Thomas Waldow

Sphingosine-1-phosphate induces contraction of valvular interstitial cells from porcine aortic valves

AIMS Sphingosine-1-phosphate (S1P) has emerged as a potent bioactive lipid with multiple functions in cardiovascular pathophysiology. Potential roles of S1P in heart valve diseases and expression of relevant receptors (S1P1, S1P2, or S1P3) in valve tissue and in valvular interstitial cells (VICs), the major cell population with essential functions in maintenance of valvular structure, are currently unknown. METHODS AND RESULTS Exposure to S1P (62-2000 nM) of cultured VICs from porcine aortic valves on cell culture polystyrene resulted in contraction and nodule formation. The S1P-dependent contraction was completely inhibited by blockers of S1P2, RhoA, and RhoA-associated protein kinase (ROCK). Activated RhoA was clearly increased after S1P treatment, whereas activated Rac1 was only slightly reduced. In addition, exposure to S1P induced a transient increase in cytosolic Ca(2+). Application of channel blockers and other effectors of Ca(2+) homeostasis showed that the S1P effect is largely caused by Ca(2+) release from internal stores. However, resistance to blocking S1P2, different kinetics, as well as concentration dependence exclude a major role of Ca(2+) influx in S1P-induced nodule formation. In order to verify the effects in situ, contractions of valve tissue slices were measured. The S1P-induced isometric contraction of valve leaflets was of similar force amplitude as observed with adrenaline. The effect was fully reversed by blocking S1P2. CONCLUSION The results suggest that S1P induces contraction of VICs from porcine aortic valves by signalling via S1P2, RhoA, and ROCK. In this way, S1P may contribute to regulation of tissue tension in aortic valves.

Who Should We Target for Diabetes Prevention and Diabetes Risk Reduction

Screening for individual diabetes risk is crucial to identify adult and pediatric high-risk target populations for referral into successful diabetes prevention programs. Determination of impaired glucose tolerance or elevated fasting glucose levels has been the “gold standard” to classify subjects at increased risk for and/or to diagnose type 2 diabetes (T2DM). However, this led to ignoring many individuals prone to develop the disease. Therefore, using a stepped strategy consisting of a preliminary assessment of risk factors, by using risk scores such as the Finnish Diabetes Risk Score (FINDRISC) adapted to the respective population, followed by a single blood test determining blood glucose or hemoglobin A1c, respectively, or an oral glucose tolerance test is a feasible and pragmatic method to more accurately detect individuals at risk for T2DM. Inclusion of further risk factors into the assessment such as physical inactivity, waist circumference, and prenatal factors needs to be thoroughly discussed to establish a valid and reliable stepped approach applicable to real world health care. This article provides an overview of the current literature and is intentionally focused on the identification of high-risk populations (both adult and pediatric) that will help to address the key issues around the prevention of T2DM in health care settings.

Prevention of ischemia/reperfusion-induced accumulation of matrix metalloproteinases in rat lung by preconditioning with nitric oxide.

BACKGROUND Pulmonary ischemia/reperfusion (I/R) injury is associated with degradation of structural proteins. Preconditioning by short-term inhalation of nitric oxide (NO) ameliorates some of the severe consequences of an I/R cycle. The aim of this study was to evaluate the effects of NO preconditioning on I/R-induced changes of matrix metalloproteinase (MMP) activity. MATERIALS AND METHODS Left lung in situ ischemia in rats was maintained for 1 h, followed by reperfusion for 30 min or 4 h. In the NO group, animals inhaled NO (15 ppm) for 10 min directly before ischemia. Changes of expression or activity of MMPs (MMP-2, MMP-7, MMP-9, MMP-14) and of neutrophil elastase (NE) in bronchoalveolar lavage fluid (BALF), lung tissue, and arterial plasma were analyzed by zymography and Western blotting. Western blotting was also used to detect tissue inhibitors of matrix proteases, the extracellular metalloproteinase inducer (EMMPRIN or CD147), and endostatin, a proteolytic collagen fragment. RESULTS Ischemia resulted in an increase of lavagable MMP activity (12.3-fold MMP-2, 8.1-fold MMP-7) at 30 min reperfusion. The activity of MMP-9 and NE in lung tissue progressively increased with time, whereas MMP-14 and MMP-2 were constant. Inhalation of NO prevented the early increase of MMP-2 and MMP-7 in BALF, but the level of MMP-9 and NE in tissue was not affected. The expression of tissue inhibitors of matrix proteases and EMMPRIN did not respond to any treatment. The release of endostatin proceeded in parallel to the level of MMPs in BALF. Significant correlations between MMP-9 and myeloperoxidase in lung tissue and between MMP-2/MMP-7 and plasma protein extravasation were found. CONCLUSIONS The early rise of MMP-2 and MMP-7 in BALF resulted from plasma protein extravasation, whereas MMP-9 and NE were imported into lung tissue via leukocyte invasion. The effect of NO inhalation on lavagable MMPs was secondary to the sealing of the permeability barrier.

