Chemical genetics screening reveals KIAA1363 as a cytokine-lowering target

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.

Bioactive Ether Lipids: Primordial Modulators of Cellular Signaling

The primacy of lipids as essential components of cellular membranes is conserved across taxonomic domains. In addition to this crucial role as a semi-permeable barrier, lipids are also increasingly recognized as important signaling molecules with diverse functional mechanisms ranging from cell surface receptor binding to the intracellular regulation of enzymatic cascades. In this review, we focus on ether lipids, an ancient family of lipids having ether-linked structures that chemically differ from their more prevalent acyl relatives. In particular, we examine ether lipid biosynthesis in the peroxisome of mammalian cells, the roles of selected glycerolipids and glycerophospholipids in signal transduction in both prokaryotes and eukaryotes, and finally, the potential therapeutic contributions of synthetic ether lipids to the treatment of cancer.

Myeloid Tribbles 1 induces early atherosclerosis via enhanced foam cell expansion

Macrophages drive atherosclerotic plaque progression and rupture; hence, attenuating their atherosclerosis-inducing properties holds promise for reducing coronary heart disease (CHD). Recent studies in mouse models have demonstrated that Tribbles 1 (Trib1) regulates macrophage phenotype and shows that Trib1 deficiency increases plasma cholesterol and triglyceride levels, suggesting that reduced TRIB1 expression mediates the strong genetic association between the TRIB1 locus and increased CHD risk in man. However, we report here that myeloid-specific Trib1 (mTrib1) deficiency reduces early atheroma formation and that mTrib1 transgene expression increases atherogenesis. Mechanistically, mTrib1 increased macrophage lipid accumulation and the expression of a critical receptor (OLR1), promoting oxidized low-density lipoprotein uptake and the formation of lipid-laden foam cells. As TRIB1 and OLR1 RNA levels were also strongly correlated in human macrophages, we suggest that a conserved, TRIB1-mediated mechanism drives foam cell formation in atherosclerotic plaque and that inhibiting mTRIB1 could be used therapeutically to reduce CHD.

Biochemical and microbiological evaluation of N-aryl urea derivatives against mycobacteria and mycobacterial hydrolases

A focused library of 24 N-aryl urea derivatives was prepared and evaluated against serine esterases of Mycobacterium tuberculosis (Mtb) Rv3802c and Mtb Ag85C. The members of the library were evaluated for both selectivity and mode of inhibition. Furan-based urea derivative 6c was found to be the most potent non-covalent inhibitor of Rv3802c with a K i value of 5.2 ± 0.7 μM. On the other hand, triazole-based ureas 10a and 10b selectively inhibited Ag85C irreversibly with a k inact/K i value of 2.3 ± 0.3 and 5.5 ± 0.4 × 10-3 μM-1 min-1, respectively. The library was also evaluated for minimum inhibitory concentration (MIC) against two strains of Mtb, Mycobacterium smegmatis, and Mycobacterium abscessus. Compounds 4a and 4c were active against Mtb H37Rv mc26206 with MIC values of 3.12 and 1.5 μM, respectively. Closely related 4e showed similar activity against Mtb H37Rv mc26206 but also possessed activity against Mtb H37Ra, Mycobacterium smegmatis and Mycobacterium abscessus. Compounds 4a, 4c, and 4e all contained a common 1-(cyclohexylmethyl)-3-phenylurea motif. In summary, we identified a selective non-covalent inhibitor of Rv3802c and covalently irreversible inhibitors of Ag85C as well as the 1-(cyclohexylmethyl)-3-phenylurea motif which showed activity against a variety of mycobacteria.

