Structure and function of resistance arteries from BB-creatine kinase and ubiquitous Mt-creatine kinase double knockout mice.

Increasing evidence indicates that the enzyme creatine kinase (CK) is intimately involved in microvascular contractility. The mitochondrial isoenzyme catalyses phosphocreatine synthesis from ATP, while cytoplasmic CK, predominantly the BB isoenzyme in vascular tissue, is tightly bound near myosin ATPase, where it favours ATP production from phosphocreatine to metabolically support vascular contractility. However, the effect of CK gene inactivation on microvascular function is hitherto unknown. We studied functional and structural parameters of mesenteric resistance arteries isolated from 5 adult male mice lacking cytoplasmic BB-CK and ubiquitous mitochondrial CK (CK-/-) vs 6 sex/age-matched controls. Using a Mulvany Halpern myograph, we assessed the acute maximum contractile force with 125 mM K+ and 10-5 M norepinephrine, and the effect of two inhibitors, dinitrofluorobenzene, which inhibits phosphotransfer enzymes (0.1 µM), and the specific adenylate kinase inhibitor P1, P5-di(adenosine 5') pentaphosphate (10-6 to 10-5 M). WT and CK-/- did not significantly differ in media thickness, vascular elasticity parameters, or acute maximum contractile force. CK-/- arteries displayed greater reduction in contractility after dinitrofluorobenzene 38%; vs 14% in WT; and after AK inhibition, 14% vs 5.5% in WT, and displayed abnormal mitochondria, with a partial loss of the inner membrane. Thus, CK-/- mice display a surprisingly mild phenotype in vascular dysfunction. However, the mitochondrial abnormalities and greater effect of inhibitors on contractility may reflect a compromised energy metabolism. In CK-/- mice, compensatory mechanisms salvage energy metabolism, as described for other CK knock-out models.

DHA and cholesterol containing diets influence Alzheimer-like pathology, cognition and cerebral vasculature in APPswe/PS1dE9 mice.

Cholesterol and docosahexenoic acid (DHA) may affect degenerative processes in Alzheimer's Disease (AD) by influencing Abeta metabolism indirectly via the vasculature. We investigated whether DHA-enriched diets or cholesterol-containing Typical Western Diets (TWD) alter behavior and cognition, cerebral hemodynamics (relative cerebral blood volume (rCBV)) and Abeta deposition in 8- and 15-month-old APP(swe)/PS1(dE9) mice. In addition we investigated whether changes in rCBV precede changes in Abeta deposition or vice versa. Mice were fed regular rodent chow, a TWD-, or a DHA-containing diet. Behavior, learning and memory were investigated, and rCBV was measured using contrast-enhanced MRI. The Abeta load was visualized immunohistochemically. We demonstrate that DHA altered rCBV in 8-month-old APP/PS1 and wild type mice[AU1]. In 15-month-old APP/PS1 mice DHA supplementation improved spatial memory, decreased Abeta deposition and slightly increased rCBV, indicating that a DHA-enriched diet can diminish AD-like pathology. In contrast, TWD diets decreased rCBV in 15-month-old mice. The present data indicate that long-term dietary interventions change AD-like pathology in APP/PS1 mice. Additionally, effects of the tested diets on vascular parameters were observed before effects on Abeta load were noted. These data underline the importance of vascular factors in the APP/PS1 mouse model of AD pathology.

Cerebral creatine kinase deficiency influences metabolite levels and morphology in the mouse brain: a quantitative in vivo 1H and 31P magnetic resonance study.

Creatine kinase (CK)-catalysed ATP-phosphocreatine (PCr) exchange is considered to play a key role in energy homeostasis of the brain. This study assessed the metabolic and anatomical consequences of partial or complete depletion of this system in transgenic mice without cytosolic B-CK (B-CK-/-), mitochondrial ubiquitous CK (UbCKmit-/-), or both isoenzymes (CK -/-), using non-invasive quantitative magnetic resonance (MR) imaging and spectroscopy. MR imaging revealed an increase in ventricle size in a subset of B-CK-/- mice, but not in animals with UbCKmit or compound CK mutations. Mice lacking single CK isoenzymes had normal levels of high-energy metabolites and tissue pH. In the brains of CK double knockouts pH and ATP and Pi levels were also normal, even though PCr had become completely undetectable. Moreover, a 20-30% decrease was observed in the level of total creatine and a similar increase in the level of neuronal N-acetyl-aspartate compounds. Although CKs themselves are not evenly distributed throughout the CNS, these alterations were uniform and concordant across different brain regions. Changes in myo-inositol and glutamate peaks did appear to be mutation type and brain area specific. Our results challenge current models for the biological significance of the PCr-CK energy system and suggest a multifaceted role for creatine in the brain.

