Rifampicin-induced suppression of antitumor immunity

Early Detection of Acute Drug-Induced Liver Injury in Mice by Noninvasive Near-Infrared Fluorescence Imaging

Hepatocellular and cholestatic forms of drug-induced liver injury (DILI) are major reasons for late-stage termination of small-molecule drug discovery research projects. Biochemical serum markers are limited in their ability to sensitively and specifically detect both of these common DILI forms in preclinical models, and tissue-specific approaches to assessing this are labor intensive, requiring extensive animal dosing, tissue preparation, and pathology assessment. In vivo fluorescent imaging offers noninvasive detection of biologic changes detected directly in the livers of living animals. Three different near-infrared fluorescent imaging probes, specific for cell death (Annexin-Vivo 750), matrix metalloproteases (MMPSense 750 FAST), and transferrin receptor (Transferrin-Vivo 750) were used to measure the effects of single bolus intraperitoneal doses of four different chemical agents known to induce liver injury. Hepatocellular injury–inducing agents, thioacetamide and acetaminophen, showed optimal injury detection with probe injection at 18–24 hours, the liver cholestasis-inducing drug rifampicin required early probe injection (2 hours), and chlorpromazine, which induces mixed hepatocellular/cholestatic injury, showed injury with both early and late injection. Different patterns of liver responses were seen among these different imaging probes, and no one probe detected injury by all four compounds. By using a cocktail of these three near-infrared fluorescent imaging probes, all labeled with 750-nm fluorophores, each of the four different DILI agents induced comparable tissue injury within the liver region, as assessed by epifluorescence imaging. A strategy of probe cocktail injection in separate cohorts at 2 hours and at 20–24 hours allowed the effective detection of drugs with either early- or late-onset injury.

Anti-inflammatory activity of ansamycins

Inflammation represents a complex biologic and biochemical process involving cells of the immune system and a plethora of biologic mediators in response to mechanical, chemical or infectious injuries. When mobilization of effector cells and molecules becomes excessive, the beneficial aspect of this response--to limit damage and promote healing, can be overriden, resulting in host-cell and tissue dysfunction. Based on the hypothesis that chronic infections underly some inflammatory diseases, antibacterial therapy has long been assessed in various inflammatory settings. Recently, the anti-inflammatory activity of some antibacterial agents has also been suspected. Of these duel-action drugs, ansamycins represent an interesting family. Although their therapeutic use is restricted to potentially infectious inflammatory diseases, many experimental data suggest that these drugs also possess direct inhibitory activity on some crucial proinflammatory effectors. To date, the potent antimycobacterial activity of the therapeutically useful ansamycins precludes their widespread use in inflammatory diseases. However, biosynthetic manipulation remains an attractive route for the generation of pharmacologically useful analogs.

Microflora-associated defense stimulating factors

Mucosal surfaces are habitats for the physiological microflora and are closely related to the mucosal immune compartment (mucosa-associated lymphoid tissue, MALT). Recently, considerable evidence has accumulated showing that various members of the physiological microflora liberate low molecular weight substances which, apparently, are essential for the adequate immune response of the host. Antibiotic decontamination (e.g. of the BALB/c mouse gastrointestinal tract) results in a lack of generation of immunopriming microbial substances leading to immunosuppression. Biochemical analysis of the microbial substances revealed reproducible chromatographic fractions which selectively influence maturation, proliferation and activation of mononuclear immune cells.

Influence of 12 antibiotics on antitumor immunity in BALB/c-mice

The effects of 7 days' chemotherapy with penicillin G, piperacillin, mezlocillin, cephalothin, cefamandole, cefotaxime, gentamicin, amikacin, streptomycin, rifampicin, doxycycline, and clindamycin on local tumor growth and metastatic lung colonization were studied in an experimental tumor model (BALB/c-mouse-sarcoma L-1). The antibiotic dosages administered to mice were calculated on a body weight basis from doses recommended for human therapy. Except for mezlocillin, piperacillin, rifampicin and doxycycline, antibiotic treatment did not significantly influence local tumor growth, lung colonization and immune functions. Whereas mezlocillin exerted positive (tumor suppressive) or negative (tumor promoting) effects depending on the chemotherapy schedule, tumor growth and spread were significantly increased independent of the timing scheme after rifampicin or doxycycline treatment. Since certain immune functions (delayed type hypersensitivity; proliferation of spleen lymphocytes) were significantly suppressed after administration of mezlocillin, rifampicin and doxycycline, a correlation between antimicrobial chemotherapy and tumor progression may be possible.

