Inhaled NO at a crossroads in cardiac surgery: current need to improve mechanistic understanding, clinical trial design and scientific evidence.

Inhaled nitric oxide (NO) has been used in pediatric and adult perioperative cardiac intensive care for over three decades. NO is a cellular signaling molecule that induces smooth muscle relaxation in the mammalian vasculature. Inhaled NO has the unique ability to exert its vasodilatory effects in the pulmonary vasculature without any hypotensive side-effects in the systemic circulation. In patients undergoing cardiac surgery, NO has been reported in numerous studies to exert beneficial effects on acutely lowering pulmonary artery pressure and reversing right ventricular dysfunction and/or failure. Yet, various investigations failed to demonstrate significant differences in long-term clinical outcomes. The authors, serving as an advisory board of international experts in the field of inhaled NO within pediatric and adult cardiac surgery, will discuss how the existing scientific evidence can be further improved. We will summarize the basic mechanisms underlying the clinical applications of inhaled NO and how this translates into the mandate for inhaled NO in cardiac surgery. We will move on to the popular use of inhaled NO and will talk about the evidence base of the use of this selective pulmonary vasodilator. This review will elucidate what kind of clinical and biological barriers and gaps in knowledge need to be solved and how this has impacted in the development of clinical trials. The authors will elaborate on how the optimization of inhaled NO therapy, the development of biomarkers to identify the target population and the definition of response can improve the design of future large clinical trials. We will explain why it is mandatory to gain an international consensus for the state of the art of NO therapy far beyond this expert advisory board by including the different major players in the field, such as the different medical societies and the pharma industry to improve our understanding of the real-life effects of inhaled NO in large scale observational studies. The design for future innovative randomized controlled trials on inhaled NO therapy in cardiac surgery, adequately powered and based on enhanced biological phenotyping, will be crucial to eventually provide scientific evidence of its clinical efficacy beyond its beneficial hemodynamic properties.

Analysis of Patients with Severe ARDS on VV ECMO Treated with Inhaled NO: A Retrospective Observational Study.

(1) Background: This retrospective study focused on severe acute respiratory distress syndrome (ARDS) patients treated with veno-venous (VV) extracorporeal membrane oxygenation (ECMO) and who inhaled nitric oxide (NO) for pulmonary arterial hypertension (PAH) and/or right ventricular failure (RV failure). (2) Methods: Out of 662 ECMO-supported patients, 366 received VV ECMO, including 48 who inhaled NO. We examined the NO's indications, dosing, duration, and the ability to lower PAH. We compared patients with and without inhaled NO in terms of mechanical ventilation duration, ECMO weaning, organ dysfunction, in-hospital mortality, and survival. (3) Results: Patients received 14.5 ± 5.5 ppm NO for 3 days with only one-third experiencing decreased pulmonary arterial pressure. They spent more time on VV ECMO, had a higher ECMO weaning failure frequency, and elevated severity scores (SAPS II and TIPS). A Kaplan-Meier analysis revealed reduced survival in the NO group. Multiple variable logistic regression indicated a twofold increased risk of death for ARDS patients on VV ECMO with NO. We observed no increase in continuous renal replacement therapy. (4) Conclusions: This study suggests that persistent PAH and/or RV failure is associated with poorer outcomes in severe ARDS patients on VV-ECMO, with an inhaled NO responder rate of only 30%, and it does not impact acute kidney failure rates.

COVID-19 Is an Independent Risk Factor for Detrimental Invasive Fungal Disease in Patients on Veno-Venous Extracorporeal Membrane Oxygenation: A Retrospective Study.

