Intraocular pressure-lowering effect of Cordyceps cicadae mycelia extract in a glaucoma rat model

Exploiting the roles of nitrogen sources for HEA increment in Cordyceps cicadae

Cordyceps cicadae, as a new food ingredient, is a valuable edible and medicinal fungi. However, its resources are severely depleted due to environmental limitations and excessive harvesting practices. N6-(2-hydroxyethyl) adenosine (HEA), as an important product of Cordyceps cicadae, has the potential to be used in medical industry due to its diverse disease curing potential. However, the disclosure of HEA synthesis still severely limited its application until now. In this study, the kinetic curves for adenosine and HEA under shaker fermentation were explored. The kinetics of HEA and adenosine production exhibited a competitive pattern, implicating a possibility of sharing a same step during their synthesis. Due to HEA as a derivative of nitrogen metabolism, the effect of different nitrogen sources (peptone, yeast extract, ammonium sulfate, diammonium oxalate monohydrate, ammonium citrate dibasic, and ammonium citrate tribasic) on HEA production in Cordyceps cicadae strain AH 10-4 had been explored under different incubation conditions (shaker fermentation, stationary fermentation, and submerged fermentation). Our results indicated that the complex organic nitrogen sources were found to improve the accumulation of HEA content under shaker fermentation. In contrast, the optimal nitrogen source for the accumulation of HEA under stationary fermentation and submerged fermentation was ammonium citrate tribasic. But submerged fermentation obviously shortened the incubation time and had a comparable capacity of HEA accumulation by 2.578 mg/g compared with stationary fermentation of 2.535 mg/g, implicating a possibility of scaled-up production of HEA in industry by submerged fermentation. Based on the dramatic HEA production by ammonium sulfate as nitrogen resources between stationary and shaker fermentations, alanine, aspartate and glutamate as well as arginine metabolic pathway were related to the production of HEA by comparative transcriptome. Further investigation indicated that glutamic acid, which is an analog of Asp, showed an optimum production of HEA in comparison with other amino acids.

Role of Glucocorticoids and Glucocorticoid Receptors in Glaucoma Pathogenesis

The glucocorticoid receptor (GR), including both alternative spliced isoforms (GRα and GRβ), has been implicated in the development of primary open-angle glaucoma (POAG) and iatrogenic glucocorticoid-induced glaucoma (GIG). POAG is the most common form of glaucoma, which is the leading cause of irreversible vision loss and blindness in the world. Glucocorticoids (GCs) are commonly used therapeutically for ocular and numerous other diseases/conditions. One serious side effect of prolonged GC therapy is the development of iatrogenic secondary ocular hypertension (OHT) and OAG (i.e., GC-induced glaucoma (GIG)) that clinically and pathologically mimics POAG. GC-induced OHT is caused by pathogenic damage to the trabecular meshwork (TM), a tissue involved in regulating aqueous humor outflow and intraocular pressure. TM cells derived from POAG eyes (GTM cells) have a lower expression of GRβ, a dominant negative regulator of GC activity, compared to TM cells from age-matched control eyes. Therefore, GTM cells have a greater pathogenic response to GCs. Almost all POAG patients develop GC-OHT when treated with GCs, in contrast to a GC responder rate of 40% in the normal population. An increased expression of GRβ can block GC-induced pathogenic changes in TM cells and reverse GC-OHT in mice. The endogenous expression of GRβ in the TM may relate to differences in the development of GC-OHT in the normal population. A number of studies have suggested increased levels of endogenous cortisol in POAG patients as well as differences in cortisol metabolism, suggesting that GCs may be involved in the development of POAG. Additional studies are warranted to better understand the molecular mechanisms involved in POAG and GIG in order to develop new disease-modifying therapies to better treat these two sight threatening forms of glaucoma. The purpose of this timely review is to highlight the pathological and clinical features of GC-OHT and GIG, mechanisms responsible for GC responsiveness, potential therapeutic options, as well as to compare the similar features of GIG with POAG.

Evaluation of trabecular meshwork-specific promoters in vitro and in vivo using scAAV2 vectors expressing C3 transferase

AIM

To evaluate the potential of two trabecular meshwork (TM)-specific promoters, Chitinase 3-like 1 (Ch3L1) and matrix gla protein (MGP), for improving specificity and safety in glaucoma gene therapy based on self-complementary AAV2 (scAAV2) vector technologies.

