ELF-MF transiently increases skeletal myoblast migration: possible role of calpain system

Biological activities of a new crotamine-like peptide from Crotalus oreganus helleri on C2C12 and CHO cell lines, and ultrastructural changes on motor endplate and striated muscle

Crotamine and crotamine-like peptides are non-enzymatic polypeptides, belonging to the family of myotoxins, which are found in high concentration in the venom of the Crotalus genus. Helleramine was isolated and purified from the venom of the Southern Pacific rattlesnake, Crotalus oreganus helleri. This peptide had a similar, but unique, identity to crotamine and crotamine-like proteins isolated from other rattlesnakes species. The variability of crotamine-like protein amino acid sequences may allow different toxic effects on biological targets or optimize the action against the same target of different prey. Helleramine was capable of increasing intracellular Ca2+ in Chinese Hamster Ovary (CHO) cell line. It inhibited cell migration as well as cell viability (IC50 = 11.44 μM) of C2C12, immortalized skeletal myoblasts, in a concentration dependent manner, and promoted early apoptosis and cell death under our experimental conditions. Skeletal muscle harvested from mice 24 h after helleramine injection showed contracted myofibrils and profound vacuolization that enlarged the subsarcolemmal space, along with loss of plasmatic and basal membrane integrity. The effects of helleramine provide further insights and evidence of myotoxic activities of crotamine-like peptides and their possible role in crotalid envenomings.

The use of electric, magnetic, and electromagnetic field for directed cell migration and adhesion in regenerative medicine

Directed cell migration and adhesion is essential to embryonic development, tissue formation and wound healing. For decades it has been reported that electric field (EF), magnetic field (MF) and electromagnetic field (EMF) can play important roles in determining cell differentiation, migration, adhesion, and evenwound healing. Combinations of these techniques have revealed new and exciting explanations for how cells move and adhere to surfaces; how the migration of multiple cells are coordinated and regulated; how cellsinteract with neighboring cells, and also to changes in their microenvironment. In some cells, speed and direction are voltage dependent. Data suggests that the use of EF, MF and EMF could advance techniques in regenerative medicine, tissue engineering and wound healing. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:5-16, 2017.

[Modulation of Ca(2+)-Dependent Proteiolysis under the Action of Weak Low-Frequency Magnetic Fields]

The study aimed to determine the molecular targets of magnetic fields in living objects. Time-dependent effects of weak low-frequency magnetic field tuned to the parametric resonance for calcium ions were studied on model organisms (fish, whelk). The dynamics of Ca(2+)-dependent proteinase activity under the exposure to magnetic fields with given parameters was determined and minimal time of exposure in order to achieve inactivation of these proteinases was find out as well. As hyperactivation of Ca(2+)-dependent proteinases is a basis of degenerative pathology development the therapeutic potential of weak low-frequency magnetic fields enabling to modulate Ca(2+)-dependent proteinase activity is supported.

Myristoylated Alanine-Rich Protein Kinase Substrate (MARCKS) Regulates Small GTPase Rac1 and Cdc42 Activity and Is a Critical Mediator of Vascular Smooth Muscle Cell Migration in Intimal Hyperplasia Formation

BACKGROUND

Transcription of the myristoylated alanine-rich C kinase substrate (MARCKS) is upregulated in animal models of intimal hyperplasia. MARCKS knockdown inhibits vascular smooth muscle cell (VSMC) migration in vitro; however, the mechanism is as yet unknown. We sought to elucidate the mechanism of MARCKS-mediated motility and determine whether MARCKS knockdown reduces intimal hyperplasia formation in vivo.

METHODS AND RESULTS

MARCKS knockdown blocked platelet-derived growth factor (PDGF)-induced translocation of cortactin to the cell cortex, impaired both lamellipodia and filopodia formation, and attenuated motility of human coronary artery smooth muscle cells (CASMCs). Activation of the small GTPases, Rac1 and Cdc42, was prevented by MARCKS knockdown. Phosphorylation of MARCKS resulted in a transient shift of MARCKS from the plasma membrane to the cytosol. MARCKS knockdown significantly decreased membrane-associated phosphatidylinositol 4,5-bisphosphate (PIP2) levels. Cotransfection with an intact, unphosphorylated MARCKS, which has a high binding affinity for PIP2, restored membrane-associated PIP2 levels and was indispensable for activation of Rac1 and Cdc42 and, ultimately, VSMC migration. Overexpression of MARCKS in differentiated VSMCs increased membrane PIP2 abundance, Rac1 and Cdc42 activity, and cell motility. MARCKS protein was upregulated early in the development of intimal hyperplasia in the murine carotid ligation model. Decreased MARKCS expression, but not total knockdown, attenuated intimal hyperplasia formation.

CONCLUSIONS

MARCKS upregulation increases VSMC motility by activation of Rac1 and Cdc42. These effects are mediated by MARCKS sequestering PIP2 at the plasma membrane. This study delineates a novel mechanism for MARCKS-mediated VSMC migration and supports the rational for MARCKS knockdown to prevent intimal hyperplasia.

Power frequency magnetic fields induced reactive oxygen species-related autophagy in mouse embryonic fibroblasts

Power frequency magnetic fields (PFMF) have been reported to affect several cellular functions, such as cell proliferation and apoptosis. In this study, we investigated the effects of PFMF on mouse embryonic fibroblasts (MEF) autophagy. After cells were exposed to 50 Hz PFMF at 2 mT for 0.5 h, 2 h, 6 h, 12 h, and 24 h, we observed a significant increase in autophagic markers at 6 h, including (i) higher microtubule-associated protein 1 light chain 3-II (LC3-II), (ii) the increased formation of GFP-LC3 puncta, and (iii) increased numbers of autophagic vacuoles under transmission electron microscope. Moreover, we provide convincing evidence using chloroquine (CQ) that the increase of autophagic markers was the result of enhanced autophagic flux and not the suppression of lysosomal function. In a search for molecular mechanisms underlying PFMF-mediated autophagy, we observe that the autophagic process involved reactive oxygen species (ROS) and was independent of the mammalian target of rapamycin (mTOR) signaling pathway.