5-Substituted 2-amino-4,6-dihydroxypyrimidines and 2-amino-4,6-dichloropyrimidines: synthesis and inhibitory effects on immune-activated nitric oxide production.

A series of 5-substituted 2-amino-4,6-dihydroxypyrimidines were prepared by a modified condensation of the corresponding monosubstituted malonic acid diesters with guanidine in an excess of sodium ethoxide. The optimized procedure using Vilsmeier-Haack-Arnold reagent, followed by immediate deprotection of the (dimethylamino)methylene protecting groups, has been developed to convert the 2-amino-4,6-dihydroxypyrimidine analogs to novel 5-substituted 2-amino-4,6-dichloropyrimidines in high yields. Pilot screening for biological properties of the prepared compounds was done in mouse peritoneal cells using the in vitro nitric oxide (NO) assay. Irrespective of the substituent at the 5 position, 2-amino-4,6-dichloropyrimidines inhibited immune-activated NO production. The most effective was 5-fluoro-2-amino-4,6-dichloropyrimidine with an IC 50 of 2 µM (higher activity than the most potent reference compound) while the IC 50s of other derivatives were within the range of 9-36 µM. The 2-amino-4,6-dihydroxypyrimidine counterparts were devoid of any NO-inhibitory activity. The compounds had no suppressive effects on the viability of cells. The Mechanism of action remains to be elucidated.

Effects of sesquiterpene, flavonoid and coumarin types of compounds from Artemisia annua L. on production of mediators of angiogenesis.

BACKGROUND: In addition to recognized antimalarial effects, Artemisia annua L. (Qinghao) possesses anticancer properties. The underlying mechanisms of this activity are unknown. The aim of our experiments was to investigate the effects of distinct types of compounds isolated from A. annua on the immune-activated production of major mediators of angiogenesis playing a crucial role in growth of tumors and formation of metastasis. METHODS: Included in the study were the sesquiterpene lactones artemisinin and its biogenetic precursors arteannuin B and artemisinic acid. The semi-synthetic analogue dihydroartemisinin was used for comparative purposes. The flavonoids were represented by casticin and chrysosplenol D, the coumarin type of compounds by 4-methylesculetin. Their effects on the lipopolysaccharide (LPS)-induced in vitro production of nitric oxide (NO) were analyzed in rat peritoneal cells using Griess reagent. The LPS-activated production of prostaglandin E2 (PGE2) and cytokines (VEGF, IL-1ß, IL-6 and TNF-α) was determined in both rat peritoneal cells and human peripheral blood mononuclear cells using ELISA. RESULTS: All sesquiterpenes (artemisinin, dihydroartemisinin, artemisinic acid, arteannuin B) significantly reduced production of PGE2. Arteannuin B also inhibited production of NO and secretion of cytokines. All NO, PGE2 and cytokines were suppressed by flavonoids casticin and chrysosplenol D. The coumarin derivative, 4-methylesculetin, was ineffective to change the production of any of these factors. CONCLUSIONS: The inhibition of immune mediators of angiogenesis by sesquiterpene lactones and flavonoids may be one of the mechanisms of anticancer activity of Artemisia annua L.

Trilobolide and related sesquiterpene lactones from Laser trilobum possessing immunobiological properties.

Three new and five known sesquiterpene lactones were isolated from the roots of Laser trilobum (L.) Borkh. Chemical identity of the known compounds and structural analysis of the new ones were determined by HR MS and NMR spectroscopy. The two new sesquiterpene lactones: 2-acetoxytrilobolide and 2-hydroxy-10-deacetyltrilobolide belong to the guaianolide type, and the third one, eudeslaserolide, to the biogenetically related eudesmanolide type. Both types, together with their biogenetic precursor of germacranolide type (laserolide) are present in L. trilobum, as well as in the related Laserpitium species. Purposefully selected set of these native sesquiterpene lactones was tested for specific immunobiological properties. The obtained results demonstrate that trilobolide and its acetoxy analog are strong activators of cytokine secretion. On the contrary, the other L. trilobum and Laserpitium siler constituents are only very mild activators, or even inhibitors of the cytokine and nitric oxide production.

