor growth. This article discusses how tumor microenvironment alters the metabolism in immune cells leading to their tolerance and tumor progression, with emphasis on mitochondrial metabolism (OXPHOS and FAO).

Advancing osteoarthritis therapy with GMOCS hydrogel-loaded BMSCs-exos

This study investigated the mechanism of the extracellular matrix-mimicking hydrogel-mediated TGFB1/Nrf2 signaling pathway in osteoarthritis using bone marrow mesenchymal stem cell-derived exosomes (BMSCs-Exos). A GMOCS-Exos hydrogel was synthesized and evaluated for its impact on chondrocyte viability and neutrophil extracellular traps (NETs) formation. In an OA rat model, GMOCS-Exos promoted cartilage regeneration and inhibited NETs formation. Transcriptome sequencing identified TGFB1 as a key gene, with GMOCS-Exos activating Nrf2 signaling through TGFB1. Depletion of TGFB1 hindered the cartilage-protective effect of GMOCS-Exos. This study sheds light on a promising therapeutic strategy for osteoarthritis through GMOCS-Exos-mediated TGFB1/Nrf2 pathway modulation.

Mitochondria: a breakthrough in combating rheumatoid arthritis

As a chronic autoimmune disease with complex aetiology, rheumatoid arthritis (RA) has been demonstrated to be associated with mitochondrial dysfunction since mitochondrial dysfunction can affect the survival, activation, and differentiation of immune and non-immune cells involved in the pathogenesis of RA. Nevertheless, the mechanism behind mitochondrial dysfunction in RA remains uncertain. Accordingly, this review addresses the possible role and mechanisms of mitochondrial dysfunction in RA and discusses the potential and challenges of mitochondria as a potential therapeutic strategy for RA, thereby providing a breakthrough point in the prevention and treatment of RA.

NADPH oxidase-dependent free radical generation and protein adduct formation in neutrophils

Neutrophils mediate the early innate immune response through extracellular traps comprising intracellular protein and DNA. These traps play a pivotal role in both immunity against invading pathogens and the development of immunopathological reactions through the production of reactive oxygen species (ROS). Proteins serve as the main target for ROS, resulting in the formation of protein adducts. Herein, we report that the superoxide anion radical (O2˙-) plays a vital role in neutrophil function through sequential events involving 5-lipoxygenase (5-LOX) and NADPH oxidase (NOX). More specifically, differences in NOX homologs expression were observed post-stimulation with PMA and LPS. Differentiation conditions and O2˙- generation were confirmed using flow cytometry. Immunoblotting analysis confirmed the time-dependent expression of NOX underlying its requirement and 5-LOX-mediated lipid peroxidation events in neutrophil function. Protein-malondialdehyde (MDA) adducts formed were detected using immunoblotting, and quercetin was evaluated for its ability to scavenge free radicals through electron paramagnetic resonance (EPR) spin-trapping spectroscopy and results were confirmed with blotting analysis. Free radical-mediated protein oxidation events influence neutrophil function and protein adducts formed serve as markers of neutrophil activation upon infection and inflammation. The study warrants further corroboration and the study of specific proteins involved in neutrophil activation and their role in inflammation.

Abnormal metabolism in melanocytes participates in the activation of dendritic cell in halo nevus

A comprehensive analysis of spatial transcriptomics was carried out to better understand the progress of halo nevus. We found that halo nevus was characterized by overactive immune responses, triggered by chemokines and dendritic cells (DCs), T cells, and macrophages. Consequently, we observed abnormal cell death, such as apoptosis and disulfidptosis in halo nevus, some were closely related to immunity. Interestingly, we identified aberrant metabolites such as uridine diphosphate glucose (UDP-G) within the halo nevus. UDP-G, accompanied by the infiltration of DCs and T cells, exhibited correlations with certain forms of cell death. Subsequent experiments confirmed that UDP-G was increased in vitiligo serum and could activate DCs. We also confirmed that oxidative response is an inducer of UDP-G. In summary, the immune response in halo nevus, including DC activation, was accompanied by abnormal cell death and metabolites. Especially, melanocyte-derived UDP-G may play a crucial role in DC activation.

Neutrophil extracellular traps in cancer

Neutrophil extracellular traps (NETs), which consist of chromatin DNA studded with granule proteins, are released by neutrophils in response to both infectious and sterile inflammation. Beyond the canonical role in defense against pathogens, the extrusion of NETs also contributes to the initiation, metastasis, and therapeutic response of malignant diseases. Recently, NETs have been implicated in the development and therapeutic responses of various types of tumors. Although extensive work regarding inflammation in tumors has been reported, a comprehensive summary of how these web-like extracellular structures initiate and propagate tumor progression under the specific microenvironment is lacking. In this review, we demonstrate the initiators and related signaling pathways that trigger NETs formation in cancers. Additionally, this review will outline the current molecular mechanisms and regulatory networks of NETs during dormant cancer cells awakening, circulating tumor cells (CTCs) extravasation, and metastatic recurrence of cancer. This is followed by a perspective on the current and potential clinical potential of NETs as therapeutic targets in the treatment of both local and metastatic disease, including the improvement of the efficacy of existing therapies.

