Bidirectional fluxes of spermine across the mitochondrial membrane

P5B-ATPases in the mammalian polyamine transport system and their role in disease

Polyamines (PAs) are physiologically relevant molecules that are ubiquitous in all organisms. The vitality of PAs to the healthy functioning of a cell is due to their polycationic nature causing them to interact with a vast plethora of cellular players and partake in numerous cellular pathways. Naturally, the homeostasis of such essential molecules is tightly regulated in a strictly controlled interplay between intracellular synthesis and degradation, uptake from and secretion to the extracellular compartment, as well as intracellular trafficking. Not surprisingly, dysregulated PA homeostasis and signaling are implicated in multiple disorders, ranging from cancer to neurodegeneration; leading many to propose rectifying the PA balance as a potential therapeutic strategy. Despite being well characterized in bacteria, fungi and plants, the molecular identity and properties of the PA transporters in animals are poorly understood. This review brings together the current knowledge of the cellular function of the mammalian PA transport system (PTS). We will focus on the role of P5B-ATPases ATP13A2-5 which are PA transporters in the endosomal system that have emerged as key players in cellular PA uptake and organelle homeostasis. We will discuss recent breakthroughs on their biochemical and structural properties as well as their implications for disease and therapy.

Exogenous spermine inhibits high glucose/oxidized LDL‑induced oxidative stress and macrophage pyroptosis by activating the Nrf2 pathway

Evidence suggests that macrophage pyroptosis promotes the progression of diabetic atherosclerosis. Spermine, a natural cellular metabolite, demonstrates a protective effect against cardiovascular diseases. However, whether spermine has a protective effect against macrophage pyroptosis caused by high glucose (HG) and oxidized low-density lipoprotein (ox-LDL) conditions remains to be elucidated. To investigate the protective effect of spermine and the related underlying mechanism, THP-1 macrophages were treated with HG/ox-LDL, spermine, or the specific nuclear factor erythroid 2-related factor 2 (Nrf2) inhibitor ML385. Cell viability was detected using CCK-8, cell membrane permeability was analyzed using lactate dehydrogenase (LDH) and Hoechst/propidium iodide staining and pyroptosis-related gene and protein expression levels were evaluated using polymerase chain reaction and western blot analysis. Spermine showed a potent preventive effect on THP-1 macrophage pyroptosis and oxidative stress induced by HG/ox-LDL. Cells treated with spermine showed increased cell viability, reduced reactive oxygen species (ROS) production, decreased LDH levels in the supernatant and reduced cell swelling. In addition, spermine significantly reduced NLR family pyrin domain containing 3, cleaved caspase-1, N-gasdermin D and IL-1β expression, as well as IL-1β levels in the supernatant. This demonstrated that the inhibition of pyroptosis and oxidative stress due to spermine was Nrf2 dependent. Furthermore, spermine enhanced Nrf2 nuclear translocation, thereby increasing heme oxygenase-1 and NADPH quinone oxidoreductase-1 expression, which subsequently reduced ROS production. In addition, the anti-pyroptotic and antioxidant effects of spermine were reversed by ML385 inhibition of Nrf2. It was concluded that spermine prevented macrophage pyroptosis and increased ROS overproduction by activating the Nrf2 pathway. The data suggested that spermine may be a potential novel drug for the treatment of diabetic atherosclerosis because it targets macrophage pyroptosis.

1, 8-cineole protects against ISO-induced heart failure by inhibiting oxidative stress and ER stress in vitro and in vivo

Sugemule-3 is widely adopted in clinical practice to manage cardio-cerebral diseases. 1, 8-cineole is the main ingredient of Sugemule-3, however, the underlying cellular mechanisms for its protective effect are poorly understood. 1, 8-cineole improved the survival of H9C2 cardiomyocytes during isoproterenol (ISO) injury and reduced ISO-induced apoptosis. Compared to the ISO group, 1, 8-cineole highly attenuated the generation of ISO-induced reactive oxygen species (ROS), the depolarization of △ψm, suppression of the Bax/Bcl-2 ratio, and p-caspase 3 expression, in vitro. Furthermore, 1, 8-cineole treatment in H9C2 cardiomyocytes lowered the expressions of 78-kDa glucose-regulated protein (GRP78), p-protein kinase-like ER kinase (PERK), activation of transcription factor (ATF) 4, and ER stress effector protein C/EBP and homologous protein (CHOP). These findings implied that 1, 8-cineole contribute to cardioprotection via the GRP78/CHOP pathways. Using animal models, 1, 8-cineole was revealed to markedly alleviate ISO-induced heart injury, and reduce cardiac hypertrophy, formation of the cytoplasmic vacuole, loss of myofiber, and fibrosis by inhibiting oxidative stress and ER stress. 1, 8-cineole reduces apoptosis by inhibiting signaling pathways related to oxidative stress and ER stress. These findings implicate 1, 8-cineole as a potential therapeutic target for cardiac hypertrophy-related heart diseases, including heart failure.

