Biomedical subjects

Daniel G Remick

Publications and source records attributed to Daniel G Remick.

45 records · Page 3Linked to original sources

PubMed2003

Inflammatory status in sepsis alters efficacy of interleukin-18 binding protein therapy.

OBJECTIVE: Sepsis remains a serious clinical problem, and multiple attempts at blocking inflammation have failed to decrease mortality rate. Interleukin-18 has been demonstrated to be an important component of the innate immune response to bacterial infections. DESIGN: Previous work demonstrated that elevated plasma concentrations of interleukin-6 obtained in the first 6 hrs of sepsis predict a worse outcome. Mice were subjected to cecal ligation and puncture and, on the basis of the plasma concentration of interleukin-6, were randomized to receive either interleukin-18 binding protein or vehicle approximately 8 hrs after the onset of sepsis. SETTING: University research laboratory. SUBJECTS: Adult, female BALB/c mice. INTERVENTIONS: We sought to determine the role of interleukin-18 in sepsis by blocking its biological activity with the interleukin-18 binding protein in the murine model of sepsis induced by cecal ligation and puncture. MEASUREMENTS AND MAIN RESULTS: In this study, elevated plasma concentrations of interleukin-6 were associated with a worse outcome. Treatment with interleukin-18 binding protein decreased inflammation as determined by lower concentrations of plasma interleukin-6 obtained 48 hrs after the onset of sepsis. In mice with increased risk of dying, interleukin-18 binding protein slightly decreased mortality rate. However, in those mice with a predicted low mortality rate, interleukin-18 binding protein significantly increased mortality rate. CONCLUSIONS: In this study, mice at low risk of death due to sepsis had decreased survival when treated with interleukin-18 binding protein. These results have potential implications for the use of interleukin-18 binding protein for treatment of chronic inflammatory conditions since it may place the host at increased risk of infectious complications.

Animals↗

PubMed2003

Relative cytokine and cytokine inhibitor production by mononuclear cells and neutrophils.

Mononuclear cells represent the major source of cytokines in blood; however, it has been postulated that neutrophils may produce and/or release modest amounts of cytokines. In this study, we compared the production of cytokines and cytokine inhibitors in lipopolysaccharide (LPS)-stimulated whole blood, peripheral blood mononuclear cells (PBMCs), and neutrophils (PMNs) separated by density gradient centrifugation. Contamination of PBMCs in the isolated PMNs was less than 0.1% as determined by morphological analysis and flow cytometry. LPS (50 ng/mL) induced a strong increase of the proinflammatory cytokines tumor necrosis factor, interleukin (IL)-1beta, IL-8, and IL-6 in whole blood. In the isolated cell preparations, proinflammatory cytokine production was significantly greater in the PBMCs compared with the PMNs. On a per cell basis, PMNs produced less than 1.5% of these cytokines compared with PBMCs. For cytokine inhibitors, TNF-soluble receptor type II and IL-1 receptor antagonist were increased by LPS stimulation in whole blood, PBMCs, and PMNs. On a per cell basis, LPS-induced TNF-soluble receptor type II and IL-1 receptor antagonist production by PMNs was 9.8% and 15.4% of those of PBMCs, respectively. These data show that a highly purified population of PMNs makes a relatively minor to nonexistent contribution to the production of proinflammatory cytokines.

Antigens, CD↗

PubMed2003

Cytokine therapeutics for the treatment of sepsis: why has nothing worked?

Several clinical trials have attempted to treat sepsis by blocking certain aspects of the inflammatory response. Tumor necrosis factor and interleukin 1 have been specific targets for inhibition but none of the trials have been successful. These trials were started on the basis of preclinical trials that suggested these would be effective. There were three lines of evidence to support the idea of cytokine inhibition. First, patients with increased levels of cytokines are more likely to die. Second, experimental animal models demonstrated that blocking the cytokines would improve outcome. Third, injection of purified, recombinant cytokines would cause both organ injury and death in experimental animals. Several additional aspects of the inflammatory response have been discovered since these trials were initiated. Included among these potential new targets are interleukin 18 and HMG-1. However, before new clinical trials are started there must be careful consideration of why previous interventions were not effective. The concept of blocking a single elevated cytokine may be too simple to deal with the complex problem of sepsis. As patients move through different phases of the septic response, there may be intervals when it is appropriate to inhibit multiple cytokines while at other times it may be appropriate to augment the immune response.

Animals↗

PubMed2002

Thrombin-induced platelet microparticles improved the aggregability of cryopreserved platelets.

