Investigation of lipase-ligand interactions in porcine pancreatic extracts by microscale thermophoresis.

The evaluation of binding affinities between large biomolecules and small ligands is challenging and requires highly sensitive techniques. Microscale thermophoresis (MST) is an emerging biophysical technique used to overcome this limitation. This work describes the first MST binding method to evaluate binding affinities of small ligands to lipases from crude porcine pancreatic extracts. The conditions of the MST assay were thoroughly optimized to successfully evaluate the dissociation constant (Kd) between pancreatic lipases (PL) and triterpenoid compounds purified from oakwood. More precisely, the fluorescent labeling of PL (PL*) using RED-NHS dye was achieved via a buffer exchange procedure. The MST buffer was composed of 20 mM NaH2PO4 + 77 mM NaCl (pH 6.6) with 0.05% Triton-X added to efficiently prevent protein aggregation and adsorption, even when using only standard, uncoated MST capillaries. Storage at -20 °C ensured stability of PL* and its fluorescent signal. MST results showed that crude pancreatic extracts were suitable as a source of PL for the evaluation of binding affinities of small ligands. Quercotriterpenoside-I (QTT-I) demonstrated high PL* binding affinity (31 nM) followed by 3-O-galloylbarrinic acid (3-GBA) (500 nM) and bartogenic acid (BA) (1327 nM). To enrich the 50 kDa lipase responsible for the majority of hydrolysis activity in the crude pancreatic extracts, ammonium sulfate precipitation was attempted and its efficiency confirmed using capillary electrophoresis (CE)-based activity assays and HRMS. Moreover, to accurately explain enzyme modulation mechanism, it is imperative to complement binding assays with catalytic activity ones.

The Prolidase Activity, Oxidative Stress, and Nitric Oxide Levels of Bladder Tissues with or Without Tumor in Patients with Bladder Cancer.

This study was designed to evaluate the malondialdehyde (MDA), glutathione (GSH) and nitric oxide (NO) levels, and also prolidase, glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) enzyme activities in malignant and benign cancers of bladder tissue. A total of 59 patients admitted to our clinic due to microscopic or macroscopic haematuria, were prospectively included in the study. Because of some reasons (no request to participate in the study, the inability to reach, other malignancies, alcohol consumption, metabolic disease), eight patients were excluded from study. Of the 51 patients, 25 were bladder tumor patients, and 26 were patients without cancers. The bladder tissue samples were obtained from all patients under anesthesia (spinal, epidural or general) for the measurement of MDA, GSH and NO levels, and prolidase, GSH-Px and SOD enzyme activities. Among the patients with bladder cancers, 7 patients were females and 18 patients were males, with an average age of 68.4 ± 2.49. Among patients without tumors, 6 patients were females and 20 patients were males, with an average age of 58 ± 2.05. In patients with bladder tumors, the oxidants (MDA, NO, prolidase) were higher, and the antioxidants (SOD, GSH, GSH-Px) were lower than those in patients without tumors. It was concluded that the oxygen free radicals play a role in the etiology of bladder cancers similar to many other tumors and inflammatory conditions. Therefore, we assume that antioxidants may provide benefits in the prevention and treatment of bladder cancer.

Optimization of pancreatic trypsin extraction in PEG/citrate aqueous two-phase systems.

Enzyme extraction using aqueous two-phase systems (ATPS) has been increasingly used as a primary recovery technique which integrates the clarification, concentration and partial purification of important biomolecules from their natural source in a single step. The goal of this work was to optimize the extraction of trypsin from pancreas homogenate with polyethylene glycol and sodium citrate (PEG/NaCit) ATPS by using the tools of experimental design. The variables NaCl concentration - added inert salt -, the top/bottom phase volume ratio - Vr - and the biomass loaded into the system - in percentage - were selected as the main factors in the trypsin extraction. The yield (%) and the purification factor of trypsin were considered the responses to be optimized. The central composite design and the response surface analysis proved to be suitable tools for a quick and efficient study. As a result, the optimal extraction conditions in PEG3350/NaCit system were 3.34% wt/wt for NaCl concentration, a biomass load which represented 9.30% wt/wt of the total ATPS mass and 6.37 top/bottom volume ratio giving a purification factor of 2.55 and a yield of 99.7% in top phase.

