Early Proteomic Characteristics and Changes in the Optic Nerve Head, Optic Nerve, and Retina in a Rat Model of Ocular Hypertension.

The pathogenesis of glaucoma is still unknown. There are few studies on the dynamic change of tissue-specific and time-specific molecular pathophysiology caused by ocular hypertension (OHT). This study aimed to identify the early proteomic alterations in the retina, optic nerve head (ONH), and optic nerve (ON). After establishing a rat model of OHT, we harvested the tissues from control and glaucomatous eyes and analyzed the changes in protein expression using a multiplexed quantitative proteomics approach (TMT-MS3). Our study identified 6403 proteins after 1-day OHT and 4399 proteins after 7-days OHT in the retina, 5493 proteins after 1-day OHT and 4544 proteins after 7-days OHT in ONH, and 5455 proteins after 1-day OHT and 3835 proteins after 7-days OHT in the ON. Of these, 560 and 489 differential proteins were identified on day 1 and 7 after OHT in the retina, 428 and 761 differential proteins were identified on day 1 and 7 after OHT in the ONH, and 257 and 205 differential proteins on days 1 and 7 after OHT in the ON. Computational analysis on day 1 and 7 of OHT revealed that alpha-2 macroglobulin was upregulated across two time points and three tissues stably. The differentially expressed proteins between day 1 and 7 after OHT in the retina, ONH, and ON were associated with glutathione metabolism, mitochondrial dysfunction/oxidative phosphorylation, oxidative stress, microtubule, and crystallin. And the most significant change in retina are crystallins. We validated this proteomic result with the Western blot of crystallin proteins and found that upregulated on day 1 but recovered on day 7 after OHT, which are promising as therapeutic targets. These findings provide insights into the time- and region-order mechanisms that are specifically affected in the retina, ONH, and ON in response to elevated IOP during the early stages.

Mechanosensitive channel Piezo1 is an essential regulator in cell cycle progression of optic nerve head astrocytes.

Optic nerve head (ONH) astrocytes provide structural and metabolic support to neuronal axons in developmental, physiological, and pathological progression. Mechanosensitive properties of astrocytes allow them to sense and respond to mechanical cues from the local environment. We confirmed that ONH astrocytes express the mechanosensitive ion channel Piezo1 in vivo. By manipulating Piezo1 knockdown or overexpression in vitro, we found that Piezo1 is necessary but insufficient for ONH astrocyte proliferation. Loss of Piezo1 can lead to cell cycle arrest at G0/G1 phase, a possible mechanism involving decreased yes-associated protein (YAP) nuclear localization and downregulation of YAP-target cell cycle-associated factors, including cyclin D1 and c-Myc. Gene ontology enrichment analysis of differential expression genes from RNA-seq data indicates that the absence of Piezo1 affects biological processes involving cell division. Our results demonstrate that Piezo1 is an essential regulator in cell cycle progression in ONH astrocytes.

Human Pro370Leu Mutant Myocilin Induces the Phenotype of Open-Angle Glaucoma in Transgenic Mice.

