Aldosterone activates Na+/H+ exchange in vascular smooth muscle cells by nongenomic and genomic mechanisms

BACKGROUND

In vascular smooth muscle cells (VSMCs), Na+/H+ exchange (NHE) plays an important role in intracellular pH (pHi) regulation. Recently, nongenomic effect of aldosterone (ALDO) on NHE activity has been suggested in VSMCs. However, the nongenomic and genomic effects of ALDO on NHE and the intracellular signaling mechanisms for these effects have not fully been determined in VSMCs.

METHODS

The effects of short- (3 hr) and long- (24 hr) term exposure to ALDO on NHE activity were examined in cultured VSMCs from rat thoracic aortae by using single-cell pHi measurement with the pH-sensitive dye 2'7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. The NHE activity was calculated from the initial rate of Na+-dependent pHi recovery after acid load.

RESULTS

The NHE activity significantly increased after short- and long-term exposure of VSMCs to ALDO (10(-6) M). The inhibitors of gene transcription (actinomycin D) and of protein synthesis (cycloheximide) had no effect on the short-term ALDO effect, but inhibited the long-term ALDO effect. The antagonists of the mineralocorticoid receptor (MR) (spironolactone) and of the glucocorticoid receptor (GR) (RU38486) caused no effect on the short-term ALDO effect, but inhibited the long-term ALDO effect. Two protein kinase C (PKC) inhibitors (staurosporine A and calphostin C) and PKC down-regulation (24 hr pre-exposure to phobol 12-myristate 13-acetate, PMA) inhibited both the short- and long-term ALDO effects. Exposure of VSMCs to PMA for 3 hours mimicked the short-term effect of ALDO on NHE activity. ALDO significantly increased PKC activity in VSMCs. The short-term ALDO effect was inhibited by disruptors of microtubule (colchicine) and of filamentous-actin (cytochalasin B). Long-term exposure of ALDO caused a threefold increase in NHE (NHE-1) mRNA levels.

CONCLUSIONS

The short-term effect of ALDO on NHE activity is not mediated through either MR or GR, occurs independent of gene transcription and protein synthesis, and occurs through a mechanism involving the structural elements of cytoskeleton. The long-term effect of ALDO on NHE activity occurs through both MR and GR and requires gene transcription and protein synthesis. Both short- and long-term effects of ALDO are mediated through PKC activation. Therefore, ALDO activates NHE by nongenomic and genomic mechanisms in VSMCs.

AVP inhibits LPS- and IL-1beta-stimulated NO and cGMP via V1 receptor in cultured rat mesangial cells

The present study examined how arginine vasopressin (AVP) affects nitric oxide (NO) metabolism in cultured rat glomerular mesangial cells (GMC). GMC were incubated with test agents and nitrite, and intracellular cGMP content, inducible nitric oxide synthase (iNOS) mRNA, and iNOS protein were analyzed by the Griess method, enzyme immunoassay, and Northern and Western blotting, respectively. AVP inhibited lipopolysaccharide (LPS)- and interleukin-1beta (IL-1beta)-induced nitrite production in a dose- and time-dependent manner, with concomitant changes in cGMP content, iNOS mRNA, and iNOS protein. This inhibition by AVP was reversed by V1- but not by oxytocin-receptor antagonist. Inhibition by AVP was also reproduced on LPS and interferon-gamma (IFN-gamma). Protein kinase C (PKC) inhibitors reversed AVP inhibition, whereas PKC activator inhibited nitrite production. Although dexamethasone and pyrrolidinedithiocarbamate (PDTC), inhibitors of nuclear factor-kappaB, inhibited nitrite production, further inhibition by AVP was not observed. AVP did not show further inhibition of nitrite production with actinomycin D, an inhibitor of transcription, or cycloheximide, an inhibitor of protein synthesis. In conclusion, AVP inhibits LPS- and IL-1beta-induced NO production through a V1 receptor. The inhibitory action of AVP involves both the activation of PKC and the transcription of iNOS mRNA in cultured rat GMC.

