Successful pregnancy outcome in a woman with Turner's syndrome

Women with Turner's syndrome have a high incidence of cardiovascular complications, endocrine and hypertensive disorders. Those with the 45X chromosome complement require oocyte donation and in vitro fertilisation to conceive. Pregnancies in such women are challenging to manage due to the high risk of pregnancy-related hypertensive disorders, impaired glucose tolerance, fetal growth restriction and preterm birth. Women also need to be aware of the significant risk of aortic dilatation, dissection or rupture in pregnancy, which may be fatal. Despite these risks, favourable obstetric outcomes are achievable with careful pre-pregnancy counselling and cardiovascular assessment, intensive multidisciplinary antenatal monitoring and individualised delivery planning. We report the case of a 33-year-old woman with Turner's syndrome, pre-existing hypertension, insulin-dependent diabetes and primary hypoparathyroidism who had a successful pregnancy with good maternal and fetal outcomes despite the complexity of her medical conditions.

Resolution of neonatal hypertrophic cardiomyopathy presumed secondary to acquired maternal ribonucleoprotein and smith autoantibodies

Severe asymmetrical hypertrophic cardiomyopathy without heart block accompanied by neuromuscular hypotonia and feeding difficulties was evident shortly after birth in the second child of a mother with systemic lupus erythematosus who had no indication of gestational diabetes. High-level anti-ribonucleoprotein (RNP) and Smoth (Sm) antibodies arising from transplacental transfer of maternal antibodies were detected in the child's serum. The cardiac abnormalities improved with a commensurate decline in antibody titers. Previously reported cases of neonatal cardiomyopathy with endocardial fibroelastosis have been ascribed to the transplacental transfer of maternal Sjogrens Syndrome (SS) A (Ro) and Sjogrens Syndrome (SS) B (La) antibodies and have been more severe and persistent compared with our patient. We advocate close monitoring of all babies of mothers with systemic autoimmunity for changes in heart rate during pregnancy and signs of heart failure and neuromuscular weakness after delivery.

Abstract 502: Enhanced Tubular Chymase Protein Expression in Diabetic Kidneys Activates the Epithelial Sodium Channel (ENaC)

We tested the hypothesis that enhanced tubular chymase protein expression in diabetic kidneys activates the epithelial sodium channel (ENaC). Diabetic ( db/db) and control ( db/m ) mice were studied during prediabetes, type II diabetes, and progression to type I diabetes at 5-, 18-, and 36-wks of age, respectively. In 5-wk-old diabetic (n=11), body weights (25.6 ± 0.7 vs 20.3 ± 0.6 g) were significantly increased, while plasma glucose (143 ± 29 vs 160 ± 13 mg/dL) and insulin (1.2 ± 0.1 vs 1.2 ± 0.1 μg/L) levels were not different than control (n=11) mice. In 18-wk-old diabetic (n=8) mice, body weights (53.7 ± 0.7 vs 29.7 ± 0.3 g), blood glucose (400 ± 16 vs 137 ± 6 mg/dL), and insulin (20 ± 6 vs 1.9 ± 0.7 μg/L) levels were increased compared to control (n=9) mice. In 36-wk-old diabetic (n=7), body weights (33 ± 3 vs 40 ± 2 g) were decreased, plasma glucose levels (552 ± 40 vs 220 ± 21 mg/dL) increased, and insulin levels (0.8 ± 0.1 vs 0.4 ± 0.1 μg/L) not different from control (n=8) mice. Immunohistochemistry revealed chymase localization to apical membranes of principal cells of connecting tubules and collecting ducts. Densitometric analyses revealed that diabetic renal papillary chymase immunostaining levels were 4 to 28 fold higher relative to control papilla at all ages (p≤0.05). In 5-wk-old diabetic mice, renal cortical chymase expression was increased 1.8 ± 0.3 fold, but decreased to 0.5 ± 0.1 fold in 36-wk-old diabetic compared to control mice (p≤0.05). Relative amiloride-sensitive Na + currents were increased by chymase (5 μg/mL) perfused Xenopus laevis oocytes injected with α-, β-, and γ- ENaC (1.57 ± 0.08; n=6) relative to mock control (1.13 ± 0.02; n=3) oocytes (p≤0.01). In conclusion, these are the first studies to demonstrate chymase protein localization to the ENaC expressing principal cells of the distal nephron. Papillary chymase expression is unique to prediabetic and diabetic kidneys and does not correlate with glycemia, insulinemia, or body weight. Elevated renal chymase expression may serve as an early biomarker for prediabetic patients with a high risk of developing diabetic renal disease. Enhanced chymase activity, associated with diabetes mellitus, may increase ENaC activity, potentially leading to hypertension and diabetic renal disease.

