title: Glucotoxic conditions induce endoplasmic reticulum stress to cause caspase 3 mediated lamin B degradation in pancreatic β-cells: protection by nifedipine.
abstract: Nuclear lamins form the lamina on the interior of the nuclear envelope, and are involved in the regulation of various cellular processes, including DNA replication and chromatin organization. Despite this evidence, little is known about potential alterations in nuclear metabolism, specifically lamin structure and integrity in isolated β-cells subjected to stress conditions, including chronic exposure to hyperglycemia (i.e., glucotoxicity). Herein, we investigated effects of glucotoxic conditions on the catalytic activation of caspase 3 and the associated degradation of one of its substrate proteins, namely lamin-B. We report that incubation of insulin-secreting INS-1 832/13 cells, normal rat islets or human islets under glucotoxic conditions (20 mM; 12-48 h) results in the degradation of native lamin B leading to accumulation of the degraded products in non-relevant cellular compartments, including cytosol. Moreover, the effects of high glucose on caspase 3 activation and lamin B degradation were mimicked by thapsigargin, a known inducer of endoplasmic reticulum stress (ER stress). Nifedipine, a known blocker of calcium channel activation, inhibited high glucose-induced caspase 3 activation and lamin B degradation in these cells. 4-Phenyl butyric acid, a known inhibitor of ER stress, markedly attenuated glucose-induced CHOP expression (ER stress marker), caspase 3 activation and lamin B degradation. We conclude that glucotoxic conditions promote caspase 3 activation and lamin B degradation, which may, in part, be due to increased ER stress under these conditions. We also provide further evidence to support beneficial effects of calcium channel blockers against metabolic dysfunction of the islet β-cell induced by hyperglycemic conditions.
authors.affiliation: Beta-Cell Biochemistry Laboratory, John D. Dingell VA Medical Center and Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI 48201, United States.
authors.forename: Khadija
authors.initials: K
authors.lastname: Syeda
authors.forename: Abiy M
authors.initials: AM
authors.lastname: Mohammed
authors.forename: Daleep K
authors.initials: DK
authors.lastname: Arora
authors.forename: Anjaneyulu
authors.initials: A
authors.lastname: Kowluru
mesh_terms: D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D053148:Caspase 3 / Q000378:metabolism*; D002478:Cells, Cultured; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D005947:Glucose / Q000378:metabolism; D006801:Humans; D050417:Insulin-Secreting Cells / Q000187:drug effects* / Q000378:metabolism; D034921:Lamin Type B / Q000378:metabolism*; D008297:Male; D009543:Nifedipine / Q000494:pharmacology*; D010654:Phenylbutyrates / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D019284:Thapsigargin / Q000494:pharmacology; D051742:Transcription Factor CHOP / Q000378:metabolism
chemical_list: D002121:Calcium Channel Blockers; C497251:Ddit3 protein, rat; D034921:Lamin Type B; D010654:Phenylbutyrates; D051742:Transcription Factor CHOP; D019284:Thapsigargin; C075773:4-phenylbutyric acid; D053148:Caspase 3; D009543:Nifedipine; D005947:Glucose
keywords: 4-phenylbutyric acid; C/EBP homologous protein; CHOP; Caspase 3; ER; FTI; FTase; Glucotoxicity; Nif; Nifedipine; Nuclear lamin B; PBA; Pancreatic islet β-cell; Tg; endoplasmic reticulum; farnesyl transferase; farnesyl transferase inhibitor; nifedipine; thapsigargin