Proteomic analysis of laser captured tubular tissues reveals complement activation and mitochondrial dysfunction in...

Autoimmune related kidney diseases (ARKDs), including minimal change nephropathy (MCN), membranous nephropathy (MN), IgA nephropathy (IgAN), and lupus nephritis (LN), significantly affect renal function. These diseases are characterized by the formation of local immune complexes and the subsequent activation of the complement system, leading to kidney damage and proteinuria. Despite the known patterns of glomerular injury, the specific molecular mechanisms that contribute to renal tubular damage across ARKDs remain underexplored. Laser capture microdissection and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to conduct a comparative proteomic analysis of renal tubular tissues from formalin-fixed paraffin-embedded samples. The cohort comprised of 10 normal controls (NC), 5 MCN, 4 MN, 17 IgAN, and 21 LN patients. Clinical parameters and histopathological assessments were integrated with proteomic findings to comprehensively investigate underlying pathogenic processes. Clinical evaluation indicated significant glomerular damage, as reflected by elevated urinary protein levels and reduced plasma albumin levels in patients with ARKD. Histological analyses confirmed varying degrees of tubular damage and deposition of immune complexes. Proteomic analyses identified significant changes in protein expression, particularly in complement components (C3, C4A, C4B, C8G, CFB, and SERPINA1) and mitochondrial proteins (ATP5F1E and ATP5PD), highlighting the common alterations in the complement system and mitochondrial proteins across ARKDs. These alterations suggest a novel complement-mitochondrial-epithelial-mesenchymal transition (EMT) pathway axis that contributes to tubular damage in ARKDs. Notably, significant alterations in CFB in tubular ARKD patients were revealed, implicating it as a therapeutic target. This study underscores the importance of complement activation and mitochondrial dysfunction in the pathogenesis of ARKDs, and proposes CFB as a potential therapeutic target to inhibit complement activation and mitigate tubular damage. Future research should validate the complement-mitochondrial-EMT pathway axis and explore the effects and mechanisms of CFB inhibitors in alleviating ARKD progression.