Design and synthesis of pyrimido[4,5-b][1,4]benzothiazine derivatives, as potent 15-lipoxygenase inhibitors

Thiourea compounds as multifaceted bioactive agents in medicinal chemistry

Microbial resistance (MR) and cancer are global healthcare pitfalls that have caused millions of deaths and pose a significant pharmaceutical challenge, with clinical cases increasing. Thioureas are preferred structures in medicinal chemistry, chemosensors, and organic synthesis platforms. In fact, thiourea (TU) moieties serve as a common framework for several medications and bioactive substances, demonstrating a wide range of therapeutic and pharmacological accomplishments. The integration of the thiourea moiety into a diverse range of organic molecules has resulted in very flexible compounds with widespread uses in medicinal chemistry. Moreover, for over a century, TU and its metal complexes have been characterized for their biological activity. Finally, we provide an assessment and future outlook of different organo-thiourea derivatives, from the very beginning to the most recent discoveries in medicinal activity.

Evaluation of several farnesyloxycarbostyril derivatives as potential 15-LOX-1 inhibitors for prostate cancer treatment

The impact of 15-lipoxygenase-1 (15-LOX-1) in the progression of prostate cancer (PCa) is noteworthy, as it correlates with the Gleason score of the disease. Thus, development of specific 15-LOX-1 inhibitors would be desirable for targeted therapy of PCa. This study focused on evaluating the anti-prostate cancer potency of three farnesyloxycarbostyril derivatives, 6-, 7- and 8-farnesyloxycarbostyril (6-, 7- and 8-FQ), as potential inhibitors of 15-LOX-1 on PCa cells. To this end, the enzymatic activity of 15-LOX was first assessed in PCa and human dermal fibroblast (HDF) cells. Subsequently, the cytotoxic effects and apoptosis-inducing capabilities of the compounds were assessed through MTT assay and FITC-annexin V/PI staining, respectively. Among the compounds, 8-FQ was selected for further assessment in a mouse model bearing xenograft human PCa tumor. The results demonstrated that the most effective compound, 8-FQ, caused an 84-fold and 15.7-fold reduction in 15-LOX activity in PC-3 cells at 30 and 14 μM concentrations, respectively. The MTT assay revealed a dose- and time-dependent toxicity of the compounds on PCa cells, and flow cytometry results indicated that apoptosis served as the dominant mechanism of cell death. Given the upregulation of 15-LOX-1 in human PCa cells, the study concludes that the heightened sensitivity to 8-FQ is likely associated with elevated levels of 15-LOX-1. In vivo experiments using immunosuppressed C57BL/6 mice bearing human PC-3 tumors revealed that 8-FQ, at a dosage of 10 mg/kg, exhibited strong antitumor effects with minimal side effects, indicating its potential as a promising therapeutic agent for PCa following further optimization.

Design, synthesis, and pharmacological evaluation of indazole carboxamides of N-substituted pyrrole derivatives as soybean lipoxygenase inhibitors

In this paper, we attempted to develop a novel class of compounds against lipoxygenase, a key enzyme in the biosynthesis of leukotrienes implicated in a series of inflammatory diseases. Given the absence of appropriate human 5-lipoxygenase crystallographic data, solved soybean lipoxygenase-1 and -3 structures were used as a template to generate an accurate pharmacophore model which was further used for virtual screening purposes. Eight compounds (1-8) have been derived from the in-house library consisting of N-substituted pyrroles conjugated with 5- or 6-indazole moieties through a carboxamide linker. This study led to the discovery of hit molecule 8 bearing a naphthyl group with the IC50 value of 22 μM according to soybean lipoxygenase in vitro assay. Isosteric replacement of naphthyl ring with quinoline moieties and reduction of carbonyl carboxamide group resulted in compounds 9-12 and 13, respectively. Compound 12 demonstrated the most promising enzyme inhibition. In addition, compounds 8 and 12 were found to reduce the carrageenan-induced paw edema in vivo by 52.6 and 49.8%, respectively. In view of the encouraging outcomes concerning their notable in vitro and in vivo anti-inflammatory activities, compounds 8 and 12 could be further optimized for the discovery of novel 5-lipoxygenase inhibitors in future.

