Mitochondrial uncoupling proteins as potential targets for pharmacological agents

It is widely acknowledged that the function of the original uncoupling protein, UCP1, is uncoupling of substrate oxidation from ATP synthesis, and that its physiological purpose is thermogenesis. The mechanisms and physiological functions of the novel uncoupling proteins, identified within the past seven years, are as yet poorly understood. These novel uncoupling proteins are part of a large family comprising approximately 35 mitochondrial anion carrier proteins. UCP2 and UCP3 appear to function in reactive oxygen species handling and/or in fatty acid metabolism; uncoupling might occur secondarily. There is little information on UCP4 and UCP5 (BMCP1), and phylogenetic analyses indicate that they are further removed from UCP1 than mitochondrial anion carrier proteins, and have distinct functions.     

The potential of antioxidant enzymes as pharmacological agents in vivo

1. Oxygen radicals have been associated with a number of unrelated pathological processes including ageing, radiation sickness, inflammation, oxygen toxicity, reoxygenation of ischaemic tissues, etc. The partial reduction of oxygen to superoxide anion (O₂^?) and H₂O₂ leads to the formation of more deleterious species such as hydroxyl radical (OH-) starting a chain reaction ultimately causing lipid peroxidation and cell death.

2. To prevent the increased steady-state concentration of oxygen radicals many researchers have designed potential treatments including the i.v. injection of antioxidant enzymes or enzyme derivatives with longer half-life in circulation (i.e. enzymes encapsulated in liposomes or covalently modified).

3. Tissue distribution and half-life in circulation depend upon the type of enzyme being used as well as whether the enzyme is or is not in its native form.

4. This review comments on some of the scenarios where these enzymes have been utilized, and discusses relevant problems of stability of different enzymes in circulation.     

Azapeptides as pharmacological agents

Azapeptides, formed by replacing the C(alpha) of amino acid residues by nitrogen, are promising peptidomimetic compounds. Azaamino acids impart a unique conformational property to peptide structures because of the loss of chirality and reduction of flexibility of the parent linear peptide. The peculiar conformational properties make azaamino acids an attractive tool for drug design involving specific secondary structures in peptides and proteins. Additionally, since azapeptides are less susceptible to enzymatic breakdown by proteases, they may possibly lead to orally active drugs with longer duration of action. One of the advantages of azapeptides is their unproblematic synthesis allowing retention of the amino acid side chain. Azapeptides have been developed by several groups for the design of hormone analogues, protease inhibitors and active site titrants.     

The potential of antioxidant enzymes as pharmacological agents in vivo.

1. Oxygen radicals have been associated with a number of unrelated pathological processes including ageing, radiation sickness, inflammation, oxygen toxicity, reoxygenation of ischaemic tissues, etc. The partial reduction of oxygen to superoxide anion (O2-.) and H2O2 leads to the formation of more deleterious species such as hydroxyl radical (OH.) starting a chain reaction ultimately causing lipid peroxidation and cell death. 2. To prevent the increased steady-state concentration of oxygen radicals many researchers have designed potential treatments including the i.v. injection of antioxidant enzymes or enzyme derivatives with longer half-life in circulation (i.e. enzymes encapsulated in liposomes or covalently modified). 3. Tissue distribution and half-life in circulation depend upon the type of enzyme being used as well as whether the enzyme is or is not in its native form. 4. This review comments on some of the scenarios where these enzymes have been utilized, and discusses relevant problems of stability of different enzymes in circulation.     

Combination antiplatelet agents for secondary prevention of ischemic stroke

Stroke is a leading cause of death and the primary cause of serious, long-term disability in the United States. Joint guidelines from the American Heart Association (AHA) and American Stroke Association (ASA), as well as recent guidelines from the Eighth American College of Chest Physicians (ACCP) Conference on Antithrombotic and Antiplatelet Therapy, recommend aspirin, clopidogrel, or extended-release dipyridamole plus aspirin as acceptable first-line options for secondary prevention of ischemic events in patients with a history of ischemic stroke or transient ischemic attack (TIA). The ACCP strongly recommends the combination of extended-release dipyridamole plus aspirin over aspirin monotherapy (highest level of evidence) and suggests clopidogrel monotherapy over aspirin monotherapy (lower level of evidence). The AHA-ASA guidelines suggest that either extended-release dipyridamole plus aspirin or clopidogrel monotherapy should be used over aspirin monotherapy. Both guidelines recommend avoiding the combination of clopidogrel and aspirin for most patients with previous stroke or TIA. Results from recent trials evaluating combination antiplatelet therapy have been published that enhance the AHA-ASA recommendations and provide the foundation for the updated ACCP guideline. To identify pertinent combination antiplatelet trials, a MEDLINE search of the literature from 1967-2007 was performed. Two trials were identified--the European-Australasian Stroke Prevention in Reversible Ischemia Trial (ESPRIT) and Clopidogrel for High Atherothrombotic Risk and Ischemic Stabilization, Management, and Avoidance (CHARISMA). The ESPRIT compared aspirin monotherapy with the combination of aspirin plus extended-release dipyridamole for prevention of secondary ischemic events in patients with a history of TIA or minor stroke. The CHARISMA trial compared aspirin plus clopidogrel with aspirin alone in a population at high risk for atherothrombotic events using the composite outcome of myocardial infarction, stroke, and death from cardiovascular causes. Data from ESPRIT add to evidence that the combination of aspirin plus extended-release dipyridamole is superior to aspirin alone. The findings of the CHARISMA trial reinforce recommendations from both AHA-ASA and ACCP that the combination of aspirin and clopidogrel be reserved for special populations requiring this antiplatelet combination (e.g., those who have had coronary artery stenting).     

