1,550 nm Erbium-Doped and 1,927 nm Thulium Nonablative Fractional Laser System: Best Practices and Treatment Setting Recommendations.

BACKGROUND: The Fraxel Dual laser system (Solta Medical, Inc., Bothell, WA) contains a 1,550 and 1,927 nm wavelength single handpiece with different indications for each wavelength. OBJECTIVE: To discuss treatment setting recommendations and best practices for select on-label and investigational applications of the 1,550 and 1,927 nm dual laser system. MATERIALS AND METHODS: Eight board-certified dermatologists with 10 or more years of experience with the 1,550 and 1,927 nm laser system completed an online survey about their clinical experience with the system and then participated in a roundtable to share clinical perspectives and best practices for using the laser system. RESULTS: For all Fitzpatrick skin types, treatment recommendations were described for selected approved indications for the 1,550 and 1,927 nm laser system, including both lasers in combination. Treatment recommendations were also reached for investigational applications with the 1,550 nm laser and 1,927 nm laser. Best practices for using the lasers during the treatment session to achieve optimal outcomes and decrease the post-treatment recovery time were compiled. CONCLUSION: The 1,550 and 1,927 nm dual laser system is effective for a wide range of aesthetic and therapeutic applications, on and off the face and across all Fitzpatrick skin types.

Gamma tocopherol upregulates the expression of 15-S-HETE and induces growth arrest through a PPAR gamma-dependent mechanism in PC-3 human prostate cancer cells.

Chronic inflammation and dietary fat consumption correlates with an increase in prostate cancer. Our previous studies in the colon have demonstrated that gamma-tocopherol treatment could upregulate the expression of peroxisome proliferator-activated preceptors (PPAR) gamma, a nuclear receptor involved in fatty acid metabolism as well modulation of cell proliferation and differentiation. In this study, we explored the possibility that gamma-tocopherol could induce growth arrest in PC-3 prostate cancer cells through the regulation of fatty acid metabolism. Growth arrest (40%) and PPAR gamma mRNA and protein upregulation was achieved with gamma-tocopherol within 6 h. gamma-Tocopherol-mediated growth arrest was demonstrated to be PPAR gamma dependent using the agonist GW9662 and a PPAR gamma dominant negative vector. gamma-tocopherol was shown not to be a direct PPAR gamma ligand, but rather 15-S-HETE (an endogenous PPAR gamma ligand) was upregulated by gamma-tocopherol treatment. 15-Lipoxygenase-2, a tumor suppressor and the enzyme that converts arachidonic acid to 15-S-HETE, was upregulated at 3 h following gamma-tocopherol treatment. Expression of proteins downstream of the PPAR gamma pathway were examined. Cyclin D1, cyclin D3, bcl-2, and NFkappa B proteins were found to be downregulated following gamma-tocopherol treatment. These data demonstrate that the growth arrest mediated by gamma-tocopherol follows a PPAR-gamma-dependent mechanism.

The novel synthetic triterpenoid, CDDO-imidazolide, inhibits inflammatory response and tumor growth in vivo.

1[2-Cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole (CDDO-Im) is a novel synthetic triterpenoid more potent than its parent compound, 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO), both in vitro and in vivo. CDDO-Im is highly active in suppressing cellular proliferation of human leukemia and breast cancer cell lines (IC(50), approximately 10-30 nM). In U937 leukemia cells, CDDO-Im also induces monocytic differentiation as measured by increased cell surface expression of CD11b and CD36. In each of these assays, CDDO-Im is several-fold more active than CDDO. Although CDDO and CDDO-Im both bind and transactivate peroxisome proliferator-activated receptor (PPAR) gamma, the irreversible PPARgamma antagonist GW9662 does not block the ability of either CDDO or CDDO-Im to induce differentiation; moreover, PPARgamma-null fibroblasts are still sensitive to the growth-suppressive effects of CDDO. Thus, CDDO-Im has significant actions independent of PPARgamma transactivation. In addition, the rexinoid LG100268 and the deltanoid ILX23-7553 (ILX7553) synergize with CDDO and CDDO-Im to induce differentiation. In vivo, CDDO-Im is a potent inhibitor of de novo inducible nitric oxide synthase expression in primary mouse macrophages. Moreover, CDDO-Im inhibits growth of B16 murine melanoma and L1210 murine leukemia cells in vivo. The potent effects of CDDO-Im, both in vitro and in vivo, suggest it should be considered for clinical use.

