Trypsin decorated self-emulsifying drug delivery systems (SEDDS): Key to enhanced mucus permeation.

It was the aim of this study to prepare trypsin decorated mucus permeating self-emulsifying drug delivery systems (SEDDS). Lipophilicity of enzyme was increased by hydrophobic ion pairing (HIP) with the anionic surfactants sodium dodecyl sulfate (SDS), sodium taurocholate (ST) and sodium deoxycholate (SDO) to facilitate its incorporation in SEDDS. Blank SEDDS and trypsin decorated SEDDS were characterized regarding droplet size, polydispersity index (PI), zeta potential and proteolytic activity using Nα-benzoyl-l-arginine ethyl ester (BAEE) assay. Log DSEDDS/release medium of each complex was determined to assess its affinity towards SEDDS oily droplet upon emulsification. Ability of trypsin decorated SEDDS to enhance mucus permeation was studied on mucus gel from porcine small intestine for the period of 4 h at 37 °C. Degree of enzyme precipitation via HIP was 94.5%, 85.7% and 48.2% for SDS, ST and SDO complex, respectively. SEDDS composed of 50% (w/w) cremophor EL, 20% (w/w) captex 300, and 30% (w/w) propylene glycol with a complex payload of 1% (w/w) exhibited a droplet size in the range of 29.92 ±â€¯0.09 nm to 39.15 ±â€¯0.37 nm, a polydispersity index of 0.116-0.265 and zeta potential in the range of -2.36 mv to -4.25 mv. The enzymatic activity of trypsin complexed with SDO, SDS and ST in SEDDS was 51.9%, 44.8%, and 40.7% respectively, of the corresponding activity of free trypsin. Log D values of trypsin, SDS, ST and SDO complex were -2.73, 1.97, 1.89 and 1.68, respectively, suggesting higher lipophilicity of trypsin complexes as compare to free trypsin and ability to reside on SEDDS droplets. Enzyme decorated SEDDS improved mucus permeation 1.6- to 2.6-fold in comparison to blank SEDDS. Results demonstrated that decorating SEDDS with trypsin can be a promising technique to improve their mucus permeating properties.

Correlating enzyme density, conformation and activity on nanoparticle surfaces in highly functional bio-nanocomposites.

The biological activity of the immobilized enzyme is crucial for the performance of different nanoparticle mediated enzymatic assays, where enzymatic conversion can be used for label-free analyte detection. In this article we have addressed two significant aspects of enzyme-nanoparticle interactions. First, we have developed copper sulfide (CuS) nanoparticles with an average diameter of 25 nm as a potential enzyme-interface using trypsin protease as a model enzyme. CuS nanoparticles showed high trypsin immobilization capacity of about 14.0 mg m(-2) with the significant retention of native enzymatic activity (75-98%) at room temperature, even beyond the calculated tightly packed monolayer coverage (which is around 4.1 mg m(-2)). Second, we report a quantitative correlation between the structure-functional relationship and the density of immobilized trypsin on a nanoparticle surface. The in situ conformation of immobilized trypsin could be efficiently analyzed by fluorescence, circular dichroism and FT-IR spectroscopic measurements because of the small size of the nanoparticles. Trypsin molecules appear to retain their close-native tertiary and secondary structural features (with a small loss of 1-2% of helical content) in the entire surface density range (2.0-14.0 mg m(-2)) on the CuS nanoparticles. However, interestingly, at a low surface coverage (2.0 mg m(-2)), immobilized trypsin retains almost 98% of its native enzymatic activity, leading to a highly functional bio-nanocomposite. However, at higher surface coverages, the enzyme activity decreases to 77%, indicating the influence of steric crowding. Furthermore, the high functionality of the immobilized trypsin at low surface density on CuS nanoparticle was also confirmed by determining the kinetic parameters of enzymatic activity.

Immobilization of trypsin on water-soluble dendrimer-modified carbon nanotubes for on-plate proteolysis combined with MALDI-MS analysis.

A novel on-plate digestion method combined with MALDI-MS analysis is reported, using trypsin-linked dendrimer-modified carbon nanotubes (dCNTs) as the enzyme immobilization probe. Excellent digestion performance was achieved in a short time without any complicated reduction and alkylation procedures.

Kinetics of proteolytic reactions in nanoporous materials.

