Oxidative Stress in the Protection and Injury of the Lacrimal Gland and the Ocular Surface: are There Perspectives for Therapeutics?

Camila Nunes Lemos,Monica Alves,Adriana De Andrade Batista Murashima,Leidiane Adriano,Eduardo Melani Rocha,Lilian Eslaine Costa Mendes Da Silva,Marina Zilio Fantucci,Jacqueline Ferreira Faustino

doi:10.3389/fcell.2022.824726

Abstract

Oxidative stress (OS) is a major disruption in the physiology of the lacrimal functional unit (LFU). Antioxidant enzymes have dual protective activities: antioxidant and antimicrobial activities. Peroxidases have been indistinctly used as markers of the secretory activity of the LFU and implicated in the pathophysiology, diagnosis and treatment of dry eye disease (DED), even though they comprise a large family of enzymes that includes lactoperoxidase (LPO) and glutathione peroxidase (GPO), among others. Assays to measure and correlate OS with other local LFU phenomena have methodological limitations. Studies implicate molecules and reactions involved in OS as markers of homeostasis, and other studies identify them as part of the physiopathology of diseases. Despite these conflicting concepts and observations, it is clear that OS is influential in the development of DED. Moreover, many antioxidant strategies have been proposed for its treatment, including calorie restriction to nutritional supplementation. This review offers a critical analysis of the biological mechanisms, diagnostic outcomes, drug use, dietary supplements, and life habits that implicate the influence of OS on DED.

Highlights

Oxidative stress (OS) takes part in both the protection and injury to the lacrimal functional unit (LFU) (Bron and Seal 1986; Stern et al, 2004; Davies et al, 2008; Uchino et al, 2012; Wakamatsu et al, 2013)
It is clear that OS and the expression of the antioxidant elements in the LFU is a growing research field for understanding the mechanisms of dry eye (DE), the ocular surface response to environmental aggression, and autoimmune mechanisms such as those observed in s Syndrome (SS)
Biomarkers are still limited in identifying disease mechanisms due to lack of specificity and differences in tissues and species expression, as well as in the duration of diseases

Summary

INTRODUCTION

Oxidative stress (OS) takes part in both the protection and injury to the lacrimal functional unit (LFU) (Bron and Seal 1986; Stern et al, 2004; Davies et al, 2008; Uchino et al, 2012; Wakamatsu et al, 2013). Other enzymes associated with antimicrobial, antioxidant, and chemical scavenger functions were found in the LG, tear secretion, and the ocular surface These include peroxidase isoforms, lactoferrin, and lysozyme, and their expression has been associated with age-related diseases (McGill et al, 1984; De et al, 1987; Gogia et al, 1998; Higuchi et al, 2012; Soria et al, 2017). Enzymatic investigations using samples of the LG showed that those samples were capable of catalyzing the free radical hydrogen peroxide (H2O2) into water and oxygen in vitro after blocking peroxidase activity This confirms the presence of catalase in the LG, assuming that it is a constitutive enzyme of this gland but not a substantial part of the secretory elements of the tear film (Herzog and Fahimi 1976). To deeply understand these paradoxes, it is important to evaluate the biomedical literature in the following topics: 1) available peroxidase assays and limitations; 2) clinical evidence of a relationship between ROS and disease; and 3) potential therapeutic approaches

LIMITATIONS

Limitations

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CONCLUSION

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METHOD OF LITERATURE SEARCH