The acute extracellular flux (XF) assay to assess compound effects on mitochondrial function.

Numerous investigations have linked mitochondrial dysfunction to adverse health outcomes and drug-induced toxicity. The pharmaceutical industry is challenged with identifying mitochondrial liabilities earlier in drug development and thereby reducing late-stage attrition. Consequently, there is a demand for reliable, higher-throughput screening methods for assessing the impact of drug candidates on mitochondrial function. The extracellular flux (XF) assay described here is a plate-based method in which galactose-conditioned HepG2 cells were acutely exposed to test compounds, then real-time changes in the oxygen consumption rate and extracellular acidification rate were simultaneously measured using a Seahorse Bioscience XF-96 analyzer. The acute XF assay was validated using marketed drugs known to modulate mitochondrial function, and data analysis was automated using a spline curve fitting model developed at GlaxoSmithKline. We demonstrate that the acute XF assay is a robust, sensitive screening platform for evaluating drug-induced effects on mitochondrial activity in whole cells.

Validation of an optical microplate label-free platform in the screening of chemical libraries for direct binding to a nuclear receptor.

Optical microplate-based biosensors combine the advantages of label-free detection with industry-standard assay laboratory infrastructure and scalability. A plate-based label-free platform allows the same basic platform to be used to quantify molecular interactions of macromolecules and to screen and characterize drug-like small-molecule interactions. The ligand-binding domain of orphan estrogen-related nuclear receptor-γ (ERRγ) is utilized, as a model system of a challenging type of target, to illustrate the rapid development and utility of a range of biochemical assay formats on these biosensors. Formats in which either the domain, or a peptide derived from its cognate corepressor, RIP140, were immobilized were utilized. The direct binding of small drug molecules to the domain was characterized using immobilized domain. Subsequent addition of peptide distinguished whether compounds acted as either antagonists of peptide binding, or as agonists promoting a ternary complex. The format with peptide immobilized gave a more sensitive procedure for establishing the effect of compounds on the domain-peptide interaction. Using a direct-binding format, a diverse chemical library of 1,408 compounds in DMSO was screened for ability to bind to biosensors coated with ERRγ ligand-binding domain. Hits were then characterized using the other biosensor assay formats. The standard requirements for a full primary screening campaign were fulfilled by the acceptable hit-rate, quality-performance parameters, and throughput of the direct-binding assay format. Such a format allows direct screening of targets, such as orphan receptors, without the requirement for prior knowledge of a validated ligand.

Lysophosphatidic acid activates peroxisome proliferator activated receptor-γ in CHO cells that over-express glycerol 3-phosphate acyltransferase-1.

Lysophosphatidic acid (LPA) is an agonist for peroxisome proliferator activated receptor-γ (PPARγ). Although glycerol-3-phosphate acyltransferase-1 (GPAT1) esterifies glycerol-3-phosphate to form LPA, an intermediate in the de novo synthesis of glycerolipids, it has been assumed that LPA synthesized by this route does not have a signaling role. The availability of Chinese Hamster Ovary (CHO) cells that stably overexpress GPAT1, allowed us to analyze PPARγ activation in the presence of LPA produced as an intracellular intermediate. LPA levels in CHO-GPAT1 cells were 6-fold higher than in wild-type CHO cells, and the mRNA abundance of CD36, a PPARγ target, was 2-fold higher. Transactivation assays showed that PPARγ activity was higher in the cells that overexpressed GPAT1. PPARγ activity was enhanced further in CHO-GPAT1 cells treated with the PPARγ ligand troglitazone. Extracellular LPA, phosphatidic acid (PA) or a membrane-permeable diacylglycerol had no effect, showing that PPARγ had been activated by LPA generated intracellularly. Transient transfection of a vector expressing 1-acylglycerol-3-phosphate acyltransferase-2, which converts endogenous LPA to PA, markedly reduced PPARγ activity, as did over-expressing diacylglycerol kinase, which converts DAG to PA, indicating that PA could be a potent inhibitor of PPARγ. These data suggest that LPA synthesized via the glycerol-3-phosphate pathway can activate PPARγ and that intermediates of de novo glycerolipid synthesis regulate gene expression.

