Reactive oxygen species are involved in BMP-induced dendritic growth in cultured rat sympathetic neurons

Abstract

Previous studies have shown that bone morphogenetic proteins (BMPs) promote dendritic growth in sympathetic neurons; however, the downstream signaling molecules that mediate the dendrite promoting activity of BMPs are not well characterized. Here we test the hypothesis that reactive oxygen species (ROS)-mediated signaling links BMP receptor activation to dendritic growth. In cultured rat sympathetic neurons, exposure to any of three mechanistically distinct antioxidants, diphenylene iodinium (DPI), nordihydroguiaretic acid (NGA) or desferroxamine (DFO), blocked de novo BMP-induced dendritic growth. Addition of DPI to cultures previously induced with BMP to extend dendrites caused dendritic retraction while DFO and NGA prevented further growth of dendrites. The inhibition of the dendrite promoting activity of BMPs by antioxidants was concentration-dependent and occurred without altering axonal growth or neuronal cell survival. Antioxidant treatment did not block BMP activation of SMAD 1,5 as determined by nuclear localization of these SMADs. While BMP treatment did not cause a detectable increase in intracellular ROS in cultured sympathetic neurons as assessed using fluorescent indicator dyes, BMP treatment increased the oxygen consumption rate in cultured sympathetic neurons as determined using the Seahorse XF24 Analyzer, suggesting increased mitochondrial activity. In addition, BMPs upregulated expression of NADPH oxidase 2 (NOX2) and either pharmacological inhibition or siRNA knockdown of NOX2 significantly decreased BMP-7 induced dendritic growth. Collectively, these data support the hypothesis that ROS are involved in the downstream signaling events that mediate BMP7-induced dendritic growth in sympathetic neurons, and suggest that ROS-mediated signaling positively modulates dendritic complexity in peripheral neurons.

Dissecting the role of redox signaling in neuronal development

“…Reduced neurite outgrowth is also been observed in cerebellar granule neurons derived form NOX2 À/À mice (Olguin-Albuerne and Moran 2015). Likewise, either pharmacological inhibition or siRNA-mediated knock down of NOX2 decreased bone morphogenetic protein-7-induced dendritic growth in cultured rat sympathetic neurons (Chandrasekaran et al 2015). Neuronal cell lines differentiation is also dependent on the role of ROS.…”

“…Likewise, either pharmacological inhibition or siRNA‐mediated knock down of NOX2 decreased bone morphogenetic protein‐7‐induced dendritic growth in cultured rat sympathetic neurons (Chandrasekaran et al . ). Neuronal cell lines differentiation is also dependent on the role of ROS.…”

Physiological role of reactive oxygen species as promoters of natural defenses

“…More recently, Chandrasekaran et al (142) hypothesized that ROS‐mediated signaling is linked to bone morphogenetic protein (BMP) receptor activation to dendritic growth. In cultures of rat sympathetic neurons that were exposed to different antioxidants, BMP‐induced dendritic growth was blocked in a concentration‐dependent manner without altering axonal growth or neuronal cell survival (142). In addition, BMPs up‐regulated the expression of NOX2 in different cell types, and small interfering RNA knockdown of NOX2, but not NOX4, significantly decreased BMP7‐induced dendritic growth.…”

Regulation of Dendritogenesis in Sympathetic Neurons

“…While the deleterious effects of ROS at high concentrations are well documented, over the past decade, there is growing appreciation of the beneficial role of ROS at physiological concentrations [80][81][82][83][84], and of the importance of the NOX family of enzymes in regulating many aspects of neuronal development including neurogenesis, neurite outgrowth and synaptic plasticity [80,83,85]. NOX2 is expressed in neonatal rat SCG neuronal cell cultures [86], and exposure of cultured embryonic SCG neurons to BMP-7 increases the expression of NOX2 [87]. Pharmacologic inhibition or siRNA knockdown of NOX2 significantly decreases BMP-7-induced dendritic growth in primary sympathetic neurons, an effect that is also observed in cultures co-exposed to BMP-7 and any of three mechanistically and structurally distinct antioxidants that block ROS generation [87].…”

“…NOX2 is expressed in neonatal rat SCG neuronal cell cultures [86], and exposure of cultured embryonic SCG neurons to BMP-7 increases the expression of NOX2 [87]. Pharmacologic inhibition or siRNA knockdown of NOX2 significantly decreases BMP-7-induced dendritic growth in primary sympathetic neurons, an effect that is also observed in cultures co-exposed to BMP-7 and any of three mechanistically and structurally distinct antioxidants that block ROS generation [87]. Antioxidants block BMP-induced dendritic growth downstream of Smad signaling since BMP-induced nuclear translocation of Smads is unaffected by antioxidant treatment [87].…”