Utilization of therapeutic plasma exchange for hyperbilirubinemia in a premature newborn on extracorporeal membrane oxygenation.

BACKGROUND: We report a case of a premature newborn girl with a hospital course complicated by suspected respiratory syncytial virus pneumonitis for which she was placed on veno-arterial extracorporeal membrane oxygenation (VA-ECMO). Despite phototherapy, her total bilirubin steadily increased to a peak of 50.4 mg/dL with concern for bilirubin-induced neurologic dysfunction, kernicterus. STUDY DESIGN AND METHODS: Therapeutic plasma exchange (TPE) was achieved via connection with the VA-ECMO circuit. Our institution's standard apheresis procedural parameters were adjusted to account for the small body weight and thus the low blood volume of the neonate while on ECMO. These included calculating the total blood volume to include the patient as well as the ECMO circuit, priming of the apheresis instrument with packed red blood cells to limit the extracorporeal volume, using a lower inlet flow rate, the connection setup of the inlet and return line, and monitoring of ionized calcium and anticoagulation throughout the procedure. RESULTS: A total of three TPE procedures were performed over three consecutive days. This resulted in improvement and stabilization of the patient's bilirubin. CONCLUSION: This case emphasizes that TPE is feasible on a neonate with a suboptimal body weight and thus a low blood volume due to the increased blood volume provided while on ECMO. In the absence of ECMO, whole blood manual exchange transfusion is recommended as TPE would be unsafe due to significant extracorporeal volume that would occur during TPE in a pediatric patient with low body weight.

Stanniocalcin-1 inhibits renal ischemia/reperfusion injury via an AMP-activated protein kinase-dependent pathway.

AKI is associated with increased morbidity, mortality, and cost of care, and therapeutic options remain limited. Reactive oxygen species are critical for the genesis of ischemic AKI. Stanniocalcin-1 (STC1) suppresses superoxide generation through induction of uncoupling proteins (UCPs), and transgenic overexpression of STC1 inhibits reactive oxygen species and protects from ischemia/reperfusion (I/R) kidney injury. Our observations revealed high AMP-activated protein kinase (AMPK) activity in STC1 transgenic kidneys relative to wild-type (WT) kidneys; thus, we hypothesized that STC1 protects from I/R kidney injury through activation of AMPK. Baseline activity of AMPK in the kidney correlated with the expression of STCs, such that the highest activity was observed in STC1 transgenic mice followed (in decreasing order) by WT, STC1 knockout, and STC1/STC2 double-knockout mice. I/R in WT kidneys increased AMPK activity and the expression of STC1, UCP2, and sirtuin 3. Inhibition of AMPK by administration of compound C before I/R abolished the activation of AMPK, diminished the expression of UCP2 and sirtuin 3, and aggravated kidney injury but did not affect STC1 expression. Treatment of cultured HEK cells with recombinant STC1 activated AMPK and increased the expression of UCP2 and sirtuin 3, and concomitant treatment with compound C abolished these responses. STC1 knockout mice displayed high susceptibility to I/R, whereas pretreatment of STC1 transgenic mice with compound C restored the susceptibility to I/R kidney injury. These data suggest that STC1 is important for activation of AMPK in the kidney, which mediates STC1-induced expression of UCP2 and sirtuin 3 and protection from I/R.

Clinical Utility of Multidetector Computed Tomography in Redo Valve Procedures.