Heteroaryl-substituted phenols as potential antioxidants

A series of O-heteroaryl phenols have been synthesised and structurally characterised. Photo-Fries rearrangement of these compounds represents a useful way to access the corresponding C-heteroaryl derivatives. The activity of the new phenolic compounds as radical scavengers towards the 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonate) (ABTS(+*)) has been evaluated. 2-tert-Butyl-4-(4-phenyl-isoxazol-3-ylmethoxy)-phenol (compound 3c) showed the highest scavenger activity (IC50 value (i.e. the concentration that scavenged 50% of the radicals) 3.17 x 10(-6) M), which was one order of magnitude greater than that of the corresponding lead compound tert-butylhydroxy-anisole (BHA) (IC50 1.04 x 10(-5) M). In further experiments, compound 3c showed dose-dependent inhibition of the oxidation of linoleic acid, as well as methaemoglobin formation, promoted by the presence of the radical generator 2,2'-azobis(amidino-propane) hydrochloride (AAPH) and it was markedly more potent than BHA in these assays.     

Synthesis of N-substituted aminoalkyl derivatives of some epoxyisoindoles as potential pharmacological agents

Grogan and Rice reported a number of imides of epoxyisoindole sort. Some pharmacological testing was performed which revealed their bioactivity. Except of their work, only scattered examples of derivatives with oxygen-bridged ring have appeared in the literature; this approach has also been used by us in the synthesis of some new potential drugs. This paper reports the synthesis of a number of epoxyisoindole derivatives, as well as in vitro tests of some selected representants.     

Hydroxamic acids as pharmacological agents

A variety of hydroxamic acid derivatives have recently been touted for their potential use as inhibitors of hypertension, tumor growth, inflammation, infectious agents, asthma, arthritis, and more. Here we provide a comprehensive review of the basic medicinal chemistry and pharmacology of hydroxamic acid derivatives that have been examined as inhibitors of zinc metalloproteases, matrix metalloproteinases, leukotriene A(4) hydrolases, ureases, lipoxigenases, cyclooxygenases, as well as peptide deformilases.     

Central nervous system agents for ischemic stroke: neuroprotection mechanisms

Stroke is the third leading cause of mortality and disability in the United States. Ischemic stroke constitutes 85% of all stroke cases. However, no effective treatment has been found to prevent damage to the brain in such cases except tissue plasminogen activator with narrow therapeutic window, and there is an unmet need to develop therapeutics for neuroprotection from ischemic stroke. Studies have shown that mechanisms including apoptosis, necrosis, inflammation, immune modulation, and oxidative stress and mediators such as excitatory amino acids, nitric oxide, inflammatory mediators, neurotransmitters, reactive oxygen species, and withdrawal of trophic factors may lead to the development of the ischemic cascade. Hence, it is essential to develop neuroprotective agents targeting either the mechanisms or the mediators leading to development of ischemic stroke. This review focuses on central nervous system agents targeting these biochemical pathways and mediators of ischemic stroke, mainly those that counteract apoptosis, inflammation, and oxidation, and well as glutamate inhibitors which have been shown to provide neuroprotection in experimental animals. All these agents have been shown to improve neurological outcome after ischemic insult in experimental animals in vivo, organotypic brain slice/acute slice ex vivo, and cell cultures in vitro and may therefore aid in preventing long-term morbidity and mortality associated with ischemic stroke.     

Synthesis and pharmacological evaluation of novel quinoxalines as potential nonulcerogenic anti-inflammatory and analgesic agents

Some new substituted quinoxaline and furo[2,3-b]quinoxaline derivatives have been synthesized and tested for their anti-inflammatory and analgesic activities and for their ulcerogenic potential. The pharmacological evaluation of selected synthesized compounds revealed that 5a was equipotent and compounds 3, 4b, 4e and 5b possessed strong anti-inflammatory activity in chronic inflammatory models compared with indometacin (CAS 53-86-1) as reference drug. In addition, compound 4a was the safest one and the others showed little ulcerogenic activity. All the tested compounds showed moderate analgesic activity compared to the reference drug.     

