Discovery of Novel Chemical Series of OXA-48 ß-Lactamase Inhibitors by High-Throughput Screening.

The major cause of bacterial resistance to ß-lactams is the production of hydrolytic ß-lactamase enzymes. Nowadays, the combination of ß-lactam antibiotics with ß-lactamase inhibitors (BLIs) is the main strategy for overcoming such issues. Nevertheless, particularly challenging ß-lactamases, such as OXA-48, pose the need for novel and effective treatments. Herein, we describe the screening of a proprietary compound collection against Klebsiella pneumoniae OXA-48, leading to the identification of several chemotypes, like the 4-ideneamino-4H-1,2,4-triazole (SC_2) and pyrazolo[3,4-b]pyridine (SC_7) cores as potential inhibitors. Importantly, the most potent representative of the latter series (ID2, AC50 = 0.99 µM) inhibited OXA-48 via a reversible and competitive mechanism of action, as demonstrated by biochemical and X-ray studies; furthermore, it slightly improved imipenem's activity in Escherichia coli ATCC BAA-2523 ß-lactam resistant strain. Also, ID2 showed good solubility and no sign of toxicity up to the highest tested concentration, resulting in a promising starting point for further optimization programs toward novel and effective non-ß-lactam BLIs.

Pharmacological Characterization of the Microsomal Prostaglandin E2 Synthase-1 Inhibitor AF3485 In Vitro and In Vivo.

RATIONALE: The development of inhibitors of microsomal prostaglandin (PG)E2 synthase-1 (mPGES-1) was driven by the promise of attaining antiinflammatory agents with a safe cardiovascular profile because of the possible diversion of the accumulated substrate, PGH2, towards prostacyclin (PGI2). OBJECTIVES: We studied the effect of the human mPGES-1 inhibitor, AF3485 (a benzamide derivative) on prostanoid biosynthesis in human whole blood in vitro. To characterize possible off-target effects of the compound, we evaluated: i)the impact of its administration on the systemic biosynthesis of prostanoids in a model of complete Freund's adjuvant (CFA)-induced monoarthritis in rats; ii) the effects on cyclooxygenase (COX)-2 expression and the biosynthesis of prostanoids in human monocytes and human umbilical vein endothelial cells (HUVECs) in vitro. METHODS: Prostanoids were assessed in different cellular models by immunoassays. The effect of the administration of AF3485 (30 and 100 mg/kg,i.p.) or celecoxib (20mg/kg, i.p.), for 3 days, on the urinary levels of enzymatic metabolites of prostanoids, PGE-M, PGI-M, and TX-M were assessed by LC-MS. RESULTS: In LPS-stimulated whole blood, AF3485 inhibited PGE2 biosynthesis, in a concentration-dependent fashion. At 100µM, PGE2 levels were reduced by 66.06 ± 3.30%, associated with a lower extent of TXB2 inhibition (40.56 ± 5.77%). AF3485 administration to CFA-treated rats significantly reduced PGE-M (P < 0.01) and TX-M (P < 0.05) similar to the selective COX-2 inhibitor, celecoxib. In contrast, AF3485 induced a significant (P < 0.05) increase of urinary PGI-M while it was reduced by celecoxib. In LPS-stimulated human monocytes, AF3485 inhibited PGE2 biosynthesis with an IC50 value of 3.03 µM (95% CI:0.5-8.75). At 1µM, AF3485 enhanced TXB2 while at higher concentrations, the drug caused a concentration-dependent inhibition of TXB2. At 100 µM, maximal inhibition of the two prostanoids was associated with the downregulation of COX-2 protein by 86%. These effects did not involve AMPK pathway activation, IkB stabilization, or PPARγ activation. In HUVEC, AF3485 at 100 µM caused a significant (P < 0.05) induction of COX-2 protein associated with enhanced PGI2 production. These effects were reversed by the PPARγ antagonist GW9662. CONCLUSIONS: The inhibitor of human mPGES-1 AF3485 is a novel antiinflammatory compound which can also modulate COX-2 induction by inflammatory stimuli. The compound also induces endothelial COX-2-dependent PGI2 production via PPARγ activation, both in vitro and in vivo, which might translate into a protective effect for the cardiovascular system.

The anti-inflammatory agent bindarit acts as a modulator of fatty acid-binding protein 4 in human monocytic cells.

