Supplementary Material for: Gene Microarray Integrated with High-Throughput Proteomics for the Discovery of Transthyretin in Rhabdomyolysis-Induced Acute Kidney Injury

Background/Aims: Rhabdomyolysis, one of the leading causes of acute kidney injury (AKI), develops after trauma, drug toxicity, infections, burns, and physical exertion. The aim of this study was to investigate differences in gene and protein expression to elucidate the pathogenesis of rhabdomyolysis (RM)-induced AKI. Methods: In this study, we used glycerol induced renal injury as a model of RM-induced AKI. Affymetrix U133 plus 2.0 microarrays were used to perform gene microarray analysis. Isobaric tagging with related and absolute quantitation (iTRAQ) labeling mass spectrometry (MS) was applied to screen and identify differentially expressed proteins between RM-induced AKI and normal murine renal tissue. Verification experiments included immunohistochemistry (IHC), real-time PCR, Western blotting, and the measurement of ATP and ROS production. HK-2 cells were incubated in vitro with ferrous myoglobin and pcDNA-TTR, followed by assays to detect cell proliferation, ROS and apoptosis. Results: According to gene microarray and iTRAQ-MS analysis, we screened 17 common elements. After multiple analyses, we selected transthyretin (TTR) as our focus and investigated TTR in the kidney. Verification experiments with IHC confirmed differential expression levels of TTR proteins. Furthermore, Western blotting showed a stepwise decrease in TTR in AKI renal tissues. Cell-based experiments showed that overexpression of TTR could improve HK-2 cell viability and inhibit apoptosis. TTR reduced apoptosis by decreasing the accumulation of reactive oxygen species (ROS). Conclusion: This study reports a possible mechanism for RM-induced AKI and suggests that reductions in TTR could increase the generation of ROS and induce apoptosis. TTR may be a potentially valuable target for RM-induced AKI.