Genetic Deletion of NOD1 Prevents Cardiac Ca2+ Mishandling Induced by Experimental Chronic Kidney Disease

Cardiomyopathy in chronic kidney disease: clinical features, biomarkers and the contribution of murine models in understanding pathophysiology

The cardiorenal syndrome (CRS) is described as a multi-organ disease encompassing bidirectionally heart and kidney. In CRS type 4, chronic kidney disease (CKD) leads to cardiac injury. Different pathological mechanisms have been identified to contribute to the establishment of CKD-induced cardiomyopathy, including a neurohormonal dysregulation, disturbances in the mineral metabolism and an accumulation of uremic toxins, playing an important role in the development of inflammation and oxidative stress. Combined, this leads to cardiac dysfunction and cardiac pathophysiological and morphological changes, like left ventricular hypertrophy, myocardial fibrosis and cardiac electrical changes. Given that around 80% of dialysis patients suffer from uremic cardiomyopathy, the study of cardiac outcomes in CKD is clinically highly relevant. The present review summarizes clinical features and biomarkers of CKD-induced cardiomyopathy and discusses underlying pathophysiological mechanisms recently uncovered in the literature. It discloses how animal models have contributed to the understanding of pathological kidney-heart crosstalk, but also provides insights into the variability in observed effects of CKD on the heart in different CKD mouse models, covering both "single hit" as well as "multifactorial hit" models. Overall, this review aims to support research progress in the field of CKD-induced cardiomyopathy.

Chronic kidney disease promotes atrial fibrillation via inflammasome pathway activation

Chronic kidney disease (CKD) is associated with a higher risk of atrial fibrillation (AF). The mechanistic link between CKD and AF remains elusive. IL-1β, a main effector of NLR family pyrin domain-containing 3 (NLRP3) inflammasome activation, is a key modulator of conditions associated with inflammation, such as AF and CKD. Circulating IL-1β levels were elevated in patients with CKD who had AF (versus patients with CKD in sinus rhythm). Moreover, NLRP3 activity was enhanced in atria of patients with CKD. To elucidate the role of NLRP3/IL-1β signaling in the pathogenesis of CKD-induced AF, Nlrp3-/- and WT mice were subjected to a 2-stage subtotal nephrectomy protocol to induce CKD. Four weeks after surgery, IL-1β levels in serum and atrial tissue were increased in WT CKD (WT-CKD) mice versus sham-operated WT (WT-sham) mice. The increased susceptibility to pacing-induced AF and the longer AF duration in WT-CKD mice were associated with an abbreviated atrial effective refractory period, enlarged atria, and atrial fibrosis. Genetic inhibition of NLRP3 in Nlrp3-/- mice or neutralizing anti-IL-1β antibodies effectively reduced IL-1β levels, normalized left atrial dimensions, and reduced fibrosis and the incidence of AF. These data suggest that CKD creates a substrate for AF development by activating the NLRP3 inflammasome in atria, which is associated with structural and electrical remodeling. Neutralizing IL-1β antibodies may be beneficial in preventing CKD-induced AF.

Partial Genetic Deletion of Klotho Aggravates Cardiac Calcium Mishandling in Acute Kidney Injury

Acute kidney injury (AKI) is associated with an elevated risk of cardiovascular major events and mortality. The pathophysiological mechanisms underlying the complex cardiorenal network interaction remain unresolved. It is known that the presence of AKI and its evolution are significantly associated with an alteration in the anti-aging factor klotho expression. However, it is unknown whether a klotho deficiency might aggravate cardiac damage after AKI. We examined intracellular calcium (Ca²⁺) handling in native ventricular isolated cardiomyocytes from wild-type (+/+) and heterozygous hypomorphic mice for the klotho gene (+/kl) in which an overdose of folic acid was administered to induce AKI. Twenty-four hours after AKI induction, cardiomyocyte contraction was decreased in mice with the partial deletion of klotho expression (heterozygous hypomorphic klotho named +/kl). This was accompanied by alterations in Ca²⁺ transients during systole and an impairment of sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA2a) function in +/kl mice after AKI induction. Moreover, Ca²⁺ spark frequency and the incidence of Ca²⁺ pro-arrhythmic events were greater in cardiomyocytes from heterozygous hypomorphic klotho compared to wild-type mice after AKI. A decrease in klotho expression plays a role in cardiorenal damage aggravating cardiac Ca²⁺ mishandling after an AKI, providing the basis for future targeted approaches directed to control klotho expression as novel therapeutic strategies to reduce the cardiac burden that affects AKI patients.

Intestinal microbiota-derived membrane vesicles and their role in chronic kidney disease

Intestinal microbiota-derived membrane vesicles (MVs) play essential roles in immunomodulation and maintenance of the intestinal micro-ecosystem. The relationship between MVs and chronic kidney disease (CKD) has remained undefined. This review provides a survey of the structure and biological function of different vesicle types and summarizes the possible pathogenic mechanisms mediated by MVs, which may be of great clinical significance in the diagnosis and treatment of chronic kidney disease.

A systematic review and meta-analysis of murine models of uremic cardiomyopathy

Chronic kidney disease (CKD) triggers the risk of developing uremic cardiomyopathy as characterized by cardiac hypertrophy, fibrosis and functional impairment. Traditionally, animal studies are used to reveal the underlying pathological mechanism, although variable CKD models, mouse strains and readouts may reveal diverse results. Here, we systematically reviewed 88 studies and performed meta-analyses of 52 to support finding suitable animal models for future experimental studies on pathological kidney-heart crosstalk during uremic cardiomyopathy. We compared different mouse strains and the direct effect of CKD on cardiac hypertrophy, fibrosis and cardiac function in "single hit" strategies as well as cardiac effects of kidney injury combined with additional cardiovascular risk factors in "multifactorial hit" strategies. In C57BL/6 mice, CKD was associated with a mild increase in cardiac hypertrophy and fibrosis and marginal systolic dysfunction. Studies revealed high variability in results, especially regarding hypertrophy and systolic function. Cardiac hypertrophy in CKD was more consistently observed in 129/Sv mice, which express two instead of one renin gene and more consistently develop increased blood pressure upon CKD induction. Overall, "multifactorial hit" models more consistently induced cardiac hypertrophy and fibrosis compared to "single hit" kidney injury models. Thus, genetic factors and additional cardiovascular risk factors can "prime" for susceptibility to organ damage, with increased blood pressure, cardiac hypertrophy and early cardiac fibrosis more consistently observed in 129/Sv compared to C57BL/6 strains.