Permeation, metabolism and site of action concentration of nicotinic acid derivatives in human skin

Revealing the 1H-NMR Profiling of Six Edible Mushrooms Consumed in the Northeastern Highlands of Puebla, Mexico

The 1H-NMR metabolomics profiling of six edible mushrooms consumed in the northeastern highlands of Puebla, Mexico is presented. These fungi were morpho- and molecularly identified as Infundibulicybe squamulosa, Amanita jacksonii, Lepista nuda, Russula delica, Russula brevipes, and Lactarius indigo. The chemical profiling confirmed the presence of eight essential amino acids and their derivatives, six organic acids, six nucleosides, low amounts of reducing sugars, and valuable nutraceuticals such as betaine, carnitine, glycero-3-phosphocholine and O-acetylcarnitine which were differentially determined and quantified in the six mushrooms by qNMR. Principal component analysis (PCA) and orthogonal projections to latent structures discriminant analysis (OPLS-DA) generated four different groups. Two of these groups were constituted by fungal species with phylogenic relationships whereas non-phylogenetic related species were separated from each other. The potential use of 1H-NMR metabolomics and chemometrics to group macromycetes and determine the nutritional and nutraceutical potential of these local foods is demonstrated.

Human Skin Drug Metabolism: Relationships between Methyl Salicylate Metabolism and Esterase Activities in IVPT Skin Membranes

The presence of esterase enzymes in human skin and their role in drug metabolism has been reported, but their distribution in the various skin layers and the relative contributions of those layers to metabolism is poorly defined. To gain further insight into esterase distribution, we performed in vitro skin permeation of a commercial 28.3% methyl salicylate (MeSA) cream (Metsal™) in Franz diffusion cells, using a range of human skin membranes, all from the same donor. The membranes were viable epidermis separated by a dispase II enzymatic method, heat separated epidermis, dermatomed skin, and dermis separated by a dispase II enzymatic method. Methyl salicylate and its metabolite, salicylic acid (SA), were measured by high-performance liquid chromatography. Alpha naphthyl acetate and Hematoxylin and Eosin staining provided qualitative estimations of esterase distribution in these membranes. The permeation of methyl salicylate after 24 h was similar across all membranes. Salicylic acid formation and permeation were found to be similar in dermatomed skin and dermis, suggesting dermal esterase activity. These results were supported by the staining studies, which showed strong esterase activity in the dermal-epidermal junction region of the dermis. In contrast with high staining of esterase activity in the stratum corneum and viable epidermis, minimal stained and functional esterase activity was found in heat-separated and dispase II-prepared epidermal membranes. The results are consistent with dispase II digesting hemidesmosomes, penetrating the epidermis, and affecting epidermal esterases but not those in the dermis. Accordingly, whilst the resulting dispase II-generated dermal membranes may be used for in vitro permeation tests (IVPT) involving esterase-based metabolic studies, the dispase II-generated epidermal membranes are not suitable for this purpose.

Evaluation of Transdermal Transport and Concurrent Cutaneous Hydrolysis of Timolol Prodrug for the Treatment of Infantile Hemangiomas

Infantile hemangiomas (IH) leave sequelae after involution. Topical application of timolol maleate (TM) is the mainstream treatment for superficial lesions but is limited by its low penetrable properties. We aimed to develop a superior skin permeation drug while maintaining the therapeutic properties of timolol. We predict that this drug will promote the involution of thick and deep IH lesions and avoid sequelae. We chemically modified drug structure to prepare butyryl timolol maleate (BT) prodrug and conducted in vitro and in vivo toxicity evaluations of BT with rat dorsal skin and normal skin cells. Skin permeation and absorption comparisons of TM and BT were conducted using rat and porcine skin models. Conversion efficiency of BT to timolol was also tested on human skin ex vivo. BT did not cause skin irritation on rat dorsal skin and exhibited low cytotoxicity overall. BT exhibited superior skin permeation ability compared with that of TM, whilst maintaining a low systemic absorbance. Further, BT was converted to timolol in human skin in a time-dependent manner. Noticeably, timolol accumulation in the skin from BT was higher than that from TM. Finally, BT demonstrated similar biocompatibility with TM in the IH tumor. BT enhances local delivery of timolol and its skin permeation. Using BT, we could eliminate thicker IH lesions that are prone to leave sequelae, and potentially help young children avoid dermal sequelae, disfigurement, and concomitant therapy.

