Oxidative stress-related proteins in a Conn's adenoma tissue. Relevance for aldosterone's prooxidative and proinflammatory activity

Cellular Senescence in Adrenocortical Biology and Its Disorders

Cellular senescence is considered a physiological process along with aging and has recently been reported to be involved in the pathogenesis of many age-related disorders. Cellular senescence was first found in human fibroblasts and gradually explored in many other organs, including endocrine organs. The adrenal cortex is essential for the maintenance of blood volume, carbohydrate metabolism, reaction to stress and the development of sexual characteristics. Recently, the adrenal cortex was reported to harbor some obvious age-dependent features. For instance, the circulating levels of aldosterone and adrenal androgen gradually descend, whereas those of cortisol increase with aging. The detailed mechanisms have remained unknown, but cellular senescence was considered to play an essential role in age-related changes of the adrenal cortex. Recent studies have demonstrated that the senescent phenotype of zona glomerulosa (ZG) acts in association with reduced aldosterone production in both physiological and pathological aldosterone-producing cells, whereas senescent cortical-producing cells seemed not to have a suppressed cortisol-producing ability. In addition, accumulated lipofuscin formation, telomere shortening and cellular atrophy in zona reticularis cells during aging may account for the age-dependent decline in adrenal androgen levels. In adrenocortical disorders, including both aldosterone-producing adenoma (APA) and cortisol-producing adenoma (CPA), different cellular subtypes of tumor cells presented divergent senescent phenotypes, whereby compact cells in both APA and CPA harbored more senescent phenotypes than clear cells. Autonomous cortisol production from CPA reinforced a local cellular senescence that was more severe than that in APA. Adrenocortical carcinoma (ACC) was also reported to harbor oncogene-induced senescence, which compensatorily follows carcinogenesis and tumor progress. Adrenocortical steroids can induce not only a local senescence but also a periphery senescence in many other tissues. Therefore, herein, we systemically review the recent advances related to cellular senescence in adrenocortical biology and its associated disorders.

ROCK (RhoA/Rho Kinase) in Cardiovascular-Renal Pathophysiology: A Review of New Advancements

Rho-associated, coiled-coil containing kinases (ROCK) were originally identified as effectors of the RhoA small GTPase and found to belong to the AGC family of serine/threonine kinases. They were shown to be downstream effectors of RhoA and RhoC activation. They signal via phosphorylation of proteins such as MYPT-1, thereby regulating many key cellular functions including proliferation, motility and viability and the RhoA/ROCK signaling has been shown to be deeply involved in arterial hypertension, cardiovascular–renal remodeling, hypertensive nephropathy and posttransplant hypertension. Given the deep involvement of ROCK in cardiovascular–renal pathophysiology and the interaction of ROCK signaling with other signaling pathways, the reports of trials on the clinical beneficial effects of ROCK’s pharmacologic targeting are growing. In this current review, we provide a brief survey of the current understanding of ROCK-signaling pathways, also integrating with the more novel data that overall support a relevant role of ROCK for the cardiovascular–renal physiology and pathophysiology.

GSTA1 Expression Is Correlated With Aldosterone Level in KCNJ5-Mutated Adrenal Aldosterone-Producing Adenoma

CONTEXT

KCNJ5 mutation is a major cause of aldosterone-producing adenomas (APAs). The development of APA apart from KCNJ5 mutation is less investigated.

OBJECTIVE

To investigate other mechanisms affecting aldosterone secretion apart from KCNJ5.

PATIENTS AND METHODS

Six pairs of KCNJ5-mutated, high and low aldosterone-secreting APAs, five non-KCNJ5-mutated APAs, and four normal adrenal glands were assayed by Affymetrix GeneChip Human Transcriptome Array 2.0. A total of 113 APA samples were investigated to explore the expression of glutathione-S-transferase A1 (GSTA1). H295R cells were used to verify the function of GSTA1.

RESULTS

GSTA1 was the top gene downregulated in high-aldosterone KCNJ5-mutated APAs. GSTA1 was also downregulated in KCNJ5-mutated APAs compared with wild-type KCNJ5 APAs. Accordingly, mutant KCNJ5 decreased GSTA1 messenger RNA and protein expression levels. GSTA1 overexpression suppressed aldosterone secretion whether in wild-type or mutant KCNJ5 H295R cells. Adding ethacrynic acid or silencing of GSTA1 increased aldosterone secretion by increasing reactive oxygen species (ROS), superoxide, H2O2 levels, and Ca2+ influx. The expression of the transcription factors NR4A1, NR4A2, and CAMK1 and intracellular Ca2+ were significantly upregulated by GSTA1 inhibition. The reduced form of NAD phosphate oxidase inhibitor or H2O2 scavenger or blocking calmodulin or calcium channels could significantly reduce aldosterone secretion in GSTA1-inhibited cells.

CONCLUSIONS

(1) GSTA1 expression is reversely correlated with aldosterone level in KCNJ5-mutated APAs, (2) GSTA1 regulates aldosterone secretion by ROS and Ca2+ signaling, and (3) KCNJ5 mutation downregulates GSTA1 expression, and overexpression of GSTA1 reverses increased aldosterone in KCNJ5-mutated adrenal cells.

