Enhanced Platelet-Activating Factor Synthesis Facilitates Acute and Delayed Effects of Ethanol-Intoxicated Thermal Burn Injury

Abstract

Thermal burn injuries in patients who are alcohol-intoxicated result in greater morbidity and mortality. Murine models combining ethanol and localized thermal burn injury reproduce the systemic toxicity seen in human subjects, which consists of both acute systemic cytokine production with multiple organ dysfunction, as well as a delayed systemic immunosuppression. However, the exact mechanisms for these acute and delayed effects are unclear. These studies sought to define the role of the lipid mediator platelet-activating factor in the acute and delayed effects of intoxicated burn injury. Combining ethanol and thermal burn injury resulted in increased enzymatic platelet-activating factor generation in a keratinocyte cell line in vitro, human skin explants ex vivo, as well as in murine skin in vivo. Further, the acute increase in inflammatory cytokines, such as IL-6, and the systemic immunosuppressive effects of intoxicated thermal burn injury were suppressed in mice lacking platelet-activating factor receptors. Together, these studies provide a potential mechanism and treatment strategies for the augmented toxicity and immunosuppressive effects of thermal burn injury in the setting of acute ethanol exposure, which involves the pleotropic lipid mediator platelet-activating factor.

Acute Ethanol Exposure Augments Low-Dose UVB-Mediated Systemic Immunosuppression via Enhanced Production of Platelet-Activating Factor Receptor Agonists

“…Of interest, structural analysis of PAF-R agonistic activity following the combination of EtOH þ UVB in HaCaT cells by mass spectrometric analysis revealed only enzymatically generated PAF agonists 1-hexadecyl-2-acetyl GPC and 1-octadecyl-2-acetyl GPC, not significant amounts of oxidized GPCs (data not shown), which we have described are generated following higher fluences of UVB (Marathe et al, 2005). Previously, we have demonstrated that topical application of 20% EtOH to de-identified discarded human skin explants derived from surgical contouring procedures (exempted study, Wright State University) 30 minutes before a thermal burn injury results in an augmentation of PAF production (Harrison et al, 2018). Using this protocol, we tested whether topical EtOH pretreatment can increase PAF following UVB treatment.…”

“…Recently, our group demonstrated that ethanol (EtOH) exposure results in an augmentation of enzymatic PAF synthesis in response to thermal burn injury, in a process involving cytosolic phospholipase A 2 (Harrison et al, 2018). The present study was designed to test the hypothesis that EtOH exposure could generate increased levels of PAF in response to UVB, and that UVB will be more immunosuppressive when EtOH intoxicated.…”

“…Ten minutes after UVB treatment, the lipids were extracted as described previously (Marathe et al, 2005) using the Bligh & Dyer method (Bligh and Dyer, 1959). As multiple GPC species can act as PAF-R agonists, we quantified total PAF-R biochemical activity using PAF-Reexpressing KBP cells that produce IL-8 when the receptor is activated (model in Figure 1a) (Harrison et al, 2018;Pei et al, 1998). KBP and PAF-Renegative human epithelial KB cell line cells were exposed to lipid extracts from HaCaT cells treated with sham, UVB, EtOH alone, or EtOH þ UVB and incubated for 6 hours.…”

“…We next tested whether EtOH intoxication can increase the ability of UVB to generate PAF-R agonists in murine skin in vivo. These studies used a previously published murine model of intraperitoneal injection of 2.4 g/kg (approximately 400 ml of 20%) EtOH (Faunce et al, 1997;Harrison et al, 2018) into anesthetized C57BL6 mice followed 30 minutes later by UVB treatment (2,500 J/m 2 ) of an area of 2 Â 2 cm 2 of shaved lower back skin. All animal studies were approved by the Institutional Review Boards of Indiana University and Wright State University.…”

New Insights Into the Pathologic Roles of the Platelet-Activating Factor System

“…Of interest, melanocytes, skin fibroblasts, and T cells do not, yet B cells express PAFRs ( 34 , 115 , 116 ). Elevated PAFR agonist levels can be detected following multiple pathophysiologic stressors ranging from burn injury to X-radiation ( 41 , 117 , 118 ). Moreover, PAF can be detected in cold urticaria ( 119 ), immunobullous diseases such as bullous pemphigoid ( 120 ), following sunburn ( 121 ), and in the skin disease psoriasis ( 122 ).…”