Fluctuations of inspired concentrations of nitric oxide and nitrogen dioxide during mechanical ventilation

BACKGROUND: Nitric oxide (NO) is a very reactive agent with potentially toxic oxidation products such as nitrogen dioxide (NO(2)). Therefore, during NO inhalation a constant inspired concentration and accurate measurement of NO and NO(2) concentrations are essential. The objective of this study was to test the NO concentrations at various positions along the inspiratory limb of the breathing circuit using a recently developed system to administer NO in phase with inspiratory flow during mechanical ventilation (Servo 300 NO-A, Siemens, Sweden). Furthermore, we tested whether an active heating system would interfere with inspired NO concentrations. RESULTS: A sharp decline in the NO concentration was found between the respirator's inspiratory outlet and more distal points along the inspiratory limb of the circuit. This finding was most evident when an active heating system was mounted between those points. CONCLUSIONS: The concentrations of NO and NO(2) should be measured as near to the patient as possible, as significant fluctuations of these concentrations might be found along the inspiratory limb of the respiratory circuit especially when an active heating system is used

Inhaled carbon monoxide protects time-dependently from loss of hypoxic pulmonary vasoconstriction in endotoxemic mice

Background: Inhaled carbon monoxide (CO) appears to have beneficial effects on endotoxemia-induced impairment of hypoxic pulmonary vasoconstriction (HPV). This study aims to specify correct timing of CO application, it’s biochemical mechanisms and effects on inflammatory reactions. Methods: Mice (C57BL/6; n = 86) received lipopolysaccharide (LPS, 30 mg/kg) intraperitoneally and subsequently breathed 50 ppm CO continuously during defined intervals of 3, 6, 12 or 18 h. Two control groups received saline intraperitoneally and additionally either air or CO, and one control group received LPS but breathed air only. In an isolated lung perfusion model vasoconstrictor response to hypoxia (FiO2 = 0.01) was quantified by measurements of pulmonary artery pressure. Pulmonary capillary pressure was estimated by double occlusion technique. Further, inflammatory plasma cytokines and lung tissue mRNA of nitric-oxide-synthase-2 (NOS-2) and heme oxygenase-1 (HO-1) were measured. Results: HPV was impaired after LPS-challenge (p < 0.01). CO exposure restored HPV-responsiveness if administered continuously for full 18 h, for the first 6 h and if given in the interval between the 3rd and 6th hour after LPS-challenge (p < 0.05). Preserved HPV was attributable to recovered arterial resistance and associated with significant reduction in NOS-2 mRNA when compared to controls (p < 0.05). We found no effects on inflammatory plasma cytokines. Conclusion: Low-dose CO prevented LPS-induced impairment of HPV in a time-dependent manner, associated with a decreased NOS-2 expression

In vitro validation and characterization of pulsed inhaled nitric oxide administration during early inspiration

Purpose: Admixture of nitric oxide (NO) to the gas inspired with mechanical ventilation can be achieved through continuous, timed, or pulsed injection of NO into the inspiratory limb. The dose and timing of NO injection govern the inspired and intrapulmonary effect site concentrations achieved with different administration modes. Here we test the effectiveness and target reliability of a new mode injecting pulsed NO boluses exclusively during early inspiration. Methods: An in vitro lung model was operated under various ventilator settings. Admixture of NO through injection into the inspiratory limb was timed either (i) selectively during early inspiration ("pulsed delivery"), or as customary, (ii) during inspiratory time or (iii) the entire respiratory cycle. Set NO target concentrations of 5-40 parts per million (ppm) were tested for agreement with the yield NO concentrations measured at various sites in the inspiratory limb, to assess the effectiveness of these NO administration modes. Results: Pulsed delivery produced inspiratory NO concentrations comparable with those of customary modes of NO administration. At low (450 ml) and ultra-low (230 ml) tidal volumes, pulsed delivery yielded better agreement of the set target (up to 40 ppm) and inspiratory NO concentrations as compared to customary modes. Pulsed delivery with NO injection close to the artificial lung yielded higher intrapulmonary NO concentrations than with NO injection close to the ventilator. The maximum inspiratory NO concentration observed in the trachea (68 +/- 30 ppm) occurred with pulsed delivery at a set target of 40 ppm. Conclusion: Pulsed early inspiratory phase NO injection is as effective as continuous or non-selective admixture of NO to inspired gas and may confer improved target reliability, especially at low, lung protective tidal volumes

