Mitochondrial dysfunction in sepsis is associated with diminished intramitochondrial TFAM despite its increased...

Area of Science:

• Cellular Biology
• Immunology
• Biochemistry

Background:

• Sepsis involves immune dysregulation, metabolic issues, and bioenergetic failure.
• Mitochondrial dysfunction is a key feature of sepsis, persisting despite increased nuclear-encoded transcription factor A (TFAM).
• The paradox of increased TFAM expression with impaired mitochondrial function suggests altered TFAM distribution.

Purpose of the Study:

• To investigate the hypothesis that enhanced extramitochondrial TFAM expression in sepsis does not lead to increased intramitochondrial TFAM abundance.
• To explore the impact of altered TFAM distribution on mitochondrial function and bioenergetics during sepsis and endotoxemia.

Main Methods:

• Prospective analysis of peripheral blood mononuclear cells (PBMCs) from septic patients and healthy volunteers stimulated with lipopolysaccharide.
• Quantification of extramitochondrial and intramitochondrial TFAM protein levels.
• Measurement of mitochondrial DNA copy numbers, mtND1 expression, cellular ATP content, and TFAM-TFB2M interaction.

Main Results:

• Septic patients showed 1.8-fold higher extramitochondrial TFAM but 80% less intramitochondrial TFAM compared to controls.
• Significant reductions in mitochondrial DNA copy numbers, mtND1 expression, and cellular ATP content were observed in sepsis.
• TFAM-TFB2M protein interaction within the mitochondrial transcription initiation complex was reduced by 74% in septic patients.
• Similar findings were observed in lipopolysaccharide-stimulated PBMCs from healthy volunteers.

Conclusions:

• Sepsis and endotoxemia are characterized by diminished mitochondrial TFAM abundance.
• The reduced intramitochondrial TFAM explains the paradox of impaired bioenergetic recovery despite increased TFAM expression in sepsis.
• These findings offer insights into the mechanisms underlying sepsis-induced mitochondrial dysfunction.