Klotho mitigates diquat-induced myocardial injury in rats by activating Nrf2/ARE-mediated suppression of oxidative stress.

OBJECTIVES: Diquat (DQ) induces severe cardiotoxicity through oxidative stress, yet no specific antidote is currently available. Klotho, a known agonist of nuclear factor erythroid 2-related factor 2 (Nrf2), exerts antioxidative effects in various diseases. However, its role in DQ-induced myocardial injury remains undefined. METHODS: Acute myocardial injury was induced in rats by intragastric DQ administration, followed by treatment with recombinant Klotho protein. Myocardial histopathology, oxidative stress markers, and components of the Nrf2/antioxidant response elements (ARE) pathway - including Nrf2, heme oxygenase-1 (HO-1), and NAD(P)H:quinone oxidoreductase 1 (NQO1) - were evaluated. Additionally, DQ-exposed H9c2 cardiomyocytes were treated with Klotho or the Nrf2 inhibitor ML385. cell viability, apoptosis, oxidative stress markers, and Nrf2 pathway protein expression were evaluated. RESULTS: DQ administration induced significant oxidative stress and upregulated mRNA levels (2-3-fold; all P<0.0001) and protein expression (1.3-1.4-fold; P=0.0018, P=0.0039, P=0.0030) of Nrf2, HO-1, NQO1 in rat myocardial tissues. Klotho treatment effectively preserved H9c2 cell viability (by 60%; P<0.0001), reduced apoptosis (by 43%; P<0.0001), and alleviated oxidative stress (all P<0.0001). Klotho also enhanced Nrf2, HO-1, and NQO1 protein expression (2.5-3-fold; all P<0.0001). ML385 abrogated the protective effects of Klotho against DQ-induced oxidative stress (all P<0.0001) and apoptosis (all P<0.0001) in H9c2 cells. In vivo, recombinant Klotho administration attenuated myocardial histopathologic damage, normalized oxidative stress markers (all P<0.0001), and increased Nrf2, HO-1, NQO1 protein levels (1.8-2-fold; all P<0.0001). CONCLUSION: Klotho mitigates DQ-induced myocardial injury in rats by activating Nrf2/ARE signaling pathway and suppressing oxidative stress.