文献快讯 | 岩藻黄质对实验性青光眼模型中视网膜神经节细胞的保护作用及对 Parkin 介导的线粒体自噬的调控

在实验性青光眼模型的研究中，ICare Tonolab大小鼠眼压计被证实是监测大鼠眼压（IOP）的高效且可靠的工具。

研究目的

青光眼是一种可导致不可逆失明的常见神经退行性疾病。本研究旨在探究岩藻黄质能否通过调控实验性青光眼模型中 Parkin 介导的线粒体自噬，实现对视网膜神经节细胞（RGCs）的保护作用。

研究方法

通过经角膜缘激光光凝法，在 Sprague-Dawley（SD）大鼠体内构建实验性青光眼模型；采用 Tonolab 大小鼠眼压计(Icare Finland Oy) 监测大鼠眼压（IOP）；利用荧光金（FluoroGold）标记法评估视网膜神经节细胞的存活情况。在眼压升高后第 3 天和第 2 周两个时间点，采集大鼠视网膜与视神经样本，通过免疫组织化学技术及分子检测方法，分析线粒体形态变化及相关基因 / 蛋白的表达水平。

研究结果

研究结果显示，高眼压大鼠体内的线粒体自噬呈现 “短期急性过度激活、长期功能受损” 的特征。玻璃体内注射岩藻黄质可提高视网膜神经节细胞存活率、上调 Bcl-2 蛋白表达，同时降低 Bax 与胶质纤维酸性蛋白（GFAP）水平：在眼压急性升高阶段，岩藻黄质可抑制 Parkin 蛋白表达及线粒体自噬体形成，从而减轻过度线粒体自噬；在眼压长期升高状态下，其可上调线粒体自噬相关蛋白表达、恢复线粒体自噬功能，进而促进受损线粒体的清除。

Figure 1. Effect of fucoxanthin on RGC survival in ocular hypertensive rat retinas. The retinal flat mounts of blank control rats (A, D and G), vehicle-treated ocular hypertensive rats (B, E and H) and fucoxanthin-treated ocular hypertensive rats (C, F and I). Quantitative analysis of RGC survival (J) (n=6; data are expressed as mean±SD; **p<0.01; scale bar=100 µm (A–I)). (K) Proposed mechanism by which fucoxanthin mitigates RGC loss in glaucomatous rats by modulating Parkin-mediated mitophagy (created by biorender.com). LAMP1, lysosomal-associated membrane protein 1; LC3, microtubule-associated protein 1A/1B-light chain 3; NC, normal control; OHT, ocular hypertension; OHT+FX, fucoxanthin-treated ocular hypertension; RGC, retinal ganglion cell.

Figure 2. Impact of fucoxanthin on apoptotic protein expression and Müller glial activation in glaucomatous rats. In untreated ocular hypertensive retinas, GFAP (B) and Bax (D) protein levels were elevated, while Bcl-2 (F) levels were reduced at both 3 days and 2 weeks post-IOP elevation. Fucoxanthin treatment resulted in a decrease in GFAP levels at both time points compared with vehicle-treated groups (B). Bax levels initially increased at 3 days but decreased at 2 weeks following fucoxanthin treatment (D), whereas Bcl-2 expression showed an increase at 14 days (F). At the mRNA level, ocular hypertensive retinas exhibited increased GFAP (C) and Bax (E) mRNA levels, with GFAP elevated at both 3 days and 2 weeks, and Bax increased at 2 weeks. Conversely, Bcl-2 (G) mRNA was decreased at both time points. Fucoxanthin treatment led to a reduction in GFAP mRNA at 3 days and 2 weeks, a decrease in Bax mRNA at 2 weeks and an increase in Bcl-2 mRNA at both 3 days and 2 weeks compared with the vehicle-treated group (n=3; data are expressed as mean±SD; *p<0.05; **p<0.01). BAX, Bcl-2 associated X protein; Bcl-2, B-cell lymphoma-2; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; GFAP, glial fibrillar acidic protein;mRNA, messenger RNA; NC, normal control; OHT, ocular hypertension; OHT+FX, fucoxanthin-treated ocular hypertension.

