Analysis of Galpha protein recognition profiles of angiotensin II receptors using chimeric Galpha proteins.

Receptors with a heptahelical structure initiate signal transduction by interacting with specific Galpha proteins. The aim of this study was to analyze the ability of type 1 (AT1) and type 2 (AT2) angiotensin receptors to recognize the receptor coupling regions of Galpha proteins using our previously described technique (Ikezu, T., Okamoto, T., Komatsuzaki, K., Matsui, T., Martyn, J.A.J., Nishimoto, I., 1996. Negative transactivation of cAMP response element by familial Alzheimer's mutants of APP. EMBO J. 15, 2468-2475; Komatsuzaki, K., Murayama, Y., Giambarella, U., Ogata, E., Seino, S., Nishimoto, I., 1996. A novel system that reports the G-proteins linked to a given receptor: a study of the type 3 somatostatin receptor. FEBS Lett. 406, 165-170). Chimeric Galphas protein constructs, whose receptor binding regions contained sequences from the four major families of Galpha proteins (Galphaq, Galphai, Galpha12, Galphas), were cotransfected with AT1 or AT2 receptors in COS cells, then stimulated with angiotensin II (Ang II). Changes in cellular cAMP were assayed on cell lysates by enzyme immunoassay. In the case of the Galphaq family, cotransfection of AT1 with Galpha11/Galphas, Galpha14/Galphas, Galpha16/Galphas, elicited significant increases in cAMP after agonist stimulation. Confirmatory results were found using an independent [35S]GTPgammaS binding assay. Further examination using chimeric G proteins for Galpha12 proteins and Galphai family proteins provided evidence that the AT1 receptor can recognize sequences from Galpha12, Galphai1/i2, Galphaz, Galphao, while both receptors interacted with Galphai3. These results provide a Galpha protein recognition database for both AT1 and AT2 receptors, which may be important for understanding the full spectrum of cellular responses mediated by the hormone Ang II.

Effect of molecular charges on renal uptake of 111In-DTPA-conjugated peptides.

The effect of molecular charges on renal accumulation of 111In-DTPA-labeled low molecular weight (LMW) peptides was investigated using 111In-DTPA-octreotide derivatives as models to design radiolabeled peptides that are taken up less by renal cells. The N-terminal D-phenylalanine (Phe) of 111In-DTPA-D-Phe(1)-octreotide was replaced with L-aspartic acid (Asp), L-lysine (Lys), L-methionine (Met) or L-Phe. Cellulose acetate electrophoresis indicated that both 111In-DTPA-L-Phe(1)-octreotide and 111In-DTPA-L-Met(1)-octreotide showed similar net charges, whereas 111In-DTPA-L-alphaLys(1)-octreotide and 111In-DTPA-L-Asp(1)-octreotide had more positive and negative charges, respectively, at pH values similar to those in blood and glomerular filtrate. When injected into mice, significant differences were observed in the renal radioactivity levels. 111In-DTPA-L-alphaLys(1)-octreotide showed the highest radioactivity levels from 10 min to 6 h postinjection, whereas the lowest radioactivity levels were observed with 111In-DTPA-L-Asp(1)-octreotide at all the postinjection intervals. These findings indicated that the replacement of only one amino acid in 111In-DTPA-D-Phe(1)-octreotide significantly altered net molecular charges of the resulting peptides and that the net charges of the 111In-DTPA-octreotide derivatives significantly affected their renal uptake. Thus, an increase of negative charges in peptide molecules may constitute a strategy for designing 111In-DTPA-conjugated LMW peptides with low renal radioactivity levels.

Significance of (111)In-DTPA chelate in renal radioactivity levels of (111)In-DTPA-conjugated peptides.