Low dose aprotinin and low dose tranexamic acid in elective cardiac surgery with cardiopulmonary bypass.

The antifibrinolytic agents aprotinin and tranexamic acid have both been proven to be efficient in reducing postoperative blood loss and transfusion requirements in patients in cardiac surgery. In light of recent safety issues regarding aprotinin, this single-centre study compared efficacy and safety of low dose aprotinin (2 million KIU, pump-prime volume only) and low dose tranexamic acid (1 g, pump-prime volume) in 708 consecutive patients from two prospective registers undergoing elective cardiac procedures with cardiopulmonary bypass (CPB). Incidences of postoperative complications showed no significant differences between groups. Postoperative blood loss and transfusion requirements were significantly lower in aprotinin compared to tranexamic acid patients. Overall, both antifibrinolytic low dose regimens are safe components of perioperative patient management in elective cardiac surgery with CPB. Cardiac procedures requiring longer CPB times might benefit from the administration of low dose aprotinin.

Omega-3 polyunsaturated Fatty acids reduce the incidence of postoperative atrial fibrillation in patients with history of prior myocardial infarction undergoing isolated coronary artery bypass grafting.

INTRODUCTION The impact of omega-3 polyunsaturated fatty acids (PUFAs) for prevention of atrial fibrillation (AF) is still part of a lively debate. The present study evaluates the impact of orally administered omega-3 ethyl ester concentrate (omega-3 PUFA) on postoperative onset of AF in patients with recent myocardial infarction (≤ 3 months) undergoing isolated coronary artery bypass grafting (CABG). Patients and METHODS The study included a total of 198 patients with recent (≤ 3 months) myocardial infarction. The treatment group consisted of 99 prospectively and randomly assigned patients. A matched control group was generated out of the entirety of patients undergoing isolated CABG during the same time period, being not treated with omega-3 PUFA. Primary endpoint was onset of postoperative AF. Patients of the treatment group received a daily dose of 2 g omega-3 PUFA, initiated 5 days before surgery. Effective serum levels were confirmed by laboratory testing. RESULTS Patients of the treatment group had less frequently postoperative AF (treatment: 31.3% vs. control: 48.0%; p = 0.017). The reduction in relative risk was 34.8% in the treatment group, which conforms a number needed to treat (NNT) of 6.0 patients. A more pronounced effect with a NNT of 4.1 was observed in patients ≤ 70 years (p = 0.007). Besides, patients of the treatment group had a shorter intensive care unit stay (p = 0.001) and suffered less frequently from impaired wound healing by trend (p = 0.063). One patient out of treatment group and two out of control group died during hospital stay (p = 1.000). CONCLUSION Preoperative administration of 2 g omega-3 PUFA reduces incidence of postoperative AF in patients with recent (≤ 3 months) myocardial infarction undergoing isolated CABG.

Reversal of myofibroblastic activation by polyunsaturated fatty acids in valvular interstitial cells from aortic valves. Role of RhoA/G-actin/MRTF signalling

Valvular interstitial cells (VICs), the fibroblast-like cellular constituents of aortic heart valves, maintain structural integrity of valve tissue. Activation into contractile myofibroblasts occurs under pathological situations and under standard cell culture conditions of isolated VICs. Reversal of this phenotype switch would be of major importance in respect to fibrotic valve diseases. In this investigation, we found that exogenous polyunsaturated fatty acids (PUFAs) decreased contractility and expression of myofibroblastic markers like α-smooth muscle actin (αSMA) in cultured VICs from porcine aortic valves. The most active PUFAs, docosahexaenoic acid (DHA) and arachidonic acid (AA) reduced the level of active RhoA and increased the G/F-actin ratio. The G-actin-regulated nuclear translocation of myocardin-related transcription factors (MRTFs), co-activators of serum response factor, was also reduced by DHA and AA. The same effects were observed after blocking RhoA directly with C3 transferase. In addition, increased contractility after induction of actin polymerisation with jasplakinolide and concomitant expression of αSMA were ameliorated by active PUFAs. Furthermore, reduced αSMA expression under PUFA exposure was observed in valve tissue explants demonstrating physiological relevance. In conclusion, RhoA/G-actin/MRTF signalling is operative in VICs, and this pathway can be partially blocked by certain PUFAs whereby the activation into the myofibroblastic phenotype is reversed.