Microglial TNF-α mediates enhancement of dopaminergic degeneration by brain angiotensin.

In vitro and in vivo models of Parkinson's disease were used to investigate whether TNF-α plays a major role in the enhancement of the microglial response and dopaminergic degeneration induced by brain angiotensin hyperactivity. Treatment of primary mesencephalic cultures with low doses of the neurotoxin MPP(+) induced a significant loss of dopaminergic neurons, which was enhanced by cotreatment with angiotensin II and inhibited by TNF-α inhibitors. Treatment of primary cultures with angiotensin induced a marked increase in levels of TNF-α, which was inhibited by treatment with angiotensin type-1-receptor antagonists, NADPH-oxidase inhibitors and NFK-ß inhibitors. However, TNF-α levels were not significantly affected by treatment with angiotensin in the absence of microglia. The microglial origin of the angiotensin-induced increase in TNF-α levels was confirmed using dopaminergic (MES 23.5) and microglial (N9) cell lines. Inhibition of the microglial Rho-kinase activity also blocked the AII-induced increase in TNF-α levels. Treatment of the dopaminergic cell line with TNF-α revealed that NFK-ß activation mediates the deleterious effect of microglial TNF-α on dopaminergic neurons. Treatment of mice with MPTP also induced significant increases in striatal and nigral TNF-α levels, which were inhibited by angiotensin type-1-receptor antagonists or NFK-ß inhibitors. The present results show that microglial TNF-α plays a major role in angiotensin-induced dopaminergic cell death and that the microglial release of TNF-α is mediated by activation of angiotensin type-1 receptors, NADPH-oxidase, Rho-kinase and NFK-ß.

Role of the twin-arginine translocation pathway in Staphylococcus.

In Staphylococcus, the twin-arginine translocation (Tat) pathway is present only in some species and is composed of TatA and TatC. The tatAC operon is associated with the fepABC operon, which encodes homologs to an iron-binding lipoprotein, an iron-dependent peroxidase (FepB), and a high-affinity iron permease. The FepB protein has a typical twin-arginine (RR) signal peptide. The tat and fep operons constitute an entity that is not present in all staphylococcal species. Our analysis was focused on Staphylococcus aureus and S. carnosus strains. Tat deletion mutants (DeltatatAC) were unable to export active FepB, indicating that this enzyme is a Tat substrate. When the RR signal sequence from FepB was fused to prolipase and protein A, their export became Tat dependent. Since no other protein with a Tat signal could be detected, the fepABC-tatAC genes comprise not only a genetic but also a functional unit. We demonstrated that FepABC drives iron import, and in a mouse kidney abscess model, the bacterial loads of DeltatatAC and Deltatat-fep mutants were decreased. For the first time, we show that the Tat pathway in S. aureus is functional and serves to translocate the iron-dependent peroxidase FepB.

Fat malabsorption in cystic fibrosis patients receiving enzyme replacement therapy is due to impaired intestinal uptake of long-chain fatty acids.

BACKGROUND: Pancreatic enzyme replacement therapy frequently fails to correct intestinal fat malabsorption completely in cystic fibrosis (CF) patients. The reason for this failure is unknown. OBJECTIVE: We investigated whether fat malabsorption in CF patients treated with pancreatic enzymes is caused by insufficient lipolysis of triacylglycerols or by defective intestinal uptake of long-chain fatty acids. DESIGN: Lipolysis was determined on the basis of breath 13CO2 recovery in 10 CF patients receiving pancreatic enzyme replacement therapy after they ingested 1.3-distearoyl,2[1-13C]octanoyl glycerol ([13C]MTG). Intestinal uptake of long-chain fatty acids was determined by analyzing plasma [13C]linoleic acid ([13C]LA) concentrations after patients ingested [13C]LA. For 3 d, dietary intakes were recorded and feces were collected. RESULTS: Fecal fat excretion ranged from 5.1 to 27.8 g/d (mean+/-SD: 11.1+/-7.0 g/d) and fat absorption ranged from 79% to 93% (89+/-5%). There was no relation between breath 13CO2 recovery and dietary fat absorption (r = 0.04) after ingestion of [13C]MTG. In contrast, there was a strong relation between 8-h plasma [13C]LA concentrations and dietary fat absorption (r = 0.88, P < 0.001). CONCLUSION: Our results suggest that continuing fat malabsorption in CF patients receiving enzyme replacement therapy is not likely due to insufficient lipolytic enzyme activity, but rather to incomplete intraluminal solubilization of long-chain fatty acids, reduced mucosal uptake of long-chain fatty acids, or both.

