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Cytochrome P450 epoxygenase Cyp2c44, a murine epoxyeicosatrienoic acid (EET)-producing enzyme, promotes insulin sensitivity, and Cyp2c44 −/− mice show hepatic insulin resistance. Because insulin resistance leads to hepatic lipid accumulation and hyperlipidemia, we hypothesized that Cyp2c44 regulates hepatic lipid metabolism. Standard chow diet (SCD)-fed male Cyp2c44 −/− mice had significantly decreased EET levels and increased hepatic and plasma lipid levels compared with wild-type mice. We showed increased hepatic plasma membrane localization of the FA transporter 2 (FATP2) and total unsaturated fatty acids and diacylglycerol (DAG) levels. Cyp2c44 −/− mice had impaired glucose tolerance and increased hepatic plasma membrane–associated PKCδ and phosphorylated IRS-1, two negative regulators of insulin signaling. Surprisingly, SCD and high-fat diet (HFD)-fed Cyp2c44 −/− mice had similar glucose tolerance and hepatic plasma membrane PKCδ levels, suggesting that SCD-fed Cyp2c44 −/− mice have reached their maximal glucose intolerance. Inhibition of PKCδ resulted in decreased IRS-1 serine phosphorylation and improved insulin-mediated signaling in Cyp2c44 −/− hepatocytes. Finally, Cyp2c44 −/− HFD-fed mice treated with the analog EET-A showed decreased hepatic plasma membrane FATP2 and PCKδ levels with improved glucose tolerance and insulin signaling. In conclusion, loss of Cyp2c44 with concomitant decreased EET levels leads to increased hepatic FATP2 plasma membrane localization, DAG accumulation, and PKCδ-mediated attenuation of insulin signaling. Thus, Cyp2c44 acts as a regulator of lipid metabolism by linking it to insulin signaling. Article Highlights: Loss of epoxygenase Cyp2c44 leads to glucose intolerance, characterized by an increase in hepatic lipids and hyperlipidemia. Cyp2c44 participates in the regulation of hepatic fatty acid accumulation by limiting the plasma membrane localization of FATP2 and, in turn, intracellular levels of diacylglycerol. Cyp2c44-mediated downregulation of intracellular diacylglycerol levels results in decreased plasma membrane–associated PKCδ and phosphorylated IRS-1, two negative regulators of insulin signaling. Thus, Cyp2c44 acts as a regulator of lipid metabolism by linking it to insulin signaling. [ABSTRACT FROM AUTHOR]

We previously showed that global deletion of the cytochrome P450 epoxygenase Cyp2c44, a major epoxyeicosatrienoic acid (EET) producing enzyme in mice, leads to impaired hepatic insulin signaling resulting in insulin resistance. This finding led us to investigate whether administration of a water soluble EET analog restores insulin signaling in vivo in Cyp2c44(-/-) mice and investigated the underlying mechanisms by which this effect is exerted. Cyp2c44(-/-) mice treated with the analog EET-A for 4 weeks improved fasting glucose and glucose tolerance compared to Cyp2c44(-/-) mice treated with vehicle alone. This beneficial effect was accompanied by enhanced hepatic insulin signaling, decreased expression of gluconeogenic genes and increased expression of glycogenic genes. Mechanistically, we show that insulin-stimulated phosphorylation of insulin receptor β (IRβ) is impaired in primary Cyp2c44(-/-) hepatocytes and this can be restored by cotreatment with EET-A and insulin. Plasma membrane fractionations of livers indicated that EET-A enhances the retention of IRβ in membrane rich fractions, thus potentiating its activation. Altogether, EET analogs ameliorate insulin signaling in a genetic model of hepatic insulin resistance by stabilizing membrane-associated IRβ and potentiating insulin signaling. [ABSTRACT FROM AUTHOR]

