Mitochondrial Ultrastructural Alterations and Declined M2 Receptor Density Were Involved in Cardiac Dysfunction in Rats after Long Term Treatment with Autoantibodies against M2 Muscarinic Receptor

Background

Previous studies showed that autoantibodies (M₂-AA) against the second extracellular loop of M₂ muscarinic receptor (M₂AChR-el2) from dilated cardiomyopathy (DCM) serum could induce DCM-like morphological changes in mice hearts. However, the effects of M₂-AA on the cardiac function during the process of DCM and the potential mechanisms are not fully known. The present study was designed to dynamically observe the cardiac function, mitochondrial changes, and M₂ receptor binding characteristics in rats long-term stimulated with M₂-AA in vivo.

Methods

M₂-AA-positive model was established by actively immunizing healthy male Wistar rats with synthetic M₂AChR-el2 peptide for 18 months. Meanwhile, vehicle group rats were administrated with physiological saline. The change of mitochondrial membrane potential (ΔΨm) was detected by radionuclide imaging. The ultrastructure of mitochondria was observed under electron microscopy. The M₂ receptor binding characteristics were determined by radioactive ligand binding assay.

Results

After immunization for 12 months, compared with vehicle group, M₂AChR-el2-immunized rats showed decreased myocardial contractility and cardiac diastolic function evidenced by declined maximal rate of rise of ventricular pressure and increased left ventricular end-diastolic pressure, respectively. Additionally, mitochondrial swelling and vacuolation were observed. At 18 months, M₂AChR-el2-immunized rats manifested significant decreased cardiac systolic and diastolic function and pathological changes such as enlargement of right ventricular cavity and wall thinning; and the mitochondrial damage was aggravated. Furthermore, the M₂ receptor maximum binding capacity (B_max) of the M₂AChR-el2-immunized rats significantly decreased, while the M₂ receptor dissociation constant (K_d) was increased.

Conclusions

Our study suggested that long-term stimulation with M₂-AA leaded to the ventricular dilatation and gradual deterioration of cardiac dysfunction. Mitochondrial damage and the down-regulation of M₂ receptor density and affinity may be involved in the process.     

MicroRNA-590 Inhibits Lipoprotein Lipase Expression and Prevents Atherosclerosis in apoE Knockout Mice

Recent studies have suggested that miR-590 may play critical roles in cardiovascular disease. This study was designed to determine the effects of miR-590 on lipoprotein lipase (LPL) expression and development of atherosclerosis in apolipoprotein E knockout (apoE^−/−) mice and explore the potential mechanisms. En face analysis of the whole aorta revealed that miR-590 significantly decreased aortic atherosclerotic plaque size and lipid content in apoE^−/− mice. Double immunofluorescence staining in cross-sections of the proximal aorta showed that miR-590 agomir reduced CD68 and LPL expression in macrophages in atherosclerotic lesions. MiR-590 agomir down-regulated LPL mRNA and protein expression as analyzed by RT-qPCR and western blotting analyses, respectively. Consistently, miR-590 decreased the expression of CD36 and scavenger receptor A1 (SRA1) mRNA and protein. High-performance liquid chromatography (HPLC)analysis confirmed that treatment with miR-590 agomir reduced lipid levels either in plasma orinabdominal cavity macrophages of apoE^−/− mice. ELISA analysis showed that miR-590 agomir decreased plasma levels of pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α), monocyte chemotactic protein-1 (MCP-1), interleukin-1β (IL-1β)and interleukin-6 (IL-6). In contrast, treatment with miR-590 antagomir prevented or reversed these effects. Taken together, these results reveal a novel mechanism of miR-590 effects, and may provide new insights into the development of strategies for attenuating lipid accumulation and pro-inflammatory cytokine secretion.     

SPX proteins regulate Pi homeostasis and signaling in different subcellular level

To cope with low phosphate (Pi) availability, plants have to adjust its gene expression profile to facilitate Pi acquisition and remobilization. Sensing the levels of Pi is essential for reprogramming the gene expression profile to adapt to the fluctuating Pi environment. AtPHR1 in Arabidopsis and OsPHR2 in rice are central regulators of Pi signaling, which regulates the expression of phosphate starvation-induced (PSI) genes by binding to the P1BS elements in the promoter of PSI genes. However, how the Pi level affects the central regulator to regulate the PSI genes have puzzled us for a decade. Recent progress in SPX proteins indicated that the SPX proteins play important role in regulating the activity of central regulator AtPHR1/OsPHR2 in a Pi dependent manner at different subcellular levels.     

Identification of kinship and occupant status in Mongolian noble burials of the Yuan Dynasty through a multidisciplinary approach

The Yuan Dynasty (AD 1271–1368) was the first dynasty in Chinese history where a minority ethnic group (Mongols) ruled. Few cemeteries containing Mongolian nobles have been found owing to their tradition of keeping burial grounds secret and their lack of historical records. Archaeological excavations at the Shuzhuanglou site in the Hebei province of China led to the discovery of 13 skeletons in six separate tombs. The style of the artefacts and burials indicate the cemetery occupants were Mongol nobles. However, the origin, relationships and status of the chief occupant (M1m) are unclear. To shed light on the identity of the principal occupant and resolve the kin relationships between individuals, a multidisciplinary approach was adopted, combining archaeological information, stable isotope data and molecular genetic data. Analysis of autosomal, mitochondrial and Y-chromosomal DNA show that some of the occupants were related. The available evidence strongly suggests that the principal occupant may have been the Mongol noble Korguz. Our study demonstrates the power of a multidisciplinary approach in elucidating information about the inhabitants of ancient historical sites.