Abstract 56: Mast Cell Chymase: An Angiotensin II (Ang II)-Independent Therapeutic Target in the Post-Myocardial Infarction Heart

Mast cell chymase (CHY), a multifunctional protease with Ang II-forming activity, garnered interest due to the success of angiotensin converting enzyme inhibitors (ACEi) in the treatment of heart failure. The VALIANT trial evaluated the contribution of this alternate Ang II pathway by adding an AT 1 Ang II receptor blocker (ARB) to an ACEi post-myocardial infarction (MI), but the combination showed no additional benefit, suggesting CHY was unimportant post-MI. However, the role of CHY, independent of its Ang II-forming activity, remains unaddressed. To test this, we first re-evaluated the role of CHY-generated Ang II by blocking the effects of ACE+CHY-generated Ang II using an ACEi+ARB+AT 2 receptor blocker (PD122139) combination (AAA), and compared this to ACEi monotherapy in wild-type (WT) mice. We then addressed the Ang II-independent role of CHY by comparing these therapies in chymase (MMCP-4)-deficient (KO) vs WT mice. WT and KO mice (N=10-20) underwent sham or MI (90-min ischemia-reperfusion) surgery, and were treated daily with vehicle (Veh), ACEi, or AAA 24h post reperfusion. After 14 days, echocardiographic and hemodynamic analyses indicated no significant inter-genotype differences in sham animals. In post-MI WT mice, ACEi vs Veh resulted in improved ejection fraction (EF) (34±1.8% vs 28±1.7%; p<0.05) and reduced LV end-diastolic dimension (LVEDD) (4.2+0.09 mm vs 4.7±0.1 mm; p<0.05). However, AAA did not result in further improvements in either parameter as compared to ACEi, suggesting that CHY-generated Ang II is unimportant post-MI, confirming VALIANT. While the initial (24-h post-MI) infarct sizes were similar between genotypes (WT: 63±5% vs KO: 65±2% infarct as percent of area at risk; p=0.6), EF was superior in KO vs WT mice in all treatment groups (36±3% vs 28±2% (Veh); 47±3% vs 34±2% (ACEi); 49±3% vs 36±3% (AAA); p<0.05). Further, LV dilatation was also more pronounced in WT mice (LVEDD: 4.7±0.4 mm, WT-Veh vs 4.3±0.5 mm, KO-Veh; p<0.05). ACEi decreased mean arterial pressure post-MI (p<0.01), but not differentially in WT vs KO (Veh: 70±5 mmHg vs 66±3 mmHg; p=0.47; ACEi: 48±3.7 mmHg vs 38±4.8 mmHg; N=6−10; p=0.1). Thus, we conclude that CHY, independent of Ang II, is a potential therapeutic target for the treatment of the post-MI heart.

Abstract 393: Chymase: Augmented Renal Tubular Protein Expression in Diabetes

Chymase is a serine protease that is predominantly found stored in granules of mast cells. Chymase expression is increased in mesangial cells, podocytes, vascular smooth muscle cells, and cardiomyocytes under hyperglycemic culture conditions. We have presented evidence for enhanced intrarenal chymase-dependent Ang II formation on afferent arteriole vasoconstriction in the diabetic kidney ( Hypertension. 56: e55, 2010). We tested the hypothesis that renal chymase protein expression is enhanced in the diabetic kidney. Kidneys were harvested from littermate control ( db/m ) and type II diabetic ( db/db ) mice at 36-wk-old. Body weight was significantly lower (33 ± 3 vs 40 ± 2 g), while plasma glucose was significantly higher (552 ± 40 vs 220 ± 21 mg/dl) in diabetic (n=6) compared to control (n=7) mice. However, plasma insulin levels were not different from controls (0.77 ± 0.10 vs 0.43 ± 0.11 mg/L), indicating that the diabetic mice are transitioning from type II to type I diabetic disease. Immunohistochemistry was performed using primary rabbit polyclonal antibodies [mMCP-4 (chymase, A Husain), anti-malignant T cell amplified sequence 1 (chymase, Abcam), H + -ATPase (D Brown), and aquaporin 2 (AQP2, J Sands)]. Renal subcapsular and adipose tissue mast cell granules stained positively for toluidine blue and chymase. Chymase protein expression was localized to the apical membrane of connecting tubules and cortical collecting ducts of both control and diabetic kidneys. Chymase was co-localized to AQP2 positive and H + -ATPase negative cells indicating that chymase is specifically expressed in the principal cells of the distal nephron. Prominent chymase immunostaining was observed in the renal papilla and endothelial cells of renal arteries and arterioles in all diabetic, but none of the control kidneys. Chymase was not localized to renal vascular smooth muscle cells. The renal localization of chymase was identical using custom and commercially available polyclonal antibodies. These are the first studies to identify chymase protein expression in the principal cells of the distal nephron. These novel data suggest that the serine protease actions of chymase may be linked to altered epithelial transport mechanisms in the distal nephron in diabetic kidney disease.

