Identification of miRNAs That Mediate Protective Functions of Anti-Cancer Drugs During White Matter Ischemic Injury.

We have previously shown that two anti-cancer drugs, CX-4945 and MS-275, protect and preserve white matter (WM) architecture and improve functional recovery in a model of WM ischemic injury. While both compounds promote recovery, CX-4945 is a selective Casein kinase 2 (CK2) inhibitor and MS-275 is a selective Class I histone deacetylase (HDAC) inhibitor. Alterations in microRNAs (miRNAs) mediate some of the protective actions of these drugs.

Ex Vivo Studies of Optic Nerve Axon Electrophysiology.

The use of ex vivo compound action potential (CAP) recordings from intact optic nerves is an ideal model to study white matter function without the influence of gray matter. Here, we describe how freshly dissected optic nerves are placed in a humidified recording chamber and how evoked CAPs are recorded and monitored in real time for up to 10 h. Evoked CAP recordings allow for white matter to be studied under acute challenges such as anoxia, hypoxia, aglycemia, and ischemia.

Role of Brain Glycogen During Ischemia, Aging and Cell-to-Cell Interactions.

The astrocyte-neuron lactate transfer shuttle (ANLS) is one of the important metabolic systems that provides a physiological infrastructure for glia-neuronal interactions where specialized architectural organization supports the function. Perivascular astrocyte end-feet take up glucose via glucose transporter 1 to actively regulate glycogen stores, such that high ambient glucose upregulates glycogen and low levels of glucose deplete glycogen stores. A rapid breakdown of glycogen into lactate during increased neuronal activity or low glucose conditions becomes essential for maintaining axon function.

Preserving Mitochondrial Structure and Motility Promotes Recovery of White Matter After Ischemia.

Stroke significantly affects white matter in the brain by impairing axon function, which results in clinical deficits. Axonal mitochondria are highly dynamic and are transported via microtubules in the anterograde or retrograde direction, depending upon axonal energy demands. Recently, we reported that mitochondrial division inhibitor 1 (Mdivi-1) promotes axon function recovery by preventing mitochondrial fission only when applied during ischemia.

Mitochondrial dynamics and preconditioning in white matter.

Mechanisms of ischemic preconditioning have been extensively studied in gray matter. However, an ischemic episode affects both the gray matter (GM) and white matter (WM) portions of the brain. Inhibition of mitochondrial fission is one of the mechanisms of preconditioning neuronal cell bodies against ischemia.

CK2 inhibition protects white matter from ischemic injury.

Strokes occur predominantly in the elderly and white matter (WM) is injured in most strokes, contributing to the disability associated with clinical deficits. Casein kinase 2 (CK2) is expressed in neuronal cells and was reported to be neuroprotective during cerebral ischemia. Recently, we reported that CK2 is abundantly expressed by glial cells and myelin.

NOS3 Inhibition Confers Post-Ischemic Protection to Young and Aging White Matter Integrity by Conserving Mitochondrial Dynamics and Miro-2 Levels.

White matter (WM) damage following a stroke underlies a majority of the neurological disability that is subsequently observed. Although ischemic injury mechanisms are age-dependent, conserving axonal mitochondria provides consistent post-ischemic protection to young and aging WM. Nitric oxide synthase (NOS) activation is a major cause of oxidative and mitochondrial injury in gray matter during ischemia; therefore, we used a pure WM tract, isolated male mouse optic nerve, to investigate whether NOS inhibition provides post-ischemic functional recovery by preserving mitochondria.

BACE1 regulates the proliferation and cellular functions of Schwann cells.

BACE1 is an indispensable enzyme for generating β-amyloid peptides, which are excessively accumulated in brains of Alzheimer's patients. However, BACE1 is also required for proper myelination of peripheral nerves, as BACE1-null mice display hypomyelination. To determine the precise effects of BACE1 on myelination, here we have uncovered a role of BACE1 in the control of Schwann cell proliferation during development.

Proteolipid protein-deficient myelin promotes axonal mitochondrial dysfunction via altered metabolic coupling.

