Successful Implementation of Enhanced Recovery After Surgery (ERAS) in Paediatric Cardiac Surgery in Australia

BACKGROUND & AIM

Fast-track or enhanced recovery after surgery (ERAS) is a care pathway for surgical patients based on a multidisciplinary team approach aimed at optimising recovery without increasing risk with protocols based on scientific evidence, which is monitored continuously to ensure compliance and improvement. These protocols have been shown to reduce the duration of postoperative mechanical ventilation and intensive care unit (ICU) length of stay (LOS) following paediatric cardiac surgery. We present the first structured implementation of ERAS in paediatric cardiac surgery in Australia.

METHODS

All patients enrolled in the ERAS pathway between October 2019 and July 2023 were identified. Demographic and perioperative data were collected retrospectively from hospital records for patients operated before June 2021 and prospectively from June 2021. A control group (non-ERAS) was identified using propensity matching from patients who underwent similar procedures and were not enrolled in the ERAS pathway (prior to October 2019). Patients were matched for age, weight, and comprehensive Aristotle score. Outcomes of interest were duration of postoperative mechanical ventilation, ICU LOS, readmission to the ICU, hospital LOS, cardiac reintervention rate, postoperative complication rate, and number of 30-day readmissions.

RESULTS

Of 1,084 patients who underwent cardiac surgery during the study period (October 2019-July 2023), 121 patients (11.2%) followed the ERAS pathway. The median age at the time of surgery was 4.8 years (interquartile range [IQR] 2.8-8.8 years). The most common procedure was the closure of atrial septal defect (n=58, 47.9%). The median cardiopulmonary bypass and cross-clamp times were 40 min (IQR 28-53.5 minutes) and 24.5 min (IQR 13-34 minutes) respectively. The majority were extubated in the operating theatre (n=108, 89.3%). The median ICU and hospital LOS were 4.5 hrs (IQR 4.1-5.6 hours) and 4 days (IQR 4-5 days) respectively. None of the patients required readmission to the ICU within 24 hrs of discharge from the ICU. Three (3) patients (2.5%) required reintervention. When compared with the non-ERAS group, the duration of postoperative mechanical ventilation, ICU and hospital LOS were significantly lower in the ERAS group. There was no significant difference in the ICU readmission rate, reintervention rate, complication rate, and number of 30-day readmissions between both groups.

CONCLUSIONS

ERAS after paediatric cardiac surgery is feasible and safe in select patients with low preoperative risk. This pathway reduces the duration of postoperative mechanical ventilation, ICU and hospital LOS without increasing risks, enabling the optimisation of resources.

Upper partial sternal split for pediatric cardiac surgery

OBJECTIVES

We introduced the use of an upper partial sternal split for pediatric cardiac surgical procedures in our unit in 2016. We report the outcomes of our experience in 51 patients using this approach.

METHODS

From February 2016 to September 2022, 51 patients underwent congenital cardiac surgical procedures using an upper partial sternal split including vascular ring repair (n = 20), subaortic membrane (n = 12), ventricular septal defect closure with aortic valve resuspension (n = 9), aortic arch repair (n = 4), pulmonary artery band (n = 2), pulmonary artery sling (n = 1), supravalvular aortic stenosis (n = 1), aortic valve replacement (n = 1), and pulmonary artery plasty (n = 1). The surgical approach involved a midline skin incision, based on the manubrium, followed by an upper manubriotomy. No special surgical instrumentation was required. Median patient age was 2.9 years (IQR 1.3, 6.0); median body weight was 15 kg (IQR 9.8, 20).

RESULTS

There was no mortality and no patient required intraoperative conversion to full sternotomy. One patient required re-exploration for bleeding when the incision was converted to a full sternotomy. There were no wound complications in any patient. Twenty-one patients (41%) were extubated on the table and of the remaining 30 patients, 23 patients (76%) were extubated within 24 h of surgery. Eleven patients did not require intensive care unit (ICU) admission. Median ICU and hospital stay was 1 day (IQR 1, 1.25) and 5 days (IQR 4, 8) ,respectively.

CONCLUSION

An upper partial sternal split approach is straightforward and can be performed safely with a preferable cosmetic result in selected pediatric cardiac operations.

