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Lungs are pharmacologically active organs and the pulmonary drug metabolism is of interest for inhaled drugs design. Carboxylesterases (CESs) are enzymes catalyzing the hydrolysis of many structurally different ester, amide and carbamate chemicals, including prodrugs. For the first time, the presence, kinetics, inhibition and inter-individual variations of the major liver CES isozymes (CES1 and CES2) were investigated in cytosol and microsomes of human lungs from 20 individuals using 4-nitrophenyl acetate (pNPA), 4-methylumbelliferyl acetate (4-MUA), and fluorescein diacetate (FD) as substrates the rates of hydrolysis (V max ) for pNPA and 4-MUA, unlike FD, were double in microsomes than in cytosol. In these cellular fractions, the V max of pNPA, as CES1 marker, were much greater (30–50-fold) than those of FD, as a specific CES2 marker. Conversely, the K m values were comparable suggesting the involvement of the same enzymes. Inhibition studies revealed that the FD hydrolysis was inhibited by bis-p-nitrophenylphosphate, phenylmethanesulfonyl fluoride, and loperamide (specific for CES2), whereas the pNPA and 4-MUA hydrolysis inhibition was limited. Inhibitors selective for other esterases missed having any effect on above-mentioned activities. In cytosol and microsomes of 20 lung samples, inter-individual variations were found for the hydrolysis of pNPA (2.5–5-fold), FD or 4-MUA (8–15-fold). Similar variations were also observed in CES1 and CES2 gene expression, although determined in a small number (n = 9) of lung samples. The identification of CES1 and CES2 and their variability in human lungs are important for drug metabolism and design of prodrugs which need to be activated in this organ. [ABSTRACT FROM AUTHOR]

Human carboxylesterases (CESs) and arylacetamide deacetylase (AADAC) are serine-esterase enzymes catalyzing the hydrolysis of many compounds containing esters, amides, thioesters, or acetyl groups. This study aimed to investigate the presence, kinetic parameters, and inhibition of CES1, CES2, and AADAC in A549, H460, and H727 pulmonary cells in both living cells and S9 fractions. The p -nitrophenyl acetate (p NPA) and 4-methylumbelliferyl acetate (4-MUA) were used as non-selective esterase substrates, whereas phenacetin as selective AADAC substrate. CESs activities were also investigated in living cells by cellular bioimaging using selective fluorescent probes. AADAC gene was detected in A549 and H460 cells; nevertheless, arylesterase activity was not found in relative S9 fractions. Besides, CES1 and CES2 were expressed to a different extent by all lung cells, and enzymatic activities were quite overlapping each other. All enzymes exhibited a typical Michaelis-Menten saturation curve and, regarding 4-MUA, similar K m values were found in both living cells and S9 fractions. Conversely, kinetic parameters relative to the p NPA hydrolysis by S9 fractions were significantly lower than those detected in living cells. Inhibition studies revealed that 4-MUA hydrolysis was inhibited by bis- p -nitrophenyl phosphate and phenylmethanesulfonyl fluoride more than loperamide; on the contrary, p NPA hydrolysis inhibition was limited with similar inhibition profiles being obtained in both living cells and S9 fractions. The presence of carboxylesterases was definitely confirmed by cellular bioimaging. These findings add information to esterase knowledge in pulmonary cells that could be used as in vitro models for toxicological and pharmacological studies. [Display omitted] • Lung cells comparison toward carboxylesterase and arylacetamide deacetylase enzymes • Esterase activities estimation in human A549, H460, and H727 pulmonary cells • CES1 and CES2 genes were expressed by all analyzed cell lines. • AADAC gene was found expressed by only A549 and H460 cell lines. • Comparable CESs activities were detected among all analyzed lung cells. [ABSTRACT FROM AUTHOR]

