Protective Effects of L-Carnitine Against Oxidative Injury by Hyperosmolarity in Human Corneal Epithelial Cells

Ectoine Enhances Mucin Production Via Restoring IL-13/IFN-γ Balance in a Murine Dry Eye Model

Purpose

This study aimed to explore protective effects and potential mechanism of ectoine, a natural osmoprotectant, on ocular surface mucin production in dry eye disease.

Methods

A dry eye model was established in C57BL/6 mice exposed to desiccating stress (DS) with untreated (UT) mice as controls. DS mice were topically treated with 2.0% ectoine or PBS vehicle. Corneal epithelial defects were assessed by Oregon Green Dextran (OGD) fluorescent staining. Conjunctival goblet cells, ocular mucins, and T help (Th) cytokines were evaluated by immunofluorescent staining or ELISA, and RT-qPCR.

Results

Compared with UT mice, corneal epithelial defects were detected as strong punctate OGD fluorescent staining in DS mice with vehicle, whereas ectoine treatment largely reduced OGD staining to near-normal levels. Conjunctival goblet cell density and cell size decreased markedly in DS mice, but was significantly recovered by ectoine treatment. The protein production and mRNA expression of two gel-forming secreted MUC5AC and MUC2, and 4 transmembrane mucins, MUC1, MUC4, MUC16, and MUC15, largely decreased in DS mice, but was restored by ectoine. Furthermore, Th2 cytokine IL-13 was inhibited, whereas Th1 cytokine IFN-γ was stimulated at protein and mRNA levels in conjunctiva and draining cervical lymph nodes (CLNs) of DS mice, leading to decreased IL-13/IFN-γ ratio. Interestingly, 2.0% ectoine reversed their alternations and restored IL-13/IFN-γ balance.

Conclusions

Our findings demonstrate that topical ectoine significantly reduces corneal damage, and enhances goblet cell density and mucin production through restoring imbalanced IL-13/IFN-γ signaling in murine dry eye model. This suggests therapeutic potential of natural osmoprotectant ectoine for dry eye disease.

L-Carnitine in the Treatment of Psychiatric and Neurological Manifestations: A Systematic Review

OBJECTIVE

L-carnitine (LC), a vital nutritional supplement, plays a crucial role in myocardial health and exhibits significant cardioprotective effects. LC, being the principal constituent of clinical-grade supplements, finds extensive application in the recovery and treatment of diverse cardiovascular and cerebrovascular disorders. However, controversies persist regarding the utilization of LC in nervous system diseases, with varying effects observed across numerous mental and neurological disorders. This article primarily aims to gather and analyze database information to comprehensively summarize the therapeutic potential of LC in patients suffering from nervous system diseases while providing valuable references for further research.

METHODS

A comprehensive search was conducted in PubMed, Web Of Science, Embase, Ovid Medline, Cochrane Library and Clinicaltrials.gov databases. The literature pertaining to the impact of LC supplementation on neurological or psychiatric disorders in patients was reviewed up until November 2023. No language or temporal restrictions were imposed on the search.

RESULTS

A total of 1479 articles were retrieved, and after the removal of duplicates through both automated and manual exclusion processes, 962 articles remained. Subsequently, a meticulous re-screening led to the identification of 60 relevant articles. Among these, there were 12 publications focusing on hepatic encephalopathy (HE), while neurodegenerative diseases (NDs) and peripheral nervous system diseases (PNSDs) were represented by 9 and 6 articles, respectively. Additionally, stroke was addressed in five publications, whereas Raynaud's syndrome (RS) and cognitive disorder (CD) each had three dedicated studies. Furthermore, migraine, depression, and amyotrophic lateral sclerosis (ALS) each accounted for two publications. Lastly, one article was found for other symptoms under investigation.

CONCLUSION

In summary, LC has demonstrated favorable therapeutic effects in the management of HE, Alzheimer's disease (AD), carpal tunnel syndrome (CTS), CD, migraine, neurofibromatosis (NF), PNSDs, RS, and stroke. However, its efficacy appears to be relatively limited in conditions such as ALS, ataxia, attention deficit hyperactivity disorder (ADHD), depression, chronic fatigue syndrome (CFS), Down syndrome (DS), and sciatica.

Ectoine protects corneal epithelial survival and barrier from hyperosmotic stress by promoting anti-inflammatory cytokine IL-37

PURPOSE

To explore novel role and molecular mechanism of a natural osmoprotectant ectoine in protecting corneal epithelial cell survival and barrier from hyperosmotic stress.

METHODS

Primary human corneal epithelial cells (HCECs) were established from donor limbus. The confluent cultures in isosmolar medium were switched to hyperosmotic media (400-500 mOsM), with or without ectoine or rhIL-37 for different time periods. Cell viability and proliferation were evaluated by MTT or WST assay. The integrity of barrier proteins and the expression of cytokines and cathepsin S were evaluated by RT-qPCR, ELISA, and immunostaining with confocal microscopy.

RESULTS

HCECs survived well in 450mOsM but partially damaged in 500mOsM medium. Ectoine well protected HCEC survival and proliferation at 500mOsM. The integrity of epithelial barrier was significantly disrupted in HCECs exposed to 450mOsM, as shown by 2D and 3D confocal immunofluorescent images of tight junction proteins ZO-1 and occludin. Ectoine at 5-20 mM well protected these barrier proteins under hyperosmotic stress. The expression of TNF-α, IL-1β, IL-6 and IL-8 were dramatically stimulated by hyperosmolarity but significantly suppressed by Ectoine at 5-40 mM. Cathepsin S, which was stimulated by hyperosmolarity, directly disrupted epithelial barrier. Interestingly, anti-inflammatory cytokine IL-37 was suppressed by hyperosmolarity, but restored by ectoine at mRNA and protein levels. Furthermore, rhIL-37 suppressed cathepsin S and rescued cell survival and barrier in HCECs exposed to hyperosmolarity.

CONCLUSION

Our findings demonstrate that ectoine protects HCEC survival and barrier from hyperosmotic stress by promoting IL-37. This provides new insight into pathogenesis and therapeutic potential for dry eye disease.

Potential New Target for Dry Eye Disease-Oxidative Stress

Dry eye disease (DED) is a multifactorial condition affecting the ocular surface. It is characterized by loss of tear film homeostasis and accompanied by ocular symptoms that may potentially result in damage to the ocular surface and even vision loss. Unmodifiable risk factors for DED mainly include aging, hormonal changes, and lifestyle issues such as reduced sleep duration, increased screen exposure, smoking, and ethanol consumption. As its prevalence continues to rise, DED has garnered considerable attention, prompting the exploration of potential new therapeutic targets. Recent studies have found that when the production of ROS exceeds the capacity of the antioxidant defense system on the ocular surface, oxidative stress ensues, leading to cellular apoptosis and further oxidative damage. These events can exacerbate inflammation and cellular stress responses, further increasing ROS levels and promoting a vicious cycle of oxidative stress in DED. Therefore, given the central role of reactive oxygen species in the vicious cycle of inflammation in DED, strategies involving antioxidants have emerged as a novel approach for its treatment. This review aims to enhance our understanding of the intricate relationship between oxidative stress and DED, thereby providing directions to explore innovative therapeutic approaches for this complex ocular disorder.

Ectoine, from a Natural Bacteria Protectant to a New Treatment of Dry Eye Disease

Ectoine, a novel natural osmoprotectant, protects bacteria living in extreme environments. This study aimed to explore the therapeutic effect of ectoine for dry eye disease. An experimental dry eye model was created in C57BL/6 mice exposed to desiccating stress (DS) with untreated mice as controls (UT). DS mice were dosed topically with 0.5-2.0% of ectoine or a vehicle control. Corneal epithelial defects were detected via corneal smoothness and Oregon Green dextran (OGD) fluorescent staining. Pro-inflammatory cytokines and chemokines were evaluated using RT-qPCR and immunofluorescent staining. Compared with UT mice, corneal epithelial defects were observed as corneal smoothness irregularities and strong punctate OGD fluorescent staining in DS mice with vehicle. Ectoine treatment protected DS mice from corneal damage in a concentration-dependent manner, and ectoine at 1.0 and 2.0% significantly restored the corneal smoothness and reduced OGD staining to near normal levels. Expression of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) and chemokines CCL3 and CXCL11 was significantly elevated in the corneas and conjunctivas of DS mice, whereas 1.0 and 2.0% ectoine suppressed these inflammatory mediators to near normal levels. Our findings demonstrate that ectoine can significantly reduce the hallmark pathologies associated with dry eye and may be a promising candidate for treating human disease.

