Designing the polyamine pharmacophore: influence of N-substituents on the transport behavior of polyamine conjugates

Polyamine-Based Nanostructures Share Polyamine Transport Mechanisms with Native Polyamines and Their Analogues: Significance for Polyamine-Targeted Therapy

Polyamines are small polycationic alkylamines involved in many fundamental cellular processes, including cell proliferation, survival, and protection from oxidative stress. Polyamine homeostasis is tightly regulated through coordinated biosynthesis, catabolism, and transport. Due to their continual proliferation, cancer cells maintain elevated intracellular polyamine pools. Both polyamine metabolism and transport are commonly dysregulated in cancer, and as such, polyamine analogues are a promising strategy for exploiting the increased polyamine requirement of cancer cells. One potential polyamine analogue resistance mechanism is the downregulation of the poorly defined polyamine transport system. Recent advances in nanomedicine have produced nanostructures with polyamine analogue-based backbones (nanopolyamines). Similar nanostructures with non-polyamine backbones have been shown to be transported by endocytosis. As these polyamine-based nanoparticles could be a method for polyamine analogue delivery that bypasses polyamine transport, we designed the current studies to determine the efficacy of polyamine-based nanoparticles in cells lacking intact polyamine transport. Utilizing polyamine transport-deficient derivatives of lung adenocarcinoma lines, we demonstrated that cells unable to transport natural polyamines were also resistant to nanopolyamine-induced cytotoxicity. This resistance was a result of transport-deficient cells being incapable of importing and accumulating nanopolyamines. Pharmacological modulation of polyamine transport confirmed these results in polyamine transport competent cells. These studies provide additional insight into the polyamine transport pathway and suggest that receptor-mediated endocytosis is a likely mechanism of transport for higher-order polyamines, polyamine analogues and the nanopolyamines.

Towards the Development of Frustrated Lewis Pair (FLP) Catalyzed Hydrogenations of Tertiary and Secondary Carboxylic Amides

The development of the frustrated Lewis pair catalyzed hydrogenation of tertiary and secondary amides is reviewed. Detailed insight into our strategies in order to overcome challenges during the reaction development process is provided. Furthermore, the developed chemistry is extended to the hydrogenation of polyamides and of trifluoroacetamides for the convenient introduction of trifluoroethyl groups into organic molecules.

Development of Polyamine Lassos as Polyamine Transport Inhibitors

Nine- and twelve-membered triaza-macrocycles were appended to one end of homospermidine to make polyamine lassos. These compounds were shown to be potent polyamine transport inhibitors (PTIs) using pancreatic ductal adenocarcinoma L3.6pl cells, which have high polyamine transport activity. The smaller triazacyclononane-based lasso significantly reduced the uptake of a fluorescent polyamine probe and inhibited spermidine uptake and reduced intracellular polyamine levels in difluoromethylornithine (DFMO)-treated L3.6pl cells. Both designs were shown to be effective inhibitors of ³H-spermidine uptake, with the smaller lasso outperforming the larger lasso. When the smaller lasso was challenged to inhibit each of the three radiolabeled native polyamines, it had similar K _i values as those of the known PTIs, Trimer44NMe and AMXT1501. Because of these promising properties, these materials may have future anticancer applications in polyamine blocking therapy, an approach that couples a polyamine biosynthesis inhibitor (DFMO) with a PTI to lower intracellular polyamines and suppress cell growth.

Hydrazine Hydrate Accelerates Neocuproine-Copper Complex Generation and Utilization in Alkyne Reduction, a Significant Supplement Method for Catalytic Hydrogenation

Diimine (HN═NH) is a strong reducing agent, but the efficiency of diimine oxidized from hydrazine hydrate or its derivatives is still not good enough. Herein, we report an in situ neocuproine-copper complex formation method. The redox potential of this complex enable it can serve as an ideal redox catalyst in the synthesis of diimine by oxidation of hydrazine hydrate, and we successfully applied this technique in the reduction of alkynes. This reduction method displays a broad functional group tolerance and substrate adaptability as well as the advantages of safety and high efficiency. Especially, nitro, benzyl, boc, and sulfur containing alkynes can be reduced to the corresponding alkanes directly, which provides a useful complementary method to traditional catalytic hydrogenation. Besides, we applied this method in the preparation of the Alzheimer's disease drug CT-1812 and studied the mechanism.

Synthesis and antiproliferative evaluation of some iron chelators as polyamine transporter targeting agents

A series of kojic acid derivatives based on monoamines, diamines, and triamines have been synthesized in good yield and purity. A spermidine (spd) rescue experiment was applied against MCF-7 cells to evaluate the polyamine transporter selectivity, and in vitro antiproliferative effects were determined against Hela and DU-145 cell lines. Overall, 5b showed the best selectivity for the polyamine transporter and antiproliferative effects. Therefore, the in-silico metabolism profile and ADMET properties of the title compounds were calculated by the PreADMET server. Additionally, physicochemical properties of ligands were predicted by using the Molinspiration online property calculation server.

