Toshiaki Sendo

Role of poly(ADP-ribose)polymerase in cisplatin-induced injury in LLC-PK1 cells

Acute renal failure is a dose-limiting factor during cisplatin chemotherapy. We have previously shown in rats that the hydroxyl radical scavenger edaravone reverses cisplatin-induced in vivo renal damage. In the present study, the role of poly(ADP-ribose) polymerase (PARP) in cisplatin nephrotoxicity was investigated in porcine tubular cells LLC-PK1. Cell injury was elicited by transient exposure to 500 microM cisplatin for 1 h or continuous exposure to 30 microM cisplatin for 24 h. Various hydroxyl radical scavengers reversed cell damage in a transient but not permanent model. The cell injury seemed to be necrosis and apoptosis in transient and permanent models, respectively, as assessed by TUNEL method and Annexin V stain. PARP inhibitors such as 3-aminobenzamide and benzamide inhibited cell damage in transient but not permanent model. PARP-dependent cell injury was also observed after transient exposure to hydroxyl radical-generating solution. We demonstrated for the first time the activation of PARP in renal tubular cells by transient cisplatin exposure, as determined by immunofluorescent stain with anti-poly(ADP-ribose) antibody. Moreover, ATP was depleted by transient exposure to cisplatin or hydroxyl radical, both of which were reversed by PARP inhibitors. These findings suggest that hydroxyl radical generation followed by PARP activation contributes to the necrotic cell injury caused by a transient exposure to cisplatin.

Ovariectomy aggravates hypersensitivity reactions to paclitaxel in rats

Hypersensitivity reactions is still a matter of serious concern during chemotherapy with paclitaxel, particularly in patients with ovarian cancer. We recently reported that intravenous injection of paclitaxel causes acute lung injury characterized by vascular hyperpermeability, edema and respiratory dysfunction in rats. In the present study, we investigated the influence of ovariectomy on the paclitaxel- induced acute lung injury in rats. Ovariectomy worsened paclitaxel- induced acute lung injury, which was reversed by 17b-estradiol. The mRNA expression for endothelial nitric oxide synthase was reduced in lungs of ovariectomized rats. To determine the role for nitric oxide, we examined the effects of several agents that modulate nitric oxide concentration on the pulmonary response to paclitaxel. In ovary- intact rats, a nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester exaggerated paclitaxel- induced acute lung injury, while nitric oxide donors such as sodium nitroprusside and isosorbide dinitrate attenuated the lung injury. Sodium nitroprusside was also effective in alleviating the paclitaxel- induced acute lung injury in ovariectomized rats. These findings suggest that ovariectomy enhances the susceptibility to paclitaxel hypersensitivity, in which decrease in estrogen and subsequent reduction in nitric oxide synthesis may be involved.

A prostacyclin analog prevents radiocontrast nephropathy via phosphorylation of cyclic AMP response element binding protein.

We reported previously that radiocontrast medium induces caspase-dependent apoptosis and that cAMP analogs inhibit cell injury in cultured renal tubular cells. In the present study, cellular mechanisms underlying the protective effects of cAMP were determined. Ioversol, a radiocontrast medium, caused cell injury accompanied by decreases in Bcl-2, increases in Bax, and caspase activation in LLC-PK1 cells. Both cell injury and cellular events induced by ioversol were inhibited by dibutyryl cAMP and the prostacyclin analog beraprost. Dibutyryl cAMP increased phosphorylation of Akt and CREB, both of which were reversed by H89, wortmannin and the Akt inhibitor SH-6. The protective effect of dibutyryl cAMP was also reversed by these kinase inhibitors. In dominant-negative CREB-transfected cells, dibutyryl cAMP no longer prevented cell injury or inhibited changes in mRNA expression of Bcl-2 and Bax. In mice with unilateral renal occlusion, ioversol increased urinary excretion of N-acetyl-beta-d-glucosaminidase with concomitant decreases in Bcl-2 mRNA, increases in Bax mRNA, activation of caspase-3, and induction of apoptosis in tubular and interstitial cells. Beraprost completely reversed these in vivo effects of ioversol. These findings suggest that elevation of endogenous cAMP effectively prevents radiocontrast nephropathy through activation of A kinase/PI 3-kinase/Akt followed by CREB phosphorylation and enhanced expression of Bcl-2.

