Fast therapeutic hypothermia prevents post-cardiac arrest syndrome through cyclophilin D-mediated mitochondrial permeability transition inhibition.

The opening of the mitochondrial permeability transition pore (PTP), which is regulated by the matrix protein cyclophilin D (CypD), plays a key role in the pathophysiology of post-cardiac arrest (CA) syndrome. We hypothesized that therapeutic hypothermia could prevent post-CA syndrome through a CypD-mediated PTP inhibition in both heart and brain. In addition, we investigated whether specific pharmacological PTP inhibition would confer additive protection to cooling. Adult male New Zealand White rabbits underwent 15 min of CA followed by 120 min of reperfusion. Five groups (n = 10-15/group) were studied: control group (CA only), hypothermia group (HT, hypothermia at 32-34 °C induced by external cooling at reperfusion), NIM group (injection at reperfusion of 2.5 mg/kg NIM811, a specific CypD inhibitor), HT + NIM, and sham group. The following measurements were taken: hemodynamics, echocardiography, and cellular damage markers (including S100ß protein and troponin Ic). Oxidative phosphorylation and PTP opening were assessed on mitochondria isolated from both brain and heart. Acetylation of CypD was measured by immunoprecipitation in both the cerebral cortex and myocardium. Hypothermia and NIM811 significantly prevented cardiovascular dysfunction, pupillary areflexia, and early tissue damage. Hypothermia and NIM811 preserved oxidative phosphorylation, limited PTP opening in both brain and heart mitochondria and prevented increase in CypD acetylation in brain. There were no additive beneficial effects in the combination of NIM811 and therapeutic hypothermia. In conclusion, therapeutic hypothermia limited post-CA syndrome by preventing mitochondrial permeability transition mainly through a CypD-dependent mechanism.

Reassessment of mitochondrial cyclophilin D as a target for improving cardiac arrest outcomes in the era of therapeutic hypothermia.

Uncertainty exists regarding whether cyclophilin D (CypD), a mitochondrial matrix protein that plays a key role in ischemia-reperfusion injury, can be a pharmacological target for improving outcomes after cardiac arrest (CA), especially when therapeutic hypothermia is used. Using CypD knockout mice (CypD-/-), we investigated the effects of loss of CypD on short-term and medium-term outcomes after CA. CypD-/- mice or their wild-type (WT) littermates underwent either 5 minute CA followed by resuscitation with and/or without hypothermia at 33°C-34°C (targeted temperature reached within minutes after resuscitation), or a sham procedure. Brain and cardiac injury were assessed using echocardiography, neurological scores, MRI and biomarkers. Seven day survival was compared using Kaplan-Meier estimates. The rate of restoration of spontaneous circulation was significantly higher in CypD-/- mice (with shorter cardiac massage duration) than in WT mice (P < 0.05). Loss of CypD significantly attenuated CA-induced release of troponin and S100ß protein, and limited myocardial dysfunction at 150 minutes after CA. Loss of CypD combined with hypothermia led to the best neurological and MRI scores at 24 hours and highest survival rates at 7 days compared to other groups (P < 0.05). In animals successfully resuscitated, loss of CypD had no benefits on day 7 survival while hypothermia was highly protective. Pharmacological inhibition of CypD with cyclosporine A combined with hypothermia provided similar day 7 survival than loss of CypD combined with hypothermia. CypD is a viable target to improve success of cardiopulmonary resuscitation but its inhibition is unlikely to improve long-term outcomes, unless therapeutic hypothermia is associated.

Therapeutic Hypothermia After Cardiac Arrest: Involvement of the Risk Pathway in Mitochondrial PTP-Mediated Neuroprotection.

