Tumor Necrosis Factor Changes Sensitivity of Differentiation of Mouse Leukemia M1 Cells by Lipopolysaccharide

A clone of mouse leukemia M1 cells was induced to differentiate by lipopolysaccharide (LPS) (LPS-sensitive clone) while another clone of the same cells was resistant (LPS-resistant clone). LPS and lipid A preparations from Pseudomonas diminuta and Pseudomonas vesicularis were as active as Escherichia coli LPS in the induction of differentiation of the LPS-sensitive clone. Synthetic lipid A precursor Ia (compound 406), which has no interleukin 1 (IL-1)-inducing activity toward monocytes, had strong differentiation-inducing activity toward the LPS-sensitive clone. The combined treatment of the LPS-sensitive clone with LPS and recombinant tumor necrosis factor (rTNF) did not further increase the degree of differentiation induced by LPS alone. By contrast, the LPS-resistant clone was markedly induced to differentiate by LPS in the presence of rTNF. Combined treatment of the LPS-resistant clone with LPS and other cytokines such as recombinant IL-1α, recombinant granulocyte colony-stimulating factor, and interferon-γ was not effective in inducing marked synergistic differentiation. These results raise the possibility that rTNF changes the sensitivity of M1 cells to induction of differentiation by LPS.     

Relationship between in vitro binding activity and in vivo tumor accumulation of radiolabeled monoclonal antibodies

The relationship between in vitro cell binding and in vivo tumor accumulation of radiolabeled antibodies was studied using 125I- and 111In-labeled monoclonal antibodies to human osteosarcoma, and a human osteosarcoma xenograft (KT005) in nude mice. Three monoclonal antibodies--OST6, OST7, and OST15--raised against human osteosarcoma recognize the same antigen molecule. Although the binding of both 125I- and 111In-labeled OST6 to KT005 cells was higher than that of radiolabeled OST7 in vitro, 125I-labeled OST6 showed a faster clearance from the circulation and a lower accumulation in the transplanted tumor than 125I-labeled OST7. In contrast to the radioiodinated antibodies, the in vivo tumor accumulation of 111In-labeled OST6 was higher, although not significantly, than that of 111In-labeled OST7. OST15 showed the lowest binding in vitro, and its in vivo tumor localization was also lower than the others. The discrepancy in tumor uptake between OST6 and OST7 labeled with either 125I or 111In may have been a result of differing blood clearance. These results suggest that binding studies can be used to exclude from in vivo use those antibodies which show very poor binding in vitro, while in vivo serum clearance may be a better test for choosing antibodies with similar binding.     

Cholecystokinin antagonism by anthramycin, a benzodiazepine antibiotic, in the central nervous system in mice

Anthramycin (ATM) which is a product of some streptomyces micro-organisms was shown to antagonize the central effects of cholecystokinin (CCK) such as antinociception and satiety and to displace CCK bound to the slices from the brains of mice. Sulfated octapeptide CCK (CCK8) was administered intracisternally to mice at doses of 1 microgram/mouse for inducing antinociception and 200 ng/mouse for satiety. ATM was administered intraperitoneally to mice at doses such as 0.3 and 0.5 mg/kg. CCK8-induced antinociception and satiety were significantly reversed by ATM in those doses. [125I]CCK8 binding to the brain slices was observed autoradiographically. The autoradiograms from the slices were converted to false color images by using a microcomputer. The radioactivity in the autoradiograms was expressed by color spectra in the false color images. Comparison of the binding of [125I]CCK8 to the brain slices in the presence and the absence of ATM revealed that ATM (10(-6) M) clearly displaced the CCK8 binding in the various regions, especially in the cortex, of the brain. These findings suggest that ATM acts as an potent antagonist of CCK in the central nervous system in mice.     

Suppression of c-myc mRNA expression by steroid hormones in HTLV-I-infected T-cell line, KH-2

The effects of 1,25(OH)2D3 and dexamethasone on cellular proliferation and gene expression of the HTLV-I-infected T-cell line, KH-2, established from a patient with adult T-cell leukemia, endemic in the south-west Japanese islands and the Caribbean, were examined. KH-2 cells are integrated by HTLV-I proviral DNA and expressed mRNA for c-myc, IL-2 receptor alpha-chain (IL-2R alpha), and T-cell receptor beta-chain (TCR beta) while it did not express IL-2 mRNA. 1,25(OH)2D3 and dexamethasone did not suppress the mRNA levels of HTLV-I, IL-2R alpha or TCR beta but reduced the c-myc mRNA level. The reduction of c-myc mRNA level was marked in 1,25(OH)2D3-treated cells but relatively weak in dexamethasone-treated cells. This inhibitory effect of the steroid hormones correlated with the inhibition of KH-2 cell proliferation.     

Oxygen toxicity in rats. Varied effect of dexamethasone treatment depending on duration of hyperoxia

The low rate of survival in patients with the adult respiratory distress syndrome (ARDS) may in part reflect a failure to consider that the lung's response to applied therapies may not be constant throughout the course of illness. To test this notion, we used hyperoxia to produce progressive lung damage in rats and administered dexamethasone at different times during O2 exposures of various lengths. Dexamethasone improved survival and decreased lung damage if given when exposure to hyperoxia was to be soon terminated; pulmonary inflammation was marked at the time at which the administration of dexamethasone led to increased survival. Dexamethasone worsened lung damage and diminished survival when given early during exposure to hyperoxia; inflammation was minimal early in the course of exposure to hyperoxia. These findings point to the need for a more analytical approach to research on therapy of ARDS; agents that are harmful at one time may be beneficial at another time.