Interactions, functions, and independence of plasma membrane STIM1 and TRPC1 in vascular smooth muscle cells.

Stromal interaction molecule 1 (STIM1) is a predicted single membrane-spanning protein involved in store-operated calcium entry and interacting with ion channels including TRPC1. Here, we focus on endogenous STIM1 of modulated vascular smooth muscle cells, which exhibited a nonselective cationic current in response to store depletion despite strong buffering of intracellular calcium at the physiological concentration. STIM1 mRNA and protein were detected and suppressed by specific short interfering RNA. Calcium entry evoked by store depletion was partially inhibited by STIM1 short interfering RNA, whereas calcium release was unaffected. STIM1 short interfering RNA suppressed cell migration but not proliferation. Antibody that specifically bound STIM1 revealed constitutive extracellular N terminus of STIM1 and extracellular application of the antibody caused fast inhibition of the current evoked by store depletion. The antibody also inhibited calcium entry and cell migration but not proliferation. STIM1 interacted with TRPC1, and TRPC1 contributed partially to calcium entry and cationic current. However, the underlying processes could not be explained only by a STIM1-TRPC1 partnership because extracellular TRPC1 antibody suppressed cationic current only in a fraction of cells, TRPC1-containing channels were important for cell proliferation as well as migration, and cell surface localization studies revealed TRPC1 alone, as well as with STIM1. The data suggest a complex situation in which there is not only plasma membrane-spanning STIM1 that is important for cell migration and TRPC1-independent store-operated cationic current but also TRPC1-STIM1 interaction, a TRPC1-dependent component of store-operated current, and STIM1-independent TRPC1 linked to cell proliferation.

A sphingosine-1-phosphate-activated calcium channel controlling vascular smooth muscle cell motility.

In a screen of potential lipid regulators of transient receptor potential (TRP) channels, we identified sphingosine-1-phosphate (S1P) as an activator of TRPC5. We explored the relevance to vascular biology because S1P is a key cardiovascular signaling molecule. TRPC5 is expressed in smooth muscle cells of human vein along with TRPC1, which forms a complex with TRPC5. Importantly, S1P also activates the TRPC5-TRPC1 heteromultimeric channel. Because TRPC channels are linked to neuronal growth cone extension, we considered a related concept for smooth muscle. We find S1P stimulates smooth muscle cell motility, and that this is inhibited by E3-targeted anti-TRPC5 antibody. Ion permeation involving TRPC5 is crucial because S1P-evoked motility is also suppressed by the channel blocker 2-aminoethoxydiphenyl borate or a TRPC5 ion-pore mutant. S1P acts on TRPC5 via two mechanisms, one extracellular and one intracellular, consistent with its bipolar signaling functions. The extracellular effect appears to have a primary role in S1P-evoked cell motility. The data suggest S1P sensing by TRPC5 calcium channel is a mechanism contributing to vascular smooth muscle adaptation.

Surgeon length of service and risk-adjusted outcomes: linked observational analysis of the UK National Adult Cardiac Surgery Audit Registry and General Medical Council Register.

OBJECTIVES: To explore the relationship between in-hospital mortality following adult cardiac surgery and the time since primary clinical qualification for the responsible consultant cardiac surgeon (a proxy for experience). DESIGN: Retrospective analysis of prospectively collected national registry data over a 10-year period using mixed-effects multiple logistic regression modelling. Surgeon experience was defined as the time between the date of surgery and award of primary clinical qualification. SETTING: UK National Health Service hospitals performing cardiac surgery between January 2003 and December 2012. PARTICIPANTS: All patients undergoing coronary artery bypass grafts and/or valve surgery under the care of a consultant cardiac surgeon. MAIN OUTCOME MEASURES: All-cause in-hospital mortality. RESULTS: A total of 292,973 operations performed by 273 consultant surgeons (with lengths of service from 11.2 to 42.0 years) were included. Crude mortality increased approximately linearly until 33 years service, before decreasing. After adjusting for case-mix and year of surgery, there remained a statistically significant (p=0.002) association between length of service and in-hospital mortality (odds ratio 1.013; 95% CI 1.005-1.021 for each year of 'experience'). CONCLUSIONS: Consultant cardiac surgeons take on increasingly complex surgery as they gain experience. With this progression, the incidence of adverse outcomes is expected to increase, as is demonstrated in this study. After adjusting for case-mix using the EuroSCORE, we observed an increased risk of mortality in patients operated on by longer serving surgeons. This finding may reflect under-adjustment for risk, unmeasured confounding or a real association. Further research into outcomes over the time course of surgeon's careers is required.

Tissue perfusion in non-donor and donor forearm/hand after radial artery harvest: 1- and 5-year follow-up.

Radio-labeled red cell perfusion scan of the non-donor/donor forearm/hand was undertaken, 1- and 5-years post operation, in 12 patients who had received a radial artery graft during myocardial revascularisation. Results were analysed using a Wilcoxon Signed Rank test (P-value <0.05 was taken as statistically significant). Mean tissue perfusion (in milliliters/100 ml tissue/min) declined in the non-donor (-10.06%, P=0.07) and donor (-6.65%, P=0.15) forearm, respectively, compared to 1 year post radial artery harvest. The statistically significant observed difference in tissue perfusion between the non-donor (21.9+/-5.1) and donor (17.5+/-3.7) forearm (P=0.0007) at 1 year was maintained at 5 years, non-donor and donor, 19.5+/-3.7 and 16.2+/-3.4 (P=0.001), respectively. The same pattern in tissue perfusion was observed in the non-donor/donor hand. This study demonstrates that, over time, there is little recovery in perfusion in the donor forearm/hand from ulnar artery collateral circulation. There is a significant and persistent difference in tissue perfusion between the non-donor/donor forearm/hand at 5 years post radial artery harvest. Although no functional deficit or overt ischaemic events were recorded, these findings may influence the choice of conduit and the information given when obtaining consent in patients undergoing myocardial revascularisation.