Dreffs Alyssa, Henderson Desmond, Dmitriev Andrey V, Antonetti David A, Linsenmeier Robert A
a Department of Ophthalmology and Visual Sciences , University of Michigan , Ann Arbor , MI , USA.
b Department of Biomedical Engineering , Northwestern University , IL , Evanston , USA.
Curr Eye Res. 2018 Jul;43(7):902-912. doi: 10.1080/02713683.2018.1458882. Epub 2018 Apr 11.
Changes in retinal pH may contribute to a variety of eye diseases. To study the effect of acidosis alone, we induced systemic metabolic acidosis and hypothesized that the retina would respond with altered expression of genes involved in acid/base regulation.
Systemic metabolic acidosis was induced in Long-Evans rats for up to 2 weeks by adding NHCl to the drinking water. After 2 weeks, venous pH was 7.25 ± 0.08 (SD) and [HCO] was 21.4 ± 4.6 mM in acidotic animals; pH was 7.41 ± 0.03 and [HCO] was 30.5 ± 1.0 mM in controls. Retinal mRNAs were quantified by quantitative reverse transcription polymerase chain reaction. Protein was quantified with Western blots and localized by confocal microscopy. Retinal [H] was measured in vivo with pH microelectrodes in animals subjected to metabolic acidosis and in controls.
NHCl in drinking water or given intravenous was effective in acidifying the retina. Cariporide, a blocker of Na/H exchange, further acidified the retina. Metabolic acidosis for 2 weeks led to increases of 40-100% in mRNA for carbonic anhydrase isoforms II (CA-II) and XIV (CA-XIV) and acid-sensing ion channels 1 and 4 (ASIC1 and ASIC4) (all p < 0.005). Expression of anion exchange protein 3 (AEP-3) and Na/H exchanger (NHE)-1 also increased by ≥50% (both p < 0.0001). Changes were similar after 1 week of acidosis. Protein for AEP-3 doubled. NHE-1 co-localized with vascular markers, particularly in the outer plexiform layer. CA-II was located in the neural parenchyma of the ganglion cell layer and diffusely in the rest of the inner retina.
The retina responds to systemic acidosis with increased expression of proton and bicarbonate exchangers, carbonic anhydrase, and ASICs. While responses to acidosis are usually associated with renal regulation, these studies suggest that the retina responds to changes in local pH presumably to control its acid/base environment in response to systemic acidosis.
视网膜pH值的变化可能导致多种眼部疾病。为了单独研究酸中毒的影响，我们诱导了全身性代谢性酸中毒，并假设视网膜会通过改变参与酸碱调节的基因表达来做出反应。
通过在饮用水中添加氯化铵，在Long-Evans大鼠中诱导全身性代谢性酸中毒，持续2周。2周后，酸中毒动物的静脉血pH值为7.25±0.08（标准差），[HCO]为21.4±4.6 mM；对照组的pH值为7.41±0.03，[HCO]为30.5±1.0 mM。通过定量逆转录聚合酶链反应对视网膜mRNA进行定量。用蛋白质印迹法定量蛋白质，并用共聚焦显微镜进行定位。在代谢性酸中毒动物和对照组中，用pH微电极在体内测量视网膜[H]。
饮用水中或静脉注射的氯化铵有效地使视网膜酸化。钠/氢交换阻滞剂卡立泊利进一步使视网膜酸化。2周的代谢性酸中毒导致碳酸酐酶同工酶II（CA-II）和XIV（CA-XIV）以及酸敏感离子通道1和4（ASIC1和ASIC4）的mRNA增加40%-100%（所有p<0.005）。阴离子交换蛋白3（AEP-3）和钠/氢交换体（NHE）-1的表达也增加了≥50%（两者p<0.0001）。酸中毒1周后变化相似。AEP-3的蛋白质增加了一倍。NHE-1与血管标记物共定位，特别是在外丛状层。CA-II位于神经节细胞层的神经实质中，并在内视网膜的其余部分弥散分布。
视网膜对全身性酸中毒的反应是质子和碳酸氢盐交换体、碳酸酐酶和ASICs的表达增加。虽然对酸中毒的反应通常与肾脏调节有关，但这些研究表明，视网膜对局部pH值变化的反应可能是为了在全身性酸中毒时控制其酸碱环境。