Tear and Saliva Metabolomics in Evaporative Dry Eye Disease in Females

Accurate diagnosis of dry eye disease (DED) is challenging, and even today there is no gold standard biomarker of DED. Hypothesis-free global metabolomic studies of tears from DED patients have great potential to discover metabolites and pathways affected in the pathophysiology of DED, and to identify possible future biomarkers. These metabolites and biomarkers could be important for diagnosing and monitoring disease as well as for new therapeutic targets and strategies. As DED is associated with dry mouth, this study aimed to perform metabolomic analyses of tears and saliva from patients with decreased tear film break-up time but normal Schirmer test, and age-matched controls with both tear production and stability within physiological range. We applied strict inclusion criteria to reduce sampling bias in the metabolomic analyses and selected only age-matched females with Schirmer test values between 10-15 mm/5 min. The tear film analysis arm included 19 patients (with tear film break-up time 0-5 s) and 12 controls (with tear film break-up time 10-30 s), while the salivary analysis arm consisted of a subset which included 18 patients and six controls. Metabolomic analyses were performed using liquid chromatography and high-resolution mass spectrometry. Analyses using a global database search detected a total of 56 metabolites in tear samples that were significantly different between the groups. Of these, several have known associations with DED. These metabolites are present in meibum and have anti-oxidative characteristics or associations with the ocular microbiome, and altered concentrations suggest that they may play a significant role in DED associated with decreased tear film stability. In saliva, hypotaurine levels were lower among patients with tear film instability. In this pilot study, we found different levels of several metabolites in patients with decreased tear film break-up time that may have associations with DED. Future studies are required to replicate our findings and clarify the exact roles of these metabolites.

The cGAS-STING pathway-dependent sensing of mitochondrial DNA mediates ocular surface inflammation

The innate immune response is the main pathophysiological process of ocular surface diseases exposed to multiple environmental stresses. The epithelium is central to the innate immune response, but whether and how innate immunity is initiated by ocular epithelial cells in response to various environmental stresses in ocular surface diseases, such as dry eye, is still unclear. By utilizing two classic experimental dry eye models-a mouse ocular surface treated with benzalkonium chloride (BAC) and a mouse model with surgically removed extraorbital lachrymal glands, as well as dry eye patient samples-along with human corneal epithelial cells (HCE) exposed to hyperosmolarity, we have discovered a novel innate immune pathway in ocular surface epithelial cells. Under stress, mitochondrial DNA (mtDNA) was released into the cytoplasm through the mitochondrial permeability transition pore (mPTP) and further activated the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway, aggravating downstream inflammatory responses and ocular surface damage. Genetic deletion or pharmacological suppression of STING and inhibition of mtDNA release reduced inflammatory responses, whereas mtDNA transfection supported cytoplasmic mtDNA-induced inflammatory responses by activating the cGAS-STING pathway. Our study clarified the cGAS-STING pathway-dependent sensing of mitochondrial DNA-mediated ocular surface inflammation, which elucidated a new mechanism of ocular surface diseases in response to multiple environmental stresses.

L-Carnitine Suppresses Transient Receptor Potential Vanilloid Type 1 Activation in Human Corneal Epithelial Cells

Tear film hyperosmolarity induces dry eye syndrome (DES) through transient receptor potential vanilloid type 1 (TRPV1) activation. L-carnitine is a viable therapeutic agent since it protects against this hypertonicity-induced response. Here, we investigated whether L-carnitine inhibits TRPV1 activation by blocking heat- or capsaicin-induced increases in Ca²⁺ influx or hyperosmotic stress-induced cell volume shrinkage in a human corneal epithelial cell line (HCE-T). Single-cell fluorescence imaging of calcein/AM-loaded cells or fura-2/AM-labeled cells was used to evaluate cell volume changes and intracellular calcium levels, respectively. Planar patch-clamp technique was used to measure whole-cell currents. TRPV1 activation via either capsaicin (20 µmol/L), hyperosmolarity (≈450 mosmol/L) or an increase in ambient bath temperature to 43 °C induced intracellular calcium transients and augmented whole-cell currents, whereas hypertonicity induced cell volume shrinkage. In contrast, either capsazepine (10 µmol/L) or L-carnitine (1-3 mmol/L) reduced all these responses. Taken together, L-carnitine and capsazepine suppress hypertonicity-induced TRPV1 activation by blocking cell volume shrinkage.

Mucin-targeting-aptamer functionalized liposomes for delivery of cyclosporin A for dry eye diseases

Traditional eye drops are convenient to use; however, their effectiveness is limited by their poor retention time and bioavailability in the eyes due to ocular barriers. Therefore, strategies to enhance ocular drug delivery are required. Herein, we constructed a mucin-1 aptamer-functionalized liposome and loaded it with cyclosporin A, a common ocular drug in eye drops used to treat dry eye diseases (DED). Drug encapsulation slightly reduced the liposome size without changing the surface potential of liposomes. Approximately 90% of the cholesterol-modified aptamers were inserted to the liposomes. We evaluated the cytotoxicity, anti-inflammatory effects, cell permeability regulation, and retention time of liposomes in human corneal epithelial cells under dry eye conditions. These results suggest that the aptamer-functionalized liposomes are more efficient as nanocarriers than non-functionalized liposomes and drug-free liposomes. They restore inflammation levels by 1-fold and remain in the cells for up to 24 h. An in vivo study was also performed in a rat DED model, which demonstrated the efficacy of aptamer-functionalized liposomes in restoring tear production and corneal integrity. The present study demonstrated the capability of aptamer-functionalized liposomes in the delivery of ocular drugs for the management of ocular diseases.

L-Carnitine and synbiotic co-supplementation: beneficial effects on metabolic-endotoxemia, meta-inflammation, and oxidative-stress biomarkers in obese patients: a double blind, randomized, controlled clinical trial

Obesity, a chronic pandemic disease, is characterized by low-grade chronic inflammation, accompanied by over-expression of pro-inflammatory cytokines, thereby contributing to metabolic disorders pathogenesis. Oxidative-stress, an adverse cellular response to adipocyte hypertrophy, promotes inflammation. Furthermore, gut-microbiota dysbiosis may induce oxidative-stress, low-grade inflammation, and metabolic-endotoxemia as major drivers of obesity. Functional-foods/nutraceuticals have attracted extensive attention due to their plausible anti-inflammatory/anti-oxidative properties; evidence supports the superiority of the nutraceutical combined-supplementation approach versus conventional mono-therapies. Current data suggest the anti-oxidative/anti-inflammatory properties of either L-carnitine or pre/pro/synbiotics. This trial compared the effects of co-supplementing L-carnitine and multi-species/multi-strain synbiotic versusL-carnitine mono-therapy on inflammatory/anti-inflammatory, oxidative-stress, and metabolic-endotoxemia biomarkers in 46 female obese patients, receiving either co-supplementation (L-carnitine-tartrate (2 × 500 mg d^-1) + multi-species/multi-strain synbiotic (1 capsule per day)) or mono-therapy (L-carnitine-tartrate (2 × 500 mg d^-1) + maltodextrin (1 capsule per day)) for eight weeks. L-Carnitine + synbiotic co-supplementation significantly decreased interleukin-6 (IL-6, -33.98%), high-sensitivity-C-reactive-protein (hs-CRP, -10%), tumor-necrosis-factor-alpha (TNF-α, -18.73%), malondialdehyde (MDA, -21.73%), and lipopolysaccharide (LPS, -10.14%), whereas the increase in interleukin-10 (IL-10, 7.69%) and total-antioxidant-capacity (TAC, 4.13%) levels was not significant. No significant changes were observed for the above-mentioned parameters in the L-carnitine + placebo group, except for a significant reduction in IL-10 (-17.59%) and TNF-α (-14.78%); however, between-group differences did not reach the significant threshold. Co-supplementing L-carnitine + multi-strain synbiotic led to significant amelioration of inflammatory, oxidative, and metabolic-endotoxemia responses in female obese patients; nevertheless, no improving effects were observed in patients receiving single-supplementation, suggesting that L-carnitine + synbiotic co-supplementation might represent an adjuvant approach to improve oxidative-stress/pro-inflammatory indicators in women with obesity, possibly through beneficial effects of the synbiotic alone. Further longer duration studies with higher doses of L-carnitine in a three-group setting are warranted to elucidate the possibility of synergistic or complementary mechanisms.

