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Christopher C Silliman

Publications and source records attributed to Christopher C Silliman.

33 records · Page 2Linked to original sources
PubMed2003

Clinically relevant hypertonicity prevents stored blood- and lipid-mediated delayed neutrophil apoptosis independent of p38 MAPK or caspase-3 activation.

BACKGROUND: Delayed apoptosis of primed neutrophils (PMNs) may facilitate PMN-mediated tissue injury leading to postinjury multiple organ failure. Aged (42-day-old) stored red blood cells (RBC42) delay PMN apoptosis through proinflammatory phospholipids such as platelet-activating factor (PAF) and lyso-phosphatidylcholine (LPC). Hypertonic saline (HTS) attenuates PMN cytotoxic functions. We hypothesized that clinically relevant HTS would provoke PMN apoptosis, as well as prevent stored blood- and lipid-mediated delayed PMN apoptosis through activation of p38 mitogen-activated protein kinase (MAPK) and caspase-3. METHODS: PMNs harvested from healthy volunteers were incubated (5% CO(2), 37 degrees C, 24 hr) with RBC42 plasma, PAF (20 microM), or LPC (4.5 microM), with or without the p38 MAPK inhibitor SB 203580, the caspase-3 inhibitor zDEVD-fmk (10 micromol/L) or the pan-caspase inhibitor zVAD-fmk (20 micromol/L). Duplicate samples were preincubated in HTS (Na [180 mM]). Apoptotic index (% PMNs undergoing apoptosis) was assessed morphologically. p38 MAPK activation was assessed by Western blotting. Caspase-3 activity was measured colorimetrically. RESULTS: PAF, LPC, and RBC42 plasma delayed apoptosis; HTS increased apoptosis compared with controls. HTS prevented PAF, LPC, and RBC42-delayed apoptosis. p38 MAPK was not activated by HTS; its inhibition had no effect on the actions of HTS. Caspase inhibition attenuated the ability of HTS to increase apoptosis, but it did not affect the ability of HTS to restore healthy PMN apoptosis in the presence of RBC42. CONCLUSION: HTS increases PMN apoptosis and prevents stored blood- and lipid-mediated delayed PMN apoptosis. HTS may activate caspase-3, but alternative signaling pathways appear to be involved in modulating the effects of lipids on PMN apoptosis.

Apoptosis↗
PubMed2003

Alteration of the postinjury hyperinflammatory response by means of resuscitation with a red cell substitute.

BACKGROUND: Transfusion of stored packed red blood cells (PRBCs) has unintended effects beyond the desired results of increased oxygen delivery. A particular concern is the potential for lipid and cytokine mediators present in PRBCs to augment the postinjury inflammatory response that sometimes culminates in multiple organ failure. Through the use of a polymerized human hemoglobin (PolyHeme), we have been able to measure the inflammatory response in patients resuscitated with minimal exposure to banked components in the early postinjury period. METHODS: Critically injured patients requiring urgent transfusion were resuscitated with either PRBCs or PolyHeme in the early postinjury period. Proinflammatory cytokines (interleukin [IL]-8 and IL-6), counterregulatory cytokines (IL-10 and IL-11), and markers of endothelial injury (soluble intercellular adhesion molecule and soluble E-selectin) were serially measured. RESULTS: Increases in IL-8, IL-6, and IL-10 were greater in patients resuscitated with PRBCs. IL-11 plasma levels were largely below the level of detection of the assay. There was no difference in markers of endothelial injury. CONCLUSION: Consistent with concerns about the immunoinflammatory response to transfusion of PRBCs, we observed exaggerated levels of three markers associated with adverse outcome. The clinical significance of these findings with respect to the development of multiple organ failure awaits further study.

Adult↗
PubMed2003

Acute Philadelphia chromosome-positive leukemia in an adolescent boy after liver transplantation.

