Exosomal Micro‐RNA‐96 Derived From Bone Marrow Mesenchymal Stem Cells Inhibits Doxorubicin‐Induced Myocardial Toxicity by Inhibiting the Rac1/Nuclear Factor‐κB Signaling Pathway

Background Exosomes are small membranous structures released from cells into the blood, regulating various biological processes. However, the role of exosomes in cardiotoxicity remains largely unclear. This study investigated the functional mechanism of exosomal microRNA‐96 (miR‐96) derived from bone marrow mesenchymal stem cells (BMSCs) in myocardial toxicity induced by doxorubicin. Methods and Results BMSCs were transfected with miR‐96 mimic, miR‐96 inhibitor, or the negative control before exosome isolation. The functional mechanism of BMSC‐derived exosomal miR‐96 was investigated in doxorubicin‐induced cell and rat models. The cardiac function, histological morphology, and fiber content of myocardium were examined. The expression levels of the following biomarkers were measured for assessment of cardiac injury: creatine kinase isoenzyme MB, cardiac troponin I, brain natriuretic peptide, soluble suppression of tumorigenesis‐2, tumor necrosis factor‐α, interleukin‐1β, interleukin‐6, superoxide dismutase, glutathione peroxidase, and malondialdehyde. Cell Counting Kit‐8 assay was used to measure the survival rate of cardiomyocytes. The expressions of miR‐96, Rac1, p‐IKKα/IKKα, p‐IKKβ/IKKβ, p‐IκBα/IκBα and p‐p65/p65 in myocardium and cardiomyocytes were also assessed. The targeting relationship between miR‐96 and Rac1 was verified by dual‐luciferase reporter assay. miR‐96 was downregulated, Rac1 was upregulated and the nuclear factor‐κB signaling pathway was activated in doxorubicin‐induced cell and animal models. Doxorubicin decreased antioxidative enzymes (superoxide dismutase and glutathione peroxidase) and increased myocardial injury biomarkers (creatine kinase isoenzyme MB, cardiac troponin I, and brain natriuretic peptide), proinflammatory cytokines (tumor necrosis factor‐α, interleukin‐1β, and interleukin‐6), malondialdehyde, and myocardial fibers. Exosomes derived from BMSCs ameliorated doxorubicin‐induced myocardial injuries. Overexpression of miR‐96 in exosomes derived from BMSCs further enhanced the protection of myocardium and cardiomyocytes against doxorubicin‐induced toxicity while miR‐96 knockdown abolished the protective effects of exosomes derived from BMSCs. Rac1 was a target gene of miR‐96. Rac1 inhibition could downregulate the expression of the nuclear factor‐κB signaling and further reverse the promotion of miR‐96 knockdown on doxorubicin‐induced myocardial toxicity. Conclusions BMSC‐derived exosomal miR‐96 protects myocardium against doxorubicin‐induced toxicity by inhibiting the Rac/nuclear factor‐κB signaling pathway.

Test results comparison and sample stability study

Introduction: The aim was to evaluate the BD Barricor tubes by comparison with the BD Rapid Serum Tubes (RST) through measuring 25 analytes and monitoring sample stability after 24 hours and 7 days. Materials and methods: Samples of 52 patients from different hospital departments were examined. Blood was collected in BD RST and BD Barricor tubes (Becton, Dickinson and Company, Franklin Lakes, USA). Analytes were measured by Beckman Coulter AU 480 (Beckman Coulter, Brea, USA), Dimension EXL (Siemens Healthcare Diagnostics, Newark, USA) and ARCHITECT i2000SR (Abbott Diagnostics, Lake Forest, USA). Between-tube comparison for each analyte was performed, along with testing analyte stability after storing samples at 4 °C. Results: BD Barricor tubes showed unacceptable bias compared to BD RST tubes for potassium (K) (- 4.5%) and total protein (4.4%). Analyte stability after 24 hours was acceptable in both tested tubes for most of analytes, except for glucose, aspartate aminotransferase (AST) and lactate dehydrogenase (LD) in BD Barricor and free triiodothyronine in BD RST sample tubes. Analyte stability after 7 days was unacceptable for sodium, K, calcium, creatine kinase isoenzyme MB, AST, LD and troponin I in both samples; additionally for glucose, alkaline phosphatase and albumin in BD Barricor. Conclusion: All analytes, except K and total protein, can be measured interchangeably in BD RST and BD Barricor tubes, applying the same reference intervals. For most of the analytes, sample re-analysis can be performed in both tubes after 24 hours and 7 days, although BD RST tubes show better 7-day analytes stability over BD Barricor tubes.

