Tissue-type plasminogen activator. A review of its pharmacology and therapeutic use as a thrombolytic agent

Coronary arterial thrombolysis is becoming an established treatment of acute myocardial infarction. If given early enough, it recanalises occluded coronary arteries, salvages myocardial function and reduces mortality. A reduction of mortality in patients with acute myocardial infarction has now been demonstrated for streptokinase, anisoylated plasminogen streptokinase activator complex (APSAC; anistreplase) and recombinant tissue-type plasminogen activator (rt-PA). From the biochemical point of view, rt-PA has several attractive properties. It is similar to or identical with the physiological plasminogen activator in blood, it does not induce an antibody response, and it is more fibrin-specific than most or all other currently known thrombolytic agents. The rate of recanalisation of occluded coronary arteries with rt-PA is about 60 to 80% in non-comparative and placebo-controlled trials. rt-PA was similar in efficacy to urokinase in the only trial to compare the 2 agents. In 2 comparative trials evaluated by meta-analysis, rt-PA appeared more effective than streptokinase for the early recanalisation of occluded arteries. Both agents were comparable in their effects on left ventricular function in 2 comparative trials, but further study is needed to conclusively evaluate this parameter. Moreover, both agents reduce inhospital mortality, but much larger direct comparative trials are required before scientifically valid statements can be made on the relative clinical efficacy of available thrombolytic agents in terms of their effects on both morbidity and mortality. Thus, rt-PA constitutes a notable contribution of recombinant DNA technology to the treatment of thromboembolic disease, the main cause of death and disability in Western societies.     

The impact of beta-lactamases on the development of novel antimicrobial agents

beta-Lactamases have been critical factors for the selection and development of beta-lactam-containing antibacterial agents for almost 60 years. New agents under investigation continue to be evaluated based on their interactions with beta-lactamases. Oral carbapenems, penems and antimethicillin-resistant Staphylococcus aureus cephalosporins are all being selected for development, in part, because of their stability to hydrolysis by the beta-lactamases of their target organisms. beta-Lactamase inhibitors must selectively inhibit the major beta-lactamase groups appearing in current clinical isolates. For all agents, the multiplicity of beta-lactamases in single organisms or in mixed infections poses a new set of challenges requiring agents that can respond to enzymes with varying functional characteristics.     

五味子甲素对K562/ADR、HL60/ADR、MCF-7/ADR多药耐药逆转机制的研究

目的探讨五味子甲素(schizandrin A or deoxyschizan-drin,schA)对白血病细胞K562/ADR、HL60/ADR、乳腺癌细胞MCF-7/ADR多药耐药的逆转作用,并初步探讨其逆转机制。方法 MTT法检测schA对耐药细胞的逆转作用;流式细胞仪检测schA对细胞内柔红霉素、罗丹明-123含量和细胞表面P-gp表达水平的变化;用Real-time PCR方法检测schA对细胞内mdr1 mRNA和mrp1 mRNA表达;生化检测法检测schA对细胞内GSH含量的变化。结果耐药逆转实验显示:不同浓度的schA对作用机制不同的化疗药物耐药产生不同的逆转效果;蓄积实验表明schA可增加柔红霉素、罗丹明123在耐药细胞内的蓄积,并且有良好的剂量依赖关系;schA处理K562/ADR、HL60/ADR细胞24 h后,能降低P-gp蛋白和mdr1、mrp1基因的表达;schA处理K562/ADR、HL60/ADR细胞4 h后,可降低细胞内谷胱甘肽含量。结论 schA对耐药机制不同的细胞株K562/ADR、HL60/ADR均有耐药逆转作用,推测可能是与抑制细胞表面的P-gp蛋白功能和表达,降低mdr1、mrp1耐药基因的表达和降低细胞内谷胱甘肽含量有关,schA通过影响上述机制,进而增加细胞内的药物浓度,达到有效杀灭肿瘤细胞的作用。     

Limits of stimulation of proliferation and differentiation of bone marrow cells of mice treated with swainsonine

