Immune deficiency following thermal trauma is associated with apoptotic cell death

Long-term sequelae of critical illness in sepsis, trauma and burns: A systematic review and meta-analysis

BACKGROUND

Sepsis, major trauma, and severe burn injury are life-threatening critical illnesses that remain significant contributors to worldwide morbidity and mortality. The three underlying etiologies share pathophysiological similarities: hyperinflammation, hypermetabolism, and acute immunomodulation. The aims of this study were to assess the current state of long-term outcome research and to identify key outcome parameters between the three forms of critical illness.

METHODS

This systematic review and meta-analysis (MA) were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. PubMed was searched from January 1, 1975, to December 31, 2019. Studies were assessed for eligibility by independent reviewers. Inclusion criteria were studies reporting at least a 6-month follow-up of health-related quality of life and organ-specific sequelae within the three etiologies: severe burn injury, sepsis, and major trauma.

RESULTS

In total, 125 articles could be included in the systematic review and 74 in the MA. The mean follow-up time was significantly longer in burn studies, compared with sepsis and trauma studies. The majority of patients were from the sepsis group, followed by burns, and major trauma studies. In the overall health-related quality of life, as assessed by Short Form 36 and European Quality-of-Life Index, the three different etiologies were comparable with one another.

CONCLUSION

The effects of critical illness on survivors persist for years after hospitalization. Well-reported and reliable data on the long-term outcomes are imperative, as they can be used to determine the treatment choice of physicians and to guide the expectations of patients, improving the overall quality of care of three significant patient cohorts.

LEVEL OF EVIDENCE

Systematic review and MA, level III.

Safety, Pharmacodynamics, and Efficacy of High- Versus Low-Dose Ascorbic Acid in Severely Burned Adults

In sepsis and burns, ascorbic acid (AA) is hypothesized advantageous during volume resuscitation. There is uncertainty regarding its safety and dosing. This study evaluated high dose AA (HDAA: 66 mg/kg/h for 24 hours) versus low dose AA (LDAA: 3.5 g/days) administration during the first 24 hours in severely burned adults. We conducted a retrospective study comparing fluid administration before and after switching from low dose to HDAA in severely burned adults. A total of 38 adults with burns >20% TBSA, who received either HDAA or LDAA were included in this retrospective study. AA serum concentrations were quantified at 0, 24, and 72 hours postburn. HDAA impact on hemodynamics, acid-base homeostasis, acute kidney injury, vasopressor use, resuscitation fluid requirement, urinary output, and the incidence of adverse effects was evaluated; secondary clinical outcomes were analyzed. AA plasma levels were 10-fold elevated in the LDAA and 150-fold elevated in the HDAA group at 24 hours and decreased in both groups afterwards. HDAA was not associated with a significantly increased risk of any complications. A significant reduction in colloid fluid requirements was noted (LDAA: 947 ± 1722 ml/24 hours vs HDAA: 278 ± 667 ml/24 hours, P = 0.029). Other hemodynamic and resuscitation measures, as well as secondary clinical outcomes were comparable between groups. HDAA was associated with higher AA levels and lower volumes of colloids in adults with severe burns. The rate of adverse events was not significantly higher in patients treated with HDAA. Future studies should consider prolonged administration of AA.

Effects of Carvacrol in an Experimentally Induced Esophageal Burn Model: Expression of VEGF and Caspase-3 Proteins

INTRODUCTION

We investigated the therapeutic effects of carvacrol in an experimental esophageal burn rat model with immunohistochemical techniques. Materials and Methods: Three groups were included in this study, composed of eight Wistar albino rats each. The control group was given 1 mL 0.9% (wt/vol) NaCl; esophageal burns were induced in groups 2 and 3 by administration of 1 mL 40% NaOH in the distal 2 cm of the esophagus. The treatment group was administered 75 mg/kg carvacrol in 2 mL 0.9% NaCl for 10 days. After a routine histological examination of the tissues, sections were stained with vascular endothelial growth factor (VEGF) and caspase-3 for immunohistochemical analysis and were examined under a light microscope. Results: In the control group, there were regular cells in the cornified epithelial tissue and cylindrical cells in the basal layer, which faced toward the apical surface in the mitotic phase. The burn group displayed wide degeneration, necrosis, and abundant apoptotic cells in the epithelial tissue as well as intense inflammatory cell infiltration. In the treatment group, there was an increase in mitotic activity in the basal cells of the epithelial layer and degenerative changes, but a preserved epithelial layer and significant cornified structures. The treatment group showed positive caspase-3 expression in some apoptotic cells within the epithelial layer and in connective tissue, and there were only a small number of degenerated cells in the muscle layer. Additionally, in the treatment group, VEGF expression was evident in small numbers of inflammatory cells in the papillary region of the epithelium, and in dilated vascular endothelial cells. Conclusions: Carvacrol may contribute to a reduction in fibrosis by decreasing inflammation and preventing cell apoptosis.

