Summary Glomerular crescent formation is a hallmark of rapidly progressive forms of glomerulonephritis. Thrombosis and macrophage infiltration are features of crescent formation in human and experimental kidney disease. Protease‐activated receptor‐2 (PAR‐2) is a G‐protein coupled receptor that links coagulation and inflammation. This study investigated whether pharmacological inhibition of PAR‐2 can suppress glomerular crescent formation in rat nephrotoxic serum nephritis (NTN). Disease was induced in Wistar Kyoto rats by immunisation with sheep IgG followed by administration of sheep nephrotoxic serum. Rats (n = 8/group) received the PAR‐2 antagonist (GB88, 10 mg/kg/p.o.), vehicle or no treatment starting 3 days before nephrotoxic serum injection and continuing until day 14. Vehicle and untreated rats developed thrombosis and macrophage infiltration in the glomerular tuft and Bowman's space in conjunction with prominent crescent formation. Activation of JNK signalling and proliferation in parietal epithelial cells was associated with crescent formation. GB88 treatment significantly reduced crescent formation with a substantial reduction in glomerular thrombosis, reduced macrophage infiltration in Bowman's space, and reduced activation of parietal epithelial cells. However, GB88 did not protect against the development of proteinuria, renal function impairment, inflammation or tubular cell damage in the NTN model. In conclusion, PAR‐2 plays a specific role in glomerular crescent formation by promoting glomerular thrombosis, macrophage accumulation in Bowman's space and activation of parietal epithelial cells.
Background Numerous immunohistochemical (IHC) biomarkers have been employed to aid in the difficult differentiation between chromophobe renal cell carcinoma (chRCC) and renal oncocytoma (RO). A systematic review and meta-analysis of the published literature was carried out to summarise and analyse the evidence for discriminatory IHC biomarkers to differentiate the two entities. Methods PubMed database was used to identify relevant literature. Primary end point was comparison of positive immunostaining of the biomarkers in chRCC and RO, with extracted data used to calculate OR and 95% CI and statistical I 2 test of heterogeneity for multiple studies. Results One hundred and nine manuscripts were available for review. Data extracted were subjected to quantitative meta-analysis. Ten most effective biomarkers (OR of chRCC/RO and CI) are: amylase α1A (n=129, OR=0.001, 95% CI 0.0001 to 0.019); Wnt-5a (n=38, OR=0.0076, 95% CI 0.0004 to 0.015); FXYD2 (n=57, OR=130, 95% CI 14.2 to 1192.3); ankyrin-repeated protein with a proline-rich region (ARPP) (n=25, OR=0.0054, 95% CI 0.0002 to 0.12); cluster of differentiation 63 (CD63) (n=62, diffuse (chRCC) vs apical/polar (RO) stain pattern); transforming growth factor β 1 (TGFβ1) (n=34, membranous (chRCC) vs cytoplasmic (RO)); cytokeratin 7 (CK7) (11 studies, n=448, pooled OR=44.22, 95% CI 22.52 to 86.64, I 2 =15%); S100A1 (4 studies, n=124, pooled OR=0.01, 95% CI 0 to 0.03, I 2 =0%); caveolin-1 (2 studies, n=102, pooled OR=32.95, 95% CI 3.67 to 296.1, I 2 =70%) and claudin-7 (3 studies, n=89, pooled OR=24.7, 95% CI 6.28 to 97.1, I 2 =0%). Conclusions We recommend a panel of IHC biomarkers of amylase α1A, Wnt-5a, FXYD2, ARPP, CD63, TGFβ1, CK7, S100A1, caveolin-1 and claudin-7 to aid in the differentiation of chRCC and RO.
Drug resistance continues to be a major problem in the effective treatment of many diseases. Resistance to chemotherapy, whether intrinsic or extrinsic, is the result of at least three well defined mechanisms: prevention of the interaction of drug with the target, decreased intracellular concentration of the drug due to an increased efflux or a decreased influx, and enzymatic modification or destruction of the drug. With the advancement in technology, the molecular mechanisms of drug resistance have been unravelling at a rapid rate. This book is a timely review of such advances in drug resistance research. The nine chapters of this book, written by a group of clinicians and scientists, elegantly summarises recent advances in our understanding of this important clinical problem with emphasis on cisplatin, fibroblasts, natural compounds, erythropoiesis-stimulating agents, prostate cancer and kidney cancer. This book will be an important contribution to science, and an invaluable tool for researchers who are interested in drug resistance.