Acute leukemia is an untoward event following immunosuppression for solid organ transplantation and is related to the oncogenic effects of Epstein-Barr viral infections. The authors report a case of acute, Philadelphia chromosome-positive, T-cell lymphoblastic leukemia following liver transplantation. Molecular typing demonstrated a minor bcr-abl rearrangement (190 kD), which persisted in remission in 71% of peripheral neutrophils as determined by fluorescence in situ hybridization. The authors conclude that this patient may have presented in a lymphoid blast crisis of chronic myelogenous leukemia with an acute T-cell leukemia/lymphoma syndrome.

Adolescent↗
PubMed2003

The abdominal compartment syndrome as a second insult during systemic neutrophil priming provokes multiple organ injury.

In our recent clinical study of damage control laparotomy, the abdominal compartment syndrome (ACS) emerged as an independent risk factor for postinjury multiple organ failure (MOF). We and others have shown previously that the ACS promotes the systemic production of proinflammatory cytokines. Our study objective was to develop a clinically relevant two-event animal model of postinjury MOF using the ACS as a second insult during systemic neutrophil priming to provoke organ dysfunction. Male adult rats underwent hemorrhagic shock (30 mmHg x 45 min) and were resuscitated with crystalloids and shed blood. The timing of postshock systemic neutrophil (PMN) priming was determined by the surface expression of CD11b via flow cytometry. Finding maximal PMN priming at 8 h, but no priming at 2 h (early) and 18 h (late), the ACS (25 mmHg x 60 min) was introduced at these time points. At 24 h postshock, lung injury was assessed by lung elastase concentration and Evans blue dye extravasation in bronchoalveolar lavage. Liver and renal injuries were determined by serum alanine aminotransferase, serum creatinine, and blood urea nitrogen. The ACS during the time of maximal systemic PMN priming (8 h) provoked lung and liver injury, but did not if introduced at 2 or 18 h postshock when there was no evidence of systemic PMN priming. The 24-h mortality of this two-event model was 33%. These findings corroborate the potential for the ACS to promote multiple organ injury when occurring at the time of systemic PMN priming. This clinically relevant two-event animal model of PMN organ injury may be useful in elucidating therapy strategies to prevent postinjury MOF.

Animals↗
PubMed2003

Post-hemorrhagic shock mesenteric lymph activates human pulmonary microvascular endothelium for in vitro neutrophil-mediated injury: the role of intercellular adhesion molecule-1.

BACKGROUND: Splanchnic hypoperfusion is believed to be central in the pathogenesis of hemorrhagic shock-induced acute respiratory distress syndrome and multiple organ failure. Our previous work focused on the portal circulation as the conduit for gut-derived mediators of acute respiratory distress syndrome. Our current focus is the proinflammatory effects of postshock mesenteric lymph. We hypothesize that postshock lymph induces neutrophil (PMN)-mediated endothelial cell damage in an intercellular adhesion molecule-1 (ICAM-1)-dependent fashion, and devised a two-insult model to test this hypothesis. METHODS: Rats (n > or = 5) underwent hemorrhagic shock (mean arterial pressure, 40 mm Hg for 30 minutes) and resuscitation (shed blood plus two times crystalloid) with lymph collection. Human pulmonary microvascular endothelial cells (HMVECs) were divided into three groups and grown to near confluence. Group 1 was incubated for 6 hours in 1% preshock or postshock lymph and ICAM-1 was measured by flow cytometry. Group 2 consisted of coculture of HMVECs and PMNs after endothelial cell activation to determine whether postshock lymph would stimulate PMN adherence. Group 3 was incubated under identical conditions, but PMNs were added for 30 minutes, and then activated with 4.5 micromol/L lysophosphatidylcholine (lyso-PC) for 1 hour to ascertain cytotoxicity. HMVEC density was measured using microscopy and recorded as HMVECs per millimeter squared. ICAM-1-blocking antibody and isotype control were used to assess the effects of ICAM-1 on PMN cytotoxicity. A buffer control was used for comparison using analysis of variance with Tukey's correction. RESULTS: Postshock lymph activated HMVECs for increased surface expression of ICAM-1 and stimulated PMNs to adhere to endothelial cell monolayers. Activation of PMNs with lyso-PC in the presence of postshock lymph resulted in marked HMVEC death. The addition of an ICAM-1-blocking antibody abrogated this effect. Neither postshock lymph alone (758 +/- 35 HMVECs/mm(2)), nor postshock lymph in the presence of quiescent PMNs alone (734 +/- 28 HMVECs/mm(2)), nor lymph plus lyso-PC (834 +/- 21 HMVECs/mm(2)) provoked endothelial cell damage. CONCLUSION: Postshock mesenteric lymph activates endothelial cells for increased ICAM-1 expression and PMN adherence. Furthermore, postshock lymph acts as an inciting event in a two-event in vitro model of PMN-mediated endothelial cell injury. These findings further substantiate the key mechanistic role of mesenteric lymph in hemorrhagic shock-induced acute lung injury and suggest that ICAM-1 expression is pivotal in the two-event model of multiple organ failure.

