Caspase-3-dependent organ apoptosis early after burn injury

Burn-Induced Apoptosis in the Livers of Aged Mice Is Associated With Caspase Cleavage of Bcl-xL

INTRODUCTION

Older adult burn victims have poorer outcomes than younger burn victims. The liver is critical for the recovery of patients with burns. Postburn hepatic apoptosis in young individuals compromises liver integrity; however, this pathway has not yet been studied in older individuals. Because aged animals with burns suffer significant liver damage, we hypothesized that apoptosis is altered in these animals and may affect liver function. Understanding postburn hepatic apoptosis and its effects on liver function in aged animals may help improve outcomes in older patients.

METHODS

We compared the protein and gene expression levels in young and aged mice after a 15% total-body-surface-area burn. Liver and serum samples were collected at different time points after injury.

RESULTS

Caspase-9 expression in liver tissue was downregulated by 47% in young animals and upregulated by 62% in aged animals 9 h postburn (P < 0.05). The livers of aged mice showed a Bcl-extra-large (Bcl-xL) transcription increase only after 6 h; however, the livers of young mice exhibited 4.3-fold, 14.4-fold, and 7.8-fold Bcl-xL transcription increases at 3, 6, and 9 h postburn, respectively (P < 0.05). The livers of young mice showed no changes in Caspase-9, Caspase-3, or Bcl-xL protein levels during the early postburn period. In contrast, the livers of aged mice contained cleaved caspase-9, reduced full-length caspase-3, and an accumulation of ΔN-Bcl-x at 6 and 9 h postburn (P < 0.05). p21 expression decreased in aged mice; however, it was significantly increased in the liver tissue of young mice postburn (P < 0.05). Serum amyloid A1 and serum amyloid A2 serum protein levels were 5.2- and 3.1-fold higher in young mice than in aged mice, respectively, at 6 and 9 h postburn (P < 0.05).

CONCLUSIONS

Livers of aged mice exhibited different apoptotic processes compared to those of young mice early after burn injury. Collectively, burn-induced liver apoptosis in aged mice compromises hepatic serum protein production.

Level of Decoy Receptor 3 for Monitoring Clinical Progression of Severe Burn Patients

The clinical value of Decoy receptor 3 (DcR3) in severe burn is investigated. Ten patients with severe burns were monitored for DcR3, PCT, CRP, IL6, SOFA score, white blood cell (WBC), and platelet. The correlations were analyzed. DcR3 increased on day 1. The nonsurvivors had a steady high level of DcR3 while the survivors had a relatively low level of DcR3. The peak magnitude of DcR3 was high in five nonsurvivors and low in five survivors without overlap. Three patients had a continuously increasing DcR3 level and then died. In the other two nonsurvivors, DcR3 reached the peak and then decreased before death. DcR3 correlated well with PCT (ρ = 0.4469, P < .0001), less with CRP, platelet, IL6, SOFA score and WBC (ρ = 0.4369, 0.4078, 0.3995, 0.2631, 0.1504, respectively, all P < .001). To explore the mechanisms, the HaCaT or THP-1 cells were stimulated by the plasma of burn patients, 45°C, LPS or stimulators of TLRs or NOD2 (PGN, CL264, MDP, iE-DAP, Gardiquimod), and their DcR3 was increased, which could be reduced by GDC-0941 or BEZ235 (inhibitors of PI3K and mTOR). The levels of DcR3 appeared to be a useful biomarker for monitoring the clinical severity and a predictor of mortality of severe burns.

Cell-free nuclear, but not mitochondrial, DNA concentrations correlate with the early host inflammatory response after severe trauma

Severe blunt trauma is associated with an early ‘genomic storm’ which causes simultaneous up- and down-regulation of host protective immunity. Excessive inflammation can lead to organ injury. In the absence of infection, the inflammatory response is presumably driven by release of endogenous alarmins called danger-associated molecular patterns (DAMPs), which initiate immune responses through pattern-recognition receptors (PRR). Here we examined the relationship between concentrations of cell-free (cf) nuclear DNA (ncDNA) and mitochondrial DNA (mtDNA) within 24 hours post trauma with circulating leukocyte transcriptomics and plasma IL-6 concentrations, as well as the patients’ clinical trajectories. In 104 patients enrolled from two level-1 trauma centers, ncDNA and mtDNA concentrations were increased within 24 hours of severe trauma, but only ncDNA concentrations correlated with leukocyte gene expression and outcomes. Surprisingly, ncDNA, not mtDNA concentrations, were significantly elevated in trauma patients who developed chronic critical illness versus rapid clinical recovery. Plasma IL-6 and leukocyte transcriptomics were better predictors of outcomes than cfDNA levels. Although mtDNA and ncDNA are significantly increased in the immediate post-trauma period, the dramatic inflammatory and gene expression changes seen after severe trauma are only weakly correlated with ncDNA concentrations, and more importantly, mtDNA concentrations are not associated with adverse clinical trajectories.

SOCS-1 ameliorates smoke inhalation-induced acute lung injury through inhibition of ASK-1 activity and DISC formation

Smoke inhalation leads to acute lung injury (ALI), a devastating clinical problem associated with high mortality. Suppressor of cytokine signaling-1 (SOCS-1) is a negative regulator of apoptosis and pro-inflammatory cytokine signaling, two major contributors to the pathogenesis of ALI. We have found that SOCS-1 protects lung epithelial cells from smoke-induced apoptosis through two mechanisms. One is that SOCS-1 enhances degradation of ASK-1 and diminishes cleavage of pro-caspase-3 to repress smoke-triggered apoptosis in lung epithelial cells. The other is that SOCS-1 represses smoke-triggered DISC formation through altering TRADD-caspase-8 interaction rather than TNFR-1-TRADD interaction or TNFR-1-TRAF-2 interaction. In conclusion, SOCS-1 relieves smoke inhalation-induced lung injury by repressing ASK-1 and DISC-mediated epithelium apoptosis.

Effect of parenteral glutamine supplementation combined with enteral nutrition on Hsp90 expression and lymphoid organ apoptosis in severely burned rats

OBJECTIVE

The aim of this study is to investigate the effects of parenteral glutamine(GLN) supplementation combined with enteral nutrition (EN) on heat shock protein 90(Hsp90) expression, apoptosis of lymphoid organs and circulating lymphocytes, immunological function and survival in severely burned rats.

METHODS

Male SD rats were randomly assigned into 4 groups: a sham burn+EN+GLN-free amino acid (AA) group (n=10), a sham burn+EN+GLN group (n=10), a burn+EN+AA group (n=10), and a burn +EN +GLN group (n=10). Two hours after a 30% total body surface area (TBSA), full-thickness scald burn injury on the back was made, the burned rats in two experimental groups (the burn+EN+AA group and the burn+EN +GLN group) were fed with a conventional enteral nutrition solution by oral gavage for 7 days. Simultaneously, the rats in the burn+EN+GLN group were given 0.35g GLN/kg body weight/day once via a tail vein injection for 7 days, whereas those in the burn+EN+AA group were administered isocaloric/isonitrogenous GLN-free amino acid solution (Tyrosine) for comparison. The rats in two sham burn control groups (the sham burn+EN+AA group and the sham burn+EN +GLN group) were treated in the same procedure as above, except for burn injury. All rats in each of the four groups were given 175kcal/kg body wt/day. There was isonitrogenous, isovolumic and isocaloric intake among four groups. At the end of the 7th day after nutritional programme were finished, all rats were anesthetized and samples were collected for further analysis. Serum immunoglobulin quantification was conducted by ELISA. Circulating lymphocyte numbers were counted by Coulter LH-750 Analyzer. The percentages and apoptotic ratio of CD4 and CD8T lymphocytes in circulation were determined by flow cytometry (FCM). The neutrophil phagocytosis index (NPI) was examined. The GLN concentrations in plasma, thymus, spleen and skeletal muscle were measured by high performance liquid chromatography (HPLC). The organ index evaluation and TUNEL analysis of thymus and spleen were carried out. The expression of Hsp90 in thymus and spleen was analyzed by western blotting. Moreover, the survival in burned rats was observed.

