Activated protein C in sepsis: emerging insights regarding its mechanism of action and clinical effectiveness

Visual LAMP method for the detection of Vibrio vulnificus in aquatic products and environmental water

Background

A visual, rapid, simple method was developed based on a loop-mediated isothermal amplification (LAMP) assay to detect Vibrio vulnificus in aquatic products and aquaculture waters.

Results

Genomic DNA was extracted from Vibrio vulnificus using the boiling method, and optimized primers were used to detect the gyrB gene using a visual LAMP method. The sensitivity of the assay was 10 fg/μL, and the obtained results were stable and reliable. Out of 655 aquatic product samples and 558 aquaculture water samples, the positive rates of Vibrio vulnificus detection were 9.01% and 8.60%, respectively, which are markedly higher than those of the traditional culture identification methods.

Conclusion

The relatively simple technical requirements, low equipment cost, and rapid detection make the visual LAMP method for the detection of Vibrio vulnificus a convenient choice for field detection in the aquaculture industry.

Mechanisms of human complement factor B induction in sepsis and inhibition by activated protein C

To investigate the potential role of the local expression of alternative complement factor B (hBf) in human sepsis, we examined the induction of Bf gene expression in human peripheral blood monocytes (PBMCs) from patients with septic shock and the mechanisms of hBf gene regulation by tumor necrosis factor (TNF)-α, interferon (IFN)-γ, and lipopolysaccharide (LPS) in human monocytes. PBMCs from septic shock patients showed increased hBf mRNA expression when compared with control patients. Costimulation with TNF-α and IFN-γ or stimulation with LPS demonstrated a time- and dose-dependent induction of hBf mRNA expression in human PBMCs. A region of the hBf promoter between −735 and +128 bp was found to mediate IFN-γ, TNF-α, and LPS responsiveness as well as the synergistic effect of IFN-γ/TNF-α on hBf promoter activity. Site-directed mutagenesis of a IFN-γ-activation site (GAS) cis element (−90 to −82 bp) abrogated IFN-γ responsiveness. Mutagenesis of a nuclear factor (NF)-κB cis element at −466 to −456 bp abrogated TNF-α and LPS responsiveness of the Bf promoter. Thus hBf gene expression is induced in PBMCs from septic shock patients, and the induction of hBf by IFN-γ, TNF-α, and LPS is through GAS and NF-κB cis-binding sites on the hBf promoter. Furthermore, activated protein C (APC) inhibited LPS-stimulated hBf promoter activity and protein expression in human monocytes suggesting that the beneficial effect of APC therapy in sepsis may in part be due to inhibition of complement induction and/or activation via the alternative pathway.

RNA-binding protein HuR interacts with thrombomodulin 5'untranslated region and represses internal ribosome entry site-mediated translation under IL-1 beta treatment

Reduction in host-activated protein C levels and resultant microvascular thrombosis highlight the important functional role of protein C anticoagulant system in the pathogenesis of sepsis and septic shock. Thrombomodulin (TM) is a critical factor to activate protein C in mediating the anticoagulation and anti-inflammation effects. However, TM protein content is decreased in inflammation and sepsis, and the mechanism is still not well defined. In this report, we identified that the TM 5' untranslated region (UTR) bearing the internal ribosome entry site (IRES) element controls TM protein expression. Using RNA probe pulldown assay, HuR was demonstrated to interact with the TM 5'UTR. Overexpression of HuR protein inhibited the activity of TM IRES, whereas on the other hand, reducing the HuR protein level reversed this effect. When cells were treated with IL-1beta, the IRES activity was suppressed and accompanied by an increased interaction between HuR and TM 5'UTR. In the animal model of sepsis, we found the TM protein expression level to be decreased while concurrently observing the increased interaction between HuR and TM mRNA in liver tissue. In summary, HuR plays an important role in suppression of TM protein synthesis in IL-1beta treatment and sepsis.