Proteolysis with proteases preloaded within nanopores of porous material is a very fast process, where proteins can be digested in minutes compared to the conventional bulk enzyme reactions taking place over hours. To model this surprising phenomenon, a modified sequential proteolytic mechanism has been developed to simulate the kinetics of the reaction. Digestion of myoglobin was used as an example to show the high efficiency of the in-nanopore enzymatic reaction, while angiotensin 1 and ACTH (1-14) were selected as model peptides to validate the theoretical considerations. The proteolytic peptides were quantified by capillary electrophoresis and sequenced by mass spectrometry using bottom-up strategy. The simulation clearly shows that the major factor for the very fast digestion kinetics observed stems from a peptide confinement effect, where the generated peptides are trapped within a confined space for further proteolysis to the final products. On the other hand, the ingress and diffusion of the proteins into the porous cavity can accelerate or limit the first proteolytic step requiring the encounter between the substrates and enzymes. The present model can be widely applied to different enzyme catalyzed reactions for high-throughput protein profiling, and can promote the study of enzyme reactions occurring inside the cell.

Low-volume continuous hemodiafiltration with nafamostat mesilate increases trypsin clearance without decreasing plasma trypsin concentration in severe acute pancreatitis.

Continuous hemodiafiltration (CHDF) has recently been used for treatment of severe acute pancreatitis. CHDF is capable of eliminating small molecules from blood, but whether trypsin can be eliminated by CHDF is not clear. In this study, elimination of trypsin-like enzyme activity (TLE) and cationic trypsin-like immunoreactivity (TLI) using low-volume CHDF was examined at the first CHDF session in eight patients with severe acute pancreatitis. CHDF was performed with a polysulfone hemofilter (membrane area, 0.7 m2) and nafamostat mesilate, a protease inhibitor and anticoagulant, at a blood flow rate of 100 ml/min and a filtration and dialysis flow rate of 10 ml/min each. Before beginning CHDF, plasma TLE was 3.41 +/- 2.86 nmol/(ml.min), and TLI was 5,900 +/- 9,008 ng/ml. The average plasma clearances of TLE and TLI achieved by the circuit during the 12-hour therapy were 56.7 +/- 4.9 ml/min and 8.0 +/- 7.2 ml/min, respectively. The average plasma clearance of TLI into the waste fluid was 2.4 +/- 1.6 ml/min whereas TLE was below the measurable sensitivity. The plasma concentration of TLE and TLI remained unchanged. These results indicate that low-volume CHDF using nafamostat mesilate as an anticoagulant can increase trypsin plasma clearance. However, low-volume CHDF is not effective to eliminate the plasma trypsin concentration.

Modification of poly(glycidyl methacrylate-divinylbenzene) porous microspheres with polyethylene glycol and their adsorption property of protein.

Rigid porous poly(glycidyl methacrylate-divinylbenzene) (P(GMA-DVB)) microspheres were synthesized through suspension polymerization with a mixture of isooctane and 4-methyl-2-pentonal as the porogen. The microspheres were intended to use as column packing materials for protein separation. However, irreversible adsorption of protein was found on the polymer microsphere. To circumvent the problem, polyethylene glycol (PEG) was coupled to the microspheres. The coupling reaction took place between the hydroxyl group of PEG and the epoxy group of the P(GMA-DVB) solid medium in the presence of boron trifluoride. The density of PEG immobilized onto the P(GMA-DVB) can be determined easily by saponification of modified microsphere firstly and then titration of glycerol-PEG. The effect of the cross-linker content of microsphere on the density of PEG immobilization was investigated. Molecular weight of PEG was found to influence the PEG-immobilization density, which subsequently affects the hydrophilicity of the modified P(GMA-DVB). Bovine serum albumin (BSA) and trypsin were used as model proteins to examine the adsorption and desorption properties of the modified P(GMA-DVB) microspheres. The results demonstrated that P(GMA-DVB) porous microsphere with 20% DVB and modified with PEG4000 showed excellent adsorption and desorption properties. Adsorption capacity of BSA on the modified microsphere attained to 51.6 mg/g microsphere, and BSA mass recovery and trypsin activity recovery was up to 97.6% and 98.7%, respectively. The modified microsphere was demonstrated to be a promising hydrophobic interaction chromatography material for purification of protein.

