Background Apoptosis plays a crucial role in not only renal physiological homeostasis but also development of renal damage. Hyperuricemia is well known to lead to impairment of renal function.
Objectives The aim of this study is to clarify the mechanism of monosodium urate (MSU)-medicated apoptosis of renal cells.
Methods The quantitative real time-polymerase chain reaction and immonoblotting for Bcl-2, caspase-9, caspase-3, iNOS, COX-2, interleukin-1b (IL-1b), or IL-18 using human embryonic kidney 293 (HEK293) cell line, which was stimulated by MSU crystals. Fluorescence-activated cell sorter (FACS) for apoptosis was performed using annexin V. Reactive oxygen species (ROS) assay was measured. siRNA IL-1b was used for blocking IL-1b expression.
Results MSU crystals promoted ROS generation and IL-1b and IL-18 mRNA expressions in HEK293 cells, which were inhibited by ascorbic acid. Exposure of MSU crystals to HEK293 cells induced caspase-dependent apoptosis pathway through down-regulation of Bcl-2 and enhanced caspase-3 and caspase-9 expression in gene and protein levels, which were significantly reversed by ascorbic acid. Enhanced annexin V positive cells by MSU crystals were attenuated by ascorbic acid and siRNA IL-1b. ROS generation by MSU crystals activated TNF receptor associated factor-6 and mitogen-activated protein kinases (MAPKs) of IL-1b signaling. Inhibitors for MAPKs attenuated ROS production. Blocking IL-1b expression using siRNA IL-1b inhibited caspase-dependent apoptosis pathway in HEK293 cells.
Conclusions ROS generated by MSU crystals promote renal apoptosis through mitochondrial caspase-dependent apoptosis pathway. It suggests that blocking ROS and IL-1b could be considered a therapeutic strategy in the prevention of renal damage caused by MSU crystals.
Acknowledgements This work was supported by a grant from the Research Institute of Medical Science, Catholic University of Daegu (2013).
Disclosure of Interest None declared