Cytoprotective Effects of Human Platelet Lysate during the Xeno-Free Culture of Human Donor Corneas

We evaluated the suitability of 2% human platelet lysate medium (2%HPL) as a replacement for 2% fetal bovine serum medium (2%FBS) for the xeno-free organ culture of human donor corneas. A total of 32 corneas from 16 human donors were cultured in 2%FBS for 3 days (TP1), then evaluated using phase contrast microscopy (endothelial cell density (ECD) and cell morphology). Following an additional 25-day culture period (TP2) in either 2%FBS or 2%HPL, the pairs were again compared using microscopy; then stroma and Descemet membrane/endothelium (DmE) were processed for next generation sequencing (NGS). At TP2 the ECD was higher in the 2%HPL group (2179 ± 288 cells/mm²) compared to 2%FBS (2113 ± 331 cells/mm²; p = 0.03), and endothelial cell loss was lower (ECL HPL = -0.7% vs. FBS = -3.8%; p = 0.01). There were no significant differences in cell morphology between TP1 and 2, or between 2%HPL and 2%FBS. NGS showed the differential expression of 1644 genes in endothelial cells and 217 genes in stromal cells. It was found that 2%HPL led to the upregulation of cytoprotective, anti-inflammatory and anti-fibrotic genes (HMOX1, SERPINE1, ANGPTL4, LEFTY2, GADD45B, PLIN2, PTX3, GFRA1/2), and the downregulation of pro-inflammatory/apoptotic genes (e.g., CXCL14, SIK1B, PLK5, PPP2R3B, FABP5, MAL, GATA3). 2%HPL is a suitable xeno-free substitution for 2%FBS in human cornea organ culture, inducing less ECL and producing potentially beneficial alterations in gene expression.

Development of In Vitro Dry Eye Models to Study Proliferative and Anti-Inflammatory Effects of Allogeneic Serum Eye Drops

This study aimed to develop valid in vitro models for preclinical evaluation of proliferative and anti-inflammatory effects of human allogeneic serum eye drops for dry eye disease (DED) treatment. A DED wound healing model was developed by analyzing the influence of coating and serum concentrations on human corneal epithelial (HCE-T) wound closure. Further, intralaboratory variance, freeze-thaw cycle effects, donor variability and stability assays were conducted. Interleukin-1β (IL-1β) and tumor necrosis factor α (TNFα) were used to induce the gene expression of matrix metalloproteinase 9 (MMP9), cyclooxygenase 2 (COX2), transforming growth factor-β (TGFβ) and IL-1β. MMP9 induction was optimized using a design-of-experiments (DoE) approach and applied to examine serum under static and dynamic conditions. MMP9 protein expression was analyzed by ELISA. The DED wound healing model detected proliferative effects of serum down to 1% with a small intralaboratory variance. Serum stability was shown over six months, donor variance could be detected, and freeze-thaw cycle effects did not affect wound closure. Serum decreased MMP9 expression on the gene and protein levels. The induction method was successfully optimized using DoE modeling and transferred to a dynamic setting mimicking tear film fluidics. The DED wound healing and inflammatory DED model present useful in vitro models for the preclinical evaluation of allogeneic serum eye drops without the use of animal experiments.

Essential Roles of Peroxiredoxin IV in Inflammation and Cancer

Peroxiredoxin IV (Prx4) is a 2-Cysteine peroxidase with ubiquitous expression in human tissues. Prx4 scavenges hydrogen peroxide and participates in oxidative protein folding in the endoplasmic reticulum. In addition, Prx4 is secreted outside the cell. Prx4 is upregulated in several cancers and is a potential therapeutic target. We have summarized historical and recent advances in the structure, function and biological roles of Prx4, focusing on inflammatory diseases and cancer. Oxidative stress is known to activate pro-inflammatory pathways. Chronic inflammation is a risk factor for cancer development. Hence, redox enzymes such as Prx4 are important players in the crosstalk between inflammation and cancer. Understanding molecular mechanisms of regulation of Prx4 expression and associated signaling pathways in normal physiological and disease conditions should reveal new therapeutic strategies. Thus, although Prx4 is a promising therapeutic target for inflammatory diseases and cancer, further research needs to be conducted to bridge the gap to clinical application.

Imbalanced IL-37/TNF-α/CTSS signaling disrupts corneal epithelial barrier in a dry eye model in vitro

PURPOSE

To explore novel role and molecular mechanism of a natural anti-inflammatory cytokine interleukin (IL) 37 in preventing corneal epithelial barrier disruption from hyperosmolar stress as can occur in dry eye disease.

METHODS

Primary human corneal epithelial cells (HCECs) were cultured from fresh donor limbal explants. An in vitro dry eye model with hyperosmolar stress was established by switching HCECs from isosmolar (312mOsM) to hyperosmolar medium (350-500 mOsM), and some cells were treated with rhIL-37 or rhTNF-α, for different periods (2-48 h). The expression of cytokines and cathepsin S, and barrier protein integrity were evaluated by RT-qPCR, ELISA, and immunofluorescent staining with confocal microscopy.

RESULTS

The integrity of epithelial barrier was significantly disrupted in HCECs exposed to hyperosmolar medium, as shown by immunofluorescent images of tight junction (TJ, ZO-1, occludin and claudin-1) and adheren junction (E-cadherin) proteins. TNF-α accentuated hyperosmolar-induced disruption of TJ barrier functional integrity whereas exposure to IL-37 blunted or even reversed these changes. Cathepsin S, encoded by CTSS gene, was found to directly disrupt epithelial barrier integrity. Interestingly, CTSS expression was significantly induced by TNF-α and hyperosmolarity, while exogenous rhIL-37 inhibited TNF-α and CTSS expression at mRNA and protein levels following hyperosmolar stress. Furthermore, rhIL-37 restored barrier protein integrity, observed in 2D and 3D confocal immunofluorescent images, in HCECs under hyperosmolar stress.

CONCLUSION

Our findings demonstrate a novel signaling pathway by which anti-inflammatory cytokine IL-37 prevents corneal epithelial barrier disruption under hyperosmotic stress via suppressing TNF-α and CTSS expression. This study provides new insight into mechanisms protecting corneal barrier in dry eye disease.

Transient Receptor Potential Channels: Important Players in Ocular Pain and Dry Eye Disease

Dry eye disease (DED) is a multifactorial disorder in which the eyes respond to minor stimuli with abnormal sensations, such as dryness, blurring, foreign body sensation, discomfort, irritation, and pain. Corneal pain, as one of DED’s main symptoms, has gained recognition due to its increasing prevalence, morbidity, and the resulting social burden. The cornea is the most innervated tissue in the body, and the maintenance of corneal integrity relies on a rich density of nociceptors, such as polymodal nociceptor neurons, cold thermoreceptor neurons, and mechano-nociceptor neurons. Their sensory responses to different stimulating forces are linked to the specific expression of transient receptor potential (TRP) channels. TRP channels are a group of unique ion channels that play important roles as cellular sensors for various stimuli. These channels are nonselective cation channels with variable Ca²⁺ selectivity. TRP homologs are a superfamily of 28 different members that are subdivided into 7 different subfamilies based on differences in sequence homology. Many of these subtypes are expressed in the eye on both neuronal and non-neuronal cells, where they affect various stress-induced regulatory responses essential for normal vision maintenance. This article reviews the current knowledge about the expression, function, and regulation of TRPs in ocular surface tissues. We also describe their implication in DED and ocular pain. These findings contribute to evidence suggesting that drug-targeting TRP channels may be of therapeutic benefit in the clinical setting of ocular pain.

Can the cGAS-STING Pathway Play a Role in the Dry Eye?

Dry eye is one of the most common ocular surface diseases in the world and seriously affects the quality of life of patients. As an immune-related disease, the mechanism of dry eye has still not been fully elucidated. The cGAS-STING pathway is a recently discovered pathway that plays an important role in autoimmune and inflammatory diseases by recognizing dsDNA. As an important signal to initiate inflammation, the release of dsDNA is associated with dry eye. Herein, we focused on the pathophysiology of the immune-inflammatory response in the pathogenesis of dry eye, attempted to gain insight into the involvement of dsDNA in the dry eye immune response, and investigated the mechanism of the cGAS-STING pathway involved in the immune-inflammatory response. We further proposed that the cGAS-STING pathway may participate in dry eye as a new mechanism linking dry eye and the immune-inflammatory response, thus providing a new direction for the mechanistic exploration of dry eye.

Copolymer micelle-administered melatonin ameliorates hyperosmolarity-induced ocular surface damage through regulating PINK1 mediated mitophagy

PURPOSE

To investigate the role and mechanism of melatonin-loaded polymer polyvinyl caprolactam-polyvinyl acetate-polyethyleneglycol graft copolymer (PVCL-PVA-PEG) micelles (Mel-Mic) in dry eye disease (DED).

METHODS

In vitro, the apoptosis and reactive oxygen species (ROS) generation in HCECs were analyzed by immunostaining and flow cytometry (FCM). The effect of Mel-Mic on autophagy and mitophagy was evaluated by immunostaining and western blots. PINK1 knockdown was analyzed by small interfering RNA (siRNA). In vivo, sodium fluorescein staining, tear secretion test, and periodic acid-schiff (PAS) staining were used to determine whether Mel-Mic can alleviate the severity of DED. Small molecule antagonists were pretreated to investigate whether melatonin type 1 and/or 2 receptors (MT1/MT2) mediate the effects of Mel-Mic.

RESULTS

Mel-Mic improved the solubility and biological activities of Mel in aqueous solutions. Treatment with Mel-Mic decreased the apoptosis of HCECs exposed to hyperosmotic medium, accompanied by downregulation of cleaved Caspase-3 and upregulation of Bcl-2. In addition, Mel-Mic application suppressed ROS overproduction, rescued mitochondrial function, and decreased the level of oxidative stress associated biomarkers (COX-2 and 4-HNE) in HCECs. Interestingly, HCECs treated with Mel-Mic exhibited increased levels of mitophagy markers (PINK1, PARKIN, Beclin 1 and LC3B) and restored impaired mitophagic flux under hyperosmolarity. While PINK1 knock down largely abolished its protective effects. In vivo, compared to vehicle group, topical Mel-Mic solution treated mice showed significantly improved clinical parameters, increased tear production and decreased goblet cells loss in a dose-dependent manner. Also, TEM assay revealed increased autophagosome number in the corneal epithelium of Mel-Mic group. Moreover, luzindole, a non-selective MT1/MT2 antagonist, but not 4-P-PDOT, a selective MT2 antagonist, blocked the protective effect of Mel-Mic.

CONCLUSIONS

Our findings demonstrated that Mel-Mic ameliorates hyperosmolarity induced ocular surface damage via PINK1 mediated mitophagy and may represent an effective treatment for DED possibly through acting MT1 receptor.

IL-36α/IL-36RA/IL-38 signaling mediates inflammation and barrier disruption in human corneal epithelial cells under hyperosmotic stress

PURPOSE

To explore the distinct expression and diverse roles of IL-36 cytokines in dry eye disease using an in vitro hyperosmolarity model of human corneal epithelial cells (HCECs).

METHODS

Primary HCECs were cultured from fresh donor limbal explants. Hyperosmolarity model was established by switching HCECs from isosmotic (312 mOsM) to hyperosmotic medium (350-500 mOsM) alone or with addition of rhIL-36RA or rhIL-38 for 2-48 h. Some cultures were treated with IL-36α (1-10 ng/ml) with or without rhIL-36RA or rhIL-38. Gene expression was detected by RT-qPCR; and protein production and barrier disruption were evaluated by ELISA and/or immunofluorescent staining.

RESULTS

IL-36 cytokines were differential expressed in primary HCECs. Among 3 pro-inflammatory agonists, IL-36α, but not IL-36β and IL-36γ, was distinctly induced at osmolarity-dependent manner while two antagonist IL-36RA and IL-38 were significantly suppressed in HCECs exposed to hyperosmotic stress. IL-36α increased to 4.4-fold in mRNA and 6.9-fold at protein levels (116.0 ± 36.33 pg/ml vs 16.79 ± 6.51 pg/ml in controls) by 450 mOsM, but dramatically inhibited by addition of rhIL-36RA or rhIL-38. Exogenous rhIL-36α stimulated expression of TNF-α and IL-1β at mRNA and protein levels and disrupted tight junction proteins ZO-1 and occludin. However, rhIL-36RA or rhIL-38 suppressed TNF-α and IL-1β production and protected HCECs from barrier disruption in response to IL-36α or hyperosmolarity.

CONCLUSIONS

Our findings demonstrate that the stimulated pro-inflammatory IL-36α with the suppressed antagonists IL-36RA and IL-38 is a novel mechanism by which hyperosmolarity induces inflammation in dry eye. IL-36RA and IL-38 may have a therapeutic potential in dry eye.

Combined hyperosmolarity and inflammatory conditions in stressed human corneal epithelial cells and macrophages to evaluate osmoprotective agents as potential DED treatments

PURPOSE

To develop an easy-to-perform combined model in human corneal epithelial cells (HCECs) and Balb/c mice macrophages J774.A1 (MP) for preliminary screening of potential ophthalmic therapeutic substances.

METHODS

HCECs were exposed to different osmolarities (350-500 mOsm/L) and MTT assay was employed for cell survival and flow cytometry to assess apoptosis-necrosis and relative cell size (RCS) distribution. Effectiveness of Betaine, L-Carnitine, Taurine at different concentrations (ranging from 20 mM to 200 mM) was studied. Also, mucoadhesive polymers such as Hyaluronic acid (HA) and Hydroxypropylmethylcellulose (HPMC) (0.4 and 0.8%) were evaluated. Cells were pre-incubated with the compounds (8h) and then exposed to hyperosmotic stress (470 mOsm/L) for 16h. Moreover, anti-inflammatory activity was performed in LPS-stimulated MP.

RESULTS

Exposure to hyperosmotic solutions between 450 and 500 mOsm/L promoted the highest cell death after 16h exposures (p < 0.0001) with a drop in viability to 34.96% ± 11.77 for 470 mOsm/L. Pre-incubation with Betaine at 150 mM and 200 mM provided the highest cell survival against hyperosmolarity (66.01% ± 3.65 and 65.90% ± 0.78 respectively) while HA 0.4% was the most effective polymer in preventing cell death (42.2% ± 3.60). Flow cytometry showed that Betaine and Taurine at concentrations between 150-200 mM and 20-80 mM respectively presented the highest anti-apoptotic activity. Also, HA and HPMC polymers reduced apoptotic-induced cell death. All osmoprotectants modified RCS, and polymers increased their value over 100%. L-Carnitine 50 mM, Taurine 40 mM and HA 0.4% presented the highest TNF-α inhibition activity (60%) albeit all of them showed anti-inflammatory inhibition percentages higher than 20% CONCLUSIONS: HCECs hyperosmolar model combined with inflammatory conditions in macrophages allows the screening of osmoprotectants by simulating chronic hyperosmolarity (16h) and inflammation (24h).

Topical Delivery of Levocarnitine to the Cornea and Anterior Eye by Thermosensitive in-situ Gel for Dry Eye Disease

Purpose

To prepare the levocarnitine thermosensitive in situ gel (LCTG) and evaluate its effect on dry eye disease (DED).

Methods

Draize eye irritation test and other examinations were used to evaluate the eye irritation after multiple administration of LCTG. The Schirmer test, fluorescein sodium staining, HE staining and TUNEL staining were used to detect the tear secretion, corneal injury, histopathological changes of the cornea and lacrimal gland, and the apoptosis rate of cornea epithelial cells after 3 days of the administration. The conjunctival goblet cell density was detected by PAS staining, and the expression levels of matrix metalloproteinase-3 (MMP-3) and matrix metalloproteinase-9 (MMP-9) of corneal epithelial cells were detected by immunofluorescence staining after 7 days of the administration.

Results

LCTG is non-irritating to rabbit eyes and has good biocompatibility. LCTG administration for 3 days can significantly increase the amount of tear secretion in mice with DED, promote corneal epithelial integrity and central corneal epithelium thickness recovery, and improve the pathological morphology and structure of corneal and lacrimal gland tissues, and reduce the apoptosis rate of the corneal epithelial cells. After 7 days of the administration, the preparation can promote the proliferation of conjunctival goblet cells and down-regulate the cornea expression levels of MMP-3 and MMP-9 in epithelial cells.

Conclusion

The LCTG has a good curative effect on mice with DED, and the overall curative effect is better than that of levocarnitine solution.

L-carnitine suppresses transient receptor potential vanilloid type 1 activity and myofibroblast transdifferentiation in human corneal keratocytes

Corneal stromal wound healing is a well-balanced process promoted by overlapping phases including keratocyte proliferation, inflammatory-related events, and tissue remodeling. L-carnitine as a natural antioxidant has shown potential to reduce stromal fibrosis, yet the underlying pathway is still unknown. Since transient receptor potential vanilloid 1 (TRPV1) is a potential drug target for improving the outcome of inflammatory/fibrogenic wound healing, we investigated if L-carnitine can mediate inhibition of the fibrotic response through suppression of TRPV1 activation in human corneal keratocytes (HCK). We determined TRPV1-induced intracellular calcium transients using fluorescence calcium imaging, channel currents by planar patch-clamping, and cell migration by scratch assay for wound healing. The potential L-carnitine effect on TRPV1-induced myofibroblast transdifferentiation was evaluated by immunocytochemical detection of alpha smooth muscle actin. RT-PCR analysis confirmed TRPV1 mRNA expression in HCK. L-carnitine (1 mmol/l) inhibited either capsaicin (CAP) (10 µmol/l), hypertonic stress (450 mOsmol/l), or thermal increase (>43 °C) induced Ca2+ transients and corresponding increases in TRPV1-induced inward and outward whole-cell currents. This was accompanied by suppression of injury-induced increases in myofibroblast transdifferentiation and cell migration. In conclusion, L-carnitine contributes to inhibit stromal scarring through suppressing an injury-induced intrinsic TRPV1 activity that is linked with induction of myofibroblast transdifferentiation in HCK cells.

