Models Of Critical Illness Research Articles

Detailed Characterization of Brain Dysfunction in a Long-Term Rodent Model of Critical Illness.

Critical illness encompasses a wide spectrum of life-threatening clinical conditions requiring intensive care. Our objective was to evaluate cognitive, inflammatory and cellular metabolism alterations in the central nervous system in an animal model of critical illness induced by zymosan. For this Wistar rats that were divided into Sham and zymosan. Zymozan was administered once intraperitoneally (30g/100g body weight) diluted in mineral oil. The animals were submitted to behavioral tests of octagonal maze, inhibitory avoidance and elevated plus maze. Brain structures (cortex, prefrontal and hippocampus) were removed at 24h, 4, 7 and 15days after zymosan administration for analysis of cytokine levels (TNF-α, IL-1b, IL-6 and IL-10), oxidative damage and oxygen consumption. Zymosan-treated animals presented mild cognitive impairment both in aversive (inhibitory avoidance) and non-aversive (octagonal maze) tasks by day 15. However, they did not show increase in anxiety (elevated-plus maze). The first neurochemical alteration found was an increase in brain pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α) at day 4th in the hippocampus. In cortex, a late (7 and 15days) increase in TNF-α was also noted, while the anti-inflammatory cytokine IL-10 decrease from 4 to 15days. Oxygen consumption was decreased in the hippocampus and pre-frontal, but not cortex, only at 7days. Additionally, it was observed a late (15days) increase in oxidative damage parameters. This characterization of brain dysfunction in rodent model of critical illness reproduces some of the alterations reported in humans such neuropsychiatric disorders, especially depression, memory loss and cognitive changes and can add to the nowadays used models.

Flow-dependent regulation of endothelial Tie2 by GATA3 in vivo

BackgroundReduced endothelial Tie2 expression occurs in diverse experimental models of critical illness, and experimental Tie2 suppression is sufficient to increase spontaneous vascular permeability. Looking for a common denominator among different critical illnesses that could drive the same Tie2 suppressive (thereby leak inducing) phenotype, we identified “circulatory shock” as a shared feature and postulated a flow-dependency of Tie2 gene expression in a GATA3 dependent manner. Here, we analyzed if this mechanism of flow-regulation of gene expression exists in vivo in the absence of inflammation.ResultsTo experimentally mimic a shock-like situation, we developed a murine model of clonidine-induced hypotension by targeting a reduced mean arterial pressure (MAP) of approximately 50% over 4 h. We found that hypotension-induced reduction of flow in the absence of confounding disease factors (i.e., inflammation, injury, among others) is sufficient to suppress GATA3 and Tie2 transcription. Conditional endothelial-specific GATA3 knockdown (B6-Gata3tm1-Jfz VE-Cadherin(PAC)-cerERT2) led to baseline Tie2 suppression inducing spontaneous vascular leak. On the contrary, the transient overexpression of GATA3 in the pulmonary endothelium (jet-PEI plasmid delivery platform) was sufficient to increase Tie2 at baseline and completely block its hypotension-induced acute drop. On the functional level, the Tie2 protection by GATA3 overexpression abrogated the development of pulmonary capillary leakage.ConclusionsThe data suggest that the GATA3–Tie2 signaling pathway might play a pivotal role in controlling vascular barrier function and that it is affected in diverse critical illnesses with shock as a consequence of a flow-regulated gene response. Targeting this novel mechanism might offer therapeutic opportunities to treat vascular leakage of diverse etiologies.