Levels of protein C activity and clinical factors in early phase of pediatric septic shock may be associated with the risk of death

Severe sepsis and septic shock are major causes of morbidity and mortality among children in pediatric intensive care units (PICUs) worldwide. Activated protein C (PC) is a critical endogenous regulator of coagulation and inflammation in patients with sepsis. However, the role of PC in pediatric sepsis is still obscure. We prospectively recruited infants and children aged between 1 month and 15 years old who were admitted to PICU with a clinical diagnosis of systemic inflammatory response syndrome, sepsis, or septic shock. Clinical data were recorded and blood samples kept for further analysis. We then measured the levels of PC activity. Of the approximately 1,100 pediatric patients admitted to PICU from January 1, 2004 to December 31, 2005, 75 were diagnosed with septic shock (6.8%), and 67 samples were available for analysis. Out of these, 41 (61%) were survivors, and 26 (39%) were nonsurvivors. The average plasma PC activity (%) was at 37.8 +/- 4.4. Plasma PC activity (%) was significantly lower in the nonsurvivors compared with the survivors at 23.6 +/- 4.3 and 46.8 +/- 6.3 (P = 0.002), respectively. D-Dimer levels were not significantly different between the survivors (1,461 +/- 266 ng/mL) and the nonsurvivors (1,989 +/- 489 ng/mL) (P = 0.68). Also, there was no correlation between plasma PC activity and D-dimer levels (r = -0.07; P = 0.6). Importantly, the odds of dying were significantly higher in patients whose level of PC activity was less than 25% (odds ratio = 5.6; P = 0.02). Pediatric patients with septic shock demonstrate very low levels of PC activity, and this may be associated with an increased risk of death.

Activated protein C reduces endotoxin-induced white matter injury in the developing rat brain

Periventricular leukomalacia (PVL), the dominant form of brain injury in premature infants, is characterized by white matter injury (WMI) and is associated with cerebral palsy. The pathogenesis of PVL is complex and likely involves ischemia/reperfusion, free radical formation, excitotoxicity, impaired regulation of cerebral blood flow, a procoagulant state, and inflammatory mechanisms associated with maternal and/or fetal infection. Using an established animal model of human PVL, we investigated whether activated protein C (APC), an anti-coagulant factor with anti-inflammatory, anti-apoptotic, anti-oxidant, and cytoprotective activities, could reduce endotoxin-induced WMI in the developing rat brain. Intraperitoneal injections of lipopolysaccharide (LPS) (0.5 mg/kg body weight) were given at embryonic days 18 (E18) and 19 (E19) to pregnant Sprague-Dawley rats; control rats were injected with sterile saline. A single intravenous injection of recombinant human (rh) APC (0.2 mg /kg body weight) was given to pregnant rats following the second LPS dose on embryonic day 19 (E19). Reduced cell death in white matter and hypomyelination were shown on TUNEL and myelin basic protein (MBP) staining, respectively, on late postnatal days (P7) in APC-treated groups. There were significantly fewer TUNEL+nuclei in the periventricular WM in the APC+LPS group than in the untreated LPS group. Compared to the APC+LPS and control group, MBP expression was weak in the LPS group on P7, indicating endotoxin-induced hypomyelination in the developing rat brain. APC attenuated the LPS-induced protein expression of inflammatory cytokines, tumor necrosis factor-alpha, and interleukin-6, as evaluated by ELISA in neonatal rat brains. A single intraperitoneal injection of rhAPC (0.2 mg/kg body weight) to neonatal rats on P1 also had similar protective and anti-inflammatory effects against maternally administered LPS. Collectively, these data support the hypothesis that APC may provide protection against an endotoxin-evoked inflammatory response and WMI in the developing rat brain. Moreover, our results suggest that the possible use of APC in treatment of preterm infants and pregnant women with maternal or placental infection may minimize the risk of PVL and cerebral palsy.

Cardiovascular protective role for activated protein C during endotoxemia in rats

OBJECTIVE

We examined whether activated protein C (APC) treatment improves cardiovascular inflammation and dysfunction in endotoxemic rats.