Anti-lung Cancer Activity of Synthesized Substituted 1,4-Benzothiazines: An Insight from Molecular Docking and Experimental Studies

BACKGROUND

Thiazine, a 6-membered distinctive heterocyclic motif with sulfur and nitrogen atoms, is one of the heterocyclic compounds that functions as a core scaffold in a number of medicinally significant molecules. Small thiazine-based compounds may operate simultaneously on numerous therapeutic targets and by employing a variety of methods to halt the development, proliferation, and vasculature of cancer cells. We have, herein, reported a series of substituted 1,4 benzothiazines as potential anticancer agents for the treatment of lung cancer.

METHODS

In order to synthesize 2,3-disubstituted-1,4 benzothiazines in good yield, a facile green approach for the oxidative cycloaddition of 2-amino benzenethiol and 1,3-dicarbonyls employing a catalytic amount of ceric ammonium nitrate has been devised. All the molecules have been characterized by spectral analysis and tested for anticancer activity against the A-549 lung cancer cell line using various functional assays. Further in silico screening of compound 3c against six crucial inflammatory molecular targets, such as Il1-α (PDB ID: 5UC6), Il1- β (PDB ID: 6Y8I), Il6 (PDB ID: 1P9M), vimentin (PDB ID: 3TRT), COX-2 (PDB ID: 5KIR), Il8 (PDB ID: 5D14), and TNF-α (PDB ID: 2AZ5), was done using AutoDock tool.

RESULTS

Among the synthesized compounds, propyl 3-methyl-3,4-dihydro-2H-benzo[b][1,4]thiazine-2- carboxylate (3c) was found to be most active based on cell viability assays using A-549 lung cancer cell line and was found to effectively downregulate various pro-inflammatory genes, like Il1-α, Il1-β, Il6, vimentin, COX-2, Il8, and TNF-α in vitro. The ability of the molecule to effectively suppress the proliferation and migration of lung cancer cells in vitro has been further demonstrated by the colony formation unit assay and wound healing assay. Molecular docking analysis showed the maximal binding affinity (- 7.54 kcal/mol) to be exhibited by compound 3c against IL8.

CONCLUSION

A green unconventional route for the synthesis of 2,3-disubstituted-1,4 benzothiazines has been developed. All the molecules were screened for their activity against lung cancer and the data suggested that the presence of an additional unbranched alkyl group attached to the thiazine ring increased their activity. Also, in vitro and in silico modeling confirmed the anti-cancer efficiency of compound 3c, encouraging the exploration of such small molecules against cancer.

Magic shotgun approach to anti-inflammatory pharmacotherapy: Synthesis of novel thienopyrimidine monomers/heterodimer as dual COX-2 and 15-LOX inhibitors endowed with potent antioxidant activity

Emerging evidence points to the intertwining framework of inflammation and oxidative stress in various ailments. We speculate on the potential impact of the magic shotgun approach in these ailments as an attempt to mitigate the drawbacks of current NSAIDs. Hence, we rationally designed and synthesized new tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine monomers/heterodimer as dual selective COX-2/15-LOX inhibitors with potent antioxidant activity. The synthesized compounds were challenged with diverse in vitro biological assays. Regarding the monomeric series, compound 5k exerted the highest COX-2 inhibitory activity (IC50 = 0.068 μM, SI = 160.441), while compound 5i showed the highest 15-LOX inhibitory activity (IC50 = 1.97 μM). Surpassing the most active monomeric members, the heterodimer 11 stemmed as the most potent and selective one in the whole study (COX-2 IC50 = 0.065 μM, SI = 173.846, 15-LOX IC50 = 1.86 μM). Heterodimer design was inspired by the cross-talk between the partner monomers of the COX-2 isoform. Moreover, some of our synthesized compounds could significantly reverse the LPS-enhanced production of ROS and proinflammatory cytokines (IL-6, TNF-α, and NO) in RAW 264.7 macrophages. Again, the heterodimer showed the strongest suppressor activity against ROS (IC50 = 18.79 μM) and IL-6 (IC50 = 4.15 μM) production outperforming the two references, celecoxib and diclofenac. Regarding NO suppressor activity, compound 5j (IC50 = 18.62 μM) surpassed the two references. Only compound 5a significantly suppressed TNF-α production (IC50 = 19.68 μM). Finally, molecular modeling simulated the possible binding scenarios of our synthesized thienopyrimidines within the active sites of COX-2 and 15-LOX. These findings suggest that those novel thienopyrimidines are promising leads showing pharmacodynamics synergy against the selected targets.