Metabolic studies of (111)In-DTPA-labeled polypeptides and peptides showed that the radiolabeled (poly)peptides generated (111)In-DTPA-adducts of amino acid that possess long residence times in the lysosomal compartment of the tissues where (poly)peptides accumulated. However, a recent study suggested that metal-chelate-methionine (Met) might possess in vivo behaviors different from metal-chelate adducts of other amino acids. In this study, to elucidate whether some biological characteristics of Met may accelerate the renal elimination rate of (111)In-DTPA-adduct of Met into urine, (111)In-DTPA-Met(1)-octreotide was synthesized and the renal handling of (111)In-DTPA-Met was investigated using (111)In-DTPA-L-Phe(1)-octreotide (Phe represents phenylalanine), which was reported previously, as a reference. Both (111)In-DTPA-conjugated octreotide analogs were stable against 3-h incubation in murine serum at 37 degrees C. Both (111)In-DTPA-octreotide analogs also showed rapid clearance of the radioactivity from the blood and similar accumulation of the radioactivity in the kidney. No significant differences were observed in the renal radioactivity levels from 10 min to 24 h postinjection between the two. Metabolic studies indicated that (111)In-DTPA-Met(1)-octreotide and (111)In-DTPA-L-Phe(1)-octreotide generated (111)In-DTPA-adducts of Met and Phe, respectively, as the final radiometabolites at similar rates. These findings suggested that the long residence times of the radioactivity in tissues after administration of (111)In-DTPA-labeled peptides and polypeptides would be attributed to inherent characteristics of (111)In-DTPA chelate.

Residential randon exposure and lung cancer risk in Misasa, Japan: a case-control study.

In order to investigate an association between residential radon exposure and risk of lung cancer, a case-control study was conducted in Misasa Town, Tottori Prefecture, Japan. The case series consisted of 28 people who had died of lung cancer in the years 1976-96 and 36 controls chosen randomly from the residents in 1976, matched by sex and year of birth. Individual residential radon concentrations were measured for 1 year with alpha track detectors. The average radon concentration was 46 Bq/m3 for cases and 51 Bq/m3 for controls. Compared to the level of 24 or less Bq/m3, the adjusted odds ratios of lung cancer associated with radon levels of 25-49, 50-99 and 100 or more Bq/m3, were 1.13 (95% confidence interval; 0.29-4.40), 1.23 (0.16-9.39) and 0.25 (0.03-2.33), respectively. None of the estimates showed statistical significance, due to small sample size. When the subjects were limited to only include residents of more than 30 years, the estimates did not change substantially. This study did not find that the risk pattern of lung cancer, possibly associated with residential radon exposure, in Misasa Town differed from patterns observed in other countries.

Glutathione oxidase-like activity of glass beads, silica gel and anion-exchange resin modified with cobalt(III)-tetrakis(4-carboxyphenyl)porphine.

Silica gel and glass beads were modified by using acid chloride of metal-tetrakis(4-carboxyphenyl)porphine (M-TCPP) through a peptide bond, and an anion-exchange resin with M-TCPP by ion-exchange reaction and physical adsorption. The carriers modified with Co(3+)-TCPP proved to accelerate the redox reaction which is catalyzed by glutathione oxidase (GSHOx), while those modified with Mn(3+)-TCPP exhibited no activity. Formation of GS-SG and hydrogen peroxide was confirmed by means of mass spectroscopy and colored reaction, respectively. The silica gel modified with Co(3+)-TCPP exhibited the strongest activity among the tested carriers, and was expected to be useful practically as a solid catalyst for the determination of glutathione.

Uricase-like catalytic activity of ion-exchange resins modified with metalloporphyrins.

The uricase-like catalytic activity of the ion-exchange resins modified with metalloporphyrins has been investigated through the oxidation of uric acid. The anion-exchange resins modified with Mn(3+)-tetrakis(sulfophenyl)porphine and the cation-exchange resin modified with Mn(3+)-tetrakis(1-methylpyridinium-4-yl)porphine exhibited the highest uricase-like activity among the modified resins tested. The fact that these resins accelerated the oxidation of uric acid even after ten cycles of use indicates that the modified resins act as catalysts in the reaction catalysed by uricase. Some of the modified resins may be effectively used for the determination of uric acid in place of uricase.

Determination of hydrogen peroxide with N,N-diethylaniline and 4-aminoantipyrine by use of an anion-exchange resin modified with manganese-tetrakis(sulphophenyl)porphine, as a substitute for peroxidase.

Amberlite IRA 900 anion-exchange resin modified with manganese-tetrakis(sulphophenyl)-porphine has been used as a catalyst instead of peroxidase for the determination of hydrogen peroxide by the reaction 2H(2)O(2) + N,N-diethylaniline + 4-aminoantipyrine (catalyst)--> quinonoid dye (lambda(max) 550 nm) + 4H(2)O. The apparent molar absorptivity for hydrogen peroxide was 1.1 x 10(4) 1.mole(-1).cm(-1), coefficient of variation 0.7%. This value is approximately 84% of that obtained by the use of peroxidase as catalyst. Similar conditions to those in the enzymatic reaction were suitable for use of the modified resin as catalyst, and the results show it to be a good substitute for peroxidase in this reaction system.

Effects of trimethylsilylation of copper(II)-phthalocyanine sulfonyl-aminopropyl silica gels on the separation of pi-electron-rich compounds by high-performance liquid chromatography.

As an attempt to elucidate the factor(s) responsible for the poor performance of a copper(II)-phthalocyanine aminopropylsilica gels (CU-PCSD) column for HPLC, the silanol and/or amino groups remaining on Cu-PCSD were endcapped with trimethylchlorosilane (TMCS) or N-trimethylsilylimidazole (TMSI). The trimethylsilylated Cu-PCS(D)S (Cu-PCSD-TMCS and -TMSI) were investigated concerning their performance as an HPLC-stationary phase in the separation of pi-electron-rich polyaromatic hydrocarbons (PAHs), such as mutagenic anthracene and pyrene. As a result, trimethylsilylation with TMSI, which reacts only with silanol-groups, was not effective to improve the column efficiency. In contrast, trimethylsilylation by TMCS, which reacts with both the silanol- and amino-groups, improved the theoretical plate numbers (N) for PAHs separation with the Cu-PCS(D) column, indicating that the low N values on the Cu-PCSD column were caused by electrostatic interactions between PAHs and the remaining amino-groups on Cu-PCS(D). Furthermore, the retention data of mutagenic heterocyclic amines (HCAs) indicated that the remaining amino groups interact with the polar groups of HCAs.

A widely applicable electrode sensitive to basic drugs based on poly(vinyl chloride) membrane plasticized with tricresyl phosphate.

A plastic membrane ion-selective electrode applicable to many basic drugs has been developed. The electrode developed was constructed with tricresyl phosphate and a poly(vinyl chloride) matrix on a polytetrafluoroethylene film. The electrode showed a near-Nernstian response to chlorpromazine, trihexyphenidyl, imipramine, dibucaine, papaverine, propranolol, tetracaine, trazodone, quinidine and cinnarizine. The determination of 50 to 3000 micrograms/ml of trazodone hydrochloride in a pH 4.0 acetate buffer solution showed an average recovery of 99.4% (mean standard deviation 0.7%) by direct potentiometry. Inorganic cations and pharmaceutical excipients did not interfere with the determination. Trazodone hydrochloride and trihexyphenidyl hydrochloride in tablets were determined, and the results compared favorably with those obtained by conventional methods.

Metalloprotease-dependent ErbB ligand shedding in mediating EGFR transactivation and vascular remodelling.

AngII (angiotensin II) and its G-protein-coupled AT(1) receptor play critical roles in mediating cardiovascular diseases such as hypertension, atherosclerosis and restenosis after vascular injury. It is widely believed that AngII promotes these diseases by inducing vascular remodelling that involves hypertrophy, hyperplasia and migration of VSMCs (vascular smooth muscle cells). We have shown that transactivation of an ErbB family receptor, EGFR (epidermal growth factor receptor; ErbB1), is essential for VSMC hypertrophy and migration induced by AngII. However, the precise signal transduction mechanism by which AngII transactivates EGFR/ErbB1 and whether other ErbBs are also required for AngII function remains unclear. Recent studies suggest an involvement of a metalloprotease-dependent ErbB family ligand production in the transactivation. Here, we will discuss the roles and mechanisms of AngII/AT(1) receptor in promoting ErbB receptors transactivation in VSMCs. Further elucidation of this ErbB activation machinery not only will give us a better understanding of the critical molecular mechanism underlying vascular remodelling stimulated by AngII, but will also contribute to development of novel treatment strategies for cardiovascular diseases.

Cancer mortality survey in a spa area (Misasa, Japan) with a high radon background.