Spin trapping of a free radical intermediate formed during microsomal metabolism of hydrazine

A radical formed during oxidative metabolism of hydrazine in rat liver microsomes was spin-trapped with alpha-phenyl-t-butylnitrone. The trapped species was identified as hydrazine radical by comparison of its ESR parameters and mass spectrum with those of the adduct formed during CuCl2 catalyzed oxidation of hydrazine. The requirement for oxygen and NADPH in the microsomal oxidation and the occurrence of a typical binding spectrum by difference spectroscopy suggest the involvement of the participation of the cytochrome P-450 enzyme system in the formation of hydrazine radical which must be a precursor of diimide during microsomal oxidation of hydrazine.

Nitric oxide protects against contrast media-increased pulmonary vascular permeability in rats.

RATIONALE AND OBJECTIVES Nitric oxide (NO) regulation of endothelial function is involved in the development of acute lung injury. The role of NO in contrast media-induced increases in pulmonary vascular permeability was investigated in a rat model. METHODS Nonionic (iohexol) and ionic (ioxaglate) contrast media were intravenously injected at 1.5 mL/min in rats. Pulmonary vascular permeability was evaluated by measuring the amount of Evans blue dye uptake as a quantitative marker of albumin extravasation in lung tissue. RESULTS Intravenous injections of contrast media at doses of 4 and 6 g I/kg induced a dose-dependent increase in pulmonary vascular permeability. L-Arginine (an NO synthase substrate) and N(G)-nitro-L-arginine (L-NNA) (an NO synthase inhibitor) prevented and aggravated, respectively, the increase in pulmonary vascular permeability induced by the contrast medium. An aggravating action of L-NNA was confirmed by morphological and histological observations, this action being blocked by L-arginine (300 mg/kg) but not by D-arginine. Isosorbide dinitrate (1-20 mg/kg), an NO donor, had a dose-dependent protective effect on ioxaglate-increased vascular permeability. CONCLUSIONS Our experimental findings suggest that contrast media at high doses produce pulmonary edema by inhibiting endothelial NO production, and nitrovasodilators protect against this adverse effect in rats.

A rapid and simultaneous determination of several analgesic antiinflammatory agents by capillary zone electrophoresis.

&NA; A rapid and simultaneous determination of several analgesic antiinflammatory agents—ibuprofen, acetaminophen, indomethacin, and salicylic acid—in human serum was developed by using capillary zone electrophoresis (CZE) coupled with diode‐array ultraviolet detection. After precipitation of serum protein with acetonitrile containing 3‐isobutyl‐1‐methylxanthine as the internal standard, an aliquot of deproteinized samples was applied directly to the CZE system. It enabled us to measure all of these four agents within 6 min, and there were no peaks interfering with the assay of these agents or 3‐isobutyl‐1‐methylxanthine. Both the separation and quantification of these agents in human serum were reproducible after repeated analysis within a day or day‐to‐day analysis. In addition, there was a good correlation for each drug (r = 0.997‐0.999) between the values in serum determined by CZE analysis and those measured either by high‐performance liquid chromatography with ultraviolet detection (ibuprofen and indomethacin) or by fluorescence polarization immunoassay (acetaminophen and salicylic acid). Therefore, the present CZE analysis could provide a simple, rapid, and efficient method for the identification as well as monitoring of analgesic antiinflammatory agents, particularly in serum of patients suffering from intoxication by overdosage of these agents.

Stimulation of adenosine A2A receptor inhibits LPS-induced expression of intercellular adhesion molecule 1 and production of TNF-α in human peripheral blood mononuclear cells

LPS stimulates CD14/Toll-like receptor (TLR) 4, leading to induce TNF-&agr; production. Cell-to-cell interaction through the engagement between intercellular adhesion molecule (ICAM) 1 on monocytes and its ligand on T cells has been suggested to play a role in the TNF-&agr; production by LPS-treated human peripheral blood mononuclear cells (PBMCs). Adenosine is reported to inhibit LPS-induced TNF-&agr; production. However, little is known about the mechanism of the inhibitory effects induced by adenosine on the LPS-induced immune responses. We found that adenosine inhibited the expression of ICAM-1 and the production of TNF-&agr; by human PBMC via adenosine A2A receptor in the presence of LPS. However, the stimulation of A1R or A3R enhanced the actions of adenosine. Adenosine had no effect on the expression of CD14 and TLR-4, suggesting that the inhibitory effects of adenosine on the LPS actions might be independent of the expression of CD14 and TLR-4. Thus, adenosine differentially regulates the expression of ICAM-1 and the production of TNF-&agr; through plural subtypes of receptors.