Invasive fungal disease (IFD) is associated with the mortality of patients on extracorporeal membrane oxygenation (ECMO). Several risk factors for IFD have been identified in patients with or without ECMO. Here, we assessed the relevance of coronavirus disease (COVID-19) for the occurrence of IFD in patients on veno-venous (V-V) ECMO for respiratory failure. In a retrospective analysis of all ECMO cases between January 2013 and December 2022 (2020-2022 for COVID-19 patients), active COVID-19 and the type, timing and duration of IFD were investigated. Demographics, hospital, ICU length of stay (LoS), duration of ECMO, days on invasive mechanical ventilation, prognostic scores (Respiratory ECMO Survival Prediction (RESP) score, Charlson Comorbidity Index (CCI), Therapeutic Intervention Scoring System (TISS)-10, Sequential Organ Failure Assessment (SOFA) score and Simplified Acute Physiology Score (SAPS)-II) and length of survival were assessed. The association of COVID-19 with IFD was investigated using propensity score matching and uni- and multivariable logistic regression analyses. We identified 814 patients supported with ECMO, and 452 patients were included in further analyses. The incidence of IFD was 4.8% and 11.0% in patients without and with COVID-19, respectively. COVID-19 status represented an independent risk factor for IFD (OR 4.30; CI 1.72-10.85; p: 0.002; multivariable regression analysis). In patients with COVID-19, 84.6% of IFD was candidemia and 15.4% represented invasive aspergillosis (IA). All of these patients died. In patients on V-V ECMO, we report that COVID-19 is an independent risk factor for IFD, which is associated with a detrimental prognosis. Further studies are needed to investigate strategies of antifungal therapy or prophylaxis in these patients.

Vancomycin and daptomycin modulate the innate immune response in a murine model of LPS-induced sepsis.

Sepsis is a leading cause of death worldwide, despite the use of multimodal therapies. Common antibiotic regimens are being affected by a rising number of multidrug-resistant pathogens, and new therapeutic approaches are therefore needed. Antibiotics have immunomodulatory properties which appear to be beneficial in the treatment of sepsis. We hypothesized that the last-resort antibiotics vancomycin (VAN) and daptomycin (DMC) modulate cell migration, phagocytosis, and protein cytokine levels in a murine model of lipopolysaccharide (LPS)-induced sepsis. Ten to twelve-week-old C57BL/6 mice (n = 4-6 animals per group) were stimulated with LPS for 20 h, followed by the administration of VAN or DMC. The outcome parameters were leukocyte accumulation and effector function. Quantification of the immune cells in the peritoneal lavage was performed using flow cytometry analysis. Phagocytosis was measured using pHrodo E. coli BioParticles. The response of the cytokines TNFα, IL-6, and IL-10 was measured in vitro using murine peritoneal macrophages stimulated with LPS and VAN or DMC. VAN decreased both the peritoneal macrophage and the dendritic cell populations following LPS stimulation. DMC reduced the dendritic cell population in the peritoneal cavity in LPS-infected mice. Both antibiotics increased the phagocytic activity in peritoneal macrophages, but this effect was diminished in response to LPS. Phagocytosis of dendritic cells was increased in LPS-infected animals treated with VAN. VAN and DMC differently modulated the levels of pro-and anti-inflammatory cytokines. In a murine model of LPS-induced sepsis, VAN and DMC exhibit immunomodulatory effects on cells involved in innate immunity. The question of whether these antibiotics exhibit synergistic effects in the treatment of septic patients, beyond their bactericidal properties, should be further evaluated in future studies.

Secondary ARDS Following Acute Pancreatitis: Is Extracorporeal Membrane Oxygenation Feasible or Futile?

OBJECTIVE: To assess the feasibility of extracorporeal membrane oxygenation (ECMO) or life support (ECLS) as last resort life support therapy in patients with acute pancreatitis and subsequent secondary acute respiratory distress syndrome (ARDS). METHODS: Retrospective analysis from January 2013, to April 2020, of ECMO patients with pancreatitis-induced ARDS at a German University Hospital. Demographics, hospital and ICU length of stay, duration of ECMO therapy, days on mechanical ventilation, fluid balance, need for decompressive laparotomy, amount of blood products, prognostic scores (CCI (Charlson Comorbidity Index), SOFA (Sequential Organ Failure Assessment), RESP(Respiratory ECMO Survival Prediction), SAVE (Survival after Veno-Arterial ECMO)), and the total known length of survival were assessed. RESULTS: A total of n = 495 patients underwent ECMO. Eight patients with acute pancreatitis received ECLS (seven veno-venous, one veno-arterial). Five (71%) required decompressive laparotomy as salvage therapy due to abdominal hypertension. Two patients with acute pancreatitis (25%) survived to hospital discharge. The overall median length of survival was 22 days. Survivors required less fluid in the first 72 h of ECMO support and showed lower values for all prognostic scores. CONCLUSION: ECLS can be performed as a rescue therapy in patients with pancreatitis and secondary ARDS, but nevertheless mortality remains still high. Thus, this last-resort therapy may be best suited for patients with fewer pre-existing comorbidities and no other organ failure.