BACKGROUND: Transesophageal echocardiography (TEE) is recommended for diagnosis in patients suspected of prosthetic valve dysfunction, but could be limited in its ability to identify the etiology of these dysfunctions and to assess extracardiac structures. Our objective is to examine the usefulness of multidetector computed tomography (MDCT) in establishing the etiology of the dysfunctions and its clinical utility in preoperative assessment in these patients. METHODS: Twenty-two prosthetic heart valves from 20 consecutive patients who had a preoperative MDCT and underwent redo prosthetic valve procedures from December 2008 to February 2013 were examined retrospectively. Results from MDCT and TEE were compared to intraoperative findings. Extravalvular MDCT findings including coronary artery/bypass graft, high-risk features for reoperative cardiac surgery, and extracardiac findings were also assessed. RESULTS: MDCT correctly identified 15 valve regurgitation and seven valve obstructions compared to intraoperative findings. Both TEE and MDCT were able to correctly identify the etiologies in 93% (14/15) of regurgitant valves. However, MDCT was better able to identify the etiology of obstructive valves than TEE (86% [6/7] vs. 43% [3/7]) compared to intraoperative findings. In patients who had preoperative invasive angiography, MDCT correctly identified two patients with significant coronary artery disease (CAD) and ruled out 11 without significant CAD. Furthermore, MDCT detected five high-risk features for postoperative complications and eight clinically relevant extracardiac findings. CONCLUSIONS: MDCT displayed comparable or better diagnostic performance than TEE for identifying the type of dysfunction and its etiology, as well as providing additional coronary and other extravalvular evaluations useful for preoperative planning.

AKI after conditional and kidney-specific knockdown of stanniocalcin-1.

Stanniocalcin-1 is an intracrine protein; it binds to the cell surface, is internalized to the mitochondria, and diminishes superoxide generation through induction of uncoupling proteins. In vitro, stanniocalcin-1 inhibits macrophages and preserves endothelial barrier function, and transgenic overexpression of stanniocalcin-1 in mice protects against ischemia-reperfusion kidney injury. We sought to determine the kidney phenotype after kidney endothelium-specific expression of stanniocalcin-1 small hairpin RNA (shRNA). We generated transgenic mice that express stanniocalcin-1 shRNA or scrambled shRNA upon removal of a floxed reporter (phosphoglycerate kinase-driven enhanced green fluorescent protein) and used ultrasound microbubbles to deliver tyrosine kinase receptor-2 promoter-driven Cre to the kidney to permit kidney endothelium-specific shRNA expression. Stanniocalcin-1 mRNA and protein were expressed throughout the kidney in wild-type mice. Delivery of tyrosine kinase receptor-2 promoter-driven Cre to stanniocalcin-1 shRNA transgenic kidneys diminished the expression of stanniocalcin-1 mRNA and protein throughout the kidneys. Stanniocalcin-1 mRNA and protein expression did not change in similarly treated scrambled shRNA transgenic kidneys, and we observed no Cre protein expression in cultured and tyrosine kinase receptor-2 promoter-driven Cre-transfected proximal tubule cells, suggesting that knockdown of stanniocalcin-1 in epithelial cells in vivo may result from stanniocalcin-1 shRNA transfer from endothelial cells to epithelial cells. Kidney-specific knockdown of stanniocalcin-1 led to severe proximal tubule injury characterized by vacuolization, decreased uncoupling of protein-2 expression, greater generation of superoxide, activation of the unfolded protein response, initiation of autophagy, cell apoptosis, and kidney failure. Our observations suggest that stanniocalcin-1 is critical for tubular epithelial survival under physiologic conditions.

Convolutional Neural Networks to Study Contrast-Enhanced Magnetic Resonance Imaging-Based Skeletal Calf Muscle Perfusion in Peripheral Artery Disease.