Metabolomic Analysis in Corneal Lenticules From Contact Lens Wearers

PURPOSE

To investigate the mechanisms of pathological changes in corneal stroma and the wearing time of soft contact lenses using the metabolomic method.

METHODS

Laser scanning confocal microscopy was used to evaluate the pathological changes of corneal stroma between wearing time groups before small incision lenticule extraction. After small incision lenticule extraction, 190 corneal stroma samples were obtained, and a metabolomic method using high performance liquid chromatography coupled with time of flight mass spectrometry was established to analyze the changes in metabolites between wearing time groups.

RESULTS

Laser scanning confocal microscope results demonstrated that the corneal nerve fiber length, the number of corneal anterior stromal cells, and the number of corneal posterior stromal cells were reduced gradually with increasing wearing time. The metabolomic study demonstrated that 11 biomarkers were identified between patients who did and did not wear soft contact lenses and 6 biomarkers were identified between less than 5 years and more than 5 years of wearing time. These biomarkers participate in energy metabolism, lipid metabolism, inflammatory reactions, and neuroprotecton processes, and partially lead to the pathology of dry eyes, eye inflammation, and corneal nerve fiber length decrease. Five biomarkers in the citrate cycle metabolism pathway were found demonstrating that energy metabolism was seriously disturbed.

CONCLUSIONS

This study systematically revealed the metabolite mechanism for eye discomfort and related disease after wearing soft contact lenses. The identified biomarkers and related physiology pathways supply a new direction for avoiding the side effects of wearing soft contact lenses. [J Refract Surg. 2020;36(5):317-325.].

Categorization of Marketed Artificial Tear Formulations Based on Their Ingredients: A Rational Approach for Their Use

Dry eye disease is a common ocular condition affecting millions of people worldwide. Artificial tears are the first line therapy for the management of dry eye disease. Artificial tear formulations contain a variety of active ingredients, biologically active excipients, and preservatives. Many of these formulations are also available as preservative-free. This study was conducted to inspect artificial tear formulations currently marketed in the United States for their active ingredients, biologically relevant excipients, and preservatives. The marketed artificial tears were examined at various US retail pharmacy chains and using the manufacturers’ website to compile information about active ingredients, inactive ingredients, and preservatives. The currently marketed artificial tears can be grouped into four categories based on their active ingredients. The artificial tears also contain biologically active chemicals listed as inactive ingredients, which have osmoprotectant, humectant, and tear film lipid layer or mucous layer mimicking properties. Most artificial tears contain vanishing type preservatives such as purite or sodium perborate and safer quaternary compound polyquaternium-1. The majority of these artificial tear formulations are also available as preservative-free single dose unit. The study provides a formulary of artificial tears based on active ingredients, biologically active excipients, and the preservative-free option. The formulary should assist healthcare providers in making a stepwise and rational selection of appropriate artificial tears for patients suffering from dry eye disease.

Trehalose Induces Autophagy Against Inflammation by Activating TFEB Signaling Pathway in Human Corneal Epithelial Cells Exposed to Hyperosmotic Stress

Purpose

Autophagy plays an important role in balancing the inflammatory response to restore homeostasis. The aim of this study was to explore the mechanism by which trehalose suppresses inflammatory cytokines via autophagy activation in primary human corneal epithelial cells (HCECs) exposed to hyperosmotic stress.

Methods

An in vitro dry eye model was used in which HCECs were cultured in hyperosmolar medium with the addition of sodium chloride (NaCl). Trehalose was applied in different concentrations. The levels of TNF-α, IL-1β, IL-6, and IL-8 were detected using RT-qPCR and ELISA. Cell viability assays, immunofluorescent staining of LC3B, and western blots of Beclin1, Atg5, Atg7, LC3B, and P62 were conducted. The key factors in upstream signaling pathways of autophagy activation were measured: P-Akt, Akt, and transcription factor EB (TFEB).

Results

Trehalose reduced the proinflammatory mediators TNF-α, IL-1β, IL-6, and IL-8 in primary HCECs at 450 mOsM. This effect was osmolarity dependent, and a level of 1.0% trehalose showed the most suppression. Trehalose promoted autophagosome formation and autophagic flux, as evidenced by increased production of Beclin1, Atg5, and Atg7, as well as higher LC3B I protein turnover to LC3B II, with decreased protein levels of P62/SQSTM1. The addition of 3-methyladenine blocked autophagy activation and increased the release of proinflammatory cytokines. Trehalose further activated TFEB, with translocation from cytoplasm to the nucleus, but diminished Akt activity.

Conclusions

Our findings demonstrate that trehalose, functioning as an autophagy enhancer, suppresses the inflammatory response by promoting autophagic flux via TFEB activation in primary HCECs exposed to hyperosmotic stress, a process that is beneficial to dry eye.

Autophagy Activation Protects Ocular Surface from Inflammation in a Dry Eye Model In Vitro

Inflammation is the main pathophysiology of dry eye, characterized by tear film instability and hyperosmolarity. The aim of this study was to investigate the association of inflammation and cellular autophagy using an in vitro dry eye model with primary cultured human corneal epithelial cells (HCECs). Primary HCECs cultured with fresh limbal explants from donors were switched to a hyperosmotic medium (450 mOsM) by adding sodium chloride into the culture medium. We observed the stimulated inflammatory mediators, TNF-α, IL-1β, IL-6 and IL-8, as well as the increased expression of autophagy related genes, Ulk1, Beclin1, Atg5 and LC3B, as evaluated by RT-qPCR and ELISA. The immunofluorescent staining of LC3B and Western blotting revealed the activated autophagosome formation and autophagic flux, as evidenced by the increased LC3B autophagic cells with activated Beclin1, Atg5, Atg7 and LC3B proteins, and the decreased levels of P62 protein in HCECs. Interestingly, the autophagy activation was later at 24 h than inflammation induced at 4 h in HCECs exposed to 450 mOsM. Furthermore, application of rapamycin enhanced autophagy activation also reduced the inflammatory mediators and restored cell viability in HCECs exposed to the hyperosmotic medium. Our findings for the first time demonstrate that the autophagy activation is a late phase response to hyperosmotic stress, and is enhanced by rapamycin, which protects HCECs by suppressing inflammation and promoting cells survival, suggesting a new therapeutic potential to treat dry eye diseases.

Esculetin protects human corneal epithelial cells from oxidative stress through Nrf-2 signaling pathway

Dry eye formation often originates from oxidative damage to the ocular surface, which can be caused by external environment or internal pathologic factors. Esculetin (6, 7-dihydroxycoumarin) is a natural product found in many plants, and has been reported to have multiple pharmacological activities. The objective of our present study is to investigate if esculetin could protect the corneal epithelial cells from oxidative damages and its underlying antioxidant molecular mechanisms. Our experimental results demonstrated that pretreatment with esculetin markedly increased the cell viability while decreased the apoptosis in H₂O₂-treated human corneal epithelial (HCE) cells, by regulating Bcl-2, Bax and caspase-3 protein expressions and by altering the imbalance of activities of intracellular reactive oxygen species (ROS) and superoxide dismutase (SOD). Our data revealed that esculetin played an antioxidant role not only through its antioxidant activity, but also by highly inducing Nrf-2 translocation to the nucleus, which in turn, enhanced Nrf2 signaling regulated antioxidant genes (HO-1, NQO1, GCLM, SOD1 and SOD2) mRNA expression levels in H₂O₂-treated HCE cells. In the present study, the protective effects of esculetin on the corneal epithelium were also confirmed by a murine desiccating stress induced dry eye model in vivo. These data illustrated, for the first time, that esculetin may have the ability to protect human corneal epithelial cells from oxidative damages through its scavenging of free radical properties and through the activation of Nrf2 signaling.

Modulation of Oxidative Stress and Inflammation in the Aged Lacrimal Gland

Inflammation and oxidative stress accompany aging. This study investigated the interplay between oxidative stress and inflammation in the lacrimal gland. C57BL/6 mice were used at 2 to 3, 12, and 24 months of age. Nuclear factor erythroid derived-2-related factor 2 (Nrf2)^-/- and corresponding wild-type mice were used at 2 to 3 and 12 to 13 months of age. A separate group of 15.5 to 17 months of age C57BL/6 mice received a diet containing an Nrf2 inducer (Oltipraz) for 8 weeks. Aged C57BL/6 lacrimal glands showed significantly greater lymphocytic infiltration, higher levels of MHC II, IFN-γ, IL-1β, TNF-α, and cathepsin S (Ctss) mRNA transcripts, and greater nitrotyrosine and 4-hydroxynonenal protein. Young Nrf2^-/- mice showed an increase in IL-1β, IFN-γ, MHC II, and Ctss mRNA transcripts compared with young wild-type mice and greater age-related changes at 12 to 13 months of age. Oltipraz diet significantly decreased nitrotyrosine and 4-hydroxynonenal and decreased the expression of IL-1β and TNF-α mRNA transcripts, while decreasing the frequency of CD45⁺CD4⁺ cells in lacrimal glands and significantly increasing conjunctival goblet cell density compared with a standard diet. The findings provide novel insight into the development of chronic, low-grade inflammation and oxidative stress in age-related dry eye. New therapies targeting oxidative stress pathways will be valuable in treating age-related dry eye.