Extensive Therapeutic Drug Monitoring of Colistin in Critically Ill Patients Reveals Undetected Risks.

(1) Background: With the rise of multi-/pan-drug resistant (MDR/PDR) pathogens, the less utilized antibiotic Colistin has made a comeback. Colistin fell out of favor due to its small therapeutic range and high potential for toxicity. Today, it is used again as a last resort substance in treating MDR/PDR pathogens. Although new guidelines with detailed recommendations for Colistin dosing are available, finding the right dose in critically ill patients with renal failure remains difficult. Here, we evaluate the efficiency of the current guidelines' recommendations by using high resolution therapeutic drug monitoring of Colistin. (2) Methods: We analyzed plasma levels of Colistin and its prodrug colisthimethate sodium (CMS) in 779 samples, drawn from eight PDR-infected ICU patients, using a HPLC-MS/MS approach. The impact of renal function on proper Colistin target levels was assessed. (3) Results: CMS levels did not correlate with Colistin levels. Over-/Underdosing occurred regardless of renal function and mode of renal replacement therapy. Colistin elimination half-time appeared to be longer than previously reported. (4) Conclusion: Following dose recommendations from the most current guidelines does not necessarily lead to adequate Colistin plasma levels. Use of Colistin without therapeutic drug monitoring might be unsafe and guideline adherence does not warrant efficient target levels in critically ill patients.

Electrical Impedance Tomography for Cardio-Pulmonary Monitoring.

Electrical impedance tomography (EIT) is a bedside monitoring tool that noninvasively visualizes local ventilation and arguably lung perfusion distribution. This article reviews and discusses both methodological and clinical aspects of thoracic EIT. Initially, investigators addressed the validation of EIT to measure regional ventilation. Current studies focus mainly on its clinical applications to quantify lung collapse, tidal recruitment, and lung overdistension to titrate positive end-expiratory pressure (PEEP) and tidal volume. In addition, EIT may help to detect pneumothorax. Recent studies evaluated EIT as a tool to measure regional lung perfusion. Indicator-free EIT measurements might be sufficient to continuously measure cardiac stroke volume. The use of a contrast agent such as saline might be required to assess regional lung perfusion. As a result, EIT-based monitoring of regional ventilation and lung perfusion may visualize local ventilation and perfusion matching, which can be helpful in the treatment of patients with acute respiratory distress syndrome (ARDS).

Diagnostic accuracy of physician-staffed emergency medical teams: a retrospective observational cohort study of prehospital versus hospital diagnosis in a 10-year interval.

