ABSTRACT
Three camptothecin-resistant sublines (V79r, IRS-1r and IRS-2r) of V79 cells and their irradiation-sensitive mutants, IRS-1 and IRS-2, were developed by stepwise, continuous exposure to camptothecin (CPT). The degree of resistance varied among these cells. Based on the biochemical characterizations of these resistant cell lines, the mechanisms which could be responsible for the resistance to CPT were proposed to be: (a) a decrease in the intracellular accumulation of CPT with or without alteration of DNA topoisomerase I, (b) a decrease in the amount of DNA topoisomerase I, or (c) a decrease in the sensitivity of DNA topoisomerase I to CPT. The resistant cells which exhibited down-regulation of DNA topoisomerase I were collaterally sensitive to etoposide (VP-16) and its analogue, 4'-demethy-4 beta-(4"-fluoroanilino)-4-desoxypodophyllotoxin, despite the fact that there were equal amounts of DNA topoisomerase II in the parental and in the resistant cell lines. Alternating the usage of CPT and VP-16 for the treatment of cancer is indicated.
Subject(s)
Camptothecin/pharmacology , Lung/drug effects , Animals , Base Sequence , Cell Line/drug effects , Cricetinae , Cricetulus , DNA/isolation & purification , DNA Topoisomerases, Type I/genetics , DNA Topoisomerases, Type I/metabolism , DNA Topoisomerases, Type II/metabolism , Dose-Response Relationship, Drug , Drug Resistance/genetics , Etoposide/analogs & derivatives , Etoposide/pharmacology , Molecular Sequence Data , Podophyllotoxin/pharmacology , RNA, Messenger/analysis , Vincristine/pharmacologyABSTRACT
Tumor necrosis factor (TNF) is an endogenously produced cytokine that plays a critical role in mediating septic shock and multi-organ failure, but previous studies of the role TNF in disease have not examined its role in mucosal disease processes. In an experimental model of acute gonococcal salpingitis, gonococcal infection of human fallopian tube mucosa resulted in increased mucosal production of TNF. Recombinant human TNF-alpha damaged fallopian tube mucosa in a dose-response manner and produced epithelial damage with the same ultrastructural features as those observed in gonococcal infection. Blocking production of TNF during gonococcal infection diminished the extent of damage to fallopian tube mucosa. In addition to mediating systemic disease, such as septic shock, TNF is also produced locally, and can play a critical role in mediating mucosal disease processes, such as acute gonococcal salpingitis.
Subject(s)
Fallopian Tubes/microbiology , Neisseria gonorrhoeae/pathogenicity , Tumor Necrosis Factor-alpha/physiology , Dexamethasone/pharmacology , Fallopian Tubes/metabolism , Fallopian Tubes/ultrastructure , Female , Humans , Models, Biological , Mucous Membrane/microbiology , Mucous Membrane/ultrastructure , Organ Culture Techniques , Tumor Necrosis Factor-alpha/antagonists & inhibitors , Tumor Necrosis Factor-alpha/biosynthesisABSTRACT
The possible effect of human chorionic gonadotropin (hCG) on the mucosal immune response and susceptibility of the fallopian tube mucosa to invasion by Neisseria gonorrhoeae (gonococci) was investigated in the fallopian tube organ culture (FTOC) model. Immunohistochemical and radioreceptor assay techniques showed specific high affinity binding of hCG in vitro to the apices of non-ciliated fallopian tube cells (Kd approximately 10(-9) M). Continuous exposure of the FTOC mucosa to hCG during infection with gonococci resulted in a marked increase (6- to 15-fold) in IgA secretion and significantly reduced gonococcal invasion (invasion score range 0.7 to 1.75) compared to infected control tissue which was not exposed to hCG (invasion score range 2.9 to 4.95, P less than or equal to 0.01). By contrast, exposure of the mucosa to hCG during the 24 h preceding gonococcal infection followed by the removal of hCG from the system at the time of infection resulted in enhanced gonococcal invasion (invasion score range 7.95 to 9.7, P less than 0.001). We conclude that hCG can modulate the mucosal immune response and susceptibility of fallopian tube epithelium to gonococcal invasion.
Subject(s)
Chorionic Gonadotropin/pharmacology , Fallopian Tubes/immunology , Gonorrhea/immunology , Immunoglobulin A/metabolism , Neisseria gonorrhoeae/pathogenicity , Endocytosis/physiology , Fallopian Tubes/microbiology , Female , Humans , Mucous Membrane/immunology , Mucous Membrane/microbiology , Organ Culture Techniques , Radioimmunoassay , Receptors, Gonadotropin/analysisABSTRACT
In contrast to nonpathogenic microorganisms that exist happily in biofilms on various organic and inorganic surfaces, many pathogenic microbes have the additional ability to invade host tissues by inducing their own endocytosis and transport across normally protective barriers. This phenomenon, designated "parasite-directed endocytosis," has been observed with a variety of surfaces (intestinal, genital, nasopharyngeal, and tracheal epithelium) as well as in endothelial cells. The mechanisms involved in invasion may involve a single factor as described for some species of Yersinia, or may require multiple factors as observed in Shigellae. For the majority of pathogens, the molecular mechanisms of invasion are not well understood (e.g., Neisseria gonorrhoeae). Because parasite-directed endocytosis is reminiscent of receptor-mediated endocytosis, it is quite possible that some pathogens engage in biologic mimicry by producing a molecule that resembles a natural host ligand, for which there is a host cell receptor. Such a masquerade may allow some microbes to enter the host's inner sanctum covertly in a manner analogous to the Trojan horse, rather than overtly by destroying the mucosa and entering host tissues directly. Whereas this hypothesis is speculative at present, bacteria that produce molecules resembling insulin, calmodulin, and chorionic gonadotropin have been described.
