Prodomains--adaptors--oligomerization: the pursuit of caspase activation in apoptosis

The fly caspases

Caspases, a group of cysteine proteases, constitute the effector arm of the cell death machinery. There are seven caspases known in Drosophila, three of which contain long amino-terminal prodomains. Although, compared to mammalian caspases, much less is known about the biology of Drosophila caspases, many studies have shown that caspases are essential for programmed cell death in the fly and are likely to be regulated in ways similar to their mammalian counterparts. Studies on fly caspases have revealed some new insights on cell death regulation. For example, the transcript for the fly caspase DRONC is regulated by the hormone ecdysone during programmed cell death in specific tissues. Recent data on DRONC also suggest that some fly caspases may have unique substrate specificities not ascribed to mammalian caspases. The presence of multiple caspases in Drosophila indicates that apoptotic pathways in insects are likely to be as complex as in vertebrates.

Frequent nuclear localization of ICAD and cytoplasmic co-expression of caspase-8 and caspase-3 in human lymphomas

Lymphoma cells often display in vitro resistance to FAS-induced apoptosis, in which caspases act as crucial cell death effectors. Following FAS stimulation, caspase-8 activates caspase-3, which in turn activates the caspase-activated DNAse (CAD) by proteolysis of its inhibitor (ICAD). To investigate the mechanism of FAS resistance, the expression of caspase-8 was analysed by immunohistochemistry, together with that of the substrates caspase-3 and ICAD, in 52 representative samples from non Hodgkin's lymphoma (NHL), 12 from Hodgkin's disease (HD), and eight benign lymphoid tissues. In benign tissues, caspase-8 was co-expressed with caspase-3 in the cytoplasm in germinal centre (GC) cells and was co-expressed with ICAD in the nuclei of the mantle and marginal zone cells. ICAD expression was weak or absent in GC cells. Cytoplasmic staining for both caspase-8 and caspase-3 was present in 11/12 cases of diffuse large cell B-NHL. Caspase-8 positivity was nuclear and cytoplasmic in 9/9 follicular NHLs, in 5/5 mantle cell NHLs and in 6/6 marginal zone NHLs. Five out of six peripheral T-cell NHLs expressed cytoplasmic caspase-8. Ten out of the 12 HD cases lacked significant cytoplasmic staining for caspase-3 and caspase-8 in the majority of Reed-Sternberg cells. All lymphoma cases exhibited predominant nuclear ICAD positivity. Subcellular fractionation analysis of three lymphoma samples and normal mantle zone cells confirmed that ICAD and caspase-8 were at least partly localized in the nucleus. These results show that the profile of caspase-8 expression is correlated with histological lymphoma subtypes; that caspase-8 is co-expressed with caspase-3 in GC cells and their neoplastic counterparts; that ICAD has an immunohistochemical nuclear localization in vivo; and that caspase-8 and ICAD can be co-expressed in the nuclei of mantle zone and marginal zone cells; their unexpected nuclear localization allows a reappraisal of the biochemical cascade of caspase activation.

Mildly oxidized low density lipoprotein activates multiple apoptotic signaling pathways in human coronary cells

Apoptosis of arterial cells induced by oxidized low density lipoproteins (OxLDL) is thought to contribute to the progression of atherosclerosis. However, most data on apoptotic effects and mechanisms of OxLDL were obtained with extensively oxidized LDL unlikely to occur in early stages of atherosclerotic lesions. We now demonstrate that mildly oxidized LDL generated by incubation with oxygen radical-producing xanthine/xanthine oxidase (X/XO) induces apoptosis in primary cultures of human coronary endothelial and SMC, as determined by TUNEL technique, DNA laddering, and FACS analysis. Apoptosis was markedly reduced when X/XO-LDL was generated in the presence of different oxygen radical scavengers. Apoptotic signals were mediated by intramembrane domains of both Fas and tumor necrosis factor (TNF) receptors I and II. Blocking of Fas ligand (FasL) reduced apoptosis by 50% and simultaneous blocking of FasL and TNF receptors by 70%. Activation of apoptotic receptors was accompanied by an increase of proapoptotic and a decrease in antiapoptotic proteins of the Bcl-2 family and resulted in marked activation of class I and II caspases. Mildly oxidized LDL also activated MAP and Jun kinases and increased p53 and other transcription factors (ATF-2, ELK-1, CREB, AP-1). Inhibitors of Map and Jun kinase significantly reduced apoptosis. Our results provide the first evidence that OxLDL-induced apoptosis involves TNF receptors and Jun activation. More important, they demonstrate that even mildly oxidized LDL formed in atherosclerotic lesions may activate a broad cascade of oxygen radical-sensitive signaling pathways affecting apoptosis and other processes influencing the evolution of plaques. Thus, we suggest that extensive oxidative modifications of LDL are not necessary to influence signal transduction and transcription in vivo.

