Identification of neutral and acidic sphingomyelinases in Helicobacter pylori

Abstract

We demonstrated for the first time the presence of sphingomyelinase (SMase) in Helicobacter pylori. Activation of SMase has been implicated as the cause of elevation of cellular ceramide levels and consequently of apoptosis. The data indicate that there are two classes of SMase, defined by their optimal pHs and cellular locations, existing in H. pylori. One is an Mg P+ -dependent membrane-bound enzyme with an optimal activity at pH 7, and the other is an Mg P+ -independent cytosolic enzyme with an optimal activity at pH 5. Bisalumin, a bismuth salt, was found to inhibit the activities of both forms of SMase regardless of the presence of Mg P+ . By Western blot analysis, the membrane-bound SMases of H. pylori and Bacillus cereus were shown to be antigenically related and to have a similar denatured molecular mass of 28 kDa.z 1998 Federation of European Biochemical Societies.

Eryptosis triggered by bismuth

“…Sphingomyelinase has previously been shown to play a critical role in host pathogen interaction (Dreschers et al 2007;Grassme et al 1997Grassme et al , 2003Grassme et al , 2005Gulbins et al 2004;Kempe et al 2007), and it is seducing to speculate that the powerful stimulation of ceramide formation by bismuth contributes to or even accounts for the therapeutic efficacy of bismuth. Helicobacter has previously been shown to express sphingomyelinase (Lin et al 1998), but an influence of bismuth on sphingomyelinase activity and its putative role in its therapeutic action has never been explored.…”

Helicobacter pylori-induced Prostaglandin E2 Synthesis Involves Activation of Cytosolic Phospholipase A2 in Epithelial Cells

“…The H. pylori-induced predominant hydrolysis of PI, which is exclusively located in the inner leaflet of the plasma membrane (47), suggests that the host epithelial cell membrane was not damaged by the H. pylori phospholipases A 1 , A 2 , or C (48 -50) or sphingomyelinase (51). Moreover, by using the isogenic PAI mutant strain, which does not induce cPLA 2 activation, we exclude the possibility that the bacterial phospholipases are able to activate host cell AA release from the epithelial cells, as has been shown in the case of the Clostridium perfringens ␣-toxin (52).…”

Cell-Associated Hemolysis Induced by Helicobacter pylori Is Mediated by Phospholipases with Mitogen-Activated Protein Kinase-Activating Properties

“…agalactiae and S. aureus were initially tested for the CAMP reaction on TSAII blood agar plates and reproducibly exhibited synergistic hemolysis (data not shown) as previously reported (4). Since SMases (17) as well as pore-forming toxins (20) have been described within H. pylori, we developed a protocol to test for H. pylori-induced synergistic hemolysis. Media containing tryptic soy agar with 5% sheep blood (TSBA), TSBA with CAMP factor (from S. agalactiae supernatant), or TSBA with SMase (from S. aureus filtered supernatant) were prepared, and an assay was performed using S. aureus supernatant and Bacillus cereus sphingomyelinase C (Sigma) as positive controls for synergistic hemolysis (Fig.…”

“…pylori can activate MAPK pathways in gastric epithelial cells in a strain-specific manner, and activation of ERK1/2 may play a role in pathogenesis (15). H. pylori encodes SMases that catalyze the conversion of host cell sphingomyelin to ceramide, which can activate MAPK (17,34). We therefore determined if phospholipases HP0499 and HP0190 were required for activation of ERK1/2 signaling in gastric epithelial cells.…”