Palmitate mediated diacylglycerol accumulation causes endoplasmic reticulum stress, Plin2 degradation, and cell death in H9C2 cardiomyoblasts.
We have previously shown that palmitate causes ER stress in primary cardiomyocytes and this was associated with a diffuse lipid staining histology. In contrast, oleate, which was non-toxic, led to the formation of abundant, clearly delineated lipid droplets. The aberrant lipid histology in palmitate treated cells led us to hypothesize that perhaps there was an impairment in lipid droplet formation, which could lead to accumulation of lipids in the ER and consequent ER stress. To test this hypothesis we treated H9C2s (a cardiomyoblast cell line) with either 300µM oleate or palmitate for 8h. We found that palmitate resulted in significantly less lipid droplet abundance despite elevated intracellular lipid accumulation. Next we showed that palmitate was packaged primarily as diacylglycerol (DAG), in contrast oleate formed primarily triacylglycerol (TAG). Furthermore, the palmitate induced DAG accumulated mostly in the ER, while oleate treatment resulted in accumulation of TAG primarily in lipid droplets. The palmitate-induced accumulation of lipid in the ER was associated with a strong ER stress response. Interestingly, we found that ER stress induced by either palmitate, tunicamycin, or thapsigargin led to the degradation of Plin2, an important lipid droplet binding protein. In contrast palmitate had little effect on either Plin3 or Plin5. Furthermore, we found that acute MG132 administration significantly attenuated palmitate mediated ER stress and cell death. This protection was associated with a moderate attenuation of Plin2 degradation.
Universite de Montréal, Department of Biomedical Science, Canada; Montreal Heart Institute, Canada.
Ali
A
Akoumi
Universite de Montréal, Department of Biomedical Science, Canada; Montreal Heart Institute, Canada.
Taha
T
Haffar
Universite de Montréal, Department of Biochemistry, Canada; Montreal Heart Institute, Canada.
Maria
M
Mousterji
McGill University, Department of Medicine, Canada.
Robert Scott
RS
Kiss
Universite de Montréal, Department of Surgery, Canada; Montreal Heart Institute, Canada. Electronic address: nicolas.bousette@umontreal.ca.
Nicolas
N
Bousette
D000818:Animals; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D004075:Diglycerides / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D005227:Fatty Acids / Q000378:metabolism; D007976:Leupeptins / Q000494:pharmacology; D066292:Lipid Droplets / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D019301:Oleic Acid / Q000494:pharmacology; D010084:Oxidation-Reduction / Q000187:drug effects; D019308:Palmitic Acid / Q000494:pharmacology*; D000070780:Perilipin-2 / Q000378:metabolism*; D061988:Proteasome Inhibitors / Q000494:pharmacology; D059748:Proteolysis / Q000187:drug effects; D051381:Rats
C011439:1,2-diacylglycerol; D004075:Diglycerides; D005227:Fatty Acids; D007976:Leupeptins; D000070780:Perilipin-2; C000602984:Plin2 protein, rat; D061988:Proteasome Inhibitors; D019301:Oleic Acid; D019308:Palmitic Acid; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde
Diabetic cardiomyopathy; ER stress; Lipid droplet; Lipotoxicity; Plin2