Acetylcholinesterase function in apoptotic retina pigment epithelial cells induced by H2O2

The Contribution of Fluoride to the Pathogenesis of Eye Diseases: Molecular Mechanisms and Implications for Public Health

This study provides diverse lines of evidence demonstrating that fluoride (F) exposure contributes to degenerative eye diseases by stimulating or inhibiting biological pathways associated with the pathogenesis of cataract, age-related macular degeneration and glaucoma. As elucidated in this study, F exerts this effect by inhibiting enolase, τ-crystallin, Hsp40, Na⁺, K⁺-ATPase, Nrf2, γ -GCS, HO-1 Bcl-2, FoxO1, SOD, PON-1 and glutathione activity, and upregulating NF-κB, IL-6, AGEs, HsP27 and Hsp70 expression. Moreover, F exposure leads to enhanced oxidative stress and impaired antioxidant activity. Based on the evidence presented in this study, it can be concluded that F exposure may be added to the list of identifiable risk factors associated with pathogenesis of degenerative eye diseases. The broader impact of these findings suggests that reducing F intake may lead to an overall reduction in the modifiable risk factors associated with degenerative eye diseases. Further studies are required to examine this association and determine differences in prevalence rates amongst fluoridated and non-fluoridated communities, taking into consideration other dietary sources of F such as tea. Finally, the findings of this study elucidate molecular pathways associated with F exposure that may suggest a possible association between F exposure and other inflammatory diseases. Further studies are also warranted to examine these associations.

Intravitreal Injection of Hydrogen Peroxide Induces Acute Retinal Degeneration, Apoptosis, and Oxidative Stress in Mice

PURPOSE

Oxidative stress is a common pathological condition for multiple retinal diseases. Hydrogen peroxide (H₂O₂) has been applied as an oxidative stress inducer for the in vitro studies. Here, we report the in vivo effect of H₂O₂ exposure to the mouse retina and its underlying mechanism.

METHODS

The H₂O₂ or saline solution was intravitreally injected into the eyes of female C57BL/6J mice for two consecutive days. The retinal structure was evaluated by in vivo imaging using spectral domain optical coherence tomography (OCT) and validated by histological assessment as well as retinal marker expression. In addition, retinal stress, cell apoptosis, and antioxidant enzyme expression were also determined.

RESULTS

Retinal and outer nuclear layer thickness thinning was observed at days 7 and 14 by OCT imaging with the treatment of 10 μg H₂O₂, which was confirmed by the histopathological analysis. The expressions of photoreceptor (Rho, Rora, Rorb, and Rcvrn), bipolar cell (Chat and Calb2), and retinal pigment epithelial (Rpe65) markers were reduced in the H₂O₂-treated group, whereas the expression of retinal ganglion cell marker (Tubb3) was increased. TUNEL-positive cells were obviously found in the outer nuclear layer and inner nuclear layer of H₂O₂-treated mice but sparely found in the ganglion cell layer. Coherently, apoptotic gene expressions (Casp3, Casp9, Bax, and Parp8) were significantly increased in the retina with increasing dosages of H₂O₂, while Bcl2 expression was mildly decreased. In addition, the expressions of Gfap and antioxidant enzyme genes (Txn2, Sod2, and Gpx4) were significantly upregulated in the retina after the H₂O₂ treatment, compared to the vehicle control group.

CONCLUSIONS

This study revealed that intravitreal injection of H₂O₂ induces acute retinal damage by increasing oxidative stress and cell apoptosis in the retina. This acute retinal degeneration mouse model could provide a platform for drug screening against oxidative stress and retinal diseases.

Mitochondrial expression and activity of P-glycoprotein under oxidative stress in outer blood-retinal barrier

AIM

To investigate the role of oxidative stress in regulating the functional expression of P-glycoprotein (P-gp) in mitochondria of D407 cells.

