Correlation of anorectal symptoms and endoanal ultrasound findings after obstetric anal sphincter injuries (OASIS)

INTRODUCTION

Obstetric anal sphincter injuries (OASIS) predispose to development of anorectal symptoms that affect women's quality of life.

METHODS

A retrospective cohort study was conducted for all women with singleton vaginal deliveries who had a primary OASIS repair and attended the Postpartum Perineal Clinic between July 1st 2017 and December 31st 2020. This study was approved by the Research Ethics Board. The purpose of this study was (1) to determine correlation between endoanal ultrasound (EAUS) findings and anorectal symptoms quantified by the St. Mark's Incontinence Score (SMIS), (2) to determine the incidence of residual anal sphincter defects, and (3) to determine the rate of clinical overdiagnosis of OASIS. Pearson correlation coefficient was used to assess correlation between anorectal symptoms and EAUS findings.

RESULTS

A total of 247 participants with clinical diagnosis of OASIS met the inclusion criteria. A 3rd-degree tear was identified in 126 (51.0%) and 4th-degree tear was identified in 30 (12.1%) participants. In participants with sonographic evidence of OASIS, there was a statistically significant weak positive correlation between the size of residual defect and SMIS for both external anal sphincter (EAS) (r = .3723, p < .0001) and internal anal sphincter (IAS) (r = .3122, p = .0180). Residual defect in the anorectal sphincter of greater than 1 hour (> 30°) in width was present in 64.3% participants with 3rd-degree tear and 86.7% participants with 4th-degree tear. The rate of overdiagnosis was 36.8%.

CONCLUSION

The size of residual defect of EAS and IAS has a weak positive correlation with anorectal symptoms, emphasizing the importance of EAUS for counselling regarding mode of subsequent delivery.

Murradambirra Dhangaang (make food secure): Aboriginal community and stakeholder perspectives on food insecurity in urban and regional Australia

Background

It is widely acknowledged that the invasion by colonial powers of the Australian continent had profound and detrimental impacts on Aboriginal Communities, including food security. Policies of successive governments since European arrival have since further exacerbated the situation, with food insecurity now affecting 20–25% of Aboriginal and Torres Strait Islander people. Food insecurity contributes to long-term impacts on health, in particular diet-sensitive chronic diseases. This study aimed to describe Aboriginal community and stakeholder perspectives on food insecurity to get a better understanding of the key contributing factors and recommendations for potential strategies to address this issue in Aboriginal communities in urban and regional Australia.

Methods

Semi-structured interviews were conducted with 44 participants who were purposively selected. This included Aboriginal people in two communities and both Aboriginal and non-Aboriginal stakeholders from local food relief agencies, food suppliers, schools, and government in an urban and regional location in NSW. A conceptual framework was developed from literature on food security, and sensitizing concepts of availability, affordability, accessibility and acceptability or the lack thereof of healthy food were used to elicit responses from the participants. Interview transcripts were analysed thematically.

Results

All participants felt strongly that food insecurity was a major problem experienced in their local Aboriginal communities. Five core areas impacting on food security were identified: trapped in financial disadvantage; gaps in the local food system; limitations of non-Aboriginal food relief services; on-going impacts of colonization; and maintaining family, cultural and community commitments and responsibilities. Participants suggested a number of actions that could help ease food insecurity and emphasized that Aboriginal values and culture must be strongly embedded in potential programs.

Conclusions

This study found Aboriginal families in urban and regional Australia are experiencing food insecurity on a regular basis, which is impacted by a range of socio-economic, environmental, systemic and cultural factors, as reported by the participants. Study findings highlight the need to address system level changes in the food environment and acknowledge Aboriginal history, culture and food preferences when considering the development of programs to alleviate food insecurity among Aboriginal people.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-13202-z.

