Zhi-Guo Shi

The significance of changes in high mobility group-1 protein mRNA expression in rats after thermal injury.

There has been a widespread impression that tumor necrosis factor-&agr; (TNF-&agr;) and interleukin-1&bgr; (IL-1&bgr;) mediate the toxicity of high doses of lipopolysaccharide (LPS, endotoxin) and are key factors in septic shock. However, the clinical efficacy of treatment with antagonists of TNF-&agr; and IL-1&bgr; is still controversial, suggesting that mediators other than TNF-&agr; and IL-1&bgr; might contribute causally to endotoxin-induced death. Recent studies implicated high mobility group-1 (HMG-1) protein as a late mediator of endotoxin lethality in mice. However, the role of HMG-1 in mediating multiple organ damage-associating trauma has not been studied. This study was designed to investigate changes in HMG-1 gene expression in vital organs, and its potential role in mediating multiple organ damage following major burns. Wistar rats were subjected to a 35 percent full-thickness thermal injury, and randomly divided into three groups as follows: normal controls (n = 7), thermal injury (n = 24), and recombinant bactericidal/permeability-increasing protein (rBPI21) treatment (n = 12). Tissue samples from liver and lungs were collected to measure tissue endotoxin levels and HMG-1 mRNA expression. In addition, blood samples were obtained for measurement of organ function parameters. Our data demonstrated a significant increase in HMG-1 gene expression in tissues at 24 h postburn, which remained markedly elevated up to 72 h after thermal injury (P < 0.05–0.01). Treatment with rBPI21 could significantly decrease tissue HMG-1 mRNA expression in the liver and lung (P < 0.01). In addition, there were high positive correlations between hepatic HMG-1 mRNA and serum aminoleucine transferase (ALT) and aspartate aminotransferase (AST) levels, and also between pulmonary HMG-1 mRNA and myeloperoxidase activities (P < 0.05–0.01). Taken together, these findings indicate that thermal injury per se can markedly enhance HMG-1 gene expression in various organs. Up-regulation of HMG-1 expression may be involved in the pathogenesis of endogenous endotoxin-mediated multiple organ damage secondary to major burns.

Influence of selective decontamination of the digestive tract on cell-mediated immune function and bacteria/endotoxin translocation in thermally injured rats

OBJECTIVE To determine the influence of pretreatment with selective decontamination of the digestive tract (SDD) on systemic immunosuppression, and the relationship between bacteria/endotoxin translocation and abnormalities of immune function in thermally injured rats. DESIGN, MATERIALS, AND METHODS Animals were subjected to a 40% full-thickness scald injury, and divided into SDD-treated and control groups. The treatment group received SDD (polymyxin E, tobramycin, and 5-flucytosine) by gavage twice daily for 3 days before the experiment and continued for 5 days after thermal injury. The control group was given the same amount of water. The parameters reflecting cell-mediated immunity, including splenocyte proliferation in response to mitogens, interleukin 2 (IL-2) production, and lymphocyte subpopulation, were measured before injury and 1 and 5 days after burn, respectively. MEASUREMENTS AND MAIN RESULTS Thermal injury resulted in marked reduction in splenocyte proliferative response to T-cell mitogens, IL-2 production, and T-helper/suppressor cells (CD4/CD8) ratio. Prophylactic treatment with SDD significantly decreased the incidences of bacterial translocation and endotoxemia, prevented suppressive mitogenic response and inadequate IL-2 production (p < 0.05-0.01) but did not affect the abnormal ratio of CD4 to CD8 T lymphocytes in blood (p > 0.05). CONCLUSIONS These results suggest that bacteria/endotoxin translocation from the gut appears to be involved in cell-mediated immune dysfunction as a consequence of thermal injury. Pretreatment with SDD might attenuate postburn immunosuppression by preventing translocation events.

Effect of recombinant bactericidal/permeability-increasing protein on endotoxin translocation and lipopolysaccharide-binding protein/CD14 expression in rats after thermal injury

ObjectiveTo investigate the potential mechanisms underlying the in vivo effect of recombinant bactericidal/permeability-increasing protein (rBPI21) on endogenous bacteria or endotoxin translocation and lipopolysaccharide-binding protein/CD14 expression secondary to thermal injury. DesignProspective, randomized, controlled animal study. SettingCollege hospital animal research laboratory. SubjectsThirty-six male Wistar rats weighing 250–300 g. InterventionsThe rats were anesthetized, and a 35% total body surface area full-thickness burn was created. Animals were randomized to receive treatment with either rBPI21 or the control protein (albumin). rBPI21 (2 mg/kg body wt, BPI group) or a protein control preparation (burn group) in the same dose was administered in an intravenous bolus at 30 mins and 4 hrs after thermal injury. All animals were killed at 12 and 24 hrs postburn (six to ten rats for each interval). In addition, eight rats were taken as normal controls. Measurement and Main Results Our data showed that treatment with rBPI21 was effective in preventing endotoxin translocation secondary to severe burns. Meanwhile, tissue lipopolysaccharide-binding protein, CD14, and tumor necrosis factor-&agr; mRNA expression in various organs were inhibited markedly by rBPI21 secondary to acute insults (p < .05–.01). Furthermore, significant reduction in serum aminoleucine transferase concentrations and elevation in intestinal diamine oxidase activities in the rBPI21-treated group were found compared with controls (p < .05–.01). ConclusionsThese findings indicate that endotoxin accumulated in local sites after thermal injury can markedly up-regulate lipopolysaccharide-binding protein/CD14 and tumor necrosis factor-&agr; mRNA expression in various organs. Meanwhile, up-regulation of lipopolysaccharide-binding protein/CD14 expression would be the major molecular mechanism of increasing sensitivity to endogenous endotoxin response after burns. Early treatment with rBPI21may be effective in attenuating multiple organ damage resulting from gut-origin endotoxin translocation. This might be associated with the down-regulation effects of tissue lipopolysaccharide-binding protein and CD14 gene expression by the use of rBPI21.