Delayed peripheral nerve regeneration and central nervous system collateral sprouting in leucocyte common antigen-related protein tyrosine phosphatase-deficient mice.

Cell adhesion molecule-like receptor-type protein tyrosine phosphatases have been shown to be important for neurite outgrowth and neural development in several animal models. We have previously reported that in leucocyte common antigen-related (LAR) phosphatase deficient (LAR-deltaP) mice the number and size of basal forebrain cholinergic neurons, and their innervation of the hippocampal area, is reduced. In this study we compared the sprouting response of LAR-deficient and wildtype neurons in a peripheral and a central nervous system lesion model. Following sciatic nerve crush lesion, LAR-deltaP mice showed a delayed recovery of sensory, but not of motor, nerve function. In line with this, neurofilament-200 immunostaining revealed a significant reduction in the number of newly outgrowing nerve sprouts in LAR-deltaP animals. Morphometric analysis indicated decreased axonal areas in regenerating LAR-deltaP nerves when compared to wildtypes. Nonlesioned nerves in wildtype and LAR-deltaP mice did not differ regarding myelin and axon areas. Entorhinal cortex lesion resulted in collateral sprouting of septohippocampal cholinergic fibres into the dentate gyrus outer molecular layer in both genotype groups. However, LAR-deltaP mice demonstrated less increase in acetylcholinesterase density and fibre number at several time points following the lesion, indicating a delayed collateral sprouting response. Interestingly, a lesion-induced reduction in number of (septo-entorhinal) basal forebrain choline acetyltransferase-positive neurons occurred in both groups, whereas in LAR-deltaP mice the average cell body size was reduced as well. Thus, regenerative and collateral sprouting is significantly delayed in LAR-deficient mice, reflecting an important facilitative role for LAR in peripheral and central nervous system axonal outgrowth.

Delayed NGF infusion fails to reverse axotomy-induced degeneration of basal forebrain cholinergic neurons in adult p75(LNTR)-deficient mice.

The p75 low-affinity neurotrophin receptor (p75(LNTR)) appears to have various functions that include enhancing nerve growth factor (NGF)-mediated survival by increasing TrkA (high-affinity NGF receptor) efficiency, and mediating apoptosis by acting as a ligand-regulated pro-apoptotic receptor. Here, we investigated the role of p75(LNTR) for adult cholinergic basal forebrain neurons by comparing neuronal responses to injury in control and p75(LNTR)-deficient mice. In both types of mice, approximately 70% of the cholinergic neurons in the ipsilateral medial septum had lost their markers choline acetyltransferase and tyrosine kinase A by 28 days following unilateral transection of the dorsal septohippocampal pathway (fimbria fornix). A 7-day delayed infusion of NGF that started 28 days after the injury resulted in reversal of choline acetyltransferase expression and cell atrophy in control, but not in p75(LNTR)-deficient, mice. This lack of response to delayed NGF treatment in p75(LNTR)-deficient mice was most likely not due to cell death, as all of the septohippocampal neurons, labeled with Fluorogold before the lesion, were present at 28 days post-lesion, similar to control mice. p75(LNTR)-deficient cholinergic neurons can respond to NGF as they were protected by NGF infusions that started immediately after the injury. These observations, the fact that lesioned p75(LNTR)-deficient neurons atrophy faster, and that non-lesioned neurons hypertrophy in response to NGF in control but not in p75(LNTR)-deficient mice, suggest that p75(LNTR) is needed for tyrosine kinase A and NGF signaling efficiency.In conclusion, during adulthood p75(LNTR) appears to play a beneficial role in the response of cholinergic neurons to injury, consistent with the proposed role of p75(LNTR) in the enhancement of TrkA signaling and the transport of neurotrophins by these neurons.