Nitric oxide production by tumor targets in response to TNF: paradoxical correlation with susceptibility to TNF-mediated cytotoxicity without direct involvement in the cytotoxic mechanism

N-Heterocyclic choline analogues based on 1,2,3,4-tetrahydro(iso)quinoline scaffold with anticancer and anti-infective dual action

BACKGROUND

Pharmacological effects of biologically active "small molecules" can be improved by their targeted modification, which affects drug delivery and interaction with tumor cells and microorganisms. We aimed to evaluate anticancer and antimicrobial activity of lipid-like choline derivatives modified via simultaneous introduction of tetrahydro(iso)quinoline based pharmacophore system at nitrogen atom and long chain alkyl substituent at oxygen atom.

METHODS

Target compounds were synthesized under phase-transfer catalysis conditions followed by quaternization, and evaluated for cytotoxicity and NO-generation ability on HT-1080 and MG-22A tumor cell lines and NIH 3T3 normal mouse fibroblasts, and screened for antimicrobial activity against gram-positive (Staphylococcus aureus and Bacillus cereus) and gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa and Proteus mirabilis) and fungi (Candida albicans and Aspergillus niger). Inhibitory action of active compounds towards E. coli DNA gyrase was investigated.

RESULTS

Target compounds exhibit high selective cytotoxicity (LC₅₀ < 1 μg/mL) and NO-induction ability, and reveal strong antimicrobial activity with MIC and MBC/MFC values of 0.5-32 μg/mL, predominantly vs. gram-positive bacteria and fungi. Tested substances displayed inhibitory effect towards E. coli DNA gyrase, though less than ciprofloxacin. Tetrahydroisoquinoline derivatives and compounds possessing substituents with chain length of 10 and 11 carbon atoms have highest indices of activities.

CONCLUSIONS

Lipid-like N-heterocyclic choline analogues based on 1,2,3,4-tetrahydro(iso)quinoline scaffold, possessing very high cytotoxicity with attendant strong antimicrobial activity are the leads for developing effective dual action therapeutics.

Interferon regulatory factor (IRF)-1 is a master regulator of the cross talk between macrophages and L929 fibrosarcoma cells for nitric oxide dependent tumoricidal activity

Macrophage tumoricidal activity relies, mainly, on the release of Tumor Necrosis Factor alpha (TNFα) and/or on reactive oxygen or nitrogen intermediates. In the present work, we investigated the cytotoxic activity of resident peritoneal macrophages against L929 fibrosarcoma cell line in vitro and in vivo. Resident macrophages lysed L929 cells in a mechanism independent of TNFα and cell-to-cell contact. The cytotoxic activity was largely dependent on nitric oxide (NO) release since treatment with L-NAME (NOS inhibitor) inhibited L929 cells killing. Macrophages from mice with targeted deletion of inducible NO synthase (iNOS) together with L929 cells produced less NO and displayed lower, but still significant, tumoricidal activity. Notably, NO production and tumor lysis were abolished in co-cultures with macrophages deficient in Interferon Regulatory Factor, IRF-1. Importantly, the in vitro findings were reproduced in vivo as IRF-1 deficient animals inoculated i.p with L929 cells were extremely susceptible to tumor growth and their macrophages did not produce NO, while WT mice killed L929 tumor cells and their macrophages produced high levels of NO. Our results indicate that IRF-1 is a master regulator of bi-directional interaction between macrophages and tumor cells. Overall, IRF-1 was essential for NO production by co-cultures and macrophage tumoricidal activity in vitro as well as for the control of tumor growth in vivo.

Synthesis and biological evaluation of lipid-like 5-(2-hydroxyethyl)-4-methyl-1,3-thiazole derivatives as potential anticancer and antimicrobial agents

The observed coupling of high anticancer and antimicrobial activity for novel lipid-like compounds9,10and13based on the 5-(2-hydroxyethyl)-4-methyl-1,3-thiazole scaffold can be important as a basis for further drug development.

