(1/4453) Activation of c-Abl tyrosine kinase requires caspase activation and is not involved in JNK/SAPK activation during apoptosis of human monocytic leukemia U937 cells.
Genotoxic stress triggers the activation of several sensor molecules, such as p53, JNK1/SAPK and c-Abl, and occasionally promotes the cells to apoptosis. We previously reported that JNK1/SAPK regulates genotoxic stress-induced apoptosis in p53-negative U937 cells by activating caspases. c-Abl is expected to act upstream of JNK1/SAPK activation upon treatment with genotoxic stressors, but its involvement in apoptosis development is still unclear. We herein investigated the kinase activities of c-Abl and JNK1/SAPK during apoptosis elicited by genotoxic anticancer drugs and tumor necrosis factor (TNF) in U937 cells and their apoptosis-resistant variant UK711 cells. We found that the activation of JNK1/SAPK and c-Abl correlated well with apoptosis development in these cell lines. Unexpectedly, however, the JNK1/SAPK activation preceded the c-Abl activation. Moreover, the caspase inhibitor Z-Asp suppressed c-Abl activation and the onset of apoptosis but not the JNK1/SAPK activation. Interestingly, c-Abl tyrosine kinase inhibition by CGP 57148 reduced apoptosis without interfering with JNK1/SAPK activation. These results indicate that c-Abl acts not upstream of JNK1/ SAPK but downstream of caspases during the development of p53-independent apoptosis and is possibly involved in accelerating execution of the cell death pathway. (+info)
(2/4453) Meta-analysis of the reversible inhibitors of monoamine oxidase type A moclobemide and brofaromine for the treatment of depression.
The reversible inhibitors of monoamine oxidase type A (RIMAs) are a newer group of antidepressants that have had much less impact on clinical psychopharmacology than another contemporary class of medications, the selective serotonin reuptake-inhibitors (SSRIs). The RIMAs agents are distinguished from the older monoamine oxidase inhibitors (MAOIs) by their selectivity and reversibility. As a result, dietary restrictions are not required during RIMA therapy, and hypertensive crises are quite rare. In this article, we describe a series of meta-analyses of studies of the two most widely researched RIMAs, moclobemide (MOC; Aurorex) and brofaromine (BRO). Our findings confirm that both BRO and MOC are as effective as the tricyclic antidepressants, and they are better tolerated. However, BRO is not being studied at present for reasons unrelated to efficacy or side effects. MOC, which is available throughout much of the world (but not the United States), is significantly more effective than placebo and, at the least, comparable to the SSRIs in both efficacy and tolerability. For MOC, higher dosages may enhance efficacy for more severe depressions. We also found evidence that supports clinical impressions that MOC is somewhat less effective, albeit better tolerated, than older MAOIs, such as phenelzine or tranylcypromine. Little evidence has yet emerged to suggest that the RIMAs share older MAOIs' utility for treatment of depressions characterized by prominent reverse neurovegetative features. Based on available evidence, the RIMAs appear to have a limited, but useful, role in the differential therapeutics of the depressive disorders. (+info)
(3/4453) The geranylgeranyltransferase I inhibitor GGTI-298 induces hypophosphorylation of retinoblastoma and partner switching of cyclin-dependent kinase inhibitors. A potential mechanism for GGTI-298 antitumor activity.
The geranylgeranyltransferase I inhibitor GGTI-298 has recently been shown to arrest human tumor cells in the G1 phase of the cell cycle, induce apoptosis, and inhibit tumor growth in nude mice. In the present manuscript, we provide a possible mechanism by which GGTI-298 mediates its tumor growth arrest. Treatment of the human lung carcinoma cell line Calu-1 with GGTI-298 results in inhibition of the phosphorylation of retinoblastoma protein, a critical step for G1/S transition. The kinase activities of two G1/S cyclin-dependent kinases, CDK2 and CDK4, are inhibited in Calu-1 cells treated with GGTI-298. Furthermore, GGTI-298 has little effect on the expression levels of CDK2, CDK4, CDK6, cyclins D1 and E, but decreases the levels of cyclin A. GGTI-298 increases the levels of the cyclin-dependent kinase inhibitors p21 and p15 and had little effect on those of p27 and p16. Most interesting is the ability of GGTI-298 to induce partner switching for several CDK inhibitors. GGTI-298 promotes binding of p21 and p27 to CDK2 while decreasing their binding to CDK6. Reversal of partner switching and G1 block was observed after removal of GGTI-298. Furthermore, GGTI-298 treatment results in an increased binding of p15 to CDK4, which is paralleled with decreased binding to p27. The results demonstrate that the GGTI-298-mediated G1 block in Calu-1 cells involves increased expression and partner switching of CDK inhibitors resulting in inhibition of CDK2 and CDK4, and retinoblastoma protein phosphorylation. (+info)
(4/4453) Vasoconstriction in human isolated middle meningeal arteries: determining the contribution of 5-HT1B- and 5-HT1F-receptor activation.
