Abstract Aims Cyclic AMP inhibits vascular smooth muscle cell (VSMC) proliferation which is important in the aetiology of numerous vascular diseases. The anti-mitogenic properties of cAMP in VSMC are ...dependent on activation of protein kinase A (PKA) and exchange protein activated by cAMP (EPAC), but the mechanisms are unclear. Methods and results Selective agonists of PKA and EPAC synergistically inhibited Egr1 expression, which was essential for VSMC proliferation. Forskolin, adenosine, A2B receptor agonist BAY60-6583 and Cicaprost also inhibited Egr1 expression in VSMC but not in endothelial cells. Inhibition of Egr1 by cAMP was independent of cAMP response element binding protein (CREB) activity but dependent on inhibition of serum response element (SRE) activity. SRF binding to the Egr1 promoter was not modulated by cAMP stimulation. However, Egr1 expression was dependent on the SRF co-factors Elk1 and 4 but independent of MAL. Inhibition of SRE-dependent Egr1 expression was due to synergistic inhibition of Rac1 activity by PKA and EPAC, resulting in rapid cytoskeleton remodelling and nuclear export of ERK1/2. This was associated with de-phosphorylation of the SRF co-factor Elk1. Conclusion cAMP inhibits VSMC proliferation by rapidly inhibiting Egr1 expression. This occurs, at least in part, via inhibition of Rac1 activity leading to rapid actin-cytoskeleton remodelling, nuclear export of ERK1/2, impaired Elk1-phosphorylation and inhibition of SRE activity. This identifies one of the earliest mechanisms underlying the anti-mitogenic effects of cAMP in VSMC but not in endothelial cells, making it an attractive target for selective inhibition of VSMC proliferation.
Proliferation and migration of vascular smooth muscle cells (VSMCs) or endothelial cell (ECs) promote or inhibit, respectively, restenosis after angioplasty, vein graft intimal thickening and ...atherogenesis. Here we investigated the effects of cAMP-induced cytoskeletal remodelling on the serum response factor (SRF) co-factors Megakaryoblastic Leukemia-1 and -2 (MKL1 and MKL2) and their role in controlling VSMC and EC proliferation and migration. Elevation of cAMP using forskolin, dibutyryl-cAMP (db-cAMP), BAY60-6583 or Cicaprost induced rapid cytoskeleton remodelling and inhibited proliferation and migration in VSMCs but not EC. Furthermore, elevated cAMP inhibited mitogen-induced nuclear-translocation of MKL1 and MKL2 in VSMCs but not ECs. Forskolin also significantly inhibited serum response factor (SRF)-dependent reporter gene (SRE-LUC) activity and mRNA expression of pro-proliferative and pro-migratory MKL1/2 target genes in VSMCs but not in ECs. In ECs, MKL1 was constitutively nuclear and MKL2 cytoplasmic, irrespective of mitogens or cAMP. Pharmacological or siRNA inhibition of MKL1 significantly inhibited the proliferation and migration of VSMC and EC. Our new data identifies and important contribution of MKL1/2 to explaining the strikingly different response of VSMCs and ECs to cAMP elevation. Elucidation of these pathways promises to identify targets for specific inhibition of VSMC migration and proliferation.
Although early intervention for chronic kidney disease (CKD) and renal anemia are desirable, these conditions are often asymptomatic during their early stages and may be underdiagnosed.
We ...retrospectively analyzed Japanese administrative claims data for general and hospital populations. The data period for the general and hospital data ranged from January 2011 to December 2016 and from April 2008 to July 2017, respectively. CKD stage was determined by estimated glomerular filtration rate (eGFR). Anemia was defined per Japanese guidelines using hemoglobin (Hb) values. The proportion of patients who had eGFR-defined stages G3–G5 CKD without a CKD diagnosis, and Hb-defined anemia without an anemia diagnosis or treatment records, was estimated.
Among 16,779 (general) and 68,161 (hospital) patients, a high proportion of G3 CKD patients did not have a CKD-related diagnosis (general: G3a, 95.0%; G3b, 68.4%; hospital: G3a, 89.2%; G3b, 67.9%); however, some patients were treated with antihypertensives. Among anemic patients, 75.7% (G3a) and 66.7% (G3b) of the general population, and 56.2% (G3a) and 47.5% (G3b) of the hospital population, did not have an anemia-related diagnosis or treatment. CKD and anemia were more likely to be diagnosed in patients with G4 and G5 CKD.
A high proportion of G3 CKD patients did not have a CKD-related diagnosis. Likewise, many anemic patients with G3 CKD did not have an anemia-related diagnosis. Despite the lack of a CKD-related diagnosis, some patients received appropriate treatment (e.g., antihypertensives). Further outreach to CKD and anemia patients at earlier stages may be warranted.
