FK506 induces interleukin-6 secretion from UVB irradiated cultured human keratinocytes via p38 mitogen-activated protein kinase pathway: Implication on mechanisms of tacrolimus-induced skin irritation

Topical Delivery of Rapamycin by Means of Microenvironment-Sensitive Core-Multi-Shell Nanocarriers: Assessment of Anti-Inflammatory Activity in an ex vivo Skin/T Cell Co-Culture Model

Introduction

Rapamycin (Rapa) is an immunosuppressive macrolide that inhibits the mechanistic target of rapamycin (mTOR) activity. Thanks to its anti-proliferative effects towards different cell types, including keratinocytes and T cells, Rapa shows promise in the treatment of skin diseases characterized by cell hyperproliferation. However, Rapa skin penetration is limited due to its lipophilic nature (log P = 4.3) and high molecular weight (MW = 914 g/mol). In previous studies, new microenvironment-sensitive core multishell (CMS) nanocarriers capable of sensing the redox state of inflamed skin were developed as more efficient and selective vehicles for macrolide delivery to inflamed skin.

Methods

In this study, we tested such redox-sensitive CMS nanocarriers using an inflammatory skin model based on human skin explants co-cultured with Jurkat T cells. Serine protease (SP) was applied on skin surface to induce skin barrier impairment and oxidative stress, whereas phytohaemagglutinin (PHA), IL-17A, and IL-22 were used to activate Jurkat cells. Activation markers, such as CD45 and CD69, phosphorylated ribosomal protein S6 (pRP-S6), and IL-2 release were monitored in activated T cells, whereas pro-inflammatory cytokines were measured in skin extracts and culture medium.

Results

We found that alteration of skin barrier proteins corneodesmosin (CDSN), occludin (Occl), and zonula occludens-1 (ZO-1) as well as oxidation-induced decrease of free thiol groups occurred upon SP-treatment. All Rapa formulations exerted inhibitory effects on T cells after penetration across ex vivo skin. No effects on skin inflammatory markers were detected. The superiority of the oxidative-sensitive CMS nanocarriers over the other formulations was observed with regard to drug delivery as well as downregulation of IL-2 release.

Conclusion

Overall, our results demonstrate that nanocarriers addressing features of diseased skin are promising approaches to improve the topical delivery of macrolide drugs.

Heat-related changes in skin tissue dielectric constant (TDC)

The impact of 20 min of whole-body heating (WBH) on the tissue dielectric constant (TDC) of forearm and hand skin was evaluated in 24 young adults. TDC was measured in triplicate at 300 MHz using an open-ended transmission line method in which the effective measurement depth was about 2 mm. TDC measurements are an effective way to assess and track localized oedema and lymphoedema. The underlying hypothesis was that heat-induced eccrine gland activation would increase TDC values via an increase in fluid within the TDC measurement volume. The goal was to test this concept and to determine the magnitude of the change when environmental temperatures were elevated to near 42°C and to estimate TDC recovery time. The practical aspect of this research is motivated by the fact that patients in whom such measurements are made may arrive at the clinic in various states of sweat gland activation. Thus, knowledge of the effect of such activation on measured TDC values permits better understanding of possible relationships between such activation and TDC values. Results showed that increasing environmental temperature from 23·3 ± 1·6 to 41·5 ± 1·3°C increased forearm and thenar eminence skin temperatures to 37·8 ± 0·5 and 37·9 ± 0·4°C, respectively. These changes were associated with increases in TDC at arm from 30·7 ± 4·6 to 36·3 ± 5·7 (18·2%) and at hand from 34·7 ± 4·9 to 45·1 ± 5·5 (30%). Based on calculated TDC recovery rates, it is concluded that temperature-related TDC variability can be minimized using a wait time of at least 15 min after bandage removal prior to TDC measurements in affected limbs.