Cycloidal-spiral sampling for three-modal x-ray CT flyscans with two-dimensional phase sensitivity

We present a flyscan compatible acquisition scheme for three-modal X-Ray Computed Tomography (CT) with two-dimensional phase sensitivity. Our approach is demonstrated using a "beam tracking" setup, through which a sample's attenuation, phase (refraction) and scattering properties can be measured from a single frame, providing three complementary contrast channels. Up to now, such setups required the sample to be stepped at each rotation angle to sample signals at an adequate rate, to prevent resolution losses, anisotropic resolution, and under-sampling artefacts. However, the need for stepping necessitated a step-and-shoot implementation, which is affected by motors' overheads and increases the total scan time. By contrast, our proposed scheme, by which continuous horizontal and vertical translations of the sample are integrated with its rotation (leading to a "cycloidal-spiral" trajectory), is fully compatible with continuous scanning (flyscans). This leads to greatly reduced scan times while largely preserving image quality and isotropic resolution.

Cerebral Infarction During Cervical Veno-Arterial Extracorporeal Membrane Oxygenation in Children: Can it be Predicted?

Veno-arterial extra-corporeal membrane oxygenation (VA ECMO) in children is often established by cannulation of the right carotid artery and the right internal jugular vein. Cerebral infarction which is sometimes seen in such cases may be secondary to an incomplete circle of Willis. We present 3 cases with VA ECMO using cervical cannulation who suffered cerebral infarction which may be attributed to an incomplete circle of Willis.

Coronavirus Disease 2019 (COVID-19) Vaccination for Children: Position Statement of Indian Academy of Pediatrics Advisory Committee on Vaccination and Immunization Practices

JUSTIFICATION

Data generated after the first wave has revealed that some children with coronavirus 19 (COVID-19) can become seriously ill. Multi-inflammatory syndrome in children (MIS-C) and long COVID cause significant morbidity in children. Prolonged school closures and quarantine have played havoc with the psychosocial health of children. Many countries in the world have issued emergency use authorisation (EUA) of selected Covid-19 vaccines for use in children. In India, a Subject Expert Committee (SEC) has recommended the use of Covaxin (Bharat Biotech) for children from the ages of 2-18 years. The recommendation has been given to the Drugs Controller General of India (DCGI) for final approval.

OBJECTIVE

To provide an evidence-based document to guide the pediatricians on the recommendation to administer COVID vaccines to children, as and when they are available for use.

PROCESS

Formulation of key questions was done by the committee, followed by review of literature on epidemiology and burden of Covid-19 in children, review of the studies on COVID vaccines in children, and the IAP stand on Covid-19 vaccination in children. The available data was discussed in the ACVIP focused WhatsApp group followed by an online meeting on 24 October, 2021, wherein the document was discussed in detail and finalized.

RECOMMENDATIONS

The IAP supports the Government of India's decision to extend the COVID-19 vaccination program to children between 2-18 years of age. Children with high-risk conditions may be immunized on a priority basis. The IAP and its members should be a partner with the Government of India, in the implementation of this program and the surveillance that is necessary following the roll-out.

Coronavirus Disease 2019 (COVID-19) Vaccination for Children: Position Statement of Indian Academy of Pediatrics Advisory Committee on Vaccination and Immunization Practices

Justification

Data generated after the first wave has revealed that some children with Coronavirus 19 (COVID-19) can become seriously ill. Multi-inflammatory syndrome in children (MIS-C) and long COVID cause significant morbidity in children. Prolonged school closures and quarantine have played havoc with the psychosocial health of children. Many countries in the world have issued emergency use authorisation (EUA) of selected COVID-19 vaccines for use in children. In India, a Subject Expert Committee (SEC) has recommended the use of Covaxin (Bharat Biotech) for children from the ages of 2–18 years. The recommendation has been given to the Drugs Controller General of India (DCGI) for final approval.

Objective

To provide an evidence-based document to guide the pediatricians on the recommendation to administer COVID vaccines to children, as and when they are available for use.

Process

Formulation of key questions was done by the committee, followed by review of literature on epidemiology and burden of COVID-19 in children, review of the studies on COVID vaccines in children, and the IAP stand on COVID-19 vaccination in children. The available data was discussed in the ACVIP focused WhatsApp group followed by an online meeting on 24 October, 2021, wherein the document was discussed in detail and finalized.

Recommendations

The IAP supports the Government of India’s decision to extend the COVID-19 vaccination program to children between 2–18 years of age. Children with high-risk conditions may be immunized on a priority basis. The IAP and its members should be a partner with the Government of India, in the implementation of this program and the surveillance that is necessary following the roll-out.

Calcification Causing Failure of Tissue Engineered Bovine Pericardium After Aortic Valve Repair

CardioCel^® is bovine pericardium which is subjected to a novel tissue engineering process (ADAPT^®) to reduce cytotoxicity and retard calcification while maintaining strength and elasticity. We present a case where CardioCel^® showed rapid degeneration and calcification after repair of an aortic valve.