Microglia ferroptosis is regulated by SEC24B and contributes to neurodegeneration

Iron dysregulation has been implicated in multiple neurodegenerative diseases, including Parkinson's disease (PD). Iron-loaded microglia are frequently found in affected brain regions, but how iron accumulation influences microglia physiology and contributes to neurodegeneration is poorly understood. Here we show that human induced pluripotent stem cell-derived microglia grown in a tri-culture system are highly responsive to iron and susceptible to ferroptosis, an iron-dependent form of cell death. Furthermore, iron overload causes a marked shift in the microglial transcriptional state that overlaps with a transcriptomic signature found in PD postmortem brain microglia. Our data also show that this microglial response contributes to neurodegeneration, as removal of microglia from the tri-culture system substantially delayed iron-induced neurotoxicity. To elucidate the mechanisms regulating iron response in microglia, we performed a genome-wide CRISPR screen and identified novel regulators of ferroptosis, including the vesicle trafficking gene SEC24B. These data suggest a critical role for microglia iron overload and ferroptosis in neurodegeneration.

Convenient synthesis of benzothiazinoisoindol-11-ones and benzoindenothiazin-11-ones, and antimicrobial testing thereof

Benzo[5,6][1,4]thiazino[3,4-a]isoindol-11-ones 5a-t and benzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones 6a-e were synthesized conveniently via cyclocondensation of 2-bromo-2-(2/3-substitutedphenyl)-1H-indene-1,3(2H)-diones and 2-aminobenzenethiols in freshly dried ethanol with 70-85% yields. The synthesized derivatives were well characterized by employing different spectral techniques (FTIR, ¹H & ¹³C NMR and HRMS) and X-ray crystallographic analysis. Further, all the reported compounds were tested for their antibacterial and antifungal activities using Ciprofloxacin and Fluconazole as standard drugs, respectively. The results of antimicrobial evaluation revealed that compounds 5o and 5t displayed remarkable inhibitory activity against B. subtilis, S. aureus, P. aeruginosa and A. niger with MIC values in the range of 0.0141-0.0283 µmol/mL, whereas 5j was found active against E. coli and C. albicans with MIC values of 0.0286 µmol/mL and 0.0143 µmol/mL, respectively. Additionally, among all the benzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones, 6c exhibited excellent inhibition against all the tested bacterial and fungal strains with MIC values ranging from 0.0143 to 0.1145 µmol/mL. Structure activity relationships were also established for all the tested benzo[5,6][1,4]thiazino[3,4-a]isoindol-11-ones 5a-t.

Investigating the effects of two novel 4-MMPB analogs as potent lipoxygenase inhibitors for prostate cancer treatment

Background

Lipoxygenases are one of the critical signaling mediators which can be targeted for human prostate cancer (PC) therapy. In this study, 4-methyl-2-(4-methylpiperazinyl)pyrimido[4,5-b]benzothiazine (4-MMPB) and its two analogs, 4-propyl-2-(4-methylpiperazinyl)pyrimido[4,5-b]benzothiazine (4-PMPB) and 4-ethyl-2-(4-methylpiperazinyl)pyrimido[4,5-b]benzothiazine (4-EMPB), were proposed to have anti-tumor properties in prostate cancer.