Determination of lymphocytes surface markers in patients with thermal burns and the influence of burn size on mononuclear cell subsets

Background: Thermal burn injuries impair the host defence system. Hence, in the present study, we aimed at investigating the changes in the number and phenotype of peripheral blood lymphocyte populations (T, B, and natural killer cells) and their subpopulations in patients with thermal burns and determining the relationships with different sizes of total body surface area (TBSA). Methods: Blood samples from 67 patients, admitted to Motahary Burn Center in Tehran, with burns from 30% to more than 70% TBSA were collected on Days 3 and 7 postburn. Lymphocytes and their subpopulations were identified by monoclonal antibodies. The cells were analyzed using flow cytometry. The results were compared with healthy controls. Results: In this study, 3 and 7 days after burn injury, the percentages of CD3+, CD4+ and CD8+ lymphocyte significantly decreased, CD4+/CD8+ ratios were below the normal range, and CD19+ (B cells) significantly increased. No significant difference was obtained in the mean percentage of CD16+ (NK cells) between Days 3 and 7 postburn. Patients with burns of 30% TBSA or greater (>70%) had a significant reduction in CD3+, CD4+ and CD8+ ( T cells) numbers up to 7 days compared with 3 days after burn injury. Patients with 30% to >70 % TBSA burn failed to show any significant changes in CD4+/CD8+ ratio as well as CD16+ (NK cells) 3 to 7 days after burn. In patients with burns more than 30% to>70% TBSA, CD19+ (B cells) number changes were found to be complicated after 3 and 7 days. Conclusion: The results of this study suggest that alterations of immune cell surface markers and TBSA% can reflect postburn lymphocyte activation.

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.

Cutting edge: critical role for C5aRs in the development of septic lymphopenia in mice

In the early stages of sepsis, lymphocytes undergo apoptosis, resulting in lymphopenia and immunosuppression. The trigger for septic lymphopenia is unknown. Using the polymicrobial model of murine sepsis, we investigated the role of C5a receptors in septic lymphopenia. In wild-type mice, cecal ligation and puncture resulted in splenocyte apoptosis and significant lymphopenia after 3 d, which was not observed in C5aR1(-/-) or C5aR2(-/-) mice. Our data show that mouse neutrophils exposed to recombinant mouse C5a cause release of histones in a dose-dependent and time-dependent manner. Histone levels in spleen were significantly elevated following cecal ligation and puncture but were reduced by the absence of C5aR1. Histones induced significant lymphocyte apoptosis in vitro. Ab-mediated neutralization of histones prevented the development of lymphopenia in sepsis. Together, these results describe a new pathway of septic lymphopenia involving complement and extracellular histones. Targeting of this pathway may have therapeutic benefit for patients with sepsis or other serious illness.

Increased apoptosis of peripheral blood neutrophils is associated with reduced incidence of infection in trauma patients with hemorrhagic shock

OBJECTIVE

We aimed to describe the relationship between early peripheral leukocyte apoptosis and incidence of subsequent infection in trauma patients with hemorrhagic shock (T/HS).

METHODS

T/HS patients requiring emergency surgery were prospectively enrolled. Nucleosome ELISA and TUNEL staining were performed on peripheral blood drawn pre-operatively, post-operatively and at 24 h. Subjects were followed for 30 days or until death or hospital discharge to record all episodes of infection.

RESULTS

Forty-one subjects were enrolled. Six died within 24 h of surgery and were not included in the analysis. Nucleosome levels peaked post-operatively and dropped to baseline levels at 24 h (p = 0.03). TUNEL analysis revealed that polymorphonuclear neutrophils (PMNs) accounted for 72% of apoptotic leukocytes; the remaining apoptotic cells were mainly lymphocytes. Increased post-operative leukocyte apoptosis was associated with decreased systemic inflammatory response syndrome (SIRS) severity. Seventeen of the 35 survivors (48.6%) developed infections, while 18 (51.4%) did not. Pre-operative and post-operative nucleosome levels were 2.5 and 3 times higher, respectively, in T/HS patients who did not develop infection compared to those who did. Increased nucleosome levels were associated in particular with protection against sepsis (p=0.03) and multiple infections (p = 0.01).

CONCLUSION

Peripheral blood PMN apoptosis in the early resuscitative period is associated with decreased incidence of subsequent infection in T/HS patients.

Th17 (IFNγ- IL17+) CD4+ T cells generated after burn injury may be a novel cellular mechanism for postburn immunosuppression

BACKGROUND

The mechanism responsible for initiating and controlling the immunosuppressive response after burn injury remains unknown. Interleukin-17 (IL-17) secreting Th17 (interferon [IFN]γ IL17) cells are a novel subset of CD4 T cells associated with a weak, proinflammatory response that antagonizes the proinflammatory Th1 (IFNγ IL17) response. Given that transforming growth factor-β and IL6 mediate Th17 cell development, we hypothesized that burn injury may generate Th17 cells that could mediate postburn immunosuppression.

METHODS

After a 20% total body surface area burn in female C57BL/6 mice, wound-draining lymph nodes were harvested 3 days, 7 days, or 14 days after injury. CD4 T cells were enriched by magnetic selection, and flow cytometry was used to identify intracellular IL17 and IFNγ in CD3CD4 T cells. Additional purified CD3CD4 T cells were cultured with Th17 polarizing IL6 and transforming growth factor-β for 4 days, and flow cytometry was again used to identify intracellular IL17 and IFNγ in CD4 T cells.

RESULTS

The number and percentage of preformed Th17 cells was significantly greater in burn mice compared with sham at all time points. In addition, the ratio of Th17 cells to Th1 cells was always significantly higher in burn mice compared with sham. These differences were eliminated in Th17 polarizing conditions in vitro. CD4 T cells never generated both IL17 and IFNγ.

