What’s New in Shock, March 2012?

Abstract

For March, once again Shock presents an exceptional compilation of informative and topical investigations exploring potential mechanisms, treatments, and aspects of sepsis, shock, and inflammatory injury. To open this month’s journal selections, in a “Rapid Communication” article, Seok et al. (1) present their study supporting the efficacy of Delta neutrophil index (DN) for sepsis diagnosis and prognosis for the development of severe sepsis. Delta neutrophil index data were collected using automated immature granulocyte counts acquired during routine blood culture and calculated based on the difference between blood leukocyte myeloperoxidase activity and nuclear lobularity differentials in the leukocyte subfraction of complete blood counts. Their retrospective study involving 273 patients (systemic inflammatory response syndrome, sepsis, severe sepsis, and control groups) compared the diagnostic accuracy of C-reactive protein values with DN values. C-reactive protein and DN analysis from blood cultures drawn on patient’s first day were assessed for diagnostic sensitivity and correlation to 28-day mortality associated with sepsis. Delta neutrophil index demonstrated greater sensitivity, especially between sepsis and severe sepsis. Subsequent analysis of C-reactive protein and DN on days 1 to 3 before sepsis highlighted DN as a more sensitive prognostic tool for the development of severe sepsis. Obesity is recognized as contributing to a significant number of health issues, with chronic inflammation cited as a common underlying factor. To better understand how this chronic inflammatory state impacts outcome in severely injured obese patients, Winfield et al. (2) performed a retrospective study of clinical data and serum cytokine concentrations over a 96-h postinjury period, for obese (n = 40) and nonobese (n = 34) adult blunt trauma patients. Data were collected from level I trauma centers in the United States. Surprisingly, in their investigation of postinjury immune dysfunction (as evidenced by susceptibility to nosocomial infection and multiple organ failure), the authors found consistent (days 0–4) suppression of systemic cytokine levels in obese versus nonobese patients (2). The authors point out that these data support recent clinical and animal studies reporting increased susceptibility to infection in association with obesity. In a prospective, observational study, Napoli et al. (3) investigated an association between elevated cytolytic effector molecule, granzyme B, in cytotoxic T lymphocytes (CTLs) and sepsis severity. Granzymes (A and B) are released by mature CTLs and play a role in host defense by inducing apoptosis in target cells. However, the presence of these cytotoxic effector molecules in the plasma of septic patients is believed to contribute to increased mortality or multiple organ failure in these patients. In an analysis of peripheral blood mononuclear cells from emergency department admissions of patients lacking infection/inflammation, acutely ill nonseptic patients, and patients with severe sepsis, the authors show novel data demonstrating that septic patients have higher percentages of CTLs containing higher levels of granzyme B and that this corresponds to severity of sepsis. Genome-wide screening of sepsis survivors versus nonsurvivors has identified a number of differentially expressed biomarkers. In this article, Wang et al. (4) describe the prognostic value of two such differentially expressed micro(mi)RNAs detected in the serum of sepsis survivors versus nonsurvivors. Serum samples from 12 survivors and 12 nonsurvivors were screened using microarrays. miR-297 and miR-574-5p were identified as potential biomarker candidates, and their expression was subsequently assessed in another group of sepsis patients (66 survivors/52 nonsurvivors). The authors found levels of miR-574-5p significantly elevated in survivors, and importantly, this was shown to be predictive of survival when assessed with SOFA (Sepsis-Related Organ Failure Assessment) scores and sepsis stage (4). Over the years, there have been a number of efforts to approach the treatment of various forms of bacterial and/or septic shock through detoxication strategies using different forms of plasmapheresis. Here, Brummelhuis et al. (5) “review” the subject of toxin/immune absorption technological approaches potentially relevant to septic shock, from the perspective of what has been learned from such considerations for toxic shock syndrome toxin 1. They take the reader through an initial primer on what is and is not understood about the biology, biodistribution, and its physical/chemical properties. The idea being that many of these issues will be comparable for bacterial toxins considered as targets. An overview of the various modes of toxin removal, plasmapheresis, hemofiltration, blood exchange, and leukapheresis is then provided, which together give the message that, to optimize such therapies, a fuller understanding of biology of any toxin and its distribution is needed. Relative to the question of the sufficiency of allogenic blood cell transfusion, it has been appreciated that the classic global indices of perfusion, such as mean arterial pressure or base deficit along