Browsing by Subject "EGCG"

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    EGCG-Encapsulated Halloysite Nanotube Modified-Adhesive for Longer-Lasting Dentin-Resin Interfaces
    (2022-07) Alhijji, Saleh Mohammed; Windsor, L. Jack; Platt, Jeffrey A.; Bottino, Marco C.; Manicke, Nicholas; Sochacki, Sabrina Feitosa
    The degradation of the resin-dentin interface after restoration placement is multifactorial and can be attributed in part to matrix metalloproteinases (MMPs) enzymes associated with recurrent and secondary caries progression. This dissertation aimed to synthesize and characterize the effects of Epigallocatechin-3-gallate (EGCG) from green tea extract as an MMP-inhibitor loaded into a dental adhesive using slow therapeutic compound release nanotubes as a reservoir to allow sustained and slow release. Loading efficiency and drug release were evaluated using a UV-vis spectrometer. The effects on the degree of conversion (DC), polymerization conversion (PC), and Vickers Micro-Hardness (VHN) tests were performed. MMP mediated β-casein (bCN) cleavage rate was used to determine the potency of the eluates contained EGCG to inhibit MMP-9 activity. The results indicated that HNTs could hold about 21.35% (±4.2%) of the EGCG used in the encapsulation process. The addition of 7.5% HNT or 7.5% EGCG-encapsulated HNT adhesive groups did not alter the curing efficiency indicated by the degree of conversion, polymerization conversion, and surface hardness results compared to the control group (p> 0.05). A statistically significant influence of adding HNTs was found to slow down the EGCG release measured up to 8 weeks (p< 0.05). There was a significant decrease in the degradation of β-casein mediated by pre-activated MMP-9 exposed to eluates from EGCG adhesives compared to non-EGCG adhesive groups (p< 0.05). The results suggested that using HNTs for EGCG encapsulating can remedy the negative impact of EGCG on the adhesive’s polymerization and still have the MMP-inhibitory effect and longer release period. Dentin adhesive containing EGCG-encapsulated HNT may contribute to the long-term preservation of restorations through slow and controlled release to maintain the dentin-resin interface's integrity by inhibiting MMP activity.
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    Epigallocatechin-3-gallate (EGCG) consumption in the Ts65Dn model of Down syndrome fails to improve behavioral deficits and is detrimental to skeletal phenotypes
    (Elsevier, 2017-08) Stringer, Megan; Abeysekera, Irushi; Thomas, Jared; LaCombe, Jonathan; Stancombe, Kailey; Stewart, Robert J.; Dria, Karl J.; Wallace, Joseph M.; Goodlett, Charles R.; Roper, Randall J.; Department of Biology, School of Science
    Down syndrome (DS) is caused by three copies of human chromosome 21 (Hsa21) and results in phenotypes including intellectual disability and skeletal deficits. Ts65Dn mice have three copies of ~ 50% of the genes homologous to Hsa21 and display phenotypes associated with DS, including cognitive deficits and skeletal abnormalities. DYRK1A is found in three copies in humans with Trisomy 21 and in Ts65Dn mice, and is involved in a number of critical pathways including neurological development and osteoclastogenesis. Epigallocatechin-3-gallate (EGCG), the main polyphenol in green tea, inhibits Dyrk1a activity. We have previously shown that EGCG treatment (~ 10 mg/kg/day) improves skeletal abnormalities in Ts65Dn mice, yet the same dose, as well as ~ 20 mg/kg/day did not rescue deficits in the Morris water maze spatial learning task (MWM), novel object recognition (NOR) or balance beam task (BB). In contrast, a recent study reported that an EGCG-containing supplement with a dose of 2–3 mg per day (~ 40–60 mg/kg/day) improved hippocampal-dependent task deficits in Ts65Dn mice. The current study investigated if an EGCG dosage similar to that study would yield similar improvements in either cognitive or skeletal deficits. Ts65Dn mice and euploid littermates were given EGCG [0.4 mg/mL] or a water control, with treatments yielding average daily intakes of ~ 50 mg/kg/day EGCG, and tested on the multivariate concentric square field (MCSF)—which assesses activity, exploratory behavior, risk assessment, risk taking, and shelter seeking—and NOR, BB, and MWM. EGCG treatment failed to improve cognitive deficits; EGCG also produced several detrimental effects on skeleton in both genotypes. In a refined HPLC-based assay, its first application in Ts65Dn mice, EGCG treatment significantly reduced kinase activity in femora but not in the cerebral cortex, cerebellum, or hippocampus. Counter to expectation, 9-week-old Ts65Dn mice exhibited a decrease in Dyrk1a protein levels in Western blot analysis in the cerebellum. The lack of beneficial therapeutic behavioral effects and potentially detrimental skeletal effects of EGCG found in Ts65Dn mice emphasize the importance of identifying dosages of EGCG that reliably improve DS phenotypes and linking those effects to actions of EGCG (or EGCG-containing supplements) in specific targets in brain and bone.
