Electronic cigarette vaping with aged coils causes acute lung injury in mice

Electronic cigarettes (e-cigarettes) have been used widely as an alternative to conventional cigarettes and have become particularly popular among young adults. A growing body of evidence has shown that e-cigarettes are associated with acute lung injury and adverse effects in multiple other organs. Previous studies showed that high emissions of aldehydes (formaldehyde and acetaldehyde) in aerosols were associated with increased usage of the same e-cigarette coils. However, the impact on lung function of using aged coils has not been reported. We investigated the relationship between coil age and acute lung injury in mice exposed to experimental vaping for 1 h (2 puffs/min, 100 ml/puff). The e-liquid contains propylene glycol and vegetable glycerin (50:50, vol) only. The concentrations of formaldehyde and acetaldehyde in the vaping aerosols increased with age of the nichrome coils starting at 1200 puffs. Mice exposed to e-cigarette aerosols produced from 1800, but not 0 or 900, puff-aged coils caused acute lung injury, increased lung wet/dry weight ratio, and induced lung inflammation (IL-6, TNF-α, IL-1β, MIP-2). Exposure to vaping aerosols from 1800 puff-aged coils decreased heart rate, respiratory rate, and oxygen saturation in mice compared to mice exposed to air or aerosols from new coils. In conclusion, we observed that the concentration of aldehydes (formaldehyde and acetaldehyde) increased with repeated and prolonged usage of e-cigarette coils. Exposure to high levels of aldehyde in vaping aerosol was associated with acute lung injury in mice. These findings show significant risk of lung injury associated with prolonged use of e-cigarette devices.

Veno-venous extracorporeal blood phototherapy increases the rate of carbon monoxide (CO) elimination in CO-poisoned pigs

BACKGROUND AND OBJECTIVES

Carbon monoxide (CO) inhalation is the leading cause of poison-related deaths in the United States. CO binds to hemoglobin (Hb), displaces oxygen, and reduces oxygen delivery to tissues. The optimal treatment for CO poisoning in patients with normal lung function is the administration of hyperbaric oxygen (HBO). However, hyperbaric chambers are only available in medical centers with specialized equipment, resulting in delayed therapy. Visible light dissociates CO from Hb with minimal effect on oxygen binding. In a previous study, we combined a membrane oxygenator with phototherapy at 623 nm to produce a "mini" photo-ECMO (extracorporeal membrane oxygenation) device, which improved CO elimination and survival in CO-poisoned rats. The objective of this study was to develop a larger photo-ECMO device ("maxi" photo-ECMO) and to test its ability to remove CO from a porcine model of CO poisoning.

STUDY DESIGN/MATERIALS AND METHODS

The "maxi" photo-ECMO device and the photo-ECMO system (six maxi photo-ECMO devices assembled in parallel), were tested in an in vitro circuit of CO poisoning. To assess the ability of the photo-ECMO device and the photo-ECMO system to remove CO from CO-poisoned blood in vitro, the half-life of COHb (COHb-t_1/2 ), as well as the percent COHb reduction in a single blood pass through the device, were assessed. In the in vivo studies, we assessed the COHb-t_1/2 in a CO-poisoned pig under three conditions: (1) While the pig breathed 100% oxygen through the endotracheal tube; (2) while the pig was connected to the photo-ECMO system with no light exposure; and (3) while the pig was connected to the photo-ECMO system, which was exposed to red light.

RESULTS

The photo-ECMO device was able to fully oxygenate the blood after a single pass through the device. Compared to ventilation with 100% oxygen alone, illumination with red light together with 100% oxygen was twice as efficient in removing CO from blood. Changes in gas flow rates did not alter CO elimination in one pass through the device. Increases in irradiance up to 214 mW/cm² were associated with an increased rate of CO elimination. The photo-ECMO device was effective over a range of blood flow rates and with higher blood flow rates, more CO was eliminated. A photo-ECMO system composed of six photo-ECMO devices removed CO faster from CO-poisoned blood than a single photo-ECMO device. In a CO-poisoned pig, the photo-ECMO system increased the rate of CO elimination without significantly increasing the animal's body temperature or causing hemodynamic instability.

CONCLUSION

In this study, we developed a photo-ECMO system and demonstrated its ability to remove CO from CO-poisoned 45-kg pigs. Technical modifications of the photo-ECMO system, including the development of a compact, portable device, will permit treatment of patients with CO poisoning at the scene of their poisoning, during transit to a local emergency room, and in hospitals that lack HBO facilities.

UBA6 and NDFIP1 regulate the degradation of ferroportin

Hepcidin regulates iron homeostasis by controlling the level of ferroportin, the only membrane channel that facilitates export of iron from within cells. Binding of hepcidin to ferroportin induces the ubiquitination of ferroportin at multiple lysine residues and subsequently causes the internalization and degradation of the ligand-channel complex within lysosomes. The objective of this study was to identify components of the ubiquitin system that are involved in ferroportin degradation. A HepG2 cell line, which inducibly expresses ferroportingreen fluorescent protein (FPN-GFP), was established to test the ability of small interfering (siRNA) directed against components of the ubiquitin system to prevent BMP6- and exogenous hepcidin-induced ferroportin degradation. Of the 88 siRNA directed against components of the ubiquitin pathway that were tested, siRNA-mediated depletion of the alternative E1 enzyme UBA6 as well as the adaptor protein NDFIP1 prevented BMP6- and hepcidin-induced degradation of ferroportin in vitro. A third component of the ubiquitin pathway, ARIH1, indirectly inhibited ferroportin degradation by impairing BMP6-mediated induction of hepcidin. In mice, the AAV-mediated silencing of Ndfip1 in the murine liver increased the level of hepatic ferroportin and increased circulating iron. The results suggest that the E1 enzyme UBA6 and the adaptor protein NDFIP1 are involved in iron homeostasis by regulating the degradation of ferroportin. These specific components of the ubiquitin system may be promising targets for the treatment of iron-related diseases, including iron overload and anemia of inflammation.

Pleural Pressure Targeted Positive Airway Pressure Improves Cardiopulmonary Function in Spontaneously Breathing Patients With Obesity

BACKGROUND

Increased pleural pressure affects the mechanics of breathing of people with class III obesity (BMI > 40 kg/m²).

RESEARCH QUESTION

What are the acute effects of CPAP titrated to match pleural pressure on cardiopulmonary function in spontaneously breathing patients with class III obesity?

STUDY DESIGN AND METHODS

We enrolled six participants with BMI within normal range (control participants, group I) and 12 patients with class III obesity (group II) divided into subgroups: IIa, BMI of 40 to 50 kg/m²; and IIb, BMI of ≥ 50 kg/m². The study was performed in two phases: in phase 1, participants were supine and breathing spontaneously at atmospheric pressure, and in phase 2, participants were supine and breathing with CPAP titrated to match their end-expiratory esophageal pressure in the absence of CPAP. Respiratory mechanics, esophageal pressure, and hemodynamic data were collected, and right heart function was evaluated by transthoracic echocardiography.

RESULTS

The levels of CPAP titrated to match pleural pressure in group I, subgroup IIa, and subgroup IIb were 6 ± 2 cmH₂O, 12 ± 3 cmH₂O, and 18 ± 4 cmH₂O, respectively. In both subgroups IIa and IIb, CPAP titrated to match pleural pressure decreased minute ventilation (IIa, P = .03; IIb, P = .03), improved peripheral oxygen saturation (IIa, P = .04; IIb, P = .02), improved homogeneity of tidal volume distribution between ventral and dorsal lung regions (IIa, P = .22; IIb, P = .03), and decreased work of breathing (IIa, P < .001; IIb, P = .003) with a reduction in both the work spent to initiate inspiratory flow as well as tidal ventilation. In five hypertensive participants with obesity, BP decreased to normal range, without impairment of right heart function.

