Remodeling of t-system and proteins underlying excitation-contraction coupling in aging versus failing human heart.

It is well established that the aging heart progressively remodels towards a senescent phenotype, but alterations of cellular microstructure and their differences to chronic heart failure (HF) associated remodeling remain ill-defined. Here, we show that the transverse tubular system (t-system) and proteins underlying excitation-contraction coupling in cardiomyocytes are characteristically remodeled with age. We shed light on mechanisms of this remodeling and identified similarities and differences to chronic HF. Using left ventricular myocardium from donors and HF patients with ages between 19 and 75 years, we established a library of 3D reconstructions of the t-system as well as ryanodine receptor (RyR) and junctophilin 2 (JPH2) clusters. Aging was characterized by t-system alterations and sarcolemmal dissociation of RyR clusters. This remodeling was less pronounced than in HF and accompanied by major alterations of JPH2 arrangement. Our study indicates that targeting sarcolemmal association of JPH2 might ameliorate age-associated deficiencies of heart function.

Erdosteine salvages cardiac necrosis: Novel effect through modulation of MAPK and Nrf-2/HO-1 pathway.

Isoproterenol (ISO) induced oxidative stress and inflammation is involved in the pathogenesis of myocardial necrosis. To optimize the effect of erdosteine against myocardial necrosis, male albino Wistar rats were divided into eight groups (n = 6), that is, normal, ISO-control, erdosteine pretreatment with ISO. Rats were administered erdosteine orally for 28 days. Two doses of ISO (85 mg/kg), s.c. were given to ISO-C and erdosteine treatment groups on the 27th and 28th day. On the 29th day, hemodynamic parameters were recorded and the heart was excised for further parameters. In ISO-C rats, significantly increased levels of inflammatory markers, pro-oxidants, and structural damage were observed as compared with normal group. Furthermore, immunohistochemistry and terminal deoxynucleotidyl transferase dUTP nick end labeling revealed an increased expression of apoptotic proteins. Erdosteine at 80 mg/kg reversed the deleterious effects of ISO and normalized myocardium. Erdosteine showed anti-inflammatory, antiapoptotic, and antioxidant activities through inhibition of MAPK and Nrf-2/HO-1 pathways. To conclude, erdosteine was found protective in ISO-induced myocardial necrosis through MAPK and Nrf-2/HO-1 pathway.

Mechanism Involved in Fortification by Berberine in CDDP-Induced Nephrotoxicity.

BACKGROUND: The activation of Nrf2/HO-1 pathway has been shown to protect against cisplatin- induced nephrotoxicity by reducing oxidative stress. Berberine (Ber), an isoquinoline alkaloid, has demonstrated antioxidant, anti-inflammatory and anti-apoptotic activities in various experimental models. AIM: To check the effect of Ber on cisplatin-induced nephrotoxicity and to explore the involved mechanism. METHODS: Adult male Wistar rats were divided into 6 groups: Normal, cisplatin-control, treatment groups and per se group. Normal saline and Ber (20, 40 and 80 mg/kg; p.o.) was administered to rats for 10 days. A single intraperitoneal injection of cisplatin (8 mg/kg) was injected on 7th day to induced nephrotoxicity. On 10th day, rats were sacrificed, the kidney was removed and stored for the estimation of various parameters. RESULTS: As compared to cisplatin-control group, Ber pretreatment improved renal function system and preserved renal architecture. It also diminished oxidative stress by upregulating the expression of Nrf2/HO-1 proteins. In addition, Ber attenuated the cisplatin mediated inflammation and apoptosis. Furthermore, it also reduced the phosphorylation of p38/JNK and PARP/Beclin-1 expression in the kidney. CONCLUSION: Ber attenuated renal injury by activating Nrf2/HO-1 and inhibiting JNK/p38MAPKs/ PARP/Beclin-1 expression which prevented oxidative stress, inflammation, apoptosis and autophagy in renal tissue.

Cardiomyocyte SMAD4-Dependent TGF-ß Signaling is Essential to Maintain Adult Heart Homeostasis.

The role of the transforming growth factor (TGF)-ß pathway in myocardial fibrosis is well recognized. However, the precise role of this signaling axis in cardiomyocyte (CM) biology is not defined. In TGF-ß signaling, SMAD4 acts as the central intracellular mediator. To investigate the role of TGF-ß signaling in CM biology, the authors deleted SMAD4 in adult mouse CMs. We demonstrate that CM-SMAD4-dependent TGF-ß signaling is critical for maintaining cardiac function, sarcomere kinetics, ion-channel gene expression, and cardiomyocyte survival. Thus, our findings raise a significant concern regarding the therapeutic approaches that rely on systemic inhibition of the TGF-ß pathway for the management of myocardial fibrosis.

