The Influence of Different Doses of Melatonin on Activin A and Follistatin Gene Expression in Benzene-Induced Pre-Leukemia in Rats

Background: Benzene exposure leads to early leukemogenic changes via oxidative stress and alterations in cytokine signaling in the marrow microenvironment. Melatonin has antioxidant and immunomodulatory action, but the regulatory effects of mediating the Activin A/Follistatin axis during benzene-induced pre-leukemia are still unclear. Materials and Methods: Rats were randomized to one of experimental groups. The pre-leukemic model was established by repeated tail-vein administration of 0.2 mL benzene solution prepared in 2-propanol and distilled water (1:5:5, v/v) every 48 hours for a total duration of four weeks, or benzene plus oral melatonin (5, 10, 20, or 40 mg/kg/day for 4 weeks). Serum Activin A and Follistatin were measured by ELISA. Oxidative/antioxidant biomarkers 8-OHdG, MDA, SOD, and CAT were assessed by ELISA or TBA methods. Bone marrow Activin A and Follistatin transcripts were quantified by qPCR (ΔCt, 2^-ΔΔCt). Results: Benzene significantly reduced serum Activin A versus control and lowered CAT activity; Follistatin showed a modest, non-significant rise. MDA and 8-OHdG were lower than in the control after benzene. Melatonin produced dose-specific effects: (i) Activin A protein was not meaningfully restored at any dose; (ii) Follistatin peaked at 20 mg/kg; (iii) CAT improved at low-to-moderate doses, whereas SOD changes were not significant and MDA remained largely unchanged; (iv) 8-OHdG increased at 5-10 mg/kg but was comparatively lower at 20 mg/kg among melatonin groups. qPCR showed benzene downregulated Activin A and Follistatin transcripts versus control; melatonin 10 mg further reduced both relatives to benzene. Conclusions: In benzene-exposed rats, melatonin modulated the Activin A/Follistatin pathway and selectively improved antioxidant defenses most consistently in CAT while further suppressing Activin A and Follistatin transcription, indicating a nuanced dose-dependent interaction without full normalization of Activin A protein levels.