bims-polyam Biomed News
on Polyamines
Issue of 2020‒07‒19
six papers selected by
Alexander Ivanov
Engelhardt Institute of Molecular Biology

  1. Immunity. 2020 Jul 14. pii: S1074-7613(20)30270-3. [Epub ahead of print]53(1): 16-18
      The role of keratinocyte metabolism in psoriasis is not fully elucidated. In this issue of Immunity, Lou et al. describe that interleukin-17 (IL-17) re-programs the urea cycle in keratinocytes increasing polyamines that stabilize RNA-Ag-complexes that upon cellular turnover activate dendritic cells, which amplify psoriasis inflammation.
  2. Gastroenterology. 2020 Jul 09. pii: S0016-5085(20)34921-0. [Epub ahead of print]
      BACKGROUND & AIMS: The intestinal barrier protects intestinal cells from microbes and antigens in the lumen-breaches can alter the composition of the intestinal microbiota, the enteric immune system, and metabolism. We performed a screen to identify molecules that disrupt and support the intestinal epithelial barrier and tested their effects in mice.METHODS: We performed an imaging-based, quantitative, high-throughput screen (using CaCo-2 and T84 cells incubated with lipopolysaccharide; tumor necrosis factor; histamine; receptor antagonists; and libraries of secreted proteins, microbial metabolites, and drugs) to identify molecules that altered epithelial tight junction (TJ) and focal adhesion morphology. We then tested the effects of TJ stabilizers on these changes. Molecules we found to disrupt or stabilize TJs were administered mice with dextran sodium sulfate-induced colitis or Citrobacter rodentium-induced intestinal inflammation. Colon tissues were collected and analyzed by histology, fluorescence microscopy, and RNA sequencing.
    RESULTS: The screen identified numerous compounds that disrupted or stabilized (after disruption) TJs and monolayers of epithelial cells. We associated distinct morphologic alterations with changes in barrier function, and identified a variety of cytokines, metabolites, and drugs (including inhibitors of actomyosin contractility) that prevent disruption of TJs and restore TJ integrity. One of these disruptors (putrescine) disrupted TJ integrity in ex vivo mouse colon tissues; administration to mice exacerbated colon inflammation, increased gut permeability, reduced colon transepithelial electrical resistance, increased pattern recognition receptor ligands in mesenteric lymph nodes, and decreased colon length and survival times. Putrescine also increased intestine levels and fecal shedding of viable C rodentium, increased bacterial attachment to the colonic epithelium, and increased levels of inflammatory cytokines in colon tissues. Colonic epithelial cells from mice given putrescine increased expression of genes that regulate metal binding, oxidative stress, and cytoskeletal organization and contractility. Co-administration of taurine with putrescine blocked disruption of TJs and the exacerbated inflammation.
    CONCLUSIONS: We identified molecules that disrupt and stabilize intestinal epithelial TJs and barrier function and affect development of colon inflammation in mice. These agents might be developed for treatment of barrier intestinal impairment-associated and inflammatory disorders in patients, or avoided to prevent inflammation.
    Keywords:  IBD; cytokine; microbiota; model
  3. ACS Chem Biol. 2020 Jul 13.
      The cytosolic class IIb histone deacetylase HDAC10 is an emerging target for drug design. As an inducer of autophagy, its selective inhibition suppresses the autophagic response that otherwise attenuates the efficacy of cytotoxic cancer chemotherapy drugs. HDAC10 is a zinc-dependent polyamine deacetylase exhibiting maximal catalytic activity against N8-acetylspermidine. As revealed in the structure of Danio rerio (zebrafish) HDAC10, two conserved structural motifs direct this narrow substrate specificity: a 310 helix containing the P(E,A)CE motif that sterically constricts the active site, and an electrostatic "gatekeeper", E274, that confers selectivity for cationic polyamine substrates. To accelerate drug design efforts targeting human HDAC10, we now report the preparation of "humanized" zebrafish HDAC10 in which two amino acid substitutions, A24E and D94A, yield an active site contour more similar to that of human HDAC10. X-ray crystal structures of this HDAC10 variant complexed with Tubastatin A and indole analogues bearing pendant tertiary amines reveal that inhibitors capable of hydrogen bonding with gatekeeper E274 exhibit high affinity and selectivity for HDAC10 over HDAC6 (the other class IIb isozyme). Moreover, these structures reveal that the P(E,A)CE motif helix can shift by up to 2 Å to accommodate the binding of bulky inhibitors. Thus, slender polyamine-like inhibitor structures are not exclusively required for selective, high affinity binding to HDAC10. Indeed, the flexibility of the P(E,A)CE motif helix could conceivably enable the binding of certain protein substrates.
