Protection of retinal function and morphology in MNU-induced retinitis pigmentosa rats by ALDH2: an in-vivo study

Effect of molecular hydrogen, a novelly-established antioxidant, on the retinal degeneration of hereditary retinitis pigmentosa: an in-vivo study

Objective Our research was performed in order to explore the effects of molecular hydrogen (H2), a novelly-established antioxidant, on the retinal degeneration in rd1 mice, an animal model of inherited retinitis pigmentosa (RP). Methods The rd1 mice were divided randomly into control and H2 intervention groups. Mice from other groups received H2 intervention in three modes, two modes of the hydrogen gas (HG) and one model of hydrogen-rich saline (HRS). At 14 days post born (P14) and P21, various indicators were detected in all mice, including eletroretinogram (ERG), fundus phography, optical coherence tomography (OCT), and retinal immunotaining of microglia cells' marker, Iba1. Results The ERG amplitude in mice from the control and H2 intervention groups showed no statistical differences (p > 0.05). At P14 and P21, no significant difference in the distance from the retinal pigment epithelium to the outer plexiform layer on OCT from mice of the above two groups was found (p > 0.05). The thickness of the outer nuclear layer (ONL) in mice at P14 and P21 showed no statistical differences between the control group and the H2 intervention group (p > 0.05). In the aspect of the number of Iba1-positive cells, we did not found any significant differences between the two groups (p > 0.05). Conclusion Different forms of H2 intervention (hydrogen-rich saline and hydrogen gas) had no obvious effects on the course of retinal degeneration in rd1 mice. The specific mechanism of photoreceptor degeneration in the hereditary RP mouse model may be different, requiring different medical interventions.

Lutein combined with EGCG improved retinitis pigmentosa against N-methyl-N nitrosourea-induced

In order to investigate the synergistic improving effect of lutein (LUT) and epigallocatechin-3-gallate (EGCG) treatment on retinitis pigmentosa (RP), an N-methyl-N-nitrosourea (MNU)-induced mouse model was conducted in the present study. Compared to the LUT alone treatment group, in the LUT combined with EGCG (LUT-EGCG) treatment group, the accumulation content of LUT was significantly increased by 50.24% in the liver. The morphological results indicated that LUT-EGCG treatment significantly improved the retina structure with the thickness of the outer nuclear layer restored to 185.28 ± 0.29 μm, showing no significant difference compared to the control group. The LUT-EGCG treatment also increased the production of short-chain fatty acids, such as acetic and propionic acids. Compared with the LUT alone treatment, the LUT-EGCG treatment significantly increased the relative abundance of Lachnospiraceae and Helicobacteraceae. RT-qPCR results indicated that LUT-EGCG treatment significantly increased the antiapoptotic gene Bcl-2 expression. In addition, the expression of IL-6 was significantly down-regulated in the LUT-EGCG group, while there was no significance in NF-κβ, TNF-α, IL-1β, and IL-18 compared with the LUT group. Correlation analysis supported the conclusion that LUT combined with EGCG may improve RP by modulating antiapoptotic gene expression and regulating the abundance of gut microbiota. However, the underlying mechanism still needs further research.

The impacts of resveratrol on the retinal degeneration in a rat model of retinitis pigmentosa induced by alkylation: an in-vivo study

Upregulation of Sirtuin Type 1 (SIRT1), a nicotinamide adeninedinucleotide (NAD+)-dependent deacetylase, has been proved to protect against ample ocular diseases, while its effect on retinitis pigmentosa (RP) has not been illustrated. The study was aimed to explore the impacts of resveratrol (RSV), a SIRT1 activator, on the photoreceptor degeneration in a rat model of RP induced by N-methyl-N-nitrosourea (MNU), an alkylation. The rats were induced RP phenotypes via the intraperitoneal injection of MNU. The electroretinogram was conducted and revealed that RSV could not prevent the decline of retinal function in the RP rats. The optical coherence tomography (OCT) and the retinal histological examination were performed and showed that the reduced thickness of the outer nuclear layer (ONL) was not preserved by RSV intervention. The immunostaining technique was applied. Afther the MNU administration, the number of the apoptotic photoreceptors in the ONL throughout the retinasand the number of microglia cells present among the outer part throughout the retinas were not significantly reduced by RSV. Western blotting was also performed. The data showed that the level of SIRT1 protein was decreased after MNU administration, while RSV was not able to obviously alleviate the downregulation. Our data together indicated that RSV was not able to rescue the photoreceptor degeneration in the MNU-induced RP rats, which might be due to the MNU-induced consumption of the NAD+.