A novel polyamine blockade therapy activates an anti-tumor immune response

Most tumors maintain elevated levels of polyamines to support their growth and survival. This study explores the anti-tumor effect of polyamine starvation via both inhibiting polyamine biosynthesis and blocking the upregulated import of polyamines into the tumor. We demonstrate that polyamine blockade therapy (PBT) co-treatment with both DFMO and a novel polyamine transport inhibitor, Trimer PTI, significantly inhibits tumor growth more than treatment with DFMO or the Trimer PTI alone. The anti-tumor effect of PBT was lost in mice where CD4⁺ and CD8⁺ T cells were antibody depleted, implying that PBT stimulates an anti-tumor immune effect that is T-cell dependent. The PBT anti-tumor effect was accompanied by an increase in granzyme B⁺, IFN-γ⁺ CD8⁺ T-cells and a decrease in immunosuppressive tumor infiltrating cells including Gr-1⁺CD11b⁺ myeloid derived suppressor cells (MDSCs), CD4⁺CD25⁺ Tregs, and CD206⁺F4/80⁺ M2 macrophages. Stimulation with tumor-specific peptides elicited elevated antigen-specific IFN-γ secretion in splenocytes from PBT-treated mice, indicating that PBT treatment stimulates the activation of T-cells in a tumor-specific manner. These data show that combined treatment with both DFMO and the Trimer PTI not only deprives polyamine-addicted tumor cells of polyamines, but also relieves polyamine-mediated immunosuppression in the tumor microenvironment, thus allowing the activation of tumoricidal T-cells.

Important role of phosphoramido linkage in imidazole-based dioleyl helper lipids for liposome stability and primary cell transfection

BACKGROUND

To optimize synthetic gene delivery systems, there is a need to develop more efficient lipid formulations. Most cationic lipid formulations contain 'helper' neutral lipids because of their ability to increase DNA delivery, in particular by improving endosomal escape of DNA molecules via the pH-buffering effect of protonatable groups and/or fusion with the lipid bilayer of endosomes.

METHODS

We evaluated the influence of the linker structure between the two oleyl chains in the helper lipid on transfection efficiency in cell lines, as well as in primary cells (hepatocytes/cardiomyocytes). We reported the synthesis of two new pH-buffering imidazole helper lipids characterized by a polar headgroup containing one (compound 6) or two (compound 5) imidazole groups and two oleyl chains linked by an amide group. We studied their association with the aminoglycoside lipidic derivative dioleylsuccinylparomomycin (DOSP), which contains two oleyl chains linked to the aminoglycoside polar headgroup via an amide function. We compared the morphology and transfection properties of such binary liposomes of DOSP/5 and DOSP/6 with those of liposomes combining DOSP with another imidazole-based dioleyl helper lipid (MM27) in which a phosphoramido group acts as a linker between the two oleyl chains and imidazole function.

RESULTS

The phosphoramido linker in the helper lipid induces a major difference in terms of morphology and resistance to decomplexation at physical pH for DOSP/helper lipid complexes.

CONCLUSIONS

This hybrid dioleyl linker composition of DOSP/MM27 led to higher transfection efficiency in cell lines and in primary cells compared to complexes with homogeneous dioleyl linker.

Assembly of plasmid DNA with pyrene-amines cationic amphiphiles into nanoparticles and their visible lysosome localization

In this study, we constructed a visible model for drug/gene dual delivery.

Conjugation with polyamines enhances the antibacterial and anticancer activity of chloramphenicol

Chloramphenicol (CAM) is a broad-spectrum antibiotic, limited to occasional only use in developed countries because of its potential toxicity. To explore the influence of polyamines on the uptake and activity of CAM into cells, a series of polyamine–CAM conjugates were synthesized. Both polyamine architecture and the position of CAM-scaffold substitution were crucial in augmenting the antibacterial and anticancer potency of the synthesized conjugates. Compounds 4 and 5, prepared by replacement of dichloro-acetyl group of CAM with succinic acid attached to N4 and N1 positions of N⁸,N⁸-dibenzylspermidine, respectively, exhibited higher activity than CAM in inhibiting the puromycin reaction in a bacterial cell-free system. Kinetic and footprinting analysis revealed that whereas the CAM-scaffold preserved its role in competing with the binding of aminoacyl-tRNA 3′-terminus to ribosomal A-site, the polyamine-tail could interfere with the rotatory motion of aminoacyl-tRNA 3′-terminus toward the P-site. Compared to CAM, compounds 4 and 5 exhibited comparable or improved antibacterial activity, particularly against CAM-resistant strains. Compound 4 also possessed enhanced toxicity against human cancer cells, and lower toxicity against healthy human cells. Thus, the designed conjugates proved to be suitable tools in investigating the ribosomal catalytic center plasticity and some of them exhibited greater efficacy than CAM itself.

