Dose-dependent effects of L-carnosine on the renal sympathetic nerve and blood pressure in urethane-anesthetized rats

The physiological function of L-carnosine (beta-alanyl-L-histidine) synthesized in mammalian muscles has been unclear. Previously, we observed that intravenous (i.v.) injection of L-carnosine suppressed renal sympathetic nerve activity (RSNA) in urethane-anesthetized rats, and L-carnosine administered via the diet inhibited the elevation of blood pressure (BP) in deoxycorticosterone acetate salt hypertensive rats. To identify the mechanism, we examined effects of i.v. or intralateral cerebral ventricular (l.c.v.) injection of various doses of L-carnosine on RSNA and BP in urethane-anesthetized rats. Lower doses (1 microg i.v.; 0.01 microg l.c.v.) of L-carnosine significantly suppressed RSNA and BP, whereas higher doses (100 microg i.v.; 10 microg l.c.v.) elevated RSNA and BP. Furthermore, we examined effects of antagonists of histaminergic (H1 and H3) receptors on L-carnosine-induced effects. When peripherally and centrally given, thioperamide, an H3 receptor antagonist, blocked RSNA and BP decreases induced by the lower doses of peripheral L-carnosine, whereas diphenhydramine, an H1 receptor antagonist, inhibited increases induced by the higher doses of peripheral L-carnosine. Moreover, bilateral lesions of the hypothalamic suprachiasmatic nucleus eliminated both effects on RSNA and BP induced by the lower (1 microg) and higher (100 microg) doses of peripheral L-carnosine. These findings suggest that low-dose L-carnosine suppresses and high-dose L-carnosine stimulates RSNA and BP, that the suprachiasmatic nucleus and histaminergic nerve are involved in the activities, and that L-carnosine acts in the brain and possibly other organs.     

Characterization and Transcription of the Genes Involved in Butyrate Production in Butyrivibrio fibrisolvens TypeI and II Strains

The genes in Butyrivibrio fibrisolvens that encode the enzymes involved in butyrate production were sequenced. In a type I strain (ATCC 19171(T)), the genes coding for the enzymes that catalyze the conversion from acetyl-CoA to butyryl-CoA, thl (thiolase), crt (crotonase), hbd (beta-hydroxybutyryl-CoA dehydrogenase), bcd (butyryl-CoA dehydrogenase), etfB (electron transfer flavoprotein [ETF]-beta), and etfA (ETF-alpha), were found to be clustered and arranged in this order. A type II strain (ATCC 51255) had the same clustered genes with the same arrangement, except that crt was not present in the clustered genes. The deduced amino acid sequences of these enzymes did not greatly differ between the two strains, and even between B. fibrisolvens and clostridia. Amino acid identity appeared to be higher within the same type than between types I and II. The clustered genes were shown to be cotranscribed, and constitutively transcribed without being affected significantly by culture conditions.     

Functional changes in adenylyl cyclases and associated decreases in relaxation responses in mesenteric arteries from diabetic rats

To assess the functional change in adenylyl cyclases (AC) associated with the diabetic state, we investigated AC-mediated relaxations and cAMP production in mesenteric arteries from rats with streptozotocin (STZ)-induced diabetes. The relaxations induced by the water-soluble forskolin (FSK) analog NKH477, which is a putative AC5 activator, but not by the beta-adrenoceptor agonist isoproterenol (Iso) and the AC activator FSK, were reduced in intact diabetic mesenteric artery. In diabetic rats, however, Iso-, FSK-, and NKH477-induced relaxations were attenuated in the presence of inhibitors of nitric oxide synthase and cyclooxygenase. To exclude the influence of phosphodiesterase (PDE), we also examined the relaxations induced by several AC activators in the presence of 3-isobutyl-1-methylxanthine (IBMX; a PDE inhibitor). Under these conditions, the relaxation induced by Iso was greatly impaired in STZ-diabetic rats. This Iso-induced relaxation was significantly attenuated by pretreatment with SQ-22536, an AC inhibitor, in mesenteric rings from age-matched controls but not in those from STZ-diabetic rats. Under the same conditions, the relaxations induced by FSK or NKH477 were impaired in STZ-diabetic rats. Neither FSK- nor A-23187 (a Ca2+ ionophore)-induced cAMP production was significantly different between diabetics and controls. However, cAMP production induced by Iso or NKH477 was significantly impaired in diabetic mesenteric arteries. Expression of mRNAs and proteins for AC5/6 was lower in diabetic mesenteric arteries than in controls. These results suggest that AC-mediated relaxation is impaired in the STZ-diabetic rat mesenteric artery, perhaps reflecting a reduction in AC5/6 activity.     