Protective effect of ZYMT, a traditional Chinese patent medicine in a mouse model of retinitis pigmentosa

Retinitis pigmentosa (RP) is the most common genetic disorder that causes blindness. At present, there exists no remedy for the disease. The aim of the current research was to investigate the protective effect of Zhangyanming Tablets (ZYMT) in a mouse model of RP, and explore the underlying mechanism. Eighty RP mice were randomly divided into two groups. The mice in ZYMT group were administered with ZYMT suspension(0.0378 g/mL), while the mice in model group were given the same volume of distilled water. At day 7 and day 14 after intervention, electroretinogram (ERG), fundus photography, and histological examination were used to assess the retinal function and structure. TUNEL, immunofluorescence and qPCR were used to evaluate cell apoptosis and expressions of Sirt1, Iba1, Bcl-2, Bax and Caspase-3. A significantly shortened latency of ERG waves was observed in ZYMT-treated mice, in comparison to those in the model group (P < 0.05). Histologically, ultrastructure of the retina was better preserved, and the outer nuclear layer (ONL) exhibited marked increase in thickness and cell count in ZYMP group (P < 0.05). The apoptosis rate was decreased markedly in ZYMT group. Immunofluorescence analysis showed that the expressions of Iba1 and Bcl-2 in the retina were increased, Bax and Caspase-3 were decreased after ZYMT intervention, while the qPCR revealed that the expressions of Iba1 and Sirt1 were significantly increased (P < 0.05). This study indicated that ZYMT has protective effect on retinal function and morphology of inherited RP mice in the early stage, possibly mediated via the regulation of antioxidant and anti-/pro-apoptotic factors expressions.

The Temporal Topography of Central Serous Chorioretinopathy in the Chinchilla Rabbits Induced by Intravenous Injection of Adrenaline: An in vivo Study

PURPOSE

To explore the temporal topography of the chorioretinopathy in an animal model of central serous chorioretinopathy (CSC) induced by intravenous injection of adrenalin in the Chinchilla rabbits.

METHODS

Ten Chinchilla rabbits received a daily intravenous injection of adrenaline at 0.04 mg/kg for 8 weeks. Fluorescence fundus angiography (FFA) and electroretinogram (ERG) were performed every week afterwards to see whether there was fluorescence leakage in the fundus and to evaluate the retinal function. Indocyanine green angiography (ICGA) and optical coherence tomography (OCT) were also conducted to detect the change of choroidal vessels. Finally, the eyes of the rabbits were enucleated to make the retinal sections for histological examination with hematoxylin-eosin (HE) staining.

RESULTS

Within 8 weeks of the adrenalin administration, 7 out of the 10 rabbits showed different degrees of fluorescence leakage on FFA. The leakage was more obvious during 2-3 weeks after the adrenalin administration. With the progress of disease, the leakage subsided gradually and a scar-like lesion formed. ICGA revealed the local choroidal ischemia and the dilated choroidal vessels. An obvious detachment of retina and an increased thickness of the choroid were found on OCT, which was most obvious 2 weeks after the adrenalin administration (P<0.01). ERG revealed no obvious decline of the b-wave amplitude before and after the adrenalin administration (P>0.05). A circumscribed retinal detachment, the depigmentation of retinal pigment epithelium and enlarged choroidal vessels were shown by the histological examination.

CONCLUSION

The temporal topography of the chorioretinopathy in the Chinchilla rabbits by intravenous injection of adrenaline somewhat mimicked that of the human CSC, which could enhance its application in the exploration for the pathogenesis and the therapeutic measures for human CSC.

The Potential Role of Mitochondrial Acetaldehyde Dehydrogenase 2 in Urological Cancers From the Perspective of Ferroptosis and Cellular Senescence

Overproduction of reactive oxygen species (ROS) and superlative lipid peroxidation promote tumorigenesis, and mitochondrial aldehyde dehydrogenase 2 (ALDH2) is associated with the detoxification of ROS-mediated lipid peroxidation-generated reactive aldehydes such as 4-hydroxy-2-nonenal (4-HNE), malondialdehyde, and acrolein due to tobacco smoking. ALDH2 has been demonstrated to be highly associated with the prognosis and chemoradiotherapy sensitivity of many types of cancer, including leukemia, lung cancer, head and neck cancer, esophageal cancer, hepatocellular cancer, pancreatic cancer, and ovarian cancer. In this study, we explored the possible relationship between ALDH2 and urological cancers from the aspects of ferroptosis, epigenetic alterations, proteostasis, mitochondrial dysfunction, and cellular senescence.

