66 Sugarcane Ash and Sugarcane Ash-Derived Silica Nanoparticles Alter Mitochondrial Function and Metabolic Activity in Human Proximal Tubular Kidney Cells

Abstract

Abstract Multiple epidemics of chronic kidney disease of an unknown etiology (CKDu), primarily in young healthy agricultural workers, have emerged in agricultural communities around the world. We have hypothesized that the harvest and burning of sugarcane leading to inhalation of sugarcane ash may contribute to development of CKDu. Sugarcane stalks consist of ~80% amorphous silica and we have demonstrated that following burning of sugarcane, nano-sized silica particles (~200nm) are generated. To determine what effect such exposures have on kidney cells, a human proximal convoluted tubule (PCT) cell line (HK-2) was subjected to treatments ranging in concentration from 0.025µg/mL to 25µg/mL of sugarcane ash, desilicated sugarcane ash, sugarcane ash-derived silica nanoparticles (SAD SiNPs), or manufactured pristine 200nm silica nanoparticles. Following 6 to 48 hours of exposure, mitochondrial activity and viability were found to be significantly reduced when exposed to SAD particles at concentrations 2.5µg/mL or higher. Oxygen consumption rate (OCR) and pH were investigated with a Seahorse XF Analyzer, revealing significant changes to cellular metabolism across treatments as early as 6 hours following exposure. While most treatments slightly increased respiration, SAD SiNPs were found to inhibit mitochondrial function, reduce ATP generation, increase reliance on glycolysis, and reduce glycolytic reserve. Metabolomic analysis following 24 hours of exposure found several cellular energetics pathways (e.g., fatty acid metabolism, glycolysis, and TCA cycle) significantly altered across ash-based treatments. Such changes indicate that exposure to sugarcane ash and its derivatives can promote mitochondrial dysfunction and disrupt metabolic activity of human PCT cells.