Severe acute pancreatitis between systematic inflammatory response syndrome and sepsis: insights from a mathematical model of endotoxin tolerance

Fractal-like kinetics of intracellular enzymatic reactions: a chemical framework of endotoxin tolerance and a possible non-specific contribution of macromolecular crowding to cross-tolerance

BACKGROUND

The response to endotoxin (LPS), and subsequent signal transduction lead to the production of cytokines such as tumor necrosis factor-α (TNF-α) by innate immune cells. Cells or organisms pretreated with endotoxin enter into a transient state of hyporesponsiveness, referred to as endotoxin tolerance (ET) which represents a particular case of negative preconditioning. Despite recent progress in understanding the molecular basis of ET, there is no consensus yet on the primary mechanism responsible for ET and for the more complex cases of cross tolerance. In this study, we examined the consequences of the macromolecular crowding (MMC) and of fractal-like kinetics (FLK) of intracellular enzymatic reactions on the LPS signaling machinery. We hypothesized that this particular type of enzyme kinetics may explain the development of ET phenomenon.

METHOD

Our aim in the present study was to characterize the chemical kinetics framework in ET and determine whether fractal-like kinetics explains, at least in part, ET. We developed an ordinary differential equations (ODE) mathematical model that took into account the links between the MMC and the LPS signaling machinery leading to ET. We proposed that the intracellular fractal environment (MMC) contributes to ET and developed two mathematical models of enzyme kinetics: one based on Kopelman's fractal-like kinetics framework and the other based on Savageau's power law model.

RESULTS

Kopelman's model provides a good image of the potential influence of a fractal intracellular environment (MMC) on ET. The Savageau power law model also partially explains ET. The computer simulations supported the hypothesis that MMC and FLK may play a role in ET.

CONCLUSION

The model highlights the links between the organization of the intracellular environment, MMC and the LPS signaling machinery leading to ET. Our FLK-based model does not minimize the role of the numerous negative regulatory factors. It simply draws attention to the fact that macromolecular crowding can contribute significantly to the induction of ET by imposing geometric constrains and a particular chemical kinetic for the intracellular reactions.

Effects of enteral immunonutrition on the maintenance of gut barrier function and immune function in pigs with severe acute pancreatitis

BACKGROUND

This study evaluated the effects of enteral immunonutrition (EIN) supplemented with glutamine, arginine, and probiotics on gut barrier function and immune function in pigs with severe acute pancreatitis (SAP).

METHODS

The model was induced by retrograde injection of 5% sodium taurocholate and trypsin via the pancreatic duct. After induction of SAP, 18 pigs were randomly divided into 3 groups, in which either parenteral nutrition (PN), control enteral nutrition (CEN), or EIN was applied for 8 days. Serum and pancreatic fluid amylase concentration was determined. Intestinal permeability (lactulose to mannitol ratio) was measured by high-performance liquid chromatography, and plasma endotoxin was quantified by the chromogenic limulus amebocyte lysate technique. Samples of venous blood and organs were cultured using standard techniques. Pancreatitis severity and villi of ileum were scored according to histopathologic grading. Plasma T-lymphocyte subsets were measured by flow cytometry, and immunoglobulins (Igs) were determined via enzyme-linked immunosorbent assay.

RESULTS

There were no significant differences in serum and pancreatic fluid amylases concentrations or in pancreatitis severity between any 2 of the 3 groups. Compared with PN and CEN, EIN significantly decreased intestinal permeability, plasma endotoxin concentration, and the incidence and magnitudes of bacterial translocation, but increased ileal mucosal thickness, villous height, crypt depth, and percentage of normal intestinal villi. Significant differences were found in CD3+, CD4+ lymphocyte subsets, the ratio of CD4+: CD8+ lymphocyte subsets, and serum IgA and IgG, but not IgM, between any 2 of the 3 groups.

CONCLUSIONS

EIN maintained gut barrier function and immune function in pigs with SAP.

Regulation of omega-3 fish oil emulsion on the SIRS during the initial stage of severe acute pancreatitis

The aim of this study was to explore the effects of parenteral supplementation with omega-3 fish oil emulsion (Omegaven) on systemic inflammatory response syndrome (SIRS) during the initial stage of severe acute pancreatitis (SAP). In a prospective, randomized and controlled trial, 60 patients with SAP were randomized either to treat with conventional therapy (Con group, n=30) or conventional therapy plus intravenous supplementation with omega-3 fish oil emulsion 0.2 g/kg every day (FO group, n=30). The effects were analyzed by the SIRS-related indexes. The results showed that APACHE-II scores in FO group were significantly lower, and the gap increased much farther after the 4th day than those in Con group (P<0.05). Fluid equilibrium time became shorter markedly in FO group than in Con group (5.1+/-2.2 days vs 8.4+/-2.3 days). In FO group, SIRS scores were markedly decreased and the SIRS state vanished after the 4th day; Plasma level of TNF-alpha was significantly reduced, while IL-10 decreased markedly, most prominently between the 4th and 7th day, and the ratio of IL-10/TNF-alpha raised as compared with Con group (P<0.05). During the initial stage of SAP, parenteral supplementation with omega-3 fish oil emulsion could efficiently lower the magnitude and persistence time of the SIRS, markedly retrieve the unbalance of the pro-/anti-inflammatory cytokines, improve severe condition of illness and may provide a new way to regulate the SIRS.