Temporal involvement of phosphatidylinositol 4-phosphate 5-kinase γ in differentiation of Z-bands and myofilament bundles as well as intercalated discs in mouse heart at mid-gestation

Considering the occurrence of serious heart failure in a gene knockout mouse of PIP5Kγ and in congenital abnormal cases in humans in which the gene was defective as reported by others, the present study attempted to localize PIP5Kγ in the heart during prenatal stages. It was done on the basis of the supposition that phenotypes caused by gene mutation of a given molecule are owed to the functional deterioration of selective cellular sites normally expressing it at significantly higher levels in wild mice. PIP5Kγ-immunoreactivity was the highest in the heart at E10 in contrast to almost non-significant levels of the immunoreactivity in surrounding organs and tissues such as liver. The immunoreactivity gradually weakened in the heart with the prenatal age, and it was at non-significant levels at newborn and postnatal stages. Six patterns in localization of distinct immunoreactivity for PIP5Kγ were recognized in cardiomyocytes: (1) its localization on the plasma membranes and subjacent cytoplasm without association with short myofibrils and (2) its localization on them as well as short myofibrils in association with them in cardiomyocytes of early differentiation at E10; (3) its spot-like localization along long myofibrils in cardiomyocytes of advanced differentiation at E10; (4) rare occurrences of such spot-like localization along long myofibrils in cardiomyocytes of advanced differentiation at E14; (5) its localization at Z-bands of long myofibrils; and (6) its localization at intercellular junctions including the intercalated discs in cardiomyocytes of advanced differentiation at E10 and E14, especially dominant at the latter stage. No distinct localization of PIP5Kγ-immunoreactivity of any patterns was seen in the heart at E18 and P1D. The present finding suggests that sites of PIP5Kγ-appearance and probably of its high activity in cardiomyocytes are shifted from the plasma membranes through short myofibrils subjacent to the plasma membranes and long myofibrils, to Z-bands as well as to the intercalated discs during the mid-term gestation. It is further suggested that PIP5Kγ is involved in the differentiation of myofibrils as well as intercellular junctions including the intercalated discs at later stages of the mid-term gestation. Failures in its involvement in the differentiation of these structural components are thus likely to cause the mid-term gestation lethality of the mutant mice for PIP5Kγ.

Erratum: SIRT1 activation and its effect on intercalated disc proteins as a way to reduce doxorubicin cardiotoxicity

[This corrects the article DOI: 10.3389/fphar.2022.1035387.].

SIRT1 activation and its effect on intercalated disc proteins as a way to reduce doxorubicin cardiotoxicity

According to the World Health Organization, the neoplasm is one of the main reasons for morbidity and mortality worldwide. At the same time, application of cytostatic drugs like an independent type of cancer treatment and in combination with surgical methods, is often associated with the development of cardiovascular complications both in the early and in the delayed period of treatment. Doxorubicin (DOX) is the most commonly used cytotoxic anthracycline antibiotic. DOX can cause both acute and delayed side effects. The problem is still not solved, as evidenced by the continued activity of researchers in terms of developing approaches for the prevention and treatment of cardiovascular complications. It is known, the heart muscle consists of cardiomyocytes connected by intercalated discs (ID), which ensure the structural, electrical, metabolic unity of the heart. Various defects in the ID proteins can lead to the development of cardiovascular diseases of various etiologies, including DOX-induced cardiomyopathy. The search for ways to influence the functioning of ID proteins of the cardiac muscle can become the basis for the creation of new therapeutic approaches to the treatment and prevention of cardiac pathologies. SIRT1 may be an interesting cardioprotective variant due to its wide functional significance. SIRT1 activation triggers nuclear transcription programs that increase the efficiency of cellular, mitochondrial metabolism, increases resistance to oxidative stress, and promotes cell survival. It can be assumed that SIRT1 can not only provide a protective effect at the cardiomyocytes level, leading to an improvement in mitochondrial and metabolic functions, reducing the effects of oxidative stress and inflammatory processes, but also have a protective effect on the functioning of IDs structures of the cardiac muscle.

Chronic consumption of a high-fat diet rich in corn oil activates intrinsic cell death pathway and induces several ultrastructural changes in the atria of healthy and type 1 diabetic rat

This study investigates the effect of chronic consumption of a high-fat diet rich in corn oil (CO-HFD) on atrial cells ultrastructure, antioxidant levels and markers of intrinsic cell death of both control and type 1 diabetes mellitus (T1DM)-induced rats. Adult male rats (10 rats/group) were divided into four groups: control fed standard diet (STD) (3.82 kcal/g, 9.4% fat), CO-HFD (5.4 kcal/g, 40% fat), T1DM fed STD, and T1DM + CO-HFD. CO-HFD and T1DM alone or in combination impaired systolic and diastolic functions of rats and significantly reduced levels of GSH and the activity of SOD, enhanced lipid peroxidation, increased protein levels of P53, Bax, cleaved caspase-3, and ANF and decreased levels of Bcl-2 in their atria. Concomitantly, atrial cells exhibited fragmentation of the myofibrils, disorganized mitochondria, decreased number of atrionatriuretic factor (ANF) granules, and loss of gap junctions accompanied by changes in capillary walls. Among all treatments, the severity of all these findings was more severe in T1DM and most profound in the atria of T1DM + CO-HFD. In conclusion, chronic consumption of CO-HFD by T1DM-induced rats elicits significant biochemical and ultrastructural damage to rat atrial cells accompanied by elevated oxidative stress and mitochondria-mediated cell death.

AuNP-Collagen Matrix with Localized Stiffness for Cardiac-Tissue Engineering: Enhancing the Assembly of Intercalated Discs by β1-Integrin-Mediated Signaling

A schematic for the mechanism of accelerating the assembly of intercalated discs (IDs) in cardiac myocytes regulated by gold nanoparticles (AuNPs) is presented. AuNPs with local nanoscale stiffness in the substrate activate β1-integrin signaling, which mediates the activation of integrin-linked kinase (ILK) and its downstream signal kinase by stimulating expression of the transcription factors GATA4 and MEF-2c.