γ-Tocotrienol induces growth arrest through a novel pathway with TGFß2 in prostate cancer.

Regions along the Mediterranean and in southern Asia have lower prostate cancer incidence compared to the rest of the world. It has been hypothesized that one of the potential contributing factors for this low incidence includes a higher intake of tocotrienols. Here we examine the potential of γ-tocotrienol (GT3) to reduce prostate cancer proliferation and focus on elucidating pathways by which GT3 could exert a growth-inhibitory effect on prostate cancer cells. We find that the γ and δ isoforms of tocotrienol are more effective at inhibiting the growth of prostate cancer cell lines (PC-3 and LNCaP) compared with the γ and δ forms of tocopherol. Knockout of PPAR-γ and GT3 treatment show inhibition of prostate cancer cell growth, through a partially PPAR-γ-dependent mechanism. GT3 treatment increases the levels of the 15-lipoxygenase-2 enzyme, which is responsible for the conversion of arachidonic acid to the PPAR-γ-activating ligand 15-S-hydroxyeicosatrienoic acid. In addition, the latent precursor and the mature forms of TGFß2 are down-regulated after treatment with GT3, with concomitant disruptions in TGFß receptor I, SMAD-2, p38, and NF-κB signaling.

Human PXR forms a tryptophan zipper-mediated homodimer.

The human nuclear receptor pregnane X receptor (PXR) responds to a wide variety of potentially harmful chemicals and coordinates the expression of genes central to xenobiotic and endobiotic metabolism. Structural studies reveal that the PXR ligand binding domain (LBD) uses a novel sequence insert to form a homodimer unique to the nuclear receptor superfamily. Terminal beta-strands from each monomeric LBD interact in an ideal antiparallel fashion to bury potentially exposed surface beta-strands, generating a 10-stranded intermolecular beta-sheet. Conserved tryptophan and tyrosine residues lock across the dimer interface and provide the first tryptophan-zipper (Trp-Zip) interaction observed in a native protein. We show using analytical ultracentrifugation that the PXR LBD forms a homodimer in solution. We further find that removal of the interlocking aromatic residues eliminates dimer formation but does not affect PXR's ability to interact with DNA, RXRalpha, or ligands. Disruption of the homodimer significantly reduces receptor activity in transient transfection experiments, however, and effectively eliminates the receptor's recruitment of the transcriptional coactivator SRC-1 both in vitro and in vivo. Taken together, these results suggest that the unique Trp-Zip-mediated PXR homodimer plays a role in the function of this nuclear xenobiotic receptor.

Inhibition of peroxisome proliferator-activated receptor (PPAR)-mediated keratinocyte differentiation by lipoxygenase inhibitors.

Lipoxygenase (LOX) metabolites from arachidonic acid and linoleic acid have been implicated in atherosclerosis, inflammation, keratinocyte differentiation and tumour progression. We previously showed that peroxisome proliferator-activated receptors (PPARs) play a role in keratinocyte differentiation and that the PPARalpha ligand 8S-hydroxyeicosatetraenoic acid is important in this process. We hypothesized that blocking LOX activity would block PPAR-mediated keratinocyte differentiation. Three LOX inhibitors, nordihydroguaiaretic acid, quercetin and morin, were studied for their effects on primary keratinocyte differentiation and PPAR activity. All three LOX inhibitors blocked calcium-induced expression of the differentiation marker keratin 1. In addition, activity of a PPAR-responsive element was inhibited in the presence of all three inhibitors, and this effect was mediated primarily through PPARalpha and PPARgamma. LOX inhibitors decreased the activity of a chimaeric PPAR-Gal4-ligand-binding domain reporter system and this effect was reversed by addition of PPAR ligands. Ligand-binding studies revealed that the LOX inhibitors bind directly to PPARs and demonstrate a novel mechanism for these inhibitors in altering PPAR-mediated gene expression.

