Human NKG2E is expressed and forms an intracytoplasmic complex with CD94 and DAP12.

The NKG2 family of NK receptors includes activating and inhibitory members. With the exception of the homodimer-forming NKG2D, NKG2 receptors recognize the nonclassical MHC class I molecule HLA-E, and they can be subdivided into two groups: those that associate with and signal through DAP12 to activate cells, and those that contain an ITIM motif to promote inhibition. The function of NKG2 family member NKG2E is unclear in humans, and its surface expression has never been conclusively established, largely because there is no Ab that binds specifically to NKG2E. Seeking to determine a role for this molecule, we chose to investigate its expression and ability to form complexes with intracellular signaling molecules. We found that NKG2E was capable of associating with CD94 and DAP12 but that the complex was retained intracellularly at the endoplasmic reticulum instead of being expressed on cell surfaces, and that this localization was dependent on a sequence of hydrophobic amino acids in the extracellular domain of NKG2E. Because this particular sequence has emerged and been conserved selectively among higher order primates evolutionarily, this observation raises the intriguing possibility that NKG2E may function as an intracellular protein.

Reprogramming of CTLs into natural killer-like cells in celiac disease.

Celiac disease is an intestinal inflammatory disorder induced by dietary gluten in genetically susceptible individuals. The mechanisms underlying the massive expansion of interferon gamma-producing intraepithelial cytotoxic T lymphocytes (CTLs) and the destruction of the epithelial cells lining the small intestine of celiac patients have remained elusive. We report massive oligoclonal expansions of intraepithelial CTLs that exhibit a profound genetic reprogramming of natural killer (NK) functions. These CTLs aberrantly expressed cytolytic NK lineage receptors, such as NKG2C, NKp44, and NKp46, which associate with adaptor molecules bearing immunoreceptor tyrosine-based activation motifs and induce ZAP-70 phosphorylation, cytokine secretion, and proliferation independently of T cell receptor signaling. This NK transformation of CTLs may underlie both the self-perpetuating, gluten-independent tissue damage and the uncontrolled CTL expansion leading to malignant lymphomas in severe forms of celiac disease. Because similar changes were detected in a subset of CTLs from cytomegalovirus-seropositive patients, we suggest that a stepwise transformation of CTLs into NK-like cells may underlie immunopathology in various chronic infectious and inflammatory diseases.

Akt1 genetic deficiency limits hypothermia cardioprotection following murine cardiac arrest.

Therapeutic hypothermia (TH) cardioprotection has recently been associated with increased Akt signaling in a rat model of cardiac arrest. However, it is not known whether Akt is required for this beneficial effect of TH. We used a mouse model of cardiac arrest demonstrating TH cardioprotection to study the response of mice deficient in an Akt1 allele. We hypothesized that Akt1 mediates TH cardioprotection and that decreases in Akt1 content would diminish such protection. Adult C57BL/6 wild-type (WT) mice underwent an 8-min cardiac arrest. After 6 min, the mice were randomized to normothermia (WT(NT), 37 degrees C) or TH (WT(TH), 30 degrees C). Following cardiopulmonary resuscitation and the return of spontaneous circulation (ROSC), the animals were hemodynamically monitored for 240 min (R240). At R240, cardiac tissue Akt content and phosphorylation were assayed. Studies were repeated in Akt1 heterozygous (Akt1(+/-)) mice. As a result, baseline characteristics and ROSC rates were equivalent across groups. At R240, WT(TH) mice exhibited lower heart rate, larger stroke volume, and higher cardiac output than WT(NT) animals (P < 0.05). Cardioprotection in WT(TH) at R240 was associated with increased cardiac Akt phosphorylation at Ser473 and Thr308 compared with that in WT(NT) (P < 0.05). TH-associated alterations in Akt phosphorylation, stroke volume, heart rate, and cardiac output were abrogated in Akt1(+/-) animals. In conclusion, TH improves post-ROSC cardiac function and increases Akt phosphorylation in WT, but not Akt1(+/-), mice. The Akt1 isoform appears necessary for TH-mediated cardioprotection.

The emergency cardiac arrest response team (eCART): a novel strategy for improving therapeutic hypothermia utilization following out-of-hospital cardiac arrest.