RESULTS

The results revealed that parenteral GLN supplementation combined with EN significantly increased the GLN concentrations of plasma and tissues, the serum immunoglobulin content, the circulating lymphocyte number, the CD4/CD8 ratio, the indexes of thymus and spleen, NPI and survival as compared with the burn+EN+AA group (p<0.05). The expression of Hsp90 in thymus and spleen in the burn+EN+GLN group was significantly up-regulated as compared with the burn+EN+AA group (p<0.05). The apoptosis in circulating CD4 and CD8 lymphocytes, thymus and spleen in the burn+EN+GLN group was significantly decreased as compared with the burn+EN+AA group (p<0.05).

CONCLUSION

The results of this study show that parenteral GLN supplementation combined with EN may increase the GLN concentrations of plasma and tissues, up-regulate the expression of Hsp90, attenuate apoptosis in lymphoid organ and circulating lymphocyte, enhance the immunological function and improve survival in severely burned rats. Clinically, therapeutic efforts at the modulation of the immune dysfunction may contribute to a favorable outcome in severely burned patients.

Ethanol intoxication prolongs post-burn pulmonary inflammation: role of alveolar macrophages

In this study, the role and fate of AMs were examined in pulmonary inflammation after intoxication and injury. Clinical evidence has revealed that half of all burn patients brought to the emergency department are intoxicated at the time of injury. This combined insult results in amplified neutrophil accumulation and pulmonary edema, with an increased risk of lung failure and mortality, relative to either insult alone. We believe that this excessive pulmonary inflammation, which also parallels decreased lung function, is mediated in part by AMs. Restoration of lung tissue homeostasis is dependent on the eradication of neutrophils and removal of apoptotic cells, both major functions of AMs. Thirty minutes after binge ethanol intoxication, mice were anesthetized and given a 15% total body surface area dorsal scald injury. At 24 h, we found a 50% decrease in the total number of AMs (P < 0.05) and observed a proinflammatory phenotype on the remaining lung AMs. Loss of AMs paralleled a 6-fold increase in the number of TUNEL⁺ lung apoptotic cells (P < 0.05) and a 3.5-fold increase in the percentage of annexin V⁺ apoptotic cells in BAL (P < 0.05), after intoxication and injury, relative to controls. In contrast to the reduction in the number of cells, AMs from intoxicated and injured mice had a 4-fold increase in efferocytosis (P < 0.05). In summary, these data suggest that loss of AMs may delay resolution of inflammation, resulting in the pulmonary complications and elevated mortality rates observed in intoxicated and burn-injured patients.

Immune responses in relation to the type and time of thermal injury: an experimental study

BACKGROUND

Thermal injuries are followed by a complex immune response, but the relationship between the severity of burn injury and the time exposure to the thermal injury on the extent of the immune response is still not known.

OBJECTIVE

This study focuses on characterising the effect of temperature and time exposure on the post-burn immune response.

METHODS

We used 120 C57BL/6 male mice divided equally in 5 burn groups and one sham operated group (groups A-E and sham). Ten mice per group were sacrificed at 24 and 48 h after burn injury and whole blood was collected; specimens of liver, lung, spleen, kidney and bowel were excised. Apoptosis and TREM-1 expression on circulating blood cells were measured. Splenocytes were isolated and stimulated for cytokine production; the rate of apoptosis of splenocytes was also measured.

RESULTS

Production of IL-17 from splenocytes of mice group D was enhanced. Considerable effects were shown on the apoptosis of circulating lymphocytes and of spleen cells. The apoptotic rates varied between groups and also evolved after 24 and 48 h. To examine the origin of this differential response, quantitative bacterial cultures of liver, lung and kidney were made but no differences were observed compared with sham-operated animals.

LIMITATIONS

This study was based on an experimental murine model.

CONCLUSION

There is a unique response for each type of injury depending on the temperature of the thermal source and the exposure time.

The temporal and spatial profiles of cell loss following experimental spinal cord injury: effect of antioxidant therapy on cell death and functional recovery

Background

Traumatic spinal cord injury (SCI)-induced overproduction of endogenous deleterious substances triggers secondary cell death to spread damage beyond the initial injury site. Substantial experimental evidence supports reactive species (RS) as important mediators of secondary cell death after SCI. This study established quantitative temporal and spatial profiles of cell loss, characterized apoptosis, and evaluated the effectiveness of a broad spectrum RS scavenger - Mn (III) tetrakis (4-benzoic acid) porphyrin (MnTBAP) and a combination of MnTBAP plus nitro-L-arginine to prevent cell loss and neurological dysfunction following contusion SCI to the rat spinal cord.

Results

By counting the number of surviving cells in spinal cord sections removed at 1, 6, 12, 24, 48, 72 h and 1 week post-SCI and at 0 – 4 mm from the epicenter, the temporal and spatial profiles of motoneuron and glia loss were established. Motoneurons continued to disappear over a week and the losses decreased with increasing distance from the epicenter. Significant glia loss peaked at 24 to 48 h post-SCI, but only at sections 0–1.5 mm from the epicenter. Apoptosis of neurons, motoneurons and astrocytes was characterized morphologically by double immuno-staining with cell-specific markers and apoptosis indicators and confirmed by transmission electron microscopy. DNA laddering, ELISA quantitation and caspase-3 activation in the spinal cord tissue indicated more intense DNA fragments and greater caspase-3 activation in the epicenter than at 1 and 2 cm away from the epicenter or the sham-operated sections. Intraperitoneal treatment with MnTBAP + nitro-L-arginine significantly reduced motoneuron and cell loss and apoptosis in the gray and white matter compared with the vehicle-treated group. MnTBAP alone significantly reduced the number of apoptotic cells and improved functional recovery as evaluated by three behavioral tests.

Conclusions

Our temporal and spatial profiles of cell loss provide data bases for determining the time and location for pharmacological intervention. Our demonstration that apoptosis follows SCI and that MnTBAP alone or MnTBAP + nitro-L-arginine significantly reduces apoptosis correlates SCI-induced apoptosis with RS overproduction. MnTBAP significantly improved functional recovery, which strongly supports the important role of antioxidant therapy in treating SCI and the candidacy of MnTBAP for such treatment.

Intestinal barrier disruption as a cause of mortality in combined radiation and burn injury

Nuclear disaster associated with combined radiation injury (CRI) and trauma or burns results in higher mortality than component injuries. Early death is caused by sequelae of gastrointestinal (GI) leakiness such as bacterial translocation and shock. We developed a murine model to characterize GI injury after CRI and determine the extent of barrier disruption. Animals received radiation (5.5 Gy) alone or with 15% total body surface area (TBSA) scald burn and were euthanized at 24, 48, and 72 h. Mesenteric lymph node homogenate was plated on tryptic soy agar to assess for bacterial translocation. Tight junction protein, occludin, was characterized by Western blot and immunofluorescence. Intestinal histology was evaluated, and apoptosis was quantified using histone-associated DNA fragmentation enzyme-linked immunosorbent assay and Western blot for caspase-3 and caspase-8. At 72 h, a 100-fold increase in bacterial growth after CRI was observed. Occludin colocalization was reduced by radiation exposure, with largest differences in CRI at 24 and 48 h. Histopathology exhibited increased apoptosis in radiation alone and CRI animals at 24 and 48 h (P < 0.05). Further evidence of apoptotic activity in CRI was seen at 48 h, with 3-fold increases in enzyme-linked immunosorbent assay detection relative to all groups and caspase-8 activity relative to radiation alone and sham (P < 0.05). Prolonged epithelial apoptosis and disruption of tight junctions likely contribute to gut leakiness after CRI. Subsequent bacterial translocation to mesenteric lymph node potentially leads to sepsis and death and could serve as a target for mitigating agents to improve survival from CRI.

