32 results on '"Myrtani Pieri"'
Search Results
2. The genome sequence of Rhynchonycteris naso, Peters, 1867 (Chiroptera, Emballonuridae, Rhynchonycteris) [version 1; peer review: 3 approved]
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Erich Jarvis, Emma C. Teeling, Ine Alvarez van Tussenbroek, Martina Nagy, Mirjam Knörnschild, Philip Philge, Brian P. O'Toole, Myrtani Pieri, Nadolina Brajuka, Giulio Formenti, Linelle Abueg, Ning Zhang, Sonja C. Vernes, Thomas L. Volkert, Jonathan L. Gray, and Meike Mai
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Rhynchonycteris naso ,genome sequence ,chromosomal ,Bat1K ,eng ,Medicine ,Science - Abstract
We present a reference genome assembly from an individual male Rhynchonycteris naso (Chordata; Mammalia; Chiroptera; Emballonuridae). The genome sequence is 2.46 Gb in span. The majority of the assembly is scaffolded into 22 chromosomal pseudomolecules, with the Y sex chromosome assembled.
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- 2024
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3. The genome sequence of Tadarida brasiliensis I. Geoffroy Saint-Hilaire, 1824 [Molossidae; Tadarida] [version 1; peer review: 2 approved, 1 approved with reservations]
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Michael Smotherman, Cara F. Webster, Thomas Brown, Martin Pippel, Meike Mai, Eugene W. Myers, Sylke Winkler, Sonja C. Vernes, Emma C. Teeling, and Myrtani Pieri
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Tadarida brasiliensis ,genome sequence ,chromosomal ,Bat1K ,eng ,Medicine ,Science - Abstract
We present a genome assembly from an individual male Tadarida brasiliensis (The Brazilian free-tailed bat; Chordata; Mammalia; Chiroptera; Molossidae). The genome sequence is 2.28 Gb in span. The majority of the assembly is scaffolded into 25 chromosomal pseudomolecules, with the X and Y sex chromosomes assembled.
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- 2024
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4. Exploring the Dynamic Relationship between the Gut Microbiome and Body Composition across the Human Lifespan: A Systematic Review
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Ifigeneia Komodromou, Eleni Andreou, Angelos Vlahoyiannis, Maria Christofidou, Kyriacos Felekkis, Myrtani Pieri, and Christoforos D. Giannaki
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gut microbiota ,obesity ,overweight ,body fat ,fat mass ,muscle mass ,Nutrition. Foods and food supply ,TX341-641 - Abstract
This systematic review aimed to identify different gut microbiome profiles across the human lifespan and to correlate such profiles with the body composition. PubMed, Scopus, and Cochrane were searched from inception to March 2022. Sixty studies were included in this systematic review. Overall, the gut microbiome composition in overweight participants exhibited decreased α-diversity, decreased levels of the phylum Bacteroidetes and its taxa, and increased levels of the phylum Firmicutes, its taxa, and the Firmicutes/Bacteroidetes ratio, in comparison to normal-weight participants. Other body composition parameters showed similar correlations. Fat mass and waist circumference were found to correlate positively with the Firmicutes taxa and negatively with the Bacteroidetes taxa. In contrast, lean body mass and muscle mass demonstrated a positive correlation with the Bacteroidetes taxa. Notably, these correlations were more pronounced in athletes than in obese and normal-weight individuals. The composition of the gut microbiome is evidently different in overweight individuals or athletes of all age groups, with the former tending towards decreased Bacteroidetes taxa and increased Firmicutes taxa, while a reversed relationship is observed concerning athletes. Further studies are needed to explore the dynamic relationship between energy intake, body composition, and the gut microbiome across the human lifespan.
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- 2024
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5. The genome sequence of Molossus nigricans (Chiroptera, Molossidae; Miller, 1902) [version 1; peer review: 2 approved, 1 approved with reservations]
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Melissa R. Ingala, Nancy B. Simmons, Thomas L. Volkert, Myrtani Pieri, Philge Philip, Larry N. Singh, Ning Zhang, Laramie L. Lindsey, Brian P. O'Toole, Jonathan L. Gray, Emma C. Teeling, Meike Mai, and Sonja C. Vernes
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Molossus nigricans ,genome sequence ,chromosomal ,Bat1K ,eng ,Medicine ,Science - Abstract
We present a genome assembly from an individual male Molossus nigricans (Chordata; Mammalia; Chiroptera; Molossidae). The genome sequence is 2.41 gigabases in span. The majority of the assembly is scaffolded into 24 chromosomal pseudomolecules, with the X sex chromosome assembled.
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- 2023
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6. A bovine miRNA, bta‐miR‐154c, withstands in vitro human digestion but does not affect cell viability of colorectal human cell lines after transfection
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Myrtani Pieri, Elena Theori, Harsh Dweep, Myrofora Flourentzou, Foteini Kalampalika, Maria‐Arsenia Maniori, Gregory Papagregoriou, Christos Papaneophytou, and Kyriacos Felekkis
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bovine ,colorectal cancer ,digestion ,epithelial cell lines ,miroRNAs ,XenomiRs ,Biology (General) ,QH301-705.5 - Abstract
Colorectal cancer (CRC) is the third most frequent human cancer with over 1.3 million new cases globally. CRC is a complex disease caused by interactions between genetic and environmental factors; in particular, high consumption of red meat, including beef, is considered a risk factor for CRC initiation and progression. Recent data demonstrate that exogenous microRNAs (miRNAs) entering the body via ingestion could pose an effect on the consumer. In this study, we focused on bovine miRNAs that do not share a seed sequence with humans and mice. We identified bta‐miR‐154c, a bovine miRNA found in edible parts of beef and predicted via cross‐species bioinformatic analysis to affect cancer‐related pathways in human cells. When bovine tissue was subjected to cooking and a simulation of human digestion, bta‐miR‐154c was still detected after all procedures, albeit at reduced concentrations. However, lipofection of bta‐miR‐154c in three different colorectal human cell lines did not affect their viability as evaluated at various time points and concentrations. These data indicate that bta‐miR‐154c (a) may affect cancer‐related pathways in human cells, (b) can withstand digestion and be detected after all stages of an in vitro digestion protocol, but (c) it does not appear to alter epithelial cell viability after entering human enterocytes, even at supraphysiological amounts. Further experiments will elucidate whether bta‐miR‐154c exerts a different functional effect on the human gut epithelium, which may cause it to contribute to CRC progression through its consumption.