The 1952-88 cancer mortality records for inhabitants of the Misasa spa area, Japan, which has a high radon background, and a neighboring control area without any radon spa were analyzed (average outdoor Rn concentration: 26 mBq.liter-1 in Misasa vs. 11 mBq.liter-1 in the control area). Standardized mortality ratios (SMRs) for cancers of all sites were significantly lower among the inhabitants of both Misasa (male 0.538; female 0.463) and the control area (male 0.850; female 0.770), than in the whole Japanese population. Poisson regression analysis showed that the relative risks among the inhabitants of Misasa were significantly lower than in the control area for deaths from cancers of all sites (0.67) and stomach cancer (0.59). The relative risk of lung cancer death was also lower (0.55 times) in Misasa than in the control area, although the difference was not statistically significant. These results suggest that the linear no-threshold hypothesis for radiation risk may not be valid for exposure to low doses of radon.

Multi-dimensional high-performance liquid chromatography of opioid peptides following pre-column derivatization with naphthalene-2,3-dicarboxaldehyde in the presence of cyanide ion. Preliminary results on the determination of leucine- and methionine-enkephalin-like fluorescence in the striatum region of the rat brain.

The reversed-phase high-performance liquid chromatography of three synthetic opioid peptides, 5leucine-enkephalin, 5methionine-enkephalin and [D-2alanine]-5methionine enkephalin, has been studied after their pre-column fluorogenic derivatization with naphthalene-2,3-dicarboxaldehyde in the presence of cyanide to the corresponding 1-cyanobenz[f]isoindole (CBI) derivatives. The chromatographic properties of the three synthetic CBI-peptides were characterized using three different stationary phases, ODS Hypersil, CPS Hypersil and Spherisorb Phenyl, eluted with mobile phases containing various concentrations of methanol, tetrahydrofuran or acetonitrile in 26 mM trifluoroacetic acid, adjusted to pH 3.5. The data obtained using single chromatographic columns were used to design a multi-dimensional system in which the three synthetic CBI-peptides of interest were transferred as a single fraction from one column to a second. The first column served to separate the peptides from the majority of the material in the samples, and the second column was used to separate the three CBI-peptides from each other. The best separation was achieved in which the first column was Spherisorb Phenyl and the second column was ODS Hypersil. Both columns were eluted with a mobile phase of 45% acetonitrile (v/v) in 26 mM trifluoroacetic acid (pH 3.5) at a flow-rate of 1.0 ml/min. The method has been applied to the determination of leucine- and methionine-enkephalin-like fluorescence in the striatum of the rat brain.

Angiotensin II type 2 receptors stimulate collagen synthesis in cultured vascular smooth muscle cells.

Previously, we and others have shown that angiotensin II enhances vascular smooth muscle cell extracellular matrix synthesis via stimulation of the angiotensin II type 1 (AT(1)) receptor. Recently, expression of the type 2 (AT(2)) receptor has been confirmed in the adult vasculature, but its role has not yet been fully defined. The aim of the present study was to examine the effects of stimulation of AT(2) receptors on collagen synthesis in vascular smooth muscle cells. Retroviral gene transfer was used to supplement adult vascular smooth muscle cells with AT(2) receptors to mimic the vasculature in vivo. The treatment of these cells with the AT(2) receptor agonist CGP42212A (10(-7) mol/L) alone did not cause a significant change in p42/p44 MAP kinase activity but caused a modest (30% to 50%) decrease in protein tyrosine phosphatase activity. Treatment with CGP42112A also caused a dose- and time-dependent increase in both cell-associated and secretory collagen synthesis (148+/-17% of control at 48 hours, P<0.05), which was completely inhibited by the AT(2) receptor antagonist PD123319, unaffected by the AT(1) receptor antagonist losartan, and attenuated by treatment with pertussis toxin or G(alpha)(i) antisense oligonucleotides. Interestingly, studies in other cell lines demonstrated that CGP42112A caused similar results in transfected mesangial cells but had essentially opposite effects in fibroblasts (NIH-3T3-AT(2)). These results suggest that AT(2) receptor stimulation can increase collagen synthesis in vascular smooth muscle cells via a G(alpha)(i)-mediated mechanism and provide evidence for heterogeneity in the effects of AT(2) receptor stimulation in different tissues.

Reduction of Mn(3+)-tetrakis(4-methylpyridyl)porphine with albumin observed in resonance Raman spectra.

When the resonance Raman spectra of Mn(3+)-tetrakis(4-methylpyridyl)-porphine are measured in the presence of albumins, the resonance Raman bands of Mn(2+)-tetrakis(4-methylpyridyl)porphine are frequently observed. This reduction of Mn3+ to Mn2+ could be caused by an action of unfolding albumins resulting from heat and/or light.