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    Epigallocatechin-3-gallate (EGCG) consumption in the Ts65Dn model of Down syndrome fails to improve behavioral deficits and is detrimental to skeletal phenotypes
    (Elsevier, 2017-08-01) Stringer, Megan; Abeysekera, Irushi; Thomas, Jared; LaCombe, Jonathan; Stancombe, Kailey; Stewart, Robert J.; Dria, Karl J.; Wallace, Joseph M.; Goodlett, Charles R.; Roper, Randall J.; Psychology, School of Science
    Down syndrome (DS) is caused by three copies of human chromosome 21 (Hsa21) and results in phenotypes including intellectual disability and skeletal deficits. Ts65Dn mice have three copies of ~50% of the genes homologous to Hsa21 and display phenotypes associated with DS, including cognitive deficits and skeletal abnormalities. DYRK1A is found in three copies in humans with Trisomy 21 and in Ts65Dn mice, and is involved in a number of critical pathways including neurological development and osteoclastogenesis. Epigallocatechin-3-gallate (EGCG), the main polyphenol in green tea, inhibits Dyrk1a activity. We have previously shown that EGCG treatment (~10mg/kg/day) improves skeletal abnormalities in Ts65Dn mice, yet the same dose, as well as ~20mg/kg/day did not rescue deficits in the Morris water maze spatial learning task (MWM), novel object recognition (NOR) or balance beam task (BB). In contrast, a recent study reported that an EGCG-containing supplement with a dose of 2-3mg per day (~40-60mg/kg/day) improved hippocampal-dependent task deficits in Ts65Dn mice. The current study investigated if an EGCG dosage similar to that study would yield similar improvements in either cognitive or skeletal deficits. Ts65Dn mice and euploid littermates were given EGCG [0.4mg/mL] or a water control, with treatments yielding average daily intakes of ~50mg/kg/day EGCG, and tested on the multivariate concentric square field (MCSF)-which assesses activity, exploratory behavior, risk assessment, risk taking, and shelter seeking-and NOR, BB, and MWM. EGCG treatment failed to improve cognitive deficits; EGCG also produced several detrimental effects on skeleton in both genotypes. In a refined HPLC-based assay, its first application in Ts65Dn mice, EGCG treatment significantly reduced kinase activity in femora but not in the cerebral cortex, cerebellum, or hippocampus. Counter to expectation, 9-week-old Ts65Dn mice exhibited a decrease in Dyrk1a protein levels in Western blot analysis in the cerebellum. The lack of beneficial therapeutic behavioral effects and potentially detrimental skeletal effects of EGCG found in Ts65Dn mice emphasize the importance of identifying dosages of EGCG that reliably improve DS phenotypes and linking those effects to actions of EGCG (or EGCG-containing supplements) in specific targets in brain and bone.
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    Extended Treatment with a High Dosage of EGCG to Rescue Appendicular Bone Abnormalities in a Down Syndrome Mouse Model
    (Office of the Vice Chancellor for Research, 2015-04-17) Singh, Prabhjot; Roper, Randall J.; Abeysekera, Irushi
    Individuals with Down syndrome (DS) show significant abnormalities in cognitive abilities, muscle tone, and bone homeostasis. DS is caused by a triplication of the 21st human chromosome (Hsa21). Previous research conducted by our lab using mouse models indicates that three copies of Dyrk1a causes the appendicular skeletal deficits associated with DS. Ts65Dn mouse model carries 50% of the genes homologous to Hsa21, and exhibit excellent phenotypic model for the skeletal deficits seen in individuals with DS, such as low bone mineral density, altered bone structure, and decreased cortical bone. Epigallocatechin-3-gallate (EGCG) is a green tea polyphenol that inhibits Dyrk1a activity. In a previous study, we showed that a three-week, low dose (10mg/kg/day) treatment of EGCG rescued bone mineral density, and trabecular bone to that of euploid levels, but not cortical bone. We hypothesize that increasing the concentration and duration of the treatment will be sufficient enough to more fully restore bone abnormalities by rescuing femoral bone mineral density, bone volume, and improving overall bone strength. This project explores the effects of using a prolonged seven-week, high dosage (100mg/kg/day) treatment on specific bone phenotypes. Dual Energy X-ray absorptiometry (DXA), MicroCT, and mechanical testing will be used as our means of analysis of the treated and untreated bones.
