Yoshikazu Kanda

Brain eicosanoid levels in spontaneously hypertensive rats after ischemia with reperfusion: leukotriene C4 as a possible cause of cerebral edema.

The relation of brain eicosanoids to progression of cerebral edema was studied in stroke-resistant spontaneously hypertensive rats subjected to incomplete global brain ischemia induced by bilateral occlusion of the common carotid arteries. Thromboxane B2 and 6-keto prostaglandin F1 alpha levels were significantly elevated 5 minutes after reperfusion but returned to control levels by 30 minutes. In contrast, leukotriene C4 levels increased 2 hours after bilateral common carotid artery occlusion and peaked 30 minutes after reperfusion, with higher levels persisting until 60 minutes after reperfusion. Cerebral ischemia was accompanied by cerebral edema early after reperfusion. The edema correlated with increased leukotriene C4 levels. That the increased brain water content was causally related to an increase in leukotriene C4 was supported by results obtained following administration of the 5-lipoxygenase inhibitors ONO-LP-016 and AA-861. Both inhibitors suppressed the increased leukotriene C4 and brain water contents after reperfusion. Our results indicate that leukotriene C4 is closely associated with an induction of ischemic cerebral edema.

Arachidonic Acid Metabolites in Acute Myocardial Infarction

Abnormalities of arachidonic acid metabolism are implicated in spasm and thrombosis in coronary arteries. Therefore, arachidonic acid metabolites were examined in patients with acute myocardial infarction (AMI). Plasma levels of thromboxane B2 (TXB 2), 6-keto prostaglandin F1α (6KPGF1α), leukotriene B4 (LTB4), and slow reacting substance of anaphylaxis (SRS-A) composed of leukotriene C4 (LTC4), leukotriene D4 (LTD4) and leukotriene E4 (LTE4), were measured in 19 AMI patients. Plasma levels of TXB2, LTB4, and SRS-A in systemic artery blood were significantly elevated during the acute stage (within twenty-four hours after the onset of chest pain) of AMI (TXB2, 0.36 ng/mL; LTB4, 0.75 ng/mL; and SRS-A [LTC4+LTD4+LTE 4], 0.96 ng/mL) compared with those of normal controls (TXB2, 0.18 ng/mL; LTB4, 0.44 ng/mL; and SRS-A [LTC4+LTD4+LTE 4], 0.31 ng/mL). These values decreased to near-normal control levels by one month after the AMI attack. The findings in this study suggest that abnormalities of arachidonic acid metabolism accompany, and may play a role in the pathogenesis of, AMI.

Utilization of vitamin A in rats with inflammation.

Reductions in the concentration of retinol (vitamin A) in serum, lung and kidney were observed in rats subjected to inflammation-inducing treatments (turpentine oil injection of thermal injury). At the same time, the liver showed an almost normal vitamin A content. Feeding of retinol to vitamin A-depleted rats with inflammation revealed that intestinal absorption of retinol was still active in the inflamed state, and the livers of these rats showed good incorporation of retinol. The livers of normal and vitamin A-depleted rats subjected to the inflammatory treatments showed a normal RBP content (retinol-binding protein) and hepatic release of holo-RBP into the serum was not impaired functionally. These results suggest the possibility that the decreases of vitamin A in the lung, serum and kidney may be due primarily to enhanced local consumption of vitamin A related to the inflammation, rather than to a reduced supply of vitamin A from the liver or to decreased intestinal absorption. In bovine serum albumin (BSA)-sensitized rats produced by direct intubation of BSA into the lungs, the level of vitamin A in the lung decreased prior to that in the liver or serum, supporting the hypothesis that the decrease in vitamin A in the inflamed lungs of these rats may be due mainly to the consumption of vitamin A in the lung in response to inflammation.

Growth factor from human milk: Purification and characterization

A protein (HPLC-P-1) purified from human milk induced the proliferation of IMR-90 cells (human fetal lung fibroblast cells, diploid) and was named milk growth factor (MGF). The human MGF (HPLC-P-1 fraction) showed a molecular size of 8 kDa on SDS-polyacrylamide gel electrophoresis (PAGE). The band on SDS-PAGE was also detected by Western blotting with anti-human MGF. However, this MGF showed two bands (MGF-S1 and MGF-S2) on 9.8% polyacrylamide native PAGE. The amino acid compositions of MGF-S1 and MGF-S2 were almost the same, but completely different from those of EGF, IGF-1 and TGF beta. The amino acid sequence of NH2-terminal of MGF was T.K.F.E.L.Y.Q.L.L.K.D.I. Neither EGF nor IGF-1 was detectable in the human MGF fraction by RIA. The effects of human MGF on IMR 90 cells (increases in cell number, incorporation of 3H-thymidine and DNA amount) were dose dependent. The activating effect on incorporation of 3H-thymidine (methyl-3H) was suppressed by anti-human MGF antibody in a dose-dependent manner. All these results indicate that MGF purified from human milk activates the growth of IMR-90 cells.