Platelets were activated with freezing/thawing and thrombin stimulation, and platelet microparticles generated following platelet activation were isolated with ultracentrifugation. The effects of platelet microparticles on platelet activation were studied with annexin V assay, protein tyrosine phosphorylation, and platelet aggregation. Freezing-induced platelet microparticles decreased but thrombin-induced platelet microparticles increased platelet annexin V binding and aggregation. Freshly washed platelets were cryopreserved using epinephrine and dimethyl sulfoxide (Me(2)SO) as combined cryoprotectants, and stimulated with thrombin-induced platelet microparticles. Following incubation of thrombin-induced platelet microparticles, the reaction time of platelets to agonists decreased but the percentages of aggregation increased, such as washed platelets from 44% +/- 30 to 92% +/- 7, p < 0.001, and cryopreserved platelets from 66% +/- 10 to 77% +/- 7, p < 0.02. By increasing platelet aggregability, platelet microparticles recovered after thrombin stimulation improved platelet function for transfusion. A 53-kDa platelet microparticle protein showed little phosphorylation if it was released from resting platelets or platelets stimulated with ADP, epinephrine, propyl gallate or dephosphorylation if it was derived from ionophore A 23187-stimulated platelets. However, the same protein released from frozen platelets showed significant tyrosine phosphorylation. Since a microparticle protein with 53 kDa was compatible with protein tyrosine phosphatase-1B (PTP-1B), its phosphorylation suggests the inhibition of enzyme activity. The microparticle proteins derived from thrombin-stimulated platelets were significantly phosphorylated at 64 kDa and pp60c-src, suggesting that the activation of tyrosine kinases represents a possible mechanism of thrombin-induced platelet microparticles to improve platelet aggregation.

Adult↗

PubMed2002

Calcitonin gene-related peptide partially reverses decreased production of chemokines KC and MIP-2 following murine sepsis.

The secretion of calcitonin gene-related peptide (CGRP) and the chemokines KC and MIP-2 are increased in the animal models of endotoxemic and septic shock. We tested whether CGRP could modulate KC and MIP-2 secretion from different sources of macrophages after murine sepsis induced by cecal ligation and puncture (CLP). Macrophages were obtained from the peritoneal exudate and lung of female BALB/c mice 16 h after CLP and plated in culture with CGRP and/or LPS for 12 h. The results showed that peritoneal macrophage production of the chemokines (KC, MIP-2) and cytokines (TNF-alpha, IL-6) was markedly decreased in CLP mice. Alveolar macrophages did not display decreased cytokine/chemokines production after CLP. CGRP (0.1 nM-10 nM) partially reversed this decreased production of LPS-induced KC and MIP-2 from peritoneal macrophages. These results suggest that CGRP might be intimately involved in recruitment of neutrophils by promoting local production of the chemokines KC and MIP-2 in murine sepsis.

Animals↗

PubMed2002

Six at six: interleukin-6 measured 6 h after the initiation of sepsis predicts mortality over 3 days.

Virtually of the all recent therapeutic interventions for treating sepsis have failed to improve survival. One potential explanation is that the heterogeneity of the immune response to the septic challenge is such that only a portion of the patients die as a result of excessive inflammation. The clinical trials lacked power because traditional measurements do not accurately identify these patients. Previous work has shown that higher levels of interleukin (IL)-6 are found in those mice that die from septic peritonitis; therefore, we sought to determine whether IL-6 measured 6 h after surgery could predict outcome. Adult, female BALB/c mice (n = 79) were subjected to cecal ligation and puncture with a 21-gauge needle and treated with imipenem in D5W every 12 h for 5 days, resulting in a homogenous population at the outset. Six hours after surgery, 20 microL of blood was obtained from the tail vein to measure IL-6. Mortality was followed for 21 days. Overall 3-day survival was 77%, and 21-day mortality was 56%. Plasma IL-6 levels >2,000 pg/mL were determined to predict mortality within the first 3 days with a sensitivity of 58% and specificity of 97%. To further refine the mortality prediction, body weight and a complete blood count were performed 24 hours after cecal ligation and puncture. Discriminate analysis indicated that a weighted formula combining body mass, lymphocyte, and platelet count would predict death with sensitivity of 83% and a specificity of 79%. We tested the value of the IL-6 prediction by surgically resecting the cecum in those animals with IL-6 > 2000 pg/mL, which resulted in a significant improvement in survival. These data demonstrate that IL-6 measured 6 h after injury accurately predicts mortality resulting from experimental sepsis. This measurement may be determined quickly so that therapy may be targeted only to those individuals at significant risk of dying and initiated within sufficient time to be effective.

