Hyaluronic acid/Chitosan nanoparticles as delivery vehicles for VEGF and PDGF-BB

The development of a vascular network in tissue-engineered constructs is a fundamental bottleneck of bioregenerative medicine, particularly when the size of the implant exceeds a certain limit given by diffusion lengths and/or if the host tissue shows a very active metabolism. One of the approaches to achieve the vascularization of tissue constructs is generating a sustained release of proangiogenic factors from the ischemic site. This work describes the formation and characterization of hyaluronic acid-chitosan (HA/CS) nanoparticles for the delivery of two pro-angiogenic growth factors: vascular endothelial growth factor (VEGF) and platelet derived growth factor (PDGF-BB). These nanoparticles were prepared by an ionic gelification technique, and different formulations were developed by encapsulating the growth factors in association with two stabilizing agents: bovine serum albumin or heparin sodium salt. These carriers were characterized with regard to their physicochemical properties, their stability in biological media, and their cytotoxicity in the C3a hepatoma cell line. The results show that nanoparticles around 200 nm can be prepared by this method. HA/CS nanoparticles were stable when incubated in EMEM cell culture medium or in water at 37°C for 24 h. Cell culture tests confirmed that HA/CS nanoparticles are not cytotoxic within the concentration range used for growth factor delivery. Moreover, HA/CS nanoparticles were able to entrap efficiently both growth factors, reaching association values of 94% and 54% for VEGF and PDGF, respectively. In vitro release studies confirm that PDGF-BB is released from HA/CS nanoparticles in a sustained manner over approximately 1 week. On the other hand, VEGF is completely released within the first 24 h.

Y2 receptor expression and inhibition of voltage-dependent Ca2+ influx into rod bipolar cell terminals

Neuropeptide Y (NPY) is a potent inhibitory neuropeptide expressed by amacrine cells in the rat retina. NPY modulates the release of multiple neurotransmitters in mammalian retina, yet the mechanisms mediating this regulation are not well defined. To further understand the action of NPY in the retina, Y receptor coupling to voltage-dependent Ca(2+) channels was investigated using Ca(2+) imaging with fura-2 AM to measure [Ca(2+)](i) increases in rod bipolar cell terminals. Y receptor expression was studied in rat retinal tissue with reverse transcription-polymerase chain reaction (RT-PCR). NPY inhibited the depolarization-evoked Ca(2+) influx into rod bipolar cell axon terminals and caused a dose-dependent reduction and an average maximal inhibition of 72% at 1 microM, which was reversed upon washout. K(+)-evoked Ca(2+) increases were also inhibited by the selective Y2 receptor agonists, C2-NPY and NPY(13-36), at concentrations of 1 microM, but not by the selective Y1 receptor agonist, [Leu(31)Pro(34)]NPY, selective Y4 receptor agonist, rPP, or the selective Y5 receptor agonist, [d-Trp32]-NPY. Y receptor expression was determined using RT-PCR for all known Y receptor subtypes. Y2 receptor mRNA, as well as Y1, Y4, and Y5 receptor mRNAs, are present in the rat retina. Like the rod bipolar cell, other studies in central neurons have shown that the Y2 receptor is expressed predominantly as a presynaptic receptor and that it modulates transmitter release. Together, these findings suggest that NPY activates presynaptic Y2 receptors to inhibit voltage-dependent Ca(2+) influx into rod bipolar cell terminals, and establishes one mechanism by which NPY may reduce l-glutamate release from the rod bipolar cell synapse.

Structure of nicotinamide mononucleotide adenylyltransferase: a key enzyme in NAD(+) biosynthesis

BACKGROUND

Nicotinamide adenine dinucleotide (NAD(+)) is an essential cofactor involved in fundamental processes in cell metabolism. The enzyme nicotinamide mononucleotide adenylyltransferase (NMN AT) plays a key role in NAD(+) biosynthesis, catalysing the condensation of nicotinamide mononucleotide and ATP, and yielding NAD(+) and pyrophosphate. Given its vital role in cell life, the enzyme represents a possible target for the development of new antibacterial agents.

RESULTS

The structure of NMN AT from Methanococcus jannaschii in complex with ATP has been solved by X-ray crystallography at 2.0 A resolution, using a combination of single isomorphous replacement and density modification techniques. The structure reveals a hexamer with 32 point group symmetry composed of alpha/beta topology subunits. The catalytic site is located in a deep cleft on the surface of each subunit, where one ATP molecule and one Mg(2+) are observed. A strictly conserved HXGH motif (in single-letter amino acid code) is involved in ATP binding and recognition.

CONCLUSIONS

The structure of NMN AT closely resembles that of phosphopantetheine adenylyltransferase. Remarkably, in spite of the fact that the two enzymes share the same fold and hexameric assembly, a striking difference in their quaternary structure is observed. Moreover, on the basis of structural similarity including the HXGH motif, we identify NMN AT as a novel member of the newly proposed superfamily of nucleotidyltransferase alpha/beta phosphodiesterases. Our structural data suggest that the catalytic mechanism does not rely on the direct involvement of any protein residues and is likely to be carried out through optimal positioning of substrates and transition-state stabilisation, as is proposed for other members of the nucleotidyltransferase alpha/beta phosphodiesterase superfamily.

