Evaluation of NACA and diNACA in human cystinosis fibroblast cell cultures as potential treatments for cystinosis.

BACKGROUND: Cystinosis is a rare autosomal recessive lysosomal storage disease, associated with high morbidity and mortality. Mutations in the CTNS gene disable a membrane protein responsible for the transport of cystine out of the lysosome. Loss of transporter function leads to intralysosomal cystine accumulation and long-term damage to various tissues and organs, including the kidneys, eyes, liver, muscles, pancreas, and brain. The only cystine-depletion therapy for treatment of cystinosis is cysteamine which requires frequent administration of high doses and often causes gastrointestinal pain as well as pungent sulfurous odor in patients. The current in vitro study evaluated antioxidants, N-acetylcysteine amide (NACA; NPI-001) and (2R,2R')-3,3'-disulfanediyl bis(2-acetamidopropanamide) (diNACA; NPI-002), as potential treatments for cystinosis. METHODS: Cytotoxicity of cysteamine, NACA and diNACA was evaluated in cultured human cystinotic fibroblasts (HCFs). HCFs were cultured in 96 well plates incubated for 0-72 h in the presence of 25, 50 or 75 µM each of either cysteamine, NACA or diNACA along with an untreated control. Media was removed and cell viability assessed. Next, cystine-depleting activities of cysteamine, NACA and diNACA were screened in HCFs cell culture utilizing an inexpensive, proven colorimetric assay. HCFs were seeded and allowed to reach approximately 80% confluence before the addition of the test articles: 50 µM of either cysteamine, NACA or diNACA in media along with an untreated control. HCFs were incubated, harvested, and cystine was reduced to cysteine, the concentration of which was then determined per quantity of protein compared to a cysteine standard. Statistically significant cystine depletion was determined by paired t-test versus untreated control (p < 0.05). RESULTS: Neither cysteamine, NACA nor diNACA at 25, 50 or 75 µM caused cytotoxicity in HCFs. Treatment with all tested concentrations (25, 50 or 75 µM) of either NACA or diNACA at 48 or 72 h resulted in statistically significant increases in cell viability, relative to untreated control, whereas the higher concentrations (50 or 75 µM) of cysteamine achieved statistical significance at both timepoints but not the lowest concentration (25 µM). All test articles depleted cystine from HCFs compared to control. NACA depletion of cystine was statistically superior to cysteamine at 6, 24 and 48 h and numerically greater at 72 h. DiNACA depletion of cystine was statistically superior to cysteamine at 6 and 48 h, slightly numerically greater at 24 h and slightly less at 72 h. CONCLUSIONS: NACA and diNACA were non cytotoxic to HCFs and significantly increased cell viability. Cystine reduction was determined as percent of control after incubation with 50 µM of NACA, diNACA or cysteamine in HCFs cell culture for 6, 24, 48 and 72 h. Of the three test articles, NACA exhibited most rapid and greatest potency in cystine reduction. Rank order potency for cystine reduction over time was observed, NACA > diNACA ≥ cysteamine. Therefore, further study of NACA and diNACA as potential treatments for cystinosis is warranted.

Preformulation of cysteamine gels for treatment of the ophthalmic complications in cystinosis.

Nephropathic cystinosis is a rare autosomal recessive disease characterised by raised lysosomal levels of cystine in the cells of all organs. It is treated by regular administration of the aminothiol, cysteamine. Corneal crystal deposition is one of the most troublesome complications affecting patients and requires the hourly administration of cysteamine eye drops. In an attempt to reduce this frequency and improve the treatment, the preformulation and evaluation of cysteamine containing gels is reported. Suitability for ophthalmic delivery was determined by analysis of rheology, bioadhesion, dissolution and stability. The results demonstrated that three polymers were suitable for ophthalmic delivery of cysteamine; namely sodium hyaluronate, hydroxyethyl cellulose and carbomer 934. Sodium hyaluronate displayed optimum performance in the preformulation tests, being pseudoplastic (reduction in apparent viscosity under increasing shear rate), bioadhesive, releasing cysteamine over 40min and displaying stability over time. In conclusion these results offer the possibility to formulate cysteamine in an ocular applicable gel formulation.

The hen's egg chorioallantoic membrane (HET-CAM) test to predict the ophthalmic irritation potential of a cysteamine-containing gel: Quantification using Photoshop® and ImageJ.

