Several lines of evidence suggest that some of the neurotoxicity in Alzheimer’s disease (AD) is attributed to proteolytic fragments of amyloid precursor protein (APP) and β-amyloid (Aβ) may not be the sole active component involved in the pathogenesis of AD. The potential effects of other cleavage products of APP need to be explored. The CTFs, carboxy-terminal fragments of APP, have been found in AD patients’ brain and reported to exhibit much higher neurotoxicity in a variety of preparations than Aβ. Furthermore CTFs are known to impair calcium homeostasis and learning and memory through blocking LTP, triggering a strong inflammatory reaction through MAPKs- and NF-κB-dependent astrocytosis and iNOS induction. Recently, it was reported that CTF translocated into the nucleus, binding with Fe65 and CP2, and in turn, affected transcription of genes including glycogen synthase kinase-3β, which results in the induction of tau-rich neurofibrillary tangles and subsequently cell death. Spatial memory of transgenic (Tg) mice overexpressing CT100 was significantly impaired and CTFs were detected in the neurons as well as in plaques of the Tg mice and double Tg mice carrying CT100 and mutant tau. In this review, we summarize observations indicating that both CTF and Aβ may participate in the neuronal degeneration in the progress of AD by differential mechanisms.
Acute renal failure still occurs as a complication after radiographic examination using iodinated radiocontrast medium. The incidence rate of radiocontrast medium-induced nephropathy (radiocontrast nephropathy) is low (2 – 3%) in general. However, the rate is remarkably elevated in patients with pre-existing renal insufficiency. Radiocontrast nephropathy is associated with increased morbidity and mortality, particularly in patients with percutaneous coronary interventions. Although the reduction in renal blood flow and direct toxic action on renal tubular cells are considered to be involved, little is known about the etiology of radiocontrast nephropathy. A number of agents that improve renal circulation have been clinically tested for prevention of radiocontrast nephropathy, but none of them has succeeded. Protection of renal tubular cells against oxidative stress is another approach to avoid radiocontrast nephropathy. Prophylactic effects of antioxidants such as N-acetylcysteine and ascorbic acid have been reported by several investigators, although the effectiveness of these compounds is still a matter of debate. At present, hydration is regarded as the only effective, though incomplete, prophylactic regimen for radiocontrast nephropathy. Recently, we have shown that caspase-dependent apoptosis is an important factor in the pathogenesis of radiocontrast nephropathy and clarified cellular mechanisms underlying the radiocontrast media-induced apoptosis. This review summarizes clinical and experimental evidence for the etiology and prevention of radiocontrast nephropathy.
In patients with hypoalbuminemia, the total serum concentration of valproic acid may offer poor clinical information; however, very few clinical laboratories routinely analyze the free concentration of the drug. The aim of this study was to design a procedure to normalize the total concentration of valproic acid according to the level of serum albumin and using previously published free fraction values. In 121 adult patients, with albumin levels of 18 – 41 g/L, the total concentration of valproic acid was normalized using the derived equation: CN = αHCH/6.5, where αH is the free fraction of the drug corresponding to the patient’s particular albuminemia and CH is the total concentration of valproic acid. The value of 6.5 corresponds to the free fraction of the drug for a serum albumin of 42 g/L (percentile 50 of the reference range). For total concentrations lower than 75 mg/L, the predicted normalized valproic acid concentrations were reasonably concordant with the observed normalized concentrations calculated using the data from a protein-binding study. In a significant number of cases, subtherapeutic concentrations of the drug became therapeutic and even supratherapeutic when corrected according to the albumin levels. Furthermore, cases with therapeutic drug concentrations frequently became supratherapeutic when normalized. The limitations and clinical aplications of the proposed formula for normalizing the total concentration of valproic acid are presented. It is concluded that it may be useful for the posological management of hypoalbuminemic patients when the free concentration of the drug is not available, and decisions have to be made based on the total serum concentration.