BACKGROUND: In Germany, emergency medical teams are staffed with physicians but evidence regarding their prehospital diagnostic accuracy remains poor. OBJECTIVE: To evaluate the out-of-hospital diagnostic accuracy of physician-staffed emergency medical teams (PEMTs). METHODS: A retrospective observational cohort study involving the Emergency Medical Service Bonn, Germany, from January to December 2004 and 2014 respectively. A total of 8346 patients underwent medical treatment by PEMTs, of which 1960 adult patients (inclusion criteria: ≥18 years of age, hospital diagnosis available) were included for further analysis. Reasons for non-inclusion: death on scene, outpatient, interhospital transfer, mental illness, false alarm, no hospital medical history available. The overall diagnostic accuracy (correct or false) of PEMTs was measured after matching the prehospital diagnosis with the corresponding diagnosis of the hospital. Secondary outcome measures were incidence of common PEMT diagnoses (acute coronary syndrome (ACS), dyspnea, stroke/intracerebral bleeding), recognition rate of a given disease by PEMTs, and prehospital diagnostic accuracy in elderly patients. RESULTS: PEMT calls increased 2-fold over a decade (2004: n = 3151 vs. 2014: n = 5195). Overall diagnostic accuracy of PEMTs increased from 87.5% in 2004 to 92.6% in the year 2014. The incidence of common PEMT diagnoses such as ACS, dyspnea or stroke/intracerebral bleeding increased 2-fold from 2004 to 2014. The recognition rate of a given disease by the PEMT varied between 2004 and 2014: an increase was observed when a stroke/intracerebral bleeding was diagnosed (2004: 67% vs. 2014: 83%; p = 0.054), a decreased rate of recognition occurred when a syncope/collapse was diagnosed (2004: 81% vs. 2014: 56%; p = 0.007) and a sepsis appears to be a rare event for EMS personnel (2004: 0% vs. 2014: 23%). Linear regression analysis revealed that the prehospital diagnostic accuracy decreases in the elderly patient. CONCLUSIONS: The overall prehospital diagnostic accuracy of PEMTs improved between the year 2004 and 2014 respectively. Our findings suggest that the incidence of common diseases (ACS, dyspnea stroke/intracerebral bleeding, sepsis) increased over a 10-year period. Diagnostic accuracy of different diseases varied but generally decreased in the elderly patient. Regular training of EMS personnel and public campaigns should be implemented to improve the diagnostic accuracy in the future.

Decompressive laparotomy for the treatment of the abdominal compartment syndrome during extracorporeal membrane oxygenation support.

PURPOSE: Extracorporeal membrane oxygenation (ECMO) is increasingly used with various indications. The clinical course can be complicated by an abdominal compartment syndrome (ACS). A decompressive laparotomy (DL) can be an option. MATERIALS AND METHODS: Between 2014 and 2016 175 patients underwent ECMO support. Indications, demographic data, comorbidities, morbidity, mortality and length of stay were analyzed. RESULTS: Indications for ECMO were acute respiratory distress syndrome (n = 65), postpericardiotomy syndrome (n = 37), myocardial infarction (n = 26), extracorporeal cardiopulmonary resuscitation (n = 11), and others (n = 36). ECMO support was performed as veno-venous (VV, n = 91) or veno-arterial (VA, n = 84). Eleven patients developed ACS (VV-ECMO: n = 4; VA-ECMO: n = 7) and underwent DL. Three patients survived to hospital discharge. Risk factors were age (57 vs. 60.5 years, P = 0.032), a Charlson comorbidity index >1 (CCI, P = 0.004), a Simplified Acute Physiology Score (SAPS II) ≥ 42 at admission to ICU (P = 0.013) and ≥44 at the beginning of ECMO support (P = 0.004). When an ACS/DL occurred, mortality did not differ (DL: n = 11; 73% vs. no DL: n = 164; 65%; P = 0.749). Multivarate analysis revealed CCI and SAPS as independent predictors for mortality. CONCLUSIONS: Approximately 10% of patients undergoing VA-ECMO support developed an ACS. If DL is undertaken, SAPS II scores can be used as predictive factor for mortality.

The Ability of Nitric Oxide to Lower Intraocular Pressure Is Dependent on Guanylyl Cyclase.

