title: Nicotine-Induced Apoptosis in Human Renal Proximal Tubular Epithelial Cells.
abstract: BACKGROUND
  Nicotine is, to a large extent, responsible for smoking-mediated renal dysfunction. This study investigated nicotine's effects on renal tubular epithelial cell apoptosis in vitro and it explored the mechanisms underlying its effects.
  
  
  METHODS
  Human proximal tubular epithelial (HK-2) cells were treated with nicotine. Cell viability was examined by using the WST-1 assay. Intracellular levels of reactive oxygen species (ROS) and the expression of mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) proteins were determined. The messenger ribonucleic acid and the protein expression associated with the nicotine acetylcholine receptors (nAChRs) in HK-2 cells was examined, and apoptosis was detected using flow cytometry, cell cycle analysis, and immunoblot analysis.
  
  
  RESULTS
  The HK-2 cells were endowed with nAChRs. Nicotine treatment reduced cell viability dose dependently, increased ROS levels, and increased extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 MAPK expression. Nicotine increased NF-κB activation, which was attenuated by N-acetyl-L-cysteine, and ERK and JNK inhibitors, but was not affected by a p38 MAPK inhibitor. Nicotine increased the Bax/Bcl-2 ratio, which was attenuated by N-acetyl-L-cysteine, the NF-κB inhibitor, Bay 11-7082, and hexamethonium, a non-specific nAChR blocker. Flow cytometry revealed nicotine-induced G2/M phase arrest. While nicotine treatment increased the expression of phosphorylated cdc2 and histone H3, a marker of G2/M phase arrest, hexamethonium and Bay 11-7082 pretreatment reduced their expression.
  
  
  CONCLUSIONS
  Nicotine caused apoptosis in HK-2 cells by inducing ROS generation that activated the NF-κB signaling pathway via the MAPK pathway and it arrested the cell cycle at the G2/M phase. Nicotine-induced apoptosis in HK-2 cells involves the nAChRs.
authors.affiliation: Department of Internal Medicine, Chonnam National University Medical School, Gwangju, Korea.
authors.forename: Chang Seong
authors.initials: CS
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Chonnam National University Medical School, Gwangju, Korea.
authors.forename: Joon Seok
authors.initials: JS
authors.lastname: Choi
authors.affiliation: Department of Internal Medicine, Chonnam National University Medical School, Gwangju, Korea.|Department of Physiology, Chonnam National University Medical School, Gwangju, Korea.
authors.forename: Soo Yeon
authors.initials: SY
authors.lastname: Joo
authors.affiliation: Department of Internal Medicine, Chonnam National University Medical School, Gwangju, Korea.
authors.forename: Eun Hui
authors.initials: EH
authors.lastname: Bae
authors.affiliation: Department of Internal Medicine, Chonnam National University Medical School, Gwangju, Korea.
authors.forename: Seong Kwon
authors.initials: SK
authors.lastname: Ma
authors.affiliation: Department of Physiology, Chonnam National University Medical School, Gwangju, Korea.
authors.forename: JongUn
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine, Chonnam National University Medical School, Gwangju, Korea.
authors.forename: Soo Wan
authors.initials: SW
authors.lastname: Kim
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D059566:M Phase Cell Cycle Checkpoints / Q000187:drug effects; D016328:NF-kappa B / Q000378:metabolism; D009538:Nicotine / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D011978:Receptors, Nicotinic / Q000378:metabolism*
chemical_list: D016328:NF-kappa B; D017382:Reactive Oxygen Species; D011978:Receptors, Nicotinic; D009538:Nicotine; D048049:Extracellular Signal-Regulated MAP Kinases