The role of aldosterone and aldosterone blockade in hypertension

Hypertension is the most prevalent and significant modifiable risk factor for cardiovascular disease.1 It has been estimated that 7.6 million premature deaths and 54% of stroke and 47% of ischemic heart disease worldwide are attributable to elevated blood pressure levels.2 Blood pressure regulation is a complex process involving several organs, including the heart, brain, kidneys and vasculature. The renin-angiotensin-aldosterone system (RAAS) has a central role in blood pressure regulation. A decrease in renal perfusion leads to the synthesis and release of renin by the juxtaglomerular cells in the afferent arterioles of the kidney. Renin converts angiotensinogen, which is produced in the liver, to angiotensin I (Ang I). This is subsequently converted to angiotensin II (Ang II) by angiotensin-converting enzyme (ACE) in vascular tissues. Ang II increases blood pressure via Ang II type 1 receptor (AT1R)-mediated vasoconstriction, by increasing sympathetic tone and by stimulation of arginine vasopressin release.3 Ang II also stimulates sodium and water reabsorption by a direct action in the kidney, and indirectly by stimulating aldosterone synthesis and release in the adrenal gland.3 When blood pressure goes up, the increase in renal perfusion will slow down renin release, thereby providing a negative feedback mechanism regulating RAAS activity to its required level. Figure 1 shows a schematic overview of the RAAS

Drug mechanisms to help in managing resistant hypertension in obesity

Obesity is a major risk factor for the development of hypertension. Because the prevalence of obesity is increasing worldwide, the prevalence of obesity hypertension is also increasing. Importantly, hypertension in obesity is commonly complicated by dyslipidemia and type 2 diabetes mellitus and hence imposes a high cardiovascular disease risk. Furthermore, obesity is strongly associated with resistant hypertension. Activation of the sympathetic nervous system and the renin-angiotensin system, leading to renal sodium and water retention, links obesity with hypertension. There is also evidence for the release of factors by visceral adipose tissue promoting excessive aldosterone production, and a more central role of aldosterone in obesity hypertension is emerging. Randomized studies evaluating the effect of different classes of antihypertensive agents in obesity hypertension are scarce, short-lasting, and small. Considering the emerging role of aldosterone in the pathogenesis of obesity hypertension, mineralocorticoid receptor antagonism may play a more central role in the pharmacologic treatment of obesity hypertension in the near future

Host–receptor post-translational modifications refine staphylococcal leukocidin cytotoxicity

Staphylococcal bi-component pore-forming toxins, also known as leukocidins, target and lyse human phagocytes in a receptor-dependent manner. S-components of the leukocidins Panton-Valentine leukocidin (PVL), γ-haemolysin AB (HlgAB) and CB (HlgCB), and leukocidin ED (LukED) specifically employ receptors that belong to the class of G-protein coupled receptors (GPCRs). Although these receptors share a common structural architecture, little is known about the conserved characteristics of the interaction between leukocidins and GPCRs. In this study, we investigated host cellular pathways contributing to susceptibility towards S. aureus leukocidin cytotoxicity. We performed a genome-wide CRISPR/Cas9 library screen for toxin-resistance in U937 cells sensitized to leukocidins by ectopic expression of different GPCRs. Our screen identifies posttranslational modification (PTM) pathways involved in the sulfation and sialylation of the leukocidin-receptors. Subsequent validation experiments show differences in the impact of PTM moieties on leukocidin toxicity, highlighting an additional layer of refinement and divergence in the staphylococcal host-pathogen interface. Leukocidin receptors may serve as targets for anti-staphylococcal interventions and understanding toxin-receptor interactions will facilitate the development of innovative therapeutics. Variations in the genes encoding PTM pathways could provide insight into observed differences in susceptibility of humans to infections with S. aureus

