A quantitative model of thermal injury-induced acute inflammation

Aging-induced fragility of the immune system

The adaptive and innate branches of the vertebrate immune system work in close collaboration to protect organisms from harmful pathogens. As an organism ages its immune system undergoes immunosenescence, characterized by declined performance or malfunction in either immune branch, which can lead to disease and death. In this study we develop a mathematical framework of coupled innate and adaptive immune responses, namely the integrated immune branch (IIB) model. This model describes dynamics of immune components in both branches, uses a shape-space representation to encode pathogen-specific immune memory, and exhibits three steady states - health, septic death, and chronic inflammation - qualitatively similar to clinically-observed immune outcomes. In this model, the immune system (initialized in the health state) is subjected to a sequence of pathogen encounters, and we use the number of prior pathogen encounters as a proxy for the "age" of the immune system. We find that repeated pathogen encounters may trigger a fragility in which any encounter with a novel pathogen will cause the system to irreversibly switch from health to chronic inflammation. This transition is consistent with the onset of "inflammaging", a condition observed in aged individuals who experience chronic low-grade inflammation even in the absence of pathogens. The IIB model predicts that the onset of chronic inflammation strongly depends on the history of encountered pathogens; the timing of onset differs drastically when the same set of infections occurs in a different order. Lastly, the coupling between the innate and adaptive immune branches generates a trade-off between rapid pathogen clearance and a delayed onset of immunosenescence. Overall, by considering the complex feedback between immune compartments, our work suggests potential mechanisms for immunosenescence and provides a theoretical framework at the system level and on the scale of an organism's lifetime to account for clinical observations.

Dynamical modeling of pro- and anti-inflammatory cytokines in the early stage of septic shock

A dynamical model of the pathophysiological behaviors of IL18 and IL10 cytokines with their receptors is tested against data for the case of early sepsis. The proposed approach considers the surroundings (organs and bone marrow) and the different subsystems (cells and cyctokines). The interactions between blood cells, cytokines and the surroundings are described via mass balances. Cytokines are adsorbed onto associated receptors at the cell surface. The adsorption is described by the Langmuir model and gives rise to the production of more cytokines and associated receptors inside the cell. The quantities of pro and anti-inflammatory cytokines present in the body are combined to give global information via an inflammation level function which describes the patient’s state. Data for parameter estimation comes from the Sepsis 48 H database. Comparisons between patient data and simulations are presented and are in good agreement. For the IL18/IL10 cytokine pair, 5 key parameters have been found. They are linked to pro-inflammatory IL18 cytokine and show that the early sepsis is driven by components of inflammatory character.

A Full-Body Model of Burn Pathophysiology and Treatment Using the BioGears Engine

We have created a model of systemic burn pathophysiology by incorporating a mathematical model of acute inflammation within the BioGears Engine. This model produces outputs consistent with burns of varying severities and leverages existing BioGears functionality to simulate the effect of treatment on virtual patient outcome. The model performs well for standard resuscitation scenarios and we thus expect it to be useful for educational and training purposes.

Nutrition: reducing the hypermetabolic response to thermal injury

Nutritional support is seen as a vital component in the battle to attenuate the extreme hypermetabolic response experienced by patients suffering from large thermal injuries. Protein catabolism precipitating protein malnutrition places patients at greater risk of wound infection and sepsis due to delayed wound healing. Underfeeding, aggressive feeding, feeding routes, timing of initiation of feeding and tight insulin control have all been explored extensively in the quest to understand what nutritional treatment will best attenuate the hypermetabolic response. Despite this it is suggested that the majority of patients with large thermal injuries do not receive adequate nutritional support immediately post injury. Nurses have a pivotal role to play in ensuring that thermal injury patients receive appropriate nutritional support based on the best available evidence.

Understanding Physiology in the Continuum: Integration of Information from Multiple -Omics Levels

In this paper, we discuss approaches for integrating biological information reflecting diverse physiologic levels. In particular, we explore statistical and model-based methods for integrating transcriptomic, proteomic and metabolomics data. Our case studies reflect responses to a systemic inflammatory stimulus and in response to an anti-inflammatory treatment. Our paper serves partly as a review of existing methods and partly as a means to demonstrate, using case studies related to human endotoxemia and response to methylprednisolone (MPL) treatment, how specific questions may require specific methods, thus emphasizing the non-uniqueness of the approaches. Finally, we explore novel ways for integrating -omics information with PKPD models, toward the development of more integrated pharmacology models.

