Abstract Body (Do not enter title and authors here): Introduction
Sympathoexcitation is a central diver of cardiovascular mortality in patients with chronic kidney disease (CKD). However, the molecular mechanisms underlying excess sympathetic nerve activity (SNA) in CKD are still not well understood. We have previously shown that microglia activation precedes neuroinflammation and excess SNA in CKD. However, whether restoring microglial function attenuates sympathoexcitation in CKD is unknown.
Hypothesis
We hypothesize that microglial activation drives SNA and its depletion and or repopulation of microglia will mitigate sympathoexcitation in CKD.
Methods
C57/BL6 mice (18-22gm, 8-11 weeks old) were randomized into groups as below: 0.2% adenine in casein (CKD), casein-only diet (Control), and 0.2% adenine + PLX 3397 (CKD and Microglia depletion) for 2/4 weeks. CKD was confirmed by serum creatinine and cystatin C levels. Heart rate variability (LF/HF ratio) and catecholamine levels (ELISA) were used as a measured of SNA. Neuroinflammation was assessed by microglia phenotyping via flowcytometry, immunofluorescence and Luminex cytokine/chemokine array.
Results
SNA was significantly increased at 4week in CKD mice LF/HF ratio (0.46 ± 0.10 in CKD vs. 0.21 ± 0.05 in controls; P = 0.02) but was nonsignificant at two weeks. Microglial activation was evident as early as 2 weeks in CKD mice (CD11b+ P2RY12+ CD86+ / CD11b+ P2RY12+ CD45HIGH CD86+) (P = 0.001/0.045). Microglia specific chemokine, RANTES was also significantly increase in CKD by 2/4 week. Pre-emptive microglial depletion (prior to CKD induction) significantly reduced SNA at 4 weeks (LF/HF ratio: 0.23 ± 0.11 in CKD + PLX3397 vs. 0.54 ± 0.22 in CKD, P = 0.009). In contrast, microglial depletion after CKD onset did not alter SNA. However, repopulation of microglia following depletion after CKD onset significantly attenuated SNA (LF/HF: 0.38 ± 0.29 in repopulated vs. 0.71 ± 0.29 in non-repopulated group).
Conclusion
These results suggested that CKD is linked with early microglial activation. Microglial depletion before CKD and microglia repopulation attenuates sympathetic overactivity, identifying microglia as a mechanistic driver of excess SNA in CKD and a potential therapeutic target.