Manipulations of core temperatures in ischemia-reperfusion lung injury in rabbits

Design and rationale of the CHILL phase II trial of hypothermia and neuromuscular blockade for acute respiratory distress syndrome

The Cooling to Help Injured Lungs (CHILL) trial is an open label, two group, parallel design multicenter, randomized phase IIB clinical trial assessing the efficacy and safety of targeted temperature management with combined external cooling and neuromuscular blockade to block shivering in patients with early moderate-severe acute respiratory distress syndrome (ARDS). This report provides the background and rationale for the clinical trial and outlines the methods using the Consolidated Standards of Reporting Trials guidelines. Key design challenges include: [1] protocolizing important co-interventions; [2] incorporation of patients with COVID-19 as the cause of ARDS; [3] inability to blind the investigators; and [4] ability to obtain timely informed consent from patients or legally authorized representatives early in the disease process. Results of the Reevaluation of Systemic Early Neuromuscular Blockade (ROSE) trial informed the decision to mandate sedation and neuromuscular blockade only in the group assigned to therapeutic hypothermia and proceed without this mandate in the control group assigned to a usual temperature management protocol. Previous trials conducted in National Heart, Lung, and Blood Institute ARDS Clinical Trials (ARDSNet) and Prevention and Early Treatment of Acute Lung Injury (PETAL) Networks informed ventilator management, ventilation liberation and fluid management protocols. Since ARDS due to COVID-19 is a common cause of ARDS during pandemic surges and shares many features with ARDS from other causes, patients with ARDS due to COVID-19 are included. Finally, a stepwise approach to obtaining informed consent prior to documenting critical hypoxemia was adopted to facilitate enrollment and reduce the number of candidates excluded because eligibility time window expiration.

Expression profiling of microRNAs in lipopolysaccharide-induced acute lung injury after hypothermia treatment

We investigated the expression profiles of miRNAs in acute lung injury (ALI) rats after hypothermia treatment. ALI rats were induced with lipopolysaccharide (LPS) and maintained with hypothermia (HT) or normothermia (NT) for 6 hours. HT attenuated inflammatory cell infiltration in the lung and improved biochemical indicators of multi-organ dysfunction. Nineteen miRNAs were significantly differentially expressed in the HT group compared with the NT group. miR-142, miR-98, miR-541, miR-503, miR-653, miR- 223, miR-323 and miR-196b exhibited opposite patterns of expression between the two groups. These dysregulated miRNAs were mainly involved in the immune and inflammatory response on functional annotation analyses. This study shows that HT has lung protective effects and influences expression profiles of miRNAs in ALI. And dysregulated miRNAs after HT modulate the immune and inflammation in ALI. These results suggest that dysregulated miRNAs play a role in the mechanism of the lung protective effects of HT in ALI.

Extracranial hypothermia during cardiac arrest and cardiopulmonary resuscitation is neuroprotective in vivo

There is increasing evidence that ischemic brain injury is modulated by peripheral signaling. Peripheral organ ischemia can induce brain inflammation and injury. We therefore hypothesized that brain injury sustained after cardiac arrest (CA) is influenced by peripheral organ ischemia and that peripheral organ protection can reduce brain injury after CA and cardiopulmonary resuscitation (CPR). Male C57Bl/6 mice were subjected to CA/CPR. Brain temperature was maintained at 37.5°C ± 0.0°C in all animals. Body temperature was maintained at 35.1°C ± 0.1°C (normothermia) or 28.8°C ± 1.5°C (extracranial hypothermia [ExHy]) during CA. Body temperature after resuscitation was maintained at 35°C in all animals. Behavioral testing was performed at 1, 3, 5, and 7 days after CA/CPR. Either 3 or 7 days after CA/CPR, blood was analyzed for serum urea nitrogen, creatinine, alanine aminotransferase, aspartate aminotransferase, and interleukin-1β; mice were euthanized; and brains were sectioned. CA/CPR caused peripheral organ and brain injury. ExHy animals experienced transient reduction in brain temperature after resuscitation (2.1°C ± 0.5°C for 4 minutes). Surprisingly, ExHy did not change peripheral organ damage. In contrast, hippocampal injury was reduced at 3 days after CA/CPR in ExHy animals (22.4% ± 6.2% vs. 45.7% ± 9.1%, p=0.04, n=15/group). This study has two main findings. Hypothermia limited to CA does not reduce peripheral organ injury. This unexpected finding suggests that after brief ischemia, such as during CA/CPR, signaling or events after reperfusion may be more injurious than those during the ischemic period. Second, peripheral organ hypothermia during CA reduces hippocampal injury independent of peripheral organ protection. While it is possible that this protection is due to subtle differences in brain temperature during early reperfusion, we speculate that additional mechanisms may be involved. Our findings add to the growing understanding of brain-body cross-talk by suggesting that peripheral interventions can protect the brain even if peripheral organ injury is not altered.

