Chemokine receptor antagonists

Chemokines belong to a large family of chemoattractant molecules involved in the directed migration of immune cells. They achieve their cellular effects by direct interaction with cell surface receptors. Chemokines appear to be involved in a variety of proinflammatory and autoimmune diseases and this makes them and their receptors very attractive therapeutic targets. This review highlights current efforts toward obtaining highly specific chemokine receptor antagonists and discusses their chemistry and potential role as disease modifiers.     

Endothelin receptor antagonists

Endothelin receptor antagonists (ERAs) have been developed to block the effects of endothelin-1 (ET-1) in a variety of cardiovascular conditions. ET-1 is a powerful vasoconstrictor with mitogenic or co-mitogenic properties, which acts through the stimulation of 2 subtypes of receptors [endothelin receptor subtype A (ETA) and endothelin receptor subtype B (ETB) receptors]. Endogenous ET-1 is involved in a variety of conditions including systemic and pulmonary hypertension (PH), congestive heart failure (CHF), vascular remodeling (restenosis, atherosclerosis), renal failure, cancer, and cerebrovascular disease. The first dual ETA/ETB receptor blocker, bosentan, has already been approved by the Food and Drug Administration for the treatment of pulmonary arterial hypertension (PAH). Trials of endothelin receptor antagonists in heart failure have been completed with mixed results so far. Studies are ongoing on the effects of selective ETA antagonists or dual ETA/ETB antagonists in lung fibrosis, cancer, and subarachnoid hemorrhage. While non-peptidic ET-1 receptor antagonists suitable for oral intake with excellent bioavailability have become available, proven efficacy is limited to pulmonary hypertension, but it is possible that these agents might find a place in the treatment of several cardiovascular and non-cardiovascular diseases in the coming future.     

Competitive AMPA receptor antagonists

Glutamic acid (Glu) is the major excitatory neurotransmitter in the mammalian central nervous system (CNS) where it is involved in the physiological regulation of different processes. It has been well established that excessive endogenous Glu is associated with many acute and chronic neurodegenerative disorders such as cerebral ischaemia, epilepsy, amiotrophic lateral sclerosis, Parkinson's, and Alzheimer's disease. These data have consequently added great impetus to the research in this field. In fact, many Glu receptor antagonists acting at the N-methyl-D-aspartic acid (NMDA), 2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA), and/or kainic acid (KA) receptors have been developed as research tools and potential therapeutic agents. Ligands showing competitive antagonistic action at the AMPA type of Glu receptors were first reported in 1988, and the systemically active 2,3-dihydroxy-6-nitro-7-sulphamoyl-benzo[f]quinoxaline (NBQX) was first shown to have useful therapeutic effects in animal models of neurological disease in 1990. Since then, the quinoxaline template has represented the backbone of various competitive AMPA receptor antagonists belonging to different classes which had been developed in order to increase potency, selectivity and water solubility, but also to prolong the "in vivo" action. Compounds that present better pharmacokinetic properties and less serious adverse effects with respect to the others previously developed are undergoing clinical evaluation. In the near future, the most important clinical application for the AMPA receptor antagonists will probably be as neuroprotectant in neurodegenerative diseases, such as epilepsy, for the treatment of patients not responding to current therapies. The present review reports the history of competitive AMPA receptor antagonists from 1988 up to today, providing a systematic coverage of both the open and patent literature.     

Comparison of angiotensin II receptor antagonists

Nonpeptide orally active angiotensin II type 1 (AT1) receptor antagonists are the most specific means presently available to block the renin-angiotensin enzymatic cascade. Six of these drugs have already been licensed in Europe and in the United States for the treatment of high blood pressure, and additional candidates are in the pipeline. The World Health Organisation has also recently endorsed their use for this condition. Inasmuch as AT1 receptor antagonists have proven themselves the equals of angiotensin converting enzyme inhibitors with respect to antihypertensive efficacy, but demonstrated better safety profiles, this class of drugs may be considered to be a qualitative improvement in the treatment of essential hypertension. Interestingly, the six agents now on the market diverge considerably with respect to their pharmacokinetic and pharmacodynamic properties, although it is not certain whether such differences are clinically relevant. A considerable number of large, multicentre trials are in progress to ascertain the possible longer-term organoprotective effects of these substances on cardiovascular morbidity and mortality. Because of their noteworthy safety record to date, and simple once-a-day dosage regimen, AT1 receptor antagonists have the potential to improve compliance in patients with chronic hypertension.     

Integrase inhibitors and CCR5 receptor antagonists

Integrase inhibitors and CCR5 receptor antagonists, novel class of antiretrovirals, were introduced into clinical practice in late 2000s. Currently available drugs in these classes, raltegravir and maraviroc, show good tolerability and have little impact on lipid or glucose metabolism compared to traditional classes. Disadvantage of these two drugs is the need for twice-daily dosing. The usefulness of raltegravir in both treatment-na?ve and treatment-experienced setting has been well established through clinical trials and five years' clinical use, whereas the usefulness of maraviroc in treatment-na?ve setting is still unclear. These drugs will be utilized as a key component of NRTI-sparing regimens in the future.     

Gastroprotective effects of thromboxane receptor antagonists.

