Browsing by Subject "Müller cell dysfunction"

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    Advanced glycation end (AGE) product modification of laminin downregulates Kir4.1 in retinal Müller cells
    (PLOS, 2018-02-23) Thompson, Kayla; Chen, Jonathan; Luo, Qianyi; Xiao, Yucheng; Cummins, Theodore R.; Bhatwadekar, Ashay D.; Ophthalmology, School of Medicine
    Diabetic retinopathy (DR) is a major cause of adult blindness. Retinal Müller cells maintain water homeostasis and potassium concentration via inwardly rectifying Kir4.1 channels. Accumulation of advanced glycation end products (AGEs) is a major pathologic event in DR. While diabetes leads to a decrease in the Kir4.1 channels, it remains unknown whether AGEs-linked to the basement membrane (BM) affect normal Kir4.1 channels. For this study, we hypothesized that AGE-modification of laminin is detrimental to Kir4.1 channels, therefore, disrupting Müller cell function. The AGE-modified laminin-coated substrates were prepared by incubating Petri-dishes with laminin and methylglyoxal for seven days. The rat Müller cells (rMC-1) were propagated on AGE-modified laminin, and Kir4.1 expression and function were evaluated. Quantification of AGEs using ELISA revealed a dose-dependent increase in methylglyoxal-hydro-imidazolone adducts. The rMC-1 propagated on AGE-modified laminin demonstrated a decrease in Kir4.1 levels in immunofluorescence and western blot studies and a decrease in the Kir4.1 channel function. Kir4.1 decrease on AGE-modified laminin resulted in a disorganization of an actin cytoskeleton and disruption of α-dystroglycan-syntrophin-dystrophin complexes. Our studies suggest that AGE-modification of laminin is detrimental to Kir4.1 channels. By studying the role of AGEs in Kir4.1 channels we have identified a novel mechanism of Müller cell dysfunction and its subsequent involvement in DR.
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    Metformin Corrects Abnormal Circadian Rhythm and Kir4.1 Channels in Diabetes
    (The Association for Research in Vision and Ophthalmology, 2020-06-22) Alex, Alpha; Luo, Qianyi; Mathew, Deepa; Di, Rong; Bhatwadekar, Ashay D.; Ophthalmology, School of Medicine
    Purpose Diabetic retinopathy (DR) is a leading cause of visual impairment. Müller cells in DR are dysfunctional due to downregulation of the inwardly rectifying potassium channel Kir4.1. Metformin, a commonly used oral antidiabetic drug, is known to elicit its action through 5′ adenosine monophosphate-activated protein kinase (AMPK), a cellular metabolic regulator; however, its effect on Kir4.1 channels is unknown. For this study, we hypothesized that metformin treatment would correct circadian rhythm disruption and Kir4.1 channel dysfunction in db/db mice. Methods Metformin was given orally to db/db mice. Wheel-running activity, retinal levels of Kir4.1, and AMPK phosphorylation were determined at study termination. In parallel, rat retinal Müller cell line (rMC-1) cells were treated using metformin and 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) to assess the effect of AMPK activation on the Kir4.1 channel. Results The wheel-running activity of the db/db mice was improved following the metformin treatment. The Kir4.1 level in Müller cells was corrected after metformin treatment. Metformin treatment led to an upregulation of clock regulatory genes such as melanopsin (Opn4) and aralkylamine N-acetyltransferase (Aanat). In rMC-1 cells, AMPK activation via AICAR and metformin resulted in increased Kir4.1 and intermediate core clock component Bmal-1 protein expression. The silencing of Prkaa1 (gene for AMPKα1) led to decreased Kir4.1 and Bmal-1 protein expression. Conclusions Our findings demonstrate that metformin corrects abnormal circadian rhythm and Kir4.1 channels in db/db mouse a model of type 2 diabetes. Metformin could represent a critical pharmacological agent for preventing Müller cell dysfunction observed in human DR.