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>

Relationship between cutaneous glycometabolic disorders and cutaneous neuropathy in diabetic rats / 中华烧伤杂志

<p><b>OBJECTIVE</b>To analyze the relationship between cutaneous glycometabolic disorders and cutaneous neuropathy in diabetic rats, and to look for the mechanism of neuropathy and impaired wound healing.</p><p><b>METHODS</b>Eighty male SD rats were randomly divided into the normal control group (NC, n = 20), diabetic group (D, n = 20), aminoguanidine-interfered group (AI, n = 20), and insulin-interfered group (II, n = 20) by drawing lots. Diabetes was reproduced in rats of D, AI, and II groups with intraperitoneal injection of streptozotocin (STZ). Then, rats in AI group were fed with 100 mg×kg(-1)×d(-1) aminoguanidine, while rats in II group were subcutaneously injected with insulin for satisfactory control of blood glucose. Changes in mechanical and heat pain thresholds of pad of hind limb were measured at post injection week (PIW) 2, 4, 8. Skin specimens were collected during PIW 2-8 from pads for determination of contents of glucose, advanced glycation end product (AGE), substance P (SP), calcitonin gene-related peptide (CGRP), and observation of distribution and ultrastructure of skin nerve fibers. Data were processed with t test.</p><p><b>RESULTS</b>The mechanical and heat pain thresholds in D group at PIW 2 [(6.3 ± 1.5) g, (6.0 ± 0.9) s, respectively ] were obviously lower than those in NC group [(13.0 ± 3.2) g, (10.3 ± 1.2) s, with t value respectively 2.71, 3.42, P values all below 0.05]. Contents of glucose and AGE in skin tissue in D group were significantly increased when compared with those in NC group, especially at PIW 8 [(2.85 ± 0.33) mg/g, (31.7 ± 3.2) U/mg of hydroxyproline vs. (0.82 ± 0.22) mg/g, (22.2 ± 1.9) U/mg of hydroxyproline, with t value respectively 1.65, 6.47, P values all below 0.01]. The myelinated nerve fibers were edematous and degenerated, with axons compressed, while the unmyelinated nerve fibers were vacuolated, with microfilament and microtubule disorderly arranged. Content of SP in skin tissue in D group was lower as compared with that in NC group, especially at PIW 2 [(16.8 ± 3.4) pg/g vs. (28.5 ± 5.0) pg/g, t = 2.42, P < 0.01]. There was no obvious difference in content of CGRP between NC and D groups, and also in content of glucose in skin between D and AI groups. Compared with those in D group, content of AGE in AI group at PIW 8 was decreased markedly [(27.2 ± 1.4) U/mg of hydroxyproline, t = 3.38, P < 0.05]; contents of glucose and AGE in II group at PIW 8 were significantly decreased [(1.42 ± 0.38) mg/g, (23.6 ± 1.3) U/mg of hydroxyproline, with t value respectively 1.74, 8.17, P < 0.05 or P < 0.01]. Compared with that in D group, contents of SP in AI and II groups were increased, with a delay in time of trough value. Content of CGRP showed no obvious difference among D, AI, and II groups.</p><p><b>CONCLUSIONS</b>High glucose and accumulation of AGE are key mediators of cutaneous neuropathy and impaired wound healing in diabetes mellitus, which confirms that diabetic wound takes an atypical footing during wound repairing. Aminoguanidine and insulin can reduce contents of glucose and AGE in diabetic skin tissue, and ameliorate diabetic cutaneous neuropathy.</p>