Neutrophils are classically characterized as merely reactive innate effector cells. However, the microbiome is known to shape the education and maturation process of neutrophils, improving their ...function and immune-plasticity. Recent reports demonstrate that murine neutrophils possess the ability to exert adaptive responses after exposure to bacterial components such as LPS (Gram-negative bacteria) or LTA (Gram-positive bacteria). We now ask whether small extracellular vesicles (EVs) from the gut may directly mediate adaptive responses in neutrophils in vitro. Murine bone marrow-derived neutrophils were primed in vitro by small EVs of high purity collected from colon stool samples, followed by a second hit with LPS. We found that low-dose priming with gut microbiota-derived small EVs enhanced pro-inflammatory sensitivity as indicated by elevated levels of TNF-α, IL-6, ROS and MCP-1 and increased migratory and phagocytic activity. In contrast, high-dose priming resulted in a tolerant phenotype, marked by increased IL-10 and decreased transmigration and phagocytosis. Alterations in TLR2/MyD88 as well as TLR4/MyD88 signaling were correlated with the induction of adaptive cues in neutrophils in vitro. Taken together, our study shows that small EVs from stools can drive adaptive responses in neutrophils in vitro and may represent a missing link in the gut-immune axis.
For almost nearly a century, memory functions have been attributed only to acquired immune cells. Lately, this paradigm has been challenged by an increasing number of studies revealing that innate ...immune cells are capable of exhibiting memory-like features resulting in increased responsiveness to subsequent challenges, a process known as trained immunity (known also as innate memory). In contrast, the refractory state of endotoxin tolerance has been defined as an immunosuppressive state of myeloid cells portrayed by a significant reduction in the inflammatory capacity. Both training as well tolerance as adaptive features are reported to be accompanied by epigenetic and metabolic alterations occurring in cells. While training conveys proper protection against secondary infections, the induction of endotoxin tolerance promotes repairing mechanisms in the cells. Consequently, the inappropriate induction of these adaptive cues may trigger maladaptive effects, promoting an increased susceptibility to secondary infections-tolerance, or contribute to the progression of the inflammatory disorder-trained immunity. This review aims at the discussion of these opposing manners of innate immune and non-immune cells, describing the molecular, metabolic and epigenetic mechanisms involved and interpreting the clinical implications in various inflammatory pathologies.
We recently reported expression of hematopoietic growth factor GM-CSF and its receptor (GM-CSFR) in CNS neurons. Here we evaluated this system in learning and memory formation using GM-CSF deficient ...mice. In complementation, GM-CSF signalling was manipulated specifically in adult murine hippocampus by adeno-associated virus (AAV)-mediated GM-CSFR alpha overexpression or knock-down. GM-CSF ablation caused various hippocampus and amygdala-dependent deficits in spatial and fear memory while rendering intact basic parameters like motor function, inherent anxiety, and pain threshold levels. Corroborating these data, spatial memory of AAV-injected mice was positively correlated with GM-CSFRα expression levels. Hippocampal neurons of knock-out mice showed markedly pruned dendritic trees, reduced spine densities, and lower percentages of mature spines. Despite such morphological alterations, long-term potentiation (LTP) was unimpaired in the knock-out hippocampus. Collectively, these results suggest that GM-CSF signalling plays a major role in structural plasticity relevant to learning and memory.
A growing body of evidence suggests that innate immune cells can respond in a memory-like (adaptive) fashion, which is referred to as trained immunity. Only few in vivo studies have shown training ...effects in neutrophils; however, no in vitro setup has been established to study the induction of trained immunity or tolerance in neutrophils by microbial agents. In light of their short lifespan (up to 48 h), we suggest to use the term trained sensitivity for neutrophils in an in vitro setting. Here, we firstly describe a feasible two-hit model, using different doses of lipopolysaccharide (LPS) in bone marrow neutrophils. We found that low doses (10 pg/mL) induce pro-inflammatory activation (trained sensitivity), whereas priming with high doses (100 ng/mL) leads to suppression of pro-inflammatory mediators such as TNF-α or IL-6 (tolerance) (p < 0.05). On a functional level, trained neutrophils displayed increased phagocytic activity and LFA-1 expression as well as migrational capacity and CD11a expression, whereas tolerant neutrophils show contrasting effects in vitro. Mechanistically, TLR4/MyD88/PI3Ks regulate the activation of p65, which controls memory-like responses in mouse bone marrow neutrophils (p < 0.05). Our results open a new window for further in vitro studies on memory-like inflammatory responses of short-lived innate immune cells such as neutrophils.