Purpose: While nitric oxide (NO) donors are emerging as treatments for glaucoma, the mechanism by which NO lowers intraocular pressure (IOP) is unclear. NO activates the enzyme guanylyl cyclase (GC) to produce cyclic guanosine monophosphate. We studied the ocular effects of inhaled and topically applied NO gas in mice and lambs, respectively. Methods: IOP and aqueous humor (AqH) outflow were measured in WT and GC-1α subunit null (GC-1-/-) mice. Mice breathed 40 parts per million (ppm) NO in O2 or control gas (N2/O2). We also studied the effect of ocular NO gas exposure (80, 250, 500, and 1000 ppm) on IOP in anesthetized lambs. NO metabolites were measured in AqH and plasma. Results: In awake WT mice, breathing NO for 40 minutes lowered IOP from 14.4 ± 1.9 mm Hg to 10.9 ± 1.0 mm Hg (n = 11, P < 0.001). Comparable results were obtained in anesthetized WT mice (n = 10, P < 0.001). In awake or anesthetized GC-1-/- mice, IOP did not change under similar experimental conditions (P ≥ 0.08, n = 20). Breathing NO increased in vivo outflow facility in WT but not GC-1-/- mice (+13.7 ± 14.6% vs. -12.1 ± 9.4%, n = 4 each, P < 0.05). In lambs, ocular exposure to NO lowered IOP in a dose-dependent manner (-0.43 mm Hg/ppm NO; n = 5 with 40 total measurements; P = 0.04) without producing corneal pathology or altering pulmonary and systemic hemodynamics. After ocular NO exposure, NO metabolites were increased in AqH (n = 8, P < 0.001) but not in plasma. Conclusions: Breathing NO reduced IOP and increased outflow facility in a GC-dependent manner in mice. Exposure of ovine eyes to NO lowers IOP.

Sensitivity to Sevoflurane anesthesia is decreased in mice with a congenital deletion of Guanylyl Cyclase-1 alpha.

BACKGROUND: Volatile anesthetics increase levels of the neurotransmitter nitric oxide (NO) and the secondary messenger molecule cyclic guanosine monophosphate (cGMP) in the brain. NO activates the enzyme guanylyl cyclase (GC) to produce cGMP. We hypothesized that the NO-GC-cGMP pathway contributes to anesthesia-induced unconsciousness. METHODS: Sevoflurane-induced loss and return of righting reflex (LORR and RORR, respectively) were studied in wild-type mice (WT) and in mice congenitally deficient in the GC-1α subunit (GC-1-/- mice). Spatial distributions of GC-1α and the GC-2α subunit in the brain were visualized by in situ hybridization. Brain cGMP levels were measured in WT and GC-1-/- mice after inhaling oxygen with or without 1.2% sevoflurane for 20 min. RESULTS: Higher concentrations of sevoflurane were required to induce LORR in GC-1-/- mice than in WT mice (1.5 ± 0.1 vs. 1.1 ± 0.2%, respectively, n = 14 and 14, P < 0.0001). Similarly, RORR occurred at higher concentrations of sevoflurane in GC-1-/- mice than in WT mice (1.0 ± 0.1 vs. 0.8 ± 0.1%, respectively, n = 14 and 14, P < 0.0001). Abundant GC-1α and GC-2α mRNA expression was detected in the cerebral cortex, medial habenula, hippocampus, and cerebellum. Inhaling 1.2% sevoflurane for 20 min increased cGMP levels in the brains of WT mice from 2.6 ± 2.0 to 5.5 ± 3.7 pmol/mg protein (n = 13 and 10, respectively, P = 0.0355) but not in GC-1-/- mice. CONCLUSION: Congenital deficiency of GC-1α abolished the ability of sevoflurane anesthesia to increase cGMP levels in the whole brain, and increased the concentration of sevoflurane required to induce LORR. Impaired NO-cGMP signaling raises the threshold for producing sevoflurane-induced unconsciousness in mice.

Exposure of Stored Packed Erythrocytes to Nitric Oxide Prevents Transfusion-associated Pulmonary Hypertension.

