Aristolochic acid (AA) is a generic term that describes a group of structurally related compounds found in the Aristolochiaceae plants family. These plants have been used for decades to treat various diseases. However, the consumption of products derived from plants containing AA has been associated with the development of nephropathy and carcinoma, mainly the upper urothelial carcinoma (UUC). AA has been identified as the causative agent of these pathologies. Several studies on mechanisms of action of AA nephrotoxicity have been conducted, but the comprehensive mechanisms of AA-induced nephrotoxicity and carcinogenesis have not yet fully been elucidated, and therapeutic measures are therefore limited. This review aimed to summarize the molecular mechanisms underlying AA-induced nephrotoxicity with an emphasis on its enzymatic bioactivation, and to discuss some agents and their modes of action to reduce AA nephrotoxicity. By addressing these two aspects, including mechanisms of action of AA nephrotoxicity and protective approaches against the latter, and especially by covering the whole range of these protective agents, this review provides an overview on AA nephrotoxicity. It also reports new knowledge on mechanisms of AA-mediated nephrotoxicity recently published in the literature and provides suggestions for future studies.

Background: Sepsis, a systemic inflammatory disease that leads to life-threatening organ functions disorders, such as liver and kidney injury. Ulinastatin (UTI) and Thrombomodulin (TM) are active macromolecules isolated from human urine. UTI and TM have been found to have therapeutic effects on inflammatory diseases. In this study, we verified protective effect of UTI combined with TM on liver and kidney injury caused by sepsis, and further explored the mechanisms.Methods: The sepsis model was established by intravenous injection of LPS into the tail vein of rats. Blood, liver and kidney tissues were collected after injection of UTI or TM. ELISA was used to measure serum levels of pro-inflammatory cytokines. The characteristic functional indexes of liver and kidney in serum and multiple coagulation function indexes of rats were detected via corresponding kits. Histological changes of liver and kidney tissues were investigated by HE staining. Apoptosis in liver and kidney tissues were examined by TUNEL staining, and the expression levels of apoptosis-related proteins were also analyzed. HMGB1/TLR4/NF-κB pathway in liver and kidney tissues were examined by Western Blot. PCNA-positive cells were detected by immunohistochemistry. The survival rate of rats in each group was statistically analyzed.Results: UTI combined with TM reduced LPS-induced secretion of IL-6 and TNF-α in the serum. The drug combination reduced the liver and kidney functional indicators ALT, AST, BUN and Cr, and ameliorated liver and kidney pathology injury of rats. It inhibited apoptosis of liver and kidney cells via down-regulating the expression of apoptotic protein Bax, Cleaved caspase-3, up-regulating the expression of anti-apoptotic protein bcl-2, and promoted the proliferation of liver and kidney cells. The drug combination reversed the up-regulation of HMGB1, TLR4, and phosphorylated NF-κB protein mediated by LPS. Anticoagulation test indicated UTI does not affect the anticoagulant effect of TM when they are used in combination. Moreover, the drug combination significantly improved the survival rate of septic rats. Conclusions: These results indicate that UTI combined with TM plays a key role in protecting liver and kidney injury in septic rats, which will suggest a promising treatment for sepsis-induced organ injury.

Aristolochic acid I (AA I) is one of the most abundant and toxic aristolochic acids that is reported to cause Aristolochic acid nephropathy (AAN). This paper was designed to assess whether mitochondrial Uncoupling Protein 2 (UCP2), which plays an antioxidative and antiapoptotic role, could protect human renal proximal tubular epithelial (HK-2) cells from toxicity induced by AA I. In this study, HK-2 cells were treated with different concentrations of AA I with or without UCP2 inhibitor (genipin). To upregulate the expression of UCP2 in HK-2 cells, UCP2-DNA transfection was performed. The cell viability was evaluated by colorimetric method using MTT. A series of related biological events such as Reactive Oxygen Species (ROS), Glutathione peroxidase (GSH-Px), and Malondialdehyde (MDA) were evaluated. The results showed that the cytotoxicity of AA I with genipin group was much higher than that of AA I alone. Genipin dramatically boosted oxidative stress and exacerbated AA I-induced apoptosis. Furthermore, the increased expression of UCP2 can reduce the toxicity of AA I on HK-2 cells and upregulation of UCP2 expression can reduce AA I-induced oxidative stress and apoptosis. In conclusion, UCP2 might be a potential target for alleviating AA I-induced nephrotoxicity.