Role of subcellular calcium redistribution in regulating apoptosis and autophagy in cadmium-exposed primary rat proximal tubular cells.
Ca2+signaling plays a vital role in regulating apoptosis and autophagy. We previously proved that cytosolic Ca2+overload is involved in cadmium (Cd)-induced apoptosis in rat proximal tubular (rPT) cells, but the source of elevated cytosolic Ca2+concentration ([Ca2+]c) and the effect of potential subcellular Ca2+redistribution on apoptosis and autophagy remain to be elucidated. Firstly, data showed that Cd-induced elevation of [Ca2+]cwas primarily generated intracellularly. Moreover, elevations of [Ca2+]cand mitochondrial Ca2+concentration ([Ca2+]mit) with depletion of endoplasmic reticulum (ER) Ca2+levels ([Ca2+]ER) were revealed in Cd-treated rPT cells, but this subcellular Ca2+redistribution was significantly suppressed by 2-Aminoethoxydiphenyl borate (2-APB). Elevated inositol 1,4,5-trisphosphate (IP3) levels with up-regulated IP3receptor (IP3R) protein levels were shown in Cd-exposed cells, confirming that IP3R-mediated ER Ca2+release results in the elevation of [Ca2+]c. Up-regulated sequestosome 1 (p62) protein levels and autophagic flux assay demonstrated that Cd impaired autophagic degradation, while N-acetylcysteine (NAC) markedly attenuated Cd-induced p62 and microtubule-associated protein 1 light chain 3-II (LC3-II) accumulation, implying that the inhibition of autophagic flux was due to oxidative stress. Furthermore, pharmacological modulation of [Ca2+]cwith 1,2-Bis (2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester (BAPTA-AM) and 2-APB alleviated Cd-mediated apoptosis, inhibition of autophagic degradation and subsequent cytotoxicity, while thapsigargin (TG) had the opposite regulatory effect on them. In summary, cytosolic calcium overload originated from IP3R-mediated ER Ca2+release has a negative impact on Cd nephrotoxicity through its promotion of apoptosis and inhibition of autophagic flux.
College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Daizong Road No. 61, Tai'an 271018, People's Republic of China.
Fei
F
Liu
Laboratory Animal Center of Shandong University of Traditional Chinese Medicine, Jinan 250355, People's Republic of China.
Zi-Fa
ZF
Li
College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Daizong Road No. 61, Tai'an 271018, People's Republic of China.
Zhen-Yong
ZY
Wang
College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Daizong Road No. 61, Tai'an 271018, People's Republic of China. Electronic address: wanglin2013@sdau.edu.cn.
Lin
L
Wang
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy / Q000187:drug effects*; D002104:Cadmium / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D051381:Rats
D002104:Cadmium; D002118:Calcium
Apoptosis; Autophagy; Cadmium; Cytosolic calcium overload; Endoplasmic reticulum; Proximal tubular cells