Sappington Rebecca M, Sidorova Tatiana, Long Daniel J, Calkins David J
Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, Tennessee 37232-0654, USA.
Invest Ophthalmol Vis Sci. 2009 Feb;50(2):717-28. doi: 10.1167/iovs.08-2321. Epub 2008 Oct 24.
Elevated hydrostatic pressure induces retinal ganglion cell (RGC) apoptosis in culture. The authors investigated whether the transient receptor potential vanilloid 1 (TRPV1) channel, which contributes to pressure sensing and Ca(2+)-dependent cell death in other systems, also contributes to pressure-induced RGC death and whether this contribution involves Ca(2+).
trpv1 mRNA expression in RGCs was probed with the use of PCR and TRPV1 protein localization through immunocytochemistry. Subunit-specific antagonism (iodo-resiniferatoxin) and agonism (capsaicin) were used to probe how TRPV1 activation affects the survival of isolated RGCs at ambient and elevated hydrostatic pressure (+70 mm Hg). Finally, for RGCs under pressure, the authors tested whether EGTA chelation of Ca(2+) improves survival and whether, with the Ca(2+) dye Fluo-4 AM, TRPV1 contributes to increased intracellular Ca(2+).
RGCs express trpv1 mRNA, with robust TRPV1 protein localization to the cell body and axon. For isolated RGCs under pressure, TRPV1 antagonism increased cell density and reduced apoptosis to ambient levels (P <or= 0.05), whereas for RGCs at ambient pressure, TRPV1 agonism reduced density and increased apoptosis to levels for elevated pressure (P <or= 0.01). Chelation of extracellular Ca(2+) reduced RGC apoptosis at elevated pressure by nearly twofold (P <or= 0.01). Exposure to elevated hydrostatic pressure induced a fourfold increase in RGC intracellular Ca(2+) that was reduced by half with TRPV1 antagonism. Finally, in the DBA/2 mouse model of glaucoma, levels of TRPV1 in RGCs increased with elevated IOP.
RGC apoptosis induced by elevated hydrostatic pressure arises substantially through TRPV1, likely through the influx of extracellular Ca(2+).
升高的流体静压在培养中可诱导视网膜神经节细胞（RGC）凋亡。作者研究了在其他系统中参与压力感知和钙（Ca2+）依赖性细胞死亡的瞬时受体电位香草酸受体1（TRPV1）通道是否也参与压力诱导的RGC死亡，以及这种作用是否涉及Ca2+。
通过PCR检测RGC中trpv1 mRNA的表达，并通过免疫细胞化学检测TRPV1蛋白的定位。使用亚基特异性拮抗剂（碘树脂毒素）和激动剂（辣椒素）来探究TRPV1激活如何影响在环境压力和升高的流体静压（+70 mmHg）下分离的RGC的存活。最后，对于处于压力下的RGC，作者测试了EGTA螯合Ca2+是否能提高存活率，以及使用Ca2+染料Fluo-4 AM时，TRPV1是否会导致细胞内Ca2+增加。
RGC表达trpv1 mRNA，TRPV1蛋白大量定位于细胞体和轴突。对于处于压力下的分离RGC，TRPV1拮抗剂增加了细胞密度并将凋亡减少至环境压力水平（P≤0.05），而对于处于环境压力下的RGC，TRPV1激动剂降低了细胞密度并将凋亡增加至升高压力水平（P≤0.01）。细胞外Ca2+的螯合使升高压力下的RGC凋亡减少了近两倍（P≤0.01）。暴露于升高的流体静压会使RGC细胞内Ca2+增加四倍，而TRPV1拮抗剂可使其减少一半。最后，在青光眼的DBA/2小鼠模型中，RGC中TRPV1的水平随眼压升高而增加。
升高的流体静压诱导的RGC凋亡主要通过TRPV1发生，可能是通过细胞外Ca2+的内流。