Organosilicon-containing thiazole derivatives as potential lipoxygenase inhibitors and anti-inflammatory agents

A number of trimethylsiloxyalkyl and trialkylsilylalkyl thiazole derivatives have been evaluated for their anti-inflammatory activity, lipoxygenase inhibiting properties, and cytotoxicity. The investigated compounds have been found to protect in vivo against carrageenin-induced edema, especially 3-(4-trimethylsiloxypiperidin-1-yl)-N-(thiazol-2-yl)-propionamide (21) and 2-amino-3-(γ-trimethylsilylpropyl)thiazolium iodide (22), which exhibited good anti-inflammatory activity: 57.2% CPE inhibition in dose of 0.2 mmol/kg for compound 21 and 55.0% in dose of 0.01 mmol/kg for compound 22. All the compounds tested inhibited soybean lipoxygenase activity. 2-(4-Trimethylsilyloxypiperidin-1-yl)-N-[4-(p-methoxyphenyl)-thiazol-2-yl]-acetamide (19) was the most potent displaying inhibition against lipoxygenase (ID₅₀ = 0.01 mmol). It also possessed moderate cytotoxic effect (LC₅₀ = 13 μ g/mL, 3 × 10⁻⁸ mmol/mL) concerning MG-22A cell lines.

Paradoxical effects of two oximes on nitric oxide production by purified NO synthases, in cell culture and in animals

We have studied the impact of two novel compounds TO-85 (2,6-di-(alpha-aziridino-alpha-hydroxyiminomethyl)pyridine and TO-133 (bis-(diaziridinoglyoximato)copper), designed as NO donors, on nitrite production by cell cultures, NO production in rat tissues and their ability to inhibit purified NO synthases (NOS). Both substances induced considerable increase of nitrite production in cell cultures. When NO production was assayed in rat organs by means of ESR using Fe(DETC) as a spin trap the anticipated NO-increasing activity of TO-85 was observed only in kidneys; the NO level increasing almost 10-fold. Treatment of rats with TO-133, decreased the NO concentration in brain cortex, cerebellum and liver. When the drugs were administered to animals with high level of iNOS expression induced by LPS, TO-85 did not significantly modify the LPS-induced NO production; administration of TO-133 caused a significant decrease of NO production in blood, brain cortex and cerebellum. Only high concentrations of TO-85 were capable of inhibiting iNOS (IC50=7 mM), the substance inhibited eNOS at lower concentrations (IC50=250 microM). Inhibitory activities of TO-85 on nNOS were dependent on BH4 concentrations, suggesting eventual competition of TO-85 with BH4 when the substance interacts with nNOS. TO-133 reduced eNOS activity with IC50=200 microM, nNOS activity with IC50=200 microM, iNOS activity was not much affected by this substance. Thus, the two tested compounds manifest opposite effects on NO production by purified enzymes and in cell culture. The pattern of the NO synthesis modification in a living animal appears to be even more complex. Our results stress the importance of direct measurements of NO in the tissues using the ESR method.

4-Methyl-1,2,3-selenadiazole-5-carboxylic acid amides: Antitumor action and cytotoxic effect correlation

Synthesis and cytotoxic activity of a series of 4-methyl-1,2,3-selenadiazole-5-carboxylic acid amides on human fibrosarcoma HT-1080, mouse hepatoma MG-22A, and mouse fibroblasts 3T3 cell lines are described. The correlation between compound LD(50) and 3T3 fibroblast cell line morphology was shown. In vivo evaluation of amides on mouse sarcoma S-180 confirms high antitumor activity (58-85%).

