Ethanol and lipid metabolic signaling

Episodic binge ethanol exposure impairs murine macrophage infiltration and delays wound closure by promoting defects in early innate immune responses

BACKGROUND

Exacerbation of cutaneous wound infections and delayed wound closure are frequent complications seen in alcohol exposed subjects who sustain injuries. We previously reported that acute alcohol exposure alters the early dermal inflammatory phase of wound healing and also several parameters of the proliferative wound healing phase in wounds from ethanol (EtOH)-treated mice for several days or weeks after EtOH exposure. Hence, it is likely that the cumulative defects arising in the early phases of the wound healing process directly contribute to the increased complications observed in intoxicated patients at the time of injury.

METHODS

C57BL/6 mice were given intraperitoneal EtOH (2.2 g/kg body weight) or vehicle (saline) EtOH using our episodic binge EtOH exposure protocol (3 days EtOH, 4 days off, 3 days EtOH) to yield a blood alcohol concentration (BAC) of 300 mg/dl at the time of wounding. Mice were subjected to six 3 mm full-thickness dorsal wounds and immediately treated topically with 10 μl of sterile saline (control) or diluted Staphylococcus aureus corresponding to 1 × 10(4) CFU/wound. Wounds were harvested at 24 hours post injury to evaluate wound area, neutrophil and macrophage accumulation, and the protein levels of cytokines, interleukin-6 (IL-6), IL-1β, and IL-10, and chemokines, macrophage inflammatory protein-2 (MIP-2) and MIP-1α, monocyte chemotactic protein-1 (MCP-1), and keratinocyte-derived chemokine (KC). The abundance and localization of cathelicidin-related antimicrobial peptide (CRAMP) and the kallikrein epidermal proteases (KLK5 and KLK7) were also determined.

RESULTS

Compared to control mice, EtOH-treated mice exhibited delayed wound closure, decreased macrophage accumulation, and impaired production of MIP-1α. Furthermore, skin from EtOH-treated mice demonstrated a reduction in the abundance of epidermal CRAMP and KLK7.

CONCLUSIONS

These findings suggest that EtOH exposure hinders several distinct components of the innate immune response, including phagocyte recruitment and chemokine/cytokine and AMP production. Together, these effects likely contribute to delayed wound closure and enhanced infection severity observed in intoxicated patients.

Heritability and inter-population differences in lipid profiles of Drosophila melanogaster

Characterizing and understanding the complex spectrum of lipids in higher organisms lags far behind our analysis of genome and transcriptome sequences. Here we generate and evaluate comprehensive lipid profiles (>200 lipids) of 92 inbred lines from five different Drosophila melanogaster populations. We find that the majority of lipid species are highly heritable, and even lipids with odd-chain fatty acids, which cannot be generated by the fly itself, also have high heritabilities. Abundance of the endosymbiont Wolbachia, a potential provider of odd-chained lipids, was positively correlated with this group of lipids. Additionally, we show that despite years of laboratory rearing on the same medium, the lipid profiles of the five geographic populations are sufficiently distinct for population discrimination. Our data predicts a strikingly different membrane fluidity for flies from the Netherlands, which is supported by their increased ethanol tolerance. We find that 18% of lipids show strong concentration differences between males and females. Through an analysis of the correlation structure of the lipid classes, we find modules of co-regulated lipids and begin to associate these with metabolic constraints. Our data provide a foundation for developing associations between variation in lipid composition with variation in other metabolic attributes, with genome-wide variation, and with metrics of health and overall reproductive fitness.

Phosphatidylethanol in blood as a marker of chronic alcohol use: a systematic review and meta-analysis

The present paper aims at a systematic review of the current knowledge on phosphatidylethanol (PEth) in blood as a direct marker of chronic alcohol use and abuse. In March 2012, the search through “MeSH” and “free-text” protocols in the databases Medline/PubMed, SCOPUS, Web of Science, and Ovid/Embase, combining the terms phosphatidylethanol and alcohol, provided 444 records, 58 of which fulfilled the inclusion criteria and were used to summarize the current evidence on the formation, distribution and degradation of PEth in human blood: (1), the presence and distribution of different PEth molecular species (2), the most diffused analytical methods devoted to PEth identification and quantization (3), the clinical efficiency of total PEth quantification as a marker of chronic excessive drinking (4), and the potential utility of this marker for identifying binge drinking behaviors (5). Twelve papers were included in the meta-analysis and the mean (M) and 95% confidence interval (CI) of total PEth concentrations in social drinkers (DAI ≤ 60 g/die; M = 0.288 μM; CI 0.208–0.367 μM) and heavy drinkers (DAI > 60 g/die; M = 3.897 μM; CI 2.404–5.391 μM) were calculated. The present analysis demonstrates a good clinical efficiency of PEth for detecting chronic heavy drinking.

Effectors of alcohol-induced cell killing in Drosophila

Heavy alcohol consumption provokes an array of degenerative pathologies but the signals that couple alcohol exposure to regulated forms of cell death are poorly understood. Using Drosophila as a model, we genetically establish that the severity of ethanol challenge dictates the type of death that occurs. In contrast to responses seen under acute exposure, cytotoxic responses to milder challenges required gene encoding components of the apoptosome, Dronc and Dark. We conducted a genome-wide RNAi screen to capture targets that specifically mediate ethanol-induced cell death. One effector, Drat, encodes a novel protein that contains an ADH domain but lacks essential residues in the catalytic site. In cultured cells and neurons in vivo, depletion of Drat conferred protection from alcohol-induced apoptosis. Adults mutated for Drat showed both improved survival and enhanced propensities toward sedation after alcohol challenge. Together, these findings highlight novel effectors that support regulated cell death incited by alcohol stress in vitro and in vivo.

