Citations

Ano1 is a recently discovered Ca2+-activated Cl− channel expressed on interstitial cells of Cajal (ICC) that has been implicated in slow-wave activity in the gut. However, Ano1 is expressed on all classes of ICC, even those that do not contribute to generation of the slow wave, suggesting that Ano1 may have an alternate function in these cells. Ano1 is also highly expressed in gastrointestinal stromal tumors. Mice lacking Ano1 had fewer proliferating ICC in whole mount preparations and in culture, raising the possibility that Ano1 is involved in proliferation. Cl− channel blockers decreased proliferation in cells expressing Ano1, including primary cultures of ICC and in the pancreatic cancer-derived cell line, CFPAC-1. Cl− channel blockers had a reduced effect on Ano1(−/−) cultures, confirming that the blockers are acting on Ano1. Ki67 immunoreactivity, 5-ethynyl-2′-deoxyuridine incorporation, and cell-cycle analysis of cells grown in low-Cl− media showed fewer proliferating cells than in cultures grown in regular medium. We confirmed that mice lacking Ano1 had less phosphorylated retinoblastoma protein compared with controls. These data led us to conclude that Ano1 regulates proliferation at the G1/S transition of the cell cycle and may play a role in tumorigenesis.

Background— There is a paucity of randomized trials regarding diagnostic testing in women with suspected coronary artery disease (CAD). It remains unclear whether the addition of myocardial perfusion imaging (MPI) to the standard ECG exercise treadmill test (ETT) provides incremental information to improve clinical decision making in women with suspected CAD. Methods and Results— We randomized symptomatic women with suspected CAD, an interpretable ECG, and ≥5 metabolic equivalents on the Duke Activity Status Index to 1 of 2 diagnostic strategies: ETT or exercise MPI. The primary end point was 2-year incidence of major adverse cardiac events, defined as CAD death or hospitalization for an acute coronary syndrome or heart failure. A total of 824 women were randomized to ETT or exercise MPI. For women randomized to ETT, ECG results were normal in 64%, indeterminate in 16%, and abnormal in 20%. By comparison, the exercise MPI results were normal in 91%, mildly abnormal in 3%, and moderate to severely abnormal in 6%. At 2 years, there was no difference in major adverse cardiac events (98.0% for ETT and 97.7% for MPI; P =0.59). Compared with ETT, index testing costs were higher for exercise MPI ( P <0.001), whereas downstream procedural costs were slightly lower ( P =0.0008). Overall, the cumulative diagnostic cost savings was 48% for ETT compared with exercise MPI ( P <0.001). Conclusions— In low-risk, exercising women, a diagnostic strategy that uses ETT versus exercise MPI yields similar 2-year posttest outcomes while providing significant diagnostic cost savings. The ETT with selective follow-up testing should be considered as the initial diagnostic strategy in symptomatic women with suspected CAD. Clinical Trial Registration— http://www.clinicaltrials.gov . Unique identifier: NCT00282711.

There are a variety of approaches to assess the efficacy of reperfusion therapy, and myocardial protection, in acute myocardial infarction. This review summarizes the available evidence validating the use of technetium-99m sestamibi single-photon emission computed tomography (SPECT) for this purpose. Multiple lines of evidence have validated its clinical utility. SPECT sestamibi infarct size has been used as an endpoint in multiple randomized clinical trials. A smaller number of clinical trials have used both early and later imaging with SPECT sestamibi to assess myocardium at risk and myocardial salvage. SPECT sestamibi has a number of limitations which must be recognized. Nevertheless, SPECT sestamibi infarct size is a well-validated measurement with a long track record of performance as an endpoint in multicenter, randomized clinical trials.

99mTc-hexakis-2-methoxy-2-methylpropyl-isonitrile (Tc-Sestamibi), a new myocardial perfusion radiopharmaceutical, was injected intravenously in 11 patients within 4 hours of the onset of acute myocardial infarction before treatment with intravenous tissue-type plasminogen activator and 6-14 days later. Five patients with acute myocardial infarction who did not receive intravenous thrombolytic therapy underwent a similar injection of radiopharmaceutical. The absence of redistribution of Tc-Sestamibi permitted imaging with single-photon emission computed tomography up to 6 hours after intravenous injection to assess the distribution of myocardial perfusion at the time of administration. The region of hypoperfused myocardium on the initial images varied widely from 9% to 68% of the left ventricle and was significantly greater in anterior than in inferior infarcts (p less than 0.01). The region of hypoperfused myocardium on the final images varied widely from 0% to 63% of the left ventricle and was also greater in anterior infarcts (p less than 0.01). The final hypoperfused region correlated (r = -0.82) with the late resting ejection fraction and with the late regional wall motion score in the infarct segment for both anterior (r = -0.74) and inferior (r = -0.97) infarcts. There was a significant decrease (-13 +/- 11%, p less than 0.003) in the extent of hypoperfused myocardium between the initial and final studies in the patients who received thrombolytic therapy compared with an insignificant increase (4 +/- 6%, p greater than 0.5) in the patients who did not receive thrombolytic therapy. Tomographic imaging with Tc-Sestamibi permits determination of the amount of hypoperfused myocardium "at risk" in acute myocardial infarction. The change in myocardial perfusion determined by Tc-Sestamibi before and after therapy in acute myocardial infarction is a promising tool for assessing treatment.