To investigate the characteristics of mutation myocilin proteins and glaucoma pathological phenotype in transgenic mice with full-length human Pro370Leu mutant myocilin gene (Tg-MYOCP370L). Tg-MYOCP370L mice were established using the CRISPR/Cas9 system. Long-term intraocular pressure (IOP) was measured, myocilin protein expressions in anterior chamber angle, retina, optic nerve tissues and aqueous humor were detected by western blot. RBPMS, myocilin, Iba-1 and GFAP expression were visualized by immunofluorescence. H&E staining was applied to assess the ocular angle and retinal morphology. Aqueous humor dynamics were visualized by Gadolinium magnetic resonance imaging (Gd-MRI). TUNEL assay was used to evaluate the specific cell apoptosis in trabecular meshwork and retina. Optomotor and electroretinography tests were employed to evaluate the visual function in Tg-MYOCP370L and wild-type (WT) mice. Homozygous myocilin mutation at position 503 (C > T) was identified by PCR and sequencing in Tg-MYOCP370L mice. Myocilin protein expression was overexpressed in eye tissues of Tg-MYOCP370L mice with reduced myocilin secretion in aqueous humor. H&E staining showed normal histological morphology of anterior chamber angle whereas decreased thickness and nuclei in ganglion cell layer were found (P < 0.05). Gd signals were significantly increased in the anterior chamber of Tg-MYOCP370L compared with WT eyes (P < 0.05). IOP was elevated in Tg-MYOCP370L mice starting at 5 months of age, with significant RGC loss (P < 0.05). Upregulation of caspase-3 and caspase-9 expressions and increased TUNEL-positive cells were found in eyes of Tg-MYOCP370L mice. Excessive activation of retinal glial cells and impaired visual function were detected in Tg-MYOCP370L mice. Tg-MYOCP370L mice can induce the phenotype of open-angle glaucoma, featured as IOP elevation, activated retinal glial cells, loss of RGCs and impaired visual function. These pathologic changes may arise from the abnormal mutant myocilin protein accumulation in the trabecular meshwork and injured aqueous humor drainage. Therefore, Tg-MYOCP370L mice model can serve as an effective animal model for glaucoma research, especially for glaucoma-associated myocilin mutation studies.

Leaf Cuticular Waxes of Bermudagrass Response to Environment-Driven Adaptations of Climate Effect Inferred from Latitude and Longitude Gradient in China.

Bermudagrass (Cynodon dactylon) is a widely used warm season lawn grass. Cuticular wax covering the surface of plant leaves plays an important role in helping plants resist biotic and abiotic stresses. We analyzed the changes of cuticle wax in 25 bermudagrass populations from different longitude and latitude gradients, in order to verify how environmental conditions affect the structure and chemical composition of cuticle wax. Five wax components were identified, including alkanes, esters, alkenes, aldehydes and primary alcohols. The wax characteristics were divided into two principal components, explaining 58.2 % and 66.7 % of the total variability in latitude and longitude, even some populations had a certain correlation with each other. Pearson correlation analysis further showed that the total wax coverage, wax component content and antioxidant enzyme activity of bermudagrass populations on the latitudinal gradient had different responses to environmental factors. Finally, nineteen key genes involved in wax biosynthesis, redox and photosynthesis were identified and verified by RT-qPCR. The results showed that the responses of bermudagrass in different populations to climate change were quite different, which was of great significance for the evolution of bermudagrass populations.

The heterogeneous drivers of CO2 emissions in China's two major economic belts: new evidence from spatio-temporal analysis.

CO2 emissions have become increasingly prominent in China, and the primary emitters are economic belts that are spread throughout China. Two major economic belts, i.e., the Yangtze River Economic Belt (YTREB) and the Yellow River Economic Belt (YREB). Combined with stochastic impacts by regression on population, affluence and technology model, the spatial Durbin model under the space-and-time fixed effect and the Geographical and Time-Weighted Regression are employed to explore the spatio-temporal distribution characteristics and heterogeneous drivers of CO2 emissions in the two economic belts. The results are as follows. First, CO2 emissions exhibit obvious spatial correlation features in the YREB, but no such obvious spatial correlation is found in the YRETB. Second, in the YREB, the magnitude of the total influencing factors on CO2 emissions follows an order where affluence (A) is the biggest driver, followed by energy intensity (EI), technology (TEC) and openness (OP), while the biggest driver in the YRETB is industrial structure supererogation (ISS), followed by population (P), energy intensity (EI), and affluence (A). Both direct and spatial spillover effects of the drivers are observed in the two economic belts. Third, the CO2 emissions show a notable temporal lag effect in the YREB, but not in the YRETB. Fourth, the effects of the CO2 emission drivers illustrate significant spatio-temporal heterogeneity in the two economic belts.

