The STIM1 inhibitor ML9 disrupts basal autophagy in cardiomyocytes by decreasing lysosome content

Area of Science:

• Cardiovascular Biology
• Cellular Physiology
• Molecular Medicine

Background:

• Stromal-interaction molecule 1 (STIM1)-mediated store-operated Ca2+ entry (SOCE) is implicated in cardiomyocyte hypertrophy and ischemia/reperfusion injury.
• STIM1 inhibition is a potential therapeutic strategy for cardiovascular conditions.

Purpose of the Study:

• To investigate the effects of ML9, a STIM1 inhibitor, on cardiomyocyte viability.
• To elucidate the mechanism underlying ML9-induced cardiomyocyte death.

Main Methods:

• Primary culture of neonatal rat cardiomyocytes.
• Assessment of cell death markers (caspase-3 activation, LDH release, apoptotic index).
• Evaluation of reactive oxygen species (ROS), ATP levels, and autophagy markers (LC3-II, Beclin1, p62).
• Analysis of lysosomal function using LysoTracker® Green staining and bafilomycin-A1 treatment.

Main Results:

• ML9 induced significant cardiomyocyte death.
• ML9-induced death was not linked to apoptosis, necrosis, increased ROS, or decreased ATP.
• ML9 treatment increased LC3-II levels, suggesting autophagy induction, but impaired autophagic flux and lysosomal function.

Conclusions:

• ML9 induces cardiomyocyte death through a mechanism involving disrupted autophagic flux.
• Lysosomal dysfunction is a key factor in ML9-mediated cardiomyocyte cell death.
• STIM1 inhibition via ML9 may have detrimental effects on cardiomyocyte viability due to impaired autophagy.