Serum Response Factor Protects Retinal Ganglion Cells Against High-Glucose Damage

Evaluation of thickness of individual macular retinal layers in diabetic eyes from optical coherence tomography

The effect of diabetes mellitus (DM) on individual retinal layers remains incompletely understood. We evaluated the intra-retinal layer thickness alterations in 71 DM eyes with no diabetic retinopathy (DR), 90 with mild DR, and 63 with moderate DR without macular edema, using spectral-domain optical coherence tomography (SD-OCT) and the Iowa Reference Algorithm for automated retinal layer segmentation. The average thickness of 10 intra-retinal layers was then corrected for ocular magnification using axial length measurements, and pairwise comparisons were made using multivariable linear regression models adjusted for gender and race. In DM no DR eyes, significant thinning was evident in the ganglion cell layer (GCL; p < 0.001), inner nuclear layer (INL; p = 0.001), and retinal pigment epithelium (RPE; p = 0.014) compared to normal eyes. Additionally, mild DR eyes exhibited a thinner inner plexiform layer (IPL; p = 0.008) than DM no DR eyes. Conversely, moderate DR eyes displayed thickening in the INL, outer nuclear layer, IPL, and retinal nerve fiber layer (all p ≤ 0.002), with notably worse vision. These findings highlight distinctive patterns: early diabetic eyes experience thinning in specific retinal layers, while moderate DR eyes exhibit thickening of certain layers and slightly compromised visual acuity, despite the absence of macular edema. Understanding these structural changes is crucial for comprehending diabetic eye complications.

The MADS-box genes SOC1 and AGL24 antagonize XAL2 functions in Arabidopsis thaliana root development

MADS-domain transcription factors play pivotal roles in numerous developmental processes in Arabidopsis thaliana. While their involvement in flowering transition and floral development has been extensively examined, their functions in root development remain relatively unexplored. Here, we explored the function and genetic interaction of three MADS-box genes (XAL2, SOC1 and AGL24) in primary root development. By analyzing loss-of-function and overexpression lines, we found that SOC1 and AGL24, both critical components in flowering transition, redundantly act as repressors of primary root growth as the loss of function of either SOC1 or AGL24 partially recovers the primary root growth, meristem cell number, cell production rate, and the length of fully elongated cells of the short-root mutant xal2-2. Furthermore, we observed that the simultaneous overexpression of AGL24 and SOC1 leads to short-root phenotypes, affecting meristem cell number and fully elongated cell size, whereas SOC1 overexpression is sufficient to affect columella stem cell differentiation. Additionally, qPCR analyses revealed that these genes exhibit distinct modes of transcriptional regulation in roots compared to what has been previously reported for aerial tissues. We identified 100 differentially expressed genes in xal2-2 roots by RNA-seq. Moreover, our findings revealed that the expression of certain genes involved in cell differentiation, as well as stress responses, which are either upregulated or downregulated in the xal2-2 mutant, reverted to WT levels in the absence of SOC1 or AGL24.

The Role of Nrf2/sMAF Signalling in Retina Ageing and Retinal Diseases

Age-related diseases, such as Parkinson's disease, Alzheimer's disease, cardiovascular diseases, cancers, and age-related macular disease, have become increasingly prominent as the population ages. Oxygen is essential for living organisms, but it may also cause disease when it is transformed into reactive oxygen species via biological processes in cells. Most of the production of ROS occurs in mitochondrial complexes I and III. The accumulation of ROS in cells causes oxidative stress, which plays a crucial role in human ageing and many diseases. Nuclear factor-erythroid 2-related factor 2 (Nrf2) is a key antioxidant transcription factor that plays a central role in many diseases and ageing in general. It regulates many downstream antioxidative enzymes when cells are exposed to oxidative stress. A basic-region leucine zipper (bZIP) transcription factor, MAF, specifically the small MAF subfamily (sMAFs), forms heterodimers with Nrf2, which bind with Maf-recognition elements (MAREs) in response to oxidative stress. The role of this complex in the human retina remains unclear. This review summarises the current knowledge about Nrf2 and its downstream signalling, especially its cofactor-MAF, in ageing and diseases, with a focus on the retina. Since Nrf2 is the master regulator of redox homeostasis in cells, we hypothesise that targeting Nrf2 is a promising therapeutic approach for many age-related diseases.

