Tandem facial amphiphiles for membrane protein stabilization

We describe a new type of synthetic amphiphile that is intended to support biochemical characterization of intrinsic membrane proteins. Members of this new family displayed favorable behavior with four of five membrane proteins tested, and these amphiphiles formed relatively small micelles.

Recellularization of aortic valves in pigs

OBJECTIVES

Decellularized porcine heart valves treated with deoxycholic acid (DOA) have demonstrated complete recellularization and absence of calcification when implanted into the pulmonary position in sheep. We studied recellularization and calcification in stented DOA-treated heart valves compared with conventional stented glutaraldehyde-treated valves in the aortic position in juvenile pigs 6 months after implantation.

METHODS

DOA heart valves (n=12) and glutaraldehyde-treated valves (Carpentier-Edwards) (n=15) were implanted into the aortic position in 8-month old 90 kg female pigs. Six months postoperatively, the valves were explanted and subjected to gross pathology examination, high-resolution (HR) X-ray imaging, and histological evaluation.

RESULTS

Five DOA valves and five glutaraldehyde-treated valves were explanted after 6 months. Fourteen animals died before follow-up because of non-valve related causes and three because of infective endocarditis. Gross pathologic examination showed all DOA valves to be well functioning with only minor thrombotic depositions located mostly in the commissural area. Three glutaraldehyde valves had limited thrombosis and two had severe thrombosis. HR X-ray imaging demonstrated almost complete absence of cusp calcification in the DOA valves, but severe calcification in all glutaraldehyde valves. Overgrowth of endothelial cells and ingrowth of fibroblasts in the stent-adjacent area and basal part of the cusps were seen in all DOA valves, but not in glutaraldehyde valves. Immunohistochemistry revealed larger amounts of inflammatory cells in all glutaraldehyde valves compared with DOA valves.

CONCLUSIONS

DOA-treated heart valves demonstrated greater recellularization and less calcification compared with standard glutaraldehyde-treated valves 6 months after implantation in the aortic position in pigs. DOA-treated heart valves demonstrated less calcification compared with standard glutaraldehyde-treated valves by qualitative analysis. Endothelial and fibroblast recellularization of the cusps was only observed in DOA-treated valves.

Recellularization of decellularized mitral heart valves in juvenile pigs

BACKGROUND AND AIM OF THE STUDY

Glutaraldehyde-preserved bioprosthetic heart valves are non-viable and have a limited durability because of calcification, tissue wear, and inflammation, especially in children. Decellularized porcine heart valves, when treated with deoxycholic acid (DOA), have exhibited complete recellularization and an absence of calcification when implanted into the pulmonary position in juvenile sheep. The study aim was to determine the degree of recellularization and calcification in DOA-treated heart valve prostheses in the mitral position in juvenile pigs.

METHODS

A mitral heart valve prosthesis was implanted into each of 17 pigs, and subsequently explanted and fixed in formaldehyde after between five and 26 weeks. A gross pathologic assessment, high-resolution X-ray imaging and histological examination were then performed on each valve.

RESULTS

Eight pigs survived the observational period. Five valves had only a slight fibrin deposition and calcification foci within the fibrin deposits. Three valves had severe thrombotic material deposits with disseminated calcification and valve stenosis, and one valve had infective endocarditis. A myofibroblast-like cell ingrowth was observed at different locations of the valve housing in all explanted heart valves, but ingrowth in the basal part of the cusp matrix was limited. In four valve prostheses, endothelial cells covered up to 10% of the cusp surface after six months. Inflammatory cells were observed in large numbers in those valves showing endocarditis and severe thrombosis, but in only limited numbers in the other valves.

CONCLUSION

All valves showed the deposition of fibrin and platelet material, in three cases to a severe degree. A limited ingrowth of both endothelial and myofibroblast-like cells was observed in five valves in which calcification was limited to a few commissural foci. The non-endothelialized surface of the decellularized valves makes them very susceptible to platelet and fibrin deposition; however, slow revitalization seems possible.

Comparative study of effects of two bile acid derivatives on Staphylococcus aureus by multiple analytical methods

The effects of two bile acid derivatives, cholic acid (CA) and deoxycholic acid (DCA) on Staphylococcus aureus (S. aureus) growth were investigated and compared by microcalorimetry coupled with multiple analytical methods. The heat power (HP)-time curves of S. aureus growth affected by CA and DCA were studied by similarity analysis (SA), respectively. Then the quantitative thermo-kinetic parameters obtained from these curves were investigated by the multivariate analysis of variance (MANOVA) and principal component analysis (PCA). By analyzing the two main parameters, growth rate constant k(2) of the second exponential phase and the heat power P(2) of the second highest peak, together with the minimum inhibitory concentration (MIC) values of 10 microg/mL for CA and 20 microg/mL for DCA, it could be concluded that the antibacterial effect of CA was stronger than that of DCA. The existence of alpha-OH at C-7 position of steroid nucleus of bile acid derivatives enhanced the hydrophilicity of compound CA and its inhibitory effect on S. aureus. This study provides a useful method and idea to accurately evaluate the antibacterial effects of bile acid derivatives, which provides some references for screening out new antibacterial agents with high efficacy and low toxicity.