The limits of stimulation of the immunomodulatory alkaloid swainsonine (8alphabeta-indolizidine-1alpha,2alpha,8beta-triol) were studied in inbred C57BL/6 mice for potential support of intense high dose cancer chemotherapy and/or radiation because of its attractive pharmacologic profile on the hematopoietic system. Specifically, the effects of swainsonine on bone marrow cellularity and on in vitro progenitor cell proliferation to total colony forming units (CFU) and differentiation to different lineages were studied as a function of number of days post drug administration. The lineages evaluated were colony forming units-granulocyte-macrophage (CFU-GM), erythroid-burst forming units (BFU-e) and CFU-granulocyte-erythrocyte-monocyte-megakaryocyte (CFU-GEMM or CFU-Mix). Groups of mice were treated with swainsonine or plain vehicle, phosphate buffered saline for 10 consecutive days. The effects of these agents on the hematopoietic system were studied up to 60 days following their discontinuation. The magnitude of the effects of swainsonine on bone marrow system gradually declined with increasing duration of days following its discontinuation. Nevertheless, its residual stimulatory effects on bone marrow cellularity, total CFU, CFU-GM, BFU-e and CFU-Mix continued to be significant (P<0.0001) up to 45, 50, 50, 55 and 50 days, respectively, compared to those of diluent buffer or untreated controls. Since cancer chemotherapeutic agents or radiation are normally given in schedules and/or cycles, these results strongly suggest that swainsonine effects are sustained long enough to potentially support and facilitate hematopoietic recovery during anti-cancer cytotoxic treatment.     

The novel non-steroidal selective androgen receptor modulator S-101479 has additive effects with bisphosphonate, selective estrogen receptor modulator, and parathyroid hormone on the bones of osteoporotic female rats

We have studied non-steroidal selective androgen receptor modulators (SARMs) to develop anti-osteoporosis drugs for males and females. Many SARMs have been studied for their anabolic effects on bone or muscle with reduced virilizing effects in male animals. However, the tissue selectivities of these agents in female animals have not been fully evaluated. We evaluated the novel SARM S-101479 from tetrahydroquinoline libraries in ovariectomized (OVX) rats. S-101479 preferentially bound to the androgen receptor with nanomolar affinity among nuclear receptors. It increased the bone mineral density (BMD) of femurs and diminished the effects on the uterus and clitoral gland in OVX rats. We then compared the effect of S-101479 on bone with those of commercial anti-osteoporosis drugs such as alendronate, raloxifene, and teriparatide. Furthermore, we evaluated the effects of combination treatments with these agents in OVX rats. After 16-week treatment, all agents significantly increased BMD, but the magnitude of bone mineral content (BMC) and/or bone size (projected bone area) were different. Alendronate, raloxifene, and teriparatide maintained BMC and bone size in this experimental dose. Only S-101479 increased BMC with bone size on single treatments. In combination treatment, S-101479 significantly increased BMC and bone size compared with single treatments of other agents. S-101479, like natural androgen, may have showed periosteal bone formation of the cortical area and indicated additive effects with commercial anti-osteoporosis drugs. These results indicate that S-101479 may be a useful anti-osteoporosis drug, particularly for patients with established severe osteoporosis.     

The pharmacology of seizures induced by sensitization with low intensity brain stimulation

Daily low-intensity electrical stimulation of selected brain sites causes seizures to gradually develop. Because the limbic area is particularly susceptible to both the sensitization phenomenon and psychotropic drugs, we evaluated several classes of centrally-active agents for activity against these seizures. For comparative purposes, seizures elicited from the amygdala and a nonlimbic site, the sensorimotor cortex, were tested. Rats with chronically-implanted electrodes were stimulated for one min each day with a 50-μA, 60-Hz current. Initially, no overt effects occurred; but eventually seizures wereestablished. Once the seizures stabilized, drug effects on seizure duration were measured. Antidepressive drugs were more potent in suppressing amygdaloid-elicited seizures than cortically-evoked seizures. Both antianxiety and antiepileptic drugs exerted nonselective blockade but the antianxiety agents were extremely potent in comparison to the antiepileptics. Representative neuroleptic drugs failed to block the seizures, even at doses completely debilitating the animals. Stimulants prolonged the seizures but the activity was weak. Thus, the low-intensity brain stimulation (LIBS) procedure has proved to be not only an interesting phenomenon, but one that responds differentially to various classes of CNS drugs.     

The in-vitro antiproliferative effect of PRI-2191 and imatinib applied in combined treatment with cisplatin, idarubicin, or docetaxel on human leukemia cells

Imatinib mesylate (Gleevec, STI571) is a specific inhibitor of the Bcr/Abl fusion tyrosine kinase that exhibits potent antileukemic effects in chronic myelogenous leukemia. Bcr/Abl-positive K562 and Bcr/Abl-negative HL-60 human leukemia cells were used to investigate the effect of PRI-2191, a calcitriol analog, on the biological effects of imatinib combined with other anticancer drugs. The results show that PRI-2191 enhances the antiproliferative effect of imatinib on HL-60 cells. When these two agents together are applied with either docetaxel or cisplatin, but not with idarubicin, the antiproliferative effect could still be enhanced. Moreover, when the interaction between the chemotherapy agents was antagonistic or additive, PRI-2191 could even shift it to synergism. This effect correlated with an accumulation of HL-60 cells in the G0/G1 phase of the cell cycle and a decrease in the percentage of cells in the G2/M and S stage in the ternary combinations used. PRI-2191 did not influence apoptosis induced by imatinib alone or in ternary combinations with all the chemotherapy agents used. These results may suggest that the stronger antiproliferative effect of the combined treatment with PRI-2191 on HL-60 cells is related to cell cycle arrest rather than to the induction of apoptosis.     