Neuroprotective Effects of Erinacine A on an Experimental Model of Traumatic Optic Neuropathy

Erinacine A (EA), a natural neuroprotectant, is isolated from a Chinese herbal medicine, Hericium erinaceus. The aim of this study was to investigate the neuroprotective effects of EA in a rat model of traumatic optic neuropathy. The optic nerves (ONs) of adult male Wistar rats were crushed using a standardized method and divided into three experimental groups: phosphate-buffered saline (PBS control)-treated group, standard EA dose-treated group (2.64 mg/kg in 0.5 mL of PBS), and double EA dose-treated group (5.28 mg/kg in 0.5 mL of PBS). After ON crush, each group was fed orally every day for 14 days before being euthanized. The visual function, retinal ganglion cell (RGC) density, and RGC apoptosis were determined using flash visual-evoked potentials (fVEP) analysis, retrograde Fluoro-Gold labelling, and TdT-dUTP nick end-labelling (TUNEL) assay, respectively. Macrophage infiltration of ON was detected by immunostaining (immunohistochemistry) for ED1. The protein levels of phosphor-receptor-interacting serine/threonine-protein kinase1 (pRIP1), caspase 8 (Cas8), cleaved caspase 3 (cCas3), tumour necrosis factor (TNF)-α, tumour necrosis factor receptor1 (TNFR1), interleukin (IL)-1β, inducible nitric oxide synthase (iNOS), nuclear factor erythroid 2-related factor 2 (Nrf2), haem oxygenase-1 (HO-1), and superoxide dismutase 1 (SOD1) were evaluated by Western blotting. When comparing the standard EA dose-treated group and the double EA dose-treated group with the PBS-treated group, fVEP analysis showed that the amplitudes of P1−N2 in the standard EA dose group and the double EA dose-treated group were 1.8 and 2.4-fold, respectively, higher than that in the PBS-treated group (p < 0.05). The density of RGC in the standard EA dose-treated group and the double EA dose-treated group were 2.3 and 3.7-fold, respectively, higher than that in the PBS-treated group (p < 0.05). The TUNEL assay showed that the standard EA dose-treated group and the double EA dose-treated group had significantly reduced numbers of apoptotic RGC by 10.0 and 15.6-fold, respectively, compared with the PBS-treated group (p < 0.05). The numbers of macrophages on ON were reduced by 1.8 and 2.2-fold in the standard EA dose-treated group and the double EA dose-treated group, respectively (p < 0.01). On the retinal samples, the levels of pRIP, Cas8, cCas3, TNF-α, TNFR1, IL-1β, and iNOS were decreased, whereas those of Nrf2, HO-1, and SOD1 were increased in both EA-treated groups compared to those in the PBS-treated group (p < 0.05). EA treatment has neuroprotective effects on an experimental model of traumatic optic neuropathy by suppressing apoptosis, neuroinflammation, and oxidative stress to protect the RGCs from death as well as preserving the visual function.

