Oral bisphosphonates and upper gastrointestinal tract problems: what is the evidence?

OBJECTIVE: To review and evaluate the evidence regarding possible associations of bisphosphonate use with upper gastrointestinal (GI) tract adverse events (AEs). METHODS: We reviewed and summarized published information and abstracts regarding upper GI tract safety and tolerability of bisphosphonates, including laboratory and animal studies, epidemiological (observational) studies, endoscopy studies, and randomized controlled trials (RCTs). The evidence was summarized by using the principles of evidence-based medicine, giving the greatest credence to high-quality RCTs. RESULTS: Clinical reports of esophagitis associated with bisphosphonate use appear to have declined in frequency once the importance of proper administration was explained to physicians after early reports of complications. Conflicting results have been reported in endoscopy studies; some reported no significant increase in upper GI tract lesions, whereas others reported a higher incidence of gastric (but not esophageal) lesions among patients taking oral bisphosphonates. Endoscopy studies that reported differences were of short duration (2 weeks) and were not of double-blind design. Results from large RCTs involving thousands of participants detected no increase in upper GI tract AEs among individuals treated with bisphosphonates. Other studies of patients who discontinued taking bisphosphonates and were randomized to blinded re-treatment with either a bisphosphonate or placebo show that most patients (>85%) were able to continue treatment, with no difference in AEs between the bisphosphonate and placebo groups. CONCLUSIONS: The highest level of evidence, RCTs, suggests little or no increase in risk of upper GI tract problems if bisphosphonates are administered properly. Upper GI tract symptoms are common among patients with osteoporosis. The evidence suggests that many upper GI tract AEs reported during therapy with bisphosphonates may reflect a high background incidence of upper GI tract complaints and an increased sensitivity to detection rather than a causal relationship to therapy.     

Effects of the temperature, the duration of frozen storage, and the freezing container on in vitro measurements in human peripheral blood mononuclear cells

Background: Bone marrow, peripheral blood, and umbilical cord blood have been used to prepare autologous and allogeneic pluripotential mononuclear cells for use in the repopulation of bone marrow. Study Design and Methods: The purpose of this study was to evaluate how the temperature and duration of frozen storage of human peripheral blood mononuclear cells (PBMCs), as well as the freezing container, affected the in vitro recovery and viability of the mononuclear cells and their growth in colony-forming unit-granulocytic-erythroid-monocytic- megakaryocytic (CFU-GEMM) tissue culture assay. PBMCs were isolated from ficoll-hypaque-treated cellular residue obtained during the plateletpheresis of blood from 15 healthy donors. The PBMCs were treated with dimethyl sulfoxide (DMSO) to achieve a final DMSO concentration of 10 percent. Each unit was then separated into six aliquots: one stored in a polyvinylchloride (PVC) plastic bag, one in a polyolefin plastic bag, and four in polyethylene cryostorage vials. Each aliquot was frozen in a -80 degrees C mechanical freezer at a freezing rate of 2 to 4 degrees C per minute. The frozen PBMCs in PVC bags were stored in a -80 degrees C mechanical freezer and those in polyolefin bags in a -135 degrees C mechanical freezer. Each of the four frozen samples in a vial was stored at a different temperature: one in the -80 degrees C freezer, one in the -135 degrees C freezer, one in the vapor phase of liquid nitrogen at -150 degrees C, and one in liquid nitrogen at -197 degrees C. Some of the frozen PBMCs were stored for periods of 1 to 1.5 years and others for 2 to 2.4 years, after which they were thawed, washed, and tested. Results: The samples stored in PVC bags and those stored in polyolefin bags exhibited in vitro recoveries that were 90 percent of the recovery of fresh PBMCs and viabilities of 90 percent after 2.4 years of frozen storage. The PBMCs stored in PVC bags exhibited no loss of CFU-GEMM activity after 1 to 1.5 years, but a 40-percent loss of activity was observed after 2 to 2.4 years. PBMCs stored in polyolefin bags, however, exhibited no loss of CFU-GEMM activity, even after 2 to 2.4 years of storage. In vitro recovery was significantly lower in PBMCs stored in vials at -80 degrees C or -135 degrees C than in cells stored in PVC or polyolefin bags at these temperatures, both in the 1- to 1.5-year and the 2- to 2.4-year time frames. In vitro recovery and viability were similar in PBMCs stored in vials at -80 degrees C, -135 degrees C, -150 degrees C, and -197 degrees C. The growth patterns in the CFU-GEMM assay in PBMCs stored in vials were significantly lower after storage at -80 degrees C than after storage at -135 degrees C, -150 degrees C, or -197 degrees C. Conclusion: PBMCs isolated by leukapheresis and ficoll-hypaque treatment can be frozen with 10-percent DMSO in a -80 degrees C mechanical freezer. When a PVC bag is used for freezing and storage of PBMCs at -80 degrees C, the duration of frozen storage should not exceed 1.5 years, whereas PBMCs frozen in a polyolefin bag can be stored in a -135 degrees C freezer for as long as 2.4 years. When these guidelines were followed, in vitro recovery was 90 percent that of fresh PBMCs, viability was 90 percent, and growth in the CFU-GEMM tissue culture assay was similar to that of fresh PBMCs. The PBMCs frozen and stored in PVC or polyolefin bags exhibited satisfactory results, whereas those stored in cryostorage vials did not.     

