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Trastuzumab (TZM) is commonly used for target therapy in breast cancer patients with high HER2 although the cardiotoxicity restricts its clinical usage. DNA damage and ferroptosis are implicated in anti-tumor drug cardiotoxicity. Given the emerging use of SGLT2 inhibitors in clinical cardiology, this study evaluated the impact of SGLT2 inhibitor Empagliflozin on TZM-induced cardiotoxicity, and mechanism involved with a focus on DNA damage and ferroptosis. Adult C57BL/6 mice were challenged with TZM (10 mg/kg/week, i.p.) or saline for six weeks. A cohort of mice received Empagliflozin (10 mg/kg, i.p.) at the same time. Myocardial function, morphology, ultrastructure, mitochondrial integrity, oxidative stress, DNA damage and various cell death domains were evaluated in TZM-challenged mice with or without Empagliflozin treatment. Our data revealed that TZM challenge overtly increased levels of serum LDH and troponin I, promoted adverse myocardial remodeling (increased heart weight, chamber size, cardiomyocyte area and interstitial fibrosis), contractile dysfunction and intracellular Ca

Cerebrovascular diseases such as ischemic stroke, brain hemorrhage, and subarachnoid hemorrhage provoke cardiac complications such as heart failure, neurogenic stress-related cardiomyopathy and Takotsubo cardiomyopathy. With regards to the pathophysiology of stroke-induced heart injury, several mechanisms have been postulated to contribute to this complex interaction between brain and heart, including damage from gut dysbiosis, immune and systematic inflammatory responses, microvesicle- and microRNA-mediated vascular injury and damage from a surge of catecholamines. All these cerebrovascular diseases may trigger pronounced catecholamine surges through diverse ways, including stimulation of hypothalamic-pituitary adrenal axis, dysregulation of autonomic system, and secretion of adrenocorticotropic hormone. Primary catecholamines involved in this pathophysiological response include norepinephrine (NE) and epinephrine. Both are important neurotransmitters that connect the nervous system with the heart, leading to cardiac damage via myocardial ischemia, calcium (Ca2+) overload, oxidative stress, and mitochondrial dysfunction. In this review, we will aim to summarize the molecular mechanisms behind catecholamine-induced cardiotoxicity including Ca2+ overload, oxidative stress, apoptosis, cardiac hypertrophy, interstitial fibrosis, and inflammation. In addition, we will focus on how synchronization among these pathways evokes cardiotoxicity.

Aims Accumulation of advanced glycation endproduct (AGE) contributes to diabetic complication including diabetic cardiomyopathy although the precise underlying mechanism still remains elusive. Recent evidence depicted a pivotal role of protein kinase C (PKC) in diabetic complications. To this end, this study was designed to examine if PKCβII contributes to AGE-induced cardiomyocyte contractile and intracellular Ca 2 + aberrations. Main methods Adult rat cardiomyocytes were incubated with methylglyoxal-AGE (MG-AGE) in the absence or presence of the PKCβII inhibitor LY333531 for 12 h. Contractile and intracellular Ca 2 + properties were assessed using an IonOptix system including peak shortening (PS), maximal velocity of shortening/relengthening (± dL/dt), time-to-PS (TPS), time-to-90% relengthening (TR 90 ), rise in intracellular Ca 2 + Fura-2 fluorescence intensity and intracellular Ca 2 + decay. Oxidative stress, O 2 − production and mitochondrial integrity were examined using TBARS, fluorescence imaging, aconitase activity and Western blotting. Key findings MG-AGE compromised contractile and intracellular Ca 2 + properties including reduced PS, ± dL/dt, prolonged TPS and TR 90 , decreased electrically stimulated rise in intracellular Ca 2 + and delayed intracellular Ca 2 + clearance, the effects of which were ablated by the PKCβII inhibitor LY333531. Inhibition of PKCβII rescued MG-AGE-induced oxidative stress, O 2 − generation, cell death, apoptosis and mitochondrial injury (reduced aconitase activity, UCP-2 and PGC-1α). In vitro studies revealed that PKCβII inhibition-induced beneficial effects were replicated by the NADPH oxidase inhibitor apocynin and were mitigated by the mitochondrial uncoupler FCCP. Significance These findings implicated the therapeutic potential of specific inhibition of PKCβII isoform in the management of AGE accumulation-induced myopathic anomalies.

