The Journal of pharmacology and experimental therapeutics
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J. Pharmacol. Exp. Ther. · Jun 2009
Resistance to mitogen-activated protein kinase kinase (MEK) inhibitors correlates with up-regulation of the MEK/extracellular signal-regulated kinase pathway in hepatocellular carcinoma cells.
The extracellular signal-regulated (ERK), mitogen-activated protein kinase (p42/p44 MAPK) pathway is up-regulated in hepatocellular carcinoma (HCC). Molecular targeting of this critical mitogenic pathway may have therapeutic potential for the treatment of HCC; however, chemoresistance to long-term therapy may develop. In the present study, we employed small-molecule MAPK kinase (MEK) inhibitors, including U0126 [1,4-diamino-2,3-dicyano-1,4-bis(2-aminophynyltio)butadiene] and PD184161 (Neoplasia 8:1-8, 2006), in HepG2 and Hep3B human HCC cell lines to identify potential mechanism(s) of resistance. ⋯ Finally, we showed that combining two chemically distinct MEK inhibitors enhanced growth inhibition and apoptosis compared with the single agents. Taken together, these results suggest that up-regulated expression or activity of the MEK/ERK pathway contributes to MEK inhibitor resistance in HCC cells. Our findings also provide preclinical evidence suggesting that the status of the MEK/ERK pathway in patients may predict response to MEK/ERK-targeted therapeutics.
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J. Pharmacol. Exp. Ther. · Jun 2009
Scratching behavior and Fos expression in superficial dorsal horn elicited by protease-activated receptor agonists and other itch mediators in mice.
Protease-activated receptor (PAR)-2 and PAR-4 are implicated in nonhistaminergic itch. We investigated dose dependence, tachyphylaxis, and cross-tachyphylaxis of itch-associated scratching elicited by intradermal injections of PAR-2 and PAR-4 agonists, serotonin (5-hydroxytryptamine, 5-HT), and histamine in ICR mice, as well as mu-opioid modulation of PAR-2 agonist-evoked scratching. Each agent elicited dose-related increases in scratch bouts. ⋯ High-dose morphine also significantly increased circling behavior, which may have interfered with scratching. The PAR-2 agonist and 5-HT produced overlapping distributions of Fos-like immunoreactivity in the superficial dorsal horn. These results indicate that PAR-2 and PAR-4 agonists, histamine, and 5-HT elicit itch-related scratching and activate superficial dorsal horn neurons that may participate in scratch reflex and ascending itch signaling pathways.
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J. Pharmacol. Exp. Ther. · Jun 2009
The free radical scavenger edaravone rescues rats from cerebral infarction by attenuating the release of high-mobility group box-1 in neuronal cells.
Edaravone, a potent free radical scavenger, is clinically used for the treatment of cerebral infarction in Japan. Here, we examined the effects of edaravone on the dynamics of high-mobility group box-1 (HMGB1), which is a key mediator of ischemic-induced brain damage, during a 48-h postischemia/reperfusion period in rats and in oxygen-glucose-deprived (OGD) PC12 cells. HMGB1 immunoreactivity was observed in both the cytoplasm and the periphery of cells in the cerebral infarction area 2 h after reperfusion. ⋯ In vitro, edaravone dose-dependently (1-10 microM) suppressed OGD- and H(2)O(2)-induced HMGB1 release in PC12 cells. Furthermore, edaravone (3-30 microM) blocked HMGB1-triggered apoptosis in PC12 cells. Our findings suggest a novel neuroprotective mechanism for edaravone that abrogates the release of HMGB1.
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J. Pharmacol. Exp. Ther. · May 2009
Glycogen synthase kinase-3beta mediates endoplasmic reticulum stress-induced lysosomal apoptosis in leukemia.
Glycogen synthase kinase (GSK)-3beta may modulate endoplasmic reticulum (ER) stress-induced apoptosis; however, the mechanism remains unclear. Our data showed that human monocytic leukemia/lymphoma U937 and acute myeloid leukemia HL-60, but not chronic myeloid leukemia K562, cells were susceptible to apoptosis induced by ER stressor tunicamycin, a protein glycosylation inhibitor. Tunicamycin caused early activation of caspase-2, -3, -4, and -8, followed by apoptosis, whereas caspase-9 was slowly activated. ⋯ Unlike U937 and HL-60 cells, K562 cells showed nonresponsive ER stress and failure of activation of GSK-3beta and caspase-2 in response to tunicamycin. Activating GSK-3beta caused K562 cells to be susceptible to tunicamycin-induced apoptosis. Taken together, we show that GSK-3beta exhibits a mechanism of ER stress-induced lysosomal apoptosis in leukemia involving caspase-2-induced LMP and cathepsin B relocation, which result in caspase-8 and -3 activation.
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J. Pharmacol. Exp. Ther. · May 2009
Smoke, choline acetyltransferase, muscarinic receptors, and fibroblast proliferation in chronic obstructive pulmonary disease.
Acetylcholine (ACh), synthesized by choline acetyltransferase (ChAT), and muscarinic M(1), M(2), and M(3) receptors (MRs) are involved in fibroblast proliferation. We evaluated ChAT, MRs, and extracellular signal-regulated kinase (ERK) 1/2 and nuclear factor (NF) kappaB activation in lung fibroblasts from patients with chronic obstructive pulmonary disease (COPD), control smokers, and controls. Human fetal lung fibroblasts (HFL-1) stimulated with interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha, and cigarette smoke extracts (CSEs) were evaluated for ChAT and MR expression. ⋯ H(2)O), gallamine triethiodide (C(19)H(22)N(4)O(2)S.2HCl. H(2)O), telenzepine [4,9-d-dihydro-3-methyl-4-[(4-methyl-1piperazinyl) acetyl]-10H-thieno [3,4-b][1,5]benzodiazepine-10-one dihydrobromide, C(30)H(60)I(3)N(3)O(3)], 4-diphenylacetoxy-N-methylpiperidine, PD098059 [2-(2-amino-3methoxyphenyl)-4H-1benzopyran-4-one, C(16)H(13)NO(3)], and BAY 11-7082 [(E)-3-(4-methylphenylsulfonyl)-2-propenetrile, C(10)H(9)NO(2)C], down-regulated the ACh-induced fibroblast proliferation, promoting the MRs and ERK1/2 and NFkappaB pathways involvement in this phenomenon. These results suggest that cigarette smoke might alter the expression of ChAT and MRs, promoting airway remodeling in COPD and that anticholinergic drugs, including tiotropium, might prevent these events.