The pH dependence of the hemolytic potency of bile salts

Phosphatidylserine (PS) and phosphatidylglycerol (PG) enriched mixed micelles (MM): A new nano-drug delivery system with anti-inflammatory potential?

Phosphatidylserine (PS) and phosphatidylglycerol (PG) are naturally occurring phospholipids (PL) with intrinsic anti-inflammatory properties. The therapeutic potential of PS and PG has not been extensively explored and the main focus had been directed towards PS- and PG-liposomes. In order to increase the formulation options, we explored whether mixed micelles (MM) could be an alternative to liposomes. Potential advantages of MM are their thermodynamic stability, small size and ease of manufacture. DOPS- and DOPG-enriched MM were obtained via a co-precipitation technique and physicochemical characterization was performed. The MM, approximately 10 nm in diameter, showed no toxicity on fibroblast cell lines in vitro and virtually no hemolytic activity. The MM suppressed the TNFα-production of mIFNγ/LPS-stimulated mouse peritoneal macrophages (MPM) in vitro similar to DOPS- and DOPG-liposomes. Therefore, DOPS- and DOPG-loaded MM are promising new options for the treatment of inflammatory diseases.

Factors associated with hemolysis during extracorporeal membrane oxygenation (ECMO)-Comparison of VA- versus VV ECMO

Venovenous (VV) and venoarterial (VA) extracorporeal membrane oxygenation (ECMO) are effective support modalities to treat critically ill patients. ECMO-associated hemolysis remains a serious complication. The aim was to disclose similarities and differences in VA- and VV ECMO-associated hemolysis. This is a retrospective single-center analysis (January 2012 to September 2018) including 1,063 adult consecutive patients (VA, n = 606; VV, n = 457). Severe hemolysis (free plasma hemoglobin, fHb > 500 mg/l) during therapy occurred in 4% (VA) and 2% (VV) (p≤0.001). VV ECMO showed significantly more hemolysis by pump head thrombosis (PHT) compared to VA ECMO (9% vs. 2%; p≤0.001). Pretreatments (ECPR, cardiac surgery) of patients who required VA ECMO caused high fHb pre levels which aggravates the proof of ECMO-induced hemolysis (median (interquartile range), VA: fHb pre: 225.0 (89.3–458.0); VV: fHb pre: 72.0 (42.0–138.0); p≤0.001). The survival rate to discharge from hospital differed depending on ECMO type (40% (VA) vs. 63% (VV); p≤0.001). Hemolysis was dominant in VA ECMO patients, mainly caused by different indications and not by the ECMO support itself. PHT was the most severe form of ECMO-induced hemolysis that occurs in both therapies with low frequency, but more commonly in VV ECMO due to prolonged support time.

A structure-property relationship study of the well-defined telodendrimers to improve hemocompatibility of nanocarriers for anticancer drug delivery

A series of telodendrimer (a linear polyethyelene glycol-block-dendritic oligo-cholic acid) have been synthesized via a bottom-up approach to optimize the hemocompatibility of the nanocarrier. Numbers of hydrophilic glycerol groups were introduced onto the polar surface of cholic acid to reduce the plasma membrane lytic activity of telodendrimers. An interesting result was observed: only an optimum number of glycerol introduced could reduce the hemolytic properties of the nanocarrier; on the contrary, more glycerols or the amino-glycerol substitution onto cholic acid significantly increased the hemolytic properties of the nanocarriers. To further elucidate the structure-property relationship, the molecular dynamic approach was used to simulate the conformation of the subunits of telodendrimers with different glycerol substitution, and the binding energies and the polar surface areas of the hairpin conformations were calculated to explain the membrane activities of nanocarriers. In addition, these telodendrimer subunits were synthesized and their membrane activities were tested directly, which validated the computational prediction and correlated with the observed hemolytic activity of nanocarriers. The glycerol substitution sustained the facial amphiphilicity of cholic acid, maintaining the superior drug loading capacity (paclitaxel and doxorubicin), stability, cell uptake, and anticancer efficacy of payloads. The in vivo optical imaging study indicated that the optimized nanocarriers can specifically deliver drug molecules to the tumor sites more efficiently than free drug administration, which is essential for the enhanced cancer treatment.