Oxidative stress has been speculated to play an essential role in diabetic cardiomyopathy. This study was designed to examine the effect of the antioxidant catalase on diabetes-induced cardiomyocyte dysfunction and the cellular mechanisms involved. Adult wild-type (FVB) and transgenic mice with cardiac-specific overexpression of catalase were made diabetic by a single injection of streptozotocin (STZ, 220 mg/kg; i.p., maintained for two weeks). Cardiomyocyte contractile properties were evaluated including peak shortening (PS), time-to-PS (TPS), time-to-relengthening (TR(90)), maximal velocity of shortening/relengthening (+/-dL/dt), intracellular Ca(2+) level and decay rate. STZ depressed -dL/dt, prolonged TPS and TR(90), elevated resting intracellular Ca(2+) level and reduced intracellular Ca(2+) decay in FVB myocytes. While catalase exhibited little effect on contractile and intracellular Ca(2+) properties in control myocytes, it negated diabetes-induced cardiomyocyte mechanical abnormalities. Diabetic myocytes exhibited enhanced levels of reactive oxygen species and apoptosis, which were alleviated by catalase. Western blot analysis revealed that diabetes reduced Akt phosphorylation, enhanced the silent information regulator 2 (Sirt2), and upregulated Forkhead transcriptional factor Foxo3a as well as glycogen synthase kinase-3beta (GSK-3beta) and pGSK-3beta. While catalase itself exhibited little effect on these proteins or their phosphorylation (with the exception of Sirt2), it significantly attenuated diabetes-induced alteration in pAkt, Foxo3a and Sirt2 without affecting GSK-3beta. Inhibition of Sirt2 using splitomicin impaired cardiomyocyte contractile function (reduced PS, +/-dL/dt, prolonged TPS and TR(90)). In summary, our data suggest potential roles of Akt, Foxo3a and Sirt2 in the onset of diabetic cardiomyopathy and the therapeutic potential of catalase.

Accumulation of advanced glycation endproduct (AGE) has been implicated in the pathogenesis of diabetic complications. However, the precise role and mechanism behind AGE-associated diabetic heart injury are not fully clear. This study was designed to evaluate the effect of AGE on accumulation of reactive oxygen species (ROS), apoptosis, mitogen-activated protein kinase (MAPK) activation and nuclear O -GlcNAcylation in fetal human cardiac myocytes. Myocytes were maintained for 24–72 h in a defined culture medium containing high glucose, the AGE carbon precursor methylglyoxal (MG), and MG-AGE derived from MG and bovine serum albumin (BSA). Generation of ROS was detected by 5-(6)-chloromethyl-2′,7′-dichlorodihydrofluorescein diacetate. Apoptosis was evaluated by caspase-3 activity and quantitative DNA fragmentation. Both high glucose (25.5 mM) and MG (200 μM) significantly enhanced ROS and AGE formation with greater effects elicited by MG. Both high glucose and MG-AGE significantly facilitated apoptosis with a more predominant effect from MG-AGE. In addition, phosphorylation of MAPK cascade [extracellular signal-regulated kinase-1/2 (ERK1/2) and p38] and nuclear O -GlcNAcylation were enhanced in MG-AGE-treated myocytes, similar to those elicited by high glucose. MG-AGE-induced phosphorylation of ERK1/2 and p38 was nullified by neutralizing AGE with specific anti-AGE antibody but not nonspecific antiserum. Collectively, these results indicated that AGE or its precursor MG may trigger ROS generation, apoptosis, MAPK activation and nuclear O -GlcNAcylation in human cardiac myocytes, in a manner reminiscent of high extracellular glucose.

Mice are extensively used for gene modification research and isolated cardiomyocytes are essential for evaluation of cardiac function without interference from non-myocyte contribution. This study was designed to characterize cardiomyocyte excitation–contraction coupling in FVB/N-C57BL/6 intercrossed brown mice. Mechanical and intracellular Ca 2+ properties were evaluated using an IonOptix softedge system including peak shortening (PS), time-to-PS (TPS), time-to-90% relengthening (TR 90 ), maximal velocity of shortening and relengthening (± d L / d t ), intracellular Ca 2+ rise and decay rate. Resting cell length was longer in age- and gender-matched C57BL/6 and brown mice compared to FVB strain. PS and ± d L / d t were significantly lower in brown mice compared to FVB/N and C57BL/6 groups. TPS was shortened in C57BL/6 mice and TR 90 was prolonged in brown mice compared to other groups. Resting intracellular Ca 2+ level and single exponential intracellular Ca 2+ decay constant were comparable among all three mouse lines. Rise in intracellular Ca 2+ in response to electrical stimulus was higher in C57BL/6 mouse myocytes whereas bi-exponential intracellular Ca 2+ decay was faster in brown mice. Myocytes from all three groups exhibited similar fashion of reduction in PS in response to increased stimulus frequency. These data suggest that inherent differences in cardiomyocyte excitation–contraction coupling exist between strains, which may warrant caution when comparing data from these mouse lines.

