Use of glucocorticoids in the critical care setting: Science and clinical evidence.

Glucocorticoids (GC) in all its various forms and formulations are likely one of the most commonly used pharmacologic agents in medicine. Their use can be profoundly therapeutic but are also associated with a myriad of acute and chronic side effects. It is fairly well-accepted in the medical community that GC can be life-saving when used in critically ill patients with severe exacerbations of asthma and chronic obstructive pulmonary disease, HIV-associated pneumocystosis, and systemic vasculitides. However, the adjunctive role of GC is much more controversial in acute respiratory distress syndrome (ARDS), septic shock, community-acquired pneumonia, and several other serious medical conditions. Despite such controversies, GC should at least be considered for patients with fulminant manifestations of the following conditions as there is equipoise to indicate that GC may improve outcome with acceptable risks: (i) severe ARDS with refractory hypoxemia despite one to two weeks of state-of-the-art management, (ii) recalcitrant, vasopressor-dependent septic shock, (iii) non-influenza, severe community-acquired pneumonia, and (iv) severe alcoholic hepatitis. The bases for these controversies is likely due to both host factors (e.g., differences in GC resistance and susceptibility to adverse effects) and different phenotypes of any one disease state; e.g., different pathogenesis and pathogens under the rubric of "sepsis." Elucidation of better biomarkers to determine the underlying pathogenic phenotype will significantly advance our understanding and prediction of which critically ill patients will benefit from GC and who would experience a deleterious effect from its use.

Urinary Biomarkers are Associated with Severity and Mechanism of Injury.

Combat-related blast trauma results in massive tissue injury and tends to involve multiple systems. Further, an acute measure of injury severity based on underlying biological mechanisms may be important for the triage and treatment of these types of patients. We hypothesized that urinary biomarkers (UBs) would reflect severity of injury and that they would be elevated for blast injuries compared with gunshot wounds (GSW) in a cohort of combat casualties. We also postulated that UBs would be higher in patients with burns compared with patients with non-burn trauma in a civilian cohort. Among 80 service members who sustained combat-related injuries, we performed generalized estimating equations to compare differences in log-transformed concentrations of the UBs by both injury severity and injury mechanism. Among 22 civilian patients, we performed Kruskal-Wallis tests to compare differences for the UBs stratified by burn and non-burn trauma. In the military cohort, with the exception of IL-18, all UBs were significantly (P <0.05) higher for patients with a severe combat-related injury (Injury Severity Score ≥25). In addition, all crude UBs concentrations were significantly higher for blast versus GSW patients (P < 0.05). After adjusting for injury severity score and time of UB draw, KIM-1 (2.80 vs. 2.31; P = 0.03) and LFABP (-1.11 vs. -1.92; P = 0.02) were significantly higher for patients with a blast mechanism of injury. There were no significant differences in UBs between burn and non-burn civilian trauma patients. Future studies are needed to understand the physiologic response to trauma and the extent that UBs reflect these underlying processes.

Human IL-32 expression protects mice against a hypervirulent strain of Mycobacterium tuberculosis.

Silencing of interleukin-32 (IL-32) in a differentiated human promonocytic cell line impairs killing of Mycobacterium tuberculosis (MTB) but the role of IL-32 in vivo against MTB remains unknown. To study the effects of IL-32 in vivo, a transgenic mouse was generated in which the human IL-32γ gene is expressed using the surfactant protein C promoter (SPC-IL-32γTg). Wild-type and SPC-IL-32γTg mice were infected with a low-dose aerosol of a hypervirulent strain of MTB (W-Beijing HN878). At 30 and 60 d after infection, the transgenic mice had 66% and 85% fewer MTB in the lungs and 49% and 68% fewer MTB in the spleens, respectively; the transgenic mice also exhibited greater survival. Increased numbers of host-protective innate and adaptive immune cells were present in SPC-IL-32γTg mice, including tumor necrosis factor-alpha (TNFα) positive lung macrophages and dendritic cells, and IFN-gamma (IFNγ) and TNFα positive CD4(+) and CD8(+) T cells in the lungs and mediastinal lymph nodes. Alveolar macrophages from transgenic mice infected with MTB ex vivo had reduced bacterial burden and increased colocalization of green fluorescent protein-labeled MTB with lysosomes. Furthermore, mouse macrophages made to express IL-32γ but not the splice variant IL-32ß were better able to limit MTB growth than macrophages capable of producing both. The lungs of patients with tuberculosis showed increased IL-32 expression, particularly in macrophages of granulomas and airway epithelial cells but also B cells and T cells. We conclude that IL-32γ enhances host immunity to MTB.

