Annotated Chromosome Maps for Renal Disease

A combination of linkage analyses and association studies are currently employed to promote the identification of genetic factors contributing to inherited renal disease. We have standardized and merged complex genetic data from disparate sources, creating unique chromosomal maps to enhance genetic epidemiological investigations. This database and novel renal maps effectively summarize genomic regions of suggested linkage, association, or chromosomal abnormalities implicated in renal disease. Chromosomal regions associated with potential intermediate clinical phenotypes have been integrated, adding support for particular genomic intervals. More than 500 reports from medical databases, published scientific literature, and the World Wide Web were interrogated for relevant renal-related information. Chromosomal regions highlighted for prioritized investigation of renal complications include 3q13-26, 6q22-27, 10p11-15, 16p11-13, and 18q22. Combined genetic and physical maps are effective tools to organize genetic data for complex diseases. These renal chromosome maps provide insights into renal phenotype-genotype relationships and act as a template for future genetic investigations into complex renal diseases. New data from individual researchers and/or future publications can be readily incorporated to this resource via a user-friendly web-form accessed from the website: www.qub.ac.uk/neph-res/CORGI/index.php.

Interleukin-8 signaling promotes androgen-independent proliferation of prostate cancer cells via induction of androgen receptor expression and activation

The aim of our study was to assess the importance of the CXC chemokine and interleukin (IL)-8 in promoting the transition of prostate cancer (CaP) to the androgen-independent state. Stimulation of the androgen-dependent cell lines, LNCaP and 22Rv1, with exogenous recombinant human interleukin-8 (rh-IL-8) increased androgen receptor (AR) gene expression at the messenger RNA (mRNA) and protein level, assessed by quantitative polymerase chain reaction and immunoblotting, respectively. Using an androgen response element-luciferase construct, we demonstrated that rh-IL-8 treatment also resulted in increased AR transcriptional activity in both these cell lines, and a subsequent upregulation of prostate-specific antigen and cyclin-dependent kinase 2 mRNA transcript levels in LNCaP cells. Blockade of CXC chemokine receptor-2 signaling using a small molecule antagonist (AZ10397767) attenuated the IL-8-induced increases in AR expression and transcriptional activity. Furthermore, in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays, coadministration of AZ10397767 reduced the viability of LNCaP and 22Rv1 cells exposed to bicalutamide. Our data show that IL-8 signaling increases AR expression and promotes ligand-independent activation of this receptor in two androgen-dependent cell lines, describing two mechanisms by which this chemokine may assist in promoting the transition of CaP to the androgen-independent state. In addition, our data show that IL-8-promoted regulation of the AR attenuates the effectiveness of the AR antagonist bicalutamide in reducing CaP cell viability.

Genetic association analyses of non-synonymous single nucleotide polymorphisms in diabetic nephropathy

Aims/hypothesis: Diabetic nephropathy, characterised by persistent proteinuria, hypertension and progressive kidney failure, affects a subset of susceptible individuals with diabetes. It is also a leading cause of end-stage renal disease (ESRD). Non-synonymous (ns) single nucleotide polymorphisms (SNPs) have been reported to contribute to genetic susceptibility in both monogenic disorders and common complex diseases. The objective of this study was to investigate whether nsSNPs are involved in susceptibility to diabetic nephropathy using a case-control design.

Methods: White type 1 diabetic patients with (cases) and without (controls) nephropathy from eight centres in the UK and Ireland were genotyped for a selected subset of nsSNPs using Illumina's GoldenGate BeadArray assay. A ? 2 test for trend, stratified by centre, was used to assess differences in genotype distribution between cases and controls. Genomic control was used to adjust for possible inflation of test statistics, and the False Discovery Rate method was used to account for multiple testing.

Results: We assessed 1,111 nsSNPs for association with diabetic nephropathy in 1,711 individuals with type 1 diabetes (894 cases, 817 controls). A number of SNPs demonstrated a significant difference in genotype distribution between groups before but not after correction for multiple testing. Furthermore, neither subgroup analysis (diabetic nephropathy with ESRD or diabetic nephropathy without ESRD) nor stratification by duration of diabetes revealed any significant differences between groups.

