The effects of ketamine and propofol on bacterial translocation in rats after burn injury

Molecular mechanism mediating enteric bacterial translocation after severe burn: the role of cystic fibrosis transmembrane conductance regulator

Background

Gut ischemia and hypoxia post severe burn leads to breakdown of intestinal epithelial barrier and enteric bacterial translocation (EBT), resulting in serious complications, such as systemic inflammatory response syndrome, sepsis and multiple organ failure. Cystic fibrosis transmembrane conductance regulator (CFTR) is known to be downregulated by hypoxia and modulate junctional complexes, which are crucial structures maintaining the intestinal barrier. This study aimed to investigate whether CFTR plays a role in both regulating the intestinal barrier and mediating EBT post severe burn, as well as the signaling pathways involved in these processes.

Methods

An in vitro Caco-2 cell model subjected to hypoxic injury and an in vivo mouse model with a 30% total body surface area full-thickness dermal burn were established. DF 508 mice (mice with F508del CFTR gene mutation) were used as an in vivo model to further demonstrate the role of CFTR in maintaining normal intestinal barrier function. QRT-PCR, western blot, ELISA, TER assay and immunofluorescence staining were used to detect the expression and localization of CFTR and tight junction proteins, as well as the function of tight junctions.

Results

Our data indicated that, in Caco-2 cells, the hypoxia condition significantly reduced CFTR expression; activated extracellular signal-regulated kinase and nuclear factor-κB signaling; elevated secretion of inflammatory factors (tumor necrosis factor-α, interleukin-1β and interleukin-8); downregulated zonula occludens-1, occludin and E-cadherin expression; decreased transepithelial electrical resistance values; and led to a cellular mislocation of ZO-1. More importantly, knockdown of CFTR caused similar alterations. The upregulation of inflammatory factors and downregulation of tight junction proteins (ZO-1 and occludin) induced by knockdown of CFTR could be reversed by specific extracellular signal-regulated kinase or nuclear factor-κB inhibition. In support of the in vitro data, exuberant secretion of pro-inflammatory mediators and EBT was observed in the intestine of severely burnt mice in vivo. EBT occurred in DF508 mice (mice with the F508del CFTR gene mutation), accompanied by augmented tumor necrosis factor-α, interleukin-1β and interleukin-8 levels in the ileum compared to wildtype mice. In addition, vitamin D3 was shown to protect the intestinal epithelial barrier from hypoxic injury.

Conclusions

Collectively, the present study illustrated that CFTR and downstream signaling were critical in modulating the intestinal epithelial junction and EBT post severe burn.

Propofol increases morbidity and mortality in a rat model of sepsis

INTRODUCTION

Severe sepsis is associated with approximately 50% mortality and accounts for tremendous healthcare costs. Most patients require ventilatory support and propofol is commonly used to sedate mechanically ventilated patients. Volatile anesthetics have been shown to attenuate inflammation in a variety of different settings. We therefore hypothesized that volatile anesthetic agents may offer beneficial immunomodulatory effects during the course of long-term intra-abdominal sepsis in rats under continuous sedation and ventilation for up to 24 hours.

METHODS

Sham operation or cecal ligation and puncture (CLP) was performed in adult male Wistar rats followed by mechanical ventilation. Animals were sedated for 24 hours with propofol (7 to 20 mg/kg/h), sevoflurane, desflurane or isoflurane (0.7 minimal alveolar concentration each).

RESULTS

Septic animals sedated with propofol showed a mean survival time of 12 hours, whereas >56% of all animals in the volatile groups survived 24 hours (P <0.001). After 18 hours, base excess in propofol + CLP animals (-20.6 ± 2.0) was lower than in the volatile groups (isoflurane + CLP: -11.7 ± 4.2, sevoflurane + CLP: -11.8 ± 3.5, desflurane + CLP -14.2 ± 3.7; all P <0.03). Plasma endotoxin levels reached 2-fold higher levels in propofol + CLP compared to isoflurane + CLP animals at 12 hours (P <0.001). Also blood levels of inflammatory mediators (tumor necrosis factor-α, interleukin-1β, interleukin-10, CXCL-2, interferon-γ and high mobility group protein-1) were accentuated in propofol + CLP rats compared to the isoflurane + CLP group at the same time point (P <0.04).

CONCLUSIONS

This is the first study to assess prolonged effects of sepsis and long-term application of volatile sedatives compared to propofol on survival, cardiovascular, inflammatory and end organ parameters. Results indicate that volatile anesthetics dramatically improved survival and attenuate systemic inflammation as compared to propofol. The main mechanism responsible for adverse propofol effects could be an enhanced plasma endotoxin concentration, leading to profound hypotension, which was unresponsive to fluid resuscitation.