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- 2022
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7. Trust in Authorities and Demographic Factors Affect Vaccine Acceptance During the COVID-19 Pandemic in Cyprus
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Nikos Konstantinou, Stella A. Nicolaou, Christos Petrou, and Myrtani Pieri
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COVID-19 ,seasonal vaccine acceptance ,vaccine hesitancy ,public trust ,online self-report survey ,Psychology ,BF1-990 - Abstract
Abstract. The COVID-19 pandemic has had a devastating impact on all aspects of human life. Accurately measuring vaccine acceptance and understanding the factors that influence vaccine attitudes and behaviors is crucial to designing public-health interventions to reduce the impact of COVID-19 through vaccinations. The current study adapted the vaccine acceptance scale (Sarathchandra et al., 2018) to the Greek language and assessed the relationship between key components of vaccine acceptance to COVID-19 vaccine beliefs and attitudes, personal and family vaccination history and attitudes, and demographic variables (age, sex, education, and having children). The adapted vaccine acceptance instrument was found to have high internal consistency reliability. Further analyses indicated that younger and less-educated individuals are more vaccine-hesitant, and that vaccine acceptance is influenced by trust in authorities. These findings may have implications for understanding vaccine hesitancy and for the design and implementation of vaccine-related public health policies.
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- 2021
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8. Exploring the Feasibility of Circulating miRNAs as Diagnostic and Prognostic Biomarkers in Osteoarthritis: Challenges and Opportunities
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Kyriacos Felekkis, Myrtani Pieri, and Christos Papaneophytou
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osteoarthritis ,circulating miRNAs ,diagnosis ,prevention ,Biology (General) ,QH301-705.5 ,Chemistry ,QD1-999 - Abstract
Osteoarthritis (OA) is a prevalent degenerative joint disease characterized by progressive cartilage degradation and joint inflammation. As the most common aging-related joint disease, OA is marked by inadequate extracellular matrix synthesis and the breakdown of articular cartilage. However, traditional diagnostic methods for OA, relying on clinical assessments and radiographic imaging, often need to catch up in detecting early-stage disease or i accurately predicting its progression. Consequently, there is a growing interest in identifying reliable biomarkers that can facilitate early diagnosis and prognosis of OA. MicroRNAs (miRNAs) have emerged as potential candidates due to their involvement in various cellular processes, including cartilage homeostasis and inflammation. This review explores the feasibility of circulating miRNAs as diagnostic and prognostic biomarkers in OA, focusing on knee OA while shedding light on the challenges and opportunities associated with their implementation in clinical practice.
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- 2023
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9. Special Issue: The Impact of Early Life Nutrition on Gut Maturation and Later Life Gut Health
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Myrtani Pieri, Vicky Nicolaidou, and Christos Papaneophytou
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n/a ,Nutrition. Foods and food supply ,TX341-641 - Abstract
Nutrition during early life plays a crucial role in determining a child’s long-term health [...]
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- 2023
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10. Seroprevalence of immunoglobulin G antibodies against SARS-CoV-2 in Cyprus.
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Christos Papaneophytou, Andria Nicolaou, Myrtani Pieri, Vicky Nicolaidou, Eleftheria Galatou, Yiannis Sarigiannis, Markella Pantelidou, Pavlos Panayi, Theklios Thoma, Antonia Stavraki, Xenia Argyrou, Tasos Kalogiannis, Kyriacos Yiannoukas, Christos C Petrou, and Kyriacos Felekkis
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Medicine ,Science - Abstract
Monitoring the levels of IgG antibodies against the SARS-CoV-2 is important during the coronavirus disease 2019 (COVID-19) pandemic, to plan an adequate and evidence-based public health response. After this study we report that the plasma levels of IgG antibodies against SARS-CoV-2 spike protein were higher in individuals with evidence of prior infection who received at least one dose of either an mRNA-based vaccine (Comirnaty BNT162b2/Pfizer-BioNTech or Spikevax mRNA-1273/Moderna) or an adenoviral-based vaccine (Vaxzervia ChAdOx1 nCoV-19 /Oxford-Astra Zeneca) (n = 39) compared to i) unvaccinated individuals with evidence of prior infection with SARS-CoV-2 (n = 109) and ii) individuals without evidence of prior infection with SARS-CoV-2 who received one or two doses of one of the aforementioned vaccines (n = 342). Our analysis also revealed that regardless of the vaccine technology (mRNA-based and adenoviral vector-based) two doses achieved high anti- SARS-CoV-2 IgG responses. Our results indicate that vaccine-induced responses lead to higher levels of IgG antibodies compared to those produced following infection with the virus. Additionally, in agreement with previous studies, our results suggest that among individuals previously infected with SARS-CoV-2, even a single dose of a vaccine is adequate to elicit high levels of antibody response.
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- 2022
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11. Detection of SARS-CoV-2–Specific Antibodies in Human Breast Milk and Their Neutralizing Capacity after COVID-19 Vaccination: A Systematic Review
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Vicky Nicolaidou, Rafaela Georgiou, Maria Christofidou, Kyriacos Felekkis, Myrtani Pieri, and Christos Papaneophytou
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SARS-CoV-2 ,COVID-19 ,breast milk ,antibodies ,vaccines ,lactating ,Biology (General) ,QH301-705.5 ,Chemistry ,QD1-999 - Abstract
SARS-CoV-2 is the virus that causes the infectious disease known as Corona Virus Disease 2019 (COVID-19). The severe impact of the virus on humans is undeniable, which is why effective vaccines were highly anticipated. As of 12 January 2022, nine vaccines have obtained Emergency Use Listing by the World Health Organization (WHO), and four of these are approved or authorized by the Centers for Disease Control and Prevention (CDC) in the United States. The initial clinical trials studying COVID-19 vaccine efficacy excluded pregnant and lactating individuals, meaning that data on the effects of the vaccine on breast milk were lacking. Until today, none of the authorized vaccines have been approved for use in individuals under six months. During the first months of life, babies do not produce their own antibodies; therefore, antibodies contained in their mothers’ breastmilk are a critical protective mechanism. Several studies have shown the presence of SARS-CoV-2 antibodies in the breast milk of women who have been vaccinated or had been naturally infected. However, whether these are protective is still unclear. Additionally, research on the BNT162b2 mRNA vaccine developed by Pfizer-BioNTech and the mRNA-1273 vaccine developed by Moderna suggests that these vaccines do not release significant amounts, if any, of mRNA into breast milk. Hence, there is no evidence that vaccination of the mother poses any risk to the breastfed infant, while the antibodies present in breast milk may offer protection against the virus. The primary objective of this systematic review is to summarize the current understanding of the presence of immunoglobulins in human milk that are elicited by SARS-CoV-2 vaccines and to evaluate their ability to neutralize the virus. Additionally, we aim to quantify the side effects experienced by lactating mothers who have been vaccinated, as well as the potential for adverse effects in their infants. This study is critical because it can help inform decision-making by examining the current understanding of antibody secretion in breastmilk. This is particularly important because, although the virus tends to be less severe in younger individuals, infants who contract the disease are at a higher risk of requiring hospitalization compared to older children.
