Unknown,Transcriptomics,Genomics,Proteomics

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Stress-related gene expression in HK-2 cells exposed to pH 7.4, 7.0 or 6.7

ABSTRACT: Chronic metabolic acidosis occurs commonly in patients with diseased kidneys and is linked with progression to renal failure. As renal function declines there is loss of nephron mass and adaptive proximal tubular hypertrophy and hypermetabolism. We have previously demonstrated in an in vitro model of chronic acidosis in porcine LLC-PK1 cells increased ammonia generation (oxidative hypermetabolism) linked with tubular cellular dysfunction and increased markers of oxidative stress. The aim of this study was to determine the effect of chronic acidosis in HK-2 cells on changes in gene and protein expression stimulated by oxidative stress. HK-2 cells were were seeded onto 6 well plates at a density of 4x104 cells/well and cultured for 72 h in growth medium (DMEM/Ham s F12 medium supplemented with 5.5 mM glucose, 2 mM L-glutamine, 5 ug/ml insulin, 5 ug/ml transferrin, 5 ng/ml sodium selenite, 0.4 ug/ml hydrocortisone, 5 ng/ml epidermal growth factor, 100 U/ml penicillin, 100 ug/ml streptomycin, and 10% FCS). The medium was then replaced by growth media buffered to pH 7.4, 7.0 or 6.7 with 12.5 mM bis-Tris and cells were cultured for further 48 h. Media were changed to serum free media (SFM) buffered by 12.5 mM bis-Tris to pH 7.4, 7.0 or 6.7 and cells were harvested and RNA isolated after 24 h. Total RNA was isolated from HK-2 cells on 3 different occasions using Tri-reagent (Sigma, UK) as recommended by the manufacturer's protocol. The RNA from the respective replicate samples were pooled together and the RNA content was measured using RiboGreen RNA Quantitation Reagent (Molecular Probes, Invitrogen, UK). The integrity of the total RNA was verified on a denaturing agarose-formaldehyde gel.

ORGANISM(S): Homo sapiens

SUBMITTER: Rana Rustom

PROVIDER: E-GEOD-23995 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Aim： Use microarray analysis to understand the molecular mechanism underlying the effect of aristolochic acid (AA), a major active component of plants from the Aristolochiaceae family, in normal human kidney (HK-2) cells. Methods： HK-2 cells were treated with AA for 24 hours and cell viability was measured by a 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide assay. Complementary DNA microarrays were used to investigate the gene expression pattern of HK-2 cells exposed to AA and the results of this study were in triplicate. Quantitative real-time RT-PCR assay was used to verify the microarray data for selected nuclear factor kappa B (NF-κB)-regulated genes. Furthermore, subcellular localization of NF-κB p65 was visualized by immunofluorescence confocal microscopy in HK-2 cells. NF-κB activity was examined by luciferase reporter assay in HK-2/NF-κB transgenic cells. Results： AA exhibited a dose-dependent cytotoxic effect in HK-2 cells and induced alterations in gene expression profiles related to DNA damage response, stress response, etc. In addition, 9 biological pathways associated with immunomodulatory functions were down-regulated in AA-treated HK-2 cells. Network analysis revealed that NF-κB played a central role in the network topology. Among NF-kB-regulated genes, 8 differentially expressed genes were verified by real-time RT-PCR. The inhibition of NF-κB activity by AA was further confirmed by immunofluorescence confocal microscopy and by NF-κB luciferase reporter assay. Conclusion： Our data revealed that AA could suppress NF-κB activity in normal human cells, perhaps partially accounting for the reported anti-inflammatory effects of some plants from the genus Aristolochia. HK-2 cells were grown in keratinocyte serum-free basal medium (Gibco) supplemented with 5 ng/ml of recombinant epidermal growth factor and 50 μg/ml of bovine pituitary extract without antibiotics in 5 % CO2 at 370C. HK-2 cells were seeded in 25-T flasks and incubated for 24 h before aristolochic acid treatment. Aristolochic acid (10 90 μM) were added to HK-2 cells for 24 h. The control cells received equal amounts of water only.

Project description:Lactic acidosis and hypoxia are two prominent tumor microenvironmental stresses that are both known to exert important influences on gene expression and phenotypes of cancer cells. But very little is known about the cross-talk and interaction between these two stresses. We performed gene expression analysis of MCF7 cells exposed to lactic acidosis, hypoxia and combined lactic acidosis and hypoxia. We found the hypoxia response elicited under hypoxia was mostly abolished upon simultaneous exposure to lactic acidosis. The repression effects are due to loss of HIF-1Î± protein synthesis under lactic acidosis. In addition, we showed lactic acidosis strongly synergizes with hypoxia to activate the unfold protein response (UPR) and inflammation response which are highly similar to amino acid deprivation responses (AAR). The statistical factor analysis of hypoxia and lactic acidosis responses indicated that ATF4 locus, an important activator in the UPR/AAR pathway, is amplified in subsets of breast tumors and cancer cell lines. Varying ATF4 levels dramatically affect the ability to survive the post-stress recovery from hypoxia and lactic acidosis and may suggest its selection of ATF4 amplification in human cancers. These data suggest that lactic acidosis interacts with hypoxia by both inhibiting the canonical hypoxia response and while activating the UPR and inflammation response. Gain of ATF4 locus may offer survival advantages to allow successful adaptation to frequent fluctuations of oxygen and acidity in tumor microenvironment. Collectively, our studies have provided linkage between the short-term transcriptional responses to the long term selection of the DNA copy number alterations (CNAs) under tumor microenvironmental stresses. RNAs from MCF7 cells exposed to control condition (ambient air ~21% O2, no lactate and neutral pH), lactic acidosis (ambient air, 10 mM Lactate and pH 6.7), hypoxia (1% pO2, no lactate and neutral pH) and the combined lactic acidosis and hypoxia (1% pO2, 10 mM Lactate and pH 6.7) condition for 24 hours were extracted by miRVana kits (Ambion) and hybridized to Affymetrix Human genome 133A 2.0 arrays with standard protocol.

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Stress-related gene expression in HK-2 cells exposed to pH 7.4, 7.0 or 6.7

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