The changing hydrodynamic performance of the decellularized intact porcine aortic root: considerations on in-vitro testing

BACKGROUND AND AIM OF THE STUDY

The most effective method for decellularization of the intact porcine aortic root remains controversial. Additionally, the hydrodynamic effect that such treatment may have on aortic roots has never been previously investigated. The study aim was to compare the in-vitro hydrodynamic performances of intact porcine aortic roots, both before and after decellularization treatment.

METHODS

Fifteen fresh porcine aortic roots were tested in the aortic chamber of the Sheffield pulse duplicator (SPD). For study purposes, the roots were first sutured to a silicone aortic root and then hydrodynamically tested. After in-vitro testing, the fresh porcine aortic roots, while still fixed within the silicone root, were decellularized according to various protocols (TRI-COL, TRI-DOC, sodium dodecyl sulfate (SDS) 0.03%, and SDS 0.1%). After decellularization, the valve roots were re-tested, adopting identical testing conditions. Forward flow pressure drop, closing leakage volumes, effective orifice area (EOA), and stroke work loss were each monitored. Three roots, used as a control group, were tested in identical fashion before and after storage (without decellularization) for comparative purposes.

RESULTS

The TRI-COL- and TRI-DOC-treated porcine aortic roots showed significantly lower transvalvular gradients, lower stroke work loss, lower valve resistance, and higher EOA than fresh intact porcine roots. In contrast, SDS 0.1%-treated porcine aortic roots showed opposing results, with the transvalvular gradients, stroke work loss and valve resistance each higher, and the EOA lower, than pre-treatment values. SDS 0.03% treatment had no significant effect on the hydrodynamic performance. After decellularization in all treatment groups, the diastolic parameters, total regurgitant volume and valve closing volume were each non-significantly increased. The aortic roots used as a control group showed similar results before and after storage.

CONCLUSION

Based on these results using the SPD, all treatments except for SDS 0.03% modified the systolic and diastolic functions of intact porcine aortic roots.

Hydrophobicity and haemolytic potential of oxo derivatives of cholic, deoxycholic and chenodeoxycholic acids

The objective of this work was to study the effect of structure of bile acids on their membranolytic potential and extent of overlapping of the information about the membranolytic potential of bile acids and their physico-chemical parameters, namely: retention index R(M0) (as a measure of bile acid hydrophobicity, reversed-phase thin-layer chromatography (RPTLC)), lecithin solubilisation (measure of the interaction of bile acids with phospholipids) and critical micellar concentration (CMC). It was found that bile acid concentrations at 100% lysis of erythrocyte membranes is described best by their CMC values, whereas at 50% lysis the parameter used is lecithin solubilisation. This indicates that different mixed micelles are formed in the membrane lysis at lower and higher concentrations of bile acids. Replacement of the hydroxyl (OH) group in the bile acid molecule with an oxo group yields derivatives with lowered hydrophobicity, power of lecithin solubilisation, tendency for self-aggregation as well as the membranolytic activity.

Effect of indomethacin on bile acid-phospholipid interactions: implication for small intestinal injury induced by nonsteroidal anti-inflammatory drugs

The injurious effect of nonsteroidal anti-inflammatory drugs (NSAIDs) in the small intestine was not appreciated until the widespread use of capsule endoscopy. Animal studies found that NSAID-induced small intestinal injury depends on the ability of these drugs to be secreted into the bile. Because the individual toxicity of amphiphilic bile acids and NSAIDs directly correlates with their interactions with phospholipid membranes, we propose that the presence of both NSAIDs and bile acids alters their individual physicochemical properties and enhances the disruptive effect on cell membranes and overall cytotoxicity. We utilized in vitro gastric AGS and intestinal IEC-6 cells and found that combinations of bile acid, deoxycholic acid (DC), taurodeoxycholic acid, glycodeoxycholic acid, and the NSAID indomethacin (Indo) significantly increased cell plasma membrane permeability and became more cytotoxic than these agents alone. We confirmed this finding by measuring liposome permeability and intramembrane packing in synthetic model membranes exposed to DC, Indo, or combinations of both agents. By measuring physicochemical parameters, such as fluorescence resonance energy transfer and membrane surface charge, we found that Indo associated with phosphatidylcholine and promoted the molecular aggregation of DC and potential formation of larger and isolated bile acid complexes within either biomembranes or bile acid-lipid mixed micelles, which leads to membrane disruption. In this study, we demonstrated increased cytotoxicity of combinations of bile acid and NSAID and provided a molecular mechanism for the observed toxicity. This mechanism potentially contributes to the NSAID-induced injury in the small bowel.

