Purpose: Interleukin-6 (IL-6) is an inflammatory cytokine implicated in various retinal pathologies and functions primarily through two signaling pathways: cis-signaling via IL-6 binding to its membrane-bound receptor (IL-6Rα), and trans-signaling via IL-6 binding to soluble IL-6 receptor (sIL-6R). Because the differential effects of IL-6 signaling in retinal Müller glial cells (MGCs) remain unclear, we generated an MGC-specific Il6ra-/- knockout (KO) mouse to eliminate IL-6Rα and, consequently, IL-6 cis-signaling in MGCs. In this study, we examined the proteomic changes in MGCs isolated from KO mice lacking a functional IL-6Rα.
Methods: The proteomes of MGCs isolated from wild-type (WT) and KO mice were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and validated by parallel reaction monitoring (PRM). Relevant biological functions and pathways were examined using Gene Ontology and Ingenuity Pathway Analysis.
Results: LC-MS/MS detected 1866 proteins, of which 81 were significantly altered (41 upregulated, 40 downregulated). PRM analysis confirmed differential expression of Ptgis (fold change [FC] = 3.63), Dpep1 (FC = 2.79), Fmo1 (FC = 2.77), Igfbp7 (FC = 2.07), Rpb1 (FC = 1.73), Pygp (FC = 1.46), Niban 1 (FC = 0.58), Mest (FC = 0.48), and Aldh3a1 (FC = 0.30). The significantly altered proteins are involved in oxidative stress balance, inflammation, mitochondrial dysfunction, and regulation of vascular endothelial growth factor (VEGF) signaling.
Conclusions: The absence of IL-6Rα in KO MGCs corresponded to significant changes in their proteomic profile, highlighting the impact of autocrine IL-6 signaling on MGC function. This study provides a basis for future research evaluating distinct roles of IL-6 in MGCs and subsequent effects on retinal pathology.