Gene therapy for chronic myocardial ischemia using platelet-derived endothelial cell growth factor in dogs

Platelet-derived endothelial cell growth factor (PD-ECGF), also known as thymidine phosphorylase (TP), has been reported to possess angiogenic activity and to inhibit apoptosis. This study was performed to determine whether PD-ECGF/TP can be used to ameliorate chronic myocardial ischemia. Myocardial ischemia was created in 40 mongrel dogs by placement of an ameroid constrictor on the proximal left anterior descending coronary artery (LAD). Plasmid vector encoding human PD-ECGF/TP cDNA (pCIhTP group; n = 12), empty vector pCI (pCI group; n = 12), or saline (Saline group; n = 12) was directly injected into the LAD territory 3 wk after ameroid constrictor implantation. Myocardial blood flow was detected using PET at baseline, 3 wk after ameroid constrictor implantation, and 2 wk after therapeutic treatment. At the end of the experiment, the hearts were isolated for biological and histological analysis. In the pCIhTP group, the transfected heart strongly expressed PD-ECGF/TP. The size of the infarct was smaller in the pCIhTP group than in the pCI or Saline group. The number of apoptotic myocardial cells was decreased in the pCIhTP group compared with the control groups based on triple immunohistochemical staining for von Willebrand factor, alpha-actin smooth muscle cells, and single-strand DNA. The level of proapoptotic protein Bax markedly decreased in the pCIhTP group compared with the other groups. Double immunohistochemical staining for von Willebrand factor and alpha-actin smooth muscle cells demonstrated that angiogenesis and arteriogenesis occurred, and paralleled the changes in myocardial blood flow and myocardial function in the pCIhTP group. We conclude that genetic approaches using PD-ECGF/TP to target the myocardium are effective for alleviating chronic myocardial ischemia.     

A simple PCR-RFLP method for identification and differentiation of 11 Malassezia species

A PCR-RFLP method targeted toward 26S rDNA and with 2 restriction enzymes, CfoI and BstF51, was developed to identify 11 Malassezia species. Not only type and standard strains but also 13 clinical isolates were identified successfully in this study. The results of identifications were confirmed by DNA sequencing.     

Transforming growth factor beta2 is a neuronal death-inducing ligand for amyloid-beta precursor protein

APP, amyloid beta precursor protein, is linked to the onset of Alzheimer's disease (AD). We have here found that transforming growth factor beta2 (TGFbeta2), but not TGFbeta1, binds to APP. The binding affinity of TGFbeta2 to APP is lower than the binding affinity of TGFbeta2 to the TGFbeta receptor. On binding to APP, TGFbeta2 activates an APP-mediated death pathway via heterotrimeric G protein G(o), c-Jun N-terminal kinase, NADPH oxidase, and caspase 3 and/or related caspases. Overall degrees of TGFbeta2-induced death are larger in cells expressing a familial AD-related mutant APP than in those expressing wild-type APP. Consequently, superphysiological concentrations of TGFbeta2 induce neuronal death in primary cortical neurons, whose one allele of the APP gene is knocked in with the V642I mutation. Combined with the finding indicated by several earlier reports that both neural and glial expression of TGFbeta2 was upregulated in AD brains, it is speculated that TGFbeta2 may contribute to the development of AD-related neuronal cell death.     

Synergistic biofilm formation by Treponema denticola and Porphyromonas gingivalis

Biofilm formation is an important step in the etiology of periodontal diseases. In this study, in vitro biofilm formation by Treponema denticola and Porphyromonas gingivalis 381 displayed synergistic effects. Confocal microscopy demonstrated that P. gingivalis attaches to the substratum first as a primary colonizer followed by coaggregation with T. denticola to form a mixed biofilm. The T. denticola flagella mutant as well as the cytoplasmic filament mutant were shown to be essential for biofilm formation as well as coaggregation with P. gingivalis. The major fimbriae and Arg-gingipain B of P. gingivalis also play important roles in biofilm formation with T. denticola.     

Crystal structure and possible catalytic mechanism of microsomal prostaglandin E synthase type 2 (mPGES-2)