Hereditary spastic paraplegia (HSP) is a neurological syndrome characterized by degeneration of central nervous system (CNS) axons. Mutated HSP proteins include myelin proteolipid protein (PLP) and axon-enriched proteins involved in mitochondrial function, smooth endoplasmic reticulum (SER) structure, and microtubule (MT) stability/function. We characterized axonal mitochondria, SER, and MTs in rodent optic nerves where PLP is replaced by the peripheral nerve myelin protein, P (P-CNS mice).

Age-Related Changes in Axonal and Mitochondrial Ultrastructure and Function in White Matter.

Unlabelled: The impact of aging on CNS white matter (WM) is of general interest because the global effects of aging on myelinated nerve fibers are more complex and profound than those in cortical gray matter. It is important to distinguish between axonal changes created by normal aging and those caused by neurodegenerative diseases, including multiple sclerosis, stroke, glaucoma, Alzheimer's disease, and traumatic brain injury. Using three-dimensional electron microscopy, we show that in mouse optic nerve, which is a pure and fully myelinated WM tract, aging axons are larger, have thicker myelin, and are characterized by longer and thicker mitochondria, which are associated with altered levels of mitochondrial shaping proteins.

Glutamate and ATP at the Interface Between Signaling and Metabolism in Astroglia: Examples from Pathology.

Glutamate is the main excitatory transmitter in the brain, while ATP represents the most important energy currency in any living cell. Yet, these chemicals play an important role in both processes, enabling them with dual-acting functions in metabolic and intercellular signaling pathways. Glutamate can fuel ATP production, while ATP can act as a transmitter in intercellular signaling.

Neutrophil depletion after subarachnoid hemorrhage improves memory via NMDA receptors.

Cognitive deficits after aneurysmal subarachnoid hemorrhage (SAH) are common and disabling. Patients who experience delayed deterioration associated with vasospasm are likely to have cognitive deficits, particularly problems with executive function, verbal and spatial memory. Here, we report neurophysiological and pathological mechanisms underlying behavioral deficits in a murine model of SAH.

Phosphorylation sites in the Hook domain of CaVβ subunits differentially modulate CaV1.2 channel function.

Regulation of L-type calcium current is critical for the development, function, and regulation of many cell types. Ca(V)1.2 channels that conduct L-type calcium currents are regulated by many protein kinases, but the sites of action of these kinases remain unknown in most cases.

Differential connexin function enhances self-renewal in glioblastoma.

The coordination of complex tumor processes requires cells to rapidly modify their phenotype and is achieved by direct cell-cell communication through gap junction channels composed of connexins. Previous reports have suggested that gap junctions are tumor suppressive based on connexin 43 (Cx43), but this does not take into account differences in connexin-mediated ion selectivity and intercellular communication rate that drive gap junction diversity. We find that glioblastoma cancer stem cells (CSCs) possess functional gap junctions that can be targeted using clinically relevant compounds to reduce self-renewal and tumor growth.

Increased intracellular magnesium attenuates β-adrenergic stimulation of the cardiac Ca(V)1.2 channel.

Increases in intracellular Mg(2+) (Mg(2+)(i)), as observed in transient cardiac ischemia, decrease L-type Ca(2+) current of mammalian ventricular myocytes (VMs). However, cardiac ischemia is associated with an increase in sympathetic tone, which could stimulate L-type Ca(2+) current. Therefore, the effect of Mg(2+)(i) on L-type Ca(2+) current in the context of increased sympathetic tone was unclear.

Cardiomyocytes from AKAP7 knockout mice respond normally to adrenergic stimulation.

Protein kinase A (PKA) is activated during sympathetic stimulation of the heart and phosphorylates key proteins involved in cardiac Ca(2+) handling, including the L-type Ca(2+) channel (Ca(V)1.2) and phospholamban (PLN). This results in acceleration and amplification of the beat-to-beat changes in cytosolic Ca(2+) in cardiomyocytes and, in turn, an increased rate and force of contraction.

Cooperative regulation of Ca(v)1.2 channels by intracellular Mg(2+), the proximal C-terminal EF-hand, and the distal C-terminal domain.

