No participation of adenosine A1 receptor in acute nephrotoxicity by 4-pentenoic acid administration in dogs

Intrarenal infusion of 4-pentenoic acid is known to lower renal cortical ATP content and cause a reduction in glomerular filtration rate (GFR). The alteration in nucleotide metabolism might augment the production of adenosine, thereby eliciting the fall in GFR. This study was conducted to examine whether 4-pentenoic acid stimulates renal production of adenosine, and if so, to examine the role of adenosine A1 receptor in the reduction of GFR by 4-pentenoic acid. With infusion of 4-pentenoic acid (1 micromol x kg(-1) x min(-1)) into the renal artery of anesthetized dogs, GFR gradually decreased and reached minimum at 60 min with values ranging from 33.9+/-2.2 to 20.2+/-2.8 ml/min. Neither renal blood flow nor mean arterial pressure was affected, but tubular reabsorption of water and sodium was significantly attenuated. Renal venous plasma concentration and urinary excretion of adenosine rose markedly (20-fold) without any change in arterial concentration, suggesting that renal adenosine production was augmented by 4-pentenoic acid. However, KW-3902 (8-(noradamantan-3-yl)-1,3-dipropylxanthine), a selective antagonist of the adenosine A1 receptor, did not affect the action of 4-pentenoic acid on GFR or renal handling of water and sodium. It is concluded that 4-pentenoic acid markedly increases renal adenosine production, but adenosine A1 receptor is not involved in the 4-pentenoic acid-induced nephrotoxicity.

Contribution of extracellular signal-regulated kinase to angiotensin II-induced transforming growth factor-beta1 expression in vascular smooth muscle cells

We have previously demonstrated that angiotensin II (Ang II) contributes to the increase in aortic transforming growth factor-beta(1) (TGF-beta(1)) mRNA levels in hypertensive rats. However, the molecular mechanism whereby Ang II promotes TGF-beta(1) expression in vascular smooth muscle cells (VSMCs) is poorly understood. In this study, we examined the role of extracellular signal-regulated kinase (ERK) in Ang II-mediated TGF-beta(1) expression in VSMCs and the role of Ang II in aortic ERK activity of stroke-prone spontaneously hypertensive rats. Treatment of quiescent VSMCs with 100 nmol/L Ang II induced rapid phosphorylation and activation of ERK1 and ERK2 with a peak at 5 minutes followed by an increase in activator protein-1 (AP-1) DNA binding activity, as shown by gel mobility shift assay. An increase in TGF-beta(1) mRNA was shown by Northern blot analysis. Treatment of VSMCs with PD98059, a specific inhibitor of the ERK pathway, attenuated both the activation of AP-1 and the increase in TGF-beta(1) mRNA induced by Ang II. Inhibition of Ang II-induced AP-1 activation with c-fos antisense oligodeoxynucleotide led to a significant reduction of TGF-beta(1) mRNA in VSMCs. Furthermore, in vivo treatment of stroke-prone spontaneously hypertensive rats with losartan, an Ang II type 1 receptor antagonist, decreased aortic ERK activity. Thus, we show that ERK, through AP-1 activation, is involved in Ang II-induced TGF-beta(1) mRNA expression in VSMCs and suggest that ERK may participate in vascular remodeling of hypertension. However, it remains to be determined whether the increase in TGF-beta(1) mRNA leads to the increase in its active protein.

Effects of activation of renal adenosine A2 receptor on renal function and renin release in dogs

Direct effects of adenosine A2 receptor activation on renal function were examined in dogs. When renal perfusion pressure was maintained constant at 100 mmHg, renal administration of a selective A2 receptor agonist, CGS 21680C (sodium salt of CGS 21680, 2-[p-(2-carboxyethyl) phenethylamino]-5'-N-ethylcarboxamido adenosine) (1 microg x kg(-) x min (-1)), although it decreased blood pressure by 20 mmHg, increased renal blood flow and renin release, whereas glomerular filtration rate and urine flow were unaffected. These results suggest that stimulation of renal A2 receptor led to both afferent and efferent arteriolar dilatation, whereas renal A2 receptor plays a minor role in urine formation. CGS 21680C induced renin release and tachycardia that were blocked by propranolol, indicating these effects of A2 receptor stimulation appeared to be indirect.

