The ATP-P2X7 Signaling Pathway Participates in the Regulation of Slit1 Expression in Satellite Glial Cells

Abstract

Slit1 is one of the known signaling factors of the slit family and can promote neurite growth by binding to its receptor, Robo2. Upregulation of Slit1 expression in dorsal root ganglia (DRG) after peripheral nerve injury plays an important role in nerve regeneration. Each sensory neuronal soma in the DRG is encapsulated by several surrounding satellite glial cells (SGCs) to form a neural structural unit. However, the temporal and spatial patterns of Slit1 upregulation in SGCs in DRG and its molecular mechanisms are not well understood. This study examined the spatial and temporal patterns of Slit1 expression in DRG after sciatic nerve crush by immunohistochemistry and western blotting. The effect of neuronal damage signaling on the expression of Slit1 in SGCs was studied in vivo by fluorescent gold retrograde tracing and double immunofluorescence staining. The relationship between the expression of Slit1 in SGCs and neuronal somas was also observed by culturing DRG cells and double immunofluorescence labeling. The molecular mechanism of Slit1 was further explored by immunohistochemistry and western blotting after intraperitoneal injection of Bright Blue G (BBG, P2X7R inhibitor). The results showed that after peripheral nerve injury, the expression of Slit1 in the neurons and SGCs of DRG increased. The expression of Slit1 was presented with a time lag in SGCs than in neurons. The expression of Slit1 in SGCs was induced by contact with surrounding neuronal somas. Through injured cell localization, it was found that the expression of Slit1 was stronger in SGCs surrounding injured neurons than in SGCs surrounding non-injured neurons. The expression of vesicular nucleotide transporter (VNUT) in DRG neurons was increased by injury signaling. After the inhibition of P2X7R, the expression of Slit1 in SGCs was downregulated, and the expression of VNUT in DRG neurons was upregulated. These results indicate that the ATP-P2X7R pathway is involved in signal transduction from peripheral nerve injury to SGCs, leading to the upregulation of Slit1 expression.

Astrocytic and Oligodendrocytic P2X7 Receptors Determine Neuronal Functions in the CNS

“…It has repeatedly been suggested that neuronal P2X7Rs may be absent or down-regulated at resting conditions but become expressed on stressful conditions such as temporal lobe epilepsy (Engel et al, 2012 ; Jimenez-Pacheco et al, 2016 ), ischemic damage to the brain (Franke et al, 2004 ), neuropathic pain (Andó and Sperlagh, 2013 ; Zhang et al, 2019 ), and neurodegenerative diseases (AD; Diaz-Hernandez et al, 2012 ; Rodrigues et al, 2015 ; Huntington’s disease and PD, Diaz-Hernandez et al, 2009 ; Glaser et al, 2020 ; MS, Sharp et al, 2008 ; Grygorowicz et al, 2010 ). Without any doubt these injurious conditions activate microglial cells as well as astrocytes/oligodendrocytes and facilitate the release of neurodamaging signaling molecules (cytokines, chemokines, reactive oxygen and nitrogen species, glutamate/ATP), possibly facilitating neuronal functions.…”

Unraveling Axon Guidance during Axotomy and Regeneration

“…In the case of the Slit family, it has been observed that Slit2 is upregulated after rat sciatic nerve transection, but not after crush, localizing in Schwann cells [ 196 ]. Slit1 is upregulated after sciatic nerve transection [ 197 ] and crush [ 198 ], while no changes are detected after dorsal rhizotomy [ 197 ]. In DRG cells, a biphasic expression is reported for Slit1, 2, and 3 after adult mouse sciatic nerve transection, with an initial downregulation, followed by a subsequent upregulation [ 165 ].…”

Oxidative Stress Caused by Ozone Exposure Induces Changes in P2X7 Receptors, Neuroinflammation, and Neurodegeneration in the Rat Hippocampus

“…In the presence of trauma, ischemia, hypoxia, and inflammation, damaged cells release ATP in large quantities, increasing the extracellular concentrations of this molecule [ 8 ]. This leads to an alteration in energy metabolism and inflammatory processes, since neurons, astrocytes, microglia, and endothelial cells have ATP receptors on their membranes, which mediate the processes of neuronal inflammation and death [ 9 – 18 ]. In an oxidoreduction equilibrium, ATP plays a double role, depending on its cellular location.…”