Aldehyde Dehydrogenase 2 as a Therapeutic Target in Oxidative Stress-Related Diseases: Post-Translational Modifications Deserve More Attention

Aldehyde dehydrogenase 2 (ALDH2) has both dehydrogenase and esterase activity; its dehydrogenase activity is closely related to the metabolism of aldehydes produced under oxidative stress (OS). In this review, we recapitulate the enzyme activity of ALDH2 in combination with its protein structure, summarize and show the main mechanisms of ALDH2 participating in metabolism of aldehydes in vivo as comprehensively as possible; we also integrate the key regulatory mechanisms of ALDH2 participating in a variety of physiological and pathological processes related to OS, including tissue and organ fibrosis, apoptosis, aging, and nerve injury-related diseases. On this basis, the regulatory effects and application prospects of activators, inhibitors, and protein post-translational modifications (PTMs, such as phosphorylation, acetylation, S-nitrosylation, nitration, ubiquitination, and glycosylation) on ALDH2 are discussed and prospected. Herein, we aimed to lay a foundation for further research into the mechanism of ALDH2 in oxidative stress-related disease and provide a basis for better use of the ALDH2 function in research and the clinic.

Wedelolactone Attenuates N-methyl-N-nitrosourea-Induced Retinal Neurodegeneration through Suppression of the AIM2/CASP11 Pathway

N-methyl-N-nitrosourea (NMU) is widely used to model oxidative stress and inflammation mediated retinal neurodegeneration. Wedelolactone (WD) is known to have antioxidant, anti-inflammatory, and neuroprotective roles. This study tested the therapeutic potential of WD in NMU-induced retinal neurodegeneration and investigated the underlying mechanisms in mice. NMU (40 mg/kg) was injected intraperitoneally into C57BL/6J mice with/without an intravitreal injection of WD (1 μL/eye, 200 μM). Seven days later, retinal function and structure were evaluated by electroretinography (ERG) and Spectral Domain Optical Coherence Tomography (SD-OCT). The expression of inflammasome components (Aim2, Caspase 1/11, and Il1b/Il18) in the total retina lysate was evaluated by RT-qPCR. In vitro, 661W photoreceptor cells were transfected with synthetic double-strand DNA (Poly(dA:dT)) with/without WD pre-incubation. The aim2-related inflammasome expression was evaluated by RT-qPCR and immunocytochemistry. The production of IL18 was measured by ELISA. NMU treatment significantly impaired A- and B-wave response (ERG) and reduced neuroretina thickness (OCT). This was significantly attenuated upon intravitreal injection of WD. The expression of Aim2, ACasp1, and Casp11 was increased in the retina from NMU-treated mice, and this was prevented by WD treatment. Transfection of Poly(dA:dT) upregulated Aim2, Casp11, and Il18 expression in 661W cells. WD prevented their upregulation and reduced IL18 production. Aim2 inflammasome activation is critically involved in NMU-induced retinal neurodegeneration and WD can protect the retina particularly through the suppression of this inflammasome-linked pathway.

Protective effect of aldehyde dehydrogenase 2 against rat corneal dysfunction caused by streptozotocin-induced type I diabetes

Aldehyde dehydrogenase 2 plays a pivotal role in detoxifying aldehydes, and our previous study revealed that aldehyde dehydrogenase 2 could alleviate diabetic retinopathy-associated damage. We aimed to characterize the potential role of aldehyde dehydrogenase 2 in diabetic keratopathy. Twenty-four rats with streptozotocin-induced (60 mg/kg, single intraperitoneal injection) type 1 diabetes mellitus (T1DM) were divided the T1DM group and the T1DM + Alda1 (an activator of aldehyde dehydrogenase 2) group (5 mg/kg/d, intraperitoneal injection, 1/2/3 months), while an additional 12 healthy rats served as the control group. Corneal morphology was examined in vivo and in vitro at one, two, and three months after T1DM induction. Additionally, serum inflammatory factors were measured by ELISA, and the expression of corneal vascular endothelial growth factor A (VEGF-A) and aldehyde dehydrogenase 2 was measured by immunofluorescence staining. Corneal cell death was evaluated by terminal-deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) staining. Slit lamp analysis showed that the area of corneal epithelial cell injury in the T1DM + Alda1 group was significantly smaller than that in the T1DM group at one and two months after T1DM induction (all P < 0.05). OCT analysis and HE staining showed that the central corneal thickness (indication of corneal edema) and the epithelial keratinization level in the T1DM + Alda1 group was evidently decreased compared with those in the T1DM group (all P < 0.05). The serum inflammatory factors interleukin-1 and interleukin-6 were significantly upregulated in the T1DM group compared with the T1DM + Alda1 group at three months after T1DM induction (all P < 0.05), while there were no differences in SOD or TNF-α levels among all groups. Furthermore, corneal VEGF-A expression and corneal cell death in the T1DM + Alda1 group were dramatically reduced compared to those in the T1DM group (all P < 0.05). In conclusion, the aldehyde dehydrogenase 2 agonist Alda1 attenuated rat corneal dysfunction induced by T1DM by alleviating corneal edema, decreasing corneal cell death, and downregulating corneal VEGF-A expression.