Remuscularization with triiodothyronine and β1-blocker therapy reverses post-ischemic left ventricular dysfunction and adverse remodeling

Renewal of the myocardium by preexisting cardiomyocytes is a powerful strategy for restoring the architecture and function of hearts injured by myocardial infarction. To advance this strategy, we show that combining two clinically approved drugs, but neither alone, muscularizes the heart through cardiomyocyte proliferation. Specifically, in adult murine cardiomyocytes, metoprolol, a cardioselective β1-adrenergic receptor blocker, when given with triiodothyronine (T3, a thyroid hormone) accentuates the ability of T3 to stimulate ERK1/2 phosphorylation and proliferative signaling by inhibiting expression of the nuclear phospho-ERK1/2-specific phosphatase, dual-specificity phosphatase-5. While short-duration metoprolol plus T3 therapy generates new heart muscle in healthy mice, in mice with myocardial infarction-induced left ventricular dysfunction and pathological remodeling, it remuscularizes the heart, restores contractile function and reverses chamber dilatation; outcomes that are enduring. If the beneficial effects of metoprolol plus T3 are replicated in humans, this therapeutic strategy has the potential to definitively address ischemic heart failure.

Mechanism-Based Cardiac Regeneration Strategies in Mammals

Heart failure in adults is a leading cause of morbidity and mortality worldwide. It can arise from a variety of diseases, with most resulting in a loss of cardiomyocytes that cannot be replaced due to their inability to replicate, as well as to a lack of resident cardiomyocyte progenitor cells in the adult heart. Identifying and exploiting mechanisms underlying loss of developmental cardiomyocyte replicative capacity has proved to be useful in developing therapeutics to effect adult cardiac regeneration. Of course, effective regeneration of myocardium after injury requires not just expansion of cardiomyocytes, but also neovascularization to allow appropriate perfusion and resolution of injury-induced inflammation and interstitial fibrosis, but also reversal of adverse left ventricular remodeling. In addition to overcoming these challenges, a regenerative therapy needs to be safe and easily translatable. Failure to address these critical issues will delay the translation of regenerative approaches. This review critically analyzes current regenerative approaches while also providing a framework for future experimental studies aimed at enhancing success in regenerating the injured heart.

Thyroid hormone plus dual-specificity phosphatase-5 siRNA increases the number of cardiac muscle cells and improves left ventricular contractile function in chronic doxorubicin-injured hearts

Rationale: Doxorubicin is a widely used anticancer drug. However, its major side effect, cardiotoxicity, results from cardiomyocyte loss that causes left ventricle (LV) wall thinning, chronic LV dysfunction and heart failure. Cardiomyocyte number expansion by thyroid hormone (T3) during preadolescence is suppressed by the developmental induction of an ERK1/2-specific dual specificity phosphatase 5 (DUSP5). Here, we sought to determine if a brief course of combined DUSP5 suppression plus T3 therapy replaces cardiomyocytes lost due to preexisting doxorubicin injury and reverses heart failure. Methods: We used in vivo-jetPEI to deliver DUSP5 or scrambled siRNA to ~5-week-old C57BL6 mice followed by 5 daily injections of T3 (2 ng/µg body weight). Genetic lineage tracing using Myh6-MerCreMer::Rosa26fs-Confetti mice and direct cardiomyocyte number counting, along with cell cycle inhibition (danusertib), was used to test if this treatment leads to de novo cardiomyocyte generation and improves LV contractile function. Three doses of doxorubicin (20 µg/g) given at 2-weekly intervals, starting at 5-weeks of age in C57BL6 mice, caused severe heart failure, as evident by a decrease in LV ejection fraction. Mice with an ~40 percentage point decrease in LVEF post-doxorubicin injury were randomized to receive either DUSP5 siRNA plus T3, or scrambled siRNA plus vehicle for T3. Age-matched mice without doxorubicin injury served as controls. Results: In uninjured adult mice, transient therapy with DUSP5 siRNA and T3 increases cardiomyocyte numbers, which is required for the associated increase in LV contractile function, since both are blocked by danusertib. In mice with chronic doxorubicin injury, DUSP5 siRNA plus T3 therapy rebuilds LV muscle by increasing cardiomyocyte numbers, which reverses LV dysfunction and prevents progressive chamber dilatation. Conclusion: RNA therapies are showing great potential. Importantly, a GMP compliant in vivo-jetPEI system for delivery of siRNA is already in use in humans, as is T3. Given these considerations, our findings provide a potentially highly translatable strategy for addressing doxorubicin cardiomyopathy, a currently untreatable condition.