INTERPRETATION

In ambulatory patients with class III obesity, CPAP titrated to match pleural pressure decreased work of breathing and improved respiratory mechanics while maintaining hemodynamic stability, without impairing right heart function.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT02523352; URL: www.clinicaltrials.gov.

d-dimer and Death in Critically Ill Patients With Coronavirus Disease 2019

OBJECTIVES

Hypercoagulability may be a key mechanism for acute organ injury and death in patients with severe coronavirus disease 2019, but the relationship between elevated plasma levels of d-dimer, a biomarker of coagulation activation, and mortality has not been rigorously studied. We examined the independent association between d-dimer and death in critically ill patients with coronavirus disease 2019.

DESIGN

Multicenter cohort study.

SETTING

ICUs at 68 hospitals across the United States.

PATIENTS

Critically ill adults with coronavirus disease 2019 admitted to ICUs between March 4, 2020, and May 25, 2020, with a measured d-dimer concentration on ICU day 1 or 2.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The primary exposure was the highest normalized d-dimer level (assessed in four categories: < 2×, 2-3.9×, 4-7.9×, and ≥ 8× the upper limit of normal) on ICU day 1 or 2. The primary endpoint was 28-day mortality. Multivariable logistic regression was used to adjust for confounders. Among 3,418 patients (63.1% male; median age 62 yr [interquartile range, 52-71 yr]), 3,352 (93.6%) had a d-dimer concentration above the upper limit of normal. A total of 1,180 patients (34.5%) died within 28 days. Patients in the highest compared with lowest d-dimer category had a 3.11-fold higher odds of death (95% CI, 2.56-3.77) in univariate analyses, decreasing to a 1.81-fold increased odds of death (95% CI, 1.43-2.28) after multivariable adjustment for demographics, comorbidities, and illness severity. Further adjustment for therapeutic anticoagulation did not meaningfully attenuate this relationship (odds ratio, 1.73; 95% CI, 1.36-2.19).

CONCLUSIONS

In a large multicenter cohort study of critically ill patients with coronavirus disease 2019, higher d-dimer levels were independently associated with a greater risk of death.

Hypoxia ameliorates brain hyperoxia and NAD+ deficiency in a murine model of Leigh syndrome

Leigh syndrome is a severe mitochondrial neurodegenerative disease with no effective treatment. In the Ndufs4-/- mouse model of Leigh syndrome, continuously breathing 11% O2 (hypoxia) prevents neurodegeneration and leads to a dramatic extension (~5-fold) in lifespan. We investigated the effect of hypoxia on the brain metabolism of Ndufs4-/- mice by studying blood gas tensions and metabolite levels in simultaneously sampled arterial and cerebral internal jugular venous (IJV) blood. Relatively healthy Ndufs4-/- and wildtype (WT) mice breathing air until postnatal age ~38 d were compared to Ndufs4-/- and WT mice breathing air until ~38 days old followed by 4-weeks of breathing 11% O2. Compared to WT control mice, Ndufs4-/- mice breathing air have reduced brain O2 consumption as evidenced by an elevated partial pressure of O2 in IJV blood (PijvO2) despite a normal PO2 in arterial blood, and higher lactate/pyruvate (L/P) ratios in IJV plasma revealed by metabolic profiling. In Ndufs4-/- mice, hypoxia treatment normalized the cerebral venous PijvO2 and L/P ratios, and decreased levels of nicotinate in IJV plasma. Brain concentrations of nicotinamide adenine dinucleotide (NAD+) were lower in Ndufs4-/- mice breathing air than in WT mice, but preserved at WT levels with hypoxia treatment. Although mild hypoxia (17% O2) has been shown to be an ineffective therapy for Ndufs4-/- mice, we find that when combined with nicotinic acid supplementation it provides a modest improvement in neurodegeneration and lifespan. Therapies targeting both brain hyperoxia and NAD+ deficiency may hold promise for treating Leigh syndrome.

Comparison of pulmonary vein sizing by transesophageal echocardiogram and by direct angiogram

Funding Acknowledgements

Type of funding sources: None.

Background

Pulmonary vein (PV) anatomy and sizing is important to know before performing PV isolation. This information is conventionally obtained by angiography or by CT scan.

Aim

We undertook this study to identify and measure the PVs during TEE studies and validate these against angiography.

Method

17 consecutive patients due to undergo PV isolation for paroxysmal atrial fibrillation were analysed. Using TEE, the PVs were visualised (Upper panel) as follows:  i) From the mid-esophageal four chamber view, the chamber probe was turned to the right at 110-130º for the bicaval view, where the RSPV was seen entering the left atrium adjacent to the SVC. ii) At 0º the SVC was imaged in its short axis, and the probe advanced till the interatrial septum was seen. The angle was changed to 30º to visualise the right inferior PV (RIPV). iii) From the two chamber view (70-90º), the probe was turned to the left and withdrawn to display the left superior PV (LSPV) entering the left atrium parallel to the appendage.iv) Keeping the LSPV in focus, the angle was changed to 135º and the probe advanced till the AV groove, where the left inferior PV (LIPV) was visualised. After transseptal puncture, each PV was cannulated. The PV angiograms were performed in several projections to obtain the best PV profile (lower panel). Using electronic callipers, each PV was measured within 1 cm of its entry into the left atrium, after having received all tributaries. Those PVs were considered for analysis which were measured by both TEE and angiography. The paired ‘T’ test was used to compare the PV diameters by TEE and angiography and the Bland Altman analysis was done to see the level of agreement.

Results

Of a total of 68 PVs, 62 could be adequately visualised by TEE and 50 by angiography. These 50 PVs were measured using both methods. The diameters of the PVs measured by TEE and angiography were not statistically different by the paired t test; LSPV14 ± 1.8 mm v/s 14.4 ± 2.1 mm; RSPV 13 ± 1.8 mm v/s 14.6 ± 3.5 mm; LIPV 11.9 ± 2.1 vs 13.2 ± 2.8 mm and RIPV 10.5 ± 2.7 vs 12.1 ± 2.9 mm. Bland Altman analysis showed most PV sizes estimated by TEE and angiography lay within limits of agreement.

Conclusions

A majority of PVs can be visualised by TEE using a defined protocol. TEE is a good technique to visualise and assess the size of PVs, avoiding the need for contrast medium and radiation.

Abstract Figure. TEE and angiographic images of PVs

Is the right ventricular function affected by permanent pacemaker?

Funding Acknowledgements

Type of funding sources: None.

Background

The effect of right ventricular (RV) pacing on left ventricular (LV) function has been extensively evaluated, and so has the effect of the RV pacing lead on tricuspid valve function. However, the effects on RV function per se have not been evaluated systematically.

Purpose

We aimed to assess the RV dimensions and RV function six months after dual chamber pacemaker implantation

performed for atrioventricular (AV) block by detailed echocardiography, including three-dimensional (3D) echocardiography.

Method

All adult patients undergoing dual chamber pacemaker from January 2018 to March 2019 for symptomatic AV block with a structurally normal heart were included in the study. They underwent pre-procedure detailed echocardiography specifically directed at measuring RV dimensions and function [including 3D RV ejection fraction (EF)] and a repeat detailed echocardiogram at six-month follow-up, by the same echocardiographer. The echocardiographic parameters at baseline and after six-month follow-up were compared.

Results

All patients had more than 75% ventricular pacing in these six months. At six-month follow-up, there was no significant change in LVEF, while there was a mild decrease in RVEF as outlined in the Table 1. While there was some overlap between RVEF range of values at baseline and after six months, 23 (38.3%) patients showed a drop in RVEF by &gt;5%.

