Reprogramming the hepatic immune microenvironment with mirtazapine in early neoplastic transformation: Evidence from a diethylnitrosamine-induced rat model

Hepatic neoplastic transformation is a multistep process driven by chronic inflammation, oxidative stress, immune evasion, and dysregulated cell proliferation. Intercepting these early events may offer a viable strategy for preventing hepatocellular carcinoma. In this study, we investigated the chemopreventive potential of mirtazapine, an FDA-approved antidepressant with known anti-inflammatory and antioxidant properties, in a diethylnitrosamine-induced rat model of early hepatic neoplasia. Mirtazapine significantly attenuated hepatotoxicity, reducing serum transaminases, oxidative stress markers, and restoring antioxidant defenses. Histopathological evaluation revealed that mirtazapine markedly reduced the incidence of foci of altered hepatocytes (FAH), nuclear atypia, and inflammatory infiltration. Our results showed enhanced infiltration and tissue levels of CD4⁺ and CD8⁺ T cells, along with upregulation of Th1/Th17 cytokines (IFN-γ, IL-2, IL-12, IL-17) and the chemokine CXCL10, alongside suppression of immunosuppressive mediators (IL-10, TGF-β, sCD163). Additionally, mirtazapine downregulated pro-inflammatory cytokines IL-6 and TNF-α, promoted macrophage recruitment (CD68), and shifted polarization toward an M1-like phenotype, as evidenced by increased iNOS expression. Mirtazapine also inhibited pro-proliferative and angiogenic markers (Ki67, Cyclin D1, VEGF, MMP-2), reactivated apoptotic pathways (Bax, caspase-3, p53), and suppressed oncogenic STAT3 and ERK1/2 signaling. Correlation and disease prediction analyses identified immune activation markers as strong negative predictors of FAH burden. Importantly, systems biology and network analysis confirmed these findings by demonstrating that mirtazapine modulates key immune-regulatory networks, particularly those governing T cell responses, cytokine signaling, and macrophage polarization, thus mechanistically validating its immunomodulatory and anti-tumor effects. These results highlight mirtazapine's potential for repurposing as a chemopreventive agent in inflammation-driven hepatic neoplasia.