Enhancement of bradykinin-induced prostacyclin synthesis in porcine aortic endothelial cells by pertussis toxin Possible implication of lipocortin I

Bradykinin-stimulated prostacyclin synthesis in porcine aortic endothelial cells was enhanced by pretreatment of the cells with pertussis toxin or islet-activating protein (IAP) for 5 hr or longer. Although ADP-ribosylation of a protein with a molecular weight of 41–42 kD in the cell membranes was completed by 3 hr after the addition of IAP into the incubation medium, there was good correlation between enhancement of bradykinin-induced prostacyclin synthesis and ADP-ribosylation of the IAP substrate over a wide range of IAP concentrations. Furthermore, even if IAP was removed from the incubation medium at 3 hr, bradykinin-induced prostaglandin synthesis at 24 hr was still potentiated. Cycloheximide and actinomycin D enhanced bradykinin-induced prostacyclin synthesis and apparently blocked the effect of IAP. Since this result suggested the involvement of an inhibitor protein(s) of prostacyclin synthesis in the IAP effect, we studied the effect of IAP on the level of lipocortin I which is known to inhibit phospholipase A₂. Western and Northern blot analyses revealed that IAP decreased the amounts of protein and mRNA of lipocortin I. These results suggest that the enhancement of bradykinin-induced prostacyclin synthesis by IAP is associated with a decrease in the level of lipocortin I.     

The effects of prenatal protein-energy malnutrition on ossification of fetal rat bones: a biochemical study

In fetal rats whose dams were fed a low-protein diet, 35S sulfate uptake into the growth plate of the long bone and rib was higher than in the control group. The elution pattern of guanidine-HCl extract in gel chromatography revealed that the malnourished group had more high molecular weight proteoglycans in the dissociative condition and a larger aggregated portion in the associative condition than did the control group; however, the same chondroitin-sulfate chain size existed. Calcium content did not differ in both groups. Aggregated proteoglycan or a high molecular weight proteoglycan that existed in the malnourished group probably played an inhibitory role in calcification. Prenatal protein-energy malnutrition may delay the change of proteoglycan character, which could affect mineralization of fetal bones.     

Effect of magnetic field on pineal gland volume and pinealocyte size in the rat

Abstract: Light microscopic observations on the superficial pineal gland of Wistar-King rats were made to examine whether or not pineal volume and pinealocyte size, expressed as nuclear density, at daytime or nighttime are affected by long-term exposure to 50 Hz rotating magnetic field (MF) at 5.0 μT. Determinations of pineal volume and pinealocyte size were repeated twice (April and October) during the year. Size of pinealocytes in MF-exposed and sham-exposed rats exhibited, in addition to the difference between peripheral and central regions, regional differences in a proximodistal direction; pinealocytes in the distal and middle-peripheral regions were usually larger than those in the proximal and middle-central regions at daytime or nighttime. In October, distal and proximal pinealocytes showed significant day-night changes in size in sham-exposed rats, but not in MF-exposed animals. The situations in the two groups were almost reversed in April. Significant day-night differences were scarcely found in pinealocyte size in the middle region in the two groups. Throughout the study, pineal volume and pinealocyte size in each region were generally the same between MF-exposed and sham-exposed rats at daytime or nighttime. The results suggest that pinealocytes in the distal and proximal regions, but not those in the middle region, are affected by MF-exposure; day-night differences in sizes of distal and proximal pinealocytes appear in April and disappear in October under the influence of MF. MF may exert an effect on mechanisms controlling day-night rhythms of pinealocyte size in the rat.     

Aggressive resection for advanced pancreatic carcinoma

An aggressive pancreatectomy was performed on a 53 year old Japanese man with advanced cancer of the pancreas. The tumor originated from the body of the pancreas and invaded the stomach, duodenum, left kidney, transverse colon and common hepatic artery. An unexpected cancer was also found in the head of the pancreas during the operation. Therefore, total pancreatectomy, total gastrectomy, left adrenonephrectomy, resection of the left transverse colon and dissection of the regional lymph nodes were performed. Resection of the common hepatic artery was also performed, followed by an end-to-end anastomosis between the common hepatic artery and celiac trunk. The postoperative course was uneventful and the patient was doing well until nine months after the operation when multiple metastatic lesions were noted in the liver. He died 391 days after the operation from hepatic failure.     

Skeletal unloading induces resistance to insulin-like growth factor-I (IGF-I) by inhibiting activation of the IGF-I signaling pathways.

