Pro-caspase-3 protects cells from polymyxin B-induced cytotoxicity by preventing ROS accumulation

Area of Science:

• Cell Biology
• Pharmacology
• Toxicology

Background:

• Polymyxin B (PMB) is a critical last-line antibiotic for treating infections caused by multidrug-resistant bacteria.
• The precise mechanisms underlying PMB's cytotoxic side effects remain poorly understood.
• Understanding these mechanisms is crucial for developing safer antibiotic therapies.

Purpose of the Study:

• To investigate the role of caspase-3 in Polymyxin B-induced cytotoxicity.
• To elucidate the involvement of reactive oxygen species (ROS) in PMB's side effects.
• To identify potential protective mechanisms against PMB toxicity.

Main Methods:

• Utilized caspase-3 knockout (KO) and wild-type (WT) cells for comparative analysis.
• Assessed cell viability and reactive oxygen species (ROS) levels following PMB treatment.
• Investigated the processing of pro-caspase-3 in response to PMB exposure.
• Evaluated the protective effect of the antioxidant N-acetylcysteine (NAC).

Main Results:

• Caspase-3 knockout cells showed increased susceptibility to PMB-induced cytotoxicity compared to WT cells.
• PMB treatment led to elevated levels of reactive oxygen species (ROS) in caspase-3 KO cells.
• The antioxidant N-acetylcysteine (NAC) significantly rescued cell viability in PMB-treated cells.
• PMB did not promote the activation of caspase-3, indicating a non-proteolytic protective role for pro-caspase-3.

Conclusions:

• Pro-caspase-3, rather than its active form, plays a protective role against PMB-induced cytotoxicity by nonenzymatically suppressing ROS accumulation.
• PMB has the potential to induce ROS generation, a process normally mitigated by pro-caspase-3-dependent mechanisms.
• These findings offer novel insights into the mechanisms of Polymyxin B's adverse effects and suggest potential therapeutic targets.