Figure 3. Effect of fucoxanthin on mitophagy marker expression in glaucomatous rats. In untreated ocular hypertensive retinas, mRNA levels of Parkin (A), optineurin (B) and LAMP1 (D) increased at 3 days but decreased at 2 weeks, while LC3 (C) mRNA levels increased at both 3 days and 2 weeks. Following fucoxanthin treatment, mRNA levels of Parkin (A), optineurin (B), LC3 (C) and LAMP1 (D) decreased at 3 days but increased at 2 weeks compared with the vehicle-treated group (n=3; data are expressed as mean±SD; *p<0.05; **p<0.01). (E) Immunofluorescence analysis of Parkin and GFAP expression in vehicle-treated and fucoxanthin-treated ocular hypertensive retinas. Compared with vehicle-treated ocular hypertensive retinas (a–d), GFAP immunoreactivity decreased, whereas Parkin immunoreactivity increased, particularly in the retinal nerve fibre layer of fucoxanthin-treated ocular hypertensive retinas (e–h). Scale bar=50 µm. GAPDH, glyceraldehyde-3-phosphate dehydrogenase; GCL, ganglion cell layer; GFAP, glial fibrillar acidic protein; INL, inner nuclear layer; IPL, inner plexiform layer; LAMP1, lysosomal-associated membrane protein 1; LC3, microtubule-associated protein 1A/1B-light chain 3; mRNA, messenger RNA; NC, normal control; OHT, ocular hypertension; OHT+FX, fucoxanthin-treated ocular hypertension; ONL, outer nuclear layer; OPL, outer plexiform layer.

Figure 4. Effects of fucoxanthin on mitochondrial morphology and mitophagy. (A) Mitochondrial health was assessed using a scoring system based on the appearance of cristae in ultrastructural analyses. (B) NC group, where green arrows indicate healthy mitochondria. (C) OHT group, characterised by yellow arrows pointing to unhealthy mitochondria. (D) OHT+FX group, with red arrows indicating mitophagosomes. Relative to the control group (B), ocular hypertensive optic nerves (C) demonstrated a significant increase in the number of mitochondria (F), autophagosomes (G) and mitophagosomes (H) at both 3 days and 2 weeks post-treatment. Treatment with fucoxanthin resulted in a higher mitochondrial health score (E) and a greater number of mitochondria (F) at 3 days and 2 weeks compared with the vehicle-treated group. Notably, the number of autophagosomes (G) was reduced at 3 days but increased at 2 weeks in the fucoxanthin-treated group (n=3; data are expressed as mean±SD; *p<0.05; **p<0.01). Scale bar=500 nm (B–D). IOP, intraocular pressure; NC, normal control; OHT, ocular hypertension; OHT+FX, fucoxanthin-treated ocular hypertension.

Figure 5. Impact of fucoxanthin on mitophagy-related proteins in glaucomatous rats. Compared with the control group, the protein levels of Parkin (B) and LAMP1 (E) were significantly elevated at 3 days but decreased at 2 weeks. The protein levels of optineurin (C) and the ratio of LC3-II/LC3-I (D) were increased at both 3 days and 2 weeks in the ocular hypertensive optic nerves. In the fucoxanthin-treated group, the protein expression of Parkin (B), optineurin (C), LAMP1 (E) and the ratio of LC3-II/LC3-I (D) was notably reduced at 3 days and increased at 2 weeks compared with the vehicle-treated group (n=3; data are expressed as mean±SD; *p<0.05; **p<0.01). GAPDH, glyceraldehyde-3-phosphate dehydrogenase; LC3, microtubule-associated protein 1A/1B-light chain 3; LAMP1, lysosomal-associated membrane protein 1; NC, normal control; OHT, ocular hypertension; OHT+FX, fucoxanthin-treated ocular hypertension.

研究结论

岩藻黄质可通过调控 Parkin 介导的线粒体自噬，在实验性青光眼模型中发挥神经保护作用。该研究表明，维持线粒体自噬稳态有望成为青光眼治疗的潜在靶点。

文献来源： https://pubmed.ncbi.nlm.nih.gov/40841125