Heparin-binding epidermal growth factor-like growth factor attenuates acute lung injury and multiorgan dysfunction after scald burn

BACKGROUND

Impaired gut barrier function and acute lung injury (ALI) are significant components of the multiorgan dysfunction syndrome that accompanies severe burns. Heparin-binding epidermal growth factor-like growth factor (HB-EGF) has been shown to reduce inflammation, preserve gut barrier function, and protect the lungs from acute injury in several models of intestinal injury; however, comparable effects of HB-EGF after burn injury have never been investigated. The present studies were based on the hypothesis that HB-EGF would reduce the severity of ALI and multiorgan dysfunction after scald burns in mice.

MATERIALS AND METHODS

Mice were randomized to sham, burn (25% of total body surface area with full thickness dorsal scald), and burn + HB-EGF groups. The HB-EGF group was pretreated with two enteral doses of HB-EGF (1200 μg/kg/dose). Mice were resuscitated after injury and sacrificed at 8 h later. Their lungs were harvested for determination of pulmonary myeloperoxidase activity, wet:dry ratios, and terminal deoxynucleotidyl transferase dUTP nick end label and cleaved caspase 3 immunohistochemistry. Lung function was assessed using the SCIREQ Flexivent. Splenic apoptosis was quantified by Western blot for cleaved caspase 3, and intestinal permeability was measured using the everted gut sac method.

RESULTS

Mice subjected to scald burn injury had increased lung myeloperoxidase levels, increased pulmonary and splenic apoptosis, elevated airway resistance and bronchial reactivity, and increased intestinal permeability compared with sham mice. These abnormalities were significantly attenuated in mice that were subjected to scald burn injury but treated with enteral HB-EGF.

CONCLUSIONS

These data suggest that HB-EGF protects mice from ALI after scald burn and attenuates the severity of postburn multiorgan dysfunction.

Effects of glucagon-like peptide 1 on glycemia control and its metabolic consequence after severe thermal injury--studies in an animal model

BACKGROUND

Hyperglycemia with insulin resistance is commonly seen in severely burned patients and tight glycemia control with insulin may be beneficial in this condition. The most potent insulinotropic hormone, glucagon-like peptide 1 (GLP-1), stimulates insulin secretion in a glucose-dependent manner. Because infusion of GLP-1 never reduces glucose levels to below ∼70 mg/dL, the risk of hypoglycemia by using insulin is reduced. In this study we investigated the metabolic effects of GLP-1 infusion after burn injury in an animal model.

METHODS

Male CD rats were divided in 3 groups: burn injury with saline, burn injury with GLP-1 treatment, and sham burn (SB). Burn injury was full thickness 40% total body surface area. The burn injury with GLP-1 treatment group received GLP-1 infusion via osmotic pump. Fasting blood glucose, plasma insulin, and plasma GLP-1 levels were measured during intraperitoneal glucose tolerance tests. Expressions of caspase 3 and bcl-2 were evaluated in pancreatic islets. In a subset of animals, protein metabolism and total energy expenditure were measured.

RESULTS

Fasting GLP-1 was reduced in burn injury with saline compared to SB or burn injury with GLP-1 treatment. Burn injury with GLP-1 treatment showed reduced fasting blood glucose, improved intraperitoneal glucose tolerance test results, with increased plasma insulin and GLP-1 responses to glucose. GLP-1 reduced protein breakdown and total energy expenditure in burn injury with GLP-1 treatment versus burn injury with saline, with improved protein balance. Increased expression of caspase 3 and decreased expression of bcl-2 in islet cells by burn injury were ameliorated by GLP-1.

CONCLUSION

Burn injury reduced plasma GLP-1 in association with insulin resistance. GLP-1 infusion improved glucose tolerance and showed anabolic effects on protein metabolism and reduced total energy expenditure after burn injury, possibly via insulinotropic and non insulinotropic mechanisms.

Estrogen treatment following severe burn injury reduces brain inflammation and apoptotic signaling

Background

Patients with severe burn injury experience a rapid elevation in multiple circulating pro-inflammatory cytokines, with the levels correlating with both injury severity and outcome. Accumulations of these cytokines in animal models have been observed in remote organs, however data are lacking regarding early brain cytokine levels following burn injury, and the effects of estradiol on these levels. Using an experimental animal model, we studied the acute effects of a full-thickness third degree burn on brain levels of TNF-α, IL-1β, and IL-6 and the protective effects of acute estrogen treatment on these levels. Additionally, the acute administration of estrogen on regulation of inflammatory and apoptotic events in the brain following severe burn injury were studied through measuring the levels of phospho-ERK, phospho-Akt, active caspase-3, and PARP cleavage in the placebo and estrogen treated groups.

Methods

In this study, 149 adult Sprague-Dawley male rats received 3rd degree 40% total body surface area (TBSA) burns. Fifteen minutes following burn injury, the animals received a subcutaneous injection of either placebo (n = 72) or 17 beta-estradiol (n = 72). Brains were harvested at 0.5, 1, 2, 4, 6, 8, 12, 18, and 24 hours after injury from the control (n = 5), placebo (n = 8/time point), and estrogen treated animals (n = 8/time point). The brain cytokine levels were measured using the ELISA method. In addition, we assessed the levels of phosphorylated-ERK, phosphorylated-Akt, active caspase-3, and the levels of cleaved PARP at the 24 hour time-point using Western blot analysis.

Results

In burned rats, 17 beta-estradiol significantly decreased the levels of brain tissue TNF-α (~25%), IL-1β (~60%), and IL-6 (~90%) when compared to the placebo group. In addition, we determined that in the estrogen-treated rats there was an increase in the levels of phospho-ERK (p < 0.01) and Akt (p < 0.05) at the 24 hour time-point, and that 17 beta-estradiol blocked the activation of caspase-3 (p < 0.01) and subsequent cleavage of PARP (p < 0.05).

Conclusion

Following severe burn injury, estrogens decrease both brain inflammation and the activation of apoptosis, represented by an increase in the levels of phospho-Akt and inhibition of caspase-3 activation and PARP cleavage. Results from these studies will help further our understanding of how estrogens protect the brain following burn injury, and may provide a novel, safe, and effective clinical treatment to combat remote secondary burn injury in the brain and to preserve cognition.

The influence of Peyer's patch apoptosis on intestinal mucosal immunity in burned mice

The aim of this study was to investigate the influence of apoptosis on Peyer's patches and the intestinal immunoglobulin A (IgA) response in burned mice. Sixty male Balb/c mice were randomly assigned into the sham-burn (control) group (n=30) and the burn group (n=30). The mice in the burn group received a full-thickness scald burn over 20% of the total body surface area (TBSA), on the back. At 12, 24 and 72 h, respectively, after injury, the burned mice (n=10, at every time point) were anaesthetised and their entire intestines were collected. The mice in the sham-burn group were treated with the same procedure as above, except for the burn injury. The number of Peyer's patches on every entire intestine and the total Peyer's patches cell yield were counted. The changes of lymphocyte subpopulations in Peyer's patches were measured by flow cytometry (FCM). And the levels of intestinal IgA were examined by enzyme-linked immunosorbent assay (ELISA). Fluoresceinisothiocyanate (FITC)-conjugated Annexin-tau and propidium iodide (PI) double-staining cells were analysed by FCM for apoptotic ratio in Peyer's patches. The results showed that the total Peyer's patch cell yield and the numbers of CD3, CD4, CD8 and CD19 cells were significantly decreased at 12, 24 and 72 h after injury (P<0.05), and that the intestinal IgA levels were markedly reduced at 24 and 72 h (P<0.05). On the other hand, total apoptotic ratio and all cell subpopulation apoptosis in Peyer's patches were dramatically increased at 12, 24 and 72 h after injury (P<0.05). These results indicated that severe burns led to a significant decrease in the number of Peyer's patch cells and in intestinal IgA levels, which was closely associated with strongly increased apoptosis in Peyer's patches.

