Puerarin attenuates severe burn-induced acute myocardial injury in rats.

BACKGROUND: Puerarin, the main isoflavone glycoside extracted from the root of Pueraria lobata, is widely prescribed for patients with cardiovascular disorders in China. This study investigates the effect of puerarin on severe burn-induced acute myocardial injury in rats and its underlying mechanisms. MATERIALS AND METHODS: Healthy adult Wistar rats were divided into three groups: (1) sham group, sham burn treatment; (2) burn group, third-degree burns over 30% of the total body surface area (TBSA) with lactated Ringer's solution for resuscitation; and (3) burn plus puerarin group, third-degree burns over 30% of TBSA with lactated Ringer's solution containing puerarin for resuscitation. The burned animals were sacrificed at 1, 3, 6, 12, and 24 h after burn injury. Myocardial injury was evaluated by analyzing serum creatine kinase MB fraction (CK-MB) activity and cardiac troponin T (cTNT) level. Changes in cardiomyocyte ultrastructure were also determined using a transmission electron microscope. Tumor necrosis factor (TNF)-α concentration in serum was measured by radioimmunoassay. Cardiac myeloperoxidase (MPO) activity and malondialdehyde (MDA) concentration were measured to determine neutrophil infiltration and oxidative stress in the heart, respectively. The expression of p38 mitogen-activated protein (MAP) kinase in the heart was determined by Western blot analysis. RESULTS: After the 30% TBSA full-thickness burn injury, serum CK-MB activities and cTnT levels increased markedly, both of which were significantly decreased by the puerarin treatment. The level of serum TNF-α concentration in burn group at each time-point was obviously higher than those in sham group (1.09±0.09 ng/ml), and it reached the peak value at 12 h post burn. Burn trauma also resulted in worsen ultrastructural condition, elevated MPO activity and MDA content in heart tissue, and a significant activation of cardiac p38 MAP kinase. Administration of puerarin improved the ultrastructural changes in cardiomyocytes, decreased TNF-α concentration in serum as well as suppressed cardiac MPO activity and reduced MDA content, and abolished the activation of p38 MAP kinase in heart tissue after severe burn. CONCLUSIONS: These results suggest that puerarin attenuates inflammatory responses, reduces neutrophil infiltration and oxidative stress in the heart, and protects against acute myocardial injury induced by severe burn.

[Effect of high mobility group box protein 1 on the Kupffer cells of rats with severe burn and the role of receptor for advanced glycation end products in the process].

OBJECTIVE: To investigate the effect of high mobility group box protein 1 (HMGB1) on the production of pro-inflammatory cytokines by Kupffer cell (KC) of rats with severe burn and the role of receptor for advanced glycation end products (RAGE) in the process. METHODS: Model of 30% TBSA full-thickness burn was reproduced in 32 SD rats through immersing the back in 98°C water for 12 s. KC (32 samples) was isolated from rat liver 24 h after injury and inoculated in 24-well plate in the concentration of 1×10(6) cell per well. (1) Cells were divided into control group (cultured with 1 mL PBS) and HMGB1 group (stimulated with 100 ng/mL HMGB1 in the volume of 1 mL) according to the random number table, with 8 samples in each group. At post culture hour (PCH) 48, the expression of RAGE (denoted as grey value ratio) was detected with Western blotting. (2) Another portion of cells were divided into control group (cultured with 1 mL PBS), HMGB1 group (treated with 100 ng/mL HMGB1 in the volume of 1 mL), HMGB1 + anti-RAGE antibody group (treated with 100 ng/mL HMGB1 in the volume of 1 mL after being pre-incubated with 20 µg/mL anti-RAGE monoclonal antibody in the volume of 1 mL for 2 hours), HMGB1 + recombinant rat RAGE/Fc chimera (rrRAGE/Fc) group (treated with the mixture of 100 ng/mL HMGB1 in the volume of 0.5 mL and 5 µg/mL rrRAGE/Fc in the volume of 0.5 mL which were pre-incubated for 2 hours) according to the random number table, with 8 samples in each group. At PCH 48, the protein levels of TNF-α and IL-1ß in supernatant were determined with enzyme-linked immunosorbent assay, while the mRNA expression of TNF-α and IL-1ß (denoted as grey value ratio) were determined with Northern blotting. Data were processed with one-way analysis of variance, t test, and LSD test. RESULTS: (1) The expression of RAGE in HMGB1 group (1.036 ± 0.101) was significantly higher than that of control group at PCH 48 (0.191 ± 0.024, t = -23.158, P = 0.000). (2) In HMGB1 group, HMGB1 + anti-RAGE antibody group, and HMGB1 + rrRAGE/Fc group, the contents of TNF-α in supernatant were respectively (10.59 ± 1.39), (9.91 ± 1.68), (11.51 ± 2.27) ng/mL; the contents of IL-1ß in supernatant were respectively (2.49 ± 0.33), (2.08 ± 0.32), (2.42 ± 0.42) ng/mL; the mRNA levels of TNF-α in cells were respectively 0.311 ± 0.009, 0.301 ± 0.047, 0.326 ± 0.016; the mRNA levels of IL-1ß in cells were respectively 0.237 ± 0.021, 0.244 ± 0.041, 0.245 ± 0.013. There were no statistically significant differences in the above indexes among these three groups (with P values all above 0.05). Their levels were all significantly higher than those of control group [with contents of TNF-α and IL-1ß in supernatant respectively (2.69 ± 0.14), (0.43 ± 0.05) ng/mL, and mRNA levels of TNF-α and IL-1ß in cells respectively 0.140 ± 0.022, 0.077 ± 0.005, P values all below 0.01]. CONCLUSIONS: HMGB1 can induce the production of pro-inflammatory cytokines TNF-α and IL-1ß from the KC in rats with severe burn. However, RAGE does not play a predominant role in this process.

