Background— Lysosomal carboxypeptidase, cathepsin A (protective protein, CathA), is a component of the lysosomal multienzyme complex along with β-galactosidase (GAL) and sialidase Neu1, where it activates Neu1 and protects GAL and Neu1 against the rapid proteolytic degradation. On the cell surface, CathA, Neu1, and the enzymatically inactive splice variant of GAL form the elastin-binding protein complex. In humans, genetic defects of CathA cause galactosialidosis, a metabolic disease characterized by combined deficiency of CathA, GAL, and Neu1 and a lysosomal storage of sialylated glycoconjugates. However, several phenotypic features of galactosialidosis patients, including hypertension and cardiomyopathies, cannot be explained by the lysosomal storage. These observations suggest that CathA may be involved in hemodynamic functions that go beyond its protective activity in the lysosome. Methods and Results— We generated a gene-targeted mouse in which the active CathA was replaced with a mutant enzyme carrying a Ser190Ala substitution in the active site. These animals expressed physiological amounts of catalytically inactive CathA protein, capable of forming lysosomal multienzyme complex, and did not develop secondary deficiency of Neu1 and GAL. Conversely, the mice showed a reduced degradation rate of the vasoconstrictor peptide, endothelin-1, and significantly increased arterial blood pressure. CathA-deficient mice also displayed scarcity of elastic fibers in lungs, aortic adventitia, and skin. Conclusions— Our results provide the first evidence that CathA acts in vivo as an endothelin-1–inactivating enzyme and strongly confirm a crucial role of this enzyme in effective elastic fiber formation.
Abstract This study demonstrates the presence of both atrial natriuretic peptide (ANP) precursor and ANP transcripts in the rat olfactory bulb (OB), a key brain structure involved in the generation of olfaction‐dependent behavior. In addition to synthesizing ANP, the OB contains ANP‐transducing receptors coupled to the guanylate cyclase system but it is devoid of ANP “clearance receptors.” The characterization of biologically active ANP receptors and the evidence for in situ ANP synthesis in this region of the CNS adds credence to the hypothesis that the peptide plays a putative role in olfaction.
Bilateral macronodular adrenal hyperplasia (BMAH) is a rare cause of Cushing's syndrome (CS) and its familial clustering has been described previously. Recent studies identified that ARMC5 mutations occur frequently in BMAH, but the relation between ARMC5 mutation and the expression of aberrant G-protein-coupled receptor has not been examined in detail yet.We studied a large French-Canadian family with BMAH and sub-clinical or overt CS. Screening was performed using the 1-mg dexamethasone suppression test (DST) in 28 family members. Screening for aberrant regulation of cortisol by various hormone receptors were examined in vivo in nine individuals. Sequencing of the coding regions of ARMC5 gene was carried out.Morning ambulating cortisol post 1 mg DST were >50 nmol/l in 5/8 members in generation II (57-68 years old), 9/22 in generation III (26-46 years old). Adrenal size was enlarged at different degrees. All affected patients increased cortisol following upright posture, insulin-induced hypoglycemia and/or isoproterenol infusion. β-blockers led to the reduction of cortisol secretion in all patients with the exception of two who had adrenalectomies because of β-blockers intolerance. We identified a heterozygous germline variant in the ARMC5 gene c.327_328insC, (p.Ala110Argfs*9) in nine individuals with clinical or subclinical CS, in four out of six individuals with abnormal suppression to dexamethasone at initial investigation and one out of six individuals with current normal clinical screening tests.Systematic screening of members of the same family with hereditary BMAH allows the diagnosis of unsuspected subclinical CS associated with early BMAH. The relation between the causative ARMC5 mutation and the reproducible pattern of aberrant β-adrenergic and V1-vasopressin receptors identified in this family remains to be elucidated.
