Adaptive and maladaptive mechanisms of cellular priming

Early-life exposure to cigarette smoke primes lung function and DNA methylation changes at Cyp1a1 upon exposure later in life

Prenatal and early-life exposure to cigarette smoke (CS) has repeatedly been shown to induce stable, long-term changes in DNA methylation (DNAm) in offspring. It has been hypothesized that these changes might be functionally related to the known outcomes of prenatal and early-life CS exposure, which include impaired lung development, altered lung function, and increased risk of asthma and wheeze. However, to date, few studies have examined DNAm changes induced by prenatal CS in tissues of the lung, and even fewer have attempted to examine the specific influences of prenatal versus early postnatal exposures. Here, we have established a mouse model of CS exposure which isolates the effects of prenatal and early postnatal CS exposures in early life. We have used this model to measure the effects of prenatal and/or postnatal CS exposures on lung function and immune cell infiltration as well as DNAm and expression of Cyp1a1, a candidate gene previously observed to demonstrate DNAm differences on CS exposure in humans. Our study revealed that exposure to CS prenatally and in the early postnatal period causes long-lasting differences in offspring lung function, gene expression, and lung Cyp1a1 DNAm, which wane over time but are reestablished on reexposure to CS in adulthood. This study creates a testable mouse model that can be used to investigate the effects of prenatal and early postnatal CS exposures and will contribute to the design of intervention strategies to mediate these detrimental effects.NEW & NOTEWORTHY Here, we isolated effects of prenatal from early postnatal cigarette smoke and showed that exposure to cigarette smoke early in life causes changes in offspring DNA methylation at Cyp1a1 that last through early adulthood but not into late adulthood. We also showed that smoking in adulthood reestablished these DNA methylation patterns at Cyp1a1, suggesting that a mechanism other than DNA methylation results in long-term memory associated with early-life cigarette smoke exposures at this gene.

Hormesis: A potential strategic approach to the treatment of neurodegenerative disease

This review describes neuroprotective effects mediated by pre- and post-conditioning-induced processes that act via the quantitative features of the hormetic dose response. These lead to the development of acquired resilience that can protect neuronal systems from endogenous and exogenous stresses and insult. Particular attention is directed to issues of dose optimization, inter-individual variation, and potential ways to further study and employ hormetic-based preconditioning approaches in medical and public health efforts to treat and prevent neurodegenerative disease.

Graphene Oxide Induced Perturbation to Plasma Membrane and Cytoskeletal Meshwork Sensitize Cancer Cells to Chemotherapeutic Agents

The outstanding physicochemical properties endow graphene materials (e.g., graphene oxide, GO) with beneficial potentials in diverse biomedical fields such as bioimaging, drug delivery, and biomolecular detection. GO recently emerged as a chemosensitizer; however, the detailed molecular basis underlying GO-conducted sensitization and corresponding biological effects are still elusive. Based on our recent findings that GO treatment at sublethal concentrations could impair the general cellular priming state, including disorders of plasma membrane and cytoskeleton construction, we aimed here to explore the mechanism of GO as a sensitizer to make cancer cells more susceptible to chemotherapeutic agents. We discovered that GO could not only compromise plasma membrane and cytoskeleton in J774A.1 macrophages and A549 lung cancer cells at sublethal concentrations without incurring significant cell death but also dampen a number of biological processes. Using the toxicogenomics approaches, we laid out the gene expression signature affected by GO and further defined those genes involved in membrane and cytoskeletal impairments responding to GO. The mechanistic investigation uncovered that the interactions of GO-integrin occurred on the plasma membrane and consequently activated the integrin-FAK-Rho-ROCK pathway and suppressed the expression of integrin, resulting in compromised cell membrane and cytoskeleton and a subsequent cellular priming state. By making use of this mechanism, the efficacy of chemotherapeutic agents (e.g., doxorubicin and cisplatin) could be enhanced by GO pretreatment in killing cancer cells. This study unveiled a feature of GO in cancer therapeutics: sensitizing cancer cells to chemotherapeutic agents by undermining the resistance capability of tumor cells against chemotherapeutic agents, at least partially, by compromising plasma membrane and cytoskeleton meshwork.

Immunological priming requires regulatory T cells and IL-10-producing macrophages to accelerate resolution from severe lung inflammation

Overwhelming lung inflammation frequently occurs following exposure to both direct infectious and noninfectious agents and is a leading cause of mortality worldwide. In that context, immunomodulatory strategies may be used to limit severity of impending organ damage. We sought to determine whether priming the lung by activating the immune system, or immunological priming, could accelerate resolution of severe lung inflammation. We assessed the importance of alveolar macrophages, regulatory T cells, and their potential interaction during immunological priming. We demonstrate that oropharyngeal delivery of low-dose LPS can immunologically prime the lung to augment alveolar macrophage production of IL-10 and enhance resolution of lung inflammation induced by a lethal dose of LPS or by Pseudomonas bacterial pneumonia. IL-10-deficient mice did not achieve priming and were unable to accelerate lung injury resolution. Depletion of lung macrophages or regulatory T cells during the priming response completely abrogated the positive effect of immunological priming on resolution of lung inflammation and significantly reduced alveolar macrophage IL-10 production. Finally, we demonstrated that oropharyngeal delivery of synthetic CpG-oligonucleotides elicited minimal lung inflammation compared with low-dose LPS but nonetheless primed the lung to accelerate resolution of lung injury following subsequent lethal LPS exposure. Immunological priming is a viable immunomodulatory strategy used to enhance resolution in an experimental acute lung injury model with the potential for therapeutic benefit against a wide array of injurious exposures.

Unintentional discontinuation of statins may increase mortality after traumatic brain injury in elderly patients: a preliminary observation

Background

The abrupt discontinuation of statin therapy has been suggested as being deleterious to patient outcomes. Although pre-injury statin (PIS) therapy has been shown to have a protective effect in elderly trauma patients, no study has examined how this population is affected by its abrupt discontinuation. This study examined the effects of in-hospital statin discontinuation on patient outcomes in elderly traumatic brain injury (TBI) patients.

Methods

This was a multicenter, retrospective cohort study on consecutively admitted elderly (≥ 55) PIS patients who were diagnosed with a blunt TBI and who had a hospital length of stay (LOS) ≥ 3 days. Patients who received an in-hospital statin within 48 hours of admission were considered continued, and patients who never received an in-hospital statin were considered discontinued. Differences in in-hospital mortality, having at least one complication, and LOS > 1 week were examined between those who continued and discontinued PIS.

Results

Of 93 PIS patients, 46 continued and 15 discontinued statin therapy. The two groups were equivalent vis-a-vis demographic and clinical characteristics. Those who discontinued statin therapy had a 4-fold higher mortality rate than those who continued (n = 4, 27% vs. n = 3, 7%, P = 0.055). Statin discontinuation did not have a higher complication rate, compared to statin continuation (n = 3, 20% vs. n = 7, 15%, P = 0.70), and no difference was seen in the proportion with a hospital LOS > 1 week (P > 0.99).

Conclusions

Though our study is not definitive, it does suggest that the abrupt, unintended discontinuation of statin therapy is associated with increased mortality in the elderly TBI population. Continuing in-hospital statin therapy in PIS users may be an important factor in the prevention of in-hospital mortality in this elderly TBI population.

Influence of preoperative 7.5% hypertonic saline on neutrophil activation after reamed intramedullary nailing of femur shaft fractures: a prospective randomized pilot study

OBJECTIVES

Femoral reaming and intramedullary nailing (IMN) primes polymorphonuclear leukocytes (PMNL) and thereby increases the posttraumatic systemic inflammatory response. Resuscitation with hypertonic saline (HTS) attenuates PMNL activation after trauma-hemorrhage. We hypothesized that preoperative administration of 7.5% HTS attenuates PMNL priming after IMN of unilateral femur shaft fractures compared with 0.9% normal saline.

DESIGN

Prospective, randomized, double-blind study.

SETTING

Level I trauma center.

PATIENTS

Twenty patients between 18 and 80 years of age with an Injury Severity Score less than 25 and a unilateral femur shaft fracture amenable to IMN fixation within 24 hours after injury.

INTERVENTION

Patients were allocated to equally sized HTS or normal saline treatment groups (n = 10) before surgery. Solutions were administered in a blinded bag as a single bolus of 4 mL/kg body weight immediately before surgery. Whole blood samples were collected directly before saline application (t0) and at 6, 12, and 24 hours after surgery.

MAIN OUTCOME MEASUREMENTS

PMNL surface expression of CD11b and CD62L, as determined by flow cytometry analysis.