Effects of propofol on damage of rat intestinal epithelial cells induced by heat stress and lipopolysaccharides

Gut-derived endotoxin and pathogenic bacteria have been proposed as important causative factors of morbidity and death during heat stroke. However, it is still unclear what kind of damage is induced by heat stress. In this study, the rat intestinal epithelial cell line (IEC-6) was treated with heat stress or a combination of heat stress and lipopolysaccharide (LPS). In addition, propofol, which plays an important role in anti-inflammation and organ protection, was applied to study its effects on cellular viability and apoptosis. Heat stress, LPS, or heat stress combined with LPS stimulation can all cause intestinal epithelial cell damage, including early apoptosis and subsequent necrosis. However, propofol can alleviate injuries caused by heat stress, LPS, or the combination of heat stress and LPS. Interestingly, propofol can only mitigate LPS-induced intestinal epithelial cell apoptosis, and has no protective role in heat-stress-induced apoptosis. This study developed a model that can mimic the intestinal heat stress environment. It demonstrates the effects on intestinal epithelial cell damage, and indicated that propofol could be used as a therapeutic drug for the treatment of heat-stress-induced intestinal injuries.

Propofol attenuation of renal ischemia/reperfusion injury involves heme oxygenase-1

AIM

To examine the protective effect of propofol in renal ischemia/reperfusion (I/R) injury and the role of heme oxygenase-1 (HO-1) in this process.

METHODS

Sprague-Dawley rats were randomly divided into 3 groups: (i) sham-operated group; (ii) I/R group; and (iii) propofol group. Bilateral renal warm ischemia for 45 min was performed. After 2, 6, and 24 h reperfusion, blood samples and kidneys were collected for assessment of renal injury, and HO-1 expressions were analyzed by immunohistochemical analysis, RT-PCR and Western blotting.

RESULTS

Blood urea nitrogen and serum creatinine levels in the propofol group were significantly lower than that in the I/R group at 24 h after reperfusion. The mean histological score by Palleros standard showed that propofol significantly attenuated renal I/R injury after 6 h reperfusion. Propofol increased HO-1 mRNA and protein levels 2 h after reperfusion, whereas HO-1 expressions were present at exceedingly low levels in the I/R group and the sham-operated group at same time point. Propofol also markedly increased HO-1 mRNA and protein levels than I/R at 6 and 24 h after reperfusion.

CONCLUSION

These results suggest that propofol mitigates renal I/R injury in rats. This protection may be partly through the induction of the HO-1 expression.

The effects of propofol and ketamine on gut mucosal epithelial apoptosis in rats after burn injury

BACKGROUND AND OBJECTIVES

Apoptosis occurs after thermal injury and may result from either ischaemic intestinal insult or inflammatory mediators released after burn injury. The aim of the study was to investigate the effects of propofol and ketamine on gut epithelium apoptosis after burn injury.

METHODS

Sixty male Wistar Albino rats were randomly assigned into four groups. Anaesthesia was induced and maintained with propofol in Groups 1 and 2, and ketamine in Groups 3 and 4 over 12 h. Groups 2 and 4 received 30% total body surface area burn. Groups 1 and 3 had no burn injury. Mean arterial pressure was maintained within 10% of baseline levels in all animals. At 12 h postburn, animals were sacrificed and tissue samples were taken from small intestine for determination of lipid peroxidation, apoptosis and proliferation. Also blood samples were taken for measurement of serum tumor necrosis factor-alpha (TNF-alpha) levels.

RESULTS

Ileal malondialdehyde (MDA) concentration (extent of lipid peroxidation) increased significantly in Group 4 (112.4 +/- 10.2 nmol g-1) compared to Group 3 (48.4 +/- 5.6 nmol g-1) and Group 2 (59.8 +/- 3.2 nmol g-1). The mean TNF-alpha level in Group 4 (118.9 +/- 10.5 pg mL-1) at 12 h postburn was significantly higher than the mean in Group 2 (56.4 +/- 4.3 pg mL-1). Group 4 had the highest mean TUNEL index (terminal deoxyuridine nick-end labelling--an index of extent of apoptosis) of all the groups (265/10). Also the mean TUNEL index value in Group 2 (53/10) was higher than that of Group 1 (3/10) and Group 3 (5/10). The proliferating cell nuclear antigen index (extent of proliferation) remained unchanged among groups.

CONCLUSIONS

Propofol could offer a protection against apoptosis of enterocytes with a stable tissue MDA and serum TNF-alpha level compared to ketamine anaesthesia in an animal model of burn injury.