Revealing NOTCH-dependencies in synaptic targets associated with Alzheimer's disease

Recent studies have identified NOTCH signaling as a contributor of neurodegeneration including Alzheimer's disease' (AD) pathophysiology. As part of the efforts to understand molecular mechanisms and players involved in neurodegenerative dementia, we employed transgenic mouse models with Notch1 and Rbpjk loss of function (LOF) mutation in pyramidal neurons of the CA fields. Using RNA-seq, we have investigated the differential expression of NOTCH-dependent genes either upon environmental enrichment (EE) or upon kainic acid (KA) injury. We found a substantial genetic diversity in absence of both NOTCH1 receptor or RBPJK transcriptional activator. Among differentially expressed genes, we observed a significant upregulation of Gabra2a in both knockout models, suggesting a role for NOTCH signaling in the modulation of E/I balance. Upon excitotoxic stimulation, loss of RBPJK results in decreased expression of synaptic proteins with neuroprotective effects. We confirmed Nptx2, Npy, Pdch8, TncC as direct NOTCH1/RBPJK targets and Bdnf and Scg2 as indirect targets. Finally, we translate these findings into human entorhinal cortex containing the hippocampal region from AD patients performing targeted transcripts analysis. We observe an increased trend for RBPJK and the ligand DNER starting in the mild-moderate stage of the disease with no change of NOTCH1 expression. Alongside, expression of the Notch targets Hes5 and Hey1 tend to rise in the intermediate stage of the disease and drop in severe AD. Similarly the newly discovered NOTCH targets, NPTX2, NPY, BDNF show an up-warding tendency during the mild-moderate stage, and decline in the severe phase of the disease. This study identifies NOTCH as a central signaling cascade capable of modulating synaptic transmission in response to excitatory insult through the activation of neuroprotective genes that have been associated to AD.

Tetralogy of Fallot with coronary crossing the right ventricular outflow tract: A tale of a bridge and the artery

A coronary artery crossing the right ventricular outflow tract is a subset of a larger pathomorphological cohort known as an anomalous coronary artery (ACA) in the tetralogy of Fallot (TOF). The best possible outcome in a patient with TOF and ACA is decided by judicious selection of optimum preoperative investigative information, the timing of surgery, astute assessment of preoperative surgical findings, and appropriate surgical technique from a wide array of choices. In most instances, the choice of surgical technique is determined by the size of the pulmonary annulus and the anatomical relation of ACA to the pulmonary annulus. In the present era, complete, accurate preoperative diagnosis and primary repair is a routine procedure with strategies to avoid a right ventricle-to-pulmonary artery conduit.

Biventricular repair versus Fontan completion for patients with d- or l-transposition of the great arteries with ventricular septal defect and left ventricular outflow tract obstruction

OBJECTIVES

D-transposition of the great arteries and l-transposition of the great arteries with ventricular septal defect and left ventricular outflow tract obstruction are complex biventricular congenital heart diseases for which decision-making regarding surgical strategy remains challenging. We investigated the intermediate-term outcomes of Fontan versus biventricular procedures in these patients.

METHODS

We analyzed 129 patients with d-transposition of the great arteries/ventricular septal defect/left ventricular outflow tract obstruction (n = 85) or l-transposition of the great arteries/ventricular septal defect/left ventricular outflow tract obstruction (n = 44) and 2 functional ventricles from Australia who had primary surgical management (29 Fontan, 100 biventricular repair) undertaken between 1990 and 2015.

RESULTS

Median operative age of patients was 2.9 years (range, 0.2-26.8 years). During a median follow-up of 6.2 years (range, 2 days to 25.8 years), 9 patients died after biventricular repair (3 early and 6 late deaths). One patient received a transplant 1.2 years after Fontan completion. Overall transplant-free survivals at 1, 5, 10, and 15 years were 95%, 93%, 92%, and 90%, respectively. Overall reintervention-free survivals at 1, 5, 10, and 15 years were 79%, 64%, 45%, and 29% respectively. Biventricular repair tended to be associated with a higher rate of death, transplantation, or reintervention than the Fontan pathway (hazard ratio, 1.83; 95% confidence interval, 0.90-3.71; P = .10). Some 73% of transplant-free survivors had New York Heart Association class I. Functional status was similar between the Fontan and biventricular groups.

