Topical Pimecrolimus 1% Reverses Long-term Suberythemal Ultraviolet B—induced Epidermal Langerhans Cell Reduction and Morphologic Changes in Mice

September 2012 | Volume 11 | Issue 9 | Original Article | 25 | Copyright © September 2012

ZhiQiang Yin MD,a* JiaLi Xu MD,b* Yan Lu MD,c Dan Luo MD,PhDd*

a,c,dDepartment of Dermatology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China bDepartment of Oncology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China *ZhiQiang Yin, JiaLi Xu, and Yan Lu contributed equally to this work.

Abstract
Objective: Some literature reported that topical calcineurin inhibitors (TCIs) did not accelerate photocarcinogenesis in hairless mice after long-term simulated solar radiation. In this work, we investigate the effects of topical pimecrolimus 1% on long-term suberythemal ultraviolet B (UVB)—irradiated epidermal Langerhans cells (LCs) in mice.
Methods:Thirty female mice were randomly divided into two groups, including four subgroups: (1A) control, (1B) pimecrolimus 1% only, (2A) 25 mJ/cm2 UVB only, (2B) UVB plus pimecrolimus. After being treated for 60 days, the dorsal skin was collected and given immunohistochemical staining of active caspase 3, and immunofluorescence staining for cluster of differentiation 1a (CD1a).
Results:Our results show that, compared with the control subgroup, the CD1a+ LC number in the epidermal sheet of the UVB-only subgroup decreased substantially from 578.6 per mm2 to 227 per mm2 (P<.001). Compared with the UVB-only subgroup, the UVB plus pimecrolimus subgroup significantly restored the LC number from 227 per mm2 to 475.7 per mm2 (P<.001). Compared with other subgroups, the LC morphology of the UVB-only subgroup became rounder, and the LC dendrites became shorter. There were no significant active caspase 3-positive cells in the epidermis in any of the four subgroups.
Conclusion:Our results show that topical pimecrolimus 1% reverses long-term UVB-induced epidermal LC reduction and morphologic changes in mice, where the exact mechanism is likely not related to apoptosis.

J Drugs Dermatol. 2012;11(9):e25-e27.

INTRODUCTION

Long-term ultraviolet (UV) radiation facilitates the development of skin tumors. Lerche et al have reported that TCIs, including topical pimecrolimus and tacrolimus, did not accelerate photocarcinogenesis in hairless mice after simulated solar radiation (SSR).1,2
Epidermal Langerhans cells (LCs) play a role in immunosurveillance, which is one important pathway against tumorigenesis. Langerhans cells process antigens and migrate from the epidermis to draining lymph nodes, expressing CD1a.3 The LC morphology becomes rounder, and the LC dendrites become shorter in the process of migration.
We designed this study to investigate the effects of topical pimecrolimus 1% on long-term suberythemal UVB-irradiated epidermal LCs.

METHODS

Thirty female CByJ-Cg-Foxn1nu/NJU mice (6-8 weeks old) were purchased from the Model Animal Research Center of Nanjing University and housed in separate boxes where standard laboratory food and water were provided ad libitum. The animals were kept on a 12-hour light-dark cycle.
The source of UVB was a BLE-1T158 fluorescent lamp (Spectronics Corporation, Westbury, NY). The UVB dose was quantified using a Waldmann UV meter (model no. 585100; Waldmann Co, VS-Schwenningen, Germany), and 25 mJ/cm2 of UVB was delivered once daily to the dorsal skin of the mice for up to 60 days.
Topical pimecrolimus 1% (Elidel®; Novartis Pharma GmbH, Wehr, Germany) was applied on the right dorsal skin of the mice after UVB radiation (or without UVB radiation) once daily for 60 days.
The 30 female mice were randomly divided into two groups of 15 mice, and further subdivided into four subgroups: Group 1A, left dorsal skin (control); Group 1B, right dorsal skin (pimecrolimus1% only daily); Group 2A, left dorsal skin (UVB only daily); Group 2B, right dorsal skin (pimecrolimus daily after UVB).
After being treated for 60 days, the mice were killed by cervical dislocation, and their dorsal skin was collected. Each skin specimen was cut in two. One part was frozen in liquid nitrogen, embedded in optimal cutting temperature compound and stored at -30°C until further processing for immunohistochemical staining. The other part was prepared for an epidermal sheet that was processed for immunofluorescence staining.