with hemoglobin and/or hematocrit, are likely inadequate in telling the clinician about maladies in microvascular perfusion/regional blood flow. This may underpin the pathological process ongoing in the traumatically injured patient that leads to organ dysfunction. Here, Weinberg and colleagues (6) extend the use of sidestream dark-field illumination microscopic sublingual microcirculatory imaging from septic shock patients to trauma patients receiving red blood cell transfusion. While not only documenting the utility of this approach in assessing regional blood perfusion, they also show, in this moderate-size study of 30 severely injured patients, that the pretransfusion portion of perfused capillaries may be selectively deranged in otherwise stable individuals. Inasmuch, although the clinical/physiological significance regarding such changes of microcirculation/regional blood remains to be clarified, the study not only has the potential utility of such technology but also has possible value in aiding clinical decision making someday. Along these lines, we have a study in this issue of Shock by Van Haren and colleagues (7) that also utilizes sidestream dark-field illumination microscopic sublingual imaging along with gastric tonometry to look at regional microcirculation, along with a variety of hemodynamic parameters, to assess the impact of hypertonic fluid administration versus isotonic fluids on short-term global hemodynamic changes versus alterations in microcirculation in a small cohort of septic shock patients. Clearly, in the face of the frustrations associated with trying to move forward with resuscitation of traumatically injured patients, it is important to evaluate hypertonic saline resuscitant’s capacity both on the global and regional tissue level. This is done independently in the setting of septic shock as the etiology of this condition is likely distinct from that encountered during injury. Interestingly, these investigators’ findings suggest that hypertonic saline effects are not local, but more global in nature, e.g., targeting cardiac contractility and/or vascular tone. In a “Basic Science” investigation into the underlying pathophysiology of polymicrobial sepsis in a cecal ligation and puncture mouse model, Hasan et al. (8) present a study first to show that neutrophil influx to the lung is in part regulated by Rho kinase. The authors demonstrated that i.p. administration of Rho kinase inhibitor, Y-27632, 30 min before cecal ligation and puncture, significantly reduced neutrophil recruitment to the lung, pulmonary edema, and disruption of lung tissue architecture. Chemokines CXCL1 and CXCL2, released primarily by macrophages, are associated with neutrophil activation and targeting to the lung. Hasan et al. (8) showed that inhibition of Rho kinase significantly reduced gene expression of CXCL1 and CXCL2 in alveolar macrophage and reduced Mac-1 expression on peripheral blood neutrophils. Although inhibition of Rho kinase signaling significantly reduced neutrophil activation and recruitment to lung, it did not impact plasma levels of CD40L or MMP-9, thus demonstrating that Rho kinase signaling is platelet CD40L independent (8). This month’s journal also includes two laboratory research investigations into the regulation of barrier function following ischemic events. Chang et al. (9) used a splanchnic arterial occlusion (SAO) model of intestinal ischemia in rats to assess the early mechanisms of gut barrier disruption. The authors determined that, within 15 min of ischemia, significant digestive enzyme activity was present in the intestinal wall, concurrent with intestinal villus injury. Mucosal barrier breakdown was associated with a decrease in mucin density in intestinal epithelium (microscopic observation) and detected disruption of both intracellular and extracellular E-cadherin domains (Western analysis) in the SAO-treated rats. Detection of trypsin and chymotrypsin proteins in plasma from SAO rats provided further confirmation of barrier disruption, suggesting a potential mechanism for ischemia-induced intestinal injury. The significant attenuation of intestinal injury observed after enteral pretreatment with tranexamic acid (a trypsin inhibitor) in SAO rats suggests that trypsin activity plays a role in early mucosal barrier disruption (9). Loss of endothelial barrier function is also associated with vascular hyperpermeability and tissue edema and is characteristic of a number of injury states including hemorrhagic shock. To better understand the molecular mechanisms of this derangement, Tharakan et al. (10) examined changes in expression of β-catenin, a member of the adherens junction complex, on rat lung microvascular endothelial cell monolayers after proapoptotic enzyme, caspase 3, treatment. Caspase 3 was shown to decrease β-catenin at adherens junctions, and confocal microscopy showed disruption of rat lung microvascular endothelial cell monolayer integrity from 1 to 2 h after enzyme treatment. Junction complex recovery and restored β-catenin expression were observed after 4 h. Interestingly, the authors found perinuclear accumulation of β-catenin following caspase 3 activation, but no increase in β-catenin phosphorylation (ubiquitin degradation) and no increase in transcriptional