The recent discovery of potent, specific, long-acting thromboxane receptor antagonists, like SQ 33,961, mandated that studies be conducted to follow up an earlier study, which showed potential antiulcer activity of the short-acting thromboxane antagonist, SQ 28,668, in the taurocholic acid gastric erosion model in rats. In experiments conducted with the same taurocholic acid protocol, SQ 33,961 caused a dose-related reduction in taurocholate-induced gastric erosions, with an ID50 value of 12 micrograms/kg, i.p. In additional studies, aspirin and indomethacin were shown to produce gastric erosions in rats, and SQ 33,961 also inhibited gastric erosion in response to these anti-inflammatory drugs. The ID50 values were 0.24 and 0.26 mg/kg i.p. vs. aspirin (200 mg/kg, p.o.) and indomethacin (200 mg/kg, s.c.), respectively. The inhibition of aspirin-induced gastric injury by SQ 33,961 was confirmed histologically. This gastroprotective activity was not peculiar to SQ 33,961, because the structurally unrelated thromboxane receptor antagonist, BM 13,505, also significantly inhibited the development of aspirin-induced gastric lesions. In a more severe model, SQ 33,961 (10 mg/kg, i.p.) reduced gastric erosions by only 32% (not significant) 1 hr after ethanol ingestion (1 ml, p.o.) in rats. SQ 33,961 did not inhibit the antiphlogistic activity (carrageenan paw edema assay) of indomethacin, nor did it inhibit the analgesic activity (phenylquinone writhing assay) of aspirin. A dose of SQ 33,961 producing > or = 95% inhibition of nonsteroidal anti-inflammatory drug-induced gastric erosion (10 mg/kg, i.p.) produced a 37% reduction in the volume of gastric secretion without changing the titratable acidity of gastric contents.(ABSTRACT TRUNCATED AT 250 WORDS)     

The cardioprotective effects of mineralocorticoid receptor antagonists

Despite state-of-the-art reperfusion therapy, morbidity and mortality remain significant in patients with an acute myocardial infarction. Therefore, novel strategies to limit myocardial ischemia–reperfusion injury are urgently needed. Mineralocorticoid receptor (MR) antagonists are attractive candidates for this purpose, since several clinical trials in patients with heart failure have reported a survival benefit with MR antagonist treatment. MRs are expressed by several cells of the cardiovascular system, including cardiomyocytes, cardiac fibroblasts, vascular smooth muscle cells, and endothelial cells. Experiments in animal models of myocardial infarction have demonstrated that acute administration of MR antagonists, either before ischemia or immediately at the moment of coronary reperfusion, limits infarct size. This action appears to be independent of the presence of aldosterone and cortisol, which are the endogenous ligands for the MR. The cardioprotective effect is mediated by a nongenomic intracellular signaling pathway, including adenosine receptor stimulation, and activation of several components of the Reperfusion Injury Salvage Kinase (RISK) pathway. In addition to limiting infarct size, MR antagonists can improve scar healing when administered shortly after reperfusion and can reduce cardiac remodeling post myocardial infarction. Clinical trials are currently being performed studying whether early administration of MR antagonists can indeed improve prognosis in patients with an acute myocardial infarction, independent of the presence of heart failure.     

The clinical potential of chemokine receptor antagonists

Chemokines belong to a family of chemotactic cytokines that direct the migration of immune cells towards sites of inflammation. They mediate their biological effects by binding to cell surface receptors, which belong to the G protein-coupled receptor superfamily. Since chemokines and their receptors have been implicated in the pathophysiology of a number of autoinflammatory diseases, chemokine receptor antagonists could prove to be useful therapeutics to target these diseases. Here, we review the role of chemokines in autoimmunity, concentrating mainly on the chemokine receptors CCR1 and CCR5, and discuss the potential utility of antagonists that target these 2 receptors as they progress through the clinic.     

Bradykinin B2 receptor activates extracellular signal-regulated protein kinase in mIMCD-3 cells via epidermal growth factor receptor transactivation

Bradykinin (BK) has been implicated in the regulation of renal function. Activation of extracellular signal-regulated protein kinase (ERK1/2) has been demonstrated in several models of toxic or proliferative renal injury. We studied activation of ERK1/2 by BK in a cell model of the most distal part of the nephron, inner medullary collecting duct (mIMCD-3) cells. Exposure of mIMCD-3 cells to BK (10(-10)-10(-5) M) resulted in a concentration-dependent increase in tyrosine phosphorylation of ERK1/2, with maximal effect at 10(-8) M BK. ERK1/2 activation by BK was observed as early as 1 min, peaked at 5 min, and was sustained at least for 1 h. The effect of BK was mediated by the B(2) receptor and was pertussis toxin-independent. Inhibition of phospholipase C, protein kinase C, or phosphatidylinositol 3-kinase did not alter ERK1/2 activation by BK. BK-induced ERK1/2 activation was Ca(2+)-calmodulin-independent but was sensitive to genistein, an inhibitor of tyrosine kinase(s). AG1478, a specific inhibitor of epidermal growth factor receptor (EGFR) kinase, completely blocked the effect of BK, suggesting an essential role of EGFR in ERK1/2 activation by BK. Immunoprecipitation/Western blot studies revealed that BK stimulated tyrosine phosphorylation of EGFR, its association with an adapter molecule Grb2, and complex formation between Grb2 and the adapter protein Shc. Activation studies of monomeric G protein Ras showed that BK-induced stimulation of Ras was dependent on EGFR tyrosine kinase activity. These studies demonstrate that BK stimulates Ras-dependent activation of ERK1/2 in mIMCD-3 cells via transactivation of EGFR through a novel mechanism.     

内皮素、内皮素受体拮抗剂与类风湿关节炎

1984年O B rien首先报告牛肺动脉及主动脉内皮细胞分泌一种可以持续收缩牛肺动脉血管活性多肽样物质,此后多位学者的研究发现培养的动物内皮细胞可释放一种强烈的血管收缩物质,至1988年,日本学者Y anagisaw a从培养的猪主动脉内皮细胞上清液成功分离和纯化了这种生物活性多肽,并...