Long-circulating perfluorooctyl bromide nanocapsules for tumor imaging by 19FMRI

PLGA-PEG nanocapsules containing a liquid core of perfluorooctyl bromide were synthesized by an emulsion-evaporation process and designed as contrast agents for (19)F MRI. Physico-chemical properties of plain and PEGylated nanocapsules were compared. The encapsulation efficiency of PFOB, estimated by (19)F NMR spectroscopy, is enhanced when using PLGA-PEG instead of PLGA. PLGA-PEG nanocapsule diameter, measured by Dynamic Light Scattering is around 120 nm, in agreement with Transmission Electron microscopy (TEM) observations. TEM and Scanning Electron Microscopy (SEM) reveal that spherical core-shell morphology is preserved. PEGylation is further confirmed by Zeta potential measurements and X-ray Photoelectron Spectroscopy. In vitro, stealthiness of the PEGylated nanocapsules is evidenced by weak complement activation. Accumulation kinetics in the liver and the spleen was performed by (19)F MRI in mice, during the first 90 min after intravenous injection. In the liver, plain nanocapsules accumulate faster than their PEGylated counterparts. We observe PEGylated nanocapsule accumulation in CT26 xenograft tumor 7 h after administration to mice, whereas plain nanocapsules remain undetectable, using (19)F MRI. Our results validate the use of diblock copolymers for PEGylation to increase the residence time of nanocapsules in the blood stream and to reach tumors by the Enhanced Permeation and Retention (EPR) effect.

Biological activities of steroid glycosides from starfish

Glycosides of polyhydroxysteroids from starfish were compared with regard to hemolytic activities on mouse red blood cells and cytotoxicity on developing eggs of sea urchin Strongylocentrotus intermedius. Mediasteroside M(1) from Mediaster murrayi with a 2-O-methyl group at a xylose residue exerted lower activity than mediasteroside M(2) without this group. Ceramasteroside C(2) from Ceramaster patagonicus having a 2,4-di-O-Me-Xylp residue had more activity in comparison with ceramasteroside C(3) with 2-O-Me-Xylp. Activities of rathbuniosides R(1) (four OH-groups) and R(2) (five OH-groups) from Asterias rathbuni, and culcitosides C(2) (six OH-groups) and C(3) (five OH-groups) from Culcita novaeguineae were inversely proportional to the number of hydroxyl groups of the aglycon. There was a correlation between cytotoxic and hemolytic activities. The results indicated that salt concentration, temperature and pH values are important for the hemolytic activity of steroid glycosides.

Autoimmune hemolysis associated with primary biliary cirrhosis responding to ursodeoxycholic acid as sole treatment

Coombs' positive autoimmune hemolytic anemia (AIHA) has been rarely described in association with primary biliary cirrhosis (PBC). The previously reported cases have responded to treatment with a combination of corticosteroids and ursodeoxycholic acid (UDCA). We report a case of AIHA occurring in association with PBC, which has responded to treatment with UDCA alone. Possible mechanisms of autoimmune hemolysis in this patient include bile salt induced immune dysregulation and direct damage to red cell membranes by bile salts leading to exposure of neoantigens and development of red cell autoantibodies. A trial of UDCA as a single agent should be considered as initial treatment in this rare disorder.

Physiologic concentrations of bile salts inhibit rat hepatic alkaline phosphatase but not the intestinal isoenzyme

OBJECTIVE

The effect of bile salts on alkaline phosphatase (EC 3.1.3.1) activity from Wistar rat liver, duodenum, jejunum, and serum was investigated.

DESIGN AND RESULTS

For concentrations higher than 1 mM conjugated bile salts (glycocholate, glycochenodeoxycholate, taurocholate, taurodeoxycholate, and taurochenodeoxycholate) inhibited hepatic ALP but, up to concentrations of 10 mM, had no effect on intestinal ALP. Also cholate, deoxycholate, and chenodeoxycholate, within the same concentration range, did not have any effect on intestinal ALP. ALP inhibition induced by conjugated bile salts was significantly higher in serum of starved rats than in serum of fed animals, what is in good agreement with the known higher proportion of hepatic ALP and lower proportion of intestinal ALP in serum of starved rats.

CONCLUSIONS

Bile salts can, thus, be used to help discriminating between tissue-nonspecific and intestinal ALP isoenzymes and identifying pathologic conditions where the relative quantities of these isoenzymes are altered in serum. Inhibition of hepatic ALP by physiologic concentrations of bile salts may bear some relation to the bile salts effects on their own enterohepatic circulation and/or biosynthesis.

Bile salt deconjugation by lactobacillus plantarum 80 and its implication for bacterial toxicity

The effects of bile salts on the survival of lactobacilli were investigated using glycocholic acid, cholic acid and deoxycholic acid as model compounds and the bile salt hydrolase active Lactobacillus plantarum 80 (BSH+) and its BSH negative mutant. The detrimental effects of cholic acid, i.e. growth inhibition and cytotoxicity at a concentration of 1 and 5 mmol l-1, respectively, were considered to be due to the hydrophobic protonated form of the molecule, which brings about membrane damage. The conversion of glycocholic acid to cholic acid by the BSH active L. plantarum 80 caused a growth inhibition which was comparable with the inhibition observed in the broth supplemented with 1 mmol l-1 cholic acid. Deoxycholic acid caused toxicity through membrane damage when the compound was in solution. Its toxicity disappeared in the culture broth as the molecule precipitated. In case of cholic acid, the toxicity could be removed by buffering the solution at pH 7.0. It was calculated that at this pH most of the cholic acid molecules were ionized. The results led to the formulation of an extended hypothesis about the ecological significance of bile salt transformations. Primary deconjugation is carried out to counteract intracellular acidification. Yet, the deconjugated molecule can be harmful at moderately acidic pH-values. In this case, the BSH+ strains could effectively profit from their activity in case they are associated with 7alpha-dehydroxylating bacteria which dehydroxylate the deconjugated bile salts. The dehydroxylated molecule has a low solubility and precipitates at moderately acidic pH.

The membranotropic activity of cyclic acyldepsipeptides from bacterium Bacillus pumilus, associated with the marine sponge Ircinia sp

The isolate of Bacillus pumilus associated with the marine sponge Ircinia sp. produced the surfactin-like lipopeptides, cyclic acyldepsipeptides. The hemolytic activity of individual cyclic acyldepsipeptides, bacircines (BI) 2, 3, 4, 5 and 5A having different acyl side chain structures (anteiso-C13, iso-C14, normal-C14, anteiso-C15, and iso-C15, respectively) was studied. The hemolytic power of bacircines depended on both the structure of the side chain (n->iso->anteiso-) and pH values (5.6 and 6.5 > 7.4). Hemolytic potency as a function of BI 5 concentration was given for pH 6.5; 7.4; 8.0; 9.0. pH dependent hemolysis induced by BI 5 was shown to be reversible. The membrane damaging potential of bacircine 5 (5 microM) at pH 6.5 was characterized by a higher rate of hemolysis and by a shorter time between the introduction of BI 5 solution into the RBC samples and the onset of hemolysis. Under this condition, BI 5 decreased abnormally the microviscosity of erythrocyte ghosts bilayer. The damaging potency of BI 5 decreased with an increase pH from 6.5 to 7.4 or its decrease from 6.5 to 4.9. It was shown that fatty acid bacircine fragment penetrated into the lipid bilayer to a depth of minimum 7 carbon atoms. Constants of dissociation of the Asp (pK 4.75) and Glu (pK 6.65) residues of bacircine in the lipid bilayer were obtained. These results showed that at pH 6.5 BI 5 possessed membranotropic activity in the monoionic form.

Low pH-induced hemolysis of erythrocytes is related to the entry of the acid into cytosole and oxidative stress on cellular membranes

HCl-induced lysis of mammalian erythrocytes, pretreated with DIDS, which is a specific inhibitor of the anion transport in their membranes, was markedly delayed. After acidification of a suspension of DIDS-inhibited cells, hemolysis was initiated by addition of a protonophore (Na-salicylate) at any moment chosen by will. These findings revealed that low-pH hemolysis depended on the rate of the transfer of acid equivalents into cytosole. Erythrocyte acid resistance was studied in a group of mammals and found to be inversely related to the rate of monovalent anion exchange in membranes which supported the above observations. In human erythrocytes, the critical level of cytosole acidification was found to be about pH 5.7 by measuring the acid equivalent absorbed by cells prior to hemolysis. HCl-induced hemolysis was also studied in human erythrocyte ghosts resealed with one-sixth of the initial hemoglobin content of cells. During the prelytic interval the ghosts suspended in isotonic NaCl/sucrose media shrunk, indicating an increase in ion permeability. The increase in prelytic permeability and hemolysis were strongly delayed in ghosts prepared from DIDS-treated cells, suggesting a uniform mechanism of lysing in cells and their ghosts. The prelytic increase in ion permeability was measured by the corresponding rate of ghost shrinkage and was found to be pH-dependent, with a high value below pH 3.4 and a very low one above pH 4.0. Compared to cells, the prelytic barrier impairment in ghosts had more mild character although it required greater concentration of cytosolic H+. While finally complete, hemolysis of cells was strongly delayed in the presence of catalase (500-1500 U/ml) and superoxide dismutase (200-600 U/ml) in hemolytic media. In conclusion, the acid-induced hemolysis could be associated with an oxidative injury of membranes, mainly triggered by the entry of acid equivalents into the cytosole.