DESIGN AND SETTING

Randomized, controlled trial in an experimental laboratory of a university physiology department

SUBJECTS

Male Sprague Dawley rats.

INTERVENTIONS

Internal carotid artery and external jugular vein were catheterized under sterile conditions in rats. Instrumented rats infused or not with APC (240 microg/kg per hour) were challenged with E. coli endotoxin (10 mg/kg). Four hours after endotoxin challenge rats were prepared for cardiovascular functional studies and tissue and blood analyses.

MEASUREMENTS AND RESULTS

Endotoxin administration induced systemic hypotension, depression of myocardial systolic performance and reduction in capillary density of the small intestine muscularis layer. Plasma levels of nitrite/nitrate, tumor necrosis factor alpha and macrophage migration inhibitory factor, mesentery venule leukocyte-endothelium interactions, heart and small intestine myeloperoxidase activities were increased in endotoxin-treated rats. APC largely prevented endotoxin-induced cardiovascular dysfunction with improved systemic hemodynamics, functional capillary density, and myocardial contractile performance. Beneficial cardiovascular effects of APC were associated with attenuation of entotoxin-induced inflammatory response in terms of plasma levels of nitrite/nitrate, tumor necrosis factor alpha, macrophage migration inhibitory factor, and endothelial cell-leukocyte activation.

CONCLUSION

APC reduces systemic and tissue inflammation and preserves cardiovascular function during experimental endotoxemia.

A meta-analysis of controlled trials of recombinant human activated protein C therapy in patients with sepsis

Background

Meta-analysis of two randomised controlled trials in severe sepsis performed with recombinant human activated protein C may provide further insight as to the therapeutic utility of targeting the clotting cascade in this syndrome.

Methods

In search for relevant studies published, two randomized clinical trials were found eligible.

Results

The studies, PROWESS and ADDRESS, enrolled a total of 4329 patients with risk ratio (RR) and 95% confidence interval (CI) data for effect on 28-day mortality relative to control treatment of 0.92 (0.83–1.02) suggesting that recombinant human activated protein C is not beneficial in severe sepsis. In PROWESS, 873 of 1690 patients presented with low risk, and 2315 of 2639 patients in ADDRESS as defined by APACHE II score < 25. In this low-risk stratum, no effect of recombinant human activated protein C administration on 28-day mortality was observed. This observation appears to be consistent and homogenous. Heterogeneity between the two studies, however, was seen in patients with APACHE II score ≥ 25 in whom recombinant activated protein C was effective in PROWESS (n = 817; RR 0.71, CI 0.59–0.85) whereas a tendency toward harm was present in ADDRESS (n = 324; RR 1.21, CI 0.85–1.74). Even though the overall treatment effect in this high-risk population was still in favour of treatment with recombinant activated protein C (n = 1141; RR 0.80, CI 0.68–0.94), the observed heterogeneity suggests that the efficacy of recombinant human activated protein C is not robust. Not unlikely, the adverse tendency observed could have become significant with higher statistical power would ADDRESS not have been terminated prematurely.

Conclusion

This meta-analysis, therefore, raises doubts about the clinical usefulness of recombinant activated protein C in patients with severe sepsis and an APACHE II score ≥ 25 which can only be resolved by another properly designed clinical trial.

Mice with a severe deficiency in protein C display prothrombotic and proinflammatory phenotypes and compromised maternal reproductive capabilities

Anticoagulant protein C (PC) is important not only for maintenance of normal hemostasis, but also for regulating the host immune response during inflammation. Because mice with a designed total genetic deficiency in PC (PC-/- mice) die soon after birth, attempts to dissect PC function in various coagulation/inflammation-based pathologies through use of mice with less than 50% of normal PC levels have not been successful to date. In the current investigation, we have used a novel transgenic strategy to generate different mouse models expressing 1-18% of normal PC levels. In contrast to PC-/- mice, mice with only partial PC deficiency survived beyond birth and also developed thrombosis and inflammation. The onset and severity of these phenotypes vary significantly and are strongly dependent on plasma PC levels. Our findings additionally provide the first evidence that maternal PC is vital for sustaining pregnancy beyond 7.5 days postcoitum, likely by regulating the balance of coagulation and inflammation during trophoblast invasion. These low PC-expressing transgenic mouse lines provide novel animal models that can be used to elucidate the importance of PC in maintenance of the organism and in disease.

