title: Nicotine Induces Podocyte Apoptosis through Increasing Oxidative Stress.
abstract: BACKGROUND
  Cigarette smoking plays an important role in the progression of chronic kidney disease (CKD). Nicotine, one of the major components of cigarette smoking, has been demonstrated to increase proliferation of renal mesangial cells. In this study, we examined the effect of nicotine on podocyte injury.
  
  
  METHODS
  To determine the expression of nicotinic acetylcholine receptors (nAChR subunits) in podocytes, cDNAs and cell lysate of cultured human podocytes were used for the expression of nAChR mRNAs and proteins, respectively; and mouse renal cortical sections were subjected to immunofluorescant staining. We also studied the effect of nicotine on podocyte nephrin expression, reactive oxygen species (ROS) generation (via DCFDA loading followed by fluorometric analysis), proliferation, and apoptosis (morphologic assays). We evaluated the effect of nicotine on podocyte downstream signaling including phosphorylation of ERK1/2, JNK, and p38 and established causal relationships by using respective inhibitors. We used nAChR antagonists to confirm the role of nicotine on podocyte injury.
  
  
  RESULTS
  Human podocytes displayed robust mRNA and protein expression of nAChR in vitro studies. In vivo studies, mice renal cortical sections revealed co-localization of nAChRs along with synaptopodin. In vitro studies, nephrin expression in podocyte was decreased by nicotine. Nicotine stimulated podocyte ROS generation; nonetheless, antioxidants such as N-acetyl cysteine (NAC) and TEMPOL (superoxide dismutase mimetic agent) inhibited this effect of nicotine. Nicotine did not modulate proliferation but promoted apoptosis in podocytes. Nicotine enhanced podocyte phosphorylation of ERK1/2, JNK, and p38, and their specific inhibitors attenuated nicotine-induced apoptosis. nAChR antagonists significantly suppressed the effects of nicotine on podocyte.
  
  
  CONCLUSIONS
  Nicotine induces podocyte apoptosis through ROS generation and associated downstream MAPKs signaling. The present study provides insight into molecular mechanisms involved in smoking associated progression of chronic kidney disease.
authors.affiliation: Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Hofstra North Shore LIJ Medical School, New York, United States of America.
authors.forename: Xiqian
authors.initials: X
authors.lastname: Lan
authors.affiliation: Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Hofstra North Shore LIJ Medical School, New York, United States of America.
authors.forename: Rivka
authors.initials: R
authors.lastname: Lederman
authors.affiliation: Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Hofstra North Shore LIJ Medical School, New York, United States of America.
authors.forename: Judith M
authors.initials: JM
authors.lastname: Eng
authors.affiliation: Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Hofstra North Shore LIJ Medical School, New York, United States of America.
authors.forename: Seyedeh Shadafarin Marashi
authors.initials: SS
authors.lastname: Shoshtari
authors.affiliation: Academic Renal Unit, Southmead Hospital, Bristol, United Kingdom.
authors.forename: Moin A
authors.initials: MA
authors.lastname: Saleem
authors.affiliation: Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Hofstra North Shore LIJ Medical School, New York, United States of America.
authors.forename: Ashwani
authors.initials: A
authors.lastname: Malhotra
authors.affiliation: Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Hofstra North Shore LIJ Medical School, New York, United States of America.
authors.forename: Pravin C
authors.initials: PC
authors.lastname: Singhal
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D002461:Cell Line, Transformed; D049109:Cell Proliferation / Q000187:drug effects; D003497:Cyclic N-Oxides / Q000494:pharmacology; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D048670:MAP Kinase Kinase 4 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D009538:Nicotine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D018733:Nicotinic Antagonists / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects*; D050199:Podocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000819:agonists* / Q000037:antagonists & inhibitors / Q000378:metabolism; D011978:Receptors, Nicotinic / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013113:Spin Labels; D046509:Tissue Culture Techniques; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism
chemical_list: D003497:Cyclic N-Oxides; D008565:Membrane Proteins; D018733:Nicotinic Antagonists; D047428:Protein Kinase Inhibitors; D017382:Reactive Oxygen Species; D011978:Receptors, Nicotinic; D013113:Spin Labels; C113267:nephrin; D009538:Nicotine; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; C001803:tempol; D000111:Acetylcysteine