Safety and Efficacy of a Preservative-Free Artificial Tear Containing Carboxymethylcellulose and Hyaluronic Acid for Dry Eye Disease: A Randomized, Controlled, Multicenter 3-Month Study

Purpose

To compare the efficacy and safety of an artificial tear combining the polymers carboxymethylcellulose (CMC) and hyaluronic acid (HA), to a formulation of CMC alone in subjects with dry eye.

Methods

A preservative-free artificial tear (CMC-HA) was compared with an existing artificial tear (CMC). Subjects with mild-to-severe signs and symptoms of dry eye were enrolled in this double-masked, randomized, multicenter trial, and dosed at least twice daily for 90 days, with follow-up visits at Days 7, 30, 60, and 90. Ocular Surface Disease Index (OSDI) was the primary outcome measure. Secondary outcome measures were tear break-up time (TBUT), ocular surface staining, Schirmer test with anesthesia, and visual analog scale (VAS) scores of dry eye symptom severity and formulation acceptability. Safety measures included adverse events, biomicroscopy, and visual acuity.

Results

A total of 460 subjects were enrolled across 45 sites (38 in Europe; 7 in Australia), of whom 454 were randomized to receive treatment. The per-protocol (PP) population consisted of 394 subjects, 364 (92.4%) of whom completed the study. In the PP population, the mean ± SD change from baseline in OSDI score at the primary timepoint, Day 90, was −16.9±17.5 for CMC-HA and −16.0±16.1 for CMC. CMC-HA was non-inferior to CMC based upon a confidence interval method. Both treatments significantly improved (P<0.001) OSDI, symptom VAS scores, TBUT, and ocular surface staining from baseline at all follow-up visits, with minimal differences between groups. Greater reduction of overall ocular pain/discomfort was reported in subjects using CMC-HA versus CMC (P=0.048). Approximately 10% of subjects in each group reported treatment-related adverse events of generally mild to moderate severity.

Conclusion

The new CMC-HA formulation was effective and well tolerated, and demonstrates a greater potential for symptom relief compared with CMC. These data support implementation of this formula for the management of dry eye patients.

The cornea in keratoconjunctivitis sicca

The lacrimal functional unit (LFU) regulates tear production, composition, distribution and clearance to maintain a stable protective tear layer that is essential for maintaining corneal epithelial health. Dysfunction of the LFU, commonly referred to as dry eye, leads to increased tear osmolarity and levels of inflammatory mediators in tears that cause ocular surface epithelial disease, termed keratoconjunctivitis sicca (KCS). Corneal changes in KCS include glycocalyx loss, barrier disruption, surface irregularity inflammatory cytokine/chemokine production, cornification and apoptosis. These can reduce visual function and the increased shear force on the corneal epithelium can stimulate nociceptors sensitized by inflammation causing irritation and pain that may precede frank clinical signs. Therapy of keratoconjunctivitis sicca should be tailored to improve tear stability, normalize tear composition, improve barrier function and minimize shear forces and damaging inflammation to improve corneal epithelial health.

Preparation and characterization of a pterostilbene-peptide prodrug nanomedicine for the management of dry eye

In the present study, a pterostilbene-peptide amphiphile (PS-GA-RGD) that can spontaneously self-assemble into prodrug nanomedicine, was rationally designed and developed as a novel ophthalmic formulation for the potential management of dry eye. The formed PS-GA-RGD nanomedicine was characterized by dynamic latter scattering (DLS) and transmission electron microscopy (TEM). After esterase treatment, active pterostilbene (PS) sustainably released from the PS-GA-RGD nanomedicine within 48 h, as indicated by an in vitro release study. In comparison with native PS, the formed PS-GA-RGD nanomedicine caused minimal cytotoxicity towards RAW 264.7 and HCEC cells in the 0-20 μM range and did not delay wound healing of HCEC monolayer within 6 h. Furthermore, PS-GA-RGD nanomedicine effectively reduced the intracellular reactive oxygen species (ROS) level in H₂O₂ challenged RAW264.7 macrophages and remarkably suppressed the secretion of inflammatory cytokines (e.g., NO, TNF-α, and IL-6) in lipopolysaccharide (LPS) activated RAW264.7 macrophages. Ocular tolerance to the proposed PS-GA-RGD nanomedicine was good after a single instillation in in vivo ocular irritation tests. Overall, the proposed PS-GA-RGD nanomedicine had potent anti-oxidant capacity and anti-inflammatory efficacy, which may be a promising ophthalmic formulation for the management of dry eye.

Preventive Role of L-Carnitine and Balanced Diet in Alzheimer's Disease

The prevention or alleviation of neurodegenerative diseases, including Alzheimer's disease (AD), is a challenge for contemporary health services. The aim of this study was to review the literature on the prevention or alleviation of AD by introducing an appropriate carnitine-rich diet, dietary carnitine supplements and the MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay) diet, which contains elements of the Mediterranean diet and the Dietary Approaches to Stop Hypertension (DASH) diet. L-carnitine (LC) plays a crucial role in the energetic metabolism of the cell. A properly balanced diet contains a substantial amount of LC as well as essential amino acids and microelements taking part in endogenous carnitine synthesis. In healthy people, carnitine biosynthesis is sufficient to prevent the symptoms of carnitine deficiency. In persons with dysfunction of mitochondria, e.g., with AD connected with extensive degeneration of the brain structures, there are often serious disturbances in the functioning of the whole organism. The Mediterranean diet is characterized by a high consumption of fruits and vegetables, cereals, nuts, olive oil, and seeds as the major source of fats, moderate consumption of fish and poultry, low to moderate consumption of dairy products and alcohol, and low intake of red and processed meat. The introduction of foodstuffs rich in carnitine and the MIND diet or carnitine supplementation of the AD patients may improve their functioning in everyday life.

Genome-Protecting Compounds as Potential Geroprotectors

Throughout life, organisms are exposed to various exogenous and endogenous factors that cause DNA damages and somatic mutations provoking genomic instability. At a young age, compensatory mechanisms of genome protection are activated to prevent phenotypic and functional changes. However, the increasing stress and age-related deterioration in the functioning of these mechanisms result in damage accumulation, overcoming the functional threshold. This leads to aging and the development of age-related diseases. There are several ways to counteract these changes: 1) prevention of DNA damage through stimulation of antioxidant and detoxification systems, as well as transition metal chelation; 2) regulation of DNA methylation, chromatin structure, non-coding RNA activity and prevention of nuclear architecture alterations; 3) improving DNA damage response and repair; 4) selective removal of damaged non-functional and senescent cells. In the article, we have reviewed data about the effects of various trace elements, vitamins, polyphenols, terpenes, and other phytochemicals, as well as a number of synthetic pharmacological substances in these ways. Most of the compounds demonstrate the geroprotective potential and increase the lifespan in model organisms. However, their genome-protecting effects are non-selective and often are conditioned by hormesis. Consequently, the development of selective drugs targeting genome protection is an advanced direction.

Involvement of glutathione peroxidases in the occurrence and development of breast cancers

Glutathione peroxidases (GPxs) belong to a family of enzymes that is important in organisms; these enzymes promote hydrogen peroxide metabolism and protect cell membrane structure and function from oxidative damage. Based on the establishment and development of the theory of the pathological roles of free radicals, the role of GPxs has gradually attracted researchers' attention, and the involvement of GPxs in the occurrence and development of malignant tumors has been shown. On the other hand, the incidence of breast cancer in increasing, and breast cancer has become the leading cause of cancer-related death in females worldwide; breast cancer is thought to be related to the increased production of reactive oxygen species, indicating the involvement of GPxs in these processes. Therefore, this article focused on the molecular mechanism and function of GPxs in the occurrence and development of breast cancer to understand their role in breast cancer and to provide a new theoretical basis for the treatment of breast cancer.

Lipid Annotation by Combination of UHPLC-HRMS (MS), Molecular Networking, and Retention Time Prediction: Application to a Lipidomic Study of In Vitro Models of Dry Eye Disease

Annotation of lipids in untargeted lipidomic analysis remains challenging and a systematic approach needs to be developed to organize important datasets with the help of bioinformatic tools. For this purpose, we combined tandem mass spectrometry-based molecular networking with retention time (t_R) prediction to annotate phospholipid and sphingolipid species. Sixty-five standard compounds were used to establish the fragmentation rules of each lipid class studied and to define the parameters governing their chromatographic behavior. Molecular networks (MNs) were generated through the GNPS platform using a lipid standards mixture and applied to lipidomic study of an in vitro model of dry eye disease, i.e., human corneal epithelial (HCE) cells exposed to hyperosmolarity (HO). These MNs led to the annotation of more than 150 unique phospholipid and sphingolipid species in the HCE cells. This annotation was reinforced by comparing theoretical to experimental t_R values. This lipidomic study highlighted changes in 54 lipids following HO exposure of corneal cells, some of them being involved in inflammatory responses. The MN approach coupled to t_R prediction thus appears as a suitable and robust tool for the discovery of lipids involved in relevant biological processes.