CONCLUSIONS

Intermediate-term outcomes were comparable between patients with d-transposition of the great arteries/ventricular septal defect/left ventricular outflow tract obstruction and patients with l-transposition of the great arteries/ventricular septal defect/left ventricular outflow tract obstruction. Both Fontan and biventricular pathways are associated with excellent mortality and functional outcomes. Biventricular patients have a greater risk of reintervention. The Fontan procedure is a viable option when anatomic risk factors preclude biventricular repair.

Discontinuity of the arch beyond the origin of the left subclavian artery in an adult: Interruption or coarctation?

Congenital aortic anomalies are uncommon causes of secondary hypertension and are seldom suspected in the adult age group. We present a case of aortic interruption unexpectedly diagnosed on autopsy in a 38-year-old male who presented with cardiovascular collapse. Apart from interruption, a finding unique to our case was aneurysmal dilation of the proximal descending aorta just before the obstruction with thrombosis. We also attempt to review the literature for interrupted aortic arch in adults and clarify the nomenclature of interruption versus coarctation.

Lutembacher's syndrome: Is the mitral pathology always rheumatic?

The mitral valve disease (MVD) in Lutembacher's syndrome has been infrequently analyzed from a pathological standpoint. In this study, we have attempted to elucidate the pathology of MVD in this interesting syndrome in 44 autopsied cases of combined non-primum atrial septal defect (ASD) and MVD collected over 16 years. The patients were divided into 3 groups: Group 1: non-primum ASD with clinically diagnosed mitral stenosis (MS)±regurgitation, Group 2: non-primum ASD with clinically diagnosed mitral regurgitation (MR) and, Group 3: non-primum ASD with no clinically evident MVD, but with mitral valve pathology diagnosed at autopsy. All 44 patients were symptomatic. There were 26 males (59%). The ages ranged from 13 to 73 years. A history of rheumatic fever was available in 2 patients while 16 patients had undergone surgery or intervention for the disease. Of the 18 patients in Group 1, six patients did not show histological features of rheumatic heart disease, although they shared similar gross morphological features. Furthermore, the mitral regurgitation in 12 of 19 patients in Group 2 was non-rheumatic. Also, only one patient had histological evidence of rheumatic activity among seven cases in Group 3. In spite of a high rheumatic load at our center, more than half (54.5%) of patients had "non-rheumatic" mitral valve pathology. Thus, the mitral valvular lesions commonly labeled 'rheumatic' in Lutembacher's syndrome are not always so. The distinction into rheumatic and non-rheumatic MVD in non-primum ASD has to be made on the basis of microscopic criteria.

Differential antigen expression and aberrant signaling via PI3/AKT, MAP/ERK, JAK/STAT, and Wnt/β catenin pathways in Lin-/CD38-/CD34+ cells in acute myeloid leukemia

Acute myeloid leukemia is often called as stem cell disease that presents with treatment failure and poor disease outcome. Leukemic stem cells in acute myeloid leukemia (AML) are enriched in Lineage-/CD38-/CD34+ compartment of CD34-positive AML. Many markers important for stem cell biology have been reported for their association with leukemic stem cell population, but what remains clinically most important is a rapid identification of prognostic information. In this study, we evaluated four signal transduction pathways and thirteen markers on Lin-/CD38-/CD34+ population in AML. Expressions were compared in different AML subtypes, survival, and treatment outcome groups. We observed that markers important in homing, cell quiescence, and signal propagation such as CD44, CD96, CD90, WT-1, CD123 and CD25 were most significantly differentially expressed on Lin-/CD38-/CD34+ population in AML from their normal counterparts (P < 0.05, Mann-Whitney). Constitutive activation of phospho ERK, AKT, and STAT5 in these cells was associated with poor outcome. Also, an increased frequency of putative leukemic stem cell population shows negative impact on treatment outcome and overall survival, suggesting that initial evaluation of AML samples for pLSC frequency and constitutively activated signaling pathway can provide prognostic and therapeutic information at the time of diagnosis.

Notch signaling in response to excitotoxicity induces neurodegeneration via erroneous cell cycle reentry

Neurological disorders such as Alzheimer's disease, stroke and epilepsy are currently marred by the lack of effective treatments to prevent neuronal death. Erroneous cell cycle reentry (CCR) is hypothesized to have a causative role in neurodegeneration. We show that forcing S-phase reentry in cultured hippocampal neurons is sufficient to induce neurodegeneration. We found that kainic-acid treatment in vivo induces erroneous CCR and neuronal death through a Notch-dependent mechanism. Ablating Notch signaling in neurons provides neuroprotection against kainic acid-induced neuronal death. We further show that kainic-acid treatment activates Notch signaling, which increases the bioavailability of CyclinD1 through Akt/GSK3β pathway, leading to aberrant CCR via activation of CyclinD1-Rb-E2F1 axis. In addition, pharmacological blockade of this pathway at critical steps is sufficient to confer resistance to kainic acid-induced neurotoxicity in mice. Taken together, our results demonstrate that excitotoxicity leads to neuronal death in a Notch-dependent manner through erroneous CCR.

