Tear Film Amphiphilic and Anti-Inflammatory Lipids in Bovine Pink Eye

The Emerging Role of Ferroptosis in Sepsis, Opportunity or Challenge?

Sepsis is a syndrome in multi-organ dysfunction triggered by a deleterious immunological reaction of the body to a condition caused by infection, surgery, or trauma. Currently, sepsis is thought to be primarily associated with abnormal immune responses resulting in organ microcirculatory disturbances, cellular mitochondrial dysfunction, and induced cell death, although the exact pathogenesis of sepsis is still inconclusive. In recent years, the role of abnormal metabolism of trace nutrients in the pathogenesis of sepsis has been investigated. Ferroptosis is a type of cell death that relies on iron and is characterized by unique morphological, biochemical, and genetic features. Unlike other forms of cell death, such as autophagy, apoptosis, necrosis, and pyroptosis, ferroptosis is primarily driven by lipid peroxidation. Ferroptosis cells may be immunogenic, amplify inflammatory responses, cause more cell death, and ultimately induce multi-organ failure. An increasing number of studies have indicated the significance of ferroptosis in sepsis and its role in reducing inflammation. The effectiveness of sepsis treatment has been demonstrated by the use of drugs that specifically target molecules associated with the ferroptosis pathway, including ferroptosis inhibitors. Nevertheless, there is a scarcity of studies investigating the multi-organ dysfunction caused by ferroptosis in sepsis. This article presents a summary and evaluation of recent progress in the role of ferroptosis through molecularly regulated mechanisms and its potential mechanisms of action in the multi-organ dysfunction associated with sepsis. It also discusses the current challenges and prospects in understanding the connection between sepsis and ferroptosis, and proposes innovative ideas and strategies for the treatment of sepsis.

Sphingolipidomics of Bovine Pink Eye: A Pilot Study

Simple Summary

The liquid tear film, which protects the eye from the environment, is a dynamic fluid containing a large number of complex lipids. Disruptions of these lipids by infections can result in damage to the eye and ultimately blindness. In this study we characterized various lipid subfamilies present in the tear film of the eye and the effect of pink eye infections in cattle. Our findings demonstrate that the pink eye infections dramatically decrease the levels of lipids in the tear film covering the eye and suggest that this is a major factor in the development of blindness in infected cattle.

Abstract

Sphingolipids are essential structural components of tear film that protect the surface of the eye from dehydration. A detailed analysis of the effects of pink eye infections on the sphingolipidome in cattle has not previously been undertaken. We recently published a new assay utilizing high-resolution mass spectrometric monitoring of the chloride adducts of sphingolipids that provides enhanced sensitivity and specificity. Utilizing this assay, we monitored decreases in the levels of tear film ceramides with short-chain fatty acids, hydroxy-ceramides, phytoceramides, and hydroxy-phytoceramides. Dihydroceramide levels were unaltered and increased levels of ceramides with long-chain fatty acids (24:0 and 24:1) were monitored in cattle with pink eye. The data from this pilot study (n = 8 controls and 8 pink eye) demonstrate a major disruption of the lipid tear film layer in pink eye disease, that can result in severe eye irritation and damage.

Antimicrobial Tear Lipids in the Ocular Surface Defense

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.

Branched and linear fatty acid esters of hydroxy fatty acids (FAHFA) relevant to human health

Fatty acid esters of hydroxy fatty acids (FAHFAs) represent a complex lipid class that contains both signaling mediators and structural components of lipid biofilms in humans. The majority of endogenous FAHFAs share a common chemical architecture, characterized by an estolide bond that links the hydroxy fatty acid (HFA) backbone and the fatty acid (FA). Two structurally and functionally distinct FAHFA superfamilies are recognized based on the position of the estolide bond: omega-FAHFAs and in-chain branched FAHFAs. The existing variety of possible HFAs and FAs combined with the position of the estolide bond generates a vast quantity of unique structures identified in FAHFA families. In this review, we discuss the anti-diabetic and anti-inflammatory effects of branched FAHFAs and the role of omega-FAHFA-derived lipids as surfactants in the tear film lipid layer and dry eye disease. To emphasize potential pharmacological targets, we recapitulate the biosynthesis of the HFA backbone within the superfamilies together with the degradation pathways and the FAHFA regioisomer distribution in human and mouse adipose tissue. We propose a theoretical involvement of cytochrome P450 enzymes in the generation and degradation of saturated HFA backbones and present an overview of small-molecule inhibitors used in FAHFA research. The FAHFA lipid class is huge and largely unexplored. Besides the unknown biological effects of individual FAHFAs, also the enigmatic enzymatic machinery behind their synthesis could provide new therapeutic approaches for inflammatory metabolic or eye diseases. Therefore, understanding the mechanisms of (FA)HFA synthesis at the molecular level should be the next step in FAHFA research.