Procathepsin L self-association as a mechanism for selective secretion

The lysosomal cysteine pro-protease procathepsin L was enriched in dense vesicles detectable when microsomes prepared from wild-type or transformed mouse fibroblasts were resolved on sucrose gradients. These dense vesicles did not comigrate with proteins characteristic of the endoplasmic reticulum, Golgi, endosomes or lysosomes. When gradient fraction vesicles were lysed at acidic pH in the presence of excess mannose 6-phosphate to prevent binding to mannose phosphate receptors, the majority of the procathepsin L was associated with the membrane, not the soluble, fraction. Immunogold labeling of procathepsin L in thin sections of cells or gradient fractions, using antibodies directed against the propeptide to avoid detection of the mature enzyme in dense lysosomes, revealed that the proenzyme was concentrated in dense cores localized in small vesicles near the plasma membrane and in multivesicular bodies. Consistent with the density of the gradient fraction and the electron density of the cores, yeast two-hybrid assays indicated the proenzyme could bind itself but could not interact with the aspartic proprotease procathepsin D. The data suggest that in mouse fibroblasts procathepsin L may self-associate into aggregates, initiating the formation of dense vesicles that could mediate the selective secretion of procathepsin L independent of mannose phosphate receptors.

Bcl-2 inhibits calcineurin-mediated Fas ligand expression in antitumor drug-treated baby hamster kidney cells

It is well known that human leukemia cells, such as HL-60 and U937 are sensitive to antitumor drugs, but human normal lung fibroblasts, such as WI-38 cells are resistant to the drugs. However, the mechanisms of the different responses to apoptosis in these cell lines remain unclear. We report here that an increase of Fas and Fas ligand (FasL) expression was required for antitumor drug-induced apoptosis in WI-38 and baby hamster kidney (BHK) cells, but not in HL-60 cells. Then, we used BHK cells transfected with the bcl-2 gene to investigate the involvement of complex formation of Bcl-2 and calcineurin. Calcineurin was imported to the nucleus in response to the drug treatment. Overexpression of Bcl-2 and cyclosporin A treatment inhibited the nuclear import and FasL expression, and as a result, both inhibited apoptosis. Although a caspase inhibitor, z-Asp-CH2-DCB, suppressed the drug-induced apoptosis, it failed to inhibit the drug-induced expression of Fas and FasL. These findings suggest that initially the Fas / FasL system is activated by calcineurin-dependent transcription followed by activation of the downstream caspase cascade resulting in antitumor drug-induced apoptosis in BHK cells, but not in HL-60 cells. Furthermore, Bcl-2 inhibits the nuclear import of calcineurin and suppresses calcineurin-mediated FasL expression during antitumor drug-induced apoptosis.

Heat shock proteins--modulators of apoptosis in tumour cells

Apoptosis is a genetically programmed, physiological method of cell destruction. A variety of genes are now recognised as positive or negative regulators of this process. Expression of inducible heat shock proteins (hsp) is known to correlate with increased resistance to apoptosis induced by a range of diverse cytotoxic agents and has been implicated in chemotherapeutic resistance of tumours and carcinogenesis. Intensive research on apoptosis over the past number of years has provided significant insights into the mechanisms and molecular events that occur during this process. The modulatory effects of hsps on apoptosis are well documented, however, the mechanisms of hsp-mediated protection against apoptosis remain to be fully defined, although several hypotheses have been proposed. Elucidation of these mechanisms should reveal novel targets for manipulating the sensitivity of leukaemic cells to therapy. This review aims to explain the currently understood process of apoptosis and the effects of hsps on this process. Several proposed mechanisms for hsp protection against apoptosis and the therapeutic implications of hsps in leukaemia are also discussed.

