Akanksha Thakur

c-Jun phosphorylation in Alzheimer disease.

The c‐Jun N‐terminal kinase (JNK) pathway is known to be activated by oxidative stress and can lead to either defensive‐protective adaptations in the cell or apoptosis. The JNK pathway is activated in Alzheimer disease (AD), as demonstrated in studies showing higher levels of phospho‐JNK in affected neurons in AD brains than in controls. c‐Jun, a transcription factor, is the downstream effector of JNK, whose activation requires phosphorylation of Ser63/Ser73. In this study, we characterized and compared the localization of c‐Jun phosphorylated at either Ser63 or Ser73 in the hippocampi of AD cases with that in age‐matched controls. Phospho‐c‐Jun (Ser73) was found to be strongly associated with neurofibrillary tangles and granulovacuolar degeneration (GVD) in addition to the nuclei in neurons in the hippocampal regions of the AD brain, but was virtually absent in most controls. Phospho‐c‐Jun (Ser63) was also found to be associated with GVD in AD brains. Indeed, phospho‐c‐Jun (Ser73) immunostaining was much more extensive than that of phospho‐c‐Jun (Ser63), with all the phospho‐c‐Jun (Ser63)–positive neurons also being phospho‐c‐Jun (Ser73) positive. Significant overlap between phospho‐c‐Jun and phospho‐JNK suggested a mechanistic link. In addition, the neurons showing increased levels of phospho‐c‐Jun (Ser73) in the cytoplasmic GVD were negative for TUNEL, suggesting a mechanism protecting the cells from death. Overall, this study demonstrated specific alterations in c‐Jun phosphorylation and distribution in AD which is not necessarily linked to apoptosis but rather may represent an adaptation process in the face of oxidative stress.

Cancer Therapy-Induced Left Ventricular Dysfunction: Interventions and Prognosis

BACKGROUND For multiple chemotherapeutics, cardiotoxicity is dose limiting and can lead to substantial morbidity and mortality. Early cardiac intervention has the potential to positively affect clinical course. METHODS AND RESULTS We reviewed 247 consecutive patients referred to the Stanford cardiology clinic for cancer therapy-associated cardiac abnormalities from 2004 to 2012. A comprehensive review of records was performed, with documentation of baseline characteristics, cardiac imaging, medications, and clinical course. Seventy-nine patients who had left ventricular ejection fraction (LVEF) declines temporally associated with cancer therapy were included. The most common malignancies were breast (46%) and hematologic (35%); 71% of the patients were female, and overall mean age was 52 years. The primary cancer therapeutics associated with LVEF decline included anthracyclines, trastuzumab, and tyrosine kinase inhibitors. The mean LVEF was 60% before cancer therapy and 40% after cancer therapy. The most common cardiac interventions included beta-blockers (84%) and angiotensin-converting enzyme inhibitors/angiotensin receptor blockers (83%). Mean LVEF after cardiac intervention rose to 53%; 77% of patients had LVEF recovery to ≥50%, and 68% of these patients had recovery within 6 months of starting cardiac therapy; 76% of patients were able to continue their planned cancer therapy. CONCLUSIONS With appropriate cardiac intervention, the majority of patients with LVEF decline from cancer therapy can achieve LVEF recovery and complete their cancer therapy.

Pulmonary hypertension associated with advanced systolic heart failure: dysregulated arginine metabolism and importance of compensatory dimethylarginine dimethylaminohydrolase-1.

OBJECTIVES This study sought to examine the hemodynamic determinants of dysregulated arginine metabolism in patients with acute decompensated heart failure and to explore possible mechanisms of arginine dysregulation in human heart failure. BACKGROUND Accumulating methylated arginine metabolites and impaired arginine bioavailability have been associated with heart failure, but the underlying pathophysiology remains unclear. METHODS This study prospectively determined plasma levels of asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, and global arginine bioavailability ratio [GABR = arginine/(ornithine + citrulline)] by tandem mass spectrometry in subjects with advanced decompensated heart failure in the intensive care unit (n = 68) and with stable chronic heart failure (n = 57). RESULTS Compared with chronic heart failure subjects, plasma ADMA was significantly higher (median [interquartile range]: 1.29 [1.04 to 1.77] μmol/l vs. 0.87 [0.72 to 1.05] μmol/l, p < 0.0001), and global arginine bioavailability ratio significantly lower (median [interquartile range]: 0.90 [0.69 to 1.22] vs. 1.13 [0.92 to 1.37], p = 0.002) in advanced decompensated heart failure subjects. Elevated ADMA and diminished global arginine bioavailability ratio were associated with higher systolic pulmonary artery pressure (sPAP) and higher central venous pressure, but not with other clinical or hemodynamic indices. We further observed myocardial levels of dimethylarginine dimethylaminohydrolase-1 were increased in chronic heart failure without elevated sPAP (<50 mm Hg), but diminished with elevated sPAP (≥50 mm Hg, difference with sPAP <50 mm Hg, p = 0.02). CONCLUSIONS Dysregulated arginine metabolism was observed in advanced decompensated heart failure, particularly with pulmonary hypertension and elevated intracardiac filling pressures. Compared with hearts of control subjects, we observed higher amounts of ADMA-degradation enzyme dimethylarginine dimethylaminohydrolase-1 (but similar amounts of ADMA-producing enzyme, protein methyltransferase-1) in the human failing myocardium.