A growing body of evidence defines inflammation as a hallmark feature of disease pathogenesis of Duchenne muscular dystrophy. To tailor potential immune modulatory interventions, a better ...understanding of immune dysregulation in Duchenne muscular dystrophy is needed. We now asked whether dystrophin deficiency affects the cascade of leukocyte recruitment.
We performed intravital microscopy on the cremaster muscle of wild-type and dystrophin-deficient mdx mice. Recruitment was triggered by preparation alone (traumatic inflammation) or in combination with scrotal TNFα injections. Neutrophilic infiltration of the cremaster muscle was assessed on tissue sections. Integrin expression on circulating neutrophils and serum levels of pro-inflammatory cytokines were measured by flow cytometry.
Mdx mice show increased rolling and adhesion at baseline (traumatic inflammation) and a more profound response upon TNFα injection compared with wild-type animals. In both models, neutrophilic infiltration of the cremaster muscle is increased. Upregulation of the integrins LFA-1 and Mac-1 on circulating leukocytes and pro-inflammatory cytokines IL-6 and CCL2 in the serum points toward systemically altered immune regulation in mdx mice.
We are the first to show exaggerated activation of the leukocyte recruitment cascade in a dystrophin-deficient organism in vivo.
•Immune priming and trained immunity have been shown for many innate immune cells.•Neutrophils are mainly considered as mere effector cells in memory-like inflammation.•We show that LTA-priming may ...induce both pro- or anti-inflammatory properties.•The dose of LTA regulates the two opposing priming states of neutrophils.•Neutrophils can be primed and may contribute to innate immune-memory.
Neutrophils primarily act as first responders in acute infection and directly maintain inflammatory responses. However, a growing body of evidence suggests that neutrophils also bear the potential to mediate chronic inflammation by exhibiting memory-like features. We now asked whether bone marrow-derived murine neutrophils can be primed by lipoteichoic acid (LTA) from gram-positive S. aureus. We found that low-dose (1 ng/mL) LTA-priming promoted increased production of pro-inflammatory mediators (TNF-α, IL-6, ROS), whereas high-dose (10 µg/mL) priming resulted in opposing reactions marked by increased IL-10 and suppressed pro-inflammatory mediators upon a second stimulus. A similar pattern of pro-inflammatory activation (trained sensitivity) and anti-inflammatory properties (tolerance) was recapitulated in cellular functional in vitro assays (transmigration and phagocytosis). Priming by LTA correlated with TLR2/MyD88-mediated regulation of NFκB-p65 through intermediate PI3Ks/MAPK. Collectively, our data suggest a previously unknown capacity of neutrophils to be differentially primed by varying doses of LTA, endorsing memory-like features in neutrophils.
ABSTRACT
Third-generation cephalosporin-resistant Enterobacterales is a major threat for newborns in neonatal intensive care units (NICUs). The route of acquisition in a non-outbreak setting should ...be investigated to implement adequate infection prevention measures. To identify risk factors for colonization with and to investigate the transmission pattern of third-generation cephalosporin-resistant Enterobacterales in a NICU setting. This monocentric observational cohort study in a tertiary NICU in Heidelberg, Germany, enrolled all hospitalized neonates screened for cephalosporin-resistant Enterobacterales. Data were collected from 1 January 2018 to 31 December 2021. Weekly screening by rectal swabs for colonization with third-generation cephalosporin-resistant Enterobacterales was performed for all newborns until discharge. Whole-genome sequencing was performed for molecular characterization and transmission analysis. In total, 1,287 newborns were enrolled. The median length of stay was 20 (range 1–250) days. Eighy-eight infants (6.8%) were colonized with third-generation cephalosporin-resistant Enterobacterales. Low birth weight <1500 g (adjusted odds ratio, 5.1; 95% CI 2.2–11.5;
P
< 0.001) and longer hospitalization per 30 days (adjusted odds ratio, 1.7; 95% CI 1.5–2.0;
P
< 0.001) were associated with colonization or infection with drug-resistant Enterobacterales in a multivariate analysis.