Role of p38 mitogen-activated protein kinase pathway on heart failure in the infant rat after burn injury

We examined the hypothesis that post-burn activation of the p38 mitogen-activated protein kinase (MAPK) pathway is one aspect of the signalling cascade culminating in post-burn secretion of tumour necrosis factor (TNF)-alpha which contributes to post-burn myocardial apoptosis. Studies were designed to determine the time course of the induction of p38MAPK, TNF-alpha and myocardial apoptosis after burn injury. Our quantitative bacterial culture data demonstrated that viable bacteria reached the heart, and Western blotting data identified the increase in the phosphorylation of p38MAPK at an early time after burn. The peak incidence of myocardial apoptosis was also seen at an early time after burn. The expression of TNF-alpha mRNA, infiltrated neutrophils and serum creatine phosphokinase myocardial band data peaked at a late time after burn. FR167653, a specific inhibitor of p38MAPK, prevented the induction of myocardial apoptosis, TNF-alpha expression and myocardial injury after burn. Presumably, the bacterial LPS-induced activation of p38MAPK pathway occurring at an early time after burn induced the subsequent myocardial apoptosis. The p38MAPK-induced activation of pro-inflammatory cytokine appeared to promote the degenerative myocardial injury at a late time after burn. Our present data provided evidence for the hypothesis that the p38MAPK pathway controls both myocardial apoptosis and the pro-inflammatory mediator.

Protective effect of caspase inhibitor on intestinal integrity in experimental severe acute pancreatitis

BACKGROUND AND AIM

Endotoxin/bacterial translocation (E/BT) plays an important role in systemic complications in severe acute pancreatitis (SAP). The breakdown of intestinal integrity is considered to be implicated in E/BT. We recently demonstrated that accelerated apoptosis of intestinal mucosa may have a part in E/BT. On the other hand, caspase is believed to play a central role in apoptosis. The aim of this study was to investigate the efficacy of caspase inhibitor on intestinal integrity and E/BT in SAP.

METHODS

SAP was induced by retrograde injection of 3% sodium deoxycholate into the biliopancreatic ducts in rats. At the same time, polycaspase inhibitor (Z-VAD-fmk) was administered intraperitoneally. Caspase activation in the intestine was evaluated by immunohistochemical staining and Western blotting. Apoptosis of intestinal mucosa was detected by TdT-mediated dUTP-biotin nick end labeling staining and DNA fragmentation enzyme-linked immunosolvent assay. Intestinal permeability was assayed ex vivo by measuring the leaked amount of FITC-dextran. Blood endotoxin level, bacterial culture of the ascites and mesenteric lymph nodes, and 24-h mortality rate were evaluated.

RESULTS

Immunoreactivities for activated caspase-10, -9, and -3 were increased 2 h after induction of SAP. Apoptosis and permeability of ileum were significantly increased 6 h after induction of SAP. Caspase inhibitor significantly improved the increasing apoptosis and permeability. It did not prevent the bacterial translocation but improved the disorder of intestinal mucosa and elevation of blood endotoxin 18 h after induction of SAP. Moreover, caspase treatment significantly improved the 24-h mortality rate. Z-VAD-fmk indeed inhibited the caspase-3 activation in intestinal mucosa of SAP.

CONCLUSIONS

These results suggest that caspase activation has a key role in the accelerated apoptosis of intestinal epithelial cells in SAP and that breakdown of intestinal mucosa via accelerated apoptosis causes the increase in intestinal permeability following endotoxin translocation in SAP.

“Systemic apoptotic response” after thermal burns

The systemic pathophysiologic changes following thermal injuries affect multiple organs and body systems leading to clinical manifestations including shock, intestinal alterations, respiratory and renal failure, immunosuppression and others. Recent advances in the comprehension of mechanisms underlying systemic complications of thermal injuries have contributed to uncover part of the cellular and molecular basis that underlie such changes. Recently, programmed cell death (apoptosis) has been considered playing an important role in the development of such pathological events. Therefore, investigators utilizing animal models and clinical studies involving human primates have produced a large body of information suggesting that apoptosis is associated with most of the tissue damages triggered by severe thermal injuries. In order to draw the attention on the important role of apoptosis on systemic complications of thermal injuries, in this review we describe most of these studies, discuss possible cellular and molecular mechanisms and indicate ways to utilize them for the development of therapeutic strategies by which apoptosis may be prevented or counteracted.

Local thymic caspase-9 inhibition improves survival during polymicrobial sepsis in mice

Caspase-9 is believed to play an essential role in sepsis-induced lymphocyte apoptosis. The aim of this study was therefore to evaluate its contribution within the caspase-dependent apoptosis pathway in a murine model of polymicrobial sepsis. Local injections of Z-LEHD-fmk, a specific caspase-9 inhibitor, into thymi of septic mice led to the complete inhibition of caspase-9, decreased apoptosis of resident tissue cells, and, in addition, reduced further downstream caspase-3 activity. In contrast to its systemic administration, only local injections improved the overall survival of septic mice. However, local injections of a pancaspase inhibitor (Z-VAD-fmk) did not improve survival, although caspase-3 activity was reduced to a similar degree as by the administration of Z-LEHD-fmk. These results indicate that local apoptosis of lymphatic tissue in polymicrobial sepsis is processed dependent of caspase-9 and suggests alternative caspase-dependent beneficial effects, which may determine a positive outcome.

Transgenic and gene knock-out techniques and burn research

The development of transgenic technology has given researchers a powerful tool to examine biological effects, and the response to injury is no exception. Techniques such as pronuclear injection, targeted homologous recombination, and Cre/loxP gene excision are being used to construct animals with specific genetic designs; these are exploited to learn the role of genes in the response to severe burn. We review the construction of transgenic animals, pitfalls and benefits of this relatively new technique, and how this technique has been used in burn research.

Increased lymphoid tissue apoptosis in baboons with bacteremic shock

The molecular mechanisms of immune cell apoptosis during sepsis remain unclear. Two young adult baboons (Papio sp.) received a lethal dose of live Escherichia coli and were sacrificed at either 16 (for animal welfare concerns) or 24 h post-septic shock. An additional baboon, which received no bacteria, served as a control. Necropsy was performed immediately with subsequent immunohistochemical staining of lymphoid tissue. Immunohistologic analysis of tissues from the septic baboons revealed marked systemic lymphocyte apoptosis occurring in all lymphoid tissues examined. Focally, pyknotic and karyorrhectic lymphocytes demonstrated activation of a mitochondrial-dependent cell death pathway (active caspase 9 and apoptosis-inducing factor). Other regions demonstrated apoptotic lymphocytes with activation of a death receptor-dependent cell pathway (Fas ligand). Thus, we have demonstrated for the first time in primates that overwhelming gram-negative bacteremia produces an early and profound lymphocyte death that occurs through multiple cell death pathways. Bacteremic shock in the baboon may be an appropriate model for studying experimental therapies aimed at blocking lymphocyte apoptosis because their response appears comparable to humans dying from sepsis.

Burn injury induces a change in T cell homeostasis affecting preferentially CD4+T cells

Burn injuries are known to be associated with altered immune functions, resulting in decreased resistance to subsequent infection. In the present study, we determined the in vivo changes in T cell homeostasis following burn injury. Two groups of mice were used: a sham-burn group receiving buprenorphine as an analgesic and a burn group receiving buprenorphine and subjected to burn injury on 20% of the total body surface area. Results showed an important decrease in splenocytes following burn injury. This decrease persisted for 5 days and was followed, at day 10, by a 63% increase in number of cells. In vivo cell proliferation, as determined by the incorporation of 5-bromo-2'-dexoxyuridine, showed a significant increase of cycling splenocytes between days 2 and 10 after burn injury. The percentage of CD4+ and CD8+ T cells in the spleen was altered for 10 days after thermal injury. Analysis of naive (CD62Lhigh CD44low) and effector/memory (CD62Llow CD44high) T cells showed a percent decrease, independent of the expression of CD4 or CD8 molecules. However, early activation markers, such as CD69+, were expressed only on CD4+ T cells after a number of days following injury. Even with an activated phenotype, 10 days post-burn injury, CD4+ naive T cells significantly increased spontaneous apoptosis, detected by using a fluorescent DNA-binding agent 7-amino-actinomycin D. CD8+ T lymphocytes did not express early activation markers and were more resistant to apoptosis. Using purified T cells, we have shown unresponsiveness at day 10. Overall, these results demonstrate that mechanisms of T cell homeostasis were perturbed following burn injury. However, after 10 days, this perturbation persisted only in CD4+ T cells.