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    Targeting trisomic treatments: optimizing Dyrk1a inhibition to improve Down syndrome deficits
    (Wiley, 2017-09-20) Stringer, Megan; Goodlett, Charles R.; Roper, Randall J.; Biology, School of Science
    Overexpression of Dual‐specificity tyrosine‐phosphorylated regulated kinase 1A (DYRK1A), located on human chromosome 21, may alter molecular processes linked to developmental deficits in Down syndrome (DS). Trisomic DYRK1A is a rational therapeutic target, and although reductions in Dyrk1a genetic dosage have shown improvements in trisomic mouse models, attempts to reduce Dyrk1a activity by pharmacological mechanisms and correct these DS‐associated phenotypes have been largely unsuccessful. Epigallocatechin‐3‐gallate (EGCG) inhibits DYRK1A activity in vitro and this action has been postulated to account for improvement of some DS‐associated phenotypes that have been reported in preclinical studies and clinical trials. However, the beneficial effects of EGCG are inconsistent and there is no direct evidence that any observed improvement actually occurs through Dyrk1a inhibition. Inconclusive outcomes likely reflect a lack of knowledge about the tissue‐specific patterns of spatial and temporal overexpression and elevated activity of Dyrk1a that may contribute to emerging DS traits during development. Emerging evidence indicates that Dyrk1a expression varies over the life span in DS mouse models, yet preclinical therapeutic treatments targeting Dyrk1a have largely not considered these developmental changes. Therapies intended to improve DS phenotypes through normalizing trisomic Dyrk1a need to optimize the timing and dose of treatment to match the spatiotemporal patterning of excessive Dyrk1a activity in relevant tissues. This will require more precise identification of developmental periods of vulnerability to enduring adverse effects of elevated Dyrk1a, representing the concurrence of increased Dyrk1a expression together with hypothesized tissue‐specific‐sensitive periods when Dyrk1a regulates cellular processes that shape the long‐term functional properties of the tissue. Future efforts targeting inhibition of trisomic Dyrk1a should identify these putative spatiotemporally specific developmental sensitive periods and determine whether normalizing Dyrk1a activity then can lead to improved outcomes in DS phenotypes.
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    Treatment and genetic analysis of craniofacial deficits associated with down syndrome
    (2014-12-12) Tumbleson, Danika M.; Roper, Randall J.; Belecky-Adams, Teri; Yost, Robert; Picard, Robert
    Down syndrome (DS) is caused by trisomy of human chromosome 21 (Hsa21) and occurs in ~1 of every 700 live births. Individuals with DS present craniofacial abnormalities, specifically an undersized, dysmorphic mandible which may lead to difficulty with eating, breathing, and speech. Using the Ts65Dn DS mouse model, which mirrors these phenotypes and contains three copies of ~50% Hsa21 homologues, our lab has traced the mandibular deficit to a neural crest cell (NCC) deficiency in the first pharyngeal arch (PA1 or mandibular precursor) at embryonic day 9.5 (E9.5). At E9.5, the PA1 is reduced in size and contains fewer cells due to fewer NCC populating the PA1 from the neural tube (NT) as well as reduced cellular proliferation in the PA1. We hypothesize that both the deficits in NCC migration and proliferation may cause the reduction in size of the PA1. To identify potential genetic mechanisms responsible for trisomic PA1 deficits, we generated RNA-sequence (RNA-seq) data from euploid and trisomic E9.25 NT and E9.5 PA1 (time points occurring before and after observed deficits) using a next-generation sequencing platform. Analysis of RNA-seq data revealed differential trisomic expression of 53 genes from E9.25 NT and 364 genes from E9.5 PA1, five of which are present in three copies in Ts65Dn. We also further analyzed the data to find that fewer alternative splicing events occur in trisomic tissues compared to euploid tissues and in PA1 tissue compared to NT tissue. In a subsequent study, to test gene-specific treatments to rescue PA1 deficits, we targeted Dyrk1A, an overexpressed DS candidate gene implicated in many DS phenotypes and predicted to cause the NCC and PA1 deficiencies. We hypothesize that treatment of pregnant Ts65Dn mothers with Epigallocatechin gallate (EGCG), a known Dyrk1A inhibitor, will correct NCC deficits and rescue the undersized PA1 in trisomic E9.5 embryos. To test our hypothesis, we treated pregnant Ts65Dn mothers with EGCG from either gestational day 7 (G7) to G8 or G0 to G9.5. Our study found an increase in PA1 volume and NCC number in trisomic E9.5 embryos after treatment on G7 and G8, but observed no significant improvements in NCC deficits following G0-G9.5 treatment. We also observed a developmental delay of embryos from trisomic mothers treated with EGCG from G0-G9.5. Together, these data show that timing and sufficient dosage of EGCG treatment is most effective during the developmental window the few days before NCC deficits arise, during G7 and G8, and may be ineffective or harmful when administered at earlier developmental time points. Together, the findings of both studies offer a better understanding of potential mechanisms altered by trisomy as well as preclinical evidence for EGCG as a potential prenatal therapy for craniofacial disorders linked to DS.