The Plasmin Heavy Chain - Urokinase Conjugate: A Specific Thrombolytic Agent

Low molecular weight urokinase (LMW-UK) was coupled to the heavy chain of plasmin to make it able to bind to fibrin. The purified conjugate (PHC-UK conjugate), which consisted of equimolar concentrations of each starting material had a molecular weight of 93,600, bound tightly to fibrin-monomer-Sepharose and was not washed off with 1 M NaCl, but was eluted specifically with s-amino caproic acid. The conjugate showed higher fibrinolytic activity than HMW-UK. A control conjugate prepared by coupling human serum albumin to LMW-UK (HSA-UK conjugate) showed the same fibrinolytic activity as HMW-UK. The half-lives of these two conjugates in rabbits were about 3 times that of HMW-UK. In an experimental pulmonary embolism model in rabbits, the PHC-UK conjugate showed about 10 times higher thrombolytic activity than HMW-UK, while the HSA-UK conjugate showed similar thrombolytic activity as HMW-UK, and moreover caused severe systemic fibrinogen breakdown. Thus the significant increase in thrombolytic activity after injection of PHC-UK conjugate into rabbits may be due to its newly acquired fibrin binding activity, and not to increase in its half-life. It is concluded that the PHC-UK conjugate may be useful in treatment of thrombosis.

Increased metallothionein in mouse liver, kidneys, and duodenum during lactation

Lactation-induced increases in cadmium absorption and retention have been demonstrated in mid-lactating mice, but no systematic measurements of endogenous metal-binding protein concentrations during lactation have been reported. Using Cd/hemoglobin radioassay, this study detected significant increases in metallothionein (MT) concentrations in liver (4-fold), kidneys (2-fold), and duodenum (2-fold), but not jejunum, of mouse dams on days 13 and 20 of lactation. These increases occurred in the absence of cadmium exposure and were specific to the lactation period; dams 5 days after weaning showed MT levels that were similar to those of nonpregnant (NP) mice. Similarly, Northern blot analyses of livers from lactating mice demonstrated that MT mRNA concentrations in maternal liver during mid-lactation were 6-fold higher than those observed 5 days after pups were weaned. Gel filtration of final supernatants from the Cd/hemoglobin assay confirmed that the Cd-binding molecule induced during lactation was indeed metallothionein. In addition, chromatographic analyses of cytosols from tissues taken from dams administered small amounts of Cd (66 ng/mouse) showed that the trace amounts of Cd absorbed through the maternal gastrointestinal tract during mid-lactation were also bound to the MT. These results indicate MT induction in mouse dams occurs as a physiological consequence of lactation, requiring no external stimulus. This induced MT participates in binding low levels of dietary cadmium consumed by the dam. During lactation, elevated maternal MT may affect pathways for essential trace metals as well as sequester toxic metals harmful to the neonate. Multiparous humans may have increased risk of accumulating environmental Cd.

Effect of anticomplement agent K76 COOH on hamster-to-rat and guinea pig-to-rat heart xenotransplantation

In normal rats, the xenobiotic K76 inhibited the C5 and probably the C2 and C3 steps of complement and effectively depressed classical complement pathway activity, alternative complement pathway activity, and the C3 complement component during and well beyond the drug's 3-hr half-life. It was tested alone and with intramuscular tacrolimus (TAC) and/or intragastric cyclophosphamide (CP) in rat recipients of heterotopic hearts from guinea pig (discordant) and hamster (concordant) donors. Single prevascularization doses of 100 and 200 mg/kg increased the median survival time of guinea pig hearts from 0.17 hr in untreated controls to 1.7 hr and 10.2 hr, respectively; with repeated injections of the 200-mg dose every 9-12 hr, graft survival time was increased to 18.1 hr. Pretreatment of guinea pig heart recipients for 10 days with TAC and CP, with or without perioperative splenectomy or infusion of donor bone marrow, further increased median graft survival time to 24 hr. Among the guinea pig recipients, the majority of treated animals died with a beating heart from respiratory failure that was ascribed to anaphylatoxins. Hamster heart survival also was increased with monotherapy using 200 mg/kg b.i.d. i.v. K76 (limited by protocol to 6 days), but only from 3 to 4 days. Survival was prolonged to 7 days with the addition of K76 of intragastric CP at 5 mg/kg per day begun 1 day before operation (to a limit of 9 days); it was prolonged to 4.5 days with the addition of intramuscular TAC at 2 mg/kg per day beginning on the day of transplantation and continued indefinitely. In contrast to the limited efficacy of the single drugs, or any two drugs in combination, the three drugs together (K76, CP, and TAC) in the same dose schedules increased median graft survival time to 61 days. Antihamster antibodies rapidly increased during the first 5 days after transplantation, and plateaued at an abnormal level in animals with long graft survival times without immediate humoral rejection. However, rejection could not be reliably prevented, and was present even in most of the xenografts recovered from most of the animals dying (usually from infection) with a beating heart. Thus, although effective complement inhibition with K76 was achieved in both guinea pig- and hamster-to-rat heart transplant models, the results suggest that effective interruption of the complement cascade will have a limited role, if any, in the induction of xenograft acceptance.