DUSP5 expression in left ventricular cardiomyocytes of young hearts regulates thyroid hormone (T3)-induced proliferative ERK1/2 signaling

Cardiomyocytes of newborn mice proliferate after injury or exposure to growth factors. However, these responses are diminished after postnatal day-6 (P6), representing a barrier to building new cardiac muscle in adults. We have previously shown that exogenous thyroid hormone (T3) stimulates cardiomyocyte proliferation in P2 cardiomyocytes, by activating insulin-like growth factor-1 receptor (IGF-1R)-mediated ERK1/2 signaling. But whether exogenous T3 functions as a mitogen in post-P6 murine hearts is not known. Here, we show that exogenous T3 increases the cardiomyocyte endowment of P8 hearts, but the proliferative response is confined to cardiomyocytes of the left ventricular (LV) apex. Exogenous T3 stimulates proliferative ERK1/2 signaling in apical cardiomyocytes, but not in those of the LV base, which is inhibited by expression of the nuclear phospho-ERK1/2-specific dual-specificity phosphatase, DUSP5. Developmentally, between P7 and P14, DUSP5 expression increases in the myocardium from the LV base to its apex; after this period, it is uniformly expressed throughout the LV. In young adult hearts, exogenous T3 increases cardiomyocyte numbers after DUSP5 depletion, which might be useful for eliciting cardiac regeneration.

Pressure overload by suprarenal aortic constriction in mice leads to left ventricular hypertrophy without c-Kit expression in cardiomyocytes

Animal models of pressure overload are valuable for understanding hypertensive heart disease. We characterised a surgical model of pressure overload-induced hypertrophy in C57BL/6J mice produced by suprarenal aortic constriction (SAC). Compared to sham controls, at one week post-SAC systolic blood pressure was significantly elevated and left ventricular (LV) hypertrophy was evident by a 50% increase in the LV weight-to-tibia length ratio due to cardiomyocyte hypertrophy. As a result, LV end-diastolic wall thickness-to-chamber radius (h/R) ratio increased, consistent with the development of concentric hypertrophy. LV wall thickening was not sufficient to normalise LV wall stress, which also increased, resulting in LV systolic dysfunction with reductions in ejection fraction and fractional shortening, but no evidence of heart failure. Pathological LV remodelling was evident by the re-expression of fetal genes and coronary artery perivascular fibrosis, with ischaemia indicated by enhanced cardiomyocyte Hif1a expression. The expression of stem cell factor receptor, c-Kit, was low basally in cardiomyocytes and did not change following the development of robust hypertrophy, suggesting there is no role for cardiomyocyte c-Kit signalling in pathological LV remodelling following pressure overload.

Inhibition of urea transporter ameliorates uremic cardiomyopathy in chronic kidney disease

Uremic cardiomyopathy, characterized by hypertension, cardiac hypertrophy, and fibrosis, is a complication of chronic kidney disease (CKD). Urea transporter (UT) inhibition increases the excretion of water and urea, but the effect on uremic cardiomyopathy has not been studied. We tested UT inhibition by dimethylthiourea (DMTU) in 5/6 nephrectomy mice. This treatment suppressed CKD-induced hypertension and cardiac hypertrophy. In CKD mice, cardiac fibrosis was associated with upregulation of UT and vimentin abundance. Inhibition of UT suppressed vimentin amount. Left ventricular mass index in DMTU-treated CKD was less compared with non-treated CKD mice as measured by echocardiography. Nephrectomy was performed in UT-A1/A3 knockout (UT-KO) to further confirm our finding. UT-A1/A3 deletion attenuates the CKD-induced increase in cardiac fibrosis and hypertension. The amount of α-smooth muscle actin and tgf-β were significantly less in UT-KO with CKD than WT/CKD mice. To study the possibility that UT inhibition could benefit heart, we measured the mRNA of renin and angiotensin-converting enzyme (ACE), and found both were sharply increased in CKD heart; DMTU treatment and UT-KO significantly abolished these increases. Conclusion: Inhibition of UT reduced hypertension, cardiac fibrosis, and improved heart function. These changes are accompanied by inhibition of renin and ACE.