Cell-Cell Junctions and Vascular Endothelial Growth Factor in Rat Lung as Affected by Ischemia/Reperfusion and Preconditioning With Inhaled Nitric Oxide

BACKGROUND Previous investigations have shown that short term inhalation of nitric oxide (NO) before ischemia and reperfusion (I/R) prevents I/R-related consequences on lung function. Here we correlate effects of NO-induced preconditioning, especially on the lung permeability barrier, with analysis of cell junction proteins and the level of vascular endothelial growth factor (VEGF). METHODS A rat model of left lung in situ I/R was used. After left lateral thoracotomy, left lung ischemia was maintained for 60 min, followed by 30 min or 4 h (h) reperfusion (I/R groups). In the NO groups, inhalation of NO (10 min, 15 ppm) preceded I/R. Animals in control groups underwent sham surgery without NO inhalation and ischemia. The extent of I/R injury was assessed in terms of oxygenation (arterial PO(2)) and lung permeability (Evans blue extravasation). Expression of junctional proteins and phosphorylation was determined in complete protein extracts from lung tissue, whereas the adherens junction (AJ) core complex was analyzed in Triton extracts by co-immunoprecipitation using antibodies against E-cadherin and VE-cadherin. RESULTS The inhalation of NO prevented the I/R-induced increase of permeability at 30 min reperfusion, and the PO(2) increased from 27% of controls in the I/R group to 77% in the NO group. Left lung I/R correlated with a progressive loss of cadherins (VE-cadherin, E-cadherin, desmoglein 1) during reperfusion, whereas AJ catenins were largely preserved. Preconditioning with NO resulted in an increased ratio of catenins (alpha- and beta-catenin) to E-cadherin in immunoprecipitates and in reduced phosphorylation of beta-catenin. A reduction of VEGF in left lung lavage fluid was observed at 4 h but not at 30 min reperfusion. CONCLUSIONS The NO-induced changes of the AJ complex may have contributed to the stabilization of the lung permeability barrier during reperfusion.

Heparinized blood better preserves cellular energy charge and vascular functions of intraoperatively stored saphenous vein grafts in comparison to isotonic sodium-chloride-solution

OBJECTIVE Several studies have addressed the optimal storage conditions for vascular grafts during surgery. The results remain contradictionary. This may be attributed to the fact, that the various vascular beds have a different sensitivity to storage. We analyzed the impact of storage in isotonic saline solution (NaCl) or heparinized blood the vascular functions of human saphenous vein grafts. Special care was taken to choose storage conditions which are relevant for intraoperative storage of a saphenous vein graft in a setting of coronary artery bypass grafting with vein and internal mammary artery as grafts. METHODS Intraoperatively isolated V. saphena-segments (n = 36) were stored in NaCl or heparinized blood for approximately 30 minutes at room temperature. Subsequently, the segments were examined in a Mulvany-myograph. Following preconstriction with norepinephrine, concentration-relaxation curves were assessed for bradykinin and sodium-nitroprusside to assess developed vessel-wall tension as well as endothelium- and smooth-muscle-cell dependent vasorelaxation. The availability of adenosintriphosphate (energy charge) was determined based on liquid chromatography measurements of nucleotide tissue levels. RESULTS Mean storage time was 27.4 ± 2.4 min in NaCl- and 26.3 ± 2.7 min in blood-group, respectively. After this period, receptor-dependent and-independent maximum of developed vessel wall tension was significantly reduced in NaCl-group (p = 0.05 and p = 0.045, respectively). Furthermore, the energy charge was significantly (p = 0.046) better preserved after blood storage (74 ± 1%) in comparison to NaCl-group (68 ± 2%). Endothelium-induced vasodilatation in response to bradykinin reached only 12.3 ± 2.5% in NaCl-group, but 19.3 ± 5.2% in blood-group (p = 0.033). Alike, EC50-concentration of bradykinin for half-maximal relaxation was significantly lower in blood- than in NaCl-group (log EC50 -7.08 ± 0.3 and -5.91 ± 0.4; respectively; p = 0.046). Endothelium-independent smooth muscle relaxation in response to sodium-nitroprusside was not different between both groups. CONCLUSION Heparinized blood better preserves vascular contractile and endothelial functions of the saphenous vein graft. Storage in NaCl rapidly compromises vascular functions and impaires cellular energy. NaCl should no longer be recommended for intraoperative storage of harvested V. saphena grafts.

