Abstract
Purpose :
Interleukin-6 (IL-6) functions through multiple signaling modalities, including “cis-signaling” through a membrane-bound IL-6 receptor and “trans-signaling” through a soluble IL-6 receptor, and disruption of the “cis-trans balance” in diabetic retinopathy (DR) can adversely affect cells that express the IL-6 receptor, such as Müller glial cells (MGCs). The purpose of this study is to determine how the disruption of the IL-6 cis-trans balance alters critical MGC functions, including VEGF production and oxidative homeostasis.
Methods :
For in vitro studies, MGCs were isolated from C57BL/6J mice and activated with IL-6 or IL-6 + sIL-6R. Proteomic profiling was performed using LC-MS/MS and gene expression was measured by RT-PCR. Mitochondrial superoxide generation was measured with MitoSox Red ± VEGF inhibitor sunitinib. For in vivo studies, diabetes was induced in C57BL/6J mice with streptozotocin (STZ), mice were treated with sgp130Fc, and retinal VEGFA and VEGFB expression was evaluated by immunofluorescence staining.
Results :
IL-6 cis- and trans-signaling induce distinct expression profiles in MGCs, including differential regulation of Vegfa and Vegfb. Cis-signaling does not significantly alter mRNA expression of Vegfa and Vegfb, however trans-signaling upregulates Vegfa (2.06-fold) and downregulates Vegfb (0.72-fold). Trans-signaling induced changes are inhibited by pretreatment with sgp130Fc. IL-6 cis-signaling does not alter mitochondrial superoxide generation in MGCs, but IL-6 trans-signaling significantly increases mitochondrial superoxide (1.75-fold). Pretreatment of MGCs with the VEGF-inhibitor sunitinib abrogates this trans-signaling induced superoxide generation, suggesting this response is VEGF-dependent. In diabetic mice, inhibition of IL-6 trans-signaling with sgp130Fc decreases diabetes-induced VEGFA expression in the inner nuclear layer and restores VEGFB expression to near-control levels.
Conclusions :
Our data shows that IL-6 cis- and trans-signaling differentially modulate VEGFA and VEGFB expression in MGCs, and shows that trans-signaling induced oxidative stress in MGCs is VEGF-dependent. Furthermore, selective inhibition of IL-6 trans-signaling with sgp130Fc restored normal expression of VEGFA and VEGFB within the inner nuclear layer (INL) of the diabetic retina, suggesting potential for use in the treatment of DR.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.