Incubation of OKP cells in low-K+ media increases NHE3 activity after early decrease in intracellular pH

Chronic hypokalemia increases the activity of proximal tubule apical membrane Na+/H+ antiporter NHE3. The present study examined the effect of the incubation of OKP cells (an opossum kidney, clone P cell line) in control medium (K+ concn ([K+]) = 5.4 mM) or low-K+ medium ([K+] = 2.7 mM) on NHE3. The activity of an ethylisopropyl amiloride-resistant Na+/H+ antiporter, whose characteristics were consistent with those of NHE3, was increased in low-K+ cells beginning at 8 h. NHE3 mRNA and NHE3 protein abundance were increased 2.2-fold and 62%, respectively, at 24 h but not at 8 h. After incubation in low-K+ medium, intracellular pH (pHi) decreased by 0.27 pH units (maximum at 27 min) and then recovered to the control level. Intracellular acidosis induced by 5 mM sodium propionate increased Na+/H+ antiporter activity at 8 and 24 h. Herbimycin A, a tyrosine kinase inhibitor, blocked low-K+- and sodium propionate-induced activation of the Na+/H+ antiporter at 8 and 24 h. Our results demonstrate that low-K+ medium causes an early decrease in pHi, which leads to an increase in NHE3 activity via a tyrosine kinase pathway.

Treatment with steroids and double filtration plasmapheresis for a case of anti-GQ1b antibody-positive Bickerstaff's encephalitis

The treatment of Bickerstaff's brainstem encephalitis (BBE) is still controversial. We report a case of BBE with positive anti-GQ1b antibody. The patient was successfully treated with steroids and double filtration plasmapheresis.

Differential induction of apoptosis in B16 melanoma and EL-4 lymphoma cells by cytostatin and bactobolin

Most solid tumor cells are less sensitive to apoptosis induced by anticancer drugs than hematopoietic cancer cells. However, the mechanisms of the different responses to apoptosis in these cell types remain unknown. To explore this question, we used B16 melanoma and EL-4 lymphoma cells as solid tumor- and hematopoietic cancer-derived cell lines, and examined the effects of two apoptosis inducers, cytostatin and bactobolin, on both cell lines. Apoptosis in B16 cells was induced strongly by bactobolin, but weakly by cytostatin. In contrast, apoptosis in EL-4 cells was induced strongly by cytostatin, but weakly by bactobolin. While caspase-3 was activated upon induction of apoptosis in both cell lines, Ac-DEVD-CHO, a specific inhibitor of caspase-3, suppressed only the apoptosis in B16 cells. In B16 cells, cyclins E, A, and B1 were decreased by strongly apoptosis-inducing bactobolin prior to apoptosis commitment, but cyclin E was not decreased by weakly apoptosis-inducing cytostatin. On the other hand, in EL-4 cells cyclins D1, E, A, and B1 were decreased by strongly apoptosis-inducing cytostatin prior to apoptosis commitment, but neither cyclin A nor B1 was decreased by weakly apoptosis-inducing bactobolin. These results indicate that the dependency of apoptosis induction on caspase activity is different between the two cell lines. Furthermore, there may be an inverse correlation between specific cyclins and apoptosis induction in the two cell lines.

IC202A, a new siderophore with immunosuppressive activity produced by Streptoalloteichus sp. 1454-19. II. Physico-chemical properties and structure elucidation

IC202A (1) was isolated from the culture filtrate of Streptoalloteichus sp. 1454-19. The structure of 1 was determined by spectral analysis including a variety of two-dimentional NMR and FAB-MS experiments. IC202A is a ferrioxamine-related compound containing a butylidene N-oxide function.