44 Defects in Mitophagy Response in Burns Involved in Poor Regeneration Capacity

Abstract Introduction Wound healing is a biological process directed to the restoration of tissue that has suffered an injury. One of the important functions of wound healing is individual and collective cellular migration. This migration response can largely dictate the outcomes and success of a healing wound. Mitophagy, autophagic degradation of mitochondria, sequesters damaged mitochondria and functions as the essential quality control (QC) system of this organelle. When mitophagy is disturbed, damaged mitochondria are not cleared and will produce superoxide, imposing a risk for cell death. Our previous study documented a compromised mitophagy response in burns, suggestive of poor QC of mitochondria in the severely burned subjects. The relationship between defects in mitophagy response and cellular regeneration capacity was not investigated in detail. We have previously shown that trehalose can serve as an important autophagy modulator and ameliorates the defect in mitophay response. Thus we investigated whether trehalose could improve poor regeneration capacity caused by defects in mitophagy response under burn or oxidative stress in myocytes. Methods We examined the effect of trehalose on migration by performing a wound-healing scratch assay. C2C12 myocyte was cultured on 6cm dishes to 95–100% confluence, the cells were treated with or without trehalose for 1 hour before the scratch. The wound was made by scratching a line across the bottom of the dish. By incubating the cells with day 3 burn or sham-burn serum harvested from rats (30%, systemic burn), To simulate the burn injury and/or oxidative stress in diseases, cells were primed with a serum derived from rats with 40% burn injury (or sham-burn control), or with or without hydrogen peroxide treatment. Nine hours later, the gap obtained by scratching a line in C2C12 was observed by time-lapse microscopy. Results Oxidative stress decreased the gap closure of C2C12 and delayed wound healing. Under the oxidative stress, the gap closure in C2C12 treated with trehalose is significantly higher than that C2C12 treated without trehalose (54.6 vs 79.1%; p< 0.05). Similarly, burn stress showed a slower the gap closure of C2C12. Among the burn groups with or without trehalose treatment, the gap closure in C2C12 treated with trehalose is also higher than that C2C12 treated without trehalose. Conclusions Using a cell culture system simulating the two models of critical illnesses (oxidative stress and burn injury), we found that mitigating the defect of mitophagy response by trehalose treatment can improve poor regeneration capacity under burn or oxidative stress in myocytes. Applicability of Research to Practice This is the first study that demonstrated that defects in mitophagy response under disease conditions can serve a novel therapeutic target for enhancing the regeneration capacity in critically ill patients.

Innate T cells in the intensive care unit

Rapid onset of acute inflammation is a hallmark of critical illnesses that bring patients to the intensive care unit (ICU). In critical illness, innate T cells rapidly reach full activation and drive a robust acute inflammatory response. As “cellular adjuvants,” innate T cells worsen inflammation and mortality in several common critical illnesses including sepsis, ischemia-reperfusion injury, stroke, and exacerbations of respiratory disease. Interestingly, innate T cell subsets can also promote a protective and anti-inflammatory response in sepsis, ischemia-reperfusion injury, and asthma. Therapies that target innate T cells have been validated in several models of critical illness. Here, we review the role of natural killer T (NKT) cells, mucosal-associated invariant T (MAIT) cells and γδ T cells in clinical and experimental critical illness.

A diet pill for critical illness weakness?

The serotoninergic drug Lorcaserin rescued motor neuron electrophysiological abnormalities in an animal model of critical illness–induced weakness.

Effect of endotoxemia in mice genetically deficient in cystathionine-γ-lyase, cystathionine-β-synthase or 3-mercaptopyruvate sulfurtransferase.