Transperitoneal transport of uric acid: impact of p-cresol, sodium hyaluronan, and sodium deoxycholate in vitro

Our study investigated uric acid transport across isolated parietal peritoneum taken from the anterior abdominal wall of white New Zealand rabbits and placed inside a modified Ussing-type chamber. Values for transfer from the mesothelial to the interstitial side of membrane (M --> I) were calculated using the mathematical model of mass transport and are expressed as a coefficient of diffusive permeability [P (in centimeters per second)]. Four separate series of experiments were done. In the first series, we examined uric acid transfer in control conditions (for 120 minutes). In the second and third series, P was calculated before (15 - 60 minutes) and after introduction of p-cresol (0.005 g/dL) or sodium hyaluronan (0.04 g/dL) on the M side of the membrane. In the fourth series, transfer parameters were measured before (15 - 75 minutes) and after (90 - 150 minutes) application of sodium deoxycholate (0.104 g/dL). The dynamics of transperitoneal transport of uric acid were stable. The values of P +/- standard error of the mean (x0.0001) were 1.936 +/- 0.324 cm/s and 2.078 +/- 0.186 cm/s. Application of p-cresol on the M side of membrane lowered uric acid transport by 10%. Application of sodium hyaluronan produced no change, but application of sodium deoxycholate increased the transfer of uric acid by 155%. These observations may have clinical importance.

Histological changes associated with mesotherapy for fat dissolution

Mesotherapy is a form of medical therapy popular in Europe and South America. It is used for treating a variety of medical conditions, including the treatment of localized fat deposits and cellulite. Phosphatidylcholine/deoxycholate injections are a popular technique to treat localized fat accumulations and have recently become synonymous with mesotherapy, although their history and technique are distinct. To treat localized fat deposits, phosphatidylcholine (PC) and deoxycholate (DC) are utilized. To date, there have been no published histological studies that explain the mechanism of action of PC and DC.Method. In this study the authors have obtained skin biopsies from a patient who had undergone mesotherapy with PC and DC. Punch biopsies were taken at one and two weeks after the procedure.Results. Each of the biopsies taken at one and two weeks after treatment with PC and DC showed a normal epithelium and dermis, with a mixed septal and lobular panniculitis. The fat lobules were infiltrated by increased numbers of lymphocytes and, in particular, macrophages. The macrophages consisted of conventional forms, foam cells, and multinucleated fat-containing giant cells. The inflammation was associated with serous atrophy and microcyst formation.Conclusion. This study demonstrates that mesotherapy with PC and DC affects the subcutaneous fat. We theorize that the reduction of subcutaneous fat likely follows inflammatory-mediated necrosis and resorption.

Immunoblot detection of soluble protein antigens from sodium dodecyl sulfate- and sodium deoxycholate-treated candidate bioscaffold tissues

BACKGROUND AND AIMS OF THE STUDY

The detergent-based 'decellularization' of xenogeneic tissues is one approach to scaffolding a tissue-engineered heart valve construct; however, concern persists regarding the immunogenicity of decellularized xenogeneic bioscaffolds. The study aims were to: (i) develop a sensitive and robust immunoblot-based assay for the detection of soluble protein antigens in xenogeneic bioscaffolds; and (ii) evaluate the completeness of protein antigen removal from sodium dodecyl sulfate (SDS)- or sodium deoxycholate (SD)-treated bovine pericardium (BP) or porcine aortic valve (PAV) conduit.

METHODS

Homogenized BP or PAV were injected into rabbits to generate immune serum towards these tissues. Soluble proteins were extracted from untreated BP and PAV. Immunoblot analyses of the extracts were performed using pre-immune and 14-, 28-, 42-, 56- and 70-day post-immune serum. BP and PAV were treated sequentially with 4 h hypotonic lysis; with 0, 0.01, 0.025, 0.05, 0.1, 0.25 or 0.5% SDS or SD for 24 h; and with 96 h of aqueous wash-out. Immunoblot analyses of protein extracts from treated tissues were performed using 70-day post-immune rabbit serum.

