Endocannabinoid hydrolases in avian HD11 macrophages identified by chemoproteomics: inactivation by small-molecule inhibitors and pathogen-induced downregulation of their activity

Response of Staphylococcus aureus physiology and Agr quorum sensing to low-shear modeled microgravity

Staphylococcus aureus is commonly isolated from astronauts returning from spaceflight. Previous analysis of omics data from S. aureus low Earth orbit cultures indicated significantly increased expression of the Agr quorum sensing system and its downstream targets in spaceflight samples compared to ground controls. In this current study, the rotary cell culture system (RCCS) was used to investigate the effect of low-shear modeled microgravity (LSMMG) on S. aureus physiology and Agr activity. When cultured in the same growth medium and temperature as the previous spaceflight experiment, S. aureus LSMMG cultures exhibited decreased agr expression and altered growth compared to normal gravity control cultures, which are typically oriented with oxygenation membrane on the bottom of the high aspect rotating vessel (HARV). When S. aureus was grown in an inverted gravity control orientation (oxygenation membrane on top of the HARV), reduced Agr activity was observed relative to both traditional control and LSMMG cultures, signifying that oxygen availability may affect the observed differences in Agr activity. Metabolite assays revealed increased lactate and decreased acetate excretion in both LSMMG and inverted control cultures. Secretomics analysis of LSMMG, control, and inverted control HARV culture supernatants corroborated these results, with inverted and LSMMG cultures exhibiting a decreased abundance of Agr-regulated virulence factors and an increased abundance of proteins expressed in low-oxygen conditions. Collectively, these studies suggest that the orientation of the HARV oxygenation membrane can affect S. aureus physiology and Agr quorum sensing in the RCCS, a variable that should be considered when interpreting data using this ground-based microgravity model.IMPORTANCES. aureus is commonly isolated from astronauts returning from spaceflight and from surfaces within human-inhabited closed environments such as spacecraft. Astronaut health and immune function are significantly altered in spaceflight. Therefore, elucidating the effects of microgravity on S. aureus physiology is critical for assessing its pathogenic potential during long-term human space habitation. These results also highlight the necessity of eliminating potential confounding factors when comparing simulated microgravity model data with actual spaceflight experiments.

Exploring the versatile roles of the endocannabinoid system and phytocannabinoids in modulating bacterial infections

The endocannabinoid system (ECS), initially identified for its role in maintaining homeostasis, particularly in regulating brain function, has evolved into a complex orchestrator influencing various physiological processes beyond its original association with the nervous system. Notably, an expanding body of evidence emphasizes the ECS's crucial involvement in regulating immune responses. While the specific role of the ECS in bacterial infections remains under ongoing investigation, compelling indications suggest its active participation in host-pathogen interactions. Incorporating the ECS into the framework of bacterial pathogen infections introduces a layer of complexity to our understanding of its functions. While some studies propose the potential of cannabinoids to modulate bacterial function and immune responses, the outcomes inherently hinge on the specific infection and cannabinoid under consideration. Moreover, the bidirectional relationship between the ECS and the gut microbiota underscores the intricate interplay among diverse physiological processes. The ECS extends its influence far beyond its initial discovery, emerging as a promising therapeutic target across a spectrum of medical conditions, encompassing bacterial infections, dysbiosis, and sepsis. This review comprehensively explores the complex roles of the ECS in the modulation of bacteria, the host's response to bacterial infections, and the dynamics of the microbiome. Special emphasis is placed on the roles of cannabinoid receptor types 1 and 2, whose signaling intricately influences immune cell function in microbe-host interactions.