Methods

After synthesizing the compounds, cytotoxic effects of 4-MMPB and its two analogs against PC-3 cancerous and HDF normal cells were investigated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay and then mechanism of cell death was assessed by flow cytometry. Finally, the anti-tumor effects of the mentioned compounds were investigated in an immunocompromised C57BL/6 mouse model.

Results

4-PMPB and 4-EMPB had similar anti-cancer effects on PC-3 cells as compared with 4-MMPB, while they were not effective on normal cells. Moreover, apoptosis and ferroptosis were the main mechanisms of induced cell death in these cancerous cells. Furthermore, in vivo results indicated that both analogs had similar anti-cancer effects as 4-MMPB, leading to delayed tumor growth without any noticeable side effects in weight loss and histological investigations.

Conclusion

Thus, our results suggest that specific targeting of lipoxygenases via 4-MMPB analogs can be considered as a treatment of choice for PC therapy, although it requires further investigations.

Insights into the inhibitory mechanism and molecular interaction of novel alkaloids from Beilschmiedia glabra with lipoxygenase and acetylcholinesterase

In this study, the mechanism underlying acetylcholinesterase (AChE) and 5-lipoxygenase (LOX) inhibition by two novel alkaloids, beilschglabrine A and beilschglabrine B, as well as their interaction footprints on the binding pockets were investigated. The results showed that beilschglabrine A and beilschglabrine B inhibit both AChE and LOX in a competitive manner by binding to their active sites thereby interfering with substrate access. The interaction of the alkaloids with the enzymes was favorable and stable with low binding energy values which correlate well with their IC[Formula: see text]. The depicted molecular interaction, structure-energetic pattern and binding conformations confirmed that beilschglabrine A is more potent than beilschglabrine B. The differences in the binding pose and potency of the alkaloids is occasioned by an extra methyl moiety on beilschglabrine B. The chemical scaffold of the alkaloids respected Lipinski’s rule of five and may be relevant in the development of new anti-inflammatory and anti-neurodegenerative disease drugs acting via AChE and LOX inhibition.

Stylosin and some of its synthetic derivatives induce apoptosis in prostate cancer cells as 15-lipoxygenase enzyme inhibitors

Overexpression of 15-lipoxygenase-1 (15-LOX-1) enzyme has been reported in prostate tumors, and its expression levels are associated with the degree of cancer malignancy. The aim of this study was to investigate inhibitory effects of stylosin and some similar synthetic monoterpenoids on 15-LOX and also their cytotoxic and anti-cancer activities on prostate cancer cells. Cytotoxicity of compounds was evaluated on prostate cancer cell line "PC-3" and normal human fibroblast "HFF3" cells using AlamarBlue reduction test. The inhibitory effects of the compounds against soybean 15-LOX, a commercially available enzyme, were also assessed. Finally, mechanism of cell death was investigated by flow cytometry. Some of these terpenoids had cytotoxic effects on PC-3 cells, and strong positive correlation was observed between the 15-LOX-1 inhibition potential and the cytotoxicity of the compounds. Moreover, flow cytometry results indicated that apoptosis was the predominant mechanism of induced cell death, which emphasizes the potential of these compounds in prostate cancer therapy. Among studied terpenoids, "fenchyl ferulate" exhibited about three times more cytotoxicity than cisplatin. Strong positive correlation observed between 15-LOX inhibition potential and cytotoxicity of the compounds indicates selective anti-cancer properties of the compounds might be exerted via inhibition of 15-LOX-1 in PC-3 cells. Furthermore, observed cytotoxicity is mediated through apoptosis, which is probably triggered via 15-LOX-1 inhibition.

