This issue of Shock provides another great collection of articles, which covers a wide range of topics of some of the latest research in clinical and basic science in pathophysiology and novel therapeutic targets of sepsis, trauma, ischemia/reperfusion injury, and other shock-like conditions of organ inflammation and dysfunction.
CLINICAL SCIENCE ASPECTS
The first clinical article addresses the important topic of resuscitation management of critically ill patients with hypovolemia. If early use of fluid resuscitation is certainly beneficial, optimal fluid titration is equally necessary to restore the intravascular volume loss. In a prospective randomized trial in critically ill surgical patients, Yu et al. (1) used direct measurement of blood volume in addition to central hemodynamic pressures and hematocrit to guide fluid resuscitation. The authors report that when blood volume analysis was not used, there was a delay (1-2 days) in recognizing and treating the volume status of the patient. On the contrary, information provided by blood volume analysis led to a change in treatment in 44% patients. There was also a significant survival advantage in the group of patients who were treated based on blood volume findings. As the authors themselves mention, however, this study needs to be confirmed in other clinical trials, and questions remain regarding the feasibility of the monitoring technology. Nevertheless, the authors conclude that blood volume analysis probably allows more reliable assessment of the patient's status and more efficacious fluid resuscitation.
The second article by Foteinou et al. (2) highlights the importance of the use of in silico mathematical models as an essential and valid complement to clinical research of the systemic inflammatory response induced by sepsis. By using data of heart rate variation from a well-established human model of endotoxemia, the authors have developed a computational model that quantifies the complex relationship between inflammation and the autonomic control systems. In this in silico study, the performance of the proposed physiology-based human inflammation model was then demonstrated through its potential to reproduce biologically relevant situations, such as the resolution of the inflammatory response following low-dose endotoxin and the cardiovascular effects of antecedent stress with hormone excess (i.e., epinephrine). The authors propose that mathematical modeling can yield significant insights into the complex relationship between injury and pathophysiologic responses and may be useful for predicting clinical events.
An important effort toward a better understanding of the cellular mechanisms of acute lung injury is the article by Eun et al. (3). In this well-designed investigation, by using neutrophils from healthy volunteers, the authors demonstrated that leukotriene B4 and its ω-oxidation and nonenzymatic derivatives induced superoxide formation and increased adhesiveness of neutrophils to pulmonary microvascular endothelial cells. With RNA silencing technology and pharmacological tools, the authors also identified the contributions of specific BLT1 and BLT2 receptors. As the authors conclude, this report further supports the complex contribution of the 5-lipoxygenase pathway in the inflammatory response leading to multiple organ failure.
It is clear that microarrays are becoming more integral to the clinical and basic science research. The last clinical aspect article by Bogner et al. (4) of this issue of Shock deals with the major challenge of interpretation of microarray results, because standardized analytical tools are not yet available. The authors compared two different commercially available pathway analysis programs on the same experimental data set obtained from trauma patients. The authors report that the results of the analyses were not uniform, and the two programs substantially differed in identifying the five most common biological pathways, functions, and diseases. The authors therefore suggest to researchers not to rely on a single analysis program but to always compare data from different applications and to confirm the biological relevance of the results with the current available literature.
BASIC SCIENCE ASPECTS
This issue of Shock highlights the outstanding research accomplishments of two young emerging scientists who were recipients of the highly prestigious New Investigator Award at the 33rd Annual Conference of the Shock Society (5, 6). In the first basic science article, Hanschen et al. (5) address the important problem of immune dysfunction that develops after severe burn injury. By using a murine model of burn injury, the authors report that CD4+ regulatory T cells displayed an early activation of the T-cell receptor signaling pathways, which was restricted to the injury-site-draining lymph nodes. As the authors mention, these data are certainly important to further characterize the immune response following burn injury and may contribute to the search for therapeutic targets to modulate the adaptive immune system. In the second basic science article, Cheyuo et al. (6) provide information on pathogenetic mechanisms and potential therapeutic approaches for brain injury and neurological deficit after stroke. By using a rat model of permanent focal cerebral ischemia, the authors report that administration of human ghrelin, a stomach-derived 28-amino-acid peptide, significantly attenuated cerebral ischemic injury and improved neurobehavioral function. This neuroprotective effect was associated with downregulation of neutrophil trafficking and nitrosative stress and reduction of tissue proinflammatory cytokines. The authors also demonstrated that the mechanism of action of ghrelin is through activation of cholinergic anti-inflammatory pathway, because bilateral truncal vagotomy in the rat blunted the neuroprotective effects of the peptide. Although the exact neuronal circuitry and neurotransmitters remain to be determined, this study further supports the crucial importance of vagal activation in the control of inflammatory response.