Altered quorum sensing and physiology of Staphylococcus aureus during spaceflight detected by multi-omics data analysis

Staphylococcus aureus colonizes the nares of approximately 30% of humans, a risk factor for opportunistic infections. To gain insight into S. aureus virulence potential in the spaceflight environment, we analyzed RNA-Seq, cellular proteomics, and metabolomics data from the "Biological Research in Canisters-23" (BRIC-23) GeneLab spaceflight experiment, a mission designed to measure the response of S. aureus to growth in low earth orbit on the international space station. This experiment used Biological Research in Canisters-Petri Dish Fixation Units (BRIC-PDFUs) to grow asynchronous ground control and spaceflight cultures of S. aureus for 48 h. RNAIII, the effector of the Accessory Gene Regulator (Agr) quorum sensing system, was the most highly upregulated gene transcript in spaceflight relative to ground controls. The agr operon gene transcripts were also highly upregulated during spaceflight, followed by genes encoding phenol-soluble modulins and secreted proteases, which are positively regulated by Agr. Upregulated spaceflight genes/proteins also had functions related to urease activity, type VII-like Ess secretion, and copper transport. We also performed secretome analysis of BRIC-23 culture supernatants, which revealed that spaceflight samples had increased abundance of secreted virulence factors, including Agr-regulated proteases (SspA, SspB), staphylococcal nuclease (Nuc), and EsxA (secreted by the Ess system). These data also indicated that S. aureus metabolism is altered in spaceflight conditions relative to the ground controls. Collectively, these data suggest that S. aureus experiences increased quorum sensing and altered expression of virulence factors in response to the spaceflight environment that may impact its pathogenic potential.

Technologies for Direct Detection of Covalent Protein—Drug Adducts

In the past two decades, drug candidates with a covalent binding mode have gained the interest of medicinal chemists, as several covalent anticancer drugs have successfully reached the clinic. As a covalent binding mode changes the relevant parameters to rank inhibitor potency and investigate structure-activity relationship (SAR), it is important to gather experimental evidence on the existence of a covalent protein–drug adduct. In this work, we review established methods and technologies for the direct detection of a covalent protein–drug adduct, illustrated with examples from (recent) drug development endeavors. These technologies include subjecting covalent drug candidates to mass spectrometric (MS) analysis, protein crystallography, or monitoring intrinsic spectroscopic properties of the ligand upon covalent adduct formation. Alternatively, chemical modification of the covalent ligand is required to detect covalent adducts by NMR analysis or activity-based protein profiling (ABPP). Some techniques are more informative than others and can also elucidate the modified amino acid residue or bond layout. We will discuss the compatibility of these techniques with reversible covalent binding modes and the possibilities to evaluate reversibility or obtain kinetic parameters. Finally, we expand upon current challenges and future applications. Overall, these analytical techniques present an integral part of covalent drug development in this exciting new era of drug discovery.

Effects of Chlorpyrifos on Serine Hydrolase Activities, Lipid Mediators, and Immune Responses in Lungs of Neonatal and Adult Mice

Chlorpyrifos (CPF) is an organophosphate (OP) pesticide that causes acute toxicity by inhibiting acetylcholinesterase (AChE) in the nervous system. However, endocannabinoid (eCB) metabolizing enzymes in brain of neonatal rats are more sensitive than AChE to inhibition by CPF, leading to increased levels of eCBs. Because eCBs are immunomodulatory molecules, we investigated the association between eCB metabolism, lipid mediators, and immune function in adult and neonatal mice exposed to CPF. We focused on lung effects because epidemiologic studies have linked pesticide exposures to respiratory diseases. CPF was hypothesized to disrupt lung eCB metabolism and alter lung immune responses to lipopolysaccharide (LPS), and these effects would be more pronounced in neonatal mice due to an immature immune system. We first assessed the biochemical effects of CPF in adult mice (≥8 weeks old) and neonatal mice after administering CPF (2.5 mg/kg, oral) or vehicle for 7 days. Tissues were harvested 4 h after the last CPF treatment and lung microsomes from both age groups demonstrated CPF-dependent inhibition of carboxylesterases (Ces), a family of xenobiotic and lipid metabolizing enzymes, whereas AChE activity was inhibited in adult lungs only. Activity-based protein profiling (ABPP)-mass spectrometry of lung microsomes identified 31 and 32 individual serine hydrolases in neonatal lung and adult lung, respectively. Of these, Ces1c/Ces1d/Ces1b isoforms were partially inactivated by CPF in neonatal lung, whereas Ces1c/Ces1b and Ces1c/BChE were partially inactivated in adult female and male lungs, respectively, suggesting age- and sex-related differences in their sensitivity to CPF. Monoacylglycerol lipase (MAGL) and fatty acid amide hydrolase (FAAH) activities in lung were unaffected by CPF. When LPS (1.25 mg/kg, i.p.) was administered following the 7-day CPF dosing period, little to no differences in lung immune responses (cytokines and immunophenotyping) were noted between the CPF and vehicle groups. However, a CPF-dependent increase in the amounts of dendritic cells and certain lipid mediators in female lung following LPS challenge was observed. Experiments in neonatal and adult Ces1d^-/- mice yielded similar results as wild type mice (WT) following CPF treatment, except that CPF augmented LPS-induced Tnfa mRNA in adult Ces1d^-/- mouse lungs. This effect was associated with decreased expression of Ces1c mRNA in Ces1d^-/- mice versus WT mice in the setting of LPS exposure. We conclude that CPF exposure inactivates several Ces isoforms in mouse lung and, during an inflammatory response, increases certain lipid mediators in a female-dependent manner. However, it did not cause widespread altered lung immune effects in response to an LPS challenge.