Evaluation of the Fracture Liaison Service within the Canadian Healthcare Setting

Previous studies evaluating fracture liaison service (FLS) programs have found them to be cost-effective, efficient, and reduce the risk of fracture. However, few studies have evaluated the clinical effectiveness of these programs. We compared the patient populations of those referred for osteoporosis management by FLS to those referred by primary care physicians (PCP), within the Canadian healthcare system in the province of Ontario. Specifically, we investigated if a referral from FLS is similarly effective as PCP at identifying patients at risk for future osteoporotic fractures and if osteoporosis therapies have been previously initiated. A retrospective chart review of patients assessed by a single Ontario rheumatology practice affiliated with FLS between January 1, 2014, and December 31, 2017, was performed identifying two groups: those referred by FLS within Hamilton and those referred by their PCP for osteoporosis management. Fracture risk of each patient was determined using FRAX. A total of 573 patients (n = 225 (FLS group) and n = 227 (PCP group)) were evaluated. Between the FLS and PCP groups, there were no significant differences in the absolute 10-year risk of a major osteoporotic fracture (15.6% (SD = 10.2) vs 15.3% (SD = 10.3)) and 10-year risk of hip fracture (4.7% (SD = 8.3) vs 4.7% (SD = 6.8)), respectively. 10.7% of patients referred by FLS and 40.5% of patients referred by their PCP were on osteoporosis medication prior to fracture. Our study suggests that referral from FLS is similarly effective as PCP at identifying patients at risk for future osteoporotic fractures, and clinically effective at identifying the care gap with the previous use of targeted osteoporosis therapies from referral from PCP being low and much lower in those referred by FLS. Interventional programs such as FLS can help close the treatment gap by providing appropriate care to patients that were not previously identified to be at risk for fracture by their primary care physician and initiate proper medical management.

Role of DJ-1 in Modulating Glycative Stress in Heart Failure

Background

DJ‐1 is a ubiquitously expressed protein typically associated with the development of early onset Parkinson disease. Recent data suggest that it also plays a role in the cellular response to stress. Here, we sought to determine the role DJ‐1 plays in the development of heart failure.

Methods and Results

Initial studies found that DJ‐1 deficient mice (DJ‐1 knockout; male; 8–10 weeks of age) exhibited more severe left ventricular cavity dilatation, cardiac dysfunction, hypertrophy, and fibrosis in the setting of ischemia‐reperfusion–induced heart failure when compared with wild‐type littermates. In contrast, the overexpression of the active form of DJ‐1 using a viral vector approach resulted in significant improvements in the severity of heart failure when compared with mice treated with a control virus. Subsequent studies aimed at evaluating the underlying protective mechanisms found that cardiac DJ‐1 reduces the accumulation of advanced glycation end products and activation of the receptor for advanced glycation end products—thus, reducing glycative stress.

Conclusions

These results indicate that DJ‐1 is an endogenous cytoprotective protein that protects against the development of ischemia‐reperfusion–induced heart failure by reducing glycative stress. Our findings also demonstrate the feasibility of using a gene therapy approach to deliver the active form of DJ‐1 to the heart as a therapeutic strategy to protect against the consequences of ischemic injury, which is a major cause of death in western populations.

Redox activation of JNK2α2 mediates thyroid hormone-stimulated proliferation of neonatal murine cardiomyocytes

Mitochondria-generated reactive oxygen species (mROS) are frequently associated with DNA damage and cell cycle arrest, but physiological increases in mROS serve to regulate specific cell functions. T3 is a major regulator of mROS, including hydrogen peroxide (H₂O₂). Here we show that exogenous thyroid hormone (T3) administration increases cardiomyocyte numbers in neonatal murine hearts. The mechanism involves signaling by mitochondria-generated H₂O₂ (mH₂O₂) acting via the redox sensor, peroxiredoxin-1, a thiol peroxidase with high reactivity towards H₂O₂ that activates c-Jun N-terminal kinase-2α2 (JNK2α2). JNK2α2, a relatively rare member of the JNK family of mitogen-activated protein kinases (MAPK), phosphorylates c-Jun, a component of the activator protein 1 (AP-1) early response transcription factor, resulting in enhanced insulin-like growth factor 1 (IGF-1) expression and activation of proliferative ERK1/2 signaling. This non-canonical mechanism of MAPK activation couples T3 actions on mitochondria to cell cycle activation. Although T3 is regarded as a maturation factor for cardiomyocytes, these studies identify a novel redox pathway that is permissive for T3-mediated cardiomyocyte proliferation—this because of the expression of a pro-proliferative JNK isoform that results in growth factor elaboration and ERK1/2 cell cycle activation.

