Galectin-1 attenuates cardiomyocyte hypertrophy through splice-variant specific modulation of CaV1.2 calcium channel

Pressure overload-induced cardiac hypertrophy occurs in response to chronic blood pressure increase, and dysfunction of Ca_V1.2 calcium channel involves in cardiac hypertrophic processes by perturbing intracellular calcium concentration ([Ca²⁺]_i) and calcium-dependent signaling. As a carbohydrate-binding protein, galectin-1 (Gal-1) is found to bind with Ca_V1.2 channel, which regulates vascular Ca_V1.2 channel functions and blood pressure. However, the potential roles of Gal-1 in cardiac Ca_V1.2 channel (Ca_V1.2_CM) and cardiomyocyte hypertrophy remain elusive. By whole-cell patch clamp, we find Gal-1 decreases the I_Ca,L with or without isoproterenol (ISO) application by reducing the channel membrane expression in neonatal rat ventricular myocytes (NRVMs). Moreover, Gal-1 could inhibit the current densities of Ca_V1.2_CM by an alternative exon 9*-dependent manner in heterologously expressed HEK293 cells. Of significance, overexpression of Gal-1 diminishes ISO or KCl-induced [Ca²⁺]_i elevation and attenuates ISO-induced hypertrophy in NRVMs. Mechanistically, Gal-1 decreases the ISO or Bay K8644-induced phosphorylation of intracellular calcium-dependent signaling proteins δCaMKII and HDAC4, and inhibits ISO-triggered translocation of HDAC4 in NRVMs. Pathologically, we observe that the expressions of Gal-1 and Ca_V1.2_E9* channels are synchronously increased in rat hypertrophic cardiomyocytes and hearts. Taken together, our study indicates that Gal-1 reduces the channel membrane expression to inhibit the currents of Ca_V1.2_CM in a splice-variant specific manner, which diminishes [Ca²⁺]_i elevation, and attenuates cardiomyocyte hypertrophy by inhibiting the phosphorylation of δCaMKII and HDAC4. Furthermore, our work suggests that dysregulated Gal-1 and Ca_V1.2 alternative exon 9* might be attributed to the pathological processes of cardiac hypertrophy, and provides a potential anti-hypertrophic target in the heart.     

Nr5a1-Cre-mediated Tspo conditional knockout mice with low growth rate and prediabetes symptoms – A mouse model of stress diabetes

Translocator protein (TSPO) is a high-affinity cholesterol- and drug-binding mitochondrial protein. Nuclear receptor subfamily 5 group A member 1 or steroidogenic factor 1 (Nr5a1)-Cre mice were previously used to generate steroidogenic cell-specific Tspo gene conditional knockout (cKO) mice. TSPO-depleted homozygotes showed no response to adrenocorticotropic hormone (ACTH) in stimulating adrenal cortex corticosterone production but showed increased epinephrine synthesis in the medulla. No other phenotype was observed under normal growth conditions. During these studies, we noted that pairing two cKO mice resulted in the generation of small pups. These pups showed low growth rate at weaning, which has been linked to the development of type 2 diabetes (T2D) in adulthood. Experimental verification of T2D symptoms via blood testing of the adult mice, including glycated hemoglobin and insulin C-peptide measurements, showed that these Tspo cKO mice exhibited sustained hyperglycemia, a sign of prediabetes, likely due to the augmentation of hepatic glucose production mediated by the increased epinephrine. We also observed increased expression of the S100a8 gene, which is upregulated after chronic glucose stimulation. Taken together, the observed prediabetes phenotype and lack of response to ACTH indicate that Tspo cKO mice (Nr5a1-Cre^+/?, Tspo^fl/fl) could provide a useful model to study the link between diabetes and stress.     

