Levodopa and piribedil enhance endogenous Aβ generation and γ-secretase activity in SK-N-SH cells.

<p>(A) A focused screening of Aβ generation in response to levodopa, piribedil, bromocriptine or carbidopa at indicated concentrations in SK-N-SH cells. Data are mean + s.e.m., n = 3–4. *p < 0.05; ***p < 0.001 versus the control of each group. (B) Representative image of Western-blot showing the expression of APP and the level of secreted sAPPα in response to the treatments. Actin was used as loading control. (C) The dosage-dependent response curves of Aβ generation and cell viability after the treatment with levodopa at indicated concentrations. Data are mean ± s.e.m., n = 5. (D) The level of Aβ produced by SK-N-SH cells in response to vehicle (control) or levodopa at 30 nM either with or without L685,458 pre-treatment. Data are mean + s.e.m., n = 3–4. #p < 0.05 versus the control within the group; ***p < 0.001 versus the corresponding treatment without L685,458. (E and F) The measurements of γ-secretase (E) and BACE1 (F) activities after the treatment with vehicle (control) or the indicated chemicals. Data are mean + s.e.m., n = 3–5. ***p < 0.001 versus control. (G) Representative image of Western-blot showing the expressions of BACE1 and γ-secretase components (NCT, PS1-NTF, APH1aL, and Pen2) after the treatment with vehicle (control) or indicated chemicals. Actin was used as loading control.</p

Levodopa and piribedil enhance Aβ generation in primary APP/PS1 mouse neuronal cells.

<p>(A) The mRNA level of D₁R, D₂R, D₃R, D₄R, and D₅R in the hippocampus of WT (-/-) or APP/PS1 (+/+) mice at the age of 2.5 months (Mo). n = 4 per group. *p < 0.05 versus WT group. (B) Aβ determination after the treatment with vehicle (control), levodopa (30 nM), piribedil (30 nM) or L685,458 (1 μM) in primary APP/PS1 mouse neuronal cells. Data are mean + s.e.m., n = 6. *p < 0.05; **p < 0.01; ***p < 0.001 versus the control. (C) Cell viability measurement for the cells in (B).</p

Levodopa or piribedil-mediated increases of Aβ generation and γ-secretase activity are reduced by the knockdown of β-arrestin 2.

<p>(A and B) Aβ generation after the challenge with vehicle (control), levodopa (A) or piribedil (B) in SK-N-SH cells infected with scrambled or βarr2 gene specific shRNA. Data are mean + s.e.m., n = 4. **p < 0.01; ***p < 0.001 versus the control within the group. Western-blot image showing the knockdown efficiency. Actin was used as loading control. (C and D) The activity of γ-secretase in response to vehicle (control), levodopa (C) or piribedil (D) in SK-N-SH cells infected with scrambled or βarr2 gene specific shRNA. Data are mean + s.e.m., n = 3. *p < 0.05; **p < 0.01 versus the control within the group.</p

Dopamine D₂ receptor and β-arrestin 2 mediate Amyloid-β elevation induced by anti-parkinson’s disease drugs, levodopa and piribedil, in neuronal cells

<div><p>Although levodopa is the first-line medication for the treatment of Parkinson’s disease (PD) showing unsurpassable efficiency, its chronic use causes dyskinesia. Accordingly, dopamine agonists are increasingly employed as monotherapy or in combination with levodopa to reduce the risk of motor complications. It is well recognized that patients with PD often exhibit cognitive deficits. However, clinical and animal studies assessing the effects of dopaminergic medications on cognition are controversial. Amyloid-β (Aβ) is one of the major hallmarks of Alzheimer’s disease (AD), leading to progressive memory loss and cognitive deficit. Interestingly, the abnormal accumulation of Aβ is also detected in PD patients with cognitive deficits. Evidence indicated that levodopa induced a mild increase of Aβ plaque number and size in the brain of AD mouse. However, the underlying mechanism is unclear. Here we present that both levodopa and piribedil enhance the generation of Aβ and the activity of γ-secretase in human neuronal cells and primary neurons isolated from AD mouse. This effect was reduced by either the antagonism or the knockdown of dopamine D₂ receptor (D₂R). We further showed that in the cells expressing β-arrestin 2-biased D₂R mutant, piribedil promoted cellular Aβ production to the extent comparable to the wild-type D₂R whereas this activity was absent in those with G protein-biased D₂R mutant. Moreover, the knockdown of β-arrestin 2 attenuated the increases of Aβ generation and γ-secretase activity mediated by levodopa or piribedil. Thus, our study suggests that targeting D₂R-mediated β-arrestin function may have potential risk in the modulation of Aβ pathology.</p></div

The antagonism or the knockdown of D₂R reduces levodopa or piribedil-mediated increase of Aβ generation or γ-secretase activity.

