Sustained-release multiparticulates for oral delivery of a novel peptidic ghrelin agonist: Formulation design and in vitro characterization

There is an impetus to provide appropriate sustained release oral delivery vehicles to protect biofunctional peptide loads from gastric degradation in vivo. This study describes the generation of a high load capacity pellet formulation for sustained release of a freely water-soluble dairy-derived hydrolysate, FHI-2571. The activity of this novel peptidic ghrelin receptor agonist is reported using in vitro calcium mobilization assays. Conventional extrusion spheronization was then used to prepare peptide-loaded pellets which were subsequently coated with ethylcellulose (EC) film coats using a fluid bed coating system in bottom spray (Wurster) mode. Aqueous-based EC coating dispersions produced mechanically brittle coats which fractured due to osmotic pressure build-up within pellets in simulated media. In contrast, an ethanolic-based EC coating solution provided robust, near zero-order release in both USP Type 1 and Type 4 dissolution studies. Interestingly, the functionality of aqueous-based EC film coats was restored by first layering pellets with a methacrylic acid copolymer (MA) subcoat, thereby hindering pellet core swelling in acidic media. Broadband Acoustic Resonance Dissolution Spectroscopy (BARDS) was utilised as a complementary technique to confirm the results seen in USP dissolution studies. Retention of activity of the ghrelinergic peptide hydrolysate in the final encapsulated product was confirmed as being greater than 80%. The described pellet formulation is amenable to oral dosing in small animal studies in order to assess in vivo efficacy of the whey-derived ghrelinergic hydrolysate. In more general terms, it is also suitable as a delivery vehicle for peptide-based bioactives to special population groups e.g paediatric and geriatric

Adsorption of Components of the Plasma Kinin-Forming System on the Surface of Porphyromonas gingivalis Involves Gingipains as the Major Docking Platforms▿

Enhanced production of proinflammatory bradykinin-related peptides, the kinins, has been suggested to contribute to the pathogenesis of periodontitis, a common inflammatory disease of human gingival tissues. In this report, we describe a plausible mechanism of activation of the kinin-generating system, also known as the contact system or kininogen-kallikrein-kinin system, by the adsorption of its plasma-derived components such as high-molecular-mass kininogen (HK), prekallikrein (PK), and Hageman factor (FXII) to the cell surface of periodontal pathogen Porphyromonas gingivalis. The adsorption characteristics of mutant strains deficient in selected proteins of the cell envelope suggested that the surface-associated cysteine proteinases, gingipains, bearing hemagglutinin/adhesin domains (RgpA and Kgp) serve as the major platforms for HK and FXII adhesion. These interactions were confirmed by direct binding tests using microplate-immobilized gingipains and biotinylated contact factors. Other bacterial cell surface components such as fimbriae and lipopolysaccharide were also found to contribute to the binding of contact factors, particularly PK. Analysis of kinin release in plasma upon contact with P. gingivalis showed that the bacterial surface-dependent mechanism is complementary to the previously described kinin generation system dependent on HK and PK proteolytic activation by the gingipains. We also found that several P. gingivalis clinical isolates differed in the relative significance of these two mechanisms of kinin production. Taken together, these data show the importance of this specific type of bacterial surface-host homeostatic system interaction in periodontal infections

The Role of Central Serotonin Neurons and 5-HT Heteroreceptor Complexes in the Pathophysiology of Depression : A Historical Perspective and Future Prospects

Serotonin communication operates mainly in the extracellular space and cerebrospinal fluid (CSF), using volume transmission with serotonin moving from source to target cells (neurons and astroglia) via energy gradients, leading to the diffusion and convection (flow) of serotonin. One emerging concept in depression is that disturbances in the integrative allosteric receptor-receptor interactions in highly vulnerable 5-HT1A heteroreceptor complexes can contribute to causing major depression and become novel targets for the treatment of major depression (MD) and anxiety. For instance, a disruption and/or dysfunction in the 5-HT1A-FGFR1 heteroreceptor complexes in the raphe-hippocampal serotonin neuron systems can contribute to the development of MD. It leads inter alia to reduced neuroplasticity and potential atrophy in the raphe-cortical and raphe-striatal 5-HT pathways and in all its forebrain networks. Reduced 5-HT1A auto-receptor function, increased plasticity and trophic activity in the midbrain raphe 5-HT neurons can develop via agonist activation of allosteric receptor-receptor interactions in the 5-HT1A-FGFR1 heterocomplex. Additionally, the inhibitory allosteric receptor-receptor interactions in the 5-HT1AR-5-HT2AR isoreceptor complex therefore likely have a significant role in modulating mood, involving a reduction of postjunctional 5-HT1AR protomer signaling in the forebrain upon activation of the 5-HT2AR protomer. In addition, oxytocin receptors (OXTRs) play a significant and impressive role in modulating social and cognitive related behaviors like bonding and attachment, reward and motivation. Pathological blunting of the OXTR protomers in 5-HT2AR and especially in 5-HT2CR heteroreceptor complexes can contribute to the development of depression and other types of psychiatric diseases involving disturbances in social behaviors. The 5-HTR heterocomplexes are novel targets for the treatment of MD