Relación entre estrés oxidativo y ciclo celular en la etiología de la muerte neuronal en la enfermedad de Parkinson. Efectos de los antioxidantes / Oxidative stress and cell cycle in the ethiology of neuronal cell death in Parkinson disease

La enfermedad de Parkinson es un trastorno neurodegenerativo caracterizado por la pérdida progresiva de las neuronas dopaminérgicas de la Sustancia Negra. Recientes trabajos relacionan al estrés oxidativo, implicado en la etiología de esta patología, con una sobreexpresión en las neuronas de proteínas reguladoras del ciclo celular. Las células postmitóticas, en respuesta a esta sobreexpresión, mueren por apoptosis en lugar de progresar a través de un ciclo celular descoordinado y por ello fatal. En este trabajo hemos comprobado el efecto neuroprotector de la melatonina frente a la muerte inducida por las neurotoxinas catecolinérgicas, MPP+ y 6-0HDA, en dos líneas celulares dopaminérgicas diferenciadas (UR61 y PC12), observando una prevención de entre el 10-20% (p<0.05). Un efecto similar fue observado con el empleo de antioxidantes y de inhibidores del ciclo celular, por lo que la neuroprotección mostrada por la melatonina podría estar mediada tanto por su actividad antioxidante, como su capacidad para impedir la reentrada en el ciclo celular

Parkinson's disease is a neurodegenerative disorder that leads to a progressive death of dopaminergic neurons in the Substantia Nigra. The generation of reactive oxygen species is considered to be implicated in its etiology. Recent works connect oxidative stress with the overexpresion of cell cycle proteins in neurons. Postmitotic neurons, because of said overexpresion, undergo apoptosis instead of going through a deregulated, therefore fatal, cell cycle. Our work shows the neuroprotector etTect of melatonin against neuronal death induced by the catecolinergic toxins MPP+ and 6-0HDA on two ditTerentiated dopaminergic celllines (UR61 and PC12). Melatonin was able to reduce cell death over a 10-20% (p<0.05). Other antioxidants, as well as other cell cycle inhibitors tested, produced a similar effect. Thus, it appears that either melatonin antioxidant properties or cell cycle reentry inhibiting properties may mediate its neuroprotector effect

Core-shell microspheres by dispersion polymerization as promising delivery systems for proteins.

Functional poly(methyl methacrylate) core-shell microspheres were prepared by dispersion polymerization. An appropriate selection of experimental parameters and in particular of the initiator and stabilizer amount and of the medium solvency power allowed a monodisperse sample as large as 600 nm to be prepared. To this purpose, low initiator concentration, high steric stabilizer amount and a low solvency power medium were employed. The microspheres present a core-shell structure in which the outer shell is constituted by the steric stabilizer which affords carboxylic groups able to interact with basic proteins, such as trypsin, whose adsorption is essentially driven by the carboxylic group density in the microsphere shell. Finally, fluorescent microspheres were prepared for biodistribution studies and shown to be readily taken up by the cells both in vitro and in vivo. These results suggest that these microspheres are promising delivery systems for the development of novel protein-based vaccines.

Effective removal of alginate-poly-L-lysine microcapsules from pancreatic islets by use of trypsin-EDTA.

Although the transplantation of alginate-poly-L-lysine-alginate encapsulated islets of Langerhans usually is successful, graft survival is still limited. Molecular analysis by RT-PCR of the encapsulated islets may provide insight into the mechanisms that affect islets during graft failure. However, RT-PCR on encapsulated islets is not possible because the poly-L-lysine of the capsule interferes with both cDNA synthesis and PCR amplification. We applied a method that mechanically removes the microcapsules from the islets after a short trypsin-EDTA treatment (decapsulation), thereby enabling RT-PCR analysis. The results of this study show that the decapsulation procedure does not affect islet vitality and has only minor effects on islet function and morphology. The decapsulation does not affect GAPDH, beta-actin, Bcl-2, or Bax gene expression. This method is an improvement over the time-consuming manual dissection of microcapsules because it allows for the rapid and relatively harmless removal of capsules on a larger scale. Decapsulation offers the possibility of applying RT-PCR, as well as other methods, which cannot be performed on encapsulated islets.

Activation of mast cells induced by agonists of proteinase-activated receptors under normal conditions and during acute inflammation in rats.