Use of Gene Therapy in Retinal Ganglion Cell Neuroprotection: Current Concepts and Future Directions

We systematically reviewed published translational research on gene-based therapy for retinal ganglion cell (RGC) neuroprotection. A search was conducted on Entrez PubMed on 23 December 2020 using the keywords "gene therapy", "retinal ganglion cell" and "neuroprotection". The initial search yielded 82 relevant articles. After restricting publications to those with full text available and in the English language, and then curating for only original articles on gene-based therapy, the final yield was 18 relevant articles. From the 18 papers, 17 of the papers utilized an adeno-associated viral (AAV) vector for gene therapy encoding specific genes of interest. Specifically, six of the studies utilized an AAV vector encoding brain-derived neurotrophic factor (BDNF), two of the studies utilized an AAV vector encoding erythropoietin (EPO), the remaining 10 papers utilized AAV vectors encoding different genes and one microRNA study. Although the literature shows promising results in both in vivo and in vitro models, there is still a significant way to go before gene-based therapy for RGC neuroprotection can proceed to clinical trials. Namely, the models of injury in many of the studies were more acute in nature, unlike the more progressive and neurodegenerative pathophysiology of diseases, such as glaucoma. The regulation of gene expression is also highly unexplored despite the use of AAV vectors in the majority of the studies reviewed. It is also expected that with the successful launch of messenger ribonucleic acid (mRNA)-based vaccinations in 2020, we will see a shift towards this technology for gene-based therapy in glaucoma neuroprotection.

The MADS-box transcription factor GlMADS1 regulates secondary metabolism in Ganoderma lucidum

MADS-box transcription factors play crucial roles in regulating development processes and biosynthesis of secondary metabolites in eukaryotes. However, the role of MADS-box transcription factors vary among fungal species, and their function remains unclear in the medicinally and economically important fungus Ganoderma lucidum. In this study, we characterized a MADS-box gene, GlMADS1, in G. lucidum. Analyses using quantitative real-time polymerase chain reaction (qRT-PCR) showed that GlMADS1 expression levels were up-regulated from the mycelia to the primordia stage. In order to further evaluate the effect of MADS-box transcription factors on secondary metabolism, we utilized RNA interference (RNAi) to silence GlMADS1 in G. lucidum. Ganoderic acid (GA) and flavonoid contents were enhanced in GlMADS1-silenced strains, suggesting that GlMADS1 negatively regulates GA and flavonoid accumulation.

The cells involved in the pathological process of diabetic retinopathy

Diabetic retinopathy(DR) is an expanding global health problem, the exact mechanism of which has not yet been clarified clearly, new insights into retinal physiology indicate that diabetes-induced retinal dysfunction may be viewed as an impairment of the retinal neurovascular unit, including retinal ganglion cells, glial cells, endothelial cells, pericytes, and retinal pigment epithelium. Different retinal cells have unique structure and functions, while the interactions among which are less known. Cells are the basic unit of organism structure and function, their impairment could lead to abnormal physiological functions and even organ disorder. Considering the body is multi-dimension and the complexity of DR, one point or a single type of cell can't be used to illustrate the mechanism of occurrence and development of DR. In this review, we provided a systematic and comprehensive elaboration of the cells that are involved in the process of DR. We underlined the importance of considering the neurovascular unit, not just retinal vascular and neural cells, in understanding the pathophysiology of DR. Our studies provided a better understanding of the pathological process in DR and provide a theoretical basis for further research.

Serum response factor increases renal cell carcinoma migration and invasion through promoting epithelial-mesenchymal transition

OBJECTIVE

To explore the regulation and function of serum response factor in epithelial-mesenchymal transition in renal cell carcinoma.

METHODS

First, bioinformatics analysis of human renal cell carcinoma tissues was carried out. Then, the expression of serum response factor, mesenchymal markers (N-cadherin, vimentin and fibronectin) and epithelial markers (zonula occludens-1 and epithelial cadherin) was examined in 786-O cells (a human renal cell carcinoma cell line). Serum response factor was overexpressed with pcDNA-serum response factor plasmid, and suppressed by CCG-1423 (a small molecule inhibitor of serum response factor) to study how serum response factor affects epithelial-mesenchymal transition in renal cell carcinoma. A xenograft nude mouse model was established to explore whether serum response factor affected the tumorigenic ability of renal cell carcinoma cells.

