Why is apoptosis important to clinicians?

Chloral Hydrate Treatment Induced Apoptosis of Macrophages via Fas Signaling Pathway

BACKGROUND There are recent reports on several anesthetics that have anti-inflammatory and anti-infective effects apart from their uses for pain relief and muscle relaxation. Chloral hydrate is a clinical anesthetic drug and sedative that has also been reported to attenuate inflammatory response, but the mechanisms are not clearly understood. MATERIAL AND METHODS This study investigated the effect of chloral hydrate treatment on the apoptosis of macrophages and explored the underlying mechanisms. RAW264.7 macrophages were treated with various concentrations of chloral hydrate for various lengths of time. Morphological changes were observed under a light microscope and apoptosis was detected with annexin-V-FITC/PI double-staining assay, Hochest 33258 and DNA ladder assay, the expression of Fas/FasL was detected with a flow cytometer, and the Fas signaling pathway was assessed by Western blotting. RESULTS The results showed that chloral hydrate treatment induced the morphology of RAW264.7 macrophages to change shape from typical fusiform to round in a concentration- and time-dependent manner, and was finally suspended in the supernatant. For the induction of apoptosis, chloral hydrate treatment induced the apoptosis of RAW264.7 macrophages from early-to-late stage apoptosis in a concentration- and time-dependent manner. For the mechanism, chloral hydrate treatment induced higher expression of Fas on RAW264.7 macrophages, and was also associated with changes in the expression of proteins involved in Fas signaling pathways. CONCLUSIONS Chloral hydrate treatment can induce the apoptosis of RAW264.7 macrophages through the Fas signaling pathway, which may provide new options for adjunctive treatment of acute inflammation.

Caspase-3-mediated splenic lymphocyte apoptosis in a porcine model of cardiac arrest

BACKGROUND

Postresuscitation immunologic dysfunction contributes to the low survival rate after successful resuscitation, but its mechanism remains poorly understood. The mitochondrial apoptosis pathway is initiated by the Bcl-2/Bax-controlled and caspase-3-mediated pathway, this study investigated whether mitochondrial pathway-mediated splenic lymphocyte apoptosis is involved in the postresuscitation immunosuppression in a porcine model of cardiac arrest.

METHODS

Twenty-eight Wuzhishan miniature pigs were randomly divided into 2 groups: return of spontaneous circulation (ROSC; n = 22) and sham-operated (n = 6). Return of spontaneous circulation was initiated after 8 minutes of untreated ventricular fibrillation. After successful ROSC, CD4(+) and CD8(+) lymphocyte subsets were determined by flow cytometry. Surviving pigs were randomly assigned to be humanely killed at 24 and 72 hours after ROSC (n = 8 per group). Spleens were removed for histopathologic analysis, Western blotting, quantitative real-time polymerase chain reaction, and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay.

RESULTS

A high degree of splenic lymphocyte apoptosis was observed in the ROSC group. Expression of Bax and activated caspase-3 was markedly increased in splenic tissue, whereas Bcl-2 was significantly decreased in the post-ROSC group compared with the sham-operated group (P < .05) at 24 and 72 hours after ROSC. The messenger RNA levels of activated caspase-3 of splenic tissue were significantly elevated at 24 and 72 hours after ROSC.

CONCLUSION

These results demonstrates that Bcl-2/Bax and caspase-3-mediated mitochondrial apoptosis signaling pathway may contribute to abnormal splenic lymphocyte apoptosis, which may be one of the main pathologic mechanisms of postresuscitation disturbance of immunologic function in a porcine model of cardiac arrest.

Is suppression of apoptosis a new therapeutic target in sepsis?

Sepsis remains as a leading cause of death in critically ill patients. Unfortunately, there have been very few successful specific therapeutic agents that can significantly reduce the attributable mortality and morbidity of sepsis. Developing novel therapeutic strategies to improve outcomes of sepsis remains an important focus of ongoing research in the field of critical care medicine. Apoptosis has recently been identified as an important mechanism of cell death and evidence suggests that prevention of cell apoptosis can improve survival in animal models of sepsis and endotoxaemia. In this review article, we summarise the critical role of apoptosis of the immune cells in the pathophysiology of sepsis and propose that blocking cell-signaling pathways leading to apoptosis may present a promising specific therapy for sepsis. Various methods to inhibit apoptosis including the cell surface Fas receptor pathway inhibitors, caspase inhibitors, over-expression of anti-apoptotic genes and small interfering ribonucleic acid therapy are discussed.