METHODS

D407 cells were exposed to different ranges of concentrations of H₂O₂. The mitochondrial location of P-gp in the cells subjected to oxidative stress was detected by confocal analysis. Expression of P-gp in isolated mitochondria was assessed by Western blot. The pump activity of P-gp was evaluated by performing the efflux study on isolated mitochondria with Rhodamine 123 (Rho-123) alone and in the presence of P-gp inhibitor (Tariquidar) using flow cytometry analysis. The cells were pretreated with 10 mmol/L N-acetylcysteine (NAC) for 30min before exposing to H₂O₂, and analyzed the mitochondrial extracts by Western blot and flow cytometry.

RESULTS

P-gp was co-localized in the mitochondria by confocal laser scanning microscopy, and it was also detected in the mitochondria of D407 cells using Western blot. Exposure to increasing concentrations of H₂O₂ led to gradually increased expression and location of P-gp in the mitochondria of cells. Rho-123 efflux assay showed higher uptake of Rho-123 on isolated mitochondria in the presence of Tariquidar both in normal and oxidative stress state. H₂O₂ up-regulated P-gp in D407 cells, which could be reversed by NAC treatment.

CONCLUSION

H₂O₂ could up-regulate the functional expression of P-gp in mitochondria of D407 cells, while antioxidants might suppress oxidative-stress-induced over-expression of functional P-gp. It is indicative that limiting the mitochondrial P-gp transport in retinal pigment epithelium cells would be to improve the effect of mitochondria-targeted antioxidant therapy in age-related macular degeneration-like retinopathy.

The protective role of tacrine and donepezil in the retina of acetylcholinesterase knockout mice

AIM

To determine the effect of different concentrations of the acetylcholinesterase (AChE) inhibitors tacrine and donepezil on retinal protection in AChE(+/-) mice (AChE knockout mice) of various ages.

METHODS

Cultured ARPE-19 cells were treated with hydrogen peroxide (H2O2) at concentrations of 0, 250, 500, 1000 and 2000 µmol/L and protein levels were measured using Western blot. Intraperitoneal injections of tacrine and donepezil (0.1 mg/mL, 0.2 mg/mL and 0.4 mg/mL) were respectively given to AChE(+/-) mice aged 2mo and 4mo and wild-type S129 mice for 7d; phosphate buffered saline (PBS) was administered to the control group. The mice were sacrificed after 30d by in vitro cardiac perfusion and retinal samples were taken. AChE-deficient mice were identified by polymerase chain reaction (PCR) analysis using specific genotyping protocols obtained from the Jackson Laboratory website. H&E staining, immunofluorescence and Western blot were performed to observe AChE protein expression changes in the retinal pigment epithelial (RPE) cell layer.

RESULTS

Different concentrations of H2O2 induced AChE expression during RPE cell apoptosis. AChE(+/-) mice retina were thinner than those in wild-type mice (P<0.05); the retinal structure was still intact at 2mo but became thinner with increasing age (P<0.05); furthermore, AChE(+/-) mice developed more slowly than wild-type mice (P<0.05). Increased concentrations of tacrine and donepezil did not significantly improve the protection of the retina function and morphology (P>0.05).

CONCLUSION

In vivo, tacrine and donepezil can inhibit the expression of AChE; the decrease of AChE expression in the retina is beneficial for the development of the retina.

Role of acetylcholinesterase in lung cancer

Acetylcholinesterase (AChE) plays a key role in catalytic hydrolysis of cholinergic neurotransmitters. Intensive research has proven the involvement of this protein in novel functions, such as cell adhesion, differentiation, and proliferation. In addition, several recent studies have indicated that acetylcholinesterase is potentially a marker and regulator of apoptosis. Importantly, AChE is also a promising tumor suppressor. In this review, we briefly summarize the involvement of AChE in apoptosis and cancer, focusing on the role of AChE in lung cancer, as well as the therapeutic consideration of AChE for cancer therapy.