A proteasome inhibitor confers cardioprotection.
OBJECTIVE
In several cell types, proteasome inhibitors like carbobenzoxyl-leucinyl-leucinyl-leucinal (MG132) induce the 72 kDa heat shock protein (Hsp72) and exert cell protective effects. However, data in cardiomyocytes are currently lacking.


RESULTS
We investigated the effects of MG132 in cultured neonatal rat cardiomyocytes. MG132 time- and concentration-dependently induced Hsp72 and Hsp32 at mRNA and protein levels. Although Hsp60 mRNA was induced, Hsp60 protein levels were not altered. MG132 activated p38 MAP kinase already after 0.5 h. Hsp mRNA induction started after 2 h of MG132 treatment. Subsequently, Hsp72 and Hsp32 protein levels were increased after 4 h. SB202190, an inhibitor of p38 MAP kinase, concentration-dependently attenuated MG132-induced Hsp72-and Hsp32-elevations (by 59% and 41%, respectively, at 1 microM SB202190). In contrast, herbimycin A, a known inductor of Hsp72 in cardiomyocytes, enhanced the MG132-induced Hsp72 and Hsp32 expression even further: additionally applied 2 microM herbimycin A induced Hsp72 and Hsp32 about 2-fold higher than 1 microM MG132 alone. MG132 (1 microM) decreased the hyperthermia- or hydrogen peroxide-induced release of lactate dehydrogenase by 45% and by 35%, respectively (P<0.05, n=5). MG132 (1 microM) prolonged the spontaneous beating time of cardiomyocytes at 46 degrees C from 5+/-2 min (control hyperthermia) to 28+/-5 min (P<0.05, n=4). Thus, inhibition of the proteasome function by MG132 protects cardiomyocytes against hyperthermic or oxidative injury. This protective effect and Hsp induction were abolished by 1 microM SB202190.


CONCLUSIONS
Proteasome inhibition results in p38 MAP kinase-dependent induction of Hsp72 and Hsp32 and might be a novel cardioprotective modality.
Lüss
Hartmut
H
Institut für Pharmakologie und Toxikologie, Westfälische Wilhelms-Universität Münster, Domagkstrasse 12, Germany. luss@uni-muenster.de
Schmitz
Wilhelm
W
Neumann
Joachim
J
D000818:Animals; D016227:Benzoquinones; D015153:Blotting, Western; D002478:Cells, Cultured; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005334:Fever / Q000378:metabolism; D050884:HSP72 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics / Q000378:metabolism*; D051547:Heme Oxygenase-1; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D047029:Lactams, Macrocyclic; D007976:Leupeptins / Q000494:pharmacology*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D018384:Oxidative Stress; D010210:Papillary Muscles / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D011809:Quinones / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017828:Rifabutin / Q000031:analogs & derivatives; D048051:p38 Mitogen-Activated Protein Kinases
D016227:Benzoquinones; D015853:Cysteine Proteinase Inhibitors; D004791:Enzyme Inhibitors; D050884:HSP72 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D007093:Imidazoles; D047029:Lactams, Macrocyclic; D007976:Leupeptins; D011725:Pyridines; D011809:Quinones; D012333:RNA, Messenger; D017828:Rifabutin; C020754:herbimycin; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde