Tissue pharmacokinetics, inhibition of DNA synthesis and tumor cell kill after high-dose methotrexate in murine tumor models.
(1/4505)
In Sarcoma 180 and L1210 ascites tumor models, the initial rate of methotrexate accumulation in tumor cells in the peritoneal cavity and in small intestine (intracellularly) after s.c. doses up to 800 mg/kg, showed saturation kinetics. These results and the fact that initial uptake in these tissues within this dosage range was inhibited to the expected relative extent by the simultaneous administration of leucovorin suggest that carrier mediation and not passive diffusion is the major route of drug entry at these extremely high doses. Maximum accumulation of intracellular drug occurred within 2 hr and reached much higher levels in small intestine than in tumor cells at the higher dosages. At a 3-mg/kg dose of methotrexate s.c., intracellular exchangeable drug levels persisted more than four times longer in L1210 cells than in small intestine, but differences in persistence (L1210 cell versus gut) diminished markedly with increasing dosage. At 96 mg/kg, the difference in persistence was less than 2-fold. In small intestine and L1210 cells, theduration of inhibition of DNA synthesis at different dosages correlated with the extent to which exchangeable drug was retained. Toxic deaths occurred when inhibition in small intestine lasted longer than 25 to 30 hr. Recovery of synthesis in small intestine and L1210 cells occurred synchronously and only below dosages of 400 mg/kg. Within 24 hr after dosages of greater than 24 mg/kg, the rate of tumor cell loss increased to a point characterized by a single exponential (t1/2=8.5 hr). The total cell loss, but not the rate of cell loss, was dose dependent. (+info)
Interleukin-18 binding protein: a novel modulator of the Th1 cytokine response.
(2/4505)
An interleukin-18 binding protein (IL-18BP) was purified from urine by chromatography on IL-18 beads, sequenced, cloned, and expressed in COS7 cells. IL-18BP abolished IL-18 induction of interferon-gamma (IFNgamma), IL-8, and activation of NF-kappaB in vitro. Administration of IL-18BP to mice abrogated circulating IFNgamma following LPS. Thus, IL-18BP functions as an inhibitor of the early Th1 cytokine response. IL-18BP is constitutively expressed in the spleen, belongs to the immunoglobulin superfamily, and has limited homology to the IL-1 type II receptor. Its gene was localized on human chromosome 11q13, and no exon coding for a transmembrane domain was found in an 8.3 kb genomic sequence. Several Poxviruses encode putative proteins highly homologous to IL-18BP, suggesting that viral products may attenuate IL-18 and interfere with the cytotoxic T cell response. (+info)
Cardiomegaly in the juvenile visceral steatosis (JVS) mouse is reduced with acute elevation of heart short-chain acyl-carnitine level after L-carnitine injection.
(3/4505)
The long-term administration of L-carnitine was very effective in preventing cardiomegaly in juvenile visceral steatosis (JVS) mice, which was confirmed by heart weight as well as the lipid contents in heart tissue. After i.p. injection of L-carnitine, the concentration of free carnitine in heart remained constant, although serum free carnitine level increased up to 80-fold. On the other hand, a significant increase in short-chain acyl-carnitine level in heart was observed. These results suggest that increased levels of short-chain acyl-carnitine, not free carnitine, might be a key compound in the protective effect of L-carnitine administration in JVS mice. (+info)
Neuroprotection of the developing brain by systemic administration of vasoactive intestinal peptide derivatives.
(4/4505)
Periventricular leukomalacia (PVL), a necrotic and often cystic lesion of the cerebral white matter occurring in very premature babies, is the leading cause of cerebral palsy in this population. Increased glutamate release and the excitotoxic cascade thus triggered may be critical factors in the development of PVL. The glutamatergic analog ibotenate injected intracerebrally into newborn mice produces white matter cysts that mimic human PVL. Concomitant injection of vasoactive intestinal peptide (VIP), a trophic factor, protects the white matter against excitotoxic lesions. The goal of the present study was to assess the protective properties of systemically injected VIP analogs against ibotenate-induced excitotoxic white matter lesions in newborn mice. VIP analogs were selected on the basis of their low susceptibility to endopeptidases and their potential ability to cross biological membranes. RO-25-1553, a long-lasting cyclic VIP analog, and stearyl-norleucine-VIP, a fatty derivative of VIP, reduced ibotenate-induced white matter cysts by up to 87% and 84%, respectively, when injected i.p. immediately after ibotenate. By comparison, i.p. coadministration of VIP and ibotenate was not protective against the excitotoxic insult. Furthermore, RO-25-1553 and stearyl-norleucine-VIP still induced significant neuroprotection of the developing white matter when injected systemically 8 and 12 h, respectively, after ibotenate, establishing these peptides as therapeutic agents in this murine model. VIP analogs may have therapeutic potential in human premature babies at high risk for PVL. (+info)
Divergent effects of intracerebroventricular and peripheral leptin administration on feeding and hypothalamic neuropeptide Y in lean and obese (fa/fa) Zucker rats.