We investigated the cellular and molecular mechanisms by which bindarit, a small indazolic derivative with prominent anti-inflammatory effects, exerts its immunoregulatory activity in lipopolysaccharide (LPS) stimulated human monocytic cells. We found that bindarit differentially regulates the release of interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1), enhancing the release of IL-8 and reducing that of MCP-1. These effects specifically required a functional interaction between bindarit and fatty acid binding protein 4 (FABP4), a lipid chaperone that couples intracellular lipid mediators to their biological targets and signaling pathways. We further demonstrated that bindarit can directly interact with FABP4 by increasing its expression and nuclear localization, thus impacting on peroxisome proliferator-activated receptor γ (PPARγ) and LPS-dependent kinase signaling. Taken together, these findings suggest a potential key-role of FABP4 in the immunomodulatory activity of bindarit, and extend the spectrum of its possible therapeutic applications to FABP4 modulation.

The mTOR kinase inhibitor rapamycin enhances the expression and release of pro-inflammatory cytokine interleukin 6 modulating the activation of human microglial cells.

Emerging evidence suggests the potential use of rapamycin in treatment of several neurological disorders. The drug readily crosses the blood brain barrier and may exert direct immunomodulatory effects within the brain. Microglia are the main innate immune cells of the brain, thus critically involved in the initiation and development of inflammatory processes at this level. However, there are conflicting data from rodent studies about the pharmacological effects of rapamycin on microglial inflammatory responses. Considering that rodent microglia display relevant biochemical and pharmacological differences compared to human microglia, in the present study we studied the effects of rapamycin in an experimental model of human microglia, the human microglial clone 3 (HMC3) cell line. Rapamycin was tested in the nM range both under basal conditions and in cells activated with a pro-inflammatory cytokine cocktail, consisting in a mixture of interferon-γ and interleukin-1ß (II). The drug significantly increased II stimulatory effect on interleukin-6 (IL-6) expression and release in the HMC3 cells, while reducing the production of free oxygen radicals (ROS) both under basal conditions and in cells activated with II. Consistently with its known molecular mechanism of action, rapamycin reduced the extent of activation of the so-called 'mechanistic' target of rapamycin complex 1 (mTORC1) kinase and the total amount of intracellular proteins. In contrast to rodent cells, rapamycin did not alter human microglial cell viability nor inhibited cell proliferation. Moreover, rapamycin did not exert any significant effect on the morphology of the HMC3 cells. All together these data suggest that the inhibition of mTORC1 in human microglia by rapamycin results in complex immunomodulatory effects, including a significant increase in the expression and release of the pro-inflammatory IL-6.

The human microglial HMC3 cell line: where do we stand? A systematic literature review.

Microglia, unique myeloid cells residing in the brain parenchyma, represent the first line of immune defense within the central nervous system. In addition to their immune functions, microglial cells play an important role in other cerebral processes, including the regulation of synaptic architecture and neurogenesis. Chronic microglial activation is regarded as detrimental, and it is considered a pathogenic mechanism common to several neurological disorders. Microglial activation and function have been extensively studied in rodent experimental models, whereas the characterization of human cells has been limited due to the restricted availability of primary sources of human microglia. To overcome this problem, human immortalized microglial cell lines have been developed. The human microglial clone 3 cell line, HMC3, was established in 1995, through SV40-dependent immortalization of human embryonic microglial cells. It has been recently authenticated by the American Type Culture Collection (ATCC®) and distributed under the name of HMC3 (ATCC®CRL-3304). The HMC3 cells have been used in six research studies, two of which also indicated by ATCC® as reference articles. However, a more accurate literature revision suggests that clone 3 was initially distributed under the name of CHME3. In this regard, several studies have been published, thus contributing to a more extensive characterization of this cell line. Remarkably, the same cell line has been used in different laboratories with other denominations, i.e., CHME-5 cells and C13-NJ cells. In view of the fact that "being now authenticated by ATCC®" may imply a wider distribution of the cells, we aimed at reviewing data obtained with the human microglia cell line clone 3, making the readers aware of this complicated nomenclature. In addition, we also included original data, generated in our laboratory with the HMC3 (ATCC®CRL-3304) cells, providing information on the current state of the culture together with supplementary details on the culturing procedures to obtain and maintain viable cells.

Murine mPGES-1 3D structure elucidation and inhibitors binding mode predictions by homology modeling and site-directed mutagenesis.