Microalgae as a Sustainable, Natural-Oriented and Vegan Dermocosmetic Bioactive Ingredient: The Case of Neochloris oleoabundans

“Vegan” and “sustainable” characteristics are strong claim trends behind the development of innovative skincare, fragrances, and makeup products. This created a need in the market for compliant ingredients. To date, there have been no records evidencing the use of the microalgae Neochloris oleoabundans (NA) in dermocosmetics. Therefore, we studied the applicability of such a natural compound in this context. NA was cultivated, and the scavenging activity (SA) of the NA extracts was evaluated. The highest SA was from the aqueous extract (54.8% ± 2.1%), being higher than that of the positive control. Two hydrogels were prepared with 1.0% ammonium acryloyldimethyltaurate/VP copolymer: (1) control gel; and (2) gel with a 1.0% NA aqueous extract. In vivo experiments were performed in healthy male and female volunteers with skin phototypes of II–IV. The stratum corneum (SC) hydration and the transepidermal water loss (TEWL) were measured in the forearm of participants to determine their biocompatibility. This parameter was determined by skin bioengineering measurements, confirming that SC hydration and TEWL were not affected by the samples. The laser Doppler measurements results showed a delayed erythema onset in the sites, where the NA hydrogel was applied. The results confirmed the biocompatibility and the anti-inflammatory activity of an innovative ingredient derived from microalgae suitable for a natural and vegan lifestyle.

Reduction of telogen rate and increase of hair density in androgenetic alopecia by a cosmetic product: Results of a randomized, prospective, vehicle-controlled double-blind study in men

BACKGROUND

Considerable parts of the global population are affected by androgenetic alopecia (AGA).

AIMS

The efficacy of a foam containing nicotinic acid hexyl ester, polyphenols, zinc, glycine, and caffeine in comparison with a vehicle control foam was assessed in a double-blind vehicle-controlled study in men with AGA over 6 months.

PATIENTS/METHODS

Sixty-two men with AGA were assigned either to the active ingredients (verum) or the vehicle group. They applied the products twice daily on affected scalp areas over 6 months. Automated phototrichograms were obtained at baseline, after 3 and 6 months. In addition, a clinical rating by a dermatologist and by the subjects themselves was documented using standardized questionnaires.

RESULTS

The reduction of the telogen rate from T0 to T6 was significantly stronger in the verum group compared to the vehicle group. The reduction was significant from T0 to T3 and T6 in the verum group, but in the vehicle group only from T0 to T3, not to T6. Significantly increased hair density was noticed in both groups at all time points, but the change from T0 to T6 did not differ significantly between the groups. Cosmetic acceptance of the foam and its application regimen was generally good in both groups. Slight reddening and burning after application of verum in six cases was probably due to the presence of hexyl nicotinate.

CONCLUSION

The study demonstrated a reduction of the telogen rate by a cosmetic foam in men affected by AGA, indicating a benefit for cosmetic intervention against male pattern hair loss.