Apicomplexan co-infections impair with phagocytic activity in avian macrophages

Mixed infections of Toxoplasma gondii and Eimeria tenella are likely to occur frequently due to the high prevalence of both pathogens in free-ranging chickens. In this study, we investigated the co-occurrence of the two parasites in the same immune-competent host cell towards altered patterns of parasite-host interactions. Chicken blood monocyte-derived macrophages were co-infected with T. gondii RH tachyzoites and E. tenella Houghton sporozoites in vitro for 24 h. Through monitoring the uptake of pH-sensitive pHrodo™ Zymosan BioParticles ("Zymosan") by macrophages, we created a three-dimensional model and to analyze quantitatively phagocytosis using confocal laser scanning microscopy. Assessments of parasite populations were performed by qPCR at 2, 6, 12, and 24 h post-infection (hpi). At 6 hpi, phagocytosis was inhibited in the E. tenella-infected cultures while no inhibition of phagocytosis was observed due to T. gondii. Phagocytosis activity revealed more complex interactions during co-infection. At 12 and 24 hpi, phagocytosis response to "Zymosan" was distinctly weaker in co-infected cells than in all other groups except for cells mono-infected with high doses of E. tenella at 24 hpi. By qPCR, significantly reduced numbers of both intracellular parasites were recorded (10-fold) in all infected groups at 2 hpi. At 12 hpi, the T. gondii population reached lowest values but dramatically increased by 24 hpi. Our data confirm that macrophage phagocytosis is involved in the control of invasion by apicomplexan parasites in chicken which particularly applies to E. tenella infection and it was able to be altered by the co-existing parasites.

An atlas of the catalytically active liver and spleen kinases in chicken identified by chemoproteomics

Phosphorylation is a post-translational protein modification regulating most known cellular processes. While protein kinases constitute a large family of highly conserved enzymes, identification of active kinases is challenging due to a low abundance of some of these signaling molecules. Although chicken is the first agricultural animal to have a sequenced genome, annotation of the kinome, i.e., a complement of all protein kinases in the genome is limited. We used chemical probes consisting of ATP and ADP derivatives binding to specific lysine (Lys) residues within the ATP-binding pocket of kinases, combined with proteomics, to identify 267 peptides labeled with the ATP and ADP acyl derivatives and 188 corresponding chicken kinases in chicken spleen and liver. Our description of active chicken kinases and ATP binding sites will support future studies focused on identifying the role of this important class of enzymes in chicken health and disease. SIGNIFICANCE: Advances made in understanding chicken enzymes are critical for the improved knowledge of the regulatory pathways controlling physiological processes in chicken. Since protein phosphorylation controls multiple aspects of cell fate, it is often linked to pathological conditions, and understanding of the kinase expression in chicken is essential for future therapeutic approaches. We coupled proteomics and labeling with active-site probes binding to Lys residues within the ATP-binding pocket of kinases to identify 188 kinases and corresponding 267 peptides labeled with the ATP and ADP acyl derivatives in chicken spleen and liver. Results of the present study describing catalytically active kinases is a starting point for chemoproteomic-based interrogation of kinases in chicken exposed to different conditions. Kinases identified in this study are available through the Chickspress genome browser that has previously published mRNA, miRNA, and shotgun proteomics data.