Risk Factors for Death Among the First 80 543 Coronavirus Disease 2019 (COVID-19) Cases in China: Relationships Between Age, Underlying Disease, Case Severity, and Region.

BACKGROUND: Knowledge of COVID-19 epidemiology remains incomplete and crucial questions persist. We aimed to examine risk factors for COVID-19 death. METHODS: A total of 80 543 COVID-19 cases reported in China, nationwide, through 8 April 2020 were included. Risk factors for death were investigated by Cox proportional hazards regression and stratified analyses. RESULTS: Overall national case-fatality ratio (CFR) was 5.64%. Risk factors for death were older age (≥80: adjusted hazard ratio, 12.58; 95% confidence interval, 6.78-23.33), presence of underlying disease (1.33; 1.19-1.49), worse case severity (severe: 3.86; 3.15-4.73; critical: 11.34; 9.22-13.95), and near-epicenter region (Hubei: 2.64; 2.11-3.30; Wuhan: 6.35; 5.04-8.00). CFR increased from 0.35% (30-39 years) to 18.21% (≥70 years) without underlying disease. Regardless of age, CFR increased from 2.50% for no underlying disease to 7.72% for 1, 13.99% for 2, and 21.99% for ≥3 underlying diseases. CFR increased with worse case severity from 2.80% (mild) to 12.51% (severe) and 48.60% (critical), regardless of region. Compared with other regions, CFR was much higher in Wuhan regardless of case severity (mild: 3.83% vs 0.14% in Hubei and 0.03% elsewhere; moderate: 4.60% vs 0.21% and 0.06%; severe: 15.92% vs 5.84% and 1.86%; and critical: 58.57% vs 49.80% and 18.39%). CONCLUSIONS: Older patients regardless of underlying disease and patients with underlying disease regardless of age were at elevated risk of death. Higher death rates near the outbreak epicenter and during the surge of cases reflect the deleterious effects of allowing health systems to become overwhelmed.

A Novel Beta-Glucosidase Gene for Plant Type Was Identified by Genome-Wide Association Study and Gene Co-Expression Analysis in Widespread Bermudagrass.

Bermudagrass (Cynodon spp.) is one of the most widely distributed warm-season grasses globally. The growth habits and plant type of bermudagrass are strongly associated with the applied purpose of the landscape, livestock, and eco-remediation. Therefore, persistent efforts are made to investigate the genetic basis of plant type and growth habits of bermudagrass. Here, we dissect the genetic diversity of 91 wild bermudagrass resources by genome-wide association studies (GWAS) combined with weighted gene co-expression analysis (WGCNA). This work is based on the RNA-seq data and the genome of African bermudagrass (Cynodon transvaalensis Burtt Davy). Sixteen reliable single-nucleotide polymorphisms (SNPs) in transcribed regions were identified to be associated with the plant height and IAA content in diverse bermudagrass by GWAS. The integration of the results from WGCNA indicates that beta-glucosidase 31 (CdBGLU31) is a candidate gene underlying a G/A SNP signal. Furthermore, both qRT-PCR and correlation coefficient analyses indicate that CdBGLU31 might play a comprehensive role in plant height and IAA biosynthesis and signal. In addition, we observe lower plant height in Arabidopsis bglu11 mutants (homologs of CdBGLU31). It uncovers the breeding selection history of different plant types from diverse bermudagrass and provides new insights into the molecular function of CdBGLU31 both in plant types and in IAA biosynthetic pathways.

Piezo2 downregulation via the Cre-lox system affects aqueous humor dynamics in mice.