Tissue distribution of placenta-type 6-phosphofructo- 2-kinase/fructose-2,6-bisphosphatase

Several isozymes of 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase have been characterized from mammalian tissues and, based on tissue origin, they are classified as liver, skeletal muscle, heart, testis, and placenta isozymes. In this paper, we examined the tissue distribution of placenta-type isozyme in rat tissues at the levels of transcription and translation. Analysis by Northern blotting showed that placenta, brain, testis, liver, kidney, and skeletal muscle expressed mRNA of placenta-type isozyme. Western blot analysis of fractions from POROS-HQ column chromatography of extracts from various rat tissues showed that proteins of placenta-type isozyme are expressed in placenta, brain, testis, liver, spleen, heart and lung, but not in kidney and skeletal muscle. An immunohistochemical study showed that, in liver, placenta-type isozyme is localized in Kupffer cells. These results indicate that isozymes of this particular enzyme may occur in particular cell types within each tissue.

Conversion of brain-specific complex type sugar chains by N-acetyl-beta-D-hexosaminidase B

The N-linked sugar chains, GlcNAcbeta1-2Manalpha1-6(GlcNAcbeta1-4)(Manalpha1++ +-3)Manbeta1-4GlcNAcb eta1-4(Fucalpha1-6)GlcNAc (BA-1) and GlcNAcbeta1-2Manalpha1-6(GlcNAcbeta1-4)(GlcNAcbeta1 -2Manalpha1-3)Manb eta1-4GlcNAcbeta1-4(Fucalpha1-6)GlcNAc (BA-2), were recently found to be linked to membrane proteins of mouse brain in a development-dependent manner [S. Nakakita, S. Natsuka, K. Ikenaka, and S. Hase, J. Biochem. 123, 1164-1168 (1998)]. The GlcNAc residue linked to the Manalpha1-3 branch of BA-2 is lacking in BA-1 and the removal of this GlcNAc residue is not part of the usual biosynthetic pathway for N-linked sugar chains, suggesting the existence of an N-acetyl-beta-D-hexosaminidase. Using pyridylaminated BA-2 (BA-2-PA) as a substrate the activity of this enzyme was found in all four subcellular fractions obtained. The activity was much greater in the cerebrum than in the cerebellum. To further identify the N-acetyl-beta-D-hexosaminidase, BA-1 and BA-2 in brain tissues of Hex gene-disrupted mutant mice were detected and quantified. PA-sugar chains were liberated from the cerebrum and cerebellum of the mutant mice by hydrazinolysis-N-acetylation followed by pyridylamination. PA-sugar chains were separated by anion-exchange HPLC, size-fractionation, and reversed-phase HPLC. Each peak was quantified by measuring the peaks at the elution positions of authentic BA-1-PA and BA-2-PA. BA-2-PA was detected in all the PA-sugar chain fractions prepared from Hexa, Hexb, and both Hexa and Hexb (double knockout) gene-disrupted mice, but BA-1 was not found in the fractions from Hexb gene-disrupted and double knockout mice. These results indicate that N-acetyl-beta-D-hexosaminidase B encoded by the Hexb gene hydrolyzed BA-2 to BA-1.

Noonan syndrome and cavernous hemangioma of the brain

We present two patients with multiple characteristics that occur in Noonan phenotype and cavernous hemangioma of the brain. The first patient, who had been diagnosed radiographically as having a cavernous hemangioma in the left basal ganglia at age 15 years, developed massive intracerebral hemorrhage, resulting in sudden death at home at 19 years. The second patient, who was diagnosed radiographically as having a cavernous hemangioma in the left parietal lobe at age 17 years, is being followed carefully (the patient is currently 18 years old). A review disclosed four cases of structural cerebrovascular abnormalities with or without subsequent hemorrhage. Neither these four patients nor our two patients had any severe anomalies in the heart or large vessels, which are frequently seen in patients with Noonan syndrome. Cerebrovascular abnormalities might have a significant influence on the prognosis of patients with Noonan syndrome, especially those having no severe abnormalities in the heart or large vessels.

