Aristolochic acid suppresses DNA repair and triggers oxidative DNA damage in human kidney proximal tubular cells
ABSTRACT Aristolochic acid (AA), derived from plants of the Aristolochia genus, has been proven to be associated with aristolochic acid nephropathy (AAN) and urothelial cancer in AAN patients. In this study, we used toxicogenomic analysis to clarify the molecular mechanism of AA-induced cytotoxicity in normal human kidney proximal tubular (HK-2) cells, the target cells of AA. AA induced cytotoxic effects in a dose-dependent (10, 30, 90 microM for 24 h) and time-dependent manner (30 microM for 1, 3, 6, 12 and 24 h). The cells from those experiments were then used for microarray experiments in triplicate. Among the differentially expressed genes analyzed by Limma and Ingenuity Pathway Analysis software, we found that genes in DNA repair processes were the most significantly regulated by all AA treatments. Furthermore, response to DNA damage stimulus, apoptosis, and regulation of cell cycle, were also significantly regulated by AA treatment. Among the differentially expressed genes found in the dose-response and time-course studies that were involved in these biological processes, two up-regulated (GADD45B, NAIP), and six down-regulated genes (TP53, PARP1, OGG1, ERCC1, ERCC2, and MGMT) were con-firmed by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). AA exposure also caused a down-regulation of the gene expression of anti-oxidant enzymes, such as superoxide dismutase, glutathione reductase, and glutathione peroxidase. Moreover, AA treatment led to increased frequency of DNA strand breaks, 8-hydroxydeoxyguanosine-positive nuclei, and micronuclei in a dose-dependent manner in HK-2 cells, possibly as a result of the inhibition of DNA repair. These data suggest that oxidative stress plays a role in the cytotoxicity of AA. In addition, our results provide insight into the involvement of down-regulation of DNA repair gene expression as a possible mechanism for AA-induced genotoxicity.
- SourceAvailable from: José Carlos de Magalhães[Show abstract] [Hide abstract]
ABSTRACT: The appearance of new antibiotic-resistant bacteria is a societal problem that requires the development of new alternative treatments. Therefore, this work evaluated the antibacterial activity of ethanolic (EHI), dichloromethanic (EDI) and hexanic (EHE) extracts from Aristolochia cymbifera stems and the combination of these extracts with an antimicrobial drug to develop a new antibacterial therapy. The EDI, EHE and EHI extracts were obtained by maceration using three different solvents. The minimal inhibitory concentrations (MIC) of these extracts were determined using the microdilution test to determine the antibacterial potential of these extracts and their combination with streptomycin against Staphylococcus aureus, Bacillus cereus, Klebsiella pneumoniae and Shigella flexneri. The extract dose leading to the cytotoxicity of 50% of the cells (CC50) was evaluated using mammalian cells MA104 and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay. The extracts had a MIC under 500 mg/L and a CC50 lower than 50 mg/L. The antibiotic/extract proportion influenced the antibacterial activity of the mixtures, and the proportion that optimized the antibacterial activity of streptomycin was a mixture that contained 75 percent of extract. This composition included less than 6.5 mg/L of extract and 2.5 mg/L of streptomycin and has potential as a new antibacterial therapy. Electronic supplementary material The online version of this article (doi:10.1186/2193-1801-2-430) contains supplementary material, which is available to authorized users.SpringerPlus 09/2013; 2:430. DOI:10.1186/2193-1801-2-430
Article: Pax5[Show abstract] [Hide abstract]
ABSTRACT: The B cell lineage of the hematopoietic system is responsible for the generation of high-affinity antibodies, which provide humoral immunity for protection against foreign pathogens. B cell commitment and development depend on many transcription factors including Pax5. Here, we review the different functions of Pax5 in regulating various aspects of B lymphopoiesis. At B cell commitment, Pax5 restricts the developmental potential of lymphoid progenitors to the B cell pathway by repressing B-lineage-inappropriate genes, while it simultaneously promotes B cell development by activating B-lymphoid-specific genes. Pax5 thereby controls gene transcription by recruiting chromatin-remodeling, histone-modifying, and basal transcription factor complexes to its target genes. Moreover, Pax5 contributes to the diversity of the antibody repertoire by controlling VH-DJH recombination by inducing contraction of the immunoglobulin heavy-chain locus in pro-B cells, which is likely mediated by PAIR elements in the 5′ region of the VH gene cluster. Importantly, all mature B cell types depend on Pax5 for their differentiation and function. Pax5 thus controls the identity of B lymphocytes throughout B cell development. Consequently, conditional loss of Pax5 allows mature B cells from peripheral lymphoid organs to develop into functional T cells in the thymus via dedifferentiation to uncommitted progenitors in the bone marrow. Pax5 has also been implicated in human B cell malignancies because it can function as a haploinsufficient tumor suppressor or oncogenic translocation fusion protein in B cell precursor acute lymphoblastic leukemia.
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ABSTRACT: Injection of aristolochic acid (AA) in mice causes AA-induced nephrotoxicity, in which oxidative stress contributes to development of tubulointerstitial damage (TID). Liver-type fatty acid binding protein (L-FABP) is expressed in human proximal tubules and has an endogenous antioxidative function. The renoprotection of renal L-FABP was examined in a model of AA-induced nephrotoxicity. Established human L-FABP (hL-FABP) transgenic (Tg) mice and wild-type (WT) mice were treated with AA for up to 5 days. Mice were sacrificed on days 1, 3, and 5 after the start of AA injection. Although mouse L-FABP was not expressed in proximal tubules of WT mice, hL-FABP was expressed in proximal tubules of Tg mice. The expression of renal hL-FABP was significantly increased in Tg mice administered AA (Tg-AA), compared with the control (saline-treated Tg mice). In WT-AA mice, there was high urinary excretion of N(ε)-(hexanoyl)-lysine, the production of heme oxygenase-1 and receptor for advanced glycation end products increased, and TID was provoked. In contrast, renal hL-FABP in Tg-AA mice suppressed production of N(ε)-(hexanoyl)lysine, heme oxygenase-1, and receptor for advanced glycation end products. Renal dysfunction was significantly milder in Tg-AA mice than in WT-AA mice. The degree of TID was significantly attenuated in Tg-AA mice, compared with WT-AA. In conclusion, renal hL-FABP reduced the oxidative stress in AA-induced nephrotoxicity and attenuated TID.American Journal Of Pathology 03/2011; 178(3):1021-32. DOI:10.1016/j.ajpath.2010.12.002 · 4.60 Impact Factor