Mitigation of nitrogen mustard mediated skin injury by a novel indomethacin bifunctional prodrug

Aspirin in the Form of Microneedle Repairs DNA and Reduces Inflammation in Persistent Skin Damage

Skin damage caused by chemical corrosion is currently one of the common skin diseases and poisoning symptoms, with nitrogen mustard compounds causing the most persistent and severe damage. These chemicals penetrate the top layer of the skin, enter the dermis, and cause DNA damage, oxidative stress, and inflammation. However, to date, no effective drug treatment has been found. Even the potential antidotes could not effectively penetrate the top layer of the skin to exert their effects due to the skin barrier. To address this problem, an innovative transdermal drug delivery strategy based on aspirin microneedles was proposed. The classic medicine aspirin was first discovered not only to reduce inflammation and oxidative stress but also to promote DNA repair and reduce DNA damage. The aspirin microneedles directly delivered the drug to the damaged area, released aspirin through the skin barrier, and exhibited good biocompatibility. These findings indicate that aspirin microneedles have great potential for promoting wound healing and broad application prospects.

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

NDH-4338 is a highly lipophilic prodrug comprising indomethacin and an acetylcholinesterase inhibitor. A design of experiments approach was used to synthesize, characterize, and evaluate the wound healing efficacy of optimized NDH-4338 nanosuspensions against nitrogen mustard-induced skin injury. Nanosuspensions were prepared by sonoprecipitation in the presence of a Vitamin E TPGS aqueous stabilizer solution. Critical processing parameters and material attributes were optimized to reduce particle size and determine the effect on dissolution rate and burn healing efficacy. The antisolvent/solvent ratio (A/S), dose concentration (DC), and drug/stabilizer ratio (D/S) were the critical sonoprecipitation factors that control particle size. These factors were subjected to a Box-Behnken design and response surface analysis, and model quality was assessed. Maximize desirability and simulation experiment optimization approaches were used to determine nanosuspension parameters with the smallest size and the lowest defect rate within the 10-50 nm specification limits. Optimized and unoptimized nanosuspensions were prepared and characterized. An established depilatory double-disc mouse model was used to evaluate the healing of nitrogen mustard-induced dermal injuries. Optimized nanosuspensions (A/S = 6.2, DC = 2% w/v, D/S = 2.8) achieved a particle size of 31.46 nm with a narrow size range (PDI = 0.110) and a reduced defect rate (42.2 to 6.1%). The optimized nanosuspensions were stable and re-dispersible, and they showed a ~45% increase in cumulative drug release and significant edema reduction in mice. Optimized NDH-4338 nanosuspensions were smaller with more uniform sizes that led to improved physical stability, faster dissolution, and enhanced burn healing efficacy compared to unoptimized nanosuspensions.

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

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.

Combination of ebselen and hydrocortisone substantially reduces nitrogen mustard-induced cutaneous injury

The purpose of the present study was to investigate the vesicant countermeasure effects of hydrocortisone (HC) and ebselen (EB-1), administered as monotherapy or as a combination treatment. The mouse ear vesicant model (MEVM) was utilized and test doses of HC (0.016, 0.023, 0.031, 0.047, 0.063, 0.125 or 0.250 mg/ear), EB-1 (0.125, 0.187, 0.250, 0.375 or 0.500 mg/ear) or the combination of HC + EB-1 were topically applied at 15 min, 4 h and 8 h after nitrogen mustard exposure. Ear punch biopsies were obtained 24 h after mechlorethamine (HN2) exposure. Compared to control ears, ear tissues exposed topically to HN2 (0.500 µmol/ear) presented with an increase in ear thickness, vesication, TUNEL fluorescence and expression of matrix metalloproteinase 9 (MMP-9) and inducible nitric oxide synthase (iNOS). In contrast, HN2 exposed ears treated topically with EB-1 showed a significant decrease in morphometric thickness and vesication vs. HN2 alone. Ear tissues exposed to HN2 and then treated with HC also demonstrated reductions in morphometric thickness and vesication. Combination treatment of HC + EB-1 was found to be the most effective at reducing HN2-induced ear edema and vesication. The combination also dramatically decreased HN2-mediated cutaneous expression of iNOS and MMP-9 and decreased HN2-induced TUNEL staining. Taken together, our study demonstrates that the combination of HC + EB-1 is an efficacious countermeasure to HN2.

Characterization of the rabbit conjunctiva: Effects of sulfur mustard

Sulfur mustard (SM; bis (2-chloroethyl) sulfide) is a potent vesicant which causes irritation of the conjunctiva and damage to the cornea. In the present studies, we characterized the ocular effects of SM in New Zealand white rabbits. Within one day of exposure to SM, edema and hazing of the cornea were observed, followed by neovascularization which persisted for at least 28 days. This was associated with upper and lower eyelid edema and conjunctival inflammation. The conjunctiva is composed of a proliferating epithelium largely consisting of stratified columnar epithelial cells overlying a well-defined dermis. Superficial layers of the conjunctival epithelium were found to express keratin 1, a marker of differentiating squamous epithelium, while in cells overlying the basement membrane expressed keratin 17, a marker of stratified squamous epithelium. SM exposure upregulated keratin 17 expression. Mucin 5 ac producing goblet cells were interspersed within the conjunctiva. These cells generated both acidic and neutral mucins. Increased numbers of goblet cells producing neutral mucins were evident after SM exposure; upregulation of expression of membrane-associated mucin 1 and mucin 4 in the superficial layers of the conjunctival epithelium were also noted. These data demonstrate that ocular exposure of rabbits to SM causes significant damage not only to the cornea, but to the eyelid and conjunctiva, suggesting multiple targets within the eye that should be assessed when evaluating the efficacy of potential countermeasures.

