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Tag: MKK6 (Page 1 of 3)

p38γ/δ activation alters cardiac electrical activity and predisposes to ventricular arrhythmia

Rafael Romero-Becerra, Francisco M. Cruz, Alfonso Mora, Juan Antonio Lopez, Daniela Ponce-Balbuena, Andrew Allan, Roberto Ramos-Mondragón, Bárbara González-Terán, Marta León, Maria Elena Rodríguez, Luis Leiva-Vega, Guadalupe Guerrero-Serna, Eric N. Jimenez-Vazquez, David Filgueiras-Rama, Jesús Vázquez, José Jalife & Guadalupe Sabio.

Ventricular fibrillation (VF) is a leading immediate cause of sudden cardiac death. There is a strong association between aging and VF, although the mechanisms are unclear, limiting the availability of targeted therapeutic interventions.

Heart depolarizations recorded by optical membrane potential (Imagen: Rafael Romero-Becerra).

Here we found that the stress kinases p38γ and p38δ are activated in the ventricles of old mice and mice with genetic or drug-induced arrhythmogenic conditions. We discovered that, upon activation, p38γ and p38δ cooperatively increase the susceptibility to stress-induced VF. Mechanistically, our data indicate that activated p38γ and p38δ phosphorylate ryanodine receptor 2 (RyR2) disrupt Kv4.3 channel localization, promoting sarcoplasmic reticulum calcium leak, Ito current reduction and action potential duration prolongation. In turn, this led to aberrant intracellular calcium handling, premature ventricular complexes and enhanced susceptibility to VF. Blocking this pathway protected genetically modified animals from VF development and reduced the VF duration in aged animals.

These results indicate that p38γ and p38δ are a potential therapeutic target for sustained VF prevention.

MKK6 deficiency promotes cardiac dysfunction through MKK3-p38γ/δ-mTOR hyperactivation

Rafael Romero-Becerra, Alfonso Mora, Elisa Manieri, Ivana Nikolic, Ayelén Melina Santamans, Valle Montalvo-Romeral, Francisco Miguel Cruz, Elena Rodríguez, Marta León, Luis Leiva-Vega, Laura Sanz, Víctor Bondía, David Filgueiras-Rama, Luis Jesús Jiménez-Borreguero, José Jalife, Barbara Gonzalez-Teran & Guadalupe Sabio.

Stress-activated p38 kinases control a plethora of functions, and their dysregulation has been linked to the development of steatosis, obesity, immune disorders, and cancer. Therefore, they have been identified as potential targets for novel therapeutic strategies. There are four p38 family members (p38α, p38β, p38γ, and p38δ) that are activated by MKK3 and MKK6.

Cardiac hypertrophy under the microscope.
Cardiac hypertrophy in a heart lacking MKK6 (Image: Bárbara González-Terán).

Here, we demonstrate that lack of MKK6 reduces the lifespan in mice. Longitudinal study of cardiac function in MKK6 KO mice showed that young mice develop cardiac hypertrophy which progresses to cardiac dilatation and fibrosis with age. Mechanistically, lack of MKK6 blunts p38α activation while causing MKK3-p38γ/δ hyperphosphorylation and increased mammalian target of rapamycin (mTOR) signaling, resulting in cardiac hypertrophy. Cardiac hypertrophy in MKK6 KO mice is reverted by knocking out either p38γ or p38δ or by inhibiting the mTOR pathway with rapamycin.

In conclusion, we have identified a key role for the MKK3/6-p38γ/δ pathway in the development of cardiac hypertrophy, which has important implications for the clinical use of p38α inhibitors in the long-term treatment since they might result in cardiotoxicity.

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