Ascorbic acid maintenance in HaCaT cells prevents radical formation and apoptosis by UV-B

We have investigated the enzymatic reduction and accumulation of vitamin C in HaCaT epithelial cells. The subcellular localization and the activities of ascorbyl free radical reductase and dehydroascorbate reductase showed that mitochondrial, microsomal and plasma membranes fractions express high levels of ascorbyl free radical reductase activity, whereas dehydroascorbate reductase activity was found at low levels only in the post microsomal supernatant. We have also investigated cell proliferation and vitamin C accumulation induced by ascorbic acid 2-phosphate. This derivative caused no inhibition of cell growth, was uptaken from the extracellular medium and accumulated as ascorbic acid in mM concentrations. These results show that HaCaT cells possess very efficient systems to maintain high levels of both intracellular and extracellular ascorbic acid. The regeneration and uptake of ascorbic acid from extracellular medium contributes to the intracellular antioxidant capacity, as evaluated by 2',7'-dihydrodichlorofluorescein staining. Consequently, cells became more resistant to free radical generation and cell death induced by UV-B irradiation.

Ascorbic acid recycling in N-myc amplified human neuroblastoma cells

The present study investigated the ability of two neuroblastoma cell lines (SK-N-SH, with one copy of N-myc, and SK-N-BE(2), with over 150 copies of N-myc) to recycle ascorbate by quantifying semidehydroascorbate reductase and dehydroascorbate reductase activities. Both cell lines expressed dehydroascorbate activity (SK-N-SH 28.4 +/- 9.8, SK-N-BE(2) 21.7 +/- 5.2 nmol/min/mg protein). Intracellular semidehydroascorbate activity was present only in SK-N-BE(2) cells (4.7 +/- 1.2 nmol/min/mg protein). Extracellular ascorbate was regenerated by semidehydroascorbate membrane activity, the activity of SK-N-BE(2) being twice that of SK-N-SH cells. The present data may explain the ability of the tumor to progress or regress through mechanisms involving both myc oncogene and apoptosis.

Fibroblast growth and polymorphonuclear granulocyte activation in the presence of a new biologically active sol-gel glass

The search for chemical devices to be used in clinical orthopaedics must find substances that are biocompatible and do not elicit inflammatory responses in vivo. To this end, a new form of glass has been prepared, composed of 8.1% CaO, 2.9% P2O5, 6.7% N2O5 and 82.3% SiO2, using sol-gel procedures. In order to evaluate the in vitro biocompatibility of this glass, the proliferation of cultured murine fibroblasts and the activation of human polymorphonuclear leukocytes has been studied. The performance of the sol-gel glass has been compared with that of a biocompatible non-resorbable soda-lime glass. Unlike the soda-lime glass, the sol-gel glass neither caused the inhibition of fibroblast growth nor elicited a marked inflammatory response by polymorphonuclear leukocytes, as demonstrated by chemiluminescence assay for reactive oxygen metabolites.

[Angiogenetic capacity of breast neoplasms and correlation with color-Doppler semiology]

The authors correlated the presence/absence of color signal-as shown by color-Doppler ultrasonography (CDUS) in 22 cases of breast carcinoma-with lesion angiogenesis potentials, as evaluated in the histologic sections with the determination of the microscopic angiogenesis grading system (MAGS) index. In all 4 cases in which CDUS showed no color signal, MAGS index value exceeded 30, which is suggestive of high neoplastic neoangiogenesis potentials. In contrast, in 17 of 18 cases positive to CDUS, MAGS index value remained below 30 and the microscopic analysis showed the presence of many fresh vessels more than 1 mm in caliber. Consequently, the presence of color signals at CDUS exams may be related to the features of tumor feeding vessels and therefore a negative CDUS exam cannot be considered as a reliable sign to exclude a malignant lesion.

Ichthyosis accompanied by neurological symptoms with special reference to epilepsy

5 patients with ichthyosis had a neurological accompaniment: epilepsy in 4, congenital palpebral ptosis, facial pain and neurosis in 1. In one patient epilepsy was combined with multiple malformations (normal dwarfism, prematurely old face, skeletal abnormalities) and oligophrenia. There was considerable variability genetically: 2 sporadic cases, 1 with X-linked transmission, 1 with autosomal dominant and 1 with apparent autosomal recessive heredity. In one case the co-existence of glucose-6-phosphate dehydrogenase deficiency provided proof of X-linked transmission. Further study of larger case-series is needed for a better definition of the nosographic and genetic aspects of non blastomatous neuroectodermatoses in which ichthyosis figures.

Multiple pigmented naevi in an albino

A case of pigmented naevi arising in an albino is described. The histological appearance of a naevus is described in the nature of the pigment discussed.