Breast gangrene in an HIV-positive patient

INTRODUCTION

Breast gangrene has been reported as a complication following puerperal sepsis, breast surgery, nipple piercings, warfarin toxicity, etc. We report a case of primary breast gangrene in an HIV-positive individual which, to the best of our knowledge, is the first of its kind.

CASE REPORT

A 40-year-old previously healthy woman presented with fulminating left breast gangrene. She was detected to be HIV positive. Mastectomy was performed. The detailed management of the condition is discussed.

CONCLUSION

Severe necrotising infections may be initial manifestations of HIV infection and patients with such infections should be screened for HIV.

Non seminomatous germ cell tumour of a solitary testis in a 70-year-old man: a rare case

We report a rare case of a 70-year-old patient who presented with undifferentiated malignant teratoma arising from a solitary testis. The literature review highlights the rarity of such tumour in this age group, and this may represent the oldest reported patient with non seminomatous germ cell tumour of testicle.

Thermo-expandable Intra-prostatic Stent in the Treatment of Acute Urinary Retention in Elderly Patients with Significant Co-morbidities

We assess the use of thermo-expandable intra-prostatic stent (Memokath, Engineers and Doctors A/S, Denmark) for the treatment of acute urinary retention (AUR) in men with significant co-morbidities for transurethral resection of prostate (TURP). We evaluate the pre- and post-operative complications, duration of stents in-situ and patients quality of life after the stent insertion. Patients with significant co-morbidities presenting with AUR were selected, who were unfit for TURP. The co-morbidities included ischaemic heart disease, congestive heart failure, and chronic obstructive pulmonary disease. The exclusion criteria were bladder tumour and atonic bladder. The Memokath stents were inserted using a flexible cystoscope under local anaesthesia. The patients were followed up at 3 and 6 months after the procedure and the ones who remained alive were asked to complete self-administered questionnaires and IPSS scores. Fifteen men with acute urinary retention were recruited for stent insertion with the mean age of 87 years. No peri-operative complications were recorded. Three patients died after the insertion with functional Memokath in-situ. Nine patients had good functioning stents post-operatively, and remain catheter free up to 30 months after the procedure. The mean duration of stent life was 18 months. Three long-term complications were detected, including stent migration and prostate overgrowth. The Memokath is a good option for frail elderly patients presenting with AUR. The procedure is safe and has minimal long term complications. The stent also provides a sustained good quality of life for patients and avoids the necessity of long term catheterisation.

Therapeutic potential of yoga practices in modifying cardiovascular risk profile in middle aged men and women

AIMS OF STUDY

To study effect of yoga on the physiological, psychological well being, psychomotor parameter and modifying cardiovascular risk factors in mild to moderate hypertensive patients.

METHODS

Twenty patients (16 males, 4 females) in the age group of 35 to 55 years with mild to moderate essential hypertension underwent yogic practices daily for one hour for three months. Biochemical, physiological and psychological parameters were studied prior and following period of three months of yoga practices, biochemical parameters included, blood glucose, lipid profile, catecholmines, MDA, Vit. C cholinesterase and urinary VMA. Psychological evaluation was done by using personal orientation inventory and subjective well being.

RESULTS

Results showed decrease in blood pressure and drug score modifying risk factors, i.e. blood glucose, cholesterol and triglycerides decreased overall improvement in subjective well being and quality of life. There was decrease in VMA catecholamine, and decrease MDA level suggestive decrease sympathetic activity and oxidant stress.

CONCLUSION

Yoga can play an important role in risk modification for cardiovascular diseases in mild to moderate hypertension.