Peripheral artery disease (PAD) is associated with impaired blood flow in the lower extremities and histopathologic changes of the skeletal calf muscles, resulting in abnormal microvascular perfusion. We studied the use of convolution neural networks (CNNs) to differentiate patients with PAD from matched controls using perfusion pattern features from contrast-enhanced magnetic resonance imaging (CE-MRI) of the skeletal calf muscles. We acquired CE-MRI based skeletal calf muscle perfusion in 56 patients (36 patients with PAD and 20 matched controls). Microvascular perfusion imaging was performed after reactive hyperemia at the midcalf level, with a temporal resolution of 409 ms. We analyzed perfusion scans up to 2 minutes indexed from the local precontrast arrival time frame. Skeletal calf muscles, including the anterior muscle, lateral muscle, deep posterior muscle group, and the soleus and gastrocnemius muscles, were segmented semiautomatically. Segmented muscles were represented as 3-dimensional Digital Imaging and Communications in Medicine stacks of CE-MRI perfusion scans for deep learning (DL) analysis. We tested several CNN models for the 3-dimensional CE-MRI perfusion stacks to classify patients with PAD from matched controls. A total of 2 of the best performing CNNs (resNet and divNet) were selected to develop the final classification model. A peak accuracy of 75% was obtained for resNet and divNet. Specificity was 80% and 94% for resNet and divNet, respectively. In conclusion, DL using CNNs and CE-MRI skeletal calf muscle perfusion can discriminate patients with PAD from matched controls. DL methods may be of interest for the study of PAD.

A machine learning-based approach to identify peripheral artery disease using texture features from contrast-enhanced magnetic resonance imaging.

Diagnosing and assessing the risk of peripheral artery disease (PAD) has long been a focal point for medical practitioners. The impaired blood circulation in PAD patients results in altered microvascular perfusion patterns in the calf muscles which is the primary location of intermittent claudication pain. Consequently, we hypothesized that changes in perfusion and increase in connective tissue could lead to alterations in the appearance or texture patterns of the skeletal calf muscles, as visualized with non-invasive imaging techniques. We designed an automatic pipeline for textural feature extraction from contrast-enhanced magnetic resonance imaging (CE-MRI) scans and used the texture features to train machine learning models to detect the heterogeneity in the muscle pattern among PAD patients and matched controls. CE-MRIs from 36 PAD patients and 20 matched controls were used for preparing training and testing data at a 7:3 ratio with cross-validation (CV) techniques. We employed feature arrangement and selection methods to optimize the number of features. The proposed method achieved a peak accuracy of 94.11% and a mean testing accuracy of 84.85% in a 2-class classification approach (controls vs. PAD). A three-class classification approach was performed to identify a high-risk PAD sub-group which yielded an average test accuracy of 83.23% (matched controls vs. PAD without diabetes vs. PAD with diabetes). Similarly, we obtained 78.60% average accuracy among matched controls, PAD treadmill exercise completers, and PAD exercise treadmill non-completers. Machine learning and imaging-based texture features may be of interest in the study of lower extremity ischemia.

Contrast-Enhanced Magnetic Resonance Imaging Based T1 Mapping and Extracellular Volume Fractions Are Associated with Peripheral Artery Disease.

BACKGROUND: Extracellular volume fraction (ECV), measured with contrast-enhanced magnetic resonance imaging (CE-MRI), has been utilized to study myocardial fibrosis, but its role in peripheral artery disease (PAD) remains unknown. We hypothesized that T1 mapping and ECV differ between PAD patients and matched controls. METHODS AND RESULTS: A total of 37 individuals (18 PAD patients and 19 matched controls) underwent 3.0T CE-MRI. Skeletal calf muscle T1 mapping was performed before and after gadolinium contrast with a motion-corrected modified look-locker inversion recovery (MOLLI) pulse sequence. T1 values were calculated with a three-parameter Levenberg-Marquardt curve fitting algorithm. ECV and T1 maps were quantified in five calf muscle compartments (anterior [AM], lateral [LM], and deep posterior [DM] muscle groups; soleus [SM] and gastrocnemius [GM] muscles). Averaged peak blood pool T1 values were obtained from the posterior and anterior tibialis and peroneal arteries. T1 values and ECV are heterogeneous across calf muscle compartments. Native peak T1 values of the AM, LM, and DM were significantly higher in PAD patients compared to controls (all p < 0.028). ECVs of the AM and SM were significantly higher in PAD patients compared to controls (AM: 26.4% (21.2, 31.6) vs. 17.3% (10.2, 25.1), p = 0.046; SM: 22.7% (19.5, 27.8) vs. 13.8% (10.2, 19.1), p = 0.020). CONCLUSIONS: Native peak T1 values across all five calf muscle compartments, and ECV fractions of the anterior muscle group and the soleus muscle were significantly elevated in PAD patients compared with matched controls. Non-invasive T1 mapping and ECV quantification may be of interest for the study of PAD.

