Substrate-selective positive allosteric modulation of PTPRD's phosphatase by flavonols.

The receptor type protein tyrosine phosphatase D (PTPRD) is expressed by neurons and implicated in interesting phenotypes that include reward from addictive substances, restless leg syndrome and neurofibrillary tangle densities in Alzheimer's disease (AD-NFTs). However, the brain phosphotyrosine phosphoprotein (PTPP) substrates for PTPRD's phosphatase have not been clearly defined. Although we have identified small molecule inhibitors of PTPRD's phosphatase that are candidates for reducing reward from addictive substances, no positive allosteric modulators of this phosphatase that might be candidates for reducing AD-NFTs have been reported. We now report identification of candidate brain substrates for PTPRD based on their increased phosphorylation in knockout vs wildtype animals, coexpression with PTPRD in neuronal subtypes and brisk dephosphorylation by recombinant human PTPRD phosphatase. We also report discovery that quercetin and other flavonols, though not closely-related flavones, enhance rates of PTPRD's dephosphorylation of a group of these candidate substrate PTPPs but not others. This substrate-selective positive allosteric modulation provides a novel pharmacological action. Flavonol-mediated increases in PTPRD's dephosphorylation of the GSK3 ß and α kinases that hyperphosphorylate tau, the major component of AD-NFTs, could help to explain recent data concerning genetic and dietary impacts on Alzheimer's disease.

Structure-activity studies of PTPRD phosphatase inhibitors identify a 7-cyclopentymethoxy illudalic acid analog candidate for development.

Interest in development of potent, selective inhibitors of the phosphatase from the receptor type protein tyrosine phosphatase PTPRD as antiaddiction agents is supported by human genetics, mouse models and studies of our lead compound PTPRD phosphatase inhibitor, 7-butoxy illudalic acid analog 1 (7-BIA). We now report structure-activity relationships for almost 70 7-BIA-related compounds and results that nominate a 7- cyclopentyl methoxy analog as a candidate for further development. While efforts to design 7-BIA analogs with substitutions for other parts failed to yield potent inhibitors of PTPRD's phosphatase, ten 7-position substituted analogs displayed greater potency at PTPRD than 7-BIA. Several were more selective for PTPRD vs the receptor type protein tyrosine phosphatases S, F and J or the nonreceptor type protein tyrosine phosphatase N1 (PTPRS, PTPRF, PTPRJ or PTPN1/PTP1B), phosphatases at which 7-BIA displays activity. In silico studies aided design of novel analogs. A 7-position cyclopentyl methoxy substituted 7-BIA analog termed NHB1109 displayed 600-700 nM potencies in inhibiting PTPRD and PTPRS, improved selectivity vs PTPRS, PTPRF, PTPRJ or PTPN1/PTP1B phosphatases, no substantial potency at other protein tyrosine phosphatases screened, no significant potency at any of the targets of clinically-useful drugs identified in EUROFINS screens and significant oral bioavailability. Oral doses up to 200 mg/kg were well tolerated by mice, though higher doses resulted in reduced weight and apparent ileus without clear organ histopathology. NHB1109 provides a good candidate to advance to in vivo studies in addiction paradigms and toward human use to reduce reward from addictive substances.

Sex-specific deficits in biochemical but not behavioral responses to delay fear conditioning in prenatal alcohol exposure mice.