Isolation of myxobacteria from the marine environment

In an attempt to isolate indigenous marine myxobacteria from coastal samples, we obtained two swarm forming bacteria. Both isolates formed cell aggregates which, at least in one isolate, developed to fruiting body-like structures consisting of a mass of myxospore-like cells. The optimum NaCl concentrations for their growth were between 2 and 3%, comparable to the NaCl concentration of seawater. This growth characteristic strongly suggests that the two isolates are specific marine bacteria. The 16S rDNA sequence studies indicated that the two isolates were related to the genus Nannocystis. Based on the phylogenetic distances between branches, we concluded that the isolates should be assigned to two new myxobacterial genera.

[Analysis of the factors involving in the success or failure of home infusion therapy (HIT)]

A survey was conducted from April through September, 1997, of 24 hospitalized terminal lung cancer patients connected to IVH and CSC, for whom the possibility of release from hospital was considered, and of their families. A comparative survey was made between patients who accepted HIT and those who did not. No difference was found between the groups by age, sex, or disease stage, nor was there a difference in physical symptoms such as pain and respiratory difficulty. However, the percentage of patients who were told the name of their disease was significantly higher in the group switched to HIT, 3 of whom were even given prognoses. There was no difference in the percentage of patients who lived with their families, although there was a higher percentage in the HIT group whose spouses also lived with the family. Nineteen of the 24 patients wished to return home, but 8 of those patients were not released from hospital for such reasons as the patient not wanting to be a burden on his or her family or the family's lack of ability to provide care. It was found that important factors in urging home care for the terminal cancer patient were whether or not the patient was told the name of his or her disease, and whether or not the patient lived with a healthy spouse.

The human gene encoding the lectin-type oxidized LDL receptor (OLR1) is a novel member of the natural killer gene complex with a unique expression profile

LOX-1 is an endothelial receptor for oxidized low-density lipoprotein that plays essential roles in atherogenesis. LOX-1 has the highest homology with C-type lectin receptors expressed on natural killer cells. In the present study, we cloned and characterized the human LOX-1 gene (HGMW-approved symbol OLR1). The gene structure of LOX-1 resembles that of the natural killer cell receptors. Fluorescence in situ hybridization and analyses of a yeast artificial chromosome contig revealed that the human LOX-1 gene is located in the natural killer gene complex on chromosome 12p12-p13, where the genes of the natural killer cell receptors cluster. In contrast, the expression pattern of LOX-1 is different from that of the natural killer cell receptors; LOX-1 is expressed in vascular-rich organs, but not in lymphocytes. A 1753-bp fragment of the 5' flanking region of the LOX-1 gene had a functional promoter activity. This region contains binding sites for several transcription factors, including the STAT family and NF-IL6, and the expression of LOX-1 was upregulated by several cytokines. These results demonstrate that the human LOX-1 gene is a new member of the natural killer gene complex with a unique expression profile.

[Clinical features and treatment of sarcoidosis involving the central nervous system]

PURPOSE

The purpose of this study was to investigate the clinical features, diagnosis, and treatment modalities of three cases with neurosarcoidosis, which involved the central nervous system (CNS).

CASES

Three men with neurosarcoidosis, aged 27, 29 and 60 years, are presented. Two of them had previously been given a diagnosis of sarcoidosis. The clinical symptoms of these cases included diabetes insipidus, pituitary dysfunction, seizure, mental disorder, visual field disturbance and pyramidal tract signs. In these cases, CT scan and MRI showed the presence of a tumor near the pituitary gland, diffuse nodules in the subarachnoid space or meningoencephalitis associated with angitis. The level of angiotensin converting enzyme (ACE) in the sera and in the cerebrospinal fluid, were elevated in the two cases who had no brain biopsy. All three cases were treated with steroids; two of them received pulse steroid therapy.

RESULTS

The two cases who received pulse steroid therapy responded quickly, with improvement in clinical features, serum ACE levels and neuroradiological findings. Under oral administration of steroids, all three cases recovered with complete remission of neurosarcoidosis except for endocrinological symptoms.

DISCUSSION

The main pathological changes of neurosarcoidosis are granulomatous angitis of the venular walls and occasionally, of the capillaries near the meninx and Virchow-Robin space. The patients also had symptoms of secondary meningoencephalitis. These changes were mainly located in the hypothalamus and pituitary gland. The patients had complex symptoms resulting from endocrine system granuloma, as well as from cerebral ischemia. The severity of the disease and effectiveness of treatment, can be evaluated by measuring ACE levels in the cerebrospinal fluid (over 1. 0 IU/l), and by Gd-enhanced MRI. Early pulse steroid therapy with subsequent oral steroid administration is thought to be important for neurosarcoidosis treatment, in order to prevent irreversible damage in the CNS.