Topical Treatment for Cutaneous Leishmaniasis: Dermato-Pharmacokinetic Lead Optimization of Benzoxaboroles

Cutaneous leishmaniasis (CL) is caused by several species of the protozoan parasite Leishmania, affecting an estimated 10 million people worldwide. Previously reported strategies for the development of topical CL treatments have focused primarily on drug permeation and formulation optimization as the means to increase treatment efficacy. Our approach aims to identify compounds with antileishmanial activity and properties consistent with topical administration. Of the test compounds, five benzoxaboroles showed potent activity (50% effective concentration [EC50] < 5 μM) against intracellular amastigotes of at least one Leishmania species and acceptable activity (20 μM < EC50 < 30 μM) against two more species. Benzoxaborole compounds were further prioritized on the basis of the in vitro evaluation of progression criteria related to skin permeation, such as the partition coefficient and solubility. An MDCKII-hMDR1 cell assay showed overall good permeability and no significant interaction with the P-glycoprotein transporter for all substrates except LSH002 and LSH031. The benzoxaboroles were degraded, to some extent, by skin enzymes but had stability superior to that of para-hydroxybenzoate compounds, which are known skin esterase substrates. Evaluation of permeation through reconstructed human epidermis showed LSH002 to be the most permeant, followed by LSH003 and LSH001. Skin disposition studies following finite drug formulation application to mouse skin demonstrated the highest permeation for LSH001, followed by LSH003 and LSH002, with a significantly larger amount of LSH001 than the other compounds being retained in skin. Finally, the efficacy of the leads (LSH001, LSH002, and LSH003) against Leishmania major was tested in vivo LSH001 suppressed lesion growth upon topical application, and LSH003 reduced the lesion size following oral administration.

Time controlled pulsatile transdermal delivery of nicotine: A phase I feasibility trial in male smokers

Nicotine substitution is a mainstay component in smoking cessation schemes. Current products including patches are poorly effective mainly because they do not give smokers the same pharmacokinetic profile of nicotine as cigarette consumption. This work evaluates a new computer operated delivery system for time controlled pulsatile transdermal administration of nicotine in a phase I clinical trial with twelve heavy smoking male volunteers. The device was affixed to the ventral side of the leading lower arm of the subjects and was programmed to deliver two pulses of drug within 16h with three delivery rates in a consecutive dose escalation study. Tolerability of the three increasing doses of nicotine was established. Plasma concentration of nicotine exhibited two peaks and one trough and reached therapeutically effective levels that behaved linearly with the drug load concentration of the device. In vivo input rate, delivered amount and elimination kinetics were deduced by pharmacokinetic modeling to analyze device performance. Timing, dose and duration of delivery were controlled by system operation parameters. Hence, feasibility of controlled pulsatile delivery of nicotine at predetermined intervals was demonstrated. After additional optimization, preprogrammed or on demand administration to meet individualized and circadian replacement needs should improve smoking cessation efficacy.

Safety and efficacy evaluation of gelatin-based nanoparticles associated with UV filters

The safety and efficacy assessment of nanomaterials is a major concern of industry and academia. These materials, due to their nanoscale size, can have chemical, physical, and biological properties that differ from those of their larger counterparts. The encapsulation of natural ingredients can provide marked improvements in sun protection efficacy. This strategy promotes solubility enhancement of flavonoids and yields an improved active ingredient with innovative physical, physicochemical and functional characteristics. Rutin, a flavonoid, has chemical and functional stability in topical vehicles exerting a synergistic effect in association with ultraviolet (UV) filters. However, the solubility of rutin is a limiting factor. Additionally, this bioactive compound does not have tendency to permeate across the stratum corneum. As an alternative to common synthetic based sunscreens, rutin-entrapped gelatin nanoparticles were designed. The present study investigated the pre-clinical safety of gelatin nanoparticles (GNPs) using an in vitro method and also assessed the clinical safety and efficacy of the association of GNPs with three commonly used chemical UV filters (ethylhexyl dimethyl PABA, ethylhexyl methoxycinnamate and methoxydibenzoylmethane). The non-irritant and adequate safety profile under sun-exposed skin conditions of the nanomaterials and the emulsions qualified the products for clinical efficacy assays. The in vivo results indicated that the GNPs increased the antioxidant protection of the emulsions developed. However, the presence of rutin in the nanosized material did not enhance performance on the SPF test. In conclusion, these findings characterized the nanomaterials as an innovative platform for multifunctional bioactive sunscreens.

