Toshio Shimada

Docosahexaenoic acid provides protection from impairment of learning ability in Alzheimer's disease model rats

Docosahexaenoic acid (C22:6, n‐3), a major n‐3 fatty acid of the brain, has been implicated in restoration and enhancement of memory‐related functions. Because Alzheimers disease impairs memory, and infusion of amyloid‐β (Aβ) peptide (1–40) into the rat cerebral ventricle reduces learning ability, we investigated the effect of dietary pre‐administration of docosahexaenoic acid on avoidance learning ability in Aβ peptide‐produced Alzheimers disease model rats. After a mini‐osmotic pump filled with Aβ peptide or vehicle was implanted in docosahexaenoic acid‐fed and control rats, they were subjected to an active avoidance task in a shuttle avoidance system apparatus. Pre‐administration of docosahexaenoic acid had a profoundly beneficial effect on the decline in avoidance learning ability in the Alzheimers disease model rats, associated with an increase in the cortico‐hippocampal docosahexaenoic acid/arachidonic acid molar ratio, and a decrease in neuronal apoptotic products. Docosahexaenoic acid pre‐administration furthermore increased cortico‐hippocampal reduced glutathione levels and glutathione reductase activity, and suppressed the increase in lipid peroxide and reactive oxygen species levels in the cerebral cortex and hippocampus of the Alzheimers disease model rats, suggesting an increase in antioxidative defence. Docosahexaenoic acid is thus a possible prophylactic means for preventing the learning deficiencies of Alzheimers disease.

DOCOSAHEXAENOIC ACID‐INDUCED PROTECTIVE EFFECT AGAINST IMPAIRED LEARNING IN AMYLOID β‐INFUSED RATS IS ASSOCIATED WITH INCREASED SYNAPTOSOMAL MEMBRANE FLUIDITY

1 In the present study, we investigated the relationship between the docosahexaenoic acid (DHA)‐induced protection of learning deficit of amyloid β(1−40)‐infused Alzheimers disease (AD) model rats and changes in synaptosomal plasma membrane fluidity of the cerebral cortex. 2 Synaptosomal membrane lateral and rotational fluidity were measured using pyrene excimer spectroscopy and fluorescence polarization of 1,6‐diphenyl‐1,3,5‐hexatriene (DPH), respectively. 3 Avoidance learning ability, as assessed by a two‐way active avoidance paradigm, decreased significantly in the AD model rats. 4 Pyrene‐determined annular/non‐annular fluidity ratio and the DPH‐determined bulk fluidity of the synaptosomal plasma membrane decreased in the amyloid β(1−40)‐infused rats. Oral pre‐administration of DHA (300 mg/kg per day for 12 weeks) significantly increased both lateral and rotational fluidity. 5 The synaptosomal membrane DHA content increased and the cholesterol to phospholipid molar ratio and lipid peroxidation decreased. 6 The annular to non‐annular fluidity ratio of the synaptic plasma membrane was positively correlated with total avoidance learning. 7 The present results indicate that DHA‐induced alterations in synaptic plasma membrane fluidity may contribute to the synaptic plasma membrane‐related functions that constitute avoidance learning‐related memory in amyloid β(1−40)‐infused rats.

Docosahexaenoic acid disrupts in vitro amyloid β1-40 fibrillation and concomitantly inhibits amyloid levels in cerebral cortex of Alzheimer’s disease model rats

We have previously reported that dietary docosahexaenoic acid (DHA) improves and/or protects against impairment of cognition ability in amyloid beta1‐40 (Aβ1‐40)‐infused Alzheimer’s disease (AD)‐model rats. Here, after the administration of DHA to AD model rats for 12u2003weeks, the levels of Aβ1‐40, cholesterol and the composition of fatty acids were investigated in the Triton X100‐insoluble membrane fractions of their cerebral cortex. The effects of DHA on the in vitro formation and kinetics of fibrillation of Aβ1‐40 were also investigated by thioflavin T fluorescence spectroscopy, transmission electron microscopy and fluorescence microscopy. Dietary DHA significantly decreased the levels of Aβ1‐40, cholesterol and saturated fatty acids in the detergent insoluble membrane fractions of AD rats. The formation of Aβ fibrils was also attenuated by their incubation with DHA, as demonstrated by the decreased intensity of thioflavin T‐derived fluorescence and by electron micrography. DHA treatment also decreased the intensity of thioflavin fluorescence in preformed‐fibril Aβ peptides, demonstrating the anti‐amyloidogenic effects of DHA. We then investigated the effects of DHA on the levels of oligomeric amyloid that is generated during its in vitro transformation from monomers to fibrils, by an anti‐oligomer‐specific antibody and non‐reducing Tris‐Glycine gradient (4–20%) gel electrophoresis. DHA concentration‐dependently reduced the levels of oligomeric amyloid species, suggesting that dietary DHA‐induced suppression of in vivo Aβ1‐40 aggregation occurs through the inhibitory effect of DHA on oligomeric amyloid species.