RESULTS

Immunoblot analysis of untreated BP or PAV with pre-immune serum showed no immune banding. The immune banding density increased progressively when immunoblots were performed with 14-day through 70-day post-immune serum. The immunoblot analysis of treated BP and PAV showed that soluble protein antigen removal from SDS- or SD-treated tissues was incomplete.

CONCLUSION

Immunoblot analysis is a sensitive and robust assay for detecting soluble protein xenogeneic antigens after the decellularization of xenogeneic bioscaffolds. Under the study conditions, hypotonic lysis, SDS or SD detergent treatment, and aqueous wash-out-based decellularization of bovine pericardium and porcine aortic valve conduit did not completely remove detectable protein antigens.

Technosphere insulin: defining the role of Technosphere particles at the cellular level

BACKGROUND

Technosphere Insulin (TI) is a novel inhalation powder for the treatment of diabetes mellitus. Technosphere Insulin delivers insulin with an ultra rapid pharmacokinetic profile that is distinctly different from all other insulin products but similar to natural insulin release. Such rapid absorption is often associated with penetration enhancers that disrupt cellular integrity.

METHODS

Technosphere Insulin was compared to a panel of known penetration enhancers in vitro using the Calu-3 lung cell line to investigate the effects of TI on insulin transport.

RESULTS

Measures of tight junction integrity such as transepithelial electrical resistance, Lucifer yellow permeability, and F-actin staining patterns were all unaffected by TI. Cell viability and plasma membrane integrity were also not affected by TI. In contrast, cells treated with comparable (or lower) concentrations of penetration enhancers showed elevated Lucifer yellow permeability, disruption of the F-actin network, reduced cell viability, and compromised plasma membranes.

CONCLUSIONS

These results demonstrate that TI is not cytotoxic in an in vitro human lung cell model and does not function as a penetration enhancer. Furthermore, TI does not appear to affect the transport of insulin across cellular barriers.

Actions and comparative efficacy of phosphatidylcholine formulation and isolated sodium deoxycholate for different cell types

BACKGROUND

Phosphatidylcholine formulation has been used to dissolve local fat deposits. This study aimed to evaluate and compare the effects of phosphatidylcholine formulation and its vehicle sodium deoxycholate alone on different cell lines to understand better its mechanism of action.

METHODS

Cells and media including 3T3-L1 preadipocytes, normal foreskin fibroblasts, neonatal human dermal microvascular endothelial cells (CADMEC), and fetal human skeletal muscle cells (HSkMC) were used. After 24 h, cells were exposed in 3-4, 5-dimethylthiazol-2-yl-2, 3-diphenyl tetrazolium bromide reagent (MTT assays) to increasing dosages of phosphatidylcholine formulation (0.0156-0.5 mg/ml) or an equivalent vehicle, sodium deoxycholate solution, pH 9.0 (0.0066-0.210 mg/ml). Viability was assessed after 1, 2, and 3 days of treatment. Fat tissue (4 x 4 cm) obtained ex vivo from the dorsal fat pads of five rabbits was injected with 2 ml of phosphatidylcholine formulation (50 mg/ml), sodium deoxycholate (21 mg/ml), or normal saline and incubated for 24 h. These were examined histologically to identify cell lysis and morphologic changes.

RESULTS

At 0.125- and 0.25-mg/ml doses of phosphatidylcholine solution, CADMEC and HSkMC were more sensitive (P < 0.001, one-way ANOVA) than adipocytes at all time points examined. Phosphatidylcholine formulation at a dose of 0.5 mg/ml and the equivalent vehicle, sodium deoxycholate, at a dose of 0.21-mg/ml both induced nearly 100% fat cell lysis after 24 h, and evidence of cell lysis as early as 6 h after exposure. After incubation of fat tissue for 24 h with phosphatidylcholine formulation, loss of intracellular lipid staining with an increase in extracellular lipids was seen.

CONCLUSIONS

Isolated sodium deoxycholate was almost as effective as the phosphatidylcholine formulation, at clinical concentrations, in reducing the viability of mature adipocytes over time. Similar cytotoxic effects of phosphatidylcholine formulation on normal foreskin fibroblasts, endothelial cells, and human skeletal muscle cells also were observed. The data prove that the formulation acts in a nonspecific manner and that its unintentional administration to other tissues causes cell death.

Bile acid alone, or in combination with acid, induces CDX2 expression through activation of the epidermal growth factor receptor (EGFR)

OBJECTIVES

Bile acids and acid are implicated in the development of Barrett's esophagus. Evidence suggests that Barrett's esophagus intestinal metaplasia may occur via induction of caudal homeobox gene 2 (CDX2). We hypothesized that induction of CDX2 by bile acids may be due to ligand-dependent transactivation of epidermal growth factor receptor (EGFR).

