Toll-like receptor 4 inhibitor protects against retinal ganglion cell damage induced by optic nerve crush in mice

Abstract

Toll-like receptor 4 (TLR4) plays key roles in innate immune responses and inflammatory reactions. TAK-242 (resatorvid) is a small-molecule cyclohexene derivative that selectively inhibits TLR4 signaling pathways and suppresses inflammatory reactions. Here we investigated the protective effects of TAK-242 against optic nerve crush (ONC) which induces axonal injury like glaucoma in mice. TAK-242 was injected intravitreally immediately after ONC. The effect of TAK-242 was evaluated by measuring the number of fluorogold-labeled retinal ganglion cells (RGCs) at 10 days after ONC. Furthermore, the expression levels of phosphorylated-nuclear factor-kappa B (p-NF-κB) and phosphorylated-p38 (p-p38) were measured by Western blotting. In addition, we examined activated astrocytes by immunostaining. TAK-242 significantly abrogated the loss of RGCs associated with ONC. Moreover, the expression levels of p-NF-κB and p-p38 were significantly reduced by TAK-242 treatment. Furthermore, TAK-242 and C34, a TLR4 inhibitor, significantly reduced astrocyte activation in the ganglion cell and inner plexiform layers, compared with vehicle treatment. These findings indicate that TAK-242 inhibits not only the TLR4 signaling pathway but also astrocyte activation downstream of this pathway, suggesting that the inhibition of TLR4 signaling is a promising candidate for the treatment of glaucoma.

AIBP protects retinal ganglion cells against neuroinflammation and mitochondrial dysfunction in glaucomatous neurodegeneration

“…AIBP plays a unique role of targeting cholesterol efflux machinery to TLR4-occupied inflammarafts [ 10 , 11 ]. Evidence from clinical and animal studies indicates that TLR4-dependent signaling is an important factor in the pathogenesis of POAG and that this signaling is associated with activated glial cells and contributes to inflammatory responses in experimental glaucoma [ [43] , [44] , [45] ]. First, we determined the expression level and distribution of TLR4 and IL-1β proteins in glaucomatous retinas from human patients with POAG and DBA/2J mice.…”

“…Epidemiological studies indicate that human POAG is linked to single-nucleotide polymorphisms of TLR4 [ 43 , 45 ] and recent evidence from animal studies further suggests that TLR4-dependent signaling is an important factor in the pathogenesis of POAG [ 14 , 44 ]. In the current study, we found that glaucomatous retina significantly increased Tlr4 gene expression.…”

VGF nerve growth factor inducible is involved in retinal ganglion cells death induced by optic nerve crush

“…The ONC was performed as described in detail 68 , 69 . Briefly, mice were anesthetized with a mixture of 120 mg/kg ketamine (Daiichi-Sankyo, Tokyo, Japan) and 6 mg/kg xylazine (Bayer Health Care, Tokyo, Japan) for the surgery.…”

“…To determine the number of RGCs surviving after the ONC, the RGCs were retrogradely labeled with fluorogold three days before the ONC as described in detail 68 . Briefly, 1 µL of 4% fluorogold (Biotium, Hayward, CA, USA) was injected at a depth of 2 mm from the brain surface into the superior colliculus under anesthesia.…”

“…Retinal samples were prepared as described in detail 68 , and western blot analysis was performed according to a reported protocol 67 . Goat anti-VGF polyclonal antibody (1:400 dilution; Santa Cruz Biotechnologies, CA, USA) and mouse anti-β-actin monoclonal antibody (1:1000; Sigma-Aldrich) were used as the primary antibodies for immunoblotting.…”