Cadmium-induced Heme-Oxygenase-1 Expression Plays Dual Roles in Autophagy and Apoptosis and is Regulated by both PKC-δ and PKB/Akt Activation in NRK52E Kidney Cells

• Published in: Toxicology (Amsterdam) 2016-08, Vol.370, p.49-59
• Main Authors: So, Keum-Young, Oh, Seon-Hee
• Format: Article
• Language: English
• Subjects: Acetylcysteine - pharmacology; Activation; Animals; Apoptosis; Apoptosis - drug effects; Autophagy; Autophagy - drug effects; Cadmium; Cadmium - toxicity; Cell Line, Tumor; Cell Survival - drug effects; Cleavage; DNA Damage - drug effects; Emergency; Eukaryotic Initiation Factor-2 - genetics; Eukaryotic Initiation Factor-2 - metabolism; Exposure; Glycogen Synthase Kinase 3 - genetics; Glycogen Synthase Kinase 3 - metabolism; Heme Oxygenase (Decyclizing) - genetics; Heme Oxygenase (Decyclizing) - metabolism; Heme oxygenase-1; Inhibitory Concentration 50; Kidney - cytology; Kidney - drug effects; Kinases; NRK52E cells; Oxidative Stress - drug effects; Pharmacology; Phosphorylation; Poly (ADP-Ribose) Polymerase-1 - antagonists & inhibitors; Poly (ADP-Ribose) Polymerase-1 - genetics; Poly (ADP-Ribose) Polymerase-1 - metabolism; Protein kinase B; Protein kinase C; Protein Kinase C-delta - genetics; Protein Kinase C-delta - metabolism; Proto-Oncogene Proteins c-akt - genetics; Proto-Oncogene Proteins c-akt - metabolism; Rats; Signal Transduction; Transcription Factor CHOP - genetics; Transcription Factor CHOP - metabolism; Up-Regulation; Viability
• ISSN: 0300-483X; 1879-3185
• DOI: 10.1016/j.tox.2016.09.010

Abstract Heme oxygenase-1 (HO-1) protects cells against cadmium (Cd)-induced oxidative stress. However, the mechanism underlying this protection is not well understood. In this study, we elucidated the role of HO-1 in Cd-induced cytotoxicity. Exposure of NRK52E cells to Cd induced protein kinase B (PKB)/Akt, protein kinase C (PKC)-δ, and glycogen synthase kinase (GSK) 3αb phosphorylation, and eukaryotic initiation factor (eIF) 2α dephosphorylation. Pharmacological inhibition of Akt resulted in HO-1 suppression and eIF2α activation, which partially suppressed CHOP and PARP-1 cleavage, but promoted autophagy and decreased cell viability. Pharmacological inactivation of PKC-δ markedly suppressed Cd-induced phospho-serine (p-Ser) GSK3αβ, and HO-1, and partially inhibited PARP-1 cleavage, but massively induced autophagy and decreased cell viability. Pharmacological upregulation of p-Ser GSK3αβ enhanced Cd-induced HO-1, CHOP, and PARP-1 cleavage, but decreased autophagy. Genetic deficiency of GSK3β suppressed HO-1 and PARP-1 cleavage and increased autophagy. Genetic suppression of HO-1 reduced Cd-induced PARP-1 cleavage, but increased LC3-II. Cd exposure led to accumulation of p-PKC-δ, p-Ser GSK3αβ, and HO-1 in the nucleus and particulate fractions, suggesting that they have dual functions in response to Cd. N -acetylcysteine treatment suppressed Cd-induced activation of PKC-δ and Akt. These results indicate that HO-1 induced by Cd exposure is regulated by PKC-δ, p-Ser GSK3αβ, and PKB/Akt, which restrain autophagic cell death, but mildly induce apoptosis in NRK52E cells. Together, the results suggest that HO-1 expression in response to Cd maintains cellular homeostasis during oxidative stress.