RESULTS

Serum response factor interacted with several important differentially expressed genes in renal cell carcinoma. In 786-O cells, serum response factor, N-cadherin, vimentin and fibronectin were upregulated, whereas zonula occludens-1 and epithelial cadherin were downregulated. Serum response factor upregulation in 786-O cells increased the Snail expression. Serum response factor suppression reduced Snail induction, and migration and invasion in renal cell carcinoma, which decreased the xenograft tumor volume.

CONCLUSIONS

Serum response factor is a critical transcription factor in human renal cell carcinoma. Increased serum response factor activity induces epithelial-mesenchymal transition, migration and invasion in 786-O cells, and facilitates the progression of renal cell carcinoma. Targeting serum response factor with CCG-1423 might be an attractive therapeutic strategy for renal cell carcinoma.

Role of Mesenchymal Stem Cells in Counteracting Oxidative Stress-Related Neurodegeneration

Neurodegenerative diseases include a variety of pathologies such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis, and so forth, which share many common characteristics such as oxidative stress, glycation, abnormal protein deposition, inflammation, and progressive neuronal loss. The last century has witnessed significant research to identify mechanisms and risk factors contributing to the complex etiopathogenesis of neurodegenerative diseases, such as genetic, vascular/metabolic, and lifestyle-related factors, which often co-occur and interact with each other. Apart from several environmental or genetic factors, in recent years, much evidence hints that impairment in redox homeostasis is a common mechanism in different neurological diseases. However, from a pharmacological perspective, oxidative stress is a difficult target, and antioxidants, the only strategy used so far, have been ineffective or even provoked side effects. In this review, we report an analysis of the recent literature on the role of oxidative stress in Alzheimer’s and Parkinson’s diseases as well as in amyotrophic lateral sclerosis, retinal ganglion cells, and ataxia. Moreover, the contribution of stem cells has been widely explored, looking at their potential in neuronal differentiation and reporting findings on their application in fighting oxidative stress in different neurodegenerative diseases. In particular, the exposure to mesenchymal stem cells or their secretome can be considered as a promising therapeutic strategy to enhance antioxidant capacity and neurotrophin expression while inhibiting pro-inflammatory cytokine secretion, which are common aspects of neurodegenerative pathologies. Further studies are needed to identify a tailored approach for each neurodegenerative disease in order to design more effective stem cell therapeutic strategies to prevent a broad range of neurodegenerative disorders.

Crucial role of serum response factor in renal tubular epithelial cell epithelial-mesenchymal transition in hyperuricemic nephropathy

Objective: To explore the regulation and function of serum response factor (SRF) in epithelial-mesenchymal transition (EMT) in renal tubular epithelial cells (TECs) in hyperuricemic nephropathy (HN).

Results: In NRK-52E cells treated with UA and renal medulla tissue samples from hyperuricemic rats, SRF, fibronectin, α-SMA and FSP-1 expression was upregulated, while ZO-1 and E-cadherin expression was downregulated. SRF upregulation in NRK-52E cells increased slug expression. Blockade of SRF by an SRF-specific siRNA or CCG-1423 reduced slug induction and protected TECs from undergoing EMT both in vitro and in vivo.

Conclusion: Increased SRF activity promotes EMT and dysfunction in TECs in HN. Targeting SRF with CCG-1423 may be an attractive therapeutic strategy in HN.

Methods: The expression of SRF, mesenchymal markers (fibronectin, α-SMA, and FSP-1), epithelial markers (ZO-1 and E-cadherin) and was examined in rat renal TECs (NRK-52E cells) or renal medulla tissue samples following uric acid (UA) treatment. SRF overexpressed with pcDNA-SRF plasmid and suppressed by CCG-1423 (a small molecule inhibitor of SRF) to study how SRF influences EMT in TECs in HN. Oxonic acid (OA) was used to establish HN in rats.