METHODS

Human mucosal epithelial cells (SEG-1) were treated for 0 to 24 h with up to 300 microM deoxycholic acid (DCA) at pH 7 or 5 with or without (w/wo) antibodies against EGFR ligand-binding site (Mab528, 3-5 mug/ml). Treatment with 100 ng/ml EGF served as control. CDX2 mRNA expression was determined by real-time polymerase chain reaction. EGFR activation was analyzed by Westerns of phosphorylated EGFR tyrosines.

RESULTS

Acid (pH 5) increased the induction of CDX2 mRNA expression caused by DCA. CDX2 mRNA induction was markedly reduced by EGFR blockade with Mab528. Each treatment (pH 5, DCA or pH 5 plus DCA) activated the EGFR on all tyrosines tested but in different time courses. Phosphorylation by DCA was inhibited by Mab528. Activation of EGFR by DCA at pH 5 resulted in EGFR degradation, while that by DCA alone did not.

CONCLUSION

Thus, CDX2 induction by DCA w/wo acid occurs through ligand-dependent transactivation of the EGFR. The variations in EGFR degradation pattern with DCA or DCA at pH 5 indicate differential transactivation pathways. The molecular pathogenesis of Barrett's esophagus may occur via bile-stimulated cell signaling through the EGFR.

The inhibitory effects of cholalic acid and hyodeoxycholalic acid on the expression of TNFalpha and IL-1beta after cerebral ischemia in rats

Previous studies have shown that Qing Kai Ling, a traditional Chinese medicine, was able to effectively prevent the inflammation from cerebral ischemia (Chen et al., 2002). The cholalic acid and hyodeoxycholalic acid (cholalic acid mixture) was major active components in Qing Kai Ling. To study the effects of cholalic acid mixture on the damage cascade of cerebral ischemia, rat model of focal cerebral ischemia was established by permanent occlusion of left middle cerebral artery. We found that the administration of cholalic acid mixture could reduce the ischemic infarct size after 24 h of ischemia, and cholalic acid mixture could be detected in cerebrospinal fluid after 2h of administration. We also found that the concentrations of tumor necrosis factor-alpha and interlukin-1beta in rat brain were significantly lower when compared to the untreated animals after 12 h and 24 h of ischemia. The concentrations of von Willebrand factor and neuron specific enolase in the plasma were remarkably decreased in cholalic acid mixture treated animals than in the untreated ones after 12h of ischemia. Our results suggested that cholalic acid mixture is able to decrease the expression of inflammation factors including tumor necrosis factor-alpha and interlukin-1beta after focal cerebral ischemia.

Modulating effect of polyethylene glycol on the intestinal transport and absorption of prednisolone, methylprednisolone and quinidine in rats by in-vitro and in-situ absorption studies

The effects of polyethylene glycol 20000 (PEG 20000) on the intestinal absorption of prednisolone, methylprednisolone and quinidine, three P-glycoprotein (P-gp) substrates, across the isolated rat intestinal membranes were examined by an in-vitro diffusion chamber system. The serosal-to-mucosal (secretory) transport of these P-gp substrates was greater than their mucosal-to-serosal (absorptive) transport, indicating that their net movement across the intestinal membranes was preferentially in the secretory direction. The polarized secretory transport of these drugs was remarkably diminished and their efflux ratios decreased in the presence of PEG 20000. In addition, PEG 20000 did not affect the transport of Lucifer yellow, a non-P-gp substrate. The intestinal membrane toxicity of PEG 20000 was evaluated by measuring the release of alkaline phosphatase (ALP) and protein from the intestinal membranes. The release of ALP and protein was enhanced in the presence of 20 mM sodium deoxycholate (NaDC), a positive control, while these biological parameters did not change in the presence of 0.1-5% (w/v) PEG 20000. These findings indicated that the intestinal membrane damage caused by PEG 20000 was not a main reason for the enhanced absorptive transport of these P-gp substrates in the presence of PEG 20000. Furthermore, the transepithelial electrical resistance (TEER) of rat jejunal membranes in the presence or absence of PEG 20000 was measured by a diffusion chamber method. PEG 20000 (0.1-5.0 % w/v) did not change the TEER values of the rat jejunal membranes, indicating that the increase in the absorptive transport of these P-gp substrates might not be due to the increased transport of these P-gp substrates via a paracellular pathway caused by PEG 20000. Finally, the effect of PEG 20000 on the intestinal absorption of quinidine was examined by an in-situ closed-loop method. The intestinal absorption of quinidine was significantly enhanced in the presence of 0.1-1.0% (w/v) PEG 20000. These findings suggest that PEG 20000 might be a useful excipient to improve the intestinal absorption of quinidine, which is mainly secreted by a P-gp-mediated efflux system in the intestine.