The Roles and Challenges of Advanced Therapies in the Management of Refractory Immune Thrombocytopenia: A Case Report and Review of the Literature.

The management of primary immune thrombocytopenia (ITP) is becoming a subject of interest as there appears to be treatment failure and resistance to modern conventional treatment, necessitating a more universal and goal-directed approach to management. Our patient is a 74-year-old male who was diagnosed with ITP six years ago and recently presented to the emergency department (ED) with complaints of melena stools and severe fatigue lasting for two days. Prior to the ED presentation, he had received multiple lines of treatment including splenectomy. On admission, the pathology after splenectomy showed a benign enlarged spleen with a focal area of intraparenchymal hemorrhage/rupture and changes compatible with ITP. He was managed with multiple platelet transfusions, IV methyl prednisone succinate, rituximab, and romiplostim. His platelet counts improved to 47,000, and he was discharged home on oral steroids with outpatient hematology follow-up. However, in a few weeks, his condition deteriorated, and he presented with an increased platelet count and further multiple complaints. Romiplostim was discontinued, and he was continued on prednisone 20 mg daily, after which he improved, and his platelet count reduced to 273,000 on 20 mg prednisone. This case calls attention to the need to review the role of combination therapy in treating refractory ITP and the prevention of complications of thrombocytosis secondary to advanced therapy. Treatment needs to be more streamlined, focused, and goal-directed. Escalation and de-escalation of treatment should be synchronized to prevent adverse complications from overtreating or undertreating.

Magnetic Resonance Imaging-Derived Microvascular Perfusion Modeling to Assess Peripheral Artery Disease.

Background Computational fluid dynamics has shown good agreement with contrast-enhanced magnetic resonance imaging measurements in cardiovascular disease applications. We have developed a biomechanical model of microvascular perfusion using contrast-enhanced magnetic resonance imaging signal intensities derived from skeletal calf muscles to study peripheral artery disease (PAD). Methods and Results The computational microvascular model was used to study skeletal calf muscle perfusion in 56 individuals (36 patients with PAD, 20 matched controls). The recruited participants underwent contrast-enhanced magnetic resonance imaging and ankle-brachial index testing at rest and after 6-minute treadmill walking. We have determined associations of microvascular model parameters including the transfer rate constant, a measure of vascular leakiness; the interstitial permeability to fluid flow which reflects the permeability of the microvasculature; porosity, a measure of the fraction of the extracellular space; the outflow filtration coefficient; and the microvascular pressure with known markers of patients with PAD. Transfer rate constant, interstitial permeability to fluid flow, and microvascular pressure were higher, whereas porosity and outflow filtration coefficient were lower in patients with PAD than those in matched controls (all P values ≤0.014). In pooled analyses of all participants, the model parameters (transfer rate constant, interstitial permeability to fluid flow, porosity, outflow filtration coefficient, microvascular pressure) were significantly associated with the resting and exercise ankle-brachial indexes, claudication onset time, and peak walking time (all P values ≤0.013). Among patients with PAD, interstitial permeability to fluid flow, and microvascular pressure were higher, while porosity and outflow filtration coefficient were lower in treadmill noncompleters compared with treadmill completers (all P values ≤0.001). Conclusions Computational microvascular model parameters differed significantly between patients with PAD and matched controls. Thus, computational microvascular modeling could be of interest in studying lower extremity ischemia.

Overexpression of stanniocalcin-1 inhibits reactive oxygen species and renal ischemia/reperfusion injury in mice.

