L-Arginine as an Adjuvant Chemosensitizer: Enhancement of Intestinal Permeability and Cytotoxic Activity of Doxorubicin.

Background/

Objectives

Doxorubicin is an anthracycline chemotherapeutic agent widely used in the treatment of breast cancer. However, its clinical utility is limited by the drug's resistance development, low oral bioavailability, and dose-dependent side effects. The semi-essential amino acid, L-arginine, has gained attention as a potential adjuvant that could improve the drug distribution and cytotoxic effectiveness of chemotherapeutics. This study aimed to explore the multifunctional effect of L-arginine on the intestinal absorption and anti-breast cancer activity of doxorubicin.

Methods

The rabbit in situ intestinal perfusion technique was employed to investigate the membrane transport parameters of doxorubicin both in the absence and presence of L-arginine. Furthermore, the effect of L-arginine on the cytotoxic activity of doxorubicin against breast cancer cells (MCF-7) was assessed using the MTT assay.

Results

Co-perfusion of L-arginine with doxorubicin enhanced the fraction of doxorubicin absorbed, with a recorded 4.3-fold enhancement in the jejuno-ileum and a 1.5-fold enhancement in the colon segment. In MCF-7 cells, co-treatment with L-arginine resulted in a significant potentiation of doxorubicin cytotoxicity. At L-arginine concentrations of 10 μM and 50 μM, the recorded IC50 decreased from 41.3 μM to 8.2 μM and to 22.1 μM, respectively. The superior efficacy of 10 μM L-arginine compared to 50 μM reflected a biphasic concentration-dependent response.

Conclusions

L-arginine modulated two critical aspects of doxorubicin efficacy, intestinal absorption and cytotoxic activity. The biphasic response emphasizes the importance of L-arginine dose optimization. These findings support the potential of L-arginine as a safe adjuvant for developing oral doxorubicin formulations. This approach can reduce the dose-related toxicity of doxorubicin and improve therapeutic outcomes.