Hydrogen sulfide (H2S) is produced endogenously by l-cysteine metabolism. H2S modulates several ion channels with an unclear mechanism of action. A possible mechanism is through reduction-oxidation reactions attributable to the redox potential of the sulfur moiety. The aims of this study were to determine the effects of the H2S donor NaHS on NaV1.5, a voltage-dependent sodium channel expressed in the gastrointestinal tract in human jejunum smooth muscle cells and interstitial cells of Cajal, and to elucidate whether H2S acts on NaV1.5 by redox reactions. Whole cell Na+ currents were recorded in freshly dissociated human jejunum circular myocytes and NaV1.5-transfected human embryonic kidney-293 cells. RT-PCR amplified mRNA for H2S enzymes cystathionine β-synthase and cystathionine γ-lyase from the human jejunum. NaHS increased native Na+ peak currents and shifted the half-point ( V1/2) of steady-state activation and inactivation by +21 ± 2 mV and +15 ± 3 mV, respectively. Similar effects were seen on the heterologously expressed NaV1.5 α subunit with EC50s in the 10−4 to 10−3 M range. The reducing agent dithiothreitol (DTT) mimicked in part the effects of NaHS by increasing peak current and positively shifting steady-state activation. DTT together with NaHS had an additive effect on steady-state activation but not on peak current, suggesting that the latter may be altered via reduction. Pretreatment with the Hg2+-conjugated oxidizer thimerosal or the alkylating agent N-ethylmaleimide inhibited or decreased NaHS induction of NaV1.5 peak current. These studies show that H2S activates the gastrointestinal Na+ channel, and the mechanism of action of H2S is partially redox independent.

Diabetic gastroparesis is associated with increased oxidative stress attributable to loss of upregulation of heme oxygenase-1 (HO1), with resultant damage to interstitial cells of Cajal and delayed gastric emptying. These changes can be reversed by induction of HO1. HO1 catalyzes the breakdown of heme into iron, biliverdin and, carbon monoxide (CO). The aim of this study was to determine whether inhalation of CO can mimic the protective effects of HO1. Nonobese diabetic (NOD) mice with delayed gastric emptying were treated with CO inhalation. Serum malondialdehyde was measured as a marker of oxidative stress. Gastric emptying of solids was measured using a [13C]octanoic acid breath test. Kit expression levels were determined in immunoblots of protein extracted from the external muscle layers of the gastric body and antrum. The effect of CO on oxidative stress and gastric emptying was also determined in the presence of HO activity inhibitor chromium mesoporphyrin. CO inhalation reduced oxidative stress, restored Kit expression and reversed delayed gastric emptying in diabetic NOD mice with delayed gastric emptying. CO inhalation maintained this effect in the presence of the HO activity inhibitor, chromium mesoporphyrin, also resulting in restoration of the delay in gastric emptying. CO inhalation mimics the protective effect of upregulation of HO1 and decreased oxidative stress, increased Kit expression, and restored delay in gastric emptying. This effect of CO was independent of HO activity, suggesting that its effects were downstream of HO1. CO represents a potential therapeutic option for treatment of diabetic gastroparesis.

Antispasmodics are used clinically to treat a variety of gastrointestinal disorders by inhibition of smooth muscle contraction. The main pathway for smooth muscle Ca2+entry is through L-type channels; however, there is increasing evidence that T-type Ca2+channels also play a role in regulating contractility. Otilonium bromide, an antispasmodic, has previously been shown to inhibit L-type Ca2+channels and colonic contractile activity. The objective of this study was to determine whether otilonium bromide also inhibits T-type Ca2+channels. Whole cell currents were recorded by patch-clamp technique from HEK293 cells transfected with cDNAs encoding the T-type Ca2+channels, CaV3.1 (α1G), CaV3.2 (α1H), or CaV3.3 (α1I) alpha subunits. Extracellular solution was exchanged with otilonium bromide (10−8to 10−5M). Otilonium bromide reversibly blocked all T-type Ca2+channels with a significantly greater affinity for CaV3.3 than CaV3.1 or CaV3.2. Additionally, the drug slowed inactivation in CaV3.1 and CaV3.3. Inhibition of T-type Ca2+channels may contribute to inhibition of contractility by otilonium bromide. This may represent a new mechanism of action for antispasmodics and may contribute to the observed increased clinical effectiveness of antispasmodics compared with selective L-type Ca2+channel blockers.