pH (Low) Insertion Peptide (pHLIP) Targets Ischemic Myocardium

The pH (low) insertion peptide (pHLIP) family enables targeting of cells in tissues with low extracellular pH. Here, we show that ischemic myocardium is targeted, potentially opening a new route to diagnosis and therapy. The experiments were performed using two murine ischemia models: regional ischemia induced by coronary artery occlusion and global low-flow ischemia in isolated hearts. In both models, pH-sensitive pHLIPs [wild type (WT) and Var7] or WT-pHLIP–coated liposomes bind ischemic but not normal regions of myocardium, whereas pH-insensitive, kVar7, and liposomes coated with PEG showed no preference. pHLIP did not influence either the mechanical or the electrical activity of ischemic myocardium. In contrast to other known targeting strategies, the pHLIP-based binding does not require severe myocardial damage. Thus, pHLIP could be used for delivery of pharmaceutical agents or imaging probes to the myocardial regions undergoing brief restrictions of blood supply that do not induce irreversible changes in myocytes

Cyclophilin D deficiency rescues Aβ-impaired PKA/CREB signaling and alleviates synaptic degeneration

The coexistence of neuronal mitochondrial pathology and synaptic dysfunction is an early pathological feature of Alzheimer's disease (AD). Cyclophilin D (CypD), an integral part of mitochondrial permeability transition pore (mPTP), is involved in amyloid beta (Aβ)-instigated mitochondrial dysfunction. Blockade of CypD prevents Aβ-induced mitochondrial malfunction and the consequent cognitive impairments. Here, we showed the elimination of reactive oxygen species (ROS) by antioxidants probucol or superoxide dismutase (SOD)/catalase blocks Aβ-mediated inactivation of protein kinase A (PKA)/cAMP regulatory-element-binding (CREB) signal transduction pathway and loss of synapse, suggesting the detrimental effects of oxidative stress on neuronal PKA/CREB activity. Notably, neurons lacking CypD significantly attenuate Aβ-induced ROS. Consequently, CypD-deficient neurons are resistant to Aβ-disrupted PKA/CREB signaling by increased PKA activity, phosphorylation of PKA catalytic subunit (PKA C), and CREB. In parallel, lack of CypD protects neurons from Aβ-induced loss of synapses and synaptic dysfunction. Furthermore, compared to the mAPP mice, CypD-deficient mAPP mice reveal less inactivation of PKA–CREB activity and increased synaptic density, attenuate abnormalities in dendritic spine maturation, and improve spontaneous synaptic activity. These findings provide new insights into a mechanism in the crosstalk between the CypD-dependent mitochondrial oxidative stress and signaling cascade, leading to synaptic injury, functioning through the PKA/CREB signal transduction pathway

Cyclophilin D deficiency rescues Aβ-impaired PKA/CREB signaling and alleviates synaptic degeneration

AbstractThe coexistence of neuronal mitochondrial pathology and synaptic dysfunction is an early pathological feature of Alzheimer's disease (AD). Cyclophilin D (CypD), an integral part of mitochondrial permeability transition pore (mPTP), is involved in amyloid beta (Aβ)-instigated mitochondrial dysfunction. Blockade of CypD prevents Aβ-induced mitochondrial malfunction and the consequent cognitive impairments. Here, we showed the elimination of reactive oxygen species (ROS) by antioxidants probucol or superoxide dismutase (SOD)/catalase blocks Aβ-mediated inactivation of protein kinase A (PKA)/cAMP regulatory-element-binding (CREB) signal transduction pathway and loss of synapse, suggesting the detrimental effects of oxidative stress on neuronal PKA/CREB activity. Notably, neurons lacking CypD significantly attenuate Aβ-induced ROS. Consequently, CypD-deficient neurons are resistant to Aβ-disrupted PKA/CREB signaling by increased PKA activity, phosphorylation of PKA catalytic subunit (PKA C), and CREB. In parallel, lack of CypD protects neurons from Aβ-induced loss of synapses and synaptic dysfunction. Furthermore, compared to the mAPP mice, CypD-deficient mAPP mice reveal less inactivation of PKA–CREB activity and increased synaptic density, attenuate abnormalities in dendritic spine maturation, and improve spontaneous synaptic activity. These findings provide new insights into a mechanism in the crosstalk between the CypD-dependent mitochondrial oxidative stress and signaling cascade, leading to synaptic injury, functioning through the PKA/CREB signal transduction pathway

The origin of Rosenthal fibers and their contributions to astrocyte pathology in Alexander disease

Abstract Rosenthal fibers (RFs) are cytoplasmic, proteinaceous aggregates. They are the pathognomonic feature of the astrocyte pathology in Alexander Disease (AxD), a neurodegenerative disorder caused by heterozygous mutations in the GFAP gene, encoding glial fibrillary acidic protein (GFAP). Although RFs have been known for many years their origin and significance remain elusive issues. We have used mouse models of AxD based on the overexpression of human GFAP (transgenic, TG) and a point mutation in mouse GFAP (knock-in, KI) to examine the formation of RFs and to find astrocyte changes that correlate with the appearance of RFs. We found RFs of various sizes and shapes. The smallest ones appear as granular depositions on intermediate filaments. These contain GFAP and the small heat shock protein, alphaB-crystallin. Their aggregation appears to give rise to large RFs. The appearance of new RFs and the growth of previously formed RFs occur over time. We determined that DAPI is a reliable marker of RFs and in parallel with Fluoro-Jade B (FJB) staining defined a high variability in the appearance of RFs, even in neighboring astrocytes. Although many astrocytes in AxD with increased levels of GFAP and with or without RFs change their phenotype, only some cells with large numbers of RFs show a profound reconstruction of cellular processes, with a loss of fine distal processes and the appearance of large, lobulated nuclei, likely due to arrested mitosis. We conclude that 1) RFs appear to originate as small, osmiophilic masses containing both GFAP and alphaB-crystallin deposited on bundles of intermediate filaments. 2) RFs continue to form within AxD astrocytes over time. 3) DAPI is a reliable marker for RFs and can be used with immunolabeling. 4) RFs appear to interfere with the successful completion of astrocyte mitosis and cell division