Computational Analysis of LOX1 Inhibition Identifies Descriptors Responsible for Binding Selectivity

Lipoxygenases are a family of cytosolic, peripheral membrane enzymes, which catalyze the hydroperoxidation of polyunsaturated fatty acids and are implicated in the pathogenesis of major human diseases. Over the years, a substantial number of scientific reports have introduced inhibitors active against one or another subtype of the enzyme, but the selectivity issue has proved to be a major challenge for drug design. In the present work, we assembled a dataset of 317 structurally diverse molecules hitherto reported as active against 15S-LOX1, 12S-LOX1, and 15S-LOX2 and identified, using supervised machine learning, a set of structural descriptors responsible for the binding selectivity toward the enzyme 15S-LOX1. We subsequently incorporated these descriptors in the training of QSAR models for LOX1 activity and selectivity. The best performing classifiers are two stacked models that include an ensemble of support vector machine, random forest, and k-nearest neighbor algorithms. These models not only can predict LOX1 activity/inactivity but also can discriminate with high accuracy between molecules that exhibit selective activity toward either one of the isozymes 15S-LOX1 and 12S-LOX1.

8-Farnesyloxycoumarin induces apoptosis in PC-3 prostate cancer cells by inhibition of 15-lipoxygenase-1 enzymatic activity

Prostate cancer is the second most common cancer in men worldwide. Overexpression of 15-lipoxygenase-1 (15-LOX-1) has been reported in prostate cancer patients. This study aimed to investigate the cytotoxic and anticancer effects of 8-farnesyloxycoumarin (8f), a prenylated coumarin, by inhibition of 15-LOX-1 activity, in prostate cancer cells. The activity of 15-LOX-1 and the inhibitory effects of 8f on this enzyme were first assessed in PC-3 and DU145 prostate cancer cells. The MTT assay was used to examine the cytotoxicity effects of 8f on PC-3 cells following 15-LOX-1 inhibition. To determine the type of cell death, chromatin condensation and DNA damage were examined by DAPI staining and comet assay, respectively. Furthermore, the effects of 8f on the cell cycle were evaluated by PI staining and flow cytometry. The activity of 15-LOX-1 was determined to be higher in PC-3 compared with DU145 cells; thus, this cell line was selected for further experiments. 8f induced cell death in PC-3 cells in a dose-dependent and time-dependent manner, with IC50 values similar to cisplatin, which was used as a control. However, 8f did not significantly affect the viability of HFF3, human foreskin fibroblast cells, under identical conditions. The appearance of apoptotic cells after 8f treatment was confirmed by the presence of PC-3 cells containing condensed chromatin as shown by DAPI staining. The comet assay indicated the induction of DNA damage in cancerous cells compared with normal cells. In addition, 8f induced a potent G1 cell-cycle arrest in PC-3 cells. Our results showed that the antitumor effects of 8f on PC-3 cells were promoted by apoptosis induction, probably via inhibition of 15-LOX-1 activity, thus suggesting that 8f may have therapeutic value in prostate cancer treatment.

Azaphenothiazines - promising phenothiazine derivatives. An insight into nomenclature, synthesis, structure elucidation and biological properties

For the last two decades, classical phenothiazines have attracted attention of researchers, as the hitherto investigations have revealed many significant biological activities within this class of compounds, other than originally discovered neuroleptic ones. Important, new pharmaceutical results on phenothiazines, as 10-substituted dibenzothiazines, were recently highlighted in several reviews. Azaphenothiazines are structurally modified phenothiazines by substitution of one or both benzene rings in the phenothiazine ring system with the azine rings, such as: pyridine, pyridazine, pyrimidine, pyrazine, 1,2,4-triazine, quinoline, quinoxaline, benzoxazine and benzothiazine. They form over 50 different heterocyclic systems, of tri-, tetra-, penta- and hexacyclic structures, and contain from one to even four azine nitrogen atoms. This review summarizes the methodical knowledge on azaphenothiazines, referring to their nomenclature, synthesis, structure analysis and above all significant varied biological activities, examined in vitro and in vivo. It describes, in addition, current trends in the synthesis of azaphenothiazines. The influence of the azaphenothiazine ring system, the nature of the substituents, predominantly at the thiazine nitrogen atom, as well as at the azine nitrogen atom and carbon atom, on the biological activities, were also discussed.

