High-sodium intake aggravates myocardial injuries induced by aldosterone via oxidative stress in Sprague-Dawley rats

Associations Between Metabolic Profiles and Target-Organ Damage in Chinese Individuals With Primary Aldosteronism

Purpose: Patients with primary aldosteronism (PA) have an increased risk of target-organ damage (TOD), but whether metabolic syndrome (MetS) is more prevalent and contributes to TOD in PA patients remains unresolved. We aimed to evaluate the associations between MetS profiles and TOD in Chinese PA individuals. Methods: Metabolic parameters and pre-clinical TOD including left ventricular hypertrophy, estimated glomerular filtration, and microalbuminuria; insulin sensitivity or resistance; and islet β-cell function were assessed by the homeostasis models (HOMA-IR, HOMA-β) and the other surrogate indexes [composite insulin sensitivity index (ISI), modified β-cell function index (MBCI)] determined from the oral glucose tolerance test were compared in PA vs. matched essential hypertension (EH) patients. Results: A total of 109 PA patients and 109 essential hypertension (EH) controls individually matched for sex, age, and office systolic blood pressure and duration of hypertension were studied. The prevalence of MetS and its individual components in PA was significantly lower than in EH [MetS: 28 (25.6%) vs. 54 (49.5%), P < 0.001]. PA patients had a higher composite ISI but a lower HOMA-IR, HOMA-β, and MBCI than EH controls (all P < 0.05). Concerning TOD, PA patients had significantly higher prevalence of microalbuminuria and left ventricular hypertrophy (LVH), and lower levels of estimated glomerular filtration (eGFR) than EH controls (all P < 0.05). On multivariate logistic regression analysis, female gender and elevated plasma aldosterone levels were significantly associated with TOD in PA. However, there were no significant associations between MetS and its individual components and TOD in PA patients. Conclusions: PA patients had a lower MetS prevalence but exhibited more severe TOD than matched EH controls. The study highlights the deleterious effects of aldosterone excess on the development of TOD, whereas MetS or its individual components might be less influential in PA.

Steroidogenic acute regulatory protein/aldosterone synthase mediates angiotensin II-induced cardiac fibrosis and hypertrophy

Aldosterone produced in adrenal glands by angiotensin II (Ang II) is known to elicit myocardial fibrosis and hypertrophy. This study was designed to test the hypothesis that Ang II causes cardiac morphological changes through the steroidogenic acute regulatory protein (StAR)/aldosterone synthase (AS)-dependent aldosterone synthesis primarily initiated in the heart. Sprague-Dawley rats were randomized to following groups: Ang II infusion for a 4-week period, treatment with telmisartan, spironolactone or adrenalectomy during Ang II infusion. Sham-operated rats served as control. Relative to Sham rats, Ang II infusion significantly increased the protein levels of AT1 receptor, StAR, AS and their tissue expression in the adrenal glands and heart. In coincidence with reduced aldosterone level in the heart, telmisartan, an AT1 receptor blocker, significantly down-regulated the protein level and expression of StAR and AS. Ang II induced changes in the expression of AT1/StAR/AS were not altered by an aldosterone receptor antagonist spironolactone. Furthermore, Ang II augmented migration of macrophages, protein level of TGFβ1, phosphorylation of Smad2/3 and proliferation of myofibroblasts, accompanied by enhanced perivascular/interstitial collagen deposition and cardiomyocyte hypertrophy, which all were significantly abrogated by telmisartan or spironolactone. However, adrenalectomy did not fully suppress Ang II-induced cell migration/proliferation and fibrosis/hypertrophy, indicating a role of aldosterone synthesized within the heart in pathogenesis of Ang II induced injury. These results indicate that myocardial fibrosis and hypertrophy stimulated by Ang II is associated with tissue-specific activation of aldosterone synthesis, primarily mediated by AT1/StAR/AS signaling pathways.