Animals↗
PubMed2003

Lysophosphatidylcholines prime the NADPH oxidase and stimulate multiple neutrophil functions through changes in cytosolic calcium.

A mixture of lysophosphatidylcholines (lyso-PCs) are generated during blood storage and are etiologic in models of acute lung injury. We hypothesize that lyso-PCs stimulate polymorphonuclear neutrophils (PMNs) through Ca(2)(+)-dependent signaling. The lyso-PC mix (0.45-14.5 micro M) and the individual lyso-PCs primed formyl-Met-Leu-Phe (fMLP) activation of the oxidase (1.8- to 15.7-fold and 1.7- to 14.8-fold; P<0.05). Labeled lyso-PCs demonstrated a membrane association with PMNs and caused rapid increases in cytosolic Ca(2)(+). Receptor desensitization studies implicated a common receptor or a family of receptors for the observed lyso-PC-mediated changes in PMN priming, and cytosolic Ca(2)(+) functions were pertussis toxin-sensitive. Lyso-PCs caused rapid serine phosphorylation of a 68-kD protein but did not activate mitogen-activated protein kinases or cause changes in tyrosine phosphorylation. With respect to alterations in PMN function, lyso-PCs caused PMN adherence, increased expression of CD11b and the fMLP receptor, reduced chemotaxis, provoked changes in morphology, elicited degranulation, and augmented fMLP-induced azurophilic degranulation (P<0.05). Cytosolic Ca(2)(+) chelation inhibited lyso-PC-mediated priming of the oxidase, CD11b surface expression, changes in PMN morphology, and serine phosphorylation of the 68-kD protein. In conclusion, lyso-PCs affect multiple PMN functions in a Ca(2)(+)-dependent manner that involves the activation of a pertussis toxin-sensitive G-protein.

CD11 Antigens↗
PubMed2002

Transfusion-related acute lung injury: epidemiology and a prospective analysis of etiologic factors.

Transfusion-related acute lung injury (TRALI) is a life-threatening complication of hemotherapy. We report a series of 90 TRALI reactions in 81 patients secondary to transfusion with whole blood platelets (72 reactions), apheresis platelets (2), packed red cells (15), and plasma (1). The overall prevalence was 1 in 1120 cellular components. To examine the epidemiology of TRALI, we completed a nested case-control study of the first 46 patients with TRALI compared with 225 controls who had received transfusions. We then completed a prospective analysis of possible biologic response modifiers responsible for 51 of the TRALI cases, including human leukocyte antigen (HLA) class I, class II, and granulocyte antibodies in donors and neutrophil (PMN) priming activity in the plasma of the implicated units and recipients. Two groups were at risk: patients with hematologic malignancies (P <.0004) and patients with cardiac disease (P <.0006). TRALI was associated with older platelets (P =.014). In the prospective study, antileukocyte antibodies were found in only 3.6% of cases. The implicated blood components had greater PMN priming activity than controls (P <.05), and compared with pretransfusion samples, TRALI patients' plasma demonstrated increases in both interleukin 6 (IL-6) and lipid (neutral lipids and lysophosphatidylcholines) priming activity (P <.05). We conclude that TRALI may be more frequent than previously recognized and that patient susceptibility, product age, and increased levels of bioactive lipids in components may predispose patients to TRALI. TRALI, like the acute respiratory distress syndrome, may be a 2-event phenomenon with both recipient predisposition and factors in the stored units playing major roles.