Evidence for Agrobacterium-induced apoptosis in maize cells

Agrobacterium spp. can genetically transform most dicotyledonous plant cells whereas many monocot species are recalcitrant to Agrobacterium-mediated transformation. One major obstacle is that co-cultivation of Agrobacterium spp. with plant tissues often results in cell death. Report here is that, in maize tissues, this process resembles apoptosis, with characteristic DNA cleavage into oligonucleosomal fragments and morphological changes. Two anti-apoptotic genes from baculovirus, p35 and iap, had the ability to prevent the onset of apoptosis triggered by Agrobacterium spp. in maize tissues. p35 is reported to act as a direct inhibitor of a certain class of proteases (caspase) whereas i.a.p. may act upstream to prevent their activation. This evidence raises the possibility that caspase-like proteases may also be involved in the apoptotic pathway in plant cells.

Apoptotic crosstalk between the endoplasmic reticulum and mitochondria controlled by Bcl-2

Apoptosis involves mitochondrial steps such as the release of the apoptogenic factor cytochrome c which are effectively blocked by Bcl-2. Although Bcl-2 may have a direct action on the mitochondrial membrane, it also resides and functions on the endoplasmic reticulum (ER), and there is increasing evidence for a role of the ER in apoptosis regulation as well. Here we uncover a hitherto unrecognized, apoptotic crosstalk between the ER and mitochondria that is controlled by Bcl-2. After triggering massive ER dilation due to an inhibition of secretion, the drug brefeldin A (BFA) induces the release of cytochrome c from mitochondria in a caspase-8- and Bid-independent manner. This is followed by caspase-3 activation and DNA/nuclear fragmentation. Surprisingly, cytochrome c release by BFA is not only blocked by wild-type Bcl-2 but also by a Bcl-2 variant that is exclusively targeted to the ER (Bcl-2/cb5). Similar findings were obtained with tunicamycin, an agent interfering with N-linked glycosylations in the secretory system. Thus, apoptotic agents perturbing ER functions induce a novel crosstalk between the ER and mitochondria that can be interrupted by ER-based Bcl-2.

DNA repair is activated in early stages of p53-induced apoptosis

p53 is a complex molecule involved in apoptosis, cell cycle arrest, and DNA repair. Since apoptosis may play an important role in deletion of neoplastic cells, an understanding of the mechanism of p53-induced apoptosis may be critical for possible future therapeutic interventions. Recent evidence suggests that p53-induced apoptosis may involve members of the nucleotide excision repair (NER) family, linking these two cellular events. Our work using a temperature-sensitive p53 construct further analyzes p53-induced apoptosis in cultured murine mammary epithelial cells and also suggests that DNA repair plays a role in that process. Although p21 is induced in our system, apoptosis occurs without a detectable preceding G1 cell cycle arrest and independent of cellular alterations brought on by the temperature shift. In addition, clonogenic assays suggest that early stages of p53-induced apoptosis may be reversible upon removal of the apoptosis stimulus. As a possible explanation for this reversibility, our results show that general DNA repair activity increases early in p53-induced apoptosis. We also show that caspase-3 is activated at a timepoint when colony formation begins to drop, suggesting a possible mechanism for the point of no return in p53-induced apoptosis.

Receptors in neurodegenerative diseases

The ability of trophic factors to regulate developmental neuronal survival and adult nervous system plasticity suggests the use of these molecules to treat neurodegeneration associated with human diseases, such as Alzheimer's, Huntington's and Parkinson's disease, of amyotrophic lateral sclerosis and peripheral sensory neuropathies. Recent biological data on the neutrotrophins NGF and BDNF, on GDNF, CNTF and IGF-I are discussed together with first results from clinical trials. Literature is presented on the three-dimensional structures of these trophic factors and on models proposed for ligand-receptor interactions. Substantial progress has been made in the understanding of the mechanisms of apoptosis. The cascade consisting of interaction of apoptosis-inducing ligands with death receptors, the coupling of this complex to adaptor proteins via death domains, the further recruitment of procaspases via death effector or caspase recruitment domains and the execution of cell death via the effector caspases is briefly outlined.

