Objectives
- Cardiorenal syndrome type 4 is characterized by primary chronic kidney disease (CKD) leading to an impairment of cardiac function. We recently showed a reduced expression of several cardiac mitochondrial genes in short-term CKD rat model. We aimed to evaluate whether cardiac mitochondrial structure and function is modified in long-term CKD and if so, to characterize the potential associated mechanisms.
Methods
- Lewis rats underwent 5/6 nephrectomy for induction of CKD. Upon necroscopy, eight months later, cardiac sections were analyzed by histology and electron microscopy (EM). Mitochondrial DNA content was determined by the mitochondrial gene, cytochrome B. Mitochondrial content was assessed by citrate synthase (CS) activity in tissue homogenate and respiratory chain function was determined by the activity of complexes I-IV in isolated mitochondria. The levels of PGC1a, a transcription factor for mitochondrial biogenesis, Angiotensin II type 1 receptor and cytosolic cytochrome C were assayed by western blot. Cytokine serum profile was determined by microarray.
Results
- Long-term CKD leads to cardiac hypertrophy and increased interstitial fibrosis. EM analysis revealed a massive spatial disarrangement accompanied by a considerably increased volume of swollen-damaged mitochondria in CKD hearts (32±3%, n=5, 48±6%, n=4; respectively; p<0.05). Total mitochondrial DNA content was decreased in cardiac tissue of CKD rats. Concomitantly, active mitochondrial content was significantly reduced. Conversely, no differences were observed in respiratory chain enzymes’ functions (complexes I-IV) in isolated active mitochondria. Moreover, inflammatory response and activation of Renin-Angiotensin-Aldosterone-System (RAAS) were detected in the CKD setting.
Conclusion
- CKD results in a marked reduction of active mitochondria in the heart. Inflammatory cytokines and RAAS, may set a deleterious environment to cardiac mitochondria, as suggested in non-CKD models. The data may represent a significant milestone in the personalized medicine strategy for treating CKD patients who present with normal cardiac function accompanied by positive biomarkers for cardiac mitochondria damage.
Subcutaneous nerve activity and mechanisms of sudden death in a rat model of chronic kidney disease
