Dr. Ananth Karumanchi
Narrative Report of Research Activities in the
Role of angiogenesis in the pathogenesis of preeclampsia (PE) (currently the major focus of the laboratory): Our laboratory has identified sFlt-1, an antagonist of circulating vascular endothelial growth factor (VEGF) and placental growth factor (PlGF), from preeclamptic placentas and has confirmed that it is released into the blood stream in vast excess in patients with preeclampsia. Exogenous administration of sFlt-1 into pregnant rats reproduces the phenotype of preeclampsia, namely proteinuria, hypertension and glomerular endotheliosis, the classic lesion of preeclampsia. These observations suggest that excess circulating sFlt-1 contributes to the pathogenesis of preeclampsia. We have also demonstrated that circulating sFlt-1 and PlGF levels can be used for the clinical diagnosis and the prediction of preeclampsia. Work is in progress to understand the regulation of sFlt-1 production by the cytotrophoblasts of the placenta. We are also testing the effects of antagonizing excess sFlt-1 with growth factors and small molecule compounds in our animal model of preeclampsia with the goal of finding novel treatment options for this disease. Additionally, we are currently characterizing other gene products that are elevated in preeclampsia and which may be synergistic to sFlt-1 in the pathogenesis of preeclampsia and may serve as biomarkers for the early diagnosis of preeclampsia. This project is part of our interest in studying the contribution of endothelium in the pathogenesis of proteinuria and other vascular diseases.
Molecular mechanisms of proteinuria: We are very interested in understanding the molecular mechanisms of proteinuria (a common phenotype of several renal diseases). Preliminary microarray data generated from podocytes grown in high and normal glucose have revealed several novel targets and pathways. The laboratory is currently confirming the cell culture data in diabetic rats by in-situ hybridization. Newer in vitro assays to mimic in vivo proteinuria are currently in development. Transcriptional profiles of podocytes lacking nephrin (mutated in congenital Finnish nephritic syndrome) and LMX-1b (mutated in nail-patella syndrome) are in progress. Urine proteomics data from diabetic patients with and without nephropathy are being analyzed in order to identify novel urine markers that predict worse renal outcomes. Goals would be to identify common pathways that lead to proteinuria, which in the future may lead to specific therapies.
Renal Cancer and angiogenesis: Our laboratory is interested in the area of angiogenesis related to cancer and development. The PI's initial research effort (while a post-doc in Dr. Sukhatme's laboratory) was directed towards understanding the function of von Hippel-Lindau (VHL) protein and its role in cancer. The PI discovered several novel targets, which are regulated by pVHL including TGF beta1, TGF alpha, VEGF and AE2. All these targets seem to be regulated at the level of mRNA stability. In collaboration with the Mukhopadhyay laboratory (Mayo clinic), we have recently found that the mRNA binding protein HuR play a significant role in this process. VHL protein interacts with HuR and prevents HuR from stabilizing VEGF mRNA. Work is in progress to determine if HuR is the central player in the post-transcriptional regulation of other cytokines such as TGF beta and TGF alpha. Delineation of the cis-elements in the TGF beta and TGF alpha mRNA, identification and characterization of other RNA binding proteins which are regulated by pVHL are also in progress. Dramatic inhibition of renal tumor growth can be elicited by treatment with anti-TGF-b neutralizing antibodies, with the major mechanism being an anti-angiogenic one. In collaboration with Sukhatme lab we are testing combination therapies with other anti-angiogenic molecules such as endostatin and restin to treat metastatic renal cancer. We are also involved in the characterization of two novel targets in VHL-associated renal cancer identified by the P.I. -N-myc downregulated gene (Ndr1 or RTP) and pregnancy associated plasma protein (PAPP-A) genes.