Impact of Mast Cell Chymase on Renal Disease Progression

Chymase, a serine protease found in mast cell granules, is released into the interstitium following injury or inflammation. Chymase is the primary ACE-independent pathway of angiotensin II formation, and also functions to activate TGF-beta and other promoters of extracellular matrix degradation, thereby playing a role in tissue remodeling. In the diseased kidney, chymase-containing mast cells markedly increase and their density correlates with tubulointerstitial fibrosis severity. Studies in humans support the pathologic role of chymase in diabetic nephropathy, while animal studies form the basis for the importance of increased chymase-dependent angiotensin II formation in progressive hypertensive, diabetic and inflammatory nephropathies. Moreover, humans with kidney disease express chymase in diseased blood vessels in concordance with significantly elevated plasma chymase levels. Conversely, specific chymase inhibitors attenuate angiotensin II production and renal fibrosis in animal models, suggesting their potential therapeutic benefit in human nephropathy, where chymase-containing mast cells accumulate and contribute to progressive disease.

Increased plasma chymase concentration and mast cell chymase expression in venous neointimal lesions of patients with CKD and ESRD

The underlying inflammatory component of chronic kidney disease may predispose blood vessels to intimal hyperplasia (IH), which is the primary cause of dialysis access failure. We hypothesize that vascular pathology and markers of IH formation are antecedent to arteriovenous (AV) fistula creation. Blood, cephalic, and basilic vein segments were collected from predialysis chronic kidney disease (CKD) patients with no previous AV access and patients with end-stage renal disease (ESRD). Immunohistochemistry was performed with antibodies against mast cell chymase, transforming growth factor-beta (TGF-β) and interleukin-6 (IL-6), which cause IH. Plasma chymase was measured by ELISA. IH was present in 91% of CKD and 75% of ESRD vein segments. Chymase was abundant in vessels with IH, with the greatest expression in intima and medial layers, and virtually absent in the controls. Chymase colocalized with TGF-β1 and IL-6. Plasma chymase concentration was elevated up to 33-fold in patients with CKD versus controls and was associated with increased chymase in vessels with IH. We show that chymase expression in vessels with IH corresponds with plasma chymase concentrations. As chymase inhibition attenuates IH in animal models, and we find chymase is highly expressed in IH lesions of patients with CKD and ESRD, we speculate that chymase inhibition could have therapeutic value in humans.

Mast cell chymase limits the cardiac efficacy of Ang I-converting enzyme inhibitor therapy in rodents

Ang I-converting enzyme (ACE) inhibitors are widely believed to suppress the deleterious cardiac effects of Ang II by inhibiting locally generated Ang II. However, the recent demonstration that chymase, an Ang II-forming enzyme stored in mast cell granules, is present in the heart has added uncertainty to this view. As discussed here, using microdialysis probes tethered to the heart of conscious mice, we have shown that chronic ACE inhibitor treatment did not suppress Ang II levels in the LV interstitial fluid (ISF) despite marked inhibition of ACE. However, chronic ACE inhibition caused a marked bradykinin/B2 receptor-mediated increase in LV ISF chymase activity that was not observed in mast cell-deficient KitW/KitW-v mice. In chronic ACE inhibitor-treated mast cell-sufficient littermates, chymase inhibition decreased LV ISF Ang II levels substantially, indicating the importance of mast cell chymase in regulating cardiac Ang II levels. Chymase-dependent processing of other regulatory peptides also promotes inflammation and tissue remodeling. We found that combined chymase and ACE inhibition, relative to ACE inhibition alone, improved LV function, decreased adverse cardiac remodeling, and improved survival after myocardial infarction in hamsters. These results suggest that chymase inhibitors could be a useful addition to ACE inhibitor therapy in the treatment of heart failure.