We showed that unloading markedly diminished the effects of IGF-I to activate its signaling pathways, and the disintegrin echistatin showed a similar block in osteoprogenitor cells. Furthermore, unloading decreased alphaVbeta3 integrin expression. These results show that skeletal unloading induces resistance to IGF-I by inhibiting activation of the IGF-I signaling pathways at least in part through downregulation of integrin signaling. INTRODUCTION: We have previously reported that skeletal unloading induces resistance to insulin-like growth factor-I (IGF-I) with respect to bone formation. However, the underlying mechanism remains unclear. The aim of this study was to clarify how skeletal unloading induces resistance to the effects of IGF-I administration in vivo and in vitro with respect to bone formation. MATERIALS AND METHODS: We first determined the response of bone to IGF-I administration in vivo during skeletal unloading. We then evaluated the response of osteoprogenitor cells isolated from unloaded bones to IGF-I treatment in vitro with respect to activation of the IGF-I signaling pathways. Finally we examined the potential role of integrins in mediating the responsiveness of osteoprogenitor cells to IGF-I. RESULTS: IGF-I administration in vivo significantly increased proliferation of osteoblasts. Unloading markedly decreased proliferation and blocked the ability of IGF-I to increase proliferation. On a cellular level, IGF-I treatment in vitro stimulated the activation of its receptor, Ras, ERK1/2 (p44/42 MAPK), and Akt in cultured osteoprogenitor cells from normally loaded bones, but these effects were markedly diminished in cells from unloaded bones. These results were not caused by altered phosphatase activity or changes in receptor binding to IGF-I. Inhibition of the Ras/MAPK pathway was more impacted by unloading than that of Akt. The disintegrin echistatin (an antagonist of the alphaVbeta3 integrin) blocked the ability of IGF-I to stimulate its receptor phosphorylation and osteoblast proliferation, similar to that seen in cells from unloaded bone. Furthermore, unloading significantly decreased the mRNA levels both of alphaV and beta3 integrin subunits in osteoprogenitor cells. CONCLUSION: These results indicate that skeletal unloading induces resistance to IGF-I by inhibiting the activation of IGF-I signaling pathways, at least in part, through downregulation of integrin signaling, resulting in decreased proliferation of osteoblasts and their precursors.     

Bezafibrate improves hypertension and insulin sensitivity in humans.

We examined cellular membrane fatty acid composition and insulin sensitivity in patients with mild essential hypertension and hyperlipidemia, and investigated whether bezafibrate, a lipid-lowering drug, could improve elevated blood pressure and insulin sensitivity in these subjects by ameliorating cellular membrane fatty acid composition. Twenty-seven subjects were recruited. Twelve men with mild essential hypertension [systolic blood pressure (SBP) between 140 mmHg and 160 mmHg] and hypertriglyceridemia (plasma triglyceride concentration over 150 mg/dl) were designated the HL group. Fifteen men with mild essential hypertension and normotriglyceridemia (plasma triglyceride concentration below 150 mg/dl) were designated the NL group. Subjects in the HL group were given bezafibrate 400 mg/dl and those in the NL group were given placebo for 3 months. Bezafibrate significantly reduced SBP (140 +/- 2.6 to 131.8 +/- 2.6 mmHg, mean +/- SEM), diastolic blood pressure (DBP) (87.8 +/- 2.0 to 82.8 +/- 2.6 mmHg), fasting plasma triglyceride concentration (225.5 +/- 23.5 to 102.9 +/- 10.9 mg/dl), fasting plasma insulin concentration (9.6 +/- 0.8 to 7.1 +/- 0.8 microU/ml), and homeostasis model assessment scores (HOMA-R, 2.4 +/- 0.2 to 1.7 +/- 0.2), and significantly improved the insulin sensitivity index (56.0 +/- 3.0 to 70.7 +/- 4.8 mg x l2/mmol x mU x min) in the HL group. Regarding erythrocyte membrane fatty acid composition, bezafibrate reduced the percentages of saturated fatty acids (SFA) and increased the percentage of polyunsaturated fatty acids (PUFA). Plasma triglyceride concentrations were positively correlated with HOMA-R (r = 0.50, p < 0.01) and SFA (r = 0.39, p < 0.05), and negatively correlated with PUFA (r = -0.45, p < 0.05) before administration of placebo or bezafibrate. In conclusion, an improvement of hyperlipidemia by bezafibrate may be attributed to reduction of blood pressure and amelioration of insulin sensitivity. Abnormalities in membrane lipid composition may play an important role in these metabolic disorders.     

Augmentation of intrarenal angiotensin II levels in uninephrectomized aldosterone/salt-treated hypertensive rats; renoprotective effects of an ultrahigh dose of olmesartan.

Recent studies have suggested that aldosterone plays a role in the pathogenesis of renal injury. In this study, we investigated whether local angiotensin II (Ang II) activity contributes to the progression of renal injury in aldosterone/salt-induced hypertensive rats. Uninephrectomized rats were treated with 1% NaCl in a drinking solution and one of the following combinations for 6 weeks: vehicle (2% ethanol, s.c.; n=9), aldosterone (0.75 mug/h, s.c.; n=8), aldosterone+Ang II type 1 receptor blocker olmesartan (10 mg/kg/day, p.o.; n=8), or aldosterone+olmesartan (100 mg/kg/day, p.o.; n=9). Aldosterone/salt-treated hypertensive rats exhibited severe proteinuria and renal injury characterized by glomerular sclerosis and tubulointerstitial fibrosis. Aldosterone/salt-induced renal injury was associated with augmented expression of angiotensin converting enzyme and Ang II levels in the renal cortex and medullary tissues. Renal cortical and medullary mRNA expression of transforming growth factor-beta (TGF-beta) and connective tissue growth factor (CTGF) as well as the collagen contents were increased in aldosterone/salt-treated hypertensive rats. Treatment with olmesartan (10 or 100 mg/kg/day) had no effect on blood pressure but attenuated proteinuria in a dose-dependent manner. Olmesartan at 10 mg/kg/day tended to decrease renal cortical and medullary Ang II levels, TGF-beta and CTGF expression, and collagen contents; however, these changes were not significant. On the other hand, an ultrahigh dose of olmesartan (100 mg/kg/day) significantly decreased these values and ameliorated renal injury. These data suggest that augmented local Ang II activity contributes, at least partially, to the progression of aldosterone/salt-dependent renal injury.