Chronic hyperosmolality increases NHE3 activity in OKP cells

This study investigated the effect of chronic hypertonicity on the OKP cell Na/H antiporter, encoded by Na/H exchanger 3 (NHE3). Chronic (48 h) increases in extracellular glucose, mannitol, or raffinose concentration caused a significant increase in Na/H antiporter activity, while increases in urea concentration were without effect. This effect was seen with changes in osmolality of only 20 mOsm/liter, a magnitude that is observed clinically in poorly controlled diabetes mellitus. Increases in mannitol concentration acutely inhibited and chronically stimulated Na/H antiporter activity. The increase in Na/H antiporter activity induced by hypertonic incubation was resistant to 10(-7) and 5 x 10(-6) M but inhibited by 10(-4) M ethylisopropyl amiloride, consistent with regulation of NHE3. In addition, hypertonicity increased total cellular and plasma membrane NHE3 protein abundance twofold, with only a small increase in NHE3 mRNA abundance. We conclude that chronic pathophysiologically relevant increases in tonicity lead to increases in NHE3 protein abundance and activity. This may be responsible for increased proximal tubule apical membrane Na/H antiporter activity in poorly controlled diabetes mellitus, which could then contribute to hypertension, glomerular hyperfiltration and diabetic nephropathy.

A guinea-pig model of ultrasonically nebulized distilled water-induced bronchoconstriction

Ultrasonically nebulized distilled water-induced bronchoconstriction (UNDW-IB) is specific to asthma. The mechanisms underlying UNDW-IB are not fully understood, and no reproducible animal model has been reported. The purpose of this study was to develop a guinea-pig model of UNDW-IB. Ultrasonically nebulized distilled water (UNDW) was inhaled 20 min after an aerosolized antigen challenge in passively sensitized and artificially ventilated guinea-pigs. UNDW was also inhaled 5 and 20 min after 0.1 mg x mL(-1) methacholine inhalation in nonsensitized animals. In addition, 0.1 mg x kg(-1) S-1452, a thromboxane A2 antagonist, or saline was given intravenously 5 min before UNDW inhalation in sensitized animals. The inhalation of UNDW caused bronchoconstriction, when inhaled 20 min after an antigen challenge in sensitized guinea-pigs. UNDW inhalation did not produce bronchoconstriction after saline inhalation in nonsensitized or sensitized guinea-pigs, or after antigen inhalation in nonsensitized animals. Methacholine-induced bronchoconstriction did not evoke UNDW-IB. Neither did S-1452 reduce the UNDW-IB. In conclusion, the guinea-pig model of ultrasonically nebulized distilled water-induced bronchoconstriction developed in this study suggests that allergic reaction, but not bronchoconstriction, can induce bronchial hyperresponsiveness to ultrasonically nebulized distilled water, and that thromboxane A2 is not involved in ultrasonically nebulized distilled water-induced bronchoconstriction.

Chronic metabolic acidosis increases NHE3 protein abundance in rat kidney

Chronic metabolic acidosis increases the activity of the proximal tubule apical membrane Na/H antiporter, which is encoded predominantly by the NHE3 isoform. The present studies examined the effect of chronic metabolic acidosis on apical membrane NHE3 protein abundance in rats. Rats subjected to NH4Cl in their drinking water developed a metabolic acidosis, which decreased in magnitude over 14 days. During this time, renal cortical brush-border membrane NHE3 protein abundance, assessed by Western blot, increased progressively (28% at 3 days, 59% at 7 days, and 90% at 14 days). Immunohistochemistry revealed that the acidosis-induced increase in NHE3 abundance occurred in the apical membranes of the S1 and S2 segments of the proximal tubule and the thick ascending limb. NHE3 mRNA abundance was not significantly increased in these animals, whereas phosphoenolpyruvate carboxykinase and glyceraldehyde-3-phosphate dehydrogenase mRNA abundances were significantly increased. These studies demonstrate that the increase in Na/H antiporter activity seen in metabolic acidosis involves an increase in NHE3 protein abundance, which is distributed along the proximal tubule and the thick ascending limb. In addition, these studies suggest that a component of this adaptation is unrelated to changes in NHE3 mRNA abundance.