An assembly of proteins and lipid domains regulates transport of phosphatidylserine to phosphatidylserine decarboxylase 2 in Saccharomyces cerevisiae.

Saccharomyces cerevisiae uses multiple biosynthetic pathways for the synthesis of phosphatidylethanolamine. One route involves the synthesis of phosphatidylserine (PtdSer) in the endoplasmic reticulum (ER), the transport of this lipid to endosomes, and decarboxylation by PtdSer decarboxylase 2 (Psd2p) to produce phosphatidylethanolamine. Several proteins and protein motifs are known to be required for PtdSer transport to occur, namely the Sec14p homolog PstB2p/Pdr17p; a PtdIns 4-kinase, Stt4p; and a C2 domain of Psd2p. The focus of this work is on defining the protein-protein and protein-lipid interactions of these components. PstB2p interacts with a protein encoded by the uncharacterized gene YPL272C, which we name Pbi1p (PstB2p-interacting 1). PstB2p, Psd2, and Pbi1p were shown to be lipid-binding proteins specific for phosphatidic acid. Pbi1p also interacts with the ER-localized Scs2p, a binding determinant for several peripheral ER proteins. A complex between Psd2p and PstB2p was also detected, and this interaction was facilitated by a cryptic C2 domain at the extreme N terminus of Psd2p (C2-1) as well the previously characterized C2 domain of Psd2p (C2-2). The predicted N-terminal helical region of PstB2p was necessary and sufficient for promoting the interaction with both Psd2p and Pbi1p. Taken together, these results support a model for PtdSer transport involving the docking of a PtdSer donor membrane with an acceptor via specific protein-protein and protein-lipid interactions. Specifically, our model predicts that this process involves an acceptor membrane complex containing the C2 domains of Psd2p, PstB2p, and Pbi1p that ligate to Scs2p and phosphatidic acid present in the donor membrane, forming a zone of apposition that facilitates PtdSer transfer.

Octreotide: a drug often used in the critical care setting but not well understood.

While the canonical function of somatostatin (SST) is to inhibit the secretion of growth hormone, it has a number of other physiologic effects that are less widely appreciated. Octreotide, an analog of SST, is not uncommonly used in the critical care setting, particularly for the treatment of variceal hemorrhage. Herein, we discuss the biology and pharmacology of SST, octreotide, and other SST analogs. We also review the evidence behind their use in esophageal variceal bleeds, hepatorenal syndrome, hypoglycemia due to sulfonylurea poisoning, and chylous pleural effusions.

Phosphatidylglycerol provides short-term prophylaxis against respiratory syncytial virus infection.

Respiratory syncytial virus (RSV) causes respiratory tract infections in young children, and significant morbidity and mortality in the elderly, immunosuppressed, and immunocompromised patients and in patients with chronic lung diseases. Recently, we reported that the pulmonary surfactant phospholipid palmitoyl-oleoyl-phosphatidylglycerol (POPG) inhibited RSV infection in vitro and in vivo by blocking viral attachment to epithelial cells. Simultaneous application of POPG along with an RSV challenge to mice markedly attenuated infection and associated inflammatory responses. Based on these findings, we expanded our studies to determine whether POPG is effective for prophylaxis and postinfection treatment for RSV infection. In vitro application of POPG at concentrations of 0.2-1.0 mg/ml at 24 h after RSV infection of HEp-2 cells suppressed interleukin-8 production up to 80% and reduced viral plaque formation by 2-6 log units. In vivo, the turnover of POPG in mice is relatively rapid, making postinfection application impractical. Intranasal administration of POPG (0.8-3.0 mg), 45 min before RSV inoculation in mice reduced viral infection by 1 log unit, suppressed inflammatory cell appearance in the lung, and suppressed virus-elicited interferon-γ production. These findings demonstrate that POPG is effective for short-term protection of mice against subsequent RSV infection and that it has potential for application in humans.