BACKGROUND: Studies in clinical populations and preclinical models have shown that prenatal alcohol exposure (PAE) is associated with impairments in the acquisition, consolidation and recall of information, with deficits in hippocampal formation-dependent learning and memory being a common finding. The glucocorticoid receptor (GR), mineralocorticoid receptor (MR), and extracellular signal-regulated kinase 2 (ERK2) are key regulators of hippocampal formation development, structure and functioning and, thus, are potential mediators of PAE's effects on this brain region. In the present studies, we employed a well-characterized mouse model of PAE to identify biochemical mechanisms that may underlie activity-dependent learning and memory deficits associated with PAE. METHODS: Mouse dams consumed either 10% (w/v) ethanol in 0.066% (w/v) saccharin (SAC) or 0.066% (w/v) SAC alone using a limited (4-h) access, drinking-in-the-dark paradigm. Male and female offspring (∼180-days of age) were trained using a delay conditioning procedure and contextual fear responses (freezing behavior) were measured 24 h later. Hippocampal formation tissue and blood were collected from three behavioral groups of animals: 20 min following conditioning (conditioning only group), 20 min following the re-exposure to the context (conditioning plus re-exposure group), and behaviorally naïve (naïve group) mice. Plasma corticosterone levels were measured by enzyme immunoassay. Immunoblotting techniques were used to measure protein levels of the GR, MR, ERK1 and ERK2 in nuclear and membrane fractions prepared from the hippocampal formation. RESULTS: Adult SAC control male and female mice displayed similar levels of contextual fear. However, significant sex differences were observed in freezing exhibited during the conditioning session. Compared to same-sex SAC controls, male and female PAE mice demonstrated context fear deficits While plasma corticosterone concentrations were elevated in PAE males and females relative to their respective SAC naïve controls, plasma corticosterone concentrations in the conditioning only and conditioning plus re-exposure groups were similar in SAC and PAE animals. Relative to the respective naïve group, nuclear GR protein levels were increased in SAC, but not PAE, male hippocampal formation in the conditioning only group. In contrast, no difference was observed between nuclear GR levels in the naïve and conditioning plus re-exposure groups. In females, nuclear GR levels were significantly reduced by PAE but there was no effect of behavioral group or interaction between prenatal treatment and behavioral group. In males, nuclear MR levels were significantly elevated in the SAC conditioning plus re-exposure group compared to SAC naïve mice. In PAE females, nuclear MR levels were elevated in both the conditioning only and conditioning plus re-exposure groups relative to the naïve group. Levels of activated ERK2 (phospho-ERK2 expressed relative to total ERK2) protein were elevated in SAC, but not PAE, males following context re-exposure, and a significant interaction between prenatal exposure group and behavioral group was found. No main effects or interactions of behavioral group and prenatal treatment on nuclear ERK2 were found in female mice. These findings suggest a sex difference in which molecular pathways are activated during fear conditioning in mice. CONCLUSIONS: In PAE males, the deficits in contextual fear were associated with the loss of responsiveness of hippocampal formation nuclear GR, MR and ERK2 to signals generated by fear conditioning and context re-exposure. In contrast, the contextual fear deficit in PAE female mice does not appear to be associated with activity-dependent changes in GR and MR levels or ERK2 activation during training or memory recall, although an overall reduction in nuclear GR levels may play a role. These studies add to a growing body of literature demonstrating that, at least partially, different mechanisms underlie learning, memory formation and memory recall in males and females and that these pathways are differentially affected by PAE.

Sex-Dependent Effects of the Histone Deacetylase Inhibitor, Sodium Valproate, on Reversal Learning After Developmental Arsenic Exposure.

Several studies have demonstrated that exposure to arsenic in drinking water adversely affects brain development and cognitive function in adulthood. While the mechanism by which arsenic induces adverse neurological outcomes remains elusive, studies suggest a link between reduced levels of histone acetylation and impaired performance on a variety of behavioral tasks following arsenic exposure. Using our developmental arsenic exposure (DAE) paradigm, we have previously reported reduced histone acetylation and associated histone acetyltransferase enzyme expression in the frontal cortex of C57BL/6J adult male mice, with no changes observed in the female frontal cortex. In the present study, we sought to determine if DAE produced sex-dependent deficits in frontal cortical executive function using the Y-maze acquisition and reversal learning tasks, which are specific for assessing cognitive flexibility. Further, we tested whether the administration of valproic acid, a class I-IIa histone deacetylase inhibitor, was able to mitigate behavioral and biochemical changes resulting from DAE. As anticipated, DAE inhibited acquisition and reversal learning performance in adult male, but not female, mice. Valproate treatment for 2 weeks restored reversal performance in the male arsenic-exposed offspring, while not affecting female performance. Protein levels of HDACs 1, 2, and 5 were elevated following behavioral assessment but only in DAE male mice; restoration of appropriate HDAC levels occurred after valproate treatment and was concurrent with improved behavioral performance, particularly during reversal learning. Female frontal cortical levels of HDAC enzymes were not impacted by DAE or valproate treatment. Finally, mRNA expression levels of brain-derived neurotrophic factor, Bdnf, which has been implicated in the control of frontal cortical flexibility and is regulated by HDAC5, were elevated in DAE male mice and restored to normal levels following HDACi treatment. Levels of mRNA encoding glutamate receptor ionotropic NMDA type subunits, which have been linked to cognitive flexibility, were not related to the reversal learning deficit in the DAE mice and were not altered by HDACi treatments. These findings demonstrate that DAE alters frontal cortical HDAC levels and Bdnf expression in males, but not females, and that these molecular changes are associated with sex-dependent differences in cognitive flexibility in a reversal-learning task.