Camera-based photoplethysmography in critical care patients

BACKGROUND Camera-based photoplethysmography (cbPPG) is an optical measurement technique that reveals pulsatile blood flow in cutaneous microcirculation from a distance. cbPPG has been shown to reflect pivotal haemodynamic events like cardiac ejection in healthy subjects. In addition, it provides valuable insight into intrinsic microcirculatory regulation as it yields dynamic, two-dimensional perfusion maps. In this study, we evaluate the feasibility of a clinical cbPPG application in critical care patients. METHODS A mobile camera set-up to record faces of patients at the bed site was constructed. Videos were made during the immediate recovery after cardiac surgery under standard critical care conditions and were processed offline. Major motion artefacts were detected using an optical flow technique and suitable facial regions were manually annotated. cbPPG signals were highpass filtered and Fourier spectra out of consecutive 10s signal segments calculated for heart rate detection. Signal-to-noise ratios (SNR) of the Fourier spectra were derived as a quality measure. Reference data of vital parameters were synchronously acquired from the bed site monitoring system. RESULTS Seventy patient videos of an average time of 28.6±2.8 min were analysed. Heart rate (HR) was detected within a±5 bpm range compared to reference in 83% of total recording time. Low SNR and HR detection failure were mostly, but not exclusively, attributed to non-physiological events like patient motion, interventions or sudden changes of illumination. SNR was reduced by low arterial blood pressure, whereas no impact of other perioperative or disease-related parameters was identified. CONCLUSION Cardiac ejection is detectable by cbPPG under pathophysiologic conditions of cardiovascular disease and perioperative medicine. cbPPG measurements can be seamlessly integrated into the clinical work flow of critical care patients.

Prospective clinical trial on dosage optimizing of tranexamic acid in non-emergency cardiac surgery procedures.

UNLABELLED After withdrawal of aprotinin in 2008 only tranexamic acid (TxA, Cyclocapron, Pfitzer, Germany) remains available as antihyperfibrinolytic agent in Europe. Dosage (from 1 g to 20 g) and application strategy (single shot i.v., infusion i.v., topical) reflect an indiscriminate use of TXA in cardiac surgery. We use data analysis of three registries to evaluate safety issues and sufficiency of different TxA dosages in our center. METHODS Registry 1: Single shot ultra-low dose TxA (1 g in priming volume). Registry 2: Single shot medium dose TxA (5 g in priming volume). Registry 3: Single shot medium dose TxA (3 g in priming volume) and continuous, weight-adapted administration during cross clamping. Independence of surgeons preference was achieved by changing dosage every surgery day regardless of operation schedule. RESULTS Data analysis was carried out on 1182 consecutive, elective patients (1 g TxA n = 415; 3 g + x g TA n = 367; mean TxA dose 4.4 g ± 1.0 g; 5 g TxA n = 400). Patient characteristics were well matched in all three registries (mean age: 69 ± 9.5y, BMI 28.2 ± 4.7, Creatinin 107.5 ± 52.8 μM), as were performed surgical procedures (excluding organ transplantation). Postoperative data showed no significant differences for blood loss and major adverse events (1 g vs. 3 + g vs. 5 g: blood loss: 894 ± 1479 vs. 903 ± 1282 vs. 1004 ± 1604 ml; stroke: 1.5 vs. 1.6 vs. 1.5%; myocardial infarction 2.7 vs. 3.3 vs. 1.3%; 30d mortality 3.9 vs. 4.2 vs. 4.8%, respectively). Secondary endpoints (de novo dialysis, transfusion requirement, ICU and total treatment time) showed no significant differences between registries. CONCLUSION Use of 1 g TxA is safe and sufficient for elective patients with on pump cardiac surgery and thus has been established as strategy of choice in our center.