Protection by chlorpromazine, albumin and bivalent cations against haemolysis induced by melittin, [Ala-14]melittin and whole bee venom

The ability of the peptides melittin, [Ala-14]melittin (P14A) and whole bee venom to lyse red blood cells (RBC) and to cause shape transformation, binding, partitioning and changes in volume of the cells during haemolysis, as well as the action of the bivalent cations Zn2+ and Ca2+, chlorpromazine, albumin and plasma on the peptide-induced haemolysis of RBC in high ionic-strength solution, have been investigated. The protective effect of all inhibitors depends on whether they have been added to the media before or after the cells. When added before the cells they reduced significantly the rate of peptide-induced haemolysis and shape transformation. The effect was maximal when agents acted simultaneously after introduction of the cells into the media containing both inhibitors and peptides. Incubation of the cells in isotonic solution before the addition of peptides enhanced 2-3-fold the RBC susceptibility (i.e. rate of haemolysis) to lytic action of the same amount of peptides, and increased the order of the haemolytic reaction, although the power law coefficient did not exceed a value of 2 for all peptides, suggesting that haemolysis is attributable to the monomeric or dimeric forms of the peptides. Partition coefficients were of the order of approximately 10(6) M-1, and P14A possessed a value 3-fold larger compared with melittin and bee venom, which correlated with its enhanced haemolytic activity. The protective action of inhibitors against peptide-induced haemolysis has been explained on the basis of their ability to compete with peptide binding at an early stage of peptide-membrane interaction, and not as a result of inhibition of a pre-existing peptide-induced pore. Whereas melittin increased the volume of RBC during haemolysis, P14A, melittin in the presence of phospholipase A2 or bee venom, reduced the volume in a concentration-dependent manner. The present data reveal the significant role of the initial stage of peptide-membrane interaction and peptide structure in the mechanism of haemolysis. These data are not consistent with a lipid-based mechanism of peptide-induced haemolysis, indicating that the mode of peptide-protein interaction is an important and decisive step in the haemolytic mechanism. It should be noted that data (in the form of three additional Tables) on the ability of inhibitors to protect cells from haemolysis when inhibitor and peptide act simultaneously are available. They are reported in Supplementary Publication SUP 50178, which has been deposited at the British Library Document Supply Centre, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1996) 313, 9.

IV chenodeoxycholate prevents calcium bilirubinate gallstones during total parenteral nutrition in the prairie dog

BACKGROUND

The purpose of this study was to determine whether IV chenodeoxycholate (CDC) could prevent total parenteral nutrition (TPN)-associated pigmented gallstones in the prairie dog.

METHODS

Twelve prairie dogs were divided into two equal groups, each receiving an identical TPN regimen. Each animal received 92 kcal/d with 61% of the calories from carbohydrate. The total volume of infusate delivered to each animal was 59 mL/d. Animals in one group, termed the TPN + CDC group, received a daily bolus injection of CDC at a dose of 15 mg/kg. Prairie dogs in the second group, termed the TPN group, received water (vehicle carrier) 1 mL/kg/d. The TPN and TPN + CDC groups received TPN for 40.3 +/- 1.3 and 42.5 +/- 0.6 days, respectively.

RESULTS

There was no statistical difference in the initial and final weights between the two groups. None of the TPN + CDC-treated animals had gallstones or calcium bilirubinate crystals. In contrast, all of the TPN-treated animals had calcium bilirubinate crystals (p = .002), and five of six had macroscopic black pigmented gallstones (p = .015). Cholesterol crystals were not observed in either group of animals. The amount of biliary bilirubin and ionized calcium was significantly greater in the TPN group (both p < .001); however, both groups had a similar total biliary calcium concentration.

CONCLUSION

IV CDC is effective in preventing TPN-associated gallstones in the prairie dog.