Animals↗

PubMed2002

An essential role for lipopolysaccharide-binding protein in pulmonary innate immune responses.

Lipopolysaccharide (LPS)-binding protein (LBP) greatly facilitates LPS activation of monocytic cells through the CD14 receptor, triggering activation of innate immune responses. An acute phase protein, LBP is produced predominantly by the liver; however, we and others have shown that LBP is produced extrahepatically in multiple locations, including the lung. The importance of LBP in the lung has remained unclear. LBP may make the host more acutely sensitive to LPS and development of septic complications; alternatively, it may be protective, aiding in detection, opsonization, and killing of bacteria. Our objective was to determine the role LBP plays in local pulmonary immune defenses to bacterial challenge. LBP knockout mice and age-matched C57BL/6 wild-type controls were challenged with direct intratracheal inoculation of Klebsiella pneumoniae. We observed a significant increase in mortality, earlier onset of bacteremia, and greater pulmonary bacterial loads in LBP knockout mice compared with controls. Total lung myeloperoxidase (MPO) activity, neutrophil recruitment to the alveolar space, and levels of KC--a chemokine involved in neutrophil recruitment--in bronchoalveolar lavage (BAL) fluid and lung homogenates were found to be significantly diminished in knockout mice compared with controls. Together, our findings suggest that LBP is essential in local pulmonary innate immune responses against bacteria.

Acute-Phase Proteins↗

PubMed2002

Keratinocyte growth factor pretreatment is associated with decreased macrophage inflammatory protein-2alpha concentrations and reduced neutrophil recruitment in acid aspiration lung injury.

A two-hit model of acid aspiration was used to examine the effect of keratinocyte growth factor (KGF) on chemokine levels and neutrophil recruitment into the lung. Mice were subjected to cecal ligation and puncture and then either KGF or saline, intratracheally (i.t.). Forty-eight hours later, the mice were given i.t. acid. After 8 h, neutrophil counts in bronchoalveolar lavage (BAL) fluid were significantly decreased in animals pretreated with KGF (23 +/- 4 x 10(3)/mouse) compared with saline (74 +/- 2 x 10(3)/mouse). In addition, the BAL fluid IL-6 levels were decreased in the KGF-treated group (88+/- 44 pg/mL) compared with the saline group (166 +/- 34 pg/mL). To examine the mechanism behind the KGF-induced reduction in neutrophil influx, the murine chemokines KC and macrophage inflammatory protein (MIP)-2alpha were measured. KC levels in plasma and BAL fluid were not significantly different between the treatment groups. Likewise, levels of MIP-2alpha in plasma were not affected by KGF treatment. However, 8 h after acid aspiration, MIP-2alpha concentrations were significantly lower in the KGF-treated group. The ratio of MIP-2alpha in BAL fluid versus plasma was lower in the KGF group (0.72 +/- 0.28) than in the saline group at 3 h (2.23 +/- 0.93) and also significantly lower in the KGF group (3.02 +/- 0.78) compared with the saline group (6.23 +/- 1.19) at 8 h. In this study, KGF pretreatment after acid aspiration was associated with reduced neutrophil recruitment into the lung and a decrease in MIP-2alpha gradients between BAL fluid and plasma.

Animals↗

PubMed2002

Activation of human and mouse Kupffer cells by lipopolysaccharide is mediated by CD14.

Upregulation of CD14 in Kupffer cells has been implicated in the pathogenesis of several forms of liver injury, including alcoholic liver disease. However, it remains unclear whether CD14 mediates lipopolysaccharide (LPS) signaling in this specialized liver macrophage population. In this series of experiments, we determined the role of CD14 in LPS activation of Kupffer cells by using several complementary approaches. First, we isolated Kupffer cells from human livers and studied the effects of anti-CD14 antibodies on LPS activation of these cells. Kupffer cells were incubated with increasing concentrations of LPS in the presence and absence of recombinant human LPS binding protein (LBP). With increasing concentrations of LPS, human Kupffer cell tumor necrosis factor-alpha (TNF-alpha) production (a marker for Kupffer cell activation) increased in a dose-dependent manner in the presence and absence of LBP. In the presence of anti-human CD14 antibodies, the production of TNF-alpha was significantly diminished. Second, we compared LPS activation of Kupffer cells isolated from wild-type and CD14 knockout mice. Kupffer cells from CD14 knockout mice produced significantly less TNF-alpha in response to the same amount of LPS. Together, these data strongly support a critical role for CD14 in Kupffer cell responses to LPS.

Acute-Phase Proteins↗