Ruta graveolens and rutin, as its major compound: investigating their effect on spatial memory and passive avoidance memory in rats

Context: There are numerous pharmacological activities for Ruta graveolens and its bioactive constituent, rutin, on learning and memory.Objective: This study aimed to examine the effect of R. graveolens and rutin on memory in rats.Materials and methods: In this study animals were treated with the hydroalcholic extract of R. graveolens and rutin by IP injection for 10 days. Behavioural and biochemical tests as well as HPLC analysis and antioxidant activity of extract have been evaluated.Results: R. graveolens extract and rutin significantly increased learning and improved spatial memory, as well as secondary latency; moreover, there were significant increases in the serum and brain antioxidant capacity as well as the level of TBARS in serum and brain tissues. Results also showed that R. graveolens has significant DPPH radical scavenging effect (IC₅₀: 159.17 ± 1.56 μg/mL). The HPLC analysis of extract showed that caffeic acid (19.92 ± 0.01), rutin (40.15 ± 0.01), and apigenin (0.84 ± 0.01) mg/g of dry extract are the main components of the extract.Discussion and conclusion: Regarding the effects of R. graveolens extract and rutin on animal brain cells, memory function, and learning, additional studies, including clinical trials, might be beneficial in producing natural supplementary drugs from this herb.

HCN channels are a novel therapeutic target for cognitive dysfunction in Neurofibromatosis type 1

Cognitive impairments are a major clinical feature of the common neurogenetic disease neurofibromatosis type 1 (NF1). Previous studies have demonstrated that increased neuronal inhibition underlies the learning deficits in NF1, however, the molecular mechanism underlying this cell-type specificity has remained unknown. Here, we identify an interneuron-specific attenuation of hyperpolarization-activated cyclic nucleotide-gated (HCN) current as the cause for increased inhibition in Nf1 mutants. Mechanistically, we demonstrate that HCN1 is a novel NF1-interacting protein for which loss of NF1 results in a concomitant increase of interneuron excitability. Furthermore, the HCN channel agonist lamotrigine rescued the electrophysiological and cognitive deficits in two independent Nf1 mouse models, thereby establishing the importance of HCN channel dysfunction in NF1. Together, our results provide detailed mechanistic insights into the pathophysiology of NF1-associated cognitive defects, and identify a novel target for clinical drug development.

Effect of Rheum Ribes Hydro-Alcoholic Extract on Memory Impairments in Rat Model of Alzheimer's Disease

Some animal models have been used to study Alzheimer's disease (AD). AD is an irreversible progressive neurodegenerative disease and the most common cause of dementia. Animal studies have shown that there is a relation between decrease in cholinergic functions in the nucleus basalis of Meynert (NBM) and loss of learning capability and memory. The aim of this study was to investigate the effect of Rheum ribes extract (RR) on memory deficit in one of the rat models of AD. Plant (1500gr) was collected from Saman (kahkesh) region of Chaharmahal Va Bakhtiari province in Iran. RR hydro-alcoholic extracts were prepared using maceration method. Rat model of Alzheimer was induced by Nucleus Basalis of Meynert lesions (NBML). Animals (n = 32) received extracts for 20 days and then passive avoidance and Morris water maze tasks were performed for memory evaluation. FRAP and HPLC methods were used for measurement of the antioxidant and Malondialdehyde (MDA) levels in blood. In water maze experiment, probe trial results showed that NBML group spent significantly less time in target quadrant, in which the platform was located on the preceding day. In addition, the time spent in target quadrant was significantly increased in NBML + RR groups (250 and 500 mg/kg) compared to the NBML group. In passive avoidance task, mean initial latency time and step-though latency were significantly decreased in NBML group. RR extracts significantly prolonged step-through latency in NBML + RR groups. Results of this study suggest that Rheum ribes extracts can improve memory deficits induced by bilateral NBM lesions in rats.

A rare pairing: myocardial noncompaction and congenital absence of pericardium

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Kinase activity is not required for alphaCaMKII-dependent presynaptic plasticity at CA3-CA1 synapses

Using targeted mouse mutants and pharmacologic inhibition of alphaCaMKII, we demonstrate that the alphaCaMKII protein, but not its activation, autophosphorylation or its ability to phosphorylate synapsin I, is required for normal short-term presynaptic plasticity. Furthermore, alphaCaMKII regulates the number of docked vesicles independent of its ability to be activated. These results indicate that alphaCaMKII has a nonenzymatic role in short-term presynaptic plasticity at hippocampal CA3-CA1 synapses.

