Polymyxin B Nephrotoxicity: From Organ to Cell Damage

Area of Science:

• Nephrology
• Toxicology
• Cell Biology

Background:

• Polymyxins, like polymyxin B, are crucial antibiotics but are known for dose-limiting toxicities.
• The precise mechanisms underlying polymyxin B-induced nephrotoxicity remain incompletely understood.
• Investigating these mechanisms is vital for safe clinical application.

Purpose of the Study:

• To elucidate the link between polymyxin B's effects on renal metabolic functions and mitochondrial morphology.
• To assess polymyxin B's impact on the structural integrity of kidney cells (LLC-PK1) and rat kidneys.
• To provide data supporting clinical studies on polymyxin B's side effects.

Main Methods:

• Wistar rats were administered polymyxin B (4 mg/kg/day) or saline intraperitoneally for 5 days.
• Renal function, hemodynamics, oxidative stress, mitochondrial injury, and histology were evaluated in rats.
• LLC-PK1 cells were exposed to varying concentrations of polymyxin B to assess cytotoxicity, apoptosis, and nitric oxide production.

Main Results:

• Polymyxin B administration in rats led to reduced creatinine clearance, increased renal vascular resistance, and elevated oxidative damage.
• Mitochondrial damage, indicated by electron microscopy and cytochrome c release, and tubular necrosis were observed.
• In LLC-PK1 cells, polymyxin B induced cytotoxicity, apoptosis, and increased lactate dehydrogenase and nitric oxide levels, with the drug localizing to mitochondria.

Conclusions:

• Polymyxin B nephrotoxicity is characterized by mitochondrial dysfunction and free radical generation.
• These mechanisms were confirmed in both an in vivo rat model and in vitro LLC-PK1 cell cultures.
• The findings highlight the critical role of mitochondrial integrity in polymyxin B-induced kidney injury.