Purpose: Proper aqueous humor (AH) dynamics is crucial for maintaining the intraocular pressure (IOP) in the eye. This study aims to investigate the function of Piezo2, a newly discovered mechanosensitive ion channel, in regulating AH dynamics. Methods: Immunohistochemistry (IHC) analysis and western blotting were performed to detect Piezo2 expression. The Cre-lox system was applied to create a conditional knockout model of Piezo2. IOP and aqueous humor outflow facility in live animals were recorded with a Tonometer and a syringe-pump system for up to 2 weeks. Results: We first detected Piezo2 with robust expression in the human trabecular meshwork (TM), Schlemm's canal (SC), the ciliary body's epithelium, and ciliary muscle. In addition, we found Piezo2 in human retinal ganglion cells (RGCs) and astrocytes in the optic nerve head (ONH). Through the Cre-lox system, Piezo2 can be successfully downregulated in mouse iridocorneal angle tissues. However, Piezo2 downregulation cannot significantly influence the IOP and outflow facility through the conventional pathway. Instead, we observed an effect of downregulated Piezo2 on decreasing the intercept in the flow rate versus pressure plot. According to the Goldmann equation, Piezo2 may function in regulating unconventional outflow, AH production, and episcleral venous pressure. Conclusions: These findings, for the first time, demonstrate that Piezo2 acts as an essential mechanosensor in maintaining the proper aqueous humor dynamics in the eye.

CuInS/ZnS quantum dots modified intraocular lens for photothermal therapy of posterior capsule opacification.

Posterior capsule opacification (PCO) after cataract surgery is one of the leading causes of visual impairment and blindness. The cause of PCO is the capsule fibrosis developed on implanted Intraocular Lens (IOLs) by the de-differentiation of Lens Epithelial Cells (LECs) undergoing epithelial mesenchymal transition. How to prevent PCO has been a challenge to scientists and ophthalmologists for decades. Here we demonstrated the use of carboxylated CuInS/ZnS quantum dots (ZCIS QDs), which are free of toxic heavy metals and are more biocompatible, as photothermal nanomedicines. The ZCIS QDs are modified onto the non-optical section of IOLs by a facial activation-immersion method. Under mild NIR laser irradiation, ZCIS QDs modified IOLs (QDs-IOLs) will generate localized heat and prevent the proliferation of LECs onto the surface of QDs-IOLs. Our findings provide experimental evidence for further application of combined nanotechnology and photothermal therapy for the clinical treatment of PCO.

Proteomic analysis of underlying apoptosis mechanisms of human retinal pigment epithelial ARPE-19 cells in response to mechanical stretch.

Our previous study demonstrated mechanical stretch (MS) could induce the apoptosis of retinal pigment epithelial (RPE) cells, but the related mechanisms remained unclear. This study was to characterize the protein expression profile in RPE cell line ARPE-19 exposed to MS, cytochalasin D (CD; an inhibitor of actin polymerization) or CD + MS at 2-time points (6, 24 hr; n = 3, at each time point) by using proteomics technique. Our data highlighted that compared with control, ECE1 was continuously downregulated in ARPE-19 cells treated by MS or CD + MS from 6 to 24 hr. Function and protein-protein interaction network analyses showed ATAD2 was downregulated in all three treatment groups compared with control, but successive upregulation of RPS13 and RPL7 and downregulation of AHSG were specifically induced by MS. ATAD2 was enriched in cell cycle; AHSG was associated with membrane organization; RPS13 and RPL7 participated in ribosome biogenesis. Furthermore, transcription factor CREB1 that was upregulated in MS group at 24 hr after treatment, may negatively regulate ATAD2. The expressions of all crucial proteins in ARPE-19 cells were confirmed by western blot analysis. Overexpression of ATAD2 and AHSG were also shown to reverse the apoptosis of ARPE-19 cells induced by MS or CD + MS, with significantly decreased apoptotic rates and caspase-3 activities. Accordingly, our findings suggest downregulation of ATAD2 and AHSG may be potential contributors to the apoptosis of RPE cells induced by MS. Overexpression of them may represent underlying preventive and therapeutic strategies for MS-induced retinal disorders.