(5/4505)
Leptin inhibits feeding and decreases body weight. It may act partly by inhibiting hypothalamic neurons that express neuropeptide Y, a powerful inducer of feeding and obesity. These neuropeptide Y neurons express the Ob-Rb leptin receptor and are overactive in the fatty (fa/fa) Zucker rat. The fa mutation affects the extracellular domain of the leptin receptor, but its impact on leptin action and neuropeptide Y neuronal activity is not fully known. We compared the effects of three doses of leptin given intracerebroventricularly and three doses of leptin injected intraperitoneally on food intake and hypothalamic neuropeptide Y mRNA, in lean and fatty Zucker rats. In lean rats, 4-h food intake was reduced in a dose-related fashion (P<0.01) by all intracerebroventricular leptin doses and by intraperitoneal doses of 300 and 600 microg/kg. Neuropeptide Y mRNA levels were reduced by 28% and 21% after the highest intracerebroventricular and intraperitoneal doses respectively (P<0. 01 for both). In fatty rats, only the highest intracerebroventricular leptin dose reduced food intake (by 22%; P<0. 01). Neuropeptide Y mRNA levels were 100% higher in fatty rats than in lean animals, and were reduced by 18% (P<0.01) after the highest intracerebroventricular leptin dose. Intraperitoneal injection had no effect on food intake and neuropeptide Y mRNA. The fa/fa Zucker rat is therefore less sensitive to leptin given intracerebroventricularly and particularly intraperitoneally, suggesting that the fa mutation interferes both with leptin's direct effects on neurons and its transport into the central nervous system. Obesity in the fa/fa Zucker rat may be partly due to the inability of leptin to inhibit hypothalamic neuropeptide Y neurons. (+info)
Receptor clearance obscures the magnitude of granulocyte-macrophage colony-stimulating factor responses in mice to endotoxin or local infections.
(6/4505)
Marrow cells from mice lacking high-affinity receptors for granulocyte-macrophage colony-stimulating factor (GM-CSF; betac-/- mice) were shown to bind and internalize much less GM-CSF than cells from normal (betac+/+) mice. betac-/- mice were used to determine the effect of negligible receptor-mediated clearance on detectible GM-CSF responses to the intravenous injection of endotoxin or the intraperitoneal injection of casein plus microorganisms. Unlike the minor serum GM-CSF responses to endotoxin seen in betac+/+ mice, serum GM-CSF levels rose 30-fold to 9 ng/mL in betac-/- mice even though loss of GM-CSF in the urine was greater than in betac+/+ mice. Organs from betac-/- and betac+/+ mice had a similar capacity to produce GM-CSF in vitro, as did peritoneal cells from both types of mice when challenged in vitro by casein. However, when casein was injected intraperitoneally, betac-/- mice developed higher and more sustained levels of GM-CSF than did betac+/+ mice. The data indicated that receptor-dependent removal of GM-CSF masks the magnitude of GM-CSF responses to endotoxin and local infections. Because of this phenomenon, serum GM-CSF concentrations can be a misleading index of the occurrence or nonoccurrence of GM-CSF responses to infections. (+info)
Systemic administration of interleukin 2 enhances the therapeutic efficacy of dendritic cell-based tumor vaccines.
(7/4505)
We have reported previously that murine bone marrow-derived dendritic cells (DC) pulsed with whole tumor lysates can mediate potent antitumor immune responses both in vitro and in vivo. Because successful therapy was dependent on host immune T cells, we have now evaluated whether the systemic administration of the T cell stimulatory/growth promoting cytokine interleukin-2 (IL-2) could enhance tumor lysate-pulsed DC-based immunizations to further promote protective immunity toward, and therapeutic rejection of, syngeneic murine tumors. In three separate approaches using a weakly immunogenic sarcoma (MCA-207), the systemic administration of nontoxic doses of recombinant IL-2 (20,000 and 40,000 IU/dose) was capable of mediating significant increases in the potency of DC-based immunizations. IL-2 could augment the efficacy of tumor lysate-pulsed DC to induce protective immunity to lethal tumor challenge as well as enhance splenic cytotoxic T lymphocyte activity and interferon-gamma production in these treated mice. Moreover, treatment with the combination of tumor lysate-pulsed DC and IL-2 could also mediate regressions of established pulmonary 3-day micrometastases and 7-day macrometastases as well as established 14- and 28-day s.c. tumors, leading to either significant cure rates or prolongation in overall survival. Collectively, these findings show that nontoxic doses of recombinant IL-2 can potentiate the antitumor effects of tumor lysate-pulsed DC in vivo and provide preclinical rationale for the use of IL-2 in DC-based vaccine strategies in patients with advanced cancer. (+info)
A different approach to treatment of phenylketonuria: phenylalanine degradation with recombinant phenylalanine ammonia lyase.
(8/4505)
Phenylketonuria (PKU), with its associated hyperphenylalaninemia (HPA) and mental retardation, is a classic genetic disease and the first to have an identified chemical cause of impaired cognitive development. Treatment from birth with a low phenylalanine diet largely prevents the deviant cognitive phenotype by ameliorating HPA and is recognized as one of the first effective treatments of a genetic disease. However, compliance with dietary treatment is difficult and when it is for life, as now recommended by an internationally used set of guidelines, is probably unrealistic. Herein we describe experiments on a mouse model using another modality for treatment of PKU compatible with better compliance using ancillary phenylalanine ammonia lyase (PAL, EC 4.3.1.5) to degrade phenylalanine, the harmful nutrient in PKU; in this treatment, PAL acts as a substitute for the enzyme phenylalanine monooxygenase (EC 1.14.16.1), which is deficient in PKU. PAL, a robust enzyme without need for a cofactor, converts phenylalanine to trans-cinnamic acid, a harmless metabolite. We describe (i) an efficient recombinant approach to produce PAL enzyme, (ii) testing of PAL in orthologous N-ethyl-N'-nitrosourea (ENU) mutant mouse strains with HPA, and (iii) proofs of principle (PAL reduces HPA)-both pharmacologic (with a clear dose-response effect vs. HPA after PAL injection) and physiologic (protected enteral PAL is significantly effective vs. HPA). These findings open another way to facilitate treatment of this classic genetic disease. (+info)