The signaling pathway of hypoxia inducible factor and its role in renal diseases

Bicalutamide Elicits Renal Damage by Causing Mitochondrial Dysfunction via ROS Damage and Upregulation of HIF-1

Combined androgen blockade using bicalutamide (Bic) is a therapeutic choice for treating prostate cancer (PCa). However, even at regular clinical dosages, Bic frequently shows adverse effects associated with cardiovascular and renal damage. Previously, we found that Bic selectively damaged mesangial cells compared to tubular cells and in an in vivo rat model, we also found renal damage caused by Bic. In the present study, a rat mesangial cell model was used to further the investigation. Results indicated that Bic enhanced lactate dehydrogenase release, reactive oxygen species (ROS) production, lysosome population and kidney injury molecule-1 and decreased N-cadherin. Bic elicited mitochondrial swelling and reduced the mitochondrial potential, resulting in severe suppression of the oxygen consumption rate (OCR), maximum respiration and ATP production. The hypoxia-inducible factor (HIF)-1α transcriptional activity and messenger RNA were significantly upregulated in dose-dependent manners. The HIF-1α protein reached a peak value at 24 h then rapidly decayed. BCL2/adenovirus E1B 19-kDa protein-interacting protein 3 and cleaved caspase-3 were dose-dependently upregulated by Bic (60 μM) and that eventually led to cell apoptosis. It is suggested that Bic induces renal damage via ROS and modulates HIF-1α pathway and clinically, some protective agents like antioxidants are recommended for co-treatment.

Hypoxic renal injury in newborns with abdominal compartment syndrome (clinical and experimental study)

BackgroundSurgical treatment for gastroschisis and congenital diaphragmatic hernia (CDH) commonly leads to abdominal compartment syndrome (ACS) associated with hypoxic renal injury. We hypothesized that measurement of urinary and serum concentrations of vascular endothelial growth factor (VEGF), π-glutathione S-transferase (π-GST), and monocyte chemoattractant protein-1 (MCP-1) may serve for noninvasive detection of hypoxic renal injury in such patients.MethodsIntra-abdominal pressure (IAP), renal excretory function, and the biomarker levels were analyzed before, 4, and 10 days after surgery. Association between the biomarker levels and renal histology was investigated using an original model of ACS in newborn rats.ResultsFour days after surgery, IAP increased, renal excretory function decreased, and the levels of VEGF, π-GST, and MCP-1 increased, indicating renal injury. Ten days after surgery, IAP partially decreased, renal excretory function completely restored, but the biomarker levels remained elevated, suggesting the ongoing kidney injury. In the model of ACS, increase in the biomarker levels was associated with progressing kidney morphological alteration.ConclusionSurgical treatment for gastroschisis and CDH is associated with prolonged hypoxic kidney injury despite complete restoration of renal excretory function. Follow-up measurement of VEGF, π-GST, and MCP-1 levels may provide a better tool for noninvasive assessment of renal parenchyma in newborns with ACS.

miR-210 protects renal cell against hypoxia-induced apoptosis by targeting HIF-1 alpha

The kidney is vulnerable to hypoxia-induced injury. One of the mechanisms underlying this phenomenon is cell apoptosis triggered by hypoxia-inducible factor-1-alpha (HIF-1α) activation. MicroRNA-210 (miR-210) is known to be induced by HIF-1α and can regulate various pathological processes, but its role in hypoxic kidney injury remains unclear. Here, in both kinds of rat systemic hypoxia and local kidney hypoxia models, we found miR-210 levels were upregulated significantly in injured kidney, especially in renal tubular cells. A similar increase was observed in hypoxia-treated human renal tubular HK-2 cells. We also verified that miR-210 can directly suppress HIF-1α expression by targeting the 3' untranslated region (UTR) of HIF-1α mRNA in HK-2 cells in severe hypoxia. Accordingly, miR-210 overexpression caused significant inhibition of the HIF-1α pathway and attenuated apoptosis caused by hypoxia, while miR-210 knockdown exerted the opposite effect. Taken together, our findings verify that miR-210 is involved in the molecular response in hypoxic kidney lesions in vivo and attenuates hypoxia-induced renal tubular cell apoptosis by targeting HIF-1α directly and suppressing HIF-1α pathway activation in vitro.

