Cytoprotection following endoplasmic reticulum stress protein induction in continuous cell lines

Area of Science:

• Cell Biology
• Toxicology
• Biochemistry

Background:

• Endoplasmic reticulum (ER) stress response induction previously showed increased tolerance to cellular toxins in vitro, particularly in renal and neuronal cells.
• Reactive intermediates contribute to toxicity across various tissues, prompting investigation into broader cytoprotective effects of ER stress.

Purpose of the Study:

• To determine if inducing an endoplasmic reticulum stress response provides general cytoprotection against various toxins in different cell types.
• To investigate the cell-type and toxin specificity of endoplasmic reticulum stress-induced cytoprotection.

Main Methods:

• Tunicamycin was used to induce ER stress in human hepatocytes (HepG2), rat hepatocytes (H4IIE), porcine kidney cells (LLC-PK1), and human lymphocytes (K562).
• ER stress protein induction (GRP78, GRP94, calreticulin, PDI) was confirmed via immunoblotting.
• Cytotoxicity was assessed after exposure to iodoacetamide, tert-butylhydrogenperoxide, menadione, sulfamethoxazole hydroxylamine, or N-acetyl-p-benzoquinoneimine.

Main Results:

• LLC-PK1 cells pretreated with tunicamycin showed a 2-6 fold increase in toxin concentration required to decrease viability.
• HepG2 and H4IIE cells exhibited modest protection against specific toxins (1.7-2.2 fold increase), while K562 cells showed no altered susceptibility.
• Protection varied significantly based on cell type and the specific toxin used.

Conclusions:

• The cytoprotective effect of inducing an endoplasmic reticulum stress response is not a general phenomenon.
• Protection is dependent on the specific cell type and the nature of the toxin.
• Differences in cell death pathways or ER stress protein function across cell types likely explain the observed variability.