Pharmacodynamic comparison of verapamil and nifedipine in anesthetized dogs

The relationships between steady-state plasma concentrations of verapamil or nifedipine and the resultant hemodynamic and electrophysiologic effects were evaluated in anesthetized, instrumented dogs. In different groups of animals, the drugs were given intravenously by loading-maintenance infusions designed to rapidly achieve and sustain stable plasma drug concentrations, over four different target ranges which span those found in clinical use of these agents. Plasma levels of nifedipine varied from 5 to 125 ng/ml, and those of verapamil, from 40 to 500 ng/ml. Nifedipine produced no apparent effects on the surface electrocardiogram. Verapamil dosing resulted in progressive prolongation of the PR interval as plasma drug levels increased from 40 to 250 ng/ml; at higher drug levels, complete atrioventricular block occurred. At the highest plasma concentrations used, the maximal vasodilation produced by both drugs was approximately equal, with mean aortic pressure levels falling to 50-60% of control values. The effects of the two agents on cardiac pump performance, however, differed: nifedipine administration produced dose-related increases in cardiac output at all plasma drug concentrations studied; the effects of verapamil were critically dependent upon drug levels in plasma, with cardiac output increased above control values at drug concentrations between 40 and 250 ng/ml, and progressively depressed at higher plasma levels of the drug. As a result, the calculated systemic vascular resistance declined progressively during nifedipine administration, while after verapamil doses, this parameter varied inversely with observed effects on cardiac output.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synthesis and biological evaluation of novel AM80 derivatives as antileukemic agents

A series of novel AM80 derivatives as antileukemic agents were synthesized and their structures were confirmed by IR, ¹H-NMR, and HR-MS spectra. All the target compounds were evaluated for in vitro antiproliferative activities against human leukemic HL-60, NB4, and K562 cell lines. Among these derivatives, compound 4g showed much stronger antiproliferative activities against all the three human leukemic cell lines than the positive control AM80, and compound 4b exhibited more active antiproliferative effects against HL-60 and K562 cells than AM80. Furthermore, the preliminary SAR analysis suggested that AM80 conjugating with HDAC inhibitors with small steric hindrance could give more effective antileukemic agents. These results would be helpful to design more potent antileukemic drugs for the treatment of human leukemia.     

Novel Water-Soluble Substituted Pyrrolo[3,2-d]pyrimidines: Design, Synthesis, and Biological Evaluation as Antitubulin Antitumor Agents

Purpose

To study the effects of a regioisomeric change on the biological activities of previously reported water soluble, colchicine site binding, microtubule depolymerizing agents.

Methods

Nine pyrrolo[3,2-d]pyrimidines were designed and synthesized. The importance of various substituents was evaluated. Their abilities to cause cellular microtubule depolymerization, inhibit proliferation of MDA-MB-435 tumor cells and inhibit colchicine binding to tubulin were studied. One of the compounds was also evaluated in the National Cancer Institute preclinical 60 cell line panel.

Results

Pyrrolo[3,2-d]pyrimidine analogs were more potent than their pyrrolo[2,3-d]pyrimidine regioisomers. We identified compounds with submicromolar potency against cellular proliferation. The structure-activity relationship study gave insight into substituents that were crucial for activity and those that improved activity. The compound tested in the NCI 60 cell line is a 2-digit nanomolar (GI₅₀) inhibitor of 8 tumor cell lines.

Conclusion

We have identified substituted pyrrolo[3,2-d]pyrimidines that are water-soluble colchicine site microtubule depolymerizing agents. These compounds serve as leads for further optimization.     

