Depilatory double‐disc mouse model for evaluation of vesicant dermal injury pharmacotherapy countermeasures

Abstract

Background Sulfur mustard (SM) is a chemical warfare vesicant that severely injures exposed eyes, lungs, and skin. Mechlorethamine hydrochloride (NM) is widely used as an SM surrogate. This study aimed to develop a depilatory double‐disc (DDD) NM skin burn model for investigating vesicant pharmacotherapy countermeasures. Methods Hair removal method (clipping only versus clipping followed by a depilatory), the effect of acetone in the vesicant administration vehicle, NM dose (0.5–20 μmol), vehicle volume (5–20 μl), and time course (0.5–21 days) were investigated using male and female CD‐1 mice. Edema, an indicator of burn response, was assessed by biopsy skin weight. The ideal NM dose to induce partial‐thickness burns was assessed by edema and histopathologic evaluation. The optimized DDD model was validated using an established reagent, NDH‐4338, a cyclooxygenase, inducible nitric oxide synthase, and acetylcholinesterase inhibitor prodrug. Results Clipping/depilatory resulted in a 5‐fold higher skin edematous response and was highly reproducible (18‐fold lower %CV) compared to clipping alone. Acetone did not affect edema formation. Peak edema occurred 24–48 h after NM administration using optimized dosing methods and volume. Ideal partial‐thickness burns were achieved with 5 μmol of NM and responded to treatment with NDH‐4338. No differences in burn edematous responses were observed between males and females. Conclusion A highly reproducible and sensitive partial‐thickness skin burn model was developed for assessing vesicant pharmacotherapy countermeasures. This model provides clinically relevant wound severity and eliminates the need for organic solvents that induce changes to the skin barrier function.

Optimizing Nanosuspension Drug Release and Wound Healing Using a Design of Experiments Approach: Improving the Drug Delivery Potential of NDH-4338 for Treating Chemical Burns

“…Reported here for the first time, NDH-4338 was formulated into an NS, formulated above a 1% dose concentration, and used to effectively treat NM skin burns after only two doses administered in 24 h. The aqueous vehicle used in the optimized NS formulation may have allowed for improved dissolution and dermal penetration of the API relative to the viscous lanolin/PEG400 vehicle previously tested by our team [ 28 , 33 , 34 ]. This optimized NS formulation did not require a viscous vehicle to increase residence time on the skin to achieve a therapeutic effect.…”

“…The mice were housed in a university animal facility under a 12 h light/dark cycle and maintained at a controlled temperature, with ad libitum access to food and water. To test the wound healing efficacy of the optimized (OT) and unoptimized (UT) treatment formulations, the depilatory double disc mouse (DDD) model was utilized as previously described [ 33 ].…”

“…Our previously established DDD NM skin burn model was used for the mouse studies [ 33 ]. In brief, NM (5 μmol) was applied to two filter discs surmounting the dorsal lumbar region of mice for 6 min.…”

“…Topical formulations used to treat SM skin burns include solvent mixture, cream, ointment, gel, and hydrogel vehicles [ 20 , 22 , 23 , 24 , 25 ]. For NM skin burn treatments, vehicles are comprised of organic and polymeric solvents, ointments, creams, and hydrogels [ 23 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. Chang et al reduced SM-induced edema by administering NDH-4338 in a dimethyl isosorbide/ethyl oleate vehicle [ 20 ].…”

“…Subsequently, NDH-4338 was utilized in a lanolin/PEG400 formulation by Joseph et al to inhibit SM-induced mast cell degranulation [ 25 ]. While initial NDH-4338 formulations produced by our team were effective in treating NM burns in mice, the onset of action may have been delayed due to slow release from the viscous lanolin/PEG400 vehicle, as more viscous formulations have been shown to slow dissolution and reduce dermal drug penetration [ 28 , 33 , 34 ]. Additionally, the NDH-4338 formulations had to be applied to NM skin burns four times daily (QID) to achieve the observed efficacy.…”