Conclusion

Our study shows a change in several RV function parameters in a majority of patients six months after

pacemaker implantation for AV block.

RV Function at six month follow-up Parameters Pre-procedure Six-Month Follow-up p value (Paired t-test) PASP (mm Hg) 20.2 ± 1.3 26.1 ± 12.2 &lt;0.001 FAC (%) 42.6 ± 3.4 39.4 ± 6 &lt;0.001 TAPSE (mm) 18.4 ±3.8 15.6 ± 4.7 &lt;0.001 RIMP 0.66 ± 0.09 0.61 ± 0.11 0.003 RV E/E’ 9.4 ± 2.1 7.7 ± 2.1 &lt;0.001 RV S’ 13.6 ± 2.4 10.7 ± 2.4 &lt;0.001 RVEF % [By 3D Echocardiography] 47.7± 5.1 44.9 ± 7.4 &lt;0.001 TR Jet Area (cm2) 0.03 ± 0.26 0.55 ± 0.96 &lt;0.001 RV= Right Ventricle; RA= Right Atrium; RVOT = Right Ventricular Outflow Tract; PASP = Pulmonary Artery Systolic Pressure; FAC= Fractional Area Change; TAPSE= Tricuspid Annular Plane Systolic Excursion; RIMP = Right Ventricular Index of Myocardial Performance; TR = Tricuspid Regurgitation S’ = Peak Systolic Annular Velocity; RVEF = Right Ventricular Ejection Fraction; 3D = Three Dimensional Abstract Figure. Change in RVEF in 6 months

Intraoperative Oxygen Concentration and Neurocognition after Cardiac Surgery

BACKGROUND

Despite evidence suggesting detrimental effects of perioperative hyperoxia, hyperoxygenation remains commonplace in cardiac surgery. Hyperoxygenation may increase oxidative damage and neuronal injury leading to potential differences in postoperative neurocognition. Therefore, this study tested the primary hypothesis that intraoperative normoxia, as compared to hyperoxia, reduces postoperative cognitive dysfunction in older patients having cardiac surgery.

METHODS

A randomized double-blind trial was conducted in patients aged 65 yr or older having coronary artery bypass graft surgery with cardiopulmonary bypass. A total of 100 patients were randomized to one of two intraoperative oxygen delivery strategies. Normoxic patients (n = 50) received a minimum fraction of inspired oxygen of 0.35 to maintain a Pao2 above 70 mmHg before and after cardiopulmonary bypass and between 100 and 150 mmHg during cardiopulmonary bypass. Hyperoxic patients (n = 50) received a fraction of inspired oxygen of 1.0 throughout surgery, irrespective of Pao2 levels. The primary outcome was neurocognitive function measured on postoperative day 2 using the Telephonic Montreal Cognitive Assessment. Secondary outcomes included neurocognitive function at 1, 3, and 6 months, as well as postoperative delirium, mortality, and durations of mechanical ventilation, intensive care unit stay, and hospital stay.

RESULTS

The median age was 71 yr (interquartile range, 68 to 75), and the median baseline neurocognitive score was 17 (16 to 19). The median intraoperative Pao2 was 309 (285 to 352) mmHg in the hyperoxia group and 153 (133 to 168) mmHg in the normoxia group (P < 0.001). The median Telephonic Montreal Cognitive Assessment score on postoperative day 2 was 18 (16 to 20) in the hyperoxia group and 18 (14 to 20) in the normoxia group (P = 0.42). Neurocognitive function at 1, 3, and 6 months, as well as secondary outcomes, were not statistically different between groups.

CONCLUSIONS

In this randomized controlled trial, intraoperative normoxia did not reduce postoperative cognitive dysfunction when compared to intraoperative hyperoxia in older patients having cardiac surgery. Although the optimal intraoperative oxygenation strategy remains uncertain, the results indicate that intraoperative hyperoxia does not worsen postoperative cognition after cardiac surgery.

EDITOR’S PERSPECTIVE

High-resolution optical microscopy for characterising microstructural deformation in microtensile testing

Imaging surface deformation of a coupon specimen in microtensile testing with an optical microscope presents challenges due to the narrow depth of field (DoF) of optical microscopes. Materials being heterogeneous at microscopic length scale, the sample surface deforms into a complex 3D surface texture, evolving continuously as the loading increases. Because of the narrow DoF, the region that is in focus within the field of view (FoV) decreases substantially in size with the increasing out-of-plane heterogeneous deformation. To address this challenge, a method based on image blending and stabilisation of the captured image frames is proposed. Image blending combines the partial regions that are in focus from a set of successive image frames captured at different working distances from the object surface plane to construct a single image that has a large part of the FoV in focus. The blended images are then obtained at different levels of macroscopic strains, that is the global homogeneous strain, in order to characterise the evolution of the heterogeneous deformation. The image stabilisation removes any misalignments of the blended images by spatially realigning them choosing a common feature as a reference point. The validation of the proposed method with conventionally and additively manufactured stainless steel 316L (SS 316L) specimens demonstrates excellent improvement in image quality. Almost 100% of the FoV is maintained in focus regardless of the amount of out-of-plane heterogeneous deformation caused during tensile testing, which is quite remarkable for optical microscopy imaging. Consequently, the blended and stabilised images enhanced the accuracy of digital image correlation (DIC). Time-lapse videos of the deformation generated using these images captured the evolution of the slip bands and their transmission through twinning boundaries in the stainless steel microstructure. Overall, this study demonstrates the feasibility of using image-processing techniques to advance optical microscopy to image complex 3D surfaces evolving with time.

High Pleural Pressure Prevents Alveolar Overdistension and Hemodynamic Collapse in ARDS with Class III Obesity

Rationale: Obesity is characterized by elevated pleural pressure (Ppl) and worsening atelectasis during mechanical ventilation in patients with acute respiratory distress syndrome (ARDS).

Objectives: To determine the effects of a lung recruitment maneuver (LRM) in the presence of elevated Ppl on hemodynamics, left and right ventricular pressure, and pulmonary vascular resistance. We hypothesized that elevated Ppl protects the cardiovascular system against high airway pressure and prevents lung overdistension.

Methods: First, an interventional crossover trial in adult subjects with ARDS and a body mass index ≥ 35 kg/m² (n = 21) was performed to explore the hemodynamic consequences of the LRM. Second, cardiovascular function was studied during low and high positive end-expiratory pressure (PEEP) in a model of swine with ARDS and high Ppl (n = 9) versus healthy swine with normal Ppl (n = 6).

Measurements and Main Results: Subjects with ARDS and obesity (body mass index = 57 ± 12 kg/m²) after LRM required an increase in PEEP of 8 (95% confidence interval [95% CI], 7–10) cm H₂O above traditional ARDS Network settings to improve lung function, oxygenation and V./Q. matching, without impairment of hemodynamics or right heart function. ARDS swine with high Ppl demonstrated unchanged transmural left ventricular pressure and systemic blood pressure after the LRM protocol. Pulmonary arterial hypertension decreased (8 [95% CI, 13–4] mm Hg), as did vascular resistance (1.5 [95% CI, 2.2–0.9] Wood units) and transmural right ventricular pressure (10 [95% CI, 15–6] mm Hg) during exhalation. LRM and PEEP decreased pulmonary vascular resistance and normalized the V./Q. ratio.

Conclusions: High airway pressure is required to recruit lung atelectasis in patients with ARDS and class III obesity but causes minimal overdistension. In addition, patients with ARDS and class III obesity hemodynamically tolerate LRM with high airway pressure.