Synthesis of new derivatives of 4-(4-methyl-5H-pyrimido[4,5-b][1,4]thiazin-2-yl)morpholine and 4-methyl-2-(piperidin-1-yl)-5H-pyrimido[4,5-b][1,4]thiazine

Several derivatives of the novel 4-(4-methyl-5 H-pyrimido[4,5- b][1,4]thiazin-2-yl)morpholine and 4-methyl-2-(piperidin-1-yl)-5 H-pyrimido[4,5- b][1,4]thiazine ring systems have been synthesised through cyclocondensation of 5-amino-6-methylpyrimidine-4-thiols and the appropriate α-haloketone in glacial acetic acid under reflux.

Easy and rapid preparation of benzoylhydrazides and their diazene derivatives as inhibitors of 15-lipoxygenase

Two series of diaza derivatives were prepared by solvent-free condensation of benzoic acid and 4-substituted phenylhydrazines in order to obtain phenylhydrazides (HYD series) and, by oxidation of these compounds, the corresponding benzoyldiazenes (DIA series). Both sets were evaluated as inhibitors of soybean 15-lipoxygenase activity and antioxidant capability in the FRAP and CUPRAC assays. The most potent inhibitors of both series exhibited IC50 values in the low micromolar range. Kinetic studies showed that at least the more active compounds were competitive inhibitors. Docking results indicated that the most potent inhibitor interacts strongly with Ile-839 and iron in the active site.

2-(chromon-3-yl)imidazole derivatives as potential antimicrobial agents: synthesis, biological evaluation and molecular docking studies

A series of novel 2-(chromon-3-yl)-4,5-diphenyl-1H-imidazoles (4a-h) were synthesized by one pot condensation of substituted 3-formylchromones (1a-h), benzil (2) and ammonium acetate (3) in refluxing acetic acid at 110 °C under N2 atmosphere. Allylation of compounds 4a-h with allyl bromide in the presence of fused K2CO3 furnished N-allyl-2-(chromon-3-yl)-4,5-diphenyl-1H-imidazoles (6a-h). The synthesized compounds were characterized spectroscopically and evaluated for in vitro antimicrobial activity against various pathogenic bacterial and fungal strains by disc diffusion method. Compounds bearing electron withdrawing substituents such as bromo (4f) showed significant inhibitory activity against S. cerevisiae (MIC 1.4 μg/ml) and 4g containing chloro substituent, displayed more inhibitory potential against C. albicans (MIC 1.5), as compared to the standard drugs. Compounds 6a and 4c exhibit remarkable inhibitory potential against B. subtilis with MIC 0.98 and 1.23, respectively. The time kill assay for active compound 6a was performed by viable cell count (VCC) method to elucidate the microbicidal nature of 2-(chromon-3-yl)imidazoles. A molecular docking study of most active compounds with target 'lanosterol 14α-demethylase' (CYP51) was performed to unravel the mode of antifungal action.

(2Z)-2-Benzylidene-4-[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]-3,4-dihydro-2H-1,4-benzothiazin-3-one

In the title molecule, C25H20N4OS, the dihedral angle between the plane of the dihydrothiazine ring and that of the fused C6ring is 1.0 (2)°, indicating a slight twist in the dihydrobenzothiophene unit; there is a roughly perpendicular relationship between the fused C6ring and the triazole ring [dihedral angle = 73.2 (1)°]. The packing comprises chains running parallel to thecaxis formed by weak C—H...O hydrogen bonds, with the benzyl rings intercalated between adjacent chains. The benzyl ring is statistically disordered. The sample was refined as a twin.

Synthesis and biological evaluation of novel propargylquinobenzothiazines and their derivatives as potential antiproliferative, anti-inflammatory, and anticancer agents

Azaphenothiazines containing the quinoline ring, 8-10-substituted 6H-quinobenzothiazines and 6H-diquinothiazine were transformed into new 6-propargyl and 6-dialkylaminobutynyl derivatives containing the triple bond. Most of them displayed strong antiproliferative actions against human peripheral blood mononuclear cells (PBMC) stimulated with phytohemagglutinin A (PHA), strongly suppressed lipopolysaccharide (LPS)-induced TNF-α production by whole blood human cell cultures, and exhibited low cytotoxicity. Three propargylquinobenzothiazines with the bromine, trifluoromethyl, and methylthio groups at position 9 and propargyldiquinothiazine exhibited comparable actions to cisplatin against the L-1210 and SW-948 tumor lines. 6-Propargyl-9-trifluoromethylquinobenzothiazine was shown to block caspase 3 expression and inhibit expression of caspase 8 and 9 in Jurkat cells indicating its possible mechanism of action. These derivatives could be promising, potential therapeutics for treatment of neoplastic diseases and autoimmune disorders.