In smooth muscles, inhibition of Na+,K+,2Cl- cotransport (NKCC) by bumetanide decreased intracellular Cl- content ([Cl-]i) and suppressed the contractions triggered by diverse stimuli. This study examines whether or not bicarbonate, a regulator of several Cl- transporters, affects the impact of NKCC in excitation-contraction coupling. Addition of 25 mM NaHCO3 attenuated the inhibitory action of bumetanide on mesenteric artery contractions evoked by 30 mM KCl and phenylephrine (PE) by 5 and 3-fold, respectively. In cultured vascular smooth muscle cells, NaHCO3 almost completely abolished inhibitory actions of bumetanide on transient depolarization and [Ca2+]i elevation triggered by PE. In bicarbonate-free medium, bumetanide decreased [Cl-]i by ∼15%; this effect was almost totally abrogated by NaHCO3. The addition of NaHCO3 resulted in 2-fold inhibition of NKCC activity and 3-fold attenuation of [Cl-]i. These data strongly suggest that extracellular HCO3- diminishes the NKCC-sensitive component of excitation-contraction coupling via suppression of this carrier.
Noninvasive micro-vascular ultrasound elastography (MicroNIVE) was recently proposed for insitu phenotyping in rat models of hypertension through the assessment of mechanical properties of carotid arteries. This paper reports comparisons between MicroNIVE and M-Mode strain measurements. Brown Norway male rats (n = 5) were investigated over 24 weeks. The common carotid arteries were imaged with an ultrasound biomicroscope equipped with a 40-MHz central frequency probe and an external workstation to collect radio-frequency (RF) data. Time-sequences of RF and M-mode signals were recorded over several consecutive cardiac cycles. MicroNIVE strain cartographies were computed for each pair of successive RF images with the Lagrangian Speckle Model Estimator. Diastolic strain (s D ) and systolic strain (s s ) parameters were estimated. M- mode strain estimations were computed as s M (t) = (w(t)-w max )/w max , with w(t) and w max being the wall thicknesses at time "t" and at end-diastole, respectively. MicroNIVE diastolic and systolic strains were consistent with a Pearson correlation coefficient (r) of 0.75 (p < 10 -11 ). M-mode and MicroNIVE strain measurements were correlated with r = 0.74 (p < 10 -5 ) between s M and s D and r = 0.67 (p < 10 -4 ) between s M and s s . Corroborated by Bland-Altman plots, M-mode and MicroNIVE were found in very good concordance.
Epidemiological studies show strong associations between kidney dysfunction and risk of ischemic stroke (IS), the mechanisms of which are incompletely understood. We investigated whether these associations may reflect shared heritability because of a common polygenic basis and whether this differed for IS subtypes.Polygenic models were derived using genome-wide association studies meta-analysis results for 3 kidney traits: estimated glomerular filtration rate using serum creatinine (eGFRcrea: n=73 998), eGFR using cystatin C (eGFRcys: n=22 937), and urinary albumin to creatinine ratio (n=31 580). For each, single nucleotide polymorphisms passing 10 P value thresholds were used to form profile scores in 4561 IS cases and 7094 controls from the United Kingdom, Germany, and Australia. Scores were tested for association with IS and its 3 aetiological subtypes: large artery atherosclerosis, cardioembolism, and small vessel disease.Polygenic scores correlating with higher eGFRcrea were associated with reduced risk of large artery atherosclerosis, with 5 scores reaching P<0.05 (peak P=0.004) and all showing the epidemiologically expected direction of effect. A similar pattern was observed for polygenic scores reflecting higher urinary albumin to creatinine ratio, of which 3 associated with large artery atherosclerosis (peak P=0.01) and all showed the expected directional association. One urinary albumin to creatinine ratio-based score also associated with small vessel disease (P=0.03). The global pattern of results was unlikely to have occurred by chance (P=0.02).This study suggests possible polygenic correlation between renal dysfunction and IS. The shared genetic components may be specific to stroke subtypes, particularly large artery atherosclerotic stroke. Further study of the genetic relationships between these disorders seems merited.
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