BACKGROUND: Transfusion of packed erythrocytes stored for a long duration is associated with increased pulmonary arterial pressure and vascular resistance. Prolonged storage decreases erythrocyte deformability, and older erythrocytes are rapidly removed from the circulation after transfusion. The authors studied whether treating stored packed ovine erythrocytes with NO before transfusion could prevent pulmonary vasoconstriction, enhance erythrocyte deformability, and prolong erythrocyte survival after transfusion. METHODS: Ovine leukoreduced packed erythrocytes were treated before transfusion with either NO gas or a short-lived NO donor. Sheep were transfused with autologous packed erythrocytes, which were stored at 4°C for either 2 ("fresh blood") or 40 days ("stored blood"). Pulmonary and systemic hemodynamic parameters were monitored before, during, and after transfusion. Transfused erythrocytes were labeled with biotin to measure their circulating lifespan. Erythrocyte deformability was assessed before and after NO treatment using a microfluidic device. RESULTS: NO treatment improved the deformability of stored erythrocytes and increased the number of stored erythrocytes circulating at 1 and 24 h after transfusion. NO treatment prevented transfusion-associated pulmonary hypertension (mean pulmonary arterial pressure at 30 min of 21 ± 1 vs. 15 ± 1 mmHg in control and NO-treated packed erythrocytes, P < 0.0001). Washing stored packed erythrocytes before transfusion did not prevent pulmonary hypertension. CONCLUSIONS: NO treatment of stored packed erythrocytes before transfusion oxidizes cell-free oxyhemoglobin to methemoglobin, prevents subsequent NO scavenging in the pulmonary vasculature, and limits pulmonary hypertension. NO treatment increases erythrocyte deformability and erythrocyte survival after transfusion. NO treatment might provide a promising therapeutic approach to prevent pulmonary hypertension and extend erythrocyte survival.

Antifungal antibiotics modulate the pro-inflammatory cytokine production and phagocytic activity of human monocytes in an in vitro sepsis model.

AIMS: The incidence of secondary systemic fungal infections has sharply increased in bacterial septic patients. Antimycotics exhibit immunomodulatory properties, yet these effects are incompletely understood in secondary systemic fungal infections following bacterial sepsis. We investigated a model of systemic inflammation to determine whether antimycotics (liposomal amphotericin B (L-AMB), itraconazol (ITC), and anidulafungin (ANI)) modulate the gene and protein expression as well as the phagocytic activity of lipopolysaccharide (LPS)-stimulated human monocytes. MAIN METHODS: THP-1 monocytes were incubated with L-AMB, ITC or ANI and LPS. Gene expression levels of cytokines (TNF-, IL-1, IL-6, and IL-10) were measured after 2h, 6h, and 24h. Cytokine protein levels were evaluated after 24h and phagocytic activity was determined following co-incubation with Escherichia coli. KEY FINDINGS: All antimycotics differentially modulated the gene and protein expression of cytokines in sepsis-like conditions. In the presence of LPS, we identified L-AMB as immunosuppressive, whereas ITC demonstrated pro-inflammatory properties. Both compounds induced remarkably less phagocytosis. SIGNIFICANCE: Our study suggests that antimycotics routinely used in septic patients alter the immune response in sepsis-like conditions by modulating cytokine gene and protein expression levels and phagocytic activity. Future treatment strategies should consider the immune status of the host and apply antimycotics accordingly in bacterial septic patients with secondary fungal infections.

Producing nitric oxide by pulsed electrical discharge in air for portable inhalation therapy.

Inhalation of nitric oxide (NO) produces selective pulmonary vasodilation and is an effective therapy for treating pulmonary hypertension in adults and children. In the United States, the average cost of 5 days of inhaled NO for persistent pulmonary hypertension of the newborn is about $14,000. NO therapy involves gas cylinders and distribution, a complex delivery device, gas monitoring and calibration equipment, and a trained respiratory therapy staff. The objective of this study was to develop a lightweight, portable device to serve as a simple and economical method of producing pure NO from air for bedside or portable use. Two NO generators were designed and tested: an offline NO generator and an inline NO generator placed directly within the inspiratory line. Both generators use pulsed electrical discharges to produce therapeutic range NO (5 to 80 parts per million) at gas flow rates of 0.5 to 5 liters/min. NO was produced from air, as well as gas mixtures containing up to 90% O2 and 10% N2. Potentially toxic gases produced in the plasma, including nitrogen dioxide (NO2) and ozone (O3), were removed using a calcium hydroxide scavenger. An iridium spark electrode produced the lowest ratio of NO2/NO. In lambs with acute pulmonary hypertension, breathing electrically generated NO produced pulmonary vasodilation and reduced pulmonary arterial pressure and pulmonary vascular resistance index. In conclusion, electrical plasma NO generation produces therapeutic levels of NO from air. After scavenging to remove NO2 and O3 and filtration to remove particles, electrically produced NO can provide safe and effective treatment of pulmonary hypertension.