Mechanism of docosahexaenoic acid-induced inhibition of in vitro Aβ1–42 fibrillation and Aβ1–42-induced toxicity in SH-S5Y5 cells

The mechanism of the effect of docosahexaenoic acid (DHA; C22:6, n‐3), one of the essential brain nutrients, on in vitro fibrillation of amyloid β (Aβ1–42), Aβ1–42‐oligomers and its toxicity imparted to SH‐S5Y5 cells was studied with the use of thioflavin T fluorospectroscopy, laser confocal microfluorescence, and transmission electron microscopy. The results clearly indicated that DHA inhibited Aβ1–42‐fibrill formation with a concomitant reduction in the levels of soluble Aβ1–42 oligomers. The polymerization (into fibrils) of preformed oligomers treated with DHA was inhibited, indicating that DHA not only obstructs their formation but also inhibits their transformation into fibrils. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (12.5%), Tris–Tricine gradient(4–20%) gel electrophoresis and western blot analyses revealed that DHA inhibited at least 2 species of Aβ1–42 oligomers of 15–20u2003kDa, indicating that it hinders these on‐pathway tri/tetrameric intermediates during fibrillation. DHA also reduced the levels of dityrosine and tyrosine intrinsic fluorescence intensity, indicating DHA interrupts the microenvironment of tyrosine in the Aβ1–42 backbone. Furthermore, DHA protected the tyrosine from acrylamide collisional quenching, as indicated by decreases in Stern–Volmer constants. 3‐[4,5‐Dimethylthiazol‐2‐yl]‐2,5‐diphenyltetrazolium bromide‐reduction efficiency and immunohistochemical examination suggested that DHA inhibits Aβ1–42‐induced toxicity in SH‐S5Y5 cells. Taken together, these data suggest that by restraining Aβ1–42 toxic tri/tetrameric oligomers, DHA may limit amyloidogenic neurodegenerative diseases, Alzheimer’s disease.

Effects of docosahexaenoic acid on in vitro amyloid beta peptide 25–35 fibrillation

Amyloid beta peptide(25-35) (Abeta(25-35)) encompasses one of the neurotoxic domains of full length Abeta(1-40/42), the major proteinaceous component of amyloid deposits in Alzheimers disease (AD). We investigated the effect of docosahexaenoic acid (DHA, 22:6, n-3), an essential brain polyunsaturated fatty acid, on the in vitro fibrillation of Abeta(25-35) and found that it significantly reduced the degree of fibrillation, as shown by a decrease in the intensity of both the thioflavin T and green fluorescence in confocal microscopy. Transmission electron microscopy revealed that DHA-incubated samples were virtually devoid of structured fibrils but had an amorphous-like consistency, whereas the controls contained structured fibers of various widths and lengths. The in vitro fibrillation of Abeta(25-35) appeared to be pH-dependent, with the strongest effect seen at pH 5.0. DHA inhibited fibrillation at all pHs, with the strongest effect at pH 7.4. It also significantly decreased the levels of Abeta(25-35) oligomers. Nonreductive gradient gel electrophoresis revealed that the molecular size of the oligomers of Abeta(25-35) was 10 kDa (equivalent to decamers of Abeta(25-35)) and that DHA dose-dependently reduced these decamers. These results suggest that DHA decreases the in vitro fibrillation of Abeta(25-35) by inhibiting the oligomeric amyloid species and, therefore, Abeta(25-35)-related neurotoxicity or behavioral impairment could be restrained by DHA.

Docosahexaenoic acid withstands the Aβ25-35-induced neurotoxicity in SH-SY5Y cells

BACKGROUNDnDocosahexaenoic acid (DHA, C22:6, n-3) ameliorates the memory-related learning deficits of Alzheimers disease (AD), which is characterized by fibrillar amyloid deposits in the affected brains. Here, we have investigated whether DHA-induced inhibition of Amyloid β-peptide(25-35) (Aβ(25-35)) fibrillation limits or deteriorates the toxicity of the human neuroblastoma cells (SH-SY5Y).nnnEXPERIMENTAL METHODSnIn vitro fibrillation of Aβ(25-35) was performed in the absence or presence of DHA. Afterwards, SH-SY5Y cells were incubated with Aβ(25-35) in absence or presence 20 μM DHA to evaluate its effect on the Aβ(25-35)-induced neurotoxicity by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)]-redox and TUNEL (TdT-mediated dUTP-biotin nick end-labeling) assay and immunohistochemistry. The level of Aβ(25-35)-induced lipid peroxide (LPO) was determined in the absence or presence of oligomer-specific antibody. Fatty acid profile was estimated by gas chromatography.nnnRESULTSnDHA significantly reduced the Aβ(25-35) in vitro fibrillation, as indicated by fluorospectroscopy and transmission electron microscopy. Aβ(25-35) decreased the MTT-redox activity and increased the apoptotic damage and levels of LPO when compared with those of the controls. However, when the SH-SY5Y cells were treated with Aβ(25-35) in the presence of DHA, MTT redox potential significantly increased and the levels LPO decreased, suggesting an inhibition of the Aβ(25-35)-induced neurotoxicity. DHA improved the Aβ(25-35) induced DNA damage and axodendritic loss, with a concomitant increase in the cellular level of DHA, suggesting DHA protects the cell from neurotoxic degeneration.nnnCONCLUSIONnDHA not only inhibits the in vitro fibrillation but also resists the Aβ(25-35)-induced toxicity in the neuronal cells. This might be the basis of the DHA-induced amelioration of Aβ-induced neurodegeneration and related cognitive deficits.

