p38δ genetic ablation protects female mice from anthracycline cardiotoxicity

Abstract

BACKGROUND: The efficacy of an anthracycline antibiotic doxorubicin (DOX) as a chemotherapeutic agent is limited by dose-dependent cardiotoxicity. DOX is associated with activation of intracellular stress signaling pathways including p38 MAPKs. While previous studies have implicated p38 MAPK signaling in DOX-induced cardiac injury, the roles of the individual p38 isoforms, specifically, of the alternative isoforms p38 and p38, remain uncharacterized. OBJECTIVES: To determine the potential cardioprotective effects of p38 and p38 genetic deletion in mice subjected to acute DOX treatment. METHODS: Male and female wild-type (WT), p38 -/-, p38 -/-and p38 -/- -/-mice were injected with 30 mg/kg DOX and their survival was tracked for ten days. During this period cardiac function was assessed by echocardiography and electrocardiography and fibrosis by PicroSirius Red staining.Immunoblotting was performed to assess the expression of signaling proteins and markers linked to autophagy. RESULTS: Significantly improved survival was observed in p38 -/-female mice post-DOX relative to WT females, but not in p38 -/-or p38 -/- -/-male or female mice. The improved survival in DOX-treated p38 -/-females was associated with decreased fibrosis, increased cardiac output and LV diameter relative to DOX-treated WT females, and similar to saline-treated controls. Structural and echocardiographic parameters were either unchanged or worsened in all other groups. Increased autophagy, as evidenced by increased LC3-II level, and decreased mTOR activation was also observed in DOX-treated p38 -/-females. CONCLUSIONS: p38 plays a crucial role in promoting DOX-induced cardiotoxicity in female mice by inhibiting autophagy. Therefore, p38 targeting could be a potential cardioprotective strategy in anthracycline chemotherapy. NEW AND NOTEWORTHY:This study for the first time identifies the roles of the alternative p38 and p38 MAPK isoforms in promoting DOX-cardiotoxicity in a sex-specific manner. While p38 systemic deletion did not affect DOX-cardiotoxicity, p38 systemic deletion was cardioprotective in female but not in male mice. Cardiac structure and function were preserved in DOX-treated p38-/-females and autophagy was increased.

Differential cardiotoxic electrocardiographic response to doxorubicin treatment in conscious versus anesthetized mice

“…Currently, echocardiography is the method of choice in the clinical setting and ejection fraction is the preferred metric (Meijers & Moslehi, 2019; Perez et al, 2019). However, in our previous study, we demonstrated the role of preserved ejection fraction in some subjects as a potential cause of undiagnosed DOX‐induced cardiotoxicity (George et al, 2020). Electrocardiography (ECG) is another method to detect DOX cardiotoxicity in patients, however, this technique too has its limitations.…”

“…Beyond 2 min, mice became stressed and motion artifacts were introduced into the signals. Mice were then anesthetized using isoflurane (1–2.5%, 1 ml/min oxygen) using an EZ anesthesia machine to maintain a heart rate of ~400 bpm (for echocardiography simultaneously performed and previously published (George et al, 2020)). Once unconscious, mice were transferred to the mouse platform of a Vevo 3100 ultrasound machine (FUJIFILM VisualSonics) and anesthesia administration was continued via a nose cone.…”

“…Each file was of about 8 s in duration. ECG files were recorded along with the echocardiography files (data previously published (George et al, 2020)). Both conscious and anesthetized ECG traces were analyzed using the same custom MATLAB program and in the same manner as described below.…”

“…DOX destroys cancer cells by inducing DNA fragmentation but it also has several detrimental side effects such as increased ROS production, inflammation, and antioxidant depletion which triggers the cellular stress signaling response (George et al, 2020; Ichikawa et al, 2014; Kim et al, 2006; Šimůnek et al, 2009). Several groups have identified the mechanistic pathways that are activated in this stress response to DOX and p38 MAPK activation and its role in promoting DOX cardiotoxicity is well established (Bernstein et al, 2005; George et al, 2020; Ma et al, 2012; Nozaki et al, 2004; Riad et al, 2008; Thandavarayan et al, 2010; Yi et al, 2007; Zhang et al, 2012). Activation of stress signaling pathways inhibits autophagy, increases apoptosis, fibrosis, cardiac dysfunction, and increases morbidity and mortality.…”

“…Our group recently reported sex differences in the stress response to DOX treatment. Specifically, p38δ activation is associated with DOX‐induced cardiotoxicity in female mice (George et al, 2020).…”