Clinical trial registered with www.clinicaltrials.gov (NCT 02503241).

Temporary Transvenous Diaphragmatic Neurostimulation in Prolonged Mechanically Ventilated Patients: A Feasibility Trial (RESCUE 1)

Prolonged mechanical ventilation promotes diaphragmatic atrophy and weaning difficulty. The study uses a novel device containing a transvenous phrenic nerve stimulating catheter (Lungpacer IntraVenous Electrode Catheter) to stimulate the diaphragm in ventilated patients. We set out to determine the feasibility of temporary transvenous diaphragmatic neurostimulation using this device.

DESIGN

Multicenter, prospective open-label single group feasibility study.

SETTING

ICUs of tertiary care hospitals.

PATIENTS

Adults on mechanical ventilation for greater than or equal to 7 days that had failed two weaning trials.

INTERVENTIONS

Stimulation catheter insertion and transvenous diaphragmatic neurostimulation therapy up to tid, along with standard of care.

MEASUREMENTS AND MAIN RESULTS

Primary outcomes were successful insertion and removal of the catheter and safe application of transvenous diaphragmatic neurostimulation. Change in maximal inspiratory pressure and rapid shallow breathing index were also evaluated. Eleven patients met all entry criteria with a mean mechanical ventilation duration of 19.7 days; nine underwent successful catheter insertion. All nine had successful mapping of one or both phrenic nerves, demonstrated diaphragmatic contractions during therapy, and underwent successful catheter removal. Seven of nine met successful weaning criteria. Mean maximal inspiratory pressure increased by 105% in those successfully weaned (mean change 19.7 ± 17.9 cm H2O; p = 0.03), while mean rapid shallow breathing index improved by 44% (mean change -63.5 ± 64.4; p = 0.04).

CONCLUSIONS

The transvenous diaphragmatic neurostimulation system is a feasible and safe therapy to stimulate the phrenic nerves and induce diaphragmatic contractions. Randomized clinical trials are underway to compare it to standard-of-care therapy for mechanical ventilation weaning.

A lung rescue team improves survival in obesity with acute respiratory distress syndrome

BACKGROUND

Limited data exist regarding ventilation in patients with class III obesity [body mass index (BMI) > 40 kg/m2] and acute respiratory distress syndrome (ARDS). The aim of the present study was to determine whether an individualized titration of mechanical ventilation according to cardiopulmonary physiology reduces the mortality in patients with class III obesity and ARDS.

METHODS

In this retrospective study, we enrolled adults admitted to the ICU from 2012 to 2017 who had class III obesity and ARDS and received mechanical ventilation for > 48 h. Enrolled patients were divided in two cohorts: one cohort (2012-2014) had ventilator settings determined by the ARDSnet table for lower positive end-expiratory pressure/higher inspiratory fraction of oxygen (standard protocol-based cohort); the other cohort (2015-2017) had ventilator settings determined by an individualized protocol established by a lung rescue team (lung rescue team cohort). The lung rescue team used lung recruitment maneuvers, esophageal manometry, and hemodynamic monitoring.

RESULTS

The standard protocol-based cohort included 70 patients (BMI = 49 ± 9 kg/m2), and the lung rescue team cohort included 50 patients (BMI = 54 ± 13 kg/m2). Patients in the standard protocol-based cohort compared to lung rescue team cohort had almost double the risk of dying at 28 days [31% versus 16%, P = 0.012; hazard ratio (HR) 0.32; 95% confidence interval (CI95%) 0.13-0.78] and 3 months (41% versus 22%, P = 0.006; HR 0.35; CI95% 0.16-0.74), and this effect persisted at 6 months and 1 year (incidence of death unchanged 41% versus 22%, P = 0.006; HR 0.35; CI95% 0.16-0.74).

CONCLUSION

Individualized titration of mechanical ventilation by a lung rescue team was associated with decreased mortality compared to use of an ARDSnet table.

Improvement in Outcomes After Cardiac Arrest and Resuscitation by Inhibition of S-Nitrosoglutathione Reductase

BACKGROUND

The biological effects of nitric oxide are mediated via protein S-nitrosylation. Levels of S-nitrosylated protein are controlled in part by the denitrosylase, S-nitrosoglutathione reductase (GSNOR). The objective of this study was to examine whether GSNOR inhibition improves outcomes after cardiac arrest and cardiopulmonary resuscitation (CA/CPR).

METHODS

Adult wild-type C57BL/6 and GSNOR-deleted (GSNOR^-/-) mice were subjected to potassium chloride-induced CA and subsequently resuscitated. Fifteen minutes after a return of spontaneous circulation, wild-type mice were randomized to receive the GSNOR inhibitor, SPL-334.1, or normal saline as placebo. Mortality, neurological outcome, GSNOR activity, and levels of S-nitrosylated proteins were evaluated. Plasma GSNOR activity was measured in plasma samples obtained from post-CA patients, preoperative cardiac surgery patients, and healthy volunteers.

RESULTS

GSNOR activity was increased in plasma and multiple organs of mice, including brain in particular. Levels of protein S-nitrosylation were decreased in the brain 6 hours after CA/CPR. Administration of SPL-334.1 attenuated the increase in GSNOR activity in brain, heart, liver, spleen, and plasma, and restored S-nitrosylated protein levels in the brain. Inhibition of GSNOR attenuated ischemic brain injury and improved survival in wild-type mice after CA/CPR (81.8% in SPL-334.1 versus 36.4% in placebo; log rank P=0.031). Similarly, GSNOR deletion prevented the reduction in the number of S-nitrosylated proteins in the brain, mitigated brain injury, and improved neurological recovery and survival after CA/CPR. Both GSNOR inhibition and deletion attenuated CA/CPR-induced disruption of blood brain barrier. Post-CA patients had higher plasma GSNOR activity than did preoperative cardiac surgery patients or healthy volunteers ( P<0.0001). Plasma GSNOR activity was positively correlated with initial lactate levels in postarrest patients (Spearman correlation coefficient=0.48; P=0.045).

CONCLUSIONS

CA and CPR activated GSNOR and reduced the number of S-nitrosylated proteins in the brain. Pharmacological inhibition or genetic deletion of GSNOR prevented ischemic brain injury and improved survival rates by restoring S-nitrosylated protein levels in the brain after CA/CPR in mice. Our observations suggest that GSNOR is a novel biomarker of postarrest brain injury as well as a molecular target to improve outcomes after CA.

Hepcidin Deficiency Protects Against Atherosclerosis

Objective- Inflammatory stimuli enhance the progression of atherosclerotic disease. Inflammation also increases the expression of hepcidin, a hormonal regulator of iron homeostasis, which decreases intestinal iron absorption, reduces serum iron levels and traps iron within macrophages. The role of macrophage iron in the development of atherosclerosis remains incompletely understood. The objective of this study was to investigate the effects of hepcidin deficiency and decreased macrophage iron on the development of atherosclerosis. Approach and Results- Hepcidin- and LDL (low-density lipoprotein) receptor-deficient ( Hamp^-/-/ Ldlr^-/-) mice and Hamp^+/+/ Ldlr^-/- control mice were fed a high-fat diet for 21 weeks. Compared with control mice, Hamp^-/-/ Ldlr^-/- mice had decreased aortic macrophage activity and atherosclerosis. Because hepcidin deficiency is associated with both increased serum iron and decreased macrophage iron, the possibility that increased serum iron was responsible for decreased atherosclerosis in Hamp^-/-/ Ldlr^-/- mice was considered. Hamp^+/+/ Ldlr^-/- mice were treated with iron dextran so as to produce a 2-fold increase in serum iron. Increased serum iron did not decrease atherosclerosis in Hamp^+/+/ Ldlr^-/- mice. Aortic macrophages from Hamp^-/-/ Ldlr^-/- mice had less labile free iron and exhibited a reduced proinflammatory (M1) phenotype compared with macrophages from Hamp^+/+/ Ldlr^-/- mice. THP1 human macrophages treated with an iron chelator were used to model hepcidin deficiency in vitro. Treatment with an iron chelator reduced LPS (lipopolysaccharide)-induced M1 phenotypic expression and decreased uptake of oxidized LDL. Conclusions- In summary, in a hyperlipidemic mouse model, hepcidin deficiency was associated with decreased macrophage iron, a reduced aortic macrophage inflammatory phenotype and protection from atherosclerosis. The results indicate that decreasing hepcidin activity, with the resulting decrease in macrophage iron, may prove to be a novel strategy for the treatment of atherosclerosis.