L-type Ca(2+) currents conducted by Ca(v)1.2 channels initiate excitation-contraction coupling in cardiac myocytes. Intracellular Mg(2+) (Mg(i)) inhibits the ionic current of Ca(v)1.

Intracellular adaptation of Brucella abortus.

Macrophages were infected with virulent Brucella abortus strain 2308 or attenuated strain 19. Intracellular bacteria were recovered at different times after infection and their proteomes compared. The virulent strain initially reduced most biosynthesis and altered its respiration; adaptations reversed later in infection.

PPARalpha-mediated remodeling of repolarizing voltage-gated K+ (Kv) channels in a mouse model of metabolic cardiomyopathy.

Diabetes is associated with increased risk of diastolic dysfunction, heart failure, QT prolongation and rhythm disturbances independent of age, hypertension or coronary artery disease. Although these observations suggest electrical remodeling in the heart with diabetes, the relationship between the metabolic and the functional derangements is poorly understood. Exploiting a mouse model (MHC-PPARalpha) with cardiac-specific overexpression of the peroxisome proliferator-activated receptor alpha (PPARalpha), a key driver of diabetes-related lipid metabolic dysregulation, the experiments here were aimed at examining directly the link(s) between alterations in cardiac fatty acid metabolism and the functioning of repolarizing, voltage-gated K(+) (Kv) channels.

Distinct cellular and molecular mechanisms underlie functional remodeling of repolarizing K+ currents with left ventricular hypertrophy.

Left ventricular hypertrophy (LVH) is associated with electric remodeling and increased arrhythmia risk, although the underlying mechanisms are poorly understood. In the experiments here, functional voltage-gated (Kv) and inwardly rectifying (Kir) K(+) channel remodeling was examined in a mouse model of pressure overload-induced LVH, produced by transverse aortic constriction (TAC). Action potential durations (APDs) at 90% repolarization in TAC LV myocytes and QT(c) intervals in TAC mice were prolonged.

Abnormal hepatobiliary and circulating lipid metabolism in the Long-Evans Cinnamon rat model of Wilson's disease.

Long-Evans Cinnamon (LEC) rats exhibit a genetic defect in Atp7b gene, which is homologous to the human Wilson's disease gene, resulting in an inability to mobilize copper from the liver. This study was undertaken to gain insight into the relationship between liver copper accumulation and plasma lipid profile, circulating lipoprotein composition, hepatic sterol metabolism and biliary lipid secretion rates in 12-week-old LEC rats compared to control Long-Evans rats. Concomitant with hepatic copper deposition, LEC rats displayed increased content of triglycerides (TGs), free cholesterol (FC) and cholesteryl ester (CE) in the liver.

Modulation of CaV1.2 channels by Mg2+ acting at an EF-hand motif in the COOH-terminal domain.

Magnesium levels in cardiac myocytes change in cardiovascular diseases. Intracellular free magnesium (Mg(i)) inhibits L-type Ca(2+) currents through Ca(V)1.2 channels in cardiac myocytes, but the mechanism of this effect is unknown.

Gamma-secretase is a functional component of phagosomes.

Gamma-secretase is a high molecular mass protein complex that catalyzes the intramembrane cleavage of its protein substrates. Two proteins involved in phagocytosis, CD44 and the low density lipoprotein receptor-related protein, are gamma-secretase substrates, suggesting that this complex might regulate some aspects of phagocytosis. Our results indicate that the four components of gamma-secretase, viz.

Transgenic expression of fatty acid transport protein 1 in the heart causes lipotoxic cardiomyopathy.

Evidence is emerging that systemic metabolic disturbances contribute to cardiac myocyte dysfunction and clinically apparent heart failure, independent of associated coronary artery disease. To test the hypothesis that perturbation of lipid homeostasis in cardiomyocytes contributes to cardiac dysfunction, we engineered transgenic mice with cardiac-specific overexpression of fatty acid transport protein 1 (FATP1) using the alpha-myosin heavy chain gene promoter. Two independent transgenic lines demonstrate 4-fold increased myocardial free fatty acid (FFA) uptake that is consistent with the known function of FATP1.