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Query: UNIPROT:P42574 (caspase-3)
 45,978 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In human and rodent macrophages, activation of the P2X7 nucleotide receptor stimulates interleukin-1beta processing and release, apoptosis, and killing of intracellular Mycobacterium tuberculosis. Signaling pathways downstream of this ionotropic ATP receptor are poorly understood. Here we describe the rapid activation of the stress-activated protein kinase (SAPK)/JNK pathway in BAC1 murine macrophages stimulated by extracellular ATP. Brief exposure of the cells to ATP (10-30 min) was sufficient to trigger a rapid accumulation of activated SAPK that was then sustained for >120 min. Several observations indicated that the P2X7 receptor mediated this effect. 1) ATP and 3'-O-(4-benzoyl)benzoyl-ATP were the only agonistic nucleotides. 2) The effect was inhibited by oxidized ATP and the isoquinoline KN-62, two known P2X7 receptor antagonists. 3) ATP-induced SAPK activation could be recapitulated in P2X7 receptor-transfected HEK293 cells, but not in wild-type HEK293 cells. Because P2X7 receptor stimulation can rapidly activate caspase family proteases that have been implicated in the induction of the SAPK pathway, we investigated whether ATP-dependent SAPK activation involved such proteases. Brief exposure of BAC1 macrophages to extracellular ATP induced DNA fragmentation, alpha-fodrin breakdown, and elevated levels of caspase-3-type activity. Asp-Glu-Val-Asp-cho, a caspase-3 inhibitor, inhibited ATP-induced DNA fragmentation and alpha-fodrin proteolysis, but had no effect on ATP-induced SAPK activation. Tyr-Val-Ala-Asp-chloromethyl ketone, a caspase-1 inhibitor, prevented ATP-induced release of processed interleukin-1beta, but not ATP-dependent SAPK activity. We conclude that activation of ionotropic P2X7 nucleotide receptors triggers a strong activation of SAPK via a pathway independent of caspase-1- or caspase-3-like proteases.
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PMID:Stress-activated protein kinase/JNK activation and apoptotic induction by the macrophage P2X7 nucleotide receptor. 1085 31

1. Extracellular ATP is a potent signaling molecule that modulates a myriad of cellular functions through the activation of P2 purinergic receptors and is cytotoxic to a variety of cells at higher concentrations. The mechanism of ATP-elicited cytotoxicity is not fully understood. In this study, we investigated the effect of extracellular ATP on the human hepatoma Li-7A cells. 2. We observed a time- and dose-dependent growth inhibition of Li-7A cells by ATP, which is accompanied by an increase in the active form of caspase-3 as well as increased cleavage of its substrate, poly (ADP-ribose) polymerase. The cytotoxic effect of extracellular ATP was not mediated by the P2X7 receptor, since (1).the effect was not abolished by the P2X7 receptor antagonists oxidized ATP and KN-62, and (2).extracellular ADP, AMP, and adenosine were also cytotoxic. 3. We found that ATP and ADP were degraded to adenosine by Li-7A cells and that treatment of Li-7A cells by adenosine resulted in growth inhibition and caspase-3 activation, indicating that adenosine is the apoptotic agent. Using adenosine receptor agonists and antagonists, as well as inhibitors of adenosine transport and deamination, we showed that the cytotoxic effect of adenosine is specifically mediated by the A3 receptor even though transcripts of A1, A2A, A2B, and a splice variant of the P2X7 receptors were detected in Li-7A cells by RT-PCR. 4. Cytotoxicity caused by exogenous ATP and adenosine was completely abolished by the caspase-3 inhibitor Z-DEVD-FMK, demonstrating the central role of caspase-3 in apoptosis of Li-7A cells.
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PMID:Extracellular ATP and adenosine induce cell apoptosis of human hepatoma Li-7A cells via the A3 adenosine receptor. 1453 Feb 17

We have investigated the expression of P2X5, P2X7, P2Y1, and P2Y2 receptor subtypes in 8- to 11-wk-old human fetal epidermis in relation to markers of proliferation (proliferating cell nuclear antigen (PCNA) and Ki-67), keratinocyte differentiation (cytokeratin K10 and involucrin), and markers of apoptosis (TdT-mediated dUTP nick end labeling (TUNEL) and anti-caspase-3). Immunohistochemistry showed that each of the four receptors was expressed in spatially distinct zones of the developing epidermis: P2Y1 receptors were found in the basal layer, P2X5 receptors were predominantly in the basal and intermediate layers, and both P2Y2 and P2X7 receptors were in the periderm. Colocalization experiments suggested different functional roles for these receptors. P2Y1 receptors were found in fetal keratinocytes positive for PCNA and Ki-67, suggesting a role in proliferation. P2X5 receptors double labeled with differentiated fetal keratinocytes that were positive for cytokeratin K10, suggesting a role in differentiation. P2X7 receptors colocalized with anti-caspase-3 antibody and were also expressed in periderm cells positive for TUNEL, suggesting a role in periderm cell apoptosis. P2Y2 receptors were found only in periderm cells and may have a role in chloride and fluid secretion into the amniotic fluid.
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PMID:Purinergic receptors are part of a signaling system for keratinocyte proliferation, differentiation, and apoptosis in human fetal epidermis. 1470 18