Functions of thrombin as a modulator of inflammation and tissue repair are mediated by the proteinase-activated receptor (PAR) family. Some of these effects may be induced by activation of mast cells. To characterize the degranulation of rat peritoneal mast cells in response to PAR agonists, the effects of thrombin, trypsin and peptide agonists of PARs (PAR-AP, proteinase-activated receptor-activating peptides) on secretion were investigated. The release of beta-hexosaminidase by thrombin (0.01-1 microM) was concentration-dependent and mediated via PAR(1), as evidenced by cathepsin G (100 microM)-induced inactivation of PAR(1) and thrombin-stimulated PAR(1) desensitization. Trypsin (1 microM) accelerated histamine secretion. The PAR(1)-AP, TRAP (SFFLRN, 1-100 microM) and the PAR(2)-AP SLIGRL (5-100 microM) caused the release of histamine, and beta-hexosaminidase from inflammatory mast cells were obtained from a model of acute peritonitis in rats. Relative to the response to compound 48/80, the thrombin- and TRAP-induced release of beta-hexosaminidase was higher in inflammatory mast cells than in the control. This suggests that additional exposure of PAR(1) on mast cells to PAR agonists or an increase in PARs sensitivity to PAR agonists probably occurred during acute inflammation.

Peroral administration of enzymes: strategies to improve the galenic of dosage forms for trypsin and bromelain.

In this study, we investigated the presystemic metabolism of trypsin and bromelain and the influence of these proteolytic enzymes on the mucus layer covering the gastrointestinal (GI) epithelia. In vitro studies demonstrated that 77.3% +/- 4.0% (mean +/- SD, n = 3) of trypsin is autodegraded within 2 hr, whereas autodegradation of bromelain was negligible. In contrast to the metabolization of bromelain by all pancreatic serine proteases, trypsin is only degraded to some extent by elastase. Both therapeutically used enzymes remained stable after incubation with an excised porcine mucosa, demonstrating that proteolysis caused by brush border membrane-bound enzymes is negligible. Trypsin and bromelain were highly mucolytic active, thereby reducing the diffusion barrier based on the mucus gel layer. Strategies to improve the galenic of dosage forms for trypsin and bromelain include the use of bioadhesive polymers such as hydroxyethylcellulose or slightly modified chitosan-EDTA, providing strongly improved stability of these enzymes toward proteolytic degradation in vitro. The given information represents a good starting point to improve the galenic of dosage forms for orally administered proteolytic enzymes.

Incorporation of ubiquitin into the rat brain mitochondria is accompanied by increased proteolytic digestibility of MAO.

Incubation of rat brain mitochondria with ubiquitin followed by mitochondria sedimentation was accompanied by reduction of ubiquitin content in the supernatant only when ATP was included into the incubation mixture. Subsequent incubation of resedimented mitochondria revealed higher sensitivity to trypsin of MAO-A in ubiquitin-incorporated mitochondria. In control mitochondria (initially incubated with ATP) 0.5 mg/ml trypsin caused a decrease of MAO-A activity by 32.2 +/- 4.2%, whereas in ubiquitin-incorporated mitochondria (initially incubated with ATP + ubiquitin) reduction of MAO-A activity was significantly higher (51.4 +/- 2.5%, p < 0.02). Activity of MAO-B was resistant to trypsinolysis and incorporation of ubiquitin did not influence sensitivity of MAO-B to trypsin. Although there is no direct evidence yet that mitochondrial MAO is a target for ubiquitination the increased sensitivity to trypsinolysis of MAO-A suggests that incorporation of ubiquitin into mitochondria may increase susceptibility of MAO to certain proteases involved into degradation of these enzymes.

pH titration of native and unfolded beta-trypsin: evaluation of the delta delta G0 titration and the carboxyl pK values.

The stabilizing free energy of beta-trypsin was determined by hydrogen ion titration. In the pH range from 3.0 to 7.0, the change in free energy difference for the stabilization of the native protein relative to the unfolded one (delta delta G0 titration) was 9.51 +/- 0.06 kcal/mol. An isoelectric point of 10.0 was determined, allowing us to calculate the Tanford and Kirkwood electrostatic factor w. This factor presented a nonlinear behavior and indicated more than one type of titratable carboxyl groups in beta-trypsin. In fact, one class of carboxyl group with a pK = 3.91 +/- 0.01 and another one with a pK = 4.63 +/- 0.03 were also found by hydrogen ion titration of the protein in the folded state.

