Chronic kidney disease of unknown etiology: applying a multidisciplinary approach to investigate the world's most common tubulointerstitial kidney disease

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PROJECT SUMMARY/ABSTRACT Over the last twenty years, an increasing number of agricultural communities have faced an apparently new, unexplained, and fatal kidney disease, known as chronic kidney disease of unknown etiology (CKDu). First noted in sugar cane workers in El Salvador and rice farmers in Sri Lanka, reports of a similar kidney disease have emerged come from Nicaragua, Costa Rica, Guatemala, India, and (most recently) the U.S. Despite the scale and severity of this kidney disease epidemic, the epidemiological and mechanistic investigations needed to address it have been extremely limited. Because persons with the disease are otherwise healthy agricultural workers, many experts and the affected population suspect agrochemical exposure is responsible. In two key preliminary studies from Sri Lanka, we find that agricultural workers are drinking from shallow water wells that are contaminated by organophosphate and organochlorine agrochemicals above EPA drinking water regulations, and well water consumption raises likelihood of biopsy-proven CKDu and faster progression of established kidney disease. In a cohort of 600 at-risk participants identified by our preliminary work in whom we will obtain baseline environmental samples including water samples and kidney biopsies if they meet a validated clinical definition of CKDu, we propose to examine the hypothesis that specific agrochemicals contaminating well water are causing CKDu. We will: 1) run untargeted and targeted mass spectrometry analysis of well water, 2) determine the association of individual agrochemicals and their mixtures with incident CKDu case status, accounting for work intensity and heat stress, 3) measure the bioburden of nephrotoxic agrochemicals in cases versus controls, and 4) perform molecular analyses of early-stage kidney biopsies to specify the injury response pattern at a cellular level with bulk and single-cell RNA sequencing. In alignment with NIDDK-NIEHS-Fogarty recommended approach to CKDu investigations, this proposal integrates a multi- disciplinary, multi-national team of nephrologists, pathologists, molecular biologists and environmental geochemists. Based on our preliminary data we focus on agrochemical exposure via well water as the environmental risk factor of interest in this proposal, however field work will be coupled with an extensive biobanking effort to facilitate testing of multiple candidate hypotheses. The complementary molecular analyses will precisely characterize the injury in CKDu in the context of other primary tubulointerstitial kidney diseases, and create a rigorous scaffold for testing potential agents that can trigger CKDu-specific responses in the kidney. As in the case of prior regional kidney disease epidemics such as Balkan nephropathy, the intensive effort to identify cause in our outlined aims has the potential to pinpoint other vulnerable populations and regions, and more importantly, to abrogate the kidney disease by eliminating the exposure.