Mathematical Models for Immunology: Current State of the Art and Future Research Directions

The advances in genetics and biochemistry that have taken place over the last 10 years led to significant advances in experimental and clinical immunology. In turn, this has led to the development of new mathematical models to investigate qualitatively and quantitatively various open questions in immunology. In this study we present a review of some research areas in mathematical immunology that evolved over the last 10 years. To this end, we take a step-by-step approach in discussing a range of models derived to study the dynamics of both the innate and immune responses at the molecular, cellular and tissue scales. To emphasise the use of mathematics in modelling in this area, we also review some of the mathematical tools used to investigate these models. Finally, we discuss some future trends in both experimental immunology and mathematical immunology for the upcoming years.

Comparison of systemic inflammation response and vital organ damage induced by severe burns in different area

BACKGROUND

In this study, we will establish a stable and optimized rat model that can meet strictly diagnosed criteria and serve as a tool to investigate the potential of novel therapeutics in this preclinical model through comparative analysis of systemic alterations, levels of pro-inflammatory cytokines in serum and infiltrated numbers of inflammatory cells in distant organ between 30% and 50% TBSA with a full-thickness burn.

MATERIALS AND METHODS

The adult male Wistar rats were randomly divided into the following groups: control group, 30% TBSA with a full-thickness burn group, and 50% TBSA with a full-thickness burn group. The blood and serum samples in the 3 groups were collected and detected by blood routine examination and biochemical detection at 6 h, 12 h, 24 h and 48 h post burn. The levels of TNF-α, IL-1β and IL-6 in serum were detected by ELISA. The sections of lung, renal, liver and heart were analyzed by H&E and immunohistochemical staining detection.

RESULTS

Our results showed that temperature in 50% TBSA with a full-thickness burn group was always hypothermia, and lower than 36°C at defined timepoints post burn, that was in 30% TBSA with a full-thickness burn group was lower than 36°C only at 48 h post burn. The levels of TNF-α, IL-1β and IL-6 were significantly increased in 30% and 50% groups at 6 h, 12 h, 24 h and 48 h post burn. The apoptosis in distant organs and the biochemical parameters such as ALT, AST, troponin, CK, CK-MB, LDH, urea and creatinine in 30% and 50% groups were also increased at different degrees at defined timepoints after burn, but changes in 50% group were more obvious than that in 30% group.

CONCLUSION

We choose 50% TBSA with a full-thickness burn to establish a stable and optimized rat model that can meet strictly diagnosed criteria and serve as a tool to investigate the potential of novel therapeutics in this preclinical model.

Low dose of glucocorticoid decreases the incidence of complications in severely burned patients by attenuating systemic inflammation

BACKGROUND

Excessive systemic inflammatory response remains as a major problem underlying severe burns. This study aimed to assess the effect of low-dose glucocorticoid treatment in downregulating systemic inflammation in severely burned patients.

METHODS

A prospective study from 2001 to 2014 at our hospital was conducted to compare the patients who received low-dose glucocorticoid during the acute phase with those who did not. Patients with burns 70% or greater of their total body surface area were included, and their plasma levels of inflammatory cytokines and clinical outcomes were compared.

RESULTS

A total of 69 patients were included in this study, with 31 patients receiving glucocorticoid treatment and the others not. Patient demographics including age, burn size, and incidence of inhalation injury were similar in both groups. The incidence of pulmonary infection and stress ulcer (and/or hemorrhage) was 24.2% and 3.0% in the treatment group, respectively, significantly lower than 47.8% and 19.6% of the control group (P < .05). Length of hospital stay was almost 13 days shorter in the treatment group (P < .05), whereas there was no significant difference in the overall mortality, duration of mechanical ventilation, and incidence of sepsis between the 2 groups. The enzyme-linked immunosorbent assay results confirmed that the plasma levels of C-reactive protein, tumor necrosis factor-α, interleukin-6, and interleukin-8 were significantly lower in the treatment group (P < .05).