METHODS

An scAAV2 vector with C3 transferase (C3) as the reporter gene (scAAV2-C3) was selected. The scAAV2-C3 vectors were driven by Ch3L1 (scAAV2-Ch3L1-C3), MGP (scAAV2-MGP-C3), enhanced MGP (scAAV2-eMGP-C3) and cytomegalovirus (scAAV2-CMV-C3), respectively. The cultured primary human TM cells were treated with each vector at different multiplicities of infections. Changes in cell morphology were observed by phase contrast microscopy. Actin stress fibers and Rho GTPases/Rho-associated protein kinase pathway-related molecules were assessed by immunofluorescence staining, real-time quantitative polymerase chain reaction and Western blot. Each vector was injected intracamerally into the one eye of each rat at low and high doses respectively. In vivo green fluorescence was visualized by a Micron III Retinal Imaging Microscope. Intraocular pressure (IOP) was monitored using a rebound tonometer. Ocular responses were evaluated by slit-lamp microscopy. Ocular histopathology analysis was examined by hematoxylin and eosin staining.

RESULTS

In TM cell culture studies, the vector-mediated C3 expression induced morphologic changes, disruption of actin cytoskeleton and reduction of fibronectin expression in TM cells by inhibiting the Rho GTPases/Rho-associated protein kinase signaling pathway. At the same dose, these changes were significant in TM cells treated with scAAV2-CMV-C3 or scAAV2-Ch3L1-C3, but not in cells treated with scAAV2-eMGP-C3 or scAAV2-MGP-C3. At low-injected dose, the IOP was significantly decreased in the scAAV2-Ch3L1-C3-injected eyes but not in scAAV2-MGP-C3-injected and scAAV2-eMGP-C3-injected eyes. At high-injected dose, significant IOP reduction was observed in the scAAV2-eMGP-C3-injected eyes but not in scAAV2-MGP-C3-injected eyes. Similar to scAAV2-CMV-C3, scAAV2-Ch3L1-C3 vector showed efficient transduction both in the TM and corneal endothelium. In anterior segment tissues of scAAV2-eMGP-C3-injected eyes, no obvious morphological changes were found except for the TM. Inflammation was absent.

CONCLUSION

In scAAV2-transduced TM cells, the promoter-driven efficiency of Ch3L1 is close to that of cytomegalovirus, but obviously higher than that of MGP. In the anterior chamber of rat eye, the transgene expression pattern of scAAV2 vector is presumably affected by MGP promoter, but not by Ch3L1 promoter. These findings would provide a useful reference for improvement of specificity and safety in glaucoma gene therapy using scAAV2 vector.

Preventative Effects of Cordyceps cicadae Mycelial Extracts on the Early-Stage Development of Cataracts in UVB-Induced Mice Cataract Model

Cataracts, a prevalent age-related eye condition, pose a significant global health concern, with rising rates due to an aging population and increased digital device usage. In Taiwan, cataract prevalence is particularly high, reaching up to 90% among individuals aged 70 and above. The lens of the eye absorbs short-wave light, which can lead to oxidative stress in lens epithelial cells and contribute to cataract formation. Exposure to ultraviolet (UV) light further exacerbates the risk of cataracts by generating reactive oxygen species. Heat-shock proteins (HSPs), involved in protein maintenance and repair, have been linked to cataract development. Cordyceps cicadae (C. cicadae), a traditional Chinese medicine, has a long history of use and is known for its pharmacological effects. N6-(2-hydroxyethyl) adenosine (HEA), a bioactive compound found in C. cicadae, exhibits anti-inflammatory, immunomodulatory, and neuroprotective properties. Previous studies have shown that C. cicadae mycelial extracts improve dry eye disease and reduce intraocular pressure in animal models. Additionally, C. cicadae possesses antioxidant properties, which are beneficial for combating cataract formation. In this study, we aim to evaluate the preventive efficacy of C. cicadae mycelial extracts in UV-induced cataract development. By investigating the ameliorative effects of C. cicadae on eye diseases and its potential role in ocular health improvement, we hope to uncover new options for cataract prevention and provide insights into the mechanisms of action. The findings of this research could provide a novel approach for nutritional supplements targeting cataract prevention, offering potential benefits in the field of ocular health.

Amelioration of Cyclosporine A-Induced Acute Nephrotoxicity by Cordyceps cicadae Mycelia via Mg+2 Reabsorption and the Inhibition of GRP78-IRE1-CHOP Pathway: In Vivo and In Vitro

