Abstract
Botulinum neurotoxin type A (BoNT/A) and minocycline are potent drugs used in clinical therapies. The primary molecular mechanism of BoNT/A is the cleavage of SNARE proteins, which prevents cells from releasing neurotransmitters from vesicles, while the effects of minocycline are related to the inhibition of p38 activation. Both BoNT/A and minocycline exhibit analgesic effects, however, their direct impact on glial cells is not fully known. Therefore, the aim of the present study was to determine the effects of those drugs on microglial and astroglial activity after lipopolysaccharide (LPS) stimulation and their potential synergistic action. Our results show that BoNT/A and minocycline influenced primary microglial cells by inhibiting intracellular signaling pathways, such as p38, ERK1/2, NF-κB, and the release of pro-inflammatory factors, including IL-1β, IL-18, IL-6, and NOS2. We have revealed that, in contrast to minocycline, BoNT/A treatment did not decrease LPS-induced release of pro-inflammatory factors in the astroglia. In addition, BoNT/A decreased SNAP-23 in both types of glial cells and also SNAP-25 expressed only in astrocytes. Moreover, BoNT/A increased TLR2 and its adaptor protein MyD88, but not TLR4 exclusively in microglial cells. Furthermore, we have shown the impact of BoNT/A on microglial and astroglial cells, with a particular emphasis on its molecular target, TLR2. In contrast, minocycline did not affect any of those factors. We have revealed that despite of different molecular targets, minocycline, and BoNT/A reduced the release of microglia-derived pro-inflammatory factors. In conclusion, we have shown that BoNT/A and minocycline are effective drugs for the management of neuroinflammation by dampening the activation of microglial cells, with minocycline also affecting astroglial activity.
Highlights
Botulinum toxin A (BoNT/A) is a neurotoxin produced by the anaerobic bacteria Clostridium botulinum
Using primary microglial and astroglial cell cultures, we examined the effects of different doses of Botulinum neurotoxin type A (BoNT/A) [0.01, 0.1, 1, 5, 10, 50, 100 nM] and minocycline [20 μM] on cell viability
We have revealed that BoNT/A inhibits the expression of proinflammatory factors through the modulation of NF-κB, p38, and ERK1/2, and increases the expression of TLR2 and its adaptor protein, MyD88, in microglial cells
Summary
Botulinum toxin A (BoNT/A) is a neurotoxin produced by the anaerobic bacteria Clostridium botulinum. The molecular action of this neurotoxin is the Zn2+-endopeptidase activity-mediated cleavage of specific proteins involved in neuroexocytosis, BoNT/A vs Minocycline in Glial Cultures such as synaptosomal-associated proteins (SNAPs) (Schiavo et al, 2000; Luvisetto et al, 2003, 2006; Montecucco and Molgó, 2005; Snyder et al, 2006). Previous research had shown that BoNT/A strongly inhibits the release of neurotransmitters and neuropeptides, such as glutamate (Cui et al, 2004), substance P (Welch et al, 2000), and calcitonin gene-related peptide (CGRP) (Durham et al, 2004; Meng et al, 2007), which results from the ability of this toxin to cleave SNAP-25, one of the crucial SNARE proteins involved in neuroexocytosis (Schiavo et al, 1993; Rossetto et al, 2001; Montecucco et al, 2004)
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