Single-nucleus RNA-seq identifies Huntington disease astrocyte states

Huntington Disease (HD) is an inherited movement disorder caused by expanded CAG repeats in the Huntingtin gene. We have used single nucleus RNASeq (snRNASeq) to uncover cellular phenotypes that change in the disease, investigating single cell gene expression in cingulate cortex of patients with HD and comparing the gene expression to that of patients with no neurological disease. In this study, we focused on astrocytes, although we found significant gene expression differences in neurons, oligodendrocytes, and microglia as well. In particular, the gene expression profiles of astrocytes in HD showed multiple signatures, varying in phenotype from cells that had markedly upregulated metallothionein and heat shock genes, but had not completely lost the expression of genes associated with normal protoplasmic astrocytes, to astrocytes that had substantially upregulated glial fibrillary acidic protein (GFAP) and had lost expression of many normal protoplasmic astrocyte genes as well as metallothionein genes. When compared to astrocytes in control samples, astrocyte signatures in HD also showed downregulated expression of a number of genes, including several associated with protoplasmic astrocyte function and lipid synthesis. Thus, HD astrocytes appeared in variable transcriptional phenotypes, and could be divided into several different “states”, defined by patterns of gene expression. Ultimately, this study begins to fill the knowledge gap of single cell gene expression in HD and provide a more detailed understanding of the variation in changes in gene expression during astrocyte “reactions” to the disease

Impact of Socioeconomic Status Measures on Hospital Profiling in New York City

BackgroundCurrent 30-day readmission models used by the Center for Medicare and Medicaid Services for the purpose of hospital-level comparisons lack measures of socioeconomic status (SES). We examined whether the inclusion of an SES measure in 30-day congestive heart failure readmission models changed hospital risk-standardized readmission rates in New York City (NYC) hospitals.Methods and resultsUsing a Centers for Medicare & Medicaid Services (CMS)-like model, we estimated 30-day hospital-level risk-standardized readmission rates by adjusting for age, sex, and comorbid conditions. Next, we examined how hospital risk-standardized readmission rates changed relative to the NYC mean with inclusion of the Agency for Healthcare Research and Quality (AHRQ)-validated SES index score. In a secondary analysis, we examined whether inclusion of the AHRQ SES index score in 30-day readmission models disproportionately impacted the risk-standardized readmission rates of minority-serving hospitals. Higher AHRQ SES scores, indicators of higher SES, were associated with lower odds (0.99) of 30-day readmission (P<0.019). The addition of the AHRQ SES index did not change the model's C statistic (0.63). After adjustment for the AHRQ SES index, 1 hospital changed status from worse than the NYC average to no different than the NYC average. After adjustment for the AHRQ SES index, 1 NYC minority-serving hospital was reclassified from worse to no different than average.ConclusionsAlthough patients with higher SES were less likely to be admitted, the impact of SES on readmission was small. In NYC, inclusion of the AHRQ SES score in a CMS-based model did not impact hospital-level profiling based on 30-day readmission

Neuropeptide Y is important for basal and seizure induced precursor cell proliferation in the hippocampus

We have shown that neuropeptide Y (NPY) regulates neurogenesis in the normal dentate gyrus (DG) via Y(1) receptors (Howell, O.W., Scharfman, H.E., Herzog, H., Sundstrom, L.E., Beck-Sickinger, A. and Gray, W.P. (2003) Neuropeptide Y is neuroproliferative for post-natal hippocampal precursor cells. J Neurochem, 86, 646-659; Howell, O.W., Doyle, K., Goodman, J.H., Scharfman, H.E., Herzog, H., Pringle, A., Beck-Sickinger, A.G. and Gray, W.P. (2005) Neuropeptide Y stimulates neuronal precursor proliferation in the post-natal and adult dentate gyrus. J Neurochem, 93, 560-570). This regulation may be relevant to epilepsy, because seizures increase both NPY expression and precursor cell proliferation in the DG. Therefore, the effects of NPY on DG precursors were evaluated in normal conditions and after status epilepticus. In addition, potentially distinct NPY-responsive precursors were identified, and an analysis performed not only of the DG, but also the caudal subventricular zone (cSVZ) and subcallosal zone (SCZ) where seizures modulate glial precursors. We show a proliferative effect of NPY on multipotent nestin cells expressing the stem cell marker Lewis-X from both the DG and the cSVZ/SCZ in vitro. We confirm an effect on proliferation in the cSVZ/SCZ of Y(1) receptor(-/-) mice and demonstrate a significant reduction in basal and seizure-induced proliferation in the DG of NPY(-/-) mice