Effects of Lutein on Hyperosmoticity-Induced Upregulation of IL-6 in Cultured Corneal Epithelial Cells and Its Relevant Signal Pathways

MAPK Pathways in Ocular Pathophysiology: Potential Therapeutic Drugs and Challenges

Mitogen-activated protein kinase (MAPK) pathways represent ubiquitous cellular signal transduction pathways that regulate all aspects of life and are frequently altered in disease. Once activated through phosphorylation, these MAPKs in turn phosphorylate and activate transcription factors present either in the cytoplasm or in the nucleus, leading to the expression of target genes and, as a consequence, they elicit various biological responses. The aim of this work is to provide a comprehensive review focusing on the roles of MAPK signaling pathways in ocular pathophysiology and the potential to influence these for the treatment of eye diseases. We summarize the current knowledge of identified MAPK-targeting compounds in the context of ocular diseases such as macular degeneration, cataract, glaucoma and keratopathy, but also in rare ocular diseases where the cell differentiation, proliferation or migration are defective. Potential therapeutic interventions are also discussed. Additionally, we discuss challenges in overcoming the reported eye toxicity of some MAPK inhibitors.

Development of Lutein-Containing Eye Drops for the Treatment of Dry Eye Syndrome

Dry eye syndrome (DES) is a common ophthalmological disease that decreases tear secretion and causes dryness, photophobia, pain, severe corneal rupture, and even blindness. Ocular and lacrimal gland inflammation is one of the pathological mechanisms underlying DES. Therefore, effective suppression of inflammation is a crucial strategy for the treatment of DES. Lutein, commonly found in healthy foods, has anti-inflammatory effects in corneal or retina-related cells and may be a potential therapy for DES. The addition of lutein to artificial tears (AT) as an eye-drop formulation for DES treatment in a mouse model was studied in the present work. Polyvinyl alcohol (PVA) was used as a thickener to increase the viscosity of eye drops to prolong drug retention on the ocular surface. A WST-8 assay in human corneal epithelial cells (HCE-2) showed that a concentration of <5 μM lutein (L5) and <1% PVA (P1) maintained the cell viability at 80%. A real-time PCR showed that the inflamed human corneal epithelial cells (HCECs) cocultured with L5P1 had downregulated expression of inflammatory genes such as IL-1β, IL-6, and TNF-α. In a benzalkonium chloride- (BAC) induced DES mouse model, AT/L5P1 could repair damaged corneas, elevate tear secretion, increase the number of goblet cells, and inhibit the production of inflammatory cytokines, such as IL-1β, IL-6, and TNF-α, in the cornea. In conclusion, we demonstrate that lutein/PVA as eye drops could prolong the drug ocular retention time and effectively to decrease inflammation in DES mice. Therefore, lutein, obtained from eye drops, has a potential therapeutic role for DES.

Anti-Inflammatory and Anticancer Effects of Microalgal Carotenoids

Acute inflammation is a key component of the immune system’s response to pathogens, toxic agents, or tissue injury, involving the stimulation of defense mechanisms aimed to removing pathogenic factors and restoring tissue homeostasis. However, uncontrolled acute inflammatory response may lead to chronic inflammation, which is involved in the development of many diseases, including cancer. Nowadays, the need to find new potential therapeutic compounds has raised the worldwide scientific interest to study the marine environment. Specifically, microalgae are considered rich sources of bioactive molecules, such as carotenoids, which are natural isoprenoid pigments with important beneficial effects for health due to their biological activities. Carotenoids are essential nutrients for mammals, but they are unable to synthesize them; instead, a dietary intake of these compounds is required. Carotenoids are classified as carotenes (hydrocarbon carotenoids), such as α- and β-carotene, and xanthophylls (oxygenate derivatives) including zeaxanthin, astaxanthin, fucoxanthin, lutein, α- and β-cryptoxanthin, and canthaxanthin. This review summarizes the present up-to-date knowledge of the anti-inflammatory and anticancer activities of microalgal carotenoids both in vitro and in vivo, as well as the latest status of human studies for their potential use in prevention and treatment of inflammatory diseases and cancer.

A Novel Multi-Ingredient Supplement Reduces Inflammation of the Eye and Improves Production and Quality of Tears in Humans

INTRODUCTION

Dry eye is a multifactorial condition of the eye caused by insufficient tear production and imbalance in tear composition leading to faster evaporation of tear fluid. It is also associated with inflammation that often leads to ocular surface damage. Symptoms of dry eyes include itchiness, soreness, red eyes, a burning sensation, eye fatigue and blurred vision. The objective of this study was to evaluate the efficacy and safety of our multi-ingredient supplement in subjects with dry eye syndrome (DES).