Associations of aldosterone and renin concentrations with inflammation-the Study of Health in Pomerania and the German Conn's Registry

PURPOSE

Chronic inflammation is an age-independent and body mass index-independent contributor to the development of multi-morbidity. Alterations of the renin-angiotensin-aldosterone system are observed within the context of proinflammatory states. We assessed circulating aldosterone, renin, and inflammatory biomarker concentrations in healthy, normotensive subjects and patients with primary aldosteronism.

METHODS

We included 1177 normotensive individuals from the population-based Study of Health in Pomerania (first follow-up, Study of Health in Pomerania-1) and 103 primary aldosteronism patients from the German Conn's Registry. A 1:1 matching for sex, age, body mass index, smoking status, diabetes mellitus, and the estimated glomerular filtration rate was performed to determine whether primary aldosteronism patients exhibit higher inflammatory biomarker concentrations than normotensive controls. The associations of plasma aldosterone concentration or plasma renin concentration with circulating fibrinogen concentrations, white blood cell count, and high sensitive C-reactive protein concentrations in the normotensive sample were determined with multivariable linear and logistic regression analyses.

RESULTS

1:1 matched primary aldosteronism patients demonstrated significantly (p < 0.01) higher plasma aldosterone concentration (198 vs. 47 ng/l), lower plasma renin concentration (3.1 vs. 7.7 ng/l) and higher high sensitive C-reactive protein concentrations (1.5 vs. 1.0 mg/l) than normotensive controls. Within the normotensive cohort, plasma renin concentration but not plasma aldosterone concentration was positively associated with fibrinogen concentrations and white blood cell count. Further, a J-shaped association between plasma renin concentration and high sensitive C-reactive protein concentrations was detected.

CONCLUSIONS

High plasma aldosterone concentration in a primary aldosteronism cohort and high plasma renin concentration in normotensive subjects are associated with increased concentrations of inflammatory biomarkers. This suggests a link between the renin-angiotensin-aldosterone system and inflammatory processes in patients with primary aldosteronism and even in normotensive subjects.

Transcriptome Pathway Analysis of Pathological and Physiological Aldosterone-Producing Human Tissues

Supplemental Digital Content is available in the text.

Primary aldosteronism is present in ≈10% of hypertensives. We previously performed a microarray assay on aldosterone-producing adenomas and their paired zona glomerulosa and fasciculata. Confirmation of top genes validated the study design and functional experiments of zona glomerulosa selective genes established the role of the encoded proteins in aldosterone regulation. In this study, we further analyzed our microarray data using AmiGO 2 for gene ontology enrichment and Ingenuity Pathway Analysis to identify potential biological processes and canonical pathways involved in pathological and physiological aldosterone regulation. Genes differentially regulated in aldosterone-producing adenoma and zona glomerulosa were associated with steroid metabolic processes gene ontology terms. Terms related to the Wnt signaling pathway were enriched in zona glomerulosa only. Ingenuity Pathway Analysis showed "NRF2-mediated oxidative stress response pathway" and "LPS (lipopolysaccharide)/IL-1 (interleukin-1)–mediated inhibition of RXR (retinoid X receptor) function" were affected in both aldosterone-producing adenoma and zona glomerulosa with associated genes having up to 21- and 8-fold differences, respectively. Comparing KCNJ5-mutant aldosterone-producing adenoma, zona glomerulosa, and zona fasciculata samples with wild-type samples, 138, 56, and 59 genes were differentially expressed, respectively (fold-change >2; P<0.05). ACSS3, encoding the enzyme that synthesizes acetyl-CoA, was the top gene upregulated in KCNJ5-mutant aldosterone-producing adenoma compared with wild-type. NEFM, a gene highly upregulated in zona glomerulosa, was upregulated in KCNJ5 wild-type aldosterone-producing adenomas. NR4A2, the transcription factor for aldosterone synthase, was highly expressed in zona fasciculata adjacent to a KCNJ5-mutant aldosterone-producing adenoma. Further interrogation of these genes and pathways could potentially provide further insights into the pathology of primary aldosteronism.

Role of Nox2 and p22phox in Persistent Postoperative Hypertension in Aldosterone-Producing Adenoma Patients after Adrenalectomy

Adrenal aldosterone-producing adenoma (APA), producing the salt-retaining hormone aldosterone, commonly causes secondary hypertension, which often persists after unilateral adrenalectomy. Although persistent hypertension was correlated with residual hormone aldosterone, the in vivo mechanism remains unclear. NADPH oxidase is the critical cause of aldosterone synthesis in vitro. Nox2 and p22phox comprise the NADPH oxidase catalytic core, serving to initiate a reactive oxygen species (ROS) cascade that may participate in the pathology. mRNAs of seven NADPH oxidase isoforms in APA were evaluated by RT-PCR and Q-PCR and their proteins by immunohistochemistry and Western blotting. NADPH oxidase activity was also detected. Nox2 and p22phox were especially abundant in APA. Particularly higher Nox2 and p22phox gene and protein levels were seen in APA than controls. Significant correlations between Nox2 mRNA and aldosterone synthase (CYP11B2) mRNA (R = 0.66, P < 0.01) and Nox2 protein and baseline plasma aldosterone concentration (PAC) (R = 0.503, P < 0.01) were detected in APA; however, none were found between p22phox mRNA, CYP11B2 mRNA, p22phox protein, and baseline PAC. Importantly, we found that Nox2 localized specifically in hyperplastic zona glomerulosa cells. In conclusion, our results highlight that Nox2 and p22phox may be directly involved in pathological aldosterone production and zona glomerulosa cell proliferation after APA resection.