Differential responses of Bcl-2 family genes to etoposide in chronic myeloid leukemia K562 cells

Etoposide is a potent anticancer agent that is used to treat various tumors. We have investigated the dose-dependent effect of etoposide on apoptosis using chronic myeloid leukemia K562 cells treated with low (5 microM) or high (100 microM) concentrations of the drug. At a low concentration, etoposide induced little apoptosis at 24 h, while about 20% of the cells showed apoptosis morphologically at a high concentration. Processing of caspase-3 was slightly detected from 12 h and became obvious at 24 h with 100 microM etoposide. Caspase-3-like protease activity was detected at 24 h with a high concentration. Moreover, these changes were accompanied by cleavage of poly ADP ribose polymerase (PARP). Changes of the mRNA levels of most apoptosis-regulating genes were not prominent at both concentrations, except for the rapid induction of c-IAP-2/HIAP-1 and the down-regulation of Bcl-X(L) by 100 microM etoposide. The downregulation of Bcl-X(L) protein occurred from 6 h, while Bax protein conversely showed a slight increase from 6 h. Taken together, the present findings show that the dose-dependent apoptotic effect of etoposide is based on a change in the balance between Bcl-X(L) and Bax, which precedes the activation of caspase-3.

Debcl, a proapoptotic Bcl-2 homologue, is a component of the Drosophila melanogaster cell death machinery

Bcl-2 family of proteins are key regulators of apoptosis. Both proapoptotic and antiapoptotic members of this family are found in mammalian cells, but no such proteins have been described in insects. Here, we report the identification and characterization of Debcl, the first Bcl-2 homologue in Drosophila melanogaster. Structurally, Debcl is similar to Bax-like proapoptotic Bcl-2 family members. Ectopic expression of Debcl in cultured cells and in transgenic flies causes apoptosis, which is inhibited by coexpression of the baculovirus caspase inhibitor P35, indicating that Debcl is a proapoptotic protein that functions in a caspase-dependent manner. debcl expression correlates with developmental cell death in specific Drosophila tissues. We also show that debcl genetically interacts with diap1 and dark, and that debcl-mediated apoptosis is not affected by gene dosage of rpr, hid, and grim. Biochemically, Debcl can interact with several mammalian and viral prosurvival Bcl-2 family members, but not with the proapoptotic members, suggesting that it may regulate apoptosis by antagonizing prosurvival Bcl-2 proteins. RNA interference studies indicate that Debcl is required for developmental apoptosis in Drosophila embryos. These results suggest that the main components of the mammalian apoptosis machinery are conserved in insects.

Subcellular localization and CARD-dependent oligomerization of the death adaptor RAIDD

RAIDD, a caspase recruitment domain (CARD) containing molecule, interacts with procaspase-2 in a CARD-dependent manner. This interaction has been suggested to mediate the recruitment of caspase-2 to the tumour necrosis factor receptor 1 (TNFR1). In this paper we have studied the subcellular localization of RAIDD and its interaction with caspase-2. We demonstrate that endogenous RAIDD is mostly localized in the cytoplasm and to some extent in the nucleus. RAIDD localization is not affected by TNF-treatment of HeLa cells, but in cells ectopically expressing caspase-2, a fraction of RAIDD is recruited to the nucleus. In transfected cells, coexpression of RAIDD and caspase-2 leads to CARD-dependent colocalization of the two proteins to discrete subcellular structures. We further show that overexpression of the RAIDD-CARD results in the formation of filamentous structures due to CARD-mediated oligomerization. These structures were similar to death effector filaments (DEFs) formed by FADD and FLICE death effector domains (DEDs), and partially colocalized with DEFs. Our results suggest that similar to the DED, the RAIDD-CARD has the ability to form higher order complexes, believed to be important in apoptotic execution. We also present evidence that RAIDD-CARD oligomerization may be regulated by intramolecular folding of the RAIDD molecule.

Caspase-3 and caspase-7 but not caspase-6 cleave Gas2 in vitro: implications for microfilament reorganization during apoptosis

Apoptosis is characterized by proteolysis of specific cellular proteins by a family of cystein proteases known as caspases. Gas2, a component of the microfilament system, is cleaved during apoptosis and the cleaved form specifically regulates microfilaments and cell shape changes. We now demonstrate that Gas2 is a substrate of caspase-3 but not of caspase-6. Proteolytic processing both in vitro and in vivo is dependent on aspartic residue 279. Gas2 cleavage was only partially impaired in apoptotic MCF-7 cells which lack caspase-3, thus indicating that different caspases can process Gas2 in vivo. In vitro Gas2 was processed, albeit with low affinity, by caspase-7 thus suggesting that this caspase could be responsible for the incomplete Gas2 processing observed in UV treated MCF-7 cells. In vivo proteolysis of Gas2 was detected at an early stage of the apoptotic process when the cells are still adherent on the substrate and it was coupled to the specific rearrangement of the microfilament characterizing cell death. Finally we also demonstrated that Gas2 in vitro binds to F-actin, but this interaction was unaffected by the caspase-3 dependent proteolytic processing.