Protocol for orthotopic single-lung transplantation in mice as a tool for lung metastasis studies

The transplantation model provides the opportunity to assess the relevance of a molecule of interest for tumor cell extravasation by using a respective genetically modified donor animal. Here, we present a protocol for orthotopic single-lung transplantation in mice as a tool for lung metastasis studies. We describe steps for animal preparation, lung transplantation, and tumor cell injection. We then detail procedures for the direct comparison of tumor cell spreading between the genetically modified left lung and the naive right lung parenchyma. For complete details on the use and execution of this protocol, please refer to Giannou et al. (2023)

Outcomes and risk score for distal pancreatectomy with celiac axis resection (DP-CAR) : an international multicenter analysis

Background: Distal pancreatectomy with celiac axis resection (DP-CAR) is a treatment option for selected patients with pancreatic cancer involving the celiac axis. A recent multicenter European study reported a 90-day mortality rate of 16%, highlighting the importance of patient selection. The authors constructed a risk score to predict 90-day mortality and assessed oncologic outcomes. Methods: This multicenter retrospective cohort study investigated patients undergoing DP-CAR at 20 European centers from 12 countries (model design 2000-2016) and three very-high-volume international centers in the United States and Japan (model validation 2004-2017). The area under receiver operator curve (AUC) and calibration plots were used for validation of the 90-day mortality risk model. Secondary outcomes included resection margin status, adjuvant therapy, and survival. Results: For 191 DP-CAR patients, the 90-day mortality rate was 5.5% (95 confidence interval [CI], 2.2-11%) at 5 high-volume (1 DP-CAR/year) and 18% (95 CI, 9-30%) at 18 low-volume DP-CAR centers (P=0.015). A risk score with age, sex, body mass index (BMI), American Society of Anesthesiologists (ASA) score, multivisceral resection, open versus minimally invasive surgery, and low- versus high-volume center performed well in both the design and validation cohorts (AUC, 0.79 vs 0.74; P=0.642). For 174 patients with pancreatic ductal adenocarcinoma, the R0 resection rate was 60%, neoadjuvant and adjuvant therapies were applied for respectively 69% and 67% of the patients, and the median overall survival period was 19months (95 CI, 15-25months). Conclusions: When performed for selected patients at high-volume centers, DP-CAR is associated with acceptable 90-day mortality and overall survival. The authors propose a 90-day mortality risk score to improve patient selection and outcomes, with DP-CAR volume as the dominant predictor

IL-10 dampens antitumor immunity and promotes liver metastasis via PD-L1 induction

