👤 Hyang Sook Hoe

About 30% of patients with active acromegaly experience paradoxically increased growth hormone (GH) secretion during the diagnostic oral glucose tolerance test (OGTT). Endogenous glucose-dependent insulinotropic polypeptide (GIP) is implicated in this paradoxical secretion. We used the GIP receptor (GIPR) antagonist GIP(3-30)NH2 to test the hypothesis that GIP mediates this paradoxical response when GIPR is abundantly expressed in somatotropinomas. A total of 25 treatment-naive patients with acromegaly were enrolled. Each patient underwent one OGTT during simultaneous placebo infusion and one OGTT during a GIP(3-30)NH2 infusion. Blood samples were drawn at baseline and regularly after infusions to measure GH. We assessed pituitary adenoma size by magnetic resonance imaging and GIPR expression by immunohistochemistry on resected somatotropinomas. For mechanistic confirmation, we applied in vitro and ex vivo approaches. The main outcome measure was the effect of GIP(3-30)NH2 on paradoxical GH secretion during OGTT as a measure of GIP involvement. In 4 of 7 patients with paradoxical GH secretion, GIP(3-30)NH2 infusion completely abolished the paradoxical response (P = .0003). Somatotrophs were available from 3 of 4 of these patients, all showing abundant GIPR expression. Adenoma size did not differ between patients with and without paradoxical GH secretion. Of 25 patients with acromegaly, 7 had paradoxical GH secretion during OGTT, and pharmaceutical GIPR blockade abolished this secretion in 4. Corresponding somatotroph adenomas abundantly expressed GIPR, suggesting a therapeutic target in this subpopulation of patients. In vitro and ex vivo analyses confirmed the role of GIP and the effects of the antagonist. Show less

Dual specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) is associated with the pathoprogression of neurodevelopmental and neurodegenerative disorders. However, the effects of direct genetic manipulation of DYRK1A in the brain on cognitive function, neuroinflammation and Alzheimer's disease (AD) pathology and underlying molecular mechanisms have not been fully investigated. To determine whether overexpressing or knocking down DYRK1A expression directly in the brain affects cognitive function, neuroinflammation and AD pathology, adeno-associated viruses (AAVs) were injected into the hippocampus of wild-type (WT), 5xFAD, and PS19 mice. Then, cognitive function was assessed via Y-maze and novel object recognition (NOR) tests, and neuroinflammatory responses and AD pathologies were analyzed by real-time PCR, Western blotting, immunofluorescence staining, AD-associated protein activity assays and ELISA. In WT mice, hippocampal DYRK1A overexpression significantly reduced short-term spatial/recognition memory and SynGAP expression while increasing p-P38 levels. Conversely, in amyloid-beta (Aβ)-overexpressing 5xFAD mice, hippocampal DYRK1A knockdown improved short-term spatial/recognition memory and significantly increased CaMKIIα and CREB phosphorylation. Moreover, hippocampal DYRK1A knockdown in 5xFAD mice significantly suppressed mRNA levels of proinflammatory cytokines and markers of AD-associated reactive astrocytes (RAs), disease-associated microglia (DAMs), and RA-DAM interactions. However, hippocampal DYRK1A overexpression in 5xFAD mice increased mRNA levels of the proinflammatory cytokine IL-1β, RA markers and the microglial marker Iba-1. Interestingly, hippocampal DYRK1A knockdown in 5xFAD mice significantly increased levels of the anti-oxidative/inflammatory molecule HO-1 without altering p-STAT3/p-NF-κB levels. By contrast, hippocampal DYRK1A overexpression in 5xFAD mice enhanced STAT3/NF-κB phosphorylation but did not affect ROS levels. Importantly, hippocampal DYRK1A knockdown in 5xFAD mice significantly reduced Aβ plaque number, soluble Aβ40 levels, and soluble/insoluble Aβ42 levels by suppressing β-secretase BACE1 activity but not tau hyperphosphorylation. Finally, hippocampal DYRK1A knockdown in PS19 mice [a model of AD that overexpresses human mutant tau (P301S)] selectively decreased insoluble tau hyperphosphorylation at Ser396 and Ser404 and alleviated proinflammatory responses/glial-associated neuroinflammatory dynamics. Taken together, our data indicate that DYRK1A modulates cognitive function, neuroinflammation, and AD pathology (Aβ and tauopathy) in mouse models of AD and/or WT mice and support DYRK1A as a potential therapeutic target for AD. Show less

Previous studies have reported that 40 Hz visual stimulation (acute white light exposure) reduced Aβ levels in Alzheimer's disease (AD) mouse model. However, whether different light colors distinctly regulate AD pathologies has not been well characterized. In the present study, an optimized organic light-emitting diode (OLED)-based visual stimulation platform was developed to provide uniform illumination without blind spots, and the color-dependent effects on cognitive function and amyloid-β (Aβ) pathology were investigated in 5xFAD mice, an Aβ-overexpressing AD model. Acute exposure to white or red OLED light (1 h/day for 2 days) significantly improved cognitive function, reduced hippocampal Aβ plaque accumulation via increasing ADAM17 activity, and downregulated proinflammatory cytokine IL-1β levels in 3-month-old 5xFAD mice, whereas green or blue OLED light did not produce these effects. In addition, chronic white and red OLED stimulation (1 h/day for 2 weeks) was shown to enhance recognition memory; however, only red light further diminished Aβ plaque deposition by upregulating ADAM17 activity and suppressing BACE-1 activity without altering neuroinflammation in 6-month-old 5xFAD mice. Moreover, acute white and red OLED exposure (1 h, single session) was observed to enhance c-fos expression, which is associated with neural activation along the visual pathway, thereby suggesting a mechanistic link between light stimulation and cognitive enhancement. Taken together, these findings demonstrate that color-dependent visual stimulation may serve as a promising electroceutical strategy for AD, with red light uniquely combining memory enhancement, Aβ reduction via ADAM17 upregulation and BACE1 suppression, and anti-inflammatory effects. Show less

