The microphthalmia-associated transcription factor Mitf plays a critical role in regulating many aspects of melanocyte biology. It is required for melanoblast and postnatal melanocyte survival, regulates proliferation, and activates genes associated with differentiation such as tyrosinase and related genes involved in melanogenesis. Identifying the signals that regulate Mitf expression is crucial if we are to understand how cells of the melanocyte lineage respond to environmental cues. Here we show that the Mitf promoter is induced by lipid signalling via the p38 stress-activated kinase pathway that is also activated by a wide range of receptors as well as UV irradiation. Signalling via p38 leads to increased phosphorylation and activation of cyclic adenosine monophosphate response element-binding (CREB) that binds and activates the Mitf promoter via the cyclic adenosine monophosphate (cAMP) response element. Moreover, we also show that activation of p38 mediated by lipids is potentiated by inhibition of the PI3kinase pathway but not by inhibition of protein kinase A (PKA). The results identify a mechanism in which stress signalling via p38 leads to activation of CREB, enhanced Mitf expression and consequently increased tyrosinase expression. The results are relevant for the regulation of melanocytes by Mitf, but also raise the possibility that lipid mediated activation of p38 signalling may represent a potential therapy for vitiligo.

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Zinc ion fluorescence sensing and the binding properties of 4-methyl-2,6-bis(((phenylmethyl)imino)methyl)phenol (HL) have been investigated. It displays high selectivity for Zn2+ and can be used as zinc ion-selective luminescent probe for biological application under physiological conditions. The increase in emission in the presence of Zn2+ is accounted for by the formation of hexanuclear complex [Zn6(L)2(OH)2(CH3COO)8] characterized by X-ray crystallography. An approximately 6-fold Zn2+-selective chelation-enhanced fluorescence response in HEPES buffer (pH 7.4) is attributed due to the strong coordination of Zn(II) that would impose rigidity and hence decrease the nonradiative decay of the excited state. By incubation of cultured living cells (B16F10 mouse melanoma and A375 human melanoma) with HL, intracellular Zn2+ concentration could be monitored.

Results. Leishmanial lipid inhibited the release of tumor necrosis factor ␣, interleukin-1␤, and NO in the culture, decreased their cytosolic protein levels, and decreased NF-B p65 levels in SFMCs, in a dosedependent manner. It had the reverse effect on interleukin-10 levels. Leishmanial lipid-induced apoptosis involved the activation of caspase 3, caspase 9, and Bax, the release of cytochrome c, the alteration of mitochondrial membrane potential, and the downregulation of Bcl-2.Conclusion. These results suggest that leishmanial lipid has strong antiinflammatory and apoptosisinducing effects on SFMCs from patients with RA, and that apoptosis occurs via the mitochondrial pathway.

Lipids, especially sphingolipids, are emerging as inducer of apoptosis in a wide range of immortal cells, potentiating their therapeutic application in cancer. In the present study, a sphingolipid rich lipid fraction (denoted here as ALL), isolated from an attenuated strain of Leishmania donovani promastigote, was tested for its tumoricidal activity taking melanoma, the dreaded form of skin cancer cells, as model. ALL was found to induce chromatin condensation, internucleosomal DNA fragmentation and phosphatidylserine externalization with enhanced cell population in sub-G1 region in both mouse and human melanoma systems, namely B16F10 and A375 respectively. These are the hallmarks of cells undergoing apoptosis. Further analysis demonstrated that ALL treated melanoma cells showed significant increase in ROS generation, mitochondrial membrane potential depolarization, release of cytochrome c, and caspase-3 activation, which are the events closely involved in apoptosis. These findings indicate that one or more bioactive sphingolipid(s)/ceramide(s) present in ALL could be the causative agent(s) for the induction of apoptosis in melanoma cells. Further studies are thus necessary to identify these specific bioactive sphingolipid(s)/ceramide(s) and to establish their mechanism of action, in order to explore their use as anticancer agents.

A 2D coordination compound {[Cu2(HL)(N3)]ClO4}infinity (1; H3L = 2,6-bis(hydroxyethyliminoethyl)-4-methyl phenol) was synthesized and characterized by single-crystal X-ray diffraction to be a polymer in the crystalline state. Each [Cu2(HL)(N3)]+ species is connected to its adjacent unit by a bridging alkoxide oxygen atom of the ligand to form a helical propagation along the crystallographic a axis. The adjacent helical frameworks are connected by a ligand alcoholic oxygen atom along the crystallographic b axis to produce pleated 2D sheets. In solution, 1 dissociates into [Cu2(HL)2(H3L)]2H2O (2); the monomer displays high selectivity for Zn2+ and can be used in HEPES buffer (pH 7.4) as a zinc ion selective luminescent probe for biological application. The system shows a nearly 19-fold Zn2+-selective chelation-enhanced fluorescence response in the working buffer. Application of 2 to cultured living cells (B16F10 mouse melanoma and A375 human melanoma) and rat hippocampal slices was also studied by fluorescence microscopy.

The synthesis, spectroscopic characterization, X-ray powder structure determination, and thermal behavior of a binuclear bis(µ-oxo)-bridged vanadium(V) complex, [(VO 2 L) 2 ], L ) N,N′-dimethylenediamine(o-hydroxyl acetophenon), along with its DNA binding ability and photoinduced DNA cleavage activity, have been described. The compound crystallizes in a monoclinic system with a ) 7.679(3) Å, b ) 12.020(5) Å, c ) 13.882(6) Å, β ) 90.799(4)°, space group P2 1 /c, and Z ) 2. The crystal structure has been solved from laboratory X-ray powder diffraction data using the direct space approach and refined by the Rietveld method. The dimeric complex consists of two edge-sharing vanadium octahedra with each metal center coordinated to one oxo-, one phenolate-, and two bridging-oxygen ligands, and two nitrogen donor atoms. The molecular structure reveals a two-dimensional grid of R 4 4 (24) rings in the (011) plane, which on combination with one-dimensional polymeric chains along the [100] direction, forms a novel three-dimensional supramolecular framework. Thermogravimetric analysis of the complex indicates multiple overlapping decomposition steps in the temperature range 180-800 °C with the end product being V 2 O 5 . The complex binds to double-stranded DNA giving a K app value of 1.56 × 10 7 M -1 and displays DNA cleavage activity on UV (300 nm) irradiation via a mechanistic pathway involving formation of singlet oxygen as the reactive species.