Linezolid, vancomycin and daptomycin modulate cytokine production, Toll-like receptors and phagocytosis in a human in vitro model of sepsis.

Conventional antibiotics exhibit immunomodulatory properties beneficial in the treatment of sepsis. Antibiotic-resistant Gram-positive bacteria have become a problem in sepsis therapy, giving rise to increased use of last-resort antibiotics; for example, linezolid (LIN), vancomycin (VAN) and daptomycin (DAP). As the immunomodulatory properties of these antibiotics in treating sepsis are unknown, this study examined the effect of VAN, LIN and DAP on the immune response under sepsis-like conditions in vitro. Lipopolysaccharide (LPS)-activated THP-1 monocytes were incubated with LIN, VAN or DAP. Gene expression of cytokines (TNFα, IL-1ß, IL-6, IL-10) and Toll-like receptors (TLR1, 2, 4, 6, 7 and 9) was monitored and phagocytosis was determined following coincubation with E. coli. The antibiotics differentially modulated the gene expression of the investigated cytokines. While LIN and VAN upregulated the expression of all TLRs, DAP downregulated mRNA levels of TLR1, TLR2 and TLR6, which recognize pathogen-associated molecular patterns from Gram-positive bacteria. In addition, LIN inhibited, whereas VAN promoted the phagocytic activity of monocytes. Our results suggest that LIN and VAN possess pro-inflammatory properties, whereas DAP might reduce the immune response to Gram-positive bacteria in sepsis. Furthermore, VAN might be beneficial in the prevention of Gram-negative infections by increasing the phagocytosis of E. coli.

Antibiotics regulate the immune response in both presence and absence of lipopolysaccharide through modulation of Toll-like receptors, cytokine production and phagocytosis in vitro.

The inflammatory response to pathogen-associated molecular patterns such as lipopolysaccharide (LPS) in sepsis is mediated via Toll-like receptors (TLRs). Since TLRs also trigger various immune functions, including phagocytosis, their modulation is a promising strategy in the treatment of sepsis. As antibiotics have immunomodulatory properties, this study examined the effect of commonly used classes of antibiotics on i) the expression of TLRs and cytokines and ii) the phagocytic activity under sepsis-like conditions in vitro. This was achieved by incubating THP-1 monocytes and peripheral blood mononuclear cells (PBMCs) obtained from patients after open-heart surgery with the addition of LPS and six key antibiotics (piperacillin, doxycycline, erythromycin, moxifloxacin or gentamicin). After 24h, mRNA levels of both cytokines (IL-1ß, IL-6) and TLRs (1, 2, 4, and 6) were monitored and phagocytosis was determined following coincubation with Escherichia coli. Each antibiotic differentially regulated the gene expression of the investigated TLRs and cytokines in monocytes. Erythromycin, moxifloxacin and doxycyclin displayed the strongest effects and changed mRNA-levels of the investigated genes up to 5.6-fold. Consistent with this, antibiotics and, in particular, moxifloxacin, regulated the TLR-and cytokine expression in activated PBMCs obtained from patients after open-heart surgery. Furthermore, piperacillin, doxycyclin and moxifloxacin inhibited the phagocytic activity of monocytes. Our results suggest that antibiotics regulate the immune response by modulating TLR- and cytokine expression as well as phagocytosis under septic conditions. Moxifloxacin, doxycycline and erythromycin were shown to possess the strongest immunomodulatory effects and these antibiotic classes should be considered for future immunomodulatory studies in sepsis.