Conjugation with polyamines enhances the antitumor activity of naphthoquinones against human glioblastoma cells

Glioblastoma multiform (GBM) is the most common and devastating type of primary brain tumor, being considered the deadliest of human cancers. In this context, extensive efforts have been undertaken to develop new drugs that exhibit both antiproliferation and antimetastasis effects on GBM. 1,4-Naphthoquinone (1,4-NQ) scaffold has been found in compounds able to inhibit important biological targets associated with cancer, which includes DNA topoisomerase, Hsp90 and monoamine oxidase. Among potential antineoplastic 1,4-NQs is the plant-derived lapachol (2-hydroxy-3-prenyl-1,4-naphthoquinone) that was found to be active against the Walker-256 carcinoma and Yoshida sarcoma. In the present study, we examined the effect of polyamine (PA)-conjugated derivatives of lapachol, nor-lapachol and lawsone on the growth and invasion of the human GBM cells. The conjugation with PA (a spermidine analog) resulted in dose-dependent and time-dependent increase of cytotoxicity of the 1,4-NQs. In addition, in-vitro inhibition of GBM cell invasion by lapachol was increased upon PA conjugation. Previous biochemical experiments indicated that these PA-1,4-NQs are capable of inhibiting DNA human topoisomerase II-α (topo2α), a major enzyme involved in maintaining DNA topology. Herein, we applied molecular docking to investigate the binding of PA-1,4-NQs to the ATPase site of topo2α. The most active molecules preferentially bind at the ATP-binding site of topo2α, which is energetically favored by the conjugation with PA. Taken together, these findings suggested that the PA-1,4-NQ conjugates might represent potential molecules in the development of new drugs in chemotherapy for malignant brain tumors.

A novel phenolic propanediamine moiety-based lung-targeting therapy for asthma

Asthma is one of the most prevalent chronic inflammatory diseases of lung. Current asthma therapy using inhaled corticosteroid often results in undesired treatment outcome due to poor compliance and drugs’ lack of tissue specificity. N,N,N’-trimethyl-N’-(2-hydroxyl-3-methyl-5-¹²³Iiodobenzyl)-1,3-propanediamine (HIPD), a phenolic propanediamine derivative, has been used as an imaging agent for localized pulmonary diseases. Inspired by this, N,N,N’-trimethyl-N’-(4-hydroxyl-benzyl)-1,3-propanediamine (TPD), a new HIPD analog, was proposed as a lung-targeting ligand and covalently conjugated to an anti-inflammatory compound Rhein for asthma therapy. Cellular uptake efficiency of TPD-Rhein by A549 cells was significantly enhanced compared with Rhein. The enhanced cellular uptake was mainly mediated by organic cation transporters (OCTs) in an active manner, showing concentration- and energy-dependent. After systemic administration in rats, TPD-Rhein specifically distributed to lungs, displaying the highest C_max and AUC_0−t values of all tested tissues and resulting in a 13-fold increase in C_max and a 103-fold increase in AUC_0−t for lung compared with Rhein. Also, TPD-Rhein remarkably decreased serum histamine levels, serum IL-5 levels as well as bronchoalveolar lavage fluid IL-5 levels in lungs of asthmatic rats challenged by ovalbumin (OVA). Accordingly, histological examinations demonstrated that TPD-Rhein attenuated lung inflammation in rats, with no apparent toxicity against major organs. Together, phenolic propanediamine-based lung-targeting approach represents an efficient and safe strategy for asthma therapy.

Danhong injection protects cardiomyocytes against hypoxia/reoxygenation- and H2O2-induced injury by inhibiting mitochondrial permeability transition pore opening

ETHNOPHARMACOLOGICAL RELEVANCE

Danhong injection (DHI), a Chinese medical product extracted from Radix et Rhizoma Salviae Miltiorrhizae (Salvia miltiorrhiza Bge., Labiatae, Danshen in Chinese) and Flos Carthami (Carthamus tinctorius L., Compositae, Honghua in Chinese), has been widely used for the treatment of ischemic heart disease, and clinical and experimental studies have demonstrated the protective effects against myocardial ischemia/reperfusion injury. Nevertheless, the underlying cellular mechanisms responsible for this protective effect are poorly understood.