Utilizing Cardiac Biomarkers to Detect and Prevent Chemotherapy-Induced Cardiomyopathy

The success achieved in advances in cancer therapy has been marred by development of cardiotoxicity, which causes significant morbidity and mortality. This has led to the development of surveillance protocols for cardiotoxicity utilizing multimodality imaging techniques and investigation of various drugs to treat and prevent cardiotoxicity in this subset of patients. Cardiac biomarkers hold important diagnostic and prognostic value in various cardiac diseases. In this review, we discuss the use of biomarkers in patients receiving chemotherapy, highlighting data behind the use of troponin, B-type natriuretic peptide, and myeloperoxidase. We also discuss the use of dexrazoxane, angiotensin-converting enzyme inhibitors, and beta blockers in the treatment and prevention of chemotherapy-induced cardiotoxicity. Cardiac biomarkers may serve an important role in selecting patients that are at high risk of cardiotoxicity and can potentially be used to guide the administration of drugs to treat and prevent cardiotoxicity.

Widespread distribution of reticulon-3 in various neurodegenerative diseases.

Reticulons are a group of membrane‐bound proteins involved in diverse cellular functions, and are suggested to act as inhibitors of β‐secretase enzyme 1 (BACE1) activity that cleaves amyloid precursor protein. Reticulons are known to accumulate in the dystrophic neurites of Alzheimers disease (AD), and studies have suggested that alterations in reticulons, such as increased aggregation, impair BACE1 binding, increasing amyloid‐β production, and facilitating reticulon deposition in dystrophic neurites. To further characterize the cellular distribution of reticulon, we examined reticulon‐3 expression in cases of AD, Parkinsons disease, and diffuse Lewy body disease. A more widespread cellular distribution of reticulon‐3 was noted than in previous reports, including deposits in dystrophic neurites, neuropil threads, granulovacuolar degeneration, glial cells, morphologically normal neurons in both hippocampal pyramidal cell layer and cerebral neocortex, and specifically neurofibrillary tangles and Lewy bodies. These results are compatible with reticulon alterations as nonspecific downstream stress responses, consistent with its expression during periods of endoplasmic reticulum stress. This emphasizes the increasing recognition that much of the AD pathological spectrum represents a response to the disease rather than cause, and emphasizes the importance of examining upstream processes, such as oxidative stress, that have functional effects prior to the onset of structural alterations.

Usefulness of Elevated Urine Neopterin Levels in Assessing Cardiac Dysfunction and Exercise Ventilation Inefficiency in Patients With Chronic Systolic Heart Failure

Neopterin is synthesized by macrophages upon stimulation with gamma-interferon, and high neopterin production is associated with cellular immune activation and increased production of reactive oxygen species (oxidant stress), but the clinical utility of urine neopterin levels in patients with heart failure (HF) has not been explored. Fifty-three ambulatory patients with chronic systolic HF (left ventricular [LV] ejection fraction ≤40%) underwent comprehensive echocardiographic evaluation and cardiopulmonary exercise testing. Urine neopterin levels were quantified by liquid chromatography with tandem mass spectrometric analyses and corrected to urine creatinine (Cr) levels. In our study cohort, median urine neopterin level was 60 μmol/mol Cr (interquartile range 40 to 86). There were modest correlations between urine neopterin levels and abnormalities in cardiac structure and function by echocardiography: LV ejection fraction (r = -0.33, p = 0.017), indexed LV end-diastolic volume (r = 0.31, p = 0.029), indexed LV end-systolic volume (r = 0.32, p = 0.024), and E/septal Ea (r = 0.28, p = 0.041). Although there was no significant correlation between urine neopterin and maximal oxygen uptake (peak VO2: r = -0.25, p = 0.07), there was a modest correlation between urine neopterin and maximal ventilation/carbon dioxide production ratio (VE/VCO2 max: r = 0.38, p = 0.005). In conclusion, increase in urine neopterin levels tracks with disease severity in patients with chronic systolic HF.