Adiponectin stimulation of its receptors, AdipoR1 and AdipoR2, increases the activities of 5' AMP-activated protein kinase (AMPK) and peroxisome proliferator-activated receptor (PPAR), respectively, ...thereby contributing to healthy longevity as key anti-diabetic molecules. AdipoR1 and AdipoR2 were predicted to contain seven transmembrane helices with the opposite topology to G-protein-coupled receptors. Here we report the crystal structures of human AdipoR1 and AdipoR2 at 2.9 and 2.4 Å resolution, respectively, which represent a novel class of receptor structure. The seven-transmembrane helices, conformationally distinct from those of G-protein-coupled receptors, enclose a large cavity where three conserved histidine residues coordinate a zinc ion. The zinc-binding structure may have a role in the adiponectin-stimulated AMPK phosphorylation and UCP2 upregulation. Adiponectin may broadly interact with the extracellular face, rather than the carboxy-terminal tail, of the receptors. The present information will facilitate the understanding of novel structure-function relationships and the development and optimization of AdipoR agonists for the treatment of obesity-related diseases, such as type 2 diabetes.
Hyperhomocysteinemia was reported to enhance endoplasmic reticulum (ER) stress and subsequent apoptosis in several cells. However, the precise mechanisms of smoking susceptibility associated with ...hyperhomocysteinemia has not been fully elucidated. This study included 7- to 9-week-old C57BL6 male mice induced with hyperhomocysteinemia and were exposed to cigarette smoke (CS). A549 cells (human alveolar epithelial cell line) were cultured with homocysteine and were exposed to cigarette smoke extract (CSE) to observe cell viability and expression of proteins related to the ER stress. After 6 months of CS exposure, pulmonary emphysema was more severely induced in the group under the condition of hyperhomocysteinemia compared to that in the control group. The apoptotic A549 cells increased as homocysteine concentration increased and that was enhanced by CSE. Protein expression levels of ER stress markers were significantly increased after simultaneous stimulation. Notably, vitamin B12 and folate supplementation improved ER stress after simultaneous stimulation of A549 cells. In this study, we showed that hyperhomocysteinemia exacerbates CS exposure-induced emphysema in mice, suggesting that hyperhomocysteinemia and CS stimulation enhance ER stress and subsequent induced apoptosis in alveolar epithelial cells. It was suggested that there is a synergistic effect between homocysteine and CS.
Mitogen-activated protein kinase (MAPK) pathways provide a critical connection between extrinsic and intrinsic signals to cardiac hypertrophy. Extracellular signal-regulated protein kinase (ERK)5, an ...atypical MAPK is activated in the heart by pressure overload. However, the role of ERK5 plays in regulating hypertrophic growth and hypertrophy-induced apoptosis is not completely understood.
Herein, we investigate the in vivo role and signaling mechanism whereby ERK5 regulates cardiac hypertrophy and hypertrophy-induced apoptosis.
We generated and examined the phenotypes of mice with cardiomyocyte-specific deletion of the erk5 gene (ERK5(cko)). In response to hypertrophic stress, ERK5(cko) mice developed less hypertrophic growth and fibrosis than controls. However, increased apoptosis together with upregulated expression levels of p53 and Bad were observed in the mutant hearts. Consistently, we found that silencing ERK5 expression or specific inhibition of its kinase activity using BIX02189 in neonatal rat cardiomyocytes (NRCMs) reduced myocyte enhancer factor (MEF)2 transcriptional activity and blunted hypertrophic responses. Furthermore, the inhibition of MEF2 activity in NRCMs using a non-DNA binding mutant form of MEF2 was found to attenuate the ERK5-regulated hypertrophic response.
These results reveal an important function of ERK5 in cardiac hypertrophic remodeling and cardiomyocyte survival. The role of ERK5 in hypertrophic remodeling is likely to be mediated via the regulation of MEF2 activity.