miR-26a Limits Muscle Wasting and Cardiac Fibrosis through Exosome-Mediated microRNA Transfer in Chronic Kidney Disease

Uremic cardiomyopathy and muscle atrophy are associated with insulin resistance and contribute to chronic kidney disease (CKD)-induced morbidity and mortality. We hypothesized that restoration of miR-26a levels would enhance exosome-mediated microRNA transfer to improve muscle wasting and cardiomyopathy that occur in CKD.

Methods: Using next generation sequencing and qPCR, we found that CKD mice had a decreased level of miR-26a in heart and skeletal muscle. We engineered an exosome vector that contained Lamp2b, an exosomal membrane protein gene fused with a muscle-specific surface peptide that targets muscle delivery. We transfected this vector into muscle satellite cells and then transduced these cells with adenovirus that expresses miR-26a to produce exosomes encapsulated miR-26a (Exo/miR-26a). Exo/miR-26a was injected once per week for 8 weeks into the tibialis anterior (TA) muscle of 5/6 nephrectomized CKD mice.

Results: Treatment with Exo/miR-26a resulted in increased expression of miR-26a in skeletal muscle and heart. Overexpression of miR-26a increased the skeletal muscle cross-sectional area, decreased the upregulation of FBXO32/atrogin-1 and TRIM63/MuRF1 and depressed cardiac fibrosis lesions. In the hearts of CKD mice, FoxO1 was activated, and connective tissue growth factor, fibronectin and collagen type I alpha 1 were increased. These responses were blunted by injection of Exo/miR-26a. Echocardiograms showed that cardiac function was improved in CKD mice treated with Exo/miR-26a.

Conclusion: Overexpression of miR-26a in muscle prevented CKD-induced muscle wasting and attenuated cardiomyopathy via exosome-mediated miR-26a transfer. These results suggest possible therapeutic strategies for using exosome delivery of miR-26a to treat complications of CKD.

Impact of Lymphangiogenesis on Cardiac Remodeling After Ischemia and Reperfusion Injury

Background Lymphatic vessels interconnect with blood vessels to form an elaborate system that aids in the control of tissue pressure and edema formation. Although the lymphatic system has been known to exist in a heart, little is known about the role the cardiac lymphatic system plays in the development of heart failure. Methods and Results Mice (C57 BL /6J, male, 8 to 12 weeks of age) were subjected to either myocardial ischemia or myocardial ischemia and reperfusion for up to 28 days. Analysis revealed that both models increased the protein expression of vascular endothelial growth factor C and VEGF receptor 3 starting at 1 day after the onset of injury, whereas a significant increase in lymphatic vessel density was observed starting at 3 days. Further studies aimed to determine the consequences of inhibiting the endogenous lymphangiogenesis response on the development of heart failure. Using 2 different pharmacological approaches, we found that inhibiting VEGF receptor 3 with MAZ -51 and blocking endogenous vascular endothelial growth factor C with a neutralizing antibody blunted the increase in lymphatic vessel density, blunted lymphatic transport, increased inflammation, increased edema, and increased cardiac dysfunction. Subsequent studies revealed that augmentation of the endogenous lymphangiogenesis response with vascular endothelial growth factor C treatment reduced inflammation, reduced edema, and improved cardiac dysfunction. Conclusions These results suggest that the endogenous lymphangiogenesis response plays an adaptive role in the development of ischemic-induced heart failure and supports the emerging concept that therapeutic lymphangiogenesis is a promising new approach for the treatment of cardiovascular disease.