Vascular endothelial growth factor activates MAP kinase and enhances collagen synthesis in human mesangial cells.

UNLABELLED: Vascular endothelial growth factor activates MAP kinase and enhances collagen synthesis in human mesangial cells. BACKGROUND: Vascular endothelial growth factor (VEGF) is an endothelial mitogen that is constitutively expressed in normal human glomeruli, but its role in the kidney is still unclear. In this study, we examined the effects of VEGF on human mesangial cells (HMCs). Methods and Results. Reverse transcription-polymerase chain reaction analysis demonstrated the presence of VEGF receptor mRNA (flt-1 and KDR) in HMCs. The treatment of HMCs with VEGF did not cause a change in 3H-thymidine incorporation or cell numbers. In contrast, VEGF caused a dose- and time-dependent increase in collagen synthesis, with threefold to fivefold increases in both cell-associated and secreted collagen synthesis seen after treatment with 200 ng/ml VEGF. The effects of VEGF were attenuated by treatment of HMCs with the tyrosine kinase inhibitor herbimycin A or the MEK inhibitor PD 98059, but not with the protein kinase C (PKC) inhibitor chelerythrine. VEGF treatment also caused a marked increase in p42/p44 mitogen-activated protein kinase (MAPK) activity, but had no significant effect on HMC superoxide production. Finally, an increase in collagen synthesis was also seen in rat mesangial cells treated with VEGF. CONCLUSIONS: These results suggest that VEGF is not a mitogenic signal in HMCs, but may be involved in the regulation of the mesangial matrix in humans by a MAPK-dependent mechanism.

Examination of angiotensin II type 1 and type 2 receptor expression in human kidneys by immunohistochemistry.

Recent studies have suggested that both the angiotensin II type 1 (AT1) and type 2 (AT2) receptors may be involved in the control of renal function in rodents. The aim of this study was to examine the distribution of these receptors in normal and diseased human kidneys. Kidney samples were obtained from 21 patients with and without glomerular lesions (3 control kidney samples from patients undergoing nephrectomy, 4 patients with minimal change disease, 6 patients with IgA nephropathy, and 8 patients with membranous glomerulonephritis). AT1 receptor immunohistochemical staining was examined and found to be most prominent in blood vessels, but staining of the tubules and glomeruli was also seen. In the case of the AT2 receptor, mild-moderate immunohistochemical staining was seen in the blood vessels, with weaker staining in the glomeruli. A similar distribution was seen in the patients with glomerulopathy. These results suggest that both AT1 and AT2 receptors are expressed in the normal human kidney, as well as in patients with glomerular disease. The histological distribution of these receptors supports the notion that both receptors may have a physiological role in normal and diseased kidneys in humans.

Catalytic activity of anion-exchange resins modified with metal-porphine in oxidative reactions of phenols.

Anion-exchange resins modified with metal-porphine (M-Pr) have been investigated to develop a solid catalyst in the oxidative reaction of phenols by O2 in air. Co-Pr, which is easily prepared and separable from the reaction mixture, has been proved to accelerate the oxidative reaction of phenols such as 3,5-di-tertbutyl-4-hydroxyanisole. The resulting main oxidative products were identified to be quinones by using the GC-MS method.

Peroxidase-like activity on organic hydroperoxides of ion-exchange resins modified with metal-porphine analogues and analytical application for determination of linoleate hydroperoxide.

The ion-exchange resins modified with metal-porphyrins and -phthalocyanines (M-P(r)) have been found to exhibit a peroxidase (POD)-like activity on organic peroxides in a reaction wherein a quinoid dye is formed from phenol and 4-aminoantipyrine. Among them, Mn- and Co-P(r) exhibited stronger activity than hemoglobin and Fe-P(r), and hence were expected to be practically useful as a solid catalyst for the determination of linoleate hydroperoxide (LOOH). In addition, a resin modified with Co(3+)-phthalocyanine tetrasulfonate (Co-PCS(r)) lacks POD-like activity on hydrogen peroxide in contrast with Mn-P(r). We, therefore, concluded that Co-PCS(r) is superior to both Mn-P(r) and hemoglobin as a solid catalyst on organic hydroperoxides, and developed a new method for the determination of LOOH.