BACKGROUND: Out-of hospital cardiac arrest (OHCA) is associated with significant mortality. Therapeutic hypothermia is one of the few interventions that have been shown to increase post-arrest survival as well as enhance neurologic recovery. Despite clinical guidelines recommending the use of therapeutic hypothermia (TH) following cardiac arrest, utilization rates by physicians remain low. We hypothesized that the development of a multi-disciplinary emergency cardiac arrest response team (eCART) would enhance therapeutic hypothermia utilization in the emergency department for OHCA. METHODS AND RESULTS: An eCART (emergency department cardiac arrest response team) was created at a single site academic urban emergency department. The eCART team consisted of a physician hypothermia consultant, a cardiologist, a clinical pharmacist, a respiratory therapist and a chaplain. These providers were notified by page prior to the arrival of an OHCA patient and responded to the ED in person or by phone to support the resuscitation. Analysis of pre- and post-intervention data demonstrated a significant increase in the rate of TH utilization (64% to 96%). There was a non-significant decrease in the time to target temperature. CONCLUSIONS: The creation of a coordinated, multi-disciplinary care team, providing real-time support for OHCA patients increased TH utilization in an emergency department.

Inhibition of sphingosine-1-phosphate lyase rescues sphingosine kinase-1-knockout phenotype following murine cardiac arrest.

AIMS: To test the role of sphingosine-1-phosphate (S1P) signaling system in the in vivo setting of resuscitation and survival after cardiac arrest. MAIN METHODS: A mouse model of potassium-induced cardiac arrest and resuscitation was used to test the importance of S1P homeostasis in resuscitation and survival. C57BL/6 and sphingosine kinase-1 knockout (SphK1-KO) female mice were arrested for 8 min then subjected to 5 minute CPR with epinephrine bolus given at 90s after the beginning of CPR. Animal survival was monitored for 4h post-resuscitation. Upregulation of tissue and circulatory S1P levels were achieved via inhibition of S1P lyase by 2-acetyl-5-tetrahydroxybutyl imidazole (THI). Plasma and heart tissue S1P and ceramide levels were quantified by targeted ESI-LC/MS/MS. KEY FINDINGS: Lack of SphK1 and low tissue/circulatory S1P levels in SphK1-KO mice led to poor animal resuscitation after cardiac arrest and to impaired survival post-resuscitation. Inhibition of S1P lyase in SphK1-KO mice drastically improved animal resuscitation and survival. Improved resuscitation and survival of THI-treated SphK1-KO mice were better correlated with cardiac dihydro-S1P (DHS1P) than S1P levels. The lack of SphK1 and the inhibition of S1P lyase by THI were accompanied by modulation in cardiac S1PR1 and S1PR2 expression and by selective changes in plasma N-palmitoyl- and N-behenoyl-ceramide levels. SIGNIFICANCE: Our data provide evidence for the crucial role for SphK1 and S1P signaling system in resuscitation and survival after cardiac arrest, which may form the basis for development of novel therapeutic strategy to support resuscitation and long-term survival of cardiac arrest patients.

Genetic deletion of NOS3 increases lethal cardiac dysfunction following mouse cardiac arrest.

STUDY AIMS: Cardiac arrest mortality is significantly affected by failure to obtain return of spontaneous circulation (ROSC) despite cardiopulmonary resuscitation (CPR). Severe myocardial dysfunction and cardiovascular collapse further affects mortality within hours of initial ROSC. Recent work suggests that enhancement of nitric oxide (NO) signaling within minutes of CPR can improve myocardial function and survival. We studied the role of NO signaling on cardiovascular outcomes following cardiac arrest and resuscitation using endothelial NO synthase knockout (NOS3(-/-)) mice. METHODS: Adult female wild-type (WT) and NOS3(-/-) mice were anesthetized, intubated, and instrumented with left-ventricular pressure-volume catheters. Cardiac arrest was induced with intravenous potassium chloride. CPR was performed after 8min of untreated arrest. ROSC rate, cardiac function, whole-blood nitrosylhemoglobin (HbNO) concentrations, heart NOS3 content and phosphorylation (p-NOS3), cyclic guanosine monophosphate (cGMP), and phospho-troponin I (p-TnI) were measured. RESULTS: Despite equal quality CPR, NOS3(-/-) mice displayed lower rates of ROSC compared to WT (47.6% [10/21] vs. 82.4% [14/17], p<0.005). Among ROSC animals, NOS3(-/-) vs. WT mice exhibited increased left-ventricular dysfunction and 120min mortality. Prior to ROSC, myocardial effectors of NO signaling including cGMP and p-TnI were decreased in NOS3(-/-) vs. WT mice (p<0.05). Following ROSC in WT mice, significant NOS3-dependent increases in circulating HbNO were seen by 120min. Significant increases in cardiac p-NOS3 occurred between end-arrest and 15min post-ROSC, while total NOS3 content was increased by 120min post-ROSC (p<0.05). CONCLUSIONS: Genetic deletion of NOS3 decreases ROSC rate and worsens post-ROSC left-ventricular function. Poor cardiovascular outcomes are associated with differences in NOS3-dependent myocardial cGMP signaling and circulating NO metabolites.