Notch-dependent regulation of the ischemic vasodilatory response--brief report.

OBJECTIVE: We have recently described that Notch activates nitric oxide (NO) signaling in the embryonic endocardium. Both Notch signaling and NO signaling have been shown to be important during adult arteriogenesis. Notch has been shown to be required for remodeling of the collateral vessels, whereas NO is required for the initial vasodilatory response to ischemia. Whether Notch also has an impact on the vasodilatory phase of arteriogenesis after ischemia is not known. We tested the hypothesis that endothelial cell-Notch function is required for NO induction and vasodilation, in response to ischemia in the adult vasculature. METHODS AND RESULTS: We observed a significant decrease in NO levels in the dorsal aorta using a mouse model where Notch was inhibited in endothelial cell in a Tet-inducible fashion. In a femoral artery ligation model, inhibition of endothelial cell-Notch reduced reperfusion and NO generation, as quantified by laser Doppler perfusion imaging and by phosphoendothelial NO synthase, nitrotyrosine, and phosphovasodilator-stimulated phosphoprotein staining, respectively. CONCLUSIONS: Endothelial Notch activation is required for NO production and reactive vasodilation in a femoral artery ligation model.

Predictive Modelling of Diabetes Risk in Population Groups Defined by Socioeconomic and Lifestyle Factors in Canada: A Cross-Sectional Study.

Objectives: This study modelled diabetes risk for population groups in Canada defined by socioeconomic and lifestyle characteristics and investigated inequities in diabetes risk using a validated population risk prediction algorithm. Methods: We defined population groups, informed by determinants of health frameworks. We applied the Diabetes Population Risk Tool (DPoRT) to 2017/2018 Canadian Community Health Survey data to predict 10-year diabetes risk and cases across population groups. We modelled a preventive intervention scenario to estimate reductions in diabetes for population groups and impacts on the inequity in diabetes risk across income and education. Results: The population group with at least one lifestyle and at least one socioeconomic/structural risk factor had the highest estimated 10-year diabetes risk and number of new cases. When an intervention with a 5% relative risk reduction was modelled for this population group, diabetes risk decreased by 0.5% (females) and 0.7% (males) and the inequity in diabetes risk across income and education levels was reduced. Conclusion: Preventative interventions that address socioeconomic and structural risk factors have potential to reduce inequities in diabetes risk and overall diabetes burden.

Direct and Indirect Transcriptional Effects of Abiotic Stress in Zea mays Plants Defective in RNA-Directed DNA Methylation.

Plants respond to abiotic stress stimuli, such as water deprivation, through a hierarchical cascade that includes detection and signaling to mediate transcriptional and physiological changes. The phytohormone abscisic acid (ABA) is well-characterized for its regulatory role in these processes in response to specific environmental cues. ABA-mediated changes in gene expression have been demonstrated to be temporally-dependent, however, the genome-wide timing of these responses are not well-characterized in the agronomically important crop plant Zea mays (maize). ABA-mediated responses are synergistic with other regulatory mechanisms, including the plant-specific RNA-directed DNA methylation (RdDM) epigenetic pathway. Our prior work demonstrated that after relatively long-term ABA induction (8 h), maize plants homozygous for the mop1-1 mutation, defective in a component of the RdDM pathway, exhibit enhanced transcriptional sensitivity to the phytohormone. At this time-point, many hierarchically positioned transcription factors are differentially expressed resulting in primary (direct) and secondary (indirect) transcriptional outcomes. To identify more immediate and direct MOP1-dependent responses to ABA, we conducted a transcriptomic analysis using mop1-1 mutant and wild type plants treated with ABA for 1 h. One h of ABA treatment was sufficient to induce unique categories of differentially expressed genes (DEGs) in mop1-1. A comparative analysis between the two time-points revealed that distinct epigenetically-regulated changes in gene expression occur within the early stages of ABA induction, and that these changes are predicted to influence less immediate, indirect transcriptional responses. Homology with MOP1-dependent siRNAs and a gene regulatory network (GRN) were used to identify putative immediate and indirect targets, respectively. By manipulating two key regulatory networks in a temporal dependent manner, we identified genes and biological processes regulated by RdDM and ABA-mediated stress responses. Consistent with mis-regulation of gene expression, mop1-1 homozygous plants are compromised in their ability to recover from water deprivation. Collectively, these results indicate transcriptionally and physiologically relevant roles for MOP1-mediated regulation of gene expression of plant responses to environmental stress.

Collagen stimulates discoidin domain receptor 1-mediated migration of smooth muscle cells through Src.