AIM OF THE STUDY

The present study aimed to examine the mechanism of DHI in regulating hypoxia/reoxygenation- and H2O2-induced cardiomyocytes injury.

MATERIALS AND METHODS

Neonatal rat cardiomyocytes were subjected to hypoxia (9h)-reoxygenation (2h) or H2O2 (100 μM) in the presence or absence of DHI (2.5, 5, 10 μg/mL). Intracellular reactive oxygen species (ROS), cytosolic and mitochondrial Ca(2+) concentrations, mitochondrial membrane potential (ΔΨm) and mitochondrial permeability transition pore (mPTP) opening were monitored using CMH2DCFDA, Fluo-4 and rhod-2, JC-1 and calcein, respectively. Cell survival was evaluated using the 2-(4,5-dimethylthiazol-2-yl)-2,5 -diphenyltetrazolium bromide (MTT) assay and apoptosis was detected by Annexin V/propidium iodide (PI) staining.

RESULTS

DHI improved cell survival following H/R and H2O2 injury and reduced H/R-induced cytochrome c release and apoptosis when compared with non-DHI treated cells. In addition, DHI attenuated H/R-induced ROS generation, H2O2-induced cytosolic and mitochondrial Ca(2+) overload, and cellular ROS generation when compared with H/R- and H2O2-only groups. Moreover, DHI significantly inhibited both mPTP opening and ΔΨm depolarization.

CONCLUSION

These data demonstrate that the protective mechanism of DHI against H/R- and H2O2-induced injury is mediated by the inhibition of mPTP opening via mitigating Ca(2+) overload and ROS generation.

Dual pancreas- and lung-targeting therapy for local and systemic complications of acute pancreatitis mediated by a phenolic propanediamine moiety

To inhibit both the local and systemic complications with acute pancreatitis, an effective therapy requires a drug delivery system that can efficiently overcome the blood-pancreas barrier while achieving lung-specific accumulation. Here, we report the first dual pancreas- and lung-targeting therapeutic strategy mediated by a phenolic propanediamine moiety for the treatment of acute pancreatitis. Using the proposed dual-targeting ligand, an anti-inflammatory compound Rhein has been tailored to preferentially accumulate in the pancreas and lungs with rapid distribution kinetics, excellent tissue-penetrating properties and minimum toxicity. Accordingly, the drug-ligand conjugate remarkably downregulated the proinflammatory cytokines in the target organs thus effectively inhibiting local pancreatic and systemic inflammation in rats. The dual-specific targeting therapeutic strategy may help pave the way for targeted drug delivery to treat complicated inflammatory diseases.

A novel enzyme with spermine oxidase properties in bovine liver mitochondria: identification and kinetic characterization

The uptake of spermine into mammalian mitochondria indicated the need to identify its catabolic pathway in these organelles. Bovine liver mitochondria were therefore purified and their capacity for natural polyamine uptake was verified. A kinetic approach was then used to determine the presence of an MDL 72527-sensitive enzyme with spermine oxidase activity in the matrix of bovine liver mitochondria. Western blot analysis of mitochondrial fractions and immunogold electron microscopy observations of purified mitochondria unequivocally confirmed the presence of a protein recognized by anti-spermine oxidase antibodies in the mitochondrial matrix. Preliminary kinetic characterization showed that spermine is the preferred substrate of this enzyme; lower activity was detected with spermidine and acetylated polyamines. Catalytic efficiency comparable to that of spermine was also found for 1-aminododecane. The considerable effect of ionic strength on the Vmax/KM ratio suggested the presence of more than one negatively charged zone inside the active site cavity of this mitochondrial enzyme, which is probably involved in the docking of positively charged substrates. These findings indicate that the bovine liver mitochondrial matrix contains an enzyme belonging to the spermine oxidase class. Because H2O2 is generated by spermine oxidase activity, the possible involvement of the latter as an important signaling transducer under both physiological and pathological conditions should be considered.