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- 2023
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12. Alterations in Circulating miRNA Levels after Infection with SARS-CoV-2 Could Contribute to the Development of Cardiovascular Diseases: What We Know So Far
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Myrtani Pieri, Panayiotis Vayianos, Vicky Nicolaidou, Kyriacos Felekkis, and Christos Papaneophytou
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cardiovascular diseases ,circulating miRNAs ,SARS-CoV-2 ,COVID-19 ,cytokine storm ,inflammation ,Biology (General) ,QH301-705.5 ,Chemistry ,QD1-999 - Abstract
The novel coronavirus disease 2019 (COVID-19) is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and poses significant complications for cardiovascular disease (CVD) patients. MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression and influence several physiological and pathological processes, including CVD. This critical review aims to expand upon the current literature concerning miRNA deregulation during the SARS-CoV-2 infection, focusing on cardio-specific miRNAs and their association with various CVDs, including cardiac remodeling, arrhythmias, and atherosclerosis after SARS-CoV-2 infection. Despite the scarcity of research in this area, our findings suggest that changes in the expression levels of particular COVID-19-related miRNAs, including miR-146a, miR-27/miR-27a-5p, miR-451, miR-486-5p, miR-21, miR-155, and miR-133a, may be linked to CVDs. While our analysis did not conclusively determine the impact of SARS-CoV-2 infection on the profile and/or expression levels of cardiac-specific miRNAs, we proposed a potential mechanism by which the miRNAs mentioned above may contribute to the development of these two pathologies. Further research on the relationship between SARS-CoV-2, CVDs, and microRNAs will significantly enhance our understanding of this connection and may lead to the use of these miRNAs as biomarkers or therapeutic targets for both pathologies.
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- 2023
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13. Survival of Vaccine-Induced Human Milk SARS-CoV-2 IgG, IgA and SIgA Immunoglobulins across Simulated Human Infant Gastrointestinal Digestion
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Myrtani Pieri, Maria-Arsenia Maniori, Lucy Shahabian, Elie Kanaan, Irene Paphiti-Demetriou, Spyros Pipis, Kyriakos Felekkis, Vicky Nicolaidou, and Christos Papaneophytou
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immunoglobulins ,COVID-19 ,breastfeeding ,vaccination ,digestion ,Nutrition. Foods and food supply ,TX341-641 - Abstract
Breastfeeding can be a vital way of acquiring passive immunity via the transfer of antibodies from the mother to the breastfeeding infant. Recent evidence points to the fact that human milk contains immunoglobulins (Ig) against the SARS-CoV-2 virus, either after natural infection or vaccination, but whether these antibodies can resist enzymatic degradation during digestion in the infant gastrointestinal (GI) tract or indeed protect the consumers remains inconclusive. Herein, we evaluated the levels of IgG, IgA, and secretory IgA (SIgA) antibodies against the spike protein of SARS-CoV-2 in 43 lactating mothers who received at least two doses of either an mRNA-based vaccine (Pfizer/BioNTech, Moderna; n = 34) or an adenovirus-based vaccine (AstraZeneca; n = 9). We also accessed the potential persistence of SARS-CoV-2 IgA, IgG, and secretory IgA (SIgA) antibodies from vaccinated women in the GI tract of the infants by means of a static in vitro digestion protocol. Our data depict that, although slightly reduced, the IgA antibodies produced after vaccination resist both the gastric and intestinal phases of infant digestion, whereas the IgGs are more prone to degradation in both phases of digestion. Additionally, SIgA antibodies were found to greatly resist the gastric phase of digestion albeit showing some reduction during the intestinal phase. The evaluation of the vaccine induced Ig profile of breastmilk, and the extent to which these antibodies can resist digestion in the infant GI tract provide important information about the potential protective role of this form of passive immunity that could help decision making during the COVID-19 pandemic and beyond.
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- 2022
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14. A glycine substitution in the collagenous domain of Col4a3 in mice recapitulates late onset Alport syndrome
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Christoforos Odiatis, Isavella Savva, Myrtani Pieri, Pavlos Ioannou, Petros Petrou, Gregory Papagregoriou, Kyriaki Antoniadou, Neoklis Makrides, Charalambos Stefanou, Danica Galešić Ljubanović, Georgios Nikolaou, Dorin-Bogdan Borza, Kostas Stylianou, Oliver Gross, and Constantinos Deltas
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Collagen-IV ,Glomerular basement membrane ,Alport syndrome ,Glycine missense mutation ,Kidney disease ,Mouse model ,Biology (General) ,QH301-705.5 - Abstract
Alport syndrome (AS) is a severe inherited glomerulopathy caused by mutations in the genes encoding the α-chains of type-IV collagen, the most abundant component of the extracellular glomerular basement membrane (GBM). Currently most AS mouse models are knockout models for one of the collagen-IV genes. In contrast, about half of AS patients have missense mutations, with single aminoacid substitutions of glycine being the most common. The only mouse model for AS with a homozygous knockin missense mutation, Col4a3-p.Gly1332Glu, was partly described before by our group. Here, a detailed in-depth description of the same mouse is presented, along with another compound heterozygous mouse that carries the glycine substitution in trans with a knockout allele. Both mice recapitulate essential features of AS, including shorten lifespan by 30–35%, increased proteinuria, increased serum urea and creatinine, pathognomonic alternate GBM thinning and thickening, and podocyte foot process effacement. Notably, glomeruli and tubuli respond differently to mutant collagen-IV protomers, with reduced expression in tubules but apparently normal in glomeruli. However, equally important is the fact that in the glomeruli the mutant α3-chain as well as the normal α4/α5 chains seem to undergo a cleavage at, or near the point of the mutation, possibly by the metalloproteinase MMP-9, producing a 35 kDa C-terminal fragment. These mouse models represent a good tool for better understanding the spectrum of molecular mechanisms governing collagen-IV nephropathies and could be used for pre-clinical studies aimed at better treatments for AS.
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- 2021
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15. A functional variant in NEPH3 gene confers high risk of renal failure in primary hematuric glomerulopathies. Evidence for predisposition to microalbuminuria in the general population.