RESULTS

Demographic characteristics of both treatment groups were comparable. Baseline expression of CD11b and CD62L cell markers was in a similar range in the two cohorts. The expression levels of CD11b were comparable between the two groups throughout the observation time, whereas CD62L levels were significantly higher in the HTS group at 6 and 24 hours after surgery.

CONCLUSION AND SIGNIFICANCE

Preoperative infusion of HTS appears to exert an anti-inflammatory effect by attenuating the extent of postoperative PMNL activation after reamed IMN for femoral shaft fractures.

Mechanisms of the beneficial actions of ischemic preconditioning on subcellular remodeling in ischemic-reperfused heart

Cardiac function is compromised by oxidative stress which occurs upon exposing the heart to ischemia reperfusion (I/R) for a prolonged period. The reactive oxygen species (ROS) that are generated during I/R incur extensive damage to the myocardium and result in subcellular organelle remodeling. The cardiac nucleus, glycocalyx, myofilaments, sarcoplasmic reticulum, sarcolemma, and mitochondria are affected by ROS during I/R injury. On the other hand, brief periods of ischemia followed by reperfusion, or ischemic preconditioning (IPC), have been shown to be cardioprotective against oxidative stress by attenuating the cellular damage and alterations of subcellular organelles caused by subsequent I/R injury. Endogenous defense mechanisms, such as antioxidant enzymes and heat shock proteins, are activated by IPC and thus prevent damage caused by oxidative stress. Although these cardioprotective effects of IPC against I/R injury are considered to be a consequence of changes in the redox state of cardiomyocytes, IPC is considered to promote the production of NO which may protect subcellular organelles from the deleterious actions of oxidative stress. The article is intended to focus on the I/R-induced oxidative damage to subcellular organelles and to highlight the cardioprotective effects of IPC. In addition, the actions of various endogenous cardioprotective interventions are discussed to illustrate that changes in the redox state due to IPC are cardioprotective against I/R injury to the heart.

Inhaled therapies for tuberculosis and the relevance of activation of lung macrophages by particulate drug-delivery systems

Pathogenic strains of Mycobacterium tuberculosis (Mtb) induce ‘alternative activation’ of lung macrophages that they colonize, in order to create conditions that promote the establishment and progression of infection. There is some evidence to indicate that such macrophages may be rescued from alternative activation by inhalable microparticles containing a variety of drugs. This review summarizes the experience of various groups of researchers, relating to observations of induction of a number of classical macrophage activation pathways. Restoration of a ‘respiratory burst’ and upregulation of reactive oxygen species and nitrogen intermediates through the phagocyte oxidase and nitric oxide synthetase enzyme systems; induction of proinflammatory macrophage cytokines; and finally induction of apoptosis rather than necrosis of the infected macrophage are discussed. It is suggested that there is scope to co-opt host responses in the management of tuberculosis, through the route of pulmonary drug delivery.

Claude H. Organ, Jr. memorial lecture: splanchnic hypoperfusion provokes acute lung injury via a 5-lipoxygenase-dependent mechanism

Postinjury multiple organ failure (MOF) is the net result of a dysfunctional immune response to injury characterized by a hyperactive innate system and a suppressed adaptive system. Acute lung injury (ALI) is the first clinical manifestation of organ failure, followed by renal and hepatic dysfunction. Circulatory shock is integral in the early pathogenesis of MOF, and the gut has been invoked as the motor of MOF. Mesenteric lymph is recognized as the mechanistic link between splanchnic ischemia/reperfusion and distant organ dysfunction, but the specific mediators remain to be defined. Current evidence suggests the lipid fraction of postshock mesenteric lymph is central in the etiology of ALI. Specifically, our recent work suggests that intestinal phospholipase A2 generated arachidonic acid and its subsequent 5-lipoxygenase products are essential in the pathogenesis of ALI. Proteins conveyed via postshock mesenteric lymph also may have an important role. Elucidating these mediators and the timing of their participation in pulmonary inflammation is critical in translating our current knowledge to new therapeutic strategies at the bedside.

Identification and interpretation of longitudinal gene expression changes in trauma

RATIONALE

The relationship between leukocyte gene expression and recovery of respiratory function after injury may provide information on the etiology of multiple organ dysfunction.

OBJECTIVES

To find a list of genes for which expression after injury predicts respiratory recovery, and to identify which networks and pathways characterize these genes.

METHODS

Blood was sampled at 12 hours and at 1, 4, 7, 21 and 28 days from 147 patients who had been admitted to the hospital after blunt trauma. Leukocyte gene expression was measured using Affymetrix oligonucleotide arrays. A linear model, fit to each probe-set expression value, was used to impute the gene expression trajectory over the entire follow-up period. The proportional hazards model score test was used to calculate the statistical significance of each probe-set trajectory in predicting respiratory recovery. A list of genes was determined such that the expected proportion of false positive results was less than 10%. These genes were compared to the Gene Ontology for 'response to stimulus' and, using Ingenuity software, were mapped into networks and pathways.

MEASUREMENTS AND MAIN RESULTS

The median time to respiratory recovery was 6 days. There were 170 probe-sets representing 135 genes that were found to be related to respiratory recovery. These genes could be mapped to nine networks. Two known pathways that were activated were antigen processing and presentation and JAK-signaling.

CONCLUSIONS

The examination of the relationship of gene expression over time with a patient's clinical course can provide information which may be useful in determining the mechanism of recovery or lack of recovery after severe injury.

A review of metabolic staging in severely injured patients

An interpretation of the metabolic response to injury in patients with severe accidental or surgical trauma is made. In the last century, various authors attributed a meaning to the post-traumatic inflammatory response by using teleological arguments. Their interpretations of this response, not only facilitates integrating the knowledge, but also the flow from the bench to the bedside, which is the main objective of modern translational research. The goal of the current review is to correlate the metabolic changes with the three phenotypes -ischemia-reperfusion, leukocytic and angiogenic- that the patients express during the evolution of the systemic inflammatory response. The sequence in the expression of multiple metabolic systems that becomes progressively more elaborate and complex in severe injured patients urges for more detailed knowledge in order to establish the most adequate metabolic support according to the evolutive phase. Thus, clinicians must employ different treatment strategies based on the different metabolic phases when caring for this challenging patient population. Perhaps, the best therapeutic option would be to favor early hypometabolism during the ischemia-reperfusion phase, to boost the antienzymatic metabolism and to reduce hypermetabolism during the leukocytic phase through the early administration of enteral nutrition and the modulation of the acute phase response. Lastly, the early epithelial regeneration of the injured organs and tissues by means of an oxidative metabolism would reduce the fibrotic sequelae in these severely injured patients.

Injury stimulates an innate respiratory immunoglobulin a immune response in humans

BACKGROUND

Secretory immunoglobulin A (SIgA) is the specific immune antibacterial defense. Since pneumonia frequently complicates the course of trauma patients, we studied early airway immune responses after injury.

METHODS

Twelve severely injured, intubated (expected for >/=5 d) patients had tracheal and bilateral lung lavage (BAL) within 30 hours of injury (n = 12). Epithelial lining fluid (ELF) volume and SIgA were measured by urea dilution and enzyme-linked immunosorbent assay (ELISA), respectively. Control BAL specimens were obtained from eight healthy elective surgical patients. Anatomically based comparisons were made between groups with Welch's unpaired t test. To verify human data, 30 male mice received no injury (time 0, n = 7) or injury with abdominal and neck incisions and were killed for airway IgA at 4 (n = 7), 8 (n = 8), and 24 (n = 8) hours. Analysis of variance (ANOVA) and Fisher's protected least significant difference testing was used to analyze animal data.

RESULTS

Initial trauma patient SIgA concentration (SIgA/mL ELF) increased compared with control in the lungs bilaterally (p < 0.05 both right and left). ELF volume was significantly higher in the right lung (p = 0.02) and just missed statistical significance (p = 0.07) on the left. Mouse IgA increased 8 hours after stress (p < 0.05 versus 0, 4, and 24 hours) and returned to normal by 24 hours.

CONCLUSION

A previously unrecognized innate human airway mucosal immune response with increased airway SIgA and ELF occurs after severe injury and is reproducible experimentally. This accessible, quantifiable human response allows study of clinical strategies to reduce infections via mucosal immune therapies.

