Cornelius J. Busch

Ventricular Phosphodiesterase-5 Expression Is Increased in Patients With Advanced Heart Failure and Contributes to Adverse Ventricular Remodeling After Myocardial Infarction in Mice

Background— Ventricular expression of phosphodiesterase-5 (PDE5), an enzyme responsible for cGMP catabolism, is increased in human right ventricular hypertrophy, but its role in left ventricular (LV) failure remains incompletely understood. We therefore measured LV PDE5 expression in patients with advanced systolic heart failure and characterized LV remodeling after myocardial infarction in transgenic mice with cardiomyocyte-specific overexpression of PDE5 (PDE5-TG). Methods and Results— Immunoblot and immunohistochemistry techniques revealed that PDE5 expression was greater in explanted LVs from patients with dilated and ischemic cardiomyopathy than in control hearts. To evaluate the impact of increased ventricular PDE5 levels on cardiac function, PDE5-TG mice were generated. Confocal and immunoelectron microscopy revealed increased PDE5 expression in cardiomyocytes, predominantly localized to Z-bands. At baseline, myocardial cGMP levels, cell shortening, and calcium handling in isolated cardiomyocytes and LV hemodynamic measurements were similar in PDE5-TG and wild-type littermates. Ten days after myocardial infarction, LV cGMP levels had increased to a greater extent in wild-type mice than in PDE5-TG mice (P<0.05). Ten weeks after myocardial infarction, LV end-systolic and end-diastolic volumes were larger in PDE5-TG than in wild-type mice (57±5 versus 39±4 and 65±6 versus 48±4 &mgr;L, respectively; P<0.01 for both). LV systolic dysfunction and diastolic dysfunction were more marked in PDE5-TG than in wild-type mice, associated with enhanced hypertrophy and reduced contractile function in isolated cardiomyocytes from remote myocardium. Conclusions— Increased PDE5 expression predisposes mice to adverse LV remodeling after myocardial infarction. Increased myocardial PDE5 expression in patients with advanced cardiomyopathy may contribute to the development of heart failure and represents an important therapeutic target.

Pretransplant model for end stage liver disease score predicts posttransplant incidence of fungal infections after liver transplantation.

Liver transplant recipients are at a significant risk for invasive fungal infections (IFI). This retrospective study evaluated the impact of the pretransplant model for end stage liver disease (MELD) on the incidence of posttransplant IFI in a single centre. From 2004 to 2008, 385 liver transplantations were included, from which 210 transplantations were conducted allocated by Child Turcotte Pugh and 175 were allocated by MELD score. Both groups differed regarding the age of transplant recipients (50.1 ± 10.7 vs. 52.5 ± 9.9, P = 0.036), pretransplant MELD score (16.43 ± 8.33 vs. 18.29 ± 9.05), rate of re‐transplantations, duration of surgery, demand in blood transfusions and rates of renal impairments. In the MELD era, higher incidences of IFI (pre‐MELD 11.9%, MELD 24.0%, P < 0.05) and Candida infections (9% vs. 18.9%, P < 0.05) were observed. There was no difference in the incidence of probable or possible aspergillosis. Mortality, length of stay in intensive care or hospital, and duration of mechanical ventilation did not differ between the pre‐MELD and MELD era. Regardless the date of transplantation, patients with fungi‐positive samples showed higher mortality rates than patients without. MELD score was analysed as independent predictors for posttransplant IFI. Higher MELD scores predispose to a more problematic postoperative course and are associated with an increase in fungal infections.

4-Aminopyridine Restores Impaired Hypoxic Pulmonary Vasoconstriction in Endotoxemic Mice

Background:Hypoxic pulmonary vasoconstriction (HPV) is impaired during inflammatory lung processes such as pneumonia or the acute respiratory distress syndrome. Voltage-gated potassium channels play a central role in mediating HPV. The aim of this study was to determine whether 4-aminopyridine (4-AP), a known voltage-gated potassium channel inhibitor, may restore HPV in sepsis. Methods:The effects of 0.01, 0.1, and 1.0 mm 4-AP on HPV responsiveness were assessed in isolated lungs of untreated mice and of mice 18 h after lipopolysaccharide injection (20 mg/kg intraperitoneal Escherichia coli 0111:B4 lipopolysaccharide). HPV was quantified as the increase in perfusion pressure in response to hypoxic ventilation in percent of baseline perfusion pressure. Intrinsic pulmonary vascular resistance (R0) and pulmonary vascular distensibility (&agr;) were determined by nonlinear regression analysis of pulmonary vascular pressure–flow curves generated during normoxic and hypoxic ventilation, respectively. Results:HPV was impaired in lungs isolated from lipopolysaccharide-challenged mice. Addition of 4-AP to the perfusate did not alter HPV responsiveness in untreated mice but dose dependently restored HPV in endotoxemic mice. Analysis of pulmonary vascular pressure–flow curves revealed that 4-AP (1) counteracted the observed lipopolysaccharide-induced changes in &agr; and R0 under normoxic conditions and (2) augmented the hypoxia-induced increase in R0 in lungs of endotoxemic mice. Conclusions:This study demonstrates that lipopolysaccharide-induced pulmonary vascular hyporesponsiveness to hypoxia can be restored by 4-AP in murine endotoxemia and, thus, may be a new therapeutic approach to treat patients with hypoxemia due to impaired HPV.

Effects of ketamine on hypoxic pulmonary vasoconstriction in the isolated perfused lungs of endotoxaemic mice.

