The role of Smad signaling in vascular and hematopoietic development revealed by studies using genetic mouse models

Activation of BMP4-pSmad1/5 pathway impairs the function of VSMCs in intracranial aneurysms

Intracranial aneurysms (IAs) are characterized by abnormal dilatation of the cerebral vessels. Vascular smooth muscle cells (VSMCs) are implicated in maintaining vascular homeostasis. Disordered VSMCs are one of the most common causes for occurrence and development of IAs. The bone morphogenetic protein 4 (BMP4) signalling pathway is involved in regulating cell proliferation, apoptosis, and differentiation. This study aimed to investigate the effects of BMP4 on VSMCs and its underlying mechanisms. BMP4 was upregulated in the VSMCs of IAs and caused apoptosis of VSMCs through Smad1/5 phosphorylation. In addition, BMP4 overexpression significantly promoted the proliferation and migration of VSMCs and induced a phenotypic transformation from contractile to inflammatory. Our findings facilitate further understanding of the occurrence and development of IAs and provide a potential therapeutic target.

Hydrogen sulfide suppresses transforming growth factor-β1-induced differentiation of human cardiac fibroblasts into myofibroblasts

In heart disease, transforming growth factor-β1 (TGF-β1) converts fibroblasts into myofibroblasts, which synthesize and secrete fibrillar type I and III collagens. The purpose of the present study was to investigate how hydrogen sulfide (H2S) suppresses TGF-β1-induced differentiation of human cardiac fibroblasts to myofibroblasts. Human cardiac fibroblasts were serum-starved in fibroblast medium for 16 h before exposure to TGF-β1 (10 ng mL(-1)) for 24 h with or without sodium hydrosulfide (NaHS, 100 µmol L(-1), 30 min pretreatment) treatment. NaHS, an exogenous H2S donor, potently inhibited the proliferation and migration of TGF-β1-induced human cardiac fibroblasts and regulated their cell cycle progression. Furthermore, NaHS treatment led to suppression of fibroblast differentiation into myofibroblasts, and reduced the levels of collagen, TGF-β1, and activated Smad3 in TGF-β1-induced human cardiac fibroblasts in vitro. We therefore conclude that H2S suppresses TGF-β1-stimulated conversion of fibroblasts to myofibroblasts by inhibiting the TGF-β1/Smad3 signaling pathway, as well as by inhibiting the proliferation, migration, and cell cycle progression of human cardiac myofibroblasts. These effects of H2S may play significant roles in cardiac remodeling associated with heart failure.

Expression of the potential therapeutic target CXXC5 in primary acute myeloid leukemia cells - high expression is associated with adverse prognosis as well as altered intracellular signaling and transcriptional regulation

The CXXC5 gene encodes a transcriptional activator with a zinc-finger domain, and high expression in human acute myeloid leukemia (AML) cells is associated with adverse prognosis. We now characterized the biological context of CXXC5 expression in primary human AML cells. The global gene expression profile of AML cells derived from 48 consecutive patients was analyzed; cells with high and low CXXC5 expression then showed major differences with regard to extracellular communication and intracellular signaling. We observed significant differences in the phosphorylation status of several intracellular signaling mediators (CREB, PDK1, SRC, STAT1, p38, STAT3, rpS6) that are important for PI3K-Akt-mTOR signaling and/or transcriptional regulation. High CXXC5 expression was also associated with high mRNA expression of several stem cell-associated transcriptional regulators, the strongest associations being with WT1, GATA2, RUNX1, LYL1, DNMT3, SPI1, and MYB. Finally, CXXC5 knockdown in human AML cell lines caused significantly increased expression of the potential tumor suppressor gene TSC22 and genes encoding the growth factor receptor KIT, the cytokine Angiopoietin 1 and the selenium-containing glycoprotein Selenoprotein P. Thus, high CXXC5 expression seems to affect several steps in human leukemogenesis, including intracellular events as well as extracellular communication.