Converging concepts: adaptive response, preconditioning, and the Yerkes-Dodson Law are manifestations of hormesis

The adaptive response in toxicology and environmental mutagenesis, preconditioning in biomedicine and the Yerkes-Dodson Law in psychology have dominating research themes with widespread and significant scientific and societal implications. This paper suggests that these apparently independent biological dose-response phenomena are manifestations of the common and more general biphasic dose-response relationship concept called hormesis. These three types of dose-response, as well as the hormesis concept, may represent the same general type of adaptation, which were discovered independently in different biological disciplines, amongst which there has been little communication. This intellectual isolation, due principally to progressively greater disciplinary specialization, resulted in the evolution of different terminologies for dose-response phenomena with strikingly similar quantitative features. This lack of recognition of converging dose-response concepts across disciplines has important implications since it limits the recognition of a common and basic biological concept while minimizing collaborations by investigators in related areas. The paper concludes that the broadly recognized biological adaptive responses, as described by the concepts of adaptive response, preconditioning and the Yerkes-Dodson Law, are special cases of the more general hormesis dose-response concept.

Isolated head injury in children affects the neutrophil function and lymphocyte count

BACKGROUND

Outcomes of treatment of postinjury complications remain unsatisfactory and research continues into the impact of trauma on innate and acquired immunity. The aim of our study was to describe how head injury affects a child's immunity by measuring the neutrophil function and lymphocytes subsets.

METHODS

The peripheral blood of 16 children with head trauma (Glasgow Coma Score < or =9) was examined. The blood samples were collected on the first and on the seventh day after trauma. The production of reactive oxygen species (ROS), spontaneous and stimulated, the expression of CD11b, and the lymphocyte subpopulations were measured. The blood of healthy children was studied as control. The impact of endotracheal intubation on the examined parameters was analyzed as well.

RESULTS

Head trauma leads to the increase of leukocytosis; the total production of ROS by peripheral blood neutrophils does not change after head injury. Correction of the results according to the number of neutrophils revealed a significant decrease in ROS production by a single neutrophil. The expression of adhesion molecule CD11b did not change. Head injury in children causes the decrease of the total lymphocyte count, CD3, CD4, CD8, and natural killer cells count on both the first and the seventh postinjury day. On the seventh day the significant decrease of natural killer cells subset was observed. The CD4/CD8 ratio increased from 1.5 (the first day) to 2.5 (the seventh day). The intubation did not affect the examined parameters.

CONCLUSIONS

After head injury, total ROS production and adhesion molecule CD11b expression remained unchanged when compared with control. The study did not demonstrate evidence for neutrophil activation in patients with head injuries. The total lymphocyte count was found to be decreased and the composition of lymphocytes' subsets was deeply impaired.

Activation of RAGE induces elevated O2- generation by mononuclear phagocytes in diabetes

Oxidative stress has been found to play a role in the pathogenesis of diabetic complications. The aim of this study was to define the oxidative burst of diabetic monocytes to characterize the phenotype associated with poor diabetic control. Superoxide (O(2)(-)) is the first molecule generated during the respiratory burst of phagocytes by NADPH oxidase, and its generation by monocytes from 26 controls and 34 diabetic subjects was evaluated in this study. Under resting states or stimulation by PMA or opsonized zymosan, diabetic monocytes produce significantly more O(2)(-) than nondiabetic cells. The increased O(2)(-) generation was found to be correlated with glycemic control (glycated hemoglobin) of patients. To clarify the effects of hyperglycemia on O(2)(-) generation, normal human monocytes were treated with receptor for advanced glycation endproducts (RAGE) ligands (AGE protein and S100B) or high glucose media before stimulation. RAGE ligands and high glucose concentration increased O(2)(-) generation from human mononuclear phagocytes. RAGE ligands, specifically and potently, increased O(2)(-) generation from mononuclear phagocytes, and high-glucose effects were associated with correspondingly increased osmotic pressure. Differentiated THP-1 cells, from a human monocytic cell line, were used as a model of human monocytes to study the effects of S100B, the RAGE ligand. It was confirmed that RAGE is involved in the priming of O(2)(-) generation by S100B. This study demonstrates that RAGE ligands can contribute significantly to the hyper-responsive phenotype of diabetic monocytes, which might be reversible by blocking the RAGE or controlling the presence of RAGE ligands by controlling hyperglycemia.

Major hepatic trauma: warm ischemic tolerance of the liver after hemorrhagic shock

BACKGROUND

The management of severe hepatic trauma frequently involves exposing the liver to varying periods of warm ischemia. The ischemic tolerance of the liver, in the setting of hemorrhagic shock (HS) and trauma, is presently unknown. We tested the hypothesis that warm ischemic tolerance of the porcine liver will be decreased following resuscitation from HS.

MATERIALS AND METHODS

Twenty-three Yorkshire pigs were divided into three groups: 1) hepatic ischemia alone (HI, n = 9); 2) hemorrhagic shock alone (HS, n = 3); and 3) hemorrhagic shock plus hepatic ischemia combined (HSHI, n = 11). Following reperfusion, a liver biopsy was obtained and serial blood chemistries were sampled.

RESULTS

Post-operative day 7 mortality was increased in the HSHI group (7/11) compared to the HI (0/9) group, P = 0.038. Notably, deaths did not result from acute liver failure, but rather from intra-operative hemodynamic collapse shortly following hepatic reperfusion. In addition, the HSHI group experienced significantly elevated lactic acid, serum creatinine and liver enzyme levels. Analysis of the liver biopsy samples is consistent with a more severe liver injury in the HSHI group.

CONCLUSIONS

The warm ischemic tolerance of the liver following resuscitation from HS is significantly decreased in this porcine model compared to HS or HI alone. Mortality was associated with acute intra-operative hemodynamic collapse occurring shortly after hepatic reperfusion.

Murine in vivo myocardial contractile dysfunction after burn injury is exacerbated by pneumonia sepsis

We evaluated hemodynamic and cardiac contractile dysfunction in a murine model of 40% contact burn complicated by Streptococcus pneumoniae (1 x 10(5) CFU) sepsis. Male, 9- to 10-week-old C57/BL6 mice were divided into the following groups: sham burn, sham sepsis; 24 h after burn alone; 24 h after sepsis alone; 7 days after burn alone; and 7 days after burn followed by pneumonia sepsis. Hemodynamic and cardiac contractile function was assessed with carotid artery cannulation and left ventricular pressure-volume analysis. At 24 h after burn, there were significant decreases in all load-insensitive contractility variables including the end-systolic pressure volume relationship, preload-recruitable stroke work, and maximum elastance, but there were no changes in global hemodynamics. Twenty-four hours after sepsis, there was similar cardiac contractile dysfunction, along with a decrease in cardiac output, but mean arterial pressure was maintained with an increase in systemic vascular resistance. Late burn (7 days) was associated with a recovery of all contractility variables except the end-systolic pressure volume relationship. However, sepsis induced during the late burn period was associated with a significant decrease in heart rate and cardiac output, but mean arterial pressure was still maintained with increased systemic vascular resistance. With burn complicated by sepsis, all cardiac contractility variables showed profound contractile dysfunction. Our data indicate that burn complicated by sepsis is associated with more pronounced cardiac contractile dysfunction than burn alone or sepsis alone.

Transcriptomic and Proteomic Patterns of Systemic Inflammation in On-Pump and Off-Pump Coronary Artery Bypass Grafting

BACKGROUND

Coronary artery bypass grafting (CABG) using cardiopulmonary bypass (CPB) provides controlled operative conditions but induces a whole-body inflammatory response capable of initiating devastating morbidity and mortality. Although technically more demanding, deliberate avoidance of CPB in off-pump surgery attenuates the physiological insult associated with CABG.

METHODS AND RESULTS

To systematically assess the molecular mechanisms underlying the better-preserved remote organ function, we studied gene expression patterns in leukocytes and plasma proteomic response to on-pump and off-pump CABG. Proteomic analysis confirmed (tumor necrosis factor-alpha, interleukin [IL]-6, IL-10) and expanded (eg, interferon [IFN]-gamma, granulocyte colony-stimulating factor [G-CSF], monocyte chemotactic protein-1, macrophage inflammatory protein-1beta) the mediators released on CPB, whereas blood leukocyte transcriptomics suggested that circulating leukocytes are not primarily responsible for this response. Interestingly, release of some cytokines (eg, IL-6, IFN-gamma, G-CSF) was observed on off-pump surgery to a similar extent but with delayed kinetics. A total of 45 of 4868 transcripts were identified to be significantly altered as a result of initiation of CPB. Systematic analysis of transcriptional activation by CPB revealed primarily genes involved in inflammation-related cell-cell communication (such as L-selectin or intercellular adhesion molecule-2) and signaling (such as IL-1, IL-8, or IL-18 receptors and toll-like receptors 4, 5, and 6), thus confirming a "primed" phenotype of circulating peripheral blood mononuclear cells.