Novel 14S,21-dihydroxy-docosahexaenoic acid rescues wound healing and associated angiogenesis impaired by acute ethanol intoxication/exposure

Acute ethanol intoxication and exposure (AE) has been known to impair wound healing and associated angiogenesis. Here, we found that AE diminished the formation of novel reparative lipid mediator 14S,21-dihydroxy-docosa-4Z,7Z,10Z,12E,16Z,19Z-hexaenoic acid (14S,21-diHDHA) and its biosynthetic intermediate 14S-hydroxy-DHA (14S-HDHA) from docosahexaenoic acid (DHA) in murine wounds. However, AE did not reduce the formation of DHA and the intermediate 21-HDHA. These results indicate that in the biosynthetic pathways of 14S,21-diHDHA in wounds, AE suppresses the 14S-hydroxy-generating activity of 12-lipoxygenase-like (LOX-like), but does not suppress the 21-hydroxy-generating activity of cytochrome P450 and DHA-generating activities. The AE-suppression of 12-LOX-like activity was further confirmed by the diminished formation of 12-hydroxy-eicosatetraenoic acid in wounds under AE. Supplementing 14S,21-diHDHA to wounds rescued the AE-impaired healing and vascularization. 14S,21-diHDHA restored AE-impaired processes of angiogenesis in vitro: endothelial cell migration, tubulogenesis, and phosphorylation of p38 mitogen-activated protein kinase (MAPK). Taken together, the suppression of 14S,21-diHDHA formation is responsible, at least partially, for the AE-impairment of cutaneous wound healing and angiogenesis. Supplementing 14S,21-diHDHA to compensate its deficit in AE-impaired wounds rescues the healing and angiogenesis. These results provide a novel mechanistic insight for AE-impaired wound healing that involves the necessary roles of 14S,21-diHDHA. They also offer leads for developing 14S,21-diHDHA-related therapeutics to ameliorate AE-impairment of wound healing.

Brewing complications: the effect of acute ethanol exposure on wound healing

Ethanol consumption is linked to a higher incidence of traumatic wounds and increases the risk for morbidity and mortality following surgical or traumatic injury. One of the most profound effects of acute ethanol exposure on wound healing occurs during the inflammatory response, and altered cytokine production is a primary component. Acute ethanol exposure also impairs the proliferative response during healing, causing delays in epithelial coverage, collagen synthesis, and blood vessel regrowth. The accumulated data support the paradigm that acute ethanol intoxication prior to injury significantly diminishes a patient's ability to heal efficiently.

Acute ethanol exposure disrupts VEGF receptor cell signaling in endothelial cells

Physiological angiogenesis is regulated by various factors, including signaling through vascular endothelial growth factor (VEGF) receptors. We previously reported that a single dose of ethanol (1.4 g/kg), yielding a blood alcohol concentration of 100 mg/dl, significantly impairs angiogenesis in murine wounds, despite adequate levels of VEGF, suggesting direct effects of ethanol on endothelial cell signaling (40). To examine the mechanism by which ethanol influences angiogenesis in wounds, we employed two different in vitro angiogenesis assays to determine whether acute ethanol exposure (100 mg/dl) would have long-lasting effects on VEGF-induced capillary network formation. Ethanol exposure resulted in reduced VEGF-induced cord formation on collagen and reduced capillary network structure on Matrigel in vitro. In addition, ethanol exposure decreased expression of endothelial VEGF receptor-2, as well as VEGF receptor-2 phosphorylation in vitro. Inhibition of ethanol metabolism by 4-methylpyrazole partially abrogated the effect of ethanol on endothelial cell cord formation. However, mice treated with t-butanol, an alcohol not metabolized by alcohol dehydrogenase, exhibited no change in wound vascularity. These results suggest that products of ethanol metabolism are important factors in the development of ethanol-induced changes in endothelial cell responsiveness to VEGF. In vivo, ethanol exposure caused both decreased angiogenesis and increased hypoxia in wounds. Moreover, in vitro experiments demonstrated a direct effect of ethanol on the response to hypoxia in endothelial cells, as ethanol diminished nuclear hypoxia-inducible factor-1alpha protein levels. Together, the data establish that acute ethanol exposure significantly impairs angiogenesis and suggest that this effect is mediated by changes in endothelial cell responsiveness to both VEGF and hypoxia.

Epigenetic effects of ethanol on liver and gastrointestinal injury

Alcohol consumption causes cellular injury. Recent developments indicate that ethanol induces epigenetic alterations, particularly acetylation, methylation of histones, and hypo- and hypermethylation of DNA. This has opened up a new area of interest in ethanol research and is providing novel insight into actions of ethanol at the nucleosomal level in relation to gene expression and patho-physiological consequences. The epigenetic effects are mainly attributable to ethanol metabolic stress (Emess), generated by the oxidative and non-oxidative metabolism of ethanol, and dysregulation of methionine metabolism. Epigenetic changes are important in ethanol-induced hepatic steatosis, fibrosis, carcinoma and gastrointestinal injury. This editorial highlights these new advances and its future potential.