Recently we demonstrated that endothelins secreted from human keratinocytes act as intrinsic mitogens and melanogens for human melanocytes in UVB-induced melanosis. We show here that UVA-induced melanosis is associated with other keratinocyte-derived growth factors, secretion of which is specifically stimulated after exposure of human keratinocytes to UVA. Medium conditioned by UVA-exposed human keratinocytes elicited a significant increase in DNA synthesis by cultured human melanocytes in a UVA dose-dependent manner. Analysis of endothelin-1 and interleukin (IL)-1 alpha in the conditioned medium by ELISA, both of which are major keratinocyte-derived cytokines involved in UVB-associated melanocyte activation, revealed that UVA exposure did not cause human keratinocytes to stimulate the secretion of the two cytokines. In contrast, the levels of several other cytokines such as IL-6, IL-8 and granulocyte/macrophage colony-stimulating factor (GM-CSF) were significantly increased in the conditioned medium of human keratinocytes after exposure to UVA at a dose of 1.0 J/cm2. The gel chromatographic profile of UVA-exposed keratinocyte-conditioned medium demonstrated that there were two factors (P-1 and P-2) with molecular masses of approx. 20 and 1 kDa respectively that stimulate DNA synthesis in human melanocytes, and the larger species (P-1) also increased melanization as assessed by [14C]thiouracil incorporation. Quantitative analysis of cytokines in chromatographic fractions by ELISA revealed the P-1 fraction to be consistent with the molecular mass profile of GM-CSF. Furthermore the stimulatory effect of the P-1 fraction on DNA synthesis in human melanocytes was neutralized by antibodies to GM-CSF, but not to basic fibroblast growth factor or stem cell factor. Binding and proliferation assays with recombinant GM-CSF demonstrated that human melanocytes possess specific binding sites for GM-CSF(Kd 2.11 nM; binding sites, 2.5-3.5 x 10(4) per cell), and recombinant GM-CSF at concentrations of more than 10 nM significantly stimulated DNA synthesis and melanization. These findings suggest that GM-CSF secreted by keratinocytes plays an essential role in the maintenance of melanocyte proliferation and UVA-induced pigmentation in the epidermis.

To clarify the paracrine linkage between human fibroblasts and melanocytes in cutaneous pigmentation, we studied the effects of human fibroblast-derived factors on the proliferation of human melanocytes. In medium conditioned for 4 days with human fibroblast culture, factors were produced that markedly stimulated DNA synthesis of human melanocytes. The stimulatory effect was higher in medium conditioned with fibroblasts from aged skin than in medium conditioned with fibroblasts from young skin, and was interrupted by inhibitors of tyrosine kinase, such as tyrphostin, genistein and herbimycin, but not by inhibitors of protein kinases C and A, such as H-7 and phloretin. The conditioned medium was also capable of activating mitogen-activated protein kinase of human melanocytes, with old fibroblasts being more effective than young ones. Analysis of factors released into the conditioned medium revealed that levels of hepatocyte growth factor (HGF) and stem cell factor (SCF) were increased in old-fibroblast-conditioned medium compared with young-fibroblast-conditioned medium. In contrast, levels of basic fibroblast growth factor (bFGF) were similar in both media. When the conditioned medium was treated with HGF antibody with or without SCF antibody, the increase in DNA synthesis by human melanocytes was decreased to 20% of the elevated level, whereas antibodies to bFGF had no effect. Analysis of the medium conditioned for 4 days after cytokine application demonstrated that, of the cytokines tested, interleukin 1alpha and tumour necrosis factor alpha are highly effective in stimulating HGF secretion by old fibroblasts. HGF and SCF, but not bFGF, were markedly increased in culture medium in the presence of IL-1alpha, and this stimulatory effect was confined to young human fibroblasts. These findings suggest that SCF and HGF derived from human fibroblasts may play a part in regulating cutaneous pigmentation during inflammation and aging.

