Mechanical stretch and peptide growth factors in the regulation of the hypertrophic response of cardiomyocytes:ANP and BNP as model genes

Abstract Cardiac hypertrophy is the primary adaptive mechanism of the heart to increased workload, though when advanced, it becomes a leading predictor for heart failure and sudden death. The growth stimulus elicited by a hemodynamic load is attributable to a combination of mechanical and neurohumoral factors, but the precise roles of individual growth promoting components are still unclear. This study utilized atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) as model genes with which to investigate the involvement and mechanisms of mechanical stress and peptide growth factors in hypertrophic response of cardiac myocytes. The direct effect of mechanical stretch was studied in two different in vitro models of cultured neonatal rat cardiomyocytes. In the first approach, hypo-osmotic swelling -induced stretch increased ANP mRNA levels in atrial cells. In the second model, cyclic mechanical stretch of ventricular cells grown on flexible membranes evoked ANP and BNP gene expression and secretion. The mechanisms of stretch-induced BNP gene expression were studied by measurement of the activities of transcription factors and by utilizing promoter analysis together with site specific mutations. Stretch activated the binding of the transcription factor GATA-4 similarly to pressure overload in vivo. Mutational studies revealed that specific GATA consensus sites on the BNP promoter, in combination with an Nkx-2.5 binding element, were critical for stretch-activated BNP transcription. Importantly, a reduction of GATA-4 protein levels inhibited the stretch-induced hypertrophic response. Both cyclic mechanical stretchin vitro and hemodynamic overload in vivo activated the expression of peptide growth factor bone morphogenetic protein-2 (BMP-2). The effects of BMP-2 closely resembled those of mechanical stretch including the increase in the expressions of ANP and BNP. Furthermore, the BMP antagonist noggin inhibited the effect of stretch on ANP and BNP. Fibroblast growth factor 1 stimulated ANP synthesis and secretion in a protein kinase C dependent manner. In conclusion, this work demonstrates that mechanical stretch per se is sufficient to activate the hypertrophic gene program in cardiac myocytes. This effect seems to be at least partially mediated by the growth factor BMP-2 acting in a paracrine manner. The activation of the GATA-4 transcription factor, in cooperation with a factor binding to the Nkx-2.5 binding element, is essential for mechanical stretch-induced cardiomyocyte hypertrophy.Tiivistelmä Sydämen tärkein mukautumiskeino kohonneeseen työmäärään on sydänlihaksen kasvu. Sydänlihaksen liikakasvu on kuitenkin tärkein sydämen vajaatoiminnan ja äkkikuoleman ennustetekijä. Hemodynaamisen ylikuormituksen kasvua edistävä vaikutus on lukuisten mekaanisten ja neurohumoraalisten tekijöiden summa, jossa kunkin yksittäisen tekijän osuus on vielä epäselvä. Tässä väitöskirjatyössä tutkittiin mekaanisen venytyksen ja peptidikasvutekijöiden osuutta ja vaikutusmekanismeja sydämen liikakasvun synnyssä käyttämällä malligeeneinä sydämen eteispeptidiä (ANP) ja B-tyypin natriureettista peptidiä (BNP). Mekaanisen venytyksen välitöntä vaikutusta tutkittiin vastasyntyneen rotan sydänsoluviljelymalleissa. Osmolaliteetin muutoksella aiheutettu venytys lisäsi ANP:n lähetti-RNA-tasoja eteissoluissa. Venyväpohjaisilla kalvoilla kasvatettujen kammiosolujen syklinen venytys stimuloi ANP:n ja BNP:n geeniekspressiota ja eritystä. BNP:n geenisäätelymekanismeja tutkittiin mittaamalla transkriptiotekijöiden aktiivisuutta sekä geeninsiirtokokeilla hyödyntäen muunneltuja BNP:n geenisäätelyalueita. Venytys lisäsi transkriptiotekijä GATA-4:n sitoutumisaktiivisuutta samaan tapaan kuin painekuormitus koe-eläimillä. Tietyt BNP:n säätelyalueen GATA-sitoutumispaikat yhdessä Nkx-2.5:ttä sitovan elementin kanssa osoittautuivat tärkeiksi venytysvasteen kannalta. GATA-4 -proteiinitasojen vähentäminen esti venytyksen aiheuttamaa kasvuvastetta. Sekä syklinen mekaaninen venytys soluviljelykokeissa että hemodynaaminen ylikuormitus koe-eläimillä lisäsivät peptidikasvutekijä bone morphogenetic protein-2:n (BMP-2) geeniekspressiota. BMP-2:n suorat vaikutukset puolestaan muistuttivat läheisesti mekaanisen venytyksen vaikutusta, ANP:n ja BNP:n lisääntynyt geeniekspressio mukaan lukien. BMP-antagonisti noggin esti lisäksi venytyksen vaikutusta ANP:iin ja BNP:iin. Työssä osoitettiin myös, että fibroblastikasvutekijä 1 stimuloi ANP:n synteesiä ja eritystä proteiinikinaasi C:n välityksellä. Yhteenvetona tulokset osoittavat, että mekaaninen venytys itsessään riittää aktivoimaan sydänlihaksen kasvuun liittyvää geeniohjelmaa. Vasteen välittäjänä näyttää kuitenkin ainakin osittain toimivan paikallisesti tuotettu BMP-2. Edelleen, transkriptiotekijä GATA-4 yhdessä Nkx-2.5 -elementtiin sitoutuvan tekijän kanssa osoittautui välttämättömäksi mekaanisen venytyksen aiheuttamalle kasvuvasteelle