Conclusions/interpretation: The nsSNPs investigated in this study do not appear to contribute significantly to the development of diabetic nephropathy in patients with type 1 diabetes.

Genetic analysis of coronary artery disease single nucleotide polymorphisms in diabetic nephropathy

Background. Diabetic nephropathy is a leading cause of end-stage renal disease. Premature mortality is common in patients with nephropathy, largely due to cardiovascular disease. Genetic variants implicated in macrovascular disease are therefore excellent candidates to assess for association with diabetic nephropathy. Recent genome-wide association studies have identified a total of 15 single-nucleotide polymorphisms (SNPs) that are reproducibly associated with cardiovascular disease.

Methods. We initially assessed these SNPs for association in UK type 1 diabetic patients with (cases; n = 597) and without (controls; n = 502) nephropathy using iPLEXTM and TaqMan® assays. Replication studies were performed with DNA genotyped in a total of 2668 individuals from the British Isles.

Results. One SNP (rs4420638) on chromosome 19q13 was found to be significantly associated with diabetic nephropathy before (P = 0.0002) and after correction for multiple testing (Pcorrected = 0.002). We replicated this finding in a phenotypically similar case–control collection comprising 709 individuals with type 1 diabetes (P = 0.002; combined P < 0.00001; OR = 1.54, 95% CI: 1.29–1.84).

Conclusions. Our case–control data suggest that rs4420638, or a functional SNP in linkage disequilibrium with this SNP, may be associated with diabetic nephropathy.

Association of functional haem oxygenase-1 gene promoter polymorphism with polycystic kidney disease and IgA nephropathy

Background: Haem oxygenase-1 (HO-1) is a cytoprotective molecule that is reported to have a protective role in a variety of experimental models of renal injury. A functional dinucleotide repeat (GT)n polymorphism, within the HO-1 promoter, regulates HO-1 gene expression; a short number of repeats (S-allele <25) increases transcription. We report the first assessment of the role of this HO-1 gene promoter polymorphism in chronic kidney disease due to autosomal dominant polycystic kidney disease (ADPKD) and IgA nephropathy (IgAN).

Methods: The DNA from 160 patients (99% Caucasian) on renal replacement therapy (RRT) was genotyped. The primary renal disease was ADPKD in 100 patients and biopsy-proven IgAN in 60 patients.

Results: Overall, the mean age at commencement of RRT was not significantly different between patients with and without an S-allele (44.1 years versus 45.0 years, P = 0.64). In patients with ADPKD, the age at commencement of RRT was comparable regardless of the HO-1 genotype (47.7 years versus 46.7 years, P = 0.59). The same was true in patients with IgAN (38.3 years versus 42.2 years, P = 0.28).

Conclusion: This suggests that the functional HO-1 promoter polymorphism does not influence renal survival in CKD due to ADPKD or IgAN.

Chemotherapy-Induced CXC-Chemokine/CXC-Chemokine Receptor Signaling in Metastatic Prostate Cancer Cells Confers Resistance to Oxaliplatin through Potentiation of Nuclear Factor-κB Transcription and Evasion of Apoptosis