Aims To investigate the effect of locally slow-released rapamycin (RAPA) from the bionic peripheral nerve scaffold on rat sciatic nerve regeneration in the early phase of nerve injury. Main methods Slow-releasing RAPA-polyhydroxy alcohol (PLGA) microspheres were prepared and tested for microsphere diameter and slow-release effect in vitro after loading onto nerve scaffold. A total of 48 male SD rats were randomly divided into control group and 3 experimental groups as follows: group 1: RAPA-PLGA scaffold; group 2: RAPA scaffold; and group 3: scaffold alone. In the control group, a 15 mm sciatic nerve was excised and religated reversely. In the experimental groups, the scaffolds were used to bridge a defect of 15 mm sciatic nerve. The outcome of nerve regeneration was evaluated using neurophysiological and neuromuscular morphological techniques. Key findings The RAPA-PLGA microspheres displayed a smooth exterior. The slow-release of RAPA in group 1 lasted for 14 days. The sciatic nerve function index (SFI) and electrophysiological and morphological features were examined 12 weeks after the surgery in all groups to reveal various degrees of ipsilateral sciatic nerve regeneration. The SFI values at 12 weeks showed no significant difference between the RAPA-PLGA scaffold and control groups; morphological observations revealed that the outcomes of nerve regeneration in the above 2 groups were similar and significantly better than those in the RAPA scaffold and scaffold alone groups. Significance RAPA-PLGA microsphere-loaded bionic peripheral nerve scaffold gradually released RAPA locally in the early phase of sciatic nerve regeneration, reduced the secondary nerve injury, and evidently promoted the regeneration of peripheral nerve.

Insulin participates in the modulation of myocardial function, but its inotropic action in diabetes mellitus is not fully clear. In the present study, we examined contractile responses to insulin in left-ventricular papillary muscles and ventricular myocytes isolated from hearts of normal or short-term (5–7 days) streptozotocin-induced (65 mg kg ) diabetic rats. Mechanical properties of papillary muscles and ventricular myocytes were evaluated using a force transducer and an edge-detector, respectively. Contractile properties of papillary muscles or cardiac myocytes, electrically stimulated at 0.5 Hz, were analyzed in terms of peak tension development (PTD) or peak twitch amplitude (PTA), time-to-peak contraction (TPT) and time-to-90% relaxation (RT90). Intracellular Ca2+ transients were measured as fura-2 fluorescence intensity change (ΔFFI). Insulin (1–500 nM) had no effect on PTD in normal myocardium, whereas it produced a positive inotropic response in preparations from diabetic animals, with a maximal increase of 11%. Insulin did not modify TPT or RT90 in either group. Further studies revealed that insulin enhanced cell shortening in diabetic but not normal myocytes, with a maximal increase of 21%. Consistent with its action on the mechanical properties of papillary muscles and cardiac myocytes, insulin also induced a dose-dependent increase in the intracellular Ca2+ transient in diabetic but not normal myocytes. Collectively, these data suggest that the myocardial contractile response to insulin may be altered in diabetes.

Aims Hyperglycemia leads to cytotoxicity in the heart. Although theories were postulated for glucose toxicity-induced cardiomyocyte dysfunction including oxidative stress, the mechanism involved still remains unclear. Recent evidence has depicted a role of protein kinase C (PKC) in diabetic complications while high concentrations of glucose stimulate PKC. This study examined the role of PKCβII in glucose toxicity-induced cardiomyocyte contractile and intracellular Ca2 + aberrations. Main methods Adult rat cardiomyocytes were maintained in normal (NG, 5.5 mM) or high glucose (HG, 25.5 mM) medium for 12 h. Contractile and intracellular Ca2 + properties were measured using a video edge-detection system including peak shortening (PS), maximal velocity of shortening/relengthening (± dL/dt), time-to-PS (TPS), time-to-90% relengthening (TR90), rise in intracellular Ca2 + Fura-2 fluorescence intensity and intracellular Ca2 + decay. Production of ROS/O2− and mitochondrial integrity were examined using fluorescence imaging, aconitase activity and Western blotting. Key findings High glucose triggered abnormal contractile and intracellular Ca2 + properties including reduced PS, ± dL/dt, prolonged TR90, decreased electrically-stimulated rise in intracellular Ca2 + and delayed intracellular Ca2 + clearance, the effects of which were ablated by the PKCβII inhibitor LY333531. Inhibition of PKCβII rescued glucose toxicity-induced generation of ROS and O2−, apoptosis, cell death and mitochondrial injury (reduced aconitase activity, UCP-2 and PGC-1α). In vitro studies revealed that PKCβII inhibition-induced beneficial effects were mimicked by the NADPH oxidase inhibitor apocynin and were canceled off by mitochondrial uncoupling using FCCP. Significance These findings suggest the therapeutic potential of specific inhibition of PKCβII isoform in the management of hyperglycemia-induced cardiac complications.