Using the polymerase chain reaction coupled with denaturing gradient gel electrophoresis to investigate the association between bacterial translocation and systemic inflammatory response syndrome in predicted acute severe pancreatitis

Current progress of research on intestinal bacterial translocation

Under normal conditions, the intestinal flora and the body are in dynamic equilibrium. When the barrier function of the intestinal tract is damaged due to various reasons, changes in the number and proportion of bacteria or spatial displacement result in bacterial translocation (BT), which ultimately leads to multiple organ dysfunction syndrome (MODS). Endogenous infections and endotoxemia caused by intestinal flora and endotoxin translocation are the origins of inflammatory responses, and the intestinal tract is the organ in which MODS both initiates and targets. Only by ensuring the integrity of the intestinal mucosal barrier can intestinal BT be effectively prevented. Elimination of the primary disease and maintaining blood and oxygen supply to the intestine is the most basic treatment. Early initiation of the intestinal tract, establishment of enteral nutrition, and selective digestive decontamination are also highly effective treatments. Early diagnosis, intervention, or prevention of BT may be a new avenue or important connection in the treatment of various diseases. The mechanism of BT, detection techniques, prevention and treatment, and its interaction with parenteral diseases were reviewed.

Bacterial translocation in acute pancreatitis

Bacterial translocation is a phenomenon in which live bacteria or their products cross the intestinal barrier to other organs or the circulatory system. Gut translocation of bacteria has been reported in both animal models, and clinical trials often accompany acute pancreatitis and are believed to be linked to patient outcome, especially in severe acute pancreatitis. Therefore, the mechanisms of intestinal bacterial translocation in acute pancreatitis have become a topic of interest in recent years. This review discusses Bacterial translocation in acute pancreatitis, identifies possible mechanisms of action, and provides an overview of the methods used to detect Bacterial translocation in acute pancreatitis. This review also highlights areas that require further research.

A "CLEAN CASE" OF SYSTEMIC INJURY: MESENTERIC LYMPH AFTER HEMORRHAGIC SHOCK ELICITS A STERILE INFLAMMATORY RESPONSE

Postinjury multiple organ failure results from an inappropriate overwhelming immune response to injury. During trauma and hemorrhagic shock (T/HS), mesenteric ischemia causes gut mucosal breakdown with disruption of the intestinal barrier. It has been proposed that this releases the gut microbiota systemically via postshock mesenteric lymph (PSML), engendering infectious complications. Despite extensive investigation, no clear evidence has been presented for gut bacterial translocation after resuscitation from T/HS. However, such previous studies were limited by available technologies. More sensitive methods, such as quantitative polymerase chain reaction, have since emerged for detection of bacterial presence and danger-associated molecular patterns (DAMPs). Quantitative polymerase chain reaction was applied to PSML derived from a rat model of T/HS. No bacterial presence was detected in a series of 12 samples, whereas multiple lymph samples showed the presence of DAMPs after T/HS. Thus, we confirmed that bacterial translocation does not exist in PSML after resuscitation from T/HS-associated mesenteric ischemia. However, T/HS does increase the presence of mitochondrial DAMPs in PSML. These results support our current position that PSML elaborates remote organ injury by multiple inflammatory mechanisms, including lipid-mediated proinflammatory stimuli, and by contribution from gut-derived DAMPs.

Comparative study of bacterial translocation control with nitric oxide donors and COX2 inhibitor

OBJECTIVE AND DESIGN

To evaluate the beneficial effects of exogenous NO and an inhibitor of the COX2, and their action levels in a model of SIRS/bacterial translocation (BT) induced by Zymosan A(®).

MATERIAL AND METHODS

Ninety Wistar rats were submitted to different treatments, and after 12h and 24h they were anaesthetized in order to collect blood, mesenteric lymph nodes, and kidney for subsequent biochemical analyses and microbiological examinations.

TREATMENTS

A nitric oxide donor, Molsidomine(®), was compared with a COX2 inhibitor, Celecoxib(®).

METHODS

Zymosan A(®) was administered to Wistar rats. The animals were divided into 6 groups: one group for survival study, Group (1) No manipulation (BASAL); Group (2) vehicle of Zymosan A(®) given intraperitoneally (SHAM); Group I (control), with Zymosan A(®) (0.6g/kg) intraperitoneally; Group II (Molsidomine), with Molsidomine(®) (4mg/kg) through the penis dorsal vein, 30min prior to administration of the Zy(®) (0.6g/kg); Group III (Celecoxib), with Celecoxib(®) (400mg/kg) orally through a stomach tube, 6h prior to administration of the Zy (0.6g/kg).

DETERMINATIONS

The parameters survival, bacterial translocation, renal function, neutrophil accumulation, oxygen free radicals (OFR), detoxifying enzymes, and cytokines were measured at different times after Zymosan administration.