Cardiac hypertrophy limits infarct expansion after myocardial infarction in mice

We have previously demonstrated that adult transgenic C57BL/6J mice with CM-restricted overexpression of the dominant negative W v mutant protein (dn-c-kit-Tg) respond to pressure overload with robust cardiomyocyte (CM) cell cycle entry. Here, we tested if outcomes after myocardial infarction (MI) due to coronary artery ligation are improved in this transgenic model. Compared to non-transgenic littermates (NTLs), adult male dn-c-kit-Tg mice displayed CM hypertrophy and concentric left ventricular (LV) hypertrophy in the absence of an increase in workload. Stroke volume and cardiac output were preserved and LV wall stress was markedly lower than that in NTLs, leading to a more energy-efficient heart. In response to MI, infarct size in adult (16-week old) dn-c-kit-Tg hearts was similar to that of NTL after 24 h but was half that in NTL hearts 12 weeks post-MI. Cumulative CM cell cycle entry was only modestly increased in dn-c-kit-Tg hearts. However, dn-c-kit-Tg mice were more resistant to infarct expansion, adverse LV remodelling and contractile dysfunction, and suffered no early death from LV rupture, relative to NTL mice. Thus, pre-existing cardiac hypertrophy lowers wall stress in dn-c-kit-Tg hearts, limits infarct expansion and prevents death from myocardial rupture.

Exercise training provides cardioprotection by activating and coupling endothelial nitric oxide synthase via a β3-adrenergic receptor-AMP-activated protein kinase signaling pathway

Exercise training confers sustainable protection against ischemia/reperfusion injury. However, the mechanism by which this process occurs is not fully understood. Previously, it was shown that β₃-adrenergic receptors (β₃-ARs) play a critical role in regulating the activation of endothelial nitric oxide synthase (eNOS) in response to exercise and play a critical role in exercise-mediated cardioprotection. Intriguingly, a deficiency in β₃-ARs led to increased myocardial injury following exercise training. The purpose of the current study was to determine mechanisms by which β₃-ARs are linked to eNOS activation and to determine the mechanism responsible for the exacerbated ischemia/reperfusion injury displayed by β₃-AR deficient (β₃-AR KO) mice after exercise training. Wild-type (n = 37) and β₃-AR KO (n = 40) mice were subjected to voluntary wheel running for 4 weeks. Western blot analysis revealed that neither protein kinase B nor protein kinase A linked β₃-ARs to eNOS following exercise training. However, analysis revealed a role for AMP-activated protein kinase (AMPK). Specifically, exercise training increased the phosphorylation of AMPK in the hearts of wild-type mice, but failed to do so in the hearts of β₃-AR KO mice. Additional studies revealed that exercise training rendered eNOS less coupled and increased NOS-dependent superoxide levels in β₃-AR KO mice. Finally, supplementing β₃-AR KO mice with the eNOS coupler, tetrahydrobiopterin, during the final week of exercise training reduced myocardial infarction. These findings provide important information that exercise training protects the heart in the setting of myocardial ischemia/reperfusion injury by activating and coupling eNOS via the stimulation of a β₃-AR-AMPK signaling pathway.

Angiotensin type 2-receptor (AT2R) activation induces hypotension in apolipoprotein E-deficient mice by activating peroxisome proliferator-activated receptor-γ

Angiotensin II (Ang II) modulates blood pressure and atherosclerosis development through its vascular type-1 (AT1R) and type-2 (AT2R) receptors, which have opposing effects. AT2R activation produces hypotension, and is anti-atherogenic. Targeted overexpression of AT2Rs in vascular smooth muscle cells (VSMCs) indicates that these effects are due to increased nitric oxide (NO) generation. However, the role of endogenous VSMC AT2Rs in these events is unknown. Effect of 7-day low-dose Ang II-infusion (12 µg/kg/hr) on blood pressure was tested in 9-week-old apoE((-/-)) mice fed a low or high cholesterol diet (LCD or HCD, respectively). Cardiac output was measured by echocardiography. Immunohistochemistry was performed to localize and quantify AT2Rs and p-Ser(1177)-endothelial nitric oxide synthase (eNOS) levels in the aortic arch. PD123319 and GW-9662 were used to selectively block the AT2R and peroxisome proliferator-activated receptor-γ (PPAR-γ), respectively. Ang II infusion decreased blood pressure by 12 mmHg (P < 0.001) in LCD/apoE((-/-)) mice without altering cardiac output; a response blocked by PD123319. Although, AT2R stimulation neither activated eNOS (p-Ser(1177)-eNOS) nor changed plasma NO metabolites, it caused an ~6-fold increase in VSMC PPAR-γ levels (P < 0.001) and the AT2R-mediated hypotension was abolished by GW-9662. AT2R-mediated hypotension was also inhibited by HCD, which selectively decreased VSMC AT2R expression by ~6-fold (P < 0.01). These findings suggest a novel pathway for the Ang II/AT2R-mediated hypotensive response that involves PPAR-γ, and is down regulated by a HCD.

