Multiple organ dysfunction is the most severe outcome of sepsis progression and is highly correlated with a worse prognosis. Excessive neutrophil extracellular traps (NETs) are critical players in ...the development of organ failure during sepsis. Therefore, interventions targeting NET release would likely effectively prevent NET-based organ injury associated with this disease. Herein, we demonstrate that the pore-forming protein gasdermin D (GSDMD) is active in neutrophils from septic humans and mice and plays a crucial role in NET release. Inhibition of GSDMD with disulfiram or genic deletion abrogated NET formation, reducing multiple organ dysfunction and sepsis lethality. Mechanistically, we demonstrate that during sepsis, activation of the caspase-11/GSDMD pathway controls NET release by neutrophils during sepsis. In summary, our findings uncover a novel therapeutic use for disulfiram and suggest that GSDMD is a therapeutic target to improve sepsis treatment.
Vestitol is an isoflavonoid isolated from Brazilian red propolis with potential anti-inflammatory activity. This study investigated the mechanism of action of vestitol on the modulation of neutrophil ...migration in the inflammatory process. Pre-treatment with vestitol at 1, 3, or 10 mg/kg reduced LPS- or mBSA-induced neutrophil migration and the release of CXCL1/KC and CXCL2/MIP-2 in vivo. Likewise, pre-treatment with vestitol at 1, 3, or 10 μM reduced the levels of CXCL1/KC and CXCL2/MIP-2 in macrophage supernatants in vitro. Moreover, the administration of vestitol (10 mg/kg) reduced leukocyte rolling and adherence in the mesenteric microcirculation of mice. The pre-treatment with vestitol (10 mg/kg) in iNOS–/– mice did not block its activity concerning neutrophil migration. With regard to the activity of vestitol on neutrophils isolated from the bone marrow of mice, there was a reduction on the chemotaxis of CXCL2/MIP-2 or LTB4-induced neutrophils and on calcium influx after pre-treatment with the compound at 3 or 10 μM. There was no change in CXCR2 expression by neutrophils treated with vestitol at 10 μM. These findings demonstrate that vestitol is a promising novel anti-inflammatory agent.
Neutrophil extracellular traps (NETs) are innate defense mechanisms that are also implicated in the pathogenesis of organ dysfunction. However, the role of NETs in pediatric sepsis is unknown.
Infant ...(2 weeks old) and adult (6 weeks old) mice were submitted to sepsis by intraperitoneal (i.p.) injection of bacteria suspension or lipopolysaccharide (LPS). Neutrophil infiltration, bacteremia, organ injury, and concentrations of cytokine, NETs, and DNase in the plasma were measured. Production of reactive oxygen and nitrogen species and release of NETs by neutrophils were also evaluated. To investigate the functional role of NETs, mice undergoing sepsis were treated with antibiotic plus rhDNase and the survival, organ injury, and levels of inflammatory markers and NETs were determined. Blood samples from pediatric and adult sepsis patients were collected and the concentrations of NETs measured.
Infant C57BL/6 mice subjected to sepsis or LPS-induced endotoxemia produced significantly higher levels of NETs than the adult mice. Moreover, compared to that of the adult mice, this outcome was accompanied by increased organ injury and production of inflammatory cytokines. The increased NETs were associated with elevated expression of Padi4 and histone H3 citrullination in the neutrophils. Furthermore, treatment of infant septic mice with rhDNase or a PAD-4 inhibitor markedly attenuated sepsis. Importantly, pediatric septic patients had high levels of NETs, and the severity of pediatric sepsis was positively correlated with the level of NETs.
This study reveals a hitherto unrecognized mechanism of pediatric sepsis susceptibility and suggests that NETs represents a potential target to improve clinical outcomes of sepsis.
Patients who survive sepsis can develop long-term immune dysfunction, with expansion of the regulatory T (Treg) cell population. However, how Treg cells proliferate in these patients is not clear. ...Here we show that IL-33 has a major function in the induction of this immunosuppression. Mice deficient in ST2 (IL-33R) develop attenuated immunosuppression in cases that survive sepsis, whereas treatment of naive wild-type mice with IL-33 induces immunosuppression. IL-33, released during tissue injury in sepsis, activates type 2 innate lymphoid cells, which promote polarization of M2 macrophages, thereby enhancing expansion of the Treg cell population via IL-10. Moreover, sepsis-surviving patients have more Treg cells, IL-33 and IL-10 in their peripheral blood. Our study suggests that targeting IL-33 may be an effective treatment for sepsis-induced immunosuppression.
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Sepsis is one of the main causes of mortality in hospitalized patients. Despite the recent technical advances and the development of novel generation of antibiotics, severe sepsis ...remains a major clinical and scientific challenge in modern medicine. Unsuccessful efforts have been dedicated to the search of therapeutic options to treat the deleterious inflammatory components of sepsis. Recent findings on neuronal networks controlling immunity raised expectations for novel therapeutic strategies to promote the regulation of sterile inflammation, such as autoimmune diseases. Interesting studies have dissected the anatomical constituents of the so-called “cholinergic anti-inflammatory pathway”, suggesting that electrical vagus nerve stimulation and pharmacological activation of beta-2 adrenergic and alpha-7 nicotinic receptors could be alternative strategies for improving inflammatory conditions. However, the literature on infectious diseases, such as sepsis, is still controversial and, therefore, the real therapeutic potential of this neuroimmune pathway is not well defined. In this review, we will discuss the beneficial and detrimental effects of neural manipulation in sepsis, which depend on the multiple variables of the immune system and the nature of the infection. These observations suggest future critical studies to validate the clinical implications of vagal parasympathetic signaling in sepsis treatment.
