Atheroprotective effects of methotrexate via the inhibition of YAP/TAZ under disturbed flow.

BACKGROUND: Atherosclerosis preferentially develops in regions of disturbed flow (DF). Emerging evidence indicates that yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ), which are both effectors of the Hippo pathway, sense different blood flow patterns and regulate atherosclerotic lesions. We previously found that methotrexate (MTX) reduces in-stent neoatherosclerosis, decreases the plaque burden, and has an effect on local fluid shear stress. Here, we investigated the atheroprotective effect of MTX under DF and the mechanisms underlying these properties. METHODS: Human umbilical vein endothelial cells (HUVECs) were subjected to biomechanical stretch using a parallel-plate flow system and treated with or without MTX at therapeutically relevant concentrations. Additionally, an extravascular device was used to induce DF in the left common carotid artery of C57BL/6 mice, followed by treatment with MTX or 0.9% saline. The artery was then assessed histopathologically after 4 weeks on a Western diet. RESULTS: We observed that MTX significantly inhibited DF-induced endothelial YAP/TAZ activation. Furthermore, it markedly decreased pro-inflammatory factor secretion and monocyte adhesion in HUVECs but had no effect on apoptosis. Mechanistically, AMPKa1 depletion attenuated these effects of MTX. Accordingly, MTX decreased DF-induced plaque formation, which was accompanied by YAP/TAZ downregulation in vivo. CONCLUSIONS: Taken together, we conclude that MTX exerts protective effects via the AMP-dependent kinase (AMPK)-YAP/TAZ pathway. These results provide a basis for the prevention and treatment of atherosclerosis via the inhibition of YAP/TAZ.

C1q/TNF-related protein 9 inhibits the cholesterol-induced Vascular smooth muscle cell phenotype switch and cell dysfunction by activating AMP-dependent kinase.

Vascular smooth muscle cells (VSMCs) switch to macrophage-like cells after cholesterol loading, and this change may play an important role in the progression of atherosclerosis. C1q/TNF-related protein 9 (CTRP9) is a recently discovered adipokine that has been shown to have beneficial effects on glucose metabolism and vascular function, particularly in regard to cardiovascular disease. The question of whether CTRP9 can protect VSMCs from cholesterol damage has not been addressed. In this study, the impact of CTRP9 on cholesterol-damaged VSMCs was observed. Our data show that in cholesterol-treated VSMCs, CTRP9 significantly reversed the cholesterol-induced increases in pro-inflammatory factor secretion, monocyte adhesion, cholesterol uptake and expression of the macrophage marker CD68. Meanwhile, CTRP9 prevented the cholesterol-induced activation of the TLR4-MyD88-p65 pathway and upregulated the expression of proteins important for cholesterol efflux. Mechanistically, as siRNA-induced selective gene ablation of AMPKα1 abolished these effects of CTRP9, we concluded that CTRP9 achieves these protective effects in VSMCs through the AMP-dependent kinase (AMPK) pathway.

Disturbed Yin-Yang balance: stress increases the susceptibility to primary and recurrent infections of herpes simplex virus type 1.

Herpes simplex virus type 1 (HSV-1), a neurotropic herpes virus, is able to establish a lifelong latent infection in the human host. Following primary replication in mucosal epithelial cells, the virus can enter sensory neurons innervating peripheral tissues via nerve termini. The viral genome is then transported to the nucleus where it can be maintained without producing infectious progeny, and thus latency is established in the cell. Yin-Yang balance is an essential concept in traditional Chinese medicine (TCM) theory. Yin represents stable and inhibitory factors, and Yang represents the active and aggressive factors. When the organism is exposed to stress, especially psychological stress caused by emotional stimulation, the Yin-Yang balance is disturbed and the virus can re-engage in productive replication, resulting in recurrent diseases. Therefore, a better understanding of the stress-induced susceptibility to HSV-1 primary infection and reactivation is needed and will provide helpful insights into the effective control and treatment of HSV-1. Here we reviewed the recent advances in the studies of HSV-1 susceptibility, latency and reactivation. We included mechanisms involved in primary infection and the regulation of latency and described how stress-induced changes increase the susceptibility to primary and recurrent infections.

