Deficiency in Apoptosis-Inducing Factor Recapitulates Chronic Kidney Disease via Aberrant Mitochondrial Homeostasis

Area of Science:

• Mitochondrial biology
• Nephrology
• Cellular signaling

Background:

• Apoptosis-inducing factor (AIF) is a mitochondrial protein involved in redox signaling and programmed cell death.
• AIF deficiency typically impairs oxidative phosphorylation (OXPHOS) and Complex I activity in various tissues.
• Kidney function heavily relies on OXPHOS for metabolic homeostasis, suggesting a potential role for AIF in kidney health.

Purpose of the Study:

• To investigate the role of AIF in the development of chronic kidney disease (CKD).
• To examine the impact of AIF deficiency on kidney mitochondrial function and structure.
• To determine if AIF deficiency is a risk factor for diabetic nephropathy.

Main Methods:

• Partial knockdown of Aif in mice to model reduced AIF levels.
• Assessment of kidney pathology, mitochondrial function (OXPHOS, ATP pool, ROS production), and mitochondrial dynamics (fusion).
• Analysis of AIF expression in human diabetic nephropathy patient samples and correlation with kidney function (glomerular filtration rate).
• In vitro studies using human proximal tubule cells to assess the effect of AIF overexpression on glucose-induced mitochondrial dysfunction.

Main Results:

• Aif knockdown in mice mimicked CKD features, including increased mitochondrial fusion, reactive oxygen species (ROS) production, and Nox4 upregulation, without impairing Complex I activity.
• Superimposing diabetes onto Aif knockdown exacerbated kidney lesions and altered mitochondrial function.
• Reduced AIF in renal tubules and lower AIFM1 gene expression in patients with diabetic nephropathy correlated with decreased glomerular filtration rate.
• Overexpression of AIF in human proximal tubule cells protected against glucose-induced mitochondrial respiration defects.

Conclusions:

• AIF deficiency is implicated in CKD pathogenesis, characterized by altered mitochondrial dynamics and increased oxidative stress.
• AIF deficiency acts as a significant risk factor for the progression of diabetic kidney disease.
• Restoring AIF levels may offer a therapeutic strategy for mitigating mitochondrial dysfunction in diabetic nephropathy.