We previously demonstrated that evodimine isolated from Evodia rutaecarpa (Goshuyu in Japan) induced apoptosis in human malignant melanoma A375-S2 cells within 24 h. In this study, TUNEL assay also indicated that one cause of A375-S2 cell death induced by evodiamine was apoptosis. After treatment with evodiamine for the indicated time periods, anti-apoptotic protein SIRT1 expression was decreased; p53 expression and its phosphorylation were both enhanced, whereas transient induction of downstream p21 was not enough to promote cell cycle arrest. Inhibition of the phosphoinositide 3-OH kinase (PI3-K)/protein kinase C (PKC) survival pathway as well as subsequent inhibition of the ERK cascade might contribute to evodiamine-induced cell death. In addition, p53 activation in response to evodiamine administration was correlated with the activation of the PI3-K/PKC pro-apoptotic pathway, but did not require ERK participation. The inhibition of the PI3-K/PKC survival pathway might be responsible for SIRT1 inactivation and increased Bax/Bcl-2 expression ratio in evodiamine-induced cell death.
The aim of the present study is to clarify the mechanism for the decrease in intraocular pressure by 2-alkynyladenosine derivatives in rabbits. The receptor binding analysis revealed that 2-(1-octyn-1-yl)adenosine (2-O-Ado) and 2-(6-cyano-1-hexyn-1-yl)adenosine (2-CN-Ado) selectively bound to the A2a receptor with a high affinity. Ocular hypotensive responses to 2-O-Ado and 2-CN-Ado were inhibited by the adenosine A2a-receptor antagonist 1,3,7-trimethyl-8-(3-chlorostyryl)xanthine (CSC), but not by the adenosine A1-receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) or the adenosine A2b-receptor antagonist alloxazine. In addition, 2-O-Ado and 2-CN-Ado caused an increase in outflow facility, which was inhibited by CSC, but not by DPCPX or alloxazine. Moreover, 2-O-Ado and 2-CN-Ado increased cAMP in the aqueous humor, and the 2-O-Ado-induced an increase in cAMP was inhibited by CSC. These results suggest that 2-O-Ado and 2-CN-Ado reduced intraocular pressure via an increase in outflow facility. The ocular hypotension may be mailnly mediated through the activation of adenosine A2a receptor, although a possible involvement of adenosine A1 receptor cannot be completely ruled out. 2-O-Ado and 2-CN-Ado are useful lead compounds for the treatment of glaucoma.
Forskolin-induced Ca2+ signals were examined in isolated rat olfactory receptor neurons (ORNs) using a Ca2+ indicator, fura-2. In the soma of the ORNs, forskolin caused an increase in the intracellular Ca2+ concentration ([Ca2+]i) that was enhanced by a phosphodiesterase (PDE) 1 inhibitor, 8-methoxymethyl-3-isobutyl-1-methyl-xanthine, but not a PDE4 inhibitor, rolipram. Forskolin-induced Ca2+ signals were abolished with the removal of extracellular Ca2+ and un-affected by treatment with thapsigargin or caffeine plus ryanodine. Niflumic acid, a Ca2+-activated Cl− channel inhibitor, or nifedipine, an L-type Ca2+ channel inhibitor, slowed the initial rate of the increase in [Ca2+]i in response to forskolin. Nifedipine did not affect the increase in [Ca2+]i that was slowed by niflumic acid. In Ca2+ measurements with a confocal microscope and a calcium indicator, Fluo-4, the onset of the response to forskolin in the knob region occurred simultaneously or earlier, but not later, than that in the soma. It is suggested that the forskolin-induced Ca2+ signals are due to Ca2+ influx, but not the release of Ca2+ from Ca2+ stores, and that the initial rapid increase in [Ca2+]i is associated with the activation of the voltage-dependent Ca2+ channels in rat ORNs.
