leukotriene-c4 and Vomiting

Many chemotherapeutic agents activate multiple signaling systems, including potentially emetogenic arachidonic acid metabolites. Of these messengers, the emetic role of the leukotriene family has been neglected. The aims of this study were to test the emetic potential of key leukotrienes (LTA(4), LTB(4), LTF(4), and the cysteinyl leukotrienes LTC(4), LTD(4) and LTE(4)), and to investigate whether the leukotriene CysLT(1) receptor antagonist pranlukast or mixed leukotriene CysLT(1/2) receptor antagonist Bay u9773 can prevent the LTC(4)-induced emesis. Least shrews were injected with varying doses of one of the six tested leukotrienes and vomiting parameters were measured for 30min. LTC(4) and LTD(4) were most efficacious, and significantly increased both the frequency and percentage of animals vomiting at doses from 0.1 and 0.05mg/kg, respectively. The other tested leukotrienes were either weakly emetic or ineffective at doses up to 4mg/kg. The relative emetogenic activities of the cysteinyl leukotrienes (LTC(4)=LTD(4)>LTE(4)) suggest that leukotriene CysLT(2) receptors have a key role in emesis. However, pranlukast dose-dependently, and at 10mg/kg completely, blocked LTC(4)-induced vomiting, implicating a leukotriene CysLT(1) receptor-mediated emetic effect. Bay u9773 dose-dependently reduced the percentage of animals vomiting, but did not significantly reduce vomiting frequency. Fos immunoreactivity, measured subsequent to LTC(4)-induced vomiting to define its putative anatomical substrates, was significantly increased in the enteric nervous system and medullary dorsal vagal complex following LTC(4) (P<0.05) versus vehicle injections. This study is the first to show that some leukotrienes induce emesis, possibly involving both central and peripheral leukotriene CysLT(1) and/or leukotriene CysLT(2) receptors.

Topics: Animals; Chromones; Cysteine; Dose-Response Relationship, Drug; Eulipotyphla; Female; Immunohistochemistry; Injections; Leukotriene C4; Leukotrienes; Male; Proto-Oncogene Proteins c-fos; SRS-A; Vomiting

YM976 is a novel and selective inhibitor of phosphodiesterase type 4 (PDE4) with a different chemical structure from rolipram. Orally administered YM976 showed anti-inflammatory activity (ED(50) = 2.8 mg/kg) similar to rolipram (3.5 mg/kg). On the other hand, the emetogenicity of YM976, one of the main adverse effects of PDE4 inhibitors, was lower (maximal non-emetic dose = 10 mg/kg) than that of rolipram (1 mg/kg). The reasons for this low emetogenicity of YM976 remain unclear, and the present study endeavored to elucidate the mechanisms. Candidates for the possible mechanisms included 1) PDE4 subtype selectivity, 2) binding affinity for HAR-conformation, and 3) brain penetration. YM976 exhibited affinity for high affinity for rolipram-conformation (HAR-conformation) (IC(50) = 2.6 nM) identical to that of rolipram (1.2 nM), and failed to show significant selectivity for the individual PDE4 subtype. These results suggested that neither subtype selectivity nor the affinity for HAR-conformation may be related to the low emetogenicity of YM976. YM976 showed a minor effect on reserpine-induced hypothermia, in contrast to rolipram. To estimate brain penetration, we then measured cAMP contents in peripheral tissues (peritoneal macrophages) and in the brain. YM976 increased the cAMP content of peritoneal macrophages, but caused no significant increase in brain cAMP levels, while rolipram elevated the cAMP content of both tissues at the same dose. In conclusion, YM976 shows an apparent dissociation between its anti-inflammatory effects and emetogenicity, perhaps because of the poor brain penetration.

Topics: 3',5'-Cyclic-AMP Phosphodiesterases; Animals; Body Temperature; Brain Chemistry; Cyclic Nucleotide Phosphodiesterases, Type 4; Eosinophils; Ferrets; Humans; Leukotriene C4; Leukotriene D4; Leukotriene E4; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Inbred ICR; Phosphodiesterase Inhibitors; Pyridines; Pyrimidinones; Rats; Rats, Wistar; Rolipram; Tumor Necrosis Factor-alpha; Vomiting