Microsomal prostaglandin E synthase-1 (mPGES-1) constitutes an inducible glutathione-dependent integral membrane protein that catalyzes the oxido-reduction of cyclooxygenase derived PGH2 into PGE2. mPGES-1 is an essential enzyme involved in a variety of human diseases or pathological conditions, such as rheumatoid arthritis, fever, and pain; it is therefore regarded as a primary target for development of next-generation anti-inflammatory drugs. Several compounds targeting human mPGES-1 have been reported in the literature. However, none of them is really specific for mPGES-1, and quite surprisingly, all of these compounds have very low or no activity against murine mPGES-1, making preclinical development hard and very expensive. In order to overcome this unresolved question, the current study focuses on the elucidation of the molecular determinants of murine mPGES-1 ligand binding modes combining protein homology modeling and site-directed mutagenesis approaches. We have developed, for the first time, two murine mPGES-1 models, describing both the closed and the open/active conformation of the enzyme. The 3D structure of human mPGES-1 having been recently disclosed, the main differences between the human and the murine enzyme models are described, emphasizing the smaller dimensions of the rodent substrate binding site, which could account for different activity of a ligand toward the two species. Furthermore, active binding modes are hypothesized, highlighting the most likely important residues for inhibition activity, whose identification is supported by in-house mutagenesis experiments. The results of our work could provide grounds for a rational structure-based drug design aimed to identify new inhibitors active against both human and murine mPGES-1.

Pharmacological inhibition of microsomal prostaglandin E synthase-1 suppresses epidermal growth factor receptor-mediated tumor growth and angiogenesis.

BACKGROUND: Blockade of Prostaglandin (PG) E(2) production via deletion of microsomal Prostaglandin E synthase-1 (mPGES-1) gene reduces tumor cell proliferation in vitro and in vivo on xenograft tumors. So far the therapeutic potential of the pharmacological inhibition of mPGES-1 has not been elucidated. PGE(2) promotes epithelial tumor progression via multiple signaling pathways including the epidermal growth factor receptor (EGFR) signaling pathway. METHODOLOGY/PRINCIPAL FINDINGS: Here we evaluated the antitumor activity of AF3485, a compound of a novel family of human mPGES-1 inhibitors, in vitro and in vivo, in mice bearing human A431 xenografts overexpressing EGFR. Treatment of the human cell line A431 with interleukin-1beta (IL-1ß) increased mPGES-1 expression, PGE(2) production and induced EGFR phosphorylation, and vascular endothelial growth factor (VEGF) and fibroblast growth factor-2 (FGF-2) expression. AF3485 reduced PGE(2) production, both in quiescent and in cells stimulated by IL-1ß. AF3485 abolished IL-1ß-induced activation of the EGFR, decreasing VEGF and FGF-2 expression, and tumor-mediated endothelial tube formation. In vivo, in A431 xenograft, AF3485, administered sub-chronically, decreased tumor growth, an effect related to inhibition of EGFR signalling, and to tumor microvessel rarefaction. In fact, we observed a decrease of EGFR phosphorylation, and VEGF and FGF-2 expression in tumours explanted from treated mice. CONCLUSION: Our work demonstrates that the pharmacological inhibition of mPGES-1 reduces squamous carcinoma growth by suppressing PGE(2) mediated-EGFR signalling and by impairing tumor associated angiogenesis. These results underscore the potential of mPGES-1 inhibitors as agents capable of controlling tumor growth.

Effects of AF3442 [N-(9-ethyl-9H-carbazol-3-yl)-2-(trifluoromethyl)benzamide], a novel inhibitor of human microsomal prostaglandin E synthase-1, on prostanoid biosynthesis in human monocytes in vitro.

