ENDOGENOUS REACTIVE OXYGEN AND NITROGEN SPECIES IN INFLAMMATORY DISEASES: CHEMICAL SIGNALING OR CYTOTOXICITY

Abstract

This study investigates the paradoxical roles of endogenous reactive oxygen species (ROS) and reactive nitrogen species (RNS) in inflammatory diseases, aiming to delineate their function as either chemical signaling mediators or cytotoxic agents. Employing a problem-based experimental design, we conducted quantitative analyses using THP-1 and HUVEC cell lines subjected to LPS and TNF-α to simulate inflammation, and a DSS-induced murine colitis model to examine systemic effects. Fluorescence assays revealed that inflamed cells exhibited a significant increase in ROS (THP-1: 57.3 a.u.; HUVEC: 64.8 a.u.) and RNS levels (THP-1: 45.5 a.u.; HUVEC: 52.6 a.u.), accompanied by a marked decrease in cell viability. Gene expression analysis demonstrated upregulation of NF-κB, iNOS, and COX-2, affirming redox-mediated inflammatory activation. In vivo, elevated malondialdehyde levels and impaired antioxidant enzyme activities in the colon and brain indicated tissue-level oxidative stress. Serum cytokine assays showed significant increases in IL-6, TNF-α, and IL-1β in the inflamed group, while redox ratio imaging and TUNEL assays confirmed mitochondrial dysfunction and apoptosis, particularly in high-damage tissues. Statistical correlations revealed strong associations between ROS/RNS levels and cytotoxic outcomes (Spearman ρ > 0.88, p < 0.01). These findings demonstrate that ROS and RNS act as a double-edged sword in inflammatory diseases—essential for signaling at physiological levels but deleterious at pathological concentrations. This study provides crucial insight into the redox-dependent mechanisms underlying inflammation and highlights the importance of selectively targeting oxidative pathways to develop effective therapeutic strategies.