Diosgenin protects retinal pigment epithelial cells from inflammatory damage and oxidative stress induced by high glucose by activating AMPK/Nrf2/HO-1 pathway

Natural plant medications for the treatment of retinal diseases: The blood-retinal barrier as a clue

BACKGROUND

Retinal diseases significantly contribute to the global burden of visual impairment and blindness. The occurrence of retinal diseases is often accompanied by destruction of the blood‒retinal barrier, a vital physiological structure responsible for maintaining the stability of the retinal microenvironment. However, detailed summaries of the factors damage the blood‒retinal barrier and treatment methods involving natural plant medications are lacking.

PURPOSE

To comprehensively summarize and analyze the protective effects of active substances in natural plant medications on damage to the blood-retina barrier that occurs when retinal illnesses, particularly diabetic retinopathy, and examine their medicinal value and future development prospects.

METHODS

In this study, we searched for studies published in the ScienceDirect, PubMed, and Web of Science databases. The keywords used included natural plant medications, plants, natural herbs, blood retinal barrier, retinal diseases, diabetic retinopathy, age-related macular degeneration, and uveitis. Chinese herbal compound articles, non-English articles, warning journals, and duplicates were excluded from the analysis.

RESULTS

The blood‒retinal barrier is susceptible to high glucose, aging, immune responses, and other factors that destroy retinal homeostasis, resulting in pathological changes such as apoptosis and increased vascular permeability. Existing studies have shown that the active compounds or extracts of many natural plants have the effect of repairing blood-retinal barrier dysfunction. Notably, berberine, puerarin, and Lycium barbarum polysaccharides exhibited remarkable therapeutic effects. Additionally, curcumin, astragaloside IV, hesperidin, resveratrol, ginsenoside Rb1, luteolin, and Panax notoginseng saponins can effectively protect the blood‒retinal barrier by interfering with distinct pathways. The active ingredients found in natural plant medications primarily repair the blood‒retinal barrier by modulating pathological factors such as oxidative stress, inflammation, pyroptosis, and autophagy, thereby alleviating retinal diseases.

CONCLUSION

This review summarizes a series of plant extracts and plant active compounds that can treat retinal diseases by preventing and treating blood‒retinal barrier damage and provides reference for the research of new drugs for treating retinal diseases.

Targeting autophagy with natural products as a potential therapeutic approach for diabetic microangiopathy

As the quality of life improves, the incidence of diabetes mellitus and its microvascular complications (DMC) continues to increase, posing a threat to people's health and wellbeing. Given the limitations of existing treatment, there is an urgent need for novel approaches to prevent and treat DMC. Autophagy, a pivotal mechanism governing metabolic regulation in organisms, facilitates the removal of dysfunctional proteins and organelles, thereby sustaining cellular homeostasis and energy generation. Anomalous states in pancreatic β-cells, podocytes, Müller cells, cardiomyocytes, and Schwann cells in DMC are closely linked to autophagic dysregulation. Natural products have the property of being multi-targeted and can affect autophagy and hence DMC progression in terms of nutrient perception, oxidative stress, endoplasmic reticulum stress, inflammation, and apoptosis. This review consolidates recent advancements in understanding DMC pathogenesis via autophagy and proposes novel perspectives on treating DMC by either stimulating or inhibiting autophagy using natural products.

Therapeutic Potential of Diosgenin in Amelioration of Carbon Tetrachloride-Induced Murine Liver Injury

Diosgenin is a sapogenin with antidiabetic, antioxidant, and anti-inflammatory properties. The current study investigated whether diosgenin could ameliorate carbon tetrachloride (CCL4)-induced liver injury. To cause liver injury, CCL4 was injected intraperitoneally twice a week for 8 weeks. Daily oral administration of diosgenin at doses of 20, 40, and 80 mg/kg was started one day before CCL4 injection and continued for 8 weeks. Finally, serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and also albumin were assessed. Catalase and superoxide dismutase (SOD) activities in addition to glutathione (GSH) and malondialdehyde (MDA) levels were also quantified in the liver homogenate and routine histological evaluation was also conducted. Elevated serum levels of liver enzymes and decreased serum level of albumin caused by CCL4 were significantly restored following diosgenin administration at doses of 40 and 80 mg/kg. Long-term administration of CCL4 increased inflammatory and apoptotic factors such as IL-1β, caspase 3, TNF-α, and IL-6 and decreased SOD and catalase activities as well as GSH level in liver homogenates; while MDA level was increased. Treatment with diosgenin increased SOD and catalase activities and GSH levels in the liver of injured animals. In addition, liver MDA, IL-1β, caspase 3, TNF-α, and IL-6 level or activity decreased by diosgenin treatment. Additionally, diosgenin aptly prevented aberrant liver histological changes. According to obtained results, diosgenin can dose-dependently diminish CCl4-induced liver functional deficits and histological changes in a dose-dependent manner, possibly due to its antioxidant and anti-inflammation properties, and its beneficial effect is comparable to known hepatoprotective agent silymarin.