Metastatic renal cell carcinoma is a largely incurable disease, and existing treatments targeting angiogenesis and tyrosine kinase receptors are only partially effective. Here we reveal that MUC13, a cell surface mucin glycoprotein, is aberrantly expressed by most renal cell carcinomas, with increasing expression positively correlating with tumor grade. Importantly, we demonstrated that high MUC13 expression was a statistically significant independent predictor of poor survival in two independent cohorts, particularly in stage 1 cancers. In cultured renal cell carcinoma cells MUC13 promoted proliferation and induced the cell cycle regulator, cyclin D1, and inhibited apoptosis by inducing the anti-apoptotic proteins, BCL-xL and survivin. Silencing of MUC13 expression inhibited migration and invasion, and sensitized renal cancer cells to killing by the multi-kinase inhibitors used clinically, sorafenib and sunitinib, and reversed acquired resistance to these drugs. Furthermore, we demonstrated that MUC13 promotion of renal cancer cell growth and survival is mediated by activation of nuclear factor κB, a transcription factor known to regulate the expression of genes that play key roles in the development and progression of cancer. These results show that MUC13 has potential as a prognostic marker for aggressive early stage renal cell cancer and is a plausible target to sensitize these tumors to therapy.
One of the molecules regulated by the transcription factor, hypoxia inducible factor (HIF), is the hypoxia-responsive hematopoietic factor, erythropoietin (EPO). This may have relevance to the development of renal cell carcinoma (RCC), where mutations of the von Hippel-Lindau (VHL) gene are major risk factors for the development of familial and sporadic RCC. VHL mutations up-regulate and stabilize HIF, which in turn activates many downstream molecules, including EPO, that are known to promote angiogenesis, drug resistance, proliferation and progression of solid tumours. HIFs typically respond to hypoxic cellular environment. While the hypoxic microenvironment plays a critical role in the development and progression of tumours in general, it is of special significance in the case of RCC because of the link between VHL, HIF and EPO. EPO and its receptor, EPOR, are expressed in many cancers, including RCC. This limits the use of recombinant human EPO (rhEPO) to treat anaemia in cancer patients, because the rhEPO may be stimulatory to the cancer. EPO may also stimulate epithelial-mesenchymal transition (EMT) in RCC, and pathological EMT has a key role in cancer progression. In this mini review, we summarize the current knowledge of the role of EPO in RCC. The available data, either for or against the use of EPO in RCC patients, are equivocal and insufficient to draw a definitive conclusion.
Differentiation of chromophobe renal cell carcinoma (chRCC) from benign renal oncocytoma (RO) can be challenging especially when there are overlapping histological and morphological features. In this study we have investigated immunohistochemical biomarkers (cytokeratin 7/CK7, Caveolin-1/Cav-1 and S100 calcium-binding protein A1/S100A1) to aid in this difficult differentiation and attempted to validate their use in human renal tumour tissue to assess their discriminatory ability, particularly for chRCC and RO, in an Australian cohort of patients.Retrospective study was carried out of archived formalin-fixed paraffin-embedded renal tumours from tumour nephrectomy specimens of 75 patients: 30 chRCC, 15 RO and 30 clear cell RCC (ccRCC). Sections were cut and immunostained with specific polyclonal antibodies of CK7, Cav-1 and S100A1. Morphometry was used to determine expression patterns of the biomarkers using Aperio ImageScope. Results were assessed with student t-test and ANOVA with significance at P<0.05.From this cohort, male-to-female ratio was 1.9:1. Median age was 64 (45-88 years) and median tumour size was 3.8 cm (range, 1.2-18 cm). There were 47 (62.7%) T1, 7 T2, 20 T3 and one T4 stage of RCC; with 2 patients presenting with M1 stage. There was significantly higher CK7 expression in chRCC compared to RO (P=0.03), and chRCC also had a different staining pattern and higher expression of Cav-1 compared to RO. There was higher expression of S100A1 in RO compared to chRCC.Immunohistochemical staining and standard morphometry of CK7, Cav-1 and S100A1 can aid in the differentiation of chRCC and RO. This may guide clinicians in management of patients when faced with difficult diagnostic histological distinction between the two tumour subtypes.