Mismatch of duodenal deliveries of dietary fat and pancreatin from enterically coated microspheres.

Gastric emptying of dietary fat is affected by both chemical and physical factors; but when ingested as a free oil or an aqueous emulsion, fat may empty most rapidly immediately after the meal. In contrast, gastric transit of 1- to 3-mm spheres (like those of enterically coated pancreatins) is known to vary inversely with sphere diameter; and spheres leave the stomach initially slowly, if their diameter is > or = 1.6 mm. Our objective was to determine whether 2-mm microspheres of Pancrease would empty much more slowly than free or emulsified oil and whether 1.2-mm microspheres of Creon would empty as fast as free oil. We used a gamma camera to track the concurrent gastric emptying of 123I-labeled oil and 113mIn-labeled spheres of Pancrease or Creon in pancreatic-insufficient subjects with cystic fibrosis who ingested 20 g of free oil in spaghetti meals or 20 g of oil emulsified in a milk meal. We found that either type of oil emptied rapidly initially but slowed later, whereas either dosage form emptied slowly initially but rapidly later. Unexpectedly, the smaller spheres of Creon emptied about the same as Pancrease did after the spaghetti meal. For example, 50% of oil but < 25% of either dosage form had left the stomach by 90 min after the meals. Both dosage forms were lipophilic, forming aggregates in vitro. We concluded that the gastric emptying of either dosage form frequently lagged behind the emptying of oil from ordinary meals. We speculated that the similar transits of the 1.2-mm Creon and the 2-mm Pancrease resulted from aggregation of these microspheres in the presence of free oil.

Inactivation of gastric and pancreatic lipases by diethyl p-nitrophenyl phosphate.

Reacting gastric and pancreatic lipases with mixed diethyl p-nitrophenyl phosphate/bile salt micelles resulted in a stoichiometric inactivation of these enzymes as tested on emulsified tributyroylglycerol and trioleoylglycerol as substrates. Diethyl p-nitrophenyl phosphate treated gastric lipases were also inactive on water-soluble p-nitrophenyl acetate, whereas the modified pancreatic lipase was still able to hydrolyze this water-soluble substrate. The binding of diethyl p-nitrophenyl phosphate modified pancreatic and gastric lipases to tributyroylglycerol/water interface was comparable to that of native lipases. The essential free sulfhydryl group of gastric lipases underwent no chemical changes due to the reaction with micellar diethyl p-nitrophenyl phosphate. All in all, these results indicate that, in both gastric and pancreatic lipases, the essential serine residue which was stoichiometrically labeled by this organophosphorus reagent is involved in catalysis and not in lipid binding.

Pancrease gastroresistance: in vitro evaluation of pH-determined dissolution.

In order to avoid inactivation in the stomach, pancreatic enzymes have been prepared as pH-sensitive, enteric-coated microspheres (Pancrease). An in vitro study was performed to evaluate the pH-related dissolution of Pancrease and to confirm its resistance to gastric acidity. Two assay methods were used with three different batches of Pancrease: (a) Enzyme absorbency at 280 nm was measured at unit pH intervals from pH 1 to pH 8 and at 0.5 pH intervals from the start of dissolution to pH 8. (b) Proteolytic activity was measured at pH 6.8. Significant enzyme dissolution started at pH 5.5 and was maximal at pH 6.0. At pH 6.8, the pH of simulated intestinal fluid, dissolution was complete in less than 15 min. At pH 5.0, no dissolution occurred within the first 10 min and only 13% dissolution was observed after 2 h. At pH 7.0, 100% dissolution was seen within 10 min. Results of the two assay methods were comparable with all three enzyme batches assayed. This study confirmed the gastroresistance of Pancrease. Because of the enteric coating of Pancrease, liberation of enzymes occurs in the duodenum and jejunum, providing maximal enzymatic efficacy in exocrine pancreatic insufficiency.

Influence of antacid and formulation on effectiveness of pancreatic enzyme supplementation in cystic fibrosis.