Reactive oxygen species, endothelial dysfunction, inflammation, and mitogen-activated protein kinases have important roles in the pathogenesis of ischemia/reperfusion kidney injury. Stanniocalcin-1 (STC1) suppresses superoxide generation in many systems through the induction of mitochondrial uncoupling proteins and blocks the cytokine-induced rise in endothelial permeability. Here we tested whether transgenic overexpression of STC1 protects from bilateral ischemia/reperfusion kidney injury. This injury in wild-type mice caused a halving of the creatinine clearance; severe tubular vacuolization and cast formation; increased infiltration of macrophages and T cells; higher vascular permeability; greater production of superoxide and hydrogen peroxide; and higher ratio of activated extracellular regulated kinase/activated Jun-N-terminal kinase and p38, all compared to sham-treated controls. Mice transgenic for human STC1 expression, however, had resistance to equivalent ischemia/reperfusion injury indicated as no significant change from controls in any of these parameters. Tubular epithelial cells in transgenic mice expressed higher mitochondrial uncoupling protein 2 and lower superoxide generation. Pre-treatment of transgenic mice with paraquat, a generator of reactive oxygen species, before injury restored the susceptibility to ischemia/reperfusion kidney injury, suggesting that STC1 protects by an anti-oxidant mechanism. Thus, STC1 may be a therapeutic target for ischemia/reperfusion kidney injury.

A Rare Case of Metastatic Gastric Signet Ring Cell Adenocarcinoma in a 23-Year-Old Female Presenting as Malignant Pleural Effusion.

Signet ring cell carcinoma (SRCC) is a poorly differentiated mucin-producing adenocarcinoma with greater than 50% signet ring cells. It commonly arises from the gastrointestinal (GI) tract and rarely from extraintestinal organs. This is a rare case of a young African American female who presented with metastatic spread of signet ring cell gastric cancer (pleural and lymph nodal involvement) as the initial presentation of SRCC. Knowledge of the various clinical manifestations of SRCC can help with its early diagnosis, and there is a high need for detailed physical examination, early referral, and prompt treatment in patients with SRCC.

Relation of Magnetic Resonance Imaging Based Arterial Signal Enhancement to Markers of Peripheral Artery Disease.

Peripheral artery disease (PAD) is associated with impaired lower extremity function. We hypothesized that contrast-enhanced magnetic resonance imaging (CE-MRI) based arterial signal enhancement (SE) measures are associated with markers of PAD. A total of 66 participants were enrolled, 10 were excluded due to incomplete data, resulting in 56 participants for the final analyses (36 PAD, 20 matched controls). MR imaging was performed postreactive hyperemia using bilateral thigh blood-pressure cuffs. First pass-perfusion images were acquired at the mid-calf region with a high-resolution saturation recovery gradient echo pulse sequence, and arterial SE was measured for the lower extremity arteries. As expected, peak walking time (PWT) was reduced in PAD patients compared with controls (282 [248 to 317] sec, vs 353 [346 to 360] sec; p = 0.002), and postexercise ankle brachial index (ABI) decreased in PAD patients but not in controls (PAD: 0.75 ± 0.2, 0.60 [0.5 to 0.7]; p <0.001; vs Controls: 1.17 ± 0.1, 1.19 [1.1 to 1.2]; p = 0.50). Intraclass correlation coefficients were excellent for inter- and intraobserver variability of arterial tracings (n = 10: 0.95 (95%-confidence interval [CI]: 0.94 to 0.96), n = 9: 1.0 (CI: 1.0 to 1.0). Minimum arterial SE was reduced in PAD patients compared with matched controls (128 [110 to 147] A.U. vs 192 [149 to 234] A.U., p = 0.003). Among PAD patients but not in controls the maximum arterial SE was associated with the estimated glomerular filtration rate (eGFR), a marker of renal function (n = 36, ß = 1.37, R2 = 0.12, p = 0.025). In conclusion, CE-MRI first-pass arterial perfusion is impaired in PAD patients compared with matched controls and associated with markers of lower extremity ischemia.