ROS-dependent genotoxicity, cell cycle perturbations and apoptosis in mouse bone marrow cells exposed to formulated mixture of cypermethrin and chlorpyrifos.

Swiss albino mice were exposed to formulated cypermethrin (CMR) and/or or chlorpyrifos (CPF) through oral gavages for 60 days. Test doses of CMR (0.69, 1.38 or 2.76mg/kg/day) or CPF (0.5, 1.0 or 2.0mg/kg/day) or CMR + CPF (0.69 + 0.5, 1.38 + 1.0 or 2.76 + 2.0mg/kg/day) were based on the acute oral median lethal doses of CMR or CPF. Chromosome aberrations (CA), micronucleus (MN) induction, cell cycle perturbations, apoptosis and reactive oxygen species (ROS) generation were analysed in bone marrow cells. To explore the involvement of ROS induction, HaCat cells were exposed in vitro to arbitrary concentrations of CMR and/or CPF. Exposure of CMR (2.76mg/kg/day) induced significant inhibition of mitotic index. Significant (P < 0.01) frequencies of CA and MN were observed with the CMR at 1.38mg/kg/day, whereas CPF or its mixture CMR + CPF showed at highest doses. Chromosome/chromatid breaks and fragments were found to be major aberrations in all the treatment groups. Highest doses of CMR or CMR + CPF revealed significant (P < 0.01 or 0.001) elevation of G0/G1 peak, while CPF-exposed cells revealed significant (P < 0.01) declined in G1 phase. Decline in S phase was observed with highest dose of CMR only. Apoptosis induction measured by gating cell population beside G1 peak showed 3- to 4-fold increase in apoptotic cells in CPF-exposed mice as compared to control or CMR or CMR + CPF-treated mice. Further, all the treatment groups in vivo as well as in vitro revealed significant generation of ROS in comparison with the control group. Present results, together with the earlier reports, which substantiate ROS generation may be major cause of genotoxicity, cell cycle perturbations and apoptosis, nonetheless co-exposure of low doses of CMR and CPF mixture does not potentiate genotoxicity.

Loss of Adult Cardiac Myocyte GSK-3 Leads to Mitotic Catastrophe Resulting in Fatal Dilated Cardiomyopathy.

RATIONALE: Cardiac myocyte-specific deletion of either glycogen synthase kinase (GSK)-3α and GSK-3ß leads to cardiac protection after myocardial infarction, suggesting that deletion of both isoforms may provide synergistic protection. This is an important consideration because of the fact that all GSK-3-targeted drugs, including the drugs already in clinical trial target both isoforms of GSK-3, and none are isoform specific. OBJECTIVE: To identify the consequences of combined deletion of cardiac myocyte GSK-3α and GSK-3ß in heart function. METHODS AND RESULTS: We generated tamoxifen-inducible cardiac myocyte-specific mice lacking both GSK-3 isoforms (double knockout). We unexpectedly found that cardiac myocyte GSK-3 is essential for cardiac homeostasis and overall survival. Serial echocardiographic analysis reveals that within 2 weeks of tamoxifen treatment, double-knockout hearts leads to excessive dilatative remodeling and ventricular dysfunction. Further experimentation with isolated adult cardiac myocytes and fibroblasts from double-knockout implicated cardiac myocytes intrinsic factors responsible for observed phenotype. Mechanistically, loss of GSK-3 in adult cardiac myocytes resulted in induction of mitotic catastrophe, a previously unreported event in cardiac myocytes. Double-knockout cardiac myocytes showed cell cycle progression resulting in increased DNA content and multinucleation. However, increased cell cycle activity was rivaled by marked activation of DNA damage, cell cycle checkpoint activation, and mitotic catastrophe-induced apoptotic cell death. Importantly, mitotic catastrophe was also confirmed in isolated adult cardiac myocytes. CONCLUSIONS: Together, our findings suggest that cardiac myocyte GSK-3 is required to maintain normal cardiac homeostasis, and its loss is incompatible with life because of cell cycle dysregulation that ultimately results in a severe fatal dilated cardiomyopathy.