A dose-titration trial of guanadrel as step-two therapy in essential hypertension

The efficacy and safety of low-dose guanadrel sulfate were evaluated in 20 patients with essential hypertension based on seated diastolic blood pressures (SDBP) ranging from 95 to 115 mm Hg despite a trial dosage of hydrochlorothiazide 50 mg/d for up to five weeks. These patients had been resistant to, or intolerant of, one or more step-two antihypertensive drugs in the past (i.e., methyldopa, beta-adrenergic blocking agents, clonidine, or prazosin). The majority of patients demonstrated a satisfactory response (SDBP 95 mm Hg or reduction in SDBP of 10 mm Hg) to guanadrel. Nine patients responded at a low dosage, 10 to 20 mg/d and remained free from adverse effects throughout the study (up to 12 weeks of treatment). Of the remaining 11 patients titrated to higher dosages of guanadrel (30 to 60 mg/d), three had no discernible response while six developed adverse effects. The results of the study suggest that guanadrel has an acceptable benefit-to-risk ratio only when used in low dosages (10 to 30 mg/d) and may be successfully employed as step-two antihypertensive therapy in patients resistant to, or intolerant of, other step-two agents.     

Modification of C2 functional group on asiatic acid and the evaluation of hepatoprotective effects

For the development of novel hepatoprotective agents, C2 functional group on asiatic acid was modified, and evaluated for their hepatoprotective effects. Among prepared compounds, compounds 10 and 14 showed better hepatoprotective effects compared to silymarin.     

Yohimbine increases human salivary secretion.

The effect of oral yohimbine (14 mg) on salivary secretion was evaluated in healthy volunteers. Yohimbine significantly increased salivary secretion when compared with placebo. This effect was significant from 60 min until 180 min after administration under our experimental conditions. Yohimbine (or alpha 2-adrenoceptor blocking agents) could have a potential interest in the treatment of dry mouths.     

抗菌药物对氟康唑动态抗真菌作用及透过生物膜的影响

目的：测定试验用抗菌药物与氟康唑联合的动态抗真菌作用,并评价试验用抗菌药物对氟康唑透过生物膜的影响。方法：采用活菌计数法描绘联合用药对白色念珠菌的动态杀菌曲线,以“三明治”透膜实验法评价试验用抗菌药物对氟康唑透过生物膜的影响。结果：试验抗菌药物对氟康唑有不同程度的增效作用,其中米诺环素和利福平对氟康唑透过耐药白色念珠菌生物膜的作用及其对氟康唑动态抗真菌的增效作用最强,氧氟沙星、阿奇霉素等次之。结论：试验用抗菌药物能促进氟康唑透过白色念珠菌生物膜,增强氟康唑的动态抗真菌作用。     

Cyclic AMP elevating agents and nitric oxide modulate angiotensin II-induced leukocyte-endothelial cell interactions in vivo

Angiotensin (Ang-II) is a key molecule in the development of cardiac ischaemic disorders and displays proinflammatory activity in vivo. Since intracellular cyclic nucleotides elevating agents have proved to be effective modulators of leukocyte recruitment, we have evaluated their effect on Ang-II-induced leukocyte-endothelial cell interactions in vivo using intravital microscopy within the rat mesenteric microcirculation. Pretreatment with iloprost significantly inhibited (1 nM) Ang-II-induced increase in leukocyte rolling flux, adhesion and emigration at 60 min by 96, 92 and 90% respectively, and returned leukocyte rolling velocity to basal levels. Pretreatment with salbutamol or co-superfusion with forskolin exerted similar effects. When theophylline was administered, leukocyte rolling flux, adhesion and emigration elicited by Ang-II were significantly attenuated by 81, 89 and 71% respectively. Rolipram administration caused similar reduction of Ang-II-induced leukocyte responses. Co-superfusion of Ang-II with the NO-donor, spermine-NO, or 8-Br-cyclic GMP, or pretreatment with a transdermal nytroglycerin patch, resulted in a significant reduction of the leukocyte-endothelial cell interactions elicited by Ang-II. Salbutamol preadministration did not modify leukocyte-endothelial cell interactions elicited by either L-NAME or L-NAME+Ang-II, indicating that the inhibitory leukocyte effects caused by cyclic AMP-elevating agents are mediated through NO release. In conclusion, we have provided evidence that cyclic AMP elevating agents and NO donors, are potent inhibitors of Ang-II-induced leukocyte-endothelial cell interactions. Thus, they could constitute a powerful therapeutical tool in the control of the leukocyte recruitment characteristic of the vascular lesions that occur in cardiovascular disease states where Ang-II plays a critical role.     

Enhancement of sodium fluoride-induced cell death by centrifugal force

As an initial step in the study of the influence of orthodontic force on cellular function in vitro, the effects of centrifugal force on the cytotoxicity induced by various apoptosis inducers were investigated. When human oral squamous cell carcinoma (HSC-2) and human promyelocytic leukemia (HL-60) cell lines were treated with increasing magnitudes of centrifugal force (evaluated by g-value), the viability assessed by the MTT method and trypan blue dye exclusion began to decline. Centrifugal force enhanced the cytotoxicity of sodium fluoride (NaF), but not that of redox compounds (hydrogen peroxide, sodium ascorbate, gallic acid) or chemotherapeutic agents (daunorubicin, doxorubicin, idarubicin, mitoxantrone, peplomycin, 5-FU). The combination of NaF and centrifugal force enhanced caspase-3 activity. The present study suggests that centrifugal force is an additional factor that modifies the biological activity of NaF.     