A modified hen's egg chorioallantoic membrane (HET-CAM) test has been developed, combining ImageJ analysis with Adobe(®) Photoshop(®). The irritation potential of an ophthalmic medicine can be quantified using this method, by monitoring damage to blood vessels. The evaluation of cysteamine containing hyaluronate gel is reported. The results demonstrated that the novel gel formulation is non-irritant to the ocular tissues, in line with saline solution (negative control). In conclusion, the modification of the established HET-CAM test can quantify the damage to minute blood vessels. These results offer the possibility to formulate cysteamine in an ocular applicable gel formulation.

Three salts from the reactions of cysteamine and cystamine with L-(+)-tartaric acid.

Reaction between cysteamine (systematic name: 2-aminoethanethiol, C2H7NS) and L-(+)-tartaric acid [systematic name: (2R,3R)-2,3-dihydroxybutanedioic acid, C4H6O6] results in a mixture of cysteamine tartrate(1-) monohydrate, C2H8NS(+)·C4H5O6(-)·H2O, (I), and cystamine bis[tartrate(1-)] dihydrate, C4H14N2S2(2+)·2C4H5O6(-)·2H2O, (III). Cystamine [systematic name: 2,2'-dithiobis(ethylamine), C4H12N2S2], reacts with L-(+)-tartaric acid to produce a mixture of cystamine tartrate(2-), C4H14N2S2(2+)·C4H4O6(2-), (II), and (III). In each crystal structure, the anions are linked by O-H···O hydrogen bonds that run parallel to the a axis. In addition, hydrogen bonding involving protonated amino groups in all three salts, and water molecules in (I) and (III), leads to extensive three-dimensional hydrogen-bonding networks. All three salts crystallize in the orthorhombic space group P2(1)2(1)2(1).

Suppository formulations as a potential treatment for nephropathic cystinosis.

Nephropathic cystinosis is a rare autosomal recessive disease characterised by raised lysosomal levels of cystine in the cells of all the organs. It is treated by the 6-h oral administration of the aminothiol, cysteamine, which has an offensive taste and smell. In an attempt to reduce this frequency and improve the treatment, cysteamine-containing polyethylene glycol suppositories were prepared and evaluated for dissolution and stability. The results demonstrated that cysteamine release was complete after 30 min, and that there was a uniform drug distribution within the formulations. Twelve-month stability tests highlighted a potential incompatibility among some excipients, although stability was demonstrated for the cysteamine suppositories up to 6 months. These suppositories may provide a useful alternative to the current oral therapy for cystinosis.

Synthesis and in vitro evaluation of novel pro-drugs for the treatment of nephropathic cystinosis.

As part of our continuing work to obtain new pro-drugs for the treatment of nephropathic cystinosis, a number of glutaric and succinic acid derivatives of cystamine have been designed, synthesised and biologically evaluated in vitro. These compounds have been designed as odourless and tasteless pro-drugs which will release multiple molecules of cysteamine upon administration. All of the synthesised compounds evaluated in this study were non-cytotoxic and displayed a greater ability than cysteamine to deplete the levels of cystine in cultured fibroblasts.

Folate pro-drug of cystamine as an enhanced treatment for nephropathic cystinosis.

Nephropathic cystinosis is a rare autosomal recessive disease characterised by raised intracellular levels of the amino acid, cystine. If untreated, the disease, progressively deteriorates towards end stage renal disease (ESRD) at the end of the first decade. The disease is caused by a defect in the lysosomal transport mechanism for cystine. The treatment of choice is the aminothiol cysteamine which acts as a lysine mimic. However, cysteamine possesses an offensive taste and smell and irritates the gastrointestinal tract leading to nausea and vomiting following administration. Furthermore, the rapid metabolism of cysteamine requires oral administration every 6 h for life, in consequence, the patient compliance is poor. As part of our continuing work to obtain new pro-drugs for the treatment of this genetic disease, we have synthesised a folate derivative of cystamine, the disulfide derivative of cysteamine. This new pro-drug was non cytotoxic, showed greater ability to deplete intralysosomal cystine than the current treatment, and, in fact has been the most effective reducer of intralysosomal cystine discovered in our laboratories to date.

PEGylated derivatives of cystamine as enhanced treatments for nephropathic cystinosis.