Dermal Delivery of the High-Molecular-Weight Drug Tacrolimus by Means of Polyglycerol-Based Nanogels

Polyglycerol-based thermoresponsive nanogels (tNGs) have been shown to have excellent skin hydration properties and to be valuable delivery systems for sustained release of drugs into skin. In this study, we compared the skin penetration of tacrolimus formulated in tNGs with a commercial 0.1% tacrolimus ointment. The penetration of the drug was investigated in ex vivo abdominal and breast skin, while different methods for skin barrier disruption were investigated to improve skin permeability or simulate inflammatory conditions with compromised skin barrier. The amount of penetrated tacrolimus was measured in skin extracts by liquid chromatography tandem-mass spectrometry (LC-MS/MS), whereas the inflammatory markers IL-6 and IL-8 were detected by enzyme-linked immunosorbent assay (ELISA). Higher amounts of tacrolimus penetrated in breast as compared to abdominal skin or in barrier-disrupted as compared to intact skin, confirming that the stratum corneum is the main barrier for tacrolimus skin penetration. The anti-proliferative effect of the penetrated drug was measured in skin tissue/Jurkat cells co-cultures. Interestingly, tNGs exhibited similar anti-proliferative effects as the 0.1% tacrolimus ointment. We conclude that polyglycerol-based nanogels represent an interesting alternative to paraffin-based formulations for the treatment of inflammatory skin conditions.

Role of handedness on forearm skin tissue dielectric constant (TDC) in relation to detection of early-stage breast cancer-related lymphedema

skin tissue dielectric constant (TDC) measurements help assess local skin water to detect incipient early-stage lymphedema subsequent to breast cancer treatment-related lymphedema. However, presurgery measurements are not always obtained and assessments for evolving lymphedema are only made after surgery. Thus, subsequent TDC assessments may be biased in an unknown way dependent on a patient's handedness in relation to the at-risk arm. We investigated this issue by comparing TDC values in dominant and non-dominant volar forearms of 31 left-handed women and 31 right-handed women (age range 24-84 years). Body fat and water percentages were assessed by bioimpedance at 50 KHz. Results showed that TDC values of dominant versus non-dominant arms did not significantly differ for left-handers or for right-handers. There was also no statistically significant difference in absolute TDC values between left- and right-handers or a statistically significant difference in dominant-to-non-dominant arm ratios between left- and right-handers. For the composite data set (N = 62), TDC values for dominant and non-dominant arms were, respectively, 30·0 ± 4·6 and 29·6 ± 4·2 and the dominant-to-non-dominant arm TDC ratio for combined left- and right-handers was 1·015 ± 0·075. These results suggest that handedness is not a major factor when assessing lymphedema status in women who have previously been treated for breast cancer but for whom pretreatment TDCvalues have not been obtained. Moreover, these results suggest that threshold ratios of incipient subclinical unilateral lymphedema based on interarm TDC ratios apply independent of a patient's handedness for the site and tissue depths herein measured.

Topical tacrolimus has a limited direct effect on ultraviolet B-irradiated keratinocytes: implications for its photocarcinogenic potential

BACKGROUND

Topical tacrolimus has shown remarkable clinical efficacy in treating many dermatoses. Combining ultraviolet (UV) B and tacrolimus is an intriguing therapeutic regimen, especially for treatment of vitiligo, for which combination therapy may show greater clinical efficacy than topical tacrolimus alone. The photocarcinogenic potential of such a regimen is unclear, and conflicting results have been reported by different investigators.

AIM

To clarify this important clinical issue, we investigated the effects of tacrolimus on UVB-irradiated cultured keratinocytes in terms of apoptosis, differentiation, cell-cycle regulation and DNA damage.

METHODS

Cultured keratinocytes were treated with tacrolimus before and after UVB irradiation and the various cellular physiological changes were evaluated using trypan blue exclusion, terminal dUTP nick-end labelling, flow cytometry and Western blotting analyses.

RESULTS

Our results showed that treatment of tacrolimus before or after UVB irradiation had no significant effects on cultured keratinocytes in terms of cell apoptosis, transglutaminase-1, involucrin expression, cell-cycle progression and phospho-H(2)AX compared with UVB irradiation alone.

CONCLUSION

The direct effect of tacrolimus on UVB-irradiated keratinocytes is small, suggesting that clinical regimens combining UVB and tacrolimus also have a limited direct effect on healthy skin compared with UVB irradiation alone.