Effects of heat exposure and vitamin C intervention on oxidative stress and blood pressure changes in treadmill rats / 中华劳动卫生职业病杂志

Objective: To investigate the effect of oxidative stress caused by heat exposure on the blood pressure increase of treadmill rats and the intervention of antioxidants. Methods: In June 2021, Twenty-four healthy SD male rats were randomly divided into four groups: normal temperature feeding, normal temperature treadmill, high temperature treadmill and high temperature treadmill supplementation with vitamin C groups, 6 rats in each group. The rats run on the platform in normal temperature or heat exposure environment for 30 min in the morning and in the afternoon daily, 6 days per week. The daily vitamin C supplement dose of high temperature treadmill supplementation with vitamin C group was 10 mg/kg. BP recordings were done at the end of the week. The rat vascular lipofuscin (LF) was detected by ELISA, the rat serum nitric oxide (NO) was detected by nitrate reductase method, the serum malondialdehyde (MDA) was detected by thibabituric acid method, the serum glutathione peroxidase (GPx) and superoxide dismutase (SOD) were detected by chemiluminescence method, and the serum catalase (CAT) was detected by ammonium molybdate method. The total antioxidant capacity (T-AOC) of serum was measured by iron reduction/antioxidant capacity method, and the content of nuclear erythroid 2-related factor 2 (Nrf2) in vascular tissue was measured by Western blot. The intra-group mean was compared by repeated measurement analysis of variance, and the inter-group mean was compared by single-factor analysis of variance and post-event LSD-t test. Results: Compared with the previous time point, the systolic BP and diastolic BP of the high temperature treadmill group were significantly increased at 7, 14 and 21 d, and decreased at 28 d which were higher than the initial level (P<0.05), and the systolic BP and diastolic BP values at each experimental time point were significantly higher than those of normal temperature treadmill group (P<0.001). The changes of thickening of the artery wall, no smoothing of the endodermis and irregular arrangement of muscle cells in high temperature treadmill group were observed. Compared with the normal temperature treadmill group, the content of MDA in serum, and LF in vascular tissue were significantly increased, the activities of SOD, CAT, T-AOC, the content of NO in serum, and the expression of Nrf2 in vascular tissue were significantly decreased in high temperature treadmill group (P<0.05). Compared with the high temperature treadmill group, the systolic BP and diastolic BP values at 7, 14, 21 and 28 d, the content of serum MDA and LF in vascular tissue were significantly decreased, the activities of CAT and T-AOC, and the expression of Nrf2 in vascular tissue significantly increased (P<0.05), the histopathological changes of the artery wall improved in high temperature treadmill supplementation with vitamin C group. Conclusion: Heat exposure has effect on oxidative stress, which may be related to the increase of BP. Vitamin C as an anti-oxidative enhancer can prevent those negative effects, which could alleviate the pathological changes of vessel intima in heat-exposed rats. And the Nrf2 may be a regulated factor to vascular protection.

Effect of compound nutrients on behavior and fatigue in mice with high temperature exercise / 中国职业医学