Inhibitors of microsomal prostaglandin (PG) E synthase-1 (mPGES-1) are being developed for the relief of pain. Redirection of the PGH(2) substrate to other PG synthases, found both in vitro and in vivo, in mPGES-1 knockout mice, may influence their efficacy and safety. We characterized the contribution of mPGES-1 to PGH(2) metabolism in lipopolysaccharide (LPS)-stimulated isolated human monocytes and whole blood by studying the synthesis of prostanoids [PGE(2), thromboxane (TX)B(2), PGF(2alpha) and 6-keto-PGF(1alpha)] and expression of cyclooxygenase (COX)-isozymes and down-stream synthases in the presence of pharmacological inhibition by the novel mPGES-1 inhibitor AF3442 [N-(9-ethyl-9H-carbazol-3-yl)-2-(trifluoromethyl)benzamide]. AF3442 caused a concentration-dependent inhibition of PGE(2) in human recombinant mPGES-1 with an IC(50) of 0.06microM. In LPS-stimulated monocytes, AF3442 caused a concentration-dependent reduction of PGE(2) biosynthesis with an IC(50) of 0.41microM. At 1microM, AF3442 caused maximal selective inhibitory effect of PGE(2) biosynthesis by 61+/-3.3% (mean+/-SEM, P<0.01 versus DMSO vehicle) without significantly affecting other prostanoids (i.e. TXB(2), PGF(2alpha) and 6-keto-PGF(1alpha)). In LPS-stimulated whole blood, AF3442 inhibited in a concentration-dependent fashion inducible PGE(2) biosynthesis with an IC(50) of 29microM. A statistically significant inhibition of mPGES-1 activity was detected at 10 and 100microM (38+/-14%, P<0.05, and 69+/-5%, P<0.01, respectively). Up to 100microM, the other prostanoids were not significantly affected. In conclusion, AF3442 is a selective mPGES-1 inhibitor which reduced monocyte PGE(2) generation also in the presence of plasma proteins. Pharmacological inhibition of mPGES-1 did not translate into redirection of PGH(2) metabolism towards other terminal PG synthases in monocytes. The functional relevance of this observation deserves to be investigated in vivo.

Regulation of the microsomal prostaglandin E synthase-1 in polarized mononuclear phagocytes and its constitutive expression in neutrophils.

PGs are potent mediators of pain and inflammation. PGE synthases (PGES) catalyze the isomerization of PGH(2) into PGE(2). The microsomal (m)PGES-1 isoform serves as an inducible PGES and is responsible for the production of PGE(2), which mediates acute pain in inflammation and fever. The present study was designed to investigate the regulation of expression of mPGES-1 in polarized phagocytes, which represent central, cellular orchestrators of inflammatory reactions. Here, we report that human peripheral blood monocytes did not express mPGES-1. Exposure to LPS strongly induced mPGES-1 expression. Alternatively activated M2 monocytes-macrophages exposed to IL-4, IL-13, or IL-10 did not express mPGES-1, whereas in these cells, IL-4, IL-13, and to a lesser extent, IL-10 or IFN-gamma inhibited LPS-induced, mPGES-1 expression. It is unexpected that polymorphonuclear leukocytes expressed high basal levels of mPGES-1, which was up-regulated by LPS and down-regulated by IL-4 and IL-13. Induction of mPGES-1 and its modulation by cytokines were confirmed at the protein level and correlated with PGE(2) production. Cyclooxygenase 2 expression tested in the same experimental conditions was modulated in monocytes and granulocytes similarly to mPGES-1. Thus, activated M1, unlike alternatively activated M2, mononuclear phagocytes express mPGES-1, and IL-4, IL-13, and IL-10 tune expression of this key enzyme in prostanoid metabolism. Neutrophils, the first cells to enter sites of inflammation, represent a ready-made, cellular source of mPGES-1.

Acetaminophen down-regulates interleukin-1beta-induced nuclear factor-kappaB nuclear translocation in a human astrocytic cell line.

In previous studies performed to elucidate acetaminophen mechanism of action, we demonstrated that acetaminophen inhibits prostaglandin E2 production by interleukin (IL)-1beta-stimulated T98G human astrocytic cells, without affecting cyclooxygenase-2 enzymatic activity. As this result suggests an effect at transcriptional level, we examined whether the drug interferes with the activation of nuclear factor (NF)-kappaB and STAT3 transcription factors and with SAPK signal transducing factor. Western blot analysis of IkappaBalpha protein in the cytoplasm of IL-1beta-stimulated T98G cells and electrophoretic mobility shift assay (EMSA) on corresponding nuclear extracts indicate that acetaminophen (10-1000 microM) dose-dependently inhibits both IkappaBalpha degradation and NF-kappaB nuclear translocation. In the same cell type neither IL-1beta-dependent SAPK activation nor IL-6-induced STAT3 phosphorylation is affected by the drug. These data indicate that therapeutic concentrations of acetaminophen induce an inhibition of IL-1beta-dependent NF-kappaB nuclear translocation. The selectivity of this effect suggests the existence of an acetaminophen specific activity at transcriptional level that may be one of the mechanisms through which the drug exerts its pharmacological effects.