HDAC9 is implicated in atherosclerotic aortic calcification and affects vascular smooth muscle cell phenotype

Aortic calcification is an important independent predictor of future cardiovascular events. We performed a genome-wide association meta-analysis to determine single nucleotide polymorphisms (SNPs) associated with the extent of abdominal (AAC, n = 9,417) or descending thoracic (TAC, n = 8,422) aortic calcification. Two genetic loci, HDAC9 and RAP1GAP, were associated with AAC at a genome-wide level (P < 5.0 × 10⁻⁸). No SNPs were associated with TAC at the genome-wide threshold. Increased expression of HDAC9 in human aortic smooth muscle cells (HASMCs) promoted calcification and reduced contractility, while inhibition of HDAC9 in HASMCs inhibited calcification and enhanced cell contractility. In matrix Gla protein (MGP)-deficient mice, a model of human vascular calcification, mice lacking HDAC9 had a 40% reduction in aortic calcification and improved survival. This translational genomic study identifies the first genetic risk locus associated with calcification of the abdominal aorta and describes a novel role for HDAC9 in the development of vascular calcification.

Genome-wide analyses identify variants near HDAC9 associated with abdominal aortic calcification and other cardiovascular phenotypes. Functional work shows that HDAC9 promotes an osteogenic vascular smooth muscle cell phenotype, enhancing calcification and reducing contractility.

The Bispectral Index and Induced Hypothermia— Electrocerebral Silence at an Unusually High Temperature

The optimal temperature for deep hypothermic circulatory arrest remains undefined. We present a case in which Bispectral Index monitoring during hypothermic cardiopulmonary bypass showed electrocerebral silence at a higher temperature than previously reported. Bispectral Index monitoring may be a potentially useful tool in surgery employing deep hypothermic circulatory arrest.

Intrinsic anti-inflammatory properties in the serum of two species of deep-diving seal

Weddell and elephant seals are deep-diving mammals, which rely on lung collapse to limit nitrogen absorption and prevent decompression injury. Repeated collapse and re-expansion exposes the lungs to multiple stressors, including ischemia-reperfusion, alveolar shear stress and inflammation. There is no evidence, however, that diving damages pulmonary function in these species. To investigate potential protective strategies in deep-diving seals, we examined the inflammatory response of seal whole blood exposed to lipopolysaccharide (LPS), a potent endotoxin. Interleukin-6 (IL6) cytokine production elicited by LPS exposure was 50 to 500 times lower in blood of healthy northern elephant seals and Weddell seals compared with that of healthy human blood. In contrast to the ∼6× increased production of IL6 protein from LPS-exposed Weddell seal whole blood, isolated Weddell seal peripheral blood mononuclear cells, under standard cell culture conditions using medium supplemented with fetal bovine serum (FBS), produced a robust LPS response (∼300×). Induction of Il6 mRNA expression as well as production of IL6, IL8, IL10, KC-like and TNFα were reduced by substituting FBS with an equivalent amount of autologous seal serum. Weddell seal serum also attenuated the inflammatory response of RAW 267.4 mouse macrophage cells exposed to LPS. Cortisol level and the addition of serum lipids did not impact the cytokine response in cultured cells. These data suggest that seal serum possesses anti-inflammatory properties, which may protect deep divers from naturally occurring inflammatory challenges such as dive-induced hypoxia-reoxygenation and lung collapse.

The association of postoperative pulmonary complications in 109,360 patients with pressure-controlled or volume-controlled ventilation

We thought that the rate of postoperative pulmonary complications might be higher after pressure-controlled ventilation than after volume-controlled ventilation. We analysed peri-operative data recorded for 109,360 adults, whose lungs were mechanically ventilated during surgery at three hospitals in Massachusetts, USA. We used multivariable regression and propensity score matching. Postoperative pulmonary complications were more common after pressure-controlled ventilation, odds ratio (95%CI) 1.29 (1.21-1.37), p < 0.001. Tidal volumes and driving pressures were more varied with pressure-controlled ventilation compared with volume-controlled ventilation: mean (SD) variance from the median 1.61 (1.36) ml.kg^-1 vs. 1.23 (1.11) ml.kg^-1 , p < 0.001; and 3.91 (3.47) cmH₂ O vs. 3.40 (2.69) cmH₂ O, p < 0.001. The odds ratio (95%CI) of pulmonary complications after pressure-controlled ventilation compared with volume-controlled ventilation at positive end-expiratory pressures < 5 cmH₂ O was 1.40 (1.26-1.55) and 1.20 (1.11-1.31) when ≥ 5 cmH₂ O, both p < 0.001, a relative risk ratio of 1.17 (1.03-1.33), p = 0.023. The odds ratio (95%CI) of pulmonary complications after pressure-controlled ventilation compared with volume-controlled ventilation at driving pressures of < 19 cmH₂ O was 1.37 (1.27-1.48), p < 0.001, and 1.16 (1.04-1.30) when ≥ 19 cmH₂ O, p = 0.011, a relative risk ratio of 1.18 (1.07-1.30), p = 0.016. Our data support volume-controlled ventilation during surgery, particularly for patients more likely to suffer postoperative pulmonary complications.

Mice lacking the chromodomain helicase DNA-binding 5 chromatin remodeler display autism-like characteristics

Although autism spectrum disorders (ASDs) share a core set of nosological features, they exhibit substantial genetic heterogeneity. A parsimonious hypothesis posits that dysregulated epigenetic mechanisms represent common pathways in the etiology of ASDs. To investigate this hypothesis, we generated a novel mouse model resulting from brain-specific deletion of chromodomain helicase DNA-binding 5 (Chd5), a chromatin remodeling protein known to regulate neuronal differentiation and a member of a gene family strongly implicated in ASDs. RNA sequencing of Chd5-/- mouse forebrain tissue revealed a preponderance of changes in expression of genes important in cellular development and signaling, sociocommunicative behavior and ASDs. Pyramidal neurons cultured from Chd5-/- cortex displayed alterations in dendritic morphology. Paralleling ASD nosology, Chd5-/- mice exhibited abnormal sociocommunicative behavior and a strong preference for familiarity. Chd5-/- mice further showed deficits in responding to the distress of a conspecific, a mouse homolog of empathy. Thus, dysregulated chromatin remodeling produces a pattern of transcriptional, neuronal and behavioral effects consistent with the presentation of ASDs.