Synthesis and Evaluation of Novel Quinazolinone-1,2,3-Triazoles as Inhibitors of Lipoxygenase

This work reports the successful synthesis of quinazolinones carrying triazole derivatives with potent lipoxygenase inhibitory activities. This protocol involves sequential reactions affording novel products in high yields without the need for a tedious work-up procedure.

Involvement of gap junctions between smooth muscle cells in sustained hypoxic pulmonary vasoconstriction development: a potential role for 15-HETE and 20-HETE

In response to hypoxia, the pulmonary artery normally constricts to maintain optimal ventilation-perfusion matching in the lung, but chronic hypoxia leads to the development of pulmonary hypertension. The mechanisms of sustained hypoxic pulmonary vasoconstriction (HPV) remain unclear. The aim of this study was to determine the role of gap junctions (GJs) between smooth muscle cells (SMCs) in the sustained HPV development and involvement of arachidonic acid (AA) metabolites in GJ-mediated signaling. Vascular tone was measured in bovine intrapulmonary arteries (BIPAs) using isometric force measurement technique. Expression of contractile proteins was determined by Western blot. AA metabolites in the bath fluid were analyzed by mass spectrometry. Prolonged hypoxia elicited endothelium-independent sustained HPV in BIPAs. Inhibition of GJs by 18β-glycyrrhetinic acid (18β-GA) and heptanol, nonspecific blockers, and Gap-27, a specific blocker, decreased HPV in deendothelized BIPAs. The sustained HPV was not dependent on Ca(2+) entry but decreased by removal of Ca(2+) and by Rho-kinase inhibition with Y-27632. Furthermore, inhibition of GJs decreased smooth muscle myosin heavy chain (SM-MHC) expression and myosin light chain phosphorylation in BIPAs. Interestingly, inhibition of 15- and 20-hydroxyeicosatetraenoic acid (HETE) synthesis decreased HPV in deendothelized BIPAs. 15-HETE- and 20-HETE-stimulated constriction of BIPAs was inhibited by 18β-GA and Gap-27. Application of 15-HETE and 20-HETE to BIPAs increased SM-MHC expression, which was also suppressed by 18β-GA and by inhibitors of lipoxygenase and cytochrome P450 monooxygenases. More interestingly, 15,20-dihydroxyeicosatetraenoic acid and 20-OH-prostaglandin E2, novel derivatives of 20-HETE, were detected in tissue bath fluid and synthesis of these derivatives was almost completely abolished by 18β-GA. Taken together, our novel findings show that GJs between SMCs are involved in the sustained HPV in BIPAs, and 15-HETE and 20-HETE, through GJs, appear to mediate SM-MHC expression and contribute to the sustained HPV development.

Crystal structure of (Z)-ethyl 2-{5-[(2-benzyl-idene-3-oxo-2,3-di-hydro-benzo[b][1,4]thia-zin-4-yl)meth-yl]-1H-1,2,3-triazol-1-yl}acetate

The title compound, C22H20N4O3S, features two fused six-membered rings linked to a 1,2,3-triazole ring which is attached to an ethyl acetate group. The heterocycle in the benzo-thia-zine residue has an envelope conformation with the S atom being the flap. The conformation of the ethyl acetate side chain, which is directed to the same side of the mol-ecule as the C6 ring of the fused-ring system, may be partially established by a pair of weak intra-molecular C-H⋯O(carbon-yl) inter-actions. The three-dimensional packing is aided by inter-molecular C-H⋯O and C-H⋯N inter-actions.