KLF16 overexpression deleteriously affects the proliferation and migration of retinoblastoma by transcriptionally repressing BCL2L15.

Krüppel-like factors (KLFs) are transcription factors that control the expression of downstream genes. The role of KLFs has been reported in cancers. KLF16 promotes the proliferation of gastric cancer cells by upregulating p21, while suppresses the tumorigenesis of glioma through targeting TFAM. The function of KLF16 is controversial in cancer development. In this study, we aimed to investigate the role of KLF16 in retinoblastoma (RB). KLF16 was highly expressed in RB tissues and cells. Overexpression of KLF16 promoted the proliferation, growth and migration of RB cells. By contrast, KLF16 interference showed opposite effects. Cell cycle arrest and apoptosis were induced or repressed by KLF16 knockdown or overexpression, respectively. Mechanistically, BCL2 like 15 (BCL2L15), an apoptosis gene, was negatively regulated by KLF16. Luciferase reporter and ChIP assay showed that KLF16 transcriptionally repressed the expression of BCL2L15 by binding to its promoter. BCL2L15 was lowly expressed in RB tissues. Additionally, overexpression of BCL2L15 inhibited the proliferation and increased the apoptosis in RB cells. Our study identifies that KLF16 contributes to RB cell proliferation and migration by negatively regulating BCL2L15.

Accumulation of Asn450Tyr mutant myocilin in ER promotes apoptosis of human trabecular meshwork cells.

Purpose: In a previous study, we identified the Asn450Tyr mutant myocilin gene (Myoc-N450Y) in the pedigree of families with juvenile open angle glaucoma (JOAG), but whether N450Y is a pathogenic mutation remained to be determined. The present study aimed at exploring the role of Myoc-N450Y in primary human trabecular meshwork (HTM) cells. Methods: Primary HTM cells were infected with lentivirus with wild-type myocilin (Myoc-WT) or Myoc-N450Y. Primary HTM cells overexpressing Myoc-WT or Myoc-N450Y was treated with sodium 4-phenylbutyrate (4-PBA) or not. The secretion and intracellular distribution of Myoc were analyzed with western blotting and immunofluorescence. Expression of endoplasmic reticulum (ER) stress-related proteins was detected with quantitative real-time PCR (qRT-PCR) and western blotting. Cell viability, apoptosis, and expression of the related proteins were examined with Cell Counting Kit-8 (CCK-8), flow cytometry analysis, and western blotting, respectively. Results: We found that non-secretion of Myoc-N450Y induced ER stress by colocalization with the ER marker calreticulin (CALR), and upregulating the expression of ER stress markers in primary HTM cells. Moreover, overexpression of Myoc-N450Y inhibited the viability and induced apoptosis of primary HTM cells, and inhibition of PI3K/AKT signaling was induced by ER stress. Reduction in ER stress with 4-PBA decreased the level of ER stress markers, promoted secretion, and prevented accumulation of myocilin in the Myoc-N450Y group. Apoptosis was rescued, and inhibition of PI3K/AKT signaling was reversed, after PBA treatment in primary HTM cells with Myoc-N450Y overexpression. Conclusions: The study results suggest that Myoc-N450Y promotes apoptosis of primary HTM cells via the ER stress-induced apoptosis pathway, in which the PI3K/AKT signaling pathway plays a crucial role.

Lattice self-consistent field calculations of confined symmetric block copolymers of various chain architectures.

The effects of chain architecture and confinement on the structure and orientation of lamellae formed by incompressible and symmetric AB-type block copolymer melts confined between two parallel and identical surfaces are investigated using self-consistent field calculations on a simple cubic lattice. Five systems of various chain architectures (linear, ring, and star) and lengths are studied, with their bulk lamellar period L0 chosen such that they have comparable L0/Rg, where Rg denotes the ideal-chain radius of gyration. For thin films of thickness D = L0 confined between two neutral surfaces, we define the rescaled volume fraction profiles of A, B, chain end, and joint segments in the parallel and perpendicular lamellae such that these profiles can be directly compared among the five systems to quantitatively reveal the interplay between the chain-end enrichment near confining surfaces and the surface-induced A-B compatibilization, and how such interplay is affected by the chain architectures (for example, the chain-crowding effects in the star block copolymers). The effects of D and surface preference for one of the blocks are also investigated.