Insights into the characteristics of mammalian cardiomyocyte terminal differentiation shown through the study of mice with a dysfunctional c-kit

Mammalian cardiomyocytes withdraw from the cell cycle soon after birth. This process is called terminal differentiation. The c-kit, a receptor tyrosine kinase, is expressed on cardiomyocytes immediately after birth but for only a few days. In mice with genetic c-kit dysfunction, adult cardiomyocytes are phenotypically indistinguishable from those of wild type mice, except that they are capable of proliferation in vivo after acute pressure overload. This review explores the idea that postnatal cardiomyocyte differentiation and cell cycle withdrawal are distinct processes and that terminal differentiation may not simply be due to altered expression of genes that regulate the cell cycle but could involve c-kit induced epigenetic change.

c-kit is required for cardiomyocyte terminal differentiation

c-kit, the transmembrane tyrosine kinase receptor for stem cell factor, is required for melanocyte and mast cell development, hematopoiesis, and differentiation of spermatogonial stem cells. We show here that in the heart, c-kit is expressed not only by cardiac stem cells but also by cardiomyocytes, commencing immediately after birth and terminating a few days later, coincident with the onset of cardiomyocyte terminal differentiation. To examine the function of c-kit in cardiomyocyte terminal differentiation, we used compound heterozygous mice carrying the W (null) and W(v) (dominant negative) mutations of c-kit. In vivo, adult W/W(v) cardiomyocytes are phenotypically indistinguishable from their wild-type counterparts. After acute pressure overload adult W/W(v) cardiomyocytes reenter the cell cycle and proliferate, leading to left ventricular growth; furthermore in transgenic mice with cardiomyocyte-restricted overexpression of the dominant negative W(v) mutant, pressure overload causes cardiomyocytes to reenter the cell cycle. In contrast, in wild-type mice left ventricular growth after pressure overload results mainly from cardiomyocyte hypertrophy. Importantly, W/W(v) mice with pressure overload-induced cardiomyocyte hyperplasia had improved left ventricular function and survival. In W/W(v) mice, c-kit dysfunction also resulted in an approximately 14-fold decrease (P<0.01) in the number of c-kit(+)/GATA4(+) cardiac progenitors. These findings identify novel functions for c-kit: promotion of cardiac stem cell differentiation and regulation of cardiomyocyte terminal differentiation.

The molecular basis for the selection of captopril cis and trans conformations by angiotensin I converting enzyme

Enzyme-inhibitor recognition is considered one of the most fundamental aspects in the area of drug discovery. However, the molecular mechanism of this recognition process (induced fit or prebinding and adaptive selection among multiple conformers) in several cases remains unexplored. In order to shed light toward this step of the recognition process in the case of human angiotensin I converting enzyme (hACE) and its inhibitor captopril, we have established a novel combinatorial approach exploiting solution NMR, flexible docking calculations, mutagenesis, and enzymatic studies. We provide evidence that an equimolar ratio of the cis and trans states of captopril exists in solution and that the enzyme selects only the trans state of the inhibitor that presents architectural and stereoelectronic complementarity with its substrate binding groove.

A new formula for blood transfusion volume in the critically ill

BACKGROUND

Published formulae, frequently used to predict the volume of transfused red cells required to achieve a desired rise in haemoglobin (Hb) or haematocrit (Hct), do not appear to have been validated in clinical practice.

AIMS

To examine the relation between transfusion volume and the resulting rise in Hb and Hct in critically ill children.

METHODS

Phase 1: Sample of 50% of children admitted during 1997; 237 of these 495 patients received at least one packed red cell transfusion; 82 children were transfused without confounding factors that could influence the Hb/Hct response to transfusion and were analysed further. Actual rise in Hb concentration or haematocrit was compared to that expected from use of existing formulae. A new formula was developed. Phase 2: In 50 children receiving a packed red cell transfusion during 2001, actual rise in Hb concentration was compared to expected rise in Hb with use of the new formula.

