Gastrointestinal Absorption of Recombinant Hirudin-2 in Rats

Extracellular secretion of anticoagulant peptide hirudin in Lactococcus lactis using SP310mut2 signal peptide

Hirudin can be used as an oral anticoagulant and antithrombotic agent. The hirudin variant III gene, derived from the medicinal leech, Hirudo medicinalis, was fused to SP310mut2 signal sequence and expressed by a nisin-controlled gene expression system in Lactococcus lactis which was then grown in a 7 l fermenter. After induction with 8 ng nisin ml(-1), the product was secreted into the culture medium and accumulated up to ~2.7 mg l(-1). MALDI-TOF/MS and anticoagulant activity analyses on the purified product confirmed its authenticity. This is the first demonstration that hirudin can be extracellularly secreted and correctly processed in L. lactis.

Enhancement of gastrointestinal absorption of ovalbumin caused by spermine induces an increase in plasma histamine levels in mice sensitized to ovalbumin

The aim of this study was to determine whether a spermine (SPM)-induced increase in gastrointestinal absorption of an allergen leads to an anaphylactic response in sensitized mice. First, we examined the enhancing effect of SPM on the gastrointestinal absorption of ovalbumin (OVA) in an in situ jejunum loop study in rats and an in vivo oral absorption study in mice. Second, we investigated whether enhancement of gastrointestinal absorption of OVA caused by SPM induces an anaphylactic response in mice sensitized to OVA. In the in situ jejunum loop study in rats, a significant amount of immune-reactive OVA was detected in the plasma after co-administration of OVA and SPM. Oral co-administration of OVA and SPM to mice in vivo also increased plasma OVA concentrations in an SPM dose-dependent manner. Furthermore, in sensitized mice, a significant increase in plasma histamine levels occurred along with the increase in plasma OVA levels after co-administration of OVA with SPM. This finding suggests that an SPM-induced increase in gastrointestinal absorption of OVA leads to an anaphylactic response. These results indicate that excess oral ingestion of SPM may have widespread health effects, including the induction of food allergies, via modulation of the function of the gastrointestinal epithelial barrier.

Enhancement of intestinal absorption of macromolecules by spermine in rats

The aim of this study was to investigate the enhancing effect of polyamines on intestinal absorption of fluorescein isothiocyanate-labeled dextran (MW 4400, FD-4) in the in situ loop study and in vivo oral absorption study. Absorption of FD-4 from the jejunum was significantly enhanced by 5 mM spermine without serious membrane damage in the jejunum. An in vivo oral absorption study was also performed, and plasma FD-4 levels increased significantly after co-administration of 30 mM spermine. In the in vitro transport studies with Caco-2 cells, prolonged incubation with spermine resulted in a gradual decrease in transepithelial electrical resistance. This finding suggests that the absorption-enhancing mechanism of spermine partly includes opening the tight junctions of the epithelium via the paracellular route. These results indicate that excess oral ingestion of polyamines may have widespread health effects via the modulation of the intestinal epithelial barrier function.

Enhanced secretion of adhesive recognition sequence containing hirudin III mutein in E. coli

It has been previously shown that Escherichia coli L-asparaginase II (L-ASP) signal peptide is capable of being utilized to direct extracellular secretion of hirudin III (HV3) in shake flask. In this study HV3 muteins R33G34D35(S36)-HV3 were generated by introduction of adhesive recognition sequence RGD(S) into the non-functional region of HV3. The resultant recombinants were cultivated on 30 l bioreactor scale using L-ASP signal peptide expression system and the optimized fed-batch cultivation was well established. After cultivation for approximately 11 h the secreted product accumulated up to approximately 1 g l(-1), which means 17-fold increase in productivity compared to initial expression in shake flask. N-terminal analysis, pI measurement, and MALDI mass spectral analysis on mutein R33G34D35S36-HV3 confirmed the authenticity of the product. Compared to wild-type HV3 and R33G34D35HV3, the mutein R33G34D35S36-HV3 exhibits the improved pharmacological activity. Collectively, a novel secretion strategy using L-ASP signal peptide for the rapid, efficient and cost-effective production of HV3 mutein possessing improved pharmacological activity on bioreactor scale has been well established. Using this expression system downstream processing becomes very simple because secreted product is mature, soluble, active, and without N-terminal extension of Met, which is quite critical for most therapeutic protein to reduce the side effect in clinic use. Thus, it provides a promising alternative for extracellular production of other difficult-to-express protein for biopharmaceutical use.