Transcriptomic analysis of immune response to bacterial lipopolysaccharide in zebra finch (Taeniopygia guttata)

BACKGROUND

Despite the convergence of rapid technological advances in genomics and the maturing field of ecoimmunology, our understanding of the genes that regulate immunity in wild populations is still nascent. Previous work to assess immune function has relied upon relatively crude measures of immunocompetence. However, with next-generation RNA-sequencing, it is now possible to create a profile of gene expression in response to an immune challenge. In this study, captive zebra finch (Taeniopygia guttata; adult males) were challenged with bacterial lipopolysaccharide (LPS) or vehicle to stimulate the innate immune system. 2 hours after injection, birds were euthanized and hypothalami, spleen, and red blood cells (RBCs) were collected. Taking advantage of the fully sequenced genome of zebra finch, total RNA was isolated, sequenced, and partially annotated in these tissue/cells.

RESULTS

In hypothalamus, there were 707 significantly upregulated transcripts, as well as 564 and 144 in the spleen and RBCs, respectively, relative to controls. Also, 155 transcripts in the hypothalamus, 606 in the spleen, and 61 in the RBCs were significantly downregulated. More specifically, a number of immunity-related transcripts (e.g., IL-1β, RSAD2, SOCS3) were upregulated among tissues/cells. Additionally, transcripts involved in metabolic processes (APOD, LRAT, RBP4) were downregulated.

CONCLUSIONS

These results suggest a potential trade-off in expression of genes that regulate immunity and metabolism in birds challenged with LPS. This finding is consistent with a hypothermic response to LPS treatment in small birds. Unlike mammals, birds have nucleated RBCs, and these results support a novel transcriptomic response of avian RBCs to immune challenge.

Paradoxical effects of JZL184, an inhibitor of monoacylglycerol lipase, on bone remodelling in healthy and cancer-bearing mice

BACKGROUND

Cancer-associated bone disease is a serious complication in bone sarcomas and metastatic carcinomas of breast and prostate origin. Monoacylglycerol lipase (MAGL) is an enzyme of the endocannabinoid system, and is responsible for the degradation of the most abundant endocannabinoid in bone, 2-arachidonoyl glycerol (2AG).

METHODS

The effects of the verified MAGL inhibitor on bone remodelling were assessed in healthy mice and in mouse models of bone disease caused by prostate and breast cancers and osteosarcoma.

FINDINGS

JZL184 reduced osteolytic bone metastasis in mouse models of breast and prostate cancers, and inhibited skeletal tumour growth, metastasis and the formation of ectopic bone in models of osteosarcoma. Additionally, JZL184 suppressed cachexia and prolonged survival in mice injected with metastatic osteosarcoma and osteotropic cancer cells. Functional and histological analysis revealed that the osteoprotective action of JZL184 in cancer models is predominately due to inhibition of tumour growth and metastasis. In the absence of cancer, however, exposure to JZL184 exerts a paradoxical reduction of bone volume via an effect that is mediated by both Cnr1 and Cnr2 cannabinoid receptors.

INTERPRETATION

MAGL inhibitors such as JZL184, or its novel analogues, may be of value in the treatment of bone disease caused by primary bone cancer and bone metastasis, however, activation of the skeletal endocannabinoid system may limit their usefulness as osteoprotective agents.

ABHD6: Its Place in Endocannabinoid Signaling and Beyond

The endocannabinoid (eCB) signaling system modulates neurotransmission and inflammation, among other physiological functions. Its newest member, α/β-hydrolase domain-containing 6 (ABHD6), has emerged as a promising therapeutic target to treat several devastating diseases, including epilepsy. Here, we review the molecular mechanisms that mediate and control eCB signaling and, within it, the specific role of ABHD6. We also discuss how ABHD6 controls the abundance of additional lipids and the trafficking of ionotropic receptors to plasma membranes. We finish with several unexplored questions regarding this novel enzyme. Our current understanding of the molecular mechanism and biological function of ABHD6 provides a strong foundation for the development of small-molecule therapeutics to treat devastating diseases.