Effect of left and right lateral decubitus positions on mitral flow pattern by Doppler echocardiography in congestive heart failure

Abstract In patients with congestive heart failure (CHF), dyspnea is a clinical manifestation of pulmonary venous and capillary hypertension. Patients with CHF usually have 1 type of dyspnea that is limited to 1 lateral decubitus position: trepopnea. 1 In general, patients prefer lying on the right lateral to lying on the left lateral decubitus position. Doppler echocardiographic assessment of the mitral flow provides a considerable amount of information regarding the diastolic filling characteristics of the left ventricle. Mitral flow velocity is mainly determined by the pressure gradient between the left atrium and ventricle, and therefore can be considered to represent the driving force across the mitral valve. 2–4 Previous observations suggested that peak early filling velocity is mainly dependent on the initial driving pressure across the mitral valve. 5,6 Several investigators have shown that increased left atrial pressure increases the early diastolic mitral pressure gradient and peak mitral flow velocity in early diastole, resembling the normal pattern (“pseudonormalization”). 7–9 Little attention is given to the effects of positions on Doppler-derived mitral flow velocities. This study examines the effects of the left and right lateral decubitus positions on Doppler-derived mitral flow velocities in patients with CHF.

Vascular Involvement in a Patient with Mitochondrial Myopathy, Encephalopathy, Lactic Acidosis, and Stroke-Like Episodes

A 26-year-old man with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) was admitted to our hospital for further cardiovascular examination. A muscle biopsy demonstrated strongly succinate dehydrogenase-reactive blood vessels. Pulse wave contour analysis revealed that both capacitive and oscillatory compliance were markedly reduced in this patient compared with 45 normal age-matched control subjects. Hepatocyte growth factor was remarkably elevated in this patient over that of 10 normal control subjects. These findings suggest that a MELAS patient has not only pathologic but also functional vascular involvement. If so, patients with MELAS need systemic vascular assessment.

Effects of supine and lateral recumbent positions on pulmonary venous flow in healthy subjects evaluated by transesophageal Doppler echocardiography

OBJECTIVESnThis study attempted to evaluate the effects of supine and lateral recumbent positions on pulmonary venous flow by transesophageal Doppler echocardiography in healthy subjects.nnnBACKGROUNDnAlthough transesophageal echocardiographic examination is usually performed with the patient lying in the left lateral decubitus or supine position, little attention has been paid to the effects of these positions on pulmonary venous flow.nnnMETHODSnWe performed pulsed Doppler transesophageal echocardiography of the left and right pulmonary veins in 16 normal subjects as they lay in the left and right lateral decubitus and supine positions.nnnRESULTSnData are reported as mean value +/- SD. Adequate recordings were obtained in 12 subjects (75%). In the left pulmonary vein, peak systolic velocity and time-velocity integral of systolic flow increased significantly in the left compared with the right lateral decubitus position (56 +/- 12 vs. 44 +/- 13 cm/s, p < 0.05, and 15 +/- 4 vs. 9 +/- 4 cm, p < 0.05, respectively). In the right pulmonary vein, peak systolic velocity and time-velocity integral of systolic flow decreased significantly in the left compared with the right lateral decubitus position (38 +/- 10 vs. 48 +/- 9 cm/s, p < 0.05, and 9 +/- 2 vs. 12 +/- 2 cm, p < 0.05, respectively). There were no significant differences between positions in peak diastolic flow velocity, time-velocity integral of diastolic flow or peak velocity of flow reversal at atrial contraction.nnnCONCLUSIONSnPulmonary venous systolic peak velocities and time-velocity integrals of systolic flow increase when the pulmonary venous recording is from the recumbent subjects lower side. Therefore, the effects of position should be considered in evaluating left ventricular diastolic function by transesophageal Doppler echocardiography.

Effect of a Decrease in Aortic Compliance on the Isovolumic Relaxation Period of the Left Ventricle in Man

A decrease in aortic compliance can modify the loading sequence to the left ventricular ejection in the elderly. To determine whether a decreased aortic compliance influences the left ventricular relaxation in man, 83 healthy volunteers, aged 34-87 years, were studied. The left ventricular relaxation was characterized by the isovolumic relaxation period (IRP) of the left ventricle. The aortic compliance was characterized by the aortic pulse wave velocity (AoPWV)