Synthesis of Dihydrobenzo[b]pyrimido[4,5-e][1,4]Thiazepines; Derivatives of a Novel Ring System

Several derivatives of the novel dihydrobenzo[b]pyrimido[4,5-e][1,4]thiazepine ring system have been synthesised through the initial heterocyclisation of 2,4-dichloro-5-(chloromethyl)-6-methylpyrimidine with o-aminothiophenol followed by treatment with various secondary amines in boiling ethanol.

Synthesis of new derivatives of 10H-benzo[b]pyridazino[3,4-e][1,4]thiazines

New 10H-benzo[b]pyridazino[3,4-e][1,4]thiazines were prepared and evaluated for inhibitory activity against soybean 15-lipoxygenase enzyme. These compounds were synthesized by the sequential treatment of 4-bromo-3,6-dichloropyridazine with 2-aminothiophenol and a secondary amine with the subsequent heterocyclization in the presence of sodium amide.

Crystal structure of (E)-2-benzyl-idene-4-[(3-phenyl-4,5-di-hydro-isoxazol-5-yl)meth-yl]-2H-benzo[b][1,4]thia-zin-3(4H)-one

In the title compound, C₂₅H₂₀N₂O₂S, the di­hydro­isoxazole ring exhibits an envelope conformation with the methine atom being the flap, while the 1,4-thia­zine ring displays a screw-boat conformation. The six-membered ring fused to the 1,4-thia­zine ring makes dihedral angles of 63.04 (2) and 54.7 (2)° with the mean planes through the five-membered heterocycle and the attached phenyl ring, respectively. The phenyl group connected to the 1,4-thia­zine ring is disordered over two sites [major component = 0.57 (2)]. The most prominent inter­actions in the crystal structure are C—H⋯O hydrogen bonds that link mol­ecules, forming inversion dimers, and C—H⋯N hydrogen bonds that link the dimers into columns parallel to the b axis.

An Alternative Approach to the Synthesis of New Pyrimido[5′,4′:5,6][1,4] Thiazino[2,3-B]Quinoxaline Derivatives

An alternative approach to the synthesis of a series of new pyrimido[5′,4′:5,6][1,4]thiazino[2,3-b]quinoxaline derivatives is described. Reaction of 5-bromo-2,4-dichloro-6-methylpyrimidine and 3-aminoquinoxaline-2-thiol leads to the key intermediate 3-[(5-bromo-2-chloro-6-methylpyrimidin-4-yl)thio]quinoxalin-2-amine. This intermediate can be transformed into the title ring systems by subsequent treatment either with secondary amines followed by intramolecular cyclisation or initial intramolecular cyclisation with subsequent reaction with secondary amines.

Synthesis and evaluation of a new series of 3,5-bis((5-bromo-6-methyl-2-t-aminopyrimidin-4-yl)thio)-4H-1,2,4-triazol-4-amines and their cyclized products 'pyrimidinylthio pyrimidotriazolothiadiazines' as 15- lipo-oxygenase inhibitors

A series of new 3,5-bis((5-bromo-6-methyl-2-t-aminopyrimidin-4-yl)thio)-4H-1,2,4-triazol-4-amines and their cyclized products 'pyrimidinylthio pyrimidotriazolothiadiazines' were designed, synthesized, and evaluated as potential inhibitors of 15-lipo-oxygenase (15-LO). Their syntheses started by initial condensation of 2:1 equivalents of pyrimidine with triazole and subsequent nucleophilic displacement of the chlorine atoms with secondary amines and finally cyclocondensation in the presence of NaNH2. The compounds 4d and 4f showed the best IC50 of 15-LO inhibition (IC50 = 9 and 12 μm, respectively). Compounds 4a-g were docked into 15-LO. We suggest that the hydrogen bonds in quaternary nitrogen of piperazine ring of compounds 4d and 4f appear to play major role in lipo-oxygenase inhibition by this set of synthesized analogs and hydrophobic nature of this protein's binding site should be considered in ongoing investigations.