Hydrogen sulfide (H2S) has been proposed to exert pro- as well as anti-inflammatory effects in various models of critical illness. In this study, we compared bacterial lipopolysaccharide (LPS)-induced changes in inflammatory mediator production, indices of multiple organ injury and survival in wild-type (WT) mice and in mice with reduced expression of one of the three H2S-producing enzymes, cystathionine-γ-lyase (CSE), cystathionine-β-synthase (CBS) or 3-mercaptopyruvate sulfurtransferase (3MST). Mice were injected intraperitoneally (i.p.) with LPS (10 mg/kg). After 6 h, the animals were sacrificed, blood and organs were collected and the following parameters were evaluated: blood urea nitrogen (BUN) levels in blood, myeloperoxidase (MPO) and malondialdehyde (MDA) in the lung, cytokine levels in plasma and the expression of the three H2S-producing enzymes (CBS, CSE and 3MST) in the spleen, lung, liver and kidney. LPS induced a tissue-dependent upregulation of some of the H2S-producing enzymes in WT mice (upregulation of CBS in the spleen, upregulation of 3MST in the liver and upregulation of CBS, CSE and 3MST in the lung). Moreover, LPS impaired glomerular function, as evidenced by increased BUN levels. Renal impairment was comparable in the CSE−/− and Δ3MST mice after LPS challenge; however, it was attenuated in the CBS+/− mice. MPO levels (an index of neutrophil infiltration) and MDA levels (an index of oxidative stress) in lung homogenates were significantly increased in response to LPS; these effects were similar in the WT, CBS+/−, CSE−/− and Δ3MST mice; however, the MDA levels tended to be lower in the CBS+/− and CSE−/− mice. LPS induced significant increases in the plasma levels of multiple cytokines [tumor necrosis factor (TNF)α, interleukin (IL)-1β, IL-6, IL-10, IL-12 and interferon (IFN)γ] in plasma; TNFα, IL-10 and IL-12 levels tended to be lower in all three groups of animals expressing lower levels of H2S-producing enzymes. The survival rates after the LPS challenge did not show any significant differences between the four animal groups tested. Thus, the findings of this study indicate that a deficiency in 3MST does not significantly affect endotoxemia, while a deficiency in CBS or CSE slightly ameliorates the outcome of LPS-induced endotoxemia in vivo.

Both the H2S biosynthesis inhibitor aminooxyacetic acid and the mitochondrially targeted H2S donor AP39 exert protective effects in a mouse model of burn injury

Hydrogen sulfide (H2S) exerts beneficial as well as deleterious effects in various models of critical illness. Here we tested the effect of two different pharmacological interventions: (a) inhibition of H2S biosynthesis using the cystathionine-beta-synthase (CBS)/cystathionine-gamma-lyase (CSE) inhibitor aminooxyacetic acid (AOAA) and the mitochondrially targeted H2S donor [10-oxo-10-[4-(3-thioxo-3H-1,2-dithiol-5-yl)phenoxy]decyl]triphenyl-phosphonium (AP39). A 30% body surface area burn injury was induced in anesthetized mice; animals were treated with vehicle, AOAA (10mg/kg i.p. once or once a day for 6days), or AP39 (0.3mg/kg/day once or once a day for 6days). In two separate groups, animals were sacrificed, at 24h post-burn or on Day 7 post-burn, blood and lungs were collected and the following parameters were evaluated: myeloperoxidase (MPO) and malondialdehyde (MDA) in lung homogenates, plasma cytokines (Luminex analysis) and circulating indicators of organ dysfunction (Vetscan analysis). Lung MPO levels (an index of neutrophil infiltration) and MDA levels (an index of oxidative stress) were significantly increased in response to burn injury both at 24h and at 7days; both AOAA and AP39 attenuated these increases. From a panel of inflammatory cytokines (TNFα, IL-1β, IL-6, IL-10, MCP-1, MIP-2, VEGF and IFNγ) in the plasma, IL-6 and IL-10 levels were markedly elevated at 24h and VEGF was slightly elevated. IL-6 remained highly elevated at 7days post-burn while IL-10 levels decreased, but remained slightly elevated over baseline 7days post-burn. The changes in cytokine levels were attenuated both by AP39 and AOAA at both time points studied. The burn-induced increases in the organ injury markers ALP and ALT, amylase and creatinine were reduced by both AOAA and AP39. We conclude that both H2S biosynthesis inhibition (using AOAA) and H2S donation (using AP39) suppresses inflammatory mediator production and reduces multi-organ injury in a murine model of burn injury, both at an early time point (when systemic H2S levels are elevated) and at a later time point (at which time systemic H2S levels have returned to baseline). These findings point to the complex pathogenetic role of H2S in burns.