Characterization of the systemic loss of dendritic cells in murine lymph nodes during polymicrobial sepsis

Dendritic cells (DCs) play a key role in critical illness and are depleted in spleens from septic patients and mice. To date, few studies have characterized the systemic effect of sepsis on DC populations in lymphoid tissues. We analyzed the phenotype of DCs and Th cells present in the local (mesenteric) and distant (inguinal and popliteal) lymph nodes of mice with induced polymicrobial sepsis (cecal ligation and puncture). Flow cytometry and immunohistochemical staining demonstrated that there was a significant local (mesenteric nodes) and partial systemic (inguinal, but not popliteal nodes) loss of DCs from lymph nodes in septic mice, and that this process was associated with increased apoptosis. This sepsis-induced loss of DCs occurred after CD3(+)CD4(+) T cell activation and loss in the lymph nodes, and the loss of DCs was not preceded by any sustained increase in their maturation status. In addition, there was no preferential loss of either mature/activated (MHCII(high)/CD86(high)) or immature (MHCII(low)/CD86(low)) DCs during sepsis. However, there was a preferential loss of CD8(+) DCs in the local and distant lymph nodes. The loss of DCs in lymphoid tissue, particularly CD8(+) lymphoid-derived DCs, may contribute to the alterations in acquired immune status that frequently accompany sepsis.

Sepsis and the dendritic cell

Sepsis is a syndrome of significant morbidity and mortality. Unlike the advances made in other diseases processes, improvements in outcome from sepsis, severe sepsis, and septic shock have been modest. Current research has altered our understanding of sepsis pathogenesis such that present models and definitions are still evolving. One relatively novel cell type, the dendritic cell, is the subject of much current investigation in sepsis. Although our present understanding of dendritic cell biology is incomplete, growing evidence supports the importance of this antigen-presenting cell in the normal and maladaptive responses to microbial invasion and tissue injury. A better understanding of this cell's basic biology as well as its potential as a therapeutic target will undoubtedly play increasing roles in the development of new strategies for the treatment of the septic patient.

Smoke/burn injury-induced respiratory failure elicits apoptosis in ovine lungs and cultured lung cells, ameliorated with arteriovenous CO2 removal

STUDY OBJECTIVE

s: The purpose of this study was to examine the effects of two supportive therapies, conventional mechanical ventilation (CMV) and arteriovenous CO(2) removal (AVCO(2)R), during treatment of severe smoke/burn injury-induced ARDS.

DESIGN

Sheep were exposed to a smoke/burn injury (lethal dose causing death in 40% of animals); lung tissue and blood was collected prior to injury (control), when an ARDS criterion was met (PaO(2)/fraction of inspired oxygen ratio < 200), then after 72 h of either CMV (group 1) or AVCO(2)R (group 2). Lung tissue was studied by standard histopathologic techniques; cultured lung cells were studied in media supplemented with serum from all four groups.

MEASUREMENTS AND RESULTS

In vivo assays demonstrate less apoptotic cell death, and in vitro assays show significantly greater (p < 0.05) cell survival in group 2 (AVCO(2)R) than in group 1 (CMV) or baseline. Differential gene expression demonstrates significantly higher messenger RNA levels of proapoptotic and tumor necrosis factor (TNF)-alpha in cells incubated in baseline media. After exposure of cultured lung cells to conditioned media, protein expression assay of the culture medium revealed no TNF-alpha, TNF receptor (TNFR)-1, or TNFR-2, however, cultured cell lysate reveals elevated levels of TNF-alpha, TNFR-1 and caspase-3 in all groups; most occurred in cells incubated in baseline media (p < 0.05). HOECHST stain, DNA fragmentation, and caspase-3 cleavage show that AVCO(2)R ameliorates apoptosis in this model.

CONCLUSIONS

This in vitro work specifically examines cell death in lung cells as a result of smoke/burn injury and effects of therapeutic interventions. Our in vivo studies temporally correlate the clinical pathology to that studied in these lung cells and show that both in vivo and in vitro cell death is predominantly apoptotic and is significantly reduced by AVCO(2)R.

Inhibition of Fas/Fas ligand signaling improves septic survival: differential effects on macrophage apoptotic and functional capacity

Signaling through the Fas/Fas ligand (FasL) pathway plays a central role in immune-cell response and function; however, under certain pathological conditions such as sepsis, it may contribute to the animal's or patient's morbidity and mortality. To determine the contribution of FasL to mortality, we conducted survival studies by blocking Fas/FasL with Fas receptor fusion protein (FasFP) in vivo. C3H/HeN mice received FasFP or the saline vehicle (veh) immediately (0 h) or delayed (12 h), after sepsis induced by cecal ligation and puncture (CLP). Subsequently, we examined the effect of FasFP treatment (12 h post-CLP) on macrophage apoptosis and functional capacities. Peritoneal and splenic macrophages and Kupffer cells from sham-veh-, CLP-veh-, sham-FasFP-, or CLP-FasFP-treated mice were harvested 24 h after CLP and stimulated with lipopolysaccharide (LPS) for 24 h. The results indicate that only delayed (12 h) but not 0 h administration of FasFP demonstrated a significant increase in survival. The ability of all macrophage populations to release interleukin (IL)-6 was significantly depressed, and IL-10 release was augmented after CLP. FasFP treatment attenuated the increased IL-10 release in Kupffer cells. However, althogh enhanced susceptibility to LPS-induced apoptosis could be suppressed in CLP mouse Kupffer cells by FasFP, FasFP did not change the peritoneal or splenic macrophage response. Furthermore, FasFP attenuated the elevated plasma levels of liver enzymes after sepsis. These data indicate that in vivo inhibition of Fas/FasL signaling has tissue-specific effects on the induction of macrophage apoptosis, functional changes, and liver damage, which may contribute to the host's ability to ward off a septic challenge.

Burn injury-mediated alterations in cell cycle progression in lymphoid organs of mice

A key event in the cellular and molecular pathogenesis of multiple organ failure (MOF) after burn injury may be the change in profiles of the cell cycle progression in affected organs. We investigated the effects of burn injury on cell cycle progression in immune organs. Cell cycle analysis in the lymphoid tissues of mice after 18% burn injury revealed that S phase entry was temporarily arrested in the thymus 1 day after injury, whereas the spleen had substantially increased S phase entry at day 8. This mode of cell cycle regulation was reproduced in different age groups and strains of mice. Furthermore, the reactivity to the Ki-67 antibody (indicative of proliferation) was markedly reduced in the thymic cortex at day 1. There was a distinct pattern of hematopoietic foci formation and increased reactivities to the Ki-67 antibody in myelogenous cells in the red pulp of spleen at day 7, consistent with the elevated S phase entry. These data suggest that differential regulation of cell cycle progression may play a crucial role in the phenotypic changes in immune organs after burn injury.

Nitric oxide inhibits spleen cell proliferative response after burn injury by inducing cytostasis, apoptosis, and necrosis of activated T lymphocytes: role of the guanylate cyclase

We previously showed that an overproduction of nitric oxide (NO) by macrophages was responsible for the collapse of lymphoproliferative responses after burn injury in rats. First, we demonstrate here that 10 days post-burn, the inhibition of splenocyte response to concanavalin-A results from cytostatic, apoptotic, and necrotic effects of NO on activated T cells. This was evidenced by various criteria at the levels of DNA, mitochondria, and plasma membrane. Inhibition of NO synthase by S-methylisothiourea (10 microM) normalized all the parameters. Second, we show that two soluble guanylate cyclase (sGC) inhibitors, LY83583 and ODQ, restored the proliferative response in a concentration-dependent manner. LY83583 (0.5 microM) rescued T cells from apoptosis. Similar results were obtained with KT5823 (5 microM) a specific inhibitor of protein kinase G (PKG). In contrast, neither LY83583 nor KT5823 inhibited NO-induced necrosis. These results suggest that NO blocked T cells in the G1 phase and induced apoptosis through a sGC-PKG-dependent pathway and necrosis through an independent one.