DECAY, a novel Drosophila caspase related to mammalian caspase-3 and caspase-7

Caspases are key effectors of programmed cell death in metazoans. In Drosophila, four caspases have been described so far. Here we describe the identification and characterization of the fifth Drosophila caspase, DECAY. DECAY shares a high degree of homology with the members of the mammalian caspase-3 subfamily, particularly caspase-3 and caspase-7. DECAY lacks a long prodomain and thus appears to be a class II effector caspase. Ectopic expression of DECAY in cultured cells induces apoptosis. Recombinant DECAY exhibited substrate specificity similar to the mammalian caspase-3 subfamily. Low levels of decay mRNA are ubiquitously expressed in Drosophila embryos during early stages of development but its expression becomes somewhat spatially restricted in some tissues. During oogenesis decay mRNA was detected in egg chambers of all stages consistent with a role for DECAY in apoptosis of nurse cells. Relatively high levels of decay mRNA are expressed in larval salivary glands and midgut, two tissues which undergo histolysis during larval/pupal metamorphosis, suggesting that DECAY may play a role in developmentally programmed cell death in Drosophila.

Rhodamine 110-linked amino acids and peptides as substrates to measure caspase activity upon apoptosis induction in intact cells

Caspases (cysteine aspartate-specific proteases) are a structurally related group of cysteine proteases that cleave peptide bonds following specific recognition sequences. They play a central role in activating apoptosis of vertebrate cells. To measure apoptosis induced by various stimuli and at an early apoptotic stage, caspases are an ideal target. This is especially the case when apoptotic cells have to be analyzed ex vivo before phagocytes remove them. A new and sensitive caspase assay is based on a substrate that contains only aspartate residues linked to rhodamine 110. With this and similar substrates, we are able to detect intracellular caspase activation by flow cytometry after apoptosis induction in intact hematopoetic cell lines.

The mitochondrial permeability transition pore and its role in cell death

This article reviews the involvement of the mitochondrial permeability transition pore in necrotic and apoptotic cell death. The pore is formed from a complex of the voltage-dependent anion channel (VDAC), the adenine nucleotide translocase and cyclophilin-D (CyP-D) at contact sites between the mitochondrial outer and inner membranes. In vitro, under pseudopathological conditions of oxidative stress, relatively high Ca2+ and low ATP, the complex flickers into an open-pore state allowing free diffusion of low-Mr solutes across the inner membrane. These conditions correspond to those that unfold during tissue ischaemia and reperfusion, suggesting that pore opening may be an important factor in the pathogenesis of necrotic cell death following ischaemia/reperfusion. Evidence that the pore does open during ischaemia/reperfusion is discussed. There are also strong indications that the VDAC-adenine nucleotide translocase-CyP-D complex can recruit a number of other proteins, including Bax, and that the complex is utilized in some capacity during apoptosis. The apoptotic pathway is amplified by the release of apoptogenic proteins from the mitochondrial intermembrane space, including cytochrome c, apoptosis-inducing factor and some procaspases. Current evidence that the pore complex is involved in outer-membrane rupture and release of these proteins during programmed cell death is reviewed, along with indications that transient pore opening may provoke 'accidental' apoptosis.