Effects of a two-year home-based exercise training program on oxidized LDL and HDL lipids in coronary artery disease patients with and without type-2 diabetes

Abstract We investigated the effect of two-year home-based exercise training program on oxidized low-density lipoprotein LDL (ox-LDL) and high-density lipoprotein HDL (ox-HDL) lipids in patients with coronary artery disease (CAD), both with and without type-2 diabetes (T2D). Analysis of lipoprotein-oxidized lipids was based on the determination of baseline conjugated dienes in lipoprotein lipids. In order to study the effect of an exercise load on ox-LDL and ox-HDL lipids patients in both CAD and CAD + T2D intervention, groups were divided in three based on exercise load (high, medium, and low). During the two-year home-based exercise training program, the study showed that only higher training volume resulted in a decreased concentration of ox-LDL, while the two groups with lower training volumes showed no change. This result indicates that the training load needs to be sufficiently high in order to decrease the concentration of atherogenic ox-LDL lipids in patients with CAD and CAD + T2D. Interestingly, the concentration of ox-HDL did not change in any of the subgroups. This could indicate that the lipid peroxide-transporting capacity of HDL, suggested by results from exercise training studies in healthy adults, may not function similarly in CAD patients with or without T2D. Moreover, the lipid-lowering medication used may have had an influence on these results

Thymic neuroendocrine tumors in patients with multiple endocrine neoplasia type 1

Abstract Objective: MEN1 is associated with an increased risk of developing tumors in different endocrine organs. Neuroendocrine tumors of the thymus (TNETs) are very rare but often have an aggressive nature. We evaluated patients with MEN1 and TNET in three university hospitals in Finland. Design/Methods: We evaluated patient records of 183 MEN1-patients from three university hospitals between the years 1985–2019 with TNETs. Thymus tumor specimens were classified according to the new WHO 2021 classification of TNET. We collected data on treatments and outcomes of these patients. Results: There were six patients (3.3%) with MEN1 and TNET. Five of them had the same common gene mutation occurring in Finland. They originated from common ancestors encompassing two pairs of brothers from sequential generations. The mean age at presentation of TNET was 44.7 ± 11.9 years. TNET was classified as atypical carcinoid (AC) in five out of six patients. One patient had a largely necrotic main tumor with very few mitoses and another nodule with 25 mitoses per 2 mm², qualifying for the 2021 WHO diagnosis of large cell neuroendocrine carcinoma (LCNEC). In our patients, the 5-year survival of the TNET patients was 62.5% and 10-year survival 31.3%. Conclusion: In this study, TNETs were observed in one large MEN1 founder pedigree, where an anticipation-like earlier disease onset was observed in the most recent generation. TNET in MEN1 patients is an aggressive disease. The prognosis can be better by systematic screening. We also show that LCNEC can be associated with TNET in MEN1 patients

A family with A20 haploinsufficiency presenting with novel clinical manifestations and challenges for treatment

Abstract Background: Tumor necrosis factor α–induced protein 3 gene (TNFAIP3, also called A20) haploinsufficiency (HA20) leads to autoinflammation and autoimmunity. We have recently shown that a p.(Lys91*) mutation in A20 disrupts nuclear factor κB signaling, impairs protein-protein interactions of A20, and leads to inflammasome activation. Methods: We now describe the clinical presentations and drug responses in a family with HA20 p.(Lys91*) mutation, consistent with our previously reported diverse immunological and functional findings. Results: We report for the first time that inflammasome-mediated autoinflammatory lung reaction caused by HA20 can be treated with interleukin 1 antagonist anakinra. We also describe severe anemia related to HA20 successfully treated with mycophenolate. In addition, HA20 p.(Lys91*) was found to associate with autoimmune thyroid disease, juvenile idiopathic arthritis, psoriasis, liver disease, and immunodeficiency presenting with specific antibody deficiency and genital papillomatosis. Conclusions: We conclude that HA20 may lead to combination of inflammation, immunodeficiency, and autoimmunity. The condition may present with variable and unpredictable symptoms with atypical treatment responses