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Konstantinos Voskarides, Charalambos Stefanou, Myrtani Pieri, Panayiota Demosthenous, Kyriakos Felekkis, Maria Arsali, Yiannis Athanasiou, Dimitris Xydakis, Kostas Stylianou, Eugenios Daphnis, Giorgos Goulielmos, Petros Loizou, Judith Savige, Martin Höhne, Linus A Völker, Thomas Benzing, Patrick H Maxwell, Daniel P Gale, Mathias Gorski, Carsten Böger, Barbara Kollerits, Florian Kronenberg, Bernhard Paulweber, Michalis Zavros, Alkis Pierides, and Constantinos Deltas
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Medicine ,Science - Abstract
BACKGROUND:Recent data emphasize that thin basement membrane nephropathy (TBMN) should not be viewed as a form of benign familial hematuria since chronic renal failure (CRF) and even end-stage renal disease (ESRD), is a possible development for a subset of patients on long-term follow-up, through the onset of focal and segmental glomerulosclerosis (FSGS). We hypothesize that genetic modifiers may explain this variability of symptoms. METHODS:We looked in silico for potentially deleterious functional SNPs, using very strict criteria, in all the genes significantly expressed in the slit diaphragm (SD). Two variants were genotyped in a cohort of well-studied adult TBMN patients from 19 Greek-Cypriot families, with a homogeneous genetic background. Patients were categorized as "Severe" or "Mild", based on the presence or not of proteinuria, CRF and ESRD. A larger pooled cohort (HEMATURIA) of 524 patients, including IgA nephropathy patients, was used for verification. Additionally, three large general population cohorts [Framingham Heart Study (FHS), KORAF4 and SAPHIR] were used to investigate if the NEPH3-V353M variant has any renal effect in the general population. RESULTS AND CONCLUSIONS:Genotyping for two high-scored variants in 103 TBMN adult patients with founder mutations who were classified as mildly or severely affected, pointed to an association with variant NEPH3-V353M (filtrin). This promising result prompted testing in the larger pooled cohort (HEMATURIA), indicating an association of the 353M variant with disease severity under the dominant model (p = 3.0x10-3, OR = 6.64 adjusting for gender/age; allelic association: p = 4.2x10-3 adjusting for patients' kinships). Subsequently, genotyping 6,531 subjects of the Framingham Heart Study (FHS) revealed an association of the homozygous 353M/M genotype with microalbuminuria (p = 1.0x10-3). Two further general population cohorts, KORAF4 and SAPHIR confirmed the association, and a meta-analysis of all three cohorts (11,258 individuals) was highly significant (p = 1.3x10-5, OR = 7.46). Functional studies showed that Neph3 homodimerization and Neph3-Nephrin heterodimerization are disturbed by variant 353M. Additionally, 353M was associated with differential activation of the unfolded protein response pathway, when overexpressed in stressed cultured undifferentiated podocyte cells, thus attesting to its functional significance. Genetics and functional studies support a "rare variant-strong effect" role for NEPH3-V353M, by exerting a negative modifier effect on primary glomerular hematuria. Additionally, genetics studies provide evidence for a role in predisposing homozygous subjects of the general population to micro-albuminuria.
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- 2017
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16. Frequency of COL4A3/COL4A4 mutations amongst families segregating glomerular microscopic hematuria and evidence for activation of the unfolded protein response. Focal and segmental glomerulosclerosis is a frequent development during ageing.
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Louiza Papazachariou, Panayiota Demosthenous, Myrtani Pieri, Gregory Papagregoriou, Isavella Savva, Christoforos Stavrou, Michael Zavros, Yiannis Athanasiou, Kyriakos Ioannou, Charalambos Patsias, Alexia Panagides, Costas Potamitis, Kyproula Demetriou, Marios Prikis, Michael Hadjigavriel, Maria Kkolou, Panayiota Loukaidou, Androulla Pastelli, Aristos Michael, Akis Lazarou, Maria Arsali, Loukas Damianou, Ioanna Goutziamani, Andreas Soloukides, Lakis Yioukas, Avraam Elia, Ioanna Zouvani, Polycarpos Polycarpou, Alkis Pierides, Konstantinos Voskarides, and Constantinos Deltas
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Medicine ,Science - Abstract
Familial glomerular hematuria(s) comprise a genetically heterogeneous group of conditions which include Alport Syndrome (AS) and thin basement membrane nephropathy (TBMN). Here we investigated 57 Greek-Cypriot families presenting glomerular microscopic hematuria (GMH), with or without proteinuria or chronic kidney function decline, but excluded classical AS. We specifically searched the COL4A3/A4 genes and identified 8 heterozygous mutations in 16 families (28,1%). Eight non-related families featured the founder mutation COL4A3-p.(G1334E). Renal biopsies from 8 patients showed TBMN and focal segmental glomerulosclerosis (FSGS). Ten patients (11.5%) reached end-stage kidney disease (ESKD) at ages ranging from 37-69-yo (mean 50,1-yo). Next generation sequencing of the patients who progressed to ESKD failed to reveal a second mutation in any of the COL4A3/A4/A5 genes, supporting that true heterozygosity for COL4A3/A4 mutations predisposes to CRF/ESKD. Although this could be viewed as a milder and late-onset form of autosomal dominant AS, we had no evidence of ultrastructural features or extrarenal manifestations that would justify this diagnosis. Functional studies in cultured podocytes transfected with wild type or mutant COL4A3 chains showed retention of mutant collagens and differential activation of the unfolded protein response (UPR) cascade. This signifies the potential role of the UPR cascade in modulating the final phenotype in patients with collagen IV nephropathies.
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- 2014
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17. Biodiversity: the overlooked source of human health
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Yuliya Linhares, Alexander Kaganski, Christian Agyare, Isil A. Kurnaz, Vidushi Neergheen, Bartlomiej Kolodziejczyk, Monika Kędra, Muhammad Wahajuddin, Lahcen El-Youssf, Thomas Edison dela Cruz, Yusuf Baran, Milica Pešić, Uttam Shrestha, Rigers Bakiu, Pierre-Marie Allard, Stanislav Rybtsov, Myrtani Pieri, Velia Siciliano, and Yensi Flores Bueso
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Biomolecules ,Biomedicine ,Molecular Medicine ,Biodiversity ,Conservation ,Molecular Biology ,Synthetic biology - Abstract
Biodiversity is the measure of the variation of lifeforms in a given ecological system. Biodiversity provides ecosystems with the robustness, stability, and resilience that sustains them. This is ultimately essential for our survival because we depend on the services that natural ecosystems provide (food, fresh water, air, climate, and medicine). Despite this, human activity is driving an unprecedented rate of biodiversity decline, which may jeopardize the life-support systems of the planet if no urgent action is taken. In this article we show why biodiversity is essential for human health. We raise our case and focus on the biomedicine services that are enabled by biodiversity, and we present known and novel approaches to promote biodiversity conservation.