Fruiting bodies of Cordyceps cicadae (CC) have been reported to have a therapeutic effect in chronic kidney disease. Due to the rare and expensive resources from natural habitats, artificially cultivated mycelia using submerged liquid cultivation of CC (CCM) have been recently developed as an alternative to scarce sources of CC. However, little is known regarding potential protective effects of CCM against cyclosporine A (CsA)-induced acute nephrotoxicity in vivo and in vitro. In this study, male Sprague-Dawley rats were divided into six groups: control, CCM (40 mg and 400 mg/kg, orally), CsA (10 mg/kg, oral gavage), and CsA + CCM (40 mg and 400 mg/kg, orally). At the end of the study on day 8, all rats were sacrificed, and the blood and kidneys retrieved. CsA-induced acute nephrotoxicity was evident by increased levels of blood urea nitrogen (BUN). Levels of the endoplasmic reticulum (ER) resident chaperone glucose regulated protein 78 (GRP 78) were increased significantly in rats with acute nephrotoxicity. BUN and GRP 78 were significantly ameliorated in synchronous oral groups of CCM (40 or 400 mg/kg) plus CsA. Examination of hematoxylin and eosin stained kidney tissues revealed that the combined treatment of CCM slightly improved vacuolization in renal tubules upon CsA-induced damage. CsA-induced down-regulation of protein expression of magnesium ion channel proteins and transient receptor potential melastatin 6 and 7 were abolished by the combined treatment of CCM. CCM has the potential to protect the kidney against CsA-induced nephrotoxicity by reducing magnesium ion wasting, tubular cell damage, and ER stress demonstrated further by human renal proximal tubular epithelial cell line HK-2. Our results contribute to the in-depth understanding of the role of polysaccharides and nucleobases as the main secondary metabolites of CCM in the defense system of renal functions in CsA-induced acute nephrotoxicity.

Lowering the Intraocular Pressure in Rats and Rabbits by Cordyceps cicadae Extract and Its Active Compounds

Cordyceps cicadae (CC), an entomogenous fungus that has been reported to have therapeutic glaucoma, is a major cause of blindness worldwide and is characterized by progressive retinal ganglion cell (RGC) death, mostly due to elevated intraocular pressure (IOP). Here, an ethanolic extract of C. cicadae mycelium (CCME), a traditional medicinal mushroom, was studied for its potential in lowering IOP in rat and rabbit models. Data showed that CCME could significantly (60.5%) reduce the IOP induced by microbead occlusion after 56 days of oral administration. The apoptosis of retinal ganglion cells (RGCs) in rats decreased by 77.2%. CCME was also shown to lower the IOP of normal and dextrose-infusion-induced rabbits within 60 min after oral feeding. There were dose effects, and the effect was repeatable. The active ingredient, N6-(2-hydroxyethyl)-adenosine (HEA), was also shown to alleviate 29.6% IOP at 0.2 mg/kg body weight in this rabbit model. CCME was confirmed with only minor inhibition in the phosphorylated myosin light chain 2 (pMLC2) pathway.

Current situation and progress of drugs for reducing intraocular pressure

Glaucoma, the most common cause of irreversible blindness worldwide, usually causes characteristic optic nerve damage. Pathological intraocular pressure (IOP) elevation is a major risk factor. Drug reduction of IOP is the preferred treatment for clinicians because it can delay the progression of disease. However, the traditional IOP-lowering drugs currently used by patients may be poorly tolerated. Therefore, in recent years, some new drugs have been put into clinical application or in clinical phase I–III studies. They have a better IOP-lowering effect and fewer adverse reactions. Because glaucoma is a chronic disease, drugs need to be administered continuously for a long time. For patients, good compliance and high drug bioavailability have a positive effect on the prognosis of the disease. Therefore, clinicians and scientists have developed drug delivery systems to solve this complex problem. In addition, natural compounds and dietary supplements have a good effect of reducing IOP, and they can also protect the optic nerve through antioxidant action. We summarize the current traditional drugs, new drugs, sustained-release drug delivery systems, and complementary drugs and outline the mechanism of action and clinical effects of these drugs on glaucoma and their recent advances.

Baicalin suppresses glaucoma pathogenesis by regulating the PI3K/AKT signaling in vitro and in vivo

Glaucoma, characterized with progressive degeneration of retinal ganglion cells (RGCs), is the second frequently leading cause of sight loss in the word after cataract. Baicalin plays a protective role in age-related macular degeneration, retinopathy of prematurity, branch retinal vein occlusion, and ischemia-induced neurodegeneration in the retina. The present study aimed to investigate the role of baicalin in glaucoma. RGCs were stimulated with N-methyl-D-aspartate (NMDA) to mimic the in vitro model of glaucoma. A mouse model of glaucoma induced by chronic elevated intraocular pressure was also established. The apoptosis, oxidative stress, and autophagy of RGCs were detected by flow cytometry analysis, 2,7-dichlorodihydrofluorescein diacetate staining, and Western blotting, respectively. Retinal pathological changes were exhibited by hemotoxylin and eosin staining. Baicalin restrained the NMDA-induced cell apoptosis, autophagy, and oxidative stress of RGCs by activating the PI3K/AKT signaling in vitro. The elevated intraocular pressure-induced pathological changes in retinas of glaucoma mice were attenuated by baicalin. Moreover, the number of RGCs was significantly decreased in glaucoma mice, and then increased by baicalin treatment. Baicalin also inhibited autophagy and activated PI3K/AKT signaling in vivo. In conclusion, baicalin suppresses glaucoma pathogenesis by regulating the PI3K/AKT signaling in vitro and in vivo.