The potential role of Staphylococcal enterotoxin B in rats with postburn Staphylococcus aureus sepsis.

Staphylococcal enterotoxin B (SEB) is an important member of the superantigen family, which exerts a number of pathological effects in the human, as well as susceptible animals. The present study was conducted to observe the time course and tissue distribution of SEB in postburn Staphylococcus aureus infection; meanwhile, the relationship between SEB and multiple organ dysfunction was also studied. Eighty-six male Wistar rats were randomly divided into four groups as follows: normal control group (n = 10); scald control group (n = 10); postburn sepsis group (n = 50) in which rats inflicted with 20% total body surface area (TBSA) III° scald followed by SEB-producing S. aureus challenge were further divided into 0.5-, 2-, 6-, 12-, and 24-h subgroups, with 10 rats in each subgroup; and SEB monoclonal antibody (MAb) treatment group (n = 16) in which a dose of 4 mg/kg SEB MAb was given intravenously just before S. aureus challenge, and the rats were further divided into 2- and 6-h subgroups. It was found that after thermal injury combined with S. aureus infection, SEB was widely distributed to the liver, kidneys, lungs, and heart, exacerbating the pathophysiology of multiple organ dysfunction induced by postburn sepsis. At the same time, the gene and protein expressions of tumor necrosis factor-&agr; (TNF-&agr;) and interferon-&ggr; (IFN-&ggr;) were also markedly upregulated in various tissues. Early treatment with SEB-specific MAb—MAb2D1—could markedly decrease SEB levels in plasma as well as in various tissues, and could significantly reduce the 6-h mortality rate (17.64% [3/17] vs. 55.6% [20/36], P = 0.02). These data suggested that neutralization of SEB is effective in ameliorating S. aureus sepsis and subsequent multiple organ damage, which might be attributed to its inhibitory effect on inflammatory mediator formation.

Reduction of circulating prostaglandin E2 level by antiserum against core lipopolysaccharide in a rabbit model of multiple organ failure.

OBJECTIVE To determine the potential role of prostaglandin E2 (PGE2) in the development of multiple organ dysfunction or failure (MOF), the possible effects of antiserum directed against Re chemotype lipopolysaccharide (LPS, from Re mutant of Escherichia coli F515) on circulating PGE2 level and survival rate, and whether there is an elevation in the plasma LPS concentration that could account for the induction of arachidonic acid metabolite in a rabbit model of MOF caused by acute hypovolemic insult. DESIGN, MATERIALS, AND METHODS An animal model of MOF in rabbits, engendered by feeding live Escherichia coli O111:B4 before hemorrhagic shock (35-40 mm Hg for 60 min), was used in the present study. Re-LPS antiserum was given intravenously in the treatment group at the onset of hemorrhage and 4 hours after resuscitation. The animals that received equal volumes of normal rabbit serum and antiserum served as the control group. MEASUREMENTS AND MAIN RESULTS The circulating PGE2 level was not increased at the end of shock (p > 0.05), but it was found to be significantly elevated 24 hours after hemorrhage and resuscitation in both groups. However, Re-LPS antiserum administration markedly decreased peak PGE2 level (p < 0.05) and attenuated multiple organ damage caused by acute insult. Concomitantly, there were also lower LPS concentrations in the treatment group as compared with the control group (p < 0.05-0.01). The survival rate was significantly increased in antiserum-treated rabbits 96 hours postinjury (treatment vs. control: 58.0% vs. 11.1%, p < 0.01). CONCLUSIONS The results suggest that an excessive generation and release of PGE2 may be involved in the pathogenesis of immunosuppression and MOF following hemorrhage and resuscitation. Re-LPS antiserum has an inhibitory effect on overproduction of circulating PGE2 and the ability to improve survival with MOF. Gut-derived endotoxemia, bacterial translocation, or both, could account, at least in part, for the PGE2 formation and release in animals response to acute hypovolemic insult.

Significance of biopterin induction in rats with postburn Staphylococcus aureus sepsis.

It has been demonstrated that biopterin, an essential cofactor of nitric oxide synthase (NOS), plays an important role in the pathogenesis of endotoxin-induced shock, yet its biological significance in gram-positive sepsis remains unclear. In this study, we adopted a rat model of postburn Staphylococcus aureus sepsis to investigate the potential role of biopterin in the pathogenesis of gram-positive sepsis. Wistar rats were inflicted with a 20% total body surface area (TBSA) full-thickness scald injury followed by S. aureus challenge, and then guanosine triphosphate-cyclohydrolase I (GTP-CHI) mRNA expression and biopterin levels in liver, kidneys, lungs, and heart were determined. We found that after S. aureus challenge, GTP-CHI gene expressions and biopterin levels were markedly upregulated in various tissues. Meanwhile, multiple organ dysfunction was induced by S. aureus challenge. It was shown that cardiac GTP-CHI mRNA expression and renal BH4 levels were positively correlated with MB isoenzyme of creatine kinase (CK-MB) and creatinine (r = 0.892, P = 0.0012 and r = 0.9423, P = 0.0015, respectively). These results suggested that thermal injury combined with S. aureus challenge could induce de novo biosynthesis of biopterin, which might play a role in the development of multiple organ dysfunction syndrome secondary to postburn sepsis.