OBJECTIVE: To explore the effects of high temperature on learning and memory ability, behavioral activity, and fatigue as well as the intervention effect of compound nutrients on the exercising mice. METHODS: Thirty specific pathogen-free healthy male Kunming mice were randomly divided into the normal-temperature exercise, high-temperature exercise, and high-temperature exercise supplement groups, with 10 mice in each group. The mice in these three groups performed treadmill exercise for one hour every day, six days per week, and continued for four weeks. The mice in the high-temperature exercise supplement group were fed with 0.3 mL of compound nutrients 30 minutes before each treadmill exercise, whereas the mice in the normal-temperature exercise and the high-temperature exercise groups were fed with an equal volume of distilled water. At the end of the treadmill exercise, the mice were subjected to experiments on their neurological behaviors. The serum of mice in each group were collected to detect the lactic acid level, urea nitrogen level, and creatine kinase activity. The liver and gastrocnemius muscle tissues were then taken for detecting the levels of liver glycogen and muscle glycogen.RESULTS: Compared with the mice in the normal-temperature exercise group, the escape latency of the mice in the high-temperature exercise group was prolonged(P<0.05), whereas the number of platform crossings, percentage of target quadrant time, and distance were reduced(all P<0.05). Compared with the mice in the high-temperature exercise group, the escape latency of the mice in the high-temperature exercise supplement group was shortened(P<0.05), whereas the number of platform crossings, percentage of target quadrant time, and distance were increased(all P<0.05). Compared with the mice in the normal-temperature exercise group, the first fall time and grip strength of the mice in the high-temperature exercise group were reduced(all P<0.05), whereas the number of falls was increased(P<0.05). Compared with the mice in the high-temperature exercise group, the first fall time and grip strength of the mice in the high-temperature exercise supplement group were increased(all P<0.05), whereas the number of falls was reduced(P<0.05). Compared with the mice in the normal-temperature exercise group, the serum lactic acid level, urea nitrogen level, and creatine kinase activity of the mice in the high-temperature exercise group were increased(all P<0.05), whereas the levels of liver glycogen and muscle glycogen were decreased(all P<0.05). Compared with the mice in the high-temperature exercise group, the serum lactic acid level, urea nitrogen level, and creatine kinase activity of the mice in the high-temperature exercise supplement group were decreased(all P<0.05), whereas the levels of liver glycogen and muscle glycogen were increased(all P<0.05). CONCLUSION: High temperature exercise can lead to decreased learning and memory ability and behavioral activity in mice, resulting in exercise-induced fatigue. Supplemental compound nutrients can prevent these changes.

Effect of N-acetyl-seryl-aspartyl-lysyl-proline on regulation of expression of ras-raf-ERK1/2 signal transduction pathway in lung of rats with silicosis / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>to investigate the effect of N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP) on the expressions of c-Raf, ERK1/2 and TGF-β1 in the lung of rats with silicosis, thus to investigate the regulating of AcSDKP on the Ras-Raf-ERK1/2 signal transduction pathway.</p><p><b>METHODS</b>rats were instilled with silica through trachea as silicotic models and administered AcSDKP in the experiment. Rats were divided into 6 groups randomly, 10 rats in each group: Control 1 and 2 of silicotic model: each rat was intratracheally instilled with 1.0 ml normal sodium and was killed after 4 or 8 weeks; Silicotic model 1 and Silicotic model 2: each rat was intratracheally instilled with 1ml silica suspension and was killed after 4 or 8 weeks; Anti-fibrosis treatment of AcSDKP: after each rat was intratracheally instilled with 1ml silica suspension for 4 weeks, AcSDKP 800 microg × kg(-1) × d(-1) was administered into every rat and rats were killed at the eighth week; Preventing fibrosis treatment of AcSDKP: after AcSDKP 800 microg × kg(-1) × d(-1) was administered into every rat for 48 hours, each rat was intratracheally instilled with 1.0 ml silica suspension and rats were killed at the eighth week. The expression of c-Raf, phospho-c-Raf, ERK1/2, phospho-ERK1/2 and TGF-β1 was measured by immunohistochemistry and western blot assay.</p><p><b>RESULTS</b>compared with the corresponding control groups, the expressions of phospho-c-Raf, phospho-ERK1/2 and TGF-β1 increased in the lung tissue of the silicotic models. Compared with the corresponding model groups, after administration AcSDKP, the expressions of phospho-c-Raf, phospho-ERK1/2 and TGF-β1 in the lung tissue reduced obviously. In anti-fibrosis treatment of AcSDKP group, expressions of phospho-c-Raf, phospho-ERK1/2 and TGF-β1 decreased to 52.25%, 51.72% and 67.74% compared with those of the silicotic model 1, and expressions of phospho-c-Raf, phospho-ERK1/2 and TGF-β1 decreased to 49.37%, 55.76%, 65.63% compared with those of the silicotic model 2; In preventing fibrosis treatment of AcSDKP group, expressions of phospho-c-Raf, phospho-ERK1/2 and TGF-β1 decreased to 54.64%, 55.76% and 78.91% compared with those of the silicotic model 2 (P < 0.05) while the expressions of c-Raf and ERK1/2 were not different significantly among each groups.</p><p><b>CONCLUSION</b>AcSDKP possibly plays an important role in anti-silicotic fibrosis by blocking the TGF-β-induced Ras-Raf-ERK1/2 signal transduction pathway.</p>