Laspas Panagiotis, Goloborodko Evgeny, Sniatecki Jan J, Kordasz Marcin L, Manicam Caroline, Wojnowski Leszek, Li Huige, Patzak Andreas, Pfeiffer Norbert, Gericke Adrian
Department of Ophthalmology, University Medical Center, Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131 Mainz, Germany.
Department of Pharmacology, University Medical Center, Johannes Gutenberg University Mainz, Obere Zahlbacher Str. 67, 55131, Mainz, Germany.
Exp Eye Res. 2014 Oct;127:1-8. doi: 10.1016/j.exer.2014.06.018. Epub 2014 Jul 10.
Nitric oxide synthases (NOS) are involved in regulation of ocular vascular tone and blood flow. While endothelial NOS (eNOS) has recently been shown to mediate endothelium-dependent vasodilation in mouse retinal arterioles, the contribution of individual NOS isoforms to vascular responses is unknown in the retrobulbar vasculature. Moreover, it is unknown whether the lack of a single NOS isoform affects neuron survival in the retina. Thus, the goal of the present study was to examine the hypothesis that the lack of individual nitric oxide synthase (NOS) isoforms affects the reactivity of mouse ophthalmic arteries and neuron density in the retinal ganglion cell (RGC) layer. Mice deficient in one of the three NOS isoforms (nNOS-/-, iNOS-/- and eNOS-/-) were compared to respective wild type controls. Intraocular pressure (IOP) was measured in conscious mice using rebound tonometry. To examine the role of each NOS isoform for mediating vascular responses, ophthalmic arteries were studied in vitro using video microscopy. Neuron density in the RGC layer was calculated from retinal wholemounts stained with cresyl blue. IOP was similar in all NOS-deficient genotypes and respective wild type controls. In ophthalmic arteries, phenylephrine, nitroprusside and acetylcholine evoked concentration-dependent responses that did not differ between individual NOS-deficient genotypes and their respective controls. In all genotypes except eNOS-/- mice, vasodilation to acetylcholine was markedly reduced after incubation with L-NAME, a non-isoform-selective inhibitor of NOS. In contrast, pharmacological inhibition of nNOS and iNOS had no effect on acetylcholine-induced vasodilation in any of the mouse genotypes. Neuron density in the RGC layer was similar in all NOS-deficient genotypes and respective controls. Our findings suggest that eNOS contributes to endothelium-dependent dilation of murine ophthalmic arteries. However, the chronic lack of eNOS is functionally compensated by NOS-independent vasodilator mechanisms. The lack of a single NOS isoform does not appear to affect IOP or neuron density in the RGC layer.
一氧化氮合酶（NOS）参与眼血管张力和血流的调节。虽然最近已证明内皮型一氧化氮合酶（eNOS）介导小鼠视网膜小动脉的内皮依赖性血管舒张，但在球后血管系统中，单个NOS同工型对血管反应的贡献尚不清楚。此外，单一NOS同工型的缺失是否会影响视网膜中的神经元存活也不清楚。因此，本研究的目的是检验以下假设：单个一氧化氮合酶（NOS）同工型的缺失会影响小鼠眼动脉的反应性以及视网膜神经节细胞（RGC）层中的神经元密度。将三种NOS同工型之一缺陷的小鼠（nNOS-/-、iNOS-/-和eNOS-/-）与各自的野生型对照进行比较。使用回弹眼压计在清醒小鼠中测量眼压。为了研究每种NOS同工型在介导血管反应中的作用，使用视频显微镜在体外研究眼动脉。从用甲酚蓝染色的视网膜整装片中计算RGC层中的神经元密度。所有NOS缺陷基因型和各自的野生型对照中的眼压相似。在眼动脉中，去氧肾上腺素、硝普钠和乙酰胆碱引起浓度依赖性反应，单个NOS缺陷基因型与其各自对照之间没有差异。在除eNOS-/-小鼠外的所有基因型中，与NOS的非同工型选择性抑制剂L-NAME孵育后，对乙酰胆碱的血管舒张作用明显降低。相反，药理学抑制nNOS和iNOS对任何小鼠基因型中乙酰胆碱诱导的血管舒张均无影响。所有NOS缺陷基因型和各自对照中RGC层中的神经元密度相似。我们的研究结果表明，eNOS有助于小鼠眼动脉的内皮依赖性舒张。然而，eNOS的长期缺失在功能上由非NOS依赖性血管舒张机制补偿。单一NOS同工型的缺失似乎不影响眼压或RGC层中的神经元密度。