Systematic Development and Characterization of Novel, High Drug-Loaded, Photostable, Curcumin Solid Lipid Nanoparticle Hydrogel for Wound Healing

The study aims to develop high drug-loaded (about 15% lipid matrix) curcumin solid lipid nanoparticles (CSLNs) for wound healing. CSLNs prepared by hot, high-pressure homogenization, without using organic solvents, were optimized using the Taguchi design followed by the central composite design. The optimized CSLNs exhibited a high assay/drug content (0.6% w/w), solubility (6 × 105 times), and EE (75%) with a particle size < 200 nm (PDI-0.143). The CSLNs were safe (in vitro and in vivo), photostable, autoclavable, stable up to one year at 30 °C and under refrigeration and exhibited a controlled release (zero-order; 5 days). XRD, FTIR, and DSC confirmed solubilization and entrapment of the curcumin within the SLNs. TEM and FESEM revealed a smooth and spherical shape. The CSLNs showed a significant antimicrobial effect (MIC of 64 µg/mL for planktonic cells; 512 µg/mL for biofilm formation; and 2 mg/mL for mature biofilm) against Staphylococcus aureus 9144, while free curcumin dispersion did not exhibit any effect. This is the first report on the disruption of mature biofilms by curcumin solid lipid nanoparticles (CSLNs). The cell proliferation potential of CSLNs was also evaluated in vitro while the wound healing potential of CSLNs (incorporated in a hydrogel) was assessed in vivo. In (i) nitrogen mustard gas and (ii) a full-thickness excision wound model, CSLNs exhibited (a) significantly faster wound closure, (b) histologically and immunohistochemically better healing, (c) lower oxidative stress (LPO) and (d) inflammation (TNFα), and (e) increased angiogenesis (VEGF) and antioxidant enzymes, i.e., catalase and GSH levels. CSLNs thus offer a promising modern wound therapy especially for infected wounds, considering their effects in mature biofilm disruption.

Vitamin D3 ameliorates nitrogen mustard-induced cutaneous inflammation by inactivating the NLRP3 inflammasome through the SIRT3-SOD2-mtROS signaling pathway

Nitrogen mustard (NM) causes severe skin injury with an obvious inflammatory response, which is lack of effective and targeted therapies. Vitamin D3 (VD3) has excellent anti-inflammatory properties and is considered as a potential candidate for the treatment of NM-induced dermal toxicity; however, the underlying mechanisms are currently unclear. Cyclooxygenase-2 (COX2; a widely used marker of skin inflammation) plays a key role in NM-induced cutaneous inflammation. Herein, we initially confirmed that NM markedly promoted COX2 expression in vitro and in vivo. NM also increased NOD-like receptor family pyrin domain containing 3 (NLRP3) expression, caspase-1 activity, and interleukin-1β (IL-1β) release. Notably, treatment with a caspase-1 inhibitor (zYVAD-fmk), NLRP3 inhibitor (MCC950), and NLRP3 or caspase-1 siRNA attenuated NM-induced NLRP3 inflammasome activation, with subsequent suppression of COX2 expression and IL-1β release in keratinocytes. Meanwhile, NM increased mitochondrial reactive oxygen species (mtROS) and decreased manganese superoxide dismutase 2 (SOD2) and sirtuin 3 (SIRT3) activities. Mito-TEMPO (a mtROS scavenger) ameliorated NM-caused NLRP3 inflammasome activation in keratinocytes. Moreover, VD3 improved SIRT3 and SOD2 activities, decreased mtROS contents, inactivated the NLRP3 inflammasome, and attenuated cutaneous inflammation induced by NM in vitro and in vivo. The beneficial activity of VD3 against NM-triggered cutaneous inflammation was enhanced by the inhibitors of IL-1, mtROS, NLRP3, caspase-1, and NLRP3 or caspase-1 siRNAs, which was abolished in SIRT3 inhibitor or SIRT3 siRNA-treated keratinocytes and skins from SIRT3-/- mice. In conclusion, VD3 ameliorated NM-induced cutaneous inflammation by inactivating the NLRP3 inflammasome, which was partially mediated through the SIRT3-SOD2-mtROS signaling pathway.