Prostate cancer is the most prevalent cancer in males in Western countries. The reported incidence in Asia is much lower than that in African Americans and European Caucasians. A/though the tack of ...systematic prostate cancer screening system in Asian countries explains part of the difference, this alone cannot fully explain the lower incidence in Asian immigrants in the United States and west-European countries compared to the black and non-Hispanic white in those countries, nor the somewhat better prognosis in Asian immigrants with prostate cancer in the United States. Soy food consumption, more popular in Asian populations, is associated with a 25% to 30% reduced risk of prostate cancer. Prostate- specific antigen（PSA） is the only established and routinely implemented clinical biomarker for prostate cancer detection and disease status. Other biomarkers, such as urinary prostate cancer antigen 3 RNA, may increase accuracy of prostate cancer screening compared to PSA alone. Several susceptible loci have been identified in genetic linkage analyses in populations of countries in the West, and approximately 30 genetic polymorphisms have been reported to modestly increase the prostate cancer risk in genome- wide association studies. Most of the identified polymorphisms are reproducible regardless of ethnicity. Somatic mutations in the genomes of prostate tumors have been repeatedly reported to include deletion and gain of the 8p and 8q chromosomal regions, respectively; epigenetic gene silencing of glutathione S- transferase Pi （GSTP1）; as well as mutations in androgen receptor gene. However, the molecular mechanisms underlying carcinogenesis, aggressiveness, and prognosis of prostate cancer remain largely unknown. Gene-gene and/or gene-environment interactions still need to be learned. In this review, the differences in PSA screening practice, reported incidence and prognosis of prostate cancer, and genetic factors between the populations in East and West factors are discussed.
Noroviruses have been identified as major causative agents of acute nonbacterial gastroenteritis in humans. Histo‐blood group antigens (HBGAs) are thought to play a major role among the host cellular ...factors influencing norovirus infection. Genogroup I, genotype 9 (GI.9) is the most recently identified genotype within genogroup I, whose representative strain is the Vancouver 730 norovirus. However, the molecular interactions between host antigens and the GI.9 capsid protein have not been investigated in detail. In this study, we demonstrate that the GI.9 norovirus preferentially binds Lewis antigens over blood group A, B, and H antigens, as revealed by an HBGA binding assay using virus‐like particles. We determined the crystal structures of the protruding domain of the GI.9 capsid protein in the presence or absence of Lewis antigens. Our analysis demonstrated that Lewis fucose (α1–3/4 fucose) represents a key moiety for the GI.9 protein–HBGA interaction, thus suggesting that Lewis antigens might play a critical role during norovirus infection. In addition to previously reported findings, our observations may support the future design of antiviral agents and vaccines against noroviruses.
Here we demonstrated the preferential binding of the GI.9 norovirus to Lewis antigens over blood group A, B, and H antigens . In addition, X‐ray crystallography revealed that the VP1 capsid protein interacted mainly with the fucose moiety (α1–3/4‐Fuc, ‘LeFuc’) of Lewis antigens, thus suggesting a critical role of Lewis antigens during norovirus infection. Our observations could support the future design of antiviral agents and vaccines against noroviruses.
Desmosomes in tissues are resistant to disruption by chelation of extracellular calcium. It has been suggested that this represents a hyper-adhesive state of these intercellular junctions that is ...crucial for the maintenance of epidermal integrity. Desmosomes change to a lower affinity, calcium-dependent adhesive state when cells are cultured at low density or when an intact epithelial cell sheet is wounded. Here we demonstrate that cells of the immortalized human keratinocyte line HaCaT acquire calcium-independent desmosomes in confluent culture. An adhesion assay shows that HaCaT cells with calcium-independent desmosomes are more cohesive than cells with calcium-dependent desmosomes. This assay relates directly to desmosomal adhesion because it involves splitting of the desmosomal adhesive material. Moreover, the difference in adhesiveness between calcium-dependent and calcium-independent desmosomes involves no quantitative change in the known protein composition of desmosomes. Instead, switching between the two adhesive states can be achieved by activation or inhibition of protein kinase C (PKC), suggesting a direct effect of PKC signalling on desmosomal adhesion. These results provide direct support for the concept of hyper-adhesiveness in desmosomes.
The food-poisoning bacterium Clostridium perfringens produces an enterotoxin (~35 kDa) that specifically targets human claudin-4, among the 26 human claudin proteins, and causes diarrhea by fluid ...accumulation in the intestinal cavity. The C-terminal domain of the Clostridium perfringens enterotoxin (C-CPE, ~15 kDa) binds tightly to claudin-4, and disrupts the intestinal tight junction barriers. In this study, we determined the 3.5-Å resolution crystal structure of the cell-free synthesized human claudin-4•C-CPE complex, which is significantly different from the structure of the off-target complex of an engineered C-CPE with mouse claudin-19. The claudin-4•C-CPE complex structure demonstrated the mechanism underlying claudin assembly disruption. A comparison of the present C-CPE-bound structure of claudin-4 with the enterotoxin-free claudin-15 structure revealed sophisticated C-CPE-induced conformation changes of the extracellular segments, induced on the foundation of the rigid four-transmembrane-helix bundle structure. These conformation changes provide a mechanistic model for the disruption of the lateral assembly of claudin molecules. Furthermore, the present novel structural mechanism for selecting a specific member of the claudin family can be used as the foundation to develop novel medically important technologies to selectively regulate the tight junctions formed by claudin family members in different organs.
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