Influence of Nanomolar Deltamethrin on the Hallmarks of Primary Cultured Cortical Neuronal Network and the Role of Ryanodine Receptors

Abstract

Background:The pyrethroid deltamethrin (DM) is broadly used for insect control. Although DM hyperexcites neuronal networks by delaying inactivation of axonal voltage-dependent Na+ channels, this mechanism is unlikely to mediate neurotoxicity at lower exposure levels during critical perinatal periods in mammals.Objectives:We aimed to identify mechanisms by which acute and subchronic DM altered axonal and dendritic growth, patterns of synchronous Ca2+ oscillations (SCOs), and electrical spike activity (ESA) functions critical to neuronal network formation.Methods:Measurements of SCOs using Ca2+ imaging, ESA using microelectrode array (MEA) technology, and dendritic complexity using Sholl analysis were performed in primary murine cortical neurons from wild-type (WT) and/or ryanodine receptor 1 (RyR1T4826I/T4826I) mice between 5 and 14 d in vitro (DIV). [H3]ryanodine binding analysis and a single-channel voltage clamp were utilized to measure engagement of RyRs as a direct target of DM.Results:Neuronal networks responded to DM (30–70 nM) as early as 5 DIV, reducing SCO amplitude and depressing ESA and burst frequencies by 60–70%. DM (10–300 nM) enhanced axonal growth in a nonmonotonic manner. DM≥100 nM enhanced dendritic complexity. DM stabilized channel open states of RyR1, RyR2, and cortical preparations expressing all three isoforms. DM (30 nM) altered gating kinetics of RyR1 channels, increasing mean open time, decreasing mean closed time, and thereby enhancing overall open probability. SCO patterns from cortical networks expressing RyR1T4826I/T4826I were more responsive to DM than WT. RyR1T4826I/T4826I neurons showed inherently longer axonal lengths than WT neurons and maintained less length-promoting responses to nanomolar DM.Conclusions:Our findings suggested that RyRs were sensitive molecular targets of DM with functional consequences likely relevant for mediating abnormal neuronal network connectivity in vitro. https://doi.org/10.1289/EHP4583

BmK NSPK, a Potent Potassium Channel Inhibitor from Scorpion Buthus martensii Karsch, Promotes Neurite Outgrowth via NGF/TrkA Signaling Pathway

“…In the current study, we demonstrated that BmK NSPK, a short-chain scorpion peptide, enhanced neurite outgrowth in a nonmonotonic manner. This nonmonotonic stimulation on the neurite outgrowth is consistent with activity-dependent neurite outgrowth by activation of VGSCs [ 52 ], activation of ryanodine receptors [ 32 ], or suppression of K v 1 channels [ 18 ]. We previously have reported a long-chain α-scorpion toxin (BmK NSP) that directly activated VGSCs by delaying inactivation of VGSCs [ 7 ].…”

“…Primary cultured SCNs display synchronized spontaneous calcium oscillations (SCOs) [ 7 ] that are balanced by excitatory and inhibitory neuronal inputs [ 28 , 29 ]. Alteration of the pattern of SCOs has been used to discover the neuroprotective compound for seizure [ 30 ] and pain [ 31 ], and also to discover neurotoxicants and explore their mechanisms [ 18 , 32 , 33 ]. We therefore explored the influence of BmK NSPK on SCOs in primary cultured SCNs.…”

“…SCO profile in spinal cord neuronal cultures is dependent on the action potential generation and is orchestrated by both neuronal excitatory and inhibitory inputs [ 46 ]. The release of Ca 2+ from intracellular Ca 2+ store through inositol 1, 4, 5-triphosphate (IP 3 ) receptors, and ryanodine receptors was also involved in the occurrence of SCOs [ 18 , 32 , 47 ]. In the current study, we demonstrated that BmK NSPK increased the SCO frequency and amplitude and depolarized membrane with low apparent nanomolar affinity in SCN cultures, consistent with its high affinity on the outward potassium channels.…”

“…The intracellular Ca 2+ concentration [Ca 2+ ] i of SCNs was measured using FLIPR Tetra® system (Molecular Devices, Sunnyvale, CA, USA) as described previously [ 32 ].…”

The effect and mechanism of cypermethrin-induced hippocampal neurotoxicity as determined by network pharmacology analysis and experimental validation

“…In agriculture, pesticides can improve crop yield and quality by killing or controlling insects, weeds, and detrimental microorganisms [ 1 ]. Pyrethroids are a large family of synthetic insecticides with chemical structures similar to that of the natural pesticide pyrethrum, which is produced by the chrysanthemum flower [ 2 ]. Cypermethrin (CMN, [cyano-(3-phenoxyphenyl)methyl] 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane-1-carboxylate, PubChem CID: 2912) is a type II synthetic pyrethroid that is extensively used in residential, industrial, and agriculture applications [ 3 ].…”