activity. These observations led the authors to conclude that, after a disruptive injury, β-catenin is recycled to the cell membrane and subsequently recovered at adherens junctions in conjunction with endothelial barrier recovery (10). From a basic science–cellular perspective, there are two articles in this month’s edition looking at mechanisms and mediators contributing to tubular necrosis in the kidney during sepsis or after ischemia/reperfusion injury (I/R). Hsiao et al. (11) look specifically into autophagy’s significance in sepsis-induced proximal tubular injury, observing that loss of the early autophagic process predicates the development of sepsis-induced apoptosis and necrosis. This is nicely delineated using a variety of immunohistochemical, biochemical, and morphological approaches. The potentiating of the protective nature of the autophagic process is further documented by using complementary autophagic antagonistic (Atg7 siRNA) versus agonistic (rapamycin) treatment. Alternatively, Wang et al. (12) look at the impact of an anti-inflammatory protein construct, IL-18–binding protein (IL-18BP), as an early posttreatment for the development of acute kidney injury and tubular necrosis, in response to bilateral renal pedicle clamping (to induce I/R). Here, the investigators find not only that I/R induces an increase in morphological evidence of kidney injury, an increased blood urea nitrogen/creatinine, and increased endothelial cell apoptosis and thrombospondin 1, but also that this is ameliorated by treatment with IL-18BP. Interestingly, in contrast to Hsiao et al. (11), they find increased autophagy in tubular epithelial cells in I/R animals juxtaposed to rising endothelial cell apoptosis. Finally, they suggest that inhibition of macrophage influx and/or their release of proinflammatory cytokines may be driving this response to I/R as treatment with IL-18BP blocks this. Myocardial dysfunction/depression remains one of the hallmarks of multiple organ dysfunction syndrome developing in response to severe septic shock. However, our understandings of the mechanisms underpinning the process are still incomplete. An et al. (13) take advantage of two strains of rats, the brown Norway and Dahl S, which exhibit unique responsiveness to developing hypertension when placed on a high-salt diet. Here, they look at their intrinsic myocardial response to endotoxin challenge, using a combination of ex vivo Langendorff heart preparation, isolated mitochondrial O2 consumption/H2O2 release, mitochondrial complex I and II enzymatic assays, tissue cytokine, and Western blot assessments. Ignoring the drawbacks of lipopolysaccharide (LPS) as a surrogate for the septic state and the inherent differences in rodent versus human NO biology, it is interesting that not only they observe that differences are evident to the extent of mitochondrial dysfunction seen, but also these correlate well with changes in cardiac tissue cytokine levels and the activation of nuclear factor κB, but not the MAPK pathway. Finally, two studies in this issue focus on divergent aspects of mediators (LPS/6-hydroxydopamine [6-OHDA]) (14) on neurotoxicity or baroreflex and/or sympathetic neural activity in the development of chronic heart failure (15). Tseng et al. (14) look at the capacity of a novel herbal compound, paeonol, to inhibit LPS-induced microglia cell production of inflammatory/oxidative stress–induced neurotoxic agents, which in turn lead to the dysfunction and/or death of local cortical neurons in states such as stroke and traumatic brain injury, as well as chronic neurodegenerative conditions. Again, appreciating the limitations of stimuli such as LPS and 6-OHDA as surrogates for septic or oxidant stress, what they show in this ex vivo rodent primary cell system is that posttreatment of microglial cells exposed to LPS can attenuate various indices of inflammation, and this appears to be through suppression of ERK and/or JNK activation while upregulating HO-1. Interestingly, paeonol also inhibited the neurotoxic activity of microglial condition media transferred to cortical neurons as well as decreased to neurotoxic effects of 6-OHDA treatment. The study by Fahim et al. (15) look at the development of impaired baroreflex sensitivity and sympathetic function during chronic heart failure, in a ventricular paced rabbit model (pacing duration varied from 1–3 weeks). Applying a combination of in vivo conscious hemodynamic monitoring techniques, e.g., echocardiography, indwelling arterial catheters for blood pressure/heart rate, or implanted renal sympathetic nerve electrodes (for assessing renal sympathetic nerve electrodes), to establish arterial baroreflex function (BRS) in response to nitroprusside/phenylephrine challenges, as well as end-point assessments of rostral ventrolateral medulla angiotensin II type 1 receptor/NAD(P)H oxidase subunit (gp61) message/protein expression. They establish a dissociation between the early development of BRS dysfunction to the late potentiation of angiotensin II type 1 receptor/gp61 expression in the rostral ventrolateral medulla. Put another way, they document that, during the development of chronic heart failure, changes in BRS proceed in the absence of significant early sympathoexcitation.