Role of Inducible Nitric Oxide Synthase and Interleukin-6 Proteins Expression in Estimation of Skin Burn Age and Vitality: Immunohistochemical Study in Rat

Estimation of age and vitality of burn injury both in the living and dead is essential in forensic practice. Nitric oxide and interleukin-6 (IL-6) play an important role in skin burn healing. In this immunohistochemical study, the expression of inducible nitric oxide synthase (iNOS) and IL-6 proteins during skin burn injury healing in rats was studied for purposes of burn dating and to differentiate between ante-mortem and post-mortem burn. Ante-mortem full- thickness skin burns were created on forty five rats with a heated soldering iron applied for three seconds. Normal and burnt skin samples were taken at 1, 3, 5, 7, 9, 11, 13, 15 and 21 days following burn induction (5 rats for each stage). Post-mortem burn was inflicted 6h. after scarification in another five rats. There was a statistically significant difference in both iNOS and IL-6 expression between the different studied time intervals of the ante-mortem burn. Expression of both iNOS and IL-6 decreased remarkably in the post-mortem burn with a statistically significant difference from all the studied ante-mortem intervals. A statistically significant positive association between the two markers was found; both increased gradually in the inflammatory and early proliferation stages and started to decrease in late proliferative and remodeling stages while reaching the minimum in the post-mortem burn. These results indicate that both iNOS and IL-6 expression in ante-mortem burnt skin was time dependent and significantly differed from post-mortem burn. Further research on humans is recommended.