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- 2023
18. Variability in the levels of exosomal miRNAs among human subjects could be explained by differential interactions of exosomes with the endothelium
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Christos Papaneophytou, Myrtani Pieri, and Kyriacos Felekkis
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Endothelium ,Research Subjects ,Clinical Biochemistry ,Cancer ,RNA ,Inflammation ,Cell Biology ,Biology ,Bioinformatics ,medicine.disease ,Exosomes ,Biochemistry ,Microvesicles ,MicroRNAs ,medicine.anatomical_structure ,Blood circulation ,microRNA ,Genetics ,medicine ,Humans ,Exosomal mirnas ,RNA, Messenger ,medicine.symptom ,Molecular Biology - Abstract
Exosomes are 30-100 nm endosome-derived membrane vesicles, that contain specific RNA transcripts including mRNAs, and microRNAs (miRNAs) and have been implicated in cell-to-cell communication. Exosomal miRNAs in blood circulation have been attracting major interest as potential diagnostic and prognostic biomarkers in a variety of diseases including stroke, cancer, and inflammatory disorders. Despite the progress made in the utilization of circulating exosomal miRNAs as biomarkers for various human diseases and conditions, there are still difficulties in functionally utilizing such methods in the clinic due to the high variability observed among subjects. Attempts to use miRNA signatures have improved but have not eliminated the problem. Additionally, standardized laboratory practices may partially reduce variability but there is still an unknown biological factor that hinders the proper use of miRNAs as biomarkers. We hypothesize that this variability might be partially attributed to a differential interaction among circulating exosomes carrying those miRNAs with endothelial surface molecules that themselves may vary among individuals due to secondary conditions, for example, inflammation status. This differential interaction could potentially add variability to the level of the examined miRNA that is not directly attributed to the primary condition under study.
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- 2021
19. Survival of vaccine-induced human milk SARS-CoV-2 IgG and IgA immunoglobulins across simulated human infant gastrointestinal digestion
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Myrtani Pieri, Christos Papaneophytou, Kyriacos Felekkis, Spyros Pipis, Vicky Nicolaidou, and Irene Paphiti
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education.field_of_study ,biology ,business.industry ,medicine.medical_treatment ,Population ,Breastfeeding ,Passive immunity ,Virus ,Vaccination ,Pandemic ,Immunology ,biology.protein ,Medicine ,Antibody ,Digestion ,education ,business - Abstract
Four vaccines have been approved to date by the European Medicines Agency for the management of the COVID-19 pandemic in Europe, with all four being targeted to adults over 18 years of age. One way to protect the younger population such as infants or younger children until pediatric vaccines are licensed is through passive immunity via breastfeeding. Recent evidence points to the fact that human milk contains immunoglobulins (Ig) against the SARS-CoV-2 virus, both after natural infection or vaccination, but it is not known whether these antibodies can resist enzymatic degradation during digestion in the infant gastrointestinal (GI) tract or indeed protect the consumers. Here, we describe our preliminary experiments where we validated commercially available ELISA kits to detect IgA and IgG antibodies in human milk from two lactating mothers vaccinated with either the Pfizer/BioNTech or the Astra Zeneca vaccine, and the effect of a static in vitro digestion protocol on the IgA and IgG concentrations. Our data, even preliminary, provide an indication that the IgA antibodies produced after vaccination with the Pfizer/BioNTech vaccine resist the gastric phase but are degraded during the intestinal phase of infant digestion, whereas the IgGs are more prone to degradation in both phases of digestion. We are in the process of recruiting more individuals to further evaluate the vaccine induced immunoglobulin profile of breastmilk, and the extent to which these antibodies can resist digestion in the infant GI tract.
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- 2021
20. A glycine substitution in the collagenous domain of Col4a3 in mice recapitulates late onset Alport syndrome
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Kostas Stylianou, Charalambos Stefanou, Myrtani Pieri, Constantinos Deltas, Kyriaki Antoniadou, Neoklis Makrides, Christoforos Odiatis, Oliver Gross, Dorin-Bogdan Borza, Gregory Papagregoriou, Pavlos Ioannou, Georgios Nikolaou, Isavella Savva, Petros Petrou, and Danica Galešić Ljubanović
- Subjects
Histology ,Mutant ,030232 urology & nephrology ,Biophysics ,Biology ,Compound heterozygosity ,urologic and male genital diseases ,Biochemistry ,Article ,TBM, tubular basement membrane ,Mouse model ,03 medical and health sciences ,0302 clinical medicine ,UPR, unfolded protein response ,Glomerulopathy ,Genetics ,medicine ,Missense mutation ,Allele ,Alport syndrome ,Molecular Biology ,lcsh:QH301-705.5 ,030304 developmental biology ,0303 health sciences ,Metalloproteinase ,EM, electron microscopy ,ARAS, autosomal recessive alport syndrome ,AS, alport syndrome ,BSA, bovine serum albumin ,Collagen-IV ,ESRD, end stage renal disease ,GBM, glomerular basement membrane ,Glomerular basement membrane ,Glycine missense mutation ,Kidney disease ,PAS, periodic acid schiff ,TGF-b1, transforming growth factor beta1 ,Cell Biology ,medicine.disease ,Molecular biology ,medicine.anatomical_structure ,lcsh:Biology (General) - Abstract
Alport syndrome (AS) is a severe inherited glomerulopathy caused by mutations in the genes encoding the α-chains of type-IV collagen, the most abundant component of the extracellular glomerular basement membrane (GBM). Currently most AS mouse models are knockout models for one of the collagen-IV genes. In contrast, about half of AS patients have missense mutations, with single aminoacid substitutions of glycine being the most common. The only mouse model for AS with a homozygous knockin missense mutation, Col4a3-p.Gly1332Glu, was partly described before by our group. Here, a detailed in-depth description of the same mouse is presented, along with another compound heterozygous mouse that carries the glycine substitution in trans with a knockout allele. Both mice recapitulate essential features of AS, including shorten lifespan by 30–35%, increased proteinuria, increased serum urea and creatinine, pathognomonic alternate GBM thinning and thickening, and podocyte foot process effacement. Notably, glomeruli and tubuli respond differently to mutant collagen-IV protomers, with reduced expression in tubules but apparently normal in glomeruli. However, equally important is the fact that in the glomeruli the mutant α3-chain as well as the normal α4/α5 chains seem to undergo a cleavage at, or near the point of the mutation, possibly by the metalloproteinase MMP-9, producing a 35 kDa C-terminal fragment. These mouse models represent a good tool for better understanding the spectrum of molecular mechanisms governing collagen-IV nephropathies and could be used for pre-clinical studies aimed at better treatments for AS., Highlights • Two mouse models were generated that recapitulate essential features of AS patients. • Glomeruli and tubuli respond differently to mutant collagen IV protomers. • The mutant colIV protomers in glomeruli probably undergo a cleavage process by MMP9. • The two AS mouse models represent a good tool for studying collagen-IV nephropathies. • These models could be used for pre-clinical studies aimed at better treatments.