Carnitine plays a physiologically important role in the β-oxidation of fatty acids, facilitating the transport of long-chain fatty acids across the inner mitochondrial membrane. Distribution of carnitine within the body tissues is mainly performed by novel organic cation transporter (OCTN) family, including the isoforms OCTN1 (SLC22A4) and OCTN2 (SLC22A5) expressed in human. We performed here a characterization of carnitine transport in human airway epithelial cells A549, Calu-3, NCl-H441, and BEAS-2B, by means of an integrated approach combining data of mRNA/protein expression with the kinetic and inhibition analyses of L-[ 3 H]carnitine transport. Carnitine uptake was strictly Na + -dependent in all cell models. In A549 and BEAS-2B cells, carnitine uptake was mediated by one high-affinity component (K m < 2 μM) identifiable with OCTN2. In both these cell models, indeed, carnitine uptake was maximally inhibited by betaine and strongly reduced by SLC22A5/OCTN2 silencing. Conversely, Calu-3 and NCl-H441 exhibited both a high (K m ~ 20 μM) and a low affinity (K m > 1 mM) transport component. While the high affinity component is identifiable with OCTN2, the low affinity uptake is mediated by ATB 0,+ , a Na + , and Cl – -coupled transport system for neutral and cationic amino acids, as demonstrated by the inhibition by leucine and arginine, as well as by SLC6A14/ATB 0,+ silencing. The presence of this transporter leads to a massive accumulation of carnitine inside the cells and may be of peculiar relevance in pathologic conditions of carnitine deficiency, such as those associated to OCTN2 defects. [ABSTRACT FROM AUTHOR]

Organic cation transporters (OCT1–3) mediate the transport of organic cations including inhaled drugs across the cell membrane, although their role in lung epithelium hasn't been well understood yet. We address here the expression and functional activity of OCT1–3 in human airway epithelial cells A549, Calu-3 and NCl-H441. Kinetic and inhibition analyses, employing [ 3 H]1-methyl-4-phenylpyridinium (MPP+) as substrate, and the compounds quinidine, prostaglandine E2 (PGE 2 ) and corticosterone as preferential inhibitors of OCT1, OCT2, and OCT3, respectively, have been performed. A549 cells present a robust MPP+ uptake mediated by one high-affinity component ( K m ~ 50 μM) which is identifiable with OCT3. Corticosterone, indeed, completely inhibits MPP+ transport, while quinidine and PGE 2 are inactive and SLC22A3/OCT3 silencing with siRNA markedly lowers MPP+ uptake. Conversely, Calu-3 exhibits both a high ( K m < 20 μM) and a low affinity ( K m > 0.6 mM) transport components, referable to OCT3 and OCT1, respectively, as demonstrated by the inhibition analysis performed at proper substrate concentrations and confirmed by the use of specific siRNA. These transporters are active also when cells are grown under air–liquid interface (ALI) conditions. Only a very modest saturable MPP+ uptake is measurable in NCl-H441 cells and the inhibitory effect of quinidine points to OCT1 as the subtype functionally involved in this model. Finally, the characterization of MPP+ transport in human bronchial BEAS-2B cells suggests that OCT1 and OCT3 are operative. These findings could help to identify in vitro models to be employed for studies concerning the specific involvement of each transporter in drug transportation. [ABSTRACT FROM AUTHOR]

Abstract: A series of pyrazoles and pyrazolo[3,4-d]pyridazinones were synthesized and evaluated for their PDE4 inhibitory activity. All the pyrazoles were found devoid of activity, whereas some of the novel pyrazolo[3,4-d]pyridazinones showed good activity as PDE4 inhibitors. The most potent compounds in this series showed an IC50 in the nanomolar range. The ability to inhibit TNF-α release in human PBMCs was determined for two representative compounds, finding values in the sub-micromolar range. SARs studies demonstrated that the best arranged groups around the heterocyclic core are 2-chloro-, 2-methyl- and 3-nitrophenyl at position 2, an ethyl ester at position 4 and a small alkyl group at position 6. Molecular modeling studies performed on a representative compound allowed to define its binding mode to the PDE4B isoform. [Copyright &y& Elsevier]