, we showed that SR-BI-mediated cholesterol efflux was highly correlated (r 2 ‫؍‬ 0.985) with HDL phosphatidylcholine content. The effects of varying HDL phospholipid composition on SR-BI-mediated free cholesterol flux were not correlated with changes in either the K d or B max values for high affinity binding to SR-BI. We conclude that SR-BI-mediated free cholesterol flux is highly sensitive to HDL phospholipid composition. Thus, factors that regulate cellular SR-BI expression and the local modification of HDL phospholipid composition will have a large impact on reverse cholesterol transport.The deposition of cholesterol in peripheral cells is opposed by the process of reverse cholesterol transport (RCT) 1 where high density lipoproteins (HDL) remove free cholesterol (FC) from cells and deliver it back to the liver for excretion (1-3). The flux of FC between cells and HDL is bi-directional. Depending on the direction of the FC concentration gradient between cells and lipoproteins, either net efflux or net influx of cholesterol can occur (4, 5). The creation of a cholesterol gradient depends upon many properties of the acceptors and the cell plasma membrane. Such factors include the cholesterol and phospholipid content of the acceptors and plasma membrane (4, 5), the existence of cholesterol domains within the plasma membrane (6 -10), and the size, number, and composition of acceptor particles (11-13).Recent studies have shown that, when cells express scavenger receptor BI (SR-BI), the bi-directional flux of FC between cells and HDL is accelerated (8,14,15). The mechanism by which SR-BI mediates FC flux is uncertain. However, recent studies from our laboratory demonstrated that binding of the acceptor particles to SR-BI is not a requirement for SR-BImediated cholesterol efflux (7,8). Rather SR-BI induces a reorganization of the plasma membrane cholesterol, and this reorganization is linked to enhanced FC flux (7,8,16). Regardless of the mechanism, evidence is accumulating to support the importance of SR-BI-mediated FC flux in RCT. Recent studies of Ji and colleagues (17) showed that either attenuation or overexpression of hepatic SR-BI in mice led to significantly decreased or increased delivery of HDL FC into bile. In addition, the expression of SR-BI in peripheral cells and in foam cells of the arterial wall suggests a role for SR-BI in the removal of FC from the periphery (15, 18, 19).SR-BI-mediated FC flux requires phospholipid in the acceptor (15), and studies have shown that cholesterol efflux from cells is highly correlated with the concentration of HDL phospholipid in serum (20,21). Also, the stimulation of cholesterol efflux upon phospholipid supplementation of serum is closely linked to the levels of SR-BI among cell types (14). These observations are consistent with epidemiological data demonstrating that humans with low HDL phospholipid levels have a high incidence of coronary artery disease (22). These findings suggest that changes in HDL phospholipid content may alter SR-BI-mediated FC flux. The cu...

Treatment failure is a major cause of concern for the Helicobacter pylori-related gastroduodenal diseases like gastritis, peptic ulcer, and gastric cancer. Curcumin, diferuloylmethane from turmeric, has recently been shown to arrest H. pylori growth. The antibacterial activity of curcumin against 65 clinical isolates of H. pylori in vitro and during protection against H. pylori infection in vivo was examined. The MIC of curcumin ranges from 5 g/ml to 50 g/ml, showing its effectiveness in inhibiting H. pylori growth in vitro irrespective of the genetic makeup of the strains. The nucleotide sequences of the aroE genes, encoding shikimate dehydrogenase, against which curcumin seems to act as a noncompetitive inhibitor, from H. pylori strains presenting differential curcumin MICs showed that curcumin-mediated growth inhibition of Indian H. pylori strains may not be always dependent on the shikimate pathway. The antimicrobial effect of curcumin in H. pylori-infected C57BL/6 mice and its efficacy in reducing the gastric damage due to infection were examined histologically. Curcumin showed immense therapeutic potential against H. pylori infection as it was highly effective in eradication of H. pylori from infected mice as well as in restoration of H. pylori-induced gastric damage. This study provides novel insights into the therapeutic effect of curcumin against H. pylori infection, suggesting its potential as an alternative therapy, and opens the way for further studies on identification of novel antimicrobial targets of curcumin.