Enterobacter cloacae
complex was the most prevalent third-generation cephalosporin-resistant Enterobacterales detected, 64.8% (59 of 91). Whole-genome sequencing, performed for the available 85 of 91 isolates, indicated 12 transmission clusters involving 37 patients. This cohort study suggests that transmissions of third-generation cephalosporin-resistant Enterobacterales in newborns occur frequently in a non-outbreak NICU setting, highlighting the importance of surveillance and preventive measures in this vulnerable patient group.
IMPORTANCE
Preterm newborns are prone to infections. Therefore, infection prevention should be prioritized in this vulnerable patient group. However, outbreaks involving drug-resistant bacteria, such as third-generation resistant Enterobacterales, are often reported. Our study aims to investigate transmission and risk factors for acquiring third-generation cephalosporin-resistant Enterobacterales in a non-outbreak NICU setting. Our data indicated that premature birth and low birth weight are significant risk factors for colonization/infection with third-generation cephalosporin-resistant Enterobacterales. Furthermore, we could identify putative transmission clusters by whole-genome sequencing, highlighting the importance of preemptive measures to prevent infections in this patient collective.
Preterm newborns are prone to infections. Therefore, infection prevention should be prioritized in this vulnerable patient group. However, outbreaks involving drug-resistant bacteria, such as third-generation resistant Enterobacterales, are often reported. Our study aims to investigate transmission and risk factors for acquiring third-generation cephalosporin-resistant Enterobacterales in a non-outbreak NICU setting. Our data indicated that premature birth and low birth weight are significant risk factors for colonization/infection with third-generation cephalosporin-resistant Enterobacterales. Furthermore, we could identify putative transmission clusters by whole-genome sequencing, highlighting the importance of preemptive measures to prevent infections in this patient collective.
Aims
Cardiac resynchronization therapy (CRT) is sometimes complicated by elevated pacing thresholds and phrenic nerve stimulation (PNS), both of which may require that the coronary sinus lead be ...repositioned. The purpose of this study was to evaluate the performance of a novel quadripolar electrode lead and cardiac resynchronization therapy-defibrillator (CRT-D) device that enables electrical repositioning, potentially obviating a lead reposition procedure.
Methods and results
Patients indicated for CRT were enrolled and received a quadripolar electrode lead and CRT-D device (Quartet®model 1458Q and Promote Q®; St Jude Medical, Sylmar, CA, USA). Electrical data, and the presence of PNS during pacing from each left ventricular (LV) configuration, were documented at pre-hospital discharge and at 1 month. Seventy-five patients were enrolled and 71 were successfully implanted with a Quartet®lead. Electrical measurements were stable over the follow-up period. Ninety-seven per cent (64 of 66) of patients had one or more programmable configurations with a threshold <2.5 V and no PNS vs. 86% (57 of 66) if only conventional bipolar configurations were considered. Physicians were able to use the increased programming options to manage threshold changes and PNS.
Conclusion
The new quadripolar electrode LV lead provides more programming options to address common problems faced when managing CRT patients. Electrical measurements from new vectors are comparable with conventional configurations. Furthermore, 11% of patients in the study suffered PNS on all conventional bipolar vectors.
Abstract Background A novel quadripolar left ventricular (LV) pacing lead has the ability to deliver multisite LV pacing (MSLV). We set out to characterize the safety and changes in acute mechanical ...dyssynchrony with MSLV in cardiac resynchronization therapy (CRT) patients. Methods and Results Prospective multicenter study in 52 patients receiving CRT. An acute pacing protocol comprising 8 MSLV configurations covering a range of delays was compared with conventional CRT (baseline). Transthoracic tissue Doppler imaging (TDI) was used to measure the standard deviation of time to peak contraction of 12 LV segments (Ts-SD) and delayed longitudinal contraction. No ventricular arrhythmia occurred in any of the 52 patients. Complete TDI datasets were collected in 41 patients. Compared with baseline: 1) The mean Ts-SD was significantly lower for the optimal MSLV configuration (35.3 ± 36.4 vs 50.2 ± 29.1 ms; P < .001); 2) at least 1 MSLV configuration exhibited a significant dyssynchrony improvement in 63% of patients; and 3) the mean number of LV segments with delayed longitudinal contractions was significantly reduced with the optimal MSLV configuration (0.37 ± 7.99 vs 2.20 ± 0.19; P < .001). Conclusions Acute MSLV was acutely safe, and a proportion of MSLV vectors resulted in a significant reduction in echocardiographic dyssynchrony compared with conventional CRT.
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