Tacrolimus-loaded chitosan-based nanoparticles as an efficient topical therapeutic for the effective treatment of atopic dermatitis symptoms

Atopic dermatitis (AD) is a chronic cutaneous disease with a complex underlying mechanism, and it cannot be completely cured. Thus, most treatment strategies for AD aim at relieving the symptoms. Although corticosteroids are topically applied to alleviate AD, adverse side effects frequently lead to the withdrawal of AD therapy. Tacrolimus (TAC), a calcineurin inhibitor, has been used to treat AD, but its high molecular weight and insolubility in water hinder its skin permeability. Herein, we developed and optimized TAC-loaded chitosan-based nanoparticles (TAC@CNPs) to improve the skin permeability of TAC by breaking the tight junctions in the skin. The prepared nanoparticles were highly loadable and efficient and exhibited appropriate characteristics for percutaneous drug delivery. TAC@CNP was stable for 4 weeks under physiological conditions. CNP released TAC in a controlled manner, with enhanced skin penetration observed. In vitro experiments showed that CNP was non-toxic to keratinocyte (HaCaT) cells, and TAC@CNP dispersed in an aqueous solution was as anti-proliferative as TAC solubilized in a good organic solvent. Importantly, an in vivo AD mouse model revealed that topical TAC@CNP containing ~1/10 of the dose of TAC found in commercially used Protopic® Ointment exhibited similar anti-inflammatory activity to that of the commercial product. TAC@CNP represents a potential therapeutic strategy for the management of AD.

Development of a Novel Approach to Studying Corneodesmosomes and Stratum Corneum Adhesion: Extending Knowledge on the Pathophysiology of Sensitive Skin

BACKGROUND/AIMS

Aberrant skin barrier and intercorneocyte adhesion are potential contributors to the pathomechanism of sensitive skin (SS). Here we aimed to develop a novel and easy-to-apply method to analyze corneodesmosomes and to interrogate potential differences between corneocytes of subjects with SS and non-SS (NSS).

METHODS

Corneocytes of the volar forearm and upper outer quadrant of the left buttock of SS (n = 10) and NSS (n = 8) subjects were extracted as a function of depth using adhesive tape and stained with anti-desmoglein 1 (DSG1) antibody. The total area of corneocytes and the number and average size of cells per tape was estimated using image processing.

RESULTS

The total area of extracted corneocytes and the quantity of DSG1 decreased with depth. The level of decrease, total area of corneocytes, and average area of individual cells differed between anatomical locations. In SS, a larger total area of extracted corneocytes and a larger average cell size per tape was found at all inspected depths.

CONCLUSION

The developed novel and easy-to-apply approach allows investigation of corneodesmosome components. We confirm a role of altered corneocytes in the pathomechanism of SS. The disclosed protocol can further be optimized in studies of skin conditions with strongly affected corneodesmosomes.

Sensitive Skin: Assessment of the Skin Barrier Using Confocal Raman Microspectroscopy

BACKGROUND/AIMS

Sensitive skin (SS), a frequently reported condition in the Western world, has been suggested to be underlined by an impaired skin barrier. The aim of this study was to investigate the skin barrier molecular composition in SS subjects using confocal Raman microspectroscopy (CRS), and to compare it with that of non-SS (NSS) individuals as well as atopic dermatitis (AD) and allergic rhinoconjunctivitis (AR) subjects, who frequently report SS.

METHODS

Subjects with SS (n = 29), NSS (n = 30), AD (n = 11), and AR (n = 27) were included. Stratum corneum (SC) thickness, water, ceramides/fatty acids, and natural moisturizing factor (NMF) were measured by CRS along with transepidermal water loss and capacitance on the ventral forearm, thenar, and cheek. Sebum levels were additionally measured on the forearm and cheek.

RESULTS

No differences between SS and NSS subjects were found regarding SC thickness, water, and NMF content, yet a trend towards lower ceramides/fatty acids was observed in the cheek. Compared to AD subjects, the SS group showed higher ceramides/fatty acid content in the forearm, whereas no differences emerged with AR. The correlation of macroscopic biophysical techniques and CRS was weak, yet CRS confirmed the well-known lower content of NMF and water, and thinner SC in subjects with filaggrin mutations.

CONCLUSION

The skin barrier in SS is not impaired in terms of SC thickness, water, NMF, and ceramides/fatty acid content. The failure of biophysical techniques to follow alterations in the molecular composition of the skin barrier revealed by CRS emphasizes a strong need in sensitive and specific tools for in vivo skin barrier analysis.

The evaluation of neural and vascular hyper-reactivity for sensitive skin

BACKGROUND

The impaired barrier function has been studied comprehensively but few about the heighted neural and vascular reaction for the pathogenesis of sensitive skin.

METHODS

Lactic acid stinging test (LAST) was used to identify sensitive subjects in selection phase. In the subsequent test phase, the baseline value of the blood flow (BF) and the current perception threshold (CPT) was measured by non-invasive instruments firstly. Then, the 0.001% capsaicin was applied to the nasolabial fold for 5 min. After the capsaicin test (CAT), the BF (immediately after the CAT) and CPT (1 h later after the CAT) were measured again. Blood sample were collected for genetic analysis of four TRPV1 gene single nucleotide polymorphisms between the positive-group and the negative-group.

RESULT

The positive-group had lower baseline value of CPT at 5 and 250 Hz compared with the negative-group, but no difference in baseline value of BF. After the CAT, significant variation in CPT at 5 and 250 Hz values and the BF were found in positive-group but not in negative-group. The genotype frequencies of AG/GG in RS224534 and AC/CC in RS4790523 in positive-group were higher than that of negative-group.

CONCLUSION

The sensitive subjects were prone to be stimulated by capsaicin to trigger neural and vascular hyper-reactivity. The genetic variation of TRPV1 and the unpleasant sensation demonstrate that TRPV1 play an important role in the pathogenesis of sensitive skin. Our study supports that sensory irritation inhibitors and anti-inflammatory compounds should be considered to be added in cosmetics to reduce the heighted neural and vascular reaction of sensitive skin.