<p>(A) The mRNA expressions of dopamine receptor subtypes including D₁R, D₂R, D₃R, D₄R, and D₅R in SK-N-SH cells. Data are mean + s.e.m., normalized to HPRT. n = 3. (B) The dose-dependent cAMP response after the treatment with piribedil at indicated concentrations in HEK293 cells either with or without L741,626 (1 μM) pre-incubation. Data are mean ± s.e.m., n = 3. (C) Aβ generation in SK-N-SH cells in the absence or presence of 1 μM L741,626. Data are mean + s.e.m., n = 3. *p < 0.05; **p<0.01 versus the control within the group. (D) The protein level of D₂R in SK-N-SH cells with the infection of scrambled or D₂R gene specific shRNA. The overexpression of human D₂R in HEK293 cells indicates that the band at over 50 KD is D₂R. endo, the endogenous D₂R in SK-N-SH cells. Actin was used as a loading control. (E and F) Measurement of Aβ level after the stimulation with vehicle (control), levodopa or piribedil at 30 nM (E) or FSK at 1 μM (F) in the cells infected as described in (D). Data are mean + s.e.m., n = 5–6. **p < 0.01; ***p < 0.001 versus the control within the group. FSK, forskolin. (G) Measurement of γ-secretase activity after the stimulation with vehicle (control), levodopa or piribedil at 30 nM in the cells infected as described in (D). Data are mean + s.e.m., n = 3. ***p < 0.001 versus the control within the group.</p

β-arrestin 2-biased D₂R mediates piribedil-increased Aβ generation.

<p>(A) The partial sequence of WT and mutant D₂R. TM3, the 3^rd transmembrane domain; IC3, the 3^rd intracellular loop. Gprot, G protein-biased D₂R; βarr, β-arrestin 2-biased D₂R; A3, three alanine substitutions at 213–215. The amino acids in red indicate the mutant positions. (B) HEK293 cells were transiently transfected with HT, ^[WT]D₂R-HT, ^[Gprot]D₂R-HT, ^[βarr]D₂R-HT or ^[3A]D₂R-HT. After 36 h, the expressions of D₂Rs were verified. Actin was used as loading control. (C) The cAMP responses after the stimulation with piribedil at indicated concentrations in HEK293 cells transfected with ^[WT]D₂R, ^[Gport]D₂R, ^[βarr]D₂R or ^[A3]D₂R. Data are mean ±s.e.m., n = 3. (D) The recruitment of β-arrestin 2-NLuc (βarr2-NL) to the C-terminal HT-tagged ^[WT]D₂R, ^[Gport]D₂R, ^[βarr]D₂R or ^[A3]D₂R in response to piribedil at indicated concentrations. NL, Nluc; HT, Halotag. Data are mean ± s.e.m., n = 3. (E) Aβ generation after the treatment with piribedil in HEK293/APPswe cells transfected with ^[WT]D₂R, ^[Gport]D₂R, ^[βarr]D₂R or ^[A3]D₂R. Data are mean + s.e.m., n = 4–5. *p < 0.05; **p < 0.01 versus the control within each group.</p

TM resonance in one period time in chalcogenide photonic crystal cavity

TM resonance cavity mode of normalized frequecy 0.5484, having a Q value of 3989.The cavity was formed by filling the center zone of the connected-chalcogenide-annular-rods-photonic-crystal with chalcogenide material. Outside the cavity zone, there are total 7 square-rings-of-annular-rods surrounding the defect. The photonic crystal supports both a TE and TM photonic band gap in the normalized frequencies range from 0.540976218045288 to 0.553136564955634

TE resonance in one period time in chalcogenide photonic crystal cavity

TE resonance cavity mode of normalized frequecy 0.54947, having a Q value of 19234. The cavity was formed by filling the center zone of the connected-chalcogenide-annular-rods-photonic-crystal with chalcogenide material. Outside the cavity zone, there are total 7 square-rings-of-annular-rods surrounding the defect. The photonic crystal supports both a TE and TM photonic band gap in the normalized frequencies range from 0.540976218045288 to 0.553136564955634

Clinical manifestations and blood routine tests of the 31 patients with small bowel volvulus.

<p>Clinical manifestations and blood routine tests of the 31 patients with small bowel volvulus.</p

Contrast-enhanced abdominal CT demonstrated the dilation of small bowels and whirl-like pattern of distended small bowels encircling the mesenteric artery or its branches (red arrows).

<p>Contrast-enhanced abdominal CT demonstrated the dilation of small bowels and whirl-like pattern of distended small bowels encircling the mesenteric artery or its branches (red arrows).</p