CONCLUSIONS

Gene array and multiplex protein analysis, only in concert, can illuminate the molecular mechanisms responsible for systemic sequelae of CPB and indicate that circulating leukocytes overexpress adhesion and signaling factors after contact with CPB, which potentially facilitates their trapping, eg, in the lungs and may promote a subsequent tissue-associated inflammatory response.

No detrimental effects of repeated laparotomies on early healing of experimental intestinal anastomoses

BACKGROUND

Little is known about the impact of repeated laparotomies on intestinal anastomotic healing. While experimental data are completely lacking, the sparse data available from clinical studies report high anastomotic failure rates, suggesting a negative effect in this respect. Since the unequivocal determination of such an effect may have important consequences for choosing the optimal treatment strategy for patients suffering from intra-abdominal infection, an experimental study has been performed in an established rodent model.

METHODS

Intestinal anastomoses were constructed in healthy Wistar rats (ileal and colonic anastomoses) or 24 h after peritonitis was induced by caecal ligation and puncture (colonic anastomosis only). Rats were then scheduled to undergo no, one (after 24 h) or two relaparotomies (after 24 and 48 h). Anastomotic strength was assessed 3 and 5 days after anastomotic construction. On the third post-operative day anastomotic hydroxyproline levels, matrix metalloproteinase activity and myeloperoxidase activity were measured.

RESULTS

No negative impact of repeated laparotomies was measured on any of the parameters measured. Under non-infectious conditions even an improvement in breaking strength (+48%, p=0.017) but not bursting pressure was found after two relaparotomies, but only in the ileum on the third post-operative day.

CONCLUSIONS

In this experimental setting, early anastomotic healing is not adversely affected by repeated laparotomies.

The Pseudomonas aeruginosa quorum-sensing molecule N-(3-oxododecanoyl)-L-homoserine lactone stimulates phagocytic activity in human macrophages through the p38 MAPK pathway

Quorum-sensing is an important mechanism for the regulation of bacteria-to-bacteria communication. Recent advances have demonstrated that the Pseudomonas aeruginosa signaling molecule N-(3-oxododecanoyl)-L-homoserine lactone (3O-C(12)-HSL) is also a potent modulator of eukaryotic cells and may thus play an important role in the host response during P. aeruginosa infections. Little is known, however, about specific effects of 3O-C(12)-HSL molecules on human macrophages. To address this issue, we investigated the influence of 3O-C(12)-HSL on the phagocytic activity, production of reactive oxygen species, and activation of p38 and p42/44 MAPK signaling pathways in human macrophages. We show an effect of 3O-C(12)-HSL on the phagocytic capacity in human macrophages, which depends on concentration and time of exposure. When cells were exposed to 100 microM 3O-C(12)-HSL for 30 min or 1 h, the phagocytic activity increased 1.8 and 1.6 times, respectively. The 3O-C(12)-HSL treatments had no significant effect on the level of reactive oxygen species production. Furthermore, the p38 MAPK, but not the p42/44 MAPK, signaling pathway was activated in response to 3O-C(12)-HSL. In addition, specific blocking of p38 MAPK activation with 10 microM SB 203580 prevented the 3O-C(12)-HSL-induced increase in the phagocytic activity. These findings demonstrate that the bacterial quorum-sensing can play a significant role also in regulation of macrophage activity during infections caused by P. aeruginosa.

15-DEOXY-??12,14-PROSTAGLANDIN J2 (15D-PGJ2), A PEROXISOME PROLIFERATOR ACTIVATED RECEPTOR ?? LIGAND, REDUCES TISSUE LEUKOSEQUESTRATION AND MORTALITY IN ENDOTOXIC SHOCK

Peroxisome proliferator-activated receptor-gamma (PPARgamma) is a nuclear receptor that requires ligand activation for transcription. Experimental studies have shown that 15-deoxy-Delta-PGJ2 (15d-PGJ2) is a natural PPARgamma ligand which has potent anti-inflammatory properties. This study was designed to examine the effect and the molecular mechanisms of 15d-PGJ2 on tissue neutrophil infiltration and survival in endotoxic shock. Male Swiss albino mice were subjected to intraperitoneal injection of Escherichia coli lipopolysaccharide (LPS, 25 mg/kg). Three hours after LPS mice received vehicle or 15d-PGJ2 (1 mg/kg) and continued treatment every 12 hours. Survival was monitored for 72 hours. In a separate experiment, mice were sacrificed 6 hours after LPS and tissue examined. In vehicle-treated mice, LPS injection resulted in a survival rate of 9%. Marked lung injury was characterized by hemorrhage, infiltration of inflammatory cells and reduction of alveolar space. Elevated levels of myeloperoxidase activity in lung and small intestine were indicative of infiltration of neutrophils. Increased expression of intercellular adhesion molecule-1, vascular cellular adhesion molecule-1 and E-selectin were observed in the lung and small intestine. These inflammatory events were associated with reduced expression of PPARgamma and with activation of nuclear factor-kappaB (NF-kappaB) in the lung. Treatment with 15d-PGJ2 improved survival rate to 55%, downregulated expression of adhesion molecules and reduced neutrophil infiltration in tissues. These beneficial effects were associated with reduced activation of NF-kappaB DNA binding, whereas expression and DNA binding of PPARgamma and expression of the cytoprotective heat shock protein (HSP) 70 were increased in the lung. Our data demonstrate that 15d-PGJ2 ameliorates endotoxic shock most likely through repressing the proinflammatory pathway of NF-kappaB and enhancement of the cytoprotective heat shock response.

Myocardial inflammatory responses to sepsis complicated by previous burn injury

BACKGROUND

It is generally accepted that an initial injury such as burn trauma alters immune function such that a second insult increases the morbidity and mortality over that observed with each individual insult. We have shown previously that either burn trauma or sepsis promotes cardiomyocyte secretion of TNF-alpha and IL-1beta, cytokines that have been shown to produce myocardial contractile dysfunction. This study determined whether a previous burn injury (given eight days prior to sepsis) (1) provides a preconditioning phenomenon, decreasing inflammatory responses to a second insult or (2) exacerbates inflammatory response observed with either injury alone.

METHODS

Anesthetized Sprague-Dawley rats were given either burn injury over 40% total body surface area, sepsis alone (intratracheal S. pneumoniae, 4 x 10(6) colony forming units) or sepsis eight days after burn; all rats received lactated Ringer's solution. Hearts harvested 24 h after onset of sepsis alone or sepsis plus eight-day burn were used to (1) isolate cardiomyocytes (collagenase) or (2) assess contractile function (Langendorff). Cardiomyocytes loaded with 2 microg/mL Fura-2AM or sodium-binding benzofuran isophthalate were used to measure intracellular calcium and sodium concentrations (Nikon inverted microscope, Grooney optics, InCyt Im2 Fluorescence Imaging System). Additional cardiomyocytes were used to measure myocyte-secreted TNFalpha, IL-1, IL-6, IL-10 (pg/ml, ELISA).

RESULTS

Either burn trauma alone or sepsis alone promoted TNF-alpha, IL-1beta, nitric oxide, IL6 and IL-10 secretion by cardiomyocytes (p < 0.05). Producing aspiration-related pneumonia eight days postburn produced myocardial pro- and anti-inflammatory responses and increased myocyte Ca2+/Na+ concentrations to a significantly greater degree than the responses observed after either insult alone.

CONCLUSIONS

A previous burn injury alters myocardial inflammatory responses, predisposing the burn-injured subject to exaggerated inflammation, which correlates with greater myocardial dysfunction.

The 2003 Carl A Moyer Award: real-time metabolic monitors, ischemia-reperfusion, titration endpoints, and ultraprecise burn resuscitation

Real-time metabolic monitoring of varied vascular beds provides the raw data necessary to conduct ultraprecise burn shock resuscitation based on second-by-second assessment of regional tissue perfusion. It also illustrates shortcomings of current clinical practices. Arterial base deficit was continuously monitored during 11 clinical resuscitations of patients suffering burn shock using a Paratrend monitor. Separately, in a 30% TBSA rat burn model (N = 70), three Paratrend monitors simultaneously recorded arterial blood gas and tissue pCO2 of the burn wound and colonic mucosa during resuscitation at 0, 2, 4, 6, and 8 ml/kg/%TBSA. Paratrend data were analyzed in conjunction with previously reported laser Doppler images of actual burn wound capillary perfusion. With current clinical therapy, continuous monitoring of arterial base deficit revealed repetitive cycles of resolution/worsening/resolution during burn shock resuscitation. In the rat model, tissue pCO2 in both burn wounds and splanchnic circulation differed depending on the rate of fluid resuscitation (P <.01 between sham and 0 ml/kg/%TBSA and between 2 ml/kg/%TBSA and 4 ml/kg/%TBSA). Burn wound pCO2 values correlated well with laser Doppler determination of actual capillary perfusion (rho = -.48, P <.01). The following conclusions were reached: 1). Gratuitous and repetitive ischemia-reperfusion-ischemia cycles plague current clinical therapy as demonstrated by numerous "false starts" in the resolution of arterial base deficit; 2). in a rat model, real-time monitoring of burn wound and splanchnic pCO2 demonstrate a dose-response relationship with rate of fluid administration; and 3). burn wound and splanchnic pCO2 are highly correlated with direct measurement of burn wound capillary perfusion by laser Doppler imager. Either technique can serve as a resuscitation endpoint for real-time feedback-controlled ultraprecise resuscitation.