A branched monomethoxypoly(ethylene glycol) for protein modification.

Procedures are described for linking monomethoxypoly(ethylene glycol) (mPEG) to both epsilon and alpha amino groups of lysine. The lysine carboxyl group can then be activated as a succinimidyl ester to obtain a new mPEG derivative (mPEG2-COOSu) with improved properties for biotechnical applications. This branched reagent showed in some cases a lower reactivity toward protein amino groups than the linear mPEG from which it was derived. A comparison of mPEG- and mPEG2-modified enzymes (ribonuclease, catalase, asparaginase, trypsin) was carried out for activity, pH and temperature stability, Km and Kcat values, and protection to proteolytic digestion. Most of the adducts from mPEG and mPEG2 modification presented similar activity and stability toward temperature change and pH change, although in a few cases mPEG2 modification was found to increase temperature stability and to widen the range of pH stability of the adducts. On the other hand, all of the enzymes modified with the branched polymer presented greater stability to proteolytic digestion relative to those modified with the linear mPEG. A further advantage of this branched mPEG lies in the possibility of a precise evaluation of the number of polymer molecules bound to the proteins; upon acid hydrolysis, each molecule of mPEG2 releases a molecule of lysine which can be detected by amino acid analysis. Finally, dimerization of mPEG by coupling to lysine provides a needed route to monofunctional PEGs of high molecular weight.

[The in-vitro digestive availability of lipase and trypsin in pancreatic supplements under different degrees of acidity]. / Disponibilidad digestiva in vitro de lipasa y tripsina en suplementos pancreáticos bajo diferentes grados de acidez.

We evaluated the in vitro disintegration time and the remanent digestive activity of eight pancreatic supplements under pH conditions similar to the gastrointestinal tract. They were incubated for 45 min at various pH levels (1, 3 or 6) and continued thereafter at pH 6, for another 135 min. The activities of lipase and trypsin were evaluated titrimetrically every 15 min. At pH 6, the products without an enteric coat and Creon, showed the shortest disintegration times; under acidic conditions, those times were longer in all the enteric coated products. At constant pH 6, lipase activity was greater in Creon, Pankreon and Cotazym-B; trypsin activity was greater in Nutrizym-C, Onoton and Cotazym-B. After acidic pH exposure enzyme bioavailability was decreased in all the products. Disintegration times and acid inactivation of enzymes, should be considered when prescribing PS.

Role of the scavenger receptor in the uptake of methylamine-activated alpha 2-macroglobulin by rat liver.

Alpha 2-Macroglobulin (alpha 2M) requires activation by small nucleophiles (e.g. methylamine; giving alpha 2M-Me) or proteolytic enzymes (e.g. trypsin; giving alpha 2M-Tr) in order to be rapidly removed from the circulation by the liver. Separation of rat liver cells into parenchymal, endothelial and Kupffer cells at 10 min after injection indicates that liver uptake of alpha 2M-Me is shared between parenchymal and endothelial cells, with relative contributions of 51.3% and 48.3% respectively of total liver-associated radioactivity. In contrast, alpha 2M-Tr is almost exclusively taken up by the parenchymal cells (90.1% of liver-associated radioactivity). A preinjection of 5 mg of poly(inosinic acid) decreased liver uptake of alpha 2M-Me to 39.9% of the control value, while it had no effect on liver uptake of alpha 2M-Tr. It appears that poly(inosinic acid) specifically reduces the uptake of alpha 2M-Me in vivo by endothelial cells, leaving uptake by parenchymal cells unaffected. In vitro studies with isolated liver cells indicate that the association of alpha 2M-Me with endothelial cells is 21-fold higher per mg of cell protein than with parenchymal cells. The capacity of endothelial cells to degrade alpha 2M-Me appears to be 46 times higher than that of parenchymal cells. Competition studies show that poly(inosinic acid) or acetylated low-density lipoprotein effectively competes with the association of alpha 2M-Me with endothelial and Kupffer cells, but association with parenchymal cells is unaffected. It is suggested that activation of alpha 2M by methylamine induces a charge distribution on the protein which triggers specific uptake by the scavenger receptor on endothelial cells. It is concluded that the uptake of alpha 2M-Me by the scavenger receptor might function as an additional system for the uptake of activated alpha 2M.