Dipyridamole enhances interleukin-1beta-stimulated nitric oxide production by cultured rat vascular smooth muscle cells

We examined whether dipyridamole affected interleukin-1beta-stimulated nitric oxide (NO) production by cultured rat vascular smooth muscle cells. Interleukin-1beta stimulated the production of nitrite and nitrate, stable metabolites of NO, in a dose- and time-dependent manner in vascular smooth muscle cells. Dipyridamole (1-100 mu M) enhanced interleukin-1beta-induced nitrite production in a dose- and time-dependent manner. The mRNA expression of inducible NO synthase was up-regulated by dipyridamole (0.3-10 mu M) treatment in a dose-dependent manner. Both 8-bromo-guanosine 3',5'-cyclic monophosphate (8-bromo-cGMP) and dibutyryl adenosine 3',5'-cyclic monophosphate (db-cAMP) enhanced the nitrite production in the presence of interleukin-1beta. Dipyridamole up-regulated the effect of both 8-bromo-cGMP and db-cAMP on the interleukin-1beta-induced nitrite production. Dipyridamole increased the intracellular cAMP content in the presence of interleukin-1beta (10 ng/ml), but did not affect the intracellular cGMP content. 8R*,9S*,11S*-(-)-9-hydroxy-9-n-hexyloxy-8-methyl-2,3,9,10- tetrahydro-8,11-epoxy-1H,8H,11H-2,7b,11a-triazadibenzo-(a,g)-cy cloocta ++-(c,d,e)-trinden-1-one (KT 5720), a selective inhibitor of cAMP-dependent protein kinase, abolished the enhancement of interleukin-1beta-induced nitrite production by dipyridamole, whereas 8R*,9S*,11S*-(-)-9-methoxy-carbamyl-8-methyl-2,3,9,10-tetrahydro-8,11-ep oxy-1H,8H,11H-2,7b,11a-trizadibenzo-(a,g)-cyclo-octa-(c,d,e)-tr inden-1-one (KT 5823), an inhibitor of cGMP-dependent protein kinase, did not attenuate the enhancement. Furthermore, Rolipram and 4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone (Ro-20-1724), cAMP-specific phosphodiesterase type IV inhibitors, augmented the interleukin-1beta-induced nitrite production. We concluded that dipyridamole enhanced the interleukin-1beta-induced NO production via an increase in intracellular cAMP content in cultured rat vascular smooth muscle cells.

PMA and ionomycin differently affect atrial natriuretic peptide stimulated cyclic GMP production in rat mesangial cells

How 4 beta-phorbol 12-myristate 13-acetate (PMA) and ionomycin (Io), a calcium ionophore, affect on the atrial natriuretic peptide (ANP) stimulated cyclic-3',5'-guanosine monophosphate (cGMP) production in cultured rat mesangial cells was examined. Cultured mesangial cells were prepared by isolated glomeruli from Sprague Dawley rats employing the sieving method and were used between the 3rd and 15th passage for experiments. cGMP and protein contents were measured by radioimmunoassay and Lowry method. Incubations with effectors were carried out either in the presence or absence of 0.5 mM 1-methyl-3-isobutyl-xanthine (MIX). The intracellular concentration of calcium ([Ca2+]i) was determined by using the Fura-2 method. Pretreatment with PMA, an activator of protein kinase C (PKC), attenuated ANP stimulated cGMP production in a time- and dose-dependent fashion, while alpha PDD (an inactive analog of PMA) did not inhibit cGMP production. PMA inhibition was reversed by addition of staurosporine, a protein kinase C inhibitor. Io attenuated ANP stimulated cGMP production in the absence but not in the presence of MIX. These findings suggested that PMA acts on ANP receptor or guanylate cyclase via activation of PKC in rat mesangial cells. Io may inhibit ANP stimulated cGMP production via activation of cyclic nucleotide phosphodiesterase.

