Project description:The decline of cognitive function is a feature of normal human aging and is exacerbated in AlzheimerM-bM-^@M-^Ys disease (AD). DNA repair declines in brain cells during normal aging and even more so in AD. Here we show that experimental reduction in levels of the base excision repair enzyme, DNA polymerase M-NM-2 (Polb) renders neurons vulnerable to age-related dysfunction and degeneration in a mouse model of AD. Whereas 3xTgAD mice exhibit age-related extracellular amyloid b-peptide (Ab) accumulation and cognitive deficits, but no neuronal death, 3xTg/Polb+/- mice accumulates intracellular Ab and neurons die in the hippocampus and cerebral cortex. The DNA repair-deficient 3xTgAD mice exhibited increased DNA strand breaks and apoptotic caspase activation with loss of hippocampal volume, and impaired synaptic plasticity and memory retention. Molecular profiling revealed remarkable similarities in gene expression alterations in brain cells of AD patients and 3xTgAD/Polb+/- mice including multiple abnormalities suggestive of impaired cellular bioenergetics. Our findings demonstrate that a modest decrement in oxidative DNA damage processing is sufficient to render neurons vulnerable to AD-related pathogenic molecular and cellular alterations that result in the dysfunction and death of neurons, and associated cognitive deficits. 4 mouse strains were used in these experiments, the 3xTgAD and Pol M-NM-2 (+/-) mice were bred at the National Institute on Aging (Baltimore, Maryland). The original line 3xTgAD line was generated as described previously (Oddo, et. al 2003) and possess APPswe, PS1M146V, and tauP301L mutations. DNA polymerase beta heterozygous mice, Pol M-NM-2 (+/-), were crossed with the 3xTgAD mice to generate a 3xTgAD/Pol M-NM-2 (+/-) mouse. The Wt strain is C57Bl/6. At 20 months of age these mice were euthanized by cervical dislocation, the brain removed from the skull and dissected into regions of interest, the prefrontal cortex was used for the microarray studies.
Project description:Cockayne syndrome (CS) is a photosensitive, DNA repair disorder associated with progeria caused by a defect in the transcription-coupled repair (TCR) subpathway of nucleotide excision repair (NER). Here, complete inactivation of NER in Csbm/m/Xpa-/- mutants causes a phenotype that reliably mimics the human progeroid CS syndrome. Newborn Csbm/m/Xpa-/- mice display attenuated growth, progressive neurological dysfunction, retinal degeneration, cachexia, kyphosis and die before weaning. To investigate whether a disturbance in growth and metabolism could explain the pronounced accelerated organismal deterioration seen in Csbm/m/Xpa-/- mice, we evaluated the liver transcriptome of 15-day old wt, single and double mutant mice (n=4). At this age, the Csbm/m/Xpa-/- pups have not yet become cachectic. Mouse liver transcriptome analysis and several physiological endpoints revealed systemic suppression of the GH/IGF1 somatotroph axis and oxidative metabolism, increased antioxidant responses, hypoglycemia together with hepatic glycogen and fat accumulation. Broad genome-wide parallels between Csbm/m/Xpa-/- and naturally aged mouse liver transcriptomes suggested that these changes are intrinsic to natural aging and the DNA repair-deficient mice. Importantly, wild type (wt) mice exposed to a low dose of chronic genotoxic stress and adult Csbm/m mutant mice recapitulated this response, thereby pointing to a novel link between genome instability and the age-related decline of the somatotroph axis.
Project description:The decline of cognitive function is a feature of normal human aging and is exacerbated in Alzheimer’s disease (AD). DNA repair declines in brain cells during normal aging and even more so in AD. Here we show that experimental reduction in levels of the base excision repair enzyme, DNA polymerase β (Polb) renders neurons vulnerable to age-related dysfunction and degeneration in a mouse model of AD. Whereas 3xTgAD mice exhibit age-related extracellular amyloid b-peptide (Ab) accumulation and cognitive deficits, but no neuronal death, 3xTg/Polb+/- mice accumulates intracellular Ab and neurons die in the hippocampus and cerebral cortex. The DNA repair-deficient 3xTgAD mice exhibited increased DNA strand breaks and apoptotic caspase activation with loss of hippocampal volume, and impaired synaptic plasticity and memory retention. Molecular profiling revealed remarkable similarities in gene expression alterations in brain cells of AD patients and 3xTgAD/Polb+/- mice including multiple abnormalities suggestive of impaired cellular bioenergetics. Our findings demonstrate that a modest decrement in oxidative DNA damage processing is sufficient to render neurons vulnerable to AD-related pathogenic molecular and cellular alterations that result in the dysfunction and death of neurons, and associated cognitive deficits.
Project description:Oxidative stress generating DNA damage has been shown to be a key characteristic in Alzheimer’s disease (AD). However, how it affects the pathogenesis of AD is not yet fully understood. NEIL3 is a DNA glycosylase initiating oxidative DNA repair and with a distinct expression pattern in proliferating cells. In brain, its function has been linked to hippocampal-dependent memory and to induction of neurogenesis after stroke and in prion disease. Here, we generated a novel AD mouse model deficient for Neil3 to study the impact of impaired oxidative base lesion repair on the pathogenesis of AD. Our results demonstrate an age-dependent decrease in amyloid-β (Aβ) plaque deposition in female NEIL3-deficient AD mice. Moreover, male NEIL3-deficient AD mice show reduced neural stem cell proliferation in the adult hippocampus and impaired working memory. These effects seem to be independent of DNA repair as both sexes show increased level of oxidative base lesions in the hippocampus upon loss of NEIL3. Thus, our findings suggest a sex-dependent role of NEIL3 in the progression of AD by altering cerebral Aβ accumulation and promoting adult hippocampal neurogenesis to maintain cognitive function.