Multiple cyclin kinase inhibitors promote bile acid-induced apoptosis and autophagy in primary hepatocytes via p53-CD95-dependent signaling

Previously, using primary hepatocytes residing in early G1 phase, we demonstrated that expression of the cyclin-dependent kinase (CDK) inhibitor protein p21Cip-1/WAF1/mda6 (p21) enhanced the toxicity of deoxycholic acid (DCA) + MEK1/2 inhibitor. This study examined the mechanisms regulating this apoptotic process. Overexpression of p21 or p27(Kip-1) (p27) enhanced DCA + MEK1/2 inhibitor toxicity in primary hepatocytes that was dependent on expression of acidic sphingomyelinase and CD95. Overexpression of p21 suppressed MDM2, elevated p53 levels, and enhanced CD95, BAX, NOXA, and PUMA expression; knockdown of BAX/NOXA/PUMA reduced CDK inhibitor-stimulated cell killing. Parallel to cell death processes, overexpression of p21 or p27 profoundly enhanced DCA + MEK1/2 inhibitor-induced expression of ATG5 and GRP78/BiP and phosphorylation of PKR-like endoplasmic reticulum kinase (PERK) and eIF2alpha, and it increased the numbers of vesicles containing a transfected LC3-GFP construct. Incubation of cells with 3-methyladenine or knockdown of ATG5 suppressed DCA + MEK1/2 inhibitor-induced LC3-GFP vesicularization and enhanced DCA + MEK1/2 inhibitor-induced toxicity. Expression of dominant negative PERK blocked DCA + MEK1/2 inhibitor-induced expression of ATG5, GRP78/BiP, and eIF2alpha phosphorylation and prevented LC3-GFP vesicularization. Knock-out or knockdown of p53 or CD95 abolished DCA + MEK1/2 inhibitor-induced PERK phosphorylation and prevented LC3-GFP vesicularization. Thus, CDK inhibitors suppress MDM2 levels and enhance p53 expression that facilitates bile acid-induced, ceramide-dependent CD95 activation to induce both apoptosis and autophagy in primary hepatocytes.

Association of ompU gene in Vibrio cholerae from patients and environment with bile resistance

The objective of this study was to determine whether Vibrio cholerae, possessing ompU isolated from patients and the environment, conferred bile resistance and whether other virulence genes were also related to bile resistance. Fifty-two V cholerae O1 and non-O1 isolates were examined by PCR for the presence of the virulence-associated and regulatory genes, ctxA, tcpA, zot, ace, ompU, toxR, hlyA and stn/sto. V. cholerae possessing ompU resistant to equal or greater than 10% sodium deoxycholate were found in 93% of isolates but only in 9% of V. cholerae isolates not possessing ompU. The effects of other virulence genes on bile resistance could not be ascertained in this study. Thus V cholerae non-O1 with ompU and possibly other virulence genes isolated from the environment have the potential of affecting public health.

Sodium-deoxycholate-assisted tryptic digestion and identification of proteolytically resistant proteins

Identification of proteolytically resistant proteins with compact molecular structure and/or poor water solubility is a challenge in current proteomic study. In this study, sodium deoxycholate (SDC)-assisted tryptic digestion and identification of proteolytically resistant myoglobin and integral membrane proteins were systematically investigated. When the effect of SDC up to 10% on trypsin activity was investigated, little decrease in the trypsin activity was observed in 1% SDC solution, 2-5% SDC decreased the enzyme activity only by about 13.6%, and even in the presence of 10% SDC trypsin still retained 77.4% of its activity. Matrix-assisted laser desorption ionization time of flight mass spectrometry analysis showed that SDC could be removed from sample solution with acid treatment followed by centrifugation, and the remaining SDC, if any, had little effect on mass spectrometry analysis with regard to the number and signal/noise ratio of ions in the mass spectra. Compared with urea and methanol, two other commonly used additives in addition to SDS in proteomic analysis, SDC improved more efficiently the denaturation, solubilization, and tryptic digestion of proteins, particularly proteolytically resistant myoglobin and integral membrane proteins, thereby enhancing the efficiency of their identification with regard to the number of identified proteins and unique peptides and the sequence coverage of matched proteins.