Staphylococcal alpha-toxin elicits hypertension in isolated rabbit lungs. Evidence for thromboxane formation and the role of extracellular calcium.

Staphylococcal alpha-toxin is known to damage mammalian cell membranes. Studies of erythrocytes indicate that the native toxin generates a discrete transmembrane channel with an effective diameter of 2-3 nm. (Füssle, R., S. Bhakdi, A. Szeigoleit, J. Tranum-Jensen, T. Kranz, and H.J. Wellensiek. 1981. J. Cell Biol. 91:83-94.) In isolated rabbit lungs, perfused with recirculating blood- and plasma-free perfusion fluid, the mediation of a toxin-provoked vascular pressor response by the triggering of the arachidonic acid cascade and its dependence on extracellular calcium were investigated. Dose-dependent pulmonary artery pressor responses were elicited by the injection of 0.5-5 micrograms staphylococcal alpha-toxin into the pulmonary artery. The pressor responses were completely abolished by preincubation of the toxin with neutralizing antibodies or by preformation of alpha-toxin hexamers in vitro. They were accompanied by the release of the arachidonic acid metabolites thromboxane B2 and 6-keto-prostaglandin F1 alpha (stable metabolites of thromboxane A2 and prostaglandin I2, respectively) into the perfusion fluid. They were blocked by inhibitors of thromboxane synthetase, cyclooxygenase, and phospholipase, as well as by substances that interfere with calcium-calmodulin function. alpha-Toxin induced selective release of potassium, but not lactatedehydrogenase into the medium. Calcium depletion of the intravascular space did not suppress the toxin-dependent potassium release but did abrogate the pressor response and the release of the arachidonic acid metabolites. When calcium was reintroduced into the circulation without the application of a second toxin stimulus, marked pressor responses paralleled by the release of arachidonic acid metabolites occurred. The conclusion drawn from these studies is that staphylococcal alpha-toxin provokes pulmonary vascular hypertension which is apparently mediated by thromboxane A2 formation, which surpasses the biological effect of the simultaneously formed prostaglandin I2. The triggering of the arachidonic acid cascade is strictly dependent on extracellular calcium and may be mediated by a nonphysiological calcium bypass through transmembrane toxin channels with subsequent stimulation of phospholipase activity.     

Quantification of cerebral A1 adenosine receptors in humans using [18F]CPFPX and PET: an equilibrium approach

The cerebral A(1) adenosine receptor (A(1)AR) has recently become accessible for in vivo imaging using the selective A(1)AR ligand [(18)F]CPFPX and PET. For broad application in neurosciences, imaging at distribution equilibrium is advantageous to quantify stimulus-dependent changes in receptor availability and to avoid arterial blood sampling. Here we propose a bolus/infusion (B/I) protocol to assess the total distribution volume (DV(t)) of [(18)F]CPFPX under equilibrium conditions. Employing a bolus-to-infusion ratio of 0.8 h, (near) equilibrium conditions were attained within 60 min. The regional DV(t)' given by arterial and venous equilibrium analyses agreed well with conventional two-tissue compartment model analyses (r(2) > 0.94 and r(2) > 0.84, respectively) and Logan's graphical analyses (r(2) = 1.0 and r(2) > 0.93, respectively) (n = 4 healthy volunteers). The mean regional DV(t)' values of these equilibrium analyses and of venous equilibrium analyses in additional seven volunteers demonstrated excellent agreement with the results of earlier bolus studies (r(2) > 0.98). Error simulations show that minor deviations from true equilibrium are associated with negligible to small DV(t) errors. In conclusion, [(18)F]CPFPX shows suitable characteristics for A(1)AR quantification by B/I PET scanning. Carefully standardized venous equilibrium analyses may substitute arterial analyses and thus considerably enhance applicability of A(1)AR PET in clinical routine.     