AIMS: Sumatriptan is a 5-HT1B/1D-receptor agonist which also has affinity for 5-HT1F-receptors. The vasoconstrictor effects of sumatriptan are thought to be 5-HT1B-receptor mediated and these receptors have been shown to be expressed in human cranial blood vessels. However, in the same tissue mRNA coding for 5-HT1F-receptors has also been identified and this study addresses the possibility of whether 5-HT1F-receptor activation contributes to vasoconstriction. METHODS: The ability of two selective 5-HT1B/1D-receptor antagonists (GR125,743 and GR127,935) with no affinity for 5-HT1F-receptors, to inhibit sumatriptan evoked contractions in human isolated middle meningeal artery was investigated. Using a series of 5-HT1B/1D-receptor agonists (sumatriptan, zolmitriptan, CP122,288, L-741,519 and L-741,604), some with high affinity for 5-HTIF-receptors and the non-selective 5-HT-receptor agonists 5-HT and 5-CT, we compared the vasoconstrictor potency of these drugs in human isolated middle meningeal artery with their affinities at cloned human 5-HT1B-, 5-HT1D-and 5-HT1F-receptors expressed in CHO cell lines. RESULTS: GR125,743 antagonized sumatriptan evoked contractions in a competitive manner (apparent pA2 9.1) and GR127,935 antagonized sumatriptan-induced responses in a non-competitive manner (reducing the maximum contraction to 27%). There was a significant correlation between vasoconstrictor potency and 5-HT1B-receptor affinity (r=0.93, P=0.002) but not with 5-HT1D- or 5-HT1F-receptor affinity (r=0.74, P=0.06; r= 0.31, P= 0.49, respectively). CONCLUSIONS: These experiments show that in human middle meningeal artery vasoconstriction to sumatriptan-like agents is 5-HT1B-receptor mediated with little if any contribution from 5-HT1F-receptor activation. (+info)
(5/4453) Involvement of tachykinin receptors in sensitisation to cow's milk proteins in guinea pigs.
BACKGROUND: There is growing evidence for a pivotal role for tachykinins in gut neuroimmune interactions. AIMS: To determine whether NK1, NK2, and NK3 tachykinin receptors are involved in milk protein induced allergic sensitisation. METHODS: Eight groups of 12 Dunkin-Hartley guinea pigs (250-300 g) were used. Four groups were sensitised to milk proteins for three weeks. During this period, these animals were injected intraperitoneally each day with NK1 (SR 140333; 0.3 mg/kg), NK2 (SR 48968; 5 mg/kg), or NK3 (SR 142801; 5 mg/kg) receptor antagonist or vehicle. The fifth group had water available instead of milk and was used as a non-sensitised control. The three other groups received the NK receptor antagonists for three weeks but were not sensitised to milk proteins. RESULTS: Sensitised animals treated with NK1 and NK3 receptor antagonists had both lower IgE and IgG serum titres, evaluated by passive cutaneous anaphylaxis, and lower specific IgG serum titres, determined by enzyme linked immunosorbent assay (ELISA), than vehicle treated animals. Sensitisation induced an increase in intestinal mast cell number which was abolished by treatment with the NK1 receptor antagonist. Antigenic challenge-induced jejunal hypersecretion was also blocked by treatment with the NK1 receptor antagonist. CONCLUSION: In guinea pigs, NK1 and NK3 but not NK2 receptors are involved in sensitisation to cow's milk. However, NK1 but not NK3 receptor antagonists abolish both the hypermastocytosis induced by food allergy and the hypersecretion induced by antigenic challenge, suggesting different roles for NK1 and NK3 receptors in the mechanisms of sensitisation to beta-lactoglobulin. (+info)
(6/4453) Neurogenic plasma leakage in mouse airways.
