To obtain an unbiased, thorough understanding of the biological pathways implicated in atRAL-induced cytotoxicity and PDE inhibitor-mediated cytoprotection, we performed a mass spectrometry-based quantitative proteomic analysis of ARPE19 cells, using stable-isotope labeling of amino acids in cell culture (SILAC). We identified differentially expressed proteins in ARPE19 cells exposed to stress (60 μM atRAL or 5 mM H2O2) in the absence or presence of PDE inhibitor (10 μM BAY 60-7550, rolipram, or BC11-38), relative to vehicle-treated controls. We also performed combined label-free mass spectrometry-based quantitative proteomic and phosphoproteomic analyses of retinas from the Abca4-/-Rdh8-/- double-knockout (dKO) light-sensitive mouse model of photoreceptor degeneration. First, we identified differentially expressed proteins in retinas exposed to bright-light stress (10,000 lux for 30 min) relative to unstressed controls. Next, we identified differentially expressed proteins in PDE inhibitor-treated mice (2 mg/kg intraperitoneal BAY 60-7550, rolipram, or BC11-38) exposed to stress relative to DMSO vehicle-treated controls. Altogether, these analyses provided insights into the proteomic and phosphoproteomic changes induced by stress and modulated by PDE-inhibitor therapy.