Vascular endothelium derived endothelin-1 is required for normal heart function after chronic pressure overload in mice

Abstract

Background: Endothelin-1 participates in the pathophysiology of heart failure. The reasons for the lack of beneficial effect of endothelin antagonists in heart failure patients remain however speculative. The anti-apoptotic properties of ET-1 on cardiomyocytes could be a reasonable explanation. We therefore hypothesized that blocking the pro-apoptotic TNF-α pathway using pentoxifylline could prevent the deleterious effect of the lack of ET-1 in a model for heart failure.

Methods: We performed transaortic constriction (TAC) in vascular endothelial cells specific ET-1 deficient (VEETKO) and wild type (WT) mice (n = 5-9) and treated them with pentoxifylline for twelve weeks.

Results: TAC induced a cardiac hypertrophy in VEETKO and WT mice but a reduction of fractional shortening could be detected by echocardiography in VEETKO mice only. Cardiomyocyte diameter was significantly increased by TAC in VEETKO mice only. Pentoxifylline treatment prevented cardiac hypertrophy and reduction of fractional shortening in VEETKO mice but decreased fractional shortening in WT mice. Collagen deposition and number of apoptotic cells remained stable between the groups as did TNF-α, caspase-3 and caspase-8 messenger RNA expression levels. TAC surgery enhanced ANP, BNP and bcl2 expression. Pentoxifylline treatment reduced expression levels of BNP, bcl2 and bax.

Conclusions: Lack of endothelial ET-1 worsened the impact of TAC-induced pressure overload on cardiac function, indicating the crucial role of ET-1 for normal cardiac function under stress. Moreover, we put in light a TNF-α-independent beneficial effect of pentoxifylline in the VEETKO mice suggesting a therapeutic potential for pentoxifylline in a subpopulation of heart failure patients at higher risk.

Figure 1. TAC-induced cardiac hypertrophy and reduction of cardiac function in VEETKO mice was prevented by PTX.

(A) Heart weight to body weight ratio. (B) Cardiomyocyte diameter measured on hematoxylin-eosin stained sections. (C) Fractional shortening measured by echocardiography. Values are mean±sem, n = 6–9, Student's T-test: * p<0.05.

Figure 2. Apoptotic myocyte number and cardiac collagen deposition remained stable between the groups while TAC induced cardiomyocyte enlargement, significantly in VEETKO mice only.

TUNEL staining (left panel), hematoxylin-eosin staining (central panel) and Sirius red staining (right panel) show apoptotic cells, tissue structure and collagen deposition, respectively. Quantification of cardiomyocyte diameter based on hematoxylin-eosin staining is shown in figure 1C.

Figure 3. Gene expression level of (A) ET-1, (B) TNF-α, (C) ANP, (D) BNP, (E) bcl2, (F) bax,(H) caspase 3 and (I) caspase 8.

Messenger RNA expression levels were determined by real time-PCR analysis and normalized to actin expression using the ΔΔC_T method. (G) The expression ratio bax/bcl2 was also calculated. Values are mean±sem, n = 6–9, Student's T-test: * p<0.05; ** p<0.01.