Controlled delivery of recombinant hirudin based on thermo-sensitive Pluronic® F127 hydrogel for subcutaneous administration: In vitro and in vivo characterization

Here we investigated thermo-sensitive Pluronic(R) F127 (PF127) hydrogel for the controlled release of peptide and protein drugs after subcutaneous injection, using an antithrombotic polypeptide, recombinant hirudin variant-2 (rHV2), as the model drug. The in vitro release experiment performed with a membrane-less model at 37 degrees C showed that the release of antithrombotic activity of rHV2 from PF127 gel followed zero-order kinetics and correlated well with the weight percentage of PF127 dissolved, indicating a dissolution-controlled release mechanism. The in vivo result obtained after subcutaneous injection of rHV2-loaded PF127 gel in normal rats demonstrated that PF127 gel improved the bioavailability, prolonged the antithrombotic effect of rHV2, and induced detectable plasma rHV2 concentration for a longer time in comparison with rHV2 aqueous solution. Differential scanning calorimetry, dynamic light scattering and Fourier transform infrared spectroscopy provided evidence of the interaction between PF127 and rHV2, but such interaction was unlikely to interfere the feasibility of this drug delivery system. Our current in vitro and in vivo study suggested that PF127 gel may be useful as an injectable delivery vehicle for peptides and proteins with short half-lives to prolong their therapeutic effect, increase their bioavailability and improve the clinic outcome.

Nasal recombinant hirudin-2 delivery: absorption and its mechanism in vivo and in vitro studies

The objective of this study was to investigate the feasibility of systemic absorption of recombinant hirudin-2 (rHV2) by nasal delivery, and its possible absorption mechanism. The degradation of rHV2 in the nasal tissue homogenate and extracts of mucosae of rabbit, as well as the degradation inhibition of enzyme inhibitor (bacitracin) was evaluated. The bioavailability of rHV2 and the improvement with enhancers, after nasal administration in rats was investigated. For further understanding of the transport and uptake characteristics of rHV2, in vitro transport experiment under various conditions using diffusion chamber technique in excised rabbit nasal epithelium was performed. It was found that rHV2 underwent rapid degradation in rabbit nasal homogenate, but it was more stable in the extracts of nasal mucosae surface. Bacitracin was able to inhibit the degradation of rHV2 to certain extent. rHV2 was detected in the rat plasma by chromogenic substrate assay after nasal administration and some enhancers also significantly increased the nasal absorption of rHV2. The transport and uptake of rHV2 across nasal epithelium was concentration-dependent and unsaturated, and was significantly inhibited by low temperature, NaN(3), DNP and colchicines, while was less affected by alteration of transport direction. These results demonstrate that the possible absorption mechanism of rHV2 by nasal mucosa appears to be associated with the endocytosis as well as passive diffusion process.