- Published
- 2021
21. Hypothesis as to How a Common Missense Mutation in COL4A3 May Confer Protection against Diabetic Kidney Disease
- Author
-
Myrtani Pieri
- Subjects
medicine.medical_specialty ,Diabetic kidney ,business.industry ,General Medicine ,Disease ,Podocyte ,medicine.anatomical_structure ,Endocrinology ,Nephrology ,Internal medicine ,Diabetic glomerulopathy ,Unfolded protein response ,Missense mutation ,Medicine ,business - Published
- 2020
22. FP070PHENOTYPIC ANALYSIS OF TWO ALPORT SYNDROME MODEL MICE WITH A COL4Α3 G1332E MUTATION
- Author
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Isavella Savva, Myrtani Pieri, Petros Petrou, Dorin-Bogdan Borza, Neoklis Makrides, George Nikolaou, Gregory Papagregoriou, Pavlos Ioannou, Christoforos Odiatis, and Constantinos Deltas
- Subjects
Genetics ,Transplantation ,Nephrology ,business.industry ,Mutation (genetic algorithm) ,Medicine ,Alport syndrome ,business ,medicine.disease - Published
- 2019
23. An energy supply network of nutrient absorption coordinated by calcium and T1R taste receptors in rat small intestine
- Author
-
Rachel Pettcrew, Myrtani Pieri, David W. Foley, E. J. Shepherd, David Meredith, Pat D. Bailey, Norma Lister, Philip A. Helliwell, George L. Kellett, Richard Boyd, Julie Affleck, Oliver J. Mace, John R. Bronk, and Emma L. Morgan
- Subjects
Biochemistry ,biology ,Physiology ,Taste receptor ,Excitatory Amino Acid Transporter 3 ,Symporter ,biology.protein ,GLUT2 ,Apical membrane ,Receptor ,Protein kinase C ,Intestinal absorption ,Cell biology - Abstract
T1R taste receptors are present throughout the gastrointestinal tract. Glucose absorption comprises active absorption via SGLT1 and facilitated absorption via GLUT2 in the apical membrane. Trafficking of apical GLUT2 is rapidly up-regulated by glucose and artificial sweeteners, which act through T1R2 + T1R3/alpha-gustducin to activate PLC beta2 and PKC betaII. We therefore investigated whether non-sugar nutrients are regulated by taste receptors using perfused rat jejunum in vivo. Under different conditions, we observed a Ca(2+)-dependent reciprocal relationship between the H(+)/oligopeptide transporter PepT1 and apical GLUT2, reflecting the fact that trafficking of PepT1 and GLUT2 to the apical membrane is inhibited and activated by PKC betaII, respectively. Addition of L-glutamate or sucralose to a perfusate containing low glucose (20 mM) each activated PKC betaII and decreased apical PepT1 levels and absorption of the hydrolysis-resistant dipeptide L-Phe(PsiS)-L-Ala (1 mM), while increasing apical GLUT2 and glucose absorption within minutes. Switching perfusion from mannitol to glucose (75 mM) exerted similar effects. c-glutamate induced rapid GPCR internalization of T1R1, T1R3 and transducin, whereas sucralose internalized T1R2, T1R3 and alpha-gustducin. We conclude that L-glutamate acts via amino acid and glucose via sweet taste receptors to coordinate regulation of PepT1 and apical GLUT2 reciprocally through a common enterocytic pool of PKC betaII. These data suggest the existence of a wider Ca(2+) and taste receptor-coordinated transport network incorporating other nutrients and/or other stimuli capable of activating PKC betaII and additional transporters, such as the aspartate/glutamate transporter, EAAC1, whose level was doubled by L-glutamate. The network may control energy supply.
- Published
- 2009
24. Site-directed mutagenesis of Arginine282 suggests how protons and peptides are co-transported by rabbit PepT1
- Author
-
David Meredith, Dashiell Hall, Myrtani Pieri, Patrick D. Bailey, and Richard D. Price
- Subjects
Peptide ,Protein structure function ,Biology ,Arginine ,Peptide Transporter 1 ,Biochemistry ,Article ,Membrane Potentials ,Xenopus laevis ,03 medical and health sciences ,Diethyl Pyrocarbonate ,Animals ,SLC15a1 ,Site-directed mutagenesis ,030304 developmental biology ,chemistry.chemical_classification ,Membrane transport ,0303 health sciences ,Symporters ,030302 biochemistry & molecular biology ,Mutagenesis ,Biological Transport ,Transporter ,Cell Biology ,Hydrogen-Ion Concentration ,Protein structure–function ,Electrophysiology ,Nutrient absorption ,Transmembrane domain ,chemistry ,Symporter ,Mutagenesis, Site-Directed ,Oocytes ,Female ,Rabbits ,Epithelia ,Protons ,Peptides - Abstract
The mammalian proton-coupled peptide transporter PepT1 is the major route of uptake for dietary nitrogen, as well as the oral absorption of a number of drugs, including β-lactam antibiotics and angiotensin-converting enzyme inhibitors. Here we have used site-directed mutagenesis to investigate further the role of conserved charged residues in transmembrane domains. Mutation of rabbit PepT1 arginine282 (R282, transmembrane domain 7) to a positive (R282K) or physiologically titratable residue (R282H), resulted in a transporter with wild-type characteristics when expressed in Xenopus laevis oocytes. Neutral (R282A, R282Q) or negatively charged (R282D, R282E) substitutions gave a transporter that was not stimulated by external acidification (reducing pHout from 7.4 to 5.5) but transported at the same rate as the wild-type maximal rate (pHout 5.5); however, only the R282E mutation was unable to concentrate substrate above the extracellular level. All of the R282 mutants showed trans-stimulation of efflux comparable to the wild-type, except R282E-PepT1 which was faster. A conserved negatively charged residue, aspartate341 (D341) in transmembrane domain 8 was implicated in forming a charge pair with R282, as R282E/D341R- and R282D/D341R-PepT1 had wild-type transporter characteristics. Despite their differences in ability to accumulate substrate, both R282E- and R282D-PepT1 showed an increased charge:peptide stoichiometry over the wild-type 1:1 ratio for the neutral dipeptide Gly-l-Gln, measured using two-electrode voltage clamp. This extra charge movement was linked to substrate transport, as 4-aminobenzoic acid, which binds but is not translocated, did not induce membrane potential depolarisation in R282E-expressing oocytes. A model is proposed for the substrate binding/translocation process in PepT1.
