Antioxidant status in delayed healing type of wounds

Abstract

This investigation studied the contribution of antioxidants in delaying healing in excision cutaneous wounds (8 mm) in diabetic, aged and immunocompromised animals. Skin levels of catalase, glutathione (GSH), ascorbic acid (AA) and vitamin E in streptozotocin-induced diabetic rat were lower as compared to nondiabetics. The 7-d wound tissue of diabetic rats showed an increased vitamin E level along with depleted GSH content. In aged rats (18 months old), higher levels of skin superoxide dismutase (SOD), glutathione peroxidase (Gpx) and thiobarbituric acid reactive substances (TBARS) and lower levels of catalase and GSH were found as compared to their values in young rats (3-4 months old). The levels of SOD, GPx, catalase, AA, GSH and vitamin E in 7-d wound tissue of aged rats were significantly lower in comparison to those in young rats. However, TBARS were elevated in these wound tissues. The non-wounded skin of immunocompromised (athymic) mice showed lower levels of SOD, catalase, and TBARS and higher GSH and GPx levels in comparison to those present in normal mouse skin. Surprisingly, the analysis of 7-d wound tissue showed higher levels of SOD, catalase, GPx, and GSH and lower TBARS level in athymic mice compared to the wound tissue of normal mice. Thus low levels of antioxidants accompanied by raised levels of markers of free radical damage play a significant role in delaying wound healing in aged rats. In diabetic rats reduced glutathione levels may have a contributory role in delaying the healing process. However, in immunocompromised mice the antioxidant status following injury showed an adapted response.

Figure 1

Antioxidant status of skin and wound tissue of diabetic rats (a) superoxide dismutase (SOD), unit represents the amount of enzyme that inhibited the rate of reaction by 50%; catalase (CAT), unit represents 100 nmol H₂O₂ utilized/min; and glutathione peroxidase (GPx), unit represents 10 nmol NADPH oxidized/min (b) Vitamin E and ascorbic acid (AA) content (c) reduced glutathione (GSH) (μg/mg protein) and thiobarbituric acid reactive substances (TBARS, nmol/mg protein) in skin and wound tissue of diabetic rats as compared to control rat. Values are represented as mean ± SE (n = 6), *P ≤ 0.05.

Figure 2

Antioxidant status of skin and wound tissue of aged rats (a) superoxide dismutase (SOD), unit represents the amount of enzyme that inhibited the rate of reaction by 50%; catalase (CAT), unit represents 100 nmol H₂O₂ utilized/min; and glutathione peroxidase (GPx), unit represents 10 nmol NADPH oxidized/min (b) Vitamin E and ascorbic acid (AA) content (c) GSH (μg/mg protein) and thiobarbituric acid reactive substances (TBARS, nmol/mg protein) in skin and wound tissue of aged rats as compared to control rat. Values are represented as mean ± SE (n = 6), *P ≤ 0.05.

Figure 3

Antioxidant status of skin and wound tissue of immunocompromised mice (a) superoxide dismutase (SOD), unit represents the amount of enzyme that inhibited the rate of reaction by 50%; catalase (CAT), unit represents 100 nmol H₂O₂ utilized/min; and glutathione peroxidase (GPx), unit represents 100 nmol NADPH oxidized/min (b) GSH (μg/mg protein) and thiobarbituric acid reactive substances (TBARS, nmol/mg protein) in skin and wound tissue of immunocompromised mice as compared to control mice. Values are represented as mean ± SE (n = 6), *P ≤ 0.05.