Chemoproteomics-Enabled Covalent Ligand Screening Reveals ALDH3A1 as a Lung Cancer Therapy Target

Chemical genetics is a powerful approach for identifying therapeutically active small molecules, but identifying the mechanisms of action underlying hit compounds remains challenging. Chemoproteomic platforms have arisen to tackle this challenge and enable rapid mechanistic deconvolution of small-molecule screening hits. Here, we have screened a cysteine-reactive covalent ligand library to identify hit compounds that impair cell survival and proliferation in nonsmall cell lung carcinoma cells, but not in primary human bronchial epithelial cells. Through this screen, we identified a covalent ligand hit, DKM 3-42, which impaired both in situ and in vivo lung cancer pathogenicity. We used activity-based protein profiling to discover that the primary target of DKM 3-42 was the catalytic cysteine in aldehyde dehydrogenase 3A1 (ALDH3A1). We performed further chemoproteomics-enabled covalent ligand screening directly against ALDH3A1, and identified a more potent and selective lead covalent ligand, EN40, which inhibits ALDH3A1 activity and impairs lung cancer pathogenicity. We show here that ALDH3A1 represents a potentially novel therapeutic target for lung cancers that express ALDH3A1 and put forth two selective ALDH3A1 inhibitors. Overall, we show the utility of combining chemical genetics screening of covalent ligand libraries with chemoproteomic approaches to rapidly identify anticancer leads and targets.

Organophosphorus Xenobiotic Toxicology

Originally, organophosphorus (OP) toxicology consisted of acetylcholinesterase inhibition by insecticides and chemical threat agents acting as phosphorylating agents for serine in the catalytic triad, but this is no longer the case. Other serine hydrolases can be secondary OP targets, depending on the OP structure, and include neuropathy target esterase, lipases, and endocannabinoid hydrolases. The major OP herbicides are glyphosate and glufosinate, which act in plants but not animals to block aromatic amino acid and glutamine biosynthesis, respectively, with safety for crops conferred by their expression of herbicide-tolerant targets and detoxifying enzymes from bacteria. OP fungicides, pharmaceuticals including calcium retention agents, industrial chemicals, and cytochrome P450 inhibitors act by multiple noncholinergic mechanisms, often with high potency and specificity. One type of OP-containing fire retardant forms a highly toxic bicyclophosphate γ-aminobutyric acid receptor antagonist upon combustion. Some OPs are teratogenic, mutagenic, or carcinogenic by known mechanisms that can be avoided as researchers expand knowledge of OP chemistry and toxicology for future developments in bioregulation.

Interaction of the serine hydrolase KIAA1363 with organophosphorus agents: Evaluation of potency and kinetics

Oxons are bioactive metabolites of organophosphorus insecticides (OPs) that covalently inactivate serine hydrolases. KIAA1363 is one of the most abundant serine hydrolases in mouse brain. Although the physiological consequences related to the inhibition of KIAA1363 due to environmental exposures to OPs are poorly understood, the enzyme was previously shown to have a role in the detoxification of oxons. Here, we overexpressed human KIAA1363 and CES1 in COS7 cells and compared the potency of inhibition (IC50s, 15 min) of KIAA1363 and CES1 by chlorpyrifos oxon (CPO), paraoxon (PO), and methyl paraoxon (MPO). The order of potency was CPO > PO >> MPO for both enzymes. We also determined the bimolecular rate constants (kinact/Ki) for reactions of CPO and PO with KIAA1363 and CES1. KIAA1363 and CES1 were inactivated by CPO at comparable rates (4.4 × 10(6) s(-1) M(-1) and 6.7 × 10(6) s(-1) M(-1), respectively), whereas PO inactivated both enzymes at slower rates (0.4 × 10(6) s(-1) M(-1) and 1.5 × 10(6) s(-1) M(-1), respectively). Finally, the reactivation rate of KIAA1363 following inhibition by CPO was evaluated. Together, the results define the kinetics of inhibition of KIAA1363 by active metabolites of agrochemicals and indicate that KIAA1363 is highly sensitive to inhibition by these compounds.

Transition from identity to bioactivity-guided proteomics for biomarker discovery with focus on the PF2D platform

Proteomic strategies provide a valuable tool kit to identify proteins involved in diseases. With recent progress in MS technology, high throughput proteomics has accelerated protein identification for potential biomarkers. Numerous biomarker candidates have been identified in several diseases, and many are common among pathologies. An overall strategy that could complement and strengthen the search for biomarkers is combining protein identity with biological outcomes. This review describes an emerging framework of bridging bioactivity to protein identity, exploring the possibility that some biomarkers will have a mechanistic role in the disease process. A review of pulmonary, cardiovascular, and CNS biomarkers will be discussed to demonstrate the utility of combining bioactivity with identification as a means to not only find meaningful biomarkers, but also to uncover functional mediators of disease.