METHODS

We recruited 60 subjects with mild to moderate DES who were randomized in a 1:1 ratio in a single-center study to receive LCD (lutein 20 mg, zeaxanthin 4 mg, curcumin 200 mg curcuminoids, vitamin D3 600 IU) or placebo (soybean oil) capsules for 8 weeks. The primary outcomes evaluated were changes in tear volume by Schirmer's test and ocular symptoms by the Ocular Surface Disease Index (OSDI); secondary outcomes included evaluation of changes in Standard Patient Evaluation of Eye Dryness (SPEED) questionnaire, tear film break-up time (TBUT), corneal and conjunctival staining, tear osmolarity, matrix metalloproteinase-9 (MMP-9), artificial tear use and safety assessments. The outcomes were compared between the LCD and placebo groups at baseline and day 56 of supplementation.

RESULTS

Fifty-nine subjects, 30 from LCD and 29 from placebo group, completed the study. The LCD group showed significant improvements (P < 0.0001) for Schirmer's test, OSDI, TBUT, SPEED, ocular staining scores, tear osmolarity (P = 0.0005), MMP-9 (P = 0.0017) and reduced artificial tear use (P = 0.0004) and its frequency of use (P < 0.0001) in subjects compared to placebo from baseline to day 56. No safety issues were observed in the study.

CONCLUSION

The LCD supplement showed significant improvements in the production, stability and quality of tears by reducing ocular surface damage and tear inflammation and can be used as an adjuvant to artificial tears in subjects with DES.

TRIAL REGISTRATION

Clinical Trials Registry of India (http://ctri.nic.in/) identifier: CTRI/2021/01/030493.

Pigment epithelium-derived factor (PEDF) plays anti-inflammatory roles in the pathogenesis of dry eye disease

PURPOSE

To investigate the expression of pigment epithelium-derived factor (PEDF) in ocular surface in dry eye disease (DED) and its anti-inflammatory roles and mechanisms, clinically and by experiments in vivo and in vitro.

METHODS

A cross-sectional study was conducted to detect the expression of PEDF in tears of dry eye patients by enzyme-linked immunosorbent assay (ELISA). Using dry eye mouse model and human corneal epithelial cells (hCECs) stimulated by hyperosmolarity or inflammatory cytokines, expression of PEDF in corneal epithelial cells, stroma and conjunctiva was quantified by real-time polymerase chain reaction, ELISA and Western blot. Next, either dry eye mice or hyperosmotic hCECs were treated with recombinant PEDF or neutralizing antibodies, and the expressions of inflammatory cytokines and immune cells were detected. Finally, Western blot was performed on MAPK and NF-κB to investigate the signaling pathways by which PEDF played its roles.

RESULTS

Concentrations of PEDF were increased in tears of dry eye patients. Increased PEDF was observed in corneal epithelial cells (CECs) rather than corneal stroma or conjunctiva in dry eye mice. Furthermore, hCECs exposed to hyperosmolarity showed upregulation of PEDF. In vivo and in vitro studies showed that PEDF suppressed the expression of inflammatory cytokines including IL-1β, IL-6, TNF-α and IL-17A, as well as the percentage of Th17 cells in DED. Further investigation showed that PEDF inhibited the phosphorylation of MAPK p38 and JNK in hyperosmotic hCECs.

CONCLUSIONS

CECs derived PEDF is increased in DED. PEDF plays anti-inflammatory and immunoregulatory roles in the pathogenesis of DED.

A Novel Integrated Active Herbal Formulation Ameliorates Dry Eye Syndrome by Inhibiting Inflammation and Oxidative Stress and Enhancing Glycosylated Phosphoproteins in Rats

Dry eye syndrome (DES) is a chronic condition of the eye with insufficient production of tears leading to inadequate lubrication of eyes. Symptoms of DES are associated with discomfort and redness of the eye, blurred vision, and tear film instability which leads to the damaged ocular surface. Inflammation and oxidative stress play a significant role in the pathogenesis of the disease. In this study, the protective effect of different doses (100 or 200 mg/kg) of a novel multi-component oral formulation of lutein/zeaxanthin, curcumin, and vitamin D3 (LCD) was evaluated using a rat model with benzalkonium chloride (BAC)-induced dry eye syndrome. The formulation was administered orally to rats for 4 weeks. We observed a significant improvement in tear volume, tear breakup time, tear film integrity, and reduction in overall inflammation in rats fed with the LCD at dose 200 mg/kg performing better than 100 mg/kg. Furthermore, the formulation helped in lowering oxidative stress by increasing antioxidant levels and restored protective tear protein levels including MUC1, MUC4, and MUC5AC with 200 mg of LCD having the most significant effect. The results strongly suggest that the combination of lutein/zeaxanthin, curcumin, and vitamin-D3 is effective in alleviating the symptoms of dry eye condition with a multi-modal mechanism of action.