Posttraumatic inflammation is a complex response based on the pathological expression of the nervous, immune, and endocrine functional systems

The successive phases that make up both the local and systemic posttraumatic acute inflammatory response could represent the expression of three concatenated pathological or "primitive" functional systems with trophic properties: the nervous, immune, and endocrine ones. The nervous functional system would play an important role in the phenomenon of ischemia-reperfusion, which would be represented by nutrition by diffusion that is either anaerobic (ischemia) or with defective use of oxygen (reperfusion) and, thus, with a limited energy requirement. The immune functional system would be represented by the infiltration of the tissues by inflammatory cells and bacteria, which would become mediators in providing nutrition to the injured tissues. Although the use of oxygen would still be defective, hypermetabolism and fever would occur. In these inflammatory response phases, the lymphatic is the most important circulation. The endocrine functional system would be the most specialized and would have high energy requirements because it would be represented by the blood capillary-mediated nutrition. Highly specialized epithelial cells would already possess a perfected oxidative metabolism. The successive expression of these three functional systems during embryonic development and also during the evolutionary development of our species could explain why the inflammatory response is a ubiquitous mechanism that is common to multiple diseases, because it is an integrator of the ontogeny and phylogeny.

The role of estrogen in cardiovascular disease

Cardiovascular disease is the number one cause of death among women, accounting for nearly 50% of female deaths. Statistics show that women on average develop cardiovascular disease 10 to 15 years later in life than men, and that the risk may increase after menopause. This observation has led to much speculation as to what physiological change(s) associated with menopause is responsible for the higher risk of atherosclerosis. Estrogen, with its potential as a cardioprotective agent and as an immunomodulator of the inflammatory response in atherosclerosis, has received the most attention. Understanding the mechanisms that lead to these differences may allow beneficial therapeutic intervention to enhance this effect in females and evoke this protection in males. This review will do the following: (1) characterize mechanisms of atherosclerosis, (2) explore the role of estrogen-replacement therapy, (3) define the effect of gender on inflammation, (4) compare and contrast the effects of estrogen and testosterone on endothelial functional, and (5) suggest mechanistic based therapeutic opportunities.

Cardiac effects of burn injury complicated by aspiration pneumonia-induced sepsis

Early fluid resuscitation, antimicrobials, early excision, and grafting have improved survival in the early postburn period; however, a significant incidence of pneumonia-related sepsis occurs after burn injury, often progressing to multiple organ failure. Recent studies have suggested that this initial injury (burn injury) primes the subject, producing an exaggerated response to a second insult, such as pneumonia-related sepsis. We developed an experimental animal model that included a third-degree burn over 40% of the total body surface area, followed by sepsis (intratracheal administration of Streptococcus pneumoniae, 4 x 106 colony-forming unit), which was produced either 48 or 72 h after burn injury in adult male rats. Hearts harvested after either burn alone, sepsis alone, or burn plus sepsis were used to assess either contractile function (Langendorff) or cardiomyocyte secretion of tumor necrosis factor-alpha, interleukin (IL)-1beta, IL-6, and IL-10 (ELISA). Experimental groups included the following: 1). sham (sham burn and no sepsis); 2). burn injury alone studied either 24, 48, or 72 h postburn; 3). pneumonia-related sepsis in the absence of burn injury; and 4). pneumonia-induced sepsis studied either 48 or 72 h after an initial burn injury. Burn injury alone (24 h) or sepsis alone produced myocardial contractile defects and increases in pro- and anti-inflammatory cytokine secretion by cardiomyocytes. Sepsis that occurred 48 h postburn exacerbated the cardiac contractile defects seen with either burn alone or sepsis alone. Sepsis that occurred 72 h postburn produced contractile defects resembling those seen in either burn alone or sepsis alone. In conclusion, our data suggest that burn injury primes the subject such that a second insult early in the postburn period produces significantly greater cardiac abnormalities than those seen with either burn alone or sepsis alone.

Pathophysiology and Management of Abdominal Compartment Syndrome

Abdominal compartment syndrome is a potentially lethal condition caused by any event that produces intra-abdominal hypertension; the most common cause is blunt abdominal trauma. Increasing intra-abdominal pressure causes progressive hypoperfusion and ischemia of the intestines and other peritoneal and retroperitoneal structures. Pathophysiological effects include release of cytokines, formation of oxygen free radicals, and decreased cellular production of adenosine triphosphate. These processes may lead to translocation of bacteria from the gut and intestinal edema, predisposing patients to multiorgan dysfunction syndrome. The consequences of abdominal compartment syndrome are profound and affect many vital body systems. Hemodynamic, respiratory, renal, and neurological abnormalities are hallmarks of abdominal compartment syndrome. Medical management consists of urgent decompressive laparotomy. Nursing care involves vigilant monitoring for early detection, including serial measurements of intra-abdominal pressure.

Shock-induced neutrophil mediated priming for acute lung injury in mice: divergent effects of TLR-4 and TLR-4/FasL deficiency

Acute lung injury (ALI) leading to respiratory distress is a common sequela of shock/trauma, however, modeling this process in mice with a single shock or septic event is inconsistent. One explanation is that hemorrhage is often just a "priming insult," thus, secondary stimuli may be required to "trigger" ALI. To test this we carried out studies in which we assessed the capacity of hemorrhage alone or hemorrhage followed by septic challenge (CLP) to induce ALI. Lung edema, bronchoalveolar lavage interleukin (IL)-6, alveolar congestion, as well as lung IL-6, macrophage inflammatory protein (MIP)-2, and myeloperoxidase (MPO) activity were all increased in mice subjected to CLP at 24 but not 72 hours following hemorrhage. This was associated with a marked increase in the susceptibility of these mice to septic mortality. Peripheral blood neutrophils derived from 24 hours post-hemorrhage, but not Sham animals, exhibited an ex vivo decrease in apoptotic frequency and an increase in respiratory burst capacity, consistent with in vivo "priming." Subsequently, we observed that adoptive transfer of neutrophils from hemorrhaged but not sham-hemorrhage animals to neutropenic recipients reproduce ALI when subsequently septically challenged, implying that this priming was mediated by neutrophils. We also found marked general increases in lung IL-6, MIP-2, and MPO in mice deficient for toll-like receptor (TLR-4) or the combined lack of TLR-4/FasL. However, the TLR-4 defect markedly attenuated neutrophil influx into the lung while not altering the change in local cytokine/chemokine expression. Alternatively, the combined loss of FasL and TLR-4 did not inhibit the increase in MPO and exacerbated lung IL-6/MIP-2 levels even further.

Ischemic preconditioning: fact or fantasy?

Fifteen years ago, an experimental effort to magnify a myocardial infarction, with preinfarction episodes of transient ischemia, proved paradoxically protective. In the ensuing years, surgeons have learned to discriminate a biochemical/metabolic/functional spectrum of cardiac states ranging from healthy myocardium to "stunned" or "hibernating" heart to the modes of "apoptotic" or "necrotic" cardiomyocyte death. It is now clear that "protective cardiac preconditioning" influences all of these cardiac states. The cellular mechanisms of preconditioning (PC) are now sufficiently understood to permit clinical application. Ligation of adrenergic, adenosine, bradykinin or opioid receptors involves signaling via both tyrosine and calcium-dependent protein kinases (PKC), which activate mitochondrial ATP-dependent potassium channels. Subsequently, the release of oxygen radicals induces nuclear translocation of transcriptional regulators, which transform the cardiomyocyte into a more resilient cell. Although preconditioning was initially recognized as protecting only against infarction, PC also limits postischemic dysrhythmias and enhances contractile function. Phase I (safety) and phase II (efficacy) clinical trials now persuasively support pharmacological preconditioning as a safe mode of preventing postcardiac surgical complications. Indeed, preconditioning is currently being proposed as adjunctive to hypothermic perfusates in protecting against the obligate organ ischemia during transplantation.