Synthesis,characterization and pharmacological evaluation of pyrazolyl urea derivatives as potential anti-inflammatory agents

p38α mitogen activated protein kinase (MAPK) inhibitors provide a novel approach for the treatment of inflammatory disorders. A series of fifteen pyrazolyl urea derivatives (3ao) were synthesized and evaluated for their p38α MAPK inhibition and antioxidant potential. Compounds 3ae, 3g and 3h showed low micromolar range potency (IC₅₀ values ranging from 0.037 ± 1.56 to 0.069 ± 0.07 µmol/L) compared to the standard inhibitor SB 203580 (IC₅₀ = 0.043 ± 3.62 µmol/L) when evaluated for p38α MAPK inhibition by an immunosorbent-based assay. Antioxidant activity was measured by a 2,2′-diphenyl-1-picryl hydrazyl radical (DPPH) free radical scavenging method and one of the compounds, 3c, showed better percentage antioxidant activity (75.06%) compared to butylated hydroxy anisole (71.53%) at 1 mmol/L concentration. Compounds 3ae, 3g and 3h showed promising in vivo anti-inflammatory activity (ranging from 62.25% to 80.93%) in comparison to diclofenac sodium (81.62%). The ulcerogenic liability and lipid peroxidation activity of these compounds were observed to be less in comparison to diclofenac sodium. These compounds also potently inhibited the lipopolysaccharide (LPS)-induced TNF-α release in mice (ID₅₀ of 3ac = 19.98, 11.32 and 9.67 mg/kg, respectively). Among the screened compounds, derivative 3c was found to be the most potent and its binding mode within the p38α MAPK is also reported.     

神经保护剂治疗缺血性脑卒中的研究进展

脑卒中的治疗包括超早期溶栓和神经保护药物。溶栓治疗有时间限制,而无时间限制的神经保护治疗也陷入了困境。常规途径的神经保护药物治疗脑缺血性损伤的效果不理想。来自卒中动物模型中的阳性结果和来自人类试验的阴性结果所引起的惊人偏差普遍引起对神经保护治疗的怀疑。2008年的卒中圆桌会议对迄今耗资数百亿美元,而基本均宣告无效的神经保护药物治疗进行了全面的反思和分析。尽管目前神经保护治疗的现状惨淡,但仍有少数药物的神经保护疗效得到随机试验证实,新型抗氧化自由基清除剂依达拉奉就是其中的一种,在Ⅲ期临床试验中取得良好的结果,是目前临床试验证明惟一有效的自由基清除剂。脑活素是另外一个引起关注的药物,在不同的脑缺血动物模型中表现出神经保护和神经营养特性,在几个小规模针对缺血性卒中的对照临床试验中显示了临床有效性和安全性,目前正在进行Ⅲ期临床试验。神经保护治疗的时间窗、改变治疗模式可能是今后神经保护的研究方向。     

溶栓药物治疗缺血性卒中的进展

自16年前首次被证明静脉溶栓可有效治疗急性缺血性卒中以来,溶栓率一直不高。尽管很多试验证明了许多溶栓药物的疗效,但静脉注射用组织型纤溶酶原激活剂(rt-PA,0.9 mg.kg-1)几乎成为惟一用于溶栓治疗的溶栓剂。针对这种情况,研究者正在多方面对研究工作进行改进,包括使用新的溶栓药物。另外,研究者正在尝试用新的溶栓剂、低剂量的rt-PA、神经保护剂等减少症状性脑出血的危险。     

Vasopressin receptor antagonists: pharmacological tools and potential therapeutic agents

The present survey deals with the development and applications of non-peptidergic vasopressin receptor antagonists. The existence of at least three vasopressin receptors (V(1), V(2) and V(3) respectively) is firmly established. V(1)-receptors play a relevant role in the regulation of vascular tone, whereas V(2)-receptors are known to mediate the antidiuretic activity of vasopressin at the level of the renal collecting ducts. The V(3)-receptor appears to be involved in the release of the adreno-corticotropic hormone. Vasopressin receptor antagonists which are peptides have been known for several decades, more recently, both V(1)- and V(2)-receptor blockers which are non-peptidergic have been introduced, as well as agents with affinity for both V(1)- and V(2)-receptor subtypes. A survey of these non-peptidergic antagonists is presented here. Such compounds are useful as pharmacological tools, and they can also be thought of as therapeutic agents as therapeutic agents in cardiovascular and renal diseases. Selective V(1)- and V(2)-receptor antagonists were used to study the interaction between vasopressin receptors and sympathetic neurones. Depending on the experimental model used this interaction can occur at either the pre- or postsynaptic sites. In both cases predominantly V(1)-receptors are involved. A brief survey is given of the potential use of V-receptor antagonists in the drug therapy of syndrome of inappropriate antidiuretic hormone secretion and other water retaining disorders, congestive heart failure and certain forms of hypertension (in particular in the Negroid hypertensive patients).