Pig Liver Esterases Hydrolyze Endocannabinoids and Promote Inflammatory Response

The Effects of Endogenous Cannabinoids on the Mammalian Respiratory System: A Scoping Review of Cyclooxygenase-Dependent Pathways

Introduction: The endogenous cannabinoid (endocannabinoid) system is an emerging target for the treatment of chronic inflammatory disease with the potential to advance treatment for many respiratory illnesses. The varied effects of endocannabinoids across tissue types makes it imperative that we explore their physiologic impact within unique tissue targets. The aim of this scoping review is to explore the impact of endocannabinoid activity on eicosanoid production as a measure of human airway inflammation. Methods: A scoping literature review was conducted according to PRISMA-ScR (Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews) guidelines. Search strategies using MeSH terms related to cannabinoids, eicosanoids, cyclooxygenase (COX), and the respiratory system were used to query Medline, Embase, Cochrane, CINAHL, Web of Science, and Biosis Previews in December 2021. Only studies that investigated the relationship between endocannabinoids and the eicosanoid system in mammalian respiratory tissue after 1992 were included. Results: Sixteen studies were incorporated in the final qualitative review. Endocannabinoid activation increases COX-2 expression, potentially through ceramide-dependent or p38 and p42/44 Mitogen-Activated Protein Kinase pathways and is associated with a concentration-dependent increase in prostaglandin (PG)E2. Inhibitors of endocannabinoid hydrolysis found either an increase or no change in levels of PGE2 and PGD2 and decreased levels of leukotriene (LT)B4, PGI2, and thromboxane A2 (TXA2). Endocannabinoids increase bronchial epithelial cell permeability and have vasorelaxant effects in human pulmonary arteries and cause contraction of bronchi and decreased gas trapping in guinea pigs. Inhibitors of endocannabinoid hydrolysis were found to have anti-inflammatory effects on pulmonary tissue and are primarily mediated by COX-2 and activation of eicosanoid receptors. Direct agonism of endocannabinoid receptors appears to play a minor role. Conclusion: The endocannabinoid system has diverse effects on the mammalian airway. While endocannabinoid-derived PGs can have anti-inflammatory effects, endocannabinoids also produce proinflammatory conditions, such as increased epithelial permeability and bronchial contraction. These conflicting findings suggest that endocannabinoids produce a variety of effects depending on their local metabolism and receptor agonism. Elucidation of the complex interplay between the endocannabinoid and eicosanoid pathways is key to leveraging the endocannabinoid system as a potential therapeutic target for human airway disease.

Carboxylesterase 1d Inactivation Augments Lung Inflammation in Mice

Carboxylesterases are members of the serine hydrolase superfamily and metabolize drugs, pesticides, and lipids. Previous research showed that inhibition of carboxylesterase 1 (CES1) in human macrophages altered the immunomodulatory effects of lipid mediators called prostaglandin glyceryl esters, which are produced by cyclooxygenase-catalyzed oxygenation of the endocannabinoid 2-arachidonoylglycerol (2-AG). Ces1d - the mouse ortholog of human CES1 - is the most abundant Ces isoform in murine lung tissues and alveolar macrophages and a major target of organophosphate poisons. Monoacylglycerol lipase (Magl) is also expressed in murine lung and is the main enzyme responsible for 2-AG catabolism. Several metabolic benefits are observed in Ces1d-/- mice fed a high-fat diet; thus, we wondered whether pharmacological and genetic inactivation of Ces1d in vivo might also ameliorate the acute inflammatory response to lipopolysaccharide (LPS). C57BL/6 mice were treated with WWL229 (Ces1d inhibitor) or JZL184 (Magl inhibitor), followed 30 min later by either LPS or saline. Wild-type (WT) and Ces1d-/- mice were also administered LPS to determine the effect of Ces1d knockout. Mice were sacrificed at 6 and 24 h, and cytokines were assessed in serum, lung, liver, and adipose tissues. Lipid mediators were quantified in lung tissues, while activity-based protein profiling and enzyme assays determined the extent of lung serine hydrolase inactivation by the inhibitors. WWL229 was shown to augment LPS-induced lung inflammation in a female-specific manner, as measured by enhanced neutrophil infiltration and Il1b mRNA. The marked Ces inhibition in female lung by 4 h after drug treatment might explain this sex difference, although the degree of Ces inhibition in female and male lungs was similar at 6 h. In addition, induction of lung Il6 mRNA and prostaglandin E2 by LPS was more pronounced in Ces1d-/- mice than in WT mice. Thus, WWL229 inhibited lung Ces1d activity and augmented the female lung innate immune response, an effect observed in part in Ces1d-/- mice and Ces1d/CES1-deficient murine and human macrophages. In contrast, JZL184 attenuated LPS-induced Il1b and Il6 mRNA levels in female lung, suggesting that Ces1d and Magl have opposing effects. Mapping the immunomodulatory molecules/pathways that are regulated by Ces1d in the context of lung inflammation will require further research.

Isolation and Characterization of Two Pseudorabies Virus and Evaluation of Their Effects on Host Natural Immune Responses and Pathogenicity

Pseudorabies, caused by the pseudorabies virus (PRV), is an acute fatal disease, which can infect rodents, mammals, and other livestock and wild animals across species. Recently, the emergence of PRV virulent isolates indicates a high risk of a variant PRV epidemic and the need for continuous surveillance. In this study, PRV-GD and PRV-JM, two fatal PRV variants, were isolated and their pathogenicity as well as their effects on host natural immune responses were assessed. PRV-GD and PRV-JM were genetically closest to PRV variants currently circulating in Heilongjiang (HLJ8) and Jiangxi (JX/CH/2016), which belong to genotype 2.2. Consistently, antisera from sows immunized with PRV-Ea classical vaccination showed much lower neutralization ability to PRV-GD and PRV-JM. However, the antisera from the pigs infected with PRV-JM had an extremely higher neutralization ability to PRV-TJ (as a positive control), PRV-GD and PRV-JM. In vivo, PRV-GD and PRV-JM infections caused 100% death in mice and piglets and induced extensive tissue damage, cell death, and inflammatory cytokine release. Our analysis of the emergence of PRV variants indicate that pigs immunized with the classical PRV vaccine are incapable of providing sufficient protection against these PRV isolates, and there is a risk of continuous evolution and virulence enhancement. Efforts are still needed to conduct epidemiological monitoring for the PRV and to develop novel vaccines against this emerging and reemerging infectious disease.