- Published
- 2008
25. MP036A NOVEL KNOCKIN MOUSE MODEL FOR ALPORT SYNDROME
- Author
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Myrtani Pieri, Gregoris Papagregoriou, Dorin B Borza, Charalampos Stefanou, Isavella Savva, Constantinos Deltas, Kostas Stylianou, George Lapathitis, and Christos Karaiskos
- Subjects
Transplantation ,Pathology ,medicine.medical_specialty ,Nephrology ,business.industry ,Medicine ,Alport syndrome ,business ,medicine.disease - Published
- 2016
26. The apical (hPepT1) and basolateral peptide transport systems of Caco-2 cells are regulated by AMP-activated protein kinase
- Author
-
Myrtani Pieri, C. A. R. Boyd, Robert Wilkins, Helen C. Christian, and David Meredith
- Subjects
Physiology ,AMP-Activated Protein Kinases ,Guanidines ,chemistry.chemical_compound ,0302 clinical medicine ,AMP-activated protein kinase ,Electric Impedance ,Fluorometry ,SLC15a1 ,Intestinal Mucosa ,Glucose Transporter Type 2 ,0303 health sciences ,biology ,Symporters ,Sodium-Hydrogen Exchanger 3 ,Gastroenterology ,Cell Polarity ,Dipeptides ,Hydrogen-Ion Concentration ,5-aminoimidazole-4-carboxamine ribonucleoside ,Cell biology ,Biochemistry ,Methacrylates ,Sodium-Hydrogen Exchangers ,membrane transport ,Enzyme Activators ,Peptide Transporter 1 ,03 medical and health sciences ,Microscopy, Electron, Transmission ,Mucosal Biology ,glucose transporter 2 ,Physiology (medical) ,Humans ,intestinal epithelium ,Protein kinase A ,Cell Shape ,030304 developmental biology ,Dipeptide ,Hepatology ,Dose-Response Relationship, Drug ,Peptide transporter 1 ,AMPK ,Biological Transport ,Epithelial Cells ,Membrane transport ,Ribonucleotides ,Aminoimidazole Carboxamide ,Enzyme Activation ,Kinetics ,chemistry ,Peptide transport ,Symporter ,biology.protein ,Caco-2 Cells ,030217 neurology & neurosurgery - Abstract
The effect of 5-aminoimidazole-4-carboxamide-ribonucleoside (AICAR) activation of the AMP-activated protein kinase (AMPK) on the transport of the model radiolabeled dipeptide [3H]-D-Phe-L-Gln was investigated in the human epithelial colon cancer cell line Caco-2. Uptake and transepithelial fluxes of [3H]-D-Phe-L-Gln were carried out in differentiated Caco-2 cell monolayers, and hPepT1 and glucose transporter 2 (GLUT2) protein levels were quantified by immunogold electron microscopy. AICAR treatment of Caco-2 cells significantly inhibited apical [3H]-D-Phe-L-Gln uptake, matched by a decrease in brush-border membrane hPepT1 protein but with a concomitant increase in the facilitated glucose transporter GLUT2. A restructuring of the apical brush-border membrane was seen by electron microscopy. The hPepT1-mediated transepithelial (A-to-B) peptide flux across the Caco-2 monolayers showed no significant alteration in AICAR-treated cells. The electrical resistance in the AICAR-treated monolayers was significantly higher compared with control cells. Inhibition of the sodium/hydrogen exchanger 3 (NHE3) had an additive effect to AICAR, suggesting that the AMPK effect is not via NHE3. Fluorescence measurement of intracellular pH showed no reduction in the proton gradient driving PepT1-mediated apical uptake. The reduction in apical hPepT1 protein and dipeptide uptake after AICAR treatment in Caco-2 cells demonstrates a regulatory effect of AMPK on hPepT1, along with an influence on both the microvilli and tight junction structures. The absence of an associated reduction in transepithelial peptide movement implies an additional stimulatory effect of AICAR on the basolateral peptide transport system in these cells. These results provide a link between the hPepT1 transporter and the metabolic state of this model enterocyte.
- Published
- 2010
27. Investigation of Hellenic families with microscopic hematuria reveals the frequency of collagen IV mutations and evidence for activation of the unfolded protein response
- Author
-
Constantinos Deltas, Louiza Papazachariou, Panagiota Demothenous, Myrtani Pieri, Konstantinos Voskarides, Alkis Pierides, Hellenic Nephrogenetics Research Consortium, Constantinos Deltas, Louiza Papazachariou, Panagiota Demothenous, Myrtani Pieri, Konstantinos Voskarides, Alkis Pierides, and Hellenic Nephrogenetics Research Consortium
- Published
- 2014
- Full Text
- View/download PDF
28. Targeting ketone drugs towards transport by the intestinal peptide transporter, PepT1
- Author
-
David Meredith, David W. Foley, Myrtani Pieri, and Patrick D. Bailey
- Subjects
Ketone ,Stereochemistry ,Nabumetone ,Stereoisomerism ,Peptide ,01 natural sciences ,Biochemistry ,Peptide Transporter 1 ,03 medical and health sciences ,Intestine, Small ,medicine ,Humans ,Prodrugs ,Sulfhydryl Compounds ,Physical and Theoretical Chemistry ,030304 developmental biology ,chemistry.chemical_classification ,0303 health sciences ,Molecular Structure ,Symporters ,010405 organic chemistry ,Chemistry ,Organic Chemistry ,Transporter ,Biological Transport ,Dipeptides ,Prodrug ,Ketones ,In vitro ,Butanones ,3. Good health ,0104 chemical sciences ,Symporter ,medicine.drug - Abstract
Thiodipeptide prodrugs of the ketone nabumetone are shown to have affinity for, and be transported by, PepT1 in vitro.