Improved cardiac function after catheter ablation in a patient with type B Wolff-Parkinson-White syndrome with an old myocardial infarction

A 67-year-old man was admitted to hospital for the treatment of exertional dyspnea. He suffered from congestive heart failure due to an old inferior myocardial infarction with type B Wolff-Parkinson-White syndrome. Asynchronous wall motion caused by pre-excitation through a right-side bypass tract caused his cardiac function to deteriorate. Catheter ablation of the bypass tract increased the ejection fraction, and improved his symptoms, prior to surgical revascularization.

Differential activation of cardiac c-jun amino-terminal kinase and extracellular signal-regulated kinase in angiotensin II-mediated hypertension

Two subgroups of mitogen-activated protein kinases, c-jun NH2-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK), are thought to be involved in cultured cardiac myocyte hypertrophy and gene expression. To examine the in vivo activation of these kinases, we measured cardiac JNK and ERK activities in conscious rats subjected to acute or chronic angiotensin II (Ang II) infusion, by using in-gel kinase methods. About 50 mm Hg rise in blood pressure by Ang II (1000 ng . kg-1 . min-1) infusion caused larger activation of left ventricular JNK than ERK, via the AT1 receptor. In spite of short duration (about 30 minutes) of maximal blood pressure elevation by Ang II, JNK sustained the peak value (more than 5-fold increase) from 15 minutes up to at least 3 hours. Similar activation of JNK was seen in the right ventricle. Thus, cardiac JNK activation by Ang II seems to be in part mediated by its direct action via the AT1 receptor. The dose-response relationships for Ang II-induced rises in blood pressure and cardiac JNK and ERK activation indicated that cardiac JNK or ERK was not activated by a mild increase in blood pressure and that cardiac JNK was activated by Ang II-mediated hypertension in a more sensitive manner than ERK. Cardiac hypertrophy, induced by chronic Ang II infusion, was preceded by JNK activation without ERK activation. Furthermore, gel mobility shift analysis showed that cardiac JNK activation was followed by increased activator protein-1 DNA binding activity due to c-Fos and c-Jun. These results provided the first evidence for the preferential activation of cardiac JNK in Ang II-induced hypertension and suggested that JNK might play some role in Ang II-induced cardiac hypertrophic response in vivo. However, further study is needed to elucidate the role of JNK in cardiac hypertrophy in vivo.

Pancreatoblastoma: optically clear nuclei in squamoid corpuscles are rich in biotin

Pancreatoblastoma is a rare pancreatic neoplasm that generally occurs in children and demonstrates unique histopathologic features, including squamoid corpuscles. We encountered five cases of pancreatoblastoma and unexpectedly found the presence of optically clear nuclei (OCN) only in tumor cells of squamoid corpuscles. Recent studies showed that OCN seen in some types of neoplastic and non-neoplastic tissues were rich in biotin and revealed false-positive immunostaining by the avidin-biotin peroxidase complex method. We conducted an investigation to see if the same were true for pancreatoblastoma. As a result, the OCN were positively stained when the tissue section was incubated with peroxidase-labeled avidin or streptavidin and developed in a chromogen solution. The reaction was completely blocked by pretreatment with free avidin. An identical nuclear staining pattern was observed by the indirect immunoperoxidase method with the antibiotin antibody. Ultrastructurally, the OCN were occupied by filamentous substructures of chromatin measuring approximately 10 to 12 nm in diameter. These results suggested to us that the OCN in pancreatoblastomas were part of the unique nuclear change in which abundant biotin accumulated in association with the characteristically arranged chromatin substructure. When immunostaining with biotin as the linkage agent is performed in pancreatoblastomas, the false positivity in the OCN should be kept in mind to avoid any misinterpretation of the results.