Genetic diversity of Colletotrichum gloeosporioides species complex associated with Citrus wither‐tip of twigs in Tunisia using microsatellite markers

Anthracnose Citrus disease has been associated with several symptoms worldwide and it is recently compromising Citrus production in the Mediterranean area. Four species complexes are mainly involved: Colletotrichum boninense, C. acutatum, C. gloeosporioides and C. truncatum. In this study, we investigated the genetic diversity of Colletotrichum spp. in Tunisia associated with wither‐tip of twigs on Citrus. Specific primers ITS4‐CgInt allowed the identification of C. gloeosporioides species complex in all the 54 isolates, sampled from three regions and four Citrus species. Overall, our genotypic analysis using 10 SSR markers showed a moderate diversity level in Tunisian C. gloeosporioides population and highlighted that C. gloeosporioides reproduce mainly clonally. In addition, heterothallic isolates were present in our population, suggesting that the pathogen population may undergo parasexual recombinations. The highest genetic diversity in C. gloeosporioides was recorded in Nabeul and on orange, which likely constitutes the area and the host of origin for the Citrus anthracnose disease in Tunisia. In addition, no population subdivision was detected at the geographic, host species or cultivars’ origin levels. However, our study identified two genetic subpopulations and indicated a rapid C. gloeosporioides population change at temporal scale that should be further examined over several consecutive growing seasons in order to understand its population dynamics.     

Inhibitors of HIV protease: Unique non-peptide active site templates

New templates were designed and prepared which straddle the active site of HIV-1 protease. These templates were designed to be ‘flexible scaffolds’ upon which substituents could be appended to fill the pockets of HIV protease. The new templates prepared and analysed were 4-hydroxy-5H-furan-2-ones, 4-hydroxy-5,6-dihydropyrones, 3-hydroxy-cyclohex-2-enones, and 4-hydroxy-2(1H)-pyridinones, of which the 4-hydroxy- 5,6-dihydropyrones were found to be the most potent inhibitors of HIV-1 protease.     

Absolute stereochemistry of methanopterin and 5,6,7,8-tetrahydromethanopterin

The configuration at the C-9 of methanopterin (MPT) has been determined by comparing the circular dichroism (CD) spectra of MPT and its hydrolytic fragment, 1-[4-[[1-(2-amino-7-methyl-4-hydroxy-6-pteridinyl)-ethyl]amino]phenyl]-1-deoxy-D -ribitol (HP-1), with the CD spectra of a series of model compounds of known stereochemistry. These compounds included (S)-6-[1-(4-carboxymethylanilino)ethyl]pterin, (S-6(1-hydroxyethyl)-7-methylpterin, (S-6-(1-hydroxyethyl)pterin, (R)-6-(1-phenoxyethyl)pterin, D (+)-neopterin, and L -biopterin. From this comparison it was concluded that MPT has the R configuration at C-9 and is thus configurationally related to D (+)-neopterin, which has the S configuration at C-1. From previous work establishing the relative stereochemistry at C-6, C-7, and C-9 of N⁵-N¹⁰-methenyl-5,6,7,8-tetrahydromethanopterin (N⁵-N¹⁰-methenyl-H₄MPT) as R, S, and R, respectively, it is clear that the remaining asymmetric carbons at C-6 and C-7 of H₄MPT have the S and S configuration, respectively. Comparison of these latter two positions to the equivalent carbons in 5,6,7,8-tetrahydrofolate (H₄folate) show that the steps involved in the biological reduction of MPT to H₄MPT occur with the same stereochemical outcome as those involved in the biological reduction of folate to H₄folate. © 1996 Wiley-Liss, Inc.     