- Published
- 2009
29. An energy supply network of nutrient absorption coordinated by calcium and T1R taste receptors in rat small intestine
- Author
-
Oliver J, Mace, Norma, Lister, Emma, Morgan, Emma, Shepherd, Julie, Affleck, Philip, Helliwell, John R, Bronk, George L, Kellett, David, Meredith, Richard, Boyd, Myrtani, Pieri, Pat D, Bailey, Rachel, Pettcrew, and David, Foley
- Subjects
Glucose Transporter Type 2 ,Male ,Symporters ,Biological Transport, Active ,Glutamic Acid ,In Vitro Techniques ,Models, Biological ,Peptide Transporter 1 ,Rats ,Receptors, G-Protein-Coupled ,Perfusion ,Enterocytes ,Excitatory Amino Acid Transporter 3 ,Glucose ,Jejunum ,Intestinal Absorption ,Alimentary ,Protein Kinase C beta ,Animals ,Calcium ,Rats, Wistar ,Energy Metabolism ,Protein Kinase C ,Signal Transduction - Abstract
T1R taste receptors are present throughout the gastrointestinal tract. Glucose absorption comprises active absorption via SGLT1 and facilitated absorption via GLUT2 in the apical membrane. Trafficking of apical GLUT2 is rapidly up-regulated by glucose and artificial sweeteners, which act through T1R2 + T1R3/alpha-gustducin to activate PLC beta2 and PKC betaII. We therefore investigated whether non-sugar nutrients are regulated by taste receptors using perfused rat jejunum in vivo. Under different conditions, we observed a Ca(2+)-dependent reciprocal relationship between the H(+)/oligopeptide transporter PepT1 and apical GLUT2, reflecting the fact that trafficking of PepT1 and GLUT2 to the apical membrane is inhibited and activated by PKC betaII, respectively. Addition of L-glutamate or sucralose to a perfusate containing low glucose (20 mM) each activated PKC betaII and decreased apical PepT1 levels and absorption of the hydrolysis-resistant dipeptide L-Phe(PsiS)-L-Ala (1 mM), while increasing apical GLUT2 and glucose absorption within minutes. Switching perfusion from mannitol to glucose (75 mM) exerted similar effects. c-glutamate induced rapid GPCR internalization of T1R1, T1R3 and transducin, whereas sucralose internalized T1R2, T1R3 and alpha-gustducin. We conclude that L-glutamate acts via amino acid and glucose via sweet taste receptors to coordinate regulation of PepT1 and apical GLUT2 reciprocally through a common enterocytic pool of PKC betaII. These data suggest the existence of a wider Ca(2+) and taste receptor-coordinated transport network incorporating other nutrients and/or other stimuli capable of activating PKC betaII and additional transporters, such as the aspartate/glutamate transporter, EAAC1, whose level was doubled by L-glutamate. The network may control energy supply.
- Published
- 2008
30. Additions and Corrections
- Author
-
Denis Courtier-Murias, Jonathan Burton, Timothy Woodman, Guillaume Clavé, Paul Davies, Anthony ROMIEU, Richard Payne, Luke Lavis, Pierre-yves Renard, Derek Tocher, Matthew Lloyd, and Myrtani Pieri
- Subjects
Isotope ,010405 organic chemistry ,Chemistry ,Organic Chemistry ,Physical and Theoretical Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Combinatorial chemistry ,0104 chemical sciences - Published
- 2009
31. The in vitro transport of model thiodipeptide prodrugs designed to target the intestinal oligopeptide transporter, PepT1
- Author
-
Stephen Miles, Richard D. Price, David Meredith, Patrick D. Bailey, Myrtani Pieri, David W. Foley, Ho Kam Lam, and Rachel Pettecrew
- Subjects
chemistry.chemical_classification ,Drug Carriers ,Oligopeptide ,Symporters ,Carrier system ,organic chemicals ,Organic Chemistry ,Peptide ,Transporter ,Dipeptides ,Prodrug ,Peptide Transporter 1 ,Biochemistry ,In vitro ,Intestines ,chemistry ,Drug Design ,Drug delivery ,Humans ,Prodrugs ,Caco-2 Cells ,Physical and Theoretical Chemistry ,Sulfur ,Conjugate - Abstract
A thiodipeptide carrier system is shown to be effective at enabling a range of covalently bound molecules, including benzyl, benzoyl and ibuprofen conjugates, to be transported via the intestinal peptide transporter PepT1, demonstrating its potential as a rational drug delivery target.
- Published
- 2009
32. The transmembrane tyrosines Y56, Y91 and Y167 play important roles in determining the affinity and transport rate of the rabbit proton-coupled peptide transporter PepT1
- Author
-
Myrtani Pieri, Christine Gan, David Meredith, and Patrick D. Bailey
- Subjects
Xenopus ,Peptide ,Protein structure function ,Biochemistry ,Peptide Transporter 1 ,Article ,03 medical and health sciences ,Structure-Activity Relationship ,Xenopus laevis ,Animals ,SLC15a1 ,030304 developmental biology ,chemistry.chemical_classification ,0303 health sciences ,Membrane transport ,Site-directed mutagenesis ,biology ,Symporters ,Chemistry ,030302 biochemistry & molecular biology ,Peptide transporter 1 ,Cell Membrane ,Cell Biology ,Dipeptides ,Hydrogen-Ion Concentration ,Protein structure–function ,Transmembrane protein ,3. Good health ,Transport protein ,Transmembrane domain ,Kinetics ,Protein Transport ,Nutrient absorption ,Amino Acid Substitution ,Symporter ,Mutation ,biology.protein ,Oocytes ,Tyrosine ,Mutant Proteins ,Rabbits ,Epithelia - Abstract
The mammalian proton-coupled peptide transporter PepT1 is widely accepted as the major route of uptake for dietary nitrogen, as well as being responsible for the oral absorption of a number of classes of drugs, including β-lactam antibiotics and angiotensin-converting enzyme (ACE) inhibitors. Using site-directed mutagenesis and zero-trans transport assays, we investigated the role of conserved tyrosines in the transmembrane domains (TMDs) of rabbit PepT1 as predicted by hydropathy plots. All the individual TMD tyrosines were substituted with phenylalanine and shown to retain the ability to traffic to the plasma membrane of Xenopus laevis oocytes. These single substitutions of TMD tyrosines by phenylalanine residues did not affect the proton dependence of peptide uptake, with all retaining wild-type PepT1-like pH dependence. Individual mutations of four of the nine TMD residue tyrosines (Y64, Y287, Y345 and Y587) were without measurable effect on PepT1 function, whereas the other five (Y12, Y56, Y91, Y167 and Y345) were shown to result in altered transport function compared to the wild-type PepT1. Intriguingly, the affinity of Y56F-PepT1 was found to be dramatically increased (approximately 100-fold) in comparison to that of the wild-type rabbit PepT1. Y91 mutations also affected the substrate affinity of the transporter, which increased in line with the hydrophilicity of the substituted amino acid (F > Y > Q > R). Y167 was demonstrated to play a pivotal role in rabbit PepT1 function since Y167F, Y167R and Y167Q demonstrated very little transport function. These results are discussed with regard to a proposed mechanism for PepT1 substrate binding.
- Full Text
- View/download PDF
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