Effects of prednisolone on glomerular signal transduction cascades in experimental glomerulonephritis

In vitro data support that activator protein-1 (AP-1) and nuclear factor-kappaB (NF-kappaB) regulate the gene expression of numerous growth factors and cytokines involved in the development of glomerulonephritis (GN). However, the in vivo activation and role of these transcription factors are poorly understood. This study examines whether these transcription factors are activated in antithymocyte serum (ATS)-induced GN in vivo and whether prednisolone suppresses activation of them. As assessed by gel mobility shift assay, glomerular DNA binding activity of AP-1 containing both c-Jun and c-Fos and NF-kappaB composed of P-50 and P-65 subunits was significantly increased after ATS injection. Furthermore, as estimated by in-gel kinase assay, glomerular activity of extracellular signal-regulated kinases (ERK) and c-jun NH2-terminal kinases (JNK), which are mitogen-activated protein kinases (MAPK) known to activate AP-1 and NF-kappaB in vitro, was significantly increased after ATS injection, preceding the increase in AP-1 activity. Prednisolone treatment significantly prevented the increase in urinary protein and albumin excretion and glomerular cell proliferation in ATS-induced GN, indicating the beneficial effects of prednisolone on this GN. Prednisolone significantly suppressed the increased glomerular ERK and JNK activities and AP-1 binding activity, but not glomerular NF-kappa binding activity. This study provides the first evidence of the marked increase in glomerular MAPK activities, and AP-1 and NF-kappa binding activities in ATS-induced GN. The beneficial effect of prednisolone on this GN may be partially mediated by the suppression of MAPK, followed by the suppression of AP-1.

Low expression of the apolipoprotein B mRNA-editing transgene in mice reduces LDL levels but does not cause liver dysplasia or tumors

Hepatic expression of apolipoprotein (apo) B mRNA-editing enzyme catalytic polypeptide 1 (APOBEC-1) has been proposed as a gene therapy approach for lowering plasma low density lipoprotein (LDL) levels. However, high-level expression of APOBEC-1 in transgenic mouse and rabbit livers causes liver dysplasia and hepatocellular carcinoma. To determine the physiological and pathological effects of low-level hepatic expression of APOBEC-1, we used a 52-kb rat APOBEC-1 genomic clone (RE4) to generate transgenic mice expressing low levels of APOBEC-1 (2 to 5 times those in nontransgenic mice). Liver function, liver histology, editing of apoB mRNA at the normal editing site (C6666), and abnormal editing at multiple sites (hyperediting) in these mice were compared with those in transgenic mice expressing intermediate (I-20) or high (I-28) levels of APOBEC-1 in the liver. Hyperediting of mRNA coding for the novel APOBEC-1 target 1 (NAT1) was also examined. In the high-expressing I-28 line, 50% of the mice had palpable tumors at 15 weeks of age, whereas in the intermediate-expressing I-20 line, 50% of the mice had evidence of liver tumors after 1 year. In contrast, low-expressing RE4 mice had normal liver function and histology and did not develop liver tumors when examined at 3 to 17 months of age. Moreover, hyperediting of apoB and NAT1 mRNA in the liver was robust in the I-20 mice but barely detectable in the RE4 mice. The low-level expression resulted in sufficient APOBEC-1 to edit essentially all apoB mRNA at the normal editing site, virtually eliminating apoB-100 and LDL in the plasma of RE4 mice. When RE4 mice were crossed with human apoB transgenic mice, which possess high plasma LDL concentrations, plasma LDL levels in the offspring were reduced to very low levels. These results indicates that long-term hepatic expression of APOBEC-1 at low levels sufficient to eliminate LDL does not cause apparent liver damage or liver tumors in transgenic mice. RE4 APOBEC-1 transgenic mice should prove valuable for studying the roles of apoB-containing lipoproteins in lipid metabolism and atherosclerosis.

Molecular cloning of the transglutaminase gene from Bacillus subtilis and its expression in Escherichia coli

We cloned and characterized a gene, tgl, encoding transglutaminase in Bacillus subtilis. The tgl gene contained a open reading frame 735-nucleotides long that encoded a 245-residue protein with the molecular weight of 28,300. The deduced amino acid sequence had little sequence similarity with sequences of other transglutaminases from a Streptoverticillium sp. or from mammals. The -10 and -35 regions of a putative promoter resembled the consensus sequence for the sigma K-dependent promoter. In addition, a sequence similar to the consensus sequence for the GerE binding site was found upstream from this region. These findings suggested that tgl was transcribed in the mother cells during a late stage of sporulation. Evidence for this suggestion was that transglutaminase activity was detected in sporulating cells during the same stage. Transglutaminase activity was detected in Escherichia coli cells transformed with a plasmid for expression of the tgl gene.