The positive inotropic effects of milrinone but not of digoxin are attenuated at short cycle lengths

The effects of inotropically active agents on the left ventricular force-interval relation are a potential determinant of their clinical utility and safety. However, little information is available concerning the effects of noncatecholamine positive inotropic agents on this relation. Therefore this study compared the short-term effects of digoxin and milrinone on resting hemodynamics, frequency potentiation (FP), and mechanical restitution (MR) in patients undergoing nonemergency cardiac catheterization. Both digoxin and milrinone produced similar increases in LV + dP/dt at rest (12.2 +/- 1.3%, p < 0.000001 and 11.4 +/- 3.2%, p < 0.01, respectively). The positive inotropic effects of digoxin were marginally attenuated during FP (by 8.5 +/- 4.2% and 4.6 +/- 2.9% at 10 and 60 s, respectively, both p = NS compared with baseline). Similarly, on MRC analysis, the parameter c (a measure of sensitivity of contractile performance to reductions in cycle length) increased by 3.6 +/- 3.7% (p = NS). Whereas the positive inotropic effects of milrinone were not significantly attenuated during FP, they were abolished and possibly reversed at short cycle lengths on MR curve construction (6.8 +/- 5.9% negative inotropic effect at 60% of resting cycle length; p = NS; p < 0.05 vs. resting cycle length). In conclusion, in patients with well-preserved left ventricular systolic function, the positive inotropic effects of milrinone but not of digoxin are markedly dependent on heart rate. These properties may influence both relative safety and efficacy of both agents.     

Synthesis and antiproliferative activity of a new compound containing an alpha-methylene-gamma-lactone group

The biological activity of compound 9 obtained by introducing an alpha-methylene-gamma-butyrolactone group into 3-(4-hydroxyphenyl)propionic acid, 1, was studied for possible effects on HL-60 cells, murine splenocytes, and human peripheral mononuclear cells (PBMC). 9 induced apoptosis in the HL-60 cell line and has a clear capacity to inhibit proliferation induced in murine splenocytes and PBMC by different mitogenic agents with no apparent toxic side effects. 9 was synthesized from 1, and its structure and stereochemistry were elucidated by spectroscopic methods.     

Chemistry and positive inotropic effect of pelrinone and related derivatives. A novel class of 2-methylpyrimidones as inotropic agents

A novel series of pyrimidine derivatives was synthesized and evaluated for positive inotropic activity. Inotropic and chronotropic effects were determined in vitro in cat papillary muscle and right atrium, respectively. Selected compounds were then evaluated in vivo in a dog heart failure model. Changes in ventricular dP/dt, heart rate, and blood pressure were monitored. Several of these agents produced relatively minor changes in heart rate. This class of agents demonstrated a varying degree of vasodilator effects concomitant with increases in ventricular contractility. The most potent analogues, 9, 48, and 49, were evaluated orally in conscious dogs with implanted Konisberg pressure transducers, and their effect on left ventricular dP/dt was compared with that of milrinone. Mechanistically, the agents of this novel class appear not to mediate their effect via beta-receptors or inhibition of Na+/K+-ATPase. A major component of their inotropic effect is mediated by the inhibition of cardiac phosphodiesterase (PDE)-Fr. III. This was clearly demonstrated by 9, 48, and 49. Compound 48 was found to be the most potent inhibitor of PDE-Fr. III from among the compounds tested in this assay.     

Central nervous system side effects of beta-adrenergic blocking agents with high and low lipid solubility

beta-adrenergic blocking agents have undesirable effects believed to be mediated through the central nervous system (CNS). If these effects are due to direct CNS action, less lipid soluble agents ought to have fewer effects. Accordingly, several formal psychological tests of items such as mood, motivation, and anxiety were used in a double-blinded crossover study in 17 hypertensive subjects taking equipotent beta blocking agents with high (propranolol) and low (atenolol) lipid solubility. Patients had less negative effects (p less than 0.05) on 12 of 21 items evaluated with atenolol compared to propranolol while peripheral beta blockade [beta 1, exercise heart rate (HR), and blood pressure (BP)] was equivalent. These results suggest that the mental changes which accompany beta blockade therapy are mediated directly in the CNS and that less soluble drugs can be expected to have fewer CNS effects.