ORCID
https://orcid.org/0000-0002-9800-7846
Date of Award
2022
Document Type
Dissertation
Degree Name
Psychology (Psy.D.)
Department
Pharmaceutical Sciences
First Advisor
Blase Billack
Second Advisor
Russell DiGate
Third Advisor
Francis Schanne
Abstract
Sulfur Mustard (SM) is a chemical warfare agent first utilized on the battlefield more than 100 years ago. To the present time, no antidote to combat the dermatotoxicity of SM exists. Mechlorethamine (HN2) is a derivative of SM which is used in anticancer therapy. Dermal exposure of HN2 is associated with dermal-epidermal junction (DEJ) disruption (vesication) which limits its clinical usefulness. The primary purpose of the present study was to investigate the mechanisms of vesication caused by HN2 using an in vivo mouse ear vesicant model (MEVM). The ears of male or female C57BL/ 6J mice were exposed to a single topical dose of HN2 (25, 50, 100 or 200 mM) or vehicle control (DMSO). Mice were then euthanized 24 h following exposure. Both female and male mouse ears exposed to HN2 showed an increase in wet weights, morphometric thickness, myeloperoxidase (MPO, neutrophil marker) expression, matrix metalloproteinase (MMP-9, tissue remodeling marker) expression and vesication at all test doses when compared to control. In order to analyze the effect of MMP-9 on tissue blistering, the ears of male or female Mmp-9-/- mice were exposed to 100 mM HN2, DMSO or left untreated. Mice were then euthanized at 24 h following exposure. Female and male mice ears exposed to HN2 showed an increase in wet weights, morphometric thickness and vesication when compared to control. However, incidence of vesication in knockout mice was decreased relative to wildtype mice indicating that MMP-9 plays an important role in DEJ disruption. The role of mast cell tryptase, an upstream mediator of MMP-9, in DEJ disruption was also investigated. Mouse ear tissues exhibited a dose-dependent increase in tryptase expression upon HN2 administration via immunohistochemistry (IHC). Mast cell counts increased in HN2 treated samples when compared to control. However, mRNA expression was reduced in HN2 treated cells. Western Blots could not detect tryptase protein in either control or HN2 treated samples. These data do not strongly support a role for tryptase in HN2-induced DEJ disruption. Next, the role played by mammalian target of rapamycin (mTOR) signaling pathway in maintaining the DEJ was investigated. Tissues treated with HN2 (100 mM) exhibited reduced expression of Raptor, an important protein involved in the activation of mTOR at 24 h. HN2 reduced the downstream effectors (phospho S6 (Ser 240/244) ribosomal protein and phospho 4E-BP1 (Thr 37/46)) of the mTOR pathway in the epidermis at 30 min, 1 h and 24 h following HN2 exposure but not in the dermis. The results suggest that dysregulation of the mTOR pathway contributes to DEJ disruption. All in all, the work represented in the present thesis supports the hypotheses that HN2-mediated vesication involves upregulation of MMP-9 and downregulation of the mTOR signaling pathway. The role of tryptase in HN2-mediated DEJ disruption remains to be codified.
Recommended Citation
Janardhanam Raghavendra Rao, Trishaal, "EVALUATING THE EFFECTS OF MECHLORETHAMINE ON THE DERMAL-EPIDERMAL JUNCTION" (2022). Theses and Dissertations. 723.
https://scholar.stjohns.edu/theses_dissertations/723