Hepatocyte growth on polycapronolactone and 2-hydroxyethylmethacrylate nanofiber sheets enhanced by bone marrow-derived mesenchymal stromal cells.

BACKGROUND/AIMS: The development of hepatocyte-based Bioartificial Liver Assist Devices, intended for the therapy of chronic and fulminant liver failure, is one of the important tasks in the area of tissue engineering. New advances in the development of semipermeable non-woven nanofiber biomaterials and the co-cultivation of bone marrow mesenchymal stromal cells (BMSC) and hepatocytes could be utilized in order to maintain hepatocyte cultures in these devices. METHODOLOGY: We have compared rat hepatocyte growth on nanofiber biomaterials from different polymers, 2-hydroxyethylmethacrylate (HEMA) and ethoxyethylmethacrylate (EOEMA) copolymers, polyurethane (PUR), chitosan and polycapronolactone (PCL) spun from different solvent mixtures. RESULTS: In all cases the adhesion of hepatocytes to nanofibers was significantly better/stronger than to unstructured polymer surfaces; coating the nanofibers with collagen did not increase cell adhesion. We found the best hepatocyte adhesion on HEMA/EOEMA copolymer nanofibers and PCL nanofibers spun from a mixture of ethylacetate and dimethyl sulphoxide. Using a migration assay, we observed the migration of BMSC towards hepatocytes; hepatocytes cocultivated with BMSC excreted lower amounts of stress enzymes. CONCLUSIONS: The results demonstrate that nonwoven nanofiber layers, particularly those containing BMSC, are a suitable biocompatible support for functional hepatocyte cultures and that they can be used in a laboratory bioreactor or potentially in clinical setting.

Microfiltration method of removal of bacterial contaminants and their monitoring by nitric oxide and Limulus assays.

Similar to lipopolysaccharide (LPS), a product of Gram-negative bacteria, the signal macromolecules of Gram-positive bacteria lipoteichoic acid (LTA) and peptidoglycan (PGN) possess multiple biological activities. They may be a source of misinterpretation of experimental findings. We have found that not only LPS but also LTA and PGN can be detected by the Limulus amebocyte lysate (LAL) assay. All of them stimulate the high output in vitro nitric oxide (NO) production of in rat peritoneal cells. The onset of the NO enhancement was observed with 25-100pg/ml of LPS and 25-100ng/ml of PGN and LTA. Polymyxin B (PMX), if applied at concentration 10,000-fold higher than that of LPS, can completely inhibit the NO and LAL binding responses of LPS. The NO-stimulatory and LAL-binding properties of LTA and PGN are not eliminated by PMX. Handling of LPS contamination with PMX may be associated with serious problems because it possesses intrinsic biological activity and becomes cytotoxic at concentration >25µg/ml. The present findings suggest a convenient alternative avoiding these issues. As monitored by the NO and LAL assays, even high amounts of LPS as well as PGN and LTA can be removed by molecular mass cutoff microfiltration. All types of the filters (3kDa to 100kDa) are equally effective. It is suggested that the microfiltration procedure may be considered as a preferable, general and easy method of sample decontamination.

Stimulation of nitric oxide, cytokine and prostaglandin production by low-molecular weight fractions of probiotic Lactobacillus casei lysate.