Esterase Activity and Intracellular Localization in Reconstructed Human Epidermal Cultured Skin Models

Background

Reconstructed human epidermal culture skin models have been developed for cosmetic and pharmaceutical research.

Objective

This study evaluated the total and carboxyl esterase activities (i.e., K_m and V_max, respectively) and localization in two reconstructed human epidermal culture skin models (LabCyte EPI-MODEL [Japan Tissue Engineering] and EpiDerm [MatTek/Kurabo]). The usefulness of the reconstruction cultured epidermis was also verified by comparison with human and rat epidermis.

Methods

Homogenized epidermal samples were fractioned by centrifugation. p-nitrophenyl acetate and 4-methylumbelliferyl acetate were used as substrates of total esterase and carboxyl esterase, respectively.

Results

Total and carboxyl esterase activities were present in the reconstructed human epidermal culture skin models and were localized in the cytosol. Moreover, the activities and localization were the same as those in human and rat epidermis.

Conclusion

LabCyte EPI-MODEL and EpiDerm are potentially useful for esterase activity prediction in human epidermis.

Dermal uptake of 18 dilute aqueous chemicals: in vivo disappearance-method measures greatly exceed in vitro-based predictions

Average rates of total dermal uptake (Kup ) from short-term (e.g., bathing) contact with dilute aqueous organic chemicals (DAOCs) are typically estimated from steady-state in vitro diffusion-cell measures of chemical permeability (Kp ) through skin into receptor solution. Widely used ("PCR-vitro") methods estimate Kup by applying diffusion theory to increase Kp predictions made by a physico-chemical regression (PCR) model that was fit to a large set of Kp measures. Here, Kup predictions for 18 DAOCs made by three PCR-vitro models (EPA, NIOSH, and MH) were compared to previous in vivo measures obtained by methods unlikely to underestimate Kup . A new PCR model fit to all 18 measures is accurate to within approximately threefold (r = 0.91, p < 10(-5) ), but the PCR-vitro predictions (r > 0.63) all tend to underestimate the Kup measures by mean factors (UF, and p value for testing UF = 1) of 10 (EPA, p < 10(-6) ), 11 (NIOSH, p < 10(-8) ), and 6.2 (MH, p = 0.018). For all three PCR-vitro models, log(UF) correlates negatively with molecular weight (r(2) = 0.31 to 0.84, p = 0.017 to < 10(-6) ) but not with log(vapor pressure) as an additional predictor (p > 0.05), so vapor pressure appears not to explain the significant in vivo/PCR-vitro discrepancy. Until this discrepancy is explained, careful in vivo measures of Kup should be obtained for more chemicals, the expanded in vivo database should be compared to in vitro-based predictions, and in vivo data should be considered in assessing aqueous dermal exposure and its uncertainty.

Ex vivo evaluation of the percutaneous penetration of proanthocyanidin extracts from Guazuma ulmifolia using photoacoustic spectroscopy

In this work photoacoustic spectroscopy has been applied to determine ex vivo the percutaneous penetration of proanthocyanidins present in extracts obtained from Guazuma ulmifolia, in rats. Lotion formulations containing 0.0663 mg of procyanidin B2 day(-1)animal(-1) were topically applied during 7, 10 and 13 days in each group of the animals. After the end of treatment the animals were killed, the skin dissected to remove the basal content, and the measurements were carried out as a function of the period of time of treatment. The results showed that despite the very low concentration of the active principle (procyanidin B2) in the lotion, the photoacoustic method was able to show the presence of optical absorption bands from this substance in the dermis region, evidencing once again that this method may be useful for studies of topically applied formulations of interest in the pharmacokinetic area.