Sphingosine-1-phosphate promotes barrier-stabilizing effects in human microvascular endothelial cells via AMPK-dependent mechanisms.

Breakdown of the endothelial barrier is a critical step in the development of organ failure in severe inflammatory conditions such as sepsis. Endothelial cells from different tissues show phenotypic variations which are often neglected in endothelial research. Sphingosine-1-phosphate (S1P) and AMP-dependent kinase (AMPK) have been shown to protect the endothelium and phosphorylation of AMPK by S1P was shown in several cell types. However, the role of the S1P-AMPK interrelationship for endothelial barrier stabilization has not been investigated. To assess the role of the S1P-AMPK signalling axis in this context, we established an in vitro model allowing real-time monitoring of endothelial barrier function in human microvascular endothelial cells (HMEC-1) and murine glomerular endothelial cells (GENCs) with the electric cell-substrate impedance sensing (ECIS™) system. Following the disruption of the cell barrier by co-administration of LPS, TNF-α, IL-1ß, IFN-γ, and IL-6, we demonstrated self-recovery of the disrupted barrier in HMEC-1, while the barrier remained compromised in GENCs. Under physiological conditions we observed a rapid phosphorylation of AMPK in HMEC-1 stimulated with S1P, but not in GENCs. Consistently, S1P enhanced the basal endothelial barrier in HMEC-1 exclusively. siRNA-mediated knockdown of AMPK in HMEC-1 led to a less pronounced barrier enhancement. Thus we present evidence for a functional role of AMPK in S1P-mediated barrier stabilization in HMEC-1 and we provide insight into cell-type specific differences of the S1P-AMPK-interrelationship, which might influence the development of interventional strategies targeting endothelial barrier dysfunction.

KCNQ1 is internalized by activation of α1 adrenergic receptors.

KCNQ1 (Kv7.1 or KvLQT1) plays important physiological roles in various tissues forming potassium channels with KCNE subunits. Among the channels formed by KCNQ1 and KCNE subunits, the best studied is the slow delayed rectifier potassium channel in the heart, the IKs (KCNQ1/KCNE1) channel, which is critical for repolarization of cardiac action potential. The KCNQ1 channel is internalized by Nedd4/Nedd4-like ligase-dependent ubiquitination. It is also reported that phosphorylation of KCNE1 by PKC results in internalization of the KCNQ1/KCNE1 channel. Because we have observed down-regulation of KCNQ1/KCNE1 currents by activation of the α1-adrenergic receptor (α1AR) that activates PKC, this study investigated whether α1AR causes internalization of the KCNQ1 protein. We fused HaloTag to the extracellular region of KCNQ1 (Halo-KCNQ1) and co-expressed it with α1ARs in HEK293 cells. The KCNQ1 protein on the cell surface was selectively labeled with membrane-impermeable HaloTag ligands, and changes in its localization were monitored by confocal fluorescence microscopy. Activation of α1AAR and α1BAR caused marked internalization of KCNQ1, which was not KCNE1-dependent. Internalization of KCNQ1 by α1AR activation was inhibited by disruption of the PY motif or the YXXΦ motif in the C-terminus. Double staining for the receptor and the channel revealed that KCNQ1 internalization was independent of α1AR internalization. Our results suggest that α1AR-mediated direct internalization of KCNQ1 is AP2/clathrin-dependent and may be triggered by ubiquitination of KCNQ1 via the AMP dependent kinase (AMPK)/Nedd4-2 pathway. When phenylephrine was applied to rat neonatal cardiomyocytes transfected with KCNQ1 and α1AR, the KCNQ1 protein was internalized. The internalization of KCNQ1 by α1AR would affect pathophysiology in a variety of tissues expressing KCNQ1, which merits further in vivo study.