Ca2+/calmodulin‐dependent protein kinase II and Dimethyl Sulfoxide affect the sealing frequencies of transected hippocampal neurons

Abstract

Traumatic injury often results in axonal severance, initiating obligatory Wallerian degeneration of distal segments, whereas proximal segments often survive. Calcium ion (Ca ) influx at severed proximal axonal ends activates pathways that can induce apoptosis. However, this same Ca -influx also activates multiple parallel pathways that seal the plasmalemma by inducing accumulation and fusion of vesicles at the lesion site that reduce Ca -influx and enhance survival. We examined whether various inhibitors of Ca /calmodulin-dependent protein kinases (CaMKs), and/or dimethyl sulfoxide (DMSO), a common solvent for biologically active substances, affected the ability of a hippocampal-derived neuronal cell line (B104 cells) to seal membrane damage following axotomy. Axolemmal sealing frequencies were assessed at different transection distances from the axon hillock and at various times after Ca -influx (PC times) by observing whether transected cells took-up fluorescent dyes. Inhibition of CaMKII by tatCN21 and KN-93, but not inhibition of CaMKI and CaMKIV by STO-609, affected axonal sealing frequencies. That is, CaMKII is a component of previously reported parallel pathways that induce membrane sealing, whereas CaMKI and CaMKIV are not involved. The effects of these CaMKII inhibitors on plasmalemmal sealing depended on their mechanism of inhibition, transection distance, and PC time. DMSO at low concentrations (90 µM-28 mM or 0.00064%-0.2% v/v) significantly increased membrane-sealing frequencies at most PC times and transection distances, possibly by permeabilizing the plasmalemma to Ca . Inhibition of CaMKII, DMSO, PC time, and the transection distance significantly affect plasmalemmal sealing that is critical to somal survival in traumatic lesions.

Differential importance of nucleus accumbens Ox1Rs and AMPARs for female and male mouse binge alcohol drinking

“…Any possible lingering toxicity of DMSO should impact drinking on subsequent days, but this was not observed (see 29 ). However, others have reported the possibility of DMSO-related damage 71 , 72 , and thus, despite within-animal comparisons used here and in our other studies, we cannot rule out the possibility of DMSO-related changes in animals studied here.…”

Optimization and evaluation of an in vitro model of PEG-mediated fusion of nerve cell bodies

“…PEG being highly hydrophilic, and only requiring a brief exposure time for cell-cell fusions [9,11,12], our observation could be explained by the slight increase in PEG removing and sequestering most of the water from the cell membrane, before any DMSO effects can be observed. Additionally, low concentrations of DMSO have been implicated in the influx of Ca 2+ , leading to vesicle formation to ''seal" leaky membranes [36] and increased plasmalemmal sealing following axotomies [37]. As the experimental purpose is to test substances which may enhance cell-cell fusion, any additive that may initiate sealing prior to cell-cell fusion occurring would preferentially be avoided.…”

Wound Repair of the Cell Membrane: Lessons from Dictyostelium Cells

“…Calmodulin, a multifunctional Ca 2+ -binding messenger protein, is reported to contribute to cellular wound repair in neurons, green algae, and Dictyostelium cells [51,222,223]. Calmodulin activates calpain, a Ca 2+ -dependent protease, to degrade fodrin, an actinrelated protein, and thereby disassembles the actin cortex, which facilitates the resealing of wounded membrane in neurons and axons [224].…”