Calcification of Vascular Smooth Muscle Cells and Imaging of Aortic Calcification and Inflammation

Cardiovascular disease is the leading cause of morbidity and mortality in the world. Atherosclerotic plaques, consisting of lipid-laden macrophages and calcification, develop in the coronary arteries, aortic valve, aorta, and peripheral conduit arteries and are the hallmark of cardiovascular disease. In humans, imaging with computed tomography allows for the quantification of vascular calcification; the presence of vascular calcification is a strong predictor of future cardiovascular events. Development of novel therapies in cardiovascular disease relies critically on improving our understanding of the underlying molecular mechanisms of atherosclerosis. Advancing our knowledge of atherosclerotic mechanisms relies on murine and cell-based models. Here, a method for imaging aortic calcification and macrophage infiltration using two spectrally distinct near-infrared fluorescent imaging probes is detailed. Near-infrared fluorescent imaging allows for the ex vivo quantification of calcification and macrophage accumulation in the entire aorta and can be used to further our understanding of the mechanistic relationship between inflammation and calcification in atherosclerosis. Additionally, a method for isolating and culturing animal aortic vascular smooth muscle cells and a protocol for inducing calcification in cultured smooth muscle cells from either murine aortas or from human coronary arteries is described. This in vitro method of modeling vascular calcification can be used to identify and characterize the signaling pathways likely important for the development of vascular disease, in the hopes of discovering novel targets for therapy.

Thiamine as a neuroprotective agent after cardiac arrest

AIMS

Reduction of pyruvate dehydrogenase (PDH) activity in the brain is associated with neurological deficits in animals resuscitated from cardiac arrest. Thiamine is an essential co-factor of PDH. The objective of this study was to examine whether administration of thiamine improves outcomes after cardiac arrest in mice. Secondarily, we aimed to characterize the impact of cardiac arrest on PDH activity in mice and humans.

METHODS

Animal study: Adult mice were subjected to cardiac arrest whereupon cardiopulmonary resuscitation was performed. Thiamine or vehicle was administered 2min before resuscitation and daily thereafter. Mortality, neurological outcome, and metabolic markers were evaluated. Human study: In a convenience sample of post-cardiac arrest patients, we measured serial PDH activity from peripheral blood mononuclear cells and compared them to healthy controls.

RESULTS

Animal study: Mice treated with thiamine had increased 10-day survival (48% versus 17%, P<0.01) and improved neurological function when compared to vehicle-treated mice. In addition, thiamine markedly improved histological brain injury compared to vehicle. The beneficial effects of thiamine were accompanied by improved oxygen consumption in mitochondria, restored thiamine pyrophosphate levels, and increased PDH activity in the brain at 10 days. Human study: Post-cardiac arrest patients had lower PDH activity in mononuclear cells than did healthy volunteers (estimated difference: -5.8O.D./min/mg protein, P<0.001).

CONCLUSIONS

The provision of thiamine after cardiac arrest improved neurological outcome and 10-day survival in mice. PDH activity was markedly depressed in post-cardiac arrest patients suggesting that this pathway may represent a therapeutic target.

Predictive value of serum actin-free Gc-globulin for complications and outcome in acute liver failure

This prospective study was designed to evaluate whether early changes in actin-free Gc-globulin levels were associated with complications and outcomes and to identify factors associated with persistent low actin-free Gc-globulin levels in acute liver failure (ALF). Thirty-two consecutive ALF patients admitted from October 2011 to December 2012 were followed up until death or complete recovery. All had serum actin-free Gc-globulin estimation at admission and at day three or expiry. Logistic regression analysis was performed to identify independent predictors of mortality. A receiver operating characteristic curve analysis was also performed. Nonsurvivors had significantly lower median actin-free Gc-globulin levels than survivors (87.32 vs 180 mg/L; P < 0.001). A receiver operating characteristic curve analysis revealed an area under curve (AUC) of 0.771 and showed that serum actin-free Gc-globulin level of ≤124 mg/L would predict mortality with 92% sensitivity and 71.4% specificity. Patients with lower serum actin-free Gc-globulin levels and decreasing trend in serum actin-free Gc-globulin levels were found to have more mortality and developed more complications. Logistic regression analysis showed that serum actin-free Gc-globulin, total leucocyte count and serum creatinine at admission were independent predictors of mortality. Incorporating these variables, a score predicting mortality risk at admission was derived. The scoring system was compared to MELD score and King's College Criteria as individual predictor of mortality. Serum actin-free Gc-globulin level at presentation is predictive of outcome and can be used for risk stratification. Its persistent low-level predicts mortality and is correlated with various complications.

Bacterial lipoprotein TLR2 agonists broadly modulate endothelial function and coagulation pathways in vitro and in vivo

TLR2 activation induces cellular and organ inflammation and affects lung function. Because deranged endothelial function and coagulation pathways contribute to sepsis-induced organ failure, we studied the effects of bacterial lipoprotein TLR2 agonists, including peptidoglycan-associated lipoprotein, Pam3Cys, and murein lipoprotein, on endothelial function and coagulation pathways in vitro and in vivo. TLR2 agonist treatment induced diverse human endothelial cells to produce IL-6 and IL-8 and to express E-selectin on their surface, including HUVEC, human lung microvascular endothelial cells, and human coronary artery endothelial cells. Treatment of HUVEC with TLR2 agonists caused increased monolayer permeability and had multiple coagulation effects, including increased production of plasminogen activator inhibitor-1 (PAI-1) and tissue factor, as well as decreased production of tissue plasminogen activator and tissue factor pathway inhibitor. TLR2 agonist treatment also increased HUVEC expression of TLR2 itself. Peptidoglycan-associated lipoprotein induced IL-6 production by endothelial cells from wild-type mice but not from TLR2 knockout mice, indicating TLR2 specificity. Mice were challenged with TLR2 agonists, and lungs and plasmas were assessed for markers of leukocyte trafficking and coagulopathy. Wild-type mice, but not TLR2 mice, that were challenged i.v. with TLR2 agonists had increased lung levels of myeloperoxidase and mRNAs for E-selectin, P-selectin, and MCP-1, and they had increased plasma PAI-1 and E-selectin levels. Intratracheally administered TLR2 agonist caused increased lung fibrin levels. These studies show that TLR2 activation by bacterial lipoproteins broadly affects endothelial function and coagulation pathways, suggesting that TLR2 activation contributes in multiple ways to endothelial activation, coagulopathy, and vascular leakage in sepsis.

4-N-pyridin-2-yl-benzamide nanotubes compatible with mouse stem cell and oral delivery in Drosophila

p-aminobenzoic acid (PABA), a structural moiety of many commercial drugs, is self-assembled with linker alkyl side chains to form tubular nanostructures. The tubes exhibited fluorescence either intrinsic or from fluorescent molecules embedded in the wall during self-assembly. Uptake and inter-cellular delivery of the conjugated nanotubes in human cancer cells and in mouse embryonic stem cells were demonstrated by fluorescence imaging and flow cytometry. Biocompatibility, cytotoxicity and clearance were monitored both ex vivo in mouse multipotent embryonic stem cells and in vivo in adult Drosophila. Accumulation of nanotubes had no adverse effects and abnormalities on stem cell morphology and proliferation rate. A distinct distribution of two separate nanotubes in various internal organs of Drosophila interprets that accumulation of nanomaterials might be interdependent on the side chain modifications and physiological settings of cell or tissue types. Unlike carbon nanomaterials, exposure of PABA nanotubes does not produce any hazards including locomotion defects and mortality of adult flies. Despite differential uptake and clearance from multiple live tissues, the use of self-assembled nanotubes can add new dimensions and scope to the development of dual-purpose oral carriers for the fulfilment of many biological promises.

Cross-referral between HIV counselling and testing centres and smear microscopy centres in Tamil Nadu

BACKGROUND

The combined tuberculosis and human immunodeficiency virus (TB-HIV) epidemic demands effective and urgent action.

OBJECTIVE

To assess the effectiveness of the system of referral of TB suspects from the integrated HIV counselling and testing centres (ICTCs) to the designated microscopy centres (DMCs) in Tamil Nadu, and to identify reasons for dropping out.