CONCLUSION

These results demonstrate for the first time that Th17 cells (IFNγ IL17) are spontaneously generated after burn injury. Given that Th17 cells (IFNγ IL17) are antagonistic to Th1 (IFNγ IL17) cells, these results suggest a novel mechanism for initiating and controlling postburn immunosuppression that deserves further investigation.

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.

Enhanced T-cell apoptosis in human septic shock is associated with alteration of the costimulatory pathway

T-cell apoptosis during septic shock (SS) has been associated with deleterious outcome, but the mechanisms of apoptosis are not well understood. As T-cells are not infected in bacterial infection, our hypothesis was that deleterious interactions between lymphocytes and monocytes could be involved. This is a cross-sectional study of 27 patients presenting with community-acquired SS, 23 infected patients without SS and 18 controls. Cytofluorometric techniques were used to study apoptosis, the costimulatory pathway and cytokine synthesis. Apoptosis was increased in SS compared to infected patients without SS and controls: the median values were 18, 2 and 3%, respectively, for CD4(+) T-cells (P < 0.001), and 12, 5 and 2%, respectively, for CD8(+) T-cells (P < 0.001). Patients with SS exhibited significant CD152 over-expression on T-cells, while CD86 expression was decreased on monocytes (P = 0.004). The synthesis of interleukin-2 was decreased in patients with SS compared to the other groups, while secretions of interferon-gamma and TNF-alpha were not altered. Ten surviving patients with SS showed a trend towards the normalisation of these parameters on day 7. In SS, T-cell apoptosis is related, at least in part, to the alteration of the costimulatory pathway, which, in turn, leads to significant modification of the cytokine network.

“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.

The immunological consequences of injury

Immediate and early trauma death rates are determined by "first hits" such as hypoxia, hypotension and organ injury, while late mortality correlates closely with "second hits" such as infection. An imbalance between the early systemic inflammatory response (SIRS), and the later compensatory counter-inflammatory response (CARS), is considered to be responsible for much post-traumatic morbidity and mortality. From a clinical perspective, this remains a significant healthcare problem, which has stimulated decades of experimental and clinical research aimed at understanding the functional effects of injury on the immune system. This review describes the impact of injury on the innate and adaptive immune systems. Though it is worth noting that the features of the immune response to injury overlap in many areas with immune dysregulation in sepsis, we attempt here to elucidate the mechanism by which injury predisposes to infection rather than to describe the alterations in host immunity consequent to established sepsis.

Corticosterone binding globulin regulation and thymus changes after thermal injury in mice

Thermal injury is extremely stressful, and data characterizing the systemic endocrine stress response to this injury are sparse. The objective of this study was to measure the effects of thermal injury on mice on corticosterone (Cort) levels in relation with corticosteroid-binding globulin (CBG) and thymus cell populations. The endocrine stress response was determined by measuring total Cort, free Cort, CBG binding capacity, liver CBG mRNA, and circulating CBG levels at 1, 2, 5, and 10 days postburn. Thymus cell populations were also analyzed. After thermal injury, a rapid increase of total Cort was observed in the first 48 h. This was associated with a decrease of hepatic CBG mRNA, protein levels, and binding capacity. Percentage of free Cort in the burn group peaked at day 2 postburn with a dramatic (+500%) increase. This correlated with a significant decrease of thymus cellularity (50% less). Phenotypic analyses showed that corticosensitive cells were significantly altered. After treatment (5 days), both endocrine and immune parameters returned to control levels. Our results demonstrate that, after a thermal injury, CBG is mainly responsible for Cort's action on corticosensitive immune cells.

Leukocyte apoptosis and its significance in sepsis and shock

Sepsis and multiple organ failure continue to be significant problems among trauma, burn, and the critically ill patient population. Thus, a number of laboratories have focused on understanding the role of altered apoptotic cell death in contributing to immune and organ dysfunction seen in sepsis and shock. Immune cells that undergo altered apoptotic changes include neutrophils, macrophages, dendritic cells, as well as various lymphocyte populations. Evidence of epithelial as well as endothelial cell apoptotic changes has also been reported. Although mediators such as steroids, tumor necrosis factor, nitric oxide, C5a, and Fas ligand (FasL) appear to contribute to the apoptotic changes, their effects are tissue- and cell population-selective. As inhibiting Fas-FasL signaling (e.g., gene deficiency, Fas fusion protein, or Fas short interfering RNA administration), caspase inhibition (caspase mimetic peptides), and/or the overexpression of downstream antiapoptotic molecules (e.g., Bcl-2, Akt) improve survival of septic mice, it not only demonstrates the pathological significance of this process but points to novel targets for the treatment of sepsis.

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.

Use of intracellular cytokine staining and bacterial superantigen to document suppression of the adaptive immune system in injured patients

OBJECTIVE

To determine the percentages of major T lymphocyte subsets in the circulating peripheral blood mononuclear cell population in patients with major traumatic injury at early and late time points and to determine the expression of coreceptors and cytokine production by these T cell subsets.

SUMMARY BACKGROUND DATA

Prior studies suggest that serious injury in humans suppresses the adaptive immune system as revealed by diminished proliferation and altered cytokine production in response to polyclonal T cell activation. However, the contribution of individual cell types to this immune dysfunction has not been well characterized.

METHODS

The percentage of circulating CD4+ and CD8+ T cells and the relative density of CD4 and CD8 coreceptor expression was determined by flow cytometry in 17 consecutive trauma patients (injury severity score > 20) within 24 hours of injury and at day 7. Intracellular expression of the cytokines interleukin 2 (IL-2), interferon gamma (IFNgamma), IL-4, and IL-10 were also studied after stimulation with bacterial superantigen (SEB). Patients were compared with age- and sex-matched controls and to themselves for differences between early and late cytokine expression.