Virulence properties of Campylobacter jejuni isolates of poultry and human origin

Campylobacter jejuni is one of the leading causes of food-borne gastroenteritis. Because of the high prevalence of C. jejuni in poultry, poultry meat is considered a major source of C. jejuni infections for humans. However, it is not known whether all poultry-associated C. jejuni strains are capable of causing disease in humans. Four different virulence properties of C. jejuni strains were compared between 20 poultry isolates and 24 human isolates. Strains were chosen based on their PFGE pattern to represent a heterogeneous population. The isolates were compared for their ability to invade and induce interleukin-8 (IL-8) production in T84 cells, their production of functional cytolethal distending toxin (CDT) using HEp-2 cells, and their sodium deoxycholate resistance. All four virulence factors were present among strains of human and poultry origin, with strong differences observed among strains. For invasion and IL-8 induction, no difference was observed between the two populations. However, on average, human isolates arrested more HEp-2 cells in their cell cycle than did the poultry isolates (P=0.041), suggesting higher CDT production by the former. The ability to survive 16 000 mug sodium deoxycholate ml(-1) was significantly more pronounced (P=0.006) among human isolates than poultry isolates, although all strains possessed the cmeABC operon. These data suggest that all four virulence properties are widespread among C. jejuni isolates, but that a higher degree of bile-salt resistance and more pronounced CDT production are associated with strains causing enteritis in humans.

17-Allylamino-17-demethoxygeldanamycin enhances the lethality of deoxycholic acid in primary rodent hepatocytes and established cell lines

Ansamycin antibiotics that target heat shock protein 90 function are being developed as anticancer agents but are also known to be dose limiting in patients due to hepatotoxicity. Herein, to better understand how the normal tissue toxicity of geldanamycins could be ameliorated to improve the therapeutic index of these agents, we examined the interactions of 17-allylamino-17-demethoxygeldanamycin (17AAG) and the secondary bile acid deoxycholic acid (DCA) in hepatocytes and fibroblasts. DCA and 17AAG interacted in a greater than additive fashion to cause hepatocyte cell death within 2 to 6 h of coadministration. As single agents DCA, but not 17AAG, enhanced the activity of extracellular signal-regulated kinase 1/2, AKT, c-Jun NH(2)-terminal kinase 1/2 (JNK1/2), and p38 mitogen-activated protein kinase (MAPK). Combined exposure of cells to DCA and 17AAG further enhanced JNK1/2 and p38 MAPK activity. Inhibition of JNK1/2 or p38 MAPK, but not activator protein-1, suppressed the lethality of 17AAG and of 17AAG and DCA. Constitutive activation of AKT, but not MAPK/extracellular signal-regulated kinase kinase 1/2, suppressed 17AAG- and DCA-induced cell killing and reduced activation of JNK1/2. DCA and 17AAG exposure promoted association of BAX with mitochondria, and functional inhibition of BAX or caspase-9, but not of BID and caspase-8, suppressed 17AAG and DCA lethality. DCA and 17AAG interacted in a greater than additive fashion to promote and prolong the generation of reactive oxygen species (ROS). ROS-quenching agents, inhibition of mitochondrial function, expression of dominant-negative thioredoxin reductase, or expression of dominant-negative apoptosis signaling kinase 1 suppressed JNK1/2 and p38 MAPK activation and reduced cell killing after 17AAG and DCA exposure. The potentiation of DCA-induced ROS production by 17AAG was abolished by Ca(2+) chelation and ROS generation, and cell killing following 17AAG and DCA treatment was abolished in cells lacking expression of PKR-like endoplasmic reticulum kinase. Thus, DCA and 17AAG interact to stimulate Ca(2+)-dependent and PKR-like endoplasmic reticulum kinase-dependent ROS production; high levels of ROS promote intense activation of the p38 MAPK and JNK1/2 pathways that signal to activate the intrinsic apoptosis pathway.

A newly developed oral heparin derivative for deep vein thrombosis: Non-human primate study

The development of orally active heparin will have tremendous clinical importance since it can be used to effectively prevent deep vein thrombosis (DVT) in a long-term chronic treatment. We developed in this study a new orally active heparin derivative (Db-LHD), which has heparin chemically conjugated with deoxycholic acid and DMSO molecules by secondary interactions. Db-LHD was prepared in the powder form in soft capsules. When we administered Db-LHD capsules to monkeys, its oral physiological availability was increased up to 16.6%. The maximum anti-FXa activity at 5 mg/kg of Db-LHD was more than twice the minimum effective anti-FXa activity (MEC, 0.1 IU/mL) for preventing DVT, and the anti-FXa activity in plasma was maintained for 10 h above the MEC in monkeys. Also, we evaluated anti-thrombogenic effect of Db-LHD in a rat thrombosis model. A subcutaneous administration of enoxaparin (100 IU/kg), which was the highest recommended dose for the prevention of venous thromboembolism, reduced thrombus formation by 38.9+/-14.2%. On the other hand, 5 mg/kg (425 IU/kg) of orally administered Db-LHD reduced thrombus formation by 51.0+/-2.0. We propose a new orally active heparin, Db-LHD, in a solid dosage form to effectively prevent DVT and PE.

