As industrialization accelerates, there is an increasing need to find a quick, easy, and affordable method to assess the potential DNA damage caused by newly developed chemicals. Electrochemical voltammetry using intracellular purine bases as markers shows promise for detecting DNA damage. However, it is unclear whether drugs with different DNA damage mechanisms will impact purine metabolism in cells and consequently disturb the electrochemical indicators of DNA damage. In this paper, the electrochemical behaviors of HepG2 cells exposed to the direct DNA-damaging agent (MNNG), the indirect DNA-damaging agent (CPT11), and the non-DNA-damaging agent (KCl) were studied. The findings showed that the electrochemical signals of cells increased with the rising concentration of DNA-damaging drugs. A time-dependent effect was observed, with a lower threshold dose for 4 h compared to 1 h. However, the non-DNA-damaging agent did not induce an increase in the cellular electrochemical signal. Despite the higher cytotoxicity of CPT11, MNNG triggered DNA damage at a lower dose, as detected by electrochemical indicators. The results of the electrochemical indicators assessment of DNA damage correlated significantly with those of the γH2AX focus and alkaline comet assays, with r > 0.98 and P < 0.01. Particularly, there was a stronger correlation with the alkaline comet assay. Furthermore, electrochemical voltammetry detected DNA damage at a lower threshold compared to other assessment methods, demonstrating a higher sensitivity to DNA damage. These findings suggest that by using purine bases as markers, electrochemical voltammetry enables precise assessment of DNA damage caused by various mechanisms.
Irinotecan (CPT11), a broad-spectrum cytotoxic anticancer agent, induces a series of toxic side-effects. The most conspicuous side-effect is gastrointestinal mucositis, including nausea, vomiting, and diarrhea. A growing body of evidence indicates that bacteria β-glucuronidase (GUS), an enzyme expressed by intestinal microbiota, converts the inactive CPT11 metabolite SN38G to the active metabolite SN38 to ultimately induce intestinal mucositis. We sought to explore the potential efficacy and underlying mechanisms of berberine on CPT11-induced mucositis. Our study showed that berberine (50 mg/kg; i. g.) mitigated the CPT11-induced loss of mucosal architecture, ulceration, and neutrophil infiltration. Meanwhile, berberine improved mucosal barrier function by increasing the number of globlet cells, protecting trans-endothelial electrical resistance (TEER), reducing permeability and increasing tight junction proteins expression. LC-MS analysis showed that berberine decreased the content of SN38 in feces, which correlated with decreases in both GUS activity and GUS-producing bacteria. Further molecular docking and Lineweaver-Burk plots analyses suggested that berberine functions as a potential non-competitive inhibitor against GUS enzyme. Of note, berberine maintained the anti-tumor efficacy of CPT11 in a tumor xenograft model while abrogating the intestinal toxicity of CPT11. Overall, we identified for the first time the remission effects of berberine on intestinal mucositis induced by CPT11 without impairing the anti-colorectal cancer efficacy of CPT11 partially via inhibiting bacterial GUS enzyme.
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