RESULTS

The percentage of circulating CD4+ and CD8+ T cells was decreased versus controls at day 1 and further decreased by day 7 following injury. CD4 and CD8 cell surface expression was also decreased at days 1 and 7. CD4+ T cells in injured patients responded to SEB activation with decreased expression of IFNgamma and IL-2 on day 1 versus controls (P < 0.05) and of all 4 cytokines by day 7 (P < 0.05), while CD8+ T cells showed diminished expression of IFNgamma and IL-2 only at both time points. When day 1 and day 7 cytokine expression results were compared in the same patients, CD4+ T cells showed diminished expression of IFNgamma, IL-2, and IL-4 by day 7 (P < 0.05), but maintained expression of IL-10. CD8 T cells showed diminished expression of IFNgamma only.

CONCLUSIONS

Severe injury induces a loss of circulating CD4+ and CD8+ T lymphocytes and diminished coreceptor expression by these cells. Both T cell subsets show progressive loss of immunostimulatory cytokine production with maintenance of potentially suppressive IL-10 production. These events may have negative consequences for host defense.

Mechanisms of immune resolution

Initially after injury, the innate/proinflammatory and some aspects of the acquired immune response are up-regulated to maintain a defense against foreign pathogens, clear tissue debris present at the wound site, and orchestrate aspects of tissue remodeling, cell proliferation and angiogenic process, associated with the wound response. However, for proper wound healing to progress, this initial inflammatory response has to be regulated or shut down so as to allow for the reestablishment of matrix, recellularization, and tissue remodeling. Inability to properly resolve the extent of innate/acquired response at a site of injury can lead to poor wound healing, immune suppression, and recurrent infectious episodes. This review attempts to summarize information on regulatory mechanisms that are thought to be involved in controlling/resolving innate or acquired immune responses so as to provide a framework for use in thinking about the impact these processes and their manipulation may have on wound healing and its potential management.

Peripheral blood lymphocytes immunophenotype and serum concentration of soluble HLA class I in burn patients

The level of the soluble form of histocompatibility class I antigens, associated with beta(2)-microglobulin (sHLA-I) has been determined by an ELISA sandwich method in serum from burned patients (n=42) and healthy volunteers (n=30). The sHLA-I level was insignificantly increased in burn patients at the stage of burn shock (1284+/-324U/ml, mean+/-S.E.M.) and after day 28 postburn (1368+/-258U/ml) compared to volunteers (1150+/-90U/ml). At the same time a decrease of sHLA-I levels between 4 and 14 days (638+/-178U/ml) was determined (P<0.05). Increased levels of sHLA, though not significant, were detected in patients with TBSAB >70% in comparison to patients with TBSAB from 30 to 70% during burn shock (1493+/-528 and 1075+/-339U/ml, respectively). Expression of membranous HLA class I antigens (mHLA-I) in peripheral blood lymphocytes (PBLs) was assayed simultaneously by indirect immunofluorescence. The number of CD3(+), CD4(+), CD8(+), CD25(+), CD71(+) and CD26(+) lymphocytes was also evaluated. The expression of mHLA-I in PBLs was increased significantly in patients with TBSAB <70% at early postburn period. Daily monitoring showed that the relative numbers of CD25(+) and CD71(+) lymphocytes in patients varied greatly within short intervals of time during burn shock. The data obtained suggest that mHLA-I expression can reflect postburn lymphocyte activation. The serum content of sHLA-I does not depend on lymphocyte number or activated lymphocyte number in peripheral blood at burned patients.

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.

Pathological aspects of apoptosis in severe sepsis and shock?

Today, despite the application of contemporary operative/pharmacological approaches in the treatment of the critically ill trauma/surgery patient, we are still faced with a high incidence of patients who develop sepsis and subsequent multiple organ failure. This review attempts to summarize data gathered over the last few years, from both experimental and patient settings, that not only documents the presence of apoptosis, but begins to define its contribution to the pathology of sepsis and shock, which in turn precipitate organ injury/damage.

Burn-induced thymic apoptosis corresponds with altered TGF-beta(1) and Smad 2/3

Immune suppression is a common complication of injury. Transforming growth factor-beta(1) (TGF-beta(1)), a cytokine with diverse anti-inflammatory and anti-apoptotic effects, may play an important role. Smad 2 and Smad 3 are transcription factors that mediate the effects of TGF-beta(1). We hypothesized that burn-induced immunosuppression would be accompanied by increased apoptosis in lymphoid organs, a change likely associated with changes in TGF-beta(1) and Smad 2/3 expression. Mice were subjected to 18% body surface area flame burn. Lymph nodes, spleen, and thymus were harvested at multiple time points after injury. TGF-beta(1) and Smad 2/3 expression and levels of apoptosis were determined in whole tissue and in sorted T-cells by flow cytometry, RT-PCR, ELISA, and Western blot. TGF-beta(1) protein expression in the thymus increased from 1 to 7 days. Smad 2/3 protein expression was decreased at the same time points. This down-regulation was more dramatic in the non-T-cells than in the T-cells themselves. RT-PCR confirmed down-regulation of Smad 3 mRNA in the thymus from 3 to 6 h. Apoptosis in the thymus doubled at 1 day (6.4% control vs 12.8% burned), which corresponded with a marked decrease in thymus mass on subjective assessment. No changes were observed in other lymphoid organs. Burn injury in mice increases TGF-beta(1) expression in the thymus, while suppressing expression of its intracellular mediator, Smad 2/3. This response is most pronounced in the non-T-cell tissue, which suggests the thymic epithelial cells may be responsible for the increased thymic apoptosis. This TGF-beta(1) and Smad 2/3 counterregulation in response to injury may represent a potential mechanism for postinjury immune suppression.