Therapeutic hypothermia is neuroprotective after cardiac arrest (CA) via poorly understood mechanisms. It may prevent mitochondrial permeability transition pore (PTP) opening, an event which plays a pivotal role in ischemia-reperfusion injury. PTP is the main end-effector of the reperfusion injury salvage kinase (RISK) signaling pathway. We hypothesized that therapeutic hypothermia activates the RISK pathway, thereby preventing PTP opening and its deleterious neurological consequences after CA. Four groups of New Zealand White rabbits were subjected to 15 min of CA and 120 min of reperfusion: Control, HT (hypothermia at 32°-34°C), NIM (specific PTP inhibition with N-methyl-4-isoleucine-cyclosporine at the onset of reperfusion), and HT+NIM. A Sham group only underwent surgery. The following measurements were taken: pupillary reflexes and brain damage biomarkers (NSE and S100ß), RISK pathway activation in brain cortex (total and phosphorylated forms of both protein kinase B [Akt] and extracellular signal-regulated kinase [ERK]) and PTP opening in isolated brain mitochondria. Therapeutic hypothermia and pharmacological PTP inhibition preserved the pupillary reflexes and prevented the increase in both NSE and S100ß (P < 0.05 vs. controls). These two interventions also enhanced (P < 0.05 vs. controls) the phospho-Akt/Akt ratio to a similar extent while preventing a CA-induced increase in phospho-ERK/ERK ratio. This Akt activation in the HT and NIM groups was associated with an attenuation of CA-induced PTP opening. In this model, therapeutic hypothermia promoted the activation of the RISK signaling pathway via Akt and limited CA-induced brain injury by preventing PTP opening.

Cirrhotic Patients Admitted to the ICU With Septic Shock: Factors Predicting Short and Long-Term Outcome.

Cirrhotic patients with septic shock have a poor prognosis in ICU compared to general population of critically ill patients. Little is known about long-term outcome in these patients. We performed a retrospective analysis of a prospective cohort of cirrhotic patients with septic shock. The aim of this study was to describe both short and long-term outcomes and to evaluate factors predicting mortality. Data from 149 patients were analyzed (mean age: 60 ±â€Š11 years, sex ratio: 2.4). Mortality rate in the ICU was 54% and at 1 year it was 73%. Among factors associated with adverse outcome, independent factors predicting ICU mortality were early need for renal replacement therapy (odds ratios, OR 13.95, 95% confidence interval, CI 3.30; 59.03) and arterial lactate >5 mmol.L (OR 7.27, 95% CI 2.92; 18.10), and early use of mechanical ventilation (OR 3.05, 95% CI 1.08; 8.58). For 1-year mortality, independent prognostic factors were the need for renal replacement therapy during ICU stay (OR 9.60, 95% CI 2.90; 31.82), prothrombin time ≤40% (OR 3.47, 95% CI 1.43; 8.43), and Charlson score (OR 1.36 per point, 95% CI 1.11; 1.67). The results emphasize the poor prognosis of cirrhotic patients with septic shock admitted to the ICU. The need for organ supports appears to be a better predictor of short-term outcome than the underlying hepatic disease. Renal replacement therapy is associated with both short and long-term outcomes.

Short- and long-term outcomes in onco-hematological patients admitted to the intensive care unit with classic factors of poor prognosis.

Although the overall mortality of patients admitted to intensive care units (ICU) with hematological malignancy has decreased over the years, some groups of patients still have low survival rates. We performed a monocentric retrospective study including all patients with hematological malignancy in a ten-year period, to identify factors related to the outcome for the whole cohort and for patients with allogeneic hematopoietic stem cell transplantation (HSCT), neutropenia, or those requiring invasive mechanical ventilation (IMV). A total of 418 patients with acute leukemia (n=239; 57%), myeloma (n=69; 17%), and lymphoma (n=53; 13%) were studied. Day-28 and 1-year mortality were 49% and 72%, respectively. The type of disease was not associated with outcome. The disease status was independentlty associated with 1-year mortality only. Independent predictors of day-28 mortality were IMV, renal replacement therapy (RRT), and performance status. For allogeneic HSCT recipients (n=116), neutropenic patients (n=124) and patients requiring IMV (n=196), day-28 and 1-year mortality were 52%, 54%, 74% and 81%, 78%, 87%, respectively. Multivariate analysis showed that IMV and RRT for allogeneic HSCT recipients, performance status and IMV for neutropenic patients, and RRT for patients requiring IMV were independently associated with short-term mortality (p<0.05).These results suggest that IMV is the strongest predictor of mortality in hematological patients admitted to ICUs, whereas allogeneic HSCT and neutropenia do not worsen their short-term outcome.