Abstract P229: Chymase-mediated Igf-1 Degradation Promotes Delayed Cell Death in Post-ischemic Hearts

Heart disease is a leading cause of death in adults. Here we show that a few days after coronary artery ligation and reperfusion, the ischemia-injured heart elaborates the cardioprotective polypeptide, insulin-like growth factor-1 (IGF-1), which activates IGF-1 receptor prosurvival signaling and improves cardiac left ventricular systolic function. However, this is antagonized by the chymase, mouse mast cell protease-4 (MMCP-4), which degrades IGF-1 (Fig. 1). We found that MMCP-4 deficiency, resulted in sustained IGF-1 levels and IGF-1 receptor prosurvival signaling post-I/R. MMCP-4 deficiency markedly reduced late, but not early, infarct size (~50% reduction: n=5-7, p value= 0.001) by suppressing IGF-1 degradation and, consequently, improving cardiac function (EF: 26% greater, n=21, p value= 0.001) and adverse structural remodeling (Fig. 2). Our findings represent the first demonstration of tissue IGF-1 regulation through proteolytic degradation and suggest that chymase inhibition may be a viable therapeutic approach to enhance late cardioprotection in post-ischemic heart disease.

Sodium Sulfide Attenuates Ischemic-Induced Heart Failure by Enhancing Proteasomal Function in an Nrf2-Dependent Manner

BACKGROUND

Therapeutic strategies aimed at increasing hydrogen sulfide (H2S) levels exert cytoprotective effects in various models of cardiovascular injury. However, the underlying mechanism(s) responsible for this protection remain to be fully elucidated. Nuclear factor E2-related factor 2 (Nrf2) is a cellular target of H2S and facilitator of H2S-mediated cardioprotection after acute myocardial infarction. Here, we tested the hypothesis that Nrf2 mediates the cardioprotective effects of H2S therapy in the setting of heart failure.

METHODS AND RESULTS

Mice (12 weeks of age) deficient in Nrf2 (Nrf2 KO; C57BL/6J background) and wild-type littermates were subjected to ischemic-induced heart failure. Wild-type mice treated with H2S in the form of sodium sulfide (Na2S) displayed enhanced Nrf2 signaling, improved left ventricular function, and less cardiac hypertrophy after the induction of heart failure. In contrast, Na2S therapy failed to provide protection against heart failure in Nrf2 KO mice. Studies aimed at evaluating the underlying cardioprotective mechanisms found that Na2S increased the expression of proteasome subunits, resulting in an increased proteasome activity and a reduction in the accumulation of damaged proteins. In contrast, Na2S therapy failed to enhance the proteasome and failed to attenuate the accumulation of damaged proteins in Nrf2 KO mice. Additionally, Na2S failed to improve cardiac function when the proteasome was inhibited.

CONCLUSIONS

These findings indicate that Na2S therapy enhances proteasomal activity and function during the development of heart failure in an Nrf2-dependent manner and that this enhancement leads to attenuation in cardiac dysfunction.