Prevalence and clinical correlates of somatic mutation in aldosterone producing adenoma-Taiwanese population

Primary aldosteronism (PA) is a common form of secondary hypertension and has significant cardiovascular consequences. Mutated channelopathy due to the activation of calcium channels has been recently described in aldosterone-producing adenoma (APA). The study involved 148 consecutive PA patients, (66 males; aged 56.3 ± 12.3years) who received adrenalectomy, and were collected from the Taiwan PA investigator (TAIPAI) group. A high rate of somatic mutation in APA was found (n=91, 61.5%); including mutations in KCNJ5 (n=88, 59.5%), ATP1A1 (n=2, 1.4%), and ATP2B3 (n=1, 0.7%); however, no mutations in CACNA1D were identified. Mutation-carriers were younger (<0.001), had lower Cyst C (p=0.042), pulse wave velocity (p=0.027), C-reactive protein (p=0.042) and a lower rate of proteinuria (p=0.031) than non-carriers. After multivariate adjustment, mutation carriers had lower serum CRP levels than non-carriers (p=0.031. Patients with mutation also had a greater chance of recovery from hypertension after operation (p=0.005). A high incidence of somatic mutations in APA was identified in the Taiwanese population. Mutation-carriers had lower CRP levels and a higher rate of cure of hypertension after adrenalectomy. This raises the possibility of using mutation screening as a tool in predicting long-term outcome after adrenalectomy.

Aldosterone, oxidative stress, and NF-κB activation in hypertension-related cardiovascular and renal diseases

The mineralocorticoid aldosterone regulates electrolyte and fluid balance and is involved in blood pressure homoeostasis. Classically, it binds to its intracellular mineralocorticoid receptor to induce expression of proteins influencing the reabsorption of sodium and water in the distal nephron. Aldosterone gained special attention when large clinical studies showed that blocking its receptor in patients with cardiovascular diseases reduced their mortality. These patients present increased plasma aldosterone levels. The exact mechanisms of the potential toxic effects of aldosterone leading to cardiovascular damage are not known yet. The observation of reduced nitric oxide bioavailability in hyperaldosteronism implied the generation of oxidative stress by aldosterone. Subsequent studies confirmed the increase of oxidative stress markers in patients with chronic heart failure and in animal models of hyperaldosteronism. The effects of reactive oxygen species have been related to the activation of transcription factors, such as NF-κB. This review summarizes the present-day knowledge of aldosterone-induced oxidative stress and NF-κB activation in humans and different experimental models.

Salinomycin inhibits prostate cancer growth and migration via induction of oxidative stress

BACKGROUND

We have shown that a sodium ionophore monensin inhibits prostate cancer cell growth. A structurally related compound to monensin, salinomycin, was recently identified as a putative cancer stem cell inhibitor.

METHODS

The growth inhibitory potential of salinomycin was studied in a panel of prostate cells. To get insights into the mechanism of action, a variety of assays such as gene expression and steroid profiling were performed in salinomycin-exposed prostate cancer cells.

RESULTS

Salinomycin inhibited the growth of prostate cancer cells, but did not affect non-malignant prostate epithelial cells. Salinomycin impacted on prostate cancer stem cell functions as evidenced by reduced aldehyde dehydrogenase activity and the fraction of CD44(+) cells. Moreover, salinomycin reduced the expression of MYC, AR and ERG, induced oxidative stress as well as inhibited nuclear factor-κB activity and cell migration. Furthermore, profiling steroid metabolites revealed increased levels of oxidative stress-inducing steroids 7-ketocholesterol and aldosterone and decreased levels of antioxidative steroids progesterone and pregnenolone in salinomycin-exposed prostate cancer cells.

CONCLUSION

Our results indicate that salinomycin inhibits prostate cancer cell growth and migration by reducing the expression of key prostate cancer oncogenes, inducing oxidative stress, decreasing the antioxidative capacity and cancer stem cell fraction.

Diagnosis and treatment of primary aldosteronism

Primary aldosteronism involves more than 11% of hypertensive patients who are referred to specialized centers for the diagnosis and treatment of hypertension. If not diagnosed early it causes an excess damage to the heart, vessels and kidney, which translates into an cardiovascular events. Since these ominous consequences can be corrected with a timely diagnosis and an appropriate therapy, physicians should exercise a high degree of alert concerning the possibility that primary aldosteronism is present in hypertensive patients. The purpose of this review is to provide up-dated information on the strategy for case detection, the subtype differentiation and the management of primary aldosteronism.