Rescue of neurological deficits in a mouse model for Angelman syndrome by reduction of alphaCaMKII inhibitory phosphorylation

Angelman syndrome (AS) is a severe neurological disorder characterized by mental retardation, motor dysfunction and epilepsy. We show that the molecular and cellular deficits of an AS mouse model can be rescued by introducing an additional mutation at the inhibitory phosphorylation site of alphaCaMKII. Moreover, these double mutants no longer show the behavioral deficits seen in AS mice, suggesting that these deficits are the direct result of increased inhibitory phosphorylation of alphaCaMKII.

Modulation of presynaptic plasticity and learning by the H-ras/extracellular signal-regulated kinase/synapsin I signaling pathway

Molecular and cellular studies of the mechanisms underlying mammalian learning and memory have focused almost exclusively on postsynaptic function. We now reveal an experience-dependent presynaptic mechanism that modulates learning and synaptic plasticity in mice. Consistent with a presynaptic function for endogenous H-ras/extracellular signal-regulated kinase (ERK) signaling, we observed that, under normal physiologic conditions in wild-type mice, hippocampus-dependent learning stimulated the ERK-dependent phosphorylation of synapsin I, and MEK (MAP kinase kinase)/ERK inhibition selectively decreased the frequency of miniature EPSCs. By generating transgenic mice expressing a constitutively active form of H-ras (H-rasG12V), which is abundantly localized in axon terminals, we were able to increase the ERK-dependent phosphorylation of synapsin I. This resulted in several presynaptic changes, including a higher density of docked neurotransmitter vesicles in glutamatergic terminals, an increased frequency of miniature EPSCs, and increased paired-pulse facilitation. In addition, we observed facilitated neurotransmitter release selectively during high-frequency activity with consequent increases in long-term potentiation. Moreover, these mice showed dramatic enhancements in hippocampus-dependent learning. Importantly, deletion of synapsin I, an exclusively presynaptic protein, blocked the enhancements of learning, presynaptic plasticity, and long-term potentiation. Together with previous invertebrate studies, these results demonstrate that presynaptic plasticity represents an important evolutionarily conserved mechanism for modulating learning and memory.

Rapid, specific, and sensitive measurements of plasma sphingomyelin and phosphatidylcholine

Sphingomyelin (SM) and phosphatidylcholine (PC) are two major phospholipids on plasma lipoproteins. Their concentration is classically measured by lipid extraction, thin-layer chromatography, and phosphate determination on separated SM or PC spots. Here, we describe two rapid, specific, and sensitive enzymatic measurements for both phospholipids. Plasma was incubated with bacterial sphingomyelinase (for SM measurement) or bacterial PC-specific phospholipase D (for PC measurement), alkaline phosphatase, choline oxidase, peroxidase, N-ethyl-N-(2-hydroxy-3-sulfopropyl)-3,5-dimethoxyaniline, and 4-aminoantipyrine for 45 min. A blue dye, with an optimal absorption at 595 nm, was generated. PC levels did not influence SM measurement and vice versa. The linear range for the SM measurement was 0.5-5 microg, and that for PC was 2.5-20 microg. The mean percentage recovery was 98.0 +/- 5.2% for SM and 96.6 +/- 3.8% for PC. The interassay coefficient of variation of the assay was 1.7 +/- 0.05% for SM and 3.1 +/- 0.13% for PC. These two new methods are amenable to automation and can be adapted for large-scale, high-throughput assays.

The effect of dietary sphingolipids on plasma sphingomyelin metabolism and atherosclerosis

Sphingomyelin (SM) plays a very important role in cell membrane formation and plasma lipoprotein metabolism. All these functions may have an impact on atherosclerotic development. To investigate the relationship between SM metabolism and atherosclerosis, we utilized a sphingolipid-rich diet to feed LDL receptor gene knockout (LDLr KO) mice and studied lipid metabolism and atherosclerosis in the mice. After 3 months of a sphingolipid-rich diet, we found a significant increase in SM, cholesterol, and SM/phosphatidylcholine (PC) ratio (50%, P<0.001; 62%, P<0.01; and 45%, P<0.01, respectively), compared to chow fed diet. HDL-lipids were not significantly altered. Non-HDL-SM, non-HDL-C, and non-HDL-SM/non-HDL-PC ratio were significantly increased (115%, P<0.001; 106%, P<0.001; and 106%, P<0.01, respectively). FPLC confirmed the results. SDS-PAGE showed an increase of apoB48 and apoB100, but no changes of apoAI. Moreover, we found that an SM-rich diet significantly increased atherosclerotic lesion area in both root assay and en face assay, compared to chow diet (58,210+/-15,300 microm(2) vs. 9670+/-2370 microm(2), P<0.001; 5.9+/-3.1% vs. 1.1+/-0.9%, P<0.001). These results indicate that the enrichment of sphingolipids in diet has proatherogenic properties.