Interaction between cisplatin treated murine peritoneal macrophages and L929 cells: involvement of adhesion molecules, cytoskeletons, upregulation of Ca2+ and nitric oxide dependent cytotoxicity

Murine peritoneal macrophages on treatment with cisplatin (10 microg/ml) showed increased binding to L929 cells. Cisplatin treated macrophage on co-incubation with L929 cells form a distinct cytoplasmic contact between the two cells. The plasmalemmae of the two cells fuse over a large surface area. The formation of contact between the cisplatin treated macrophage and L929 cell results in the induction of apoptosis in L929 cell. Untreated macrophages did not form a contact with L929 cells and no apoptosis is observed in L929 cells. Immunofluorescence microscopical studies clearly show the participation of cytoskeleton and the adhesion molecules in the formation of contact between the two cells. Further, a significant enhancement of the expression of iNOS and cytosolic Ca2+ was observed in cisplatin treated macrophages co-incubated with L929 cells. Cisplatin treated macrophages produced significant amount of NO when co-incubated with L929 cells, while there was minimal production of NO by untreated macrophages co-incubated with L929 cells. Cisplatin treated macrophage-induced L929 cell death was NO dependent, since L-NMMA (500 microM) significantly inhibited the cytotoxicity of L929 cells. The addition of excess L-arginine (2mM) reversed the L-NMMA induced inhibition of NO production and L929 cell cytotoxicity.

Cyclosporine A and NAC on the inducible nitric oxide synthase expression and nitric oxide synthesis in rat renal artery cultured cells

BACKGROUND

The immunosuppressor cyclosporine A (CsA) presents the nephrotoxicity as its major side effect that is mostly attributed to a renal vasoconstriction. This may be due to an excessive generation of vasoconstrictors like reactive oxygen species (ROS), or due to a reduction of vasodilators such as the nitric oxide, which in turn, can be caused by increased amounts of ROS. We evaluated the effect of CsA and the antioxidant N-acetylcysteine (NAC) on inducible nitric oxide synthase (iNOS) mRNA expression and nitric oxide synthesis, in rat renal artery vascular smooth muscle cells (rVSMCs) primary culture.

METHODS

In cells treated during 72 hours with CsA (10 microg/mL), its vehicle (control) (10 microL/mL), Escherichia coli lipopolysaccharide (LPS) (100 microg/mL), CsA + LPS, NAC (6.13 mmol/L), or CsA + NAC, we determined the nitric oxide synthesis (Griess and chemiluminescence methods), iNOS expression [reverse transcription-polymerase chain reaction (RT-PCR)] and cell viability (acridine orange method).

RESULTS

In rVSMCs, LPS increased nitric oxide and iNOS expression; CsA decreased basal and LPS-induced nitric oxide and iNOS expression; NAC increased nitric oxide and blunted the nitric oxide reduction caused by CsA, with no effect on iNOS. CsA reduced cell viability.

CONCLUSION

In this study, CsA reduced nitric oxide synthesis in rVSMCs, both through iNOS down-regulation and reduction of cell viability, which could be responsible for the vasoconstrictive effect of the CsA. In the effect of CsA on nitric oxide, probably a role is also played by free radical production, as this effect was blunted by NAC.

Nitric oxide generated by iNOS reduces deformability of Lewis lung carcinoma cells

Previous studies have indicated that NO plays a crucial role in the metastasis of tumor cells and that tumor cells produce nitric oxide (NO) via inducible nitric oxide synthase (iNOS). Since the deformability of tumor cells is an important factor governing their metastatic potential, in this study we investigated the regulation of tumor cell deformability by NO. Lewis lung tumor cells (3LL cells) were also incubated with a cytokine mixture (IL-1 beta, IFN gamma, and TNF alpha). The nitrite/nitrate content of the supernatant was then measured by the Griess method, and iNOS expression was evaluated by RT-PCR in vitro. Nitrite/nitrate was produced in response to administration of the cytokine mixture, and iNOS mRNA was expressed in the cytokine-treated cells. The deformability of the 3LL cells was evaluated by measuring the peak pressure generated during their passage through a microfilter at a constant flow rate. Both the cytokine mixture and NO donor (NOC 18) significantly increased the filtration pressure, and the staining of the cells with rhodamine-phalloidin revealed assembly of F-actin in the cell membrane. In conclusion, NO plays a role in the decreased deformability of tumor cells, suggesting that NO is one of the factors that regulates metastasis.