Pyruvate Dehydrogenase Activity and Quantity Decreases After Coronary Artery Bypass Grafting: a Prospective Observational Study.

Pyruvate dehydrogenase (PDH) is a key gatekeeper enzyme in aerobic metabolism. The main purpose of this study was to determine if PDH activity is affected by major stress in the form of coronary artery bypass grafting (CABG), which has previously been used as a model of critical illness. We conducted a prospective, observational study of patients undergoing CABG at an urban, tertiary care hospital. We included adult patients undergoing CABG with or without concomitant valve surgery. Measurements of PDH activity and quantity and thiamine were obtained prior to surgery, at the completion of surgery, and 6 h after surgery. Fourteen patients were enrolled (aged 67 ± 10 years, 21% female). Study subjects had a mean 41.7% (SD, 27.7%) reduction in PDH activity after surgery and a mean 32.0% (SD, 31.4%) reduction 6h after surgery (P < 0.001). Eight patients were thiamine deficient (≤ 7 nmol/L) after surgery compared with none prior to surgery (P = 0.002). Thiamine level was significantly associated with PDH quantity at all time points (P = 0.01). Postsurgery lactate levels were inversely correlated with postsurgery thiamine levels (r = -0.58 and P = 0.04). The stress of major surgery causes decreased PDH activity and quantity and depletion of thiamine levels.

Bleeding, hypothermia, acidosis and the normal ROTEM®

shock (HS) and acute pancreatitis (AP) is associated with multiple organ dysfunction syndrome (MODS) and death. Most common in MODS are cardiac and pulmonary dysfunction.The ‘gut-lymphhypothesis’ states thatMODSisdue to the releaseof toxic factors fromthe intestine intomesenteric lymph (ML). Significant composition changes to ML are associated with acute pancreatitis and other CI’s. ML is delivered to the systemic circulation via the thoracic duct and en route bypasses the liver avoidingpotential detoxification, beforefirst encountering the heart and then lungs. The aim of this study was to determine the effect of HS and AP conditioned ML on cardiac function and the effect of external drainage of ML. Methods: Groups (n=8 / group) of normal rats and those with taurocholate induced severe AP, a model of critical illness, had either no lymphatic intervention or thoracic duct (TD) ligation with external ML drainage (to protect the hearts from exposure to ML). After 6 hours the heart was removed from both groups for ex vivo functional measurements, including cardiac output and ventricular contractility (+dP/dt), relaxation (-dP/dt). In a separate experiment ML was collected from normal rats and those with HS and AP and infused into ex vivo perfused working hearts from donor normal rats to assess the impact on cardiac function. Results: Significant cardiac dysfunction was found in the hearts removed from rats with established AP alone (no lymphatic intervention) compared to the control group (p<0.05). Strikingly this dysfunction did not occur in rats with established AP and TD ligation with ML drainage. In the second experiment infusion of HS and AP conditioned ML resulted in an immediate, similar and significant reduction of cardiac output (p< 0.05) with corresponding significant reductions in the measures of cardiac contractility and relaxation (p<0.05) compared with normal lymph. Discussion:HS and AP conditioned ML causes significant cardiac dysfunction which can be prevented by TD ligation and external ML drainage. This cardio-depressant effect is likely to be important in other CI’s. The nature of the mediators in ML is still speculative but likely to be gut and pancreas derived serine proteases. The findings from this study have future implications in how we treat cardiac dysfunction and failure in critically ill patients.

Oxidative stress contributes to orthopedic trauma-induced acute kidney injury in obese rats.