Synthesis of novel vasodilatory active nicotinate esters with amino acid function

A variety of N-[(ethyl-4,6-diaryl-3-pyridinecarboxylate)-2-yl]amino acid esters 6a-h were synthesized through the reaction of 2-bromonicotinates 4 with a number of primary amino acid ester hydrochlorides 5 in refluxing tetrahydrofuran in the presence of triethylamine as dehydrohalogenating agent. Similarly, reaction of 4 with N-glycylglycine ethyl ester hydrochloride 7 'as a representative example of dipeptide derivative' afforded smoothly the corresponding N-[(ethyl-4,6-diaryl-3-pyridinecarboxylate)-2-yl]-N'-glycylglycine ethyl ester analogues 8. However, reaction of 4 with 5 in refluxing pyridine yielded the unexpected 2-aminonicotinate esters 9. Vasodilation activity screening for the synthesized nicotinate esters was investigated in vitro on the contractile response of vascular thoracic aorta smooth muscle from Wistar rats, where all the tested compounds exhibit considerable vasodilatory properties. In addition, few prepared compounds especially, 6b, 6h and 9b reveal remarkable vasodilation potency (IC(50)).

Kinetics of blood flow after topical application of benzyl nicotinate on different anatomic sites

Cutaneous characteristics, e.g., thickness of the SC and density of follicles, affect the penetration of topically applied substances. In the present study, the penetration of benzyl nicotinate, causing a vasodilation, was studied on three anatomic sites (forearm, forehead and calf) differing in their skin characteristics. Therefore, the blood flow of the superficial dermal plexus and that of the larger capillaries in the deeper skin layers was simultaneously measured using a laser Doppler flowmeter. In addition, the cutaneous temperature and redness were determined as a function of time. These four biological reactions were measured in turn on a skin area treated with a gel containing benzyl nicotinate and on an untreated control area. The highest basal levels were observed on the forehead. Topical application of benzyl nicotinate resulted in an increase in each biological response. Compared to the other sites, the maximal values were reached earliest on the forehead, which also showed the fastest decrease. No significant differences were obtained comparing the kinetic data of the calf with that of the forearm. The results indicate an additional contribution by the numerous vellus hair follicles of the forehead to the penetration and exposure of the drug.

Clinical microneedle injection of methyl nicotinate: stratum corneum penetration

BACKGROUND/PURPOSE

In recent years, microneedles were proposed as a method to painlessly deliver drugs past the stratum corneum. Microneedles have been fabricated in several designs, but limited studies have tested microneedle injections in humans. In this work, we compare microneedle injections with topical application (TA) to investigate if microneedles enhance in vivo drug delivery past the stratum corneum.

METHOD

In vitro tests were used to measure microneedle pressures and injection volumes. In vivo microneedle injections were performed on the volar forearm of 11 healthy volunteers. Two sets of microneedles, pointed and symmetric, were used to develop microneedle/syringe apparatuses that were used to inject approximately 1 microL of 0.1 M methyl nicotinate, and were compared against TA. A Laser Doppler Perfusion Monitor was used to record maximum blood flow and the time to maximum blood flow at the treatment sites.

RESULTS

Pointed and symmetric microneedle-injected sites showed a significantly faster time to maximum blood flow than TA. The pointed microneedle injections also resulted in a higher maximum blood flux. Volunteers reported feeling pressure but no pain from the microneedles during the injections.

CONCLUSION

The microneedles aid in bypassing the stratum corneum and enhance drug delivery through it. The design of the microneedle influences its delivery capabilities, because the pointed microneedles seem to be less susceptible to clogging during the injection.

The transdermal revolution

Historically, developments in transdermal drug delivery have been incremental, focusing on overcoming problems associated with the barrier properties of the skin, reducing skin irritation rates and improving the aesthetics associated with passive patch systems. More-recent advances have concentrated on the development of non-passive systems to aid delivery of larger drug molecules, such as proteins and nucleotides, as the trend for discovering and designing biopharmaceuticals continues. Fundamentally, improvements in transdermal delivery will remain incremental until there is wider acceptance of this route of administration within the pharmaceutical industry. Only then will the transdermal revolution live up to its true potential.