Normal human ectocervical epithelial (hECE) cells undergo apoptosis in culture. Baseline apoptosis could be increased by shifting cells to serum-free medium and blocked by lowering extracellular calcium. Treatment with the ATPase apyrase attenuated baseline apoptosis, suggesting that extracellular ATP and purinergic mechanisms control the apoptosis. Treatment with ATP and the P2X7 receptor analog 2'-3'-O-(4-benzoylbenzoyl)adenosine 5'-triphosphate (BzATP) increased apoptosis significantly, in a time- and dose-related manner. The threshold of ATP effect was 0.5 microM in hECE cells and approximately 1 microM in CaSki cancer cells. The apoptotic effect of BzATP was additive in part to that of tumor necrosis factor (TNF)-alpha, and it could be attenuated by lowering extracellular calcium and by treatment with the caspase-9 inhibitor Leu-Glu-His-Asp-O-methyl-fluoromethylketone (LEHD-FMK). Treatment with BzATP activated caspase-9, and, in contrast to TNF-alpha, it had only a mild effect on caspase-8. Both BzATP and TNF-alpha activated caspase-3, suggesting that BzATP activates predominantly the mitochondrial apoptotic pathway. Both hECE and CaSki cells secrete ATP into the extracellular fluid, and mean ATP activity in conditioned medium was approximately 0.5 microM, which is in the range of values that suffice to activate the P2X7 receptor. On the basis of these findings we propose a novel autocrine-paracrine mechanism of cervical cell apoptosis that operates by P2X7 receptor control of cytosolic calcium and utilizes the mitochondrial apoptotic pathway.
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PMID:P2X7 receptor-mediated apoptosis of human cervical epithelial cells. 1526 6

Large amounts of adenosine 5'-triphosphate (ATP) released from cellular sources under pathological conditions such as ischemia may activate purinoceptors of the P2X and P2Y types. In the present study, the expression of the P2X7 receptor-subtype in the brain cortex of spontaneously hypertensive rats was investigated using a permanent focal cerebral ischemia model. Immunocytochemistry with antibodies raised against the intracellular C-terminus of the P2X7 receptor showed a time-dependent upregulation of labeled cells in the peri-infarct region after right middle cerebral artery occlusion (MCAO) in comparison to controls. Double immunofluorescence visualized with confooal laser scanning microscopy indicated the localization of the P2X7 receptor after ischemia on microglial cells (after 1 and 4 days), on tubulin betaIII-labeled neurons (after 4 and 7 days), and on glial fibrillary acidic protein (GFAP)-positive astrocytes (after 4 days). In the following experiments, changes occurring 4 days after MCAO were investigated in detail. Western blot analysis of the cortical tissue around the area of necrosis indicated an increase in the P2X7 receptor protein. Immunoelectron microscopy revealed the receptor localization on synapses (presynaptically), on dendrites, as well as on the nuclear membrane of neurons (postsynaptically) and glial cells. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling in combination with P2X7 receptor immunocytochemistry indicated a co-expression on the apoptotic cells. Active caspase 3 was especially observed on GFAP-positive astrocytes. In conclusion, the present data demonstrate a postischemic, time-dependent upregulation of the P2X7 receptor-subtype on neurons and glial cells and suggest a role for this receptor in the pathophysiology of cerebral ischemia in vivo.
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PMID:P2X7 receptor expression after ischemia in the cerebral cortex of rats. 1529 Aug 94

The present study investigated the antiapoptotic effects of estrogen in normal and cancer human cervical cells and the mechanisms involved. Baseline apoptosis in human cervical epithelial cells is mediated predominantly by P2X7-receptor-induced, Ca(2+)-dependent activation of the mitochondrial (caspase-9) pathway. Treatment with 10 nM 17beta-estradiol blocked apoptosis induced by the P2X7-receptor ligands ATP and 2',3'-0-(4-benzoylbenzoyl)-ATP in normal human cervical epithelial cells (hECEs) and attenuated the effect in hECEs immortalized with human papillomavirus-16 (ECE16-1) and the cancer cervical cells HT3 and CaSki. Diethylstilbestrol and to a lesser degree estrone could mimic the effects of 17beta-estradiol, whereas actinomycin-D and cycloheximide attenuated the response. The antiapoptotic effect of estrogen did not depend on cell cycle phase, and in both normal and cancer cervical cells, it involved attenuation of activation of caspase-9 and the terminal caspase-3. However, involvement of cascades upstream to the caspase-9 differed in normal vs. cancer cervical cells. In the normal hECEs estrogen blocked P2X7-receptor-induced calcium influx. In contrast, in the cancer CaSki cells, estrogen up-regulated expression of Bcl-2 and attenuated Ca(2+)-induced mitochondrial swelling (i.e. formation of mitochondrial permeability transition pores). Estrogen had no effect on P2X7-receptor-induced apoptosis in the anaplastic SiHa and Hela cells. These results point to a novel antiapoptotic effect of estrogen in the cervix that is independent of its mitogenic function. The results also suggest that cancer cervical cells evolved antiapoptotic mechanisms that enable the cells to evade apoptosis and could therefore promote tumor progression.
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PMID:Antiapoptotic effects of estrogen in normal and cancer human cervical epithelial cells. 1531 52

