A2B adenosine receptor inhibition by the dihydropyridine calcium channel blocker nifedipine involves colonic fluid secretion.

The adenosine A2B receptor is a critical protein in intestinal water secretion. In the present study, we screened compound libraries to identify inhibitors of the A2B receptor and evaluated their effect on adenosine-induced intestinal fluid secretion. The screening identified the dihydropyridine calcium antagonists nifedipine and nisoldipine. Their respective affinities for the A2B receptor (Ki value) were 886 and 1,399 nM. Nifedipine and nisoldipine, but not amlodipine or nitrendipine, inhibited both calcium mobilization and adenosine-induced cAMP accumulation in cell lines. Moreover, adenosine injection into the lumen significantly increased fluid volume in the colonic loop of wild-type mice but not A2B receptor-deficient mice. PSB-1115, a selective A2B receptor antagonist, and nifedipine prevented elevated adenosine-stimulated fluid secretion in mice. Our results may provide useful insights into the structure-activity relationship of dihydropyridines for A2B receptor. As colonic fluid secretion by adenosine seems to rely predominantly on the A2B receptor, nifedipine could be a therapeutic candidate for diarrhoea-related diseases.

Mepenzolate bromide displays beneficial effects in a mouse model of chronic obstructive pulmonary disease.

The clinical treatment of chronic obstructive pulmonary disease (COPD) requires not only an improvement of airflow by bronchodilation but also the suppression of emphysema by controlling inflammation. Here we screen a compound library consisting of clinically used drugs for their ability to prevent elastase-induced airspace enlargement in mice. We show that intratracheal administration or inhalation of mepenzolate bromide, a muscarinic antagonist used to treat gastrointestinal disorders, decreases the severity of elastase-induced airspace enlargement and respiratory dysfunction. Although mepenzolate bromide shows bronchodilatory activity, most other muscarinic antagonists do not improve elastase-induced pulmonary disorders. Apart from suppressing elastase-induced pulmonary inflammatory responses and the production of superoxide anions, mepenzolate bromide reduces the level of cigarette smoke-induced airspace enlargement and respiratory dysfunction. Based on these results, we propose that mepenzolate bromide may be an effective therapeutic for the treatment of COPD due to its anti-inflammatory and bronchodilatory activities.

Expression of 150-kDa oxygen-regulated protein (ORP150) stimulates bleomycin-induced pulmonary fibrosis and dysfunction in mice.

Idiopathic pulmonary fibrosis (IPF) involves pulmonary injury associated with inflammatory responses, fibrosis and dysfunction. Myofibroblasts and transforming growth factor (TGF)-ß1 play major roles in the pathogenesis of this disease. Endoplasmic reticulum (ER) stress response is induced in the lungs of IPF patients. One of ER chaperones, the 150-kDa oxygen-regulated protein (ORP150), is essential for the maintenance of cellular viability under stress conditions. In this study, we used heterozygous ORP150-deficient mice (ORP150(+/-) mice) to examine the role of ORP150 in bleomycin-induced pulmonary fibrosis. Treatment of mice with bleomycin induced the expression of ORP150 in the lung. Bleomycin-induced inflammatory responses were slightly exacerbated in ORP150(+/-) mice compared to wild-type mice. On the other hand, bleomycin-induced pulmonary fibrosis, alteration of lung mechanics and respiratory dysfunction was clearly ameliorated in the ORP150(+/-) mice. Bleomycin-induced increases in pulmonary levels of both active TGF-ß1 and myofibroblasts were suppressed in ORP150(+/-) mice. These results suggest that although ORP150 is protective against bleomycin-induced lung injury, this protein could stimulate bleomycin-induced pulmonary fibrosis by increasing pulmonary levels of TGF-ß1 and myofibroblasts.

Acetaminophen-induced differentiation of human breast cancer stem cells and inhibition of tumor xenograft growth in mice.

It is now believed that cancer stem cells (CSCs) that are resistant to chemotherapy due to their undifferentiated nature drive tumor growth, metastasis and relapse, so development of drugs that induce differentiation of CSCs should have a profound impact on cancer eradication. In this study, we screened medicines that are already in clinical use for drugs that induce differentiation of CSCs. We used MDA-MB-231, a human breast cancer cell line that contains cancer stem cell-like cells. We found that acetaminophen, an anti-inflammatory, antipyretic and analgesic drug, induces differentiation of MDA-MB-231 cells. Differentiation was assessed by observing alterations in cell shape and expression of differentiated and undifferentiated cell markers, a decrease in cell invasion activity and an increase in susceptibility to anti-tumor drugs. This increased susceptibility seems to involve suppression of expression of multidrug efflux pumps. We also suggest that this induction of differentiation is mediated by inhibition of a Wnt/ß-catenin canonical signaling pathway. Treatment of MDA-MB-231 cells with acetaminophen in vitro resulted in the loss of their tumorigenic ability in nude mice. Furthermore, administration of acetaminophen inhibited the growth of tumor xenografts of MDA-MB-231 cells in both the presence and absence of simultaneous administration of doxorubicine, a typical anti-tumor drug for breast cancer. Analysis with various acetaminophen derivatives revealed that o-acetamidophenol has a similar differentiation-inducing activity and a similar inhibitory effect on tumor xenograft growth. These results suggest that acetaminophen may be beneficial for breast cancer chemotherapy by inducing the differentiation of CSCs.

Low direct cytotoxicity of loxoprofen on gastric mucosal cells.

Pro-drugs of non-steroidal anti-inflammatory drugs (NSAIDs), such as loxoprofen are widely used for clinical purposes because they are not so harmful to the gastrointestinal mucosa. We recently showed that NSAIDs such as indomethacin and celecoxib have direct cytotoxicity (ability to induce necrosis and apoptosis in gastric mucosal cells) due to their membrane permeabilizing activities, which is involved in NSAID-induced gastric lesions. We show here that under conditions where indomethacin and celecoxib clearly induce necrosis and apoptosis, loxoprofen and its active metabolite loxoprofen-OH, do not have such effects in primary culture of guinea pig gastric mucosal cells. Loxoprofen and loxoprofen-OH induced apoptosis more effectively in cultured human gastric cancer cells than in the primary culture. Loxoprofen and loxoprofen-OH exhibited much lower membrane permeabilizing activities than did indomethacin and celecoxib. We thus consider that the low direct cytotoxicity of loxoprofen observed in vitro is involved in its relative safety on production of gastric lesions in clinical situation.