Feedback regulation of coronary artery disease susceptibility gene ADTRP and LDL receptors LDLR/CD36/LOX-1 in endothelia cell functions involved in atherosclerosis

A high level of low-density lipoprotein cholesterol (LDL) is one of the most important risk factors for coronary artery disease (CAD), the leading cause of death worldwide. However, a low concentration of LDL may be protective. Genome-wide association studies revealed that variation in ADTRP gene increased the risk of CAD. In this study, we found that a low concentration of oxidized-LDL induced the expression of ADTRP. Further analyses showed that knockdown of the expression of LDL receptor genes LDLR, CD36, or LOX-1 significantly downregulated ADTRP expression, whereas overexpression of LDLR/CD36/LOX-1 markedly increased ADTRP expression through the NF-κB pathway. Like ADTRP, LDLR, CD36 and LOX-1 were all involved in endothelial cell (EC) functions relevant to the initiation of atherosclerosis. Downregulation of LDLR/CD36/LOX-1 promoted monocyte adhesion to ECs and transendothelial migration of monocytes by increasing expression of ICAM-1, VCAM-1, E-selectin and P-selectin, decreased EC proliferation and migration, and increased EC apoptosis, thereby promoting the initiation of atherosclerosis. Opposite effects were observed with the overexpression of ADTRP and LDLR/CD36/LOX-1 in ECs. Interestingly, through the NF-κB and AKT pathways, overexpression of ADTRP significantly upregulated the expression of LDLR, CD36, and LOX-1, and knockdown of ADTRP expression significantly downregulated the expression of LDLR, CD36, and LOX-1. These data suggest that ADTRP and LDL receptors LDLR/CD36/LOX-1 positively regulate each other, and form a positive regulatory loop that regulates endothelial cell functions, thereby providing a potential protective mechanism against atherosclerosis. Our findings provide a new molecular mechanism by which deregulation of ADTRP and LDLR/CD36/LOX-1 promote the development of atherosclerosis and CAD.     

Cancer spheroids derived exosomes reveal more molecular features relevant to progressed cancer

Cancer cell spheroids have been shown to be more physiologically relevant to native tumor tissue than monolayer 2D culture cells. Due to enhanced intercellular communications among cells in spheroids, spheroid secreted exosomes which account for transcellular transportation should exceed those from 2D cell culture and may display a different expression pattern of miRNA or protein. To test this, we employed a widely used pancreatic cancer cell line, PANC-1, to create 3D spheroids and compared exosomes generated by both 2D cell culture and 3D PANC-1 spheroids. We further measured and compared exosomal miRNA and GPC-1 protein expression with qRT-PCR and enzyme-linked immunosorbent assay, respectively. It showed that PANC-1 cells cultured in 3D spheroids can produce significantly more exosomes than PANC-1 2D cells and exosomal miRNA and GPC-1 expression derived from spheroids show more features relevant to the progression of pancreatic cancer. These findings point to the potential importance of using spheroids as in vitro model to study cancer development and progression.     

A Kelch Motif-Containing Serine/Threonine Protein Phosphatase Determines the Large Grain QTL Trait in Rice

A thorough understanding of the genetic basis of rice grain traits is critical for the improvement of rice (Oryza sativa L.) varieties. In this study, we generated an F₂ population by crossing the large‐grain japonica cultivar CW23 with Peiai 64 (PA64), an elite indica small‐grain cultivar. Using QTL analysis, 17 QTLs for five grain traits were detected on four different chromosomes. Eight of the QTLs were newly‐identified in this study. In particular, qGL3‐1, a newly‐identified grain length QTL with the highest LOD value and largest phenotypic variation, was fine‐mapped to the 17 kb region of chromosome 3. A serine/threonine protein phosphatase gene encoding a repeat domain containing two Kelch motifs was identified as the unique candidate gene corresponding to this QTL. A comparison of PA64 and CW23 sequences revealed a single nucleotide substitution (C→A) at position 1092 in exon 10, resulting in replacement of Asp (D) in PA64 with Glu (E) in CW23 for the 364^th amino acid. This variation is located at the D position of the conserved sequence motif AVLDT of the Kelch repeat. Genetic analysis of a near‐isogenic line (NIL) for qGL3‐1 revealed that the allele qGL3‐1 from CW23 has an additive or partly dominant effect, and is suitable for use in molecular marker‐assisted selection.     

Fibrillar seeds alleviate amyloid-β cytotoxicity by omitting formation of higher-molecular-weight oligomers

Amyloid-β (Aβ) peptides can exist in distinct forms including monomers, oligomers and fibrils, consisting of increased numbers of monomeric units. Among these, Aβ oligomers are implicated as the primary toxic species as pointed by multiple lines of evidence. It has been suggested that toxicity could be rendered by the soluble higher-molecular-weight (high-n) Aβ oligomers. Yet, the most culpable form in the pathogenesis of Alzheimer’s disease (AD) remains elusive. Moreover, the potential interaction among the insoluble fibrils that have been excluded from the responsible aggregates in AD development, Aβ monomers and high-n oligomers is undetermined. Here, we report that insoluble Aβ fibrillar seeds can interact with Aβ monomers at the stoichiometry of 1:2 (namely, each Aβ molecule of seed can bind to two Aβ monomers at a time) facilitating the fibrillization by omitting the otherwise mandatory formation of the toxic high-n oligomers during the fibril maturation. As a result, the addition of exogenous Aβ fibrillar seeds is seen to rescue neuronal cells from Aβ cytotoxicity presumably exerted by high-n oligomers, suggesting an unexpected protective role of Aβ fibrillar seeds.     

Cancer-associated adipocytes promote the invasion and metastasis in breast cancer through LIF/CXCLs positive feedback loop

Cancer-associated adipocytes (CAAs), which are adipocytes transformed by cancer cells, are of great importance in promoting the progression of breast cancer. However, the underlying mechanisms involved in the crosstalk between cancer cells and adipocytes are still unknown. Here we report that CAAs and breast cancer cells communicate with each other by secreting the cytokines leukemia inhibitory factor (LIF) and C-X-C subfamily chemokines (CXCLs), respectively. LIF is a pro-inflammatory cytokine secreted by CAAs, which promotes migration and invasion of breast cancer cells via the Stat3 signaling pathway. The activation of Stat3 induced the secretion of glutamic acid-leucine-arginine (ELR) motif CXCLs (CXCL1, CXCL2, CXCL3 and CXCL8) in tumor cells. Interestingly, CXCLs in turn activated the ERK1/2/NF-κB/Stat3 signaling cascade to promote the expression of LIF in CAAs. In clinical breast cancer pathology samples, the up-regulation of LIF in paracancerous adipose tissue was positively correlated with the activation of Stat3 in breast cancer. Furthermore, we verified that adipocytes enhanced lung metastasis of breast cancer cells, and the combination of EC330 (targeting LIF) and SB225002 (targeting C-X-C motility chemokine receptor 2 (CXCR2)) significantly reduced lung metastasis of breast cancer cells in vivo. Our findings reveal that the interaction of adipocytes with breast cancer cells depends on a positive feedback loop between the cytokines LIF and CXCLs, which promotes breast cancer invasion and metastasis.