Transdermal Permeability of N-Acetyl-D-Glucosamine

N-acetylglucosamine microemulsions: Assessment of skin penetration, cytotoxicity, and anti-melanogenesis

BACKGROUND

N-acetylglucosamine (NAG) is an amino sugar which can reduce melanin production. NAG has previously been formulated for topical use in many nanocarrier systems, excluding microemulsions (MEs). In this study, NAG was prepared in the form of MEs and assessed in terms of skin permeability, cytotoxicity, and effectiveness for cosmetic applications.

AIMS

To investigate the skin penetration, cytotoxicity, and anti-melanogenesis of N-acetylglucosamine loaded microemulsions (NAG-MEs).

METHODS

Two NAG-MEs (NME1 and NME2) were prepared. The in vitro penetration study of NAG-MEs was evaluated by modified Franz diffusion cells using full-thickness porcine ear skin as the membrane. The optimized formula was then selected for further assessment of cytotoxicity and efficiency. In vitro cytotoxicity was examined using human keratinocytes (HaCaT cells) and B16 melanoma cells. Anti-melanogenic activity was investigated by determination of melanin production of B16 melanoma cells.

RESULTS

The cumulative amounts of NAG from NME1 and NME2 in the receptor fluid at 24 hours were 1010.46 ± 31.63 and 1260.99 ± 100.19 µg/cm² and those accumulated in the skin membrane were 155.59 ± 19.19 and 181.11 ± 20.38 µg/cm² , respectively. NME2 and its blank counterpart (Blank-ME2) showed no adverse effects on the viability of both HaCaT and B16 melanoma cells. The anti-melanogenic activity data showed that the NME2 treated B16 cells exhibited a significant melanin reduction.

CONCLUSIONS

NAG-MEs could allow NAG penetrate through and accumulate in full-thickness porcine ear skin. NME2 was safe for both normal human keratinocytes and melanoma cells. It also showed effectiveness on anti-melanogenic activity in B16 melanoma cells.

Structural and functional characterization of a glycoside hydrolase family 3 β-N-acetylglucosaminidase from Paenibacillus sp. str. FPU-7

Chitin, a β-1,4-linked homopolysaccharide of N-acetyl-d-glucosamine (GlcNAc), is one of the most abundant biopolymers on Earth. Paenibacillus sp. str. FPU-7 produces several different chitinases and converts chitin into N,N′-diacetylchitobiose ((GlcNAc)2) in the culture medium. However, the mechanism by which the Paenibacillus species imports (GlcNAc)2 into the cytoplasm and divides it into the monomer GlcNAc remains unclear. The gene encoding Paenibacillus β-N-acetyl-d-glucosaminidase (PsNagA) was identified in the Paenibacillus sp. str. FPU-7 genome using an expression cloning system. The deduced amino acid sequence of PsNagA suggests that the enzyme is a part of the glycoside hydrolase family 3 (GH3). Recombinant PsNagA was successfully overexpressed in Escherichia coli and purified to homogeneity. As assessed by gel permeation chromatography, the enzyme exists as a 57-kDa monomer. PsNagA specifically hydrolyses chitin oligosaccharides, (GlcNAc)2–4, 4-nitrophenyl N-acetyl β-d-glucosamine (pNP-GlcNAc) and pNP-(GlcNAc)2–6, but has no detectable activity against 4-nitrophenyl β-d-glucose, 4-nitrophenyl β-d-galactosamine and colloidal chitin. In this study, we present a 1.9 Å crystal structure of PsNagA bound to GlcNAc. The crystal structure reveals structural features related to substrate recognition and the catalytic mechanism of PsNagA. This is the first study on the structural and functional characterization of a GH3 β-N-acetyl-d-glucosaminidase from Paenibacillus sp.

Inhibition of melanin synthesis and melanosome transfer by chitosan biomaterials

Decreasing skin pigmentation is desirable for various medical or cosmetic conditions. Although numerous pharmaceutical agents are currently available, their depigmentation effects are still not satisfactory. In this study, we investigated the effects of chitosan, a natural marine product, on melanin synthesis and melanosome transfer. Treating B16F10 melanoma cells caused the inhibitory effect of chitosan on melanogenesis to be more prominent under α-melanocyte-stimulating hormone (α-MSH) stimulation. Chitosan samples of different molecular weights inhibited melanogenesis to a comparable extent, whereas increasing the deacetylation of chitosan enhanced its depigmentation effects. Chitosan was found to effectively reduce basal or α-MSH-stimulated melanogenesis by suppressing the expression of melanogenic-related proteins (microphthalmia transcription factor, tyrosinase, and tyrosinase-related protein-1 and protein-2) as well as inhibiting tyrosinase activity. Moreover, the inhibitory effect of chitosan on melanogenesis in human melanocytes was confirmed. A transwell coculture system using permeable inserts was designed to allow the contact of human melanocytes and human HaCaT keratinocytes through the tiny holes on the membrane. When chitosan was added to this melanocyte-keratinocyte coculture system, we observed decreased melanosome release from melanocytes. Reduced melanosome uptake by keratinocytes was also observed, and was probably mediated by inhibiting protease-activated receptor 2 expression. Many skin-whitening agents can modulate the process of melanogenesis, but few have been shown to inhibit the melanosome transfer and uptake process. We demonstrated that chitosan exhibits a robust effect on depigmentation by inhibiting melanogenesis as well as melanosome transfer and uptake. Therefore, chitosan represents a potential therapeutic agent for hyperpigmentation disorders.

Molecular mechanisms and biomedical applications of glucosamine as a potential multifunctional therapeutic agent

Glucosamine and its acetylated derivative, N-acetyl glucosamine, are naturally occurring amino sugars found in human body. They are important components of glycoproteins, proteoglycans and glycosaminoglycans. Scientific studies have supported that glucosamine has the beneficial pharmacological effects to relieve osteoarthritis symptoms. Glucosamine can also be as a promising candidate for the prevention and/or treatment of some other diseases due to its anti-oxidant and anti-inflammatory activities. Most of its function is exerted by modulation of inflammatory responses especially through Nuclear Factor-κB (NF-κB) that can control inflammatory cytokine production and cell survival. In this review, we present a concise update on additional new therapeutic applications of glucosamine including treatment of cardiovascular disease, neurological deficits, skin disorders, cancer and the molecular mechanistic rationale for these uses. This article will also examine safety profile and adverse effects of glucosamine in human.

Transdermal permeation of novel n-acetyl-glucosamine/NSAIDs mutual prodrugs

The current investigation reports skin permeation of three novel mutual prodrugs (MP) which couple n-acetyl-glucosamine with an NSAID, either ketoprofen or ibuprofen. They were evaluated for transdermal permeation using shed snakeskin, and to our knowledge represent the first MPs synthesized for this purpose, although they also could be used for subcutaneous delivery. MPs are defined as two active drug compounds usually connected by an ester linkage. Glucosamine administration has been linked to damaged cartilage repair, and pain relief in joints afflicted with osteoarthritis. NSAIDs are commonly used orally in transdermal creams or gels for joint pain relief. Two novel compounds we report (MP1 and MP2) covalently link ibuprofen and ketoprofen directly to the amide nitrogen of n-acetyl-glucosamine (NAG); the other compound (MP3) covalently links ibuprofen to the amide nitrogen, using a short chain acetyl linker. Permeability studies show that the ketoprofen mutual prodrug (MP2) permeates shed snakeskin more than three times greater than either ibuprofen derivative, while ethanol markedly increases the permeation for all three. The ketoprofen mutual prodrug appears the most likely candidate for transdermal administration; all three mutual prodrugs may be candidates for subcutaneous injection.