Recent advances on neuronal caspases in development and neurodegeneration

In view of a large and growing literature, this overview emphasizes recent advances in neuronal caspases and their role in cell death. To provide historical perspective, morphology and methods are surveyed with emphasis on early studies on interleukin converting enzyme (ICE) as a prototype for identifying zymogen subunits. The unexpected homology of ICE (caspase-1) to Caenorhabditis elegans death gene CED-3 provided early clues linking caspases to programmed cell death, and led later to discovery of bcl-2 proteins (CED-9 homologs) and 'apoptosis associated factors' (Apafs). Availability of substrates, inhibitors, and cDNAs led to identification of up to 16 caspases as a new superfamily of unique cysteine proteinases targeting Asp groups. Those acting as putative death effectors dismantle neurons by catabolism of proteins essential for survival. Caspases degrade amyloid precursor protein (APP), presenilins (PS1, PS2), tau, and huntingtin, raising questions on their role in neurodegeneration. Brain contains 'inhibitors of apoptosis proteins' (IAPs) survivin and NAIP associated also with some neuronal disorders. Apoptotic stress in neurons initiates a chain of events leading to activation of distal caspases by pathways that remain to be fully mapped. Neuronal caspases play multiple roles for initiation and execution of cell death, for morphogenesis, and in non-mitotic neurons for homeostasis. Recent studies focus on cytochrome c as pivotal in mediating conversion of procaspase-9 as a major initiator for apoptosis. Identifying signaling pathways and related events paves the way to design useful therapeutic remedies to prevent neuronal loss in disease or aging.

DRONC, an ecdysone-inducible Drosophila caspase

Caspases play an essential role in the execution of programmed cell death in metazoans. Although 14 caspases are known in mammals, only a few have been described in other organisms. Here we describe the identification and characterization of a Drosophila caspase, DRONC, that contains an amino terminal caspase recruitment domain. Ectopic expression of DRONC in cultured cells resulted in apoptosis, which was inhibited by the caspase inhibitors p35 and MIHA. DRONC exhibited a substrate specificity similar to mammalian caspase-2. DRONC is ubiquitously expressed in Drosophila embryos during early stages of development. In late third instar larvae, dronc mRNA is dramatically up-regulated in salivary glands and midgut before histolysis of these tissues. Exposure of salivary glands and midgut isolated from second instar larvae to ecdysone resulted in a massive increase in dronc mRNA levels. These results suggest that DRONC is an effector of steroid-mediated apoptosis during insect metamorphosis.

Gastric mucosal inflammatory responses toHelicobacter pylori lipopolysaccharide: suppression of caspase-3 and nitric oxide synthase-2 by omeprazole and sucralfate

AIMS

Helicobacter pylori lipopolysaccharide is a primary virulence factor responsible for eliciting acute mucosal inflammatory responses associated with H. pylori infection. In this study, we investigated the activity of a key apoptotic protease, caspase-3, and the expression of inducible nitric oxide synthase (NOS-2) during H. pylori lipopolysaccharide-induced acute gastritis, and evaluated the effect of anti-ulcer agents, omeprazole and sucralfate, on this process.

METHODS

Rats, pretreated twice daily with omeprazole at 40 mg/kg, sucralfate at 100 mg/kg, or the vehicle, were subjected to intragastric application of H. pylori lipopolysaccharide at 50 microg/animal, and after 4 additional days on the anti-ulcer drug or vehicle regimen their mucosal tissue was used for histologic assessment, assays of epithelial cells apoptosis, and the measurements of caspase-3 and NOS-2 activities.

RESULTS

In the absence of anti-ulcer agents,H. pylori lipopolysaccharide induced acute reaction characterized by the inflammatory infiltration of the lamina propria, hyperemia, and epithelial hemorrhage. This was accompanied by an 11.2-fold increase in epithelial cell apoptosis, a 6.5-fold induction in mucosal expression of NOS-2, and a 5.4-fold increase in caspase-3 activity. Treatment with proton pump inhibitor, omeprazole, produced a 39.6% reduction in the extent of mucosal inflammatory changes elicited by H. pylori lipopolysaccharide and a 75.5% decrease in the epithelial cells apoptosis, while the activity of caspase-3 decreased by 26.8% and that of NOS-2 showed a 46.7% decline. The gastroprotective agent, sucralfate, evoked a 62.3% reduction in the extent of mucosal inflammatory changes caused by the lipopolysaccharide, epithelial cell apoptosis decreased by 85.8%, and NOS-2 showed a 68.2% decline, while the activity of caspase-3 decreased by 39.7%.

CONCLUSIONS

Our findings implicate caspase-3 involvement in gastric mucosal inflammatory responses toH. pylori lipopolysaccharide, and point towards participation of NOS-2 in the amplification of the cell death-signaling cascade. We also show that anti-ulcer agents, omeprazole and sucralfate, are capable of suppressing the H. pylori-induced mucosal inflammatory responses by interfering with the events propagated by NOS-2 and caspase-3.