Retinal tissue develops an inflammatory reaction to tobacco smoke and electronic cigarette vapor in mice

Modeling complex age-related eye disease

Modeling complex eye diseases like age-related macular degeneration (AMD) and glaucoma poses significant challenges, since these conditions depend highly on age-related changes that occur over several decades, with many contributing factors remaining unknown. Although both diseases exhibit a relatively high heritability of >50%, a large proportion of individuals carrying AMD- or glaucoma-associated genetic risk variants will never develop these diseases. Furthermore, several environmental and lifestyle factors contribute to and modulate the pathogenesis and progression of AMD and glaucoma. Several strategies replicate the impact of genetic risk variants, pathobiological pathways and environmental and lifestyle factors in AMD and glaucoma in mice and other species. In this review we will primarily discuss the most commonly available mouse models, which have and will likely continue to improve our understanding of the pathobiology of age-related eye diseases. Uncertainties persist whether small animal models can truly recapitulate disease progression and vision loss in patients, raising doubts regarding their usefulness when testing novel gene or drug therapies. We will elaborate on concerns that relate to shorter lifespan, body size and allometries, lack of macula and a true lamina cribrosa, as well as absence and sequence disparities of certain genes and differences in their chromosomal location in mice. Since biological, rather than chronological, age likely predisposes an organism for both glaucoma and AMD, more rapidly aging organisms like small rodents may open up possibilities that will make research of these diseases more timely and financially feasible. On the other hand, due to the above-mentioned anatomical and physiological features, as well as pharmacokinetic and -dynamic differences small animal models are not ideal to study the natural progression of vision loss or the efficacy and safety of novel therapies. In this context, we will also discuss the advantages and pitfalls of alternative models that include larger species, such as non-human primates and rabbits, patient-derived retinal organoids, and human organ donor eyes.

Combustion conditions influence toxicity of flame-generated soot to ocular (ARPE-19) cells

Soot is a prevalent aerosol found both indoors and outdoors that has several sources, such as natural (e.g., wildfires), civilian (e.g., cooking), or military (e.g., burn pit operation). Additionally, within the sources, factors that influence the physicochemical properties of the soot include combustion temperature, oxygen availability, and fuel type. Being able to reproduce soot in the laboratory and systematically assess its toxicity is important in the pursuit of elucidating pathologies associated with its exposure. Of the organs of interest, we targeted the eye given the scant attention received. Yet, air pollution constituents such as soot have been linked to diseases such as age-related macular degeneration and proliferative vitreoretinopathy. We developed a bench-scale system to synthesize different types of soot, that is, soot with a systematically varied physical attributes or chemical composition. We used common analytical techniques to probe such properties, and used statistical analyses to correlate them with toxicity in vitro using ARPE-19 cells. Within the range of flame conditions studied, we find that soot toxicity increases with increasing oxygen concentration in fuel-rich premixed flames, and weakly increases with decreasing flame temperature. Additionally, soot particles produced in premixed flames are generally smaller in size, exhibit a lesser fractal structure, and are considerably more toxic to ARPE-19 cells than soot particles produced in non-premixed flames.

Ocular Symptoms in Adolescents and Young Adults With Electronic Cigarette, Cigarette, and Dual Use

Importance

Despite increasing use of cigarettes and electronic cigarettes (e-cigarettes) and related health effects among youth, few studies have reported their effects on eyes.

Objective

To examine the frequency and severity of ocular symptoms (ocular discomfort, pain, burning, itching, redness, dryness, glare, blurriness, strain, and headaches) in young e-cigarette and cigarette users.

Design, Setting, and Participants

In an observational cross-sectional study, a survey conducted in May 6 to 14, 2020, asked participants about use (ever, past 30 days, and past 7 days) of e-cigarettes and cigarettes. The participants included US individuals aged 13 to 24 years.

Main Outcomes and Measures

Associations between vision-related outcomes (general vision, severity/frequency of ocular symptoms) and tobacco use were analyzed using weighted multivariable logistic regressions, adjusting for sociodemographic factors, contact lens use, and other combustible use.

Results

There were 2168 never users, 2183 ever users, 1092 past 30-day users, and 919 past 7-day users of e-cigarettes; 55.9% of e-cigarette ever users also used cigarettes (dual users). Of the 4351 respondents, 63.8% identified as female, and mean (SD) age was 19.1 (2.9) years. Between 1.1% and 3.9% of ever dual users reported severe to very severe ocular symptoms; between 0.9% and 4.3% reported daily symptoms, which was higher than the proportion of symptoms in e-cigarette- or cigarette-only users. Past 7-day dual users had more severe itching (adjusted odds ratio [AOR], 2.37; 95% CI, 1.36-4.13; P = .002), redness (AOR, 2.58; 95% CI, 1.50-4.46; P = .001), dryness (AOR, 2.89; 95% CI, 1.64-5.08; P < .001), glare (AOR, 2.56; 95% CI, 1.50-4.35; P = .001), blurriness (AOR, 2.47; 95% CI, 1.36-4.50; P = .003), headaches (AOR, 2.31; 95% CI, 1.34-4.00; P = .003); and more frequent pain (AOR, 3.45; 95% CI, 2.09-5.68; P < .001), burning (AOR, 3.08; 95% CI, 1.86-5.09; P < .001), and redness (AOR, 2.72; 95% CI, 1.69-4.36; P < .001) than all other participants. Past 30-day dual users had more severe dryness (AOR, 2.65; 95% CI, 1.61-4.36; P < .001) and more frequent pain (AOR, 3.33; 95% CI, 2.12-5.21; P < .001) than all other participants. Ever dual users experienced more severe dryness (AOR, 1.60; 95% CI, 1.05-2.43; P = .03) and blurriness (AOR, 1.79; 95% CI, 1.21-2.64; P = .003) and more frequent pain (AOR, 1.69; 95% CI, 1.13-2.53; P = .01) and blurriness (AOR, 1.63; 95% CI, 1.13-2.36; P = .009) than never users.