Grape Seed Procyanidin Extract Mediates Antineoplastic Effects against Lung Cancer via Modulations of Prostacyclin and 15-HETE Eicosanoid Pathways.

Grape seed procyanidin extract (GSE) has been reported to exert antineoplastic properties via the inhibition of cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2) eicosanoid pathways. In addition, ample data link carcinogenesis to inflammatory events involving other major eicosanoid metabolic pathways, including prostacyclin (PGI2) and 15-hydroxyeicosatetraenoic acid (15-HETE). We therefore evaluated the effects of GSE on prostacyclin synthase (PTGIS)/PGI2 and 15-lipoxigenase-2 (15-LOX-2)/15-HETE productions by human lung premalignant and malignant cells and correlated the findings with antiproliferative or proapoptotic effects of GSE. The effects of GSE on PGI2 and 15-HETE productions by human bronchoalveolar lavage (BAL) cells ex vivo were also determined. We further evaluated the bioactivity of oral administration of leucoselect phytosome (a standardized GSE) in the lungs of subjects participating in a lung cancer chemoprevention trial, by comparing the antiproliferative effects of coculturing matched pre- versus posttreatment BAL fluids with lung premalignant and malignant cells. GSE significantly increased PGI2 (as measured by 6-keto PGF1α) and 15-HETE productions by these cells. Transfections of PTGIS or 15-LOX-2-specific siRNA partially abrogated the antiproliferative or proapoptotic effects of GSE in lung premalignant and malignant cells, respectively. GSE also increased PTGIS and inhibition of caspase-3, and transfection of 15-LOX-2 siRNA abrogated the GSE-induced apoptosis in A549 cells. In addition, culture supernatants from ex vivo GSE-treated baseline BAL cells, as well as BAL fluids from subjects treated with leucoselect phytosome, significantly decreased proliferations of lung premalignant and malignant cells. Our findings support the continued investigation of GSE as an anti-neoplastic and chemopreventive agent against lung cancer. Cancer Prev Res; 9(12); 925-32. ©2016 AACR.

MicroRNA-19a/b mediates grape seed procyanidin extract-induced anti-neoplastic effects against lung cancer.

Oncomirs are microRNAs (miRNA) associated with carcinogenesis and malignant transformation. They have emerged as potential molecular targets for anti-cancer therapy. We hypothesize that grape seed procyanidin extract (GSE) exerts antineoplastic effects through modulations of oncomirs and their downstream targets. We found that GSE significantly down-regulated oncomirs miR-19a and -19b in a variety of lung neoplastic cells. GSE also increased mRNA and protein levels of insulin-like growth factor II receptor (IGF-2R) and phosphatase and tensin homolog (PTEN), both predicted targets of miR-19a and -19b. Furthermore, GSE significantly increased PTEN activity and decreased AKT phosphorylation in A549 cells. Transfection of miR-19a and -19b mimics reversed the up-regulations of IGF2R and PTEN gene expression and abrogated the GSE induced anti-proliferative response. Additionally, oral administration of leucoselect phytosome, comprised of standardized grape seed oligomeric procyanidins complexed with soy phospholipids, to athymic nude mice via gavage, significantly down-regulated miR-19a, -19b and the miR-17-92 cluster host gene (MIR17HG) expressions, increased IGF-2R, PTEN, decreased phosphorylated-AKT in A549 xenograft tumors, and markedly inhibited tumor growth. To confirm the absorption of orally administered GSE, plasma procyanidin B1 levels, between 60 and 90 min after gavage of leucoselect phytosome (400 mg/kg), were measured by LC/MS at week 2 and 8 of treatment; the estimated concentration that was associated with 50% growth inhibition (IC50) (1.3 µg/mL) in vitro was much higher than the IC50 (0.032-0.13 µg/ml) observed in vivo. Our findings reveal novel antineoplastic mechanisms by GSE and support the clinical translation of leucoselect phytosome as an anti-neoplastic and chemopreventive agent for lung cancer.