Spectroscopic Fingerprints of Intermolecular H-Bonding Interactions in Carbon Nitride Model Compounds

The effect of intermolecular H-bonding interactions on the local electronic structure of N-containing functional groups (amino group and pyridine-like N) that are characteristic of polymeric carbon nitride materials p-CN(H), a new class of metal-free organophotocatalysts, was investigated. Specifically, the melamine molecule, a building block of p-CN(H), was characterized by X-ray photoelectron (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The molecule was studied as a noninteracting system in the gas phase and in the solid state within a H-bonded network. With the support of DFT simulations of the spectra, it was found that the H-bonds mainly affect the N 1s level of the amino group, leaving the N 1s level of the pyridine-like N mostly unperturbed. This is responsible for a reduction of the chemical shift between the two XPS N 1s levels relative to free melamine. Consequently, N K-edge NEXAFS resonances involving the amino N 1s level also shift to lower photon energies. Moreover, the solid-state absorption spectra showed significant modification/quenching of resonances related to transitions from the amino N 1s level to σ* orbitals involving the NH₂ termini.

Mitochondrial reactive oxygen species-mediated NLRP3 inflammasome activation contributes to aldosterone-induced renal tubular cells injury

Aldosterone (Aldo) is an independent risk factor for chronic kidney disease (CKD), and although Aldo directly induces renal tubular cell injury, the underlying mechanisms remain unclear. NLRP3 inflammasome and mitochondrial reactive oxygen species (ROS) have recently been implicated in various kinds of CKD. The present study hypothesized that mitochondrial ROS and NLRP3 inflammasome mediated Aldo–induced tubular cell injury. The NLRP3 inflammasome is induced by Aldo in a dose- and time-dependent manner, as evidenced by increased NLRP3, ASC, caspase-1, and downstream cytokines, such as interleukin (IL)-1β and IL-18. The activation of the NLRP3 inflammasome was significantly prevented by the selective mineralocorticoid receptor (MR) antagonist eplerenone (EPL) (P < 0.01). Mice harboring genetic knock-out of NLRP3 (NLRP3^−/−) showed decreased maturation of renal IL-1β and IL-18, reduced renal tubular apoptosis, and improved renal epithelial cell phenotypic alternation, and attenuated renal function in response to Aldo-infusion. In addition, mitochondrial ROS was also increased in Aldo-stimulated HK-2 cells, as assessed by MitoSOX^TM red reagent. Mito-Tempo, the mitochondria-targeted antioxidant, significantly decreased HK-2 cell apoptosis, oxidative stress, and the activation of NLRP3 inflammasome. We conclude that Aldo induces renal tubular cell injury via MR dependent, mitochondrial ROS-mediated NLRP3 inflammasome activation.

Rotenone Attenuates Renal Injury in Aldosterone-Infused Rats by Inhibiting Oxidative Stress, Mitochondrial Dysfunction, and Inflammasome Activation

BACKGROUND

Reactive oxygen species (ROS) and inflammation both contribute to the progression of aldosterone-induced renal injury. To better understand the underlying mechanisms, we examined mitochondrial dysfunction and NLRP3 inflammasome activation in aldosterone-infused rats, and explored the role of rotenone in attenuating these injuries.

MATERIAL AND METHODS

Sprague-Dawley rats were divided into 3 groups: vehicle-treated, aldosterone-infused, and aldosterone plus rotenone. Renal damage was evaluated using PAS staining and electron microscopy. Levels of ROS were measured from renal tissue and serum; immunohistochemistry analysis examined the inflammation pathway; Western blot and real-time PCR assessed NLRP3 inflammasome activity.

RESULTS

Glomerular segmental sclerosis, foot process effacement, and proteinuria were demonstrated in the aldosterone-infused rats. Specifically, the thiobarbituric acid-reactive substances (TBARS) oxidative stress marker, MDA, was significantly increased; ATP content and mtDNA copy number were markedly decreased; inflammatory mediators NF-κB p65 and CTGF were upregulated; and NLRP3 inflammasome and its related target proteins, IL-1β and IL-18, were also increased. Treatment with rotenone, an inhibitor of mitochondrial complex I, significantly attenuated oxidative stress, mitochondrial dysfunction, and inflammasome response in aldosterone-infused rats.

CONCLUSIONS

Rotenone ameliorated aldosterone-infused renal injury, possibly by inhibiting oxidative stress, mitochondrial dysfunction, and NLRP3 inflammasome activity. These results provide novel evidence for the role of rotenone in aldosterone-induced renal injury or other chronic kidney disease.