Conclusions and Relevance

In this cross-sectional US study, adolescents and young adult users of both e-cigarettes and cigarettes had a higher likelihood of experiencing severe and frequent ocular symptoms, with past 7-day users reporting more symptoms than past 30-day users or ever users. These findings provide additional reasons for users of e-cigarettes and cigarettes to reduce their tobacco use to possibly prevent or minimize ocular symptoms.

Oxidative Stress and Antioxidants in Age-Related Macular Degeneration

Oxidative stress plays a crucial role in aging-related eye diseases, including age-related macular degeneration (AMD), cataracts, and glaucoma. With age, antioxidant reparative capacity decreases, and excess levels of reactive oxygen species produce oxidative damage in many ocular cell types underling age-related pathologies. In AMD, loss of central vision in the elderly is caused primarily by retinal pigment epithelium (RPE) dysfunction and degeneration and/or choroidal neovascularization that trigger malfunction and loss of photo-sensing photoreceptor cells. Along with various genetic and environmental factors that contribute to AMD, aging and age-related oxidative damage have critical involvement in AMD pathogenesis. To this end, dietary intake of antioxidants is a proven way to scavenge free radicals and to prevent or slow AMD progression. This review focuses on AMD and highlights the pathogenic role of oxidative stress in AMD from both clinical and experimental studies. The beneficial roles of antioxidants and dietary micronutrients in AMD are also summarized.

Role of Oxidative Stress in Ocular Diseases: A Balancing Act

Redox homeostasis is a delicate balancing act of maintaining appropriate levels of antioxidant defense mechanisms and reactive oxidizing oxygen and nitrogen species. Any disruption of this balance leads to oxidative stress, which is a key pathogenic factor in several ocular diseases. In this review, we present the current evidence for oxidative stress and mitochondrial dysfunction in conditions affecting both the anterior segment (e.g., dry eye disease, keratoconus, cataract) and posterior segment (age-related macular degeneration, proliferative vitreoretinopathy, diabetic retinopathy, glaucoma) of the human eye. We posit that further development of therapeutic interventions to promote pro-regenerative responses and maintenance of the redox balance may delay or prevent the progression of these major ocular pathologies. Continued efforts in this field will not only yield a better understanding of the molecular mechanisms underlying the pathogenesis of ocular diseases but also enable the identification of novel druggable redox targets and antioxidant therapies.

A critical review on air pollutant exposure and age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of visual impairments and blindness worldwide in the elderly and its incidence strongly increases with ages. The etiology of AMD is complex and attributed to the genetic modifiers, environmental factors and gene-environment interactions. Recently, the impacts of air pollution on the development of eye diseases have become the new area of focus, and disordered air exposure combined with inadequate health management has caused problems for the eye health, such as dry eye, glaucoma, and retinopathy, while its specific role in the occurrence of AMD is still not well understood. In order to summarize the progress of this research field, we performed a critical review to summarize the epidemiological and mechanism evidence on the association between air pollutants exposure and AMD. This review documented that exposure to air pollutants will accelerate or worsen the morbidity and prevalence of AMD. Air pollutants exposure may change the homeostasis, interfere with the inflammatory response, and take direct action on the lipid metabolism and oxidative stress in the macula. More attention should be given to understanding the impact of ambient air pollution on AMD worldwide.

Effects of E-Cigarette Refill Liquid Flavorings with and without Nicotine on Human Retinal Pigment Epithelial Cells: A Preliminary Study

Smoking is an etiologic factor for age-related macular degeneration (AMD). Although cigarette smoke has been extensively researched for retinal pigment epithelial (RPE) cell degeneration, the potential for adverse effects on the retinal epithelium following exposure to flavored e-cigarette refill liquid has never been explored. In this preliminary study, we have examined the effects of 20 e-liquids (10 different flavored nicotine-free and 10 nicotine-rich e-liquids) used in e-cigarettes on the metabolic activity, membrane integrity, and mitochondrial membrane potential of RPE cells. Our results showed that of the flavors studied over the concentration range: 0.5, 1, and 2% v/v for a duration of 48 h, cinnamon was the most toxic and menthol was the second most toxic, while other flavors showed lesser or no cytotoxicity. The presence of nicotine augmented cytotoxicity for cinnamon, menthol, strawberry, vanilla, and banana while for other flavors there was no synergism. Together, our results demonstrate that exposure of RPE to flavored e-cigarette refill liquids caused significant cytotoxicity and may be a risk factor for the development of retinal pathogenesis, although further in-depth studies are necessary.