Characterization of Endocannabinoid-Metabolizing Enzymes in Human Peripheral Blood Mononuclear Cells under Inflammatory Conditions

Endocannabinoid-metabolizing enzymes are downregulated in response to lipopolysaccharide (LPS)-induced inflammation in mice, which may serve as a negative feedback mechanism to increase endocannabinoid levels and reduce inflammation. Increased plasma levels of the pro-inflammatory cytokine interleukin-6 (IL-6) and decreased fatty acid amide hydrolase (FAAH) activity in peripheral lymphocytes from individuals diagnosed with Huntington’s disease (HD) suggests that a similar negative feedback system between inflammation and the endocannabinoid system operates in humans. We investigated whether CpG- (unmethylated bacterial DNA) and LPS-induced IL-6 levels in peripheral blood mononuclear cells (PBMCs) from non-HD and HD individuals modulated the activities of endocannabinoid hydrolases monoacylglycerol lipase (MAGL) and carboxylesterase (CES). Baseline plasma IL-6 levels and 2-arachidonoylglycerol (2-AG) hydrolytic activity in PBMC lysates were not different in HD and non-HD individuals. Inhibition of MAGL and CES1 activity in PBMCs using the inhibitors JZL184 and WWL113, respectively, demonstrated that MAGL was the dominant 2-AG hydrolytic enzyme in PBMCs, regardless of disease state. Correlative analyses of 2-AG hydrolytic activity versus enzyme abundance confirmed this conclusion. Flow cytometric analysis of PBMCs showed that MAGL and CES1 were primarily expressed in monocytes and to a lesser extent in lymphocytes. In conclusion, these data suggest that IL-6 did not influence 2-AG hydrolytic activity in human PBMCs; however, monocytic MAGL was shown to be the predominant 2-AG hydrolytic enzyme.

PGE2 Augments Inflammasome Activation and M1 Polarization in Macrophages Infected With Salmonella Typhimurium and Yersinia enterocolitica

Eicosanoids are cellular metabolites, which shape the immune response, including inflammatory processes in macrophages. The effects of these lipid mediators on inflammation and bacterial pathogenesis are not clearly understood. Certain eicosanoids are suspected to act as molecular sensors for the recruitment of neutrophils, while others regulate bacterial uptake. In this study, gene expression analyses indicated that genes involved in eicosanoid biosynthesis including COX-1, COX-2, DAGL, and PLA-2 are differentially regulated in THP-1 human macrophages infected with Salmonella enterica Typhimurium or Yersinia enterocolitica. By using targeted metabolomics approach, we found that the eicosanoid precursor, arachidonic acid (AA) as well as its derivatives, including prostaglandins (PGs) PGF2α or PGE2/PGD2, and thromboxane TxB2, are rapidly secreted from macrophages infected with these Gram-negative pathogenic bacteria. The magnitude of eicosanoid biosynthesis in infected host cells depends on the presence of virulence factors of Y. enterocolitica and S. Typhimurium strains, albeit in an opposite way in Y. enterocolitica compared to S. Typhimurium infection. Trials with combinations of EP2/EP4 PGE2 receptor agonists and antagonists suggest that PGE2 signaling in these infection models works primarily through the EP4 receptor. Downstream of EP4 activation, PGE2 enhances inflammasome activation and represses M2 macrophage polarization while inducing key M1-type markers. PGE2 also led to a decreased numbers of Y. enterocolitica within macrophages. To summarize, PGE2 is a potent autocrine/paracrine activator of inflammation during infection in Gram-negative bacteria, and it affects macrophage polarization, likely controlling bacterial clearance by macrophages.

Activity-Based Protein Profiling at the Host-Pathogen Interface

Activity-based protein profiling (ABPP) is a technique for selectively detecting reactive amino acids in complex proteomes with the aid of chemical probes. Using probes that target catalytically active enzymes, ABPP can rapidly define the functional proteome of a biological system. In recent years, this approach has been increasingly applied to globally profile enzymes active at the host-pathogen interface of microbial infections. From in vitro co-culture systems to animal models of infection, these studies have revealed enzyme-mediated mechanisms of microbial pathogenicity, host immunity, and metabolic adaptation that dynamically shape pathogen interactions with the host.