The Chikungunya virus (CHIKV) is a re-emerging arbovirus, in which its infection causes a febrile illness also commonly associated with severe joint pain and myalgia. Although the immune response to ...CHIKV has been studied, a better understanding of the virus-host interaction mechanisms may lead to more effective therapeutic interventions. In this context, neutrophil extracellular traps (NETs) have been described as a key mediator involved in the control of many pathogens, including several bacteria and viruses, but no reports of this important protective mechanism were documented during CHIKV infection. Here we demonstrate that the experimental infection of mouse-isolated neutrophils with CHIKV resulted in NETosis (NETs release) through a mechanism dependent on TLR7 activation and reactive oxygen species generation.
, mouse-isolated neutrophils stimulated with phorbol 12-myristate 13-acetate release NETs that once incubated with CHIKV, resulting in further virus capture and neutralization.
, NETs inhibition by the treatment of the mice with DNase resulted in the enhanced susceptibility of IFNAR
mice to CHIKV experimental acute infection. Lastly, by accessing the levels of MPO-DNA complex on the acutely CHIKV-infected patients, we found a correlation between the levels of NETs and the viral load in the blood, suggesting that NETs are also released in natural human infection cases. Altogether our findings characterize NETosis as a contributing natural process to control CHIKV acute infection, presenting an antiviral effect that helps to control systemic virus levels.
Rocio virus (ROCV) was the causative agent of an unprecedented outbreak of encephalitis during the 1970s in the Vale do Ribeira, Sao Paulo State, in the Southeast region of Brazil. Surprisingly, no ...further cases of ROCV infection were identified after this outbreak; however, serological surveys have suggested the circulation of ROCV among humans and animals in different regions of Brazil. Cross-protective immunity among flaviviruses is well documented; consequently, immunity induced by infections with other flaviviruses endemic to Brazil could potentially be responsible for the lack of ROCV infections. Herein, we evaluated the cross-protection mediated by other flaviviruses against ROCV infection using an experimental C57BL/6 mouse model. Cross-protection against ROCV infection was observed when animals had prior exposure to Ilheus virus or Saint Louis encephalitis virus, suggesting that cross-reactive anti-flavivirus antibodies may limit ROCV disease outbreaks.
Sepsis-surviving adult individuals commonly develop immunosuppression and increased susceptibility to secondary infections, an outcome mediated by the axis IL-33/ILC2s/M2 macrophages/Tregs. ...Nonetheless, the long-term immune consequences of paediatric sepsis are indeterminate. We sought to investigate the role of age in the genesis of immunosuppression following sepsis.
Here, we compared the frequency of Tregs, the activation of the IL-33/ILC2s axis in M2 macrophages and the DNA methylation of epithelial lung cells from post-septic infant and adult mice. Likewise, sepsis-surviving mice were inoculated intranasally with Pseudomonas aeruginosa or by subcutaneous inoculation of the B16 melanoma cell line. Finally, blood samples from sepsis-surviving patients were collected and the concentration of IL-33 and Tregs frequency were assessed.
In contrast to 6-week-old mice, 2-week-old mice were resistant to secondary infection and did not show impairment in tumour controls upon melanoma challenge. Mechanistically, increased IL-33 levels, Tregs expansion, and activation of ILC2s and M2-macrophages were observed in 6-week-old but not 2-week-old post-septic mice. Moreover, impaired IL-33 production in 2-week-old post-septic mice was associated with increased DNA methylation in lung epithelial cells. Notably, IL-33 treatment boosted the expansion of Tregs and induced immunosuppression in 2-week-old mice. Clinically, adults but not paediatric post-septic patients exhibited higher counts of Tregs and seral IL-33 levels.
These findings demonstrate a crucial and age-dependent role for IL-33 in post-sepsis immunosuppression. Thus, a better understanding of this process may lead to differential treatments for adult and paediatric sepsis.
Chemical compounds belonging to the class of coumarins have promising anti-inflammatory potential. Cinnamoyloxy-mammeisin (CNM) is a 4-phenylcoumarin that can be isolated from Brazilian geopropolis. ...To our knowledge, its anti-inflammatory activity has never been studied. Therefore, the present study investigated the anti-inflammatory activity of CNM and elucidated its mechanism of action on isolated macrophages. Pretreatment with CNM reduced neutrophil migration into the peritoneal and joint cavity of mice. Likewise, CNM reduced the in vitro and in vivo release of TNF-α and CXCL2/MIP-2. Regarding the possible molecular mechanism of action, CNM reduced the phosphorylation of proteins ERK 1/2, JNK, p38 MAPK, and AP-1 (subunit c-jun) in PG-stimulated macrophages. Pretreatment with CNM also reduced NF-κB activation in RAW 264.7 macrophages stably expressing the NF-κB-luciferase reporter gene. On the other hand, it did not alter IκBα degradation or nuclear translocation of p65. Thus, the results of this study demonstrate promising anti-inflammatory activity of CNM and provide an explanation of its mechanism of action in macrophages via inhibition of MAPK signaling, AP-1, and NF-κB.
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