Glucocorticoids regulate NHE-3 transcription in OKP cells

OKP cells express NHE-3, an amiloride-resistant Na+/H+ antiporter, which is likely an isoform responsible for apical proton secretion by the proximal tubule. We have previously shown that an amiloride-resistant Na+/H+ antiporter in OKP cells is regulated by dexamethasone, a synthetic glucocorticoid. The purpose of the present study was to examine the mechanism for the glucocorticoid-mediated increase in Na+/H+ antiporter activity. Incubation of OKP cells with 10(-6) M dexamethasone resulted in a two- to threefold increase in NHE-3 mRNA abundance. This increase was seen after 4 h of incubation with dexamethasone, a time course similar to that found for Na+/H+ antiporter activity. To examine the mechanism for the increase in NHE-3 mRNA abundance, mRNA half-life and in vitro transcription experiments were performed. NHE-3 mRNA had a half-life of 8 h in control and dexamethasone-treated cells. The rate of in vitro transcription was 1.8-fold greater when OKP cells were treated with dexamethasone. These data suggest that the glucocorticoid-mediated increase in Na+/H+ antiporter activity is due to an increase in NHE-3 gene transcription.

Activation of protein kinase A acutely inhibits and phosphorylates Na/H exchanger NHE-3

In the mammalian renal proximal tubule, protein kinase A (PKA) plays an important role in mediating hormonal regulation of apical membrane Na/H exchanger activity. This exchanger is likely encoded by NHE-3. The present studies examined regulation of NHE-3 by PKA. NHE-3 was stably expressed in Na/H exchanger-deficient fibroblasts (AP-1/NHE-3 cells). PKA activation (0.1 mM 8-BrcAMP x 20 min) inhibited NHE-3 activity by 39% (P < 0.01) with no change in NHE-3 protein abundance in the plasma membrane. To define the structural requirements for PKA-mediated inhibition, full-length NHE-3 and a cytoplasmic domain-truncated mutant (NHE-3 delta cyto) were expressed in Xenopus laevis oocytes. 8-BrcAMP inhibited NHE-3 activity by 27% (P < 0.05), an effect that was blocked by 10(-7) M PKA inhibitor peptide. NHE-3 delta cyto had baseline activity similar to that of full-length NHE-3 but its activity was not regulated by 8-BrcAMP. The purified recombinant cytoplasmic domain of NHE-3 was phosphorylated in vitro by the catalytic subunit of PKA on serine residues. In AP-1/NHE-3 cells, NHE-3 was immunoprecipitated as a approximately 87-kD phosphoprotein. Addition of 0.1 mM 8-BrcAMP increased the phosphocontent of NHE-3 by threefold. In summary, acute activation of PKA inhibits NHE-3 activity, an effect that is likely mediated by phosphorylation of its cytoplasmic domain.

Screening for apoptosis inducers in microbial products and induction of apoptosis by cytostatin

We have employed the DNA-methylgreen binding assay as a primary screening method for identifying apoptosis inducers in microbial products. Capsimycin, toyocamycin and cytostatin affect the binding of methylgreen to DNA of FS3 cells in this test system. The effect of cytostatin on apoptosis induction was confirmed by means of the ELISA system.

Expression of NHE-3 in the apical membrane of rat renal proximal tubule and thick ascending limb

Apical membrane Na/H exchange is a principal mechanism of renal proximal tubule Na absorption and H secretion, and thick ascending limb H secretion. Based on current data on Na/H exchanger isoforms (NHE-1 to 5), NHE-3 is the likeliest candidate for the apical membrane isoform. The present study localizes NHE-3 in rat kidney using polyclonal antisera against cytoplasmic epitopes of rat NHE-3. These antisera recognized an approximately 87 kD protein in Na/H exchanger-deficient cells transfected with the rat NHE-3 gene but not in mock-transfected cells. All antisera labeled an approximately 87 kD protein in plasma membranes from cortex and outer medulla. Fractionation of cortical membranes showed labeling in apical but not basolateral membranes. Cross linking studies suggested existence of oligomeric forms of the transporter. Immunohistochemistry showed strong staining of the apical membrane of S1 convoluted, and S2 convoluted tubule with lesser staining of the S2 straight tubule and absent staining of S3. Weak staining was observed in thin descending limbs in the inner stripe and intense staining was seen in the apical membrane of medullary and cortical thick ascending limbs. NHE-3 staining was absent in the remainder of the nephron. In summary, NHE-3 is the isoform responsible for NaCl and NaHCO3 absorption in the proximal convoluted tubule, and NaHCO absorption in the thick ascending limb. In the S3 proximal tubule and the distal convoluted tubule, apical membrane Na/H exchange activity is likely mediated by other isoform(s) of the NHE family.

