Mast cells and epsilonPKC: a role in cardiac remodeling in hypertension-induced heart failure - PubMed (original) (raw)

Mast cells and epsilonPKC: a role in cardiac remodeling in hypertension-induced heart failure

Suresh Selvaraj Palaniyandi et al. J Mol Cell Cardiol. 2008 Dec.

Abstract

Heart failure (HF) is a chronic syndrome in which pathological cardiac remodeling is an integral part of the disease and mast cell (MC) degranulation-derived mediators have been suggested to play a role in its progression. Protein kinase C (PKC) signaling is a key event in the signal transduction pathway of MC degranulation. We recently found that inhibition of epsilonPKC slows down the progression of hypertension-induced HF in salt-sensitive Dahl rats fed a high-salt diet. We therefore determined whether epsilonPKC inhibition affects MC degranulation in this model. Six week-old male Dahl rats were fed with a high-salt diet to induce systemic hypertension, which resulted in concentric left ventricular hypertrophy at the age of 11 weeks, followed by myocardial dilatation and HF at the age of 17 weeks. We administered epsilonV1-2, an epsilonPKC-selective inhibitor peptide (3 mg/kg/day), deltaV1-1, a deltaPKC-selective inhibitor peptide (3 mg/kg/day), TAT (negative control; at equimolar concentration; 1.6 mg/kg/day) or olmesartan (angiotensin receptor blocker [ARB] as a positive control; 3 mg/kg/day) between 11 weeks and 17 weeks. Treatment with epsilonV1-2 attenuated cardiac MC degranulation without affecting MC density, myocardial fibrosis, microvessel patency, vascular thickening and cardiac inflammation in comparison to TAT- or deltaV1-1-treatment. Treatment with ARB also attenuated MC degranulation and cardiac remodeling, but to a lesser extent when compared to epsilonV1-2. Finally, epsilonV1-2 treatment inhibited MC degranulation in isolated peritoneal MCs. Together, our data suggest that epsilonPKC inhibition attenuates pathological remodeling in hypertension-induced HF, at least in part, by preventing cardiac MC degranulation.

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Figures

Fig. 1

Fig. 1. Disease progression in high-salt diet Dahl rats from 11 weeks to 17 weeks

Micrographs showing cardiac fibrosis at 11 weeks (A) and 17 weeks (B) are provided (X100). Perivascular and interstitial fibrosis at 11 weeks and 17 weeks respectively (C, D and E, F). (X400). The myocardial sections were stained with Masson’s Trichrome. Blue color depicts the fibrotic area versus the red-colored normal myocardial region. The extent of coronary vessel patency and intimal thickening (B, D) can be seen at 17 weeks (as indicated by black arrows). Hematoxylin-eosin (H-E) stained tissue from high-salt diet Dahl rats at 11 weeks depict almost no inflammation (G). At 17 weeks, there are more inflammatory cells in the myocardium (H). Magnification of G and H is X400. Representative micrograph from each group are shown. MC degranulation (I) and the number of MCs (J) were increased significantly in 17 week-old hypertensive rat hearts as compared with 11 week-old rat hearts. MCs were counted using toluidine blue-stained myocardial sections.*p < 0.05 vs. 11 weeks; n=3.

Fig. 2

Fig. 2. Attenuation of MC degranulation in myocardial tissue by εPKC inhibition

Shown are micrographs of heart sections from 17 week-old hypertensive Dahl rats treated with TAT (A), εV1-2 (B), δV1-1 (C) and ARB (D). Tissue was stained with toluidine blue. Violet color adjacent to darker violet stained cells are degranulating MCs, whereas dark blue-colored cells are MCs that did not discharge recently. TAT (A) and δV1-1 (C) treated myocardial sections show staining patterns that indicate MC degranulation (arrows). Boxed areas in panels A-D are magnified in A1-D1, respectively. Quantification graph of degranulated MCs (E). MCs showing partial or complete degranulation were counted as degranulating MCs. Data are provided as percent of total MCs. Degranulation of MCs decreased in εV1-2 and ARB treated rats, whereas TAT and δV1-1 treatments did not attenuate degranulation. MC density in heart. MC density is calculated by counting both degranulating and non-degranulating MCs and plotted as a graph (F). MCP-1 levels in the myocardium (G). Representative Western blot images of MCP-1 and GAPDH from each group and quantification of the band density from at least 5 different animals from each group are shown. The data are expressed as the mean ± SEM. *p < 0.05 and **p < 0.01 vs. TAT treatment; #p < 0.05 and ##p < 0.01 vs. δV1-1 treatment. n=3.

Fig. 3

Fig. 3. PMA-induced MC degranulation in isolated rat peritoneal MCs was inhibited by εV1-2 pretreatment

β-Hex release is considered as an index of MC degranulation. δV1-1 pretreatment did not alter PMA-induced MC degranulation. PMA-induced MC degranulation was comparable to a degranulating agent of MCs, compound 48/80. n=3 to 5. The data are expressed as the mean ± SEM. **p < 0.01 vs. vehicle; ##p < 0.01 vs. εV1-2 + PMA

Fig. 4

Fig. 4. Suppression of perivascular localization of TGFβ1 in hypertensive Dahl rats by εPKC inhibition

Immunohistochemical staining of myocardial TGFβ1 in 17 week-old hypertensive rats treated with TAT (A), εV1-2(B),δV1-1 (C) or ARB (D) (dark brown color): X400. Negative control for the immunostaining (without primary antibody) in the TAT treated animals is provided in E. The perivascular regions (circled areas) show more TGFβ1 staining in samples from TAT or δV1-1 treated animals as compared with εV1-2 -or ARB-treated animals; n=3.

Fig. 5

Fig. 5. εPKC inhibition causes reduction in coronary vasculopathy and myocardial inflammation in hypertensive rats

Masson’s Trichrome-stained sections are showing vasculopathy (intimal thickening and patency of medium sized coronary vessels) of hypertensive Dahl rats treated with TAT (A), εV1-2 (B), δV1-1 (C) and ARB (D); X400. The infiltration of inflammatory cells (indicated by asterisks) is shown by hematoxylin-eosin stained myocardial sections of hypertensive Dahl rats treated with TAT (E), εV1-2 (F), δV1-1 (G) and ARB (H); X400. Vessel patency of small coronary vessels is shown by yellow arrow heads of the H-E stained cardiac sections that were treated with TAT (I), εV1-2 (J), δV1-1 (K) and ARB (L). Quantitation of vessel patency (M) and inflammatory cells (N) is provided as graphs. The data are expressed as the mean ± SEM. *p < 0.05 and **p < 0.01 vs. TAT treatment; #p < 0.05 and ##p < 0.01 vs. δV1-1 treatment. NS-Not statistically significant compared with TAT treatment. n=3.

Fig. 6

Fig. 6. A scheme demonstrating how MCs in the myocardium may contribute to remodeling events and the role of εPKC in this process

Degranulating MCs are increased in the myocardium of hypertensive rats. MC degranulation, in turn, increases TGFβ1 levels (and other MC mediators) and thus promotes infiltration of inflammatory cells into the myocardium. All of this leads to increased perivascular and interstitial fibrosis (proliferation and activation of cardiac fibroblasts as well as secretion of collagen), and vasculopathy (not shown). Our data suggest that all these events are mediated, at least in part, by εPKC activation. The steps in the cascade that were inhibited by εPKC treatment in vivo are indicated in the scheme. However, whether these events are regulated by εPKC directly or indirectly remains to be determined.

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