Ascorbate deficiency results in impaired neutrophil apoptosis and clearance and is associated with up-regulation of hypoxia-inducible factor 1alpha

Some cells, including neutrophils, accumulate high intracellular ascorbate concentrations, which suggests that they have an important function in these cells. In this study we have used L-gulono-gamma-lactone oxidase (Gulo)-/- mice, which are unable to synthesize ascorbate, to generate ascorbate-deficient neutrophils and have used these to investigate the effect of ascorbate on neutrophil function. Peritoneal neutrophils from ascorbate-deficient animals had normal morphology and respiratory burst activity but failed to undergo spontaneous apoptosis, determined by morphology and the surface expression of phosphatidylserine. Initially, there was increased cell survival, but death eventually occurred by necrosis within 48 h. Neutrophils persisted in thioglycollate-induced inflammation in Gulo-/- mice with the later appearance of necrotic cells, suggesting that apoptosis was also affected in vivo. Also, ascorbate-deficient neutrophils were not recognized by macrophages in an in vitro assay for phagocytosis, providing further evidence for defective apoptosis and clearance. Neutrophils from Gulo-/- mice had elevated levels of hypoxia-inducible factor (HIF)-1alpha, a transcription factor regulated by Fe2+-dependent hydroxylases which require ascorbate for optimal activity. HIF-1alpha has been shown previously to inhibit neutrophil apoptosis under hypoxic conditions. Our results suggest that in ascorbate deficiency, up-regulation of HIF-1alpha blocks neutrophil apoptosis under normoxic conditions and that this represents a novel and important function for vitamin C in inflammatory cells.

Apoptotic Changes of Middle East Jaw Lymphoma

Jaw lymphoma a highly malignant tumor affects children between two and eight years, duration of illness between two and three weeks, and the general condition of severe toxicity, and the death rate is 91.9%. The aim of this cellular study is to show the apoptotic changes associated with these tumors. Twenty-four children, 13 boys and 11 girls, were reported with jaw lymphoma and studied for apoptotic detection of the tumor through morphological assessment by using ground section and electron microscopy. Ground section shows lymphoblastic lymphoma, darkly-stained of ribonucleic acid, also apoptotic changes seen in some of the cells. Electron microscopy showed high mitotic figures, lymphoblast transformed to plasma cell, high nucleocytoplasmic ratio, some cells showed double nuclei, some nuclei are crested in shape or convoluted, degenerative changes seen in some of the cells, chromatin clumps near the nuclear membrane, mitochondria showing homogenous and degenerative changes, virus like particles seen in this nucleus and cytoplasm. The presence of low-level of apoptosis is a poor prognostic feature of jaw lymphoma due to homogeneity and degenerative changes of the mitochondria and disruption of the cell surface.

Accelerated lymphocyte death in sepsis occurs by both the death receptor and mitochondrial pathways

Patients with sepsis are immune compromised, as evidenced by their failure to clear their primary infection and their propensity to develop secondary infections with pathogens that are often not particularly virulent in normal healthy individuals. A potential mechanism for immunosuppression in sepsis is lymphocyte apoptosis, which may occur by either a death receptor or a mitochondrial-mediated pathway. A prospective study of blood samples from 71 patients with sepsis, 55 nonseptic patients, and 6 healthy volunteers was undertaken to quantitate lymphocyte apoptosis and determine cell death pathways and mechanisms of apoptosis. Apoptosis was evaluated by flow cytometry and Western blotting. Lymphocyte apoptosis was increased in CD4 and CD8 T cells, B cells (CD20), and NK cells (CD56) in septic vs nonseptic patients. Samples taken sequentially from 10 patients with sepsis showed that the degree of CD3 T cell apoptosis correlated with the activity of his/her sepsis. In septic patients, apoptotic lymphocytes were positive for active caspases 8 and 9, consistent with death occurring by both mitochondrial-mediated and receptor-mediated pathways. In support of the concept that both death pathways were operative, lymphocyte apoptosis occurred in cells with markedly decreased Bcl-2 (an inhibitor of mitochondrial-mediated apoptosis) as well as cells with normal concentrations of Bcl-2. In conclusion, apoptosis occurs in a broad range of lymphocyte subsets in patients with sepsis and correlates with the activity of the disease. Lymphocyte loss occurs by both death receptor and mitochondrial-mediated apoptosis, suggesting that there may be multiple triggers for lymphocyte apoptosis.