Minor Changes in Core Temperature Prior to Cardiac Arrest Influence Outcomes: An Experimental Study.

AIM: To investigate whether slight variations in core temperature prior to cardiac arrest (CA) influence short-term outcomes and mitochondrial functions. METHODS AND MATERIALS: Three groups of New Zealand White rabbits (n = 12/group) were submitted to 15 minutes of CA at 38°C (T-38 group), 39°C (T-39), or 40°C (T 40) and 120 minutes of reperfusion. A Sham-operated group (n = 6) underwent only surgery. Restoration of spontaneous circulation (ROSC), survival, hemodynamics, and pupillary reactivity were recorded. Animals surviving to the end of the observation period were euthanized to assess fresh brain and heart mitochondrial functions (permeability transition and oxidative phosphorylation). Markers of brain and heart damages were also measured. RESULTS: The duration of asphyxia required to induce CA was significantly lower in the T-40 group when compared to the T-38 group (P < .05). The rate of ROSC was >80% in all groups (P = nonsignificant [ns]). Survival significantly differed among the T-38, T-39, and T-40 groups: 10 (83%) of 12, 7 (58%) of 12, and 4 (33%) of 12, respectively (log-rank test, P = .027). At the end of the protocol, none of the animals in the T-40 group had pupillary reflexes compared to 8 (67%) of 12 in the T-38 group (P < .05). Troponin and protein S100B were significantly higher in the T-40 versus T-38 group (P < .05). Cardiac arrest significantly impaired both inner mitochondrial membrane integrity and oxidative phosphorylation in all groups. Brain mitochondria disorders were significantly more severe in the T-40 group compared to the T-38 group (P < .05). CONCLUSION: Small changes in body temperature prior to asphyxial CA significantly influence brain mitochondrial functions and short-term outcomes in rabbits.

Ubiquitous protective effects of cyclosporine A in preventing cardiac arrest-induced multiple organ failure.

Opening of the mitochondrial permeability transition pore (mPTP) appears to be a pivotal event in myocardial ischemia-reperfusion (I/R) injury. Resuscitated cardiac arrest (CA) leads to the post-CA syndrome that encompasses, not only myocardial dysfunction, but also brain injury, failure of other organs (kidney, liver, or lung), and systemic response to I/R. We aimed to determine whether cyclosporine A (CsA) might prevent multiple organ failure following CA through a ubiquitous mPTP inhibition in each distant vital organ. Anesthetized New Zealand White rabbits were subjected to 15 min of CA and 120 min of reperfusion. At the onset of resuscitation, the rabbits received CsA, its non-immunosuppressive derivative NIM811, or vehicle (controls). Survival, hemodynamics, brain damage, organ injuries, and systemic I/R response were analyzed. Fresh mitochondria were isolated from the brain, heart, kidney, liver, and lung to assess both oxidative phosphorylation and permeability transition. CsA analogs significantly improved short-term survival and prevented multiple organ failure, including brain damage and myocardial dysfunction (P < 0.05 vs. controls). Susceptibility of mPTP opening was significantly increased in heart, brain, kidney, and liver mitochondria isolated from controls, while mitochondrial respiration was impaired (P < 0.05 vs. sham). CsA analogs prevented these mitochondrial dysfunctions (P < 0.05 vs. controls). These results suggest that CsA and NIM811 can prevent the post-CA syndrome through a ubiquitous mitochondrial protective effect at the level of each major distant organ.