RESULTS

Phase 1: Existing formulae performed poorly; median ratio of actual/predicted rise in Hb or Hct ranged from 0.61 to 0.85. Using the regression coefficients new formulae were developed for both Hb and Hct. These formulae were applicable across all age and diagnostic groups. Phase 2: Median ratio of actual/predicted rise in Hb improved to 0.95 with use of the new formula.

CONCLUSIONS

Existing formulae underestimate the volume of packed red cells required to achieve a target Hb or Hct. Adoption of the new formulae could reduce the number of transfusion episodes in PICU, cutting costs and reducing risk.

Molecular basis of exopeptidase activity in the C-terminal domain of human angiotensin I-converting enzyme: insights into the origins of its exopeptidase activity

Proteolytic processing is a primary means of biological control. Exopeptidases use terminal anchoring interactions to restrict cleavage at peptide substrate N or C termini. In contrast, internal peptide bond targeting by endopeptidases is through context-driven recognition. Angiotensin I-converting enzyme (ACE), a zinc metalloproteinase, has tandem duplicate catalytic domains, N- and C-terminal, each of which is a dual specificity enzyme with exo- and endocarboxypeptidase activities. The mechanisms by which ACE evolved from its endopeptidase ancestors as a dual specificity enzyme have not been defined. Based on kinetic studies of wild-type and mutant forms of the C-terminal catalytic domain of human ACE and of the ACE substrates angiotensin I, substance P, and bradykinin, as well as considerations of the ACE x-ray structure, we provide evidence that the acquisition of its exopeptidase activity is due to novel evolutionary specializations. These involve not only interactions between the S(2)' subsite cognate for the C-terminal substrate P(2)' side chain, acting in concert with carboxylate-docking interactions with Lys(1087) and Tyr(1096), but also electrostatic selection against a cationic C-terminal substrate carboxylate. With a blocked C terminus, substrate side chain interactions are dominant in cleavage site selection. In the evolution of obligate exopeptidases from endopeptidase ancestors, mutations that destroy context-driven peptide bond targeting are likely to have followed the acquisition of terminal docking interactions. Evolutionary intermediates between endopeptidases and obligate exopeptidases could therefore have been dual specificity proteinases like ACE.

Standard cardiac rehabilitation is less effective for diabetics

To assess clinical outcomes and lifestyle modifications in diabetic patients attending a standard cardiac rehabilitation programme following myocardial infarction (MI), a retrospective longitudinal study was undertaken in a district general hospital in the north west of England. A total of 1804 patients attended the cardiac rehabilitation programme over 10 years, of whom 223 (12.4%) had diabetes mellitus. Drugs were underprescribed in all patients, aspirin and beta-blockers especially in diabetics (75.3% vs 90.3%, p < 0.0001; 38.6% vs 60.8%, p < 0.0001). Smoking cessation was poor in diabetics (54.2% vs 69.1%, p < 0.003) and diabetics were less likely to attend at least one session of physiotherapy (26.9% vs 58.6%, p < 0.0001). Diabetics had higher mortality at one year (15.7% vs 5.6%; p < 0.0001), mostly associated with cardiovascular disease (13.4% vs 5.4%, p < 0.0001). Standard cardiac rehabilitation programmes appear to be less effective for patients with diabetes mellitus. We suggest that patients presenting with an existing chronic condition need specialised programmes of rehabilitation to integrate the care of that condition with their recent MI. Aggressive drug therapy following acute MI should also be prescribed in all patients when not contraindicated by other evidence.

Early filtration and mortality in meningococcal septic shock?

Following the introduction of a policy of early therapeutic filtration for presumed meningococcal septicaemic shock, the overall mortality has decreased.

Asymptomatic pituitary apoplexy after aortocoronary bypass surgery

Pituitary apoplexy usually presents with acute neuro-ophthalmological complications that require urgent neurosurgical intervention. We present a case of pituitary apoplexy following aortocoronary bypass surgery that was asymptomatic until the patient presented with features of hormonal deficiency three months later. Only one case of pituitary apoplexy has been described in the literature following cardiac surgery that did not require operative intervention. We discuss the aetiology of pituitary apoplexy and the possible mechanisms for such an event after cardiac surgery. Although this is rare, any unusual feature after operation such as lethargy or erectile dysfunction should remind us of hypopituitarism.