Lipid Oxidation Derived Aldehydes and Oxysterols Between Health and Disease

Lipid peroxidation can be described generally as a process under which oxidants such as free radicals attack lipids containing carbon-carbon double bond(s), especially polyunsaturated fatty acids (PUFAs). Over the last four decades, an extensive body of literature regarding lipid peroxidation has shown its important role in cell biology and human health. Since the early 1970s, the total published research articles on the topic of lipid peroxidation was 98 (1970–1974) and has been increasing at almost 135-fold, by up to 13165 in last 4 years (2010–2013). New discoveries about the involvement in cellular physiology and pathology, as well as the control of lipid peroxidation, continue to emerge every day. Given the enormity of this field, this review focuses on biochemical concepts of lipid peroxidation, production, metabolism, and signaling mechanisms of two main omega-6 fatty acids lipid peroxidation products: malondialdehyde (MDA) and, in particular, 4-hydroxy-2-nonenal (4-HNE), summarizing not only its physiological and protective function as signaling molecule stimulating gene expression and cell survival, but also its cytotoxic role inhibiting gene expression and promoting cell death. Finally, overviews of in vivo mammalian model systems used to study the lipid peroxidation process, and common pathological processes linked to MDA and 4-HNE are shown.

Interferons (IFN) are essential antiviral cytokines that establish the cellular antiviral state through upregulation of hundreds of interferon-stimulated genes (ISGs), most of which have uncharacterized functions and mechanisms. We identified cholesterol-25-hydroxylase (CH25H) as a broadly antiviral ISG. CH25H converts cholesterol to a soluble antiviral factor, 25-hydroxycholesterol (25HC). 25HC treatment in cultured cells broadly inhibited growth of enveloped viruses including VSV, HSV, HIV, and MHV68 and acutely pathogenic EBOV, RVFV, RSSEV, and Nipah viruses under BSL4 conditions. It suppressed viral growth by blocking membrane fusion between virus and cell. In animal models, Ch25h-deficient mice were more susceptible to MHV68 lytic infection. Moreover, administration of 25HC in humanized mice suppressed HIV replication and reversed T cell depletion. Thus, our studies demonstrate a unique mechanism by which IFN achieves its antiviral state through the production of a natural oxysterol to inhibit viral entry and implicate membrane-modifying oxysterols as potential antiviral therapeutics. Copyright © 2013 Elsevier Inc. All rights reserved.

n-3 Fatty acids have important visual, mental, and cardiovascular health benefits throughout the life cycle. Biodistribution, interconversion, and dose response data are reviewed herein to provide a basis for more rational n-3 dose selections. Docosahexaenoic acid (DHA) is the principal n-3 fatty acid in tissues and is particularly abundant in neural and retinal tissue. Limited storage of the n-3 fatty acids in adipose tissue suggests that a continued dietary supply is needed. A large proportion of dietary alpha-linolenic acid (ALA) is oxidized, and because of limited interconversion of n-3 fatty acids in humans, ALA supplementation does not result in appreciable accumulation of long-chain n-3 fatty acids in plasma. Eicosapentaenoic acid (EPA) but not DHA concentrations in plasma increase in response to dietary EPA. Dietary DHA results in a dose-dependent, saturable increase in plasma DHA concentrations and modest increases in EPA concentrations. Plasma DHA concentrations equilibrate in approximately 1 mo and then remain at steady state throughout supplementation. DHA doses of approximately 2 g/d result in a near maximal plasma response. Both dietary DHA and EPA reduce plasma arachidonic acid concentrations. Tissue contents of DHA and EPA also increase in response to supplementation with these fatty acids. Human milk contents of DHA are dependent on diet, and infant DHA concentrations are determined by their dietary intake of this fatty acid. We conclude that the most predictable way to increase a specific long-chain n-3 fatty acid in plasma, tissues, or human milk is to supplement with the fatty acid of interest.