Plasma levels of leukotriene C4, B4 slow reacting substance of anaphylaxis in chloronological phases of cerebrovascular disease

In this study we report and compare plasma leukotriene (LT) levels in seventeen (17) patients with cerebral infarction, five (5) patients with cerebral hemorrhage and twelve (12) age-matched healthy volunteers. Plasma samples were collected at intervals of 1-7 days, 8-14 days, 15-30 days and 31 days- after cerebrovascular accident. Plasma immunoreactive LTC4, LTB4 and SRS-A (Slow Reacting Substance of Anaphylaxis or total peptido-LTs) levels were measured for each sample. Immunoreactive LTC4 (and SRS-A) levels were elevated in patients with cerebral infarction whilst LTB4 levels were raised in the patients with cerebral hemorrhage. In particular, cerebral infarcted patients exhibited significantly elevated levels in phases 1-7 days and after 15 days when compared with the age-matched healthy volunteers. In patients with cerebral hemorrhage, significant increases in LTB4 were measured in days 1-7 only. These results suggest a clinical relationship between the plasma levels of LTs and cerebrovascular disease.

Effects of bepridil on silent myocardial ischemia and eicosanoid metabolism in chronic stable angina pectoris after healing of myocardial infarction.

To investigate the effects of bepridil on silent myocardial ischemia and on eicosanoid metabolism, 10 patients with chronic stable angina underwent exercise treadmill testing and 48-hour ambulatory electrocardiographic monitoring both before and after 4 weeks of bepridil administration (150 mg/day). Fasting venous levels of thromboxane B2, 6-keto-prostaglandin F1 alpha, and leukotriene C4 were measured by radioimmunoassay. Bepridil decreased heart rate responses to daily activities during ambulatory monitoring, and significantly (p < 0.05) reduced the median frequency and duration of silent myocardial ischemic episodes (from 5.5 to 0 events/48 hours and from 86 to 0 minutes/48 hours respectively). Bepridil significantly decreased the blood pressure heart rate product at peak exercise and significantly prolonged the mean exercise tolerance time (from 456.6 to 527.0 second). Bepridil also significantly decreased the plasma levels of thromboxane B2 and leukotriene C4 at rest. These results suggest that bepridil may reduce silent myocardial ischemic episodes either by the reduction of cardiac oxygen demand during daily activities and exercise stress, or by controlling coronary and systemic vasomotor tone. The drug also has a salutary effect on eicosanoid metabolism, to which its efficacy on silent myocardial ischemic episodes may be related.

Milk growth factor (MGF)-induced differentiation of NT2/D1 cells.

The differentiation activity of milk growth factor (MGF, 200 ng/ml), which also has proliferative activity, was investigated in NT2/D1 cells relative to that of retinoic acid (RA, 10(-7) M). MGF suppressed the proliferation of NT2/D1 cells to the same extent as RA after cultivation for 2x4 days. MGF enhanced Fas expression in NT2/D1 cells and prevented the decrease of Fas expression when RA was also added. MGF induced the synthesis of alpha-smooth muscle actin (alpha-SM-actin) in NT2/D1 cells without fibrils, but RA did not have such a potent activity. MGF extended glial fibrillary acidic protein (GFAP) that existed in a local area of NT2/D1 cell cytoplasm. On the other hand, RA enhanced GFAP expression and dispersed it throughout the cells. MGF slightly induced neurofilament-medium size (NF-M) synthesis in NT2/D1 cells that RA induced in the cells. MGF was less effective than RA in stimulating the synthesis of epinephrine in the cells, and the additive effect of MGF and RA enhanced epinephrine synthesis. While dopamine synthesis was less effectively stimulated by MGF than by RA, an additive effect of MGF and RA for dopamine synthesis was not observed in the cells. It was thus found that MGF differentiated NT2/D1 cells through alpha-SM-actin-synthesis.

Effects of vitamin A on eicosanoids production in the lung of rat treated by thermal injury.

After the treatment of thermal injury, contents of leukotriene C4 (LTC4) increased significantly at early stage and then kept the high level of LTC4 during the inflammation. Administration of vitamin A (VA) on vitamin A deficient- (AD) rats suppressed LTC4 induction in the lung and also inflammation and then gradually induced the significant decrease of LTC4 contents to the normal level 3 days after treatment of thermal injury. Synthesis of 6KPGF1α in the lung of AD rat was induced gradually until 24 hours after thermal injury. While the administration of VA to AD-rat enabled in the lung to induce the synthesis of 6-KPGF1α enough at early stage of thermal injury. After this induction, the production of 6KPGF1α gradually decreased. These results suggest that VA will suppress specifically the induction of lipoxygenase products but will not interfere the synthesis of cyclooxygenase products.