Skewed X-inactivation is common in the general female population

X-inactivation is a well-established dosage compensation mechanism ensuring that X-chromosomal genes are expressed at comparable levels in males and females. Skewed X-inactivation is often explained by negative selection of one of the alleles. We demonstrate that imbalanced expression of the paternal and maternal X-chromosomes is common in the general population and that the random nature of the X-inactivation mechanism can be sufficient to explain the imbalance. To this end, we analyzed blood-derived RNA and whole-genome sequencing data from 79 female children and their parents from the Genome of the Netherlands project. We calculated the median ratio of the paternal over total counts at all X-chromosomal heterozygous single-nucleotide variants with coverage ≥10. We identified two individuals where the same X-chromosome was inactivated in all cells. Imbalanced expression of the two X-chromosomes (ratios ≤0.35 or ≥0.65) was observed in nearly 50% of the population. The empirically observed skewing is explained by a theoretical model where X-inactivation takes place in an embryonic stage in which eight cells give rise to the hematopoietic compartment. Genes escaping X-inactivation are expressed from both alleles and therefore demonstrate less skewing than inactivated genes. Using this characteristic, we identified three novel escapee genes (SSR4, REPS2, and SEPT6), but did not find support for many previously reported escapee genes in blood. Our collective data suggest that skewed X-inactivation is common in the general population. This may contribute to manifestation of symptoms in carriers of recessive X-linked disorders. We recommend that X-inactivation results should not be used lightly in the interpretation of X-linked variants

SDHAF2 (PGL2-SDH5) and hereditary head and neck paraganglioma

Contains fulltext : 97331.pdf (publisher's version ) (Closed access)PURPOSE: Hereditary head and neck paraganglioma (HNPGL) syndromes are associated with mutations in the SDHD(PGL1), SDHC(PGL3), and SDHB(PGL4) genes encoding succinate dehydrogenase subunits. We recently described mutations in a previously uncharacterized human gene, now called SDHAF2, and showed that this was the long-sought "imprinted" PGL2 gene. Here, we present a new branch of the Dutch SDHAF2 (PLG2-SDH5) family. EXPERIMENTAL DESIGN: The SDHAF2 family has been collected over a 30-year period. The family described here was linked to PGL2 and at-risk family members were invited to participate in this study. Patients were investigated and treated dependent on tumor size and localization. All family members have now been analyzed for the SDHAF2 mutation status. RESULTS: Among the 57 family members, 23 were linkage positive including 7 risk-free carriers (maternal imprinting). Of the 16 at-risk individuals, 11 had a total of 24 tumors with primarily carotid (71%) and vagal locations (17%). Multifocality of tumors was prominent (91%). Malignancy was not detected. The average age at onset was 33 years, and many patients (42%) were asymptomatic prior to screening. SDHAF2 mutation analysis confirmed the findings of the previously performed linkage analysis without detection of discrepancies. CONCLUSIONS: We established the SDHAF2 mutation status of PGL2 family members. Phenotypic characterization of this family confirms the currently exclusive association of SDHAF2 mutations with HNPGL. This SDHAF2 family branch shows a young age at onset and very high levels of multifocality. A high percentage of patients were asymptomatic at time of detection

A DGGE system for comprehensive mutation screening of BRCA1 and BRCA2: Application in a Dutch cancer clinic setting

Rapid and reliable identification of deleterious changes in the breast cancer genes BRCA1 and BRCA2 has become one of the major issues in most DNA services laboratories. To rapidly detect all possible changes within the coding and splice site determining sequences of the breast cancer genes, we established a semiautomated denaturing gradient gel electrophoresis (DGGE) mutation scanning system. All exons of both genes are covered by the DGGE scan, comprising 120 amplicons. We use a semiautomated approach, amplifying all individual amplicons with the same PCR program, after which the amplicons are pooled. DGGE is performed using three slightly different gel conditions. Validation was performed using DNA samples with known sequence variants in 107 of the 120 amplicons; all variants were detected. This DGGE mutation scanning, in combination with a PCR test for two Dutch founder deletions in BRCA1 was then applied in 431 families in which 52 deleterious changes and 70 unclassified variants were found. Fifteen unclassified variants were not reported before. The system was easily adopted by five other laboratories, where in another 3,593 families both exons 11 were analyzed by the protein truncation test (PTT) and the remaining exons by DGGE. In total, a deleterious change (nonsense, frameshift, splice-site mutation, or large deletion) was found in 661 families (16.4%), 462 in BRCA1 (11.5%), 197 in BRCA2 (4.9%), and in two index cases a deleterious change in both BRCA1 and BRCA2 was identified. Eleven deleterious changes in BRCA1 and 36 in BRCA2 had not been reported before. In conclusion, this DGGE mutation screening method for BRCA1 and BRCA2 is proven to be highly sensitive and is easy to adopt, which makes screening of large numbers of patients feasible. The results of screening of BRCA1 and BRCA2 in more than 4,000 families present a valuable overview of mutations in the Dutch population