Angiotensin blockade inhibits activation of mitogen-activated protein kinases in rat balloon-injured artery

BACKGROUND

The effect of balloon injury on the arterial signal transduction pathway has not been examined. In vitro studies show that extracellular signal-regulated kinases (ERKs) and c-Jun NH2-terminal kinases (JNKs), belonging to the mitogen-activated protein kinase (MAPK) family, play a critical role in the activation of transcription factor activator protein-1 (AP-1) and cell proliferation or apoptosis. However, the activation and role of MAPKs in vascular diseases in vivo remain to be determined. Therefore, we examined the effect of balloon injury on arterial MAPKs and the possible role of angiotensin II.

METHODS AND RESULTS

Arterial JNK and ERK activities were measured by in-gel kinase assay. AP-1 DNA binding activity was determined by gel mobility shift analysis. After balloon injury of rat carotid artery, JNK (p46JNK and p55JNK) and ERK (p44ERK and p42ERK) activities were increased as early as 2 minutes, reached their peak (6- to 18-fold) at 5 minutes, and thereafter rapidly declined to control levels. JNK and ERK activations were followed by a 3.9-fold increase in arterial AP-1 DNA binding activity, which contained c-Jun and c-Fos proteins. Arterial JNK activation at 2 or 5 minutes was remarkably suppressed by E4177 (an angiotensin AT1 receptor antagonist) and cilazapril (an ACE inhibitor). E4177 also prevented activation of ERKs by suppressing their tyrosine phosphorylation, whereas cilazapril failed to prevent such activation. The increased AP-1 DNA binding activity was significantly inhibited by both E4177 and cilazapril.

CONCLUSIONS

Arterial JNKs and ERKs are dramatically activated by balloon injury associated with the activation of the AP-1 complex. These MAPK activations, followed by AP-1 activation, are mediated at least in part by the AT1 receptor. Thus, activation of JNKs and ERKs may be responsible for balloon injury-induced neointima formation.

Activation of glomerular mitogen-activated protein kinases in angiotensin II-mediated hypertension

The in vivo signal transduction pathway, responsible for hypertension-induced glomerular injury, remains to be clarified. In this study, the effect of angiotensin II (Ang II)-induced hypertension was examined on glomerular mitogen activated protein kinases (MAPK), including extracellular signal-regulated kinase (ERK) and c-jun NH2-terminal kinase (JNK), and on glomerular transcription factors activator protein-1 (AP-1) and Sp 1. MAPK activities were determined by in-gel kinase assay. DNA binding activity of AP-1 and Sp 1 was determined by gel mobility shift assay. Continuous infusion of Ang II (1000 ng/kg per min, intravenously) to conscious rats rapidly increased BP, followed by the rapid and transient activation of glomerular p42 and p44 ERK and p46 and p55 JNK with the peak at 15 to 180 min. Glomerular AP-1 binding activity was increased 2.6-fold (P < 0.01) at 24 h after the start of Ang II infusion. Supershift analysis showed that the activated AP-1 complexes contained c-Fos and c-Jun proteins. On the other hand, glomerular Sp 1 DNA binding activity was not changed throughout 7 d of Ang II infusion. These results provided the first in vivo evidence that Ang II-induced hypertension causes the activation of glomerular ERK and JNK, leading to the activation of AP-1. Thus, ERK and JNK signaling cascades, via the activation of AP-1, may be implicated in the development of hypertension-induced glomerular injury.

Cystothiazoles A and B, new bithiazole-type antibiotics from the myxobacterium Cystobacter fuscus

New bithiazole-type antibiotics, cystothiazoles A (C20H26N2O4S2) and B (C20H26N2O5S2), have been isolated from a culture broth of the myxobacterium, Cystobacter fuscus. The gross structures of these compounds were elucidated by spectroscopic analysis, and their absolute stereochemistry was determined by chemical degradation of cystothiazole A. Cystothiazole A inhibits fungi and human tumor cells, whereas it is inactive against bacteria. The antifungal activity appears to result from the inhibition of submitochondrial NADH oxidation. Although these compounds are structurally related to the known antibiotic myxothiazol, cystothiazole A was more active against fungi and less cytotoxic than myxothiazol.

