Impact of Dietary Xenobiotics on the Intestinal Activity of Sodin 5: Implications for RIP-Based Nanotherapeutics

Introduction: Ribosome-inactivating proteins (RIPs) are potent plant-derived enzymes widely investigated for experimental cancer therapy, particularly as toxic payloads in targeted nanoconjugates. Among RIPs, sodin 5, from the edible plant Salsola soda, has recently demonstrated significant cytotoxicity in colon cancer models. However, the impact of dietary xenobiotics, commonly present in the intestinal environment, on RIP activity remains poorly understood. This study aimed to evaluate whether selected dietary xenobiotics can modulate sodin 5-induced cytotoxicity in Caco-2 colon adenocarcinoma cells.

Methods: The cytotoxic effects of sodin 5 were assessed in Caco-2 cells through dose- and time-dependent experiments. Cell viability was measured using the MTS assay following treatment with sodin 5 alone or in combination with selected dietary xenobiotics (butylated hydroxyanisole, BHA; capsaicin; piperine; and caffeine). In parallel, the integrity of the epithelial monolayer was evaluated by measuring transepithelial electrical resistance (TEER) in Caco-2 monocultures.

Results: Sodin 5 significantly reduced Caco-2 cell viability starting from 10⁻⁸ M after 24h. At 72h, a pronounced reduction was already evident at 10⁻⁹ M, with an EC₅₀ in the 10⁻⁷ M range. Co-treatment with dietary xenobiotics produced distinct modulatory effects. Capsaicin and piperine enhanced sodin 5 cytotoxicity, indicating a synergistic interaction, which was particularly marked for capsaicin. In contrast, caffeine did not significantly alter sodin 5 activity. Notably, BHA exerted a strong protective effect, reducing sodin 5-induced cytotoxicity from approximately 60% to 15%, supporting a role of oxidative stress in the mechanism of cell death. TEER measurements were consistent with viability data.

Conclusions: Dietary xenobiotics significantly influence sodin 5 cytotoxicity in intestinal cells, either enhancing or attenuating its effects. These findings highlight the importance of considering diet-derived compounds in the development of RIP-based nanotherapeutics and provide new insights into factors affecting their intestinal safety and efficacy.