TNF-alpha-dependent bilateral renal injury is induced by unilateral renal ischemia-reperfusion

While tumor necrosis factor (TNF)-alpha is an important mediator of renal ischemia-reperfusion (I/R) injury, its role in contralateral renal injury after isolated renal ischemia remains unknown. We therefore investigated the effect of isolated left renal ischemia on the nonischemic contralateral kidney. To study this, male Sprague-Dawley rats were anesthetized and exposed to varying degrees of left renal I/R injury. Both kidneys were subsequently harvested, serum samples were obtained, and TNF-alpha protein expression (ELISA), TNF-alpha mRNA content (RT-PCR), TNF-alpha immunolocalization, and neutrophil infiltration (myeloperoxidase assay) were determined. The effect of TNF-alpha on neutrophil infiltration was assessed by neutralizing TNF-alpha with TNF binding protein (TNF-BP) before left renal I/R injury. TNF-alpha protein expression, TNF-alpha mRNA induction, and neutrophil infiltration increased significantly in both kidneys after unilateral renal I/R injury. Furthermore, the administration of TNF-BP before unilateral renal I/R substantially reduced the degree of neutrophil infiltration bilaterally. These results constitute the initial demonstration that unilateral renal I/R induces bilateral TNF-alpha production and neutrophil infiltration through a TNF-alpha-dependent mechanism.

Lactoferrin protects neonatal rats from gut-related systemic infection

Lactoferrin is a milk protein that reportedly protects infants from gut-related, systemic infection. Proof for this concept is limited and was addressed during in vivo and in vitro studies. Neonatal rats pretreated orally with recombinant human lactoferrin (rh-LF) had less bacteremia and lower disease severity scores (P < 0.001) after intestinal infection with Escherichia coli. Control animals had 1,000-fold more colony-forming units of E. coli per milliliter of blood than treated animals (P < 0.001). Liver cultures from control animals had a twofold increase in bacterial counts compared with cultures from rh-LF-treated pups (P < 0.02). Oral therapy with rh-LF + FeSO(4) did not alter the protective effect. In vitro studies confirmed that rh-LF interacted with the infecting bacterium and rat macrophages. An in vitro assay showed that rh-LF did not kill E. coli, but a combination of rh-LF + lysozyme was microbicidal. In vitro studies showed that rat macrophages released escalating amounts of nitric oxide and tumor necrosis factor-alpha when stimulated with increasing concentrations of rh-LF. The in vitro studies suggest that rh-LF may act with other "natural peptide antibiotics" or may prime macrophages to kill E. coli in vivo.

Bench to bedside: tumor necrosis factor-alpha: from inflammation to resuscitation

Proinflammatory mediators such as tumor necrosis factor-alpha (TNF) have been implicated in the pathophysiology in a number of acute disease states. Tumor necrosis factor-alpha can contribute to cell death, apoptosis, and organ dysfunction. Tumor necrosis factor-alpha can be generated with sepsis or ischemia-reperfusion by activation of cell mitogen-activated protein kinases and nuclear factor kappa B, leading to TNF production. A number of strategies to modulate TNF have been recently explored, including factors directed toward mitogen-activated protein kinases, TNF transcription, anti-inflammatory ligands, heat shock proteins, and TNF-binding proteins. However, TNF may also play an important role in the adaptive response to injury and inflammation. Control of the deleterious effects of TNF and other proinflammatory cytokines represents a realistic goal for clinical emergency medicine. The purpose of this article is to provide a background of relevance to emergency medicine academicians on the production and regulation of TNF, the acute effects of TNF on pathophysiology, and the rationale for therapeutic interventions directed toward TNF and the clinical experience with these strategies.

Involvement of p38 mitogen-activated protein kinase in the induction of tolerance to hemorrhagic and endotoxic shock

BACKGROUND

Exposure to sublethal hemorrhage (SLH) makes rats tolerant to subsequent hemorrhagic or septic shock and is associated with altered NF-kappaB activity. The purpose of this study was to explore whether changes in p38 mitogen-activated protein (MAP) kinase activity also occur in the induction of tolerance by SLH.

METHODS

Rats were made tolerant by SLH or sham operation. Twenty-four hours later rats were exposed to lipopolysaccharide (LPS) or had peritoneal macrophages (Mphi) isolated. CNI-1493, a p38 MAP kinase inhibitor, or saline was given prior to SLH. Lungs were harvested 1 h after SLH or LPS and total protein was extracted. Peritoneal Mphi were stimulated with LPS (10 microg/ml) and total protein was isolated 1 h later. Active, dually phosphorylated p38 MAP kinase was determined by Western blot. Tumor necrosis factor (TNF) was measured in Mphi supernatants by enzyme-linked immunosorbent assay (ELISA) 18 h after LPS.

RESULTS

SLH activated p38 MAP kinase in the lung and this was inhibited by CNI-1493. Twenty-four hours later, lung p38 MAP kinase activity increased to the same degree in tolerant and sham rats following LPS, but much more prominently in the CNI-1493 treated rats. There was no p38 activity in peritoneal Mphi at baseline, and similar to lung p38, LPS led to increased p38 activity which was most significant in Mphi from rats that received CNI-1493 prior to SLH. TNF production by tolerant Mphi in response to LPS was significantly (P < 0.05, t test) decreased and p38 inhibition with CNI-1493 at the time of SLH reversed the inhibitory effects of tolerance on TNF production.

CONCLUSIONS

TNF production by tolerant Mphi following a second insult (LPS) is attenuated despite preservation of normal p38 MAP kinase activity. However, activation of this intracellular second messenger is a necessary step in the "cellular reprogramming" that occurs during the induction of tolerance by SLH.

Early renal ischemia, with or without reperfusion, activates NFkappaB and increases TNF-alpha bioactivity in the kidney

PURPOSE

Acute tubular necrosis (ATN) and the ensuing renal failure induced by ischemia and reperfusion injury (I/R) remain a major cause of morbidity and mortality among patients in the intensive care unit. Although it is well established that exogenous tumor necrosis factor-alpha (TNF) induces renal injury, it remains unknown whether ischemia and/or reperfusion activates the signaling mechanisms required for renal TNF production. We hypothesized that ischemia and/or reperfusion would activate the oxidant sensitive TNF transcription factor, nuclear factor kappa B (NFkappaB), and thereby lead to renal TNF production.

MATERIALS AND METHODS

Male Sprague-Dawley rats were anesthetized with sodium pentobarbital, after which various periods of renal ischemia, with or without reperfusion, were induced in rats. At different time intervals, kidneys were harvested and NFkappaB activation (electrophoretic mobility shift assay), TNF mRNA content (RT-PCR), and TNF bioactivity (WEHI-164 cell clone cytotoxicity assay) were determined.

RESULTS

Results indicate that 15 minutes of ischemia alone activates NFkappaB, whereas peak activation occurred at 30 minutes of ischemia alone. NFkappaB remained activated through 60 minutes reperfusion. Thirty minutes of ischemia is required to induce renal TNF mRNA production; however, renal TNF protein expression and bioactivity peaked following 1 hour of ischemia and 2 hours reperfusion.

CONCLUSIONS

These results are the initial demonstration that renal ischemia, with or without reperfusion, activates the TNF transcription factor NFkappaB and increases TNF bioactivity in the kidney.

Sepsis Syndrome

A clinical syndrome including fever, leukocytosis, elevated cardiac output, and reduced systemic vascular resistance has been associated with severe infection (i.e., sepsis). However, during the last 15 years, many patients have demonstrated all of the findings that have traditionally been associated with “sepsis” but have not had demonstrated sources of infection. This led to the term “sepsis syndrome” to refer to that population of patients who appeared to have a physiologic and metabolic response associated with, but who did not have, severe infection. More commonly called the systemic inflammatory response syndrome (SIRS), the sepsis syndrome is now associated with the nonspecific systemic activation of the human inflammatory cascade by any of a number of clinical events. The management of the SIRS patient has been ineffective because of incomplete definition of the mechanisms responsible for the syndrome. It is argued that all of the biological mechanisms that are operative in a simple wound and are beneficial are negative for the host when activated systemically. Thus, SIRS is seen in three separate scenarios at present: (1) invasive infection; (2) dissemination of microbes secondary to failure of host defense mechanisms; and (3) severe activation of inflammation by injury, shock, severe soft tissue inflammation, and other noninfectious but proinflammatory events. Newer treatment strategies will need to focus not on the inciting event itself but on better control of the complex responses of the host.