Morphological variation in Cynodon dactylon (L.) Pers., and its relationship with the environment along a longitudinal gradient.

BACKGROUND: Geographical variation in morphological traits may reflect evolutionary patterns of morphological adaptability along environmental gradients. Comprehensive information on longitudinal patterns of morphological trait variation is very meaningful to explore morphological diversity and evolutionary trends in widespread bermudagrass. METHODS: To explore the spatial patterns of morphological traits, we investigated 10 morphological traits of bermudagrass and 10 soil nutrient indexes and collected local climate data for 13 different regions from 119°E to 105°E along the latitude 34°N. RESULTS: Considerable variations in morphological traits were observed at different longitudes, and the variations in most of the evaluated traits within populations were lower than those among populations. All of the 13 different longitudinal sites were divided into three groups based on morphological traits by cluster analysis. The major sources of diversity at the different longitudes were leaf length of the erect shoot, leaf width of the erect shoot, and the internode lengths of the erect shoot and stolon as determined by principal component analysis. Pearson correlation analysis also indicated that longitude was significantly and negatively correlated with these traits as well. Mean average rainfall was significantly correlated with leaf length of the erect shoot and the internode lengths of the erect shoot and stolon, while mean average temperature was only significantly correlated with internode length of the erect shoots. Available sulfur was significantly correlated with internode length of the erect shoot, plant height, and reproductive branch height, while the exchangeable Ca was significantly correlated with internode lengths of the erect shoot and stolon. Soil pH was significantly correlated with the internode length of the stolon. Longitude is an important factor that affects morphological trait variation in wild bermudagrass, and the leaves of the erect shoot and the internode length enlarged significantly with the collection sites moving from east to west. CONCLUSION: Different combinations and interactions of environmental factors (soil and climate) along a longitudinal gradient may have strong effects on one or more morphological traits of bermudagrass.

Cyclic stretch induced oxidative stress by mitochondrial and NADPH oxidase in retinal pigment epithelial cells.

BACKGROUND: Vitreomacular adhesion (VMA) has been reported to associated with age-related macular degeneration (AMD). Understanding the mechanisms underlying cyclic stretch induced in retinal pigment epithelial cells (RPE) may be important for the treatment of VMA-related AMD. METHOD: Cyclic stretch (1HZ, 20% elongation) was applied to cultured ARPE-19 cells for 15 min, 2 h, 6 h, 12 h, 24 h by flexcell FX-5000 Tension system. Total reactive oxygen species (ROS) were detected using DCFH-DA. Mitochondrial superoxide were detected using MitoSOX Red mitochondrial superoxide indicator. NADPH oxidases (NOX) and signaling pathways, such as p38 and PKC, were detected using western blot. Apocycin (Apo) were used as NOX inhibitors. RESULT: High levels of total ROS were detected from 15 min to 24 h, whereas mitochondrial superoxide were higher only in early time. NOX2 were significantly increased at 24 h. NOX4 were significantly increased at 2 h and reach its peak at 24 h. P-p38 was significantly increased at 12 h and 24 h. P-PKC was significantly increased at 15 min and kept a persistent high level. The upregulated expression of NOX4 by cyclic stretch can be significantly decreased under p-PKC inhibitor other than p-p38 inhibitor. CONCLUSION: Cyclic stretch induce oxidative stress from both mitochodrial and NADPH oxidase in RPE cells, which may prompt oxidative damage in VMA-related AMD.

Variations in morphological traits of bermudagrass and relationship with soil and climate along latitudinal gradients.

