Temporal dynamics of inflammatory mediators and cytokines in CEES-induced lung and liver injury: Transition from acute inflammation to chronic immune dysregulation

Sulfur mustard (SM), a potent alkylating agent, induces acute and chronic inflammatory and oxidative injuries in multiple organs. However, the temporal progression of these pathological processes remains poorly understood. This study investigated the time-dependent alterations of inflammatory mediators and cytokines in a mouse model exposed to the sulfur mustard analog, 2-chloroethyl ethyl sulfide (CEES). Male BALB/c mice (n = 10 per time point; total ≈ 100) received a single intraperitoneal injection of CEES (10 mg/kg) or vehicle. At scheduled intervals (12h-6 months), animals were euthanized, and lung, liver, and spleen tissues were collected for analysis. Levels of matrix metalloproteinase-9 (MMP-9), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) were quantified in lung and liver tissues, while tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-4 (IL-4), and interleukin-10 (IL-10) levels were measured in splenocyte cultures using ELISA. CEES exposure triggered distinct time-dependent alterations in inflammatory mediators and cytokines. In lung tissues, MMP-9, COX-2, and iNOS showed early upregulation and late reactivation, whereas hepatic changes appeared mainly in the long-term phase. Cytokine profiling revealed a biphasic response characterized by sustained TNF-α elevation, transient IL-10 recovery, long-term IL-4 suppression, and dual-phase modulation of IFN-γ (initial suppression, medium-term elevation, and late decline). These dynamic patterns reflect a transition from acute inflammation to chronic immune dysregulation and fibrotic remodeling. Overall, these findings provide mechanistic insight into the temporal dynamics of CEES-induced inflammation and highlight potential therapeutic windows for targeting oxidative stress and cytokine-mediated pathways to mitigate long-term tissue injury caused by vesicant exposure.