Protease in normal human epidermal keratinocytes

Sulfur mustard-stimulated proteases and their inhibitors in a cultured normal human epidermal keratinocytes model: A potential approach for anti-vesicant drug development

Protease stimulation in cultured normal human epidermal keratinocytes (NHEK) due to sulfur mustard (SM) exposure is well documented. However, the specific protease(s) stimulated by SM and the protease substrates remain to be determined. In this study, we observed that SM stimulates several proteases and the epidermal-dermal attachment protein laminin-5 is one of the substrates. We propose that following SM exposure of the skin, laminin-5 degradation causes the detachment of the epidermis from the dermis and, therefore, vesication. We utilized gelatin zymography, Western blotting, immuno-fluorescence staining, and real-time polymerase chain reaction (RT-PCR) analyses to study the SM-stimulated proteases and laminin-5 degradation in NHEK. Two major protease bands (64 kDa and 72 kDa) were observed by zymography in SM-exposed cells. Addition of serine protease inhibitor (aprotinin, 100 μM), or the metalloprotease inhibitor (amastatin, 100 μM) to NHEK cultures prior to SM exposure decreased the SM-stimulated protease bands seen by zymography. These inhibitors completely or partially prevented SM-induced laminin-5 γ2 degradation as seen by Western blotting as well as immuno-fluorescence staining. Our results from Western blotting and RT-PCR studies also indicated that the membrane-type matrix metalloproteinase-1 (MT-MM-1) may be involved in SM-induced skin blistering.

To summarize, our results in the NHEK model indicate the following: (a) SM stimulates multiple proteases including serine protease(s), and metalloproteases; (b) SM decreases the level of laminin-5 γ2, which is prevented by either a serine protease inhibitor or a metalloprotease inhibitor and (c) MT-MMP-1 maybe one of the proteases that is involved in skin blistering due to SM exposure.

Protective effect of topical iodine preparations upon heat-induced and hydrofluoric acid-induced skin lesions

In this study, the protective prophylactic and post-exposure effects of novel topical iodine preparations were demonstrated upon heat- and hydrofluoric acid-induced skin lesions in the haired guinea pig. Prophylactic treatment of thermal bums with a liquid iodine preparation resulted in statistically significant reductions of 39% and 30%, respectively, in acute inflammation and hemorrhage-microscopic dermal parameters indicative of acute tissue damage. A clear trend of iodine-induced reduction in dermal necrosis occurred, and the epidermal healing markers, acanthosis and hyperkeratosis, were increased. Postexposure treatment of thermal burns with an iodine ointment preparation immediately after occurrence also conferred significant therapeutic reduction in parameters of tissue damage such as epidermal ulceration (87%), acute inflammation (58%), and hemorrhage (30%). Gross pathological evaluation showed that prophylactic and postexposure treatments with the liquid iodine preparation significantly reduced the heat-induced ulceration area by 97% and 65%, respectively. In addition, immediate treatment with an ointment iodine formulation significantly decreased the ulceration area by 98%; its tetraglycol vehicle also had a beneficial effect. Postexposure treatment with the iodine ointment proved efficacious upon hydrofluoric acid-induced skin burns. We observed statistically significant reductions of 76% and 68% in ulceration areas at intervals of 5 and 10 minutes between exposure and treatment, whereas a weaker effect was observed at a longer time interval of 15 minutes. Our findings suggest the therapeutic usage of these newly developed iodine preparations for thermally induced and hydrofluoric acid-induced skin burns.

Stress gene activity in HepG2 cells after sulfur mustard exposure

Monitoring temporal stress gene (SG) levels is one method of characterizing cellular responses to toxic-level chemical exposures. The goal of this study was to determine human cellular SG profiles following sulfur mustard (SM) exposure. This would establish a baseline for development of a rapid screening method for potential therapeutic compounds that could modulate SM toxicity. We used a panel of cells consisting of 14 HepG2-derived cell lines each stably transformed with a stress gene promoter (SGP) or stress gene response element (SGRE) controlling the transcription of the reporter gene chloramphenicol acetyltransferase (CAT). The SGP and SGRE reporter constructs represent SGs associated with DNA damage, protein damage, oxidative stress, inflammation, second messenger systems and xenobiotic metabolism enzymes. All SGP and SGRE activities were changed from control following SM exposure over dose and the 24-h time-course study. Metallothionein 2A promoter (MT2A) was induced throughout the study time at high SM concentration. DNA-damage markers were induced after 12 h. Protein damage, inflammation and second messenger systems increased after 16 h post-SM exposure. These results show that over time and increasing SM exposure concentrations the HepG2 cells produced differential activation of SGPs and SGREs associated with DNA and protein damage, second messenger system activation and inflammation/oxidative stress. This suggests that the HepG2 cell reporter construct system would be a useful tool for studying the effects of known therapeutic drug families that may lower these cell-damage markers during SM exposure.