BACKGROUND: This complex environmental heterogeneity coupled with the long-standing history offers scenario suitable for and favoring the evolution and existence of variation of morphological traits. METHODS: In this study, we measured 10 morphological traits of 310 Cynodon dactylon individuals sampled at 16 different locations along latitudinal gradients between 22°35'N and 36°18'N to reveal phenotypic plasticity influenced by latitude. In addition, the relationships between morphological variation and soil nutrient and climate factors were analyzed. RESULTS: Analysis of variance, divesity examination and Mantel correlation test detected a significant effect of latitude on morphological traits. Cluster analysis and principal component analysis clearly separated the selected populations into four groups according to latitude. Larger morphological sizes of C. dactylon appeared at the low- and high-latitude regions. Correlation analysis indicated that high morphological variations were significantly correlated with climate factors and soil nutrient. CONCLUSION: This study suggests morphological variation of wild bermudagrass is greatly influenced by latitude as well as soil and climate, which could be useful resources for genetic studies and evolution.

Multi-level quantum mechanics theories and molecular mechanics study of the double-inversion mechanism of the F- + CH3I reaction in aqueous solution.

A double-inversion mechanism of the F- + CH3I reaction was discovered in aqueous solution using combined multi-level quantum mechanics theories and molecular mechanics. The stationary points along the reaction path show very different structures to the ones in the gas phase due to the interactions between the solvent and solute, especially strong hydrogen bonds. An intermediate complex, a minimum on the potential of mean force, was found to serve as a connecting-link between the abstraction-induced inversion transition state and the Walden-inversion transition state. The potentials of mean force were calculated with both the DFT/MM and CCSD(T)/MM levels of theory. Our calculated free energy barrier of the abstraction-induced inversion is 69.5 kcal mol-1 at the CCSD(T)/MM level of theory, which agrees with the one at 72.9 kcal mol-1 calculated using the Born solvation model and gas-phase data; and our calculated free energy barrier of the Walden inversion is 24.2 kcal mol-1, which agrees very well with the experimental value at 25.2 kcal mol-1 in aqueous solution. The calculations show that the aqueous solution makes significant contributions to the potentials of mean force and exerts a big impact on the molecular-level evolution along the reaction pathway.

Cyclic stretch induced-retinal pigment epithelial cell apoptosis and cytokine changes.

BACKGROUND: The pathogenesis of age-related macular degeneration (AMD) is complex. It has been shown that vitreomacular traction (VMT) plays a role in the pathogenesis of AMD. We speculate that the continuous stretch induced by VMT might impair the function of retinal pigment epithelium (RPE) cells and it might also be involved in the progression of AMD. METHODS: Cultured ARPE-19 cells were subjected to cyclic stretch on the Flexcell Strain system at a level of 25% increment on the surface area for 8 h, 14 h, 20 h, 24 h. In another group, the stretch was withdrawn at 14 h and the cell cultured for another 6 h. Then, we observed the changes in morphology, apoptosis and expression of interleukin 6 (IL6) and vascular endothelial growth factor (VEGF) in RPE cells under stretch. RESULTS: We found that stretch induced the RPE cells to change from a spreading shape into a rounded shape, and that the morphological changes were positively correlated with the duration of the stretch. The expression of pFAK397 and pRac1/cdc42 were elevated in a time-dependent fashion. The stretch resulted in an increase in the apoptosis ratio, with Bcl2, Bax and p53 also showing time-dependent changes. In addition, up-regulation of IL6 and VEGF expression levels was also observed. After withdrawal of the stretch, all of these changes were significantly diminished. CONCLUSION: Stretch may induce morphological, cell apoptosis, and up-regulation of cytokines changes in RPE cells, indicating that cyclic stretching may participate in the progression of AMD by impeding the functions of the RPE.

The influence of actin depolymerization induced by Cytochalasin D and mechanical stretch on interleukin-8 expression and JNK phosphorylation levels in human retinal pigment epithelial cells.