Matrix metalloproteinases (MMPs) are suggested to play a critical role in extracellular matrix degradation and remodeling during inflammation and wound healing processes. However, the role of MMPs in indomethacin-induced gastric ulcer and its healing process are not clearly understood. This study is aimed at determining the regulation of MMP-9 and -2 activities in indomethacin-induced acute gastric ulceration and healing. Indomethacin-ulcerated stomach extracts exhibit significant up-regulation of pro-MMP-9 (92 kDa) activity and moderate reduction of MMP-2 activity, which strongly correlate with indomethacin dose and severity of ulcer. The anti-inflammatory and antioxidant properties of curcumin, an active component of turmeric, suggest that curcumin may exert antiulcer activity through scavenging reactive oxygen species, by regulating MMP activity, or both. To test these possibilities, the effect of curcumin in indomethacin-induced gastric ulcer is examined by biochemical and histological methods. The results show that curcumin exhibits potent antiulcer activity in acute ulcer in rat model by preventing glutathione depletion, lipid peroxidation, and protein oxidation. Denudation of epithelial cells during damage of gastric lumen is reversed by curcumin through re-epithelialization. Furthermore, both oral and intraperitoneal administration of curcumin blocks gastric ulceration in a dose-dependent manner. It accelerates the healing process and protects gastric ulcer through attenuation of MMP-9 activity and amelioration of MMP-2 activity. Omeprazole, an established antiulcer drug does not inhibit MMP-9 while protecting indomethacin-induced gastric ulcer. We conclude that antiulcer activity of curcumin is primarily attributed to MMP-9 inhibition, one of the major pathways of ulcer healing.

Scavenger receptor BI (SR-BI) mediates the selective uptake of HDL cholesteryl ester into steroidogenic cells and the liver and is a major determinant of the plasma HDL concentration in the mouse. Recent studies indicate that SR-BI also alters the metabolism of apolipoprotein B-containing particles and influences the development of atherosclerosis in several animal models. These results and the similar pattern of SR-BI expression in humans emphasize that it is important to learn how this receptor influences lipoprotein metabolism and atherosclerosis in people.

The zinc-dependent matrix metalloproteinases (MMPs) are key enzymes associated with extracellular matrix (ECM) remodeling; they play critical roles under both physiological and pathological conditions. MMP-9 activity is linked to many pathological processes, including rheumatoid arthritis, atherosclerosis, gastric ulcer, tumor growth, and cancer metastasis. Specific inhibition of MMP-9 activity may be a promising target for therapy for diseases characterized by dysregulated ECM turnover. Potent MMP-9 inhibitors including an indole scaffold were recently reported in an X-ray crystallographic study. Herein, we addressed whether melatonin, a secretory product of pineal gland, has an inhibitory effect on MMP-9 function. Gelatin zymographic analysis showed a significant reduction in pro- and active MMP-9 activity in vitro in a dose- and time-dependent manner. In addition, a human gastric adenocarcinoma cell line (AGS) exhibited a reduced (~50%) MMP-9 expression when incubated with melatonin, supporting an inhibitory effect of melatonin on MMP-9. Atomic-level interaction between melatonin and MMP-9 was probed with computational chemistry tools. Melatonin docked into the active site cleft of MMP-9 and interacted with key catalytic site residues including the three histidines that form the coordination complex with the catalytic zinc as well as proline 421 and alanine 191. We hypothesize that under physiological conditions, tight binding of melatonin in the active site might be involved in reducing the catalytic activity of MMP-9. This finding could provide a novel approach to physical docking of biomolecules to the catalytic site of MMPs, which inhibits this protease, to arrest MMP-9-mediated inflammatory signals.