Sphingomyelinase converts lipoproteins from apolipoprotein E knockout mice into potent inducers of macrophage foam cell formation

The apoE knockout (E0) mouse is one of the most widely used animal models of atherosclerosis, and there may be similarities to chylomicron remnant-induced atherosclerosis in humans. Although the lesions of these mice contain large numbers of cholesteryl ester (CE)-laden macrophages (foam cells), E0 plasma lipoproteins are relatively weak inducers of cholesterol esterification in macrophages. Previous in vivo work has suggested that arterial wall sphingomyelinase (SMase) may promote atherogenesis in the E0 mouse, perhaps by inducing subendothelial lipoprotein aggregation and subsequent foam cell formation. The goal of the present study was to test the hypothesis that the modification of E0 lipoproteins by SMase converts these lipoproteins into potent inducers of macrophage foam cell formation. When d<1.063 E0 lipoproteins were pretreated with SMase and then incubated with E0 macrophages, cellular CE mass and stimulation of the cholesterol esterification pathway were increased approximately 5-fold compared with untreated lipoproteins. SMase-treated E0 lipoproteins were more potent stimulators of cholesterol esterification than either E0 lipoproteins in the presence of lipoprotein lipases or oxidized E0 lipoproteins. The uptake and degradation of SMase-treated E0 lipoproteins by macrophages were saturable and specific and substantially inhibited by partial proteolysis of cell-surface proteins. Uptake and degradation were diminished by an anti-apoB antibody and by competition with human S(f) 100-400 hypertriglyceridemic VLDL, raising the possibility that a receptor that recognizes apoB-48 might be involved. In conclusion, SMase-modification of E0 lipoproteins, a process previously shown to occur in lesions, may be an important mechanism for foam cell formation in this widely studied model of atherosclerosis. Moreover, the findings in this report may provide important clues regarding the atherogenicity of chylomicron remnants in humans.

Creation of a mouse model for non-neurological (type B) Niemann-Pick disease by stable, low level expression of lysosomal sphingomyelinase in the absence of secretory sphingomyelinase: relationship between brain intra-lysosomal enzyme activity and central nervous system function

Most lysosomal storage diseases result in neurodegeneration, but deficiencies in the same enzymes can also lead to syndromes without neurologic manifestations. The hypothesis that low levels of residual, intra-lysosomal enzymatic activities in the central nervous system (CNS) are protective has been difficult to prove because of inconsistencies in assays of tissue samples. Experimental correction of lysosomal enzyme deficiencies in animal models suggests that low-level enzymatic activity may reduce CNS pathology, but these results are difficult to interpret owing to the partial and transient nature of the improvements, the presence of secretory hydrolases, and other confounding factors. Using a novel transgenic/knockout strategy to manipulate the intracellular targeting of a hydrolase, we created a mouse that stably expresses low levels of lysosomal sphingomyelinase (L-SMase) in the complete absence of secretory sphingomyelinase (S-SMase). The brains of these mice exhibited 11.5-18.2% of wild-type L-SMase activity, but the cerebellar Purkinje cell layer, which is lost by 4 months of age in mice completely lacking L- and S-SMase, was preserved for at least 8 months. The L-SMase activities in other organs were 1-14% of wild-type levels, and by 8 months of age all peripheral organs had accumulated sphingomyelin and demonstrated pathological intracellular inclusions. Most importantly, L-SMase-expressing mice showed no signs of the severe neurologic disease observed in completely deficient mice, and their life span and general health were essentially normal. These findings show that stable, continuous, low-level expression of intra-lysosomal enzyme activity in the brain can preserve CNS function in the absence of secretory enzyme or other confounding factors.

Acute systemic inflammation up-regulates secretory sphingomyelinase in vivo: a possible link between inflammatory cytokines and atherogenesis

Inflammation plays a critical role in atherogenesis, yet the mediators linking inflammation to specific atherogenic processes remain to be elucidated. One such mediator may be secretory sphingomyelinase (S-SMase), a product of the acid sphingomyelinase gene. The secretion of S-SMase by cultured endothelial cells is induced by inflammatory cytokines, and in vivo data have implicated S-SMase in subendothelial lipoprotein aggregation, macrophage foam cell formation, and possibly other atherogenic processes. Thus, the goal of this study was to seek evidence for S-SMase regulation in vivo during a physiologically relevant inflammatory response. First, wild-type mice were injected with saline or lipopolysaccharide (LPS) as a model of acute systemic inflammation. Serum S-SMase activity 3 h postinjection was increased 2- to 2.5-fold by LPS (P < 0.01). To determine the role of IL-1 in the LPS response, we used IL-1 converting enzyme knockout mice, which exhibit deficient IL-1 bioactivity. The level of serum S-SMase activity in LPS-injected IL-1 converting enzyme knockout mice was approximately 35% less than that in identically treated wild-type mice (P < 0.01). In LPS-injected IL-1-receptor antagonist knockout mice, which have an enhanced response to IL-1, serum S-SMase activity was increased 1. 8-fold compared with LPS-injected wild-type mice (P < 0.01). Finally, when wild-type mice were injected directly with IL-1beta, tumor necrosis factor alpha, or both, serum S-SMase activity increased 1. 6-, 2.3-, and 2.9-fold, respectively (P < 0.01). These data show regulation of S-SMase activity in vivo and they raise the possibility that local stimulation of S-SMase may contribute to the effects of inflammatory cytokines in atherosclerosis.