Effects of K-76COOH (MX-1) on immune response: induction of suppressor T-cells by MX-1

K-76COOH (MX-1), isolated from the cultured supernatant of a species of fungi imperfecti, Stachybotrys complement nov. sp. K-76, is an inhibitor of the complement component, C5. The effects of MX-1 on various immune responses were investigated. MX-1 enhanced the response of spleen cells to PHA and LPS: MX-1 at 0.01-250 micrograms/ml for PHA and at 10-250 micrograms/ml for LPS. In contrast, it inhibited the response to Con A: MX-1 at 0.01-500 micrograms/ml for spleen cells and at 100-500 micrograms/ml for thymocytes. MX-1 and IL-1 synergistically acted to enhance the Con A response of spleen and thymus cells from which accessory cells and Ia-positive cells had been removed by passing through Sephadex G-10 columns and treating with anti-Ia monoclonal antibody plus complement. T-cells pretreated with MX-1, IL-1 and Con A for 3 days suppressed not only the response of B-cells to LPS but also the production of anti-SRBC antibodies. In addition, MX-1 was found to increase CD8+ T-cells. These results suggest that MX-1 acts on T-cells to induce suppressor T-cells.

The plasmin heavy chain-urokinase conjugate: a specific thrombolytic agent

Low molecular weight urokinase (LMW-UK) was coupled to the heavy chain of plasmin to make it able to bind to fibrin. The purified conjugate (PHC-UK conjugate), which consisted of equimolar concentrations of each starting material had a molecular weight of 93,600, bound tightly to fibrin-monomer-Sepharose and was not washed off with 1 M NaCl, but was eluted specifically with epsilon-amino caproic acid. The conjugate showed higher fibrinolytic activity than HMW-UK. A control conjugate prepared by coupling human serum albumin to LMW-UK (HSA-UK conjugate) showed the same fibrinolytic activity as HMW-UK. The half-lives of these two conjugates in rabbits were about 3 times that of HMW-UK. In an experimental pulmonary embolism model in rabbits, the PHC-UK conjugate showed about 10 times higher thrombolytic activity than HMW-UK, while the HSA-UK conjugate showed similar thrombolytic activity as HMW-UK, and moreover caused severe systemic fibrinogen breakdown. Thus the significant increase in thrombolytic activity after injection of PHC-UK conjugate into rabbits may be due to its newly acquired fibrin binding activity, and not to increase in its half-life. It is concluded that the PHC-UK conjugate may be useful in treatment of thrombosis.

Effects of K-76 monocarboxylic acid, an anticomplementary agent, on various in vivo immunological reactions and on experimental glomerulonephritis

K-76 monocarboxylic acid (K-76 COOH) caused rapid reduction in hemolytic activities of complement and some of its components, especially C5, when injected into guinea pigs or rats. K-76 COOH suppressed Forssman shock in guinea pigs and mice and heterologous passive cutaneous anaphylaxis in guinea pigs. It also reduced the amount of protein excreted in the urine of rats with nephrotoxic nephritis and greatly prolonged the survival of (NZB X NZW) F1 female mice with a spontaneous systemic lupus erythematosus-like disease. The glomeruli of mice treated with K-76 COOH retained almost the normal histological appearance even at 1 year of age. K-76 COOH-treated mice became less sensitive to the infection of Escherichia coli, staphylococcus aureus, or Streptococcus pneumoniae, probably by enhancement of phagocytosis due to inhibition of factor I. K-76 COOH did not have any significant effect on a delayed-type contact skin reaction in mice, or on experimental allergic encephalitis in guinea pigs.

A complement inhibitor produced by Stachybotrys complementi, nov. sp. K-76, a new species of fungi imperfecti

A complement inhibitor, K-76, was isolated and purified from the culture supernatant of a fungus, Stachybotrys complementi, nov. sp. K-76, isolated from soil of Ishigaki Island, Okinawa. K-76 is a sesquiterpene compound and it can be oxidized to a monocarboxylic derivative (K-76 COOH), the sodium salt of which is very soluble and much less toxic than K-76. K-76 and K-76 COOH both inhibited complement activation by either the classical or alternative pathway. They inhibited generation of the factor chemotactic to human polymorphonuclear leukocytes from human serum by aggregated immunoglobulin. When sensitized erythrocytes were treated with complement in the presence of K-76 COOH, the resulting unlysed cells were found to be in the state of EACl, 4b, 2a, 3b. Thus K-76 COOH is considered to block mainly the C5 intermediate step. K-76 COOH did not inhibit any proteases or esterases tested, except when tested at high concentration.

An anticomplementary agent, K-76 monocarboxylic acid: its site and mechanism of inhibition of the complement activation cascade

A monocarboxylic acid derivative (K-76 COOH) of K-76, purified from the culture filtrate of Stachybotrys complement I nov. sp. K-76, inhibits complement (C) activity. Its inhibitory action is mainly on C5 step. It strongly inhibits the generation of EAC1,4b,2a,3b,5b from C5 and EAC1,4b,2a,3b, and accelerates the decay of EAC1,4b,2a,3b,5b. It also causes some inhibition of the reactions of the reactions of C2,C3,C6,C7 and C9 with their respective preceding intermediate cells. It has no effect on the generation of EAC1,4b from C4 and EAC1, or of EAC-8 from C8 and EAC-7, and apparently increases the generation of EAC1,4b from C1 and EAC4b probably by inhibiting transfer or turnover of C1. It does not affect the rate of decay of EAC1,4b,2a or the T max of generation of EAC1,4b,2a, and it inhibits immune adherence only at high concentration. K-76 COOH also strongly inhibits hemolysis through the alternative pathway of C activation by cobra venom factor, but it does not seem to inhibit the early steps of the alternative pathway, because it has little affect on the consumption of C3 or the conversion of beta 1C to beta 1A on treatment of C serum with zymosan. K-76 COOH probably combines with C5 molecules, forming the inactive complexes, or it causes the structural alteration of C5.