The effect of activated protein C on experimental acute necrotizing pancreatitis

INTRODUCTION

Acute pancreatitis is a local inflammatory process that leads to a systemic inflammatory response in the majority of cases. Bacterial contamination has been estimated to occur in 30-40% of patients with necrotizing pancreatitis. Development of pancreatic necrosis depends mainly on the degree of inflammation and on the microvascular circulation of the pancreatic tissue. Activated protein C (APC) is known to inhibit coagulation and inflammation, and to promote fibrinolysis in patients with severe sepsis. We investigated the effects of APC on histopathology, bacterial translocation, and systemic inflammation in experimental acute necrotizing pancreatitis.

MATERIALS AND METHOD

Forty-five male Sprague-Dawley rats were studied. Rats were randomly allocated to three groups. Acute pancreatitis was induced in group II (positive control; n = 15) and group III (treatment; n = 15) rats by retrograde injection of taurocholate into the common biliopancreatic duct. Group I rats (sham; n = 15) received an injection of normal saline into the common biliopancreatic duct to mimic a pressure effect. Group III rats were treated with intravenous APC 6 hours after induction of pancreatitis. Pancreatic tissue and blood samples were obtained from all animals for histopathological examination and assessment of amylase, tumor necrosis factor-alpha, and IL-6 levels in serum. Bacterial translocation to pancreas and mesenteric lymph nodes was measured.

RESULTS

Acute pancreatitis developed in all groups apart from group I (sham), as indicated by microscopic parenchymal necrosis, fat necrosis and abundant turbid peritoneal fluid. Histopathological pancreatitis scores in the APC-treated group were lower than in positive controls (10.31 +/- 0.47 versus 14.00 +/- 0.52; P < 0.001). Bacterial translocation to mesenteric lymph nodes and to pancreas in the APC-treated group was significantly decreased compared with controls (P < 0.02 and P < 0.007, respectively). Serum amylase, tumor necrosis factor-alpha, and IL-6 levels were also significantly decreased in comparison with positive controls (P < 0.001, P < 0.04 and P < 0.001, respectively).

CONCLUSION

APC improved the severity of pancreatic tissue histology, superinfection rates and serum markers of inflammation during the course of acute necrotizing pancreatitis.

Safety of drotrecogin alfa (activated) in the treatment of patients with severe sepsis

While severe sepsis continues to plague hospitals worldwide, new treatment modalities, including activated recombinant protein C (drotrecogin alfa, Xigris, Lilly), have become a standard treatment alternative in many institutional algorithms. Drotrecogin alfa was shown to have a beneficial effect on mortality versus placebo in the PROWESS (Recombinant Human Activated Protein C Worldwide Evaluation in Severe Sepsis) trial (p = 0.005), but its use is not completely without risk. An increased risk of bleeding, including severe bleeding episodes, exists ranging 3.5 - 5.2% in the drotrecogin alfa treatment group versus 2.0 - 5.0% in the placebo group. Patients at risk include those on concomitant heparin therapy (> 15,000 units/day), those with platelet counts <or= 30,000/mm(3), and those undergoing an invasive procedure during the scheduled infusion period. After almost three years on the US market, the reported incidence of severe bleeding episodes has risen only slightly from the pre-marketing era, at that time notable for restrictive treatment protocols, devoid of at-risk patients. Drotrecogin alfa, while a promising agent for severe sepsis, requires prudent patient evaluation for bleeding risks.