Influence of amino acid side-chain modification on the uptake system for beta-lactam antibiotics and dipeptides from rabbit small intestine.

The influence of chemical modification of functional amino acid side-chains in proteins on the H(+)-dependent uptake system for orally active alpha-amino-beta-lactam antibiotics and small peptides was investigated in brush-border membrane vesicles from rabbit small intestine. Neither a modification of cysteine residues by HgCl2, NEM, DTNB or PHMB and of vicinal thiol groups by PAO nor a modification of disulfide bonds by DTT showed any inhibition on the uptake of cephalexin, a substrate of the intestinal peptide transporter. In contrast, the Na(+)-dependent uptake systems for D-glucose and L-alanine were greatly inhibited by the thiol-modifying agents. With reagents for hydroxyl groups, carboxyl groups or arginine the transport activity for beta-lactam antibiotics also remained unchanged, whereas the uptake of D-glucose and L-alanine was inhibited by the carboxyl specific reagent DCCD. A modification of tyrosine residues with N-acetylimidazole inhibited the peptide transport system and did not affect the uptake systems for D-glucose and L-alanine. The involvement of histidine residues in the transport of orally active alpha-amino-beta-lactam antibiotics and small peptides (Kramer, W. et al. (1988) Biochim. Biophys. Acta 943, 288-296) was further substantiated by photoaffinity labeling studies using a new photoreactive derivative of the orally active cephalosporin cephalexin, 3-[phenyl-4-3H]azidocephalexin, which still carries the alpha-amino group being essential for oral activity. 3-Azidocephalexin competitively inhibited the uptake of cephalexin into brush-border membrane vesicles. The photoaffinity labeling of the 127 kDa binding protein for beta-lactam antibiotics with this photoprobe was decreased by the presence of cephalexin, benzylpenicillin or dipeptides. A modification of histidine residues in brush-border membrane vesicles with DEP led to a decreased labeling of the putative peptide transporter of Mr 127,000 compared to controls. This indicates a decrease in the affinity of the peptide transporter for alpha-amino-beta-lactam antibiotics by modification of histidine residues. The data presented demonstrate an involvement of tyrosine and histidine residues in the transport of orally active alpha-amino-beta-lactam antibiotics across the enterocyte brush-border membrane.

Immunomodulation by the new synthetic thiazole derivative tiprotimod. 3rd communication: influence on host resistance to microorganisms, tumors and on experimental immune disorders.

To evaluate the influence of [2-(3-carboxy-1-probylthio)-4-methyl-1,3-thiazole]acetic acid (tiprotimod, HBW 538) on the host defense mechanisms, a number of experimental studies in different animal models were performed. The prophylactic treatment of NMRI mice with tiprotimod significantly prolonged the mean survival time of the animals after intravenous infection with Candida albicans 200/175 and increased the resistance to the fungal infection to 180% in comparison to controls. In vitro the drug showed no direct fungistatic or fungicidal activity. In an experimental model of persistent systemic candidiasis Balb/c mice infected intravenously with Candida albicans were treated with the immunomodulator tiprotimod after the fungal colonization of kidney was manifested (3 days post infection). The treatment of the mice after the infection resulted in a reduction of the infectious load and the abscess formation in kidney as well as in a decrease of numbers of yeasts in the urine. In the syngeneic B16 melanoma tumor model tiprotimod significantly prolonged the medium survival time and reduced the number of visuable metastases in the lungs even when applied after resection of the primary tumor graft. Tiprotimod also beneficially influenced the course of the disease in two murine graft-vs-host models (hemolytic anemia and immune complex glomerulonephritis) which lead to a B cell mediated autoimmune disease with fatal outcome. The application of the drug in the induction phase mitigated the development of the diseases and prevented animals from dying.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunomodulation by the new synthetic thiazole derivative tiprotimod. 2nd communication: immunopharmacological activity.

The thiazole derivative [2-(3-carboxy-1-propylthio)-4-methyl-1,3-thiazole] acetic acid (tiprotimod, HBW 538) a new synthetic immunopotentiator of low molecular weight, has been tested in vivo and ex vivo in various experimental models. Its influence on parameters of macrophage functions, on DTH (delayed type hypersensitivity)-reaction and antibodies to sheep erythrocytes (SRBC), Tetanus toxoid and heatkilled E. coli bacteria in mice, and in the popliteal lymph node assay in rats was investigated. When mice were treated with the test substance i.v., i.p., or p.o. in a dose range from 1-100 mg/kg, a time and dose-dependent stimulation of macrophage activity was observed. The drug was able to enhance the DTH-response against SRBC and to stimulate the humoral immune response against Tetanus toxoid and heat-killed E. coli. In the popliteal lymph node assay, a murine graft-vs-host model, a stimulating effect of the substance was observed when it was administered at the same time of the grafts to rats. These results demonstrate that tiprotimod is a potent immunopotentiator for both humoral and cell mediated immune response in experimental animals.

Immunomodulation by the new synthetic thiazole derivative tiprotimod. 1st communication: synthesis and structure-activity relationships.

A series of carboxyalkylthio-substituted thiazole-carboxylic acids was synthesized and examined for macrophage activation and stimulation of the DTH (delayed type of hypersensitivity)-reaction. The structure-activity relationship in this series of new immunomodulators is discussed. Broadest immunological activity was seen for [2-(3-carboxy-1-propylthio)-4-methyl-1,3-thiazole]acetic acid (tiprotimod, HBW 538) which was selected for further studies.

Cefodizime, an aminothiazolylcephalosporin. V. Synthesis and structure-activity relationships in the cefodizime series.

The synthesis as well as in vitro antibacterial activity and pharmacokinetic behavior of cefodizime (HR 221, 1a), its analogs and derivatives is described. In this comparison, cefodizime stands out for its balance between its high antibacterial activity, prolonged elimination half-life and high AUC in mice and dogs.

HR 810, a new parenteral cephalosporin with a broad antibacterial spectrum.

3-[(2,3-Cyclopenteno-1-pyridinium)-methyl]-7-[2-syn-methoximino-2-(2-aminothiazol-4-yl)-acetamido]-ceph-3-em-4-carboxylate (HR 810) is a new cephalosporin derivative with an extremely broad antimicrobial spectrum. It is active against all bacterial species of clinical relevance, including strains which are frequently resistant towards cephalosporins of the third generation.

10-Hydroxy-3,4-dihydroacridine-1,9(2H,10H)-diones, a new group of malaricidal and coccidiostatic compounds.

2-Nitrobenzaldehydes and 1,3-cyclohexanediones condense in a mixture of hydrochloric acid and glacial acetic acid to 10-hydroxy-3,4-dihydroacridine-1,9(2H,10H)-diones. Many compounds of this group reveal a pronounced coccidiostatic and malaricidal effect in vivo even against drug-resistant malaria parasites. Synthesis and chemotherapeutic results as well as structure-activity relationships are described.