The genetic disease, nephropathic cystinosis is characterized by lysosomal accumulation of the amino acid cystine. Crystallization of cystine in affected organs, if untreated, results in mortality of the affected individuals by their middle to late teens. The only approved treatment for cystinosis is administration of cysteamine. However, cysteamine is associated with an offending odor and taste and this, coupled to a rapid first pass metabolism and a 6h dosing regimen, suggest a clear need to improve the therapy. A number of PEGylated derivatives of cystamine, the disulfide counterpart of cysteamine, have been synthesised and evaluated in cultured cystinotic fibroblasts for toxicity and efficacy. All of the tested compounds were non-cytotoxic and displayed a remarkable depletion of intralysosomal cystine.

Gel formulations for treatment of the ophthalmic complications in cystinosis.

Nephropathic cystinosis is a rare autosomal recessive disease characterised by raised lysosomal levels of cystine in the cells of all organs. It is treated by regular administration of the aminothiol, cysteamine. Corneal crystal deposition is one of the most troublesome complications affecting patients and requires the hourly administration of cysteamine eye drops. In an attempt to reduce this frequency and improve the treatment, the preparation and evaluation of cysteamine containing Carbomer gel is reported. The results demonstrated that a weak gel network was formed at low shear-stress, the bioadhesion of the gel was increased with inclusion of a cysteamine derivative (e.g. mean force of 0.067N compared to 0.107N with compound included) and first-order release from the gel was observed. In conclusion these results offer the possibility to formulate cysteamine in an ocular applicable gel formulation.

A multifunctional tripodal fluorescent probe: "off-on" detection of sodium as well as two-input AND molecular logic behavior.

A simple tripodal sensor (3) with multifunctional capability has been synthesized in three steps. The sensor, a naphthalene-functionalized Schiff base, displays selectivity for sodium over other important physiological and environmentally important cations through changes in the emission spectra at lambda(max) 355 nm when excited at 270 nm. Interestingly, the combined addition of both sodium and potassium produced a new band at lambda(max) 445 nm, while the addition of sodium or potassium alone produced negligible changes at this wavelength. Therefore, the conditions of a two-input AND logic operator were also satisfied.

A potential new prodrug for the treatment of cystinosis: design, synthesis and in-vitro evaluation.

Nephropathic cystinosis is a rare autosomal recessive disease characterised by raised lysosomal levels of cystine in the cells of most organs. The disorder is treated by regular administration of the aminothiol, cysteamine, an odiferous and unpleasant tasting compound that along with its metabolites is excreted in breath and sweat, leading to poor patient compliance. In an attempt to improve patient compliance a series of novel prodrugs has been designed and evaluated as a potential new treatment for nephropathic cystinosis. The first of the prodrugs tested, 3a, was found to decrease the levels of intracellular cystine in cystinotic fibroblasts. This is the first report of a potential new therapeutic treatment for nephropathic cystinosis since the advent of cysteamine bitartrate.

Design of telomerase inhibitors for the treatment of cancer.

Telomerase is a cellular ribonucleoprotein reverse transcriptase responsible for the maintenance of telomeres, the tandemly repeating guanine-rich nucleic acid sequences at the 3'-ends of eukaryotic chromosomes that serve to protect chromosomal stability and maintain integrity. Telomerase enzyme activity is essential for the sustained proliferation of most immortal cells, including cancer cells, and is currently an important recognised target for the development of novel and potentially tumour-specific anticancer chemotherapeutics. Herein, we review recent advances in the design and development of telomerase inhibitors for the treatment of cancer. To date, these have included antisense strategies, reverse transcriptase inhibitors, and agents capable of interacting with high-order telomeric DNA tetraplex (or "G-quadruplex") structures in such a way as to prevent enzyme access to its required linear telomeric DNA substrate. Critical appraisal of each distinct approach is provided together with highlighted areas for continued development necessary to further refine the present disparate classes of telomerase inhibitors for use in clinically viable therapies.

Molecular modelling and cytotoxicity of substituted anthraquinones as inhibitors of human telomerase.

Molecular modelling has been carried out for a number of amine-functionalised anthraquinone derivatives to determine their extent of binding to G-tetraplex DNA and their ability to inhibit the enzymes telomerase and Taq polymerase. The results are compared to data obtained from a modified TRAP assay and show good correlation between the two methods. The findings suggest that anthraquinone derivatives of this type inhibit telomerase by stabilisation of four-stranded tetraplex structures associated with guanine-rich telomeric DNA regions.