Reduction in SH-SY5Y Cell Stress Induced by Corticosterone and Attenuation of the Inflammatory Response in RAW 264.7 Cells Using Endomorphin Analogs

<b>Background:</b> To identify drug candidates that reduce cellular stress, linear peptides known as endomorphin (EM) analogs containing proline surrogates in position 2 were tested in in vitro injury models induced by corticosterone (CORT). <b>Methods:</b> In this study, neuroblastoma (SH-SY5Y) cells were treated with CORT and synthesized peptides, and then the cell viability and morphology, reactive oxygen species production (ROS), mitochondrial membrane potential (ΔΨm), adenosine triphosphate (ATP), and intracellular calcium ion [Ca²⁺]_i levels were evaluated. We also conducted an in-depth analysis of the apoptosis markers using quantitative real-time PCR (qPCR). Finally, we explore the brain-derived neurotrophic factor (BDNF) expression (qPCR) and protein levels (ELI-SA and Western blot). <b>Results:</b> The strongest neuroprotective effect in the CORT-induced stress model was shown by peptide 3 and peptide 7 (in the following sequence Tyr-Inp-Trp-Phe-NH2 and Tyr-Inp-Phe-Phe-NH2, respectively). These peptides significantly improved cell viability and reduced oxidative stress in CORT-treated cells. <b>Conclusions:</b> Their neuroprotective potential appears linked to anti-apoptotic effects, along with in-creased BDNF expression. Moreover, in the lipopolysaccharide (LPS)- and interferon-γ (IFN-γ)-induced damage model in macrophage RAW 264.7 cells, these two peptides reduced the secretion of inflammatory mediators nitric oxide (NO), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6). Peptides exhibiting both neuroprotective and anti-inflammatory properties warrant further investigation as potential therapeutic agents.