The P2X7 nucleotide receptor is an ATP-gated ion channel that plays an important role in bone cell function. Here, we investigated the effects of L: -tyrosine derivatives 1-3 as potent P2X7 antagonists on human primary osteoclasts. We found that the level of expression of P2X7 receptor increased after treatment with the derivatives 1-3, together with the induction of high levels of apoptosis. This effect is associated with activation of caspase-3 and inhibition of expression of IL-6. Interestingly, no pro-apoptotic effect of compounds 1-3 was found on human osteoblasts. Our results suggest that the development of specific P2X7 receptor antagonists may be considered a useful tool to modulate apoptosis of human osteoclasts. Since bone loss due to osteoclast-mediated resorption represents one of the major unsolved problem in osteopenic disorders, the identification of molecules able to induce apoptosis of osteoclasts is of great interest for the development of novel therapeutic strategies.
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PMID:N-Arylpiperazine modified analogues of the P2X7 receptor KN-62 antagonist are potent inducers of apoptosis of human primary osteoclasts. 1622 88

Macrophage ionotropic P2X7 receptors regulate cell-death through ill-defined signaling pathways. Here, we investigated the role of ceramide, an apoptogenic sphingolipid and showed that ATP stimulated ceramide accumulation in macrophages. Benzoylbenzoyl-ATP, a potent P2X7 agonist, was able to mimic the effects of ATP on ceramide accumulation while oxidized ATP had the opposite effect. Ceramide accumulation was blocked by de novo ceramide biosynthesis inhibitors. Interestingly, ATP-induced caspase-3/7 activation was dependent on ceramide generation. Finally, we showed that de novo ceramide biosynthesis is involved in ATP-induced macrophage death in a caspase-dependent manner. Our results indicate a novel role of ceramide in P2X7-regulated cell-death.
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PMID:Involvement of de novo ceramide biosynthesis in macrophage death induced by activation of ATP-sensitive P2X7 receptor. 1635 73

Peptide antibiotics possess the potent antimicrobial activities against invading microorganisms and contribute to the innate host defense. An antibacterial cathelicidin, human cationic antibacterial protein of 18 kDa/LL-37, not only exhibits potent bactericidal activities against Gram-negative and Gram-positive bacteria, but also functions as a chemoattractant for immune cells, including neutrophils. During bacterial infections, the life span of neutrophils is regulated by various pathogen- and host-derived substances. In this study, to further evaluate the role of LL-37 in innate immunity, we investigated the action of LL-37 on neutrophil apoptosis. Neutrophil apoptosis was assessed using human blood neutrophils based on the morphological changes. Of note, LL-37 dose dependently (0.01-5 microg/ml) suppressed neutrophil apoptosis, accompanied with the phosphorylation of ERK-1/2, expression of Bcl-x(L) (an antiapoptotic protein), and inhibition of caspase 3 activity. Interestingly, LL-37-induced suppression of neutrophil apoptosis was attenuated by the antagonists for formyl-peptide receptor-like 1 (FPRL1) and P2X7 nucleotide receptor. Of importance, the agonists for FPRL1 and P2X7 apparently suppressed neutrophil apoptosis. Collectively, these observations indicate that LL-37 cannot only kill bacteria, but also modulate (suppress) neutrophil apoptosis via the activation of FPRL1 and P2X7 in bacterial infections. Suppression of neutrophil apoptosis results in the prolongation of their life span, and may be advantageous for host defense against bacterial invasion.
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PMID:An antimicrobial cathelicidin peptide, human CAP18/LL-37, suppresses neutrophil apoptosis via the activation of formyl-peptide receptor-like 1 and P2X7. 1649 63

Trauma causes immediate cytokine release and the systemic inflammatory response syndrome (SIRS), often preceding sepsis and septic shock. Mechanisms may involve P2X7 ion channel activation via adenosine 5'-triphosphate (ATP) released from surrounding tissue and platelets. A number of single nucleotide polymorphisms (SNPs) influence the nature and magnitude of P2X7-stimulated cytokine release and apoptosis. In whole blood and isolated mononuclear blood cells (PBMCs) of donors with wild-type and heterozygous mutated genotypes, we found downregulated IL-8 and caspase-3 activation but no reproducible effect on tumor necrosis factor (TNF)-alpha and IL-1beta release. IL-8 and caspase-3 activation were both influenced by paxilline, an inhibitor of calcium-activated potassium channels. Confocal laser scanning microscopy demonstrated that calcium signaling is affected by paxilline as well. We propose that blockade of potassium channels may be relevant to attenuate ATP-induced cytokine responses and apoptosis. The presence of functional SNPs in heterozygous genotypes appears to play a role.
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PMID:Role of ATP in trauma-associated cytokine release and apoptosis by P2X7 ion channel stimulation. 1738 68


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