Rho Kinase Mediates Diastolic Dysfunction in Chronic Kidney Disease Models

Background: Patients with chronic kidney disease (CKD) commonly have heart failure with preserved ejection fraction (HFpEF). We have shown that Lysyl oxidase (LOX), an enzyme that catalyzes collagen cross-linking and extracellular matrix remodeling, is increased in the aorta of mice with CKD. Rho kinases (ROCK) are powerful mechano-transducers that play an important role in the maintenance of the cytoskeleton and tissue stiffness. Hypothesis: We postulated that LOX-mediated increases in aortic stiffness activate ROCK and lead to diastolic dysfunction in mice with CKD. Method: To test this hypothesis, we used an adenine-induced CKD mouse model. 12-week-old male C57BL/6 mice were randomized to casein-only diet (control) and a casein with 0.2% adenine (CKD). LOX and ROCK were assayed in the left ventricle of the heart by PCR, simple western, and enzymatic activity assays. In a subsequent experiment, mice were divided into 4 groups casein only (CTRL), casein+adenine 0.2% (CKD), CKD+β-aminopropionitrile, a LOX inhibitor (CKD+BAPN), and CKD+Fasudil, a ROCK inhibitor (CKD+Fas). Cardiac function was assessed by echocardiography. Results: Three weeks of adenine administration caused almost 2-fold increase in the ROCK activity in the left ventricle of CKD mice compared to controls (1.00 ± 0.24 (Control), 1.77 ± 0.52 (CKD) (n=6, p=0.009). While four weeks of adenine treatment caused diastolic dysfunction, as evidenced by an elevated E/E’ ratio (26.64±2.73 (control) vs. 32.16± 4.24 (CKD) (n=8, p=0.0049). Treatment with BAPN blunted the increase in E/E’, but the differences were not statistically significant. In contrast, Fasudil significantly prevented the increase in E/E’ ratio (32.16± 4.24 (CKD) vs. 24.52 ±3.28 (CKD+Fasudil) (p=0.002). No significant differences were observed in the ejection fraction between the groups Conclusion: Our findings suggest that diastolic dysfunction evident in the adenine-induced CKD model is associated with increased ROCK activity. Further, inhibition of ROCK but not LOX attenuates diastolic dysfunction in these mice. The mechanistic basis of these findings requires further studies.