Tuning Two-Dimensional Layer to Three-Dimensional Pillar-Layered Metal–Organic Frameworks: Polycatenation and Interpenetration Behaviors

A two-dimensional honeycomb network of {[Zn₂(bpydb)₂­(H₂O)₂]­(DMA)₃­(H₂O)}_<i>n</i> (<b>1</b>) was solvothermally synthesized and structurally characterized. By employing 4,4′-bipyridine (bpy) as a pillar, two additional three-dimensional (3D) metal–organic frameworks (MOFs) of {[Zn₂(bpydb)₂­(bpy)­(EtO-H)₂]­(DMF)­(EtOH)}_<i>n</i> (<b>2</b>) and {[Zn­(bpydb)­(bpy)]­(DMA)­(EtOH)₆}<i>_n</i> (<b>3</b>) (bpydbH₂ = 4,4′-(4,4′-bipyridine-2,6-diyl) dibenzoic acid, DMA = <i>N</i>,<i>N</i>- dimethylacetamide, DMF = <i>N</i>,<i>N</i>-dimethylformamide) were obtained. MOF <b>2</b> displays a 3D pillar-bilayered network generated from polycatenation of the 2D bilayers. By carefully adjusting the reaction condition, MOF <b>3</b> was harvested, showing a 2-fold interpenetrated (3,5)-connected <b>hms</b> net. The phase purity, thermal stability, and luminescent properties of the three MOFs were studied. In addition, N₂ and CO₂ adsorption behaviors of the activated <b>3</b> were investigated

Western Blot analysis of autophagic-related protein expression after cerebral I/R injury.

<p>The level of LC3-II and Beclin 1 in ischemic cortex increased significantly from 6 to 24 h after reperfusion, with a maximal induction at 12 h. The expression of active cathepsin-B and LAMP1 in ischemic cortex increased significantly from 6 to 12 h after reperfusion, with a maximal induction at 12 h. Optical density of respective protein bands were analyzed with Sigma Scan Pro 5 and normalized to the loading control (β-actin). *p<0.05 versus sham group.</p

Protective effects of 3-mehtyladenine (3-MA) following cerebral I/R injury.

<p>3-MA (60 µg) solutions were injected icv immediately before reperfusion. (A) The changes of LC3 after the treatment of 3-MA. 3-MA significantly decreased LC3-II levels at 24 h after I/R. Effect of 3-MA on infarct volumes (B) and neurological deficits (C). 3-MA significantly reduced the infarct volume, and ameliorate the neurological symptoms at 24 h after I/R. ^#p<0.05 versus I/R group.</p

Effect of 15-PGJ₂ treatment on LC3 and cathepsin-B immunoreactivity after cerebral I/R injury.

<p>Double staining showed that LC3 punctate labeling and cathepsin-B immunoreactivity increased in neurons compared with sham-operated animals at 12 h after I/R injury. 15-PGJ2 at 50 pg effectively blocked the activation of autophagy as evidence by inhibiting immunoreactivity of LC3 (A) and cathepsin-B (B). Bar = 20 µm.</p

Neuroprotective effects of 15-PGJ₂ against cerebral I/R injury.

<p>15-PGJ₂ (1, 10, 50 pg) was administered icv immediately before reperfusion. (A) Five consecutive TTC-stained coronal brain slices arranged in cranial to caudal order 24 h after I/R. The white brain area represents infracted tissue. Infarct volume (B), neurological deficits (C) was measured 24 h after I/R. ^#p<0.05 versus I/R group.</p

Electron micrographs of morphological changes of cortical neurons after cerebral I/R injury.

<p>(A) N, nucleus; Broad arrows represent autophagosomes; Narrow arrows represent mitochondria. (B) Quantitative analysis of the nubmeber of autophagosomes. Three animals in each group and 10 fields for each animal were examined. *p<0.05 versus sham group.</p

Effect of 15-PGJ₂ treatment on autophagic-related protein expression in ischemic cortex after cerebral I/R injury.

<p>The expression of LC3-II, Beclin 1, cathepisin-B, and LAMP1 expression significantly increased at 12 h after reperfusion. Treatment with 15-PGJ₂ at 1 to 50 pg significantly decreased LC3-II, Beclin 1, cathepisin-B, and LAMP1 expression after I/R injury. Optical density of respective protein bands were analyzed with Sigma Scan Pro 5 and normalized to the loading control (β-actin). ^#p<0.05 versus I/R group.</p

PPAR-γ protein expression in cortex after cerebral I/R injury.

<p>(A) The level of PPAR-γ in ischemic cortex was higher than control in a time-dependent manner. (B) 15-PGJ₂ upregulated PPAR-γ expression in ischemic cortex in a concentration-dependent manner. *p<0.05 versus sham group, ^#p<0.05 versus I/R group.</p

Immunohistochemistry for LC3 and cathepsin B in neurons after cerebral I/R injury.

<p>(A) In sham-operated animals, cortical cells displayed diffuse and weak staining for LC3 in the cytosol. After I/R, intense LC3 staining appeared granular in the cytosol of cortical cells. Double staining for LC3 (green) and NeuN (red) showed that increase in LC3 punctate labeling occurred in cortical neurons. (B) In sham-operated animals, cortical cells displayed fine, granular, and perinuclear cathepsin-B staining. After I/R, cathepin-B granules became progressively larger and irregular, and the granular pattern was finally replaced with diffuse cytoplasmic staining. Double staining for cathepsin-B (green) and NeuN (red) showed that increased expression of cathepsin-B occurred mainly in neurons. Bar = 20 µm.</p