Kaempferol protects retinal ganglion ceils from high-glucose-induced injury by regulating vasohibin-1

Kaempferol is a medicinal flavonol derived from the roots of Kaempferia galanga L. Kaempferol can affect cell survival, apoptosis, and anti-oxidation, though its role and underlying mechanism in retinal ganglion cells with high-glucose injury remains unclear. In this study, we explored kaempferol's role in high-glucose injury in cells from the retinal ganglion cell (RGC) line. RGC cells were isolated and then cultured in high glucose (55 mmol/L) for 0 h, 12 h, 24 h, 48 h, or 72 h, and results showed decreased cell viability at 48 h and 72 h. We treated RGC cells with different concentrations of kaempferol (0 μmol/L, 20 μmol/L, 40 μmol/L, 60 μmol/L, 80 μmol/L, or 100 μmol/L) and high-glucose (55 mmol/L) for 48 h. The data indicated inhibited lactate dehydrogenase leakage, apoptosis, caspase-3 activity, and reactive oxygen species (ROS) levels. Moreover, whereas cell viability increased in RGC cells that were incubated with kaempferol (60 μmol/L, 80 μmol/L, or 100 μmol/L) and glucose (55 mmol/L), compared with glucose alone. Kaempferol (60 μmol/L) elevated ERK phosphorylation and vasohibin-1 (VASH1) expression, and inhibition of ERK phosphorylation reversed the effect of kaempferol (60 μmol/L) on VASH1 expression in RGC cells with high-glucose injury. Additionally, interference of VASH1 by VASH1 siRNA markedly reversed the effects of kaempferol (60 μmol/L) on cell viability, caspase-3 activity, and ROS levels in RGC cells with high glucose injury. Taken together, the results suggest that kaempferol protected retinal ganglion cells from high-glucose-induced injury via ERK and VASH1 signaling.

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.

MADS-Box Genes Are Key Components of Genetic Regulatory Networks Involved in Abiotic Stress and Plastic Developmental Responses in Plants

Plants, as sessile organisms, adapt to different stressful conditions, such as drought, salinity, extreme temperatures, and nutrient deficiency, via plastic developmental and growth responses. Depending on the intensity and the developmental phase in which it is imposed, a stress condition may lead to a broad range of responses at the morphological, physiological, biochemical, and molecular levels. Transcription factors are key components of regulatory networks that integrate environmental cues and concert responses at the cellular level, including those that imply a stressful condition. Despite the fact that several studies have started to identify various members of the MADS-box gene family as important molecular components involved in different types of stress responses, we still lack an integrated view of their role in these processes. In this review, we analyze the function and regulation of MADS-box gene family members in response to drought, salt, cold, heat, and oxidative stress conditions in different developmental processes of several plants. In addition, we suggest that MADS-box genes are key components of gene regulatory networks involved in plant responses to stress and plant developmental plasticity in response to seasonal changes in environmental conditions.

ETS-domain containing protein (Elk1) suppression protects cortical neurons against oxygen-glucose deprivation injury

ETS-domain containing protein (Elk1), which is a transcription factor, is reported to be closely related to the apoptosis of primary neurons and could be activated by hypoxia in human microvascular endothelial cells. In this study, we aimed to investigate the role of Elk1 in cortical neurons under oxygen-glucose deprivation (OGD) conditions. The OGD model of cortical neurons was established the anoxia/hypoglycemia-induced injury and the in vivo model was established by middle cerebral artery occlusion (MCAO). Elk1 mRNA and protein expression was significantly up-regulated in neurons exposed to OGD for 24 h, and mRNA expression was also markedly increased in cerebral cortex of rats with MCAO after 10 days. The knockdown of Elk1 in neurons without OGD obviously constrained Fra-1 and promoted Nrf2 expression. Also, Elk1 inhibition suppressed neuronal apoptosis, caspase-3 activity, LDH leakage, and MDA and SOD contents, while it increased cell viability in the neurons with OGD. The overexpression of Fra-1 showed a reverse effect on caspase-3 activity, cell viability and SOD contents in neurons under OGD conditions compared with Elk1 knockdown. Thus, Elk1 inhibition has a protective effect on neurons against OGD-induced injury.