Case Report and Literature Review of Nodular Hiradenoma, a Rare Adnexal Tumor That Mimics Breast Carcinoma, in a 20-Year-Old Woman.

Nodular hidradenoma is an uncommon cutaneous adnexal tumor arising from sweat glands. In the skin, it usually presents as a solitary dermal nodule; excision is curative in most cases. In rare instances, it may present as a breast mass and can mimic breast carcinoma clinically and radiologically, causing diagnostic dilemmas for the treating physician and pathologist. Herein, we discuss a case of nodular hidradenoma in a 20-year-old Hispanic woman as a rapidly growing mass in the breast that mimicked breast carcinoma. We discuss the rare presentation of this uncommon tumor and the differential diagnosis of this entity, as well as the results of our literature review on the topic.

Automated Diagnosis of Lymphoma with Digital Pathology Images Using Deep Learning.

Recent studies have shown promising results in using Deep Learning to detect malignancy in whole slide imaging, however, they were limited to just predicting a positive or negative finding for a specific neoplasm. We attempted to use Deep Learning with a convolutional neural network (CNN) algorithm to build a lymphoma diagnostic model for four diagnostic categories: (1) benign lymph node, (2) diffuse large B-cell lymphoma, (3) Burkitt lymphoma, and (4) small lymphocytic lymphoma. Our software was written in Python language. We obtained digital whole-slide images of Hematoxylin and Eosin stained slides of 128 cases including 32 cases for each diagnostic category. Four sets of 5 representative images, 40x40 pixels in dimension, were taken for each case. A total of 2,560 images were obtained from which 1,856 were used for training, 464 for validation, and 240 for testing. For each test set of 5 images, the predicted diagnosis was combined from the prediction of five images. The test results showed excellent diagnostic accuracy at 95% for image-by-image prediction and at 100% for set-by-set prediction. This preliminary study provided a proof of concept for incorporating automated lymphoma diagnostic screen into future pathology work-flow to augment the pathologists' productivity.

Taking Advantage of Assay Harmonization, Biotin Interference in the LOCI Digoxin Assay Could Be Eliminated by Using the ADVIA Centaur Digoxin Assay.

Biotin at elevated concentration interferes with immunoassays that utilize biotin in assay design. We earlier reported interference of biotin in the luminescent oxygen channeling assay (LOCI) digoxin assay which utilizes biotinylated antibody against digoxin. However, the ADVIA Centaur digoxin assay, also manufactured by Siemens Diagnostics, does not utilize biotin in assay design. We hypothesized that if the LOCI and the ADVIA Centaur digoxin assay are harmonized, then interference of biotin in the LOCI digoxin assay could be eliminated by using the ADVIA Centaur digoxin assay. We analyzed 25 specimens from patients receiving digoxin using both assays to investigate harmonization between these two assays. Then aliquots of drug-free serum pool were supplemented with various biotin concentrations (range: 10 ng/mL to 2000 ng/mL) followed by measuring apparent digoxin levels using the ADVIA Centaur digoxin assay. In another set of experiments, aliquots of a serum digoxin pool were supplemented with biotin (10-2000 ng/mL) and digoxin concentrations were measured by the ADVIA Centaur digoxin assay. We observed an excellent correlation between digoxin values obtained by the LOCI digoxin assay (reference method) and the ADVIA Centaur digoxin assay (y= 1.0514 x+0.1083, r=0.99) indicating that both assays are harmonized. We did not observe any interference of biotin even at a highly elevated concentration of 2000 ng/mL with the ADVIA Centaur digoxin assay. We conclude that taking advantage of assay harmonization, interference of biotin in the LOCI digoxin assay can be eliminated by using the ADVIA Centaur digoxin assay.

