Synthesis and structure-activity relationships of 2-amino-8-hydroxyadenines as orally active interferon inducing agents

Recently, we have reported the 8-hydroxyadenine derivatives (2–4) as a novel class of interferon (IFN) inducing agents. In the present study, a series of 8-hydroxyadenines, which possess various amino moieties at the adenine C(2)-position, were synthesized and evaluated for their ability to induce endogenous IFN in comparison to the known active agent, Imiquimod. Among the compounds prepared, compound 9o possessing a 2-methoxyethylamino group at C(2)-position of adenine was found to exhibit potent IFN inducing activity in vivo. Compound 9o induced IFN from the dosage of 0.1 mg/kg, which was 30-fold potent than that of Imiquimod, and showed a good oral bioavailability (F=81%).     

In vivo neuroprotective role of NMDA receptors against kainate-induced excitotoxicity in murine hippocampal pyramidal neurons

Activation of NMDA receptors has been shown to induce either neuronal cell death or neuroprotection against excitotoxicity in cultured cerebellar granule neurons in vitro. We have investigated the effects of pretreatment with NMDA on kainate-induced neuronal cell death in mouse hippocampus in vivo. The systemic administration of kainate (30 mg/kg), but not NMDA (100 mg/kg), induced severe damage in pyramidal neurons of the hippocampal CA1 and CA3 subfields 3-7 days later, without affecting granule neurons in the dentate gyrus. An immunohistochemical study using an anti-single-stranded DNA antibody and TdT-mediated dUTP nick end labeling analysis both revealed that kainate, but not NMDA, induced DNA fragmentation in the CA1 and CA3 pyramidal neurons 1-3 days after administration. Kainate-induced neuronal loss was completely prevented by the systemic administration of NMDA (100 mg/kg) 1 h to 1 day previously. No pyramidal neuron was seen with fragmented DNA in the hippocampus of animals injected with kainate 1 day after NMDA treatment. The neuroprotection mediated by NMDA was prevented by the non-competitive NMDA receptor antagonist MK-801. Taken together these results indicate that in vivo activation of NMDA receptors is capable of protecting against kainate-induced neuronal damage through blockade of DNA fragmentation in murine hippocampus.     

Plasma protein binding study of oxybutynin by high-performance frontal analysis

Plasma protein binding of oxybutynin (OXY) was investigated quantitatively and enantioselectively using high-performance frontal analysis (HPFA). An on-line HPLC system which consists of HPFA column, extraction column and analytical column was developed to determine the unbound concentrations of OXY enantiomers in human plasma, in human serum albumin (HSA) solutions, and in human alpha1-acid glycoprotein (AGP) solutions. OXY is bound in human plasma strongly and enantioselectively. The bound drug fraction in human plasma containing 2-10 microM (R)- or (S)-OXY was higher than 99%, and the unbound fraction of (R)-OXY was 1.56 times higher than that of (S)-isomer. AGP plays the dominant role in this strong and enantioselective plasma protein binding. The total binding affinities (nK) of (R)- and (S)-OXY to AGP were 6.86 x 10(6) and 1.53 x 10(7) M(-1), respectively, while the nK values of (R)- and (S)-OXY to HSA were 2.64 x 10(4) and 2.19 x 10(-4) M(-1), respectively. The binding affinity of OXY to AGP is much higher than that to HSA, and shows high enantioselectivity (SIR ratio of nK values is 2.2). It was found that both enantiomers are bound competitively at the same binding site on an AGP molecule. The binding property between OXY and low density lipoprotein (LDL) was investigated by using the frontal analysis method incorporated in high-performance capillary electrophoresis (HPCE/FA). It was found the binding is non-saturable and non-enantioselective.     