Pathophysiological implications of mitochondrial oxidative stress mediated by mitochondriotropic agents and polyamines: the role of tyrosine phosphorylation

Mitochondria, once merely considered as the "powerhouse" of cells, as they generate more than 90 % of cellular ATP, are now known to play a central role in many metabolic processes, including oxidative stress and apoptosis. More than 40 known human diseases are the result of excessive production of reactive oxygen species (ROS), bioenergetic collapse and dysregulated apoptosis. Mitochondria are the main source of ROS in cells, due to the activity of the respiratory chain. In normal physiological conditions, ROS generation is limited by the anti-oxidant enzymatic systems in mitochondria. However, disregulation of the activity of these enzymes or interaction of respiratory complexes with mitochondriotropic agents may lead to a rise in ROS concentrations, resulting in oxidative stress, mitochondrial permeability transition (MPT) induction and triggering of the apoptotic pathway. ROS concentration is also increased by the activity of amine oxidases located inside and outside mitochondria, with oxidation of biogenic amines and polyamines. However, it should also be recalled that, depending on its concentration, the polyamine spermine can also protect against stress caused by ROS scavenging. In higher organisms, cell signaling pathways are the main regulators in energy production, since they act at the level of mitochondrial oxidative phosphorylation and participate in the induction of the MPT. Thus, respiratory complexes, ATP synthase and transition pore components are the targets of tyrosine kinases and phosphatases. Increased ROS may also regulate the tyrosine phosphorylation of target proteins by activating Src kinases or phosphatases, preventing or inducing a number of pathological states.

Oep23 forms an ion channel in the chloroplast outer envelope

BACKGROUND

Metabolite, ion and protein translocation into chloroplasts occurs across two membranes, the inner and the outer envelope. Solute and metabolite channels fulfill very important functions in integrating the organelles into the metabolic network of the cell. However so far only a few have been identified. Here we describe the identification and the characterization of the outer envelope protein of 23 kDa, Oep23 from garden pea.

RESULTS

Oep23 is found in the entire plant lineage from green algae to flowering plants. It is expressed in all organs and developmental states tested so far. The reconstituted recombinant protein Oep23 from pea forms a high conductance ion channel with a maximal conductance in the fully open state of 466 ± 14pS at a holding potential of +100 mV (in 250 mM KCl). The Oep23 channel is cation selective (PK+ : PCl- = 15 : 1) with a voltage dependent open probability of maximal Vmem = 0 mV.

CONCLUSION

The data indicate that the Oep23 activity represents a single channel unit and does not assemble into a multiple pore complex like bacterial type porins or mitochondrial voltage dependent anion channel. Thus, Oep23 represents a new member of ion channels in the outer envelope of chloroplasts involved in solute exchange.

Nutrimetabolomic analysis provides new insights into spermine-induced ileum-system alterations for suckling rats

This study aimed to investigate the effects of spermine supplementation on the ileum metabolism of suckling rats.

Concentration-dependent effects of spermine on apoptosis and consequent generation of multilayer myotube sheets from mouse embryoid bodies in vitro

The concentration-dependent effect of spermine was investigated on the spermine-induced generation of multilayer myotube sheets (MMTS) from mouse embryoid bodies (EBs). During spermine treatment for 24 h, a monolayer cell sheet that had already grown radially from the periphery of an EB was exfoliated. The exfoliation was inhibited by z-VAD.fmk, indicating the occurrence of apoptosis, and inhibited also by aminoguanidine, indicating the involvement of amine oxidase. Following the exfoliation, the cell growth restarted from the fresh periphery of EB in a spermine-free medium and finally formed MMTS. To analyze the contribution of apoptosis to the cell death causing exfoliation, the numbers of apoptotic, necrotic, and 2nd apoptotic cells were counted by staining with Annexin V-Cyanine-3 (AVC3) and 7-aminoactinomycin (7AAC). AVC3-positive, 7AAC-positive, and AVC3/7AAC doubly positive cells were assigned as apoptotic, necrotic, and 2nd necrotic cells, respectively. The relative number of apoptotic and 2nd necrotic cells (N A + N A/7) to the total number of dying cells (N T) was 84 ∼ 94%, which was independent of spermine concentration in the range from 0.1 to 2.0 mM. The MMTS generation rate at the final stage, however, was dependent on the spermine concentration. It was 60 ∼ 80% in the range from 0.1 to 1.5 mM, while it decreased sharply to 1% at 2 mM. This suggests another role of spermine in the MMTS generation in addition to the induction of apoptosis. This 2nd role seems to be inhibited at a spermine concentration higher than a critical limit between 1.5 and 2.0 mM.

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.