Serine palmitoyl-CoA transferase (SPT) deficiency and sphingolipid levels in mice

Sphingolipids play a very important role in cell membrane formation, signal transduction, and plasma lipoprotein metabolism, and all these functions may have an impact on atherosclerotic development. Serine palmitoyl-CoA transferase (SPT) is the key enzyme in sphingolipid biosynthesis. To evaluate in vivo SPT activity and its role in sphingolipid metabolism, we applied homologous recombination to embryonic stem cells, producing mice with long chain base 1 (Sptlc1) and long chain base 2 (Sptlc2), two subunits of SPT, gene deficiency. Homozygous Sptlc11 and Sptlc2 mice are embryonic lethal, whereas heterozygous versions of both animals (Sptlc1(+/-), Sptlc2(+/-)) are healthy. Analysis showed that, compared with WT mice, Sptlc1(+/-) and Sptlc2(+/-) mice had: (1) decreased liver Sptlc1 and Sptlc2 mRNA by 44% and 57% (P<0.01 and P<0.0001, respectively); (2) decreased liver Sptlc1 mass by 50% and Sptlc2 mass by 70% (P<0.01 and P<0.01, respectively), moreover, Sptlc1 mass decreased by 70% in Sptlc2(+/-) mouse liver, while Sptlc2 mass decreased by 53% in Sptlc1(+/-) mouse liver (P<0.001 and P<0.01, respectively); (3) decreased liver SPT activity by 45% and 60% (P<0.01, respectively); (4) decreased liver ceramide (22% and 39%, P<0.05 and P<0.01, respectively) and sphingosine levels (22% and 31%, P<0.05 and P<0.01, respectively); (5) decreased plasma ceramide (45% and 39%, P<0.01, respectively), sphingosine-1-phosphate (31% and 32%, P<0.01, respectively) and sphingosine levels (22.5% and 25%, P<0.01, respectively); (6) dramatically decreased plasma lysosphingomyelin (17-fold and 16-fold, P<0.0001, respectively); and (7) no change of plasma sphingomyelin, triglyceride, total cholesterol, phospholipids, and liver sphingomyelin levels. These results indicated that both Sptlc1 and Sptlc2 interactions are necessary for SPT activity in vivo, and that SPT activity directly influences plasma sphingolipid levels. Furthermore, manipulation of SPT activity might well influence the course of such diseases as atherosclerosis.

Effect of myriocin on plasma sphingolipid metabolism and atherosclerosis in apoE-deficient mice

Sphingolipids play a very important role in cell membrane formation, signal transduction, and plasma lipoprotein metabolism, all of which may well have an impact on the development of atherosclerosis. To investigate the relationship between sphingolipid metabolism and atherosclerosis, we utilized myriocin to inhibit mouse serine palmitoyl-CoA transferase (SPT), the key enzyme for sphingolipid biosynthesis. We injected 8-week-old apoE-deficient mice with myriocin (0.3 mg/kg/every other day, intraperitoneal) for 60 days. On a chow diet, myriocin treatment caused a significant decrease (50%) in liver SPT activity (p < 0.001), significant decreases in plasma sphingomyelin, ceramide, and sphingosine-1-phosphate levels (54, 32, and 73%, respectively) (p < 0.0001), and a significant increase in plasma phosphatidylcholine levels (91%) (p < 0.0001). Plasma total cholesterol and triglyceride levels demonstrated no significant changes, but there was a significant decrease in atherosclerotic lesion area (42% in root and 36% in en face assays) (p < 0.01). On a high fat diet, myriocin treatment caused marked decreases in plasma sphingomyelin, ceramide, and sphingosine-1-phosphate levels (59, 66, and 81%, respectively) (p < 0.0001), and a marked increase in plasma phosphatidylcholine levels (100%) (p < 0.0001). Total cholesterol and triglyceride demonstrated no significant changes, but there was a significant decrease in atherosclerotic lesion area (39% in root and 37% in en face assays) (p < 0.01). These results indicate that, apart from cholesterol levels, sphingolipids have an effect on atherosclerotic development and that SPT has proatherogenic properties. Thus, inhibition of SPT activity could be an alternative treatment for atherosclerosis.