DESIGN

ICTC counsellors identified TB suspects among clients (excluding pregnant women and children) in six districts of Tamil Nadu in 2007 and referred them to DMCs, irrespective of their HIV status. From the records at ICTCs and DMCs, we collected information on the number of referrals to the DMCs, TB suspects attending DMCs and smear-positive TB cases with or without HIV. Clients who did not attend the DMCs were interviewed to elicit reasons for dropping out.

RESULTS

Of 18329 clients counselled, 1065 (6%) were identified as TB suspects and referred to DMCs. Of these, 888 (83%) attended and 177 (17%) dropped out; 81% of the drop-outs were interviewed. Reasons for dropping out were multiple: 51% were due to the health system, 62% due to the disease and 62% due to personal reasons. Twelve per cent of DMC attendees were smear-positive.

CONCLUSION

The ICTC-to-DMC referral system makes a significant contribution to the detection of TB cases. Reasons for dropping out were multiple, but are correctable. This study also probes into current policies on programme coordination and recommends strategies for strengthening the collaboration between the TB and HIV programmes.

Activation of Toll-like receptor 2 impairs hypoxic pulmonary vasoconstriction in mice

Toll-like receptors (TLRs) mediate inflammation in sepsis, but their role in sepsis-induced respiratory failure is unknown. Hypoxic pulmonary vasoconstriction (HPV) is a unique vasoconstrictor response that diverts blood flow away from poorly ventilated lung regions. HPV is impaired in sepsis and after challenge with the TLR4 agonist lipopolysaccharide (LPS). Unlike TLR4 agonists, which are present only in Gram-negative bacteria, TLR2 agonists are ubiquitously expressed in all of the major classes of microorganisms that cause sepsis, including both Gram-positive and Gram-negative bacteria and fungi. We tested the hypothesis that (S)-[2,3-bis(palmitoyloxy)-(2RS)-propyl]-N-palmitoyl-(R)-Cys-(S)-Ser(S)-Lys(4)-OH, trihydrochloride (Pam3Cys), a TLR2 agonist, impairs HPV and compared selected pulmonary and systemic effects of Pam3Cys vs. LPS. HPV was assessed 22 h after challenge with saline, Pam3Cys, or LPS by measuring the increase in the pulmonary vascular resistance of the left lung before and during left lung alveolar hypoxia produced by left mainstem bronchus occlusion (LMBO). Additional endpoints included arterial blood gases during LMBO, hemodynamic parameters, weight loss, temperature, physical appearance, and several markers of lung inflammation. Compared with saline, challenge with Pam3Cys caused profound impairment of HPV, reduced systemic arterial oxygenation during LMBO, weight loss, leukopenia, and lung inflammation. In addition to these effects, LPS-challenged mice had lower rectal temperatures, metabolic acidosis, and were more ill appearing than Pam3Cys-challenged mice. These data indicate that TLR2 activation impairs HPV and induces deleterious systemic effects in mice and suggest that TLR2 pathways may be important in sepsis-induced respiratory failure.

MyD88-dependent immune activation mediated by human immunodeficiency virus type 1-encoded Toll-like receptor ligands

Immune activation is a major characteristic of human immunodeficiency virus type 1 (HIV-1) infection and a strong prognostic factor for HIV-1 disease progression. The underlying mechanisms leading to immune activation in viremic HIV-1 infection, however, are not fully understood. Here we show that, following the initiation of highly active antiretroviral therapy, the immediate decline of immune activation is closely associated with the reduction of HIV-1 viremia, which suggests a direct contribution of HIV-1 itself to immune activation. To propose a mechanism, we demonstrate that the single-stranded RNA of HIV-1 encodes multiple uridine-rich Toll-like receptor 7/8 (TLR7/8) ligands that induce strong MyD88-dependent plasmacytoid dendritic cell and monocyte activation, as well as accessory cell-dependent T-cell activation. HIV-1-encoded TLR ligands may, therefore, directly contribute to the immune activation observed during viremic HIV-1 infection. These data provide an initial rationale for inhibiting the TLR pathway to directly reduce the chronic immune activation induced by HIV-1 and the associated immune pathogenesis.

Toll-like receptor 2 activation by bacterial peptidoglycan-associated lipoprotein activates cardiomyocyte inflammation and contractile dysfunction

OBJECTIVE

Although cardiac dysfunction plays an important role in the pathogenesis of sepsis, the mechanisms that underlie cardiac dysfunction in sepsis remain poorly understood. Bacterial peptidoglycan-associated lipoprotein (PAL), an outer-membrane protein of Gram-negative bacteria, was recently found to be released into the bloodstream in sepsis and to cause inflammation and death in mice. The present studies assessed the effects of PAL on cardiomyocyte function and its signal transduction in cardiomyocytes.

DESIGN

Randomized prospective animal study.

SETTING

Research laboratory.

SUBJECTS

Male C57BL/6 mice, B6;129S-Tnfrsf1a(tm1Imx) Tnfrsf1b(tm1Imx)/J knockout mice, Toll-like receptor 2 (TLR2) knockout mice, and myeloid differentiation factor 88 (MyD88) knockout mice.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Immunohistochemical staining and immunoblot analysis indicated that intravenously injected PAL bound to myocardium. Injection of PAL decreased cardiac function in vivo. Challenge with PAL altered cell shortening and Ca2+ transients in isolated mouse cardiomyocytes but not in cardiomyocytes isolated from TLR2 -/- and MyD88 -/- mice. Cytokine profiling arrays demonstrated that tumor necrosis factor-alpha (TNFalpha), granulocyte colony-stimulating factor, and interferon-gamma-production were elevated in PAL-treated cardiomyocytes. Increased TNFalpha production was abolished in MyD88 -/- cardiomyocytes but restored by adenovirally mediated expression of MyD88. PAL did not affect cell shortening and Ca2+ cycling in cardiomyocytes obtained from mice deficient for TNFalpha receptor (TNFR) 1 and TNFR2 (TNFR1/2 -/-).

CONCLUSION

Our data reveal that PAL uses the TLR2/MyD88 signaling cascade to induce cardiomyocyte dysfunction and inflammatory responses and that TNFalpha is a major mediator of PAL-induced dysfunction in cardiomyocytes. These studies suggest that circulating PAL and other TLR2 agonists may contribute to cardiac dysfunction in sepsis.

Passive immunization to outer membrane proteins MLP and PAL does not protect mice from sepsis

Multiple older studies report that immunoglobulin directed to rough mutant bacteria, such as E. coli J5, provides broad protection against challenge with heterologous strains of Gram-negative bacteria. This protection was initially believed to occur through binding of immunoglobulin to bacterial lipopolysaccharide (LPS). However, hundreds of millions of dollars have been invested in attempting to develop clinically-effective anti-LPS monoclonal antibodies without success, and no study has shown that IgG from this antiserum binds LPS. Identification of the protective mechanism would facilitate development of broadly protective human monoclonal antibodies for treating sepsis. IgG from this antiserum binds 2 bacterial outer membrane proteins: murein lipoprotein (MLP) and peptidoglycan-associated lipoprotein (PAL). Both of these outer membrane proteins are highly conserved, have lipid domains that are anchored in the bacterial membrane, are shed from bacteria in blebs together with LPS, and activate cells through Toll-like receptor 2. Our goal in the current work was to determine if passive immunization directed to MLP and PAL protects mice from Gram-negative sepsis. Neither monoclonal nor polyclonal IgG directed to MLP or PAL conferred survival protection in 3 different models of sepsis: cecal ligation and puncture, an infected burn model, and an infected fibrin clot model mimicking peritonitis. Our results are not supportive of the hypothesis that either anti-MLP or anti-PAL IgG are the protective antibodies in the previously described anti-rough mutant bacterial antisera. These studies suggest that a different mechanism of protection is involved.