Early kidney TNF-alpha expression mediates neutrophil infiltration and injury after renal ischemia-reperfusion

The purpose of this study was to determine whether isolated renal ischemia and reperfusion (I/R) induces renal tumor necrosis factor (TNF) mRNA production, TNF protein expression, or TNF bioactivity and, if so, whether local/early TNF production acts as mediator of ischemia-induced, neutrophil-mediated renal injury. After rats were anesthetized, varying periods of renal ischemia, with or without reperfusion, were induced. Kidney mRNA content (RT-PCR), TNF protein expression (ELISA), TNF bioactivity (WEHI-164 cell clone cytotoxicity assay), and neutrophil infiltration [myeloperoxidase (MPO) assay] were determined. In other animals, renal MPO and serum creatinine were assessed after TNF was neutralized [binding protein (TNF-BP)]. Thirty minutes of ischemia induced renal TNF mRNA. TNF protein expression and bioactivity peaked after 1 h ischemia and 2 h reperfusion, whereas neutrophil infiltration peaked at 4 h reperfusion. TNF-BP neutralized TNF bioactivity, reduced neutrophil infiltration, and protected postischemic function. These results constitute the initial demonstration that 1) early renal tissue TNF expression contributes to neutrophil infiltration and injury after I/R and 2) TNF-BP may offer a new adjunctive therapy in renal preservation prior to planned ischemic insults.

Role of TNF in mediating renal insufficiency following cardiac surgery: evidence of a postbypass cardiorenal syndrome

Recent evidence has implicated proinflammatory mediators such as TNF-alpha in the pathophysiology of ischemia-reperfusion (I/R) injury. Clinically, serum levels of TNF-alpha are increased after myocardial infarction and after cardiopulmonary bypass. Both cardiopulmonary bypass and renal ischemia-reperfusion injury induce a cascade of events leading to cellular damage and organ dysfunction. Tumor necrosis factor (TNF), a potent proinflammatory cytokine, is released from both the heart and the kidney in response to ischemia and reperfusion. TNF released during cardiopulmonary bypass induces glomerular fibrin deposition, cellular infiltration, and vasoconstriction, leading to a reduction in glomerular filtration rate (GFR). The signaling cascade through which renal ischemia-reperfusion induces TNF production is beginning to be elucidated. Oxidants released following reperfusion activate p38 mitogen-activated protein kinase (p38 MAP kinase) and the TNF transcription factor, NFkappaB, leading to subsequent TNF synthesis. In a positive feedback, proinflammatory fashion, binding of TNF to specific TNF membrane receptors can reactivate NFkappaB. This provides a mechanism by which TNF can upregulate its own expression as well as facilitate the expression of other genes pivotal to the inflammatory response. Following its production and release, TNF results in both renal and myocardial apoptosis and dysfunction. An understanding of these mechanisms may allow the adjuvant use of anti-TNF therapeutic strategies in the treatment of renal injury. The purposes of this review are: (1) to evaluate the evidence which indicates that TNF is produced by the heart following cardiopulmonary bypass; (2) to examine the effect of TNF on myocardial performance; (3) to outline the mechanisms by which the kidney produces significant TNF in response to ischemia and reperfusion; (5) to investigate the role of TNF in renal ischemia-reperfusion injury, (6) to describe the mechanisms of TNF-induced renal cell apoptosis, and (7) to suggest potential anti-TNF strategies designed to reduce renal insufficiency following cardiac surgery.

Calcium preconditioning, but not ischemic preconditioning, bypasses the adenosine triphosphate-dependent potassium (KATP) channel

BACKGROUND

Recent evidence has implicated the KATP channel as an important mediator of ischemic preconditioning (IPC). Indeed, patients taking oral sulfonylurea hypoglycemic agents (i.e., KATP channel inhibitors) for treatment of diabetes mellitus are resistant to the otherwise profoundly protective effects of IPC. Unfortunately, many cardiopulmonary bypass patients, who may benefit from IPC, are chronically exposed to these agents. Calcium preconditioning (CPC) is a potent form of similar myocardial protection which may or may not utilize the KATP channel in its mechanism of protection. The purpose of this study was to determine whether CPC may bypass the KATP channel in its mechanism of action. If so, CPC may offer an alternative to IPC in patients chronically exposed to these agents.

METHODS

Isolated rat hearts (n = 6-8/group) were perfused (Langendorff) and received KATP channel inhibition (glibenclamide) or saline vehicle 10 min prior to either a CPC or IPC preconditioning stimulus or neither (ischemia and reperfusion, I/R). Hearts were subjected to global warm I/R (20 min/40 min). Postischemic myocardial functional recovery was determined by measuring developed pressure (DP), coronary flow (CF), and compliance (end diastolic pressure, EDP) with a MacLab pressure digitizer.

RESULTS

Both CPC and IPC stimuli protected myocardium against postischemic dysfunction (P < 0.05 vs I/R; ANOVA with Bonferroni/Dunn): DP increased from 52 +/- 4 (I/R) to 79 +/- 2 and 83 +/- 4 mmHg; CF increased from 11 +/- 0.7 to 17 +/- 2 and 16 +/- 1 ml/min; and EDP decreased (compliance improved) from 50 +/- 7 to 27 +/- 5 and 31 +/- 7 mmHg. However, KATP channel inhibition abolished protection in hearts preconditioned with IPC (P < 0.05 vs IPC alone), but not in those preconditioned with CPC (P > 0.05 vs CPC alone).

CONCLUSIONS

(1) Both IPC and CPC provide similar myocardial protection; (2) IPC and CPC operate via different mechanisms; i.e., IPC utilizes the KATP channel whereas CPC does not; and (3) CPC may offer a means of bypassing the deleterious effects of KATP channel inhibition in diabetic patients chronically exposed to oral sulfonylurea hypoglycemic agents.

Review article: the role of tumor necrosis factor in renal ischemia-reperfusion injury

Renal ischemia-reperfusion injury induces a cascade of events leading to cellular damage and organ dysfunction. Tumor necrosis factor-alpha (TNF), a potent proinflammatory cytokine, is released from the kidney in response to, and has been implicated in the pathogenesis of, renal ischemia-reperfusion injury. TNF induces glomerular fibrin deposition, cellular infiltration and vasoconstriction, leading to a reduction in glomerular filtration rate (GFR). The signaling cascade through which renal ischemia-reperfusion induces TNF production is beginning to be elucidated. Oxidants released following reperfusion activate p38 mitogen activated protein kinase (p38 MAP kinase) and the TNF transcription factor, NFkappaB, leading to subsequent TNF synthesis. In a positive feedback, proinflammatory fashion, binding of TNF to specific TNF membrane receptors can reactivate NFkappaB. This provides a mechanism by which TNF can upregulate its own expression as well as facilitate the expression of other genes pivotal to the inflammatory response. TNF receptor binding can also induce renal cell apoptosis, the major form of cell death associated with renal ischemia-reperfusion injury. Anti-TNF strategies targeting p38 MAP kinase, NFkappaB, and TNF itself are being investigated as methods of attenuating renal ischemic injury. The control of TNF production and activity represents a realistic goal for clinical medicine.

Neutrophil priming state predicts capillary leak after gut ischemia in rats

BACKGROUND

Multiple organ failure after serious injury or illness is a major determinant of mortality. An initial insult is believed to "prime" circulating neutrophils and induce systemic inflammation. Thereafter, a second insult will precipitate distant organ injury. The aim of these studies was to evaluate circulating neutrophil function after mesenteric ischemia-reperfusion to determine the neutrophil "priming state," a quantitative and clinically useful predictor of multiple organ failure.

MATERIALS AND METHODS

Anesthetized Sprague-Dawley rats underwent superior mesenteric artery occlusion for 30 min or sham operation and were euthanized after 2, 6, or 24 h of reperfusion. Control animals had blood taken without any intervention. To determine changes in lung capillary permeability, another group of rats received Evan's blue, a dye that binds albumin, 1 h before sacrifice. Flow cytometric analysis was performed on 5 million white blood cells after removal of red cells by lysis and centrifugation. Neutrophil number, oxidative burst, and CD18 expression were measured.

RESULTS

The number of circulating neutrophils was elevated similarly in rats subjected to sham operation or ischemia-reperfusion. Oxidative burst potential was increased at 2 h, maximum at 6 h, and normal at 24 h after reperfusion, but not in sham rats. CD18 expression was similar in all groups. There was a significant temporal correlation between the "priming state" of the circulating neutrophil, defined as the product of the neutrophil number times oxidative burst, and lung leak.

CONCLUSIONS

The neutrophil "priming state" may allow the clinician to better predict those patients at greatest risk for multiple organ failure.

Tolerance to shock: an exploration of mechanism

OBJECTIVE

To determine if cross-tolerance to septic shock could be induced by a previous insult with sublethal hemorrhage (SLH) and to characterize the mechanisms involved in this induced protective response.

