PKCbII Inhibition in Heart Failure Figure 1. Protein quality control disruption and PKCbII activation during progression of heart failure in a post-myocardial infarction (MI) model of HF in rats. A. MI-induced HF protocol (10 weeks follow up) and example of heart morphology and echo data before (left) and 4 weeks after myocardial infarction (right) in rats. B. Cardiac fractional shortening, C. Oxidized protein levels, D. Soluble oligomer level and E. Proteasomal activity during the progression of cardiac dysfunction induced by myocardial infarction. *, p,0.05 compared to week 0 (before surgery). 1, p,0.05 compared to week 1 after surgery. {, p,0.05 compared to week 2 after surgery. F. Concordance between fractional shortening and proteasomal activity, and G. Concordance between accumulation of misfolded cardiac proteins and oxidized proteins at weeks 0, 1, 2, 4 and 10 after myocardial infarction surgery in rats, H. Cardiac fractional shortening, proteasomal activity, oxidized and misfolded protein levels during the progression of cardiac dysfunction induced by myocardial infarction. I. The levels of total PKC isozymes (white bars) and translocated active PKCs (gray bars; Triton-soluble proteins or the particulate fraction/total fraction) at 10 weeks after myocardial infarction relative to control, age-matched rats (n = 6). Total proteins and Triton-soluble proteins of the particulate fraction were normalized against GAPDH and Gao, respectively. Representative blots are of PKCbII total level and translocation to particulate fraction. All biochemical analyses were performed in the ventricular remote area. Error bars indicate s.e.m. *, p,0.05 compared to control-TAT. J. PKCbII activity at 10 weeks after myocardial infarction relative to control age-matched rats (n = 3). *, p,0.05 compared to control. doi:10.1371/journal.pone.0033175.g001 Sustained PKCbII inhibition and cardiac PQC in the hypertension-induced heart failure model We next determined whether the role of PKCbII and PQC in heart failure is independent of the etiology of HF, using a hypertension-induced heart failure model in Dahl salt-sensitive rats (Fig. 5A). When placed on a high-salt diet from the age of 6 weeks, Dahl rats exhibit high blood pressure (230 vs. 160 mmHg), as previously reported [13]. These hypertensive rats develop compensatory left ventricular hypertrophy by the age of 11 weeks, and die from heart failure between 16 to 21 weeks [13,20]. Here we show that 17 week-old hypertensive Dahl salt-sensitive rats also exhibit decreased cardiac proteasomal ATP-dependent proteolytic activity and increased levels of oxidized proteins and soluble misfolded protein oligomers (Fig. 5B–D). Similar to the effect of PKCbII inhibition in the myocardial infarction-induced HF model in rats, sustained treatment with bIIV5-3 (but not the bI inhibitor) between weeks 11–17, reduced PKCbII activity to basal levels (Fig. 5A), restored ATP-dependent proteasomal activity and decreased the levels of misfolded cardiac proteins to those seen in control animals (Fig. 5B–D). Importantly, bIIV5-3 (but not the bI inhibitor) treatment prevented the decrease in fractional shortening in hypertensive rats (Fig. 5E). Further, while treated with the PKCbII inhibitor (between weeks 11–17), none of the hypertensive rats died, as compared with 60% death of hypertensive rats treated with vehicle control or the selective inhibitor of the alternatively spliced form, bIPKC (Fig. 5F). PLoS ONE | www.plosone.org 3 March 2012 | Volume 7 | Issue 3 | e33175