A series of treatment trials, involving food balances based on determination of fat coefficient absorption, nitrogen faecal loss, and daily faecal weight, was performed in 82 patients with cystic fibrosis. Results showed that a conventional powdered pancreatic extract (Pancrex V) required a high dosage to achieve reasonable improvement in fat and nitrogen absorption (200 mg/kg body weight/day on average) and rarely restored digestion to normal. Bicarbonate (5.2 g/m2 body surface/day) slightly enhanced the enzymatic activity of the powdered extract, this being more apparent in those with more severe steatorrhoea. There was no advantage in providing the extract in microgranules protected by cellulose acetatephthalate. A product based on fungal lipase and protease (Krebsilasi) proved to be ineffective in correcting fat and protein absorption. The two recent products prepared in pH sensitive microspheres (Pancrex V microspheres and Pancreas-Prolipase) had similar advantages in digestive activity. Compared with the traditional preparations, they offered a number of practical advantages, including a smaller number of capsules (particularly Pancrex V microspheres) and improved palatability.

Treatment failure after substitution of generic pancrelipase capsules. Correlation with in vitro lipase activity.

Pancreatic enzyme products are formulated, manufactured, and sold without submitting efficacy or bioavailability data to the Food and Drug Administration because of a quirk in the law. We documented therapeutic failures in three patients with cystic fibrosis after pharmacists substituted generic pancrelipase capsules for the Pancrease brand. Gastrointestinal symptoms and fat malabsorption rapidly resolved after therapy was reinstituted with brand name products. In vitro analysis indicated that after 1 hour of exposure to simulated gastric fluid, lipase activity was less than 200 U per capsule from all three generic capsules dispensed to the patients compared with 6820 U per capsule from Pancrease. These data indicate that the enteric coating of the generic product was defective and that the substituted product was not bioequivalent to the prescribed brand. We conclude that the Food and Drug Administration should institute regulations over this group of products.

Differences in metabolite content between intact pancreases and their perchloric acid extracts. A 2D 1H/31P correlation NMR study.

Perchloric and hydrochloric acid extracts of intact pancreases from healthy rats and from rats with experimental acute pancreatitis were analysed using 2D 1H/31P correlation NMR spectroscopy. Major differences were found in the 2D maps between the extracts and the intact tissues. In the case of the intact diseased pancreas the prominent 31P signal at the phosphodiester region has been assigned in our previous work as lecithin/taurocholate complex. However, the signal found in the same chemical shift region in extracts of diseased pancreases as well as healthy ones, is identified here as the phosphodiester residue of oligoribonucleotides. In these extracts additional 31P signals were found and assigned as phosphomonoester and phosphodiester hydrolysis products of RNA. The amounts of these compounds, as a function of the acid concentrations were determined, and conditions for their minimization were defined.

In vivo and in vitro studies of microsphere pancreatic supplements.

Over the past 5 years, the Leeds Regional Cystic Fibrosis (CF) Unit has provided comprehensive annual assessments of CF patients that include dietary assessments and fat absorption studies. Enteric-coated microsphere pancreatic enzyme preparations (microsphere preparations) were compared to conventional enzymes as therapeutic agents for these patients. Presently in the U.K., two microsphere preparations are licensed for use and a further two products are likely to receive licenses in the near future. The success of these preparations is dependent on the ability of the microsphere coating to resist dissolution until the pH exceeds approximately 5.5 and thus prevent inactivation of lipase in the acid environment of the stomach. A study comparing Pancrex V Forte, a conventional enzyme preparation, to three microsphere preparations, Pancrease, Creon, and pancreatin Merck, confirmed the superiority of Pancrease and Creon over Pancrex V Forte and pancreatin Merck with regard to control of symptoms, and nitrogen and fat absorption. Because of differences in the physical characteristics of various microsphere preparations, the dissolution rates of Pancrease, Creon, and pancreatin Merck were compared in vitro. In aqueous buffers, striking differences among the preparations were seen at pH 5.5; whereas only 25% of available lipase was released from Creon, both Pancrease and pancreatin Merck show almost complete dissolution at this pH. Only at pH 6.5 and above do all three preparations show complete dissolution. In duodenal juice, as in aqueous buffers, lipase release from Creon takes place at a lower rate than with the other two preparations until pH 6.0 or higher is attained.(ABSTRACT TRUNCATED AT 250 WORDS)

Cholesterol esterase activities in commercial pancreatic enzyme preparations and implications for use in pancreatic insufficient cystic fibrosis.