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.

Differential expression and tissue compartmentalization of the inflammatory response following thermal injury

Studies have shown that both animal tissue-fixed immune cells and human peripheral blood mononuclear cell (PBMC) functions are altered after burn injury. Additional studies suggest that the burn injury-induced alterations in these divergent cell populations from different species are similar. It remains unknown, however, whether the observed changes in animal tissue-fixed immune cell function following thermal injury also occurs to a similar extent in the PBMC population. The aim of our study was to compare PBMC and tissue-fixed immune cell functions from the same animal using a murine burn model. At 7 days post-burn, mice were more susceptible to sepsis and delayed type hypersensitivity responses were suppressed. Splenocytes isolated from injured mice displayed suppressed proliferation and increased IL-10 production. In contrast, PBMC from injured mice displayed suppressed proliferation, IL-2 and IFN-gamma production. Splenic macrophage nitric oxide, PGE(2), TNF-alpha, IL-6 and IL-10 production was enhanced post-burn and IL-12 production was suppressed. PBMC from such animals displayed enhanced PGE(2) production and suppressed IL-6 and IL-12 production. These results indicate that while an immunosuppressive Th(2) phenotype (increased IL-10 and/or suppressed IL-2, IFN-gamma) was induced in both the splenic and PBMC compartments post-injury, differential expression and dimorphism in the response also exists. Thus, the assessment of only PBMC function in burn patients may not accurately reflect the patient's actual immune status at the tissue level.

Membrane and soluble forms of Fas (CD95) in peripheral blood lymphocytes and in serum from burns patients

Burn trauma results in disorders of regulation of programmed cell death called apoptosis. Apoptosis of immunocytes is associated with the expression of Fas antigen. There are two major forms of Fas molecule, membranous Fas (mFas) and soluble Fas (sFas). The last form is generated by alternative splicing and differs from mFas by lacking 21 amino acid residues containing the transmembrane domain. We determined the expression of mCD3, mCD4, mCD8 and mFas in peripheral blood lymphocytes and the level of the soluble form of Fas in serum in patients with acute thermal trauma (n=32). As the control blood of healthy volunteers (n=25) was investigated. Compared to healthy volunteers, burn patients showed a remarkable reduction in number of CD3+ lymphocytes in the 24 h following injury, which was accompanied by a decrease in CD4+ but not CD8+ subsets by indirect immunofluorescence method. The decrease of expression of mFas in the patients with acute thermal trauma at all burn disease time was determined simultaneously. We established the decrease of level of sFas during the first (404+/-25 U/ml) and second (352+/-38 U/ml) postburn 10-day periods by the ELISA method. The contents of sFas in serum of healthy volunteers was 534+/-31.8 U/ml. There were no relations between the level of membrane Fas expression and contents of the soluble Fas in serum both in clinical manifestation and survival. We suppose that it is impossible to predict outcomes of burn disease by quantity of CD95+ cells and contents of sFas in serum. However, it is probable that significant deviations from the level of sFas may be attributes of non-revealed accompanying pathology.

Inflammation, coagulopathy, and the pathogenesis of multiple organ dysfunction syndrome

OBJECTIVE

An improved understanding of the mechanisms through which infecting pathogens harm the host is leading to new formulations of the concept of sepsis. We review the roles of inflammation and coagulation in the pathogenesis of the multiple organ dysfunction syndrome, and explore the potential of new therapies to restore the fine biological balance between procoagulant and anticoagulant mechanisms that are disrupted during the life-threatening processes that lead to organ dysfunction.

DATA SOURCES

Narrative review of published primary sources in the basic and clinical literature.

DATA SUMMARY

Traditional models of host-pathogen interactions ascribe the morbidity of infection to the direct cytotoxic effects of micro-organisms on host tissues. However, abundant experimental and clinical evidence has revealed that it is the response of the host, rather than the trigger that elicited it, that is the more potent determinant of outcome. The elucidation of a complex network of host-derived inflammatory mediators raised the possibility that targeting these individually could improve patient outcomes, and some modest successes with this approach have been achieved. More recently, it is becoming evident that the inflammatory response, in turn, mediates its deleterious effects by inducing tissue hypoxia, and cellular injury, either through tissue necrosis or through the induction of programmed cell death or apoptosis. Thus, treatment strategies that target the downstream consequences of the activation of inflammation, for example, microvascular coagulation or acute adrenal insufficiency, represent the latest, and some of the most promising approaches to attenuation of the septic response to improve survival, and minimize organ dysfunction. The maladaptive sequelae of systemic inflammation, embodied in the concept of the multiple organ dysfunction syndrome, comprise the leading obstacle to survival for patients admitted to a contemporary intensive care unit. Further insights into this intimidatingly complex process will not only provide potent new therapeutic options, but promise to transform critical illness from a biological standoff, during which the clinician merely supports failing organs, to a disease that can be successfully treated.

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.

An open study comparing topical silver sulfadiazine and topical silver sulfadiazine-cerium nitrate in the treatment of moderate and severe burns

Sixty patients with moderate and severe burns were randomly assigned to receive topical silver sulfadiazine (SSD) alone (n=30) or SSD combined with cerium nitrate (SSD-CN) (n=30). There were four deaths in the SSD group and one in the SSD-CN group; more patients with higher risk severity survived in the SSD-CN group. Wound infection did not differ significantly between the groups. The rate of re-epithelialization of partial thickness burns was faster by 8 days in the SSD-CN group. The relatively dry shell-like eschar of the SSD-CN-treated burn allowed planned excisions with immediate autologous grafting and the tissue beneath was ready to accept grafting 11 days earlier than in the SSD group (p=0.03). This resulted in a significantly shorter hospital stay for those in the SSD-CN group than in the SSD group (23.3 vs. 30.7 days; p=0.03) with consequent cost savings. A higher incidence of transient stinging pain was reported with application of SSD-CN, but this was effectively managed with analgesics where necessary. The results of this study confirm the greater efficacy of SSD-CN in the treatment of burns patients.

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.

Increased activity of lymph node cells in experimental thermal injury: changes in accessory cells in injured area-draining lymph nodes

Accessory cell content and some of their functional characteristics were determined in regional lymph nodes which drain burn injury (DLN) in rats. Increase in percentages of non-specific esterase-positive cells and NBT+ macrophages and in numbers of dendritic cells were noted in cytospin preparations of draining lymph node cells (DLC) 24 and 72 h following thermal injury. An accumulation of B cells was also noted in the DLN paracortex region at these time points. Enrichment of ED1+ (rat macrophage marker) cells was noted in the adherent DLC population. Increased activity of interleukin-1 (IL-1) in conditioned medium from adherent DLC population and the increased stimulatory capacity of whole DLC or dendritic cell enriched-DLC fraction were noted in functional assays. Enrichment in accessory cells and an increase in their functional activity could contribute to the endogenous activity of regional lymph nodes which drain burned areas.

Induction of global anergy rather than inhibitory Th2 lymphokines mediates posttrauma T cell immunodepression

Depressed mitogen-induced IL-2 and IFN-gamma responses after severe mechanical or thermal injury are postulated to result from an expansion of Th2 lymphocytes with concomitant excessive production of IL-4 and/or IL-10. Here, we simultaneously assessed proliferation and Th1 (IFN-gamma) versus Th2 (IL-10, IL-4) lymphokine production in trauma patients' isolated T cells stimulated in a costimulation sufficient, antigen presenting cell independent system (anti CD3 + anti-CD4). T cells with depressed proliferation and IL-2 production simultaneously lost IL-4, IL-10, and IFN-gamma protein and mRNA responses. Exogenous IL-12 addition did not restore IFNgamma responses, but exogenous IL-2 partially restored IL-4, IFN-gamma, and IL-10 production. Although initially partially restored by exogenous IL-2 or stimulation with PMA + ionomycin, patient T cells with persisting anergy progressively lost even these lymphokine and proliferative responses. Development of global T cell anergy was not a result of lost T cell viability or protein synthesis, since it corresponded to predominance of anergic T cells with upregulated expression of CD11b, but downregulated CD28 and CD3 expression. Thus, the subset of posttrauma patients whose isolated T cells become unresponsive experienced progressively worsening global anergy, mediated not by an increased production of Th2 lymphokines, but possibly by T cell incapacity to be activated through TCR triggering or Ca(2+) mobilization.

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.

Relationships between T lymphocyte apoptosis and anergy following trauma

BACKGROUND

Severely injured trauma patients experience T cell depletion. A subset of these patients also develop T cell unresponsiveness (anergy), as characterized by the failure of their T cells to proliferate or to produce T lymphokines in response to a direct stimulus through the T cell receptor. We hypothesized that T cell apoptosis plays a role in the development of posttrauma T cell depletion and/or T cell anergy by deleting an activated T cell population. We found that moderately increased T cell depletion posttrauma is not innately deleterious or immediately responsible for anergy, but may predispose to later development of T cell anergy, possibly due to a more stringent requirement for activation of the remaining naive T cells.

METHODS

A total of 30 blunt trauma and burn patients were assessed twice weekly for the following parameters: (1) clinical outcome expressed as severity of organ dysfunction as measured by the multiple organ dysfunction syndrome score, (2) proliferative response of highly purified T cells to anti-CD3/anti-CD4, (3) level of apoptosis as determined by flow cytometric analysis of propidium iodide-stained monocyte reduced peripheral blood mononuclear cells, either unstimulated or in response to mitogenic challenge or Fas (CD95) stimulation.

RESULTS

A wide range of apoptosis levels are seen in the patients' T cells. Apoptosis is increased when all trauma patients' T cells are compared to T cells of normal volunteers. However, at the time a patients' T cells are anergic, there is no increased level of apoptosis. In fact, the point of maximum anergy (lowest proliferative response) correlates to diminished apoptotic response. Increased T cell apoptosis can be stimulated by anti-Fas antibody in trauma patients' responsive T cells but not in maximally anergic T cells. These data suggest that patients' T cell anergy is not an immediate result of apoptotic T cell depletion upon stimulation. However, patients who later develop T cell anergy have increased T cell apoptosis earlier in their clinical course than patients who never experience T cell anergy.