MyD88-dependent and MyD88-independent pathways in synergy, priming, and tolerance between TLR agonists

TLRs sense components of microorganisms and are critical host mediators of inflammation during infection. Different TLR agonists can profoundly alter inflammatory effects of one another, and studies suggest that the sequence of exposure to TLR agonists may importantly impact on responses during infection. We tested the hypothesis that synergy, priming, and tolerance between TLR agonists follow a pattern that can be predicted based on differential engagement of the MyD88-dependent (D) and the MyD88-independent (I) intracellular signaling pathways. Inflammatory effects of combinations of D and I pathway agonists were quantified in vivo and in vitro. Experiments used several D-specific agonists, an I-specific agonist (poly(I:C)), and LPS, which acts through both the D and I pathways. D-specific agonists included: peptidoglycan-associated lipoprotein, Pam3Cys, flagellin, and CpG DNA, which act through TLR2 (peptidoglycan-associated lipoprotein and Pam3Cys), TLR5, and TLR9, respectively. D and I agonists were markedly synergistic in inducing cytokine production in vivo in mice. All of the D-specific agonists were synergistic with poly(I:C) in vitro in inducing TNF and IL-6 production by mouse bone marrow-derived macrophages. Pretreatment of bone marrow-derived macrophages with poly(I:C) led to a primed response to subsequent D-specific agonists and vice versa, as indicated by increased cytokine production, and increased NF-kappaB translocation. Pretreatment with a D-specific agonist augmented LPS-induced IFN-beta production. All D-specific agonists induced tolerance to one another. Thus, under the conditions studied here, simultaneous and sequential activation of both the D and I pathways causes synergy and priming, respectively, and tolerance is induced by agonists that act through the same pathway.

Passive immunization to outer membrane proteins MLP and PAL does not protect mice from sepsis

Multiple older studies report that immunoglobulin directed to rough mutant bacteria, such as E. coli J5, provides broad protection against challenge with heterologous strains of Gram-negative bacteria. This protection was initially believed to occur through binding of immunoglobulin to bacterial lipopolysaccharide (LPS). However, hundreds of millions of dollars have been invested in attempting to develop clinically-effective anti-LPS monoclonal antibodies without success, and no study has shown that IgG from this antiserum binds LPS. Identification of the protective mechanism would facilitate development of broadly protective human monoclonal antibodies for treating sepsis. IgG from this antiserum binds 2 bacterial outer membrane proteins: murein lipoprotein (MLP) and peptidoglycan-associated lipoprotein (PAL). Both of these outer membrane proteins are highly conserved, have lipid domains that are anchored in the bacterial membrane, are shed from bacteria in blebs together with LPS, and activate cells through Toll-like receptor 2. Our goal in the current work was to determine if passive immunization directed to MLP and PAL protects mice from Gram-negative sepsis. Neither monoclonal nor polyclonal IgG directed to MLP or PAL conferred survival protection in 3 different models of sepsis: cecal ligation and puncture, an infected burn model, and an infected fibrin clot model mimicking peritonitis. Our results are not supportive of the hypothesis that either anti-MLP or anti-PAL IgG are the protective antibodies in the previously described anti-rough mutant bacterial antisera. These studies suggest that a different mechanism of protection is involved.

Bacterial peptidoglycan-associated lipoprotein: a naturally occurring toll-like receptor 2 agonist that is shed into serum and has synergy with lipopolysaccharide

Sepsis is initiated by interactions between microbial products and host inflammatory cells. Toll-like receptors (TLRs) are central innate immune mediators of sepsis that recognize different components of microorganisms. Peptidoglycan-associated lipoprotein (PAL) is a ubiquitous gram-negative bacterial outer-membrane protein that is shed by bacteria into the circulation of septic animals. We explored the inflammatory effects of purified PAL and of a naturally occurring form of PAL that is shed into serum. PAL is released into human serum by Escherichia coli bacteria in a form that induces cytokine production by macrophages and is tightly associated with lipopolysaccharide (LPS). PAL activates inflammation through TLR2. PAL and LPS synergistically activate macrophages. These data suggest that PAL may play an important role in the pathogenesis of sepsis and imply that physiologically relevant PAL and LPS are shed into serum and act in concert to initiate inflammation in sepsis.

Characterization of a retrotransposon-like element from Entamoeba histolytica

The protozoan parasite Entamoeba histolytica is the causative agent of amoebiasis. The genome organization of this organism is not well understood. We had earlier reported the presence of a multicopy sequence, HMc, in E. histolytica. Subsequent analysis showed that HMc is a member of a retrotransposon family that we have named the E. histolytica retrotransposon-like element (EhRLE). Four other members of this family have been characterized. The EhRLE family is distributed across all chromosomes of the parasite. There are 140 copies, which show minor sequence variation with respect to one another (2--4% from the consensus sequence). From a sequence analysis of five members of the EhRLE family, the complete EhRLE unit is estimated to be 4086 bp in length. It has a 27-mer inverted repeat at its ends. A pairwise comparison with sequences in the database showed a highly significant match of a part of EhRLE with reverse transcriptases (RT), especially those encoded by non-long terminal repeat retrotransposons. There are stop codons in all the five EhRLEs, but a continuous open reading frame of 464 amino acids could be reconstructed by comparing the sequences of several EhRLEs. The reconstructed sequence showed a much better identity with RT as compared with any of the original EhRLE sequences. The non-pathogenic species, Entamoeba dispar, also contains this element, with 85% sequence identity with EhRLE. The data suggest that EhRLE may be a retrotransposon, but many of its members are probably nonfunctional due to the accumulation of mutations.

The genome of Entamoeba histolytica

Estimation of genome size of Entamoeba histolytica by different methods has failed to give comparable values due to the inherent complexities of the organism, such as the uncertain level of ploidy, presence of multinucleated cells and a poorly demarcated cell division cycle. The genome of E. histolytica has a low G+C content (22.4%), and is composed of both linear chromosomes and a number of circular plasmid-like molecules. The rRNA genes are located exclusively on some of the circular DNAs. Karyotype analysis by pulsed field gel electrophoresis suggests the presence of 14 conserved linkage groups and an extensive size variation between homologous chromosomes from different isolates. Several repeat families have been identified, some of which have been shown to be present in all the electrophoretically separated chromosomes. The typical nucleosomal structure has not been demonstrated, though most of the histone genes have been identified. Most Entamoeba genes lack introns, have short 3' and 5' untranslated regions, and are tightly packed. Promoter analysis revealed the presence of three conserved motifs and several upstream regulatory elements. Unlike typical eukaryotes, the transcription of protein coding genes is alpha-amanitin resistant. Expressed Sequence Tag analysis has identified a group of highly abundant polyadenylated RNAs which are unlikely to be translated. The Expressed Sequence Tag approach has also helped identify several important genes which encode proteins that may be involved in different biochemical pathways, signal transduction mechanisms and organellar functions.

Lack of a chromosomal copy of the circular rDNA plasmid of Entamoeba histolytica

A number of small circular DNAs constitute a part of the genome of Entamoeba histolytica. Among them, the 24.5 kb circular DNA encoding rRNA (EhR1) is the most abundant. Pulsed field gel electrophoresis was used to determine if a chromosomal copy of EhR1 exists and what fraction of the total genome is circular. The results show that the chromosomes of E. histolytica are linear, and that no copy of EhR1 could be detected in any of the linear chromosomes.