Effects of advanced glycation end products and its receptor on oxidative stress in diabetic wounds / 中华烧伤杂志

<p><b>OBJECTIVE</b>To investigate the accumulation of advanced glycation end products (AGE) and the inflammatory response of skin and wound in diabetic patients, and to analyze their relationship in vitro.</p><p><b>METHODS</b>Histological staining and immunohistochemical staining was respectively performed on skin and wound tissue specimens collected from 10 patients with Type II diabetes mellitus (diabetes group) and 12 non-diabetic patients with skin injury (control group) to observe the arrangement of collagen and the distribution of inflammatory cells, and to determine the expression levels of AGE and its receptor (RAGE). Malondialdehyde (MDA) levels in skin and wound tissue homogenates were assayed by enzyme-linked immunosorbent assay. In vitro, human neutrophils were isolated and treated with RPMI-1640 culture medium or that containing AGE-human serum albumin in the concentration of 0.315, 0.625, 1.250 mg/mL, and they were identified as normal control (NC) group, low concentration (L) group, moderate concentration (M) group, and high concentration (H) group. Cell viability in each group was determined by MTT colorimetric assay, and the reactive oxygen species (ROS) in cell was measured with 2', 7'-dichlorofluorescein-diacetate. Data were processed with t test.</p><p><b>RESULTS</b>Compared with those of skin in control group, collagens of skin tissues in diabetes group atrophied and disorderly arranged. Inflammatory cells in wounds in diabetes group were dispersed, in which collagens arranged loosely and irregularly, as compared with those of wounds in control group. Expression levels of AGE and RAGE of skin in diabetes group were higher than those in control group. In diabetes and control groups, especially in diabetes group, the numbers of RAGE-positive cells in wound tissue were more than those in skin tissue. Large amount of inflammatory cells with positive expression of RAGE were observed in diabetes group. MDA level of skin and wound tissue in diabetes group was respectively (6.3 ± 1.0), (7.1 ± 2.4) nmol per milligram protein, which were obviously higher than those in control group [(2.9 ± 1.0), (3.6 ± 1.4) nmol per milligram protein, with t value respectively 8.017, 4.349, P < 0.05 or P < 0.01]. Cell viability and ROS levels in neutrophils were increased in L, M, and H groups [(59 ± 8)%, (77 ± 5)%, (67 ± 6)% and 1.67 ± 0.14, 2.13 ± 0.17, 3.48 ± 0.48] as compared with those in NC group [(34 ± 5)% and 0.58 ± 0.06, with t value respectively 7.195, 14.890, 11.130 and 20.195, 24.905, 16.864, P < 0.05 or P < 0.01].</p><p><b>CONCLUSIONS</b>Abnormal oxidative stress in diabetic skin leads to an atypical origin of wound repair. AGE-RAGE effect is a critical mediator for oxidative stress in diabetic wound tissue during wound healing.</p>

Effect of topical application of aminoguanidine cream on skin tissue of rats with diabetes / 中华烧伤杂志

<p><b>OBJECTIVE</b>To investigate the effects of aminoguanidine cream on the proliferation of keratinocytes (KC), content of advanced glycosylation end products (AGE) and oxidative stress in skin tissue of rats with diabetes.</p><p><b>METHODS</b>Stearic acid, liquid paraffin, vaseline, lanolin, isopropyl myristate fat, glycerol, 50 g/L alcohol paraben, aminoguanidine hydrochloride etc. were mixed in certain proportion to make aminoguanidine cream, and cream without aminoguanidine was used as matrix. The dorsal skin of normal rats were harvested and treated by aminoguanidine cream with dose of 5, 10 g/L, or 5 g/L together with 10 g/L azone. The transdermal effect was respectively measured at post treatment hour 2, 4, 7, 10, 12, 24. Thirty SD rats were divided into normal control (NC, n = 6), diabetes (D, n = 8), aminoguanidine cream-interfered (AI, n = 8), matrix cream-interfered groups (MI, n = 8) according to the random number table. Diabetes was reproduced by intraperitoneal injection of STZ (65 mg/kg) in rats of D, AI, and MI groups, and rats in NC group were injected with 0.05 mmol/L citrate buffer as control. One week later, dorsal skin of rats in AI and MI groups were respectively treated with 10 g/L aminoguanidine cream and matrix cream by external use for 4 weeks. AGE content was determined with fluorescence detection from skin collagen extract. KC cell cycle was detected by flow cytometry. Skin tissue specimens were obtained for determination of levels of superoxide dismutase (SOD), malondialdehyde (MDA), myeloperoxidase (MPO), and total antioxidant capacity. Data were processed with t test.</p><p><b>RESULTS</b>Transdermal effect of aminoguanidine cream with dose of 10 g/L was better than that with 5 g/L or 5 g/L + 10 g/L azone cream. One rat was not induced successfully in MI group. Four weeks after model reproduction, 4 rats died in D group and 1 rat died in AI group. The AGE content in D group was obviously higher than that in NC group [(36.8 +/- 2.6), (24.6 +/- 2.7) U per milligram hydroxyproline, respectively, t = 7.2, P < 0.01], and that in AI group [(28.6 +/- 3.7) U per milligram hydroxyproline] was also lower as compared with that in D group (t = -3.9, P < 0.05). There was no significant difference in AGE content between MI [(32.2 +/- 5.2) U per milligram hydroxyproline] and D groups (t = 1.6, P > 0.05). The percentage of KC in S phase was obviously lower in D group than in NC group [(5.3 +/- 0.6)%, (7.6 +/- 0.9)%, respectively, t = 4.50, P < 0.01], while that in MI group [(9.2 +/- 1.5)%] was higher as compared with that in D group ( t = 4.90, P < 0.01). It was more higher in AI group than in D group on KC percentage in S and G2/M phase (with t value respectively 6.80, 3.17, P values all below 0.01). The oxidative stress indexes of skin tissue in D group were all higher than those in NC group, in which levels of MPO and SOD showed statistical difference (with t value respectively 4.4, 3.7, P values all below 0.05). The oxidative stress indexes were all lower in AI group than in D group, especially in SOD level (t = -1.4, P < 0.05). Levels of MAD, MPO in MI group were significantly lower than those in D group (with t value respectively 2.6, 2.9, P values all below 0.05).</p><p><b>CONCLUSIONS</b>Aminoguanidine cream can promote KC proliferation and appropriately reduce oxidative stress through inhibiting AGE formation to a certain extent in skin tissue of rats with diabetes. Signal use of matrix cream can also reduce oxidative stress in skin tissue of rats with diabetes.</p>