In this work, a triphenylamine and rhodamine-B (donor–acceptor) hybrid switch (TPRH) was rationally designed, synthesised and characterised as a novel fluorescence resonance energy transfer (FRET) ratiometric fluorescent chemosensor for specific sensing of Al3+ over other important metal ions in mixed aqueous solution. We proposed that the sensor in hand (TPRH) is non-toxic and can be successfully employed to detect the Al3+ ion in human peripheral blood mononuclear cells (PBMCs), showing intracellular 'FRET-ON' mechanism. The orientation of the probe was designed in such a way that the fluorescence (or Förster) resonance energy transfer (FRET) proceeded from the 'donor moiety' triphenylamine to the 'accepter moiety' rhodamine-B. This fluorescent probe was found to be highly selective towards Al3+ over other important guest metal ions, including Fe3+ and Cr3+. Considering the adverse effects of Al3+ ions on human health and also on the environment, the development of sensitive and specific tools for the detection of Al3+ ions is of great value. The limit of detection (LOD) of TPRH was found to be in the order of 10−8 M. The TPRH–Al3+ complex showed reversible binding with demetallation in the presence of EDTA. In accordance with this reversibility, the fluorescence output at 576 nm from two active chemical inputs, namely, Al3+ and EDTA, followed a truth table of an INHIBIT logic gate. Moreover, cytotoxic studies found that the probe was safe to use in a biological system with good cell membrane permeability. More importantly, the bio-imaging of living human peripheral blood mononuclear cells (PBMCs) showed that TPRH could be used as an effective fluorescent probe for a prominent ratiometric in vitro detection of the transition trivalent metal ion Al3+. We evidenced a significant (p < 0.05) shift from blue to red fluorescence when Al3+ was added to the cell suspension, thus proving TPRH as a good candidate to detect intracellular Al3+. [ABSTRACT FROM AUTHOR]

Based on excited state intramolecular proton transfer (ESIPT) and chelation enhanced fluorescence (CHEF) mechanisms, a new fluorescence ratiometric probe for Al3+ was designed and synthesized, and its structure was confirmed through single crystal X-ray study. This probe is capable of showing excited state intramolecular proton transfer through two different pathways. The introduction of Al3+ in a mixed aqueous solution with the probe results in an abrupt change in the photophysical properties of the probe. A ratiometric emission profile was observed in the presence of Al3+. Interestingly, the presence of other metal ions (especially trivalent ions, e.g. Fe3+, Cr3+, Ga3+ and In3+) do not perturb the fluorescence intensity of the probe (except Cu2+ and Pb2+, where slight changes were noticed). This indicates that the probe shows high affinity towards Al3+. The ratiometric sensing phenomenon may be explained by the presence of two different mechanisms, namely, excited state intramolecular proton transfer and chelation induced enhanced fluorescence, which are demonstrated by the probe in presence of Al3+ in the excited state. The complexation of the probe with Al3+ inhibits excited state intramolecular proton transfer while the chelation induced enhanced fluorescence mechanism becomes dominant. The probe efficiently detected the cellular uptake of Al3+, which is demonstrated here with human blood-cell imaging. Moreover, the detection limit was found to be 6.72 × 10−8 M. [ABSTRACT FROM AUTHOR]

A new visible-light-excitable fluorescence ratiometric probe for OCl- has been developed based on a triphenylamine-diamiomaleonitrile (TAM) moiety. The structure of the dye was confirmed by single-crystal X-ray analysis. It behaves as a highly selective and sensitive probe for OCl- over other analytes with a fast response time (~100 s). OCl- reacts with the probe leading to the formation of the corresponding aldehyde in a mixed-aqueous system. The detection limit of the probe is in the 10-8m range. The probe (TAM) also exhibits solvatofluorochromism. Changing the solvent from non-polar to polar, the emission band of TAM largely red-shifted. Moreover, the probe shows an excellent performance in real-life application in detecting OCl- in human blood cells. The experimentally observed changes in the structure and electronic properties of the probe after reaction with OCl- were studied by DFT and TDDFT computational calculations. [ABSTRACT FROM AUTHOR]

A rapid fluorescent probe based on the conjugate of chromone and benzothiazole moiety was presented, which could selectively respond to HSO 3 - over other common anions and thiols. The function of the probe relies on nucleophilic addition to break down the π-conjugation. The probe can be used as a signal tool to determine HSO 3 - levels in sugar-based food and living cells., Competing Interests: The authors declare no competing financial interest.