Effect of therapeutic hypothermia on gas exchange and respiratory mechanics: a retrospective cohort study

Targeted temperature management (TTM) may improve respiratory mechanics and lung inflammation in acute respiratory distress syndrome (ARDS) based on animal and limited human studies. We aimed to assess the pulmonary effects of TTM in patients with respiratory failure following cardiac arrest. Retrospective review of consecutive cardiac arrest cases occurring out of hospital or within 24 hours of hospital admission (2002-2012). Those receiving TTM (n=44) were compared with those who did not (n=42), but required mechanical ventilation (MV) for at least 4 days following the arrest. There were no between-group differences in age, gender, body mass index, APACHE II, or fluid balance during the study period. The TTM group had lower ejection fraction, Glasgow Coma Score, and more frequent use of paralytics. Matched data analyses (change at day 4 compared with baseline of the individual subject) showed favorable, but not statistically significant trends in respiratory mechanics endpoints (airway pressure, compliance, tidal volume, and PaO2/FiO2) in the TTM group. The PaCO2 decreased significantly more in the TTM group, as compared with controls (-12 vs. -5 mmHg, p=0.02). For clinical outcomes, the TTM group consistently, although not significantly, did better in survival (59% vs. 43%) and hospital length of stay (12 vs. 15 days). The MV duration and Cerebral Performance Category score on discharge were significantly lower in the TTM group (7.3 vs. 10.7 days, p=0.04 and 3.2 vs. 4, p=0.01). This small retrospective cohort suggests that the effect of TTM ranges from equivalent to favorable, compared with controls, for the specific respiratory and clinical outcomes in patients with respiratory failure following cardiac arrest.

Autologous transplantation of adipose-derived mesenchymal stem cells markedly reduced acute ischemia-reperfusion lung injury in a rodent model

Background

This study tested the hypothesis that autologous transplantation of adipose-derived mesenchymal stem cells (ADMSCs) can effectively attenuate acute pulmonary ischemia-reperfusion (IR) injury.

Methods

Adult male Sprague-Dawley (SD) rats (n = 24) were equally randomized into group 1 (sham control), group 2 (IR plus culture medium only), and group 3 (IR plus intravenous transplantation of 1.5 × 10⁶ autologous ADMSCs at 1h, 6h, and 24h following IR injury). The duration of ischemia was 30 minutes, followed by 72 hours of reperfusion prior to sacrificing the animals. Blood samples were collected and lungs were harvested for analysis.

Results

Blood gas analysis showed that oxygen saturation (%) was remarkably lower, whereas right ventricular systolic pressure was notably higher in group 2 than in group 3 (all p < 0.03). Histological scoring of lung parenchymal damage was notably higher in group 2 than in group 3 (all p < 0.001). Real time-PCR demonstrated remarkably higher expressions of oxidative stress, as well as inflammatory and apoptotic biomarkers in group 2 compared with group 3 (all p < 0.005). Western blot showed that vascular cell adhesion molecule (VCAM)-1, intercellular adhesion molecule (ICAM)-1, oxidative stress, tumor necrosis factor-α and nuclear factor-κB were remarkably higher, whereas NAD(P)H quinone oxidoreductase 1 and heme oxygenase-1 activities were lower in group 2 compared to those in group 3 (all p < 0.004). Immunofluorescent staining demonstrated notably higher number of CD68+ cells, but significantly fewer CD31+ and vWF+ cells in group 2 than in group 3.

Conclusion

ADMSC therapy minimized lung damage after IR injury in a rodent model through suppressing oxidative stress and inflammatory reaction.

Pretreatment with edaravone reduces lung mitochondrial damage in an infant rabbit ischemia-reperfusion model

PURPOSE

Free radical scavenger edaravone has been approved as a new drug for treatment of stroke patients. The purpose of this study was to examine whether pretreatment with edaravone could attenuate ischemia-reperfusion (IR)-induced lung damage in infant rabbits.

METHODS

New Zealand White rabbits (Experimental Animal Center, Nanjing Medical University, Nanjing, China) at age from 15 to 21 days were subjected to sham operation, IR, or edaravone plus IR. Ischemia/reperfusion was induced by clamping the right pulmonary hilum for 1 hour and then removal of the clamp for 4 hours. Edaravone (1 mg/kg, intravenous) was given 5 minutes before ischemia. Concentrations of reactive oxygen species-hydroxyl radical (ROS-HR) and malondialdehyde (MDA), and activities of glutathione peroxidase (GSH-PX) and superoxide dismutase (SOD) in the lung tissue were measured. Mitochondrial membrane potential, swelling rate, and ultrastructure of the lung were analyzed, and histologic condition of the lung was evaluated.

RESULTS

Edaravone pretreatment reduced markedly the productions of ROS-HR and MDA and increased the activities of GSH-PX and SOD. It attenuated both IR-induced decrease in mitochondrial membrane potential from 60% to 14% and IR-induced increase in mitochondrial swelling. As results, the mitochondrial and lung tissue damages were less, leading to an improved survival rate in IR rabbits pretreated with edaravone compared with IR rabbits without the treatment.

CONCLUSION

Edaravone pretreatment reduces the IR-induced lung mitochondrial damage in infant rabbits.