Adenocarcinoma cells exposed in vitro to Navelbine or Taxol increase Ep-CAM expression through a novel mechanism.

Ep-CAM antigen expression was shown to vary by phase across the cell cycle. Following pretreatment of various adenocarcinoma cells in culture with clinically relevant concentrations of vinorelbine tartrate (Navelbine) or paclitaxel (Taxol), cell surface expression of Ep-CAM antigen increased by two- to ten-fold compared to that of untreated control cells and was associated with arrest of cell cycle progression and accumulation of cells in the S and G2/M phases. We demonstrated that increases in cell surface antigen expression resulted in improved biological effectiveness of the targeting antibody as measured in vitro by antibody-dependent cellular cytotoxicity and in vivo by enhanced antibody targeting to Ep-CAM-expressing xenografts in mice pretreated with Navelbine. No effect on cell cycle progression or Ep-CAM antigen expression was seen with human interferon-alpha and interferon-gamma, agents that increase gene expression of various tumor and normal antigens and may upregulate some antigens. Thus, the upregulation of cell surface Ep-CAM expression following pretreatment with G2/M blockers is through a novel mechanism involving residence time of the antigen on the cell surface. This significant increase in Ep-CAM expression appears to be tumor-specific since we saw no increase in antigen expression on normal epithelial cells. Studies to reveal relative internalization rates suggest that the increase in cell surface expression of Ep-CAM following pretreatment with G2/M blockers is a consequence of an inhibition of normal cycles of antigen endocytosis and expression on the cell surface. The present work provides a mechanism for the improved clinical efficacy of therapeutic antibodies used in combination with traditional cell cycle-specific chemotherapeutic drugs.

The 15-lipoxygenase-1 product 13-S-hydroxyoctadecadienoic acid down-regulates PPAR-delta to induce apoptosis in colorectal cancer cells.

Diminished apoptosis, a critical event in tumorigenesis, is linked to down-regulated 15-lipoxygenase-1 (15-LOX-1) expression in colorectal cancer cells. 13-S-hydroxyoctadecadienoic acid (13-S-HODE), which is the primary product of 15-LOX-1 metabolism of linoleic acid, restores apoptosis. Nonsteroidal antiinflammatory drugs (NSAIDs) transcriptionally up-regulate 15-LOX-1 expression to induce apoptosis. Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors for linoleic and arachidonic acid metabolites. PPAR-delta promotes colonic tumorigenesis. NSAIDs suppress PPAR-delta activity in colon cancer cells. The mechanistic relationship between 15-LOX-1 and PPAR-delta was previously unknown. Our current study shows that (i) 13-S-HODE binds to PPAR-delta, decreases PPAR-delta activation, and down-regulates PPAR-delta expression in colorectal cancer cells; (ii) the induction of 15-LOX-1 expression is a critical step in NSAID down-regulation of PPAR-delta and the resultant induction of apoptosis; and (iii) PPAR-delta is an important signaling receptor for 13-S-HODE-induced apoptosis. The in vivo relevance of these mechanistic findings was demonstrated in our tumorigenesis studies in nude mouse xenograft models. Our findings indicate that the down-regulation of PPAR-delta by 15-LOX-1 through 13-S-HODE is an apoptotic signaling pathway that is activated by NSAIDs.

Subtype specific effects of peroxisome proliferator-activated receptor ligands on corepressor affinity.