A Case of Suspected Streptococcus Pneumoniae Hemolytic Uremic Syndrome (pHUS) with Utilization of Minor Crossmatching for Platelet Blood Products Lead to a Diagnosis of Atypical Hemolytic Uremic Syndrome (aHUS).

BACKGROUND: The action of bacterial neuraminidase of Streptococcus pneumoniae (SPN) results in exposure of the normally "hidden" Thomsen-Freidenreich antigen (T-antigen) found on erythrocytes and other tissues. This may lead to SPN-induced hemolytic uremic syndrome (pHUS) with subsequent hemolysis and end organ damage. pHUS can be identified by minor crossmatch incompatibility. We present a case of suspected pHUS that resulted in a compatible minor crossmatch which led to concern and eventually diagnosis of atypical HUS (aHUS). DESIGN: A 6-month-old boy presented with respiratory failure. He was found to have blood cultures positive for SPN. Shiga toxin was negative and he had normal levels of ADAMTS 13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13). The clinical team was concerned for pHUS and requested washed platelet product prior to a surgical procedure. Alternatively, a minor crossmatching was performed to determine the presence of T activation. An aHUS genetic panel was performed to sequence and analyze 12 genes encoding complement factors. RESULTS: Minor crossmatch was performed using the patient's erythrocytes and plasma of ABO-identical platelets to be transfused. No agglutination was seen at immediate spin, 37°C, or anti-human globulin phase with valid controls. Genetics testing for complement mutations was consistent with aHUS. CONCLUSIONS: We present a case that is clinically consistent with pHUS. Confirmation of this entity is done with lectins or anti-sera that are not readily available. An alternative means of identifying pHUS is by demonstrating minor crossmatch incompatibility. By doing so, we excluded the possibility of pHUS and helped to elucidate a definitive diagnosis of aHUS. Our goal is to share our experience of a practical approach in a time-sensitive situation that other clinical pathologists could utilize in suspected cases of T activation with a clinical picture of thrombotic microangiopathy.

Human stanniocalcin-1 suppresses angiotensin II-induced superoxide generation in cardiomyocytes through UCP3-mediated anti-oxidant pathway.

RATIONALE: We have previously shown increased cardiac stanniocalcin-1 (STC1) in patients with idiopathic dilated cardiomyopathy. STC1 localizes to the inner mitochondrial membrane and transgenic over-expression of STC1 is associated with increased energy utilization. OBJECTIVE: We examined the hypothesis that STC1 uncouples mitochondrial oxidative phosphorylation--to suppress superoxide generation and modulate neurohormonal effects on cardiomyocytes. METHODS AND RESULTS: Compared to WT mouse heart, STC1 Tg heart displays: 2-fold higher uncoupling protein 3 (UCP3) levels, but no effect on UCP2 protein; 40% lower ATP levels; but similar activities of respiratory chain complexes I-IV. In cultured adult rat and freshly-isolated mouse cardiomyocytes, rSTC1 induces UCP3, but not UCP2. Treatment of cardiomyocytes with STC1 decreases mitochondrial membrane potential and suppresses baseline and angiotensin II (Ang II)-induced superoxide generation. Furthermore, baseline superoxide generation is higher in freshly-isolated adult UCP3(-/-) mouse cardiomyocytes compared to WT, suggesting an important role for UCP3 in regulating cardiomyocyte ROS under physiologic conditions. Treatment of UCP3(-/-) cardiomyocytes with rSTC1 failed to suppress superoxide generation, suggesting that the effects of STC1 on superoxide generation in cardiomyocytes are UCP3-dependent. CONCLUSION: STC1 activates a novel anti-oxidant pathway in cardiac myocytes through induction of UCP3, and may play an important role in suppressing ROS in the heart under normal physiologic conditions and ameliorate the deleterious effects of Ang II-mediated cardiac injury. Importantly, our data point to a critical role for the mitochondria in regulating ROS generation in response to Ang II.