Eucalyptus oil reduces allergic reactions and suppresses mast cell degranulation by downregulating IgE-FcεRI signalling

Eucalyptus oil has been used since ancient times for its bactericidal, anti-inflammatory, analgesic and sedative effects. In recent years, the action of Eucalyptus oil has been scientifically proven, and there have been reports that Eucalyptus oil suppresses the production of chemokines, cytokines and lipid mediators in basophils, alveolar macrophages and monocytes. Based on this information, we aimed to verify whether Eucalyptus oil can be used for allergic dermatitis, the incidence of which has been increasing among human skin diseases. This effect was verified using a mouse IgE-mediated local allergic model. In conclusion, topical application of Eucalyptus oil suppressed oedema and vascular permeability enhancement due to IgE-mediated allergic on the skin. In addition, we also verified the degranuration of mast cells, which is a part of its action, and examined whether 1,8-cineole, which is the main component of Eucalyptus oil, suppresses the phosphorylation of PLCγ and p38 directly or indirectly. 1,8-cineole was found to suppress degranulation of mast cells.

Antioxidant/stress response in mouse epidermis following exposure to nitrogen mustard

Nitrogen mustard (NM) is a highly reactive bifunctional alkylating agent that induces inflammation, edema and blistering in skin. An important mechanism mediating the action of NM and related mustards is oxidative stress. In these studies a modified murine patch-test model was used to analyze DNA damage and the antioxidant/stress response following NM exposure in isolated epidermis. NM (20 μmol) was applied to glass microfiber filters affixed to a shaved dorsal region of skin of CD-1 mice. NM caused structural damage to the stratum corneum as reflected by increases in transepidermal water loss and skin hydration. This was coordinate with edema, mast cell degranulation and epidermal hyperplasia. Within 3 h of NM exposure, a 4-fold increase in phosphorylated histone H2AX, a marker of DNA double-stranded breaks, and a 25-fold increase in phosphorylated p53, a DNA damage marker, were observed in the epidermis. This was associated with a 40% increase in 8-oxo-2'-deoxyguanosine modified DNA in the epidermis and a 4-fold increase in 4-hydroxynonenal modified epidermal proteins. At 12 h post NM, there was a 3-75 fold increase in epidermal expression of antioxidant/stress proteins including heme oxygenase-1, thioredoxin reductase, superoxide dismutase, glutathione reductase, heat shock protein 27 and cyclooxygenase 2. These data indicate that NM induces early oxidative epidermal injury in mouse skin leading to an antioxidant/stress response. Agents that enhance this response may be useful in mitigating mustard-induced skin injury.

Sulfur mustard induced mast cell degranulation in mouse skin is inhibited by a novel anti-inflammatory and anticholinergic bifunctional prodrug

Sulfur mustard (SM, bis(2-chloroethyl sulfide) is a potent vesicating agent known to cause skin inflammation, necrosis and blistering. Evidence suggests that inflammatory cells and mediators that they generate are important in the pathogenic responses to SM. In the present studies we investigated the role of mast cells in SM-induced skin injury using a murine vapor cup exposure model. Mast cells, identified by toluidine blue staining, were localized in the dermis, adjacent to dermal appendages and at the dermal/epidermal junction. In control mice, 48-61% of mast cells were degranulated. SM exposure (1.4g/m³ in air for 6min) resulted in increased numbers of degranulated mast cells 1-14days post-exposure. Treatment of mice topically with an indomethacin choline bioisostere containing prodrug linked by an aromatic ester-carbonate that targets cyclooxygenases (COX) enzymes and acetylcholinesterase (1% in an ointment) 1-14days after SM reduced skin inflammation and injury and enhanced tissue repair. This was associated with a decrease in mast cell degranulation from 90% to 49% 1-3days post SM, and from 84% to 44% 7-14days post SM. These data suggest that reduced inflammation and injury in response to the bifunctional indomethacin prodrug may be due, at least in part, to abrogating mast cell degranulation. The use of inhibitors of mast cell degranulation may be an effective strategy for mitigating skin injury induced by SM.

Tissue injury and repair following cutaneous exposure of mice to sulfur mustard

In mouse skin, sulfur mustard (SM) is a potent vesicant, damaging both the epidermis and the dermis. The extent of wounding is dependent on the dose of SM and the duration of exposure. Initial responses include erythema, pruritus, edema, and xerosis; this is followed by an accumulation of inflammatory leukocytes in the tissue, activation of mast cells, and the release of mediators, including proinflammatory cytokines and bioactive lipids. These proinflammatory mediators contribute to damaging the epidermis, hair follicles, and sebaceous glands and to disruption of the epidermal basement membrane. This can lead to separation of the epidermis from the dermis, resulting in a blister, which ruptures, leading to the formation of an eschar. The eschar stimulates the formation of a neoepidermis and wound repair and may result in persistent epidermal hyperplasia. Epidermal damage and repair is associated with upregulation of enzymes generating proinflammatory and pro-growth/pro-wound healing mediators, including cyclooxygenase-2, which generates prostanoids, inducible nitric oxide synthase, which generates nitric oxide, fibroblast growth factor receptor 2, and galectin-3. Characterization of the mediators regulating structural changes in the skin during SM-induced tissue damage and wound healing will aid in the development of therapeutic modalities to mitigate toxicity and stimulate tissue repair processes.