Acute exposure to 50 Hz magnetic field does not affect hematologic or immunologic functions in healthy young men: A circadian study

Some epidemiological studies report a relationship between magnetic field exposure and such human diseases as leukemia and immune system disturbances. The few published studies on animals do not demonstrate field exposure-related alterations in hematologic and immune systems. The data presented here are part of a broader study designed to investigate the possible effects of acute exposure to a 50 Hz linearly polarized magnetic field (10 μT) on hematologic and immunologic functions. Thirty-two young men (20–30 years old) were divided into two groups (control group, i.e., sham-exposed, 16 subjects; exposed group, 16 subjects). All subjects participated in two 24 h experiments to evaluate the effects of both continuous and intermittent (1 h “off” and 1 h with the field switched “on” and “off” every 15 s) exposure to linearly polarized magnetic fields. The subjects were exposed to the magnetic field (generated by three Helmholtz coils per bed) from 23:00 to 08:00 while lying down. Blood samples were collected during each session at 3 h intervals from 11:00 to 20:00 and hourly from 22:00 to 08:00. No significant differences were observed between sham-exposed (control) and exposed men for hemoglobin concentration, hematocrit, red blood cells, platelets, total leukocytes, monocytes, lymphocytes, eosinophils, or neutrophils. Immunologic variables [CD3, CD4, CD8, natural killer (NK) cells and B cells] were unaltered. To our knowledge, this study is the first to document the effects of a 50 Hz magnetic field on the circadian rhythm of human hematologic and immune functions, and it suggests that acute exposure to either a continuous or an intermittent 50 Hz linearly polarized magnetic field of 10 μT, at least under the conditions of our experiment, does not affect either these functions or their circadian rhythms in healthy young men. © 1996 Wiley-Liss, Inc.     

Uncoupling the BMP receptor antagonist function from the WNT agonist function of R-spondin 2 using the inhibitory peptide dendrimer RWd

Signaling by bone morphogenetic proteins (BMPs) plays pivotal roles in embryogenesis, adult tissue homeostasis, and disease. Recent studies revealed that the well-established WNT agonist R-spondin 2 (RSPO2) is also a BMP receptor (BMP receptor type 1A) antagonist, with roles in early Xenopus embryogenesis and human acute myeloid leukemia (AML). To uncouple the BMP antagonist function from the WNT agonist function and to promote development of AML therapeutics, here we identified a 10-mer peptide (RW) derived from the thrombospondin 1 domain of RSPO2, which specifically prevents binding between RSPO2 and BMP receptor type 1A without altering WNT signaling. We also show that a corresponding RW dendrimer (RW^d) exhibiting improved half-life relieves inhibition of BMP receptor signaling by RSPO2 in human AML cells, reduces cell growth, and induces differentiation. Moreover, microinjection of RW^d in Xenopus embryos ventralizes the dorsoventral embryonic patterning by upregulating BMP signaling without affecting WNT signaling. Our study corroborates the function of RSPO2 as a BMP receptor antagonist and provides a proof of concept for pharmacologically uncoupling BMP antagonist from WNT agonist functions of RSPO2 using the inhibitor peptide RW^d with enhanced target selectivity and limited side effects.     

A circular intronic RNA ciPVT1 delays endothelial cell senescence by regulating the miR‐24‐3p/CDK4/pRb axis

Circular RNAs (circRNAs) have been established to be involved in numerous processes in the human genome, but their function in vascular aging remains largely unknown. In this study, we aimed to characterize and analyze the function of a circular intronic RNA, ciPVT1, in endothelial cell senescence. We observed significant downregulation of ciPVT1 in senescent endothelial cells. In proliferating endothelial cells, ciPVT1 knockdown induced a premature senescence‐like phenotype, inhibited proliferation, and led to an impairment in angiogenesis. An in vivo angiogenic plug assay revealed that ciPVT1 silencing significantly inhibited endothelial tube formation and decreased hemoglobin content. Conversely, overexpression of ciPVT1 in old endothelial cells delayed senescence, promoted proliferation, and increased angiogenic activity. Mechanistic studies revealed that ciPVT1 can sponge miR‐24‐3p to upregulate the expression of CDK4, resulting in enhanced Rb phosphorylation. Moreover, enforced expression of ciPVT1 reversed the senescence induction effect of miR‐24‐3p in endothelial cells. In summary, the present study reveals a pivotal role for ciPVT1 in regulating endothelial cell senescence and may have important implications in the search of strategies to counteract the development of age‐associated vascular pathologies.