Age Distribution↗
PubMed2002

A two-insult in vitro model of PMN-mediated pulmonary endothelial damage: requirements for adherence and chemokine release.

Lysophosphatidylcholines (lyso-PCs), generated during blood storage, are etiologic in a two-insult, sepsis-based model of transfusion-related acute lung injury (TRALI). Individually, endotoxin (LPS) and lyso-PCs prime but do not activate neutrophils (PMNs). We hypothesized that priming of PMNs alters their reactivity such that a second priming agent causes PMN activation and endothelial cell damage. PMNs were primed or not with LPS and then treated with lyso-PCs, and oxidase activation and elastase release were measured. For coculture experiments, activation of human pulmonary microvascular endothelial cells (HMVECs) was assessed by ICAM-1 expression and chemokine release. HMVECs were stimulated or not with LPS, PMNs were added, cells were incubated with lyso-PCs, and the number of viable HMVECs was counted. Lyso-PCs activated LPS-primed PMNs. HMVEC activation resulted in increased ICAM-1 and release of ENA-78, GRO alpha, and IL-8. PMN-mediated HMVEC damage was dependent on LPS activation of HMVECs, chemokine release, PMN adhesion, and lyso-PC activation of the oxidase. In conclusion, sequential exposure of PMNs to priming agents activates the microbicidal arsenal, and PMN-mediated HMVEC damage was the result of two insults: HMVEC activation and PMN oxidase assembly.

Cell Adhesion↗
PubMed2002

Increased rate of infection associated with transfusion of old blood after severe injury.

HYPOTHESIS: Blood components undergo changes during storage that may affect the recipient, including the release of bioactive agents, with significant immune consequences. We hypothesized that transfusion of old blood increases infection risk in severely injured patients. DESIGN: Prospective cohort study. SETTING: Urban level I regional trauma center. PATIENTS: Sixty-one trauma patients with an Injury Severity Score greater than 15, age older than 15 years, and survival longer than 48 hours who were transfused with 6 to 20 U of red blood cells in the first 12 hours after injury were studied. By means of blood bank records, the age of each unit of blood was determined. INTERVENTION: Transfusion of allogeneic red blood cells. MAIN OUTCOME MEASUREMENTS: Major infectious complications. RESULTS: The early (<12 hours) transfusion requirement was 12 +/- 0.6 U, with a mean age 27 +/- 1 days. Major infections developed in 32 patients (52%). Age and Injury Severity Score were not significantly different between patients who developed infections and those who did not (age, 39 +/- 4 vs 36 +/- 3 years; Injury Severity Score, 33 +/- 1.5 vs 29 +/- 1.5). Transfusion of older blood was associated with subsequent infection; patients who developed infections received 11.7 +/- 1.0 and 9.9 +/- 1.0 U of red blood cells older than 14 and 21 days, respectively, compared with 8.7 +/- 0.8 and 6.7 +/- 0.08 in patients who did not develop infections (both P<.05, t test). Multivariate analysis confirmed age of blood as an independent risk factor for major infections. CONCLUSIONS: Transfusion of old blood is associated with increased infection after major injury. Other options, such as leukocyte-depleted blood or blood substitutes, may be more appropriate in the early resuscitation of trauma patients requiring transfusion.

Adult↗
PubMed2002

The injured child is resistant to multiple organ failure: a different inflammatory response?

