Antimicrobial Tear Lipids in the Ocular Surface Defense

Abstract

The concept of antimicrobial lipids as effectors of innate host defense is an emerging field. There is limited knowledge on the antimicrobial role of lipids in the ocular environment. Tears act as first line of defense to protect the ocular surface from infections. Antimicrobial effects of tear lipids have been demonstrated using meibomian lipids that are the source of majority of lipids in tears. This article describes the knowledge available on the antimicrobial role of tear lipids at the ocular surface and the antimicrobial potential of various lipid classes present in tears that can contribute to antimicrobial protection of the eye. Like other mucosal secretions, tears contain many proteins and lipids with known antimicrobial effects. The antimicrobial defense of tears is far stronger than can be demonstrated by the effects of individual compounds many of which are present in low concentrations but synergistic and additive interactions between them provide substantial antimicrobial protection to the ocular surface. It is inferred that antimicrobial lipids play important role in innate defense of tears, and cooperative interactions between various antimicrobial lipids and proteins in tears provide a potent host defense mechanism that is effective against a broad spectrum of pathogens and renders self-sterilizing properties to tears for keeping the microbial load low at the ocular surface.

Development of an Ex Vivo Porcine Eye Model for Exploring the Pathogenicity of Acanthamoeba

“…The human cornea also has several physical and chemical mechanisms that enable it to resist infection by external pathogens [ 26 ]. The amoebae would normally be removed through the blinking action of the eyes [ 27 ].…”

Integrated multi-omics and machine learning approach reveals lipid metabolic biomarkers and signaling in age-related meibomian gland dysfunction

“…Reduction in ChE can inversely influence the melting point of meibum, leading to an increase in meibum viscosity characteristic of MGD [49] . In addition, there is increasing evidence that ChE may serve multiple immunological roles and impart antimicrobial protection to the ocular surface [50] , [51] . Through UPLC Orbitrap mass spectrometry system, our lipidomic results revealed a decline in the proportion of saturated ChE and TG during the aging process.…”

Tear Biomarkers in Alzheimer’s and Parkinson’s Diseases, and Multiple Sclerosis: Implications for Diagnosis (Systematic Review)

“…Among the proteins detected are growth factors [ 16 , 17 ], cytokines [ 18 ], matrix metalloproteinases [ 19 ], immunoglobulins [ 20 , 21 , 22 , 23 ], sex hormones [ 24 , 25 , 26 , 27 , 28 ], proteases and protease inhibitors [ 29 , 30 , 31 , 32 , 33 ], calcium-binding proteins [ 34 , 35 ], and glycoproteins [ 36 , 37 , 38 ]. The tear film lipid layer (TFLL) acts as an interface between the aqueous layer and air and is the composition of different types of lipids, including cholesteryl esters (CE), wax esters (WE), and triacylglycerol (TAG) [ 17 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ]. In tears, circulating microRNAs (cimiRNAs) as potential biomarkers were also found [ 46 ].…”