Beraprost sodium,a prostaglandin I2 analogue,protects against advanced gycation end products-induced injury in cultured retinal pericytes

BACKGROUND: Beraprost sodium, a prostaglandin I2 analogue, has been recently reported to exhibit beneficial effects on atherosclerosis in patients with diabetes. However, effects of beraprost sodium on microvascular injury in diabetes remain to be elucidated. We have previously shown that advanced glycation end products (AGE), senescent macroproteins formed at an accelerated rate in diabetes, caused pericyte apoptosis, thus being involved in the pathogenesis of the early phase of diabetic retinopathy. In this study, we examined whether beraprost sodium can protect against AGE-induced cytotoxicity in cultured retinal pericytes. MATERIALS AND METHODS: Intracellular formation of reactive oxygen species (ROS) was detected using a fluorescent probe. DNA synthesis was determined by measuring [3H]thymidine incorporation into cells. Apoptosis was determined by DNA fragmentations, which were quantitatively measured in an enzyme-linked immunosorbent assay. RESULTS: Beraprost sodium or forskolin, a stimulator of adenylate cyclase, was found to significantly inhibit AGE-induced ROS generation and the subsequent decrease in DNA synthesis in pericytes. Both treatments significantly prevented AGE-induced apoptotic cell death in pericytes. Furthermore, beraprost sodium was found to down-regulate AGE receptor mRNA levels in pericytes. CONCLUSION: The results demonstrated that cyclic AMP-elevating agents such as beraprost sodium and forskolin protected retinal pericytes from AGE-induced cytotoxicity through its anti-oxidative properties. Our present study suggests that beraprost sodium may have therapeutic potentials in treatment of patients with early diabetic retinopathy.     

Advanced glycation end products-induced apoptosis and overexpression of vascular endothelial growth factor in bovine retinal pericytes.

The influence of advanced glycation end products (AGEs) on apoptotic cell death and vascular endothelial growth factor (VEGF) gene expression in cultured bovine retinal pericytes was investigated. When pericytes were incubated with three immunochemically distinct AGEs, which were prepared in vitro by incubating bovine serum albumin with glucose, glyceraldehyde, or glycolaldehyde, apoptotic cell death and DNA ladder formation were significantly induced. The cytopathic effects of glyceraldehyde- or glycolaldehyde-derived AGEs were significantly enhanced in AGE receptor-transfected pericytes. Furthermore, all of these AGEs were found to upregulate the secretory forms of VEGF mRNA levels in retinal pericytes. These results suggest that AGEs disturbed retinal microvascular homeostasis by inducing pericyte apoptosis and VEGF overproduction and thus were involved in the pathogenesis of early phase diabetic retinopathy.     

Overexpression of AtCPS and AtKS in Arabidopsis confers increased ent-kaurene production but no increase in bioactive gibberellins

The plant growth hormone gibberellin (GA) is important for many aspects of plant growth and development. Although most genes encoding enzymes at each step of the GA biosynthetic pathway have been cloned, their regulation is less well understood. To assess how up-regulation of early steps affects the biosynthetic pathway overall, we have examined transgenic Arabidopsis plants that overexpress either AtCPS or AtKS or both. These genes encode the enzymes ent-copalyl diphosphate synthase (CPS) and ent-kaurene synthase, which catalyze the first two committed steps in GA biosynthesis. We find that both CPS and CPS/ent-kaurene synthase overexpressors have greatly increased levels of the early intermediates ent-kaurene and ent-kaurenoic acid, but a lesser increase of later metabolites. These overexpression lines do not exhibit any GA overdose morphology and have wild-type levels of bioactive GAs. Our data show that CPS is limiting for ent-kaurene production and suggest that conversion of ent-kaurenoic acid to GA12 by ent-kaurenoic acid oxidase may be an important rate-limiting step for production of bioactive GA. These results demonstrate the ability of plants to maintain GA homeostasis despite large changes in accumulation of early intermediates in the biosynthetic pathway.     

SOCS-3 regulates onset and maintenance of T(H)2-mediated allergic responses

Members of the suppressor of cytokine signaling (SOCS) family are involved in the pathogenesis of many inflammatory diseases. SOCS-3 is predominantly expressed in T-helper type 2 (T(H)2) cells, but its role in T(H)2-related allergic diseases remains to be investigated. In this study we provide a strong correlation between SOCS-3 expression and the pathology of asthma and atopic dermatitis, as well as serum IgE levels in allergic human patients. SOCS-3 transgenic mice showed increased T(H)2 responses and multiple pathological features characteristic of asthma in an airway hypersensitivity model system. In contrast, dominant-negative mutant SOCS-3 transgenic mice, as well as mice with a heterozygous deletion of Socs3, had decreased T(H)2 development. These data indicate that SOCS-3 has an important role in regulating the onset and maintenance of T(H)2-mediated allergic immune disease, and suggest that SOCS-3 may be a new therapeutic target for the development of antiallergic drugs.