BACKGROUND: Although postinjury multiple organ failure (MOF) is a well-described phenomenon in adults, the incidence of this syndrome in children is unknown. The purpose of this study was to describe the incidence, course, and severity of pediatric postinjury MOF. We hypothesized that the incidence and severity of postinjury MOF in children would be less when compared with adults. METHODS: Patients were retrospectively identified from the trauma registry of a regional pediatric trauma center and an adult Level I trauma center with pediatric commitment for a 3-year period. All trauma patients less than 16 years old who survived for longer than 24 hours and had an Injury Severity Score > 15 were eligible. An accepted MOF score was used. Categorical variables were compared by chi2 and continuous variables by t test. A value of p< 0.05 was considered statistically significant. RESULTS: Of 534 patients identified, 334 (63%) were admitted for evaluation of isolated head injury and excluded from further analysis. The rate of postinjury MOF in children was found to be only 3%, with a low (17%) mortality when compared with historical adult data (50%). CONCLUSION: The incidence of postinjury MOF in the child is less than in the adult, given equivalent injury severity. These observations solidify the contention that postinjury MOF is rare in children, and is less severe when it occurs. Delineating the mechanism(s) whereby children are protected from postinjury MOF may provide insight into the development of strategies to prevent MOF in other age groups as well as various disease states.

Adolescent↗
PubMed2002

Acute hypoxemia in humans enhances the neutrophil inflammatory response.

The neutrophil (PMN) is regarded as a key component in the hyperinflammatory response known as the systemic inflammatory response syndrome. Acute respiratory distress syndrome (ARDS) and subsequent multiple organ failure (MOF) are related to the severity of this hyperinflammation. ICU patients who are at highest risk of developing MOF may have acute hypoxic events that complicate their hospital course. This study was undertaken to evaluate the effects of acute hypoxia and subsequent hypoxemia on circulating PMNs in human volunteers. Healthy subjects were exposed to a changing O2/N2 mixture until their O2 saturation (SaO2) reached a level of 68% saturation. These subjects were then exposed to room air and then returned to their baseline SaO2. PMNs were isolated from pre- and post-hypoxemic arterial blood samples and were then either stimulated with N-formyl-methionyl-leucyl-phenylalanine (fMLP) or PMA alone, or they were primed with L-alpha-phosphatidylcholine, beta-acetyl-gamma-O-alkyl (PAF) followed by fMLP activation. Reactive oxygen species generation as measured by superoxide anion production was enhanced in primed PMNs after hypoxemia. Protease degranulation as measured by elastase release was enhanced in both quiescent PMNs and primed PMNs after fMLP activation following the hypoxemic event. Adhesion molecule upregulation as measured by CD11b/CD18, however, was not significantly changed after hypoxemia. Apoptosis of quiescent PMNs was delayed after the hypoxemic event. TNFalpha, IL-1, IL-6, and IL-8 cytokine levels were unchanged following hypoxemia. These results indicate that relevant acute hypoxemic events observed in the clinical setting enhance several PMN cytotoxic functions and suggest that a transient hypoxemic insult may promote hyperinflammation.

Acute Disease↗
PubMed2002

Hyperosmolarity abrogates neutrophil cytotoxicity provoked by post-shock mesenteric lymph.