Diosgenin as a substitute for cholesterol alleviates NAFLD by affecting CYP7A1 and NPC1L1-related pathway

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) rapidly becomes the leading cause of end-stage liver disease or liver transplantation. Nowadays, there has no approved drug for NAFLD treatment. Diosgenin as the structural analogue of cholesterol attenuates hypercholesterolemia by inhibiting cholesterol metabolism, which is an important pathogenesis in NAFLD progression. However, there has been no few report concerning its effects on NAFLD so far.

METHODS

Using a high-fat diet & 10% fructose-feeding mice, we evaluated the anti-NAFLD effects of diosgenin. Transcriptome sequencing, LC/MS analysis, molecular docking simulation, molecular dynamics simulations and Luci fluorescent reporter gene analysis were used to evaluate pathways related to cholesterol metabolism.

RESULTS

Diosgenin treatment ameliorated hepatic dysfunction and inhibited NAFLD formation including lipid accumulation, inflammation aggregation and fibrosis formation through regulating cholesterol metabolism. For the first time, diosgenin was structurally similar to cholesterol, down-regulated expression of CYP7A1 and regulated cholesterol metabolism in the liver (p < 0.01) and further affecting bile acids like CDCA, CA and TCA in the liver and feces. Besides, diosgenin decreased expression of NPC1L1 and suppressed cholesterol transport (p < 0.05). Molecular docking and molecular dynamics further proved that diosgenin was more strongly bound to CYP7A1. Luci fluorescent reporter gene analysis revealed that diosgenin concentration-dependently inhibited the enzymes activity of CYP7A1.

CONCLUSION

Our findings demonstrated that diosgenin was identified as a specific regulator of cholesterol metabolism, which pave way for the design of novel clinical therapeutic strategies.

Silva H, P. de Carvalho R, Ventura ALM, Calaza KC, Silveira MS, Kubrusly RCC, de Melo Reis RA. The Healthy and Diseased Retina Seen through Neuron-Glia Interactions

The retina is the sensory tissue responsible for the first stages of visual processing, with a conserved anatomy and functional architecture among vertebrates. To date, retinal eye diseases, such as diabetic retinopathy, age-related macular degeneration, retinitis pigmentosa, glaucoma, and others, affect nearly 170 million people worldwide, resulting in vision loss and blindness. To tackle retinal disorders, the developing retina has been explored as a versatile model to study intercellular signaling, as it presents a broad neurochemical repertoire that has been approached in the last decades in terms of signaling and diseases. Retina, dissociated and arranged as typical cultures, as mixed or neuron- and glia-enriched, and/or organized as neurospheres and/or as organoids, are valuable to understand both neuronal and glial compartments, which have contributed to revealing roles and mechanisms between transmitter systems as well as antioxidants, trophic factors, and extracellular matrix proteins. Overall, contributions in understanding neurogenesis, tissue development, differentiation, connectivity, plasticity, and cell death are widely described. A complete access to the genome of several vertebrates, as well as the recent transcriptome at the single cell level at different stages of development, also anticipates future advances in providing cues to target blinding diseases or retinal dysfunctions.

Exploring the protective effects of herbal monomers against diabetic retinopathy based on the regulation of autophagy and apoptosis: A review

Diabetic retinopathy (DR) has become one of the top 3 blinding eye diseases in the world. In spite of recent therapeutic breakthroughs, it is not yet possible to cure DR through pharmacotherapy. Cell death is thought to play a key role in the pathogenesis of DR. Moderate modulation of cellular autophagy and inhibition of apoptosis have been identified as effective targets for the treatment of DR. Numerous phytochemicals have emerged as potential new drugs for the treatment of DR. We collected basic DR research on herbal monomers through keywords such as autophagy and apoptosis, and conducted a systematic search for relevant research articles published in the PubMed database. This review provides the effects and reports of herbal monomers on various DR cellular and animal models in vivo and in vitro in the available literature, and emphasizes the importance of cellular autophagy and apoptosis as current DR therapeutic targets. Based on our review, we believe that herbal monomers that modulate autophagy and inhibit apoptosis may be potentially effective candidates for the development of new drugs in the treatment of DR. It provides a strategy for further development and application of herbal medicines for DR treatment.

Jin-Gui-Shen-Qi Wan ameliorates diabetic retinopathy by inhibiting apoptosis of retinal ganglion cells through the Akt/HIF-1α pathway

BACKGROUND

Jin-Gui-Shen-Qi Wan (JGSQ) has been used in China for thousands of years to treat various ailments, including frequent urination, blurred vision, and soreness in the waist and knees. It has traditional therapeutic advantages in improving eye diseases.

AIM OF THE STUDY

Clinical studies have confirmed the therapeutic efficacy of JGSQ in improving diabetes and vision; however, its efficacy and pharmacological effects in treating diabetic retinopathy (DR) remain unclear. Therefore, the aim of this study was to investigate the specific pharmacological effects and potential mechanisms of JGSQ in improving DR through a db/db model.