Pulmonary Hypertension Associated With Advanced Systolic Heart Failure

OBJECTIVES This study sought to examine the hemodynamic determinants of dysregulated arginine metabolism in patients with acute decompensated heart failure and to explore possible mechanisms of arginine dysregulation in human heart failure. BACKGROUND Accumulating methylated arginine metabolites and impaired arginine bioavailability have been associated with heart failure, but the underlying pathophysiology remains unclear. METHODS This study prospectively determined plasma levels of asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, and global arginine bioavailability ratio [GABR = arginine/(ornithine + citrulline)] by tandem mass spectrometry in subjects with advanced decompensated heart failure in the intensive care unit (n = 68) and with stable chronic heart failure (n = 57). RESULTS Compared with chronic heart failure subjects, plasma ADMA was significantly higher (median [interquartile range]: 1.29 [1.04 to 1.77] μmol/l vs. 0.87 [0.72 to 1.05] μmol/l, p < 0.0001), and global arginine bioavailability ratio significantly lower (median [interquartile range]: 0.90 [0.69 to 1.22] vs. 1.13 [0.92 to 1.37], p = 0.002) in advanced decompensated heart failure subjects. Elevated ADMA and diminished global arginine bioavailability ratio were associated with higher systolic pulmonary artery pressure (sPAP) and higher central venous pressure, but not with other clinical or hemodynamic indices. We further observed myocardial levels of dimethylarginine dimethylaminohydrolase-1 were increased in chronic heart failure without elevated sPAP (<50 mm Hg), but diminished with elevated sPAP (≥50 mm Hg, difference with sPAP <50 mm Hg, p = 0.02). CONCLUSIONS Dysregulated arginine metabolism was observed in advanced decompensated heart failure, particularly with pulmonary hypertension and elevated intracardiac filling pressures. Compared with hearts of control subjects, we observed higher amounts of ADMA-degradation enzyme dimethylarginine dimethylaminohydrolase-1 (but similar amounts of ADMA-producing enzyme, protein methyltransferase-1) in the human failing myocardium.

Dysregulated Arginine Metabolism and Importance of Compensatory Dimethylarginine Dimethylaminohydrolase-1 in Pulmonary Hypertension Associated with Advanced Systolic Heart Failure

OBJECTIVES This study sought to examine the hemodynamic determinants of dysregulated arginine metabolism in patients with acute decompensated heart failure and to explore possible mechanisms of arginine dysregulation in human heart failure. BACKGROUND Accumulating methylated arginine metabolites and impaired arginine bioavailability have been associated with heart failure, but the underlying pathophysiology remains unclear. METHODS This study prospectively determined plasma levels of asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, and global arginine bioavailability ratio [GABR = arginine/(ornithine + citrulline)] by tandem mass spectrometry in subjects with advanced decompensated heart failure in the intensive care unit (n = 68) and with stable chronic heart failure (n = 57). RESULTS Compared with chronic heart failure subjects, plasma ADMA was significantly higher (median [interquartile range]: 1.29 [1.04 to 1.77] μmol/l vs. 0.87 [0.72 to 1.05] μmol/l, p < 0.0001), and global arginine bioavailability ratio significantly lower (median [interquartile range]: 0.90 [0.69 to 1.22] vs. 1.13 [0.92 to 1.37], p = 0.002) in advanced decompensated heart failure subjects. Elevated ADMA and diminished global arginine bioavailability ratio were associated with higher systolic pulmonary artery pressure (sPAP) and higher central venous pressure, but not with other clinical or hemodynamic indices. We further observed myocardial levels of dimethylarginine dimethylaminohydrolase-1 were increased in chronic heart failure without elevated sPAP (<50 mm Hg), but diminished with elevated sPAP (≥50 mm Hg, difference with sPAP <50 mm Hg, p = 0.02). CONCLUSIONS Dysregulated arginine metabolism was observed in advanced decompensated heart failure, particularly with pulmonary hypertension and elevated intracardiac filling pressures. Compared with hearts of control subjects, we observed higher amounts of ADMA-degradation enzyme dimethylarginine dimethylaminohydrolase-1 (but similar amounts of ADMA-producing enzyme, protein methyltransferase-1) in the human failing myocardium.