Hypertonic saline (HTS) resuscitation inhibits acute lung injury in animal models of shock, but some argue this may simply represent more efficient fluid resuscitation. Inflammatory mediators within mesenteric lymph have been identified as a link between splanchnic hypoperfusion and acute respiratory distress syndrome (ARDS). We hypothesize that HTS resuscitation abrogates post-shock lymph-mediated neutrophil (PMN) priming and PMN-mediated human endothelial cell cytotoxicity. Mesenteric lymph was collected from rats (n = 5) before (control), during non-lethal hemorrhagic shock, defined as a mean arterial pressure (MAP) of 40 mmHg for 30 min, and after resuscitation (shed blood + 2 x lactated Ringers (LR) versus 7.5% NaCl, 4 cc/kg, over 5 min). Isolated human PMNs were primed with physiologic concentrations (5% v:v) of lymph either from animals resuscitated with LR or HTS and activated with either PMA or fMLP. In a separate set of experiments, human PMNs were primed with LR lymph after incubation with HTS (180 mM NaCl). The maximal rate of superoxide production was measured by reduction of cytochrome C. In addition, the effect of HTS pretreatment on PMN adherence to human pulmonary microvascular endothelial cells (HMVEC) and PMN-mediated cytotoxicity was determined after lymph-mediated PMN priming. PHSML primed isolated PMNs above buffer controls and pre-shock lymph in a normotonic environment; HTS resuscitation abrogated this effect. HTS preincubation of isolated PMNs inhibited PHSML-induced PMN priming, adherence to HMVECs, and PMN-mediated HMVEC cytotoxicity. Hypertonic resuscitation (HTS) abrogates PHSML pniming of the PMN and PMN-mediated HMVEC cytotoxicity. Furthermore, incubation of PMNs in clinically relevant HTS (180 mM NaCl) prevents PHSML PMN priming and PMN:HMVEC interactions. These studies suggest inhibition of PMN signal transduction is a mechanism whereby HTS resuscitation abrogates acute lung injury.

Animals↗
PubMed2002

Presence of the M-type sPLA(2) receptor on neutrophils and its role in elastase release and adhesion.

Secretory phospholipase A(2) (sPLA(2)) produces lipids that stimulate polymorphonuclear neutrophils (PMNs). With the discovery of sPLA(2) receptors (sPLA(2)-R), we hypothesize that sPLA(2) stimulates PMNs through a receptor. Scatchard analysis was used to determine the presence of a sPLA(2) ligand. Lysates were probed with an antibody to the M-type sPLA(2)-R, and the immunoreactivity was localized. PMNs were treated with active and inactive (+EGTA) sPLA(2) (1-100 units of enzyme activity/ml, types IA, IB, and IIA), and elastase release and PMN adhesion were measured. PMNs incubated with inactive, FITC-linked sPLA(2)-IB, but not sPLA(2)-IA, demonstrated the presence of a sPLA(2)-R with saturation at 2.77 fM and a K(d) of 167 pM. sPLA(2)-R immunoreactivity was present at 185 kDa and localized to the membrane. Inactive sPLA(2)-IB activated p38 MAPK, and p38 MAPK inhibition attenuated elastase release. Active sPLA(2)-IA caused elastase release, but inactive type IA did not. sPLA(2)-IB stimulated elastase release independent of activity; inactive sPLA(2)-IIA partially stimulated PMNs. sPLA(2)-IB and sPLA(2)-IIA caused PMN adhesion. We conclude that PMNs contain a membrane M-type sPLA(2)-R that activates p38 MAPK.

Binding, Competitive↗
PubMed2002

Physiological levels of interleukin-18 stimulate multiple neutrophil functions through p38 MAP kinase activation.

Patients with sepsis and acute lung injury have increased interleukin (IL)-18 levels systemically. We hypothesize that IL-18 stimulates neutrophils (PMNs) at physiologic concentrations. IL-18 primed the oxidase at 15 min (10-100 ng/ml), 30 min (0.1-100 ng/ml), and 60 min (100 ng/ml; P<0.05) and caused translocation of p47(phox) to the membrane similar to lipopolysaccharides. CD11b surface expression was increased by IL-18 in a time- and concentration-dependent manner. IL-18 caused up-regulation of the formyl-Met-Leu-Phe receptor, changes in PMN size, and elastase release. Investigation of signaling demonstrated IL-18-mediated activation of p38 mitogen-activated protein (MAP) kinase in a concentration (0.1-100 ng/ml)-, time (5-15 min)-, and Ca2+-dependent manner. IL-18 directly increased cytosolic Ca2+ concentration. IL-18 activation of PMNs was blocked by inhibition of p38 MAP kinase activity (SB203580) or by inhibition of p38 MAP kinase activation by chelation of cytosolic Ca2+. We conclude that IL-18, at physiologic concentrations, is an effective PMN priming agent that requires p38 MAP kinase activity.

Adult↗