Synthesis of antitumor 6-alkylidenepenicillanate sulfones and related 3-alkylidene-2-azetidinones

6-alkylidenepenicillanate sulfoxides and sulfones were synthesized on the base of 6-oxopenicillanate esters. The targeted splitting of their thiazolidine ring led to the formation of 3-alkylidene substituted 4-heteryldithio and 4-methylsulfonyl azetidin-2-ones. Some of mono and bicyclic beta-lactams revealed potent cytotoxic properties towards monolayer tumor cells in <10-microM concentrations.

Different effects of constitutive nitric oxide synthase and heme oxygenase on pulmonary or liver metastasis of colon cancer in mice

It has recently been reported that not only endogenous nitric oxide (NO) but also carbon monoxide (CO) produced by heme oxygenase (HO) have many physiological functions. The objective of the present study was to determine whether endogenous NO or CO is involved in the experimental pulmonary or liver metastasis of colon cancer in mice. Intravenous or intrasplenic injection of colon 26 cells from a mouse colon adenocarcinoma cell line resulted in multiple pulmonary or liver metastases. NG-nitro-L-arginine methyl ester (L-NAME), a competitive inhibitor of NO synthase (NOS), or zinc deuteroporphyrin 2, 4-bis glycol (ZnDPBG), a competitive inhibitor of HO, was administered to the mice only on the day of tumor inoculation. We assessed the number of tumor cells 24 h later and the outcome of metastases of the target organ. In the pulmonary metastasis model, L-NAME increased both the number of tumor cells 24 h later and outcome of metastases 18 days later, but did not have a significant effect on liver metastasis. On the other hand, metastasis to the liver, but not that to the lung, increased following administration of ZnDPBG. These results suggest that the activities of NOS and HO could influence experimental metastasis in an organ-specific manner.

Nitric oxide mediates apoptosis induction selectively in transformed fibroblasts compared to nontransformed fibroblasts

Nitric oxide (NO) mediates apoptosis induction in fibroblasts with constitutive src or induced ras oncogene expression, whereas nontransformed parental cells and revertants are not affected. This direct link between the transformed phenotype and sensitivity to NO-mediated apoptosis induction seems to be based on the recently described extracellular superoxide anion generation by transformed cells, as NO-mediated apoptosis induction in transformed cells is inhibited by extracellular superoxide dismutase (SOD), by SOD mimetics and by apocynin, an inhibitor of NADPH oxidase. Furthermore, nonresponsive nontransformed cells can be rendered sensitive for NO-mediated apoptosis induction when they are supplemented with xanthine oxidase/xanthine as an extracellular source for superoxide anions. As superoxide anions and NO readily interact in a diffusion-controlled reaction to generate peroxynitrite, peroxynitrite seems to be the responsible apoptosis inducer in NO-mediated apoptosis induction. In line with this conclusion, NO-mediated apoptosis induction in superoxide anion-generating transformed cells is inhibited by the peroxynitrite scavengers ebselen and FeTPPS. Moreover, direct application of peroxynitrite induces apoptosis both in transformed and nontransformed cells, indicating that peroxynitrite is no selective apoptosis inducer per se, but that selective apoptosis induction in transformed cells by NO is achieved through selective peroxynitrite generation. The interaction of NO with target cell derived superoxide anions represents a novel concept for selective apoptosis induction in transformed cells. This mechanism may be the basis for selective apoptosis induction by natural antitumor systems (like macrophages, natural killer cells, granulocytes) that utilize NO for antitumor action. Apoptosis induction mediated by NO involves mitochondrial depolarization and is blocked by Bcl-2 overexpression.