Synthesis of heteroaromatic analogues of (2-aryl-1-cyclopentenyl-1-alkylidene)-(arylmethyloxy)amine COX-2 inhibitors: effects on the inhibitory activity of the replacement of the cyclopentene central core with pyrazole, thiophene or isoxazole ring.

Several heteroaromatic analogues of (2-aryl-1-cyclopentenyl-1-alkylidene)-(arylmethyloxy)amine COX-2 inhibitors, in which the cyclopentene moiety was replaced by pyrazole, thiophene or isoxazole ring, were synthesized, in order to verify the influence of the different nature of the central core on the COX inhibitory properties of these kinds of molecules. Among the compounds tested, only the 3-(p-methylsulfonylphenyl) substituted thiophene derivatives 17 and 22, showed a certain COX-2 inhibitory activity, accompanied by an appreciable COX-2 versus COX-1 selectivity. Only one of the 1-(p-methylsulfonylphenyl)pyrazole compounds (16) displayed a modest inhibitory activity towards both type of isoenzymes, while the pyrazole 1-(p-aminosulfonylphenyl) substituted 12 proved to be significantly active only towards COX-1. All the isoxazole derivatives were inactive on both COX isoforms.

Aryl-substituted methyleneaminoxymethyl (MAOM) analogues of diarylcyclopentenyl cyclooxygenase-2 inhibitors: effects of some structural modifications on their biological properties.

The (E)-[2-(4-aminosulfonylphenyl)-1-cyclopentenyl-1-methyliden]-(arylmethyloxy)amines (6a,b), which are the sulfonamidic analogues of the previously described methylsulfonyl derivatives 5a,b, and their corresponding sulfides (7a,b) and sulfoxides (8a,b) were synthesised in order to obtain information about the role played by these different sulphur-containing groups in the cyclooxygenase-2 inhibitory activity of this class of compounds. In addition, other chemical manipulations concerning the oxime-ether substituent of this type of derivatives were affected by preparing compounds 9a,b, which present a methyl group on the oximic carbon of the oxime-ether chain of 5a,b, and compounds 10 and 11, in which the atomic sequence (C=NOCH(2)) of the MAOMM of 8b and 5b, respectively, is inverted. Compounds 6-11 were tested in vitro for their inhibitory activity towards COX-1 and COX-2 by measuring prostaglandin E2 (PGE2) production in U937 cell lines and activated J774.2 macrophages, respectively. Some of the new compounds showed an appreciable in vitro COX-2 inhibitory activity, with IC(50) values in the microM (7a,b, 8a and 9b) or sub-microM (8b) range. This last compound was also assayed in vivo for its antiinflammatory activity by means of the carrageenan-induced paw edema test in rats. No inhibitory effects were detected up to dose of 30 mg kg(-1) orally administered.

(E)-[2-(4-Methylsulphonylphenyl)-1-cyclopentenyl-1-methyliden](arylmethyloxy)amines. Methyleneaminoxymethyl (MAOM) analogues of diarylcyclopentenyl cyclooxygenase-2 inhibitors: synthesis and biological properties.

The (E)-[2-(4-Methylsulphonylphenyl)-1-cyclopentenyl-1-methyliden](methyloxy)amine (5) and (arylmethyloxy)amines (6-12) were designed in order to verify the effects on the biological properties of the substitution of an aryl of selective diarylcyclopentenyl cyclooxygenase-2 (COX-2) inhibitors of type 3 with a methyleneaminoxymethyl moiety (MAOMM). Compounds 5-12 were tested in vitro for their inhibitory activity towards COX-1 and COX-2 by measuring prostaglandin E2 (PGE2) production in U937 cell lines and activated J774.2 macrophages, respectively. The compound with the highest in vitro activity towards COX-2 (9) was also assayed in vivo for its antiinflammatory activity by means of the carrageenan-induced paw edema test in rats. Some of the new compounds showed an appreciable in vitro COX-2 inhibitory activity, with IC(50) values in the microM (6,7,9,10,11) range. Compound 9 also exhibited an appreciable in vivo activity (29% inhibition at a dose of 30 mg kg(-1)) when administered intraperitoneally. The structural parameters of 9 were determined by X-ray crystallographic analysis.