BACKGROUND: Although clinical symptoms in pancreatic insufficiency are often dramatically improved by pancreatic preparations, these often fail to normalize biochemical indicators of malabsorption. It seemed relevant, therefore, to investigate the amounts of cholesterol esterase in these preparations and, using in-vitro methods, some of the activities of this enzyme. The enzyme is just as physiologically important as lipase in accomplishing lipid digestion and absorption. METHODS: Cholesterol esterase was assayed in commercial pancreatic extract preparations, lyophilized pig pancreas and human duodenal fluid. The in-vitro activities of the enzyme were also investigated on single and mixed dietary substrates. RESULTS: Other than Creon, the commercial preparations showed negligible cholesterol esterase activities, whereas considerable activities were found in pancreatic tissue and duodenal fluids. In-vitro, pig cholesterol esterase was confirmed to be dependent on 3-hydroxy bile salt concentration for hydrolysis and synthesis and that the rate for hydrolysis greatly exceeds that of synthesis in normal concentrations of bile salts. However, with mixed lipid substrates, no bile salt concentration was found at which hydrolysis or synthesis predominates. CONCLUSIONS: When pancreatic or hepato-biliary function is compromised, optimum lipid hydrolysis may not be achieved in therapeutic use, and the pig enzyme may perform differently to the human enzyme. In-vivo trials may reveal whether augmentation of the commercial products with this enzyme would be worthwhile.

An in vitro animal model for the study of cereal components toxic in celiac disease.

Peptic-tryptic-Cotazym (PTC) digests were obtained, simulating in vivo protein digestion, from rice, maize, rye, oats, barley, and sorghum prolamines and tested on small intestine cultures from rat fetus. The PTC digests of the prolamine fractions from rice and maize, even when tested at a concentration as high as 0.5 mg/ml, did not affect in vitro differentiation and maturation of fetal rat jejunum that took place in vitro in a way comparable to what happens in vivo. On the contrary, the PTC digests of prolamines from rye, oats, barley, and sorghum were very active in slowing down in vitro development of fetal rat intestine. These results further strengthen earlier findings and all together show that there is a strong correlation between toxicity results of cereal and/or cereal components assessed with clinical trials or in vitro systems based on bioptic specimens of intestinal mucosa from celiac patients and with the culture of rat fetal intestine. Therefore, the rat fetal intestine culture is considered to be an adequate model for screening and investigating cereal peptides which are toxic for the celiac small intestinal mucosa.

CCK-B receptor antagonist YF476 inhibits pancreatic enzyme secretion at a duodenal level in pigs.

BACKGROUND: To evaluate the mechanisms by which cholecystokinin (CCK) regulates the exocrine pancreas, the role and location of CCK receptors in the pig were investigated using the CCK-B receptor antagonist YF476 and different administration routes of CCK. METHODS: In 11 anaesthetized pigs, catheters were surgically implanted in the pancreatic duct for juice collection, and in the gastric arteries and jugular vein, so that infusions of CCK-33 could be directed to the duodenal/gastric, duodenal/pancreatic or general circulations, respectively. Experiments were performed under control conditions, and after pretreatment by gavage feeding with YF476, using either a single, low dose of 0.3 micromol kg, which would block the CCK-B receptors, or a 1000 times higher dose (300 micromol kg), which would also block the CCK-A receptors. RESULTS: The increase in the pancreatic output of protein and the enzymes trypsin and amylase observed after the infusion of CCK-33 at 13 pmol kg to the duodenum/stomach or duodenum/pancreas was inhibited by pretreatment with YF476 at both dosages. In contrast, the increase in protein and enzyme output after the infusion of a supraphysiological dose of CCK-33 (130 pmol kg) to the general circulation was not affected by pretreatment with low dosage YF476, whereas high dosage YF476 completely inhibited the stimulated secretion. CONCLUSIONS: These data indicate that CCK-33 given locally to the duodenum in doses raising CCK to physiological plasma levels stimulates the pancreatic enzyme secretion via duodenal CCK-B receptors. Supra-physiological doses of CCK-33 to the general circulation appeared to affect the pancreatic enzyme secretion via CCK-A receptors located elsewhere than in the pancreatic and duodenal tissue.