Sphingomyelinase, an enzyme implicated in atherogenesis, is present in atherosclerotic lesions and binds to specific components of the subendothelial extracellular matrix

Atherosclerotic lesions contain an extracellular sphingomyelinase (SMase) activity that hydrolyzes the sphingomyelin of subendothelial low density lipoprotein (LDL). This SMase activity may promote atherosclerosis by enhancing subendothelial LDL retention and aggregation, foam cell formation, and possibly other atherogenic processes. The results of recent cell-culture studies have led to the hypothesis that a specific molecule called secretory SMase (S-SMase) is responsible for the SMase activity known to be in lesions, although its presence in atheromata had not been examined directly. Herein we provide immunohistochemical and biochemical support for this hypothesis. First, 2 different antibodies against S-SMase detected extracellular immunoreactive protein in the intima of mouse, rabbit, and human atherosclerotic lesions. Much of this material in lesions appeared in association with the subendothelial matrix. Second, binding studies in vitro demonstrated that (125)I-S-SMase adheres to the extracellular matrix of cultured aortic smooth muscle and endothelial cells, specifically to the laminin and collagen components. Third, in its bound state, S-SMase retains substantial enzymatic activity against lipoprotein substrates. Overall, these data support the hypothesis that S-SMase is an extracellular arterial wall SMase that contributes to the hydrolysis of the sphingomyelin of subendothelial LDL. S-SMase may therefore be an important participant in atherogenesis through local enzymatic effects that stimulate subendothelial retention and aggregation of atherogenic lipoproteins.

Multiple forms of arginase are differentially expressed from a single locus in Neurospora crassa

The Neurospora crassa catabolic enzyme, arginase (L-arginine amidinohydrolase, EC 3.5.3.1), exists in multiple forms. Multiple forms of arginase are found in many vertebrates, but this is the only reported example in a microbial organism. The two major forms are structurally similar with subunit sizes of 36 and 41 kDa, respectively. The larger form is produced by mycelia growing in arginine-supplemented medium. Both forms are localized in the cytosol. The structural gene for arginase, aga, has been cloned and sequenced; it contains a 358-codon open reading frame with three in-frame ATGs at the amino terminus. Mutagenesis of these ATGs revealed that the first ATG initiates the 41-kDa protein and the third ATG initiates the 36-kDa protein. Mutation of the second ATG has no effect on translation. Northern analysis demonstrated that a 1.4-kilobase (kb) transcript is synthesized in minimal medium and both a 1.4- and 1.7-kb transcript are produced in arginine-supplemented medium. Primer extension identified the 5' ends of each transcript and demonstrated that the first and third ATG of the open reading frame are the initial AUGs of the 1.7- and 1. 4-kb mRNA, respectively. The results suggest that a basal promoter produces the 1.4-kb transcript and an arginine "activated" promoter is responsible for the 1.7-kb transcript. Tandem promoters are rare in eukaryotic organisms, and they often regulate developmental or tissue-specific gene expression. The possibility that arginase has a role in differentiation in N. crassa is being investigated.

Human vascular endothelial cells are a rich and regulatable source of secretory sphingomyelinase. Implications for early atherogenesis and ceramide-mediated cell signaling

We recently reported that macrophages and fibroblasts secrete a Zn2+-dependent sphingomyelinase (S-SMase), which, like lysosomal SMase, is a product of the acid SMase gene. S-SMase may cause subendothelial retention and aggregation of lipoproteins during atherogenesis, and the acid SMase gene has been implicated in ceramide-mediated cell signaling, especially involving apoptosis of endothelial cells. Because of the central importance of the endothelium in each of these processes, we now sought to examine the secretion and regulation of S-SMase by vascular endothelial cells. Herein we show that cultured human coronary artery and umbilical vein endothelial cells secrete massive amounts of S-SMase (up to 20-fold more than macrophages). Moreover, whereas S-SMase secreted by macrophages and fibroblasts is almost totally dependent on the addition of exogenous Zn2+, endothelium-derived S-SMase was partially active even in the absence of added Zn2+. Secretion of S-SMase by endothelial cells occurred both apically and basolaterally, suggesting an endothelial contribution to both serum and arterial wall SMase. When endothelial cells were incubated with inflammatory cytokines, such as interleukin-1beta and interferon-gamma, S-SMase secretion by endothelial cells was increased 2-3-fold above the already high level of basal secretion, whereas lysosomal SMase activity was decreased. The mechanism of interleukin-1beta-stimulated secretion appears to be through increased routing of a SMase precursor protein through the secretory pathway. In summary, endothelial cells are a rich and regulatable source of enzymatically active S-SMase, suggesting physiologic and pathophysiologic roles for this enzyme.