RESULTS

The model established induced a mortality rate of 100% and generated BT and systemic inflammatory response syndrome (SIRS) in all samples. It also significantly increased all variables, with p<.001 for MPO and all pro-inflammatory cytokines, and p<.01 for all OFR. Treatment with Molsidomine reduced mortality to 0%, decreased BT, MPO, pro-inflammatory cytokines and OFR (p<.001) significantly and increased IL-10 and IL-6 production. Moreover, the Celecoxib(®) showed a lower capacity for SIRS regulation.

CONCLUSIONS

The exogenous administration of NO prevented BT and controlled SIRS. Therefore these results suggest that Molsidomine could be used as a therapeutic strategy to protect against BT.

Effects of rhubarb on intestinal flora and toll-like receptors of intestinal mucosa in rats with severe acute pancreatitis

OBJECTIVE

The aim of this study was to examine the effects of rhubarb on intestinal flora and toll-like receptors (TLRs) of intestinal mucosa in rats with severe acute pancreatitis (SAP).

METHODS

Healthy male Sprague-Dawley rats were randomly allocated into sham-operated surgical model of SAP without or with postoperative rhubarb treatment groups (7 in each group). Rats in with rhubarb group received 10% rhubarb decoction (1 mL/200 g) through tube feeding at every 8 hours during postoperative 24 hours. Serum amylase, amount of intestinal flora, and TLR2/TLR4 messenger RNA expression in intestinal mucosa were tested among 3 groups at postoperative 24 hours.

RESULTS

TLR2 and TLR4 messenger RNA expression levels in intestinal mucosa in SAP without rhubarb group were significantly higher than those in sham-operated or SAP with rhubarb groups (P < 0.05). The amount of intestinal lactobacilli and bifidobacteria in SAP without rhubarb group were significantly fewer than in those sham-operated group (P < 0.05) but not significantly different from those in SAP with rhubarb group (P > 0.05). The amount of intestinal Escherichia coli was relatively higher in SAP group than in sham-operated group (P > 0.05) but lesser in rhubarb treatment group (P > 0.05).

CONCLUSIONS

Rhubarb might maintain the intestinal mucosal barrier through regulating intestinal flora and inhibiting intestinal inflammatory response in rats with SAP.

Protecting effects of a large dose of dexamethasone on spleen injury of rats with severe acute pancreatitis

BACKGROUND AND AIMS

To explore the protecting effects and mechanisms of dexamethasone on spleen injury in rats with severe acute pancreatitis (SAP).

METHODS

The rats were randomly divided into a model control group, treated group and sham-operated group. The contents of plasma endotoxin, serum NO, phospholipase A(2) enzyme (PLA(2)) and endothelin-1 (ET-1) were determined. The mortality rate, pathological changes and changes of Bax and Bcl-2 protein expression levels and apoptotic indexes in the spleen of rats were observed in all groups, respectively, at 3, 6 and 12 h after operation.

RESULTS

Although the survival rate was significantly higher in the treated group than in the model control group, there was no significantly different between them (P > 0.05). The expression levels of Bax and Bcl-2 proteins and apoptotic indexes were significantly higher in the treated group than in the model control group at different time points (P < 0.05 or P < 0.01) while other blood indexes contents and pathological severity scores of spleen were significantly lower in the treated group than in the model control group (P < 0.05, P < 0.01 or P < 0.001).

CONCLUSION

Dexamethasone can protect spleen from injury during SAP mainly by reducing the content of inflammatory mediators in blood.

HIV-1 RNA dysregulates the natural TLR response to subclinical endotoxemia in Kenyan female sex-workers

Background

Subclinical endotoxemia has been reported in HIV-1 infected persons and may drive systemic immune activation and pathogenesis. Proinflammatory responsiveness to endotoxin (LPS) is mediated by Toll-like receptor 4 (TLR4). We therefore examined the association between plasma LPS levels, HIV RNA, and TLR4 expression and cytokine responses in the blood of HIV infected and uninfected participants in a cohort of female sex-workers in Kenya.

Methodology/Principal Findings

Ex vivo plasma and peripheral blood mononuclear cells (PBMC) were assessed for LPS and TLR mRNA, respectively. The effects of HIV single stranded RNA, a TLR8 ligand, on TLR4 and LPS signaling were further assessed in short term PBMC culture. Both HIV uninfected and infected subjects frequently had low detectable LPS levels in their plasmas. Significantly increased LPS levels were associated with chronic HIV-1 infection, both treated and untreated, but not with other acute or semi-chronic conditions reported. In HIV-uninfected subjects, TLR4 mRNA expression levels correlated inversely with plasma LPS levels, suggesting chronic endotoxin ‘tolerance’ in vivo. A similar effect of reduced TLR4 mRNA was seen in short term PBMC culture after stimulation with LPS. Interestingly, the apparent in vivo tolerance effect was diminished in subjects with HIV infection. Additionally, pre-stimulation of PBMC with LPS lead to proinflammatory (TNF-α) tolerance to subsequent LPS stimulation; however, pre-treatment of PBMC with HIV single-stranded RNA40, could enhance TLR4-mediated LPS responsiveness in vitro.