OBJECTIVES: Major medical indications of probiotic bacteria are conditions associated with the gastrointestinal tract. They exhibit not only the local but also systemic effects, the molecular mechanisms of which are poorly understood. We hypothesized that the action at remote sites of the body could be at least partially attributed to substances of the low molecular mass released from digested bacteria and able to cross the intestinal barrier. The aim of the study was the analysis of immunobiological properties of bacterial lysates and characterization of chemical constituents participating on this mode of action. METHODS: Lactobacillus casei probiotic strain DN-114001 was employed. Lysates were prepared by passing bacteria through a French press (1500 psi) followed by lyophilisation. The fractions were prepared by the microfiltration of the crude lysate using the 3-, 10-, 30-, 50-, and 100-kDa cutoff filters (Amicon® Ultra 0.5 ml, Millipore Corp.). This procedure completely removes biologically active bacterial macromolecules such as peptidoglycan (PGN), lipoteichoic acid (LTA) and lipopolysaccharide (LPS). Effects of microfiltrates on the in vitro production of nitric oxide (NO), cytokines, and prostaglandin E2 (PGE2) were investigated in rat peritoneal cells. RESULTS: The original crude lysate (≤10 µg/ml) activated the biosynthesis of NO, PGE2, and secretion of cytokines. The amount of the lysate needed for the preparation of microfiltered fractions exhibiting immunostimulatory effects was 10-fold higher (100 µg/ml). The molecules with the molecular mass ≤3 kDa were responsible for approximately 45% and 83% of the NO- and PGE2-enhancing activities of the crude lysate, respectively. The microfiltered fractions of the lysate also enhanced secretion of interleukin-6 and tumor necrosis factor-α but not that of interleukin-10 and interferon-γ. CONCLUSION: The Lactobacillus casei probiotic strain DN-114001 contains low molecular mass (≤3 kDa) molecules possessing immunostimulatory properties. Their chemical nature remains to be identified.

Differential effects of acyclic nucleoside phosphonates on nitric oxide and cytokines in rat hepatocytes and macrophages.

Acyclic nucleoside phosphonates (ANP) are virostatics effective against viruses like hepatitis B virus and human immunodeficiency virus. Our previous reports indicated immunomodulatory activities of ANP in mouse and human innate immune cells. Recently, evidence has increased that hepatocytes may play an active role in immune regulation of the liver homeostasis or injury. In this study we investigated possible immunomodulatory effects of ANP on rat hepatocytes and macrophages. Nitric oxide (NO) production and secretion of cytokines (IL-1α, IL-1ß, IL-2, IL-4, IL-6, IL-10, IL-13, IL-18, IFN-γ, TNF-α and GM-CSF) were analyzed under in vitro conditions. Test compounds included: 9-[2-(phosphonomethoxy)ethyl]adenine (PMEA; adefovir); 9-[2-(phosphonomethoxy)ethyl]-2,6-diaminopurine (PMEDAP); (R)- and (S)-enantiomers of 9-[2-(phosphonomethoxy)propyl]adenine [(R)-PMPA; tenofovir] and [(S)-PMPA]; 9-[2-(phosphonomethoxy)propyl]-2,6-diaminopurine [(R)-PMPDAP] and [(S)-PMPDAP]. The group of test compounds also included their N(6)-substituted derivatives. Some of ANP which are able to induce NO production and cytokine secretion in cultured macrophages possess the same immunobiological activity in isolated hepatocytes. The extent of responses is in range of LPS/IFN-γ stimulation in both types of cells. The effects of active ANP on NO expression and cytokine secretion are dose- and time-dependent. Interestingly, the spectrum of detected cytokines induced by ANP is broader in hepatocytes. The results also confirm immunomodulatory effects of some ANP on rodent macrophages. Moreover, we demonstrate for the first time immunobiological reactivity of primary rat hepatocytes induced by exogenous ANP compounds. The potential of hepatocytes to synthesize cytokines can contribute to better understanding of liver immune function and can serve for pharmacological intervention in liver diseases.

Sesquiterpene lactone trilobolide activates production of interferon-γ and nitric oxide.

Trilobolide (TB), a sesquiterpene lactone isolated from Laser trilobum is an inhibitor of sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA). We have found that upon the in vitro exposure to TB, rodent peritoneal cells and human peripheral blood mononuclear cells secrete high amounts of IFN-γ. The effect is associated with the stimulation of high output NO biosynthesis in rat cells. The stimulatory potential of TB depends on the activation of MAP kinases p38 and ERK1/2, and transcription factor NF-κB. BAPTA-AM, a chelator of the intracellular calcium, remained without any effect on the secretion of IFN-γ triggered by TB. These results demonstrate that TB is a potent immunostimulatory agent.