Maturation and Protection Effect of Retinal Tissue-Derived Bioink for 3D Cell Printing Technology

Retinal degeneration is a leading cause of incurable vision loss and blindness. The increasing incidence of retinal degeneration has triggered research into the development of in vitro retinal models for drug development and retinal alternatives for transplantation. However, the complex retinal structure and the retinal microenvironment pose serious challenges. Although 3D cell printing technology has been widely used in tissue engineering, including in vitro model development and regeneration medicine, currently available bioinks are insufficient to recapitulate the complex extracellular matrix environment of the retina. Therefore, in this study, we developed a retinal decellularized extracellular matrix (RdECM) from the porcine retina and evaluated its characteristics. The RdECM conserved the ECM components from the native retina without cellular components. Then, we mixed the RdECM with collagen to form a bioink and confirmed its suitability for 3D cell printing. We further studied the effect of the RdECM bioink on the differentiation of Muller cells. The retinal protective effect of the RdECM bioink was confirmed through a retinal degeneration animal model. Thus, we believe that the RdECM bioink is a promising candidate for retinal tissue engineering.

ALDH2 protects naturally aged mouse retina via inhibiting oxidative stress-related apoptosis and enhancing unfolded protein response in endoplasmic reticulum

During the process of aging, the retina exhibits chronic oxidative stress (OS) damage. Our preliminary experiment showed that acetaldehyde dehydrogenase 2 (ALDH2) could alleviate retinal damage caused by OS. This study aimed to explore whether ALDH2 could inhibit mice retinal cell apoptosis and enhance the function of unfolded protein response in endoplasmic reticulum (UPRER) through reducing OS in aging process. Retinal function and structure in vivo and in vitro were examined in aged ALDH2+ overexpression mice and ALDH2 agonist Alda1-treated aged mice. Levels of ALDH2, endoplasmic reticulum stress (ERS), apoptosis and inflammatory cytokines were evaluated. Higher expression of ALDH2 was observed at the outer nuclear layer (ONL) and the inner nuclear layer (INL) in aged ALDH2+ overexpression and aged Alda1-treated mice. Moreover, aged ALDH2+ overexpression mice and aged Alda1-treated mice exhibited better retinal function and structure. Increased expression of glucose-regulated protein 78 (GRP78) and ERS-related protein phosphorylated eukaryotic initiation factor 2 (peIF2α) and decreased expression of apoptosis-related protein, including C/EBP homologous protein (CHOP), caspase12 and caspase9, and retinal inflammatory cytokines were detected in the retina of aged ALDH2+ overexpression mice and aged Alda1-treated mice. The expression of ALDH2 in the retina was decreased in aging process. ALDH2 could reduce retinal oxidative stress and apoptosis, strengthen UPRER during the aging process to improve retinal function and structure.

Retinitis Pigmentosa and Retinal Degenerations: Deciphering Pathways and Targets for Drug Discovery and Development

Inherited retinal diseases (IRDs) are a group of retinopathies generally caused by genetic mutations. Retinitis pigmentosa (RP) represents one of the most studied IRDs. RP leads to intense vision loss or blindness resulting from the degeneration of photoreceptor cells. To date, RP is mainly treated with palliative supplementation of vitamin A and retinoids, gene therapies, or surgical interventions. Therefore, a pharmacologically based therapy is an urgent need requiring a medicinal chemistry approach, to validate molecular targets able to deal with retinal degeneration. This Review aims at outlining the recent research efforts in identifying new drug targets for RP, especially focusing on the neuroprotective role of the Wnt/β-catenin/GSK3β pathway and apoptosis modulators (in particular PARP-1) but also on growth factors such as VEGF and BDNF. Furthermore, the role of spatiotemporally expressed G protein-coupled receptors (GPR124) in the retina and the emerging function of histone deacetylase inhibitors in promoting retinal neuroprotection will be discussed.