The Nrf2 Signaling in Retinal Ganglion Cells under Oxidative Stress in Ocular Neurodegenerative Diseases

Retinal ganglion cells (RGCs) are one of the important cell types affected in many ocular neurodegenerative diseases. Oxidative stress is considered to be involved in retinal RGCs death in ocular neurodegenerative diseases. More and more attention has been focused on studying the agents that may have neuroprotective effects. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is a key nuclear transcription factor for the systemic antioxidant defense system. This review elucidates the underlying mechanism of the Nrf2-mediated neuroprotective effects on RGCs in ocular neurodegenerative diseases, such as diabetic retinopathy and retinal ischemia-reperfusion injury. Several Nrf2 inducers that shield RGCs from oxidative stress-induced neurodegeneration via regulating Nrf2 signaling are discussed.

High glucose levels impact visual response properties of retinal ganglion cells in C57 mice-An in vitro physiological study

This study investigated visual response properties of retinal ganglion cells (RGCs) under high glucose levels. Extracellular single-unit responses of RGCs from mouse retinas were recorded. And the eyecup was prepared as a flat mount in a recording chamber and superfused with Ames medium. The averaged RF size of the ON RGCs (34.1±2.9, n=14) was significantly smaller than the OFF RGCs under the HG (49.3±0.3, n=12) (P<0.0001) conditions. The same reduction pattern was also observed in the osmotic control group (HM) between ON and OFF RGCs (P<0.0001). The averaged luminance threshold (LT) of ON RGCs increased significantly under HG or HM (HG: P<0.0001; HM: P<0.0002). OFF RGCs exhibited a similar response pattern under the same conditions (HG: P<0.01; HM: P<0.0002). The averaged contrast gain of ON cells was significantly lower than that of OFF cells with the HM treatment (P<0.015, unpaired Student's t test). The averaged contrast gain of ON cells was significantly higher than OFF cells with the HG treatment (P<0.0001). The present results suggest that HG reduced receptive field center size, suppressed luminance threshold, and attenuated contrast gain of RGCs. The impact of HG on ON and OFF RGCs may be mediated via different mechanisms.

NFAT5 protects astrocytes against oxygen-glucose-serum deprivation/restoration damage via the SIRT1/Nrf2 pathway

Nuclear factor of activated T cells (NFAT) is a multifunctional cytokine family. NFAT5 was recently reported to be involved in many neuronal functions, but its specific function remains unclear. In this study, our aim is to investigate whether NFAT5 overexpression can protect astrocytes against oxygen-glucose-serum deprivation/restoration (OGSD/R) damage. In vivo, rats were subjected to ischemia-reperfusion injury, resulting in increased water content, infarct volume, and expression of NFAT5 protein in rat spinal cord. After primary culture for spinal cord astrocytes, the in vitro OGSD/R model was established. The results of the CCK8 assay and flow cytometry showed that, in the OGSD/R group, astrocyte cell viability was downregulated, but astrocyte apoptosis increased. Caspase 3 activity increased as well. Levels of NFAT5, as detected by real-time quantitative PCR and western blot, decreased under OGSD/R, as did SIRT1. Commercial kits for activity assays were used to show that OGSD/R inhibited SIRT1 activation but accelerated SOD activation after OGSD/R. Next, pcDNA-NFAT5 or NFAT5 siRNA was transfected into astrocytes. Overexpression of NFAT5 not only promoted the survival of the astrocytes and SIRT1 activation under OGSD/R but also inhibited cell apoptosis and SOD activation. Moreover, overexpression of NFAT5 apparently diminished histone acetylation and promoted the nuclear transport of Nrf2. Our results show that NFAT5 protects spinal astrocytes in a manner that depends on activation of the SIRT1/Nrf2 pathway. These findings present a novel potential molecular mechanism for NFAT5 therapy in the context of spinal cord injury.