Changes in ocular aquaporin expression following optic nerve crush

[摘要] Purpose: Changes in the expression ofwater channels (aquaporins; AQP) have been reported in severaldiseases. However, such changes and mechanisms remain to be evaluatedfor retinal injury after optic nerve crush (ONC). This study wasdesigned to analyze changes in the expression of AQP4 (water selectivechannel) and AQP9 (water and lactate channel) following ONC in the rat.Methods: Rat retinal ganglion cells(RGCs) were retrogradely labeled by applying FluoroGold onto the leftsuperior colliculus 1 week before ONC. Retinal injuries were induced byONC unilaterally. Real-time PCR was used to measure changes in AQP4,AQP9, thy-1, Kir4.1 (K+ channel), andβ-actin messages. Changes in AQP4, AQP9, Kir4.1, B cell lymphoma-x(bcl-xl), and glial fibrillary acidic protein (GFAP) expression weremeasured in total retinal extracts using western blotting. Results: The number of RGCs labeledretrogradely from the superior colliculus was 2,090±85 cells/mm2in rats without any treatment, which decreased to 1,091±78 (47% loss)and 497±87 cells/mm2 (76% loss) on days 7 and 14,respectively. AQP4, Kir4.1, and thy-1 protein levels decreased at days2, 7, and 14, which paralleled a similar reduction in mRNA levels, withthe exception of Kir4.1 mRNA at day 2 showing an apparentupregulation. In contrast, AQP9 mRNA and protein levels showedopposite changes to those observed for the latter targets. Whereas AQP9mRNA increased at days 2 and 14, protein levels decreased at both timepoints. AQP9 mRNA decreased at day 7, while protein levelsincreased. GFAP (a marker of astrogliosis) remained upregulatedat days 2, 7, and 14, while bcl-xl (anti-apoptotic) decreased. Conclusions: The reduced expression of AQP4and Kir4.1 suggests dysfunctional ion coupling in retinafollowing ONC and likely impaired retinal function. The sustainedincrease in GFAP indicates astrogliosis, while the decreased bcl-xlprotein level suggests a commitment to cellular death, as clearly shownby the reduction in the RGC population and decreased thy-1expression. Changes in AQP9 expression suggest a contributionof the channel to retinal ganglion cell death and response of distinctamacrine cells known to express AQP9 following traumaticinjuries.

[学科分类] 生物化学/生物物理