Department of Ophthalmology, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216-8511, Japan.
Department of Molecular Neuroscience, St. Marianna University Graduate School of Medicine, Kawasaki, Japan.
Int Ophthalmol. 2023 Sep;43(9):3067-3074. doi: 10.1007/s10792-023-02706-1. Epub 2023 Apr 16.
A relationship between p38 and autophagy remains debated. The aim of the current study is to investigate whether an inhibitor of p38 prevents axon loss induced by TNF and whether it affects autophagy.
Rats were given intravitreal injection of TNF, TNF plus SB203580, a p38 inhibitor, or SB203580 alone. Immunoblot analysis was performed to examine p62 expression which is a marker of autophagic flux and LC3-II expression which is an autophagy marker in optic nerves 1 week after intravitreal injection. Morphometric analysis of axons was performed to evaluate the effects of SB203580 against TNF-induced optic nerve damage 2 weeks after intravitreal injection. Immunohistochemical analysis was performed to evaluate the expressions of LC3, neurofilament, phosphorylated p38 and p62 in the optic nerve.
Quantification of axon number showed that TNF-induced axon loss was significantly protected by SB203580. Immunoblot analysis showed that the increase of p62 induced by TNF was totally eliminated by SB203580, and the SB203580 alone injection decreased the expression of p62. The level of LC3-II was significantly upregulated in the TNF plus SB203580 group compared with the TNF alone group, and the SB203580 alone injection increased the expression of LC3-II. Immunohistochemical analysis showed that LC3 immunoreactivity was found in the neurofilament positive fibers and that these immunoreactivities were enhanced by SB203580. Some colocalizations of p-p38 and p62 were observed in the TNF-treated optic nerve.
These results suggest that inhibition of p38 exerts axonal protection with upregulated autophagy in TNF-induced optic nerve damage.
p38 与自噬之间的关系仍存在争议。本研究旨在探讨 p38 抑制剂是否能预防 TNF 诱导的轴突丢失，以及是否影响自噬。
向大鼠眼内注射 TNF、TNF 加 p38 抑制剂 SB203580 或 SB203580 单独注射。眼内注射后 1 周，通过免疫印迹分析检查视神经中 p62 表达（自噬流的标志物）和 LC3-II 表达（自噬标志物）。眼内注射后 2 周，通过形态计量分析评估 SB203580 对 TNF 诱导的视神经损伤的作用。免疫组织化学分析评估 LC3、神经丝、磷酸化 p38 和 p62 在视神经中的表达。
轴突数量的定量分析表明，SB203580 显著保护 TNF 诱导的轴突丢失。免疫印迹分析表明，TNF 诱导的 p62 增加被 SB203580 完全消除，而 SB203580 单独注射降低了 p62 的表达。与 TNF 单独注射组相比，TNF 加 SB203580 组的 LC3-II 水平显著上调，而 SB203580 单独注射增加了 LC3-II 的表达。免疫组织化学分析表明，LC3 免疫反应性存在于神经丝阳性纤维中，并且 SB203580 增强了这种免疫反应性。在 TNF 处理的视神经中观察到一些 p-p38 和 p62 的共定位。
这些结果表明，抑制 p38 在 TNF 诱导的视神经损伤中通过上调自噬发挥轴突保护作用。