Role of TNF-alpha in gut mucosal changes after severe burn

Gut epithelial cell death by apoptosis is increased in the gut epithelium after severe burn associated with mucosal atrophy. We hypothesized that tumor necrosis factor (TNF)-alpha-TNF receptor (TNFR) interaction activates apoptosis in small bowel mucosal cells after severe burn. C57BL6 mice received a 30% total body surface area scald burn and were treated with neutralizing anti-TNF-alpha. The proximal small bowel was assessed for mucosal atrophy. Proliferation and apoptosis of mucosal cells were assessed by proliferative cell nuclear antigen-immunostaining and terminal deoxyuridine nick-end labeling assay, respectively. Mucosal height and mucosal cell number decreased after burn. Anti-TNF-alpha-treated mice showed significantly less mucosal atrophy. Proliferation of intestinal cells was not changed with burn or anti-TNF-alpha treatment. An over threefold increase in apoptotic cell number was seen after burn, which was diminished by anti-TNF-alpha treatment. Changes in gut mucosal homeostasis after severe burn are affected, in part, by the activation of apoptosis by TNF-alpha-TNFR interaction.

Impairment of splenic B and T lymphocytes in the early period after severe thermal injury: immunohistochemical and electron microscopic analysis

Immunocompetent cells, such as lymphocytes and macrophages are easily damaged after severe thermal injury. In the present study, we investigated structural changes in splenic lymphocytes in the early period after a full skin thickness burn of 30% of the body surface area in rats. At 2h after thermal injury, numerous B lymphocytes had accumulated in the markedly expanded marginal zone of the splenic white pulp. Electron microscopy showed a small number of apoptotic cells in the marginal zone of the white pulp. After 5h, B lymphocytes in the marginal zone as well as in the lymphoid sheath and follicles were markedly decreased in number with an increase of tingible bodies and tingible body macrophages. The number of apoptotic cells had increased not only in the marginal zone, but also in the lymphoid sheath and follicles. After 12h, the splenic white pulp became atrophic with the appearance of a small number of large blastic cells and mitotic figures. After 24h, the splenic white pulp was still atrophic with a decrease in the number of lymphocytes, especially B lymphocytes. On the other hand, the large blastic cells and mitotic figures increased in number. Apoptotic cells decreased in number in the white pulp. After 48h, the lymph follicles were slightly enlarged and a small germinal centre occasionally appeared. A small number of T lymphocytes were observed in the splenic white pulp of the normal rats. However, the T lymphocytes almost disappeared shortly after thermal injury. A recovery in T cell number was observed only after 48h. These findings indicate that severe impairment of both B and T lymphocytes, circulating and in the lymphoid organs, occurs shortly after thermal injury and continues for several days. This severe damage to the lymphocytes is considered to be closely related to severe immune suppression after thermal injury.

Interleukin-10: a complex role in the pathogenesis of sepsis syndromes and its potential as an anti-inflammatory drug

Interleukin (IL)-10 is a pleiotropic cytokine produced by both T cells and macrophages and possesses both anti-inflammatory and immunosuppressive properties. IL-10 circulates in the blood of patients with sepsis syndromes, and increased concentrations of IL-10 have been associated with an adverse clinical outcome. Experimental studies in rodents and primates have demonstrated that endogenously produced and exogenously administered IL-10 can reduce the magnitude of the inflammatory response and improve outcome, primarily in models of endotoxemic and bacteremic shock. However, endogenous IL-10 production and systemic administration can also exacerbate T-cell dysfunction, decrease T-cell apoptosis, reduce antimicrobial function, and increase mortality in other less acute bacterial models of sepsis or after thermal injury. Targeted delivery of IL-10 to individual tissues may obviate the adverse effects of systemic delivery. The potential anti-inflammatory properties of IL-10 will have to be carefully weighed against its immunosuppressive properties when considering its use in patients with acute inflammation and sepsis syndromes.

Nicotine inhibition of apoptosis in murine immune cells

Nicotine, the addictive component of tobacco, is thought to be at least partially responsible for the deleterious effects of smoking such as heart disease and cancer. Evidence shows that nicotine is an immunomodulator and that one of its possible mechanisms is regulation of apoptosis, or programmed cell death, in immune cells. This study examined the effects and the mechanisms of action of nicotine on dexamethasone (DEX)-induced apoptosis in murine immune cells by examining the expression of levels of the 17-kDa active caspase-3, a marker of apoptosis. Thymocytes and splenocytes from adult BALB/c female mice were incubated with concentrations of nicotine correlating to those found in the blood and tissue of smokers (0.01 microg/ml [0.022 microM] and 1 microg/ml [2.2 microM]), concurrently with 100 nM DEX, to induce apoptosis. Cytosolic protein fractions were analyzed by Western blotting with polyclonal antibodies that recognize the active form of caspase-3. The data showed that nicotine significantly blocked the formation of the DEX-induced 17-kDa caspase-3 subunit expression. This downregulation ranged from 65% to 100% of the active caspase-3 expressed in cultures treated with DEX alone. Addition of d-tubocurarine chloride (dTC), a general nicotinic receptor antagonist, inhibited nicotine downregulation of the DEX-induced active caspase-3 expression, providing evidence that this action of nicotine was receptor-mediated. These data support that nicotine is an important immunomodulator at the level of immune cell apoptosis, a process thought to be a contributory mechanism of autoimmunity, cardiovascular disease, and carcinogenesis.

Targeted adenovirus-induced expression of IL-10 decreases thymic apoptosis and improves survival in murine sepsis

Sepsis remains a significant clinical conundrum, and recent clinical trials with anticytokine therapies have produced disappointing results. Animal studies have suggested that increased lymphocyte apoptosis may contribute to sepsis-induced mortality. We report here that inhibition of thymocyte apoptosis by targeted adenovirus-induced thymic expression of human IL-10 reduced blood bacteremia and prevented mortality in sepsis. In contrast, systemic administration of an adenovirus expressing IL-10 was without any protective effect. Improvements in survival were associated with increases in Bcl-2 expression and reductions in caspase-3 activity and thymocyte apoptosis. These studies demonstrate that thymic apoptosis plays a critical role in the pathogenesis of sepsis and identifies a gene therapy approach for its therapeutic intervention.

Nuclear factor-kappa B is upregulated in colorectal cancer

BACKGROUND

Chemoresistance may involve the anti-apoptotic transcriptional regulator, nuclear factor-kappa B (NF-kappa B). The purpose of this study was to determine whether chemotherapy induces NF-kappa B activation in a human colon cancer cell line (SW48) and whether NF-kappa B is constitutively activated in colorectal cancer.

METHODS

SW48 cells were incubated with gemcitabine hydrochloride (Gemzar) in the presence and absence of the 26s proteasome inhibitor, MG132, and NF-kappa B binding (electrophoretic mobility shift assay), DNA synthesis (tritiated thymidine uptake), cell viability (3-[4,5-dimethylthiazol-2-yl]-diphenyl-tetrazolium bromide assay), and apoptosis (caspase-3 activity) were measured at 24 hours. NF-kappa B binding (electrophoretic mobility shift assay) was also assayed in 10 colorectal cancer tumors.