The mechanism(s) underlying renoprotection by peroxisome proliferator-activated receptor (PPAR)-γ agonists in diabetic and nondiabetic kidney disease are not well understood. Mitochondrial dysfunction and oxidative stress contribute to kidney disease. PPAR-γ upregulates proteins required for mitochondrial biogenesis. Our aim was to determine whether PPAR-γ has a role in protecting the kidney proximal tubular epithelium (PTE) against mitochondrial destabilisation and oxidative stress. HK-2 PTE cells were subjected to oxidative stress (0.2-1.0 mM H₂O₂) for 2 and 18 h and compared with untreated cells for apoptosis, mitosis (morphology/biomarkers), cell viability (MTT), superoxide (dihydroethidium), mitochondrial function (MitoTracker red and JC-1), ATP (luminescence), and mitochondrial ultrastructure. PPAR-γ, phospho-PPAR-γ, PPAR-γ coactivator (PGC)-1α, Parkin (Park2), p62, and light chain (LC)3β were investigated using Western blots. PPAR-γ was modulated using the agonists rosiglitazone, pioglitazone, and troglitazone. Mitochondrial destabilization increased with H₂O₂concentration, ATP decreased (2 and 18 h; P < 0.05), Mitotracker red and JC-1 fluorescence indicated loss of mitochondrial membrane potential, and superoxide increased (18 h, P < 0.05). Electron microscopy indicated sparse mitochondria, with disrupted cristae. Mitophagy was evident at 2 h (Park2 and LC3β increased; p62 decreased). Impaired mitophagy was indicated by p62 accumulation at 18 h (P < 0.05). PPAR-γ expression decreased, phospho-PPAR-γ increased, and PGC-1α decreased (2 h), indicating aberrant PPAR-γ activation and reduced mitochondrial biogenesis. Cell viability decreased (2 and 18 h, P < 0.05). PPAR-γ agonists promoted further apoptosis. In summary, oxidative stress promoted mitochondrial destabilisation in kidney PTE, in association with increased PPAR-γ phosphorylation. PPAR-γ agonists failed to protect PTE. Despite positive effects in other tissues, PPAR-γ activation appears to be detrimental to kidney PTE health when oxidative stress induces damage.
Mercury (Hg) is a hazardous chemical that accumulates in many cells and tissues, thereby producing toxicity. The kidney is a key target organ for Hg accumulation and toxicity. The contributing factors to Hg accumulation in humans include: (1) elemental and inorganic Hg exposure, often occurring by inhalation of Hg vapors; (2) exposure to methyl Hg (meHg), for example, through contaminated seafood; and (3) exposure to ethyl mercury (etHg) via thimerosal-containing vaccines. Systematic investigations on the toxic effects of etHg/thimerosal on the nervous system were carried out, and etHg/thimerosal emerged as a possible risk factor for autism and other neurodevelopmental disorders. There is, however, little known about the mechanisms and molecular interactions underlying toxicity of etHg/thimerosal in the kidney, which is the focus of the current review. Susceptible populations such as infants, pregnant women, and the elderly are exposed to etHg through thimerosal-containing vaccines, and in-depth study of the potential adverse effects on the kidney is needed. In general, toxicity occurring in association with different forms of Hg is related to: intracellular thiol metabolism and oxidative stress reactions; mitochondrial function; intracellular distribution and build-up of calcium; apoptosis; expression of stress proteins; and also interaction with the cytoskeleton. Available evidence for the etHg-induced toxicity in the kidney was examined, and the main mechanisms and molecular interactions of cytotoxicity of etHg/thimerosal exposure in kidney described. Such accumulating knowledge may help to indicate molecular pathways that, if modulated, may better handle Hg-mediated toxicity.
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