Background &amp; Aims: The liver is one of the organs most commonly affected by metastasis. The presence of liver metastases has been reported to be responsible for an immunosuppressive microenvironment and diminished immunotherapy efficacy. Herein, we aimed to investigate the role of IL-10 in liver metastasis and to determine how its modulation could affect the efficacy of immunotherapy in vivo. Methods: To induce spontaneous or forced liver metastasis in mice, murine cancer cells (MC38) or colon tumor organoids were injected into the cecum or the spleen, respectively. Mice with complete and cell type-specific deletion of IL-10 and IL-10 receptor alpha were used to identify the source and the target of IL-10 during metastasis formation. Programmed death ligand 1 (PD-L1)-deficient mice were used to test the role of this checkpoint. Flow cytometry was applied to characterize the regulation of PD-L1 by IL-10. Results: We found that Il10-deficient mice and mice treated with IL-10 receptor alpha antibodies were protected against liver metastasis formation. Furthermore, by using IL-10 reporter mice, we demonstrated that Foxp3+ regulatory T cells (Tregs) were the major cellular source of IL-10 in liver metastatic sites. Accordingly, deletion of IL-10 in Tregs, but not in myeloid cells, led to reduced liver metastasis. Mechanistically, IL-10 acted on Tregs in an autocrine manner, thereby further amplifying IL-10 production. Furthermore, IL-10 acted on myeloid cells, i.e. monocytes, and induced the upregulation of the immune checkpoint protein PD-L1. Finally, the PD-L1/PD-1 axis attenuated CD8-dependent cytotoxicity against metastatic lesions. Conclusions: Treg-derived IL-10 upregulates PD-L1 expression in monocytes, which in turn reduces CD8+ T-cell infiltration and related antitumor immunity in the context of colorectal cancer-derived liver metastases. These findings provide the basis for future monitoring and targeting of IL-10 in colorectal cancer-derived liver metastases. Impact and implications: Liver metastasis diminishes the effectiveness of immunotherapy and increases the mortality rate in patients with colorectal cancer. We investigated the role of IL-10 in liver metastasis formation and assessed its impact on the effectiveness of immunotherapy. Our data show that IL-10 is a pro-metastatic factor involved in liver metastasis formation and that it acts as a regulator of PD-L1. This provides the basis for future monitoring and targeting of IL-10 in colorectal cancer-derived liver metastasis.</p

IL-10 dampens antitumor immunity and promotes liver metastasis via PD-L1 induction

Background &amp; Aims: The liver is one of the organs most commonly affected by metastasis. The presence of liver metastases has been reported to be responsible for an immunosuppressive microenvironment and diminished immunotherapy efficacy. Herein, we aimed to investigate the role of IL-10 in liver metastasis and to determine how its modulation could affect the efficacy of immunotherapy in vivo. Methods: To induce spontaneous or forced liver metastasis in mice, murine cancer cells (MC38) or colon tumor organoids were injected into the cecum or the spleen, respectively. Mice with complete and cell type-specific deletion of IL-10 and IL-10 receptor alpha were used to identify the source and the target of IL-10 during metastasis formation. Programmed death ligand 1 (PD-L1)-deficient mice were used to test the role of this checkpoint. Flow cytometry was applied to characterize the regulation of PD-L1 by IL-10. Results: We found that Il10-deficient mice and mice treated with IL-10 receptor alpha antibodies were protected against liver metastasis formation. Furthermore, by using IL-10 reporter mice, we demonstrated that Foxp3+ regulatory T cells (Tregs) were the major cellular source of IL-10 in liver metastatic sites. Accordingly, deletion of IL-10 in Tregs, but not in myeloid cells, led to reduced liver metastasis. Mechanistically, IL-10 acted on Tregs in an autocrine manner, thereby further amplifying IL-10 production. Furthermore, IL-10 acted on myeloid cells, i.e. monocytes, and induced the upregulation of the immune checkpoint protein PD-L1. Finally, the PD-L1/PD-1 axis attenuated CD8-dependent cytotoxicity against metastatic lesions. Conclusions: Treg-derived IL-10 upregulates PD-L1 expression in monocytes, which in turn reduces CD8+ T-cell infiltration and related antitumor immunity in the context of colorectal cancer-derived liver metastases. These findings provide the basis for future monitoring and targeting of IL-10 in colorectal cancer-derived liver metastases. Impact and implications: Liver metastasis diminishes the effectiveness of immunotherapy and increases the mortality rate in patients with colorectal cancer. We investigated the role of IL-10 in liver metastasis formation and assessed its impact on the effectiveness of immunotherapy. Our data show that IL-10 is a pro-metastatic factor involved in liver metastasis formation and that it acts as a regulator of PD-L1. This provides the basis for future monitoring and targeting of IL-10 in colorectal cancer-derived liver metastasis.</p