Therapeutic effects and molecular mechanisms of steroids on acute and chronic aristolochic acid nephropathy in mice

• Main Authors: Hui-Ni Cheng, 鄭惠倪
• Other Authors: Su-yin Chiang
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/59785702840663995015

碩士 === 中國醫藥大學 === 中醫學系 === 98 === Aristolochic acid (AA), an established nephrotoxin and carcinogen, was known as the causal factor of Aristolochic acid Nephropathy (AAN). Clinical studies reveal that prednisolone therapy significantly slows the progression of renal failure in AAN patients. The transcription factor NF-κB has multiple crucial roles in the regulation of the immune/inflammatory responses, apoptosis, and carcinogenesis. In this study, we examined the correlation between the AA-induced nephritis and the activation of NF-κB, and the therapeutic effects and molecular mechanisms of steroids on acute and chronic AAN in mice Firstly, we used NF-kB/luciferase transgenic mice to construct an AA-induced nephritis model for noninvasive whole-body real-time imaging of NF-kb activity. NF-kB/luciferase transgenic mice were dosed by gavage with AA 4 mg/kg bw for 8 consecutive days, stopped for 2 days, and then gave prednisolone 1 mg/kg bw for 4 days. In vivo real time instantaneous imaging analysis showed that high levels of bioluminescence intensity were observed in AA-treated mouse kidney as compared with mock-treated mice, and prednisolone therapy significantly decreased the level of bioluminescence intensity. Microarray analysis of AA-treated mouse kidney and bladder tissues revealed that AA modulated the expression of genes involved in inflammation, DNA repair, carcinogenesis, extracellular matrix and cell adhesion. The down regulation by prednisolone of AA-induced NF-κB activation was confirmed by immunohistochemistry results demonstrated that AA profoundly increased the number of activated NF-κB p65-stained cells, while this increase was significantly decreased by prednisolone treatment. To investigate the protective effects of prednisolone on AA-induced inflammation and tumor formation, male FVB mice were dosed by gavage with AA 4 mg/kg bw for 14 consecutive days, then prednisolone (1 mg/kg bw and tapered off 1/2 every 2 weeks until 0.1 mg/kg bw) for 76 days, and followed by a life-time observation period. AA caused the tumor formation in kidney, stomach, liver and urinary bladder. However, after undergoing prednisolone treatment, the life-span of AA-exposed mice had significantly prolonged. Histopathological examination showed that prednisolone treatment significantly suppressed the formation of AA-induced renal and stomach carcinoma. Moreover, microarray analysis of renal and bladder tissues exposed to AA with or without prednisolone showed that several signal pathways involved in inflammation and carcinogenesis were significantly regulated. Results from immunohistochemistry demonstrated that the number of NF-κB stained cells in AA-treated groups as compared to Mock groups while this increase was significantly decreased by prednisolone treatment. Our results revealed that the anti-inflammatory effect of prednisolone may partly account for its beneficial effect on the life-span, its suppression on AA-induced inflammation and possibly the tumor formation in AA-treated mice, and those effects are may be through the down-regulation of NF-κB. Glycyrrhizinic acid (Glycyrrhizin), a steroid-like glycoside obtained from Glycyrrhiza glabra, possesses anti-inflammatory activities. In this pilot study, we examined the effects of glycyrrhizinic acid on acute AAN. Male FVB mice were dosed by gavage with AAⅠ (2.5 mg/kg bw) for 8 consecutive days, and stopped for 2 days, then gave glycyrrhizinic acid (25 mg/kg bw) for 7 days, or FVB mice were dosed by gavage with AAⅠ (2.5 mg/kg bw), 5 minutes later, gave glycyrrhizinic acid (25 mg/kg bw) for 17 consecutive days. Since there is no significant increase of urinary total protein/creatinine ratio, plasma creatinine and BUN level after AA exposure, further experiments are needed to examine the effects of glycyrrhizinic acid on acute AAN.