Levels Of ADR Research Articles

Aging and deffective lymphoid cell activation

Activation of lymphocytes for proliferation is a crucial process in the immune response. Age-related deficiencies in this cellular response strongly correlate with deficiencies in the immune system response, with concomitant increase in disease severity and mortality. Defects associated with the transmission of the initial activation signal and with IL-2 production contribute to the depressed response, but defects in the IL-2 response mechanism also play important roles. A major factor in this area is the inability of the nuclei of these cells to respond to the intracellular factor ADR, which plays a crucial role in the initiation of DNA replication. These cells produce normal levels of ADR; thus, either the nuclei cannot bind ADR in a productive manner or the defect lies beyond the point of ADR binding, perhaps in one of the other proteins of the initiation complex. An interesting contrast to the age-related failure of nuclei to respond to ADR is the failure of neoplastic nuclei to respond to the ADR inhibitor. This inhibitor, found in the cytoplasm of quiescent cells, suppresses both the activation of quiescent nuclei by ADR and the ongoing DNA synthesis in isolated nuclei from activated cells. Nuclei from spontaneous proliferating cell lines were not affected by this inhibitor, which may be an important factor in the uncontrolled growth seen in neoplastic cells. The investigation of ADR has given hints that perhaps two of the fundamental questions in biology, namely why some cells don't proliferate and why some others won't stop proliferating, may be two sides of the same coin.

Intracellular mechanisms of lymphoid cell activation

Activation of lymphocytes for proliferation is associated with the appearance of an intracellular factor (ADR) that can induce DNA synthesis in isolated quiescent nuclei. ADR plays a role in the sequence of intracellular events leading to activation for IL-2-mediated proliferation. Because of the nature of the defining assay, the locus of ADR action appears to be near the terminal end of the transduction pathway. Interestingly, although lymphocytes from aged individuals respond poorly to proliferative stimuli, they appear to produce normal to above-normal levels of ADR. In contrast, their nuclei are only poorly responsive to stimulation by ADR. Preparations rich in ADR activity have proteolytic activity as well. In addition, aprotinin, as well as a variety of other protease inhibitors, suppresses ADR-induced DNA synthesis in a dose-dependent manner. ADR activity can be removed from active extracts by absorption with aprotinin-conjugated agarose beads, and can be removed from the beads by elution at pH 5.0. This latter suggests that ADR itself is a protease. However, its endogenous substrate is not yet known. We have also detected an inhibitor of ADR activity in the cytoplasm of resting lymphocytes. This is a heat-stable protein of approximately 60,000 Da. In addition to suppressing the interaction of ADR with quiescent nuclei, the inhibitor can suppress DNA synthetic activity of replicative nuclei isolated from mitogen-activated lymphocytes. Interestingly, these preparations had little or no activity on replicative nuclei derived from several neoplastic cell lines. The resistance of tumor cell nuclei to spontaneously occurring cytoplasmic inhibitory factors such as the one described here may provide one explanation for the loss of growth control in neoplastic cells.

Systemic thermochemotherapy: Toxicity and plasma pharmacokinetics of methotrexate and doxorubicin

Chemotherapy administered during systemic hyperthermia is more tumoricidal than either modality used alone. The purpose of this study was to evaluate plasma drug pharmacokinetics and host toxicity when methotrexate (MTX) or doxorubicin (adriamycin—ADR) was given at 37 or 43°C. Eight dogs were heated to 43°C for 1 hr without chemotherapy; eight dogs received MTX (5 mg/kg) and four dogs received ADR (2 mg/kg) intravenously as a constant infusion at 43 or 37°C. Blood samples were obtained at 0, 1, 2, 24, and 48 hr. Mean plasma MTX levels were not significantly different at 1, 2, and 6 hours in 43 and 37°C dogs, but at 24 and 48 hr mean plasma MTX levels were significantly elevated in heated (43°C) dogs compared with sham-heated (37°C) dogs. Plasma MTX concentration multiplied by time (area under curve) was 131 g · hr/liter in 43°C dogs compared with 73 g · hr/liter in 37°C dogs ( P < 0.001). Vomiting and bloody diarrhea lasted an average of 4 days in heated control dogs (no drugs) 4 days in 37°C dogs, and 5 to 7 days in 43°C MTX dogs. Mean plasma ADR levels were similar in 37 and 43°C dogs at all time intervals. Vomiting and bloody diarrhea lasted at least 7 days in 43°C dogs compared with only 1 day in 37°C dogs treated with ADR. MTX administered during systemic hyperthermia at 43°C resulted in prolonged gastrointestinal toxicity, which correlated with elevated mean plasma MTX levels at 24 and 48 hr. Mean plasma ADR levels were unaffected by systemic hyperthermia, but gastrointestinal toxicity was increased when systemic hyperthermia was combined with administration of ADR.