Effect of lithium on ventricular remodelling in infarcted rats via the Akt/mTOR signalling pathways

Figures

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  Figure 1. Western analysis of RhoA membrane fraction and cytosolic fraction from the border zone at day 3 after MI. (a) Representative Masson trichrome-stained section of a vehicle-treated heart at 4 weeks after infarction (blue colour, from 12 to 4 o’clock); Bar =2 mm. (b) Representative cardiomyocytes (magnification 400×) and quantitative analysis of the cardiomyocyte sizes in the remote zone. Staining with FITC-labelled wheat germ haemagglutinin of cross-sectional sections of myocardium; Bar =50 μm. (c) Representative sections from the remote area with Sirius Red staining (red, magnification 400×) at 4 weeks after infarction; Bar =50 μm. (S-Sa), saline-treated sham; (S-LiCl), LiCl-treated sham; (MI-Sa), saline-treated infarcted rat; (MI-LiCl), LiCl-treated infarcted rat. Each column and bar represents mean ± S.D. (n=5–6 per group). *P<0.05 compared with saline-treated sham; †P<0.05 compared with LiCl-treated sham; ‡P<0.05 compared with saline-treated infarcted group

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  Figure 2. Representative M-mode image Representative M-mode image reveals a hypokinetic-to-akinetic anterior wall and LV dilation in the infarcted hearts treated with either saline (c) or LiCl (d). There are markedly dilated LVEDD and LVESD in the saline-treated infarcted group compared with those in the LiCl-treated infarcted group.

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  Figure 3. Western blot in an in vivo study (Part 1 experiment) Western blots show the expression of p-Akt, p-4E-BP1 and p-ERK. There was a significant increase in the levels of p-Akt and p-4E-BP1 in the LiCl-treated infarcted rats compared with the saline-treated infarcted rats. Bar graphs represent the quantitative analysis and difference in the expression of p-Akt and p-4E-BP1, after they were normalized with corresponding total proteins respectively, in arbitrary units. The values are mean ± S.D. (n=5–6 per group). Experiments were replicated three times and results expressed as the mean value. S, sham; Sa, saline. *P<0.05 compared with saline-treated sham; †P<0.05 compared with LiCl-treated sham; ‡P<0.05 compared with saline-treated infarcted group.

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  Figure 4. Western blot in an ex vivo study (Part 2 experiment) Western blot analysis of 4E-BP1 and ERK to furthermore confirm the Akt and mTOR on kinase activity in homogenates of the LV from the remote zone in a rat-isolated infarcted heart model. A significantly increased p-4E-BP1 level is noted in the LiCl-treated group compared with that seen in the saline-treated group, which was attenuated after administering deguelin (a specific Akt inhibitor) and rapamycin (an mTORC1 inhibitor). The values are mean ± S.D. (n=5 per group). Experiments were replicated three times and results expressed as the mean value. *P<0.05 compared with saline-, LiCl-deguelin-, and LiCl-rapamycin-treated infarcted rats; †P<0.05 compared with saline-treated infarcted rats.

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  Figure 5. NFAT activity and RT-PCR of GATA4, ANP, β-MHC and skeletal α-actin Each mRNA was corrected for an mRNA level of cyclophilin. Each column and bar represents mean ± S.D. *P<0.05 compared with saline-treated sham; †P<0.05 compared with LiCl-treated sham; ‡P<0.05 compared with saline-treated infarcted group.

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  Figure 6. Signalling cascades leading to physiological and pathological hypertrophy after infarction The diagram summarizes the histological, molecular and pharmacological evidence. Inhibition of these signalling pathways by their respective inhibitors is indicated by the vertical lines. Our data suggest that lithium is efficient at selectively inhibiting important regulators involved in pathological hypertrophy (such as NFAT and ERK), while augmenting pathways involved in physiological hypertrophy (such as 4E-BP1).