Overexpression of csk inhibits acid-induced activation of NHE-3

Opossum kidney OKP cells express an apical membrane Na+/H+ antiporter that is encoded by NHE-3 (for Na+/H+ exchanger 3) and is similar in many respects to the renal proximal tubule apical membrane Na+/H+ antiporter. Chronic incubation of OKP cells in acid medium for 24 hr increases Na+/H(+)-antiporter activity and NHE-3 mRNA abundance. The increase in Na+/H(+)-antiporter activity was not prevented by H7, a protein kinase C/protein kinase A inhibitor, but was prevented by herbimycin A, a tyrosine kinase inhibitor. Incubation of cells in acid medium increased c-src activity, and this was inhibited by herbimycin A. To determine the role of the src family of nonreceptor protein-tyrosine kinases, Csk (for carboxyl-terminal src kinase), a physiologic inhibitor of these kinases, was overexpressed in OKP cells. In three clones overexpressing csk, acid-induced increases in Na+/H(+)-antiporter activity and NHE-3 mRNA abundance were inhibited. In these clones, inhibition of acid activation of Na+/H(+)-antiporter activity paralleled inhibition of acid activation of c-src. Neither herbimycin A nor overexpression of csk inhibited dexamethasone-induced increases in Na+/H(+)-antiporter activity. These studies show that decreases in pH activate c-src and that the src family nonreceptor protein-tyrosine kinases play a key role in acid activation of NHE-3.

Acid incubation increases NHE-3 mRNA abundance in OKP cells

With the use of degenerate primers based on conserved amino acid sequences in human, rat, and rabbit Na/H exchanger-3 (NHE-3), a polymerase chain reaction product was obtained from reverse-transcribed OKP (a clonal opossum kidney cell line) mRNA and used to screen an OKP cDNA library. The clone obtained predicted an amino acid sequence that was 86% identical to rat NHE-3, 33% to NHE-1, 35% to NHE-2, and 30% to NHE-4. Expression of the corresponding cRNA in Xenopus oocytes induced 22Na uptake with ethylisopropylamiloride. (EIPA) resistance similar to that of the OKP Na/H antiporter. On RNA blot, the cDNA labeled a 9.5-kb transcript whose abundance was increased 2.2-fold by 24-h incubation of OKP cells at pH 7.0 and 2.5-fold by 24-h incubation at pH 6.8. The acid-induced increase in NHE-3 mRNA was detectable at 12 h and increased further at 24 h. Incubation in acid media caused an increase in EIPA-resistant Na/H antiporter activity that preceded the increase in NHE-3 mRNA. In summary, OKP cells express an NHE-3 transcript that encodes an EIPA-resistant Na/H antiporter and is chronically regulated by acid.

Suppressive effects of central opioids on delayed type hypersensitivity to trinitrochlorobenzene: comparative study with morphine and electroacupuncture

We reported previously that electroacupuncture (Acu) applied to the acu-point equivalent to GV4 in the mouse just before the 2,4,6-trinitrochlorobenzene (TNCB) challenge suppressed the delayed type hypersensitivity (DTH) through endogenous opioidergic systems in the brain, and the pituitary was pivotal in this immunosuppression. The purpose of the present study was to compare the suppressive effects of Acu with those of single, acute doses of morphine on TNCB-DTH in intact and hypophysectomized (HPX) mice. Subcutaneous morphine 10 mg/kg in ddY mice, 30 mg/kg in BALB/c mice or intracisternal morphine 40 micrograms/mouse in BALB/c mice given just before TNCB challenge suppressed (40-53%) the maximal extent of ear swelling at 24 hrs after challenge in intact mice. In HPX mice, the suppressive effects of intracisternal morphine 10 and 100 micrograms/mouse were less pronounced than those observed in intact mice and there was no significant difference between intact and HPX groups. In addition, suppressive effects observed with Acu or subcutaneous morphine (30 mg/kg) were effectively antagonized by pretreatment with intracisternal naloxone at a dose of as low as 2 micrograms/mouse. Naloxone alone had no effect of its own. These results suggest that 1) the activation of opioid receptor-mediated pathways in the brain, which occurs when opioids are endogenously released (Acu) or exogenously given (morphine), is important in the suppression of TNCB-induced DTH, a cell-mediated immune response, and 2) the pituitary is less pivotal in the suppressive effects of acute morphine than in those of Acu.

