The progressive loss of cardiomyocytes caused by cell death leads to cardiac dysfunction and heart failure (HF). Rapamycin has been shown to be cardioprotective in pressure-overloaded and ischemic heart diseases by regulating the mechanistic target of rapamycin (mTOR) signaling network. However, the impact of rapamycin on cardiomyocyte death in chronic HF remains undetermined. Therefore, in the current study we addressed this issue using a rat myocardial infarction (MI)-induced chronic HF model induced by ligating the coronary artery. Following surgery, rats were randomly divided into six groups, including the sham-, vehicle- and rapamycin-operated groups, at 8 or 12 weeks post-MI. A period of 4 weeks after MI induction, the rats were treated with rapamycin (1.4 mg-kg-day) or vehicle for 4 weeks. Cardiac function was determined using echocardiography, the rats were subsequently euthanized and myocardial tissues were harvested for histological and biochemical analyses. In the cell culture experiments with H9c2 rat cardiomyocytes, apoptosis was induced using angiotensin II (100 nM; 24 h). Cardiomyocyte apoptosis and autophagy were assessed via measuring apoptosis- and autophagy-associated proteins. The activities of mTOR complex 1 (mTORC1) and mTORC2 were evaluated using the phosphorylation states of ribosomal S6 protein and Akt, respectively. The activity of the endoplasmic reticulum (ER) stress pathway was determined using the levels of GRP78, caspase-12, phospho-JNK and DDIT3. Echocardiographic and histological measurements indicated that rapamycin treatment improved cardiac function and inhibited cardiac remodeling at 8 weeks post-MI. Additionally, rapamycin prevented cardiomyocyte apoptosis and promoted autophagy at 8 weeks post-MI. Rapamycin treatment for 4 weeks inhibited the mTOR and ER stress pathways. Furthermore, rapamycin prevented angiotensin II-induced H9c2 cell apoptosis and promoted autophagy by inhibiting the mTORC1 and ER stress pathways. These results demonstrated that rapamycin reduced cardiomyocyte apoptosis and promoted cardiomyocyte autophagy, by regulating the crosstalk between the mTOR and ER stress pathways in chronic HF.

In order to identify the effects of land-use/ cover types, soil types and soil properties on the soilatmosphere exchange of greenhouse gases (GHG) in semiarid grasslands as well as provide a reliable estimate of the midsummer GHG budget, nitrous oxide (N 2 O), methane (CH 4 ) and carbon dioxide (CO 2 ) fluxes of soil cores from 30 representative sites were determined in the upper Xilin River catchment in Inner Mongolia. The soil N 2 O emissions across all of the investigated sites ranged from 0.18 to 21.8 μg N m -2 h -1 , with a mean of 3.4 μg N m -2 h -1 and a coefficient of variation (CV, which is given as a percentage ratio of one standard deviation to the mean) as large as 130%. CH 4 fluxes ranged from -88.6 to 2,782.8 μg C m -2 h -1 (with a CV of 849%). Net CH 4 emissions were only observed from cores taken from a marshland site, whereas all of the other 29 investigated sites showed net CH 4 uptake (mean: -33.3 μg C m -2 h -1 ). CO 2 emissions from all sites ranged from 3.6 to 109.3 mg C m -2 h -1 , with a mean value of 37.4 mg C m -2 h -1 and a CV of 66%. Soil moisture primarily and positively regulated the spatial variability in N 2 O and CO 2 emissions (R 2 =0.15-0.28, P<0.05). The spatial variation of N 2 O emissions was also influenced by soil inorganic N contents (P< 0.05). By simply up-scaling the site measurements by the various land-use/cover types to the entire catchment area (3,900 km 2 ), the fluxes of N 2 O, CH 4 and CO 2 at the time of sampling (mid-summer 2007) were estimated at 29 t CO 2 -C-eq d -1 , -26 t CO 2 -C-eq d -1 and 3,223 t C d -1 , respectively. This suggests that, in terms of assessing the spatial variability of total GHG fluxes from the soils at a semiarid catchment/region, intensive studies may focus on CO 2 exchange, which is dominating the global warming potential of midsummer soil-atmosphere GHG fluxes. In addition, average GHG fluxes in midsummer, weighted by the areal extent of these land-use/cover types in the region, were approximately -30.0 μg C m -2 h -1 for CH 4 , 2.4 μg N m -2 h -1 for N 2 O and 34.5 mg C m -2 h -1 for CO 2 .

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