Downregulation of nuclear factor erythroid 2-related factor 2 (Nrf2) contributes to doxorubicin (DOX)-induced myocardial oxidative stress, and inhibition of mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) increased Nrf2 protein level in rat heart suffering ischemia/reperfusion, indicating a connection between MALT1 and Nrf2. This study aims to explore the role of MALT1 in DOX-induced myocardial oxidative stress and the underlying mechanisms.

The E3 ubiquitin ligase function of MALT1 accounts for the downregulation of Nrf2 and aggravation of myocardial oxidative stress in DOX-treated mice, and CaMKII-δ-dependent phosphorylation of CARD11 triggered the assembly of CBM complex and the subsequent activation of MALT1.

The mice received a single injection of DOX (15 mg/kg, i.p.) to induce myocardial oxidative stress, evidenced by increases in the levels of reactive oxidative species as well as decreases in the activities of antioxidative enzymes, concomitant with a downregulation of Nrf2; these phenomena were reversed by MALT1 inhibitor. Similar phenomena were observed in DOX-induced oxidative stress in cardiomyocytes. Mechanistically, knockdown or inhibition of MALT1 notably attenuated the interaction between Nrf2 and MALT1 and decreased the k48-linked ubiquitination of Nrf2. Furthermore, inhibition or knockdown of calcium/calmodulin-dependent protein kinase II (CaMKII-δ) reduced the phosphorylation of caspase recruitment domain-containing protein 11 (CARD11), subsequently disrupted the assembly of CARD11, B cell lymphoma 10 (BCL10), and MALT1 (CBM) complex, and reduced the MALT1-dependent k48-linked ubiquitination of Nrf2 in DOX-treated mice or cardiomyocytes. Innovation and