Immunoprotection Strategies in β-Cell Replacement Therapy: A Closer Look at Porcine Islet Xenotransplantation

Type 1 diabetes mellitus (T1DM) is characterized by absolute insulin deficiency primarily due to autoimmune destruction of pancreatic β-cells. The prevailing treatment for T1DM involves daily subcutaneous insulin injections, but a substantial proportion of patients face challenges such as severe hypoglycemic episodes and poorly controlled hyperglycemia. For T1DM patients, a more effective therapeutic option involves the replacement of β-cells through allogeneic transplantation of either the entire pancreas or isolated pancreatic islets. Unfortunately, the scarcity of transplantable human organs has led to a growing list of patients waiting for an islet transplant. One potential alternative is xenotransplantation of porcine pancreatic islets. However, due to inter-species molecular incompatibilities, porcine tissues trigger a robust immune response in humans, leading to xenograft rejection. Several promising strategies aim to overcome this challenge and enhance the long-term survival and functionality of xenogeneic islet grafts. These strategies include the use of islets derived from genetically modified pigs, immunoisolation of islets by encapsulation in biocompatible materials, and the creation of an immunomodulatory microenvironment by co-transplanting islets with accessory cells or utilizing immunomodulatory biomaterials. This review concentrates on delineating the primary obstacles in islet xenotransplantation and elucidates the fundamental principles and recent breakthroughs aimed at addressing these challenges.

Elevated circulating levels of neutrophil extracellular traps after cardiopulmonary bypass surgery as risk factors of postoperative atrial fibrillation and mortality

Background

Cardiopulmonary bypass (CPB) can trigger a systemic inflammatory response during the perioperative period, which may lead to the consumption of the contact system and the production of neutrophil extracellular traps (NETs). This study attempted to determine whether the formation of NETs and contact activation are a vivid occurrence during CPB and whether they are related to post-operative atrial fibrillation (AF) and survival.

Methods

A prospective observational study was conducted in 97 patients who underwent aortic valve and/or aorta replacement surgery with CPB. Circulating markers of NETs [histone-DNA complex, cell-free double stranded DNA (dsDNA), neutrophil elastase] and the contact system [prekallikrein, high molecular weight kininogen (HMWK), activated factor XII (FXIIa)] were measured at four-time points: before surgery (T0), immediately after surgery (T1), 1 day after surgery (T2), and 3 days after surgery (T3).

Results

Elevated levels of circulating NETs markers were observed across post-CPB time. Significantly elevated levels of histone-DNA complex and cell-free dsDNA measured T3 were detected in patients with post-operative AF compared to those without. In logistic regression analysis, levels of histone-DNA complex and cell-free dsDNA measured at T3 were significant markers of risk for occurrence of AF. The levels of cell-free dsDNA measured T2 were significantly higher in non-survivors than in survivors. The level of cell-free dsDNA showed significant prognostic value.

Conclusions

NETs markers may be useful for the assessment of risk for post-operative AF and mortality. Conduct of additional research regarding the role of NETs as clinical markers and as a therapeutic target in CPB is anticipated.

Immune dysregulation is an important factor in the underlying complications in Influenza infection. ApoH, IL-8 and IL-15 as markers of prognosis

Introduction

Influenza virus infection can cause a range of clinical symptoms, including respiratory failure (RF) and even death. The mechanisms responsible for the most severe forms of the disease are not yet well understood. The objective is to assess the initial immune response upon admission and its potential impact on infection progression.

Methods

We conducted a prospective observational study of patients with influenza virus infection who required admission to a tertiary hospital in the 2017/18 and 2018/19 flu seasons. Immune markers, surrogate markers of neutrophil activation, and blood levels of DNase I and Apolipoprotein-H (ApoH) were determined in the first serum sample available during hospital care. Patients were followed until hospital discharge or death. Initially, 792 patients were included. From this group, 107 patients with poor evolution were selected, and a random control group was matched by day of admission.

Results

Patients with poor outcomes had significantly reduced ApoH levels, a soluble protein that regulate both complement and coagulation pathways. In multivariate analysis, low plasma levels of ApoH (OR:5.43; 2.21-13.4), high levels of C- reactive protein (OR:2.73: 1.28-5.4), hyperferritinemia (OR:2.83; 1.28-5.4) and smoking (OR:3.41; 1.04-11.16), were significantly associated with a worse prognosis. RF was independently associated with low levels of ApoH (OR: 5.12; 2.02-1.94), while high levels of IL15 behaved as a protective factor (OR:0.30; 0.12-0.71).

Discussion

Therefore, in hospitalized influenza patients, a dysregulated early immune response is associated with a worse outcome. Adequate plasma levels of ApoH are protective against severe influenza and RF and High levels of IL15 protect against RF.