The pathogenetic mechanism of gut injury and distant multiple organ failure associated with splanchnic hypoperfusion is a common theme of investigation of two basic science articles. By using a rat model of segmental splanchnic ischemia and reperfusion injury, Qin et al. (7) investigated the contribution of pancreatic digestive proteases in mucus layer integrity. The authors elegantly demonstrated that loss of the mucus layer, as obtained by a brief exposure to the mucolytic N-acetyl cysteine, contributed to gut injury and impaired the restitution of gut barrier function. The magnitude of injury was exacerbated by the presence of intraluminal pancreatic proteases. As the authors acknowledged, these findings suggest the concept that fortifying the mucus layer may be a therapeutic approach of gut injury. In line with this effort in treating splanchnic injury and preventing distant organ injury is also the article by Shih et al. (8). By using a murine model of mesenteric ischemia and reperfusion injury, the authors report that combined treatment with 17β-estradiol and hypertonic saline reduced gut and lung injury and significantly improved survival when compared with single treatment. Although the molecular mechanisms of combined treatment were not fully delineated in the study, the authors provide evidence that pulmonary protection was associated with reduction of lung expression of inflammatory and signaling modulators, such as macrophage migration inhibitory factor, inducible nitric oxide synthetase, toll-like receptor 4, and phosphorylated inhibitory κBα.
Understanding the pathophysiology behind the injury of ischemia and reperfusion is also the basis of the article by Dhupar et al. (9). In a comprehensive mechanistic investigation, the authors address the contribution of the nuclear transcription factor interferon regulatory factor 1 (IRF-1) in the activation of the inflammatory cascades subsequent to reperfusion in ischemic liver. The authors demonstrated that IRF-1 activation contributes to the release of high-mobility group box 1 by modulating its acetylation status during liver ischemia and reperfusion injury. By using in vitro mutant hepatocytes and chimeric mice, the authors also provide evidence that IRF-1 is upregulated through a toll-like receptor 4-dependent pathway and is restricted to hepatic parenchymal cells. As the authors mention, results from this study may have implications for the identification of novel therapeutic targets of "sterile" inflammation.
Despite antibiotic therapy and resuscitative management, sepsis still carries unacceptably high morbidity and mortality rates. Three basic science articles examined the potential beneficial effects of novel therapeutic approaches on the altered systemic inflammatory and catabolic responses and on myocardial dysfunction in experimental models of sepsis. The article by Bertsch et al. (10) evaluated the effect of glycogen synthase kinase 3β inhibition on sepsis-induced muscle wasting using lithium chloride (LiCl). The authors demonstrated that in vitro treatment with LiCl reversed protein degradation in epitrochlearis muscles from rats infected with intraperitoneal fecal-agar pellets with Escherichia coli and Bacteroides fragilis. However, treatment with LiCl failed to improve muscle protein synthesis. At molecular analysis, LiCl partially reversed the sepsis-induced 26S proteosome activity, but did not exert any effects on autophagic-lysosomal or downstream pathways of glycogen synthase kinase 3β, which are known to regulate protein metabolism. The rationale of the article by Hagiwara et al. (11) is based on the known strong association of coagulopathy and platelet activation with inflammatory response observed in patients with severe sepsis. By using a rat model of endotoxin shock, the authors demonstrated that pretreatment with clopidogrel sulfate, an inhibitor of ADP-induced platelet aggregation, reduced endotoxin-induced lung and liver injury and blunted the systemic release of proinflammatory cytokines. In another interventional study, Wang et al. (12) tested the effect of berberine, a natural component of Rhizoma coptidis that has been reported to have similar pharmacological actions to α2-adrenergic agonists, on endotoxin-induced myocardial dysfunction. The authors demonstrated that pretreatment of mice subjected to endotoxic shock ameliorated both cardiac systolic and diastolic function and reduced cardiac expression of inflammatory and signaling modulators, such as cytokines and phosphorylated inhibitory κBα. Interestingly, the combined treatment of berberine with yohimbine, an α2-adrenergic receptor antagonist, led to a puzzling and paradoxical effect, as yohimbine enhanced the cardioprotective effects of berberine. Although the clinical relevance of these three reports still needs to be confirmed in other preclinical models and the mechanisms of action of the proposed compounds to be established, these articles further emphasize the pathophysiologic complexity of sepsis.
The pathological events of pulmonary fibrosis and excess collagen deposition in lung injury are the topic of the next two articles. By using a well-established ovine model of burn and smoke inhalation injury, Sousse et al. (13) report that in a late stage (i.e., weeks after injury) excess collagen deposition and pulmonary dysfunction are associated with increased arginase activity and reduced NO synthesis. When comparing this interesting observation with the kinetics of NO, which appears to have a more pathological role in the acute phase (i.e., hours after injury), this report underscores the notion that a delicate balance of the NO/arginase pathways may contribute for the maintaining of lung function. In the next study, Xu et al. (14) examined how an α-melanocyte-stimulating hormone analog, STY39, would influence the development of bleomycin-induced pulmonary inflammation and fibrosis in mice. The authors found that chronic treatment with STY39 significantly ameliorated lung architecture, reduced local production of proinflammatory and profibrosis cytokines, and improved survival of mice subjected to lung injury. Importantly, from a mechanistic perspective, their data suggested that maintaining a balanced extracellular matrix remodeling is most probably a potential therapeutic signature of this hormone analog.
