Neutrophil virucidal activity against SARS-CoV-2 is mediated by NETs.

BACKGROUND: The inflammation in the lungs and other vital organs in COVID-19 are characterized by the presence of neutrophils and high concentration of neutrophil extracellular traps (NETs), which also seems to mediate host tissue damage. However, it is not known whether NETs could have virucidal activity against SARS-CoV-2. METHODS: We investigated whether NETs could prevent SARS-CoV-2 replication in neutrophils and epithelial cells, and what the consequence of NETs degradation in K18-humanized ACE2 transgenic mice infected with SARS-CoV-2. RESULTS: Here, by immunofluorescence microscopy we observed that viral particles co-localize with NETs in neutrophils isolated from COVID-19 patients or from healthy individuals and infected in vitro. The inhibition of NETs production increased virus replication in neutrophils. In parallel, we observed that NETs inhibited virus abilities to infect and replicate in epithelial cells after 24 h of infection. Degradation of NETs with DNase I prevented their virucidal effect in vitro. Using K18-humanized ACE2 transgenic mice we observed a higher viral load in animals treated with DNase I. On the other hand, the virucidal effect of NETs was not dependent on neutrophil elastase or myeloperoxidase activity. CONCLUSION: Our results provide evidence of the role of NETosis as a mechanism of SARS-CoV-2 viral capture and inhibition.

Plasmin and plasminogen prevent sepsis severity by reducing neutrophil extracellular traps and systemic inflammation.

Sepsis is a lethal syndrome characterized by systemic inflammation and abnormal coagulation. Despite therapeutic advances, sepsis mortality remains substantially high. Herein, we investigated the role of the plasminogen/plasmin (Plg/Pla) system during sepsis. Plasma levels of Plg were significantly lower in mice subjected to severe compared with nonsevere sepsis, whereas systemic levels of IL-6, a marker of sepsis severity, were higher in severe sepsis. Plg levels correlated negatively with IL-6 in both septic mice and patients, whereas plasminogen activator inhibitor-1 levels correlated positively with IL-6. Plg deficiency render mice susceptible to nonsevere sepsis induced by cecal ligation and puncture (CLP), resulting in greater numbers of neutrophils and M1 macrophages, liver fibrin(ogen) deposition, lower efferocytosis, and increased IL-6 and neutrophil extracellular trap (NET) release associated with organ damage. Conversely, inflammatory features, fibrin(ogen), and organ damage were substantially reduced, and efferocytosis was increased by exogenous Pla given during CLP- and LPS-induced endotoxemia. Plg or Pla protected mice from sepsis-induced lethality and enhanced the protective effect of antibiotics. Mechanistically, Plg/Pla-afforded protection was associated with regulation of NET release, requiring Pla-protease activity and lysine binding sites. Plg/Pla are important host-protective players during sepsis, controlling local and systemic inflammation and collateral organ damage.

Role of cholecystokinin and oxytocin in slower gastric emptying induced by physical exercise in rats.

Vigorous exercise can induce gastrointestinal disorders such decreased gastric emptying pace, while low-intensity exercise can accelerate gastric motility. However, the mechanisms of these effects are still unknown. We investigated the possible neurohumoral mechanisms involved in these phenomena. In sedentary (Sed) and acute exercise (Ex) groups of rats, we assessed the activation of c-Fos in NTS and DVMN and the plasma levels of CCK and OXT. Separate groups received pretreatment with the oxytocin antagonist atosiban (AT), the cholecystokinin antagonist devazepide (DVZ), or the TRPV1 receptor inhibitor capsazepine (CAPZ). AT, DVZ and CAPZ treatments prevented (p<0.05) slower gastric emptying induced by acute exercise. The gene expression of OXT decreased (P<0.05) while that of CCK increased (P<0.05) in the gastric fundus and pylorus of the Ex group, while the plasma levels of OXT rose (p<0.05) and of CCK declined (p<5.05). We also observed activation (p<0.05) of c-Fos-sensitive neurons in the NTS and DVMN of exercised rats. In conclusion, acute exercise slowed gastric emptying by the vagal afferent pathway, which involved activation of CCK1/OXT/TRPV1 sensitivity.

Paradoxical interaction between cancer and long-term postsepsis disorder: impairment of de novo carcinogenesis versus favoring the growth of established tumors.

BACKGROUND: Previous data have reported that the growth of established tumors may be facilitated by postsepsis disorder through changes in the microenvironment and immune dysfunction. However, the influence of postsepsis disorder in initial carcinogenesis remains elusive. METHODS: In the present work, the effect of postsepsis on inflammation-induced early carcinogenesis was evaluated in an experimental model of colitis-associated colorectal cancer (CAC). We also analyzed the frequency and role of intestinal T regulatory cells (Treg) in CAC carcinogenesis. RESULTS: The colitis grade and the tumor development rate were evaluated postmortem or in vivo through serial colonoscopies. Sepsis-surviving mice (SSM) presented with a lower colonic DNA damage, polyp incidence, reduced tumor load, and milder colitis than their sham-operated counterparts. Ablating Treg led to restoration of the ability to develop colitis and tumor polyps in the SSM, in a similar fashion to that in the sham-operated mice. On the other hand, the growth of subcutaneously inoculated MC38luc colorectal cancer cells or previously established chemical CAC tumors was increased in SSM. CONCLUSION: Our results provide evidence that postsepsis disorder has a dual effect in cancer development, inhibiting inflammation-induced early carcinogenesis in a Treg-dependent manner, while increasing the growth of previously established tumors.

Neutrophils contribute to the pathogenesis of hemorrhagic cystitis induced by ifosfamide.

Ifosfamide (IFO) is an antineoplastic drug that is commonly used to treat gynecological and breast cancers. Hemorrhagic cystitis (HC) is a common side effect associated with IFO injection, which courses with neutrophil accumulation and affects 6-50% of patients depending on dose intensity. Here, we investigated the role of neutrophils in this inflammatory process. Female Swiss mice (n = 8/group) were injected with saline, IFO (400 mg/kg, i.p.), fucoidan (a P- and L-selectins inhibitor, 100 mg/kg, i.v.) or IFO + fucoidan (1-100 mg/kg) alone or combined with mesna (80 mg/kg i.p.). Another group of mice received anti-Ly6G antibody (500 µg/mouse, once daily for 2 days) for neutrophil depletion before IFO injection. In another experimental setting, animals received granulocyte colony-stimulating factor (G-CSF, 400 µg/kg), IFO (200 mg/kg), G-CSF (25-400 µg/kg, for 5 days) + IFO (200 mg/kg, i.p.) or fucoidan + G-CSF + IFO. Bladder injury was evaluated 12 h after IFO injection. IFO 400 mg/kg significantly increased visceral hyperalgesia, bladder edema, hemorrhage, vascular permeability, MPO, IL-1ß and IL-6 tissue levels, and COX-2 immunostaining and expression versus the saline group (P < 0.05). Conversely, fucoidan (100 mg/kg) significantly attenuated these parameters compared to IFO-injected mice (P < 0.05). Additionally, fucoidan potentiated mesna protective effect when compared with IFO + mesna group (P < 0.05). Accordingly, neutrophil depletion with anti-Ly6G reduced inflammatory parameters and bladder injury compared to IFO (P < 0.05). In contrast, G-CSF enhanced IFO (200 mg/kg)-induced HC, which was significantly attenuated by treatment with fucoidan (P < 0.05). Therefore, neutrophils contribute to the pathogenesis of HC.