Liquid filled nanoparticles as a drug delivery tool for protein therapeutics

In the present study, an attempt was made to study the feasibility of nanoparticulate adsorbents in the presence of an absorption enhancer, as a drug delivery tool for the administration of erythropoietin (EPO) to the small intestine. Liquid filled nano- and micro-particles (LFNPS/LFMPS) were prepared using solid adsorbents such as porous silicon dioxide (Sylysia 550), carbon nanotubes (CNTs), carbon nanohorns, fullerene, charcoal and bamboo charcoal. Surfactants such as a saturated polyglycolysed C8-C18 glyceride (Gelucire 44/14), PEG-8 capryl/caprylic acid glycerides (Labrasol) and polyoxyethylene hydrogenated castor oil derivative (HCO-60) were used as an absorption enhancer at 50mg/kg along with casein/lactoferrin as enzyme inhibitors. The absorption of EPO was studied by measuring serum EPO levels by an ELISA method after small intestinal administration of EPO-LFNPS preparation to rats at the EPO dose level of 100 IU/kg. Among the adsorbents studied, CNTs showed the highest serum EPO level of 62.7 +/- 11.6 mIU/ml. In addition, with the use of casein, EPO absorption was improved, C(max) 143.1 +/- 15.2 mIU/ml. Labrasol showed the highest absorption enhancing effect after intra-jejunum administration than Gelucire 44/14 and HCO-60, 25.6 +/- 3.2 and 22.2 +/- 3.6 mIU/ml, respectively. Jejunum was found to be the best absorption site for the absorption of EPO from LFNPS. The use of CNTs as LFNPS, improved the bioavailability of EPO to 11.5% following intra-small intestinal administration.

Permeation-enhancing effects of chitosan formulations on recombinant hirudin-2 by nasal delivery in vitro and in vivo

AIM

To investigate the enhancing effects of chitosan with or without enhancers on nasal recombinant hirudin-2 (rHV2) delivery in vitro and in vivo, and to evaluate the ciliotoxicity of these formulations.

METHODS

The permeation-enhancing effect of various chitosan formulations was estimated by using the permeation coefficient of fluorescein isothiocyanate recombinant hirudin-2 (FITC-rHV2) across the excited rabbit nasal epithelium in vitro. The effect was further evaluated by measuring the blood concentration level after nasal absorption of FITC-rHV2 in rats. The mucosal ciliotoxicity of different formulations was evaluated with an in situ toad palate model.

RESULTS

Chitosan at a concentration of 0.5% with or without various enhancers significantly increased the permeability coefficient (P) and relative bioavailability (Fr) of FITC-rHV2 compared with the blank control. The addition of 1% sodium dodecylsulfate, 5% Brij35, 5% Tween 80, 1.5% menthol, 1% glycyrrhizic acid monoammonium salt (GAM) or 4% Azone into the 0.5% chitosan solution resulted in a further increase in absorption (P<0.05) compared with 0.5% chitosan alone. But co-administration of chitosan with 5% hydroxyl-propyl-beta-cyclodextrin (HP-beta-CD), 5% lecithin or 0.1% ethylenediamine tetraacetic acid (EDTA) was not more effective than using the 0.5% chitosan solution alone. Chitosan alone and with 5% HP-beta-CD, 0.1% EDTA, 1% GAM or 5% Tween 80 was relatively less ciliotoxic.

CONCLUSION

Chitosan with or without some enhancers was able to effectively promote the nasal absorption of recombinant hirudin, while not resulting in severe mucosal ciliotoxicity. A chitosan formulation system would be a useful approach for the nasal delivery of recombinant hirudin.

Pharmacodynamics and pharmacokinetics of recombinant hirudin via four non-parenteral routes

One of recombinant hirudin variants, rHV2, a polypeptide used as an anticoagulant agent in clinic, was administered to anesthetized rats via intratracheal, buccal, nasal and rectal routes. Prolongation in clotting time and thrombin time was measured to calculate pharmacological bioavailability. Plasma concentration of rHV2 was determined using a chromogenic thrombin substrate assay and pharmacokinetic parameters were obtained on the basis of a non-compartmental model. Intravenous administration was also performed as the gold standard by which the other routes were compared. Difference in pharmacological bioavailability (P.A.), bioavailability (F) and absorption rate of rHV2 was found for the four non-parenteral routes. The rank order for both P.A. and F was intratracheal>nasal>buccal>rectal. Absorption was more rapid after both intratracheal and rectal administration (tmax approximately 20-40 min), compared with that after nasal and rectal administration. It is evident that the pulmonary route is preferable to other three routes for successful systemic delivery of rHV2.