Prostaglandin (PG) H(2) (PGH(2)), formed from arachidonic acid, is an unstable intermediate and is converted efficiently into more stable arachidonate metabolites (PGD(2), PGE(2), and PGF(2)) by the action of three groups of enzymes. Prostaglandin E synthase catalyzes an isomerization reaction, PGH(2) to PGE(2). Microsomal prostaglandin E synthase type-2 (mPGES-2) has been crystallized with an anti-inflammatory drug indomethacin (IMN), and the complex structure has been determined at 2.6A resolution. mPGES-2 forms a dimer and is attached to lipid membrane by anchoring the N-terminal section. Two hydrophobic pockets connected to form a V shape are located in the bottom of a large cavity. IMN binds deeply in the cavity by placing the OMe-indole and chlorophenyl moieties into the V-shaped pockets, respectively, and the carboxyl group interacts with S(gamma) of C110 by forming a H-bond. A characteristic H-bond chain formation (N-H...S(gamma)-H...S(gamma)...H-N) is seen through Y107-C113-C110-F112, which apparently decreases the pK(a) of S(gamma) of C110. The geometry suggests that the S(gamma) of C110 is most likely the catalytic site of mPGES-2. A search of the RCSB Protein Data Bank suggests that IMN can fit into the PGH(2) binding site in various proteins. On the basis of the crystal structure and mutation data, a PGH(2)-bound model structure was built. PGH(2) fits well into the IMN binding site by placing the alpha and omega-chains in the V-shaped pockets, and the endoperoxide moiety interacts with S(gamma) of C110. A possible catalytic mechanism is proposed on the basis of the crystal and model structures, and an alternative catalytic mechanism is described. The fold of mPGES-2 is quite similar to those of GSH-dependent hematopoietic prostaglandin D synthase, except for the two large loop sections.     

Proteolytic degradation of glutamate decarboxylase mediates disinhibition of hippocampal CA3 pyramidal cells in cathepsin D-deficient mice

Although of clinical importance, little is known about the mechanism of seizure in neuronal ceroid lipofuscinosis (NCL). In the present study, we have attempted to elucidate the mechanism underlying the seizure of cathepsin D-deficient (CD-/-) mice that show a novel type of lysosomal storage disease with a phenotype resembling late infantile NCL. In hippocampal slices prepared from CD-/- mice at post-natal day (P)24, spontaneous burst discharges were recorded from CA3 pyramidal cells. At P24, the mean amplitude of IPSPs after stimulation of the mossy fibres was significantly smaller than that of wild-type mice, which was substantiated by the decreased level of gamma-aminobutyric acid (GABA) contents in the hippocampus measured by high-performance liquid chromatography (HPLC). At this stage, activated microglia were found to accumulate in the pyramidal cell layer of the hippocampal CA3 subfield of CD-/- mice. However, there was no significant change in the numerical density of GABAergic interneurons in the CA3 subfield of CD-/- mice at P24, estimated by counting the number of glutamate decarboxylase (GAD) 67-immunoreactive somata. In the hippocampus and the cortex of CD-/- mice at P24, some GABAergic interneurons displayed extremely high somatic granular immunoreactivites for GAD67, suggesting the lysosomal accumulation of GAD67. GAD67 levels in axon terminals abutting on to perisomatic regions of hippocampal CA3 pyramidal cells was not significantly changed in CD-/- mice even at P24, whereas the total protein levels of GAD67 in both the hippocampus and the cortex of CD-/- mice after P24 were significantly decreased as a result of degradation. Furthermore, the recombinant human GAD65/67 was rapidly digested by the lysosomal fraction prepared from the whole brain of wild-type and CD-/- mice. These observations strongly suggest that the reduction of GABA contents, presumably because of lysosomal degradation of GAD67 and lysosomal accumulation of its degraded forms, are responsible for the dysfunction of GABAergic interneurons in the hippocampal CA3 subfield of CD-/- mice.     

Suppression of thymic lymphoma induction by life-long low-dose-rate irradiation accompanied by immune activation in C57BL/6 mice

The induction of thymic lymphomas by whole-body X irradiation with four doses of 1.8 Gy (total dose: 7.2 Gy) in C57BL/6 mice was suppressed from a high frequency (90%) to 63% by preirradiation with 0.075 Gy X rays given 6 h before each 1.8-Gy irradiation. This level was further suppressed to 43% by continuous whole-body irradiation with 137Cs gamma rays at a low dose rate of 1.2 mGy/h for 450 days, starting 35 days before the challenging irradiation. Continuous irradiation at 1.2 mGy/h resulting in a total dose of 7.2 Gy over 258 days yielded no thymic lymphomas, indicating that this low-dose-rate radiation does not induce these tumors. Further continuous irradiation up to 450 days (total dose: 12.6 Gy) produced no tumors. Continuously irradiated mice showed no loss of hair and a greater body weight than unirradiated controls. Immune activities of the mice, as measured by the numbers of CD4+ T cells, CD40+ B cells, and antibody-producing cells in the spleen after immunization with sheep red blood cells, were significantly increased by continuous 1.2-mGy/h irradiation alone. These results indicate the presence of an adaptive response in tumor induction, the involvement of radiation-induced immune activation in tumor suppression, and a large dose and dose-rate effectiveness factor (DDREF) for tumor induction with extremely low-dose-rate radiation.