Inhibition of renal ornithine decarboxylase by aminoglycoside antibiotics in vitro

The inhibition of renal ornithine decarboxylase (ODC) by aminoglycoside antibiotics was characterized in the postmitochondrial fraction of a kidney homogenate from adult pigmented guinea pigs. Enzymatic activity was defined as the rate of decarboxylation of [14C]ornithine sensitive to a specific ODC inhibitor, [alpha]-difluoromethylornithine (DFMO). The Km for ornithine was 61 +/- 32 , [mu]M. There were two forms of the enzyme with respect to their affinity for pyridoxal phosphate (PLP): (I) Km = 2.1 +/- 1.8 [mu]M; (II) Km = 36.2 +/- 12.7 [mu]M. Putrescine, a known ODC inhibitor, acted competitively on the renal enzyme with Ki = 1.7 +/- 1.4 mM. Aminoglycoside antibiotics inhibited ODC by an uncompetitive mechanism with inhibitor constants of comparable magnitude: neomycin, Ki = 1.3 +/- 0.1 mM; gentamicin, Ki = 1.6 +/- 0.1 mM; kanamycin, Ki = 1.9 +/- 0.2 mM; and netilmicin, Ki = 1.7 +/- 0.2 mM. Neomycin inhibited both forms of the enzyme (low and high affinity for PLP) uncompetitively with similar inhibitor constants (1.5 +/- 0.3 and 1.8 +/- 0.4 mM respectively), suggesting a single mechanism of action. Inhibition of ODC suggests that aminoglycoside-polyamine interactions may be an important component of the sequence of biochemical events associated with aminoglycoside toxicity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27327/1/0000350.pd

Expression of RFC/SLC19A1 is Associated with Tumor Type in Bladder Cancer Patients

Urinary bladder cancer (UBC) ranks ninth in worldwide cancer. In Egypt, the pattern of bladder cancer is unique in that both the transitional and squamous cell types prevail. Despite much research on the topic, it is still difficult to predict tumor progression, optimal therapy and clinical outcome. The reduced folate carrier (RFC/SLC19A1) is the major transport system for folates in mammalian cells and tissues. RFC is also the primary means of cellular uptake for antifolate cancer chemotherapeutic drugs, however, membrane transport of antifolates by RFC is considered as limiting to antitumor activity. The purpose of this study was to compare the mRNA expression level of RFC/SLC19A1 in urothelial and non-urothelial variants of bladder carcinomas. Quantification of RFC mRNA in the mucosa of 41 untreated bladder cancer patients was performed using RT-qPCR. RFC mRNA steady-state levels were ∼9-fold higher (N = 39; P<0.0001) in bladder tumor specimens relative to normal bladder mRNA. RFC upregulation was strongly correlated with tumor type (urothelial vs. non-urothelial; p<0.05) where median RFC mRNA expression was significantly (p<0.05) higher in the urothelial (∼14-fold) compared to the non-urothelial (∼4-fold) variant. This may account for the variation in response to antifolate-containing regimens used in the treatment of either type. RFC mRNA levels were not associated with tumor grade (I, II and III) or stage (muscle-invasive vs. non-muscle invasive) implying that RFC cannot be used for prognostic purposes in bladder carcinomas and its increased expression is an early event in human bladder tumors pathogenesis. Further, RFC can be considered as a potential marker for predicting response to antifolate chemotherapy in urothelial carcinomas

Anti-asthmatic and Anti-allergic Effects of Thymoquinone on Experimentally-Induced Hypersensitivity

Nigella sativa L. has been used in folk medicine for treatment of many diseases. Thymoquinone (TQ), a main constituent of its oil and seeds, has shown promising medicinal properties in the treatment and prevention of various diseases. The present study aims to investigate the potential effect of TQ on airway-induced hypersensitivity. Ovalbumin (OVA) sensitization and challenge in guinea pig tracheal muscle preparation were used in order to investigate the anti-asthmatic activity of TQ. To study the effect of TQ on acute lung injury, lipopolysaccharide (LPS) - induced lung injury method was used. In addition, rat peritoneal mast cells (RPMCs) were collected to investigate the release of histamine from these cells. Furthermore, to study the anti-allergic activity of TQ, the systemic anaphylactic shock technique induced by compound 48/80 was performed. Pretreatment with TQ (3 mg/kg, i.p.) for 5 days prior to ovalbumin sensitization showed a marked decrease in the response of the tracheal spirals to acetylcholine and histamine, as spasmogens in a cumulative dose response–curve. TQ (8mg/kg, i.p.) prevented most of the pathological detrimental changes that occurred in response to the endotoxin LPS as the inflammatory cells infiltration, lipid peroxidation (LP), glutathione depletion (GSH), tumor necrosis factor-alpha (TNF- α) and interlukin-1 beta (IL-1β) levels in both boronchoalevolar lavage fluid (BALF) and lung tissue homogenates. Sensitization of rats induced a significant increase in the histamine release from RPMCs which is inhibited by pretreatment with TQ (8 mg/ kg, i.p.). Similarly, pretreatment of mice with TQ (50 and 100 mg/kg), 1hr prior to injection of compound 48/80 (8mg/kg, i.p.) significantly inhibited the % of mortality of mice following the systemic anaphylactic reaction. Considering the anti-asthmatic, anti-inflammatory, antioxidant and anti-allergic activities of TQ reported in this study, one can conclude that TQ could be of therapeutic potentials in treating various diseases associated with airway-induced hypersensitivity

Altered expression of miR-181a and miR-146a does not change the expression of surface NCRs in human NK cells

MicroRNAs (miRNAs) play an important role in regulating gene expression and immune responses. Of interest, miR-181a and miR-146a are key players in regulating immune responses and are among the most abundant miRNAs expressed in NK cells. Bioinformatically, we predicted miR-181a to regulate the expression of the natural cytotoxicity receptor NCR2 by seeded interaction with the 3′-untranslated region (3′-UTR). Whereas, miR-146a expression was not significantly different (P = 0.7361), miR-181a expression was, on average 10-fold lower in NK cells from breast cancer patients compared to normal subjects; P &lt; 0.0001. Surface expression of NCR2 was detected in NK cells from breast cancer patients (P = 0.0384). While cytokine receptor-induced NK cell activation triggered overexpression of miR-146a when stimulated with IL-2 (P = 0.0039), IL-15 (P = 0.0078), and IL-12/IL-18 (P = 0.0072), expression of miR-181a was not affected. Overexpression or knockdown of miR-181a or miR-146a in primary cultured human NK cells did not affect the level of expression of any of the three NCRs; NCR1, NCR2 or NCR3 or NK cell cytotoxicity. Expression of miR-181a and miR-146a did not correlate to the expression of the NCRs in NK cells from breast cancer patients or cytokine-stimulated NK cells from healthy subjects