CD163 interacts with TWEAK to regulate tissue regeneration after ischaemic injury

Macrophages are an essential component of the immune response to ischaemic injury and play an important role in promoting inflammation and its resolution, which is necessary for tissue repair. The type I transmembrane glycoprotein CD163 is exclusively expressed on macrophages, where it acts as a receptor for haemoglobin:haptoglobin complexes. An extracellular portion of CD163 circulates in the blood as a soluble protein, for which no physiological function has so far been described. Here we show that during ischaemia, soluble CD163 functions as a decoy receptor for TWEAK, a secreted pro-inflammatory cytokine of the tumour necrosis factor family, to regulate TWEAK-induced activation of canonical nuclear factor-κB (NF-κB) and Notch signalling necessary for myogenic progenitor cell proliferation. Mice with deletion of CD163 have transiently elevated levels of TWEAK, which stimulate muscle satellite cell proliferation and tissue regeneration in their ischaemic and non-ischaemic limbs. These results reveal a role for soluble CD163 in regulating muscle regeneration after ischaemic injury.

CD163 is a glycoprotein receptor expressed on the surface of macrophages. Here, the authors demonstrate that a soluble form of CD163 can act as a decoy receptor for the pro inflammatory cytokine TWEAK, thereby revealing a new mechanism for the regulation of tissue repair after ischaemic injury.

Abstract 409: CD163-TWEAK Interaction Regulates Tissue Regeneration After Ischemic Injury

Macrophages are an essential component of the response to ischemic injury and direct inflammation and its resolution necessary for proper tissue repair. However, a complete understanding of their exact roles in this process is lacking. CD163, a type I transmembrane glycoprotein, is a receptor for hemoglobin:haptoglobin complexes and is exclusively expressed on macrophages. Its extracellular portion circulates in the blood as a soluble protein of unknown function. Here we show that during hindlimb ischemia, soluble CD163 functions as a decoy receptor for TWEAK (tumor necrosis factor-like weak inducer of apoptosis), a secreted pro-inflammatory cytokine of the tumor necrosis factor family, to regulate TWEAK-induced activation of canonical NF-κB and Notch signaling necessary for myogenic progenitor cell proliferation. Mice with deletion of CD163 demonstrated transiently elevated levels of TWEAK, which activated of both canonical NF-KB and Notch signaling, and muscle satellite cell proliferation and tissue regeneration not limited to the site of injury. Our findings highlight a novel mechanism by which macrophages coordinate systemic tissue repair after ischemic injury through control of the pro-inflammatory cytokine TWEAK.

A proliferative burst during preadolescence establishes the final cardiomyocyte number

It is widely believed that perinatal cardiomyocyte terminal differentiation blocks cytokinesis, thereby causing binucleation and limiting regenerative repair after injury. This suggests that heart growth should occur entirely by cardiomyocyte hypertrophy during preadolescence when, in mice, cardiac mass increases many-fold over a few weeks. Here, we show that a thyroid hormone surge activates the IGF-1/IGF-1-R/Akt pathway on postnatal day 15 and initiates a brief but intense proliferative burst of predominantly binuclear cardiomyocytes. This proliferation increases cardiomyocyte numbers by ~40%, causing a major disparity between heart and cardiomyocyte growth. Also, the response to cardiac injury at postnatal day 15 is intermediate between that observed at postnatal days 2 and 21, further suggesting persistence of cardiomyocyte proliferative capacity beyond the perinatal period. If replicated in humans, this may allow novel regenerative therapies for heart diseases.

Thyroid hormone action in postnatal heart development

Thyroid hormone is a critical regulator of cardiac growth and development, both in fetal life and postnatally. Here we review the role of thyroid hormone in postnatal cardiac development, given recent insights into its role in stimulating a burst of cardiomyocyte proliferation in the murine heart in preadolescence; a response required to meet the massive increase in circulatory demand predicated by an almost quadrupling of body weight during a period of about 21 days from birth to adolescence. Importantly, thyroid hormone metabolism is altered by chronic diseases, such as heart failure and ischemic heart disease, as well as in very sick children requiring surgery for congenital heart diseases, which results in low T3 syndrome that impairs cardiovascular function and is associated with a poor prognosis. Therapy with T3 or thyroid hormone analogs has been shown to improve cardiac contractility; however, the mechanism is as yet unknown. Given the postnatal cardiomyocyte mitogenic potential of T3, its ability to enhance cardiac function by promoting cardiomyocyte proliferation warrants further consideration.

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.