Polyamine transport inhibitors: design, synthesis, and combination therapies with difluoromethylornithine

The development of polyamine transport inhibitors (PTIs), in combination with the polyamine biosynthesis inhibitor difluoromethylornithine (DFMO), provides a method to target cancers with high polyamine requirements. The DFMO+PTI combination therapy results in sustained intracellular polyamine depletion and cell death. A series of substituted benzene derivatives were evaluated for their ability to inhibit the import of spermidine in DFMO-treated Chinese hamster ovary (CHO) and L3.6pl human pancreatic cancer cells. Several design features were discovered which strongly influenced PTI potency, sensitivity to amine oxidases, and cytotoxicity. These included changes in (a) the number of polyamine chains appended to the ring system, (b) the polyamine sequence, (c) the attachment linkage of the polyamine to the aryl core, and (d) the presence of a terminal N-methyl group. Of the series tested, the optimal design was N(1),N(1'),N(1″)-(benzene-1,3,5-triyltris(methylene))tris(N(4)-(4-(methylamino)butyl)butane-1,4-diamine, 6b, which contained three N-methylhomospermidine motifs. This PTI exhibited decreased sensitivity to amine oxidases and low toxicity as well as high potency (EC50 = 1.4 μM) in inhibiting the uptake of spermidine (1 μM) in DFMO-treated L3.6pl human pancreatic cancer cells.

The use of novel C-methylated spermidine derivatives to investigate the regulation of polyamine metabolism

The polyamines are organic polycations present at millimolar concentrations in eukaryotic cells where they participate in the regulation of vital cellular functions including proliferation and differentiation. Biological evaluation of rationally designed polyamine analogs is one of the cornerstones of polyamine research. Here we have synthesized and characterized novel C-methylated spermidine analogs, that is, 2-methylspermidine, 3-methylspermidine, and 8-methylspermidine. 3-Methylspermidine was found to be metabolically stable in DU145 cells, while 8-methylspermidine was a substrate for spermidine/spermine N(1)-acetyltransferase (SSAT) and 2-methylspermidine was a substrate for both SSAT and acetylpolyamine oxidase. All the analogs induced the splicing of the productive mRNA splice variant of SSAT, overcame growth arrest induced by 72-h treatment with ornithine decarboxylase (ODC) inhibitor α-difluoromethylornithine, and were transported via the polyamine transporter. Surprisingly, 2-methylspermidine was a weak downregulator of ODC activity in DU145 cells. Our data demonstrates that it is possible to radically alter the biochemical properties of a polyamine analog by changing the position of the methyl group.

Mononaphthalimide spermidine conjugate induces cell proliferation inhibition and apoptosis in HeLa cells

Developing polyamine-drug conjugates that are capable of specific entry to tumor cells is attractive in improving chemotherapeutic efficacy. Currently, the exact cytotoxic mechanism of these conjugates is not well known. Here, our research revealed the effect of a mononaphthalimide-spermidine (MNISpd) conjugate on the growth and survival of HeLa cells and possible mechanisms. In characterizing the mechanism of MNISpd cytotoxicity, inhibition of proliferation is observed in the 0.5-6 μM range and there is evidence of apoptosis at equal or greater than 6 μM, but with less toxicity on HELF cell. The lower concentrations of MNISpd induced a cell cycle arrest correlated with enhanced p21 expression and decreased cdc2 but not Cdk2 expression. MNISpd-induced apoptosis was correlated with caspase-3 activation, decreased XIAP expression and a loss of mitochondrial membrane potential. Apoptosis but not cell cycle arrest was susceptible to N-acetyl-L-cysteine (NAC) treatment. It is proposed that MNISpd-induced apoptosis in HeLa cells is related to oxidative stress and that at lower exposure concentrations effects on cell proliferation predominate while at higher concentrations apoptosis develops.

Current status of the polyamine research field

This chapter provides an overview of the polyamine field and introduces the 32 other chapters that make up this volume. These chapters provide a wide range of methods, advice, and background relevant to studies of the function of polyamines, the regulation of their content, their role in disease, and the therapeutic potential of drugs targeting polyamine content and function. The methodology provided in this new volume will enable laboratories already working in this area to expand their experimental techniques and facilitate the entry of additional workers into this rapidly expanding field.

Mammalian polyamine metabolism and function

Polyamines are ubiquitous small basic molecules that play multiple essential roles in mammalian physiology. Their cellular content is highly regulated and there is convincing evidence that altered metabolism is involvement in many disease states. Drugs altering polyamine levels may therefore have a variety of important targets. This review will summarize the current state of understanding of polyamine metabolism and function, the regulation of polyamine content, and heritable pathological conditions that may be derived from altered polyamine metabolism.