Pulse oximetry: understanding its basic principles facilitates appreciation of its limitations.

Pulse oximetry has revolutionized the ability to monitor oxygenation in a continuous, accurate, and non-invasive fashion. Despite its ubiquitous use, it is our impression and supported by studies that many providers do not know the basic principles behind its mechanism of function. This knowledge is important because it provides the conceptual basis of appreciating its limitations and recognizing when pulse oximeter readings may be erroneous. In this review, we discuss how pulse oximeters are able to distinguish oxygenated hemoglobin from deoxygenated hemoglobin and how they are able to recognize oxygen saturation only from the arterial compartment of blood. Based on these principles, we discuss the various conditions that can cause spurious readings and the mechanisms underlying them.

Phototrophic phylotypes dominate mesothermal microbial mats associated with hot springs in Yellowstone National Park.

The mesothermal outflow zones (50-65°C) of geothermal springs often support an extensive zone of green and orange laminated microbial mats. In order to identify and compare the microbial inhabitants of morphologically similar green-orange mats from chemically and geographically distinct springs, we generated and analyzed small-subunit ribosomal RNA (rRNA) gene amplicons from six mesothermal mats (four previously unexamined) in Yellowstone National Park. Between three and six bacterial phyla dominated each mat. While many sequences bear the highest identity to previously isolated phototrophic genera belonging to the Cyanobacteria, Chloroflexi, and Chlorobi phyla, there is also frequent representation of uncultured, unclassified members of these groups. Some genus-level representatives of these dominant phyla were found in all mats, while others were unique to a single mat. Other groups detected at high frequencies include candidate divisions (such as the OP candidate clades) with no cultured representatives or complete genomes available. In addition, rRNA genes related to the recently isolated and characterized photosynthetic acidobacterium "Candidatus Chloracidobacterium thermophilum" were detected in most mats. In contrast to microbial mats from well-studied hypersaline environments, the mesothermal mats in this study accrue less biomass and are substantially less diverse, but have a higher proportion of known phototrophic organisms. This study provides sequences appropriate for accurate phylogenetic classification and expands the molecular phylogenetic survey of Yellowstone microbial mats.

Increased NaCl-induced interleukin-8 production by human bronchial epithelial cells is enhanced by the DeltaF508/W1282X mutation of the cystic fibrosis transmembrane conductance regulator gene.

A satisfactory model describing the airway surface fluid (ASF) in the airways of persons with cystic fibrosis (CF) remains to be established due to theoretical challenges to both the "Hydration Hypothesis" and the "Salt Hypothesis." Irrespective of these models, inhaled hypertonic saline is often used to facilitate clearance of inspissated secretions. Hypertonicity induces interleukin-8 (IL-8) expression, a potent chemokine for neutrophils. The objectives of this study were: (i) to determine the relative contribution of three potential cis-regulatory elements in the regulation of NaCl-induced IL-8 production in BEAS-2B human bronchial epithelial cells, (ii) to compare NaCl-induced IL-8 expression in IB3-1 bronchial epithelial cells, which have the DeltaF508/W1282X mutation of the CF transmembrane conductance regulator (CFTR) gene, with that in C38 cells, which are IB3-1 cells stably transfected with a truncated but functional CFTR gene, and (iii) to compare equal osmolar concentrations of NaCl and D-sorbitol in the induction of IL-8 in all three cell types. In human bronchial epithelial cells, binding sites for NFkappaB, AP-1, and NF-IL6 in the 5'-flanking region of the IL-8 promoter are necessary for optimal NaCl induction of IL-8. Human bronchial epithelial cells with the DeltaF508/W1282X CFTR mutation produce an exaggerated amount of basal and NaCl-induced IL-8.