Amphotericin B Colloidal Dispersion Combined with Flucytosine with or without Fluconazole for Treatment of Murine Cryptococcal Meningitis

Studies with animals and in vitro studies have demonstrated that flucytosine plus amphotericin B or fluconazole has significantly improved mycologic activity against meningitis caused by Cryptococcus neoformans compared to the activity of amphotericin B or fluconazole used alone. However, few doses have been tested in combination. This study evaluated the antifungal efficacy of amphotericin B colloidal dispersion (ABCD) combined with flucytosine with and without fluconazole in a murine model of cryptococcal meningitis. The following dosages were tested: ABCD at 0 to 12.5 mg/kg of body weight given intravenously 3 days/week, flucytosine at 0 to 110 mg/kg/day, and fluconazole at 0 to 50 mg/kg/day. Meningitis was established in male BALB/c mice by intracerebral injection of C. neoformans. Treatment with flucytosine with or without fluconazole dissolved in the sole source of drinking water was started on day 2; animals were sacrificed at 16 days, and the numbers of fungal colonies in the brain were quantified. A survival rate of 100% was achieved with ABCD plus flucytosine without fluconazole; however, the addition of fluconazole was required to prevent weight loss (P < 0.00001) and to achieve the maximum antifungal effect (P < 0.00001). The only region of dose combinations for which the 99% confidence intervals were less than 100 CFU/g of brain was defined by ABCD at 5.0 to 7.5 mg/kg combined with flucytosine at 20 to 60 mg/kg/day and fluconazole at 30 to 40 mg/kg/day. The triple combination of ABCD plus flucytosine and fluconazole was necessary to achieve the greatest antifungal activity.     

Regulation of interleukin 6 receptor expression in human monocytes and monocyte-derived macrophages. Comparison with the expression in human hepatocytes

IL-6 is a cytokine with pleiotropic biological functions, including induction of the hepatic acute phase response and differentiation of activated B cells into Ig-secreting plasma cells. We found that human peripheral blood monocytes express the IL-6-R, which is undetectable on the large majority of lymphocytes of healthy individuals. Stimulation of monocytes by endotoxin or IL-1 causes a rapid downregulation of IL-6-R mRNA levels and a concomitant enhancement of IL-6 mRNA expression. IL-6 itself was found to suppress the IL-6-R at high concentrations. A gradual decrease of IL-6-R mRNA levels was observed along in vitro maturation of monocytes into macrophages. We show that downregulation of IL-6-R mRNA levels by IL-1 and IL-6 is monocyte specific, since IL-6-R expression is stimulated by both IL-1 and IL-6 in cultured human primary hepatocytes. Our data indicate that under noninflammatory conditions, monocytes may play a role in binding of trace amounts of circulating IL-6. Repression of monocytic IL-6-R and stimulation of hepatocytic IL-6-R synthesis may represent a shift of the IL-6 tissue targets under inflammatory conditions.     

Effects of angiotensin-converting enzyme inhibition and calcium channel blockade on cardiac apoptosis in rats with 2K1C (two-kidney/one-clip) renovascular hypertension

Apoptosis plays a role in the regulation of heart mass and architecture, and might contribute to the cardiac remodelling seen in renovascular hypertension. It is not known whether the beneficial effects of angiotensin-converting enzyme (ACE) inhibition or calcium channel blockade on cardiac remodelling are linked to the modulation of apoptosis. To test this hypothesis, we established four groups of rats: (i) sham-operated controls, (ii) a group that underwent the two-kidney/one-clip (2K1C) procedure, (iii) a group with 2K1C treated for 12 weeks with quinapril (6 mg x day(-1) x kg(-1)), and (iv) a group with 2K1C treated for 12 weeks with diltiazem (24 mg x day(-1) x kg(-1)). Treatment started 2 weeks after clipping. Systolic blood pressure was reduced to a similar extent by quinapril and diltiazem (2K1C, 223+/-19 mmHg; 2K1C+quinapril, 149+/-15 mmHg; 2K1C+diltiazem, 160+/-40 mmHg; both P <0.01 compared with 2K1C alone). Left ventricular weight, interstitial fibrosis and perivascular fibrosis were reduced significantly by both drugs. The apoptotic index (apoptotic cells/total cell number) was increased 21.6-fold (P <0.01) after quinapril treatment as compared with the 2K1C group, but was not affected by calcium channel blockade. In conclusion, our study demonstrates that ACE inhibition, in contrast with calcium channel blockade, may cause regression of cardiac hypertrophy/remodelling in 2K1C renovascular hypertensive rats through enhanced apoptosis.