Sodium butyrate protects against severe burn-induced remote acute lung injury in rats.

High-mobility group box 1 protein (HMGB1), a ubiquitous nuclear protein, drives proinflammatory responses when released extracellularly. It plays a key role as a distal mediator in the development of acute lung injury (ALI). Sodium butyrate, an inhibitor of histone deacetylase, has been demonstrated to inhibit HMGB1 expression. This study investigates the effect of sodium butyrate on burn-induced lung injury. Sprague-Dawley rats were divided into three groups: 1) sham group, sham burn treatment; 2) burn group, third-degree burns over 30% total body surface area (TBSA) with lactated Ringer's solution for resuscitation; 3) burn plus sodium butyrate group, third-degree burns over 30% TBSA with lactated Ringer's solution containing sodium butyrate for resuscitation. The burned animals were sacrificed at 12, 24, and 48 h after burn injury. Lung injury was assessed in terms of histologic changes and wet weight to dry weight (W/D) ratio. Tumor necrosis factor (TNF)-α and interleukin (IL)-8 protein concentrations in bronchoalveolar lavage fluid (BALF) and serum were measured by enzyme-linked immunosorbent assay, and HMGB1 expression in the lung was determined by Western blot analysis. Pulmonary myeloperoxidase (MPO) activity and malondialdehyde (MDA) concentration were measured to reflect neutrophil infiltration and oxidative stress in the lung, respectively. As a result, sodium butyrate significantly inhibited the HMGB1 expressions in the lungs, reduced the lung W/D ratio, and improved the pulmonary histologic changes induced by burn trauma. Furthermore, sodium butyrate administration decreased the TNF-α and IL-8 concentrations in BALF and serum, suppressed MPO activity, and reduced the MDA content in the lungs after severe burn. These results suggest that sodium butyrate attenuates inflammatory responses, neutrophil infiltration, and oxidative stress in the lungs, and protects against remote ALI induced by severe burn, which is associated with inhibiting HMGB1 expression.

High-mobility group box-1 induces proinflammatory cytokines production of Kupffer cells through TLRs-dependent signaling pathway after burn injury.

Kupffer cells (KCs) were a significant source of cytokine release during the early stage of severe burns. High mobility group box protein 1 (HMGB1) was recently identified as a new type of proinflammatory cytokine. The ability of HMGB1 to generate inflammatory responses after burn trauma has not been well characterized. KCs were isolated from sham animals and rats with a 30% full-thickness burn, and then were stimulated with increasing concentrations of HMGB1. The levels of Tumor necrosis factor (TNF)-α and interleukin (IL)-1ß in culture supernatant were measured by enzyme-linked immunosorbent assay. Northern blot analysis was performed to detect the expressions of TNF-α and IL-1ß mRNAs. The activities of p38 MAPK and JNK (by Western blot analysis) as well as NF-κB (by EMSA) in KCs were also examined. As a result, HMGB1 in vitro upregulated expressions of TNF-α and IL-1ß of KCs in a dose-dependent manner, and HMGB1 promoted KCs from burn rats to produce significantly more TNF-α and IL-1ß proteins than those from sham animals. After harvested from burn rats, KCs were pre-incubated with anti-TLR2 or anti-TLR4 antibody prior to HMGB1 administration. HMGB1 exposure not only significantly increased expressions of TNF-α and IL-1ß mRNAs in KCs from burn rats, but also enhanced activities of p38 MAPK, JNK and NF-κB. However, these upregulation events were all reduced by pre-incubation with anti-TLR2 or anti-TLR4 antibody. These results indicate that HMGB1 induces proinflammatory cytokines production of KCs after sever burn injury, and this process might be largely dependent on TLRs-dependent MAPKs/NF-κB signal pathway.