Development of Novel Regimens for the Prevention of Chronic Renal Failure

Massachusetts General Hospital, Boston MA

Investigators

Abstract

ABSTRACT In the United States the prevalence of end-stage renal disease (ESRD) has reached epidemic proportions with over 19 million adults being affected. The rates of ESRD among the elderly are disproportionably high. Consequently, as life expectancy increases and the baby-boom generation reaches retirement age, the already heavy burden imposed by ESRD on the United States health care system is set to increase dramatically. The main cause of ESRD is chronic renal failure (CRF) driven by risk factors such as anemia, diabetic hyperglycemia, hypertension, hypercholesterolemia, cigarette smoking, air pollution, atherosclerosis, repeated episodes of acute renal failure (ARF) and sleep apnea. All the risk factors associated with CRF produce inappropriately low oxygen tensions within the kidney. This has lead to hyperbaric oxygenation being used as a treatment for kidney failure and the contention that [unreadable]chronic hypoxia is a common pathway to end-stage renal failure[unreadable]. Numerous studies have demonstrated that hypoxic conditions within the kidney produce CRF by inducing a sustained inflammatory attack mediated by resident and infiltrating macrophages. Indispensable to the role of macrophages in causing CRF is activation of their ability to bind renal tissue and generate pro-inflammatory cytokines. It was thought that such activation resulted exclusively from macrophages responding to cytokines released from ischemic renal endothelium. However, we have demonstrated that cells of the macrophage lineage also become activated independent of the hypoxic response of endothelial cells. We found that this independent mechanism involves macrophage precursors directly sensing hypoxia and responding by transcriptional induction of the genes that encode the [unreadable]2-integrin family of adhesion molecules. Other groups have shown that resident macrophages also respond directly to hypoxia by enhanced synthesis of the cytokines TNF-a and IL-6. Based on these data, it is our hypothesis that transcriptional activation of the [unreadable]2-integrin, TNF-a and IL-6 genes in macrophages maintains the long-term inflammation by which hypoxia produces CRF. We propose to test this hypothesis by accomplishing three specific aims. In Specific Aim 1, genomic fingerprinting and homologous recombination will be used in the Identification of Cis-Acting Gene Elements that Mediate Macrophage Activation in Response to Hypoxia. In Specific Aim 2 molecular cloning, electrophoretic mobility shift assays and chromatin immunoprecipitation will be used in the Identification of Novel Trans-Acting Gene Control Factors that Mediate Macrophage Activation in Response to Hypoxia. Finally, in Specific Aim 3 small interfering RNA and/or constitutive expression vectors will be tested in vitro, ex vivo and in vivo to determine the efficacy of Protection Against Renal Failure by Modulating Trans-Acting Macrophage Hypoxia-Response Factors. In this way we expect to provide proof-of-principal for new therapeutic regimens that reduce the ability of hypoxia to cause CRF.