Assessment of the neutralizing potency of antisera raised against native and γ-irradiated Naja nigricollis (black-necked spitting cobra) venom in rabbits, concerning its cardiotoxic effect

The present study was designed to prepare a specific safe antiserum for Naja nigricollis using γ-irradiated (1.5KGy and3KGy) venoms. Rabbits were used for active immunization using irradiated venoms (1.5 and 3 kGy) as a toxoid, mice were used for determination of LD50 post immunization and the rats were used for neutralization of the cardiotoxic effect of venom. Results of the immunodiffusion test indicated that the sera of rabbits raised against non-irradiated, 1.5- and 3-kGy γ-irradiated venom, had the same results of precipitin bands. A significant inhibition of phospholipase A2 activities was obtained when neutralized with native, γ-irradiated (1.5KGy and3KGy) venoms. On the other hand, preincubation of the venom ½ LD50 (0.154 mg/kg i.p.) with each antiserum (non-irradiated or irradiated venom) at 37°C for 1 h in a ratio (1:4) produced a significant reduction in the values of creatine kinase and creatine kinase isoenzyme-MB. However, significant elevation in aspartate aminotransferase level and no change in lactate dehydrogenase level were observed. So the results of this study indicated that the irradiated venom treatment reduces the cardiotoxic effect of venom in immunized immunization animals for preparing vaccines.

Safety of Single-Dose Histidine-Tryptophan-Ketoglutarate Cardioplegia during Minimally Invasive Mitral Valve Surgery

Objective Minimally invasive mitral valve surgery may require a prolonged period of myocardial ischemia. Cardioplegic solutions that necessitate a single dose for adequate myocardial protection are evoked to simplify surgery and result to be appealing in this setting. The aim of this study was to assess early outcomes after minimally invasive mitral valve surgery using one single dose of histidine-tryptophanketoglutarate solution (HTK; Custodiol) for myocardial protection. Methods Between February 2003 and October 2012, a total of 49 consecutive patients underwent minimally invasive mitral valve surgery using a single dose of HTK solution for myocardial protection. The patients’ mean (SD) age was 57 (14) years; the preoperative ejection fraction was normal in all cases. The mean (SD) CPB time and aortic cross-clamp time were 148 (45) minutes and 97 (45) minutes, respectively. Results The heart spontaneously restarted after cross-clamp removal in 37 patients (75.5%). Five patients (10.2%) required prolonged inotropic drug support. Postoperatively, no significant increase in myocardial cytonecrosis enzymes was found [mean (SD) creatine kinase isoenzyme MB, 77.14 (53.67) μg/L at 3 hours, 71.2 (55.67) μg/L at 12 hours, and 42.53 (38.38) μg/L at 24 hours)], and no ischemic electrocardiogram modifications were observed before discharge. Conclusions During minimally invasive mitral valve surgery, HTK solution provided excellent myocardial protection even after prolonged periods of cardioplegic arrest. The avoidance of repetitive infusions may reduce the risk for coronary malperfusion due to dislodgement of the endoaortic clamp (if used) and increase the surgeon's comfort during the procedure.

Elevated Cardiac Biomarkers With Normal Right Ventricular Size Indicate an Unlikely Diagnosis of Acute Pulmonary Embolism in Stable Patients

The purpose of this investigation is to assess the prevalence of elevated cardiac biomarkers, with or without estimates of right ventricular (RV) size, in stable patients with acute pulmonary embolism (PE). Our hypothesis is that the combination of high levels of cardiac troponin I (cTnI), high creatine kinase isoenzyme MB (CK-MB), and normal size RV are sufficiently uncommon in stable patients with PE to make the diagnosis of PE unlikely. Retrospective review showed a high cTnI plus high CK-MB in 20 (3.4%) of 585 stable patients with acute PE. A high cTnI plus high CK-MB with normal RV size was shown in 5 (1.9%) of 264 patients. In stable patients with such findings, therefore, PE is unlikely and other diagnoses, particularly acute coronary syndrome, should be considered before pursuing a diagnosis of PE.