7,8-Dihydroxiflavone Protects Adult Rat Axotomized Retinal Ganglion Cells through MAPK/ERK and PI3K/AKT Activation

• Published in: International journal of molecular sciences Vol. 22; no. 19; p. 10896
• Main Authors: Galindo-Romero, Caridad, Vidal-Villegas, Beatriz, Asís-Martínez, Javier, Lucas-Ruiz, Fernando, Gallego-Ortega, Alejandro, Vidal-Sanz, Manuel
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.10.2021; MDPI
• Subjects: 1-Phosphatidylinositol 3-kinase; 7,8-dihydroxiflavone (DHF); 7,8-dihydroxiflavone/TrkB signaling; adult rats; AKT protein; axotomy; Brain-derived neurotrophic factor; Brn-3 protein; Extracellular signal-regulated kinase; Gene expression; Intracellular signalling; intraorbital optic nerve transection; Kinases; MAP kinase; Mueller cells; Neuroprotection; Optic nerve; Phosphorylation; Photoreceptors; Protein kinase; Proteins; Retina; Retinal ganglion cells; Sodium chloride; TrkB receptors; Vimentin; Western blotting
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms221910896

We analyze the 7,8-dihydroxyflavone (DHF)/TrkB signaling activation of two main intracellular pathways, mitogen-activated protein kinase (MAPK)/ERK and phosphatidylinositol 3 kinase (PI3K)/AKT, in the neuroprotection of axotomized retinal ganglion cells (RGCs). Methods: Adult albino Sprague-Dawley rats received left intraorbital optic nerve transection (IONT) and were divided in two groups. One group received daily intraperitoneal DHF (5 mg/kg) and another vehicle (1%DMSO in 0.9%NaCl) from one day before IONT until processing. Additional intact rats were employed as control (n = 4). At 1, 3 or 7 days (d) after IONT, phosphorylated (p)AKT, p-MAPK, and non-phosphorylated AKT and MAPK expression levels were analyzed in the retina by Western blotting (n = 4/group). Radial sections were also immunodetected for the above-mentioned proteins, and for Brn3a and vimentin to identify RGCs and Müller cells (MCs), respectively (n = 3/group). Results: IONT induced increased levels of p-MAPK and MAPK at 3d in DHF- or vehicle-treated retinas and at 7d in DHF-treated retinas. IONT induced a fast decrease in AKT in retinas treated with DHF or vehicle, with higher levels of phosphorylation in DHF-treated retinas at 7d. In intact retinas and vehicle-treated groups, no p-MAPK or MAPK expression in RGCs was observed. In DHF- treated retinas p-MAPK and MAPK were expressed in the ganglion cell layer and in the RGC nuclei 3 and 7d after IONT. AKT was observed in intact and axotomized RGCs, but the signal intensity of p-AKT was stronger in DHF-treated retinas. Finally, MCs expressed higher quantities of both MAPK and AKT at 3d in both DHF- and vehicle-treated retinas, and at 7d the phosphorylation of p-MAPK was higher in DHF-treated groups. Conclusions: Phosphorylation and increased levels of AKT and MAPK through MCs and RGCs in retinas after DHF-treatment may be responsible for the increased and long-lasting RGC protection afforded by DHF after IONT.