BACKGROUND: This study explores the role of actin cytoskeleton depolymerization induced by Cytochalasin D and mechanical stretch on the interleukin-8 (IL-8) expression and c-jun N-terminal kinase (JNK) phosphorylation levels in human retinal pigment epithelial (RPE) cells. METHODS: A Flexcell FX-5000 Tension system was used to apply cyclic stretch to cultured human RPE cells (ARPE-19) at 0.33 Hz with 20% elongation for 0 h, 6 h or 24 h. The cells were stretched alone or pre-treated with Cytochalasin D. The redistribution of the actin cytoskeleton was evaluated using phalloidin immunofluorescence staining. The protein expression levels of IL-8 and JNK in the RPE cells were determined via Western blotting. RESULTS: The cells in the control groups displayed abundant and uniform phalloidin staining. After exposure to mechanical stretch for 24 h, phalloidin staining revealed an unclear and irregular actin cytoskeleton. In all Cytochalasin D-treated cells, the shrinkage and disruption of the cytoskeletal structure was observed regardless of mechanical stress. The stimulation of the RPE cells with cyclic stretch alone did not induce a significant increase in IL-8 expression and JNK phosphorylation levels, which were similar to those of the control groups. After pre-treatment with Cytochalasin D alone, IL-8 expression and JNK phosphorylation levels were not significantly different at 6 h but were significantly increased by approximately 1.2-fold (1.18 ± 0.05; P<0.01) and 3.0-fold (3.01 ± 0.02; P<0.01) at 24 h, respectively. After the pre-incubation of the RPE cells with Cytochalasin D followed by exposure to cyclic stretch, IL-8 expression and JNK phosphorylation levels increased by approximately 1.3-fold (1.31 ± 0.02; P<0.01) and 1.3-fold (1.31 ± 0.02; P<0.01) at 6 h, respectively, and by 1.7-fold (1.69 ± 0.06; P<0.01) and 3.2-fold (3.21 ± 0.12; P<0.01) at 24 h, respectively. CONCLUSIONS: This study demonstrates that disruption of actin polymerization by cytochalasin D and mechanical stretch upregulates interleukin-8 expression and JNK phosphorylation levels in human RPE cells, which indicates that the integrity of the actin cytoskeleton may play important roles in the pro-inflammatory processes in RPE cells.

A multi-level quantum mechanics and molecular mechanics study of SN2 reaction at nitrogen: NH2Cl + OH(-) in aqueous solution.

We employed a multi-level quantum mechanics and molecular mechanics approach to study the reaction NH2Cl + OH(-) in aqueous solution. The multi-level quantum method (including the DFT method with both the B3LYP and M06-2X exchange-correlation functionals and the CCSD(T) method, and both methods with the aug-cc-pVDZ basis set) was used to treat the quantum reaction region in different stages of the calculation in order to obtain an accurate potential of mean force. The obtained free energy activation barriers at the DFT/MM level of theory yielded a big difference of 21.8 kcal mol(-1) with the B3LYP functional and 27.4 kcal mol(-1) with the M06-2X functional respectively. Nonetheless, the barrier heights become very close when shifted from DFT to CCSD(T): 22.4 kcal mol(-1) and 22.9 kcal mol(-1) at CCSD(T)(B3LYP)/MM and CCSD(T)(M06-2X)/MM levels of theory, respectively. The free reaction energy obtained using CCSD(T)(M06-2X)/MM shows an excellent agreement with the one calculated using the available gas-phase data. Aqueous solution plays a significant role in shaping the reaction profile. In total, the water solution contributes 13.3 kcal mol(-1) and 14.6 kcal mol(-1) to the free energy barrier heights at CCSD(T)(B3LYP)/MM and CCSD(T)(M06-2X)/MM respectively. The title reaction at nitrogen is a faster reaction than the corresponding reaction at carbon, CH3Cl + OH(-).