Effects of cefodizime and cefotaxime on cellular and humoral immune responses

Cefodizime is a new cephalosporin antibiotic which has shown some remarkable immunomodulating activities. To mimic possible immunopharmacological effects of prolonged chemotherapy in vivo, we investigated the influence of a seven-day treatment with cefodizime on cellular and humoral parameters of the immune system in BALB/c mice. The dosages (0.4, 0.8 and 1.8 mg cefodizime per day) were calculated on a per kg bodyweight basis according to therapy recommendations for humans. Delayed type hypersensitivity (oxazolone test) as well as the production of IgM and IgG antibodies (direct and indirect plaque forming test) were investigated in BALB/c mice. Leukocyte and monocyte activities were measured using human cells. The results are discussed using cefotaxime as comparable reference drug.

Additive interaction between tamoxifen and rifampicin in human biliary tract carcinoma cells

A novel two-drug combination of tamoxifen and rifampicin has been investigated for the treatment of biliary tract-associated malignancies. Their effects, alone and in combination, on human tumour cells were studied using two pancreatic carcinoma cell lines. MIA PaCa-2 and AsPC-1, and a gall bladder carcinoma cell line, G-415. Inhibition of growth was used as an endpoint. The cells differed in sensitivity to equimolar doses of the two drugs given as single agents. Combined doses of rifampicin and tamoxifen resulted in growth inhibition to an extent that was suggestive of additive or synergistic drug effects. More detailed analysis was carried out, involving the production of an 'envelope of additivity' for each cell line. An additive effect of drug combination was shown to occur in all three cell lines, thus providing a basis for use of this novel two-drug combination in the treatment of biliary tract-associated malignancies.

Antibiotic treatment, intestinal aerobic microflora and experimental sarcoma L-1 growth in Balb/c-mice

The present paper deals with the influence of a 10 days treatment with mezlocillin, piperacillin, cefotaxime, clindamycin or gentamicin on the endogenous intestinal microflora of Balb/c-mice and on the local growth of sarcoma L-1 tumor. Clindamycin and gentamicin demonstrated no influence, whereas cefotaxime and piperacillin caused the eradication of gram-negative resp. gram-positive bacteria but these antibiotics didn't produce a growth inhibition of local L-1 sarcoma tumor. The oral or parenteral application of mezlocillin (a 3 days treatment was sufficient) eradicated the complete aerobic and anaerobic intestinal microflora. This effect was significantly correlated with an increase of the cecum weight and the inhibition of local tumor growth. Possible mechanisms of these effects are discussed.

Antibiotics and immunomodulation: effects of cefotaxime, amikacin, mezlocillin, piperacillin and clindamycin

The effects of 7 days' chemotherapy on the humoral and cellular parameters of the host immune system are described. In Balb/c mice the effects of cefotaxime, amikacin, mezlocillin, piperacillin and clindamycin were examined. The delayed-type hypersensitivity reaction, as well as the IgM and IgG responses, were suppressed by four of the five drugs tested: cefotaxime, amikacin, mezlocillin and piperacillin. One to two weeks after completion of chemotherapy with cefotaxime and amikacin, these parameters returned to normal values, whereas the mezlocillin- or piperacillin-modified reactions were still suppressed after 20 days. The concanavalin A and lipopolysaccharide-induced proliferative activities of mouse spleen cells were suppressed, especially by mezlocillin. The possible consequences of the immunomodulating effects of antibiotics for antimicrobial chemotherapy are discussed.