Background and objective During sepsis and endotoxaemia, hypoxic pulmonary vasoconstriction (HPV) is impaired. Sedation of septic patients in ICUs is performed with various anaesthetics, most of which have pulmonary dilatory properties. Ketamine is a sympathetic nervous system-activating anaesthetic that preserves cardiovascular stability. The effects of ketamine on the pulmonary vasculature and HPV during sepsis have not been characterized yet. Methods Therefore, isolated lungs of mice were perfused with ketamine (0, 0.1, 1.0, and 10 mg kg−1 body weight min−1) 18 h following intraperitoneal injection of lipopolysaccharide (LPS); untreated mouse groups served as controls (n = 7 per group, respectively). Pulmonary artery pressure (PAP) and pressure–flow curves during normoxic (FiO2 = 0.21) and hypoxic (FiO2 = 0.01) ventilation were obtained. Results HPV was reduced in endotoxaemic animals when compared with controls (means ± SD; ΔPAP control 103 ± 28% vs. LPS 23 ± 25%, P < 0.05). Ketamine caused a dose-dependent reduction of HPV in the lungs of control (ΔPAP 0 mg kg−1 min−1 ketamine 103 ± 28% vs. 10 mg kg−1 min−1 ketamine 28 ± 21%, P < 0.05) and septic animals (ΔPAP 0 mg kg−1 min−1 ketamine 23 ± 25% vs. 10 mg kg−1 min−1 ketamine 0 ± 4%, P < 0.05). Analysis of pressure–flow curves revealed that ketamine partly reversed the endotoxin-induced changes in basal pulmonary vascular wall properties rather than interfering with the HPV response itself. Conclusion Ketamine modified baseline pulmonary vascular properties, resulting in a reduced HPV responsiveness in untreated mice. Further, ketamine counteracted the LPS-induced changes in pulmonary vascular pressure–flow relationships, but did not affect impaired HPV in this murine endotoxaemia model.

Nitric Oxide Regulates Pulmonary Vascular Smooth Muscle Cell Expression of the Inducible cAMP Early Repressor Gene

Nitric oxide (NO) regulates vascular smooth muscle cell (VSMC) structure and function, in part by activating soluble guanylate cyclase (sGC) to synthesize cGMP. The objective of this study was to further characterize the signaling mechanisms by which NO regulates VSMC gene expression using transcription profiling. DNA microarrays were hybridized with RNA extracted from rat pulmonary artery smooth muscle cells (RPaSMC) exposed to the NO donor compound, S-nitroso-glutathione (GSNO). Many of the genes, whose expression was induced by GSNO, contain a cAMP-response element (CRE), of which one encoded the inducible cAMP early repressor (ICER). sGC and cAMP-dependent protein kinase, but not cGMP-dependent protein kinase, were required for NO-mediated phosphorylation of CRE-binding protein (CREB) and induction of ICER gene expression. Expression of a dominant-negative CREB in RPaSMC prevented the NO-mediated induction of CRE-dependent gene transcription and ICER gene expression. Pre-treatment of RPaSMC with the intracellular calcium (Ca(2+)) chelator, BAPTA-AM, blocked the induction of ICER gene expression by GSNO. The store-operated Ca(2+) channel inhibitors, 2-ABP, and SKF-96365, reduced the GSNO-mediated increase in ICER mRNA levels, while 2-ABP did not inhibit GSNO-induced CREB phosphorylation. Our results suggest that induction of ICER gene expression by NO requires both CREB phosphorylation and Ca(2+) signaling. Transcription profiling of RPaSMC exposed to GSNO revealed important roles for sGC, PKA, CREB, and Ca(2+) in the regulation of gene expression by NO. The induction of ICER in GSNO-treated RPaSMC highlights a novel cross-talk mechanism between cGMP and cAMP signaling pathways.

Response to Letter Regarding Article, “Ventricular Phosphodiesterase-5 Expression Is Increased in Patients With Advanced Heart Failure and Contributes to Adverse Ventricular Remodeling After Myocardial Infarction in Mice”

We appreciate the comments by Cingolani et al on a possible involvement of Na+/H+ exchanger (NHE-1) in signaling mechanisms downstream of cGMP that can mediate cardioprotection after myocardial infarction. These authors previously reported that NHE-1 expression and activity are increased after myocardial infarction in rats (as a result of myocardial acidosis) and that sustained …

Inhibition of Kv channels by 4-aminopyridine restores impaired hypoxic pulmonary vasoconstriction (HPV) in endotoxemic mice: 5AP2-2

in PAP ([mean SD] LPS: 7 5% vs. control: 55 5%; p 0.05). There was no effect of iCO exposure on PAP in untreated control animals. Exposure of LPS-pretreated mice to 50 ppm iCO completely prevented the development of impaired HPV ( PAP 49 21%; p 0.05 vs. LPS). However, this effect vanished with increasing iCO doses and was absent at 500 ppm iCO ( PAP 12 8%). This was associated with increasing CO-Hb blood levels, but could be overcome by reducing these by exposure with 500 ppm iCO in 50% O2 ( PAP 60 18%). Conclusions: Here we showed that low dose CO inhalation may prevent LPS-induced impairment of HPV in mice. Of interest, this effect vanished with increasing doses of iCO. Our data further suggest, that high CO-Hb levels associated with CO exposure may counteract the beneficial effects of iCO during sepsis. Reference: 1 Spöhr F, Cornelissen AJM, Busch C, et al. Am J Physiol Heart Circ Physiol 2005; 289: 823-831.