Contrast medium-induced pulmonary vascular hyperpermeability: Is aggravated in a rat climacterium model

Tominaga K, Kataoka Y, Sendo T, et al. Contrast medium–induced pulmonary vascular hyperpermeability is aggravated in a rat climacterium model. Invest Radiol 2001;36:131–135. rationale and objectives. To test whether climacterium influences adverse pulmonary reactions to contrast media, the authors investigated the effect of ioxaglate on pulmonary vascular permeability in ovariectomized rats as a climacterium model. methods.From 7 days after surgery, ovariectomized rats were treated with estradiol valerate or vehicle once per week for 3 weeks. At 28 days after surgery, ioxaglate, an ionic contrast medium, was intravenously injected at 1.5 mL/min in rats. Pulmonary vascular permeability was evaluated by measuring the amount of Evans blue dye in the lung tissue. results.Ioxaglate dose-dependently increased pulmonary vascular permeability in sham-operated and ovariectomized rats. Ovariectomized rats showed a 2.6-fold increased aggravation of vascular permeability by ioxaglate 4 g I/kg compared with sham-operated rats. Estradiol valerate (0.2–5.0 mg/kg) dose-dependently blocked ioxaglate-increased vascular permeability in ovariectomized rats. conclusions.These findings suggest that climacterium is included, at least in part, in the risk factors for contrast-induced adverse pulmonary reactions, and this risk is lowered by estrogen replacement therapy.

Incidence and risk factors for paclitaxel hypersensitivity during ovarian cancer chemotherapy

Hypersensitivity reaction (HSR) is still a major concern during cancer chemotherapy with paclitaxel. In the present study, we investigated retrospectively the incidence of HSRs to paclitaxel and the risk factors in 105 patients (553 courses) who received adjuvant chemotherapy (paclitaxel and carboplatin) for ovarian cancer. Moderate to severe HSRs that led to cessation or discontinuation of the chemotherapy, including respiratory distress and hypotension, were observed in 14 patients (13.3%) and 16 courses (2.9%), regardless of the use of conventional premedication with glucocorticoid, and histamine H1 and H2 antagonists. The incidence of HSRs to paclitaxel in patients with ovarian cancer seemed to be considerably higher than those reported by other investigators in patients with other carcinomas such as non-small-cell lung cancer and breast cancer. Four risk factors were identified: (1) history of mild dermal reactions such as facial flushing and urticaria in previous courses, (2) presence of respiratory dysfunction, (3) obesity (body mass index >25), and (4) postmenopausal at the time of ovariectomy. The incidence of hypersensitivity increased linearly as the number of risk factors increased (r=0.992, P=0.008). It is likely that disappearance of the estrous cycle facilitates the occurrence of HSRs to paclitaxel.

Pemirolast potently attenuates paclitaxel hypersensitivity reactions through inhibition of the release of sensory neuropeptides in rats

The effects of anti-allergic agents on the hypersensitivity reactions to paclitaxel, an anti-cancer agent, were examined in rats. Intravenous injection of paclitaxel (15 mg/kg) caused a marked extravasation of plasma protein in lungs and a transient decrease in arterial partial oxygen pressure (PaO(2)). The paclitaxel-induced protein extravasation was inhibited by low doses (0.1-1 mg/kg) of pemirolast or high doses (30-100 mg/kg) of cromoglycate. However, ketotifen was not effective. The decrease in PaO(2) induced by paclitaxel was also significantly reversed by pemirolast. On the other hand, the paclitaxel-induced plasma extravasation was not attenuated by a histamine H(1) blocker diphenhydramine or an H(2) blocker famotidine, but was significantly reduced by a neurokinin NK(1) antagonist LY303870 (0.5 mg/kg) and an NK(2) antagonist SR48968 (1 mg/kg). The concentrations of proteins and sensory peptides such as substance P, neurokinin A and calcitonin gene-related peptide but not histamine in the rat bronchoalveolar lavage fluid were elevated by paclitaxel injection. Both cromoglycate and pemirolast reduced the paclitaxel-induced rise in proteins and sensory peptides. Therefore, we demonstrated for the first time that sensory nerve peptides are involved in paclitaxel hypersensitivity and that an anti-allergic agent pemirolast attenuates the paclitaxel response by inhibiting the release of sensory nerve peptides.