Antibodies Against Potassium Channel Interacting Protein 2 Induce Necrosis in Isolated Rat Cardiomyocytes

Auto-antibodies against cardiac proteins have been described in patients with dilated cardiomyopathy. Antibodies against the C-terminal part of KChIP2 (anti-KChIP2 [C-12]) enhance cell death of rat cardiomyocytes. The underlying mechanisms are not fully understood. Therefore, we wanted to explore the mechanisms responsible for anti-KChIP2-mediated cell death. Rat cardiomyocytes were treated with anti-KChIP2 (C-12). KChIP2 RNA and protein expressions, nuclear NF-κB, mitochondrial membrane potential Δψm, caspase-3 and -9 activities, necrotic and apoptotic cells, total Ca2+ and K+ concentrations, and the effects on L-type Ca2+ channels were quantified. Anti-KChIP2 (C-12) induced nuclear translocation of NF-κB. Anti-KChIP2 (C-12)-treatment for 2 h significantly reduced KChIP2 mRNA and protein expression. Anti-KChIP2 (C-12) induced nuclear translocation of NF-κB after 1 h. After 6 h, Δψm and caspase-3 and -9 activities were not significantly changed. After 24 h, anti-KChIP2 (C-12)-treated cells were 75 ± 3% necrotic, 2 ± 1% apoptotic, and 13 ± 2% viable. Eighty-six ± 1% of experimental buffer-treated cells were viable. Anti-KChIP2 (C-12) induced significant increases in total Ca2+ (plus 11 ± 2%) and K+ (plus 18 ± 2%) concentrations after 5 min. Anti-KChIP2 (C-12) resulted in an increased Ca2+ influx through L-type Ca2+ channels. In conclusion, our results suggest that anti-KChIP2 (C-12) enhances cell death of rat cardiomyocytes probably due to necrosis. J. Cell. Biochem. 115: 678–689, 2014. © 2013 Wiley Periodicals, Inc.