CONCLUSIONS

Increased levels of apoptosis are not directly associated with negative trauma patient outcome nor the immediate cause of T cell anergy. However, unusually high levels of apoptosis and development of severe T cell depletion occurring before complete activation and expansion of the posttrauma T cell response may presage anergy and subsequent organ failure.

Effects of temperature on tissue thermal injury and wound strength after photothermal wound closure

BACKGROUND AND OBJECTIVES

Our goal was to determine the effect of temperature on the induction of tissue damage after laser-welded wound closure with and without albumin solder.

STUDY DESIGN/MATERIALS AND METHODS

Multiple full-thickness skin incisions were made in a porcine model. Incisions were repaired by using a 1.32-microm laser at temperatures of 65 degrees C, 75 degrees C, 85 degrees C, or 95 degrees C with and without a 50% human albumin solder. The rate of apoptosis (programmed cell death) was quantified by counting the proportion of cells that stained positively for nuclear DNA fragmentation (nick end labeling). The distance that necrosis extended from the wound edge was also measured. The strength of the weld was measured with a tensiometer.

RESULTS

For laser-welded repairs with solder, the amount of apoptosis at 65 degrees C and 75 degrees C was comparable to that of controls but became significantly elevated at 85 degrees C and 95 degrees C. The extent of necrosis was similar to that of controls at low temperature but also increased at 95 degrees C. Incisions repaired without solder showed increased necrosis compared with those repaired with solder at temperatures of 65 degrees C, 75 degrees C, and 95 degrees C at 0-0.5 mm from the incision. Wounds repaired at 85 degrees C and 95 degrees C showed more apoptosis in the absence of solder. The increased cell death at higher temperatures correlated with significantly decreased wound strengths at 3 days after repair in the solder group. A lower rate of cell death was observed in the solder group, which correlated with superior wound strength when compared with repairs without solder at days 0 (65-95 degrees C) and 3 (95 degrees C).

CONCLUSION

Both apoptotic and necrotic cell death were used as quantitative measures of tissue injury and were accurate predictors of short-term wound strength. The addition of albumin solder decreased overall tissue injury. These results suggest that temperatures of 65-75 degrees C with solder provide the optimal conditions for maximizing acute wound strength and minimizing tissue injury.

Caspase-3-dependent organ apoptosis early after burn injury

OBJECTIVE

To examine the role played by endotoxin, tumor necrosis factor-alpha (TNF-alpha), and caspase-3 in the increased apoptosis seen in solid organs in the early period after a burn injury.

SUMMARY BACKGROUND DATA

Burn injury is often associated with immune suppression. Bacterial translocation and systemic endotoxemia have been reported after a burn injury, and caspase-3 activation due to TNF-alpha and Fas ligand (FasL) are presumed to initiate apoptosis. We hypothesized that endotoxin-induced TNF-alpha expression and caspase-3 activation could be the stimulus for the apoptosis after burn injury.

METHODS

A 20% full-thickness scald burn was used in C57BL/6 mice. Three hours after burn injury, tissue samples were obtained from the thymus, lung, liver, and spleen. Lipopolysaccharide-nonresponsive (C3H/HeJ) and TNFalpha null B6x129tnf-/- mice were also used. To detect apoptosis, hematoxylin and eosin stain, in situ TUNEL, DNA extraction, and gel electrophoresis were all performed. Caspase-3 activity and TNF-alpha and FasL mRNA were also measured.

RESULTS

Increased apoptosis and caspase-3 activity were observed in the thymus and spleen 3 hours after burn injury but were not seen in liver or lung. In the thymus and spleen, increased expression of FasL mRNA was also observed, whereas increased TNF-alpha mRNA was not. Increased apoptosis in thymus and spleen were also observed in C3H/HeJ and B6x129tnf-/- mice after burn injury. An inhibitor of the caspase-3 (Z-VAD-fmk) reduced apoptosis in both thymus and spleen.

CONCLUSIONS

In the early period after a burn injury, increased apoptosis is observed primarily in the lymphoid organs and is independent of endotoxin or TNF-alpha. The increased caspase-3 activity in thymus and spleen contributes to apoptosis in these organs.

Increased inducible apoptosis in CD4+ T lymphocytes during polymicrobial sepsis is mediated by Fas ligand and not endotoxin

Recent studies suggest that increased lymphocyte apoptosis (Ao) detected in peripheral blood T cells from burn patients appears to contribute to decreased lymphocyte immunoresponsiveness. However, while it is known that sepsis induces a marked depression in the splenocyte immune response (i.e. decreased interleukin-2, interferon-gamma production and proliferation) in response to the T-cell mitogen concanavalin A (Con A), it is unknown whether this depression is associated with an increase in inducible Ao and if so, which mediators control this process. To assess this, splenocytes were harvested from mice at 24 hr (a period associated with decreased Con A response) after the onset of polymicrobial sepsis [caecal ligation and puncture (CLP)] or sham-CLP (Sham) and then stimulated with 2.5 microg Con A/ml (24 hr). Septic mouse splenocytes stimulated with Con A, while not showing a change in their phenotypic make-up, did exhibit a marked increase in the percentage of splenocyte that were Ao+ which was associated with altered cytokine release. This appears to be due to an increase in the percentage of Ao+ cells in the CD4+ CD8- population and was associated with enhanced Fas antigen expression as well as an increase in mRNA for the Fas-FasL gene family. To determine if the changes in Ao are due to either endotoxin (a product of Gram-negative bacteria seen in CLP mice) or the expression of Fas ligand (FasL; a mediator of activation-induced lymphocyte Ao), a second set of studies examining Con A-inducible Ao was performed with splenocytes harvested from septic endotoxin-tolerant C3H/HeJ and the FasL-deficient C3H/HeJ-Fasl gld mice. The results show that increased splenocyte Ao detected following CLP is due to a FasL-mediated process and not to endotoxin. Thus the inadvertent up-regulation of FasL-mediated splenocyte Ao may contribute to the depression of splenocyte immune responses seen during polymicrobial sepsis.

Impact of treadmill exercise on early apoptotic cells in mouse thymus and spleen

Lymphocyte apoptosis occurs in response to stressors such as thermal injury, trauma, sepsis, and surgery. This study evaluated the effect of a single bout of physical exercise stress on the induction of apoptosis in murine thymocytes and splenic lymphocytes. Female C57BL/6 mice, treadmill exercised at a submaximal intensity (35 m/min, 6% grade) for 90 min or serving as controls (walking on treadmill at 12 m/min, 6% grade, 5 min), were sacrificed 5 min or 120 min after completion of exercise. The percent of apoptotic, necrotic, and viable thymocytes and splenocytes were determined by flow cytometry using annexin V FITC and propidium iodide. There was a significantly higher percent of viable splenocytes in the mice sampled 120 min after cessation of exercise than treadmill control animals (p<0.05). In the thymus, there was a significantly lower percent of apoptotic (p<0.5) and a significantly higher percent of viable (p<0.05) cells in exercised mice sampled at 120 min after exercise relative to controls. Absolute numbers of thymocytes and splenocytes did not differ by exercise treatment condition. Plasma corticosterone levels were elevated immediately after exercise and were negatively correlated with the percent of viable lymphocytes in the spleen. During the time frame sampled, submaximal exercise is associated with a lower % of thymocytes expressing early markers of apoptosis, despite elevated plasma corticosterone levels. Retention of self-reactive, viable thymocytes which would normally be deleted or selective trafficking of apoptotic thymocytes out of the thymus may be involved in the exercise effect. Additional studies are necessary to identify the mechanisms for this shift in proportions of apoptotic and viable cells in lymphoid compartments with exercise.

Splenic T lymphocytes die preferentially during heat-induced apoptosis: NuMA reorganization as a marker

We are investigating nuclear events during apoptosis in mouse splenic lymphocytes cultured immediately after isolation (controls) or after heat treatment (42 degreesC, 30 minutes), and have found that hyperthermia increased the level of apoptosis to double that of spontaneous apoptosis in controls within 6 hours. Immunolabelling for Nuclear Mitotic Apparatus Protein (NuMA) suggested that splenocytes were responding heterogeneously to the heat treatment. Whereas all nuclei in controls and about half of nuclei in heat-treated samples showed the usual diffuse nucleoplasmic labelling, 40–60% of nuclei in heated samples also contained numerous bright spots. We then examined whether the heterogeneity in NuMA organization might be an indication of a differential response of B and T lymphocytes to hyperthermia, and whether the presence of NuMA spots is related to the apoptotic process. NuMA labelling of heated fractionated splenocyte populations showed that 90% of nuclei in T-enriched cultures (less than or equal to 4% IgG+ cells), but only 25% of nuclei in B-enriched samples (less than or equal to 80% IgG+ cells), contained spots. As well, 2 hours after heat treatment of unfractionated cultures, greater than or equal to 90% of nuclei that were accumulating DNA strand breaks, as detected by TUNEL, exhibited NuMA spots. These data indicate that cells with NuMA spots are targetted for, or have initiated, the death program. Since most T cells, but few or no B cells, were spotty after heating, we conclude further that hyperthermia induces apoptosis preferentially in splenic T lymphocytes. The observation that the proportion of T cells was, on average, threefold greater in control than in heated samples after 24 hours in culture reinforces this conclusion.

Interleukin-10 promotes activation-induced cell death of SLE lymphocytes mediated by Fas ligand

Immune function in SLE is paradoxically characterized by active T cell help for autoantibody production, along with impaired T cell proliferative and cytokine responses in vitro. To reconcile these observations, we investigated the possibility that the accelerated spontaneous cell death of SLE lymphocytes in vitro is caused by an activation-induced cell death process initiated in vivo. 27 SLE patients, three patients with systemic vasculitis, seven patients with arthritis, and 14 healthy subjects were studied. Patients with clinically active SLE or systemic vasculitis had accelerated spontaneous death of PBMC with features of apoptosis at day 5 of culture. A prominent role for IL-10 in the induction of apoptosis was observed, as neutralizing anti-IL-10 mAb markedly reduced cell death in the active SLE patients by 50%, from 22.3 +/- 5.2% to 11.2 +/- 2.8%, and the addition of IL-10 decreased viability in the active SLE group, but not in the control group, by 38%. In addition, apoptosis was shown to be actively induced through the Fas pathway. The potential clinical relevance of T cell apoptosis in active SLE is supported by the correlation of increased apoptosis and IL-10 levels in vitro with low lymphocyte counts in vivo. We conclude that the spontaneous cell death observed in vitro in lymphocytes from patients with SLE and other systemic autoimmune disorders results from in vivo T cell activation, is actively induced by IL-10 and Fas ligand, and reflects pathophysiologically important events in vivo. Activation-induced cell death in vivo provides a pathogenic link between the aberrant T helper cell activation and impaired T cell function that are characteristic features of the immune system of patients with SLE.