CONCLUSION

Low dose of glucocorticoid treatment during the acute phase could reduce the levels of proinflammatory cytokines in severely burned patients and subsequently decrease the incidence of pulmonary infection and stress ulcer, as well as the length of hospital stay.

Modeling the intra- and extracellular cytokine signaling pathway under heat stroke in the liver

Heat stroke (HS) is a life-threatening illness induced by prolonged exposure to a hot environment that causes central nervous system abnormalities and severe hyperthermia. Current data suggest that the pathophysiological responses to heat stroke may not only be due to the immediate effects of heat exposure per se but also the result of a systemic inflammatory response syndrome (SIRS). The observation that pro- (e.g., IL-1) and anti-inflammatory (e.g., IL-10) cytokines are elevated concomitantly during recovery suggests a complex network of interactions involved in the manifestation of heat-induced SIRS. In this study, we measured a set of circulating cytokine/soluble cytokine receptor proteins and liver cytokine and receptor mRNA accumulation in wild-type and tumor necrosis factor (TNF) receptor knockout mice to assess the effect of neutralization of TNF signaling on the SIRS following HS. Using a systems approach, we developed a computational model describing dynamic changes (intra- and extracellular events) in the cytokine signaling pathways in response to HS that was fitted to novel genomic (liver mRNA accumulation) and proteomic (circulating cytokines and receptors) data using global optimization. The model allows integration of relevant biological knowledge and formulation of new hypotheses regarding the molecular mechanisms behind the complex etiology of HS that may serve as future therapeutic targets. Moreover, using our unique modeling framework, we explored cytokine signaling pathways with three in silico experiments (e.g. by simulating different heat insult scenarios and responses in cytokine knockout strains in silico).

Treatment of cachexia: melanocortin and ghrelin interventions

Cachexia is a condition typified by wasting of fat and LBM caused by anorexia and further endocrinological modulation of energy stores. Diseases known to cause cachectic symptoms include cancer, chronic kidney disease, and chronic heart failure; these conditions are associated with increased levels of proinflammatory cytokines and increased resting energy expenditure. Early studies have suggested the central melanocortin system as one of the main mediators of the symptoms of cachexia. Pharmacological and genetic antagonism of these pathways attenuates cachectic symptoms in laboratory models; effects have yet to be studied in humans. In addition, ghrelin, an endogenous orexigenic hormone with receptors on melanocortinergic neurons, has been shown to ameliorate symptoms of cachexia, at least in part, by an increase in appetite via melanocortin modulation, in addition to its anticatabolic and anti-inflammatory effects. These effects of ghrelin have been confirmed in multiple types of cachexia in both laboratory and human studies, suggesting a positive future for cachexia treatments.

Pharmacokinetics and pharmacodynamics of phase II drug metabolizing/antioxidant enzymes gene response by anticancer agent sulforaphane in rat lymphocytes

This study assesses the pharmacokinetics (PK) and pharmacodynamics (PD) of Nrf2-mediated increased expression of phase II drug metabolizing enzymes (DME) and antioxidant enzymes which represents an important component of cancer chemoprevention in rat lymphocytes following intravenous (iv) administration of an anticancer phytochemical sulforaphane (SFN). SFN was administered intravenously to four groups of male Sprague-Dawley JVC rats each group comprising four animals. Blood samples were drawn at selected time points. Plasma were obtained from half of each of the blood samples and analyzed using a validated LC-MS/MS method. Lymphocytes were collected from the remaining blood samples using Ficoll-Paque Plus centrifuge medium. Lymphocyte RNAs were extracted and converted to cDNA, quantitative real-time PCR analyses were performed, and fold changes were calculated against those at time zero for the relative expression of Nrf2-target genes of phase II DME/antioxidant enzymes. PK-PD modeling was conducted based on Jusko's indirect response model (IDR) using GastroPlus and bootstrap method. SFN plasma concentration declined biexponentially and the pharmacokinetic parameters were generated. Rat lymphocyte mRNA expression levels showed no change for GSTM1, SOD, NF-κB, UGT1A1, or UGT1A6. Moderate increases (2-5-fold) over the time zero were seen for HO-1, Nrf2, and NQO1, and significant increases (>5-fold) for GSTT1, GPx1, and Maf. PK-PD analyses using GastroPlus and the bootstrap method provided reasonable fitting for the PK and PD profiles and parameter estimates. Our present study shows that SFN could induce Nrf2-mediated phase II DME/antioxidant mRNA expression for NQO1, GSTT1, Nrf2, GPx, Maf, and HO-1 in rat lymphocytes after iv administration, suggesting that Nrf2-mediated mRNA expression in lymphocytes may serve as surrogate biomarkers. The PK-PD IDR model simultaneously linking the plasma concentrations of SFN and the PD response of lymphocyte mRNA expression is valuable for quantitating Nrf2-mediated effects of SFN. This study may provide a conceptual framework for future clinical PK-PD studies of dietary cancer chemopreventive agents in human.

