TLR4 and TNF-alpha polymorphisms are associated with an increased risk for severe sepsis following burn injury

CONTEXT

Sepsis, organ failure, and shock remain common among patients with moderate to severe burn injuries. The inability of clinical factors to identify at-risk patients suggests that genetic variation may influence the risk for serious infection and the outcome from severe injury.

OBJECTIVE

Resolution of genetic variants associated with severe sepsis following burn injury.

PATIENTS

A total of 159 patients with burns > or =20% of their total body surface area or any smoke inhalation injury without significant non-burn related trauma (injury severity score (ISS)> or =16), traumatic or anoxic brain injury, or spinal cord injury and who survived more than 48 h post-admission.

METHODS

Candidate single nucleotide polymorphisms (SNPs) within bacterial recognition (TLR4 +896, CD14 -159) and inflammatory response (TNF-alpha -308, IL-1beta -31, IL-6 -174) loci were evaluated for association with increased risk for severe sepsis (sepsis plus organ dysfunction or septic shock) and mortality.

RESULTS

After adjustment for age, full-thickness burn size, ethnicity, and gender, carriage of the TLR4 +896 G-allele imparted at least a 1.8-fold increased risk of developing severe sepsis following a burn injury, relative to AA homozygotes (adjusted odds ratio (aOR) 6.4; 95% confidence interval (CI) 1.8 to 23.2). Carriage of the TNF-alpha -308 A-allele imparted a similarly increased risk, relative to GG homozygotes (aOR = 4.5; 95% CI 1.7 to 12.0). None of the SNPs examined were significantly associated with mortality.

CONCLUSIONS

The TLR4 +896 and TNF-alpha -308 polymorphisms were significantly associated with an increased risk for severe sepsis following burn trauma.

Exogenous and endogenous nitric oxide but not iNOS inhibition improves function and survival of ischemically injured livers

The role of nitric oxide (NO) in liver ischemia/reperfusion (I/R) injury remains controversial and few works have shed more information regarding the effect of exogenous (EX) and/or endogenous NO (EN) under conditions of I/R of the liver. We investigated the role of exogenous and endogenous NO and inducible nitric oxide synthase (iNOS) inhibition in liver function, neutrophil infiltration, and animal survival after liver I/R. Sprague-Dawley rats were subjected to total hepatic ischemia for 90 min using an extracorporeal porto-systemic shunt. The animals were divided into five groups, including the sham porto-systemic shunt with no ischemia, the control ischemic group, the L-arginine-treated group, the sodium nitroprusside (SNP or NaNP)-treated group, and the L-N6-(1-iminoethyl) lysine hydrochloride (L-NIL) (selective iNOS inhibitor)-treated group. The animal survival was followed for 7 days. Liver injury tests, tissue myeloperoxidase (MPO), and histology were analyzed at 6 h postreperfusion. L-Arginine- and sodium nitroprusside-treated groups demonstrated significant improvement in 7 days survival in comparison to the control (20%) (p < .05). The best overall survival was obtained with SNP (70%), followed by survival in the L-arginine treated group (60%). The iNOS inhibitor group (40%) did not show any statistical significance when compared to the control group (p > .05). Liver injury tests and histology scores in the SNP- and L-arginine-treated groups showed significant improvement when compared to the control group (p < .01 and p < .05, respectively). The iNOS group demonstrated only a slight improvement in these parameters. The liver MPO (as a measurement of neutrophil migration into the liver parenchyma) was significantly decreased only in the SNP and L-arginine groups (p < .05) but not in the iNOS group (p > .5). We conclude that NO exogenous donors and substrates for the endogenous pathway are beneficial for the liver after severe I/R and could be important therapeutic targets to prevent damage following this phenomenon.

L-selectin blockade and liver function in rats after uncontrolled hemorrhagic shock

Hemorrhagic shock (HS) and resuscitation can be seen as a global body ischemia-reperfusion (I/R) injury characterized by neutrophil infiltration and organ damage. Liver dysfunction occurs early after HS. Adhesion molecules are needed for the first steps ofneutrophil migration. Thus, the purpose of this study was to investigate the role of L-selectin in the liver after uncontrolled HS and resuscitation. Forty-eight Sprague Dawley rats were subjected to uncontrolled HS and resuscitation. Animals were divided into three groups: sham, uncontrolled HS and resuscitation, and uncontrolled HS and resuscitation with anti-L-selectin treatment. At 6 we evaluated liver injury tests, liver tissue myeloperoxidase (MPO), and liver histology. Survival was followed for 3 days and compared between groups. Statistical analysis included Fisher's exact test and one-way analysis of variance. Survival significantly increased from 30% in the control group to 60% in the treated group (p < .05). Hepatocellular and structural injury as well as neutrophil infiltration was significantly decreased in treated animals (p < .05). Thus, blockade of L-selectin resulted in decreased hepatocellular injury and increased survival in our model of uncontrolled HS. Selectins may be important therapeutic targets for blockade in the treatment of HS.

Upregulation of lung chemokines associated with hemorrhage is reversed with a small molecule multiple selectin inhibitor

BACKGROUND

Hemorrhage can modify the leukocyte-endothelial cell response leading to tissue injury. The selectin family of adhesion molecules and chemokines mediate the leukocyte-endothelial cell interaction, resulting in neutrophil sequestration and activation. This work studies whether a small molecule inhibitor of selectins can ameliorate the effect of hemorrhage on chemokine expression and neutrophil infiltration in the lung. We also aimed to assess the regulatory effect of this small molecule inhibitor of selectins in the lung functional and structural response of animals subjected to hemorrhagic shock.

STUDY DESIGN

We subjected 36 Sprague-Dawley rats to uncontrolled hemorrhagic shock for a period of 150 minutes. Three groups of animals were included (n = 12 per group)-the sham, control, and treated groups, with the latter receiving a small molecule selectin inhibitor (TBC-1269) at 25 mg/kg, which was given after tail artery transection. The following measurements were evaluated: fluid requirements during resuscitation for 150 minutes; PO2/FIO2 ratio, lung water, and lung histology, lung myeloperoxidase and lung macrophage inflammatory protein-2 (MIP-2) mRNA and cytokine induced neutrophil chemoattractant mRNA at 6 hours. Statistical analysis included Student's t-test and ANOVA.

RESULTS

There was significant improvement in lung function as expressed by PO2/FIO2 ratio and wet to dry lung water ratio in the treated group. There were no significant changes in fluid requirements between the three groups. Neutrophil infiltration, measured by tissue myeloperoxidase, was significantly (p < 0.05) decreased in the lungs of the treated animals. Lung histology was considerably improved in the treated group. The small molecule selectin inhibitor had a profound downregulating effect on macrophage inflammatory protein-2 and cytokine-induced neutrophil chemoattractant as expressed in lung tissue.

CONCLUSIONS

Our study confirms the key role that selectins play in the pathogenesis of hemorrhagic shock. The multiple selectin blockade allowed for better function and structure of the lung. The mechanism of protection may be secondary to the downregulation of chemokine expression and neutrophil infiltration.