Project description:Hunner-type interstitial cystitis (HIC) is a rare, enigmatic inflammatory disease of the urinary bladder with no curative treatments. In this study, we aimed to characterize the unique cellular and immunological factors specifically involved in HIC by comparing with cystitis induced by Mycobacterium bovis bacillus Calmette–Guérin, which presents similar clinicopathological features to HIC. Here, we show that T helper 1/17 polarized immune responses accompanied by prominent overexpression of interferon (IFN)-γ, enhanced cGAS-STING cytosolic DNA sensing pathway, and increased plasma cell infiltration are the characteristic inflammatory features in HIC bladder. Further, we developed a novel mouse anti-IFN-γ DNA aptamer and observed that intravesical instillation of the aptamer significantly ameliorated bladder inflammation, pelvic pain and voiding dysfunction in a recently developed novel murine HIC mouse model with little migration into the blood. Our study provides the plausible basis for clinical translation of the anti-IFN-γ DNA aptamer in the treatment of human HIC.
Project description:Oxidative DNA damage is recognised by 8-oxoguanine (8-oxoG) DNA glycosylase 1 (OGG1), which excises 8-oxoG, leaving a substrate for apurinic endonuclease 1 (APE1), initiating repair. Here, we describe a small molecule (TH10785) that interacts with the Phe319 and Gly42 amino acids of OGG1, increases the enzyme activity 10-fold and generates a novel β,δ-lyase enzymatic function. TH10785 controls the catalytic activity mediated by a nitrogen base within its molecular structure. In cells, TH10785 increases OGG1 recruitment to and repair of oxidative DNA damage. This alters the repair process, which no longer requires APE1 but instead is dependent on polynucleotide kinase phosphatase (PNKP1) activity. The increased repair of oxidative DNA lesions with a small molecule may have therapeutic applications in various diseases and ageing.
Project description:Oxidative DNA damage in neurons activates a DNA damage response (DDR) to promote repair. Under a chronic oxidative environment these processes may be altered and promote accumulation of unrepaired DNA damage and continued activation of a DDR, leading to apoptosis or senescence activation. Accumulation of oxidative DNA damage are features of brain ageing and neurodegeneration but the effects of persistent DNA damage in neurons are not well characterised. We developed a model of persistent oxidative DNA damage in human neurons in vitro (LUHMES) by exposing them to a sub-lethal concentration of hydrogen peroxide (H2O2) following a "single stress" and “double stress” protocols. We characterised the neuronal transcriptome under these circumstances using microarray analysis.
Project description:Oxidative stress has a ubiquitous role in neurodegenerative diseases and oxidative damage in specific regions of the brain is associated with selective neurodegeneration. We previously reported that Alzheimer disease (AD) model mice showed decreased insulin-degrading enzyme (IDE) levels in the cerebrum and accelerated phenotypic features of AD when crossbred with alpha-tocopherol transfer protein knockout (Ttpa-/-) mice. To further investigate the role of chronic oxidative stress in AD pathophysiology, we performed DNA microarray analysis using young and aged wild-type mice and aged Ttpa-/- mice. Among the genes whose expression changed dramatically was Phospholipase A2 group 3 (Pla2g3); Pla2g3 was identified because of its expression profile of cerebral specific up-regulation by chronic oxidative stress in silico and in aged Ttpa-/- mice. Immunohistochemical studies also demonstrated that human astrocytic Pla2g3 expression was significantly increased in human AD brains compared with control brains. Moreover, transfection of HEK293 cells with human Pla2g3 decreased endogenous IDE expression in a dose-dependent manner. Our findings show a key role of Pla2g3 on the reduction of IDE, and suggest that cerebrum specific increase of Pla2g3 is involved in the initiation and/or progression of AD.
Project description:Objective: The ApoE (apolipoprotein) allele epsilon 4 is a major genetic risk factor for Alzheimer disease, cardiovascular disorders, and stroke, indicating that it significantly impacts cerebral and vascular systems. However, very little is known about how APOE genotype affects brain endothelial cells, which form a network of tight junctions to regulate communication between the brain and circulating blood factors. Approach and Results: Here, we present a novel model of endothelial dysfunction using isogenic human induced pluripotent stem cell-derived cells harboring different alleles of the APOE gene, specifically ApoE 3/3, 3/4, and 4/4. We show for the first time that ApoE4 expression by endothelial cells is sufficient to cause a toxic gain of cellular dysfunction. Using RNAseq, we found significant effects of ApoE4 on signaling pathways involved in blood coagulation and barrier function. These changes were associated with altered cell function, including increased binding of platelets to ECs with the 3/4 or 4/4 genotype. ApoE4-positive cells exhibited a proinflammatory state and prothrombotic state, evidenced by higher secretion of Aβ (amyloid-β) 40 and 42, increased release of cytokines, and overexpression of the platelet-binding protein VWF (vonWillebrand factor). Immunohistochemistry of human brain Alzheimer disease brains also showed increased VWF expression with the ApoE4/4 genotype. Finally, pharmacological inhibition of inflammation in ECs by celastrol rescued overexpression of VWF in cells expressing ApoE4. Conclusions: These cells provide novel insight into ApoE4-mediated endothelial dysfunction and provide a new platform to test potential therapies for vascular disorders.