The Nutraceutical Value of Carnitine and Its Use in Dietary Supplements

Carnitine can be considered a conditionally essential nutrient for its importance in human physiology. This paper provides an updated picture of the main features of carnitine outlining its interest and possible use. Particular attention has been addressed to its beneficial properties, exploiting carnitine's properties and possible use by considering the main in vitro, in animal, and human studies. Moreover, the main aspects of carnitine-based dietary supplements have been indicated and defined with reference to their possible beneficial health properties.

L-Carnitine counteracts in vitro fructose-induced hepatic steatosis through targeting oxidative stress markers

PURPOSE

Nonalcoholic fatty liver disease (NAFLD) is defined by excessive lipid accumulation in the liver and involves an ample spectrum of liver diseases, ranging from simple uncomplicated steatosis to cirrhosis and hepatocellular carcinoma. Accumulating evidence demonstrates that high fructose intake enhances NAFLD development and progression promoting inhibition of mitochondrial β-oxidation of long-chain fatty acids and oxidative damages. L-Carnitine (LC), involved in β-oxidation, has been used to reduce obesity caused by high-fat diet, which is beneficial to ameliorating fatty liver diseases. Moreover, in the recent years, various studies have established LC anti-oxidative proprieties. The objective of this study was to elucidate primarily the underlying anti-oxidative mechanisms of LC in an in vitro model of fructose-induced liver steatosis.

METHODS

Human hepatoma HepG2 cells were maintained in medium supplemented with LC (5 mM LC) with or without 5 mM fructose (F) for 48 h and 72 h. In control cells, LC or F was not added to medium. Fat deposition, anti-oxidative, and mitochondrial homeostasis were investigated.

RESULTS

LC supplementation decreased the intracellular lipid deposition enhancing AMPK activation. However, compound C (AMPK inhibitor-10 μM), significantly abolished LC benefits in F condition. Moreover, LC, increasing PGC1 α expression, ameliorates mitochondrial damage-F induced. Above all, LC reduced ROS production and simultaneously increased protein content of antioxidant factors, SOD2 and Nrf2.

CONCLUSION

Our data seemed to show that LC attenuate fructose-mediated lipid accumulation through AMPK activation. Moreover, LC counteracts mitochondrial damages and reactive oxygen species production restoring antioxidant cellular machine. These findings provide new insights into LC role as an AMPK activator and anti-oxidative molecule in NAFLD.

An artificial tear containing flaxseed oil for treating dry eye disease: A randomized controlled trial

PURPOSE

To evaluate the efficacy and safety of a nano-emulsion artificial tear (OM3) containing carboxymethylcellulose (CMC) and glycerin, flaxseed oil and castor oil, and three osmoprotectants (levocarnitine, erythritol, and trehalose) compared with an artificial tear (Refresh Optive Advanced [ROA]) containing the same ingredients with the exception of trehalose and flaxseed oil.

METHODS

In this multicenter, double-masked, randomized, two-arm, parallel-group, 6-visit study (screening, baseline, and days 7, 30, 60, and 90), subjects with dry eye disease underwent an open-label, 7-day run-in with CMC 0.5% (Refresh Plus), before 1:1 randomization to OM3 or ROA for 90 days (both instilled ≥2 daily). Ocular Surface Disease Index (OSDI; primary endpoint change from baseline at day 90), tear film breakup time (TBUT), and ocular staining (combined/corneal/conjunctival) were assessed; change from baseline in these parameters was calculated at each timepoint. Treatment-related adverse events (AEs) were assessed at each visit.

RESULTS

Overall, 242 subjects were randomized (OM3, n = 120; ROA, n = 122). At day 90, significant improvements in OSDI, ocular staining and TBUT were evident in both treatment groups. Significant (P < 0.05) between-group differences in favor of OM3 were observed for combined ocular staining (all timepoints), corneal staining (day 90), and conjunctival staining (day 30). Treatment-related AEs were higher in the ROA (9.8%) versus OM3 (6.7%) group; blurred vision was among the most commonly reported AE (OM3 0% vs ROA 4.1%).

CONCLUSION

These findings support the application of OM3, a novel preservative-free, nano-emulsion tear formulation with trehalose and flaxseed oil, for the treatment of dry eye disease.

Anti-inflammatory effects of paeoniflorin from Paeonia lactiflora Pall. on human corneal epithelial cells and a mouse model of dry eye disease

Dry eye disease (DED) is characterized by increased osmolality of tears due to a lack of production or increased evaporation of tears.

Levels of oxidative DNA damage are low in ex vivo engineered human limbal epithelial tissue

PURPOSE

To examine levels of oxidative DNA base damage and expression of selected genes and proteins related to DNA damage repair in human limbal epithelium engineered ex vivo.

METHODS

Cells were expanded from limbal tissue on cell culture-treated inserts in medium containing fetal bovine serum, recombinant growth factors, hormones and cholera toxin (COM) and in medium with human serum as the single growth-promoting additive (HS). Cells were analysed after two, three and four weeks in culture for DNA strand breaks and oxidized purine bases (Comet assay using the enzyme formamidopyrimidine DNA glycosylase, Fpg) and for expression of DNA repair enzymes APE1, OGG1 and Polβ by in situ hybridization (ISH) and by immunohistochemistry (IHC).

RESULTS

Levels of strand breaks were substantial while levels of net Fpg-sensitive sites (8-oxoguanine and ring-opened FaPy bases) were relatively low in cells engineered in COM and in HS. Both types of medium were found to support expression of base excision repair (BER) enzymes APE1, OGG1 and Polβ at the gene level. At the protein level, expression of APE1 and OGG1 was noticeable in both conditions while expression of Polβ was low.

CONCLUSION

Our findings indicate low levels of oxidative stress and/or efficient DNA purine base damage repair in human limbal epithelium engineered in a medium with human serum as the single growth-promoting additive as well as in traditional medium with xenobiotics.

Different Effects of Pro-Inflammatory Factors and Hyperosmotic Stress on Corneal Epithelial Stem/Progenitor Cells and Wound Healing in Mice

Chronic inflammation and severe dry eye are two important adverse factors for the successful transplant of cultured limbal stem cells. The aim of this study was to investigate the effects of inflammation and hyperosmotic stress (a key pathological factor in dry eye) on corneal epithelial stem cells (CESCs) and corneal epithelial wound healing. We observed that the CESCs exhibited significant morphological changes when treated with interleukin‐1 beta (IL‐1β), tumor necrosis factor alpha (TNF‐α), or hyperosmotic stress. Colony‐forming efficiency or colony‐forming size was decreased with the increasing concentrations of IL‐1β, TNF‐α, or hyperosmotic stress, which was exacerbated when treated simultaneously with pro‐inflammatory factors and hyperosmotic stress. However, the colony‐forming capacity of CESCs recovered more easily from pro‐inflammatory factor treatment than from hyperosmotic stress treatment. Moreover, when compared with pro‐inflammatory factors treatment, hyperosmotic stress treatment caused a more significant increase of apoptotic and necrotic cell numbers and cell cycle arrest in the G2/M phase. Furthermore, the normal ability of corneal epithelial wound healing in the mice model was suppressed by both pro‐inflammatory factors and hyperosmotic stress treatment, and especially severely by hyperosmotic stress treatment. In addition, inflammation combined with hyperosmotic stress treatment induced more serious epithelial repair delays and apoptosis in corneal epithelium. Elevated levels of inflammatory factors were found in hyperosmotic stress‐treated cells and mice corneas, which persisted even during the recovery period. The results suggested that pro‐inflammatory factors cause transient inhibition, while hyperosmotic stress causes severe apoptosis and necrosis, persistent cell cycle arrest of CESCs, and severe corneal wound healing delay. Stem Cells Translational Medicine2019;8:46–57

Dry eye disease and oxidative stress

Dry eye, an age-related condition, is a multifactorial disease of the tears and ocular surface that results in symptoms of discomfort, visual disturbance and tear film instability. Environmental factors are also often implicated in dry eye including exposure to pollutants, ultraviolet (UV) radiation and ozone as well as the chronic use of preserved eyedrops such as in the treatment of glaucoma. These factors increase oxidative stress and ocular surface inflammation. Here, we reviewed the cellular, animal and clinical studies that point to the role of oxidative stress in dry eye disease. The biomarkers used to indicate oxidative damage in ocular surface tissues include 8-hydroxy-2 deoxyguanosine (8-OHdG), 4-hydroxynonenal (HNE) and malondialdehyde (MDD). Antioxidative defences in the ocular surface occur in the form of tear proteins such as lactoferrin and S100A proteins, and enzymes such as superoxide dismutase (SOD), peroxidase, catalase and mitochondrial oxidative enzymes. An imbalance between the level of reactive oxygen species (ROS) and the action of protective enzymes will lead to oxidative damage, and possibly inflammation. A small number of interventional studies suggest that oxidative stress may be directly targeted in topical therapy of dry eye treatment. For example, in vitro studies suggest that L-carnitine and pterostilbene, a blueberry component may reduce oxidative stress, and in animal studies, alpha-lipoic acid (ALP) and selenoprotein P may be helpful. Examples of treatments used in clinical trials include vitamin B12 eyedrops and iodide iontophoresis. With recent emphasis on ageing medicine and preventive holistic health, as well as the role of environmental science, research on oxidative stress in the ocular surface is likely to have increasing impact in the coming years.