Heat stroke is characterized by hyperthermia, arterial hypotension, decreased baroreflex sensitivity, and increased serum levels of β-endorphin. Whereas naltrexone may have therapeutic potential in heat stroke, the underlying mechanism remains unclear. We tested the hypothesis that naltrexone may attenuate heat stroke by reducing hyperthermia, hypotension, decreased baroreceptor sensitivity, and/or increased serum levels of β-endorphin. Heat stroke was induced by exposing the anesthetized adult Sprague-Dawley rats in an incubator at 43°C. The moment in which the mean arterial pressure dropped irreversibly from the peak level was taken as the onset of heat stroke. Control rats were exposed to 24°C. Mean arterial pressure, baroreceptor sensitivity, and maximal reflex bradycardia, after the onset of heat stroke, were all significantly lower than in control rats. However, rectal temperature and serum levels of β-endorphin were all greater after the onset of heat stroke. Intravenous delivery of naltrexone (10 mg/kg) 20 min before the initiation of heat stress, but not immediately at the onset of heat stroke, significantly attenuated the above-mentioned reactions. Accordingly, naltrexone improved survival during heat stroke. These results suggest that naltrexone protects against hypotension and decrement of both baroreceptor sensitivity and maximal reflex bradycardia during heat stroke by reducing both hyperthermia and increment of serum β-endorphin and thus improves survival.
It is well accepted that bacterial and virus infections elevate the levels of cytokines in serum and cerebrospinal fluids. Such high levels of cytokines might alter the integrity of the blood-brain barrier (BBB) and/or blood-cerebrospinal fluid barrier (BCSFB), subsequently affecting brain penetration of drugs. However, few reports have addressed this issue. Thus, we investigated brain penetration of cyclooxygenase (COX) inhibitors, commonly used as antipyretics, in mice treated with Shiga-like toxin II (SLT-II) derived from E. coli O157:H7, which significantly elevates cytokine levels. As antipyretics, we used diclofenac, mefenamic acid, and acetaminophen. We found that SLT-II significantly increased the brain-to-plasma concentration ratio (Kp) of diclofenac and mefenamic acid, but not of acetaminophen. Moreover, the Kp of diclofenac and mefenamic acid was increased by probenecid, an anionic compound. These results suggest that efflux anion transporters might be involved in the transport of diclofenac and mefenamic acid. Western blot analysis revealed that SLT-II decreased the expression of organic anion transporter-3, an efflux transporter located on the BBB and/or BCSFB. Taken together, these results suggest that SLT-II and/or SLT-II-stimulated cytokines might change brain penetration of drugs and could possibly increase the risk of their side-effects by altering the expression of transporters.
Z24, a small molecular compound with similar chemical structure to SU5416 designed and synthesized by our lab, has been proved to be an angiogenesis inhibitor. In this study, Z24 was shown to induce human umbilical venous endothelial cell (HUVEC) apoptosis confirmed by morphologic changes including the presence of apoptotic bodies, significant apoptotic sub-G1 peak upon flow-cytometric analysis, formation of DNA ladders upon agarose gel electrophoresis, and TUNEL (TdT mediated X-dUTP nick-end labeling) results. Systemic administration of Z24 at non-toxic dose in nude mice resulted in inhibition of subcutaneous tumor growth of human colon cancer HCT-8, while it did not inhibit this cell line in vitro, with 100-fold more potent growth-inhibition against endothelial cells. The immunohistochemical results showed that the microvessel density of tumor tissue of the Z24 group was significantly lower than that of the control groups (P<0.05), which supported its anti-angiogenic property. We further found that Z24 inhibited the pulmonary metastasis of mouse lung adenocarcinoma LA795, with fewer surface lung metastases (89.6%, P<0.0001) and decreased lung weights (38.5%, P<0.01) compared to the vehicle group. All these findings support that Z24 is a promising angiogenesis inhibitor for limiting tumor growth and metastasis.
To clarify the hepatoprotective effects of tectoridin and tectorigenin from Puerariae Flos, their effects on tert-butyl hyperoxide (t-BHP)-injured HepG2 cells and mice were investigated. When tectorigenin at a dose of 50 mg/kg was intraperitoneally administered to mice injured by t-BHP, it significantly inhibited the increase the activities of plasma ALT and AST by 39% and 41%, respectively, in the t-BHP-treated group. The inhibitory effect of tectorigenin is much more potent than that of a commercially available dimethyl diphenyl bicarboxylate. Orally administered tectoridin showed hepatoprotective activity. However, when tectoridin was intraperitoneally administrated to mice, no hepatoprotective activity was observed. Tectorigenin also protected against the cytotoxicity of HepG2 cells induced by t-BHP. This protection may have originated from the inhibition of apoptosis. Tectorigenin may be hepatoprotective and tectoridin should be a prodrug that is transformed to tectorigenin.