After trauma, obese patients have an increased risk of developing acute kidney injury (AKI). We have demonstrated that obese Zucker (OZ) rats, but not lean Zucker (LZ) rats, develop AKI 24 h after orthopedic trauma. ROS have been implicated in the pathophysiology of AKI in models of critical illness. However, the contribution of ROS to trauma-induced AKI in the setting of obesity has not been determined. We hypothesized that AKI in OZ rats after trauma is mediated by increased oxidative stress. Male LZ and OZ rats were divided into control and trauma groups, with a subset receiving treatment after trauma with the antioxidant apocynin (50 mg/kg ip, 2 mM in drinking water). The day after trauma, glomerular filtration rate, plasma creatinine, urine kidney injury molecule-1, and albumin excretion as well as renal oxidant and antioxidant activity were measured. After trauma, compared with LZ rats, OZ rats exhibited a significant decrease in glomerular filtration rate along with significant increases in plasma creatinine and urine kidney injury molecule-1 and albumin excretion. Additionally, oxidative stress was significantly increased in OZ rats, as evidenced by increased renal NADPH oxidase activity and urine lipid peroxidation products (thiobarbituric acid-reactive substances), and OZ rats also had suppressed renal superoxide dismutase activity. Apocynin treatment significantly decreased oxidative stress and AKI in OZ rats but had minimal effects in LZ rats. These results suggest that ROS play an important role in AKI in OZ rats after traumatic injury and that ROS may be a potential future therapeutic target in the obese after trauma.

0030. Effect of exercise training on muscle function in a recovery model of critical illness

Survivors of critical illness experience significant skeletal muscle weakness and physical disability, which may persist for years [1]. Early mobilization is being encouraged to improve functional outcomes [2]. Decreased mitochondrial function and altered mitochondrial biogenesis are implicated in the pathogenesis of sepsis-induced muscle dysfunction [3]. Mitochondrial biogenesis can be stimulated by physical activity [4].

P35 Exacerbation of the septic response in cystathionine-gamma-lyase deficient mice

Previous studies reported both beneficial and detrimental roles of hydrogen sulfide (H2S) in various models of critical illness. The goal of our study was to compare the outcome of septic shock in wild-type mice and in mice deficient in cystathionine-gamma-lyase (CSE). Mice were subjected to sepsis by cecal ligation and puncture and survival was monitored for 48 h. In a separate study, animals were sacrificed at 24 h post-CLP, vascular function was evaluated ex vivo and indices of organ function were measured. At 30 h, there was 20% mortality in CSE−/− mice, while no mortality in the wild-type controls. By 36 h, the mortality increased to 50% in CSE−/− mice, while it remained low (10%) in the wild-type controls. However, by 46 h, the two survival curves converged, and showed a similar, 60% mortality in both groups. Analysis of the plasma markers of organ injury revealed slight trends for a CLP-induced increase in the liver injury markers ALT and AST and the pancreatic injury marker amylase in wild-type mice. More pronounced increases were noted in the same parameters in the CSE−/− mice. Blood urea nitrogen levels were elevated 3-fold over baseline in wild-type mice subjected to CLP and 4-fold over baseline in CSE−/− mice. There was an impairment of endothelium-dependent relaxation responses in the thoracic aorta after CLP, which was more pronounced in the CSE−/− mice. These data indicate that CSE, and its product, H2S, exerts protective effects against the development of sepsis, especially in the early stages of the disease.

Aberrant bone metabolism in critical illness

Critically ill patients present with distinct alterations in bone metabolism. We have previously reported a decrease in bone formation markers and a dramatic increase in bone resorption markers. In a rabbit model of critical illness, we observed significantly lower bone mineral content in the trabeculae of critically ill rabbits compared to healthy controls. This suggested uncoupling between bone formation and degradation during critical illness, and could increase risk of fracture during rehabilitation or impaired healing of bone fractures. In this study, we investigated the effect of critical illness on bone metabolism at the tissue and cellular level.