Hemolytic activities of triterpene glycosides from the holothurian order Dendrochirotida: some trends in the evolution of this group of toxins

Hemolysis and K+ loss from mouse erythrocytes, induced by triterpene glycosides and their derivatives from this order of sea cucumbers were studied. Sulfate groups, attached to position 4 of the first xylose residue and to position 6 of the third glucose residue of the branched pentaosides, having 3-O-methyl-groups in terminal monosaccharide moieties increase K+ loss. A sulfate group at C-4 of the first xylose residue increases the hemolytic activity while a sulfate at C-6 of the third monosaccharide unit decreases it. A sulfate group at C-6 of terminal 3-O-methylglucose drastically decreases the hemolytic activity and rate of K+ loss. The presence of a sulfate group at the first xylose residue in glycosides having no 3-O-methyl group at the terminal monosaccharide decreases hemolytic activity and rate of K+ loss. The presence of the 16-ketone group in aglycones having the 7(8)-double bond significantly decreases activity. These results correlate with the previously proposed trends in evolution of sea cucumber glycosides from substances having sulfate groups at C-6 of glucose and 3-O-methylglucose units to substances sulfated at C-4 of the first xylose or having no sulfate groups, and from substances with aglycone 16-ketone to substances having no oxygen functions in this position.

Cation-sensitive pore formation in rehydrated erythrocytes

Rehydration of red blood cells (RBC) in isotonic media after dehydration in hypertonic electrolyte or nonelectrolyte saline leads to their posthypertonic hemolysis (PH). Ca2+ ions at a concentration of more than 5 mM stimulated hemolysis of RBC treated by hypertonic sucrose but not NaCl if rehydration was carried out in the presence of cations. Zn2+ produced a more complex response of stimulation followed by inhibition as a concentration is increased. Mg2+, Ca2+, Zn2+, EDTA and sucrose exhibited only inhibition when added to isotonic NaCl media immediately after onset of rehydration or later on. At low ionic strength inhibition produced by divalent cations was markedly reduced and sucrose was ineffective. An equimolar concentration of EDTA abolished the inhibition of PH by Zn2+ ions if they were introduced into the isotonic media after the cells, but activated hemolysis when rehydration was carried out in the presence of ions. The same divalent cations prevented shape transformation and hemolysis induced by melittin if they interacted with the plasma membrane prior to the addition of melittin. Subsequent chelation of cations by EDTA triggers the full sequence of events characteristic to the action of melittin alone and resulted in cell spherulation followed by hemolysis. Inhibition of melittin-induced hemolysis produced by all cations was reversible because EDTA abolished the action of divalent cations and even stimulated hemolysis in isotonic sucrose. Similarities in the mode of action of divalent cations and EDTA on posthypertonic hemolysis which is attributed to endogenous stimuli and melittin-induced hemolysis as far as the exogenous agent is concerned imply that in both cases common intrinsic mechanisms are involved in the process of cation-sensitive pore formation in erythrocyte membranes, while differences indicate that more complex pores are formed during posthypertonic injury.

Glycochenodeoxycholate-induced lethal hepatocellular injury in rat hepatocytes. Role of ATP depletion and cytosolic free calcium

Chenodeoxycholate is toxic to hepatocytes, and accumulation of chenodeoxycholate in the liver during cholestasis may potentiate hepatocellular injury. However, the mechanism of hepatocellular injury by chenodeoxycholate remains obscure. Our aim was to determine the mechanism of cytotoxicity by chenodeoxycholate in rat hepatocytes. At a concentration of 250 microM, glycochenodeoxycholate was more toxic than either chenodeoxycholate or taurochenodeoxycholate. Cellular ATP was 86% depleted within 30 min after addition of glycochenodeoxycholate. Fructose, a glycolytic substrate, maintained ATP concentrations at 50% of the initial value and protected against glycochenodeoxycholate cytotoxicity. ATP depletion in the absence of a glycolytic substrate suggested impairment of mitochondrial function. Indeed, glycochenodeoxycholate inhibited state 3 respiration in digitonin-permeabilized cells in a dose-dependent manner. After ATP depletion, a sustained rise in cytosolic free calcium (Cai2+) was observed. Removal of extracellular Ca2+ abolished the rise in Cai2+, decreased cellular proteolysis, and protected against cell killing by glycochenodeoxycholate. The results suggest that glycochenodeoxycholate cytotoxicity results from ATP depletion followed by a subsequent rise in Cai2+. The rise in Cai2+ leads to an increase in calcium-dependent degradative proteolysis and, ultimately, cell death. We conclude that glycochenodeoxycholate causes a bioenergetic form of lethal cell injury dependent on ATP depletion analogous to the lethal cell injury of anoxia.