The pVHL172 isoform is not a tumor suppressor and up-regulates a subset of pro-tumorigenic genes including TGFB1 and MMP13

The von Hippel-Lindau (VHL) tumor suppressor gene is often deleted or mutated in ccRCC (clear cell renal cell carcinoma) producing a non-functional protein. The gene encodes two mRNA, and three protein isoforms (pVHL₂₁₃, pVHL₁₆₀ and pVHL₁₇₂). The pVHL protein is part of an E3 ligase complex involved in the ubiquitination and proteasomal degradation of different proteins, particularly hypoxia inducible factors (HIF) that drive the transcription of genes involved in the regulation of cell proliferation, angiogenesis or extracellular matrix remodelling. Other non-canonical (HIF-independent) pVHL functions have been described. A recent work reported the expression of the uncharacterized protein isoform pVHL₁₇₂ which is translated from the variant 2 by alternative splicing of the exon 2. This splice variant is sometimes enriched in the ccRCCs and the protein has been identified in the respective samples of ccRCCs and different renal cell lines. Functional studies on pVHL have only concerned the pVHL₂₁₃ and pVHL₁₆₀ isoforms, but no function was assigned to pVHL₁₇₂. Here we show that pVHL₁₇₂ stable expression in renal cancer cells does not regulate the level of HIF, exacerbates tumorigenicity when 786-O-pVHL₁₇₂ cells were xenografted in mice. The pVHL₁₇₂-induced tumors developed a sarcomatoid phenotype. Moreover, pVHL₁₇₂ expression was shown to up regulate a subset of pro-tumorigenic genes including TGFB1, MMP1 and MMP13. In summary we identified that pVHL₁₇₂ is not a tumor suppressor. Furthermore our findings suggest an antagonistic function of this pVHL isoform in the HIF-independent aggressiveness of renal tumors compared to pVHL₂₁₃.

Hsa‑miR‑371‑5p inhibits human mesangial cell proliferation and promotes apoptosis in lupus nephritis by directly targeting hypoxia‑inducible factor 1α

MicroRNAs (miRNAs/miR) have emerged as a novel class of gene expression modulators in kidney disease. Lupus nephritis (LN) is the predominant cause of morbidity and mortality in patients with systemic lupus erythematosus (SLE). Hsa‑miR‑371‑5p has previously been reported to be dysregulated in LN using a miRNA microarray analysis. The present study aimed to determine the function and molecular mechanisms of hsa‑miR‑371‑5p in human mesangial cells of LN. Quantitative polymerase chain reaction (qPCR) was used to detect hsa‑miR‑371‑5p expression in LN tissues. Furthermore, the MTT assay and flow cytometric analyses were performed to analyze the effects of hsa‑miR‑371‑5p on mesangial cell proliferation and apoptosis. Bioinformatics analysis, luciferase reporter assay, qPCR and western blotting were also conducted to predict and confirm the target gene of hsa‑miR‑371‑5p in mesangial cells. The results demonstrated that hsa‑miR‑371‑5p expression was markedly downregulated in LN renal tissues compared with in normal kidney tissues. Restoration of hsa‑miR‑371‑5p expression using synthetic hsa‑miR‑371‑5p mimics was able to significantly inhibit mesangial cell proliferation and induce apoptosis. In addition, mechanistic exploration demonstrated that hypoxia‑inducible factor 1α (HIF‑1α) was a direct target gene of hsa‑miR‑371‑5p in mesangial cells. In conclusion, these results suggested that hsa‑miR‑371‑5p is downregulated in LN, and overexpression of hsa‑miR‑371‑5p may inhibit mesangial cell proliferation and promote apoptosis by directly targeting HIF‑1α.