Dynamics of short-term gene expression profiling in liver following thermal injury

BACKGROUND

Severe trauma, including burns, triggers a systemic response that significantly impacts on the liver, which plays a key role in the metabolic and immune responses aimed at restoring homeostasis. While many of these changes are likely regulated at the gene expression level, there is a need to better understand the dynamics and expression patterns of burn injury-induced genes in order to identify potential regulatory targets in the liver. Herein we characterized the response within the first 24 h in a standard animal model of burn injury using a time series of microarray gene expression data.

METHODS

Rats were subjected to a full thickness dorsal scald burn injury covering 20% of their total body surface area while under general anesthesia. Animals were saline resuscitated and sacrificed at defined time points (0, 2, 4, 8, 16, and 24 h). Liver tissues were explanted and analyzed for their gene expression profiles using microarray technology. Sham controls consisted of animals handled similarly but not burned. After identifying differentially expressed probe sets between sham and burn conditions over time, the concatenated data sets corresponding to these differentially expressed probe sets in burn and sham groups were combined and analyzed using a "consensus clustering" approach.

RESULTS

The clustering method of expression data identified 621 burn-responsive probe sets in four different co-expressed clusters. Functional characterization revealed that these four clusters are mainly associated with pro-inflammatory response, anti-inflammatory response, lipid biosynthesis, and insulin-regulated metabolism. Cluster 1 pro-inflammatory response is rapidly up-regulated (within the first 2 h) following burn injury, while Cluster 2 anti-inflammatory response is activated later on (around 8 h post-burn). Cluster 3 lipid biosynthesis is down-regulated rapidly following burn, possibly indicating a shift in the utilization of energy sources to produce acute phase proteins, which serve the anti-inflammatory response. Cluster 4 insulin-regulated metabolism was down-regulated late in the observation window (around 16 h post-burn), which suggests a potential mechanism to explain the onset of hypermetabolism, a delayed but well-known response that is characteristic of severe burns and trauma with potential adverse outcome.

CONCLUSIONS

Simultaneous analysis and comparison of gene expression profiles for both burn and sham control groups provided a more accurate estimation of the activation time, expression patterns, and characteristics of a certain burn-induced response based on which the cause-effect relationships among responses were revealed.

Fractal immunology and immune patterning: potential tools for immune protection and optimization

Fractals are self-similar geometric patterns that are inherently embedded throughout nature. Their discovery and application have produced significant benefits across a wide variety of biomedical applications. Recently, complex physiological systems (e.g., neurological, respiratory, cardiovascular) have been shown to exhibit fractal dimensions that are capable of distinguishing among physiologic function versus dysfunction and, in turn, health versus disease. Additionally, fractal data suggest that the immune system operates under similar patterned relationships, and this is in keeping with the recent findings that immune-based diseases are organized according to specific patterns. This review considers the potential benefits of using fractal analysis along with considerations of nonlinearity, scaling, and chaos as calibration tools to obtain holistic information on immune-environment interactions. The potential uses of both synthetic and artificial immune systems for improved protection of the biological immune system are also discussed. The addition of holistic measures of immune status to currently collected biomarkers of immunotoxicity has the potential to increase the effectiveness of health risk assessment. The objective of extending fractal physiology analyses to the immune system would be to promote immune optimization as a public health benefit, which would include improved: (1) immunotoxicity testing and effective health risk reduction and (2) measures of effective immune management for children, adults, and aged individuals.