In the last decade, erythropoietin (EPO), a critical growth factor that is produced in the adult kidney to regulate erythropoiesis and is used for the treatment of anemia, has emerged as an important cytoprotective modulator, which possesses the ability to protect several tissues from inflammatory or ischemia and reperfusion injury. The last basic science article by Contaldo et al. (15) provides a well-designed investigation of the effect of EPO pretreatment on TNF-α-induced microcirculatory dysfunction in a model of dorsal skinfold chamber. By using knockout mice, the authors demonstrated that EPO maintained tissue perfusion and reduced leukocyte rolling and adhesiveness most probably through an endothelial nitric oxide synthetase-mediated mechanism. This report highlights how important in basic and clinical science is also the investigation in redefining the mechanisms of well-established conventional therapy for a potential novel application in shock conditions.
1. Yu M, Pei K, Moran S, Edwards KD, Domingo S, Steinemann S, Ghows M, Takiguchi S, Tan A, Lurie F, et al.: A prospective randomized trial using blood volume analysis in addition to pulmonary artery catheter, compared with pulmonary artery catheter alone, to guide shock resuscitation in critically ill surgical patients. Shock
2. Foteinou PT, Calvano SE, Lowry SF, Androulakis IP: A physiological model for autonomic heart rate regulation in human endotoxemia. Shock
3. Eun JC, Moore EE, Banerjee A, Kelher MR, Khan SY, Elzi DJ, McLaughlin NJD, Silliman CC: Leukotriene B4
and its metabolites prime the neutrophil oxidase and induce proinflammatory activation of human pulmonary microvascular endothelial cells. Shock
4. Bogner V, Leidel BA, Kanz K-G, Mutschler W, Neugebauer EAM, Biberthaler P: Pathway analysis in microarray data: a comparison of two different pathway analysis devices in the same data set. Shock
5. Hanschen M, Tajima G, O'Leary F, Ikeda K, Lederer JA: Injury induces early activation of T-cell receptor signaling pathways in CD4+
regulatory T cells. Shock
6. Cheyuo C, Wu R, Zhou M, Jacob A, Coppa G, Wang P: Ghrelin suppresses inflammation and neuronal nitric oxide synthase in focal cerebral ischemia via the vagus nerve. Shock
7. Qin X, Sheth SU, Sharpe SM, Dong W, Lu Q, Xu D, Deitch EA: The mucus layer is critical in protecting against ischemia-reperfusion-mediated gut injury and in the restitution of gut barrier function. Shock
8. Shih H-C, Huang M-S, Lee C-H: Estrogen augments the protection of hypertonic saline treatment from mesenteric ischemia-reperfusion injury. Shock
9. Dhupar R, Klune JR, Evankovich J, Cardinal J, Zhang M, Ross M, Murase N, Geller DA, Billiar TR, Tsung A: Interferon regulatory factor 1 mediates acetylation and release of high mobility group box 1 from hepatocytes during murine liver ischemia-reperfusion injury. Shock
10. Bertsch S, Lang CH, Vary TC: Inhibition of glycogen synthase kinase 3β activity with lithium in vitro
attenuates sepsis-induced changes in muscle protein turnover. Shock
11. Hagiwara S, Iwasaka H, Hasegawa A, Oyama M, Imatomi R, Uchida T, Moguchi T: Adenosine diphosphate receptor antagonist clopidogrel sulfate attenuates LPS-induced systemic inflammation in a rat model. Shock
12. Wang Y, Li H, Wang H, Peng X, Wang Y, Lu D, Qi R, Hu C, Jiang J: Pretreatment with berberine and yohimbine protects against LPS-induced myocardial dysfunction via inhibition of cardiac I-κBα phosphorylation and apoptosis in mice. Shock
13. Sousse LE, Yamamoto Y, Enkhbaatar P, Rehberg SW, Wells SM, Leonard S, Traber MG, Yu YM, Cox RA, Hawkins HK, et al.: Acute lung injury-induced collagen deposition is associated with elevated asymmetric dimethylarginine and arginase activity. Shock
14. Xu P, Mao Y, Meng H, Tian Y, Deng X: STY39, a novel alpha-melanocyte-stimulating hormone analogue, attenuates bleomycin-induced pulmonary inflammation and fibrosis in mice. Shock
15. Contaldo C, Lindenblatt N, Elsherbiny A, Ho¨gger DC, Borozadi MK, Vetter ST, Lang KS, Handschin AE, Giovanoli P: Erythropoeitin requires endothelial nitric oxide synthase to counteract TNF-α-induced microcirculatory dysfunction in murine striated muscle. Shock