Insufficient autophagy relates to mitochondrial dysfunction, organ failure and adverse outcome in an animal model of critical illness

Increasing evidence implicates mitochondrial dysfunction in the pathogenesis of critical illness-induced multiple organ failure. We previously demonstrated that prevention of hyperglycemia limits mitochondrial damage in vital organs [1,2], thereby reducing morbidity and mortality [3]. We now hypothesize that inadequate activation of mitochondrial repair processes (mitochondrial clearance by autophagy, mitochondrial fusion and fission, and biogenesis) may contribute to accumulation of mitochondrial damage, persistence of organ failure and adverse outcome of critical illness.

'Professor Galveston' has departed. Obituary - Daniel Traber

'Professor Galveston' has departed. Obituary - Daniel Traber

Cytoprotective effect of γ-tocopherol against tumor necrosis factor α induced cell dysfunction in L929 cells

The antioxidant vitamin γ-tocopherol exerts protective and anti-inflammatory effects in various models of critical illness. The combination of actinomycin D and tumor necrosis factor α (TNFα) in the immortalized fibroblast cell line L929 is a well-established method to model pro-inflammatory cytotoxicity in cultured cells in vitro. The present study had two aims. First, we wished to characterize the contribution of reactive oxygen species (ROS) to the cell dysfunction and this commonly used model system of cell death. Second, we wished to investigate the effects of γ-tocopherol on this response. Cells were exposed to actinomycin D (0.5 µg/ml) + TNFα (100 pg/ml) in the absence or presence of 1 h of γ-tocopherol pre-treatment. The earliest change that was detected in our system in response to TNFα was an increase in mitochondrial oxidant production, already apparent at 45 min. Changes in glycolysis and oxidative phosphorylation parameters were already apparent at 2 h, as detected by the Seahorse Biosciences XF24 Flux Analyzer. By 6 h, a slight decrease in Cell Index was detected by impedance-based analysis, employing an electronic sensor array system (XCelligence). At the same time, a slight decrease in cell viability was detected by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) method, along with a significant increase in lactate dehydrogenase (LDH) release into the culture medium, and a detectable degree of mitochondrial membrane depolarization. Between 12 and 24 h, the cell viability (already at a low level) further declined, which coincided with a secondary, marked decline in the mitochondrial membrane potential. Pre-treatment of the cells with γ-tocopherol (10-300 µM) provided a significant protection against all of the functional alterations induced by actinomycin D and TNFα. The current study provides direct evidence that reactive oxidant formation plays an important role in the current experimental model of cell dysfunction, and demonstrates the protective effects of the potent endogenous antioxidant vitamin, γ-tocopherol. The mechanisms described in the current study may, in part, contribute to the protective effects of γ-tocopherol in various models of critical illness.

REPETITIVE LOW-VOLUME BLOOD SAMPLING METHOD AS A FEASIBLE MONITORING TOOL IN A MOUSE MODEL OF SEPSIS

Blood-based monitoring of immunoinflammatory and organ function fluctuations is essential in models of critical illness. This is challenging in diseased mice as repetitive blood collection may be harmful and/or affect end points. We studied the influence of daily sampling in acutely septic (days 1-5) mice upon survival and selected hematologic and organ function parameters. In addition, we tested the reliabilty of complete blood cell (CBC) count using resuspended blood cells. Female OF-1 and CD-1 mice underwent cecal ligation and puncture (CLP) and were subdivided into Daily and Day 5 groups. Blood was collected daily for 5 days in the Daily group and only on day 5 post-CLP in the Day 5 group. We tested 20 μL (both strains) and 35 μL (OF-1 mice) sampling volumes. The 35-μL volume simultaneously served to test the CBC reliabilty in resuspended versus unprocessed blood. Daily sampling did not affect the 14-day CLP mortality. Compared with the Day 5 group, daily 35-μL sampling in OF-1 mice decreased the red blood cell count and hemoglobin concentration by 22% and 23% (P < 0.05). In neither strain did daily 20-μL sampling affect the red blood cell count, whereas there was a 9% hemoglobin decrease (P < 0.05) in OF-1 mice. Although alanine aminotransferase, lactate dehydrogenase, and glucose levels were comparable, urea significantly increased by 24% in the Daily group (20-μL volume, OF-1 mice). Interleukin 6, platelets, and white blood cell counts remained unaffected. There was an excellent correlation between regular and resuspended CBC for all cell types (r ≥ 0.9; slope, ≥0.9), except lymphocytes (r > 0.5; slope, >0.5). This method provides a feasible and safe translation of clinically relevant daily immunomonitoring to the mouse sepsis model.