1. This study sought to determine whether neurogenic inflammation occurs in the airways by examining the effects of capsaicin or substance P on microvascular plasma leakage in the trachea and lungs of male pathogen-free C57BL/6 mice. 2. Single bolus intravenous injections of capsaicin (0.5 and 1 micromol kg(-1), i.v.) or substance P (1, 10 and 37 nmol kg(-10, i.v.) failed to induce significant leakage in the trachea, assessed as extravasation of Evans blue dye, but did induce leakage in the urinary bladder and skin. 3. Pretreatment with captopril (2.5 mg kg(-1), i.v.), a selective inhibitor of angiotensin converting enzyme (ACE), either alone or in combination with phosphoramidon (2.5 mg kg(-1), i.v.), a selective inhibitor of neutral endopeptidase (NEP), increased baseline leakage of Evans blue in the absence of any exogenous inflammatory mediator. The increase was reversed by the bradykinin B2 receptor antagonist Hoe 140 (0.1 mg kg(-1), i.v.). 4. After pretreatment with phosphoramidon and captopril, capsaicin increased the Evans blue leakage above the baseline in the trachea, but not in the lung. This increase was reversed by the tachykinin (NK1) receptor antagonist SR 140333 (0.7 mg kg(-1), i.v.), but not by the NK2 receptor antagonist SR 48968 (1 mg kg(-1), i.v.). 5. Experiments using Monastral blue pigment as a tracer localized the leakage to postcapillary venules in the trachea and intrapulmonary bronchi, although the labelled vessels were less numerous in mice than in comparably treated rats. Blood vessels of the pulmonary circulation were not labelled. 6. We conclude that neurogenic inflammation can occur in airways of pathogen-free mice, but only after the inhibition of enzymes that normally degrade inflammatory peptides. Neurogenic inflammation does not involve the pulmonary microvasculature. (+info)
(7/4453) A synthetic inhibitor of histone deacetylase, MS-27-275, with marked in vivo antitumor activity against human tumors.
Synthetic benzamide derivatives were investigated for their ability to inhibit histone deacetylase (HDA). In this study, one of the most active benzamide derivatives, MS-27-275, was examined with regard to its biological properties and antitumor efficacy. MS-27-275 inhibited partially purified human HDA and caused hyperacetylation of nuclear histones in various tumor cell lines. It behaved in a manner similar to other HDA inhibitors, such as sodium butyrate and trichostatin A; MS-27-275 induced p21(WAF1/CIP1) and gelsolin and changed the cell cycle distribution, decrease of S-phase cells, and increase of G1-phase cells. The in vitro sensitivity spectrum of MS-27-275 against various human tumor cell lines showed a pattern different than that of a commonly used antitumor agent, 5-fluorouracil, and, of interest, the accumulation of p21(WAF1/CIP1) tended to be faster and greater in the cell lines sensitive to MS-27-275. MS-27-275 administered orally strongly inhibited the growth in seven of eight tumor lines implanted into nude mice, although most of these did not respond to 5-fluorouracil. A structurally analogous compound to MS-27-275 without HDA-inhibiting activity showed neither the biological effects in cell culture nor the in vivo therapeutic efficacy. These results suggest that MS-27-275 acts as an antitumor agent through HDA inhibition and may provide a novel chemotherapeutic strategy for cancers insensitive to traditional antitumor agents. (+info)
(8/4453) Selective induction of apoptosis in Philadelphia chromosome-positive chronic myelogenous leukemia cells by an inhibitor of BCR - ABL tyrosine kinase, CGP 57148.
The BCR - ABL tyrosine kinase has been implicated as the cause of Philadelphia chromosome (Ph1)-positive leukemias. We report herein that CGP 57148, a selective inhibitor of the ABL tyrosine kinase, caused apoptosis specifically in bcr - abl-positive chronic myelogenous leukemia (CML) cells, K562 and KYO-1. Upon treatment with CGP 57148, CRKL, a specific substrate for BCR - ABL that propagates signals via phosphatidylinositol-3' kinase (PI3K), was dephosphorylated, indicating inhibition of BCR - ABL tyrosine kinase at the cellular level. Likewise, MAPK/ERK, a downstream mediator of Ras, was also dephosphorylated. Caspase activation and cleavage of retinoblastoma protein (pRB) accompanied the development of CGP 57148-induced apoptosis. Inhibition of caspase suppressed apoptosis and the cleavage of pRB, and in turn arrested cells in the G1 phase. These results indicate that CGP 57148 shows apoptogenic and anti-proliferative effects on bcr - abl-positive cells by blocking BCR - ABL-initiated signaling pathways. (+info)