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Helicobacter pylori cag pathogenicity island (PAI) is a major determinant of gastric injury via induction of several matrix metalloproteinases (MMPs). In the present study, we examined the influence of the cag PAI on gastric infection and MMP-9 production in mice and in cultured cells. A new mouse colonizing Indian H. pylori strain (AM1) that lacks the cag PAI was used to study the cag PAI importance in inflammation. Groups of C57BL/6 mice were inoculated separately with H. pylori strains AM1 and SS1 (cag ؉ ), gastric tissues were histologically examined, and bacterial colonization was scored by quantitative culture. Mice infected with either cag ؉ or cag ؊ H. pylori strains showed gastric inflammation and elevated MMP-3 production. Significant up-regulation of pro-MMP-9 secretion and gene expression in H. pylori infected gastric tissues indicate dispensability of cag PAI for increased pro-MMP-9 secretion and synthesis in mice. In agreement, cell culture studies revealed that both AM1 and SS1 were equipotent in pro-MMP-9 induction in human gastric epithelial cells. Both strains showed moderate increase in MMP-2 activity in vivo and in vitro. In addition, increased secretion of tumor necrosis factor (TNF)-␣, interleukin (IL)-1␤, and IL-6 induced pro-MMP-9 secretion and synthesis in AM1 or SS1 strain-infected mice suggesting elicitation of pro-inflammatory cytokines by both cag ؊ and cag ؉ genotype. Moreover, tissue inhibitors of metalloproteinase-1 expression were decreased with increase in pro-MMP-9 induction. These data show that H. pylori may act through different pathways other than cag PAI-mediated for gastric inflammation and contribute to upregulation of MMP-9 via pro-inflammatory cytokines.Helicobacter pylori is a microaerophilic bacterium with an extraordinary ability to chronically infect human stomachs for years together despite gastric mucosal turnover and other host defenses (1). It colonizes more than half of all people worldwide and is still unknown why most remain asymptomatic (2). Persistent H. pylori infection is associated with chronic gastritis and gastric cancer, one of the most lethal of malignancies worldwide (2-4). It may also cause childhood malnutrition and increase the risk or severity of infection by other gastrointestinal pathogens such as Vibrio cholerae, especially in developing countries (5, 6). H. pylori appears to be one of the most genetically diverse of bacterial species and shows significant geographic differences among strains (7-11). Studies of strains from Europe and North America indicated that H. pylori genotypes can be important in colonization and disease outcome (12). Recent studies revealed that Indian H. pylori strains are genetically distinct from European and East Asian strains (9, 10). Variation in the clinical outcome of H. pylori infection seems to be multifaceted and involves a complex interplay between virulence factors, host immune responses, and other features of the H. pylori gastric mucosal niche. Prominent among the H. pylori virulence-associated determin...

Scavenger receptor, class B, type I (SR-BI) is a cellsurface glycoprotein that mediates selective uptake of high density lipoprotein cholesteryl ester (CE) without the concomitant uptake and degradation of the particle. We have investigated the endocytic and selective uptake of low density lipoprotein (LDL)-CE by SR-BI using COS-7 cells transiently transfected with mouse SR-BI. Analysis of lipoprotein uptake data showed a concentration-dependent LDL-CE-selective uptake when doubly labeled LDL particles were incubated with SR-BI-expressing COS-7 cells. In contrast to vector-transfected cells, SR-BI-expressing COS-7 cells showed marked increases in LDL cell association and CE uptake by the selective uptake pathway, but only a modest increase in CE uptake by the endocytic pathway. SR-BI-mediated LDL-CE-selective uptake exceeded LDL endocytic uptake by 50 -100-fold. SR-BI-mediated LDL-CE-selective uptake was not inhibited by the proteoglycan synthesis inhibitor, p-nitrophenyl-␤-D-xylopyranoside or by the sulfation inhibitor sodium chlorate, indicating that SR-BI-mediated LDL-CE uptake occurs independently of LDL interaction with cell-surface proteoglycan. Analyses with subclones of Y1 adrenocortical cells showed that LDL-CE-selective uptake was proportional to the level of SR-BI expression. Furthermore, antibody directed to the extracellular domain of SR-BI blocked LDL-CE-selective uptake in adrenocortical cells. Thus, in cells that normally express SR-BI and in transfected COS-7 cells SR-BI mediates the efficient uptake of LDL-CE via the selective uptake mechanism. These results suggest that SR-BI may influence the metabolism of apoB-containing lipoproteins in vivo by mediating LDL-CE uptake into SR-BI-expressing cells. Scavenger receptor class B, type I (SR-BI)1 is a cell-surface glycoprotein of molecular mass ϳ82 kDa that binds HDL, LDL, modified LDL, and VLDL (1-4). In transfected cells, SR-BI mediates the selective uptake of HDL-CE (1), a process in which HDL-CE is transferred into the cell without the concomitant uptake and degradation of the HDL particle (5). Immunochemical analysis of SR-BI in rodents indicates that it is expressed most abundantly in the liver and in steroidogenic cells of the adrenal gland and ovary (1, 6, 7), where the selective uptake of HDL-CE is greatest. In humans, SR-BI (also referred to as Cla-1 (4)) shows a similar tissue distribution (8, 9). Direct evidence for SR-BI function is provided by studies in which antibody to the extracellular domain of mouse (m) SR-BI blocked HDL-CE-selective uptake and the delivery of HDL cholesterol to the steroidogenic pathway in cultured murine adrenocortical cells (10). In addition, inactivation of the SR-BI gene in mice increased plasma HDL cholesterol levels and reduced neutral lipid stores in the adrenal glands (11). Similarly, mice carrying an induced SR-BI mutation that reduced hepatic SR-BI expression levels by 50% showed a similar reduction in hepatic HDL-CE-selective uptake (12). These studies with reduced SR-BI expression are complemented b...