Role of apoptotic cell death in sepsis

Sepsis is the leading cause of morbidity and mortality in critically ill patients in many intensive care units. The pathophysiology of organ failure and death in patients with sepsis remain elusive. This review focuses on recent advances in our understanding of the mechanisms of cell death in sepsis, the types of cells that are dying and the consequences on immunity. Extensive apoptotic death results in immune cell depletion and may compromise the ability of the patient to eradicate the primary infection and predispose to secondary nosocomial infections. Peripheral circulating lymphocyte apoptosis is also increased in patients with sepsis and correlates with the severity of the disease. In addition, recent evidence indicates that uptake of apoptotic cells impairs the immune function of surviving cells and contributes to immunosuppression. This new understanding of sepsis may lead to novel therapeutic approaches including pharmacological agents that block apoptosis.

A curious experiment: the paradigm switch from observation and speculation to experimentation, in the understanding of neuromuscular function and disease

The four-link chain of the motor unit represents the contemporary end-point of some two millennia of evolving knowledge in neuroscience. The paradigm shift in neuromuscular epistemology occurred in the mid-17th century. In 1666, the newly graduated Dutch doctor, Jan Swammerdam (1637-1680) published his former investigations of dissected nerve-muscle preparations. These experiments comprised the quantum leap from observation and speculation, to that of experimentation in the field of neuroanatomy and neurophysiology. In what he termed 'A Curious Experiment' he also described the phenomenon of intrinsic muscle excitability - "I cannot observe that the muscle in the living animal ever absolutely ceases from all motion". Eighty years later (1752), von Haller demonstrated experimentally that irritability (contractility) was an intrinsic property of all muscular tissue; and distinguished between the sensibility of nerve impulses and the irritability of muscular contraction. This experimental progression from Swammerdam to von Haller culminated in 1850, when Claude Bernard's studies in experimental pharmacology confirmed that muscle was a functional unit, independent of any electrical innervation via its supplying nerve. This account comprises an audit of Swammerdam's work in the perspective of neuromuscular knowledge.

Endothelial cell apoptosis in sepsis

OBJECTIVE

To discuss a potential role for endothelial cell apoptosis in the pathogenesis of sepsis.

DATA SOURCES

Studies published in biomedical journals and studies from the authors' laboratory.

STUDY SELECTION

In vitro and in vivo studies of endothelial cell apoptosis in endotoxin and sepsis models.

DATA EXTRACTION AND SYNTHESIS

Relevant studies that investigate the role of apoptosis in endotoxemia and sepsis are presented. The divergent results of the different studies and the potential reasons for the discrepant findings are presented. The importance of apoptosis in sepsis and the potential impact on endothelial cells and organ function are highlighted.

CONCLUSIONS

Apoptosis is an important mechanism of lymphocyte and gastrointestinal epithelial cell death in sepsis. Although abundant in vitro studies indicate that endothelial cell apoptosis can occur in response to certain pathogenic organisms (e.g., Rickettsia rickettsii), data documenting endothelial cell apoptosis in in vivo models of sepsis are lacking. Because endothelial cells that undergo apoptosis detach from the vessel basement membrane, enter the circulation, and are rapidly cleared, it may be difficult to detect endothelial cell apoptosis in in vivo models of sepsis. The impact of endothelial cell apoptosis in sepsis may either be detrimental or beneficial to host survival, depending on the particular pathogen.