Diffusion-induced lithium isotopic heterogeneity in olivines from peridotites of an oceanized mantle lithosphere at the Yunzhug ophiolite (central Tibet).

This paper reports lithium concentrations and isotopic compositions of olivines in the oceanized subcontinental lithospheric mantle (SCLM) peridotites of the Tibetan Yunzhug ophiolite. The results show systematic Li isotope changes with distance from the rim of olivine grains. δ7Li values of olivine in dunites decrease from + 10.46 to + 1.33‰ with increasing distance to olivine rim from 26.15 to 124.71 µm. A negative correlation of δ7Li and Li content in olivine from dunite and harzburgite indicates recent diffusive ingress of Li into the peridotites. The extremely heavy Li isotopic composition requires the seawater or seawater alteration endmember in the mixing model, and reveals Li diffusion from seawater into olivine. As in dunites, olivines in a harzburgite sample show similar variations in δ7Li as a function of distance from the grain rim (e.g., 6.01 to 1.73 in sample 14YZ13). We suggest that the behavior of Li in the oceanized SCLM peridotites may be controlled by Li diffusion from seawater, as Li activity in the liquid state is higher than the solid state in transporting Li through the olivines in the peridotites. This study supports that seawater Li diffusion is one of the important factors for the heterogeneity of mantle Li isotopes in ophiolites.

Follistatin-like 1 protects mesenchymal stem cells from hypoxic damage and enhances their therapeutic efficacy in a mouse myocardial infarction model.

BACKGROUND: Cell therapy remains the most promising approach against ischemic heart injury. However, poor survival of engrafted cells in ischemic sites diminishes its therapeutic efficacy. Follistatin-like 1 (Fstl1) is documented as a novel pro-survival cardiokine for cardiomyocytes, and it is protective during ischemic heart injury. In the present study, we characterize the potential of Fstl1 as an effective strategy to enhance hypoxia resistance of donor cells and optimize stem cell-based therapy. METHODS: Murine bone marrow-derived mesenchymal stem cells (MSCs) were expanded in monolayer culture and characterized by flow cytometry. MSCs were subjected to hypoxia to mimic cardiac ischemic environment. Expression of Fstl1 was monitored 0, 24, and 48 h following hypoxia. Constitutive expression of Fstl1 in MSCs was achieved by lentivirus-mediated Fstl1 overexpression. Genetically modified MSCs were further collected for cell death and proliferation assay following 48 h of hypoxic treatment. Acute myocardial infarction (MI) model was created by ligating the left anterior descending coronary artery, while control MSCs (MSCs-mCherry) or Fstl1-overexpressing MSCs (MSCs-Fstl1) were injected into the peri-infarct zone simultaneously. Subsequently, retention of the donor cells was evaluated on post-therapy 1, 3, & 7 days. Finally, myocardial function, infarct size, inflammation, and neovascularization of the infarcted hearts were calculated thereafter. RESULTS: Expression of Fstl1 in hypoxic MSCs declines dramatically in a time-dependent manner. In vitro study further demonstrated that Fstl1 promotes survival and proliferation of hypoxic MSCs. Moreover, Fstl1 significantly prolongs MSC survival/retention after implantation. Finally, transplantation with Fstl1-overexpressing MSCs significantly improves post-MI cardiac function by limiting scar formation, reducing inflammatory response, and enhancing neovascularization. CONCLUSIONS: Our results suggest Fstl1 is an intrinsic cardiokine promoting survival and proliferation of MSCs, thereby optimizing their engraftment and therapeutic efficacy during cell therapy.

Urolithin A shows anti-atherosclerotic activity via activation of class B scavenger receptor and activation of Nef2 signaling pathway.

BACKGROUND: This study investigates the therapeutic potential of urothelin A in attenuating atherosclerotic lesion in wistar rat models and explore the role of Scavenger receptor-class B type I (SR-BI) and activation of Nrf-2 singling pathway. METHODS: Wistar rats (n=48) were feed with high cholesterol diet supplemented with Vitamin D3 and subjected to balloon injury of the aorta. Three days prior to the aortal injury, rats (n=16) were administered urothelin A (3mg/kg/d; po). Positive control were rats receiving high cholesterol diet and balloon injury of the aorta (n=16). The sham group (n=16) consisted of rats fed on basal diet. After twelve weeks blood was collected from all animals for estimation of lipid and angiotensin II (Ang II) levels along, subsequently all animals were sacrificed and morphologic analysis of the aorta was performed. Expression of SR-BI and phosphorylated extracellular signal regulated kinase 1/2 (p-ERK1/2) protein were evaluated by Western blot. RESULTS: After twelve weeks of treatment with urolithin A, there was a significant decrease in the plasma lipid and Ang II levels and improvement of aortic lesion compared with the sham group. There was an increased expression of SR-BI and inhibition of p-ERK1/2 (p<0.05). The expression of SR-BI was inversely correlated with levels of Ang II. CONCLUSION: From the results it can be safely concluded that administration of urolithin A attenuates atherosclerosis via upregulation of SR-BI expression and inhibition of p-ERK1/2 levels.

MicroRNA-497 Inhibits Cardiac Hypertrophy by Targeting Sirt4.

Cardiac hypertrophy is an adaptive enlargement of the myocardium in response to overload pressure of heart. From abundant studies, a conclusion is drawn that many microRNAs (miRNAs) are associated with cardiac hypertrophy and heart failure. To investigate the role of microRNA-497 (miR-497) in myocardial hypertrophy, two models were established in this study from cell level to integral level. Cardiac hypertrophy was induced by using angiotensin Ⅱ (Ang Ⅱ) in vitro and was created by transverse abdominal aortic constriction (TAC) in vivo. There was a significant decrease expression of miR-497 in cardiac hypertrophy models. Moreover, overexpression of miR-497 inhibited myocardial hypertrophy both in vitro and in vivo without heart function variation. In addition, luciferase reporter assays demonstrated that Sirt4 was a direct target gene of miR-497. Taking together, our study indicates that miR-497 modulates cardiac hypertrophy by targeting Sirt4 and may serve as a potential therapeutic substance in the course.