Constitutive activation of nuclear factor (NF)-kappa B is linked with the intrinsic resistance of androgen-independent prostate cancer (AIPC) to cytotoxic chemotherapy. Interleukin-8 (CXCL8) is a transcriptional target of NF-kappa B whose expression is elevated in AIPC. This study sought to determine the significance of CXCL8 signaling in regulating the response of AIPC cells to oxaliplatin, a drug whose activity is reportedly sensitive to NF-kappa B activity. Administration of oxaliplatin to PC3 and DU145 cells increased NF-kappa B activity, promoting antiapoptotic gene transcription. In addition, oxaliplatin increased the transcription and secretion of CXCL8 and the related CXC-chemokine CXCL1 and increased the transcription and expression of CXC-chemokine receptors, especially CXC-chemokine receptor (CXCR) 2, which transduces the biological effects of CXCL8 and CXCL1. Stimulation of AIPC cells with CXCL8 potentiated NF-kappa B activation in AIPC cells, increasing the transcription and expression of NF-kappa B-regulated antiapoptotic genes of the Bcl-2 and IAP families. Coadministration of a CXCR2-selective antagonist, AZ10397767 (Bioorg Med Chem Lett 18:798-803, 2008), attenuated oxaliplatin-induced NF-kappa B activation, increased oxaliplatin cytotoxicity, and potentiated oxaliplatin-induced apoptosis in AIPC cells. Pharmacological inhibition of NF-kappa B or RNA interference-mediated suppression of Bcl-2 and survivin was also shown to sensitize AIPC cells to oxaliplatin. Our results further support NF-kappa B activity as an important determinant of cancer cell sensitivity to oxaliplatin and identify the induction of autocrine CXCR2 signaling as a novel mode of resistance to this drug.

Investigation of DNA polymorphisms in SMAD genes for genetic predisposition to diabetic nephropathy in patients with type 1 diabetes mellitus

Aims/hypothesis: SMAD proteins are involved in multiple signalling pathways and are key modulators of gene expression. We hypothesised that genetic variation in selected SMAD genes contributes to susceptibility to diabetic nephropathy. Methods: We selected 13 haplotype tag (ht) single nucleotide polymorphisms (SNPs) from 67 variants identified by resequencing the SMAD2 and SMAD3 genes. For SMAD1, SMAD4 and SMAD5 genes, genotype data were downloaded for 217 SNPs from Phase II of the International HapMap project. Of these, 85 SNPs met our inclusion criteria, resulting in the selection of 13 tag SNPs for further investigation. A case-control approach was employed, using 267 nephropathic patients and 442 controls with type 1 diabetes from Ireland. Two further populations (totalling 1,407 patients, 2,238 controls) were genotyped to validate initial findings. Genotyping was conducted using iPLEX, TaqMan and gel electrophoresis.
Results: The distribution of genotypes was in Hardy-Weinberg equilibrium. Analysis by the ? 2 test of genotype and allele frequencies in patients versus controls in the Irish population (n?=?709) revealed evidence for the association of one allele at 5% level of significance (rs10515478, p uncorrected?=?0.006; p corrected?=?0.04). This finding represents a relatively small difference in allele frequency of 6.4% in the patient group compared with 10.7% in the control group; this difference was not supported in subsequent investigations using DNA from European individuals with similar phenotypic characteristics.
Conclusions/interpretation: We selected an appropriate subset of variants for the investigation of common genetic risk factors and assessed SMAD1 to SMAD5 genes for association with diabetic nephropathy. We conclude that common polymorphisms in these genes do not strongly influence genetic susceptibility to diabetic nephropathy in white individuals with type 1 diabetes mellitus.

Pathophysiology of anemia and erythrocytosis.

An increasing understanding of the process of erythropoiesis raises some interesting questions about the pathophysiology, diagnosis and treatment of anemia and erythrocytosis. The mechanisms underlying the development of many of the erythrocytoses, previously characterised as idiopathic, have been elucidated leading to an increased understanding of oxygen homeostasis. Characterisation of anemia and erythrocytosis in relation to serum erythropoietin levels can be a useful addition to clinical diagnostic criteria and provide a rationale for treatment with erythropoiesis stimulating agents (ESAs). Recombinant human erythropoietin as well as other ESAs are now widely used to treat anemias associated with a range of conditions, including chronic kidney disease, chronic inflammatory disorders and cancer. There is also heightened awareness of the potential abuse of ESAs to boost athletic performance in competitive sport. The discovery of erythropoietin receptors outside of the erythropoietic compartment may herald future applications for ESAs in the management of neurological and cardiac diseases. The current controversy concerning optimal hemoglobin levels in chronic kidney disease patients treated with ESAs and the potential negative clinical outcomes of ESA treatment in cancer reinforces the need for cautious evaluation of the pleiotropic effects of ESAs in non-erythroid tissues.