We recently reported that the dopamine (DA) analogue CA140 modulates neuroinflammatory responses in lipopolysaccharide-injected wild-type (WT) mice and in 3-month-old 5xFAD mice, a model of Alzheimer's disease (AD). However, the effects of CA140 on Aβ/tau pathology and synaptic/cognitive function and its molecular mechanisms of action are unknown. To investigate the effects of CA140 on cognitive and synaptic function and AD pathology, 3-month-old WT mice or 8-month-old (aged) 5xFAD mice were injected with vehicle (10% DMSO) or CA140 (30 mg/kg, i.p.) daily for 10, 14, or 17 days. Behavioral tests, ELISA, electrophysiology, RNA sequencing, real-time PCR, Golgi staining, immunofluorescence staining, and western blotting were conducted. In aged 5xFAD mice, a model of AD pathology, CA140 treatment significantly reduced Aβ/tau fibrillation, Aβ plaque number, tau hyperphosphorylation, and neuroinflammation by inhibiting NLRP3 activation. In addition, CA140 treatment downregulated the expression of cxcl10, a marker of AD-associated reactive astrocytes (RAs), and c1qa, a marker of the interaction of RAs with disease-associated microglia (DAMs) in 5xFAD mice. CA140 treatment also suppressed the mRNA levels of s100β and cxcl10, markers of AD-associated RAs, in primary astrocytes from 5xFAD mice. In primary microglial cells from 5xFAD mice, CA140 treatment increased the mRNA levels of markers of homeostatic microglia (cx3cr1 and p2ry12) and decreased the mRNA levels of a marker of proliferative region-associated microglia (gpnmb) and a marker of lipid-droplet-accumulating microglia (cln3). Importantly, CA140 treatment rescued scopolamine (SCO)-mediated deficits in long-term memory, dendritic spine number, and LTP impairment. In aged 5xFAD mice, these effects of CA140 treatment on cognitive/synaptic function and AD pathology were regulated by dopamine D1 receptor (DRD1)/Elk1 signaling. In primary hippocampal neurons and WT mice, CA140 treatment promoted long-term memory and dendritic spine formation via effects on DRD1/CaMKIIα and/or ERK signaling. Our results indicate that CA140 improves neuronal/synaptic/cognitive function and ameliorates Aβ/tau pathology and neuroinflammation by modulating DRD1 signaling in primary hippocampal neurons, primary astrocytes/microglia, WT mice, and aged 5xFAD mice. Show less

Opioidergic SLP (sustained ligand-activated preconditioning) induced by 3-5 days of opioid receptor (OR) agonism induces persistent protection against ischemia-reperfusion (I-R) injury in young and aged hearts, and is mechanistically distinct from conventional preconditioning responses. We thus applied unbiased gene-array interrogation to identify molecular effects of SLP in pre- and post-ischemic myocardium. Male C57Bl/6 mice were implanted with 75 mg morphine or placebo pellets for 5 days. Resultant SLP did not modify cardiac function, and markedly reduced dysfunction and injury in perfused hearts subjected to 25 min ischemia/45 min reperfusion. Microarray analysis identified 14 up- and 86 down-regulated genes in normoxic hearts from SLP mice (≥1.3-fold change, FDR≤5%). Induced genes encoded sarcomeric/contractile proteins (Myh7, Mybpc3,Myom2,Des), natriuretic peptides (Nppa,Nppb) and stress-signaling elements (Csda,Ptgds). Highly repressed genes primarily encoded chemokines (Ccl2,Ccl4,Ccl7,Ccl9,Ccl13,Ccl3l3,Cxcl3), cytokines (Il1b,Il6,Tnf) and other proteins involved in inflammation/immunity (C3,Cd74,Cd83, Cd86,Hla-dbq1,Hla-drb1,Saa1,Selp,Serpina3), together with endoplasmic stress proteins (known: Dnajb1,Herpud1,Socs3; putative: Il6, Gadd45g,Rcan1) and transcriptional controllers (Egr2,Egr3, Fos,Hmox1,Nfkbid). Biological themes modified thus related to inflammation/immunity, together with cellular/cardiovascular movement and development. SLP also modified the transcriptional response to I-R (46 genes uniquely altered post-ischemia), which may influence later infarction/remodeling. This included up-regulated determinants of cellular resistance to oxidant (Mgst3,Gstm1,Gstm2) and other forms of stress (Xirp1,Ankrd1,Clu), and repression of stress-response genes (Hspa1a,Hspd1,Hsp90aa,Hsph1,Serpinh1) and Txnip. Protection via SLP is associated with transcriptional repression of inflammation/immunity, up-regulation of sarcomeric elements and natriuretic peptides, and modulation of cell stress, growth and development, while conventional protective molecules are unaltered. Show less