Dynamics of DHA and EPA supplementation: incorporation into equine plasma, synovial fluid, and surfactant glycerophosphocholines

INTRODUCTION

Horses with asthma or osteoarthritis frequently receive ω-3 fatty acid supplements. Docosahexaenoic (DHA; 22:6) and eicosapentaenoic (EPA; 20:5) acids are essential ω-3 fatty acid precursors of anti-inflammatory mediators and components of structural glycerophospholipids (GPL) that act as reservoirs of these fatty acids. Analysis of the incorporation of dietary DHA + EPA into GPL pools in different body compartments has not been undertaken in horses.

OBJECTIVES

We undertook a detailed study of dietary supplementation with DHA + EPA in horses and monitored incorporation into DHA- and EPA-containing glycerophosphocholines (GPC) 38:5, 38:6, 40:5, and 40:6 in plasma, synovial fluid (SF), and surfactant.

METHODS

Horses (n = 20) were randomly assigned to the supplement or control group and evaluated on days 0, 30, 60, and 90. GPC in plasma, SF, and surfactant were measured by high-resolution mass spectrometry with less than 3 ppm mass error. Validation of DHA and EPA incorporation into these GPC was conducted utilizing MS² of the [M + Cl]^- adducts of GPC.

RESULTS

Dietary supplementation resulted in augmented levels of GPC 38:5, 38:6, 40:5, and 40:6 in all compartments. Maximum incorporation into GPCs was delayed until 60 days. Significant increases in the levels of GPC 38:5, 40:5, and 40:6, containing docosapentaenoic acid (DPA; 22:5), also was noted.

CONCLUSIONS

DHA and EPA supplementation results in augmented storage pools of ω-3 essential fatty acids in SF and surfactant GPC. This has the potential to improve the ability of anti-inflammatory mechanisms to resolve inflammatory pathways in these critical compartments involved in arthritis and asthma.

Lipidomics of the chicken egg yolk: high-resolution mass spectrometric characterization of nutritional lipid families

While previous studies have characterized the fatty acids and global lipid families of the chicken egg yolk, there have been no publications characterizing the individual lipids in these lipid families. Such an in-depth characterization of egg yolk lipids is essential to define the potential benefits of egg yolk consumption for the supply of structural and anti-inflammatory lipids. Historically, the major focus has been on the cholesterol content of eggs and the potential negative health benefits of this lipid, while ignoring the essential roles of cholesterol in membranes and as a precursor to other essential sterols. A detailed analysis of egg yolk lipids, using high-resolution mass spectrometric analyses and tandem mass spectrometry to characterize the fatty acid substituents of complex structural lipids, was used to generate the first in-depth characterization of individual lipids within lipid families. Egg yolks were isolated from commercial eggs (Full Circle Market) and lipids extracted with methyl-t-butylether before analyses via high-resolution mass spectrometry. This analytical platform demonstrates that chicken egg yolks provide a rich nutritional source of complex structural lipids required for lipid homeostasis. These include dominant glycerophosphocholines (GPC) (34:2 and 36:2), plasmalogen GPC (34:1, 36:1), glycerophosphoethanolamines (GPE) 38:4 and 36:2), plasmalogen GPE (36:2 and 34:1), glycerophosphoserines (36:2 and 38:4), glycerophosphoinositols (38:4), glycerophosphoglycerols (36:2), N-acylphosphatidylethanolamines (NAPE) (56:6), plasmalogen NAPE (54:4 and 56:6), sphingomyelins (16:0), ceramides (22:0 and 24:0), cyclic phosphatidic acids (16:0 and 18:0), monoacylglycerols (18:1 and 18:2), diacylglycerols (36:3 and 36:2), and triacylglycerols (52:3). Our data indicate that the egg yolk is a rich source of structural and energy-rich lipids. In addition, the structural lipids possess ω-3 and ω-6 fatty acids that are essential precursors of endogenous anti-inflammatory lipid mediators. These data indicate that eggs are a valuable nutritional addition to the diets of individuals that do not have cholesterol issues.

Fatty Acyl Esters of Hydroxy Fatty Acid (FAHFA) Lipid Families

Fatty Acyl esters of Hydroxy Fatty Acids (FAHFA) encompass three different lipid families which have incorrectly been classified as wax esters. These families include (i) Branched-chain FAHFAs, involved in the regulation of glucose metabolism and inflammation, with acylation of an internal branched-chain hydroxy-palmitic or -stearic acid; (ii) ω-FAHFAs, which function as biosurfactants in a number of biofluids, are formed via acylation of the ω-hydroxyl group of very-long-chain fatty acids (these lipids have also been designated as o-acyl hydroxy fatty acids; OAHFA); and (iii) Ornithine-FAHFAs are bacterial lipids formed by the acylation of short-chain 3-hydroxy fatty acids and the addition of ornithine to the free carboxy group of the hydroxy fatty acid. The differences in biosynthetic pathways and cellular functions of these lipid families will be reviewed and compared to wax esters, which are formed by the acylation of a fatty alcohol, not a hydroxy fatty acid. In summary, FAHFA lipid families are both unique and complex in their biosynthesis and their biological actions. We have only evaluated the tip of the iceberg and much more exciting research is required to understand these lipids in health and disease.