MATERIALS AND METHODS

db/db mice were given three different doses of orally administered JGSQ and metformin for 8 weeks, and then PAS staining of the retinal vascular network patch, transmission electron microscopy, H&E staining, and TUNEL staining were performed to determine the potential role of JGSQ in improving DR-induced neuronal cell apoptosis. Furthermore, network pharmacology analysis and molecular docking were carried out to identify the main potential targets of JGSQ, and the efficacy of JGSQ in improving DR was evaluated through western blotting and immunofluorescence staining, revealing its mechanism of action.

RESULTS

According to the results from H&E, TUNEL, and PAS staining of the retinal vascular network patch and transmission electron microscopy, JGSQ does not have an advantage in improving the abnormal morphology of vascular endothelial cells, but it has a significant effect on protecting retinal ganglion cells from apoptosis. Through network pharmacology and molecular docking, AKT, GAPDH, TNF, TP53, and IL-6 were identified as the main core targets of JGSQ. Subsequently, through western blot and immunofluorescence staining, it was found that JGSQ can inhibit HIF-1α, promote p-AKT expression, and inhibit TP53 expression. At the same time, inhibiting the release of inflammatory factors protects retinal ganglion cells and improves apoptosis in DR.

CONCLUSION

These results indicated that in the db/db DR mouse model, JGSQ can inhibit the expression of inflammatory cytokines and protect retinal ganglion cells from apoptosis, possibly by modulating the Akt/HIF-1α pathway.

LIN28A attenuates high glucose-induced retinal pigmented epithelium injury through activating SIRT1-dependent autophagy

AIM

To evaluate the effects of LIN28A (human) on high glucose-induced retinal pigmented epithelium (RPE) cell injury and its possible mechanism.

METHODS

Diabetic retinopathy model was generated following 48h of exposure to 30 mmol/L high glucose (HG) in ARPE-19 cells. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot tested the expression of the corresponding genes and proteins. Cell viability as well as apoptosis was determined through cell counting kit-8 (CCK-8) and flow cytometry assays. Immunofluorescence assay was adopted to evaluate autophagy activity. Caspase 3 activity, oxidative stress markers, and cytokines were appraised adopting their commercial kits, respectively. Finally, ARPE-19 cells were preincubated with EX527, a Sirtuin 1 (SIRT1) inhibitor, prior to HG stimulation to validate the regulatory mechanism.

RESULTS

LIN28A was downregulated in HG-challenged ARPE-19 cells. LIN28A overexpression greatly inhibited HG-induced ARPE-19 cell viability loss, apoptosis, oxidative damage as well as inflammatory response. Meanwhile, the repressed autophagy and SIRT1 in ARPE-19 cells challenged with HG were elevated after LIN28A overexpression. In addition, treatment of EX527 greatly inhibited the activated autophagy following LIN28A overexpression and partly abolished the protective role of LIN28A against HG-elicited apoptosis, oxidative damage as well as inflammation in ARPE-19 cells.

CONCLUSION

LIN28A exerts a protective role against HG-elicited RPE oxidative damage, inflammation, as well as apoptosis via regulating SIRT1/autophagy.

Diosgenin, a Natural Steroidal Sapogenin, Alleviates the Progression of Diabetic Retinopathy in Diabetic Mice

BACKGROUND/AIM

Diabetic retinopathy (DR) is the most common microvascular complication of diabetes and a major cause of blindness in working-age adults. Diosgenin (DG), a natural steroidal sapogenin extracted from fenugreek seeds and wild yam roots, has hypolipidemic, hypoglycemic, anticancer, and anti-inflammatory properties. Given its pharmacological effects, we speculated that DG may be a promising treatment for DR. Therefore, this study was aimed at evaluating the effectiveness of DG in preventing or slowing DR progression in a mouse model (+Lepr^db/+Lepr^db strain) of type 2 diabetes (T2D).

MATERIALS AND METHODS

DG (5.0 mg/kg body weight) or phosphate-buffered saline (PBS) was administered to 8-week-old T2D mice via oral gavage daily for 24 weeks. Paraffin-embedded eye tissues from the mice were collected and stained with hematoxylin and eosin to evaluate retinal histopathology. Apoptosis-related proteins BCL2-associated X (Bax), B-cell lymphoma 2 (Bcl-2), and cleaved caspase-3 were evaluated by western blotting of mouse retinas.

RESULTS

Body weight was slightly reduced in the DG-treated group; however, glucose levels were not markedly different between the DG- and PBS-treated groups. Total retinal thickness, thickness of the photoreceptor and outer nuclear layers, and loss of ganglion cells significantly improved in the retina of the DG-treated T2D mice compared with those in the PBS-treated T2D mice. Cleaved caspase-3 level significantly decreased in the retina of the DG-treated T2D mice. Conclusion: DG alleviates DR pathology and exerts a protective effect on the T2D mouse retina. The inhibitory effects of DG on DR may involve mechanisms of the anti-apoptotic pathway.