Identification of ARNT-regulated BIRC3 as the target factor in cadmium renal toxicity

Abstract

Cadmium (Cd) is an environmental contaminant that exhibits renal toxicity. The target transcription factors involved in Cd renal toxicity are still unknown. In this study, we demonstrated that Cd decreased the activity of the ARNT transcription factor, and knockdown of ARNT significantly decreased the viability of human proximal tubular HK-2 cells. Microarray analysis in ARNT knockdown cells revealed a decrease in the expression of a number of genes, including a known apoptosis inhibitor, BIRC3, whose gene and protein expression level was also decreased by Cd treatment. Although the BIRC family consists of 8 members, Cd suppressed only BIRC3 gene expression. BIRC3 is known to suppress apoptosis through the inhibition effect on caspase-3. Knockdown of BIRC3 by siRNA as well as Cd treatment increased the level of active caspase-3. Moreover, knockdown of BIRC3 not only triggered cell toxicity and apoptosis but also strengthened Cd toxicity in HK-2 cells. Meanwhile, the activation of caspase-3 by suppression of BIRC3 gene expression was mostly specific to Cd and to proximal tubular cells. These results suggest that Cd induces apoptosis through the inhibition of ARNT-regulated BIRC3 in human proximal tubular cells.

Effect of chronic cadmium exposure on the gene expression of Birc family in the mouse kidney and liver

“…These results suggest that Cd may suppress BIRC3 gene expression specifical- ly in the kidney. Our previous research indicated that Cd-induced suppression of BIRC3 gene expression increased the level of the active form of caspase-3 (Lee et al, 2017). However, recent studies have shown that BIRC family members are functionally non-equivalent and regulate caspase activities via distinct mechanisms (Choi et al, 2009;Eckelman and Salvesen, 2006;Tenev et al, 2005).…”

“…Our previous research demonstrated that Cd inhibited ARNT transcription factor activity in human proximal tubular cells (HK-2 cells) (Lee et al, 2017). Furthermore, we showed that Cd decreased the gene expression of BIRC3, an apoptosis-inhibiting factor, through the suppression of ARNT activity.…”

“…BIRC3 is one of eight members (seven members in mice) of the BIRC family (LaCasse et al, 2008). Cd has been shown to suppress only BIRC3 expression in HK-2 cells; moreover, methylmercury and arsenic did not suppress BIRC3 (Birc3) gene expression in human neuroblastoma and mouse hepatocytes, respectively (Lee et al, 2017). In this study, we examined the expression of Birc family genes in the kidney and liver of mice chronically exposed to Cd.…”

Transcription Factors and Downstream Genes in Cadmium Toxicity

“…Protein/DNA arrays were used to identify transcription factors of which the activities are altered by nontoxic levels of Cd in NRK-52E and HK-2 cells. [27][28][29] Protein/DNA arrays screen a maximum of 345 transcription factors with activities that can be affected by a test substance. Cd downregulated the activity of a diverse set of transcription factors.…”

Comprehensive Analysis of BIRC Family Gene Expression Changes by Mercury Compounds and Arsenic Exposure in Neuroblastoma, Kidney, and Hepatic Cells

“…[1][2][3][4] Our previous study demonstrated that cadmium, which causes chronic renal toxicity, induced apoptosis in human proximal tubular cells (HK-2 cells) and in the mouse kidney. 5,6) Strikingly, cadmium-induced apoptosis involves BIRC3 gene suppression. 5) BIRC3 is a member of the BIRC family of apoptosis inhibitors, which consists of eight family members in human and seven family members in mouse.…”