BACKGROUND: Discoidin domain receptor 1 (DDR1) is a collagen-binding receptor tyrosine kinase which mediates the migration and proliferation of several cell types. DDR1 is expressed in vascular smooth muscle cells (SMCs) during atherosclerosis and following vascular injury, mediating cell migration and contributing to disease pathogenesis. However, very little is known about the signaling pathways activated by the DDR1 in SMCs. Therefore we have studied the involvement of Src and mitogen-activated protein kinase (MAPK) signaling pathways downstream of DDR1 in vascular SMCs. METHODS: Cells harvested from DDR1(-/-), DDR1(+/+) mice, and DDR1(+/+) cells overexpressing human DDR1b (O/hDDR1b) were used for these studies. RESULTS: Stimulation of O/hDDR1b cells with type I collagen resulted in increased tyrosine phosphorylation of DDR1. The non-receptor kinase Src co-immunoprecipitated with DDR1, and the Src inhibitor PP2 inhibited type I collagen-induced tyrosine phosphorylation of DDR1. Stimulation of DDR1-expressing cells with collagen resulted in the activation of extracellular signal-regulated kinase 1/2 (ERK1/2); however, ERK1/2 was not activated in DDR1-deficient cells. By contrast, p38 MAPK (p38) was activated by collagen stimulation in both DDR1-expressing and DDR1-deficient cells. Treatment with PP2 attenuated DDR1-dependent ERK1/2 activation, but not p38 activation. Finally, treatment of SMCs with PP2, or the MEK inhibitor PD98059, inhibited migration toward type I collagen in a chemotaxis chamber. However, PP2 but not PD98059 had a greater effect in reducing the migration of DDR1(+/+) cells compared to DDR1(-/-) cells, suggesting that Src but not ERK1/2 was important in regulating DDR1-dependent SMC migration. CONCLUSIONS: Type I collagen induces SMC migration through DDR1 and this is mediated via Src signaling.

Adhesion-dependent activation of CaMKII and regulation of ERK activation in vascular smooth muscle.

Cell adhesion-dependent activation of ERK1/2 has been linked functionally to focal adhesion dynamics. We previously reported that in adherent vascular smooth muscle (VSM) cells, CaMKII mediates ERK1/2 activation in response to Ca(2+)-mobilizing stimuli. In the present study, we tested whether CaMKII regulates ERK1/2 signaling in response to VSM cell adhesion. Using an antibody that specifically recognizes CaMKII autophosphorylated on Thr(287), we determined that CaMKII is rapidly activated (within 1 min) after the adherence of cells on multiple ECM substrates. Activation of CaMKII on fibronectin was unaffected in cells overexpressing focal adhesion kinase (FAK)-related nonkinase (FRNK), an endogenous inhibitor of FAK. Furthermore, CaMKII was rapidly and robustly activated in VSM cells plated on poly-l-lysine. These results suggest that adhesion-dependent CaMKII activation is integrin independent. Adhesion-dependent FAK activation on fibronectin was not affected in cells treated with the selective CaMKII inhibitor KN-93 (30 muM) or in cells in which the expression of CaMKII with small interfering RNA (siRNA) was suppressed, although tyrosine phosphorylation of paxillin was inhibited in CaMKII-delta(2)-suppressed cells. Sustained ERK1/2 activation that was dependent on FAK activation (inhibited by FRNK) was also attenuated by CaMKII inhibition or siRNA-mediated gene silencing. Rapid ERK1/2 activation that preceded FAK and paxillin activation was detected upon VSM cell adhesion to poly-l-lysine, and this response was inhibited by CaMKII gene silencing. These results indicate that integrin-independent CaMKII activation is an early signal during VSM cell adhesion that positively modulates ERK1/2 signaling through FAK-dependent and FAK-independent mechanisms.

Modulation of vascular smooth muscle cell migration by calcium/ calmodulin-dependent protein kinase II-delta 2.

Previous studies demonstrated a requirement for multifunctional Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) in PDGF-stimulated vascular smooth muscle (VSM) cell migration. In the present study, molecular approaches were used specifically to assess the role of the predominant CaMKII isoform (delta(2) or delta(C)) on VSM cell migration. Kinase-negative (K43A) and constitutively active (T287D) mutant forms of CaMKII delta(2) were expressed using recombinant adenoviruses. CaMKII activities were evaluated in vitro by using a peptide substrate and in intact cells by assessing the phosphorylation of overexpressed phospholamban on Thr(17), a CaMKII-selective phosphorylation site. Expression of kinase-negative CaMKII delta(2) inhibited substrate phosphorylation both in vitro and in the intact cell, indicating a dominant-negative function with respect to exogenous substrate. However, overexpression of the kinase-negative mutant failed to inhibit endogenous CaMKII delta(2) autophosphorylation on Thr(287) after activation of cells with ionomycin, and in fact, these subunits served as a substrate for the endogenous kinase. Constitutively active CaMKII delta(2) phosphorylated substrate in vitro without added Ca(2+)/calmodulin and in the intact cell without added Ca(2+)-dependent stimuli, but it inhibited autophosphorylation of endogenous CaMKII delta(2) on Thr(287). Basal and PDGF-stimulated cell migration was significantly enhanced in cells expressing kinase-negative CaMKII delta(2), an effect opposite that of KN-93, a chemical inhibitor of CaMKII activation. Expression of the constitutively active CaMKII delta(2) mutant inhibited PDGF-stimulated cell migration. These studies point to a role for the CaMKII delta(2) isoform in regulating VSM cell migration. An inclusive interpretation of results using both pharmacological and molecular approaches raises the hypothesis that CaMKII delta(2) autophosphorylation may play an important role in PDGF-stimulated VSM cell migration.