Renal Proximal Tubule Response to Acid

Changes in dietary acid and blood pH lead to adaptations in key enzymes and transport proteins of the renal proximal tubule that tend to return blood pH to normal. The mechanisms responsible, as well as acid-regulated signaling pathways that may effect these responses, are reviewed.

Cytostatin, a novel inhibitor of cell adhesion to components of extracellular matrix produced by Streptomyces sp. MJ654-NF4. II. Physico-chemical properties and structure determination

The structure of cytostatin was determined to be 5,6-dihydro-5-methyl-6-(6-hydroxy,1,5-dimethyl-4-phosphonooxy-7,9, 11-tridecatrienyl)-2H-pyran-2-one sodium salt on the basis of physico-chemical properties and NMR studies.

Cytostatin, a novel inhibitor of cell adhesion to components of extracellular matrix produced by Streptomyces sp. MJ654-NF4. I. Taxonomy, fermentation, isolation and biological activities

Cytostatin has been identified as a novel inhibitor of cell adhesion to components of extracellular matrix (ECM) in cultured broth of Streptomyces sp. MJ654-NF4. Though cytostatin did not inhibit EL-4 cell adhesion to ECM components such as laminin and fibronectin; it inhibited the adhesion of B16 melanoma cells to laminin and collagen type IV but not to fibronectin. It exhibited antimetastatic activity on B16 melanoma cells in mice. The cytotoxicity of cytostatin are also reported.

Biosynthesis of antitumor antibiotic, cytogenin

The biosynthesis of antitumor antibiotic cytogenin, 3-hydroxymethyl-6-methoxy-8-hydroxy-isocoumarin, was studied by feeding 14C- or 13C-labeled compounds to culture of the producing organism, Streptoverticillium eurocidicum MI43-37F11. 14C-Acetate and 14C-methionine were efficiently incorporated into cytogenin as precursors. 13C NMR studies proved that the carbon skeleton of cytogenin is derived from pentaketide intermediate due to head-to-tail condensation of five acetate units and methyl group of 6-OCH3 is derived from methionine. It was suggested that 3-hydroxymethyl and/or 6-methoxy group of cytogenin were metabolized by hydroxylation and/or methylation from three intermediates.

IC101, extracellular matrix antagonist produced by Streptomyces sp. MJ202-72F3. Production, isolation, structure determination and biological activity

In our search for inhibitors of cell adhesion to components of extracellular matrix (ECM), fibronectin, laminin and collagen type IV, we succeeded in finding a novel cyclic hexadepsipeptide antibiotic, named IC101, which was isolated from cultured mycelium of Streptomyces albulus MJ202-72F3. It was purified by centrifugal partition chromatography, preparative reverse phase HPLC and Sephadex LH-20 and was obtained as a white powder. IC101 strongly inhibited cell adhesion to ECM components, suppressed immune responses in vitro and in vivo, and exhibited antimicrobial activity on Gram-positive bacteria.

Delaminomycins, novel extracellular matrix receptor antagonists. V. Biosynthesis

The biosynthesis of delaminomycin A, produced by Streptomyces albulus MJ202-72F3, was investigated by feeding 13C-labeled compounds followed by 13C NMR analyses. The results indicate that delaminomycin A is derived from six acetate units, five propionate units and one glycine unit.