Increased blood flow by insulin infusion targeting normoglycemia in patients with severe sepsis: friend or foe?

A small study in patients with severe sepsis suggested that insulin infused to normalize blood glucose levels increased forearm flow. This clinical observation supports the effect of insulin on the endothelium, as previously shown by in vitro studies and by in vivo animal models of critical illness, but the clinical consequences remain unclear.

Effects of Substitution and High-Dose Thyroid Hormone Therapy on Deiodination, Sulfoconjugation, and Tissue Thyroid Hormone Levels in Prolonged Critically Ill Rabbits

To delineate the metabolic fate of thyroid hormone in prolonged critically ill rabbits, we investigated the impact of two dose regimes of thyroid hormone on plasma 3,3'-diiodothyronine (T(2)) and T(4)S, deiodinase type 1 (D1) and D3 activity, and tissue iodothyronine levels in liver and kidney, as compared with saline and TRH. D2-expressing tissues were ignored. The regimens comprised either substitution dose or a 3- to 5- fold higher dose of T(4) and T(3), either alone or combined, targeted to achieve plasma thyroid hormone levels obtained by TRH. Compared with healthy animals, saline-treated ill rabbits revealed lower plasma T(3) (P=0.006), hepatic T(3) (P=0.02), and hepatic D1 activity (P=0.01). Substitution-dosed thyroid hormone therapy did not affect these changes except a further decline in plasma (P=0.0006) and tissue T(4) (P=0.04). High-dosed thyroid hormone therapy elevated plasma and tissue iodothyronine levels and hepatic D1 activity, as did TRH. Changes in iodothyronine tissue levels mimicked changes in plasma. Tissue T(3) and tissue T(3)/reverse T(3) ratio correlated with deiodinase activities. Neither substitution- nor high-dose treatment altered plasma T(2). Plasma T(4)S was increased only by T(4) in high dose. We conclude that in prolonged critically ill rabbits, low plasma T(3) levels were associated with low liver and kidney T(3) levels. Restoration of plasma and liver and kidney tissue iodothyronine levels was not achieved by thyroid hormone in substitution dose but instead required severalfold this dose. This indicates thyroid hormone hypermetabolism, which in this model of critical illness is not entirely explained by deiodination or by sulfoconjugation.

The impact of burn injury and ethanol on the cytokine network of the mouse hypothalamus: Reproductive implications

Nearly 50% of the patients admitted to hospitals for burn injuries have detectable levels of alcohol (EtOH) in their circulation. In fact, EtOH is often a causal factor in their injury. It is well known that EtOH as well as burn injury disrupt function of the hypothalamic–pituitary–gonadal (HPG) axis. The cellular mechanisms by which EtOH and/or burn impacts on the HPG are not entirely understood. In the studies reported here, we tested the hypothesis that these injuries mediated their effects by local hypothalamic inflammation. Young adult male mice were subjected to either a 15% total body surface area, full thickness scald, to EtOH, or to both and compared to appropriate controls. They were sacrificed 48 h later. EtOH and burn, as well as the combined injury, consistently and impressively reduced serum testosterone, while increasing hypothalamic concentrations of all three of the pro-inflammatory cytokines, TNFα, IL-1β, and IL-6. In general, the increases induced by burn were greater than those caused by EtOH and the effect of the combined insult was not additive. Hypothalamic concentrations of LHRH were also increased. The data are consistent with the idea that EtOH and/or burn, as models of critical illness, medicate their hypothalamic suppressive effects via increase in pro-inflammatory cytokines.