Conclusions/Significance

Thus, dysregulation of endotoxin tolerance by HIV-1 RNA may exacerbate HIV chronic immune activation and pathogenesis.

Validation criteria for nucleic acid amplification techniques for bacterial infections

Nucleic acid techniques (NATs), such as species-specific and universal polymerase chain reactions (PCRs), are finding ever wider use in the diagnosis of bacterial infection. However, although universal PCR assays, in particular, approach a type of modern Petri dish, they have a number of limitations which restrict their applicability. The sensitivity of universal PCR is lower than that of many species-specific PCRs, and the contamination of samples and PCR reagents with irrelevant DNA from various sources remains a problem. Thus, NATs in general and universal PCR assays in particular require careful validation to be of value for the diagnosis of infection. Validation includes sampling, DNA extraction/isolation, template amplification and visualisation of the results. Furthermore, it implies the establishment of measures of asepsis, the inclusion of positive and negative controls, techniques to optimise the release of DNA from bacterial cells, adequate repetition of the amplification reaction, and routine testing of reagent negative and inhibition controls. Finally, it entails the comparison of results obtained by NATs with those obtained by conventional microbiological methods and matching with clinical evidence of infection. Validation of NATs in clinical diagnosis remains an ongoing challenge. Because of these limitations, NATs can only serve as adjunct tools for the diagnosis of infection in selected cases; they cannot replace conventional culturing techniques.

Study of the protective effects of dexamethasone on ileum mucosa injury in rats with severe acute pancreatitis

OBJECTIVES

To study the protecting effects of dexamethasone on ileum mucosa injury of rats with severe acute pancreatitis (SAP).

METHODS

The SAP rats were prepared by improved Aho's methods. The plasma endotoxin and inflammatory mediators in serum were determined. The rat mortality, pathological changes of terminal ileum, nuclear factor kappa B (NF-kappaB), apoptotic indexes, and apoptotic related protein expression were observed.

RESULTS

The plasma endotoxin, inflammatory mediators, and NF-kappaB protein expression as well as pathological scores of the treatment group of ileum mucosa were lower than those of the model group at different time points. P selectin in model group significantly exceeded the dexamethasone treatment group at 3 and 6 hours (P < 0.01, P < 0.05). Caspase-3 protein expression in dexamethasone treatment group significantly exceeded the model group at 3 and 6 hours (P < 0.05), and apoptotic indexes were higher than those of the model group at 6 hours (P < 0.05), but Bax protein has shown no marked difference among groups.

CONCLUSIONS

Dexamethasone can reduce the endotoxin level and inflammatory mediators and down-regulate NF-kappaB protein expression of ileum mucosa, and ileum mucosa epithelial cell apoptosis induction was involved as well. The tissue microarrays technique is of advantage in SAP study.

Role of cytokine-induced neutrophil chemoattractant in acute lung injury during acute pancreatitis

AIM: To investigate the role of cytokine-induced neutrophil chemoattractant (CINC) in the pathogenesis of acute lung injury (ALI) during acute pancreatitis (AP).

METHODS: AP model was induced by intraperitoneal injection of cerulein or retrograde infusion of 50 g/L sodium taurocholate into the bili-pancreatic duct in Sprague Dawley rats. A total of 84 rats were randomly divided into 4 groups: cerulein group, saline control group, sodium taurocholate group and operational control group. The level of serum amylase, the pulmonary dry/wet weight ratio and histological changes were measured at different time points in each group. The expression of pulmonary CINC protein and mRNA were detected by immunohistochemistry and semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR), respectively.

RESULTS: No significant difference was found between cerulein group and saline control group at different time points (P > 0.05). In comparison with those in operational control group, the level of serum amylase and pulmonary dry/wet weight ratio were significantly higher in sodium taurocholate group 1 h after operation (P < 0.01), and the expression of pulmonary CINC mRNA started to increase at the 1st h after operation (1 h: 0.23 ± 0.07 vs 0.07 ± 0.04, P < 0.05; 3 h: 0.36 ± 0.07 vs 0.06 ± 0.04, P < 0.05; 6 h: 0.56 ± 0.07 vs 0.09 ± 0.05, P < 0.01; 12 h: 0.49 ± 0.09 vs 0.11 ± 0.03, P < 0.01). The expression of pulmonary CINC protein was detected at 3rd h after operation, and then up-regulated gradually. Moreover, the expression of CINC was correlated with pulmonary histological changes.

CONCLUSION: CINC plays an important role in the pathogenesis of ALI during AP.