Evidence that the initial up-regulation of phosphatidylcholine biosynthesis in free cholesterol-loaded macrophages is an adaptive response that prevents cholesterol-induced cellular necrosis. Proposed role of an eventual failure of this response in foam cell necrosis in advanced atherosclerosis

Macrophages in atherosclerotic lesions accumulate free cholesterol (FC) as well as cholesteryl ester and appear to have high rates of phospholipid (PL) synthesis and increased PL mass. Previous short term (i.e. </=24 h) studies with cultured macrophages have shown that these cells respond to FC loading by up-regulating phosphatidylcholine biosynthesis. We propose that this response is adaptive by keeping the FC:PL ratio in the macrophages from reaching toxic levels. We further propose that one cause of macrophage necrosis, a prominent and important event in atherosclerosis, is an eventual decrease of this adaptive response. To explore these ideas, cultured macrophages were loaded with FC for up to 4 days and assayed for phosphatidylcholine biosynthesis, FC and PL mass, and cytotoxicity. For the first 24 h, cellular phosphatidylcholine biosynthesis and FC and PL mass increased 3-4-fold, and thus the FC:PL molar ratio was prevented from reaching very high levels; at this point, there were no overt signs of cytotoxicity. Over the next 24-48 h, however, phosphatidylcholine biosynthesis, and then phosphatidylcholine mass, began to decrease. Initially, the macrophages remained healthy and continued to accumulate FC, but eventually these macrophages, but not unloaded macrophages, became necrotic (swollen organelles and disrupted membranes). Lipoprotein dose studies indicated a close relationship between the onset of macrophage necrosis and the FC:PL ratio. To test further the causal nature of these relationships, cellular FC and PL mass were independently manipulated by using high density lipoprotein3 (HDL3) to decrease cellular FC and choline depletion to decrease cellular PC. As predicted by our hypotheses, HDL3 protected FC-loaded macrophages from necrosis, whereas choline depletion accelerated cytotoxic changes. These findings support the idea that the initial increase in phosphatidylcholine biosynthesis in FC-loaded macrophages is an adaptive response that prevents cholesterol-induced macrophage necrosis. We propose that an eventual failure of the PL response in foam cells may represent one cause of macrophage necrosis in advanced atherosclerotic lesions.

Duplication-induced mutation of a new Neurospora gene required for acetate utilization: properties of the mutant and predicted amino acid sequence of the protein product

A cloned Neurospora crassa genomic sequence, selected as preferentially transcribed when acetate was the sole carbon source, was introduced in extra copies at ectopic loci by transformation. Sexual crossing of transformants yielded acetate nonutilizing mutants with methylation and restriction site changes within both the ectopic DNA and the normally located gene. Such changes are typical of the duplication-induced premeiotic disruption (the RIP effect) first described by Selker et al. (E. U. Selker, E. B. Cambareri, B. C. Jensen, and K. R. Haack, Cell 51:741-752, 1987). The mutants had the unusual phenotype of growth on ethanol but not on acetate as the carbon source. In a cross to the wild type of a mutant strain in which the original ectopic gene sequence had been removed by segregation, the acetate nonutilizing phenotype invariably segregated together with a RIP-induced EcoRI site at the normal locus. This mutant was transformed to the ability to use acetate by the cloned sequence. The locus of the mutation, designated acu-8, was mapped between trp-3 and un-15 on linkage group 2. The transcribed portion of the clone, identified by probing with cDNA, was sequenced, and a putative 525-codon open reading frame with two introns was identified. The codon usage was found to be strongly biased in a way typical of most Neurospora genes sequenced so far. The predicted amino acid sequence shows no significant resemblance to anything previously recorded. These results provide a first example of the use of the RIP effect to obtain a mutant phenotype for a gene previously known only as a transcribed wild-type DNA sequence.