Activation of the Nrf2 pathway by a novel bipyrazole compound mitigates doxorubicin-induced cardiotoxicity in Wistar albino rats

Background

Doxorubicin (DOX) clinical utility is limited by its dose-dependent cardiotoxicity. This study aimed to evaluate the cardioprotective potential of 2′,3,3,5′-Tetramethyl-4′-nitro-2′H-1,3′-bipyrazole (TMNB) in a rat model of DOX-induced cardiac injury.

Methods

Rats were divided into control, DOX, TMNB, and TMNB + DOX groups. TMNB was administered for 14 days. A single dose of DOX was given on day 7. Serum, oxidative stress, cytokines, apoptosis markers, and Nrf2 pathway gene expression were assessed. One-way ANOVA followed by Tukey's post-hoc test were used.

Results

TMNB pretreatment reduced CK-MB and LDH levels by 42.9 % and 50 %, respectively (Cohen's d > 6.4, p < 0.001). Histologically, TMNB significantly reduced myocardial damage (d = 6.63). MDA levels declined by 45.1 % in TMNB-treated rats (d = 7.18), while antioxidant enzymes SOD and CAT increased by 99.4 % and 74.1 %, respectively (p < 0.001). TMNB restored GSH and GPx-1 levels, reversing DOX-induced oxidative depletion (all d > 4.7). Pro-inflammatory cytokines TNF-α and IL-1β were reduced with TMNB pretreatment by over 40 % (d > 9.3, p < 0.001). Similarly, TMNB significantly downregulated NF-κB gene expression (d = 9.46). Caspase-3 and Bax were reduced by 44.9 % and 65.5 %, respectively (p < 0.001), while Bcl-2 expression was restored. TUNEL staining confirmed reduced apoptosis (d = 11.20). TMNB increased Nrf2, HO-1, and NQO1 expression (Nrf2 d = 8.21) while decreasing Keap1 (p < 0.0001).

Conclusion

TMNB significantly mitigates DOX-induced cardiotoxicity likely via Nrf2 pathway activation. These findings support TMNB's potential as a cardioprotective adjunct during chemotherapy, warranting further investigation in chronic and clinical models.