Natural ligands for nuclear receptors are believed to activate gene transcription by causing dissociation of corepressors and promoting the association of coactivator proteins. Using multiple biophysical techniques, we find that peptides derived from one of the nuclear receptor interacting motifs of the corepressors nuclear receptor corepressor (NCoR) and silencing mediator of retinoid and thyroid receptors (SMRT) are able to bind the ligand binding domains (LBD) of all three PPAR (peroxisome proliferator activated receptor) subtypes. Using these peptides as tools, we find that ligands designed as selective agonists for PPAR gamma promote the association of coactivator peptides and dissociation of corepressor peptides as expected on PPAR gamma but surprisingly have varied effects on the binding of corepressor peptides to the other PPAR subtypes. In particular, some members of a class of L-tyrosine-based compounds designed as selective agonists for PPAR gamma reduce the affinity for corepressor peptides on PPAR gamma but increase the affinity for the same peptides on PPAR delta and in one case on PPAR alpha. We provide structural data that suggests that the molecular basis for these observations are variations in the ligand binding pockets of the three PPAR subtypes that are perturbed differentially by individual ligands and result in altered presentations of the overlapping coactivator/corepressor binding surfaces.

Functional consequences of cysteine modification in the ligand binding sites of peroxisome proliferator activated receptors by GW9662.

In the course of a high throughput screen to search for ligands of peroxisome proliferator activated receptor-gamma (PPARgamma), we identified GW9662 using a competition binding assay against the human ligand binding domain. GW9662 had nanomolar IC(50) versus PPARgamma and was 10- and 600-fold less potent in binding experiments using PPARalpha and PPARdelta, respectively. Pretreatment of all three PPARs with GW9662 resulted in the irreversible loss of ligand binding as assessed by scintillation proximity assay. Incubation of PPAR with GW9662 resulted in a change in the absorbance spectra of the receptors consistent with covalent modification. Mass spectrometric analysis of the PPARgamma ligand binding domain treated with GW9662 established Cys(285) as the site of covalent modification. This cysteine is conserved among all three PPARs. In cell-based reporter assays, GW9662 was a potent and selective antagonist of full-length PPARgamma. The functional activity of GW9662 as an antagonist of PPARgamma was confirmed in an assay of adipocyte differentiation. GW9662 showed essentially no effect on transcription when tested using both full-length PPARdelta and PPARalpha. Time-resolved fluorescence assays of ligand-modulated receptor heterodimerization, coactivator binding, and corepressor binding were consistent with the effects observed in the reporter gene assays. Control activators increased PPAR:RXR heterodimer formation and coactivator binding to both PPARgamma and PPARdelta. Corepressor binding was decreased. In the case of PPARalpha, GW9662 treatment did not significantly increase heterodimerization and coactivator binding or decrease corepressor binding. The experimental data indicate that GW9662 modification of each of the three PPARs results in different functional consequences. The selective and irreversible nature of GW9662 treatment, and the observation that activity is maintained in cell culture experiments, suggests that this compound may be a useful tool for elucidation of the role of PPARgamma in biological processes.

Structural basis for antagonist-mediated recruitment of nuclear co-repressors by PPARalpha.

Repression of gene transcription by nuclear receptors is mediated by interactions with co-repressor proteins such as SMRT and N-CoR, which in turn recruit histone deacetylases to the chromatin. Aberrant interactions between nuclear receptors and co-repressors contribute towards acute promyelocytic leukaemia and thyroid hormone resistance syndrome. The binding of co-repressors to nuclear receptors occurs in the unliganded state, and can be stabilized by antagonists. Here we report the crystal structure of a ternary complex containing the peroxisome proliferator-activated receptor-alpha ligand-binding domain bound to the antagonist GW6471 and a SMRT co-repressor motif. In this structure, the co-repressor motif adopts a three-turn alpha-helix that prevents the carboxy-terminal activation helix (AF-2) of the receptor from assuming the active conformation. Binding of the co-repressor motif is further reinforced by the antagonist, which blocks the AF-2 helix from adopting the active position. Biochemical analyses and structure-based mutagenesis indicate that this mode of co-repressor binding is highly conserved across nuclear receptors.