Rifampin is an important chemotherapeutic agent for use against tuberculosis, leprosy, and infections by organisms related to those causing these diseases (3, 7). The antimicrobial activity of rifampin is due to its inhibition of DNA-dependent RNA polymerase, and most rifampin-resistant bacteria have been reported to have an alteration in the ␤-subunit of this enzyme (2). Such a resistance mechanism has been reported for Mycobacterium tuberculosis, Mycobacterium avium, Mycobacterium africanum, and Mycobacterium leprae (14, 16). During our studies of fast-growing mycobacterial strains, we found that several strains inactivate rifampin (1, 5). We analyzed the inactivated antibiotics and found them to differ in mass spectrum and chromatographic mobility from those previously reported, i.e., the glycosylated (glucosylated) or phosphorylated compounds produced by pathogenic Nocardia spp. (11,17). These results prompted us to determine the detailed structures of the inactivated compounds. In this paper the isolation, structures, and antimicrobial activities of the inactivated compounds are reported.Rifampin was generously provided by CIBA-GEIGY Pharmaceuticals, Basel, Switzerland. MICs were determined by an agar dilution method with brain heart infusion agar (Difco Laboratories, Detroit, Mich.) medium. The inoculum size of each test organism was adjusted to 10 6 CFU/ml. The plates were spotted with a multipoint inoculator (A 400; Denly Instruments, Ltd., Sussex, England) that delivered 0.005 ml of inoculum, resulting in a spot inoculum of approximately 5 ϫ 10 4 CFU. Inactivation of rifampin was monitored by a bioassay method with Bacillus subtilis PCI 219 as a test organism (17). Inactivated compounds were monitored with a thin-layer chromatography scanner (CS-910; Shimadzu Seisakusho, Kyoto, Japan) (17, 18) at 238 nm.One loopful of the culture from slant cultures of Mycobacterium smegmatis DSM 43756 was inoculated into a 100-ml Erlenmeyer shake flask containing 20 ml of a seed culture medium (2% glycerol-enriched brain heart infusion medium; Difco Laboratories) with 4-mm-diameter glass beads to reduce aggregation of the mycobacterial cells (18). The inoculated flasks were shaken at 250 rpm (5.8-cm stroke) for 4 days at 33ЊC. For large-scale preparation of the inactivation products, the seed culture was used as an inoculum. Ten milliliters of seed culture was inoculated into 500-ml shake flasks containing 100 ml of the same medium. After 24 h of incubation at 33ЊC, rifampin (stock solution in methanol at 100 mg/ml) was added to a final concentration of 50 g/ml, and the mixture was incubated for 3 days. Following separation from mycelia by centrifugation at 6,000 rpm (5,800 ϫ g), the supernatant was adjusted to pH 2.0 with 1 N HCl and extracted three times with an equal volume of ethylacetate. The extracts were combined, dehydrated with Na 2 SO 4 , and concentrated in vacuo to dryness. The dried material was purified by silica gel column chromatography (column size, 3.5 by 15 cm) by using 75 g of Wakogel C-200 (Wako Pu...

Rifampin was glycosylated by a pathogenic species of Nocardia, i.e., Nocardia brasiliensis. The structures of two glycosylated compounds (RIP-1 and RIP-2) isolated from the culture broth of the bacterium were Rifamycins are members of the naphthalenic ansamycin group of antibiotics characterized by a 17-membered ansa chain (1,5,11,17 (Becton Dickinson, Cockeysville, Md.). One loopful of spores or mycelial fragments from the slant cultures of Nocardia spp. was inoculated into a 10-ml Erlenmeyer shake flask containing 5 ml of a seed medium (2% glucose-enriched brain heart infusion medium; Difco Laboratories, Detroit, Mich.) with 4-mm glass beads intended to reduce aggregation of the nocardial cells (21). The inoculated flasks were shaken at 250 rpm (5.8-cm stroke) for 4 days at 27°C. The mature seed cultures were used as inocula for the inactivation or MIC experiments. Other bacterial inocula were prepared by the method previously described (21).MIC determination. The MIC, defined as the lowest drug concentration causing complete inhibition of visible growth, was determined by an agar dilution method using MuellerHinton II agar medium to give final concentrations from 0.39 to 400 ,ug/ml. Drug-free plates were included as a bacterial growth control. The inoculum size of a test organism was adjusted to 107 CFU/ml for Nocardia spp. and 106 CFU/ml for other bacteria. The plates were spotted with a multipoint inoculator (A 400; Denly Instruments, Ltd., Sussex, England) that delivered 0.005 ml, resulting in a spot inoculum of approximately 5 x 104 CFU.Time course of rifampin inactivation. The mature seed cultures were inoculated at a 10% rate into 100-ml Erlenmeyer flasks containing 50 ml of brain heart infusion medium. Methanol-sterilized rifampin was added aseptically at a final concentration of 20 or 200 ,ug/ml. For determination of the rifampin concentration, 2 ml of the flask cultures was harvested at various time intervals and filtered. The pH of the filtrate was adjusted to 2.0 with 2 N HCl, and the filtrate was then extracted with 2 ml of ethyl acetate. After concentration of the extract in vacuo to dryness, 100 ,ul of methanol was added and 50 ,ul of the mixture was tested for antibacterial activity. The rifampin concentration was measured by the size of the inhibition zone on a lawn of Bacillus subtilis PCI 219 grown on nutrient agar (Difco) (15). Inactivation products were monitored by thin-layer chromatography (TLC) using CHCl3-MeOH (4:1) as a developing solvent. Although rifampin or its inactivation products were easily detected by their characteristic reddish brown spots on untreated TLC plates, the inactivation products were usually monitored additionally by a dual-wavelength TLC scanner (CS-91OM; Shimadzu Seisakujyo, Tokyo, Japan) at 238 nm. Growth was determined by measuring the dry weight of mycelia: specifically, 5 ml of the culture was harvested at 1313

Ustiloxin F, a microtubule inhibitor, was isolated as a minor metabolite of Ustilaginoidea virens. The structure was determined from the spectral data and by chemical interrelation to ustiloxin B through reductive removal of the sulfoxide-containing side chain of ustiloxin B to give ustiloxin F. Ustiloxin F inhibited microtubule assembly with