Dihydroxy bile acids increase mucosal permeability and bacterial uptake in human colon biopsies

OBJECTIVE

Bile acids in mM concentrations are known to increase chloride secretion and alter mucosal permeability in animal colon. Increased mucosal permeability is believed to play an important role in the development of intestinal inflammation. The aim of this study was to investigate the influence of microM concentrations of dihydroxy bile acids on permeability and bacterial uptake in the normal human colon.

MATERIAL AND METHODS

Endoscopic biopsies from the sigmoid colon of 18 subjects with normal colonic histology were mounted in modified Ussing chambers. Chenodeoxycholic acid (CDCA) and deoxycholic acid (DCA) were added to the mucosal compartment. Short-circuit current (Isc) and transepithelial resistance (TER) were studied for 120 min. Cr-EDTA and horseradish peroxidase (HRP) were used to assess paracellular and transcellular permeability, respectively. The transmucosal passage of chemically killed Escherichia coli was quantified and investigated using confocal microscopy.

RESULTS

A significant decrease in TER was seen after 60 min of exposure to 1000 micromol/l CDCA and DCA. The combination of E. coli and 100 micromol/l CDCA gave a decrease in TER compared to controls (p = 0.06). DCA showed a dose-related increase in Cr-EDTA permeability, which was most pronounced at 1000 micromol/l (p = 0.02). Increased E. coli uptake was induced by 500 micromol/l (p = 0.01) and 1000 micromol/l CDCA (p = 0.04). Bacterial uptake was increased at 100 micromol/l by exposure to DCA (p = 0.03). Confocal microscopy revealed the presence of E. coli bacteria in the lamina propria after 15 min of exposure to 1000 micromol/l CDCA and DCA.

CONCLUSIONS

Our study suggests that dihydroxy bile acids in microM concentrations alter barrier function in normal human colon biopsies, causing increased antigen and bacterial uptake; thereby bile acids may contribute to the development of intestinal inflammation.

Aqueous sodium dehydrocholate–sodium deoxycholate mixtures at low concentration

The behavior of the sodium dehydrocholate (NaDHC)-sodium deoxycholate (NaDC) mixed system was studied by a battery of methods that examine effects caused by the different components of the system: monomers, micelles, and both components. The behavior of the mixed micellar system was studied by the application of Rubingh's model. The obtained results show that micellar interaction was repulsive when the aggregates were rich in NaDHC. The gradual inclusion of NaDC in micelles led to a structural transformation in the aggregates and the interaction became attractive. The bile salts' behavior in mixed monolayers at the air-solution interface was also investigated. Mixed monolayers are monotonically rich in NaDC, giving a stable and compact adsorbed layer. Results have shown that the interaction in both micelles and monolayer is not ideal and such behavior is assumed to be due to a structural factor in their hydrocarbon backbone.

Proteolytic cleavage of ostrich and turkey pancreatic lipases: production of an active N-terminal domain

OBJECTIVES

The aim of this study was to check some biochemical and structural properties of ostrich and turkey pancreatic lipases (OPL and TPL, respectively).

METHODS

Limited proteolysis of OPL and TPL was performed in conditions similar to those reported for porcine pancreatic lipase.

RESULTS

In the absence of bile salts and colipase, OPL failed to catalyze the hydrolysis of pure tributyrin or efficiently hydrolyze olive oil emulsion. When bile salts and colipase were preincubated with the substrate, the OPL kinetic behavior remained linear for more than 30 minutes. The enzyme presented a penetration power value into an egg phosphatidylcholine monomolecular film that was comparable to that of HPL and lower than that of TPL. Chymotrypsin, trypsin, and thermolysin were able to hydrolyze OPL and TPL in different ways. In both cases, only N-terminal fragments accumulated during the hydrolysis, whereas no C-terminal fragment was obtained in either case. Tryptic cleavage of OPL and TPL completely degraded the enzymes. Nevertheless, chymotryptic attack generated 35-kd and 43-kd forms for TPL and OPL, respectively. Interestingly, the OPL 43-kd form was inactive, whereas the TPL 35-kd protein conserved its lipolytic activity.

CONCLUSIONS

OPL, TPL, and mammal pancreatic lipases share a high amino acid sequence homology. Further investigations are, however, needed to identify key residues involved in substrate recognition responsible for biochemical differences between the 2 classes of lipases.