Liver uptake of trypsin-inhibitor complexes; differences between suckling and adult rats.

Previous studies have demonstrated increased intestinal trypsin uptake in newborn rats compared to adults. The mechanisms that protect tissues against proteolytic damage by trypsin include trypsin-inhibitor binding and subsequent liver uptake. In order to examine these mechanisms, bovine trypsin (1.25 mg/100 g body weight) plus trace 125I-trypsin were injected into the portal vein of 2-week-old and adult rats. Liver, kidney and plasma 125I activity were assessed at 1, 5 or 15 min following infusion and the different trypsin inhibitor fractions were separated and examined for 125I activity. Newborn rats had significantly increased plasma levels of 125I-trypsin and significantly decreased liver 125I levels 1 min after infusion compared to adults. In addition, the slow decline in liver 125I activity seen in the adult rats did not occur in the newborns. The pattern of trypsin-inhibitor binding was not significantly different at 1, 5 and 15 min and there were no differences at these time intervals between newborns and adults. We suggest that the newborn liver is less effective in clearing infused trypsin leading to increased plasma levels, and this increased plasma trypsin concentration subsequently leads to increased liver levels of 125I-trypsin. The increased trypsin levels in the liver may predispose newborns to protease-induced liver damage.

Reaction of proteinases with alpha 2-macroglobulin: evidence for alternate reaction pathways in the inhibition of trypsin.

Titration experiments were employed to measure the binding stoichiometry of alpha 2M for trypsin at high and low concentrations of reactants. These titration experiments were performed by measuring the SBTI-resistant trypsin activity and by direct binding measurements using 125I-labeled trypsin. The binding stoichiometry displayed a marked dependence upon protein concentration. At high alpha 2M concentrations (micromolar), 2 mol of trypsin are bound/mol of inhibitor. However, at low alpha 2M concentrations (e.g., 0.5 nM), only 1.3 mol of trypsin were bound/mol of inhibitor. Sequential additions of subsaturating amounts of trypsin to a single aliquot of alpha 2M also resulted in a reduction in the final binding ratio. A model has been formulated to account for these observations. A key element of this model is the observation that purified 1:1 alpha 2M-proteinase complexes are not capable of binding a full mole of additional proteinase [Strickland et al. (1988) Biochemistry 27, 1458-1466]. The model predicts that once the 1:1 alpha 2M-proteinase complex forms, this species undergoes a time-dependent conformational rearrangement to yield a complex with greatly reduced proteinase binding ability. According to this model, the ability of alpha 2M to bind 2 mol of proteinase depends upon the association rate of the second enzyme molecule with the binary (1:1) complex, the enzyme concentration, and the rate of the conformational alteration that occurs once the initial complex forms. Modeling experiments suggest that the magnitude of the rate constant for this conformational change is in the order of 1-2 s-1.

[Study on the kinetics of isolation of trypsin immobilized on dialdehyde cellulose during hydrolytic destruction]. / Issledovanie kinetiki vydeleniia tripsina, immobilizovannogo na dial'degidtselliuloze, pri gidroliticheskoi destruktsii.

The kinetics of isolation of trypsin immobilized on a dialdehyde cellulose carrier in buffer solutions with pH 7.0 and 8.0 was studied. The number of the aldehyde groups amounted to 15-60 per cent of the initial one. The kinetics of hydrolytic destruction of the collected samples with the immobilized trypsin and the carrier in buffer solutions with pH 7.0 and 8.0 was also studied. The constants of the rates of trypsin isolation from the materials and the constants of the rates of liberation into the buffer solutions of the compounds containing CO-groups were determined. The groups were used for estimating hydrolytic destruction of the materials and the time of complete destruction of the materials in the solutions.

Immobilization of enzymes on alumina by means of pyridoxal 5'-phosphate.

A number of proteases have been immobilized on alumina in a two-step procedure: the first step converted them into semisynthetic phosphoproteins which, in the second step, spontaneously bonded to alumina through their phosphate function. The immobilized enzymes thus obtained showed the physical properties typical of the inorganic carrier and a high activity on low molecular weight substrates.