BACKGROUND DATA

It is possible to condition animals by prior SLH such that they tolerate an otherwise lethal hemorrhage. It is also possible to condition animals with low doses of lipopolysaccharide (LPS) so that they survive a "lethal" septic insult. However, a paucity of information exists on cross-tolerance between hemorrhage and sepsis.

METHODS

Rats were made tolerant by conditioning SLH or sham operation. Twenty-four hours later, tolerant and sham rats were exposed to a lethal dose of LPS. To explore the mechanism of tolerance induction, rats were given the macrophage (Mphi) inhibitor CNI-1493 or saline carrier before SLH. Survival and pulmonary vascular injury were determined after LPS. Serum tumor necrosis factor (TNF) levels and splenic Mphi TNF gene expression were measured at several time points.

RESULTS

Prior SLH indeed made rats tolerant and imparted a significant survival benefit and reduction in pulmonary vascular injury after LPS. The tolerance induced by SLH was reversed by Mphi inhibition. Tolerant animals had low serum TNF levels immediately after SLH and reduced circulating TNF levels after LPS. SLH, however, did not inhibit the augmentation of TNF gene expression after LPS.

CONCLUSIONS

Sublethal hemorrhage bestows protection against a lethal LPS challenge. Inhibition of the Mphi attenuated the benefit of the tolerance induced by SLH. Circulating TNF but not TNF gene after LPS is lessened by SLH. This implicates changes in Mphi intracellular signaling in induction of the tolerant state.

Induction of tolerance to hemorrhagic or endotoxic shock involves activation of NF-kappaB

BACKGROUND

Tolerance to hemorrhagic or endotoxic shock can be induced by prior sublethal hemorrhage (SLH). The purpose of this study was to explore whether alterations in signal transduction pathways involving NF-kappaB occur in macrophages (Mphi) following induction of tolerance by SLH.

METHODS

Using a model of SLH previously shown in our lab to impart a survival benefit to subsequent hemorrhagic or endotoxic shock, rats (n = 30) were conditioned by SLH. Peritoneal Mphi were harvested 24 h after conditioning and stimulated with lipopolysaccharide (LPS) (10 microg/mL). Nuclear and cytosolic proteins were isolated 1 h later for determination of NF-kappaB activation by gel-shift assay and IkappaB-alpha by Western blot. TNF mRNA gene expression was measured 4 h after LPS stimulation by reverse transcription/polymerase chain reaction (RT/PCR). TNF protein levels were measured in cellular supernatants by enzyme-linked immunosorbent assay (ELISA) 18 h after LPS. RESULTS. LPS stimulation of sham Mphi increased NF-kappaB activation with corresponding loss of its inhibitor IkappaB-alpha. In contrast, IkappaB-alpha was not detectable following conditioning, and conditioned Mphi had NF-kappaB activation at baseline which increased minimally with LPS stimulation. LPS increased TNF gene expression and significantly increased protein production by both sham and conditioned Mphi, but this increase was greater in the sham-conditioned group.

CONCLUSIONS

The ability of Mphi from animals made tolerant by SLH to produce TNF in vitro is conserved. Nevertheless, these same Mphi exhibit alterations in TNF gene induction and expression as well as signal transduction, specifically, changes in IkappaB-alpha and NF-kappaB activation. This suggests a role for activation of NF-kappaB in the induction of tolerance.

Multiple organ failure. How valid is the "two hit" model?

Inflammatory "one hit" and "two hit" models have recently been proposed to account for the development of multiple organ failure (MOF) in trauma and critically ill surgical patients when no source of infection can be found. In the "one hit" model, the initial insult is so massive that a systemic inflammatory response syndrome is triggered and leads rapidly to MOF. In the "two hit" scenario, initially less severely injured patients eventually develop MOF as a result of a reactivation of their inflammatory response caused by an adverse and often minor intercurrent event. At first sight, the theory is attractive because it seems to fit commonly observed clinical patterns. Indeed, injured patients often respond to initial resuscitation but, after an insult of some sort, develop organ dysfunction and die. The "two hit" model is furthermore mirrored at the cellular level. Inflammatory cells are indeed susceptible of being primed by an initial stimulus and reactivated subsequently by a relatively innocuous insult. However, in the absence of clinical and biological corroboration based on cytokine secretion patterns, these models should not be accepted uncritically.

Ischemia-reperfusion protects the rat small intestine against subsequent injury

BACKGROUND

It has been suggested that multiple sublethal insults are commonly associated with the development of multiple organ failure (MOF). The gut is considered to be pivotal in the pathogenesis of MOF. This study investigated the effects of repeated ischemia-reperfusion of the rat small intestine.

METHODS

Groups of rats underwent 30 min of superior mesenteric artery occlusion or sham operation followed by 24 h of reperfusion. They then received an additional 30 min of superior mesenteric artery occlusion and 2 h of reperfusion or sham operation. Small intestine was examined for mucosal injury, neutrophil infiltration, goblet cell number, and generation of the eicosanoids, prostaglandin E2, and leukotriene B4. Activation of neutrophils was assessed in systemic venous blood.

RESULTS

Animals subjected to two insults of ischemia-reperfusion demonstrated significantly less mucosal injury than animals undergoing one episode of ischemia and 2 h of reperfusion, despite increased neutrophil infiltration, leukotriene B4, and activated systemic neutrophils. Goblet cell number was elevated in animals 24 h after the first ischemia-reperfusion insult and remained enhanced after the second episode of ischemia-reperfusion.

CONCLUSIONS

The initial episode of ischemia-reperfusion caused an adaptive response associated with cytoarchitectural preservation following the subsequent insult. Increased mucus production was associated with mucosal protection. Nevertheless, repeated ischemia-reperfusion potentiated the local inflammatory response and the systemic activation of neutrophils.

Nitric oxide downregulates lung macrophage inflammatory cytokine production

BACKGROUND

Inflammatory cytokine production contributes to lung injury after lung ischemia reperfusion and during lung transplant rejection. Although nitric oxide has been demonstrated to reduce lung injury associated with the adult respiratory distress syndrome, it remains unknown whether the mechanism of nitric oxide's beneficial effects involves reducing lung macrophage inflammatory cytokine production. The purpose of this study was to determine whether nitric oxide downregulates lung macrophage inflammatory cytokine production.

METHODS

Lung macrophages were harvested by bronchoalveolar lavage (10(6) macrophage per milliliter from normal Sprague-Dawley rats, 6 animals per group) and treated under ex vivo tissue culture conditions with the nitric oxide releasing compound S-nitoso-N-acetyl-D, L-penicillamine (0, 10(-5) 10(-4), 10(-3), 10(-2) mol/L) before induction of inflammatory cytokines with endotoxin, (50 ng/mL for 24 hours). Supernatants were assayed for inflammatory cytokine production (tumor necrosis factor alpha, interleukin-1beta) by enzyme-linked immunosorbent assay.

RESULTS

Continuous nitric oxide release by S-nitoso-N-acetyl-D, L-penicillamine decreased lung macrophage tumor necrosis factor-alpha and interleukin-1beta production in a dose-dependent fashion (6 rats per group; data were analyzed for significance [p < 0.05] using two-way analysis of variance with Tukey's post-hoc correction).

CONCLUSIONS

Nitric oxide decreases inflammatory cytokine production by lung macrophage. The mechanism of nitric oxide's beneficial effects may be partially attributable to decreased production of inflammatory cytokines. Nitric oxide may serve an expanded role for reducing inflammatory cytokine production during acute lung injury, ischemia-reperfusion-induced inflammation, or lung transplant rejection.

Responses of hepatic TNF-alpha mRNA to repeated hemorrhage in the conscious rat

Trauma victims may suffer from repeated hemorrhage, but responses of cytokines to it have not been described. To study this question, we first detected the time course of changes in serum tumor necrosis factor (TNF) activity and hepatic TNF-alpha mRNA by cytotoxicity against L929 cells and by reverse transcription (RT) and polymerase chain reaction (PCR), respectively, after different sizes of hemorrhage (10-20 ml/kg) with chronically cannulated rats. Then we examined the changes in TNF-alpha mRNA when two sequential 10 ml/kg hemorrhages were performed. TNF activity showed no significant increases after either size of hemorrhage. At mRNA level, both 15 ml/kg and 20 ml/kg hemorrhages induced significant increases after hemorrhage, whereas a 10 ml/kg hemorrhage did not. When the 10 ml/kg hemorrhage was repeated 24 h later, however, TNF-alpha mRNA showed a significant increase. There were no significant differences in blood pressure and heart rate after single and repeated 10 ml/kg hemorrhage. This potentiation persisted for >/=48 h. These results show that responses of hepatic TNF-alpha mRNA are augmented when moderate hemorrhage is repeated.