Cardiac mitogen-activated protein kinase activities are chronically increased in stroke-prone hypertensive rats

To examine chronic changes in mitogen-activated protein (MAP) kinases in cardiac hypertrophy, we determined the activities of two subfamilies of MAP kinases, including extracellular signal-regulated kinases (ERKs) and c-Jun NH2-terminal kinases (JNKs), in the heart of stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar-Kyoto rats (WKY) aged 5, 8, 14, and 24 weeks. MAP kinases were determined by using in-gel kinase assay. In both the left and right ventricles of WKY, the activities of ERKs (p44ERK and p42ERK) and JNKs (p46JNK and p55JNK) decreased significantly with age, indicating that aging remarkably downregulated cardiac MAP kinase activities. In SHRSP, left ventricular ERK and JNK activities were already significantly higher at the mild hypertensive phase than they were in the same age of WKY, and they remained higher until development of left ventricular hypertrophy. On the contrary, the right ventricle of SHRSP, which did not exhibit cardiac hypertrophy, had no significant increase in ERK or JNK activities compared with WKY, except for the slight increase in p55JNK in 24-week-old SHRSP. Antihypertensive treatment of SHRSP with imidapril, an angiotensin-converting enzyme inhibitor, decreased the left ventricular JNK activities (P<.01) but did not affect ERK activities, suggesting the contribution of hypertension or the renin-angiotensin system to the increase in JNKs. Our observations provide the first evidence that both ERK and JNK activities are higher in the left ventricle of SHRSP than WKY. However, further study is needed to elucidate the mechanism and the significance of the increased cardiac MAP kinases in SHRSP.

Renal endothelin in FK506-induced nephrotoxicity in spontaneously hypertensive rats

FK506, a major immunosuppressive agent, often causes nephrotoxicity accompanied by renal vasoconstriction. It is recognized that endothelin (ET) plays a role in the cyclosporin A-induced nephrotoxicity, but the involvement of ET in the FK506-induced renal dysfunction is still poorly understood. We elicited nephrotoxicity by daily administration of FK506 in spontaneously hypertensive rats, and we examined the renal gene expression of ET and its receptors and the effects of an ET receptor antagonist on FK506-induced renal dysfunction. FK506 administration (4 mg/kg/day, i.m.) for 14 days induced nephrotoxicity, including a renal vasoconstriction and a decrease in glomerular filtration rate. The renal dysfunction was accompanied by an increase in ET-1 mRNA levels, while ET(B)-receptor mRNA was unaffected. Continuous administration of an ET(A)/ET(B) antagonist, TAK-044 (3 mg/day, s.c.), which effectively blocked systemic and renal vascular responses to exogenously administered ET-1, partially attenuated the FK506-induced renal vasoconstriction. However the reduced glomerular filtration rate were not affected by TAK-044. Thus, although enhanced gene expression of ET-1 in the kidney is involved in the renal vasoconstriction, ET does not play a major role in the FK506-induced renal dysfunction.

Angiotensin blockade improves cardiac and renal complications of type II diabetic rats

Using Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a new model of human non-insulin-dependent diabetes mellitus (NIDDM), we examined the role of local angiotensin II in cardiovascular and renal complications of NIDDM. OLETF rats were orally given cilazapril (an angiotensin-converting enzyme inhibitor, 1 or 10 mg/kg), E4177 (an angiotensin AT1 receptor antagonist, 10 mg/kg), or vehicle for 26 or 40 weeks (from the age of 20 to 46 or 60 weeks). Cardiac mRNAs were measured by Northern blot analysis, and the thickening of the coronary arterial wall and the degree of perivascular fibrosis were determined by an image analyzer. Cilazapril or E4177 did not significantly affect body weight or plasma glucose and insulin levels of OLETF rats, indicating the minor effects on diabetes itself. However, both drugs significantly and similarly prevented coronary microvascular remodeling (the increase in wall thickening and perivascular fibrosis in coronary arterioles and small coronary arteries) in OLETF rats, and they were associated with the suppression of cardiac transforming growth factor-beta1 expression. Both drugs suppressed not only the increase in left ventricular weight but also the downregulation of cardiac alpha-myosin heavy chain expression in OLETF rats. Glomerulosclerosis and glomerular hypertrophy in OLETF rats were improved by cilazapril and E4177 to a comparable extent. These results, taken together with the fact that OLETF rats show normal plasma renin levels, support that the AT1 receptor is involved in the pathogenesis of cardiac and renal complications in NIDDM.