ABSTRACT
Sphingosine 1-phosphate (S1P) is a bioactive lipid whose levels are tightly regulated by its synthesis and degradation. Intracellularly, S1P is dephosphorylated by the actions of two S1P-specific phosphatases, sphingosine-1-phosphate phosphatases 1 and 2. To identify the physiological functions of S1P phosphatase 1, we have studied mice with its gene, Sgpp1, deleted. Sgpp1(-/-) mice appeared normal at birth, but during the 1st week of life they exhibited stunted growth and suffered desquamation, with most dying before weaning. Both Sgpp1(-/-) pups and surviving adults exhibited multiple epidermal abnormalities. Interestingly, the epidermal permeability barrier developed normally during embryogenesis in Sgpp1(-/-) mice. Keratinocytes isolated from the skin of Sgpp1(-/-) pups had increased intracellular S1P levels and displayed a gene expression profile that indicated overexpression of genes associated with keratinocyte differentiation. The results reveal S1P metabolism as a regulator of keratinocyte differentiation and epidermal homeostasis.
Subject(s)
Cell Differentiation/genetics , Epidermis/metabolism , Keratinocytes/metabolism , Membrane Proteins/genetics , Phosphoric Monoester Hydrolases/genetics , Animals , Animals, Newborn , Cells, Cultured , Cluster Analysis , Epidermis/embryology , Epidermis/growth & development , Female , Gene Expression Profiling , Gene Expression Regulation, Developmental , Homeostasis/genetics , Keratinocytes/cytology , Lysophospholipids/metabolism , Male , Membrane Proteins/deficiency , Mice , Mice, Inbred C57BL , Mice, Knockout , Oligonucleotide Array Sequence Analysis , Phosphoric Monoester Hydrolases/deficiency , Reverse Transcriptase Polymerase Chain Reaction , Skin/embryology , Skin/growth & development , Skin/metabolism , Sphingosine/analogs & derivatives , Sphingosine/metabolism , Time FactorsABSTRACT
Dialkyl 4,4'-bipyridinium compounds are widely employed for their useful redox properties, and are commonly known as viologens due to their intense coloration upon reduction. Despite their prevalence and amphiphilic nature, the antibacterial activity of these compounds remains largely unreported. We have thus prepared a series of mono- and bis-alkylated analogs of 4,4'-bipyridine to investigate structure-activity relationships in their inhibition of a battery of Gram positive and Gram negative bacteria. The prepared cationic compounds were conventional (one cationic head, one non-polar tail), bicephalic (two heads, one tail), or gemini (two heads, two tails) in their amphiphilic structure. Additionally, an isomeric series of six bis-alkylated compounds ranging from symmetric (PQ-11,11) to highly asymmetric (PQ-20,2) were prepared. Four themes of bioactivity emerged: (1) the most bioactive compounds were gemini in structure; (2) 22 carbons in the alkyl chains, with little to modest asymmetry, led to optimal activity; (3) bicephalic compounds were generally comparable to conventional amphiphiles, though only about 12 carbons in the alkyl chains were solubilized in water by each cationic nitrogen; (4) the effects of counterion identity were not evident between chlorides and bromides; however, the presence of the iodide counterion inhibited dissolution in all compounds tested. Three isomeric compounds with little to no asymmetry in tail length, PQ-11,11, PQ-12,10, and PQ-14,8, prepared as the bromide salts, showed comparable and highly potent activity, with MIC levels around 2 µM against 3 of 4 bacteria tested. The simple (one- to two-step) syntheses of potent antimicrobials portend well for future optimization.
Subject(s)
Anti-Bacterial Agents/chemical synthesis , Gram-Negative Bacteria/drug effects , Gram-Positive Bacteria/drug effects , Pyridines/chemical synthesis , Pyridinium Compounds/chemical synthesis , Surface-Active Agents/chemical synthesis , Alkylation , Anti-Bacterial Agents/pharmacology , Color , Gram-Negative Bacteria/growth & development , Gram-Positive Bacteria/growth & development , Isomerism , Microbial Sensitivity Tests , Molecular Conformation , Oxidation-Reduction , Pyridines/pharmacology , Pyridinium Compounds/pharmacology , Solubility , Structure-Activity Relationship , Surface-Active Agents/pharmacologyABSTRACT
A series of cationic amphiphiles, each with an aromatic core, was prepared and investigated for antimicrobial properties. The synthesized amphiphiles in this study are bicephalic (double-headed) in that they each possess two trimethylammonium head groups and a single linear alkoxy tail. Minimum inhibitory and minimum bactericidal concentrations of these amphiphiles were in the low micromolar range. Antimicrobial activities are highly sensitive to the chain length of the hydrophobic region, and modestly reliant on the relative positioning of the head groups on the aromatic core. These trends were more pronounced in time kill assays, wherein longer chain compounds required significantly shorter times to completely kill bacteria. Microscopy suggested that the mode of cell death was lysis. Strong inhibition was observed with both biscationic compounds and monocationic comparisons against Gram-positive bacteria; only biscationic amphiphiles maintained good activity versus the Gram-negative bacteria tested. These observations provide direction for future antimicrobial structural investigations.