RESULTS

SW48 cells demonstrated constitutive NF-kappa B binding that was enhanced by gemcitabine hydrochloride in a dose-dependent manner. MG132 inhibited NF-kappa B binding and enhanced gemcitabine hydrochloride's inhibition of DNA synthesis (gemcitabine hydrochloride = 73% +/- 1.4% vs gemcitabine hydrochloride + MG132 = 6% +/- 0.4%, P <.05), cell killing (gemcitabine hydrochloride = 87% +/- 2.0 vs gemcitabine hydrochloride + MG132 = 25% +/- 1.3%, P <.05), and caspase-3 activity (gemcitabine hydrochloride = 870 +/- 17.4 vs gemcitabine hydrochloride + MG132 = 1075 +/- 20.4, P <.05). NF-kappa B binding was increased in 8 of 10 colorectal cancer tumors compared with adjacent normal mucosa.

CONCLUSIONS

Gemcitabine hydrochloride enhances NF-kappa B binding in a colorectal cancer cell line, whereas inhibition of NF-kappa B enhances gemcitabine hydrochloride's antitumor activity. NF-kappa B is also activated in human colorectal cancer. NF-kappa B may identify chemoresistant tumors, whereas inhibition of NF-kappa B may be a novel, biologically based therapy. (Surgery 2001;130:363-9).

Parallel Self-Induction of TNF-α and Apoptosis in the Thymus of Mice after Burn Injury

BACKGROUND

Burn injury often causes multiple organ failure as well as skin damage. Several studies suggest that TNF-alpha plays an important role in postinjury immunosuppression by altering lymphoid tissues. We investigated the regulation of TNF-alpha expression and apoptosis in the spleen and thymus of mice after burn injury.

MATERIALS AND METHODS

C57BLKS/J mice were subjected to 18% TBSA full-thickness burn and the spleen and thymus were harvested at various time points (3 h to 29 days). The expression of TNF-alpha mRNA and protein in tissue extracts was analyzed by RT-PCR and ELISA. Apoptosis was measured by flow cytometry using annexin V staining.

RESULTS

Burn injury induced TNF-alpha mRNA expression in the thymus at Day 1 and it returned to the basal levels at Day 14 and thereafter. Similarly, TNF-alpha mRNA up-regulation peaked between Day 1 and Day 3 in the spleen. Induction of TNF-alpha protein peaked at Day 1 in the thymus, whereas, TNF-alpha protein was unchanged in the spleen after burn injury. There was a twofold increase in apoptotic cells at Day 1 in the thymus, which is consistent with mRNA and protein data. In contrast, burn injury did not change apoptotic events in the spleen.

CONCLUSIONS

The parallel induction of TNF-alpha mRNA, TNF-alpha protein, and apoptosis suggests that TNF-alpha may contribute to immunosuppression after burn injury by inducing apoptosis in the thymus.

IL-10 mediation of activation-induced TH1 cell apoptosis and lymphoid dysfunction in polymicrobial sepsis

Recent studies suggest that increased activation-induced lymphocyte apoptosis (AICD) is detected in mouse splenocytes during polymicrobial sepsis which may contribute to lymphocyte immune dysfunction [i.e., decreased interleukin (IL-)2 and interferon-gamma (IFN-gamma) production] leading to the associated morbidity seen in those animals. Thus, we wanted to examine the hypothesis that immune suppressive agents, such as IL-4, IL-10 or prostaglandin E2(PGE2), known to be elevated in septic animals, also contribute to this increase in AICD. Here we demonstrate that the inclusion of monoclonal antibody (mAb) to IL-10, but not anti-IL-4 or ibuprofen (IBU), blunted this sepsis induced increase in splenocyte AICD. Additionally, septic mice deficient in the IL-10 gene product (-/-) showed neither an increase in AICD nor a loss of IL-2/IFN-gamma release capacity. Interestingly, mAb to IL-10 did not altered the extent of AICD in a Th2-cell line, but exogenous IL-10 did potentiate Th1-like cell line AICD. This was consistent with the finding that the increased AICD seen in septic mouse splenocytes was restricted largely to the CD4+ cells producing IL-2 (Th1-cells) and that mAb to IL-10 treatment suppressed this change. Furthermore, IL-10 appears to mediate its AICD effect by upregulation of the Fas receptor and Fas receptor signaling protein components, but not by altered expression of Bcl/Bax/Bad family members, in septic mouse splenocytes. To the extent that these processes contribute in a pathological fashion to the animal's capacity to survive sepsis we have previously observed that in vivo post-treatment of mice with mAb IL-10 markedly attenuated septic mortality. Collectively, these data indicate that in the septic mouse the Th2 cytokine IL-10 not only serves to actively induce Th1 lymphocyte immune dysfunction but also plays a role in their apoptotic depletion. These processes in turn appear to contribute to the animal's inability to ward off lethal septic challenge.

Apoptosis in sepsis: a new target for therapeutic exploration

The treatment of sepsis and septic shock remains a clinical conundrum, and recent prospective trials with biological response modifiers aimed at the inflammatory response have shown only modest clinical benefit. Recently, interest has shifted toward therapies aimed at reversing the accompanying periods of immune suppression. Studies in experimental animals and critically ill patients have demonstrated that increased apoptosis of lymphoid organs and some parenchymal tissues contributes to this immune suppression, anergy, and organ system dysfunction. During sepsis syndromes, lymphocyte apoptosis can be triggered by the absence of IL-2 or by the release of glucocorticoids, granzymes, or the so-called 'death' cytokines: tumor necrosis factor alpha or Fas ligand. Apoptosis proceeds via auto-activation of cytosolic and/or mitochondrial caspases, which can be influenced by the pro- and anti-apoptotic members of the Bcl-2 family. In experimental animals, not only can treatment with inhibitors of apoptosis prevent lymphoid cell apoptosis; it may also improve outcome. Although clinical trials with anti-apoptotic agents remain distant due in large part to technical difficulties associated with their administration and tissue targeting, inhibition of lymphocyte apoptosis represents an attractive therapeutic target for the septic patient.

Considering immunomodulatory therapies in the septic patient: should apoptosis be a potential therapeutic target?

Treatment of sepsis and septic shock remains a clinical conundrum. Recent prospective trials with anti-cytokine and anti-inflammatory therapies have shown only modest clinical benefit. The successful treatment of the patient with sepsis syndrome will likely require multi-modal therapies aimed at several of the immunological and physiological disturbances which are occurring simultaneously. Recent studies in experimental animals and critically ill patients have suggested that increased apoptosis of lymphoid organs and some parenchymal tissues may contribute to the immune suppression, anergy and organ system dysfunction. Therapies aimed at inhibiting lymphoid cell apoptosis may contribute to improved outcome, and should be considered in the treatment of hospitalized patients with sepsis syndromes. Although clinical trials with anti-apoptotic agents remain distant due in large part to technical difficulties associated with their administration and tissue targeting, inhibition of lymphocyte apoptosis may be an appropriate therapeutic target for the septic patient.

Caspase inhibitors improve survival in sepsis: a critical role of the lymphocyte

Sepsis induces lymphocyte apoptosis and prevention of lymphocyte death may improve the chances of surviving this disorder. We compared the efficacy of a selective caspase-3 inhibitor to a polycaspase inhibitor and to caspase-3-/- mice. Both inhibitors prevented lymphocyte apoptosis and improved survival. Caspase-3-/- mice shared a decreased, but not total, block of apoptosis. The polycaspase inhibitor caused a very substantial decrease in bacteremia. Caspase inhibitors did not benefit RAG-1-/- mice, which had a > tenfold increase in bacteremia compared to controls. Adoptive transfer of T cells that overexpressed the anti-apoptotic protein Bcl-2 increased survival. T cells stimulated with anti-CD3 and anti-CD28 produced increased interleukin 2 and interferon gamma by 6 h. Thus, caspase inhibitors enhance immunity by preventing lymphocyte apoptosis and lymphocytes act rapidly, within 24 h, to control infection.

Electroporation-mediated gene transfer in free-swimming embryonic Xenopus laevis

Xenopus laevis are a rich resource for vertebrate embryology and cell biology. Transplantation and transgenesis have provided much information about the developmental mechanisms of embryogenesis and molecule function, however existing methods have faced limitations regarding either the precise localization of gene expression or flexibility in the timing of gene transfer. Here we have found that electroporation of tailbud (stage 29/30) embryos is a rapid and efficient method of combining cell-specific expression with variation in temporal delivery. At the low voltages required for electroporation, embryos resumed normal swimming behavior and development. We conclude that electroporation has wide experimental application to Xenopus developmental and cell biology.