Combination of hyaluronic acid, carmellose, and osmoprotectants for the treatment of dry eye disease

Background

Dry Eye Disease (DED) is a multifactorial disease, with a high prevalence, that can have a great impact on the quality of life of patients. The first step of treatment includes the use of lacrimal substitutes composed of polymers, possible to associate osmoprotectant agents to the lacrimal substitutes. The aim of this article is to analyze the properties of the combination of hyaluronic acid (HA), carmellose, and osmoprotectors (Optava Fusion^®; Allergan, Inc., Irvine, CA, USA) on DED. General considerations on the use of artificial tears are also proposed.

Methods

A group of ophthalmologists, experts in the management of the ocular surface, analyzed different aspects related to DED; among them, the use of artificial tears in general and the properties of the combination of HA, carmellose, and osmoprotectors, in particular, were discussed. A review of the literature was carried out, which included different articles published in Spanish, English, and French until April 2017.

Conclusions

DED is a common chronic pathology that usually requires sustained treatment. In addition, the combination of HA, carmellose, and osmoprotectors has proven to be effective in the treatment of symptoms and signs of dry eye by the synergistic action of all its components. This review provides key elements to help ophthalmologists who begin in the management of DED.

Matrix regeneration agents improve wound healing in non-stressed human corneal epithelial cells

PurposeMatrix regenerating agents (RGTAs) emerged as promising in vivo wound-healing agents. These agents could prove beneficial for the treatment of dry eye disease-associated corneal micro-erosions; therefore, we aimed to evaluate the wound healing efficacy of regenerative agents (RGTAs or serum) in an in vitro model of hyperosmolarity (HO) stressed and non-stressed human corneal epithelial cells.Patients and methodsThe migration and proliferation induced by the regenerative agents was evaluated using an in vitro scratch wound assay and brome-deoxy-uridine incorporation. The inflammatory profile and effects of osmoregulators were also investigated. The two-tailed paired t-test calculated the statistical significance, with P-value<0.05 considered significant.ResultsThe most efficient inducer of re-epithelization was 2% serum, followed closely by 2% RGTA with an average improvement in cell migration of 1.8- and 1.4-fold, respectively, when compared with the non-treated control. Hyperosmolar stress significantly reduced the restorative effects of both serum and RGTAs; these effects were, however, neutralized by the osmoregulator betaine.ConclusionThese findings suggest that RGTAs could provide efficient treatment for dry-eye associated corneal micro-lesions if ocular surface HO is neutralized.

The Pathophysiology of Dry Eye Disease: What We Know and Future Directions for Research

Clinical and laboratory studies performed over the past few decades have discovered that dry eye is a chronic inflammatory disease that can be initiated by numerous extrinsic or intrinsic factors that promote an unstable and hyperosmolar tear film. These changes in tear composition, in some cases combined with systemic factors, lead to an inflammatory cycle that causes ocular surface epithelial disease and neural stimulation. Acute desiccation activates stress signaling pathways in the ocular surface epithelium and resident immune cells. This triggers production of innate inflammatory mediators that stimulate the production of matrix metalloprotease, inflammatory cell recruitment, and dendritic cell maturation. These mediators, combined with exposure of autoantigens, can lead to an adaptive T cell-mediated response. Cornea barrier disruption develops by protease-mediated lysis of epithelial tight junctions, leading to accelerated cell death; desquamation; an irregular, poorly lubricated cornea surface; and exposure and sensitization of epithelial nociceptors. Conjunctival goblet cell dysfunction and death are promoted by the T helper 1 cytokine interferon gamma. These epithelial changes further destabilize the tear film, amplify inflammation, and create a vicious cycle. Cyclosporine and lifitegrast, the 2 US Food and Drug Administration-approved therapies, inhibit T-cell activation and cytokine production. Although these therapies represent a major advance in dry eye therapy, they are not effective in improving discomfort and corneal epithelial disease in all patients. Preclinical studies have identified other potential therapeutic targets, biomarkers, and strategies to bolster endogenous immunoregulatory pathways. These discoveries will, it is hoped, lead to further advances in diagnostic classification and treatment.

Mitochondria-Targeted Antioxidant SkQ1 Prevents Anesthesia-Induced Dry Eye Syndrome

Dry eye syndrome (DES) is an age-related condition increasingly detected in younger people of risk groups, including patients who underwent ocular surgery or long-term general anesthesia. Being a multifactorial disease, it is characterized by oxidative stress in the cornea and commonly complicated by ocular surface inflammation. Polyetiologic DES is responsive to SkQ1, a mitochondria-targeted antioxidant suppressing age-related changes in the ocular tissues. Here, we demonstrate safety and efficacy of topical administration of SkQ1 at a dosage of 7.5 μM for the prevention of general anesthesia-induced DES in rabbits. The protective action of SkQ1 improves clinical state of the ocular surface by inhibiting apoptotic and prenecrotic changes in the corneal epithelium. The underlying mechanism involves the suppression of the oxidative stress supported by the stimulation of intrinsic antioxidant activity and the activity of antioxidant enzymes, foremost glutathione peroxidase and glutathione reductase, in the cornea. Furthermore, SkQ1 increases antioxidant activity and stability of the tear film and produces anti-inflammatory effect exhibited as downregulation of TNF-α and IL-6 and pronounced upregulation of IL-10 in tears. Our data suggest novel features of SkQ1 and point to its feasibility in patients with DES and individuals at risk for the disease including those subjected to general anesthesia.

In Vitro Inhibition of NFAT5-Mediated Induction of CCL2 in Hyperosmotic Conditions by Cyclosporine and Dexamethasone on Human HeLa-Modified Conjunctiva-Derived Cells

Purpose

To investigate the pro-inflammatory intracellular mechanisms induced by an in vitro model of dry eye disease (DED) on a Hela-modified conjunctiva-derived cells in hyperosmolarity (HO) stress conditions. This study focused on CCL2 induction and explored the implications of the nuclear factor of activated T-cells 5 (NFAT5) as well as mitogen-activated protein kinases (MAPK) and nuclear factor kappa B (NFĸB). This work was completed by an analysis of the effects of cyclosporine A (CsA), dexamethasone (Dex) and doxycycline (Dox) on HO-induced CCL2 and NFAT5 induction.

Methods

A human HeLa-modified conjunctiva-derived cell line was cultured in NaCl-hyperosmolar medium for various exposure times. Cellular viability, CCL2 secretion, NFAT5 and CCL2 gene expression, and intracytoplasmic NFAT5 were assessed using the Cell Titer Blue^® assay, enzyme-linked immunosorbent assay (ELISA), RT-qPCR and immunostaining, respectively. In selected experiments, inhibitors of MAPKs or NFκB, therapeutic agents or NFAT5 siRNAs were added before the hyperosmolar stimulations.

Results

HO induced CCL2 secretion and expression as well as NFAT5 gene expression and translocation. Adding NFAT5-siRNA before hyperosmolar stimulation led to a complete inhibition of CCL2 induction and to a decrease in cellular viability. p38 MAPK (p38), c-Jun NH₂-terminal kinase (JNK) and NFĸB inhibitors, CsA and Dex induced a partial inhibition of HO-induced CCL2, while Dox and extracellular signal-regulated kinase (ERK) inhibitor did not. Dex also induced a partial inhibition of HO-induced NFAT5 gene expression but not CsA or Dox.

Conclusions

These in vitro results suggest a potential role of CCL2 in DED and highlight the crucial role of NFAT5 in the pro-inflammatory effect of HO on HeLa-modified conjunctiva-derived cells, a rarely studied cellular type. This inflammatory pathway involving NFAT5 and CCL2 could offer a promising target for developing new therapies to treat DED, warranting further investigations to fully grasp the complete intracellular mechanisms.