  4. Plant Signal Behav. 2020 Jul 11. 1790844
      To assess the role of genes involved in polyamines synthesis, nitric oxide synthase (NOS), copper amine oxidase activity (CuAO) and hydrogen peroxide (H2O2) in regulation of stomatal aperture to drought stress in Rosa canina L., a study was performed at three irrigating levels (25%, 50%, and 100% field capacity) with three replications at 1, 3, 6 and 12 days. The results showed that putrescine (Put) accumulation occurred under both 50% and 25% FC at 1 d. Furthermore, the role of the Put direct biosynthesis pathway ornithine decarboxylase (ODC) was more effective under 50% FC whereas in the 25% FC the Put indirect production pathway (agmatine iminohydrolase (AIH), N-carbamoyl putrescine amidohydrolase (CPA) and arginine decarboxylase (ADC)) was more effective. HPLC results showed that the accumulation of spermidine (Spd) and spermine (Spm) is consistent with the expression of S-adenosyl methionine decarboxylase (SAMDC), spermidine synthase (SPDS) and spermine synthase (SPMS) genes. Spd accumulation under both 50% and 25% FC occurred on the 3 d and then decreased in the other days. Spm content showed an increasing trend from 6 d under 50% FC and from 3 d under 25% FC. Our results suggest that among the measured polyamines, Put oxidation through CuAO activity increased resulted in an increase in H2O2 production. The H2O2 accumulation also as a secondary messenger led to enhance in NOS gene expression. Increase in NOS gene expression can act as a signal resulting in stomatal closure.
    Keywords:  Abscisic acid; amine oxidase; amino acid; nitric oxide; reactive oxygen species; stomatal closure
  5. Plant J. 2020 Jul 15.
      Polyamines, such as putrescine, spermidine and spermine (Spm), are low-molecular-weight polycationic molecules present in all living organisms. Despite their implication in plant cellular processes, little is known about their molecular mode of action. Here, we demonstrate that polyamines trigger a rapid increase in the regulatory membrane lipid, phosphatidylinositol-4,5-bisphosphate (PIP2 ), and that this increase is required for polyamine effects on K+ efflux in Arabidopsis roots. Using in vivo 32 Pi -labelling of Arabidopsis seedlings, low physiological (μM) concentrations of Spm were found to promote a rapid PIP2 increase in roots that was time- and dose-dependent. Confocal imaging of a genetically encoded-PIP2 biosensor revealed that this increase was triggered at the plasma membrane. Differential 32 Pi -labelling suggested that the increase in PIP2 was generated through activation of phosphatidylinositol-4-phosphate 5-kinase (PIP5K) activity rather than inhibition of a phospholipase C or PIP2 5-phosphatase activity. Systematic analysis of T-DNA insertion mutants identified PIP5K7 and PIP5K9 as the main candidates involved in the Spm induced-PIP2 response. Using non-invasive microelectrode ion-flux estimation (MIFE), we discovered that the Spm-triggered K+ -efflux response was strongly reduced in pip5k7 pip5k9 seedlings. Together, our results provide biochemical- and genetic evidence for a physiological role of PIP2 in polyamine-mediated signalling controlling K+ flux in plants.
    Keywords:  Arabidopsis; K+ flux; phosphatidic acid (PA); phosphatidylinositol 4,5-bisphosphate (PIP2); phosphatidylinositol 4-phosphate 5-kinase (PIP5K); phosphoinositide signalling; phospholipids; polyamines
  6. Exp Neurol. 2020 Jul 10. pii: S0014-4886(20)30229-6. [Epub ahead of print] 113398
      We investigated the ability of agmatine to potentiate the antidepressant-like and synaptic effects of ketamine in mice. Agmatine (0.1 and 1 mg/kg, p.o.) and ketamine (1 and 10 mg/kg, i.p.) produced an antidepressant-like effect in the tail suspension test. The combination of agmatine (0.01 mg/kg, p.o.) and ketamine (0.1 mg/kg, i.p.), at subthreshold doses, produced an antidepressant-like effect 1 h, 24 h and 7d after treatment. Western blot analysis from prefrontal cortex tissue showed that the combined treatment, after 1 h, increased p70S6K and GluA1, and reduced synapsin 1 phosphorylation. Additionally, after 24 h, Akt, p70S6K, GluA1, and synapsin 1 phosphorylation; and PSD95 immunocontent increased (which persisted for up to 7d). Dendritic architecture analysis of the prefrontal cortex revealed that the combined treatment improved dendritic arbor complexity (after 24 h, up to 7d), and increased spine density (after 1 h, up to 24 h). Morphometric analysis revealed a filopodia-shaped dendrite spine upregulation after 1 h. A predominance of stubby, mushroom, branched and filopodia; and a reduction in thin protrusions were observed after 24 h. Finally, mushroom-shaped dendritic spines predominance increased after 7d. Agmatine potentiated ketamine's antidepressant, and dendritic arbors and spines remodeling effects in a time-dependent manner. Our data indicate Akt/p70S6K signaling as a likely target for these effects.
    Keywords:  AMPA receptor subunit GluR1; Agmatine; Akt/p70S6K signaling; Dendritic arbor; Dendritic spine; Ketamine