Reduced susceptibility of nonobese diabetic mice to TNF-alpha and D-galactosamine-mediated hepatocellular apoptosis and lethality

Nonobese diabetic (NOD/LtJ or NOD) mice are resistant to doses of LPS and D-galactosamine that uniformly produce lethality in C57BL/6J (B6) mice (p < 0.01). Liver caspase-3-like activity, serum transaminase levels (both p < 0.05), and the numbers of apoptotic liver nuclei were also reduced in NOD compared with B6 mice treated with LPS (100 ng) and D-galactosamine (8 mg). NOD mice were also at least 100-fold more resistant to recombinant human TNF-alpha and D-galactosamine treatment than B6 mice (p < 0.001). Binding of recombinant human TNF-alpha to splenocytes from NOD mice was similar to that seen in B6 mice, suggesting that the defect in responsiveness was not due to an inability of recombinant human TNF-alpha to bind the NOD TNF type 1 (p55) receptor. Because the TNF type 1 (p55) receptor shares a common signaling pathway with Fas (CD95), NOD and B6 mice were treated with the Fas agonist antibody, Jo-2. Surprisingly, NOD mice were as sensitive as B6 mice to Fas-induced lethality and hepatic injury. In addition, primary hepatocytes isolated from NOD mice and cultured in vitro in the presence of D-galactosamine with or without TNF-alpha were found to be resistant to apoptosis and cytotoxicity when compared with B6 mice. In contrast, Jo-2 treatment produced similar increases in caspase-3 activity and cytotoxicity in primary hepatocytes from NOD and B6 mice. The resistance to LPS- and TNF-alpha-mediated lethality and hepatic injury in D-galactosamine-sensitized NOD mice is apparently due to a post-TNFR binding defect, and independent of signaling pathways shared with Fas.

Glucocorticoid and Fas ligand induced mucosal lymphocyte apoptosis after burn injury

BACKGROUND

The purpose of this study was to examine the effects of a steam burn injury on apoptosis in gut-associated lymphoid tissue and to determine whether endogenous glucocorticoid and Fas ligand signaling were involved in this process.

METHODS

Histologic analysis, in situ deoxynucleotidyl transferase dUTP nick-end labeling staining and annexin V and 7-amino-actinomycin-D flow cytometry of lymphocyte populations were evaluated in intraepithelial lymphocytes and Peyer's patch. Additional mice were pretreated with a glucocorticoid receptor antagonist (mifepristone) before the steam burn. Similarly, C3H/HeJ-FasL(gld) mice lacking functional Fas ligand were also studied.

RESULTS

Apoptosis was significantly increased in intraepithelial lymphocytes and Peyer's patch after the burn injury. Mifepristone pretreatment significantly reduced apoptosis in both T- and B-cell populations in intraepithelial lymphocytes after the burn injury. In contrast, the increased apoptosis seen in B-cells from Peyer's patch was not seen in C3H/HeJFasL(gld) mice, whereas the increased apoptosis in CD8+ T-cells was unaffected.

CONCLUSION

Both corticosteroids and FasL contribute to the apoptosis in gut-associated lymphoid tissues early after burn injury.

A central role for CD95 (Fas) in T-cell reactivity after injury

BACKGROUND

Recent findings indicate that severe injury primes the immune system for an enhanced and lethal proinflammatory cytokine response against bacterial-derived superantigens. This study asked whether this response to injury involves the CD95 (Fas) signaling pathway.

METHODS

To assess superantigen-mediated mortality, wild-type (WT) C57BL/6 and Fas-deficient C57BL/6 lpr (-/-) (lpr) mice underwent burn or sham injury and were challenged 2 hours later with staphylococcal enterotoxin B (SEB). Spleen cells from sham and burn WT or lpr mice were stimulated in vitro with SEB to assess injury effects on IL-2, TNF-alpha, and IFN-gamma production.

RESULTS

Lpr burn mice survived the SEB challenge (100% survival), while WT burn mice showed a high mortality (17% survival, P < 001, analysis of variance [ANOVA]). Sham lpr or WT mice suffered no mortality to the SEB challenge. In vitro studies demonstrated that burn lpr mice produced significantly less TNF-alpha, IFN-gamma, IL-2 than burn WT mice (P <.01, ANOVA). Burn injury markedly enhanced SEB-stimulated IFN-gamma production by WT spleen cells and CD8+ T cells, while this did not occur in SEB-stimulated lpr spleen cells.

CONCLUSIONS

These findings support the hypothesis that the CD95 (Fas) signaling pathway plays an integral role in the injury-induced enhanced and lethal T-cell reactivity against bacterial superantigens.

Neither Fas ligand nor endotoxin is responsible for inducible peritoneal phagocyte apoptosis during sepsis/peritonitis

Regulation of the phagocyte apoptotic response appears to play a significant role in the pathophysiology of sepsis. In this regard, prior studies have shown that the onset of phagocyte apoptosis, as well as those agents that regulate it at the nidus of infection, differ significantly from those seen in circulation. The aim of this study therefore was to determine if the increase in inducible phagocyte apoptosis and caspase activities seen in the peritoneum during sepsis is due to endotoxin or Fas ligand. To study this, male C3H/HeN (endotoxin-sensitive), C3H/HeJ (endotoxin-tolerant), and C3H/HeJ-FasL(gld) (endotoxin-tolerant/FasL-deficient) mice were subjected to cecal ligation and puncture or sham operation. Twenty-four hours later, phagocytes were collected and cultured with lipopolysaccharide (LPS), then harvested for apoptosis (propidium iodide cell cycle or cell death ELISA analysis), cytokine release (ELISA), and caspase activity (fluorogenic assay) determination. The data indicate that there was a marked increase in apoptosis in LPS-stimulated phagocytes which was associated with a significant increase in caspase 3, 8, and 9 activities but a decrease in caspase 1 activity from C3H/HeN and C3H/HeJ-FasL(gld) septic mice and an increase in caspase 3 and 8 activities in phagocytes from C3H/HeJ septic mice. Furthermore, cells from septic mice, including all three strains, lost their ability to produce IL-1beta and IL-6 in response to LPS stimulation. The inability to completely suppress these changes suggests that neither endotoxin (via signaling through TLR-4 pathway) nor Fas ligand regulates the peritoneal phagocyte apoptotic responses seen during the late phase of polymicrobial sepsis/peritonitis.

Glucocorticoid-induced, caspase-dependent organ apoptosis early after burn injury

Immune suppression and increased apoptotic loss of circulating lymphocytes have been reported after burn injury. However, little is known about the underlying mechanisms responsible for the increased apoptosis of lymphoid and parenchymal cells in solid organs and the role played by inflammatory mediators, such as tumor necrosis factor-alpha (TNF-alpha) and Fas ligand (FasL), as well as by glucocorticoids. To evaluate the role of endogenously produced glucocorticoids and FasL, mice subjected to a 20% steam burn were pretreated with a glucocorticoid receptor antagonist (mifepristone) or a neutralizing murine Fas fusion protein. Three and twenty-four hours after burn injury, histological analysis, caspase-3 activity, and in situ terminal deoxynucleotidyl transferase dUTP nick-end labeling staining and phenotyping of lymphocyte populations for apoptosis were evaluated. Burn injury increased the number of apoptotic cells and caspase-3 activity in thymus and spleen, but not in other solid organs. Increased apoptosis was seen in several T and B cell populations from both thymus and spleen. Mifepristone pretreatment significantly reduced the apoptosis and caspase-3 activity after burn injury, whereas blocking FasL activity had only minimal effects. We conclude that corticosteroids, and not FasL, are primarily responsible for the increased caspase-3 activity and apoptosis in thymus and spleen cell populations early after burn injury.